Power control of point to multipoint physical channels

The present invention is related to wireless communication. More specifically, the present invention relates to power control for point-to-multipoint (PtM) services.

The demand for using point-to-point services in wireless communication systems is gradually growing. In point-to-multipoint (PtM) services, a service is sent from a single point like a base station to as many as multiple wireless transmit/receive units (WTRUs) One example of point-to-multipoint is multimedia broadcasting and multi-broadcasting services. In traditional point-to-point (PtP) services, power control takes into account the effective use of wireless resources. Power control allows a specific wireless transmit/receive unit (WTRU) to receive the PtP service at the required quality of service (QoS) and will Interference from other WTRUs is minimized.

In PtP, such as the 3rd Generation Partnership Project (3GPP), when the WTRU's dedicated downlink physical channel is power controlled, the WTRU typically determines a signal-to-interference ratio based on the received block error rate (BLER) of the dedicated physical channel (SIR) index value. The WTRU predicts the SIR of the receiving dedicated physical channel. The closest item to determine the SIR is the ratio of received signal coding power (RSCP) divided by interference signal coding power (ISCP).

When the WTRU determines that the SIR index value is much greater than the calculated and estimated received SIR value, the WTRU signal is sent to the base station through a transmit power control (TPC) command to increase the transmit power of the downlink channel dedicated channel. When the SIR index value is less than the calculated and estimated value When receiving the SIR value, a TPC command will be generated to reduce the DL transmission power.

Nowadays, a channel that has the potential to support PtM services is the Forward Access Channel (FACH). The FACH is a channel broadcast all over a cell, and the FACH will be maintained at a power level to facilitate any of the cells. The user can receive the FACH. As a result, the adaptive power control mechanism is not used by FACH. One problem is that the disadvantage of FACH power control is that when a high data rate service is transmitted through FACH, considerable interference will be generated. The FACH transmit power level must be set at A power level so that a WTRU located at the edge of a cell can receive the high data rate service at an acceptable quality.

Therefore, the ability of PtM service to have adaptive power control becomes what we need.

Data is sent from a transmitter to a plurality of receivers through a specific channel, and the specific channel is received by the plurality of receivers. Each of the receivers sends power control information to the transmitter, which is based on a measured reception quality and a reception quality request of each receiver. The transmitter uses the power control information from each receiver and adjusts the transmit power level of one of the specific channels so that if any receiver requests an increase in the transmit power level to meet the received quality request, the transmit power The level increases, and if all receivers exceed their quality requirements, the transmit power level decreases.

Although the preferred embodiment is combined with the Third Generation Partnership Project (3GPP) Wideband Code Division Multiple Access (W-CDMA) system, the embodiment can also be applied to any wireless system using PtM services.

The present invention will be described in full with reference numbers in the illustrations to represent elements. Thereafter, a wireless transmit/receive unit (WTRU) includes but is not limited to a user equipment, a mobile station, a fixed or mobile user unit, a pager, or any form of equipment compatible with operation in a wireless environment. When referring to a base station hereinafter, it includes but is not limited to a base station, node B, station controller, access point, or other interface devices in a wireless environment.

Three different general implementations of the invention will be described next. In the first embodiment, each WTRU receiving the PtM service has an associated dedicated channel to support the PtM service. In the second embodiment, the WTRUs receiving the PtM service do not have a dedicated channel to support the service. In the third embodiment, some users have dedicated channels to support the service, while other users do not.

The first figure is a flowchart, which is the PtM service of adaptive power control when the associated dedicated channel exists. The second figure is a simple block diagram of a base station 54 and WTRU 56 for sending and receiving the service. The PtM service data can be sent through one of different channels, such as a shared channel, such as W-CDMA as mentioned. The high-speed shared channel used or a general channel. For the PtM service, multiple WTRUs 56 registered with the service will simultaneously receive the service through the PtM channel.

For each WTRU 56 that enters the PtM service area and is registered with the service, an uplink channel and a downlink channel dedicated physical channel are established, that is, step 20. The dedicated physical channel can be independent or include a distributed dedicated physical channel for control and data, or just a physical control channel.

As shown in the second figure, relating to the downstream channel (DL) dedicated channel of the PtM channel, a DL dedicated channel transmitter 30 generates the channel, an amplifier adjusts the transmission power level of the DL dedicated channel, and an antenna 42 or antenna The array transmits the DL dedicated channel through the wireless interface 44. At the WTRU 56, a DL dedicated channel receiver 50 connected to the WTRU antenna 46 will receive the channel.

Each WTRU 56 evaluates the reception quality of one of the DL dedicated channels, such as a received signal-to-interference ratio (SIR), step 22. The SIR can be measured using the received signal coding power (RSCP) and interference signal coding power (ISCP) associated with the DL dedicated physical channel, and the estimated reception quality is compared with the index reception quality as the index SIR. Based on the comparison, a transmit power control (TPC) command will be generated by a TPC command generator 52, and the TPC command will be sent to the base station 54, for example, using the uplink dedicated channel or one of the general uplink channels Layer 3 information.

A TPC receiver 40 of the base station 54 receives the command. The TPC command is used to adjust the transmission power of the DL dedicated command for the required quality of service (QoS) to achieve the target reception level, such as the target SIR And the block error rate (BLER) request, the power amplifier 34 of the DL dedicated channel will be changed accordingly.

For each power-controlled PtM physical channel or the entire group of physical channels, the base station equipment maintains a database of the specific WTRU 56 receiving the PtM channel, and the group of WTRUs 56 associated with each PtM channel will be regarded as a PtM group Group (PtM-G), a WTRU 56 can be a member of more than one PtM-G.

The transmit power of each DL dedicated channel or the group of dedicated channels of the WTRUs is adjusted to the minimum necessary power to meet the respective QoS requirements of the WTRU 56. Preferably, for each WTRU 5, the transmission power of the PtM physical channel or the group of physical channels is derived from the current transmission power of the related DL dedicated channel in the PtM-G, that is, step 26. A closer one to determine the required PtM channel power of one of the PtM-G WTRU 56 is based on Equation 1 and Equation 2.

PtM_TxPwr=DL_DchPwr+PtM_Power_Offset equation 1

PtM_TxPwr=DL_DchPwr*PtM_Power_Ratio equation 2

PtM_TxPwr is the transmit power of the desired PtM channel of the WTRU 56. DL_DcgPwr is the transmit power of the WTRU's DL dedicated channel, which is adjusted according to the TPC command and the configuration TPC step size. PtM_Power_Offset is the adjustment or compensation for the difference between the DL dedicated channel and the PtM channel, such as coding rate, QoS, and so on. PtM_Power_Ratio is a ratio to correct the difference between the DL dedicated channel and the PtM channel.

The PtM power compensation and the PtM power ratio are preferably derived from using multiple factors as shown in Equation 3 for PtM power compensation and Equation 4 for PtM power ratio.

PtM_Power_Offset=RelDch+RelTF+RelQoS+X equation 3

Ptm_Power_Ratio=RelDch*RelTF*RelQoS*X Equation 4

RelDch is configured by the operator to correct the difference in power compensation between the dedicated channel and the PtM channel. RelTF is a factor to compensate for the difference in the size of the transmitted data block and the encoding rate between the dedicated channel and the PtM channel. RelQoS is a factor to compensate for the difference between the BLER requests between the dedicated channel and the PtM channel. X is a general Factor for any other related transmit power correction/proportion that can be implemented.

The PtM transmit power (PtM_Tx_Pwr_PtM-G) is determined by determining the maximum WTRU PtM transmit power request within PtM-G, and is calculated by Equation 6.

PtM_Tx_Pwr_PtM-G=MAX (PtM_TxPwr (WTRU)) equation 6

PtM_TxPwr (WTRU) is a set of determined PtM transmit power levels. PtM_Tx_Pw is for each user in group G. MAX (PtM_TxPwr (WTRU)) is the maximum PtM transmit power level outside the group. By using the maximum PtM transmit power level required by any WTRU 56 in this group, it is ensured that all PtM transmission power levels in this group are Other WTRUs 56 (which require less transmit power) will be able to receive the PtM signal (step 28). The PtM transmission power may be recalculated and adjusted on the basis of a slot, wireless frame, or transmission time interval (TTI) in other time periods to achieve the best performance.

A PtM transmitter (Xmitter) 32 generates the PtM channel, and a transmission power calculation device 38 adjusts the transmission power of the PtM channel to the required transmission power level, for example, by changing the gain of the power amplifier 36. The base station transmit power bit criterion is adjusted according to the highest WTRU transmit power request, and TPC commands from all WTRUs 56 in the group are processed to determine the power adjustment. In fact, in order to increase the transmission power of the PtM, only a single WTRU 56 needs to request an increase in the transmission power. In order to reduce the transmission power, all the WTRUs 56 in the group need to request a power reduction.

Equation 7 is an equation that may be used to determine the PtM transmit power adjustment.

New_PtM_Power_PtM-G=Current_PtM_Power_PtM-G+Ptpc+Pbal equation 7

Current_PtM_Power_PtM-G is the current PtM transmit power, Ptpc is an increase or decrease by the step size, the Ptpc adjustment is preferably a configuration power control step size (0.5, 1, 1.5 or 2dB), which is based on the received The TPC command increases or decreases. Pbal is a general reference power for forward balance used for selective correction.

The third figure is a flow chart, which is used for adaptive power control of PtM service when the dedicated channel does not exist or is not used to support the PtM service. The fourth figure is a simple block diagram, which is used by the base station 54 and the WTRU 56 to transmit and receive a service.

A PtM transmitter (Xmitter) generates a PtM channel, and the transmission power level of the PtM channel is controlled, for example, by an amplifier 36. The initial PtM transmit power level can be a power level pre-configured by an operator. The manipulator takes into account the full cell coverage or is based on the RSCP and ISCP measurements of WTRUs 56 in the PtM group. The PtM channel is transmitted through an antenna 42 or antenna array of the base station 54 through a wireless interface 44. Each WTRU 56 connected to the PtM service receives the PtM channel through an antenna 46, and a PtM receiver will be from The data of the PtM channel is restored to its original state.

A TPC command generator should send TPC commands to the base station 54 for PtM. The TPC commands may be based on the SIR value of the receiving PtM channel or other channels received by the WTRU 56. For example, a channel is composed of multiple WTRUs 56 in the group. Receive, namely steps 58 and 60. The SIR value can be obtained using RSCP and ISCP values, path loss, and/or the measurement channel.

A preferred technique to obtain these measurements is to send them using physical control signals. These measurements, such as RSCP, ISCP, and/or path loss, will be sent directly during the physical control signal sending or in the L2 header information sent on the general channel of the uplink. This procedure is a bit like the procedure for setting the initial power of the PtM channel. . The update of the measurement is preferably provided on an "as best as possible" basis, which is based on the effectiveness of the upstream channel of the WTRUs. For example, it may use the "continuous" indication sent and the "access service level" zoning technology of the general channel of the uplink channel.

Equation 8 is a possible equation used in such general channels to calculate the PtM transmission power, that is, PtM_TxPwr.

PtM_TxPwr=DL_PtM_Pwr*a*(Target RSCP/ISCP)/(Measured RSCP/ISCP) Equation 8

DL_PtM_Pwr is the previous PtM transmission power setting. a is an operator control factor that affects the ratio of RSCP/ISCP. The path loss can alternately replace the RSCP/ISCP ratio in Equation 8.

A TPC receiver at the base station 54 receives the TPC command, step 62. Using the received TPC command, a transmit power calculation device adjusts the transmit power level of the base station 54. The transmit power level of the base station is adjusted according to the highest WTRU transmit power request, from all WTRUs 56 in the group. The TPC command will be processed to determine the power adjustment. In fact, in order to increase the transmission power of the PtM, only a single WTRU 56 needs to request an increase in the transmission power. In order to reduce the transmission power, all the WTRUs 56 in the group need to request a power reduction (step 64).

In another embodiment, some WTRUs 56 have dedicated channels for power control of the PtM channels, while others do not. In this embodiment, the power control can be implemented without using dedicated channels as shown in the third and fourth figures. However, preferably, the WTRU 56 with dedicated channels uses these channels to generate TPC commands, and the WTRU 56 without dedicated channels uses other channels, such as the PtM channel or the general channel to multiple WTRUs 56 in the group to generate the TPC command. TPC command. The base station 54 sets its transmit power level based on the command from all WTRUs of a specific PtM group. In fact, in order to increase the transmit power of the PtM, only a single WTRU 56 is required to request an increase in the transmit power. In order to reduce With this transmission power, all WTRUs 56 in the group need to request power reduction.

<p>20For each WTRU registered with PtM service, a dedicated channel for uplink and downlink channels will be established (or maintained)</p><p>22Each WTRU receives quality through one of its dedicated channels such as the air underpass</p><p>24Each WTRU compares the evaluation reception quality and the index reception quality, and generates a TPC command</p><p>26Determine a transmit power level for each WTRU that uses the received TPC command</p><p>28The transmit power level of PTM service will be set to the maximum transmit power level determined by each WTRU</p><p>30DL dedicated channel transmitter</p><p>32PTM transmitter</p><p>38Transmission power calculation device</p><p>40TPC receiver</p><p>44Wireless interface</p><p>48PTM receiver</p><p>50DL dedicated channel receiver</p><p>52TPC Command Generator</p><p>54Base station</p><p>58Each WTRU evaluates a reception quality through the PTM channel or other channels</p><p>60Each WTRU compares the evaluation reception quality and the index reception quality, and generates a TPC command</p><p>62The base station receives the TPC command from WTRUs</p><p>64Using the TPC command to adjust the PTM channel will be determined. If any WTRU requests a power increase, the power increases; if all WTRUs request a power decrease, the power decreases</p>

The first figure is a flow chart of the power control of PtM service using the dedicated channel.

The second figure is a simplified diagram of the power control used by the base station and the WTRU. It uses the PtM service of the related dedicated channel.

The third figure is a flow chart of power control of PtM service using related dedicated channels.

The fourth figure is a simplified diagram of the base station and the WTRU for power control. It is a PtM service that does not use the dedicated channel.

Function control of point-to-multipoint actual channel