Multichannel MDA (MMDA) algorithm can make full use of multichannel environment to improve the overall performance and capacity of wireless mesh LAN, but the MMDA algorithm uses fixed contention period mechanism which causes the waste problem of network resources when wireless mesh LAN is at heavy-loading situation. Besides, the MMDA algorithm using the contention mechanism to reserve MDAOPs will cause the unfairness problem between MPs.
The proposed scheme uses the DACP mechanism and ABP, so it can further improve the network performance when wireless mesh LAN is at heavy-loading situation and alleviate the unfairness problem. The simulation results clearly show that in heavy-loading wireless mesh LAN environment, the MMDA algorithm using DACP mechanism and ABP outperforms the MMDA algorithm in average throughput, average waiting time, packet drop ratio, collision ratio, and fairness. The proposed scheme can truly improve the performance of the MMDA algorithm.
List of symbols
r The evaluation parameter for ABP
MDAOPown The durations of MDAOPs reserved by the MP itself
MDAOPavg The durations of MDAOPs reserved by neighbor MPs
n Total numbers of MPs in wireless mesh LAN
W0 The initial contention window
p
c
Collision probability caused by at least one of n − 1 MP transmissions
p
t
Transmission probability of each MP
psucc Probability of successful transmission
p
i
Probability of the idle channel
pcoll Collision probability caused by two above MP transmissions
Tcp The durations of contention period
Tcp_c The critical duration of CP
I A random variable; an MP will experience i times of collision before successfully reserving a MDAOP in CP
J A random variable; an MP will experience j empty slot times before successfully reserving a MDAOP in CP
Pss(i, j, n) The joint probability mass function of the random variables I and J with n MPs
The mean of I
The mean of J
T
s
The duration of each successful MMDA four-way handshaking contention
T
c
The duration of each collision
TMDASRQ The duration of MDA setup request
TMDASRP The duration of MDA setup reply
TMDAACK The duration of MDA acknowledge
TMDAADV The duration of MDA advertisement
TDIFS The duration of DIFS
TSIFS The duration of SIFS
T
r
The average time to reserve an MDAOP for an MP in CP
TDTIM The duration of mesh DTIM interval
TDTP The duration of data transmission period
T
i
A slot time that should be long enough to access the channel state information
N
a
The available MDAOPs provided for MPs to reserve in DTP
N
c
The number of channels in DTP
B The bandwidth of each channel
D MDAOP duration
L The average interval between two MDAOPs
Nmin The minimum value of n and N
a
T
m
The m th subcritical duration of CP that m MPs can successfully reserve MDAOPs
X The original CP ratio
Y The shortened CP ratio
G The number of MPs that can successfully reserve MDAOPs
SNCP The average throughput of the NCP MP
Tcp_s The duration of shortened CP
Tap The duration of the additional period
G
s
The number of MPs that can successfully reserve MDAOPs in an additional period
SECPS The average throughput of the ECPS MP
Pkt
i
The total transmitted packets of MP
i
s Packet size
T The total simulation time
Tx_Pkt The total successful transmitted packets
Tl
i
The time that the i th packet leaves the queue
Ta
i
The time that the i th packet enters the queue
Pkt
g
The numbers of generated packets
Pkt
d
The numbers of dropped packets
S
i
The throughput of MP
i
Ncoll,i The total collision numbers of MP
i
Ncont,i The total contention numbers of MP
i