PCS-Personal Communications Systems Architecture, Operation, Standards

Bernd J. Kurz Faculty of Computer Science, University of New Brunswick Fredericton, N.B., Canada E3B 5A3

1. Introduction 2. Historical Path 3. PCS Evolution Objectives, Architecture Services, Standards 4. PCS Status - Today USA and Canada The World 5. PCS - the Future 6. Conclusions 7. References Fredericton, N.B., February 1997 ==========================================================

1. Introduction

CS Seminar March 1994

PCS/PCN - Emerging Technologies overview of 1st generation PCS system components potential technologies conclusion was: many promising but isolated implementations no vertical integration chaotic scenario

Developments since then

2nd generation PCS system adoption of tighter standards worldwide new technologies beginning of commercialization

What is PCS ?

many names: PCS, PCN, PCN+PCS many definitions Personal Communications System tetherless to the terminal allowing mobility achieving reachability single personal identification number transparency of data and services Fig.1 Personal Communications - A Scenario ==========================================================

2. Historical Path: Pre-PCS

PCS is synonymous with

wireless communication over the 'last mile' in an all-encompassing communications framework

Historical events

Citizen Band a victim of its own success Mobile Radio proprietary, regional limitation and costly Cellular Telephone the crucial step towards PCS space and time multiplexing of scarce frequency estate, roaming capability Cellular Data GSM900 II (SMS to 12kbps) Specialized networks RAM (Mobitex Ericsson), Ardis (Motorola) Wireless LAN (MAN) separate development directions for data limited extent, isolated regional coverage no roaming incompatible competing technologies Altair (Motorola), WaveLan (NCR) recent standard IEEE802.11 (CSMA/CA) Hybrid systems data over voice media cellular modems CDPD, channel-stealing analog

Overcrowding of cellular systems

'brick-wall' technology of analog systems need new vision to scale up personal communications catalyst for PCS development rearrange communications traffic in the cell structure hierarchical layering of cellular systems (pico) - micro - mini - macro - (global) cells use of cell layers according to terminal traffic patterns from analog to digital systems Fig.2 IEEE802.x Reference Model Fig.3 Cellular Telephone ==========================================================

Cellular Technologies

Fig.4a GEO Satellite Fig.4b GEO VSAP (Mobility MSAT) Satellite geo-stationary orbit geo-stationary orbit VSAP broad-coverage macro cells quick channel depletion reusable channels high transmitter power medium transmitter power no hand-offs infrequent hand-offs (if at all) propag. delay to 0.3 sec propag. delay to 0.3 sec costly medium cost Fig. 4c Standard Cellular System Fig. 4d LEO Satellite (e.g. Mobility, Cantel) System (Iridium) terrestrial cellular low earth orbit mini cells mini-macro cells in motion reusable channels reusable channels low transmission power low transmission power propag. impairments clear line-of-sight frequent hand-offs frequent hand-offs (even if stationary) lowest cost low cost ==========================================================

Paths of implementation in mini cells (10...50km)

Analog systems Europe Nordic Mobile, C-net, and derivatives North America AMPS (advanced mobile phone system) rest of world NAMTS (Nippon advanced mobile telephone system), and above technologies Digital systems Europe GSM900, I+II single standard, full implementation North America PCS-1900 (GSM-derived) IS-54 (D-AMPS, IS-136) IS-95 (Qualcomm) competing incompatible systems sporadic implementations rest of world JDC (Japan digital cellular) >200 countries GSM900/1800 >40 countries IS-54 or derivative

Paths of implementation in micro cells (30...100m)

Analog systems world-wide cordless telephone CT, CT1, no roaming Digital systems Europe CT2, DECT (Digital European cordless tel.) roaming North America PACS (Personal access communic. system) rest of world mostly CT2, HandiPhone (Japan)

Paths of implementation in mega-global cells

In-flight aeronautical EUTELTRACS, PRODAT service provider SkyTel Maritime Inmarsat A, B, C service provider ComSat Fig. 7 MSAT Technology Fig. 8 INMARSAT Global Chart and COMSAT ==========================================================

Overview of Wireless Technologies


early analog systems FDMA digital systems TDMA CDMA

FDMA (frequency domain, multiple access)

used by AMPS single connection per frequency slot, narrow-band no voice compression no idle time reduction inefficient bandwidth management not scaleable Fig. 9a FDMA Frequency Band Slotting

TDMA (time domain, multiple access)

used by GSM 8 time slots per channel, narrow-band exploit redundancy in voice digital voice compression efficient bandwidth management good scalability Fig. 9b TDMA Time Domain Slotting

CDMA (code domain, multiple access, DS)

used by Qualcomm IS-95 roots in military commun. for covert channels resistant to jamming, noise spread-spectrum technology, wide-band whitening of voice signal by ‘chip’ code all voice signals overlaid in shared medium decoding by ‘chip’ code correlation complex DSP circuitry Fig. 9c CDMA Frequency Band, Spread-Spectrum Generation and Decoding

RF Frequency allocation

Fig. 10 Wireless Frequency Band Allocation 0.4...18 GHz ==========================================================

Technological Challenges

Consequences of wireless communication over 'last mile'

harsh error environment fading, reflection, shadowing, Doppler effect, absorption bit, burst, drop-out, hand-off errors BER to 10E-1 limited bandwidth possible long propagation delays (satellite communication)

In the framework of ISO's 7-layer OSI Protocol Reference Model

MAC (layers 1-2) providing efficient and fair multi-access (FDMA - TDMA - CDMA) invisible stations unreliable communication and service past trend: layer 1/2 protocols delegate error recovery to higher layers (based on optical fiber reliability, FR, ATM) Network-wireless (layers 2, lower-3) depletion of channels per cell, regionally non- homogeneous dynamic channel 'loaning' hand-off procedures, blocking of handed-off calls Network-routing (layer upper-3) interface to existing global land-line, satellite networks innovative routing on universal personal number (UPT-N) mobility of terminal (address) mobility of person (UPT) UPT/address mapping, SmartCard (GSM, DECT using SIM) Transport and Session (layers 4-5) reliable communication costly end-to-end recovery over non-reliable lower layers (data) guaranteed throughput, QoS (quality of service) hands-off pose serious problems for R/T data

Evidence of reversing a trend

move reliability aspects back into lower layers 2-3 (proposed ATM-AAL6) Fig. 11 RF Wave Propagation in Urban Areas Fig. 12 OSI 7-Layer Protocol Reference Model ==========================================================

3. PCS/PCN Architecture


in which personal communication can take place in an ordely manner.


architecture, cell-layering, services, technologies

Developed by standardization bodies

with industrial input (1992+) ETSI (European Telecomm. Standards Institute), SMG5, RACE ITU (International Telecomm. Union) ANSI (American National Standards Institute)

Specific standards

UMTS (Universal mobile telecomm. system by ETSI) FPLMTS (Future public land mobile telecomm. system by ITU) both offer: global coverage for speech and low/medium data rates with optional high data rate N-ISDN compatible differ in: implementation technologies


terminal mobility personal mobility service mobility data transparency Fig. 13 Mobile Services, Categories and Scenario ===========================================================

Mobility versus capacity trade-off

Cellular design problem

infrequent hand-offs versus re-usability of channels pedestrian-automobile-airplane urban-rural population density PCS implementation by a two-tier hierarchical cell layering low tier (micro to mini cells, <5km) for higher population density slow moving terminals, <50km/h lower-power terminals, <100mW data rates 32kbps high-tier (mini to macro cells, <50km) for lower population density fast moving terminals, <200km/h higher-power terminals, <1W data rates 13kbps combines advantages of capacity and mobility terminals select tier access according to usage

'Last mile' technology

wireless two-tier licensed and unlicensed (nomadic and non-nomadic)

Connectivity technology

wireless, mega cells with satellite technology land-line N and/or B-ISDN using ATM-SONET

Implementation technology choices

vary from global region to global region incompatibilities result Fig. 14 Two-Tier Structure of PCS ==========================================================

4. PCS Status - Today

Incompatible evolution

around the world


ETSI versus ITU versus ANSI PCS evolution: technology-driven (Non-North America) market-driven (North America)

Non-North-America region

one single standard, ETSI based on GSM900, migrating to DCS1800 scaleable architecture seamless integration into N-ISDN services GSM Phase II integrated data and voice over 'last mile' GSM suitable for both low tier and high tier simplified terminal circuitry trade-off optimality and scalability adopted by >200 countries

North-American region

standard framework by ANSI competing incompatible technologies low tier: DCT, PACS high tier: IS-54 (D-AMPS, IS-136) IS-95 (Qualcomm) PCS1900 (DCS1800/GSM900 derived) to be deployed in US influence area (NA, CA, SA) adopted by >40 countries

Hope for world-wide roaming ?

multi-mode cellular terminals predominantly in high tier Fig. 15 Roaming and the World ==========================================================

Canadian Scenario

Four PCS licenses granted in 1996

Mobility Canada and Clearnet IS-95 Qualcomm CDMA primarily high-tier functionality Cantel IS-136 (IS-54), TDMA primarily high-tier functionality Microcell PCS-1900 (GSM in 1900 band) scaleable to needs Currently operating in Montreal, Ottawa, Toronto corridor Expected availability country-wide by 1997-1998 True PCS system functionality with world-wide GSM roaming (SIM) offered by Microcell

Proposed integration of incompatible systems

on network level IS-41 Network Interface, under development accepts APMS.....PCS1900 (GSM) on 'last-mile' level multi-mode terminals SmartCard personal identification standard for GSM, DECT Fig. 16 Network Interfaces for High-Tier Wireless Systems ==========================================================

5. PCS - The Future

Technology standards roll-out by ITU

from 2nd to 3rd PCS generation 1992 PCS concept requirements and framework definitions 1996 key choices functionality and technologies 1998 handover to industry 1999 prototyping and type approval 2000+ wide-spread deployment

Expected migration of technologies

1st generation 2nd generation 3rd generation analog cellular paging messaging GSM WLAN IS-54 IS-136 UMTS Mobile radio IS-95 FPLMTS cellular data DECT CDPD PACS CT (N-PCS) Fig. 17 Three Generations of PCS - An Overview ==========================================================

6. Conclusions

Era of restructuring of personal communications

into a more well defined PCS/PCN framework

Provides freedom

of mobility and reachability for terminals and persons (UPT number) worldwide

Data communication in PCS

data transparency high-tier to 9.6...12kbps (GSM SMS) proposed to 100kpbs Special wireless data networks for higher data rates (CSMA/CA)

Multi-standard framework for PCS/PCN

FPLMTS (ITU) and UMTS (ETSI) with similar objectives different technology recommendations

Current evolution of PCS/PCN systems

mainly a 2-pronged approach Europe: single-standard GSM-based full ISDN network and service integration also in >200 countries N. America: multi-standards IS-54 (D-AMPS) vs IS-95 (CDMA) vs PCS1900(GSM) also in >40 countries Canada specific, being deployed Mobility, Clearnet (IS-95) Cantel (IS-136/IS-54) Cellnet (PCS1900/GSM) only Cellnet has the PCS-specified high/low- tier capability

A missed opportunity for a single world-wide PCS standard

roaming by SIM SmartCard (all GSM-variations) multi-mode terminals Fig. 19 PCS Voice and Data around the Globe ==========================================================

7. References

R. Steele, The Evolution of Personal Communications, IEEE Personal Communications, Vol.1., No.2, 2nd Q. 1994, pp. 6-11 D. Cox, Wireless Personal Communications: What is it ?, IEEE Personal Communications, Vol.2, No.2, April 1995, pp. 20-35 A. Noerpel et. al., PACS: Personal Access Communication System - A Tutorial, IEEE Personal Communications, Vol.3, No.3, June 1996, pp. 32-43 K. Brown, Kenryn Communications, PCS and the Big Picture, Industry Canada - Inform. Technology Industry Branch, PCS Seminar IT Canada, Moncton NB, December 1996, 35 pages IEEE Standards Dept, Draft Std. IEEE 802.11 Wireless LANS (P802.11D3), 1996 M. Mouly and M.-B.Pautet, Current Evolution of the GSM System, IEEE Personal Communications, Vol.2, No.5, October 1995, pp. 9-19 N. Abramson, Wideband Access for the Last Mile (Aloha, CDMA), Aloha Networks Inc., IEEE Personal Comm., Vol 3, No. 6, December 1996, pp. 29-35 CDPD Forum, Cellular Digital Packet Data System Specifications Rel. 1.1, 1995 pcssem2.doc ==========================================================

Standard Public Cellular Telephone System North America

Fig. 5 Cellular Layout and Frequency Reuse Pattern Fig. 6 A Practical Cellular Layout and Roaming ==========================================================

Capability Trade-Off of Wireless Communication Systems PCS and Other Systems

Fig. 18a Overview: Applications versus Network Types (LAN...WAN) Fig. 18b Ranking: Network Capacity versus Cell Size

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Last revised: 27 February 1997, BJK