Generalized multicarrier CDMA: Unification and linear equalization

Relying on block-symbol spreading and judicious design of user codes, this paper builds on the generalized multkarrier (GMC) quasisynchronous CDMA system that is capable of multiuser interference (MUI) elimination and intersymbol interference (ISI) suppression with guaranteed symbol recovery, regardless of the wireless frequency-selective channels. GMC-CDMA affords an all-digital unifying framework, which encompasses single-carrier and several multicarrier (MC) CDMA systems. Besides the unifying framework, it is shown that GMC-CDMA offers flexibility both in full load (maximum number of users allowed by the available bandwidth) and in reduced load settings. A novel blind channel estimation algorithm is also derived. Analytical evaluation and simulations illustrate the superior error performance and flexibility of uncoded GMC-CDMA over competing MC-CDMA alternatives especially in the presence of uplink multipath channels

Full-length non-linear binary sequences with Zero Correlation Zone for multiuser communications

The research on new sets of sequences to be used asspreading codes in multiple user communications is still an activearea, despite the great amount of literature available since manyyears on this topic. In fact, new paradigms like dense anddecentralized wireless networks, where there is no centralcontroller to assign the resources to the nodes, are revamping theinterest on large sets of sequences providing adequate correlationproperties to support a big number of nodes, in potentially hostilechannels. This paper focuses on the Zero Correlation Zone (ZCZ)property exhibited by a family of non-linear binary sequencesfeaturing a great cardinality of their set and good securityrelatedfeatures, and provides evidence of their suitability tomultiuser communications, in channels affected by multipath

Full-length non-linear binary sequences with Zero Correlation Zone for multiuser communications

none3noThe research on new sets of sequences that can be applied as spreading codes in multiple user communications is still an active area, even if this topic has been extensively investigated since long time. In fact, new communication paradigms like dense and decentralized wireless networks, where there is no central controller to assign the resources to the nodes, are revamping the interest on finding large sets of sequences providing adequate correlation properties to support a big number of nodes, in potentially hostile channels. This paper focuses on the Zero Correlation Zone (ZCZ) property exhibited by a family of nonlinear binary sequences featuring a great cardinality of their set, and good security-related features, and provides evidence of their suitability to multiuser communications, in channels affected by multipath.Sarayloo, M.; Gambi, E.; Spinsante, S.Sarayloo, Mahdiyar; Gambi, Ennio; Spinsante, Susann

Design and Analysis of Ternary m-sequences with Interleaved Structure by d-Transform

Multilevel sequences find more and more applications in modern modulation schemes [4QPSK, 8QPSK,16QAM..]  for the 3G ,4G system air interface [1,2].Furthermore, in modern cryptography they are also widerly used. It is also interesting to point out that the length L of these sequences are composite numbers( L=NS),that means the sequence can be easily implemented by interleaving S subsequences, each of length S.Therefore, the methods to develop multilevel sequence with interleaved structure draw a lot of attentions [3, 4]. In this contribution, a method for design and analysis of ternary m-sequences with interleaved structure is presented, based on the d-transform, Which turns out to be a very effective and versal tool for this purpose. Simulations have been made to verify the theory. We first introduce d-transform and its properties and then work out the procedure to design an interleaving sequence in d-transform. Keywords: d-transform,q-ary sequences, interleaved sequence

Spreading sequences selection algorithm for CDMA systems considering the interference from adjacent cells

Orientador: Celso de Almeida, Rodrigo Pereira RamosDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de ComputaçãoResumo: O desempenho de sistemas de comunicações sem fio que utilizam técnicas de espalhamento espectral e múltiplo acesso por divisão de código (CDMA) é limitado pela interferência. Nesta dissertação, analisamos o desempenho de um algoritmo de seleção de seqüências de espalhamento de comprimento fixo, que busca a minimização dos efeitos de interferência em sistemas CDMA operando em canais com desvanecimento seletivo em freqüência e possuindo células adjacentes interferentes. Analisamos o desempenho deste sistema no qual o espalhamento espectral é feito usando duas seqüências: seqüências do usuário e seqüências identificadoras de células. Dentre as seqüências analisadas, podemos citar as Walsh, a Gold, as de comprimento máximo e também um tipo de seqüência de espalhamento baseado nas seqüências de comprimento máximoAbstract: The performance of wireless communication systems using spread spectrum techniques and code division multiple access (CDMA) is interference-limited. In this dissertation, we evaluate the performance of a selection algorithm for fixed-length spreading sequences, aimed on minimizing the interference effects in CDMA systems operating in frequency selective fading channels and having adjacent interfering cells. We check the performance of this system where the spread spectrum operation is performed using two sequences: user sequences and cell identification sequences. Among the sequences considered, we use Walsh, Gold, maximum length and a type of spreading sequence based on the maximum length classMestradoTelecomunicações e TelemáticaMestre em Engenharia Elétric

New Spectrally Constrained Sequence Sets With Optimal Periodic Cross-Correlation

Spectrally constrained sequences (SCSs) play an important role in modern communication and radar systems operating over non-contiguous spectrum. Despite numerous research attempts over the past years, very few works are known on the constructions of optimal SCSs with low cross-correlations. In this paper, we address such a major problem by introducing a unifying framework to construct unimodular SCS families using circular Florentine rectangles (CFRs) and interleaving techniques. By leveraging the uniform power allocation in the frequency domain for all the admissible carriers (a necessary condition for beating the existing periodic correlation lower bound of SCSs), we present a tighter correlation lower bound and show that it is achievable by our proposed SCS families including multiple SCS sets with zero correlation zone properties

Sequences design for OFDM and CDMA systems

With the emergence of multi-carrier (MC) orthogonal frequency division multiplexing (OFDM) scheme in the current WLAN standards and next generation wireless broadband standards, the necessitation to acquire a method for combating high peak to average power ratio (PMEPR) becomes imminent. In this thesis, we will explore various sequences to determine their PMEPR behaviours, in hopes to find some sequences which could potentially be suitable for PMEPR reduction control under MC system settings. These sequences include $m$ sequences, Sidelnikov sequences, new sequences, Golay sequences, FZC sequences and Legendre sequences. We will also examine the merit factor properties of these sequences, and then we will derive a bound between PMEPR and merit factor. Moreover, in the design of code division multiple access (CDMA) spreading sequence sets, it is critical that each sequence in the set has low autocorrelations and low cross-correlation with other sequences in the same set. In the thesis, we will present a class of GDJ Golay sequences which contains a large zero autocorrelation zone (ZACZ), which could satisfy the low autocorrelation requirement. This class of Golay sequences could potentially be used to construct new CDMA spreading sequence sets