JPH09233051A - Multi-access method, mobile station and base station in CDMA mobile communication system - Google Patents

Abstract

(57) Abstract: In a CDMA mobile communication system, the probability of packet collision is reduced, and more efficient and low-delay communication is enabled. In a CDMA mobile communication system, a common uplink channel 1 is used to realize multiple access.
0 for access channel 10A and message channel 10
When data (packet) to be transmitted is generated in the mobile stations 1 to 4, the mobile station having the data transmits a transmission request signal including information such as a packet size using the access channel 10A. In response to this, the base station 30 sends a transmission permission signal that specifies the transmission timing of the data and the spreading code to be used at the time of transmission, based on the usage status of the message channel 10B and the data generation status. Then, the mobile stations 1 to 4 transmit the data in accordance with the designated spreading code and transmission timing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CDMA (Code Division Multiple A) in which a plurality of mobile stations try to access a base station at arbitrary timing using a common channel.
ccess) The present invention relates to a multi-access method, a mobile station and a base station in a mobile communication system.

[0002]

2. Description of the Related Art Conventionally, packet communication in a mobile communication system has been employed for transmitting control signals.
For example, in the Japanese digital car telephone system standard (RCR STD-27C), when a mobile station makes a call, the mobile station uses a call signal (hereinafter referred to as “calling signal”) that can be commonly used by all mobile stations. Call packet). However,
In a TDMA (Time Division Multiple Access) mobile communication system, when a plurality of mobile stations transmit call signals at the same time, call packets collide in a common channel and transmission efficiency deteriorates.

The above-mentioned example is an example of the case of TDMA mobile communication, but in the case of CDMA mobile communication in which each channel is separated by a code, even if a plurality of mobile stations transmit call packets at the same time, all of them are transmitted at the base station. It is possible to receive the outgoing call packet of. However, if the number of channels used at the same time is large, interference between signals increases and reception at the base station becomes impossible (hereinafter, this is referred to as “collision” in CDMA). Therefore, even in CDMA mobile communication,
The situation is similar in that the transmission efficiency is deteriorated due to collisions when a large number of mobile stations transmit call packets at the same time (for example, the CDMA digital mobile communication system (TIA
IS-95))).

[0004]

As described above, the CD
Since packet collisions can occur in MA mobile communication as well, if the number of channels in use in the common channel reaches a prescribed number, new packet transmission is performed until the number of channels in use decreases, that is, , It is necessary to wait until the packet transmission from another mobile station is completed.
However, the waiting mobile station cannot know when the transmission of the packet from the other mobile station is completed, and must retry at a predetermined time interval or constantly monitor the channel state. Retrying at a predetermined time interval may cause deterioration of transmission efficiency due to packet collision, and
It is difficult for a mobile station to receive a transmission signal from another mobile station and constantly monitor the channel state in mobile communication in which other mobile stations are often out of sight. Even if the mobile station were able to constantly monitor the channel status, a considerable burden would be imposed on the mobile station.

The present invention has been made in view of the above circumstances, and reduces the probability of packet collision and enables more efficient and low delay communication.
An object is to provide a multi-access method, a mobile station and a base station in a mobile communication system.

[0006]

In order to solve the above-mentioned problems, a multi-access method in a CDMA mobile communication system according to claim 1 is used when a plurality of mobile stations transmit data to a base station at arbitrary timing. In the multi-access method in the CDMA mobile communication system, which comprises a common channel commonly used by the base station and one broadcast channel used when the base station transmits data to the plurality of mobile stations, the common channel is accessed. A process of notifying the base station of the occurrence of data to be transmitted by the mobile station via the access channel, and a notification of the transmission timing of the data to be transmitted by the base station. A process of notifying the mobile station via a channel, and the mobile station using the message channel It is characterized by having a process of transmitting data to be the transmission at the transmission timing which is notified from the earth station.

A multi-access method in a CDMA mobile communication system according to claim 2 is characterized in that, in the method according to claim 1, there is one message channel. A multi-access method in a CDMA mobile communication system according to claim 3 is characterized in that, in the method according to claim 1, there are a plurality of message channels.

A multi-access method in a CDMA mobile communication system according to a fourth aspect is the method according to the third aspect, wherein a spreading code corresponding to each of the message channels is pre-assigned to each of the mobile stations and transmitted by the mobile station. Generation of data to be transmitted and spreading code assigned to itself is notified to the base station via the access channel, and the mobile station sets the same number of message channels corresponding to at least one spreading code assigned to itself. It is characterized in that the data to be transmitted is transmitted at the transmission timing notified from the base station.

A multi-access method in a CDMA mobile communication system according to claim 5 is the method according to claim 3, wherein the base station transmits the transmission timing of the data to be transmitted and the at least one spreading code. The transmission timing reported to the mobile station via a broadcast channel, the mobile station using the same number of message channels corresponding to at least one spreading code broadcast from the base station In the above, the data to be transmitted is transmitted.

A multi-access method in a CDMA mobile communication system according to claim 6 is characterized in that, in the method according to claim 1, there are a plurality of access channels. The multi-access method in a CDMA mobile communication system according to claim 7, wherein in the method according to claim 6, each access channel is pre-assigned to each mobile station and the generation of data to be transmitted by the mobile station is assigned to itself. It is characterized by notifying to the base station via the established access channel.

A multi-access method in a CDMA mobile communication system according to claim 8, wherein the mobile station has a probability distribution regarding the use of each access channel for each mobile station, One access channel is selected from a plurality of the access channels based on the probability distribution, and the data to be transmitted is transmitted at the transmission timing notified from the base station using the access channel. There is. A multi-access method in a CDMA mobile communication system according to claim 9 is the method according to claim 8, wherein the base station broadcasts the probability distribution to the mobile stations via the broadcast channel.

In the mobile station in the CDMA mobile communication system according to claim 10, a common channel commonly used when a plurality of mobile stations transmit data to a base station at an arbitrary timing and the base station has a plurality of common channels. CD with one broadcast channel used when transmitting data to mobile station
In a mobile station in an MA mobile communication system, a transmitting / receiving means for transmitting / receiving a signal to / from the base station via the common channel and the broadcast channel, and the common channel are used by being separated into an access channel and a message channel. Means for modulating data to be transmitted and supplying the modulated data to the transmitting / receiving means, demodulating a signal received by the transmitting / receiving means, and generation of data to be transmitted via the access channel to the base station. The station, and controls the transmission / reception means and the processing means to modulate the data to be transmitted at the transmission timing notified from the base station using the message channel and supply the modulated data to the transmission / reception means. And a control means.

A mobile station in the CDMA mobile communication system according to claim 11 is the mobile station according to claim 10,
The number of message channels is one. The mobile station in the CDMA mobile communication system according to claim 12, wherein the message channel is plural in number, and the processing means modulates data to be transmitted by using a spreading code. The message channel used for transmitting the data to be transmitted is a message channel corresponding to the spread code.

A mobile station in the CDMA mobile communication system according to claim 13 is the mobile station according to claim 12,
The control means holds a spreading code corresponding to at least one of the message channels, and transmits the generation of the data to be transmitted and the spreading code held by itself to the base station via the access channel. The processing means and the transmission / reception means are controlled, and the processing means and the transmission / reception means are controlled to transmit the data to be transmitted at the transmission timing notified from the base station using the at least one message channel. It is characterized by doing.

A mobile station in the CDMA mobile communication system according to claim 14 is the mobile station according to claim 12,
The control means uses the same number of message channels corresponding to at least one spreading code notified from the base station to transmit the data to be transmitted at the transmission timing notified from the base station. It is characterized by controlling the processing means and the transmitting / receiving means.

A mobile station in the CDMA mobile communication system according to claim 15 is the mobile station according to claim 10,
It is characterized in that there are a plurality of access channels. The mobile station in the CDMA mobile communication system according to claim 16 is the mobile station according to claim 15, wherein the control means generates the data to be transmitted using the access channel previously associated with the mobile station. The processing means and the transmission / reception means are controlled so as to notify the base station.

A mobile station in the CDMA mobile communication system according to claim 17 is the mobile station according to claim 15,
The control means holds a probability distribution regarding use of each access channel, selects one access channel from the plurality of access channels based on the probability distribution, and notifies from the base station using the access channel. It is characterized in that the processing means and the transmission / reception means are controlled so as to transmit the data to be transmitted at the designated transmission timing. The mobile station in the CDMA mobile communication system according to claim 18 is the mobile station according to claim 17, characterized in that the probability distribution is reported from the base station to each of the mobile stations.

A base station in the CDMA mobile communication system according to claim 19 is a common channel commonly used when a plurality of mobile stations transmit data to the base station at arbitrary timing, and the base station has a plurality of common channels. CD with one broadcast channel used when transmitting data to mobile station
In a base station in an MA mobile communication system, a transmitting / receiving means for transmitting / receiving a signal to / from the base station via the common channel and the broadcast channel, and the common channel are separated into an access channel and a message channel for use. Means for modulating data to be transmitted and supplying it to the transmitting / receiving means, processing means for demodulating a signal received by the transmitting / receiving means, and monitoring a signal received by the transmitting / receiving means, When the generation of the data to be transmitted is notified, the transmission timing of the data to be transmitted is determined based on the monitoring result, and the transmission timing is notified to the mobile station via the notification channel. Control means for controlling the transmitting / receiving means and the processing means so as to receive and demodulate the data transmitted at the timing. It is characterized in that Bei.

A base station in the CDMA mobile communication system according to claim 20 is the base station according to claim 19,
The number of message channels is one. The base station in the CDMA mobile communication system according to claim 21 is the base station according to claim 19, wherein the message channel is plural, and the processing means demodulates a signal supplied from the transmitting / receiving means based on a spread code. It is characterized by that.

The base station in the CDMA mobile communication system according to claim 22 is the base station according to claim 21,
The control means determines the transmission timing of the data to be transmitted based on the monitoring result when the generation of the data to be transmitted and the spread code from the mobile station are notified via the access channel, The processing means and the transmission / reception means for notifying this to the mobile station via the broadcast channel and receiving and demodulating the data transmitted at the transmission timing via the message channel corresponding to the spread code. It is characterized by controlling.

A base station in the CDMA mobile communication system according to claim 23 is the base station according to claim 21,
When the generation of data to be transmitted is notified from the mobile station, the control means responds to at least one of the transmission timing of the data to be transmitted and the plurality of message channels based on the monitoring result. A spread code is determined, and these are broadcast to the mobile station via the broadcast channel, and at the transmission timing, data transmitted via the message channel corresponding to the spread code is received and demodulated. It is characterized in that the transmitting / receiving means and the processing means are controlled.

The base station in the CDMA mobile communication system according to claim 24 is the base station according to claim 19,
The access channel is plural, and the control means is
The processing means and the transmission / reception means are controlled so as to determine a probability distribution regarding the use of each access channel and notify each mobile station via the notification channel. A base station in the CDMA mobile communication system according to claim 25 is the base station according to claim 14, wherein the control means determines the probability distribution based on the monitoring result.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION First, a CDM which is a premise of the present invention.
The A mobile communication system will be described. FIG. 3 is a diagram for explaining the CDMA mobile communication system. In this figure, an example of multiplex communication using two channels ch1 and ch2 is shown.

In each of the channels ch1 and ch2, on the transmitting side, the modulated wave modulated (primary modulation) by phase modulation or the like is further modulated (secondary modulation) by the spread code independently assigned to each channel, After that, frequency conversion is performed and transmission is performed. On the receiving side, the reference spreading code corresponding to the spreading code assigned to each channel is used, and transmission is performed via the desired channel by detecting the correlation between the received signal and the spreading code assigned to the desired channel. The extracted information is being extracted.

As the spreading code, for example, a pseudo noise (PN) code and a Walsh (Walsh) code are used.
) Function is used together, a code having a high orthogonality between codes is used. Therefore, each channel ch1, c
Even if communication using h2 is performed at the same time, on the receiving side,
The transmitted information can be extracted accurately. That is, each of the channels ch1 and ch2 can occupy the entire band provided for communication during the entire communication time.

Next, each embodiment of the present invention will be described with reference to the drawings. However, since the physical configuration is basically the same in each embodiment, first, the configuration of the CDMA mobile communication system to which the multi-access method according to each embodiment is applied will be described with reference to FIG.
In the following description, the term "channel" means not only a communication path separated by frequency but also a communication path separated by code, frequency or time.

FIG. 1 is a diagram showing a configuration of a CDMA mobile communication system to which the multi-access method according to each embodiment of the present invention is applied. In the figure, reference numeral 30 is a base station that covers a predetermined range of sectors (cells), and 1 to 4 are mobile stations existing in the sectors covered by the base station 30, respectively, and access the base station 30 at arbitrary timing. To do. Although four mobile stations are shown in the figure,
Of course, the number of mobile stations is arbitrary.

Reference numerals 10 and 20 denote mobile stations 1 to 4, respectively.
10 is an uplink channel from the mobile station side to the base station 30 side, and 20 is a broadcast channel that broadcasts the same information from the base station 30 side to the mobile stations 1 to 4 at the same time. Is. The uplink channel 10 is accessed by the mobile stations 1 to 4 and the base station 30.
A and the message channel 10B are separated, and the respective channels 10A and 10B are given different roles.
The role of each channel 10A, 10B will be described later in connection with each embodiment.

In the base station 30, reference numeral 31 is a transceiver for transmitting and receiving a signal via an antenna, which frequency-converts a transmission baseband signal by a predetermined carrier and transmits it through a broadcast channel 20 and also through an uplink channel 10. The received signal is frequency-converted based on the carrier and a received baseband signal is output. Reference numeral 32 denotes a traffic control unit that controls traffic on the upstream channel 10, checks the usage status and packet generation status of the message channel 10B based on the received baseband signal from the transceiver 31, and outputs information based on these. To do. The information output here will be described later in connection with each embodiment.

Reference numeral 33 is a baseband signal processing unit, which detects the correlation between the received baseband signal output from the transceiver 31 and the reference spreading code, extracts the information transmitted from the mobile station, and performs multiplexing in the subsequent stage. The information is supplied to a control station (not shown) via a multiplexing device (not shown), and the information supplied via the multiplexing device is multiplied by a spread code to generate a transmission baseband signal, which is sent to the transceiver 31. Output. Further, the baseband signal processing unit 33 puts the information output from the traffic control unit 32 on a predetermined bit position of the transmission baseband signal and outputs the information to the transceiver 31.

Next, the configuration of the mobile stations 1 to 4 will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the mobile station in FIG. 1. Reference numeral 41 denotes a transceiver that transmits and receives a signal via an antenna. 10 through the broadcast channel 20
The frequency of the signal received via the carrier is converted based on the carrier and output as a received baseband signal.

Reference numeral 43 is a baseband signal processing unit, which detects the correlation between the received baseband signal output from the transceiver 41 and the spread code, extracts the information transmitted from the base station 30, and outputs the voice code in the subsequent stage. The information is supplied to a decoder (not shown) or the like, and the information supplied from the voice code decoder or the like is multiplied by a spread code to generate a transmission baseband signal, which is output to the transceiver 41. Further, 44 is a display device such as a liquid crystal display, and 45 is an instruction input device including a keypad and the like.

Reference numeral 42 is a control unit for controlling each component, and based on the information input by the instruction input device 45, a preset operation program, and the information extracted by the baseband signal processing unit 43. It controls the transceiver 41, the baseband signal processing unit 43, and the display device 44. The base station 30 and the mobile stations 1 to 4 respectively include a CPU (central processing unit) and a RAM (Random Acces).
s Memory), ROM (Read Only Memory), DSP (D
igital Signal Processor), various interfaces, and the like, and these components operate in cooperation with each other to realize each of the above components.

A: First Embodiment FIG. 4 is a timing chart showing the operation of the CDMA mobile communication system to which the multi-access method according to the first embodiment of the present invention is applied, and the traffic on each channel shown by the dotted line. And the relationship of traffic on each channel. In order to realize the operation shown in this figure,
CDM to which the multi-access method according to the present embodiment is applied
The A mobile communication system includes a plurality of message channels 10B and has a function described below in addition to the above-described configuration.

Before transmitting the information, the control unit 42 of each mobile station judges whether or not the size of the information to be transmitted is equal to or smaller than a predetermined size, and if it is equal to or smaller than the predetermined size, Each unit is controlled so that the information is transmitted using only the access channel 10A. Here, the predetermined size is a size that can be arbitrarily set, and it is possible for the base station 30 to dynamically set the size according to the usage states of the access channel 10A and all the message channels 10B. In the embodiment, the size is fixed, and for example, the size of one packet is defined in advance.

On the other hand, when the size of the information to be transmitted is not smaller than the predetermined size, the control unit 42 reserves the transmission of the information in order to reserve the size of the information (actually, the packet Information such as total size) is supplied to the baseband signal processing unit 43, and the baseband signal processing unit 43 and the transmitter / receiver 41 generate a transmission request signal including the information, which is transmitted to the access channel 10A.
To the base station 30 via.

The traffic control unit 32 of the base station 30 stores the information indicating the occurrence status of traffic using any one of the message channels 10B (that is, the total reception schedule of the data transmitted via each message channel 10B). At the same time, the usage status (for example, usage rate and usage amount) of all the message channels 10B is checked from the received baseband signal supplied via each message channel 10B and the transceiver 31. In addition, the base station 30
When receiving a reception baseband signal including a signal corresponding to a transmission request signal, determines the transmission timing and spreading code that can avoid packet collision based on the above occurrence status and usage status at that time, and determines these. The represented information is supplied to the baseband signal processing unit 33, placed on a predetermined bit position of the transmission baseband signal, and supplied to the transceiver 31.

As a result, the transmission timing and spreading code determined by the traffic control unit 32 are transmitted from the transceiver 31 via the broadcast channel 20 as a transmission permission signal to the mobile station that has transmitted the transmission request signal. The traffic control unit 32 stores the total packet size, the offset of the transmission timing, and the time when the offset is set so that the correspondence with the transmission request signal PS1_R can be understood.

Further, the control unit 42 of each mobile station extracts the transmission timing and the spread code from the baseband signal obtained by frequency-converting the transmission permission signal addressed to the own station, which is transmitted via the broadcast channel 20, Data corresponding to the transmission permission signal (that is, data corresponding to the transmission request signal) using the spreading code and at the transmission timing
The baseband signal processing unit 43 is controlled so as to transmit.

Next, the operation of the mobile communication system having the above configuration will be described with reference to FIG. In FIG. 4, first,
The mobile station 1 uses the access channel 10A to access the base station 30.
The transmission request signal PS1_R is transmitted to. The transmission request signal PS1_R includes information indicating the total packet size of the information (data PS1_D) to be transmitted by the mobile station 1. When the base station 30 receives the transmission request signal PS1_R from the mobile station 1, at that time, the traffic control unit 32 reads out the occurrence status of traffic using any one of the message channels 10B and informs the usage status of all the message channels 10B. Find out.

In the example of FIG. 4, the message channel 10B is not used at the time of extraction of the transmission request signal PS1_R, and data reception via any one of the message channels 10B is not scheduled. 30 immediately permits the transmission of data PS1_D. Specifically, the traffic control unit 32 sets the transmission timing offset to 0, selects an appropriate spreading code (spreading code 1 in the example of FIG. 4), and outputs these to the baseband signal processing unit 33. As a result, the base station 30 transmits the transmission permission signal PS1_A including the information indicating the transmission timing and spreading code to be used when transmitting the data PS1_D to the mobile station 1 via the broadcast channel 20. At this time, the traffic control unit 32 stores the total packet size, the offset of the transmission timing, and the time when the offset is set so that the correspondence relationship with the transmission request signal PS1_R can be understood.

Upon receiving the transmission permission signal PS1_A, the control unit 42 of the mobile station 1 sets the instructed spreading code 1 in the baseband signal processing unit 43 and waits for the time represented by the instructed offset. In this case, since the offset is 0, the control unit 42 informs the baseband signal processing unit 43 of the information to be transmitted and the spread code 1.
Directs immediate multiplication with and. As a result, the mobile station 1 uses the message channel 10B
1_D is transmitted and received at the base station 30.

Next, the mobile station 2 accesses the access channel 10A.
When a transmission request signal PS2_R is transmitted to the base station 30 via the base station 30 and the base station 30 receives the transmission request signal PS2_R, at that time, the traffic control unit 32 confirms the occurrence status of traffic using one of the message channels 10B. Read and all message channels 10B
Check the usage status of. At the time of extraction of the transmission request signal PS2_R, only the reception of the data PS1_D is scheduled, and the traffic on all the message channels 10B is small. Therefore, the transmission timing offset is zero. In addition, as a spreading code used when transmitting the data PS2_D, it is not currently used,
And the spreading code 2 which is not scheduled to be used is selected. Since then
The same processing as that at the time of transmitting the data PS1_D is performed, and the data PS2 modulated using the spreading code 2 is transmitted from the mobile station 2.
_D is transmitted using the message channel 10B and received at the base station 30.

Next, the mobile station 3 accesses the access channel 10A.
When a transmission request signal PS3_R is transmitted to the base station 30 via the base station 30 and the transmission request signal PS2_R is received by the base station 30, at that time, the traffic control unit 32 confirms the occurrence status of traffic using one of the message channels 10B. Read and all message channels 10B
Check the usage status of. At the time of extraction of the transmission request signal PS3_R, transmission of the data PS1_D and PS2_D has started, there is a lot of traffic on all the message channels 10B, and interference has occurred, although a “collision” has occurred, but not so much. Therefore, the transmission timing offset is set to the time until the time when the traffic on the message channel 10B is expected to decrease.

In this case, the transmission request signals PS1_R, PS
Since the transmission of the data PS1_D and PS2_D for 2_R has started, it can be seen that the transmission using any one of the message channels 10B is not scheduled in the future. Assuming that the communication speed between the mobile station and the base station is substantially constant, the current time, the time and the transmission timing corresponding to the transmission request signals PS1_R and PS2_R, and the transmission request signals PS1_R and PS2_R are used. Based on the transmitted total packet size of each data PS1_D, PS2_D, each data PS1_D, P
The time when the transmission of S2_D ends can be estimated. Therefore, the base station 30 uses the data PS1_D, P
The offset of the transmission timing of the data PS3_D is determined based on the time when either one of S2_D will end and the current time.

The traffic control unit 32 is connected to the base station 3
The offset may be corrected in consideration of the data propagation delay time between 0 and the mobile station 3.
In a mobile communication system, it is not necessary to perform strict control of transmission timing as in a system employing TDMA, and thus the correction process is omitted in this embodiment to simplify the process. Further, as the spreading code used when transmitting the data PS3_D, the spreading codes 3 and 4 which are not currently used and are not scheduled to be used are selected.
As is clear from this, the number of channels used for one data transmission is arbitrary. After that, the data PS1_
The same processing as that at the time of transmitting D is performed, and the mobile station 3 transmits the data PS3_D modulated using the spreading code 3 using the message channel 10B and is received by the base station 30.

When transmitting information from the mobile station 4, the mobile station 4
The control unit 42 determines that the size of the information to be transmitted is smaller than the predetermined size, and the access channel 10A
The respective units are controlled so as to transmit the data PS4_D using only the data. As a result, the data PS4_D is transmitted using the access channel 10A, and the base station 30 transmits P
S4_D is received similarly to PS1_D to PS3_D, and the communication is completed.

As described above, according to the first embodiment,
Basically, since only a short transmission request signal for making a reservation for data transmission is transmitted on the access channel 10A, the probability of packet collision occurring on the access channel 10A is suppressed to a very low level. Further, since data transmission on the message channel 10B is performed at the transmission timing determined by the base station 30, if the transmission timing determination algorithm is appropriate, packets do not collide on all message channels 10B. Therefore, the transmission efficiency can be improved.

Further, since the data transmission is reserved by the transmission request signal and the transmission timing is notified from the base station 30 to the mobile station, it is not necessary for the mobile station to retry at a predetermined time interval, The probability of collision can be reduced. Further, the base station 30 determines the optimum spreading code to be used for data transmission, notifies the mobile station of this, and enables communication using an empty channel. Therefore, “desired transmission code (channel)”
Information (data) that cannot be sent because it is in use
It is possible to avoid such a problem that "there is a long wait even when sending a message." That is, it is possible to avoid the disadvantage that the transmission delay becomes long regardless of the packet size.

Further, since it is applied to the CDMA mobile communication system, it is not necessary to strictly determine the transmission timing as compared with the system adopting TDMA, the base station configuration can be simplified, and the base station can be used. The load can be reduced. If the total packet size of the information to be transmitted is sufficiently small, the information (data) is transmitted using the access channel 10A,
Since the transmission is not reserved, the overhead can be reduced without impairing the above-mentioned various advantages.

B: Second Embodiment FIG. 5 is a timing chart showing the operation of the CDMA mobile communication system to which the multi-access method according to the second embodiment of the present invention is applied. The example shown in this figure is shown in FIG.
Similarly to the example shown in FIG. 3, the mobile stations 1 to 4 sequentially make calls. As is clear from FIG. 5, in the present embodiment, the information indicating the spread code is included in the transmission request signal, and is not included in the transmission permission signal. This is because the spreading code is fixedly assigned to each mobile station in advance and the message channel used by each mobile station is fixedly set. Hereinafter, a difference in configuration from the first embodiment caused by such a difference in premise will be described.

The control unit 42 of each mobile station in this embodiment
Prior to the transmission of information, it judges whether the size of the information to be transmitted is less than or equal to a predetermined size, and if it is not less than or equal to the predetermined size, in order to reserve the transmission of the information, Information including the total packet size of information and the spreading code fixedly assigned to itself is supplied to the baseband signal processing unit 43, and the baseband signal processing unit 4 is supplied.
3 and the transmitter / receiver 41 generate a transmission request signal including the information and transmit the signal to the base station 30 via the access channel 10A.

The traffic control unit 32 of the base station 30
Stores, for each channel (spreading code), information indicating the occurrence status of traffic using one of the message channels 10B, and from the received baseband signal supplied via each message channel 10B and the transceiver 31 to the message channel. The usage status of 10B is checked for each channel (spread code). Also, the traffic control unit 32
Upon receiving the reception baseband signal corresponding to the transmission request signal, the spread code is extracted from the information included in the transmission request signal, and based on the occurrence status and the usage status of the spreading code (channel) at that time. Then, the transmission timing at which packet collision can be avoided is determined, information indicating this is supplied to the baseband signal processing unit 33, and the transmitter / receiver 3 puts it on a predetermined bit position of the transmission baseband signal.
Output to 1. The traffic control unit 32 stores the total packet size, the transmission timing offset, and the time when the offset is set so that the correspondence with the spreading code can be understood.

Next, the operation of the mobile communication system having the above configuration will be described with reference to FIG. 5, focusing on the difference from the operation of the first embodiment. First, the mobile station 1 sends a transmission request signal PS1 to the base station 30 via the access channel 10A.
_R is transmitted, but the transmission request signal PS1_R includes
The information including the total packet size of the data PS1_D to be transmitted by the mobile station 1 and the spreading code 1 fixedly assigned to the mobile station 1 in advance are included.

When the base station 30 receives the transmission request signal PS1_R from the mobile station 1, at that time, the traffic control unit 32 reads out the traffic generation status using any one of the message channels 10B and at the same time all the message channels 10B. Check usage. What is read out and examined here is the occurrence status and the usage status corresponding to the spread code 1, but in the example of FIG. 5, the message channel represented by the spread code 1 at the time of extraction of the transmission request signal PS1_R. Is not used, and no data is expected to be received via that channel, and there is no interference from channels corresponding to other spreading codes, so
The base station 30 immediately permits the transmission of the data PS1_D. Specifically, the traffic control unit 32 sets the transmission timing offset to 0, and outputs this to the baseband signal processing unit 33, so that the base station 30 transmits the data PS1_D to the mobile station 1 via the broadcast channel 20. A transmission permission signal PS1_A including information indicating the transmission timing to be used at times is transmitted. At this time, the traffic control unit 32 stores the total packet size, the offset of the transmission timing, and the time when the offset is set so that the correspondence with the spreading code can be understood.

Upon receiving the transmission permission signal PS1_A, the control unit 42 of the mobile station 1 instructs the baseband signal processing unit 43 to immediately perform the multiplication of the information to be transmitted and the spread code 1. As a result, the mobile station 1 transmits the data PS1_D using the message channel 10B, and the data PS1_D is received by the base station 30. After that, similar to the first embodiment, the processing for the calls from the mobile stations 2 to 4 is performed.

As is apparent from the above description, according to the present embodiment, the information notified from the base station 30 to the mobile station is only the transmission timing, and the load on the base station 30 can be reduced. It is also possible to allocate a plurality of spreading codes to the mobile station, select one of the spreading codes at the time of transmitting the information, and transmit the information indicating this by including it in the transmission request signal. In this case, for example, a channel represented by a specific spreading code is used as an emergency channel, and communication using this channel is not performed except during an emergency.
That is, if the spread code is set not to be used as much as possible during normal times, communication in an emergency can be smoothly performed.

[Modification] A modification of the second embodiment described above will be described with reference to FIG. FIG. 6 is a CDM to which the multi-access method according to the second embodiment of the present invention is applied.
A is a timing chart showing an operation of a modified example of the mobile communication system A, and the example shown in this figure is such that the mobile stations 1 to 4 sequentially make calls, as in the example shown in FIG.

As is apparent from FIG. 6, in this modification, there is only one message channel 10B, and each data is transmitted using this one message channel. Therefore, the spreading code used to select the channel in the message channel 10B in the second embodiment is not used here. Hereinafter, a difference in configuration from the second embodiment caused by such a difference in premise will be described.

Prior to transmitting information, the control unit 42 of each mobile station determines whether or not the size of the information to be transmitted is smaller than or equal to a predetermined size. The unit 42 supplies information such as the total packet size of the information to the baseband signal processing unit 43 in order to reserve the transmission of the information, and the baseband signal processing unit 43 and the transceiver 41 include the information. A transmission request signal is generated and transmitted to the base station 30 via the access channel 10A.

The traffic control unit 32 of the base station 30 stores information indicating the occurrence status of traffic using the message channel 10B, and also the message channel 1
0B and the received baseband signal supplied via the transceiver 31 to check the usage status of the message channel 10B (for example, whether it is used or not). Also,
When the base station 30 receives the reception baseband signal corresponding to the transmission request signal, the base station 30 determines the transmission timing at which packet collision can be avoided, based on the above occurrence status and usage status at that time, and provides information indicating this. It is supplied to the baseband signal processing unit 33. In addition, the control unit 42 of each mobile station
Is a baseband signal processing unit that extracts the transmission timing from the information obtained from the transmission permission signal transmitted through the broadcast channel 20 and transmits the data corresponding to the transmission permission signal at the transmission timing. Control 43.

Next, the operation of the mobile communication system having the above configuration will be described with reference to FIG. 6 while focusing on the difference from the operation of the second embodiment. First, the mobile station 1 sends a transmission request signal PS1 to the base station 30 via the access channel 10A.
_R is transmitted, but the transmission request signal PS1_R includes
Information to be transmitted by the mobile station 1 (data PS1_D)
Information indicating the total packet size of the message channel 1
It also includes information indicating that the use of 0B is requested.

When the base station 30 receives the transmission request signal PS1_R from the mobile station 1, at that time, the traffic control unit 32 reads out the occurrence status of the traffic using the message channel 10B and the message channel 10B.
Check the usage status of B. In the example of FIG. 6, the transmission request signal P
At the time of extracting S1_R, the message channel 10
Since B is not used and data reception via the channel is not scheduled, the base station 30 immediately permits the transmission of the data PS1_D. At this time, the traffic control unit 32 stores the total packet size, the transmission timing offset, and the time when the offset is set.

When the transmission permission signal PS1_A is received, the control unit 42 of the mobile station 1 instructs the baseband signal processing unit 43 to immediately multiply the information to be transmitted and the spread code 1. As a result, the mobile station 1 transmits the data PS1_D using the message channel 10B, and the data PS1_D is received by the base station 30. After that, the same processing as the above-described processing for the transmission request signal PS1_R is sequentially repeated for each transmission request signal PS2_R, PS3_R. The process for the transmission request signal PS4_R is
Since the processing is the same as in the first and second embodiments, its description is omitted.

In the above-described modification, the bandwidth of the channel for transmitting data can be widened, and the data transmission speed can be increased, for example. If the data transmission speed is increased, the time from the start of data transmission to the end of data transmission is shortened, so the total packet size of each data (information) is sufficient compared to the generation interval of each data. When it is very small, as can be seen by comparing FIG. 6 and FIG. 5, the time from the start of transmission of the transmission request signal to the completion of data transmission can be shortened.

C: Third Embodiment FIG. 7 is a timing chart showing the operation of the CDMA mobile communication system to which the multi-access method according to the third embodiment of the present invention is applied. The example shown in this figure is a mobile station. 1 and mobile station 2 make a call at the same time, and then mobile station 3,
4 sequentially makes calls. As is clear from FIG. 7, in this embodiment, a plurality of access channels 1
0A exists and is set so that each mobile station can make a call using an arbitrary access channel. The configuration of the third embodiment will be described below, focusing on the functions that are not present in the first embodiment, which are caused by such a difference in the premise.

Before transmitting the information, the control unit 42 of each mobile station judges whether or not the size of the information to be transmitted is smaller than or equal to a predetermined size. In order to reserve the transmission of information, information such as the total packet size of the information is supplied to the baseband signal processing unit 43, and the baseband signal processing unit 43 and the transceiver 41 generate a transmission request signal including the information. In addition, the access channel used for transmitting the transmission request signal is selected based on the probability distribution previously notified from the base station 30 or the preset probability distribution, and the transmission request signal is transmitted via the selected access channel to the base station. Three
Send to 0.

An example of the above probability distribution will be given below. However, the sum of the probabilities for each channel is 1, p, q, and r are real numbers from 0 to 1 and p + q + r = 1.
It is assumed that [First example] Probability of using the first access channel 1/3 Probability of using the second access channel 1/3 Probability of using the third access channel 1/3 [Second example] First access Probability of using channel 1/5 Probability of using second access channel 2/5 Probability of using third access channel 2/5 [Third example] Probability of using first access channel p Second Probability of using access channel q Probability of using third access channel r

The first example is an example in which the probability of using each access channel is the same in each mobile station and the packet collision probability in the access channel is ⅓.
The second example shows the probability distribution of a mobile station when each mobile station is grouped by service class (type of contracted service content) and a different probability distribution is reported for each group. In each mobile station belonging to a group different from the group to which the indicated mobile station belongs,
The probability of using the second and third access channels is set low (for example, set to 0). In this case, each mobile station belonging to the group shown in the second example can occupy and use the second and third access channels, and if the number of mobile stations belonging to the same group is appropriate, it can be assigned to another group. It is possible to receive a service in which the probability of packet collision on the access channel is lower than that of the mobile station to which it belongs.

The third example is an example in which the probability distribution is changed, and the values of p, q, and r are changed according to various situations. When such a probability distribution is used, for example, it is attempted to realize more efficient communication in a situation where there are differences in characteristics such as transmission speed and carrier frequency between the first to third access channels. The case may be mentioned. In such a case, efficient communication is realized by dynamically changing the probability distribution according to the amount of traffic on each access channel, the radio wave condition, the function of each mobile station, and the like.

In this embodiment, the first example is adopted,
The traffic control unit 32 of the base station 30 sets the probability distributions of using the access channels 10A in the mobile stations 1 to 4 to 1/3, 1/3, and 1/3, and the information representing this probability distribution is subjected to baseband signal processing. It is output to the unit 33. Since the baseband signal processing unit 33 puts this information on a predetermined bit position of the broadcast channel 20 and outputs it to the transceiver 31,
The above-mentioned probability distribution is obtained from the mobile stations 1 to 4 via the broadcast channel 20.
Will be notified.

Next, the operation of the mobile communication system having the above configuration will be described with reference to FIG. 7, focusing on the points different from the operation of the first embodiment. However, it is assumed that the probability distribution (1/3, 1/3, 1/3) of using each access channel 10A is broadcast from the base station 30 to the mobile stations 1 to 4 in advance. In such a state, first, the mobile station 1 sends the transmission request signal P to the base station 30 via the first access channel included in the first access channel 10A.
At the same time as transmitting S1_R, the mobile station 2 transmits a transmission request signal PS2_R to the base station 30 via the second access channel included in the second access channel 10A. Here, the access channel selected by both mobile stations is the channel selected based on the probability distribution reported from the base station 30.

In the message controller 32 of the base station 30,
The transmission request signals PS1_R and PS2_R are extracted,
Processed in order of arrival. In FIG. 7, the transmission request signal P
S1_R and transmission request signal PS2_R are processed in this order. Specifically, first, at the time of extraction of the transmission request signal PS1_R, the traffic control unit 32 reads out the traffic generation status using any one of the message channels 10B and checks the usage status of all the message channels 10B.

In the example of FIG. 7, at the time of extraction of the transmission request signal PS1_R, the message channel represented by the spreading code 1 is not used, and data reception via the channel is not scheduled, Moreover, since there is no interference from channels corresponding to other spreading codes, the base station 30 immediately permits the transmission of the data PS1_D. Next, the traffic control unit 32 reads out the occurrence status of traffic using any one of the message channels 10B and checks the usage status of all the message channels 10B in response to the transmission request signal PS2_R. Transmission request signal PS
At the time of extracting 2_R, the data PS1_D is only scheduled to be received, and the message channel 10
There is little traffic on B. Therefore, the base station 30 immediately permits the transmission of the data PS1_D.

As a result of the above-mentioned processing, the transmission permission signals PS1_A and PS1 are transmitted from the base station 30 to the mobile stations 1 to 4, respectively.
2_A is transmitted, but since there is only one broadcast channel 20, transmission permission signals PS1_A and PS2_A are transmitted in this order. Similar to the first embodiment, these transmission permission signals include information indicating the spreading code used for data transmission and the transmission timing.

Since the transmission processing of the data PS1_D and PSD_2 is the same as that of the first embodiment, the description thereof will be omitted. Next, the mobile stations 3 and 4 respectively use the access channels selected based on the probability distribution notified from the base station 30 to request transmission signals PS3_R and PS4_.
R is transmitted sequentially. The processing for these transmission request signals PS3_R is similar to the processing for the transmission request signal PS1_R described above. Also, the transmission request signal PS4
Since the processing for _R is the same as that in the first embodiment, the description thereof will be omitted.

As is clear from the above description, according to the present embodiment, since there are a plurality of access channels 10A, packet collision does not occur even if transmission request signals are simultaneously transmitted from a plurality of mobile stations. Further, if the probability distribution for each access channel 10A is set appropriately, more efficient transmission can be performed.

[0078]

As described above, according to the present invention,
In the CDMA mobile communication system, since the size of the packet transmitted via the access channel set by separating the common channel can be reduced, the probability of packet collision on the access channel can be suppressed low. Further, since the transmission timing of the data to be transmitted is notified to each mobile station, packets do not collide on the message channel set by separating the common channel. Therefore, more efficient packet communication can be realized than before.

Further, since the generation of data to be transmitted is notified to the base station via the access channel, even when a certain mobile station is transmitting data using the message channel, the base station is always able to It is possible to grasp the generation status of data to be transmitted. Therefore, effective traffic control by the base station is enabled, and efficient packet communication can be realized.

A reservation type packet communication system adopting TDMA (for example, SRMA (Split channel Rese
rvation Multiple Access) and PRMA (Packet Reserv)
, etc.), the capacity of the entire system decreases (deteriorates) when either the traffic on the access channel or the traffic on the message channel exceeds the capacity limit, so the effect of the reservation type is sufficient. In order to obtain the above, it is indispensable to control the band of the access channel and the message channel according to the traffic, whereas the CDMA mobile communication system to which the present invention is applied employs CDMA. Since the sum of the traffic on the access channel and the traffic on the message channel does not exceed the capacity limit, the effect of the reservation type can be obtained without performing the above-mentioned special control. In addition, strict control on frame synchronization is indispensable in a system adopting TDMA, whereas a system adopting the present invention adopting CDMA does not require strict control as in the case of TDMA. Therefore, according to the present invention, a large-capacity and flexible communication system can be realized without performing special control.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a CDMA mobile communication system to which a multi-access method according to each embodiment of the present invention is applied.

FIG. 2 is a block diagram showing a configuration of a mobile station in FIG.

FIG. 3 is a diagram for explaining a CDMA mobile communication system.

FIG. 4 is a timing chart showing the operation of the CDMA mobile communication system to which the multi-access method according to the first embodiment of the present invention is applied.

FIG. 5 is a timing chart showing the operation of the CDMA mobile communication system to which the multi-access method according to the second embodiment of the present invention is applied.

FIG. 6 is a timing chart showing an operation of a CDMA mobile communication system to which a modification of the multi-access method according to the second embodiment of the present invention is applied.

FIG. 7 is a timing chart showing an operation of the CDMA mobile communication system to which the multi-access method according to the third embodiment of the present invention is applied.

[Explanation of symbols]

 1 to 4 mobile station 10 common channel 10A access channel 10B message channel 20 broadcast channel 30 base station 31 transceiver 32 traffic control unit 33 baseband signal processing unit 41 transceiver 42 control unit 43 baseband signal processing unit 44 display device 45 instruction Input device

Claims (25)

[Claims] 1. A common channel commonly used when a plurality of mobile stations transmits data to a base station at arbitrary timing, and a common channel used when the base station transmits data to the plurality of mobile stations. In a multi-access method in a CDMA mobile communication system having one broadcast channel, the common channel is separated into an access channel and a message channel, and the generation of data to be transmitted by the mobile station is transmitted to the base station via the access channel. A step of notifying the mobile station of the transmission timing of the data to be transmitted by the base station to the mobile station via the notification channel; and a step of notifying the mobile station of the base station using the message channel. And a step of transmitting the data to be transmitted at the notified transmission timing.
Multi-access method in MA mobile communication system. 2. The multi-access method in a CDMA mobile communication system according to claim 1, wherein there is one message channel. 3. The multi-access method in a CDMA mobile communication system according to claim 1, wherein there are a plurality of message channels. 4. A spreading code corresponding to each message channel is pre-assigned to each mobile station, and the generation of data to be transmitted by the mobile station and the spreading code assigned to the mobile station are assigned via the access channel. Notifying the base station, the mobile station transmits the data to be transmitted at the transmission timing notified by the base station using the same number of message channels corresponding to at least one spreading code assigned to the mobile station. The multi-access method in a CDMA mobile communication system according to claim 3, wherein 5. The base station reports the transmission timing of the data to be transmitted and the at least one spreading code to the mobile station via the broadcast channel, and the mobile station broadcasts from the base station. 4. The CDMA mobile according to claim 3, wherein the data to be transmitted is transmitted at the transmission timing notified from the base station using the same number of the message channels corresponding to at least one spread code that has been transmitted. Multi-access method in communication system. 6. The multi-access method in a CDMA mobile communication system according to claim 1, wherein there are a plurality of access channels. 7. The mobile station allocates each of the access channels to each of the mobile stations in advance, and reports the generation of data to be transmitted by the mobile station to the base station via the access channel allocated to itself. The multi-access method in the CDMA mobile communication system according to claim 6. 8. The mobile station has a probability distribution regarding use of each access channel for each mobile station, selects one access channel from a plurality of the access channels based on the probability distribution, and 7. The multi-access method in a CDMA mobile communication system according to claim 6, wherein the data to be transmitted is transmitted at the transmission timing notified from the base station using an access channel. 9. The multi-access method in a CDMA mobile communication system according to claim 8, wherein the base station reports the probability distribution to each of the mobile stations via the broadcast channel. 10. A common channel commonly used when a plurality of mobile stations transmits data to a base station at arbitrary timing, and a common channel used when the base station transmits data to the plurality of mobile stations. CDMA with one broadcast channel
In a mobile station in a mobile communication system, transmitting / receiving means for transmitting / receiving a signal to / from the base station via the common channel and the broadcast channel, and means for separately using the common channel into an access channel and a message channel And processing means for modulating data to be transmitted and supplying the modulated data to the transmitting / receiving means, demodulating a signal received by the transmitting / receiving means, and generating the data to be transmitted via the access channel by the base station. Control for controlling the transmission / reception means and the processing means so as to modulate the data to be transmitted at the transmission timing notified from the base station using the message channel and supply the data to the transmission / reception means. And a CDM comprising:
A mobile station in a mobile communication system. 11. The mobile station in a CDMA mobile communication system according to claim 10, wherein there is one message channel. 12. A plurality of message channels are provided, and the processing means modulates data to be transmitted with a spreading code, thereby making the message channel used for transmitting the data to be transmitted correspond to the spreading code. The mobile station in the CDMA mobile communication system according to claim 10, wherein the mobile station is a message channel. 13. The base station holds the spreading code corresponding to at least one of the message channels, and generates the data to be transmitted and the spreading code held by itself, via the access channel. Controlling the processing means and the transmission / reception means to transmit the data, and the processing means and the transmission means to transmit the data to be transmitted at the transmission timing notified from the base station using the at least one message channel. 13. The transmitter / receiver means is controlled.
A mobile station in the described CDMA mobile communication system. 14. The control means uses the same number of message channels corresponding to at least one spreading code reported from the base station to transmit the data to be transmitted at the transmission timing reported from the base station. 13. The mobile station in the CDMA mobile communication system according to claim 12, wherein the processing means and the transmission / reception means are controlled to transmit the. 15. The mobile station in a CDMA mobile communication system according to claim 10, wherein there are a plurality of access channels. 16. The control means controls the processing means and the transmission / reception means to notify the base station of the occurrence of data to be transmitted using the access channel previously associated with the own station. Claim 1 characterized by the above-mentioned.
A mobile station in the CDMA mobile communication system according to 5. 17. The control means holds a probability distribution regarding use of each access channel, selects one access channel from a plurality of the access channels based on the probability distribution, and uses the access channel. 16. The C according to claim 15, wherein the processing unit and the transmission / reception unit are controlled to transmit the data to be transmitted at the transmission timing notified from the base station.
A mobile station in a DMA mobile communication system. 18. The mobile station in a CDMA mobile communication system according to claim 17, wherein the probability distribution is reported from the base station to the mobile stations. 19. A common channel commonly used when a plurality of mobile stations transmits data to a base station at arbitrary timing, and a common channel used when the base station transmits data to the plurality of mobile stations. CDMA with one broadcast channel
In a base station in a mobile communication system, a transmitting / receiving means for transmitting / receiving a signal to / from the base station via the common channel and the broadcast channel, and means for separately using the common channel into an access channel and a message channel. In addition, the data to be transmitted is modulated and supplied to the transmission / reception unit, the processing unit demodulates the signal received by the transmission / reception unit, and the signal received by the transmission / reception unit is monitored and transmitted from the mobile station. When the generation of the data to be transmitted is notified, the transmission timing of the data to be transmitted is determined based on the monitoring result, and the transmission timing is notified to the mobile station via the notification channel. And a control means for controlling the transmitting / receiving means and the processing means so as to receive and demodulate the data transmitted by. Base station in the CDMA mobile communication system, characterized by. 20. The base station of the CDMA mobile communication system according to claim 19, wherein the number of the message channels is one. 21. The base station in a CDMA mobile communication system according to claim 19, wherein the message channel is plural, and the processing means demodulates a signal supplied from the transmitting / receiving means based on a spread code. . 22. The control means transmits the data to be transmitted based on the monitoring result when the generation of the data to be transmitted and the spread code are notified from the mobile station via the access channel. The processing for determining timing, notifying it to the mobile station via the broadcast channel, and receiving and demodulating data transmitted at the transmission timing via the message channel corresponding to the spread code. The base station in the CDMA mobile communication system according to claim 21, characterized in that the base station controls the means and the transmitting / receiving means. 23. When the generation of data to be transmitted is informed from the mobile station, the control means, based on the monitoring result, transmits at least the transmission timing of the data to be transmitted and the plurality of message channels. A spreading code corresponding to one is determined, and these are notified to the mobile station via the notification channel, and data transmitted via the message channel corresponding to the spreading code at the transmission timing is determined. 22. The base station in a CDMA mobile communication system according to claim 21, wherein the transmitting / receiving means and the processing means are controlled to receive and demodulate. 24. A plurality of the access channels are provided, and the control means determines the probability distribution regarding the use of each of the access channels, and notifies the mobile stations via the broadcast channel of the processing means and the 20. The CDM according to claim 19, wherein the transmitting / receiving means is controlled.
A base station in a mobile communication system. 25. The control means determines the probability distribution based on the monitoring result.
4. A base station in the CDMA mobile communication system according to 4.