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Journal ArticleDOI

Frequency domain equalization for single-carrier broadband wireless systems

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.
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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Citations
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09 Dec 2010
TL;DR: It is confirmed that QRM-MLBD and MMSE-FDE will not be competing in the 2016 Rio Olympics.
Abstract: あらまし QR 分解と M アルゴリズムを適用した演算量削減型最尤ブロック信号検出法(QRM-MLBD)は,周波数 選択性チャネル環境下におけるシングルキャリア(SC)伝送の平均ビット誤り率(BER)特性を従来の最小平均二乗誤 差規範に基づく周波数領域等化(MMSE-FDE)と比較して大幅に改善できる.しかしながら,QRM-MLBD の演算量 は依然として MMSE-FDE よりはるかに大きいという問題がある.筆者らは最近,QRM-MLBD の演算量を削減する 手法としてMMSE-FDEによる硬判定値に基づきMLDの木構造の簡略化を行う2ステップQRM-MLBDを提案した. 本報告では,MMSE-FDE 後の軟判定値と残留符号間干渉(ISI)+雑音成分の分散に基づいて適応的に木構造を簡略化 する 2 ステップ QRM-MLBD を提案する.平均 BER 特性及び演算量を計算機シミュレーションにより明らかにし, 従来の QRM-MLBD,硬判定値に基づく 2 ステップ QRM-MLBD と比較して,本提案法がほぼ同等の BER 特性を達

Additional excerpts

  • ...MMSE-FDE による適応木構造簡略化 QRM-MLBDの演算量の多くは,木構造の探索におけ るパスメトリック演算によるものである.よって,木 構造の探索を簡略化することでQRM-MLBDの演算量 を大幅に削減できるものと考えられる.探索の簡略化 に関して,筆者らはこれまでMアルゴリズムにおける 生き残りパス数Mを削減する手法について検討を行っ た [11, 12].一方,以前提案した2ステップQRM-MLBD は木構造自体の簡略化に着目して探索の簡略化を行っ た [9].本報告では,後者のアプローチを発展させ,更 なる木構造の簡略化を実現する. まず,MMSE-FDEによる事前判定を行う.MMSE-FDE は周波数領域受信信号YにMMSE重みを乗算すること で等化を行う [2,3].周波数領域受信信号Yは式 (7)よ り次式のように変形できる. NHDNHFdY +=+= s s s s T E T E 22 (12) ここでDは周波数領域送信信号ベクトルである.次に, 次式のようにFDE重みを乗算する. WYY =ˆ ここで Wは次式で与えられる MMSE重み行列である ([.]...

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  • ...むすび 本報告では,MMSE-FDE 後の軟判定値と残留 ISI+雑 音成分の分散を用い,適応的にシンボル候補を絞り込 むことで QRM-MLBD の演算量を削減する手法を提案 した.提案手法では,MMSE-FDE 後の残留 ISI+雑音成 分をガウス変数と近似することで,送信シンボルと MMSE-FDE 後の軟判定値の信号点間距離の累積確率 が所要値 α を満たすような距離をしきい値としてシン ボル候補の絞り込みを行う.α と SER 特性の関係を計 算機シミュレーションにより明らかにし,それに基づ く α の設定を行った.BER 特性と演算量を計算機シミ ュレーションにより明らかにし,従来の QRM-MLBD, 2 ステップ QRM-MLBD と比較して演算量を大幅に削 減できることを示した. (a) QPSK (b) 16QAM 図 5 平均 BER 特性 表 2 複素乗算回数 MMSE-FDE QRM-MLBD 2-step QRM-MLBD FFT Nclog2Nc Nclog2Nc Nclog2Nc MMSE-weight calc....

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  • ...MMSE-FDE は周波数領域受信信号YにMMSE重みを乗算すること で等化を行う [2,3]....

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  • ...計算機シミュレーション 本稿では,まずαの値が平均SER特性に与える影響を 計算機シミュレーションによって明らかにし,αの設 定を行う.次に提案法の平均BER特性を明らかにし, 演算量について従来のQRM-MLBD,硬判定値に基づく 2ステップQRM-MLBDと比較する.シミュレーション 諸元を表1に示す.データ変調にはQPSK,16QAMを用 い,ブロックサイズはNc=64,ガードインターバル長 はNg=16とした.伝搬路はL=16パスで等電力遅延プロ ファイルを有する周波数選択性ブロックレイリーフェ ージングを想定した.チャネル推定は理想とした. 表 1 計算機シミュレーション諸元 Transmitter Modulation QPSK, 16QAM Data block size Nc=64 GI size Ng=16 Channel Fading type Frequency-selective block Rayleigh Power delay profile L=16-path uniform power delay profile Time delay τ l=l (l=0~L−1) Receiver Channel estimation Ideal 3.1. α の設定法の検討 まず,αが伝送特性に与える影響を測定することで, αの設定法を検討する.QPSK変調を用い,M=64とした 場合において,αの値を0....

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  • ...近 年,最小平均二乗誤差 (MMSE)規範に基づく周波数領 域等化 (FDE)を SC 伝送に用いれば,周波数ダイバーシ チ効果が得られるので周波数選択性チャネルにおける ビット誤り率 (BER)特性を大幅に改善できることが示 されてきた [2, 3]....

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Patent
11 Jan 2005
TL;DR: In this article, a method and transceiver for wireless multicarrier communications at the transmitter side, conventional OFDM symbols, after inverse fast Fourier transform, are scrambled in time domain and then guard-interval (GI) inserted, up-converted at the carrier frequency for transmission At the receiver side, after GI removal and frequency domain channel equalization, the received signal is transformed into time-domain by inverse fast-fourier transform.
Abstract: A method and transceiver for wireless multicarrier communications At the transmitter side, conventional OFDM symbols, after inverse fast Fourier Transform, are scrambled in time domain and then guard-interval (GI) inserted, up-converted at the carrier frequency for transmission At the receiver side, after GI removal and frequency domain channel equalization, the received signal is transformed into time-domain by inverse fast Fourier Transform The time-domain equalized signal is descrambled in time domain and then transformed back to the frequency domain before it is rate-matched, demodulated and decoded This time-domain scrambling and descrambling method can be used in a wireless OFDM system such as WLAN, cellular OFDM, and MC-CDMA
Proceedings ArticleDOI
01 Oct 2012
TL;DR: The proposed iterative receiver combined with SC-FDE (Single-Carrier with Frequency-Domain Equalization) block transmission technique is an effective mechanism to mitigate such impairment of UWB signals and implements an ARQ (Automatic Repeat ReQuest) error control technique.
Abstract: Since UWB (Ultra Wideband) signals usually share the spectrum with other transmissions, they tend to be subject to strong interference levels. The proposed iterative receiver combined with SC-FDE (Single-Carrier with Frequency-Domain Equalization) block transmission technique is an effective mechanism to mitigate such impairment of UWB signals. In order to further improve the performance through the exploitation of diversity, the proposed receiver implements an ARQ (Automatic Repeat ReQuest) error control technique. The combined technique results in a system able to face strong interference levels as well as deep fadings, even for fixed channels conditions.
Proceedings ArticleDOI
01 Jun 2019
TL;DR: Under certain limits in misalignments, simulation results show that beam interference has low impact on system performance.
Abstract: Power amplification and spectral efficiencies could be optimized with transmitter structures employing several branches, each one associated to a signal component of the symbol to be transmitted, with an amplifier directly connected to an antenna or an antenna array. Under these conditions the signal components transmitted by the several branches are associated to different beams to increase the separation among data streams from different users. However, even in these conditions interference among users can occur due to superposition of radiation beams carrying signal components from different users. Since the physical security level assured by these structures is not negatively affected, it is crucial the assessment of interference effects in such systems. Under certain limits in misalignments, simulation results show that beam interference has low impact on system performance.

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

  • ...To cope with channel’s frequency selectivity it can be adopted a SC-FDE block transmission technique with a iterative block decision feedback equalization (IB-DFE) receiver whose structure is depicted in Figure 3 [7, 8, 11, 12]....

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References
More filters
Book
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.
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.

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 ArticleDOI
Jr. L.J. Cimini1
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.
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.

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
Simon Haykin1
01 Mar 1991

2,447 citations

Journal ArticleDOI
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.
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. >

1,816 citations

Journal ArticleDOI
D. Chu1
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.
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.

1,624 citations