Abstract
Multiple-input-multiple-output (MIMO) orthogonal frequency-division multiple access (OFDMA) has been selected as the core physical-layer access scheme for the downlink of state-of-the-art and next-generation wireless communications standards. In these systems, scheduling and resource allocation (SRA) algorithms, jointly assigning transmission data rates, bandwidth, and power, become crucial in optimizing resource utilization while providing support to multimedia applications with heterogeneous quality-of-service (QoS) requirements. To this end, the transmitter is assumed to have channel state information at the transmitter (CSIT) that will typically be imperfect. This paper introduces a unified analytical framework for robust channel- and queue-aware QoS-guaranteed cross-layer SRA algorithms for the downlink of MIMO-OFDMA networks with imperfect CSIT. The framework is based on the statistical characterization of the signal-to-noise ratio (SNR) under imperfect CSIT and is general enough to encompass spatial correlation effects in the Tx and Rx antenna arrays, different types of traffic, uniform and continuous power allocation, discrete and continuous rate allocation, and protocols with different amounts of channel and queue awareness. Simulation results using parameters drawn from the Third-Generation Partnership Project Long-Term Evolution (3GPP-LTE) standard demonstrate the validity and advantages of the proposed robust cross-layer unified approach.
Highlights
Orthogonal frequency division multiple access (OFDMA), combined with multiple-input multipleoutput (MIMO) strategies, has been chosen as the core physical layer access scheme for state-ofthe-art and next-generation wireless communications standards such as IEEE 802.16e/m-based WiMAX systems [1] and the Third Generation Partnership Project (3GPP) networks based on the Long-Term Evolution (LTE) and LTE-Advanced (LTE-A) [2]
Where pb,m(t) is the power allocated to mobile stations (MSs) m on subband b during the time slot t, and vb,m(t) ∈ CNT ×1 denotes the unit energy linear transmit filter used by the maximum ratio transmission (MRT) transmission system, which, for the situation at hand, as stated in [27], is found to be the eigenvector associated with the maximum eigenvalue of the matrix ζ
A unicellular downlink MIMO-OFDMA wireless network with a cell radius of 500 m has been simulated with a base station (BS) serving a set of MSs uniformly distributed over the whole coverage area
Summary
Orthogonal frequency division multiple access (OFDMA), combined with multiple-input multipleoutput (MIMO) strategies, has been chosen as the core physical layer access scheme for state-ofthe-art and next-generation wireless communications standards such as IEEE 802.16e/m-based WiMAX systems [1] and the Third Generation Partnership Project (3GPP) networks based on the Long-Term Evolution (LTE) and LTE-Advanced (LTE-A) [2]. 2) In contrast to previous works (i.e., [12]–[17]), our paper proposes a unified framework that, based on the statistical characterization of the SNR, takes into account the packet outage probability due to imperfect CSI and generalizes results presented in, for instance, [6], [8], [9], [11], [19] Superscripts (·)T and (·)H are used to denote the transpose and the conjugate transpose (hermitian) of a matrix
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