JP2012100094A - Receiving device, receiving method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reception level measurement accuracy.SOLUTION: An IFFT processing unit 14 obtains a correlation value for each OFDM symbol by applying IFFT processing to multiplication results supplied from an RS replica multiplication unit 12. From the correlation value for each OFDM, a peak level determination unit 19 detects the peak of the correlation value for each OFDM symbol. By comparing the peak value of the correlation values for each OFDM symbol with a prescribed threshold, a frame format determination unit 20 determines whether the subframe of concern is a unicast subframe or an MBSFN subframe. From the determination result of either the unicast subframe or the MBSFN subframe, a reception level measurement unit 21 controls a reference signal for use in the level measurement, and measures the reception level. The present invention is applicable to a receiving device.

Description

  The present invention relates to a receiving device, a receiving method, and a program.

  In recent years, the development of communication technology has been remarkable, and a system for communicating a large amount of data at high speed is being realized. This applies not only to wired communication but also to wireless communication. In other words, with the spread of mobile terminals such as mobile phones, research and development of next-generation communication methods that enable high-speed communication of large volumes of data even wirelessly and use of multimedia data such as videos and voices on mobile terminals are being promoted. It is actively done.

  As a next-generation communication method, a communication method using OFDM (Orthogonal Frequency Division Multiplexing) represented by LTE (Long Term Evolution) discussed in 3GPP (3rd Generation Partnership Project) has attracted attention. OFDM is a scheme in which a band to be used is divided into a plurality of subcarriers, and each data symbol is assigned to each subcarrier for transmission, and the subcarriers are arranged to be orthogonal to each other on the frequency axis. Excellent frequency utilization efficiency. In addition, since each subcarrier has a narrow band, the influence of multipath interference can be suppressed, and high-speed and large-capacity communication can be realized.

  Also, MBMS (Multimedia Broadcast and Multicast Service), which is a multimedia broadcast and broadcast service, has been introduced.

  In LTE, MBSFN (Multicast / Broadcast over Single Frequency Network) is introduced in the same way as W-CDMA. However, MBSFN differs from normal unicast subframes in the configuration of Reference Signal (hereinafter also simply referred to as RS), and Cell Specific Reference. Signal is transmitted only in the first symbol of the subframe.

  Therefore, the receiving terminal needs to determine a reference signal that can be used for cell reception level measurement. However, the MBSFN mapping information of other cells may not be known at the receiving terminal. Therefore, not all reference signals that can be used for level measurement are available.

  On the other hand, the existence of 1.4 MHz / 3 MHz narrowband cells is recognized in LTE, and even under such narrowband cells, level measurement accuracy equivalent to that under the broadband cells is required.

  As shown in 3GPP specification TS36.211, the physical frame format for transmitting Multicast Channel is defined differently from the physical frame format for Shared Channel. Therefore, it is necessary to perform measurement in consideration of the difference in frame format.

  However, since the receiving terminal cannot know the MBSFN information of the neighboring cell, not all Reference Symbols transmitted from the neighboring cell can be used.

  The case of Extended Cyclic prefix will be described with reference to FIG.

  FIG. 6A is a diagram illustrating a subframe format in the case of Unicast.

  In FIG. 6, R0 is a cell-specific reference signal and can be used for level measurement. In 3GPP standardization, subframe numbers 0, 4, 5, and 9 are always guaranteed to be in the Unicast subframe format.

  FIG. 6B is a diagram illustrating a subframe format in the case of MBSFN. In this case, R0 of the subframe head symbol is a cell-specific reference signal and can be used for level measurement. On the other hand, symbol R4 shown in FIG. 6B is a reference signal for MBSFN, and reference signals from other cells may be synthesized, and therefore cannot be used for level measurement.

  Also, in the 3GPP specifications, the receiving terminal cannot know whether the subframe numbers other than neighboring cell subframe numbers 0, 4, 5, and 9 are Unicast or MBSFN. Level measurement is performed using only the leading symbol R0.

  On the other hand, in order to improve frequency utilization efficiency, services in narrowband system bandwidths such as 1.4 MHz and 3 MHz are also assumed, and in such a narrowband cell environment, that is, the number of reference symbols that can be used for reception level measurement Even in the case where the number is small, it is desired to measure the peripheral cells with the same accuracy as that of the wide band.

  Conventionally, a path search circuit calculates a delay profile for a plurality of different paths from a received signal, detects a correlation value peak that is effective as a path timing from the obtained delay profile, and a finger section or a rake combining section (not shown) (For example, refer to Patent Document 1).

JP 2005-109541 A

  Thus, when MBSFN is used, it is difficult to accurately measure the reception level.

  Accordingly, an object of the present invention is to solve the above-described problem, that is, to provide a receiving apparatus, a receiving method, and a program that can improve the accuracy of reception level measurement.

  In order to solve the above problems, one aspect of the receiving apparatus of the present invention is based on a calculation unit that calculates a correlation value of an OFDM symbol for detection of a head path position, and a correlation value in a predetermined OFDM symbol, Judgment means for judging whether the frame is a unicast subframe or an MBSFN subframe.

  In addition to the above-described configuration, one aspect of the receiving device of the present invention is further provided with a measuring unit that measures the reception level using the number of reference signals corresponding to the determination result in the determining unit.

  Further, according to one aspect of the receiving apparatus of the present invention, in addition to the above-described configuration, a detecting unit that detects the head path position using the number of reference signals corresponding to the determination result in the determining unit is further provided.

  In addition to the above-described configuration, one aspect of the reception device of the present invention is that the determination unit is a unicast subframe based on an average value of predetermined values obtained from correlation values in a plurality of OFDM symbols, or MBSFN It is assumed that it is a subframe.

  Further, according to one aspect of the receiving apparatus of the present invention, in addition to the above-described configuration, the determination unit determines whether the unicast subframe or the MBSFN subframe is based on an average value related to the peak value of the correlation value. It is supposed to be.

  Also, one aspect of the reception method of the present invention is a unicast subframe based on a calculation step of calculating a correlation value of an OFDM symbol for detecting a head path position and a correlation value in a predetermined OFDM symbol. Or a determination step of determining whether it is an MBSFN subframe.

  Further, according to one aspect of the program of the present invention, a calculation step of calculating a correlation value of an OFDM symbol for detecting a head path position in a computer, and a correlation value in a predetermined OFDM symbol, a unicast subframe is calculated. And a determination step for determining whether it is an MBSFN subframe or not.

  According to one aspect of the present invention, it is possible to provide a receiving device, a receiving method, and a program that can improve the accuracy of reception level measurement.

It is a block diagram which shows the structure of a receiver. It is a flowchart explaining the process of a reception level measurement. It is a figure which shows the relationship of each value calculated or detected from a correlation value. It is a figure which shows the example of the correlation level of an OFDM symbol. It is a block diagram which shows the structural example of the hardware of a computer. It is a figure which shows the sub-frame format in the case of Extended Cyclic prefix.

  Hereinafter, a receiving apparatus according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a block diagram showing a configuration of a part of a receiving apparatus constituting a wireless communication system using OFDM. In this receiving apparatus that constitutes an LTE wireless communication system using OFDM, it is possible to measure the reception level of other cells with high accuracy while considering MBSFN.

  The receiving device can be a communication device such as a mobile phone, a PHS (Personal Handyphone System), a PDA (Personal Data Assistance, Personal Digital Assistants), or a wireless base station.

  The path search processing unit 10 of the receiving apparatus calculates a delay profile for the path from the orthogonally detected IQ signal supplied from the previous stage, detects a peak of a correlation value effective as a path timing from the delay profile, and determines the timing. Is output as path timing.

  The path search processing unit 10 includes an FFT (Fast Fourier Transform) processing unit 11, an RS (Reference signal) replica multiplication unit 12, an RS replica generation unit 13, an IFFT (Inverse Fast Fourier Transform) processing unit 14, and an inter-symbol voltage averaging unit 15. A delay profile calculator 16, a peak detector 17, and a head path position detector 18. Further, the receiving device is provided with a peak level determination unit 19, a frame format determination unit 20, and a reception level measurement unit 21.

  The FFT processing unit 11 applies FFT processing to the quadrature-detected IQ signal and supplies the FFT output obtained as a result to the RS replica multiplication unit 12. The RS replica multiplier 12 multiplies the cell-specific reference signal replica of the corresponding cell generated by the RS replica generator 13 and the FFT output, and supplies the multiplication result to the IFFT processor 14.

  The IFFT processing unit 14 obtains a correlation value for each OFDM symbol by applying IFFT processing to the multiplication result supplied from the RS replica multiplication unit 12. The IFFT processing unit 14 supplies the correlation value for each OFDM symbol to the inter-symbol voltage averaging unit 15 and the peak level determination unit 19.

  The inter-symbol voltage averaging unit 15 calculates the average between OFDM symbols from the correlation value for each OFDM symbol, and supplies the result to the delay profile calculation unit 16. The inter-symbol voltage averaging unit 15 refers to the frame format determination result supplied from the frame format determination unit 20 and calculates the average between OFDM symbols.

  The delay profile calculator 16 obtains a delay profile by calculating an average power value between OFDM symbols, and supplies the delay profile to the peak detector 17. The peak detector 17 detects the peak value in the delay profile supplied from the delay profile calculator 16. The head path position detector 18 detects the head path position with the earliest timing from the peak values obtained by the peak detector 17 and outputs the path timing as a path search result.

  The peak level determination unit 19 detects the peak of the correlation value for each OFDM symbol from the correlation value for each OFDM symbol, which is the output value of the IFFT processing unit 14. The frame format determination unit 20 compares the peak value of the correlation value for each OFDM symbol detected by the peak level determination unit 19 with a predetermined threshold value to determine whether the corresponding subframe is a unicast subframe or an MBSFN subframe. It is determined whether it is. The reception level measurement unit 21 controls the reference signal used for level measurement based on the determination result of the unicast subframe or the MBSFN subframe, and measures the reception level.

  Next, the reception level measurement process performed in units of subframes will be described with reference to the flowchart of FIG. Here, the RS number indicates the OFDM symbol number to which the Reference signal in the Unicast subframe is mapped, and takes the values of RS number = 0, 1, 2, 3.

  In step S11, the peak level determination unit 19 sets 0 to the RS number, and starts the process from the RS number = 0. In step S12, the peak level determination unit 19 determines whether or not the RS number exceeds 0. If it is determined in step S12 that the RS number does not exceed 0, the procedure proceeds to step S13, the peak level determination unit 19 increments the RS number by 1, and the procedure returns to step S12. That is, when the RS number is “0”, since it is a unicast reference signal, nothing is done and the reception of the next RS is awaited.

If it is determined in step S12 that the RS number is greater than 0, the procedure proceeds to step S14, and the peak level determination unit 19 determines the power from the correlation value for each OFDM symbol, which is the output value of the IFFT processing unit 14. Calculate the value. The peak level determination unit 19 detects (calculates) the peak value Pp in step S15, and calculates the level threshold value P _thr in step S16.

FIG. 3 is a diagram illustrating the relationship between the values calculated or detected from the correlation values. FIG. 3 shows an example of the peak value Pp and the level threshold value P _{thr and} an example of a level difference P _diff and a level difference threshold value P _{diff_thr} described later.

As a method of calculating the level threshold P _thr, the level threshold P _thr, or a fixed level (a predetermined prescribed value), or the like to electric power mean value except for the peak value Pp and the like.

Next, in step S17, the peak level determination unit 19 calculates a level difference P _diff that is a difference between the peak value Pp and the level threshold value P _thr .

In step S18, the peak level determination unit 19 determines whether or not the RS number is 3. If it is determined that the RS number is not 3, the procedure returns to step S13, and the above-described processing is repeated. That is, the procedure for calculating the level difference P _diff is repeated for RS numbers 1 to 3 (all RSs).

When it is determined in step S18 that the RS number is 3, since the level difference P _diff is obtained for all RSs, the procedure proceeds to step S19, and the peak level determination unit 19 determines the level difference P _diff The level difference average value P _{diff_ave} which is an average value is calculated. The peak level determination unit 19 supplies the level difference average value P _{diff_ave} to the frame format determination unit 20.

In step S20, the frame format determination unit 20 compares the level difference average value P _{diff_ave} with a predetermined level difference threshold P _{diff_thr,} and determines whether or not the level difference average value P _{diff_ave} is greater than the level difference threshold P _{diff_thr.} judge.

  FIG. 4 is a diagram illustrating an example of the correlation level of OFDM symbols in the case of the extended cyclic prefix. As shown in FIG. 4A, when the corresponding subframe is a Unicast subframe, the correlation level of each OFDM symbol can be obtained high.

  However, as shown in FIG. 4B, when the corresponding subframe is an MBSFN subframe, R0 is not transmitted in OFDM symbol numbers 3, 6, and 9 unlike the Unicast subframe. A low correlation with R0 is obtained.

If it is determined in step S20 that the level difference average value P _{diff_ave} is greater than the level difference threshold P _{diff_thr} , a sufficiently reliable correlation is obtained, and the same RS as the generated RS replica is transmitted. Therefore, the procedure proceeds to step S21, and the frame format determination unit 20 determines that the corresponding subframe is a Unicast subframe. In step S22, the reception level measurement unit 21 is included in the RS of the first OFDM symbol and the RS other than the first OFDM symbol, that is, the OFDM symbol numbers 0, 3, 6, and 9 shown in FIG. By measuring the reception level using the RS, the measurement accuracy is improved, and the reception level measurement process ends.

On the other hand, if it is determined in step S20 that the level difference average value P _{diff_ave} is equal to or lower than the level difference threshold value P _{diff_thr,} it is considered that the reliability of the correlation value is low and an RS different from the RS replica is transmitted. The procedure proceeds to step S23, and the frame format determination unit 20 determines that the corresponding subframe is an MBSFN subframe. In step S24, the reception level measurement unit 21 performs reception level measurement using only the first OFDM symbol, that is, the RS included in the OFDM symbol number 0 shown in FIG. The control of not using the OFDM symbol numbers 3, 6, and 9 shown in FIG.

In this manner, the subframe format is estimated by comparing the level difference average value P _{diff_ave} and the level difference threshold value P _{diff_thr} . The subframe format can be determined from the peak value of the correlation value of the OFDM symbol.

  By determining the subframe format, it is possible to appropriately control the RS used for level measurement.

  As described above, by using the reference signal correlation value calculated in the path search process, the MBSFN mapping of the peripheral cell is estimated, and the reference symbol used for reception level measurement is controlled, so that the accurate peripheral cell Receive level measurement can be realized.

  First, it is possible to improve the reception level measurement accuracy by determining the subframe pattern of another cell and increasing the number of reference signals used for level measurement.

  Secondly, in the above determination, there is an effect that an increase in circuit scale for realizing the subframe pattern determination process can be suppressed by using the intermediate result of the path search process.

  Third, by increasing the number of reference signals used for the path search by determining the subframe pattern, there is an effect that the accuracy of the path search can be improved.

Note that any method may be _used for determining the level threshold value P _thr and the level difference threshold value P _{diff_thr} .

In step S19 and step S20, it is described that controlled using a level difference average value _P diff_ave, so as to compare the maximum value of the level difference P _diff, or the minimum value of the level difference P _diff a level difference threshold P _{Diff_thr} Also good.

  Although extended CP has been described as an example, the same applies to normal CP.

  Further, the level measurement processing control has been described, but the same accuracy improvement is possible by controlling the RS used for the path search by the same method.

  In the case of the MBSFN dedicated cell, the leading symbol R0 is not transmitted, but the MBSFN dedicated cell is excluded.

  The series of processes described above can be executed by hardware or can be executed by software. When a series of processing is executed by software, a program constituting the software executes various functions by installing a computer incorporated in dedicated hardware or various programs. For example, it is installed from a program recording medium in a general-purpose personal computer or the like.

  FIG. 5 is a block diagram illustrating an example of a hardware configuration of a computer that executes the above-described series of processes using a program.

  In a computer, a central processing unit (CPU) 201, a read only memory (ROM) 202, and a random access memory (RAM) 203 are connected to each other by a bus 204.

  An input / output interface 205 is further connected to the bus 204. The input / output interface 205 includes an input unit 206 composed of a keyboard, mouse, microphone, etc., an output unit 207 composed of a display, a speaker, etc., a storage unit 208 composed of a hard disk or nonvolatile memory, and a communication unit 209 composed of a network interface. A drive 210 for driving a removable medium 211 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory is connected.

  In the computer configured as described above, the CPU 201 loads, for example, the program stored in the storage unit 208 to the RAM 203 via the input / output interface 205 and the bus 204 and executes the program. Is performed.

  The program executed by the computer (CPU 201) is, for example, a magnetic disk (including a flexible disk), an optical disk (CD-ROM (Compact Disc-Read Only Memory), DVD (Digital Versatile Disc), etc.), a magneto-optical disk, or a semiconductor. The program is recorded on a removable medium 211 that is a package medium composed of a memory or the like, or provided via a wired or wireless transmission medium such as a local area network, the Internet, or digital satellite broadcasting.

  The program can be installed in the computer by loading the removable medium 211 in the drive 210 and storing it in the storage unit 208 via the input / output interface 205. Further, the program can be installed in a computer by being received by the communication unit 209 via a wired or wireless transmission medium and stored in the storage unit 208. In addition, the program can be installed in the computer in advance by storing the program in the ROM 202 or the storage unit 208 in advance.

  The program executed by the computer may be a program that is processed in time series in the order described in this specification, or in parallel or at a necessary timing such as when a call is made. It may be a program for processing.

  The embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Path search process part, 11 ... FFT process part, 12 ... RS replica multiplication part, 13 ... RS replica production | generation part, 14 ... IFFT process part, 15 ... Inter-symbol voltage average part, 16 ... Delay profile calculation part, 17 ... Peak detection unit, 18 ... head path position detection unit, 19 ... peak level determination unit, 20 ... frame format determination unit, 21 ... reception level measurement unit, 201 ... CPU, 202 ... ROM, 203 ... RAM, 208 ... storage unit, 209: Communication unit, 211: Removable media

Claims (7)

A calculation means for calculating a correlation value of an OFDM (Orthogonal Frequency Division Multiplexing) symbol for detection of a head path position;
Receiving means comprising: a determination means for determining whether the frame is a unicast subframe or an MBSFN (Multicast / Broadcast over Single Frequency Network) subframe from the correlation value in the OFDM symbol determined in advance apparatus. The receiving device according to claim 1,
The receiving apparatus further comprising: a measuring unit that measures a reception level using a number of reference signals corresponding to a determination result in the determining unit. The receiving device according to claim 1,
The receiving apparatus further comprising: a detecting unit that detects the head path position by using a number of reference signals corresponding to a determination result in the determining unit. The receiving device according to claim 1,
The determination unit determines whether a unicast subframe or an MBSFN subframe based on an average value of predetermined values obtained from the correlation values in a plurality of OFDM symbols. The receiving device according to claim 4,
The determination unit determines from the average value regarding the peak value of the correlation value whether it is a unicast subframe or an MBSFN subframe. A calculation step of calculating a correlation value of the OFDM symbol for detection of the head path position;
And a determination step of determining whether it is a unicast subframe or an MBSFN subframe from the correlation value in the OFDM symbol determined in advance. A calculation step of calculating a correlation value of the OFDM symbol for detection of the head path position;
A program for causing a computer to perform a process including a determination step of determining whether the frame is a unicast subframe or an MBSFN subframe from the correlation value in the OFDM symbol determined in advance.

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