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Zero correlation zone (ZCZ) sequence sets play an important role in reducing multi-cell interference in quasi-synchronous code-division multiple access (QS-CDMA) systems. In this paper, we propose two novel classes of ZCZ sequence sets based on orthogonal matrices and uncorrelated ZCZ sequence sets. The subsets of the proposed ZCZ sequence sets are ZCZ sequence sets of their own. Moreover, they display inter-set zero cross-correlation zone (ZCCZ) among two different subsets. The proposed ZCZ sequence sets are optimal with respect to the Tang-Fan-Matsufuji bound. [ABSTRACT FROM AUTHOR]

The construction method of Type-Ⅱ even-length Z-complementary pair (ZCP) was proposed by using the inter-leaving technique.The basic framework of interleaving structure with Golay complementary pair (GCP) and its mate as the basic sequences was proposed.Furthermore, the necessary conditions were given for the framework in order that the resulting ZCP could have large zero correlation zone (ZCZ) width.The main parameter form of the constructed ZCP was((2k+1)N,(2k+1)N-k)-ZCP, where N was the length of the chosen GCP.Although not all even lengths can be covered, the constructed ZCP has the ZCZ width that can achieve or approach the upper bound of Type-Ⅱ even-length binary ZCP, and has small peak-to-mean envelope power ratio whose value is less than or equal to 4.The resultant sequences can be applied to multi-carrier spread spectrum system to eliminate more asynchronous interference and reduce nonlinear distortion.

Copyright of Journal on Communication / Tongxin Xuebao is the property of Journal on Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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.

In this letter, we apply code division multiple access (CDMA) technology to an integrated visible light communication and positioning (VLCP) system, which can recover the original user data and obtain the positioning information simultaneously. The two unipolar code sets with flexible construction methods, zero cross correlation (ZCC) code set and optical zero correlation zone (OZCZ) code set, are adopted and evaluated in the proposed system. Compared with the traditional spreading code set, these two code sets can directly suit to the VLCP system with higher transmission efficiency. In addition, the results show that zero correlation properties of OZCZ code set can effectively overcome non-perfect synchronization effects in the quasi-synchronous (QS) system. In a space of 6 m $\times $ 6 m $\times $ 5 m, the bit error rate (BER) of $1.58\times {10^{-3}}$ and average positioning error of 2.73 cm are successfully achieved in the synchronous system, while the BER of $1.60\times {10^{-3}}$ and average positioning error of 3.62 cm are realized in the QS system. [ABSTRACT FROM AUTHOR]

Spatial modulation (SM) is one special type of multiple-input multiple-output (MIMO) technique whose advantage is that only one radio-frequency (RF) chain is needed. Recently, the so-called cross Z-complementary pair (CZCP) was proposed as the SM training sequence. Optimal channel estimation performance over frequency-selective channels can be achieved since the CZCPs have the specific zero correlation zone (ZCZ) for auto-correlation and cross-correlation sums. However, the ZCZ width of the CZCP is theoretically upper bounded by half sequence length. In this paper, the CZCP is extended to the cross Z-complementary set (CZCS) to have larger ZCZ width which can be used in SM to combat larger delay spread. Several generic constructions of CZCSs with large ZCZ widths and flexible lengths are proposed in this paper. Even the perfect CZCS, whose ZCZ width has the maximum value, can be obtained. Numerical simulations demonstrate that the proposed CZCS-based training sequence can tolerate large delay spreads to improve the channel estimation performance in SM. [ABSTRACT FROM AUTHOR]

Z-complementary code sets (ZCCSs) can support interference-free multi-carrier code-division multiple access (MC-CDMA) in quasi-synchronous channels due to their favourable correlation properties. In this letter, based on the existing optimal ZCCSs and CCCs, we propose new class of optimal ZCCSs using Kronecker product. The resultant sequence sets have enlarged set size and sequence lengths which have not been reported before. [ABSTRACT FROM AUTHOR]

Sequences and their correlation properties have been extensively studied due to their broad applications. In this paper, we develop a connection between sequences and well-studied combinatorial objects, circular Florentine arrays. This connection allows us to derive two types of sequences with good correlation properties. The first type consists of sequences having optimal correlation with respect to the Sarwate bound. Our constructions are based on perfect polyphase sequences. The number of perfect sequences with optimal correlation depends on the existence of circular Florentine arrays, which improves the previous known results. The second type is about multiple ZCZ sequence sets with low inter-set cross-correlation. Each generated ZCZ sequence set is optimal with respect to the Tang-Fan-Matsufuji bound, and each sequence in each set is perfect. In addition, any two sequences from distinct ZCZ sequence sets possess optimal inter-set cross-correlation with respect to the Sarwate bound. Compared with the previous results, the number of ZCZ sequence sets with optimal inter-set cross-correlation property is improved, because of the existence of circular Florentine arrays. [ABSTRACT FROM AUTHOR]

For various quasi-synchronous (QS) CDMA systems, to reduce or eliminate the multiple access interference and multipath interference, it is required to design a set of spreading sequences which are mutually orthogonal within a designed shift zone. In this article, we demonstrate that a concept of irregular spatial assignment, with flexibility to assign different number of users to different cells, can be used to provide the maximal number of orthogonal sequences in any three adjacent cells in networks with a regular tessellation of hexagonal cells. We first consider p-phase spreading sequences of length p m (thus nonbinary p-valued sequences) suitable for synchronous (S)-CDMA applications, for p > 3 , and give an efficient design method for reaching the maximal cardinality achievable (being p m ). A simple solution for a flexible assignment of our orthogonal sets of spreading sequences to the cells in hexagonal networks is given. To address QS-CDMA applications as well, an efficient method to combine these orthogonal sequences with Zadeoff–Chu sequences is proposed for the purpose of designing sets of zero correlation zone (ZCZ) sequences (within a certain shift zone) with optimal parameters, thus reaching the Tang–Fan–Matsufuji bound. A similar design framework, based on the use of some special classes of Boolean functions, is then employed for the binary case to provide the maximum cardinality of pairwise orthogonal sequences of length 2 m through this irregular spatial assignment. This improves upon the best known results achieved in Zhang et al. (IEEE Trans Inf Theory 62:3757–3767, 2016), which assigns 2 m - 2 orthogonal sequences (users) per cell, by doubling the number of users in one third of the network. [ABSTRACT FROM AUTHOR]

The Z-complementary code set (ZCCS) is well-known for being used in multicarrier code-division multiple access (MC-CDMA) systems to provide interference-free communication in a quasi-synchronous environment. Based on the existing literature, the direct constructions of optimal ZCCSs are limited to their lengths. This letter proposes a direct construction of optimal ZCCSs for all possible even lengths using generalized Boolean functions. The maximum column sequence peak-to-mean envelope power ratio (PMEPR) of the proposed ZCCSs is upper-bounded by two which can benefit in managing PMEPR over a ZCCS-based MC-CDMA system. [ABSTRACT FROM AUTHOR]

The construction of zero correlation zone (ZCZ) sequence set was researched based on perfect sequences and orthogonal sequence set.With the method of constructing on finite field,the optimal zero correlation zone sequence sets were constructed,by changing the set O and R,multiple shift distinct ZCZ sequence sets could be obtained and the number of sets could be expended.Through the constructions,the length of ZCZ can be chosen flexibly to meet the requirements of different systems for channel delay under the condition of p= Z N or p n = Z N ,where p is a prime.

A pair of the complex-valued sequences is called a $Z$ -complementary pair (ZCP) if it has zero aperiodic auto-correlation sum (AACS) for all time-shifts within a certain region, commonly known as zero correlation zone (ZCZ). Type-II ZCPs have the ZCZ around the end time shifts position. Till the date, no direct construction technique is available for type-II ZCPs of length non-power-of-two. For the first time, we have advocated a direct construction of $2^h$ -ary ($h$ $\in$ $\mathbb {N}$) type-II ZCPs of length $2^mP$ with ZCZ width $2^mP$ $+1-$ $P$ , where $m$ and $P$ are positive integers, using the multivariable function. The proposed type-II ZCPs feature the optimal case, i.e., $Z$ $\le$ $ N$ $-$ 1 for the lengths in the form of power-of-two and asymptotically optimal for other even lengths. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Quasi-complementary sequence sets (QCSSs) play an important role in multi-carrier code-division multiple-access (MC-CDMA) systems. They can support more users than perfect complementary sequence sets in MC-CDMA systems. It is desirable to design QCSSs with good parameters that are a trade-off of large set size, small periodic maximum magnitude correlation and small alphabet size. The main results are to construct new infinite families of QCSSs that all have small alphabet size and asymptotically optimal periodic maximum magnitude correlation. In this paper, we propose three new constructions of QCSSs using additive characters over finite fields. Notably, these QCSSs have new parameters and small alphabet sizes. Using the properties of characters and character sums, we determine their maximum periodic correlation magnitudes and prove that these QCSSs are asymptotically optimal with respect to the lower bound. [ABSTRACT FROM AUTHOR]

Easily and flexibly deployable ad-hoc communication networks emerging in tactical military or even civilian contexts, frequently suffer from poor synchronization due to lack of coordinating infrastructure. In addition to synchronization issues, and especially in military settings, security from the aspect of detectability is also of crucial importance. Imperfect synchronization can be dealt with by making use of Quasi-Synchronous Code Division Multiple Access (QS-CDMA), relying on Loosely Synchronous Codes to maintain orthogonality in the presence of limited time delays. Security, in terms of low probability of detection (LPD) from the standpoint of a malicious adversary, can be improved (reduced detection) by employing randomization techniques that disrupt the inherent structure of the transmitted QS-CDMA signals. This is based on the fact that QS-CDMA signals are Cyclostationary, having (almost) periodic Auto-Correlation functions (ACF) due to eminent signal periodicities (such as spreading code repetition). In this paper, we propose techniques to disturb the ACF and equivalently the Spectral Correlation function, and reduce the Degree of Cyclostationarity (DCS), our LPD measure. Specifically, we investigate randomization via 1) random per symbol time dithering and 2) random selection of spreading sequences, as well as a hybrid approach combining time dithering and code randomization. In all proposed techniques knowledge of the randomization pattern is not required at the legitimate receiver. We derive the Spectral Correlation function of the QS-CDMA signal under the proposed randomization schemes and compare it to simulations. We show through analysis and extensive numerical simulations that the proposed technique can reduce the DCS by almost two orders of magnitude. We also show that enhanced LPD can be achieved using the proposed techniques while sacrificing a part of the reduced time synchronization requirement. We further analyze the implications of the friendly receiver not knowing the randomization pattern and present results on the resulting communication performance. [ABSTRACT FROM AUTHOR]

One-dimensional (1-D) Golay complementary pair (GCP) and its extension Z-complementary pair (ZCP) with additional zero autocorrelation zone property have been widely studied in the literature. Recently, the investigation of 1-D GCPs have been extended to two-dimensional (2-D) and higher dimensional Golay complementary array pairs (GCAPs). In this article, the concept of zero correlation zone (ZCZ) is applied to 2-D GCAP and the 2-D Z-complementary array pair (ZCAP) is presented. Several constructions of ZCAPs are proposed in this article and the existence of ZCAPs is discussed as well. Based on the proposed constructions, 2-D ZCAPs are shown to exist for all sizes. Furthermore, an upper bound on the rectangular ZCZ size of the 2-D ZCAP is derived when both dimensions are odd. The proposed constructions can include ZCAPs which achieve the upper bound. [ABSTRACT FROM AUTHOR]

A pair of sequences is called a Z-complementary pair (ZCP) if it has zero aperiodic autocorrelation sums at each of the non-zero time-shifts within a certain region, called the zero correlation zone (ZCZ). ZCPs are categorised into two types: Type-I ZCPs and Type-II ZCPs. Type-I ZCPs have the ZCZ around the in-phase position and Type-II ZCPs have the ZCZ around the end-shift position. Till now only a few constructions of Type-II ZCPs are reported in the literature, and all have lengths of the form 2m ± 1 or N + 1 where N = 2a 10b 26c and a, b, c are non-negative integers. In this paper, we propose a recursive construction of ZCPs based on concatenation of sequences. Inspired by Turyn’s construction of Golay complementary pairs, we also propose a construction of Type-II ZCPs from known ones. The proposed constructions can generate optimal Type-II ZCPs with new flexible parameters and Z-optimal Type-II ZCPs with any odd length. In addition, we give upper bounds for the PMEPR of the proposed ZCPs. It turns out that our constructions lead to ZCPs with low PMEPR. [ABSTRACT FROM AUTHOR]

Z-complementary code sets (ZCCSs), extended from complete complementary codes (CCCs), have ideal correlations within a zone around the in-phase position named zero correlation zone (ZCZ). In this article, two classes of aperiodic ZCCSs with good cross-correlation subsets are investigated. They are multiple CCCs with inter-set zero cross-correlation zone (ZCCZ) property and multiple aperiodic ZCCSs with ideal inter-set aperiodic cross-correlation property respectively, the latter is referred to as an aperiodic inter-group complementary (IGC) code set and each ZCCS is called a group. First of all, based on polyphase paraunitary (PU) matrices and special permutation matrices, a construction of multiple polyphase CCCs with an inter-set ZCCZ is proposed. The obtained multiple CCCs have potential applications in interference-free multi-cell environments to support a large number of users. In addition, a construction of aperiodic polyphase IGC code sets is presented from polyphase PU matrices. We remark that different groups of the derived IGC code sets yield different constituent sequence lengths, thus they could provide a variety of quality of service (QoS) in quasi-synchronous multi-cell multi-rate communication systems. To the best of our knowledge, the aforementioned constructions of ZCCSs with good cross-correlation subsets based on PU matrices have not been reported in the literature. [ABSTRACT FROM AUTHOR]

Two dimensional (2-D) Z-complementary array pair (ZCAP) is a pair of 2-D arrays or matrices, whose 2-D auto-correlation sum gives zero value at all time shifts in a zone around the (0, 0) time shift, except the (0, 0) time shift. The zone is called the zero correlation zone (ZCZ). 2-D ZCAP has found application in 2-D synchronization, phased array antenna, ultra wide band (UWB) systems and so on. To the best of authors’ knowledge, most of the constructions of 2-D ZCAPs in the existing literature need special sequences at its intial stage. In this letter, for the first time, we propose a direct construction of 2-D ZCAPs of non-power-of-two sizes, which does not need any special sequence at the initial stage. The construction is based on generalized Boolean function (GBF) and thus facilitates rapid generation for use in several fields. [ABSTRACT FROM AUTHOR]

Copyright of Journal on Communication / Tongxin Xuebao is the property of Journal on Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this letter, a new construction of Z-complementary pairs (ZCPs) with more flexible lengths based on generalized Boolean functions is proposed. Except for the powers of two, the proposed ZCPs exist for all lengths with various widths of the zero correlation zone (ZCZ). There exists a trade-off between the sequence lengths and the ZCZ widths of the proposed ZCPs. Moreover, the peak-to-average power ratio (PAPR) properties of the constructed ZCPs are investigated in this letter. Therefore, the new sequences are useful in applications in communications due to their flexible lengths, various possible ZCZ widths, and good PAPR properties. [ABSTRACT FROM AUTHOR]

Based on Gray mapping, the properties of the autocorrelation sum of quadriphase Z-complementary pairs (QZCPs) are investigated. It is proved that both the real and imaginary parts of the sum equal zero modulo 2. Additionally, a novel construction that transforms binary ZCPs (BZCPs) into QZCPs is presented. The proposed construction can produce QZCPs, which are different to the ones from existing constructions, with the same zero-correlation-zone (ZCZ) width-length ratios (ZWLRs) as the employed BZCPs. [ABSTRACT FROM AUTHOR]

A pair of sequences is called a Z-complementary pair (ZCP) if it has zero aperiodic autocorrelation sums (AACSs) for time-shifts within a certain region, called zero correlation zone (ZCZ). Optimal odd-length binary ZCPs (OB-ZCPs) display closest correlation properties to Golay complementary pairs (GCPs) in that each OB-ZCP achieves maximum ZCZ of width $({N}+1)/2$ (where N is the sequence length) and every out-of-zone AACSs reaches the minimum magnitude value, i.e. 2. Till date, systematic constructions of optimal OB-ZCPs exist only for lengths $2^{\alpha } \pm 1$ , where $\alpha $ is a positive integer. In this paper, we construct optimal OB-ZCPs of generic lengths $2^\alpha 10^\beta 26^\gamma +1$ (where $\alpha,~\beta,~\gamma $ are non-negative integers and $\alpha \geq 1$) from inserted versions of binary GCPs. The key leading to the proposed constructions is several newly identified structure properties of binary GCPs obtained from Turyn’s method. This key also allows us to construct OB-ZCPs with possible ZCZ widths of $4 \times 10^{\beta -1} +1$ , $12 \times 26^{\gamma -1}+1$ and $12 \times 10^\beta 26^{\gamma -1}+1$ through proper insertions of GCPs of lengths $10^\beta,~26^\gamma, \text {and } 10^\beta 26^\gamma $ , respectively. Our proposed OB-ZCPs have applications in communications and radar (as an alternative to GCPs). [ABSTRACT FROM AUTHOR]

A pair of sequences is called odd-length binary Z-complementary pair (OB-ZCP) if it is of odd-length and has zero aperiodic autocorrelation sums (AACSs) for all time-shifts within a certain region around the in-phase position, commonly known as zero correlation zone (ZCZ). There are two types of OB-ZCPs, namely Type-I OB-ZCPs and Type-II OB-ZCPs. Type-I OB-ZCPs have ZCZ around the in-phase position. Type-II OB-ZCPs have the ZCZ around the end-shift position. An OB-ZCP (Type-I or Type-II) of odd-length $N$ is called Z-optimal if it achieves a maximum ZCZ width of $(N+1)/2$. To date, a systematic construction of Type-II Z-optimal OB-ZCPs exist only for very limited lengths of the form $2^{m}\pm 1$ , where $m$ is a positive integer. It employs insertion method and delete method on binary Golay complementary pairs (GCPs) of length $2^m$ derived from second order Reed-Muller codes. In this article, based on iterative insertion method, we construct Type-II Z-optimal OB-ZCPs of lengths $2^m+3$. [ABSTRACT FROM AUTHOR]

• This paper analyses some important measures responsible for the performance of ZCZ in quasi synchronous direct sequence (QS-DS) CDMA. • The BER and the MUI interference of binary and ternary spreading codes were investigated as functions of the codes' even and odd periodic correlation functions. • Numerical results based on availability of ZCZ codes in the existing literature is provided. Zero correlation zone (ZCZ) codes have been recently adopted for many communication systems based on code division multiple access (CDMA). In this paper, we focus on the use of ZCZ codes in quasi-synchronous direct-sequence (QS-DS) CDMA. To ensure Interference-free communication, spreading ZCZ codes must be carefully designed. Indeed, numerous ZCZ code constructions with various correlation properties have been proposed and studied in literature. However, most of them are not adequately designed for communication systems. Here, we aim at determining specific criteria in order to choose the suitable ZCZ code family. A new bit error rate (BER) for QS-DS-CDMA as a function of the code's even and odd periodic correlation functions (PCFs) is derived. It is shown that the adequate spreading codes are those with zero even and odd PCFs. [ABSTRACT FROM AUTHOR]

Visible light communication (VLC) is a promising technology for wireless communication networks. Optical code division multiple access (OCDMA) is a strong candidate for VLC-based applications. The predominant source of bit error in OCDMA is the multiple access interference (MAI). To eliminate MAI in synchronous OCDMA, zero cross correlation (ZCC) codes have been proposed. However, synchronization problems and multipath propagation introduce relative non-zero time delays. Therefore, the zero correlation zone (ZCZ) concept was introduced. In this paper, we propose a new method for generating ZCC codes. The proposed construction can accommodate any number of users with flexible Hamming weight. The numerical results obtained show that the proposed codes significantly reduce MAI, compared to ZCC, as well as ZCZ codes.

Based on orthogonal matrices,a construction of zero-correlation zone (ZCZ) periodic complementary sequence sets are proposed.The resultant ZCZ periodic complementary sets have flexible number of subsequences.Moreover,the ZCZ periodic complementary sequence sets are optimal.ZCZ periodic complementary sequence sets with flexible subsequences are more useful in communication systems.

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. [ABSTRACT FROM AUTHOR]

Visible light communication (VLC) is a promising technology for wireless communication networks. Optical code division multiple access (OCDMA) is a strong candidate for VLC-based applications. The predominant source of bit error in OCDMA is the multiple access interference (MAI). To eliminate MAI in synchronous OCDMA, zero cross correlation (ZCC) codes have been proposed. However, synchronization problems and multipath propagation introduce relative non-zero time delays. Therefore, the zero correlation zone (ZCZ) concept was introduced. In this paper, we propose a new method for generating ZCC codes. The proposed construction can accommodate any number of users with flexible Hamming weight. The numerical results obtained show that the proposed codes significantly reduce MAI, compared to ZCC, as well as ZCZ codes. [ABSTRACT FROM AUTHOR]

Noise Radar is a rapidly developing technology which uses noise or pseudo-noise waveforms as sounding signals to de- tect targets of interest. The advantages of such waveforms are no range nor velocity ambiguities, the possibility of using continuous waveform and low probability of intercept. However, the noise waveform correlation sidelobes are spread across the entire range–Doppler plane and their level is de- termined by the time-bandwidth product. Such sidelobes limit the detection capability in the multitarget environment. Several algorithms exist that decrease the sidelobe level and thus enhance dynamic range of the radar, but they are very susceptible to distortions in an analogue channel. In this paper the author presents a method to create low-sidelobe waveforms using a filtering algorithm designed for given channel, decreasing the analogue front-end impact on the final properties of the waveforms.

In the present paper, we propose ternary zero-correlation zone (ZCZ) sequence sets with ideal correlation properties for phase shifts within the ZCZ. The proposed ternary ZCZ sequence sets can be constructed from binary mutually orthogonal complementary sets (MOCS) and ternary perfect sequences. [ABSTRACT FROM AUTHOR]

Noise radars possess several advantageous properties, including low probability of detection and identification, especially when working in continuous-wave mode. One of the main drawbacks of such radars is the occurrence of the masking effect, when a weak target echo is masked by the sidelobes of a strong target echo. The sidelobes of the ambiguity function emerge on the level of the time–bandwidth product below the main peak and are spread in the entire range–Doppler plane. While most approaches to mitigate the masking effect focus on the processing of the received signal, it is possible to move the computation burden to the waveform design phase. This paper describes a filter-based method of creating noise-like waveforms that have very low sidelobes in the area of certain range and Doppler shifts. Both theoretical analysis and measurement results are presented and compared with the lattice filter method of masking effect cancellation. [ABSTRACT FROM PUBLISHER]

By interleaving multiple shift versions of complementary sequence, a new method of constructing inter-group complementary (IGC) sequences is proposed. The resultant sequence set has zero correlation zone (ZCZ) properties in each sequence group and any two sequences from different sequence groups possess ideal periodic cross-correlation properties. When a suitable shift sequence is chosen, the constructed IGC sequence set will be optimal in terms of the corresponding theoretical bound. Compared with the existing constructions of IGC sequences, the proposed construction method may provide not only flexible ZCZ width but also flexible element sequence length, which will ensure a more freedom for the design and realization of IGC wireless communication systems. [ABSTRACT FROM AUTHOR]

A new quasi-perfect discrete signal—ZCZ array pair which has good periodic correlation property and its con-struction method was proposed. Based on perfect array pair and orthogonal matrix, ZCZ array pairs set with certain vol-ume, family size and zero correlation zone can be synthesized through row or column interleaved technique when suitable shift sequences are selected. Except the binary case, the proposed technique can be applied to synthesize polyphase ZCZ array pairs set also. These ZCZ array pairs sets are feasible as multi-user signal, and extend the selectable scope of two-dimension perfect discrete signal.

This paper proposes a new interleaving rule, with which a new IBF (IBF, intertwined bridge function) is generated. Not only does the new intertwined bridge function have a zero correlation zone, but also its cross-correlation performance is ideal. An ultra-wideband system is introduced, which uses the intertwined bridge functions as the spreading code. The sequence of interleaved bridge function with zero autocorrelation bridge area and zero cross-correlation zones can better reduce multiple access interference and multipath interference. It is shown by the simulation results that the ultra-wideband systems using the interleaved bridge function as the spreading sequence have better error rate performance. [ABSTRACT FROM AUTHOR]

Noise Radar is a rapidly developing technology which uses noise or pseudo-noise waveforms as sounding signals to detect targets of interest. The advantages of such waveforms are no range nor velocity ambiguities, the possibility of using continuous waveform and low probability of intercept. However, the noise waveform correlation sidelobes are spread across the entire range--Doppler plane and their level is determined by the time-bandwidth product. Such sidelobes limit the detection capability in the multitarget environment. Several algorithms exist that decrease the sidelobe level and thus enhance dynamic range of the radar, but they are very susceptible to distortions in an analogue channel. In this paper the author presents a method to create low-sidelobe waveforms using a filtering algorithm designed for given channel, decreasing the analogue front-end impact on the final properties of the waveforms. [ABSTRACT FROM AUTHOR]

For an even-period binary Z-complementary pair (EB-ZCP), if it is not a Golay complementary pair (GCP), we show that Z ≤ N-2, where N and Z denote the sequence length and the zero correlation zone (ZCZ) width, respectively. This result partially answers the Fan-Yuan-Tu conjecture in 2007. In addition, we present a construction of EB-ZCPs with large ZCZ widths, where N=2m+1+2m and Z=2m+1. Interestingly, each of the proposed EB-ZCPs features zero out-of-phase aperiodic auto-correlation sums except for the time-shift of ±2m+1, thus displaying a very close correlation property to that of GCPs. [ABSTRACT FROM AUTHOR]

A set of binary codes is called a Z-complementary code set if the sum of the autocorrelation functions of the codes involved is zero in the zero correlation zone (ZCZ) except at zero shift. Comparing to the traditional complementary code sets, the Z-complementary code sets not only have more freedom on the code length, but also have much more mates. In this paper, lower bounds on periodic/aperiodic correlation of Z-complementary binary code sets with respect to the number of mates, family size, sequence length, the length of ZCZ, maximum periodic/aperiodic autocorrelation sidelobe inside the ZCZ and maximum periodic/aperiodic crosscorrelation value inside the ZCZ, are derived. The proposed lower bounds provide theoretical criteria for designing, optimizing and choosing Z-complementary code set in applications. [ABSTRACT FROM AUTHOR]

In this paper, a new construction of inter-group complementary (IGC) codes is proposed based on Z-complementary codes and perfect periodic cross-correlation (PPCC) codes. The correlation properties of the new generated IGC codes are as follows: (1) the autocorrelation sidelobe values of the codes are zeros in the zero correlation zone (ZCZ), (2) the cross-correlation values between different codes in the same group are zeros in the ZCZ, (3) the cross-correlation values between codes of different groups are zeros during the whole period. Comparing to the existed IGC codes, the ZCZ length of the generated IGC codes can be predefined flexibly; the number of groups and the number of codes in each group have more freedom according to the advantages of Z-complementary codes and PPCC codes. [ABSTRACT FROM AUTHOR]

Since it is known that interference with each sonar sensor could be effectively reduced when waveforms are appropriately designed for a Sonar Sensor Network (SSN), we provide a set of new ternary codes called optimized punctured Zero Correlation Zone sequence-pair set (ZCZPS) and provide a method to construct such codes. We study the codes' properties especially using the ambiguity function to analyze the nature of the output of the matched filter. We apply our provided ternary codes to the SSN as pulse compression codes for narrowband pulse signals and simulate the target detection performance of the system. Comparing with the classical periodic Gold sequences, our codes could improve the system detection performance. [ABSTRACT FROM AUTHOR]

A general construction of inter-group complementary (IGC) codes is proposed based on perfect complementary (PC) codes, interleaving operation, and the orthogonal matrix. The correlation properties of the newly constructed IGC codes can be described as follows: (1) the autocorrelation sidelobes of the codes are zeros in the zero correlation zone (ZCZ); (2) the cross-correlation functions (CCFs) between any two different codes of the same group are zeros in the ZCZ; (3) the CCFs between any two codes of different groups are zeros everywhere. The key point of this construction is that the ZCZ length of the generated IGC codes can be chosen flexibly. It is well known that there is a limitation between the ZCZ length and the number of mates; that is, the smaller is the length of ZCZ, the more are the IGC codes that can be generated. Therefore, if we can choose the ZCZ length of the IGC codes flexibly according to the requirement of the system, more users can be accommodated in the system. [ABSTRACT FROM AUTHOR]