JP4852057B2 - Wireless communication method, wireless communication system, and wireless station apparatus - Google Patents

Description

  The present invention relates to a communication method, a communication system, and a radio station apparatus in a TDD (Time Division Duplex) communication system that performs full duplex communication by time-division of an uplink signal and a downlink signal.

  In a fixed wireless access system, there is a method using an optical fiber for an entrance line, but a method using a wireless entrance line is effective to enable flexible service area deployment (for example, Non-Patent Document 1 and Patents). Reference 1). A wireless entrance line uses a point-to-point (PP) system in which one-to-one communication is performed between wireless stations.

  FIG. 4 shows an example of a fixed wireless access system using the PP system as an entrance. The accommodation station connected to the host network and the system accommodating the subscriber station P-MP installed at the customer's home by the point-to-multipoint system are connected by a plurality of radio entrances by the PP system. Further, in applications for corporate systems, etc., a method of forming a dedicated line between two points by using the PP method alone is also widely used.

  In a PP wireless access system, it is necessary to separate uplink and downlink signals. There are FDD (Frequency Division Duplex, Frequency Division Duplex) and TDD (Time Division Duplex, Time Division Duplex) as methods of separation, but TDD is effective from the viewpoint of frequency utilization efficiency. From the viewpoint of TDD, TDD is often used.

  FIG. 5 shows an example of the configuration of a TDD-type fixed wireless access system premised on the present invention. The radio station 1 and the radio station 2 connected to the network NW communicate alternately by dividing the time domain within the same frequency channel. In this configuration, the communication counterparts are only wireless stations corresponding to each other, but the master station may use a separate fixed communication channel with a plurality of slave stations and perform TDD communication within the channel.

  FIG. 6 shows a configuration example of a radio frame in the conventional TDD communication system. The radio frame period (T) is time-divided, and the transmission period of the radio station 1 and the transmission period of the radio station 2 are provided. Within the transmission period, each wireless station transmits and receives transmission data composed of a preamble (PR) for synchronization and a plurality of transmission time slots (TS). A guard time (GT) is provided between time slots in order to absorb delay differences between transmission and reception.

  FIG. 7 shows an example of data transmission / reception in the conventional TDD communication system. During the transmission period of the wireless station 1, the time slot (TS # 1-TS # m) is assigned to the wireless station 1 regardless of the presence or absence of transmission data, and the wireless station 2 is fixed to the reception state during that period. Also, during the transmission period of the wireless station 2, time slots (TS # m + 1 to TS # n) are assigned to the wireless station 2 regardless of the presence or absence of transmission data, and the wireless station 1 is fixed to the reception state during that period. . Therefore, the communication band is not dynamically changed. Therefore, if there is no transmission data in one of the radio stations, there is a problem that the time slot in that period becomes empty and the communication band cannot be used effectively.

  As a method for dynamically changing the communication band, for example, there is a method of applying a TDMA scheme for scheduling a band by demand assignment in the P-MP scheme as shown in Non-Patent Document 1 with a configuration in which one subscriber station is used.

  FIG. 8 shows the operation of demand assignment. When the polling from the base station is received, the subscriber station transmits the amount of data waiting for transmission as a demand. The base station receives the demand, performs a calculation with the amount of data waiting to be transmitted on the base station side, determines the amount of data permitted to be transmitted for each uplink and downlink, and assigns the amount of data permitted for transmission to the subscriber station. Send as instructions. In this way, it is possible to optimize the amount of data transmitted and received. Also, there is a method of scheduling without transmitting / receiving demand assignment information as in Patent Document 1. In this case, the next transmission data amount is determined by scheduling only within the own station by comparing the number of slots waiting for transmission of the own station, the number of slots received from the partner station, and the number of reference slots for each radio frame.

Design and configuration of wireless IP access system prototype, NTT R & D Vol. 51 No. 11, Telecommunications Association, November 10, 2002 JP 2005-176192 A

  As described above, the communication band can be dynamically changed by the above-described method. However, in the method using demand assignment, it is necessary to transmit and receive demand and assignment information separately from data. FIG. 9 shows an example of a radio frame configuration of the demand assignment TDMA system. Since an area for transmitting and receiving demand and assignment information is provided, there is a problem that the ratio of transmission data in a radio frame is reduced and the upper limit value of the transmission rate is reduced.

  In addition, since scheduling is used, a calculation delay occurs, which may adversely affect transmission of an application affected by the delay.

  In Patent Document 1, although the upper limit of the transmission rate does not decrease, there is a risk that the delay will increase due to scheduling, and it is necessary to mount a CPU for performing scheduling in the device, thus simplifying the device configuration. It is difficult to make it.

  It is an object of the present invention to increase transmission speed without increasing transmission delay in a TDD (Time Division Duplex) communication system that performs time division on an uplink signal and a downlink signal and performs full duplex communication. Wireless communication method and system for enabling effective use of transmission band by a simple circuit configuration by dynamically changing a time slot between opposing radio stations without lowering the upper limit value of And providing a radio station apparatus.

  One feature of the present invention is a radio communication method in a fixed radio access system based on the TDD system in which first and second radio stations facing each other alternately transmit and receive within a radio frame period composed of a plurality of transmission time slots. The wireless frame is divided into two periods and assigned to the opposite wireless stations as transmission periods, respectively, and a fixed number of transmission time slots is assigned to the assigned period as an initial value. When data is in the transmission buffer, the radio station transmits the data using the assigned transmission time slot. When there is no data in the transmission buffer during the allocated period, the radio station sends a specific signal to the second radio station facing it. Transmit and stop transmission, switch from the transmission state to the reception state, the second facing the first radio station When the line station receives the specific signal, the line station switches from the reception state to the transmission state, and the second wireless station transmits data in the transmission time slot assigned to the first wireless station, thereby enabling the transmission band. There is a wireless communication method to be used.

  Preferably, the specific signal is a signal in a time slot having a specific pattern that can be clearly distinguished from transmission data.

  It is preferable to determine that the specific signal has been received when data has not been received for a certain period.

  In the case where no data exists in the transmission buffer, if the remaining transmission allocation time is longer than the time in which a time slot is received and processed after transmitting a pre-calculated time slot, the specific signal is It is preferable that the transmission state is switched to the reception state, and otherwise the transmission state is continued without transmitting the specific signal.

  The present invention further includes a fixed radio that has two radio stations facing each other and communicates by a TDD system in which the radio stations alternately transmit and receive within a radio frame period composed of a plurality of time slots. In the communication system, each of the wireless stations temporarily stores data to be transmitted to the opposite wireless station before transmission, specific signal insertion means for transmitting a specific signal by interrupting a transmission time slot, and Specific signal detection means for detecting reception of a time slot including the specific signal, and a specific signal interruption instruction to the specific signal insertion unit based on buffer amount information from a transmission buffer, and from a transmission state to a reception state And a timing for instructing switching from the reception state to the transmission state based on the specific signal detection information from the specific signal detection unit. Control information is exchanged between the timing control means and the transmission / reception switching means for switching the transmission and reception timings, and the radio frame is divided into two periods to oppose the radio Each station is assigned as a transmission period, and a fixed number of transmission time slots is assigned as an initial value in the assigned period, and the first wireless station assigns the assigned data when the data is in the transmission buffer. If there is no data in the transmission buffer in the allocated period during transmission in the allocated time slot, a specific signal is transmitted to the opposing second radio station and transmission is stopped to change from the transmission state to the reception state. When the second radio station opposite to the first radio station receives the specific signal, the second radio station switches from the reception state to the transmission state. Instead, the second radio station of the at transmission time slot assigned to the first radio station to provide a wireless communication system to effectively utilize the transmission band by transmitting the data.

  The present invention further includes a fixed radio that has two radio stations facing each other and communicates by a TDD system in which the radio stations alternately transmit and receive within a radio frame period composed of a plurality of time slots. In a wireless communication device in a communication system, each of the wireless devices temporarily stores data to be transmitted to an opposing wireless station before transmission, and a specific signal transmitted by interrupting a specific signal into a transmission time slot Insertion means, specific signal detection means for detecting reception of a time slot including the specific signal, and instructions for interrupting a specific signal to the specific signal insertion section based on buffer amount information from a transmission buffer and a transmission state From the reception state to the transmission state based on the specific signal detection information from the specific signal detection unit. Control information is exchanged between the timing control means and the timing control means, and transmission / reception switching means for switching the transmission and reception timings. The radio frame is divided into two periods. When the first radio station has data in the transmission buffer, the radio station is assigned as a transmission period to each of the opposing radio stations, and a fixed number of transmission time slots is assigned as an initial value during the assigned period. When transmission is performed in the allocated transmission time slot and no data exists in the transmission buffer in the allocated period, a specific signal is transmitted to the second radio station facing the transmission, and transmission is stopped and transmission is performed. When the specific signal is received, the second radio station facing the first radio station receives the signal. It switched to the transmission state from the state, the second radio station in the first transmission time slot assigned to the radio station to provide a wireless communication apparatus to effectively utilize the transmission band by transmitting the data.

  According to the present invention, in a TDD (Time Division Duplex) communication system that performs full duplex communication by time-division of an upstream signal and a downstream signal, there is no increase in transmission delay with a simple circuit configuration. In addition, it is possible to improve the frequency utilization efficiency by effectively using the transmission band by dynamically changing the time slot between the opposing radio stations without lowering the upper limit value of the transmission rate. Therefore, it is possible to expand the area where the FWA system service can be provided with limited frequency resources. Furthermore, there is an advantage that the total throughput of the system can be improved.

  FIG. 1 shows a flowchart of bandwidth allocation in the present invention.

  Each wireless station determines whether it is a transmission period or a reception period (10). The initial value has an assigned transmission period (12), and the own station basically transmits data during the transmission period of the own station.

  When the local station is in the transmission period (12), if data exists in the transmission buffer (14), the transmission state (16) is continued until the transmission period ends. If there is no data in the transmission buffer, the remainder of the transmission period is specified if the time slot is longer than the time t received and processed after transmitting the time slot calculated in advance (18) A signal is transmitted to switch to the reception state (20), and the transmission period is terminated (22). In other cases, the transmission state is continued (16) without transmitting the specific signal. When the transmission period ends (22), the period is switched to the reception period (32).

  If it is the reception period, if the specific signal is not received (34), the reception state is continued (36). When the specific signal is received (34), it is switched to the transmission state (38) and the transmission state is continued. When the reception period ends (40), the transmission period is switched to (12).

  As the specific signal, information such as a pseudo random pattern, a bit string that repeats a specific pattern, or a flag for a specific signal in a header in each time slot may be used.

  Further, it may be considered that the specific signal is received by not receiving data continuously for a certain time slot period or by receiving all zeros.

  FIG. 2 shows an example of data transmission / reception in the present invention.

  When it is detected that there is no transmission data of the wireless station 1 in the transmission period of the wireless station 1, if the remaining transmission period is equal to or longer than the time t when the time slot is received and processed after that time slot is transmitted, The specific signal is transmitted using the time slot (TS # j) assigned in step 1, and the radio station 1 switches to the reception state. Since the radio station 2 identifies the specific signal after the elapse of time t and synchronizes the transmission timing after transmission / reception switching with the time slot, t + GT + d = n × TS (where n is a natural number and TS is the time of one time slot). Thus, it is possible to transmit data using TS # m from TS # (j + k) corresponding to the time slot allocated after (t + GT + d) time elapses by adjusting the transmission timing as described above. Here, d is referred to as adjustment time. When the transmission state and reception state of the wireless station 1 and the wireless station 2 are opposite, time slots are assigned by the same process. Therefore, even if there is no transmission data in one radio station, the opposite radio station can transmit data using the time slot, so the communication band can be used effectively.

  FIG. 3 shows a configuration example of radio communication apparatuses of the radio station 1 and the radio station 2 in the embodiment of the present invention.

  The radio station 1 and the radio station 2 include an interface unit connected to the network NW, a buffer for temporarily storing transmission data before transmission, a specific signal insertion unit, a specific signal detection unit, and a signal processing unit that processes signals to be transmitted and received A transmission / reception switching unit that switches transmission / reception, a transmission unit that modulates and transmits a signal to the radio unit, a reception unit that demodulates a reception wave from the radio unit, a timing control unit that controls transmission / reception switching timing, and a conversion to a frequency for radio transmission It is comprised from the radio | wireless part which performs.

  At the time of transmission, the timing control unit determines whether or not to insert a specific signal based on the data amount information in the buffer, and if it is inserted, instructs the specific signal insertion unit to insert the specific signal. Is interrupted in the transmission time slot and transmitted to the opposite radio station, and the transmission / reception switching unit switches from the transmission state to the reception state based on the control information from the timing control unit. In reception, when the specific signal detection unit detects reception of a time slot including a specific signal, specific signal detection information is sent to the timing control unit. When receiving the specific signal detection information, the timing control unit sends the control information to the transmission / reception switching unit. The transmission / reception switching unit switches from the reception state to the transmission state based on the control information.

It is a flowchart of the band allocation in this invention. An example of data transmission / reception in the present invention will be described. The structural example of the apparatus in this invention is shown. An example of a conventional fixed wireless access system using the PP system as an entrance is shown. The structural example of the conventional fixed radio access system of a TDD system is shown. The structural example of the radio | wireless frame in the conventional TDD communication system is shown. An example of data transmission / reception in a conventional TDD communication system is shown. The operation of the conventional demand assignment is shown. The example of a radio frame structure of the conventional demand assignment TDMA system is shown.

Explanation of symbols

10 Judgment of transmission period / reception period 12 Transmission period 14 Whether data exists in the transmission buffer 16 Transmission state continuation 18 Whether the remainder of the transmission period is t time or more 20 Transmission of specific signal to transition to reception state 22 Transmission period end 32 Reception period 34 Is specific signal received? 36 Reception state continued 38 Transition to transmission state 40 End of reception period

Claims (6)

In the radio communication method in the fixed radio access system based on the TDD system in which the first and second radio stations facing each other alternately transmit and receive within a radio frame period composed of a plurality of transmission time slots,
The radio frame is divided into two periods and assigned as transmission periods to opposing radio stations, respectively, and a fixed number of transmission time slots is assigned as an initial value to the assigned period,
The first radio station transmits data in the transmission buffer when the data is in the transmission buffer. In the allocated period, when there is no data in the transmission buffer, the first radio station faces a specific signal. Transmit to the radio station 2 and stop transmission to switch from the transmission state to the reception state,
When the second radio station facing the first radio station receives the specific signal, the second radio station switches from the reception state to the transmission state, and transmits the second radio station in the transmission time slot assigned to the first radio station. A wireless communication method characterized by effectively utilizing a transmission band by transmitting data. The specific signal is a signal in a time slot having a specific pattern that can be clearly distinguished from transmission data;
The wireless communication method according to claim 1. Determining that the specific signal has been received when no data is received for a certain period of time;
The wireless communication method according to claim 1. In the case where no data exists in the transmission buffer, if the remaining transmission allocation time is longer than the time in which a time slot is received and processed after transmitting a pre-calculated time slot, the specific signal is Transmit to switch to the reception state, otherwise continue the transmission state without transmitting the specific signal,
The wireless communication method according to claim 1, wherein: In a fixed wireless communication system that has two first and second radio stations facing each other and communicates by a TDD scheme in which the radio stations alternately transmit and receive within a radio frame period composed of a plurality of time slots.
Each of the radio stations temporarily stores data to be transmitted to the opposite radio station before transmission, and a transmission buffer;
Specific signal insertion means for interrupting and transmitting a specific signal to a transmission time slot, specific signal detection means for detecting reception of a time slot including the specific signal, and the buffer amount information from the transmission buffer The specific signal insertion unit is instructed to interrupt the specific signal and instruct to switch from the transmission state to the reception state, and the switching from the reception state to the transmission state is performed based on the specific signal detection information from the specific signal detection unit. A timing control means for instructing, and exchange of control information between the timing control means, and a transmission / reception switching means for switching the timing of transmission and reception,
The radio frame is divided into two periods and assigned as transmission periods to opposing radio stations, respectively, and a fixed number of transmission time slots is assigned as an initial value to the assigned period,
The first radio station transmits data by the assigned transmission time slot when data is in the transmission buffer, and faces a specific signal when data does not exist in the transmission buffer in the allocated period. Transmit to the second radio station and stop transmission to switch from the transmission state to the reception state,
When the second radio station facing the first radio station receives the specific signal, the second radio station switches from the reception state to the transmission state, and transmits the second radio station in the transmission time slot assigned to the first radio station. A wireless communication system characterized in that the transmission band is effectively used by transmitting data. Radio communication apparatus in fixed radio communication system having first and second radio stations facing each other and communicating by TDD system in which radio stations alternately transmit and receive within a radio frame period composed of a plurality of time slots In
Each of the wireless devices temporarily stores data to be transmitted to the opposing wireless station before transmission;
Specific signal insertion means for interrupting and transmitting a specific signal to a transmission time slot, specific signal detection means for detecting reception of a time slot including the specific signal, and the buffer amount information from the transmission buffer The specific signal insertion unit is instructed to interrupt the specific signal and instruct to switch from the transmission state to the reception state, and the switching from the reception state to the transmission state is performed based on the specific signal detection information from the specific signal detection unit. A timing control means for instructing, and exchange of control information between the timing control means, and a transmission / reception switching means for switching the timing of transmission and reception,
The radio frame is divided into two periods and assigned as transmission periods to opposing radio stations, respectively, and a fixed number of transmission time slots is assigned as an initial value to the assigned period,
The first radio station transmits data by the assigned transmission time slot when data is in the transmission buffer, and faces a specific signal when data does not exist in the transmission buffer in the allocated period. Transmit to the second radio station and stop transmission to switch from the transmission state to the reception state,
When the second radio station facing the first radio station receives the specific signal, the second radio station switches from the reception state to the transmission state, and transmits the second radio station in the transmission time slot assigned to the first radio station. A wireless communication device that effectively uses a transmission band by transmitting data.

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