M. MANJUL ET AL.
approach by proposing a new equation to calculate the
throughput [4-6]
( )
1/1 p1/1 p
AIMD
X/p /1
αβ β
−−
= −
(2)
Where α = S/RTT, β is decreasing factor (0 < β < 1)
Now a proactive approach is used for congestion pre-
vention. In this, the congestion is calculated as follows:
Fcon=1-Ϫn/d (3)
Where Ϫn = RTTn − RTTn−1 and dЄ [RTTmin, RTTmax].
RTTmin and RTTmax correspond to the min. and max. RTT
experienced within the multicast ses s ion .
Then, source adjusts its rate as
(4)
Where Xn is throughput before congestion, Xn+1 is
throughput after congestion, fcon is congestion factor. If,
Ϫn > 0 then source rate is decreased else increased [4].
Other way is that, if we want to improve the through-
put of the network we use Logarithmic Increase multip-
licative Decrease (LIMD) technique instead of AIMD
technique for throughput calculations and show the better
results. The LIMD equation as follows:
(5)
Where α = S/RTT, L is Packet Size, RTT is roun d Trip
Time, p is Packet Loss Ratio, β is Reduction factor.
Another way to control congestion in Wireless Sensor
Network is Fuzzy approach by calculating the congestion
degree (Cd)
(6)
Where Ts = local packet inter-service time and Ta =
local packet inter-arrival time.
Once congestion is detected , it is notified by using Im-
plicit Congestion Notification (ICN) signaling. After re-
ceiving this signal the intermediate nodes adjust its send-
ing rate so that congestion doesn’ t occur. Further cong es-
tion is implemented using Fuzzy logic controller [7,8].
Here we define some threshold value. If the congestion
degree is greater than the defined threshold value, then
congestion occurs and ICN signal is sent to intermediate
nodes to inform that they adjust their sending rates; else
there is no congestion in the network.
The other mechanism uses the Fuzzy-logic-based Rate
Adaption (FRA) Scheme for TFMCC to control the con-
gestion in order to enhance the smoothness of TFMCC.
In order to alleviate oscillations of sending rate for TFMCC
sender, FRA introduces five actions for adjusting rate
[9-11].
These five actions are as follows:
a) MD (Multiplicative Decrease)
b) AD (Additive Decrease)
c) MI (Multiplicative Increase)
d) AI (Additive Increase)
e) KP (Keep)
And uses the Fuzzy Controller to decide which action
should be taken according to the feedback information
from CLR (Current Limiting Receiver). In dynamic net-
work environment, fuzzy controller uses the difference
between expected rate and sending rate to reflect the con-
gestion degree, as well as the difference between two
latest consecutive expected rates to predict the trend of
network. Under the fuzzy controller, KP, AD and MD
actions eliminate the “sawtooth” phenomenon in TFMCC,
which is crucial for smoothing sending rate [9]. When
the available bandwidth is turning abundant, MI action
can increase sending rate rapidly, making FRA have shorter
responding time and can fully utilize the resource. In
order to be friendly to TCP flows, the fuzzy controller
has unsymmetrical membership functions and biased in-
ference rules.
3. Proposed Work
We have seen that many algorithms have been proposed
to control the conges tion in the multicast network. These
algorithms used different protocols to reduce congestion
by adjusting the sending rate of the sender and different
mechanisms has been proposed to indicate the congestion
representative. The heterogeneous behavior of the net-
work leads to the more utilization of bandwidth which
results in congestion in the network. We propose an al-
gorithm to improve the utilization by keeping the same
sending rate while congestion occurs in the network. For
this we have to first calculate the link utilization using
existing link utilization method, then we again calculate
utilization by our own proposed formula.
Proposed Algorithm
We are proposing an algorithm to improve the utilization
by keeping the same sending rate while congestion oc-
curs in the network. For this we have to first calculate the
link utilization using old link utilization method. The
proposed algorithm entitles LUMCC is given below:
Algorithm: Link Utilization Based Multicast Conges-
tion Control (LUMCC)
1) Initialize the total link capacity.
2) Initialize the initial send ing rate.
3) Initialize the queue size.
4) Initialize the packet size.
5) Set the session time.
6) Calculate the packet loss ratio on the link.
Where Pls is the Packet loss observed on the link, Pd is
the number of Packets dropped, Ps is the number of
Packets sent on the link.
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