基于ieee 802.16a的多用户ofdm系统自适应子信道和比特、功率分配the multiuser ofdm system based on ieee 802.16 a adaptive channel and bit and power allocation.docx

摘要
正交频分复用(OFDM)技术因具有良好的抗噪声性能和抗多径信道干扰的能力以及频谱利用率高而被普遍认为是下一代宽带无线接入系统必不可少的技术。本课题重点研究了基于IEEE ——多用户OFDM 系统中的自适应分配技术。
在多径频率选择性衰落信道中,不同的子信道受到不同的衰落;在多用户OFDM 系统中,各用户的衰落又存在差异性。论文研究在MA优化准则下的自适应分配问题,即对给定的数据速率和传输带宽,在保证服务质量(QoS)所需要BER的条件下, 根据子信道的瞬时特性自适应地为多用户分配子信道和子信道上的比特率,使系统发送功率达到最小。
论文在研究自适应分配问题时,采用分两步走的思想,将子信道的分配和子信道上的比特、功率分配分离。在比特分配方案上,研究了一种最佳分配算法—— greedy算法。在动态子信道分配方案(论文中亦称为OFDMA)上,研究了两种子信道分配算法,即最佳分配算法匈牙利算法和~种降低时间复杂度的次最佳分配算法试探算法。并且将这些分配方案应用于IEEE ,在该环境下与传统的静态子信道分配方案(如OFDM—TDMA、OFDM—FDMA等)以及等比特分配
方案(EBA)作了比较。仿真结果表明,在多用户OFDM系统中,采用自适应分配
技术可以充分利用信道资源,大大优化系统性能。
Abstract
Orthogonal frequency division multiplex(OFDM)is widely known as a required technique in next generation wideband wireless access is a special case of multicarrier transmission,which has shown to be effective bating multi-path fading and at矗equency effective this thesis,the emphasis is laid on one of the key techniques in OFDM systems··--·-the adaptive allocation techniques for multiuser OFDM systems,which is based On IEEE protoc01.
In multipath frequency fading channels,different subchannel suffers different fade. And in multiuser environment,the situation es plicated,as each user will likely have different multiple fading ,it is likely that white subchannel may be in deep fade for a user,it may be in good condition for another user due to temporal and spatial diversity in user objective is to minimize the overall transmit power by allocation the subchannels to the users and by determining the number of bits and power level transmitted on each subchannel base on the instantaneous fading characteristics of a11 users.
As binatorial allocation is plicated,a suboptimal approach that separately performs subchannel allocation and bit loading is considered in this bit loading algorithm一一greedy algorithm,which is all optimal algorithm is investigated. Two dynamically subchannel allocating algorithm,which are Hungarian a