Research Of Time And Frequency Synchronization In IEEE802.11AC And System Hardware Implemention

With the rapid demand of broadband access, WLAN system is playing a more and more important role in daily life. As the newest WLAN protocol, IEEE802.11ac has adopted MIMO and OFDM techniques, it has strong resistance against frequency selective channel and can upgrade the system throughput at the same time. This paper works mainly on research of time and frequency synchronization in IEEE802.11ac based WLAN system and system hardware implementation. The major contributions are listed as follows:1. Compare IEEE802.11ac with the previous WALN protocols and diucuss the improvement of throughput and spectrum efficiency, this paper also makes a detailed introduction of MIMO and OFDM technique.2. Research on IEEE802.11ac physical layer standards as well as transmitter key technology. The baseband operations are also discussed.3. This paper mainly focused on time and frequency synchronization in IEEE802.11ac based WLAN systems. First the system model was given and the synchronization offsets were discussed. For time synchronization, this paper proposed a new frame synchronization method. This method can eliminate the "platform effect" and increase the frame synchronization ratio effectively. Meanwhile we also discussed the short training sequences and long training sequences based symbol synchronization algorithms. Simulations results shows short training based algorithm is more suitable in multiple antennas system. For carrier frequency synchronization, this paper proposed a hardware efficient estimation method, this algorithm takes advantage of the estimation range of long and short training sequence. For sampling frequency offset and phase tracking, this paper proposed a combined estimation method. This algorithm can achieve acceptable performance when nonideal channel estimation is involved.4. We discussed the hardware implementation of the transimitter and the synchronization part. For every module, functional simulation and hardware online tests are presented.5. Finally we gave the system architecture and the data flow in the platform. With the specification of system parameters, the whole hardware platform was presented.