Showing papers on "SC-FDE published in 2009"

Comparison of Frequency Offset and Timing Offset Effects on the Performance of SC-FDE and OFDM Over UWB Channels

Abstract: In this paper, the effects of carrier frequency offset (CFO) and sampling time offset (STO) on the performance of single-carrier block transmission with frequency-domain equalization (SC-FDE) and orthogonal frequency-division multiplexing (OFDM) over ultrawideband (UWB) channels are investigated. The signal-to-interference-plus-noise ratio (SINR) of SC-FDE in the presence of CFO is derived and compared with that of OFDM. The effects of CFO on the bit error rate (BER) performance of both systems are also simulated and compared. Two forms of STO are considered, i.e., a constant timing shift from its optimum sampling timing instant and a random timing jitter. We show through analysis that although SC-FDE is reasonably robust to a constant timing offset, it is fairly sensitive to random timing jitter. The BER performances of SC-FDE in the presence of a constant STO and random timing jitter are simulated and compared with OFDM.

Frequency-domain multipacket detection: a high throughput technique for SC-FDE systems

Abstract: The traditional approach to cope with collisions is to discard the packets involved in it and to ask for their retransmission. However, since the signal associated to a collision has important information concerning the packets involved, we can efficiently resolve collisions with proper retransmissions. In this paper we consider severely time-dispersive channels and we propose a technique that allows efficient packet separation. We employ SC-FDE schemes (single-carrier with frequency-domain equalization) and we propose an iterative frequency-domain multi-packet detection. Since our technique requires uncorrelated channels for different retransmissions, we also propose an SP technique (Shifted Packets) for retransmissions in fixed channels. Since the total number of transmissions is equal to the number of packets involved in the collision (even when the channel remains fixed for the retransmissions), our technique allows high throughputs. The analysis of our detection technique combined with the NMDA (network-assisted diversity multiple access) MAC (medium access control) protocol shows significant throughput and delay improvements for low Eb/N0 values compared to a TDMA (time division multiple access) approach, where collisions are avoided. This technique is particularly appealing for the uplink of broadband wireless systems, since we consider SC-FDE schemes and the complexity is concentrated in the receiver. By employing the SP scheme we can use the same channel for the retransmissions, with only a small performance degradation.

Performance of physical layer network coding in a frequency-selective fading channel

Abstract: Wireless communications are characterized by a multipath propagation that is suitable for application of network coding (NC) to improve the network performance. In particular, a physical layer network coding (PNC) is a promising technique to further improve network capacity for bi-directional information exchange between pairs of end users assisted by a relay terminal. In this paper, we present the performance of bi-directional transmission with PNC in a multipath channel. We introduce the use of frequency domain equalization (FDE) with orthogonal frequency division multiplexing (OFDM) and single carrier (SC) transmission to cope with the channel distortion. The equalization weights based on minimum mean square error (MMSE) criteria required for SC-FDE signaling are derived.

Optimum transmit filter for Single-Carrier FDMA with Frequency-Domain Linear Equalization

Abstract: Single-Carrier Frequency Division Multiple Access (SC-FDMA) has been selected as the uplink transmission scheme in the 3GPP Long Term Evolution standard. SC-FDMA is a form of Single-Carrier Frequency Domain Equalization (SC-FDE) with a flexibility in resource allocation, thus it has reduced sensitivity to phase noise and a lower Peak-to-Average Power Ratio (PAPR) compared to Orthogonal Frequency Division Multiple Access. This, consequently, makes it more attractive for low cost devices with limited transmit power. In this paper we propose an optimum power allocation scheme for SC-FDMA transmission considering Frequency-Domain Linear Equalization (FD-LE). We derive the optimum power allocation for the SC-FDMA transmission for both a Zero-Forcing (ZF) and a Minimum Mean-Square Error (MMSE) receiver in order to maximize the achievable rate subject to a constant transmit power. Results show that the optimum power allocation for the MMSE FD-LE results in greater improvement in the achievable transmission rate compared to ZF FD-LE.

CFR and SNR Estimation Based on Complementary Golay Sequences for Single-Carrier Block Transmission in 60-GHz WPAN

Abstract: The single-carrier block transmission (SCBT), a.k.a. single-carrier frequency-domain equalization (SC-FDE), is being considered as an option technique for the wireless personal area network (WPAN) operating at 60-GHz. To combat the inter-symbol interference (ISI) in non-line-of-sight (NLOS) environments, the frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion is much more effective than the one based on the zero forcing (ZF) criterion. However, MMSE-FDE needs the estimation of both the channel frequency response (CFR) and the signal-to-noise ratio (SNR). In this work, we estimated CFR and SNR based on the complementary Golay sequences whose sum auto-correlation has a unique peak and zero sidelobe. Through simulations, we proved that the proposed CFR and SNR estimation methods are very effective for SCBT system using MMSE-FDE.

Time-Domain Channel Estimation of High Accuracy for LDPC Coded SC-FDE System Using Fixed Point Decoding in 60-GHz WPAN

Abstract: The single-carrier frequency-domain equalization (SC-FDE) is now being considered as an important physical layer (PHY) option for the 60-GHz wireless personal area network (WPAN) [1][2]. We proposed using the complementary Golay sequences to improve the accuracy of the channel estimation in SC-FDE system. These sequences have the autocorrelation of unique main peak and zero sidelobe. We proved by simulations that it is very effective for SC-FDE system under fixed point low-density parity-check (LDPC) decoding.

A Novel Frequency Domain Equalization Algorithm for SC-FDE System

Abstract: Single carrier frequency domain equalization technology is an important component of physical layer technology for broadband wireless access system, which can effectively avoid the lack of great complexity for single-carrier time domain equalization, as well as the high PAPR for orthogonal frequency division multiplexing In this paper, the MMSE decision feedback frequency domain equalization (MMSE-DFE) algorithm and the LMS frequency domain adaptive equalization algorithm are researched comparably. On this basis, a new LMS decision feedback frequency domain adaptive equalization (LMS-DFE) algorithm using non-linear structure is proposed. The computer Simulation results show that the proposed algorithm can effectively update the equalizer tap coefficients by tracking the channel changes, and then lower BER are obtained.

A MAC Protocol for Half-Duplex Multi-Packet Detection in SC-FDE Systems

Abstract: This paper deals with multi-packet detection for SC modulations (Single-Carrier) with FDE (Frequency-Domain Equalization). We consider iterative frequency- domain receivers that jointly perform the equalization, multi-packet separation and channel decoding operations. Our receivers allow a high throughput provided that the number of mobile terminals that is trying to access a given slot is equal to or below the multi-packet detection capacity Q max . We propose a new MAC protocol that allows a total number of mobile terminals J above Q max by controlling the number of mobile terminals contending to transmit. The paper evaluates the uplink saturated system throughput and proposes an optimal configuration for the packet transmission probability associated to each mobile terminal. Our analytical results are validated using physical and MAC layer simulations.

Joint detection and channel estimation for SC-FDE with STBC

Abstract: We consider block transmission techniques combined with rate-1 Space Time Block Coding (STBC) for two or four transmit antennas. Since our STBC with 4 transmit antennas is not orthogonal, our receiver includes the cancellation of the residual interference, allowing performances close to the ones of an orthogonal code. We propose an iterative STBC receiver with joint detection and channel estimation. Our performance results show that the proposed Single Channel — Frequency Domain Equalization (SC-FDE) STBC receiver allows excellent performance with the use of channel data obtained from channel estimation.

SC-FDE with soft packet combining ARQ techniques for interference-limited UWB systems

Abstract: SC-FDE (Single-Carrier with Frequency-Domain Equalization) together with soft packet combining ARQ techniques (Automatic Repeat reQuest) was shown to be effective for broadband wireless systems with deep fading effects such as those inherent to shadowing. However, they are not suitable to cope with strong interference effects, especially when the channel remains fixed. In this paper, we consider UWB (Ultra Wide Band) systems employing SC-FDE techniques in the presence of strong interference signals that occupy a significant part of the transmission band and we propose suitable soft combining ARQ schemes. Our techniques are able to cope with strong interference levels as well as deep fading, even for fixed channels.

Performance evaluation for OFDM and SC-FDE systems with high power amplifier

Abstract: We utilize new performance criteria to evaluate performance of orthogonal frequency division multiplexing (OFDM) and single carrier modulation with frequency-domain equalization (SC-FDE), which is described as the required ratio of average transmitted energy per bit to power spectral density of noise at a certain bit error rate (BER) The criteria takes not only received BER performance into account, but the power loss caused by input power back off (IBO) that depends on the requirement of adjacent channel interference (AG) at transmitter Simulation results indicate that IBO for unique-word-aided SC-FDE is about 4 dB lower than that for OFDM and pilot-aided SC-FDE to keep ACI below -30 dB Under the new performance criteria, although OFDM system has poorer performance in static and slow dispersive fading channel, it has advantages over SC-FDE systems especially in fast dispersive fading channels

A Study of Frequency-domain Filtering for SC-FDE

Abstract: あらまし 広帯域シングルキャリア(SC)信号はピーク対平均電力比(PAPR)が小さく,上りリンク(移動局→基地 局)伝送に適している.平均二乗誤差(MMSE)規範に基づく周波数領域等化(FDE)を用いれば,周波数ダイバーシチ効 果が得られ,優れた伝送特性を実現できる.符号間干渉を起こさずに信号帯域幅を制限するために,送信および受 信フィルタにルートナイキストフィルタが広く用いられている.SC-FDE に関するこれまでの検討の殆どがシンボ ル間隔の離散信号表現を用いており,フィルタのロールオフファクタ α が PAPR 及びビット誤り率(BER)特性にど のような影響を及ぼすかについて詳細な検討はされていなかった.α を大きくするにつれ信号帯域幅が広くなるか ら,より大きな周波数ダイバーシチ効果が得られるとともに PAPR が低くなる.本論文では,周波数領域ルートナ イキストフィルタ送受信フィルタを用いる SC-FDE 信号伝送について,ロールオフファクタ αが PAPR および BER 特性に及ぼす影響を考察している. キーワード 周波数領域等化,周波数領域フィルタリング

A New Timing Offset Estimation Method for SC-FDE Systems

Abstract: In SC-FDE (single carrier with frequency domain equalization) systems, timing offset brings ISI (inter-symbol interference). In order to obtain better timing precision in multi-path, a new timing offset estimation method applied to SC-FDE systems is proposed based on the analysis of Schmidl & Cox’s and Minn’s algorithms. By designing new training symbols and introducing corresponding calculation method, performance of timing synchronization can be improved obviously. Finally, three algorithms are compared by computer simulations and the comparison results confirm the effectiveness of the proposed algorithm.

A SNR Mapping Scheme for ZF/MMSE Based SC-FDE Structured WPANs

Abstract: The paper presents a signal-to-noise ratio (SNR) mapping scheme for single-carrier (SC) frequency domain equalization (FDE) based millimeter-wave wireless personal area networks (WPANs). The effective SNR, defined as an average SNR over whole data frame after equalization, is a one-to-one mapper of the SNR in practical scenario in the sense of the same bit error rate (BER) performance. As the mapping is based on theoretical calculation instead of the simulation on a specific channel model, the defined effective SNR is suitable to be used as a metric, such as threshold for link adaptation, because it decides system BER performance just based on theoretical BER performance of AWGN channel instead of channel-model dependent SNR-BER table. The close form of effective SNR is proposed. A link adaptation method based on the defined effective SNR is given to show how our defined effective SNR simplifies system design. Both theoretical analysis and simulation results show that the defined effective SNR is channel-model independent and it is accuracy enough with variance of mapping error lower than 1 dB, it is therefore useful, especially for the system possibly involved in several different wireless communication scenarios.

A SC-FDE scheme adopting frequency-domain QR decomposition in MIMO system

Abstract: In this paper, a novel effective low-complexity single carrier frequency-domain equalization SC-FDE scheme in multiple-input multiple-output (MIMO) system is introduced under frequency selective channel. It contains the advantages of SC-FDE and the complexity decreasing in MMSE algorithm by frequency-domain QR (FD-QR) decomposition. Also a rearrangement is implemented according to signal to noise (SNR). So performance gain can be obtained from rearrangement, demodulation after detection and equalization on specific antenna. Simulation result shows that the proposed scheme can obtain a significant performance gain to the conventional MMSE algorithm.

Improved single-carrier frequency domain equalization systems

Abstract: Single-carrier frequency domain Equalization (SC-FDE) systems, which offer similar complexity and performance to Orthogonal Frequency Division Multiplexing (OFDM) systems but enjoy a lower peak-to-average power ratio (PAPR), are promising techniques in the future generation of wireless communications. In this paper, an improved SC-FDE system is proposed, in which the cyclic prefix (CP) is only inserted in front of even frames. In the receiver, the even frames are detected using conventional FDE techniques while two methods named overlap-save (OLS) FDE and overlap-add (OLA) FDE are proposed to detect the odd frames. Simulation results show that the improved SC-FDE receiver based on OLS FDE method can outperform about 0.5dB E b /N 0 over conventional SC-FDE system. Hence the proposed SC-FDE system can enjoy a higher spectral efficiency as well as save the sent power in the transmitter with respect to conventional SC-FDE system.

Fading estimation and equalization method for sc-fde using fft

Abstract: PROBLEM TO BE SOLVED: To provide a fading compensation method and a highly accurate fading estimation and equalization method which use an FFT for an SC-FDE (single carrier-frequency domain equalization) transmission system. SOLUTION: A frame is configured by multiplexing of an intermittent pilot symbol and an information symbol subjected to DFT (discrete fourier transform) processing, fading estimation is achieved by MMSE (minimum mean square error) estimation using the intermittent pilot symbol, and fading equalization is achieved by SINR (signal to interference and noise ratio) standard MMSE equalization using the intermittent pilot symbol. COPYRIGHT: (C)2010,JPO&INPIT

Frequency-Domain Receivers for Rate-1 Space-Time Block Codes

Abstract: This paper considers iterative frequency-domain receivers for block transmission techniques with rate-1 Space Time Block Coding (STBC) for two and four transmit antennas using both Orthogonal Frequency Division Multiplexing (OFDM) and Single-Carrier (SC) schemes. The proposed receiver includes an interference canceller which enhances the performance of the non-orthogonal STBC scheme with 4 transmit antennas, allowing performances close to those of orthogonal codes. Our performance results show that combining STBC with block transmission techniques allows excellent performances.

SC-FDE with OQPSK-Type Schemes: An Efficient Transmission Technique for Broadband Wireless Systems

Abstract: This paper considers frequency-domain re- ceiver design for OQPSK-type schemes. Since the I-Q interference can lead to significant performance degra- dation we propose an FDE design (Frequency-Domain Equalization) where there is no I-Q interference in the sampling instants for the predominant OQPSK constella- tion. We also propose iterative FDEs with I-Q interference cancelation, as well as the cancelation of unintended OQPSK components.

The simulation model of ground-to-air channel and its application in SC-FDE

Abstract: In this paper, the ground-to-air channel model is studied and the simulation results of the model are provided. Then, we implement it in the improved single carrier frequency domain equalization (SC-FDE) system and compare the transmission characteristics in different conditions. Theoretical analysis and simulation results show that the BER performance of the proposed system can reach 10-7 or even smaller as the Rice factor and the signal-to-noise ratio (SNR) increase.

Single carrier transmission with frequency domain equalization (SC/FDE) system with a PAPR Of unity

Abstract: The objective of this work is to eliminate the problems associated with the peak to average power ratio (PAPR) of the single carrier transmission with frequency domain equalization (SC/FDE) system. This could be achieved by adapting the constant envelope type modulation (continuous phase modulation CPM), which, by nature, normalizes the PAPR for the SC/FDE. Ultimately, a comprehensive treatment of the problems of the PAPR is obtained. The central question always is whether the constant envelope modulation scheme suits the block-wise transmission, which is required for SC/FDE. Also, the adaption preserves the phase continuity of the constant envelope signals.

Circular orthogonal sequences based channel estimation for MIMO SC-FDE systems

Abstract: Channel estimation in low SNRs is challenging for multiple-input multiple-output single carrier frequency domain equalization (MIMO SC-FDE) systems. This paper presents a novel design of training sequences with circular orthogonal properties, which can be applied to accurate channel estimation. The orthogonality of training sequences help to eliminate the interference between the transmit antennas, while circular orthogonality guarantees the identification of every resolvable delay bin of each multipath channel at the receiver. Compared to the traditional frequency-domain channel estimation methods, the proposed algorithm not only suppresses the interference between the antennas but also decreases the variance of the noise, resulting in the improvement in MSE of channel estimation and BER performance of the system. Simulation results demonstrate the effectiveness and feasibility of the proposed algorithm.

A New Synchronization Method for SC-FDE Systems over Time-variant Channels

Abstract: Owing to SC-FDE (single carrier with frequency domain equalization) systems perform equalization in frequency domain, carrier frequency synchronization and timing synchronization are the most important preconditions. A novel synchronization method is proposed in this paper, which adopts new structure of training symbols and new calculation method. Simulation results demonstrate that the proposed method has good estimation performance over time-variant fading channels.

Single-carrier frequency domain equalization with carrier-selection under dispersive MISO channels

Abstract: Under the multiple-input-single-output (MISO) system we propose a novel design, the carrier selection (CS) in the transmit-end, for the single carrier frequency domain equalization (SC-FDE) receiver over dispersive Nakagami-m fading channels. Simulation results reveal that our proposed scheme is much greater than that without CS and other conventional counterparts. Moreover, two common strategies of the linear equalizer, zero-forcing (ZF) and minimum mean square error (MMSE), are discussed.

Time domain spreading and frequency domain maximal ratio combining reception for frequency diversity enhancement in single carrier UWB communication systems

Abstract: Ultra-wideband technology is a promising candidate for short-range broadband communication systems. Ultra-wideband channels are characterized by dense multiple paths that provide multipath diversity, also referred to as frequency diversity. Single carrier systems with frequency domain equalization have attracted much interest for high data rate communications. In this paper, frequency diversity in single carrier ultra-wideband systems is enhanced by employing simple frequency domain maximal ratio combining (FDMRC) reception with time domain complex quadratic spreading (CQS) sequences. Since ultra-wideband channels exhibit dense multiple paths and strong frequency selectivity, the proposed system can attain significant performance improvement over traditional single carrier frequency domain equalization (SC-FDE) systems. Through the comparison of the impact of the cyclic prefix length, the proposed system shows stronger robustness to inter-block interference than the conventional SC-FDE system. Compared with multicarrier systems, like orthogonal frequency-division multiplexing and multi-carrier code division multiple access, the proposed receiver complexity is reduced greatly. To accommodate multiuser communication, block spreading is further introduced to combine with the frequency diversity enhancement technique for single carrier block transmission UWB systems, realizing multiuser interference-free reception.

A low-complexity differential MIMO SC-FDE systems over frequency selective fading channels

Abstract: In this paper, we propose a new differential MIMO single-carrier system with frequency-domain equalization (SC-FDE) aided by the insertion of cyclic prefix. This block transmission system not only inherits all the merits of the SISO SC-FDE system, but is also equipped with a differential spacetime block coding (DSTBC) such as to combat the fast-changing frequency selective fading channels without the needs to estimate and then compensate the carrier frequency offset and channel effects. Hence, for practical applications, it has the additional merits of decoding simplicity and robustness against difficult transmission environments. Computer simulation shows that with two transmit antennas, the proposed system can provide diversity benefit as the non-differential system does, while greatly reducing the receiver complexity.

EXIT chart analysis for the bit-interleaved turbo frequency domain equalization under fast fading environments

Abstract: Time variation of wireless fading channels introduces interference in block-based transmissions such as orthogonal frequency division multiplexing (OFDM) or single-carrier frequency domain equalization (SC-FDE). The interference, called inter-carrier interference (ICI) in OFDM or residual inter-symbol interference (ISI) in SC-FDE, impacts the bit error rate performance resulting in an error floor. In this paper, we investigate the performance of the bit-interleaved turbo frequency domain equalization (Bi-TFDE) over frequency-selective fading channels with the residual ISI. We focus on the impact of the residual ISI on the convergence signal-to-noise ratio (SNR) threshold using the extrinsic information transfer (EXIT) chart. We first show that the Gaussian assumption of the soft information within the TFDE corrupted by the residual ISI can accurately track the flow of the extrinsic information in the iterative procedure. Then, we demonstrate the accuracy of the EXIT chart in predicting the transfer function of the equalizer. Hence, the convergence behavior of the TFDE, with the residual ISI, is parameterized by the product of the symbol block length and Doppler spread. The accuracy of our EXIT chart prediction is verified by simulation.

Single-carrier frequency-domain equalization for STBC transmission system based on multiple blocks modulation

Abstract: A block modulated (BM) algorithm is proposed for STBC block transmission system combined with single carrier frequency domain equalization (SC-FDE) with two transmit antennas and one receive antenna, and the system redundancy caused by cyclic prefix (CP) is evidently reduced. At the transmitter, multiple blocks are jointly modulated and framed together, so one single CP is shared by the multiple blocks to reduce the system cost. The STBC blocks can be achieved by decomposing the received BM frame without inter-block interference (IBI), and the decisions on the transmitted blocks can be obtained after space-time combining and frequency domain equalization. The spectral efficiency of the new system is improved dramatically by the BM algorithm without performance degradation, and the detecting performance of the new scheme is verified by Monte Carlo simulations.