SDN-Based Centralized Downlink Scheduling with Multiple APs Cooperation in WLANs

Algorithm 1

Concurrency transmission decision algorithm.

	Require: a AP send a transmission request to the SDN controller
	Input: NRM, TL, RL, F, L, V, sender is U [i], and receiver is U [j]
	Output: concurrent transmission instruction (CTI) or no response
	Temporary variables: CTI, RT (i) and TT (j) are the transposed matrix of R (i) and T (j) respectively
(1)	get V (i) and V (j) from set V
(2)	get F [i] and L [i] from set F and L, R (i) ⟵ RL [F [i] : L [i]]
(3)	get F [j] and L [j] from set F and L, T (j) ⟵ TL [F [j] : L [j]]
(4)	RT (i) ⟵ the transposed matrix of R (i)
(5)	TT (j) ⟵ the transposed matrix of T (j)
(6)	Fi,j = V (i)  RT (i) + V (j)  TT (j)
(7)	if Fi,j = = 0 then
(8)	Enable CTI to AP and run Algorithm 2 to change the transmission and receiving status
(9)	else
(10)	no response to AP
(11)	end if