HK1091049A - Downlink power control with limit to dynamic range using detection of downlink transmit power - Google Patents

Description

Downlink power control with limited dynamic range using detection of downlink transmit power

Technical Field

The present disclosure relates generally to wireless communication systems. In particular, the present invention relates to power control in such systems.

Background

In this specification, terms such as base station (base station), wireless transmit/receive unit (wtru), and mobile unit (mobile unit) are used in their common meaning. In this specification, a wtru includes, but is not limited to, a user equipment, mobile station, fixed or mobile subscriber unit, pager, or any other type of device capable of operating in a wireless environment. WTRUs include personal communication devices such as telephones, video telephones, and internet telephones (internet telephones) with network connectivity. In addition, WTRUs include portable personal computing devices such as PDAs and notebook computers with wireless modems having similar network capabilities. WTRUs that are portable or otherwise change location are referred to as mobile units. In the following description, a base station refers to a WTRU and includes, but is not limited to, base stations, Node bs, site controllers, access points, or other interfacing devices in a wireless environment.

Wireless telecommunication systems are well known in the art. To provide a globally connectable wireless system, a number of standards have been developed and implemented. One current standard that is widely used is known as the pan-European digital Mobile telephone System (GSM). The system is considered to be a so-called second generation mobile radio system standard (2G) and is followed by a revision (2.5G). GPRS and EDGE are both examples of 2.5G technologies that provide higher speed data transfer services over (2G) GSM network systems. Each of these standards is intended to improve upon conventional standards with additional features and enhancements. In 1998, the European Telecommunications standards institute-Special Mobile group (ETSI SMG) agreed to a third generation radio Access architecture called the Universal Mobile Telecommunications System (UMTS). To further utilize the UMTS standard, the third generation partnership project (3GPP) was constructed in december 1998. The 3GPP is continuously working on a common third generation mobile radio standard.

A typical UMTS system architecture in accordance with current 3GPP specifications is depicted in FIG. 1. The UMTS network architecture includes a Core Network (CN) interconnected to a UMTS Terrestrial Radio Access Network (UTRAN) via an interface known as Iu and well defined in current publicly available 3GPP specification documents. The UTRAN is configured to provide wireless telecommunication services to users through wireless transmit/receive units (WTRUs), which are shown in 3GPP as User Equipments (UEs), over a radio interface known as Uu. The UTRAN has one or more Radio Network Controllers (RNCs) and base stations, shown in 3GPP as B-type nodes, which together provide a geometric coverage area for wireless communications with UEs. One or more node bs are connected to each RNC via an interface known as Iub in 3 GPP. The UTRAN may have several groups of B-nodes connected to different RNCs; two sets are shown in the example of fig. 1. When more than one RNC is provided in a UTRAN, inter-RNC communication is performed via an Iur interface.

Communications occurring outside of the network elements are conducted by the node B at a user level via the Uu interface and by the CN at a network level via respective CN connections to external systems.

Generally, the primary function of base stations (e.g., node-bs) is to provide a radio connection between the base station's network and WTRUs. Typically, a base station sends out common channel signals to allow unconnected WTRUs to become synchronized with the timing of the base station. In 3GPP, a node B performs physical radio connections with UEs. The node B receives signals from the RNC over the Iub interface for controlling radio signals transmitted by the node B over the Uu interface.

A CN is responsible for scheduling information to its correct destination. For example, the CN may schedule voice traffic (traffic) received by the UMTS via one of several node bs from a UE to a Public Switched Telephone Network (PSTN) or packet data intended for the internet.

The RNCs generally control the internal functions of the UTRAN. The RNCs also provide intermediary services for communication with a local component connected to a node B via a Uu interface and an external service component via a connection between the CN and an external system, such as a foreign telephone call made from a cellular telephone within a home UMTS.

Adaptive transmit power control algorithms are used in many wireless communication systems. In such systems, many communications may share the same radio spectrum. When a particular communication is received, all other communications using the same frequency spectrum may cause interference to the particular communication. Thus, an increase in the transmission power level of one communication degrades the signal quality of all other communications within the spectrum. However, excessive reduction of the transmission power level may also result in unacceptable received signal quality, such as signal-to-interference ratios (SIRs) measured at the receiver. In 3GPP W-CDMA systems, power control is used as a link adaptation method. Dynamic power control is applied to Dedicated Physical Channels (DPCHs) such that the transmission power of the DPCHs is adjusted to achieve a certain quality of service (QoS) at a minimum transmission power level, thereby limiting the interference level within the system.

One solution is to divide the transmission power control into separate parallel procedures, called Outer Loop Power Control (OLPC) and Inner Loop Power Control (ILPC). Basically, the power level of a particular transmitter is based on a target SIR value. In OLPC, the quality of the received signal is measured when a receiver receives transmitted data within a frame interval. For a TDD signal, each frame interval includes a set of time slot division (time slot division). The transmitted information is sent in Transport Blocks (TBs) and the received signal quality is monitored on a block error rate (BLER) basis. The BLER is estimated by the receiver, typically by a Cyclic Redundancy Check (CRC) of the data. The estimated BLER is compared to a target quality requirement, such as a target BLER, representative of QoS requirements for various types of data services on the channel. A target SIR adjustment control signal is generated for each CCTrCH based on the measured received signal quality.

In a 36PP wideband code division multiple access (W-CDMA) system employing Time Division Duplex (TDD) mode, the UTRAN (SRNC-RRC) sets an initial target SIR for the WTRU when a call/negotiation is established and then continuously adjusts the WTRU's target SIR during the time of the call based on observations of Uplink (UL) BLER measurements.

In the closed loop ILPC, the receiver compares a measured value of the received signal quality (e.g., SIR) for each DPCH to a target SIR. If the SIR exceeds the threshold, a Transmit Power Control (TPC) command is issued to decrease the power level. If the SIR is below the threshold, a TPC command is issued to increase the power level. Typically, the TPC command is either +1 or-1 bits multiplexed with data in a dedicated channel to the transmitter. The transmitter changes its DPCHs transmit power level by a predetermined step size in response to the received TPC bits.

However, if the base station has reached its maximum or minimum downlink power and is no longer able to respond to increasing (in the case of having reached maximum power) or decreasing (in the case of having reached minimum power) requests for TPC commands, the OLPC algorithm may continue to increase or decrease the target SIR. In addition, the base station may not be able to respond correctly to the TPC command bits due to poor signal quality. Eventually, the target SIR may be increased or decreased to the point where it takes a long time to return to the correct value, which may negatively impact system performance.

Disclosure of Invention

In a wireless receiver, an apparatus and method are provided for downlink transmit power detection by a base station to limit the dynamic range of power control. The transmit power control adjustments occur in increments of step size in response to a comparison of the received signal quality measurements to an adjustable target signal quality. Performing a power control dynamic range limiting algorithm that sets minimum and maximum thresholds for received signal quality measurements; measuring delta power variation of a received signal quality measurement of a downlink channel over a time interval; estimating, at the receiver, a transmit power level difference size; calculating an accumulated power variation based on the delta power variation and the estimated transmission power step size; comparing the accumulated power value to minimum and maximum thresholds; and sends a control signal for adjusting transmission power control. The target signal quality adjustments are deactivated if the accumulated power value is within a predetermined proximity to the maximum or minimum threshold, and activated if the accumulated power value is not within a predetermined proximity to the maximum or minimum threshold.

Broadly, the present invention also discloses a transmission power control method for a wireless transmit/receive unit (WTRU) transmitting data signals in first and second forward channels, wherein the WTRU is configured to make a first forward channel power adjustment as a function of a target metric calculated by a receiving WTRU based on data signals received over the first forward channel. Preferably, the transmitting WTRU is a base station. The method preferably includes receiving data signals from the WTRU on the first forward channel and on the second forward channel. A target metric for a first forward channel power adjustment of the WTRU is calculated based on detection of a predetermined error condition in a signal received on the first forward channel. A power difference between the data signal received for the first forward channel and the data signal received for the second forward channel is calculated. A first forward channel transmit power adjustment signal is sent to the transmitting WTRU for a reverse channel based on the calculated target metric and dependent on the calculated power difference. Preferably, the transmitting WTRU transmits data signals on the dedicated channel and the common channel such that the first forward channel signals are downlink dedicated channel signals and the second forward channel signals are downlink common channel signals. In this case, transmitting the first forward channel transmit power adjustment signal on a reverse channel includes transmitting the transmit power adjustment signal for the dedicated downlink channel on an uplink channel.

The method may be implemented in a receiving wireless transmit/receive unit (WTRU) that includes a receiver configured to receive data signals of a first forward channel from a transmitting WTRU and to receive data signals of a second forward channel from the transmitting WTRU. A processor is provided that is preferably configured to calculate a target metric for performing a first forward channel transmission power adjustment in the transmitting WTRU based on detection of a predetermined error condition in the data signal received on the first forward channel and to calculate a power difference between the data signal received on the first forward channel and the data signal received on the second forward channel. A transmitter is operatively associated with the processor and is configured to transmit a first forward channel transmission power adjustment signal on a reverse channel in response to target metric calculations made by the processor and in dependence upon a power difference calculated by the processor. Preferably, the transmitting WTRU is a base station that transmits data signals on both dedicated and common channels, with the receiver configured to receive downlink data signals on a dedicated channel as the first forward channel receive signal and receive downlink data signals on a common channel as the second forward channel receive signal, and the transmitter configured to transmit power adjustment signals for the dedicated downlink channel on an uplink channel.

Other objects and advantages of the present invention will become apparent to those skilled in the art from the following description and the accompanying drawings.

Drawings

Fig. 1 depicts a general diagram of a system architecture of a conventional UMTS network.

Fig. 2 depicts a block diagram of a receiving station implementing OLPC with limits on downlink power control dynamic range in accordance with the present invention.

Fig. 3A and 3B depict a flow chart of a method for a transmission power detection algorithm.

FIG. 4 depicts a flowchart of a method for evaluating ILPC step size for the algorithms shown in FIGS. 3A and 3B.

Detailed Description

Although the embodiments below are described in terms of a third generation partnership project (3GPP) wideband code division multiple access (W-CDMA) system, the embodiments are applicable to any hybrid Code Division Multiple Access (CDMA)/Time Division Multiple Access (TDMA) communication system. Moreover, the embodiments are generally applicable to CDMA systems such as CDMA2000, TD-SCDMA, and the recommended Frequency Division Duplex (FDD) mode of 3GPP W-CDMA.

Figure 2 depicts a block diagram of a WTRU 10 that includes an RRC layer 30 and a layer 1 control/layer 1 entity 15, and RAKE receiver 21. WTRU 10 communicates with base station 90 and receives a downlink communication 85 from base station 90. Downlink communications 85 include dedicated physical channel received signal code power (DPCH RSCP), DPCH SIR, and common pilot channel (CPICH) RSCP, which conveys downlink transmit power information to WTRU 10.

The RRC layer 30 includes an RRC control 31. As part of a starting configuration for a DL-specific CCTrCH, the SRNC selects DL power control related parameters (e.g., target BLER for each TrCH) and sends these parameters to the WTRU (via RRC signaling).

The layer 1 control/layer 1 body 15 includes a CRC checking unit 11, an SIR measuring unit 72, an OLPC unit 20, an ILPC unit 40, a DPCH configuration control unit 66, a compression mode Δ SIR calculating unit 65, an adder 77, and a power control dynamic range limiter 12. OLPC unit 20 includes a target SIR mapper 84 and a target SIR adjustment unit 74.

The CRC check unit performs a BLER estimation on the data. The initial BLER estimate is made by the target SIR mapper 84 to determine an appropriate target SIR based on received signal quality. The SIR measurement unit 72 makes a real-time measurement of the SIR of the received DPCH signal 25. The SIR measurement 82 is sent to the OLPC unit 20 so that the target SIR can be adjusted as necessary in the target SIR adjustment unit 74. The SIR measurement 82 is also received by the ILPC unit 40 for comparison to a target SIR. Based on this comparison, ILPC unit 40 generates an appropriate TPC command 45 to request base station 90 to increase or decrease transmit power.

The DPCH configuration control unit 66 controls DCH quality targets such as a target BLER for each TrCH, a Transmission Time Interval (TTI), and the number of transport blocks within a TTI. The compressed mode delta SIR calculation unit 65 determines a delta SIR value for the compressed mode received via the signaling. Since the DPCH SIR measurement value in the compressed mode is Δ SIR higher than that in the normal mode, the OLPC unit 20 must increase the target SIR of the ILPC unit 40 by Δ SIR at the adder 77.

DPCH data 25 is received from the physical layer PHY from the transmitting station 90 and processed by a RAKE receiver 21. CPICH RSCP measurement values 46 from a RAKE receiver 21, DPCH RSCP 47 from SIR measurement unit 72 and TPC commands 45 from ILPC unit 40 are used as inputs to power control dynamic range limiter 12. The power control dynamic range limiter 12 is a processor that executes an algorithm to detect whether the following three power control problem conditions occur: 1) the transmitting unit 90 has reached the maximum transmission power; 2) the transmitting unit 90 has reached a minimum transmission power; or 3) the transmitting unit 90 fails to correctly decode the TPC command 45 because of poor signal quality of the wireless signal 90. The limiter 12 takes the RSCP 47 of the DPCH 25 from the SIR measurement unit 72 and calculates a delta DPCH RSCP value for a predetermined observation interval. The TPC command 45 input is monitored to determine the amount of power change caused by the TPC command 45 during the observation interval. A third input, received CPICH power 46, is used to determine a delta CPICH power value during the observation interval. Limiter 12 analyzes these inputs and compares predetermined thresholds according to a preferred algorithm to determine whether any of the three power control conditions have occurred.

Based on the results of the algorithm of slicer 12, target SIR adjustment unit 74 receives a control signal 55 to stop target SIR adjustments since any adjustments are not valid when the base station experiences any of the above problem conditions. In addition, if the target SIR adjustment is left alone, the upper or lower bound of the target SIR may be reached inadvertently because the OLPC unit 20 is not operating correctly with the wrong signal quality measurement. For example, if the transmission power is at its maximum and the ILPC unit 40 determines based on the CRC error that the measured SIR must remain approximately the target SIR at a greater transmission power, the OLPC unit 20 attempts to excessively increase the target SIR. Since the base station 90 is unlikely to keep up at all, these excessive increases will abuse system resources, resulting in longer recovery times. By stopping the target SIR adjustment, the upper and lower bounds of the target SIR are avoided, which allows the target SIR within OLPC unit 20 to remain within a preferred operable range, away from the outer limits.

Although figure 2 is described with reference to a WTRU 10 in communication with a base station 90, it should be understood that the present invention may be applied to an ad hoc communication system in which a second WTRU operates as base station 90.

Referring to fig. 3A and 3B, an algorithm 100 is depicted as being executed by the power control dynamic range limiter 12. The algorithm 100 determines whether the base station is responding to TPC commands by monitoring a maximum or minimum threshold for downlink power. The output of the algorithm 100 is a control signal to the outer loop power control indicating whether the inner loop power control has reached maximum or minimum power or is operating at normal transmit power.

The algorithm 100 starts in step 101, wherein the following parameters are set: an observation window length with index i, Min _ power _ detection _ threshold _1, Min _ power _ detection _ threshold _2, Max _ power _ detection _ threshold _1, Max _ power _ detection _ threshold _2, and a step size alpha factor alpha. Preferred default values for these parameters are listed in table one. The window length and threshold parameters are adjusted with reference to the SIR or RSCP of the CPICH; the parameters are smaller for higher CPICH SIR and CPICH RSCP values.

Watch 1

Parameter(s)	Default value
		Observation Window Length (i)	8 frames
Min_power_detection_threshold_1	5dB
		Min_power_detection_threshold_2	3dB
Max_power_detection_threshold_1	5dB
		Max_power_detection_threshold_2	3dB
alpha	0.8

Next in step 102, the following buffers are initialized and set to zero (0): hold _ Target _ SIR, minimum measured power Min _ PD, maximum measured power Max _ PD, Delta _ power (i). The buffers Hold _ Target _ SIR, Min _ PD, and Max _ PD Hold logical values of 0 or 1. The buffer value Delta _ power (i) represents a power (dB) value of the observation window time interval index i. The buffered Hold _ Target _ SIR represents a value of one (1) when either the maximum or minimum power threshold has been detected, and provides a logic control to the OLPC that prevents any further adjustments to the Target SIR. Upon detection of a minimum threshold for the downlink power, the buffer Min PD is set to one (Min PD ═ 1). Similarly, Max _ PD is set to one when a maximum power is detected (Max _ PD ═ 1). In step 103, the received DPCH received signal code power (DPCH _ RSCP) is measured for the duration of the observation window. In step 104, a delta value of the downlink power is calculated based on the DPCH RSCP and is shown in equation 1:

ΔDPCH_RSCP(i)＝DPCH_RSCP(i)-DPCH_RSCP(i-1)(dB)

equation 1

In a Distributed Power Control (DPC) algorithm, power is updated by feedback that occurs every time slot or with an overall processing delay. For example, the delta power Δ DPCH rscp (i) calculated in equation 1 represents a value when the DPC mode is equal to zero (0), where the calculated delta power value represents the power variation over an interval of two consecutive slots. Alternatively, if the DPC mode is equal to one (1), equation 1 is modified to determine the delta power between the current time slot (i) and a predetermined previous time slot, preferably the third time slot (i-3) ahead.

In step 105, downlink power is measured for the observation window based on the cpich RSCP (CPICH RSCP). In step 106, delta power Δ CPICH _ RSCP is calculated according to equation 2:

ΔCPICH_RSCP(i)＝CPICH_RSCP(i)-CPICH_RSCP(i-1)(dB)

equation 2

The delta power Δ CPICH rscp (i) calculated in equation 2 is based on the DPC mode being equal to 0, wherein the calculated delta power value represents the power variation over an interval of two consecutive slots. In the case of DPC mode equal to 1, equation 2 is modified to calculate the delta power between the current time slot (i) and a predetermined previous time slot, preferably the third time slot (i-3) ahead. In step 107, an Inner Loop Power Control (ILPC) step size is determined. The evaluation of ILPC step size is described in more detail below with reference to fig. 4.

In step 108 of fig. 3A, an accumulated Delta power value Delta _ power (i) is calculated based on the Δ DPCH _ RSCP, Δ CPICH _ RSCP, and StepSize _ ILPC according to equations 3 and 4. Equation 3 is used to calculate the cumulative delta power when the base station has received a TPC command in the previous time slot requesting an increase in transmit power. Equation 4 is used to calculate the cumulative delta power when the base station has received a TPC command in the previous time slot requesting a decrease in transmit power. The only difference between equations 3 and 4 is that the step size of ILPC is either added or subtracted from the power change value.

Delta _ power (i) ═ Delta _ power (i-1) + Δ DPCH _ rscp (i) - Δ CPICH _ rscp (i) -StepSize _ ILPC equation 3

Delta _ power (i) ═ Delta _ power (i-1) + Δ DPCH _ rscp (i) - Δ CPICH _ rscp (i) + StepSize _ ILPC equation 4

In step 109, the algorithm 100 checks whether the Max _ PD and Min _ PD buffers indicate normal transmit power for the base station. If so, the algorithm 100 continues to step 111 where the Delta _ power (i) value is checked to see if maximum power is detected by comparing it to the Max _ power _ detection _ threshold _1 times StepSize _ ILPC as shown in equation 5:

Delta_power(i)＜-Max_power_detection_threshold_1×StepSize_ILPC

equation 5

If the Delta _ power (i) value is less than the threshold value according to equation 5, the maximum power has been measured and the buffer value Max _ PD is set to one (Max _ PD ═ 1) and Hold _ Target _ SIR is set to one (1), as shown in step 112. If the maximum power has not been detected according to step 111, the minimum power detection threshold Min _ power _ detection _ threshold _1 is compared according to equation 6 according to step 113:

Delta_power(i)＞Min_power_detection_threshold_1×StepSize_ILPC

equation 6

If the value of Delta _ power (i) is greater than the product of Min _ power _ detection _ threshold _1 and StepSize _ ILPC in step 113, then minimum power is detected. In step 114, when the minimum power is detected, the buffer Min _ PD and Hold _ Target _ SIR are set to one (1). If neither minimum nor maximum power detection occurs in steps 111, 113, the observation window index is increased in step 115 and the algorithm 100 returns to step 103 and continues therefrom. If a maximum or minimum downlink power is detected in step 112 or 114, the changes in buffer states Max _ PD, Min _ PD, and Hold _ Target _ SIR are sent to OLPC unit 20 so that the Target SIR can be maintained at its current value.

The remaining steps of the algorithm 100 shown in fig. 3B are used to detect whether the downlink transmit power has returned to normal. Returning to step 109, if neither of the buffered states Max _ PD and Min _ PD are equal to zero at this time, steps 116 and 119 are used to determine which of the buffered states Max _ PD and Min _ PD contains a value equal to one (1). In step 116, it is checked whether the buffer Max _ PD has detected the maximum downlink power (Max _ PD 1). If so, the flow proceeds to step 117, and the product of Max _ power _ detection _ threshold _2 and the step size ILPC is compared with Delta _ power (i) value as shown in equation 7:

Delta_power(i)＞-Max_power_detection_threshold_2×StepSize_ILPC

equation 7

If the comparison is true, a normal transmit power has been detected and the buffer value Max _ PD is reset to zero (0), which releases the target SIR reservation for outer loop power control (step 118).

If the comparison of step 117 is not true, step 119 is initiated to check if a minimum downlink power detection (Min _ PD ═ 1) has occurred. If the current state of the transmission power is the minimum power detection, then Min _ power _ detection _ threshold _2 is compared with Delta _ power (i) value (step 120) as shown in equation 8.

Delta_power(i)＜Min_power_detection_threshold_2×StepSize_ILPC

Equation 8

If the ratio of equation 8 is true, normal transmit power has been detected and the buffer Min PD is reset to zero (0), which releases the target SIR hold for outer loop power control (step 121). However, if the result of step 120 is not true, then the observation window index is incremented at step 115 and the algorithm 100 repeats the remainder of the observation window beginning at step 103. If the observation window index (i) has reached the final value of the observation window length and none of the minimum power, maximum power, or normal transmit power is detected in steps 111, 113, 117, or 120, then the Delta power (i) value is reset to zero and initialized for a new observation window.

In an alternative embodiment, downlink power detection is measured using the difference in SIR measurements (dB) between adjacent slots of both the downlink DPCH and the CPICH, rather than the RSCP measurement. Since the SIR value is proportional to the RSCP/interference ratio (i.e., SIR varies with interference power), the RSCP value is better for downlink power detection in algorithm 100. In this alternative, the calculation of the accumulated power value Delta _ power (i) in the case where the transmission power is not at the minimum or maximum level is simplified to equation 9 below:

Delta_power(i)＝〔Delta_power(i-1)+ΔDPCH_SIR(i)-(TPC(i-1))(StepSize_ILPC)〕＝〔Delta_power(i-1)+(TPC(i-1))(StepSize_ILPC)〕

equation 9

The TPC command value TPC is equal to positive one or negative one (TPC ═ 1, -1).

Fig. 4 depicts an algorithm 200 for determining the inner loop power control steps used by the algorithm 100. At step 201, a set of predetermined actual ILPC step sizes is established. For this example, the set of ILPC step sizes is [ 0.5, 1.1, 1.5, 2.0DB ]. Although these are preferred values for the set of ILPC step sizes, the set of values may include more than four values, and the values may be different than those listed herein. In step 202, a temporary ILPC step size is set according to equation 10.

Temp_StepSize_ILPC＝|Delta_power(i)|/observation_window_length

Equation 10

In step 203, an estimate of the ILPC step size for the current time slot is calculated using equation 11, where the estimate is based on the estimate of the previous time slot, the step size alpha factor, and the Temp _ StepSize _ ILPC temporary ILPC step size from step 202.

Stepsize _ ILPC (i) ((alpha)) Stepsize _ ILPC (i) + (1-alpha) (Temp _ Stepsize _ ILPC) equation 11

The alpha factor is digitally represented and the new estimate is updated by a single pole low pass filter. Next, in step 204, the difference between the temporary ILPC step size Temp _ StepSize _ ILPC and the estimate of the ILPC step size StepSize _ ILPC (i) is compared to a threshold value of 0.25. If the difference is less than 0.25, then the estimate of the ILPC step size StepSize _ ILPC (i) is deemed satisfactory (step 205). However, if the difference is greater than or equal to 0.25, then the estimate of the ILPC step size StepSize _ ILPC (i) is compared to each of the set of possible ILPC step sizes established in step 201 in step 206. The comparison Delta value Delta _ StepSize of step 206 for k attempts is calculated using equation 12:

Delta_StepSize＝|Temp_StepSize_ILPC-Value_StepSize(k)|

equation 12

Where k is an integer representing the number of possible ILPC step sizes, and Value _ StepSize (k) is a possible ILPC step size.

Once the estimate of the ILPC step size is compared with each of the K possible ILPC step sizes in the set, the final estimate of the ILPC step size (i) is set to the closest possible value in the set of values (step 207).

Once a minimum or maximum transmit power is detected, the state is maintained until normal transmit power is detected in the detection algorithm 100.

Claims (20)

1. In a wireless receiver, a method for detecting downlink transmit power of a base station to limit power control dynamic range, wherein transmit power control adjustments occur in increments of step size in response to a comparison of received signal quality measurements to an adjustable target signal quality, the method comprising the steps of:

a) setting minimum and maximum thresholds for received signal quality measurements;

b) measuring a delta power change of a received signal quality measurement of a downlink channel at a first interval;

c) estimating a transmit power level difference at the receiver;

d) calculating an accumulated power variation based on the delta power variation and the estimated transmission power step size;

e) comparing the accumulated power value to the minimum and maximum thresholds; and

f) transmitting a control signal for adjusting transmission power control, wherein target signal quality adjustment is released when the accumulated power value is within a predetermined approximate range with respect to the maximum or minimum threshold value, and target signal quality adjustment is enabled when the accumulated power value is not within the predetermined approximate range with respect to the maximum or minimum threshold value; and

g) repeating steps (a) to (f) at successive intervals.

2. The method of claim 1 wherein the adjusted transmission power level difference at the base station is predetermined to a set of k actual possible magnitudes, and step (c) further comprises:

calculating a temporary transmission power step size as a ratio of the accumulated power value and the observation window size;

the temporary transmit power step size is compared to each of the k possible step sizes and the closest possible step size is used as the estimated transmit power step size.

3. The method of claim 1, wherein step (c) further comprises:

calculating a temporary step size as a ratio of the accumulated power value to the observation window size;

measuring a difference between the estimated transmission power step size and the temporary step size; and

the estimated transmit power step size is used when the measured difference is less than a predetermined value.

4. The method of claim 3 wherein the evaluation in step (c) is calculated as an estimate of the previous increment multiplied by a predetermined factor alpha plus the temporary step size multiplied by (1-alpha) the magnitude of the transmission step.

5. The method of claim 1 wherein the downlink channel comprises a Dedicated Physical Channel (DPCH) and a common pilot channel (CPICH), the received signal quality measurements comprise a Received Signal Code Power (RSCP) of the DPCH and CPICH, and the adjustable signal target quality is a target signal-to-interference ratio (SIR).

6. The method of claim 5 wherein the measuring of step (b) includes determining a delta power change of the DPCH (Δ DPCH _ RSCP) and a delta power change of the CPICH (Δ CPICH _ RSCP), and the calculating of step (d) is based on (Δ DPCH _ RSCP- Δ CPICH _ RSCP) plus or minus the estimate of the transmission step size of step (c).

7. The method of claim 1 wherein the downlink channels include a Dedicated Physical Channel (DPCH) and a common pilot channel (CPICH), the received signal quality measurements include a target signal-to-interference ratio (SIR) of the DPCH and the CPICH, and the adjustable signal target quality is a target SIR.

8. The method of claim 7 wherein the measuring of step (b) includes determining a delta power change of the DPCH (DPCH _ SIR) and a delta power change of the CPICH (CPICH _ SIR) and the calculating of step (d) is adding or subtracting the estimate of the level difference of step (c) from (DPCH _ SIR- Δ CPICH _ SIR).

9. A wireless receiver that performs downlink transmit power detection for a base station in which transmit power control adjustments occur in increments of step size in response to a comparison of received signal quality measurements to an adjustable target signal quality, the receiver comprising:

a RAKE receiver for detecting a received wireless signal and determining signal quality parameters;

a signal-to-interference (sir) measurement device configured to determine sir and signal quality values based on the signal quality parameters from the RAKE receiver;

an inner loop power control device for determining a transmission power control command of the base station to increase or decrease transmission power;

an outer loop power control device for calculating the tunable target signal quality; and

a dynamic range limiting device configured to control the outer loop power control device based on whether the base station has reached a maximum or minimum transmit power or based on whether the base station has incorrectly decoded the transmit power control command due to poor signal quality.

10. The wireless receiver of claim 9 wherein the dynamic range limiting device is further configured to set minimum and maximum thresholds for received signal quality measurements; measuring a delta power change in a received signal quality measurement of a downlink channel over a first interval; evaluating the size of the transmission power step difference; calculating an accumulated power variation based on the delta power variation and the estimated transmission power step size; comparing the accumulated power value to the minimum and maximum thresholds; and transmitting a control signal for adjusting transmission power control; wherein the target signal quality adjustment is deactivated if the accumulated power value is within a predetermined proximity to the maximum or minimum threshold value, and the target signal quality adjustment is activated if the accumulated power value is not within the predetermined proximity to the maximum or minimum threshold value.

11. The receiver of claim 10 wherein the downlink channel comprises a Dedicated Physical Channel (DPCH) and a common pilot channel (CPICH), the received signal quality measurements comprise a Received Signal Code Power (RSCP) of the DPCH and CPICH, and the adjustable signal target quality is a target signal-to-interference ratio (SIR).

12. The receiver of claim 11 wherein the measurement of a delta power change of the received signal quality measurements includes determining a delta power change of the DPCH (Δ DPCH _ RSCP) and a delta power change of the CPICH (Δ CPICH _ RSCP), and the calculation of the cumulative power value is based on (Δ DPCH _ RSCP- Δ CPICH _ RSCP) plus or minus the transmit power level difference estimate.

13. The receiver of claim 10 wherein the downlink channel includes a Dedicated Physical Channel (DPCH) and a common pilot channel (CPICH), the received signal quality measurements include a signal-to-interference ratio (SIR) of the DPCH and the CPICH, and the adjustable signal target quality is a target SIR.

14. The receiver of claim 13 wherein the measuring of a delta power change of the received signal quality measurements comprises determining a delta power change of the DPCH (Δ DPCH _ SIR) and a delta power change of the CPICH (Δ CPICH _ SIR) and the calculation of the cumulative power value is based on (Δ DPCH _ RSCP- Δ CPICH _ RSCP) plus or minus the transmit power level difference estimate.

15. A method for controlling transmission power of a transmitting wireless transmit/receive unit (WTRU) transmitting data signals in first and second forward channels, wherein the transmitting WTRU is configured to make a first forward channel power adjustment as a function of a target metric calculated by a receiving WTRU based on data signals received in the first forward channel, the method comprising:

receiving a data signal from the transmitting wtru on the first forward frequency channel; receiving data signals from the transmitting wtru on the second forward frequency channel;

calculating a power difference between the data signal received on the first forward channel and the data signal received on the second forward channel;

calculating a target metric for a first forward channel power adjustment of the transmitting wtru based on the calculated power difference; and

based on the calculated target metrics and dependent on the calculated power difference, a first forward channel transmission power adjustment signal is sent to the transmitting WTRU at a reverse channel transmission.

16. The method of claim 15 wherein the transmitting wtru transmits data signals on a dedicated channel and a common channel, wherein:

receiving data signals on the first forward channel comprises receiving downlink data signals on a dedicated channel;

receiving data signals on the second forward channel comprises receiving downlink data signals on a common channel; and

transmitting a first forward channel transmit power adjustment signal on a reverse channel includes transmitting a transmit power adjustment signal for the dedicated downlink channel on an uplink channel.

17. The method of claim 15 wherein the transmitting the first forward channel transmission power adjustment signal is dependent upon whether the calculated power difference is within a predetermined proximity of a predetermined maximum threshold or a predetermined minimum threshold.

18. The method of claim 17 further comprising evaluating a transmission power control step size at the receiving wtru and using the step size estimate in calculating the power difference.

19. A receiving wireless transmit/receive unit (WTRU) for performing transmit power control of a transmitting WTRU transmitting data signals on first and second forward channels, wherein the transmitting WTRU is configured to make a first forward channel power adjustment as a function of a target metric calculated by the receiving WTRU, the receiving WTRU comprising:

a receiver for receiving data signals from a transmitting wtru on a first forward channel and receiving data signals from the transmitting wtru on a second forward channel;

a processor for calculating a target metric for a first forward channel transmit power adjustment in the transmitting wtru based on detection of a predetermined error condition in the data signal received on the first forward channel;

the processor configured to calculate a power difference between the data signal received on the first forward channel and the data signal received on the second forward channel; and

a transmitter operatively coupled to the processor and configured to transmit the first forward channel transmit power adjustment signal on a reverse channel in response to target metric calculations made by the processor and in dependence upon a power difference calculated by the processor.

20. The wtru of claim 19 wherein the transmitting wtru is a base station that transmits data signals on dedicated channels and common channels, wherein:

the receiver configured to receive the downlink data signal as a first forward channel receive signal on a dedicated channel and the downlink data signal as a second forward channel receive signal on a common channel; and

the transmitter of the receiving wtru is configured to transmit a transmit power adjustment signal for the dedicated downlink channel on an uplink channel.