Research and Latest Trends in Mobile Computing
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Transcript of Research and Latest Trends in Mobile Computing
© Tata Consultancy Services ltd. April 22, 2023 1
Research and Latest Trendsin
Mobile ComputingMobile Computing with Recent trends and Future ChallengesTCET-ISTE
22nd July 2006
Vijay T. Raisinghanislides available on http://www.it.iitb.ac.in/~rvijay
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Mobile Computing
Two word definition in itself: computing while mobile Could be wireless or even wired
Laptop connection over WiFi or Ethernet Application could be local on the device or connecting to server over
network Mobile computing becoming synonymous with wireless mobile
computing Key characteristics
Low device resources (interface, display, memory, battery, CPU) Disconnected operation Wrt Wireless
Low / varying bandwidth (compared to wire-line) Handoffs/changing servers Disconnections
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Latest trends in Mobile Computing
Converged devices (communication, consumer electronics, computing) Phone, Radio/TV, Camera, PC – all in one
Seamless mobility Mobility across heterogeneous wireless networks (WiFi GSM)
Device operating systems Moving towards Linux from Symbian and Windows CE
Motorola has already introduced Linux smart phones BREW (Binary Runtime Environment for Wireless) from Qualcomm
Device form factor Global Positioning System Built-in sensors
Gait sensors for security Ad-hoc networks M-Commerce
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Latest Trends in Mobile Computing - Examples
Killer Applications Real-time gaming, video telephony, web-browsing, multiplayer
games, streaming video/audio. An example below:
Network WiFi Mesh networks to provide outdoor mobile connectivity WiMAX (802.16): Being rolled out in many countries
802.16e – Mobile WiMAX
Movie PosterWith
Visual Code
Cell phone with camera/code scanner
Server with
video clips
Code
Media clip
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Latest Trends in Mobile Computing – ExamplesBREW
Binary Runtime for Wireless Environment® (BREW™) provides a framework for creating applications on a wide variety of mobile devices
Application examples: Email, IM, navigation (location based), address content sync, games, etc
Product of QUALCOMM Internet Services, a division QUALCOMM Incorporated
BREW applications run on phones on which BREW Application Execution Environment (AEE) is present. AEE is loaded by the manufacturers using the BREW Porting Kit
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BREW (contd.)
BREW is thin and fast Platform sits right on top of chip system software, enabling fast
C/C++ native applications BREW is open
Supports other languages beyond native C/C++, including alternative execution environments such as Java, Extensible Markup Language (XML), and Flash
Source: Qualcomm Inc.
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BREW SDK
Facilitates development of software applications Provides
general development and debugging tools sample applications with source code reference material and user guides phone emulator: lets developers run applications on PC
BREW SDK is available on Qualcomm website free of cost Microsoft VC++ is used as the development enviroment
DLL can be used on emulator ARM compiler used to create mod file for handset
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BREW uiOneTM
Traditional application
Source: uiOne: Developing the core UI, BREW Conference 2005, Qualcomm Inc.
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BREW uiOneTM
uiOne application
Source: uiOne: Developing the core UI, BREW Conference 2005, Qualcomm Inc.
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BREW uiOneTM
Flexible application Layout, etc. defined on the
server UI look and feel can be changed
by changing code on server Enables dynamic user
experience
Source: uiOne: Developing the core UI, BREW Conference 2005, Qualcomm Inc.
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Research in Mobile Computing
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Mobile Computing Example
Wireless mediumWireline
Mobile infrastructure
Data Server
Mobile device
Example Scenario
User
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Selected Mobile Computing Journals/Conferences
Journals IEEE: Transactions on Mobile Computing (TMC) ACM: Mobile Computing and Communications Review (MC2R)
Conferences ACM Mobile Computing and Networking (MobiCom) IEEE Infocom IEEE/ACM Conference on COMmunication System softWAre and
MiddlewaRE (COMSWARE) Asian International Mobile Computing Conference (AMOC)
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Mobile Computing Research Areas – Overview
Wireless mediumWireline
Mobile infrastructure
Data ServerMobile device
User
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Mobile Computing Research – Overlap
Networking and Distributed Systems Fault tolerance
Operating Systems Power management, disconnected operation
Computer Architecture Wearable computers
Software Engineering Dynamic reconfiguration
Human Computer Interaction Context awareness
Security and Privacy Biometric authentication
Sensing and Actuation Location sensing, robotics
Source: Carnegie Mellon, http://www.csd.cs.cmu.edu/research/areas/mopercomp/
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Mobile Computing Research Areas – Summary
User and Mobile Device Interface design, authentication, innovative applications, security,
performance improvement, software defined radio Mobile Infrastructure
Integration and internetworking of wired and wireless systems, support for seamless mobility, quality of service
Modeling Analysis and Simulation Mobile agents Wireless Test beds for Technology evaluation Ad-hoc networks Underwater networks
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Recent Research Papers
MobiCom 2005 Pradeep Kyasanur, Nitin Vaidya (University of Illinois at Urbana-
Champaign, US) In an ad-hoc network scenario they study the impact on
network capacity of the number of channels and number of interfaces on a mobile device
Bhaskaran Raman, Kameswari Chebrolu (IIT Kanpur, IN) 802.11 in long-distance mesh networks being designed/used
for low-cost rural connectivity. They describe a new MAC protocol suited for such networks in terms of efficiency
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Recent Research Papers
IEEE TMC 2006 Ying Cai, et al, (Iowa State, US)
Real-time monitoring of movement of mobile nodes in a region. Performance improvement proposed for lowering communication and processing costs.
Mobile patient monitored using sensor network. Data is transmitted using 3G network.
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Recent Research Papers
Infocom 2006 Srinath Perur, Sridhar Iyer (IIT Bombay)
Reachability in sparse mobile ad-hoc networks. Proposed a new way of deciding how “connected” is a sparse ad-hoc network, by looking at connected node pairs.
Raghuraman Rangarajan, Sridhar Iyer (IIT Bombay) WIND: A tool for capacity-constrained design of multi-tier
wireless networks COMSWARE 2006
Vijay Raisinghani (TCS), Sridhar Iyer (IIT Bombay) Optimized communication stacks for wireless devices
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Recent Research Papers
MC2R Sangheon Pack, et al (Seoul National University, Korea)
Selective neighbor caching scheme for fast handoff in IEEE 802.11 wireless networks: Considering hand-off patterns a mobile node’s context is propagated to selected neighboring access points
Paul Grace, et al (Lancaster, UK) Middleware proposed to enable mobile client to discover
services and interact with them
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Detailed Example:Cross Layer Feedback in Mobile Devices
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Typical Mobile Wireless Network
MWN characteristics High bit error rate of wireless channel Mobility induced disconnections
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Typical Protocol Stack Architecture – Layered
Application
Transport
Network
MAC
Physical
User programs, interface
Connection management, flow/error control (e.g. TCP)
Routing, addressing (e.g. IP)
Error free tx; medium access (e.g. 802.11)
Tx of raw bits (e.g. 802.11)
•Application has very low awareness of physical layer and vice-versa•Layered architecture: Layer n has function specific Service Access Points for layers n-1, n+1
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Layered example: TCP
In wireless networks many packet losses are due to bit errors
TCP on packet loss assumes network congestion reduces throughput TCP’s congestion assumption fails
unaware of wireless physical layer reduction in send window inappropriate
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Cross layer feedback: Motivation
Protocol stack layering useful: software engineering perspective
Strictly layered stacks do not perform well over wireless networks network conditions are highly variable: random errors;
intermittent disconnection mobile nodes are “resource poor” Several assumptions from fixed wired networks do not
hold for wireless: packet losses, disconnections, mobility
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Observation
Cross layer information can help improve performance over wireless networks
Upper to lower layers TCP timer information application QoS requirements user feedback
Lower to upper layers link characteristics network connectivity status
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Some existing approaches
TCP thruput information to tune physical layer power (Chiang. IEEE JSAC, 2005)
ATCP / RWC for TCP (Raisinghani VT, Singh A, Iyer S. IEEE ICPWC, 2002)
TCP QoS information to adapt link layer retransmissions (Chiasserini, Meo. IEEE Globecom, 2001)
Layer2 information to MobileIP for IP handoff (Wu, et al. MONET, 2001 )
TCP fast retransmit (Caceres, Iftode. IEEE JSAC 95)
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Cross Layer Feedback: Optimizing TCP for MWN
Several approaches focus on mitigating Adverse effect of wireless channel Mobility induced disconnections
Any approach involves one or more of: Fixed Host (FH) TCP stack modification Base Station (BS) per-connection support Mobile Host (MH) TCP stack modification
Typically assume TCP sender at the FH
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Our approach: Optimizing TCP for MWN
Modification to TCP stack at MH only Optimizing TCP to mitigate effect of
mobility induced disconnections Focus on TCP sender at Fixed Host (FH) Approach: Use of cross-layer feedback
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User feedback: Motivation
Cross layer feedback has useful optimizations Designed for standard problems: handoff, link layer retx,
etc. Optimizations may not fulfill user needs
User aware of exact self needs User can take better decisions which are contrary to system
behavior Required for improving user experience
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User Feedback
User feedback examples: Impending disconnection information Dynamic changes in application priorities
For example: In view of impending disconnection, an ongoing FTP may become more important than an ongoing video conference; contrary to default system priorities
System can avoid performance degradation by mapping user input to protocol specific actions
E.g. Map user priorities to TCP receiver window of each application on device
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Background: TCP receiver window Reflects receivers available buffer through advertised
window (awnd) in ACKs Optimum awnd = bandwidth*delay (bdp) to fill pipe and
maximize sender throughput awnd < bdp decreases sender throughput Each application on MH may require different awnd,
according to bdp
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Receiver Window Control (RWC)
Exploits idea: Sender throughput decreases as awnd < bdp Higher awnd for high priority applications Restrict awnd for low priority applications
Assume total awnd is a fixed resource (Re)distribute awnd according to priority Results in download bandwidth change for
applications on device
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Cross Layer Feedback: Issues
How to pass layer n information to layer m ? When incorporating feedback from other layers in layer n
How to protect layer n’s correctness, reliability ? How to resolve conflict due to feedback from multiple
layers to layer n? How to pass event information to other layers (interrupt
v/s polling)? How to ensure
maintainability of CLF ? minimum overhead due to CLF ?
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Cross Layer Feedback: “Punch hole” approach
Ad-hoc approach Introduce additional code in
layer for CLFApp
TCP
IP
MAC
Phy
get_handover_info()
Code block
for CLF
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CLF:“Punch hole”
Each additional CLF code block can slow down data path (thruput) of layer
Porting CLF will require rewriting for specific OS
Difficult to control to layer’s correctness since updates by different CLF code blocks
Difficult to disable/ remove code intertwined with regular layer code
Difficult to do fast prototyping/additions since ad-hoc
Multiple event monitors within a layer could slow down data path (thruput) of layer
App
TCP
IP
MAC
Phy
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CLF Architecture
CLF basically stack modification Multiple ad-hoc cross layer modifications can affect
stack's reliability, efficiency, maintainability Design goals for architecture
Efficiency: minimal overheads (e.g. cpu, memory, data path delay); enhanced performance
Minimum intrusion: protect stack correctness; easy to extend / reverse CLF
Portability: easy porting to different systems Rapid prototyping: new CLF idea easy to develop/deploy
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ECLAIR: CLF architecture
Optimizing SubSystem: Cross layer feedback algorithms (protocol optimizer – PO); receive layer events; decide other layers behavior
Tuning Layer: Monitor layer events; API to protocol optimizer; access layer's control data structure values
Minimal CLF code in stack, if required
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ECLAIR details
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ECLAIR: (e.g.)TL APIs
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Linux internals: TCP (for RWC)
sock.h header file.Contains socket and tcp data structure
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ECLAIR implementation (Linux): RWC
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ECLAIR implementation (Linux): RWC (contd…)
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ECLAIR validation
Simulation: no RWC wget: no RWC
•Similar setup; no CLF; equal thruput
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ECLAIR validation
•Similar setup; RWC
Simulation: with RWC wget: ECLAIR RWC
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ECLAIR performance
m applications
n reads
O(m x n)•non-ECLAIR RWC invoked on each read()• read() involves user-kernel crossing
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ECLAIR: Salient features
Event Notification: TLs provide facility for POs to register for interesting events at a layer. E.g. TCP can register for handover events at Mobile-IP layer
Switch on/off: Cross layer system is separate. Can be easily/dynamically switched on or off. Individual POs may be switched on/off
Seamless mobility: through POs that monitor/ control multiple protocol stacks. E.g., seamless mobility PO monitors CDMA (or GPRS) / WLAN interfaces’ signal strength. Algorithm maps signal strength to throughput achievable on interface. PO takes decision to change interface
User Tuning Layer(UTL): UTL allows device user or external entity e.g.: a distributed algorithm or base station, to tune the device behavior
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Related Work
Sudame, Badrinath, MONET 2001 CLF: link conditions; internal ICMP messages / handler Each application defines application/transport layer
adaptation Inouye, Binkley, Walpole, Mobicom 1997
CLF: interface – add/remove, cost, bandwidth Adaptation module(per layer) manages
adaptation/sequential propagation of (a) events (b) policies
Any to any layer CLF / generic architecture/optimizations not discussed
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Future Work
Multiple cross layer interactions could affect protocol correctness Resolve cross layer feedback conflict
Extend ECLAIR for seamless mobility Add components for interaction with network nodes
ECLAIR is good for asynchronous CLF Improve ECLAIR for synchronous CLF
© Tata Consultancy Services ltd. April 22, 2023 64
Thank you
[email protected]@it.iitb.ac.in
http://www.it.iitb.ac.in/~rvijay http://www.it.iitb.ac.in/~sri