摘要
针对多速率传输的物理层实现,通过将可变扩频长度(VSL)和多码(MC)的概念扩展到多载波码分多址(MC-CDMA)系统,分析了MC-CDMA系统的两种多速率方式,并在每个等效用户的虚拟扩频码的基础上,提出两种方式的统一数学模型.借助于统一数学模型,利用子空间方法,实现了多速率MC-CDMA系统的盲信道估计.数值仿真结果表明,该统一模型能够有效地对各种速率用户的信道进行辨识.在相同条件下,多码方式的性能优于VSL方式.
In wireless communications,the data rates of diverse multimedia services vary largely.Therefore,achievaing multirate physical-layer transmission is an effective approach for wireless multimedia communications by adapting the concepts of multi-code(MC) and variable spreading length(VSL) to MC-CDMA system.Via the virtual spreading codes of effective users,a general and uniform matrix model for VSL and multicode MC-CDMA systems is built.Furthermore,the blind channel estimation of these two multirate systems is obtained with subspace method.For typical distributions of the inputs and channel noise,closed-form expressions for the channel estimation error is thrived as functions of the signal-noise ratio(SNR).Simulation results are provided to verify the validity of proposed method and also show the superiority of multicode access over VSL access.
出处
《陕西师范大学学报(自然科学版)》
CAS
CSCD
北大核心
2006年第S2期97-100,共4页
Journal of Shaanxi Normal University:Natural Science Edition