Abstract
We propose a spectrally efficient design that guarantees the statistical delay quality-of-service (QoS) for delay-sensitive traffic in the downlink of orthogonal frequency-division multiple-access (OFDMA) networks. This design is based on the so-called effective capacity (EC) concept, which describes the maximum throughput, a system can achieve under a specific statistical delay-QoS violation probability constraint. We investigate the EC maximization problem, in which, the statistical delay profile of the traffic is characterized by the QoS-exponent $\theta $ determining the exponential decay rate of the delay-QoS violation probability. By exploiting the properties of concave programming and Slater’s condition, the Lagrangian dual decomposition method is applied and an iterative algorithm that does not depend on the instantaneous channel state information (CSI) is proposed for solving the concave problem formulated. Extensive simulations demonstrate the efficacy and robustness of the proposed iterative algorithm. Furthermore, we show that the system’s achievable EC does not depend on the specific choice of the subcarrier allocation, but rather on the number of subcarriers allocated to each user. This is, because, the EC is calculated using the channel’s statistics, instead of the instantaneous CSI, implying that the EC is more of a long term channel capacity metric.
Highlights
CONTRIBUTIONS OF THIS PAPER Against the above background, in this paper we propose an analytical power and subcarrier allocation method for maximizing the effective capacity (EC) of downlink orthogonal frequency-division multipleaccess (OFDMA) networks that operate on the non-line-of-sight (NLOS) Rayleigh fading channels,1 while providing statistical delay-QoS guarantee
SIMULATION RESULTS AND DISCUSSIONS our numerical simulation results are presented and discussed, which demonstrates the efficacy and robustness of the Lagrangian dual decomposition (LDD) method conceived for solving the sum EC maximization problem, as well as the role played by the statistical delay-QoS exponent θ
The proposed resource allocation optimization approach is appealing in practice, because it only has to know the channel statistics
Summary
Ubiquitous advanced wireless technologies and prevalent multimedia services, such as ultra-high-definition (UHD) video and music streaming, have resulted in an exponentially increasing amount of delay-sensitive data [1], [2]. C. CONTRIBUTIONS OF THIS PAPER Against the above background, in this paper we propose an analytical power and subcarrier allocation method for maximizing the EC of downlink OFDMA networks that operate on the non-line-of-sight (NLOS) Rayleigh fading channels, while providing statistical delay-QoS guarantee. We derive an analytical EC expression for the downlink OFDMA network operating in Rayleigh fading channels and prove the concavity of this EC expression Based on these analytical results, we propose a deterministic power-and-subcarrier-allocation scheme for OFDMA networks only relying on statistical rather than instantaneous CSI knowledge.
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