1	Adaptive Mobile Applications Thomas Kunz Systems and Computer Engineering Carleton University http://kunz-pc.sce.carleton.ca/ tkunz@sce.carleton.ca
2	The “Mobile Warrior”
3	Mobile Computing Challenges
4	Adaptive Mobile Applications: System Overview
5	Related Work Typically, related work focuses on bandwidth variation Other resources are also constrained (memory, power, CPU capabilities) and may vary over time Majority of solutions: introduce proxy between client (application executing on mobile device) and server, proxy compresses and filters data stream sometimes, degree of compression depends on available bandwidth user mobility often not addressed/supported Other solutions: view mobile purely as User Interface (WWW browsers, Teleporting, ....) partition client application between mobile and proxy partition directed by application (Rover, MaROS, ....) partition transparent to application (our own focus)
6	Additional Problem: Mobility
7	Mobility: Issues and Ideas As mobile devices roam, the proxy (or proxies) might have to migrate as well: schemes are only efficient if proxy is on direct path between mobile and correspondent host however, not every move requires a proxy migration When to migrate: performance question e.g., when are advantages of migration higher than costs? How to migrate: infrastructure question Consequences of migration: mobility models, simulations e.g., what happens if all cellular subscribers move into same cell (the one that covers the big shopping mall)
8	Proposed Architecture
9	Summary of Achievements Mobile IP software under Linux, including route optimization Comma (provides feedback about execution environment): redesigned to deal with limited devices such as Palm Pilots Trace data analysis (Bell’s Microbrowser) and performance prediction models: scalability of approach Mobile code toolkit for Windows CE (DOMT), redesigned for Palm Pilots based on KVM (KMOT) Sample applications (MPEG and MP3 player), based on Objectspace Voyager and our own toolkits
10	Summary of Achievements Explored mobile applications in WAP Explored traditional adaptation concepts (filter/compress data stream) Prototype for adaptive web browsing “Controls,” both interactive and configuration Known standards & data types enable transcoding at proxy In concert with Comma & other tools for environmental information Prototype of “Geo-web” for geographic organization of information Adaptive map browsing for constrained environments
11	Summary of Achievements Training of Highly Qualified Personnel: Carleton: 2 Research Associates (Thomas Barry, Yang Wang) 6 Master’s students graduated 3 additional students expected to graduate in 2001/2 Waterloo: 2 Master’s students graduated 3 additional graduate students expected to graduate in 2001 1 PhD expected in 2002 Publications: 1 book chapter 2 journal publications 4 refereed conference/workshop papers 7 others (position papers, conferences with abstract reviewed, …)
12	Trace Collection Infrastructure
13	The Big Picture: Traffic Profile (Jan. – Dec. 2000)
14	Sessions: Average Number of Concurrent Sessions, December 2000
15	WAP vs. WWW Traffic Some similarities: Periodicity Daily patterns (and to some extent half-daily patterns) Weekly patterns (and to some extent half-weekly patterns) Not enough trace data to confirm/test for seasonal patterns Self-similarity (Hurst Parameter between 0.79 and 0.82) But also some differences: Smaller packets (95% of all packets less than 220 bytes) Shorter sessions Traffic more balanced (dowlink traffic “only” about 3 times as much data as uplink traffic) No growth trend in data presented in paper, but long-term growth trend clearly visible since
16	Performance Prediction Models: Simple Model
17	Performance Prediction Model: Adding Proxy Layer
18	Model Predictions Capacity limitations: between 8 to 50 concurrent clients Effects of more powerful CPU or parallel gateway servers Effects of adding a proxy layer Changes in user behavior New/more complicated services
19	Mobile Code Toolkits Exploration with Voyager, a free mobile code toolkit based on Java Handoff between proxies Handoff between proxies and handheld device (ongoing) Development of own Toolkits for PDAs: Java-based toolkit for Windows CE devices: DOMT KVM-based toolkit for Palm Pilot/Handspring Visors: KMOT (KVM-based Mobile Object Toolkit) Visualizing code mobility
20	Case Study: MP3 Player over DOMT Required Info: Application Object Graph
21	Objects
22	Inter-Object Communication
23	Experimental Results (DOMT) Implemented MP3 player, decoder (set of heavily communicating objects) can execute locally or remotely Various performance experiments, study impact of Available Bandwidth (19.2 kbps – 2 Mbps) Relative CPU speed (Mobile CPU: Proxy CPU) 1:4 for laptop as client device 1:116 for Windows CE palmtop as client device Results: for high bandwidth and slow client, offloading decoder to proxy can speed up application performance by a factor of 20 and reduce power consumption by 95% For faster client devices, independent of bandwidth, no benefit (actually worse performance) when decoding sound samples in access network
24	KMOT: Mobile Code Toolkit for KVM Based on DOMT, redesigned toolkit to fit KVM constrains: No serialization No reflection mechanism Experiments with “MP3 player” clone (time per frame in ms):
25	Visualizing Mobile Code Executions Applications involving mobile code are complex: All the problems of parallel and distributed applications (concurrency, scale, non-determinism, etc.) Additional problem: where are mobile components? Visual tools used widely in parallel and distributed programming environments for program understanding, fault and performance debugging, … Some popular visualization tools: Poet XPVM Polka Paragraph All support visualizing execution dynamics, none explicitly shows mobility of code
26	Event Visualization
27	Event Visualization (cont)
28	Event Visualization (cont)
29	Conclusions and Future Work Work to date shows feasibility of approach MP3 player: improvement in performance and reduction in power when offloading decoding from slow handset to access network, if there is enough bandwidth Platforms: Windows CE, Palm Pilot Future Work: future 3G systems all IP, devices all support JVM/KVM/Brew/…. Enhance KMOT (KVM-based Mobile Object Toolkit) Automatic construction of the object graph Design of an efficient partition strategies Apply to multimedia applications Larger-scale tests (multiple devices, proxies, more complicated network topology) Other topics of interest: location and location-based services, ad-hoc access networks, etc.