Abstract-In this paper we study on the one hand under delayedacknowledgement (Dly-ACK) mechanisms the option of using ACK Request to improve system robustness, and on the other hand the incorporation of effective retransmission schemes such as hybrid automatic repeat request (HARQ) to improve system throughput for an IEEE 802.15.3 compliant system. An expression of throughput is derived in terms of system parameters and channel conditions. A constrained optimization problem for system throughput is formulated. It is then solved numerically due to the high degree of nonlinearity in the payload size.Our results indicate that under poor channel conditions, the optimal throughput under HARQ scheme is significantly higher than that with ARQ, and larger payload size is proposed to further improve the performance.
In this paper, we consider the performances in terms of system throughput and response time of various channel-aware scheduling algorithms for both MPEG streams and non-MPEG flows in a high-data-rate (HDR) wireless personal area network (WPAN). The algorithms under investigation are the shortest remaining processing time rule, the exponential rule, the modified largest weighted delay first rule, the maximum rate rule, and the proportionally fair rule. Decodability issues are taken care of by means of the frame-decodability aware technique and the burst transfer eligibility decision mechanism. The impacts of a number of factors including deadline and interference-plus-noise level are also examined. The investigations are carried out through extensive ns-2 simulations. Based on the numerical results, we propose a heuristic scheduling algorithm for MPEG streams that outperforms the above algorithms in terms of system throughput. The findings are useful for system designers.Index Terms-IEEE 802.15.3, medium access control (MAC), channel-aware scheduler, high data rate (HDR), heuristic.
In this paper we analyze the problem of optimizing the switching levels of adaptive modulation for a two-user system under constant power condition, in order to maximize the overall system throughput for a target average bit-error-rate (BER) for each user. Since the optimal switching levels depend on the probability density of the signal-to-interference-noise ratio (SINR), expression for this probability density is derived and the optimal switch levels are obtained through a Lagrange optimization technique. This approach can be readily extended to multiple-user case. It is shown by simulation that the proposed jointly optimizing method achieves the average BER target for each user while an individually optimizing method fails. The effects of these two methods and of the interference coefficients on the average system throughput are also analyzed.
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