改进的LOFDM系统实现方法  

Improved Implementation of LOFDM Systems

作　　者：简伟[1] 沈越泓[1] 修国浩 

机构地区：[1]解放军理工大学通信工程学院 [2]南京长城信息系统有限公司

出　　处：《吉林大学学报（信息科学版）》2006年第3期276-282,共7页Journal of Jilin University（Information Science Edition）

摘　　要：利用网格正交频分复用(LOFDM:Lattice O rthogonal Frequency D ivision Mu ltip lexing)可使系统的频谱利用率比采用脉冲成形OFDM(O rthogonal Frequency D ivision Mu ltip lexing)技术时更高,但带来实现上的复杂化。为此,在对LOFDM信号结构进行分析的基础上,给出了LOFDM系统调制解调器的有效实现。该方法先利用信号的反傅立叶变换(IFFT:Inverse Fast FourierTransform),可方便地分解出奇偶下标信号的反傅立叶变换的特点,把LOFDM系统的实现简化为一个脉冲成形OFDM系统的实现,再参考脉冲成形OFDM系统的有效实现方法,从而简化了系统结构。与已有方法相比,在成形脉冲是实序列时,计算量上,每个LOFDM符号周期减少4(Lg-N)次实乘和4Lg-6N实加;存储量上,发送端和接收端从分别存储两个长Lg的成形脉冲减少为发送端存储一个长Lg的成形脉冲,接收端存储一个长Lg的成形脉冲和一个长N/2的序列e-j2πn/N。The spectral efficiency of the system is higher when adopting LOFDM （ Lattice Orthogonal Frequency Division Multiplexing） than when adopting the pulse shaping OFDM （Orthogonal Frequency Division Multiplexing）. But implementation of LOFDM systems is highly complicated. On the basis of analysis of LOFDM symbols structure, the efficient implementation of modem of LOFDM systems is presented. First, using the characteristics of inverse IFFT （ Fast Fourier Transform ）, implementation of LOFDM systems is reduced to implementation of a pulse-shaping OFDM systems. Then, referring to efficient implementation of pulse-shaping OFDM systems, the structure of the system is reduced. When shaping pulse is real-value sequences, compared with the approach mentioned in literature, a LOFDM symbol duration reduces computationally 4（Lg - N） real-value multiplication and 4Lg - 6N real-value addition. Transmitter and receiver store two shaping pulse that their length are Lg in terms of the approach mentioned in literature, respectively. In this paper, transmitter stores a shaping pulse that its length is Ls, and receiver stores a shaping pulse its length is Ls and a sequence e^-j2πn/N that its length is N/2.

关 键 词：网格正交频分复用 脉冲成形OFDM 反傅立叶变换 双弥散信道 

分 类 号：TN911[电子电信—通信与信息系统]