JPWO2007040210A1 - Multi-carrier receiver - Google Patents

Abstract

Signals transmitted from a plurality of transmission devices and transmitted through a propagation path are received by the antenna unit 120, and the frequency is converted to a frequency band where A / D conversion is possible in the wireless reception unit 121. The signal converted into the digital signal by the A / D conversion unit 122 is OFDM symbol-synchronized by the synchronization unit 123, and the guard interval is removed by the GI removal unit 124. Thereafter, the signal is separated into signals for each subcarrier in the FFT unit 126 via the S / P conversion unit 125. Pilot extraction section 127 separates the pilot signal and the information signal, and the pilot signal is sent to code multiplication / phase rotation section 10 and the information signal is sent to propagation path compensation section 132. The pilot signal sent to the code multiplication / phase rotation unit 10 is subjected to multiplication with each code and phase rotation different for each code in the code multiplication / phase rotation unit 10. The code multiplication / phase rotation unit is provided with the same number of code multiplication units as the signals to be simultaneously separated, and here, multiplication of the received pilot signal and the complex conjugate of each code is performed separately. At this time, information for specifying a code to be multiplied is sent from the control unit 13 as control information. Thus, after multiplying the received pilot signal by the complex conjugate of the plurality of codes notified from the control unit, the code multiplication / phase rotation unit 10 performs phase rotation on the pilot signal after the complex conjugate multiplication of the code. .

Description

  In a cellular system that performs wireless communication using a multicarrier transmission scheme typified by OFDM (Orthogonal Frequency Division Multiplexing), each base station performs a search for a cell (base station) that is an initial cell search or a handoff candidate. The present invention relates to a receiving apparatus that calculates power of a signal coming from a station and propagation path fluctuation at high speed.

  In recent years, the number of users seeking high speed in a wireless communication system has increased. As one of the wireless communication systems that can realize high speed and large capacity, a multicarrier transmission system represented by OFDM attracts attention.

  The OFDM system is a system in which tens to thousands of carriers are arranged at a minimum frequency interval where theoretically no interference occurs and information signals are transmitted in parallel by frequency division multiplexing. This OFDM scheme has the advantage that if the number of subcarriers used is increased, the symbol time becomes longer than that of a single carrier scheme of the same transmission rate, so that it is less susceptible to multipath interference.

As a system in which this OFDM technology is applied to a one-cell repetitive cellular system excellent in frequency utilization efficiency, there is a one-cell repetitive OFDM / (TDMA, FDMA) (OFDM / Time Division Multiple Access, Frequency Division Multiple Access) system. This is a system in which communication is performed using the same frequency in all cells of the cellular system, OFDM is used as a modulation method for communication, and TDMA and FDMA are used as access methods.

  As described above, in a system using the same frequency in all cells, detection of a connected base station (cell search) and detection of a base station that is a handoff candidate are performed using signals simultaneously received from a plurality of base stations. In such a situation, there is a possibility that optimal detection cannot be performed.

  Even in a situation where signals transmitted from a plurality of base stations arrive at the same time, a pilot signal shown in Patent Document 1 below is used as a method for separating each received signal and calculating power and propagation path fluctuation of each received signal. There is a technique. Here, the transmission / reception method of the pilot signal in Document 1 will be described with reference to FIGS.

  FIG. 6 is a diagram illustrating a configuration of a base station side transmitter in Patent Document 1. In FIG. In FIG. 6, reference numeral 100 denotes a pilot signal generator, reference numerals 101 and 104 denote mapping parts, reference numeral 102 denotes an error correction code part, reference numeral 103 denotes a serial / parallel (S / P) converter, reference numeral 105 denotes a multiplex part, Reference numeral 106 denotes an IFFT unit, reference numeral 107 denotes a parallel / serial (P / S) conversion unit, reference numeral 108 denotes a guard interval (GI) insertion unit, reference numeral 109 denotes a digital / analog (D / A) conversion unit, and reference numeral 110 denotes wireless transmission. Reference numeral 111 denotes an antenna unit. However, in FIG. 6, the number of subcarriers used is N.

  In pilot signal generation section 100 in FIG. 6, the transmitter-specific code ρ is multiplied to each subcarrier having the same amplitude and the same phase. As this code ρ, for example, a random code such as a PN sequence is used. The signal of each subcarrier multiplied by the code is mapped in mapping section 101, and the pilot signal generated in this way is multiplexed with the information signal in multiplex section 105. This information signal is a signal that is encoded by the error correction encoding unit 102 and then mapped by the mapping unit 104 via the S / P conversion unit 103. The pilot signal and the information signal multiplexed in the multiplex unit 105 are IFFT processed in the IFFT unit 106 and converted into a time domain signal. Then, the P / S conversion unit 107 performs parallel / serial conversion, the GI insertion unit 108 adds a guard interval, the D / A conversion unit 109 converts the signal into an analog signal, and the wireless transmission unit 110 can perform wireless transmission. Frequency conversion to the frequency band is performed. Thereafter, the transmission signal is transmitted from the antenna unit 111.

  FIG. 7 is a diagram showing a terminal-side receiver configuration in Patent Document 1. In FIG. Reference numeral 120 in FIG. 7 denotes an antenna unit, reference numeral 121 denotes a wireless reception unit, reference numeral 122 denotes an analog / digital (A / D) conversion unit, reference numeral 123 denotes an OFDM symbol synchronization unit, reference numeral 124 denotes a guard interval removal unit, reference numeral 125. Is an S / P conversion unit, 126 is an FFT unit, 127 is a pilot extraction unit, 128 is a code multiplication unit, 129 is an IFFT unit, 130 is a time window unit, 131 is an FFT unit, and 132 is a propagation A path compensation unit, reference numeral 133 is an error correction decoding unit.

  A signal transmitted from the transmitter illustrated in FIG. 6 and transmitted through the propagation path is received by the antenna unit 120 in FIG. 7, and the frequency is converted to a frequency band that can be A / D converted by the wireless reception unit 121. The signal converted into the digital signal by the A / D conversion unit 122 is OFDM symbol-synchronized by the synchronization unit 123, and the guard interval is removed by the GI removal unit 124. Thereafter, the signal is separated into signals for each subcarrier in the FFT unit 126 via the S / P conversion unit 125. Pilot extraction section 127 separates the pilot signal and information signal, and the pilot signal is sent to code multiplication section 128 and the information signal is sent to propagation path compensation section 132.

  The pilot signal sent to the code multiplier 128 is multiplied by the complex conjugate of the code ρ (value obtained by normalizing the complex conjugate with the square of the absolute value) used on the transmission side. By this processing, the frequency response of the received pilot signal is obtained. This frequency response is sent to IFFT section 129, where IFFT section 129 converts it into time-domain propagation path fluctuation (impulse response). Then, after unnecessary noise components and the like are removed in the time window section 130, the FFT section 131 converts the frequency response again. The output of the FFT unit 131 is a channel estimation value in the frequency domain that is necessary to compensate for the channel variation of the information signal. However, since the noise component is removed in the time window unit 130, the output is highly accurate. A propagation path estimate is obtained. The propagation path compensation unit 132 performs propagation path compensation of the information signal using the propagation path estimation value obtained in this way, and the error correction decoding unit 133 decodes the information signal to reproduce the information data.

  When calculating the power and propagation path fluctuation of a plurality of signals received at the same time using the transceivers shown in FIGS. 6 and 7, it is necessary to use different codes for each base station. . This is because the impulse response of the received signal is obtained when the same code is used on the transmitting side and the receiving side, but when the code different from the transmitting side is used on the receiving side, the impulse response is not obtained, This is to use the property of spreading like noise in the time domain.

  This is shown in FIG. However, here, when signals arriving from three base stations A to C (respectively codes ρa, ρb, and ρc are used) are received, one code in the code multiplier 128 of the receiving terminal. An example of a signal (impulse response) output when the complex conjugate of (ρa) is multiplied and input to the IFFT unit 129 is shown. First, when the code ρa transmitted from the base station A is also multiplied by the complex conjugate of ρa in the code multiplier of the receiving terminal, as shown in FIG. An impulse response is calculated. In contrast, as shown in FIGS. 8B and 8C, the codes ρb and ρc transmitted from the base stations B and C are multiplied by the complex conjugate of ρa in the code multiplier of the receiving apparatus. In this case, an impulse response is not obtained, and a noise-like waveform is obtained.

That is, when the same code as the transmitted code is used in the code multiplier of the receiving device, the impulse response of the propagation path through which the transmitted code has passed can be obtained, but the code different from the transmitted code Is used in the code multiplier of the receiving apparatus, only a noise-like waveform can be obtained. Therefore, even when a plurality of codes are mixed in the received signal, only the desired impulse response can be calculated by multiplying the complex conjugate of the code whose impulse response is to be calculated by the code multiplier.
Japanese Patent Laid-Open No. 5-75568 (invention relating to a device for coherently demodulating digital data multiplexed in the time-frequency domain with evaluation of frequency response of channel and determination of limit)

  However, in the configuration shown in Patent Document 1, when signals arriving from a plurality of base stations are separated and each received power and propagation path fluctuation are calculated, the reception operation is performed by the number of signals (base stations) to be separated. There is a problem that must be repeated. Therefore, when signals arriving from many base stations are received at the terminal, there is a problem that it takes a long time to detect an optimal connection destination (handoff destination) base station.

  An object of the present invention is to shorten the time for detecting a connection destination base station on the terminal side.

  According to one aspect of the present invention, in a multicarrier transmission system, a time-frequency conversion unit that converts a received time domain signal into a frequency domain signal and a subcarrier of the received signal converted into the frequency domain are different. A plurality of code multipliers that multiply the codes separately, a plurality of phase rotation units that give different phase rotations to subcarriers multiplied by different codes, and receptions that are subjected to different code multiplications and phase rotations, respectively. There is provided a receiving device comprising: an adding unit that adds signals; and a frequency-time converting unit that converts a signal into a time domain signal after adding the received signals.

  In the receiving apparatus, the impulse response of each signal can be shifted in time and separated by multiplying the received signal by the code used on the transmission side and applying different phase rotations. Therefore, the impulse responses of a plurality of received signals can be calculated collectively.

  It is preferable to have a power calculator that calculates received signal power of each signal from impulse responses of a plurality of received signals obtained by the frequency-time converter. A cell search can be performed based on the calculated power.

  The different phase rotation amounts given in the plurality of phase rotation units are equal to each other in the phase rotation amount difference between the processing points of the time-frequency conversion unit in the frequency domain, and all of the time-frequency conversion units. It is preferable to set the rotation to be an integral multiple of 2π at the processing point. It is preferable to set the phase rotation amount given in the plurality of phase rotation units to a value corresponding to the maximum delay time of the signal. The maximum delay time of the signal corresponds to the maximum delay time assumed in the system design. Further, the phase rotation amount given by the plurality of phase rotation units is rotated by 2π × guard interval length ÷ effective symbol length × different integer value for each phase rotation unit at all processing points of the time-frequency conversion unit. It is also possible to set to.

  By using the OFDM receiver of the present invention, it is possible to simultaneously and accurately obtain an impulse response of a propagation path through which each signal passes from a received signal in which signals transmitted from a plurality of transmitters are mixed. . In addition, when performing cell search or handoff to detect base stations to be connected by receiving signals transmitted from a plurality of base stations, it is possible to detect base stations to be connected at high speed and accurately. There is.

It is a functional block diagram which shows the example of 1 structure of the receiver by embodiment of this invention. It is a figure which shows the detailed structural example of a code multiplication and a phase rotation part. It is a figure which shows the example of the impulse response obtained when receiving the signal which (rho) a, (rho) b, and (rho) c each transmitted from three different transmission apparatuses mixed. It is a figure which shows the example of a frame structure made into object. FIG. 5 is a diagram illustrating a transmission-side apparatus configuration example when transmitting the pilot signal illustrated in FIG. 4. 10 is a diagram showing a configuration of a base station side transmitter in Patent Document 1. FIG. It is a figure which shows the terminal side receiver structure in patent document 1. FIG. FIG. 8A is a diagram showing the impulse response of the propagation path through which ρa passes. FIGS. 8B and 8C are received with respect to the codes ρb and ρc transmitted from the base stations B and C. It is a figure which shows the waveform in the case of multiplying the complex conjugate of (rho) a in the code | symbol multiplication part of an apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Code multiplication / phase rotation part, 11 ... Addition part, 12 ... Power calculation part, 13 ... Control part, 14 ... Phase rotation compensation part, 120 ... Antenna part, 121 ... Radio | wireless reception part, 122 ... A / D conversion part , 123 ... Synchronizer, 124 ... GI remover, 125 ... S / P converter, 126 ... FFT part, 127 ... Pilot extractor, 129 ... IFFT part, 130 ... Time window part, 131 ... FFT part, 132 ... Propagation Path compensation unit, 133... Error correction decoding unit.

  Hereinafter, an OFDM reception technique according to an embodiment of the present invention will be described with reference to the drawings.

[Example 1]
The receiving technique according to the first embodiment of the present invention transmits a different code for each transmitting apparatus (base station), and simultaneously receives these signals on the receiving (terminal) side, from each transmitting apparatus (each base station). The present invention relates to a receiving (terminal) device that can separate impulse responses of propagation paths through which transmitted signals pass and can calculate them simultaneously.

  The transmission-side apparatus in the present embodiment can be realized by the same configuration as that shown in FIG. However, in the pilot signal generation unit 100, the code multiplied by the input signal differs for each transmission apparatus. This means that, for example, a code of ρa is used in a certain transmission (base station) apparatus, and different codes such as ρb and ρc are used in other transmission (base station) apparatuses having the same configuration. By using such a configuration, a unique pilot signal can be transmitted for each transmission (base station) device.

  When a plurality of transmission devices having the same configuration as the transmission device shown in FIG. 6 transmit different codes at the same time, the reception side receives a signal in which signals (codes) transmitted from the plurality of transmission devices are mixed. It becomes. FIG. 1 shows a configuration example of a receiving apparatus that can simultaneously calculate an impulse response of a propagation path through a code unique to each transmitting apparatus from such a received signal. However, here, a configuration is shown in which the impulse response of the propagation path through three different codes can be calculated simultaneously.

  In FIG. 1, the same functional blocks as those in FIG. As shown in FIG. 1, the receiving apparatus according to the present embodiment is newly provided with a code multiplication / phase rotation unit 10 and an addition unit 11, a power calculation unit 12, a control unit 13, and a phase rotation compensation unit 14 at the subsequent stage. Can be realized.

  Signals transmitted from a plurality of transmission apparatuses having the same configuration as the transmission apparatus and transmitted through the propagation path are received by the antenna unit 120 in FIG. 1 and are transmitted to a frequency band that can be A / D converted by the wireless reception unit 121. Is converted. The signal converted into the digital signal by the A / D conversion unit 122 is OFDM symbol-synchronized by the synchronization unit 123, and the guard interval is removed by the GI removal unit 124. Thereafter, the signal is separated into signals for each subcarrier in the FFT unit 126 via the S / P conversion unit 125. Pilot extraction section 127 separates the pilot signal and the information signal, and the pilot signal is sent to code multiplication / phase rotation section 10 and the information signal is sent to propagation path compensation section 132.

  The pilot signal sent to the code multiplication / phase rotation unit 10 is subjected to multiplication with each code and phase rotation different for each code in the code multiplication / phase rotation unit 10.

  A detailed configuration of the code multiplication / phase rotation unit 10 is shown in FIG. As shown in FIG. 2, the code multiplication / phase rotation unit 10 in the receiving apparatus according to the present embodiment is provided with the same number (three in this case) of code multiplication units as the signals to be simultaneously separated. Multiplication of the pilot signal and the complex conjugate of each code is performed separately. At this time, it is assumed that information for specifying a code to be multiplied is sent from the control unit 13 as control information. After multiplying the received pilot signal by the complex conjugate of the three codes notified from the control unit in this way, the code multiplication / phase rotation unit 10 performs phase rotation on the pilot signal after the complex conjugate multiplication of the code. .

In this phase rotation unit, for example, by multiplying the k (k = 1, 2,... N) th subcarrier by e ^{−j2πMk / N} (M is an integer), continuous phase rotation is performed on each subcarrier. Giving. Thus, by giving a phase rotation that is continuous between the samples of the IFFT part (processing points or subcarriers of the IFFT part) and becomes 2πM for all the samples of the IFFT part (all processing points of the IFFT part) The signal after IFFT in the IFFT unit 129 can be shifted in time by M samples.

  However, here, the signal after multiplication by the complex conjugate of the code ρb is multiplied by the phase rotation value obtained by continuously increasing the rotation amount by Δθk for each subcarrier (processing point of the IFFT unit), and the code The signal multiplied by the complex conjugate of ρc is multiplied by a phase rotation value obtained by continuously increasing the rotation amount by Δθl for each subcarrier (processing point of the IFFT unit). Here, the values satisfy Δθk = 2πk / N and Δθl = 2πl / N, and k and l are integers of 1 or more, respectively, and k ≠ l. By giving such phase rotation to each signal after code multiplication, it is possible to give different time shifts to the impulse response obtained after IFFT in IFFT section 129, and the impulse response of the propagation path through which each code passes. Can be calculated simultaneously.

  As shown in FIG. 2, this phase rotation may be performed on the number 3 of the code multipliers 3-1 = 2, that is, at least two signals after code multiplication (that is, the complex of the code ρa). The impulse response of the signal multiplied by the conjugate may have no time shift). At this time, the amount of phase rotation to be given to each signal, if the maximum delay time of each received signal is known in advance (when the maximum delay time assumed in the system design is known, etc.) A value corresponding to the propagation path condition is indicated by a control signal from the control unit 13. Each time shift amount is equal to an integral multiple of the guard interval length (for example, guard interval length × 1 in the system multiplied by ρb and guard interval × 2 in the system multiplied by ρc). By fixing the phase rotation amount, in a normal OFDM reception environment where the delayed wave does not exceed the guard interval, it is possible to prevent a plurality of impulse responses from being separated due to overlapping in time. However, in cell search and handoff candidate search, it is only necessary to detect a certain amount of received power of signals coming from several base stations, and the accuracy with respect to detection of an impulse response is not necessarily high. Therefore, when processing such as cell search is performed, the amount of time shift given to each received signal is shortened (a plurality of impulse responses may be slightly overlapped), and propagation path estimation processing for demodulation of the desired signal is performed. When performing, the time shift amount may be set to be an integral multiple of the guard interval length so that the impulse responses do not overlap. Here, in order to set the time shift amount to be an integral multiple of the guard interval length, the amount of phase rotation given to each sample is 2π × guard interval length ÷ effective symbol length × an integer value different for each phase rotation unit, Should be set. By setting to such a value, in the time domain, it is possible to shift the time by the number of samples corresponding to the guard interval length × a different integer value for each phase rotation unit, so that the impulse responses do not overlap. be able to. In this way, the time shift amount (phase rotation amount) is not a fixed value, and may be set to a different value depending on the difference in reception mode (cell search, handoff candidate search, normal packet reception, etc.).

  Next, the output of the code multiplying / phase rotating unit 10 is input to the adding unit 11, and the frequency domain pilot signal multiplied by the complex conjugate of each code is added and then sent to the IFFT 129, where the IFFT unit 129 It is converted into propagation path fluctuation (impulse response) in the region. As described above, since the code multiplication / phase rotation unit 10 gives different time shift amounts (phase rotation amounts in the frequency domain) for each code, the addition unit 11 also adds a plurality of signals. After the IFFT, it is possible to calculate the impulse response of the propagation path through which three codes pass without interfering with each other. With respect to the impulse responses of a plurality of received signals calculated simultaneously in this way, each received signal power and the like are calculated by performing processing such as summing the power of each path for each signal in the power calculation unit 12. It is possible.

  At this time, the range of the paths to be summed for each signal can be determined based on the phase rotation amount respectively given by the code multiplication / phase rotation unit 10. The power of each received signal obtained in this way can be used as a base station selection criterion during cell search or handoff.

  From a plurality of impulse responses calculated in this way, a desired base station (a base station selected as a connection destination by a cell search or a connected base station that performs data communication even during a search for a handoff candidate) In the case of performing propagation path compensation of an information signal by calculating propagation path fluctuations, first, in the time window unit 130, only the impulse response of a necessary code is extracted from the impulse responses calculated from the reception signals of the three codes, and the FFT is performed. The unit 131 converts the signal in the time domain into a signal in the frequency domain. At this time, in order to extract only the desired impulse response, it is necessary to set a time window so that only the desired impulse response can be obtained from the signal in which the impulse responses of the three received signals are arranged side by side. The timing and width of the window are instructed from the control unit 13. Further, since the phase rotation is given to the output of the FFT unit 131 by the code multiplication / phase rotation unit 10, the phase rotation compensation unit 14 compensates the phase rotation. However, the phase rotation given to each subcarrier in the phase rotation compensation unit 14 is the phase rotation given to the impulse response extracted in the time window unit 130 from the three impulse responses output from the FFT unit 131. It is assumed that Δθk is an amount to compensate. This phase rotation compensation can also be performed by time-shifting a signal in the time domain before processing in the FFT unit 131.

  In this way, the propagation path compensation unit uses the propagation path estimation value obtained by applying the time window in accordance with the timing of the desired impulse response, performing FFT of only the desired impulse response, and performing phase rotation compensation. Information signal propagation path compensation is performed at 132, and the error correction decoding unit 133 decodes the information signal to reproduce information data.

  Here, with reference to FIG. 3, an example of an impulse response obtained when receiving a signal in which ρa, ρb, and ρc mixed from three different transmission apparatuses are received will be described. However, for convenience of explanation, FIG. 3A shows an impulse response when IFFT processing is performed on a signal obtained by multiplying a complex conjugate of ρa, and FIG. 3B shows a phase of a signal obtained by multiplying a complex conjugate of ρb. FIG. 3C shows the impulse response when IFFT processing is performed after rotation, and FIG. 3C shows the impulse response when IFFT processing is performed after phase rotation is performed on the signal obtained by multiplying the complex conjugate of ρc. FIG. 3D shows an impulse response (sum of FIGS. 3A, 3B, and 3C) obtained when a signal in which ρa, ρb, and ρc are mixed is received by the receiving apparatus of FIG. . First, FIG. 3A is a diagram showing a state where only the impulse response of the propagation path through ρa is calculated by multiplying the reception signal mixed with ρa, ρb, and ρc by the complex conjugate of ρa. Similarly, also in FIGS. 3B and 3C, by multiplying the reception signal in which ρa, ρb, and ρc are mixed by the complex conjugate of ρb or ρc, the impulse of the propagation path through ρb or ρc is obtained. Only the response is calculated, but the phase rotation of Δθk is given to the multiplication result of the complex conjugate of ρb by the phase rotation unit, so the calculated impulse response is shifted by k samples (dotted impulse response In FIG. 3C, the impulse response is shifted by 1 sample (shifted from the dotted impulse response to the solid impulse response).

  Thus, by applying continuous phase rotation to each received subcarrier, the impulse response after IFFT can be shifted by a certain number of samples. By using such a property, the receiving apparatus shown in FIG. 1 can give different time shift amounts to the impulse response of the propagation path through which each code passes by giving a different phase rotation amount for each code. Therefore, as shown in FIG. 3D, a plurality of impulse responses can be separated and calculated simultaneously. Further, when calculating a plurality of impulse responses in parallel, a plurality of IFFT units (IFFT unit 129) after code multiplication are usually required, but by using the configuration of the receiving apparatus according to the present embodiment, Even in the case of obtaining a plurality of impulse responses, only one IFFT unit needs to be provided, and an increase in circuit scale can be suppressed.

  As described above, by using the receiving apparatus according to the present embodiment, it is possible to simultaneously and accurately measure the impulse response of the propagation path through which each signal passes from the received signal in which signals transmitted from a plurality of transmitting apparatuses are mixed. In the case of cell search or handoff to detect base stations to be connected by receiving signals transmitted from multiple base stations, the base stations to be connected to can be detected quickly and accurately. can do.

  In the above embodiment, a receiving device that can collectively calculate impulse responses of signals simultaneously transmitted from three different transmitting devices has been described. However, when receiving a normal packet that does not perform cell search or handoff. Need only be able to calculate the impulse responses of the signals transmitted from the connected base stations, and it is not necessary to collectively calculate the impulse responses of the signals transmitted from the plurality of base stations.

  Therefore, in the receiving apparatus shown in FIGS. 1 and 2, only when the cell search or handoff is performed (when the entire receiving apparatus is turned on, or when the received power or error rate has deteriorated), It is assumed that all the multipliers are operated and only one system of code multiplication and phase rotation is operated when receiving a normal packet. At this time, multiplication of the remaining two systems and activation / deactivation of the phase rotation unit are instructed from the control unit 13.

  By doing so, since the other two systems of code multiplication and phase rotation units do not operate during normal packet reception, a reduction in power consumption can be expected. At this time, of course, the code multiplier to be operated multiplies the complex conjugate of the code used in the connected base station and the received pilot signal.

  Further, since the system of the code multiplication / phase rotation unit 10 that is operated when performing normal packet reception is always set to the uppermost system in FIG. 2, the phase rotation calculation is omitted. Compared with the case where only the stage or the third stage system is operated, there is an advantage that it is possible to further increase the calculation speed and reduce the power consumption.

[Example 2]
In Embodiment 2 of the present invention, a code multiplied by a pilot signal transmitted from one transmission apparatus (base station) is circulated in the frequency direction for each transmission timing of several pilot signals in a frame. Next, the configuration of a receiving (terminal) device that can detect at high speed which timing signal in a frame the received signal is described.

  First, an example of a frame configuration targeted in this embodiment will be described with reference to FIG. As shown in FIG. 4, a frame configuration example is shown in two-dimensional coordinates with two axes of frequency and time. In FIG. 4, the minimum square represents one subcarrier in one OFDM symbol, white represents a pilot signal, and gray represents a data signal. Also, the numbers in parentheses attached to the squares representing the pilot signals represent the chip number of the symbol ρ, and as shown in FIG. 4, in this embodiment, the symbols used for the pilot signals in the frame are the respective transmission timings. Every time, 8 chips are circulated in the frequency direction.

  FIG. 5 shows an example of the device configuration on the transmission side when transmitting such a pilot signal. In FIG. 5, blocks having the same functions as those in FIG. 6 and 5 differs in whether or not it includes a code storage / shift register unit 20 that cyclically circulates the code multiplied by each subcarrier in the pilot signal generation unit 100. In the transmission apparatus shown in FIG. 6, each subcarrier is always multiplied by the same chip with the same code. However, in the transmission apparatus according to the second embodiment shown in FIG. Thus, each subcarrier is multiplied by a different chip for each pilot signal transmission timing.

  Reception (terminal) capable of receiving a signal transmitted from a transmission apparatus as shown in FIG. 5 and detecting at what timing the received signal is a signal in the frame using the received pilot signal The apparatus can be realized by the same configuration as that shown in FIGS. However, the code multiplied by each subcarrier of the received pilot signal in the code multiplication / phase rotation unit 10 in FIG. 2 is a code used for each transmission timing of the pilot signal in the transmission apparatus (one code as shown in FIG. 4). ). In such a configuration, the impulse response of the propagation path through which the received signal has passed is obtained only from the system multiplied by the code that completely matches the code multiplied by the pilot signal, and is multiplied by the pilot signal. An impulse response cannot be obtained from a system multiplied by a code (a code shifted in the frequency direction) that has been circulated several chips from the code.

  Thus, if the order of the cyclic codes used for each pilot signal in the frame on the transmission side (how many cyclic codes are multiplied at which pilot signal transmission timing) is determined in advance, the received signal is received by the receiver. It is possible to detect the timing of the signal in the frame. With such an operation, when a terminal device not connected to the control station device performs frame synchronization, timing detection such as detecting the head of the frame can be performed at high speed.

  The present invention is applicable to an OFDM receiver.

Claims (20)

A multicarrier receiver that receives one or more multicarrier signals multiplied by different codes,
A time-frequency converter that converts the received signal into a frequency domain signal;
A plurality of code multipliers for separately multiplying the different signals by the received signal transformed into the frequency domain;
A plurality of phase rotation units that separately give different phase rotations to each signal after code multiplication by the plurality of code multiplication units;
An adder for adding signals subjected to separate code multiplication and phase rotation;
A frequency-time conversion unit that converts a signal resulting from the addition by the addition unit into a time-domain signal;
A multi-carrier receiving apparatus that collectively calculates impulse responses of propagation paths through which received multi-carrier signals respectively pass. A multicarrier receiver that receives multicarrier signals multiplied by different codes at different timings,
A time-frequency converter that converts the received signal into a frequency domain signal;
A plurality of code multipliers for separately multiplying the different signals by the received signal transformed into the frequency domain;
A plurality of phase rotation units that separately give different phase rotations to each signal after code multiplication by the plurality of code multiplication units;
An adder for adding signals subjected to separate code multiplication and phase rotation;
A frequency-time conversion unit that converts a signal resulting from the addition by the addition unit into a time-domain signal;
A multicarrier receiving apparatus for detecting a timing at which a signal is received from an output of the frequency-time conversion unit. The different code is a code periodically circulated in the frequency direction,
The multicarrier receiver according to claim 2, wherein a periodic position of a received signal is detected from an output of the frequency-time conversion unit. When N (N is an integer of 2 or more) code multiplying units are provided,
4. The code multiplied by the received signal in each of the code multipliers is N codes (M is an integer equal to or greater than N) selected from M candidates. The multicarrier receiver according to any one of the above. When N (N is an integer of 2 or more) code multiplying units are provided,
4. The multicarrier receiver according to claim 1, wherein only N−1 of the plurality of phase rotation units are included. 5. The amount of phase rotation given in each of the plurality of phase rotation units,
The difference in the amount of phase rotation between the processing points in the frequency-time conversion unit is constant,
The multicarrier receiver according to any one of claims 1 to 5, wherein rotation is set to an integral multiple of 2π at all processing points of the frequency-time converter. The amount of phase rotation given in each of the plurality of phase rotation units,
The multicarrier receiving apparatus according to claim 6, wherein the multicarrier receiving apparatus is set to a value corresponding to a maximum signal delay time. The amount of phase rotation given in each of the plurality of phase rotation units,
The multicarrier receiving apparatus according to claim 6, wherein 2π × guard interval length ÷ effective symbol length × set to rotate by a different integer value for each phase rotation unit. The amount of phase rotation given in each of the plurality of phase rotation units,
The multicarrier receiver according to claim 6, wherein the multicarrier receiver is set according to a reception mode. The amount of phase rotation given in each of the plurality of phase rotation units,
When performing cell search or handoff destination search, set a small value,
The multicarrier receiving apparatus according to claim 9, wherein when a propagation path estimation of a received signal is performed, a large value is set. From the impulse response of one or more propagation paths obtained by the frequency-time converter,
The multicarrier receiver according to any one of claims 1 to 10, further comprising a power calculator that calculates received signal power of each signal. From the impulse response of one or more propagation paths obtained by the frequency-time conversion means,
A time filtering unit that extracts only the impulse response of the propagation path through which the received signal to be demodulated passes,
A time-frequency conversion unit that converts a signal obtained by the time filtering unit into a frequency domain signal;
The phase rotation compensation unit that compensates for the phase rotation amount given in the phase rotation unit to the received signal to be demodulated, according to any one of claims 1 to 11. Multicarrier receiver. The timing of the time filter in the time filtering unit used to extract the impulse response of the propagation path through which the received signal to be demodulated passes,
The multicarrier receiver according to claim 12, wherein the multicarrier receiver is calculated from a phase rotation amount given by the phase rotation unit. Among the N code multiplying units and K (K = N or K = N−1) number of the phase rotating units,
Only L code multipliers and L ′ (L and L ′ are integers and N> L, K> L ′) phase rotation units are operated. 6. The multicarrier receiving apparatus according to any one of the above. The number (L, L ′) of the code multiplier and phase rotator to be operated is
The multicarrier receiving apparatus according to claim 14, wherein the multicarrier receiving apparatus changes according to a propagation path condition through which the received signal passes. The number (L, L ′) of the code multiplier and the phase rotator to be operated is
L = 1 and L ′ = 1 or L = 1 and L ′ = when a received signal power equal to or higher than a predetermined threshold is obtained or when an error rate equal to or lower than a predetermined threshold is obtained. The multicarrier receiving apparatus according to claim 15, wherein the multicarrier receiving apparatus is set to 0. A plurality of multicarrier transmitters for transmitting multicarrier signals each multiplied by a different code;
A multicarrier transmission system comprising: the multicarrier reception apparatus according to claim 1. A multicarrier transmission device for transmitting a multicarrier signal multiplied by a code periodically circulated in the frequency direction;
A multicarrier transmission system comprising: the multicarrier reception apparatus according to claim 2. A reception method in a multicarrier receiver for receiving one or more multicarrier signals multiplied by different codes,
A time-frequency conversion step of converting the received signal into a frequency domain signal;
A plurality of code multiplication steps for separately multiplying the received signal transformed into the frequency domain by the different codes;
A plurality of phase rotation steps for separately giving different phase rotations to each signal after code multiplication by the plurality of code multipliers;
An addition step of adding signals each subjected to separate code multiplication and phase rotation;
A frequency-time conversion step of converting the signal of the addition result by the addition unit into a signal in the time domain,
A receiving method comprising: collectively calculating impulse responses of propagation paths through which received multicarrier signals have passed. A reception method in a multicarrier receiving apparatus for receiving a multicarrier signal multiplied by a code periodically circulated in the frequency direction,
A time-frequency conversion step of converting the received signal into a frequency domain signal;
A plurality of code multiplication steps for separately multiplying several cyclic results of the code cyclically circulated in the frequency direction by the received signal transformed into the frequency domain;
A plurality of phase rotation steps for separately giving different phase rotations to each signal after code multiplication by the plurality of code multipliers;
An addition step of adding signals each subjected to separate code multiplication and phase rotation;
A frequency-time conversion step of converting the signal of the addition result by the addition unit into a signal in the time domain,
A reception method, comprising: detecting a periodic position of a reception signal from an output of the frequency-time conversion unit.

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