一種基于最大容量的多載波系統(tǒng)自適應(yīng)調(diào)制和功率分配算法
A capacity-maximization-based adaptive modulation and power allocation algorighm fo multicarrier systems
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摘要: 該文從最大化信道容量(數(shù)據(jù)通過速率)的目標(biāo)出發(fā),基于簡(jiǎn)化的QAM調(diào)制統(tǒng)一誤比特率表達(dá)式,用Lagrange乘數(shù)法給出了給定發(fā)送功率和QoS要求約束條件下最優(yōu)功率和調(diào)制方式分配的閉式解,并利用Obit分配排除衰落大的子載波,成功地解決了實(shí)際的正功率和調(diào)制方式分配的要求。最后使用連續(xù)調(diào)制離散化近似(O,QPSK,16QAM和64QAM)的方法逼近基于連續(xù)調(diào)制優(yōu)化的分配結(jié)果,仿真結(jié)果說明這種離散逼近的方法帶來的信道容量損失可以忽略,并且能夠保證給定的QoS要求,這種方式適合于可變速率的業(yè)務(wù)。Abstract: In this paper, the optimization of channel capacity (equivalent to data throughput) is proposed for variable-rate service, which is solved with the Lagrangian multiplier method based on a simplified BER formula for m-QAM modulation. The closed-form solution for the optimization problem is given and the practical constraint of positive power and modulation mode allocation is solved by null transmission on those deep-faded subcarriers. Finally discrete modulation mode (0, QPSK, 16QAM and 64QAM) is used to approach the optimally allocated continuous modulation mode, and simulation results demonstrate that the capacity loss from this approaching is negligible and QoS is guaranteed.
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T. Keller, L. Hanzo, Adaptive multicarrier modulation: a convenient frame work for timefrequency processing in wireless communications, Proc. IEEE, 2000, 88(5), 611-640.[2]T. Keller, Lajos Hanzo, Adaptive modulation techniques for duplex OFDM transmission, IEEE Trans. on Vehicular Technology, 2000, 49 (5), 1893-1906.[3]C. Yui Wong, R. S. Cheng, K. B. Lataief, Multiuser OFDM with adaptive subcarrier, bit and power allocation, IEEE J. on Selected Areas in Communications, 1999,17 (10), 1747-1758.[4]S.K. Lai, R. S. Cheng, K. B. Letaief, Adaptive trellis coded MQAM and power optimization for OFDM transmission, Vehicular Technology Confercnce, 1999 IEEE 49th , Houston, 1999, vol.1,290-294[5]Andrea J. Goldsmith, Soon-Ghee Chua, Variable-rate variable-power MQAM for fading channels,IEEE Trans. on Comm., 1997, 45(10), 1218-1229.[6]S.T. Chung, Andrea J. Goldsmith, Degrees of freedom in adaptive modulation: a unified view,IEEE Trans. on Comm., 2001, 49(9), 1561-1571. -
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