JP2012249001A - Receiver, and channel quality measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a receiver and channel quality measurement method for measuring accurate channel quality for each stream in a MIMO system where inter-stream interference occurs.SOLUTION: MIMO interference adjustment value calculation part 112 calculates a MIMO interference adjustment value by using a propagation path estimation value. An interference adjustment part 113 obtains post-adjustment interference power by multiplying CPICH reception power by the MIMO interference adjustment value. A HS-PDSCH interference conversion part 114 obtains inter-stream interference power by converting the post-adjustment interference power to HS-PDSCH interference power. A HS-PDSCH SNR calculation part calculates a SNR by using the inter-stream interference power, HS-PDSCH reception power, and CPICH noise power. A CQI determination part 116 determines a CQI for each stream from the obtained SNR.

Description

  The present invention relates to a receiving apparatus and a channel quality measuring method for measuring channel quality for each of a plurality of streams.

  One of the specifications of 3GPP (3rd Generation Partnership Project) is HSPA (High Speed Packet Access). HSPA is a collection of technologies aimed at improving peak data rate and frequency utilization efficiency. Among these techniques, there is a technique called MIMO (Multiple Input Multiple Output) system using a plurality of transmission / reception antennas.

  In HSPA MIMO, two different antennas (also referred to as streams) can be spatially multiplexed and transmitted in parallel using two transmitting antennas and two receiving antennas.

  Further, in HSPA, an index value indicating channel quality called CQI (Channel Quality Indicator) is reported from the terminal to the base station, and the base station transmits the downlink transmission rate (for example, transport block size, modulation, etc.) according to the reported CQI. System, code multiplexing number, etc.). Thereby, it is possible to efficiently perform data transmission at a transmission rate adapted to the quality of the propagation path.

  When CQI is applied to MIMO, independent transmission rate control is performed for each stream by measuring and reporting CQI for each stream. Therefore, the terminal measuring the CQI for each stream with high accuracy leads to an improvement in transmission throughput. As such a technique, a channel quality measurement method disclosed in Patent Document 1 is known.

  Here, a receiving apparatus 10 in which the channel quality measurement method disclosed in Patent Document 1 is applied to an HSPA communication system using the MIMO scheme will be described with reference to FIG. Here, it is assumed that a transmitting device (not shown) for transmitting data has two transmitting antennas, and the receiving device 10 shown in FIG. 1 also has two receiving antennas, and can transmit a maximum of two streams simultaneously. And

  In FIG. 1, signals received from two receiving antennas 11 are subjected to predetermined reception processing (processing such as filtering and AD conversion) by a reception processing unit, and a signal subjected to reception processing is a CPICH (Common Pilot Channel). The channel estimator 14 is despread by the despreading unit 13 and the channel estimation unit 14 obtains the channel estimation value using the CPICH despread symbol obtained thereby.

  The equalizer 15 performs an equalization process on the signal output from the reception processing unit 12 using the propagation path estimation value, and the CPICH despreading unit 16 despreads the equalized signal. I do. Using the CPICH despread symbol obtained in this way, CPICH power calculation section 17 calculates CPICH reception power, and CPICH noise calculation section 18 calculates CPICH noise power.

  The CL1 gain adjustment value calculation unit 19 calculates a CL1 gain adjustment value using the propagation path estimation value. Here, in the MIMO scheme in which two streams are transmitted simultaneously, two different sets of precoding weights are multiplied on the transmission side, so that the reception side uses two sets of corresponding weights for each of the first stream and the second stream. It is necessary to obtain the CL1 gain adjustment value. For this reason, all the processes after the gain adjusting unit 20 are performed for each stream.

  The gain adjusting unit 20 multiplies the CPICH received power by the CL1 gain adjustment value, thereby obtaining an adjusted CPICH received power. The CPICH SNR (Signal to Noise Ratio) calculation unit 21 calculates the CPICH SNR from the adjusted CPICH received power and the CPICH noise power, and the HS-PDSCH (High Speed-Physical Downlink Shared Channel) SNR conversion unit 22 calculates the CPICH. SNR is converted to HS-PDSCH SNR. The CQI determination unit 23 determines CQI that is channel quality for each stream from the HS-PDSCH SNR.

  As described above, the receiving apparatus 10 shown in FIG. 1 can measure the channel quality reflecting the gain of the closed loop transmission diversity.

Special table 2009-503913

  However, in the MIMO scheme in which a plurality of streams are simultaneously transmitted, the streams mutually interfere with each other. Therefore, the measured channel quality is higher than the actual channel quality in the receiving apparatus of FIG. The result will be high. Therefore, as in the HSPA communication system, when determining the transmission rate based on the channel quality fed back from the receiving device to the transmitting device, the transmission error rate becomes higher than necessary, and the reception error rate deteriorates. Furthermore, there is a problem that the transmission throughput is reduced.

  An object of the present invention is to provide a receiving apparatus and a channel quality measuring method that measure channel quality with high accuracy for each stream in a MIMO scheme in which inter-stream interference occurs.

  The receiving apparatus of the present invention includes a receiving means for receiving a pilot channel signal, a propagation path estimating means for obtaining a propagation path estimated value using the pilot channel signal, and a gain adjustment value using the propagation path estimated value. Gain adjustment value calculation means to be obtained, gain adjustment means for multiplying the gain adjustment value by pilot channel reception power to obtain adjustment pilot channel reception power, and data channel power for converting the adjustment pilot channel reception power to data channel reception power Conversion means; interference adjustment value calculation means for obtaining an interference adjustment value using the propagation path estimated value; and interference adjustment means for obtaining an adjusted pilot channel interference power by multiplying the interference adjustment value by the pilot channel reception power; , Data for converting the adjusted pilot channel interference power into data channel interference power Taking a Yaneru interference converting means, the data channel received power, the configuration comprising a channel quality calculating means for calculating a channel quality of a data channel from the data channel interference power and a pilot channel noise power.

  The channel quality measurement method of the present invention includes a reception step of receiving a pilot channel signal, a propagation channel estimation step of obtaining a propagation channel estimation value using the pilot channel signal, and a gain adjustment using the propagation channel estimation value. A gain adjustment value calculation step for obtaining a value; a gain adjustment step for obtaining an adjusted pilot channel reception power by multiplying the gain adjustment value by a pilot channel reception power; and data for converting the adjustment pilot channel reception power into a data channel reception power A channel power conversion step, an interference adjustment value calculation step for obtaining an interference adjustment value using the propagation path estimation value, and an interference adjustment for obtaining an adjusted pilot channel interference power by multiplying the interference adjustment value by the pilot channel reception power. And adjusting pilot channel interference power A data channel interference conversion step for converting to data channel interference power, and a channel quality calculation step for calculating the channel quality of the data channel from the data channel reception power, the data channel interference power and the pilot channel noise power. did.

  According to the present invention, it is possible to measure channel quality with high accuracy for each stream in a MIMO scheme in which inter-stream interference occurs.

FIG. 2 is a block diagram showing the configuration of a receiving apparatus in which the channel quality measurement method disclosed in Patent Document 1 is applied to an HSPA communication system using the MIMO scheme. The block diagram which shows the structure of the receiver which concerns on one embodiment of this invention

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

(One embodiment)
FIG. 2 is a block diagram showing a configuration of receiving apparatus 100 according to an embodiment of the present invention. Hereinafter, the configuration of the receiving apparatus 100 will be described with reference to FIG.

  The reception processing unit 102 performs processing such as filtering and AD conversion on the signals received from the two reception antennas 101 to convert them into baseband digital signals, and the baseband digital signals are converted into CPICH despreading units 103 and an equalizer 105. Output to.

  The CPICH despreading unit 103 performs direct descrambling and CPICH despreading on the baseband digital signal output from the reception processing unit 102. The CPICH despread symbol obtained in this way is output to propagation path estimation section 104.

  The propagation path estimation unit 104 calculates a propagation path estimated value from the CPICH despread symbol output from the CPICH despreading unit 103, and calculates the propagation path estimated value using an equalizer 105, a MIMO gain adjustment value calculation unit 109, and Each is output to the MIMO interference adjustment value calculation unit 112.

  The equalizer 105 performs equalization processing on the baseband digital signal output from the reception processing unit 102 using the channel estimation value output from the channel estimation unit 104, and the signal subjected to equalization processing Is output to the CPICH despreading unit 106.

  CPICH despreading section 106 performs descrambling and CPICH despreading on the signal output from equalizer 105, and outputs the obtained CPICH despread symbols to CPICH power calculation section 107 and CPICH noise calculation section 108, respectively.

  CPICH power calculation section 107 calculates CPICH reception power from the CPICH despread symbol output from CPICH despreading section 106 and outputs the calculated CPICH reception power to gain adjustment section 110 and interference adjustment section 113, respectively.

  CPICH noise calculation section 108 calculates CPICH noise power from the CPICH despread symbol output from CPICH despreading section 106, and outputs the calculated CPICH noise power to HS-PDSCH SNR calculation section 115.

MIMO gain adjustment value calculation section 109 calculates a MIMO gain adjustment value using the propagation path estimation value output from propagation path estimation section 104, and outputs the calculated MIMO gain adjustment value to gain adjustment section 110. The MIMO gain adjustment value is calculated by the following equations (1) and (2).

Here, GainRatio ₁ is MIMO gain adjustment value for the first stream, GainRatio ₂ is MIMO gain adjustment value for the second ^stream, _{h ^ xy} is the channel estimation value between the receiving antennas x transmitting antennas _{y, w mn} sender The value of m rows and n columns of the precoding weight matrix applied to the HS-PDSCH.

The MIMO gain adjustment value obtained here is a value representing the ratio of the received power when using MIMO to the received power when using open-loop transmission diversity, and information on the amplitude and phase fluctuation amount of the propagation path is obtained. Since it is necessary, it is obtained from the estimated channel value. That is, since the signal after the equalization process loses information on the amplitude and phase variation of the propagation path, the signal after the equalization process cannot be used here. The precoding weight matrix w _mn is a value multiplied to each stream on the transmission side, and may be notified from the transmission device to the reception device through a control channel (HS-SCCH: High Speed-Shared Control Channel) or the like. The receiving device may detect.

Gain adjustment section 110 multiplies the CPICH reception power output from CPICH power calculation section 107 by the MIMO gain adjustment value output from MIMO gain adjustment value calculation section 109, and gain-adjusted CPICH reception obtained thereby. The power (hereinafter referred to as “adjusted CPICH received power”) is output to HS-PDSCH power conversion unit 111. The calculation performed by the gain adjustment unit 110 is as shown in the following formulas (3) and (4).

_{Here, RSCP CPICH} is CPICH reception _{power, RSCP MIMO1} adjusted CPICH reception power of the first _stream, the _{RSCP MIMO2} is adjusted CPICH reception power of the second stream.

HS-PDSCH power conversion section 111 converts the adjusted CPICH reception power output from gain adjustment section 110 into HS-PDSCH reception power, and outputs the converted HS-PDSCH reception power to HS-PDSCH SNR calculation section 115. That is, the HS-PDSCH power conversion unit 111 converts the received power of the pilot channel signal into the received power of the data channel. The calculation performed by the HS-PDSCH power conversion unit 111 is as shown in the following formulas (5) and (6).

Here, RSCP _'MIMO1 the HS-PDSCH reception power of the first stream, RSCP' is _MIMO2 HS-PDSCH reception power of the second stream, gamma is a transmission power ratio of the CPICH and HS-PDSCH reception power. Γ is a value in dB that is signaled in advance from the transmission device to the reception device. 16/256 is a spreading gain adjustment coefficient when the SF (Spread Factor) of HS-PDSCH is 16 and the SF of CPICH is 256.

MIMO interference adjustment value calculation section 112 calculates a MIMO interference adjustment value for each stream using the propagation path estimation value output from propagation path estimation section 104, and outputs the calculated MIMO interference adjustment value to interference adjustment section 113. To do. The MIMO interference adjustment value is calculated by the following equations (7) and (8).

Here, IsiRatio ₁ is a MIMO interference adjustment value for the first stream, IsiRatio ₂ is a MIMO interference adjustment value for the second stream, and N _code is the number of multiplexed codes of HS-PDSCH. The superscript * represents a complex conjugate.

  The MIMO interference adjustment value obtained here is a value representing the ratio of the amount of interference received from other streams to the received power when open loop transmission diversity is used.

The interference adjustment unit 113 multiplies the CPICH reception power output from the CPICH power calculation unit 107 by the MIMO interference adjustment value output from the MIMO interference adjustment value calculation unit 112, and the adjusted CPICH interference power obtained thereby. (Hereinafter referred to as “adjusted CPICH interference power”) is output to the HS-PDSCH interference conversion unit 114. The calculation performed by the interference adjustment unit 113 is as shown in the following equations (9) and (10).

Here, ISI ₁ is the adjusted CPICH interference power of the first stream, and ISI ₂ is the adjusted CPICH interference power of the second stream.

The HS-PDSCH interference conversion unit 114 converts the adjusted CPICH interference power output from the interference adjustment unit 113 into HS-PDSCH interference power, and outputs the converted HS-PDSCH interference power to the HS-PDSCH SNR calculation unit 115. That is, the HS-PDSCH interference conversion unit 114 converts pilot channel interference power into data channel interference power (inter-stream interference power). The calculations performed by the HS-PDSCH interference conversion unit 114 are as shown in the following equations (11) and (12).

Here, ISI ′ ₁ is the HS-PDSCH interference power of the first stream, and ISI ′ ₂ is the HS-PDSCH interference power of the second stream.

The HS-PDSCH SNR calculator 115 outputs the HS-PDSCH received power output from the HS-PDSCH power converter 111, the CPICH noise power output from the CPICH noise calculator 108, and the HS-PDSCH interference converter 114. The HS-PDSCH SNR is calculated using the HS-PDSCH interference power thus generated, and the calculated HS-PDSCH SNR is output to the CQI determination unit 116. The HS-PDSCH SNR is calculated by the following equations (13) and (14).

Here, SNR _MIMO1 is the SNR of the first stream, SNR _MIMO2 is the SNR of the second stream, and ISCP is the noise power. In the equations (13) and (14), the SNR is obtained in dB units, but it is not necessarily calculated in dB units.

  The CQI determination unit 116 determines the CQI corresponding to the HS-PDSCH SNR output from the HS-PDSCH SNR calculation unit 115 for each stream. For example, a correspondence table between HS-PDSCH SNR and CQI is prepared in advance, and the CQI may be determined based on the correspondence table.

  Thus, according to Embodiment 1, the MIMO interference adjustment value is calculated using the channel estimation value, the adjusted interference power is obtained by multiplying the MIMO interference adjustment value by the CPICH reception power, and the adjusted interference power is obtained. MIMO that causes inter-stream interference by calculating inter-stream interference power for each stream in terms of HS-PDSCH interference power and calculating SNR using inter-stream interference power, HS-PDSCH received power, and CPICH noise power In the system, it is possible to measure the channel quality with high accuracy for each stream, so that data can be transmitted at an appropriate transmission rate, and the reception error rate and transmission throughput can be improved.

(Other embodiments)
In the above embodiment, the channel quality measurement in the case of simultaneously transmitting two streams in a communication system having two transmitting antennas and two receiving antennas has been described. However, the present invention limits the number of antennas to this. Instead, the number of transmitting antennas and receiving antennas can be expanded to three or more. For example, in the case of a communication system having N transmission antennas and N reception antennas (N is 2 or more), each stream is expressed as k-th stream (k = 1, 2,..., N). And Formula (2) can be represented by Formula (15). Similarly, Formula (3) and Formula (4) are Formula (16), Formula (5) and Formula (6) are Formula (17), Formula (7) and Formula (8) are Formula (18), Formula ( 9) and Expression (10) can be expressed by Expression (19), Expression (11) and Expression (12) can be expressed by Expression (20), and Expression (13) and Expression (14) can be expressed by Expression (21).

  In the above description, the case where the obtained SNR is used for determining the channel quality has been described. However, the present invention is not limited to this, and the measured SNR may be used for other purposes.

  The receiving apparatus and the channel quality measurement method according to the present invention can be applied to a MIMO mobile communication system.

DESCRIPTION OF SYMBOLS 100 Receiver 101 Reception antenna 102 Reception processing part 103, 106 CPICH de-spreading part 104 Channel estimation part 105 Equalizer 107 CPICH power calculation part 108 CPICH noise calculation part 109 MIMO gain adjustment value calculation part 110 Gain adjustment part 111 HS- PDSCH power conversion unit 112 MIMO interference adjustment value calculation unit 113 interference adjustment unit 114 HS-PDSCH interference conversion unit 115 HS-PDSCH SNR calculation unit 116 CQI determination unit

Claims (5)

Receiving means for receiving a pilot channel signal;
Channel estimation means for determining a channel estimation value using the pilot channel signal;
Gain adjustment value calculation means for obtaining a gain adjustment value using the propagation path estimated value;
Gain adjusting means for obtaining an adjusted pilot channel received power by multiplying the gain adjustment value by the pilot channel received power;
Data channel power conversion means for converting the adjusted pilot channel received power into data channel received power;
An interference adjustment value calculating means for obtaining an interference adjustment value using the propagation path estimation value;
Interference adjustment means for multiplying the interference adjustment value by the pilot channel received power to obtain adjusted pilot channel interference power;
Data channel interference conversion means for converting the adjusted pilot channel interference power into data channel interference power;
Channel quality calculating means for calculating the channel quality of the data channel from the data channel received power, the data channel interference power and the pilot channel noise power;
A receiving apparatus comprising: The receiving apparatus according to claim 1, wherein the gain adjustment value calculation unit calculates the gain adjustment value using Equation (1).

Where GainRatio _k is the gain adjustment value for the k-th stream, h ^{^} _xy is the estimated channel value between the receiving antenna x and the transmitting antenna y, and _wyk is the y row of the precoding weight matrix applied to the data channel on the transmitting side. The value of k column and N is the number of antennas. The receiving apparatus according to claim 1, wherein the interference adjustment value calculation unit calculates the interference adjustment value using Expression (2).

However, the interference adjustment value for the kth stream of IsiRatio _k , N _code is the number of data channel codes, superscript * is a complex conjugate, and h ^{^} _xy (h ^{^} _zx , h ^{^} _zy ) is a receiving antenna x and a transmitting antenna y. (Estimated propagation path between receiving antenna z and transmitting antenna x, receiving antenna z and transmitting antenna y), w _yk (w _xk , w _yl ) is y row of precoding weight matrix applied to data channel on transmitting side A value of k columns (x rows and k columns, y rows and 1 columns), and N is the number of antennas. The receiving apparatus according to claim 1, wherein the channel quality calculation means calculates the channel quality of the data channel using Equation (3).

Here, SNR _MIMOk is the SNR of the k-th stream, RSCP ′ _MIMOk is the data channel received power of the k-th stream, ISI ′ _k is the data channel interference power of the k-th stream, and ISCP is the noise power. A receiving step of receiving a pilot channel signal;
A propagation path estimation step for obtaining a propagation path estimated value using the pilot channel signal;
A gain adjustment value calculation step for obtaining a gain adjustment value using the propagation path estimated value;
A gain adjustment step of multiplying the gain adjustment value by a pilot channel reception power to obtain an adjustment pilot channel reception power;
A data channel power conversion step of converting the adjusted pilot channel received power into data channel received power;
An interference adjustment value calculation step for obtaining an interference adjustment value using the propagation path estimation value;
An interference adjustment step of multiplying the interference adjustment value by the pilot channel received power to obtain an adjusted pilot channel interference power;
A data channel interference conversion step of converting the adjusted pilot channel interference power into data channel interference power;
A channel quality calculation step of calculating the channel quality of the data channel from the data channel received power, the data channel interference power and the pilot channel noise power;
A channel quality measurement method comprising:

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