KR100354165B1 - method for fast forward power control - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system, and in particular, to improve overall system performance in a next generation communication system of Code Division Multiplexing Access (hereinafter, referred to as CDMA) in which a plurality of channels are allocated to one user. The present invention relates to a forward power control method.

To this end, in the present invention, in a CDMA-based next-generation communication system in which a plurality of channels are assigned to one user, priority is given to a channel whose transmission rate does not change in units of frames as a reference channel for accurate reception SIR measurement. The present invention provides a high speed forward power control method in which accurate forward power control is performed on all dedicated channels by giving priority to a channel having the fastest transmission rate among the unchanged channels.

Description

Method for fast forward power control

The present invention relates to a mobile communication system, and more particularly, to a fast forward power control method for improving overall system performance in a CDMA-type next-generation communication system in which a plurality of channels are assigned to one user.

IMT-2000, the standardization standard for the next generation mobile communication system, uses a channel capable of transmitting each media to provide various multimedia services such as voice, video, and data at 64Kbps or more. For example, several channels may be simultaneously assigned to one user, such as a channel transmitting at a low speed such as a voice, a channel transmitting at a high speed such as an image, and a channel transmitting a control message.

The next-generation communication system based on CDMA technology uses a wider frequency band than the conventional CDMA communication system and supports high-speed data transmission for various services. In addition, several channels are allocated to each user according to each service type.

As described above, fast power control is essential when various channels are variably used according to each service type, and high speed power control methods in the forward link as well as power control in the reverse link are continuously proposed.

High speed forward link power control includes fast open loop power control and fast closed loop power control, and fast closed loop power control includes inner loop power control. And outer loop power control.

Briefly describing fast closed-loop power control for a particular channel, the received signal-to-interference ratio (hereinafter, abbreviated as SIR) for the channel is measured through internal loop power control, and the measured reception is performed. The SIR is compared with a reference SIR value determined by the external loop power control, and then a power control bit is generated according to the comparison result. Thereafter, the external loop power control newly generates a reference SIR value to maintain the quality of service (hereinafter, referred to as QoS) required by the channel. In this case, the frame redundancy check bit (CRC: Cyclic Redundancy Check bit) is checked on a frame-by-frame basis using a frame quality indicator to generate a new reference SIR value.

In the fast forward power control, a dedicated channel is assigned to a user, but power control bits are generated through internal loop power control for some channels, instead of generating power control bits for all dedicated channels. This is because the transmission of the power control bits for high-speed power control is not using a dedicated channel but transmits using the existing channel, so that the portion capable of transmitting the power control bits is limited.

In the high speed power control, the general high speed power control measures the reception SIR for only one dedicated channel, compares the measured SIR with a reference SIR value by external loop power control, and transmits the generated power control bit. Thereafter, the base station receives the transmitted power control bits to control power for all dedicated channels allocated to the corresponding user.

Separately, in high-speed power control, a special high-speed power control measures SIRs from a received signal only for some dedicated channels, compares these measured SIRs with reference SIR values by external loop power control, and transmits them after generating several power control bits. . The transmission rate of all the power control bits transmitted at this time is the same as the transmission rate of the power control bits generated by the general fast power control described above. In practice, however, the speed of the power control bits transmitted for each channel is reduced.

As an example of such a special high-speed power control, in a next generation communication system, the IMT-2000 system, when a user is located in the handover area, the received SIR is measured for two channels allocated to the user. Compared with the reference SIR value by the external loop power control, each power control bit is generated and transmitted accordingly. This is because the forward power control cannot be performed with the same power control bit for the channel performing the hard handover and the channel performing the soft handover. This is to perform forward power control.

However, in case of using high transmission speed channels such as IMT-2000 system, only hard handover is supported for these channels and soft handover is not supported in order to prevent channel performance degradation. Therefore, when a user assigned a channel having a high transmission rate enters a handover area, only hard handover is supported, and thus, the general fast power control described above cannot be used. For example, when the user exists in the handover region in the IMT-2000 system, the received SIR is detected for two channels, and a power control bit is generated and transmitted accordingly. This is because a channel performing hard handover and a channel performing soft handover cannot control forward power with the same power control bit.

As a result, in the handover region, forward power control is performed with one power control bit on channels supporting soft handover, and forward power control is performed on channels that do not support soft handover with another power control bit. . In this case, forward power control is performed at 400 ㎐ (or 200 ㎐) in one frame for channels that support soft handover, and 400 ㎐ (or 600 에서 at next frame for channels that do not support soft handover. Forward power control. Basically, the fundamental channel has the highest priority in measuring SIR among the channels that support soft handover.

In the conventional forward power control described above, since a plurality of channels are allocated to one user, forward power control is performed on all dedicated channels allocated to the user with one power control bit generated for one channel as a reference. In this case, forward power control is performed on all dedicated channels allocated to the user with two power control bits generated for the two reference channels.

In this case, the performance of the remaining dedicated channels in which power control is subsequently performed depends on how accurate the reference channel performs for forward power control.

For example, since the SIR measured in the frame unit is not accurate for the forward basic channel whose transmission rate changes in the frame unit, if the forward base channel is used as a reference channel for fast forward power control, power control is performed later. The performance for power control of the remaining channels is poor.

At this time, even if the correct SIR is measured from the reference channel, it is not considered that the accurate power control is performed on the remaining channels that must maintain different QoS with the generated power control bits.

In addition, due to the difference in distortion due to the multipath environment that may occur between the channel that is currently the reference for forward power control and the rest of the channels that must maintain different QoS, the power control between these channels is different. Bits may be required, performance degradation may occur due to existing power control procedures, and may also fail to satisfy the QoS of the channel.

SUMMARY OF THE INVENTION An object of the present invention was devised in consideration of the above-mentioned point. The present invention provides a high speed forward power control method in which priority is given and priority is given to a channel having the highest transmission rate among channels whose transmission rate does not change so that accurate forward power control is performed on all dedicated channels.

A feature of the fast forward power control method according to the present invention for achieving the above object is that the signal to interference ratio is measured based on the transmission rate and channel type of each channel for a plurality of channels assigned to any user, A reference signal-to-interference ratio is generated according to the frame error rate of the specific channel in which the signal-to-interference ratio is measured, and the power control bit is transmitted after comparing the measured signal-to-interference ratio with the reference signal-to-interference ratio.

Preferably, the specific channel for which the signal-to-interference ratio is measured is a channel having the fastest transmission rate among channels in which the transmission rate does not change, and the signal-to-interference ratio for the specific channel is despread and demodulated by an orthogonal code. The signal component and the phase shift and attenuation component detected using the pilot channel signal are used.

In addition, as the user enters a handover region, a priority of channel selection for measuring a signal-to-interference ratio is determined according to whether each channel supports handover, and supports variable voice service for channels supporting handover. The priority is given to the channel which does not support the channel, and the priority is given to the channel with the highest transmission rate among the channels whose transmission rate does not change for channels that do not support handover.

1 is a block diagram showing a partial configuration of a terminal for explaining a fast forward power control procedure according to the present invention.

Figure 2 is a block diagram showing the internal structure of the baseband receiving bank in the terminal configuration of the present invention.

* Description of the symbols for the main parts of the drawings *

3,4 baseband receiver bank

5: power control processor 7: comparator

8: power control bit generator 10: PN despreader

20: Walsh despreader 30: Channel estimator

40: QPSK demodulator 50: Combiner

60: decoder 70: external loop power control unit

Hereinafter, a preferred embodiment of a high speed forward power control method according to the present invention will be described with reference to the accompanying drawings.

In the present invention, in performing the fast forward power control, whether a corresponding channel is a variable data rate or a fixed data rate is first checked, priority is given to a channel having a fixed transmission rate. Since the transmission power of a channel having a variable transmission rate is also changed by a variable transmission rate, it is difficult for a receiver (terminal) to determine whether the transmission power is changed due to the change in the transmission speed, or whether the reception power is changed due to the change in the transmission channel environment. Because. In addition, since the receiver needs to determine a variable transmission rate, a time delay occurs in generating power control bits for power control, and as a result, performance degradation of forward power control occurs.

Subsequently, when receiving SIR is measured from a fixed rate forward channel where the rate does not change, the highest priority is given to the channel with the highest rate, since the error always occurs when the receiver measures received power. to be. However, since the channel having the fastest transmission speed is often high in magnitude of the received power, this error can be reduced a lot, so priority is given.

FIG. 1 is a block diagram showing some components of a terminal for explaining a fast forward power control procedure according to the present invention, and FIG. 2 is a block diagram showing an internal structure of a baseband receiving bank in the terminal configuration of the present invention.

1 shows some components of a receiver and a transmitter of a terminal, and the high frequency signal received through the antenna and the duplexer 1 is down-frequency processed through the RF / IF receiver 2 and converted into a baseband signal. .

The converted baseband signals are input to K baseband receive banks 3 to 4 which perform demodulation and decoding on each assigned channel according to different QoS.

The detailed internal structure of each baseband receive banks 3 to 4 is shown in FIG. 2, and the baseband signal converted above is despread with a pseudo noise code (hereinafter, abbreviated as PN).

Accordingly, the converted baseband signal is input to the PN despreader 10 and despread, and the despread signal is input to the Walsh Despreader 20 and the channel estimator 30. do.

The Walsh despreader 20 demodulates the signal components by correlating a signal despread with the PN code using a orthogonal code assigned to the corresponding channel.

The channel estimator 30 detects a phase shift and attenuation component generated in a wireless channel environment with respect to the signal despread with the PN code. In this case, the pilot channel signal is used for detection.

The phase shift and attenuation components detected by the channel estimator 30 are multiplied by the channel signal demodulated by the Walsh despreader 20 to restore the phase shift and attenuation components generated in the channel signal.

Thereafter, the channel signal in which the phase shift and attenuation components are restored is summed by the I-channel component and the Q-channel component by quadrature phase shift keying (hereinafter, referred to as QPSK) demodulation. This is performed by the QPSK demodulator 40 receiving a channel signal in which the phase shift and attenuation components are restored.

Then, the I channel component and Q channel component combined in the QPSK demodulator 40 are combined by the combiner 50 and the respective channel components demodulated in the QPSK demodulator (not shown) of the other baseband receiving bank of FIG. 1. do.

The combined signal that is the output of the combiner 50 is decoded in the decoder 60.

In order to perform fast forward power control in the operation of such a receiver, SIR needs to be measured from a corresponding channel signal through internal loop power control. Accordingly, the signal components demodulated by the Walsh despreader 20 and the phase shift and attenuation components detected by the channel estimator 30 are provided to the power control processor 5 of FIG. 1. Used for SIR measurements.

For SIR measurement, the power control processor 5 has information on the transmission rate and channel type of the channels currently assigned to the user.

In this case, in performing high-speed forward power control, since the channel to be selected as the reference channel may change the transmission speed in units of frames, the outer loop power control unit is included in the baseband receiving banks 3 to 4 for each channel. 70 is provided. This is because the fast forward power control of the present invention gives priority to SIR measurement to a channel having a fixed transmission rate rather than a channel having a variable transmission rate.

The external loop power controller 70 uses a frame quality indicator for the decoded signal, checks the frame error rate after checking the cyclic redundancy check bit (CRC) on a frame-by-frame basis. FER: Create a new reference SIR value according to Frame Error Rate. In this case, a new reference SIR value is generated to maintain the QoS required by the channel.

Then, the power control processor 5 performs the inner loop power control on the channel of the fastest transmission rate among the currently assigned fixed transmission rate channels, and transmits the measured SIR _Measured to the comparator 7, and simultaneously the channel. The control signal is sent to the switch unit 6 so that the reference SIR value generated by the external loop power control unit 70 is switched to the comparison unit 7.

The comparison unit 7 compares the SIR _Measured transmitted from the power control processor 5 and the reference SIR value transmitted from the external loop power control unit 70, and based on the comparison result, a power control bit generator (PCB Generator) ( 8) generates a forward power control bit, which is transmitted to the user side along with the user data.

Then, when the channel selected as the reference channel for the fast forward power control is released, the power control processor 5 gives the highest priority to the channel having the highest transmission rate among the channels of the fixed transmission rate except the released channel and gives the highest priority. Measure

Accordingly, the power control processor 5 switches so that the reference SIR value generated by the external loop power control unit (not shown) inside the baseband reception bank (not shown) for the channel on which the SIR is measured is switched to the comparator 7. Send a control signal to the unit (6). The switch unit 6 may also be implemented in software in the power control processor 5.

In the high-speed forward power control method up to now, in selecting a channel to measure the SIR, priority is given first according to whether the channel is a variable transmission rate or a fixed transmission rate, and the transmission channel rates of the channels using the fixed transmission rate. Based on the following priority was given. However, in the present invention, when the user enters the handover region, priority is given to the SIR measurement based on other criteria so that accurate fast forward power control can be performed even during the handover.

The fast forward power control method in the handover region is as follows.

First, the channel is divided into channels that can be handed over and channels that are not capable of handover.

For example, in fast power control for soft handover enabled channels, priorities for SIR measurement are given to channels that do not support Variable Voice Service, so that the external loop power control and the internal control described above are performed. Loop power control is performed. Similarly to the fast forward power control described above, in the handoff region, since the transmission power of a channel having a variable transmission rate is also changed by a variable transmission rate, the receiver (terminal) receives the transmission rate by changing it. It is difficult to determine whether the power has changed or the reception power has changed due to a change in the transmission channel environment. Therefore, priority for SIR measurement is given to a channel that does not support the variable voice service as described above.

However, in the high-speed power control for the channels where soft handover is not possible, the same priority is given to the fixed-rate channel as in the high-speed power control described above, and then the transmission rate among the fixed-rate channels is the highest. SIR is measured by giving the fast channel the highest priority.

In the fast forward power control method according to the present invention described above, in performing the fast forward power control, a channel having a fixed transmission rate is selected as a reference channel for measuring the SIR, not a channel having a variable transmission rate. Since the fastest transmission channel is selected among the channels, the accuracy of the SIR measured in units of frames can be improved.

In addition, when the degree of distortion due to the multipath environment that can be generated between the channel which is the standard for the high speed forward power control and the other channels that must maintain different QoS, the entire system according to the high speed power control The performance degradation can be prevented, and the elements that do not satisfy the QoS of the channel can be reduced.

Claims (6)

The signal-to-interference ratio is measured with the highest priority among the channels whose transmission rate does not change among the multiple channels assigned to any user, A reference signal to interference ratio is generated according to the frame error rate of the specific channel in which the signal to interference ratio is measured. And comparing the measured signal-to-interference ratio with the reference signal-to-interference ratio and transmitting power control bits accordingly. delete The signal-to-interference ratio measurement of the specific channel is characterized by using a signal component despread and demodulated by an orthogonal code and a phase shift and attenuation component detected by using a pilot channel signal. High speed forward power control method. The fast forward power of claim 1, wherein a priority of channel selection in which a signal-to-interference ratio is measured as the user enters a handover region is given priority to a channel that does not support variable voice service. Control method. delete 2. The method of claim 1, wherein the priority of channel selection in which signal-to-interference ratio is to be measured as the user enters a handover region is that the transmission rate of the channels for which the transmission rate does not change for channels that do not support handover is determined. And the priority is given to the fastest channel.