KR100876722B1 - Power control method and apparatus for wireless communication system - Google Patents

Abstract

Provided is an efficient power control method between a base station and a terminal for a terminal receiving a high speed packet data service in a mobile communication system. In particular, it provides a more accurate power control method by providing a method for increasing the reliability of the power control bit transmitted from the terminal for power control of the forward channel.

Data Services, Power Control, F-CPCCH, R-PCSCH

Description

Power control method and apparatus for wireless communication system {POWER CONTROLLING METHOD AND APPARATUS FOR WIRELESS TELECOMMUNICATION SYSTEM}             

1 is a diagram illustrating a transmitter configuration of an F-CPCCH used in a conventional wireless communication system.

2 is a diagram illustrating a power control procedure performed through a forward and a reverse power control channel according to an embodiment of the present invention.

3 is a diagram illustrating a forward power control process for a case where N = 24 in an F-CPCCH transmitter configuration according to an embodiment of the present invention.

4 is a view showing a reverse power control process for the case of N = 24 in the F-CPCCH transmitter configuration according to an embodiment of the present invention

5 is a diagram illustrating a forward power control process for the case of N = 48 in the F-CPCCH transmitter configuration according to another embodiment of the present invention.

6 is a diagram illustrating a reverse power control process for the case of N = 48 in the F-CPCCH transmitter configuration according to another embodiment of the present invention.

The present invention relates to a wireless communication system, and more particularly, to a method and apparatus for efficient power control of a forward link.

In general, wireless communication systems such as Code Division Multiple Access (CDMA) 2000, Wideband Code Division Multiple Access / Universal Mobile Telecommunications System (WCDMA / UMTS), General Packet Radio System (GPRS), and CDMA2000 1xEV-DO (Evolution Data Only) The third generation wireless communication system. Unlike the typical second generation wireless communication system which used only a voice service or a low speed data service, the third generation wireless communication system supports a high speed packet data service such as a video as well as a voice service. . The wireless communication system includes at least a base station controller (BSC), a base transceiver system (BTS), and a mobile station (MS). The base station controller is wired to the base station controller and the base station is connected to and communicates with the mobile terminal through a wireless channel.

In a wireless communication system supporting voice and data services through Code Division Multiple Access (CDMA), power control has a significant effect on the performance of the system. Typically, the base station and the user terminal performs power control with each other. Such power control is usually performed through a dedicated power control channel (PCCH), which is called a power control group (PCG), which is a time unit in which power control is performed. This is accomplished by transmitting and receiving a predetermined number of power control bits (hereinafter referred to as PCB). Typically, the length of 1 PCG is 1.25ms, so power control in units of 1 PCG is equivalent to power control in an 800 Hz period.

An example in which power control is performed through the power control bit described above is as follows. The terminal receives the power control bit from the base station through the power control channel, and if the value is '0', the transmission power of the terminal is increased by xdB in the next PCG period, and if it is '1', the transmission power of the terminal is reduced by xdB in the next PCG period. Wherein the x value is adjustable. In the same way, the base station also adjusts the transmission power of the channel transmitted to the terminal through the power control bit received from the terminal.

In a typical wireless communication system, a base station performs forward power backward through a forward common power control channel (hereinafter, referred to as a CPCCH or F-CPCCH) for backward power control for a terminal receiving a high-speed packet data service. The terminal transmits a control bit and receives the terminal to control the transmission power according to the reverse power control bit value. On the other hand, the UE transmits the forward power control bit in the reverse direction through a reverse power control subchannel (hereinafter referred to as R-PCSCH) for power control of the F-CPCCH transmitted from the base station in the forward direction. The base station which receives this control the transmission power of the F-CPCCH according to the forward power control bit value. In the above direction, the reverse means transmission from the terminal to the base station, and the forward direction means transmission from the base station to the terminal.                         

In the above procedure, the base station and the terminal measure the received power or signal to noise ratio (hereinafter referred to as SNR) for the channel for which power is to be controlled, and if the measured value is higher than a predetermined threshold, A power control bit is generated to mean a command to lower the transmission power, while a power control bit is generated to mean a command to increase the transmission power to the counterpart when the measured value is lower than a predetermined threshold.

1 shows a transmitter configuration of an F-CPCCH used in a conventional wireless communication system.

Referring to FIG. 1, reference numerals 102 to 104 denote blocks for I channel transmission, and reference numerals 112 to 114 denote blocks for Q channel transmission. Each power control bit for N users is transmitted on each of the I and Q channels, so that a total of 2N power control bits are transmitted on one F-CPCCH. Reference numerals 101 and 111 denote N power control bits for the I and Q channels, respectively. The power control bits 101, 111 are symbol mapped by the signal point mappers 102, 112 to a '+1' or '1' or '0' value and then multiplied by the power gain in the channel gain regulators 103, 113. The power gain value is controlled by the forward power control bit value received from each terminal. The power control symbols of all the power gain controlled users are multiplexed by I and Q channels in the multiplexers 104 and 114 and then transmitted on the F-CPCCH.

In a typical wireless communication system, the N value is 12, 24, or 48, and the base stations are notified to the terminals. In the F-CPCCH transmitter configuration shown in FIG. 1, N = 12 means that power control bits for 12 users are transmitted for each of the I or Q channels, and N = 24 means 24 users for each of the I or Q channels. Power control bits for users are transmitted, and N = 48 means power control bits for 48 users for each of the I or Q channels.

In the forward and reverse power control procedures as described above, it should be noted that the bit duration of each power control bit is always the same regardless of the value of N. As an example, a time interval of 1/12 PCG is allocated to the UE in every PCG interval. That is, a power control bit for a specific terminal is transmitted during the third 1/12 PCG time interval in each PCG.

As such, two PCGs are required to transmit power control bits to 24 users, each of which must be transmitted for 1/12 PCG. That is, when N = 24, the unique 1/12 PCG time interval allocated to a specific terminal appears every 2 PCG. For example, in an F-CPCCH composed of PCG1, PCG2, PCG3, etc., which are temporally contiguous, the third 1/12 PCG interval of PCG1 is assigned to UE A, and the third 1/12 of PCG2 is assumed. The PCG interval is allocated to the terminal B which is another terminal. The next 1/12 PCG interval for UE A appears in PCG3. In other words, when N = 24 in the F-CPCCH, the base station transmits a power control bit for a specific terminal once every 2 PCG. Therefore, when N = 24, power control is performed at a speed of 400 Hz.

Similarly, if N = 48, the unique 1/12 PCG interval assigned to a specific terminal appears every 4 PCG. Accordingly, in the case of N = 48 in the F-CPCCH configuration, the base station transmits a power control bit for every specific UE once every 4 PCG. Therefore, when N = 48, power control is performed at a rate of 200 Hz.

Therefore, in a conventional wireless communication system, as the number of users subjected to power control increases, the period in which power control is performed becomes longer. In this case, if the base station fails to receive the power control bit for one user, the power control could not be normally performed for a relatively long time until the next power control bit is received. Therefore, the reliability of the power control is lowered and a problem arises in that it cannot effectively cope with changes in the rapidly changing radio wave environment.

SUMMARY OF THE INVENTION An object of the present invention, which was devised to solve the above problems, is to provide a method and apparatus for performing efficient power control in a wireless communication system.

Another object of the present invention is to provide a power control method and apparatus for improving reception reliability of power control bits in a wireless communication system.

Another object of the present invention is to provide a method and apparatus for forward power control for a plurality of user terminals in a wireless communication system.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

The present invention to be described below provides a method and apparatus for generating and transmitting a power control bit by a terminal in an F-CPCCH, and a method and apparatus for analyzing a power control bit value by a base station receiving the same. Actual power control is delayed by 1 PCG or 2 PCG due to the time it takes for the base station and the terminal to transmit the received power control bits in the forward and reverse power control processes to be described below, and the time required to interpret them. do. However, this delay time is taken as an example to help the understanding of the present invention and may have different values depending on the system characteristics and the propagation environment.

FIG. 2 shows an example of a power control procedure performed through the forward and reverse power control channels. In particular, FIG. 2 illustrates a process in which the base station and the terminal mutual power control according to the time flow between the F-CPCCH and the reverse power control channel when N = 12.

In FIG. 2, the upper part shows an F-CPCCH channel transmitted by a base station for power control on the reverse channel, and the lower part is a reverse power control transmitted in the reverse direction for power control on the F-CPCCH transmitted in the forward direction. The subchannels are shown.

As shown in FIG. 2, the pilot channel and the power control subchannel are 3: 1 time division multiplexed (TDM) in the reverse direction to form one PCG, and the reverse pilot channel and the reverse power control subchannel are the same power in one PCG. Is sent to. That is, the transmission power is controlled by the PCG unit. In FIG. 2, PCG1, PCG2, PCG3, etc. represent PCG units over time. In addition, the height of each rectangle representing transmission of an F-CPCCH, a reverse pilot channel (R-PICH), and an R-PCSCH indicates the strength of transmission power. As shown in FIG. 2, the change in the height of the rectangle in units of PCG means power control is performed in units of PCG.

Since a base station and a terminal transmit and receive a one-to-many relationship, the base station must have a power control channel for each terminal in order to control power for each terminal. In FIG. 2, 12 bits are transmitted within one PCG of the F-CPCCH, and each of the 12 bits represents a power control bit for a corresponding UE. The number 12 corresponds to the number of power control bits transmitted in each of the I channel and the Q channel, as shown in the F-CPCCH transmitter configuration described above with reference to FIG. 1.

In other words, one PCG is divided into 12 time intervals, and a power control bit for a specific terminal is transmitted in each time interval. 2 illustrates an example in which a power control bit for a specific terminal (terminal A) is transmitted in a third section in the 12 time sections. The specific time interval for each terminal described above is allocated by the base station in the process of accessing the system by the corresponding terminal.

An example of a forward power control process will be described with reference to FIG. 2.

The base station transmits the power control bit for the terminal A through the F-CPCCH at a specific position (for example, the third position) of every PCG interval. The terminal receiving the power control bits transmitted from the PCG1 of the F-CPCCH measures the received power or SNR for the received power control bits and compares them with a predetermined threshold. If the measured result is higher than the threshold, a forward power control bit (eg, '1') is generated to instruct the base station to lower the transmission power, and the generated forward power control bit is generated in the PCG2 interval of the R-PCSCH. send. The forward power control bit is received by the base station during the PCG3 period of the forward channel. The base station interprets the value for the power control bit, and if the value is '1', the transmission power of PCG4, which is the next PCG of the F-CPCCH, is lowered by x dB compared to PCG3, which is the previous PCG. The above-described forward power control process is performed continuously in subsequent PCGs.

In addition, an example of a reverse power control process will be described with reference to FIG. 2.

The base station measures the received power or SNR from the terminal A in the PCG2 interval of the R-PICH and compares the result with a predetermined threshold. If the measured result is lower than the threshold, the base station generates a bit (for example '0') to command the terminal A to increase the reverse transmission power, and the generated power control bit of the PCG3 interval of the F-CPCCH Transmit in the third time interval. The terminal A receives the power control bit in the third time interval of the PCG3 section of the F-CPCCH and interprets the value. When the value is '0', the terminal A compares the transmission power of the next PCG PCG5 with the previous PCG4. Increase by x dB. The aforementioned reverse power control process is performed continuously in subsequent PCGs.

FIG. 3 is a diagram illustrating a forward power control process for the case of N = 24 in the F-CPCCH transmitter configuration, and an operation principle according to an exemplary embodiment of the present invention will be described with reference to the figure.

Referring to FIG. 3, the base station transmits a reverse power control bit for the terminal A through the F-CPCCH at a specific position (shown as the third position) of the interval PCG1, PCG3, PCG5 .... The terminal receiving the power control bits transmitted from the PCG1 of the F-CPCCH measures the received power or SNR for the received power control bits and compares them with a predetermined threshold. If the measured result is lower than the threshold, the terminal generates a power control bit (for example, '0') to command the base station to increase the transmission power, and transmits the power control bit in the PCG2 interval of the R-PCSCH .

Meanwhile, the terminal maintains the same power control bit value transmitted in the PCG3 section of the R-PCSCH as in the PCG2. In other words, the terminal repeatedly transmits the power control bit transmitted during the PCB2 section to the same value once more in the PCB3 section. The base station then uses both power control bit values transmitted during PCG2 and PCG3 to control the transmit power of PCG5 of the F-CPCCH. Since the two power control bits have the same value, the base station combines the two power control bits to obtain a final power control bit value and uses the same to control the transmission power of the PCG5 section of the F-CPCCH.

If both power control bits have a value of '0', the base station increases the transmit power of PCG5 of the F-CPCCH by x dB compared to the previous PCG (PCG3). The above-described forward power control process is performed continuously in subsequent PCGs.                     

FIG. 4 is a diagram illustrating a reverse power control process for the case of N = 24 in the F-CPCCH transmitter configuration, and the operation principle according to an exemplary embodiment of the present invention will be described with reference to the figure.

Referring to FIG. 4, the base station measures the received power or SNR for the power control bits transmitted in a reverse direction in the PCG2 interval of the R-PICH from a specific terminal A and compares the result with a predetermined threshold. If the measured result is lower than the threshold, the base station generates a bit (for example, '0') to instruct the terminal to increase the transmission power, and the generated power control bit 3 of the PCG3 interval of the F-CPCCH Transmit in the first time interval.

UE A receives the power control bit in the third time interval of the PCG3 interval of the F-CPCCH assigned to it and interprets the value. If the value of the power control bit is '0', the terminal A transmits the transmission power of the next PCG (PCG4) of the R-PICH and the R-PCSCH by x dB higher than the previous PCG (PCG3). In addition, the UE maintains the transmission power of the R-PICH and the R-PCSCH transmitted during the PCG5 interval as in PCG4. Therefore, as shown in FIG. 4, the transmission power for two consecutive PCGs (PCG4 and PCG5) becomes the same. The aforementioned reverse power control process is performed continuously in subsequent PCGs.

FIG. 5 is a diagram illustrating a forward power control process for the case of N = 48 in the F-CPCCH transmitter configuration, and an operation principle according to an exemplary embodiment of the present invention will be described with reference to the figure.                     

Referring to FIG. 5, the base station transmits a power control bit for a specific terminal A through a F-CPCCH at a specific position (shown as a third position) of a PCG1, PCG5, PCG9. Upon receiving the power control bit transmitted in the PCG1 section of the F-CPCCH, the terminal A measures the received power or SNR of the received power control bit and compares it with a predetermined threshold. If the measured result is lower than the threshold, the terminal generates a power control bit (for example, '0') to command the base station to increase the transmission power, and the generated power control bit in the PCG2 interval of the R-PCSCH Transfer from

On the other hand, the terminal maintains the power control bit transmitted during the PCG3 ~ PCG5 period of the R-PCSCH to the same value as the power control bit transmitted from the PCG2. In other words, the UE repeatedly transmits the power control bit transmitted during the PCB2 time interval three times with the same value in the PCB3 to PCG5 time interval.

In controlling the transmit power of PCG9 of the F-CPCCH, the base station uses all four power control bits transmitted during PCG2 to PCG5. That is, since all four power control bits have the same value, the base station combines the values of the four power control bits to obtain a final power control bit value, and uses the PCG9 section of the F-CPCCH. To control the power.

If all four power control bits have a value of '0', the base station increases the transmit power of PCG5 of the F-CPCCH by x dB compared to the previous PCG (PCG3). The above-described forward power control process is performed continuously in subsequent PCGs.

FIG. 6 is a diagram illustrating a reverse power control process for the case of N = 48 in the F-CPCCH transmitter configuration, and the operation principle according to an exemplary embodiment of the present invention will be described with reference to the figure.

Referring to FIG. 6, the base station measures the received power or SNR for a power control bit received backward from a specific terminal A in the PCG4 section of the R-PICH and compares the result with a predetermined threshold. If the measured result is higher than the threshold, the base station generates a bit (for example, '1') to command the terminal to lower the transmission power, and the generated power control bit in the third time of the PCG5 interval of the F-CPCCH Transmit in section.

UE A receives the power control bit during the third time interval allocated to it in the PCG5 section of the F-CPCCH and interprets the value. When the value of the power control bit is '1', the UE transmits the transmission power of the next PCG (PCG6) of the R-PICH and the R-PCSCH lower by x dB than the previous PCG (PCG5). In addition, the UE maintains the transmission power of the PCG7 to PCG9 sections of the R-PICH and the R-PCSCH as in PCG5. Therefore, as shown in FIG. 6, the transmission power is the same for four consecutive PCGs (PCG6 to PCG9). The aforementioned reverse power control process is performed continuously in subsequent PCGs.

By the power control performed as described above, the reception reliability of the power control bit can be increased. For example, when N = 24 in the transmitter configuration of the F-CPCCH of FIG. 1, the base station receives two repeated power control bits for power control bits transmitted in the reverse direction for forward power control, By combining the two power control bits and interpreting the values, the reliability of the power control bits can be improved. As another example, when N = 48 in the transmitter configuration of the F-CPCCH of FIG. 1, the base station receives four repeated power control bits for power control bits transmitted in the reverse direction for forward power control. By combining four power control bits and interpreting the values, the reliability of the power control bits can be increased.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present invention provides an efficient power control method between a base station and a terminal for a terminal receiving a high speed packet data service in a wireless communication system. Thus, the base station can increase the reception reliability of the power control bit received from the terminal. More accurate forward power control can be achieved through the reliable power control bit.

Claims (8)

A method for performing forward power control in a terminal of a wireless communication system performing power control at least two power control groups by using a reverse power control channel composed of power control groups that are consecutive in time, Measuring the signal strength of the forward channel and comparing it with a predetermined threshold; Generating a power control bit for controlling power of the forward channel according to the comparison result; And transmitting the generated power control bits to the base station repeatedly for every power control group during the at least two power control groups. 1. A method for performing forward power control in a base station of a wireless communication system performing power control at least two power control groups using a reverse power control channel consisting of temporally continuous power control groups. Receiving one power control bit in a time interval allocated to a specific terminal of every power control group during the at least two power control groups; Summing the received at least two power control bits; And controlling transmission power of a forward channel transmitted to the specific terminal by using the summed power control bits. 1. A method for performing reverse power control in a base station of a wireless communication system performing power control in at least two power control groups in a forward power control channel consisting of temporally continuous power control groups. Measuring a signal strength of a reverse channel received from a specific terminal and comparing the signal with a predetermined threshold value; Generating a power control bit for controlling power of the reverse channel according to the comparison result; And transmitting the generated power control bit to the specific terminal in a time interval of a power control group allocated to the specific terminal among the at least two power control groups. 1. A method for performing reverse power control in a terminal of a wireless communication system performing power control at least two power control groups in a forward power control channel including temporally continuous power control groups. Receiving a power control bit in a time interval of a pre-allocated power control group of a forward channel, And controlling transmission power of a reverse channel transmitted to a base station during the at least two power control groups by using the received power control bits. An apparatus for performing forward power control in a terminal of a wireless communication system that performs power control at least two power control groups periodically using a reverse power control channel composed of consecutive power control groups. Means for measuring the signal strength of the forward channel and comparing it to a predetermined threshold; Means for generating a power control bit for controlling power of the forward channel according to the comparison result; And means for transmitting the generated power control bits to the base station repeatedly for every power control group during the at least two power control groups. An apparatus for performing forward power control in a base station of a wireless communication system that performs power control at least two power control groups periodically using a reverse power control channel consisting of time continuous power control groups. Means for receiving one of the power control bits in a time interval allocated to a particular terminal of every power control group during the at least two power control groups; Means for summing the received at least two power control bits; And means for controlling the transmit power of a forward channel transmitted to the specific terminal by using the summed power control bits. An apparatus for performing reverse power control in a base station of a wireless communication system that performs power control at least two power control groups in a forward power control channel consisting of temporally continuous power control groups. Means for measuring a signal strength of a reverse channel received from a specific terminal and comparing the signal strength with a predetermined threshold value; Means for generating a power control bit for controlling power of the reverse channel according to the comparison result; And means for transmitting the generated power control bit to the specific terminal in a time interval of a power control group assigned to the specific terminal among the at least two power control groups. An apparatus for performing reverse power control in a terminal of a wireless communication system that performs power control in at least two power control groups in a forward power control channel consisting of temporally continuous power control groups. Means for receiving a power control bit in a time interval of a pre-allocated power control group of the forward channel; Means for controlling transmit power of a reverse channel transmitted to a base station during the at least two power control groups using the received power control bits.

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