In this paper, we study the scheduler design problems over delay-constrained wireless communication links. Following a crosslayer design approach, the wireless system is modeled as a joint link-PHY layer architecture with a finite-length buffer and continuousstate fading links. A heuristic and efficient fixed rate transmission scheduler scheme (FRT) is proposed. We formulate and analyze the performance of the FRT scheme in terms of power efficiency and packet drop rate. Compared with variable rate schemes, the FRT scheme can considerably simplify the hardware implementation of transmitter. In addition, we show that the optimization of FRT scheme can be conducted with significantly reduced computational cost by utilizing the sparse feature of the transition probability matrix. Moreover, the simulation results show that at the packet drop rate of 10-3, the optimized average transmit power of FRT scheme is only 0.5 dB higher than the known optimal variable rate scheme, indicating that the FRT scheme is quite power efficient as well. Therefore, we conclude that the FRT scheme is more feasible than variable rate schemes in practical delayconstrained wireless systems with regard to both hardware cost and power efficiency.
2. Rajan, D., A. Sabharwal, and B. Aazhang, "Delay-bound packet scheduling of bursty traffic over wireless channels," IEEE Trans. Inf. Theory, Vol. 50, No. 1, 125-144, 2004.
3. Wu, D. and R. Negi, "Effective capacity: A wireless link model for support of quality of service," IEEE Trans. Wireless Commun., Vol. 2, No. 4, 630-643, 2003.
4. Tang, J. and X. Zhang, "Quality-of-service driven power and rate adaption over wireless links," IEEE Trans. Wireless Commun., Vol. 6, No. 8, 3058-3068, 2007.
5. Hoang, A. T. and M. Motani, "Cross-layer adaptive transmission: Optimal strategies in fading channels," IEEE Commun. Letters, Vol. 56, No. 5, 799-807, 2008.
6. Zafer, M. and E. Modiano, "Optimal rate control for delay-constrained data transmission a wireless channel," IEEE Trans. Inf. Theory, Vol. 54, No. 9, 4020-4039, 2008.
7. Li, X., X. Dong, and D. Wu, "On optimal power control for delay-constrained communication over fading channels," IEEE Trans. Inf. Theory, Vol. 57, No. 6, 3371-3389, 2011.
8. Chung, J. Y., T. Yang, and J. Lee, "Low correlation MIMO antennas with negative group delay," Progress In Electromagnetics Research C, Vol. 22, 151-163, 2011.
9. Mahmood, K., A. Rizk, and Y. Jiang, "On the flow-lever delay of a spatial multiplexing MIMO wireless channel," IEEE International Conference on Commun., 1-6, Kyoto, Japan, 2011.
10. Deng, Y., C. Lin, F. Ren, and D. Wu, "Optimal power scheduling in 802.11n wireless networks for real-time services," Wireless Commun. and Mobile Computing, Published Online in Wiley Online Library, 2012.
11. Brzaraa, M., H. Sherali, and C. Shetty, Nonlinear Programming: Theory and Algorithms, Wiley-Interscience, New York, 2006.