tate diagrams which differ slightly and have different semantics. State diagrams can be used to graphically represent finite state machines (i.e., a model of behavior composed of a finite number of states, transitions between those states, and actions). A state is defined as a finite set of procedures or functions that are executed in a unique order. In the state diagram, each state may have some inputs and outputs, where deterministic transitions to other states or the same state happen based on certain conditions. In this chapter, the notion of mode is used to describe a sub-state or a collection of procedures/protocols that are asso- ciated with a certain state. The unique definition of states and their corresponding modes and Mobile WiMAX. DOI: 10.1016/B978-0-12-374964-2.10004-9 Copyright © 2011 Elsevier Inc. All rights reserved. CHAPTER 4 IEEE 802. 16m System Operation and State Diagrams protocols, and internal and external transitions, is imperative to the unambiguous behavior of the system. Also, it is important to show the reaction of the system to an unsuccessful execution of a certain procedure. The state diagrams described in the succeeding sections are used to characterize the behavior of IEEE 802. .16m system entities. This chapter provides a top-down systematic description of IEEE 802. 16m entities' state transition models and corresponding procedures, starting at the most general level and working toward the details or specifics of the protocols and transition paths. An overview of 3GPP LTE/LTE-Advanced states and user equipment state transitions is further provided to enable readers to contrast the corresponding terminal and base station behaviors, protocols, and functionalities. Such contrast is crucial in the design of inter-system interworking functions. 4.1 IEEE 802. 16M MOBILE STATION STATE DIAGRAMS A mobile state diagram (i.e., a set of states and procedures between which the mobile station transits when operating in the system to receive and transmit data or control signals) for the IEEE 80