HARQ Performance Analysis of a Long-Term Evolution System Yih-Guang Jan Department of Electrical Engineering Tamkang University Tamsui District, New Taipei City 25137, Taiwan yihjan@yahoo.com Hsien-Wei Tseng Department of Computer and Communication Engineering De Lin Institute of Technology Tucheng District, New Taipei City 23654, Taiwan hsienwei.tseng@gmail.com Liang-Yu Yen Department of Electrical Engineering Tamkang University Tamsui District, New Taipei City 25137, Taiwan skyslj@gmail.com Yang-Han Lee Department of Electrical Engineering Tamkang University Tamsui District, New Taipei City 25137, Taiwan yhleepp@gmail.com Le-Pong Chin Department of Information Technology and Management Shih Chien University New Taipei City 10462, Taiwan chin@mail.usc.edu.tw Chuan-Yuan Huang V200, Information & Communications Research Laboratories, Industrial Technology Research Institute Rm. 255, Bldg. 11, No. 195, Sec. 4, Chung Hsing Rd., Chutung, Hsinchu, 31040, Taiwan, R.O.C. cyhuang@itri.org.tw Heng-Iang Hsu Alifecom Technology Corp. Jhubei City, Hsinchu County, Tai Yuen Street, 2nd Floor, No. 28, 2 hi_hsu@alifecom.com Abstract—This study investigated an existing cellular wireless communication system and found that the system performance was severely limited by co-channel interferences (CCI) within the cell and from users of other cells. Therefore, in addition to simulating the shadow fading and path loss models caused by the attenuation of wide-range signals and the Rayleigh fading caused by the attenuation of short-range signals required for general channel exploration, a co-channel interference model was also constructed. Finally, a structured simulation method is presented in the Conclusion section. Keywords- Hybrid automatic repeated request (HARQ); interference; co-channel; chase combining; high-speed factor mobility. I. INTRODUCTION Wireless communication has numerous advantages. However, various attending interferences and channel attenuations can cause packet transmission failures. Therefore, various retransmission mechanisms have been proposed to ensure transmission accuracy. Generally, two types of retransmission mechanisms exist. One mechanism is automatic repeat requests (ARQs). However, the disadvantage of ARQs is that a status report is not provided at the time the packet is lost, significantly delaying verification that a packet has been lost. The other retransmission mechanism is hybrid ARQ (HARQ). HARQ [7] integrates forward error correction and ARQ technology and can retain useful information from previous failed save attempts for subsequent decoding. During communication, the base station obtains the channel’s status information through the positive or negative acknowledgments (ACK/NACK) returned in every transmission time interval and through the channel quality indicator (CQI). In Chapter 2, this study achieved long-term evolution (LTE) [1-6] of the co-channel and other interference model environments. In Chapter 3, various signal-to-interference ratio (SIR) to symbol error rate (SER) graphs under modulation and coding schemes (MCS) were introduced and an error judgment system for the basic retransmission units of HARQ was developed. In Chapter 4, various parameter combinations were tested to obtain the final simulation results. In Chapter 5, the conclusion and future implications of this study are presented. II. SIMULATION ENVIRONMENT In cellular systems, service coverage can be divided into smaller geographical areas, called cells. The strength of the base stations’ power output is controlled and limited within the 2012 IEEE International Symposium on Intelligent Signal Processing and Communication Systems (ISPACS 2012) November 4-7, 2012 978-1-4673-5082-2 ©2012 IEEE 178