Abstract
The problem of blind multiuser detection for an asynchronous multicarrier DS-CDMA system employing multiple transmit and receive antennae over a Rayleigh fading channel is considered in this paper. The solutions that we develop require prior knowledge of the spreading code of the user to be decoded only, while no further information either on the user to be decoded or on the other active users is required. Several combining rules for the observables at the output of each receive antenna are proposed and assessed, and the implications of the different options are studied in depth in terms of both detection performance and computational complexity. A closed form expression is also derived for the conditional error probability and a lower bound for the near-far resistance is provided. Results confirm that the proposed blind receivers can cope with both multiple access interference suppression and channel estimation at the price of a limited performance loss as compared to the ideal linear receivers which assume perfect channel state information.
Highlights
Multicarrier code division multiple access (MC-CDMA) has been conceived as a transmission format which retains the potentials of direct sequence CDMA (DS-CDMA)— and in particular its resistance to multipath effects induced by the radio channel as the communication rate grows larger and larger [1]—while relaxing some very demanding requirements posed by its competitor
(1) We develop a signal model for an MC DS-CDMA system operating over a fading dispersive channel and employing multiple transmit and receive antennae that resembles the signal model developed in [16, 17, 18] with reference to a single-antenna DS-CDMA system operating in the same conditions
We have considered the problem of blind multiuser detection for asynchronous MC DS-CDMA systems equipped with multiple transmit and receive antennae
Summary
Multicarrier code division multiple access (MC-CDMA) has been conceived as a transmission format which retains the potentials of direct sequence CDMA (DS-CDMA)— and in particular its resistance to multipath effects induced by the radio channel as the communication rate grows larger and larger [1]—while relaxing some very demanding requirements posed by its competitor. Multiple transmit antennae generate a spatial diversity which can be successfully exploited at the receiver end to improve performance, especially if space-time coding techniques are employed at the transmitter [12] Motivated by these considerations, many studies have been recently published for either single-user or multiuser multiantenna systems [13, 14]. It is worth pointing out that in a CDMA multiaccess network, the signal-to-interferenceplus-noise ratio is expected to be quite low, at least as far as the network load increases, whereby the task of reducing—if not nullifying—the training phase is more and more stringent Motivated by these results, the present paper deals with the problem of blind multiantenna systems employing an MC DS-CDMA modulation format.. N (μ, C) denotes the distribution of a Gaussian vector with mean μ and covariance matrix C while Q(·) is the area under the leading tail of standard Gaussian pdf; Q1(·, ·) and I0(·) are the Marcum function and the modified Bessel function of the first kind and order zero, respectively
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