Portwood_Bluetooth_Java

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Lookup • Lookup refers to the things that you can do with the lookup services that are determined via discovery • Lookup is similar to a name server – A process – Keeps track of all services that have joined a Jini community • Differs from a name server – Richer set of semantics than provided by traditional name server

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Nội dung Text: Portwood_Bluetooth_Java

Bluetooth™ and Java™ Technologies in the Wireless Environment Michael T. Portwood, MS President & CEO Exuberance, LLC
Agenda • What is Bluetooth™ wireless technology – Technology Overview – Weaknesses – Strengths • What is Jini™ technology • Bluetooth, Jini™ technology, and the Wireless Environment • Conclusion • Question & Answer
What is Bluetooth™ Wireless Technology Overview • Technology started by Ericsson • Named after 10th century Viking king (Harald Blatand) • A global wireless technology specification • “Always on” communication • Radio frequency based • Inexpensive • Intended for … – Portable devices – Desktop machines – Peripherals
Bluetooth™ Wireless Technology Details • Baseband protocols – Circuit switching – Packet switching • Uses 24 GHz globally available unlicensed ISM radio band • Effective range is 10 meters • Slow communication rate (721Kbps) • Small number of stations – 8 devices / piconet – 3 voice channels • Secure – Spread spectrum
Comparison of Wireless Technologies Feature & Function Infrared 802.11 HomeRF Bluetooth™ Wireless LANs Connection Type Infrared, narrow Spread Spread Spread beam spectrum spectrum spectrum Spectrum Optical RF RF RF 850 nm 2.4 GHz 2.4 GHz 2.4 GHz Transmission Power 100mW 100mW 100mW 1mW Data Rate 16Mbps 1Mbps, 1Mbps, 1Mbps 2Mbps 2Mbps Range 1 meter 100 meters Typical home 3 meters Supported Devices 2 127 8 Voice Channels 1 VOIP 6 3 Addressing 32 bit physical 48 bit MAC 48 bit MAC 48 bit MAC ID
Bluetooth™ Technology Strengths • Inexpensive • Superior range compared with IR • Omnidirectional, not requiring line of sight • Designed for ad hoc networking • Both voice and data channels • Well defined specification • Large number of implementing companies
Bluetooth™ Technology Weaknesses • Slow communication rate (1 Mbps) • Short networking range • Limited number of network connections • Large and complex specification (over 1000 pages)
Bluetooth™ Wireless Technology Application Areas • Pure computing • System Applications applications – In-vehicle systems – Presentations – Payment Systems – Card Scanning – Behavior Enforcement – Synchronizing Data – Collaboration – Remote Synchronization – Mobile E-commerce – Printing – Scanners • Ubiquous Applications – Communicator platforms – Electronic Books – Travel – Home Entertainment
What is Jini™ Technology • Jini™ Technology is designed for reliable distributed computing • Features – Simplicity – Reliability – Scalability
What Jini™ Technology is not • Jini is not a name server • Jini is not JavaBeans or Enterprise JavaBeans (EJBs) • Jini is not RMI • Jini is not a distributed operating system
Five Key Features of Jini™ Technology • Discovery • Lookup • Leasing • Remote Events • Transactions
Discovery • Discovery is the process of finding available lookup services • The Jini discovery protocol is the means by which Jini-aware code finds Jini communities
Jini™ Discovery Protocols • Multicast Request Protocol • Multicast Announcement Protocol • Unicast Discovery Protocol
Lookup • Lookup refers to the things that you can do with the lookup services that are determined via discovery • Lookup is similar to a name server – A process – Keeps track of all services that have joined a Jini community • Differs from a name server – Richer set of semantics than provided by traditional name server
Lookup Actions • Publishing a Service • Downloading a Proxy • Finding a Service
Leasing • Leasing refers to the process of allocating resources to community members • Leases are granted for a specified period of time • Addresses problems with network fragility
Remote Events • Remote event is a technique for members of the community to notify one another of change • Asynchronous notifications • Consistent with events used in Java
Differences Between Local and Remote Events Remote Events Local Events – Difficult to deliver – Easier to deliver events events in the order that in the order that they they were generated were generated – Events may be – Always delivered undelivered – Cost of delivery is low – Cost of delivery is high – The sender knows that – The sender does not it can safely deliver the know if it can safely deliver the event to the event to the consumer consumer
Transaction • A transaction is a unit of work • Transactions are used to complete complex units of work that may fail before complete • Two phase commit • Transactions are not heavily used in Jini™ applications
Transaction (cont.) • Transaction provide… – Atomicity – Consistency – Isolation – Durability