Protocol sequences are binary and periodic sequences used in multiple-access scheme for collision channel without feedback. Each user reads out the bits from the assigned protocol sequence periodically, and sends a packet whenever the bit is equal to one. It is assumed that any two or more packets overlapping in time result in a collision, and the collided packets are unrecoverable. Due to the lack of feedback and cooperation, there are some relative delay offsets between protocol sequences. We consider protocol sequences with the property, called user-irrepressibility, that each user is guaranteed to send at least one packet in each sequence period without collision, no matter what the delay offsets are. The period length is hence a measure of delay; each user need to wait no more than a period time before a successful transmission can be made. Our objective is to construct user-irrepressible sequences with sequence period as short as possible. In this paper, we present a new construction for prime number of users. A lower bound on period which is applicable in general for any number of users is also derived.
KeywordsProtocol sequences conflict-avoiding codes collision channel without feedback
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