Frequency domain equalization for single-carrier broadband wireless systems

doi:10.1109/35.995852

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Frequency domain equalization for single-carrier broadband wireless systems

Journal Article•DOI•

Frequency domain equalization for single-carrier broadband wireless systems

David Falconer¹, S.L. Ariyavisitakul, A. Benyamin-Seeyar², B. Eidson³•Institutions (3)

Carleton University¹, Harris Corporation², Conexant³

01 Apr 2002-IEEE Communications Magazine (IEEE)-Vol. 40, Iss: 4, pp 58-66

TL;DR: This article surveys frequency domain equalization (FDE) applied to single-carrier (SC) modulation solutions and discusses similarities and differences of SC and OFDM systems and coexistence possibilities, and presents examples of SC-FDE performance capabilities.

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Abstract: Broadband wireless access systems deployed in residential and business environments are likely to face hostile radio propagation environments, with multipath delay spread extending over tens or hundreds of bit intervals. Orthogonal frequency-division multiplex (OFDM) is a recognized multicarrier solution to combat the effects of such multipath conditions. This article surveys frequency domain equalization (FDE) applied to single-carrier (SC) modulation solutions. SC radio modems with frequency domain equalization have similar performance, efficiency, and low signal processing complexity advantages as OFDM, and in addition are less sensitive than OFDM to RF impairments such as power amplifier nonlinearities. We discuss similarities and differences of SC and OFDM systems and coexistence possibilities, and present examples of SC-FDE performance capabilities.

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Patent•

Method and apparatus for signal detection

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Nix Andrew, Kasparis Christos, Piechocki Robert

26 Aug 2004

TL;DR: In this article, a system for improving uplink performance in a CDMA environment via the implementation of a regularisation method in a multi-user detector is proposed. But the regularization method is based on a semi-hard decision rule that is used on an iterative basis.

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Abstract: A system for improving uplink performance in a CDMA environment via the implementation of a regularisation method in a multi-user detector. A suboptimal linear multiuser detector having a minimum mean square error (MMSE) detection technique is utilised. In order to obtain an improved estimate of the user's signals, a semi-hard decision rule is used in the regularisation method on an iterative basis. Specifically, a first iteration uses an estimated initial solution (to the regularisation method) and knowledge of a finite data set to obtain a first proposal solution. A second iteration uses a semi-hard proposal solution (to the regularisation method) and the first proposal solution feedback to obtain a second more accurate solution. This process is repeated iteratively.

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2 citations

Proceedings Article•DOI•

Are SC-FDE Systems Robust to CFO?

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Ying Chen¹, Jian Zhang², A.D.S. Jayalath³•Institutions (3)

University of South Australia¹, NICTA², Queensland University of Technology³

18 Apr 2010

TL;DR: In this paper, the impact of carrier frequency offset (CFO) on single-carrier wireless communication systems with frequency domain equalization (SC-FDE) is investigated.

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Abstract: This paper investigates the impact of carrier frequency offset (CFO) on Single Carrier wireless communication systems with Frequency Domain Equalization (SC-FDE). We show that CFO in SC-FDE systems causes irrecoverable channel estimation error, which leads to inter-symbol-interference (ISI). The impact of CFO on SC-FDE and OFDM is compared in the presence of CFO and channel estimation errors. Closed form expressions of signal to interference and noise ratio (SINR) are derived for both systems, and verified by simulation results. We find that when channel estimation errors are considered, SC-FDE is similarly or even more sensitive to CFO, compared to OFDM. In particular, in SC-FDE systems, CFO mainly deteriorates the system performance via degrading the channel estimation. Both analytical and simulation results highlight the importance of accurate CFO estimation in SC-FDE systems.

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2 citations

Journal Article•DOI•

A Comparison Study Between Pre-Equalization Schemes for Single and Multi Carrier Modulation Systems

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Najib A. Odhah¹, Kamal H. Awadalla¹, Moawad I. Dessouky¹, Fathi E. Abd El-Samie¹•Institutions (1)

Menoufia University¹

12 Jul 2011-International Journal of Wireless Information Networks

TL;DR: Frequency domain pre-equalization (Pre-FDE) is developed for broadband cyclic prefix-code division multiple access as a single carrier transmission scheme and for multi carrier-CDMA and orthogonal frequency division multiplexing as multi carrier transmission schemes.

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Abstract: In this paper, frequency domain pre-equalization (Pre-FDE) is developed for broadband cyclic prefix-code division multiple access (CP-CDMA) as a single carrier transmission scheme, and for multi carrier-CDMA (MC-CDMA) and orthogonal frequency division multiplexing (OFDM) as multi carrier transmission schemes. A comparison study is held between these schemes and the traditional equalization schemes. Experimental results show that pre-equalization improves significantly the performance of the single and multi carrier communication systems with a very low complexity at the receiver. The comparative study between MIMO pre-equalization for single carrier systems and for multi carrier systems shows that MIMO pre-equalization for single carrier systems outperforms that for multi carrier systems in terms of bit error rate (BER) performance since single carrier transmission has more frequency diversity than multi carrier transmission in the uncoded case.

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2 citations

Cites methods from "Frequency domain equalization for s..."

...However, the proposed LMMSE Pre-FDE scheme gives a better BER performance for MIMO CP-CDMA when compared to the other multi carrier systems since without coding, the Rayleigh fading on each OFDM subchannel presents the appearance of flat Rayleigh fading to the OFDM symbol detector, even when the multipath channel taps themselves do not fade [20]....
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Performance Comparison of Overlap FDE and Inter-block Interference Canceller for Single-carrier Transmission

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Obara Tatsunori, Takeda Kazuki, Adachi Fumiyuki

23 Feb 2011

TL;DR: FDE では,ブロック間干渉(IBI)の技術として Overlap FDE と IBI の特性比較の巡回畳み込みとするために,チャネルの最大遅延時間以上のサイクリックプレフ

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Abstract: あらましシングルキャリア(SC)伝送に最小平均二乗誤差規範に基づく周波数領域等化(MMSE-FDE)を用いれば, 周波数選択性フェージング環境下で優れた伝送特性が得られる.FDE では,ブロック間干渉(IBI)を避けて受信信号を送信信号とチャネルインパルス応答の巡回畳み込みとするために,チャネルの最大遅延時間以上のサイクリックプレフィックス(CP)をガードインターバル(GI)に挿入になければならないので,伝送効率の低下を招いてしまう. CP 挿入を行わずに IBI を低減する技術として Overlap FDE と IBI キャンセラがある.本論文では,CP 挿入を行わない SC 伝送における Overlap FDE と IBI キャンセラのビット誤り率(BER)の特性比較を計算機シミュレーションにより行っている. キーワード Overlap FDE,IBI キャンセラ,シングルキャリア伝送

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2 citations

Additional excerpts

...最小平均二乗誤差規範に基づく周波数領域等化 (MMSE-FDE)を SC 伝送に用いれば,周波数ダイバーシチ効果により優れた BER 特性が得られることが報告されている [3, 4]....
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...E+00 0 5 10 15 20 25 Av er ag e B ER Average received Eb/N0 (dB) QPSK Nc=256 L=8-path, α=6dB Overlap FDE (M=128) IBI cancellation □ i = 0 ◇ 1 △ 2 × 3 (b) α=6dB 図 4 平均 BER 特性比較文献 [1] W.C., Jakes Jr, Ed, Microwave mobile communications , Wiley, Newyork, 1974....
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...計算機シミュレーション表 1 に計算機シミュレーション条件を示す．変調方式は QPSK を仮定する．チャネルは L=8 パスの指数減衰遅延プロファイルを有する周波数選択性ブロックレイリーフェージングチャネルと仮定し，シンボル間隔の遅延時間 (τ l=l)を有するものとする．また，受信機でのタイミング再生およびチャネル推定は理想的であるとしている．図 4 に Overlap FDE と IBI キャンセラの BER 特性比較を示す．横軸は平均受信シンボルエネルギー対雑音電力スペクトル密度比 Eb/N0=0.5(Es/N0)である．Overlap FDE では十分な IBI 抑圧効果が得られる M=128 の場合の特性を示し，IBI キャンセラでは繰り返し回数 i をパラメータとしている．図 4(a)は減衰指数α=0dB（等電力プロファイル）のときの平均 BER 特性を示している．図 4(a)から分かるように， IBI キャンセラを用いた場合，用いない場合に比べて特性が改善されてはいるが，その改善量はさほど大きくなく，繰り返し回数 i を大きくしても殆ど改善効果が見られない．等化後のシンボルブロックの両端付近は残留 IBI の影響が大きいから，シンボルレプリカの生成精度が低い． IBI レプリカの生成にはシンボルレプリカブロックの後半部分を使用するため， IBI キャンセルの精度が低下する．そのため，繰り返し回数を増やしても，大きな特性改善効果が得られないと考えられる．一方，Overlap FDE では残留 IBI の影響が大きい等化出力ブロックの両端を除いているため残留 IBI を大幅に低減できる．そのため，高 Eb/N0 の領域では残留 IBI および残留 ISI の影響により誤りフロアが見られるものの， IBI キャンセラに比べ，優れた BER 特性を達成できることが分かる．図 4(b)はα=6dB の場合の BER 特性を示している．周波数選択性が弱いチャネルにおいては残留 IBI も小さくなるため， IBI キャンセルの精度が若干向上するものの，依然として高い誤りフロアが見られる．一方， Overlap FDE では，残留 IBI が非常に小さいため誤りフロアは見られず，優れた BER 特性を達成できる． 4....
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...まとめ本報告では，CP 挿入を行わないシングルキャリア伝送における Overlap FDE と IBI キャンセラの平均 BER 特性比較を行った． IBI キャンセラでは，前ブロックの判定値及び等化後の判定値を用いて繰り返し IBI をキャンセルするが， IBI レプリカの生成精度が低く，特性改善効果が小さい．一方，Overlap FDE では残留 IBI の小さい等化出力ブロックの中央部分のみを取り出すことで，残留 IBI を低減できるため，優れた BER 特性が得られる． 1....
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...まえがき次世代の移動通信では，1Gbps に近い超高速データ伝送が要求されている．ところが，高速移動無線チャネルは遅延時間の異なる独立な複数の伝搬路 (パス )から構成される周波数選択性フェージングチャネルとして特徴付けられ，シングルキャリア (SC)伝送では符号間干渉 (ISI)によりビット誤り率 (BER)特性が大幅に劣化してしまう [1, 2]．最小平均二乗誤差規範に基づく周波数領域等化 (MMSE-FDE)を SC 伝送に用いれば，周波数ダイバーシチ効果により優れた BER 特性が得られることが報告されている [3, 4]．MMSE-FDE を用いる SC 信号伝送はブロック伝送であり，高速フーリエ変換 (FFT)を用いて受信信号を直交周波数分解するため，チャネルの最大遅延時間以上のサイクリックプレフィックス (CP)をガードインターバル (GI)に挿入しなければならない．しかし，CP の挿入によって伝送効率の低下を招いてしまう．また，CP 長を超える遅延時間を有するパスが存在するとブロック間干渉 (IBI)が発生し，BER 特性が大幅に劣化してしまう．そこで，CP 挿入なしでも IBI を抑圧できる Overlap FDE が提案された [5, 6]． Overlap FDE では，等化後の残留 IBI が FFT ブロックの両端付近に集中することを利用し，等化後の信号ブロックの中央部分のみを出力する．従来の CP 挿入を行う FDE に比べ演算量は増加するものの，従来の FDE に比べ高いスループットを達成できることが明らかにされた [7]．一方，CP 挿入を行わずに IBI を低減する方法として， IBI キャンセラの検討も行われている [8, 9]．IBI キャンセラでは，一つ前のブロックの判定値を利用して干渉成分を低減し，さらに CP 挿入を行わないことによる希望信号成分の損失分を判定帰還により補償する．これまで，Overlap FDE と IBI キャンセラの特性比較はまだ行われていなかった．そこで本論文では，CP 挿入を行わない SC 伝送における，Overlap FDE と IBI キャンセラの特性比較を行っている．本論文は以下のような構成になっている．第 2 章では Overlap FDE および IBI キャンセラを用いる SC 伝送について述べ，それぞれの動作原理について述べる．次いで第 3 章では計算機シミュレーション結果を示し，第 4 章でまとめる． 2....
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Journal Article•DOI•

Iterative Frequency-Domain Packet Combining Techniques for UWB Systems with Strong Interference Levels

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Mário Marques da Silva¹, Rui Dinis, Paulo Montezuma•Institutions (1)

Universidade Autónoma de Lisboa¹

01 May 2013-Wireless Personal Communications

TL;DR: This paper considers UWB systems employing Single-Carrier with Frequency-Domain Equalization techniques and proposes the corresponding receiver, which also allows the soft packet combining associated to different Automatic Repeat ReQuest transmission attempts, as a measure to improve the performance through the exploitation of diversity.

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Abstract: UWB (Ultra Wideband) systems tend to suffer strong interference from signals that occupy a significant part of the transmission band. This is an important constraint, especially when the channel remains fixed for a long period of time. In order to overcome this limitation, this paper considers UWB systems employing Single-Carrier with Frequency-Domain Equalization techniques. We propose the corresponding receiver, which also allows the soft packet combining associated to different Automatic Repeat ReQuest transmission attempts, as a measure to improve the performance through the exploitation of diversity. Our techniques are able to cope with strong interference levels as well as deep fading, even for fixed channels.

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References

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Book•

Adaptive Filter Theory

[...]

Simon Haykin

01 Jan 1986

TL;DR: In this paper, the authors propose a recursive least square adaptive filter (RLF) based on the Kalman filter, which is used as the unifying base for RLS Filters.

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Abstract: Background and Overview. 1. Stochastic Processes and Models. 2. Wiener Filters. 3. Linear Prediction. 4. Method of Steepest Descent. 5. Least-Mean-Square Adaptive Filters. 6. Normalized Least-Mean-Square Adaptive Filters. 7. Transform-Domain and Sub-Band Adaptive Filters. 8. Method of Least Squares. 9. Recursive Least-Square Adaptive Filters. 10. Kalman Filters as the Unifying Bases for RLS Filters. 11. Square-Root Adaptive Filters. 12. Order-Recursive Adaptive Filters. 13. Finite-Precision Effects. 14. Tracking of Time-Varying Systems. 15. Adaptive Filters Using Infinite-Duration Impulse Response Structures. 16. Blind Deconvolution. 17. Back-Propagation Learning. Epilogue. Appendix A. Complex Variables. Appendix B. Differentiation with Respect to a Vector. Appendix C. Method of Lagrange Multipliers. Appendix D. Estimation Theory. Appendix E. Eigenanalysis. Appendix F. Rotations and Reflections. Appendix G. Complex Wishart Distribution. Glossary. Abbreviations. Principal Symbols. Bibliography. Index.

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16,062 citations

"Frequency domain equalization for s..." refers methods in this paper

...Adaptation can be done with LMS (least mean square), RLS, or least squares minimization (LS) techniques, analogous to adaptation of time domain equalizers [Hay96], [Cla98]....
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...Overlap-save or overlap-add signal processing techniques could also be used to avoid the extra overhead of the cyclic prefix [Fer85], [Hay96]....
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Journal Article•DOI•

Analysis and Simulation of a Digital Mobile Channel Using Orthogonal Frequency Division Multiplexing

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Jr. L.J. Cimini¹•Institutions (1)

Bell Labs¹

01 Jul 1985-IEEE Transactions on Communications

TL;DR: The analysis and simulation of a technique for combating the effects of multipath propagation and cochannel interference on a narrow-band digital mobile channel using the discrete Fourier transform to orthogonally frequency multiplex many narrow subchannels, each signaling at a very low rate, into one high-rate channel is discussed.

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Abstract: This paper discusses the analysis and simulation of a technique for combating the effects of multipath propagation and cochannel interference on a narrow-band digital mobile channel. This system uses the discrete Fourier transform to orthogonally frequency multiplex many narrow subchannels, each signaling at a very low rate, into one high-rate channel. When this technique is used with pilot-based correction, the effects of flat Rayleigh fading can be reduced significantly. An improvement in signal-to-interference ratio of 6 dB can be obtained over the bursty Rayleigh channel. In addition, with each subchannel signaling at a low rate, this technique can provide added protection against delay spread. To enhance the behavior of the technique in a heavily frequency-selective environment, interpolated pilots are used. A frequency offset reference scheme is employed for the pilots to improve protection against cochannel interference.

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2,627 citations

"Frequency domain equalization for s..." refers background in this paper

...OFDM transmits multiple modulated subcarriers in parallel [ 1 ]....
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...Several variations of orthogonal frequency-division multiplexing (OFDM) have been proposed as effective anti-multipath techniques, primarily because of the favorable trade-off they offer between performance in severe multipath and signal processing complexity [ 1 ]....
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Book•

Adaptive filter theory (2nd ed.)

[...]

Simon Haykin¹•Institutions (1)

McMaster University¹

01 Mar 1991

2,447 citations

Journal Article•DOI•

BER sensitivity of OFDM systems to carrier frequency offset and Wiener phase noise

[...]

Thierry Pollet¹, M. Van Bladel¹, Marc Moeneclaey¹•Institutions (1)

Ghent University¹

01 Feb 1995-IEEE Transactions on Communications

TL;DR: In this contribution the transmission of M-PSK and M-QAM modulated orthogonal frequency division multiplexed (OFDM) signals over an additive white Gaussian noise (AWGN) channel is considered and the degradation of the bit error rate is evaluated.

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Abstract: In this contribution the transmission of M-PSK and M-QAM modulated orthogonal frequency division multiplexed (OFDM) signals over an additive white Gaussian noise (AWGN) channel is considered. The degradation of the bit error rate (BER), caused by the presence of carrier frequency offset and carrier phase noise is analytically evaluated. It is shown that for a given BER degradation, the values of the frequency offset and the linewidth of the carrier generator that are allowed for OFDM are orders of magnitude smaller than for single carrier systems carrying the same bit rate. >

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1,816 citations

Journal Article•DOI•

Polyphase codes with good periodic correlation properties (Corresp.)

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D. Chu¹•Institutions (1)

Hewlett-Packard¹

01 Jul 1972-IEEE Transactions on Information Theory

TL;DR: This correspondence describes the construction of complex codes of the form exp i \alpha_k whose discrete circular autocorrelations are zero for all nonzero lags.

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Abstract: This correspondence describes the construction of complex codes of the form exp i \alpha_k whose discrete circular autocorrelations are zero for all nonzero lags. There is no restriction on code lengths.

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1,624 citations