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.

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

Introduction System Architecture Performance Evaluations Conclusion

Introduction

Streaming media are becoming popular in wireless mobile network

Providing smooth handoff between cells is challenging Rerouting packets may results in burst packet

loss Heterogeneous cells bandwidth

Introduction

A number of mobility management techniques have been purposed to provide smooth handoff in homogeneous networks

This paper focus on Smooth handoff of stream media in

heterogeneous best-effort wireless mobile networks

System Architecture

Principles Reduce impact of packet loss

Establishing multiple paths to the mobile node Transmitting duplicate packets (video layers) over

multiple paths Adapt to available bandwidth in new cell

Employing probing techniques to estimate available bandwidth in new cell

Change transmission rate adaptively

System Architecture

Path Management Discover and maintain m

ultiple path between sender and receiver

Make use of Mobile IP options Simultaneous binding

Allow receiver to register multiple COAs (Care-Of-Address)

Route Optimization Allow sender to be inform

ed about receiver’s COAs registrations

System Architecture

Rate Control 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

Multipath Distributor Calculate the number of

video layers and bitrates Decide the paths to trans

mit layers Video Layer-Path Adapta

tion (VLPA)

System Architecture

Multipath Distributor Video Layer-Path Adaptation (VLPA)

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

Multipath Distributor Video Layer-Path Adaptation (VLPA)

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 wh

ose transmission rate ≥ ri

VLPA runs periodically (40ms in simulations)

Performance Evaluations

Comparison Schemes 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 EvaluationsSimulator 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

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

Bandwidth in old cell= 7.8 Mbps

Node speed = 30 mph

RTT = 60 ms

SP_NF:Single Path No Forward

SP_FF:Single Path With Forward

MPATH:Multipath Handoff scheme

PROXY:Proxy-based scheme

Performance Evaluations

All, except PROXY, throughput decrease as RTT increases TFRC rate control relies on end-to-end feedback

9.4Mbps 6.2Mbps

Performance Evaluations

All, except PROXY, throughput decrease as node speed increases Node spends less time in overlapped region TFRC rate control performs end-to-end feedback less often Slower to acquire new available bandwidth

9.4Mbps 6.2Mbps

Performance Evaluations

MPATH does not suffer from rerouting loss Node continues receive p

acket from all base stations

MP_Base (Base layer of MPATH) has near zero loss Redundant transmission i

n all base stations

Performance Evaluations

(9.4Mbps) (6.2Mbps)

Performance Evaluations

(9.4Mbps) (6.2Mbps)

Performance Evaluations

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

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

9.4Mbps 6.2Mbps

Performance Evaluations

Redundant transmissions of packet lower bandwidth efficiency

Different base stations layout affect transmission redundancy

Performance Evaluations

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

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

Multipath Smooth Handoff Scheme Protect important data (base layer) through redun

dant transmissions on multiple paths Performance is comparable to proxy-based sche

me Overhead is insignificant as size of overlapping ar

ea is limited in practice

Final Thought

Extensive simulation results Reduction in number of supported nodes is

indeed large