HK1179778A - Radio transmission apparatus, radio communication system and pilot signal transmission method - Google Patents

Description

Radio transmission device, radio communication system, and pilot signal transmission method

The application is a divisional application of an invention patent application with the name of 'a pilot signal transmission method and a wireless communication device', which is No. 200780015238.X, and the application date is 24.1.2007.

Technical Field

The present invention relates to a wireless communication system, and more particularly, to a pilot signal transmission method and a wireless communication apparatus for transmitting a pilot signal in an uplink.

Background

Recently, Beyond 3G (Beyond 3G) has been developed as a next-generation wireless network that can establish seamless and secure connections between a plurality of wireless communication systems including third-generation mobile communication (3G), wireless local area network, and fourth-generation mobile communication (4G). As an uplink transmission scheme for super 3G, use of a single carrier transmission scheme is considered (see, for example, document '3 GPP, "tr25.814v1.2.2" March 2006' (hereinafter referred to as document 1)).

Fig. 1 is a diagram showing a configuration of a transmitter based on a single carrier transmission scheme described in document 1.

The transmitter shown in fig. 1 includes a data transmitter 1101, a pilot transmitter 1102, and a multiplexing section 1103 for multiplexing these outputs.

Also, the data transmitter 1101 includes a DFT (discrete fourier transform) portion 1111, a subcarrier mapping portion 1112, an IFFT (inverse fast fourier transform) portion 1113, and a cyclic prefix adder 1114.

The data transmitter 1101 shown in FIG. 1 operates as follows:

first, from

[ mathematical formula 1]

N_{Tx_d}

Data composed of symbols is generated by applying the data at DFT portion 1111

[ mathematical formula 2]

N_{Tx_d}

The point DFT is converted into a frequency domain signal. Then, in a subcarrier mapping section 1112, the frequency domain signals are mapped onto subcarriers (by inserting '0' into unused subcarriers to form up to the number

[ mathematical formula 3]

N_{FFT_d}

Data of the sub-carriers) of (a).

Then, the data is applied by IFFT 1113

[ mathematical formula 4]

N_{FFT_d}

In the point IFFT, the frequency domain signal mapped on the subcarriers is converted into a time domain signal. Finally, at cyclic prefix adder 1114, a cyclic prefix is added to the data for transmission.

Fig. 2 is a diagram illustrating how a cyclic prefix is added in cyclic prefix adder 1114 shown in fig. 1.

The cyclic prefix addition by cyclic prefix adder 1114 shown in fig. 1 is for copying the back of the block to the front of the block as shown in fig. 2.

It should be noted that a cyclic prefix is inserted in order to effectively perform frequency domain equalization at the receiver side. Preferably, the cyclic prefix length is set not to exceed a maximum delay time of a delay path within the channel.

Next, a configuration of a typical receiver corresponding to the transmitter shown in fig. 1 will be explained.

Fig. 3 is a diagram showing a configuration of a typical receiver corresponding to the transmitter shown in fig. 1.

The receiver shown in fig. 3 comprises: a demultiplexing part 1301 for separating a signal transmitted from the transmitter shown in fig. 1 into a data signal and a pilot signal; a data receiver 1302; and a pilot receiver 1303.

Further, the data receiver 1302 includes: cyclic prefix remover 1311, FFT (fast fourier transform) section 1312, subcarrier demapping section 1313, frequency equalizer 1314, IDFT (inverse discrete fourier transform) section 1315, and data demodulator 1316.

The data receiver 1302 shown in FIG. 3 operates as follows:

first, at a cyclic prefix remover 1311, a cyclic prefix is removed from a received signal. Then, by applying in the FFT section 1312

[ math figure 5]

N_{FFT_d}

And the FFT of the point converts the data into a frequency signal. Then, in a subcarrier demapping section 1313, the signal is demapped into subcarriers used by each user. After demapping, the signal is frequency domain equalized at frequency equalizer 1314 based on a channel estimate obtained by channel estimator 1324 (described later) of pilot signal receiver 1303. Then, by applying within IDFT 1315

[ mathematical formula 6]

N_{Tx_d}

IDFT of a point, converts the signal into a time domain signal, and then demodulates the received data at a data demodulator 1316.

Next, the uplink pilot signal and user multiplexing method will be explained.

Recently, as a pilot signal sequence, a CAZAC (constant amplitude zero auto correlation) sequence attracts attention. For example, as one of the CAZAC sequences, a Zadoff-Chu sequence expressed by formula 1 can be considered (see, for example, the document 'B.M. Povic, "Generalized Chirp-Like Polyphos sequences with Optium Correlation Properties," IEEE Transactions on information Theory, Vol.38, No.4, pp1406-1409, July 1992').

[ math figure 7]

(formula 1)

n: 0, 1, L-1 k: serial number (k is an integer coprime with L)

The CAZAC sequence is a sequence having a constant amplitude in the time and frequency domains and generating an autocorrelation value of '0' except when the phase difference is '0'. Since the sequence is constant in amplitude in the time domain, it is possible to suppress PAPR (peak-to-average power ratio), and since the sequence is also constant in amplitude in the frequency domain, the sequence is suitable for channel estimation in the frequency domain. Also, because the sequence is suitable for the advantage of timing detection of the received signal because it has good autocorrelation characteristics, the sequence attracts attention as a pilot sequence suitable for single carrier transmission, which is an access scheme for the uplink of super 3G.

As a user multiplexing method when a CAZAC sequence is used as a Pilot signal sequence for Uplink, Code Division Multiplexing (CDM) has been proposed (see, for example, documents '3 GPP, R1-051062, Texas Instruments "On Uplink Pilot in EUTRA SC-OFDMA", oct.2005').

Within CDM of pilot signals, all users use CAZAC sequences of the same length to which a cyclic shift unique to each user is added. If the cyclic shift time is taken to be equal to or greater than the expected maximum delay, the pilot signals of all users in a multipath environment can be made orthogonal to each other. This is possible according to the autocorrelation value of the CAZAC sequence except for the property that it always becomes '0' when the phase difference is '0'.

A transmitter and a receiver of a pilot signal when the pilot signal undergoes CDM will be described with reference to fig. 1 and 3. Since the basic configuration and operation of the pilot transmitter 1102 are the same as those of the data transmitter 1101, points different from the data transmitter 1101 will be explained.

Initially, the number of points for the DFT portion 1121 and for the IFFT portion 1123 is

[ mathematical formula 8]

N_{Tx_p}，N_{FFT_p}

(in document 1, these are defined as

[ mathematical formula 9]

N_{Tx_p}＝N_{Tx_d}/2，N_{FFT_p}＝N_{FFT_d}/2)。

When user multiplexing of pilot signals is performed by CDM so that users are separated from each other at a receiver, the cyclic shift section 1124 performs cyclic shift unique to the users. The cyclic shift is a shift by which the pilot signal sequence is processed like a loop and the pilot signal sequence is re-input from the back end to the front end, as shown in fig. 2. The number of cyclic shifts for each user is preferably equal to or greater than the maximum delay or cyclic prefix length of the delay path. Finally, a cyclic prefix is added at cyclic prefix adder 1125, and the generated data signal and pilot signal are time-multiplexed by multiplexing section 1103 to be transmitted.

Next, the pilot receiver 1303 will be described.

At the pilot receiver 1303, the data signal and the pilot signal are separated from each other by a demultiplexing part 1301, and then the cyclic prefix is removed by a cyclic prefix remover 1321. Then, the pilot signal is performed by the FFT portion 1322

[ mathematical formula 10]

N_{FFT_p}

FFT of the points in order to be converted into pilot signals in the frequency domain. Then, subcarrier demapping is performed at the subcarrier demapping portion 1323, and thereafter, channel estimation is performed by the channel estimator 1324. The channel estimates for each user are output to a frequency equalizer 1314 of the data receiver 1302.

The cross-correlation properties are also important when CAZAC sequences are used within a cellular system. In view of interference suppression between cells, it is preferable that a group of sequences for which a small cross-correlation value is obtained be allocated as pilot signal sequences for neighboring cells. The cross-correlation properties of Zadoff-Chu sequences are strongly dependent on the individual sequences. For example, when the sequence length of the Zadoff-Chu sequence includes a prime number or a large prime number, it exhibits good cross-correlation characteristics (low cross-correlation value). On the other hand, when it is a composite number composed of only small prime numbers, the cross-correlation greatly deteriorates (the cross-correlation value contains a large value). Specifically, if the sequence length L of a Zadoff-Chu sequence is a prime number, the cross-correlation value between arbitrary Zadoff-Chu sequences is considered to be kept constant at

[ mathematical formula 11]

(1/L)^1/2

(see, for example, non-patent document 3).

Within super 3G, it is assumed that transmission bandwidths of the data signal and the control signal are different between users. Therefore, the pilot signal used for demodulation of the data signal and the control signal differs in transmission bandwidth for each user, and therefore, the pilot signal of the user differing in transmission bandwidth must be multiplexed.

Fig. 4 is a diagram showing one configuration example of a conventional mobile wireless system.

The mobile radio system shown in fig. 4 is constituted by a BS1001 as a base station and a CL1000 as a service area formed by the BS1001, and a plurality of mobile stations MS1002 to 1005 are provided in the system for communicating with the BS 1001.

Fig. 5 is a diagram showing one example of frequency blocks used by users in the mobile wireless system shown in fig. 4 and pilot signal sequences for the respective users.

As shown in fig. 5, when a data signal or a control signal is transmitted with a single carrier using a frequency block having continuous frequencies, a pilot signal is also transmitted with a signal carrier using the same frequency block as that of the data signal or the control signal.

In the case where CDM is used to multiplex pilot signals, when bandwidths of signals transmitted by MSs 1002-1005 are 3W, W, W and 2W (W is a predetermined bandwidth) in, for example, fig. 5, CAZAC sequences having sequence lengths of 3L, L, L and 2L corresponding to the respective bandwidths will be used as the pilot signal sequences.

In this case, there are the following problems: the pilot signals of the users performing pilot signals using different frequency blocks of consecutive frequencies will not become orthogonal. The reason is that the sequence length of the pilot signal differs between users using different frequency blocks.

Fig. 6 is a diagram showing another configuration example of a conventional mobile wireless system.

The mobile radio system shown in fig. 6 is constituted by BSs 1001 and 1301 as base stations and CL1000 and CL1300 as service areas formed by the BS1001 and the BS1301, and a plurality of mobile stations MS1002 to 1005 and MS1302 to 1305 are provided in the system for communicating with the BS1001 and the BS1301, respectively.

Fig. 7 is a diagram showing one example of frequency blocks used by users and pilot signal sequences used by the respective users in the CL1300 of the mobile wireless system shown in fig. 6. Here, the frequency blocks used by the users within the CL1000 and the pilot signal sequences used by the respective users are assumed to be the same as those shown in fig. 5.

Note that frequency blocks used in adjacent cells, for example, MS1003 or MS1004 and MS1303 have the same bandwidth, so that it is possible to suppress interference between cells using different CAZAC sequences. In contrast, for example, MS1002 and MS1302 or MS1002 and MS1304 use frequency blocks different in bandwidth, and therefore it is impossible to suppress interference between cells. In other words, when CAZAC sequences used as pilot signals are different in sequence length, there is a problem that interference between cells cannot be suppressed. The reason is that the cross-correlation characteristics between CAZAC sequences different in sequence length become poor.

Disclosure of Invention

In order to solve the problems described above, an object of the present invention is to provide a pilot signal transmission method and a wireless communication apparatus in a mobile wireless system, whereby when a CAZAC sequence is transmitted as a pilot signal and CDM is used as a user multiplexing method, pilot signals of users different in bandwidth can be made orthogonal within a cell, and inter-cell interference with respect to a pilot signal from another cell can be reduced.

In order to achieve the above object, the present invention provides a pilot signal transmission method for use in a wireless communication system for transmitting a pilot signal sequence by using code division multiplexing at least as one of user multiplexing schemes, the pilot signal sequence having at least a first attribute that an autocorrelation value when a phase difference is not 0 is less than or equal to a predetermined threshold with respect to an autocorrelation peak value when the phase difference is 0, or a second attribute that a cross-correlation value between sequences of equal sequence length is less than a cross-correlation value between sequences of different sequence length, the method comprising the steps of:

dividing a system frequency band, which is a frequency band available within the system, into a plurality of frequency blocks having a plurality of bandwidths;

generating pilot signals of the plurality of frequency blocks in a single carrier using the pilot signal sequence having a sequence length corresponding to the plurality of frequency blocks; and is

The generated pilot signals are transmitted as pilot signals corresponding to respective users in multiple carriers using an arbitrary number of frequency blocks among the plurality of frequency blocks.

The invention is also characterized by comprising the following steps:

dividing the same frequency band of all adjacent cells into a plurality of frequency blocks with various bandwidths; and is

Using different sequences within the pilot signal sequence having the sequence length corresponding to the bandwidth of the plurality of frequency blocks between different cells transmitting pilot signals over the frequency blocks.

The invention is also characterized by comprising the steps of: the system frequency band is divided into a plurality of frequency blocks having the same bandwidth.

The invention is also characterized in that a CAZAC sequence is used as the pilot signal sequence.

The invention is also characterized by comprising the steps of: transmitting a data signal or a control signal in a single carrier using the frequency block having consecutive frequencies.

Also, in a wireless communication system, a wireless transmission apparatus for transmitting a signal by transmitting a pilot signal sequence having at least a first attribute that an autocorrelation value when a phase difference is not 0 is less than or equal to a predetermined threshold with respect to an autocorrelation peak value when the phase difference is 0 or a second attribute that a cross-correlation value between sequences of equal sequence length is less than a cross-correlation value between sequences of different sequence length while using code division multiplexing at least as one of user multiplexing schemes, characterized in that: generating the pilot signal sequence having a sequence length corresponding to a plurality of frequency blocks having a plurality of bandwidths into which a system frequency band, which is a frequency band available within the system, is divided; generating a pilot signal using the generated pilot signal sequence with a single carrier; the generated pilot signals are transmitted in multiple carriers using an arbitrary number of frequency blocks among the plurality of frequency blocks as pilot signals corresponding to the respective users.

The invention is also characterized in that: generating the pilot signal sequences having the same sequence length.

The invention is also characterized in that: a CAZAC sequence is generated as the pilot signal sequence.

The invention is further characterized in that the data signal or the control signal is transmitted in a single carrier using said frequency block with consecutive frequencies.

In the present invention thus constructed, when pilot signal sequences having at least a first attribute that is an autocorrelation value when a phase difference is not 0 is less than or equal to a predetermined threshold relative to an autocorrelation peak value when a phase difference is 0 or a second attribute that is a cross-correlation value between sequences of equal sequence length is less than a cross-correlation value between sequences of different sequence length are transmitted while using code division multiplexing at least as one of user multiplexing schemes, a system frequency band that is a frequency band available in the system is divided into a plurality of frequency blocks having a plurality of bandwidths; generating pilot signals of the plurality of frequency blocks in a single carrier using the pilot signal sequence having a sequence length corresponding to the plurality of frequency blocks; and, the generated pilot signals are transmitted as pilot signals corresponding to respective users in multiple carriers using an arbitrary number of frequency blocks among the plurality of frequency blocks.

Therefore, all the sequences for the pilot signal sequences can be made the same length, and thus it is possible to select a sequence having good cross-correlation characteristics.

As described above, the present invention is configured such that when pilot signal sequences having at least a first attribute that is an autocorrelation value when a phase difference is not 0 is less than or equal to a predetermined threshold with respect to an autocorrelation peak value when a phase difference is 0 or a second attribute that is a cross-correlation value between sequences of equal sequence length is less than a cross-correlation value between sequences of different sequence length are transmitted while using code division multiplexing at least as one of user multiplexing schemes, a system frequency band that is a frequency band available within the system is divided into a plurality of frequency blocks having a plurality of bandwidths; generating pilot signals of the plurality of frequency blocks in a single carrier using the pilot signal sequence having a sequence length corresponding to the plurality of frequency blocks; and, the generated pilot signals are transmitted as pilot signals corresponding to respective users in multiple carriers using an arbitrary number of frequency blocks among the plurality of frequency blocks. Therefore, it is possible to make the pilot signals of different users in the frequency band orthogonal to each other and reduce interference between cells from the pilot signals of other cells.

Drawings

Fig. 1 is a diagram of a configuration of a transmitter based on a single carrier transmission scheme shown in document 1.

Fig. 2 is a diagram illustrating a manner of performing cyclic prefix addition within the cyclic prefix adder shown in fig. 1.

Fig. 3 is a diagram showing a configuration of a typical receiver corresponding to the transmitter shown in fig. 1.

Fig. 4 is a diagram showing a configuration example of a conventional mobile wireless system.

Fig. 5 is a diagram showing one example of pilot signal sequences used by respective users of frequency blocks used by the users in the mobile wireless system shown in fig. 4.

Fig. 6 is a diagram showing another configuration example of a conventional mobile wireless system.

Fig. 7 is a diagram showing one example of a frequency block used by a user and a pilot signal sequence used by an individual user in the CL of the mobile wireless system shown in fig. 6.

Fig. 8 is a diagram showing a first embodiment mode of a mobile wireless system in which the wireless communication device of the present invention is used.

Fig. 9 is a diagram showing frequency bands in the mobile radio system shown in fig. 8, through which respective users transmit pilot signals and CAZAC sequences used thereon.

Fig. 10 is a diagram showing one configuration example of a pilot signal transmitter of the first embodiment mode of the wireless communication apparatus according to the present invention.

Fig. 11 is a diagram showing one configuration example of a pilot signal receiver corresponding to the pilot signal transmitter shown in fig. 10.

Fig. 12 is a diagram showing one configuration example of the channel estimator shown in fig. 11.

Fig. 13 is a diagram illustrating an example of a time domain signal obtained from the IDFT part illustrated in fig. 12.

Fig. 14 is a diagram showing a second embodiment mode of a mobile wireless system in which the wireless communication device of the present invention is used.

Fig. 15 is a diagram showing frequency bands in the mobile radio system shown in fig. 14, through which respective users transmit pilot signals and CAZAC sequences used thereon.

Detailed Description

Next, an embodiment mode of the invention will be described with reference to the drawings.

(first embodiment mode)

Fig. 8 is a diagram showing a first embodiment mode of a mobile wireless system in which the wireless communication device of the present invention is used.

As shown in fig. 8, in this mode, there are provided a BS101 as a base station, and a plurality of mobile stations MS102-105 for communicating with the BS101 in a CL100 as a service area formed by the BS 101. Here, the BS101 and the MSs 102 to 105 are wireless communication apparatuses of the present invention.

Fig. 9 is a diagram showing frequency bands through which respective users transmit pilot signals and CAZAC sequences used thereon in the mobile wireless system shown in fig. 8.

As shown in fig. 9, a system frequency band, which is a frequency band available within the system, is divided into frequency blocks B1 and B2. It is also assumed that each user transmits a data signal or a control signal in a single carrier using a different frequency band. In this case, all users use the same CAZAC sequence having a sequence length L1 or L2 corresponding to a frequency block bandwidth W1 ═ W or W2 ═ 2W.

Therefore, the MS102 performs simultaneous multicarrier transmission by using two frequency blocks B1 and B2 corresponding to CAZAC sequence lengths L1 ═ L and L2 ═ 2L. The MS103 and the MS104 perform single carrier transmission using a bandwidth W1 corresponding to a CAZAC sequence L1 ═ L. The MS105 performs single carrier transmission using a bandwidth W2 corresponding to a CAZAC sequence length L2 ═ 2L. Here, users performing transmission through the same frequency band use the same CAZAC sequence, which is cyclically shifted by a phase unique to each user.

In this way, by unifying the bandwidths of the frequency blocks of the pilot signals or by unifying the CAZAC sequence lengths to be used, it is possible to make the users having pilot signals of different transmission bands orthogonal to each other.

Fig. 10 is a diagram showing a configuration example of a pilot signal transmitter of the first embodiment mode of the wireless communication apparatus according to the present invention.

As shown in fig. 10, this configuration is constituted by a plurality of DFT sections 601-1 to 601-n, a plurality of subcarrier mapping sections 602-1 to 602-n, an IFFT section 603, a cyclic prefix adder 604, and a cyclic shifter 605.

The pilot signal transmitter shown in fig. 10 operates as follows.

First, CAZAC sequences having a sequence length corresponding to the bandwidth of a frequency block are inserted into DFT sections 601-1 to 601-n, whereby they are transformed into frequency domain pilot signals. Here, the number of points of DFT sections 601-1 to 601-n

[ mathematical formula 12]

N_{Tx_p_1}～N_{Tx_p_n}

Corresponding to the sequence length corresponding to the bandwidth of the respective carrier. Here, N (N ═ 1 to N) is the number of carriers to be simultaneously transmitted.

Then, the frequency-transformed pilot signals are inserted into the subcarrier mapping sections 602-1 to 602-n, whereby they are subcarrier mapped. After the subcarrier mapping, the frequency domain pilot signals subjected to the subcarrier mapping are supplied to the IFFT section 603 where they are subjected to

[ mathematical formula 13]

N_{FFT_p}

FFT of the points in order to be converted into time domain pilot signals.

Thereafter, in cyclic shifter 605, cyclic shift unique to the user is performed, and a cyclic prefix is added in cyclic prefix adder 604.

The pilot signal thus generated is time-multiplexed onto the data signal generated by the same processing as in the conventional example.

The processing described so far is processing on the transmitter side within the pilot signal transmission method of the present invention.

Fig. 11 is a diagram showing one configuration example of a pilot signal receiver corresponding to the pilot signal transmitter shown in fig. 10. Here, the receiver of the data has the same configuration as the conventional receiver, and therefore, only the receiver of the pilot signal after the multiplexer has separated the pilot signal from the data signal will be shown in fig. 11.

The pilot signal receiver shown in fig. 11 includes a cyclic prefix remover 701, an FFT section 702, a plurality of subcarrier demapping sections 703-1 to 703-n, and a plurality of channel estimators 704-1 to 704-n.

The pilot signal receiver shown in fig. 11 operates as follows.

First, a cyclic prefix is removed from a received signal within a cyclic prefix remover 701. Then, the generated signal is performed by the FFT section 702

[ mathematical formula 14]

N_{FFT_p}

FFT of the points to be converted into a received signal in the frequency domain. Thereafter, the signals are demapped to subcarriers used by individual users by subcarrier demapping sections 703-1 to 703-n. After the subcarrier demapping, the subcarrier demapped frequency signals are inserted into the channel estimators 704-1 to 704-n.

Fig. 12 is a diagram showing one configuration example of the channel estimators 704-1 to 704-n shown in fig. 11.

As shown in fig. 12, the channel estimators 704-1 to 704-n in fig. 11 each include a pilot multiplier 801, a pilot signal generator 802, an IDFT section 803, a channel filter 804, and a DFT section 805.

Within pilot multiplier 801, the frequency domain received signal with the subcarriers de-mapped is multiplied by the complex conjugate of the pilot signal represented by the frequency domain generated by pilot signal generator 802. The pilot signal generator 802 may be a memory that stores a pilot signal in frequency representation or a circuit that performs calculations based on a generation formula.

The multiplied signal is then processed by an IDFT section 803, where it is subjected to a bandwidth corresponding to a frequency block

[ mathematical formula 15]

N_{Tx_p_n}

IDFT of a point so as to be converted into a time domain signal.

Fig. 13 is a diagram showing an example of a time domain signal obtained from the IDFT section 803 shown in fig. 12.

As shown in fig. 13, by performing a cyclic shift unique to a user in the cyclic shifter 605 shown in fig. 10, a signal in which impulse responses of channels of different users are shifted with respect to time is obtained.

The channel impulse response thus obtained is passed through a channel filter 804 to obtain a channel impulse response corresponding to each user. The obtained impulse response of each user is processed by the DFT section 805 so that it can be performed

[ mathematical formula 16]

N_{Tx_p_n}

The DFT of the points to be converted into a channel estimate in the frequency domain, which provides the channel frequency response for frequency equalization.

The above-described processing is processing on the receiver side within the pilot signal transmission method of the present invention.

The first embodiment mode of the present invention has been described by adopting a case in which CAZAC sequences are transmitted as pilot signal sequences and at the same time code division multiplexing is used as a user multiplexing method. In this case, a system band is divided into a plurality of frequency blocks, and pilot signals are generated on a single carrier using sequences obtained by cyclically shifting the same pilot signal sequence having a sequence length corresponding to the bandwidth of each frequency block, and the pilot signal corresponding to each user is constructed to be transmitted in n multiple carriers using arbitrary n frequency blocks of the frequency blocks. Therefore, since CAZAC sequences of the same sequence length can be used for different users in the same frequency band, it is possible to make user pilot signals orthogonal to each other.

(second embodiment)

Fig. 14 is a diagram showing a second embodiment mode of a mobile wireless system in which the wireless communication device of the present invention is used.

As shown in fig. 14, in this mode, BS101 and BS301 as base stations, and a plurality of mobile stations MS102 to 105 and MS302 to 305 for performing communication with BS101 and BS301, respectively, within CL100 and CL300 as service areas formed by BS101 and BS301, respectively, are provided. Here, BSs 101, 301, MSs 102-105 and 302-305 are wireless communication devices of the present invention.

Fig. 15 is a diagram showing frequency bands through which respective users transmit pilot signals and CAZAC sequences used thereon in the mobile wireless system shown in fig. 14. Here, similarly to the conventional configuration, it is assumed that a data signal or a control signal is transmitted with a single carrier using a frequency block having continuous frequencies.

In the first embodiment mode, the frequency bands used by the respective users to transmit their pilot signals through a single carrier are unified. In the second embodiment mode, the frequency band used to transmit the pilot signal by a single carrier is unified, and users in another cell are also included.

Therefore, referring to fig. 15, the MS102 of CL100 performs multicarrier transmission by simultaneously transmitting three carriers (bandwidth W1W 2W 3W) corresponding to a CAZAC sequence length of L1L 2L 3L. The MS103 and the MS104 perform single carrier transmission using a bandwidth W1 corresponding to a CAZAC sequence length L1 ═ L. The MS105 performs multicarrier transmission by simultaneously transmitting two carriers (bandwidth W2-W3-W) corresponding to the CAZAC sequence length of L2-L3-L.

On the other hand, the MS302 of the CL300 performs multicarrier transmission by simultaneously transmitting two carriers (bandwidth W1-W2-W) corresponding to the CAZAC sequence length of L1-L2-L. The MS303 performs single carrier transmission using a bandwidth W1 corresponding to a CAZAC sequence length L1 ═ L. MS304 and MS305 perform single carrier transmission by using a bandwidth W3 corresponding to a CAZAC sequence length of L3 ═ L.

As a sequence for a pilot signal, a sequence obtained by cyclically shifting the same CAZAC sequence by a phase unique to a user is used in the same frequency band within a cell, and a different CAZAC sequence is used in the same frequency band of a different cell. Since the CAZAC sequence has a property that a sequence generating a low cross-correlation function exists only when the sequences have the same length, it is possible to unify the bandwidths of the frequency blocks of pilot signals within the same frequency band of all cells. That is, when the sequence lengths of CAZAC sequences are unified, it is possible to reduce interference between cells.

The pilot signal transmitter and receiver of the second embodiment mode have the same configuration as those in fig. 10 to 12 described in the first embodiment mode, and the description will be omitted.

In the second embodiment mode of the present invention, the same frequency band used for the adjacent cells of the adjacent service areas is divided into the same frequency blocks. Users of different cells transmitting pilot signals through the divided frequency blocks use different CAZAC sequences within a CAZAC sequence having a sequence length corresponding to the frequency block bandwidth to generate pilot signals using a single carrier. Pilot signals corresponding to each user are transmitted in n multiple carriers using arbitrary n frequency blocks among the frequency blocks. Therefore, CAZAC sequences having the same sequence length can be used in the same frequency band for users in a cell and in different cells. As a result, it is possible to make the pilot signals within the cells orthogonal to each other and reduce interference between the cells.

Although the second embodiment mode has been described with a case where the same CAZAC sequence is used for different frequency bands within a cell within the cell, the same effect can be expected if different CAZAC sequences are used.

Also, although the second embodiment mode of the present invention is described with the case where there are two serving cells for a service area, needless to say, the same effect can be expected also in the case where there are three or more serving cells.

Also, although the second embodiment mode has been described with the case where the adjacent serving cells have the same system frequency band, even if the system frequency bands of the adjacent serving cells are different from each other, the same effect can be expected if the same frequency band is divided into frequency blocks in the same mode.

Also, although the embodiment mode of the present invention is explained using a case where frequency blocks have different bandwidths (W1 ≠ W2), the same effect can be obtained when the bandwidths of the frequency blocks are equal to each other (W1 ≠ W2).

Also, although the embodiment mode of the present invention is described using the case in which the system band is divided into three frequency blocks, the same effect can be expected when there are two or more frequency blocks.

Also, although the embodiment mode of the present invention has been described using the case where the frequency block used to transmit the pilot signal is composed of the bandwidth W and its integer multiple, the same effect can be expected when a frequency block not having an integer multiple of the bandwidth W is included.

Also, although the embodiment mode of the present invention has been described using the case in which the pilot signal of each user is transmitted in multiple carriers using frequency blocks whose frequencies are continuous, the same effect can be expected when the pilot signal is transmitted in multiple carriers using frequency blocks whose frequencies are discontinuous.

Also, in the above description, the BS101, 301 and the MSs 102-105 and 302-305 are described as wireless communication devices including the above-described pilot signal transmitter and pilot signal receiver to transmit signals.

Also, the above-described first and second embodiment modes have been described by taking an example in which CAZAC sequences are taken as pilot signal sequences. A pilot signal sequence having at least a first property that an autocorrelation value when the phase difference is not 0 is equal to or smaller than a predetermined threshold with respect to a peak autocorrelation value when the phase difference is 0 or a second property that a cross-correlation value between sequences of equal sequence length is smaller than a cross-correlation value between sequences of different sequence lengths may be used. In this case, when the data signal to be demodulated has a low operating point (Eb/N0 ═ 0 to 5dB), such as QPSK, if the autocorrelation value when the phase difference is not 0 is-20 dB (10%) with respect to the threshold value of the autocorrelation peak when the phase difference is 0, no deterioration in characteristics occurs. However, when the data signal to be demodulated has a high operating point, such as 16QAM and 64QAM, the threshold value of the autocorrelation value needs to be set at a lower level.

Claims (3)

1. A wireless transmission apparatus that transmits a pilot signal in a wireless communication system, the wireless transmission apparatus comprising:

a pilot signal generator for generating pilot signals for respective ones of frequency blocks that are part of a system bandwidth, wherein a sequence length of the respective pilot signals corresponds to the respective frequency blocks; and

a transmitter for transmitting the pilot signal in multiple carriers using a plurality of the frequency blocks.

2. A wireless communication system including a wireless transmission apparatus that transmits a pilot signal in the wireless communication system, the wireless communication system comprising:

a pilot signal generator for generating pilot signals for respective ones of frequency blocks that are part of a system bandwidth, wherein a sequence length of the respective pilot signals corresponds to the respective frequency blocks; and

a transmitter for transmitting the pilot signal in multiple carriers using a plurality of the frequency blocks.

3. A method of transmitting a pilot signal in a wireless communication system, comprising:

generating pilot signals for respective ones of frequency blocks that are part of a system bandwidth, wherein a sequence length of the respective pilot signals corresponds to the respective frequency blocks; and

the pilot signal is transmitted in multiple carriers using a plurality of the frequency blocks.