JP2002171573A - Mobile communication system and mobile terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mobile communication system where no throughput is deteriorated due to collision among reservation control packets. SOLUTION: A mobile terminal 5 having a transmission request transmits a reservation packet through a reservation channel 7 by means of the CDMA system and a base station 4 uses a reply packet outputted to a reply channel 8 to assign a transmission channel 9 and a time slot available by a mobile terminal of a request source. The reserved channel employs short spread codes corresponding to a matched filter 70. Thus, when the mobile terminal adopting the CDMA system transmits the reservation packet, since the base station can independently extract the reservation packets having deviated timings even on the occurrence of the reservation packets in temporally duplicated state and no re-transmission of the reservation packets due to collision is required, the system can enhance the throughput.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system and a mobile terminal device, and more particularly to a code division multiple access (CDMA).
The present invention relates to a mobile communication system and a mobile terminal device of a reservation system to which the system is applied.

[0002]

2. Description of the Related Art Conventionally, for example,
Transactions on Communications, Packet Switching in Radio Channels: Part 3-Polling and (Dynamic) Split-Channels Reservation Multiple
Access, COM-24, 8 (1976) pp. 832-845 (IEEE Transactions on Communications,
Packet Switching in Radio Channels: Part3-Polling a
nd (Dynamic) Split-Channel Reservation Multiple Ac
cess, COM-24, 8 (1976) pp. 833-8
45) (hereinafter referred to as prior art 1), as described in the related art 1, frequency division multiple access (FDMA).
2. Description of the Related Art There is known a communication system in which reservation type access control is desired to be performed by a sion multiple access method.

In the reservation type access method, a mobile terminal having a data transmission request reserves a transmission channel to a base station using a reservation control packet, and the base station determines a transmission channel to be assigned to the terminal and a transmission timing (time slot). And notifies each terminal of a transmission channel and a time slot to be used by a response control packet. According to this method, basically, no packet collision occurs in the transmission channel. Other examples of the communication system of the reservation type access control include, for example,
No. 311160 (hereinafter referred to as prior art 2) discloses a time division multiple access (TDMA).
ccess) method has been proposed. On the other hand, FP
LMTS (Future Public Land Mobile Telecommunicat)
As a standard system of ion systems, a code division multiple access (CDMA) system is promising. A CDMA mobile communication system includes:
For example, Japanese Unexamined Patent Publication No. 7-38496 (hereinafter referred to as prior art 3)
It is proposed in).

[0004]

However, in the mobile communication system of the reservation type access system using FDMA and TDMA proposed in the prior arts 1 and 2, each mobile terminal uses the reservation control channel asynchronously with the reservation control channel. Since a packet is transmitted, there is a high possibility that a plurality of reservation control packets collide, and retransmission of the reservation control packet due to the collision is repeated, which is a factor of deteriorating the throughput of the entire system. On the other hand, the prior art 3 employing CDMA does not give particularly effective information on the above problem in the reservation-type access control.

An object of the present invention is to solve the problem of collision of reservation control packets in a mobile communication system of a reservation type access control system, and to provide a mobile communication system and a mobile terminal device with high throughput. Another object of the present invention is to solve the problem of reservation control packet collisions in a mobile communication system of a reservation type access control method, and to provide a mobile communication system and a mobile terminal device with high throughput.

[0006]

In order to achieve the above object, in a mobile communication system according to the present invention, an uplink data from a mobile terminal to a base station is provided in a radio communication section between the base station and the mobile terminal. A plurality of transmission channels used for transmitting packets and downlink data packets from the base station to the mobile terminal, and a reservation used for transmitting a reservation control packet indicating a transmission channel allocation request from the mobile terminal to the base station. A channel and a response channel used to transmit a response control packet indicating a transmission channel to transmit and receive data from the base station to the mobile terminal are provided. Each of the reservation, response and transmission channels includes a CDM.
A spread spectrum by the A method is applied, and a mobile terminal having a data transmission request transmits a reservation control packet to the reservation channel at an arbitrary timing, and the base station transmits a response control packet to the response channel. A transmission channel and a time slot to be used by the mobile terminal are specified, and each mobile terminal transmits and receives a data packet in a specified time slot on the transmission channel specified by the response control packet. It is characterized by.

More specifically, each of the reservation, response, and transmission channels is assigned a unique spreading code, for example, a pseudo noise (PN). Allocate a shorter spreading code than the transmission channel. The base station identifies, using a matched filter, signals of a plurality of reservation control packets transmitted from a plurality of mobile terminals with time overlap with each other, and performs a bit signal reception process for each packet. According to a preferred embodiment of the present invention, upon receiving a reservation packet from a mobile terminal, the base station allocates a time slot in each transmission channel by schedule control, and transmits the result to each mobile terminal in a response control packet. Notice. Further, in order to regulate the total amount of simultaneously communicated packets, the base station periodically transmits a busy tone signal according to traffic conditions, and each mobile terminal having a data transmission request responds to the busy tone signal. The reservation packet transmission control is performed. Note that a plurality of response channels may be prepared in the wireless section, and a response channel to be received for each mobile terminal may be designated.

According to the present invention, a time slot is defined for a transmission channel, and each mobile terminal transmits and receives data in a specific time slot designated by a base station. Since a mobile terminal having a data transmission request transmits a reservation control packet at an arbitrary timing without providing a time slot, a transmission operation of a reservation control packet in each mobile terminal is facilitated. Also, each mobile terminal spreads the spectrum of the reservation control packet with a spreading code having a shorter cycle than the data packet transmitted on the transmission channel, and the base station receives the signal of the reservation channel by a matched filter. In this case, even if two or more control packets spectrally spread by the same spreading code partially overlap on the time axis, if there is a timing shift of one chip or more on the spreading code between each packet, the matched filter Since the received packet can be identified, even if a plurality of mobile terminals each generate a reservation control packet at an arbitrary timing,
It is very unlikely that they will be unreceivable due to collision.

[0009]

FIG. 1 shows an example of a configuration of a mobile communication network to which the present invention is applied. 1 is a public network accommodating fixed terminals 3 such as telephones, and 2 is a plurality of base stations 4 (4
a, 4b,...) and is a mobile communication network connected to the public network, and each base station 4 is a mobile terminal 5 (5a, 5b,...) located in a respective service area (cell).
And communicates with the wireless channel 6. Note that, on a wireless channel, CDMA packet transmission suitable for communication of multimedia information in which data, sound, and images are mixed is applied.

FIG. 2 shows a transmission / reception protocol of the wireless communication system according to the present invention. FIG. 2A shows a protocol of a call setup process. There are two types of call setup processing. One is a process of first assigning a local ID (local address) in the service area to the wireless terminal, and the other is a process of assigning another destination terminal to the wireless terminal. This is a process for assigning a link number for communicating with. The local ID is an address number shorter than a unique address number given to each wireless terminal in advance, and the packet length can be reduced by using the local ID. Link numbers have a similar effect.

The procedure of the call setup process is common to both the above-described assignment of the local ID and the assignment of the link number, and the transmitting terminal uses the reservation channel 7 to send a control packet for call setup reservation to the base station. 10a
And the base station uses the response channel 8 to send a call setup response control packet 11a to the transmitting terminal.
Send Address information indicating a transmission source is set in the reservation control packet 10a. In the response control packet, a transmitting terminal address to perform a receiving operation and a time slot on the transmission channel 9 to perform a receiving operation are specified. As a result, the transmitting terminal specified by the response control packet includes the location registration information (local ID number) or the link information (link number) transmitted by the base station in the specified time slot on the transmission channel 9. The data packet 12a for call setup is received. If the control packet has a margin, the location registration information or the link information can be transmitted and processed by the call setup response control packet 11a without using the call setup data packet 12a.

The reservation, response, and transmission channel are selected according to the PN code to be applied. In addition, the assignment of the time slot on each transmission channel by the base station is performed, for example, by referring to a management table and selecting from available channels.
Scheduling is performed so as to allocate a vacant slot closest in time after the transmission slot of the response control packet.

FIG. 2B shows a protocol for information transmission. Each transmitting terminal having a data transmission request uses the reservation channel 7 to transmit the reservation control packet 10b to the base station. In response to this, the base station transmits the response control packet 8b to the transmitting terminal using the response control channel 8, and specifies the transmission channel 9 and the time slot that the transmitting terminal should use for the transmission operation. Upon receiving the response control packet 11b addressed to itself, each transmission terminal that has transmitted the reservation packet receives the response control packet 11b, and
The data packet 12b for information transmission is transmitted to the base station by using a specific time slot in the data packet.

The data packet 12b is received once by the base station. The base station checks the destination address of the data packet. If the destination terminal (receiving terminal) is a mobile terminal located in the service area, the base station utilizes the response channel 8 to communicate with the receiving terminal using a transmission channel to be operated. Then, after transmitting the control packet 13 specifying the time slot, the reception packet 12b from the transmitting terminal is transferred in the specified time slot. The receiving terminal receives the data packet 14 transferred by the base station in the time slot of the transmission channel 9 specified by the control packet 13.

According to the information transmission protocol described above, a control packet for reservation is required for uplink data transfer from a mobile terminal to a base station, but downlink control data is required for downlink data transfer from a base station to a mobile terminal. Does not require a control packet for reservation. The base station gives a reference timing in the transmission / reception operation to each mobile terminal by the pilot signal, and each mobile terminal can receive the data packet 14 for information transmission from the base station and the pilot signal with the same delay time. Therefore, if the pilot signal is referred to, the synchronization of the data packet can be easily performed.

FIG. 3 shows an access control method in a conventional reservation type wireless communication system. The reservation method is shown in FIG.
As described above, prior to transmission of a data packet for information transmission, a reservation packet is transmitted, and a data packet is transmitted after a reservation is established. A response channel 8 is provided. Channel division is performed by frequency division (see prior art 1) or time division (see prior art 2).

In FIG. 3, time 21 is shown on the horizontal axis. When the wireless terminal transmits a control packet for reservation to the base station on the reservation channel 7, the base station performs scheduling 24 of time slots on the transmission channel, and indicates the reservation result to the wireless terminal using the response channel 8. Send a control packet. According to the conventional method, there is a possibility that reservation packets from a plurality of mobile terminals collide on a reservation channel, as shown by 22a and 22b. After transmitting the reservation control packet, if each phase terminal does not return a response control packet addressed to itself after a certain period of time, it determines that a collision has occurred on the reservation channel, and The control packet is retransmitted (23a, 23b). The throughput of the reservation method is limited depending on the above-described collision of reservation packets.

FIG. 4 shows that the reserved channel according to the present invention has a CD.
An access control method based on MA (Code Division Multiple Access) is shown. The present invention is different from the conventional reservation system in that access control of the reservation control channel is performed by the CDMA system (see Prior Art 3). In the reserved channel 7 shown in FIG. 3, the horizontal axis represents time 21 and the vertical axis represents the transmitting terminal 25, and represents a situation where reserved packets from a plurality of terminals are partially overlapped and transmitted on the time axis. I have. In the CDMA system, spectrum spreading is performed by replacing each symbol ("1", "0") of transmission data with a spread code (orthogonal code or PN code) of a plurality of chips having a channel-specific pattern. . For example, in the direct spreading method, when a plurality of transmitting terminals spread spectrum data using the same PN (Pseudo Noise, pseudo noise) sequence and transmit data at the same carrier frequency, 1
If there is a time lag of more than a chip, the receiving side can identify each transmission data independently.

In the present invention, CDMA packet communication is applied to a reservation channel, and a control packet for reservation is transmitted to a plurality of mobile terminals at an arbitrary timing.
If the transmission timings of the reservation control packets from a plurality of terminals completely match, it means that the packets have collided, but such perfect match is rare and usually 26 (26
As shown by a and 26b), even if they are temporally overlapped, if two packets have a timing difference of one chip or more, collision has been avoided and retransmission is not necessary.
Therefore, according to the method of the present invention, the throughput is remarkably improved as compared with the conventional reservation method.

In the present invention, each mobile terminal having a data transmission request transmits a control packet for reservation of a transmission channel time slot at an arbitrary timing on a reservation channel, and transmits a response control packet transmitted by a base station on a response channel. The transmission data is transmitted in the specified time slot of the transmission channel specified by. Data transmission is performed in units of time slots in principle, and when transmission data extends over a plurality of time slots, a reservation is made for each time slot. However, in order to impose an efficient reservation process, one reservation control packet is used. The transmission channel of a plurality of time slots is made reservable, and the base station responds to one reservation control packet with one response control packet or a plurality of response control packets for each time slot. A time slot may be assigned.

In the present invention, the reservation packet is allowed to be transmitted at an arbitrary timing, but the transmission and reception of the response control packet and the information transmission data packet are synchronized with a predetermined fixed time slot. Do. By dividing the response channel and each transmission channel into time slots having a fixed length, high-speed synchronization between each wireless terminal and the base station is facilitated. That is, the base station continues to transmit a pilot signal generated by spread spectrum using a PN sequence having an appropriate period on a common channel (pilot channel), and each wireless terminal monitors the pilot signal to generate a synchronization signal. (Reference signal) is extracted, and a time slot synchronized with the base station is set in the response channel and each transmission channel. Since the pilot signal is intended for synchronizing the spreading code, the content of the transmission information may be anything. Therefore, instead of using a dedicated pilot channel, the pilot signal can use, for example, a control channel for response.

FIG. 5 shows a format of a packet used in the mobile communication system of the present invention. As shown in FIG. 5A, the reservation control packet includes, in order from the beginning, a preamble 31a for acquiring synchronization, and a reservation type 432b indicating the type of the packet (for position registration, link securing, and information transmission). , A source address 33 (use a local ID if the location is already registered), a destination address 34 (use a link number if a link is already secured), the number of transmission packets (time slot number) 35 to be reserved, and a CRC (error detection code). Cy
clic Redundancy Check) 36a. It should be noted that the number of transmission packets is not required in location registration or call setup processing for link securing.

As shown in FIG. 5B, the response control packet includes, in order from the beginning, a destination address 34, a packet type (for position registration, for link securing, for uplink information transmission, and for downlink information transmission). ), A PN type 37 representing the assigned spreading code of the channel, timing information 38 representing the assigned transmission timing, and a CRC 36b. In the present invention, the response control packet does not require a preamble. This is because each mobile terminal (wireless terminal) constantly monitors a pilot signal, synchronizes each time slot in a response channel, and can capture each response packet based on the pilot signal. As shown in FIG. 5C, the data packets for information transmission are, in order from the beginning, a preamble 31b, a packet type (for position registration, link securing, uplink information transmission, and downlink information transmission) 32c, and transmission. Source address 33 (use local ID if location registered), destination address 34 (use link number if link secured), data 39 (PN code of information transmission channel or response control channel, transmission or reception timing , Transmission information) and a CRC 36c.
Since the response control channel and the information transmission channel are time-slotted, it is necessary to standardize the packet size to a fixed length even if the packet type is different. For this purpose, for example, a dummy bit is inserted into an address portion located in front of each packet, and the start position of each field thereafter is adjusted. In the downlink communication, the preamble can be omitted as in the case of the response control packet.

FIG. 6 is a block diagram showing a schematic configuration of the base station 4. As shown in FIG. The base station includes an antenna 41 and CDMA
It comprises a transmitting / receiving unit 50, a packet control unit 90, and a BSC interface 42 connected to a control device (BSC 43) interposed between the base station and the mobile communication network.

FIG. 7 is a block diagram showing a detailed configuration of the CDMA transceiver 50 of the base station. Reference numerals 52 and 53 denote wireless modules for reception and transmission, respectively, which perform modulation / demodulation of a baseband signal and transmission / reception processing at a high / intermediate frequency. The response control packet transmitted by the base station is input to the encoding circuit 58a via the response channel signal line 45a, and after performing encoding for error correction using, for example, a convolutional code, the multiplier 56a In, the spectrum is spread by the orthogonal code for the response channel output from the orthogonal code generator 59 and input to the adder 60. Similarly, the transmission data output to the plurality of signal lines 45b corresponding to the transmission channels is coded by the coding circuit 58b, spread in the multiplier 56b with the orthogonal codes corresponding to the respective transmission channels, and then added. Is supplied to the vessel 60. The pilot signal output to the signal line 45c is also coded by the coding circuit 58c, and spectrum-spread by the multiplier 56c with the orthogonal code unique to the pilot channel, and then supplied to the adder 60. The output of the adder 60 is spread in a multiplier 56 by a PN (long code) unique to each base station, which is output from a PN generator 57a, and then transmitted by the transmission radio module 53.
Supplied to

On the other hand, the signal received and processed by the receiving wireless module 52 is supplied to a matched filter 70a for a reserved channel and a plurality of matched filters 7 for a transmission channel.
0b to 70b '. The received packet of the reserved channel is subjected to despreading processing of the received signal by the matched filter 70a using the PN unique to the reserved channel, and is received by the packet separating circuit 80 by separating packets having a temporal overlap. . In this case, as described later in FIGS. 8 and 9, if the period of the PN sequence applied to the despreading is set equal to the number of taps of the matched filter, the output of the matched filter becomes the result of the despreading process. High-speed synchronization becomes possible. The reserved packets separated from each other are output to the decoding circuit 55a.
For example, after decoding with error correction such as Viterbi decoding,
It is supplied to the packet control unit 90.

The received signal of the transmission channel is first subjected to synchronous acquisition in matched filters 70b to 70b ', and thereafter, the PN generator 57b generates a PN sequence corresponding to each channel starting from the acquired timing. , Multipliers 56 to 56 ', and the received signal and the P corresponding to each channel generated from the PN generator 57b.
Despreading is performed by multiplying the N series, deaccumulation results for one symbol are accumulated in accumulators 54 to 54 ', and the accumulation results are supplied to packet control unit 90 via decoding circuits 55 to 55'.

FIG. 8 shows a process of receiving a reservation control packet by the matched filter 70a. (A) of the figure is a principle diagram of a matched filter. The matched filter is
It comprises a plurality of delay elements 71 connected in multiple stages having a delay time T equal to the chip width of the PN series, and a plurality of coefficient multipliers 72 provided for the input tap of the first stage and the output tap of each delay element, The received signal input for each chip time propagates between the taps with a delay time T71. Therefore,
If the delay time of each delay element is made equal to the chip width of the PN sequence for the reserved channel, and the period length (number of chips) of the PN sequence is made equal to the number of taps of the matched filter, the first chip of the input signal becomes the rightmost output. At the time when the tap is reached, the PN sequence for one cycle is simultaneously visible in the tap output. Each tap output and the binary PN code (“1” or “−”) for the reserved channel set in each coefficient multiplier 72
1 "), and the sum is obtained by the accumulator 73 and output as a correlation value. The point in time at which the correlation value that changes after the chip time reaches the peak value is the time of synchronization acquisition. Also, the output value at this time indicates a demodulated value obtained by inverse spectrum spreading the received signal. In the present invention, the spreading code length and the number of taps of the matched filter are made equal so that the output value of the matched filter is information (symbol code) for one bit of the reserved packet. In addition, by applying a short code as a PN sequence for the reserved channel, the number of taps of the matched filter is reduced, and synchronization supplementation is facilitated.

FIG. 12B is a diagram showing an operation of identifying a reserved packet by the matched filter 70a in a case where two reserved packets A and B are partially overlapped on the time axis and issued. is there. Starting from the point in time when the output of the accumulator 73 shows the peak value (synchronization supplementary point), P
By grouping the subsequent filter output signals appearing in the accumulator 73 at N periods (symbol periods), a bit data string belonging to the same reserved packet can be reproduced. In the illustrated example, the signal value (“1”) that starts from the first peak value 75-1 and that appears every PN period 75 thereafter
Or "-1") 76-2, 76-3, 76-4, ...
Are collected as one bit data group, the reservation packet (A) 76 can be reproduced. Further, starting from the peak value 77-1 appearing asynchronously with the bit data group, signal values (“1” or “−1”) 77-2, 77-3, 77-4, ... 1
When collected as one bit data group, the reservation packet (B) 77 can be reproduced. As a result, even if packets are temporally overlapped, in principle, if there is a phase shift of one or more chips, they can be identified as separate packets.

FIG. 9 shows one of the configurations of the packet separating circuit 80.
Here is an example. An output signal 79a of the matched filter 70a is input to an absolute value circuit (ABS) 81, and is output from a comparator 83a.
The absolute value of the matched filter output signal 79a is compared with a predetermined threshold output from the threshold circuit 82. When the absolute value is larger than the threshold, the output of the comparator 82 is turned on ("1" state) and input to the AND circuit 84a. Other input signals of the AND circuit 84a are off in the initial state, and are inverted and input. Therefore, the AND circuit 84a is opened by the output of the comparator, and its output signal is turned on ( "1" state). The ON output of the AND circuit 84a is output from the AND circuit 84b.
And 84d.

In the AND circuit 84b, a negative signal of the output of the timer 85a is input to the other input terminal. In the initial state, the output of the timer 85a is off ("0"), so that when the output of the AND circuit 84a turns on, the output of the AND circuit 84b also turns on. The ON output of the AND circuit 84b is
The value of the counter 87 is input to the timing register 86a as an enable signal. At this time, the value of the counter 87 that counts in the chip cycle of the PN code and returns to the initial value in the symbol cycle is set in the register 86a. Note that the output value of the counter 87 indicates the chip position (synchronous capture timing) at the time of synchronization capture described in FIG. 8B.

The ON output of the AND circuit 84b is given by
A timer 85a for controlling the other input of the D circuits 84b and 84d is started. The timer 85a keeps its output on until one packet period of the reservation packet elapses, closes the AND circuit 84b until this period elapses, and stores another counter value in the timing register 86a. To be set. When the next peak value is output from the matched filter before the timer 85 times out, the ON output output from the AND circuit 84a is output to the AND circuit 84d which is open by the output of the timer 85a and the next output. Timing register 86b
The signal is input to an enable terminal of the next timing register 86b via an AND circuit 84b 'paired with the timing register 86b. As a result, the output value of the counter 87 is set in the timing register 86b. At this time, the timer 85b paired with the register 86b is started, and by the same operation as the above-described timer 85a, setting of another value to the register 86b is prohibited until one packet period elapses. The generated enable signal is further stored in the next register 8.
6c. In this embodiment, since four timing registers 86a to 86d are provided,
Hereinafter, by repeating the same operation, the synchronization acquisition timing is stored for four packets in the order of occurrence among a plurality of reserved packets that are generated in time overlap.

The value of the synchronization acquisition timing set in the timing register 86a is compared with the output value of the counter 87 in the comparator 83b, and each time the counter value matches the synchronization acquisition timing set in the timing register 86a. , The output of the comparator 83b is turned on.
The ON output of the comparator is output through the AND circuit 84c which is open while the timer 85a is ON.
The data is input to the enable terminal of the data register 87a.
As a result, the output of the matched filter at the synchronization acquisition timing is input to the data register 87a. The other timing registers 86b to 86d operate in the same manner as described above, and the output of the matched filter for each reserved packet is stored in the data registers 87b to 87d. Since data is input to the data registers 87a to 87d in accordance with the synchronization capture timing of each reservation packet, these data registers 87a to 87d are synchronized with the clock of the bit cycle generated by the clock generation circuit 88.
d is transferred to the output registers 88a to 88d, and the decoding circuit 5 shown in FIG.
The received data of each reservation packet is transferred to 5a.

FIG. 10 shows the packet control unit 90 of the base station 4.
The detailed configuration of is shown. The packet control unit 90 has a digital signal processor (DSP) 91. After the received data (contents of the reserved packet) of the reserved channel is decrypted by the decryption routine 92 of the DSP 91, it is transmitted by the uplink schedule control routine 93. , A transmission channel and a time slot are allocated (scheduled). The transmission channel and the time slot determined by the uplink schedule control routine 93 are transmitted to the response packet generation circuit 97, and the response packet generated by the response packet generation circuit 97 and transmitted to each terminal is transmitted on the response channel. It is possible to make an upstream transmission packet from the base station to the base station according to the scheduling of the base station.

Data received from each transmission channel is input via signal lines 44b to 44b 'to reception processing circuits 96b to 96b' provided for each transmission channel, and is transferred as a data packet to the BSC interface.
On the other hand, the downstream data packets are temporarily stored in the transmission buffer 99 and then subjected to transmission control according to the schedule performed by the downstream schedule control routine 95 of the DSP. That is, according to the downlink schedule,
First, the response packet created by the response packet structure creation circuit 97 is sent out from the response channel, and thereafter, the transmission packet structure creation circuits 98a to 98a 'are transmitted at predetermined time slots of the transmission channel determined by the downlink schedule.
Send out the data packet generated in. In this embodiment, in order to suppress the issue of the reservation packet from the mobile terminal when the transmission channel is busy, the number of reservation packets received on the reservation channel and the uplink schedule control routine 93 are determined. The busy tone value calculation routine 94 of the DSP 91 generates busy tone information in accordance with the use state information of the transmission channel used, and notifies each mobile terminal of the busy tone information through the response channel 45a.

FIG. 11 is a block diagram showing a configuration of the mobile terminal (wireless terminal) 5. The mobile terminal has an antenna 100
And a CDMA transceiver 110 connected to the antenna
And a packet control unit 130 connected to the CDMA transmitting / receiving unit 110 and a data processing device connected to the packet control unit 130. The data processing device includes a microprocessor (MPU) 101, a memory 102 for storing data and programs, and an I / O on an internal bus.
It comprises a plurality of input / output devices connected via the O interface 103. As the input / output device, for example, a camera 104a, a speaker 104b, a display 104
c, keyboard 104d, and the like.

FIG. 12 shows a CDMA transmitting / receiving section 1 of a mobile terminal.
10 shows a detailed configuration. Reference numerals 112 and 113 denote wireless modules that perform modulation / demodulation of a baseband signal and reception processing and transmission processing at a high / intermediate frequency. In the transmission circuit, the coding circuit 1 is used in each of the reserved channel and the transmission channel.
After encoding the error correction of the transmission packet in 20a and 120b, the multiplier 114 uses the PN sequence unique to each channel generated by the PN generators 121a and 121b.
The transmission packet is spread by a and 114b and sent to the transmission wireless module 113. At this time, the spreading process in the transmission channel is performed in synchronization with the reference timing 105c generated from the PN generator 119.

On the other hand, in the receiving circuit, the received signal output from the receiving wireless module 112 is input to a multiplier 114c, and a P-N unique to the base station generated by a PN generator 119 is generated.
The spectrum is despread using N codes. Multiplier 114c
Are output from multipliers 114d, 114e, 114 provided for response channels, transmission channels, and pilot channels.
f, and is despread by an orthogonal code unique to each channel generated by the orthogonal code generator 117. In the response channel and the transmission channel, the signals despread with the orthogonal code are input to decoding circuits 116d and 116e via accumulators 115d and 115e, respectively, and the error-corrected decoded signals are sent to signal lines 105d and 105d. The packet is transferred to the packet control unit 130 via 105e. In the pilot channel,
An accumulator 115f stores the pilot signal despread with the orthogonal code.
To a DLL (Delay Locked Loop) circuit 118 through which the synchronization is tracked. The PN generator 119 uses the DDL
A PN sequence is generated in synchronization with the output of the circuit 118. Further, the decoding circuits 116d and 116e are provided with accumulators 115f
To operate in synchronization with the pilot signal output from

FIG. 13 shows the packet control unit 13 of the mobile terminal.
0 shows an example of the configuration. The decoded data of the response channel is
The contents of the response packet, which is decoded by the monitoring routine 132 of the DSP 131, are stored in the upstream schedule control routine 134 and the downstream schedule control routine 1.
The busy tone signal provided at 35 and received on the response channel is provided to a busy tone calculation routine 133.

The packet reception processing circuit 136 on the downlink transmission channel is controlled by the output of the downlink schedule control routine 135 and the reference timing signal 105c. The transmission data is temporarily stored in the transmission buffer 138, and the uplink schedule control routine 134
Transmission packet structure creation circuit 1 in accordance with a control signal from
The data packet is sent to the transmission channel 39 and is transmitted to the transmission channel. Uplink schedule control routine 1
34 generates a signal 106 for specifying a transmission channel to which a transmission packet is to be transmitted according to the contents of the response packet, and activates the transmission packet structure creation circuit 139 at the timing of the time slot specified by the base station. PN generator 12
1b generates the PN code of the channel designated by the transmission channel designation signal 106.

A busy tone value calculation routine 133
Calculates the busy tone value from the busy tone signal received on the response channel, and notifies the uplink schedule control routine 134 of the traffic status information. The uplink schedule control routine 134 controls the generation of the reservation packet according to the traffic situation. When there is transmission data in the transmission buffer and there is no instruction to suppress the reservation packet from the base station, the reservation packet structure at any timing. The creation circuit 137 is activated to instruct the transmission of the reservation packet. The transmission processing of the transmission packet is also performed in a time slot synchronized with the reference timing 105c.

As described above, in the present invention, by applying the CDMA method to the reserved channel, even if each mobile terminal transmits the reservation control packet at an arbitrary timing, retransmission due to packet collision is possible. Performance can be reduced. However, when a plurality of packets are generated with a time overlap, the packet signals affect each other as noise. Therefore, when the number of simultaneously generated packets increases, all of the packet signals are buried in the noise, and the receiving side There is a problem that it becomes impossible to identify with the.

In the mobile communication system of the present invention comprising a reservation control channel, a response control channel, and a plurality of information transmission channels, the total amount of response control packets and data packets can be controlled by the base station. On the other hand, the reservation control packet is issued autonomously by each mobile terminal and cannot be directly controlled by the base station.
In order to solve the problem of the packet total amount regulation, in one embodiment of the present invention, the base station generates a busy tone signal indicating a traffic situation, and each mobile terminal refers to the busy tone signal to transmit a reservation control packet. Sending is controlled. The busy tone signal may be transmitted on a dedicated channel for the busy tone, or may use an idle time period that periodically appears in a response control channel that is a downlink control channel.

FIG. 14 is a diagram showing a control system for transmitting a busy tone signal by using the idle time zone of the response control channel. In the figure, “t−1”, “t”, “t”
“+1” is a time slot number in the response control channel, and 143 is a busy tone signal transmitted in an idle time zone in the response control channel. Also,
148 is a reservation control packet, R (t) is the number of reservation control packets transmitted by the mobile terminal in time slot t,
R (t) 'is the number of transmission requests for reservation control packets in time slot t, 149 is the data packet for information transmission, I (t) is the number of data packets generated in time slot t, and T allows simultaneous transmission. The number of stations that can be performed (the number of packets allowed at the same time), P (t), indicates the transmission probability of the reservation control packet. Here, R (t) ′ and R (t) are numbers normalized by the length of the data packet for information transmission.

First, the following equation (1) is assumed.

[0046]

(Equation 1)

This equation is derived as follows. First, the number R (t) ′ of reservation control packets of all mobile terminals in the service area in the time slot “t”, and 1
It is estimated that the number R (t-1) 'of reservation control packets in the immediately preceding time slot "t-1" is equal.

If R (t-1) 'is rewritten using the number R (t-1) of reservation control packets known by the base station,
It is equal to the right side of equation (1). Hereinafter, R (t) ′ is estimated from Expression (1), and if the total amount of communication packets exceeds the allowable value T, Expression (2)

[0049]

(Equation 2)

When it is estimated, the busy tone control is performed so that the transmission probability P (t) follows the equation (3), and the amount of reservation control packets actually transmitted from each mobile terminal is suppressed. The sum of the number of control packets and the number of data packets for information transmission is made substantially equal to the allowable value T.

[0051]

(Equation 3)

Here, since the number of reservation control packets to be transmitted is determined stochastically, it is necessary to consider that T should be set small in consideration of a margin. On the other hand, equation (4)

[0053]

(Equation 4)

In the case of the relation, the transmission probability P (t)
Follows the equation (5).

[0055]

(Equation 5)

That is, all the reservation control packets requested to be transmitted are transmitted. The transmission probability of Expression (3) or Expression (4) becomes busy tone information.

As shown in FIG. 2, the response control channel is converted into a time slot corresponding to the data packet length in the information transmission channel based on the pilot signal. Here, the response control packet length is set to be shorter than the data packet length, and if each time slot set based on the pilot signal is further subdivided according to the response packet length, for example, the time slot length (data If the packet length) is 512 bits and the response packet length is 42 bits, 12 response packet subslots can be set in one time slot, and an empty time zone of 8 bits is finally formed. The busy tone 143 of FIG. 14 is periodically transmitted at intervals of one slot of the information transmission channel using the idle time zone obtained in this manner.

[0058]

As is apparent from the above description, the present invention applies a CDMA to a reservation type packet access control type mobile communication system to transmit a reservation control packet to each mobile terminal at an arbitrary timing. Even in this case, the possibility of occurrence of retransmission due to collision is reduced, and the throughput is improved. According to the present invention, for example, a plurality of mobile terminals transmitted a reservation control packet asynchronously with each other by applying a short spreading code to the reservation control packet and causing the base station to perform synchronous acquisition with a matched filter. Even in this case, each reservation packet can be identified at high speed on the base station side. Further, the transmission efficiency can be improved by using a local address (own address) or a link number (transmission destination address) shorter than the original address number for the terminal address information set in each packet. Furthermore, when each terminal device controls transmission of a reservation control packet in accordance with a busy tone signal from a base station, it is possible to avoid an excessive amount of simultaneous communication packets and to guarantee good communication. .

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a configuration of a mobile communication network to which the present invention is applied.

FIG. 2 is a diagram for explaining a transmission / reception protocol in the wireless communication system according to the present invention.

FIG. 3 is a diagram for explaining a channel access control method in a conventional wireless communication system.

FIG. 4 is a diagram for explaining a channel access control method in the wireless communication system of the present invention to which the CDMA method is applied.

FIG. 5 is a diagram showing a packet format used in the mobile communication system of the present invention.

FIG. 6 is a block diagram showing a configuration of a base station.

FIG. 7 is a block diagram showing a configuration of a CDMA transmission / reception unit 50 of the base station.

FIG. 8 is a diagram showing a configuration of a matched filter 70 and a process of receiving a reservation control packet.

FIG. 9 is a diagram showing a configuration of a packet separation circuit 80.

FIG. 10 is a diagram showing a configuration of a packet control unit 90 of the base station.

FIG. 11 is a block diagram showing a configuration of a mobile terminal.

FIG. 12 is a diagram showing a configuration of a CDMA transmitting / receiving unit 110 of a mobile terminal.

FIG. 13 is a diagram showing a configuration of a packet control unit 130 of the mobile terminal.

FIG. 14 is a diagram for explaining busy tone control.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 public network, 2 mobile communication network, 4 base station, 5 mobile terminal, 7 reserved channel, 8 response channel, 9 transmission channel, 41, 100 antenna, 50, 110 CD
MA transmitting / receiving section, 90, 130 ... packet control section, 42 ...
BSC interface, 101 MPU, 102 memory, 103 input / output interface, 55, 116 decoder, 57, 121 PN generator, 118 DLL, 5
8, 120: encoder, 70: matched filter, 83
… Comparator, 84… AND circuit, 85… timer, 86…
Register, 87 ... Counter, 88 ... Clock.

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[Procedure amendment]

[Submission date] December 3, 2001 (2001.12.
3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04L 12/56 H04J 13/00 A 5K067 (72) Inventor Takashi Yano 1-280, Higashi-Koigabo, Kokubunji-shi, Tokyo Stock (72) Inventor Nobunori Doi 1-280 Higashi-Koigakubo, Kokubunji-shi, Tokyo F-term (reference) 5K022 EE01 EE11 EE21 EE33 EE36 5K028 AA11 BB04 CC05 DD01 DD02 KK32 LL02 LL42 MM12 MM19 NN47 5K030 GA03 HA08 HB01 HB11 HB14 HC09 JA11 JL01 JT03 JT09 KA05 LA18 LB01 LB05 5K033 AA01 CA11 CB01 CB06 CB15 CC01 DA01 DA19 DB10 DB18 EC01 5K047 AA11 BB01 GG34 HH15A13 GG34 HH15 DD13

Claims (13)

[Claims] 1. A wireless communication section between a base station and a plurality of mobile terminals, which is used for transmitting an uplink data packet from the mobile terminal to the base station and a downlink data packet from the base station to the mobile terminal. A plurality of transmission channels, a reservation channel used to transmit a reservation control packet indicating a transmission channel assignment request from the mobile terminal to the base station, and a transmission channel to transmit and receive data from the base station to the mobile terminal. And a response channel used to transmit a response control packet indicating the reservation,
In a mobile communication system to which a code division multiple access (CDMA) system using a unique spreading code is applied to each of response and transmission channels, a mobile terminal having a data transmission request transmits a reservation control packet to the reservation channel at an arbitrary timing. And the response control packet transmitted from the base station to the response channel specifies the transmission channel and time slot to be used for each mobile terminal, and each mobile terminal is designated by the response control packet. A mobile communication system wherein data packets are transmitted and received in designated time slots on a transmission channel. 2. A mobile station having a data transmission request, wherein each mobile terminal applies a spreading code specific to a reserved channel having a shorter cycle than a spreading code applied to a data packet transmitted on the transmission channel, and controls each reservation control. The base station spreads the spectrum of the packet, the base station processes the received signal by a matched filter in which a spreading code unique to the reserved channel is set, and outputs the output of the matched filter to the packet using the periodicity of the spreading code. The mobile communication system according to claim 1, wherein the signal is separated into a plurality of signal trains. 3. The base station assigns, to each mobile terminal, a local address shorter than address information unique to each terminal, and each mobile terminal transmits the response control packet among the response control packets transmitted on the response channel. 2. The mobile communication system according to claim 1, wherein a packet including a local address as a transmission destination address is received. 4. The base station assigns to each mobile terminal a link number shorter than address information unique to each terminal, and each mobile terminal transmits a data packet including the link number as a destination address to a transmission channel. The mobile communication system according to claim 1, wherein transmission is performed. 5. The base station has means for periodically transmitting busy tone information according to the status of traffic in a service area through the control channel for response or a channel dedicated to busy tone. 2. The mobile communication system according to claim 1, wherein each mobile terminal having the terminal controls transmission of a reservation control packet based on the busy tone information. 6. The base station further includes means for estimating the number of reservation control packets generated in the next predetermined period based on the number of reservation control packets received in the past predetermined period. The mobile communication system according to claim 5, wherein the busy tone information is generated based on a value and a number of packets scheduled to be transmitted in a next predetermined period. 7. The mobile communication system according to claim 1, wherein each of said mobile terminals requests transmission of a plurality of data packets with one reservation control packet. 8. The mobile communication system according to claim 3, wherein said base station specifies a response channel to be received by said mobile terminal by a control packet for assigning a local address to said mobile terminal. 9. The base station continuously transmits a pilot signal including a synchronization signal component on a pilot channel or the response channel, and each mobile terminal transmits a time slot of the transmission channel based on the received pilot signal. 2. The mobile communication system according to claim 1, wherein 10. A wireless communication system in which a base station and a plurality of wireless terminals communicate via a reservation channel, a response channel and a plurality of transmission channels formed by a code division multiple access (CDMA) method in a wireless section. In the system, each wireless terminal requesting data transmission transmits a reservation control packet to the reservation channel asynchronously with each other, and the base station has a plurality of overlapping radio stations partially overlapping on a period axis received on the reservation channel. After the reservation control packet signal is separated into packets and subjected to reception processing, a response signal for designating a transmission channel and a time slot to be used for a wireless terminal as a transmission source of the received reservation control packet is used. A control packet is transmitted on the response channel, and each of the wireless terminals transmits a command on the transmission channel specified by the response control packet. Wireless communication system and transmitting the data packets in time slots. 11. A response control packet for the base station to specify a transmission channel and a time slot for receiving operation for a wireless terminal specified by a destination address of a data packet received from the transmission channel. Is transmitted in the response channel, the received data packet is transmitted in the specified time slot on the specified transmission channel, and the wireless terminal that is the destination of the response control packet is specified in the response control packet. 11. The wireless communication system according to claim 10, wherein a data packet receiving operation is performed in a designated time slot of the transmission channel. 12. A wireless terminal device for wirelessly communicating with a base station, wherein a reservation control packet processed with a spreading code unique to a reservation channel is asynchronously transmitted to the base station. Means for transmitting; means for receiving a control packet for response processed with a spreading code specific to the response channel transmitted from the base station at a predetermined time slot timing synchronized with the base station; Means for transmitting or receiving a data packet processed with a spreading code specific to the transmission channel at a specific time slot timing on a specific transmission channel specified by the response control packet. A wireless terminal device. 13. A spread spectrum packet between a plurality of wireless terminals each having a unique address, via a reservation channel, a response channel, and a plurality of transmission channels each associated with a unique spreading code. A base station for a wireless communication system that communicates, comprising: receiving, from the reserved channel, a reservation control packet signal for a transmission channel access request transmitted by a plurality of wireless terminals asynchronously to each other; Means for separating and receiving processing, and for the wireless terminal of the transmission source of the reservation control packet,
Means for transmitting, via the response channel, a response control packet designating a transmission channel to be used and a time slot; and receiving processing of a data packet transmitted by the wireless terminal in each time slot of the transmission channel. Or means for performing a process of transmitting a data packet addressed to a wireless terminal.