New User-Irrepressible Protocol Sequences

Protocol sequences are binary and periodic sequences used for deterministic multiple access in a collision channel without feedback. In this paper, we focus on user-irrepressible (UI) protocol sequences that can guarantee a positive individual throughput per sequence period with probability one for a slot-synchronous channel, regardless of the delay offsets among the users. As the sequence period has a fundamental impact on the worst-case channel access delay, a common objective of designing UI sequences is to make the sequence period as short as possible. Consider a communication channel that is shared by M active users, and assume that each protocol sequence has a constant Hamming weight w. To attain a better delay performance than previously known UI sequences, this paper presents a CRTm construction of UI sequences with w = M + 1, which is a variation of the previously known CRT construction. For all non-prime M ≥ 8, our construction produces the shortest known sequence period and the shortest known worst-case delay of UI Y. Zhang School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing, China National Mobile Communications Research Laboratory, Southeast University, Nanjing, China E-mail: [email protected] Y.-H. Lo School of Mathematical Sciences, Xiamen University, Xiamen, China E-mail: [email protected] K. W. Shum Institute of Network Coding, The Chinese University of Hong Kong, Hong Kong E-mail: [email protected] W. S. Wong Department of Information Engineering, The Chinese University of Hong Kong, Hong Kong E-mail: [email protected] The material in this paper was presented in part at Globecom 2014 Workshop on ULTRA, Austin, USA, Dec. 2014. 2 Yijin Zhang et al. sequences. Numerical results show that the new construction enjoys a better average delay performance than the optimal random access scheme and other constructions with the same sequence period, in a variety of traffic conditions. In addition, we derive an asymptotic lower bound on the minimum sequence period for w = M + 1 if the sequence structure satisfies some technical conditions, called equi-difference, and prove the tightness of this lower bound by using the CRTm construction.