LTE与WCDMA系统下行链路容量比较的研究

Study on Downlink Capacity Comparison Between LTE and WCDMA Systems

比较了长期演进LTE(long-term evolution,LTE)系统下行链路OFDM(Orthogonal Frequency Division Multiplexing,OFDM,)容量和宽带码分多址WCDMA(wideband code division multiple access,WCDMA)系统下行链路容量。在接收端采用Rake接收机的情况下,OFDM与WCDMA的主要区别是后者在多径弥散衰落信道环境下会造成严重的码间干扰。如果没有多径,即在单径平坦衰落信道下,OFDM容量和WCDMA容量相差无几,容量的差别取决于多径干扰的程度。一般来说,在多径弥散衰落信道环境下传输信号的带宽越宽,多址干扰越严重,OFDM对WCDMA的优势越明显。

In this paper, we compare the downlink capacity performance of LTE （Long Term Evolution） （or OFDM for short） and WCDMA （Wideband Code Division Multiple Access） systems. A key difference between LTE OFDM （Orthogonal Frequency Division Multiplexing） and WCDMA with Rake receiver is that the latter suffers from ISI （Inter Symbol Interference） in multi-path dispersive fading channels. In the absence of multi-paths, which is the case for a single-path flat-fading channel, the capacity performance of OFDM and WCDMA is similar. The capacity performance difference between OFDM and WCDMA depends upon the extent of multi-path interference. In general, the use of larger bandwidths in multi-path dispersive fading channels leads to more multi-path interference and therefore favoring OFDM which is expected to provide the greatest advantage over WCDMA.