WO2005006595A1

WO2005006595A1 - Radio reception method and communication terminal device

Info

Publication number: WO2005006595A1
Application number: PCT/JP2003/008882
Authority: WO
Inventors: Takashi Toda; Takashi Kitade; Motoyasu Taguchi
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2003-07-14
Filing date: 2003-07-14
Publication date: 2005-01-20
Also published as: AU2003248062A1

Abstract

A phase estimation section (103a) estimates the phase of received signals from a plurality of base stations according to the phase of the CPICH signal from the base stations. A DPCH power measurement section (104) detects respective reception powers of the DPCH signals from the base stations. A synchronous detection section (106) weights the phase information estimated by the phase estimation section (103a) according to the reception powers detected by the DPCH power measurement section (104) and by using the weighted phase estimation value, synchronous-detects the DPCH signals from the base stations. An RAKE combining section (107) RAKE-combines the DPCH signals from the base stations after the synchronous detection.

Description

Description Wireless reception method and communication terminal device

The present invention relates to a radio reception method and a communication terminal device used for communication in a CDMA (Code Division Multiple Access) system. Background art

In recent years, the demand for land mobile communications such as automobiles and mobile phones has increased remarkably, and in addition to high-speed and high-quality transmission, effective use of frequency to secure more subscriber capacity at a limited frequency Technology is important.

As one of the multiple access for effective use of frequency, the CDMA system is drawing attention. The CDMA method is a multiple access using spread-spectrum communication technology, is less susceptible to multipath distortion, and has the characteristic of being able to expect a diversity effect by performing rake reception.

Here, the outline of RAKE reception is as follows.In mobile communication, the direct wave that the transmitted wave directly reaches from the transmitting station to the receiving station and the reflected wave that is reflected by the building and arrives at the receiving station are synthesized. Will be received. In this case, since there are many paths of the reflected wave, a wave that has passed through many paths (multipath) is received. In this way, the receiving station synthesizes and receives signals that have passed through many paths. As a result, in the receiving station, signals on different paths interfere with each other and fading occurs.

The autocorrelation of the spreading code of the CDMA method becomes small when it is offset in time. By utilizing this, if the despreading unit performs despreading with a spreading code given a phase offset corresponding to the propagation delay time, a signal with a propagation delay time corresponding to the phase offset can be obtained. . That is, by giving a phase offset corresponding to the propagation delay time to the phase of the spreading code, it is possible to obtain a signal of each path from the received signal. Therefore, by providing a plurality of despreading units in parallel and performing despreading processing in each despreading unit using a despreading code given a phase offset corresponding to the propagation delay time of the signal of each path, The signal that has passed through can be obtained independently.

A good demodulated signal can be obtained by adding and combining (that is, RAKE combining) the signals of each path obtained in this way with a predetermined weight in the combining unit. Such a method is called RAKE reception, and signals of a plurality of paths can be selectively weighted and combined, so that path diversity reception can be performed.

On the other hand, in the CDMA communication system that is currently being standardized in 3GPP (3rd Generation Partnership Project), there is a channel called Common Pilot CHannel (CPICH). This is a channel that constantly transmits pilot symbols.By using this channel, the mobile station can perform channel estimation and perform synchronous detection even on communication channels that do not include pilot symbols. become.

One of the transmission power controls is S SDT (Site Selection Diversity Transmit power control). This is because, as shown in FIG. 1, the mobile station MS transmits the first common pilot channel (P—CPI) transmitted from each cell C e1 l #l to Cel 1 # 3 (that is, each base station BTS). CH: Primary CPICH) is measured, and the cell with the highest reception level is determined as a Primary cell. Then, an ID label indicating Primary cell is included in FBI (FeedBack Information) and transmitted to the base station.

The base station determines whether or not the own station is P rima r y c e l l based on the ID label of the FB I, and only the base station that is P r i

Data Channel). On the other hand, the base station of a cell other than Primarycell (N on Primaryce11) transmits only the DPCCH. this Accordingly, the base station that performs downlink data transmission can be limited, so that the amount of interference of the downlink signal can be reduced.

The DPD CH transmits actual transmission data, the DPC CH transmits a pilot signal and the like, and these channels are collectively called a DP CH (Dedicated Physical Channel), and transmission power is controlled. .

The wireless receiver used in such a CDMA wireless communication system performs synchronous detection of DPCH using phase estimation of CP ICH. This is because the transmission power of the CP ICH is generally higher than the transmission power of the DP CH, and therefore, the accuracy of phase estimation using the CP I CH is higher than that of the DPCH.

FIG. 2 shows a receiving system of a communication terminal device used in a CDMA wireless communication system. The communication terminal device inputs the received signal received by antenna AN to radio processing section RF. The radio processing unit RF performs radio reception processing such as amplification and frequency conversion on the received signal. Radio processing unit The received signal subjected to radio reception processing by RF is passed through an analog-to-digital converter (A / D) 1. Entered in 2 b.

Here, a plurality of despreading sections 2a and 2b are provided to correspond to a plurality of downlink signals from a plurality of radio base stations, respectively, and the despreading sections 2a and 2b are respectively provided. The despreading process is performed using different spreading codes and code phases. Specifically, the plurality of despreading units 2a regenerate pilot signals included in the CP ICH using spreading codes corresponding to the spreading codes of the respective base stations. On the other hand, the plurality of despreading sections 2b despread the DPCH using spreading codes (actually, double spreading codes assigned to each base station and its own terminal) corresponding to the spreading code of each base station. The transmission data contained in the DPCH is reproduced by spreading.

The phase estimating unit 3 obtains a phase estimation value of the signal after despreading based on the pilot signal, and sends it to the synchronous detection unit 4. Synchronous detector 4 is the position from phase estimator 3 By calculating the complex conjugate of the phase estimation value and multiplying it by the despread signal, phase compensation and RAKE weighting are performed. RAKE combining section 5 assigns the signal after the synchronous detection to the finger and combines the synchronous detection output. The decoding unit 6 performs an error correction decoding process on the signal after RAKE combining.

However, the following problems occur in the wireless receiving device used in the conventional CDMA wireless communication system as described above.

At the time of handover, each base station independently controls the transmission power of DPCH, so the transmission power ratio of DPCH and CP ICH transmitted from each base station differs for each base station. Weights will not be accurate. As an extreme example, the received power of DPCH may be very small even if the received power of CPICH from a certain base station is very large. In such a case, the noise signal is multiplied by a large rake weight and synthesized, and the signal quality of the RAKE-combined signal deteriorates.

In addition, during site selection diversity transmission control, if the mobile station specifies Primary cell, or if the FBI received from the mobile station is not reliable for + minutes, the base station transmits DPCCH and DPDCH, and The base station designated as rimarycell transmits only DPCCH. Here, if the ID label specified by the mobile station is transmitted correctly, no problem will occur, but if it is not transmitted correctly, the following problems will occur.

One is that if the base station does not transmit DPDCH even though the mobile station specifies Primary 11, the mobile station considers that base station as a target for RAKE combining and therefore reduces the noise component. It will be the target of composition. Conversely, even if the base station transmits the DPDCH even though it is designated as "No Primary cell", the mobile station cannot target the DPDCH for RAKE combining. Disclosure of the invention

An object of the present invention is to improve reception quality by performing RAKE combining accurately. It is an object of the present invention to provide a wireless receiving method and a communication terminal device capable of receiving the information.

This object is achieved by weighting and RAKE combining DPCH signals from each base station based on the received power of the DPCH signal instead of the CP ICH.

In this way, even when the transmission power ratio between the DPCH transmitted from each base station and the CP ICH differs from base station to base station, as in the case of handover, a large weight is assigned to the DPCH that actually has high reception power. Since the RAKE combining can be performed by adding the RAKE combining, the reception quality of the signal after the RAKE combining can be improved. In addition, even if the ID label cannot be transmitted correctly during site selection diversity transmission control, the DPCH with high received power can be RAKE-combined with a large weight, so that noise components are not subject to synthesis. However, the base station signal that is actually transmitting the DPDCH can be the target of RAKE combining.

In addition, the power ratio between the DPCH and CPICH of the path with the highest received power received from each base station is calculated, and for the path that does not have the maximum received power, the power ratio is calculated separately.The PICH received power is multiplied by the power ratio. Is more preferable if is the received power of the DPCH.

In other words, with this configuration, it is possible to accurately estimate the size of the DPCH of the path having a low received power, so that it is possible to more accurately estimate the R AKE weight. Brief Description of Drawings

FIG. 1 is a diagram for explaining site selection diversity transmission control; FIG. 2 is a block diagram showing a configuration of a conventional communication terminal device;

FIG. 3 is a block diagram showing a configuration of a communication terminal device according to Embodiment 1 of the present invention;

FIG. 4 is a block diagram showing another configuration example of the communication terminal device according to the first embodiment; FIG. 5 is a block diagram showing another configuration example of the communication terminal device according to the first embodiment; FIG. 6 is a block diagram showing another configuration example of the communication terminal device according to Embodiment 1;

FIG. 5 is a block diagram showing a configuration of a communication terminal apparatus according to Embodiment 2. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(Embodiment 1)

In FIG. 3, reference numeral 100 denotes the overall configuration of a communication terminal device that receives signals from a plurality of base stations as a wireless receiving device according to Embodiment 1 of the present invention.

Communication terminal apparatus 100 inputs a received signal received by antenna AN to radio processing section RF. The radio processing unit RF performs radio reception processing such as amplification and frequency conversion on the received signal. Radio processing unit The received signal subjected to radio reception processing by RF is subjected to de-spreading of the CP I CH via analog-to-digital converter (AZD) 101. De-spreading unit 102a and de-spreading unit 102 for de-spreading DP CH. Entered in b. Here, a plurality of despreading sections 102a and 102b are provided to respectively correspond to a plurality of downlink signals from a plurality of radio base stations, and each despreading section 102a and 102b has a different spreading code. And despreading processing is performed using the code phase. Specifically, each of the plurality of despreading units 102a reproduces a pilot signal included in the CPICH using a spreading code corresponding to the spreading code of each base station. On the other hand, the plurality of despreading sections 102b despread the DPCH using the spreading code corresponding to the spreading code of each base station (actually, the double spreading code assigned to each base station and its own terminal). By performing the spreading process, the transmission data included in the DPCH from each base station is reproduced.

The despread result of the CP I CH is sent to phase estimating section 103a, and phase estimating section 103a averages one or more symbols to obtain a phase estimated value of the signal after despreading, and weights this by weighting section 105a. To send to. On the other hand, the result of the despreading of the DPCH is sent to phase estimating section 103b, and phase estimating section 103b performs an inverse averaging by performing symbol averaging of one or more symbols. The phase estimation value of the spread signal is obtained, and this is transmitted to DPCH power measurement section 104.

DPCH power measurement section 104 measures the received power of DPCH by squaring the estimated value of DPCH phase of each finger. The power of D PCH may be directly measured from the D PCH despread value.

The weighting unit 105 calculates a phase estimation value used for synchronous detection from the CPHICH phase information and the RAKE weight, which is the magnitude of the DPCH phase estimation value. That is, in the present embodiment, the magnitude of the DPCH phase estimation value (that is, the DPCH reception level) is used instead of the CPICH reception level as the RAKE weight.

Synchronous detection section 106 performs synchronous detection by multiplying the complex conjugate of the phase estimation value calculated by weighting section 105 on the DPCH despread signal. The RAKE combining unit 107 obtains the sum of the synchronous detection outputs. Since the RAKE weight is reflected in the phase estimation value itself by the weighting unit 105, a simple addition is performed here. The decoding unit 108 performs error correction decoding and the like on the RAKE synthesized signal.

Here, a method of calculating a phase estimation value weighted by RAKE according to the reception level of the DPCH in weighting section 105 will be described.

The weighting unit 105 performs the following calculation on the phase estimation value calculated from the C P I CH of each finger, thereby setting the magnitude to 1.

cp i chd,) = i _{cpi ch} (l,) / | _pich (l, m) |

(1) where, in equation (1), e _cpich (1, m) is a phase estimation vector calculated from the _CPICH of the m-th slot in one pass.

Next, using the following equation, the magnitude of the phase estimation value is defined as the magnitude of the phase estimation value of DPCH.

fo rDe tecti ond 'ξ, _{cp i ch} (l, Π1 ノ X | ξ _{dp ch} (l, Hi) |

(2) In Equation (2), _dpch (1, m) is a phase estimation vector calculated from the DPCH pilot symbol in the m-th slot in one pass.

As described above, in communication terminal apparatus 100, weighting of each finger of RAKE combining section 107 is performed in accordance with the reception power of DPCH from a plurality of base stations.

As a result, even when the transmission power ratio between the DPCH and the CP ICH transmitted from each base station differs from base station to base station, as in the case of handover, a weight is assigned to the DPCH that actually has large reception power. Since RAKE combining can be performed, the reception quality of the RAKE combined signal can be improved.

Also, if the DPDCH signal size is used instead of the DPCH phase estimation value during the site selection diversity transmission control, even if the ID label cannot be transmitted accurately, a large weight is assigned to the DPCH with high received power. Since it is possible to perform RAKE combining by adding, the base station that is actually transmitting the DP DCH can be the RAKE combining target without making the noise component the combining target.

According to the above configuration, phase estimation for synchronous detection is performed based on the CP ICH, and weighting for RAKE combining is performed based on the received power of the DPCH, so that RAKE combining is performed accurately. As a result, it is possible to obtain the communication terminal device 100 with improved reception quality.

In this embodiment, a weighting section 105 for weighting each phase estimation value estimated by phase estimating section 103a according to each received power measured by DPCH power measuring section 104, and a weighted phase When a synchronous detector 106 that synchronously detects DPCH signals from multiple base stations using estimated values and a RAKE combiner 107 that RAKE-combines DPCH signals from multiple base stations after synchronous detection are provided Was explained. According to such a configuration, in synchronous detection section 106, phase compensation and weighting processing according to the received power of the DPCH can be performed simultaneously to obtain a weighted synchronous detection output. Combining section 107 only needs to add a plurality of DPCH signals after synchronous detection, and processing in RAKE combining section 107 can be simplified.

However, the configuration of the communication terminal device of the present invention is not limited to this. Synchronous detection is performed based on the phase estimation value of the CP I CH as usual, and the weight of each finger in the RAKE combining unit is determined by the received power of the DP CH. May be performed according to the conditions. In other words, a synchronous detection section that synchronously detects DPCH signals from multiple base stations using the phase information shown in equation (1) estimated by phase estimation section 103a, and a DPCH signal from multiple base stations after synchronous detection. By providing a weighting unit for weighting the signal according to the received power of each DPCH signal and a RAKE combining unit for RAKE combining the weighted DPCH signals, the same effect as in the above-described embodiment can be obtained. it can. Further, the communication terminal device of the present invention may be configured as shown in FIG. In FIG. 4, in which parts corresponding to those in FIG. 3 are assigned the same reference numerals, communication terminal apparatus 200 has CPICH power measurement section 201 and power ratio measurement section 202. CP I CH power measuring section 201 measures the power of CP I CH from each base station based on the output of each phase estimating section 103a.

Power ratio measuring section 202 calculates the power ratio between the DP CH and the CP I CH of the path having the highest reception strength among the received signals received from each base station. Weighting section 203 uses, as a weighting factor for each phase estimation value, a value obtained by multiplying the individually calculated CPICH reception power by this power ratio for paths that do not have the maximum reception power.

This makes it possible to more accurately estimate the RAKE weight. This is because the power ratio between the CP I CH and the DP CH is constant on the path from the same base station, and in general, the CP I CH has higher transmission power than the DP CH, so that it is possible to estimate with higher accuracy. It is. Also, the power ratio can be calculated more accurately for paths with higher reception strength than for paths with lower reception strength. By doing so, it becomes possible to accurately estimate the magnitude of the DPCH of the path having a low received power, and it is possible to more accurately estimate the RAKE weight.

Further, the communication terminal device of the present invention may be configured as shown in FIG. With Figure 3 In FIG. 5, in which corresponding parts are assigned the same reference numerals, communication terminal apparatus 300 includes noise measuring section 301 and noise compensating section 302. The noise measurement unit 301 measures the noise and interference of the DPCH signal for each finger. The noise compensator 302 corrects the RAKE weight of each path according to the noise and interference components. For example, the larger the measured noise, the smaller the RAKE weight. Weighting section 303 weights the phase estimation value using the noise-compensated RAKE weight.

By this means, it is possible to accurately estimate the RAKE weight of the DPCH. This is because the RAKE weight contains noise and interference wave components, and the RAKE weight is larger than the actual received level especially for paths with low received levels. It is because it can solve.

In addition, if the DPKE RAKE weight is 1 _edpch (1, m) 1 or less than a certain threshold, if the phase estimation value is set to 0, the received signal at the level that causes deterioration can be excluded from the target of synthesis. it can. More specifically, finger assignment is performed based on a long-time averaged delay profile.However, as described above, it is effective when the reception level instantaneously decreases due to fluctuations such as fusing. Become.

Further, the communication terminal device of the present invention may be configured as shown in FIG. Correspondence with Fig. 4 In Fig. 6 where parts are assigned the same reference numerals, communication terminal apparatus 400 inputs the power ratio between CPICH and DPCH measured by power ratio measurement section 202 to threshold setting section 401. . . Power ratio measuring section 202 measures the power ratio between DPCH and CP I CH for each base station.

The threshold setting unit 401 sets the reception level threshold of the CPICH for each base station by multiplying the power ratio of each base station by the threshold level of the DPCH. The weighting section 402 uses the threshold value set in this way to determine the threshold value of the DPCH signal of each base station obtained by the DPCH measurement section 104. Then, the weight coefficient for the DPCH signal below the set threshold is set to 0. As a result, only signals from base stations that have a reception level higher than the reception level threshold of the CP ICH are weighted for RAKE combining. To be attached. As a result, unnecessary DPCH signals from base stations can be excluded from RAKE combining targets, and it becomes unnecessary to measure the received power of DPCH from all base stations.

(Embodiment 2)

In this embodiment, a description will be given of a communication terminal device capable of performing suitable RAKE combining at the time of site selection diversity transmission control.

In FIG. 7, in which parts corresponding to those in FIG. 3 are assigned the same reference numerals, communication terminal apparatus 500 has the same configuration as communication terminal apparatus 100 in FIG.

The combining determination unit 501 measures the reception power of the DP DCH signal of the synchronous detection output of each finger, and controls the RAKE combining unit 107 so that only fingers whose DPDCH reception power is equal to or greater than a certain threshold are to be RAKE combined. .

By this means, it is possible to determine whether or not to be a target for RAKE combining according to the presence / absence of the DPDCH of the actually received signal, so that it is not necessary to combine finger outputs assigned to base stations that are not transmitting DPCCH. As a result, even when the ID label is not transmitted to the base station accurately, it is possible to perform an accurate RAKE combining process.

Although FIG. 7 describes the case where the target of RAKE combining is determined based on the received power of the DPDCH signal, whether or not the target of RAKE combining may be determined based on the reception level difference between DPDCH and DPCCH. This is because the DPCCH is transmitted not only from the Primary cell or the Non-Primary cell but also from the constantly transmitted power DPDCt ^ ± Primary cell, so the reception from the NonPrimary cell 11 This is because the signal has a large power difference between DPDCH and DPCCH. According to this method, since the distance attenuation is the same for both DPDCH and DPCCH, the determination threshold can be fixed. Alternatively, only the maximum path of each base station may be determined for the purpose of preventing erroneous determination.

When measuring the DPDCH reception level, The reception power of the symbol with the highest reception level may be set to the reception level of the DPDCH, or the average value of the upper N (N is 1 or more) of the highest reception power among the symbols of the DPDCH may be set to the reception level of the DP DCH. . By this means, it is possible to measure the received power of DPDCH even when the number of DPDCH transmission bits changes due to the amount of transmission signal.

In addition, a method for determining the RAKE combining target based on the Primaryeel 1 information transmitted by the own station (communication terminal device) and transmitting the FBI, which is the original operation of the site selection diversity transmission power control, and a method using the DPDCH described above. May be switched depending on the propagation path environment. By doing so, the determination accuracy can be further improved. If the downlink TPC bit is used, the quality of FBI transmission can be estimated. For example, when there are many bits indicating that the transmission power is increased as the downlink TPC bits, it is understood that the reception environment of the base station is poor and the probability that the FBI is not correctly received is high.

The present invention is not limited to the above-described embodiment, but can be implemented with various modifications.

As described above, according to the present invention, the RAKE weight is set using the received power of the DPCH (including the DPDCH), so that the optimum RAKE combining can be performed at the time of handover or site selection diversity transmission control. Will be able to

This specification is based on Japanese Patent Application No. 2002-108928 filed on April 11, 2002. All its contents are included here. Industrial applicability

The present invention can be applied to, for example, a mobile phone.

Claims

The scope of the claims

1. Based on the CP ICH signals from multiple base stations, the DPCH signals from each base station are phase-compensated, and based on the received power of each DPCH signal, the higher the received power, the greater the weight of the DPCH signal. Performing a weighted synthesis of a plurality of DPCH signals.

2. Calculate the received power ratio between the DPCH signal and the CP I CH signal of the path with the highest received power received from each base station, and calculate the received power of the CP I CH signal separately for paths that do not have the maximum received power. 2. The wireless reception method according to claim 1, wherein a product of the power ratio and the received power ratio is used as a received power of the DPCH signal.

3. Phase estimation means for estimating the phase of the received signals from multiple base stations based on the phases of the CP I CH signals from multiple base stations, and the received power of each DPCH signal from multiple base stations. A DPCH power measuring means for measuring, a weighting means for weighting each phase estimation value estimated by the phase estimating means according to each reception power measured by the DPCH power measuring means, and a weighted phase estimator. A communication terminal device comprising: synchronous detection means for synchronously detecting each of DPCH signals from the plurality of base stations using the same; and RAKE combining means for synthesizing DPCH signals from the plurality of base stations after synchronous detection. .

4. Phase estimation means for estimating the phases of the received signals from multiple base stations based on the phases of the CP I CH signals from multiple base stations, and the received power of each DPCH signal from multiple base stations. DPCH power measuring means for measuring, synchronous detecting means for synchronously detecting DPCH signals from the plurality of base stations using the phase information estimated by the phase estimating means, and the plurality of base stations after synchronous detection. A communication terminal device comprising: weighting means for weighting the DPCH signal according to the received power of each DPCH signal; and RAKE combining means for combining the weighted DPCH signal.

5. Further, a CPICH power measuring means for measuring the reception power of each of the CPICH signals from a plurality of base stations, and a parameter having the highest reception power received from each base station. Power ratio measuring means for measuring the received power ratio between the DP CH signal and the CP I CH signal of the base station, wherein the weighting means calculates the received power of the CP I CH signal separately for the path having the maximum received power. 4. The communication terminal device according to claim 3, wherein a value obtained by multiplying the power ratio is used as a weight.

6. Furthermore, a CP ICH power measuring means for measuring the received power of each CP I CH signal from a plurality of base stations, and a DP CH signal and a CP I CH of a path having the highest received power received from each base station. Power ratio measuring means for measuring a received power ratio of a signal, wherein the weighting means weights a value obtained by multiplying the received power of the CP I CH signal individually calculated by the power ratio for a path having a maximum received power. The communication terminal device according to claim 4, which is used as:

7. Further, threshold value setting means for setting the reception level threshold value of the CP I CH for each base station by multiplying the power ratio for each base station obtained by the power ratio measuring means by the threshold level of the DP CH is provided. The communication terminal device according to claim 5, wherein the weighting unit sets a weight equal to or less than a set threshold value to 0.

8. Further, a threshold setting means is provided for setting the reception level threshold of the CP ICH for each base station by multiplying the power ratio of each base station obtained by the power ratio measuring means by the threshold level of the DPCH. 7. The communication terminal device according to claim 6, wherein the weighting unit sets a weight equal to or less than a set threshold value to 0.