S-72.158 Master’s thesis seminar 8th August 2006
QUALITY OF SERVICE AWARE
ROUTING PROTOCOLS
IN MOBILE AD HOC NETWORKS
Thesis Author: Shan Gong
Supervisor: Sven-Gustav Häggman
Outlines
Ad Hoc Networks
QoS (Challenge of implementing QoS in
ad hoc networks, QoS metrics, QoS metric
calculation)
AODV
Access admission control in QAODV
QAODV
Simulation Environment and Results
Mobile Ad hoc networks
 The application of mobile ad hoc
networks becomes more and more
popular.
 Applications of Mobile Ad Hoc
Networks (Military Applications,
Emergency Operations, Wireless Mesh
networks, Wireless sensor networks).
QoS
“Quality of Service is the performance
level of a service offered by the network to
the user”.
QoS considered in this thesis work: low
end to end delay (e.g. real time traffics)
Challenge of QoS in ad hoc networks




Dynamically varying network topology
Lack of precise state information
Shared radio channel
The resources such as data rate, battery
life, and storage space are all very
limited in ad hoc networks.
QoS metrics
Additive metrics (end to end delay)
Concave metrics (data rate)
Multiplicative metrics. (link outage
probability)
The generally used metrics for real time
applications are data rate, delay, delay
variance (jitter), and packet loss.
Calculation for locally available data rate
Method 1: Transmission range = Carrier sensing range
Available Data Rate i  Data Rate i  ( Z
i 
Z

x
)
jN i
jN i , kN i 
Case1
 

Case2
Case3
Case 1 is the data rate used by node i for receiving
data.
j
jk
Case 2 is the data rate consumed by neighbors who
are receiving.
Case 3 is the data rate consumed by neighbors who
are sending.
Calculation for local available data rate
Method 2: Carrier sensing range is more than twice of
the transmission range (more realistic)
Data Rate =(N*S*8)/T
The used data rate is the sum of the
sent, received and sensed data
rate
AODV routing protocol
Reactive
RREQ (broadcast) and RREP (unicast)
RERR
Access Admission Control
Available bandwidth ? Required bandwidth
Required data rate at each node
Method 1 carrier sensing range = transmission range
With a N-hop route, the source and destination nodes should satisfy
ABi>=2r, the second and N-1 nodes ABi >=3r and the intermediate
nodes ABi >=4r. Here, r is the required data rate requirement and ABi is
the available data rate at node i. N-1 node is the node on the path which
is next to the destination node.
A
B
C
D
E
Required data rate at each node
Method 2 carrier sensing range >= 2* transmission range
 The contention count is calculated as follows
 If hreq > 2  hreq = 2
otherwise hreq=hreq
 If hrep > 3  hrep = 3
otherwise hrep=hrep
 CC = hreq + hrep
Required data rate at each node
Method 2 carrier sensing range >= 2* transmission range
Example
2
6
1
5
3
4
7
Maximum data rate Vs. Hops of a route
Maximum data rate
Maximum data rate
4
3,5
3
2,5
2
1,5
1
0,5
0
0
2
4
6
8
Contention Count
10
12
QAODV routing protocol-draft
Session ID
Maximum delay extension field
Minimum data rate extension field
Node satisfying these requests could
broadcast the RREQ further
List of sources requesting QoS guarantees
AODV vs. QAODV
Broadcast RREQ
Enough Data
rate?
Recv RREQ
Drop RREQ
Forward RREP
Enough
rate?
Recv RREP
Data
Drop RREP
Do nothing
Periodically
Available Data rate
check
Available
rate >0
data
Send ICMP_QoS_Lost
Forward
ICMP_QoS Lost
Recv
ICMP_QoS_ Lost
Whether I am the
source node
Stop traffic
Example for QAODV—periodic check for
available data rate
550
(Interference
range)
m
Move direction of Node 3
1
3
3
3
150 m
Traffic
stopped
0
600 m
2
Scenario
Simulations with both AODV
and QAODV
Performance metrics
Average end to end delay
Packet Delivery Ratio (PDR)
Normalized Overhead Load (NOL)
Route finding time of the first route
Simulation Environment
 The channel type is “wireless channel”
 radio propagation model is “two ray ground”.
 MAC layer based on CSMA/CA as in IEEE
802.11 is used with RTS/CTS mechanism.
 The data rate at physical layer is 11 Mbps.
 Queue type is “drop tail”
 the maximum queue length is 50.
 Routing protocols are the AODV and the
QAODV.
 The transmission range and carrier sensing
range are 250 m and 550 m respectively.
Specific Scenarios for Simulations.
 The area size is 700 m * 700 m
 20 nodes in this area.
 Every experiment will be run 1000 s in total. (500 s is added at the
beginning of each simulation to stabilize the mobility model.)
 Each data point in the results represents an average of 10 trails
with same traffic model but different randomly mobility
scenarios.
 For fairness comparisons, same mobility and traffic scenarios are
used in both the AODV and the QAODV routing protocols.
 In the following set of simulations, a group of data rates
ranging from 50 kbps to 1800 kbps is applied.
 The mobility scenario is with a pause time of 10 seconds and the
maximum node speed of nodes is 1 m/s.
Traffic pattern
Average end to end delay
Packet Delivery Ratio
Normalized Overhead Load
Time used to find the first route
Time used to find the first route--First traffic flow
0,25
0,2
AODV - traffic flow 1
0,15
QAODV - traffic flow 1
0,1
0,05
The first traffic flow 553
s ~ 774 s.
The second traffic flow
680 s ~ 780 s.
0
0,05
0,3
0,6
0,9
1,2
1,5
1,8
Data rate (Mbps)
Time used to find the first route--Second traffic flow
80
Time duration (second)
Time duration (second)
0,3
70
60
50
AODV - traffic flow 2
40
QAODV - traffic flow 2
30
20
10
0
0,05
0,3
0,6
0,9
1,2
Data rate (Mbps)
1,5
1,8
Summary and Conclusions
QAODV outperforms AODV in terms of
end to end delay
Constrain the packets which might be
useless to the network
More routing packets are sent (brings
problem when node density is high)
More QoS metrics could be added to the
routing protocol (delay, packet loss)
Thank you