Adaptive power control in a radio communications system

Adaptive power control in radio communication systems

<u>Scope of invention</u>

The present invention relates to power control in radio communications, and more particularly to more efficient and cost effective open circuit power control. The adaptive open circuit power control method of the present invention is particularly well suited for communication in a code division multiple access (CDMA) cellular radio system.

<u>Background and summary of the invention</u>

Power control is an important issue in radio communication systems, especially in the third generation of Wideband Code Division Multiple Access (WCDMA) cellular systems. Before transmitting through the "uplink" channel, the mobile station must first set its transmit power potential. Similarly, the radio access network must also set the base station's transmission power on the "downlink channel". For example, in addition to the traffic channel (TCH), there is also a paging channel &lt;pagingchannel; PCH). Forward access channel (FACH). Indeed, the actual power potential set for the mobile station's and base station radio transmissions, as well as the resulting interference potential, can significantly affect the mobile radio communication system.

The physical characteristics of the radio channel can be very important for several reasons. For example, signal propagation losses between a radio transmitter and a receiver may vary due to their respective locations, obstacles, weather, and the like. As a result, the strength of the signals received by the base stations from different mobile stations can vary greatly. If the transmission power of the mobile station signal is too low, the receiving base station may not be able to correctly decode the weak signal and the signal must be corrected (if available) or retransmitted. Therefore, since the signal reception error causes the signal to be retransmitted, the delay associated with the radio access procedure is increased, the internal processing time of the data processing data processing is increased, and the available radio bandwidth is reduced. On the other hand, if the mobile transmission power is too high The signal transmitted by the mobile station will cause interference to other mobile stations and base stations in the system.

In a code division multiple access (CDMA) system, a large number of radios transmit and receive on the same frequency, so interference is a particularly serious problem. If a mobile station transmits with too high power output, the interference will result in a signal-to-interference ratio (SIR) degradation of the signal received from other mobile radios, which may cause the base station in the receiving station to not demodulate correctly. Change the transmission from other mobile stations. In fact, if the power level used by the mobile station to transmit signals is twice the power potential required for the base station receiver to accurately receive the signal, then the system capacity occupied by the motion signal is the signal transmitted at the optimized power potential. About twice. However, it is very confusing for the case where the high-power mobile station transmits the signal to the base station with many other transmission strengths and many times of the intensity. The loss of system capacity caused by such ultra-strong mobile stations is unacceptable.

There are other issues related to using too much power transfer. One of them is the so-called "party effect." If the mobile station transmits at too high a power potential, other mobile stations may increase their respective power potentials so that they can be "listened", causing the already severe interference problem to worsen. Another problem is wasting battery power. In mobile radio, it is important to save limited battery life. Obviously, the mobile station battery consumes the most power during transmission. Therefore, the primary goal of any power control method is to reduce the transmission power, and the result of the reduced transmission power does not cause the number of retransmissions to increase to an unacceptable level. In addition to battery consumption, the above-mentioned problem of setting transmission power also applies to downlink radio transmissions from a base station.

There are two basic methods of power control: open circuit and closed circuit. In open circuit power control, the transmission power calculated by the transmitter is based on one or more parameters, and the calculated value is used to set the transmission power potential. In particular, in order to match the estimated path loss, the base station receives the signal at a predetermined power potential, so the transmission power is adjusted. Closed-loop power control relies on feedback from the receiver to enable the transmitter to know, for example, what the received signal is at the power potential (and sometimes also what the interference potential is). The transmitter then uses this feedback to adjust its transmit power potential. Alternatively, the receiver can directly instruct the transmitter to increase or decrease its transmission power. Additional feedback received indicates that closed-loop power control is usually more accurate than open-circuit power control.

The common channel of the uplink and downlink shared by several mobile radios is usually used to transmit relatively short control signaling messages, delay, signal internal operating time, spreading code configuration, and bandwidth consumption of the shared channel. In this case, the control signaling message does not adjust the additional "cost". It is also possible to use a common channel to transmit short traffic data packets, which are directly attached to typical control messages transmitted on a common channel. The "lower cost" open circuit power control is suitable for transmission through common channels. Compared with the closed circuit power control commonly used for dedicated channels, the open circuit power control is faster, simpler, and occupies less radio resources.

One of the common channel types shared by the mobile station is a random access channel. If there are multiple mobile stations that have not been configured with dedicated channels, the random access channel can provide communication between multiple mobile stations and one base station. Access channel messages may include, for example, call hold, response page, indication, registration, and small user data packets. However, because multiple mobile stations may use random access channels at the same time, each additional mobile station being transmitted on the access channel contributes to background noise and interference, thereby reducing the system's limited capacity. Therefore, it is important to set the appropriate output power of the mobile station before transmission.

Therefore, before performing random access, the mobile station calculates the open transmission power γ used on the uplink direction random access channel, enabling the base station to receive the signal of the mobile station at a predetermined power potential. In particular, the mobile station is working hard to achieve the goal of carrier-to-interference ratio (CIR). The carrier-to-interference ratio (CIR) actually received by the base station is equivalent to the received uplink carrier power C._ULReduce uplink interference I_UL. Receiver carrier power C_ULEquivalent to the mobile station transmission power potential P_TxReduce the path loss L. Therefore, open circuit power control can determine the transmission power<img file="TW453056B_D0001.tif" />Carrier-To-Interference Ratio (CIR) γ, uplink interference estimation<img file="TW453056B_D0002.tif" />And path loss estimates<img file="TW453056B_D0003.tif" />function. Obtain path loss estimate<img file="TW453056B_D0003.tif" />The method may be that the mobile station measures the received power of a known signal transmitted by the base station on the downlink channel (for example, a downlink pilot or other broadcast signal). The known signal includes a signal to the mobile station about the power used by the base station to transmit the known signal. The uplink is estimated (measured) by the base station and broadcast by the base station through the cells along with the downlink pilot signal output power values. Then, the carrier-to-interference ratio (CIR) γ may be utilized according to the following open-circuit power control algorithm._tUplink interference estimation number<img file="TW453056B_D0002.tif" />And the path loss estimate L function to determine the transmission power<img file="TW453056B_D0001.tif" />：

<img file="TW453056B_D0007.tif" />

It can be borrowed that the open circuit power control algorithm of equation (1) will be due to the carrier-to-interference ratio (CIR) and carrier-to-interference ratio (CIR) γ._tDifferent from the uncertainty caused by it. For example, because many factors can cause estimated path loss<img file="TW453056B_D0008.tif" />Usually different from the actual path loss L, these factors are like: (1) the actual power of the base station transmission pilot signal may be different from the broadcast downlink pilot signal output power value, and (2) the measured mobile station signal strength is not Accurate, (3) There is fading, noise, and delay in the process of testing path loss. Similarly, the last measurement of uplink interference I from the base station_ULAfter uplink interference estimation I_ULThere may be significant changes. And, even if the open circuit power control program determines the transmission power<img file="TW453056B_D0001.tif" />It is a fairly accurate estimate that the actual transmission power Ptx transmitted by the mobile station may be different from the transmission power of the present due to the defect and hardware limitations in the implementation of the mobile station. For example, factors that significantly change the mobile transmission power include the current temperature of the mobile station and the nonlinear components used in the mobile station. The actual carrier-to-interference ratio (CIR) γ of the base station is:

γ=P_Tx-I_UL-L (2)

Unable to know exactly the actual transmission power P_TxActual uplink interference and actual path loss. The disadvantages of open circuit power control for uplink transmission descriptions also apply to open circuit power control for downlink transmissions on common channels (eg, forward access channels (FACH), etc.).

These various factors can cause the carrier-to-interference ratio (CIR) γ and the carrier-to-interference ratio (CIR) γ to be received._tThe difference is about ±10 dB or more. Figure 1 shows a graph of the carrier-to-interference ratio (CIR) probability density function (PDF) fr(γ) received to illustrate this uncertainty. In fact, the carrier-to-interference ratio (CIR) probability density function may be closer to the Gaussian distribution. Figure 1 simply shows the fact that there is a carrier-to-interference ratio (CIR) deviation.

In short, the limitations and operations of the open-circuit power control methods described above (eg, temperature) and the practicality of implementation (non-linear components) have made it difficult to achieve proper open-circuit transmission power in current transmissions in the current environment. . The end result is that communication is not possible (transmission power is too low), or unnecessary interference causes system capacity loss (transmission power is too high).

One of the ways to solve some of the above problems is to use power "ramping", as described in Ericsson's U.S. Patent No. 5,430,760. The mobile station initializes the random access with the initial low transmission power potential and gradually (e.g., increments) the transmission power potential until the base station detects and acknowledges the access signal. Once detected, the power potential of the message is maintained by detecting the potential. One of the disadvantages of this power ramp-up method is that it can cause significant delays in the access procedure. In particular, when a mobile station or the like holds a response to the most recently transmitted access signal, there may be a substantial delay between access attempts. This delay is particularly unpopular under low traffic load balancing where the interference caused by random access transmission is less important. On the other hand, if a ramp-up occurs too quickly, the power potential may be too high in response to the detected signal. Loss or failure to respond to a response message adds some level of complexity.

In order to reduce the delay in the power ramping process, the power "ramping" of the preamble potential may be used, as described in U.S. Patent Application Serial No. 09/166,679, filed on Oct. 5, 1998. This is incorporated herein by reference. The mobile station transmits only the short preamble signal and increments the power until the base station detects the received preamble energy (as opposed to decoding the entire random access message) and passes the backed acquisition indicator back to the mobile station. However, no matter how the power "ramping" is performed, the transmitter must determine the initial transmission power potential to start "ramping" based on the open circuit power control described above.

One of the objects of the present invention is to achieve an optimal power control method for illustrating current transmission conditions.

One of the objects of the present invention is to provide an adaptive power control technique for determining good communication quality with minimal interference.

One of the objects of the present invention is to determine a compensation type transmission power potential such that the carrier-to-interference ratio (CIR) actually received is equal to or close to the carrier-to-interference ratio (CIR). ).

One of the objects of the present invention is to reduce the transmission power, and the result of the reduction in transmission power does not cause an increase in the number of retransmissions.

One of the objects of the present invention is to extend the life of a mobile station battery by controlling the transmission power potential of the mobile station to a minimum, but still effectively transmitting the power potential.

One of the objects of the present invention is to avoid unnecessary delays in radio access when using open circuit power control in access transmission, especially in the case of low traffic.

One of the objects of the present invention is to avoid unnecessary delays in radio access when using preamble power ramping in access transmission, especially in the case of low traffic.

It is an object of the present invention to provide a flexible mobile station power control technique that takes into account current interference levels, mobile station specific parameters, and other factors without the need for power detection response signals or other power related components from the receiver. feedback of.

One of the objects of the present invention is that the mobile station adapts the open circuit power setting by identifying power potential feedback in the response message received from the base station on successful and unsuccessful random access.

One of the objects of the present invention is to adapt and compensate for temperature, mobile station system errors, and base station system errors.

The adaptive power control of the present invention overcomes the problems as described above and meets these and other objectives. In a preferred exemplary embodiment, the delay in the common radio transmission channel is a plurality of mobile stations located in the corresponding geographic cell area by adapting the transmission power according to the traffic load. The channel used by the base station to communicate. A lower communication traffic load allows for higher transmission power, while a higher communication traffic load sets a lower transmission power.

The conditions for determining the transmission power setting include: a desired signal ratio (for example, a target CIR (carrier noise ratio)), a transmission path loss on a radio transmission channel, and an interference value. An adaptive power parameter is also used, which determines how to adapt the open circuit power control based on one or more current communication conditions and/or characteristics of the mobile station. For example, the adaptive power parameter may be a function of current interference in a single base station cell, or a function of a combination of current interferences in one or more neighboring cells. The adaptive power parameters also describe the following: after random access, the type of data packet used between the mobile station and the base station, the description of the mobile station, the current temperature of the mobile station, the base station currently used by the mobile station, The current estimated path loss between the mobile station and the base station, and/or other factors.

<u>Detailed description of the schema</u>

The following description is intended to be illustrative of the invention, and is not intended to It will be apparent to those skilled in the art, however, that the present invention may be embodied in other specific embodiments without departing from the specific details. For example, the present invention facilitates the use of mobile transmission on a random access channel uplink in a code division multiple access (CDNIA) communication system, and the present invention also facilitates control of any direction, through any particular channel type, and any type. The transmission power of a radio in a communication system (eg, divided multiple access FDMA, time division multiple access (TDMA), etc.). Although the invention is sometimes illustrated in terms of the random access type of the common channel, the invention is equally applicable to other common channels and dedicated channels. Indeed, the invention can be employed in any transmission power control situation. In other instances, detailed descriptions of well-known methods, interfaces, devices, and signalling techniques are omitted to avoid obscuring the description of the invention in unnecessary detail.

The first exemplary embodiment will now be described in conjunction with the power control routine (step 2) shown in FIG. First, the transmission radio determines the initial transmission power (step 4). However, when the radio transmission power potential is set according to the initial transmission power of this decision, it is highly likely that the receiving radio will receive the signal with an undesired carrier-to-interference ratio (CIR), that is, the carrier. The Carrier-To-Interference Ratio (CIR) is too high or too low. Therefore, the initial transmission power in step 4 is adjusted using the adaptation parameters to account for one or more of the current communication flow conditions (step 6). In this preferred exemplary embodiment, the adaptability parameter describes the current communication traffic affecting the radio communication. Then, the transmission power of the radio is controlled based on the adapted transmission power value (step 8). In particular, at low traffic load, a higher transmission power value is set to produce a higher transmission power value. Or, at higher traffic load, set a lower transmission power value, or even a negative value, to minimize interference from nearby nearby radios. Otherwise, in some cases, extremely high transmission power can cause additional radio transmission power (ie, party effect) to be added without control until its maximum transmission power is reached.

Figure 3 shows the carrier-to-interference ratio (CIR) γ relative to the target carrier._t, the carrier-to-interference ratio (CIR) γ probability density function (PDF) pattern, and the effects of different adaptive parameter values. The larger adaptive power parameter value shifts the fr(γ) pattern to the right, indicating that the carrier-to-interference ratio (CIR) γ is higher than the target carrier noise ratio (Carrier- To-Interference Ratio; CIR). The result is that the probability of success is greater, and the communication power parameter value with shorter communication delay is smaller, and the fr(γ) pattern is shifted to the left, which can reduce the total amount of interference caused by each user, however, The result is a lower chance of success. The present invention also provides that the mobile station can vary the adaptive power parameters due to temperature, mobile station system errors, and base station system errors to reduce the width of fr([gamma]).

The present invention is applicable to any radio communication and any direction (e.g., uplink and downlink), and the next exemplary embodiment of the present invention illustrates a common communication (particularly random access communication) Uplink communication content of one or more mobile stations. For example, such a common random access channel is employed in the third generation of Wideband Code Division Multiple Access (WCDMA) cellular systems. Figure 4 shows a mobile radio cell communication system 10, which may be code division multiple access (CDMA) or wideband code division multiple access (Wideband Code Division Multiple) Access; WCDMA) communication system. Radio Network Controllers (RNC) 12 and 14 control various radio network functions including, for example, radio access transmission channel settings, diversity handover, and the like. A Radio Network Controller (RNC) 12 is coupled to a plurality of base stations 16, 18, and 20. A Radio Network Controller (RNC) 14 is coupled to a plurality of base stations 22, 24, and 26. Each base station serves a geographical area called a cell, and a cell can be divided into a plurality of sections. The base station 26 shown in Figure 4 has six antenna areas S1-S6. The base station is connected to a corresponding Radio Network Controller (RNC) by various means (e.g., dedicated telephone lines, fiber optic connections, microwave connections, etc.). Radio Network Controllers (RNCs) 12 and 14 are connected to external networks, such as the Public Switched Telephone Network (FSTN), through one or more mobile switching centers and/or packet radio service nodes (not shown). , internet, and more. The Radio Network Controller (RNC) delivers the call via the appropriate base station.

The two mobile stations 28 and 30 shown in Figure 4 communicate with a plurality of base stations. The mobile station 28 communicates with the base stations 16, 18, and 20, and the mobile station 30 communicates with the base stations 20, and 22. The control link between the Radio Network Controllers (RNC) 12 and 14 permits diversity communication with the mobile station 30 via the base stations 20 and 22. Each radio communication channel established between the mobile station and the base station has an uplink component and a downlink component. Because multiple communications utilize the same radio frequency (RF) in code division multiple access (CDMA) communications, spread code and other well-known code division multiple access (CDMA) techniques are used to distinguish between various mobile and base station communications. In this exemplary embodiment, the term "channel" means a code division multiple access (CDMA) channel for any mobile station and defines channels for radio frequency (RF) frequencies and specific code sequence aspects.

The base station and radio network controller (RNC) functions will now be described in more detail in conjunction with FIG. Each Radio Network Controller (RNC) includes a network interface 52 for communicating with various base stations via an interface. Within the Radio Network Controller (RNC), the network interface 52 is coupled to the controller 50 and to the Diversity Transfer Unit (DHO) 54. Diversity Switching Unit (DHO) 54 performs various functions required, such as establishing, maintaining, and removing diversity connections, such as diversity combining, diversity partitioning, power control, and other connected phase radio resource control algorithms.

Each base station includes a corresponding network interface 60 for communicating with a Radio Network Controller (RNC) via an interface. In addition, the base station includes a controller 62 coupled to a plurality of transceivers (TRX) 64, 66, 68, and 70; and a transmission power controller 72. Controller 62 controls the overall operation of the base station and the establishment, maintenance, and release of radio connections. Representative Transceivers (TRX) 64 through 70 are individually assigned to specific communications with the mobile station. At least one transceiver is used as a common control channel through which the base station transmits signals, such as pilot, synchronization, or other broadcast signals. A mobile station in or near the base station cell monitors the common control channel.

The mobile station uses a common channel called the Random Access Channel (RACH) to transmit (uplink) stations in order to request dedicated channels, which can also be used for a limited amount of user data. The mobile station uses the common channel of the forward access channel (FACH) to transmit (uplink) a limited amount of user data. For common channels such as RACH and FACH, open circuit power control is preferred. The transmit power controller 72 performs open-circuit power control of the downlink, and the transmit power controller performs an uplink closed-loop power control procedure to control the transmit power of all mobile transmissions received from the base station, for example, assuming all large mobile stations When the same type of service is being used, approximately the same power potential is processed.

Figure 6 shows a more detailed functional block diagram of the mobile station shown in Figure 4. The mobile station includes a controller 80 coupled to a RAKE receiver 82, a transmission power controller 88, and a transmitter 90. RAKE receiver 82 includes a plurality of receivers 84 and 85 (and possibly additional receivers) that are coupled to diversity combiner 86. The action receiver 82 employs one or more signal strength detectors (not shown) or similar detectors for detecting signal strength or other received signal parameters. The transmissions from the base station are received as multiple paths in receivers 84 and 85, combined with diversity combiner 86, and processed as a single signal. The transmission power controller 88 determines the power potential of the received and diversity combined signals (preferably as a carrier-to-interference ratio (CIR) or as a signal to interference ratio (SIR) (R)._b/I_o)。

The operation of this exemplary embodiment in accordance with the present invention will now be described in conjunction with the flowchart of the adaptive open circuit power control routine (step 100) shown in FIG. The mobile station 30 detects a carrier-to-interference ratio (CIR) γ broadcast by the base station through the downlink access channel._tThe carrier-to-interference ratio (CIR) γ may also be predefined in the system._tTherefore, the mobile station already knows the carrier-to-interference ratio (CIR) γ._t. The mobile station 30 also detects the current measured uplink interference estimate.<img file="TW453056B_D0002.tif" />And estimate the uplink interference through the corresponding geographical cells of the base station<img file="TW453056B_D0002.tif" />Broadcast with downlink pilot (or other broadcast) signal transmission power values. Then, the action controller 80 determines the path loss.<img file="TW453056B_D0008.tif" />The estimate is obtained by using the difference between the transmission power broadcast value (step 102) of the downlink pilot signal actually transmitted from the base station and the actual received power of the downlink pilot signal. According to the equation described above<img file="TW453056B_D0013.tif" />The action controller 80 can derive from these determined parameters γ,<img file="TW453056B_D0002.tif" />,and<img file="TW453056B_D0008.tif" />To determine the transmission power<img file="TW453056B_D0001.tif" />。

However, the mobile station 30 (e.g., the motion controller 80) also determines a cell-specific adaptive power parameter based on current conditions and parameters, referred to as the power shift value Δ in this exemplary embodiment (step 104). Then, the transmission power of the mobile station is determined according to the following equation (step 106):

<img file="TW453056B_D0017.tif" />

The power shift value Δ is preferably a cell-specific shift Δ depending on the current communication flow load in the cell._C. For example, in a cell that performs random access on a mobile station, and in uplink interference in one or more neighboring cells, Δ_CMay be the uplink interference of the test<img file="TW453056B_D0002.tif" />The function. Therefore, it is possible to define the power shift value Δ_CAs a function of the uplink interference values of a plurality of measurements currently in neighboring cells, as follows:

<img file="TW453056B_D0019.tif" />

Uplink + scrambling<img file="TW453056B_D0002.tif" />Perform measurements in cells that perform random access on the mobile station, and<img file="TW453056B_D0021.tif" />Is the uplink interference value measured in N neighboring cells. Therefore, it is possible to use only the native uplink interference value.<img file="TW453056B_D0002.tif" />Preferably, several uplink interference values from neighboring cells are used. This is because in a code division multiple access (CDMA) system, all mobile stations transmit and receive on the same channel because uplink interference in neighboring cells is also generated. As a result, interference programs in these cells often affect the overall uplink interference of the mobile station.

A simple exemplary function of equation (4) is<img file="TW453056B_D0023.tif" />, where A is a constant, and I_ULmaxIs the maximum allowable uplink interference. Of course, other functions may be used. In general, lower interference values, Δ_CMay be larger. Best, the interference in the current cell of the mobile station is Δ_CThe effect should also be greater than the effect of adjacent cell interference values.

Random access must generate more uplink interference. Therefore, other enabled mobile stations must increase their respective transmission powers in order to maintain the same carrier-to-interference ratio (CIR), thereby increasing uplink interference. But at low traffic load (ie, low I_UL), the system can allow this to happen, because I_ULIt does not increase above the maximum allowable value, which defines the maximum uplink capacity of a code division multiple access (CDMA) system. In addition, other enabled mid-motion stations in cells using open-circuit power control may compensate for interference caused by random access.

Therefore, set a higher parameter Δ for low traffic load_CLead to higher transmission power. As shown in Figure 3, the carrier-to-interference ratio (CIR) probability density function (PDF) moves to the right of the carrier-to-interference ratio (CIR), and the result is successful. The probability of random access is large and the packet delay is short. It is foreseeable that low traffic load conditions will be quite common, as cell systems are best planned with higher traffic load conditions, and high traffic loads typically have specific spike times. Therefore, this higher transmission power will improve the system performance in the case of typical communication traffic. Conversely, at higher traffic load, set the lower power shift value Δ when the uplink interference receives the maximum allowable value._CPerhaps even a negative value, as shown in Figure 3, to avoid interfering with other users on the uplink. Although this provides a lower probability of carrier-to-interference ratio (CIR) reception, and thus provides the lowest probability of successful random access and larger packet delay, it still needs to be during periods of high interference. Exchange to ensure continued communication without gradual increase in transmission power (ie, party effect) to all users.

The above explains how to shift the power shift value Δ according to the present invention._CThe mobile transmission power applied to the uplink common channel (for example, the RACH channel) is applied. In addition, the power shift value Δ_CIt may be applied to the downlink common channel with open circuit power control. In the downlink common channel, path loss and interference on the mobile station are measured and reported by a mobile station connected to the radio network. Alternatively, the power potential on the FACH should be compared to the broadcast pilot signal transmission power potential. After calculating the FACH transmission power potential, then the radio network may shift the power to a value of Δ_CThe transmit power potential is applied and the transmit power potential is adapted to high or low traffic load conditions, as described above for uplink transmission.

The transmission power of the mobile station for random access may also depend on the parameters specified by the user alone or in addition to the parameters specified in the uplink interference. For example, the power shift value may depend on the particular data packet mode employed by the mobile station after random access. For example, if a dedicated communication traffic channel is configured for the mobile station immediately after random access, it may be possible to set a higher power shift value in order to provide fast random access and thereby facilitate rapid transfer to dedicated aisle. The dedicated communication flow channel has a high capacity and usually adopts more precise closed-circuit power control. Compared with the shared or common communication flow channel that usually does not use closed-circuit power control, the dedicated communication flow channel does not interfere with the whole system. . In addition, the power shift value may depend on the registration of the mobile station. The mobile user can register the priority access function , with the result that a larger power shift value increases the chance of fast random access and low latency on the common channel. Therefore, the user-specific power shift value Δ can also be increased._UTo set the mobile transmission power in a manner similar to the power shift value Δ as described above._Cthe same.

<img file="TW453056B_D0024.tif" />

May not use Δ_CThe power shift value Δ is used in the case_UAnd set the transmission power potential on the downlink common channel (eg, FACH channel).

The mobile transmission power on random access may still depend on other factors. As illustrated in the background of the invention, due to the calculated transmission power of the mobile station<img file="TW453056B_D0001.tif" />The uncertainty of the actual transmission, resulting in the carrier-to-interference ratio (CIR) and the carrier-to-interference ratio (CIR) (γ)_tThere is a gap between them. Indeed, the mobile station may be at actual power P_TxTransmission, and actual power P_TxComputable or desired transmission power<img file="TW453056B_D0001.tif" />There are quite a few differences. Although the transmit power controller 88 provides the desired transmit power potential for the transmitter 90, the following exemplary variables may still significantly affect the actual transmit power potential:

Action table temperature

The actual power potential in the current transmission of the mobile station

Individual electronic components contained in specific mobile stations

Another important factor is that the mobile station may also have system errors in estimating the path loss. Estimated path loss due to measurement error in the signal strength detector in the mobile station<img file="TW453056B_D0008.tif" />It may be different from the actual path loss L. Path loss estimates may also differ from actual path losses due to fading, noise, and delay in the process of loss of test paths. In addition, the actual transmission power of the base station actually transmitting the pilot signal may be different from the broadcaster pilot signal output power value used by the mobile station for path loss estimation. These factors are called mobile station specific errors and base station specific errors.

The device-specific power shift value Δ is utilized in the present invention_ETo compensate for this type of mobile station specific error and base station specific errors. It is known that mobile station specific parameters may be accumulated and stored in the mobile station. It is known that the base station may accumulate and store base station specific errors for each base station. The mobile station then supplies the appropriate compensation.

In the following example, it is assumed that the base station accurately measures the received power potential and assumes that the broadcast power potential of the base station pilot signal is equal to the power potential of the pilot actual transmission. The example illustrates the mobile station compensating for temperature drift, system errors in signal strength detection, and the systematic difference between the actual transmitted output power and the specified output power. Other factors that cause transmission power errors may be compensated in a similar manner.

During random access transmission, the base station measures the received random access signal power from the mobile station, C=P_Tx-L, and the measured value<img file="TW453056B_D0028.tif" />Provided to the mobile station. The goal of the mobile station is to achieve the target received random access signal power C_tequal<img file="TW453056B_D0029.tif" />. Thus, the mobile station determines that the received signal power error E is

<img file="TW453056B_D0030.tif" />

If E is a positive number, the power transmitted by the mobile station is too low; and if E is negative, the mobile station uses a power higher than the required power to achieve the received power target C._t. The mobile station measures its current temperature, current transmission power potential, and signal power error E, and stores these specific temperature and power potential measurements in a lookup table. The next time the mobile station performs a random access transmission, the mobile station queries the signal power errors stored in the table for the actual temperature and the transmission power potential to compensate for such errors. There are many ways to perform this compensation. One of the methods is to define the device-specific compensation term Δ at time t._E,as follows:

<img file="TW453056B_D0031.tif" />

Where E(t-1) represents the previous received signal power error value for this temperature and transmission power, and E(t-2) represents the second previous value. The coefficient α (&lt;1) indicates that Δ is updated based on the new data._EDegree.

Therefore, for a given temperature and absolute power potential, the mobile station calculates the compensation term Δ_EAnd Δ_EIncreased to the mobile transmission power in a manner similar to the cell-specific shift value Oc and the user-specific shift value Δ in equation (5) as described above_UThe same, it uses all, part, or only one of the specific power shift values, for example

<img file="TW453056B_D0032.tif" />

The mobile station controller 80 calculates one or more specific power shift values Δ_EFor uplink common channel transmission, it is best to calculate Δ in the Radio Network Controller (RNC)_CAnd Δ_UAnd broadcast to the mobile station. For downlink common channel transmission, it is preferable to calculate all power shift values in the Radio Network Controller (RNC). The Radio Network Controller (RNC) 50 preferably calculates the power shift value for each cell for centralized processing and broadcast.

The present invention has been described in connection with what is presently described as the preferred exemplary embodiments. The implementations of the present invention may also be practiced with different formats, specific embodiments, adaptations, and many modifications, variations, and equivalent arrangements. For example, the invention is also applicable to both uplink and downlink channels. Additionally, the invention may be used in conjunction with other applications, such as power ramping. In the case of power ramping, the use of the present invention helps to determine the transmission power of the ramping.

The detailed description of the specific examples explained below in accordance with the drawings will be described in detail.

The above and other objects, functions, and advantages of the present invention will become more apparent.

Point, the reference text in the whole figure represents the same part. The illustration does not have to be

Drawing with a scale, the focus of the invention is emphasized.

FIG. 1 shows a probability density function (PDF) pattern of a carrier-to-interference ratio (CIR) γ received;

2 shows a flow chart of a power control procedure in accordance with an exemplary embodiment of the present invention;

3 is a diagram showing the effect of different adaptive power parameter values on a carrier-to-interference ratio (CIR) γ probability density function (PDF) in accordance with an exemplary embodiment of the present invention;

4 shows a functional block diagram of an exemplary radio communication system having the advantages of employing the present invention;

Figure 5 shows a more detailed functional block diagram of the Radio Network Controller (RNC) and the base station shown in Figure 4;

Figure 6 shows a more detailed functional block diagram of the mobile station shown in Figure 4;

7 shows an adaptive open circuit power control routine in accordance with another exemplary embodiment of the present invention.