JP2002044055A - Wireless mobile station and wireless communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless mobile station which can eliminate the interference of downlink signals by a small size of hardware by reducing the number of interference components to be eliminated, and also provide a wireless communication system comprising the mobile station and a base station. SOLUTION: Each mobile station comprises a receiver which receives a time-division spread spectrum signal; and a decoder which eliminates the interference of received signals and decodes the signals only during the time slot period assigned to itself. The mobile stations eliminate only the multipath interference with respect to themselves. The wireless communication system comprises these wireless mobile stations and the base station provided with the transmitter which transmits the time-division spread spectrum signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio mobile station for removing interference of a received spread spectrum signal, and a radio communication system having the radio mobile station and a base station.

[0002]

2. Description of the Related Art Conventionally, in a mobile radio communication system using a spread spectrum signal, a different code is assigned to each communication channel so that the same frequency is shared at the same time and multiple access is realized. Here, interference occurs between these communication channels in accordance with the mutual correlation value of the assigned codes. In a wireless propagation environment, there are multipath arriving waves, and these multipath signals are also interference signals. Further, signals from other base stations and signals from other sectors of the same base station are also considered as interference components. The signal-to-interference ratio is determined based on the power ratio between the sum of these interference signals and noise and the desired signal, the number of mobile stations capable of simultaneous communication within a range where the signal-to-interference ratio satisfies a desired value is determined, and the system capacity is determined. Will be determined.

As a technique for improving communication quality or increasing system capacity by reducing these interference signals, there is an interference elimination technique. For reference, see Multiuser Dete
ction for CDMA Systems (AD Hallen et al, IEEE P
Personal Commun. April 1995), "Outdoor Experimental Characteristics of Coherent Multi-Stage Interference Canceller in DS-CDMA (IEICE Technical Report RCS99-17)" and "Multi-User Receiver (JP-A-2000-138605)". Estimate interference signal components
It is intended to improve the signal-to-interference ratio of the desired signal by duplicating and removing the duplicate component from the received signal. This technology makes it possible to increase the capacity of the system.

[0004]

However, in order to remove interference components, it is necessary to perform calculations on all received signals to be removed, and the circuit scale increases as the number of interference signals to be removed increases. There is a problem that it becomes larger. As an interference canceller configuration characterized by a reduction in circuit size, there is an "approximate cross-correlation elimination method in asynchronous DS / CDMA systems (Suzuki et al., IEICE RCS96-34)". The circuit scale increases in proportion to the number of channels. For this reason, it is difficult to introduce an interference canceller into a mobile station in order to prevent a decrease in downlink quality due to multipath interference, due to hardware scale and power saving.

[0005] Therefore, the present invention provides a radio mobile station that realizes the elimination of interference of a downlink signal on a small hardware scale by reducing the interference components to be eliminated, and a radio communication system having the radio mobile station and a base station. The purpose of the system is to provide.

[0006]

SUMMARY OF THE INVENTION A wireless mobile station according to the present invention comprises:
It has a receiving means for receiving a time-divided spread spectrum signal, and a demodulating means for demodulating by removing interference only during a time slot of the received signal to its own station. Thereby, the same base station (sector) in the same frequency band at the same time
It is possible to provide a wireless mobile station that realizes the removal of downlink signal interference with a small hardware scale by reducing the number of interference components to be removed to one wireless mobile station that is communicating with the mobile station.

[0007] According to another embodiment of the present invention, it is preferable that the demodulation means removes multipath interference to its own station.

[0008] According to another embodiment of the present invention, the demodulation means separates the received signal into a plurality of path components, generates one or more interference replicas which are copies of the path components, and generates an interference replica of the interference replica. It is also preferable that the intensity is adjusted, the interference replica whose intensity is adjusted is subtracted from the received signal, and the received signal whose interference replica is reduced is subjected to despreading.

A radio communication system according to the present invention includes the above-mentioned radio mobile station, and a base station having a transmitting means for transmitting a time-division spread spectrum signal.

According to another embodiment of the present invention, a base station includes a modulation unit for adaptively selecting a modulation scheme from among a plurality of modulation schemes and generating a downlink signal, and demodulating a radio mobile station. The means creates a duplicate signal of the signal received from the communication base station by the hard decision or soft decision criterion, creates a duplicate signal of the signal received from the interference base station by the soft decision criterion, and subtracts these duplicate signals from the received signal. It is also preferable to demodulate a target signal from the reduced received signal.

According to another embodiment of the present invention, the demodulation means of the radio mobile station separates the received signal received from the communication base station into a plurality of path components, and converts one or more copy signals of the path components. Creating and subtracting the duplicated signal from the received signal, and demodulating a target signal from the reduced received signal, wherein the radio mobile station measures the quality of the demodulated signal so that the quality is improved. It is preferable to further include means for adjusting the directivity of the receiving antenna and removing interference from the interference base station.

[0012] According to another embodiment of the present invention, the radio mobile station further includes means for measuring communication quality and transmitting the measured communication quality information to the base station, wherein the base station receives the communication quality information. It is preferable that the apparatus further comprises means for determining a transmission rate based on the communication quality information and controlling a downlink signal based on the determined transmission rate.

According to another embodiment of the present invention, a radio mobile station measures communication quality, determines a transmission rate based on the measured communication quality information, and transmits the determined transmission rate information to a base station. It is preferable that the base station further includes means for transmitting to the station, and the base station further includes means for controlling a downlink signal based on the received transmission rate information.

[0014] According to another embodiment of the present invention, it is preferable that the transmitting means of the base station transmits user data by multicode, and the demodulating means of the radio mobile station demodulates the received multicode.

[0015]

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

First, a first embodiment will be described.

FIG. 1 shows a time division CDM according to the present invention.
It is a block diagram of A system. This system is composed of one base station and three mobile stations for simplicity and specificity, and will be described below with reference to FIG.

The base station transmits time-division multiplexed information to each mobile station using a spread spectrum signal. FIG. 1 shows how information is transmitted in the order of mobile stations A, B, and C. The amount of information transmitted at one time may be constant, or may be changed according to the amount of information transmission required by each mobile station or the state of radio wave propagation.

Normally, when performing multiplex transmission using a spread spectrum signal, transmission is performed not by time division but by division by a spread code. In multiplex transmission by code division, information is transmitted to multiple mobile stations using the same frequency at the same time,
Inter-station interference rather than self-station interference becomes dominant, and the processing for removing the interference signal becomes very large. Therefore, it is difficult to realize the interference canceller in a place where there are many physical restrictions such as a small mobile station. In order to solve this, in the present embodiment, the base station transmits information to each mobile station by time-division multiplexing using a spread spectrum signal.

FIG. 2 is a block diagram of the receiver of the mobile station.
A transmission signal of a base station generally reaches a mobile station via a plurality of radio wave paths (multipath), and the plurality of signals interfere with each other to degrade reception quality. The receiver of FIG. 2 reduces the influence of this interference. FIG.
Converts the received signal into a baseband quantized digital signal by a down-converter and an A / D converter, and then performs interference elimination in an interference elimination unit, and then converts a desired signal into a digital signal. To receive.

However, when the configuration as shown in FIG. 2 is used, there is a problem that the circuit scale of the interference removing unit becomes large. That is, since the base station simultaneously transmits information to a plurality of mobile stations using the same frequency, the number of spread signals to be removed increases, and an interference removal circuit corresponding to each spread signal is required.

FIG. 3 is a specific configuration diagram of the interference removing unit according to the present invention. According to the present invention, information is transmitted to only one mobile station at the same time by time division as shown in FIG. 1, so that the interference signal to be eliminated is only its own component (in FIG. 3, the signal spread with the spreading code C1) Only). Therefore, the number of duplicate interference signals (N in FIG. 3) subtracted from the received signal may be at most the number of multipaths or less, and the circuit scale can be reduced. Here, N is a spread band of one carrier wave of 1.25 MHz.
It is known that about 3 or less at 5 MHz and about 4 or less at 5 MHz.

A feature of the demodulation means according to the present invention is to remove multipath interference to the own station, separate a received signal into a plurality of path components, and make an interference replica which is a copy of one or more path components. Is generated, the intensity of the interference replica is adjusted, the interference replica whose intensity is adjusted is subtracted from the received signal, and the interference replica is despread with respect to the reduced received signal. The configuration of the interference removing unit is shown in FIG.
This will be described below with reference to FIG.

First, the timing of each multipath component of the received signal is detected by a correlator. The received signal is despread at the detected timing. Each signal is multiplied by a suppression coefficient and spread again (respread). Here, the re-spread signal is converted by an A /
Subtract from the signal from the D converter. The output value is despread again, and the suppression coefficient is integrated. These multipath interference signals are added to the value obtained by integrating the above-described suppression coefficients to obtain respective signal components. In FIG. 3, the interference canceling unit surrounded by a thick gray line can be connected to a cascade and used in a multistage type. FIG. 3 shows M interference cancellation units. Finally, each signal component from which the multipath interference signal has been removed is RAKE-received to obtain a received signal.

With this receiver, multipath components of the signal from the base station are decomposed and reception is performed, and reception can be performed while eliminating interference between the multipath components. In addition, since it is only necessary to remove interference of a signal addressed to itself, the circuit scale does not increase, and application to a mobile station is easy. As the configuration of the interference removing unit, any configuration that removes interference between multipath components can be used in the present invention.

FIG. 4 is a diagram showing a first configuration of an interference canceller according to the present invention. FIG. 6 is a diagram showing a second configuration of the interference canceller according to the present invention.
(The RAKE receiver at the last stage is omitted.) These are general parallel removal configurations, and configurations equivalent to these can also be taken. FIG. 5 is a configuration diagram of the interference cancellation circuit of FIG. 4, and FIG. 7 is a configuration diagram of the interference cancellation circuit of FIG. Thus, the interference cancellation circuit may create a copy of the multipath interference signal based on the soft decision value of the received signal. Also, an ICU (interference removing unit) disclosed in JP-A-10-51353 or JP-A-11-31772 is disclosed.
As described in IEU (Interference Estimation Unit) disclosed in No. 5, the method may be a method of creating based on a hard decision of received information and a transmission path state estimated from pilot signal reception. In addition, instead of collectively subtracting multipath interference signals in parallel (parallel elimination), for example, one or more multipath interference signals may be sequentially subtracted (serial elimination). In some cases, a copy of the multipath interference signal may be created based on the soft decision value of the received signal, or may be created based on the hard decision of the received information and the channel state estimated from the pilot signal reception. It may be. Regardless of the configuration,
The circuit scale of the interference removing unit shown in FIG. 2 is reduced.

FIG. 8 is a block diagram of a system for determining a rate according to the reported quality. The mobile station inputs a signal from the interference cancellation unit to the reception quality determination unit, and reports the reception state to the base station. The base station determines a transmission rate in accordance with the quality reported from another mobile station according to the reported reception state, and performs communication at the determined rate. That is, by determining the transmission rate based on the reception quality improved by the interference cancellation, the throughput of the entire system is improved.

Although the configuration of FIG. 8 uses a method in which the base station determines the communication rate, the mobile station autonomously determines the communication rate based on the reception quality and reports it to the base station. The station may determine the transmission rate based on the request rate from the mobile station.

Next, a second embodiment will be described.

FIG. 9 is a system configuration diagram showing that signals arrive from a plurality of base stations to one mobile station. In a general land mobile communication system, a method is used in which a large area is covered by many base stations, and signals from a plurality of base stations reach mobile stations in the system.
Of course, it is assumed that each base station has transmitted a time-spread spectrum spread signal to the mobile station. FIG.
In, the interference components received by the mobile station, the interference component from the desired sector of the base station that is communicating, interference components from other sectors of the base station that is communicating, and other base stations that are not communicating And interference components. Since the mobile station of the system of FIG. 9 includes the above-described receiver, it is possible to receive each of the mobile stations after removing each interference component.

FIG. 10 is a block diagram of an interference canceling unit for canceling interference from other sectors and other base stations. FIG. 10 shows an interference canceling circuit 0 for multipath from a desired sector and interference canceling circuits 1 to N for multipath from another sector of another base station or communication base station in the configuration shown in FIG.
And For example, normal time-division CDMA
If the system is used, since the signal from the desired sector is directed to a plurality of mobile stations, the circuit scale of the interference cancellation circuit 0 for removing these interference components increases. Here, since each base station transmits a time-division spread spectrum signal, only multipath components need to be removed for a desired sector in communication, and interference removal can be performed without increasing the circuit scale. It is possible.

FIG. 11 is a system configuration diagram in which each base station communicates with each mobile station while adaptively changing the modulation scheme. The desired sector of the communicating base station is
The modulation scheme A is used, the interference base station B selects the modulation scheme B, and the interference base station C selects the modulation scheme C to communicate with each mobile station. In this case, the mobile station cannot obtain information on the modulation scheme in which the interference component from the non-communicating base station is transmitted unless each base station transmits the information. Also, transmitting information of a modulation scheme increases overhead.

As described above, when each base station is adaptively selecting a modulation scheme from among a plurality of modulation schemes and transmitting a downlink signal, the demodulation means of the mobile station uses the signal received from the communication base station. Create a duplicate signal of the hard decision or soft decision criterion, create a duplicate signal of the signal received from the interference base station by the soft decision criterion, subtract those duplicate signals from the received signal,
It is preferable to demodulate an intended signal from the reduced received signal.

In the case where the signal from the desired sector is subjected to hard-decision interference elimination and the signals from other sectors and other base stations of the communication base station are subjected to soft-decision elimination, for example, FIG.
Alternatively, in the basic configuration of FIG. 6, the interference elimination circuits 0 of the interference elimination units 1 to K are used for processing a signal from a desired sector, and the circuit configuration is disclosed in, for example, ICU disclosed in Japanese Patent Application Laid-Open No. H10-51353, or 11 or 317725, and the other interference canceling circuits 1 to N are used for processing signals from other sectors and other base stations. The configuration shown in FIG. At this time, the signal from which interference has been removed from the signal from the desired sector is obtained as the output signal 0 of the interference removal unit K.

In addition, a configuration of serial elimination instead of parallel elimination may be adopted. In this case, interference elimination may be performed by soft decision, or interference elimination by hard decision may be performed on a signal from a desired sector. May be performed.

FIG. 12 is a circuit configuration diagram in the case where all are determined by soft decisions. This involves separating a received signal into a plurality of path components, generating an interference replica that is a copy of one or more of the path components, adjusting the intensity of the interference replica, and receiving the interference replica with the adjusted intensity. The despreading is performed on the received signal subtracted from the signal and the interference replica is subtracted. Here, interference removal is performed for each code timing from each base station.

With this configuration, even if another sector or another base station of the communicating base station has not obtained information on the modulation method of the signal transmitted to the other mobile station, the communication is performed. It is possible to remove an interference component from another sector or another base station of the base station. Also, using the configuration shown in FIG. 8, it is possible to implement a function of determining a communication rate according to the communication quality of the mobile station.

Next, a third embodiment will be described.

FIG. 13 is a configuration diagram of a receiver using an array antenna in an environment where a plurality of base stations exist as shown in FIG. The weight control unit of the receiver monitors the reception state and adjusts the directivity of the reception antenna so that the reception quality is increased. For the weighting method, see "Theoretical system of adaptive antenna (IEICE '92 / 1
1, Vol.J75-B-II No.11, pp713-720) and "Progress and Future Prospects of Adaptive Antenna Theory (IEICE'92 / 11, Vol.J75-B-II No.11 , pp721-732) ". In the example of FIG. 13, reception is performed by directing the antenna directivity to a desired base station, and an interference signal from another base station is removed by controlling the directivity of the antenna. Unlike the case of the second embodiment, the directivity is controlled so that an interference signal from another base station is not received, so that it is not necessary for the interference canceller to consider a signal from another base station. However, since signals from other sectors of the same base station may remain as interference, a canceling circuit for this interference signal is necessary.

FIG. 14 is a block diagram of an interference canceling unit for canceling interference in the same beam. This configuration is different from the configuration in FIG. 4 in that the interference elimination circuit 0 is an interference elimination circuit for a desired sector, and the interference elimination circuits 1 to N are for eliminating interference from other sectors of the communication base station. FIG. 6
It is also possible to apply Since signals of other sectors in the same base station have different modulation schemes, interference signals are removed by soft decision considering the same as in the second embodiment. The interference removal of the multipath signal from the desired sector may be performed by hard decision or soft decision. For example, as shown in FIG. 12, all the interference elimination circuits can be realized using a soft decision circuit. Further, similarly to the second embodiment, it is possible to remove interference from signals from a desired sector by hard decision and to remove signals from other sectors by soft decision. In addition, instead of parallel elimination, a configuration of serial elimination may be adopted, in which case interference elimination by soft decision may be performed, or interference elimination by hard decision is performed on a signal from a desired sector. Is also good.

Thus, interference can be removed while preventing an increase in the circuit scale of the interference removing unit. Although it is necessary to control the antenna directivity, since the calculation and control need only be performed on the signal to the own station, the circuit scale does not increase significantly.

FIG. 15 is a configuration diagram of a receiver using an array antenna for reporting quality to a base station, as in the first embodiment.

Finally, a fourth embodiment will be described.

FIG. 16 is a block diagram of a system for performing multi-rate transmission. As shown in the first to third embodiments, a multi-code communication is used in a system including a plurality of base stations transmitting a time-division spread spectrum signal. The user data is divided into several pieces of transmission data (N in the figure) in the user data division unit according to the transmission rate, and the respective divided data are mutually orthogonal codes (W1 to WN in the figure). ) To perform diffusion. Examples of orthogonal codes used here include:
Walsh code and the like. After adding them, they are spread with a common code (spread code C) and transmitted. In a system using this multicode, high-speed communication can be realized in a system having a limited spread band. For example, when transmitting a signal having a transmission rate of 2000 kbps in a system having a band of a chip rate of 1000 kcps, the signal cannot be transmitted by being spread with a single code. This is because the chip rate is smaller than the user data rate. Here, if this user transmission data is divided into eight blocks having a rate of 250 kbps, each block can be transmitted by spreading it four times.

The reason why orthogonal codes are used here is to avoid interference by setting the correlation value to zero, but in a multipath environment, codes with different timings interfere with each other. Needs to be considered.

FIG. 17 is a block diagram showing the application of the interference canceller having the basic structure shown in FIG. 4 to multi-code interference cancellation.
The configuration of the receiver of the mobile station can be the one shown in FIG. 2 including an interference canceller or shown in FIG. 13 using an array antenna. Here, the interference removing unit needs to be configured to remove the interference between the multicodes. In this example, it is assumed that a signal transmitted by a multicode using N orthogonal codes (W1 to WN) is received by a mobile station as K multipath signals. For this reason, it is composed of an interference canceling circuit for timing 1 to timing K of each code. Finally, the signals of all the codes are demodulated and then combined to obtain a received signal. In this configuration, the interference removal processing is performed only on the multi-code signal of the desired sector.
When the process of removing interference from another cell is also performed, in addition to the interference removal circuit corresponding to the multicode signal from the desired sector, a signal from another sector / other cell (multicode signal)
May be provided.

The interference cancellation circuit changes depending on the configuration of the receiver. For example, in a system such as the first embodiment,
A soft decision or a hard decision may be used to remove a multipath signal. Here, as in the second embodiment, when interference from another base station is conceivable, it is necessary to remove interference from another base station or interference from another sector of the communication base station by soft decision.

In the above-described various embodiments of the wireless mobile station and the wireless communication system of the present invention, various changes, modifications, and omissions of the technical idea and scope of the present invention can be easily performed by those skilled in the art. Can be. The foregoing description is merely an example, and is not intended to be limiting. The invention is limited only as defined by the following claims and equivalents thereof.

[0049]

As described in detail above, according to the present invention, an interference canceller having a small circuit scale is realized.

In the first embodiment, a base station that transmits a spread spectrum signal in a time-division manner is used, and each mobile station performs interference cancellation only in a time slot addressed to the own station.
An interference suppression device that considers only the multipath component from the desired sector can be realized. This reduces the circuit scale,
Implementation in mobile stations, which has been considered difficult so far, becomes possible.

Further, in the second embodiment, a configuration is provided in which interference is also removed from a base station which is not performing communication or another sector of a communication base station, so that application to a system having a plurality of base stations is possible. did.

Similarly, in the third embodiment, an interference canceling device that can be mounted on a mobile station in an environment where a plurality of base stations exist by combining with an array antenna has been described. In addition, even in a system which performs multi-band transmission with a limited bandwidth by applying multi-code transmission, it is possible to realize a system having an interference canceller having a smaller circuit scale than before.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a time division CDMA system according to the present invention.

FIG. 2 is a configuration diagram of a receiver of a mobile station.

FIG. 3 is a specific configuration diagram of an interference removing unit according to the present invention.

FIG. 4 is a first configuration diagram of an interference removing unit according to the present invention.

FIG. 5 is a configuration diagram of the interference elimination circuit of FIG. 4;

FIG. 6 is a second configuration diagram of the interference removing unit according to the present invention.

FIG. 7 is a configuration diagram of the interference removal circuit of FIG. 6;

FIG. 8 is a configuration diagram of a system that determines a rate according to reported quality.

FIG. 9 is a system configuration diagram showing that signals reach a single mobile station from a plurality of base stations.

FIG. 10 is a configuration diagram of an interference canceling unit that cancels interference from another sector and another base station.

FIG. 11 is a system configuration diagram in which each base station communicates with each mobile station while changing the modulation scheme adaptively.

FIG. 12 is a circuit configuration diagram in a case where all are performed by soft decisions.

13 is a configuration diagram of a receiver using an array antenna in an environment where a plurality of base stations exist as shown in FIG.

FIG. 14 is a configuration diagram of an interference removing unit that removes interference in the same beam.

FIG. 15 is a configuration diagram of a receiver that uses an array antenna to report quality to a base station.

FIG. 16 is a system configuration diagram for performing multi-rate transmission.

FIG. 17 is a configuration diagram in which the interference canceller of FIG. 4 is applied to multi-code interference cancellation.

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) H04J 3/00 H04B 7/26 CD (72) Inventor Yoshio Takeuchi 2-1-1 Ohara, Kamifukuoka-shi, Saitama Shares EE02 EE21 EE35 5K028 AA07 BB04 CC02 CC05 HH03 QQ00 RR03 5K052 AA01 BB01 CC06 DD03 EE30 FF32 5K059 CC03 CC04 DD32 DD35 5K067 AA03 AA42 CC04 CC10 CC24 DD

Claims (9)

[Claims] 1. A receiving means for receiving a time-divided spread spectrum signal, and a demodulating means for removing interference and demodulating only during a time slot of the received signal to its own station. Radio mobile station. 2. The wireless mobile station according to claim 1, wherein the demodulation unit removes multipath interference to the own station. 3. The demodulation unit separates the received signal into a plurality of path components, generates an interference replica that is a copy of one or more path components, adjusts the intensity of the interference replica, and adjusts the intensity of the interference replica. The wireless mobile station according to claim 1, wherein the adjusted interference replica is subtracted from the received signal, and the interference replica is despread with respect to the reduced received signal. 4. A radio communication system comprising: the radio mobile station according to claim 1; and a base station having a transmission unit that transmits the time-division spread spectrum signal. 5. The base station has a modulating means for adaptively selecting a modulation method from among a plurality of modulation methods to create a downlink signal, and the demodulation means of the radio mobile station includes a communication base station. Create a duplicate signal of the signal received from the hard decision or soft decision criterion, create a duplicate signal of the signal received from the interference base station by the soft decision criterion, subtract those duplicate signals from the received signal, the subtracted The wireless communication system according to claim 4, wherein a target signal is demodulated from the received signal. 6. The demodulation means of the wireless mobile station separates a received signal received from a communication base station into a plurality of path components, creates one or more duplicate signals of the path components, and generates the duplicate signals. Subtracting from the received signal, demodulating a target signal from the subtracted received signal, the radio mobile station measures the quality of the demodulated signal,
5. The radio mobile station according to claim 4, further comprising: means for adjusting the directivity of the receiving antenna so as to improve the quality and removing interference from an interference base station. 7. The wireless mobile station measures communication quality,
The base station further includes means for transmitting the measured communication quality information to the base station, wherein the base station determines a transmission rate based on the received communication quality information, and based on the determined transmission rate. The wireless communication system according to any one of claims 4 to 6, further comprising means for controlling a downlink signal. 8. The wireless mobile station measures communication quality,
Determining a transmission rate based on the measured communication quality information, and further comprising means for transmitting the determined transmission rate information to the base station, the base station based on the received transmission rate information The wireless communication system according to any one of claims 4 to 6, further comprising means for controlling a downlink signal. 9. The radio communication system according to claim 4, wherein the transmitting means of the base station transmits user data in a multicode, and the demodulating means of the radio mobile station demodulates the received multicode. The wireless communication system according to claim 1.