We characterize the stability, metastability, and the stationary regime of traffic dynamics in a singlecell uplink wireless system. The traffic is represented in terms of spatial birth-death processes, in which users arrive as a Poisson point process in time and space, each with a file to transmit to the base station. The service rate of each user is based on its signal to interference plus noise ratio (SINR), where the interference is from other active users in the cell. Once the file is fully transmitted, the user leaves the cell. We derive the necessary and sufficient condition for network stability, which is independent of the specific path loss function as long as it satisfies mild boundedness conditions. A novel observation, shown through mean-field analysis and simulations, is that for a certain range of arrival rates, the network appears stable for possibly a long time, but can suddenly become unstable. This property is called metastability which is widely known in statistical physics but rarely observed in wireless communication. Finally, using mean-field analysis, we propose a heuristic characterization of the network steady-state regime when it exists, and demonstrate that it is tight for the whole range of arrival rates.have sporadic traffic to send. In such a scenario, devices enter the network without warning, wish to transmit some data quickly and without going through a lengthy acquisition and scheduling process, and then go back to sleep. The stability, latency, and scalability of such a random access scenario -despite considerable study, as explained below -is largely unknown, and very challenging to analyze. This paper takes a step forward in this direction by studying the dynamics of a single-cell uplink wireless system, along with its stability and metastability. Our approach and analysis rely on tools form mean-field theory along with queuing theory, and allows us to derive the exact stability condition of the system, along with some simple heuristics to describe the stationary regime when it exists.
A. History and Motivation: Wired Random Access NetworksThe history of analyzing dynamics in communication networks goes back to wired data networks, where multiple nodes share a common wire to a common destination [2]. A benchmark random access protocol for these networks that has been extensively analyzed in the past three decades is slotted Aloha, where N nodes share the same resource to the destination, each has a packet arrival rate of λ i , and node i transmits at the beginning of each time slot with a probability p i if its queue is not empty. If more than one node transmit in the same time slot, then a collision is declared, and the packets are queued back at their sources. Although the slotted Aloha protocol is simple, its stability region for general N -which is the set of arrival ratesthat leads to stable queues -is a long-standing open problem [3]. In some special cases, the stability region is known. For example, if the arrivals follow a Bernoulli process, then the exact stability re...