Transcript An End-to-End Multipath Smooth Handoff Scheme for Stream …

An End-to-End Multipath
Smooth Handoff Scheme
for Stream Media
Yi Pan
Meejeong Lee
Jaime Bae Kim
Tatsuya Suda
IEEE Journal On Selected Areas In Communications. Vol. 22, No. 4, May 2004
Outline
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Introduction
System Architecture
Performance Evaluations
Conclusion
Introduction
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Streaming media are becoming popular in
wireless mobile network
Providing smooth handoff between cells is
challenging
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Rerouting packets may results in burst packet
loss
Heterogeneous cells bandwidth
Introduction
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A number of mobility management
techniques have been purposed to provide
smooth handoff in homogeneous networks
This paper focus on
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Smooth handoff of stream media in
heterogeneous best-effort wireless mobile
networks
System Architecture
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Principles
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Reduce impact of packet loss
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Establishing multiple paths to the mobile node
Transmitting duplicate packets (video layers) over
multiple paths
Adapt to available bandwidth in new cell
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Employing probing techniques to estimate available
bandwidth in new cell
Change transmission rate adaptively
System Architecture
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Path Management
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Discover and maintain
multiple path between
sender and receiver
Make use of Mobile IP
options
 Simultaneous binding
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Allow receiver to register
multiple COAs (Care-OfAddress)
Route Optimization
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Allow sender to be
informed about receiver’s
COAs registrations
System Architecture
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Rate Control
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Estimate available
bandwidth on paths
Make use of TCP friendly
rate control (TFRC)
Receiver send packet
loss ratio report to
sender every RTT
System Architecture
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Multipath Distributor
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Calculate the number of
video layers and bitrates
Decide the paths to
transmit layers
Video Layer-Path
Adaptation (VLPA)
System Architecture
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Multipath Distributor
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Video Layer-Path Adaptation (VLPA)
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ri – Cumulative rate from layer 0 (base) to (and
including) layer i
rilayer = ri – ri-1
Number of video layers = Number of distinct
transmission rates on the paths
ri = ith transmission rates (sorted, ascending) on
the paths
System Architecture
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Multipath Distributor
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Video Layer-Path Adaptation (VLPA)
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If transmission rates on paths are 1, 2, 2, 4 Mbps
Number of layers = 3
r0 = 1Mbps, r1 = 2Mbps, r2 = 4Mbps
Layer i is transmitted redundantly through all paths
whose transmission rate ≥ ri
VLPA runs periodically (40ms in simulations)
Performance Evaluations
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Comparison Schemes
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Single path without packet forwarding
 Packets in transit to old base station is discarded
Single path with packet forwarding
 Packets in transit to old base station is forwarded to new
base station
Proxy-based
 Proxy located in each base station for transcoding
 New cell’s proxy retransmit last incomplete video frame
 Assume a centralized controller to inform proxies about the
available bandwidth in new cell immediately
Performance Evaluations
Simulator
OPNET
Coverage radius
300m
Distance between base
stations
500m
Wireless link
802.11b
11Mbps
Wireless link BER
10-3 to 10-5
Wired link
155Mbps
Wired link BER
10-12
Wired Propagation Delay 10μs
Packet Size
1024bytes
Mobile node movement
Trajectory
model
Performance measures are obtained
during handoff
Performance Evaluation
SP_NF:
Single Path No Forward
SP_FF:
Single Path With Forward
MPATH:
Multipath Handoff scheme
Bandwidth in old cell
= 7.8 Mbps
PROXY:
Proxy-based scheme
Node speed = 30 mph
RTT = 60 ms
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MPATH utilize all available paths as soon as enter the
node enters overlapped zone
SP_NF, SP_FF and PROXY may not choose to use the
link with more available bandwidth due to handoff
Bandwidth estimation by TFRC is slow, so SP_NF and
SP_FF are slow in acquiring new available bandwidth
Performance Evaluations
9.4Mbps
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6.2Mbps
All, except PROXY, throughput decrease as RTT
increases
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TFRC rate control relies on end-to-end feedback
Performance Evaluations
9.4Mbps
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6.2Mbps
All, except PROXY, throughput decrease as node speed
increases
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Node spends less time in overlapped region
TFRC rate control performs end-to-end feedback less often
Slower to acquire new available bandwidth
Performance Evaluations
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MPATH does not suffer
from rerouting loss
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Node continues receive
packet from all base
stations
MP_Base (Base layer
of MPATH) has near
zero loss
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Redundant transmission
in all base stations
Performance Evaluations
(9.4Mbps)
(6.2Mbps)
Performance Evaluations
(9.4Mbps)
(6.2Mbps)
Performance Evaluations
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SP_NF and SP_FF has largest packet loss
ratio in most cases
SP_FF significantly reduce rerouting loss,
and thus total loss
MP_Base (Base layer of MPATH) has
virtually zero packet loss ratio due to
redundant transmissions
Performance Evaluations
9.4Mbps
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6.2Mbps
Frame rate = 25fps
Frame with less than 10% packet loss is considered successfully received
Small fluctuation in all schemes in (a) as the new cell has larger bandwidth
and, thus, no congestion
Large fluctuation in SP_NF and SP_FF in (b) as the new cell has smaller
bandwidth and congestion occurs
MPATH shows smooth changes in all case, due to rate control and
redundant transmissions
Performance Evaluations
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Redundant transmissions of packet lower bandwidth
efficiency
Different base stations layout affect transmission redundancy
Performance Evaluations
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Transmission Efficiency = number of unique packets to total
number of transmitted packets
Transmission efficiency decrease as available path increases
Largest reduction occurs when all paths have same
bandwidth
Performance Evaluations
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Each node is guaranteed to get at least 400kbps
Proxy based scheme is used as comparison base
MPATH does not significantly impact the number of
mobile nodes supported
Conclusion
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Multipath Smooth Handoff Scheme
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Protect important data (base layer) through
redundant transmissions on multiple paths
Performance is comparable to proxy-based
scheme
Overhead is insignificant as size of overlapping
area is limited in practice
Final Thought
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Extensive simulation results
Reduction in number of supported nodes is
indeed large