Final Gsm Pmr

Public Mobile Radio Systems

GSM-an overview

GSM System Architecture

PSTN

Data Terminal

HLR/VLR

MSCBSC

OMC(Operation & Maintenance

Center)

OperationTerminal

BTS

HandsetA

X.25

A-bis SS7

Network sub-system PSTNRadiosub-system

Mobilestation

UM

SIMcard

Mobile System network

• Two Components– Fixed Installed Infrastructure (network)– Mobile Subscribers (who uses the services of

network)

Fixed Installed Infrastructure (network)

• Divided into subnets known as subsystems

1. Radio Networks

2. Mobile switching network

3. Management Network

Subsystems

Radio Networks

Base Station

Subsystems

(BSS)

Mobile switching networkSwitching and Management

Subsystem (SMSS)

Management NetworkOperation and Management

Subsystems (OMSS)

GSM Network Elements

• Handset• BTS: Base Transceiver Station

• MSC: Mobile Switching Center

• BSC: Base Station Controller

• HLR/VLR: Home Location Register/Visiting Location Register

• SIM Card: Subscriber Identity Module Card

Subsystem-BSS

• BSS-two components1. Base Station Controller (BSC)

2. Base Transceiver Station/Base Station (BTS/BS).

BSS- BTS

• BTS-provides interface– Mobile’s interface to the network– A BTS is usually located in the centre of a cell.– The BTS provides the radio channels for

signaling and user data traffic in the cells.– A BS has between 1 and 16 transceivers, each

of which represents a separate radio frequency channel

BSS- BTS

• BSC-Controller– frequency administration– control of the BTS– The BSC also translates the 13 kbps voice

channel used over the radio link to the standard 64 kbps channel used by the Public Switched Telephone Network or ISDN

• Connected to MSC

Mobile switching network

• MSN consists of – Mobile Switching Centres (MSC) and

– Databases, which store the data required for routing and service provisions (HLR, VLR)

• Responsibilities– In addition to switching it also provides all the

functionality needed to handle a mobile subscriber, such as registration, authentication, location updating, handovers, and call routing to a roaming subscriber

MSC

• Gateway MSC (GMSC)– This passes voice traffic between fixed

networks and mobile networks– GMSC requests the routing information from

the Home Location Register (HLR) and routes the connection to the local MSC in whose area the mobile station is currently staying

Databases

• Home Location Register (HLR)– Stores the identity and user data of all

subscribers belonging to the area of the related GMSC

– Permanent data such as the International Mobile Subscriber Identity (IMSI). permitted supplementary service

– Temporary data such as address of the current VLR

Databases-VLR

• Visitor Location Register (VLR)– Stores the data of all MS’s that are currently

staying in the administrative area of the associated MSC

Mobile Handset (MH)

• Used by the subscriber to access the GSM network via the air interface

• Contains the hardware and software specific to the radio interface

• Need a Subscriber Identity Module (SIM) which contains the subscriber-specific data to access GSM network, except emergency call

Subscriber Identity Module (SIM)

• Subscriber Identity Module– Contains

• phone number (MSISDN)

• international mobile subscriber identity (IMSI)

• status of SIM

• service code

• authentication key

• PIN (personal identification code)

• PUK (personal unlock code)

GSM Frame Structure

3 57 26 57 8.251 1 3

0 7

...

...Superframe6.12 sec

120 msec

4.615 msec

0.57692 msec156.25 bits

51 Multiframe

26 Frames

8 Multiframe

Coded data Midamble

Tail bit Stealing Flag Guard period

• There are two types of multiframe– 26 TDMA-frame multiframe is used to carry

TCH, SACCH and FACCH(TCH0-11,13-24)SACCH12,25,NO DATA

– 51 TDMA-frame multiframe is used to carry BCCH, SCH,FCCH,AGCH,RACH

– FCCH IS ALWAYS IN 0,10,20,30,40 SCH IS IN 1,11,21,31,AND 41 AND BCCH 2-5

– PAGCH AND RACH according to load

Frame Types

Burst• The information contained in one time slot is a

burst• Five types of burst

– Normal Burst (NB)• To carry information on traffic and control channels

– Frequency Correction Burst (FB)• To synchronize the frequency of the mobile

– Synchronization Burst (SB)• To synchronize the frames of the mobile

– Access Burst (AB)• For random and handover access

– Dummy Burst• For padding the frame

GSM Frame Structure Per Channel

3 57 26 57 8.251 1 3

0 74.615 msec

0.57692 msec156.25 bits

8 Multiframe or bursts

Coded data Training

Tail bit Flag Speech/data Or Signaling Guard period

Channels

• Physical Channels– Associated with frequency bands, time slots, codes

– Physical channels transfer bits from one network element to another

• Logical Channels– Distinguished by the nature of carried information and the

way to assemble bits into data units

– Three types• one-to-one: traffic channels between a BTS and a MS• one-to-many: synchronization signals from BTS to MSs in a cell• many-to-one: from MSs to the same BTS

Trafficchannels(TCH)

Signalingchannel

TCH/F: Full-rate Traffic Channel

TCH/H: Half-rate Traffic Channel

FCCH: Frequency correction

SCH: Synchronization

BCCH: Broadcast control

PCH: Paging

AGCH: Access grant

RACH: Random access

SDCCH: Stand-alone dedicated control

SACCH: Slow associated control

FACCH: Fast associated control

Two-way

Base-to-mobile

Two-way

Logical Channel List

BCH

CCCH

DCCH

Logical Channels

• Control Channels– Broadcast Channels (BCH)– Common Control Channels (CCCH)– Dedicated Control Channels (DCCH)

• Traffic Channels (TCH)– Full Rate (TCH/F)– Half Rate (TCH/H)

UP / Down-Link

• Down-link: the transmission path from Base Station to Mobile Station

• Up-link: the transmission path from Mobile Station to Base Station

Control Channels• Broadcast Channels (BCH)

– Frequency Correction Channel (FCCH)– Synchronization Channel (SCH)– Broadcast Control Channel (BCCH)

• Common Control Channels (CCCH)– Paging Channel (PCH)– Random Access Channel (RACH)– Access Grant Channel (AGCH)

• Dedicated Control Channels (DCCH)– Stand alone Dedicated Control Channel (SDCCH)– Cell Broadcast Channel (CBCH)– Slow Associated Control Channel (SACCH)– Fast Associated Control Channel (FACCH)

Broadcast Channels (BCH)

• To help the MS (Mobile Station) measures– to listen for the cell information

• to start roaming, waiting for calls to arrive, making calls

– Because BTSs are not synchronized with each other, every time a MH decides to camp to another cell, its FCCH, SCH, and BCCH must be read.

Frequency Correction Channel (FCCH)

• Provide MS with the frequency reference of the system– To enable the Mobile Handset (MH) to

synchronize with the frequency

• Transmission properties– Transmit on the down-link– Point to multi-point.

Synchronization Channel (SCH)• MS synchronize with the structure within the

locative cell– MS can receive information from the proper time slots

on the TDMA structure

• Transmission properties– Transmit on down-link– Point to multi-point.

Broadcast Control Channel (BCCH)

• BTS broadcast cell information to MS– LAI ( Location Area Identity), to start roaming,

waiting for calls to arrive, making calls– maximum output power allowed in the cell– information about BCCH carriers for the

neighboring cells• Transmission properties

– Transmit on down-link– Point to multi-point

Common Control Channels (CCCH)

• CCCH support the establishment of a dedicated communication path (dedicated channel) between the MS and the BTS

• Three types of CCCH– Paging Channel (PCH)– Random Access Channel (RACH)– Access Grant Channel (AGCH)

Paging Channel (PCH)• Used by BTS to page particular MS in the cell

– MH actively listen to PCH to check contact info within certain time

– Contact could be incoming call or short message

• Contact info on PCH include– IMSI (MH’s identity number), or– TMSI (temporary number)

• Transmission properties– Transmit on down-link– point to point

Random Access Channel (RACH)

• Used by MS to request a dedicated channel for call setup– Shared by any MS attempts to access the

network– Channel request message contains the reason

for the access attempt

• Transmission properties– Transmit on up-link– Point to pint.

Access Grant Channel (AGCH)

• The network assigns a signaling channel via AGCH– A Stand alone Dedicated Control Channel

(SDCCH) is assigned

• Transmission properties– Transmit on down-link– Point to point

Dedicated Control Channels (DCCH)

• DCCH are used for transferring nonuser information between the network and the MS Messages on DCCH Including

• channel maintenance• mobility management• radio resource management

• Three kinds of DCCH– Stand alone Dedicated Control Channel (SDCCH)– Slow Associated Control Channel (SACCH)– Fast Associated Control Channel (FACCH)

Stand alone Dedicated Control Channel (SDCCH)

• Transfer signaling information between the BTS and the MS

• Typically used for location updating prior to use of a traffic channel

• Transmission properties– Bi-directional channel, transmit on both up and

down-link– Point to point.

Slow Associated Control Channel (SACCH)

• Carries control and measurement parameters along with routine data necessary to maintain a radio link between the MS and the BTS– On the uplink, MS sends averaged measurements

(signal strength and quality) of current and neighboring BCCH

– On downlink, MS receives information about transmitting power to use and an instruction with time advance/retard

• Transmission properties– Bidirection channel, transmit on both up and down link– Point to point

Fast Associated Control Channel (FACCH)

• An FACCH is used over a TCH where it steals time slots from a TCH– a 20 ms segment of speech is stolen to carry

handover signaling information

• Appears on demand

Traffic Channels (TCH)

• TCH transport user information (speech/data)

• TCH are bi-directional dedicated channels between the network and the MS

Traffic Channels (TCH)

• TCH- Two types– Full-rate TCH (TCH/F): provides transmission

speed of 13 kbps for speech or 9.6, 4.8 or 2.4 kbps for data.

– Half-rate TCH (TCH/H): allows transmission of 6.5Kbps speech or 4.8 or 2.4 Kbps of data.

Handoff/Handover

A process, which allows users to remain in touch, even while breaking the

connection with one BS and establishing connection with another BS.

Old BS New BS

MSC

Old BS New BS

MSC

MSC

Old BS New BS New BSOld BS

MSC

Handoff To keep the conversation going, the Handoff procedure

should be completed while the MS (the bus) is in the overlap region.

G

Old BS New BS

Cell overlap region

Handoff detection strategies

Mobile-Controlled handoff (MCHO)

Network-Controlled handoff (NCHO)

Mobile-Assisted handoff (MAHO)

Mobile-Controlled Handoff (MCHO)

In this strategy, the MS continuously monitors the radio

signal strength and quality of the surrounding BSs.

When predefined criteria are met, then the MS checks for

the best candidate BS for an available traffic channel and

requests the handoff to occur. MCHO is used in DECT

and PACS.

Network-Controlled Handoff (NCHO)

In this strategy, the surrounding BSs, the MSC or both monitor the radio signal. When the signal’s strength and quality deteriorate below a predefined threshold, the network arranges for a handoff to another channel. NCHO is used in CT-2 Plus and AMPS

Mobile-Assisted Handoff (MAHO)

It is a variant of NCHO strategy. In this strategy, the network

directs the MS to measure the signal from the surrounding

BSs and to report those measurements back to the network.

The network then uses these measurements to determine

where a handoff is required and to which channel. MACHO is

used in GSM and IS-95 CDMA.

Handoff types with reference to the network

Intra-system handoff or Inter-BS handoff

The new and the old BSs are connected to the

same MSC.

Old BS New BS

MSC

Handoff types with reference to the network

Intersystem handoff or Inter-MSC handoff

The new and the old BSs are connected to

different MSCs

Old BS New BS

MSCMSC

Handoff types with reference to link transfer

Hard handoff

The MS connects with only one BS at a time, and there is

usually some interruption in the conversation during the link

transition

Soft handoff

The two BSs are briefly simultaneously connected to the MU while

crossing the cell boundary. As soon as the mobile's link with the new BS

is acceptable, the initial BS disengages from the MU.


Soft handoff

1. MU sends a pilot strength measurement message to the old BS,

indicating the new BS to be added.

2. The old BS sends a handoff request message to the MSC. If the

MSC accepts the handoff request, it sends a handoff request

message to the new BS.

3. The BS sends a null traffic message to the MU to prepare the

establishment of the communication link.


Soft handoff

4. The new BS sends a join request message to the MSC.

The MSC bridges the connection for the two BSs, so

that the handoff can be processed without breaking

the connection.

5. The new BS sends a handoff ack message to the old

BS via the MSC. The old BS instructs the MU to add a

link to the new BS by exchanging the handoff

command and handoff complete messages.


Soft handoff

6. The old BS and the MSC conclude this procedure by

exchanging the required handoff information. The quality

of the new link is guaranteed by the exchange of the pilot

measurement request and the pilot strength measurement

message pair between the MU and the new BS.

Handover in GSM (2.11)

3 possible types

• Intra-Cell Handover

between traffic channels within cell

• Inter-Cell Handover

between traffic channels on different cells

• Inter-MSC Handover

between cells belonging to different MSCs

Handover Situations

• To maintain Link Quality

• To minimize Interference

• Traffic Management

Four security measures in GSM

1) PIN code (authentication of user using terminal => local security measure, network is not involved)

2) SIM authentication (performed by network)

3) Ciphering of information sent over air interface

4) Usage of TMSI (instead of IMSI ) over air interface

IMSI = International Mobile Subscriber Identity(globally unique identity)

TMSI = Temporary Mobile Subscriber Identity(local and temporary identity)

CDMA

CDMA Is a Spread-Spectrum System

Traditional technologies try to squeeze the signal into the minimum required bandwidth

Direct-Sequence Spread spectrum systems mix their input data with a fast spreading sequence and transmit a wideband signal

The spreading sequence is independently regenerated at the receiver and mixed with the incoming wideband signal to recover the original data

Spread SpectrumTRADITIONAL COMMUNICATIONS SYSTEM

SlowInformation

Sent

TX

SlowInformationRecovered

RX

NarrowbandSignal

SPREAD-SPECTRUM SYSTEM

FastSpreadingSequence

SlowInformation

Sent

TX

SlowInformationRecovered

RX

FastSpreadingSequence

Wideband Signal

Spread Spectrum Principles

1.25 MHz30 KHz

Power is “Spread” Over a Larger Bandwidth

MATHHAMMER

MATHHAMMER

Spread Spectrum Principles

Many code channels are individually“spread” and then added together tocreate a “composite signal”

CDMACode division Multiple Access is a digital technology pioneered by QUALCOMM that provides crystal clear voice quality in new generation wireless communication systems

CDMA provides better and most cost effective

Voice quality

Privacy

System capacity

Flexibility.

SMS

E-mail

Internet

Diversity in CDMA

Three types of Diversity

Frequency

Spatial Diversity

Time Diversity

Frequency Diversity

• Inherent feature of CDMA due to wide part of spectrum covered by each signal

• Multipath fading is caused by different delays among alternative paths between a mobile and base station

• Use of Rack Receivers to get benefits from multipath propagation

Spatial Diversity

• Both in TDMA and CDMA

• Use of multiple antennas at the base stations

• Two antennas far apart at the receiver make it unlikely to receive the faded signal at the same instant

• CDMA allows multiple base stations to transmit to single mobile thus making soft handover possible

Time Diversity

• Channel coding and interleaving are used in GSM for time diversity

• CDMA also uses time diversity

• The Forward channel in IS-95 standard employs half-rate convolutional coding, which doubles the number of bits

• The reverse channel also employs one-third rate convolutional coding

Continue…..

• All the bits, both information and redundant, are interleaved thus separating the adjacent information bits

• At the receiver end of channel, a Viterbi decoder is used with soft decision point

• Only makes 1 or 0 bit decision as demodulator already marks noisy symbols

• Decoder simply ignores bad symbols instead of working on them

Features and Advantages of CDMA

Universal Frequency Reuse

Fast and accurate Power Control

Rake Receiver

CDMA Hand off

FDMA/TDMA Frequency Reuse Frequency Reuse

CD CDMA MA Frequency Reuse

CDMA Frequency Reuse

CDMA Power Controlwithout

CDMA Rake Receiver

Multipaths

Multipaths

Multipaths

CDMA RAKE Receiver

CDMA RAKE Receiver

CDMA RAKE Receiver

Receive set

Correlator 1

Correlator 2

Correlator 3

Searcher correlator Calculate the time delay and signal strength

Combiner The combined signal

tt

s(t) s(t)

Handoff in CDMA System

• Soft Handoff– Mobile commences Communication with a new BS without

interrupting communication with old BS– same frequency assignment between old and new BS– provides different site selection diversity

• Softer Handoff– Handoff between sectors in a cell

• CDMA to CDMA hard handoff – Mobile transmits between two base stations with different

frequency assignment

Soft Handoff

Soft Handoff Advantages

Hand Off

Hand off in GSM

a)Hard Hand Off

b)Soft Hand OffHand off in CDMA

a)Soft Hand off

b)Softer Hand off

Practical Handoff Problems

• (1)Problem Caused by high speed mobility: More handoffs are required to handle high speed mobility of MS

during a call. It will cause load on the system as well as call drops.

• (2) Problem Caused by low speed mobility: Cell dragging:

In the line of sight and smooth area signal does not drop sharply for pedestrian users so user goes on using the frequency of the previous cell in to the new cell. This causes increase in the co-channel interference.

Solution For More Handoffs• Umbrella Cell Approach: Micro cells inside A macro cell.

---- Macro cell is defined by high power and lengthy tower. ---- Micro cells are defined inside the macro cell with less power and less height towers.

---- High speed MS are handled by macro cell and low speed subscribers are handled by micro cells. ---- This strategy increases the no of capacity channels per unit area and decreases the no of handoffs.

Umbrella Cell Approach

Solution For Cell Dragging

• Handoff threshold

----and radio coverage parameters must be adjusted carefully according to the environment .

88

Forward Link Channels

89


90

Forward Link Channels• Channels

– A channel may be voice data or overhead control data.

• Forward Link Channels– On the forward link there are 4 types of channels used to transmit control and

voice data to the mobile.

– These channels are:• Pilot• Sync• Paging• Traffic

91


92

• Pilot Channel

– The pilot channel is constantly transmitted.

– The mobile uses the pilot signal to acquire the system. After the mobile has acquired the system the pilot is used for signal strength measurement.

– The strength of the pilot is used to determine the power required for mobile transmit.

– The pilot contains no information but it is the strongest signal on the forward link, containing at least 20% of the total power on the forward link. The power of the pilot is an indication to the mobile of its ability to successfully use the signals from the base station transmitting that pilot.

– After this, the phone looks for the sync channel


93

• Sync. Channel

– The sync channel is constantly transmitted providing critical timing information to the mobile.

– The mobile will decode the Sync. channel message during the power up sequence.

– It repeatedly transmits a sync channel message which contains information about the cell and the phone system, and also contains information which permits the phone to determine the absolute clock time

– Once the sync channel message has been processed, the phone has sufficient information to begin to process the paging channel and to register

– Once the mobile is synchronized with the base station the sync channel is ignored.


94

• The Sync Channel

– Mobiles must acquire the Sync Channel and decode its message in order to synchronize with the system.

– The Sync message is spread with Walsh code 32 and is broadcast continuously.

– The Sync message includes the following information:• System time• System ID• Network ID• Many more


95

Paging Channel

– A base-to-mobile forward-link communications channel used to send control, call set-up, and paging messages when the mobile is not in the traffic mode.

– The paging channel is used to transmit overhead information (i.e. commands and pages) to the mobile.

• When a call is being set up the commands and traffic channel assignment are sent on the paging channel.

• Once a traffic channel is established the paging channel is ignored by the mobile.


96

• Paging Channels

• A Paging Channel is used by the CDMA system to transmit overhead messages and mobile directed messages. Walsh codes 1 through 7 may be used for Paging Channels. A system operator may choose to support less than seven Paging Channels. In this case, unused codes may be assigned to Traffic Channels.

• A Paging Channel transmits the configuration messages:– System Parameters message– Access Parameters message– CDMA Channel List message– housekeeping information such as the PN Offsets of all nearby

cells and sectors.– Many more


97

– While the mobile is not in the traffic mode, the base sends orders and messages to the mobile on the paging channel. It receives responses and requests via the mobile's Access Channel.


98

• Forward Traffic Channel– The forward traffic channel is used when there is a call.


99

Forward Traffic Channels

100

Reverse Link Channels

101


102

The reverse link in an IS-95 system is any link from a mobile subscriber to a base station.

On the reverse link there are two types of channels used to transmit control and voice data to the mobile.

These channels are: Access Traffic


103


104

• Access Channel– The access channel is used by the mobile when not

assigned to a traffic channel.– A mobile-to-base communications channel used

primarily for control and sending messages such as call origination, page response, and registration.

– The access channel is used by the mobile to • register with the network• originate calls• respond to pages and commands from the base station• transmit overhead messages to the base station.


105

• After the mobile initially acquires the pilot of a base station and reads the data on the Synchronization channel, it transmits to the base station on an Access Channel.

• This is the first indication that the base station has that the mobile is present and active.

• All communications with the base station occur using the Access Channel until the mobile is placed in the traffic mode.


106

• Reverse Traffic Channel– The reverse traffic channel is used when there is a call.


107

Problems in a CDMA Channel

108

Problems in a CDMA Channel• Near-Far Problem

– If all mobiles transmitted at the same power level, signals received by the base station from mobiles further away would be weaker than those signals received from mobiles which were closer to the cell. This issue reduces, if not resolved, the capacity of a CDMA system.

• Path Loss– The more distance between the cell and a phone the weaker the

signal becomes.• Fading

– Fading occurs when more than two signals from the same transmitter are received due to multipath.

109

Advantages of CDMA

110

Advantages of CDMA

• Coverage

• Capacity

• Clarity

• Cost

• Compatibility

• Customer Satisfaction

111

FDMA / TDMA / CDMA Coverage

112

Coverage

• Coverage Issues– Providing adequate coverage is a basic requirement of a wireless system.

– Coverage of a BTS or network is impacted by the capacity requirements of the system, terrain of the area, and power of the base station and mobiles.

• CDMA Advantage– Forward and reverse link power control helps a CDMA network dynamically

expand the coverage area.

– The coding and interleaving techniques used in CDMA provide the ability to cover a larger area for the same amount of available power used in other systems.

– Under line of sight conditions CDMA has a 1.7 to 3 times more coverage than TDMA.

113

Capacity

114

Clarity

115

• Rake Receiver– Combines multipath and softer handoff signals to reduce

errors and power requirements.

• Variable Rate Vocoder– The dynamic rate of the vocoder reduces the amount of

data transmitted for each person and reduces the interference.

Clarity

116

• Soft Hand-off– The soft hand off in CDMA reduces the interference and power

requirements for maintaining the link. Multiple received signals can be combined to reduce the possibility of errors resulting from interference and fading.

• Power Control– Dynamic power control reduces errors by keeping the power at an

optimal level.• Wideband Signal

– CDMA’s wideband signals does not suffer from the same effects of fading experience in an FDMA or TDMA system.

• Encoding and Interleaving– Strong encoding and interleaving reduces the effects of fading.

Clarity

117

Major Mobile Radio standards in North America

Spectrum Allocation by PTA

PMR

Key features of professional mobile radio systems can include:

• Point to multi-point communications (as opposed to cell phones)

• Push to Talk, release to listen — a single button press opens communication on a radio frequency channel

• Large coverage areas

• Closed user groups

• Use of VHF or UHF frequency bands

Private Mobile Radio (PMR) System

• System setup by a company or group of users for that group of user alone

• Walkie-talkie is simplest form where there is no need of base station

• Simple to setup and cheap to run

• But lack flexibility as calls to other networks or users is impossible

• A new service called PMR446, which can support upto about 1 or 2 million users in UK

• The channels are unlicensed, hence no guaranteed access

• PMR446 equipment is not permitted to be connected with public telephone network

• The USA has a similar system called called family radio service (FRS)

• In public mobile access radio (PAMR) users may group together to run joint systems

• PAMR systems are shared by number of different users

• PAMR or PMR systems with a common standard and internetworking arrangement has advantage of direct calls

• It is useful for services in neighboring countries

Problems

• Delays as Interworking arrangement routes calls through a fixed network

• Direct mode operation without base station is impossible

• Development of good public cellular system which undermine the advantages( adequate coverage, reduce cost, supplementary services) of PMR system

• Coverage in GSM exceeds the dedicated coverage provided by PMR

• The cost of public systems has decreased drastically due to competition and innovations

• PMR handsets becoming more costly due to move to digital and drive to increase flexibility, capacity and security

• Cellular users have economies of scale due to large market

The PMR User Community

• Public Safety

Emergency Services( Police, Fire, ambulance)

• Non-safety National Govt

Customs etc

• Non safety local Govt.

• Transport

Railways, Buses, Taxis

• Other Utilities

Water, Electricity, Gas, Coal

• On-site PMR

Construction site

• PAMR

Requirements of PMR Services

• Reliability

Service availability is extremely important

• Voice and Data Capability

Data services are increasing exponentially

• Centralized and De-centralized operations

• Pt to Pt, Group and Broadcast Calls

Flexible group call structure

• Fast Call Setup

Particularly important in emergency services, push to talk, no need of dialing

• Good Coverage

Mountain rescue service

• Long Battery life

• Flexibility

Ability of system to change with the need, scalable

• Low Total Cost of ownership

Lower Capital plus maintenance cost

• Others Requirements in some cases include Security, Call priorities, Ease of licensing

PMR Configurations (3.4)

• Point to point Direct terminal communication

• Dispatch operation

• Talk through Repeater Operation

• Use of Radio port to fill blackspot

• Vehicle mounted Repeater for local handheld coverage

• Wide area coverage using several base sites

• Cellular PMR Configuration

Comparison Between PMR and Cellular

• Group call..required in PMR but not so frequent in Cellular

• Dispatcher Operation…. Many PMR needs dispatcher for controlling and monitoring, not in Cellular

• Decentralized Operation…PMR works in direct mode without the need of fixed base station and network infrastructure

• Fast Call Set-up…. PMR fast as no need to wait to be connected

• Supplementary Services….Additional call services…now equally good in Cellular

• Traffic Patterns….Calls are short in PMR, PMR calls are mostly intended for the users on the same network

• Capacity…Cellular user base is larger, need more base stations, small cells, high re-use and efficient air interface techniques. PMR operator want to minimize infrastructure cost so larger cells.

• Freq Planning… Needed in Cellular

• Control, billing and authentication…User is authenticated and bill for each call as contrast to PMR

• Relationship between the service provider and the user…QOS is directly in control of user in PMR, Cellular will provide a standard service

• Coverage….PMR operator require coverage over predefined areas of operation, Cellular may use over as wide area as possible including internationally.

PMR Standards

• Analog

• Digital

Analog PMR

• Early systems were analog and proprietary

• Later on, some standards introduced for infrastructure cost and spectrum sharing

• One such system is LTR (Logic Trunk Radio)

• Another major Analog standard is MPT1327 developed in UK in 1980s but implemented worldwide

• MPT1327 is complex and expensive but efficient in spectrum use as well as offer data services

• Difficult to replace or upgrade due to cost

Digital PMR

Advantages are

• Ability to recover the signal completely as long as noise is below threshold level

• Direct sending of data without need for a modem and trunking due to easy manipulation of digital signal

• Lower spectrum required as digital modulation allows use of efficient compression techniques

• Increased Flexibility

• Increased availability of services

• Improved efficiency

• High QoS

Digital PMR Standards

• EDCAS..Enhanced Digital Access Communication System

• Geotek-FHMA

• APCO25

• iDEN

• GSM Derivatives

• TETRAPOL

• TETRA

Terrestrial Trunked Radio (TETRA)

• Open standard within ETSI

• Feature rich system from specialized safety services to cellular operating modes

• Wide selection of data services

• More efficient use of spectrum due to TDMA access technique

• Number of operating modes with wide coverage

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