JPH1075488A - Digital communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accelerate data transmission and to house a lot of pieces of information terminal equipment in one network terminating device in the case of performing the bidirectional communication of data based on time division duplexing(TDD) between a base station and plural user stations by dynamically changing the state of channel allocation corresponding to the result of requests of a user channel. SOLUTION: Between a base station B-CS and a mobile station B-RM, a TDD communication system based on a radio interface is performed while using a time division multiple access(TDMA) frame format. When user data desired to be transmitted from the B-RM to the B-CS are generated, concerning the allocating processing of the user channel to be executed through this communication system, the B-RM transmits the allocation request of the user channel to the B-CS while using any one of up control channels. The B-CS interpretes the allocation request while including the allocation requests from the other mobile stations and determines the user channels to be allocated to the respective B-RM.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time division duplex (TDD) using a time division multiple access (TDMA) frame format.
Division Duplex), a digital communication system for performing two-way data communication between a base station and a plurality of user stations, and in particular, a wide area integrated service digital network (B-ISD).
N: Broadband Integrated Services Digital Networ
The present invention relates to a digital communication method suitable for data communication between a base station connected to k) and a plurality of mobile stations.

[0002]

2. Description of the Related Art B-ISDN uses an asynchronous transfer mode (A
It is a network that integrates high-speed packet switching and subscriber-based optical transmission services, with TM (Asynchronous Transfer Mode) as the core, and provides broadband and high-quality transmission services. In such a network termination device 2 (B-NT2: Broadband Network Terminal 2) in B-ISDN, a terminal device (B-TE: Broadband Terminal equipme) is used.
nt) was connected using an optical fiber or a coaxial cable, but due to the spread of wireless multimedia communication systems such as portable information terminals and mobile phones, BT
E is B over the air interface (ie wireless)
-There is a request to connect to ISDN.

[0003] That is, while connecting the B-TE to a mobile station (B-RM) such as a mobile phone, the B-ISDN A
It is required to connect a base station (B-CS) to a TM node and connect a B-RM serving as a user station to the B-CS via a radio interface. Note that the B-NT2 includes one B-CS and a plurality of B-RMs wirelessly connected to the B-CS. One B-NT2 can accommodate a plurality of B-TEs.

[0004]

However, when a plurality of B-RMs are connected to one B-CS, a sufficient band cannot be fixedly allocated to each B-TE at all times. There is a problem that the data transmission speed is reduced. In contrast, each B-
If sufficient bandwidth is allocated to TE, one BN
There is a problem that the number of B-TEs that can be accommodated in T2 is limited. In particular, since the transmission bandwidth of the wireless interface is narrower than that of the wired interface, when the B-CS and a plurality of B-RMs are connected by the wireless interface as compared with the case where the B-CS is connected by the wired interface, the above-described problem occurs. It was particularly noticeable.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and when performing bidirectional data communication in a time-division duplex manner between a base station and a plurality of user stations, it is possible to speed up data transmission and achieve one communication. It is an object of the present invention to provide a digital communication system capable of accommodating a large number of terminal devices in a network terminating device. Further, the present invention provides a two-way communication between a mobile station, which is a user station, and a base station by radio, and in a communication system connecting to a B-ISDN via the base station, speeds up data transmission, It is an object of the present invention to provide a digital communication system capable of accommodating a large number of terminal devices in one network termination device.

[0006]

In order to achieve the above object, in the digital communication system according to the present invention, a time division duplex is used between a base station and a plurality of user stations using a time division multiple access frame. In a digital communication system for performing bidirectional data communication, time division is performed based on the number of downlink user channel allocation requests from a digital communication network to which a base station is connected and the number of uplink user channel allocation requests from a user station. A mode in which a plurality of user channels included in a multiple access frame are allocated to downlink or uplink is changed. Therefore, the mode of allocating a plurality of user channels to downlink or uplink is changed according to each request, and the allocation of the transmission band to the plurality of user stations to which the terminal device is connected is optimized.

Further, in the digital communication system according to the present invention, the total number of downlink user channel allocation requests and uplink user channel allocation requests exceeds the number of user channels included in the time division multiple access frame. In this case, a channel reduction process is performed to adjust the total number of user channel allocation requests to be equal to or less than the number of user channels included in the time division multiple access frame, and to reduce the number of Assign a user channel to downlink or uplink. This channel reduction process is performed, for example, by lowering the priority of a downlink user channel allocation request for a virtual communication channel whose service type does not require real-time service in the digital communication network and has a large allowable delay time. This is performed by calculating the number of channels requested to be allocated based on the minimum number of cells related to the channel allocation request. As a service that does not require the real-time property, there is, for example, an ABR (Available Bit Rate) provided by a digital communication network such as B-ISDN. The ABR service is a service for data that does not need to suppress transmission delays and fluctuations and must guarantee only data quality (no error). Therefore, a limited transmission band is optimally allocated according to the degree of necessity in each case.

In the digital communication system according to the present invention, data communication is performed wirelessly between a base station and a plurality of mobile stations, which are user stations, using a time division multiple access frame format. Connected to Integrated Services Digital Network (B-ISDN). Therefore, for example, when a personal computer is connected to a
In a communication system wirelessly connected to the SDN, it is possible to speed up data transmission and accommodate a large number of personal computers in one network termination device. The present invention is suitable for use in a wireless communication system such as communication between a mobile station and a base station. Of course, the present invention can also be applied to a system for bidirectional communication.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a digital communication system according to the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of a data communication system to which the present invention is applied. In this data communication system, a terminal device (B-TE) is connected via a mobile station (B-RM) and a base station (B-CS). Wireless connection to an asynchronous transfer mode node (ATM node) of a wide area integrated services digital network (B-ISDN). That is, while the B-ISDN ATM node and the B-CS are interfaced by a wired connection at the reference point TB, the B-ISDN
B-TE, which is a terminal device for SDN, is connected to B-TE
Interface to the RM at the reference point SB by wire connection,
A communication system is configured by interfacing B-CS and B-RM by wireless connection. In this system, a plurality of B-RMs can be simultaneously wirelessly connected to one B-CS. Therefore, the function of "B-NT2" is achieved by one B-CS and a plurality of B-RMs. Has been realized.

FIG. 2 shows a configuration of a B-CS and a B-RM. A radio interface using a time division multiple access (TDMA) frame format is provided between the B-CS and the B-RM. , A time division duplex (TDD) communication system is performed. First, the B-CS includes a termination unit 1 of a physical layer (OC-3c) connected to an ATM node and a radio physical layer unit 2 connected to a radio interface. , An ATM layer termination unit 3, a valid cell extraction unit 4, a wireless LLC unit 5, and a wireless MAC unit 6 are provided as downstream communication processing units, and a wireless MAC unit is used as an upstream communication processing unit. 7, a wireless LLC section 8, an idle cell insertion section 9, and an ATM header addition section 10.

Further, the B-CS has a time stamp display cell insertion unit 11 for mounting a cell carrying only a time stamp when there is no data cell to be mounted on the channel of the TDMA frame, and a virtual communication of ATM cells. (VPI / VCI: Virtual Path ID / Virtual Ch)
annel ID) A communication path setting / release / bandwidth management unit 12 for setting or releasing a communication path corresponding to the information in a wireless section;
A signaling VC management unit 13 that performs the same signaling cell processing as the known “B-TN2”, and a known “B-TN2”.
A traffic monitoring / control unit 14 that performs the same traffic control as TN2 ”and a maintenance operation unit 15 that performs the same maintenance function and operation management function as known“ B-TN2 ”are provided. -Setting / opening of communication path in CS
In particular, the band management unit 12 also manages the number of blocks (the number of user channels) of TDMA frames to be allocated to a plurality of B-RMs.

The terminal 1 of the physical layer (OC-3c) is a synchronous digital hierarchy (SDH: Synch) at the reference point TB.
A 155 Mbps optical interface is terminated, and the wireless physical layer unit 2 performs transmission / reception, modulation / demodulation, and synchronization control of a TDMA frame in a wireless section. The ATM layer terminating unit 3 extracts a 53-byte ATM cell, and the valid cell extracting unit 4 extracts only user data by removing invalid cells (idle cells).
At the time of this processing, the valid cell extracting unit 4 adds a time stamp to the cell header.

[0013] The wireless LLC unit 5 and the wireless LLC unit 8 have a logical link control (Logical Link Control) having similar functions.
l) Each virtual communication path (VPI / VCI) has a transmission cell buffer or a reception cell buffer, and performs retransmission control of a transmission error in a wireless section while securing an allowable delay time. When a new cell is stored in the transmission cell buffer for each virtual communication channel, a sequence number is added to the cell header. The wireless MAC unit 6 and the wireless MAC unit 7 have the same function.
ol), the cell from the transmission buffer of each virtual channel is placed on the channel of the TDMA frame, or
The cell on the channel of the A frame is stored in the reception buffer of each virtual communication path. Note that the wireless MAC unit 7
Processing for detecting a transmission error in each block of the DMA frame and returning a retransmission request is also performed.

The idle cell insertion unit 9 inserts an idle cell based on the time stamp information attached to the valid cell, and performs processing for reproducing the cell stream at the reference point TB. The ATM header adding unit 10 deletes the cell header information used in the wireless section such as the time stamp and the sequence number,
A process for reproducing a 3-byte ATM cell format is performed.

Next, the B-RM is provided with a termination unit 21 of the physical layer (OC-3c) connected to the B-TE and a radio physical layer unit 22 connected to the radio interface. An ATM layer terminating unit 23, an effective cell extracting unit 24, a wireless LLC unit 25, and a wireless MAC unit 26 are provided as an upstream communication processing unit between these processing units 21 and 22, and a downstream communication processing unit is provided. A wireless MAC unit 27, a wireless LLC unit 28, an idle cell insertion unit 29, and an ATM header addition unit 30.

The B-RM further includes a time stamp display cell insertion unit 31 for mounting a cell that transmits only a time stamp when there is no data cell to be mounted on the channel of the TDMA frame on the channel, and a virtual communication of the ATM cell. A communication path setting / release / bandwidth management unit 32 for setting or releasing a communication path corresponding to path (VPI / VCI) information in a wireless section, and processing of a minimum number of signaling cells required for establishing a wireless communication path. Signaling VC management unit 33
And a traffic monitoring / control unit 34 that performs the same traffic control as the known “B-TN2”, and the known “B-TN2”.
And a maintenance operation unit 35 that performs the same maintenance function and operation management function as 2 ″.

The terminal 21 of the physical layer (OC-3c)
Terminates a synchronous digital hierarchy (SDH) -based 155 Mbps optical interface at the reference point SB, and the radio physical layer unit 22 transmits and receives the radio section, modulates and demodulates the radio section.
The synchronization of the DMA frame is controlled. The ATM layer terminating unit 23 extracts a 53-byte ATM cell, and the valid cell extracting unit 24 extracts an invalid cell (idle cell) and extracts only user data. At the time of this processing, the valid cell extracting unit 4 adds a time stamp to the cell header.

The wireless LLC unit 25 and the wireless LLC unit 28 are logical link controls having the same function. Each of the virtual communication paths (VPI / VCI) has a transmission cell buffer or a reception cell buffer, and has an allowable delay. Retransmission control of a transmission error in a wireless section is performed while securing time. When a new cell is stored in the transmission cell buffer for each virtual communication channel, a sequence number is added to the cell header. Wireless MAC
The unit 26 and the wireless MAC unit 27 are medium access controls having the same function, and place a cell coming from the transmission buffer of each virtual communication channel on a channel of a TDMA frame or a cell coming on a channel of a TDMA frame. Is stored in the reception buffer of each virtual communication path. In addition, wireless MA
The C unit 26 also detects a transmission error for each block of the TDMA frame and returns a retransmission request.

The idle cell insertion unit 29 inserts an idle cell based on the time stamp information attached to the valid cell and performs a process of reproducing the cell stream at the reference point SB. The ATM header adding unit 30 deletes the cell header information used in the radio section, such as the time stamp and the sequence number, and
A process for reproducing a 3-byte ATM cell format is performed. In each of the above-described B-CS and B-RM, a wireless LLC unit, a wireless MAC unit, a wireless physical unit, a communication path setting / release / bandwidth management unit, a time stamp display cell insertion unit, a traffic monitoring / control unit Constitutes a baseband signal processing unit. A physical layer termination unit, an ATM layer termination unit, an ATM header addition unit, a valid cell extraction unit, an idle cell insertion unit, and a signaling VC management unit
A TM interface unit is configured.

The above-described radio section (wireless interface) between the B-CS and the B-RM is communicated by the TDMA system, and a plurality of channels are multiplexed and transmitted. In addition, uplink (transmission from B-RM to B-CS) and downlink (B-CS
The switching from the transmission to the B-RM) is performed by the TDD method. FIG. 3 shows a configuration of a frame format used in a radio section between B-CS and B-RM. As shown in FIG. 1A, one frame is 19906 bytes in 2 milliseconds, and one frame includes a plurality of multiplexed channels. Each channel is shown in FIG. Has a function.

That is, the A0 channel is a downlink access channel used for notification of allocation of the Cd channel and the C0 to C15 channels, location registration acceptance, and frame synchronization acquisition. The A1 channel is an uplink access channel used for allocation requests, location registration requests, and frame synchronization acquisition of the Cd channel and the C0 to C15 channels. The Cd channel is a downlink control channel used for user channel allocation notification, user channel reception response, C0 to C15 channel reception response, and the like. C0-C1
The five channels are a total of 16 channels, and are uplink control channels used for user channel allocation requests, user channel reception responses, Cd channel reception responses, and the like. The U0 to U29 channels are 30 channels in total, and are uplink and downlink user channels used for transmitting user data cells. Note that the uplink and downlink of the user channels U0 to U29 are dynamically switched in channel units.

In the TDMA frame format used in the present embodiment, the uplink control channels C0 to C15
Is arranged before the downlink control channel Cd,
User channels (half of U0 to U14 in this example) are arranged between these control channels. Such an arrangement of channels speeds up data transmission and reduces the size of the buffer memory for holding data.
Note that the number of user channels arranged between the uplink control channel and the downlink control channel is arbitrary, and the allocation process is terminated between the uplink control channel and the downlink control channel channel as described later. Anything can be given as long as it is given a grace period.

FIG. 4 shows the structure of the above-mentioned user channel in more detail. One user channel is G
(Guard time: processing time for up / down circuit switching control), PR (preamble: processing time for establishing bit synchronization of the demodulation circuit), and UW (unique word:
Processing time for establishing channel synchronization), eight cell slots, and error correction (FEC: Forward Error Correc).
) for parity. Further, each cell slot is an AWA cell (AT for transmitting a wireless section).
M cell is particularly called an AWA cell) and C for error correction
RC (Cyclic Redundancy Check Character). Note that the AWA cell is AT
The format is such that a time stamp and a sequence number are added to the header of the M cell.
Is added, a transmission error can be detected in AWA cell units.

FIG. 5 shows the structure of the downlink control channel Cd in more detail. FIG.
As shown in the figure, the control channel Cd includes a PR (preamble), a UW (unique word), and 16 control information slots Cd0 to Cd15, each of which has a redundant part FE for error correction.
C is added. Note that one control information slot is allocated to one B-RM, and in this example, one B-CS can accommodate 16 B-RMs.

As shown in FIG. 2B, one control information slot contains information on channel allocation (the number UUALOC of the uplink user channel allocated to the B-RM in the next frame, and the next frame). Downlink user channel number DUA assigned to B-RM
LOC), the reception status information of the user channel of the previous frame (information UACK1 indicating the presence or absence of an error for each cell slot of the user channel), and the reception status information of the user channel of the immediately preceding frame (each cell slot of the user channel) Information UACK2) indicating the presence or absence of an error. Therefore, the B-RM can identify the number of the user channel of the AWA cell to be transmitted / received in the next frame based on the information on the channel allocation.

FIG. 6 shows the structure of the upstream control channels C0 to C15 in more detail. Each of the control channels C0 to C15 has the same configuration, and each of the channels has a PR as shown in FIG.
(Preamble), UW (unique word), control information, and a redundant part FEC for error correction. One control channel corresponds to one B
-Assigned to RM.

As shown in FIG. 2B, the control information of one channel includes information on channel allocation (the number UURREQ of uplink user channels to be allocated to the B-RM in the next frame). , Reception status information of the user channel of the previous frame (information UA indicating presence or absence of an error for each cell slot of the user channel)
CK1) and the reception status information of the user channel of the frame before the previous frame (information UACK2 indicating the presence or absence of an error for each cell slot of the user channel). Therefore, based on the information (request) related to the above channel assignment, the B-CS sends the AW to be transmitted / received in the next frame.
It is possible to determine the number of the user channel to which the A cell is assigned.

FIG. 7 shows the configuration of the baseband signal processing section of the B-CS described above in further detail. The main parts of the baseband signal processing unit are roughly divided into an RF unit (wireless physical unit) 2, wireless MAC units 6 and 7, and a wireless L unit.
It comprises LC units 5 and 8. The wireless MAC units 6 and 7 include a TDMA processing unit 40 for performing communication processing of TDMA frames, a U channel receiving unit 41 for receiving and processing uplink user channels, a C0 to C15 receiving unit 42 for receiving and processing uplink control channels, and an uplink access channel. A1 channel receiving unit 43 for performing reception processing, an A0 channel transmitting unit 44 for performing transmission processing for a downlink access channel, a Cd transmitting unit 45 for performing transmission processing for a downlink control channel, a U channel transmitting unit 46 for performing transmission processing for a downlink user channel, An RCCF (Radio Channel Control Function) processing unit 47 is provided. The RCCF processing unit 47
Has various tables which will be described later with reference to FIGS. 11 to 13. The random access management of the access channel, the management management of the control channel, the interpretation and management of the allocation request of the user channel, the management of the allocated user channel are performed. Performs cell transmission / reception management and the like.

The wireless LLC units 5 and 8 include a transmission cell buffer 50 for temporarily storing cells to be transmitted, and a cell transfer processing unit 51 for inputting or outputting to the transmission cell buffer 50.
, 52, a reception cell buffer 53 that temporarily holds received cells, cell transfer processing units 54 and 55 that perform input or output to the reception cell buffer 52, a cell header deletion unit 56 that deletes a routing header of a cell to be transmitted, A cell header adding unit 57 that adds a routing header to a received cell, an LLC processing unit 58 that performs logical link control, and a VPI / VCI conversion unit 59 that performs a virtual communication path conversion process are provided. The transmission cell buffer 50 and the reception cell buffer 53 are managed separately for each virtual communication path.

In this baseband signal processing section, the ATM
When a cell (in this example, a routing header is added for speeding up the processing in this example) is input from the interface unit, the cell is added with a time stamp and a sequence number, and the corresponding virtual communication channel is added. Transmission cell buffer 50
To be stored. Then, under the control of the LLC processing unit 58, the cell stored in the transmission buffer 50 is placed on the corresponding channel, and the BR is transmitted via the wireless MAC unit and the RF unit 2.
Transmit to M wirelessly. On the other hand, the user channel wirelessly received by the RF unit 2 is taken out as a cell by the U-channel receiving unit 41, and the cell is added to the cell header adding unit 57 and then stored in the receiving cell buffer 53 after the routing header is added. At the time of transmission, the U-channel transmission unit 46 adds the CRC of the AWA cell, and at the time of reception, the U-channel reception unit 41 performs a CRC check of the AWA cell, and detects the presence or absence of a transmission error in AWA cell units. You. Also, for a transmission error, retransmission control is performed while securing a transmission delay time that allows the service of the virtual communication path.

FIG. 8 shows the configuration of the above-described B-RM baseband signal processing section in more detail. The main parts of the baseband signal processing unit are roughly divided into an RF unit (wireless physical unit) 22, wireless MAC units 26 and 27,
It comprises wireless LLC units 25 and 28. Wireless M
The AC units 26 and 27 include a TDMA processing unit 60 for performing communication processing of TDMA frames, a U channel receiving unit 61 for receiving and processing downlink user channels, a Cd receiving unit 62 for receiving and processing downlink control channels Cd, and receiving downlink access channels. An A0 channel receiving unit 63 for processing, an A1 channel transmitting unit 64 for transmitting an uplink access channel,
CN transmitting unit 6 for transmitting the uplink control channel
5, a U-channel transmission unit 66 for transmitting an uplink user channel and an RCCF processing unit 67 are provided.
The RCCF processor 67 performs random access management of access channels, management management of control channels, interpretation and management of user channel allocation requests and instructions, cell transmission / reception management of allocated user channels, and the like.

The wireless LLC units 25 and 28 include a transmission cell buffer 70 for temporarily storing cells to be transmitted, a reception cell buffer 71 for temporarily storing received cells, a transmission cell buffer 70 and a reception cell buffer 71. A cell transfer processing unit 72 for inputting or outputting a cell, a cell header deleting unit 73 for deleting a routing header of a cell to be transmitted, a cell header adding unit 74 for adding a routing header to a received cell, an LLC processing unit 75 for performing logical link control, A VPI / VCI conversion unit 76 for converting a virtual communication path is provided. The transmission cell buffer 70 and the reception cell buffer 71 are managed separately for each virtual communication path.

In the baseband signal processing unit, the ATM
When a cell (in this example, a routing header is added for speeding up processing) is input from the interface unit, the cell is added with a time stamp and a sequence number, and the corresponding virtual communication path is added. Transmission cell buffer 70
To be stored. Then, under the control of the LLC processing unit 75, the cell stored in the transmission buffer 70 is placed on the corresponding channel, and the B-cell is transmitted via the wireless MAC unit and the RF unit 22.
Radio transmission to CS. On the other hand, the user channel wirelessly received by the RF unit 22 is taken out as a cell by the U-channel receiving unit 61, and the cell is added to the cell header adding unit 74 by a routing header.
To be stored. When transmitting, the U channel transmitting unit 6
In step 6, the CRC of the AWA cell is added, and upon reception, the U-channel receiving unit 61 checks the CRC of the AWA cell, and detects the presence or absence of a transmission error in AWA cell units. Also, for a transmission error, retransmission control is performed while securing a transmission delay time that allows the service of the virtual communication path.

Next, a description will be given of a user channel allocation process performed in the communication system according to the present embodiment with reference to a channel allocation sequence shown in FIG. When user data to be transmitted from the B-RM (mobile station) to the B-CS (base station) occurs, first, the B-RM uses one of the uplink control channels C0 to C15 to transmit the B-RM. -Send a user channel assignment request to the CS (frame 1). The B-CS that has received the allocation request interprets the allocation request, including allocation requests from other B-RMs, and performs allocation processing for determining a user channel to be allocated to each B-RM.

Although this allocation process requires several hundred microseconds, it takes approximately 1 millisecond to perform transmission / reception processing for the user channels U0 to U14 following the frame (frame 1). The assignment process ends while the transmission / reception process is being performed. Therefore, the user channel number determined in response to the allocation request is notified (allocation instruction) to the requesting B-RM using the downlink control channel Cd of the same frame (frame 1).

The B-RM that has received the assignment instruction performs a process of putting the user data on the assigned user channel. Although this process requires several hundred microseconds, the user channel U of the previous frame (frame 1)
Since it takes about 1 millisecond to perform the transmission / reception processing of 15 to U29, the processing of placing the user data on any of the user channels C0 to C15 is completed during the transmission / reception processing. Therefore, the user data is wirelessly transmitted by the next (frame 2). in this way,
When user data to be transmitted occurs and a user channel assignment request is transmitted, the user data can be transmitted in the next frame, and the data transmission can be performed while suppressing the time required until the actual transmission of the user data. Can be done quickly.

The B-CS performs the above-described uplink user channel allocation processing as well as the downlink user channel allocation processing from the B-ISDN, and these allocation processing is mainly performed by the B-CS RCCF processing unit 47. 10 to 13
14 is performed using the table shown in FIG.
First, as shown in FIG. 10, the RCCF processing unit 47 has four work areas (A, B, C, and D planes) called a channel allocation table. It manages how user channels are allocated in the four TDMA frames.

That is, each surface of the allocation table always corresponds to four consecutive frames (the last frame, the previous frame, the current frame, and the next frame), and 30 surfaces in the corresponding frame in each surface of the allocation table. Manage how user channels are allocated. The table pointer is updated between "0" and "3" to always indicate the table corresponding to the current frame among the four allocation tables. Therefore, the table pointer is updated to the next plane when the assignment of the user channel for one frame is completed.

FIG. 11 shows one aspect of the above allocation table in detail. The allocation table is divided into 30 areas corresponding to user channels U0 to U29, and each area has an allocation type, a B-RM number, and 8 user channels.
8 virtual communication channel numbers (V
C number) is set. The above-mentioned allocation types include “unassigned (0)”, which indicates a state where allocation to uplink and downlink is not performed, “uplink (1)”, which indicates allocation to uplink user data, and downlink users. One of "down (2)" indicating that data is allocated is set.

In the B-RM number, a number for identifying the B-RM to which the user channel is assigned is set.
In this example in which 16 B-RMs are accommodated in one B-CS,
One of “0” to “16” is set as the B-RM number. The VC number is set when the user channel is assigned to the downlink, and the VC number is set to the virtual channel number of the cell placed in the cell slot.

The RCCF processing unit 47 has a work area called a downlink VC management table as shown in FIG. 12, and uses this table to reduce the number of cells requested to be allocated to the downlink and to determine the number of downlink user channels. Manage how is assigned. 16 B-Rs for 1 B-CS
In this example accommodating M, the downlink VC management table is BR
It has 16 areas corresponding to M numbers “0” to “15”, and in each area, all VC numbers that have a virtual communication path (connection) with the B-CS are registered.
Then, a service type, an allowable delay time, the number of cells requested for transmission, and the number of cells that can be transmitted are respectively set for each VC number, and the request state of the downlink user channel is set to each R-number.
It is managed for each RM and for each virtual communication path.

The virtual communication path is allocated when a connection is set, and a unique number for identifying this virtual communication path is set in the VC number. In the service type, a type of service provided by the B-ISDN is set, and a service (Constant Bit Rate:
CBR that provides fixed-rate service, a service that allows the transmission bandwidth to be narrowed according to the amount of communication data (Variable Bit Rat)
e: variable speed service), or ABR that provides a service that does not require real-time capability. The service type is notified by the ATM interface unit to the RCCF processing unit 47 when the connection is set. A decision is made based on the parameters of the 2931 signaling information, and the decision result is set.

The maximum allowable transmission delay time is set in the allowable delay time.
Q. notified to the RCCF processing unit 47 from the interface unit. It is determined and set based on the parameters of the 2931 signaling information. Further, the number of cells requested to be transmitted is set to the number of cells to be transmitted in the next frame for each virtual communication channel when allocating a user channel, and the number of cells is transmitted to the notification from the LLC processing unit 58 of the B-CS. It is set based on. The number of transmittable cells is set to the number of cells permitted to be transmitted in the next frame for each virtual communication channel as a result of user channel allocation.
The value of the number of transmittable cells is notified to the LLC processing unit 58 of the B-CS, and actual downlink transmission of cells is performed according to this value.

The RCCF processing unit 47 has a work area called an uplink VC management table as shown in FIG. 13, and uses this table to determine the number of cells for which the B-RM has requested uplink transmission and the number of cells to be transmitted. Manages the number of cells that have been authorized. In this example in which 16 B-RMs are accommodated in one B-CS, the uplink VC management table stores the B-RM number “0”.
16 areas corresponding to .about. "15". Each area has a maximum number of transmission request cells, a minimum number of transmission request cells,
The number of transmittable cells is registered, and the required state of the uplink user channel is managed for each R-RM.

In the above-mentioned maximum transmission request cell number, the number of necessary and sufficient cells to be transmitted in the next frame is set.
This value is "UU" of the uplink control channels C0 to C15.
MAXREQ "from each B-RM. In addition, the minimum required number of cells to be transmitted is set to the minimum necessary number of cells to be transmitted in the next frame, and this value is set to" 1 "for the uplink control channels C0 to C15. UUMINRE
Q "is notified from each B-RM. Note that the maximum transmission request cell number includes the ABR cell number for the service type that does not require the real-time property, but the minimum transmission request cell number includes this type of service type. The number of cells is not included, and the difference in the number of cells according to this type is determined on the B-RM side and notified by the control channels C0 to C15.

As the number of transmittable cells, the number of cells that can be transmitted for each B-RM is set as a result of user channel allocation. The actual transmission to the uplink of the cell is performed according to the number of cells, and the value obtained by converting the number of cells into the number of channels is "UUA" of the downlink control channel Cd.
LOC ", and the B-RM executes uplink transmission of the cell according to this value.
The user channel allocation process performed by the F processing unit 47 using each of the above tables will be described with reference to FIG.

This allocation process is started every time the uplink control channels C0 to C15 of each frame are received. First, the number of transmission request cells for each virtual communication path is received from the LLC processing unit 58 of the B-CS. The value is set to the number of transmission request cells and the number of transmittable cells in the downlink VC management table (step S1). Then, the value of "UUMMAXREQ" of the uplink control channels C0 to C15 is set to the maximum number of transmission request cells and the number of transmittable cells in the uplink VC management table for each B-RM, and the value of "UUMINREQ" is set to B-RM. Each time, it is set to the minimum transmission request cell number in the uplink VC management table (step S2).

Next, the number of transmission request cells set in the downlink VC management table is added to calculate the number of user channels required for data transmission for each B-RM (step S3). That is, in the present example having eight cell slots for each user channel, one channel is required when the number of transmission request cells is eight or less, two channels when nine or more cells are 16 cells or less, and so on. Convert the number of cells to the number of channels. Then, the maximum transmission request cell number set in the uplink VC management table is added to calculate the number of user channels required for data transmission for each B-RM (step S4). The process of converting the number of cells into the number of channels is performed in the same manner as described above.

Next, the number of user channels required for uplink and downlink calculated above is added, and one TDM
The total number of user channels requested in the A frame is calculated (step S5). In this example, since one frame includes 30 user channels U0 to U29, it is determined whether the calculated total number of requested user channels is 30 or less (step S6).
It is determined whether the request of the user channel can be satisfied in one frame. As a result, when the calculated total number of requested user channels is 30 or less, all data requested in a certain frame can be transmitted, so that user channels U0 to U29 are sequentially allocated to requests. Then, this allocation mode ("up" or "down") is set as the allocation type of the allocation table (step S8). If the calculated total number of requested user channels is less than 30, and there are remaining user channels U0 to U29, "not allocated" is set as the allocation type of the user channel.

Next, the downlink control channel Cd
Using “UUALOC” and “DUALOC”, the user channel assigned to each B-RM is notified (step S9), and the number of transmittable cells is notified to the LLC processing unit 58 (step S10). Then, the table pointer for the channel allocation table is updated, the processing is temporarily terminated (step S11), and the processing waits until the uplink control channels C0 to C15 of the next frame are received. Here, each of the B-RMs and the Ls notified
The LC processing unit 58 performs data transmission processing for the next frame in accordance with the notified content of the channel assignment, and executes bidirectional communication between each B-RM and the B-CS. Therefore, the assignment mode of the user channels in the frame is appropriately changed according to the request of each case, and the assignment of the transmission band is optimized.

Here, in the above judgment (step S
6) If the calculated total number of requested user channels exceeds 30, all data requested in a certain frame cannot be transmitted, so the following process of reducing the number of requested channels (step Perform S7),
After reducing the total number of requested user channels for a certain frame to 30 or less, the above-described processing after step S8 is performed. In the process of reducing the number of requested channels, “downstream V
With reference to the C management table, a VC whose service type is ABR and whose allowable delay time is large is extracted, and the number of transmittable cells of the VC is channel unit (that is, a multiple of 8 including 0). Reduce. "," The value of the minimum transmission request cell number is set to the number of transmittable cells in the uplink VC management table. , And the total number of requested user channels is reduced to 30 or less.
Note that the priority of the transmission process is lowered for the reduced cell (channel), and the cell (channel) is further transmitted in the next frame. Therefore, a limited transmission band is optimally allocated according to the degree of necessity in each case.

[0052]

As described above, according to the present invention,
Since the mode of channel assignment is dynamically changed according to the actual situation of the user channel request, data transmission is performed when performing bidirectional data communication by time division duplex between the base station and a plurality of user stations. And a large number of information terminal devices can be accommodated in one network termination device. Further, the present invention provides a communication system which performs two-way communication between a mobile station as a user station and a base station by radio, and connects to a B-ISDN via the base station to speed up data transmission and achieve 1 A large number of information terminal devices can be accommodated in one network terminating device.
N.

[Brief description of the drawings]

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

FIG. 2 shows a B-RM and a B-CS according to an embodiment of the present invention.
FIG.

FIG. 3 is a diagram illustrating a configuration of a TDMA frame format according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating a configuration of a user channel according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating a configuration of a downlink control channel according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration of an uplink control channel according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a configuration of a baseband signal processing unit of a B-CS according to an embodiment of the present invention.

FIG. 8 is a diagram illustrating a configuration of a baseband signal processing unit of a B-RM according to an embodiment of the present invention.

FIG. 9 is a diagram showing a sequence of a user channel assignment process according to an embodiment of the present invention.

FIG. 10 is a diagram illustrating a channel allocation table pointing process according to an embodiment of the present invention.

FIG. 11 is a diagram illustrating a configuration of a channel allocation table according to an embodiment of the present invention.

FIG. 12 is a diagram showing a configuration of a downlink VC management table according to an embodiment of the present invention.

FIG. 13 is a diagram showing a configuration of an uplink VC management table according to an embodiment of the present invention.

FIG. 14 is a flowchart illustrating a procedure of a user channel assignment process according to an embodiment of the present invention.

[Explanation of symbols]

B-TE ... B-ISDN information terminal device, BR
M: mobile station, B-CS: base station, C0 to C15
... Uplink control channel, Cd ... Downlink control channel, U0 to U29 ... User channel,

Claims (4)

[Claims] 1. A digital communication system in which a base station is connected in a digital communication system for performing bidirectional data communication by time division duplex using a time division multiple access frame between a base station and a plurality of user stations. Change the mode of allocating a plurality of user channels included in a time-division multiple access frame to the downlink or uplink based on the number of allocation requests for downlink user channels from the base station and the number of allocation requests for uplink user channels from the user station. A digital communication system characterized by: 2. The digital communication system according to claim 1, wherein the total number of downlink user channel allocation requests and uplink user channel allocation requests is the number of user channels included in the time division multiple access frame. If it exceeds the priority, the service type of the digital communication network does not require the real-time property and the priority of the downlink user channel allocation request for the virtual communication path having a large allowable delay time is lowered, thereby allocating the user channel. Digital communication characterized in that the total number of requests is adjusted to be equal to or less than the number of user channels included in the time division multiple access frame, and a plurality of user channels included in the time division multiple access frame are assigned to downlink or uplink. method. 3. The time division multiple access frame according to claim 1, wherein the total number of the number of downlink user channel allocation requests and the number of uplink user channel allocation requests is included in the time division multiple access frame. When the number of user channels is exceeded, the total number of user channel allocation requests is calculated by calculating the number of channels requested to be allocated based on the minimum number of cells related to the uplink user channel allocation request. A digital communication system characterized in that the number of user channels is adjusted to be equal to or less than the number of user channels included in the time division multiple access frame, and a plurality of user channels included in the time division multiple access frame are allocated to downlink or uplink. 4. The digital communication system according to claim 1, wherein data is wirelessly transmitted between a base station and a mobile station as a user station by using a time-division multiple access frame format. A digital communication system for performing communication, wherein the base station is connected to a wide area integrated service digital network.