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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TL;DR: In this article, it was shown that the SINR for SC-FDE remains the same asymptotically with the proposed receiver without CP as that of the conventional receiver with CP.
Abstract: We show that one can do away with the cyclic prefix (CP) for SC-FDE and OFDM at the cost of a moderate increase in the complexity of a DFT-based receiver. Such an approach effectively deals with the decrease in the number of channel uses due to the introduction of the CP. It is shown that the SINR for SC-FDE remains the same asymptotically with the proposed receiver without CP as that of the conventional receiver with CP. The results are shown for $N_t$ transmit antennas and $N_r$ receive antennas where $N_r \geq N_t$.
01 Dec 2012
TL;DR: An inter-symbol data-mapping precoding scheme, which allows the receiver to adaptively select its most suitable data decoder based on the estimated SNR or channel conditions, for single carrier systems, can provide the system better flexibility in data decoding.
Abstract: This work proposes an inter-symbol data-mapping (ISDM) precoding scheme, which allows the receiver to adaptively select its most suitable data decoder based on the estimated SNR or channel conditions, for single carrier systems. For conventional modulation schemes, the only decoding method for traditional modulations, such as PSK and QAM, is to apply the maximum likelihood (ML) method after channel equalizations. Moreover, if the estimated SNR is unreliable enough to correctly decode the incoming signal, the received frame is usually discarded. As such, the communication system has to lower the symbol modulation order and re-transmit the data. The proposed ISDM scheme rearranges and re-maps a block of data bits to be transmitted so that they are correlated. Then, the receiver can decode the received signal by dynamically selecting the following three proposed decoders: post-equalization ML (PEML) decoder, full-rate most-significant-bit (FR-MSB) decoder and down-rate (DR) decoder based on estimated channel SNRs. For the FR-MSB decoder, its performance is close to the conventional BPSK decoder. On the other hand, PEML decoder can have roughly 2dB better performance than the FR-MSB one, while the DR decoder performs poorer than the FR-MSB one but with a lower computational complexity. Although the DR decoder has lower performance than the other two, its major advantage is able to decrease the ADC sampling rate with the help of multi-phase PLL. As such, the ISDM precoding scheme can provide the system better flexibility in data decoding.
Cites background from "Frequency domain equalization for s..."
...ad [5], due to some major advantages [2][3], such as requiring lower peak-to-average power (PAPR) ratio and less sensitivity to the carrier frequency offset (CFO) than OFDM transmission....
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22 Oct 2004
TL;DR: DPMA-MIMO MIMO, DS-CDMA, PICの異なる多数の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では,厳しい符号間干渉 によりシングルキャリア(SC)伝
Abstract: あらまし 最近,限られた帯域幅での超高速伝送技術としてマルチ送受信アンテナ(MIMO)多重が注目されている. しかし,遅延時間の異なる多数の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では,厳しい符号間干渉 によりシングルキャリア(SC)伝送特性が大幅に劣化してしまう.筆者らはこれまで,スペクトル拡散しない SC-MIMO多重伝送を対象として周波数領域等化と減算型並列干渉キャンセル(PIC)操作を繰り返すことで信号分 離とアンテナダイバーシチ効果を得ることができる周波数領域繰り返し PICを提案し,その伝送特性の改善効果を 明らかにした.本論文では,DS-CDMAマルチコード伝送における周波数繰り返し PICを用いるMIMO多重のビッ ト誤り率(BER)特性を計算機シミュレーションにより求め,繰り返し周波数領域等化の効果を明らかにしている. キーワード マルチコード DS-CDMA-MIMO多重,周波数領域繰り返し 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]．しかし，利用できる無 線帯域幅が限られているため，周波数利用効率の高い無 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 [2-4]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． 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，シングルキャリア(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 [5,6]．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 たマルチキャリア伝送が注目されるようになった．しかし，マ ルチキャリア伝送では送信信号のピーク対平均信号電力 比 (PAPR: Peak-to-Average Power Ratio)が大きくなるので， 線形電力増幅器の負担が増加してしまう問題がある．そこ で ， 最 近 ，周 波 数 領 域 等 化 (FDE: Frequency-domain Equalization)[9,10]を用いるスペクトル拡散なしの SC 伝送 が注目されている．SC 伝送では，PAPR の問題が少ないと いう利点がある．また，筆者らはスペクトル拡散を用いる SC すなわち DS-CDMA における FDE の研究を進めており， FDE を用いる DS-CDMA は MC-CDMA と同等の特性を得 ることができることを報告している[11]． これまで筆者らは，SC-MIMO 多重伝送を対象として，周 波数領域等化と減算型並列干渉キャンセル (PIC）操作を 繰り返すことで信号分離とアンテナダイバーシチ効果 を得ることができる周波数領域繰り返し PIC を提案した [12]．本論文では，マルチコード DS-CDMA における周波 数領域繰り返し PIC を用いる MIMO 多重のビット誤り率 (BER)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． 本論文の構成は以下のようになっている．第 2 章では，マル チコード DS-CDMA における繰り返し周波数領域 PIC を用 いるMIMO多重送受信系について述べている．第 3章では， 周波数選択性レイリーフェージングチャネルにおける平均 BER特性に対する周波数領域 PICの効果についての計算 機シミュレーション結果を述べている．第 4 章はむすびであ る． 2....
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...そこ で , 最 近 ,周 波 数 領 域 等 化 (FDE: Frequency-domain Equalization)[9,10]を用いるスペクトル拡散なしの SC 伝送 が注目されている....
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01 Jan 2004
TL;DR: IOFDM is shown to be better then most of the present scheme in terms of PAPR reduction, complexity, and redundancy added and Block OFDM is proposed and compared with IOFDM to study role of interleaving with regards to complexity.
Abstract: The relation of upper bound on Peak to Average Power Ratio (PAPR) with input constellation PAPR is derived for general constellation and it is shown that upper bound on PAPR is greater for QAM as compared to PSK of same order. A “pulse shaping scheme” is proposed for reduction of upper bound on PAPR. An analytical expression for reduction in upper bound is obtained in terms of pulse shaping weights and it is shown that more the variation in weights, more is the reduction. Interleaved OFDM (IOFDM) was proposed to increase code rate without increasing PAPR. IOFDM is studied from point of view of PAPR reduction while keeping code rate constant. Also IOFDM is shown to be superset of OFDM and Single Carrier Frequency Division Equalization (SC-FDE). IOFDM can be used for trading with respect to number of subcarriers to get best of OFDM and SCFDE. IOFDM is shown to be better then most of the present scheme in terms of PAPR reduction, complexity, and redundancy added. Block OFDM is proposed and compared with IOFDM to study role of interleaving with regards to complexity. A simple and efficient scheme “Tone based Integer Frequency Offset (IFO) Estimation“ is proposed for IFO estimation. A modification is proposed which improves the performance in ISI case. A detailed mathematical analysis is presented and the expression for Probability of error for most general case is derived. Later it is compared with present algorithms in literature. It is also shown how the proposed scheme is used in conjunction with Schmidl Cox Algorithm (SCA) for overall synchronization and channel estimation in OFDM.
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References
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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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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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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
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