University of Information Technology & Sciences (UITS) 17/A, North Gulshan C/A, Gulshan-2, Dhaka-1212 Bangladesh
Thesis Supervisor
Mohammad Tawrit. M Sc Engineer, Adjunct Faculty, University of Information Technology & Sciences (UITS), Dhaka, Bangladesh.
1 Acknowledgments
I would like to express thanks to Mr. All Mamun, Asst Manager, IT and Billing, Dhaka Phone.
Many thanks for Mr. Mostafiz, Asst. Manager Network Operation, Teletalk Bangladesh Ltd. for the information he provided regarding the Base Station Subsystem of Teletalk Bangladesh Limited.
I acknowledge the help extended by the officers and officials of Teletalk Bangladesh Ltd. for the information they have supplied, without which this thesis would have lost all its merits.
Special thanks for Mr. Mohammad Tawrit, Adjunct Faculty, UITS and DGM, Network & Operation, Teletalk Bangladesh Ltd. for his valuable advice, supervision and input. Specially he has taught me the basic and professional skill about Telecommunication Network.
Student
Name : Md. Khondakar Mashiur Rahman University of Information Technology and Science ID : 060561 Program : M.Sc. in Telecommunication
2 Abstract
The main objective of this study was to analyze the feasibility of migration from GSM Technology to UMTS technology. To accomplish the study at first the basic features of both GSM and UMTS has been explained. To make the study more effective and practical, a GSM operator was searched for. Teletalk started their GSM Network operation with Phase 2+ way back in April, 2005 and it is still continuing with the same technology. With growing demand in the market it is seriously contemplating to migrate into Release 3 (UMTS).
The migrated system will definitely provide many advantages like addition of new applications video stream taking advantage the high bandwidth of 3G technology. But, there is other side of the coin too. First of all, it involves lot of investment. Then comes the cost of the 3G Mobile Station. Teletalk is also skeptical about the increase in ARPU with these added benefits offered to the subscriber. All such issues have been duly taken care in this study one by one.
The other issue popped up regarding introduction of UMTS is whether to introduce the service globally through out the network or to introduce it on an island basis and then expand its territory in phases. All the pros and cons of such strategic decisions have been analyzed in the process. Along with that the technical hitches that might come in migrating to 3G services have been taken care in details.
Finally a recommendation has been given for Teletalk about the strategic decision it should take at the moment regarding its migration to UMTS.
3 Contents
Introduction ……………………………………………………………………….
Chapter- 1 : Migration Path 1.1. Teletalk GSM ……………………………………….………….. …... 7 1.2. Teletalk migration from GSM to 3G ……………………….………. 7 1.3. Advantage of 3G over 2.5G ………………….……………….… 8 1.4. Obstacles of 3G service for Teletalk ………….………………….. 9 1.5. 3G Service for Teletalk Network ……………………………..…. 9
Chapter- 2 : Network Architecture 2.1. Existing GSM/GPRS Architecture ……………………….………… 10 2.2. Mapping GSM/GPRS Architecture Into 3G ……………….……… 11 2.3. Teletalk Base Station Subsystem …………………………….. 13 2.4. Mapping Base Station Sub System into 3G …………………… 15 2.5. Teletalk Network Switching Subsystem ……………….……..… 18 2.6. Mapping Network Switching Subsystem into 3G ………….…….. 20
Chapter- 3 : Technology involved in GSM Network & 3G Network 3.1. Teletalk GSM/3G Area Identities ……………………………..…. 22 3.2. Teletalk GSM/3G Subscriber Code …………………………………. 23 3.3. Teletalk Example Identities and Code ………………………..…. 24 3.4. Network Security …………………..………………………………. 25 3.5. Mapping Network Security into 3G ………………………….…… 27 3.6. Location Update …………………………………………….………. 28 3.7. Mapping Location Update into 3G ……….. ………………………… 29 3.8. Teletalk Handover ………………………………………..……… .. 29 3.9. Mapping Teletalk Handover into 3G ……………………………. 31 3.10. GPRS PDP Context …………………………………….………… 33 3.11. Mapping GPRS PDP Context into 3G …………………… 34 3.12. Mapping Call Handling into 3G Call Handling ……………... …… 35
4 Chapter- 4 : Radio Access Network 4.1. Radio Interface in Physical Layer ……………………….…. ….. 37 4.2. Mapping Radio Interface of Physical Layer into 3G ……….. ……. 40 4.3. Teletalk Radio Interface in Logical Layer .………………...… ….. 43 4.4. Mapping Logical Interface Channels into 3G Radio Interface …… 44
Chapter- 5 : Signaling & NSS Dimensioning 5.1. GSM Signaling of Teletalk ……………………………………… ……. 48 5.2 Mapping GSM Signaling into 3G ……………………………. …… 51 5.3. Dimensioning Signaling Interface ………………..…………. …….. 55
Chapter- 6 : Network Planning 6.1. Teletalk GSM Radio frequency planning ……………………….. …. 56 6.2. Mapping GSM Radio frequency planning into 3G ……………… … 58 6.3. GSM Capacity & Coverage Planning while migrating into 3G…... …. 60 6.4. Mapping GSM Capacity and Coverage into 3G ……………….. …. 61 6.5. Additional Cost for Migration in 3G ……………………………………...63 6.6. Payback Period ………………………………………………...... … 63
Recommendation ……………………………….……………………………………… 64
Reference …………………………………………………………………………….. 65
5 Introduction
To study the technology of 2.5G of Teletalk network and migrating it into 3G according to WCDMA method of UMTS with coexisting of current GSM network by obtaining sufficient coverage over the entire service area to ensure that high quality voice service and high bandwidth of data service will be offered to the subscribers. BSS and NSS part the system has been migrated in 3G
Migration from 2.5G towards 3G would be based on the following steps:
1. Migration path from GSM/GPRS to 3G network 2. Migration of GSM network architecture into 3G network architecture. 3. Migration of GSM Technology into 3G Technology. 4. Migration of GSM Radio Access network into 3G Radio Access network. 5. Migration of GSM signaling system into 3G signaling systems 6. Migration of GSM network planning into 3G network planning. 3G Teletalk Cellular Mobile system has been design where both GSM BTS & UMTS Node B, GSM BSC & UMTS RNC, GSM Network Switching Subsystem (NSS) & UMTS Network Switching System (NSS) will use the same platform. UMTS Network Switching System will design for both Circuit Switched (CS) domain for speech, video telephony, real-time data transfer & Packet Switched (PS) domain for non real-time data transfer. Migrated 3G system of Teletalk will provide following services: Video on Demand Game on Demand Video Telephony Multimedia Applications Tele-shopping Electronic newspaper with image and sounds Tele-Banking financial services Database information services Email Voice Data rate = 384kbit/s for Macro cell
6 Chapter – 1 Migration Path
1.1. GSM Positioning of Teletalk
The second generation of cellular services (2G) of Teletalk Bangladesh Limited as characterized by the GSM standard is a TDM-based technology. GSM run over Plysynchronization Channel (PDH)/Synchronization Channel (SDH) access networks, relying on a wide variety of wire line and wireless transport solutions. The present positioning of Teletalk in GSM evolution path is shown in Figure 1.1.
Fig. 1.1 GSM concepts with Teletalk Position General Packet Radio Service (GPRS): The relatively new 2.5G (GPRS) data service is still very much a TDM-based technology, providing an interim solution.
1.2. Teletalk Migration from GSM to 3rd Generation (3G)
WCDMA technique is the standard modulation technique for 3G Radio Access Network. WCDMA technique is appropriate for migration from Global System for Mobile Communications (GSM)/ General Packet Radio Service (GPRS) to Third Generation (3G). According to following diagram (Fig. 1.2) Teletalk has the choice to slowly evolve along a migration path toward the original objectives of 3G to obtain the smoothest possible transition from the 2nd to the 3rd generation of mobile communications [4]. The cell parameters of 3G are Radius = several kilometers (according to Antenna NodeB parameter set) Transfer rate = 384 kbit/s Mobility = 120 km/h or high 500 km/h
Fig. 1.2 3G Migration Path
7 CDMA / WCDMA: CDMA is Code Division Multiple Access. WCDMA stand for Wideband Code Division Multiple Access. WCDMA does not assign a specific frequency to each user. Instead every channel uses the full available spectrum. Individual conversations are encoded with a pseudo-random digital sequence. Direct-sequence CDMA permits multiple users to access a single radio frequency carrier by allocating a discrete code to each. This code is used to spread the user’s data stream over a wide bandwidth for transmission over the radio link. The receiver uses the appropriate code to “dispread” the user’s required signal to reproduce the original data stream. The use of codes to distinguish individual channels also allows adjacent base stations to use the same carrier. In all cases, for bi-directional communication, separate radio frequency carriers are used for uplink (mobile station to base station) and downlink (base station to mobile station).
1.3. Advantage of 3G over 2.5G
Migration to 3G Mobile System has got the following advantages: Migration based on GSM core network & core network protocol. Migration based on GSM core network & as core network protocol will be similar. Save GSM investment Reuse of GSM supplementary services. PS – packet switch network as a result easy to compatible with LAN, WAN 3G is a path to migrate to 4G. 144 Kbps- user in high-speed motor vehicles can speed up to 500 km/hour 384 Kbps- pedestrians standing or moving slowly over small areas speed up to 120 km/hour 2 Mbps in low range outdoor at the speed of 10 km /hour Faster reduction of cost System capacity planning in data transmission rate. Facility to use more than one application. Dual traffic capacity so frequency will be available in special day Easy to capacity planning. Extended security of subscribers data Soft handover of 3G to 2G and 2G to 3G. 2G & 3G can access simultaneously.
8 1.4. Obstacles of 3G service for Teletalk
At present the following issues are there which Teletalk needs to address while thinking of 3G Migration: Simultaneous Coverage Planning 2.5G and 3G. Integration is complex because initially good handshaking is required between GSM and WCDMA. Both GSM and WCDMA need to design Complex Traffic management Unutilized GSM traffic when subscriber connected with 3G and unutilized 3G traffic when subscriber connected with GSM network. Less 3G subscriber at initial phase. Subscribers also need to upgrade his mobile station which cost significant amount of money compare to 2G mobile stations. Difficult to coverage planning. Higher Investment cost Reusability planning instead of WCDMA network because of GSM service.
1.5. 3G Service for Teletalk Network
The 3G services that Teletalk can think of offering its subscribers are: Video on demand Game on demand Video telephone will be possible after migration. Tele-shopping Tele-banking financial services Database Access Information service Internet service Tele Medicine Remote Learning, Mobile TV
9 Chapter - 2 Network Architecture
2.1. Existing GSM/GPRS Network Architecture
Existing network architecture represents the mobile network components. They consist of BTS, BSC, MSC, TRAU, HLR, VLR, AC, and Equipment Identification Register (EIR) [1]. Fig. 2.1 shows the present network architecture.
Fig. 2.1 Teletalk Present Network Architecture
10 2.2. Mapping GSM/GPRS Network Architecture into 3G
3G network architecture represents the mobile network components. They consist of NodeB, RNC, MSC, CS Domain and PS Domain. 3G Network architecture will be designed with dual capacity providing both 3G and GSM services. 3G systems will use Node B instead of BTS; RNC instead of BSC and core network will be designed based on GPRS technology. Fig.2.2 shows the 3G network Interface.
Fig. 2.2 – 3G Network Architecture
11 2.2.1. 2G/3G Network Interface:
Interface is the connection between mobile equipment. Interface diagram of both GSM and 3G are designed. Both system works simultaneously. Fig. 2.3 shows the GSM/GPRS & 3G network Interface.
Fig. 2.3 / 3G Interface
12 2.3. Base Station Subsystem
Major components of Teletalk Base Station Subsystem are BSC, TRAU and BTS.
Base Station Controller (BSC): The Base Station Controller BSC is, as the controlling element, the heart and center element of the BSS. Base Station Controller is switching part of the user traffic between individual TRAU and BTS Control and monitoring of the connected TRAU and BTS Evaluation of signaling information from MSC via TRAU and MS via BTS Radio Resource Management for all connected BTS
Transcoder Rate Adaption Unit (TRAU) : The TRAU frame is the transport unit for a 16 kbit/s traffic channel (TCH) on the Abis interface. Transcoding and Rate Adaption Unit is used for Speech compression and Rate Adaptation. Fig. 2.4 shows the TRAU functionality-
Fig. 2.4 TRAU
Speech Compression = 64 kbit/s = 13 kbit/s + in band signaling Signaling = transparent Rate Adaptation RA filters out the useful data (0.3 – 9.6 kbit/s in Phase 1/2) coming from the MSC (64kbit/s) signal and forms a 16 kbit/s signal toward the BSC
13 Base Transceiver Station (BTS) : A BTS is the module which operates an individual cell and realizes the radio interface. A BTS encompasses all applications concerning radio transmission (sending, receiving), as well as the air interface specific signal processing. Here it has been explained teletalk BTS of Huawei BTS312 model (Fig. 2.5).
Fig. 2.5 BTS Teletalk Cell coverage radius=600/800 meter in Urban area & 3.5 in rural areas. Teletalk use down tilt for controlling interference between neighbouring cells. Fig. 2.6 shows tilt function.
Fig. 2.6 Antenna Tilt.
14 2.4. Mapping Base Station Sub System into 3G
Major components of Teletalk 3G Base Station Subsystems are RNC and NodeB, For 3G 20 BTS room and Tower will be installed in Gulshan area. Both NodeB and BTS will be installed in same location. RNC & BSC will be installed same way as both system can run simultaneously
Radio Network Controller (RNC) : A Radio Network Controller (RNC) is a network component in the PLMN with the functions for control of one or more Node B. It is similar like BSC. Fig. 2.7 shows 3G RNC unit. [4]
Fig. 2.7 Functional diagram of RNC ATM switch unit - The ATM switch unit perform ATM cell switching function. RNC controller - Performs operation and maintenance (O&M) related processing and terminates the control protocol at layer 3 or above Management/control Controls routing of ATM cells between processors and switch Provides internal control signal monitoring functions Processor recovery control Periodical alarm supervision Trunk unit - Performs routing of cells between ATM software and trunk Terminates the U-MSC signal
15 Terminates the Node B signal Provides diverted handover function Provides mapping function between the transport channel and logical channel U-MSC interface unit - Performs of RNC internal AAL2 partial fill cells and AAL2 cells NodeB interface unit- Consists of a line interface unit and an AAL2 multiplexing unit Performs handling of AAL2 cells Terminates the E1 lines and performs alarm handling
Node B : A Node B is a logical network component which serves one or more cells. A Node B (Fig. 2.8) is a physical unit for implementation of the UMTS radio interface. As a central transmission and reception site, it will be 3 with 120° coverage. [4]
Fig. 2.8 Node B
The NodeB consists of the Basic modem unit (B-SHF), Expansion modem unit (T-SHF), Transmitter receiver amplifier unit (A-SHF)
TRX block - The transmitter (TX) part of TRX (Fig. 2.9) converts the base band spread signals processed by the BB block into radio frequency signals by quadrature modulator
Base band (BB) signal processing block - Use for error correction coding/decoding and channel coding. The functions of BB are modulation and spreading for transmission data, de-spreading, chip synchronization, rake composition and de-multiplexing of receiving data.
Highway interface (HWY-INT) block - Connects to the RNC with 2 Mbit/s or other circuit interface and performs ATM processing and AAL-type 2 and -type 5 signal processing.
16 Common control (CONT) - Provide call processing control function, maintenance supervisory control function, NodeB bus control function, system data storage function, reference oscillator function. Linear power amplifier (LPA) block - The transmitter receiver amplifier unit consists of one or two LPA and an amplifier supervising and control card (AMP-SC) that monitors and controls the LPA.
Fig. 2.9 Node B AMP-SC - AMP supervisory & control block that Controls the state of LPA. TTA - It is Top tower Amplifier that improve receive sensitivity TTA-M -It is Top tower amplifier (TTA) monitor block that feeds the DC power required for TTA, and monitors operation of TTA. Receiving amplifier(RX AMP) block - Used instead of TTA if the antenna feeder is short.
17 2.5. Teletalk Network Switching Subsystem
Teletalk Network Switching Subsystem (Fig. 2.1) has the following functional elements Mobile Switching Center (MSC), Visitor Location Register (VLR), Home Location Register (HLR), Authentication Center (AC), Softswitch, Media Gateway and GPRS [4]. The entire functional element has been described below briefly.
Mobile Switching Center (MSC) : MSC is Mobile Switching Center. The MSC is concerned with the central tasks of the NSS and covers the service areas of several BSS. VMSC -The MSC visited by a customer is described as a visited MSC. GMSC - A MSC, which represents an interface to other networks.
Visitor Location Register (VLR) : The Visitor Location Register VLR is responsible to aid the MSC with information on the subscriber, which are temporarily in the MSC service area
Home Location Register (HLR) : It sends all necessary data to the VLR. It transmits the Triples from AC to VLR on request.
Authentication Center (AC) : AC is stand for Authentication Center. It is consisting by MSI, Individual subscriber authentication Key (Ki). Algorithm (A3) and Algorithm (A8).
Softswitch : Teletalk use SoftX3000 for IP context. Supported protocol H.248/MGCP, SIP/SIP-T, H.323. BHCA = 16 Million, 2 Million subscriber / 360000 trunks.
Media Gateway (MGW) : Teletalk use UMG8900 Media Gateway for Voice over Internet Protocol (VoIP). It is codec. Maximum capacity = 220000 VoIP channels and 220000 TDM trunks.
18 2.5.1. Teletalk GPRS
General Packet Radio Service (GPRS) is used for data transmission. Fig. 2.10 depicts GPRS procedure [3,1]
Gateway GPRS Support Node (GGSN) Service GPRS Support Node (SGSN) Packet Control Unit (PCU) Channel Codec Unit (CCU) HLR Extension GPRS MS
Fig. 2.10 GPRS Service GPRS Support Node (SGSN) : SGSN is used for routing /Traffic-Management and Mobility Management functions. Location Update, Attach, Paging, Storing Location information Security & Access Control Collecting charging data Signaling with HLR, EIR, GGSN, MSC Gateway GPRS Support Node GGSN : GGSN is used for protocol conversion, Routing / Traffic Management and Screening / Filtering Packet Control Unit (PCU) : PCU used for protocol conversion and radio resource management Channel Codec Unit (CCU) : The CCU enables to transmit using the new Coding Schemes CS-1, CS-2, CS-3 and CS-4
19 2.6. Mapping Network Switching Subsystem into 3G
Third Generation (3G) Network Switching Subsystems (NSS) has been separated by CS (Circuit Switch) domain and PS (Packet Switch) domain [4]. As far as CS Domain is concerned it is almost similar to GSM whether PS domain is the updated phase of GPRS.
2.6.1. Circuit Switch (CS) Domain
The Core Network consists of a Circuit Switched CS Domain for speech, video telephony and real-time data transfer. The difference of CS in 3G the Transcoder is part of the MSC where as in 2G it was part of BSS.
Transcoder (TC) : Additional activities of TC in 3G- TC is part of MSC Radio Access Network (RAN) to TC Speech conversion using Adaptive MultiRate Speech (AMR) Speech Codec RAN 4.75 – 12.2 kbit/s (AMR) CN 64 kbit/s (Integrated Services Digital Network -ISDN)
Interworking Function (IWF): Additional activities of IWF in 3G - Internetworking between Time Division Multiple Access (TDM) to Asynchronous Transfer Mode (ATM) TDM based E1 = Pulse Code Modulation (PCM30) Lu (CS) ATM based
20 2.6.2. Packet Switch (PS) Domain
Packet Switched PS Domain for Non real-time data transfer and Entities common to the CS & PS Domain. Packet Switch domain work with data transmission. Basically there is no difference in 2G GPRS service connectivity and 3G PS Domain. Only thing is that instead of Gb interface between BSC and SGSN, RNC is connected to SGSN via “Iu PS” interface.
UMTS Mobile-services Switching Center (U-MSC) :The UMTS Mobile-services Switching Center controls one or more Radio Network Controllers (RNC) and provides via the Gateway MSC (GMSC) for circuit-switched and via the Gateway GPRS Service Node (GGSN) for packet-switched the connection to other networks. A Visitor Location Register (VLR) is collocated to the 3G-MSC part of U-MSC and a Subscriber Location Register (SLR) is collocated to 3G-SGSN part of UMSC. A U-MSC derives the Home Location Register (HLR)/Authentication Center (AC) from the UMTS mobile subscriber’s identity (IMSI, MSISDN).
GGSN : A GGSN is rather like an IP gateway and border router - it contains a firewall, has methods of allocating IP addresses, and can forward requests for service to corporate Intranets (as in dial-up Internet/Intranet connections today).
SGSN : The SGSN is collecting charging data and transmitting them via Ga interface to the Charging Gateway Function CGF. Additional activities in 3G-
The SGSN pulls the subscriber profiles via Gr interface from the HLR and stores it as long as the subscriber has not been registered in another SGSN. It is transmitting SMS via SMS IWF-/G-MSC (Gd interface) to the SM-SC. The SGSN is connected to the UMTS Terrestrial Radio Access Network (UTRAN) through the Iu interface.
Charging Gateway Function (CGF) : As a centralized separate Network Element, i.e. the Charging Gateway CG. As a distributed functionality resident in the SGSN and GGSN.
21 Chapter - 3 Technology involved in GSM/ GPRS and 3G Network
3.1. Teletalk GSM/3G Area Identities It is categorized by different area such as International area, National area, PLMN Area, MSC area. GSM service area and 3G service area of Teletalk will remain same [1,3]
3.1.1. Teletalk International Area : Roaming Agreements with the Visited Public Land Mobile Network (VPLMN) and his MS supports the corresponding frequency range (GSM900 / GSM1800).
3.1.2. Teletalk National Area : Consist by MCC and CC that described bellow Mobile Country Code (MCC): The MCC consists of 3 digits; it is used e.g. for the International Mobile Subscriber Identity (IMSI), Location Area Identity (LAI )and Cell Global Identity (CGI). Country Code (CC): The CC is the dialing code of the country in which the mobile subscriber is registered. The CC consists of 2 or 3 digits and is used e.g. in the Mobile Subscriber International ISDN number.
3.1.3. Telealk PLMN Area : It consist by MNC, NDC & NCC Mobile Network Code (MNC): The MNC is the mobile specific Public Land Mobile Network (PLMN) identification; it consists of 2 digits. The MNC is used in IMSI, Location Area Identity (LAI) and Cell Global Identity (CGI). National Destination Code (NDC): NDC identify the dialing code of a PLMN; it consists of 3 digits. The NDC is used in Mobile Station international ISDN number (MSISDN). National Destination Code (NCC): It is used as short identity (length: 3 bits) of a particular PLMN in overlapping PLMN areas or in border regions; it is used e.g. in the Base Station Identity Code (BSIC).
3.1.4. Teletalk MSC/VLR service area : An attached mobile subscriber is registered in the VLR, which is associated to his Visited MSC. The MSC/VLR ID. is stored in the HLR to route MTC calls..
22 Location Area Code (LAC): The LAC serves to identify a LA within a GSM-PLMN. The LAC length is 2 bytes. Location Area Identity (LAI) : MCC + MNC + LAC; the LAI serves as an unambiguous international identification of a location area.
3.1.5. BTS Service Area - the Cell : Consist of CI, CGI and BSIC
Cell Identity (CI) : The CI allows identification of a cell within a location area. The CI length is 2 bytes. Cell Global Identity (CGI) : MCC + MNC + LAC + CI = LAI + CI; the CGI represents an international unambiguous identification of a cell. BSIC = NCC + BCC (Base Station Color Code); The BSIC represents a non- unambiguous short identification (NCC: 3 bit; BCC: 3 bit) of a cell. The BSIC is emitted at a regular rate by the BTS. It enables the MS to differentiate between different surrounding cells and to identify the requested cell in a random access.
3.2. Teletalk GSM/3G Subscriber Code Same subscriber code is used in both GSM and 3G network that given bellow-
International Mobile Subscriber Identity (IMSI) : MCC + MNC + MSIN (Mobile Subscriber Identification Number); IMSI length = 3 + 2 + 10 digits. The IMSI is the unique identity of a GSM subscriber. It is used for signaling and normally not known to the subscriber. [1][3]
Mobile Station international ISDN number (MSISDN) : CC + NDC + SN. MSISDN length: 2 / 3 + 3 + max. 7 digits = max. 12 digits. The MSISDN is "the users telephone number". A user has one IMSI but he can have different MSISDN
Temporary Mobile Subscriber Identity (TMSI): The TMSI is generated by the VLR and temporarily allocated to one MS. It is only valid in this MSC/VLR service. When changing to a new MSC area, a new TMSI has to be allocated. The TMSI consists of a TMSI Code TIC with length 4 bytes. Often the TMSI is used together with the LAI.
23 3.3. Teletalk Example Identities and Code
Table 3.1 shows Teletalk Identity and Code.
MCC 470 ------First 3 digits of IMSI
th th MNC 02 ------4 & 5 digits of IMSI 02 – Aktel
LAC 4 digit hexa code ----- 00CB
MSIN 1234567890
CC 880 15 50155097
NDC 880 15 50155097
SN 880 15 50155097
LAC
LAI = MCC+MNC+LAC 470 04 00CB
CI 4 digit hexa code ------01CA
CGI = MCC+MNC+LAC+CI = LAI+CI 470 04 00CB 01CA
BSIC = NCC +BCC
IMSI = MCC + MNC + MSIN 470 + 04 + 1234567890
MSISDN = CC + NDC + SN. MSISDN 880 + 15 + 50155097
24 3.4. Network Security
Triples are the main components of network security that has been shown in Fig. 3.1. Triples are produced in the Authentication Center AC and consist of [1]- . RAND (RANDom number) . SRES (Signed RESponse): the reference value for the authentication . Kc (Cipher Key): key necessary for ciphering (Fig. 3.1)
. Fig. 3.1 Triple Calculation.
3.4.1. Teletalk Security Feature
Ciphering : User information and signaling information are ciphered via air interface Um (Uplink -UL & Downlink - DL). The cipher command is given after transmission of the user identity (TMSI / IMSI) and the authentication procedure
Authentication : The authentication procedure (Fig. 3.2) is or can be initiated by the VLR in the following cases: IMSI Attach Location Registration Location update with VLR change
25 call setup (MOC, MTC) activation of connectionless supplementary services Short Message Service (SMS)
Fig. 3.2 Authentication Procedure
TMSI Allocation : A new TMSI (TMSI re-allocation) can optionally be allocated to the MS after every authentication & cipher start, shows in Fig. 3.3.
Fig. 3.3 TMSI Allocation
26 3.5. Mapping Network Security into 3G
3G Security has been designed based on 2.5G. 3G has additional security feature that described bellow. In addition the key difference from an architectural point between 3G and 2.5G is the air interface. In 3G the mobile handset is going to communicate with Node B instead of the BTS, this is because Node B’s support the higher bandwidth provided by 3G networks. The Node B then communicates to a Radio Network Controller which replaces the BSC of 2G. In 3G there are additional 4 security groups are Network Access Security, Network Domain Security, User Domain Security and Visibility and Configurability of Security
3.5.1. 3G Additional Feature 3G feature has been designed based on 2.5G. 3G has additional feature that described bellow. Data Integrity Check is new security feature in UMTS. Fig. 3.4 shows its functionality.
Fig. 3.4 Data Integrity Check
The signaling data to be protected and the Integrity Key IK are used in the transmitter as input. The result of this calculation is a kind of a check sum of this data. This check sum is appended to the signaling data to be transmitted. Signaling data and appended check sum are send from transmitter to receiver. In the receiver, the signaling data and the IK are again used as input. The newly generated check sum (expected check sum) is compared to the transmitted check sum
If during transmission signaling data are modified or someone tries to simulate the users signaling, the expected check sum and the transmitted check sum
differ and the non-authorized modification becomes visible.
27 3.6. Location Update
IMSI Attach : When Mobile Stations are switched on the MS performs an "IMSI Attach" procedure by sending an LU request.
Normal Location Update : When MS has crossed the boarder between two different Location Areas.
Periodical Location Update : Initiated by a MS at regular intervals. The LUP is not performed during the duration of a connection. In this case, the LUP is performed after call release. Fig. 3.5. shows location update-
Fig. 3.5 Location Update Procedure
GPRS LUP : The network checks for authorization of the user, copies the user profile from HLR database to the SGSN and assign the packet temporary mobile subscriber identity to the user. This procedure is called GPRS attach. The disconnection from the GPRS network is called GPRS detach. Use BSC instead of Radio Network Controller (RNC)
28 3.7. Mapping Location Update into 3G
CS location updates same like GSM because 3G based on GSM. In PS LUP the UE sends a packet-switched attach request for this to the U-MSC which in turn attaches the relevant IMSI in the own database. During the attach procedure the U-MSC sends an update location message to the HLR in order to inform the HLR about the new location of the UE and in order to update the subscriber database. The U-MSC then sends an attach acknowledgment to the UE. No significant difference is observed between 2G and 3G Location Area Update. Fig. 3.6.The PS procedure describes.
Fig. 3.6 Location Update Procedure 3.8. Teletalk Handover
Handover (HO) is a change of the physical channel during a current connection. Intra- Cell Handover, Intra-BSC Handover and Intra-MSC Handover describe bellow.
Intra-Cell Handover: In the case of Intra-Cell Handover, a physical channel within a cell is changed.
Intra-BSC Handover: An Intra-BSC Handover is carried out between two cells of the same BSC. The procedure is decided and performed by the BSC. The MSC is informed only after the handover.
Intra-MSC Handover: An Intra-MSC handover is a handover between two BSC of the same MSC. The MSC decides about this Handover & switches between the two BSC.
29 Inter-MSC Handover: A Inter-MSC Handover include at least two MSC. The MSC has to decide and to switch.
Basic Inter-MSC Handover: If a MS changes for the first time from the area of an MSC (A) to the area of a MSC (B), this is described as Basic Handover. Fig. 3.7 bellow shows handover types-
Fig. 3.7 Handover Types
GPRS Handover : Handover in GPRS is strongly associated to GSM handover. The MS is attached to both GSM and GPRS simultaneously. The MS is attached to both but can operate in only one at a time The MS is attached to GPRS or other GSM services QoS is the main issue in handover of GPRS. HO principles are similar in various types of systems Location and Mobility Management Routing Update is part of GPRS Handover At the Gb interface, simulating mobile equipment performing GPRS handovers within the same or different routing areas, or simulating a SGSN for mobiles changing between different BSS Soft Handover happen between 2.5G to 2.5G
30 3.9. Mapping Teletalk Handover into 3G
At the Iu interface, simulating mobile equipment performing UMTS handovers for circuit or packet switched operation, or simulating a SGSN or 3GMSC for mobiles changing between different RNC. For UMTS the following types of handover are specified:
Softer handover : Softer handovers (Fig. 3.8) are handovers between sector cells in the same Node B. The transmission information received via the antenna of the different sector cells is handled by different RAKE receivers and combined in the Node B itself. Softer handovers are internal Node B affairs.
Fig. 3.8 Softer Handover Soft handover : UE can communicate with two or three Node B during soft handovers. Soft Handover happen between 3G to 3G (Fig. 3.9).
Fig. 3.9 Soft Handover In WCDMA mode due to the fact that all cells use the same frequency. If the mobile station enters the boundary area between two or three cells, the RNC can decide that a connection with two or three BTS is advantageous. The RNC reserves corresponding codes in the different cells for the UE and commands the UE to implement handover to the new BTS. The Node B receives the transmission from the UE dispreads it and forward the information over the Iub interface to the RNC. The RNC combines this information and forwards it via the Iu interface to the Core Network (CN). This procedure is implemented frame for each and every frame.
31 Inter-RNC Soft Handover : In this case, the Node B involved in the soft handover belong to different RNC. The RNC responsible for control of the soft handover is referred to as the serving RNC (SRNC). It combines information received from the different Node B in the direction of the Core Network (CN) or splits the information transmitted in the opposite direction. It also stores information regarding the cells involved in the soft handover (in an active set). Fig. 3.10 illustrates Inter-RNC Soft Handover
Fig. 3.10 Inter RNC Soft Handover
Seamless Transition: Seamless transition will be designed for simultaneous access between 3G to 2G and vice versa. PDP context will be the key factor of 3G. Handover of mobile equipment changing from a 3G cell to a 2G cell connected at the IuCS / A interface or at the IuPS / Gb interface & Handover of mobile equipment changing from a 2G cell to a 3G cell connected at the A / IuCS interface or at the Gb / IuPS interface. Seamless handover allows between GSM/GPRS to WCDMA systems and WCDMA to GSM/GPRS by modifying the proposed messaging structure. This provides a smooth service transition when a mobile station travels from one service area to another service area. During FDD handovers if the frequency of the Core Network is changed. Hard handover can be seamless or non-seamless. Seamless hard handover means that the handover is not perceptible to the user.
32 3.10. GPRS Packet Data Protocol (PDP) context
Enables the use of a packet-based air interface over the existing circuit-switched GSM network, which allows greater efficiency in the radio spectrum because the radio bandwidth is used only when packets are sent or received. Supports enhanced data rates in comparison to the traditional circuit-switched GSM data service. Supports larger message lengths than Short Message Service (SMS)
3.10.1. GPRS Packet Data Routing
GPRS Packet Data Routing is described by Uplink and Downlink. Uplink : Initiated by Mobile Station. Fig. 3.11 shows GPRS uplink procedure.
Fig. 3.11 GPRS Packet data routing procedure in uplink
Down Link: Initiated by GGSN. Fig. 3.12 shows GPRS downlink procedure.
Fig. 3.12 GPRS Packet data routing procedure in downlink
33 3.11. Mapping GPRS PDP Context into 3G A Packet Data Protocol (PDP) context offers a packet data connection over which the UE and the network can exchange IP packets.[2]. Enhanced data rates of approximately 144 kbps for satellite and rural outdoor, 384 kbps for urban outdoor, 2048 kbps for indoor and low range outdoor, Supports connection-oriented Radio Access Bearers with specified QoS and enabling end-to-end QoS
3.11.1. 3G Packet Data Routing 3G Packet Data Routing is described by Uplink and Downlink. Uplink: In Fig. 3.13 MS forwards PDU via the Node B and RNC to the U-MSC. MS forwards PDU via the Node B and RNC to the U-MSC. If a PDP context is activated then the PDU is encapsulated by the GTP layer and forwarded to the GGSN. The
GGSN de-encapsulates the PDU & directs it to the Gi interface of the appropriate ISP/PDN.
Fig. 3.13 Packet Data Routing Downlink: First the PDU is processed by the GGSN. The IP address of the PDU send to the U-MSC.. If the MS is in standby state the U-MSC initiates a paging in order to determine the location of the UE. Upon receipt of the paging request, the UE answers with a service request message. Then the U-MSC knows the exact location of the UE. Finally, the downlink PDU is sent to the UE. Fig. 3.14 shows 3G downlink procedure
Fig. 3.14 Packet data routing procedure in downlink
34 3.12. Mapping GSM Call Handling into 3G
It is 3G call setup procedure. Two types of call setup described here one is MOC (Mobile Originating Call) and another one is MTC (Mobile Terminating call). MOC is initiated by mobile station and in MTC, Mobile station is the called party
Mobile Originated Call (MOC) : Fig. 3.15 shows 3G MOC procedure. The UE sends the call setup to the U-MSC. The U-MSC requests call information from the VLR function of U-MSC via the UMTS mobile subscriber identified with the IMSI. If the U- MSC is equal to a GMSC, the U-MSC sets up the call to the fixed network exchange after allocation of a traffic channel and from there to the called subscriber in the fixed network. If the U-MSC is not equal to a GMSC, the U-MSC sets up the call to the gateway exchange (GMSC) after allocation of a traffic channel, and subsequently to the fixed network exchange and from there to the called subscriber in the fixed network
Fig. 3.15 MOC to a fixed network subscriber in the CS domain of CN
Mobile Terminated Call (MTC): Fig. 3.16 shows 3G MTC procedure. A call for a
UMTS mobile subscriber arrives at the GMSC. With the aid of the dialing information
(MSISDN), the GMSC determines the HLR and sets up a signaling connection to it. The
HLR sends a request to the VLR function in the U-MSC in whose location area the called UMTS mobile subscriber is currently located. The VLR function in the U-MSC sends the required UMTS Mobile subscriber roaming number (MSRN) back to the HLR.
The HLR passes on the LACOD to the GMSC. Based on the MSRN, the GMSC sets up
35 the call to the 3G-MSC within the U-MSC. Since the U-MSC does not know the UMTS mobile subscriber up to this point, the MSC requests from its VLR function in the U-
MSC the UMTS mobile subscriber in-formation for the call setup. The UE is now called by paging at all NodeB/RNC of the location area, since the cell in which the UE is located is not known to the U-MSC. This information is passed to the U-MSC in the response to the paging. Finally, the call to the U-MSC is set up.
Fig. 3.16 MTC
36 Chapter – 4 Radio Access Network
4.1. Radio Interface in Physical Layer
The frequency bandwidth of Teletalk is 5.2MHz in 900 band and 10 MHz in 1800 band. The content of a TS is called “Burst”. The BS and MS must be able to switch the HF power on/off within 0.028 ms over a wide dynamic range. This range is 70 dB for BS and 36 dB for MS. Time Slot duration = 0.577. Duration is divided per definition = 156.25 bit. Individual bit duration = 3692.3 ns. 156.25 bit = 142 bit for the transmission of “Information” + 3 bit as Tail Bits TB + 8.25 bit as Guard Period GP. Fig. 4.1 shows burst content
Fig. 4.1 Burst Content
The Normal Burst NB contains: 2 x 3 bits as Tail Bits TB 2 x 57 bits as Information (User Data / Signaling) 2 x 1 bits as “Stealing Flags” which inform the receiving side if user data or user related signaling is transmitted 26 bits as Training Sequence for time synchronization and transmission quality analysis
37 4.1.1. Framing A physical channel in Radio Interface is defined by a frequency pair for UL/DL and a Time Slot TS called framing.
TDMA frames : Time Division Multiple Access (TDMA) consist by 8 TS. Duration of TS = 0.576875 ms. Duration 1 TDMA Frame = 0.576875 *8 = 4.615 ms. Physical channels are = 8. Fig. 4.2 shows frame attributes-
. Fig. 4.2 Frames User traffic (TCH Multiframe ) = 26 TDMA frames TDMA Frame contain = logical contents Certain content repeated = every 120 ms TCH Multiframe = User speech, fax, data + SACCH (User related control information). They are transmitted every TCH Multiframe Full Rate TCH = Every 120 ms on the 13th TDMA frame Half Rate TCH = the first user of this physical channel on the 13th and the second user on the 26th TDMA f Full Rate TCH = the 26th TDMA frame is empty (Idle I).
38 4.1.2. Time Structure of Radio Interface It is the combination of Bit, TS, Multiframe, Superframe, Hyperframe. Bit: The shortest unit of the GSM radio interface = one bit Its information = GMSK modulated onto the HF Its duration = 1 Brust 1 Brust = 156,25 bit = 57,688 us 1 bit = 57688 / 15625 = 3,6923us = 3692.3 ns Time Slot TS: It is the shortest possible transmission time in GSM One TS = 156.25 bit. Duration = 0.57688 ms.
Multiframes: 1 TCH Multiframes = 26 TDMA frames (Repetition) Duration = 4.615 * 26= 120 ms. Multiframes of signaling = Repetition cycles of 51 TDMA frames Duration = 235.4 ms.
Superframe: 1 Superframe = 51 * 26 TDMA frames = 1326 TDMA frames Duration =51*120 ms = 6120 ms = 6.12 s Hyperframe: 1 Hyperframe = 2048 Superframes Duration = 2048*6.12 = 12,533.76 s = 3 h 28 min 56.76 s long. Timing Advance TA : The Guard Periods GP of the Normal Bursts are not able to compensate signal delays in larger GSM cells. The MS receives synchronization signals from the BS (Fig. 4.3), synchronizes their transmission based on this signals, but it cannot recognize its distance from the BS.
Fig. 4.3 Timing Advance
39 4.2. Mapping Radio Interface Physical Layer into 3G
After migration 3G network will use Frequency Division Duplex (FDD) technique which is combination of chanalization code and scrambling code. FDD frequency method has been used for 3G. Its bandwidth B = 5 MHz (including guard bands) and Chip rate Rc = 3.84 Mchip/s. Fig. 4.4. shows the attributes of FDD.[5]
Fig. 4.4 UTRA conception & harmonization
Modulation method = QPSK Re-use = 1 (i.e., same frequency possible in neighboring cells) Pulse shape Timing structure
Spreading codes: based on OVSF (Orthogonal Variable Spreading Factor) codes WCDMA use as multiplexing. Uses spreading factors of 256 to 4 (UL) or 512 to 4 (DL) Uses seamless & soft handover SF = from 256 – 4 (UL) or from 512 – 4 (DL). This gives rise to symbol rates from 15 ksymb/s (UL) or 7.5 ksymb(s) (DL) to 960 ksymb/s.
4.2.1. Codes Codes are used to generate channels. In 3G network channelization codes and scrambling code is used. Channelization Codes : Channelization codes are used to separate channels from the same source (Fig. 4.5). A symbol of user information is spread by a channelization code sequence with a specified length of chips. Bellow the attributes of Channelization codes.
40 Length - UL:4-256 chips, DL:4-512 chips For DL the separation of different users by the BTS. For UL the channelization means the separation of different applications used simultaneously by the same UE. The channelization codes work as Orthogonal Variable Spreading Factor (OVSF) codes and have orthogonal attributes. The (1x1) start matrix with the value "1" represents the channelization code with SF = 1. A code tree arises in which all codes of a particular length (SF = 1, 2, 4, 8,..., 512) are orthogonal to each other. If we take codes that are 256 long, there are 256 different orthogonal codes for 256 different users / applications for DL, for example (ignoring the codes for signaling), with 15 ksymb/s. In contrast, there are only 4 orthogonal codes of length 4 (SF = 4) with which 960 ksymb/s can be obtained.
Scrambling Codes : Scrambling codes are used to separate different sources. The scrambling codes are assigned to the UE by UTRAN. Fig. 4.5 depicts the functionality of scrambling codes
Fig. 4.5 UMTS Terrestrial Radio Access (UTRA) Code For DL this means the separation of different BTS. Each cell has a scrambling code to allow the UE to distinguish between neighboring cells. For UL the scrambling means the separation of different items of UE in a cell Length (= 38400 chips) are used periodically
41 4.2.2. Timing Structures
It consist of Chip, Frame and Superframe.
Chip : The shortest unit of time used in UMTS Terrestrial Radio Access (UTRA) corresponds. Since a chip rate of 3.84 Mchip/s is used, the duration of a chip is about
260.4 pico seconds (ps).
Frame : In the WCDMA mode, a frame is the shortest possible transmission duration.
Short data packets for setting up a connection, for transmission of SMS messages or packet-switched data packets are at least one frame in duration.
A UTRA frame is defined by the duration of 10 ms.
A frame contains 15 timeslots.
UTRA is a radio access solution allowing data rates that are not only flexible, but
that can also be dynamically adapted.
Superframe : A superframe is the counting period for defining physical channels.
A UTRA superframe is defined as the duration of 72 frames.
Duration = 720 ms.
Since it exactly 6 times longer than a traffic channel (TCH) multiframe in GSM
(= 120 ms), it enables adaptation of the timing patterns between UMTS and
GSM – as is essential for inter-system handover between the two systems.
42 4.3. Radio Interface in Logical Layer
Fig. 4.6 shows Teletalk Chanel Type & Traffic Rate- 115Kbit/s FR TCH GPRS
Data CH 9.6Kbit/s FR TCH
TCH 4.8Kbit/s HR TCH 13 Kbit/s FR Voice Traffic Channel Voice CH 12.2Kbit/s Enhanced FR Traffic Channel
5.6 kbit/s HR Traffic Channel channel FCCH (down) SCH (down) BCH BCCH (down)
RACH (up) CCH CCCH AGCH (down) PCH (down) SDCCH DCCH FACCH SACCH
Fig. 4.6 hannel Type Broadcast Channels (BCH) : BCH are used DL only for MS synchronization & information: FCCH (Frequency Correction Channel): MS frequency synchronization SCH (Synchronization Channel): MS time synchronization BCCH (Broadcast Control Channel) : Contains system & cell parameters, Channel combining, frequency hopping algorithm, cipher mode, cell capabilities: e.g. EFR/FR/HR, GPRS, EDGE) Common Control Channels (CCCH) : Common Control Channels are used unidirectional UL & DL for initial access- PCH (Paging Channel) : Search the MS in the LAI RACH (Random Access Channel): MS request for dedicated signaling resources AGCH (Access Grant Channel): Grant a dedicated channel to the MS
43 Dedicated Control Channels (DCCH) : Dedicated Control Channels are used bi- directional for dedicated signaling - SDCCH (Stand-alone Dedicated Control Channel): Signaling between MS & BS, Call Setup, Authentication, Cipher start, IMEI check, TMSI-Reallocation, LUP procedures SACCH (Slow Associated Control Channel): Together with SDCCH or TCH, DL: Power Control, Timing Advance, Comfort Noise; UL: Measurement Reports for Handover FACCH (Fast Associated Control Channel): allocated instead of TCH in case of enhanced demand for signaling resources (Handover, Call Release, IMSI- Detach, OACSU)
4.4. Mapping Logical Interface Channels into 3G
Transport Channel, Signaling Physical Channel and Physical Channels are used in 3G cellular mobile system are described bellow. WCDMA logical channel has been mapped by transport channel and logical channel
Transport Channel: All transport channels are listed bellow (UL/DL) Dedicated Channel DCH (UL) Random Access Channel RACH Physical random access channel PRACH (DL) Broadcast channel BCH (DL) Forward access channel FACH (DL) Paging channel PCH (DL) Downlink shared channel DSCH
Physical Channel: All Physical channels are listed bellow Dedicated Physical Data Channel Dedicated Physical Control Channel DPCCH Physical random access channel PRACH Primary common control physical channel P-CCPCH Secondary common control physical channel S-CCPCH Synchronization channel SCH Common pilot channel CPICH Acquisition indication channel AICH Paging indication channel PICH CPCH Status indication channel CSICH Collision detection/Channel assignment indicator channel CD/CA-ICH
44 4.4.1. Channel Mapping Logical to Transport Channels
GSM logical Interface will be mapped into WCDMA method. Different Logical Channels can be mapped together into one Transport Channel. The Transport Channels can be sub-divided into two general classes:
Common transport channels: Where there is a need for in-band identification of the User Equipments UE when particular UE is addressed
Dedicated transport channels: Where the UE is identified by the physical channel. i.e. code & frequency of the FDD mode and code.
4.4.2. Channel Mapping Logical to Physical Channels (DL)
In UMTS physical channels are characterized by the code and frequency (UL & DL).
Common Physical Channel: CPICH : Common Pilot Channel is an unmodulated code channel, carrying the Scrambling Code of the cell.
SCH : Synchronization Channel is needed for time synchronization of the UE at cell search.
P-CCPCH : Primary Common Control Physical Channel is carrying the Logical Channel Broadcast Control Channel BCCH, which is mapped to the Transport Channel Broadcast Channel BCH.
S-CCPCH : Secondary Common Control Physical Channel carries two different Common Transport Channel: the Paging Channel PCH and the Forward Access Channel FACH. They can be multiplexed together on one single S-CCPCH or use two / several S-CCPCH PICH : Page Indication Channel can be used in connection with the PCH for efficient sleep mode operation of the UE.
AICH : Acquisition Indication Channel is used in connection with the RACH for random access to prevent collisions.
45 PDSCH : Physical DL Shared Channel is used to carry the transport channel DSCH. The PDSCH is used to transmit dedicated data with high peak rate and low activity cycle on common resources. It is shared by several users based on code multiplexing. The PDSCH is always associated with a DPCH.
Dedicated Physical Channel:
DPCH : Dedicated Physical Channel is used to carry Dedicated or Common Traffic Channel DTCH / CTCH data and Dedicated Control Channel DCCH data to maintain the connection. CTCH / DTCH and DCCH information are time-multiplexed in the DPCH. Fig. 4.7 shows down link mode.
Fig. 4.7 Downlink Mode
46 4.4.3. Channel Mapping Logical to Physical Channels (UL) Common Physical Channel: PRACH : Physical Random Access Channel is used to carry the RACH data, i.e. for initial network access and transmission of small user data packets on common resources. PCPCH : Physical Common Packet Channel is used to carry the CPCH data, i.e. it is used to transmit small and medium size data packets on common resources.
Dedicated Physical Channel: Different to the WCDMA mode DL transmission, the Dedicated Traffic (DTCH) and Dedicated Control (DCCH) information of the DCH are not time-multiplexed at UL transmission. They are code-multiplexed onto different physical cannel:
DPCCH : Dedicated Physical Control Channel carries the UL Dedicated Control Channel DCCH physical layer control information to maintain the connection.
DPDCH : Dedicated Physical Data Channel carries the UL Dedicated Traffic Channel DTCH, i.e. user data and higher layer signaling. Fig. 4.8 shows down link mode.
Fig. 4.8 Uplink Mode
47 Chapter - 5
Signaling & NSS Dimensioning
5.1. GSM Signaling of Teletalk
In Teletalk the Signaling System #7 (SS7) is used in PLMN for signaling between NSS entities and also for signaling between the NSS and the BSS entities. Fig. 5.1 shows GSM signaling interface.
CC – Call Control SS –Supplementary Services ISUP – ISDN User Part L1 – Layer 1 L2 – Layer 2 L3 – Layer 3 SCCP – Signaling Connection Control Part MTP – Message Transfer Part RR – Radio Resource MM – Mobility Management MAP - Mobile Application Part LAPDM - Link Access Protocol on the Dm channel
Fig. 5.1 GSM Signaling
48 5.1.1. Radio Interface Signaling
Radio interface signaling is combination of Layer 1 + Layer 2 + Layer 3
Layer 1: Physical and electrical attributes. Pulse Code Modulation (PCM30) -is total of 30 digital user values can be transmitted in the time frame of the sampling period of an analogue value. Fig. 5.2 shows PCM30 architecture-
Fig. 5.2 PCM30 Bearer PCM30 frame = 32 time multiplexed time slots. Individual timeslot = 8 bit Individual E1 Frame = 8*32 = 256 bit Superframe = 256*16 = 4096 bit CRC checking = 4 bits Teletalk use = A law PCM30 line (Total bit rate = 2048 kbit/s Time slot 0 = Frame Synchronization Time slots 1-15 and 17-31 = voice calls or data Time slot 16 = signaling channel for CAS
49 Layer 2 : Fig. 5.3 show Layer 2 GSM interface protocol. Function of LAPD and CCSS7 has show with this diagram.
Fig. 5.3 GSM Interface Protocol
Layer 3: Layer 3 is the combination of CM + MM + RR
5.1.2. User Part Signaling
User part signaling is the combination of Signaling Connection Control Part (SCCP), Transaction Capability Part (TCAP) and ISDN User Part (ISUP). All signaling part are described bellow.
Signaling Connection Control Part (SCCP): SCCP forms the Network Service Part (NSP)
Transaction Capability Part (TCAP) :Transaction Capability Application Part provides Independent message flows
ISDN User Part (ISUP) : ISDN User Part is used in GSM for signaling between the PLMN and ISDN
50 5.1.3. Mobile Application Part (MAP)
Use for the NSS signaling among the network nodes HLR, EIR, VLR and MSC. Update Location Area. Update Location, Cancel Location, IMSI Attach / Detach, MSC-MSC Handover, Check IMEI, Authentication, Set Ciphering Mode, Provide IMSI, Forward new TMSI,
5.2. Mapping GSM Signaling into 3G
3G Signaling is constructing by Data transport protocol in the Core Network, Control signaling protocol in the Core Network, Transport signaling protocol in the Core Network and Data transport and signaling protocol in the Radio Network System. Fig. 5.4 shows 3G Protocol Stacks -
Fig. 5.4 3G Interface protocol stack
51 5.2.1. Data Transport Protocol in the Core Network
IT use in Circuit Switch Domain and Packet Switch Domain. Circuit-Switched Domain consists by AAL2, ATM and SDH/PDH. AAL2 uses an ATM connection, then called “AAL2 path. AAL2 connections for users are multiplexed. AAL2 path may be either a virtual channel or a virtual path
Packet-Switched Domain : The job of the packet switch is to deliver IP packets where they are supposed to go. Fig. 5.4 shows the packet handling
Fig. 5.5 protocol stacks for packet handling
Internet Protocol (IP) : The Internet layer describes an official packet format and protocol called IP.
User Datagram Protocol (UDP) : User datagram protocol (UDP) carries PDU for protocols that do not need a reliable data link (e.g. IP). UDP provides protection against corrupted PDU.
GPRS tunnel protocol -user plane (GTP-U) :The GTP-U is used for transport data between U-MSC (3G-SGSN) and RNC. The GTP-U layer supports transport of data packets of different users (multiplexing) via the Iu interface on a common link resource (ATM connection). The encapsulation by the GTP-U supports the transport of different packet data protocols with private or public addressing.
IP to UDP : The layers IP and UDP are the same as described in the above described
Iu protocol stack in this section.
52 GTP : The GPRS tunnel protocol (GTP) layer supports transport of data packets of different users (multiplexing) via the Gn interface on a common link resource (e.g. ATM connection). The encapsulation by the GTP supports the transport of different pack-et data protocols with private or public addressing.
Medium Access Control (MAC) : In the layer 2 the media access control (MAC) protocol is used which works with CSMA/CD methods.
5.2.2. Control Signaling Protocols in the Core Network
Asynchronous Transfer Mode (ATM) : Functions of ATM- Cell structure and encoding, Cell multiplexing and relaying, Cell header generation/extraction, Generic flow control, Traffic control and congestion control.
ATM Adaptation Layer (AAL5) : AAL5 can be used for the data services and the (control) signaling part.
SAAL : The SAAL in combination with AAL5 performs the reliability functions of the signaling protocol.
MTP3-B : The Message Transfer Part 3 -B (MTP3-B) defines the protocols for the reliable trans-mission of messages between the “broad band” PLMN control signaling nodes.
SCCP-CO : The last variant “connection-oriented” is used in the Iu interface stack.
Radio Access Network Application Part (RANAP): The RANAP uses the MTP and the SCCP to support communication between the U-MSC and the RNS.
53 SS7 in UMTS : Table 5.1 shows SS7 in the UMTS PLMN with the SS7 signaling components used.
Table 5.1 - SS7 components on the signaling routes
Signaling link Signaling components GMSC – ISDN/PSTN (/PSDN) SS7: MTP3, SCCP, ISUP GMSC – HLR/AC SS7: MTP3, SCCP, TCAP, MAP GMSC – U-MSC (3G-MSC/VLR) SS7: MTP3, SCCP, ISUP U-MSC (3G-MSC/VLR) – HLR/AC; U-MSC (3G-SGSN) SS7: MTP3, SCCP, TCAP, MAP – HLR/AC U-MSC (3G-MSC/VLR) – U-MSC (3G-MSC/VLR) SS7: MTP3, SCCP, TCAP, MAP MTP3, SCCP, ISUP M-SSP – SCP SS7: MTP3, SCCP, TCAP, CAP HLR – SCP SS7: MTP3, SCCP, TCAP, MAP v3
5.2.3. Transport signaling protocol in the Core Network AAL2L3 Signaling : For the AAL2, bearers of different calls are multiplexed in one ATM connection. For the call handling (setup, release) of each AAL2 connection the AAL2L3 will be used. Thus the signaling protocol for AAL2 connections is AAL2L3.
5.2.4. Data Transport & Signaling Protocols in Radio Network System
5.2.4.1. Layer 1 : Its activities are Carrier frequency, Modulation & transmitter / receiver
5.2.4.2. Layer 2 : The layer 2 consists of the sub-layer ATM (transport layer) which defines procedures of establishing physical connections between NodeB and RNC and the sub-layer AAL2 (radio network layer) which defines procedures related to the operation of NodeB. Other function of layer2 has been described bellow-
MAC: It is responsible for the physical allocation of a packet data channel. Furthermore the MAC provides data transfer services on logical channels Radio Link Control (RLC) : The radio link control (RLC) protocol which provides an reliable link over the radio interface that fits the block structure of the physical channel. BMC : The following sub-layer the broadcast/multicast (BMC) transmission service provides services for broadcast message handling.
PDCP: It provides mapping of network PDU from one network protocol to one RLC entity.
54 5.3. Dimensioning Signaling Interface
SS7 Signaling load per subscriber 600 byte (Standard Profile). SS7 Signaling load per subscriber1100 byte (High mobility Profile). Total Subscriber at a time = 20475.
Signaling load for the BSC of Gulshan branch calculated bellow-
Number of subscriber = Traffic Capacity / Traffic per subscriber
= 409.5 Erlang / (0.02 Erlang / subscriber)
= 20475 subscribers
Total Signaling load = Number of subscriber * Signaling load per subscriber
= 20475 * 600 byte / 3600 sec = 3412 kbyte/sec
Or
= 20475 * 1100 byte / 3600 sec = 6256 kbyte/sec
55 Chapter - 6
Network Planning
6.1. Teletalk GSM Radio for Frequency Planning
Teletalk’s GSM radio frequency planning has been divided as FDMA Planning and TDMA Planning. TDMA Planning in GSM is similar for all GSM operators and defined by standard GSM protocol. FDMA planning is also defined as 200 KHz per cell. Only thing varies is the frequency range of different operators. Teletalk at the moment is operating in dual frequency range that is it is operating in both 900MHz and 1800MHz band.
Frequency Division Multiple Accesses (FDMA) in Teletalk: (FDMA) Frequency Division Multiple access of total 26 channels in 900MHz. 200KHz is considered as Guard Band. The rest 25 channel is used for cell design. Figure 6.1 shows the attributes of FDMA.
Fig. 6.1 Frequency Distribution in Teletalk The following parameter can be considered – DL = higher frequency and UL = lower frequency One frequency band = 200 KHz Total channel pair lower frequency = 26 in 900M + 50 in 1800M Total channel pair upper frequency in 1800MHz = 50
Duplex distance lower frequency in 900MHz = 45 MHz
Duplex distance upper frequency in 1800MHz = 95 MHz
56 Time Division Multiple access (TDMA): (TDMA) Time Division Multiple access. One 200 kHz frequency bands. Total 8 time Slots TS. 8 time Slots TS equal 8 different physical channel full rates & 8 time slots TS equal 16 different physical channel half rate. Time Division Multiple Access in Teletalk follows normal GSM standard: TDMA frame duration = 4.615 ms, One TS duration = 0.577 ms. Total channel 50+26 = 76 Total Slot according to TDMA 76*8 = 608 Full Rate Total Slot according to TDMA 76*16 = 1216 Half Rate
The table 6.1 shows Teletalk frequency allocation for 900 and 1800 bands-
Table 6.1 – Frequency for Teletalk Type Transmit (MHz) Receive (MHz) Total (MHz) GSM - 900 890 – 895.2 935.0 – 940.2 5.2 GSM - 1800 1710-1720 1805-1815 10
GSM 900 : BTS receiver (uplink): fu(n) =890.2+ (n-1)*0.2 MHz BTS transmitter (downlink): fd (n) =fu (n) +45 MHz
Here n = ARFCN = Absoluter Radio Freq. Ch. no As for example for an ARFCN of 5 the respective uplink and downlink frequencies can be calculated as follows:
Teletalk uplink fu (n) = 890.2+(5-1)*0.2 MHz = 890.2+4*0.2 MHz = 890.2 + 0.8 MHz = 891 MHz Teletalk downlink fd(n) = fu (n) + 45 MHz = 891 + 45 MHz = 936 MHz
GSM 1800 : BTS receiver (uplink ): fu (n) =1710.2 + (n-512) * 0.2 MHz BTS transmitter (downlink): fd (n) =fu (n) +95 MHz
For an ARFCN of 556 the respective uplink and downlink frequencies can be calculated as follows:
Teletalk uplink fu(n) = 1710.2+ (n-512) * 0.2 MHz = 1710.2 +(556-512) * 0.2 MHz = 1710.2 + 44*0.2 MHz = 1710.2 + 8.8 MHz = 1719 MHz Teletalk downlink fd(n) = fu(n) + 45 MHz = 1719 + 45 MHz = 1764 MHz Frequency Reuse: Teletalk normally use 4*3 reuse patterns for both 900 MHz & 1800 MHz frequency band. Teletalk use tri sector antenna with 120 degree coverage/sector.
57 6.2. Mapping Radio Frequency Planning into 3G
Studying the reference in BTRC website of National_Frequency_Allocation_Plan v3.1 it is found that 2.1 GHz frequency band has been planned for 3G Cellular Mobile System in Bangladesh. Although BTRC is yet to award any 3G license as of now, but it can be taken for granted that Teletalk, having the privilege of being the only government operator in Bangladesh, is going to get the License in any case. Assuming Teletalk will be assigned the first band of 5MHz, which is the minimum amount of frequency that can be allocated as per 3G standard Teletalk’s allocated band for transmit and receive is shown in table 6.2.
Table 6.2 –3G Frequency band for Teletalk
Type Transmit (MHz) Receive (MHz) Total (MHz) UMTS 1975 – 1980 2165 – 2170 5
Figure 6.2 shows the attributes of 3G. 1 up-link carrier for transmission from the UMTS- MS to the RNC and 1 downlink carrier for transmission from the RNC to the UMTS-MS..
Fig. 6.2 UMTS Frequency of Teletalk
The following parameter can be considered – DL = higher frequency and UL = lower frequency Total channel pair of UMTS frequency = 1 Duplex distance in 1800 MHz band frequency = 190 MHz
58 RNC receivers (uplink) = fup(n) = (1975 + 5 x n) MHz Here n = UARFCN = UTRA Absoluter Radio Freq. Ch. No UARFCN 1 <= n <= 1
RNC transmitters (downlink)= fdown (n) = fup (n) + 190 MHz Radio frequency carrier spacing = 5 MHz
3G frequency Uplink and Downlink:
RNC receivers (uplink) fup(n) = (1975 + 5 x n) MHz = 1975 = 5*1 MHz = 1975 = 5 MHz = 1980 MHz
RNC transmitters (downlink) fdown (n) = fup (n) + 190 MHz
= fup (n) + 190 MHz = 1980 +190 = 2170 MHz
59 6.3. GSM Capacity & Coverage Planning while migrating into 3G
In this case study it is suggested to introduce 3G on an island basis and then expand it with demand from the customer side and availability of fund from the government. As a pilot project, in this study a sample calculation has been made considering only the Gulshan and Banani area being migrated to 3G. According to TRX calculation, 1 TRX = combined BCCH and SDCH that makes 7 TCH channels. 2 TRX = 1 BCCH and 1 SDCH that makes 14 traffic channels (TCH). 3 TRX = 1 BCCH and 2 SDCH that makes 21 traffic channels (TCH). Erlang value has been taken from Erlang Table according to GOS = 0.020. Table 6.3 shows existing BSS configuration [Appendix 5]
Table 6.3 Teletalk Existing BTS configuration.
GSM+ Traffic Traffic Total Configuration WCDMA Channels Erlang Erlang SL. BTS Name (900+1800) /Sector 1 Gulshan 2/ S House 2/2/2+1/1/1 14*3+7*3 8.20*3+2.93*3 24.6E+8.79E 33.39E 2 Gulshan BTTB 2/2/2+2/2/2 14*3+14*3 8.20*3+8.20*3 24.6E+24.6E 49.2E 3 Gulshan Rd 35 2/2/2+1/1/1 14*3+7*3 8.20*3+2.93*3 24.6E+8.79E 33.39E 4 Gulshan Road 55 2/2/2 14*3 8.20*3 24.6E 24.6E 5 Gulshan Road 107 1/1/1+3/3/3 7*3+21*3 2.93*3+14.03*3 8.79E+42.09E 50.88E 6 Gulshan Rd 116 2/2/2+1/1/1 14*3+7*3 8.20*3+2.93*3 24.6E+8.79E 33.39E 7 Kakoli 2/2/2+2/2/2 14*3+14*3 8.20*3+8.20*3 24.6E+24.6E 49.2E 8 Teletalk (Banani) 2/2/2 14*3 8.20*3 24.6E 24.6E 9 Banani Rd 5 2/2/2+1/1/1 14*3+7*3 8.20*3+2.93*3 24.6E+8.79E 33.39E 10 Banani Rd 18 2/2/2+1/1/1 14*3+7*3 8.20*3+2.93*3 24.6E+8.79E 33.39E 11 Banani Rd 19/A 2/2/2+2/2/2 14*3+14*3 8.20*3+8.20*3 24.6E+24.6E 49.2E 12 DOHS Baridhara 2/2/2 14*3 8.20*3 24.6E 24.6E 13 Baridhara Rd 2D 1/1/1 7*3 2.93*3 8.79E 8.79E 14 Baridhara Rd 13 2/2/2 14*3 8.20*3 24.6E 24.6E 15 Karail 2/2/2 14*3 8.20*3 24.6E 24.6E 882 Traffic 497.22E 15 BTS 126 TRX Channels
The following parameter can be considered – GoS = 0.020 No of BTS = 15 Cell = 72 Total Erlang = 497.22E TRX = 126 Traffic Channels = 882 Total subscriber that can be catered considering 20 mErlang/subscriber during Busy Hour = 497.22 / 0.020 = 24861 subscribers
60 6.4. Mapping GSM Capacity and Coverage into 3G
The planned network has been designed with both GSM and WCDMA technology working simultaneously. GSM band is applicable for GSM BTS and WCDMA band is applicable for 3G NodeB. Existing GSM supported BTS will remain same. Grade of service (GOS) of 0.020 for GSM and 0.015 for 3G has been calculated. After analysis it is found that 20 BTS will be required instead of 15 BTS [6]. In 3G there are 36 channels per cell and 108 channels per site has been considered. Below BTS/ NodeB configuration has been shown both for GSM and WCDMA system that is generic configuration. The configuration may change according to drive test and subscriber density. Table 6.4 shows proposed BSS configuration. Table 6.4 – Teletalk Migrated BTS configuration.
TRX Traffic Erlang Erlang BTS+ Configuration Channels 900M+1800M+ 900M+1800M+ NodeB 900M+1800+ 900M+1800M+ WCDMA WCDMA SL Area WCDMA WCDMA 1 Gulshan 1/1/1 +1/1/1 +1/1/1 7*3+7*3 +36*3 2.93*3+2.93*3+ 26.43*3 8.79E +8.79E + 79.29E 2 Gulshan 2/2/2+ 1/1/1 +1/1/1 14*3+7*3+36*3 8.20*3+ 2.93*3+26.43*3 24.6E +8.79E + 79.29E 3 Gulshan 1/1/1 +1/1/1 +1/1/1 7*3+7*3 +36*3 2.93*3+2.93*3+ 26.43*3 8.79E + 8.79E +79.29E 4 Gulshan 2/2/2 +1/1/1 +1/1/1 14*3+7*3+36*3 8.20*3+ 2.93*3+26.43*3 24.6E +8.79E + 79.29E 5 Gulshan 1/1/1 +1/1/1 +1/1/1 7*3+7*3 +36*3 2.93*3+ 2.93*3+26.43*3 8.79E +8.79E + 79.29E 6 Gulshan 2/2/2 +1/1/1 +1/1/1 14*3+7*3+36*3 8.20*3+2.93*3+ 26.43*3 24.6E + 8.79E +79.29E 7 Gulshan 1/1/1 +1/1/1 +1/1/1 7*3+7*3 +36*3 2.93*3+2.93*3+ 26.43*3 8.79E +8.79E +79.29E 8 Gulshan 1/1/1 +1/1/1 +1/1/1 7*3+7*3 +36*3 2.93*3+ 2.93*3+26.43*3 8.79E +8.79E +79.29E 9 Bonani 2/2/2 +1/1/1 +1/1/1 14*3+7*3+36*3 8.20*3+ 2.93*3+26.43*3 24.6E + 8.79E +79.29E 10 Bonani 1/1/1 +1/1/1 +1/1/1 7*3+7*3 +36*3 2.93*3 +2.93*3+26.43*3 8.79E +8.79E + 79.29E 11 Bonani 2/2/2 +1/1/1 +1/1/1 14*3+7*3 +36*3 8.20*3 +2.93*3+26.43*3 24.6E +8.79E + 79.29E 12 Bonani 1/1/1 +1/1/1 +1/1/1 7*3+7*3 +36*3 2.93*3 +2.93*3+26.43*3 8.79E +8.79E + 79.29E
13 Bonani 2/2/2 +1/1/1 +1/1/1 14*3+7*3 +36*3 8.20*3 +2.93*3+26.43*3 24.6E +8.79E + 79.29E 14 Bonani 1/1/1 +1/1/1 +1/1/1 7*3+7*3 +36*3 2.93*3 +2.93*3+26.43*3 8.79E +8.79E +79.29E 15 Bonani 1/1/1 +1/1/1 7*3 +36*3 2.93*3 +26.43*3 8.79E + 79.29E 16 Baridhara 2/2/2 +1/1/1 14*3 +36*3 8.20*3 +26.43*3 24.6E + 79.29E 17 Baridhara 1/1/1 +1/1/1 7*3 +36*3 2.93*3 +26.43*3 8.79E + 79.29E 18 Baridhara 1/1/1 +1/1/1 7*3 +36*3 2.93*3 +26.43*3 8.79E + 79.29E 19 Baridhara 1/1/1 +1/1/1 7*3 +36*3 2.93*3 +26.43*3 8.79E + 79.29E 20 Baridhara 1/1/1 +1/1/1 7*3 +36*3 2.93*3 +26.43*3 8.79E + 79.29E 20 Site 102+60 Cell 861+2160 409.5 E +1585.8 E 123+60 TRX Channels = 1995.3E Traffic E = Erlang, M = MHz
The following parameter can be considered –
GOS = 0.020 for GSM and 0.015 for 3G
61 Total TRX GSM 123 + WCDMA 60 = 183 TRX Total BTS = GSM BTS 20 + 3G NodeB 20 = 40 Total Cell = GSM 102+ 3G 60 = 162 Total Erlang = 409.5+1585.8 E = 1995.3E Subscriber at a time in GSM = 409.5 / 0.020 = 20475 subscribers. Subscriber at a time in 3G 1585.8/0.015 = 105720 subscribers Total subscribers in dual network 20475 + 105720 = 126195 subscribers
Formula for 3G Traffic channel -
Maximum number of simultaneous users
… formula -1
6.4.1. Dimensioning Television (TV) Subscriber in 3G By setting program 50% of total 3G subscribers are active TV users and others 50% of total 3G subscribers are active voice and data users. Bandwidth = 5 Mhz. 5 MHz = 500000 bps = 5000 Kbps = 5 Mpps Data transmission rate in 3G Technology 5 MHz carrier = 10Mbps (QPSK Modulation Technique) Using H.264/2.645 codec 1 TV subscriber = 256 Kbps So in peak hour 10000 / 256 = 40 TV subscriber but according to 50% of all customers considering voice/data subscribers (20 users/cell) are subscribed to Mobile TV In peak hour = 35 voice/data subscribers (according to formula -1) but according to 50% of all customers (18 users/cell) are subscribed as voice/data subscribers
62 6.5. Additional Cost for Migration in 3G In 3G additional costs has been calculated for Softswitch, HLR, IN, SMSC, MGW, GPRS, Multiplexer (Mux), RNC, NodeB, 3G TRX & Infrastructure for NodeB. Table 6.6 shows 3G total network cost mentioning total number of required equipment, capacity per equipment, equipment cost per subscriber & equipment cost per system. [Appendix 3] Table 6.6 3G Network Cost
Required Capacity of Equipment or Total Cost Additional Equipment Equipment equipment subscriber cost In Taka Cost in 3G 1Soft Soft switch Switch 50,00,000 s 105 Tk /s 105720*105 11100600 Tk. MGW 1 MGW 25,00,000 s 105 Tk /s 105720*105 11100600 Tk. 3G TRX 60 TRX Configuration 4,76,000 /TRX 60*476000 28560000 Tk. RNC 1 RNC 5,00,000 s 40 Tk/s 105720*40 4228800 Tk. NodeB 20 NodeB Configuration 20,00,000/NodeB 20*2000000 40000000 Tk. Infrastructure 20 NodeB Tower, Room 10,00,000/Tower 20*1000000 20000000 Tk. IN 1 IN 1ms 70 Tk/s 105720*70 7400400 Tk. SMSC 100 SMS 500s/SMSC 35Tk/s 105720*35 3700200 Tk. Power 20 NodeB Battery 10,00,000Tk /Sys 20*1000000 20000000 Tk. Transmission 20 Mux NodeB 2,80,000Tk/link 20*280000 5600000 Tk. Transmission 1 Mux RNC 10,50,000Tk/link 1050000 1050000 Tk. HLR 1 HLR 20,00,000 s 21Tk /s 21*105720 2220120 Tk. GPRS 0.000005K/s 0.53 /105720s 17.5 Tk /s 105720*17.5 1850100 Tk. 156810820 Tk.
Tk. = Taka, S = Subscriber, TRX = Transceivers, Mux = Multiplexer, ms = Million Subscriber
6.6. Pay back period
Pay back period is the length of time required to recover the cost of an investment calculated as Investment/Annual cash flow. In 3G revenue has been 0.5 Taka per Erlang. As a result 3G need 11 months for returning the investment based on only equipment cost where no administrative and others cost is calculated here.
Investment cost =156810820Taka. Erlang = 1585.8 E Revenue / Minute (Busy Hour) = 1585.8 Taka (Without tariff as 0.5 Taka / Minute) Revenue / Hour (Busy Hour) = 792*60 = 47550 Taka. Revenue / Day = 47550/0.1 = 475500 Taka. Total Revenue/ Month = 475500*30 = 14265000 Taka. Payback Period = Investment/monthly income =156810820 /14265000 = 11 Months (Equipment Cost)
63 Recommendation
From this study it is clearly understood that UMTS services is very much cost-effective from Teletalk’s perspective. It is to be mentioned that cost-justification is shown here using a pilot project. With increasing capacity the cost will come down further. Only thing that is to be assured the demand for such services are there and subscribers are capable of availing them. Moreover, it will give Teletalk some competitive advantage over other operators. At the same time, it will also be able to satisfy customers’ demand which should be any operator’s prime goal.
Considering all these issues the following recommendations can be made: . Teletalk should immediately start preparing a business plan regarding 3G. . The strategies should be clear and specific. It’s better to start 3G services on an island basis which should be expanded through-out the country in phases depending on the customer demand and capacity of the customer to avail this service
64 Reference
1. GSM Technology – GSM, Pocket Guide, Vol. 2, By Wandel & Golterman, Publisher Wandel & Goltermann GmbH & Co, Elektronische Meûtechnik,P. O. Box 12 62, D-72795 Eningen u.A, Germany
2. PDP Context - Siemens System Description UMTS – Network System Concept - A50016-D1701-V10-2-7618
3. GPRS - GPRS (Mobile Telematics), By Ivar Jørstad, 2002
4. 3G – Technology, UMTS Introduction, TM2201EU04TM_0002, AL: 5A001b1 EC:N, Siemens AG 2002
5. 3G Access Network – UMTS, Mobile Communication for future, By Flavio Muratore, John Wiley & Sons Ltd, Baffins Lane, Chichester, West Sussex P019 1UD, England, 2001
6. 3G Planning – Siemens System Description UMTS – Network System Concept - A50016-D1701-V10-2-7618
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