Application And Research Of Polar Codes In WLAN Wireless Communication

Polar code is a kind of channel coding scheme to research in recent years.Motivated by the phenomenon of channel polarization,E.Arikan proposed a method for constructing capacity-achieving codes for symmetric binary-input discrete memoryless channels with low encoding and decoding complexity in 2009.Consequently,the study of polar codes is becoming a hotspot.Wireless local area network(WLAN)is characterized by the short distance wireless transmission,which has become an indispensable part of our lives.Thus it is of practical significance to apply polar codes to WLAN.International Institute of Electrical and Electronics Engineers has alreadly established a series of standards for WLAN,such as IEEE802.11a/b/g.This thesis is mainly based on the standard of IEEE802.11 a.The main work of this thesis is to study the application of polar codes in wireless local area network with IEEE802.11 a.The main contents of the thesis are as follows:1)Establishing the channel models of WLAN.There are two basic multipath channel models in wireless local area network,namely,indoor and outdoor channels.Multipath consists of visual and non-visual path.In this thesis,the channel model of WLAN is an indoor channel with 3 paths,each path is a non-visual path which obeys the Rayleigh distribution.That is to say,the channel model of this thesis is a multipath fading channel model.2)On the basis of the multipath fading channel,we introduce the OFDM system to suppress the negative effects caused by multipath transmission.As the standard specifies the carrier number of the system is 52,we use the 64 points IFFT/FFT in this thesis.3)There is a one-to-one relationship between polar codes and the channel.That is to say,a code is the polar code for one channel but it is maybe not for another.Therefore it is necessary to construct polar codes according to the channel models of the WLAN.In this thesis,a method of constructing the polar codes is given in detail,that is the Monte Carlo estimation.After the construction,the polar code is simulated on the established channel model.The decoding methods are Successive Cancelation with Cyclic Redundancy Check(SC-CRC)and Successive Cancelation List with Cyclic Redundancy Check(SCL-CRC)algorithm.4)Based on simulation results,the performance of polar codes is analyzed compared with the LDPC codes for the various code length given in the standard.The code given in the standard can take 648,1296 and 1944 bits.However,the length of the polar codes should be a power of 2 in general,thus the corresponding length of the polar codes is 512,1024 and 2048,and we have compared the two codes close to the length.On one hand,when the length of the codes is short,the overall performance of the LDPC codes will outperform polar codes.On the other hand,the performance of the polar codes is superior to LDPC codes when the code length is long within a certain range of signal to noise ratio.So we could choose polar codes if they have a better performance within some range of signal tonoise ratio,and choose LDPC codes in the other ranges where LDPC codes perform better.