Performance Improvement of Cooperative Relaying Scheme Based on OFCDM in UWB Channel

Orthogonal frequency and code division (OFCDM) provides a good performance on broadband or wide-band channel, because it can mitigate multi-path interference with keeping high data rate. So, this scheme is suitable to employ the future wireless communication system. And, Cooperative relaying scheme has been proposed to get the spatial diversity gains in multiuser wireless systems. Because, this scheme need no multiple antenna, it makes devices with low cost and small size. In this paper, we proposed the cooperative relaying scheme based on OFCDM. This system has profit of OFCDM and cooperative relaying schemes. It is also not much more complex the single antenna OFCDM system. This scheme is appropriate to the next generation mobile wireless system, because of having both advantage. The performance of the proposed scheme is evaluated in terms of bit error rate (BER) performance for the OFCDM in the UWB channel.

I. Introduction

The future wireless communication system required a huge bandwidth, because of providing the high-quality service such as internet access, and multimedia with high data rate. How-ever, to use of a huge bandwidth causes too much inter symbol interference (ISI). The orthogonal frequency and code division multiplexing (OFCDM) is proposed the one of alternative for improving this problem [1]. It is technique that combines orthogonal frequency division multiplexing (OFDM) and two dimensional (2-D) spreading codes, which spreads time domain and frequency domain. It has not only good points of OFDM but also to obtain frequency diversity gain. And, in order to have frequency diversity, the same data in OFCDM modulates a number of subcarriers in terms of frequency domain spreading [2]. Fig. 1 shows difference between OFDM and OFCDM. 2-D spreading codes and the process of OFCDM modulation is explained in detail in the next section. Moreover, it is possible multiple access as an orthogonal frequency division multiple access (OFDMA)[3]. It can also achieve flexible transmission rates by employing multi-code channels. So it is suitable both high and low mobility.