KR100407932B1 - The control method of pilot to traffic power ratio and power control bit power level in reverse link - Google Patents

Abstract

The present invention relates to a method for controlling a power ratio of a wireless communication channel, wherein a terminal of a communication system sets a relative power ratio of a pilot channel and a traffic channel of a reverse link to a predetermined level to communicate with a predetermined first base station, and a terminal. Is a soft handoff mode that communicates with a plurality of second base stations by changing the power ratio, and when in the soft handoff mode, the power ratio of the reverse pilot channel and the traffic channel is adjusted differently from the normal mode, thereby improving the performance of synchronous demodulation. There is.

Description

The control method of pilot to traffic power ratio and power control bit power level in reverse link}

The present invention relates to a cellular communication system of a code division multiple access method, and more particularly, to a power control method of a communication system.

Radio waves, the core medium of wireless communication systems, were raised by Maxwell and then experimentally confirmed by Hertz. Since then, wireless communication using such radio waves has been put to practical use by Marconi for the first time, and has now expanded its application area to wireless data communication networks capable of transmitting various data as well as human voices.

The most practical areas of such a wireless communication system are a pager and a wireless telephone communication. Among them, wireless telephone communication is the most common mobile phone and personal communication system (PCS).

Such radiotelephone communication is performed in the following manner. First, a telecommunication company serving wireless telephony communication divides the entire service area into cells for efficient use of radio waves, and installs one or more base stations for each cell. In addition, one base station is in charge of wireless communication of a terminal existing in one cell area, and a telecommunication company controls each base station to service wireless communication of the entire service area. Thus, a terminal used for such a wireless communication is called a cellular phone. PCS, which is currently being serviced in our country, is the world's first wireless communication system that commercialized Code Division Multiple Access (CDMA).

The next generation of wireless communication means under development is a wireless communication terminal called IMT-2000.This IMT-2000 system provides a variety of multimedia wireless communication services to users anywhere in the world, compared to PCS where the service area is limited to a certain country or region. It can be provided, and can be used as a variety of data communication means, as well as transmitting audio data and video data.

In particular, the IMT-2000 system performs coherent demodulation on the received signal to improve performance on the reverse link. That is, the IMT-2000 system transmits a pilot channel along with the traffic channel to the base station as shown in FIG. 1 in order to perform synchronous demodulation on the traffic channel. In this case, the relative power ratio of the traffic channel to the pilot channel is determined according to a coding rate carried by the base station, an interference ratio for a signal (hereinafter referred to as a signal to interference ratio (SIR), and a transmission rate). The power ratio, once determined, is fixedly used during communication and updated upon reconnection.

As shown in FIG. 1, the pilot channel and the traffic channel having a fixed power ratio are transmitted with their respective powers adjusted by a gain value Gp controlled by reverse closed loop power control. The IMT-2000 system also uses forward fast closed loop power control to improve performance when forward linked. In order to use this fast forward loop loop power control, the terminal inserts the power control bits into the reverse pilot channel in the power control group as shown in FIG. 2 and transmits the same power level as the pilot power level (Gpilot). .

In this way, the general IMT-2000 system communicates by fixing the power ratio of the pilot channel and the traffic channel on the reverse link.

However, the general IMT-2000 system as described above has a different required SIR for each base station during soft handoff, and the signal received from the base station is selected by a base station controller. ), The transmit power of the terminal is lower than in the normal mode. However, since the power level of the pilot signal is also reduced, there is a problem in that the synchronization demodulation performance is degraded due to incorrect estimation of the reverse radio channel.

In addition, since the forward power control bit inserted and transmitted in the reverse pilot channel is independently determined at each base station during soft handoff, when the terminal transmit power decreases while the power ratio is fixed, the power control bit reception power at each base station is reduced. This decrease may cause an error in the determination of the power control bit.

The present invention is to solve this problem, the control method for improving the communication quality and the decision performance of the power control bit by adjusting the power ratio of the reverse pilot channel and traffic channel and the power level of the forward power control bit during soft hand-off The purpose is to provide.

According to the present invention, in determining the relative power ratio of the reverse pilot channel and the traffic channel and the power level of the forward power control bit, the terminal is divided into a normal mode in which one terminal communicates with one base station and a soft handoff mode in which a plurality of base stations communicate. It is characteristic.

The present invention provides a normal mode in which a terminal of a communication system communicates with a predetermined first base station by setting a relative power ratio of a pilot channel and a traffic channel of a reverse link to a predetermined level, and the terminal changes the power ratio, thereby providing a plurality of second base stations. It is in soft handoff mode.

That is, the present invention divides and adjusts the relative power ratios of the pilot channel and the traffic channel of the reverse link in the normal mode and the soft handoff mode. In addition, the present invention divides and adjusts the power level of the power control bit into a normal mode and a handoff mode.

The soft handoff mode includes reducing the relative power ratio of the pilot channel and the traffic channel transmitted from the terminal to the base station, and adjusting the transmission power of the terminal by the response value Gp of the reverse power control method. have.

In addition, the power level of the power control bit is changed according to the number of base stations included in the active set of the communication system. In particular, the power level of the power control bit is changed regardless of the power ratio adjustment of the reverse pilot channel and the traffic channel.

The present invention is to communicate in the normal mode as shown in Figure 5, the step of transmitting a handoff command signal to the terminal by a predetermined first base station, the terminal attempts to communicate to the second base station, the terminal Transmitting a handoff complete signal to the first base station; and varying the power level of the traffic channel relative to the reverse pilot channel.

The present invention operates as follows.

While the terminal and the first base station normally communicate with each other, when the terminal enters the outside of the service area of the first base station, that is, the cell boundary area, the pilot signal of the second base station received by the terminal becomes above a preset threshold. The terminal then communicates this situation to the first base station. In this case, there may be a plurality of second base stations.

The first base station receiving the strength of the pilot signal transmitted from the second base station from the terminal sends it to the base station controller, determines whether to hand off to the base station controller and transmits a handoff indication signal through the first base station. The terminal receiving the handoff instruction signal receives the signal of the first base station and simultaneously synchronizes with the second base station.

The terminal in synchronization with the second base station transmits a handoff complete signal to the first base station. At this time, the terminal changes the power level of the traffic channel relative to the power level of the reverse pilot channel to be transmitted and simultaneously communicates with the first base station and the second base station. At this time, the power level of the traffic channel may be changed before the handoff completion signal.

That is, the present invention is composed of a normal communication mode and a soft handoff communication mode. The normal communication mode is a communication mode established between a first base station and a terminal in a predetermined service area, and the soft handoff communication mode enters a cell boundary area between a first base station and a second base station adjacent to the first base station. It is a communication mode between the terminal and the first base station and between the terminal and the second base station.

The normal communication mode includes fixing the relative power ratios of the reverse pilot channel and the traffic channel, and maintaining the power level of the power control bits transmitted from the terminal to the base station at the same power level as the pilot channel. In the normal communication mode, the relative power ratio between the reverse pilot channel and the traffic channel is fixed, and the power level of the forward power control bit is maintained at the same power level as the pilot.

In the soft handoff communication mode, the coding rate and transmission rate are the same as in the normal mode, but the required frame error rate of each base station is increased, thereby reducing the required SIR. Since the required signal-to-interference ratio for the signal of each base station is reduced in this way, the power ratio of the reverse pilot channel and the traffic channel is newly determined according to the reduced signal-to-interference ratio. The power level of the forward power control bit inserted and transmitted in the reverse pilot channel is increased according to the number of base stations performing soft handoff, that is, the number of base stations included in an active set.

Hereinafter, the operation principle of the present invention will be described.

When the terminal operating in the normal mode receives a handoff direction message from the base station, after synchronizing with the target base station, the terminal transmits a handoff completion message to the base station, and then enters the soft handoff mode. It works.

When the terminal is operating in soft handoff mode, the terminal reduces the power level of the traffic channel relative to the power level of the reverse pilot channel in order for the base station to estimate the radio channel efficiently using the reverse pilot channel. That is, the power ratio of the reverse pilot channel and the traffic channel is reduced, and the overall transmit power of the terminal is adjusted by a gain value controlled by reverse fast closed loop power control as shown in FIG. 1.

The terminal operating in the normal mode transmits a power control bit inserted into the pilot channel and transmitted at the same level as the power level of the pilot as shown in FIG. 2. However, the terminal operating in the soft handoff mode transmits the power control bit by increasing the power level of the power control bit as shown in FIG. 3 according to the number of base stations included in the active set. That is, the power level of the three-way soft handoff mode is higher than the two-way soft handoff mode of two base stations included in the activation set.

In addition, the power control bit may be inserted into another channel in addition to the pilot channel, and the adjustment of the power level is adjusted according to the number of base stations included in the activation set as described above regardless of the channel into which the power control bit is inserted. In addition, the increased power level of the power control bit is determined irrespective of power ratio adjustment of the reverse pilot channel and the traffic channel. Therefore, the present invention divides the relative power ratio of the reverse pilot channel and the traffic channel and the power level of the forward power control bit into the normal mode and the soft handoff mode.

As a result, the data of the terminal according to the present invention is transmitted to a base station with a plurality of power control groups (PCGs) configured in one frame at different power levels as shown in FIG.

According to the present invention, when the soft handoff mode, the power ratio of the reverse pilot channel and the traffic channel is adjusted smaller than the normal mode, the performance of the synchronous demodulation is improved, and the present invention has the advantage of improving the reverse link communication quality in the soft handoff mode. Have. In addition, the present invention has the effect of improving the power control performance of the forward link by reducing the error probability of the power control bits received from the base station by dynamically adjusting the transmission power level of the power control bits inserted and transmitted in the pilot channel. .

FIG. 1 is a block diagram illustrating that a pilot channel and a traffic channel of a general IMT-2000 terminal are transmitted by adjusting the overall transmit power level by a gain value Gp controlled by reverse closed loop power control.

FIG. 2 is a graph showing that the power control bits transmitted in the block diagram shown in FIG. 1 are included in a pilot channel in a normal mode and have the same level as that of a pilot signal.

3 is a graph showing that the power level of the power control bit is adjusted according to the operation mode of the terminal according to the present invention.

4 is a graph showing the power level of the power control group output from the terminal according to the present invention.

5 is a flow chart schematically showing a method of operation of the present invention.

Claims (6)

The terminal of the communication system communicating with the first base station in a normal mode in which the relative power ratios of the pilot channel and the traffic channel of the reverse link are fixed and communicated; And communicating with a plurality of base stations by changing a power ratio of the reverse traffic channel to the reverse pilot channel when the terminal is in the soft handoff mode. The method of claim 1 wherein the soft handoff is And reducing a relative power ratio of the traffic channel to the pilot channel transmitted from the terminal to the base station. The terminal of the communication system communicating with the first base station in the normal mode by setting the power level of the power control bit included in the pilot channel of the reverse link to be the same as the power level of the pilot signal; And when the terminal is in the soft handoff mode, changing the power level of the power control bit according to the number of base stations included in the activation set of the communication system. Power level control method of control bit. 4. The method of claim 3, wherein the power level of the power control bit is changed to increase. In the normal mode, the terminal fixing a power ratio of a reverse pilot channel and another channel; And controlling the relative power ratio of the reverse pilot channel to another channel when the terminal is in the soft handoff mode. 6. The method of claim 5, wherein the terminal sets a power level of a power control bit included in the pilot channel differently from the normal mode in the soft handoff mode.