HK1116309A - Variable transmit power control strategies for high-speed downlink packet access systems - Google Patents

Description

Variable transmission power control strategy for high speed downlink packet access systems

Technical Field

The present invention relates to electronic digital communication systems, and more particularly to wireless telephone systems.

Background

Electronic communication systems include Time Division Multiple Access (TDMA) systems (e.g., cellular radio telephone systems that conform to the GSM telecommunications standard and its improved standards such as GSM/EDGE) and Code Division Multiple Access (CDMA) systems (e.g., cellular radio telephone systems that conform to the IS-95, CDMA2000, and wideband CDMA (wcdma) telecommunications standards). Digital communication systems also include "hybrid" TDMA and CDMA systems, such as cellular radiotelephone systems that conform to the Universal Mobile Telecommunications System (UMTS) standard, which specifies the third generation (3G) mobile system being developed by the European Telecommunications Standards Institute (ETSI) under the International Telecommunication Union (ITU) IMT-2000 framework. The third generation partnership project (3GPP) promulgates UMTS and WCDMA standards. For simplicity, the present application focuses on WCDMA systems, but it should be understood that the principles described in the present application may be applied to other digital communication systems.

WCDMA is based on direct sequence spread spectrum techniques, where the base station and physical channel (terminal or user) are separated in the downlink (base-to-terminal) direction with a pseudo-noise scrambling code and an orthogonal channelization code, respectively. Since all users share the same radio resources in a CDMA system, it is important that each physical channel does not use more power than necessary. This is achieved by a Transmit Power Control (TPC) mechanism, where the base station sends TPC commands to the user in the Downlink (DL) direction and the user implements the commands in the Uplink (UL) direction, or vice versa. The TPC commands cause the users to increase or decrease their transmit power levels in increments, thereby maintaining a target signal-to-interference ratio (SIR) for the Dedicated Physical Channel (DPCH) between the base station and the users. WCDMA terminology is used herein, but it should be understood that other systems have corresponding terminology. Scrambling and channelization codes and transmission power control are well known in the art.

Fig. 1 depicts a mobile radio cellular telecommunications system 10, which may be, for example, a WCDMA communication system. Radio Network Controllers (RNCs) 12, 14 control various radio network functions including, for example, radio access bearer setup, diversity handover, etc. More generally, each RNC directs a Mobile Station (MS) or User Equipment (UE) to make a call through an appropriate Base Station (BS) that communicates with each UE through DL (or forward) and UL (i.e., mobile to base station, or vice versa) channels. RNC12 is shown connected to BSs 16, 18, 20, while RNC 14 is shown connected to BSs 22, 24, 26. Each BS (referred to as a node B in 3GPP parlance) serves as a geographical area that may be divided into one or more cells (cells). BS 26 is shown with five antenna sectors S1-S5, which may be said to constitute the cell of BS 26, S1-S5. The BSs are connected to their corresponding RNCs by dedicated telephone lines, optical fiber links, microwave links, etc. Both RNCs 12, 14 are connected to external networks, such as the Public Switched Telephone Network (PSTN), the internet, etc., through one or more core network nodes, e.g., mobile switching centers (not shown) and/or packet radio service nodes (not shown).

High Speed Downlink Packet Access (HSDPA) is a further evolution of WCDMA communication systems that provides higher bit rates, e.g., up to greater than 10 megabits per second (Mb/s), by using higher order modulation, e.g., 16-quadrature amplitude modulation (16-QAM), multiple spreading codes, e.g., up to fifteen codes with spreading factor 16, and DL channel feedback information. HSDPA is described in the fifth release of system specification published by 3 GPP. The DL channel feedback information is information on DL channel quality transmitted by the UE to the BS through the UL channel. The BS uses this information to optimize DL modulation and coding to achieve optimal throughput.

HSDPA also employs a hybrid automatic repeat request (ARQ) scheme on the physical layer to reduce round-trip (round-trip) delays for erroneously received packets. The hybrid ARQ scheme includes transmitting Acknowledgement (ACK) and non-acknowledgement (NACK) messages to a BS providing an HSDPA service by a UE. The BS may be referred to as a "serving" BS or cell. The HS channels in DL are sent only from the HSDPA serving cell and HSDPA UL control signaling (including ACK/NACK and DL channel quality reports) is detected only by the HSDPA serving cell.

As the user terminal moves relative to the base station (and vice versa), the ongoing connection is maintained through a process of hand-off or hand-over. For example, in a cellular telephone system, as a user moves from one cell to another, the user's connection is handed off from one base station to another. Early cellular systems used Hard Handoff (HHO) in which the base station of the first cell (covering the cell that the user is leaving) would stop communicating with the user just as the second base station (covering the cell that the user is entering) began communicating. Typically, modern cellular systems use diversity handover or Soft Handover (SHO), in which a user is connected to two or more base stations simultaneously. In fig. 1, MSs 28, 30 are shown communicating with multiple base stations in the case of diversity handover. The MS28 communicates with the BSs 16, 18, 20, and the MS 30 communicates with the BSs 20, 22. The control communication link between the RNCs 12, 14 allows diversity communication to/from the MS 30 through the BSs 20, 22.

During SHO, the terminal receives TPC commands from more than one base station, and methods have been developed for handling collisions between TPC commands from different base stations. Collisions are expected because as the UE leaves one cell, the base station of that cell receives a progressively weaker signal and therefore the TPC commands for that base station require more power, while at the same time the UE may enter a new cell, and the base station of that new cell receives a progressively stronger signal and therefore the TPC commands for that new base station require less power. In a 3GPP compliant system, the UE combines TPC commands from the reliable downlink with a logical or function, which results in a reduced UE transmit power if any reliable command indicates "down". This is described in section 5.1.2.2.2.3, physical layer procedure (FDD) of 3GPP Technical Specification (TS)25.214(v6.2.0) release 6 (2004).

HSDPA may be used in mobile situations, such as where the UE and BS are moving relative to each other, but soft handover is not specified for HSDPA channels. The HSDPA channel supports only hard handover. Thus, there may be many of the following: the UE uses SHO for its DPCH while using HHO for its HSDPA channel. Fig. 2 depicts a typical one of these cases, where the UE is in a SHO situation for a non-HSDPA channel and uses a service transmitted over the HSDPA channel.

Fig. 3A is similar to fig. 2, in which a UE 202 is depicted, the UE 202 having multiple simultaneous connections with a BS 204 and a BS 206 via a Dedicated Physical Data Channel (DPDCH) and a Dedicated Physical Control Channel (DPCCH) in the UL and DL. In other words, for these non-HSDPA channels, the UE 202 is in a SHO situation. The DPDCH carries higher layer network signaling and possibly also voice and/or video services. The DPCCH carries physical layer control signaling (e.g., pilot symbols/signals, TPC commands, etc.). RNC 208 (not shown in fig. 3A) controls BS 204 and BS 206.

The UE 202 also has HSDPA channels, but these HSDPA channels are provided only by the serving cell, which in fig. 3A is BS 206 because the SIR of BS 206 is greater than the SIR of BS 204. As mentioned above, SHO is not specified for HSDPA channels. The downlink HSDPA channels include an HS packet data shared channel (HS-PDSCH) carrying HS data packets and an HS shared control channel (HS-SCCH) carrying control information for these data packets. The uplink HSDPA channel includes an HS-dedicated physical control channel (HS-DPCCH) carrying ACK/NACK reports and DL channel quality information.

Although SHO is not available for HSDPA channels, the UE regularly (e.g. five times per second) measures the average SIR (e.g. E) of the common pilot channel (CPICH) it receives from all cells in its active set (active set)_c/I₀) And the cell with the best SIR on these non-HSDPA channels is designated as the HSDPA serving cell.

As depicted in fig. 3A, the UE 202 determines an average SIR of the DL from the BS 204 that is greater than the SIR measured for the BS 206. This triggers event 1D (change of best cell) and a layer 3 Radio Resource Control (RRC) message is transmitted on the UL DPDCH. The HS channel is still transmitted from BS 206 for a short time after trigger event 1D. The RNC receives the event 1D message and transmits an "HS serving cell change message" as a layer 3 RRC message to the UE on the DL DPDCH. The change message includes information about the time at which the HS channel will be (hard) handed off to the BS 204. When the UE has received the "change" message, it transmits an ACK message on the UL DPDCH to the BS 204, 206 and RNC 208. In fig. 3B, hsdpa hho is present and BS 204 is the serving cell that transmits and receives HS channels.

Measurement of the average SIR of the DL non-HSDPA channels of the UE may cause an anomaly in HSDPA operation. Sometimes the following may be temporarily present: BS 204 has a better SIR than BS 206. Furthermore, since UL and DL fade independently of each other, the following may also be the case: the UL to BS 204 has a better quality than the UL to BS 206, even when the DL from BS 204 has a lower quality than the DL from BS 206.

As described above, DPDCH/DPCCH are controlled by transmission power and support SHO, so power control during SHO is based on a combination of TPC commands. The HS-DPCCH is power controlled but has an offset relative to the DPCCH UL, which is set by higher layer signaling. When the DPCH is in soft handover and independent fading of the channel is considered, the combination of TPC commands may be driven by a base station that does not include the HSDPA serving cell, and thus HSDPA power control may not be appropriate. In fact, in order to have SHO capacity gain, it is sufficient if only one BS can hear a UE that is good enough to obtain sufficient quality of service, so the following may be the case: the UL to the HSDPA serving cell is the cell with the weakest signal, while the other UL to the non-serving cell is the UL indicating power control on the HSDPA channel.

These behaviors can result in poor HS-DPCCH reception performance and erroneous ACK/NACK messaging and DL channel quality detection, both of which can significantly reduce throughput on the HSDPA channel. Therefore, various attempts have been made to eliminate these problems.

One approach adopted by the 3GPP standard is to specify a greater transmission power on the HS-DPCCH than on the DPCH. However, all UL synchronization (i.e., path searcher and channel estimation) is still done on the UL DPCCH. Therefore, if the reception of the DPCCH becomes poor enough, a loss of synchronization may result, and HS detection cannot be completed regardless of the HS-DPCCH power. The result is lower HS throughput.

Another approach is to perform UL power control only for the HS serving cell, but doing so would lose SHO gain and greatly reduce the communication capacity of the system. The 3GPP standard does not allow this approach.

Another approach is to vary the data rate on the HS channel according to the channel quality. For example, european patent application No. ep 1363413a1 by Hayashi et al discloses a mobile communication system that uses transmission power required on a DPCH as a control indicator (indicator) for changing the data rate of the HS-PDSCH. As described in this document, in the case where the DL transmission power of the DPCH is at a low level, the HS radio link condition is expected to be good, and therefore, even if the transmission rate of the HS-PDSCH is set high, fast transmission of the data signal can be achieved, and the risk of degradation of the communication quality is low. In contrast, in the case where the DL transmission power of the DPCH is at a high level, the radio link condition is expected to be poor, and thus sufficient communication quality cannot be maintained unless the transmission rate of the data signal using the HS-PDSCH is lowered.

Aspects of the power control of HS channels during SHO of DPCHs are described in several documents, including U.S. patent application publication No. us 2004/0203985 to Malladi et al and international patent publication No. wo 2004/019513a1 to Whinnet et al. Malladi et al describe: uplink power control is provided to maintain the integrity of the uplink HS-DPCCH when the UE enters SHO. The RNC controls the target signal-to-noise ratio threshold for the pilot signal based on the pilot signal strength of the serving node and/or the uplink channel condition of the serving node.

Disclosure of Invention

The present application describes methods and apparatus that reduce the risk of poor reception by the UE during soft handover and loss of UL synchronization to the HSDPA serving cell, even if it is sufficient for one BS to hear the DPDCH/DPCCH.

In one aspect of the present invention, a UE in a communication system is provided. The UE includes means for recovering control symbols to be used for the UE, wherein the control symbols include TPC commands directed to the UE from at least two transmitting nodes, one of the transmitting nodes being a serving node for a predetermined communication service. The UE further comprises: a TPC command filter configured to generate a ratio signal from TPC commands directed from the serving node to the UE during a plurality of time slots; and a TPC combiner responsive to the ratio signal and configured to receive TPC commands from the device. Generating a TPC control signal based on the received command and the ratio signal, the TPC control signal for controlling power of the UE transmission. The TPC control signal is based only on TPC commands directed from the serving node to the UE if the ratio signal exceeds a first threshold.

In another aspect of the present invention, a method in a UE of controlling power transmitted by the UE in an uplink in a communication system is provided. The method comprises the following steps: receiving TPC commands from at least two communication nodes, wherein one of the communication nodes is a serving node for a predetermined communication service; generating a ratio signal from TPC commands received from the serving node during a plurality of time slots; and generating a TPC control signal based on the received TPC command and the ratio signal, the TPC control signal being used to control the power of the UE transmission. The TPC control signal is based only on TPC commands received from the serving node if the ratio signal exceeds a first threshold.

In another aspect of the invention, a computer readable medium containing a computer program for controlling power of a UE transmitting in an uplink in a communication system is provided. The computer program performs the steps of: generating a TPC command ratio signal from TPC commands received from a serving node during a plurality of time slots; and generating a TPC control signal based on TPC commands received from the serving node and at least one other communication node and based on the TPC command ratio signal, the TPC control signal being used to control the power of the UE transmission. The TPC control signal is based only on TPC commands received from the serving node if the ratio signal exceeds a first threshold.

Drawings

The various aspects, features and advantages of the present invention will become apparent from the following description, when read in conjunction with the accompanying drawings, wherein:

figure 1 shows a mobile wireless cellular telecommunications system;

fig. 2 shows a UE in SHO situation of a non-HSDPA channel and using a service transmitted through the HSDPA channel;

fig. 3A, 3B show handover of HSDPA channels;

FIG. 4 is a block diagram of a portion of a UE; and

fig. 5 is a flow chart of a method according to the principles of the present invention.

Detailed Description

In any communication system using transmit power control, which is intended to use only enough power for each UL (and DL) to maintain sufficient quality, TPC commands transmitted in the DL from a BS can be used to obtain information about the quality of the UL for that particular BS. A WCDMA communication system is a typical such communication system. When the UL is of sufficient quality, the ratio of TPC up commands to TPC down commands is close to unity (i.e., about half of the TPC commands are "up" and about half are "down"). When the UL has a lower quality, more TPC "up" commands are transmitted on the DL than "down" commands. Thus, during a certain time period, more TPC "up" commands from the HSDPA serving cell are information that may indicate a greater probability of poor HS-DPCCH detection.

The UE may use this information about UL quality when adjusting its power control strategy. For example, the UE may change its power control strategy from a normal fixed strategy (combining TPC commands from all BSs in the active set and acting on the basis of that combination) to a second strategy (setting its UL transmit power only in accordance with TCP commands from the HSDPA serving cell when the up/down ratio of those commands is greater than a certain threshold indicating that the UL signal quality may be low). With this adjustable TPC strategy, the UE's UL transmit power is increased only during those time periods when the UL quality to the HS serving cell is poor, thereby optimizing the balance between HS performance and overall SHO capacity gain when non-HS channels are in SHO.

Fig. 4 is a block diagram of a portion of a UE 400, the UE 400 adapted to implement an adjustable TPC strategy as described above when the UE 400 is in connected mode and operating in SHO and is engaged in an HSDPA session. Let N_bsIs the base station BS in the number of links (i.e. active set) to which the UE is simultaneously connected₁、BS₂、...、BS_NbsNumber of) and assumes that the HSDPA serving cell is the base station BS_J。

A UE 400, e.g. a mobile terminal in a WCDMA communication system, receives and transmits radio signals via an antenna 402 and e.g. down-converts and samples the received signals in a front-end receiver (Fe RX) 404. The output samples are fed from Fe RX 404 to a rake combiner and decoder 406, which rake combiner and decoder 406 despreads and combines the received data and responses to control symbols (echo), decodes the symbols appropriately, and transmits the decoded symbols for further processing as appropriate for the particular communication system.

rake combining and channel estimation are well known in the art. Aspects of rake receivers are described in the following documents: U.S. Pat. No.5,305,349 to Dent, "Quanticoded coherent Rake Receiver"; U.S. Pat. No.6,363,104 "method and Apparatus for Interference Cancellation in a Rake Receiver" to Bottomley; U.S. Pat. No.6,801,565 "Multi-Stage Rake combining methods and Apparatus" to Bottomley et al; and U.S. patent application publication No.2001/0028677 "Apparatus and Methods for Finger Delay Selection in Rake receivers" to Wang et al.

The output samples from Fe RX 404 are also fed to SIR and channel estimator 408 for estimating the SIR and impulse response of the DU radio channel and to TPC command decoder 410. Channel estimation is described, for example, in U.S. patent application No.10/920,928 "ChannelEstimation by Adaptive interference" to l.wilhelmsson et al. The TPC decoder 410 recovers the control symbols, including TPC commands from the various nodes (e.g., base stations to which the terminals are connected), and feeds a stream of TPC commands to a TPC combiner 412, which TPC combiner 412 combines the TPC commands from the various links in the active set.

The TPC combiner 412 generates a combined TPC command that is provided to a front end transmitter (Fe TX)414, which the front end transmitter (Fe TX)414 uses to increase or decrease the transmit power of the terminal. If there is only one link in the active set, the combined TPC command is one detected TPC command stream for that particular link. Various Methods of determining and combining TPC Commands are known, such as those described in U.S. patent application No.2004/00058700 "Methods, Receivers, and Computer Program Product for determining Transmission Power Control Command Using binary Interpretation" to J.Nilsson et al. TPC combining is generally based on the idea of "transmit power down if any reliable TPC command indicates down" and can be implemented in a number of ways.

The signal provided by the Fe TX 414 is based on a signal from a suitable modulator 416, which modulator 416 receives the data to be transmitted as well as the ACK/NACK signal as described above. The modulator 416 also receives signals from a Channel Quality Indication (CQI) mapper 418 that "maps" or converts the estimated SIR values of the CPICH or other suitable channel generated by the estimator 408 to corresponding CQI values. Through modulator 416 and front end transmitter 414, UE 400 sends these CQI values to the various base stations as an indication of the modulation and coding schemes that may be used by the BS. In a typical configuration, a high SIR is mapped to represent a high CQI that may use a high code rate and more complex modulation (e.g., 16-QAM), while a low SIR is mapped to represent a low CQI that may use a low code rate and simpler modulation (e.g., QPSK).

As can be seen in fig. 4, the TPC filter 420 and control unit 422 cooperate to determine the ratio of up/down commands during the most recent slot for the HSDPA serving cell and use the ratio signal to determine whether the TPC combiner 412 should implement the normal TPC command combination or whether the transmit power of the UE should be based on TPC commands from the HSDPA serving cell only. It should be understood that although fig. 4 shows filter 420 and control unit 422 as separate devices, their functions may be combined and implemented by a single device (e.g., a suitably programmed or configured processor or circuit).

The TPC filter 420 and the control unit 422 preferably operate together as follows. The TPC "up/down" command ratio is measured for HSDPA serving cells that filter 420 and unit 422 may identify by appropriate signals obtained from higher layer signaling. It is presently believed that the ratio can be determined by considering a time window comprising the first N time slots (20 < N < 200). The ratio signal may then simply be the number of TPC "up" commands received during the N slots divided by the total number of N slots. Of course, it will be appreciated that other forms of ratio signals may be used, such as the number of "down" commands received during the N time slots divided by N, with other modifications as appropriate. For another example, the ratio signal may be in the form of the number of "up" commands received during the N time slots divided or subtracted (less) by the number of "down" commands received during the N time slots. It may also be preferable to consider ratios according to the size of N, so that when N is smaller, a larger number of "up" commands or a larger change in ratio is required to indicate a poor quality UL.

If the ratio signal is less than about 50-80% (for a ratio signal having the form of the number of "up" commands received during N slots divided by N), the UE may consider the HS serving cell UL synchronization and HS-DPCCH detection in the BS may be considered to work well. In this case, the UE may use a standard SHO TPC combining algorithm, e.g., power down if any reliable TPC command indicates a down. If the ratio signal is greater than about 80%, the UE may consider the HS serving cell UL to be of poor quality and may have almost lost synchronization. In this case, the control unit 422 may determine that: the transmit power of the UE should be based only or primarily on TPC commands from the HSDPA serving cell.

Those of ordinary skill in the art will appreciate that the above-described threshold of about 80% (e.g., 50% -80%) is merely an example, and that other values may be used. It is currently believed that a UL with good quality may have less than 60-70% of "up" commands in SHO situations (i.e., where there is more than one cell in the active set), while a UL with poor quality may have almost 100% of TPC "up" commands. It can be appreciated that when there is only one cell in the active set, it can also be expected to have a TPC up/down command ratio of 50% (greater or less) when one UL is of good quality. However, in the case where there is only one cell in the active set, the UE only always obeys TPC commands from that cell.

The filter 420 may be implemented in a variety of ways. For one example, filter 420 may include a counter and a divider, where the counter counts the "up" commands and the divider divides the number of "up" commands by the number of N time slots. For another example, the filter 420 may include only a counter, where the counter is incremented by 1 or decremented by 1 according to the TPC command, such that a count of 0 corresponds to a ratio of 50%.

It should be appreciated that there is no need for the UE to change abruptly between strategies for processing TPC commands. It may be preferable to provide a softer or smoother transition from transmit power control based on the usual strategy (combining TPC commands from all cells in the active set) to transmit power control based on a new strategy (using only TPC commands from the HSDPA serving cell). There are a number of ways to achieve a soft transition. As an example, let TPC "up" command ratio be x. If x is less than about 60%, the usual strategy is used for SHO TPC command combinations. If x is greater than about 60% and less than about 80%, the transmission power is controlled in every third slot and the usual strategy is used for the remaining slots based only on TPC commands from the HSDPA serving cell. If x is greater than about 80% and less than about 90%, the transmission power is controlled in every second slot (i.e., every other slot) and the usual strategy is used for the remaining slots based only on TPC commands from the HSDPA serving cell. If x is greater than about 90%, the transmission power is controlled in each slot only according to the TPC commands from the HSDPA serving cell.

Fig. 5 is a flow chart of a method according to the invention. In step 502, the UE is in SHO situation and the HS serving cell is BS a. In step 504, the TPC commands are combined according to the usual strategy in SHO, and the result of the TPC command combination is used in the next slot to adjust the transmit TX power of the UE by either "up" or "down" by one increment. In step 506, the TPC command stream received from BS a during the first N slots is filtered. If the obtained filtered signal indicates that the quality of the UL to BS a is not poor (step 508), the flow returns to step 504. However, if the TPC command ratio indicates poor quality of the UL to BS a, the transmission power of the UE is controlled in the next slot based on only the TPC commands from BS a (step 510). The flow then returns to step 506 and another set of N TPC commands is filtered to determine the UL quality.

It will be appreciated that the above-described process may be repeatedly performed as necessary, for example, to respond to the time-varying nature of the communication channel between the transmitter and receiver. To facilitate understanding, aspects of the invention may be described in terms of sequences of actions that can be performed by, for example, elements of a programmable computer system. It will be recognized that various actions could be performed by specialized circuits (e.g., discrete logic gates interconnected to perform a specialized function or application-specific integrated circuits), by program instructions being executed by one or more processors, or by a combination of both.

Moreover, the invention can be considered to be embodied entirely within any form of computer-readable storage medium having stored therein an appropriate set of instructions for use by or in connection with an instruction-execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch instructions from a medium and execute the instructions. As used herein, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer readable medium can be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), and an optical fiber.

Thus, the invention may be embodied in many different forms, not all of which are described above, and all of which are considered to be within the scope of the invention. For each of the various aspects of the invention, any such form may be referred to as "logic configured to" perform a described action, or alternatively as "logic that" performs a described action.

It should be emphasized that the terms "comprises" and "comprising", when used in this application, specify the presence of stated features, integers, steps or components and do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

The particular embodiments described above are illustrative only and should not be considered limiting in any way. The scope of the invention is determined by the appended claims, and all changes and equivalents that fall within the range of the claims are intended to be embraced therein.

Claims (22)

1. A User Equipment (UE) in a communication system, the UE comprising:

means for recovering control symbols to be used for the UE, wherein the control symbols include Transmit Power Control (TPC) commands directed to the UE from at least two transmitting nodes, one of the transmitting nodes being a serving node for a predetermined communication service;

a TPC command filter configured to generate a ratio signal from TPC commands directed from the serving node to the UE during a plurality of time slots; and

a TPC combiner responsive to the ratio signal and configured to receive a TPC command from the apparatus and to generate a TPC control signal based on the received command and the ratio signal, the TPC control signal being used to control the power transmitted by the UE;

wherein the TPC control signal is based only on TPC commands directed from the serving node to the UE if the ratio signal exceeds a first threshold.

2. The User Equipment (UE) of claim 1, wherein the TPC control signal is based on a combination of the TPC commands directed from the at least two transmitting nodes to the UE if the ratio signal does not exceed the first threshold.

3. The user equipment of claim 1, wherein the TPC command filter counts power up commands received during the plurality of time slots.

4. The user equipment of claim 3, wherein the first threshold is about 0.8.

5. The user equipment of claim 3, wherein the TPC command filter counts power down commands received during the plurality of time slots.

6. The User Equipment (UE) of claim 1, wherein the TPC control signal is based on a combination of TPC commands directed from the at least two transmitting nodes to the UE for a first number of slots after the plurality of slots and is based on TPC commands directed from the serving node to the UE only for a second number of slots after the plurality of slots if the ratio signal exceeds a second threshold and does not exceed the first threshold.

7. The user equipment of claim 6, wherein the TPC command filter counts power up commands received during the plurality of time slots.

8. The user equipment of claim 7, wherein the first threshold is approximately 0.9 and the second threshold is 0.6.

9. The user equipment of claim 1, wherein the communication system uses wideband code division multiple access and the predetermined communication service is a high speed downlink packet access service.

10. A method in a User Equipment (UE) for controlling power transmitted by the UE in an uplink in a communication system, the method comprising:

receiving Transmit Power Control (TPC) commands from at least two communication nodes, one of the communication nodes being a serving node for a predetermined communication service;

generating a ratio signal from TPC commands received from the serving node during a plurality of time slots; and

generating a TPC control signal for controlling power transmitted by the UE based on the received TPC command and the ratio signal;

wherein the TPC control signal is based only on TPC commands received from the serving node if the ratio signal exceeds a first threshold.

11. The method of claim 10, wherein the TPC control signal is based on a combination of TPC commands received from the at least two communication nodes if the ratio signal does not exceed the first threshold.

12. The method of claim 10, wherein generating the ratio signal comprises counting power up commands received during the plurality of time slots.

13. The method of claim 12, wherein the first threshold is about 0.8.

14. The method of claim 12, wherein generating the ratio signal comprises counting power down commands received during the plurality of time slots.

15. The method of claim 10, wherein if the ratio signal exceeds a second threshold and does not exceed the first threshold, the TPC control signal is based on a combination of TPC commands received from the at least two communication nodes for a first number of slots after the plurality of slots and is based only on TPC commands received from the serving node for a second number of slots after the plurality of slots.

16. The method of claim 15, wherein generating the ratio signal comprises counting power up commands received during the plurality of time slots.

17. The method of claim 16, wherein the first threshold is about 0.9 and the second threshold is about 0.6.

18. The method of claim 16, wherein generating the ratio signal comprises counting power down commands received during the plurality of time slots.

19. The method of claim 10, wherein the communication system uses wideband code division multiple access and the predetermined communication service is a high speed downlink packet access service.

20. A computer readable medium embodying a computer program for controlling power transmitted by a User Equipment (UE) in an uplink in a communication system, wherein the computer program performs the steps of:

generating a Transmit Power Control (TPC) command ratio signal from TPC commands received from a serving node during a plurality of time slots; and

generating a TPC control signal based on TPC commands received from the serving node and at least one other communication node and based on the TPC command ratio signal, the TPC control signal for controlling power transmitted by the UE;

wherein the TPC control signal is based only on TPC commands received from the serving node if the ratio signal exceeds a first threshold.

21. The computer readable medium of claim 20, wherein the TPC control signal is based on a combination of TPC commands received from the serving node and the at least one other communication node if the TPC command ratio signal does not exceed the first threshold.

22. The computer readable medium of claim 20, wherein the TPC control signal is based on a combination of TPC commands received from the serving node and the at least one other communication node for a first number of slots after the plurality of slots and based only on TPC commands received from the serving node for a second number of slots after the plurality of slots if the TPC command ratio signal exceeds a second threshold and does not exceed the first threshold.