Energy-Efficient User Association with Congestion Avoidance and Migration Constraint in Green WLANs

Table 1

Notations.

Symbol	Definition
	The set of access points (APs)
	The set of demand nodes (DNs)
	The set of potential association relations
	The number of APs
	The number of DNs
	An AP
	Am DN
	The traffic demand of DN
	Time interval
	The available transmission rate between AP and DN
	The received SNR at DN when signal is from AP
	The power of AP
	The baseline power of AP
	The transmit power of AP
	The efficiency factor of AP
	The distance between AP and DN
	The propagation path loss
	The background noise power
	The set of DNs that are associated with AP
	The coverage indicator between AP and DN
	The threshold of AP utilization
	The previous association indicator
	The maximum allowed number of migrations