1. PCN/PCS Overview 2. Current Commercial Products 3. Projects and Future Offerings 4. A Case Study Field Data Collectors and Remote Entry 4. Protocols for Modern Link Media 5. Conclusion Fredericton, N.B., March 1994 ========================================================== Emerging Technologies in Personal Communications - PCN/PCS
Bernd J. Kurz Faculty of Computer Science, University of New Brunswick Fredericton, N.B., Canada E3B 4P9
1. The Long Path to PCN/PCS
Early 1970's: Teletext, Telidon
Promises: data, voice and still pictures one-way / two-way interactive entertainment shopping, banking information resources, data base access home security, automated billing general data communications Reality: little sustained success no wide-spread use except in heavily populated areas costly to use Problem: inadequate networks such as public land telephone cable scarce wireless resources inadequate electronics technology Fig.1 Teletext Examples ==============================================================Mid 1970's: Citizen Band Communication (CB)
Success story: voice communication only limited frequency range and coverage uncontrolled saturation victim of its own success widely adopted and inexpensive little use for industrial communications Fig. 2 CB Wireless Scenario =========================================================End 1980's: Another PC revolution
PC = ? "Personal Communications" overcome network limitations: new network infrastructure hierarchical cellular structure: micro to macro cells hard and soft-guided media data, voice, pictures and live video contributing to eventual success: advances in microcomputer (silicone) technology time- and space multiplexing of frequency real estate Fig. 3 Personal Communicators Fig. 4 Personal Communications Scenario =========================================================Personal Communications:
PC = PCN + PCS networks and services separation allows service providers via other means for introduction and client testing call a place --> call a person telephone numbers for life and at any place mobility: automated tracking country - worldwide reachability: connectionless communications relay stations for store-and-forward new network media and protocols: optical fibre to wireless data to video, batch to real-time Fig. 5 Personal Digital Assistants - Products ==========================================================2. Current Commercial Products for PCN/PCS
Today:
Spectacular successes of isolated PCN/PCS's: 2.1 PCN Cell Structure Classification micro cell: wired LAN, Instrumentation busses wireless LAN Motorola, Wavelan, .... cordless telephones mini cell: MAN, new area network category cellular telephone saturated analog services in US, Europe affordable $0.2...0.5/min new digital services: USDC, GSM macro cells: land-line WAN for interconnection global satellite communication networks/services AT&T, RCA, GTE, INMARSAT SBS (IBM, etc.), West. Union Teleglobe, Telesat Canada, ... Fig. 6 Satellite and Cellular Technologies Tradenames used in this presentation are the property of their respective owners. ==========================================================2.2 Communications Classification
Fig. 7 Classification of Wireless Systems Data Rate versus Extent of CoverageGlobal WANs
land-line classical digital networks, T1, T3 (virtual) circuit-switched and packet-switched LAP-M or X.25 (PADs) to 1.5...45Mbps ISDN, frame relay, nx64kbps packet-switched B-ISDN, ATM, to 150Mbps fast-packet or cell-switched wireless Satellite networks VSAT and wide-area coverage broadcast or point-to-point standard or proprietary access public carrier or private ========================================================Bridging MANs
DQDB and FDDI, optical fibre redundancy, reconfigurability slotted CSMA/CD or token 100+Mbps, to 100...160km backbone networksLocal LANs
wired Multi-access or Token-passing access via CSMA/CD or token to 16Mbps, to 20km Fast-"Ethernet" 100Mbps, token or CSMA dual stand. IEEE802.12/14 draft wireless many varieties, proprietary IEEE802.11 draft Fig. 8 LAN and MAN Topolgy Examples (FDDI, DQBD) Fig. 9 IEEE802.x Protocol Model ==========================================================2.3 Commercial Product Classification
Selected Commercial Products for Wireless CommunicationsGlobal Communications
Telesat Canada MSAT continent-wide personal briefcase Terminals (Skywave) stationary and mobile wide range of services, voice to data COMSAT via INMARSAT world-wide coverage, 4 satellites voice, fax, telex, data services local access via landlines typical $10..$20 per minute Fig. 10 Satellite Technologies - MSAT and Intelsat/COMSAT =======================================================Mobile Radio
Ardis (Motorola and IBM) city wide non-public digital data network packet-switched X.25, 4.8...19.2kbps RAM Mobile Data (Mobitex network by Ericsson) city-wide, non-public digital data network X.25, 8kbps EMBARC (Motorola) wireless one-way information network E-Mail,daily news, sports, weather industry news, investment (USA TODAY) IBM PCradio for Ardis hand-held computer, 80C186-based US Soil Conservation Service 'SNOTEL' meteorite hopping WAN burst communications with random hits, 1977 NRC Wavelan spread-spectrum LAN, 100m, 1Mbps Apple Data Personal Communications LAN product, 150ft,10Mbps Motorola Altair Ethernet type 5000sqft, 10Mbps Fig. 11 Mobile Computer Technologies =========================================================Cellular networks
Grid Corp. Cellular PC Notebook Microcom 9600 modem, Powertek interface Infinidisc Corp. FaxPak for PCs Telebit modem IBM and cellular carriers (McGaw,Bell,GTE,...) CelluPlan II packetized data communication CDPD protocol over analog or digital 19,200bps Olivetti (Europe) Digital Cordless Telephone CT3 LAN, 1MbpsIR Networks
Photonics Corp. Photolink LAN 200ft, 230kbps Photonics Corp. Ethernet-type LAN 32 stations, 30ft,1 Mbps BICC Communications Corp., Token ring version Fig. 12 Infrared Computer Network Products ==========================================================3. Current Projects and Future Offerings
Motorola's 'Iridium': ($3.4 Bill) global world network of 66 satellites initiated August 1992 with 5 satellites expected $3/minute voice channel DOC Canada 'MSAT': mobile satellite network + Loran C by 1994 general data communications service in test phase since Dec 1988 (via INMARSAT) Personal terminals from Skywave, $5,000 EEC Consortium: common digital cellular data and voice network operational Spring 1993 (GSM, D1 Net) Bell regional operators in US: 65 licenses for PCN/PCS trials including USDC digital cellular Telezone Canada: country wide public cordless telephone service starting January 1994, $0.25/min VISION 2000 Canada: ($30+ Mill) stepwise provision of building blocks for PCN/PCS MSAT briefcase terminal NOMAD 2000 PCS station, tracking NovTrax vehicle positioning system microcell-identifier of location Gateways to ISDN, OSI, TCP/IP Today we have many successful building blocks of PCN/PCS but no vertically integrated infrastructure yet. ==========================================================4. A Case Study
Field-Data Collectors and Remote Data Entry
Purpose
collection of field data by hand-held Terminals remote entry into data bases inventory systems GIS replaces pencil and paper avoids propagation of human errors just-in-time inventory updatesImplementation
self-contained hand-held Terminal battery powered for 30 hrs rugged design -30...+60 deg C user interface color coded keyboard 2-line LCD display microprocessor integrates user guidance with data collection Fig. 13 Field Data Collector and Cradle LOT-100 =======================================================Data Communication
local transfer to Cradle IR optical link print capabilities remote transfer to Host access facility for public telephone and cellular network highly fail-safe dual-packet link ARQ protocol with milestone recoveryPractical Experience
Forest industry for log scaling since 1988 Geographical surveys for rock formation inventorying, NB Dept. Mines and Resources, since 1991 Fig. 14 'From the Woods to the Office' Technolgy Remote Data Entry into Daata Bases, GIS ==========================================================5. Protocols for Modern Media
Evidence of trend towards non-conventional media promoted by new PCN/PCS developments. UNB: Aziz Al-Zoman, John Dedourek, Bernd KurzMedia types
cellular telephone cordless telephones Infrared links Very-low-frequency links, VLF (industrial) Meteorite-hopping, etc....Properties are peculiar
physical obstacles, shadowing reflection, multipath mobile units in motion co-channel cell interference cell crossing Fig. 15 Radio Wave Propagation in Urban and Rural Areas ===========================================================Transmission effects
Raleigh fading signal cancellations Doppler effect varying propagation time hand-offs non-stationary behaviorPeculiar error statistics
frequent single bit errors, >1 err/s long burst errors drop-outs Fig. 16(a) Cellular Systems and Roaming Fig. 16(b) Received Signal Variation due to Fading ========================================================== Traditional standard link protocols in use are unsuitable because of fixed frame length two-level error recovery ARQ for few-bit errors frequent time-outs ! very low link efficiency 10...20% long idle times on pay-as-connect linesOur current research efforts
evaluate current and develop better protocols retain current standards as much as possible collect statistical error information in the field develop a suitable protocol testbed model channel behavior simulate standard protocol performance develop new and better protocols verify performance in field tests Fig. 17 Protocol Testbed Architecture ==========================================================Some Recent Results
Modified standard protocols HDLC based adaptive frame length using ARM mode adding forward error recovery achieved efficiencies to 30% New protocols CDLC (Racal Milgo 1988) to 30% IBM CDPD, cellular digital packet data selected cities, mid 1993 Multi-window HDLC (Kurz 1993) 'SMART' HDLC (Al Zoman 1993) 'sequenced modulo asynchronous response transmission' tentative efficiency to 45% Non-conventional links need more robust protocols for higher throughput and efficiency. More work is needed. Fig. 18 Performance of SMART-HDLC Throughput vs Frame Size ==========================================================6. Conclusions
Era of substantial changes in communicationsPromoted by Personal Communication PCN/PCS
and advances in 'silicone' technologyProvides the freedom of
mobility and reachability of personal communicators, humans or machinesTwo-pronged development
wired and wireless we will see a rearrangement wired for services to location-fixed clients wireless to mobile clients Today no full vertical integration of the PCN/PCS hierarchy but many successful building blocks available, such as cordless and cellular telephones, wireless LANS Fig. 19 Mobile Communications Freedom (Cellular Telephone) ===========================================================Future will see
a rapid change at local level: LAN from wired to wireless, where needed wireless throughput at wired rates better connectivity through standards OSI 3.5 to 4 (IP, TP1..4), IEEE802.11 an emerging intermediate level: MAN to bridge local level LANs suitable data rates for compound throughput contenders are DQDB (IEEE802.6) and FDDI (ANSI X3T9.5) a coming change at the global level: WAN broadband networks affordable bandwidth on demand mix of data, voice, video better video data compression, scalable P.x64 (H.261), MPEG-1/2, 0.1...5 Mbps contender is B-ISDN with ATM a transient period with opportunities for gateways, routers and interfaces to older technologies. A timely opportunity to join the users and makers of PCN/PCS. Fig. 20 ATM - Fast Multiplexing ==========================================================References
Halsal, F.: Data Communications, Computer Networks and Open Systems, Addison-Wesley, 1992 Kobb, B.: Personal Wireless, IEEE Spectrum, June 1993, pp.20- 25 Gecsei, J.: The Architecture of Videotex Systems, Prentice Hall, 1983 Vision 2000 Inc.: Networking the Global Village, Dept. of Communications, Govnmt of Canada, Ottawa, 1990 Lee, W.: Mobile Cellular Telecommunications Systems, McGraw- Hill Book Co., 1989 Telesat Corp.: MSAT - Reaching All Canadians, Dept. of Supply and Services, Govnmt. of Canada, Ottawa, 1988 Al-Zoman A., Dedourek J., Kurz B.: Data Communication over Non-Conventional Channels, Proc. APICS, Halifax, 1992, pp.78-87 Stallings, W.: Local and Metropolitan Area Networks, MacMillan Publishing Co., 1993 Babu, J.: Real-Time Personal Computing - Data Acquisition and Control, Prentice Hall, 1989
Last revised: 28 February 1997, BJK