KR100864390B1 - System and method for reducing rake finger processing - Google Patents

Abstract

Systems and techniques related to reducing the number of fingers in rake receiver 110 for use in processing rake finger 112 in a wireless network are disclosed. Determine E _before , which is the captured energy of all fingers, before increasing the transmit power. Increase transmit power by delta transmit power. i Determine E _after which is the captured energy of the finger. Determine the i finger needed for processing so that E _after is essentially above E _before .

Rake receiver, power control

Description

SYSTEM AND METHOD FOR REDUCING RAKE FINGER PROCESSING

background

Field of technology

TECHNICAL FIELD This disclosure relates generally to wireless communications, and more particularly to various systems and techniques for reducing rake finger processing in a wireless network.

background

Communication systems designed to allow multiple users to access common communication media include code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), space division multiple access (SDMA), and polarization. It may be based on division multiple access (PDMA) or other modulation technique known in the art. These modulation techniques demodulate signals received from multiple users of a communication system, allowing for an increase in communication system capacity. In this regard, various wireless systems have been established, including, for example, Advanced Mobile Phone Service (AMPS) and Global System for Mobile communication (GSM) and other wireless systems.

In conventional wireless communications, access networks are generally used to support communications for multiple devices. Typically, an access network is implemented with a number of fixed site base stations spread over a geographic area. In general, geographic areas are subdivided into smaller areas known as cells. Each base station may be configured to service a device in each cell. If there is a changing traffic demand across different cellular regions, the access network may not be easily reconfigured.

In contrast to conventional access networks, ad hoc networks are dynamic. An ad hoc network may be formed when a plurality of wireless communication devices, commonly referred to as terminals, come together to form a network. The terminal of the ad hoc network may operate as a host or a router. Thus, the ad hoc network may be easily reconfigured to meet existing traffic needs in a more efficient manner. In addition, ad hoc networks do not require the infrastructure required by conventional access networks, which in the future makes ad hoc networks a more attractive choice.

In a typical CDMA communication system, a subscriber station may access the network through one or more base stations and may communicate with other subscriber stations. A subscriber station is also referred to as a terminal. Each base station is configured to service all subscriber stations within a particular geographic area, commonly referred to as cells. In some high traffic applications, the cell may be divided into sectors in which the base station serves each sector. Each base station transmits a pilot signal used by the subscriber station for synchronization with the base station, and provides coherent demodulation of the transmission signal when the subscriber station is synchronized to the base station. In general, a subscriber station establishes a communication channel with a base station having the strongest pilot signal.

The subscriber station calculates a signal to noise interference ratio (C / I) for the received forward link signal. The forward link refers to transmission from the base station to the subscriber station, and the reverse link refers to transmission from the subscriber station to the base station. The subscriber station's C / I determines the data rate that can be supported for the forward link from the base station to the subscriber station. In other words, a certain level of performance for the forward link is achieved at the corresponding C / I level. A method and apparatus for selecting a data rate, filed on June 3, 2003 and assigned to the assignee of the present invention, is entitled METHOD AND APPARATUS FOR HIGH RATE PACKET TRANSMISSION. US Pat. No. 6,574,211.

The power at which the base station transmits data to the subscriber station is called forward link transmission power. Forward link transmit power is the level required to reliably transmit data over the forward link. Similarly, the power that a subscriber station transmits data to a base station is called reverse link transmission power. Reverse link transmit power is the level required to reliably transmit data on the reverse link.

Interference for each subscriber station increases as the number of subscriber stations transmitting increases. Therefore, it is desirable to control the subscriber station transmit power to avoid adverse interference with other subscriber station communications.

Ultra-Wideband (UWB) is an example of a communication technology that may be implemented in an ad hoc network. UWB provides high speed communication over a wide bandwidth of frequencies. At the same time, UWB signals are transmitted in very short pulses that consume very low power. The output power of the UWB signal is low enough to appear as noise for other RF technologies and rarely cause interference.

In an ad hoc network, terminals are added dynamically. As more terminals are added, each communication terminal generates more interference for the other terminal than the terminal with which it is communicating. Therefore, it is desirable to control the terminal transmission power to avoid adverse interference with other terminal communications.

Regardless of conventional or ad hoc, in a wireless communication system using a rake receiver, diversity combines detachable multipath. In the rake receiver, a demodulation element, or "finger", is assigned to the multipath. If power consumption at the rake finger is dominant in the received power consumption, systems and methods that reduce rake finger processing also significantly reduce power consumption.

Accordingly, what is needed is a system and method for reducing rake finger processing to reduce power consumption in a communication system.

summary

In one aspect, a method of reducing the number of fingers in a rake receiver, comprising: determining E _before , which is the captured energy of all fingers _before increasing the transmit power, increasing the transmit power by delta transmit power, i A method of reducing the number of fingers in a rake receiver is provided, comprising determining E _{after the} captured energy, and determining i fingers required for processing such that E _after is essentially above E _before .

In one aspect, the delta transmit power is 3 dB. In another aspect, the delta transmit power is based on the desired reduction in receive power consumption. In another aspect, the delta transmit power is based on signal to interference noise ratio (SINR). In another aspect, the delta transmit power is based on a multipath power profile.

Further embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which illustrates and describes various embodiments of the present invention in an illustrative manner. When realized, the present invention may be other and different embodiments, and various details may be modified in various other respects without departing from the spirit and scope of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.

Aspects of the present invention are described by way of example and not by way of limitation in the figures of the accompanying drawings.

Brief description of the drawings

1 is a functional block diagram illustrating an example of a terminal.

2 is a block diagram of a demodulation system.

3 illustrates a receiver structure that provides effective demodulation of closely spaced multipath components.

4 is a flowchart for determining the number of fingers used in the rake receiver according to one embodiment.

details

The detailed description set forth in accordance with the accompanying drawings is intended as a description of various embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced. Each embodiment disclosed herein is provided merely as an example or illustration of the present invention and need not be construed as preferred or advantageous over other embodiments. The detailed description includes specific details for the purpose of providing a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the present invention. Acronyms and other descriptive terms may be used for convenience and clarity, and are not intended to limit the scope of the invention.

As used herein, the term "exemplary" means "functioning as an example, illustration, or illustration." The "exemplary" embodiments described herein need not be construed as preferred or advantageous over other embodiments.

In the following detailed description, various aspects of the present invention may be described in the context of a CDMA wireless communication system. While this creative aspect is well suited for use in such applications, one of ordinary skill in the art will recognize that it may similarly apply to use in a variety of other communication environments, including conventional wireless communication. Thus, reference to a CDMA communication system is intended only to illustrate creative aspects, and it should be understood that these creative aspects have a wide range of applications.

CDMA technology has various advantages. An exemplary CDMA system is US Patent No. 4,901,307, assigned to the assignee of the present invention and entitled "SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS". It is disclosed in the call.

US Patent Nos. 5,102,459 and '307, assigned to the assignee of the present invention and entitled "SYSTEM AND METHOD FOR GENERATING SIGNAL WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM" The CDMA modulation technique described in the patent alleviates certain problems of terrestrial channels such as multipath and fading. When configured as a narrowband system, instead of being an obstacle to system performance, separable multipath may be diversity coupled to a mobile rake receiver for improved modem performance. The use of a RAKE receiver for improved reception of CDMA signals has been assigned to the assignee of the present invention and is entitled "DIVERSITY RECEIVER IN A CDMA CELLULAR TELEPHONE SYSTEM" US Patent No. 5,109,390 It is disclosed in the call. In mobile radio channels, multipath is created by the reflection of signals from obstacles in the environment, such as buildings, trees, cars, and people. In general, a mobile radio channel is a time-varying multipath channel due to the relative movement of the structure to create a multipath. For example, if an ideal impulse is transmitted over a time varying multipath channel, the stream of received pulses will change in temporal position, attenuation and phase as a function of the time the ideal impulse was transmitted.

The multipath characteristic of the terrestrial channel produces a signal at the receiver that travels a number of individual propagation paths. One characteristic of a multipath channel is the time spread introduced into the signal transmitted over the channel. As disclosed in the '390 patent, spread spectrum pseudonoise (PN) modulation used in CDMA systems allows different propagation paths of the same signal to be distinguished and combined when the difference in path delay exceeds the PN chip duration. If a PN chip rate of about 1 MHz is used in the CDMA system, then a full spread spectrum processing gain equal to the ratio of spread bandwidth to the system data rate may be used for paths with different delays greater than 1 microsecond. One microsecond path delay difference corresponds to a differential path distance of about 300 meters.

Another characteristic of multipath channels is that each path through the channel may cause a different attenuation factor. For example, if an ideal impulse is transmitted over a multipath channel, the pulse of each received pulse stream generally has a different signal strength than the other received pulses.

Another characteristic of a multipath channel is that each path through the channel may cause a different phase on the signal. For example, if an ideal impulse is transmitted over a multipath channel, the pulse of each received pulse stream has a different phase than the other received pulses. This results in signal fading.

Fading occurs when the multipath vector is added destructively, producing a received signal smaller than the individual vector. For example, the first path has a time delay of d with an attenuation factor of X dB, and a phase shift of Q radians, and the second path has d with an attenuation factor of X dB, and a phase shift of Q + pi radians. If a sine wave is transmitted over a multipath channel with two paths with a time delay, no signal will be received at the output of the channel.

As mentioned above, in the current CDMA demodulator architecture, the PN chip spacing defines the minimum separation that two paths must have in order to be combined. Before an individual path can be demodulated, the relative arrival time (or offset) of the received signal path must first be determined. The demodulator performs this function by "navigating" through a sequence of offsets and measuring the energy received at each offset. If the energy related to the potential offset exceeds a certain threshold, a demodulation element, or "finger," may be assigned to that offset. The signal present at that path offset can then be summed with the contribution of the other finger at each offset.

1 is a conceptual block diagram illustrating a possible configuration of a terminal. As will be appreciated by those skilled in the art, the exact configuration of the terminal may vary depending on the particular application and overall design constraints.

The terminal may be implemented with a front transceiver 102 coupled to the antenna 104. Baseband processor 106 may be coupled to transceiver 102. Baseband processor 106 may be implemented with a software-based architecture, or other type of architecture. The microprocessor may be used as a platform to execute software programs that provide overall system management functions and controls that allow a terminal to operate as a master or member terminal. The digital signal processor (DSP) may be implemented with an embedded communications software layer that executes application specific algorithms to reduce processing requirements at the microprocessor. The DSP may be used to provide various signal processing functions such as pilot signal acquisition, time synchronization, frequency tracking, spread spectrum processing, modulation and demodulation functions, and forward error correction.

The terminal may also include various user interfaces 108 coupled to the baseband processor 106. The user interface may include a keypad, mouse, touch screen, display, ringer, vibrator, audio speaker, microphone, camera and / or other input / output device.

In accordance with this embodiment, FIG. 2 is a block diagram of a demodulation system that is not suitable for processing fat multipath. Fat multipath exists when the multipath differs by less than the PN chip interval in time. In accordance with this embodiment, FIG. 3 illustrates a receiver architecture provided for effective demodulation of fat multipath. It will be apparent to those skilled in the art that the demodulation system may have various structural forms known in the art. The common element of the embodiments includes a finger required to demodulate multipath.

2 shows a general rake receiver demodulator 10 for receiving and demodulating the forward link signal 20 arriving at the antenna 18. Analog transmitter and receiver 16 includes a QPSK downconverter chain that outputs digitized I and Q channel samples 32 at baseband. The sample clock, CHIPX8 40, used to digitize the received waveform, is derived from a voltage controlled temperature compensated local oscillator (TCXO).

Demodulator 10 is managed by microprocessor 30 via databus 34. Within the demodulator, I and Q samples 32 are provided to the plurality of fingers 12a to 12c and the searcher 14. Searcher 14 searches for a window of offsets that tends to contain multipath signals suitable for assignment of fingers 12a-12c. For each offset of the search window, searcher 14 reports the pilot energy found at that offset to the microprocessor. Thereafter, the fingers 12a-12c are examined and a weaker path that is unassigned or tracked is assigned by the microprocessor 30 to an offset that includes the stronger path identified by the searcher 14.

If the fingers 12a-12c are locked with a multipath signal at the assigned offset, the path is tracked until the path is reallocated or faded using an internal time tracking loop. This finger time tracking loop measures the energy on one side of the peak at the offset the finger is currently demodulating. The difference between these energies forms a filtered and integrated metric.

The output of the integrator used to integrate the metric controls the decimator to select one of the input samples for the chip spacing for use in demodulation. As the peak moves, the finger adjusts the decimator position to move accordingly. The decimated sample stream is then despread with a PN sequence that matches the offset to which the finger is assigned. The inversely converted I and Q samples are summed for the symbols to generate pilot vectors (PI, PQ). These despread I and Q samples are Walsh uncovered using Walsh code assignments unique to the mobile user, and these uncovered despread I and Q samples are summed for the symbol to obtain a symbol data vector (DI). , DQ). Dot product operations are:

P (n) D (n) = P _I (n) D _I (n) + P _Q (n) D _Q (n) (2)

Wherein P _I (n) and P _Q (n) are the I and Q components of the pilot vector P for symbol n, respectively, and D _I (n) and D _Q (n) respectively for symbol n I and Q components of data vector D.

If the pilot signal vector is much stronger than the data signal vector, then the pilot signal vector can be used as an accurate phase reference for coherent demodulation, and the dot product computes the magnitude of the data vector component in phase with the pilot vector. As disclosed in US Pat. No. 5,506,865, entitled “Pilot Carrier Dot Product Circuit” and assigned to the assignee of the present application, dot products weight finger contributions for efficient coupling, and Each finger symbol output 42a-42c is scaled by the relative strength of the pilot received by the finger. Thus, the dot product serves as both phase projection and finger symbol weighting required for a coherent rake receiver demodulator.

Each finger has a lock detector circuit that masks the symbol 42 output to the combiner if the long term average energy does not exceed the minimum threshold. This ensures that only the fingers tracking the reliable path contribute to the combined output and thus enhance the demodulation performance.

Because of the relative difference in arrival times of the paths to which each finger 12a to 12c is assigned, each finger 12a to 12c is " soft " by the symbol combiner 22 summing the finger symbol streams 42a to 42c. Have a deskew buffer that aligns the finger symbol streams 42a through 42c to produce a " determined " demodulation symbol. This symbol is weighted by the reliability of correctly identifying the originally transmitted symbol. The symbol is sent to deinterleaver / decoder circuit 28 where the first frame is deinterleaved and then forward error correction decodes the symbol stream using the maximum Reichhood Viterbi algorithm. The decoded data is then made available to microprocessor 30 and made available to other components such as speech vocoder for further processing.

To accurately demodulate, a mechanism is needed to align the local oscillator frequency with the clock used in the cell to modulate the data. Each finger estimates the frequency error by measuring the rotation rate of the pilot vector in QPSK I, Q space using a cross-product vector operator.

P (n) × P (n-1) = P _I (n) P _Q (n-1)-P _I (n-1) P _Q (n) (3)

Frequency error estimates 44a-44c from each finger are combined and integrated in frequency error combiner 26. Then, the integrator output, LO_ADJ 36, is provided for voltage control of the TCXO of the analog transmitter and receiver 16 to adjust the clock frequency of the CHIPX8 clock 40, thus closing the loop to compensate for the frequency error of the local oscillator. Provide a mechanism.

As noted above, in current demodulator structures, the path must be different by one or more PN chips to have individual fingers assigned to that demodulation. However, there are cases where the path differs by less than the PN chip spacing in time, and this situation leads to the presence of a "pat path". In a typical demodulator configuration, only one finger will be assigned to demodulate the fat path. One of the reasons is that if a finger is assigned to a path, it tracks the path movement independently. Without central coordination of the fingers, multiple fingers will converge on the same peak of the fat path. Also, the searcher will be confused if paths that are close to each other are tracked.

On the orthogonal forward link, there is a large amount of energy in each path since all energy from the base station to all mobiles is transmitted using the same PN offset channelized using the orthogonal code sequence. In addition, in terms of high correlation between orthogonal code sequences, orthogonal code sequences have poor autocorrelation. Thus, if the paths on the forward link differ by less than PN chip spacing, the signals cannot be distinguished from each other by external PN spreading, or they are not the coding gain of orthogonal spreading realized due to time shifts. In this case, the energy of adjacent multipath components acts as noise and substantially degrades the performance of the demodulator assigned to the fat path. In addition, on the reverse link, adjacent multipath components can lead to deterioration of the demodulator assigned to the fat path.

3 shows a rake receiver demodulator 110 that receives and demodulates the forward link signal 120 arriving at the antenna 118 of the present invention. Analog transmitter and receiver 116 includes a QPSK downconverter chain that outputs digitized I and Q samples 132 at baseband. In an exemplary embodiment, the sampling clock CHIPx8 140 used to digitize the receive waveform is derived from a voltage controlled temperature compensated local oscillator (TCXO).

Demodulator 110 is managed by microprocessor 130 via databus 134. Within the demodulator, I and Q samples 132 are provided to the plurality of fingers 112a-112c and the searcher 114. While exemplary embodiments have been described in terms of QPSK demodulation, the invention is equally applicable to BPSK, Quadrature Amplitude Modulation (QAM), M-ary PSK, or any other known modulation scheme. Searcher 114 searches for a window of offsets that may include multipath signal peaks suitable for assignment of fingers 112a through 112c. For each offset of the search window, the searcher 114 reports the pilot energy found in the window of that offset to the microprocessor 130. In the present invention, microprocessor 130 determines where to assign the finger, and whether and where to assign the fat path demodulator.

Searcher 114 reports the energy in the window around the peak. Microprocessor 130 determines from the reported energy whether the peak is narrow and whether it can be successfully demodulated by a single path demodulator. In addition, the microprocessor 130 may identify the multipath component as a fat path and will assign a fat path demodulator for that demodulation. Thus, for example, fingers 112a and 112b demodulate a single path. Finger 112c, on the other hand, will be directed by microprocessor 130 to be assigned to perform fat path demodulation and demodulate the fat path.

If power consumption at the rake finger is dominant in receive power consumption, the systems and methods for reducing rake finger processing significantly reduce power consumption.

A reduction in power consumption occurs due to the reduction in the finger used in the rake finger processing. To quantify this effect, power consumption in the transmission mode, which is assumed to be invariant when the transmission power level is increased, is denoted by T. Received power consumption R is

R = R ₀ + n * P _f ,

Where R ₀ is a fixed portion of received power consumption that does not depend on the number of fingers used, n is the number of fingers activated upon reception of the signal, and P _f is the power consumption of a single finger. Thus, the reduction in received power consumption is δ n * P _f , and δ n is a decrease in the number of fingers used. In order to obtain an estimate of δ n, the operational signal-to-noise ratio (SNR) is required to be small, and the multipath power profile is required to be recognized by the terminal.

The total SNR obtained at the receiver is the sum of the SNRs of the component signals obtained at each finger. The post despread SNR obtained at the i th finger locked on the path with signal level h _i ,

,

,

Where H = Σ _i h _i (i = 1 ... ktotal), ktotal is the total number of multipaths, PG is the processing gain, and N is the thermal noise power level. The term of the denominator is the sum of the effective noise and interference after despreading.

If the operational pre-despreading SNR is low (i.e. PG >> 1) and the dominant noise, i.e., N, the noise power of the tracked finger, is N >> (Hh _i ) / PG, then a 3 dB increase in transmit power Will increase the SNR _i by 3 dB. Since the modulation used is invariant, the target SNR obtained by summing the signals at the finger remains invariant. This allows a reduction in the number of fingers used. Since assuming a low pre-spread SNR, the number of fingers required may be estimated by the captured energy metric. The _captured energy metric E _captured according to this embodiment is

E _captured = Σ _i h _i (i = 1 .... n) and n is the total number of fingers.

To obtain the same post-despread SNR after an increase in transmit power, it is only necessary to add a finger until the captured energy reaches the same value as before the increase in transmit power.

For example, suppose the multipath power profile is flat, i.e., if the received energy is spread evenly across the M multipaths, and the transmit power is increased by 3 dB, the finger required to obtain the same E _captured . The number of is half of the original finger number. If Rake finger power consumption is dominant in received power consumption, i.e.

If R ₀ << n * P _f ,

Using only half the number of fingers will reduce 50% in power consumption. Thus, for a flat multipath power profile, the best power consumption reduction is the same as for intermittent transmissions, since a duty cycle of 0.5 produces a 50% reduction in power consumption. A method and apparatus for reducing power consumption by using an intermittent transmission rate is described as "Modified Power Control for Reduction of System Power Consumption," filed June 1, 2004 and assigned to the assignee of the present invention. POWER CONTROL FOR REDUCTION OF SYSTEM POWER CONSUMPTION, "US Patent Application No. 10 / 859,411.

However, if the multipath power profile is more peak at the total energy concentrated in the initial multipath, reducing the number of fingers may produce a greater than 50% reduction in power consumption for a 3 dB increase in transmit power. For example, in the simulation of a channel model used for outdoor propagation, energy capture of 80% to 40% can change the number of required paths from 60 to 15. Similarly, energy capture of 80% to 40% can change the number of paths required from 175 to 40. Thus, if finger processing power consumption is dominant, this multipath profile can produce a reduction of about 75% in power consumption through a 3 dB increase in power consumption.

It will be apparent to those skilled in the art that the increase in transmit power may differ from the 3 dB increase depending on the design conditions.

4 is a flowchart for determining the number of fingers used in the rake receiver according to one embodiment. In step 402, E _after and index i are initialized to 0 and 1, respectively. E _after is the captured energy of the finger as the algorithm shown in FIG. 4 goes through an iterative step of the flowchart. In step 404, E _before is set to E _{captured before} increasing in transmit power. In step 406, the transmit power is increased by delta transmit power. In one embodiment, the delta transmit power is 3 dB. In step 408, E _after is set to the energy captured from the i finger.

In step 410, a check is made to determine whether E _after is above E _before or whether i is above N, where N is the number of fingers in the rake receiver. If both conditions are false, control flow proceeds to step 412. Otherwise, control flow proceeds to step 414. In step 414, i finger is used among the N fingers of the rake receiver. In one embodiment, it will be apparent to those skilled in the art that the determination as to whether E _after is greater than or _equal to E _before need not be accurate. Depending on the embodiment and / or design conditions, it may be a determination of whether E _after is approximately E _before or more.

In step 412 i is incremented and control flow proceeds to step 408.

In a system using a closed loop power control signaling mechanism, the method of FIG. 4 changes the outer loop set point by a delta increase in transmit power and returns the outer loop set point to its original value while maintaining a smaller set of fingers after delay. Equivalent to the returning receiver. This process may be initiated automatically by the receiver, and the design conditions may suggest that this decision be made at the system level and not independently by the receiver.

Various exemplary logic, logic blocks, modules, and circuits described in connection with the embodiments disclosed herein may be general purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other programs. Possible logic devices, discrete gate or transistor logic, discrete hardware components, or any combination designed to perform the functions disclosed herein, may be implemented or performed. A general purpose processor may be a microprocessor and the processor may be any conventional processor, controller, microcontroller or state machine. A processor may also be implemented as a combination of computing devices, eg, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors or any other configuration associated with the DSP.

The steps of the methods or algorithms described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, or any other type of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information and write information. In addition, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In addition, the processor and the storage medium may reside as discrete components in a user terminal.

The previous description of the embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to the embodiments will be apparent to those skilled in the art, and the inherent principles defined herein may be applied to other applications and the like without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (18)

A method of controlling rake finger processing at a receiver, Determining E _before , which is the captured energy of all fingers before the increase in transmit power; Determining E _after which is the captured energy of the i finger after the increase in the transmit power; And Determining an i finger required for processing such that the E _after is essentially greater than or _equal to the E _before . The method of claim 1, And the increase in transmit power is 3 dB. The method of claim 1, And wherein the increase in transmit power is based on a desired decrease in receive power consumption. The method of claim 1, And wherein the increase in transmit power is based on a signal to interference noise ratio (SINR). The method of claim 1, And wherein the increase in transmit power is based on a multipath power profile. Means for determining E _before , which is the captured energy of all fingers before the increase in transmit power; Means for determining E _after which is the captured energy of i fingers after the increase in the transmit power; And Means for determining an i finger required for processing such that the E _after is essentially greater than or _equal to the E _before . The method of claim 6, And the increase in the transmit power is 3 dB. The method of claim 6, Wherein the increase in transmit power is based on a desired reduction in received power consumption, one of a signal-to-interference noise ratio (SINR), or a multipath power profile, or a combination thereof. A computer readable medium containing a program of instructions executable by a computer program, Computer readable program code means for determining E _before which is the captured energy of all fingers before the increase in transmit power; Computer readable program code means for determining E _after which is the captured energy of the i finger after the increase in the transmit power; And Computer readable program code means for determining an i finger required for processing such that E _after is essentially _{equal to} or greater than E _before . The method of claim 9, And the increase in transmit power is 3 dB. The method of claim 9, And said increase in transmit power is based on a desired reduction in received power consumption, one of a signal-to-interference noise ratio (SINR), or a multipath power profile, or a combination thereof. An apparatus for use in controlling rake finger processing at a receiver, the apparatus comprising: A plurality of fingers; A demodulator having a searcher configured to report energy in a window around a peak; And Based on the reported energy, having a microprocessor configured to determine where to assign a finger, and to determine where to assign a fat path demodulator, and The microprocessor, Determine E _before , which is the captured energy of all fingers before the increase in transmit power; Determine E _after which is the captured energy of the i finger after the increase in the transmit power; And determine an i finger required for processing such that E _after is essentially _{equal to} or greater than E _before . delete The method of claim 12, And an increase in the transmit power is 3 dB. The method of claim 12, And the increase in transmit power is based on a desired reduction in received power consumption, one of a signal-to-interference noise ratio (SINR), or a multipath power profile, or a combination thereof. A microprocessor for use in controlling rake finger processing at a receiver, Determination of E _before , which is the captured energy of all fingers before the increase in transmit power; Determining E _{after which} is the captured energy of i finger after the increase in the transmit power; And And control the determination of an i finger required for processing such that the E _after is essentially greater than or _equal to the E _before . The method of claim 16, The increase in transmit power is 3 dB. The method of claim 16, The increase in transmit power is based on a desired reduction in receive power consumption, one of a signal-to-interference noise ratio (SINR), or a multipath power profile, or a combination thereof.

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