JP2016201676A - Communication system, communication station, and communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique that reduces the power consumption of a transmission/reception circuit maintaining the excellent communication performance of ZCZ-CDMA.SOLUTION: A transmission side radio communication station 10A spreads data by a bent function ZCZ (Zero Correlation Zone) sequence given by a sequence generator 11. Next, a Hadamard transform circuit 12 performs Hadamard transform, and a block encoding circuit 13 block-encodes an information symbol, and transmits the resultant symbol to a reception side radio communication station 10B via a P/S circuit 21. The radio communication station 10B performs inverse transform to detect data by the P/S circuit 21, a block decoding circuit 22, an inverse Hadamard transform circuit 23, and correlator 25.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a code division multiple access (CDMA) communication system, a communication station, and a communication method, and more particularly, to a communication system, a communication station, and a communication method using a ZCZ (Zero Correlation Zone) sequence as a spreading code. .

  In CDMA wireless communication, each wireless communication station on the transmission side performs spreading processing on a data signal using a spreading code, modulates a carrier wave using the data signal after the spreading processing, and transmits this. When receiving a signal transmitted from the transmitting side, the receiving-side wireless communication station obtains a data signal by performing a despreading process on the received signal using a spreading code. Here, multiple access is realized by using a different spreading code for each wireless communication station.

  In recent years, a technique using a ZCZ sequence having a zero correlation region (hereinafter referred to as “ZCZ-CDMA scheme”) has been proposed as the above spreading code. For example, Non-Patent Literature 1 and Non-Patent Literature 2 disclose a ZCZ-CDMA scheme of a multicarrier transmission scheme to which block coding and Rake reception are applied. In the case of this ZCZ-CDMA system, on the transmission side, information symbols on the space-time obtained by spreading information symbols on the frequency space using the ZCZ sequence and performing inverse Fourier transform on the information symbols are block-coded and transmitted. To do. On the receiving side, the information symbol is extracted by performing the reverse operation. At this time, Rake reception using a pilot signal is performed. As a result, the delayed wave of the own station can be effectively used for information demodulation and interference between symbols can be reduced, so that highly reliable communication can be realized. In general, the multi-carrier transmission scheme requires frequency domain equalization for adjusting the amplitude and phase for each carrier frequency. However, the above-described ZCZ-CDMA scheme can create a situation without inter-carrier interference. There is also an advantage that frequency domain equalization is not required.

A.Abudokeremu, S.Matsufuji, Y.Ida, T.Matsumoto, A Novel Multicarrier CDMA Scheme With Interference Free Performance in Very Large Delay Spread "in its current form for publication in the ITE Transactions on Media Technology and Applications, Vol.2 , No.4, pp.362-369, 2014. A. Abudoukeremu, J.C. Huang, Y. Ida, T. Matsumoto and S. Matsufuji, “On BER performance of Block Coding MC-ZCZ-CDMA,” in the Proc. Of ISITA 2014, 2014.

  However, in the case of the above-described ZCZ-CDMA system, there is a problem that the power consumption of the transmission / reception circuit increases with the processing of Fourier transform / inverse transform. Thus, a technique that can realize low power consumption of the transmission / reception circuit while maintaining the excellent communication performance of the ZCZ-CDMA system is expected.

  This invention is made | formed in view of such a situation, The main objective is to provide the communication system, communication station, and communication method which can solve the said subject.

  In order to solve the above-described problem, a communication system according to an aspect of the present invention is a transmission side in a code division multiple access communication system including a plurality of communication stations that perform transmission and reception of data spread by spreading codes. The communication station comprises spreading means for spreading information symbols using a ZCZ sequence subjected to Hadamard transform, and transmitting means for sending the spread symbols obtained by the spreading means. Receiving means for receiving spread symbols transmitted from the transmitting communication station; inverse transform means for performing inverse transform corresponding to the Hadamard transform on the spread symbols received by the receiving means; and a ZCZ sequence And a despreading unit that despreads the spread symbol that has been inversely transformed by the inverse transform unit.

  In the communication system of the above aspect, it is preferable that the absolute value of the element value of the ZCZ sequence is constant before and after the Hadamard transform.

  Further, in the communication system according to the above aspect, the transmission unit is configured to perform block coding on the spread symbol and transmit the block-coded spread symbol, and the reception unit is configured to transmit the communication on the transmission side. It is preferable that the spread symbol transmitted from the station is configured to perform block decoding according to the block coding.

  Further, in the communication system of the above aspect, the spreading means is configured to spread a predetermined pilot symbol using the ZCZ sequence together with the information symbol, and the receiving communication station is configured to transmit the pilot symbol. It is preferable to further comprise a Rake receiving means for acquiring the information symbol by performing Rake reception using the.

  In the communication system according to the aspect described above, it is preferable that the spreading unit is configured to spread the information symbol and the pilot symbol using a plurality of different ZCZ sequences.

  A communication station according to one aspect of the present invention uses a ZCZ sequence that is used for code division multiple access communication and performs Hadamard transform in a communication station that performs transmission and reception of data spread by spreading codes. Spreading means for spreading information symbols, transmitting means for transmitting spreading symbols obtained by the spreading means, receiving means for receiving spreading symbols transmitted from other communication stations, received by the receiving means Inverse transform means for performing inverse transform corresponding to the Hadamard transform on the spread symbol, and despread means for despreading the spread symbol subjected to the inverse transform by the inverse transform means using a ZCZ sequence It is characterized by that.

  In the communication station of the above aspect, it is preferable that the absolute value of the element value of the ZCZ sequence is constant before and after the Hadamard transform.

  According to another aspect of the present invention, there is provided a communication method for performing communication in a code division multiple access communication system including a plurality of communication stations that perform transmission and reception of data spread by a spreading code. A communication station on the side performs a step of spreading information symbols using a ZCZ sequence subjected to Hadamard transform, and a step of transmitting a spread symbol obtained by the spreading; A step of receiving a spread symbol transmitted from a communication station on the transmitting side; a step of performing an inverse transform corresponding to the Hadamard transform on the received spread symbol; and performing the inverse transform using a ZCZ sequence. Despreading the spread symbols that have been performed.

  In the communication method of the above aspect, it is preferable that the absolute value of the element value of the ZCZ sequence is constant before and after the Hadamard transform.

  According to the communication system, the communication station, and the communication method according to the present invention, it is possible to save power while maintaining excellent communication performance.

The block diagram which shows the structure of the communication system of embodiment of this invention. The time chart of the communication frame in the communication system of embodiment of this invention. The graph which shows the correlation characteristic of a ZCZ code | symbol. The block diagram which shows the structure of the communication station of the transmission side and reception side with which the communication system of embodiment of this invention is provided. The graph which shows a transmission model. The block diagram which shows the structure of the communication station of the transmission side with which the communication system of other embodiment of this invention is provided.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, each embodiment shown below illustrates the method and apparatus for actualizing the technical idea of this invention, Comprising: The technical idea of this invention is not necessarily limited to the following. Absent. The technical idea of the present invention can be variously modified within the technical scope described in the claims.

  The communication system of this embodiment is a quasi-synchronous CDMA wireless communication system. The quasi-synchronous CDMA system is a communication system in which a synchronization signal is repeatedly transmitted from a synchronization control station at a predetermined time interval, and a data signal is transmitted and received according to the timing at which each wireless communication station captures the synchronization signal. Say. The present embodiment is such a quasi-synchronous CDMA communication system, but the present invention is not limited to this, and even a so-called synchronous or asynchronous CDMA communication system may be used. Good.

  FIG. 1 is a block diagram showing a configuration of a wireless communication system according to an embodiment of the present invention. As shown in FIG. 1, a CDMA radio communication system 1 includes a plurality of radio communication stations 10, 10,... That transmit and receive radio signals, and a synchronization control station 20 that transmits synchronization signals at predetermined time intervals. ing. Each wireless communication station 10 performs transmission / reception of a wireless signal at the timing when the synchronization signal transmitted from the synchronization control station 20 is detected. The wireless communication system 1 realizes quasi-synchronous CDMA communication by performing such synchronization control.

  FIG. 2 is a time chart of communication frames in the wireless communication system according to the embodiment of the present invention. As shown in FIG. 2, a synchronization signal is repeatedly transmitted from the synchronization control station 20 at predetermined time intervals. Each wireless communication station 10 transmits a data signal at the timing when this synchronization signal is detected. As a result, as shown in the final stage of the time chart of FIG. 2, the reception signal including the synchronization signal and each data signal is input to the radio communication station 10 on the reception side.

  Each wireless communication station 10 generates a modulation or demodulation timing signal by a pulse generator based on detection of the synchronization signal transmitted from the synchronization control station 20. Each wireless communication station 10 performs modulation or demodulation in accordance with this modulation or demodulation timing signal. More specifically, the operation is as follows.

  The radio communication station 10 on the transmission side performs spreading processing on the data to be transmitted with the ZCZ code in accordance with the modulation timing signal generated based on the detection of the synchronization signal, and further performs each processing described later. A transmission signal is generated. Then, the radio communication station 10 modulates the transmission signal and transmits it to the transmission path. Various modulation schemes such as PSK, ASK, BFSK, and QAM can be employed.

  On the other hand, the radio communication station 10 on the receiving side demodulates the received signal, performs a despreading process using the ZCZ code, and obtains a received signal by performing each process described later. Then, the wireless communication station 10 extracts data from the received signal by making a threshold determination in accordance with the demodulation timing signal generated based on the detection of the synchronization signal.

  Below, the detail of operation | movement of the radio | wireless communication station 10 of a transmission side and a reception side is demonstrated. First, a ZCZ code that is a ZCZ sequence set will be described.

ここで、２相系列及び４相系列はそれぞれ式（１）−２及び式（１）−３に示す要素からなる。

また、シフトτ位相がずれた系列を式（２）のように表す。

これらの周期相関関数は、式（３）に示すように定義できる。

ここで、系列が同じ場合（l＝m）を周期自己相関、異なる場合（l≠m）を周期相互相関と呼ぶ。 [ZCZ code]
A set (code) of a complex sequence having a period N and a sequence number M is expressed as a formula (1) -1 by expressing each sequence as a vector.

Here, the two-phase series and the four-phase series are composed of elements shown in the expressions (1) -2 and (1) -3, respectively.

Further, a series in which the shift τ phase is shifted is expressed as in Expression (2).

These periodic correlation functions can be defined as shown in Equation (3).

Here, the case where the sequences are the same (l = m) is called periodic autocorrelation, and the case where the sequences are different (l ≠ m) is called periodic cross-correlation.

図３は、上記のＺＣＺ符号の相関特性を示すグラフである。なお、このＺＣＺ符号の系列数Ｍは、系列長Ｎ及び零相関領域Ｚｃｚに対して、下記の式（５）に示すように上界付けられる。

なお、以下では、式（５）で示される上界に到達するZCZ系列A(2ⁿ, 2^n-1, Zcz)を用いて説明を続けるが、有限体上のフーリエ変換等に関しては一般化して議論する。 The periodic correlation function of the sequence set of the above equation (1) -1 satisfying the following equation (4) is called a ZCZ code having a zero correlation region Zcz and expressed as A (N, M, Zcz). .

FIG. 3 is a graph showing the correlation characteristics of the ZCZ code. Note that the number M of sequences of the ZCZ code is bounded to the sequence length N and the zero correlation region Zcz as shown in the following equation (5).

In the following, the explanation will be continued by using the ZCZ sequence A (2 ⁿ , 2 ^n-1 , Zcz) reaching the upper bound shown by the equation (5). However, the Fourier transform on the finite field is generalized. To discuss.

ここで、Ｖ^ｎ _ｐから実数Ｒへの写像関数を考える。このとき、ＧＦ（ｐ）上のフーリエ変換は、以下の式（７）に示すように定義できる。

ここで、その逆変換は下記の式（８）に示すように成り立つ。

[Bent function]
Next, the bent function will be described.
Let p be a prime number and N = P ⁿ . An n-dimensional vector whose elements are coefficients obtained by expanding an integer value x (0 ≦ x <N = P ⁿ ) in p-adic numbers is defined as shown in the following formula (6).

Here, a mapping function from V ⁿ _p to a real number R is considered. At this time, the Fourier transform on GF (p) can be defined as shown in the following equation (7).

Here, the inverse transformation is established as shown in the following equation (8).

ここで、下記の式（１０）が成り立つ。

但し、添え字＊は複素共役転置を示し、Ｅ_ｎは単位行列を示している。これは、クロネッカー積を用いて、下記の式（１１）のとおり表すことができる。

例えば、ｐ＝２の場合、下記の式（１２）のとおり表すことができる。

ここで、

とすると、式（７）及び式（８）に示すフーリエ変換はそれぞれ、下記の式（１５）及び（１６）のとおりに表すことができる。

ここで、全てのｘ及びｙにおいて下記の式（１７）が成り立つ場合、その関数ｆ（ｘ）を（実数値）ｂｅｎｔ関数と呼ぶ。

なお、このｂｅｎｔ関数については、「S. Matsufuji, K. Imamura, “Real-valued Bent Function and Its Application to the Design of Balanced Quadriphase Sequences with Optimal Correlation Properties,” Lecture Note in Computer Science, Vol. 508, pp.113-121, Springer Verlag, 1991.」及び「S. Matsufuji, K. Imamura, “Balanced Quadriphase Sequences with Optimal Correlation Properties Constructed by Real Valued Bent Functions,” IEEE Transactions on Information Theory, Vol.39, No.1, pp.305-310，1993.1」に詳細が説明されている。
このように、変換の前後でその絶対値が一定であるということは、変換前と後の平均電力が一定（最小）になることを意味している。 An N = P ^n- order complex (Sylvester type) Hadamard matrix is defined as shown in Equation (9) below.

Here, the following formula (10) is established.

However, subscript * indicates a complex conjugate transpose, E _n denotes the unit matrix. This can be expressed as the following equation (11) using the Kronecker product.

For example, when p = 2, it can be expressed as the following formula (12).

here,

Then, the Fourier transforms shown in the equations (7) and (8) can be expressed as the following equations (15) and (16), respectively.

Here, when the following equation (17) holds for all x and y, the function f (x) is called a (real value) bent function.

The bent function is described in “S. Matsufuji, K. Imamura,“ Real-valued Bent Function and Its Application to the Design of Balanced Quadriphase Sequences with Optimal Correlation Properties, ”Lecture Note in Computer Science, Vol. 508, pp. .113-121, Springer Verlag, 1991. ”and“ S. Matsufuji, K. Imamura, “Balanced Quadriphase Sequences with Optimal Correlation Properties Constructed by Real Valued Bent Functions,” IEEE Transactions on Information Theory, Vol. 39, No. 1. , pp.305-310, 1993. 1 ”.
Thus, the fact that the absolute value is constant before and after the conversion means that the average power before and after the conversion is constant (minimum).

[Bent function type ZCZ series]
Next, the bent function type ZCZ sequence used in the present embodiment will be described. The above-mentioned bent function is included in the generation function (logical function) of the ZCZ code of the above-described formula (1) -1. This point will be described using the ZCZ sequence A (2 ⁿ , 2 ^n-1 , Zcz).

また、下記の式（２０）は系列の一つを示すパラメータである。

ここで、式（１８）がｂｅｎｔ関数である条件は、ｎが偶数の場合、下記の式（２１）として与えられる。

また、この条件は下記の式（２２）としても与えられる。

例えば、下記の式（２３）のとおりとすることによりＺＣＺ符号を８相系列にすることができる。

さらに、すべてのｎについて、当該条件を、下記の式（２４）として与えることもできる。

また、下記の式（２５）として与えることもできる。

なお、実際には、上述した式（１８）及び式（２３）により与えられるｎが偶数でも奇数でも存在する４相系列のＺＣＺ符号が有効であると考えられる。この場合に、全体の自己・相互相関関数を低く抑えることができると考えられる。このことは数値計算により示すことが可能である。
上記のような条件を満足する式（１８）の発生関数により発生する系列をｂｅｎｔ関数型ＺＣＺ系列と定義することができる。 The generation function of the ZCZ code can be defined as shown in Equation (18).

The following equation (20) is a parameter indicating one of the series.

Here, the condition that Expression (18) is a bent function is given as Expression (21) below when n is an even number.

This condition is also given as the following equation (22).

For example, the ZCZ code can be made into an 8-phase sequence by using the following equation (23).

Further, for all n, the condition can be given as the following equation (24).

Moreover, it can also give as a following formula (25).

In practice, it is considered that a four-phase sequence ZCZ code that is present even if n given by the above-described equations (18) and (23) is even or odd is effective. In this case, it is considered that the overall auto-cross correlation function can be kept low. This can be shown by numerical calculation.
A sequence generated by the generation function of Expression (18) that satisfies the above conditions can be defined as a bent function type ZCZ sequence.

[Communications system]
Details of the configuration and operation of the wireless communication system of the present embodiment using the above-described bent function type ZCZ sequence will be described below.
FIG. 4 is a block diagram showing a configuration of the radio communication station 10 on the transmission side and the reception side provided in the radio communication system according to the embodiment of the present invention. As shown in FIG. 4, the transmitting-side radio communication station 10 (10A) includes a sequence generator 11, a Hadamard transform circuit 12, a block coding circuit 13, a parallel / serial conversion circuit (P / S circuit) 14, It has. The radio communication station 10 (10B) on the receiving side includes a P / S circuit 21, a block decoding circuit 22, an inverse Hadamard transform circuit 23, and a correlator 25 including a data detection circuit 24. In FIG. 4, for convenience of explanation, configurations of a modulation circuit, a demodulation circuit, and the like are omitted.

このとき、情報シンボルｄ^ｍ _ｋは、シーケンスジェネレータ１１により与えられるｂｅｎｔ関数ＺＣＺ系列ａ^ｍによって、下記の式（２７）に示すように拡散される。

次に、上記の式（１５）にしたがって、アダマール変換回路１２によりアダマール変換が実行される。アダマール変換が施された情報シンボルは、下記の式（２８）で表すことができる。

１チップシフトしても周期相関を維持できるようにガードチップを付加することが好ましい。このようなガードチップを付加した長さＮハット＝Ｎ＋２の拡張シンボルは、下記の式（２９）で表すことができる。

[Operation of Radio Communication Station 10A on Transmission Side]
In this wireless communication system, L information symbols of the m-th wireless communication station 10 are expressed as the following Expression (26).

At this time, the information symbol ^d _{m k} is the bent function ZCZ sequence ^{a m} given by sequence generator 11, is diffused as shown in the following equation (27).

Next, Hadamard transform is performed by the Hadamard transform circuit 12 according to the above equation (15). An information symbol subjected to Hadamard transformation can be expressed by the following equation (28).

It is preferable to add a guard chip so that the periodic correlation can be maintained even when shifted by one chip. An extended symbol of length N hat = N + 2 to which such a guard chip is added can be expressed by the following equation (29).

送信シンボルは、Ｐ／Ｓ回路１４を経て、式（３０）の各行毎に順に送信される。具体的には、以下の式（３１）に示すように送信される。

このようにブロック符号化を行うことによって、遅延の大きい通信路においても、送信データの大容量化を実現することができる。 Next, block coding of information symbols is performed by the block coding circuit 13. When block coding is performed on L information symbols collectively, it can be expressed by the following equation (30).

The transmission symbol is transmitted in order for each row of Expression (30) via the P / S circuit 14. Specifically, it is transmitted as shown in the following equation (31).

By performing block coding in this way, it is possible to realize a large transmission data capacity even in a communication path with a large delay.

ガードチップを除去した受信信号は、下記の式（３３）のとおり表すことができる。

ここで、下記の式（３４）が成り立つ。

[Operation of receiving-side radio communication station 10B]
In the communication path, a delayed wave (reception level) as shown in FIG. 5 is generated due to the influence of multipath fading caused by reflection of a building or the like. This reception level is as shown in the following equation (32).

The received signal from which the guard chip is removed can be expressed as the following equation (33).

Here, the following equation (34) is established.

The received signal r ^m _{k that} has passed through the P / S circuit 21 and the block decoding circuit 22 is _represented by the following equation (35) by inverse Hadamard transform by the inverse Hadamard transform circuit 23.

Ｋ＋Ｊ−Ｉ次個の受信ベクトルシンボルと情報データとの関係は、以下の式（３７）のとおり表すことができる。

ここで、（Ｋ＋Ｊ−１）＊Ｋ次行列Ｐ^ｍは、式（３２）の通信路の遅延波の応答からなる。 Next, de-spreading is performed by the correlator 25 using the ZCZ sequence a, and information data is extracted by the data detection circuit 24. The inner product of the received signal U ^m _k and the ZCZ sequence a ^{m ′} _represented by the above equation (35) can be expressed as the following equation (36).

The relationship between the K + J−Ith received vector symbols and the information data can be expressed as the following equation (37).

Here, the (K + J−1) * K-order matrix P ^m is composed of the response of the delayed wave of the communication channel of Expression (32).

ここで、（）^＊は複素共役転置、σ^２は雑音電力、ＥはＫ次単位行列である。また、雑音電力が小さい場合は、σ^２＝０とするゼロフォーシングのＲａｋｅ受信も有効である。 Note that the error characteristics can be improved by the radio communication station 10B performing Rake reception using a pilot signal. Specifically, MMSE (minimum mean square error) Rake reception represented by the following equation (38) can be employed.

Here, () ^* is a complex conjugate transpose, σ ² is noise power, and E is a K-th order unit matrix. In addition, when the noise power is small, Rake reception with zero forcing with σ ² = 0 is also effective.

The pilot signal can be easily configured by changing the equation (26) to d ^m = (1, 0,..., 0). In this case, the transmission (pilot) symbol of Equation (31) is repeatedly transmitted two or more times before transmitting the data symbol. In this way, the response of each delayed wave can be given as their average.

  When Rake reception is performed in this way, the calculation of the inverse matrix must be executed, which may cause a problem that the amount of calculation increases. In order to solve this problem, it is conceivable to spread the information symbols in a plurality of ZCZ sequences instead of one ZCZ sequence. In this case, it is necessary to determine in advance which sequence is used for spreading. By using a plurality of ZCZ sequences in this way, the order of the matrix calculated at the time of Rake reception can be reduced, so that high-speed processing is possible.

  As described above, the present embodiment uses a bent function type ZCZ sequence in which the absolute value of the element value is constant before and after the Hadamard transform. Thereby, since the level of the transmission signal can be made constant, the transmission signal power is always constant, and the problem of instantaneous power caused by multicarrier transmission can be solved. In addition, since it is possible to suppress the complicated arithmetic processing such as the conventional Fourier transform and inverse transform, it is possible to realize power saving of the transmission / reception circuit.

  In the case of the present embodiment, even when the sequence period length (number of sample points in another space) corresponding to the number of multicarriers or the block length determined by the delay width is increased, the error characteristics deteriorate. Stable and highly efficient transmission is possible. In addition, since interference corresponding to inter-station interference and inter-carrier interference can be removed, there is an advantage that area equalization for adjusting amplitude or phase in another space is not required.

  Since the communication system of the present embodiment can enable high-speed and highly reliable communication between a plurality of communication stations even in a communication path that changes every moment, for example, a high-function remote control system such as a high-function remote controller. , And application to high-speed mobile communication systems and the like.

(Other embodiments)
The embodiment described above is an example in which the present invention is applied to CDMA wireless communication, but the present invention is not limited to this, and may be applied to wired communication. Moreover, although embodiment mentioned above is an example applied to communication of a multicarrier transmission system, you may apply to communication of a single carrier transmission system.

  In the above-described embodiment, the diffusion processing is performed using the bent function type ZCZ sequence. However, the diffusion processing may be performed using a ZCZ sequence that is not the bent function type. Even in this case, power consumption can be reduced because complicated arithmetic processing such as Fourier transform and inverse transform can be suppressed.

In the above-described embodiment, the transmitting-side radio communication station performs Hadamard transform, but the present invention is not limited to this, and the transmitting-side radio communication station performs Hadamard transform. Alternatively, the diffusion process may be performed using a ZCZ sequence subjected to Hadamard transform. Since the generation function can be easily derived for the information symbol of Expression (28) in the case of d ^m _k = 1, it is easy to realize such a wireless communication station. Thereby, the design of the transmission circuit can be facilitated. FIG. 6 is a block diagram showing a configuration of the transmitting-side radio communication station 100 having such a configuration. As shown in FIG. 6, the wireless communication station 100 is obtained by Hadamard transforming a bent function type ZCZ sequence a = (a ₀ , a ₁ , a ₂ , a ₃ ,..., A _N−1 ). The data d _k is spread using the sequence b = (b ₀ , b ₁ , b ₂ , b ₃ ,..., B _N−1 ). This series b can be generated by the generation function described above. A sequence obtained by Hadamard transform of a ZCZ sequence in this way is also a ZCZ sequence. Thereafter, in the radio communication station 100, the block encoding circuit 33 and the P / S circuit 34 perform the same processing as in the above-described embodiment, and transmit information symbols. This also has the same effect as the above-described embodiment.

  The communication system and the communication station of the present invention are useful as a CDMA wireless communication system and a wireless communication station, respectively. The communication method of the present invention is useful as a CDMA wireless communication method.

DESCRIPTION OF SYMBOLS 1 Communication system 10 (10A, 10B) Wireless communication station 11 Sequence generator 12 Hadamard transform circuit 13 Block coding circuit 14 P / S circuit 20 Synchronization control station 21 P / S circuit 22 Block decoding circuit 23 Inverse Hadamard transform circuit 24 Data detection Circuit 25 Correlator

Claims (9)

In a code division multiple access communication system comprising a plurality of communication stations that perform transmission and reception of data spread by a spreading code,
The sending communication station
Spreading means for spreading information symbols using a ZCZ sequence subjected to Hadamard transform;
Transmitting means for transmitting the spreading symbol obtained by the spreading means,
The receiving communication station
Receiving means for receiving spreading symbols transmitted from the transmitting communication station;
Inverse transform means for performing inverse transform corresponding to the Hadamard transform on the spread symbol received by the receiving means;
And a despreading unit that despreads the spread symbol that has been reverse-transformed by the deconversion unit using a ZCZ sequence. The absolute value of the element value of the ZCZ sequence is constant before and after the Hadamard transform.
The communication system according to claim 1. The transmission means is configured to block-code the spread symbols and transmit the block-coded spread symbols,
The receiving means is configured to perform block decoding corresponding to the block encoding on the spread symbol transmitted from the transmitting communication station,
The communication system according to claim 1 or 2. The spreading means is configured to spread a predetermined pilot symbol using the ZCZ sequence together with the information symbol,
The receiving communication station is:
The communication system according to claim 3, further comprising: Rake receiving means for acquiring the information symbol by performing Rake reception using the pilot symbol. The spreading means is configured to spread the information symbols and the pilot symbols using a plurality of different ZCZ sequences.
The communication system according to claim 4. In a communication station that is used for code division multiple access communication and performs transmission and reception of data spread by spreading codes,
Spreading means for spreading information symbols using a ZCZ sequence subjected to Hadamard transform;
Transmitting means for transmitting the spreading symbol obtained by the spreading means;
Receiving means for receiving spreading symbols transmitted from other communication stations;
Inverse transform means for performing inverse transform corresponding to the Hadamard transform on the spread symbol received by the receiving means;
A communication station, comprising: a despreading unit that despreads a spread symbol that has been inversely transformed by the inverse transforming unit using a ZCZ sequence. The absolute value of the element value of the ZCZ sequence is constant before and after the Hadamard transform.
The communication station according to claim 6. In a communication method in which communication is performed in a communication system of a code division multiple access system including a plurality of communication stations that perform transmission and reception of data spread by a spreading code,
The sending communication station
Spreading information symbols using a ZCZ sequence subjected to Hadamard transform;
Transmitting spreading symbols obtained by the spreading, and
The receiving communication station
Receiving a spreading symbol transmitted from the transmitting communication station;
Performing an inverse transform corresponding to the Hadamard transform on the received spread symbols;
And a step of despreading the spread symbol subjected to the inverse transform using a ZCZ sequence. The absolute value of the element value of the ZCZ sequence is constant before and after the Hadamard transform.
The communication method according to claim 8.

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