Wireless Personal Communications: An International Journal
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In this paper, we study the performance of a framed ALOHA system that employs slow frequency-hopping techniques. A new strategy that employs diversity transmission (multiple frequency-hopping) techniques to enhance the performance of a framed ALOHA system is presented. Two schemes differentiated by whether a frequency channel can be repeatedly selected by a ready user in a frame are proposed. In the first scheme, which we call diversity frequency-hopping using sampling with replacement scheme (DFH-SWIR), a frequency channel in a slot may be chosen by a user more than once. In the second scheme, which we call diversity frequency-hopping using sampling without replacement scheme (DFH-SWOR), all frequency channels in a slot selected by any user are distinct. For both of these two schemes, an exact combinatorial analysis is developed to evaluate the activity factor and throughput characteristics. Effects of parameter variations on the system performance are illustrated in the light of numerical examples.