Personal Communication Services.pdf reasearch paper

8/14/2019 Personal Communication Services.pdf reasearch paper

1/48

Chapter 1

Introduction to Personal Communication Services


2/48

PCS (personal communications

services) Personal communications services (PCS) refers to a wide

variety of wireless access and personal mobility servicesprovided through a small terminal, with the goal of enablingcommunications at any time, at any place, and in any form.

Business opportunities for such services are tremendous, since

every person not ust every ome cou e equ ppe , as ongas the service is fairly inexpensive. Several PCS systems have been developed to meet rapid

growth prompted by heavy market demand.

Meet of them are connected to the public Switched telephonenetwork (PSTN) to provide access to wire-line telephones.


3/48

Examples High-tier digital cellular systems (mobile phone systems ) far widespread vehicular

and pedestrian services.

Global System for Mobile Communication ( GSM ) IS-136 TDMA based Digital Advanced Mobile Phone Service(DAMPS )

Personal Digital Cellular ( PDC ) IS-95(CDMA-based cdmaOne System)

Low-tier telecommunication system standards for residential, business, and publiccordless access applications : Cordless Telephone 2 ( CT2 ) Digital Enhanced Cordless Telephone ( DECT ) Personal Access Communications Systems ( PACS )

Personal Handy Phone System ( PHS ) Wideband wireless systems have been developed to accommodate Internet andmultimedia services. Examples include: cdma2000, evolved from cdmaOne W-CDMA, proposed by Europe

SCDMA, proposed by China/Europe


4/48

The PCS umbrella also includes: Special data systems such as Cellular Digital Packet Data,

RAM Mobile Data, and Advanced Radio Data InformationSystem (ARDIS)

Paging system Specialized mobile radio (SMR) access technologies

-Mobile . Satellite Company (AMSC), as well as numerousproposed mobile satellite systems, including S-band, L-band,low-earth orbit (LEO), mid-earth orbit (MEO),geosynchronous orbit, and geostationary earth orbit (GEO), for

both data and voice applications Unlicensed industrial, scientific, and medical (ISM) band

technologies , as well as wireless local area networks (LANs)should also be thrown into the PCS mix


5/48

1.1 PCS Architecture

PCS technologies have grown rapidly inthe telecommunications industry.

Two of the most popular are: High-Tier Cellular telephony Cordless and low-Tier PCS telephony

These technologies have similararchitectures, as shown in Figure 1.1.


6/48

PCS Architecture

Wireline Transport Network

Radio Network


7/48

PCS Architecture basic architecture consists of two parts:

Radio Network. Wireline Transport Network.


8/48

PCS Architecture Radio Network

PCS use mobile stations (MSs) to communicate with the basestations (BSs) in a PCS network.

MS is also referred to as handset , mobile phone , subscriber, .

For example, subscriber unit : wireless local loop; portable: low-tier systems (PACS); and mobile station: GSM system.


9/48

PCS Architecture Modern MS technology allows the air interface to be

updated (e.g., from DECT to GSM) over the airremotely

The MS can also be remotely monitored by thesystem maintenance and diagnostic capabilities.

Different types of MSs have various power rangesand radio coverage. hand-held MSs have a lower output power (where the

maximum output power can be as low as 0.8 watts forGSM 900) and shorter range compared withvehicle-installed MSs with roof-mounted antennas (wherethe maximum output power can be as high as 8 watts inGSM900).


10/48

PCS Architecture The radio coverage of a base station, or a sector in the

base station, is called a cell . For systems such as GSM, cdmaOne, and PACS, the

base station system is partitioned into

radio port control unit in PACS) and radio transmitters/receivers (base transceiver

stations in GSM and radio ports in PACS).

The base stations usually reach the wireline transportnetwork ( core or backbone network ) via land links ordedicated microwave links.


11/48

PCS Architecture Wire-line Transport Network. The mobile switching center (MSC) connected to the base station

is a special switch tailored to mobile applications. For example, the Lucent 5ESS MSC 2000 is an MSC modified

from Lucent Technologies' 5ESS switching system. The Siemens' D900/1800/1900 GSM switch platform is based on its

EWSD (Digital Electronic Switching System) platform. The Ericsson MSC is based on its AXE switching platform. The MSC is connected to the PSTN to provide services between the

PCS users and the wire-line users. The MSC also communicates with mobility databases to track the

locations of mobile stations.


12/48

1.2 Cellular Telephony

This section gives an overview offour popular cellular telephonynetworks:

AMPS, GSM,

DAMPS (IS-136) CDMA (IS-95).


13/48

1.2.1 Advanced Mobile PhoneService (AMPS) AMPS was the first cellular system. 1970s in the Bell Laboratories, this first-generation analog cellular system has been

considered a revolutionary accomplishment. The AMPS specification was generated from a laborious

, ,a period of 10 years. From 1974 to 1978, a large-scale AMPStrial was conducted in Chicago.

Commercial AMPS service has been available since 1983 . Based on frequency division multiple access (FDMA)

technology for radio communications, high-capacity system based on a frequency reuse scheme .


14/48

1.2.1 Advanced Mobile PhoneService (AMPS) Voice channels are assigned to radio frequencies

using FDMA. A total of 50 MHz in the 824-849 MHz and 869-894

MHz bands is allocated for AMPS. -

channels using 1664 discrete frequencies , 832 downlinks and 832 uplinks.

Downlinks are the transmission paths from basestations to handsets,

Uplinks are the transmission paths from handsets tothe base stations.


15/48

1.2.1 Advanced Mobile Phone Service (AMPS) Cells are grouped into clusters. Cells of within a cluster may interfere with each other, and

thus must use different frequencies. Frequencies may be reused by cells in different clusters. In AMPS, the typical frequency reuse plan employs either a

-group requency c uster us ng omn - rect onaantennas or 7-group cluster using three sectors per base station. Thus, there are about 50 channels per cell .

Motorola uses a 4-cell, 6-sector design in its AMPS system. GS1 AMPS follows the EIA/TIA IS-41 standard for roaming

management.


16/48

1.2.1 Advanced Mobile Phone Service(AMPS)

Compared with the digital alternatives in the United States, AMPS service offers more complete geographical coverage at

a cheaper service charge (partly due to the low cost of massproduction of handsets).

However, digital networks are replacing AMPS because the,

offer lower costs . In 2000, Taiwan started replacing AMPS with the IS-95

CDMA system. After the replacement, the new system will provide the same

service at less than half the bandwidth of the radio spectrum.


17/48

1.2.1 Advanced Mobile Phone Service(AMPS)

Note that after the AMPS voice service is replaced by thedigital systems, the AMPS infrastructure can be utilized tosupport mobile data systems such as Cellular Digital PacketData (CDPD).


18/48

1.2.2 Global System for Mobile Communications(GSM)

GSM is a digital cellular system developed by Group SpecialMobile of Conference Europeans des Postes etTelecommunications (CEPT) and its successor EuropeanTelecommunications Standard Institute (ETSI).

An important goal of the GSM development process was tooffer com atibilit of cellular services amon Euro ean

countries. GSM is a revolutionary technology that combines both timedivision multiple access (TDMA) and FDMA.

With TDMA, the radio hardware in the base station can be

shared among multiple users. In GSM, a frequency carrier is divided into eight time slotswhere the speech coding rate is 13 Kbps.


19/48


In a GSM base station, every pair of radio transceiver-receiversupports eight voice channels , whereas an AMPS base stationneeds one such pair for every voice channel.

The GSM MSs control their RF output power to maintaininterference at low levels.


20/48


The GSM air interface has been evolved into Enhanced DataRate for GSM Evolution (EDGE) with variable data rate andlink adaptation.

EDGE utilizes highly spectrum-efficient modulation for bitrates higher than existing GSM technology.

EDGE requires upgrade of existing base transceiver station,which supports high-speed data transmission in smaller cellsand at short ranges within cells.

EDGE does not support ubiquitous coverage; that is, it

supports island coverage in indoor, pico, and micro cells.


21/48


The GSM development process was similar to that of AMPS,except that no large-scale trial was conducted.

The intellectual property rights of the GSM radio system fromall vendors were waived, making GSM hugely popular. It took about four years to create the GSM specification. The GSM roaming management protocol is specified by GSM

o e pp ca on ar , w c prov es s m arfunctionality as IS-41.

GSM features include most features a digital switch canprovide, point-to-point short messaging,

group addressing, call waiting, multiparty services, ...


22/48

1.2.3 EIA/TIA IS-136 Digital Cellular System

Also referred to as digital AMPS (DAMPS) , American Digital Cellular (ADC), or North American TDMA (NA-TDMA), IS-136, the successor to IS-54,

supports a TDMA air interface similar to that of GSM, and isthus considered an evolutionary technology. It took four months to create the IS-54 specification, and no

significant trial was conducted.

IS-54 was renamed IS-136 when it reached revision C.


23/48


Using TDMA , every IS-136 frequency carrier supports threevoice channels, where the speech coding rate is 7.95 Kbps.

IS-136 systems operate in the same spectrum with the samefrequency spacing (30 KHz) used by the existing AMPSsystems.

-, . An existing AMPS system can be easily upgraded to IS-136 on

a circuit-by-circuit basis. In this way, the evolution from AMPS to DAMPS can be made

gracefully.

IS-136 is also defined for the new PCS spectrum allocation at1850 to 1990 MHz.


24/48

1.2.3 EIA/TIA IS-136 Digital Cellular System Features of IS-136 include

point-to-point short messaging, broadcast messaging, group addressing, pr va e user groups, hierarchical cell structures, and slotted paging channels to support a "sleep mode"

in the handset, to conserve battery power. Like AMPS, IS-136 uses the IS-41 standard for

mobility management.


25/48

1.2.3 EIA/TIA IS-95 Digital CellularSystem This digital cellular system was developed by

Qualcomm, and has been operating in theUnited States since 1996. IS-95 is based on code division multi le

access (CDMA) technology. CDMA allows many users to share a common

frequency/time channel for transmission; theuser signals are distinguished by spreadingthem with different codes . (DSSS)


26/48

1.2.3 EIA/TIA IS-95 Digital Cellular System In theory, this technology optimizes the utilization of

the frequency bandwidth by equalizingsignal-to-noise ratio (SNR) among all the users,thereby more equitably sharing the system powerresources among them.

While AMPS users who are near base stationstypically enjoy SNRs in excess of 80 dB, users at theedge of cell coverage areas experience SNRs near thelower limit.

With CDMA, users who are near base stationstransmit less power, maintaining the same SNR asusers at the edge of a cell's coverage.


27/48

1.2.3 EIA/TIA IS-95 Digital CellularSystem By utilizing the minimum necessary amount of

power, system-wide co-channel interference iskept at a minimum. IS-95 MSs ma need to maintain links with

two or more base stations continuously duringphone calls, so that, as multi-path varies, thebase station with the best received signal on a

burst-by-burst basis will be selected tocommunicate with the MS.


28/48


The channel bandwidth used by IS-95 is 1.25 MHz .

This bandwidth is relatively narrow for a CDMAsystem, which makes the service migration fromanalog to digital within an existing network more

. In the third-generation wideband CDMA proposal,

the bandwidth has been extended to 5 MHz. The speech coding rate for IS-95 is 13 Kbps or 8

Kbps. IS-95's capacity is estimated to be 10 times thatof AMPS .


29/48


The IS-95 development has been similar to that of

AMPS, but no large-scale trial was conducted; it tooktwo years to generate the specification. Prior to 1997, the most significant IS-95 development

effort was taking place in Korea . In 1991, the Koreangovernment decided to implement IS-95 technology.

The Korean IS-95 system began commercial

operation in April 1996.


30/48


The maximum capacity consists of 512 BTS (320

traffic channels per BTS) connected to 12 BSCs.These BSCs are then connected to a mobile switchingcenter (called MX ) using 768 E1 lines.

Like AMPS, IS-95 uses the IS-41 standard formobility management.

One of the third-generation mobile system standards,

cdma2000, is evolved from the narrowband IS-95.


31/48


32/48

1.3.1 Cordless Telephone, Second Generation (CT2) CT2 was developed in Europe, and has been available

since 1989. CT2 is allocated 40 FDMA channels with a 32-Kbps

speech coding rate. - -

handset-to-base signals are transmitted in the samefrequency. This duplexing mode is referred to as timedivision duplexing (TDD) .

The maximum transmit power of a CT2 handset is 10mW.


33/48

1.3.1 Cordless Telephone, Second Generation (CT2) In the call setup procedure, CT2 moves a call path from one

radio channel to another after three seconds of handshake

failure . CT2 also supports data transmission rates of up to 2.4 Kbps

through the speech codec and up to 4.8 Kbps with an increasederror rate.

CT2 does not support handoff call delivery is not supported. Incoming calls have been supported in an enhanced version of

CT2, but its efficiency has not been proven.


34/48

1.3.2 Digital European Cordless Telephone(DECT)

DECT specifications were published in 1992 for definitiveadoption as the European cordless standard.

The name Digital European Cordless Telephone has beenreplaced by Digital Enhanced Cordless Telephone to denoteglobal acceptance of DECT.

DECT su orts hi h user densit with a ico-cell desi n.

Using TDMA , there are 12 voice channels per frequencycarrier. Sleep mode is employed in DECT to conserve the power of

handsets. DECT may move a conversation from one time slotto another to avoid interference. This procedure is called timeslot transfer .

DECT also supports seamless handoff.


35/48


36/48

1.3.3 Personal HandyPhone System(PHS) PHS is a standard developed by the Research and

Development Center for Radio Systems (RCR), a private

standardization organization in Japan . PHS is a low-tier digital PCS system that offers

telecommunications services for homes, offices, and outdoorenvironments usin radio access to the ublic tele hone

network or other digital networks. PHS uses TDMA , whereby each frequency carrier supportsfour multiplexed channels.

Sleep mode enables PHS to support five hours of talk-time , or

150 hours of sta ndby time. PHS operates in the 1895-1918.1 MHz band. This bandwidthis partitioned into 77 channels , each with 300 KHz bandwidth.


37/48

1.3.3 Personal HandyPhone System (PHS)

Like DECT, PHS supports dynamic channel allocation . PHS utilizes dedicated control channels : a fixed frequency

that carries system and signaling information is initiallyselected.

The PHS speech coding rate is 32 Kbps .

Like CT2 and DECT, the duplexing mode used by PHS isTDD . Handoff can be included in PHS as an option. PHS supports Group 3 (G3) fax at 4.2 to 7.8 Kbps and a

full-duplex modem with transmission speeds up to 9.6 Kbps.


38/48

1.3.4 Personal AccessCommunications System (PACS) PACS is a low-power PCS system developed at Telcordia

(formerly Bellcore). PACS is designed for wireless local loop and for personal

communications services. TDMA is used in PACS with eight voice channels per

frequency carrier. The speech coding rate is 32 Kbps . Both TDD and frequency division duplexing (FDD) are

accommodated by the PACS standard.

In FDD mode , the PACS uplink and downlink utilize differentRF carriers, similar to cellular systems.


39/48

1.3.4 Personal Access Communications

System (PACS)

The highly effective and reliable

mobile-controlled handoff (MCHO) completesin less than 20 msec.

IS-41-like protocol. Like GSM, PACS supports both circuit-based

and packet-based access protocols.


40/48

1.3.5 Unlicensed Systems In addition to these standardized cordless radio

technologies, unlicensed communications devices forcordless telephony may make use of the industrial,scientific, and medical (ISM) spectrum .

A number of commercially available products(wireless PBXs, wireless LANs, cordless telephones )make use of the ISM spectrum to avoid the delays

associated with spectrum allocation, licensing, andstandardization.


41/48

1.3.5 Unlicensed Systems The applicability of the AMPS analog cellular air interface for

cordless telephones and office business phones (using the 800MHz cellular spectrum) has been tested by several cellularservice providers.

From a customer's perspective, these trials have been anoverw e m ng success, n cat ng es re or nteropera tybetween private and public wire-less access.

From a service provider perspective, the service is difficult tooperate and maintain because of hard-to-control interferencefrom the private systems into the public system. The TIAinterim standard IS-94 describes the air interface requirementsfor this application of AMPS.


42/48

1.3.5 Unlicensed Systems It also describes the protocol and interface between the

cordless base station and the network, to control the base

station emissions as necessary to limit interference to thepublic system, and to register and deregister the location of thehandsets to and from the private cordless base station at theservice provider's mobility databases for the purpose of routingca s.

Authentication of the handset is included in this protocol. Thenetwork-ing protocol described by IS-94A is extensible todigital cellular systems, and it affects interoperability betweenany public systems using licensed spectrum and any privatesystems using the unlicensed spectrum.


43/48

1.4 Third-Generation WirelessSystems Mobile telecommunication systems have been evolving for

three generations. AMPS is the first-generation system ; GSM, IS-136, IS-95, and the low-tier systems described in

Section 1.3 are second-generation technologies.

These systems have been designed primarily for speech withlow-bit-rate data services. They are limited by their vertical architectures. Most system aspects have been specified from services to the

bearer services. Consequently, any enhancements or new services affect the

network from end to end.

1 4 hi d G i i l


44/48

1.4 Third-Generation Wireless

Systems Compared with second-generation systems, third-generation

systems offer better system capacity; high-speed, wireless Internet access u to 2 Mb s and

wireless multimedia services, which include audio, video, images, anddata. Several technologies, such as General Packet Radio Service(GPRS ) and EDGE ,

bridge second-generation systems into third generation systems.

1 4 Thi d G i Wi l


45/48


Systems In third-generation systems, new network technologies are

integrated into the existing second-generation core networks. ATM (Asynchronous Transfer Mode) backbone, network management, and service creation

Air interfaces such as Wideband CDMA (W-CDMA ) andcdma2000 are major third-generation radio standards.

The increasing number of Internet and multimediaapplications is a major factor driving the third-generationwideband wireless technology.

1 4 Thi d G i Wi l


46/48


Systems Some studies indicate that more than 20 percent of the adult

population in the United States are interested in wireless

Internet access . By the end of 1999, wireless data services were marketed asmodem access for laptop.

-

available, and the inexpensive wireless handheld devices (e.g.,wireless personal data assistant and wireless smart phones)become popular, subscribers will begin to enjoy instantwireless Internet access.

1 4 Thi d G ti Wi l


47/48


Systems The services include

sales force automation, dispatch, instant content access, an ng, e-commerce, and so on.


48/48

Personal Communication Services.pdf reasearch paper

Documents

Transcript of Personal Communication Services.pdf reasearch paper