Zero Correlation Zone Sequence Research Articles

Novel quadriphase ZCZ sequences for QS-CDMA systems

In this article, a novel method for constructing quadriphase Zero Correlation Zone (ZCZ) sequence sets based on the mutually orthogonal complementary sets (MOCS) matrix and polyphase perfect sequence is presented. Based on the obtained MATLAB results in terms of correlation functions, it can be mentioned that the resultant ZCZ set is suitable for quasi-synchronous Code Division Multiple Access (QS-CDMA) systems. The obtained sequence sets are near-optimal concerning mathematical bound, and their construction is more flexible than other polyphase ZCZ constructions. Furthermore, their parameters can be chosen flexibly.

Exact Analysis of MIMO Channel Estimation Based on Superimposed Training

In this paper, channel estimation capabilities of a multiple-input multiple-output (MIMO) system using superimposed training sequences are investigated. A new expression for estimation-error variance is derived. It is shown that the training sequences must be balanced and must have specific correlation properties. The latter are required only in a specific zone. Sequences that satisfy these criteria exist and are referred to as zero-correlation zone (ZCZ) solutions. Consequently, by using balanced ZCZ sequences, harmful direct current (DC) offset can be removed. Owing to their zero-cross correlation, interference from other transmitting antennas may be eliminated. Furthermore, a closed-form expression of the estimation-error variance can be obtained due to their impulse-like autocorrelation. To increase the number of antennas in the MIMO system, a new construction of ZCZ sequence set is proposed, in which all sequences are balanced

Construction of spectrally-null-constrained zero-correlation zone sequences with flexible support

Construction of spectrally-null-constrained zero-correlation zone sequences with flexible support

Accurate Analysis of Implicit SISO Channel Estimation Without DC Offset Using ZCZ Training Sequence

In this letter, an accurate analysis of implicit single-input single-output (SISO) channel estimation is provided. The appropriate correlation properties of the training sequence that result in a closed form solution for the variance of the channel estimate were derived. Indeed, it was shown that only a specific zone in the autocorrelation of the training sequence needs to be equal to zero. As a result, it is now possible to find sequences that simultaneously satisfy the balance and autocorrelation property. In fact, only a special type of sequence called zero correlation zone (ZCZ) sequences have this property and therefore can be used to provide an optimal implicit channel estimation performance when the channel length is inside the zero zone. In addition, by using balanced ZCZ sequences, the harmful Direct Current (DC) offset can be directly removed. Consequently, balanced ZCZ sequences greatly simplifies the implementation of the implicit channel estimation method.

Construction and Assignment of Orthogonal Sequences and Zero Correlation Zone Sequences Over GF(p)

Orthogonal sequences can be assigned to a regular tessellation of hexagonal cells, typical for synchronised code-division multiple-access (S-CDMA) systems. The sequences within any cell should both be orthogonal in the adjacent cells and require a sufficient number of users in each cell. However, for binary sequences, the capacity of communication system is limited. So, a new family of non-binary orthogonal sequences is constructed, which has more sequences per cell than binary sequences in the network. Next, an efficient assignment of these orthogonal sequence sets to a regular tessellation of hexagonal cells is given, and also the sequence sets have large re-use distance. Finally, based on above the construction, we construct a family of orthogonal sequences with zero correlation zone (ZCZ) property which can reduce the interference among users in a multi-path environment. The constructed ZCZ sequences can be applied to the quasi-synchronous CDMA (QS-CMDA) spread spectrum systems. And the assignment of sequences has the same re-use distance.

Construction of Multiple Optimal Polyphase Zero Correlation Zone Sequence Sets With Inter-Set Zero Cross-Correlation Zone

Based on DFT matrices and no-hit-zone (NHZ) frequency hopping sequence sets, a construction of multiple optimal polyphase zero correlation zone sequence sets with inter-set zero cross-correlation zone (ZCCZ) is proposed. The parameters of each subset are optimal, and arbitrary two sequences from different subsets have the same inter-set ZCCZ. Furthermore, new NHZ frequency hopping sequence sets are proposed, which can be used in the construction of multiple polyphase ZCZ sequence sets with inter-set ZCCZ. The resultant sequence sets presented in this letter can be applied to multi-cell QS-CDMA systems.

Generation Method of Two-Dimensional Optical ZCZ Sequences with High Correlation Peak Value

In this paper, we propose new generation methods of two-dimensional (2D) optical zero-correlation zone (ZCZ) sequences with the high peak autocorrelation amplitude. The 2D optical ZCZ sequence consists of a pair of a binary sequence which takes 1 or 0 and a bi-phase sequence which takes 1 or -1, and has a zero-correlation zone in the two-dimensional correlation function. Because of these properties, the 2D optical ZCZ sequence is suitable for optical code-division multiple access (OCDMA) system using an LED array having a plurality of light-emitting elements arranged in a lattice pattern. The OCDMA system using the 2D optical ZCZ sequence can be increased the data rate and can be suppressed interference by the light of adjacent LEDs. By using the proposed generation methods, we can improve the peak autocorrelation amplitude of the sequence. This means that the BER performance of the OCDMA system using the sequence can be improved.

Construction of optimal zero correlation zone sequence set

Construction of optimal zero correlation zone sequence set

Spread Spectrum Sensing Based on ZCZ Sequences for the Diagnosis of Noisy Wired Networks

Spread spectrum reflectometry has been shown to be an effective method for continuous health monitoring of electrical systems in many different applications. The suitability of Zero Correlation Zone (ZCZ) sequences in Sequence Time Domain Reflectometry (STDR) method has been demonstrated in a previous work. In fact, the ZCZ-STDR method showed excellent potential for simultaneous diagnosis of multiple cables. This paper focuses on evaluating the noise robustness and the effect of branched wire networks on the performance of both STDR and Spread Spectrum Time Domain Reflectometry (SSTDR) methods based on ZCZ sequences.

Adequate spreading codes to reduce MAI in quasi‐synchronous MC‐DS‐CDMA system

In this study, the authors consider the effect of multiple access interference (MAI) on the performance of a quasi-synchronous multicarrier direct-sequence code-division multiple access (QS-MC-DS-CDMA) system. An analytical expression of the bit error rate (BER) is derived for a QS-MC-DS-CDMA system over additive white Gaussian noise channel. The BER performance degradation is proportional to the squares of the even correlation function (ECF) and odd correlation function (OCF) of the spreading codes. The obtained results show that the adequate spreading code is a set of binary zero correlation zone sequences with both zero ECF and OCF. The construction of the latter codes remains a challenge for researchers in the field of code design.

Polyphase zero correlation zone sequences from generalised bent functions

Sequence families with zero correlation zone (ZCZ) have been extensively studied in recent years due to their important applications in quasi-synchronous code-division multiple-access (QS-CDMA) systems. To accommodate multiuser environments, multiple ZCZ sequence sets with low inter-set cross-correlation are expected. In this paper, we propose a construction of polyphase ZCZ sequences based on generalised bent functions. Moreover, multiple polyphase ZCZ sequence sets with good inter-set cross-correlation are presented. Each generated ZCZ sequence set is optimal with respect to the Tang-Fan-Matsufuji bound.

Constructions of polyphase ZCZ sequence sets with low cross‐correlation property

Zero correlation zone (ZCZ) sequences have received much research attention in many practical applications, such as quasi-synchronous code-division multiple-access systems and MIMO systems. In this study, three constructions of multiple polyphase ZCZ sequence sets with low inter-set cross-correlation property are proposed. The resultant periodic ZCZ sequence sets are optimal with respect to the theoretical bound and have new parameters uncovered in the literature. Consequently, a great deal of flexibility may be provided in the choice of periodic optimal ZCZ sequence sets with good inter-set cross-correlation property for their applications.

A Generic Construction of Mutually Orthogonal Optimal Binary ZCZ Sequence Sets

In this letter, a generic method to construct mutually orthogonal binary zero correlation zone (ZCZ) sequence sets from mutually orthogonal complementary sequence sets (MOCSSs) with certain properties is presented at first. Then MOCSSs satisfying conditions are generated from binary orthogonal matrices with order N×N, where N=p-1, p is a prime. As a result, mutually orthogonal binary ZCZ sequence sets with parameters (2N2,N,N+1)-ZCZ can be obtained, the number of ZCZ sets is N. Note that each single ZCZ sequence set is optimal with respect to the theoretical bound.

A Novel Class of Structured Zero-Correlation Zone Sequence Sets

A Novel Class of Structured Zero-Correlation Zone Sequence Sets

Golay Complementary Sequence Sets With Large Zero Correlation Zones

Zero correlation zone (ZCZ) sequence sets and Golay complementary sets (GCSs) have different correlation properties and hence have different engineering applications. A number of constructions of ZCZ sequence sets and GCSs have been proposed, respectively, in the literature. In addition, some ZCZ sequence sets can be constructed from mutually orthogonal GCSs. In this paper, the relationship between GCSs and ZCZ sets is discovered further. We propose a new type of sequence sets which are ZCZ sequence sets and also GCSs. They are called the Golay-ZCZ sequence sets in this paper. Therefore, they have low peak-to-average power ratios when employed in OFDM systems due to the good autocorrelation properties of GCSs. Besides, the Golay-ZCZ sets possess zero autocorrelations and cross-correlations within their ZCZ and hence have the potential application to synchronization. Furthermore, a construction of Golay-ZCZ sequence family with flexible set sizes, various sequence lengths, and large ZCZ widths is proposed in this paper.

Efficient Mutually Orthogonal Golay Complementary Set-Based Zero-Correlation Zone Sequence Set Correlator

An efficient implementation of zero-correlation-zone (ZCZ) sequence set correlators is of particular interest for integrated circuit realizations of phase-coded continuous-wave multiple-input multiple-output radar systems. Such systems require a correlation with all transmitted sequence set members at every receiver. We present an approach for an efficient circuit realization of such a sequence set correlator for a subset of mutually orthogonal Golay complementary set-based ZCZ sequence sets. Furthermore, we analyze and optimize the resource requirement. A logarithmic instead of a linear growth of the required adders could be achieved by the proposed implementation.

Interference-free pilot design and channel estimation using ZCZ sequences for MIMO-OFDM-based C-V2X communications

Cellular vehicle-to-everything (C-V2X) communications is regarded as a promising and feasible solution for 5G-enabled vehicular communications and networking. In this paper, we investigate the pilot design and channel estimation problem in MIMO-OFDM-based C-V2X systems with severe co-channel interference due to spectrum reusing among different V2X communication links. By using zero-correlation zone (ZCZ) sequences, we provide an interference-free pilot design scheme and a corresponding time-domain (TD) correlation-based channel estimation (TD-CCE) method. We employ the ZCZ sequences from the same family set to be designed as the TD pilot symbols and guarantee the pilot sequeneces for neighboring V2X communication links are code-division multiplexing (CDM). The co-channel pilot interference of the deisgned pilot symbols can be effectively eliminated by exploiting the provided TD-CCE method. Simulation results indicate that the accuracy of channel estimation can be effectively improved by the proposed scheme, whose performance is close to that of the non-interference situation.

A Construction of Multiple Optimal ZCZ Sequence Sets With Good Cross Correlation

Zero correlation zone (ZCZ) sequences are a class of spreading sequences having ideal auto-correlation and cross correlation in a zone around the origin. They have been extensively studied in recent years due to their important applications in quasi-synchronous code division multiple access systems. In this paper, a construction of ZCZ sequence sets is proposed based on perfect nonlinear functions. It generates multiple ZCZ sequence sets with the properties: 1) each sequence is perfect in the sense that its out-of-phase auto-correlation is always zero; 2) each ZCZ sequence set is optimal with respect to the Tang–Fan–Matsufuji bound in which all the sequences are pairwise cyclically distinct; and 3) the maximum inter-set cross correlation of multiple sequence sets achieves the well-known Sarwate bound.

An asymmetric ZCZ sequence set with inter-subset uncorrelated property and flexible ZCZ length

In this paper, we propose a novel method for constructing new uncorrelated asymmetric zero correlation zone (UA-ZCZ) sequence sets by interleaving perfect sequences. As a type of ZCZ sequence set, an A-ZCZ sequence set consists of multiple sequence subsets. Different subsets are correlated in conventional A-ZCZ sequence set but uncorrelated in our scheme. In other words, the cross-correlation function (CCF) between two arbitrary sequences which belong to different subsets has quite a large zero cross-correlation zone (ZCCZ). Analytical results demonstrate that the UA-ZCZ sequence set proposed herein is optimal with respect to the upper bound of ZCZ sequence set. Specifically, our scheme enables the flexible selection of ZCZ length, which makes it extremely valuable for designing spreading sequences for quasi-synchronous code-division multiple-access (QS-CDMA) systems.

Construction of Zero Correlation Zone Sequence Sets over the 16-QAM Constellation

Construction of Zero Correlation Zone Sequence Sets over the 16-QAM Constellation