JPH07273689A - Spread spectrum system receiver - Google Patents

Abstract

PURPOSE:To improve the reception performance in the worst case and to omit useless processing in the excellent reception state by controlling the number of demodulators. CONSTITUTION:A transmission line state estimate means 6 estimates a state of multi-path of a transmission line based on a reception signal 9. Demodulators 1-4 make demodulation at a phase of multi-path obtained by the transmission line state estimate means 6 and a symbol synthesizer 5 synthesizes demodulated signals. A demodulator number control means 7 obtains the number of demodulators required to obtain desired reception quality based on transmission line state information 12 and reception quality information 13 to control the operation/stop of the demodulators 1-4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver of a communication system using a spread spectrum system.

[0002]

2. Description of the Related Art In recent years, the demand for land mobile communications such as automobiles and mobile phones has remarkably increased, and it is important to use frequency effective technology for securing a larger subscriber capacity on a limited frequency band. It has become to. A code division multiple access (CDMA) system has attracted attention as one of multiple access systems for effective use of frequencies. The CDMA system is
It is a multiple access method using spread spectrum communication technology, is less susceptible to the effects of multipath distortion, and a RAKE receiver that maximizes the ratio of multipath components can also be expected to have a diversity effect.

A receiving apparatus of a communication system using a conventional spread spectrum system will be described below with reference to the drawings. FIG. 3 is a block diagram of a conventional receiver. In FIG. 3, reference numerals 1, 2, and 3 denote demodulators that operate in mutually independent phases, and 5 denotes a symbol combiner that combines the phases of the demodulated signals from the demodulators 1 to 3 and combines them. Reference numeral 6 is a transmission path state estimating means, 9 is a received signal, and 10 is phase information of each path of the multipath obtained by the transmission path state estimating means 6. Reference numeral 14 is demodulated data that has been subjected to maximum ratio combining in the symbol combining device 5.

FIG. 4 shows the demodulation timing of each demodulator in the conventional example. FIG. 4A shows a case where the number of multipath paths is 4, and the reception level of each path component is low, and the levels are relatively similar. FIG. 4B shows a case where the number of multipath paths is 3, and the reception level of a certain path component is high and the reception levels of other path components are relatively low. Figure 4
In (a), 15 to 18 indicate the correlation level of each path of the multipath, and 19, 20, and 21 indicate the multipath component 1.
Demodulation device 1 for demodulating each of 5, 16, 17
Each of the two phases is shown. The same applies to 22 to 24 and 25 to 27 in FIG. 4 (b).

Next, the operation of the above conventional example will be described with reference to FIGS. The transmission path state estimation means 6 estimates the multipath state of the transmission path from the received signal. Specifically, the received power level of each path can be estimated by measuring the correlation level at each phase of the spread code. The demodulators 1 to 3 demodulate the phase having the highest level among the received power levels estimated by the transmission path state estimating means 6. However, the respective demodulation devices perform demodulation for different phases. In the conventional example of FIG. 3, the number of demodulators is three, so that each of the demodulators 1, 2, and 3 has phases 19, 20, and 2 shown in FIG.
1 (phases 25, 26, 27 in the case of FIG. 4B) are demodulated. The signals demodulated by the demodulators 1, 2, and 3 are combined at the maximum ratio in the symbol combiner 5 to obtain demodulated data 14.

[0006]

However, when the number of demodulators is fixed as in the above-mentioned conventional receiver, as shown in FIG. 4 (a), the reception levels of the path components 15 to 17 are When the reception performance is low and the desired reception performance is not obtained, it is necessary to improve the reception performance by setting a large number of demodulation devices in advance and capturing the components of the path 18.
Further, as shown in FIG. 4B, when the reception level of a certain path is sufficiently high and sufficient quality can be obtained by the demodulator 1 and the demodulator 2, the processing of the demodulator 3 is useless.
Particularly, in a wireless communication system such as land mobile communication, the level of each path changes independently due to Rayleigh fading, and the state of the transmission line changes from moment to moment. In addition, the number of multipath passes also changes. If a larger number of demodulators are set for such a transmission line, the worst-case reception performance is improved, but wasteful processing increases when the reception state is good, and power consumption increases. Setting a large number of demodulators in this way is counterproductive to the reduction of power consumption, which is a problem in mobile communication.

The present invention solves the above-mentioned conventional problems, and provides a spread spectrum system receiving apparatus capable of improving the worst-case reception performance and omitting unnecessary processing when the reception state is good. The purpose is to do.

[0008]

In order to achieve the above object, the present invention is provided with means for controlling the number of demodulators based on information from the transmission path state estimating means and / or the receiving quality measuring means, and in the worst case, This makes it possible to improve the reception performance and to eliminate unnecessary processing in a good reception state.

[0009]

According to the present invention, with the above configuration, it is possible to improve communication quality and reduce the overall processing amount, and to realize low power consumption.

[0010]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. 1 in FIG.
2, 3, 5, 6, 9, 10, 14 and also 1 in FIG.
5 to 27 are the same as those shown in FIGS. 3 and 4 described above. In FIG. 1, 4 is a demodulator, 7 is a demodulator number control means for controlling the number of demodulators, 8 is a bit error rate (BER) and a frame error rate (FER) of demodulated data.
It is a reception quality measuring means for measuring the quality of data such as. 1
Reference numeral 1 is a signal for controlling whether to operate or stop each of the demodulation devices 1 to 4. Reference numeral 12 is transmission line state information obtained by the transmission line state estimating means 6, which is information used when determining the number of demodulators. Reference numeral 13 is reception quality information obtained by the reception quality measuring means 8 and is information used together with the above-mentioned transmission path state information 12 when determining the number of demodulators.
In FIG. 2, 28 indicates the phase of the demodulation device 4 that demodulates the multipath component 18.

The operation of the spread spectrum receiver configured as above will be described with reference to FIG. In FIG. 2A, since the reception level of each path component 15 to 18 is low, the number of demodulators is increased and the reception performance is improved by a more effective diversity effect. At this time, the demodulation device number control means 7 obtains the number of demodulation devices necessary for realizing the desired reception quality based on the transmission path state information 12 and the reception quality information 13. In this case, since the reception level is low, control is performed to increase the number of demodulators. As a result, the reception quality is improved.

In FIG. 2B, the reception level of the path 22 is high and the reception level of the path 24 is low. In this case, pass 22
Since a sufficient reception quality can be obtained only by demodulating the components of and path 23 and combining them, the demodulation of path 24 is omitted. In this case, the transmission line state information 12 that the correlation level of the phase 25 is high and the correlation level of the phase 27 is low, and the reception quality information 13 that the reception quality is sufficient.
Therefore, it is determined that the number of demodulators may be small. This determination can also be made using only one of the transmission path state information 12 and the reception quality information 13.

Depending on the determination method in the demodulation device number control means 7, it is possible to construct a receiving device capable of reducing the overall processing amount while keeping the reception quality at the same level, and to keep the overall processing amount constant. It is also possible to configure a receiving device that can improve the reception quality while maintaining the above.

As described above, the number of demodulators can be determined based on the transmission path state information 12 and the reception quality information 13, but conversely, the number of demodulators of the symbol synthesizing device 5 can be obtained so that a desired reception quality can be obtained. It is also possible to set a threshold value of the output level and to perform processing of the demodulator until the threshold value is exceeded. This is applied when the received signal is temporarily stored in a memory or the like and the processes of the demodulators 1 to 4 are sequentially performed. The processes corresponding to the demodulators 1 to 4 are sequentially performed from the phase having the highest correlation level,
The process is stopped when it is determined that the demodulated data has the desired reception quality. Even with such a processing method, the same effect as in the case where the number of demodulators is determined and then the demodulation is performed can be obtained.

[0015]

As described above, according to the present invention, by providing means for controlling the number of demodulators on the basis of the state of the transmission path and / or the reception quality, the worst case reception performance is improved and a good reception state is obtained. It is possible to realize an excellent spread spectrum receiving apparatus that can omit the wasteful processing of

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a spread spectrum receiver according to an embodiment of the present invention.

FIG. 2 is a demodulation timing chart of each demodulator according to the present embodiment.

FIG. 3 is a schematic block diagram of a conventional spread spectrum receiver.

FIG. 4 is a demodulation timing chart of each demodulator in a conventional example.

[Explanation of symbols]

1, 2, 3, 4 Demodulator 5 Reception quality measuring means 6 Transmission path state estimating means 7 Demodulator number control means 8 Reception quality measuring means 9 Received signal 10 Phase information of each path of multipath 11 Operation / stop of demodulator Control signal 12 Transmission path status information 13 Reception quality information 14 Demodulation data 15, 16, 17, 18 Multipath paths 19, 20, 21 Demodulation timings of demodulators 1 to 23, 23, 24 Multipath paths 25, 26, 27, 28 Demodulation timing of each demodulator 1 to 4

Claims (4)

[Claims] 1. A receiver of a communication system using a spread spectrum method, comprising: a transmission path state estimating means for estimating a multipath state of a transmission path by a received signal; and a multipath based on the estimated transmission path state. A plurality of demodulators that independently demodulate in each phase of each wave, a symbol combiner that combines the signals demodulated in a plurality of phases, and the demodulator according to the correlation level obtained by the transmission path state estimating means. A spread-spectrum type receiving device comprising a demodulation device number control means for controlling the number of devices. 2. A receiver of a communication system using a spread spectrum method, comprising: a transmission path state estimating means for estimating a multipath state of a transmission path by a received signal; and a multipath based on the estimated transmission path state. A plurality of demodulators that independently demodulate in the phase of each wave, a symbol combiner that combines the signals demodulated in a plurality of phases, a reception quality measuring unit that measures the quality of the combined symbols,
A spread spectrum system reception apparatus comprising: demodulation device number control means for controlling the number of demodulation devices according to the quality of the received signal obtained by the reception quality measurement means. 3. A receiver of a communication system using a spread spectrum method, comprising: a transmission path state estimating means for estimating a multipath state of a transmission path by a received signal; and a multipath based on the estimated transmission path state. A plurality of demodulators that independently demodulate in the phase of each wave, a symbol combiner that combines the signals demodulated in a plurality of phases, a reception quality measuring unit that measures the quality of the combined symbols,
Spread spectrum reception comprising a demodulator number control means for controlling the number of demodulators in accordance with the correlation level obtained by the transmission path state estimating means and the quality of the received signal obtained by the reception quality measuring means. apparatus. 4. The demodulator number control means keeps the number of demodulators constant according to the correlation level obtained by the transmission path state estimating means and the quality of the received signal obtained by the reception quality measuring means. The spread spectrum receiver according to claim 1, wherein the spread spectrum receiver is controlled to a necessary minimum so that