Engineering Internet QoS1 QoS in Mobile Wireless Networks

Engineering Internet QoS 1

QoS in Mobile Wireless Networks


Outline

oApplicationsoMobile Wireless Networks

Wireless Lan, Bluetooth, Cellular Networks

oMobile services over IP, Cellular IPoMobility and QoSoResearch Directions


Mobile Applications

o Traditional Voice calls to stayo 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


Wireless LAN

Reprinted with Permission from “Engineering Internet QoS - Jha & Hassan, Artech House Publishing, Norwood, MA, USA. www.artechhouse.com

http://www.artechhouse.com/




IEEE 802.11b

o Most popular LAN standardo Free, unlicensed instrumentation, scientific

and Medical (ISM) bando Support for 11 Mbps (Legacy Ethernet 10

Mbps)o No infrastructure neededo Quick deployment as adhoc networkso HIPERLAN (ETSI) – 23.5 Mbps

Expensive Slow deployment


Bluetooth

o Low costo 10 to 100 meter rangeo Free ISM bando Nominal data rate of 1 Mbpso Several applications

Office environment, Home environment, Personal Area network, Public environment, Adhoc networking


Cellular Networks






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)


Mobile IP






Cellular IP






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


Effect on wireless links

o Much higher bit error rate (BER) QoS mechanisms must deal with high

packet losso 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


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


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


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


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


Passive Reservations

o Future location reserved resources may be wasted

o Let “best effort” use it until neededo MRSVP not a standard yet.

Reference [11] has good coverage


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


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 onlyo Multimedia: Re-routing + context transfer

To be done in real-time During handoff for smooth context transfer IETF standard in progress


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


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


Resource Management and handoff

o Predictive resource estimationo Dynamically reserve resource in cells

likely to be visited o Admission control to account for

potential handoff from neighbourso Special packet scheduling

techniques


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


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

Documents

Engineering Internet QoS1 QoS in Mobile Wireless Networks