Shaoyi Xu

Multiple narrow-band interferences suppression based on SVD in a UWB communication system

In this paper, a novel multiple narrow-band interferences (NBI) suppression technique based on singular value decomposition (SVD) algorithm is presented. SVD is used to approximate the interferences which then are subtracted from the received signals. The proposed technique is simple and robust. Three UWB systems are considered and simulation results show that the proposed new technique is very effective.

Singular Value Decomposition-Based Algorithm for IEEE 802.11a Interference Suppression in DS-UWB Systems*This research was supported by University IT Research Center Project of Inha UWB-ITRC, Korea.

Coexisting with many concurrent narrowband services, the performance of UWB systems will be affected considerably by them. Specifically, IEEE 802.11a systems which operate around 5 GHz and overlap the band of UWB signals will interfere with UWB systems significantly. In this paper, a novel narrow-band interferences (NBI) suppression technique based on singular value decomposition (SVD) algorithm for a direct sequence ultra-wideband (DS-UWB) communication system is presented. SVD is used to approximate the interferences which then are subtracted from the received signals. The proposed technique is simple and robust. Simulation results show that the proposed new technique is very effective.

On the performance of multiple access DS-BPAM UWB system in data and image transmission

In this paper, our purpose is to get an analytical method for calculating the average probability of bit error of direct sequence ultra wideband (DS-UWB) communication system. In this multiple access DS UWB system, the bipolar pulse amplitude modulation is used in order to achieve better performance. As we know, more attention is paid to the time hopping pulse position modulation (TH-PPM) UWB systems recently. In this paper, we first introduce the accurate BER calculation method of this multiuser DS-BPAM UWB system and then give the performance analysis over an ideal AWGN channel and a correlation receiver. Furthermore, we also introduce its application in both image transmission and data transmission. The analytical method yields simple and exact formulas relating the performance to the system parameters.

Performance analysis of DS-BPAM UWB system over fading channels—uncoded and coded schemes

This paper investigates the performance of two direct sequence ultra wideband (DS-UWB) communication systems over multipath fading channels. The first system is the classic DS-UWB system and the second is obtained by adding a forward error control code (FEC), convolutional code. For the two systems, bipolar pulse amplitude modulation (BPAM) is applied. In the receiver end, the selective diversity combining receiver-SRake receiver is used as a feasible receiver. In the proposed coded scheme, we use soft output Viterbi algorithm (SOVA). The analysis shows that the coded DS-UWB system outperforms the conventional DS-UWB system significantly with the increase of the SRake fingers. The effective order of processing gains achieved by the coded scheme is the product of the number of SRake branches and the free distance of the code applied.

Pilot-aided channel estimation for multiuser MIMO-OFDM systems

This paper addresses a pilot aided maximum likelihood (ML) channel estimation scheme for the uplink of multiuser multiple-input multiple-out (MIMO) orthogonal frequency division multiplexing (OFDM) systems. We derive the optimal pilot symbols and develop the optimal placement of pilot tones with respect to the mean square error (MSE) of channel estimate. In addition, a gradient algorithm for channel tracking is proposed to enhance the channel estimation.

Multiple narrow-band interferences suppression based on SVD in UWB communication systems

In this paper, a novel multiple narrow-band interferences (NBI) suppression technique based on singular value decomposition (SVD) algorithm is presented. SVD is used to approximate the interferences which then are subtracted from the received signals. The proposed technique is simple and robust. Three UWB systems are considered and simulation results show that the proposed new technique is very effective.

M-ary Code-Selected DS-BPAM UWB System with SRake Receiver over Multipath Channels

In this paper, we consider an M-ary code selected direct sequence bipolar pulse amplitude modulation (MCSDS-BPAM) ultra wideband system. The system performance and analysis over realistic IEEE UWB multipath fading channels are evaluated in the condition of perfect time synchronization and selective diversity combining Rake (SRake) receiver. In the transmitter, a particular DS code sequence can be selected by the log2(M/2) bits from the DS code set. The corresponding SRake receiver structure is designed according to the transmitter. This scheme can improve the system performance and increase the data rate by a factor log2(M/2) compared with the conventional DS-BPAM UWB system. With the increase of the modulation level M and the SRake fingers, the system performance can be improved for the same signal energy per bit.

On the Performance of Multiple Access Uncoded and Coded DS-BPAM UWB Systems

The performance of two direct sequence ultra wideband (DS-UWB) communication systems is investigated. The first system is the classic DS-UWB system. The second is obtained by adding a forward error control codes (FEC), convolutional code. For the two systems, binary pulse amplitude modulation is applied. The performance of these two systems is analyzed in detail under AWGN channel. In our proposed coded scheme, we use soft output Viterbi algorithm (SOVA). The analysis shows that the coded DS-UWB system outperforms the DS-UWB system significantly, or more importantly, at a given bit error rate, the coding scheme increases the number of users by a factor which is logarithmic in the number of pulses used in DS UWB systems. Simulation results on the bit error rate of the proposed system indicates that the system is capable to work in lower SNRs and therefore supports higher data transmission rates compared to the previously proposed UWB communication systems.

Comparison and Analysis of the Uncoded and Coded Multi-user TH-BPAM UWB System

In this paper, we mainly analyze the performance of the classical time hopping bipolar pulse amplitude modulation (TH-BPAM) UWB system and the coded TH-BPAM system in the multi-user case. The performance of TH-BPAM system is analyzed in detail over an ideal AWGN channel and correlation receiver. For the proposed coded scheme, the Viterbi algorithm (VA) and soft output Viterbi algorithm (SOVA) are employed in the decoding process and the upper bound and lower bound of bit error probability is presented. The analysis shows that TH-BPAM suffers performance degradation with respect to the coded TH-BPAM greatly. Furthermore, we give the computer simulation and our simulation results also prove our theoretical analysis

Centralized and Decentralized Channel Estimation for Multiuser MIMO-OFDM Systems

This paper addresses pilot-aided multiuser least square (LS) channel estimation for the uplink of MIMO-OFDM systems. The systems under consideration allow all users use all available subcarriers independently and thus involve multiuser interference in the frequency domain. We develop the decentralized and centralized channel estimation algorithms according to different multiuser scenarios. Optimal multiuser pilots are proposed specially for centralized estimation methods with respect to the mean square error (MSE) of LS channel estimate