Receiving apparatus, frequency deviation calculating method, and medium storing computer program therein

A receiving apparatus includes a memory that stores parameters corresponding to lines based on a first time interval and a second time interval in a coordinate space in which first phase rotation in a reception signal is defined as a first axis and second phase rotation in a reception signal is defined as a second axis; a selecting device that selects a line that is closest to a coordinate point in the solution space, the coordinate point being represented by a first observation value of the first phase rotation and a second observation value of the second phase rotation; an acquiring device that acquires the parameters corresponding to the line from the memory; and an estimating device that estimates, based on the parameters, the first observation value, and the first time interval or the parameters, the second observation value, and the second time interval, frequency deviations of the reception signals.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2012-097180 filed on Apr. 20, 2012, the entire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein are related to a receiving apparatus, a frequency deviation calculating method, and a medium storing a computer program therein.

BACKGROUND

In the case where no shield exists between a mobile station travelling at high speed and a base station, the propagation environment of radio waves is a so-called Rician fading environment. In this case, it is known that the influence of the Doppler Effect on a reception signal appears as a frequency deviation, which greatly affects the communication quality (see, for example, 3GPP (Third Generation Partnership Project) Contribution, R4-060149, “Discussion on AFC problem under high speed train environment”, NTT DoCoMo, USA, Feb. 13-17, 2006). As a method for estimating the frequency of a reception signal, a method for estimating the phase rotation at reception intervals by calculating the correlation between reference signals received at different reception times is known (see, for example, P. Moose, “A Technique for Orthogonal Frequency Division Multiplexing Frequency Offset Correction”, IEEE Trans. Commun., vol. 42, no. 10, October. 1994).

Furthermore, a method is known in which in the case where a plurality of temporally separate reference signals are arranged in an information transmission unit received from a mobile station, a base station calculates a phase change on the basis of the plurality of reference signals and calculates a frequency deviation on the basis of the phase change (see, for example, Japanese Laid-open Patent Publication No. 2009-065581). Furthermore, a method for estimating a frequency deviation on the basis of the phase deviation and time interval between a known symbol inserted in a common control channel and a synchronization code is available (see, for example, Japanese Laid-open Patent Publication No. 2007-515109).

Furthermore, a method for calculating a first phase difference on the basis of a phase variation component between a plurality of pilot symbols arranged within one slot, calculating a second phase difference on the basis of a phase variation component between pilot symbol groups in two slots, and detecting a frequency deviation using the first phase difference and the second phase difference is available (see, for example, Japanese Laid-open Patent Publication No. 2004-153585). Furthermore, a method for calculating, for individual channels, estimate values of differences between the frequency of a receiving signal and its own operating frequency on the basis of pilot symbols of a plurality of channels and controlling the operating frequency on the basis of the calculated estimated values is available (see, for example, Japanese Laid-open Patent Publication No. 2001-086031).

A mobile station being traveling receives from a base station a downlink signal including Doppler frequency added thereto as a frequency deviation, and determines the carrier frequency of an uplink signal to the base station on the basis of the carrier frequency of the reception signal. Meanwhile, the base station receives from the mobile station being travelling an uplink signal including Doppler frequency added thereto as a frequency deviation. Thus, the uplink signal received by the base station may have a frequency deviation twice the Doppler frequency.

SUMMARY

In the case where the mobile station travels at high speed, since a large frequency deviation occurs due to the influence of the Doppler Effect, base station equipment estimates a frequency deviation over a wide frequency range. In a known method for estimating a frequency deviation, a special reference signal as well as a normal reference signal is used. The base station equipment estimates a frequency deviation over a wide frequency range on the basis of the normal reference signal and the special reference signal. Thus, the amount of calculation increases, and the throughput is deteriorated.

According to an aspect of the embodiments, a receiving apparatus includes a memory that stores parameters corresponding to equally-spaced parallel lines forming a solution space derived based on a first time interval and a second time interval in a coordinate space in which first phase rotation at the first time interval of a first reference signal included in a reception signal of a first channel is defined as a first axis and second phase rotation at the second time interval of a second reference signal included in a reception signal of a second channel is defined as a second axis; a selecting device that selects a line that is closest to a coordinate point in the solution space, the coordinate point being represented by a first observation value of the first phase rotation and a second observation value of the second phase rotation; an acquiring device that acquires the parameters corresponding to the line selected by the selecting device from the memory; and an estimating device that estimates, based on the parameters acquired by the acquiring device, the first observation value, and the first time interval or the parameters acquired by the acquiring device, the second observation value, and the second time interval, frequency deviations of the reception signals.

DESCRIPTION OF EMBODIMENTS

Hereinafter, receiving apparatuses, frequency deviation calculating methods, and media storing computer programs therein according to preferred embodiments will be illustrated in detail with reference to the attached drawings. In the explanations of the embodiments described below, similar component parts will be referred to with the same reference numerals and signs and redundant explanations will be omitted.

FIG. 1illustrates an example of a frequency deviation estimation functional block in a receiving apparatus according to a first embodiment. As illustrated inFIG. 1, a receiving apparatus1includes a selecting device2, an acquiring device3, and an estimating device4, in the frequency deviation estimation functional block. The receiving apparatus1also includes a memory5.

Regarding a reception signal received by the receiving apparatus1, a reception signal of a first channel includes a first reference signal, and a reception signal of a second channel includes a second reference signal. In an ideal environment without noise, the phase rotation of the first reference signal at a first time interval T0is defined as a first phase rotation θ0. Similarly, in an ideal environment without noise, the phase rotation of the second reference signal at a second time interval T1is defined as a second phase rotation θ1.

The reception signal of the first channel and the reception signal of the second channel are signals transmitted from the same wireless communication apparatus, with which the receiving apparatus1communicates. Thus, the frequency deviation of the first reference signal and the frequency deviation of the second reference signal in unit time are the same. When Δf represents the frequency deviation of each of the first reference signal and the second reference signal in unit time, the first phase rotation θ0and the second phase rotation θ1in an ideal environment without noise are expressed by equations (1) and (2), respectively. In addition, when Δf is removed from equation (1) and (2), equation (3) is derived.

In equation (3), “T0” and “T1” represent the time interval of first reference signals and the time interval of second reference signals, respectively, and are constants determined in advance for individual channels. Thus, θ0 and θ1 have a first-order relationship. Here, since θ0 and θ1 represent phases, θ0 and θ1 are represented by equation (4) and equation (5), respectively, using any integers k0 and k1.
θ0=θ0+2πk0(−π≦θ0≦π)  (4)
θ1=θ1+2πk1(−π≦θ1≦π)  (5)
When equation (4) and equation (5) are substituted into equation (3), equation (6) is obtained. As is clear from equation (6), in an area −π≦θ0, θ1<π in a coordinate space in which θ0represents a horizontal axis and θ1represents a vertical axis, the relationship between θ0and θ1is expressed by a plurality of equally-spaced parallel straight lines. The number of straight lines and the space between the straight lines appearing in the coordinate space are determined on the basis of T0and T1.

That is, a plurality of equally-spaced parallel straight lines expressed by equation (6) represent a solution space that satisfies possible combinations of θ0 and θ1. The solution of a combination of θ0 and θ1 exists at a point in the plurality of straight lines in the solution space.

FIG. 2illustrates an example of the solution space of combinations of θ0and θ1in the first embodiment. In the example illustrated inFIG. 2, the number of straight lines in the solution space is not particularly limited. However, for example, eleven straight lines exist in the solution space. For example, the number “l” of the straight line that intersects the θ0axis at the origin of the coordinate axes may be defined as “0”. The numbers “l” of the straight lines that intersect the θ0axis at points closer to a π side than the origin may be defined as increasing numbers, such as 1, 2, 3, etc. in order of proximity to the origin. The numbers “l” of the straight lines that intersect the θ0axis at points closer to a −π side than the origin may be defined as decreasing numbers, such as −1, −2, −3, etc. in order of proximity of the origin.

FIG. 3illustrates an example of correspondence of the number “l” of a straight line to the parameters k0and k1in the first embodiment. In a table11illustrated inFIG. 3, the values of the parameters k0and k1corresponding to the value of “l” are set in advance by a designer of the receiving apparatus1, for example.

In the receiving apparatus1illustrated inFIG. 1, the memory5stores parameters corresponding to individual straight lines in a solution space. The memory5may store, for example, the table11illustrated inFIG. 3as parameters corresponding to individual straight lines in a solution space.

In the case where a reception signal is affected by noise, the phase rotation at the first time interval T0of the first reference signal, which is actually observed by the receiving apparatus1, is shifted from the first phase rotation θ0in an ideal environment without noise. The observation value of the phase rotation at the first time interval T0of the first reference signal is defined as a first observation value φ0. The range of the first observation value φ0is represented by “−π≦φ0<π”.

In the case where a reception signal is affected by noise, the phase rotation at the second time interval T1of the second reference signal, which is actually observed by the receiving apparatus1, is shifted from the second phase rotation θ1in an ideal environment without noise. The observation value of the phase rotation at the second time interval T1of the second reference signal is defined as a second observation value φ1. The range of the second observation value φ1is represented by “−π≦φ1<π”.

Here, integers S0and S1that satisfy the relationship “S0:S1=T0:T1” and that are relatively prime are defined. The values of S0and S1are uniquely defined according to the values of T0and T1. Hereinafter, in the explanation regarding straight lines, S0and S1are used instead of T0and T1.

With the use of S0and S1, equation (6) is expressed by equation (7). Even when equation (6) is replaced using S0and S1instead of T0and T1, straight lines totally the same as those in the case where T0and T1are used are expressed. Here, the number N (l) of straight lines forming a solution space is expressed by equation (8) utilizing a ceiling function. See Wikipedia (URL http://en.wikipedia.org/wiki/Floor_and_ceiling_functions) for the floor and ceiling functions.

FIG. 4is a diagram for illustrating processing for selecting a straight line in the first embodiment. InFIG. 4, mark “x” represents a coordinate point represented by the first observation value φ0 of the phase rotation at the first time interval T0 of the first reference signal and the second observation value φ1 of the phase rotation at the second time interval T1 of the second reference signal, which are actually observed by the receiving apparatus1. The distance d (φ0, φ1) between the coordinate point (φ, φ1) marked with “x” and a straight line passing through the origin in the solution space, that is, a straight line whose straight line number “l” is “0” is expressed by equation (9).

The space D between straight lines in a solution space is expressed by equation (10). The straight line that is the closest to the coordinate point (φ0, φ1) may be selected by dividing the distance d (φ0, φ1) between the coordinate point (φ0, φ1) and the straight line whose straight line number “l” is “0” by the space D between the straight lines. Thus, the number “l” of the straight line that is the closest to the coordinate point (φ0, φ1) is obtained by equation (11) utilizing floor functions.

In the receiving apparatus1illustrated inFIG. 1, the selecting device2selects the straight line that is the closest to the coordinate point represented by the first observation value φ0 and the second observation value φ1 in the solution space. The selecting device2may obtain the number “l” of the straight line that is the closest to the coordinate point (φ0, φ1) by calculation using, for example, equation (12) utilizing a floor function as processing for selecting a straight line. Then, the selecting device2may output, for example, the number “l” of the straight line, as information of the selected straight line, to the acquiring device3of the receiving apparatus1illustrated inFIG. 1.

In the receiving apparatus1illustrated inFIG. 1, the acquiring device3acquires from the memory5parameters corresponding to a straight line selected by the selecting device2. The acquiring device3may receive, for example, the number “l” of a straight line from the selecting device2, and acquire parameters k0(l) and k1(l) corresponding to the straight line of the number “l” by referring to, for example, the table11illustrated inFIG. 3.

In the case where a sufficient signal-to-noise ratio (SNR) is ensured, the influence of noise may be regarded as being small. In such a case, the phase rotation at the first time interval T0of the first reference signal, that is, the first phase rotation θ0may be calculated by using the first observation value φ0without correcting the influence of noise. In this case, θ0is expressed by equation (13) using a parameter k0(l)corresponding to a straight line having the number “l”.
θ0=φ0+2πk0(l)(13)

Similarly, the phase rotation at the second time interval T1 of the second reference signal, that is, the second phase rotation θ1 may be calculated by using the second observation value θ1 without correcting the influence of noise. In this case, θ1 is expressed by equation (14) using a parameter k1(l) corresponding to a straight line having the number “l”.
θ1=φ1+2πk1(l)(14)

The frequency deviation Δf0 of the first reference signal is expressed by equation (15). The frequency deviation Δf1 of the second reference signal is expressed by equation (16).

In the receiving apparatus1illustrated inFIG. 1, the estimating device4estimates the frequency deviation Δf0of a reception signal of the first channel on the basis of the parameter k0(l)acquired by the acquiring device3, the first observation value φ0, and the first time interval T0. Furthermore, the estimating device4estimates the frequency deviation Δf1of a reception signal of the second channel on the basis of the parameter k1(l)acquired by the acquiring device3, the second observation value φ1, and the second time interval T1. The estimating device4may estimate the frequency deviations Δf0and Δf1by calculation, for example, using equation (15) and (16), as processing for estimating the frequency deviation of a reception signal.

The selecting device2, the acquiring device3, and the estimating device4in the receiving apparatus1may be implemented when a processor executes a computer program implementing a frequency deviation calculating method, which will be described later. Alternatively, the selecting device2and the estimating device4may be implemented by hardware such as a circuit that performs arithmetic operation.

FIG. 5illustrates an example of a frequency deviation calculating method according to the first embodiment. As illustrated inFIG. 5, when frequency deviation calculating processing starts in the receiving apparatus1, the selecting device2selects the straight line that is the closest to the coordinate point represented by the first observation value φ0at the first phase rotation θ0and the second observation value φ1at the second phase rotation θ1(operation1). Then, the acquiring device3acquires from the memory5the parameters k0(l)and k1(l)corresponding to the straight line selected by the selecting device2(operation2).

Then, the estimating device4estimates the frequency deviation Δf0of a reception signal of the first channel on the basis of the parameter k0(l)acquired by the acquiring device3, the first observation value φ0, and the first time interval T0. Furthermore, the estimating device4estimates the frequency deviation Δf1of a reception signal of the second channel on the basis of the parameter k1(l)acquired by the acquiring device3, the second observation value φ1, and the second time interval T1(operation3). Then, a series of frequency deviation calculating processing operations are terminated.

According to the first embodiment, the straight line that is the closest to the coordinate point represented by the observation values φ0and φ1of the phase rotation of two reference signals of different signal intervals is selected, and parameters k0(l)and k1(l)corresponding to the straight line are selected. Thus, over a wide range between −π and π, approximate phase rotations θ0and θ1at the time intervals T0and T1of individual reference signals are obtained. Then, on the basis of the approximate phase rotations θ0and θ1of the individual reference signals and the time intervals T0and T1, the frequency deviations Δf0and Δf1of the individual reference signals are estimated. Thus, deterioration in the throughput in estimation of the frequency deviation of a reception signal is avoided.

In a second embodiment, orthogonal projection is performed with respect to the straight line that is the closest to a coordinate point represented by observation values φ0and φ1of two reference signals from the coordinate point in the first embodiment. Explanation of portions overlapping the first embodiment will be omitted.

Processing to selection of the straight line that is the closest to the coordinate point (φ0, φ1) is performed similarly to the first embodiment. The number “l” of the straight line that is the closest to the coordinate point (φ0, φ1) is expressed by equation (11). The straight line having the number “l” is expressed by equation (17) using the parameters k0(l)and k1(l).
S1φ0−S0φ1+2π(S1k0(l)−S0k1(l))=0  (17)

As described above, the coordinate point determined on the basis of the first observation value φ0and the second observation value φ1is shifted from the true first phase rotation θ0and the true second phase rotation θ1, for example, due to the influence of noise. It is considered that the point determined on the basis of the true first phase rotation θ0and the true second phase rotation θ1exists on the straight line having the number “l” that is the closest to the coordinate point (φ0, φ1) and is the point (represented by a black triangle mark inFIG. 4) that is the closest to the coordinate point (φ0, φ1).

The point on the straight line having the number “l” that allows the distance between the coordinate point (φ0, φ1) and the straight line having the number “l” to be minimum is obtained by performing orthogonal projection with respect to the straight line having the number “l” from the coordinate point (φ0, φ1). By orthogonal projection, the true first phase rotation θ0is expressed by equation (18). The true second phase rotation θ1is expressed by equation (19). Finally, the frequency deviation Δf of a reception signal is expressed by equation (20).

In the second embodiment, in the receiving apparatus1illustrated inFIG. 1, by performing orthogonal projection with respect to a straight line selected by the selecting device2from the coordinate point (φ0, φ1) of observation values, the true first phase rotation θ0or the true second phase rotation θ1is estimated. Then, the frequency deviation Δf of a reception signal is estimated on the basis of the parameters k0(l)and k1(l)acquired by the acquiring device3, the first and second observation values φ0and φ1, S0and S1, and the first time interval T0or the second time interval T1.

The estimating device4may estimate the true first phase rotation θ0or the true second phase rotation θ1by calculation, for example, using equation (18) or (19) as processing for estimating the frequency deviation of a reception signal. Then, the estimating device4may estimate the frequency deviation Δf by calculating, for example, the middle term or the rightmost term of equation (20) using the estimated true first phase rotation θ0or the true second phase rotation θ1.

According to the second embodiment, the straight line that is the closest to the coordinate point represented by observation values φ0and φ1of the phase rotation of two reference signals of different signal intervals is selected, and parameters k0(l)and k1(l)corresponding to the selected straight line are selected. By orthogonal projection with respect to the straight line from the coordinate point (φ0, φ1), the true first phase rotation θ0or the true second phase rotation θ1at the time intervals T0and T1of individual reference signals may be estimated over a wide range between −π and π. Then, the frequency deviation Δf of a reception signal may be estimated on the basis of one of the estimate values θ0and θ1of the true phase rotation of the reference signals and the time interval T0or T1. Thus, deterioration in the throughput in estimation of the frequency deviation of a reception signal is avoided.

In a third embodiment, the receiving apparatus according to the second embodiment is applied to, for example, base station equipment in a long term evolution (LTE) system. An example in which a first channel is defined as a physical up link control channel (PUCCH), which is an uplink control signal, and a second channel is defined as a physical uplink shared channel (PUSCH), which is an uplink data signal, will be illustrated. Explanation of portions overlapping the first embodiment or the second embodiment will be omitted.

The time interval of a PUCCH reference signal is 285.417 microseconds. Thus, a possible estimate frequency deviation ranges between about −1751 Hz and about 1751 Hz. The time interval of a PUSCH reference signal is 500 microseconds. Thus, a possible estimate frequency deviation ranges between about −1000 Hz and about 1000 Hz.

FIG. 6schematically illustrates the sub-frame format of each of a PUSCH and a PUCCH. InFIG. 6, pilot symbols with hatching represent reference signals. In LTE, individual channels are allocated for 1 millisecond. A time unit of 1 millisecond represents a sub-frame. Sub-frames each include fourteen orthogonal frequency division multiplexing (OFDM) symbols divided into a slot 0 and a slot 1. In a PUSCH sub-frame21, pilot symbols are allocated to a symbol “3” and a symbol “10”. In a PUCCH sub-frame22, pilot symbols are allocated to a symbol “1”, a symbol “5”, a symbol “8”, and a symbol “12”.

The time interval TPUCCHof a PUCCH reference signal is 285.417 microseconds, and the time interval TPUSCHof a PUSCH reference signal is 500 microseconds. Thus, integers SPUCCHand SPUSCHthat satisfy the relationship “SPUCCH:SPUSCH=TPUCCH:TPUSCH” and that are relatively prime are 137 and 240, respectively.

Here, although not particularly limited, calculation is made easier, for example, by approximating SPUCCHto 4 and approximating SPUSCHto 7. Even with such approximations, the ratio of SPUCCHto SPUSCHis “ 4/7=0.5708”, which is nearly the same as “ 137/240=0.5714”. Thus, such approximations do not have a great effect on calculation of frequency deviation. It is obvious that approximation may not be performed.

FIG. 7illustrates an example of a solution space representing combinations of θPUCCHand θPUSCHin the third embodiment. In the example illustrated inFIG. 7, as is clear from equation (8), eleven straight lines exist in the solution space.

When numbers “l” are allocated to the individual straight lines as in the second embodiment, the straight line whose number “l” is “0” corresponds to a frequency deviation ranging between −1000 Hz and 1000 Hz. The straight lines whose numbers “l” are “1” and “−1” correspond to a frequency deviation ranging between 3000 Hz and 5000 Hz and a frequency deviation ranging between −5000 Hz and −3000 Hz”, respectively. The straight lines whose numbers “l” are “2” and “−2” correspond to a frequency deviation ranging between −7000 Hz and −5250 Hz and a frequency deviation ranging between 5250 Hz and 7000 Hz, respectively. The straight lines whose numbers “l” are “3” and “−3” correspond to a frequency deviation ranging between −3000 Hz and −1750 Hz and a frequency deviation ranging between 1750 Hz and 3000 Hz, respectively. The straight lines whose numbers “l” are “4” and “−4” correspond to a frequency deviation ranging between 1000 Hz and 1750 Hz and a frequency deviation ranging between −1750 Hz and −1000 Hz, respectively. The straight lines whose numbers “l” are “5” and “−5” correspond to a frequency deviation ranging between 5000 Hz and 5250 Hz and a frequency deviation ranging between −5250 Hz and −5000 Hz, respectively.

FIG. 8illustrates an example of the correspondence of the number “l” of a straight line to parameters kPUCCHand kPUSCHin the third embodiment. In a table26illustrated inFIG. 8, the values of the parameters kPUCCHand kPUSCHcorresponding to the values of “l” are set, for example, by a designer of a receiving apparatus.

FIG. 9illustrates an example of the hardware configuration of base station equipment including the receiving apparatus according to the third embodiment. As illustrated inFIG. 9, base station equipment31may include, for example, a duplexer32, a radio frequency (RF) transmitting device33, a baseband transmitting device34, an upper-level line termination device35, an RF receiving device36, and a baseband receiving device37.

The duplexer32is connected to an antenna38. The duplexer32allows a transmission path of a transmission signal to be electrically isolated from a transmission path of a reception signal in the base station equipment31. The RF receiving device36is connected to the duplexer32. The RF receiving device36removes carrier waves from an uplink reception signal received via the duplexer32from the antenna38, performs analog-to-digital conversion processing, and generates a reception signal from which the carrier waves have been removed.

The baseband receiving device37is connected to the RF receiving device36. The baseband receiving device37performs demodulation processing and decoding processing for an uplink baseband signal output from the RF receiving device36to recover a reception signal. In recovery of a reception signal, the baseband receiving device37performs processing for calculating a frequency deviation, which will be described later. The upper-level line termination device35is connected to the baseband receiving device37. The upper-level line termination device35transmits an output signal of the baseband receiving device37to an upper-level network.

The upper-level line termination device35receives a signal from the upper-level network. The baseband transmitting device34is connected to the upper-level line termination device35. The baseband transmitting device34performs encoding processing and baseband modulation processing for an output signal of the upper-level line termination device35to generate a downlink baseband signal.

The RF transmitting device33is connected to the baseband transmitting device34and the duplexer32. The RF transmitting device33performs digital-to-analog conversion processing and carrier wave modulation processing for an output signal of the baseband transmitting device34to generate a downlink modulation signal. The downlink modulation signal is output from the RF transmitting device33, and is emitted via the duplexer32from the antenna38. Individual antennas may be provided on the transmission side and the receiving side. In this case, the duplexer32may not be provided.

FIG. 10illustrates an example of the hardware configuration of the baseband receiving device37illustrated inFIG. 9. As illustrated inFIG. 10, the baseband receiving device37may include, for example, a processor41, a memory42, and an interface43. The processor41, the memory42, and the interface43may be connected to a bus44, for example.

The processor41may be, for example, a central processing unit (CPU) or a digital signal processor (DSP). Alternatively, the processor41may be, for example, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like. The memory42may store, for example, a computer program implementing a frequency deviation calculating method, which will be described later. The memory42also may store the table26illustrated inFIG. 8, while serving as a memory of the receiving apparatus1illustrated inFIG. 1. The processor41may implement the frequency deviation calculating method, which will be described later, by reading the computer program from the memory42and executing the read computer program. The interface43may be connected to the upper-level line termination device35or the RF receiving device36, for example.

FIG. 11illustrates an example of the functional configuration of a receiving circuit of the receiving apparatus according to the third embodiment.FIG. 11mainly illustrates functions relating to the explanation provided below. A receiving circuit50may include component parts other than the component parts illustrated inFIG. 11. Signal processing performed by the receiving circuit50may be performed when the processor41of the baseband receiving device37executes the computer program stored in the memory42.

The receiving circuit50includes a fast Fourier transform (FFT) device51, signal separating devices52and54, a PUCCH receiving device53, a PUSCH receiving device55, and a wide-range deviation estimating device56. The FFT device51converts an uplink baseband signal received from the RF receiving device36into a frequency range signal by fast Fourier transform. The FFT device51separates a frequency range signal for individual channels. The FFT device51inputs a PUCCH signal to the signal separating device52, and inputs a PUSCH signal to the signal separating device54.

The signal separating device52separates PUCCH signals for individual users. The signal separating device52also separates a signal of a user into data and a reference signal. The signal separating device52outputs separated signals to the PUCCH receiving device53. Similarly, the signal separating device54separates PUSCH signals for individual users. The signal separating device54also separates a signal of a user into data and a reference signal. The signal separating device54outputs separated signals to the PUSCH receiving device55. The signal processing by the signal separating device52and the signal separating device54may be performed in the same circuit by time-sharing processing. The signal processing by the PUCCH receiving device53and the PUSCH receiving device55may also be performed in the same circuit by time-sharing processing.

The PUCCH receiving device53includes a deviation estimating unit60, a compensating unit61, a channel estimating unit62, a detecting unit63, and a decoding unit64. The deviation estimating unit60estimates the phase deviation of a PUCCH reference signal at the time interval TPUCCHon the basis of the time correlation value of the PUCCH reference signal received at the time interval TPUCCH. The deviation estimating unit60outputs to the wide-range deviation estimating device56the estimated phase difference as the observation value φPUCCHof the phase difference of the PUCCH reference signal at the time interval TPUCCH.

The compensating unit61compensates for the frequency deviation of PUCCH data in accordance with the estimation result of the frequency deviation of the reception signal estimated by the wide-range deviation estimating device56by the frequency deviation calculating method, which will be described later. The channel estimating unit62performs channel estimation on the basis of the PUCCH reference signal. The detecting unit63performs channel equalization of the PUCCH data in accordance with the estimation result of the channel estimated by the channel estimating unit62, and performs demodulation processing for the data. The decoding unit64decodes the demodulated data and outputs the reception result of the PUCCH.

The PUSCH receiving device55includes a deviation estimating unit65, a compensating unit66, a channel estimating unit67, a detecting unit68, and a decoding unit69. The deviation estimating unit65estimates the phase deviation of a PUSCH reference signal at the time interval TPUSCHon the basis of the time correlation value of the PUSCH reference signal received at the time interval TPUSCH. The deviation estimating unit65outputs to the wide-range deviation estimating device56the estimated phase difference as the observation value φPUSCHof the phase difference of the PUSCH reference signal at the time interval TPUSCH.

The compensating unit66compensates for the frequency deviation of PUSCH data in accordance with the estimation result of the frequency deviation of the reception signal estimated by the wide-range deviation estimating device56by the frequency deviation calculating method, which will be described later. The channel estimating unit67performs channel estimation on the basis of the PUSCH reference signal. The detecting unit68performs channel equalization of the PUSCH data in accordance with the estimation result of the channel estimated by the channel estimating unit67, and performs demodulation processing for the data. The decoding unit69decodes the demodulated data and outputs the reception result of the PUSCH.

The wide-range deviation estimating device56performs processing for calculating a frequency deviation by the frequency deviation calculating method, which will be described later, on the basis of the observation values φPUCCHand φPUSCHof the phase differences at the reception intervals TPUCCHand TPUSCHof PUCCH and PUSCH reference signals estimated by the deviation estimating unit60and the deviation estimating unit65. The wide-range deviation estimating device56may include the selecting device2, the acquiring device3, and the estimating device4in the frequency deviation estimation functional block illustrated inFIG. 1, for example.

FIG. 12illustrates an example of the deviation estimating units60and65in the receiving apparatus according to the third embodiment. As illustrated inFIG. 12, the deviation estimating unit60includes a multiplying part71, a time averaging part72, and an angle converting part73. The multiplying part71performs complex multiplication for two PUCCH reference signals (the first half of the reference signal and the second half of the reference signal) received at the time interval TPUCCHto obtain time correlation value of the individual reference signals.

The time averaging part72averages the time correlation values obtained by the multiplying part71for a specific period of time to obtain the time correlation average value. The angle converting part73converts the time correlation value averaged by the time averaging part72into the average value of phase deviation. The estimate value (observation value φPUCCH) of the phase difference of the PUCCH reference signal at the reception interval TPUCCHobtained as described above is supplied to the wide-range deviation estimating device56.

The deviation estimating unit65has a configuration similar to the deviation estimating unit60illustrated inFIG. 12. For the deviation estimating unit65, “PUCCH”, “TPUCCH”, and “φPUCCH” in the explanation of the deviation estimating unit60provided above are replaced with “PUSCH”, “TPUSCH”, and “φPUSCH”, respectively.

FIG. 13illustrates an example of a frequency deviation calculating method according to the third embodiment. As illustrated inFIG. 13, when frequency deviation calculating processing starts in the receiving circuit50, the deviation estimating unit60calculates the estimate value (observation value φPUCCH) of the phase difference of a PUCCH reference signal at the reception interval TPUCCH. The deviation estimating unit65also calculates the estimate value (observation value φPUSCH) of the phase difference of a PUSCH reference signal at the reception interval TPUCCH.

The wide-range deviation estimating device56performs calculation using equation (21) (operation11). Accordingly, the number “l” of the straight line that is the closest to the coordinate point represented by the observation values φPUCCHand φPUSCHof the phase differences of the PUCCH and PUSCH reference signals is obtained. Equation (21) utilizing a floor function, is obtained by substituting 4 for S0and substituting 7 for S1in equation (11).

Then, the wide-range deviation estimating device56acquires parameters kPUCCHand kPUSCHcorresponding to the straight line having the number “l” obtained in operation11, for example, from the table26illustrated inFIG. 8(operation12). Then, the wide-range deviation estimating device56performs calculation using equation (22) (operation13). Accordingly, the true phase rotation θPUCCHof the PUCCH reference signal at the reception interval TPUCCHis obtained. Equation (22) is obtained by substituting 4 for S0and substituting 7 for S1in equation (18)

By calculation using equation obtained by substituting 4 and 7 for S0and S1, respectively, in equation (19), the true phase rotation θPUSCHof the PUSCH reference signal at the reception interval TPUSCHmay be obtained. Furthermore, θPUSCHmay be obtained by calculation using equation (23).

Then, the wide-range deviation estimating device56performs calculation using equation (24) (operation14). Accordingly, the frequency deviation Δf of a reception signal is obtained. Equation (24) is obtained by substituting 285.417×10−6for T0in equation (20). The frequency deviation Δf may be obtained by calculation using an equation obtained by substituting 500×10−6for T1in equation (20). The frequency deviation Δf is obtained as described above, and a series of processing operations is terminated.

In the third embodiment, in the explanation provided above, a possible frequency range for estimation of the frequency deviation Δf is between −7000 Hz and 7000 Hz, for example. The possible frequency range for estimation of the frequency deviation Δf may be restricted. For example, an example in which the possible frequency range for estimation of the frequency deviation Δf is restricted to a range between −3000 Hz and 3000 Hz will be illustrated.

FIG. 14illustrates another example of a solution space representing combinations of θPUCCHand θPUSCHin the third embodiment. In the example illustrated inFIG. 14, for selection of the straight line that is the closest to the coordinate point (φPUCCH, φPUSCH), a straight line whose number is “1” or “−1”, a straight line whose number is “2” or “−2”, and a straight line whose number is “5” or “−5”, which are expressed by broken lines, are not to be selected. That is, the straight line that is the closest to the coordinate point (φPUCCH, φPUSCH) is selected from five straight lines, that is, a straight line whose number is “0”, straight lines whose numbers are “3” and “−3”, and straight lines whose numbers are “4” and “−4”.

Furthermore, normally, the ratio of users whose frequency deviation is large is smaller than the ratio of users whose frequency deviation is small. Thus, the solution space illustrated inFIG. 14may be divided into regions A, B, C, D, and E using alternate long and short dashed lines, and a straight line may be selected in accordance with a region where the coordinate point (φPUCCH, φPUSCH) exists.

For example, a region on the side of the straight line whose number “l” is “−5” than the middle between the straight line whose number “l” is “−4” and the straight line whose number “l” is “−3” may be defined as the region A. In the case where the coordinate point (φPUCCH, φPUSCH) exists in the region A, the wide-range deviation estimating device56may select the straight line whose number “l” is “−4” as the straight line that is the closest to the coordinate point (φPUCCH, φPUSCH).

For example, a region from the middle between the straight line whose number “l” is “−4” and the straight line whose number “l” is “−3” to the middle between the straight line whose number “l” is “−3” and the straight line whose number “l” is “−2” may be defined as the region B. In the case where the coordinate point (φPUCCH, φPUSCH) exists in the region B, the wide-range deviation estimating device56may select the straight line whose number “l” is “−3” as the straight line that is the closest to the coordinate point (φPUCCH, φPUSCH).

Furthermore, for example, a region from the middle between the straight line whose number “l” is “−3” and the straight line whose number “l” is “−2” to the middle between the straight line whose number “l” is “2” and the straight line whose number “l” is “3” may be defined as the region C. In the case where the coordinate point (φPUCCH, φPUSCH) exists in the region C, the wide-range deviation estimating device56may select the straight line whose number “l” is “0” as the straight line that is the closest to the coordinate point (φPUCCH, φPUSCH).

Furthermore, for example, a region from the middle between the straight line whose number “l” is “2” and the straight line whose number “l” is “3” to the middle between the straight line whose number “l” is “3” and the straight line whose number “l” is “4” may be defined as the region D. In the case where the coordinate point (φPUCCH, φPUSCH) exists in the region D, the wide-range deviation estimating device56may select the straight line whose number “l” is “3” as the straight line that is the closest to the coordinate point (φPUCCH, φPUSCH).

Furthermore, for example, a region on a side of the straight line whose number “l” is “5” than the middle between the straight line whose number “l” is “3” and the straight line whose number “l” is “4” may be defined as the region E. In the case where the coordinate point (φPUCCH, φPUSCH) exists in the region E, the wide-range deviation estimating device56may select the straight line whose number “l” is “4” as the straight line that is the closest to the coordinate point (φPUCCH, φPUSCH).

FIG. 15illustrates another example of the correspondence of the number “l” of a straight line to parameters kPUCCHand kPUSCHin the third embodiment. A table27illustrated inFIG. 15represents combinations of the parameters kPUCCHand kPUSCHrealizing the solution space illustrated inFIG. 14.

As illustrated inFIG. 15, for example, in the case where the number “l” is “−5”, the parameters kPUCCHand kPUSCHare 0 and −1, respectively, which are the same as the case where the number “l” is “−4”. Thus, even in the case where the straight line whose number “l” is “−5” is the closest to the coordinate point (φPUCCH, φPUSCH), the straight line whose number “l is “−4” is selected.

Furthermore, in the case where the number “l” is “−2”, “−1”, “1”, and “2”, the parameters kPUCCHand kPUSCHare 0, which is the same as the case where the number “l” is “0”. Thus, even in the case where the straight line whose number “l” is “−2”, “−1”, “1”, or “2” is the closest to the coordinate point (φPUCCH, φPUSCH), the straight line whose number “l” is 0 is selected. The same applies to the case where the number “l” is “5”.

As in the example of the solution space illustrated inFIG. 14, by narrowing the estimate range of frequency deviation, noise-resistant estimation is achieved.

In a fourth embodiment, the receiving apparatus according to the first embodiment is applied to, for example, base station equipment in an LTE system. For example, a case where a first channel is defined as PUCCH, which is an uplink control signal, and a second channel is defined as a PUSCH, which is an uplink data signal, will be illustrated. In this case, that is, in the fourth embodiment, orthogonal projection with respect to the straight line that is the closest to the coordinate point (φ0, φ1) is not performed from the coordinate point (φ0, φ1) in the third embodiment. Explanations overlapping the first embodiment or the third embodiment will be omitted.

FIG. 16illustrates an example of a frequency deviation calculating method according to the fourth embodiment. As illustrated inFIG. 16, processing to calculation using equation (21) (operation21) and acquisition of parameters kPUCCHand kPUSCH(operation22) is performed similarly to operation11and operation12in the flowchart illustrated inFIG. 13.

Then, the wide-range deviation estimating device56performs calculation using equation (25) and equation (26) (operation23). Accordingly, the phase rotation θPUCCHof a PUCCH reference signal at the reception interval TPUCCHand the phase rotation θPUSCHof a PUSCH reference signal at the reception interval TPUSCHare obtained.
θPUCCH=φPUCCH+2πkPUCCH(25)
θPUSCH=φPUSCH+2πkPUSCH(26)

Then, the wide-range deviation estimating device56performs calculation using equation (27) and equation (28) (operation24). Accordingly, the frequency deviation ΔfPUCCHof the PUCCH reception signal and the frequency deviation ΔfPUSCHof the PUSCH reception signal are obtained. Equation (27) is obtained by substituting 285.417×10−6for T0in equation (15). Equation (28) is obtained by substituting 500×10−6for T1in equation (16). The frequency deviations ΔfPUCCHand ΔfPUSCHare obtained as described above, and a series of processing operations is terminated.

In the third embodiment, by performing orthogonal projection for the straight line that is the closest to the coordinate point (φ0, φ1) from the coordinate point (φ0, φ1), θPUCCHand θPUSCHare derived from the same phase rotation speed. Thus, the frequency deviation ΔfPUCCHis equal to the frequency deviation ΔfPUSCH. In contrast, in the fourth embodiment, since orthogonal projection is not performed, θPUCCHand θPUSCHdo not be derived from the same phase rotation speed due to the influence of noise. Thus, the phase deviation ΔfPUCCHdo not be equal to the phase deviation ΔfPUSCH.

According to the fourth embodiment, since orthogonal projection is not performed, frequency deviation may be calculated with a reduced calculation amount. Thus, the deterioration in the throughput in estimation of the frequency deviation of a reception signal is avoided.

The embodiments described above may be applied to a receiving apparatus that receives a plurality of channels having different time intervals of reference signals for a single user as well as a receiving apparatus in an LTE system. Furthermore, in the deviation estimating units60and65, the phase rotation of reception signals of individual channels may be estimated using, for example, cyclic prefix (also called “guard interval”) used in an OFDM system or an orthogonal frequency division multiple access (OFDMA) system and other known signals, instead of using reference signals.