HK1075981B - Method and apparatus for adjusting power control setpoint in a wireless communication system - Google Patents

Description

Method and apparatus for adjusting power control set point in wireless communication system

Background

FIELD

The present invention relates generally to data communications, and more particularly to a novel and improved method for adjusting a target received signal quality or setpoint of a power control loop in a wireless communication system.

Background

In a wireless communication system, a user of a remote terminal (e.g., a mobile phone) communicates with another user via transmissions on the forward and reverse links of one or more base stations. The forward link refers to transmission from the base station to the remote terminal, and the backward link refers to transmission from the remote terminal to the base station. The forward and reverse links are typically assigned to different frequency bands.

In a Code Division Multiple Access (CDMA) system, the total transmit power from a base station typically represents the total capacity of the forward link, since data can be transmitted to several users simultaneously using a shared frequency band. A portion of the total transmit power is allocated to each active user such that the total transmit power of all users is less than or equal to the total active transmit power.

To maximize forward link capacity, the transmit power to each remote terminal may be controlled by a first power control loop to provide a ratio of energy per bit to total noise interference (E) received at the remote terminal_b/N_t) The measured signal quality is maintained at a certain target E_b/N_tThe above. This object E_b/N_tCommonly referred to as a power control set point (or simply set point). The second power control loop is typically used to adjust the setpoint in order to maintain a desired level of performance, as measured by the Frame Error Rate (FER). Forward power control devices attempt to reduce power consumption and interference while maintaining desired link standards. This increases system capacity and reduces the delay in servicing the user.

In conventional implementations (e.g., as defined in the IS-95 standard), the set point IS adjusted based on the state of the received data frame (or packet). In one scheme, the setpoint is increased in larger steps (e.g., Δ U ═ 1dB) each time a frame erasure is detected (i.e., a frame is received in error). Conversely, when the frame is decoded correctly, the setpoint is lowered in small steps (e.g., 0.01 dB). For this scheme, the frame error rate is approximately equal to the ratio of the "up" step size to the "down" step size (i.e., FER ═ Δ D/(Δ D + Δ U)).

The set point adjustment scheme set points described above produce a sawtooth response. The saw-tooth response results in the transmission being performed at a higher power level than necessary, since the set point can only be lowered in small steps. Moreover, precise adjustment of the set point reflecting changing link conditions is hindered by fixed and small adjustment steps.

As can be seen, methods for effectively adjusting the power control loop set point that reduce transmit power consumption and interference and increase system energy are highly desirable.

SUMMARY

The present invention provides a power control method for efficiently adjusting a power control loop set point in a wireless communication system. The set point is adjusted according to a set of factors, including a frame status indicating whether the transmitted frame was received correctly. In one aspect, the set point is adjusted based on one or more received decoded frame (typically "soft" or multi-bit) metrics. These metrics may provide information indicative of link conditions and facilitate more accurate adjustment of the set point. The set point is adjusted in a different manner and/or by a different amount depending on the metric value.

Multiple metrics are used for link listen and set point adjustment. In general, one or more metrics are generated for forward error correction codes, such as convolutional codes, Turbo codes, block codes, and other codes. These metrics include re-encoded Symbol Error Rate (SER) and re-encoded power metrics (for all decoders), "modified" Yamamoto metrics (for convolutional code decoders), the number of bits in a decoded frame, and the minimum or average (log) probability ratio (LLR) (for Turbo decoders) declaring the number of iterations before decoding the frame, among other possibilities.

The setpoint, on the other hand, is adjusted in part based on the difference in received signal quality from the setpoint (i.e., power excess or deficit). This allows the setpoint to be adjusted in the same manner as the response of the identified power control device to changing link conditions (i.e., the ability of the inner power control loop to maintain the received signal quality at the power setpoint). In yet another aspect, the setpoint portion is based on the setpoint and a threshold E required to achieve a desired performance level (e.g., 1% FER)_b/N_tThe difference between them.

According to an aspect of the present invention, there is provided a method for adjusting a power control loop set point of a received signal in a wireless communication system, comprising: decoding the one or more received frames in accordance with a particular decoding scheme to provide one or more decoded frames; obtaining one or more metrics for the one or more decoded frames, including at least one of a re-encoded power metric and a modified Yamamoto metric, wherein the re-encoded power metric represents a correlation between symbols in the received frame and symbols produced by re-encoding the decoded frame; and adjusting the set point in accordance with the one or more metrics.

According to another aspect of the present invention, there is provided a method for adjusting a power control loop set point of a received signal in a wireless communication system, comprising: decoding one or more received frames in accordance with a particular decoding scheme to provide one or more decoded frames; obtaining one or more metrics for the one or more decoded frames, including at least one of a re-encoded power metric and a modified Yamamoto metric, wherein the re-encoded power metric represents a correlation between symbols in the received frame and symbols produced by re-encoding the decoded frame; determining a power surplus or deficit indicative of the received signal being greater than or less than the set point, respectively; and adjusting the set point based on the one or more metrics and the power surplus or deficit.

According to still another aspect of the present invention, there is provided a power control unit for use in a wireless communication system, including: a decoder configured to decode a received frame in accordance with a particular decoding scheme to provide a decoded frame; a metric calculation unit configured to provide one or more metrics for the one or more decoded frames, including at least one of a re-encoded power metric and a modified Yamamoto metric, wherein the re-encoded power metric represents a correlation between symbols in the received frame and symbols produced by re-encoding the decoded frame; and a power control processor configured to receive the one or more metrics for the decoded frame and adjust a setpoint of a power control loop based on the one or more metrics, wherein the setpoint represents a target received signal quality for the received frame.

The power control methods described above may be used in a variety of wireless communication systems (e.g., CDMA2000 and W-CDMA systems) to facilitate the forward and/or reverse link. Various aspects, embodiments, and features of the disclosure are described in further detail below.

Brief Description of Drawings

The features, nature, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout and wherein:

fig. 1 is a diagram of a spread spectrum communication system supporting multiple users;

fig. 2 and 3 are block diagrams of embodiments of a base station and a remote terminal, respectively, capable of implementing aspects and embodiments of the present invention;

fig. 4 is a diagram of a forward link power control apparatus capable of implementing certain aspects and embodiments of the present invention;

FIG. 5 is a diagram illustrating a large UP step size for removed frames and a small DOWN step size setpoint adjustment scheme for good frames;

FIGS. 6A and 6B are diagrams illustrating transmit power and power excess, respectively, in an exemplary transmission;

FIG. 7 is a flow chart for adjusting a set point according to an embodiment of the present invention;

FIGS. 8A and 8B show plots of scaling parameters for scaling the set point step size versus excess power for a removed frame and a correctly received frame, respectively;

FIG. 9A is a graph showing the frequency distribution of several different set point overage/deficit under the same metric; and

fig. 9B is a graph illustrating a setpoint step size curve corresponding to the histogram depicted in fig. 9A.

Detailed description of the preferred embodiments

Fig. 1 is an illustration of a spread spectrum communication system 100 supporting multiple users. System 100 provides communication for several units, each of which is served by a respective base station 104. A plurality of remote terminals 106 are dispersed throughout the system. Each remote terminal 106 may communicate with one or more base stations 104 on the forward and reverse links at any time, depending on whether the remote terminal is active and whether soft handoff is occurring. As shown in fig. 1, base station 104a communicates with remote terminals 106a, 106b, 106c, and 106d, and base station 104b communicates with remote terminals 106d, 106e, and 106 f.

In the system 100, a system controller 102 is coupled to a base station 104, which is further coupled to a Public Switched Telephone Network (PSTN). The system controller 102 provides coordination and control services for the base stations coupled thereto. The system controller 102 also controls the routing of telephone calls between the remote terminals 106 and users (e.g., conventional telephones) coupled to the PSTN for the base stations. The system controller 102 is also referred to as a Base Station Controller (BSC).

System 100 IS also designed to support one or more CDMA standards such as (1) "TIA/EIA-95-BMobject Spread Spectrum Cellular System" (IS-95 Standard), (2) "TIA/EIA-98-D Recommended Minimum Standard for Dual-Mode Wireless Spectrum Cellular State" (IS-98 Standard) (3) the Standard named "third Generation partnership project" (3GPP) set forth in a series of documents including the documents 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214 (4) the Standard set forth in the Association named "third Generation partnership project 2" (3GPP2) (CD 2000 Standard) set forth in a series of documents including the documents C.S2-A, SC 2-A, SC.0005-A, Sc 0.0010-A.0010.0010-A, C.s0011-a and c.s0026, or other criteria. These standards are incorporated herein by reference.

Fig. 2 is a block diagram of an embodiment of a base station 104 capable of implementing some aspects and embodiments of the present invention. On the forward link, the data is provided to a Cyclic Redundancy Check (CRC) generator 212, which generator 212 generates an appended series of CRC bits for each frame (packet) of data. CRC generator 212 may also format the frame into a special frame format defined by the CDMA system. The formatted frames are then encoded by an encoder 214 that uses a particular coding scheme, including a convolutional code, a Turbo code, a block-shaped code, or a combination thereof. The encoded frames are interleaved by interleaver 216 according to a special interleaving scheme defined by the system.

The interleaved data is provided to a Modulator (MOD)218 and further processed (e.g., covered with a mask, spread with short PN sequences, and scrambled with a long PN sequence assigned to a remote receiving terminal, etc.). The modulated data is then provided to an RF TX unit 220 for conditioning (e.g., conversion to one or more analog signals, amplification, filtering, quadrature modulation, etc.) to generate a forward link signal. The forward link signal is routed through a multiplexer (D)222 and transmitted via an antenna 224 to the remote terminal.

Although not shown in fig. 2 for simplicity, the base station 104 can process and transmit data to remote terminals on one or more forward channels. The processing (e.g., encoding, interleaving, and masking, etc.) for each forward channel is different from the processing for the other forward channels.

Fig. 3 is a block diagram of an embodiment of a remote terminal 106 capable of implementing aspects and embodiments of the present invention. The forward link signal is received by an antenna 312, routed through a multiplexer 314, and provided to an RF receiver unit 322. RF receiver unit 322 conditions (e.g., filters, amplifies, frequency downconverts, and digitizes) the received signal and provides samples. A demodulator (DEMOD)324 receives and processes (e.g., despreads, demasks, and pilot demodulates) the samples to provide recovered symbols. The recovered symbols are deinterleaved by a deinterleaver 326 in accordance with a deinterleaving scheme complementary to the interleaving scheme used by the base station.

The decoder 328 decodes the deinterleaved symbols in a decoding scheme complementary to the coding scheme used by the base station. The decoded data for each frame is provided to CRC checker 332 to determine whether the frame was decoded correctly or in error based on the appended CRC bits. CRC checker 322 provides a frame status for each received and decoded frame that indicates whether the frame was removed or decoded correctly.

As noted above, on the forward link, the capacity of each base station is limited by the total transmit power. To provide a desired level of performance and to increase system capacity, the transmit power of each transmission from the base station is controlled as low as possible, thereby reducing power consumption while maintaining a desired level of performance for the transmission. If the received signal quality of the remote terminal is too poor, the probability of correctly decoding the transmission is reduced and performance may be affected (e.g., high FER occurs), and conversely, if the received signal quality is too high, the transmit power level may also be too high, and an excess amount of transmit power is unnecessarily used in the transmission, reducing the capacity of the system and also causing additional transmission interference from other base stations.

On the backward link, each transmitting remote terminal causes interference to other active remote terminals in the system. The capacity of the backward link is limited by the total interference each remote terminal experiences from other transmitting remote terminals. To reduce interference and increase the reverse link capacity, the transmit power of each remote terminal is typically controlled to reduce interference to other transmitting remote terminals while maintaining a desired level of system performance.

The power control method of the present invention can be used in a variety of wireless communication systems and can be advantageously used on the forward and/or reverse links. For example, the power control methods described herein may be used in a CDMA system that conforms to the CDMA2000 standard, the W-CDMA standard, some other standard, or a combination thereof. For clarity, various aspects and embodiments of a specific implementation of the forward link are described below.

Fig. 4 is an illustration of a forward link power control apparatus 400 capable of implementing certain aspects and embodiments of the present invention. Power control apparatus 400 includes an inner loop power control 410 that operates in conjunction with an outer loop power control 420.

Inner loop 410 is a (relatively) fast loop that attempts to maintain the quality of the transmission signal received by the remote terminal as close as possible to target E_b/N_t(or simply, set point). As shown in fig. 4, an inner loop 410 runs between the remote terminal and the base station. Power regulation to the inner loop 410 is typically by measuring the remote terminalThe end received transmission signal quality (block 412), comparing the received signal quality to a setpoint (block 414), and sending power control commands to the base station.

The power control commands instructing the base station to adjust its transmit power may be implemented, for example, as "UP" commands indicating an increase in transmit power and "DOWN" commands indicating a decrease in transmit power. Each time the base station receives a power control command, the transmit power of the transmission is adjusted accordingly (block 416). For cdma2000 systems, power control commands may be sent at a frequency of 800 times per second, which may provide a relatively fast response time for inner loop 410.

Since the path loss of the communication channel or link (cloud 418) typically varies over time, particularly for mobile remote terminals, the received signal quality at the remote terminal is constantly jittering. Inner loop 410 attempts to maintain the received signal quality at or near the setpoint as the communication link changes.

Outer loop 420 is a (relatively) slow loop that constantly adjusts the set point to achieve a certain level of performance for transmissions to the remote terminal. The desired level of performance is typically a target Frame Error Rate (FER), which for some CDMA systems is 1%, other target values may also be used. Also, some other performance criteria may be used instead of FER (e.g., quality indicator) adjustment set points.

For outer loop 420, a transmission from the base station is received and processed to recover the transmitted frame, and the status of the received frame is determined (block 422). For each received frame, it is determined whether the frame is decoded correctly (good) or decoded in error (removed) or not transmitted at all. One or more metrics associated with the decoding result are also obtained. Based on the status of the decoded frame (good, removed, or no transmission), one or more metrics, and/or possibly other factors (described below), the set point is adjusted accordingly (block 424). Generally, if the frame is decoded correctly, the quality of the signal received from the remote terminal may be higher than necessary. The set point is lowered slightly causing the inner loop 410 to reduce the transmit power of the transmission. If the remote terminal detects that no frames are being transmitted, the set point is not adjusted unless other metrics are available to provide information about the potential transmit power level.

On the forward link of a cdma2000 system, transmission on the forward power control subchannel (F-PCSCH) may continue when no transport channel frames are available. The forward power control channel (F-DCCH) allows no frames. However, the F-PCSCH is still linked to the full-speed power level (e.g., the base station announces the distinction of the F-PCSCH and the full-rate F-DCCH on an overhead message or a handover indication message). Because the F-PCSCH includes punctured bits at 16 different locations over a20 microsecond frame, the power profile is inserted into the composite frame using the rank in order for the remote terminal to produce the metrics described herein. Applying the soft metrics described herein to composite frames having a power profile provided to the remote terminal may provide improved performance.

The set point is adjusted during each frame. The frame state and metrics may also be accumulated over N received frames for adjusting the set point during every N frames, where N is any integer greater than 1. Because inner loop 410 is typically adjusted multiple times during each frame, inner loop 410 has a faster response time than outer loop 420.

By controlling the set point adjustment, different power control characteristics and system performance can be achieved. For example, the target FER may be adjusted by changing the amount of upward adjustment of the bad frame set point, the amount of downward adjustment of the good frame adjustment point, the adjustment interval of the adjustment points, and so on. In one implementation, the target FER (level long term FER) may be set to Δ D/(Δ D + Δ U), where Δ U is the amount of increase to remove the frame setpoint and Δ D is the amount of decrease to the good frame setpoint. The magnitude of the absolute values of Δ U and Δ D determines the responsiveness of the system to sudden changes in the communication link.

Fig. 5 is a diagram illustrating a set point adjustment scheme in which the set point is increased in large steps for removed frames and decreased in small steps for good frames. As shown in fig. 5, at time mark t₀To t₈The received frame is decoded correctly and the adjustment point is adjusted downward by Δ D. At the time ofInterval mark t₉Here, the removed frame is detected and in response the setpoint is adjusted upward by Δ U. Thereafter, at t₁₀To t₁₇The received frame is correctly decoded and the adjustment point is adjusted down by Δ D. At the time mark t₁₈Here, the removed frame is detected and in response the setpoint is adjusted upward by Δ U. The setpoint adjustment may continue in a similar manner, resulting in the sawtooth response 510 shown in FIG. 5.

The sawtooth response of the set point may result in a higher transmit power than necessary. Line 512 represents the threshold E required to obtain the target FER_b/N_t. The up-scaling step size au is typically chosen large in order to avoid receiving a series of dropped frames when the link conditions deteriorate. Therefore, the transmit power is higher than necessary most of the time when link conditions remain unchanged, typically adjusted up by au from the time set point. The shaded area 514 below the sawtooth waveform 510 and above the line 512 approximately represents excess transmit power. Because in typical setpoint adjustment schemes, the setpoint is adjusted in only small steps for good frames, the excess transmit power (i.e., shaded region 514) can be large. The excess transmission power is greater if multiple dropped frames are received in the vicinity of the time when the link condition later improves. Moreover, the ability to more accurately adjust the set point to reflect improved link conditions is often hindered by the fixed small turndown step size.

According to some aspects of the invention, the set point is adjusted based on a series of factors including frame status. In one aspect, the set point is adjusted in part based on one or more metrics of the received and decoded frame. These metrics may provide information representing the "quality" of the received frame, not just whether the frame is good or removed when hard-decided. This information is used to monitor the link conditions and adjust the set point more accurately. The set point may be adjusted in different ways or by different amounts depending on the determined frame quality, rather than just two possible up-down amounts.

On the other hand, the setpoint is based in part on the difference between the received signal quality and the setpoint (i.e., power excess or not)Foot) to adjust. This allows the setpoint to be adjusted in the same manner as the response of the identified power control device to changing link conditions (i.e., the ability of the inner power control loop to maintain the received signal quality at the power setpoint). In yet another aspect, the setpoint portion is based on the setpoint and a threshold E required to achieve a desired performance level (e.g., 1% FER)_b/N_tThe difference between them. These and other aspects of the invention are described in further detail below.

Various metrics may be used to monitor the quality of the communication channel (i.e., link conditions). Typically, one or more metrics are obtained for forward error correction codes such as convolutional codes, Turbo codes, block codes, and others. A complementary decoder is typically used for each FEC at the receiving unit. Different sets of metrics are obtained from different types of decoders. Some decoders and their metrics are described in further detail below. With these various measures, the receiver unit can listen to the link quality and adjust the set point more accurately (e.g., before the frame is actually dropped).

Many CDMA systems use convolutional encoders at the transmitting end. The convolutional encoder encodes the bits in each frame to be transmitted in accordance with a polynomial generator to provide coded bits. Each data bit is associated with a set of code bits (called a code branch), the actual values of which are determined by adjacent data bits and a polynomial generator. Some of these codes are punctured (i.e., deleted) and the code bits that are not punctured are transmitted. A sequence of codes or symbols is sent to cause a sequence of data bits in a frame to be transmitted.

At the receiver unit, a complementary convolutional decoder is used to decode the received "soft" (multi-bit) symbols corresponding to the transmitted coded bits. Although various types of decoders are used, a Viterbi (Viterbi) decoder is most commonly used for convolutional decoding. Viterbi (Viterbi) decoding achieves decoding of the transmitted coded bits to the greatest possible extent under some assumed channel noise.

Initially, all 2 in the network^k-1Path metrics for states are initialized, where K isThe constraint length of the convolutional decoder. For each received coding branch, the branch metrics of all branches entering each state are calculated and appended to the path metric for that state to produce an updated path metric. The branch metric represents the error (or distance) between the received coding branch and the actual coding branch, and the path metric represents the confidence of a certain path through the network. The best path (corresponding to the best most recent path metric for that state) into each state is selected and stored in a path memory, and the most recent path metric corresponding to the selected path is stored as the new path metric for that state. For each frame, the path through the network using the best path metric is selected as the most likely sequence of data bits in the received symbol sequence.

The theory and implementation of Viterbi decoding is described in the article entitled "volumetric Codes and theory Performance in Communication Systems" on pages COM19, volume No.5, 1971.10, 821 and 835, which is a paper on the IEEE journal of communications technology.

Various metrics are available in conjunction with listening for link conditions and a convolutional decoder for adjusting the setpoint. These metrics include (1) the re-encoding Symbol Error Rate (SER), (2) the re-encoding power metric, (3) "modified" Yamamoto metric, and possibly others.

Referring again to fig. 3, to determine the re-encoding SER, the decoded data bits in the decoded frame are provided from the decoder 328 to the re-encoder 334, and the re-encoder 334 re-encodes the data using the same convolutional encoder as used at the transmitting end. The re-encoded data is then punctured using the same puncturing scheme as the transmitting end (if any) to generate coded bits.

SER and correlation detector 336 receives the generated coded bits from re-encoder 334 and the symbols from de-interleaver 326. The generated symbols are then compared one by one with the received symbols (possibly transformed to hard decisions or binary values). During the comparison, the bit errors between the generated bits and the received bits are counted. The re-encoding SER is then determined as the ratio of the number of symbol errors to the total number of compared symbols.

The re-encoding SER is related to the total soft symbol errors within the frame and can be obtained as the total normalized measure of the most likely path through the network. In the Viterbi decoding process, all 2's are processed according to the best path metric at each stage of the network^k-1The path metrics for each state are normalized. The symbol error can be obtained by combining the normalization on the path metric of the entire network and the final metric in the network. Thus, the re-encoded SER may be obtained from a viterbi decoding process.

Determination OF re-encoded SER is described in further detail in U.S. patent application No.5,751,725 entitled "METHOD AND APPARATUS FOR DETERMINING THE RATE OF RECEIVED DATAIN A variant COMMUNICATION SYSTEM," published on 12.5.1998, assigned to the assignee OF the present invention AND incorporated herein by reference.

A high re-encoded SER indicates poor link conditions and requires that the setpoint be increased or slightly decreased after a frame is successfully decoded. Conversely, a low re-encoding SER indicates good link conditions, allowing a relatively large reduction in the set point after a frame is successfully decoded. Generally, an increased re-encoding SER corresponds to a link condition that is worse than the link condition corresponding to the current set point.

To determine the re-encoding power metric, the decoded data bits in the decoded frame are re-encoded by the re-encoder 334 using the same convolutional decoder as the base station, and then punctured using the same puncturing scheme as the base station. SER and correlation detector 336 then receives the coded bits generated by re-encoder 334 and the received symbols from de-interleaver 326. An inner product is calculated for the received soft symbol vector and the generated coded bit vector. The inner product is calculated by multiplying each term (bit) of the two vectors correspondingly and then adding the multiplied results. The final accumulated value is the inner product of the two vectors. The inner product can be expressed as follows:

formula (1)

WhereinRefers to the number of coded bits in the re-encoded frame, y refers to the received symbols, N is the number of coded bits in the frame,is a measure of the power of the received frame.

In another embodiment, the inner product of the symbol power is also calculated. Thus, each received symbol and each generated code bit is first squared. The squared coded bits are then inner-multiplied with the squared vector of received symbols.

Determination OF the recoding power metric is described in further detail in U.S. patent application No. 6,175,590 entitled "METHOD AND APPARATUS FOR DETERMINING THE RATE OF RECEIVEDDATA IN A VARIABLE RATE COMMUNICATION SYSTEM," published 16/1/2001, assigned to the assignee OF the present invention AND incorporated herein by reference.

The re-encoding power metric incorporates some elements of the re-encoding SER. If the generated coded bits have the same sign as the received symbols (i.e., no symbol error), the calculation is a positive increase in the power metric. Conversely, if the generated coded bits have the opposite sign (i.e., are incorrectly signed) from the received symbol, the calculation is a negative reduced power metric. A larger number of received symbols increases (or decreases) the power metric to a greater extent than a smaller number of received symbols.

A higher re-encoding power metric generally indicates a better link condition, allowing a greater reduction in the set point after successful decoding of a frame. Conversely, a higher re-encoding power metric generally indicates a worse connection condition, with the setpoint being raised or lowered slightly after a successful decoding of a frame. Generally, increasing the re-encoding power metric corresponds to better link conditions than the current set point.

The modified Yamamoto metric depends on the path metric of the convolutional decoding. Viterbi decoding to 2 in network^k-1Each best path of a state maintains a path metric. The path with the best path metric for all states is typically selected as the most likely sequence of data bit sequences. The modified Yamamoto metric represents the confidence level of the decoded result, in terms of the difference between the selected (best) path through the network and the next closest path through the network. To obtain the usual Yamamoto metric, the difference between the best and second best path metrics is compared to a threshold value and a binary value is generated to indicate whether the selected path meets some confidence criterion.

The modified Yamamoto metric is also generated based on the path metrics of the selected and next closest paths. However, the modified Yamamoto metric is a soft value (i.e., multi-bit value) that includes information indicative of the difference between the best and the next best path metrics. If the difference between the two path metrics is large, the modified Yamamoto metric is high, indicating that the selected path is a correct path with high confidence. Conversely, if the difference between the two path metrics is small, the modified Yamamoto metric is low, indicating that the confidence level of the selected path is low.

Other common decoder metrics can be obtained for link listen and set point adjustment, which is within the scope of the invention.

CDMA systems are generally capable of transmitting frames at several possible data rates. The selected data rate may be based on a combination of various factors, including the amount of data transmitted and the effective transmit power value, among others. If the receiver unit does not know the data rate in advance, the received frame is decoded according to several rate hypotheses. Techniques for decoding unknown rate frames are described in the aforementioned U.S. patents 5,751,725 and 6,175,590. The metric corresponding to the most likely rate hypothesis is then used for link listen and set point adjustment.

Many CDMA systems also use parallel or serial concatenated convolutional encoders (often referred to as Turbo encoders) at the transmit unit. For clarity, aspects of the present invention are described using parallel concatenated convolutional codes, although this concept may also be applied to serial concatenated convolutional codes. The Turbo encoder consists of two parallel running encoders used in conjunction with a code interleaver. Each element encoder is generally used as a convolutional encoder. The code interleaver shuffles (i.e., interleaves) the information bits in the frame according to a specifically defined interleaving scheme. One element encoder encodes original information bits in the frame to produce a first parity bit sequence, and the other element encoder encodes interleaved information bits to produce a second parity bit sequence. Some of the parity bits in the first and second sequences are punctured (deleted). The information and parity bits that are not punctured are sent as coded bits for this frame.

At the receiver unit, a complementary Turbo decoder is used to decode the corresponding received soft bits of the transmitted coded bits. For each Turbo encoded frame, the received soft bits are stored in a buffer. The received information and parity bits from the first encoder are then retrieved from the buffer and decoded according to the first element encoding to provide "extrinsic" information indicative of the confidence in adjusting the detected values of the received information bits. The extrinsic information from the first decoder is then stored in the memory unit in an interleaving order that matches the code interleaving used by the transmitting unit.

The received information and parity bits from the second encoder are retrieved from the buffer and, in combination with corresponding extrinsic information generated by the first decoder and retrieved from the memory unit, the second element code is decoded based on the extrinsic information providing a confidence level indicative of an adjusted received information bit detection value. Extrinsic information from the second decoder is stored in the storage unit in an interleaving order complementary to the code interleaving used by the transmitting unit. The decoding by the first and second decoders is repeated a plurality of times to generate a final decoding result.

Various metrics can be obtained in conjunction with the Turbo decoder for link listen and set point adjustment. These metrics include (1) the re-encoding SER, (2) the re-encoding power metric, (3) the minimum or average (log) probability ratio among the bits of the decoded frame, (4) the number of iterations before decoding the frame is declared, and other possibilities.

The re-encoding SER and re-encoding power metrics may be obtained in a similar manner as the convolutional decoder described above. The decoded bits of the frame are re-encoded by a re-encoder 334 using the same Turbo encoder (including puncturing) as the transmission unit. The coded bits produced by the re-encoder 334 and the received soft bits are compared/processed in a similar manner as the SER and associated monitor 336 produces re-encoded SER and/or re-encoded power metrics described above.

Turbo decoders typically compute the log probability ratio (LLR) for each received information and parity bit as follows:

wherein P (b)_m0) and P (b)_m1) are each b_mIs the probability of accepting bits as 0 and 1. The initial probability depends on the received soft value of each symbol. The successive probability values are modified by repeating the decoding a number of times as described above. An LLR of 0 indicates that the probability of a bit being 0 and 1 is equal, a larger positive LLR value indicates that the probability of a bit being 0 is large, and a larger negative LLR value indicates that the probability of a bit being 1 is large.

The bit-minimum or average LLR of the decoded frame (after the final iteration) may be used as the metric. In some applications, a frame is considered unacceptable if it has been received with errors in its decoded bits. Thus, the worst LLR (i.e., the LLR of the smallest magnitude) or some worse LLR is used as an indicator of the confidence level of the decoded frame, as required by this application. The average of some worse LLRs may also be used on the metrics.

As noted above, Turbo decoding is typically repeated multiple times (e.g., 4, 6, 8, 10, or possibly more) before a frame is declared decoded. With each repetition, the confidence level of each received information bit increases until a final value is reached progressively. The Turbo decoder may detect whether the LLR of the bit in the frame exceeds a threshold value during the decoding process to finish the decoding. Alternatively, the decoder may use a built-in error detection function (e.g., a Cyclic Redundancy Code (CRC)) to determine whether the decoding was successful before the maximum allowed number of repetitions was reached. In this way, the number of decoding repetitions before declaring a decoded frame can be used as a decoder metric.

Other Turbo decoder metrics may also be obtained and used for link listen and set point adjustment, which is within the scope of the invention.

Similar to the convolutional decoder described above, if the data rate of the received frame is not known in advance, the received frame can be decoded according to a rate hypothesis, and then the metric corresponding to the most likely rate hypothesis is used for link listen and set point adjustment.

Block-shaped codes are used to encode data prior to transmission. Various block-shaped codes may be used, such as Reed-Solomon codes and others. For an (n, k) Reed-Solomon code, a block of k data bits is encoded as a block of n data bits. The (n, k) Reed-Solomon code is capable of correcting (n-k)/2-bit errors in a block of n coded bits. Reed-Solomon encoding and decoding "Error Control Coding" on pages 171-176 in precision Hall, published 1985, by s.lin and Costello: fundamentalsand Applications "are described in further detail.

Various metrics can be obtained in conjunction with the Turbo decoder for link listen and set point adjustment. These metrics include (1) the re-encoding SER, (2) the re-encoding power metric, and possibly others.

The re-encoding SER and re-encoding power metric for block-shaped encoded frames may be obtained in a similar manner as described above. The decoded bits in the frame may be re-encoded by a re-encoder 324 using the same block-shaped encoder as the transmitting unit. The coded bits produced by re-encoder 334 and the received symbols are compared/processed in a similar manner as the SER and associated monitor 336 produces a re-encoded SER and/or re-encoded power metric as described above.

The inner power control loop adjusts the transmit power of the transmission from the transmitter unit so that the signal quality of the receiver unit is maintained at a set point. Under normal operating conditions, the inner loop can allocate the transmit power required to maintain the received signal quality at a set point.

However, in some cases, the inner loop may not be able to maintain the received signal at the set point. For example, if the path loss suddenly degrades, the inner loop does not get up fast enough, the transmit power is less than the power required to compensate for the path loss, the received signal quality is less than the set point, and a negative power surplus (insufficient product power) results. If the transmitting unit is unable (or does not want) to supply the required transmit power to reach the target E_b/N_tThen alsoA power shortage occurs. Conversely, if the path loss suddenly improves, the inner loop does not turn off fast enough, the transmit power is greater than the power required to compensate for the path loss, the received signal quality is greater than the setpoint, and a power surplus results. Thus, the power surplus represents the ability of the inner loop to supply the specific requirements of the outer loop.

In accordance with an aspect of the invention, the performance of the inner loop may be monitored to verify whether the inner loop provides target E_b/N_t. The power surplus is determined and taken into account when adjusting the set point. In an embodiment, the power remaining may be calculated as an average E over a certain time interval (e.g., a frame)_b/N_tThe setpoint is subtracted (received signal quality). In another embodiment, the power surplus may be estimated from the accumulated inner loop power control commands. If the UP and DOWN commands result in the same step size (e.g., ± 0.5dB) in the transmit power adjustment, the power residual may be estimated from the sum of the DOWN commands minus the sum of the UP commands. If the UP and DOWN commands produce different step sizes, the power remaining can be estimated based on the sum of the scaling values for the DOWN commands minus the sum of the scaling values for the UP commands.

Fig. 6A is a diagram illustrating an exemplary transmission transmit power. Line 610 represents actual path loss and dashed line 612 represents achievement of target E_b/N_tThe required transmit power, the heavy dashed lines 614a, 614b, and 614c represent the actual transmit power. As shown in fig. 6A, the transmit power needs to be adjusted in a manner complementary to the path loss in order to maintain the received signal quality at the set point. This is available for all of frame 1 and for most of frame 2. By the last part of frame 2, the path loss is substantially degraded but the transmit power is limited (i.e., capped) to some maximum level indicated by dashed line 616. At the start of frames 3 and 4, the required transmit power is determined to be greater than the maximum level for which transmission is temporarily suspended. At frame 5, the required transmit power is determined to be below the maximum level and transmission is continued.

Fig. 6B is a diagram illustrating the transmission power surplus shown in fig. 6A. During frame 1, the transmission power is controlledFor maintaining the quality of the received signal at a target E_b/N_tThe power residue is zero. During a portion of frame 2, the transmit power is less than achieving target E_b/N_tBy the amount required, the average received signal quality of the frame is lower than the target E_b/N_tNegative power surplus (i.e., power deficit) occurs. These frames are power starved to a large extent because there is no transmission during frames 3 and 4. During frame 5, the transmit power is controlled to maintain the received signal quality at target E_b/N_tThe power surplus is again zero.

Fig. 7 is a flow diagram of a process 700 for adjusting a set point according to an embodiment of the invention. Initially, at step 712, the received frame is decoded, and the status of the decoded frame (i.e., whether the frame was removed or correctly decoded) is determined. One or more (typically soft) metrics for the decoded frame are then obtained at step 714. As described above, these metrics depend on the type of received frame decoding (e.g., convolutional, Turbo, or block decoding), indicating the connection condition and the confidence in the decoding result. It is then determined in step 716 whether the power of the inner power control loop is remaining or insufficient. The set point step size is determined at step 718 based on the frame state, metric and power remaining/lacking or a combination thereof. The set point is adjusted in steps 720 in the determined steps.

The metric is generally related to the power surplus described above. Thus, when adjusting the set point, the power surplus is taken into account. For example, the set point adjustment may be related to or at least partially dependent on the amount of power remaining or deficit.

In an embodiment, if the power is not enough (i.e., the inner loop supply is much less than achieving target E)_b/N_tThe required power) and the received frames are removed, the amount of adjustment to the set point according to the metric should be reduced. If there is time, the set point is raised by less than normal amounts due to the inner loop supplying more power.

In an embodiment, if power remains positive and the received frame is decoded correctly, the amount of adjustment of the set point is decreased according to the metric. Power surplus typically occurs if the link improves faster than the inner loop is broken. The inner loop may supply less power if it has time.

In an embodiment, if power remains near zero (i.e., the inner loop approximately supplies target E)_b/N_t) The normal (or possibly elevated) setpoint adjustment is established based on a metric. The metric may be used to "fine tune" the set point if the received frame is decoded correctly. For example, if the re-encoding SER is low, the re-encoding power metric is high, the modified Yamamoto metric is high, the LLR of the least reliable bit is high, or a combination thereof, and then the set point is lowered. The amount of down-regulation is related to the magnitude of the metric (i.e., the confidence of the demodulation result).

FIG. 8A shows the scaling factor S_BThe curve for power remaining is used to scale the setpoint step size when the received frame is dropped. If there is power surplus (i.e. received signal quality higher than target E)_b/N_t) But the received frame is still removed, the set point is adjusted by a large amount. As shown in the right half of curve 812, a larger set point step size can be obtained by using a larger scaling factor. Conversely, if there is insufficient power and the received frame is removed, the set point is adjusted by a small amount because the inner loop is considered to be operating with a chance to provide better received signal quality. As shown in the left half of curve 812, a smaller set point step size can be obtained by using a smaller power down scaling factor. There are upper and lower limits in curve 812 to avoid instability. For example, if the power deficiency is greater than the threshold value P_B1The scaling factor is maintained at S_BminIs measured. When the power surplus exceeds the threshold level P_B2Time, scale factor S_BProgressively reaching S_BmaxIs measured.

FIG. 8B shows the scaling factor S_GA curve for power surplus used to scale the point step size when the received frame is correctly received. If there is insufficient power (i.e., the received signal quality is below target E)_b/N_t) But the received frame is still received correctly, the set point is adjusted by a large amount. As shown in the left half of curve 814It is shown that a larger setpoint step size can be obtained by using a larger scaling factor. Conversely, if there is a power surplus and the received frame is received correctly, the set point is adjusted by a small amount because the inner loop is considered to operate with a chance to provide better received signal quality. As shown in the right half of curve 814, a smaller set point step size can be obtained by using a smaller power down scaling factor. Likewise, there are upper and lower limits in the curve 814 to avoid instability. If the power remaining is greater than the threshold value P_G1The scaling factor is maintained at S_GminIs measured. When the power shortage exceeds the threshold level P_G2Time, scale factor S_GProgressively reaching S_GmaxIs measured.

Different characteristic curves having different characteristics than those shown in fig. 8A and 8B may also be used as the scaling factor, and this is also within the scope of the present invention. The curve used as the scaling factor may be implemented by a look-up table of some other device.

Any combination of the above described metrics, if present in the receiver unit, can be used to listen for link conditions and adjust the set point. The setpoint adjustment is based on a combination of (1) frame removal information (i.e., frame status), (2) one or more metrics, (3) power surplus/deficit, and (4) setpoint surplus/deficit, as described in further detail below.

In an embodiment, for each metric used to adjust the set point, the distribution of metric values for correctly demodulated frames is collected for the threshold value E required for the desired performance level (e.g., 1% FER)_b/N_tThe associated set point setting. E of set point and threshold_b/N_tIs called a setpoint remaining or insufficient (other than power remaining/insufficient) the setpoint remaining or insufficient depends on whether the setpoint is set at the threshold E_b/N_tAbove (excess) or below (deficiency). For each metric, multiple frequency distributions of different set point residuals/deficits and different link conditions are collected.

FIG. 9A is a diagram showing several set points remaining ≦ based onA block diagram of the insufficient metric frequency distribution. In this example, profile 912 shows the threshold value E required for the setpoint to be set at the desired performance level (e.g., 1% FER)_b/N_t(e.g., 6dB) of metric values. Profiles 914 and 916 show the setpoint above or below the threshold E, respectively_b/N_tThe distribution of metric values at a certain value (e.g., 2dB, or 4dB for the setpoint of profile 914 and 8dB for the setpoint of profile 916). The metric distribution is collected from computer simulations, experimental measurements (e.g., in a laboratory or outdoors), or by other means.

FIG. 9B is a block diagram illustrating a setpoint step curve of the profile depicted in FIG. 9A. As shown in fig. 9B, curves 922, 924, and 926 represent setpoint steps used by profiles 912, 914, and 916, respectively. From these curves it can be observed that the setpoint step depends on the setpoint surplus/deficit, as indicated by the different curve characteristics and slopes of curves 922, 924 and 926. The setpoint step size also depends on the actual metric value, with higher UP step sizes generally being used for low metric confidence and higher DOWN step sizes generally being used for high metric confidence.

Fig. 9A and 9B show a profile of a single measurement and a setpoint step curve. If multiple metrics are available, similar profiles and curves are generated for each metric. The amount of adjustment of the set point for a given set of received frame metrics may be determined from a combination of values of the appropriate curve.

The metric may be used to listen for link conditions and adjust the set point before the frame is actually dropped. If the metric indicates that the link condition is better than expected (e.g., re-encoding SER is low and re-encoding power metric is high, etc.), the target E is lowered_b/N_t. Conversely, if the metric indicates that the link condition is worse than expected, the target E is increased_b/N_t. In an embodiment, the setpoint is raised despite the frames being decoded correctly (in contrast to a typical device that lowers the setpoint for all good frames in the same step size, regardless of other factors). If the metric indicates that the link condition is about the same as expected, target E is maintained_b/N_t(i.e., unchanged).

The setpoint is adjusted by different amounts depending on (1) the frame status, (2) the metric value, (3) the power surplus/deficit, (4) the setpoint surplus/deficit, (5) some other factor, or a combination thereof. Target E if the metric indicates that the link condition is better than expected (e.g., very low re-encoding SER, very high re-encoding power metric and large magnitude LLR, etc.)_b/N_tIs greatly reduced. Target E if the frame is decoded correctly but the decoding metric indicates that the result is of low confidence_b/N_tThe small amplitude decreases or possibly increases depending on the actual value of the metric and the desired power control characteristics.

In an embodiment, the set point down step size for a good frame is obtained as follows:

ΔSP_G＝K₁·C_f·S-K₂equation (2)

Wherein Δ SP_GIs the set point step size, K, of the good frame₁And K₂Is a constant, C, selected to achieve a desired power control characteristic_fIs a confidence factor related to and derived from the available metrics and S is a factor related to the frame status and power remaining/insufficient. K₁And K₂Is a positive value, K₂Is less than K in amplitude₁。K₁And K₂May be generated from a frequency distribution like the metric shown in fig. 9A. A similar equation may be defined for the set point step for the removed frame. Same or different K₁And K₂The constant and the scaling factor S may be used for good frames.

The power control methods described herein may be used to control the transmit power of multiple traffic channels. In some new generation CDMA systems (e.g., CDMA2000 and W-CDMA systems), multiple traffic channels may be simultaneously used to transmit large amounts and/or different types of data in order to support high-speed data transmission. These traffic channels are used to transmit data at different data rates and they also use different processing (e.g., coding) schemes. Typically, a certain maximum bit rate (e.g., 800bps) is assigned to each remote terminal for power control of the traffic channel. This allocated bit rate is then used to send messages/commands indicating the measured quality of the transmission signals received on these traffic channels. These messages/commands are then used to provide power control for the traffic channel. A METHOD FOR simultaneous POWER CONTROL OF multiple traffic channels is described in further detail in U.S. patent application No. 09/755,659 entitled "METHOD AND APPARATUS FOR POWER CONTROL OF multiple channels CHANNELS IN AWIRELESS COMMUNICATION SYSTEM," published 5.1.2001, assigned to the assignee OF the present invention AND incorporated herein by reference.

If multiple power control loops are maintained for multiple traffic signals (e.g., one fundamental channel and one supplemental channel in a cdma2000 system), a "delta" power control device is used. For delta power control among others, the set point of the first traffic channel is adjusted according to a number of factors as described above, and the set point of the second traffic channel is adjusted corresponding to the first traffic channel. The set point of the second traffic channel (e.g., the supplemental channel) is initialized to a small delta value relative to the set point of the first traffic channel. The receiver unit adjusts the set point for one or both traffic channels in the manner described above and informs the transmitter unit of the appropriate power delta to apply between the traffic channels. This notification is done periodically or aperiodically (e.g., the reported value is above a certain threshold when delta changes from the end).

The power control methods described herein may also be used for discontinuous transmission. If the channel is not carrying traffic load but is being transmitted on by a known signal (e.g., a pilot channel or pilot system such as used in CDMA2000 and W-CDMA systems), the receiver unit may measure the received signal quality at intervals equal to the traffic channel frame. If forward error correction coding is implemented, an "actual" frame may be formed by scaling portions of the known codewords of these successive power measurements. If the signal quality is acceptable, random noise samples are generated and added to the known codeword before it is decoded. The composite decoded metric discussed above is then used to adjust the set point.

For example, if a part of E_b/N_tAt xdB, then a normalized power of 1 is used for that portion of the signal and a random number generator is used to produce noise samples with a variance of xdB. This noise sample is added to the signal with power 1. Each portion of the signal is thus formed by the signal and the noise that reflects the transmission of the link to the receiver. The known frame is then deinterleaved and decoded. The decoder metric is then used to adjust the set point, if necessary, in the manner described herein.

The decoder at the receiver unit decodes the actual frame and provides various metrics such as erasures, re-encoding SER, re-encoding power control metrics, modified Yamamoto metrics, the number of iterations of the Turbo decoder, and the LLR of the Turbo decoder (smallest or average of the N worst bits), etc. The set point is then adjusted based on the measurement. If a power control channel is present during traffic channel non-service periods (e.g., forward or backward power control sub-channels in cdma2000 systems), this channel is used to estimate the power surplus/deficit that is later used to further refine the setpoint.

Power CONTROL techniques FOR continuous TRANSMISSION with reference pilots are disclosed IN U.S. Pat. No. 09/370,081 entitled "METHOD AND APPARATUS FOR DETERMINING THE CLOSED LOOP POWER CONTROL IN A WIRELESS PACKET DATA COMMUNICATION SYSTEM" on 6.8.1999, U.S. Pat. No. 09/755,245 entitled "METHOD AND APPARATUS FOR DETERMINING THE FORWARD LINE CLOSED LOOP POWER CONTROL CONTACTOR CONTROL IN A WIRELESS PACKET DATA COMMUNICATION SYSTEM" on 5.1.2001, AND U.S. Pat. No. 09/239,454 entitled "METHOD AND APPARATUS CONTROL TRANSMISSION POWER IN A TRANSMISSION TRANSISTOR APPARATUS COMMUNICATION" on 28.1.1999, which are assigned to AND assigned by the present inventor.

Referring again to fig. 3, for forward link power control, samples from demodulator 324 (or possibly from RF receiver unit 322) are provided to an RX signal quality measurement unit that estimates the received transmission quality. The received signal QUALITY can be estimated using a variety of METHODs, including those described IN U.S. patent application Ser. No.5,903,554 entitled "METHOD AND APPARATUS FOR MEASURING LINGK QUALITY IN A SPREAD PERRUM COMMUNICATION SYSTEM", published on 11.5.1999, AND U.S. patent application Ser. Nos. 5,056,109 AND 5,265,119 entitled "METHOD AND APPARATUS FOR CONTROLLING TRANSMISSION ION A CDMA CELLULAR MOBILE TELEPHONE SYSTEM", published on 18.10.1991, assigned to the assignee of the present invention AND incorporated herein by reference.

Power control processor 340 receives and compares the received signal quality to the set point for the traffic channel being processed and sends the correct response power control commands (e.g., UP/DOWN commands, or UP/DOWN commands expressed as x db, or some other type of command) on the power control subchannel over the backward link to the base station.

The power control processor 340 also receives the frame status from the CRC checker 332 and one or more metrics for each encoded frame such as the re-encoding SER and re-encoding power metrics from the detection machine 336, the modified Yamamoto metrics from the Yamamoto detection machine 330, and the LLRs and iteration counts for the poorly decoded bits from the decoder 328, or a combination thereof. For each encoded frame, power control processor 340 updates the set point (e.g., power remaining/insufficient, set point remaining/insufficient) based on the frame status, metrics, and/or additional information available to processor 340.

On the reverse link, the data is processed by a Transmit (TX) data processor 342, further processed (e.g., masked and spread) by a Modulator (MOD)344, and conditioned (e.g., converted to analog signals, amplified, filtered, quadrature modulated, etc.) by an RF TX unit 346 to generate a reverse link signal. The power control information from the power control processor 340 corresponds to data processed by the TX data processor 342 or the modulator 344. The reverse link signal is routed through a combiner 342 and transmitted via antenna 312 to one or more base stations 104.

Referring again to fig. 2, the reverse link signal is received by antenna 224, routed through multiplexer 222, and provided to an RF receiver unit 228. RF receiver unit 228 conditions (e.g., downconverts, filters, and amplifies) the received signal and provides a conditioned reverse link signal for each remote terminal that is receiving. Channel processor 230 receives and processes the conditioned signal to enable a remote terminal to recover the transmitted data and power control information. Power control processor 210 receives power control information (e.g., any combination of power control commands, erasure indicator bits, and quality indicator bits) and generates one or more signals for adjusting the transmit power of one or more transmissions to the remote terminal.

Returning to fig. 3, power control processor 340 implements portions of the inner and outer loops described above in fig. 4. For the inner loop, the power control processor 340 receives the received signal quality values and sends a series of power control commands, which may be sent over the power control subchannel on the backward link. For the outer loop, power control processor 340 receives the frame status and metrics and adjusts the set point for the remote terminal accordingly. In fig. 2, power control processor 210 also implements portions of the power control loop described above. Power control processor 210 receives power control information on the power control subchannel and adjusts the transmit power of one or more transmissions to the remote terminal accordingly.

The power control method may be implemented by various ways. For example, power control may be implemented in hardware, software, or a combination thereof. For a hardware implementation, the means for implementing power control may be implemented using one or more Application Specific Integrated Circuits (ASICs), Programmable Logic Devices (PLDs), controllers, microcontrollers, microprocessors, other devices designed to perform the functions described herein, or any combination thereof.

For a software implementation, the means for implementing power control may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in memory units and executed by processors (e.g., power control processors 210 or 340).

For clarity of explanation, various aspects, embodiments, and features of the power control of the present invention are described with specificity for the downlink. Many power control methods are also advantageously applied in the reverse link power control. For example, the setpoint for one or more reverse link transmissions may be adjusted based on frame status, one or more metrics, power remaining/insufficient, setpoint remaining/insufficient, or any combination thereof, as described above.

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. 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 (26)

1. A method for adjusting a power control loop set point of a received signal in a wireless communication system, comprising:

decoding the one or more received frames in accordance with a particular decoding scheme to provide one or more decoded frames;

obtaining one or more metrics for the one or more decoded frames, including at least one of a re-encoded power metric and a modified Yamamoto metric, wherein the re-encoded power metric represents a correlation between symbols in the received frame and symbols produced by re-encoding the decoded frame; and

adjusting a set point based on the one or more metrics.

2. The method of claim 1, further comprising:

for each decoded frame, determining a step size for adjusting the setpoint, an

Characterized in that the set point is adjusted according to the determined step size.

3. A method as claimed in claim 2, characterized in that the step size is variable and depends on one or more metric values.

4. The method of claim 1, wherein each of the one or more metrics represents a confidence level of the decoded frame based on a corresponding criterion.

5. The method of claim 1 wherein the modified Yamamoto metric represents decoded frame confidence based on the selected decoded frame and a next most likely decoded frame.

6. The method of claim 2, wherein the step size is determined based on a confidence level of the decoded frame represented by the one or more metrics.

7. The method of claim 6, wherein the step size is increased if the one or more metrics indicate a high confidence in the decoded frame.

8. The method of claim 6, wherein the step size is decreased if the one or more metrics indicate low confidence in the decoded frame.

9. The method of claim 1, wherein the set point is increased if the one or more metrics indicate a low confidence in the decoded frame.

10. The method of claim 1, further comprising:

for each decoded frame, determining a power surplus or deficit indicative of the received signal quality for frames above or below a set point, respectively, an

Characterised in that the set point is adjusted in dependence on the determined power surplus or deficit.

11. The method of claim 10, further comprising:

for each decoded frame, determining a step size for adjusting the setpoint based on one or more of the metrics and the power surplus or deficit, an

Wherein the set point is adjusted according to the determined step size.

12. The method of claim 1, further comprising:

determining a set point surplus or deficit indicative of a difference between the set point and a signal quality threshold required to achieve a certain performance level, an

Wherein the set point is adjusted based on the determined remaining or insufficient set point.

13. The method of claim 12, further comprising:

for the decoded frame, determining a step size for adjusting the setpoint based on one or more of the metrics and the setpoint remaining or lacking, an

Characterised in that the set point is adjusted in accordance with the determined step size.

14. The method of claim 1, wherein the wireless communication system is a CDMA system that conforms to CDMA2000 standard or W-CDMA standard, or both.

15. A method for adjusting a power control loop set point of a received signal in a wireless communication system, comprising:

decoding one or more received frames in accordance with a particular decoding scheme to provide one or more decoded frames;

obtaining one or more metrics for the one or more decoded frames, including at least one of a re-encoded power metric and a modified Yamamoto metric, wherein the re-encoded power metric represents a correlation between symbols in the received frame and symbols produced by re-encoding the decoded frame;

determining a power surplus or deficit indicative of the received signal being greater than or less than the set point, respectively; and

adjusting the set point based on the one or more metrics and the power surplus or deficit.

16. The method of claim 15, wherein the power surplus or deficit is determined for each received frame based on an average received signal quality for the frame and a setpoint for the frame.

17. The method of claim 15, further comprising:

for each decoded frame, determining a step size for adjusting the setpoint based on the determined power surplus or deficit, an

Wherein the set point is adjusted according to the determined step size.

18. The method of claim 15, wherein the step size is scaled by a larger scale factor if the received frame is decoded correctly and there is insufficient power for the frame.

19. The method of claim 15, wherein the step size is scaled by a smaller scaling factor if the received frame is decoded correctly and there is power remaining for the frame.

20. The method of claim 15, wherein the step size is scaled by a larger scale factor if the received frame is removed and there is power remaining for the frame.

21. The method of claim 15, wherein the step size is scaled by a smaller scale factor if the received frame is dropped and there is insufficient power for the frame.

22. A power control unit for use in a wireless communication system, comprising:

a decoder configured to decode a received frame in accordance with a particular decoding scheme to provide a decoded frame;

a metric calculation unit configured to provide one or more metrics for the one or more decoded frames, including at least one of a re-encoded power metric and a modified Yamamoto metric, wherein the re-encoded power metric represents a correlation between symbols in the received frame and symbols produced by re-encoding the decoded frame; and

a power control processor configured to receive the one or more metrics for the decoded frame and adjust a setpoint of a power control loop based on the one or more metrics, wherein the setpoint represents a target received signal quality for the received frame.

23. The power control unit of claim 22, further comprising:

a signal quality measurement unit configured to receive and process symbols of a received frame to provide an estimate of received signal quality of the received frame, an

Wherein the power control processor is further configured to receive the received signal quality estimate, determine a power surplus or deficit indicative of received signal quality being greater than or less than a set point, respectively, and adjust the set point based on the determined power surplus or deficit.

24. The power control unit of claim 22, wherein for each decoded frame, the power control processor is configured to adjust the set point by a particular amount based on the one or more metric values.

25. The power control unit of claim 22, configured to operate on a forward link of a CDMA system.

26. The power control unit of claim 22, configured to operate on a reverse link of a CDMA system.