Final Vv Gsm Assignment

8/3/2019 Final Vv Gsm Assignment

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LUCHMUNPERSAD RITISH

HND TEL

YEAR 2

Trainer: v.virah sawmy


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Introduction

Analog cellular telephone systems were experiencing rapid growth in Europe during theearly 1980s. Each country developed its own system, but it was incompatible with

everyone else's in equipment and operation. The mobile equipment was limited to

operation within national boundaries, and there was also a very limited market for each

type of equipment. The Europeans realized this early on, and in 1982 the Conference ofEuropean Posts and Telegraphs (CEPT) formed a study group to study and develop a

pan-European public land mobile system. The proposed system called the Global Systemfor Mobile communications (GSM) had to meet certain criteria:

yGood subjective speech qualityyLow terminal and service costySupport for international roamingySupport for range of new services and facilitiesySpectral efficiencyyAbility to support handheld terminalsy ISDN compatibility

HISTORY

In 1989, GSM responsibility was transferred to the European TelecommunicationStandards Institute (ETSI).Currently GSM is one of the worlds most widely deployed

and fastest growing digital cellular standard. It is one of the most successful digital mobiletelecommunication systems. There are over 250 million GSM subscribers world-wide -two thirds of the worlds digital mobile population - and this figure is increasing by nearly


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2004 y Emtel brings a new way of communicating to Mauritius throughMultimedia Messaging.

y Emtel launches its International Call Gateway,y November 29th, Emtel launches the first 3G (UMTS) Network in

Africa.

2006 March, Emtel initiates the Video Surveillance service which allowscustomers using a 3G mobile to keep a watch on the place of their choice

2007 January, Emtel introduces the Emtel BlackBerry which enables customersto have access to a wide range of applications which include e-mail,

phone, intranet, Internet, operating over Emtel's GSM and GPRS network.2008 Rebranding of Cellplus to Orange

2009 Orange launches HSPA or 3G+

OVERVIEW

GSM is a wireless platform that uses radio frequencies, and this way user can be fullymobile, and do wireless data computing anywhere, without worrying about adapters,

telephone jacks, cables, etc. The unique roaming features of GSM allow cellularsubscribers to use their services in any GSM service area in the world in which their

provider has a roaming agreement. GSM-enabled phones have a "smart card" inside

called the SubscriberIdentity Module (SIM). The SIM card is personalized to the user.It identifies the users account to the network and provides authentication, which allows

appropriate billing.GSM has been designed for speech services. It uses circuit switchedtransmission, reserving one radio channel for the users traffic. It also uses cells whichenables it to reuse different frequencies.GSM, provides almost complete coverage inWestern Europe, and growing coverage in the Americas, Asia and elsewhere. GSM

networks presently operate in three different frequency ranges. These are GSM 900(also called GSM) - operates in the 900 MHz frequency range and is the most commonin Europe and the world.GSM 1800 (also called PCN (Personal Communication

Network), and DCS 1800) -operates in the 1800 MHz frequency range and is found in arapidly-increasing number of countries including France, Germany, UK, and

Russia.GSM 1900 (also called PCS (Personal Communication Services), PCS 1900,andDCS1900) - the only frequency used in the United States and Canada forGSM.GSM standard circuit is a digital data bearer service offering 9.6kb/s. This data

transmission in these networks is regarded as too slow and often too expensive for manyapplications. The cost is the total time that the user occupied that channelEven though he was using the channel all the time. The performance of services such as

Internet Applications in a cellular environment is typically characterized by the low


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available bandwidth, and an inefficient use of the rare air link capacity. Furthermore, long

connection setup delay is a problem for bursty services requiring occasional datatransfers.

Architecture of the GSM network

A GSM network is composed of several subsystems whose functions and

interfaces are specified. Figure 1 shows the layout of a generic GSM network.

These are the:1) Base station subsystem (BSS)

2) Mobile station (MS)

3) Network and switching subsystem (NSS)4) Operations subsystem (OSS)5) Operations and maintenance Center (OMC)


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Base Station Subsystem

The Base Station Subsystem controls the radio link with the Mobile Station. It is

mainly composed of the Base Transceiver Station (BTS) and the Base StationController (BSC).The BSC-to-BTS link is called the Abis interface which is cable or

an optical fibre interface, and allows operation between components made by

different suppliers. The BTS is made up of the antenna and the radio transceivers. ABTS houses the radio transceivers that define a cell, and handles the radio-link

protocols with the Mobile Station. BSC manages the radio resources and handles

radio-channel setup, frequency hopping, and handovers among a number of differentcells.

The BSC connection between the MS and the Mobile service Switching Center

(MSC) is done through the Translation and Adaptation Unit (TRAU). Usually, 20 to30 BTS will be controlled by one BSC.

Mobile Station

The MS, both hand-held (or portables) and traditional mobiles, is carried by the

subscriber. The MS is made up of the mobile equipment (ME), also known as the

terminal, and a smart card known as the Subscriber Identity Module (SIM).Themobile equipment is uniquely identified by the International Mobile EquipmentIdentity (IMEI).The SIM card contains the International Mobile SubscriberIdentity

(IMSI) used to identify the subscriber to the system, a secret key for authentication,and other information. GSM subscriber information are not programmed on the

mobile equipment but rather stored in a computer chip on the SIM card. The SIM

card can be inserted into another GSM terminal, enabling the user to receive calls atthat terminal, make calls from that terminal, and receive other subscribed

services. This way personal mobility is provided as the user can have access to

subscribed services irrespective of a specific terminals. The SIM card providessubscriber account protection against unauthorized use by a password or personalidentity number. The SIM provides assistance with voice and data encryption by

deriving the variables for the encryption process.

Network Subsystem

The Network Subsystem is the MSC. It is an advanced electronic switch that providesall the functionality needed to handle a mobile subscriber, such as registration,authentication, location updating, handovers (mobility), and call routing to a roaming

subscriber. The MSC also has the interface to other networks such as private land


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mobile networks, public switched telephone networks and integrated services digital

networks (ISDN). Signalling between functional entities in the Network Subsystemuses Signalling System Number 7 (SS7).The MSC is connected to the HLR.Logically there is only one HLR per GSM network, although it may be implemented

as a distributed database. The HLR contains all the administrative information of each

subscriber registered in the corresponding GSM network, along with the currentlocation of the mobile. The location of the mobile is typically in the form of the

signalling address of the VLR associated with the mobile station. Each MSC will

also have a VLR that contains selected administrative information from the HLR,necessary for call control and provision of the subscribed services, for each mobile

currently located in the geographical area controlled by the VLR. Usually the VLR is

implemented together with the MSC, so that the geographical area controlled by theMSC corresponds to that controlled by the VLR. This way the signalling required is

simplified.

Two Main Standards of GSM

y GSM 900 (global system for mobile communications in the 900 MHzband)

y DCS 1800 (digital cellular system for the 1800 MHz band)GSM 900 is a designed for extensive radio coverage even in rural areas.

DCS 1800 is designed for radio coverage in areas with very high subscriberdensity.

GSM frequency bands

System Band Uplink (MHz) Downlink (MHz)


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y Access methodGSM utilizes the time division multiple access(TDMA) concept. TDMA is a technique in which several differentcalls may share the same carrier. Each call is assigned a particulartime slot.

y Speech coderGSM uses linear predictive coding (LPC). The purposeofLPC is to reduce the bit rate. The LPC provides parameters for afilter that mimics the vocal tract. The signal passes through this

filter, leaving behind a residual signal. Speech is encoded at 13

kbps.

Advantages of GSM

y GSM is mature; this maturity means a more stable network withrobust features

y Less signal deterioration inside buildingsy Ability to use repeatersy Talk-time is generally higher in GSM phones due to the pulse nature

of transmission

y The availability of Subscriber Identity Modules allows users toswitch networks and handsets at will

y GSM covers virtually all parts of the world so international roamingis not a problem.

y The subscriber can enjoy the broadest international coverage. It ispossible with the GSM roaming service.

y Good coverage indoors on 850/900 MHz. Repeaters possible. 35 kmhard limit.

y Very good due to simple protocol, good coverage and mature,power-efficient chipsets.

Disadvantages of GSM

y Pulse nature of TDMA transmission used in 2G interferes with someelectronics, especially certain audio amplifiers. 3G uses W-CDMAnow.

y Intellectual property is concentrated among a few industry participants, creating barriers to entry for new entrants and limitingcompetition among phone manufacturers.


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y GSM has a fixed maximum cell site range of 35 km, which isimposed by technical limitations.

CONCLUSION ON GSM

GSM is a wireless platform that uses radio frequencies. It has been designed forspeech services and uses circuit switched transmission. GSM standard circuit is adigital data bearer service offering 9.6kb/s. This data transmission in these

networks is regarded as too slow and often too expensive for many applications.The cost is the total time that the user occupied that channel even though he maynot be using the channel all the time.

GPRS

INTRODUCTION OF GPRS

GPRS is a standard for wireless communications which runs at speeds up to 150kilobits per second, compared with current GSMs systems' 9.6 kbps. GPRS is an

efficient use of limited bandwidth and is particularly suited for sending and receiving


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small bursts of data, such as e-mail and Web browsing, as well as large volumes of

data. The GPRS services reflect the GSM services with an exception that theGPRS has a higher transmission rate which makes a good impact in the most of theexisting services and creates the opportunity for the introduction of new services as

operators. This paper first introduces the two systems and then states and compares

the architecture of the two systems. It then goes over the protocols of both systemsand describes any differences and/or similarities.

HISTORY OF GPRS

GPRS was developed to support packet switching. The work on the GPRSspecification beganin 1994 as a part of GSM phases 2+ specification. GPRS is a

separate packet data network within GSM which provides a packet base platform both for the data transfer and signalling. GPRS is compatible with the GSMarchitecture. Voice and GPRS services coexist in the same environment with the

minimum changes in the system.GPRS focused strongly on the development of aservice, which overcomes these drawbacks of a mobile Internet Access. It allowsallow reduced connection setup-times, supports existing packet oriented protocols like

X.25 and IP, and provides an optimized usage of radio resources. The main idea is toallocate resources depending on the GPRS demand. This feature operates in acapacity-on-demand mode. The capacity-on-demand concept has been introduced in

order to keep compatibility with the existing GSM circuit-switched resources.

Resources for GPRS may be dynamically allocated depending on how many usersrequire them with a given quality of service and depending also on how many

resources are available at the moment. The operator can decide whether topermanently dedicate some physical resources for GPRS.Load supervision is carriedout in the MAC layer to monitor the load of the GPRS physical resources, and it's the

function that will allow increasing or decreasing the number of allocated resources

according to the existing demand. The operator has also the choice to dedicatetemporarily physical resources for GPRS as long as no other higher-priority GSM

services require them. Since GPRS is packet oriented it enables volume based

charging in contrast to GSM like charging of online time. It therefore allows users tostay constantly online while only paying for the occasional data transfer. Anotherimportant factor is the Quality of Service (QoS) offered by these services. The QoS

can be negotiated when starting the session and can be renegotiated if it is required.The QoS agreed between the user and the network can be used to charge the service.In addition, GPRS increases the capacity of the system and reduces the idle periods of

the radio channels. This is done by allowing for multiple users per physical channeland using a channel only when it is needed, and releasing it immediately after thetransmission is complete.


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GPRS in Mauritius

Orange and Emtel provide GPRS data connections up to 140.8 Kbit/s butdue to the fact that the GPRS networks in Mauritius are mostly packet

switched and not circuit switched the typical rates are closer around 56

Kbit/s.

GPRS ARCHITECTURE

GPRS is an addition to the existing GSM infrastructure. As a result the GPRS

architecture is very similar to the GSMs. The existing GSM nodes are upgraded withGPRS functionality. The same transmission links can be reused for both GSM and

GPRS. E.g. the link between BSCs and BTSs.The GSM network provided onlycircuit- switched services and thus two new network nodes were defined to givesupport for packet switching. This way packet data traffic separated from traditional

GSM speech and data traffic. The two nodes are the Serving GPRS Support Node(SGSN) and the Gateway GPRS Support Node (GGSN)(see figure3). SGSN andGGSN are mobile aware routers and are interconnected via an IP backbone network.

The SGSN is responsible for the communication between the mobile station (MS)

and the GPRS network. It carries out the basic functions of GSMS BSC of providingauthentication, ciphering and IMEI check, mobility management, logical linkmanagement towards the MS, and charging data. It also connects to the HLR, MSC,and BSC and handles packet data traffic of GPRS users in a geographical area. The

traffic is routed from the SGSN to the BSC via the BTS to the MS. The SGSN likethe GSMs MSC provides packet routing to and from the SGSN service area.


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The GGSN connects to outside data networks and to other GPRS networks. TheGGSN provides the interface to external packet data networks like X.25 andexternal IP networks which are not supported by GSM. It routes incoming packets

to the appropriate SGSN for a particular mobile station.

It also provides mobility management, access server functionality, and routing tothe right SGSN and protocol conversion. The GPRS protocols are limited to justsetting up an IP bearer, a logical link, between the MS and the Access Server. Ittranslates data formats, signalling protocols and address information permitting

communication between the different networks and enabling compatibility with

the GSM network. GGSN is a host owning all IP addresses of all subscribersserved by the GPRS network thus replacing the functionality of GSMS VLR.

GPRS uses the GSMS BSS but with enhanced functionality to support GPRS(see figure 3). The GSMs BSS is used as a shared resource of both circuit

switched and packet switched network elements to ensure backward compatibilityand keep the requirements for the introduction of GPRS at a reasonable level. Themain change that GPRS brought compared to GSM is the addition of the packet

control unit (PCU) into the BSC which controls the packet channels, separatingthe data flows of circuit and packet switched data. Circuit switched data are sendthrough the A-interface on the MSC whereas packet data are send to the SGSN

into the GPRS backbone. The BSC of GSM is given new functionality formobility management, for handling GPRS paging. The new traffic and signallinginterface from the SGSN is terminated in the BSC.

GPRS uses the MSC/VLR interface provided by GSM, between the MSC andSGSN co-ordinated signalling for mobile stations which have both circuit

switched and packets witched capabilities.


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GPRS INFRASTRUCTURE

The HLR of GSM is modified to contain GPRS subscription data and routing

information and is accessible from the SGSN. It also maps each subscriber to oneor more GGSNs. The HLR may be in a different PLMN than the current SGSNfor roaming terminals. The GSM interfaces are re-used except that they are

enhanced to support GPRS nodes (see figure 4). The existing Abis interfacetransmission towards BSC is reused .In the GSMs BTS new protocols supporting

packet data for the air interface and functions for resource allocation for slot andchannel allocation are implemented. GPRS uses the same pool of physicalchannels as speech. This way GPRS channels (PDCH) are mixed with circuit

switched channels (TCH) in one cell. A TCH is allocated to one single userwhereas several users can multiplex their traffic on one and the same PDCH.


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CONCLUSION ON GPRS

GPRS is a separate packet data network which provides a packet base platform both for the data transfer and signalling. It enables volume based charging in

contrast to GSM like charging of online time. It therefore allows users to stay

constantly online while only paying for the occasional data transfer. GPRSincreases the capacity of the system and reduces the idle periods of the radio

channels. This is done by allowing for multiple users per physical channel and

using a channel only when it is needed, and releasing it immediately after thetransmission is complete.

EDGE (Enhanced Data GSM Environment)

Introduction

EDGE is the next step in the evolution of GSM and IS- 136. The objective

of the new technology is to increase data transmission rates and spectrumefficiency and to facilitate new applications and increased capacity for

mobile use. With the introduction of EDGE in GSM phase 2+, existingservices such as GPRS and high-speed circuit switched data (HSCSD) are


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EGPRS share the same packet-handling protocols and, therefore, behave in

the same way. Reuse of the existing GPRS core infrastructure (servingGRPS support node/gateway GPRS support node) emphasizes the fact thatEGPRS is only an add-on to the base station system and is therefore

much easier to introduce than GPRS (Figure 1).

In addition to enhancing the throughput for each data user, EDGE

also increases capacity. With EDGE, the same time slot can support more

users. This decreases the number of radio resources required to support thesame traffic, thus freeing up capacity for more data or voice services.

EDGE makes it easier for circuit-switched and packet-switched traffic to

coexist, while making more efficient use of the same radio resources. Thusin tightly planned networks with limited spectrum, EDGE may also be

seen as a capacity booster for the data traffic.

EDGE Modulation Technique

The modulation type that is used in GSM is the Gaussian minimumshift keying (GMSK), which is a kind of phase modulation. This can be

visualized in an I/Q diagram that shows the real (I) and imaginary (Q)

components of the transmitted signal (Figure 3). Transmitting a zero bit orone bit is then represented by changing the phase by increments of + _ p.

Every symbol that is transmitted represents one bit; that is, each shift inthe phase represents one bit.

To achieve higher bit rates per time slot than those available in

GSM/GPRS, the modulation method requires change. EDGE is specified


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to reuse the channel structure, channel width, channel coding and the

existing mechanisms and functionality of GPRS and HSCSD. Themodulation standard selected for EDGE, 8-phase shift keying (8PSK),fulfils all of those requirements. 8PSK modulation has the same qualities

in terms of generating interference on adjacent channels as GMSK. This

makes it possible to integrate EDGE channels into an existing frequencyplan and to assign new EDGE channels in the same way as standard GSM

channels.

The 8PSK modulation method is a linear method in which threeconsecutive bits are mapped onto one symbol in the I/Q plane. The symbol

rate, or the number of symbols sent within a certain period of time,remains the same as for GMSK, but each symbol now represents three bits

instead of one. The total data rate is therefore increased by a factor ofthree.

The distance between the different symbols is shorter using 8PSKmodulation than when using GMSK. Shorter distances increase the risk for

misinterpretation of the symbols because it is more difficult for the radioreceiver to detect which symbol it has received. Under good radio

conditions, this does not matter. Under poor radio conditions, however, it

does. The extra bits will be used to add more error- correcting coding,and the correct information can be recovered. Only under very poor radio

environments is GMSK more efficient. Therefore the EDGE codingschemes are a mixture of both GMSK and 8PSK.


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ARCHITECTURE OF EDGE

EGPRS does not bring about any direct architecture impacts. Thepacket control unit may still be placed either in the base station, the

base station controller or the GPRS support node, and the centralcontrol unit is always placed in the base station. However, since the

radio link control automatic repeat request function on the networkside is located in the packet control unit, any delay introduced

between the PCU and the radio interface will directly affect the radio

link control acknowledged/unacknowledged round-trip times. This,in turn, results in a higher risk of stalling the radio link control

protocol. To mitigate this risk and to allow the operator to optimize

network behaviour, the maximum radio link control automatic repeatrequest window size has been extended for GPRS.

EGPRS benefits


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UMTS (Universal Mobile Telecommunications System)

(UMTS) is one of the third-generation (3G) mobile telecommunications

technologies, which is also being developed into a 4G technology. Thefirst deployment of the UMTS is the release99 (R99) architecture. It is

Specified by 3GPP and is part of the global ITU IMT-2000 standard. Themost common form of UMTS uses W-CDMA (IMT Direct Spread) as theunderlying air interface but the system also covers TD-CDMA and

TD-SCDMA (both IMT CDMA TDD).Being a complete network system,UMTS also covers the radio access network (UMTS Terrestrial Radio

Access Network, or UTRAN) and the core network (Mobile ApplicationPart, or MAP), as well as authentication of users via USIM cards(SubscriberIdentity Module).

History of UTMS


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y October 1, 2001 NTT DoCoMo launched the first commercialWCDMA 3G mobile network.

y November 1, 2001 Nokia and AT&T Wireless complete first live 3GEDGE call.

y December 19, 2001 Nortel Networks and Vodafone in Spain(formerly Airtel Movil) completed first live international UMTS3GPP standard roaming calls between Madrid (Vodafone network)

and Tokyo (J-Phone network).

y January 28, 2002 SK Telecom in Korea launched the world's firstcommercial CDMA2000 1xEV-DO.

y February 8, 2002 Nokia claims to have made the first end-to-end 3GWCDMA standard level 3GPP Release 99 June 2001 packet datacalls between its commercial network infrastructure and terminals inits laboratories in Finland. The Nokia 3G WCDMA network and

terminal used were based on the commercial version.

y February 18, 2002 Motorola unveils the companys first GSM/GPRSand 3G/UMTS product, the A820.

y September 24, 2002 Ericsson announces the first live, dual modeWCDMA/GSM calls with seamless handover between the twomodes and high data rate in live networks

y September 26, 2002 Nokia introduces the "worlds first handset[6650] for WCDMA [UMTS] and GSM networks".

y November 18, 2002 Nokia introduces the worlds first GSM/EDGE3G mobile phone; Nokia 6200.

y February 10, 2003 LG introduced the world's first dual band, dualmode phone for both CDMA and WCDMA


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y February 2003, Korean mobile operator KTF announced plans tobegin transmitting TV pictures direct to 3G mobile phones via theCDMA2000 1xEV-DO system.

UMTS architecture

A UMTS network consists of three interacting domains, Core Network(CN), UMTS Terrestrial Radio Access Network (UTRAN) and UserEquipment (UE). The core network consists of nodes (switches) with

connecting lines. The main function of the core network is to provideswitching, routing and transit for user traffic. Core network also contains

the database and network management functions. The basic Core Networkarchitecture for UMTS is bases on GSM network with GPRS. Allequipment has to be modified for UMTS operation and services. The Core

Network is divided in circuit switched and packet switched domains. Some

of the circuit switched elements are Mobile services Switching Centre(MSC), Visitor location register (VLR) and Gateway MSC. Packetswitched elements are Serving GPRS Support Node (SGSN) and GatewayGPRS Support Node (GGSN). Some network elements, like EIR, HLR,

VLR and AUC are shared by both domains. Wide band CDMAtechnology was selected for UTRAN air interface. UMTS WCDMA is a

Direct Sequence CDMA system where user data is multiplied with quasi-random bits derived from WCDMA Spreading codes. In UMTS, inaddition to channelization, Codes are used for synchronization and

scrambling. WCDMA has two basic modes of operation: FrequencyDivision Duplex (FDD) and Time Division Duplex (TDD).

Hierarchical cell structure of UMTS to offer global radio coverage.


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UMTS offer global radio coverage and world-wide roaming. For that

purpose the URAN will be built in hierarchical way in layers of varyingcoverage as depicted in Fig. 2. A higher layer will cover a largergeographical area than a lower layer. In the highest layer there will be

satellites covering the whole planet, the lower layers form the UMTSterrestrial radio access network UTRAN. They are divided in to macro,micro, pico-layer. Each layer is divided into cells. The lower the

hierarchical level, smaller the cells. Smaller cells allow for a higher user-density. Therefore macro-cells are used for land-wide coverage; additional

micro-cells are installed in areas with higher population density and pico-cells in buildings and for so called hot spots (e.g. airports, railwaystations).

CONCLUSIONS

UMTS has been specified as an integrated solution for mobile voice anddata with wide area coverage. Symmetry b/w up-link and down-link data

rates when using paired (FDD) spectrum also means that UMTS is ideallysuited for applications such as real-time video telephony- in contrast with

other technologies such as ADSL where there is a pronounced asymmetryb/w up-link and down-link through-put rates.


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There have been two releases of the TETRA radio standard:

y TETRA Release 1: As would be envisaged this was the firstrelease of the TETRA radio standard which occurred.

y TETRA Release 2: This release of the TETRA radio standardoccurred in 2005 as a result of work dating back to 1999. It

introduced a number of new features into the TETRA radio standard:

o TETRA Enhanced Data Service (TEDS)o Mixed Excitation Liner Predictive, enhanced (MELPe) Voice Codeco Adaptive Multiple Rate (AMR) Voice Codeco Trunked Mode Operation (TMO) Range Extension


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Main TETRA Features and Parameters

TETRA has some unique features:

Direct push-to-talk (PPT), to groups and with priority setting Centralized call control, for priority and queuing.

Direct mode, portable to portable without central radio coverage (DMO) Relay mode, one portable can use another mobile device to link to thecentral radio.

Use of one or several timeslots for (low speed) Data. Voice encryption, different algorithms available.

Advantages


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y The much lower frequency used, which permits very high levelsofgeographic coverage with a smaller number of transmitters,

cutting infrastructure cost.

y Fast call set-up - a one to-many group call is generally set-upwithin 0.5 seconds (typical less than 250 millisecond for a singlenode call) compared with the many seconds that are required for aGSM network.

y The fact that its infrastructure can be separated from that of the public mobile phone network, and made substantially morediverse and resilient by the fact that base stations can be somedistance from the area served.

y Unlike most cellular technologies, TETRA networks typicallyprovide a number of fall-back modes such as the ability for a basestation to process local calls in the absence of the rest of the

network, and for 'direct mode' where mobiles can continue toshare channels directly if the infrastructure fails or is out-of-reach.

y Gateway mode - where a single mobile with connection to thenetwork can act as a relay for other nearby mobiles that are out ofcontact with the infrastructure.

y TETRA also provides a point-to-point function that traditionalanalogue emergency services radio systems didn't provide. Thisenables users to have a one-to-one trunked 'radio' link between

sets without the need for the direct involvement of a control room

operator/dispatcher.

Disadvantages

y It can only support a much lower tele-density in a given area,compared to GSM and similar technologies (which is not a problem

in the applications for which it is used, but mostly limits it to these

applications).

y Data transfer is slow at 7.2 Kbit/s per timeslot (3.5 Kbit/s net packetdata throughput), although up to 4 timeslots can be combined into asingle data channel to achieve higher rates, due to need to fit into25kHz bandwidth channel plans.


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y Due to the pulsed nature of TDMA employed by the protocol,handsets can interfere with sensitive electronic devices such as heart

pacemakers and defibrillators, as can other RF transmittingequipment when used in close proximity.

y Handsets are more expensive than cellular.

DECT Architecture

Four application examples of DECT

WLL (Wireless Local Loop) connection, instead of wired access lines for

connecting users to the PSTN/ISDN.


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Cordless system (residential use), only one base station => only intracellhandover.

PABX wireless extension (business use, e.g. HUT), several base stations

=> intracell and intercell handover.

CTM (Cordless Terminal Mobility), wide area Mobility.


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Final Vv Gsm Assignment

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