JPH09298545A - Atm digital radio transmission method and system therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ATM digital radio communication method and a system with a high traffic efficiency without causing a cell loss or a cell delay and capable of high speed data transmission in the case of radio transmission of an ATM cell data string between a radio base station and a plurality of subscriber stations. SOLUTION: An ATM cell data string from an ATM exchange 1 or ATM terminal equipments 4-1 to N are sent in two-way between a radio base station 2 and a plurality of radio subscriber stations 3-1 to N by the TDMA/TDD system through high frequency radio channels 201-1 to N, 202'-1 to N. The TDMA/TDD system uses a plurality of burst signals each of which has a different configuration at its header part specific to radio transmission from that of a conventional ATM cell. Furthermore an idle cell is inserted to the data string so as to match the radio transmission speed, and a receiver side prevents occurrence of a cell loss or the like by detecting an error bit of a header part and a payload part of the idle cell.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an asynchronous transfer mode (ATM: Asynchronous Transfer).
ATM digital wireless transmission method and device for transferring cells in r Mode), particularly idle cell detection,
The present invention relates to an ATM digital wireless transmission method and system having a variable capacity function for separation.

[0002]

2. Description of the Related Art There is an increasing need for multimedia communication including voice communication, data communication and moving images, and such broadband communication is carried out by an ATM switch and a radio transmission system in a high frequency band higher than a microwave band. A means for providing a service to a wide area by using is considered.

The ATM system converts all information into fixed information called cells without depending on continuous information such as voice and moving images and burst information such as data, and without depending on each communication speed. And transmit at high speed. That is, in the ATM system, multiple logical links are provided on a physical line to allocate the line to a plurality of calls. And
Video data, voice data, etc. from a terminal corresponding to each call are decomposed into fixed-length information units (called cells) and sequentially sent to the line to realize multiplexing.

Using such an ATM system, a plurality of A
FIG. 8 shows a conventional example of a network configuration of an ATM digital wireless transmission system for transmitting high-speed data by a digital wireless transmission system between a TM terminal and a base station.

In the figure, 1 is an ATM switch, 20 is a radio base station, 30-1 to N are a plurality of radio subscriber stations, 4-
1 to N are a plurality of ATM terminals such as personal computers. ATM
The exchange 1 and the radio base station 2 are high-speed ATs such as optical fibers.
They are connected by M transmission lines 101 and 101 '.

As shown in FIG. 9, the ATM cells transmitted through the ATM transmission lines 101 and 101 'are composed of a fixed length block of 53 bytes, of which 5 bytes are the header part and 48 bytes are the information area. (Payload) part.

The header section multiplexes ATM cells,
It is used for routing. Regarding information transfer, the network has an important function because it interprets only the header part and does not see the payload part. The header part is used for a call identification virtual channel number (VCI), a virtual path identifier (VPI) for identifying a route, and a flow control between links so that the destination can be known even after the data is divided into blocks. G
Header error correction control (HEC: Header Err) which is a code for error correction of FC, payload part and header part
or Control) or the like. This H
In EC, 1-byte CRC (Cyclic Redun)
The error correction by the dunky check) code is used.

The above description is based on, for example, "Broadband I
SDN and ATM Technology ", IEICE, 1995.
2.20.

Next, the radio base station 2 and the plurality of radio subscriber stations 30-1 to 30-N use the Aloha method, which is widely known as a random access method for packet data, and high-frequency radio lines 201-1 to 201-1 such as microwave bands. N, 201'-1 to N.

That is, A input to the radio base station 20
The TM cell data string determines the destination of the header portion and is transmitted to the predetermined wireless subscriber stations 30-1 to 30-N by the Aloha method. In the case of collision in the wireless sections 201-1 to N and 201'-1 to N, retransmission processing is performed.

On the contrary, a system in which the wireless subscriber stations 30-1 to 30-N similarly transmit the wireless base station 2 by the Aloha system has been adopted.

[0012]

However, in the above conventional method, since the ATM digital wireless transmission method using the Aloha method for the wireless line is used, the throughput in the wireless line is effectively as low as about 20% at most, so the subscriber When the number of stations has increased, there have been problems of cell loss in which cells cannot be transmitted and cell delay that takes time for the transmitted cells to reach.

The cell loss and cell delay are 25 Mbps.
Not applicable to high-speed data transmission above, at most 2
It was limited to 10 Mbps data transmission.

These cell loss, cell delay quality deterioration, and data transmission rate limit not only affect the wireless section but also the quality of the entire ATM network, so that future B-ISDN (Broad)
band-Integrated Services
It has been a major obstacle to the realization of Digital Network).

The present invention has been made in view of the above points,
An object of the present invention is to provide an ATM digital radio transmission method and system capable of solving the problems of cell loss and cell delay in the conventional system and enabling high-speed data transmission.

[0016]

In order to achieve the above object, an ATM digital radio transmission method and system according to the present invention uses an A / A system for inputting / outputting at an ATM switch or an ATM terminal.
In an ATM digital radio communication method for bidirectionally transmitting a TM cell data string between one radio base station and a plurality of radio subscriber stations by a high frequency radio line, the bidirectional transmission of the high frequency radio line is a TDMA / TDD system. The ATM
It is characterized in that the cell is converted into a wireless ATM cell including a control bit and an error control bit of a wireless line in a header part, and the wireless ATM cell is inserted into the burst signal for the TDMA / TDD system.

Further, in the ATM digital wireless communication method, a predetermined fixed pattern is provided in a header part and an information bit part in a part of the ATM cell data string on the transmitting side of the wireless base station or the plurality of wireless subscriber stations. The inserted idle cell is inserted into the TDMA frame format and transmitted, and a signal in which the idle cell is inserted is received at the receiving side of the wireless base station or the wireless subscriber station, and the received idle cell bit and Compared with the fixed pattern stored in advance, the idle cell is separated when the error count value is equal to or less than a predetermined number.

Furthermore, in an ATM digital radio communication system for bidirectionally transmitting an ATM cell data string input / output at an ATM switch or ATM terminal between one radio base station and a plurality of radio subscriber stations by a high frequency radio line, Bidirectional transmission of the high-frequency wireless line is performed by the TDMA / TDD system, and the wireless base station and the plurality of wireless subscriber stations use an ATM cell on the transmission side and a wireless line control bit on the header section of the ATM cell. An ATM transmission interface circuit for converting into a wireless ATM cell including an error control bit, a wireless transmission circuit for transmitting the wireless ATM cell as a TDMA burst signal, and a wireless for receiving the output of the wireless transmission circuit and demodulating the wireless ATM. Reception circuit and wireless ATM
And an ATM receiving interface circuit for converting cells into the ATM cells.

Further, in the ATM digital radio communication system, the radio base station and the plurality of radio subscriber stations have a predetermined fixed pattern in a header part and an information bit part in a part of the ATM cell data string on the transmitting side. An idle insertion circuit that inserts the idle cell with the inserted idle cell into the TDMA frame format, receives a signal with the idle cell inserted on the receiving side, and compares the received idle cell bit with the previously stored fixed pattern. However, it has an idle cell detection circuit for detecting whether or not the error count value is less than or equal to a predetermined number, and an idle cell separation circuit for separating the idle cell when the count value is less than or equal to the predetermined value. It is characterized by that.

[0020]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a system configuration diagram of the ATM digital radio transmission system of the present invention. In this figure, AT
The M switch 1 is connected to the radio base station 2, and further the radio base station 2
Is a plurality of wireless subscriber stations 3-1 to N and ATM terminal 4-1.
AT to N by multiple connection with TDMA wireless line
A wireless transmission network based on the M method is configured.

Here, 1 is an ATM switch, 2 is a wireless base station, 3-1 to N are a plurality of wireless subscriber stations, and 4-1 to N are a plurality of ATM terminals such as personal computers. The ATM switch 1 and the radio base station 2 are high-speed ATM transmission lines 1 such as optical fibers.
01 and 101 'are connected.

On the other hand, the radio base station 2 and the plurality of radio subscriber stations 3-1 to N are provided with a high frequency radio line 20 such as a microwave band.
1-1 to N, 201'-1 to N, bidirectional time division multiple access-frequency alternating communication system (TDMA / TDD)
Transmitted by

[0024] Here, TDMA is Time Div
sion Multiple Access, TDD
Stands for Time Division Duplexer.

The plurality of wireless subscriber stations 3-1 to N are
The high speed transmission lines 301-1 to N and 301'-1 to N are connected to the ATM terminals 4-1 to N, respectively.

First, the wireless transmission lines 201-1 to N, 20
FIG. 2 shows the frame format of the TDMA wireless line transmitted between 1'-1 and N.

This TDMA system uses the uplink 2 of the wireless line.
01-1 to N (wireless lines from the wireless subscriber stations 3-1 to N to the wireless base station 2) and downlinks 201'-1 to N (from the wireless base station 2 to the wireless subscriber stations 3-1 to N) TDMA / TDD for time-divided transmission of TDMA system
The system is being used to effectively utilize the wireless line.

That is, a signal having a single frequency is alternately time-divided and communicated between the base station and a plurality of terminal stations at a predetermined cycle.

This figure shows one frame of a TDMA burst signal. One frame is divided into a plurality of (m) time slots, and a predetermined burst signal is assigned to these time slots.

That is, first, TDMA for adjusting the burst signal from each subscriber station to a predetermined timing.
It is a reference burst that serves as a frame reference signal. This reference burst is composed of burst signals time-divided into an uplink and a downlink.

Secondly, there are control bursts for uplink and downlink. As described above, these are data signals used for multiple connection control because the network has a configuration for multiple connection between the wireless base station 2 and a plurality of subscriber stations 3.

Further, as the third burst signal, a data signal relating to a plurality of transmission information for each subscriber station goes up,
It is arranged for each downlink.

The burst signals shown above are arranged by alternately arranging the uplink and the downlink, but the present invention is not limited to this, and the uplink is the front side of the frame and the downlink is the rear side of the frame. Various arrangements are conceivable, such as the arrangement at.

Next, in the same figure, in order to explain the details of the structure of each burst signal, an explanation will be given using an enlarged view of the reference burst of the downlink. The other burst signals have the same configuration as this configuration.

That is, the reference burst is a preamble signal used for leading carrier synchronization, clock synchronization, unique word synchronization, etc., and a wireless ATM provided after that for a plurality of wireless sections provided for each of a plurality of subscriber stations.
It is composed of cells.

The structure of this wireless ATM cell is the above-mentioned AT.
Like the M cell, it has a basic structure consisting of a 53-byte header part and a payload part. However, in the basic structure wireless section, the header part has a special structure because of the large error occurrence compared to the wired transmission path and the control of the wireless station.

FIG. 3 is a diagram showing details of the wireless ATM cell. In the figure, ST is a 1-byte radio control bit, which is used for control peculiar to the radio line, and indicates, for example, the type of service of the radio line, effective wireless ATM information, and the like. W-VCI is the VPI of FIG.
And VCI. The W-VCI bit limits the number of virtual paths and virtual channels, and PT and C
The total number including LP is limited to 2 bytes. On the other hand, since the HEC of FIG. 9 has 1 byte, its error correction capability is insufficient for errors due to fading in the wireless section and the like, so the present invention uses a 2-byte CRC code.

In the present invention, the radio control bit is one byte, but it is not limited to this, and more bits may be added depending on the network configuration.

In the present invention, the ST and CRC bits which are specially required for the wireless section are added, and the wireless AT as a whole is added.
M has been described as having the same length as the ATM cell (53 bytes). However, the wireless ATM cell length is not limited to the same length. In a line with a low received electric field such as satellite communication, the FEC control bit is added to the CRC code to make it longer than the ATM cell, but there is no problem because an independent format can be used as a wireless section.

The TDMA frame format described above shows the case where all ATM cells are generated per unit time. However, when the transmission capacity of the ATM cell data string changes, the TDMA frame format is actually transmitted per unit time. The number of cells to do will change.

In this case, in the TDMA wireless transmission system of the present invention, the transmitting side inserts a pseudo cell (idle cell) so that the frame length is always kept constant and the transmission is performed in accordance with the wireless transmission rate. The idle cell inserted is detected by detecting the type of the cell added to the header part of the above and separated.

In the present invention, the T
The constant DMA format facilitates the detection of interference waves and simplifies the TDMA timing control.

FIG. 4 is a conceptual diagram for explaining the function of inserting and separating the idle cell described above.

In this figure, FIG. 4 (a) is a diagram showing transmission data composed of an ATM cell data string. In the figure, cells are not arranged at regular intervals because the transmission data capacity from the ATM switch or ATM terminal is changing. In FIG. 4B, an idle cell is inserted in a portion of the transmission data where the cell is empty to form a TDMA transmission signal. FIG. 4C shows that an idle cell is detected and separated from the reception data that has received the transmission signal of FIG. 4B. FIG. 4D shows that the idle cells are separated and the reception data that matches the transmission data is obtained.

Next, FIG. 5 shows a specific block diagram relating to the insertion, separation and detection of the idle cell.

In the figure, as an example, the configuration is shown in which the wireless base station 2 transmits to the wireless subscriber station 3-1. However, the same applies to the other wireless subscriber stations 3-2 to N. It will be composed. Further, conversely, the wireless subscriber stations 3-1 to N to the wireless base station 2 have the same configuration, and thus the description thereof will be omitted.

Further, in the configuration of the radio base station 2, the control device configuration of a plurality of subscriber stations and the like have no relation to the present invention and are therefore omitted.

In the figure, when the ATM transmission signal 101 is received by the base station 2, it is first input to the ATM transmission interface circuit 25. The ATM transmission interface circuit 25 has a function of converting an optical signal into an electric signal and converting an ATM cell into a wireless ATM cell. Next, A
The output of the TM transmission interface circuit 25 is input to the idle cell insertion circuit 22. The idle cell insertion circuit 22 has a function of inserting predetermined data into the wireless ATM cell data string to be transmitted into the header portion and the information bit portion of predetermined data to match the wireless transmission rate. is there.

The output of the idle cell insertion circuit 22 is input to a wireless transmission circuit 23 including a digital modulator and a microwave band high frequency transmitter, is digitally modulated, and is transmitted via a base station antenna 21 to a wireless line 201 to a subscriber. It is transmitted to the station 3-1.

The subscriber station 3-1 receives the transmission signal 201-1 and demodulates it in the radio receiving circuit 33 including a high frequency receiving circuit and a digital demodulator to output demodulated data. This demodulated data is input to the idle cell separation circuit 34 and the idle cell detection circuit 32. The idle cell detection circuit 32 has idle cell pattern information of a predetermined header portion and information bit portion, and compares the received idle cell pattern information with the received cell string to detect an idle cell. The output of the idle cell detection circuit 32 is input to the idle cell separation circuit 34 to separate and delete the idle cells. The output 37 of the idle cell separation circuit 34 is input to the ATM reception interface 38, and has the functions of converting an electric signal into an optical signal and converting a wireless ATM cell into an ATM cell.

Next, the specific structure of FIG. 5 will be described below.

FIG. 6 is a diagram showing a configuration example of the idle cell insertion circuit 22. In this figure, ATM transmission signal 1
01 is input to the gate control circuit 205 and detects the timing when the ATM cell is vacant. The fixed pattern generator 202 outputs fixed pattern data to be transmitted as an idle cell. The data of the fixed pattern is all the data of the header part and the payload part, that is, 53 bytes of fixed data.

The output of the fixed pattern generator 202 controls the gate circuit 203 by the output of the gate control circuit 205 and inputs an idle cell to the adder 204 during the idle time of the cell. At the output of the adder 204, transmission data with idle cells inserted is obtained.

FIG. 7 shows the idle cell detection circuit 32 of FIG.
3 is a block diagram showing a configuration of an idle cell separation circuit 34. FIG.

In the figure, the frame synchronization signal 36 detected by the demodulator of the radio reception circuit 33 can be input to the cell timing circuit 303 to detect the timing of the cell inserted on the transmission side. Further, the fixed pattern generator 304 is a data generator that generates the same data as the fixed pattern data of the fixed pattern generator 202 of FIG. The output of the cell timing circuit 303 is input to the gate circuit 302 so that the output signal of the fixed pattern generator 304 is input to the comparator 305 at the cell insertion timing.

The comparator 305 performs bit comparison of data between the demodulated data signal 35 and the output signal of the gate circuit 302. The output of the comparator 305 is input to the error detection circuit 306 to detect whether the data match or mismatch, and input a bit error to the counter 309.

The counter 309 inputs the error of the error detection circuit 306 and counts it. Here, since the output 308 of the interval generator 307 that generates the timing for each bit of one cell is input to the counter 309, 1
Count the total number of errors for each cell. Then, when the count value is equal to or smaller than the predetermined count value set in the counter 309, the discard signal 310 is output to the cell discard circuit 311.

When the count value is equal to or larger than the predetermined count value, the discard signal 310 is not output.

By the above operation, the cell discard circuit 311
The cell data string to be transmitted is output to the output 37 of the.

The idle cell separating method described above has the following effects.

The ATM cell used in the ATM transmission line is based on HEC in the ATM header portion as described with reference to FIG. In a transmission line with few errors such as an optical transmission line, there was no problem in error detection using the CRC of the header section.

However, the wireless transmission path has a characteristic that the deterioration of the transmission quality is very large because a phenomenon such as a multipath fading or a decrease in the received electric field due to an obstacle frequently occurs. For this reason, if the HEC of the header part used in the ATM transmission line is used as it is for error detection of an idle cell in the wireless transmission line, accurate error detection cannot be performed, and an error is detected in the ATM transmission line following the wireless transmission line. There is a problem of sending out idle cells that contain it.

As a countermeasure against this, FEC is added to the idle cell.
(Forward Error Correction
Although there is also a method of inserting a bit for n) and performing a strong error correction, it has a problem that the transmission bit length becomes long and error correction becomes complicated.

The present invention solves the above problems and provides a highly reliable error detection method that does not require an increase in transmission bits.

[0065]

As described above, the ATM digital radio transmission method and apparatus of the present invention use the TDMA / TDD system for radio transmission of ATM cells, so that the throughput of the entire network can be increased.

On the wireless transmission side, an additional bit for wireless line error correction is added to the ATM cell data string to be transmitted,
High-speed data can be transmitted by TDMA / TDD by converting and transmitting it into a wireless ATM cell which is most suitable for wireless line transmission. That is, the present invention enables high-speed data transmission of 25 Mbps to 150 Mbps, which was impossible with conventional packet transmission.

Since an idle cell is inserted to match the radio transmission rate and the idle cell is separated on the receiving side, interference wave detection is facilitated, and TDMA timing control is facilitated. It is possible to achieve the effects such as

Further, regarding the insertion and separation of idle cells, a predetermined idle cell pattern is inserted in the header part and the information bit part of the idle cell on the transmitting side, and the idle cell is digitally detected on the receiving side. Are separated. As a result, it is possible to reduce the probability of erroneous distribution of idle cells and perform highly reliable ATM digital wireless transmission.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an ATM digital wireless transmission system representing an embodiment of the present invention.

FIG. 2 is a diagram showing a TDMA frame format of FIG.

FIG. 3 is a diagram showing details of a wireless ATM cell in a wireless section of FIG.

FIG. 4 is a diagram showing a concept of insertion and separation of idle cells.

5 is a block diagram showing transmission between the radio base station 2 and the radio subscriber station 3-1 of FIG.

6 is a diagram showing a configuration of an idle cell insertion circuit 22 of FIG.

7 is a diagram showing configurations of an idle cell detection circuit 32 and an idle cell separation circuit 34 of FIG.

FIG. 8 is a diagram showing a network configuration of a conventional ATM digital wireless transmission system.

FIG. 9 is a diagram showing a structure of an ATM cell.

[Explanation of symbols]

 1 ATM Switch 2, 20 Radio Base Station 3-1 to N Radio Subscriber Station 4-1 to N ATM Terminal 21 Radio Base Station Antenna 22 Idle Cell Insertion Circuit 23 Radio Transmission Circuit 25 ATM Transmission Interface 31-1 to N Subscriber Station antenna 32 Idle cell detection circuit 33 Radio reception circuit 34 Idle cell separation circuit 38 ATM reception interface 101, 101 'ATM transmission line 201-1 to N, 201'-1 to N radio transmission line 202, 304 Fixed pattern generator 203 , 302 gate circuit 204 adder 205 gate control circuit

Claims (7)

[Claims] 1. A bidirectional transmission of an ATM cell data string input / output at an ATM switch or ATM terminal between a single radio base station and a plurality of radio subscriber stations via a high frequency radio line.
In the TM digital wireless communication method, bidirectional transmission of the high frequency wireless line is performed by a TDMA / TDD system, and the ATM cell is converted into a wireless ATM cell including a control bit of the wireless line and an error control bit in a header part, An ATM digital radio transmission method, wherein the radio ATM cell is inserted into a burst signal for the TDMA / TDD system. 2. The ATM digital wireless communication method further comprises a predetermined fixed pattern in a header part and an information bit part in a part of the ATM cell data string on the transmitting side of the wireless base station or the plurality of wireless subscriber stations. An idle cell inserted in the TDMA frame format is transmitted, and a signal in which the idle cell is inserted is received at the receiving side of the wireless base station or the wireless subscriber station, and the received idle cell bit and An ATM digital radio transmission method, characterized in that the idle cell is separated when an error count value is equal to or less than a predetermined number, as compared with the fixed pattern stored in advance. 3. A bidirectional transmission of an ATM cell data string input / output at an ATM switch or ATM terminal between a single wireless base station and a plurality of wireless subscriber stations via a high frequency wireless line.
In the TM digital wireless communication system, bidirectional transmission of the high frequency wireless line is performed by a TDMA / TDD method, and the wireless base station and the plurality of wireless subscriber stations have an ATM cell on the transmission side and a header portion of the ATM cell. Wireless ATM including wireless line control bits and error control bits
An ATM transmission interface circuit for converting into a cell, a radio transmission circuit for transmitting the radio ATM cell as a TDMA burst signal, a radio reception circuit for receiving the output of the radio transmission circuit and demodulating the radio ATM, and the radio ATM cell ATM for converting the above into ATM cells
ATM digital wireless transmission characterized by having a receiving interface circuit. 4. In the ATM digital wireless communication system, the wireless base station and the plurality of wireless subscriber stations have a fixed pattern in a header part and an information bit part in a part of the ATM cell data string on a transmitting side. An idle insertion circuit that inserts the idle cell with the inserted idle cell into the TDMA frame format, receives a signal with the idle cell inserted on the receiving side, and compares the bit of the received idle cell with the previously stored fixed pattern. However, it has an idle cell detection circuit that detects whether or not the error count value is less than or equal to a predetermined number, and an idle cell separation circuit that separates the idle cell when the count value is less than or equal to the predetermined value. An ATM digital wireless transmission system characterized in that 5. The header portion of the wireless ATM cell has a length of 5 bytes, the payload portion has a length of 48 bytes, and the header portion has the control bit of 1 byte, the wireless virtual channel identifier of 2 bytes, and a CRC. 4. The ATM according to claim 1, wherein the error control bit is 2 bytes.
Digital wireless transmission method and system. 6. The idle cell is inserted into the TDMA frame format when the transmission capacity of the ATM cell data string changes and the number of cells to be transmitted per unit time changes. 2. An ATM digital wireless transmission method and system described in 2 and 4. 7. The ATM digital radio transmission method and system according to claim 1, wherein the error control bit is a CRC error control bit.