KR20070015635A - Pilot signal transmitting method and wireless communication system for allowing highly precise measurement of reception quality - Google Patents

Abstract

Disclosed is a pilot signal transmission method that reduces block error rate and improves throughput by increasing SIR measurement accuracy for transmission power control during high speed transmission. First, the first SIR value measured with the first pilot signal and the second SIR value measured with the second pilot signal are compared, and the presence or absence of the second pilot signal in the slot unit is determined from the comparison result. When the second pilot signal is present, the second pilot signal is used for SIR measurement of fast closed loop transmission power control in addition to the first pilot signal. When the second pilot signal does not exist, only the first pilot signal is used for SIR measurement of fast closed loop transmission power control.

Pilot signal

Description

PILOT SIGNAL TRANSMITTING METHOD AND WIRELESS COMMUNICATION SYSTEM FOR ALLOWING HIGHLY PRECISE MEASUREMENT OF RECEPTION QUALITY}

The present invention relates to a pilot signal transmission method in a wireless communication system for high speed packet transmission.

In a wireless communication system, Rayleigh fading occurs with the movement of a mobile station. This Rayleigh fading causes amplitude variations and phase variations in the communication channel. Therefore, in a wireless communication system such as WCDMA, the transmitting side transmits a known signal sequence (pilot signal) from the receiving side. The receiving side estimates the phase variation and amplitude variation of the propagation path from the difference between the reception point of the pilot signal and the known transmission point (channel estimation). The receiving side corrects (channel removal) the phase and amplitude variations of the information signal including the control signal and the data signal based on the channel estimation.

FIG. 1 illustrates a mode in which the influence of a channel is removed from a received information signal by using an estimated channel in communication using QPSK modulation. In a phase modulation system such as QPSK, the reception point R 'from which the influence of the channel is removed is obtained by obtaining the phase variation [theta] due to the influence of the channel and returning the reception point R by [theta]. In general, in WCDMA systems, the higher the transmission rate, the higher the channel estimation accuracy is required. In WCDMA, interference components are reduced by signal spreading. However, in the case of high-speed transmission, since the diffusion rate is set low, the rate at which the interference component is reduced is also low.

Fig. 2A shows an aspect of channel cancellation in the case where the interference component is high (high speed transmission). 2B shows an aspect of channel cancellation in the case where the interference component is low (low speed transmission). The higher the interference component, the greater the dispersion of the signal points, and the larger the circle showing the distribution of the reception points. In the case of performing channel removal using a channel estimation value [theta] Error with low estimation accuracy, the higher the interference component, the larger the area where a reception error shown by a black portion in the figure occurs. Therefore, the higher the transmission, the lower the reduction rate of the interference component due to spreading, the higher the accuracy of the channel estimate is required.

In a cellular system using direct spread code division multiple access (DS-CDMA), such as a WCDMA system, the same frequency band is used for a plurality of channels. Therefore, the radio waves of other channels become interference. Increasing the interference deteriorates the reception quality of the desired wave, resulting in disconnection of the line. Therefore, the number of lines that can perform communication while maintaining the desired reception quality, that is, the line capacity, depends on the amount of interference. In an uplink, a signal transmitted by a mobile station far from the base station has a larger power attenuation than a signal transmitted by a mobile station close to the base station. Therefore, when their mobile stations transmit signals at the same power, the far-reaching problem is that the reception power of interference waves from nearby mobile stations becomes larger than the reception power of desired waves from far mobile stations, making communication between remote stations difficult. Occurs.

Therefore, in the uplink, transmission power control for controlling the transmission power of each mobile station is an essential technique so that the signal from each mobile station is equivalent to the base station. The base station controls the transmission of the mobile station so as to have the minimum transmission power required to maintain the reception quality (receive power versus interference power: SIR) at the required quality (target SIR). The transmission power control for each mobile station is a closed loop type control. The base station compares the measured SIR with a predetermined target SIR, and if higher than the target SIR, transmits a transmit power control (TPC) signal instructing to lower the transmission power to the mobile station. If the measured SIR is lower than the target SIR, the base station transmits a TPC signal to the mobile station instructing to increase the transmission power. Since such closed loop control is performed for each slot, the transmission power follows the high speed propagation path variation.

In the uplink channel of the WCDMA, an individual channel for communication by circuit switching and an EUDCH for high-speed packet transmission are provided (3GPPTR25.896 v6.0.0 (2004-03) 3rd Generation Partnership Projcct; Tcchnical Specification Group Radio) Acccss Network; Feasibility Study for Enhanced Uplink for UTRA FDD (Release 6). Each channel is composed of a dedicated physical data channel (DPDCH) for transmitting data and a dedicated physical control channel (DPCCH) for transmitting a control signal. Similarly, the EUDCH consists of an E-DPDCH for transmitting data and an E-DPCCH for transmitting a control signal. One frame of each channel consists of 15 slots. By each channel, a data block is transmitted every predetermined transmission time interval (TTI). For the TTI of an individual channel, one of 1, 2, 4 and 8 frames is used. The TTI of the EUDCH is undecided, but either one fifth frame (one subframe) or one frame shorter than one frame is to be used.

3 shows the frame configuration of individual channels. The DPCCH includes pilot signals, TFCI, FBI, and TPC bits. The pilot signal is used for channel estimation and SIR measurement described above. The TFCI is a 30-bit control signal that notifies the transmission format (data block size, number of blocks) of the DPCCH in each TTI, and is divided into two bits per slot and transmitted. Therefore, after receiving all one frame, the base station collects and decodes the TFCI divided into respective slots, and then decodes the DPDCH using the base station.

In addition, the FBI bit is a field for sending a feedback signal required for other functions in the downlink. The TPC is a field for transmitting the above-described fast closed loop transmission power control signal. In WCDMA, uplinks and downlinks of individual channels are paired and used for transmission of transmission power control signals to each other. In addition, the EUDCH channel is transmitted at the power of applying offset power to individual channels. The frame structure of the EUDCH is undecided in 3GPP, but the signal transmitted by the E-DPCCH includes the TFCI (E-TFCI) of the EUDCH. This is to notify the transmission format of the E-DPDCH in this TTI, similar to the individual channel.

In addition, a pilot signal is required for channel estimation, and pilot signals of individual channels may be used for channel estimation. The base station also performs scheduling so that the noise rise (receive power-to-noise ratio) at the base station is equal to or less than a predetermined target value, and notifies the EUDCH of the radio resource allocated to the mobile station. There are two ways to consider scheduling. One is called time-rate scheduling, and the other is called rate scheduling.

In time and rate scheduling, the transmission time and the maximum transmission rate are designated by the scheduling information for each mobile station where the base station sets the EUDCH. The mobile station transmits the data block at a specified maximum transmission rate or less within the designated transmission time.

On the other hand, in transmission rate scheduling, the base station specifies only the maximum transmission rate by scheduling information. The mobile station may transmit the data block at an arbitrary timing as long as it is a transmission speed equal to or less than the maximum transmission rate. These scheduling information can be transmitted for each TTI.

As described above, high-speed packet transmission is performed in EUDCH, and the transmission rate can be changed in units of TTIs. As described above, the precision required for channel estimation increases as the transmission speed increases.

In addition, the higher the transmission speed, the higher the precision required for SIR measurement. This is because the SIR is used for fast closed-loop transmission power control. When the precision of the SIR measurement is low, the precision of the power control is degraded, the reception quality of the pilot signal is degraded, and the channel estimation precision is also degraded. Therefore, when the transmission speed is high, higher precision SIR measurement is required.

In general, channel estimation precision or SIR measurement precision can be improved by increasing the power of the pilot signal for the data signal, or by increasing the number of pilot bits in each slot. However, since they increase the overhead of control signals and increase interference to other mobile stations, it is not desirable to always do them. Therefore, in the EUDCH, it is necessary to improve only the channel estimation accuracy and the SIR measurement accuracy with only the frame for high-speed transmission.

This solution is proposed in "[E] -SPICH Multiplexing Options", QUALCOMM, 33rd Meeting of 3GPP RAN WG1, R1-030673. According to this, it is proposed to transmit the 2nd pilot signal by E-DPCCH in the frame which a mobile station performs high speed transmission. In this method, a predetermined transmission rate threshold is determined, and the mobile station transmits a second pilot signal on the E-DPCCH when the transmission rate is equal to or greater than the threshold. The base station decodes the E-TFCI, and determines that the mobile station is transmitting the second pilot signal if the transmission rate is greater than or equal to the threshold. In that case, the base station also uses the second pilot signal for channel estimation together with the pilot signal (first pilot signal) of the DPCCH. If the transmission rate is below the threshold, since the mobile station does not transmit the second pilot signal, interference to other mobile stations is reduced when high channel estimation is not necessary.

However, in this solution, there is a case where the second pilot signal cannot be used for SIR measurement of transmission power control. As described above, 0TFCI in the DPCCH is transmitted by dividing into all slots in one frame to increase the error correction rate. Similarly, if the E-TFCI is also transmitted in all slots or multiple slots within 1TTI, the base station can determine whether the second pilot signal has been transmitted until the E-TFCI is finished and the E-TFCI is decoded. Can't. As described above, the fast closed loop transmission power control is slot-based control, and the TPC signal should be transmitted 1 to 2 slots after receiving the pilot signal. If it does not time it, even if the mobile station transmits the second pilot signal, the base station cannot use the second pilot signal for SIR measurement. In contrast, the base station may assume that the second pilot has always been transmitted, and perform the SIR measurement using the second pilot signal. However, in that case, noise is added to the SIR measurement when the second pilot is not transmitted, so the SIR measurement accuracy is significantly degraded. As described above, when the SIR measurement accuracy deteriorates, the transmission power control precision deteriorates, so that the target reception quality cannot be achieved, and the channel estimation precision deteriorates. As a result, there is a problem that the block error increases and the throughput is reduced.

The present invention provides a pilot signal transmission method, a wireless communication system, a base station, and a mobile station that solve the above problems. Specifically, the present invention provides a pilot signal transmission in which a block error rate is reduced and throughput is improved by increasing SIR measurement accuracy for transmission power control in a high speed packet transmission system using EUDCH. A method, a wireless communication system, a base station and a mobile station are provided.

MEANS TO SOLVE THE PROBLEM In order to solve the above-mentioned subject, the pilot signal transmission method, a wireless communication system, a base station, and a mobile station by this invention employ the following characteristic structures.

The mobile station transmits the first pilot signal on the first channel, and transmits the second pilot signal on the second channel in response to the transmission rate of the data transmitted on the second channel.

The base station determines whether or not the second pilot signal is used in response to the reception quality of the first pilot signal and the second pilot signal.

When using the second pilot signal, the base station performs reception quality measurement using the first pilot signal and the second pilot signal. If the second pilot signal is not used, the base station performs reception quality measurement only with the first pilot signal.

The base station then generates a transmission power control signal based on the received reception quality measurement. The mobile station determines transmission power of the first and second channels in response to the transmission power control signal transmitted by the base station.

1 is a diagram for explaining a method of using channel estimation results.

FIG. 2A illustrates an aspect of channel rejection when the interference component is high (high speed transmission). FIG.

FIG. 2B illustrates an aspect of channel rejection when the interference component is low (slow transmission). FIG.

3 is a diagram illustrating a frame configuration of individual channels.

4 is a schematic diagram of a cellular system common to each embodiment of the present invention.

Fig. 5 is a view for explaining a pilot signal transmission method in the first embodiment according to the present invention.

Fig. 6 is a diagram showing the probability density distribution of SIR measurements when the second pilot signal in the present invention is transmitted and when it is not.

Fig. 7 is a diagram showing the configuration of a mobile station in the first embodiment of the present invention.

Fig. 8 is a diagram showing the configuration of a base station in the first embodiment in the present invention.

Fig. 9 is a view for explaining a pilot signal transmission method in a second embodiment of the present invention.

Fig. 10 is a diagram showing the configuration of a mobile station in a second embodiment of the present invention.

Fig. 11 is a diagram showing the configuration of a base station in the second embodiment of the present invention.

Fig. 12 is a diagram for explaining a pilot signal transmission method in a third embodiment of the present invention.

Fig. 13 is a diagram showing that when a reception error occurs in the differential signal, a deviation occurs between the maximum transmission rate recognized by the base station and the maximum transmission rate recognized by the mobile station.

Fig. 14 is a diagram showing the configuration of a mobile station in the third embodiment of the present invention.

Fig. 15 is a diagram showing the configuration of a base station used in the third embodiment of the present invention.

Hereinafter, the configuration and operation of a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. As an example, an embodiment using EUDCH in WCDMA will be described.

4 shows a schematic diagram of a cellular system common to the first to third embodiments of the present invention. As shown in Fig. 4, the mobile station 121 connects only with the base station 111, the mobile station 123 only with the base station 112, and the mobile station 122 connects with both base stations. Then, the mobile stations 121 to 123 transmit a DPDCH (UL / DL) for transmitting data of an individual channel, a DPCCH (UL / DL) for transmitting a control signal, and an E-DPDCH (for transmitting data of an EUDCH). UL) and an E-DPCCH (UL / DL) for transmitting a control signal to and from a base station. The base stations 111 and 112 are connected to a base station control device (not shown). The base station control apparatus informs the mobile station and the base station of the set (TFCS) of the transmission format combinations (TFCs) for allowing the mobile stations to use them. The TFC includes parameters such as the data block size and the number of blocks included in the transmission time interval (TTI). Here, the TTI of each channel is 15 slots, and the TTI of EUDCH is 3 slots. In response to the TFC, the EUDCH transmission speed is different, and the higher the transmission speed, the higher the noise rise given to the base station. Thus, the base station controls the noise rise variation in the base station by controlling the maximum TFC or maximum transmission rate that permits use. Control information for this is transmitted and received on the E-DPCCH (UL / DL).

The base station and the mobile station also transmit a TPC (Transmit Power Control) signal for fast closed loop transmission power control on the DPCCH. The TPC signal is a 2-bit signal transmitted every slot, and the base station and the mobile station measure the received SIR of the pilot signal, and if the value is higher than the target SIR, the TPC signal indicating power reduction is lower than the target SIR. Send a TPC signal indicating increase.

Example  One

The first embodiment will be described in detail.

Fig. 5 shows a method of transmitting pilot signals in the first embodiment. For simplicity, only the pilot signal and the TPCI signal are described as control signals here. DPDCH and DPCCH are transmitted continuously. On the other hand, the E-DPCCH and the E-DPDCH are intermittently transmitted, and the second pilot signal included in the E-DPCCH is transmitted only when a predetermined transmission rate threshold or more is reached. Here, the transmission rate threshold is set to 1024 kbps. Since the first data block in the figure has a transmission rate of 384 kbps, which is lower than the transmission rate threshold, the second pilot signal is not transmitted ("DTX" in the figure is a Discontinuous Tx, meaning transmission off. do). However, subsequent data blocks are also transmitted with a second pilot signal because the transmission rate is 1024 kbps. In addition, when transmitted, the second pilot signal is transmitted at the same transmission power as the first pilot signal.

The base station measures the reception quality SIR1 of the first pilot signal and the reception quality SIR2 of the second pilot signal, and determines that the second pilot signal has been transmitted when both of the following two conditions are satisfied.

Condition 1: SIR1 is greater than a predetermined reception quality threshold.

Condition 2: SIR2 is larger than the value obtained by subtracting the predetermined value (ΔSIR) from SIR1.

Here, the reception quality threshold value and the predetermined value? SIR are notified to the base station in advance or set in advance as the base station information.

Condition 1 is used for the following reasons. 6 shows the probability density distribution of the SIR measurements when the second pilot signal is transmitted and when it is not. When the base station detects the presence or absence of the second pilot signal from the SIR measurement of the second pilot signal, the following two detection error patterns may occur.

Detection Error 1: The second pilot signal has been transmitted, but the base station determines that it has not been transmitted.

Detection error 2: The second pilot signal was not transmitted, but the base station determines that it has been transmitted.

When detection error 2 occurs, the base station adds noise to the SIR measurement using the second pilot signal, so that the accuracy of the SIR measurement is significantly lowered, which is not preferable. Therefore, the reception quality threshold may be set so that the probability of occurrence of detection error 2 is smaller than the probability of occurrence of detection error 1. Therefore, the reception quality threshold may be set so that the probability A in FIG. 6 becomes smaller than the probability B. FIG. In addition, since the first pilot signal and the second pilot signal are transmitted at the same power, when the second pilot signal is transmitted, SIR2 and SIR1 are almost equal. Therefore, under condition 1 of the present embodiment, SIR1 is measured, and when SIR1 is lower than the reception quality threshold, the second pilot signal is not used to reduce the probability of occurrence of detection error 2.

If condition 1 is met, the base station measures SIR2 and checks whether condition 2 is met. As described above, when the second pilot signal is being transmitted, SIR1 and SIR2 will be about the same value. Therefore, the base station determines that the second pilot signal is transmitted when the formula SIR2> SIR1-SIR, i.e., condition 2, which considers? SIR as a predetermined margin is satisfied. ΔSIR is a design value determined by the reception performance of the base station, the slot configuration, and the like.

The base station detects the presence or absence of the second pilot signal in the above procedure, uses only the first pilot signal when determining that the second pilot has not been transmitted, and uses the first pilot signal when determining that the second pilot signal has been transmitted. In addition, the second pilot signal is also used to perform SIR measurement for channel estimation and transmission power control. SIR measurement is performed as follows.

(Justice)

[Equation 1]

 : First and second pilot signals transmitted

[Formula 2]

 : First and second pilot signals received

[Equation 3]

 : Interference component applied to the first and second pilot signals

[Equation 4]

 : Number of symbols of first and second pilot signals

[Equation 5]

 : A channel estimated only by the first pilot signal, and a channel estimated by both the first and second pilots

[Equation 6]

 : Interference component estimated with only the first pilot signal and interference component estimated with both the first and second pilot signals

(Calculation)

From the above definitions, when calculating the SIR using only the first pilot signal, it is obtained as follows.

[Formula 7]

Equation 8

[Equation 9]

On the other hand, when SIR is calculated using both the first and second pilot signals, it is obtained as follows.

Equation 10

[Equation 11]

Equation 12

7 shows the configuration of a mobile station used in this embodiment.

In Fig. 7, the configuration from generation of data transmitted on four channels (DPDCH, DPCCH, E-DPCCH, E-DPDCH) to power control after diffusion is shown.

As for the DPDCH, the individual CH data (DPDCH) block generation unit 201 generates a data block transmitted at 1 TTI for each TTI. The data block transmitted in 1 TTI is generated according to the TFC selected by the TFC selector 2012 in consideration of the priority of the data and the like from the amount of data in the individual channel data buffer 72011 from the upper layer. Thereafter, the DPDCH buffer 2011 sends the generated data block to the processing unit 2013 and performs processing such as encoding and interleaving. The data blocks after the processing are sent to the spreading unit 202 one by one.

As for the DPCCH, for each slot, the first pilot signal generation unit 203 generates the first pilot signal, and the DPCCH frame generation unit 204 together with the information of the TFCI selected by the TFC selection unit 2012 determines the DPCCH. It is inserted into a predetermined field and then sent to the diffusion section 202. Regarding the E-DPDCH, the EUDCH block generation unit 208 generates a data block transmitted at 1 TTI for each TTI. The data block transmitted in 1TTI is determined according to the TFC selected from the data amount in the E-DPDCH buffer 2082 from the upper layer in consideration of the priority of the data, the maximum TFC designated by the base station, etc. Is generated. Thereafter, the E-DPDCH buffer 2082 sends the generated data block to the processing unit 2083 and performs processing such as encoding and interleaving. The data blocks after the processing are sent to the spreading unit 202 one by one.

As for the E-DPCCH, the second pilot signal generator 205 generates a second pilot signal for each slot and sends it to the E-DPCCH frame generator 207. There is a switch 206 between the second pilot signal generator 205 and the E-DPCCH frame generator 207. The E-TFC selector 2081 sends information on the E-TFCI used in the frame to the switch 206. The switch 206 calculates the transmission rate from the E-TFCI and sends the second pilot signal to the E-DPCCH frame generation unit 207 only when it is at least 1024 kbps, which is the transmission rate threshold. The E-DPCCH frame generation unit 207 inserts the second pilot signal or the information of the E-TFCI into a predetermined field of the E-DPCCH and sends it to the spreading unit 202.

The spreading unit 202 spreads each of the received data blocks and the control signal frame and sends them to the transmission power control unit 209. The transmission power control section determines the transmission power of the DPCCH from the TPC signal received on the downlink, and adds a predetermined power offset to the power of the DPCCH to determine the power of each channel.

8 is a diagram showing the configuration of a base station used in the first embodiment.

In FIG. 8, the structure from the despreading part 301 to receiving data and sending data to an upper layer is shown.

First, the despreader 301 despreads each of the four received channels (DPDCH, DPCCH, E-DPDCH, and E-DPCCH). The control unit relating to the DPCCH only includes a buffer 303, a temporary channel estimating unit 304, and a TFCI detecting unit 308. The buffer 303 stores the despread DPCCH. The temporary channel estimator 304 receives the first pilot signal and performs channel estimation. The TFCI detection unit 308 detects the TFCI from the channel estimation result and the received signal of the TFCI field of the DPCCH. Then, the TFCI detecting unit 308 sends the detected TFCI information to the switch 307 belonging to the control unit relating to the DPDCH.

The control unit relating to the E-DPCCH only includes an E-DPCCH buffer 305 and an E-TFCI detection unit 309. The E-DPCCH buffer 305 stores the despread E-DPCCH. The E-TFCI detector 309 detects the E-TFCI from the channel estimation result sent by the temporary channel estimator 304 and the received signal of the E-TFC1 field. The E-TFCI detection unit 309 then sends the detected E-TFCI information to the switch 310 belonging to the control unit relating to the E-DPDCH.

The control unit common to the DPCCH and the E-DPCCH includes a pilot detecting unit 313, an SIR measuring unit 312, a full channel estimating unit 315, and a switch 314. The pilot detection unit 313 detects the presence or absence of the second pilot signal using the first and second pilot signals received from the DPCCH buffer 303 and the E-DPCCH buffer 305.

At that time, the pilot detection unit 313 measures the first SIR value with the first pilot signal, and measures the second SIR value with the second pilot signal. Using these, it is determined whether or not the second pilot signal has been transmitted by the above-described method.

If it is determined that the second pilot signal has not been transmitted, the pilot detector 313 turns off the switch 314 so that the second pilot signal is not sent to the SIR measuring unit 312 and the full channel estimating unit 315. Shall be. On the other hand, when it is determined that the second pilot signal has been transmitted, the pilot detection unit 313 turns on the switch 314 so that the second pilot signal is sent to the SIR measuring unit 312 and the full channel estimating unit 315. do. The SIR measurement unit 312 performs SIR measurement by the above-described method using the pilot signal (both first and second or only first) to be sent, and transmits the measurement result to the transmission power control signal generator ( 317). The transmission power control signal generation unit 317 compares the measurement result with the target SIR, generates a TPC signal indicating an increase or decrease in power, and sends it to a transmission control unit (not shown).

On the other hand, the full channel estimating unit 315 performs channel estimation using the pilot signals (both first and second or only the first) to be sent, and the estimation results are sent to the DPDCH lake synthesizing unit 311 and E-. The DPDCH rake synthesis unit 316 is sent.

The control unit relating to the DPDCH only includes a DPDCH buffer 302, a switch 307, and a DPDCH rake synthesizing unit 311. The DPDCH buffer 302 stores the despread DPDCH. The switch 307 receives the TFCI information from the TFCI detecting unit 308, and sends the data in the buffer 302 to the DPDCH lake synthesizing unit 311 when the data size indicated by the TFCI is not zero. The DPDCH rake synthesizing unit 311 corrects the amplitude variation of the received signal of the DPDCH using the channel estimates sent from the full channel estimating unit 315, performs rake combining, and performs a higher layer (not shown) on the signal after rake combining. Send to

The control unit relating to the E-DPDCH only includes an E-DPDCH buffer 306, a switch 310, and an E-DPDCH rake synthesis unit 316. The E-DPDCH buffer 306 stores the despread E-DPDCH. The switch 310 receives the E-TFCI information from the E-TFCI detecting unit 309 and, when the data size indicated by the E-TFCI is not 0, converts the data in the buffer 306 to the E-DPDCH lake synthesizing unit ( 316). The E-DPDCH rake synthesizing unit 316 corrects the amplitude variation of the received signal of the E-DPDCH using the channel estimate value sent from the full channel estimating unit 315, performs rake synthesis, and performs a higher layer on the signal after rake synthesis. Send to

As described above, according to the present embodiment, the mobile station transmits the second pilot signal when the transmission rate of the E-DPDCH to be transmitted is higher than the predetermined transmission rate threshold. However, the base station cannot detect the transmission rate unless it has received all of the E-TFCIs transmitted in the same TTI.

Therefore, conventionally, when the E-TFCI is distributed and transmitted in the TTI, the second pilot signal cannot be used for the SIR measurement used for the fast closed loop transmission power control for generating the TPC signal on a slot basis.

However, according to this embodiment, the base station compares the first SIR value measured with the first pilot signal with the second SIR value measured with the second pilot signal, and determines the presence or absence of the second pilot signal in units of slots. Therefore, when the second pilot signal is present, the second pilot signal is also used for the SIR measurement of the fast closed-loop transmission power control to improve transmission power control accuracy, improve channel reception quality, and improve throughput. Can be increased.

Example  2

Next, a second embodiment of the present invention will be described in detail.

As shown in Fig. 9, the mobile station transmits a second pilot signal when the E-DPDCH is transmitted at a transmission rate equal to or higher than a predetermined transmission rate threshold, similarly to the first embodiment.

However, unlike the first embodiment, if the mobile station in the second embodiment transmits the second pilot signal, the second pilot irrespective of the transmission rate during the predetermined pilot signal transmission time from the next TTI. Send the signal. The mobile station does not transmit the second pilot signal when transmitting the first data block (384 kbps data block) in the figure, but transmits the second pilot signal when transmitting the second data block (1024 kbps data block). In the next TTI, the E-DPDCH is not transmitted, but the second pilot signal is transmitted.

Further, the pilot signal transmission time is also notified to the base station in advance, and the base station detects the E-TFCI, and if it is equal to or greater than the predetermined transmission rate, the second pilot signal is transmitted during the TTI and subsequent pilot signal transmission time. Judging by it. Thus, the base station uses the first and second pilot signals for channel estimation on data blocks above a predetermined transmission rate and data blocks received during subsequent pilot signal transmission times. When the base station receives a data block of a predetermined transmission speed or more, the base station then performs SIR measurement for fast closed-loop transmission power control using the first and second pilot signals during the pilot signal transmission time.

As described above, since the mobile station transmits the second pilot signal when the data block transmission is performed at the transmission rate equal to or higher than the transmission rate threshold, and the subsequent pilot signal transmission time transmits the second pilot signal, The second pilot signal can be used for SIR measurement from the TTI after the transmission of the two pilot signals is started. In the case of a burst of packets such as file transmission and web browsing, and a relatively large packet size, high-speed transmission may be continued for a predetermined time, so the SIR measurement at the time of receiving a data block of the high-speed transmission according to the present invention Precision can be raised favorably. This improves the throughput because the accuracy of transmission power control is improved and the block error rate is reduced.

10 shows the configuration of a mobile station used in the present embodiment.

The mobile station in the second embodiment includes a counter 210 which the mobile station in the first embodiment did not have. The other configuration is the same as that of the mobile station in the first embodiment.

The counter 210 receives the information of the E-TFCI from the E-TFC selector 2081, and if the transmission rate indicated by the E-TFCI is equal to or greater than a predetermined transmission rate threshold (here 1024 kbps), the number of TTIs from the next TTI ( Iii) starts counting, and the switch 206 is turned on so that the second pilot signal is transmitted on the E-DPCCH. The counter 210 keeps the switch 206 on while the count value is smaller than the predetermined pilot signal transmission time. When the count value reaches the pilot signal transmission time, the counter 210 turns off the switch 206 so that the second pilot signal is not transmitted on the E-DPCCH. In addition, the counter 210 resets the count value if the transmission rate indicated by the E-TFCI is equal to or higher than the transmission rate threshold.

FIG. 11 is a diagram showing the configuration of a base station used in the second embodiment.

The base station in the second embodiment does not include the pilot detection unit 313 included in the base station in the first embodiment. Instead, the base station in the second embodiment is provided with a counter 318. The counter 318, if the transmission rate indicated by the E-TFCI from the E-TFCI detection unit 309 is equal to or higher than a predetermined transmission rate threshold (1024 kbps), the second pilot signal received by the TTI is the full channel estimation unit 315. Switch 314 to be sent on, and both switches 314 and 319 are turned on to be sent to the SIR measurement section 312 and the full channel estimator 315 from the next TTI. Start counting.

Then, the counter 318 turns both switches on while the count value is equal to or less than the predetermined pilot signal transmission time. Also, if the value of the given E-TFCI while the switch is on is greater than or equal to the transmission rate threshold, the counter 318 resets the count value and starts counting again from the next TTI of the data block. When the count value reaches the pilot signal transmission time, the counter 318 turns off both switches so that the second pilot signal from the next TTI is not sent to the SIR measuring unit 312 and the full channel estimating unit 315. do. Other control units are similar to those in the first embodiment.

In the present embodiment, when the base station incorrectly receives the E-TFCI, even though the second pilot is not transmitted, the base station synthesizes only the noise as if the second pilot signal is present, thereby reducing the channel estimation accuracy and Deteriorates SIR measurement accuracy. In order to reduce the probability of such a state, an error detection code such as CRC may be transmitted to the E-DPCCH together with the E-TFCI. This reduces the probability of misreception of the E-TFCI and reduces the probability of deteriorating channel estimation accuracy and SIR measurement accuracy by using the received signal of the second pilot signal that is not transmitted (and therefore only noise and interference components).

As described above, according to the present embodiment, the mobile station transmits the second pilot signal when the transmission rate of the data block of the E-DPDCH to be transmitted is higher than the predetermined transmission rate threshold, and after the data block transmission, the predetermined pilot. The signal transmission time transmits the second pilot signal. Since the pilot transmission time is notified to the base station in advance, when the base station detects an E-TFCI equal to or higher than the transmission rate threshold, it can then determine that the second pilot signal is transmitted during the pilot signal transmission time. Therefore, the base station can also perform the SIR measurement using the second pilot signal from the next TTI, thereby improving transmission power control accuracy. Therefore, the block error rate is reduced and throughput is improved.

Example  3

Next, a third embodiment of the present invention will be described in detail.

As shown in Fig. 12, the third embodiment also transmits the second pilot signal in accordance with the predetermined transmission rate threshold, similarly to the first embodiment. However, unlike the case of the first embodiment, the mobile station in the third embodiment performs the second pilot signal when the transmission rate (maximum transmission rate) by the maximum TFC designated to the base station is equal to or greater than a predetermined transmission rate threshold. Send. In the figure, the third bar from the top shows the data block actually transmitted on the E-DPDCH and its transmission rate. The second bar from the top shows the maximum data rate allowed for use with the E-DPDCH. In this case, since the transmission rate threshold is set to 768 kbps, the first TTI to which the maximum transmission rate of 384 kbps is assigned does not transmit the second pilot signal. However, in the second TTI to which the maximum transmission rate of 768 kbps is assigned, the data block is not. It does not transmit but transmits the second pilot signal.

Since the maximum TFC is assigned by the base station, the base station knows in advance whether the second pilot signal has been transmitted. Therefore, when the base station assigns the mobile station the maximum transmission rate above the transmission rate threshold, the first and second pilot signals are used for channel estimation and SIR measurement while the maximum transmission rate is valid. Otherwise, the base station uses only the first pilot signal.

As described above, since the mobile station transmits the second pilot signal while the maximum transmission rate designated by the base station is equal to or higher than the transmission rate threshold, the base station can know in advance the transmission timing of the second pilot signal. Therefore, since the base station can use the second pilot signal for SIR measurement for fast closed loop transmission power control, the transmission power control accuracy is improved, the block error rate is reduced, and the throughput is improved.

Further, in the present embodiment, when the maximum TFC is controlled by a differential signal, i.e., when the base station transmits a signal instructing the mobile station to increase or decrease the maximum TFC from a current value, the mobile station designates the maximum TFC. If the differential signal is received incorrectly, the maximum transmission rate recognized by the mobile station may be lower than the transmission rate threshold even though the maximum transmission rate recognized by the base station is higher than or equal to the transmission rate threshold. In this case, since the base station determines that the second pilot signal is being transmitted and performs channel estimation and SIR measurement using the received signal of the second pilot signal, the base station increases noise to degrade channel estimation accuracy and SIR measurement accuracy. Let's do it. In order to avoid such a situation, the transmission rate threshold (transmission rate threshold 1) of the base station may be set larger than the transmission rate threshold (transmission rate threshold 2) at the mobile station.

As shown in Fig. 13, when a reception error occurs in the differential signal, a deviation occurs between the maximum transmission rate recognized by the base station and the maximum transmission rate recognized by the mobile station. If the difference between the transmission rate threshold 1 and the transmission rate threshold 2 is larger than this misalignment, the mobile station will necessarily transmit the second pilot signal when the base station recognizes that the second pilot signal is being transmitted. The state as described above does not occur.

14 shows the configuration of a mobile station used in the present embodiment.

The configuration of the mobile station in the third embodiment is the same as that of the mobile station in the first embodiment. However, in the first embodiment, the E-TFC selector 2081 informs the switch 206 of the selected E-TFC, whereas in the present embodiment, the E-TFC selector 2081 is determined from the base station. Notify the switch 206 of the maximum TFC reported. As in the first embodiment, the switch 206 uses the second pilot signal when the transmission rate of the notified E-TFCI (in this case, indicates the maximum TFC) is greater than or equal to the predetermined transmission rate threshold. On to be inserted into, otherwise off. The other part is the same as the mobile station in the first embodiment.

FIG. 15 is a diagram showing the configuration of a base station used in the third embodiment.

The base station in the third embodiment does not include the counter 318 provided by the base station in the second embodiment. Instead, the switch 314 transmits the information of the maximum TFC allocated to the mobile station from the transmission control unit 320 in the base station. The switch 314 turns on the second pilot signal to be sent to the SIR measuring section 312 and the full channel estimating section 315 when the transmission rate of the maximum TFC is greater than or equal to a predetermined transmission rate threshold. If it is off. The other part is the same as the mobile station in the second embodiment.

As described above, according to the present embodiment, the mobile station transmits the second pilot signal when the transmission rate of the maximum TFC allocated by the base station is equal to or higher than a predetermined transmission rate threshold. Since the maximum TFC is determined by the base station, the base station knows in advance the timing at which the mobile station transmits the second pilot signal. Therefore, when the second pilot signal is transmitted, the base station can also perform SIR measurement for transmission power control using the second pilot signal, thereby improving transmission power control accuracy and reducing the block error rate. Thus, throughput is improved.

Claims (19)

In the mobile station, Transmitting a first pilot signal on a first channel; Transmitting a second pilot signal in a second channel in response to a transmission rate of data transmitted in the second channel, At the base station, Determining whether to use a second pilot signal in response to reception quality of the first pilot signal and the second pilot signal; In the case of using the second pilot signal, measuring reception quality using the first pilot signal and the second pilot signal; Measuring reception quality using only the first pilot signal when the second pilot signal is not used; Generating a transmission power control signal based on the measurement result of the reception quality; In the mobile station, And determining the transmission power of the first and second channels in response to the transmission power control signal generated at the base station. The method of claim 1, And the base station uses the first pilot signal and the second pilot signal to measure the reception quality when the reception quality of the second pilot signal is higher than a predetermined first reception quality threshold. Signal transmission method. The method of claim 2, And the first reception quality threshold is determined based on the reception quality of the first pilot signal. The method of claim 1, The base station is configured to determine whether the reception quality of the first pilot signal or the reception quality of the second pilot signal is higher than a predetermined second reception quality threshold and determined based on the reception quality of the first pilot signal. And when the reception quality of the second pilot signal is higher than the reception quality threshold, the first pilot signal and the second pilot signal are used to measure the reception quality. In the mobile station, Transmitting a first pilot signal on a first channel; Transmitting a second pilot signal on the second channel when transmitting a data block at a transmission rate higher than a predetermined transmission rate threshold on the second channel; Transmitting a second pilot signal from a data block transmission at a transmission rate higher than the transmission rate threshold until a predetermined pilot signal transmission time elapses; At the base station, Extracting a control signal indicating a transmission rate of a data block from the second channel; In the case where the transmission rate of the data block is higher than a predetermined transmission rate threshold, the first and second pilots after receiving the data block with the transmission rate higher than the transmission rate threshold until the pilot signal transmission time elapses. Measuring the reception quality using a signal, Measuring reception quality using only a first pilot signal other than the pilot signal transmission time; Generating the transmission power control signal in response to the measurement result of the reception quality; In the mobile station, And determining the transmission power of the first and second channels in response to the transmission power control signal generated at the base station. At the base station, Transmitting a maximum baud rate control signal for notifying information about a maximum baud rate that permits use on a second channel; In the mobile station, Transmitting a first pilot signal on a first channel; Determining a maximum transmission rate of the second channel based on the maximum transmission rate control signal notified from the base station; Transmitting a second pilot signal on the second channel when the maximum transmission rate of the second channel is higher than a predetermined mobile station transmission rate threshold; At the base station, Measuring reception quality using the first and second pilot signals when the maximum transmission rate that permits use in the second channel is higher than a predetermined base station transmission rate threshold; Measuring the reception quality using the first pilot signal when the maximum transmission rate of the second channel is lower than the base station transmission rate threshold; Generating a transmission power control signal in response to the measurement result of the reception quality; In the mobile station, And determining transmission power of the first and second channels in response to the transmission power control signal notified from the base station. The method of claim 6, And the base station transmission rate threshold is set higher than the mobile station transmission rate threshold. The method of claim 1, And the base station uses the second pilot signal for channel estimation. The method of claim 5, And the base station uses the second pilot signal for channel estimation. The method of claim 6, And the base station uses the second pilot signal for channel estimation. The transmission power of the first and second channels is determined in response to the transmission power control signal, the first pilot signal is transmitted in the first channel, and in response to the transmission rate of data transmitted to the second channel. A mobile station transmitting a second pilot signal on a second channel, In response to the reception quality of the first pilot signal and the second pilot signal, it is determined whether or not the second pilot signal is used, and when the second pilot signal is used, the first pilot signal and the second pilot signal. When the reception quality is measured using the second pilot signal, and when the second pilot signal is not used, the reception quality is measured using only the first pilot signal, and based on the measurement result of the reception quality. And a base station for generating the transmission power control signal. In response to the transmission power control signal, transmission power of the first and second channels is determined, a first pilot signal is transmitted on the first channel, and a transmission rate higher than a predetermined transmission rate threshold is transmitted to the second channel. In the case of transmitting a data block at a low rate, the second pilot signal is transmitted on the second channel, the data block having a transmission rate higher than the transmission rate threshold is transmitted, and then until the predetermined pilot signal transmission time has elapsed. A mobile station transmitting a second pilot signal, Extracting a control signal indicating the transmission rate of the data block from the second channel, and when the transmission rate of the data block is higher than a predetermined transmission rate threshold, receiving the data block having the transmission rate higher than the transmission rate threshold; Then, the reception quality is measured using the first and second pilot signals until the pilot signal transmission time elapses, and the reception quality is measured using the first pilot signal other than the pilot signal transmission time. And a base station for generating the transmission power control signal in response to the measurement result of the reception quality. Determine the transmit power of the first and second channels in response to the transmit power control signal, transmit a first pilot signal on the first channel, and notify that the maximum transmission rate of the second channel is predetermined. A mobile station that transmits a second pilot signal on the second channel when it is higher than a transmission rate threshold; Informing the mobile station of the maximum transmission rate of the second channel and using the first and second pilot signals when the maximum transmission rate of the second channel is higher than a predetermined base station transmission rate threshold. If the reception quality is measured and the maximum transmission rate of the second channel is lower than the base station transmission rate threshold, the reception quality is measured using the first pilot signal, and in response to the measurement result of the reception quality, And a base station for generating the transmission power control signal. In response to the reception quality of the first pilot signal and the second pilot signal, it is determined whether or not the second pilot signal is used, and when the second pilot signal is used, the first pilot signal and When the reception quality is measured using the second pilot signal, and when the second pilot signal is not used, the reception quality is measured using only the first pilot signal, and based on the measurement result of the reception quality. A mobile station in a wireless communication system having a base station for generating a transmission power control signal, A transmission power control unit which determines transmission power of the first and second channels in response to the transmission power control signal transmitted from the base station; A first frame generation unit configured to transmit a first pilot signal on the first channel; And a second frame generation section for transmitting said second pilot signal in said second channel in response to a transmission rate of data transmitted in said second channel. A transmission power control unit for determining transmission powers of the first and second channels in response to the transmission power control signal transmitted from the base station; A first frame generator which transmits a first pilot signal in a first channel, When transmitting a data block at a transmission rate higher than a predetermined transmission rate threshold on the second channel, a second pilot signal is transmitted on the second channel, and a data block having a transmission rate higher than the transmission rate threshold is transmitted. And a second frame generation section for transmitting the second pilot signal until a predetermined pilot signal transmission time has elapsed. A transmission power control section for determining transmission power of the first and second channels in response to a transmission power control signal notified from the base station; A first frame generation unit configured to transmit a first pilot signal on the first channel; A data generation unit for determining the maximum transmission rate of the second channel based on the maximum transmission rate control signal notified from the base station; And a second frame generator for transmitting the second pilot signal in the second channel when the maximum transmission rate of the second channel is higher than a predetermined mobile station transmission rate threshold. A pilot detection unit that determines whether to use the second pilot signal in response to the reception quality of the first pilot signal and the second pilot signal; In the case of using the second pilot signal, reception quality is measured using the first pilot signal and the second pilot signal, and in the case of not using the second pilot signal, the first pilot signal. A reception quality measuring unit measuring the reception quality with only; And a transmission power control signal generator for generating a transmission power control signal based on the measurement result of the reception quality. A control signal detection unit for extracting a control signal indicating a transmission rate of the data block from the second channel; When the transmission rate of the data block is higher than a predetermined transmission rate threshold, the first and second pilots after receiving the data block whose transmission rate is higher than the transmission rate threshold until a predetermined pilot signal transmission time elapses. A reception quality measuring unit measuring a reception quality using a signal and measuring the reception quality using the first pilot signal except for the pilot signal transmission time; And a transmission power control signal generator for generating a transmission power control signal in response to the reception quality measurement result. A transmission control unit for notifying the mobile station of the maximum transmission rate of the second channel; When the maximum transmission rate of the second channel notified to the mobile station is higher than a predetermined base station transmission rate threshold, the reception quality is measured using the first and second pilot signals, and the maximum of the second channel is measured. A reception quality measuring unit for measuring the reception quality using the first pilot signal when the transmission rate is lower than the base station transmission rate threshold; And a transmission power control signal generator for generating a transmission power control signal in response to the reception quality measurement result.

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