Scheduled Access

In a wireless network with $N$ different users, the wireless medium is a shared resource. The two major approaches to achieve this resource sharing are Random Access and Scheduled Access. In a scheduled access system, we assume that a subset $S \subseteq \{1, 2, ..., N\}$ is able to jointly use the same part of the medium. The objective of a scheduled access system is to assign a part of the medium to each subset $S$, such that a specific set of constraints is satisfied.

Centralized vs. Distributed
Scheduling algorithms are divided into two major categories: Centralized and distributed. In a centralized scheduling technique, there exists an entity that oversees and controls the whole network. In this scenario, the central scheduler is typically assumed to have complete knowledge about the network. The central scheduler's job is to assign portions of the medium to each of the subsets $S$ and communicate the assigned portion to them.

In a distributed system, each user decides what part of the medium they will use, with or without complete information about the network.

Graph Representation
A wireless network can typically be represented as graph $G(E,V)$.