HK1117286B

HK1117286B - Method and apparatus for transmit power control

Info

Publication number: HK1117286B
Application number: HK08107371.6A
Authority: HK
Inventors: 兰纳特．安德森; 王怡彬; 格雷戈里．E．博顿利
Original assignee: Lm爱立信电话有限公司
Priority date: 2005-05-20
Filing date: 2006-05-18
Publication date: 2012-08-31

Description

Method and apparatus for transmit power control

Technical Field

The present invention relates generally to transmit power control (transmit power control), and more particularly to determining transmit power control feedback.

Background

Transmit power control has an important role for interference-limited communication networks, such as networks based on Code Division Multiple Access (CDMA) technology. The target level of reliable communication and data throughput requires transmission with sufficient power to ensure adequate received signal quality, but with excessive power to be avoided as a mechanism to limit or reduce interference.

As an example of transmit power control, a first transceiver sends an information signal to a second transceiver, which sends transmit power control feedback to the first transceiver as a function of received signal quality, measured by the second transceiver for the information signal. The first transceiver then increases or decreases the transmit power of the information signal in response to the power control feedback. In this way, the transmit power rises and falls, which is typically within an allowable range or bound, as needed to maintain the quality of the signal received at the second transceiver at or around a target level as reception conditions change.

Typically, the power control feedback comprises a Transmit Power Command (TPC) which is transmitted as 1s or-1 s depending on whether the measured signal quality is above or below a reference target. This control is commonly referred to as "inner loop" power control, and as the term implies, the "outer loop" power control mechanism is typically paired with inner loop power control. One or more additional indicators, such as Bit Error Rate (BER) or Frame Error Rate (FER) or block error rate (BLER), provide a reference for adjusting the inner loop target by the outer loop power control. That is, the inner loop power control generates TPC by comparing the measured signal quality to a target value, while the outer loop power control adjusts the target value by comparing the additional indicator(s) to a corresponding target value (e.g., one percent FER or BLER target).

Some circumstances complicate the above approach to transmit power control. For example, the wideband code division multiple access (W-CDMA) standard requires that the TPC be sent to the User Equipment (UE) using a downlink Associated Dedicated Physical Channel (ADPCH), thereby ensuring that the UE transmits certain uplink control channels at a transmit power that causes the base station to receive those channels at a target signal quality. For example, in a High Speed Downlink Packet Access (HSDPA) flagged extended W-CDMA system, the high speed dedicated physical control channel (HS-DPCCH) used by the network to signal the acknowledgement or negative acknowledgement (ACK/NACK) of the hybrid automatic repeat request (H-ARQ) operation on the high speed downlink shared channel (HS-DSCH) is typically power controlled by the network to ensure reliable reception by the supported network base station(s). The UE, in turn, returns the TPC to the transmitting network to ensure that the downlink TPC is transmitted to the UE at a power sufficient for reliable reception. In other words, the UE sends transmit power control feedback for the downlink power control channel to ensure that the UE receives the network-sent TPC with a target signal quality.

Pilot information (e.g., one pilot symbol per slot) is included in the DPCH transmission and the receiving UE may use the received pilot information to estimate the DPCH signal quality used to generate the per-slot power control feedback. That is, the UE generates an uplink TPC command as feedback for the received DPCH by comparing the measurement result of the downlink signal-to-interference-plus-noise ratio (SINR) with a target SINR (set by outer loop power control).

However, to support more HS-DSCH users without the need for an additional downlink DPCH for each user, the W-CDMA standard identifies the use of a "fractional dedicated physical channel" (F-DPCH) that time-multiplexes multiple DPCHs for different UEs on one downlink channel. Although this approach consumes less spreading code resources on the downlink, it imposes complications on transmit power control at the UE because the F-DPCH does not include per-slot pilot information on which the UE relies for signal quality estimation. And the F-DPCH also does not provide enough data symbols per slot to support accurate signal quality estimation of the received data symbols. Thus, as a non-limiting example, the F-DPCH illustrates a type of channel that complicates the inner/outer loop power control.

Disclosure of Invention

According to embodiments of the methods and apparatus taught herein, power control feedback is generated for a control channel signal received with a reference channel signal based on the signal strength and quality of the reference channel and an estimate of a gain factor associated with the control and reference channel signals. As a non-limiting example set forth in a wideband cdma (wcdma) environment, the reference channel signal comprises a common pilot channel (CPICH) signal and the control channel signal comprises a fractional dedicated physical channel (F-DPCH) signal transmitted with an unknown power gain relative to the CIPCH signal. Thus, the gain factor represents a calculated estimate of the unknown gain.

In one embodiment, a method of generating power control feedback for a control channel signal comprises the steps of: calculating a gain factor with respect to the control channel signal and the reference channel signal; an estimated signal quality or strength of the reference channel signal is determined and power control feedback of the control channel signal is generated as a function of the estimated signal quality or strength and the gain factor. It should be understood that the power control circuitry included in the wireless communication device may be configured to perform the method based on the corresponding structure of hardware, software, or a combination thereof. By way of non-limiting example, the wireless communication device may comprise a mobile station, such as a cellular radiotelephone, or may comprise a wireless pager, a Portable Digital Assistant (PDA), a laptop or palmtop computer, or a communication module therein.

In at least one embodiment, the power control circuit is configured to calculate the gain factor at specified times (times) to maintain an updated value of the gain factor between the specified times, and to use the updated value to generate the power control feedback. In one or more embodiments, the step of maintaining an updated value of the gain factor includes tracking changes in the gain factor corresponding to power control feedback generated between the specified times. For example, the power control circuit is arranged to calculate the gain factor based on soft values received via a specified time interval with respect to symbols of the control channel signal and based on a network response (net response) calculated from a channel estimation performed on the reference channel signal via the specified time interval. This calculated value may be used as an initial value for the gain factor for the next interval, and during the next interval, the gain factor may be updated over the next interval based on the power control feedback generated for that next interval.

If a gain factor is not available, in one embodiment the power control circuit generates power control feedback for the control channel signal according to a predetermined sequence of power control commands (alternating up/down commands). The power control circuit may be arranged to generate ongoing power control feedback for the control channel signal at any given current time window or time frame based on an updated value of the gain factor dependent on a calculated value of the gain factor for a previous frame and the power control feedback generated at the current frame.

The initial value of the gain factor for each next frame may be calculated at each current frame by collecting measurements within the current frame. For example, the power control circuit may be arranged to calculate the value of the gain factor for the current frame based on soft values received in the frame for symbols of the control channel signal and a network response determined by estimating the reference channel signal in the frame. More broadly, the gain factor can be recalculated at any given time, over any expected interval of the control channel signal, and an updated value to maintain the gain factor between recalculations can be generated based on the tracked ongoing power control feedback.

In an embodiment, the power control circuit may be arranged to generate the power control feedback as a power control command (e.g. generating an uplink power control command for the control channel signal on a per slot basis). Each uplink power control command is generated (e.g., up, down, or hold) by comparing the adjusted signal quality to a target signal quality. For example, if the adjusted signal quality is above the target, a down command is generated. Conversely, if the adjusted signal quality is below the target signal quality, an up command is generated. The adjusted signal quality is obtained by adjusting an estimated signal quality (e.g., per slot estimate) determined from the reference channel signal as a function of the updated value of the gain factor.

In another embodiment, the uplink power control commands are generated in a similar manner, except that a mismatch value is utilized which is compared to a mismatch target threshold. In an embodiment, the mismatch value is an updated mismatch value based on an initial mismatch determined by an initial value of the gain factor and a corresponding estimate of the reference channel signal quality and an ongoing mismatch update tracking a subsequent change in the reference channel signal quality and a change to the corresponding gain factor corresponding to the uplink power control command generation.

In all such embodiments, the generation of uplink power control commands may be considered "inner" loop power control, and the power control circuitry is arranged in one or more embodiments to run an "outer loop" power control mechanism that adjusts one or more values used by the inner loop as a function of one or more performance metrics reflecting the performance of the inner loop power control in progress. For example, the values that may be adjusted include any one or more of a gain factor, an estimated signal quality, a target signal quality, a mismatch value, and a mismatch target threshold. One such performance metric is a Command Error Rate (CER) estimate, which may be calculated by a power control circuit.

Of course, the present invention is not limited to the above features and advantages. Indeed, those skilled in the art will recognize additional features and advantages upon reading the following detailed discussion, and upon viewing the accompanying drawings.

Drawings

Fig. 1 is a block diagram of an embodiment of a wireless communication device including an embodiment of a power control circuit according to methods and apparatus taught herein.

Fig. 2 is a logic flow diagram of one embodiment of processing logic that may be implemented by the wireless communication device of fig. 1.

Fig. 3 is a block diagram of one embodiment of the power control circuit shown in fig. 1.

Fig. 4 is a diagram of one frame of a control channel signal that may be received by the wireless communication device of fig. 1.

FIG. 5 is a logic flow diagram of processing logic of one embodiment, such as may be implemented by the power control circuit of FIG. 3.

Fig. 6 is a block diagram of one embodiment of the power control circuit shown in fig. 1.

FIG. 7 is a logic flow diagram of processing logic of one embodiment, such as may be implemented by the power control circuit of FIG. 6.

Fig. 8 is a diagram of example values for the processing logic of fig. 5 or 7.

Detailed Description

Fig. 1 is a block diagram illustrating one embodiment of a wireless communication device 10 including a power control circuit 12, the power control circuit 12 being configured to generate power control feedback for a received control (or data) channel signal based on a received reference channel signal. Although the implementation of the wireless communication device varies depending on its intended use, the illustrated embodiment of the wireless communication device 10 also includes one or more baseband processing circuits 14, receiver and transmitter circuits 16, 18 connected to one or more antennas 20 via a switch/duplexer 22, one or more system control circuits 24, and one or more input/output (I/O) and User Interface (UI) circuits 26.

In more detail, assume that the wireless communication device 10 receives the control channel signal at a signal quality sufficient to ensure reliable reception of the control channel information, and further assume that the control channel signal cannot readily support direct, reliable signal quality estimation over the time frame of interest. For example, the control channel signal may be transmitted at a transmit power gain unknown to the reference channel signal and not carrying pilot or reference information known as a priori on which the signal quality estimate is based, or there may not be a high enough data transmission rate to support reliable data-based signal quality estimates over the time frame of interest. However, it is assumed that the reference channel signal easily supports signal quality estimation. For example, the reference channel signal may comprise a pilot signal having a pilot symbol rate sufficient for reliable signal quality estimation over the time frame of interest.

As a non-limiting example, which may be disposed in the context of a W-CDMA based communication network, the reference channel signal may be a common pilot channel (CPICH) signal and the control channel signal may be a fractional dedicated physical channel (F-DPCH) signal transmitted at a specified transmit power gain relative to the CPICH, the gain compensation typically being unknown to the receiving mobile device. To control the uplink transmit power of individual ones of a plurality of mobile stations, the F-DPCH is used to send (downlink) power control commands to the individual ones of the mobile stations. Therefore, it is important that the mobile station receive incoming downlink power control commands at a signal quality sufficient to ensure reliable reception of the command values intended for each mobile station. To do so, a mobile station receiving power control commands located on the F-DPCH must generate power control feedback, uplink power control (TPC) commands, to ensure that downlink power control commands on the F-DPCH sent to the mobile station are received at the target signal quality. In this case, the power control feedback taught herein generates power control feedback for the F-DPCH signal based on the CPICH signal and an estimated gain factor representing the transmit power gain of the F-DPCH relative to the CPICH signal.

More broadly, in accordance with power control feedback generation as taught herein, the power control circuit 12 of the wireless communication device 10 generates power control feedback for the control channel signal from the reference channel signal. That is, the power control circuit 12 generates a power control command for controlling the transmission power of the control channel signal based on the estimation of the gain coefficient related to the control channel signal and the reference channel signal and the measurement result of the quality or strength of the reference channel signal. (it should be appreciated that the power control circuit 12 may be equivalently arranged to use the reference channel signal strength instead of an explicit estimate of the reference channel signal quality unless otherwise specified, the detailed description of signal quality operations herein may also apply to signal strength operations.)

The above operation may be understood to include an initialization phase and a stabilization phase. During the initialization phase, the gain factor cannot be estimated and the power control circuit 12 generates power control feedback according to other methods. For example, the power control circuit 12 may be arranged to generate power control feedback in accordance with a predetermined sequence of power control commands (e.g. a series of alternating up/down commands, or a series of hold commands where a hold command is defined). Alternatively, the power control circuit 12 may be arranged to generate power control feedback from a potentially coarse estimate of the control channel signal quality. For example, the signal quality estimate may be obtained by taking the absolute value of the RAKE (or G-RAKE) squared over the symbol values received for the control channel signal to obtain a noise power estimate. In any event, in generating the power control feedback during this initialization phase, the power control circuit 12 collects measurements (e.g., of received control channel symbols and (reference) channel estimates) and uses these measurements to estimate the gain factor.

In a stabilization phase operation, power control circuit 12 generates power control feedback for the control channel signal based on the gain factor estimate and the measured reference signal strength or quality. In addition, during the stabilization phase operation, the power control circuit 12 continually updates the gain factor so that it tracks the ongoing power control feedback generation. That is, the gain factor is adjusted up or down as needed to reflect changes in the control channel signal transmit power corresponding to the power control feedback generated by the wireless communication device 10 for that channel.

In at least one embodiment, the control channel signal comprises a plurality of repeating frames, each frame comprising a plurality of time slots, and the power control circuit is arranged to generate power control commands for the control channel signal during each time slot. In view of this channel timing and structure, power control circuit 12 generates per-slot Transmit Power Control (TPC) commands for controlling the transmit power of the control channel signal during an initialization phase using a predetermined sequence of commands or using potentially coarse measurements of the control channel signal quality. Once the gain factor estimate is available, the power control feedback generation transitions to a stabilization phase operation.

In the stabilization phase operation, the power control circuit 12 generates per-slot power control feedback for the control channel signal based on the gain factor estimate and the per-slot measurement of the reference channel signal quality or strength. As part of this process, the power control circuit 12 updates the gain factor as a function of its generation of power control commands per slot. I.e., up or down commands are generated on a slot-by-slot basis, the gain factor is incremented or decremented by the power control circuit 12 as appropriate to account for the corresponding change in control channel signal transmit power.

This adjustment may be based on the assumption that the (remote) transmitter accurately follows the power control feedback returned by the wireless communication device 10, or the adjustment may be based on an estimation process that takes into account the bias in the power control feedback process. For example, power control circuit 12 may be configured to estimate what the remote transmitter actually does in response to uplink power control commands returned by the wireless communication device, in accordance with the teachings of U.S. published patent application number 2003/0092447 ("447"), filed on 1/10/2005 by Bottomley et al.

In at least one embodiment of the stabilization operation, measurements are taken in each frame of the control channel signal to calculate a new estimate of the gain factor used in the next frame (e.g., using the starting value of the gain factor at the beginning of the next frame). Thus, the generation of per-slot power control in the current frame starts with the gain factor estimate of the previous frame and is adjusted during the current frame according to the process of generating reflected (reflex) power control feedback in the current frame. Of course, variations of this embodiment are contemplated, such as where one or more frames are used to calculate the gain factor, which is used as a basis for power control feedback generation in more than one consecutive frame.

In these embodiments, the original value of the gain factor is adjusted up or down in successive frames to track the power control command being generated. Since the tracking may not be completely accurate, the gain factor estimation error may accumulate in the recalculation, and thus the number of frames between recalculations of the gain factor may be set (set). More generally, as described in detail subsequently, the power control feedback generation taught herein allows for one or more mechanisms to reduce or eliminate the accumulation of errors, such as by reverting to an initialization phase from time to time or by periodically (e.g., frame-by-frame) recalculating gain factors.

Regardless of the details of such time slot/frame and error reduction, one embodiment of the power control feedback generation method taught herein generates power control feedback for a control channel signal by comparing the adjusted signal quality or strength to a corresponding target threshold. Using signal strength as an example, the power control circuit 12 is arranged to obtain an estimated signal strength from the reference channel signal and to obtain an adjusted signal strength by adjusting the estimated signal strength as a function of the current value of the gain factor. This adjusted signal strength effectively represents an indirect but accurate measurement of the control channel signal strength and so the power control circuit 12 generates up/down (or hold) power control commands for the control channel signal by comparing the adjusted signal strength to a target signal strength (which may be multiplied by a measurement of noise). The gain factor is then updated to reflect the power control commands generated by the comparison.

The same can be performed using estimated or adjusted signal quality. For example, step 100 of FIG. 2 illustrates one embodiment of signal quality based processing logic, and FIG. 3 illustrates a corresponding functional structure of one or more processing circuits including the power control circuit 12. It should be understood that this illustration may or may not represent a physical circuit implementation, e.g., depending on whether the power control circuit 12 is implemented in hardware or software, or a combination thereof. For example, in a software-based implementation, the illustrated circuit elements may include multiple processing functions implemented by stored computer program instructions, microcode, or the like.

For the illustrated embodiment, the power control circuit 12 includes an uplink TPC command generating circuit 30, an adjusted signal quality estimating circuit 32, a reference channel signal quality estimating circuit 34, a gain factor estimating circuit 36, and a gain tracking circuit 38, the gain tracking circuit 38 being incorporated in the gain factor estimating circuit 36.

For generating an uplink TPC command at a desired time (e.g., the current slot of the control channel signal), the uplink TPC command generating circuit 30 compares the adjusted signal quality to a target signal quality. A signal to interference plus noise ratio (SINR) may be used in the comparison. The interference plus noise includes all impairments in the system (e.g., inter-cell interference, intra-cell interference, and thermal noise). In at least one embodiment, the uplink TPC command generating circuit 30 outputs an up command (e.g., "1") if the adjusted signal quality is below the target signal quality. If the adjusted signal quality is above the target signal quality, the uplink TPC command generating circuit 30 generates a down command (e.g., "-1"). In some embodiments, a hold command is also generated.

The adjusted signal quality represents the reference channel signal quality estimate output by reference channel signal quality estimation circuit 34 adjusted by gain factor α' output by gain tracking circuit 38. For example, α' may be incremented up by the value of G in response to generating an up power control command, or decremented down by the value of G in response to generating a down power control command. It should also be noted that the gain tracking increment may use the value G_upWhile the gain tracking decrement may use the value G_down. In general, gain tracking adjustments should track incremental changes in the transmit power of the control channel signal made by the remote transmitter.

In any case, the gain factor α' is a dynamically updated version of the gain factor estimate α generated by the gain factor estimation circuit 36. The alpha value may be calculated based on measurements made on the control channel signal over a time window. Then α 'is set equal to α at the beginning of the next window and the gain factor α' is dynamically adjusted in the next window in response to the uplink TPC commands being generated. Generalizing to this logic, in any current window, measurements can be collected during the current window, so that a new value for α is calculated, which can be used in the next window.

Further, it should be noted that the alpha values and/or alpha' may be reset or recalculated from time to time as previously described herein. For example, fig. 4 illustrates an embodiment in which the control channel signal comprises an F-DPCH signal having repeated frames, wherein each frame comprises a plurality of time slots. The frame/slot structure of the control channel signal may be used to drive the recalculation of the gain factor alpha.

Fig. 5 illustrates one embodiment of power control feedback generation logic to supplement the frame/slot structure of the control channel signal shown in fig. 4.

The process starts with an initial frame of the F-DPCH signal in which the power control circuit 12 generates a transmit power control command without gain factor estimation using a coarse signal quality estimate or using a predetermined sequence of power control commands (step S120). Further, in this initial phase, power control circuit 12 generates an initial estimate of the gain factor, which may be used as an initial value for the gain factor for the first frame of the stabilization phase. The process continues assuming that the power control circuit 12 transitions to a stabilization phase and steps 122 to 130 illustrate the per frame/per slot processing for any ith frame of the F-DPCH during the stabilization phase processing. Therefore, from the beginning of the ith frame, the frame slot index k is set to 0 (step 122).

For each slot k of the ith frame, k ═ 0.., M-1, where M is the number of slots in the frame, power control circuit 12 calculates an estimate of the CPICH signal quality (e.g., CPICH SINR); based on alpha_i' (k) adjusting the CPICH signal, alpha_i' (k) denotes the dynamically updated value of the gain factor in slot k; by pairsComparing the adjusted signal quality with a target signal quality to generate an uplink TPC command for the time slot; updating alpha_i' (k) to be used in the next slot; and collects/stores the slot-specific measurements for recalculating the gain factors at the end of the frame (step 124).

If not at the end of the current frame (k ≠ M-1) (step 126), the slot index k is incremented (step 128) and the operation of step 124 is repeated for the next slot. If the end of the current frame (k-M-1) is reached, the gain factor for the next frame is recalculated (step 130). This prevents gain tracking errors from being left behind between frames. Of course, under certain circumstances, such errors may be minimal and the gain factors are not recalculated at the end of each frame.

Fig. 6 illustrates another functional circuit implementation of the power control circuit 12, and fig. 7 illustrates an implementation of corresponding processing logic. The circuits and associated processes of fig. 6 and 7 may be used to generate power control feedback on a slot-by-slot basis over multiple frames of a received control channel signal (and more generally for any given interval of interest in the received control channel signal), as in the circuits and associated processes of fig. 3 and 5, respectively.

Instead of using the adjusted signal quality as a basis for uplink TPC command generation, the power control circuit 12 of fig. 6 comprises mismatch (mismatch) value calculation circuitry 40, the mismatch value calculation circuitry 40 calculating and maintaining a mismatch value reflecting the delta between the target signal quality and the estimated signal quality, and the power control circuit 12 further comprises uplink TPC command generation circuitry 42, the uplink TPC command generation circuitry 42 being configured to generate the uplink TPC command by comparing the mismatch value with a mismatch target threshold.

With these circuits mentioned, the process of fig. 7 begins with an initialization phase (step 140) in which the power control circuit determines an initial gain factor estimate and mismatch value estimate for use in at least the first frame after the transition to the stabilization phase. Assuming that the operation has transitioned to the stabilization phase, the frame slot index k is set to 0 for the beginning of the ith frame (step 142).

For each slot k of the ith frame, power control circuit 12 calculates an estimate of the CPICH signal quality (e.g., CPICH SINR); adjusting the mismatch value m taking into account the measured change in the quality of the CPICH signal_i' (k); generating an uplink TPC command for the slot by comparing the adjusted mismatch value to a mismatch target threshold; updating mismatch value m_i' (k) to be used in the next frame; and collecting/storing time slot specific measurements for recalculating the gain factors at the end of the frame (step 144). If not at the end of the current frame (k ≠ M-1) (step 146), the slot index k is incremented (step 148) and the operation of step 144 is repeated for the next slot. If the end of the current frame (k-M-1) is reached, the gain factor for the next frame is recalculated (step 150). Alternatively, instead of recalculating the gain factors every frame, gain tracking is performed across multiple frames.

To better understand the above embodiment, let the gain factor of frame i when slot k is 0 beWhereinRepresenting the gain factor alpha calculated in the previous frame i-1_i-1Is estimated. Then, in any subsequent time slot k of frame i, α in linear units_iThe value of' (k) is given as follows:

(equation 1)

Where G denotes an incremental increase or decrease in transmit power associated with the uplink TPC command generated in slot k. G is commonly referred to as the power control step size. In logarithmic units (dB), the above value can be represented by the following formula:

(equation 2)

Thus, in any given time slot of the current frame, α_iA value of' (k) is equal toPlus or minus the cumulative effect of the TPC commands generated in the previous slot of the current frame. A mathematically simple way to maintain a 'over multiple slots of the current frame is to increment or decrement a' in each slot as a function of the TPC commands generated in the previous slot. For example, after the TPC command is generated in the current slot, the gain factor in slot k may be updated to α for use in k +1 slot_i′(k+1)＝α_i' (k)/G or alpha_i′(k+1)＝α_i' (k) G, which provides an increment or decrement of +/-GdB in logarithmic units.

Regardless of the particular method chosen to maintain the gain factor in the current frame, it is beneficial to describe an embodiment that collects measurements across the frame to support recalculation of the gain factor used in the next frame. As a non-limiting example, the receiver processing section of the receiver circuit 16 and/or the baseband processing circuit 14 operates as a RAKE receiver and RAKE output, i.e., the soft value (soft value) of the control channel symbol received at the k-th slot of the i-th frame can be expressed as the following expression:

(equation 3)

Wherein c is_i(k) Based on the network response determined by the reference channel and the combining weights,is a hard decision symbol value of the received symbol, and n_i(k) Is a noise sample. It should be noted that the network response describes the transmitter pulse shape, the radio channel and the receive filter response. In addition, the gain factor α can be maintained in the following two sections_i(k) The method comprises the following steps Baseline estimation of the overall gain factor (e.g., from a previous frame)Estimate); and a gain adjustment value g for tracking the generation of inter-slot power control commands within frame i_i(k) In that respect For example,

(equation 4)

Can convert g into_i(k) The values of (d) remain as:

(equation 5)

Where G is the downlink power control step size, β_i(j) Is an uplink TPC command generated by the wireless communication device 10 during the j-th slot of the i-th frame. The value of G may be set to a nominal value. For example, G may have a value of 1.122 corresponding to a 1dB step. Alternatively, the G value may be estimated by observing the RAKE receiver output between successive slots.

With the aforementioned (equation 4), it is possible to express (equation 3) as:

(equation 6)

Received control channel symbols are first demodulated and collected for generating a baseline overall gain factor α for the (i +1) th frame_i. Known as g_i(k)、c_i(k) Andis expressed as:

(equation 7)

Assume gain adjustment value g_i(k) Following the uplink TPC commands generated and transmitted by the wireless communication device 10. To prevent error propagation due to uplink TPC command reception errors or to prevent the transmitting base station from not following the uplink TPC command generated by wireless communication device 10, gain adjustment value g may be set in the last slot of each frame_i(k) Is set to 1, i.e. g_i(M-1)＝1，Where M is the number of slots per frame.

Z in all time slots of the current frame_i(k)、v_i(k) And n_i(k) Collecting the vector

z_i＝αv_i+n_i(equation 8)

The gain factor α for the current frame i based on (equation 8) can be_iThe Least Squares (LS) estimate of (a) is expressed as:

(equation 9)

It can be seen that the estimator of (equation 9) is also a Minimum Mean Square Error (MMSE) estimator. In any case, the initial gain factor value α for frame i is set_i' (k ═ 0) is set to the value obtained at frame (i-1) according to (equation 9), and then α is updated via consecutive slots_i' (k). Alternatively, for (equation 4), the running value of the gain factor for any slot k of frame i is given by the following equation:

(equation 10)

Regardless, the gain factor from frame (i-1)Provides the basis for SINR estimation at frame i. For example, if RAKE or generalized RAKE (G-RAKE) combining is used, the symbol SINR of the downlink TPC symbol received in slot k of frame i of the control channel signal is:

(equation 11)

Or

(equation 12)

Where w is the combining weights, h is the network response, and R is the covariance matrix for the impairments from the different fingers of the RAKE or G-RAKE combiner. Estimates of h and R may be obtained from measurements made on the received reference channel signal. Substituting the power offset between the CPICH and F-DPCH signals during the last slot of the previous frame intoIt should also be noted thatCorresponding to the CPICH symbol SINR. If G-RAKE combining is used, the term can be simplified as:

(equation 13)

Or

(equation 14)

To explain again, h^HR^-1h corresponds to the CPICH symbol SINR and can be estimated directly from the measurement of the received CPICH signal.

As a specific example of the above-described embodiment, reference may be made to fig. 8, in which the target signal quality of the F-DPCH signal is set at 3 dB. For the last time slot M-1 of frame i, the gain factor calculated in the previous frameIs-2.5 dB, and the gain is adjusted by a value g_i(M-1) is reset to 0 dB. Thus, byAnd g_i(M-1) is summed with the CPICH signal quality measured for slot M-1 of the i-frame (i.e., equal to 5dB + (-2.5dB) +0dB) to determine the adjustment signal generated by the uplink TPC command. Thus, the adjusted signal quality, which represents an approximation of the actual F-DPCH signal quality, is 2.5 dB. Comparing this value with the target signal quality of 3dB indicates that a (+) uplink TPC command is generated, indicating that the network transmitter should increase the transmit power of the F-DPCH.

Moving to the next frame, the process begins in time slot 0 of frame i +1, where the gain adjustment value g is adjusted_i+1(0) Updated to 1dB to reflect the (+) TPC command value just generated. Assuming that the measured signal quality of the CPICH is still 5dB at slot 0 of frame i +1, the adjusted signal quality is 5dB + (-2.5dB) +1dB is 3.5 dB. This value is compared to the target signal quality value of 3dB and the uplink TPC command generated for this 0 th slot is a (-) value, indicating that the transmit power of the F-DPCH signal should be reduced. This process is repeated for subsequent slots of frame i + 1.

Fig. 8 may also be understood to illustrate power control command generation in embodiments based on utilizing signal quality mismatch values. At the beginning of frame i +1, the mismatch value is initialized from the last slot of the previous frame to CPICH SINR (5dB) plus the gain factor (-2.5dB) minus the target F-DPCHSINR (3dB), resulting in an initial signal quality mismatch value of-0.5 dB. During slot 0, the value is incremented CPICH SINR by the change (0dB) and the effect of the previous TPC command (+1dB), resulting in an initial signal mismatch value of 0.5 dB. Since this value is positive, a down command is generated between slot 0 and slot 1 as shown in fig. 7. Similarly, at slot 1, the mismatch value is updated to-0.5 dB and an up command is generated. In slot 2, the mismatch value is 0.5dB and a down command is generated. In slot 3, the mismatch value is adjusted by a change of CPICH SINR (1dB) and the previous TPC (-1dB), resulting in a mismatch value of 0.5dB and generating another down command. In slot 4, the same situation occurs as in slot 3.

Regardless of whether an adjusted signal quality or mismatch is used in the power control feedback generation, the received estimates of the downlink symbols for the control channel signal are used during the estimation of the gain factor. For example, the F-DPCH symbols are typically detected using detection based on a Maximum Likelihood (ML) method. It is assumed that smaller values of noise implementation are more likely to occur than larger values of noise implementation. The symbols detected using ML in SINR estimation may be biased by underestimating noise variations. This deviation is taken into account in the methods taught herein. For example, a constant bias may be applied to the estimated F-DPCH SINR. Alternatively, the deviation can be avoided by squaring the output of the RAKE combiner before further averaging or smoothing. For example, by (equation 6), the magnitude squared of the output of the RAKE combiner for the k-th slot of the i-th frame is:

(equation 15)

Averaging the frame slots, an estimate of the gain factor for frame i can be obtained by the following equation:

(equation 16)

WhereinIs an estimate of the noise plus interference power, which can be estimated separately from the received CPICH signal.

In the embodiment of fig. 8, the inner loop power control of the F-DPCH has stabilized during the M-1 slot of frame i, so that the F-DPCH SINR is within the step size of the target SINR. It should be noted that this situation is not essential. Continuing with this embodiment, to determine the uplink TPC command during slot 4 of frame i +1, wireless communication device 10 estimates the CPICH symbol to be 7 dB. The last CPICH SINR is compared to CPICH SINR (in the case of the stabilization phase being implemented) of slot M-1 of the previous frame i, increased by +2 dB. Next, the "up" command and the "down" uplink TPC command generated by the wireless communication apparatus 10 between the M-1 slot of the frame i and the previous slot of the current frame (i.e., slot 3 of the i +1 th frame) are counted, there are two "up" commands and three "down" commands, which means that the transmit power of the F-DPCH is reduced by 1dB (this representation is based on the assumption that the uplink TPC command is correctly received and the network transmitter responsible for transmitting the F-DPCH signal to the wireless communication apparatus 10 operates on the command).

Since the gain of the DPCH SINR is greater than the assumed reduction of the F-DPCH transmit power, the uplink TPC command to be generated in slot 4 of frame i +1 must be set to a "down" value. It is noted that while the adjusted signal quality used to determine the uplink TPC commands represents an estimate of the actual F-DPCH signal quality, this approach to transmit power control does not require any explicit estimate of the F-DPCH symbol SINR. That is, the adjusted signal quality profile may be compared to an indirect but accurate estimate of the F-DPCH signal quality as the target signal quality for the F-DPCH. (equivalently, the mismatch value can be compared to a corresponding mismatch target threshold).

Whether using adjusted signal quality or mismatch values, comparing the calculated quality or mismatch to a target on a slot-by-slot basis embodies an "inner loop" power control mechanism in which the wireless communication device 10 generates successive up, down (or hold) commands by comparing the adjusted signal quality or strength or mismatch values to corresponding thresholds. The wireless communication device 10 may be further configured to perform "outer loop" power control, wherein it adjusts the target threshold based on some performance metric.

For example, a Command Error Rate (CER) may be estimated using received downlink commands for control channel signals, which may be used as a basis for outer loop power control adjustment of a target threshold by wireless communication device 10. Alternatively or additionally, CER or other performance indicators may be used to adjust one or more gain factors, mismatch value estimates, or reference channel signal quality estimates.

For example, if the estimated CER is higher than the target CER, the gain factor may be adjusted downwardTo reflect the fact that the effective signal quality of the received F-DPCH signal is lower than indicated by the currently determined adjusted signal quality. For gain factorThe CER-based adjustment of (c) may be based on, for example, a step size of 1 dB. Subsequent gain factorRemain unchanged until it is recalculated or until a new CER is estimated.

As another example, a target signal quality to which the adjusted signal quality is compared as a function of the CER estimate may be adjusted. That is, if the estimated CER exceeds the target CER value, the target signal quality may be adjusted upward by, for example, 1 dB. Conversely, if the estimated CER is below the target CER value, the target signal quality may be adjusted downward by 1 dB. As a further alternative, when the estimated CER is too large, the target signal quality may be adjusted upward by "a" dB, where a equals a certain value. Then, from time to time (and without necessarily measuring CER), the target signal quality is adjusted downward by "B" dB, where B is a number that is typically less than a. At some point, the CER is again estimated and compared to the target CER. If the estimated CER exceeds the target CER value, the target signal quality is ramped up again (jump up). Conversely, if the estimated CER is below the target CER value, the target signal quality may be reduced by B dB. In the alternative, mismatch values may be estimated and/or gain factors may be appliedThe same "jump up" based method is applied.

When considering the CER estimate in case of receiving downlink TPC commands on F-DPCH signals, the relevant criteria indicate that: the TPC symbols are transmitted as same valued bit pairs (same valued bit pairs). Thus, the two bits received in each downlink TPC symbol should be the same, and if the bit values are different, the reception of a given TPC symbol is considered erroneous.

Thus, the initial point in the analysis of the CER determination on the F-DPCH begins when it is noted that there may be two different TPC command symbols, but the underlying symbol modulation is the same for both command symbols. Thus, the TPC command symbol may be represented by the following equation:

u＝u₀TPC (equation 17)

Where TPC ∈ { -1, 1) is a TPC command (where-1 denotes logical down and 1 denotes logical up) and the base (unsigned) modulation symbol is:

(equation 18)

The received TPC command (i.e., the received TPC symbol) may be estimated using Maximum Ratio Combining (MRC) of the following equation:

(equation 19)

WhereinAndis estimated from the CPICH. The individual TPC symbol bits TPC may be estimated according to the following equation_rAnd TPC_i：

(equation 20)

And

(equation 21)

In addition, by definition, the two transmit bits in each TPC symbol are equal. Thus, each estimated TPC symbol can be represented by the following equation:

(equation 22)

WhereinAndboth are estimated based on the CPICH. It should be noted that the MRC is a special form of G-RAKE combining that may be used.

In the analysis framework described above, it was shown that the Additive White Gaussian Noise (AWGN) mapping between SINR and CER is relatively channel independent, which makes it possible to map the CER target directly to the SINR target. (it should also be noted that the AWGN mapping is obviously valid for AWGN channels, and in addition AWGN mapping may also approximate other types of channels well). More specifically, supposeAndis h_fAnd I_fGood approximation of (d), the following equation can be obtained:

TPC_estsign (TPC + n) (equation 23)

Wherein

(equation 24)

The TPC Command Error Rate (CER) can therefore be expressed as:

(equation 25)

And the variance of n (assuming uncorrelated noise) is given by:

(equation 26)

Thus, the CER is determined as SINR (E) by (equation 26)_s/N₀) And may use the functional mapping to identify a target SINR for inner loop power control corresponding to an expected (target) CER. That is, with knowledge that two bits are equal according to each power control command received on the F-DPCH signal by definition, the probability of receiving a command with unequal bits can be converted to a CER estimate according to a probability-CER function. The method is based on the recognition that the relationship between the probability of receiving unequal command bits and the CER is channel independent.

Assuming that the noise in the given received power control command is uncorrelated with respect to the two estimated soft TPC bits (soft TPC bits), the two estimated hard bits (TPC bits) are given by the following equation_r.，TPC_iE {1, -1}) is not equal:

(equation 27)

Wherein SIR is E_b/N₀Is the estimated SINR of the TPC bit, and variable x₁And x₂Indicating the received TPC bits located in the specified power control command. Thus, the CER is given by the formula:

(equation 28)

A suitable polynomial approximation of the probability-CER mapping function is given by:

CER_est＝2.31·ζ³+0.141ζ-4.91·10^-3(equation 29)

Wherein the command reception error probability of unequal TPC bits may be estimated as:

(equation 30)

And where λ ∈ [0, 1] is the filter constant (exponentially weighted filter). For W-CDMA applications, a suitable value for the time constant corresponding to 100 slots is λ 0.99, which compensates for the 10 to 30 reception errors (unequal TPC command bits) expected to occur during the time constant. The frequency at which the reception error occurs should generally be sufficient to satisfy excellent CER estimation performance.

Co-pending and commonly assigned U.S. patent application No. 11/296,560, filed on 7.12.2005 under attorney docket No. 4015 and 5333/P20843-US2 entitled "Method and Apparatus for communicating Channel Error Rate evaluation". The interested reader is referred to this application for further details regarding CER estimation and related mapping details.

It should of course be noted that the proposed method for determining uplink TPC commands for an F-DPCH or, more generally, for any received control or data channel of interest may further be used to estimate the average Bit Error Rate (BER) for that channel of interest. For example, at the beginning of the power control of the F-DPCH, the estimated SINR of the F-DPCHIs available and can therefore be used to estimate the average BER of the received F-DPCH signal. Then, in the stabilization phase, the wireless communication device 10 may use the current CPICH SINR and the accumulated uplink TPC commands from the reference slot to determine the F-DPCH symbol SINR.

As an example, since the gain of CPICH SINR is 1dB more than the reduction of the F-DPCH transmit power from the M-1 slot of frame i in fig. 8, it can be inferred that the F-DPCH symbol SINR of slot 4 of frame i +1 in fig. 8 is 1dB higher than the F-DPCH symbol SINR of slot M-1 (reference slot) of frame i. Since the F-DPCH symbol SINR is 2.5dB at slot M-1 of frame i, the F-DPCH symbol SINR at slot 4 of frame i +1 is estimated to be 3.5 dB.

The estimated F-DPCH symbol SINR may be mapped to an estimated Bit Error Rate (BER), e of the F-DPCH_i(k) The above. For example:

(equation 31)

Where erfc represents the complementary error function and SINR, r are linear units. The SINR-BER mapping may further take into account implementation margins of the wireless communication device, e.g.,where L is the implementation penalty. In any case, the average BER of the iF-DPCH frame can be obtained by the following equation

(equation 32)

In considering the above application and scope of embodiments, it should be understood that the present invention is not limited by the foregoing description, nor is it limited by the accompanying drawings. Rather, the invention is limited only by the claims and their legal equivalents.

Claims

1. A wireless communication device configured to receive a reference channel signal and a control channel signal, the wireless communication device comprising:

a power control circuit arranged to generate power control feedback for the control channel signal in dependence on the estimated signal quality or signal strength of the reference channel signal and the estimated gain factor relating to both the control channel signal and the reference channel signal,

wherein the power control circuit comprises:

a signal quality estimation circuit that generates an estimated signal quality of the reference channel signal;

a gain factor estimation circuit for calculating the gain factor;

a gain tracking circuit for tracking gain factor variations occurring in the ongoing generation of the power control feedback;

a signal quality adjustment circuit that maintains an adjusted signal quality by adjusting the estimated signal quality as a function of the gain factor and the gain factor variation; and

an uplink power control command generation circuit that generates an uplink power control command based on a comparison of the adjusted signal quality and a target signal quality.

2. The wireless communication apparatus of claim 1, wherein the power control circuit is configured to: estimating a command error rate, CER, of commands received in respect of the control channel signal as a performance indicator for the power control feedback being generated, and

the power control circuit is further arranged to compare the CER to a target CER and, based on the comparison, adjust any one or more of a target signal quality, a gain factor, and the estimated signal quality.

3. The wireless communications apparatus of claim 1, wherein the power control circuit is configured to recalculate the gain factor at specified time instants and maintain an updated value of the gain factor between the specified time instants by tracking power control feedback generated between the time instants.

4. The wireless communications apparatus of claim 1, wherein the control channel signal is organized into a plurality of repeating frames, each frame having a plurality of time slots, and the power control circuit is configured to generate power control feedback for the control channel signal in a current frame of the control channel signal by generating an uplink control command in each time slot of the current frame, the uplink control command being a function of the updated value of the gain factor and a per-slot estimate of a quality or strength of a reference channel signal.

5. The wireless communication apparatus of claim 4, wherein the power control circuit is configured to: maintaining the updated value of the gain factor during a plurality of time slots of a current frame by setting an initial value of the gain factor to a value calculated in a previous frame of the control channel signal and further tracking each time slot variation of the initial value corresponding to the generated uplink power control command during a subsequent time slot of the current frame.

6. The wireless communication apparatus of claim 5, wherein the power control circuit is configured to: at an arbitrarily designated current frame, an initial value of a gain factor for a next frame is calculated based on soft values received for the control channel signal during the current frame and a network response generated by channel estimation performed on the reference channel signal during the current frame.

7. The wireless communications apparatus of claim 1, wherein the power control circuit is configured to estimate the gain factor as a function of measurements made during a specified time interval such that the power control circuit operates in an initialization phase at least until a first such time interval is completed, wherein the power control circuit generates the power control feedback for the power control channel according to a predetermined sequence of power control commands during the initialization phase.

8. The wireless communication apparatus of claim 1, wherein the wireless communication apparatus is configured in accordance with a wideband code division multiple access (W-CDMA) standard, and wherein the reference channel signal comprises a common pilot channel (CPICH) signal and the control channel signal comprises a fractional dedicated physical channel (F-DPCH) signal.

9. A wireless communication device configured to receive a reference channel signal and a control channel signal, the wireless communication device comprising:

wherein the power control circuit comprises:

a gain factor estimation circuit for calculating the gain factor;

a mismatch value circuit for calculating an initial mismatch value as a function of the estimated signal quality and the gain factor and maintaining an updated mismatch value as a function of the estimated signal quality change and the gain factor change; and

uplink power control command generation circuitry to generate an uplink power control command in accordance with comparing the updated mismatch value to a mismatch target threshold.

10. The wireless communication apparatus of claim 9, wherein the power control circuit is configured to: estimating a command error rate, CER, of commands received with respect to the control channel signal as a performance indicator for the power control feedback being generated, and

the power control circuit is further arranged to compare the CER to a target CER and, based on the comparison, adjust any one or more of the mismatch target threshold, the initial mismatch value or an updated mismatch value, the gain factor and the estimated signal quality.

11. The wireless communications apparatus of claim 9, wherein the power control circuit is configured to recalculate the gain factor at specified time instants and maintain an updated value of the gain factor between the specified time instants by tracking power control feedback generated between the time instants.

12. The wireless communications apparatus of claim 9, wherein the control channel signal is organized into a plurality of repeating frames, each frame having a plurality of time slots, and the power control circuit is configured to generate power control feedback for the control channel signal in a current frame of the control channel signal by generating an uplink control command in each time slot of the current frame, the uplink control command being a function of the updated value of the gain factor and a per-slot estimate of a quality or strength of a reference channel signal.

13. The wireless communication apparatus of claim 12, wherein the power control circuit is configured to: maintaining the updated value of the gain factor during a plurality of time slots of a current frame by setting an initial value of the gain factor to a value calculated in a previous frame of the control channel signal and further tracking each time slot variation of the initial value corresponding to the generated uplink power control command during a subsequent time slot of the current frame.

14. The wireless communication apparatus of claim 13, wherein the power control circuit is configured to: at an arbitrarily designated current frame, an initial value of a gain factor for a next frame is calculated based on soft values received for the control channel signal during the current frame and a network response generated by channel estimation performed on the reference channel signal during the current frame.

15. The wireless communications apparatus of claim 9, wherein the power control circuit is configured to estimate the gain factor as a function of measurements made during a specified time interval such that the power control circuit operates in an initialization phase at least until a first such time interval is completed, wherein the power control circuit generates the power control feedback for the power control channel according to a predetermined sequence of power control commands during the initialization phase.

16. The wireless communication apparatus of claim 9, wherein the wireless communication apparatus is configured in accordance with a wideband code division multiple access (W-CDMA) standard, and wherein the reference channel signal comprises a common pilot channel (CPICH) signal and the control channel signal comprises a fractional dedicated physical channel (F-DPCH) signal.

17. A method of generating power control feedback for a control channel signal received along with a reference channel signal, the method comprising the steps of:

a calculation step of calculating a gain factor relating to both the control channel signal and a reference channel signal;

a determining step of determining an estimated signal quality or strength of the reference channel signal; and

a generating step of generating a power control feedback for the control channel signal as a function of the estimated signal quality or strength and the gain factor.

18. The method of claim 17, further comprising generating power control feedback for the control channel signal according to a predetermined sequence of power control commands if the gain factor is not available.

19. The method of claim 17, wherein calculating gain factors related to both the control channel signal and the reference channel signal comprises calculating gain factors at specified time instances, maintaining updated values of the gain factors between the specified time instances, and using the updated values to generate the power control feedback.

20. The method of claim 19, wherein maintaining the updated value of the gain factor between the specified time instances comprises: tracking changes in the gain factor corresponding to the power control feedback generated between the specified time instances.

21. The method of claim 17, wherein calculating a gain factor related to both the control channel signal and a reference channel signal comprises:

the gain factor is calculated from soft values of symbols associated with the control channel signal received during a specified time interval and from a network response calculated from channel estimation performed on the reference channel signal during the specified time interval.

22. The method of claim 17, wherein generating power control feedback for the control channel signal as a function of the estimated signal quality or strength and the gain factor comprises:

generating an estimated signal quality for the reference channel signal;

obtaining an adjusted signal quality by adjusting the estimated signal quality based on the gain factor; and

generating an uplink power control command by comparing the adjusted signal quality to a target signal quality.

23. The method of claim 22, further comprising:

updating a gain factor as a function of the uplink power control commands generated by the comparing such that the gain factor tracks changes in gain of the control channel signal corresponding to the uplink power control commands generated by the power control circuit.

24. The method of claim 22, further comprising:

estimating a commanded error rate, CER, of the received commands for the control channel signal as a performance indicator for the power control feedback being generated, comparing the CER to a target CER, and adjusting any one or more of the target signal quality, the gain factor, and the estimated signal quality based on the comparison.

25. The method of claim 17, wherein generating power control feedback for the control channel signal as a function of the estimated signal quality or strength and the gain factor comprises:

generating an estimated signal quality of the reference channel signal;

calculating an initial mismatch value as a function of the estimated signal quality, the gain factor, and a target signal quality;

maintaining an updated mismatch value by tracking changes in the estimated signal quality and gain factor; and are

Generating an uplink power control command by comparing the updated mismatch value to the target signal quality.

26. The method of claim 25, further comprising:

estimating a commanded error rate, CER, of the received commands for the control channel signal as a performance indicator for the power control feedback being generated, comparing the CER to a target CER, and adjusting any one or more of the adapted target threshold, the gain factor and the estimated signal quality based on the comparison.

27. The method of claim 17, further comprising:

the gain factor is recalculated at specified time instants and an updated value of the gain factor is maintained between the specified time instants by tracking power control feedback generated between these time instants.

28. The method of claim 17, wherein the control channel signal is organized into a plurality of repeating frames, each frame having a plurality of time slots, and generating power control feedback for the control channel signal comprises:

generating an uplink control command in each time slot of the current frame, the uplink control command being a function of the updated value of the gain factor and a per-slot estimate of the quality or strength of a reference channel signal.

29. The method of claim 28, wherein determining the estimated signal quality or strength of the reference channel signal comprises: determining an estimated signal quality for each time slot; and is

The step of calculating a gain factor associated with both the control channel signal and a reference control channel signal comprises:

maintaining an updated value of the gain factor during subsequent time slots of the current frame, the gain factor being a function of uplink power control commands generated in these successive time slots.

30. The method of claim 29, further comprising setting an initial value of the gain factor to a value calculated in a previous frame of the control channel signal, the step of maintaining an updated value of the gain factor comprising tracking a change per slot of the initial value corresponding to the uplink power control commands generated during successive slots of the current frame.

31. The method of claim 30, further comprising:

an initial value of a gain factor for a next frame is calculated based on soft values received for the control channel signal during the current frame and a network response generated from channel estimation performed on the reference channel signal during the current frame.

32. The method of claim 17, wherein the reference channel signal comprises a common pilot channel-CPICH-signal and the control channel signal comprises a fractional dedicated physical channel signal-F-DPCH-signal.

33. A power control circuit for use in a wireless communication device arranged to receive a reference channel signal and a control channel signal, the power control circuit being arranged to generate power control feedback for the control channel signal based on an estimate of the signal quality or strength of the reference channel signal and an estimate of a gain factor related to both the control channel signal and the reference channel signal, the power control circuit comprising:

a signal quality estimation circuit for generating an estimated signal quality of the reference channel signal;

a gain factor estimation circuit for calculating the gain factor;

a signal quality adjustment circuit for maintaining an adjusted signal quality by adjusting the estimated signal quality as a function of the gain factor and the gain factor variation; and

an uplink power control command generation circuit to generate an uplink power control command based on a comparison of the adjusted signal quality and a target signal quality.

34. The power control circuit of claim 33, wherein the power control circuit is configured to: estimating a commanded error rate, CER, of a received command in respect of the control channel signal as a performance indicator of ongoing power control feedback generation, and further arranged to compare the CER with a target CER and, based on the comparison, to adjust any one or more of a target signal quality, the gain factor and the estimated signal quality.

35. A power control circuit according to claim 33 wherein the power control circuit is arranged to recalculate the gain factor at specified times and maintain updated values of the gain factor between these specified times by tracking power control feedback generation occurring between these times.

36. The power control circuit of claim 33 wherein the control channel signal is organized into a plurality of repeating frames, each frame having a plurality of time slots, and the power control circuit is arranged to: generating power control feedback for a control channel signal in a current frame of the control channel signal by generating an uplink control command in each time slot of the current frame, the uplink control command being a function of the updated value of the gain factor and an estimate of each time slot of a quality or strength of a reference channel signal.

37. The power control circuit of claim 36, wherein the power control circuit is arranged to maintain the updated values of the gain factors during the plurality of time slots by setting an initial value of the gain factor to a value calculated in a previous frame of the control channel signal, and further by tracking a change per time slot of the initial value corresponding to the uplink power control command generated during a subsequent time slot of the current frame.

38. The power control circuit of claim 37, wherein the power control circuit is configured to: at an arbitrarily designated current frame, an initial value of a gain factor for a next frame is calculated from soft values received during the current frame with respect to the control channel signal and a network response generated by channel estimation performed on the reference channel signal during the current frame.

39. A power control circuit according to claim 33 wherein the power control circuit is arranged to estimate the gain factor as a function of measurements taken during a specified time interval such that the power control circuit operates in an initialisation phase at least until completion of a first such time interval, wherein the power control circuit generates the power control feedback for the power control channel in accordance with a predetermined sequence of power control commands during the initialisation phase.

40. The power control circuit of claim 33 wherein the wireless communication device is configured in accordance with wideband code division multiple access-W-CDMA-standard and wherein the reference channel signal comprises a common pilot channel-CPICH-signal and the control channel signal comprises a fractional dedicated physical channel-F-DPCH-signal.

41. A power control circuit for use in a wireless communication device arranged to receive a reference channel signal and a control channel signal, the power control circuit being arranged to generate power control feedback for the control channel signal based on an estimate of the signal quality or strength of the reference channel signal and an estimate of a gain factor related to both the control channel signal and the reference channel signal, the power control circuit comprising:

a gain factor estimation circuit for calculating the gain factor;

a mismatch value circuit to calculate an initial mismatch value as a function of the estimated signal quality and the gain factor and to maintain an updated mismatch value as a function of estimated signal quality changes and gain factor changes; and

42. The power control circuit of claim 41 wherein the power control circuit is arranged to: estimating a commanded error rate, CER, of received commands for the control channel signal as a performance indicator for the generation of ongoing power control feedback, and further arranged to compare the CER to a target CER, and based on the comparison, to adjust any one or more of the mismatch target threshold, the initial or updated mismatch value, the gain factor and the estimated signal quality.

43. A power control circuit according to claim 41 wherein the power control circuit is arranged to recalculate the gain factor at specified times and maintain updated values of the gain factor between these specified times by tracking power control feedback generation occurring between these times.

44. The power control circuit of claim 41 wherein the control channel signal is organized into a plurality of repeating frames, each frame having a plurality of time slots, and the power control circuit is arranged to: generating power control feedback for a control channel signal in a current frame of the control channel signals by generating an uplink control command in each time slot of the current frame, the uplink control command being a function of the updated value of the gain factor and an estimate of each time slot of a quality or strength of a reference channel signal.

45. The power control circuit of claim 44, wherein the power control circuit is arranged to maintain the updated values of the gain factors during the plurality of time slots by setting an initial value of the gain factor to a value calculated in a previous frame of the control channel signal, and further by tracking a change per time slot of the initial value corresponding to the uplink power control command generated during a subsequent time slot of the current frame.

46. The power control circuit of claim 45 wherein the power control circuit is arranged to: at an arbitrarily designated current frame, an initial value of a gain factor for a next frame is calculated from soft values received during the current frame with respect to the control channel signal and a network response generated by channel estimation performed on the reference channel signal during the current frame.

47. A power control circuit according to claim 41 wherein the power control circuit is arranged to estimate the gain factor as a function of measurements taken during a specified time interval such that the power control circuit operates in an initialisation phase at least until completion of a first such time interval, wherein the power control circuit generates the power control feedback for the power control channel in accordance with a predetermined sequence of power control commands during the initialisation phase.

48. The power control circuit of claim 41 wherein the wireless communication device is configured in accordance with wideband code division multiple access-W-CDMA-standards, and wherein the reference channel signal comprises a common pilot channel-CPICH-signal and the control channel signal comprises a fractional dedicated physical channel-F-DPCH-signal.