GB2391140A

GB2391140A - Power control in a CDMA receiver having RAKE fingers

Info

Publication number: GB2391140A
Application number: GB0325275A
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: GB2391141B; GB0325276D0; GB2391140B; GB2391141A; GB0325275D0

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 1 40

- 1 - CDMA RECEPTION APPARATUS AND POWER CONTROL METHOD THEREFOR

BACXRCqND OF THE INVENTION Field of the Invention:

5 The present invention relates to a CDMA reception apparatus and power control method therefor which are used for a mobile communication system and, more particularly, to a CDMA reception apparatus for performing RARE reception and a power control method for the apparatus.

10 Description of the Prior Art:

Conventionally, a mobile communication system using CDMA (Code Division Multiple Access) has been known.

In this CDMA mobile communication system, when data is to be transmitted from a mobile station to a base 15 station, transmission data is 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 assigned to each mobile station.

likewise, data transmitted from a base station to a mobile station is also spread by a corresponding one of the spreading code. assigned to the respective mobile stations before it is transmitted. The resultant data is 25 then transmitted.

- 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 these 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 waves reach the mobile station, occurs.

The respective multi-path radio waves reach the mobile station with delay times corresponding to the respective route-. The mobile station therefore can 15 improve reception quality owing to a path diversity effect by combining the multi-path radio waves in consideration of the delay times. This reception method will be referred to as a RAXE reception method.

A reception apparatus using this RAXE reception 20 method needs to have fingers for Respreading and the like equal in number to paths to a RAKE combiner. If, therefore, the number of paths to the RAXE combiner is 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

J' multi-path occurs always changes. In some case, therefore, the use of too many fingers cannot allow the RATE combiner to obtain a satisfactory reception quality improving effect, i.e., a path diversity effect.

5 For this reason, it is necessary 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, i.Q., a path diversity effect, to such an extent that the apparatus size does not increase too much.

10 In such a situation, in a CDMA reception apparatus having a limited number of fingers, the delay times in the respective fingers must he controlled to reliably capture multi-path radio waves.

As a conventional reception apparatus that solder 15 this problem, the reception apparatus disclosed in Japanese Unfed Patent Publication No. 9181704 is available. Fig. 1 is a block diagram showing the arrangement of a reception apparatus disclosed in Japanese Unexamined 20 Patent Publication No. 9-181704. The first conventional 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 Respreading; and 300, a 25 search finger for detecting the level of a reception

- 4 - signal in each phase.

Reference numeral 402 denotes a RAKE 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.

Referenee numeral 403 denotes a pilot interpolation absolute synchronous detector for performing synchronous detection of the signal Respread by the tracking finger 200. 10Referenee 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 uses this 15 spreading code replica after delaying it by a predetermined amount through a spreading code replica delay section 206 or 305.

Referenee numeral 405 denotes a RATE combiner for combining signals from the respective paths; and 410, an 20 output terminal.

Referenee numerals 201, 202, 203, and 310 denote multipliers each serving 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,

( - 5 - and 303, amplitude squaring circuits each serving 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 altar for acting 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 averaging 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 code replica timing control signal generating section 212. In 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 RATE combining path selecting section 402 for Respreading.

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

The tracking finger 200 performs Respreading by using a spreading replica code corresponding to a delayed path designated by the RAKE 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 this respreading is demodulated. A. s a demodulation scheme, delay detection, synchronous detection, or the like is available. In 5 absolute synchronous detection, an absolute phase of reception must be 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 multiplier. 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 predetermined period of time. The amplitude 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 '6 phase shift and the spreading code replica obtained by the - phase 25 shift with opposite polarities to generate a chip timing

//( - 7 - error signal associated with the spreading code replicas.

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

m is phase update information is input to the RAKE combining path selecting section 402. The RACE combining path "electing section 402 manages RATE combining paths in real time to prevent overlaps between paths.

10 The RAKE combining path Molesting section 402 updates the RAKE combining paths in predetermined cycles on the basis of an average delay profile of photo information search finger output. of spreading code replicas corresponding to the respective patina to the RAKE combiner.

15 The RATE combining path selecting section 402 generates 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 code replica 20 corresponding to each path having this time delay and the input spread/modulated signal for a predetermined period of time, and inputs the integration output signal to the modulator, i.e., the pilot interpolation absolute synchronous detector 403.

25 According to the above reception apparatus disclosed

/ - 8 - in Japanese Unexamined Patent Publication No. 9-181704, to reliably capture multi-path radio waves with a limited number of finger-, the delay times 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 mlti-path occurs.

Assume that the number of paths in a multi-path i. small, 10 and hence a much effect cannot be obtained even by RATE combining operation using many fingers. In this came, unnocessary 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 receiver disclosed in Japanese Unexamined Patent Publication No. 7-23127S, The second conventional apparatus will be described below with reference to Fig. 2.

20 Reference numerals 50: to 50N denote the first to Nth spreading means for receiving direct spread/modulated signals with N paths and despreading/d-madulating the respective direct pread/modulated signals S30 with the first to Nth spreading sequences synchronized with the N 25 direct spread/modulated signals S30 received at different

/ 9 - timings. Reference numeral 51 denotes a machining manna for combining output data D40: to D40N from the first to Nth Respreading mean. 50: to 50, and 52 represents a control 5 mean. for obtaining the level difference between one of the N direct pread/modulatod signals S30 which has the highoat 1QV.1 and each of the remaining signals. If each of the obtained level difference. is equal to or higher than a threshold T. the combining means 51 turn. off 10 deapreading means {e.g., 502, 50', and 50) for deepreading/demodulating signals having level difference.

of equal to or higher than the threshold T with roapect to the signal having the highest level.

A path diversity effect can be satisfactorily 15 obtained by using a RARE receiver when aignale having levels similar to each other to some degree are input through a multi-path. In anti tion, if a signal having a 1QVe1 noticeably (greatly) lower than the levels of a group of signals having levels similar to each other to 20 some degree is input, the obtained diversity effect is small. For a RARE receiver, thorofore, importance i.

attached to the way to extract only a signal group that provides a great diversity effect.

25 In the method of obtaining level differences from the

/: - 10 highest levels, as in the receiver disclosed in Japanese Unexamined Patent Publication No. 7-231278, 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 in a graph showing multi-path signals arranged in the descending order of level-.

Referring to Fig. 3, the signal having the highest level i. represented by In, and signal. having lower 10 levels are sequentially reprosented by In, I.,.... In addition, the level difference between the signals Lo and 1. is represented by a; the level difference between the signals and lo, b; and the level difference between the signals In and I-, c.

15 In this case, the exproeion "a signal group having levels similar to each other to Rome degree" indicates the signals 1:, In, I,, 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 by a + b T and a + b + c > T. In thin came, the signal L. is discarded although this signal can provide a great path diversity effect. If such a situation occurs in the came of a weak electric field, a deterioration in reception

25 quality cannot be avoided.

( - 11 -

At paragraph number 0028 in Japanese Unexamined Patent Publication No. 723127B, it is described that "In addition, the threshold T is preferably set to a value corresponding to the 1QVe1 difference between one of the 5 direct apread/modulated Signals S30, with which no path diversity effect can be obtained by Synthesis, and the signal having the highest level". In practice, however, the signal having the highest level always varies in lover, and it is difficult to find "one of the direct 10 apread/modulatod signal. S30, with which no path diversity effect can be obtained by Synthesis". For thin reason, it is very difficult or impossible to determine the value of the.threhold T. a. described at paragraph number 0028.

SUMMARY OF THE INVENTION

15 The present invention has k eon made in consideration of the above problma in the prior art, and has a. its

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

consumption by stopping operation of unnecessary fingers.

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

12 fingers and serving to perform RATE reception by RAXE-c^hining outputs from the plurality of fingers, comprising multi-path detecting means for detecting a multi-path consisting of a plurality of radio waves 5 arriving with some delay times by desproading 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 (a) a difference do 10 in lend between a signal having an ith highest level and a signal having an (i+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 do and a prdetormined 15 threshold d-, (a) 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 1QVQ1 1 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 20 highest level of the data of the delay profile is not more than a predetermined threshold -x, operation of all fingers is stopped. -

The present invention has the following minor 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 (il)th highest lover of data of the delay profile i. obtained, and operation of a finger corresponding to a signal having a level lower than that of the signal having the (il)th 5 highest level i" stopped if the difference d; is not lose than the predetermined threshold d-.

- In ablation, if the difference do in level between the signal having the ith highest 1QV.1 and the signal having the (is1tth highest level of data of the delay 10 profile is not more than a predetermined value, and a difference deal in level between the signal having the {il)th highest level and a signal having an (i'2)th highest level i. not foes than the predetermined value, operation of a finger corresponding to a signal having a IS level lower than that of the signal having the (i+2) th highest lover i. stopped.

If the level In of the signal having the ith highest 1QVe1 of the data of the delay 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 i. stopped.

The COMA reception apparatus according to the main aspect further comprises a user input device by which a user can net 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 (c) in the main aspect is performed from 5 the viewpoint that an improvement in reception characteristic. 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 in 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 mwlti-path consisting of a plurality of radio waves 15 arriving with sage 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 (i+l)th highest level of data of the delay profile is obtained, and operation of a finger corresponding to a signal having a low level in stopped on the basis of the difference do and a predetermined threshold d-, (b) 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 level L1 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 is not more than a 5 predetermined threshold K-, operation of all finger. is stopped. An is obvious from the above aspects, according to the present 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 is obtained, and the level difference is compared with a threshold. This makes it possible to detect "a signal group having levels similar to each other to some degree" in the prior art.

15 Hence, RARE 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, RATE 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 i. a 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 be optimized.

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

The above and many other object., 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 TEE DRAWINGS

Fig. 1 is a block diagram showing the reception apparatus disclosed in Japanese Un--,ned Patent Publication No. 9-181704; 20Fig. 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 signal.

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 COMA transmission apparatus according to the present invention in applied; 5 Fig. 5 i. a view for explaining a multi-path; Fig. 6 is a block diagram showing a mobile station according to an ombodimant of the present invention; Fig. 7 in a view showing an example of the format of a signal tranmittod from a base station to a mobile 10 station in the embodiment shown in Fig. 6; Fig. 8 is a block diagram showing an example of the arrange mont of a delay profile acquiring section in Fig. 6; Fig. 9 is a graph showing a reception signal input to 15 the delay profile acquiring section in Fig. 8; Fig. to is a graph showing the reception signal obtained by performing inverse conversion processing for the reception signal in Fig. 9 which is input to the delay profile acquiring section in Fig. 8; 20 Fig. 11 is a view for explaining the operation of a search section in Fig. 6; Fig. 12 is a block diagram showing function block. in a CPU in Fig. 6; Fig. 13 in 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 is a flow chart showing the process ng no =.

performed after the mobile station in Fig. 6 is powered on, 10 which processing differ. 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 i_ powered on, which processing differs from that shown in the flow chart 15 of Fig. 15 or 16; Fig. 18 i. a block diagram "hawing a mobile atation 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 e=-nplo of 20 the outer appearance of a display section in Fig. 18.

DETAILED DESCRIPTION OF PREEli:RRED EMBODI - NTS

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 motile communication system.

Fig. 4 is a block diagram showing the schema tic arrangement of a CDMA "while communication system to which 5 a CDMA transmission apparatus according to the present invention is applied.

ATM {Asynchronous Transfer Mode) communication technique. and the like hay. been applied to base stations, baeo station controllore, and switching contere which 10 constitute, the network of a mobile communication system from the viewpoint of the divoralfication (growing trend toward multimedia) of services provided by the mobile communication system and the efficient unto (atatistical multiplexing) of a transmission path for connecting each 15 bane station, base station controller, and switching center. A mobile unit 21 aammunicates 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., speech and data communications.

Trannsaion data from the mobile unit 21 i.

transmitted as communication data to a bane 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 regardless of whether the data is speech data, image data, or data in another form, this system can easily cope with a multimedia communication 10 form.

The base station controller 23 routes the ATM cell received from the base station 22 for each user, and transmits it to a switching center Z4 or another base station controlled by the base station controller 23. The 15 "witching center 24, like the base station controller 23, routes the ATM cell received from the base station controller 23 for each user, and transmits 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 set a transmission path for each predetermined channel as in the prior art. This makes it

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

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

Various obstacles are present between the mobile unit 21 and the base station 22. In the case shown in Fig. 5, 5 for example, an obstacle 26 in present between the mobile unit 21 and the base station 22, and radio waves that propagate straight from the base atation 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, theroforo, there are two routes taken to reach from the beae station 22 to the mobile unit 21, i.e., the route in which radio waves are reflected by the obstacle 27 and IS reach the mobile unit 21 and the route in which radio waves are reflected by the Obstacle Z8 and reach the mobile unit 21. That is, a multi-path is present.

The route in which radio waves from the base atation 22 are reflected by the obstacle 27 and reach the mobile 20 unit 21 differ. in distance from the route in which radio waves from the base station 22 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 2 5 time taken for a corresponding radio wave to be reflected

- 22 by the obstacle 28 and reach the mobile unit 21.

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 times that cancel out the time differences, thereby obtaining a path diversity effect. Since the mobile unit 21 moves as occasion demand-, routes through which radio waves from the base station 22 10 reach the mobile unit 21 also change as occasion demands.

An the mobile ''n; t 21 moves, the number of routes through which radio waves from the base station 22 reach the mobile unit 21 changes, and the intensity of radio waves received by the mobile unit 21 through each route also 15 changes. In addition, the delay times of the roapective signals to the RARE combiner change at all the times.

Fig. 6 is a block diagram showing a mobile station according to an embodiment of the present invention.

Referring to Fig. 6, the mrbilo unit 21 is comprised 20 of an antenna 30for receiving radio wave- from the baso station 22, a reception circuit 31 for, 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 resultant data as a delay profile, a search section 33 for extracting data, of the data of the delay profile from the À delay profile acquiring section 32, which correspond to the paths of signals 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 Ron 34 storing the data extracted by the search section 33 and the threshold input through the user input devico 35, a CPU 36 for executing processing 10 For determining a finger which is to be powered on the basis of the data extracted by the search section 33 and stored in the Ram 34 and the threshold input through the user input device 35, a finger section 38 constituted by finger" 38 to 38 for Respreading and demodulating an 15 output from the reception circuit 31 with predetermined delay times, a finger section power control circuit 37 for controlling power to the finger section 38 on the basis of a notification from the CPU 36, and a RATE reception section 39 for RAXE- combining signal. from the respective 20 fingers of the finger section 38.

Fig. 6 doe. not show the arrangement of the - trann-ion Ride of the mobile unit 21 because it i.

irrelevant to the gist of the present invention.

Fig. 7 is a view showing an example of the fo..mat of 25 a signal transmitted from the base station 22 to the

- 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 i. 10 me.

5 Each frame is made up of 16 slots. Each slot i. made of 256 chip-. Referring to Fig. 7, one slot is made up of a pilot signal, TPC (Transmission Power Control) signal, and data signal.

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

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

15 The delay profile acquiring section 32 is ca-risd of a plurality of correlators 40 to 40-, for depreading a reception signal from the reception circuit 31 and a timing control circuit 41 for controlling the Respreading timings of the plurality of correlators 401 to 406.

20 The 256 correlators 401 to 40. correspond to the number of chips in one slot described above, i.e., 256 chips. Each of the correlatore 401 to 40256 is controlled by the timing control circuit 41 to Respread a reception 25 signal fro n the reception circuit 31 with a time shift

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

Assam" that the aorrelator 40: starts depreading at time to. In this case, the correlator O2 a tarts 5 dopreading at time tl delayed from time to by (0.625/256) ma, and the correlator 40, starts deapreading at ff m" t2 delayed from time to by (0.625/256) ma. The subsequent correlator. sequentially Respread the signal with delay times. 10 The spreading codes used in the correlatora 401 to 402. are identi Q1 to those used by the base station 22 in spreading processing when transmitting the signal. It do-e not tter whether the spreading codes are long or short coded.

15 In the case shown in Fig. 8, aorrelatore equal in numb r to the chips in one slot are prepared. However, the present invention is not limited to this. For example, correlatore half the number of chips in one slot, i. e., 128 correlatore, may be prepared. In this cane, the first 20 correlator performs deapreading at the first time and 129th time; and the second correlator, at the second time and 130th time. In this manner, each correlator performs Respreading twice sequentially.

The delay profile acquiring section 32 performs 25 Respreading in the prove manner to generate a delay

profile representing the correspondence between each despreading timing and the intensity of the signal obtained by the despreading. The delay profile acquiring section 32 then output. thin 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. 10 is a graph showing the input reception signal in Fig. 9 which has undergone inverse conversion lo processing in the delay profile acquiring section 32 in Fig. 8.

Referring to each of Figs. 9 and 10, the ordinate represents the intensity of the signal; and the abscissa, the time.

15 An 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.

20 The delay profile acquiring section 32 Respreads the signal in Fig. 9 to obtain the signal in Fig. 10.

As is apparent from Fig. 10, there is a correlation between tomes to, to, 4, and to, and the signal is reconstructed. That is, in the case shown in Fig. 10, 25 four paths corresponding to times t,, to,, ts, and to are

l ( - 27 producod in a multi-path.

The delay profile acquiring section 32 in Fig. 8 output" times to to, and the signal intensities id., signal levels, at times to to ton, which are obtained by 5 the above doapreading processing, a. a delay profile, to the search section 33 in Fig. 6.

Fig. 11 i. a View for explaining the operation of the "oarch section 33 in Fig. 11.

The search section 33 output. N data to the cam 34 in 10 the descending order of lovele in the delay profile (-Ypreseed in a table form in the search section 33 in Fig. 11) from the delay profile acquiring section 32. In the care shown in Fig. 1O, the data are Sequentially output to the Ram 34 at times to, t,, t1, and in the 15 descending order of levels.

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

The RON 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 net value input through the user input device 35 in Fig. 6.

As the user input device 35, for dapple, buttons for inputting a user "et value may be provided in the mobile 25 station or a conventional ten-key pad for inputting a

- 28 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 Met 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 blocks in the CPU 36 in Fig. 6.

As shown in Fig. 12, the CPU 36 road. out the upon 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 lonely read out from the Ran 34. A comparing mean. 43 compares the user set value read out from the ROM 34 with each of the differences between the levels, which are output from the difference computing means 42, and output.

data selected on the basin 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

- 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 38: to 38 in the finger section 38 on the he d of 5 the recoined result. That is, the finger section power control circuit 37 controls the switches to supply power to only the fingers, of the fingers 38 to 38, which correspond to the delay tines notified by the CPU 36.

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

In the case shown in Fig. 14, the lover having the highest legal is detected at time t,; the signal having the second highest level, at time t:; the signal having the third highoat level, at time t7; and the signal having - 15 the fourth highest level, at time to. Assume that the level difference between the signal having the highest lover at time to and the signal having the second highest level at time to is represented by d,, and the level difference between the signal having the second highest 20 level at time t: and the signal havi ng the third highest level at tome to is 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 do > d-. In this case, as a result of 25 the comparison processing in the CPU 36 in Fig. 6, the CPU

- 30 36 notifies the finger section power control circuit 37 of the delay time of the signal at time t, 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 t, and the finger corresponding to the delay time of the signal at tine tl, but no power is consumed for the remaining fingers.

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

When the power is turned on (step F-1), the mobile unit 21 perfo D perch channel acquisition and repeats this processing subsequently. In this embodiment, IS processing of determining fingers to be operated i.

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 time is reset, and then operated (step F-21. 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 (-top 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 thin notification, the finger section power control circuit 37 controls the switch control section 44 in Fig. 13 to supply power to 10 the finger corroaponding to the data having the highest level to operate the finger (step F-5). In the cane shown in Fig. 10, since the signal attm" t, ha. the highest level, the time to is notified in step F-5.

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

20 mill computation result is represented by d.

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

me user set value read out from the dam 34 is used 2 5 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 numb value. For this reason, it is preferable to allow the user to "elect numerical 5 value. met 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 check. whether the difference do which has the value of the loop counter i as a 10 numerical subscript i. smaller than the threshold d-.

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

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

Aa the predetermined period of time in step Fell, for example, the time corresponding to one slot of reception data is set.

If it is determined in step F-7 that the difference 20 d1 i. 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 RUM 34, which has the highest

- 33 leel. In thin cane, 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 i. 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 4, i.e., the delay time, of the signal of the data, of the data extracted by the search section 33, which hear the lo (iel)th highest level. Upon reception of this notification, the finger section power control circuit 37 controls the switch control Faction 44 in Fig. 13 to supply power to the finger corresponding to the data having the {iel)th highest level, thus operating the 15 finger (stop F-8).

After the loop counter i in incremented by one {step F-9), the CPU 36 check- whether the value of the loop counter i is egyal to N. obtains the differences from all the data extracted by the search section 33, and checks 20 whether Prison with the threshold d" is performed Istep F-10).

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 waits for a lapse of a 25 predetermined period of ti _ 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 atop F-10 that the value of the loop counter i in not equal to N. and comparison with 5 the threshold d" is not complete, the flow returns to stop F-6 to continue the processing.

Fig. 16 in 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 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 this 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 (stop S-2). The CPU 36 then causes the search section 33 to extract a predetermined number of data hauling higher - levels from a delay profile (step S-3), and stores the extracted data in the ROM 34. The CPU 36 then sets the S initial value "1" in the loop counter i Istep S-4).

In this case, the user sot value read out from the BOM 34 is used as a threshold as a comparison target to be compared with the level of each signal. AS in the cane shown in Fig. 15, it is expected that the user has 10 difficulty in inputting this threshold as a apocific numerical value. For this reason, it is preferable to allow the user to select numerical ualuo set in the process of designing the apparatus in a step-by--tap manner by using the user input device 35 inatoad of 15 inputting a specific numerical value.

In Step S-S, provided that the level of the signal having the ith highest level is reprosentd by In, the CPU 36 checks whether the level 1 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 L" is lower than the threshold L-, the CPU 36 checks 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-1O).

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

In step Sell, the flow wait. for a lasso of a predetermined period of time, and returns to step S-2 when S the predeterninod period of time elapses, thus repeating finger operation control.

If it is determined in step S-5 that the level Ii is not lower than the threshold L-, the CPU 36 notifies the f inger 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 4, i.o., 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 Ran 34, which has 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 later 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 is equal to N. and checks whether comparison between the levels of all the signals and the threshold L. is complete (step S-8).

25 If it is determined in stop 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. i. complete, the flow waits for a lapse of a predetermined period of time (step S-11), and turn. to step S2 when the 5 predetermined period of time elapsed, thus repeating finger operation control.

If it i. determined in step g-8 that the value of the loop counter i is 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 atop S-5 to continue the proceeding. In the ambadim-nt described above, if the level of the signal, of the delay profile data, which has the highest 1QVe1 is lower than a threshold Lam' the power 15 switches for all the fingers may be turned on. In a wand electric field, an improvement in reception

characteristics takes priority over power caving. Thia makes it possible to produce a receptive state even in a weak electric field. This case will be doscribd 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. Thin processing differs from that shown in the flow charts of Figs. 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 thin embodiment, processing of determining fingers. to be operated i.

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 level" from a delay profile (step M-3), and stores the extracted data in the ROM 34.

In step M-4, the CPU 36 checks whether a level In of 15 the signal having the highest level i" lower than threshold In.

If it is determined in step M-4 that the level 1 is lower than the threshold LOX, 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 In is not lower than the threshold -x, the same processing as 25 that shown in Fig. 15 or 16 is performed. In the case

( shown in Fig. 17, the same processing a. that shown in Fig. 15 in performed. mat is, steps M-6 to M-13 in Fig. 17 Correspond to steps F-4 to Fell in Fig. 15. For this reason, a description of steps M-6 to M-13 in Fig. 17

5 will be omitted.

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

Fig. 18 is a block diagram showing a -Chile station 10 of an -bodimont 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 blase 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 soarch section 33 for 20 extracting data, of the data of the delay profile fray the delay profile acquiring section 32, which Correspond to the paths of signal. 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 ROM 34 storing the data extracted by

- ( - 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 basin 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 constituted by fingere 38: to 38 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 38 on the basis of a notification from the CPU 36, a RATE reception Section 39 for RAXE-combining signal. from the repoctivo 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 sido of the mobile unit 21 because it is irrelevant to the gist of the pageant invention. 20 The same reference numerals a. in Fig. 16 denote the same parts in Fig. 18, and a detailed description thereof

will be omitted.

A characteristic feature of this embodiment is that it has the display section 45 shown in Fig. 18. The 25 display section 45 will e described below with reference

- 41 to the accompanying drawing-.

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 can switch the contents to be displayed on the display window 46, e.g., the aA-oas book stored in a memory (not shown) or information indicating the operation state of each finger, by repeatedly pressing the display switching button 49.

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

Fig. 19 shows a case wherein the operation state of each finger idiplayod on the display window 46 upon operation of the display switching button 49. In thin case, the bar graph indicate. the magnitude of the 25 reception level of each finger in use {to which power i.

J {. - 42 supplied). In the came shown in Fig. 19, the number of fingers is 7, i.e., is 7 in the above case. Fig. l9 shows that power is supplied to only the fingers corrooponding to the 5 third, fourth, and sixth bare in the graph.

When the user presses the down button 48 in this state, the threshold decreases. In the cane shown in Fig. 16, the number of paths 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 -no, 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 embcdiment, the operation state of each finger i. displayed on the display section 45. However, the occurrence state 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 oy--m. However, the present invention i.

not limited to this and can be generally applied to other types of reception apparatuses.

Claims

- 43 CLAIMS:

1. A CDMA 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 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 (il)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.

2. An apparatus according to claim l, 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 Am, operation of a finger corresponding to a signal having a level lower than that of the signal

( having the ith highest level is stopped.

3. An apparatus according to claim 1, further comprising a user input device by which a user can set the threshold.

4. An apparatus according to claim 1 or 3, further comprising display means for displaying information indicating the number of fingers, of said plurality of fingers, to which power is supplied.

5. A power control method for a CDMA reception apparatus having a plurality of fingers and serving to perform RAKE reception by RAKEsynthesizing outputs from "aid 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 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.

( - 45

6. A method according to claim 5, wherein if the level Hi 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 "topped.

7. A COMA 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 mean" for detecting a multipath consisting of a plurality of radio wave" arriving with nome 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 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=.

( - 46

8. An apparatus according to claim 7, wherein the difference di in level between the signal having the ith highest level and the signal having the (il)th highest level of data of the delay profile is 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 di is not less than the predetermined threshold d=.

9. An apparatus according to claim 7, 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 is not more than a predetermined value, and a difference all.: 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 is stopped.

10. An apparatus according to claim 7, further comprising a user input device by which a user can set the threshold.

11. An apparatus according to claim 7 or 10, further comprising display means for displaying information

- 47 indicating the number of fingers, of said plurality of fingers, to which power i" supplied.

12. A power control method for a CDMA reception apparatus having a plurality of fingers and nerving 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 despreading 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=.

13. A method according to claim 12, 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 in obtained, and operation of a finger corresponding to a signal having a level lower than that of the signal having the (i+l)th

- 48 highest level if the difference di is not less than the predetermined threshold do is stopped.

14. A method according to claim 12, 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 is not more than a predetermined value, and a difference all.: 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 is stopped.

15. A COMA reception apparatus having a plurality of finger" 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 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

( - 49 of the data of the delay profile is not mare than a predetermined threshold Len, operation of all fingers is "topped.

16. An apparatus according to claim 15, further comprising a user input device by which a user can set the threshold.

17. An apparatus according to claim 15 or 16, further comprising display means for displaying information indicating the number of fingers, of said plurality of fingers, to which power is supplied.

18. A power control method for a COMA reception apparatus having a plurality of fingers and serving to perform RAKE reception by RAKEsynthesizing outputs from maid 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 i" not more than a predetermined threshold Lo, operation of all fingers is stopped.