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 <inline-formula> <tex-math notation="LaTeX">({N}+1)/2 </tex-math></inline-formula> (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 <inline-formula> <tex-math notation="LaTeX">2^{\alpha } \pm 1 </tex-math></inline-formula>, where <inline-formula> <tex-math notation="LaTeX">\alpha </tex-math></inline-formula> is a positive integer. In this paper, we construct optimal OB-ZCPs of generic lengths <inline-formula> <tex-math notation="LaTeX">2^\alpha 10^\beta 26^\gamma +1 </tex-math></inline-formula> (where <inline-formula> <tex-math notation="LaTeX">\alpha,~\beta,~\gamma </tex-math></inline-formula> are non-negative integers and <inline-formula> <tex-math notation="LaTeX">\alpha \geq 1 </tex-math></inline-formula>) 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 <inline-formula> <tex-math notation="LaTeX">4 \times 10^{\beta -1} +1 </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">12 \times 26^{\gamma -1}+1 </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">12 \times 10^\beta 26^{\gamma -1}+1 </tex-math></inline-formula> through proper insertions of GCPs of lengths <inline-formula> <tex-math notation="LaTeX">10^\beta,~26^\gamma, \text {and } 10^\beta 26^\gamma </tex-math></inline-formula>, respectively. Our proposed OB-ZCPs have applications in communications and radar (as an alternative to GCPs).
For one-dimensional (1-D) sequences, many lower bounds on the maximum cross-correlations have been demonstrated. For example, bounds proposed by Welch, Levenstein, Liu
et al.
, and others are the ...lower bounds on the maximum cross-correlations of aperiodic 1-D sequence sets or quasi-complementary sequence sets (QCSSs). However, in recent times, two-dimensional (2-D) arrays have emerged with promising applications in wireless communication, such as ultra wide-band (UWB), 2-D synchronization, massive multiple-input multiple-output (MIMO), 2-D multi-carrier code division multiple access (2D-MC-CDMA), etc. Although the construction of a 2-D quasi-complementary array set (QCAS) exists in literature, the lower bound on the maximum cross-correlation
δ
max
of such a 2-D QCAS has not been reported previously. In this paper, we propose, for the first time lower bounds on the maximum cross-correlations of 2-D QCASs for both periodic and aperiodic cases. The existing lower bounds on the maximum cross-correlations of 1-D QCSSs and 1-D sequence sets can be deduced from the proposed lower bounds on the maximum cross-correlations of 2-D QCASs and 2-D array sets for certain cases.
In this work, we have proposed an intelligent and secure transceiver design and implemented over RF testbed for future wireless communication. To secure the communication, first of all, physical ...layer security (PLS) has been proposed for underlay multiple-input multiple-output cognitive radio network (MIMO-CRN) by using a bi-directional zero-forcing beamforming. Secondly, (PLS) has been proposed by using transmit beamforming for non-orthogonal multiple access (NOMA) over multiple cells and in the presence of primary user and secondary users. The proposed model has been extended for MIMO-NOMA over double cell and multiple scenarios. To improve further security an adaptive transceiver has been designed where parameter can be varied as per the system requirement and meantime, an intelligent received is developed in which parameter can be estimated through a blind process. The modulation format is also classified for single carrier, orthogonal frequency division multiplexing (OFDM) and MIMO through a statistical method. Finally, sequence design has been proposed to improve peak average power ratio for OFDM and multicarrier code division multiplexing (MC-CDMA). These sequences can also remove multiuse user interference for CDMA system over asynchronous system by improving the correlation properties within a code.
In this paper, we propose a height-dependency shaping parameter ( <tex-math notation="LaTeX">$m$ </tex-math>) and a height-dependency path-loss exponent for modelling small-scale Nakagami- <tex-math ...notation="LaTeX">$m$ </tex-math> fading and a large-scale path-loss model for unmanned aerial vehicle (UAV)-assisted network coded cooperation (UA-NCC) system. The statistical parameters such as mean, variance, and probability density function (PDF) of the total noise component (TNC) are analyzed for the proposed system model to achieve the error free communication. We derive spectral efficiency, throughput, and a closed-form outage probability for the UA-NCC system by considering height-dependency shaping parameter ( <tex-math notation="LaTeX">$m$ </tex-math>) and the height-dependency path-loss exponent among ground-to-air (G2A) and air-to-ground (A2G) links, and Rayleigh channel distribution among ground users. The analytical result is validated with simulation results and compared it with the existing work (Rayleigh and Rician fading channel distribution). However, the better performance in the case of the proposed work comes over the existing state-of-the-art (Rayleigh and Rician fading distribution environment) after a UAV height of 10 m.
The zero correlation zone (ZCZ) ratio, i.e., the ratio of the width of the ZCZ and the length of the sequence plays a major role in reducing interference in an asynchronous environment of ...communication systems. However, to the best of the authors knowledge, for q = 2, the highest ZCZ ratio for even-length Zcomplementary pairs which are directly constructed using generalized Boolean functions (GBFs), is 2/3. In this letter, we present a direct construction of q-ary even-length Z-complementary pairs through GBFs, which can achieve aZCZ ratio of 3/4.In general, the constructed q-ary even-length Z-complementary pairs are of length 2 m-1 + 2 (m ∈ Z + ), having a ZCZ width of 2m -2 + 2 π(m-3) + 1 where π is a permutation over m - 2 variables.
This paper presents a direct construction of novel type cross Z-complementary sequence sets (CZCSSs), whose aperiodic correlation sums exhibit zero correlation zones at both the front-end and ...tail-end shifts. CZCSS can be regarded as an extension of the symmetrical Z-complementary code set (SZCCS). The available construction of SZCCS has a limitation on the set size, with a maximum set size of 8. The proposed generalized Boolean function-based construction can generate CZCSS/SZCCS of length in the form of a non-power-of-two with variable set size
2
n
+
1
, where each code has
2
n
+
1
constituent sequences. The proposed construction also yields cross Z-complementary pairs and cross Z-complementary sets with a larger number of constituent sequences compared to the existing work.
Spatial multiplexing is an important factor usable for improving the throughput of future millimeter-wave (mm-wave) backhaul links. One conventional strategy in mm-wave multiple-input multiple-output ...(MIMO) systems uses densely packed antennas and exploits the spatial signature of multiple paths. Meanwhile, spatial multiplexing over a single line-of-sight (LoS) path, known as LoS MIMO communication, offers an alternative option with widely spaced antennas exploiting the phases of spherical waves. In this paper, we first show that those two conventional approaches exploit two different degrees in the channel matrices, which we denote as inter - and intra -path multiplexing, respectively. Then, we show that the two kinds of spatial multiplexing can be jointly exploited and identify their different requirements on system design. Fulfilling all requirements simultaneously, we propose a system with multiple widely spaced subarrays. With the help of analog beamforming, the intra-path multiplexing of conventional LoS MIMO systems can be introduced to other non-LoS paths owing to its robustness. Merging the two kinds of spatial multiplexing in a combined channel model and connecting it with a hybrid beamforming architecture, the proposed system achieves spatial multiplexing of a higher order than conventional ones. Simulation results for a backhaul scenario illustrate that the channel of the proposed method has higher ranks than that of conventional approaches.
A pair of the complex-valued sequences is called a <inline-formula><tex-math notation="LaTeX">Z</tex-math></inline-formula>-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 <inline-formula><tex-math notation="LaTeX">2^h</tex-math></inline-formula>-ary (<inline-formula><tex-math notation="LaTeX">h</tex-math></inline-formula><inline-formula><tex-math notation="LaTeX">\in</tex-math></inline-formula><inline-formula><tex-math notation="LaTeX">\mathbb {N}</tex-math></inline-formula>) type-II ZCPs of length <inline-formula><tex-math notation="LaTeX">2^mP</tex-math></inline-formula> with ZCZ width <inline-formula><tex-math notation="LaTeX">2^mP</tex-math></inline-formula><inline-formula><tex-math notation="LaTeX">+1-</tex-math></inline-formula><inline-formula><tex-math notation="LaTeX">P</tex-math></inline-formula>, where <inline-formula><tex-math notation="LaTeX">m</tex-math></inline-formula> and <inline-formula><tex-math notation="LaTeX">P</tex-math></inline-formula> are positive integers, using the multivariable function. The proposed type-II ZCPs feature the optimal case, i.e., <inline-formula><tex-math notation="LaTeX">Z</tex-math></inline-formula><inline-formula><tex-math notation="LaTeX">\le</tex-math></inline-formula><inline-formula><tex-math notation="LaTeX"> N</tex-math></inline-formula><inline-formula><tex-math notation="LaTeX">-</tex-math></inline-formula>1 for the lengths in the form of power-of-two and asymptotically optimal for other even lengths.
Blind modulation classification (MC) is an integral part of designing an adaptive or intelligent transceiver for future wireless communications. Blind MC has several applications in the adaptive and ...automated systems of sixth generation (6G) communications to improve spectral efficiency and power efficiency, and reduce latency. It will become a integral part of intelligent software-defined radios (SDR) for future communication. In this paper, we provide various MC techniques for orthogonal frequency division multiplexing (OFDM) signals in a systematic way. We focus on the most widely used statistical and machine learning (ML) models and emphasize their advantages and limitations. The statistical-based blind MC includes likelihood-based (LB), maximum a posteriori (MAP) and feature-based methods (FB). The ML-based automated MC includes k-nearest neighbors (KNN), support vector machine (SVM), decision trees (DTs), convolutional neural networks (CNNs), recurrent neural networks (RNNs), and long short-term memory (LSTM) based MC methods. This survey will help the reader to understand the main characteristics of each technique, their advantages and disadvantages. We have also simulated some primary methods, i.e., statistical- and ML-based algorithms, under various constraints, which allows a fair comparison among different methodologies. The overall system performance in terms bit error rate (BER) in the presence of MC is also provided. We also provide a survey of some practical experiment works carried out through National Instrument hardware over an indoor propagation environment. In the end, open problems and possible directions for blind MC research are briefly discussed.
In this paper, a blind symbol timing offset (STO) estimation method is proposed for offset quadrature phase‐shift keying (OQPSK) modulated signals, which also works for other linearly modulated ...signals (LMS) such as binary‐PSK, QPSK, π/4‐QPSK, and minimum‐shift keying. There are various methods available for blind STO estimation of LMS; however, none work in the case of OQPSK modulated signals. The popular cyclic correlation method fails to estimate STO for OQPSK signals, as the offset present between the in‐phase (I) and quadrature (Q) components causes the cyclic peak to disappear at the symbol rate frequency. In the proposed method, a set of close and approximate offsets is used to compensate the offset between the I and Q components of the received OQPSK signal. The STO in the time domain is represented as a phase in the cyclic frequency domain. The STO is therefore calculated by obtaining the phase of the cyclic peak at the symbol rate frequency. The method is validated through extensive theoretical study, simulation, and testbed implementation. The proposed estimation method exhibits robust performance in the presence of unknown carrier phase offset and frequency offset.
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