Research On Signal Code Modulation Based On Multi-Hop Network

The integration of multi-hop capability through the deployment of relay stations (RSs) is one of the hot topics in wireless cellular communications. For example, IEEE recently set up the Relay Task Group (RTG) with the objective to introduce RSs into the IEEE 802.16j based systems [1]. As novel and cost-effective network architecture, the relay enhanced cellular network is proposed and can be satisfied with the ubiquitous high data rate requirement of the next generation wireless systems. The relay enhanced cellular networks integrate the "multihop" capability into the conventional cellular systems by employing the relays and deviding the directly connecting link between Base Stations (BS) and Mobile Terminals (MT) into several hops. Thus, the communication distance is reduced and the link quanlity and channel capacity can be improved significantly.In recent years, digital modulation dominates wireless communications, as they can use error correction codes which provide performance close to the theoretical limits. However, retransmitting a digital communication signal over channels with different signal-to-noise ratios (SNRs) in the multi-hop network requires a completely Demodulation and Re-modulation (Demod/Remod) of the previous signal. This thesis describes a method, which we call signal code modulation (SCM), that is proposed for relaying a digital communication signal over channels between BSs and RSs and channels between RSs and MTs. and, in particular, The SCM method is a mixed analog-digital modulation technique, which provides an alternative method to retransmit a digital signal over channels with different SNRs, besides the traditional complete Demod/Remod. This thesis mainly discusses the current situation about Signal Code Modulation applied in Multi-hop Network. Research on the performance of SCM in Additive White Gaussian Noise (AWGN) channel and Nakagami fading channel is done. This thesis gains the exact closed-form expressions for the Bit Error Rate (BER) of SCM modulation scheme both in AWGN channel and Nakagami fading channel, which are proved by the computer simulaion. Furthermore, the diversity gain for SCM is defined. The conclusion of the research shows that SCM is relatively transparent and is simpler and cheaper to implement at the cost of a small performance reduction. What's more, SCM in MIMO has the same diversity gain as the digital signals.