New binary sequences with zero-correlation durationfor approximately synchronised CDMA

Spreading Sequence Design and Theoretical Limits for Quasisynchronous CDMA Systems

“…Other binary GO sequences can be obtained from Gold sequences, Hadamard matrices, and so forth [29,40].…”

“…Therefore, in designing a QS-CDMA system, in order to reduce or eliminate the multiple access interference and multipath interference, it is generally required to design a set of spreading sequences having an orthogonal zone Z o satisfying (40). For a typical LAS-CDMA2000 system [19], the key design parameters are frame length: 20 ms, chip rate: 1.2288 Mcps, channel spacing: 1.25 MHz, LA code number: 8, LA "pulse" number/LA code: 16, LS code number/LA "pulse": 32 × 2 (Z o = 4), modulation: 16 QAM (high mobility up to 500 km/h), 32 QAM (medium mobility up to 100 km/h), duplex: 2 × 1.25 MHz frequency-division duplex (FDD) or time-division duplex (TDD), maximum apparent data rate 1634.4 kpbs (high mobility) and 2048 kbps (medium mobility).…”

“…These ideas, in fact, open a new direction in spreading sequence design. Recently, the investigation of QS-CDMA systems has been very active [19,20,21,22,23,24,25,26,27,28,29,30,31], many of the QS-CDMA systems are based on the use of GO/GQO sequences [4,29,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55]. It should be noted that the GO is also called zero correlation zone (ZCZ) [38], interference free windows (IFW) or zero correlation window (ZCW) [19], zero correlation duration (ZCD) [40], or no hit zone (NHZ) if applies to frequency/time hopping systems, where the so-called Hamming correlation play a major role on the multiaccess interference [54]; the GQO is all the previous periodic and aperiodic sequence bounds, such as Welch bound [9], Sarwate bound [11], Levenshtein bo...…”

New construction of quaternary low correlation zone sequence sets from binary low correlation zone sequence sets

“…Quasi-synchronous code division multiple access (QS-CDMA) system is the system devised for such environment [2]. In order to suppress the inter-user interference from quasisynchronized signals, low correlation zone (LCZ) sequences have been used as signature sequences in the QS-CDMA systems [2]- [4]. Let S be a set of M sequences of period N .…”

New Family of Spreading Sequences for Quasi-Synchronous CDMA Systems

“…In accordance with the property of QS-CDMA systems, Fan et al [5] proposed new spreading sequences with zero-correlation zone (ZCZ) for QS-CDMA systems; that is, periodic autocorrelation functions are zero at a specific continuous shift zone on both sides of the zero-shift, and periodic cross-correlation functions are also zero at the specific continuous shift zone. How to design ZCZ sequences is the highlight both at home and abroad [6][7][8][9][10].…”