T-ZCZ keying for infrared wireless communications

Abstract

ABSTRACT In this paper, we propose a DSSS transmission scheme called T-ZCZ (Three Zero Correlation Zone) Keyingfor indoor infrared communications. This scheme can su ccessfully remove inter-symbol interference (ISI)incurred by multipath dispersion and improve the system throughput drastically. We present the systemmodelling and show that it can oer a better Bit-Error-Ratio(BER) performance and higher data transmis-sion rate, especially in multipath infrared channels for multiple users.Keywords: T-ZCZ, T-ZCZ Keying, Ear ZCZ Windows, Infrared Communication, ISI 1. INTRODUCTION Due to the widely development of portable computers and communication terminals, the demand for high-speed wireless communication is incr easing. So infrared communication becomes an attractive choice formany short-range applications [1]. It has advantages such as virtually unlimited bandwidth, compatibleworldwide, immunity to eavesdropping, the high bit rates, low signal-processing complexity, and potentiallyvery low cost. However there are two major problems in indoor wireless infrared communications.Theyare multipath dispersion and ”uorescent light interference. And direct sequence spread spectrum (DSSS)technique is proved to be eective under the eect of multipath dispersion in infrared systems for indoorcommunication[2][3][4]. Based on the DSSS technique, we design a DSSS transmission scheme and call itT-ZCZ Keying for indoor infrared communications. Th is scheme can successfully remove ISI incurred bymultipath dispersion and improve the system throughput drastically. Speci“cally, the sequences with T-ZCZwindows both in the aperiodic auto-correlation function (ACF) and cross-correlation function (CCF) areemployed. In the infrared transmission, the sidelobes of the aperiodic ACFs and CCFs of the sequenceswith T-ZCZ windows sum to near zero at the correlator outputs, which can almost completely remove ISI.In addition, the sequences with T-ZCZ windows have a great advantage because the number of users isnot limited by the number of sequences for one user. This restriction can not be broken through in otherschemes, such as complete complementary sequences etc. So it can be applied in multi-user systems verywell. We describe the T-ZCZ Keying scheme and discuss the system modeling, generation and selection ofthe sequences with TCZ windows, performance evaluati on and simulations etc. in the paper. Results showthat the sequences with T-ZCZ windows can eectiv el y remove the ISI and are available to be constructedfor multi-user. It has better BER performance with higher data transmission rate in multipath Infraredchannels for multiple users.The paper will be organized as follows: In section 2, we give de“nition of Ear ZCZ windows and show theconstruction method of T-ZCZ sequences. Then we s how the DSSS scheme with T-ZCZ keying in section3. In addition, the mathematic modeling of this schem e is presented in Section 4. And then in section 5 thesimulations are done and analysis about the performance is given. Finally, a conclusion is drawn in section6.