Detection of unknown signals is considered under complex elliptically symmetric (CES) distributions, a wide family that includes several well-known distributions as special cases. We study the detection problem for unknown deterministic signals and random CES signals, both corrupted by CES noise. For detection of unknown deterministic signals, we form the generalized likelihood ratio test and reduce it to a sufficient test statistic, which is either the norm of the received vector or a function of it. Performance analysis is provided under both known and estimated noise scatter matrix. For detection of random CES signals, we form the likelihood ratio test, provide performance analysis, and establish conditions under which the sufficient test statistic is given by the norm of the received vector. Interestingly, this norm test statistic is proven to be the uniformly most powerful test for the detection of all CES distributed signals.

With 5G communication systems on the horizon, efficient interference management in heterogeneous multicell networks is more vital than ever. This paper investigates the linear precoder design for downlink multicell multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems, where base stations (BSs) coordinate to reduce the interference across space and frequency. In order to minimize the overall feedback overhead in next-generation systems, we consider precoding schemes that require statistical channel state information (CSI) only. We apply the random matrix theory to approximate the ergodic weighted sum rate of the system with a closed form expression. After formulating the approximation for general channels, we reduce the results to a more compact form using the Kronecker channel model for which several multicarrier concepts such as frequency selectivity, channel tap correlations, and intercarrier interference (ICI) are rigorously represented. We find the local optimal solution for the maximization of the approximate rate using a gradient method that requires only the covariance structure of the MIMO-OFDM channels. Within this covariance structure are the channel tap correlations and ICI information, both of which are taken into consideration in the precoder design. Simulation results show that the rate approximation is very accurate even for very small MIMO-OFDM systems and the proposed method converges rapidly to a near-optimal solution that competes with networked MIMO and precoders based on instantaneous full CSI.

Resource reuse schemes in relay-enhanced cooperative orthogonal frequency-division multiple access (OFDMA) networks have been well studied in the literature from an interference mitigation perspective and with cell-partitioning being the basis. In this paper however, we study dynamic intra-cell subcarrier reuse in cooperative OFDMA networks in which the users are allowed to share any subcarrier in the relay links provided that the resultant intra-cell interference is managed; an option not available in non-cooperative networks. Specifically, when the target data-rates of the users are not reachable in a conventional cooperative OFDMA network, dynamic intra-cell subcarrier reuse enables the users to achieve their target data-rates, even when the number of users surpasses the number of subcarriers. We formally define the problem of maximizing the system sum-rate subject to per node power and target data-rate constraints in a cooperative OFDMA single-cell network in which subcarriers are allowed to be reused in the relay links. After analyzing the problem in the dual domain and deriving the performance bounds, we propose a suboptimal resource allocation algorithm where subcarriers and links (relay and/or direct) are assigned to the users. Simulation results show that by employing our resource allocation algorithm, the system sum-rate and the outage ratio are significantly improved, specially in an overpopulated network.