scispace - formally typeset
Search or ask a question
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.

Content maybe subject to copyright    Report

Citations
More filters
Journal Article
TL;DR: It is confirmed that the MIMO-ARQ deal will not be affected by the U.S. government’s sanctions.
Abstract: あらまし 今後の移動通信ではパケット伝送が主流になることが予想され,誤り訂正符号化と自動再送(ARQ)と を組み合わせたハイブリッド ARQ(HARQ)が重要な技術になる.高速パケット伝送の実現には,限られた帯域幅で のより高いスループットを得ることができるマルチ送受信アンテナ(MIMO)多重と HARQ の併用が有効である.筆 者らはこれまで,シングルキャリア(SC)-MIMO 多重伝送における周波数領域繰り返し PIC を提案し,HARQ に用い たときのスループット特性を明らかにした.SC 伝送では周波数領域等化(FDE)によって大きな周波数ダイバーシチ 利得が得られるものの,等価的なチャネル利得は送信ブロックに渡って一定になるので符号化利得は小さい.一方, マルチキャリア(OFDM)伝送では,複数の直交サブキャリアを用いて異なる信号を並列送信しているため,周波数 ダイバーシチ利得は得られないが,インタリーブ効果によって大きな符号化利得が得られる.そのため,変調方式 を固定した HARQ では,周波数ダイバーシチ利得または符号化利得のどちらか一方しか期待できず,スループット 特性の向上に限界があった.そこで本論文では,繰り返し PIC を用いる MIMO 多重伝送を対象として,大きな周波 数ダイバーシチ効果と符号化利得を同時に得られるように再送に応じて適応的に変調方式変える HARQ を提案し, そのスループット特性を計算機シミュレーションにより明らかにしている. キーワード HARQ,再送基準適応変調,SC-MIMO 多重,OFDM-MIMO 多重,繰り返し PIC,移動通信

Additional excerpts

  • ...まえがき 次 世 代 の移 動 通 信 システムでは,多 様 なブロードバンド マルチメディア情 報 の提 供 が期 待 されており,超 高 速 無 線 伝 送 技 術 の実 現 が望 まれている [1].そのため,パケット伝 送 が主 流 になると予 想 される.周 波 数 選 択 性 フェージング チャネル環境下でのパケット伝送では,何らかの強力な誤り 制 御 技 術 が必 要 である.その有 効 な技 術 の 1 つに Rate compatible turbo coded(RCPT) ハ イ ブ リ ッ ド 自 動 再 送 (HARQ: Hybrid automatic repeat request) [2,3]が知られて いる. しかし,利 用 できる無 線 帯 域 幅 が限 られているため,より 高いスループットの得られる無線伝送技術の開発が必要で ある.有 望 な技 術 として知 られているものに,マルチ送 受 信 アンテナ(MIMO: Multi-Input Multi-Output)多重 [4]がある. MIMO 多重では,送信データ系列を複数の並列系列に変 換 し,それぞれを異 なる送 信 アンテナから同 一 の搬 送 波 周 波数を用いて同時送信する.受信機では,重畳された信号 を分 離した後 ,復 調 を行う.信 号 を分 離 する代 表 的 な方 法 と し て , 最 尤 判 定 (MLD)[5] , 最 小 平 均 二 乗 誤 差 (MMSE)[5] や Vertical-bell laboratories layered space-time architecture (V-BLAST)[6]などが知られている. 高速パケット伝送の実現には,RCPT-HARQ と MIMO 多重 の併用が非常に有効である. ところで,移 動 無 線チャネルは遅 延 時 間 の異なる多 数 の 独 立 パスから構 成 されている.このようなチャネルは周 波 数 選択性チャネルと呼ばれ,SC 伝送では厳しい符号間干渉 により伝送特性が大幅に劣化してしまう[5].そこで,最近で は,直交周波数分割多重 (OFDM)[7]やマルチキャリア符号 分割多元接続 (MC-CDMA)[8]といったマルチキャリア(MC) 伝 送が注目されるようになった.さらに最 近 では,周波 数 領 域等化 (FDE: Frequency-domain Equalization) [9]を用い る SC 伝 送 も 注 目 さ れ て い る [10] . こ れ ま で 筆 者 ら は , SC-MIMO 多重伝送を対象として,繰り返し並列干渉キャン セル(PIC)に関 する検 討 を行 ってきた [11-13].提案した周 波 数 領 域 繰 り 返 し PIC で は , 初 回 の 2 次 元 (2D) MMSE-FDE だけでは,符号間 干渉と他 アンテナ干渉 を十 分に抑圧することができないため,2D MMSE-FDE と PIC を 繰 り返 して信 号 分 離 精 度 を向 上 させている.この繰 り返 し PIC は MC 伝送にも適用可能である. これまで,SC や OFDM 伝送を対象に RCPT HARQ のス ループット特性比較が行われている[14].SC 伝送では FDE によって大 きな周 波 数 ダイバーシチ利 得 が得 られるが,送 信ブロックのおける全てのシンボルに渡って等価チャネル利 得が一定になるために符号化利得が小さい.一方,OFDM 伝 送では複 数 の直 交サブキャリアを用いて異なる信 号を並 列 送 信 しているため,周 波 数 ダイバーシチ利 得 は得 られな いが,インタリーブ効果によって大きな符号化利得が得られ る.Type II RCPT HARQ パケット伝送では第 1 回目の送信 では情報ビットだけを送信し,受信機で誤りが検出されて再 送が生じた場合にはパリティビットを送信する[3].このような パケット伝送では,SC では第 1 回目パケットが正しく受信す る確率は周波数ダイバーシチ利得によって大きくなるが,再 送が生じたときは符号化利得を十分得ることができない.一 方,OFDM では,周波数ダイバーシチ利得が得られないの で,第 1 回目パケットで正しく受信する確率は SC より小さい ものの,再送時には十分な符号化利得を得ることができる. このように 1 つの変調方式に固定してパケット伝送を行うと, 再送を含む全 てのパケット送 信において十分な周波数ダイ バーシチ利得と符号化利得を得ることが期待できない.そこ で,本 論 文 では,再 送 回 数 に応 じて変 調 方 式 を変 えること で周 波 数 ダイバーシチ利 得 と符 号 化 利 得 を得 る適 応 変 調 HARQ を提案している. 本論文の構成は以下のようになっている.第 2 章では, TypeII RCPT-HARQ における適応変調を説明している.第 3 章では,繰り返し PIC を用いる SC 及び OFDM-MIMO 多 重伝送系について述べている.第 4 章では,計算機シミュレ ーションにより求 めた周 波 数 選 択 性 レイリーフェージングチ ャネルにおける RCPT-HARQ のスループット特性を求め,再 送基準の適応変調の適用効果について考察している.第 5 章はむすびである....

    [...]

  • ...さらに最 近 では,周波 数 領 域等化 (FDE: Frequency-domain Equalization) [9]を用い る SC 伝 送 も 注 目 さ れ て い る [10] ....

    [...]

Journal ArticleDOI
30 Sep 2012
TL;DR: MSE Performance of proposed method with using channel information is higher than MSE performances of SISO system and conventional method in time-varying Rayleigh channel.
Abstract: In this paper, we propose a carrier frequency offset estimation method for single-carrier MIMO systems. In the proposed method, phase rotated PN (Pseudo-Noise) sequences are transmitted to prevent a cancelling out of partial PN sequences. After removing a modulation of received PN sequences by multiplying of complex conjugated PN Sequences which are locally generated in receiver, a CFO (Carrier Frequency Offset) is accurately estimated by employing L&R method which is a kind of ML (Maximum Likelihood) estimation algorithm and uses multiple auto-correlatos. In addition, the frequency offset estimation scheme by using channel state information is proposed for accurate CFO estimation in time-varying Rayleigh channel. By performing computer simulations, MSE (Mean Square Error) performance of proposed method is almost same as MSE performance of SISO systems in AWGN channel. Moreover, MSE Performance of proposed method with using channel information is higher than MSE performances of SISO system and conventional method in time-varying Rayleigh channel.

Additional excerpts

  • ...[2] D....

    [...]

Proceedings ArticleDOI
08 Mar 2010
TL;DR: In this article, the performance limits of coded asymmetric OFDM (A-OFDM) systems in multipath fading channels when maximum-likelihood (ML) detection is deployed are investigated.
Abstract: We investigate performance limits of a coded asymmetric OFDM (A-OFDM) system in multipath fading channels when maximum-likelihood (ML) detection is deployed. Our A-OFDM formulation is general and the analysis extends to coded OFDM (COFDM), precoded COFDM and single carrier systems. At first, an exact pairwise error probability is evaluated based on Craig's alternative form of the Q-function. Then we derive a tight union bound of bit error probability based on a code transfer function. The analysis shows that the coded A-OFDM system has improved diversity, whose order equals to the channel code's Hamming distance times the fast Fourier transform (FFT) or inverse FFT (IFFT) size of the A-OFDM system. The simulation results support the analysis and demonstrate superior performance of the coded A-OFDM system with the high signal to noise ratio (SNR).

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

  • ...INTRODUCTION As an effective way of combining the benefits of orthogonal frequency division multiplexing (OFDM) and single carrier with frequency domain equalisation (SC-FDE) techniques [1], asymmetric OFDM (A-OFDM) [2] is a scheme for realising various trade-offs between the system performance, complexity and power consumption....

    [...]

13 Jun 2013
TL;DR: In this paper, the average block error rate (BLER) performance of star 16/64QAM schemes using iterative decision-directed channel estimation (IDDCE) associated with the turbo frequency domain equalizer (FDE) for discrete Fourier transform (DFT)-precoded Orthogonal Frequency Division Multiple Access (OFDMA).
Abstract: This paper presents the average block error rate (BLER) performance of star 16/64QAM schemes using iterative decision-directed channel estimation (IDDCE) associated with the turbo frequency domain equalizer (FDE) for discrete Fourier transform (DFT)-precoded Orthogonal Frequency Division Multiple Access (OFDMA). We show that the turbo FDE with the IDDCE based on the a posteriori log-likelihood ratio (LLR) decreases the required average received signal-to-noise power ratio (SNR) compared to that based on the extrinsic LLR. We also show that the turbo FDE is effective in decreasing the required average received SNR considering the cubic metric (CM) compared to the linear minimum mean-square error based FF-FDE for star 16/64QAM schemes. Moreover, we show that the (8, 8) star 16QAM and (16, 16, 16, 16) star 64QAM schemes decrease the required average received SNR considering the CM at the average BLER of 10 by approximately 0.8 and 0.3 dB compared to the square 16QAM and 64QAM schemes, respectively, with a low turbo coding rate such as R = 1/3 when using the turbo FDE associated with IDDCE. 

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

  • ...In general, a one-tap linear filter based on the linear minimum mean-square error (LMMSE) criterion is used in a FDE [4], [5]....

    [...]

  • ...Discrete Fourier transform (DFT)precoded Orthogonal Frequency Division Multiple Access (OFDMA) is adopted to generate SC-FDMA signals in the frequency domain [2], [3] to achieve high commonality with OFDMA in the downlink and affinity to frequency domain equalizers (FDEs) [4], [5]....

    [...]

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]....

    [...]

  • ...Overlap-save or overlap-add signal processing techniques could also be used to avoid the extra overhead of the cyclic prefix [Fer85], [Hay96]....

    [...]

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 ]....

    [...]

  • ...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 ]....

    [...]

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