Post on 29-Jan-2016
description
August 24, 2005 QShine 2005, Orlando, Florida 1
Enhancing QoS Support forVertical Handoffs Using Implicit/Explicit Handoff Notifications
Ling-Jyh Chen, Guang Yang, Tony Sun,M. Y. Sanadidi and Mario Gerla
Computer Science DepartmentUniversity of California, Los Angeles
QShine 2005, Orlando, Florida 2August 24, 2005
QoS Enhancement for Vertical HandoffsQoS Enhancement for Vertical Handoffs
Goal: Providing highly agile system for mobile applications.
QShine 2005, Orlando, Florida 3August 24, 2005
Related WorkRelated Work Conventional adaptive method: AIMD
TCP, RAP, … TEAR, TFRC, …
They DO NOT perform well in vertical handoffs[Gurtov et al, MC2R ’04].
Our solution: Handoff Notifications: Implicit Handoff Notification Implicit Handoff Notification and
Explicit Handoff NotificationExplicit Handoff Notification Enhanced Service Agility Schemes: Fast Rate AdaptationFast Rate Adaptation and
Early Rate ReductionEarly Rate Reduction
QShine 2005, Orlando, Florida 4August 24, 2005
IImplicit mplicit HHandoff andoff NNotificationotification
Vertical handoffs usually result in drastic changes in the link capacity.
By monitoring the end-to-end capacity, one can identify the occurrence of a vertical handoff.
Passive capacity monitoring tools:TFRC ProbeTFRC Probe & TCP Probe TCP Probe (CapProbe based)
QShine 2005, Orlando, Florida 5August 24, 2005
Background on CapProbeBackground on CapProbe
T3
T2 T3
T3
T1
T3
Narrowest LinkNarrowest Link
20Mbps 10Mbps 5Mbps 10Mbps 20Mbps 8Mbps
Capacity = (Packet Size) / (Dispersion)
QShine 2005, Orlando, Florida 6August 24, 2005
TFRC: TCP Friendly Rate Control TFRC: TCP Friendly Rate Control
TFRC is an equation based unicast protocol. TFRC mimics the TCP long-term throughput by utilizing the
function:
The receiver is responsible for calculating the loss event rate p and sending it back to the sender once per round-trip time.
The sender is responsible for adjusting its sending rate Tactual to be close to T.
22 33 1 32
3 8RTO
sT
p pR t p p
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Embed CapProbe algorithm within TFRC by sending two packets back-to-back every n packets
TFRC Probe was assessed in [E2EMON’04].
TFRC ProbeTFRC Probe
QShine 2005, Orlando, Florida 8August 24, 2005
TCP ProbeTCP Probe
Delayed Ack
TCP Probe:
CapProbe:
TCP Probe was assessed in [GI’05].
QShine 2005, Orlando, Florida 9August 24, 2005
Implicit Handoff Notification
TCP/TFRC Probe continuously estimate the link capacity, using 50 samples per estimate.
A vertical handoff can be identified when a dramatic capacity change is observed.
An IHN is generated when
1. Cnew > αCpre or
2. Cnew < βCpre
where α =5 and β=0.2.
QShine 2005, Orlando, Florida 10August 24, 2005
Enhancing QoS using Enhancing QoS using IHNIHN
Fast Rate Adaptation (FRA) FRA monitors the capacity. When vertical handoff from LOW to HIGH is observed, FRA
changes ssthresh of TCP/TFRC. TCP/TFRC enter slow start, instead of staying in congestion
avoidance.
FRA+IHN is end-to-end.
However, IHN does not work with HIGH to LOW handoff. Decreasing ssthresh does not change TCP/TFRC behavior.
QShine 2005, Orlando, Florida 11August 24, 2005
Explicit Handoff Notification
Need an “Intelligent Handoff Manager”. EHN is generated prior to
the occurrence of handoff.
Smart Decision Model
QShine 2005, Orlando, Florida 12August 24, 2005
Enhancing QoS using Enhancing QoS using EHNEHN LOW-to-HIGH:
Fast Rate Adaptation (FRA)
HIGH-to-LOW: Early Rate Reduction (ERR):
Reduce rate in advance to prevent bulk packet losses.
QShine 2005, Orlando, Florida 13August 24, 2005
EvaluationEvaluation
Simulation Scenario (NS-2) Vertical handoff between 802.11b
(5.5Mbps) and 1xRTT (150kbps).
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EvaluationEvaluation
TFRC: vertical handoff from LOW to HIGH
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EvaluationEvaluation
TCP: vertical handoff from LOW to HIGH
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EvaluationEvaluation
TFRC: vertical handoff from HIGH to LOW EHN (a): EHN when the handoff occurs EHN (b): EHN one OWD before the handoff
QShine 2005, Orlando, Florida 17August 24, 2005
EvaluationEvaluation
TFRC: vertical handoff from HIGH to LOW
QShine 2005, Orlando, Florida 18August 24, 2005
SummarySummary
We have proposed IHN and EHN to notify the sender about the occurrence of vertical handoff.
We have proposed FRA (for IHN) and ERR (for IHN/EHN) for better QoS for vertical handoff.
QShine 2005, Orlando, Florida 19August 24, 2005
Thank you
Questions are welcome. For more info, please visit our web at
http://www.cs.ucla.edu/NRL/