Zhiquan Bai

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.

A Novel Frequency Coded Orthogonal UWB Pulse Design for Narrowband Interference Suppression

In this paper, a novel frequency coded orthogonal UWB pulse design method based on orthogonal carriers and PN (pseudo noise) sequence is presented. The basic idea of the new approach is that the frequency-shifted sub-pulses are used to generate the orthogonal pulses by coding with PN sequence in frequency domain. Because the orthogonal carriers and PN codes are introduced into IR-UWB (impulse radio UWB), the new method not only has the advantages of both the traditional IR-UWB and multi-banded CB-UWB (carrier based UWB), but also improves the efficiency of the instantaneous spectrum and energy of the transmitting UWB signal. Furthermore, the Auto-correlation and cross-correlation characteristic of the proposed pulses are better than those of other conventional pulses. In addition, by the aid of cognitive radio technology, it is can be guaranteed the transmitting signal in accordance with FCC spectral mask and coexistence, interference avoidance with other traditional narrow band system. And simulation result showed that the proposed pulse could reduce the effect of narrow band interference on UWB system with litter complexity.

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.

Analysis of multiuser DS-PAM and TH-PPM UWB systems in data and image transmission

In this paper, analytical methods for calculating the average probability of bit error of direct sequence ultra wideband (DS-UWB) system and time hopping pulse position modulation (TH-PPM) UWB system are given. In our proposed multiuser 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 TH-PPM UWB systems recently. In this paper, we first introduce the accurate BER calculation methods of the multiuser DS-PAM and TH-PPM UWB systems and then give the performance analysis over an ideal AWGN channel and a correlation receiver. Furthermore, we also introduce their applications in image transmission and data transmission and give the simulation results. 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.

A novel timing jitter resist method in UWB systems

Ultra wideband (UWB) is a kind of wireless communication system which can perform high data rate with nano-second pulses of baseband, and has recently received much attention for short-range applications. Thus a high sensitivity of timing synchronization between modulation and demodulation is required. Timing synchronization error named timing jitter between transmitter and receiver has been introduced and their properties have been analyzed in some papers. However, there are not many methods brought forward to improve the system performance in the scenarios that deteriorated jitter existents. We consider this problem and offer a method to resist the adverse effect by timing jitter to the whole system by adopting a new designed correlator reference signal in UWB receiver. This reference signal is formed corresponding to the timing jitter distribution of the received pulses waveforms to increase the jitter robust performance. From the simulation results of different UWB modulation systems, better performance can be achieved by adopting this reference signal in the receiver than the conventional schemes.

DS-BPAM UWB system-coded and uncoded scheme

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 our proposed coded DS-UWB system, obtained by adding a forward error correcting codes (FEC), namely convolutional code. In our coded scheme, we use two decoding strategies, one is Viterbi Algorithm, and the other is soft output Viterbi algorithm (SOVA). For the two systems, binary pulse amplitude modulation is applied. The performance of these two systems is analyzed in detail under AWGN channel. The analysis shows that the coded DS-UWB system outperforms the DS-UWB system significantly and the SOVA scheme is much better than the VA scheme. Simulation results on the bit error rate of the proposed system indicates that the coded scheme is capable to work in lower SNR and therefore supports higher data transmission rates compared to the previously proposed UWB communication systems.

DS Code Selection Criteria of M-ary Code Selected DS-BPAM UWB System

In this paper, an M-ary code selected direct sequence bipolar pulse amplitude modulation (MCSDS-BPAM) ultra wideband system is introduced and the code selection criteria of this system is investigated. The particular DS code sequence used in MCSDS-MPAM scheme is selected by the log2M/2 bits from the DS code set, which offers the system higher data rate without increasing the system bandwidth or changing the pulse shape compared to other M-ary modulation schemes. The system performance can be varied by the selection of DS code set from the common DS code set without any extra expense. The criteria based on four parameters used to evaluate the system performance under different code sets are given over an ideal AWGN channel and correlation receivers.

A Novel Cross Layer NFCAC Game Algorithm in IEEE 802.16-based Multi-radio Heterogeneous Ad Hoc Networks

The special scenario of the topology in the IEEE 802.16-based multi-radio heterogeneous ad hoc networks was analyzed and a novel cross layer game algorithm based on neural fuzzy connection admission controller (NFCAC) was proposed in this paper. NFCAC has been successfully applied in the control-related problems of neural networks. However, there is no discussion about the power control game algorithm and location recognition based on NFCAC in heterogeneous ad hoc networks. The proposed algorithm integrated the attributes both of NFCAC and the topology space in special scenario. The topology and the power consumption of each node can all be optimized due to the minimum link occupation with the help of the algorithm. Simulation results show that the novel algorithm can give more power control guarantee to heterogeneous ad hoc networks in the variable node loads and transmitting powers, and make the node more stable to support multi-hops at the same time.

Design of Delay-Locked Loop (DLL) with Low Jitter and High Lose Lock Time in UWB-IR System

Ultra-wide band impulse radio (UWB-IR) transmits data using sub-nanosecond baseband pulses with very low duty cycle. It is a promising candidate for short-range communications. However, due to the short duration of the impulse signal, very precise synchronization control is vital for the whole system. In this paper, an improved delay-locked loop (DLL) is introduced to the UWB-IR system with time hopping/spread spectrum (TH/SS). Instead of using only two central correlator branches in the DLL, more correlator branches with different delay parameters and different weight parameters are added to the conventional DLL. Lower tracking jitter and higher mean time to lose lock (MTLL) than the conventional systems can be achieved from proposed ones. Performance of several different combinations of correlator parameters are evaluated in this paper and some of them perform superior to that of the conventional DLLs