Improving QoS Support in Mobile Ad Hoc Networks Agenda Motivations Proposed Framework Packet-level...
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Improving QoS Support in Mobile Ad Hoc Networks
Agenda
Motivations Proposed Framework Packet-level FEC Multipath Routing Simulation Results Conclusions
Motivations
Challenges for improving QoS in MANET Network congestion, buffer overflow
Same as we met in wired networks, but bandwidth is much lower
Radio channel characteristicsMultipath propagation, path loss, interference …
Frequent topology reconfigurationsConstant rerouting & packet dropping due to link/path failures
Motivations
QoS provisioning in MANET requires QoS-based routing protocol, Medium Access Control (MAC) protocol, and resource reservation protocol to work together.
This work focuses on improving QoS performance at the network layer, addressing packet losses due to link and path failures resulting from node mobility. Improve packet delivery ratio Improve end-to-end delay and jitter Maintain low control overhead Reduce bursty packet losses
Proposed Framework
Multi-path routing protocol (MPR) Spatial reutilization of wireless channel Improve packet delivery ratio, end-to-end
delay and jitter, routing overhead Reduce burstiness of packet losses
Packet-level Forward Error Correction scheme Reduce average packet loss rate Avoid retransmission
Observations Packet-level FEC can reduce packet loss, avoid
retransmission and associated delay. But, no significant gains can be attained by
adopting packet-level FEC over single path routing in MANET.
Packet loss tends to be bursty due to frequent path failures A packet interleaving scheme is needed.
Delay -- packets need to be buffered for interleaving before being sent out.
Memory requirements. Multi-path routing can also act as a packet
interleaver.
Correlated Packet Loss in MANET
A 3x4 Packet Interleaver
Input sequence: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12] Output sequence: [1, 4, 7, 10, 2, 5, 8, 11, 3, 6, 9, 12] No impact on packet loss rate, but effectively reduces
the average burst length, converting bursty losses to random losses.
Multi-path Illustration
Reed-Solomon Erasure Coding
Multipath Routing Scheme Dynamic Source Routing (DSR) is chosen as the basis
protocol for MPR implementation. Major difference between MPR and DSR:
Route Discovery: Target node replies indiscriminately to all incoming route
requests carrying node-disjoint routes. Intermediate nodes no longer reply to route requests.
Route Maintenance: New route discovery initiated only after all active routes
broke. Packet Distribution:
Round robin packet distribution over multiple routes. Up to 3 node-disjoint paths are concurrently in use.
Simulation Model All modifications were integrated directly into
Qualnet. Random waypoint mobility model. 50 mobile
nodes randomly placed in a terrain of dimension (1500, 1500).
CBR traffic, 5 sessions, from 10, 11, 12, 13, 14 to 25, 26, 27, 28, 29, respectively. Each with 500 data packets of size 512 bytes.
IEEE 802.11 MAC with RTS/CTS. Metrics:
Packet delivery ratio, end-to-end delay and jitter, average routing overhead, burst length of packet loss.
Simulation Results:Comparison among MPR, SPR, MPR-FEC and SPR-FEC
Average Packet Del i very Rati o
00. 2
0. 40. 60. 8
11. 2
5 10 15 20 25 35 45Avg. Node Mobi l i ty Rate
(m/ s)
Pack
et D
eliv
ery
Rati
o
Mul t i -pathSi ngl e-pathMP-FEC(5=4+1)SP-FEC(5=4+1)
Average End- to- End Del ay
0
1
2
3
4
5
5 10 15 20 25 35 45
Avg. Node Mobi l i ty Rate(m/ s)
Time
(s) Mul t i - path
Si ngl e- pathMP- FEC(5=4+1)SP- FEC(5=4+1)
Simulation Results:Comparison among MPR, SPR, MPR-FEC and SPR-FEC
Average End- to- End J i t ter
0
1
2
3
4
5
5 10 15 20 25 35 45
Avg. Node Mobi l i ty Rate(m/ s)
Time
(s) Mul t i - path
Si ngl e- pathMP- FEC(5=4+1)SP- FEC(5=4+1)
Simulation Results:Comparison among MPR, SPR, MPR-FEC and SPR-FEC
Avg. DSR Cont rol Overhead
0
100
200
300
400
500
600
5 10 15 20 25 35 45
Avg. Node Mobi l i ty Rate(m/ s)
Ctrl
Pkt
s pe
r No
de
Mul t i - pathSi ngl e- pathMP- FEC(5=4+1)SP- FEC(5=4+1)
Simulation Results:Comparison among MPR, SPR, MPR-FEC and SPR-FEC
Correlated Packet Loss Histogram (1)
Correl ated Packet Loss Hi stogram (Pause t i me = 0)
05
10152025303540
1 2 3 4 5 6 7 8 9 10+Consecuti ve Pkt Loss
Time
s
Si ngl e-path
Mul ti -path (wi thoutFEC)MP-FEC(5=4+1)
Correlated Packet Loss Histogram (2)
Correl ated Packet Loss Hi stogram (Pause t i me = 60s)
0
5
10
15
20
25
30
1 2 3 4 5 6 7 8 9 10+Consecuti ve Pkt Loss
Time
s
Si ngl e-path
Mul ti -path (wi thoutFEC)MP-FEC(5=4+1)
Correlated Packet Loss Histogram (3)
Correl ated Packet Loss Hi stogram (Pause t i me = 120s)
02468
1012141618
1 2 3 4 5 6 7 8 9 10+Consecuti ve Pkt Loss
Time
s
Si ngl e-path
Mul t i -path (wi thoutFEC)MP-FEC(5=4+1)
Effects of Various FEC Redundancy Levels
Avg. Packet Del i very Rat i o
0
0. 2
0. 4
0. 6
0. 8
1
1. 2
5 10 15 20 25 35 45
Avg. Node Mobi l i ty Rate (m/ s)
Pack
et D
eliv
ery
Rati
o
7=4+37=5+27=6+1
Avg. DSR Rout i ng Overhead (RREQ+RREP+RERR)
0
100
200
300
400
500
600
5 10 15 20 25 35 45
Avg. Node Mobi l i ty Rate (m/ s)
DSR
Rout
ing
Over
head
7=4+37=5+27=6+1
Effects of Various FEC Redundancy Levels
Avg. End- to- End Del ay
0
0. 5
1
1. 5
2
2. 5
5 10 15 20 25 35 45
Avg. Node Mobi l i ty Rate (m/ s)
End-
to-E
nd D
elay
(s)
7=4+37=5+27=6+1
Avg. End- to- End J i t ter
0
0. 5
1
1. 5
2
2. 5
5 10 15 20 25 35 45
Avg. Node Mobi l i ty Rate (m/ s)
End-
to-E
nd J
itte
r (s
)
7=4+37=5+27=6+1
Effects of Various FEC Block Sizes
Avg. Packet Del i very Rat i o
0
0. 2
0. 4
0. 6
0. 8
1
1. 2
5 10 15 20 25 35 45
Avg. Node Mobi l i ty Rate (m/ s)
Pack
et D
eliv
ery
Rati
o
5=4+110=8+215=12+3
Avg. DSR Rout i ng Overhead (RREQ+RREP+RERR)
0
50100
150200
250300
350
5 10 15 20 25 35 45
Avg. Node Mobi l i ty Rate (m/ s)
DSR
Rout
ing
Over
head
5=4+110=8+215=12+3
Effects of Various FEC Block Sizes
Avg. End- to- End Del ay
0
0. 51
1. 52
2. 53
3. 5
5 10 15 20 25 35 45
Avg. Node Mobi l i ty Rate (m/ s)
End-
to-E
nd D
elay
(s)
5=4+110=8+215=12+3
Avg. End- to- End J i t ter
0
0. 5
1
1. 5
2
5 10 15 20 25 35 45
Avg. Node Mobi l i ty Rate (m/ s)
End-
to-E
nd J
itte
r (s
)
5=4+110=8+215=12+3
Conclusions
MPR significantly outperforms SPR in all criteria. SPR-FEC performs worse than SPR, due to
inherent packet loss correlation in MANET. MPR reduces most consecutive packet losses to
single packet losses, desirable by real-time video/audio applications.
MPR-FEC further improves packet delivery ratio, but at the cost of higher delay, jitter and control overhead (compared to MPR).
Higher FEC redundancy may not always be good.
Questions?
Thanks!
The End