KR20020025531A - Rake receiver - Google Patents

Abstract

PURPOSE: A rake receiver is provided to compare signals outputted according to each demodulator with a set value, to output the signals to a coupler if the signals are bigger than the set value, and to ignore the signals if the signals are smaller than the set value, to delay a signal processing of a correlator as a predetermined time, then to move corresponding branches to other time section to process receiving signals inputted in other multiple path, so as to improve efficiency of a signal processing. CONSTITUTION: Correlators(111,121,131) separate each receiving signal inputted at predetermined time intervals from multiple paths. Demodulators(110,120,130) demodulate original data from the separated signals. Comparators(140,150,160) compare levels of signals outputted from the demodulators(110,120,130) with a predetermined set value, and input compared result values to a variable time delay controller(170). The variable time delay controller(170) transmits a signal outputted from the demodulator(110) of a corresponding path to a coupler(180) according to the inputted compared result values, or ignores the signals of the corresponding path, then delays operations of the correlators(111,121,131) on the corresponding path as a predetermined time. The coupler(180) couples the demodulated signals outputted from the demodulators(110,120,130) to one signal to output the coupled signal.

Description

Rake receiver

The present invention relates to a rake receiver, and more particularly, to a rake receiver that can increase the processing efficiency of a signal received through a multi-path.

In general, in spread spectrum communication such as code division multiple access (CDMA), the most significant effect on transmission quality when communicating using electromagnetic waves is fading due to multipath. It is a phenomenon.

This multipath fading is caused by the phase difference (time delay difference) of the signals arriving at the receiver through different paths. Fading reduces the size of the signal, causing continuous transmission errors and Cause interference.

Spread Spectrum Communication uses a Pseudo Noise Cord (hereinafter referred to as a "PN code") so that only senders and receivers using a predetermined code can talk to each other. If the time delay caused by multipath is more than 1 chip, the signal cannot be received. In the mobile communication system using the code division multiple access method, the signals of several multipath components are separated and combined by using the above characteristics. Rake receivers are used to prevent fading by increasing the signal level.

For reference, the chip is a unit of one pulse interval of a spreading code in spread spectrum communication, and is used to distinguish it from bits of data.

FIG. 1 is a schematic block diagram of a conventional rake receiver. As can be seen from the same drawing, a conventional rake receiver includes a plurality of demodulators 10, 20, which include correlators 11, 21, and 31, respectively. 30) and coupler 40.

In Fig. 1, the correlators 11, 21, and 31 separate the respective received signals having a predetermined time difference from the multipath, and the demodulators 10, 20, and 30 correspond to the correlators 11, 21. And demodulate the original data from the signal separated by (31), and the combiner 40 combines the demodulated signals output from the respective demodulators 10, 20, and 30 into one signal and outputs them.

The operation principle of the rake receiver configured as described above is as follows.

It is assumed that a signal received in path 2 based on path 1 has a time difference of about 0.5 chips, and a signal received in path 3 has a time difference of about 1 chip.

At this time, if the despreading is synchronized with the signal of the path 1, the signals of the path 2 and the path 3 are not de-spreaded because they are not synchronized and only the signal of the path 1 is reversed when the same signal is received with different time difference. The signal can be demodulated by spreading.

Similarly, if the signal of the path 2 is despread with a delay of 0.5 chips, only the signal of the path 2 can be demodulated.

When the same signal is received with a time difference through the above processing, the rake receiver demodulates the signal according to the time difference and demodulates the signals into independent signals, and then combines them into one signal through the combiner 40, thereby providing a signal level. Increase the size and prevent interference between signals.

In the general mobile communication environment using the code division multiple access method, the bandwidth is about 1.25 MHz and the chip interval is about 0.8 ms. In this case, the maximum delay time of the signal received in the multipath in the outdoors is about 2 to 3 ms. Since a signal having a time difference of more than one chip per rake receiver cannot be processed, three to four rake receivers are installed in a mobile station and a base station to use all signals received in a multipath.

However, in a wideband code division multiple access system such as IMT-2000, which will be serviced in the future, since the chip interval is very narrow as about 0.3 dB, it is necessary to use all signals received in multipath with a time difference of up to about 3 dB. It is necessary to use a relatively large number of rake receivers or rake receivers having a large number of branches, so that the number of parts increases, resulting in a complicated hardware configuration and a significant increase in manufacturing costs.

Accordingly, the present invention has been made to solve the problems of the prior art as described above, Rake receiver that can process a multi-path signal of a wider bandwidth with a relatively small number and number of branches by increasing the processing efficiency of the rake receiver The purpose is to provide.

1 is a schematic block diagram of a conventional rake receiver according to the related art;

2 is a schematic block diagram of a rake receiver according to an embodiment of the present invention;

3 is a flow chart for explaining the operation of the rake receiver shown in FIG.

<Explanation of symbols for main parts of the drawings>

110, 120, 130: demodulator 111, 121, 131: correlator

140, 150, 160: comparator 170: variable time delay controller

180: combiner

The rake receiver of the present invention for achieving the above object is separated by a plurality of correlators and a plurality of correlators for separating a received signal received through a multipath according to the time difference with a predetermined time difference by a time delay phenomenon. A rake receiver comprising a plurality of demodulators for demodulating signals of each path, respectively, and a combiner for combining and outputting the signals output from the plurality of demodulators, the signal level output from each demodulator being compared with a predetermined set value. A plurality of comparators for outputting a comparison result, and if the signal level of the path measured by the comparator is greater than a set value, the output signal is transmitted to the combiner; if less than the set value, the operation of the correlator of the corresponding path is determined for a predetermined time. Including a variable time delay controller that delays by as much as possible to process signals from other multipaths It is characterized by.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 2 is a schematic block diagram of a rake receiver according to a preferred embodiment of the present invention, as can be seen with reference to the same diagram, the rake receiver of the present invention, each of which includes a plurality of correlators (111, 121, 131) The demodulator 110, 120, 130 and a plurality of comparators (140, 150, 160) and the variable time delay controller 170 and the combiner 180.

The correlators 111, 121, and 131 separate the respective received signals having a predetermined time difference from the multipath, and the demodulators 110, 120, and 130 are connected by the correlators 111, 121, and 131. Demodulate the original data in the separated signal.

The comparators 140, 150, and 160 compare the level of the signal output from the demodulators 110, 120, and 130 of each path with a predetermined set value, and input the comparison result to the variable time delay controller 170. .

The variable time delay controller 170 transfers the signal output from the demodulator 110 of the corresponding path to the combiner 180 according to the comparison result value input from each comparator 140, 150, 160, or the signal of the corresponding path is It ignores and delays the operation of the correlator in the path by a predetermined time.

The combiner 180 combines the demodulated signals output from the demodulators 110, 120, and 130 into one signal and outputs the combined signal.

An operation example of the present invention configured as described above will now be described with reference to the accompanying flowchart.

First, when a signal is received through a multipath, the correlators 111, 121, and 131 of each path are synchronized with each other to separate the signals received through each path, and the demodulators 110, 120, and 130 of each path are separated. The separated signal is demodulated to the original data (S10).

In this case, the comparators 140, 150, and 160 compare the level of the signal output from the demodulators 110, 120, and 130 of each path with a predetermined set value, and compare the comparison result value according to the comparison result with the variable time delay controller. Enter (170).

The variable time delay controller 170 controls the signal processing of the correlators 111, 121, 131 and the demodulators 110, 120, 130 according to the comparison result values input from the comparators 140, 150, 160 of each path. If the signal level of the corresponding path is larger than the set value by the comparison result values input from the comparators 140, 150, and 160 of each path, it is transmitted to the combiner 180 (S30).

On the other hand, if the signal level of the corresponding path is less than or equal to the set value by the comparison result values input from the comparators 140, 150, and 160 of each path, the variable time delay controller 170 may be a weak signal. The signal output from the demodulator of the corresponding path is ignored and the PN code is delayed by the number of rake fingers for the correlator of the corresponding path to process another received signal (S40). Here, rake fingers refer to each pair of correlators and demodulators.

As described above, the present invention compares a signal output for each demodulator with a set value and outputs it to the combiner as the result of the comparison is an available signal if the output signal is larger than the set value, and if the output signal is smaller than the set value, it can be used. Since it is a weak or missing signal, it ignores this and delays the signal processing of the correlator by a predetermined time, thereby moving the branch to another time interval to process a received signal input in another multipath.

In other words, the conventional rake receiver is configured to process a signal received in a multipath for each path by a predetermined time delay, which is inefficient for all branches to hang on its processing for any signal received in a multipath. In contrast to the structure, the present invention detects a signal level for each branch and ignores a signal of a path having a weak signal level so as to process another received signal, thereby improving signal processing efficiency.

By improving the signal processing efficiency of the rake receiver in this way, when performing wideband spread communication, all signals received in each multipath can be processed even with a smaller number of rake receivers or fewer rake receivers. This reduces component count, simplifies the structure of the hardware, and significantly reduces manufacturing costs.

Claims (1)

A plurality of correlators for separating received signals received through a multipath according to the time difference with a predetermined time difference due to a time delay phenomenon, and a plurality of demodulators for demodulating the signals of respective paths separated by the plurality of correlators; A rake receiver comprising a combiner for combining and outputting each signal output from a plurality of demodulators, A plurality of comparators for comparing the signal level output from each demodulator with a predetermined set value and outputting the comparison result; If the signal level of the path measured by the comparator is greater than the set value, the output signal is transmitted to the combiner. If the signal level is smaller than the set value, the operation of the correlator of the corresponding path is delayed by a predetermined time to process the signal of another multipath. Rake receiver, characterized in that comprising a variable time delay adjuster.