Lesson 21 Third-Generation Mobile Phones Digital Voice and Data.ppt
- 1. Unit 7 Audio & Speech Lesson 21 Third-Generation Mobile Phones: Digital Voice and Data
- 2. 25/8/19 2 Third-Generation Mobile Phones: Digital Voice and Data • Backgrounds • Text tour • Language in use – Vocabulary
- 3. 25/8/19 3 • Terminology – Video conferencing – m-commerce – quality-of-service – wireless LAN – VHS: Video Home System – ADSL: Asymmetrical Digital Subscriber Loop Backgrounds
- 4. 25/8/19 4 Video conferencing Videotelephony comprises the technologies for the reception and transmission of audio-video signals by users at different locations, for communication between people in real-time. Videoconferencing implies the use of this technology for a group or organizational meeting rather than for individuals, in a videoconference.
- 5. 25/8/19 5 m-commerce/ e-commerce M-commerce (mobile commerce) is the buying and selling of goods and services through wireless handheld devices such as cellular telephone and personal digital assistants (PDAs). quality-of-service Quality of service (QoS) is the overall performance of a telephony or computer network, particularly the performance seen by the users of the network.
- 6. 25/8/19 6 Wireless LAN A wireless local area network (WLAN) is a wireless computer network that links two or more devices using a wireless distribution method (often spread-spectrum or OFDM radio) within a limited area such as a home, school, computer laboratory or office building.
- 7. 25/8/19 7 VHS: Video Home System The Video Home System (VHS) is a standard for consumer- level analog video recording on tape cassettes. Developed by Victor Company of Japan (JVC) in the early 1970s, it was released in Japan in late 1976 and in the United States in early 1977.
- 8. 25/8/19 8 ADSL: Asymmetrical Digital Subscriber Line Asymmetric digital subscriber line (ADSL) is a type of digital subscriber line (DSL) technology, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. In ADSL, Bandwidth and bit rate are said to be asymmetric, meaning greater toward the customer premises (downstream) than the reverse (upstream). Providers usually market ADSL as a service for consumers for Internet access for primarily downloading content from the Internet.
- 9. 25/8/19 9 Text tour • Outline – Introduction (para.1) – IMT-2000(para.2-6) – W-CDMA and CDMA2000(para.7-10) – EDGE and GPRS(para.11-13) – The future(para.14-15)
- 10. 25/8/19 10 Introduction • What is the future of mobile telephony? A number of factors are driving the industry. • First, data traffic already exceeds voice traffic on the fixed network and is growing exponentially, whereas voice traffic is essentially flat. • Second, the telephone, entertainment and computer industries have all gone digital and are rapidly converging.
- 11. 25/8/19 11 IMT-2000 • IMT-2000 (ITU in 1992) (A blueprint for third generation mobile telephony) – IMT stood for International Mobile Telecommunications – The number 2000 stood for three things • the year it was supposed to go into service • the frequency it was supposed to operate at (in MHz) • the bandwidth the service should have (in kHz)
- 12. 25/8/19 12 IMT-2000 • The basic services that the IMT-2000 network is supposed to provide to its users are: – High-quality voice transmission. – Messaging (replacing e-mail, fax, SMS, chat etc). – Multimedia (playing music, viewing videos, films, television, etc). – Internet access (Web surfing, including pages with audio and video).
- 13. 25/8/19 13 W-CDMA and CDMA2000 • W-CDMA (Wideband CDMA) – proposed by Ericsson (Ericsson is based in Sweden;) – uses DSSS (Direct Sequence Spread Spectrum) – runs in a 5 MHz bandwidth – designed to inter-work with GSM networks, but not backward compatible with GSM – European Union called it UMTS (Universal Mobile Telecommunications System).
- 14. 25/8/19 14 W-CDMA and CDMA2000 • CDMA2000 – proposed by Qualcomm (Qualcomm is in California). – a direct sequence spread spectrum design – uses a 5-MHz bandwidth – an extension of IS-95 and backward compatible with it – not been designed to inter-work with GSM
- 15. 25/8/19 15 EDGE and GPRS • EDGE (Enhanced Data rates for GSM Evolution) – just GSM with more bits per baud • GPRS (General Packet Radio Service) – an overlay packet network on top of D-AMPS or GSM.
- 16. 25/8/19 16 The future (Future is here!) • Features of 4G systems include – high bandwidth – ubiquity (connectivity everywhere) – seamless integration with wired networks and especially IP – adaptive resource and spectrum management – software defined radio (SDR) – high quality of service for multimedia.
- 17. Software-defined radio (SDR) 25/8/19 17 Software-defined radio (SDR) is a radio communication system where components that have been traditionally implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors etc.) are instead implemented by means of software on a personal computer or embedded system.
- 18. 25/8/19 18 The future • So many 802.11 wireless LAN access points are being set up all over the place • In this vision, people will just wander from one 802.11 access point to another to stay connected. N.B. 802.11 and 802.11x refers to a family of specifications developed by the IEEE for wireless LAN (WLAN) technology
- 19. 25/8/19 19 • Vocabulary – stationary envision compatible overlay Access Language in use
- 21. 25/8/19 21 Stationary in dictionary • Not moving. • Not capable of being moved; fixed. • Unchanging: – a stationary sound.
- 22. 25/8/19 22 Stationary in text • Later, it was recognized that 2 Mbps is not currently feasible for users who are too mobile (due to the difficulty of performing handoffs quickly enough) . More realistic is 2 Mbps for stationary indoor users (which will compete head-on with ADSL), 384 kbps for people walking, and 144 kbps for connections in cars.
- 23. 25/8/19 23 Stationary in use • Stationary crane • Stationary engine • Stationary wave • Stationary random process
- 24. 25/8/19 24 Envision in dictionary • To picture in the mind; imagine.
- 25. 25/8/19 25 Envision in text • ITU envisioned a single worldwide technology for IMT- 2000, so that manufacturers could build a single device that could be sold and used anywhere in the world (like CD players and computers and unlike mobile phones and televisions).
- 26. 25/8/19 26 Compatible in dictionary • Capable of existing or performing without conflicts: – compatible family relationships. • A computer that can use software designed for another make or type. • Capable of forming a chemically or bio-chemically stable system.
- 27. 25/8/19 27 Compatible in text • In March 1999, the two companies settled the lawsuits when Ericsson agreed to buy Qualcomm’s infrastructure. They also agreed to a single 3G standard, but one with multiple incompatible options, which to a large extent just papers over the technical differences.
- 28. 25/8/19 28 Compatible in use • Compatible colour TV system • Driving a car at a speed compatible with safety • Accuracy is not always compatible with haste. • Health and hard work are compatible.
- 29. 25/8/19 29 Overlay in dictionary • To lay or spread over or on. • To cover the surface of with a decorative layer or design: • To embellish superficially: • Something that is laid over or covers something else. • A layer of decoration, such as gold leaf or wood veneer, applied to a surface.
- 30. 25/8/19 30 Overlay in text • Another 2.5G scheme is GPRS (General Packet Radio Service), which is an overlay packet network on top of D-AMPS or GSM. It allows mobile stations to send and receive IP packets in a cell running a voice system.
- 31. 25/8/19 31 Access in dictionary • A means of approaching, entering, exiting or making use of; passage. • The act of approaching. • The right to approach, enter, exit, or make use of • has access to the restricted area; has access to classified material. • Increase by addition. • An outburst or onset
- 32. 25/8/19 32 Access in text • The basic services that the IMT-2000 network is supposed to provide to its users are: – 1,2,3. … – 4. Internet access (Web surfing, including pages with audio and video). • IMT-2000 ： – 1,2,3,… – 4.
- 33. 25/8/19 33 Access in use • dual port access • frequency-division multiple access • random sequential access • space division multiple access • time division multiple access