JP2001036534A - Atm communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent expansion of an error rate due to a fact that an ATM cell itself becomes invalid by discriminating a service category of a communication form of ATM cell data, replacing a cell header on a transmission frame by a multiple connection system, transmitting the ATM cell data by removing the cell header, restoring the replaced and removed cell header when the transmission frame is received and reproducing the ATM cell. SOLUTION: The cell headers of each ATM cell of a CBR/VBR field are restored based on a TS number of time slot data transmitted by a sorting processing and information stored in a conversion table 515 from the TS number to VPI/VCI conversion by an ATM cell header reproducing part 514 by the TS number. Concretely, the TS number is read as VPI, VCI, PT, CLP and HEC are further attached and the ATM cell header is reproduced. And an ATM cell payload is reproduced by removing a TS preamble and a TS post ample by an ATM cell payload reproducing part 517.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a plurality of ATM terminal stations and at least one or more base stations connected to a public ATM network. More particularly, the present invention relates to a method for transmitting an ATM cell in a wireless space in which an error rate caused by an ATM cell header error occurring in a wireless space between a base station and an ATM terminal station is reduced. .

[0002]

2. Description of the Related Art Conventionally, the overall configuration of this type of ATM communication system is the same as that shown in FIG.

[0003] FIG. 10 shows a configuration of a transmitting section and a receiving section of a base station and an ATM terminal station in a conventional ATM communication system. In this system, A
The TDMA system is used between the TM terminal station and the base station, and the structure of a TDMA frame used in this conventional configuration is shown in FIG.

[0004] As shown in FIG. 10, in a conventional transmitting section, an ATM cell is composed of service categories (CBR, VB).
R, ABR, and UBR), the TDMA time slot generation unit 3 generates a TS (time slot) preamble and a TS (time slot) preamble as shown in FIG.
A postamble is added and converted to a TDMA time slot. Here, as shown in FIG. 11, a GT (Guard Time) constituting a TS preamble is a non-signal section provided for preventing collision between time slots, and a BTR (Bit Timing Recover).
y) is a clock reproduction code, UW (Unique Wor)
d) is a synchronization word. Also, FEC (Forward Error Corre) constituting the TS postamble
ction) is a redundant word of an error correction code (Reed-Solomon code or the like) for the ATM cell part.

Next, these TSs are sequentially given TS numbers in a time slot allocating section 5, and the TDMA
In the frame generation section 6, the frame is pasted on the TDMA frame shown in FIG. After that, the signal is modulated by the modulator 7 and output from the wireless transmitter 8 by radio.

On the other hand, in the receiving section, the demodulation section 10 demodulates the radio signal received by the radio
After the TDMA frame is reproduced by the A-frame terminating unit 11 and the time slot is extracted by the time slot extracting unit 13, the ATM cell reproducing unit 15 reproduces the ATM cell by removing the TS preamble and the TS postamble.

In the wireless ATM communication system of this type of wireless communication system, when the ATM cell is processed, the ATM cell itself is invalidated due to an error in the header of the ATM cell generated in a wireless section. Then, the error rate was equivalently increased.

[0008]

As described above, in the conventional configuration of the base station and the ATM terminal station in this type of system, when an ATM cell is processed, an error rate of an ATM cell header generated in a radio section is processed. As a result, the ATM cell itself is invalidated, so that the error rate is equivalently increased.

In view of the above, the present invention has been made to solve the above problem, and to prevent the ATM cell itself from being invalidated due to an error in the cell header of the ATM cell in the radio section, thereby preventing the error rate from increasing equivalently. It is an object of the present invention to provide an ATM communication system capable of performing the above.

[0010]

In order to achieve the above object, an invention according to claim 1 comprises a plurality of ATM terminal stations and an ATM terminal.
At least one or more base stations connected to the network,
In an ATM communication system in which each of the ATM terminal stations and the base station are connected by a radio line by a division multiple access method,
When each ATM terminal station and each base station transmits ATM cell data to the wireless line, each ATM terminal station and each base station determine the service category of the communication form of the ATM cell data, and as a result of the determination, the ATM cell of the specific service category is determined. In the above, the transmission means for replacing the cell header on the transmission frame by the division multiple access method, removing the cell header and transmitting, when receiving the transmission frame, restore the replaced and removed cell header and convert the ATM cell And a receiving means for reproducing.

According to a second aspect of the present invention, in the first aspect of the present invention, the specific service category is a real-time communication (including at least voice or image) in which a demand for delay quality is strict and a bandwidth must be guaranteed. It is characterized by being.

Further, the invention of claim 3 is characterized in that, in the invention of claim 1, the division multiple access system between each of the ATM terminal stations and each of the base stations is a TDMA (time division multiple access) system. I do.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the specific service category is allocated to a predetermined time position of a time position (time slot) divided by the TDMA system when the system is constructed in advance. And, as a result of the determination, in the ATM cell of a specific service category, the transmitting unit replaces the cell header with the predetermined time position assigned and set, removes the cell header, and transmits. Upon receiving a TDMA transmission frame, the ATM cell is reproduced by restoring the replaced and removed cell header based on the predetermined time position.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the division multiple access system between each of the ATM terminal stations and each of the base stations is an FDMA (frequency division multiple access) system. I do.

According to a sixth aspect of the present invention, in the fifth aspect of the invention, at the time of system construction, the specific service category is allocated to a predetermined frequency band of the frequency band divided by the FDMA system and set beforehand. Means are
As a result of the determination, in an ATM cell of a specific service category, the cell header is replaced with the predetermined frequency band set and assigned, the cell header is removed and transmitted,
The receiving means, when receiving the FDMA transmission frame, reproduces the ATM cell by restoring the replaced and removed cell header based on the predetermined frequency band.

The invention of claim 7 is characterized in that, in the invention of claim 1, the division multiple access system between each of the ATM terminal stations and each of the base stations is a CDMA (code division multiple access) system. I do.

According to an eighth aspect of the present invention, in the seventh aspect of the present invention, the specific service category is assigned to a predetermined code of a code group divided by the CDMA system when the system is constructed in advance. And the transmitting means comprises:
As a result of the determination, in an ATM cell of a specific service category, the cell header is replaced with the predetermined code assigned and set, the cell header is removed and transmitted, and when the receiving unit receives the CDMA transmission frame, The ATM header is reproduced by restoring the replaced and removed cell header based on the predetermined code.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing a configuration example of an ATM communication system according to the present invention.

As shown in FIG. 1, in this system, a plurality of terminal stations (subscribers) (1a to 1c) are connected to one base station (2a, 2b) through a radio line.
Further, the base stations (2a, 2b) are connected to the public ATM network 3 or the ATM.
-It is configured by being connected to an ATM switch 31 in an ATM network 3 such as a LAN. In this system, the ATM cell shown in FIG. 12 is a unit of transmission. As shown in the figure, the ATM cell is composed of an ATM cell header (5 bytes) and an ATM cell payload (48 bytes). ing.

FIG. 2 is a diagram showing the overall configuration of the base station 2 shown in FIG. 1. This base station 2 comprises an indoor unit 21, an outdoor unit 22, and an antenna 23. 21 includes a transmission unit 210, a reception unit 211, an IF up-converter 212, an IF down-converter 213, and a duplexer / combiner 214.

In this base station 2, the public A shown in FIG.
ATM cells received from the TM network are sent to the AT
The operation of the route transmitted to the M terminal station 1 will be described. First, in the indoor device 21, the transmitting unit 210 converts the transmission frame into a transmission frame of a division multiple access system used in a wireless space and outputs the transmission frame as a baseband signal. Then, IF up-converter 212 up-converts the baseband signal into an intermediate frequency signal and outputs the signal. And the demultiplexer /
A combiner 214 combines the intermediate frequency signals and outputs the combined signal. The indoor device 22 converts the synthesized intermediate frequency signal into an RF signal and outputs the RF signal to the antenna 23. The antenna 23 transmits this RF signal to a wireless space.

On the other hand, the operation of the route for transmitting the data of the transmission frame received from the ATM terminal station 1 shown in FIG. 1 to the public ATM network will be described. First, the antenna 23 receives the transmission signal transmitted from the wireless space and outputs the transmission signal to the outdoor device 22. Then, the outdoor device 22 determines that the transmission frame R
The F signal is converted into an intermediate frequency signal and output. Then
A demultiplexer / combiner 214 demultiplexes this intermediate frequency signal and outputs it. Then, the IF down converter 213
The split intermediate frequency signal is downconverted into a baseband signal and output. Then, the receiving unit 211
Regenerates ATM cells from the transmission frame of the baseband signal and sends out the ATM cells to the public ATM network.

FIG. 3 shows the ATM terminal station 1 shown in FIG.
FIG. 2 is a diagram showing the overall configuration of the ATM terminal station 1.
The indoor device 21 includes an indoor device 21, an outdoor device 22, and an antenna 23. The indoor device 21 further includes a subscriber device interface unit 110, a reception unit 111, a transmission unit 112, an IF down converter 113, an IF up converter 114,
It comprises a combiner / splitter 115.

In this configuration, each component other than the subscriber device interface unit 110 has the same function as each component of the base station 2 and performs the same operation. The subscriber device interface unit 110 interfaces with the subscriber device connected to and accommodated in the ATM terminal station 1.

FIG. 4 is a diagram showing a configuration of a transmitting unit and a receiving unit in the base station and the terminal station shown in FIGS.

Referring to FIG. 4, first, the configuration and operation of the transmitting section will be described.

In the transmitting section, the ATM cell separating section 410
It reads VPI (virtual path identifier) / VCI (virtual channel identifier) included in the cell header of the ATM cell sent from the public ATM network. The read information and the VPI / VCI-service category correspondence table 411
Based on the correspondence information stored in (see FIG. 5A), the inputted ATM cells are classified by service category.

More specifically, real-time communications (one-way real-time communication (images, etc.), two-way real-time communications (voices, etc.)) that have strict requirements for delay quality and require bandwidth guarantee, and delay quality Storage media communication (file transfer, etc.) where requests are moderate and bandwidth guarantee is not required
Classified as In this embodiment, the service categories CBR (Constant Bit Rate) in the ATM communication,
VBR (Variable Bit Rate) is treated as real-time communication, and service category ABR (Available Bit Ra
te), UBR (Unspecified Bit Rate) is handled as stored media communication.

Here, first, the ATM cell separating unit 41
The following configuration operation will be described in the case where it is determined that the service category of the ATM cell input at 0 is CBR or VBR for real-time communication.

First, the ATM cell header separation unit 412
The classified CBR / VBR ATM cells are separated into a cell header and a cell payload.

The time slot allocating unit 414 based on the header information converts the VPI (virtual path identifier) / VCI (virtual channel identifier) and VPI / VCI → TDMA slot number conversion table 413 (FIG. 5) contained in the separated cell header. Based on the conversion information stored in (b), the corresponding time slot is assigned to the separated cell payload. That is, the cell header of the ATM cell is replaced with the TDMA slot number.

Next, the CBR / VBR time slot generator 416 generates time slot data of the allocated time slot. Specifically, for example,
4 ATM cell payloads with the same time slot number
A TS preamble and a TS postamble are added for each unit to generate a CBR / VBR time slot as shown in FIG. (However, the contents of the TS preamble and the TS postamble are the same as those in the conventional example.) When the number of ATM cell payloads to which the same time slot number is given is less than four, or five or more, the number becomes two or more. TDMA
In the case of extending over a frame, there may be 0 to 3 ATM cell payloads stored in the ATM payload section in FIG.

The TDMA frame generator 418
Pastes the generated time slot data into a predetermined time slot of the TDMA frame shown in FIG.

The TDMA frame generator 418
The subsequent processing performs the same processing as the operation described in the conventional example.

On the other hand, the following configuration operation will be described in the case where it is determined that the service category of the ATM cell input by the ATM cell separating section 410 is ABR or UBR for stored media communication.

First, the TDMA time slot generator 41
5 adds a TS preamble and a TS postamble as shown in FIG.
Convert to DMA time slot data.

Next, the time slot allocating section 417 sequentially assigns the TS numbers in the ABR / UBR field to the converted time slot data.

Thereafter, the TDMA frame generator 41
At 8, it is attached to a predetermined time slot of the TDMA frame shown in FIG. 7 according to the given TS number.

Thereafter, as described above, the same processing as the operation described in the conventional example is performed.

Next, the configuration and operation of the receiving section will be described.

In the receiving unit, after processing the radio input signal in the same manner as in the conventional example, the TDMA frame terminating unit 512
Play the DMA frame. In addition, the TDMA frame terminating unit 512 distributes time slot data for each service category based on information stored in the TS number-service category correspondence table 513 (see FIG. 6A). Specifically, if the service category is CBR /
The time slot data of the VBR field is sent to the subsequent ATM cell header reproducing unit 514 based on the TS number, and the time slot data of the field whose service category is ABR / UBR is sent to the subsequent time slot extracting unit 516.

Here, the service category is CBR / VB
The processing of the R time slot data will be described first.

ATM cell header reproducing section 5 based on TS number
Reference numeral 14 denotes a CBR / CBR / TSR based on the TS number and the TS number of the time slot data transmitted by the above-mentioned distribution processing → information stored in the VPI / VCI conversion table 515.
The cell header of each ATM cell in the VBR field is restored. More specifically, the TS number is read as VPI and VCI, PT, CLP (fixed value) and HEC (calculated value) are added, and the ATM cell header is reproduced.

The ATM cell payload reproducing unit 51
7 reproduces the ATM cell payload by removing the TS preamble and the TS postamble.

Thereafter, the CBR / VBR ATM cell reproducing unit 519 combines the reproduced cell header and the cell payload, reproduces the original CBR / VBR ATM cell, and sends it to the subsequent ATM cell combining unit 520. .

On the other hand, if the service category is ABR / UBR
The processing of the time slot data will be described.

The time slot extraction unit 516 determines whether the ABR /
ABR / UBR from time slot of UBR field
Extract time slot data.

Thereafter, the ATM cell reproducing unit 518 sends the TS preamble of the extracted time slot data and T
The ATM cell is reproduced by removing the S postamble and transmitted to the ATM cell synthesizing section 520 at the subsequent stage.

Finally, the ATM cell synthesizing section 520 determines the CBR / VBR ATM cell and ABR
/ UBR ATM cells are synthesized and transmitted to the public ATM network.

In the above embodiment, two tables are provided in the transmission unit and the reception unit. However, one table may be used (for example, VPI).
/ VCI, TS number and service category. In addition, such a table may be shared between the transmission unit and the reception unit.)

The contents of the above table are set when the system is constructed, but can be changed as needed according to the demand for services.

In the above embodiment, the case where the division multiple access system between each ATM terminal station and each base station is a TDMA (time division multiple access) system has been described, but the present invention is not limited to this. The present invention can be applied to other systems, such as the FDMA (frequency division multiple access) system or the CDMA (code division multiple access) system.

As described above, in the present embodiment, since the path is secured for each connection in the service categories CBR and VBR, the fact that the TDMA slot can be secured even in the radio section is utilized, and the transmission side is used. ,
By performing negotiations so that the ATM cell header and the TDMA slot number can be associated with the receiving side,
Since it is possible to omit the ATM cell header in the wireless section, it is possible to effectively use the wireless section, and it is possible to reduce cell discard due to an error in the header.

FIG. 8 is a graph showing the error rate (BER) characteristics of the conventional method and the present invention method with respect to the radio error rate. The characteristics shown in FIG. 8 were obtained by computer simulation under the following conditions. Things. Condition (1): The error correction (HEC) of the ATM header is set to one error correction, and if there is an error of 2 bits or more in the ATM cell header, the cell is discarded. Condition (2): The error correction used for the TDMA time slot (see FIG. 6) is a Reed-Solomon code having eight error correction capabilities, and error correction is performed on the ATM cell part. Condition (3): modulation method is BPS
K, and the noise received on the wireless transmission path is assumed to be Gaussian noise.

In FIG. 8, the BER characteristics indicated by the square plot points indicate the AT
The BER characteristic in the case where the communication is performed without removing the M cell header and the cell is not discarded (real-time communication 1) is shown. The BER characteristic indicated by the circled point indicates that the ATM cell header is not removed in the real-time communication. 9 shows BER characteristics when communication is performed by performing cell discarding (real-time communication 2). The BER characteristic indicated by the diamond-shaped plot points indicates that AT
The BER characteristic when communication is performed with the M cell header removed (storage media communication 1) is shown. The BER characteristic indicated by a triangular plot point indicates the case where communication is performed without removing the ATM cell header in storage media communication. The BER characteristic of (storage media communication 2) is shown.

As can be seen from FIG. 8, in real-time communication, when a cell is discarded due to an ATM cell header error (real-time communication 2), that is, when the conventional method does not perform cell discarding (real-time communication 1), That is, it can be seen that the error rate is larger than that of the method of the present invention.

On the other hand, in the storage media communication, the AT
It can be seen that the error rate in the case where cell discarding due to an M cell header error is performed (storage media communication 2), that is, the conventional method is almost the same as that in the case where cell discarding is not performed (storage media communication 1).

For this reason, in this embodiment, for real-time communication (CBR, VBR), transmission is performed with the ATM cell header removed, and stored media communication (ABR, UBR) is performed.
(BR) is transmitted with the ATM cell header attached.

That is, in the storage media communication, TCP / IP is generally used for the upper layer,
In the P / IP layer, if there is even one bit error in a certain frame section, retransmission is requested. In an environment where an ATM cell header error occurs in a wireless section, the ATM cell payload is used. Since the probability that the ATM cell header is erroneous is higher than the probability that the ATM cell header is erroneous, the effect is not so expected even if the ATM cell header can be removed. .

In the above-mentioned storage media communication,
FIG. 9 shows a processing procedure in the case where the terminal station A and the terminal station B communicate with each other, considering a communication method using the Over ATM method. As shown in FIG. 9, this method is realized through an ATM switch in an ATM network.

In the system configuration of the above-described embodiment, all service categories CBR, VB
It is configured to perform R, ABR, and UBR processing, but is not limited to this, and for each service category, for example, for real-time communication (CBR, VBR) and for storage media communication (ABR, UBR). It is also possible to separately configure base stations.

[0063]

As described above, according to the present invention,
An AT having a plurality of ATM terminal stations and at least one or more base stations connected to a public ATM network, and connecting each ATM terminal station and the base station by a radio line by a division multiple access method.
In the M communication system, each ATM terminal station and each base station determine the service category of the communication format of the ATM cell data when transmitting the ATM cell data to the wireless line, and as a result of the determination, the specific service is determined. In the category of ATM cells, a transmission means for replacing a cell header on a transmission frame according to the split connection method and removing the cell header for transmission, and when receiving the transmission frame, restoring the replaced and removed cell header and reconstructing the ATM cell And a receiving unit that reproduces the ATM cell, it is possible to reduce an error rate caused by an error in a cell header of an ATM cell occurring in a wireless space according to a service category.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of an ATM communication system according to the present invention.

FIG. 2 is a diagram showing an overall configuration of a base station 2 shown in FIG.

FIG. 3 is a diagram showing an entire configuration of the ATM terminal station 1 shown in FIG. 1;

FIG. 4 is a diagram showing a configuration of a transmitting unit and a receiving unit in the base station and the terminal station shown in FIGS. 2 and 3;

FIG. 5 is a diagram showing a configuration of table information of a transmission unit.

FIG. 6 is a diagram showing a configuration of table information of a receiving unit.

FIG. 7 is a TDMA frame structure diagram in one embodiment of the present invention.

FIG. 8 is a diagram showing an error rate characteristic of each system (conventional system and system of the present invention) with respect to a wireless error rate.

FIG. 9 is a diagram showing a communication procedure in the IPover ATM method.

FIG. 10 is a diagram showing a configuration of a transmission unit and a reception unit in a conventional system.

FIG. 11 is a diagram showing a TDMA frame structure in a conventional example.

FIG. 12 is an ATM cell structure diagram used in an ATM communication system.

[Explanation of symbols]

1a, 1b, 1c ATM terminal station 11 Indoor unit 110 Subscriber equipment interface unit 111 Receiving unit 112 Transmitting unit 113 IF down converter 114 IF up converter 115 Combiner / demultiplexer 12 Outdoor device 13 Antenna 2a, 2b Base station 21 Indoor Device 210 Transmitter 211 Receiver 212 IF Upconverter 213 IF Downconverter 214 Duplexer / Synthesizer 22 Outdoor Equipment 23 Antenna 3 Public ATM Network 31 ATM Switch 410 ATM Cell Separation Unit 411 VPI / VCI-Service Category Correspondence Table 412 ATM Cell header separation unit 413 VPI / VCI → TDMA slot number conversion table 414 Time slot allocation unit based on header information 415 TDMA time slot generation unit 416 Time for CBR / VBR Slot generation section 417 Time slot allocation section 418 TDMA frame generation section 419 Modulation section 420 Radio transmission section 510 Radio reception section 511 Demodulation section 512 TDMA frame termination section 513 TS number-service category correspondence table 514 ATM cell header reproduction section using TS number 515 TS Number → VPI / VCI conversion table 516 Time slot extractor 517 ATM cell payload reproducer 518 ATM cell reproducer 519 CBR / VBR ATM cell reproducer 520 ATM cell combiner

Claims (8)

[Claims] 1. An ATM network comprising: a plurality of ATM terminal stations; and at least one base station connected to an ATM network.
In an ATM communication system in which a TM terminal station and the base station are connected by a wireless channel by a division multiple access method, each of the ATM terminal stations and each of the base stations transmits the ATM cell data when transmitting the ATM cell data to the wireless line.
The service category of the communication form of the TM cell data is determined, and as a result of the determination, in the ATM cell of the specific service category, the cell header is replaced on the transmission frame by the division multiple access method, and the cell header is removed and transmitted. An ATM communication system comprising: a transmitting unit; and a receiving unit that, when receiving the transmission frame, restores the cell header removed and replaced to reproduce an ATM cell. 2. The ATM communication according to claim 1, wherein the specific service category is real-time communication (including at least voice or image) that requires strict delay quality and requires bandwidth guarantee. system. 3. The ATM communication system according to claim 1, wherein a division multiple access system between each ATM terminal station and each base station is a TDMA (time division multiple access) system. 4. When the system is constructed, the specific service category is assigned to a predetermined time position of a time position (time slot) divided by the TDMA method, and the transmitting unit determines a specific service category as a result of the determination. In the ATM cell of the service category, the cell header is replaced with the predetermined time position assigned and set, the cell header is removed, and the cell header is transmitted. When the TDMA transmission frame is received, the receiving means removes the replaced cell header. The ATM communication system according to claim 3, wherein the ATM cell is reproduced by restoring the ATM cell based on the predetermined time position. 5. The ATM communication system according to claim 1, wherein a division multiple access system between each of the ATM terminal stations and each of the base stations is an FDMA (frequency division multiple access) system. 6. A system in which the specific service category is allocated to a predetermined frequency band of the frequency band divided by the FDMA system in advance when a system is constructed. In the cell, the cell header is replaced with the predetermined frequency band set and assigned, the cell header is removed and transmitted. The receiving means, when receiving the FDMA transmission frame, replaces the replaced and removed cell header with the predetermined frequency band. 6. The ATM communication system according to claim 5, wherein the ATM cell is reproduced by restoring based on the frequency band. 7. The ATM communication system according to claim 1, wherein a division multiple access system between each ATM terminal station and each base station is a CDMA (code division multiple access) system. 8. When the system is constructed in advance, the specific service category is assigned to a predetermined code of a code (code) divided by the CDMA system, and the transmitting unit determines the specific service category as a result of the determination. In the ATM cell, the cell header is replaced with the predetermined code assigned and set, the cell header is removed and transmitted. When the CDMA transmission frame is received, the receiving means replaces the replaced and removed cell header with the predetermined code. The ATM communication system according to claim 7, wherein the ATM cell is reproduced by restoring based on the code.