2. Engineering Internet QoS 2
Outline
o Applications
o Mobile Wireless Networks
Wireless Lan, Bluetooth, Cellular Networks
o Mobile services over IP, Cellular IP
o Mobility and QoS
o Research Directions
3. Engineering Internet QoS 3
Mobile Applications
o Traditional Voice calls to stay
o New services: Internet data applications
WWW, file transfer, e-mail
o Multimedia applications
Video conferencing, multicasting
3G IP-enabled handsets already supporting
voice and multimedia calls
4. Engineering Internet QoS 4
Wireless LAN
Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com
5. Engineering Internet QoS 5
IEEE 802.11b
o Most popular LAN standard
o Free, unlicensed instrumentation, scientific and
Medical (ISM) band
o Support for 11 Mbps (Legacy Ethernet 10 Mbps)
o No infrastructure needed
o Quick deployment as adhoc networks
o HIPERLAN (ETSI) – 23.5 Mbps
Expensive
Slow deployment
6. Engineering Internet QoS 6
Bluetooth
o Low cost
o 10 to 100 meter range
o Free ISM band
o Nominal data rate of 1 Mbps
o Several applications
Office environment, Home environment,
Personal Area network, Public environment,
Adhoc networking
7. Engineering Internet QoS 7
Cellular Networks
Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com
8. Engineering Internet QoS 8
Cellular Network Standards
o GSM
Circuit switched, 9.6 Kbps
o General Packet Radio System (GPRS)
9.6 – 28.8 Kbps and higher rates
o Third Generation
IP based communication between mobile handset
and network
144 Kbps inside vehicle, 384 Kbps for pedestrians
and 2 Mbps inside building (fixed wireless access)
9. Engineering Internet QoS 9
Mobile IP
Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com
10. Engineering Internet QoS 10
Cellular IP
Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com
11. Engineering Internet QoS 11
Impact of Mobility on QoS
o Several limits and constraints in mobile
environment that poses additional
challenges for QoS support
o Three major areas
Effect of wireless links
Effect of movement
Limitation on portable devices
12. Engineering Internet QoS 12
Effect on wireless links
o Much higher bit error rate (BER)
QoS mechanisms must deal with high packet
loss
o Quality Variation on links
Weather condition, interference with other
users, barriers such as buildings, distance
from Base stations
Some predictable (can be modeled
statistically) but most unpredictable
13. Engineering Internet QoS 13
Error Correction
o Forward Error Correction (FEC)
More bits to correct, higher overhead
Know link quality in advance
o Adaptive FEC
Appropriate selection of FEC dynamically
complex logic in System
14. Engineering Internet QoS 14
Effect on Movement
o User free to move
Route changes during a session
o Resource reservation for QoS
Complex when route changes frequent and not
predictable
o Handoff problem
When user moves out of coverage of a BS or AP
Easy in circuit switch network
• no Relocation of processing, data and other contexts
15. Engineering Internet QoS 15
Limitations on portable devices
o PDAs, Mobile phones, handsets have
limited processing power, memory and
interface
o Power restrictions
Intermittent availability
o Network QoS no good if device can’t cope
QoS management techniques must consider
end system capabilities
16. Engineering Internet QoS 16
Intserv and mobility
o RSVP reserves QoS along the path
Path changes dynamically in mobile networks
o MRSVP
Reserve resources in advance where the mobile host
will visit in future
Uses MSPEC to specify this
• Easy when mobility pattern regular, GPS in car etc may be of
help
• What if pattern unpredictable?
Proxy agents to reserve on behalf of mobile hosts in
future locations
17. Engineering Internet QoS 17
Passive Reservations
o Future location reserved resources may be
wasted
o Let “best effort” use it until needed
o MRSVP not a standard yet.
Reference [11] has good coverage
18. Engineering Internet QoS 18
Diffserv and mobility
o SLA needed between ISPs and users
Fixed network SLA negotiation process manual (Web
form etc. )
o Mobile user may be in a foreign netwok
SLA need to be negotiated dynamically
Needs signaling for this purpose
o Resource problems similar to Intserv
Needs must be available in new network/locaiton
19. Engineering Internet QoS 19
Context Aware handoff
o Context
QoS parameters (PHB for diffserv), packet filtering
rules, security and other features
Known to base stations
o Best effort: rerouting only
o Multimedia: Re-routing + context transfer
To be done in real-time
During handoff for smooth context transfer
IETF standard in progress
20. Engineering Internet QoS 20
Application Adaptivity
o Hideable fluctuations
Increased latency, reduced signal quality
Traditional mechanisms
• FEC, jitter buffering
o Non-hideable fluctuations
Loss of power in mobile terminals, resource shortage
in new location, moving from high-speed to low-
speed cells – typical in 3G
Application adaptivity: e.g., Switch from color to b/w
21. Engineering Internet QoS 21
Resrouce Reservation research
o MRSVP (discussed earlier), several
modifications to RSVP suggested
o Mahadevan & Sivalingam
Partition network into hierarchy
• Internet at top, base stations at bottom
• Interdomain mobility uses Mobile IP, local mobility
handled by routing table changes
• New QoS parameters such as loss profiles,
probability of seamless connection, rate redution
22. Engineering Internet QoS 22
Resource Management and handoff
o Predictive resource estimation
o Dynamically reserve resource in cells likely
to be visited
o Admission control to account for potential
handoff from neighbours
o Special packet scheduling techniques
23. Engineering Internet QoS 23
Transport Layer issues
o Traditional TCP
Missing ACK interpreted as sign of congestion
Trigger slow start algorithm
o Mobile/Wireless network
Packet loss on wireless link
Handoff of mobile terminals
o Several proposals
I-TCP, M-TCP, Freeze-TCP
24. Engineering Internet QoS 24
TCP Optimizations
o Divide connection into two parts
Fixed (traditional TCP)
Wireless segment (optimize)
o TCP connections terminated at access point that
acts as a proxy for mobile hosts
I-TCP, Snoop TCP, M-TCP (various optimisations)
o Freeze TCP: Modification of TCP on mobile host
only
Other end and intermediate routers not affected