3,652 research outputs found
A Direct Construction of Prime-Power-Length Zero-Correlation Zone Sequences for QS-CDMA System
In recent years, zero-correlation zone (ZCZ) sequences are being studied due
to their significant applications in quasi-synchronous code division multiple
access (QS-CDMA) systems and other wireless communication domains. However, the
lengths of most existing ZCZ sequences are limited, and their parameters are
not flexible, which are leading to practical limitations in their use in
QS-CDMA and other communication systems. The current study proposes a direct
construction of ZCZ sequences of prime-power length with flexible parameters by
using multivariable functions. In the proposed construction, we first present a
multivariable function to generate a vector with specific properties; this is
further used to generate another class of multivariable functions to generate
the desired -ZCZ sequence set, where is a prime
number, are positive integers, and . The constructed ZCZ
sequence set is optimal for the binary case and asymptotically optimal for the
non-binary case by the \emph{Tang-Fan-Matsufuji} bound. Moreover, a relation
between the second-order cosets of first-order generalized Reed-Muller code and
the proposed ZCZ sequences is also established. The proposed construction of
ZCZ sequences is compared with existing constructions, and it is observed that
the parameters of this ZCZ sequence set are a generalization of that of in some
existing works. Finally, the performance of the proposed ZCZ-based QS-CDMA
system is compared with the Walsh-Hadamard and Gold code-based QS-CDMA system
A Direct Construction of Optimal Symmetrical Z-Complementary Code Sets of Prime Power Lengths
This paper presents a direct construction of an optimal symmetrical
Z-complementary code set (SZCCS) of prime power lengths using a multi-variable
function (MVF). SZCCS is a natural extension of the Z-complementary code set
(ZCCS), which has only front-end zero correlation zone (ZCZ) width. SZCCS has
both front-end and tail-end ZCZ width. SZCCSs are used in developing optimal
training sequences for broadband generalized spatial modulation systems over
frequency-selective channels because they have ZCZ width on both the front and
tail ends. The construction of optimal SZCCS with large set sizes and prime
power lengths is presented for the first time in this paper. Furthermore, it is
worth noting that several existing works on ZCCS and SZCCS can be viewed as
special cases of the proposed construction
New Constructions of Zero-Correlation Zone Sequences
In this paper, we propose three classes of systematic approaches for
constructing zero correlation zone (ZCZ) sequence families. In most cases,
these approaches are capable of generating sequence families that achieve the
upper bounds on the family size () and the ZCZ width () for a given
sequence period ().
Our approaches can produce various binary and polyphase ZCZ families with
desired parameters and alphabet size. They also provide additional
tradeoffs amongst the above four system parameters and are less constrained by
the alphabet size. Furthermore, the constructed families have nested-like
property that can be either decomposed or combined to constitute smaller or
larger ZCZ sequence sets. We make detailed comparisons with related works and
present some extended properties. For each approach, we provide examples to
numerically illustrate the proposed construction procedure.Comment: 37 pages, submitted to IEEE Transactions on Information Theor
Direct Construction of Optimal Z-Complementary Code Sets for all Possible Even Length by Using Pseudo-Boolean Functions
Z-complementary code set (ZCCS) are well known to be used in multicarrier
code-division multiple access (MCCDMA) system to provide a interference free
environment. Based on the existing literature, the direct construction of
optimal ZCCSs are limited to its length. In this paper, we are interested in
constructing optimal ZCCSs of all possible even lengths using Pseudo-Boolean
functions. The maximum column sequence peakto-man envelop power ratio (PMEPR)
of the proposed ZCCSs is upper-bounded by two, which may give an extra benefit
in managing PMEPR in an ZCCS based MC-CDMA system, as well as the ability to
handle a large number of users
Cross Z-Complementary Pairs for Optimal Training in Spatial Modulation Over Frequency Selective Channels
The contributions of this article are twofold: Firstly, we introduce a novel class of sequence pairs, called “cross Z-complementary pairs (CZCPs),” each displaying zero-correlation zone (ZCZ) properties for both their aperiodic autocorrelation sums and crosscorrelation sums. Systematic constructions of perfect CZCPs based on selected Golay complementary pairs (GCPs) are presented. Secondly, we point out that CZCPs can be utilized as a key component in designing training sequences for broadband spatial modulation (SM) systems. We show that our proposed SM training sequences derived from CZCPs lead to optimal channel estimation performance over frequency-selective channels
Near-Optimal Zero Correlation Zone Sequence Sets from Paraunitary Matrices
Zero correlation zone (ZCZ) sequence sets play an important role in interference-free quasi-synchronous code-division multiple access communications. In this paper, for the first time, we investigate the periodic correlation properties of polyphase sequences obtained from paraunitary (PU) matrices, which shows the inherent relationship between PU matrix and ZCZ sequence sets. Our investigation suggests that any arbitrary PU matrix can produce ZCZ sequence sets by controlling its expanded form. The key idea is to impose certain restrictions on the expanded forms of the PU matrices to enable precise computation of the periodic correlation functions of the constructed sequences. We show that our proposed construction leads to near-optimal ZCZ sequence sets with regard to the ZCZ set size upper bound
On the Pricing of Forward Starting Options under Stochastic Volatility
We consider the problem of pricing European forward starting options in the presence of stochastic volatility. By performing a change of measure using the asset price at the time of strike determination as a numeraire, we derive a closed-form solution based on Heston’s model of stochastic volatility
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