JP4001566B2 - Data transmission device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a data transmission apparatus that transmits and receives a frame by radio communication with a base station apparatus, and is particularly suitable as a subscriber station apparatus that performs radio communication with a base station apparatus in a fixed wireless access (FWA) system. It relates to what is used.
[0002]
[Prior art]
A fixed wireless access system that performs bidirectional wireless communication between a base station and one or more subscriber stations is known (see, for example, Non-Patent Document 1).
[0003]
FIG. 6 is a block diagram showing an overall configuration of a fixed wireless access system including a conventional subscriber station apparatus. In FIG. 6, a plurality of subscriber station devices 31 and a single base station device 32 are configured to perform two-way wireless communication using a TDMA / TDD (Time Division Multiple Access / Time Division Duplex) method. Perform data transmission. Each subscriber station device 31 is connected to one or more terminals 34 via a LAN 33, and the base station device 32 is connected to one or more servers 36 via a network 35. With such a configuration, communication between the terminal 34 and the server 36 is possible.
[0004]
Transmission of frames from the server 36 to the terminal 34 is performed in the following procedure. The server 36 transmits an Ethernet (registered trademark) frame to the base station apparatus 32. The base station device 32 divides the received Ethernet frame to generate a plurality of wireless data frames, and wirelessly transmits them to the subscriber station device 31. The subscriber station device 31 combines the received plurality of radio data frames to generate an original Ethernet frame and transmits it to the terminal 34.
[0005]
On the other hand, transmission of frames from the terminal 34 to the server 36 is performed according to the following procedure. The terminal 34 transmits an Ethernet frame to the subscriber station device 31. The subscriber station device 31 divides the received Ethernet frame to generate a plurality of wireless data frames, and wirelessly transmits them to the base station device 32. The base station apparatus 32 combines the received plurality of radio data frames to generate an original Ethernet frame and transmits it to the server 36.
[0006]
FIG. 7 is a block diagram showing a configuration of a conventional subscriber station apparatus. In FIG. 7, the radio data frame transmitted from the base station apparatus 32 is received by the TDMA / TDD control unit 51 via the radio unit 40. The transmission control unit 51a in the TDMA / TDD control unit 51 monitors the reception buffer 52. When the reception buffer 52 is in a saturated state, the transmission control unit 51a discards the wireless data frame. 52 is stored. The wireless data frame stored in the reception buffer 52 is read out by the frame recombination unit 53a in the communication interface 53, recombined into an Ethernet frame, and then transmitted to the LAN 33.
[0007]
On the other hand, the Ethernet frame transmitted from the terminal 34 is divided by the frame dividing unit 53 b in the communication interface 53, converted into a plurality of wireless data frames, and stored in the transmission buffer 54. Here, when the transmission buffer 54 is saturated, the wireless data frame is discarded. The wireless data frame stored in the transmission buffer 54 is wirelessly transmitted to the base station apparatus 32 via the TDMA / TDD control unit 51 and the wireless unit 40.
[0008]
[Non-Patent Document 1]
Takayuki Hirano, edited by two others, “Wireless Broadband Textbook”, IDG Japan, June 10, 2002, p. 313-317
[0009]
[Problems to be solved by the invention]
In FIG. 6, if the base station apparatus 32 transmits a predetermined return frame, the subscriber station apparatus 31 returns this return frame, and the base station apparatus 32 receives the returned return frame, the base station apparatus The line quality such as the bit error rate between the terminal 32 and the subscriber station apparatus 31 can be evaluated.
[0010]
In this case, it is necessary to add a return function for returning the return frame to the base station apparatus in the conventional subscriber station apparatus. When a loopback function is added to the conventional subscriber station apparatus shown in FIG. 7, the configuration of the subscriber station apparatus is as shown in FIG. 8, for example.
[0011]
In FIG. 8, the radio data frame transmitted from the base station apparatus 32 is received by the TDMA / TDD control unit 71 via the radio unit 60. The transmission control unit 71a in the TDMA / TDD control unit 71 monitors the reception buffer 72, discards the wireless data frame when the reception buffer 72 is saturated, and loops back the wireless data frame when the reception buffer 72 is not saturated. The data is output to the frame detection unit 75. The return frame detection unit 75 determines whether or not the received wireless data frame is a return frame.
[0012]
If it is determined that the frame is not a folded frame, the frame is stored in the reception buffer 72. The wireless data frame stored in the reception buffer 72 is read out to the communication interface 73 and transmitted to the LAN 33.
[0013]
On the other hand, if it is determined that the frame is a folded frame, the frame is output to the address switching unit 76. The address exchange unit 76 exchanges the transmission source MAC address and the destination MAC address of the received return frame, and stores the return frame after the address replacement in the transmission buffer 74. Here, when the transmission buffer 74 is in a saturated state, the return frame after the address exchange is discarded. The return frame after the address exchange stored in the transmission buffer 74 is transmitted from the communication interface 73 to the base station via the TDMA / TDD control unit 71 and the radio unit 60 in the same manner as the normal transmission frame stored in the transmission buffer 74. Wirelessly transmitted to the device 32.
[0014]
However, the subscriber station apparatus shown in FIG. 8 has the following problems.
[0015]
When the reception buffer 72 becomes saturated with an increase in traffic from the wireless unit 60 to the LAN 33 side, the return frame is discarded as in the case of a normal reception frame.
[0016]
On the other hand, when the transmission buffer 74 becomes saturated with an increase in traffic from the LAN 33 side to the radio unit 60, the loopback frame is discarded in the same manner as a normal transmission frame.
[0017]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a data transmission apparatus capable of avoiding the return frame being discarded due to the reception buffer being saturated.
[0019]
[Means for Solving the Problems]
A first invention for solving the above-described problems and achieving the object is a data transmission apparatus that transmits and receives a frame by radio communication with a base station apparatus, and the received frame received from the base station apparatus is the base station apparatus. It is determined whether or not it is a folded frame to be sent back to the station apparatus. If the received frame is not a folded frame, if the reception buffer is not saturated, the received frame is stored in the reception buffer, and the reception buffer is saturated. When the received frame is discarded, the received frame is returned to the base station apparatus regardless of whether or not the reception buffer is saturated.
[0020]
In the above configuration, before the received frame is discarded due to the reception buffer being saturated, it is determined whether the received frame is a folded frame. If the received frame is a folded frame, the received frame is independent of the state of the received buffer. Is transmitted back to the base station apparatus. For this reason, the return frame is not discarded even if the reception buffer is saturated.
[0021]
Here, as the return frame, for example, there is a test frame for evaluating the channel quality between the base station apparatus and the data transmission apparatus, but the use of the return frame is not particularly limited. Returning the received frame to the base station apparatus includes transmitting the received frame subjected to processing such as switching the transmission source address and the destination address to the base station apparatus.
[0022]
According to a second aspect of the present invention, there is provided a data transmission apparatus for transmitting and receiving a frame by radio communication with a base station apparatus, comprising a return frame detection means, a return means, a transmission control means, and a reception buffer, and the return frame detection means. Determines whether the received frame received from the base station apparatus is a return frame to be returned to the base station apparatus, and outputs the received frame to the return means if it is a return frame; In this case, the reception frame is output to the transmission control unit, the loopback unit transmits the reception frame received from the loopback frame detection unit to the base station apparatus, and the transmission control unit stores the reception frame memory. It is determined whether the means is saturated, and if it is saturated, from the folded frame detection means Discard digit received frame, and outputs the received frame to the receiving buffer in other cases, the receiving buffer is configured to store the received frame received from the transmission control means.
[0023]
In the above configuration, the return frame detection means for detecting the return frame is provided before the transmission control means for discarding the reception frame when the reception buffer is saturated. Then, it is determined whether or not all the received frames are folded frames. If the received frame is a folded frame, the received frame is not output to the transmission control unit but is output to the folding unit. For this reason, the return frame is not discarded even if the reception buffer is saturated.
[0024]
The third invention is a data transmission apparatus that transmits and receives a frame by radio communication with a base station apparatus, and detects a return frame to be returned to the base station apparatus from received frames received from the base station apparatus And a return buffer for storing transmission frames to be transmitted to the base station apparatus other than the return frame, and a return buffer for storing the return frame detected by the return frame detection means. It is.
[0025]
In the above configuration, the folded frame is stored in the folded buffer, not the transmission buffer that stores the normal transmission frame. For this reason, the return frame is not discarded even if the transmission buffer is saturated.
[0026]
The fourth invention further comprises a transmission buffer for storing transmission frames to be transmitted to the base station apparatus other than the loopback frame in the second invention, wherein the loopback means is separate from the transmission buffer. And a loop-back buffer for storing the loop-back frame.
[0027]
In the above configuration, the folded frame is not discarded even if the reception buffer is saturated or the transmission buffer is saturated.
[0028]
According to a fifth aspect, in the third or fourth aspect, transmission control means for transmitting the loopback frame stored in the loopback buffer to the base station apparatus in preference to the transmission frame stored in the transmission buffer. In addition.
[0029]
In the above configuration, the loopback frame stored in the loopback buffer is transmitted with priority over the transmission frame stored in the transmission buffer. For this reason, the folding buffer is not easily saturated.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Exemplary embodiments of a data transmission apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.
[0031]
FIG. 1 is a block diagram showing an overall configuration of a fixed wireless access system including a data transmission apparatus according to the present embodiment. In FIG. 1, a plurality of subscriber station apparatuses 1 and a single base station apparatus 2 which are data transmission apparatuses perform bidirectional wireless data transmission by the TDMA / TDD system. Each subscriber station apparatus 1 is connected to one or more terminals 4 via a LAN 3, and the base station apparatus 2 is connected to one or more servers 6 via a network 5. With such a configuration, communication between the terminal 4 and the server 6 is possible.
[0032]
Transmission of a normal frame from the server 6 to the terminal 4 is performed according to the following procedure. The server 6 transmits an Ethernet frame to the base station apparatus 2 via the network 5. The base station device 2 divides the received Ethernet frame to generate a plurality of wireless data frames and wirelessly transmits them to the subscriber station device 1. The subscriber station apparatus 1 combines a plurality of radio data frames received from the base station apparatus 2 to generate an original Ethernet frame, and transmits the original Ethernet frame to the terminal 4 via the LAN 3.
[0033]
On the other hand, transmission of a normal frame from the terminal 4 to the server 6 is performed according to the following procedure. The terminal 4 transmits an Ethernet frame to the subscriber station device 1 via the LAN 3. The subscriber station device 1 divides the received Ethernet frame to generate a plurality of wireless data frames and wirelessly transmits them to the base station device 2. The base station apparatus 2 combines the plurality of radio data frames received from the subscriber station apparatus 1 to generate an original Ethernet frame, and transmits the original Ethernet frame to the server 6 via the network 5.
[0034]
The line quality test between the base station apparatus 2 and the subscriber station apparatus 1 is performed according to the following procedure. The base station apparatus 2 generates an Ethernet format test frame (hereinafter referred to as a folded frame). Then, the generated return frame is divided to generate return frames of a plurality of wireless data formats and wirelessly transmitted to the subscriber station apparatus 1. When the subscriber station device 1 detects that the frame received from the base station device 2 is a loopback frame, the subscriber station device 1 swaps the transmission source MAC address and the destination MAC address of the loopback frame, and replaces the loopback frame after the address swapping with the base station. Wirelessly transmit to the device 2. The base station apparatus 2 generates a return frame in the Ethernet format by combining the received return frames in the wireless data format, and evaluates channel quality such as a bit error rate by using the return frame.
[0035]
FIG. 2 is a block diagram showing a configuration of the subscriber station device 1. In FIG. 2, the subscriber station device 1 includes a radio unit 10 and a baseband processing unit 20.
[0036]
The radio unit 10 converts the radio signal received from the base station apparatus 2 into a baseband signal, and outputs this baseband signal to the baseband processing unit 20. In addition, the baseband signal received from the baseband processing unit 20 is converted into a radio signal and wirelessly transmitted to the base station apparatus 2.
[0037]
The baseband processing unit 20 includes a TDMA / TDD control unit 21, a return frame detection unit 22, a return buffer 23, a transmission control unit 24, a reception buffer 25, a communication interface 26, a transmission buffer 27, and a transmission control unit 28. Predetermined processing is performed on the baseband signals received from the wireless unit 10 and the LAN 3.
[0038]
Hereinafter, the operation of the baseband processing unit 20 will be described in detail when receiving a signal from the wireless unit 10, receiving a signal from the LAN 3, and transmitting a signal to the wireless unit 10.
[0039]
FIG. 3 is a flowchart showing an operation procedure of the baseband processing unit 20 when a signal is received from the radio unit 10. In FIG. 3, the TDMA / TDD control unit 21 receives a radio data frame from the radio unit 10 (S11), and outputs the received radio data frame (hereinafter referred to as a reception frame) to the return frame detection unit 22.
[0040]
The return frame detection unit 22 determines whether or not the received frame received from the TDMA / TDD control unit 21 is a return frame (S12). Specifically, a received frame corresponding to the head of the original Ethernet frame is detected from the received frames, and whether or not the destination MAC address of the received frame matches a preset destination MAC address for the return frame. Judging. Here, it is assumed that the received frame includes information indicating that it is the beginning of the original Ethernet frame, information indicating that it is the end, and information regarding division of other frames.
[0041]
As a result of the determination, if the received frame is a folded frame (S12: YES), the folded frame detection unit 22 stores the received frame in the folded buffer 23 (S13). Specifically, a series of received frames from the received frame corresponding to the head of the original Ethernet frame to the received frame corresponding to the end of the original Ethernet frame, where the destination MAC address matches the destination MAC address for the return frame It is stored in the return buffer 23.
[0042]
On the other hand, if it is determined that the received frame is not a folded frame (S12: NO), the folded frame detection unit 22 outputs the received frame to the transmission control unit 24 (S14). The transmission control unit 24 determines whether or not the reception buffer 25 is saturated (S15). If the state is saturated (S15: YES), the received frame received from the loopback frame detection unit 22 is discarded (S16). If the state is not saturated (S15: NO), the received frame is received by the reception buffer 25. (S17).
[0043]
The reception frame stored in the reception buffer 25 is read by the frame recombination unit 26 a in the communication interface 26, combined with the original Ethernet frame, and sent to the LAN 3.
[0044]
FIG. 4 is a flowchart showing an operation procedure of the baseband processing unit 20 when a signal is received from the LAN 3. In FIG. 4, when receiving an Ethernet frame from the LAN 3 (S21), the communication interface 26 determines whether or not the transmission buffer 27 is in a saturated state (S22). If it is saturated (S22: YES), the received Ethernet frame is discarded (S23). On the other hand, when it is not saturated (S22: NO), the received Ethernet frame is divided into a plurality of wireless data frames by the internal frame dividing unit 26b, and these wireless data frames (hereinafter referred to as transmission frames) are transmitted. The data is stored in the buffer 27 (S24).
[0045]
FIG. 5 is a flowchart showing an operation procedure of the baseband processing unit 20 when a signal is transmitted to the radio unit 10. In FIG. 5, the transmission control unit 28 determines whether or not a return frame is stored in the return buffer 23 (S31).
[0046]
When the loopback frame is stored (S31: YES), the transmission control unit 28 reads the loopback frame from the loopback buffer 23, replaces the transmission source MAC address and the destination MAC address (S32), and returns the loopback frame after the address replacement. Is transmitted to the radio unit 10 via the TDMA / TDD control unit 21 (S33).
[0047]
On the other hand, when the return frame is not stored (S31: NO), the transmission control unit 28 determines whether or not the transmission frame is stored in the transmission buffer 27 (S34). If the transmission frame is stored as a result of the determination (S34: YES), the transmission control unit 28 reads the transmission frame from the transmission buffer 27 and transmits it to the radio unit 10 via the TDMA / TDD control unit 21 (S35). ). On the other hand, when the transmission frame is not stored (S34: NO), the process returns to step S31.
[0048]
As described above, when the loopback frame is stored in the loopback buffer 23, the loopback frame is transmitted. When the loopback buffer 23 is empty, the transmission frame stored in the transmission buffer 27 is transmitted. Is transmitted prior to the transmission frame.
[0049]
As described above, according to the data transmission apparatus according to the present embodiment, the return frame detection unit 22 is provided before the transmission control unit 24 that discards the received frame when the reception buffer 25 is saturated. The data is stored in the return buffer 23 without being output to the transmission control unit 24. Thereby, it is possible to avoid the return frame being discarded due to the reception buffer 25 being saturated. That is, even if the reception buffer 25 overflows with an increase in traffic from the base station apparatus 2 to the LAN 3, the return frame is not discarded. In addition, in order to acquire such an effect, the structure for transmitting the return frame detected by the return frame detection part 22 to the base station apparatus 2 is not specifically limited. For example, similarly to the subscriber station apparatus of FIG. 8, the return frame detected by the return frame detection unit 22 may be stored in the transmission buffer 27 and transmitted to the base station apparatus 2 in the same manner as a normal transmission frame. .
[0050]
In addition, since the return buffer 23 is provided separately from the transmission buffer 27, it is possible to prevent the return frame from being discarded due to the transmission buffer 27 being saturated. That is, even if the transmission buffer 27 overflows with an increase in traffic from the LAN 3 to the base station apparatus 2, the return frame is not discarded. In order to obtain such an effect, the configuration from reception of a received frame to detection of a return frame is not particularly limited. For example, similar to the subscriber station apparatus of FIG. 8, the return frame detection unit 22 may be provided in the subsequent stage of the transmission control unit 24.
[0051]
Further, since the loopback frame stored in the loopback buffer 23 is transmitted with priority over the transmission frame stored in the transmission buffer 27, the loopback frame is delayed even when the traffic from the LAN 3 to the base station apparatus 2 is large. Can be sent back without any delay. Thereby, overflow of the folding buffer 23 can be avoided.
[0052]
Further, it is determined whether or not all received frames are return frames, the detected return frames are stored in the return buffer 23, and the return frames stored in the return buffer 23 are given priority over normal transmission frames. 2, the return frame is reliably returned to the base station apparatus 2 without being discarded even if the transmission / reception traffic is large.
[0053]
In addition, this invention is not limited to said embodiment.
[0054]
For example, an address exchange unit that exchanges the transmission source MAC address and the destination MAC address of the return frame is provided between the return frame detection unit 22 and the return buffer 23, and the return frame after the address replacement is stored in the return buffer 23. It is good.
[0055]
Needless to say, the data transmission apparatus according to the present invention is applicable to systems other than the fixed wireless access system.
[0056]
【The invention's effect】
According to the present invention, it is determined whether or not the received frame is a folded frame before the received frame is discarded due to the saturated state of the received buffer. If the received frame is the folded frame, the received buffer is saturated. The received frame is looped back to the base station apparatus regardless of whether or not it is in a state, so that it is possible to prevent the looped frame from being discarded due to the reception buffer being saturated.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of a fixed wireless access system including a data transmission apparatus according to an embodiment.
FIG. 2 is a block diagram showing a configuration of a subscriber station device 1;
FIG. 3 is a flowchart showing an operation procedure of the baseband processing unit 20 when a signal is received from the radio unit 10;
FIG. 4 is a flowchart showing an operation procedure of the baseband processing unit 20 when a signal is received from the LAN 3;
FIG. 5 is a flowchart showing an operation procedure of the baseband processing unit 20 when a signal is transmitted to the radio unit 10;
FIG. 6 is a block diagram showing an overall configuration of a fixed wireless access system including a conventional subscriber station apparatus.
FIG. 7 is a block diagram showing a configuration of a conventional subscriber station apparatus.
FIG. 8 is a block diagram showing a configuration of a subscriber station apparatus to which a return function is added.
[Explanation of symbols]
1 Subscriber station equipment (data transmission equipment)
2 Base station device 3 LAN
4 terminal 5 network 6 server 10 wireless unit 20 baseband processing unit 21 TDD / TDMA control unit 22 loopback frame detection unit 23 loopback buffer 24 transmission control unit 25 reception buffer 26 communication interface 27 transmission buffer 28 transmission control unit

Claims (3)

A data transmission device that transmits and receives a frame by wireless communication with a base station device,
A return frame detecting means, a return means, a sending control means, and a reception buffer;
The loopback frame detecting means determines whether or not a received frame received from the base station apparatus is a loopback frame to be looped back to the base station apparatus, and if it is a loopback frame, the received frame is sent to the loopback means. Output, otherwise output the received frame to the transmission control means,
The loopback means transmits the received frame received from the loopback frame detection means to the base station apparatus,
The transmission control means determines whether or not the received frame storage means is in a saturated state. If the received frame storage means is in a saturated state, the transmission control means discards the received frame received from the loopback frame detecting means, otherwise Outputting the reception frame to the reception buffer;
The data transmission apparatus, wherein the reception buffer stores a reception frame received from the transmission control means. A transmission buffer for storing a transmission frame to be transmitted to the base station apparatus other than the loopback frame;
2. The data transmission apparatus according to claim 1 , wherein the loopback unit includes a loopback buffer that stores the loopback frame separately from the transmission buffer. 3. The data transmission apparatus according to claim 2 , further comprising a transmission control unit configured to transmit the loopback frame stored in the loopback buffer to the base station apparatus in preference to the transmission frame stored in the transmission buffer. .

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