In this paper, a novel cooperative relaying road to vehicle communication system is proposed. The proposed system expands the communication area of road to vehicle communication by using the surrounding vehicles. The basic road to vehicle communication system enhanced in this paper is the MC/DS-CDMA system which can support broadcast (BC) and unicast (UC) communication in the same frequency by using variable spreading code. This basic system uses a small spreading factor for broadcast transmission to achieve high data rate and a large spreading factor for unicast transmission to reduce the interference among the signals respectively. For improving the performance of BC data transmission, Space-time block coding (STBC) technique by using adjacent plural access points (APs) is applied to BC data. In this paper, in order to improve the communication of road to vehicle communication, we propose a novel relayed system, in which the signals received at the users near to AP are relayed to the surrounding users which are in far from APs- By using this technique, the BER performance of users in far from APs can be improved and the interval of APs on the road can become large. The performance of the proposed system is evaluated by computer simulation under additive white Gaussian noise (AWGN) and Rayleigh fading environment.
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