QoS Support in MANETs:
A Modular Architecture Based on the
IEEE 802.11e Technology
C. T. Calafate, M. P. Malumbres, J. Oliver, J. C. Cano & P. Manzoni
presented by
Visva Priya Mohanakrishnan
Trilok Jain
Agenda
Introduction
 Related Work
 Proposed Architecture
 Specifics of the Architecture
 Experiments & Results
 Conclusion

Introduction
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
MANET – Mobile ad hoc networks
◦ Collection of wireless mobile nodes
◦ Multihop routing service
◦ Self-reconfiguration
Limitations
◦ Power
◦ Traffic load
◦ Noise and Attenuation (physical layer)
◦ Hidden and exposed node problems (MAC layer)
◦ Network topology changes (network layer)
◦ MANET aware applications (app layer)
Related Work
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
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Set priorities(size of Contention Window)
Select route with sufficient resources
Resource-reservation based routing
MIMO antennas
QAOMDV + ETDMA
Proposed Work
IEEE 802.11e technology
Access Categories
 Voice, Video, Best Effort and Background
 IP TOS to MAC priorities
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EDCF
QoS Architecture
DACME
DACME….

Distributed Access Control Element
◦ QoS measurement module
 Assess QoS parameters
◦ Packet filter
 Block all unaccepted traffic

Method
◦ Applications register with DACME
 QSPEC – BR , DR , JR
◦ Per source information table(destination)
◦ Port State Table(source)
DACME….

Interaction with Routing Protocols
◦ RREP
◦ Multipath DSR

Interaction with IEEE 802.11e Layer
◦ Probing packets with Video Access Priority
◦ Contention-free bursting turned off
Support for QoS
QoS (BR, DR, JR) Framework of
DACME
Bandwidth Probing
 Delay Probing
 Jitter Probing
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Probes are done in this sequence
Bandwidth Probing
Mechanism to determine Available
Bandwidth at the destination site
 n equal sized packets are sent to
Destination

◦ Inter Arrival Time (AIT) = Δt / n – 1
◦ Bandwidth = 8*packet_size / AIT bits/second

Source decides whether to accept the
connection based on Bandwidth reply
Bandwidth Probing (contd.)

Probe Size Tuning - optimum Number of
Packets per Probe (n)
◦ More packets means more accuracy but more
overhead
Bandwidth Refinement
 Correction Processes

Probe Size Tuning
System Constraints
 Factors on which Inter Arrival Time
depends

◦ End-to-End path congestion (c)
◦ Number of Hops in the path (h)
◦ Number of Packets per probe (n)
Probe Size Tuning (contd.)
Experimental Scenario for the Tuning Process
Probe Size Tuning - Results
n = 10
Bandwidth Refinement
Done by multiple probes
 Each successive probe updates the mean
and standard deviation values for the
Bandwidth
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◦
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Bandwidth is refined iteratively
Admission Control
Decision for accepting, maintaining or
refusing a connection
 After receiving Bi,

◦ Calculate the new Bandwidth Estimator B’
 If B’ > BR -> Accept
 If B’ < BR -> Reject
( with 95 % confidence level)
Repeat for Nmax times
Delay Probing

Consecutive request_probe/reply_probes
needed to access delay
◦ Calculate the average delay (De(0))
◦ Calculate the predicted delay using
 An estimation function (a function of Path
Utilization)
 De(0)
Delay Probing (contd.)
If Bandwidth Constrained/ Blocked Traffic
◦ dmin = D’e(umin) * De(0)
◦ dmax = D’e(umax) * De(0)
else
◦ dmin = 0.9 * De(0)
◦ dmax = 1.1 * De(0)
Accept if dmax < DR, Reject if dmin > DR
Repeat
Jitter Probing
Source sends packets with same size, ToS
field, data rate as the application
 Destination calculates the standard
deviation for jitter and replies
 In case, packets from application are
flowing, they can be used

Jitter Probing (contd.)
If
◦ 2.1 * SD < JR : ACCEPT
◦ 1.9 * SD > JR : REJECT
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Duration of Probing Period
◦ Depends on Bandwidth Available
◦ Source Load
Routing in MANETs

Required for Optimum Performance
◦ Highly responsive to Interruptions
◦ Should detect Path Losses
◦ Should be able to find new Paths ASAP
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MDSR – Multipath Extension to DSR
◦ Integration of route discovery & assignment
◦ Maximum path disjointness under low
additional routing load
MDSR
Consecutive paths used are disjoint most
of the time
 Additional route requests are propagated
if their route lengths <= first route
request
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Experiments
Segregation of QoS traffic from Best
Effort Traffic using IEEE 802.11e
Segregation of QoS traffic from Best
Effort Traffic using IEEE 802.11e….
Segregation of QoS traffic from Best
Effort Traffic using IEEE 802.11e…….
Reducing the impact of Routing
using Multipath Routing
Reducing the impact of Routing
using Multipath Routing……
Application level QoS support through
Distributed Admission control
Application level QoS support
through Distributed Admission
control…
Application level QoS support
through Distributed Admission
control…
Application level QoS support
through Distributed Admission
control…
Conclusions
The new Architecture overcomes the
effects of congestion and mobility in
MANETs
 Able to quickly respond to topology
changes
 Is easily deployable
 Can maintain a continuously high Video
throughput and low delays
 Probing packets do not affect the
performance of sessions negatively
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Thank you !!! 