Blind reception of multicarrier ds-cdma using antenna arrays

IEEE Trans. Signal Process.

2011

Abstract-The response of an array processing system has been widely modelled using the concept of the array manifold. The conventional array manifold is a function of the geometry of the array, the carrier frequency and the directions of arrival (DOAs) of the sources only. However, the emergence of more sophisticated array systems, for instance antenna array communication systems, dictates the extension of this array manifold into various new types of manifolds that incorporate additional system and channel parameters, such as the code-division multiple access (CDMA) (spreading and scrambling) codes, the lack of synchronization, Doppler effects, polarization parameters, subcarriers, etc. This paper is concerned with the definition and geometric investigation of a generic model for these new manifolds that can be expressed as functions of the conventional array manifolds and, hence, are defined herein as extended array manifolds. Thus, initially, the concept of the extended array manifold is introduced and is shown to accommodate both existing and newly defined extensions of the widely employed in the literature conventional (or spatial) array manifold. Next, the geometric properties and parameters of the extended array manifold are studied and linked with the properties of the associated spatial array manifold in an attempt to facilitate the geometric study of the former by taking advantage of the well understood study of the latter.Index Terms-Array manifold, array processing, differential geometry, extended array manifold. NOTATION aScalar.Column vector.Matrix.element column vector of zeros.Conjugate, transpose, Hermitian.Hadamard product, Kronecker product.Round down to integer.Euclidean norm of the column vector .Element-wise exponentiation.

Section: A Examples Of Extended Array Manifoldsmentioning

confidence: 99%

Extended Array Manifolds: Functions of Array Manifolds

Efstathopoulos

IEEE Trans. Signal Process.

2011

“…where R 11 is the covariance matrix of the desired user (assumed to be user 1, without any loss of generality) and R N +I is the covariance matrix of noise plus interference [10]. Therefore, the overall data covariance matrix is given by…”

Section: B Snir Out Performance Of Arrayed Mc-cdma Receiversmentioning

confidence: 99%

Arrayed MC‐CDMA reception in space‐time diffused multipath vector channels

Rashid

Wireless Communications

2007

Multi-Carrier Code Division Multiple Access (MC-CDMA) is a modulation scheme that combines the advantages of OFDM and CDMA to provide robustness against frequency selectivity in wireless channels. Arrayed MC-CDMA systems combine MC-CDMA and antenna array technology to harness the spatial and temporal 'signatures' of received signals, thus making it possible to realize high transmission rates envisioned for next generation wireless communications. Localized scattering, which occurs for each multipath, motivates the frequency selective wireless channel to be modelled as a diffused vector channel. In this paper, space-time diffused vector channels for arrayed MC-CDMA systems are modelled and analyzed. Simulation studies show that the use of this diffused channel modelling in arrayed MC-CDMA receivers yields better bit error rate (BER) and SNIR out performance than receivers that ignore the presence of spatial and/or temporal diffusion.

“…Joint spacetime processing schemes are discussed in [7] and [8]; however, it is assumed that the subchannels are frequency nonselective. In contrast, the authors of [9] consider an array MC-DS-CDMA system which is transmitted through a fully frequency selective radio channel. A blind zero-forcing (ZF) receiver is proposed which cancels both intersymbol interference (ISI) and MAI.…”

Section: Mmse Multiuser Detection For Array Multicarrier Ds-cdma In Fmentioning

confidence: 99%

“…It is claimed that both matrices can be found from the estimated composite channel vectors for all users . In [9], it was demonstrated that the composite channel vector for each user could be estimated in a quasistationary environment by using subspace techniques and applying the theorem of alternating projection [16], [17]. A modified, tracking version of this procedure is presented here to provide estimates under time-varying conditions.…”

Section: Blind Implementation Of the Modified Mmse Receivermentioning

confidence: 99%

“…Seven users were simulated with speeds of km/h, and the threshold between "fast" and "slow" users was set at 50 km/h. The quasistationary MMSE receiver uses the channel estimation procedure of [9] followed by application of (15), the proposed MMSE uses (23), and the proposed hybrid MMSE receiver uses (38). For this mixed-speed scenario, assuming a quasistationary environment for all users significantly reduces performance, and assuming all users channels are rapidly time-varying impairs performance to a lesser extent.…”

Section: Simulation Studiesmentioning

confidence: 99%

See 1 more Smart Citation

MMSE multiuser detection for array multicarrier DS-CDMA in fading channels

Sadler

IEEE Trans. Signal Process.

2005

Self Cite

Abstract-Reception of asynchronous, multicarrier direct-sequence-code division multiple access (DS-CDMA) in time-varying, multipath radio channels with use of a receiving antenna array is investigated. Interference reducing minimum mean squared error (MMSE) receivers are discussed, and by considering the time-variation of the channel, a modified structure is derived which is efficient for channels experiencing small-scale fading. A blind implementation of this receiver is then proposed. Subspace concepts are applied to formulate a tracking, composite channel vector estimator which operates effectively in fading situations, even when high levels of interference are present. Both the modified MMSE weight matrix and diversity combining weights are generated from these channel estimates. Simulations of the proposed receiver show it to have superior performance over a standard MMSE receiver which is periodically re-evaluated to permit it to follow the channel variations due to small-scale fading. Furthermore, a hybrid MMSE receiver is proposed which applies different processing methods depending on each transmitters mobility, resulting in improved performance.