Performance of hybrid direct sequence-slow frequency hopping spread-spectrum acquisition under partial band interference and fading channels
Ayman Y. Elezabi, Essam A. Sourour · 2006
This paper proposes two techniques for acquisition of hybrid DS-SFH spread-spectrum systems. The performance of the proposed acquisition techniques are compared to the conventional FH acquisition technique in AWGN and fading channels and superior performance is demonstrated for narrowband interference. I. INTRODUCTION FH-CDMA is an important technology currently used in many wireless systems, e.g. the popular Bluetooth standard (3). Slow Frequency Hopping (SFH) is also one modulation option for the wireless local-area networks (WLAN's) standard (4). Partial-band interference is a serious problem in mobile systems that may prevent the receiver from being able to initially synchronize and acquire the desired FH signal. In this research we focus on developing methods to mitigate the effect of partial band interference during initial acquisition of FH signals. Little work has been done to study the effect of, and overcome, partial band interference in the acquisition process (5,6). In addition, although hybrid Direct Sequence - Slow Frequency Hopping (DS-SFH) spread spectrum communication systems have been widely proposed in the literature, few or no works show the utilization of this signal structure in mitigating partial band interference during the acquisition process. In this paper we consider a hybrid DS-SFH scheme to improve acquisition in partial-band interference environments. Two different methods are proposed for processing the PN sequence and large reductions in the probability of false detection are achieved compared to conventional FH in continuous-wave interference. We consider both continuous-wave (CW) and Gaussian interference and we consider additive white Gaussian noise (AWGN) channels with and without fading. The paper is divided as follows. Section II describes the system model including the structure of the DS-SFH and acquisition strategy. Section III describes the signal and interference model and the proposed techniques for acquiring the signal as well as the simulation method. Section IV presents simulation results comparing the performance of the proposed scheme to performance of conventional FH under different conditions.. Section V contains conclusions and future work.