JP7577424B2 - Communication Systems - Google Patents

Description

The present invention relates to a communication system that communicates between communication stations.

24(A) and 24(B) show the frame structure of a physical layer frame (hereinafter also referred to as a PL frame) transmitted by a broadcast signal conforming to the DVB-S2 standard (see, for example, Patent Document 1), which is known as a transmission path standard for satellite broadcasting. The PL frame comprises a physical layer header (hereinafter also referred to as a PL header) placed at the beginning, and an XFEC frame placed after the PL header. The PL frame is repeatedly transmitted from the transmitter, and is demodulated by a demodulation section of the receiver that receives the PL frame. Note that, in FIG. 24
The PL frame shown in (B) is before physical layer scrambling is applied, and before transmission, physical layer scrambling is applied to the XFEC frame excluding the PL header.

The PL header is 90 symbols of header data modulated with π/2 BPSK (Binary Phase Shift Keying). The PL header is composed of a 24-symbol SOF and a 64-symbol PLS code. The SOF is made up of a known pattern used in frame synchronization processing and indicates the start position of the frame. The PLS code stores parameters such as the modulation method and the coding rate of the error correction code.

The XFEC frame is data to be transmitted, such as data for a broadcast program. The XFEC frame is composed of FEC data that has been FEC encoded using, for example, an outer code (BCH) and an inner code (LDPC), and is modulated using a selected modulation method such as 8PSK (Phase Shift Keying). The XFEC frame is also divided into S slots, each of which has a fixed length of 90 symbols. For example, if the XFEC frame is 64,800 bits and is modulated using 8PSK, the XFEC frame is divided into 240 slots.

In pilot mode, a pilot block (also called a pilot) is inserted every 16 slots (1,440 symbols) of FEC data. The pilot consists of a known pattern of 36 unmodulated carrier symbols. Between communication stations using the DVB-S2 standard, frame synchronization is performed using the PL header, and pull-in to the demodulation section is performed using the pilot.

JP 2008-278186 A

As mentioned above, between communication stations using the DVB-S2 standard, pilots are used to pull in to the demodulator. However, because pilots are inserted at long intervals and have a small number of symbols, the initial pull-in that is performed after frame synchronization is established takes time. This problem is particularly noticeable when the transmission path environment is poor, the C/N (carrier power to thermal noise power ratio) is low, or the symbol rate is low. Also, in the case of circuits that demodulate using only the PL header and pilots, the FEC data transmitted during initial pull-in is not used, resulting in poor efficiency.

The present invention aims to provide a communication system that can perform initial acquisition in a shorter time than conventional systems.

In order to solve the above problem, the invention described in claim 1 is a communication system for transmitting and receiving a data frame, in which data to be communicated is stored, between a first communication station and a second communication station, wherein when starting communication between the first communication station and the second communication station, a transmitter of the first communication station repeatedly transmits a pull-in frame consisting only of a known pattern to the second communication station, a receiver of the second communication station receives the pull-in frame and performs a pull-in process using the received pull -in frame , the first communication station determines whether the receiver of the second communication station has completed the pull-in process, and when it determines that the pull-in process has been completed, the transmitter of the first communication station starts transmitting the data frame instead of the pull -in frame .

The invention described in claim 2 is characterized in that, in the communication system described in claim 1, a pilot block consisting of only a known pattern is stored in the data frame, and the length of the acquisition frame is longer than the pilot block stored in one of the data frames.

The invention described in claim 3 is characterized in that, in the communication system described in claim 1 or 2, when the data frame is being transmitted and received between the first communication station and the second communication station, if communication synchronization is lost at the receiver of the second communication station, the transmitter of the second communication station transmits a pull-in incompletion notification to the first communication station, and when the receiver of the first communication station receives the pull-in incompletion notification, the transmitter of the first communication station repeatedly transmits the pull -in frame to the second communication station instead of the data frame, the receiver of the second communication station receives the pull-in frame and performs the pull-in process using the received pull -in frame , and when the pull-in process is completed, the transmitter of the second communication station transmits a pull-in completion notification to the first communication station, and when the receiver of the first communication station receives the pull-in completion notification, the transmitter of the first communication station starts transmitting the data frame instead of the pull-in frame .

According to a fourth aspect of the present invention, in the communication system according to the first or second aspect, when the first communication station changes a setting of the data frame while the data frame is being transmitted and received between the first communication station and the second communication station, a transmitter of the first communication station transmits a setting change notification to the second communication station before changing the setting of the data frame, and when a receiver of the second communication station receives the setting change notification, the transmitter of the second communication station transmits a pull-in incompletion notification to the first communication station, and when the receiver of the first communication station receives the pull-in incompletion notification, When the first communication station receives the pull-in frame, the transmitter of the first communication station changes a setting of the data frame and transmits the pull-in frame to the second communication station, the receiver of the second communication station receives the pull-in frame and performs the pull-in process using the received pull -in frame , and when the pull-in process is completed, the transmitter of the second communication station transmits a pull-in completion notification to the first communication station, and when the receiver of the first communication station receives the pull-in completion notification, the transmitter of the first communication station starts transmitting the data frame with the changed setting instead of the pull-in frame .

The invention described in claim 5 is characterized in that, in the communication system described in claim 1 or 2, when the retraction process is completed, the transmitter of the second communication station transmits a retraction completion notification to the first communication station, and when the first communication station receives the retraction completion notification via a receiver, the receiver of the second communication station determines that the retraction process has been completed.

The invention described in claim 6 is characterized in that, in the communication system described in claim 5, at least one of notification information indicating the type of frame and the status of the pull-in process is stored in at least one of the header of the data frame and the header of the pull-in frame, stored in at least some of the pull-in frames as a known pattern, or embedded in the data stored in at least some of the data frames .

According to the invention described in claim 1, when communication is started between the first communication station and the second communication station, a pull-in frame consisting of only a known pattern is repeatedly transmitted, and the pull-in process is performed using this pull-in frame , so that the pull-in process can be performed efficiently and quickly. Furthermore, when the pull-in process is completed using the pull-in frame , a normal data frame is transmitted in place of the pull-in frame , so that it is possible to smoothly transition to transmission and reception of the normal data frame.

According to the invention described in claim 2, the length of the pull-in frame is set longer than the pilot block stored in one data frame, so that the pull-in process can be efficiently performed at high speed by utilizing the pull-in frame that is long and repeatedly transmitted.

According to the invention described in claim 3, when the first communication station and the second communication station lose synchronization, the pull-in frame is repeatedly transmitted and the pull-in process is performed using the pull-in frame , so that the pull-in process can be performed again efficiently and quickly. Also, when the pull-in process is completed using the pull- in frame , a normal data frame is transmitted in place of the pull-in frame , so that a smooth transition to transmission and reception of the normal data frame can be made.

According to the invention described in claim 4, when changing the setting of the data frame, the fact that the setting change will be made is notified in advance, and in response to this notification, the pull-in process is performed using the pull-in frame . Therefore, unlike conventional communication systems, the influence of the number of protection stages for out-of-synchronization when changing the setting is not present, and it is possible to perform the re-pull-in process efficiently and quickly. Furthermore, when the pull-in process is completed using the pull-in frame, the data frame after the setting change is transmitted instead of the pull-in frame , so that the setting change of the data frame can be performed smoothly.

Furthermore, according to the invention described in claim 5, when the retraction process using the retraction frame is completed, a retraction completion notification is sent, and it is determined that the retraction process has been completed based on this retraction completion notification, so that it is possible to reliably determine that the retraction process has been completed.

According to the invention described in claim 6, when transmitting and receiving notification information including the type of data frame or pull-in frame , a pull-in completion notification, etc. between the first communication station and the second communication station, the notification information is stored in the header of the data frame or pull-in frame , or is stored in the pull-in frame as a known pattern indicating the pull-in completion, or is embedded in the data stored in the data frame, so that the notification information can be transmitted and received by various methods, and the degree of design freedom is greatly improved. Also, since at least a part of the notification information can be stored in at least a part of the header, etc., it is possible to transmit and receive highly necessary notification information even when there are many types of notification information, and it is possible to reduce the processing load associated with the transmission and reception of notification information.

1 is a schematic configuration diagram of a communication system according to an embodiment of the present invention; FIG. 11 is an explanatory diagram showing an overview of an initial entrainment process using a entrainment frame . FIG. 11 is an explanatory diagram showing an overview of a re-pull-in process using a pull-in frame . FIG. 11 is an explanatory diagram showing an overview of a high-speed pull-in process performed after a data frame setting change; 2 is a functional block diagram showing a schematic configuration of a transmitter of a first communication station and a second communication station; FIG. 4 is a functional block diagram showing a schematic configuration of a receiver of a first communication station and a second communication station; FIG. 1A to 1C are diagrams illustrating signals output from each unit of a transmitter when a normal frame is generated and transmitted. 1A to 1C are diagrams showing signals output from each part of a receiver when demodulating a normal frame. 1A to 1C are diagrams showing signals output from each section of a transmitter when generating and transmitting a pull-in frame . 3A to 3C are diagrams showing signals output from each section of a receiver when demodulating a pull-in frame . 4A and 4B are diagrams illustrating a transmission signal and a reception signal when performing an initial pull-in process in the communication system according to the first embodiment. 5 is a flowchart showing a transmission process when transmitting and receiving a data frame in the communication system according to the first embodiment. 5 is a flowchart showing a receiving process when transmitting and receiving a data frame in the communication system according to the first embodiment. 4A and 4B are diagrams illustrating a transmission signal and a reception signal when performing a re-pull-in process in the communication system according to the first embodiment. 13A and 13B are diagrams illustrating a transmission signal and a reception signal when performing an initial pull-in process in a communication system according to a second embodiment. 13A and 13B are diagrams illustrating a transmission signal and a reception signal when performing a re-pull-in process in a communication system according to a second embodiment. FIG. 11 is a functional block diagram showing a schematic configuration of a receiver used in a communication system according to a third embodiment. 13A and 13B are diagrams illustrating a transmission signal and a reception signal when performing an initial pull-in process in a communication system according to a third embodiment. 13A and 13B are diagrams illustrating a transmission signal and a reception signal when performing a re-pull-in process in a communication system according to a third embodiment. 13A and 13B are diagrams showing transmitted signals and received signals when performing initial pull-in processing in a communication system according to a fourth embodiment. 13A and 13B are diagrams illustrating a transmission signal and a reception signal when performing a re-pull-in process in a communication system according to a fourth embodiment. 13A and 13B are diagrams showing transmitted signals and received signals when performing initial pull-in processing in a communication system according to a fifth embodiment. 13A and 13B are diagrams showing transmission signals and reception signals when performing re-pull-in processing in a communication system according to a fifth embodiment. A diagram showing the frame structure of a physical layer frame of the DVB-S2 standard.

(Embodiment 1)
FIG. 1 is a schematic diagram of a communication system 1 according to a first embodiment of the present invention. The communication system 1 includes a first communication station 2A having a transmitter and a receiver, a second communication station 2B having a transmitter and a receiver, and a communication satellite 3 relaying between the first communication station 2A and the second communication station 2B. The first communication station 2A and the second communication station 2B are respectively a local station and an opposite station, and transmit and receive data frames in which data to be communicated is stored in both directions. In the communication system 1 of this embodiment, for example, a PL frame (see FIG. 24) conforming to the DVB-S2 standard is used as the data frame. In this embodiment, the PL frame is also called a normal frame, and the PL header is also called a normal header.

The following is a brief overview of the communication processing performed by the communication system 1 according to this embodiment. To simplify the explanation, the explanation will be given using one-way communication from the first communication station 2A to the second communication station 2B as an example, rather than two-way communication between the first communication station 2A and the second communication station 2B.

In the communication system 1 according to the present embodiment, when communication is started between a first communication station 2A and a second communication station 2B, the transmitter of the first communication station 2A repeatedly transmits a pull-in frame of a known pattern to the second communication station 2B as shown in Fig. 2. The pull-in frame is a frame consisting of pilots that are longer (having a larger number of symbols) than the sum of pilots (plurality of pilots ) included in one normal frame. In addition, a pull-in header that stores data (notification information) indicating that the transmitted frame is a pull-in frame is added to the beginning of the pull-in frame.

The receiver of the second communication station 2B receives the pull-in header and the pull-in frame , determines that the transmitted frame is a pull-in frame based on the pull-in header , and switches the demodulation mode from the demodulation mode for normal frames to the demodulation mode for pull-in frames . The receiver of the second communication station 2B executes high-speed pull-in processing to the demodulation circuit using the received pull-in frame .

The first communication station 2A judges whether the fast pull-in process by the receiver of the second communication station 2B is completed, and when it judges that the fast pull-in process is completed, starts transmitting a normal frame instead of the pull-in frame . The receiver of the second communication station 2B judges that the transmitted frame is a normal frame based on the normal header (PL header) of the normal frame, and switches the demodulation mode to a demodulation mode for normal frames. In this way, by using a pull-in frame that is longer than the pilot of the normal frame, it is possible to perform the pull-in process efficiently and quickly.

In addition, the determination of whether or not the high-speed retraction process is completed may be performed by transmitting a retraction completion notification from the second communication station 2B after the completion of the high-speed retraction process, and determining that the high-speed retraction process is completed when the first communication station 2A receives this retraction completion notification as shown in FIG. 2. This makes it possible to reliably confirm the completion of the high-speed retraction process. In addition, the high-speed retraction process may be determined to be completed when a predetermined time has elapsed since the first communication station 2A started transmitting a retraction frame . This makes it possible to switch the transmission from the retraction frame to the normal frame even in the case of one-way communication from the first communication station 2A to the second communication station 2B. In addition, the predetermined time from the start of transmission of the retraction frame is not limited to a specific value, and can be appropriately set according to the performance of the receiver of the second communication station 2B, the communication environment, and the like.

The pull-in frame may be composed of a unique word, or may be an unmodulated signal (CW signal) or an alternating signal. The pilot of the DVB-S2 standard is an unmodulated signal that has been PL scrambled, but the pull-in frame may also be configured similarly to the pilot, but with a longer length (with a larger number of symbols). This allows the pull-in frame to be generated using a pilot generation circuit that is normally included in a transmitter of the DVB-S2 standard, simplifying the circuit configuration.

The pull-in header may use the PL header of the DVB-S2 standard, in which case a new PLS code indicating that it is a pull-in frame may be added, or if there is an unused PLS code, that unused code may be assigned as the code indicating a pull-in frame .

In addition, in the communication system 1 according to the present embodiment, when a normal frame is being transmitted and received between the first communication station 2A and the second communication station 2B, for example, if communication synchronization is lost in the receiver of the second communication station 2B, the transmitter of the second communication station 2B transmits a pull-in incompletion notification to the first communication station 2A. As shown in Fig. 3, when the first communication station 2A receives the pull-in incompletion notification, it repeatedly transmits a pull-in header and a pull-in frame to the second communication station 2B instead of a normal frame.

The receiver of the second communication station 2B receives the pull-in frame and executes high-speed pull-in processing using the received pull-in frame . When the high-speed pull-in processing is completed, the transmitter of the second communication station 2B transmits a pull-in completion notification to the first communication station 2A. As shown in FIG. 3, the first communication station 2A
When the pull-in completion notification is received, the transmission of a normal frame starts instead of the pull-in frame . In this way, by using a pull-in frame that is longer than the pilot of a normal frame, it is possible to perform the re-pull-in process efficiently and quickly.

Furthermore, in the communication system 1 according to the present embodiment, when a normal frame is being transmitted and received between a first communication station 2A and a second communication station 2B, if the first communication station changes the setting of the normal frame (e.g., modulation method, etc.), the transmitter of the first communication station 2A transmits a setting change notification to the second communication station 2B before changing the setting of the normal frame. In the example shown in Fig. 4, the transmitter of the first communication station 2A transmits a pull-in header and a pull-in frame to the second communication station 2B as the setting change notification.

When the receiver of the second communication station 2B receives the retraction header and the retraction frame as a setting change notification, the synchronization is lost, so the transmitter of the second communication station 2B transmits a retraction incomplete notification to the first communication station 2A. As shown in FIG. 4, when the receiver of the first communication station 2A receives the retraction incomplete notification, the transmitter of the first communication station 2A changes the setting of the PL frame, and transmits the retraction header and the retraction frame to the second communication station 2B after the communication is disconnected due to the setting change. The receiver of the second communication station 2B receives the retraction frame and executes high-speed retraction processing using the received retraction frame . When the high-speed retraction processing is completed, the transmitter of the second communication station 2B transmits a retraction completion notification to the first communication station 2A. When the first communication station 2A receives the retraction completion notification as shown in FIG. 4, it starts transmitting a normal frame with the setting changed instead of the retraction frame .

In the conventional communication system, when detecting out-of-sync after changing the setting of the data frame, the detection of out-of-sync is delayed depending on the number of protection stages by the forward protection, and the re-pulling process after the setting change is delayed. However, according to the communication system 1 of the present embodiment, a setting change notification is transmitted before the setting change, and a pull-in frame is transmitted after the setting change, so that the receiving side can prepare for the re-pulling process in advance, and the re-pulling process after the setting change can be performed efficiently and quickly.

When transmitting a pull-in header and a pull-in frame as a setting change notification, the pull-in header and the pull-in frame may be repeatedly transmitted in order to reliably notify the setting change, but transmitting a pull- in header and a pull-in frame with a length equal to or greater than the number of protection stages will not provide any advantage. Therefore, it is preferable to repeatedly transmit a length shorter than the number of protection stages. Also, although the pull-in header and the pull-in frame are described as being transmitted as a setting change notification, only the pull-in header may be transmitted.

In addition, in the above, the interval of the pull-in header , i.e., the length of the pull-in frame , is described as being constant, but it does not necessarily have to be constant, and the pattern of the pull-in header or the data pattern of the pull -in frame may be increased to include interval information, so that the switching may be performed stepwise. Specifically, for high-speed pull-in processing, when starting to transmit the pull-in header and the pull-in frame , the interval of the pull-in header may be shortened (the pull-in frame may be shortened) to prioritize frame synchronization using the pull-in header , and then the interval of the pull-in header may be lengthened ( the pull-in frame may be lengthened) to prioritize the pull-in processing.

The above-mentioned data indicating the type of frame, the pull-in completion notification, and the pull-in incompletion notification correspond to the notification information of the present invention. As described above, these notification information may be stored in the header and transmitted/received, or may be stored in the pull-in frame as a known pattern indicating the frame type or communication status. Furthermore, the notification information may be embedded in the data stored in the frame and transmitted/received. Any method may be used to transmit/receive these notification information, or each method may be used in appropriate combination.

Next, the communication system 1 according to the present embodiment will be described in more detail. Figures 5 and 6 are functional block diagrams showing the schematic configurations of the transmitter 4A and receiver 5A of the first communication station 2A and the transmitter 4B and receiver 5B of the second communication station 2B. Note that since the transmitter 4A and transmitter 4B have the same configuration and function, and the receiver 5A and receiver 5B have the same configuration and function, detailed description of the transmitter 4B and receiver 5B of the second communication station 2B will be omitted below.

The transmitter 4A (4B) includes a mapping unit 4A1, a pilot adding unit 4A2, a PL scrambling unit 4A3, a header adding unit 4A4, a ROF unit 4A5, a timing generating unit 4A6, a pilot generating unit 4A7, and a header generating unit 4A8.

The mapping unit 4A1 receives an input of a binary data string that has been subjected to predetermined processing (e.g., baseband frame processing, error correction coding processing, etc.) as necessary for the information/data to be transmitted, and performs mapping processing on this binary data string so that it becomes a signal point arrangement according to the DVB-S2 standard, generating and outputting a data frame consisting of a symbol string.

The pilot adding unit 4A2 adds the pilot generated by the pilot generating unit 4A7 to the data frame generated by the mapping unit 4A1. The pilot generating unit 4A7 generates pilots with different lengths and timings according to the pilot enable output from the timing generating unit 4A6. The timing generating unit 4A6 receives opposite station attraction information (information indicating the attraction state of the opposite station) and local station attraction information (information indicating the attraction state of the local station) from the local station's receiver 5A, and generates and outputs pilot enable, header enable, and selection header information based on the opposite station attraction information and the local station attraction information.

The PL scrambling unit 4A3 is a processing unit that applies physical layer scrambling to the data frame output from the pilot adding unit 4A2.

The header adding unit 4A4 adds the header generated by the header generating unit 4A8 to the beginning of the data frame output from the PL scrambling unit 4A3. The header generating unit 4A8 generates a header based on the selected header information and the header enable output from the timing generating unit 4A6.

The ROF unit 4A5 has a roll-off filter function and performs band limiting processing on the data frame after physical layer scrambling output from the header adding unit 4A4 and outputs it. The transmission output of the ROF unit 4A5 is transmitted from the first communication station 2A to the second communication station 2B.

Next, the receiver 5A (5B) will be described. The receiver 5A includes an ROF unit 5A1, a symbol recovery unit 5A2, a PL descrambling unit 5A3, a frequency correction unit 5A4, a phase correction unit 5A5, a gain correction unit 5A6, a header removal unit 5A7, a pilot removal unit 5A8, a demapping unit 5A9, a header detection unit 5A10, a timing generation unit 5A11, and a pull-in completion determination unit 5A12.

The ROF unit 5A1 has a roll-off filter function and performs band limiting processing on the frame data received from the second communication station 2B before outputting it. The symbol recovery unit 5A2 synchronizes the symbol timing from the signal output from the ROF unit 5A1, and the PL descrambling unit 5A3 removes the physical layer scrambling applied to the data frame by the transmitter 4B of the second communication station 2B.

The frequency correction unit 5A4, phase correction unit 5A5, and gain correction unit 5A6 perform frequency, phase, and gain corrections on the data frame from which the physical layer scrambling has been removed.

The header removal unit 5A7 and pilot removal unit 5A8 remove the header and pilot from the data frame whose gain and other parameters have been corrected. The header removal unit 5A7 and pilot removal unit 5A8 remove the header and pilot according to the header enable and pilot enable output from the timing generation unit 5A11. The demapping unit 5A9 performs demapping processing on the frame, converts the symbol sequence data into a binary data sequence, and outputs it. The timing generation unit 5A11 generates and outputs a header enable and pilot enable according to the type of header detected by the header detection unit 5A10.

The pull-in completion determination unit 5A12 determines whether or not the local receiver 5A has completed pull-in (including frame synchronization) based on the frame output from the gain correction unit 5A6. If the local receiver 5A has completed pull-in, the pull-in completion determination unit 5A12 outputs "pull-in complete" as the local pull-in information to the local transmitter 4A, and if pull-in is not complete, it outputs "pull-in incomplete" as the local pull-in information.

The pull-in completion determination unit 5A12 also determines whether the opposite station receiver 5B has completed pull-in based on the type of header detected by the header detection unit 5A10. If the opposite station receiver 5B has completed pull-in, the pull-in completion determination unit 5A12 outputs "pull-in complete" as the opposite station pull-in information to the transmitter 4A of the own station, and if pull-in is not complete, it outputs "pull-in incomplete" as the opposite station pull-in information.

Figure 7 shows the output signals output by each part of the transmitter 4A (4B) when the transmitter 4A (4B) generates and transmits a normal frame. When the local station pull-in information and the opposite station pull-in information are both "pull-in complete", the timing generation part 4A6 of the transmitter 4A outputs a pilot enable at a predetermined interval (for example, every 16 slots (1440 symbols) of FEC data) in order to generate and output a normal frame, as shown in (A) of the figure. The pilot generation part 4A7 generates a pilot in response to this pilot enable, as shown in (B) of the figure, and outputs it to the pilot attachment part 4A2. The pilot attachment part 4A2 attaches a pilot to the data frame output from the mapping part 4A1, as shown in (C) of the figure. Note that "0" shown in the figure indicates a state in which no data exists.

As shown in FIG. 7(D), the timing generation unit 4A6 of the transmitter 4A outputs a header enable to the header generation unit 4A8 at a timing corresponding to the beginning of the data frame output from the mapping unit 4A1. Also, as shown in FIG. 7(E), the timing generation unit 4A6 selects the type of header to be generated according to the combination of the local station attraction information and the opposite station attraction information, and outputs selected header information indicating the selected header to the header generation unit 4A8 to generate the selected type of header.

Specifically, when the local station pull-in information and the opposite station pull-in information are both "pull-in complete", the timing generation unit 4A6 causes the header generation unit 4A8 to generate a "normal frame & pull-in complete" header. Also, when the local station pull-in information is "pull-in incomplete" and the opposite station pull-in information is "pull-in complete", the timing generation unit 4A6 causes the header generation unit 4A8 to generate a "normal frame & pull-in incomplete" header.

The header generated by the header generating unit 4A8 indicates the type of frame to which the header is added and the pull-in state of the own station, and corresponds to the header storing the notification information of the present invention.
That is, the "normal frame & pull-in complete" header is attached to a normal frame and indicates that the pull-in of the local station is complete. The "normal frame & pull-in incomplete" header is attached to a normal frame and indicates that the pull-in of the local station is not complete. The "normal frame & pull-in complete" header and the "normal frame & pull-in incomplete" header correspond to the normal header described above.

The header adding unit 4A4 adds a header to the data frame to which the pilot has been added, as shown in FIG. 7(F). This causes the transmitter 4A (4B) to generate a normal frame.

Figure 8 shows the output signals output by each section of the receiver 5A (5B) in normal mode, in which the receiver 5A (5B) demodulates a normal frame received by the receiver 5A (5B). The header detection section 5A10 of the receiver 5A detects the type of header of the received normal frame, as shown in (A) of the figure. The timing generation section 5A11 generates a header enable in accordance with the detected type of header, as shown in (B) of the figure. The header removal section 5A7 removes the header from the normal frame based on the header enable, as shown in (C) of the figure.

The timing generation unit 5A11 also generates a pilot enable in accordance with the type of detected header, as shown in FIG. 1(D). The pilot removal unit 5A8 removes pilots from the normal frame based on the pilot enable, as shown in FIG. 1(E). This causes only data to be output from the pilot removal unit 5A8.

9(A) to (F) show output signals output by each part of the transmitter 4A and the transmitter 4B when the transmitter 4A and the transmitter 4B generate and transmit a pull-in frame . When the local station pull-in information and the opposite station pull-in information are both "pull-in incomplete" as shown in FIG. 9(A), the timing generation unit 4A6 of the transmitter 4A outputs a pilot enable at a predetermined interval (for example, longer (more symbols) than the sum of pilots (plural pilots) included in one normal frame) in order to generate and output a pull-in frame. As shown in FIG. 9(B), the pilot generation unit 4A7 generates a pilot ( pull-in frame ) in response to this pilot enable and outputs it to the pilot assignment unit 4A2. As shown in FIG. 9(C), the pilot assignment unit 4A2 assigns a pilot to an empty data frame in which no data is stored. Note that "0" shown in the figure indicates a state in which no data exists.

As shown in FIG. 9(D), the timing generation unit 4A6 of the transmitter 4A outputs a header enable to the header generation unit 4A8 at a timing corresponding to the beginning of the data frame output from the mapping unit 4A1. Also, as shown in FIG. 9(E), the timing generation unit 4A6 sets the type of header to be generated according to the combination of the local station attraction information and the opposite station attraction information, and outputs selection header information indicating the set header to the header generation unit 4A8 to generate the set type of header.

Specifically, when the local station pull-in information and the opposite station pull-in information are both "pull-in incomplete", the timing generation unit 4A6 causes the header generation unit 4A8 to generate a " pull-in frame & pull-in incomplete" header. Also, when the local station pull-in information is "pull-in complete" and the opposite station pull-in information is "pull-in incomplete", the timing generation unit 4A6 causes the header generation unit 4A8 to generate a " pull-in frame & pull-in complete" header.

The header generated by the header generating unit 4A8 indicates the type of frame to which the header is attached and the pull-in status of the own station, and corresponds to the header in which the notification information of the present invention is stored. That is, the " pull-in frame & pull-in incomplete" header is attached to a pull-in frame and indicates that the pull-in of the own station is not completed. Also, the " pull-in frame & pull-in complete" header is attached to a pull-in frame and indicates that the pull-in of the own station is completed. The " pull-in frame & pull-in incomplete" header and the " pull-in frame & pull-in complete" header correspond to the pull-in header described above.

The header adding unit 4A4 adds a header to the frame to which the long pilot has been added, as shown in Fig. 9(F), whereby the transmitter 4A (4B) generates a pull-in frame .

10A to 10E show output signals output by each section of the receiver 5A and the receiver 5B in a fast pull-in mode in which the pull-in frame received by the receiver 5A and the receiver 5B is demodulated. The header detection section 5A10 of the receiver 5A detects the type of the header of the received pull-in frame as shown in FIG. 10A. The timing generation section 5A11 generates a header enable in accordance with the detected type of header as shown in FIG. 10B. The header removal section 5A7 removes the header from the pull-in frame based on the header enable as shown in FIG. 10C.

Furthermore, the timing generator 5A11 generates a pilot enable in accordance with the type of the detected header, as shown in (D) of the figure. The pilot remover 5A8 removes the pilot from the pull-in frame based on the pilot enable, as shown in (E) of the figure. As a result, no data is output from the receiver 5A during reception of the pull-in frame .

Next, the operation of the communication system 1 of embodiment 1 when starting two-way communication will be described according to the timing chart shown in FIG. 11, the flowchart of FIG. 12 showing the processing procedure of the transmitters 4A and 4B, and the flowchart of FIG. 13 showing the processing procedure of the receivers 5A and 5B. Note that the explanation of (1) to (7) given below corresponds to the timing of (1) to (7) shown in FIG. 11.

(1) When starting two-way communication between the first communication station 2A and the second communication station 2B, the transmitter 4A of the first communication station 2A and the transmitter 4B of the second communication station 2B repeatedly transmit the " pull-in frame & pull-in incomplete" header and the " pull-in frame " based on the self-station pull-in information and the opposite station pull-in information. (1)' The receiver 5A of the first communication station 2A and the receiver 5B of the second communication station 2B receive the " pull-in frame & pull-in incomplete" header and the " pull-in frame " transmitted from the opposite station, and execute frame synchronization processing using the header and demodulation processing in the high-speed pull-in mode using the " pull-in frame ". In addition, the receiver 5A of the first communication station 2A and the receiver 5B of the second communication station 2B check the pull-in status of the opposite station based on the received header, and output the opposite station pull-in information to the transmitter of the own station. Moreover, the receiver 5A of the first communication station 2A and the receiver 5B of the second communication station 2B check the pull-in status of their own stations and output their own station pull-in information to the transmitters of their own stations.

(2) In the above situation, it is assumed that the receiver 5A of the first communication station 2A completes the pull-in first. (2)' In this case, the transmitter 4A of the first communication station 2A switches the header from the " pull-in frame & pull-in incomplete" header to the " pull-in frame & pull-in complete" header, and transmits it together with the " pull-in frame " to the second communication station 2B.

(3) When the receiver 5B of the second communication station 2B receives the “ retraction frame & retraction completed” header, (3)’ the transmitter 4B of the second communication station 2B switches the header from the “ retraction frame & retraction incomplete” header to a “normal frame & retraction incomplete” header and transmits it to the first communication station 2A together with the “normal frame”.

(4) When the receiver 5A of the first communication station 2A receives the "normal frame & pull-in incomplete" header and the "normal frame", it uses the "normal frame" to perform demodulation processing in normal mode.

(5) Next, when the receiver 5B of the second communication station 2B completes the pull-in, (5)' the transmitter 4B of the second communication station 2B switches the header from a "normal frame & pull-in incomplete" header to a "normal frame & pull-in complete" header and transmits it together with a "normal frame" to the first communication station 2A.

(6) When the receiver 5A of the first communication station 2A receives the “normal frame & retraction complete” header, (6)’ the transmitter 4A of the first communication station 2A switches the header from the “ retraction frame & retraction complete” header to a “normal frame & retraction complete” header and transmits it together with the “normal frame” to the second communication station 2B.

(7) When the receiver 5B of the second communication station 2B receives the "normal frame & pull-in complete" header and the "normal frame", it uses the "normal frame" to perform demodulation processing in normal mode. This completes the initial pull-in between the first communication station 2A and the second communication station 2B.

Next, the operation of re-pulling in after a loss of synchronization occurs in communication system 1 will be described according to the timing chart shown in FIG. 14 and the flowcharts shown in FIG. 12 and FIG. 13. Note that the explanation of (1) to (6) below corresponds to the timing of (1) to (6) shown in FIG. 14.

(1) Pull-in is complete between the first communication station 2A and the second communication station 2B, and a "normal frame & pull-in complete" header and a "normal frame" are being sent and received. (2) In this situation, assume that synchronization is lost in the receiver 5B of the second communication station 2B. (2)' In this case, the transmitter 4B of the second communication station 2B switches the header from the "normal frame & pull-in complete" header to the "normal frame pull-in incomplete" header and transmits it to the first communication station 2A together with the "normal frame".

(3) When the receiver 5A of the first communication station 2A receives the “normal frame & retraction incomplete” header, (3)’ the transmitter 4A of the first communication station 2A switches the header from the “normal frame & retraction completed” header to the “ retraction frame & retraction completed” header and transmits it together with the “ retraction frame ” to the second communication station 2B.

(4) The receiver 5B of the second communication station 2B performs a demodulation process using the “ retraction frame ”, and when the retraction is completed, (4)’ the transmitter 4B of the second communication station 2B switches the header from a “normal frame & retraction incomplete” header to a “normal frame & retraction completed” header and transmits it together with the “normal frame” to the first communication station 2A.

(5) When the receiver 5A of the first communication station 2A receives the “normal frame & retraction complete” header, (5)’ the transmitter 4A of the first communication station 2A switches the header from the “ retraction frame & retraction complete” header to the “normal frame & retraction complete” header and transmits it to the second communication station 2B together with the “normal frame”.

(6) When the receiver 5B of the second communication station 2B receives the "normal frame & pull-in complete" header and the "normal frame", it uses the "normal frame" to perform demodulation processing in normal mode. This completes re-pull-in between the first communication station 2A and the second communication station 2B.

As described above, according to the communication system 1 of the first embodiment, when communication is started between the first communication station 2A and the second communication station 2B, a pull-in frame having a known pattern is repeatedly transmitted, and the pull-in process is performed using this pull-in frame , so that the pull-in process can be performed efficiently and quickly. Furthermore, when the pull-in process is completed using the pull-in frame , a normal data frame is transmitted in place of the pull-in frame , so that a smooth transition to transmission and reception of the normal data frame can be made.

Furthermore, according to the communication system 1 of the first embodiment, the length of the pull-in frame is set to be longer than the pilot block stored in one data frame, so that it is possible to perform the pull-in process efficiently and quickly by utilizing the pull-in frame that is long and is repeatedly transmitted.

Furthermore, according to the communication system 1 according to the first embodiment, when the first communication station and the second communication station lose synchronization, the retraction frame is repeatedly transmitted and the retraction process is performed using the retraction frame , so that it is possible to perform the re-retraction process efficiently and quickly. Also, when the retraction process is completed using the retraction frame , a normal data frame is transmitted in place of the retraction frame , so that it is possible to smoothly transition to the transmission and reception of the normal data frame.

Moreover, according to the communication system 1 of the first embodiment, when changing the setting of the data frame, the fact that the setting change will be made is notified in advance, and in response to this notification, the pull-in process is performed using the pull-in frame . Therefore, unlike the conventional communication system, there is no influence due to the number of protection steps for out-of-synchronization when changing the setting, so it is possible to perform the re-pull-in process efficiently and quickly. Furthermore, when the pull-in process is completed using the pull-in frame , the data frame after the setting change is transmitted instead of the pull-in frame , so that the setting change of the data frame can be performed smoothly.

Furthermore, according to the communication system 1 of embodiment 1, when the retraction process using the retraction frame is completed, a retraction completion notification is transmitted, and it is determined that the retraction process has been completed based on this retraction completion notification, so that it is possible to reliably determine that the retraction process has been completed.

In addition, according to the communication system 1 of the first embodiment, the communication station in one direction can complete the pull-in first and maintain the pull-in completed state regardless of the situation of the opposite station, thereby improving the stability of communication.

As described above, in the first embodiment, the dedicated " pulling frame & pull-in incomplete" header, "pulling frame & pull-in complete" header, "normal frame & pull-in incomplete" header, and " pulling frame & pull-in complete" header are used as the pull-in incomplete notification and the pull-in complete notification used in the pull-in frame and the normal frame, but the notification information may be added to only some frame types or the pull-in status so that they can be identified. According to this, the types of notification information such as the pull-in incomplete notification and the pull-in complete notification can be reduced, so that the processing load associated with switching the notification information can be reduced. In the following second to fifth embodiments, examples will be described in which the notification information such as the pull-in incomplete notification and the pull-in complete notification is stored in the headers of some frames, or is stored in some pull-in frames as a known pattern, or is embedded in the data stored in some frames.

(Embodiment 2)
Next, a communication system according to a second embodiment of the present invention will be described with reference to the timing chart shown in Fig. 15. This embodiment differs from the first embodiment in that it does not use the "normal frame & pull-in incomplete" header. Note that the same reference numerals are used for the same configuration as in the first embodiment, and detailed explanations are omitted. Also, the explanation of (1) to (5) described below corresponds to the timing of (1) to (5) shown in Fig. 15.

(1) When starting two-way communication between the first communication station 2A and the second communication station 2B, the transmitter 4A of the first communication station 2A and the transmitter 4B of the second communication station 2B repeatedly transmit the " pull-in frame & pull-in incomplete" header and the " pull-in frame " based on the self-station pull-in information and the opposite station pull-in information. (1)' The receiver 5A of the first communication station 2A and the receiver 5B of the second communication station 2B receive the " pull-in frame & pull-in incomplete" header and the " pull-in frame " transmitted from the opposite station, and execute frame synchronization processing using the header and demodulation processing in the high-speed pull-in mode using the " pull-in frame ". In addition, the receiver 5A of the first communication station 2A and the receiver 5B of the second communication station 2B check the pull-in status of the opposite station based on the received header, and output the opposite station pull-in information to the transmitter of the own station. Moreover, the receiver 5A of the first communication station 2A and the receiver 5B of the second communication station 2B check the pull-in status of their own stations and output their own station pull-in information to the transmitters of their own stations.

(2) In the above situation, it is assumed that the receiver 5A of the first communication station 2A completes the pull-in first. (2)' In this case, the transmitter 4A of the first communication station 2A switches the header from the " pull-in frame & pull-in incomplete" header to the " pull-in frame & pull-in complete" header, and transmits it together with the " pull-in frame " to the second communication station 2B.

(3) When the receiver 5B of the second communication station 2B receives the “ retraction frame & retraction completed” header and the “ retraction frame ”, and the retraction using the “ retraction frame ” is completed, (3)’ the transmitter 4B of the second communication station 2B switches the header from the “ retraction frame & retraction incomplete” header to a “normal frame & retraction completed” header and transmits it together with the “normal frame” to the first communication station 2A.

(4) When the receiver 5A of the first communication station 2A receives the "normal frame & pull-in complete" header, it executes demodulation processing in normal mode using the "normal frame". (4)' Also, the transmitter 4A of the first communication station 2A switches the header from the " pull-in frame & pull-in complete" header to the "normal frame & pull-in complete" header and transmits it together with the "normal frame" to the second communication station 2B.

(5) When the receiver 5B of the second communication station 2B receives the "normal frame & pull-in complete" header and the "normal frame", it uses the "normal frame" to perform demodulation processing in normal mode. This completes the initial pull-in between the first communication station 2A and the second communication station 2B.

Next, the operation of re-pulling in the communication system 1 of the second embodiment after loss of synchronization occurs will be described according to the timing chart shown in FIG. 16. Note that the explanation of (1) to (6) below corresponds to the timing of (1) to (6) shown in FIG. 16.

(1) Pull-in is completed between the first communication station 2A and the second communication station 2B, and a "normal frame & pull-in complete" header and a "normal frame" are being transmitted and received. (2) In this situation, assume that the receiver 5B of the second communication station 2B loses synchronization. (2)' In this case, the transmitter 4B of the second communication station 2B switches the header from the "normal frame & pull-in complete" header to the " pull-in frame & pull-in incomplete" header and transmits it to the first communication station 2A together with the " pull-in frame ".

(3) When the receiver 5A of the first communication station 2A receives the “ pushing frame & pulling incomplete” header, (3)’ the transmitter 4A of the first communication station 2A switches the header from the “normal frame & pulling complete” header to the “ pushing frame & pulling complete” header and transmits it together with the “ pushing frame ” to the second communication station 2B.

(4) The receiver 5B of the second communication station 2B receives the “ retraction frame & retraction completed” header and the “ retraction frame ”, and when it completes retraction using the “ retraction frame ”, (4)’ the transmitter 4B of the second communication station 2B switches the header from the “ retraction frame & retraction incomplete” header to a “normal frame & retraction completed” header and transmits it together with the “normal frame” to the first communication station 2A.

(5) When the receiver 5A of the first communication station 2A receives the “normal frame & retraction complete” header, (5)’ the transmitter 4A of the first communication station 2A switches the header from the “ retraction frame & retraction complete” header to the “normal frame & retraction complete” header and transmits it to the second communication station 2B together with the “normal frame”.

(6) When the receiver 5B of the second communication station 2B receives the "normal frame & pull-in complete" header and the "normal frame", it uses the "normal frame" to perform demodulation processing in normal mode. This completes re-pull-in between the first communication station 2A and the second communication station 2B.

As described above, according to the communication system 1 of the second embodiment, like the first embodiment, it is possible to perform the retraction process efficiently and quickly, and to smoothly transition to the transmission and reception of normal data frames. Furthermore, according to the second embodiment, since the "normal frame & retraction incomplete" header is not used, it is possible to reduce the number of header types and reduce the processing load associated with header switching.

(Embodiment 3)
Next, a communication system according to a third embodiment of the present invention will be described. This embodiment differs from the first embodiment in that it does not use a "normal frame & pull-in incomplete" header or a "normal frame & pull-in complete" header, but identifies whether pull-in is incomplete or complete for a normal frame by information embedded in the data. Note that the same reference numerals are used for the same configuration as in the first embodiment, and detailed description will be omitted.

In the following, a normal frame with embedded pull-in incomplete information is called a "normal frame (pull-in complete)", and a normal frame with embedded pull-in complete information is called a "normal frame (pull-in complete)". In addition, the headers added to "normal frames (pull-in complete)" and "normal frames (pull-in complete)" are called "normal frame" headers. The embedding of pull-in incomplete information and pull-in complete information into the data of a "normal frame" is performed by the timing generation unit 4A6 of the transmitter 4A (4B) shown in Figure 5 in accordance with the opposite station pull-in information and local station pull-in information output from the receiver.

17 is a block diagram showing the functional configuration of the receiver 51A of the first communication station 2A and the receiver 51B of the second communication station 2B according to this embodiment. In the receiver 51A (51B), an error correction unit 5A12 and a BB deframer 5A13 are connected to the rear stage of the demapping unit 5A9. The error correction unit 5A12 corrects errors in the demapping process by the demapping unit 5A9. The BB deframer 5A13 performs a deframing process on the frame. The deframed data is branched and output to the pull-in completion determination unit 5A12. The pull-in completion determination unit 5A12 distinguishes between a "normal frame (pull-in incomplete)" and a "normal frame (pull-in complete)" based on information embedded in the data output from the BB deframer 5A13.

Figure 18 is a timing chart showing the communication state between the first communication station 2A and the second communication station 2B in this embodiment. Note that the explanation of (1) to (7) below corresponds to the timing of (1) to (7) shown in Figure 18.

(1) When starting two-way communication between the first communication station 2A and the second communication station 2B, the transmitter 4A of the first communication station 2A and the transmitter 4B of the second communication station 2B repeatedly transmit the " pull-in frame & pull-in incomplete" header and the " pull-in frame " based on the self-station pull-in information and the opposite station pull-in information. (1)' The receiver 51A of the first communication station 2A and the receiver 51B of the second communication station 2B receive the " pull-in frame & pull-in incomplete" header and the " pull-in frame " transmitted from the opposite station, and execute frame synchronization processing using the header and demodulation processing in the high-speed pull-in mode using the " pull-in frame ". In addition, the receiver 51A of the first communication station 2A and the receiver 51B of the second communication station 2B check the pull-in status of the opposite station based on the received header and the information embedded in the normal frame by the pull-in completion determination unit 5A12, and output the opposite station pull-in information to the transmitter of the own station. Furthermore, the receiver 5A of the first communication station 2A and the receiver 5B of the second communication station 2B check the pull-in status of their own station by the pull-in completion determination unit 5A12, and output their own station pull-in information to the transmitter of their own station.

(2) In the above situation, it is assumed that the receiver 51A of the first communication station 2A completes the pull-in first. (2)' In this case, the transmitter 4A of the first communication station 2A switches the header from the " pull-in frame & pull-in incomplete" header to the " pull-in frame & pull-in complete" header, and transmits it together with the " pull-in frame " to the second communication station 2B.

(3) When the receiver 51B of the second communication station 2B receives the “ pulling frame & pull-in completed” header and the “ pulling frame ”, (3)’ the transmitter 4B of the second communication station 2B switches the header from the “ pulling frame & pull-in incomplete” header to a “normal frame” header and transmits a “normal frame (pulling incomplete)” with pull-in incomplete information embedded in the data to the first communication station 2A.

(4) When the receiver 51A of the first communication station 2A receives the "normal frame" header and the "normal frame (retraction incomplete)", it executes demodulation processing in normal mode using the "normal frame (retraction incomplete)". In addition, the receiver 51A of the first communication station 2A generates opposite station retraction information based on the retraction incomplete information embedded in the "normal frame (retraction incomplete)" and outputs the opposite station retraction information to the transmitter 4A of the own station.

(5) When the receiver 51B of the second communication station 2B completes the retraction using the “ retraction frame ”, (5)′ the transmitter 4B of the second communication station 2B switches from a “normal frame (retraction incomplete)” to a “normal frame (retraction completed)” and transmits it to the first communication station 2A.

(6) When the receiver 51A of the first communication station 2A receives the “normal frame” header and the “normal frame (retraction completed)”, (6)’ the transmitter 4A of the first communication station 2A switches the header from the “ retraction frame & retraction completed” header to a “normal frame” header and transmits it together with the “normal frame (retraction completed)” to the second communication station 2B.

(7) When the receiver 5B of the second communication station 2B receives the "normal frame" header and the "normal frame (pull-in complete)", it uses the "normal frame" to perform demodulation processing in normal mode. This completes the initial pull-in between the first communication station 2A and the second communication station 2B.

Next, the operation of re-pulling in the communication system 1 of the third embodiment after loss of synchronization will be described according to the timing chart shown in FIG. 19. Note that the explanation of (1) to (6) below corresponds to the timing of (1) to (6) shown in FIG. 18.

(1) Pull-in is complete between the first communication station 2A and the second communication station 2B, and a "normal frame" header and a "normal frame (pull-in complete)" are being sent and received. The "normal frame (pull-in complete)" has pull-in complete information embedded in it. (2) In this situation, assume that synchronization is lost in the receiver 51B of the second communication station 2B. (2)' In this case, the transmitter 4B of the second communication station 2B switches from the "normal frame (pull-in complete)" to the "normal frame (pull-in incomplete)" and transmits it to the first communication station 2A.

(3) When the receiver 51A of the first communication station 2A receives the “normal frame” header and the “normal frame (retraction incomplete)”, (3)’ the transmitter 4A of the first communication station 2A switches the header from the “normal frame” header to a “ retraction frame & retraction completed” header and transmits it together with the “ retraction frame ” to the second communication station 2B.

(4) When the receiver 51B of the second communication station 2B receives the “ Retraction frame & retraction completed” header and the “ Retraction frame ” and completes retraction using the “ Retraction frame ”, (4)’ the transmitter 4B of the second communication station 2B switches from a “Normal frame (retraction not completed)” to a “Normal frame (retraction completed)” and transmits it to the first communication station 2A.

(5) When the receiver 51A of the first communication station 2A receives a “normal frame (retraction completed)”, (5)’ the transmitter 4A of the first communication station 2A switches the header from the “ retraction frame & retraction completed” header to a “normal frame” header and transmits it to the second communication station 2B together with the “normal frame (retraction completed)” in which the retraction completion information is embedded.

(6) When the receiver 51B of the second communication station 2B receives the "normal frame" header and the "normal frame", it executes demodulation processing in normal mode using the "normal frame (pull-in complete)". This completes re-pull-in between the first communication station 2A and the second communication station 2B.

As described above, according to the communication system 1 of the third embodiment, as in the first embodiment, it is possible to perform the retraction process efficiently and quickly, and to smoothly transition to the transmission and reception of normal data frames. Furthermore, according to the third embodiment, the "normal frame & retraction incomplete" header and the "normal frame & retraction complete" header are not used, so it is possible to reduce the number of header types and reduce the processing load associated with header switching. Furthermore, regardless of the situation of the opposing station, it is possible to complete the retraction of the communication station in one direction first and maintain the retraction complete state, thereby improving the stability of communication.

(Embodiment 4)
Next, a communication system according to a fourth embodiment of the present invention will be described. This embodiment differs from the first embodiment in that a common header is used in each frame, and pull-in frames are identified as being incomplete or complete by the data pattern, and pull-in frames are identified as being incomplete or complete by the information embedded in the data. Note that the same reference numerals are used for the same components as in the first embodiment, and detailed descriptions are omitted.

In the following, a pull-in frame using a data pattern indicating that pull-in is not complete will be called a " pull-in frame (pull-in complete)" and a pull-in frame using a data pattern indicating that pull-in is complete will be called a " pull-in frame (pull-in complete)".
A normal frame with embedded pull-in completion information is called a "normal frame (pull-in complete)." A normal frame with embedded pull-in completion information is called a "normal frame (pull-in complete)."

Switching between " pull-in frame (pull-in incomplete)" and " pull-in frame (pull-in complete)" is performed by the timing generation unit 4A6, pilot generation unit 4A7, and pilot assignment unit 4A2 of the transmitter 4A (4B) shown in Fig. 5 in response to the opposite station pull-in information and the local station pull-in information output from the receiver. Also, embedding of pull-in incomplete information and pull-in complete information into the data of the "normal frame" is performed by the timing generation unit 4A6 in response to the opposite station pull-in information and the local station pull-in information output from the receiver.

17, the receiver 51A of the first communication station 2A and the receiver 51B of the second communication station 2B according to this embodiment distinguish between incomplete and complete pull-in of the pull-in frame based on the header and data pattern by the header detection unit 5A10. Since both the " pull-in frame (incomplete pull-in)" and the " pull-in frame (pull-in complete)" use a known data pattern, they can be distinguished even if they have a common header.

In addition, the receiver 51A (51B) of this embodiment, like the third embodiment, branches and outputs the data deframed by the BB deframer 5A13 to the pull-in completion determination unit 5A12. The pull-in completion determination unit 5A12 distinguishes between a "normal frame (pull-in incomplete)" and a "normal frame (pull-in complete)" based on the information embedded in the data.

The receiver 51A (51B) checks the pull-in status of the opposite station based on the data pattern of the pull-in frame and the information embedded in the normal frame by the pull-in completion determination unit 5A12, and outputs the pull-in information of the opposite station to the transmitter of the own station. The receiver 51A (51B) also checks the pull-in status of its own station by the pull-in completion determination unit 5A12, and outputs the pull-in information of its own station to the transmitter of the own station.

Figure 20 is a timing chart showing the communication state between the first communication station 2A and the second communication station 2B in this embodiment. Note that the explanation of (1) to (7) below corresponds to the timing of (1) to (7) shown in Figure 20.

(1) When starting two-way communication between the first communication station 2A and the second communication station 2B, the transmitter 4A of the first communication station 2A and the transmitter 4B of the second communication station 2B repeatedly transmit a common header and a " pulling-in frame (pulling incomplete)" based on the own station pull-in information and the opposite station pull-in information. (1)' The receiver 51A of the first communication station 2A and the receiver 51B of the second communication station 2B receive the common header and the " pulling-in frame (pulling incomplete)" transmitted from the opposite station, and execute a frame synchronization process using the common header and a demodulation process in the high-speed pull-in mode using the " pulling-in frame (pulling incomplete)". In addition, the receiver 51A of the first communication station 2A and the receiver 51B of the second communication station 2B check the pull-in status of the opposite station based on the data pattern of the pull-in frame and the information embedded in the normal frame, and output the opposite station pull-in information to the transmitter of the own station. Moreover, the receiver 51A of the first communication station 2A and the receiver 51B of the second communication station 2B check the pull-in status of their own station and output their own station pull-in information to the transmitter of their own station.

(2) In the above situation, it is assumed that the receiver 51A of the first communication station 2A completes the pull-in first. (2)' In this case, the transmitter 4A of the first communication station 2A switches the frame from a " pull-in frame (pull-in incomplete)" to a " pull-in frame (pull-in complete)" and transmits it to the second communication station 2B together with the common header.

(3) After the receiver 51B of the second communication station 2B receives the " retraction frame (retraction complete)", (4) it detects the retraction completion of the first communication station 2A, which is the opposite station, based on the "retraction frame (retraction complete)". (4)' In this case, the transmitter 4B of the second communication station 2B switches the frame from the " retraction frame (retraction incomplete)" to a "normal frame (retraction incomplete)" and transmits it to the first communication station 2A together with the common header.

Next, (5) it is assumed that the receiver 51B of the second communication station 2B has completed retraction. (5)' In this case, the transmitter 4B of the second communication station 2B switches the frame from a "normal frame (retraction incomplete)" to a "normal frame (retraction complete)" and transmits it to the first communication station 2A together with the common header.

(6) After the receiver 51A of the first communication station 2A receives the "normal frame (retraction complete)", it is assumed that the receiver 51A detects the retraction completion of the second communication station 2B, which is the opposite station, based on the "normal frame (retraction complete)" (7). (7)' In this case, the transmitter 4A of the first communication station 2A switches the frame from the " retraction frame (retraction complete)" to the "normal frame (retraction complete)" and transmits it to the second communication station 2B together with the common header. This completes the initial retraction between the first communication station 2A and the second communication station 2B.

Next, the operation of re-pulling in the communication system 1 of the fourth embodiment after loss of synchronization occurs will be described according to the timing chart shown in FIG. 21. The explanation of (1) to (7) below corresponds to the timing of (1) to (7) shown in FIG. 21.

(1) Pull-in is complete between the first communication station 2A and the second communication station 2B, and a "normal frame (pull-in complete)" and a common header are being transmitted and received. (2) In this situation, assume that synchronization is lost in the receiver 51B of the second communication station 2B. (2)' In this case, the transmitter 4B of the second communication station 2B switches from the "normal frame (pull-in complete)" to the "normal frame (pull-in incomplete)" and transmits it to the first communication station 2A together with the common header.

(3) When the receiver 51A of the first communication station 2A receives the common header and a “normal frame (retraction not completed)”, (3)′ the transmitter 4A of the first communication station 2A switches from the “normal frame (retraction completed)” to a “ retraction frame (retraction completed)” and transmits it together with the common header to the second communication station 2B.

(4) After the receiver 51B of the second communication station 2B receives the " retraction frame (retraction complete)", (5) assumes that the retraction is completed based on the " retraction frame (retraction complete)". (5)' In this case, the transmitter 4B of the second communication station 2B switches from the "normal frame (retraction incomplete)" to the "normal frame (retraction complete)" and transmits it to the first communication station 2A.

(6) The receiver 51A of the first communication station 2A receives the "normal frame (retraction complete)" and (7) detects the retraction completion of the opposite station, the second communication station 2B. (7)' The transmitter 4A of the first communication station 2A switches from the " retraction frame (retraction complete)" to the "normal frame (retraction complete)" and transmits it together with the common header to the second communication station 2B. This completes re-retraction between the first communication station 2A and the second communication station 2B.

As described above, according to the communication system 1 of the embodiment 4, it is possible to perform the pull-in process efficiently and at high speed and smoothly transition to the transmission and reception of normal data frames, as in the embodiment 1. Also, according to the embodiment 4, the "normal frame & pull-in incomplete" header, the "normal frame & pull-in complete" header, the " pull-in frame & pull-in incomplete" header, and the " pull-in frame & pull-in complete" header are not used, and only the common header is used, so that it is possible to reduce the processing load associated with header switching.

In addition, in the fourth embodiment, the type of frame and the pull-in status are identified from the entire data pattern of the " pull-in frame (pull-in incomplete)" and the "pull-in frame (pull-in complete)". However, in cases where a delay occurs in the demodulation process, as shown by symbol D in Figs. 20 and 21, it is also possible to distinguish between the " pull-in frame (pull-in complete)" and the " pull-in frame (pull-in complete)" by using only the first half of the data pattern.

(Embodiment 5)
Next, a communication system according to a fifth embodiment of the present invention will be described. This embodiment is different from the first embodiment in that it distinguishes whether a pull-in frame is incomplete or complete by a data pattern, and distinguishes whether a pull-in frame is incomplete or complete by whether the header is a "normal frame & pull-in incomplete" header. Note that the same reference numerals are used for the same configuration as the first embodiment, and detailed description is omitted.

In the following, a pull-in frame using a data pattern indicating that pull-in is not complete will be called a " pull-in frame (pull-in complete)," and a pull-in frame using a data pattern indicating that pull-in is complete will be called a " pull-in frame (pull-in complete)." In addition, headers other than the "normal frame & pull-in complete" header will be called common headers.

Switching between " pull-in frame (pull-in incomplete)" and " pull-in frame (pull-in complete)" is performed by the timing generation unit 4A6, pilot generation unit 4A7, and pilot assignment unit 4A2 of the transmitter 4A (4B) shown in Fig. 5 in response to the opposite station pull-in information and the local station pull-in information output from the receiver. Also, embedding of pull-in incomplete information and pull-in complete information into the data of the "normal frame" is performed by the timing generation unit 4A6 in response to the opposite station pull-in information and the local station pull-in information output from the receiver.

The receiver 5A of the first communication station 2A and the receiver 5B of the second communication station 2B according to this embodiment distinguish between incomplete and complete pull-in of a pull-in frame based on the header and data pattern by the header detection unit 5A10 as shown in Fig. 5. Since both " pull-in frame (incomplete pull-in)" and " pull-in frame (pull-in complete)" use a known data pattern, they can be distinguished even if the header is the same. In addition, the receiver 5A (5B) distinguishes between incomplete and complete pull-in of a normal frame depending on whether the header detected by the header detection unit 5A10 is a "normal frame & incomplete pull-in" header.

The receiver 5A (5B) checks the pull-in status of the opposite station based on the data pattern of the pull-in frame and the type of the header by the pull-in completion determination unit 5A12, and outputs the pull-in information of the opposite station to the transmitter of the own station. The receiver 5A (5B) also checks the pull-in status of its own station by the pull-in completion determination unit 5A12, and outputs the pull-in information of its own station to the transmitter of the own station.

Figure 22 is a timing chart showing the communication state between the first communication station 2A and the second communication station 2B in this embodiment. Note that the explanation of (1) to (7) below corresponds to the timing of (1) to (7) shown in Figure 22.

(1) When starting two-way communication between the first communication station 2A and the second communication station 2B, the transmitter 4A of the first communication station 2A and the transmitter 4B of the second communication station 2B repeatedly transmit a common header and a " pulling-in frame (pulling incomplete)" based on the own station pull-in information and the opposite station pull-in information. (1)' The receiver 5A of the first communication station 2A and the receiver 5B of the second communication station 2B receive the common header and the " pulling-in frame (pulling incomplete)" transmitted from the opposite station, and execute a frame synchronization process using the common header and a demodulation process in the high-speed pull-in mode using the " pulling-in frame (pulling incomplete)". In addition, the receiver 5A of the first communication station 2A and the receiver 5B of the second communication station 2B check the pull-in status of the opposite station based on the data pattern of the pull-in frame and the type of the header, and output the opposite station pull-in information to the transmitter of the own station. Moreover, the receiver 5A of the first communication station 2A and the receiver 5B of the second communication station 2B check the pull-in status of their own stations and output their own station pull-in information to the transmitters of their own stations.

(2) In the above situation, it is assumed that the receiver 5A of the first communication station 2A completes the pull-in first. (2)' In this case, the transmitter 4A of the first communication station 2A switches the frame from a " pull-in frame (pull-in incomplete)" to a " pull-in frame (pull-in complete)" and transmits it to the second communication station 2B together with the common header.

(3) After the receiver 5B of the second communication station 2B receives the " pulling frame (pulling complete)", (4) it detects the completion of the pulling in of the first communication station 2A, which is the opposite station, based on the " pulling frame (pulling complete)". (4)' In this case, the transmitter 4B of the second communication station 2B switches the header from the common header to the "normal frame & pulling in not complete" header, switches the frame from the " pulling frame (pulling in not complete)" to the "normal frame", and transmits it to the first communication station 2A.

Next, (5) assume that the receiver 5B of the second communication station 2B has completed the pull-in. (5)' In this case, the transmitter 4B of the second communication station 2B switches the header from the "normal frame & pull-in incomplete" header to a common header and transmits it together with the "normal frame" to the first communication station 2A.

(6) After the receiver 5A of the first communication station 2A receives the common header and the "normal frame", (7) it detects the completion of retraction of the opposite station, the second communication station 2B, based on the common header and the "normal frame". (7)' In this case, the transmitter 4A of the first communication station 2A switches the frame from the " retraction frame (retraction completed)" to the "normal frame" and transmits it to the second communication station 2B together with the common header. This completes the initial retraction between the first communication station 2A and the second communication station 2B.

Next, the operation of re-pulling in the communication system 1 of the fifth embodiment after loss of synchronization occurs will be described according to the timing chart shown in FIG. 23. The explanation of (1) to (6) below corresponds to the timing of (1) to (6) shown in FIG. 23.

(1) Pull-in is complete between the first communication station 2A and the second communication station 2B, and a "normal frame" and a common header are being sent and received. (2) In this situation, assume that synchronization is lost in the receiver 5B of the second communication station 2B. (2)' In this case, the transmitter 4B of the second communication station 2B switches the header from the common header to a "normal frame & pull-in incomplete" header, and transmits it to the first communication station 2A together with the "normal frame".

(3) When the receiver 5A of the first communication station 2A receives the “normal frame & retraction incomplete” header and the “normal frame”, (3)’ the transmitter 4A of the first communication station 2A switches from the “normal frame” to a “ retraction frame (retraction completed)” and transmits it to the second communication station 2B together with the common header.

(4) After the receiver 5B of the second communication station 2B receives the " pull-in frame (pull-in complete)", (5) it is assumed that the pull-in is completed based on the " pull-in frame (pull-in complete)". (5)' In this case, the transmitter 4B of the second communication station 2B switches the header from the "normal frame & pull-in not complete" header to a normal header and transmits it together with the "normal frame" to the first communication station 2A.

(6) When the receiver 5A of the first communication station 2A receives the "normal frame" and detects the completion of re-in of the opposing second communication station 2B, (6)' the transmitter 4A of the first communication station 2A switches from the " re-in frame (re-in completion)" to the "normal frame" and transmits it together with the common header to the second communication station 2B. This completes re-re-in between the first communication station 2A and the second communication station 2B.

As described above, according to the communication system 1 of the fifth embodiment, it is possible to perform the pull-in process efficiently and at high speed, and smoothly transition to the transmission and reception of normal data frames, as in the first embodiment. Also, according to the fifth embodiment, the "normal frame & pull-in complete" header, the " pull-in frame & pull-in incomplete" header, and the " pull-in frame & pull-in complete" header are not used, and only the "normal frame & pull-in incomplete" header and the common header are used, so that it is possible to reduce the processing load associated with header switching.

In addition, in the fifth embodiment, the type of frame and the pull-in status are identified from the entire data pattern of the " pull-in frame (pull-in complete)" and the "pull-in frame (pull-in complete)". However, as in the fourth embodiment, it is also possible to distinguish between the "pull - in frame (pull-in complete)" and the " pull-in frame (pull-in complete)" by using only the first half D of the data pattern.

The above describes an embodiment of the present invention, but the specific configuration is not limited to the above embodiment, and even if there are design changes within the scope of the invention, they are included in the present invention. For example, the above embodiment describes a wireless communication system in which communication is performed via a communication satellite 3, but the present invention can also be applied to a terrestrial communication system that does not use a communication satellite 3.

REFERENCE SIGNS LIST 1 Communication system 2A First communication station 2B Second communication station 3 Communication satellite 4A Transmitter of first communication station 4B Transmitter of second communication station 5A Receiver of first communication station 5B Receiver of second communication station

Claims (6)

A communication system for transmitting and receiving a data frame, in which data to be communicated is stored, between a first communication station and a second communication station, comprising:
When starting communication between the first communication station and the second communication station, a transmitter of the first communication station repeatedly transmits a pull-in frame consisting of only a known pattern to the second communication station;
a receiver of the second communication station receives the pull-in frame and performs a pull-in process using the received pull -in frame ;
the first communication station determines whether the receiver of the second communication station has completed the pull-in process, and when it is determined that the pull-in process has been completed, the transmitter of the first communication station starts transmitting the data frame instead of the pull-in frame ;
A communication system comprising: A pilot block consisting of only a known pattern is stored in the data frame, and the length of the acquisition frame is longer than the pilot block stored in one of the data frames.
2. The communication system according to claim 1 . when communication synchronization is lost in a receiver of the second communication station while the data frame is being transmitted and received between the first communication station and the second communication station, a transmitter of the second communication station transmits a pull-in incompletion notification to the first communication station;
When the receiver of the first communication station receives the pull-in incompletion notification, the transmitter of the first communication station repeatedly transmits the pull-in frame to the second communication station instead of the data frame;
a receiver of the second communication station receives the pull -in frame and performs the pull-in process using the received pull -in frame ;
When the pull-in process is completed, the transmitter of the second communication station transmits a pull-in completion notification to the first communication station;
When the receiver of the first communication station receives the pull-in completion notification, the transmitter of the first communication station starts transmitting the data frame instead of the pull-in frame .
3. The communication system according to claim 1 or 2. When the first communication station changes a setting of the data frame while the data frame is being transmitted and received between the first communication station and the second communication station, a transmitter of the first communication station transmits a setting change notification to the second communication station before changing the setting of the data frame;
When the receiver of the second communication station receives the setting change notification, the transmitter of the second communication station transmits a pull-in incompletion notification to the first communication station;
When the receiver of the first communication station receives the pull-in incompletion notification, the transmitter of the first communication station changes a setting of the data frame and transmits the pull-in frame to the second communication station;
a receiver of the second communication station receives the pull -in frame and performs the pull-in process using the received pull -in frame ;
When the pull-in process is completed, the transmitter of the second communication station transmits a pull-in completion notification to the first communication station;
When the receiver of the first communication station receives the pull-in completion notification, the transmitter of the first communication station starts transmitting the data frame with the changed setting instead of the pull-in frame .
3. The communication system according to claim 1 or 2. When the pull-in process is completed, the transmitter of the second communication station transmits a pull-in completion notification to the first communication station;
When the first communication station receives the pull-in completion notification by a receiver, the first communication station determines that the receiver of the second communication station has completed the pull-in process.
3. The communication system according to claim 1 or 2. At least one of notification information indicating a type of frame and a state of the pull-in process is stored in at least one of a header of the data frame and a header of the pull-in frame, stored as a known pattern in at least a part of the pull-in frames, or embedded in the data stored in at least a part of the data frames .
6. The communication system according to claim 5.

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