Research On Joint Design Of Physical Layer Network Coding And LDPC Code Based On FSK Modulation

In recent years,wireless communication technology has developed rapidly,from the early analog communication technology to the large-scale application of 5G communication technology,which has promoted the rapid development of society as a whole,and people have more stringent requirements for wireless performance.This requires wireless communication to have safer and faster data transmission,lower bit error rate,higher frequency band utilization,and so on.In actual wireless communication application scenarios,there are more complicated uncertain and open factors,which cause great challenges to the reliability of communication transmission,so the use of relay cooperation to complete information exchange has become the most commonly used communication method.In 2000,Dr.R.Alshwede and others put forward the concept of network coding;S.Zhang established the concept of physical layer network coding based on the idea of ??network coding in2006,and later applied this concept with wireless communication technology.Since then,since network coding and physical layer network coding can effectively increase the system channel capacity and increase the information transmission rate in wireless communications,they have received widespread attention.This paper uses the wireless two-way single-relay channel as the basic model,combining Frequency-shift Keying(FSK)modulation technology,Low Density Parity Check(LDPC)encoding and decoding technology and physical layer network Coding technologies are combined,and a variety of joint systems are designed.The main work of this article can be summarized as follows:First,it introduces the relevant background knowledge of network coding and physical layer network coding,the current research status and basic principles at home and abroad.By comparing and analyzing the three information transmission methods of the wireless two-way single-relay system,the performance advantage of the high throughput rate of the physical layer network coding is demonstrated.The basic theory of LDPC code and the principle of encoding and decoding are introduced to provide theoretical support for the system design later.Then,the 2FSK modulation technology is combined with the physical layer network coding system to establish the 2FSK-PNC system and design the relay detection scheme of the system.In order to improve the reliability of system information transmission and to optimize the performance of the 2FSK-PNC system,the LDPC code is introduced as the channel coding,the 2FSK-LDPC-PNC system is designed,and the relay mapping scheme is given.This scheme uses the log-likelihood ratio domain belief propagation algorithm to complete the decoding and relay mapping.Simulation shows that the 2FSK-LDPC-PNC system obtains better error rate performance after introducing LDPC codes.Finally,the modulation method is extended to high-order FSK modulation.In this paper,the 4FSK-PNC system is designed with 4FSK modulation as an example,and the corresponding relay mapping scheme is given.After introducing the LDPC code into the high-order FSK-modulated PNC system,it is found that the hard-decision bit flipping decoding algorithm is designed according to the high-order FSK modulation characteristics,and the relay decoding mapping is completed,and better performance is obtained.