JP2004165784A - Transmitter and receiver adopting mc-ds/cdma system employing spatiotemporal transmission diversity system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmitter and a receiver adopting the MC-DS/CDMA (Multiple Carrier-Directed Sequence / Code Division Multiple Access) system capable of obtaining a high speed transmission effect and a path diversity effect. <P>SOLUTION: The transmitter 1 includes: an encoding interleave means 12; a time space transmission diversity coding means 17; a pilot signal inserting means 14; a plurality of MC-DS/CDMA means 15; and a plurality of transmission antennas 16. The receiver 2 includes: a plurality of MC-DS/CDMA reception means 22; a spatiotemporal transmission diversity decoding means 25; a parallel/serial conversion means 23; and a decoding de-interleave means 24. In particular, the MC-DS/CDMA reception means 22 includes no RAKE synthesizer. <P>COPYRIGHT: (C)2004,JPO

Description

Ｃ（ｔ）は、時間ｔにおける拡散符号を表す。ｓ_０は、最初の時間シンボルを表し、ｓ_１は、２番目の時間シンボルを表す。
【００３４】
図４は、ＳＴＴＤ方式の受信装置の原理構成図である。
【００３５】
ＳＴＴＤの受信側は、原理的に、伝搬路推定器２２５と、合成器及び最尤推定器（ＭＬＤ）とからなる時空間送信ダイバーシチ（ＭＬＤ）部２５とから構成される。伝搬路推定器２２７は、伝搬路特性の変動が緩やかである（即ち、連続する２つの時間スロットでは伝搬路が変動しない）と仮定すると、アンテナ１から到来する信号の伝搬路ｈ_０及びアンテナ２から到来する信号の伝搬路ｈ_１はそれぞれ、以下の式で表すことができる。尚、ｉ＝１，２，… ，Ｎ、ｊ＝１，２，… ，Ｎであり、Ｎはサブキャリア数を表す。また、ｒ_０及びｒ_１は、２つの時間スロット信号を表す。
【００３６】
【数１】

【数２】

【００３７】
この時、受信側のアンテナで受信された２つの時間スロット信号は、全てのサブキャリアの信号が逆拡散された後、以下の式が求められる。
【数３】

【００３８】
ここでは、ｒ_０ ^ｉ及びｒ_１ ^ｉは、時刻Ｊと時刻Ｊ＋Ｔとで受信された信号であり、ｎ_０及びｎ_１は、ノイズ及び干渉成分を含む複素ランダム変数である。合成された信号は、以下のように表すことができる。
【００３９】
【数４】

【００４０】
ここで、合成器からの出力信号ｓ_０’及びｓ_１’は、以下の式で表される。
【数５】

【００４１】
そして、最尤推定器（ＭＬＤ）は、合成器からの出力信号ｓ_０’及びｓ_１’と、伝搬路推定器の出力信号ｈ_０及びｈ_１とを用いて、送信データｓ_０及びｓ_１を復元する。
【００４２】
前述した本発明における送信装置及び受信装置の種々の実施形態において、本発明の技術思想及び見地の範囲の種々の変更、修正及び省略が、当業者によれば容易に行うことができる。前述した実施形態によれば、２個の送信アンテナと１個の受信アンテナ１とについて説明したが、図２のようにＭ個の送信アンテナとＬ個の受信アンテナに拡張することは容易に実現可能である。前述の説明はあくまで例であって、何ら制約しようとするものではない。本発明は、特許請求の範囲及びその均等物として限定するものにのみ制約される。
【００４３】
【発明の効果】
以上、詳細に説明したように、本発明における時空間分割多重方式を適用したＭＣ−ＤＳ／ＣＤＭＡ方式の送信装置及び受信装置によれば、マルチパスフェージング環境下において、ＭＣ−ＤＳ／ＣＤＭＡの高速伝送と、ＳＴＴＤからのアンテナダイバーシチ効果とを同時に得ることにより、無線リンクの回線品質及び伝送特性が改善され、より高速且つ高品質なブロードバンド無線アクセス伝送を実現できる。
【００４４】
また、ＳＴＴＤ方式自体では、アンテナ間のフェージング相関が高い環境においては、アンテナダイバーシチの効果が薄れることによりＢＥＲ特性が劣化するという欠点についても補うことができる。
【００４５】
本発明は、各アンテナ間の独立な伝搬経路を利用することからフェージングによる特性劣化を防ぐことが可能となる。即ち、送信装置が複数のアンテナ（Ｍ×Ｌ）を用いて同時送信し、受信装置が各アンテナから送られた信号を分離合成することにより、送信ダイバーシチ効果（ＳＴＴＤによるアンテナダイバーシチ効果）が得られる。また、ＭＣ−ＤＳ／ＣＤＭＡ方式において、同一情報を重畳したマルチキャリア信号から逆拡散することにより高速伝送効果も得ることができる。
【図面の簡単な説明】
【図１】従来のＭＣ−ＤＳ／ＣＤＭＡ方式の送信装置及び受信装置の機能構成図である。
【図２】本発明による送信装置及び受信装置の機能構成図である。
【図３】ＳＴＴＤ方式の原理説明図である。
【図４】ＳＴＴＤ方式の受信装置の原理構成図である。
【符号の説明】
１１ ＰＮ発生器
１２ エンコーディングインタリーブ部
１３ マッピング部
１４ パイロット信号挿入部
１５ ＭＣ−ＤＳ／ＣＤＭＡ送信部
１５１ シリアル／パラレル変換部
１５２ 拡散部
１５３ 逆高速フーリエ変換部
１５４ パラレル／シリアル変換部
１５５ ガードインターバル部
１６ 送信アンテナ
１７ 時空間コーディング部
２１ 受信アンテナ
２２１ ガードインターバル部
２２２ シリアル／パラレル変換部
２２３ 高速フーリエ変換部
２２４ ＲＡＫＥ合成器
２２５ 伝搬路推定部
２２６ ＭＦ（整合フィルタ）部
２２７ 逆拡散部
２３ デコーディングデインタリーブ部
２４ 時空間送信ダイバーシチ部
２５ 時空間送信ダイバーシチ（ＭＬＤ）部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a transmission device and a reception device of an MC-DS / CDMA (Multiple Carrier-Directed Sequence / Code Division Multiple Access) system.
[0002]
[Prior art]
A wireless communication system that performs high-speed transmission is easily affected by multipath fading, and the quality of a wireless link is likely to deteriorate. Therefore, conventionally, an MC-DS / CDMA scheme that is resistant to multipath interference (MPI) caused by multipath has been proposed (for example, see Non-Patent Document 1). The MC-DS / CDMA system using a continuous wide band from the beginning is effective for realizing broadband wireless access transmission.
[0003]
FIG. 1 is a functional configuration diagram of a conventional MC-DS / CDMA transmitting apparatus and receiving apparatus.
[0004]
The transmitting apparatus 1 includes a PN generator 11 that outputs PN sequence transmission data, an encoding interleaver 12 that performs error correction coding and interleaving of the transmission data, a mapping unit 13, a pilot signal insertion unit 14, an MC- It has a DS / CDMA transmission unit 15 and a transmission antenna 16.
[0005]
MC-DS / CDMA transmitting section 15 performs serial / parallel conversion on transmission data (PN sequence) by serial / parallel converting section 151 and converts N consecutive symbols into parallel data series (s _{1 to} s _N). ). N represents the number of subcarriers. Next, the spreading section 152 multiplies each symbol by a time domain constant C (t). Next, the inversely fast Fourier transform (IFFT) unit 153 converts the multiplied N symbols into time-axis data (f _{1 to} f _N ). Next, parallel / serial conversion is performed by the parallel / serial conversion unit 154, and a guard interval is added by the guard interval (GI) unit 155. The guard interval is used to avoid intersymbol interference due to a delayed wave.
[0006]
The receiving device 2 includes a receiving antenna 21, an MC-DS / CDMA receiving unit 22, a parallel-serial converting unit 23, and a decoding deinterleaving unit 24.
[0007]
In the MC-DS / CDMA receiving unit 22, the guard interval unit 221 correlates the preamble signal and deletes the guard interval. Next, the serial / parallel converter 222 converts the serial signal into parallel. Next, after the window period is determined by the fast Fourier transform (FFT) unit 223, the data is loaded on each subcarrier. Next, each subcarrier is input to a matched filter (MF: Matched Filter) unit 226 and despread on the frequency axis by an integration operation to maximize the signal-to-noise ratio. Here, the channel estimation result for each subcarrier is derived by the propagation path estimator 225. Next, the RAKE combiner 224 combines the delayed multiplexed waves to improve the reception characteristics. Here, propagation path distortion of the signal output from MF section 226 is compensated for using a channel estimation result for each subcarrier of a pilot symbol obtained from propagation path estimator 225.
[0008]
The despread signal is subjected to parallel / serial conversion by a parallel / serial converter 23.
[0009]
Finally, the decoding deinterleaving section 24 demodulates the serial signal and restores one transmitted transmission data.
[0010]
[Non-patent document 1]
Shinhiroyuki, Abeda Sadayuki, Sawahashi Mamoru, Fumiyuki Adachi, "Comparison of Characteristics of SC / DS-CDMA and MC / DS-CDMA in Uplink Broadband Wireless Packet Transmission" IEICE Technical Report, October 1999, RCS 99-131 , P. 71-77
[0011]
[Problems to be solved by the invention]
However, in the MC-DS / CDMA system, when the number of subcarriers is large, the path separation effect obtained by the conventional DS-CDMA system cannot be obtained because the RAKE combiner, which is an advantage of the spread spectrum system, cannot perform path separation. There was a problem. In addition, since the frame efficiency is fixed, the number of pilot symbols for each subcarrier decreases, and there is a problem that channel estimation and path search characteristics deteriorate.
[0012]
Therefore, an object of the present invention is to provide a transmission device and a reception device of the MC-DS / CDMA system capable of achieving a high-speed transmission effect and a path diversity effect.
[0013]
[Means for Solving the Problems]
According to the MC-DS / CDMA transmission apparatus to which the space-time transmission diversity scheme according to the present invention is applied,
Encoding interleaving means for performing error correction coding and interleaving of one transmission data;
Space-time transmission diversity coding means for dividing the output signal of the encoding interleaving means into N units in units of two time slots and coding space-time transmission diversity;
For each of the plurality of output signals from the space-time transmission diversity coding means, a pilot signal insertion means for inserting a pilot signal,
A plurality of MC-DS / CDMA transmitting means for each of a plurality of output signals of the pilot signal inserting means;
A plurality of transmission antennas for transmitting output signals of a plurality of MC-DS / CDMA transmission units, respectively.
[0014]
According to the MC-DS / CDMA receiving apparatus to which the space-time transmission diversity scheme according to the present invention is applied,
A plurality of MC-DS / CDMA receiving means including guard interval means, serial / parallel converting means, fast Fourier transform means, despreading means and propagation path estimating means for each of the received signals of the plurality of receiving antennas;
Space-time transmission diversity decoding means for decoding space-time transmission diversity for output signals of the plurality of MC-CDMA reception means;
Parallel / serial conversion means for the decoded signal;
Decoding deinterleaving means for performing error correction decoding on the output signal of the parallel / serial conversion means and returning the interleave, and restoring one transmitted transmission data.
[0015]
Particularly, the MC-DS / CDMA receiving means is characterized in that it does not include a RAKE combiner.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0017]
FIG. 2 is a functional configuration diagram of the transmitting device and the receiving device according to the present invention. In the following, in order to simplify the description of the present invention in FIG. 2, only parts different from the functional configuration of the MC-DS / CDMA system in FIG. 1 will be described.
[0018]
The present invention is an application of the space-time transmit diversity (STTD) technology to the MC-DS / CDMA system shown in FIG.
[0019]
STTD is an anti-fading countermeasure technology that does not use feedback information, the transmitting side transmits space-time coded signals from a plurality of antennas, and the receiving side separates signals transmitted from each antenna. In this method, the antenna diversity effect is obtained by combining the signals. On the other hand, there is a disadvantage that the transmission speed is limited by transmitting the same data. Further, the STTD method itself has a disadvantage that in an environment where fading correlation between antennas is high, the effect of antenna diversity is weakened and BER characteristics are deteriorated.
[0020]
The transmitting apparatus and the receiving apparatus of FIG. 2 according to the present invention include a first stage of high-speed transmission by MC-DS / CDMA and a second stage of STTD diversity composed of M × L antennas. Here, M represents the number of transmitting antennas, and L represents the number of receiving antennas.
[0021]
In the transmitting apparatus of FIG. 2, a signal received from encoding interleave section 12 is input to space-time coding (STTD encoder) section 17 in N-bit units. The space-time coding unit 17 divides the input signal into N units in units of two time slots, and performs STTD encoding. Here, the time slot is a data symbol length T. The output of the space-time coding unit is divided into two.
[0022]
Next, a pilot signal is inserted into each signal in pilot signal insertion section 14 for the signal output from space-time coding section 17.
[0023]
MC-DS / CDMA transmitting sections 15-1 to 15 -M and transmitting antennas 1 to M are provided for each signal divided by the space-time coding section 17 and into which a pilot signal is inserted.
[0024]
The MC-DS / CDMA transmitting units 15-1 to 15-M spread N data by orthogonal Walsh Hadamard code after serial / parallel conversion. The spread signal is subjected to multicarrier modulation using the inverse fast Fourier transform unit 154 (f _{1 to} f _N ). The modulated signal is converted into a serial signal by the parallel / serial converter 154, and then transmitted simultaneously from different antennas via the guard interval unit 155.
[0025]
In order to keep the total transmission power constant, the antenna power of each antenna is distributed according to the number of antennas. The first two symbols spread for each subcarrier are transmitted using different antennas.
[0026]
In the receiving apparatus of FIG. 2, signals received from a plurality of receiving antennas 1 to L are processed by a plurality of MC-DS / CDMA receiving units 22-1 to 22-L, respectively. In each MC-DS / CDMA receiving unit 22, first, the guard interval unit 221 removes the guard interval signal of the received signal. Next, the signal is converted into a plurality of signals in the serial / parallel converter 222. Next, those signals are demodulated into multi-carrier signals in the fast Fourier transform unit 223 (f _{1 to} f _N ). The demodulated signal is despread by a despreading unit 227 using a Walsh Hadamard code for each data sequence.
[0027]
The signals output from the MC-DS / CDMA receiving units 2-1 to L are input to a space-time transmission diversity (MLD) unit 25. The space-time transmission diversity (MLD) (STTD decoder) unit 25 combines the M × L signals and outputs the result as detection data. Here, M represents the number of transmitting antennas, and L represents the number of receiving antennas. Thereafter, the signal is converted into a serial signal by the parallel / serial converter 23. The serial signal is demodulated by the decoding interleave unit 24 to restore one transmitted transmission data.
[0028]
As described above, the present invention includes the first stage for obtaining a high-speed transmission effect by MC-DS / CDMA and the second stage for obtaining STTD diversity composed of M × L antennas.
[0029]
FIG. 3 is a diagram illustrating the principle of STTD.
[0030]
According to FIG. 3, it is composed of two transmitting antennas and one receiving antenna. Here, * represents a complex conjugate.
[0031]
The transmission diversity is generally of a CloseLoop type that performs antenna selection and phase control based on feedback information. However, according to the present invention, a transmission diversity system is used in which a transmitting device transmits using a plurality of antennas and a receiving device separates and combines received signals without using feedback information.
[0032]
According to FIG. 3, the data input to the space-time coding unit 17 is processed in units of two symbols. In the first time symbols, _{s 0} is transmitted from antennas 1, _-s ^{1 *} is transmitted from antenna 2. In the next time symbols, from the antenna 1 s1 is transmitted, s ₀ ^* is transmitted from antenna 2. Then, it is spread on the frequency axis for each subcarrier and transmitted.
[0033]
Table 1 shows a transmission symbol pattern when there are two transmission antennas.
[Table 1]

C (t) represents a spreading code at time t. s ₀ represents the first time symbol and s ₁ represents the second time symbol.
[0034]
FIG. 4 is a diagram illustrating the principle of the configuration of an STTD receiver.
[0035]
The STTD receiving side is composed of a propagation path estimator 225 and a space-time transmission diversity (MLD) unit 25 composed of a combiner and a maximum likelihood estimator (MLD) in principle. Channel estimator 227, variation in the propagation path characteristic is gentle (i.e., in two consecutive time slots the channel does not change) Assuming propagation path h of the signal coming from the antenna 1 ₀ and antenna 2 each channel h ₁ of the signal coming from can be represented by the following formula. .., N, j = 1, 2,..., N, and N represents the number of subcarriers. Also, r ₀ and r ₁ represent two time slot signals.
[0036]
(Equation 1)

(Equation 2)

[0037]
At this time, for the two time slot signals received by the receiving-side antenna, the following equation is obtained after all the subcarrier signals are despread.
[Equation 3]

[0038]
Here, r ₀ ⁱ and r ₁ ⁱ are signals received at time J and time J + T, and n ₀ and n ₁ are complex random variables including noise and interference components. The combined signal can be expressed as:
[0039]
(Equation 4)

[0040]
Here, output signals s ₀ ′ and s ₁ ′ from the combiner are represented by the following equations.
(Equation 5)

[0041]
The maximum likelihood estimator (MLD) uses the output signals s ₀ ′ and s ₁ ′ from the combiner and the output signals h ₀ and h _{1 of} the propagation path estimator to transmit data s ₀ and s _1. To restore.
[0042]
In the above-described various embodiments of the transmitting device and the receiving device according to the present invention, those skilled in the art can easily perform various changes, corrections, and omissions of the technical idea and scope of the present invention. According to the above-described embodiment, two transmitting antennas and one receiving antenna 1 have been described. However, it is easily realized to extend to M transmitting antennas and L receiving antennas as shown in FIG. It is possible. The above description is merely an example and is not intended to be limiting. The invention is limited only as defined by the following claims and equivalents thereof.
[0043]
【The invention's effect】
As described above in detail, according to the MC-DS / CDMA transmitting apparatus and receiving apparatus to which the space-time division multiplexing method of the present invention is applied, the high-speed operation of MC-DS / CDMA in a multipath fading environment. By simultaneously obtaining the transmission and the antenna diversity effect from the STTD, the line quality and transmission characteristics of the radio link are improved, and higher speed and higher quality broadband radio access transmission can be realized.
[0044]
Further, the STTD system itself can compensate for the disadvantage that the effect of antenna diversity is reduced and the BER characteristic is degraded in an environment where the fading correlation between antennas is high.
[0045]
According to the present invention, it is possible to prevent characteristic degradation due to fading since an independent propagation path between each antenna is used. That is, the transmitting apparatus simultaneously transmits using a plurality of antennas (M × L), and the receiving apparatus separates and combines signals transmitted from each antenna, thereby obtaining a transmission diversity effect (antenna diversity effect by STTD). . In the MC-DS / CDMA system, a high-speed transmission effect can be obtained by despreading a multicarrier signal on which the same information is superimposed.
[Brief description of the drawings]
FIG. 1 is a functional configuration diagram of a conventional MC-DS / CDMA transmitting apparatus and receiving apparatus.
FIG. 2 is a functional configuration diagram of a transmitting device and a receiving device according to the present invention.
FIG. 3 is a diagram illustrating the principle of the STTD method.
FIG. 4 is a diagram illustrating the principle of the configuration of an STTD receiving apparatus.
[Explanation of symbols]
Reference Signs List 11 PN generator 12 Encoding interleave unit 13 Mapping unit 14 Pilot signal insertion unit 15 MC-DS / CDMA transmission unit 151 Serial / parallel conversion unit 152 Spreading unit 153 Inverse fast Fourier conversion unit 154 Parallel / serial conversion unit 155 Guard interval unit 16 Transmission antenna 17 Space-time coding unit 21 Receiving antenna 221 Guard interval unit 222 Serial / parallel conversion unit 223 Fast Fourier transform unit 224 RAKE combiner 225 Propagation path estimation unit 226 MF (matched filter) unit 227 Despreading unit 23 Decoding deinterleaving Unit 24 space-time transmission diversity unit 25 space-time transmission diversity (MLD) unit

Claims (3)

Encoding interleaving means for performing error correction coding and interleaving on one transmission data;
Space-time transmission diversity coding means for dividing the output signal of the encoding interleaving means into N units in units of two time slots and coding space-time transmission diversity;
For each of the plurality of output signals from the space-time transmission diversity coding means, pilot signal insertion means for inserting a pilot signal,
A plurality of MC-DS / CDMA transmitting means for each of a plurality of output signals of the pilot signal inserting means;
An MC-DS / CDMA transmission apparatus to which a space-time transmission diversity system is applied, comprising: a plurality of transmission antennas for transmitting output signals of the plurality of MC-DS / CDMA transmission units. A plurality of MC-DS / CDMA receiving means including guard interval means, serial / parallel converting means, fast Fourier transform means, despreading means and propagation path estimating means for each of the received signals of the plurality of receiving antennas;
Space-time transmission diversity decoding means for decoding space-time transmission diversity for output signals of the plurality of MC-CDMA reception means;
Parallel / serial conversion means for the decoded signal;
A decoding / deinterleaving means for error-correcting and decoding the output signal of the parallel / serial conversion means and returning the interleave, and restoring one transmitted transmission data. An MC-DS / CDMA receiving apparatus to which the present invention is applied. The receiving apparatus according to claim 2, wherein the MC-DS / CDMA receiving means does not include a RAKE combiner.

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