Multi-user OFDM spectrum allocation for cognitive radio
Xuezhi Tan · Harbin Gongcheng Daxue Xuebao/Journal of Harbin Engineering University · 2009
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.