| dc.description.abstract | Along with 4G wireless network, to promote effective bandwidth and transfer rate of bits , for wireless, we use the technique of Orthogonal frequency division multiplexing to transmit information frequently, because between subcarry of OFDM system orthogonal each other can not only save bandwidth effectively, but also defeat the fading of multipath channel. This system has already applied in many communication specifications. However, the users are increasing, so it’s very important about OFDM signal effective bandwidth and transfer rate of bits. Due to overlapped frequency spectrum, if the time and the frequency don’t synchronize, OFDM system will distort. Therefore, we will discuss the problem about time synchronization in two way relay network and use Zadoff-Chu Sequence as a training data to estimate time delayed in this paper.
Traditional one way relay will divide into four phases when it transmits data. Transmitter sends information to relay, and it will send information to receiver, and then receiver will do actions again to complete communications. However, when it transmits, two way relay only needs two phases. It means the transmitter and the receiver send information to relay at the same time, and relay will gather them, and send back again. We can know that it’s more useful about decreasing time transmission and increasing the bandwidth effectively than one way relay, two way relay becomes a popular research topic in few years. Because it transmits data to both sides, it can save half of transmitting time to increase the bandwidth effectively and transfer rate of bits. Moreover, it has many undeveloped potential in cellular network.
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