GB2391141A

GB2391141A - Power control in a CDMA receiver having RAKE fingers

Info

Publication number: GB2391141A
Application number: GB0325276A
Authority: GB
Inventors: Toshiyuki Oda
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 1998-12-10
Filing date: 1999-12-08
Publication date: 2004-01-28
Anticipated expiration: 2019-12-08
Also published as: GB2391140B; GB0325276D0; GB0325275D0; GB2391140A; GB2391141B

Abstract

A CDMA reception apparatus has a plurality of fingers and performs RAKE reception by RAKE-combining outputs from the plurality of fingers. The apparatus includes a multi-path detecting section and delay profile generating section. The multi-path detecting section detects a multi-path consisting of a plurality of radio waves arriving with some delay times by despreading a reception signal. The delay profile generating section generates a delay profile by obtaining the reception power levels of all reception signals in the multi-path detected by the multi-path detecting section. A difference di in level between the signal having the ith highest level and the signal having the (i+1)th highest level of the data of the delay profile is obtained. The operation of a finger corresponding to a signal having a lower level (e.g. t6, t7) is stopped on the basis of the difference di and a predetermined threshold dTH. Alternatively, fingers may be operated on the basis of comparisons of individual signal levels with a threshold value, or operation of all fingers may be stopped if the highest power level of a received signal is lower than a threshold value.

Description

2391 141

- 1 - CDMA RECEPTION APPARATUS AND POWER CONTROL METHOD THEREFOR

BAcRGRnuND OF THE INVENTION Field of the Invention:

5 m e prosant invention relator to a CDMA reception apparatus and power control method thorefor which are used for a mobile communication Hyatt and, more particularly, to a CAM reception apparatus for performing RAKE reception and a power control method for the apparatus.

10 Description of the Prior Art:

Conventionally, a mhilo communication Atom using CDMA (Code Division Multiple Ascoes) has boon known.

In this CDM Mobile oonnunication system, when data is -to be tranomittod from a mobile station to a bane 15 station, transmission data i. transmitted after it is spread by using a corresponding one of Spreading codes assigned to the respective mobile stations, and the base station demodulates the transmission data from each mobile station by Respreading the data by using the spreading 20 code a-signed to each mobile station.

Likewise, data transmitted from a bane station to a mobile station is also spread by a corresponding one of the spreading codes assigned to the respective mobile station. before it is trananotted. The resultant data is 25 then ban. mi tted.

f - 2 In urban areas, in particular, various obstacles are present between a base station and a mobile station, and hence radio waves from the base station are often reflected by those obstacles and reach the mobile station.

5 In such a situation, there are many reflected waves, which are reflected by various obstacles and reach the mobile station, between the base station and the mobile station as well as direct waves that directly reach the mobile station. That is, a so-called multi-path, in which there 10 are a plurality of routes through which radio warm roach the mobile station, occurs.

The respective multi-path radio wave. reach the mobile atation with delay time. corresponding to the ropective routes. The mobile station therefore can 15 improve reception quality owing to a path diversity effect by combining the multi-path radio wavoa in consideration of the delay times. This reception method will be referred to as a RAKE reception method.

A reception apparatus using this RAKE reception 20 method needs to have finger- for despreading and the like equal in number to paths to a RATE combiner. If, therefore, the number of paths to the RARE reshiner i. too large, many fingers are required, resulting in increases in the size and cost of the apparatus. Considering that a 25 mobile station moves all the time, the manner in which a

- 3 - multi-path occurs always change-. In -ate case, therefore, the use of too many fingers cannot allow the RARE -^mhiner to obtain a satisfactory reception quality improving effect, i.e., a path diversity effect. -

5 For this reason, it in notary to set the number of fingers to be set in the apparatus so as to obtain a reception quality improving effect by the RATE combiner, id., a path diversity effect, to such an extent that the apparatus size does not increase too much. a 10 In such a situation, in a COMA reception apparatus having a limited number of fingers, the delay times in the Prospective fingers must be controlled to reliably capture multi-path radio waves.

As a conventional reception apparatus that solves s 15 this problem, the reception apparatus disclosed in Japanese Une- my nod Patent Publication No. 9-181704 is availablo. Fig. 1 is a block diagram showing the arrangement of a reception apparatus disclosed in Japanese Un-="ind 20 Patent Publication No. 9-181704. The first conventional i apparatus will be described below with reference to Fig. 1.

Reference numeral 100 denotes a terminal to which a reception input spread signal is input; 200, a tracking finger for performing tracking and depreading; and 300, a 25 search finger for detecting the level of a reception

- 4 - signal in each phase..

Reference numeral 402 denotes a RARE combining path selecting section for selecting a phase of a spreading code in accordance with signals from the search finger 300 5 and tracking finger 200.

Reference n,'- ral 403 denotes a pilot interpolation absolute Synchronous detector for performing Synchronous detection of the signal Respread by the tracking finger 200. 10 Reference numeral 404 denotes a long code spreading code replica generator for supplying, to the tracking finger 200 or search finger 300, a spreading code replica corresponding to a Specific channel to be used. The tracking finger 200 or search finger 300 U6Q. this 15 spreading cod. replica after delaying it by a predetermined amount through a spreading code replica delay section 206 or BUS.

Reference numeral 405 denotes a RACE combiner for combining signals from the rospective paths; and 410, an 20 output terminal.

Reference numerals 201, 202, 203, and 310 denote multipliers each nerving to Respread a reception signal by multiplying it by a spreading code replica; 204, 250, 207, and 302, integration dump circuits each serving to perform 25 integration for a predetermined period of time; 208, 209,

f _ 5 _ and 303, amplit'd. squaring circuits each nerving to detect a signal level by performing amplitude squaring detection; and 304, a reception level memory for storing an output from the squaring circuit 303.

5 Reference numeral 210 denotes an adder for adding an output from the amplitude squaring circuit 208 to an output from the amplitude squaring circuit 209 with Opposite polarities to generate a chip timing error signal associated with the spreading code replicas.

10 Reference numeral 211 denotes a loop filter for av raging the chip timing error signals from the adder 210 and outputting the resultant data. The data output from the loop filter 211 is input to a spreading Chad replica timing control signal generating section 212. In b 15 accordance with an output from the spreading code replica timing control signal generating section 212, the phase of the spreading code replica used by the RAKE combining path selecting section 402 for deapreading.

The operation of the conventional technique shown in 20 Fig. 1 will be described below.

The tracking finger 200 perform. Respreading by using a spreading replica code corresponding to a delayed path designated by the RARE combining path selecting section 402 on the basis of the reception level detection 25 information of all the chip phases of the search finger;

6 - 300. The signal obtained by thin Respreading is demodulated. AN a demodulation scheme, delay detection, synchronous detection, or the like is available, In 5 absolute Synchronous detection, an absolute phase of reception must ke estimated. In this prior art, the pilot

interpolation absolute synchronous detector 403 performs absolute synchronous detection by estimating the phase of each information symbol by using a pilot signal and the 10 phase of a pilot Symbol as a reference phase.

In the tracking finger 200, the multipliers 201 and 202 perform correlation detection by using a reception spread/modulated signal and a replica code obtained by shifting a spreading code replica phase synchronized with 15 the spreading code phase of a reception signal from each path by i phase, and the integration dump circuits 204 and 205 performs integration for a prdotermined period of time. The Q litude squaring circuits 208 and 209 then perform amplitude squaring detection to remove data 20 modulation components and instantaneous phase variation components. The adder 210 adds the amplitude square outputs of the spreading code replica obtained by the t phase shift and the spreading code replica obtained by the - phase 25 shift with opposite polarities to generate a chip timing

i ) - 7 error signal associated with the spreading code replicas.

The loop filter 211 aeragea these chip timing error signals. The phase of the spreading code replica is updated in accordance with an output signal from the loop 5 filter 211.

This phase update information is input to the RAXE combining path selecting section 402. The RAXE combining path selecting section 402 manages RAXE combining patina in real tic* to prevent overlaps between patina.

10 The RAXE combining path selecting section 402 updates the RAXE combining pathe in predetermined cycles on the basis of an average delay profile of phase information search finger outputs of spreading code replicas corrosponding to the repoctive path. to the RAXE combiner.

15 The RAXE combining path selecting section 402 generator spreading code replica signals for demodulation and generation of chip timing error signals in the tracking finger 200. The tracking finger 200 performs correlation detection of the spreading Cody replica 20 corrosponding to each path having this tie" delay and the input apread/modulated signal for a predetermined period of time, and input. the integration output signal to the modulator, iffy., the pilot interpolation absolute synchronous detector 403.

25 According to the above reception apparatus disclosed

J - 8 - in Japanese Unexamined Patent Publication No. 9-181704, to reliably capture multi-path radio waves with a limited number of fingers, the delay timer of the respective fingers can be controlled.

5 The following problem is, however, posed in such a conventional reception.

The conventional reception apparatus is designed to use all fingers regardless of how a multi-path occur-.

Assume that the nut her of paths in a multi-path is small, lo and hence a much effect cannot be obtained even by RATE combining operation using many fingers. In this case, unnecessary fingers are operated to waste power.

As a conventional technique for solving such a problem, the receiver disclosed in Japanese Unexamined 15 Patent Publication No. 7-231278 is available.

Fig. 2 is a block diagram showing the arrangement of the recolver disclosed in Japanese Unexamined Patent Publication No. 7-231278. The second conventional apparatus will be described below with reference to Fig. 2.

20 Reference numerals 5 1 to 50N denote the first to Nth spreading means for receiving direct pread/modulated signals with N paths and despreading/daodulating the respective direct pread/mndulated signals S30 with the first to Nth spreading sequences synchronized with the N 25 direct spread/mwdulated signals S30 received at different

- 9 - timings. Reference nonmoral 51 denotes a combining Diana for . combining output data D4O1 to D40 from the first to Nth doapreading means 50, to 50N, and 52 represents a control 5 means for obtaining the level difference between one of the N direct aproad/modulated signals 830 which has the highest level and each of the remaining signals. If each of the obtained level different i. equal to or higher than a threshold T. the nbining means 51 turns off 10 deepreading means {o.g., 502, SO-:, and 50) for deepreading/demodulating signals having lover differences of equal to or higher than the threshold T with respect to the signal having the highest level.

A path diversity effect can be satisfactorily 15 obtained by using a RAXE roa̳iver when signals having levels similar to each other to same degree are input through a multi-path. In addition, if a signal having a level noticeably (greatly) lower than the levels of a group of signal. hating level. similar to each other to 20 some degree is input, the obtained diversity effect is small. For a RAXE receiver, therefore, importance is attached to the way to extract only a signal group that provide. a groat diversity effect.

25 In the method of obtaining level differences from the

- 10 highest levels, as in the receiver disclosed in Japanese Un-Y-=ined Patent Publication No. 7-23127S, however, it is very difficult to extract only a signal group that can provide a great diversity effect. The reason for this 5 difficulty will be described below.

Fig. 3 is a graph showing multi-path signals arranged in the descending order of levels.

Referring to Fig. 3, the signal having the highest level is ropresented by In, and signals having lower 10 levels are sequentially represented by In, 1.,.... In addition, the level difference between the signals In and 1 is represented by a; the level difference between the signals 1 and I., b; and the lover difference between the signals 1. and Is, c.

15 In this case, the expression "a signal group having levels similar to each other to come deer a" indicate- the signals 1, 1, Lo, and in Fig. 3. Assume that in the receiver disclosed in Japanese Unexamined Patent Publication No. 7-231278, the relationship between a 20 threshold T and each signal level is represented lay a + b < T and a + b + c > T. In this case, the signal I" is discarded although this signal can provide a great path diversity effect. If such a situation occurs in the case of a wand electric field, a deterioration in reception

25 quality cannot be avoided.

11 At paragraph number 0028 in Japanese Unexamined Patent Publication No. 7-231278, it is described that "In addition, the threshold T is preferably net to a value corresponding to the level difference between on. of the 5 direct spread/modulatd signals 830, with which no path diversity effect can be obtained by Synthesis, and the signal having the highest level n, In practice, however, the signal having the highest lover always varies in level, and it i. difficult to find "one of the direct 10 spread/modulated signals S30, with which no path diversity effect con be obtained by Synthesis". For this reason, it is very difficult or i-sible to determine the value of the.threshold T as described at paragraph number 0028.

SUMMARY OF THE INVENTION

15 The present invention has been made in consideration of the above problems in the prior art, and has as its

object to provide a CDMA reception apparatus designed to change the number of finger. to be used for RAKE reception in accordance with an occurrence state of multi-path, 20 which can guarantee reception quality evon in a weak electric field as much as possible, and Educe a power

consumption by stopping operation of unnecessary finger-.

In order to achieve the above object, according to the first main aspect of the present invention, there is 25 provided a CDMA reception apparatus having a plurality of

- 12 fingers and nerving to perform RARE reception by RAXE-c^bininq outputs from the plurality of fingers, comprising multi-path detecting mean. for detecting a multi-path consisting of a plurality of radio Wavea 5 arriving with some delay times by despreading a reception signal, and delay profile generating means for generating a delay profile by obtaining reception power levels of all reception signals in the multi- path detected by the multi-path detecting means, wherein ta) a difference do 10 in lover between a signal having an ith highest level and a signal having an (itl)th highest level of data of the delay profile is obtained, and operation of a finger corresponding to a signal having a low level is stopped on the basis of the difference do and a predetermined 15 threshold d-, (b) operation of a finger corresponding to a signal having a low level is stopped on the basis of a result obtained by comparing a threshold L" with a level 1 of a signal having an ith highest 1QV.1 of the data of the delay profile, or (c) if a level of a signal having a 20 highest 1QVe1 of the data of the delay profile is not more than a predetermined threshold Lam, operation of all fingers is stopped.

The present invention has the following manor aspects associated with the first main aspect.

25 The difference do in level between the signal having

- 13 the ith highest level and the signal having the (i+l)th highest level of data of the delay profile is obtained, and operation of a finger corresponding to a signal having a level lower than that of the signal having the (i+l)th 5 highest level is stopped if the difference do is not less than the predeterminod threshold d-.

- In addition, if the difference do in level between the signal having the ith highest level and the signal having the (i+l)th highest level of data of the delay 10 profile is not more than a predetermined value, and a difference dams in level between the signal having the (il)th highest level and a signal having an (i+2)th highest level is not leas than the predetermined value, operation of a finger corresponding to a signal having a 15 level lower than that of the signal having the (it2)th highest level in stoop d.

If the level In of the signal having the ith highest level of the data of the pray profile is not more than the predetermined threshold L-, operation of a finger 20 corresponding to a signal having a level lower than that of the signal having the ith highest level is stopped.

The CDMA reception apparatus according to the main aspect further comprises a user input device by which a user can set the threshold.

25 The COMA reception apparatus according to the main

- 14 aspect further comprises display means for displaying information indicating the number of fingers, of the plurality of fingers, to which power is supplied.

Processing to) in the main aspect is performed from 5 the viewpoint that an improvement in reception characteristics takes priority over power saving in a weak electric field.

In order to achieve the above object, according to the second main aspect of the present invention, there is 10 provided a power control method for a COMA reception apparatus having a plurality of fingers and serving to perform RACE reception by RAKE-combining outputs from the plurality of fingers, comprising the steps of detecting a multi-path consisting of a plurality of radio waves 15 arriving with some delay times by despreading a reception signal, and generating a delay profile by obtaining reception power levels of all reception signals in the multi-path, wherein (a) a difference do in level between a signal having an ith highest level and a signal having 20 an ti+l)th highest level of data of the delay profile i.

obtained, and operation of a finger corresponding to a signal having a low level is stopped on the basis of the difference d. and a predetermined threshold d-, to) operation of a finger corresponding to a signal having a 25 low level is stopped on the basis of a result obtained by

( - 15 comparing a threshold L. with a lover Lo of a signal having an ith highest level of the data of the delay profile, or (c) if a level of a signal having a highest level of the data of the delay profile i. not more than a 5 predetermined threshold Len, operation of all fingers is a topped.

As i. obvious from the above aspects, according to the pageant invention, when signals arriving through a plurality of radio waves in a multi-path are arranged in 10 the descending order of signal levels, the level difference between adjacent signals i. obtained, and the level difference is compared with a throshold. mix wahoo it possible to detect "a signal group having levels similar to each other to mane degree" in the prior art.

15 Hence, RAKE reception can be performed by using signals that provide a great diversity effect, and reception quality can be guaranteed even in a weak electric field as

much as possible.

According to the present invention, RARE reception is 20 performed without using signals having low levels by which only a small diversity effect can be obtained. With this operation, operation of unnecessary fingers is o topped.

An a consequence, the power consumption can be reduced.

According to the present invention, therefore, a RATE 25 reception effect can be obtained, and power consumption

- 16 can He optimized.

In addition, according to the present invention, if the level of the signal, of signals arriving through a plurality of radio waves in a multipath, which has the 5 highest level equal to or lower than the threshold Lo=, all the finger. are operated. This makes it possible to obtain relatively high reception quality even in a weak electric field.

The above and many other objects, features and 10 advantages of the present invention will become manifest to those skilled in the art upon making reference to the following detailed description and accompanying drawings

in which preferred embodiments incorporating the principle of the present invention are shown by way of illustrative 15 examples.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a block diagram showing the reception apparatus disclosed in Japanese Unexamined Patent Publication No. 9-181704; 20 Fig. 2 is a block diagram showing the reception apparatus disclosed in Japanese Unexamined Patent Publication No. 7-231278; Fig. 3 is a graph showing multi-path signals sequentially arranged from the left side in the descending 25 order of levels;

- 17 Fig. 4 is a block diagram schematically showing a COMA mobile communication system to which a CDMA transmission apparatus according to the present invention is applied; 5 Fig. 5 is a view for explaining a multi-path; Fig. 6 is a block diagram showing a mobile station according to an It of the present invention; Fig. 7 is a ViQW showing an example of the format of a signal transmitted from a base atation to a mobile 10 station in the embodiment shown in Fig. 6; Fig. 8 is a block diagram showing an example of the arrangement of a delay profile acquiring auction in Fig. 6; Fig. 9 is a graph showing a reception signal input to 15 the delay profile aoguiring section in Fig. 8; Fig. 10 is a graph showing the reception signal obtained by performing inverse conversion processing for the reception signal in Fig. 9 which i. input to the delay profile acquiring section in Fig. 8; 20 Fig. 11 i. a view for explaining the operation of a search section in Fig. 6; Fig. 12 is a block diagram showing function blocks in a CPV in Fig. 6; Fig. 13 is a block diagram showing the internal 25 arrangement of a finger section power control circuit in

- 18 Fig. 6; Fig. 14 is a graph showing an example of the delay profile output from the delay profile acquiring section in Fig. 6; 5 Fig. 15 is a flow chart showing the processing to be performed after the mobile station in Fig. 6 is powered on; Fig. 16 i. a flow chart showing the processing to be performed after the mobile station in Fig. 6 is powered on, 10 which processing differs from that shown in the flow chart of Fig. 15; Fig. 17 is a flow chart showing the processing to be performed after the mobile atation in Fig. 6 is powered on, which processing differs from that shown in the flow chart 15 of Fig. 15 or 16; Fig. 18 is a block diagram showing a mobile station according to another embodiment of the present invention, which differs from the one shown in Fig. 6; and Fig. 19 is a view schematically showing an Trample of 20 the outer appearance of a display section in Fig. 18.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

25 In the embodiment described below, the present

( J 19 invention is applied to a mobile station in a CDMA mobile communication system.

Fig. 4 is a block diagram showing the schematic arrangement of a CDMA mobile communication system to which 5 a CAM transmission apparatus according to the present in w ntion i. applied.

ATM (Asynchronous Transfer Mode) communication techniques and the like have been applied to base stations, base atation controllers, and switching centers which 10 constitute the network of a mobile communication system from the viewpoint of the diversification (growing trend toward multimedia) of service. provided by the mobile communication system and the efficient use (statistical multiplexing) of a transmission path for connecting each 15 baeo station, base station controller, and switching center. A mobile unit 21 communicates with another mobile station, a terminal apparatus connected to another network, or the like through the mobile communication System.

20 There are various types of communications, e.g., ape ech and data communications.

Transmission data from the mobile unit 21 is transmitted a. communication data to a base station 22 by radio communication. The base station 22 assembles the 25 communication data received from the mobile unit 21 or

- 20 another mobile station into an ATM cell and performs various processes for the received data. The base station 22 then transmits the resultant data to a base station controller 23.

5 As described above, since Communication data in a - radio is transmitted as ATM cell information by a base station within the network regardle6- of whether the data is speech data, image data, or data in another form, this system can easily cope with a multimedia c "unication lo form.

The base station controller 23 routes the ARM cell received from the base station 22 for each user, and transmits it to a switching center 24 or another base station controlled by the base station controller 23. The 15 switching center 24, like the base station controller 23, route. the ATM cell recoined from the b.SQ station controller 23 for each user, and transmit. it to another switching center or a gateway office 25.

Such an ATM cell may be transmitted through a 20 transmission path upon generation of an ATM cell, and there is no need to net a transmission path for each predetermined channel as in the prior art. This mates it

possible to obtain a statistical multiplexing effect and efficiently use a transmission path. Note that the 25 gateway office 25 is provided to relay a signal to another

( -, network. Fig. 5 is a view for explaining a multi-path..

Various obstacles are present between the motile unit: 21 and the base station 22. In the case shown in Fig. 5, 5 for example, an obstacle 26 i. present between the -Chile unit 21 and the base station 22, and radio wave. that propagate straight from the base station 22 to the mobile unit 21 are blocked by the obstacle 26.

Even in this case, radio waves from the base station 10 22 can reach the mobile unit 21 after they are reflected by obstacles 27 and 28. In the case shown in Fig. 5, therefore, there are two routes taken to reach from the bane station 22 to the mobile unit 21, i.e., the route in which radio waves are reflected by the obstacle 27 and 15 roach the mobile unit 21 and the route in which radio waves are reflected by the obstacle 28 and reach the I mobile unit 21. That is, a multi-path is present.

The route in which radio waves from the base station 22 are reflected by the obstacle 27 and reach the mobile 2 0 unit 21 differs in distance from the route in which radio wave" from the base station Z2 are reflected by the obstacle 28 and reach the mobile unit 21. For this reason, the time taken for a radio wave to be reflected by the obstacle 27 and reach the mobile unit 21 differs from the 25 tome taken for a corresponding radio wave to be reflected

- 22 by the obstacle 28 and reach the mobile unit 21. I In RAKE reception, the differences between the times taken for radio waves to reach through the respective multi-path routes are considered, and the respective radio 5 waves are combined with delay time. that cancel out the time differences, thereby obtaining a path diversity effect. Since the mobile unit 21 moves as occasion Uplands, routes through which radio wave. from the base station 22 10 reach the mobile unit 21 also change as occasion demands.

As the mobile unit 21 moves, the number of routes through which radio waves from the base atation 22 reach the mobile unit 21 change-, and the intensity of radio waves received by the mobile unit 21 through each route also 2 15 changes. In addition, the delay times of the respective ignals to the RARE combiner change at all the times. I Fig. 6 is a block diagram showing a mobile station according to an enbodimunt of the present invention.

Referring to Fig. 6, the mobile unit 21 i. comprised 2 20 of an antenna 30 for receiving radio waves from the base station 22, a reception circuit 31for, for example' demodulating a reception signal received through the antenna 30, a delay profile acquiring section 32 for obtaining the intensity of each multi-path signal by using 25 an output from the reception circuit 31 and outputting the

- 23 reultant data as a delay profile, a search section 33 for extracting data, of the data of the delay profile from the delay profile acquiring section 32, which correspond to: the path. of signal. having the highest intensity to an 5 intensity of predetermined ordinal number, a user input device 35 used by the user to input to a threshold {to be described later) , a Mom 34 storing the data extracted by the search section 33 and the threshold input through the user input device 35, a CPU 36 for executing processing 10 for determining a finger which i. to be powered on the basis of the data extracted by the search section 33 and stored in the RCM 34 and the threshold input through the I user input device 35, a finger section 38 constituted by -

fingers 38: to 38N for Respreading and demodulating an 15 output from the reception circuit 31 with predetermined.

delay times, a finger section power control circuit 37 for I controlling power to the finger section 38 on the basis of a notification from the CPU 36, and a RARE reception section 39 for RAXE-combining signal. from the respective 2 20 finger. of the finger section 35.

Fig. 6 does not show the arrangement of the transmission side of the mobile unit Z1 because it is irrelevant to the gist of the present invention.

Fig. 7 is a View showing an example of the format of 25 a signal transmitted from the base station 22 to the -

l - 24 mobile unit 21.

In this case, the signal transmitted from the base station 22 to the mobile unit 21 is made up of 72 frames.

The transmission time required for one frame is 10 ma.

5 Each frame is made up of 16 slots. -Each slot is made of 2S6 chips. Referring to Fig. 7, one clot is made up of a pilot signal, TIC (Transmission Power Control) signal, and data signal.

An described above, sines the transmission tram for 10 one frame is to mfi, the transmission time for one ship is (0.625/256) as.

Fig. 8 is a view showing an example of the arrangement of the delay profile acquiring section 32 in Fig. 6.

15 The delay profile acquiring section 32 is comprised of a plurality of correlators 404 to 406 for deeproading a reception signal from the reception circuit 31 and a taming control circuit 41 for controlling the Respreading timings of the plurality of corrolators 401 to 402s6 20 The 2S6 correlatore 40: to 406 correspond to the number of chips in one slot described above, i.e., 256 chips. Each of the correlators 40' to 402S6 iS controlled by the timing control circuit 41 to Respread a reception 25 signal from the reception circuit 31 with a time shift

my, ( - 25 corresponding to the transmission time for one chip, i.e., (0. 625/256) ma.

Assume that the correlator 4O1 starts depreading at time to. In this case, the correlator 4O2 a tart.

S Respreading at time t1 delayed from time to by (0.625/256) mat and the correlator 40, starts denpreading at time t2 delayed from time t1 by {0. 625/256) as. The subsequent correlators sequentially Respread the signal with delay time-. 10 The spreading codes used in the correlatore 40: to 40-, are identical to those Up by the base station 22 in spreading processing when transmitting the signal. It doe. not matter whether the spreading codes are long or short code-.

15 In the case shown in Fig. 8, correlators equal in number to the chip. in one slot are prepared. However, the present in w ntion is not limited to this. For example, correlatore half the number of chip. in one slot, i. e, 128 correlatore, --y be prepared. In this case, the first 20 correlator performs Respreading at the first time and 129th time; and the second correlator, at the socond time and 130th time. In this manner, each óorrolator performs Respreading twice sequentially The delay profile acquiring section 32 performs 25 Respreading in the above manner to generate a delay

( - 26 profile representing the correspondence between each Respreading timing and the intensity of the signal obtained by the Respreading. The delay profile acquiring section 32 then outputs this profile to the search section 5 33 in Fig. 6.

Fig. 9 is a graph showing a reception signal input to the delay profile acquiring section 32 in Fig. 8.

Fig. 1O is a graph showing the input reception signal in Fig. 9 which has undergone inferno conversion 10 processing in the delay profile acquiring section 32 in Fig. 8.

Referring to each of Fig-. 9 and 1O, the ordinate represents the intensity of the signal; and the abscissa, the time.

15 As shown in Fig. 9, the reception signal, which is transmitted after being spread by the base station 22 with a spreading code and is received by the reception circuit 31, is spread to a wide band to become a signal with a noise level. c 20 The delay profile acquiring section 32 Respreads the signal in Fig. 9 to obtain the signal in Fig. 10.

As i. apparent from Fig. 1O, there is a correlation between times tl, t,, ts, and to, and the signal is reconstructed. That is, in the case shown in Fig. lo, 25 four paths corresponding to times tl, t,, ts, and to are

- 27 produced in a multi-path. -

The delay profile acquiring section 32 in Fig. 8 -

outputs times to to t -, and the signal intensities, i.e., -

signal levels, at times to to tic, which are obtained by; 5 the above Respreading processing, as a delay profile, to -

the search section 33 in Fig. 6. -

Fig. 11 i. a view for explaining the operation of the search section 33 in Fig. 11.

The search section 33 outputs N data to the REM 34 in 10 the descending order of levels in the delay profile -

(expressed in a table form in the search section 33 in Fig. 11) from the delay profile acquiring section 32. In the case shown in Fig. 10, the data are sequentially output to the ROM 34 at times to, to, to, and to in the 15 descending order of levels.

The N data output from the search section 33 to the ROM 34 are preferably equal in number to the fingers in b the finger section 38 in Fig. 6. -

The ROM 34 in Fig. 6 is used to store the data with 20 the higher levels which are extracted from the above delay profile data by the search section 33 and the user set value input through the user input device 35 in Fig. 6.

An the user input device 35, for example, buttons for inputting a user set value may be provided in the mobile 25 station or a conventional ten- key pad for inputting a 3

telephone number may be used. Alternatively, an external input device, e. g., a personal computer, may be connected to the mobile station to input a user set value. The user ÀA set value input through the user input device 35 is used; 5 in processing performed by the CPU 36 (to be described later). Fig. 12 is a block diagram showing the functional block. in the CPU 36 in Fig. 6.

As shown in Fig. 12, the CPU 36 reads out the user 10 set value input through the user input device 35 and the -

times and levels as the data extracted from the delay profile by the search section 33 from the ROM 34. A difference computing means 42 computes and outputs the differences between the levels by using the times and 15 levels read out from the Ran 34. A comparing means 43 compares the user set value read out from the ROM 34 with each of the difference. between the levole, which are b output from the difference computing means 42, and outputs data selected on the basis of the comparison result.

20 This processing by the CPU 36 will be described in detail later with reference to the flow chart of Fig. 15.

Fig. 13 is a block diagram showing the internal arrangement of the finger section power control circuit 37 in Fig. 6.

25 The finger section power control circuit 37 has a 3

- 29 switch control section 44. The switch control section 44 receives the computation result from the CPU 36 and controls switches for turning on/off power supplied to the fingers 3B: to BEN in the finger section 38 on the basin of 5 the received result. That is, the finger section power control circuit 37 controls the switches to supply power to only the fingers, of the fingers 381 to 38, which correspond to the delay times notified by the CPU 36.

Fig. 14 shows an "sample of the delay profile output 10 from the delay profile acquiring section 32 in Fig. 6.

In the case shown in Fig. 14, the level having the highest level is detected at time t,; the signal having the second highest 1QVe1, at time tl; the signal having the third highest level, at time t7; and the signal having 15 the fourth highest level, at time t,. Assume that the level difference between the signal having the highest level at time t, and the signal having the second highest level at time tz is represented by d,, and the level differenco between the signal having the second highest 20 level at tome tz and the signal having the third highest level at hive t7 i. represented by do.

Assume that the threshold based on the user set value input through the user input device 35 is represented by d", and d: < d" and d2 > d-. In this case, as a result of 25 the comparison processing in the CPU 36 in Fig. 6, the CPU

ll - 30 36 notifier the finger section power control circuit 37 of the delay time of the signal at time to and the delay time of the signal at time t:.

Upon reception of this notification, the finger 5 section power control circuit 37 supplies power to only the finger corresponding to the delay time of the signal at time to and the finger corresponding to the delay time of the signal at time to, but no power is eonsned for the remaining fingers.

10 Figs. 15 is a flow chart showing the processing to be executer when the mobile unit 21 in Fig. 6 is powered on.

When the power is turned on tstep F-1), the mobile unit 21 performs perch channel acquisition and repeats this processing subsequently. In this embodiment, 15 processing of determining fingers to be operated is performed by this perch channel acquisition processing.

The processing performed by the CPU 36 will be described below with reference to the flow chart of Fig. 15.

20 First of all, a timer for detecting a lapse of a predetermined period of tone is reset, and then operated (step F-2). The CPU 36 then causes the search section 33 to extract a predetermined number of data having higher levels from a delay profile (step F-3), and stores the 25 extracted data in the ROM 34.

- 31 After the CPU 36 sets the initial value "1" in a loop counter i (step F-4), the CPU 36 selects the data having the highest level from the data extracted from the delay profile by the search section 33, which are read out from 5 the ROM 34, and notifies the finger section power control circuit 37 of a time to of this signal, i.e., the delay time of this signal. Upon reception of this notification, the finger section power control circuit 37 controls the switch control section 44 in Fig. 13 to supply power to 10 the finger corresponding to the data having the highest level to operate the finger (step F-5). In the case shown in Fig. 10, since the signal at time t, has the highest level, the time t, is notified in step F-5.

In step F-6, the difference computing means 42 in 15 Fig. 12 computes a difference. More specifically, in step F-6, the difference computing means 42 computes the level difference between the data having the ith highest level and the data having the (i+l)th highest level, of the data extracted from the delay profile by the search section 33.

20 This computation result is represented by do.

In step F-7, the comparing means 43 in Fig. 12 compares the differences with each other. This difference camparison processing will be described below.

The user set value read out from the ROM 34 in used 25 as a threshold d" as a comparison target to be compared

- 32 with the difference d. obtained in step F-6. It is expected that the user has difficulty in inputting this threshold as a specific n'marical value. For thin reason, it is preferable to allow the user to select numerical 5 values set in the process of designing the apparatus in a step-by-step manner by using the user input device 35 instead of inputting a specific numerical value.

In step F-7, the CPU 36 checks whether the difference d1 which ha. the value of the loop counter i as a 10 numerical subscript i. smaller than the threshold do.

If it is determined in step F-7 that the difference do is not Smaller than the threshold d-, the flow waits for a lapse of a predetermined period of time (step F-11).

When the predetermined period of time elapses, the flow 15 returns to step F-2 to repeat finger operation control.

As the predetermined period of tome in step Fell, for; example, the time corresponding to one slot of reception data i. "et.

If it is determined in step F-7 that the difference i 20 do is not smaller than the threshold d" when the value of the loop counter i is 1, the CPU 36 notifies the finger section power control circuit 37 of only the value to, i.e., the delay time, of the signal of the data, of the data extracted by the search section 33 from the delay 25 profile read out from the ROM 34, which has the highest

- 33 level. In this case, therefore, the finger section power control circuit 37 supplies power to only the finger corresponding to the delay time of only one signal notified as the result from the CPU 36.

5 If it is determined in step F-7 that the difference do is smaller than the threshold d-, the CPU 36 notifies the finger section power control circuit 37 of the value to, i.e., the delay time, of the signal of the data, of the data extracted by the search section 33, which ha. the 10 {i+ l)th highest level. Upon reception of this notification, the finger section power control circuit 37 control. the switch control section 44 in Fig. 13 to supply power to the finger corresponding to the data having the {i+l)th highest level, thus operating the 15 finger (stop F-8).

After the loop counter i i. incremented by one {step; F-9), the CPU 36 checks whether the value of the loop counter i is equal to N. obtains the differences from all the data extracted by the search section 33, and checks i 20 whether comparison with the threshold d" is performed {step F10).

If it is determined in step F-10 that the value of the loop counter i is equal to N. and comparison with the threshold d" is complete, the flow wait. for a lapse of a 25 predetermined period of tine (step Fell) and returns to

- 34 step F-2 when the predetermined period of time elapses, thus repeating finger operation control.

If it is determined in step F-1O that the value of the loop counter i is not equal to N. and comparison with 5 the threshold d" is not complete, the flow returns to step F-6 to continue the processing.

Fig. 16 i. a flow chart showing the processing to be performed after the mobile unit 21 i. powered on. This processing differs from that shown in the flow chart of 10 Fig. 15.

In the processing shown in Fig. 15, the difference from the level of each signal is acquired and compared with the threshold. In the processing shown in Fig. 16, the level of each signal is directly compared with a 15 threshold.

When the power i. turned on (step S-1), the mobile unit 21 performs perch channel acquisition processing, and repeats thi_ processing Subsequently. In this. embodiment, processing of determining fingers to be operated is 20 performed by this perch channel acquisition processing.

The processing performed by the CPU 36 will be described below with reference to the flow chart of Fig. 16.

First of all, the timer for detecting a lapse of a 25 predetermined period of time is reset, and then operated

- 35 (step So-). The CPU 36 then causes the search section 33 to extract a predetermined number of data having higher level. from a delay profile (step S-3), and stores the extracted data in the RDM 34. The CPU 36 then sets the 5 initial value "1" in the loop counter i (step S-4).

In this case, the user set value read out from the dam 34 is used as a threshold Lo a. a comparison target to be compared with the level of each signal. An in the case shown in Fig. 15, it is expected that the user ha.

10 difficulty in inputting this threshold a. a specific numerical value. For this reason, it i. preferable to allow the user to violet numerical values net in the process of designing the apparatus in a step-by-step manner by using the user input device 35 instead of 15 inputting a specific numerical value.

In step S-S, provided that the level of the signal having the ith highest level is represented by In, the CPU 36 check. whether the level Lo having the value of the loop counter i as a numerical subscript is lower than the 20 threshold L-.

If it is determined in step S-5 that the level L1 is lower than the threshold L-, the CPU 36 check" whether the value of the loop counter i is 1 (step S-9). If it is determined in step S-9 that the value of the loop counter 25 i is 1, power is supplied to all the fingers (step S-10).

me, ( - 36 The flow then advances to step S-11. Otherwise, the flow directly advances to step Sell.

In step S-11, the flow waits for a lapse of a predetermined period of time, and returns to step S-2 when S the predetermined period of time olapo-, thus repeating finger operation control.

If it is determined in c top S-5 that the level In is not lower than the threshold L-, the CPU 36 notifies the finger section power control circuit 37 of the value to of 10 the current signal. More specifically, the CPU 36 notifies the finger section power control circuit 37 of the value to, i.e., the delay time, of the signal of the data, of the data extracted by the Search section 33 from the delay profile read out from the REM 34, which ha. the 15 ith highest level. Upon reception of this notification, the finger section power control circuit 37 control. the switch control Section 44 in Fig. 13 to supply power to the finger corresponding to the current data, thereby operating the finger (step S-6) .

20 After the loop counter i is incremented by one (step S-7), the CPU 36 checks whether the value of the loop counter i in equal to N. and checks whether comparison between the levels of all the signals And the threshold Lo is complete (step S-8).

25 If it is determined in step S-8 that the value of the

( - 37 loop counter i is equal to N. and comparison between the levels of all the signals and the threshold L" is complete, . the flow wait. for a 1apae of a predetermined period of time (step S-11), and turns to step S2 when the 5 predetermined period of time elapses, thus repeating finger operation control.

If it is determined in step S-8 that the value of the loop counter i i. not equal to N. and comparison between the levels of all the signals and the threshold L. is not 10 complete, the flow returns to step S-5 to continue the processing. In the embodiment described above, if the level of the signal, of the delay profile data, which has the highest level is lower than a threshold L-x' the power 15 switches for all the fingers may be turned on. In a weak electric field, an improvement in reception

characteristics takes priority over power saving. This makes it possible to produce a receptive state even in a weak electric field. This case will be described with

20 reference to Fig. 17.

Fig. 17 is a flow chart showing the processing to be performed after the mobile unit 21 is powered on. This processing differs from that shown in the flow charts of Fig-. 15 and 16.

25 When the power is turned on (step M-1), the mobile

- 38 unit 21 performs perch channel acquisition processing, and repeats this processing subsequently. In this embodiment, procosinq of determining fingers to be operated is performed by this perch channel acquisition processing.

5 The processing performed by the CPU 36 will be described below with reference to the flow chart of Fig. 17.

First of all, the timer for detecting a lapse of a predetermined period of time is reset, and then operated 10 (step M-2). The CPU 36 then causes the search section 33 to extract a predetermined number of data having higher levels from a delay profile (step M-3), and stores the extracted data in the Ram 34.

In step M-4, the CPU 36 checks whether a level L: of 15 the signal having the highest level is lower than threshold LM.

If it i. determined in step M-4 that the lover L1 is lower than the threshold Sex, the CPU 36 supplies power to all the fingers (step M-5). Thereafter, the flow waits 20 for a lapse of a predetermined period of time (step M-13) and returns to step M-2 when the predetermined period of time elapses, thus repeating finger operation control.

If it is determined in step M-4 that the level L1 is not lower than the threshold Len, the same processing as 25 that shown in Fig. 15 or 16 is performed. In the case

- ( - 39 shown in Fig. 17, the name proceasing a. that shown in Fig. 15 is performed. That is, steps M-6 to M-13 in Fig. 17 correspond to steps F- 4 to F-11 in Fig. 15. For this reason, a description of steps M-6 to M-13 in Fig. 17

5 will be abutted.

A mobile station of an embodiment different from that shown in Fig. 6 according to the present invention will be described next.

Fig. 18 is a block diagram showing a mobile station 10 of an embodiment different from that shown in Fig. 6 according to the present invention.

Referring to Fig. 18, the mobile station has an antenna 30 for receiving radio waves from a baeo station 22, a reception circuit 31 for, for example, demodulating 15 the reception signal received through the antenna 30, a delay profile acquiring section 32 for obtaining the intensity of each multi-path signal by using an output from the reception circuit 31 and outputting the resultant data as a delay profile, a search section 33 for 20 extracting data, of the data of the delay profile from the delay profile acquiring section 32, which correspond to the paths of signals having the highest intensity to an intensity of predetermined ordinal number, a user input device 35 used by the user to input to a threshold (to be 25 described later), a RCM 34 storing the data extracted by

1 - 40 the search section 33 and the threshold input through the user input device 35, a CPU 36 for executing processing for determining a finger which is to be powered on the basis of the data extracted by the search section 33 and 5 stored in the ROM 34 and the threshold input through the user input device 35, a finger section 38 contitutod by fingers 381 to 3% for Respreading and demodulating an output from the reception circuit 31 with predetermined delay times, a finger section power control circuit 37 for 10 controlling power to the finger section 3B on the basin of a notification from the CPU 36, a RAKE reception section 39 for RAX$-combining signals fro n the respective fingers of the finger section 38, and a display section 45 for displaying the operation state of each finger upon 15 reception of the result notified from the CPU 36.

Similar to Fig. 6, Fig. 18 does not show the arrangement of the transmission aide of the mobile unit 21 because it i. irrelevant to the gist of the present invention. 20 The same reference numeral. as in Fig. 16 denote the same parts in Fig. 18, and a detailed description thereof

will be omitted.

A characteristic feature of thin "mbo;mont is that it has the display section 4S shown in Fig. 18. The 25 display section 45 will be described below with reference

- 41 -

to the accompanying drawings.

Fig. 19 schematically shows the outer appearance of an example of the display section 45 shown in Fig. 18.

Referring to Fig. 19, the display section 45 has a 5 display window 46 constituted by an LCD and the like, up and down buttons 47 and 48 operated by the user to set the above threshold, and a display switching button 49 for switching contents to be displayed on the display window 46. 10 The user man switch the contents to be displayed on the display window 46, e.g., the address book stored in a memory {not shown) or information indicating the operation state of each finger, by repeatedly pressing the display "witching button 49.

15 The up and down button" 47 and 48 are operated by the user to set the threshold d" described with reference to Fig. 15 or the threshold L" described with reference to Fig. 16. The user can increase the current threshold by pressing the up button 47, and can decrease the current 20 threshold by pressing the down button 4B.

Fig. 19 shows a case wherein the operation state of each finger in displayed on the display window 46 upon operation of the display switching button 49. In this case, the bar graph indicates the magnitude of the 25 reception level of each finger in use (to which power is

42 supplied). In the case shown in Fig. 19, the number of fingers is 7, i.e., N i. 7 in the above case. Fig. 19 show. that power is supplied to only the fingers corresponding to the 5 third, fourth, and sixth bars in the graph.

When the user presses the down button 48 in this state, the threshold decreases. In the case shown in Fig. 16, the number of path" in a multipath through which radio waves are received by the mobile station increases.

10 Consequently, the number of bars displayed on the display window 46 increases.

As in this embodiment, the use of the display section 45 allows the user to recognize a reception state, thus implementing the function of providing interesting and 15 useful information for the user.

In this embodiment, the operation state of each finger is displayed on the display section 45. Howovor, the occurrence tat. of multi-path may be displayed on the display section 45.

20 In each embodiment described above, the present invention is applied to a mobile station in a mobile communication system. However, the present invention is not limited to this and can be generally applied to other types of reception apparatuses.

Claims

- 43 CLAIMS:

1. A COMA reception apparatus having a plurality of fingers and serving to perform RAKE reception by RAKE-ynthesizing outputs from said plurality of fingers, comprising: multi-path detecting means for detecting a multipath consisting of a plurality of radio wares arriving with some delay times by despreading a reception signal; and, delay-profile generating means for generating a delay profile by obtaining reception power levels of all reception signals in the multi-path detected by said multi-path detecting means; wherein if a level of a signal having a highest level of the data of the delay profile is not more than a predetermined threshold Len, operation of all fingers is stopped. 2. An apparatus according to claim 1, further comprising a user input device by which a user can set the threshold. 3. An apparatus according to claim 1 or 2, further comprising display means for displaying information indicating the number of fingers, of "aid plurality of fingers, to which power in supplied.

( - 44 4. A power control method for a CDMA reception apparatus having a plurality of fingers and serving to perform RAKE reception by RAKEsynthesizing outputs from said plurality of fingers, comprising the steps of: detecting a multi-path consisting of a plurality of radio waves arriving with some delay times by Respreading a reception signal; and, generating a delay profile by obtaining reception power levels of all reception signals in the multi-path; wherein if a level of a signal having a highest level of the data of the delay profile is not more than a predetermined threshold Lea, operation of all fingers is stopped. 5. A CDMA reception apparatus having a plurality of fingers and serving to perform RAKE reception by RAKE-combining outputs from said plurality of fingers, comprising: multi-path detecting means for detecting a multipath consisting of a plurality of radio waves arriving with some delay times by Respreading a reception signal; and, delay profile generating means for generating a delay profile by obtaining reception power levels of all reception signals in the multi-path detected by said multi-

path detecting means; wherein a difference di in level between a signal

( - 45 -

having an ith highest level and a signal having an (i+l)th highest level of data of the delay profile is obtained, and operation of a finger corresponding to a signal having a level lower than that of the signal having the (i+l)th highest level is stopped on the basin of the difference d and a predetermined threshold do.

6. An apparatus according to claim 5, wherein the difference di in level between the signal having the ith highest level and the signal having the (i+l)th highest level of data of the delay profile i" obtained, and operation of a finger corresponding to a signal having a lower level than that of the signal having the (i+l)th highest level is stopped if the difference do is not less than the predetermined threshold d=.

7. An apparatus according to claim 5, wherein if the difference di in level between the signal having the ith highest level and the signal having the (i+l)th highest level of data of the delay profile i" not more than a predetermined value, and a difference din in level between the signal having the (i+l)th highest level and a signal having an (i+2)th highest level is not less than the predetermined value, operation of a finger corresponding to a signal having a level lower than that of the signal having the (i+2)th highest level in stopped.

( - 46 8. An apparatus according to claim 5, further comprising a user input device by which a user can set the threshold. g. An apparatus according to claim or 8, further comprising display means for displaying information indicating the number of fingers, of said plurality of fingers, to which power is supplied.

10. A power control method for a CDMA reception apparatus having a plurality of fingers and serving to perform RAKE reception by RAKEcombining outputs from said plurality of fingers, comprising the steps of: detecting a multi-path consisting of a plurality of radio waves arriving with some delay times by depreading a reception signal; and, generating a delay profile by obtaining reception power levels of all reception signals in the multi-path; wherein a difference di in level between a signal having an ith highest level and a signal having an (i+l) th highest level of data of the delay profile is obtained, and operation of a finger corresponding to a signal having a level lower than that of the signal having the (i+l)th highest level is stopped on the basis of the difference d and a predetermined threshold d=.

( - 47 11. A method according to claim 10, wherein the difference di in level between the signal having the ith highest level and the signal having the (i+l)th highest level of data of the delay profile is obtained, and operation of a finger corresponding to a signal having a level lower than that of the signal having the (i+l)th highest level if the difference di is not less than the predetermined threshold do is stopped.

12. A method according to claim 10, wherein if the difference di in level between the signal having the ith highest level and the signal having the (i+l)th highest level of data of the delay profile i" not more than a predetermined value, and a difference din in level between the signal having the (i+l)th highest level and a signal having an (i+2)th highest level in not less than the predetermined value, operation of a finger corresponding to a signal having a level lower than that of the signal having the (i+2)th highest level is stopped.

13. A COMA reception apparatus having a plurality of fingers and serving to perform RAKE reception by RAKE-synthesizing outputs from said plurality of fingers, comprising: multi-path detecting means for detecting a multi-path consisting of a plurality of radio waves arriving with some

( - 48 delay times by Respreading a reception signal; and, delay-profile generating means for generating a delay profile by obtaining reception power levels of all reception signals in the multi-path detected by said multi-path detecting means; wherein operation of a finger corresponding to a signal having a level lower than that of a signal having an (i+l)th highest level is stopped on the basis of a result obtained by comparing a threshold Lo with a level Li of a signal having an ith highest level of the data of the delay profile. 14. An apparatus according to claim 13, wherein if the level Li of the signal having the ith highest level of the data of the delay profile is not more than the predeter-mined threshold Lo, operation of a finger corresponding to a signal having a level lower than that of the signal having the ith highest level is stopped.

IS. An apparatus according to claim 13, further comprising a user input device by which a user can set the threshold. 16. An apparatus according to claim 13 or 15, further comprising display means for displaying information indicating the number of fingers, of said plurality of

( - 49 fingers, to which power in supplied.

17. A power control method for a COMA reception apparatus having a plurality of fingers and nerving to perform RAKE reception by RAKEsynthesizing outputs from said plurality of fingers, comprising the steps of: detecting a multi-path consisting of a plurality of radio waves arriving with some delay times by depreading a reception signal; and, generating a delay profile by obtaining reception power levels of all reception signal" in the multi-path; wherein operation of a finger corresponding to a signal having a level lower than that of a signal having an (i+l)th highest level is stopped on the basin of a result obtained by comparing a threshold Lo with a level Li of a signal having an ith highest level of the data of the delay profile. 18. A method according to claim 17, wherein if the level Lo of the signal having the ith highest level of the data of the delay profile is not more than the predeter-

mined threshold Lo, operation of a finger corresponding to a signal having a level lower than that of the signal having the ith highest level is stopped.