JP3010227B2 - Spread spectrum receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver for 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 cellular phones has increased remarkably, and it is important to use frequency effective technology for securing more subscriber capacity in a limited frequency band. It has become to. As one of the multiple access schemes for effective frequency utilization, a code division multiple access (CDMA) scheme has attracted attention. The CDMA system is
In a multiple access system using spread spectrum communication technology, it is hardly affected by multipath distortion, and a diversity effect can be expected by a RAKE receiver that combines multipath components at a maximum ratio.

Hereinafter, a receiving apparatus of a communication system using a conventional spread spectrum system will be described with reference to the drawings. FIG. 3 shows a block diagram of a conventional receiving apparatus. In FIG. 3, reference numerals 1, 2, and 3 denote demodulation devices that operate at mutually independent phases, and reference numeral 5 denotes a symbol combination device that combines and combines the phases of demodulated signals from the demodulation devices 1 to 3. 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 denotes demodulated data 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 paths of the multipath is four, and the reception levels of the respective path components are low and relatively similar. FIG. 4B shows a case where the number of paths of the multipath is 3, where the reception level of a certain path component is high and the reception level of the other path components is relatively low. FIG.
15A, reference numerals 15 to 18 denote correlation levels of respective paths of the multipath, and reference numerals 19, 20, and 21 denote multipath components 1
A demodulation device 1 for demodulating each of 5, 16, and 17;
2 and 3 show respective phases. The same applies to 22 to 24 and 25 to 27 in FIG.

Next, the operation of the above conventional example will be described with reference to FIGS. The transmission path state estimating means 6 estimates the multipath state of the transmission path from the received signal. Specifically, the reception power level of each path can be estimated by measuring the correlation level at each phase of the spreading code. The demodulators 1 to 3 demodulate the higher-level phase among the received power levels estimated by the transmission path state estimator 6. However, each demodulation device performs demodulation for different phases. In the conventional example of FIG. 3, since the number of demodulators is three, each of the demodulators 1, 2, and 3 has the phase 19, 20, 2 shown in FIG.
1 (in the case of FIG. 4 (b), phases 25, 26 and 27). The signals demodulated in the demodulators 1, 2, and 3 are subjected to the maximum ratio combining 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, the reception level of each of the path components 15 to 17 is reduced as shown in FIG. If the reception performance is low and the desired reception performance cannot be obtained, it is necessary to increase the number of demodulators in advance and to improve the reception performance by taking in the components of the path 18.
Further, as shown in FIG. 4B, when the reception level of a certain path is sufficiently high and the demodulation device 1 and the demodulation device 2 can obtain sufficient quality, the processing of the demodulation device 3 is useless.
In particular, in a wireless communication system such as land mobile communication, the level of each path fluctuates independently due to Rayleigh fading, and the state of the transmission path changes every moment. In addition, the number of paths of the multipath changes. If the number of demodulators is set to be relatively large for such a transmission line, the worst-case reception performance is improved, but wasteful processing when the reception state is good increases, and power consumption increases. Setting a larger number of demodulators in this way has an adverse effect on reducing power consumption, which is a problem in mobile communication.

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

[0008]

SUMMARY OF THE INVENTION The present invention, in order to achieve the above object, a means for controlling the number of demodulator based on information from the channel state estimating means and reception quality measuring means, the worst This makes it possible to improve the receiving performance at the time and to omit useless processing in a good receiving state.

[0009]

According to the present invention, the above configuration makes it possible to reduce the overall processing amount in addition to improving the communication quality, thereby realizing low power consumption.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In addition, 1 in FIG.
2, 3, 5, 6, 9, 10, 14, and 1 in FIG.
5 to 27 are the same as those shown in FIGS. 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) of demodulated data, and a frame error rate (FER).
This is a reception quality measuring unit for measuring the quality of the reception quality. 1
Reference numeral 1 denotes a signal for controlling whether each of the demodulators 1 to 4 is operated or stopped. Reference numeral 12 denotes transmission path state information obtained by the transmission path state estimating means 6, which is used when determining the number of demodulators. Reference numeral 13 denotes reception quality information obtained by the reception quality measurement means 8, which is used together with the above-described 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 thus-configured spread spectrum receiving apparatus will be described with reference to FIG. In FIG. 2A, since the reception level of each of the path components 15 to 18 is low, the number of demodulation devices 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 required to realize a 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, 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
The demodulation of the components of the path 23 is performed, and sufficient reception quality can be obtained simply by combining the components. Therefore, the demodulation of the 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.
It was decided that the number of demodulators was small.
You.

Depending on the method of determination by the demodulation device number control means 7, it is possible to configure a receiving device capable of reducing the overall processing amount while maintaining the same reception quality. It is also possible to configure a receiving apparatus capable of improving the reception quality while keeping the same.

As described above, the number of demodulators can be determined based on the transmission path state information 12 and the reception quality information 13. Conversely, the number of demodulators can be determined so that the desired reception quality can be obtained. It is also possible to set a threshold value of the output level and perform the processing of the demodulation device until the output level is exceeded. This is applied to the case where the received signal is temporarily stored in a memory or the like and the processing of each of the demodulation devices 1 to 4 is sequentially performed. The processing corresponding to each of the demodulators 1 to 4 is performed in order from the phase having the highest correlation level,
Processing is stopped when it is determined that the demodulated data has the desired reception quality. Even with such a processing method, an effect equivalent to the case where demodulation is performed after determining the number of demodulation devices described above can be obtained.

[0015]

The present invention as described above, according to the present invention, by providing means for controlling the number of demodulator based on the status you <br/> by beauty reception quality of the transmission path, the improvement of worst case the reception performance Further, it is possible to realize an excellent spread spectrum type receiving apparatus capable of eliminating useless processing in a good receiving state.

[Brief description of the drawings]

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

FIG. 2 is a demodulation timing chart of each demodulation device in the embodiment.

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

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

[Explanation of symbols]

1, 2, 3, 4 demodulation device 5 reception quality measurement means 6 transmission path state estimation means 7 demodulation device number control means 8 reception quality measurement means 9 reception signal 10 phase information of each path of multipath 11 operation / stop of demodulation device Control signal 12 Transmission path state information 13 Reception quality information 14 Demodulated data 15, 16, 17, 18 Multipath paths 19, 20, 21 Demodulation timing of demodulators 1 to 3, 22, 23, 24 Multipath paths 25, 26, 27, 28 Demodulation timing of each demodulator 1-4

Claims (3)

(57) [Claims] 1. A receiving apparatus for a communication system using a spread spectrum system, comprising: a transmission path state estimating means for estimating a multipath state of a transmission path from a received signal; and a multipath apparatus 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 signals demodulated in a plurality of phases, and a reception quality measuring unit that measures the quality of the combined symbols,
A spread spectrum type receiving apparatus comprising: a demodulation device number control unit that controls the number of the demodulation devices according to the quality of a reception signal obtained by the reception quality measurement unit. 2. A receiving apparatus for a communication system using a spread spectrum system, comprising: a transmission path state estimating means for estimating a multipath state of a transmission path based on a received signal; and a multipath apparatus 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 signals demodulated in a plurality of phases, and a reception quality measuring unit that measures the quality of the combined symbols,
A spread spectrum receiving apparatus comprising: a demodulation device number control unit that controls the number of the demodulation devices according to the correlation level obtained by the transmission path state estimation unit and the quality of the received signal obtained by the reception quality measurement unit. apparatus. 3. The number of demodulators control means for controlling the number of demodulators according to the correlation level determined by the transmission path state estimating means and the quality of the received signal determined by the reception quality measuring means. The spread spectrum receiving apparatus according to claim 2, wherein the control is performed to a minimum necessary so that