JP2002232943A - Data transmission processing method, data reception processing method, transmitter, receiver, and cellular radio communication system - Google Patents

Abstract

(57) [Summary] In a cellular radio communication system, the reception sensitivity is substantially increased even at a position distant from the base station without performing transmission power control in the base station. A receiving sensitivity of a mobile station is measured on the mobile station side based on control channel data from a base station, and a measurement result is reported to the base station. The base station determines the transmission mode based on the reported measurement result. In the base station, when the reception sensitivity on the mobile station side is low, as the specific transmission mode, the transmission target data encoded by the encoding unit 11 is duplicated by the duplication unit 13 to generate a plurality of identical data, and these are modulated. Part 15
, And spread spectrum by a plurality of codes in a plurality of spreading units 17. In the receiver of the mobile station, corresponding to the transmission mode, the plurality of despreading units 35 perform despreading with the same plurality of codes used in the transmission, demodulate by the plurality of demodulation units 47, and demodulate by the addition unit 49. The data is reproduced by adding the signals and decoding the added output by the decoding unit 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication system employing a code division multiple access (CDMA) system, and more particularly to an adaptive modulation and coding system (AMCS) in CDMA.
n and Coding Scheme).

[0002]

2. Description of the Related Art AMCS is a type of adaptive control on the transmitter side in which the reception environment of a mobile station changes depending on the distance and time between a base station and the mobile station in cellular radio communication. More specifically, in a terminal that is a mobile station,
This is a technique for switching a transmission mode from a base station to an optimum one in accordance with a received signal strength of a signal from the base station. The transmission mode is determined by a combination of a plurality of modulation schemes and coding rates.

In order to measure the strength of a signal received from a base station on the terminal side, power measurement data is transmitted from the base station through a control channel. This transmission data is known data. Also, the transmission power and the ratio between the transmission power and the transmission power of the data channel for transmitting user data are known on the terminal side. The terminal receives the power measurement data transmitted from the base station,
R (Signal to Interference Ratio) or SNR (Si
gnal to Noise Ratio). These are indices indicating signal strength (ie, reception sensitivity) with respect to interference and noise. Next, based on this power and the known power ratio, the SIR of the data channel through which the user data is transmitted is estimated.

[0004] The transmission mode from the base station is determined based on the SIR thus obtained. This transmission mode determination processing is performed in the terminal, and the result is reported to the base station, or the SIR is reported to the base station and performed in the base station.

FIG. 4 shows a plurality of transmission modes # 1, # 2, #
3A is a graph showing SIR versus FER (Frame Error Rate), and SI
The graph (b) showing R vs. throughput (Throughput) is shown. As can be seen from these graphs, the distribution of FER and throughput differs depending on the transmission mode. That is, in the transmission mode # 3, the throughput is large in a region where the SIR is large, but the error rate increases when the SIR is lowered. In the transmission mode # 1, a low but stable throughput is obtained over a wide range of SIR,
Good noise performance over a wide area. Mode # 2 has intermediate properties between mode # 1 and mode # 3.
Therefore, the transmission mode of the channel for transmitting user data to the terminal according to the SIR in each terminal is
By switching between transmission modes # 1, # 2, and # 3 in the low, middle, and high SIR regions, respectively, compared to the case where a single transmission mode is used,
As shown by the combined thick line in the graph of FIG.
The best throughput can be obtained over a wide area.

On the other hand, the CDMA system is a technology for simultaneously performing a plurality of communications using signals of the same frequency band by a spread spectrum technology, and is a technology of time division multiple access (TDM).
A) The number of user channels per bandwidth can be increased as compared with the scheme A or the frequency division multiple access (FDMA) scheme. PN (Pseudorandom), which is more resistant to frequency selective fading due to multipath signals due to the wide transmission frequency.
Noise) code, and the like. Wideband C that widens this CDMA system
DMA will be adopted as a standard for next-generation mobile phones.

As shown in FIG. 6A, in the CDMA system, normally, coded data A is modulated (primary modulation).
After that, the modulated data A ′ is spread with the assigned code. On the other hand, FIG.
As shown in (1), the divided portions A, B, C, and D of the encoded data for the same user are simultaneously modulated (primary modulation).
Later, these modulated data A ', B', C ', D'
Are spread spectrum by the codes a, b, c, and d respectively assigned thereto, and are multiplexed in one frame. This is called adaptive code allocation. “Adaptation” in this case means that how many codes are used for data transmission for one user is determined according to the amount of data to be transmitted. Thus, the throughput can be increased by increasing the number of data that can be sent per frame for one user. Note that C
When performing the above-described transmission mode control based on the SIR in the DMA system, the transmission power per code needs to be kept constant at all times. This is to make the power ratio between the power measurement channel and the data channel constant.

[0008]

The above-mentioned AMCS
As shown in FIG. 5, even in a system in which code multiplexing is used in combination, when the received SIR is small, only one type of modulation scheme and coding rate can be selected. Is the same as a system that employs Therefore, the throughput near the cell boundary could not be improved.

[0009] Conventionally, as transmission power control on the transmitter side, in order to increase the reception sensitivity near a cell boundary, a terminal located at a position where reception sensitivity is inferior to a terminal located at a position where reception sensitivity is good. For this, a technique for increasing the transmission power is known. However, such transmission power control cannot be adopted for measuring the reception SIR in the terminal as described above. Since the power measurement channel is common to all users in the cell, the data channel power (or SIR) can be estimated from the power measurement channel power (or SIR) by changing the data channel power for each terminal. Because it is gone. In other words,
This is because it is difficult to change the power of the data channel because the power ratio between the transmission power of the power measurement channel and the transmission power of the data channel for transmitting user data must be kept constant. The transmit power of the channel is always constant).

Therefore, the present invention provides a data transmission processing method, a data reception processing method, a transmitter, and a data processing method that can substantially increase the reception sensitivity even at a position distant from the base station without performing transmission power control in the base station. It is an object to provide a receiver and a cellular radio communication system.

[0011]

A data transmission processing method according to the present invention is a data transmission processing method in a radio communication system employing a code division multiple access system, and is obtained by duplicating data to be transmitted to a mobile station. And transmitting a multiplexed signal to the mobile station by performing spread spectrum on a plurality of the same data with a plurality of codes.

A data reception processing method according to the present invention corresponding to this is a data reception processing method in a cellular radio communication system employing a code division multiple access system. Receiving a signal multiplexed by performing spread spectrum with a plurality of codes, despreading and demodulating the received signal with the same plurality of codes used for the transmission, and demodulating the received signal. Adding the plurality of obtained signals.

As described above, on the transmitting side, the same data is spread with a plurality of codes, and
On the receiving side, by adding a plurality of signals obtained by despreading the received signal with the same plurality of codes used for the transmission, only the signal level is improved with respect to the noise level, and the transmission power is substantially increased. The same effect can be obtained as doubled.

According to another aspect, the data transmission processing method according to the present invention is a data transmission processing method in a base station of a cellular radio communication system employing a code division multiple access system, wherein Recognizing the current reception sensitivity of the mobile station; determining a transmission mode to be used when transmitting data to the mobile station according to the recognized reception sensitivity; and transmitting data to the mobile station in the determined transmission mode. And transmitting, as the transmission mode, at least when the reception sensitivity is low, the spread spectrum with a plurality of codes for a plurality of the same data obtained by duplicating the data to be transmitted to the mobile station. It has a transmission mode for transmitting a multiplexed signal in a row.

In this configuration, the transmission mode is determined by the base station. However, the transmission mode determined by the partner mobile station to which data is to be transmitted may be received.

The present invention also claims the cellular radio communication system and the configuration of the transmitter and receiver used in the system.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, as an embodiment of the present invention, a cellular radio communication system that performs the above-described adaptive control in a CDMA system will be described.

FIG. 1 shows a schematic configuration of a transmitter of a base station in the present system. In the present embodiment, the present invention is applied to data transmission from a base station to a terminal that is a mobile station (here, a mobile phone). Therefore, the receiver of the base station may be the same as the existing configuration, and will not be described specifically. Although the base station corresponds to a plurality of users, only one user is shown in FIG. The transmitter includes a control unit 10, an encoding unit 11, a serial / parallel conversion / copy unit (S / P or Repeat) 1
3, modulation units 15 and 16, spreading units 17 and 18, multiplexing unit 1
9, an RF unit 21 and an antenna 23.

The control section 10 is a section for controlling the entire transmitter, and can be constituted by a CPU, a ROM, a RAM and the like. The encoding unit 11 performs error correction encoding on the transmission target data received from the control unit 10. The coding rate can be switched by the control unit 10 according to the transmission mode determined by the adaptive control. That is, for example, when the index indicating the receiving sensitivity such as the receiving SIR is high, the coding rate is increased,
If it is low, the coding rate is lowered.

The serial-parallel conversion / duplication unit 13 performs serial-parallel conversion or duplication of the encoded data according to the transmission mode under the control of the control unit 10, and inputs the data to a plurality of subsequent modulation units 15. . Modulation section 15 and subsequent diffusion section 1
7 are provided in plural pairs. Modulation unit 15 used for one user
The number of pairs of the spreading unit 17 is determined according to the transmission mode determined by the adaptive control. The transmission mode is determined based on the reception SIR at the terminal as described later in detail.
The serial-parallel conversion / copying unit 13 performs serial-parallel conversion when performing code multiplexing on a plurality of divided data as described above, and performs the same number of times when performing code multiplexing on the same duplicated data in the present invention. Make a copy. The modulation method of the demodulation unit 15 is selected from a plurality of modulation methods based on the transmission mode. The signal modulated by the modulator 15 is subjected to spectrum spreading in the spreading unit 17. As mentioned in the prior art, the transmission power per code is always constant.

On the other hand, the control channel data from the control unit 10 also passes through the modulation unit 16 and is spread spectrum by the spreading unit 18. The control channel data includes SIR measurement reference data. The output signals of the spreading units 17 and 18 are multiplexed by the multiplexing unit 19, and transmitted through the RF unit 21 to the antenna 23.
Is transmitted as radio waves.

FIG. 2 shows a schematic configuration of a terminal receiver in the present system. For the same reason as described above, the transmitter of the terminal may be the same as the existing configuration, and will not be particularly described. This receiver includes an antenna 31, despreading units 35 and 3
6, SIR calculation section 39, conversion section 41, phase correction control section 4
3, a phase correction unit 45, a demodulation unit 47, a parallel / serial conversion / addition unit (P / S or Sum) 49, a channel decoding unit 50, and a control unit 60. The signal extracted by the RF unit 33 via the antenna 31 is despread by the despreading units 35 and 36 using the same plurality of codes used for transmission. A signal of control channel data (reference data for SIR measurement) is obtained from the despreading unit 35, and a signal of each data channel is obtained from the despreading unit 36. The SIR calculation unit 39 calculates the SIR of the control channel data (that is, the received signal of the power measurement channel) based on the output of the despreading unit 35. The calculated SIR is calculated by the conversion unit 41.
It is converted to the SIR of the data channel. This conversion is performed by multiplying the output SIR of the SIR calculator 39 by a known ratio a between the transmission power and the transmission power of the data channel when transmitting user data.

The SIR is specifically determined as follows. That is, the output P (i) (here, P (i) = ai + jbi) of the despreading unit 35 is in-phase added for a certain section, and the average is taken as "S". Further, the variance between the average value and the output of the despreading unit 35 derived over a certain section is defined as "I". The ratio S / I is S
It is an example of IR. The expression is as follows. From equation (1), From the equations (2) and (3), SIR = S / I The SIR obtained as described above is reported by the control unit 60 to the base station via a transmitter (not shown) after the above conversion. Here, the SIR of the control channel data
Is calculated first and converted into the SIR of the data channel. However, after converting the power of the control channel data into the power of the data channel, the SIR of the data channel is converted.
May be obtained.

In the despreading section 36 for a plurality of data channels, the user data signal is obtained by despreading.
Phase correction controller 4 based on the despread signal of the control channel
3 generates a correction signal for correcting fading of each data channel, and corrects the output of each despreading unit 36 in the corresponding phase correcting unit 45. The signal after the correction is demodulated by each corresponding demodulation unit 47. As the demodulation method of the demodulation unit 47, the control unit 60 selects a demodulation method corresponding to the modulation method of the transmitter selected by the base station from the plurality of demodulation methods. In the parallel / serial conversion / addition unit 49,
The control unit 60 performs parallel-to-serial conversion or adds data in accordance with processing at the transmitter in the base station. Based on the control of the control unit 60, the output of the parallel-serial conversion / addition unit 49 is subjected to decoding processing by the channel decoding unit 50 according to the coding rate at the transmitter of the base station.

According to the timing chart of FIG. 3, the base station (B
An example of transmission and reception of signals between S) and a terminal that is a mobile station (MS) will be described. From the base station, SI
R measurement data is constantly transmitted (broken line from BS to MS in the figure). In this embodiment, when data communication needs to be performed, the terminal measures the SIR based on the SIR measurement data, and reports the measured SIR to the base station. The reporting of the SIR to the base station may be performed periodically.

The base station can receive SIR reports from a plurality of terminals. Therefore, the base station that has received the SIR reports from a plurality of terminals first determines a user to which data is to be transmitted based on those reports (adjustment I between users). Then, based on the report from each terminal, the base station selects a modulation scheme and a coding rate to be used when transmitting data to the terminal (II), and further determines the number of codes to be used (III).

When a plurality of codes are used, it is determined whether code multiplexing is performed on duplicate data of the same data or code multiplexing on divided data. Code multiplexing for duplicate data is selected when the reported SIR is low and it is determined that normal reception is unlikely to be possible as it is. At this time, the condition of the mode may be that the capacity of the data channel at that time has a margin (the available code is surplus). Also, code multiplexing on divided data for the same user can be selected when the SIR is relatively large and the data channel has a sufficient capacity.

These determined transmission parameters are notified to the terminal of the communication partner. As a result, the method of despreading, demodulation, and decoding at the terminal is set according to the transmitting side. However, if the transmission parameters can be estimated on the terminal side, the notification processing from the base station can be omitted.
The code to be assigned to the terminal can be transmitted to the terminal together with these transmission parameters. Thereafter, data is transmitted from the base station to the terminal in the transmission mode, and the base station receives the data in the reception mode corresponding to the transmission mode, and performs despreading and demodulation to reproduce the transmission data.

FIG. 7 shows the relationship between the distance R from the base station and the SIR. As can be seen from this figure, SIR1 reported when a conventional one code is used at a position at a specific distance R1 from the base station is the SI required for reception of constant quality.
Even if it is lower than R2, SIR3 of the same data of the present invention at the same position by two-code multiplexing of the present invention is almost twice as large as SIR1 and can exceed SIR2.

From a different point of view, as shown in FIG. 8, when the SIR reported when using the conventional one code at the position of the specific distance R1 from the base station matches the SIR2 necessary for reception of a certain quality. According to the two-code multiplexing of the same data according to the present invention, the distance at which the same SIR2 can be obtained can be dramatically increased to R2 larger than R1.

Therefore, the multiple code multiplexing of the same data according to the present invention is particularly useful in a region having a low SIR, and as a result, as shown in FIG. Can be improved.

While the preferred embodiment of the present invention has been described above, various modifications and changes other than those described above are possible. For example, although only the direct spread (DS) system has been described as the spread spectrum system, the present invention is also applicable to the frequency hopping (FH) system. In that case, a hopping pattern is used instead of the PN code.

[0033]

According to the present invention, in a cellular radio communication system employing a code division multiple access system, even if the reception sensitivity is low at a position distant from the base station without performing transmission power control at the base station, Substantial reception sensitivity can be increased.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a transmitter of a base station in a cellular radio communication system according to the present invention.

FIG. 2 is a block diagram showing a schematic configuration of a receiver of a terminal in the cellular radio communication system according to the present invention.

FIG. 3 is a timing chart for explaining an example of transmission and reception of a signal between a terminal which is a base station (BS) and a mobile station (MS) in the cellular radio communication system according to the present invention.

FIG. 4 is a graph (a) showing SIR versus FER for a plurality of transmission modes # 1, # 2, and # 3, and a graph (b) showing SIR versus throughput (Throughput).

FIG. 5 is a graph showing SIR versus throughput obtained by switching transmission modes.

FIGS. 6A and 6B are explanatory diagrams of adaptive code assignment.

FIG. 7 is a graph showing a relationship between a distance R from a base station and SIR for explaining an effect of the present invention.

FIG. 8 is another graph showing the relationship between the distance R from the base station and the SIR for explaining the effect of the present invention.

FIG. 9 is a graph showing SIR versus throughput for explaining the effect of the present invention.

[Explanation of Codes] 10: control unit, 11: channel coding unit, 13: serial / parallel conversion / copying unit (S / P or Repeat), 15, 16: modulation unit,
17, 18: spreading section, 19: multiplexing section, 21: RF section,
23, 31 antenna, 33 RF section, 35, 36 despreading section, 39 SIR calculation section, 41 conversion section, 43 phase correction control section, 45 phase correction section, 47 demodulation section, 49
... parallel / serial conversion / addition unit (P / S or Sum), 50 ... channel decoding unit, 60 ... control unit

Claims (14)

[Claims] 1. A data transmission processing method in a wireless communication system employing a code division multiple access method, wherein a plurality of codes are used for a plurality of same data obtained by duplicating data to be transmitted to a mobile station. A data transmission processing method, wherein a signal multiplexed by spreading is transmitted to the mobile station. 2. A data transmission processing method in a base station of a cellular radio communication system adopting a code division multiple access system, comprising: a step of recognizing a current reception sensitivity of a mobile station to which data is to be transmitted; Determining a transmission mode to be used when transmitting data to the mobile station in accordance with the recognized reception sensitivity; andtransmitting data to the mobile station in the determined transmission mode. A transmission mode for transmitting a multiplexed signal by performing spread spectrum with a plurality of codes for a plurality of identical data obtained by duplicating data to be transmitted to the mobile station when the reception sensitivity is low. A data transmission processing method characterized by the following. 3. A data transmission processing method in a base station of a cellular radio communication system adopting a code division multiple access method, wherein the method is determined in a mobile station of a data transmission destination.
Receiving a report of a transmission mode to be used when transmitting data to the mobile station; and transmitting data to the mobile station in the reported transmission mode, wherein the transmission mode includes at least reception sensitivity at the mobile station. Is low, a transmission mode for transmitting a multiplexed signal by performing spread spectrum with a plurality of codes for a plurality of same data obtained by duplicating data to be transmitted to the mobile station. Data transmission processing method. 4. A data reception processing method in a cellular radio communication system adopting a code division multiple access system, wherein a plurality of codes are spread and multiplexed on a plurality of identical data obtained by duplicating transmission target data. Receiving the converted signal; despreading and demodulating the received signal with a plurality of codes used for the transmission; and adding a plurality of signals obtained by demodulation; A data reception processing method comprising: 5. A transmitter in a cellular radio communication system employing a code division multiple access system, comprising: encoding means for encoding data to be transmitted; and a plurality of identical data by duplicating the encoded data. A plurality of modulating / spreading means for modulating the plurality of identical data and performing spectrum spreading with a plurality of codes, respectively, and multiplexing the outputs of the plurality of modulating / spreading means and transmitting the multiplexed radio wave Transmitting means, and control means for controlling the operation of the entire transmitter, the control means having a plurality of transmission modes, one of which is that at least the reception sensitivity is low at the mobile station that is the transmission partner A signal multiplexed by performing spread spectrum with a plurality of codes on a plurality of duplicated data of data to be transmitted to the mobile station. Transmitter characterized in that it comprises a transmission mode for transmitting. 6. The transmitter according to claim 5, further comprising means for transmitting measurement data for measuring the reception sensitivity at the mobile station on the mobile station side. 7. A serial-parallel conversion means for serial-parallel-converting the encoded data and dividing the encoded data into a plurality of data parts, wherein the control means converts the plurality of data parts from the serial-parallel conversion means into the plurality of data parts. 7. The transmitter according to claim 5, further comprising another transmission mode for inputting to a plurality of modulation / spreading means, and multiplexing and transmitting the outputs of the plurality of modulation / spreading means by the transmission means. 8. A receiver in a cellular radio communication system employing a code division multiple access system, comprising: a plurality of despreading means for despreading a signal received by radio waves with a plurality of codes; and a plurality of despreading means. A plurality of demodulating means for demodulating outputs of the plurality of demodulating means, an adding means for adding outputs of the plurality of demodulating means, a decoding means for decoding an output of the adding means, and a controlling means for controlling the operation of the receiver. The control means has a plurality of reception modes, one of which is to receive a multiplexed signal obtained by performing spread spectrum with a plurality of codes on a plurality of identical data obtained by duplicating transmission target data. Then, the despreading is performed using the same plurality of codes used in the transmission by the plurality of despreading means, and the output is demodulated by the plurality of demodulation means. The demodulated output is added by the adding means,
A receiver having a reception mode in which the added output is decoded by the decoding means. 9. The apparatus according to claim 8, further comprising means for receiving measurement data for measuring the reception sensitivity of said receiver on the receiver side, and obtaining the reception sensitivity based on the measurement data. The receiver described. 10. The reception mode is transmitted to the transmitter, and the reception mode is determined by receiving a notification of the transmission mode determined by the transmitter. Receiver. 11. The receiver according to claim 9, wherein a transmission mode of the transmitter is determined based on the determined reception sensitivity, and the transmission mode is reported to the transmitter. 12. A parallel-to-serial conversion means for parallel-to-serial conversion of outputs of the plurality of demodulation means and combining them into one data, wherein the control means converts the outputs of the plurality of demodulation means to the parallel-serial conversion means. The receiver according to claim 9, 10 or 11, wherein the receiver has another reception mode in which the signal is combined into one data and the combined signal is decoded by the decoding means. 13. A cellular radio communication system adopting a code division multiple access system between a base station and a plurality of mobile stations, wherein the base station currently has a receiving sensitivity of a mobile station to which data is to be transmitted. Perform adaptive control to select a transmission mode to be used at the time of data transmission to the mobile station from a plurality of transmission modes according to the, at least when the reception sensitivity at the mobile station is low, copy the transmission target data for the mobile station A specific transmission mode for transmitting a multiplexed signal by performing spread spectrum with a plurality of codes for the obtained plurality of identical data, and a mobile station has a plurality of reception modes corresponding to the plurality of transmission modes. Having a specific reception mode for the specific transmission mode; Over de receiving a signal spread spectrum are multiplexed is performed, the despreading the received signal with the same plurality of code as used in the transmission,
A cellular radio communication system having a reception mode for demodulating and adding a plurality of signals obtained by demodulation. 14. The base station, as another transmission mode,
Dividing the data to be transmitted to the mobile station into a plurality of data portions by serial-parallel conversion, modulating these plurality of data portions, spectrum spreading with a plurality of codes, having a transmission mode for multiplexing and transmitting, The mobile station, as another reception mode corresponding to the other transmission mode, despreads a received signal with the same plurality of codes used for the transmission, combines the demodulated signal by parallel-serial conversion, and decodes the received signal. 14. The cellular wireless communication system according to claim 13, comprising a mode.