认知无线电中OFDM多用户频谱分配

Multi-user OFDM spectrum allocation for cognitive radio

针对认知无线电需要提高频谱利用率,限制功率以及保障QoS的要求,结合OFDM技术,研究了认知无线电场景中的多用户频谱分配,并给出了2种算法.其中,最优算法通过授权用户的SIR下限得到认知无线电的发射总功率,并采用拉格朗日定理为每个认知用户分配子载波和功率;次优算法引入"分配比例因子"来体现用户分配中的公平原则,并通过限制SIR得到频谱分配结果.仿真表明,最优、次优算法的性能好于基于FDMA的静态频谱分配算法,最优算法相对于FDMA能够有35%的容量提升;次优算法容量略有减小,但充分保障了用户的QoS需求.2种算法从不同层面满足了认知无线电的需求.

Cognitive Radio （CR） is intended to improve spectrum utilization, reduce power needs and guarantee quality of service （QoS）. Two algorithms using orthogonal frequency division multiplexing （OFDM） were proposed after reviewing research on spectrum allocation in multi-user CR. The ＇ optimal＇ algorithm obtains the total transmission power through the lower limit of primary users＇ signal to interference ratio （SIR） , and allots every user sub- carriers and power according to Lagrange＇s theorem. The ‘hypo-optimal＇ algorithm uses a prorating gene to deter mine equity of allocation. Results are obtained through restricting the users＇SIR. Simulations showed both algorithms are effective, with the ‘optimal algorithm＇ providing about a 35% improvement in channel capacity when compared with frequency division multiple access （FDMA） allocation. The capacity of the ‘hypo-optimal＇ algorithm decreased slightly, but the QoS of users was guaranteed. Both algorithms satisfy the needs of CR, while using different approaches.