Research On Papr Reduction In The Next Generation Wireless LAN

In recent years, Wireless Local Area Networks (WLAN) is used in various electronic communication devices such as the mobile phones, notebook computers, medical equipment and so on. WLAN is established in offices, shops, hotels and other places, and it has become indispensable in our life and work. As a major transmission techniques in WLAN system, OFDM signal suffers high PAPR (peak to average power ratio), which has become a hot topic. In the next-generation WLAN standard protocol IEEE 802.11ax, an OFDM symbol would expand four times in time domain, the high PAPR is a serious problem with the increasing of the number of subcarriers. High PAPR has become the major obstacle in the new standard framework. To find an effective way to reduce the PAPR in IEEE 802.11ax is very important. The work of this thesis can be summarized as the follows.Firstly, the reasons of causing PAPR are analyzed and summarized in this thesis. We conduct a research on the effect of the number of carrier and oversampling factors on PAPR, and PAPR impact on system error performance, which provides a theoretical basis for this study. In order to find an effective solution to reduce PAPR, we study a number of algorithms for next generation WLAN.Secondly, a scheme to reduce the PAPR in downlink based on partial transmit sequences (PTS) technology is studied. The OFDM signal is divided into several segments based on channel bonding technology, so that the PAPR is reduced while maintaining signal interference from segments. In order to ensure compatibility of the system, we will set the optional phase as{1,-1>j>-j}. Moreover, a simplified algorithm that can help to save a lot of group calculation of searching for the best phase factors is provided. In this scheme the left-over tones can be used to transmit the optimal phase factors, and it solves the data subcarrier overhead which used to transmit the assistant information. The simulation results show that this scheme can effectively reduce the PAPR of downlink signal.Finally, a scheme to reduce the PAPR in uplink based on tone reservation (TR) technology is proposed. In this mode, the left-over tones can be used as reservation tones to transmit the reservation information. Moreover, we develops a comprehensive strategy to assign left-over tones to multiple users, and set reservation information in a fixed set of values. Then it just needs to find the best solutions from all alternative reservation information sequence. To search for the best reservation information solutions, the GA-TR and Minimum value Comparison TR are proposed, which can save lots of calculation.