  Since the seminal work of Grossglauser and Tse [1], the two-hop relay
algorithm and its variants have been attractive for mobile ad hoc networks
(MANETs) due to their simplicity and efficiency. However, most literature
assumed an infinite buffer size for each node, which is obviously not
applicable to a realistic MANET. In this paper, we focus on the exact
throughput capacity study of two-hop relay MANETs under the practical finite
relay buffer scenario. The arrival process and departure process of the relay
queue are fully characterized, and an ergodic Markov chain-based framework is
also provided. With this framework, we obtain the limiting distribution of the
relay queue and derive the throughput capacity under any relay buffer size.
Extensive simulation results are provided to validate our theoretical framework
and explore the relationship among the throughput capacity, the relay buffer
size and the number of nodes.
