JP4011386B2 - PMP wireless access system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a PMP wireless access system.
[0002]
[Prior art]
FIG. 5 is a block diagram showing a general PMP wireless access system.
[0003]
A point-to-multipoint (PMP) radio access system is composed of a base station 1 serving as one parent station and subscriber terminals 2 (# 1 to #p) serving as a plurality of slave stations. A wireless communication system. The base station 1 of the PMP wireless access system performs multi-channel access control for a plurality of subscriber terminals 2 in an area of several kilometers. The subscriber terminal 2 includes an antenna 3, a transmission unit 4, and a reception unit 5, and the transmission unit 4 and the reception unit 5 are connected to an external terminal device 7. The terminal device 7 is a device used by a user, and a personal computer or the like is used.
A signal transmitted from the subscriber terminal 2 to the base station 1 uses the same frequency in the plurality of subscriber terminals 2. In response to the transmission permission signal transmitted from the base station 1, only the subscriber terminal 2 having a transmission right transmits data to the base station 1. The base station 1 transmits to each subscriber terminal 2 at the same time, and each subscriber terminal 2 extracts message data assigned to itself from the received signal. Message assignment to each subscriber terminal 2 is performed by adding addresses of the terminal device 7 and the subscriber terminal 2 to the message data of the transmission source.
[0004]
FIG. 6 shows a detailed block diagram of the subscriber terminal 2 of the conventional PMP radio access system.
[0005]
First, the transmission unit 4 of the subscriber terminal 2 will be described. The transmission unit 4 includes an input buffer 101, a filter unit 102, a buffer 104, a read control unit 106, a MAC frame generation unit 107, and a wireless transmission unit 110.
[0006]
The input buffer 101 is a buffer for storing message data from the terminal device 7, and the stored message data is sent to the filter unit 102. The filter unit 102 looks at the destination address or the source address given to the data of the message from the terminal device 7 and compares it with the frame header registered in the filter unit 102 (not shown). It is determined whether or not the message data can be transferred to the buffer 104, and only the permitted message data is transmitted to the buffer 104.
[0007]
Here, the frame is a unit of a structure having a predetermined data length and adding an address and information necessary for communication control to message data.
[0008]
The frame header is a part that stores an address given to message data, information on communication control, and the like.
[0009]
The buffer 104 is a buffer that temporarily stores the filtered message data in units of frames. The read control unit 106 reads message data from the buffer 104 in accordance with an instruction from a timing control unit 216 of the receiving unit 5 described later. The read message data is assembled into a MAC (Media Access Control) frame defined by the specifications of the PMP radio access system by the MAC frame generation unit 107 and then sent to the radio transmission unit 110. The radio transmission unit 110 further transmits data from the antenna 3 to the base station 1 using radio waves of a radio frequency subjected to addition of error correction codes and modulation.
[0010]
Next, the operation of the receiving unit 5 from receiving a signal from the base station 1 to outputting data to the terminal device 7 of the subscriber terminal 2 will be described. The reception unit 5 includes a wireless reception unit 210, a frame disassembly unit 214, a MAP message extraction unit 215, a transmission timing control unit 216, a buffer 204, a read control unit 206, and an output buffer 217.
[0011]
In the radio receiving unit 210, when the radio wave from the base station 1 is received by the antenna 3, it is converted from a radio frequency to a baseband frequency, demodulated into a digital signal, and then the presence or absence of an error is detected by an error detection / correction code, If there is an error, correct it. The frame disassembly unit 214 stores the received message user data in the assembly buffer 204.
[0012]
The user data includes control information and timing information added by the base station 1 in addition to message data input from the terminal device 7 that is the transmission source. A MAP (Message Access Protocol) message extraction unit 215 extracts a MAP message indicating transmission permission and transmission timing to the subscriber terminal 2 sent from the base station 1 from the user data and outputs it to the transmission timing control unit 216. To do.
[0013]
The transmission timing control unit 216 transmits a control signal such as a transmission timing indicated by the MAP message addressed to itself to the read control unit 106 of the transmission unit 4. The read control unit 206 reads the message data from the buffer 204 and sends the message data to the output buffer 217 that adjusts the output speed.
[0014]
In the conventional PMP wireless access system that performs the above-described operation, delay is not managed for data transmitted and received between the subscriber terminal 2 and the terminal device 7, so that the delay time and its fluctuation increase. There is a problem. Further, in the transmission / reception of data such as audio / video in which the delay is not desirable, control for keeping the delay time within a certain range has been desired.
[0015]
[Problems to be solved by the invention]
In the conventional PMP wireless access system, when data is transmitted / received between a subscriber terminal and a terminal device, the delay is not managed by a buffer for storing data, so that the delay time and fluctuation thereof increase. In addition, there has been a demand for control that keeps the delay time within a certain range for transmission / reception of data such as audio / video in which delay is not desirable.
[0016]
The present invention has been made to solve the above-described problem, and is a PMP wireless access capable of providing a data communication service having a high tolerance for delay and a communication service having a low tolerance for delay such as voice / video communication at the same time. The purpose is to provide a system.
[0017]
[Means for Solving the Problems]
The PMP wireless access system of the present invention is a PMP wireless access system that performs wireless communication between a base station and a subscriber terminal until data transmitted from the subscriber terminal to the base station is transmitted from the base station according to a transmission timing. Alternatively, a first buffer that accumulates for a period of a first allowable delay time that is set in advance, and first data that sets a smaller data storage amount as the first allowable delay time of the first buffer is smaller. An accumulation amount setting means; a second buffer for accumulating data received by the subscriber terminal from the base station for a second allowable delay time period; and the second buffer for the second buffer. The smaller the allowable delay time of the second data storage amount setting means for setting the data storage amount to be smaller, and the data exceeding the first and second allowable delay times. Characterized by comprising a means for discarding the data from the first and second buffer.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a PMP wireless access system according to an embodiment of the present invention will be described with reference to the drawings.
[0022]
FIG. 1 is a detailed block diagram of a subscriber terminal in the embodiment of the PMP wireless system of the present invention. FIG. 2 is a flowchart showing a data transmission operation in the transmission unit of the terminal. FIG. 3 is a flowchart of the data receiving operation in the receiving unit of the terminal.
[0023]
The configuration and operation of the subscriber terminal of the PMP wireless access system of the present invention will be described with reference to FIGS.
[0024]
The subscriber terminal 2 includes an antenna 3, a transmission unit 4 and a reception unit 5. First, the configuration and operation of the transmission unit 4 will be described with reference to FIGS. 1 and 2. The transmission unit 4 includes an input buffer 401, a filter unit 402, a classification unit 403, a QOS buffer 404 (1 to n), a buffer size setting unit 405, a read control unit 406, a MAC frame generation unit 407, and a wireless transmission unit 410. Composed.
[0025]
Here, the QOS buffer 404 refers to a buffer that accumulates data corresponding to a communication service quality QOS (Quality of Service) level for message data input to and output from the subscriber terminal 2. Corresponds to each quality level (QOS).
[0026]
First, the subscriber terminal 2 sets an allowable delay time for each message stored in the QOS buffer 404 (1 to n) as an initial setting at the time of installation, and also sends a QOS buffer to the buffer size setting unit 405. 404 (1 to n) sets the amount of data that can be stored respectively.
[0027]
The allowable delay time of the QOS buffer 404 is set according to the length (allowance) of the delay time corresponding to the QOS of the communication service that the subscriber terminal 2 is assumed to communicate via the base station 1. The amount of data that can be stored in 404 is set to be smaller as the allowable delay time is shorter.
[0028]
The input buffer 401 is a buffer for accumulating message data received from the terminal device 7, and the accumulated message data is sent to the filter unit 402 (step s11).
[0029]
The filter unit 402 includes a destination address and a transmission source address in a frame header added to message data from the terminal device 7, and information on a frame header (not shown) registered in the filter unit 402. Are compared to determine whether the message data can be transferred to the network, and only the permitted message data is sent to the classifying unit 403 (step s12).
Next, in the present invention, in order to guarantee the quality according to the communication service to be provided, the transmitter 4 performs the following operation.
[0030]
The classifying unit 403 monitors the frame header attached to the data of the message sent from the filter unit 402, determines the allowable delay of the connection (communication connection condition) from the destination address and the source address, The priority buffer corresponding to the allowable delay is stored in the buffer corresponding to the priority of the QOS buffer 404 (1 to n) (step s13).
[0031]
The QOS buffer 404 (1 to n) is divided according to the QOS whose priority defines each delay tolerance. The amount of data that can be stored in each of the QOS buffers 404 (1 to n) is determined by the buffer size setting unit 405. Be controlled. When data is transferred from the classifying unit 403 to the QOS buffer 404 (1 to n), the data is written with the input time added to the data for each frame.
[0032]
Further, the QOS buffer 404 (1 to n) measures the stay time of the staying data from the writing time (step s14).
[0033]
If the data retention time exceeds the allowable delay time, the message data stored in the corresponding QOS buffer is discarded (in the case of No in step s15).
[0034]
The read control unit 406 sends from the transmission timing control unit 516 of the reception unit 5 only the data of the dwell time allowed from the time of writing among the data stored in the QOS buffer 404 (1 to n). Reading is performed according to the timing signal (step s16).
[0035]
Further, the message data read from the QOS buffer 404 is assembled into a MAC frame in a format according to the specifications of the PMP radio access system in the MAC frame generation unit 407 (step s17).
The signal of the MAC frame is further added with an error correction code by the wireless transmission unit 410, modulated, and transmitted from the antenna 3 to the base station 1 at a predetermined wireless frequency (step s18).
[0036]
Next, the configuration and operation of the reception unit 5 until the signal received from the base station 1 is output to the user terminal device 7 will be described with reference to FIGS. 1 and 3. The reception unit 5 includes a wireless reception unit 510, a frame disassembly unit 514, a MAP message extraction unit 515, a transmission timing control unit 516, a classification unit 503, a QOS buffer 504, a buffer size setting unit 505, a read control unit 506, and an output. The buffer 517 is configured.
[0037]
Similarly to the transmission unit 4, the reception unit 5 also sets a delay time allowed for each message stored in the QOS buffer 504 (1 to n) when the subscriber terminal 2 is installed, and a buffer size setting unit 505. In contrast, the amount of data that can be stored in each of the QOS buffers 504 (1 to n) is initialized.
[0038]
The subscriber terminal 2 receives the radio wave from the base station 1 with the antenna 3, converts the radio frequency into a baseband frequency with the radio reception unit 510, demodulates it into a digital signal, and then adds it to the message data The presence or absence of an error is detected by an error detection / correction code, and correction is performed when there is an error. Then, the frame disassembly unit 514 separates and outputs the digital signal from the wireless reception unit 510 into MAP message data and message data (step s21).
[0039]
The MAP message extraction unit 515 extracts transmission timing data from the MAP message data output from the frame disassembly unit 514, and outputs it to the transmission timing control unit 516 (step s22).
[0040]
The transmission timing control unit 516 transmits a control signal such as a transmission timing indicated by the MAP message addressed to itself to the read control unit 406 of the transmission unit 4 (step s23).
[0041]
On the other hand, similar to the classifying unit 403, the classifying unit 503 obtains an allowable delay from the destination address and the transmission source address in the frame header of the separated message data, and a priority buffer corresponding to the allowable level That is, the message data is stored in the buffer corresponding to the priority of the QOS buffer 504 (1 to n) (step s24).
[0042]
Similarly to the buffer size setting unit 405, the buffer size setting unit 505 controls the data amount of the QOS buffer 504 (1 to n) according to the initial setting. When the data from the classifying unit 503 is stored in the QOS buffer 504 (1 to n), the data is written with the input time added to the data for each frame (step s25).
[0043]
Further, the QOS buffer 404 (1 to n) measures the stay time of the staying data by comparing the read time with the write input time, and discards the data if the allowable delay time has passed (step s26). In the case of No).
[0044]
The read control unit 506 reads the data for each frame from the QOS buffer 504 (1 to n) in order from the data with the shortest allowable delay time, and transfers the data to the output buffer 517 to output the data to the terminal device 7 ( Step s27).
[0045]
Although an undesirable delay is minimized by the above operation, each QOS buffer 504 (1 to n) and a data allocation method will be described here.
[0046]
For example, when message data having a small allowable delay time is stored in the QOS buffer 504, such as voice / video communication, in order to reduce the data residence time for each frame and the data residence time difference jitter for each frame, If the amount of data stored in the buffer is reduced and a delay occurs, it is sufficient to take measures to discard data with a long delay time.
[0047]
The reason for this is that in audio / video communication, the real-time nature of data is important, and if a delay occurs, audio and video playback will be very unnatural. Only slight noise is required, and the influence on the recipient is small, so the delayed data may be discarded.
[0048]
In such processing, the data in the QOS buffer 504 is discarded immediately after the allowable delay time has passed, so that the data staying in the buffer is small. Since unnecessary data is not accumulated in the QOS buffer when transmission is resumed, there is no need to discard unnecessary data such as resetting the buffer, and the data transmission can be resumed as it is. In particular, in a radio access system, a temporary transmission stop state is often caused by a change in radio propagation conditions, and the above effect is great.
[0049]
On the other hand, in a communication service such as data communication where data dropout is not desirable despite a long allowable delay time, the allowable delay time in the QOS buffer 504 is set large and the buffer amount is set large. The amount of disposal should be kept low. As a result, there is an effect of preventing data retransmission for data discard requested by the terminal device 7 connected to the subscriber terminal and suppressing an increase in unnecessary traffic.
[0050]
Next, the measurement of the time that data stays in the QOS buffer and the operation of discarding unnecessary data will be described.
[0051]
4A and 4B are detailed diagrams of functional blocks of the QOS buffer 404 (1 to n) and the QOS buffer 504 (1 to n). In FIG. 4, the QOS buffer 404 and the QOS buffer 504 include a stack buffer 602 (1 to m) having a stack structure, a time writing unit 601, a residence time calculation unit 603, and a data discard determination unit 604. Thereby, the dwell time of the data accumulated in the QOS buffer 404 (1 to n) or the QOS buffer 504 (1 to n) is measured, and the data for each frame exceeding the predetermined dwell time is discarded.
[0052]
Hereinafter, the operation of the QOS buffer 404 (1 to n) of the transmission unit 4 will be described as a representative with reference to FIG.
[0053]
The message data from the classifying unit 403 is written for each frame in the stack buffer 602 (1 to m) of the QOS buffer 404 (1 to n), and at the same time, the write input time from the time writing unit 601 is written.
Since the stack buffer 602 (1 to m) is configured by dividing one QOS buffer 404 into 1 to m pieces of data for each frame, the QOS buffer 404 includes n × m buffers. .
[0054]
The residence time calculation unit 603 reads the data for each frame corresponding to the stack buffer 602 (1 to m) under the control of the read control unit 406 and the write input written to the QOS buffer 404 (1 to n). The difference from the time is obtained, and the residence time of the data is measured.
[0055]
The data discard determination unit 604 determines whether or not to discard the data that exceeds the retention time by the above measurement, and discards the data for each frame of the stack when the retention time exceeds a predetermined value. Then, an instruction to calculate the residence time of the next frame (m + 1) data is transmitted to the residence time calculation unit 603, and when the residence time is equal to or less than a predetermined value, the readout control unit 406 is instructed to output the data as it is. .
[0056]
In this way, the buffer itself discards the data that exceeds the allowable delay time by itself, thereby facilitating communication control for providing a long communication service from the one with the short allowable delay time.
[0057]
Note that the allowable delay time and the data amount of the QOS buffer are initially set when the subscriber terminal 2 is installed. However, when the subscriber terminal newly establishes a connection with the base station, communication between a certain terminal is first performed. At the beginning, the information may be embedded and set in a MAC frame used for communication between the base station and the subscriber terminal.
[0058]
【The invention's effect】
According to the present invention, data stored in a buffer transmitted / received by a subscriber terminal is read from data having a short allowable delay time by providing an allowable delay time corresponding to the communication service, and data exceeding the allowable delay time is read. By performing the discard control, it is possible to realize a PMP wireless access system that can provide a communication service with a large delay time tolerance simultaneously with a communication service with a small delay time tolerance by using the buffer efficiently.
[Brief description of the drawings]
FIG. 1 is a block diagram of an embodiment of a subscriber terminal of a PMP wireless access system according to the present invention.
FIG. 2 is a flowchart of data transmission operation in the transmission unit of FIG. 1;
FIG. 3 is a flowchart of data reception operation in the reception unit of FIG. 1;
4 is a block diagram showing an internal configuration of the QOS buffer in FIG. 1. FIG.
FIG. 5 is a block diagram showing a configuration of a conventional PMP wireless access system.
FIG. 6 is a block diagram showing a configuration of a conventional subscriber terminal.
[Explanation of symbols]
1 Base station 2 Subscriber terminal 3 Antenna 4 Transmitter 5 Receiver 101, 401 Input buffer 102, 402 Filter unit 403, 503 Classifier 104, 204 Buffer 404, 504 QOS buffer 106, 206, 406, 506 Read controller 107, 407, MAC frame generation unit 110, 410 Wireless transmission unit 210, 510 Wireless reception unit 214, 514 Frame disassembly unit 215, 515 MAP message extraction unit 216, 516 Transmission timing control unit 217, 517 Output buffer 601 Time writing unit 602 Stack buffer 603 Residence time calculation unit 604 Data discard judgment unit 7 Terminal device

Claims (3)

In a PMP wireless access system that performs wireless communication between a base station and a subscriber terminal,
A first buffer for accumulating data to be transmitted from the subscriber terminal to the base station according to a transmission timing from the base station or for a preset first allowable delay time;
A first data accumulation amount setting means for setting a smaller data accumulation amount as the first allowable delay time of the first buffer is smaller;
A second buffer for storing data received from the base station by the subscriber terminal for a preset second allowable delay time;
Second data accumulation amount setting means for setting a smaller data accumulation amount as the second allowable delay time of the second buffer is smaller;
And a means for discarding data exceeding the first and second permissible delay times from the first and second buffers. A first reading means for reading data from the first buffer with a short first allowable storage time first, and a second reading unit for reading first from the second buffer with a short data with a short allowable storage time. The PMP wireless access system according to claim 1, further comprising reading means. The first and second buffers are:
A stack buffer having a stack structure of buffer memory that stores message data and its write input time in pairs for each frame;
Time writing means for writing the write input time into a frame of the stack buffer;
A residence time calculation means for obtaining a residence time of message data stored in the frame of the stack buffer from the write time;
Data discard judging means for judging whether or not to discard the message data for each frame by comparing the residence time of the message data obtained by the residence time calculating means with an allowable residence time preset in the corresponding frame. When
The PMP wireless access system according to claim 2, comprising:

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