1 / 11

Communication Technology

Communication Technology. Soochow University Library Chen Jiacui. Outline. Mobile Communication Satellite Communications Optical Fiber Communication Wireless Communication. cordless phones. wireless LAN. cellular phones. satellites. 1980: CT0. 1981: NMT 450. 1982: Inmarsat-A.

kioko
Télécharger la présentation

Communication Technology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Communication Technology Soochow University Library Chen Jiacui Jane Chen - SUL

  2. Outline • Mobile Communication • Satellite Communications • Optical Fiber Communication • Wireless Communication Jane Chen-SUL

  3. cordlessphones wireless LAN cellular phones satellites 1980:CT0 1981: NMT 450 1982: Inmarsat-A 1984:CT1 1983: AMPS 1986: NMT 900 1987:CT1+ 1988: Inmarsat-C 1991: CDMA 1991: D-AMPS 1989: CT 2 199x: proprietary 1991: DECT 1992: GSM 1992: Inmarsat-B Inmarsat-M 1995/96/97: IEEE 802.11, HIPERLAN 1993: PDC 1994:DCS 1800 1998: Iridium analog 2005?: MBS, WATM 2005?: UMTS/IMT-2000 digital Jane Chen-SUL

  4. Mobile Networks • Problems • Mobility increase fading and bit error rate • Lower throughput and higher delay • Awareness of mobile computing environment • Location of mobile unit (e.g. route information services, local yellow pages) • Tariff : switch to different interface for various functions (e.g. email, ftp) • Variable bandwidth and device/interface • Disconnected operations Jane Chen-SUL

  5. Technical Issues in Mobile Networks(1) • Mobility : network layer must… • Know where a user is • Problem : host IP name is bound to its network address and we can determine the network address but not the physical location • When a host moves, techniques to determine its recent address are: • Broadcast • Central Services(GSM: Global System for Mobile Communications) • Home base(Mobile IP) • Route message to mobile users • Store info about current location of users • Mobile IP solution • Cellular phone network solution Jane Chen-SUL

  6. Technical Issues in Mobile Networks(2) • Ad-hoc networking • Mobile hosts form networks without fixed infrastructure • Dynamic topology structure • Dynamic source routing : use cached info and route discovery protocol Jane Chen-SUL

  7. Technical Issues in Mobile Networks(3) • Portability • Low power • Power saving methods • Risk of data loss • Replicate to more secure site • Small user interface • Handwriting recognition • Speech recognition • Pen-point devices • Small storage capacity • No disk ; use ROM • Script language reduces program size Jane Chen-SUL

  8. Wireless Communications • Wireless Networks • Involves wireless communication media ; not necessarily mobile : Aloha network • Problems • Shared media • Increased bit error rate(BER) • Lower radio transmission power Jane Chen-SUL

  9. Problems – con’t • Shared media • Low bandwidth • Technique for increasing bandwidth • Divide into cells(sub-networks) ; overlap cells on different wavelength (scarce spectrum) and reuse channels from cell to cell • Reduce range to increase number of cells ( fewer objects per cell) • Compression and logging(combine short messages into long ones) Jane Chen-SUL

  10. Problems –con’t • Increased bit error rate(BER) due to… • Fading : multipath and long-term fading • Noise : quality of transmission media • Interference : concurrent usage of communication media • Frequent disconnection Jane Chen-SUL

  11. Problems –con’t • Lower radio transmission power • Scarce energy resource in mobile units • Limits transmission power to avoid interference • Signal strength decrease with inverse square of distance • Higher frequency(3-5 GHz) increase attenuation and decrease range Jane Chen-SUL

More Related