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ABSTRACTThis report is based on the study of wireless communication.Wireless communication provides mobility. TDMA, FDMA, ...
Chapter 1                                                          INTRODUCTIONWhy Wireless Communication?The popularity o...
1.1 HISTORY OF WIRELESS COMMUNICATIONThe origin of mobile communication followed quickly behind the invention of radio in ...
TDMA builds on FDMA by dividing conversations by frequency and time. Since digital compression allows voice to be sent at ...
Chapter 2                                                    GSM NETWORK CONCEPTThe Global System for Mobile Communication...
Extended GSM (EGSM)EGSM has 10MHz of bandwidth on both transmit and receive.Receive bandwidth is from 880 MHz to 890 MHz.T...
2.1 Channel ConceptFigure 2.2 Channel Concept                             7
2.1.1 Signaling ChannelThese are the main types of signaling Channels:Broadcast Channels (BCH) - Transmitted by the BTS to...
Dedicated Control Channel (DCCH)       Standalone Dedicated Control Channel (SDCCH)       Fast Associated Control Channel ...
There are two basic types of Encoded Speech channelEncoded Speech - Encoded speech is voice audio that is converted into d...
Figure 2.5: Half Rate Traffic Channel (TCH/HS)2.2 Frequency HoppingThere are two types of frequency hopping method availab...
GSM ARCHITECTURE2.3 Base Station Subsystem (BSS)To understand the paging process, we must analyse the functions of the BSS...
Figure 2.7: GSM ArchitectureThe Base Transceiver Station (BTS) is a network element maintaining the Air interface. It take...
BSC                                                           TC               BTS                              BSC       ...
BTS and TC ControlInside the BSS, all the BTSs and TCs are connected to the BSC(s). The BSC maintains the BTSs. In other w...
A Base Station Subsystem is controlled by an MSC. Typically, one MSC contains several BSSs. A BSS itself may cover aconsid...
Chapter 3                                                                     Call Setup3.1 A Mobile Terminated Call and P...
L o ca tio n A re a                                                                        P a g in g                P a g...
7. MSC/VLR sends MSRN to HLR and the HLR forwards the MSRN to the GMSC.   8. The GMSC identifies the serving MSC/VLR as th...
3.2 Location UpdateTypes of Location UpdateIn practice, there are three types of location updates:1. Location Registration...
MSC                                           VLR                                                                        L...
MS                 BSS                       M SC   VLR new          V L R o ld               HLR                   1 . c ...
1. Handover due to measurements occurs when the quality or the strength of the radio signal falls below certain parameters...
Air                                             A                                              BSC                 TC     ...
A ir                                     A                          BTS             B SC         TC                     BT...
N ew C ell / B T S                             A ir                                          A                            ...
It is important to notice, however, that the target MSC and the source MSC are two telephone exchanges. The call can be tr...
This information allows the serving MSC/VLR to connect the target MSC/VLR. When the two MSCs are connected, the call istra...
Chapter 4                                                           RF PLANNING4.1 ObjectiveThe overall objectives of any ...
4.2 RF DesignThe RF design engineer for that particular region would then decide the type of antenna to be used, the anten...
The Cell Planning Process      System Growth             Traffic Analysis       System Tuning           Nominal Cell Plan ...
Cell planning begins with traffic and coverage analysis. The analysis should produce information about the geographical ar...
It can be calculated with the following formula:A = n x T / 3600 ErlangWhere,A = offered traffic from one or more users in...
4.3 RF Drive TestEvery good RF design, after its implantation should be evaluated. There are few ways to do this, for exam...
Figure 4.1 : Drive Test SetupTypes of Drive TestThe main types of Drive Test are :       Performance Analysis       Integr...
Benchmarking               36
Figure 4.2 : Drive Test Result                                 37
Chapter 5                                                    TRANSMISSION AND PLANNING5.1 Introduction    The propagation ...
AbsorptionLine Of SightThe earth atmosphere influences the propagation of radion waves in different ways.The radio waves t...
The First Fresnel ZoneThe radio optical Earth radius can be described using the effective Earth radius factor.ClearanceEve...
Figure:5.2:The first Fresnel zone5.3 Path ProfilesThe purpose of the path profile is to provide information concerning fre...
5.4 Path and Site SurveyDuring the planning microwave radio link paths it is often necessary to closely survey the intende...
The possibilities to install antenna feeders or multi-conductors cables between indoor and outdoor equipment regardingavai...
REFERENCE       Study training material at Vodafone,Ranchi       www.google.com                                           ...
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wireless communication

  1. 1. ABSTRACTThis report is based on the study of wireless communication.Wireless communication provides mobility. TDMA, FDMA, CDMA are the various multiple access techniques. There are severalnetwork generations which evolved during the years.The development of GSM started in 1982, when the Conference of European Posts and Telegraphs (CEPT) formed a study groupcalled Groupe Spécial Mobile (the initial meaning of GSM). The group was to study and develop a pan-European public cellularsystem in the 900 MHz range, using spectrum that had been previously allocated.GSM, the Global System for Mobile communications, is a digital cellular communications system which has rapidly gainedacceptance and market share worldwide, although it was initially developed in a European context. In addition to digital transmission,GSM incorporates many advanced services and features, including ISDN compatibility and worldwide roaming in other GSMnetworks. The advanced services and architecture of GSM have made it a model for future third-generation cellular systems, such asUMTS.The objective to develop this 2G standard is to resolve the roaming problem in the six existing different 1G analog cellular systems inEurope. The global system for mobile communications (GSM) is a set of recommendations and specifications for a digital cellulartelephone network. These recommendations ensure the compatibility of equipment from different GSM manufacturers, andinterconnectivity between different administrations, including operations across international boundaries.In 1982, frequency bands of890-915 MHz and 935-960 MHz were allocated for Pan European Public land Mobile Network (PLMN), and GSM was formed. 1
  2. 2. Chapter 1 INTRODUCTIONWhy Wireless Communication?The popularity of wireless communication is due to the fact that it provides mobility. Mobility can be of two types:-  User Mobility: In this the user is mobile but not the devices. This means that user is not accessing the same telecommunication service all the time in motion. Example, a user is accessing the internet using his same account from different locations.  Device portability: In this the device moves. This means that user is accessing the telecommunication services all the time in motion. Example, a mobile phone system.All the communication devices exhibit one of the following: Fixed and wired: Device is fixed and communication medium is wired. Example, typical desktop computer. Fixed and wireless: Device is fixed but communication medium is wireless. Example, desktop computers with wireless connections. Mobile and wired: Device is mobile but communication medium is wired. Example, laptops. Mobile and wireless: Device is mobile and communication medium is wireless. Example, mobile phone systems. 2
  3. 3. 1.1 HISTORY OF WIRELESS COMMUNICATIONThe origin of mobile communication followed quickly behind the invention of radio in the late 1880s. The first application of mobileradio was related to the navigation and safety of ships at sea. As radio concepts developed so did its use as a communication tool.Frequency Division Multiple AccessEach Frequency Division Multiple Access (FDMA) subscriber is using the same medium (air) for communicating but they are assigned a specificfrequency channel. While they are using the frequency channel, no one else in that cell or neighboring cell can use the frequency channel. Incurrent analog cell systems, each channel is 30 kHz. When a FDMA cell phone establishes a call, it reserves the frequency channel for the entireduration of the call. The voice data is modulated into this channel’s frequency band (using frequency modulation) and sent over the airwaves. Atthe receiver, the information is recovered using a band-pass filter. The phone uses a common digital control channel to acquire channels.FDMA systems are the least efficient cellular system since each analog channel can only be used by one user at a time. Not only are these channelslarger than necessary given modern digital voice compression, but they are also wasted whenever there is silence during the cell phoneconversation. Analog signals are also especially susceptible to noise – and there is no way to filter it out. Given the nature of the signal, analog cellphones must use higher power (between 1 and 3 watts) to get acceptable call quality. Given these shortcomings, it is easy to see why FDMA isbeing replaced by newer digital techniques.Time Division Multiple AccessTime Division Multiple Access (TDMA) subscribers share a common frequency channel but use the channel only for a short time.They are each given a time slot and allowed to transmit only during that time slot. When all the available time slots in a givenfrequency are used the next user must be assigned to a time slot on another frequency. 3
  4. 4. TDMA builds on FDMA by dividing conversations by frequency and time. Since digital compression allows voice to be sent at wellunder 10 kilobits per second (equivalent to 10 kHz), TDMA fits three digital conversations into a FDMA channel (this is 30 kHz).Code Division Multiple AccessCode Division Multiple Access (CDMA) subscribers share a common frequency channel. All users are on the same frequency at thesame time, they are divided however by codes. CDMA systems have no channels, but instead encode each call as a coded sequenceacross the entire frequency spectrum. Each conversation is modulated, in the digital domain, with a unique code (called a pseudo-noisecode) that makes it distinguishable from the other calls in the frequency spectrum. Theoretically CDMA provides many times thechannel capacity of TDMA. Proponents of CDMA also claim that there are fewer dropped calls when crossing cell boundaries. 4
  5. 5. Chapter 2 GSM NETWORK CONCEPTThe Global System for Mobile Communications (GSM) is a set of recommendations and specifications for a digital cellulartelephone network (known as a Public Land Mobile Network, or PLMN) GSM networks are digital and can cater for high systemcapacitiesThey are consistent with the world-wide digitization of the telephone network, and are an extension of the Integrated ServicesDigital Network (ISDN), using a digital radio interface between the cellular network and the mobile subscriber equipment.GSM FREQUENCIESGSM systems use radio frequencies between 890-915 MHz for receiveand between 935-960 MHz for transmit.RF carriers are spaced every 200 kHz, allowing a total of 124 carriers for use.An RF carrier is a pair of radio frequencies, one used in each direction.Transmit and receive frequencies are always separated by 45 MHz. 5
  6. 6. Extended GSM (EGSM)EGSM has 10MHz of bandwidth on both transmit and receive.Receive bandwidth is from 880 MHz to 890 MHz.Transmit bandwidth is from 925 MHz to 935 MHz.Total RF carriers in EGSM is 50.Figure 2.1 Uplink and downlink 6
  7. 7. 2.1 Channel ConceptFigure 2.2 Channel Concept 7
  8. 8. 2.1.1 Signaling ChannelThese are the main types of signaling Channels:Broadcast Channels (BCH) - Transmitted by the BTS to the MS. This channel carries system parameters needed to identify thenetwork, synchronize time and frequency with the network, and gain access to the network.Common Control Channels (CCH) - Used for signaling between the BTS and the MS and to request and grant access to thenetwork.Standalone Dedicated Control Channels (SDCCH) - Used for call setup.Associated Control Channels (ACCH) - Used for signaling associated with calls and call-setup. An ACCH is always allocated inconjunction with a TCH or SDCCH.The above categories can be divided into the following logical channels:Broadcast Channels (BCH) Broadcast Control Channel (BCCH) Frequency Correction Channel (FCCH) Synchronization Channel (SCH) Cell Broadcast Channel (CBCH)Common Control Channels (CCCH) Paging Channel (PCH) Random Access Channel (RACH) Access Grant Channel (AGCH) 8
  9. 9. Dedicated Control Channel (DCCH) Standalone Dedicated Control Channel (SDCCH) Fast Associated Control Channel (FACCH) Slow Associated Control Channel (SACCH)Figure 2.3 DownlinkFigure 2.3 Uplink2.1.2 Traffic ChannelTraffic Channels are used to carry two types of information to and from the user: Encoded Speech Data 9
  10. 10. There are two basic types of Encoded Speech channelEncoded Speech - Encoded speech is voice audio that is converted into digital form and compressed. Full Rate Speech TCH (TCH/FS) - 13 kb/s Half Rate Speech TCH (TCH/HS) - 5.6 kb/sData - Data refers to user data such as text messages, picture messages, internet browsing, etc. It includes pretty much everythingexcept speech.Full rate Data TCH (TCH/F14.1) - 14.4 kb/sFull rate Data TCH (TCH/F9.6) - 9.6 kb/sFull rate Data TCH (TCH/F4.8) - 4.8 kb/sHalf rate Data TCH (TCH/F4.8) - 4.8 kb/sFull rate Data TCH (TCH/F2.4) - ≤2.4 kb/sHalf rate Data TCH (TCH/H2.4) - ≤2.4 kb/sFigure 2.4: Full Rate Traffic Channel (TCH/FS) 10
  11. 11. Figure 2.5: Half Rate Traffic Channel (TCH/HS)2.2 Frequency HoppingThere are two types of frequency hopping method available for the BTS: synthesizer hopping and baseband hopping.Synthesizer Hopping - This requires the TRX itself to change frequencies according to the hopping sequence. So, one TRX wouldhop between multiple frequencies on the same sequence that the MS is required to.Baseband Hopping - In this method there are several TRX and each one stays on a fixed frequency within the hopping frequencyplan. Each TRX would be assigned a single time slot within a TDMA frame. For example, time slot 1 might be assigned to TRX 2 inone TDMA frame and in the next TDMA frame it would be assigned to TRX 3, and the next frame would be TRX 3. So, the data oneach time slot would be sent on a different frequency each frame, but the TRXs on the BTS do not need to change frequency. TheBTS simply routes the data to the appropriate TRX, and the MS knows which TRX to be on for any given TDMA frame. 11
  12. 12. GSM ARCHITECTURE2.3 Base Station Subsystem (BSS)To understand the paging process, we must analyse the functions of the BSS.The Base Station Subsystem consists of the following elements:  BSC Base Station Controller  BTS Base Transceiver Station  TC TranscoderThe Base Station Controller (BSC) is the central network element of the BSS and it controls the radio network. This means that themain responsibilities of the BSC are: Connection establishment between MS and NSS, Mobility management, Statistical raw datacollection, Air and A interface signalling support. 12
  13. 13. Figure 2.7: GSM ArchitectureThe Base Transceiver Station (BTS) is a network element maintaining the Air interface. It takes care of Air interface signalling, Airinterface ciphering and speech processing. In this context, speech processing refers to all the functions the BTS performs in order toguarantee an error-free connection between the MS and the BTS.The TransCoder (TC) is a BSS element taking care of speech transcoding, i.e. it is capable of converting speech from one digitalcoding format to another and vice versa. We will describe more about the transcoder functions later. 13
  14. 14. BSC TC BTS BSC TC BTS BTSFigure2.8: The Base Station Subsystem(BSS)The BTS, BSC and TC together form the Base Station Subsystem (BSS) which is a part of the GSM network taking care of thefollowing major functions:Radio Path ControlIn the GSM network, the Base Station Subsystem (BSS) is the part of the network taking care of Radio Resources, i.e. radio channelallocation and quality of the radio connection. For this purpose, the GSM Technical Specifications define about 120 differentparameters for each BTS. These parameters define exactly what kind of BTS is in question and how MSs may "see" the network whenmoving in this BTS area. The BTS parameters handle the following major items: what kind of handovers (when and why), pagingorganization, radio power level control and BTS identification. 14
  15. 15. BTS and TC ControlInside the BSS, all the BTSs and TCs are connected to the BSC(s). The BSC maintains the BTSs. In other words, the BSC is capableof separating (barring) a BTS from the network and collecting alarm information. Transcoders are also maintained by the BSC, i.e. theBSC collects alarms related to the Transcoders.SynchronizationThe BSS uses hierarchical synchronization which means that the MSC synchronizes the BSC and the BSC further synchronizes theBTSs associated with that particular BSC. Inside the BSS, synchronization is controlled by the BSC. Synchronization is a critical issuein the GSM network due to the nature of the information transferred. If the synchronization chain is not working correctly, calls maybe cut or the call quality may not be the best possible. Ultimately, it may even be impossible to establish a call.Connection Establishment between MS and NSSThe BSS is located between two interfaces, the Air and the A interface. From the call establishment point of view, the MS must havea connection through these two interfaces before a call can be established.Collection of Statistical DataThe BSS collects a lot of short-term statistical data that is further sent to the NMS for post processing purposes. By using the toolslocated in the NMS the operator is able to create statistical "views" and thus observe the network quality. 15
  16. 16. A Base Station Subsystem is controlled by an MSC. Typically, one MSC contains several BSSs. A BSS itself may cover aconsiderably large geographical area consisting of many cells. (A cell refers to an area covered by one or more frequency resources).Each cell is identified by an identification number called Cell Global Identity (CGI) which comprises the following elements: CGI = MCC + MNC + LAC + CI MCC Mobile Country Code MNC Mobile Network Code LAC Location Area Code CI Cell IdentityThere is one 2Mbit/s PCM line reserved for each BTS to provide the connection to NSS. But as you can see, the BTS’s are used atdifferent times and on different days. Why not use the same line for both of the two BTSs? It can be done, but in this case there has tobe a concentrator between MSC and BTS. The BSC acts as a concentrator (in addition to being the radio network controller). OneBSC is capable of serving several BTSs. 16
  17. 17. Chapter 3 Call Setup3.1 A Mobile Terminated Call and Paging A- GM SC HLR M S C /V L R PSTNS u b s c r ib e r C A L L S E T U P (M S IS D N ) ANALYSE NUM BER C A L L S E T U P (M S IS D N ) M S IS D N IM S I M SRN M SRN C A L L S E T U P (M S R N ) P A G IN GFigure 3.1 : Simplified steps in setting up a call 17
  18. 18. L o ca tio n A re a P a g in g P a g in g BTS BTS M o b ile re s p o n d s P a g in g to p a g in g BTSFigure 3.2. The Paging Process 1. A subscriber in a fixed network dials a number of a mobile phone. The dialled number is the MSISDN. 2. The Public Switched Telephone Network (PSTN) exchange analyses the number and contacts the Gateway Mobile Services Switching Centre (GMSC). 3. The Gateway MSC analyses the MSISDN and sends a message to the Home Location Register (HLR). 4. The HLR checks its database to determine the current location of the called subscriber. 5. The HLR interrogates the MSC/VLR (Visitor Location Register) that is currently serving the called subscriber. 6. The serving MSC/VLR generates a temporary MSRN (Mobile Subscriber Roaming Number). 18
  19. 19. 7. MSC/VLR sends MSRN to HLR and the HLR forwards the MSRN to the GMSC. 8. The GMSC identifies the serving MSC/VLR as the destination for routing the call. 9. Destination MSC/VLR receives MSRN. It identifies the number that is called and traces the called subscriber.The destination MSC/VLR initiates a paging process in the Location Area to locate the called subscriber. The mobile phone of thecalled subscriber recognises the paging signal and answers it EXC GM SC HLR M SC VLR BSS MS 1 . c h a n n e l a s s ig n m e n t 2 . s e c u rity p ro c e d u re s 3 . c a ll s e tu p 4 . c h e c k s e rv ic e s e tc . 5 . a ll o k 6 . c a ll is p ro c e e d in g 7 . tra ffic c h a n n e l a llo c a te d 8 . s e t u p th e c a ll 9 . c a ll s e t u p c o m p le te 1 0 . a le rt 1 1 . B a n s w e rs Figure 3.3 : Mobile Originated Call Procedure 19
  20. 20. 3.2 Location UpdateTypes of Location UpdateIn practice, there are three types of location updates:1. Location Registration (power on)2. Generic3. PeriodicLocation registration takes place when a mobile station is turned on. This is also known as IMSI Attach because as soon as themobile station is switched on it informs the Visitor Location Register (VLR) that it is now back in service and is able to receive calls.As a result of a successful registration, the network sends the mobile station two numbers that are stored in the SIM (SubscriberIdentity Module) card of the mobile station.These two numbers are the Location Area Identity (LAI) and the Temporary Mobile Subscriber Identity (TMSI). The network, viathe control channels of the air interface, sends the LAI. The TMSI is used for security purposes, so that the IMSI of a subscriber doesnot have to be transmitted over the air interface. The TMSI is a temporary identity, which regularly gets changed.A Location Area Identity (LAI) is a globally unique number.A Location Area Code (LAC) is only unique in a particular network. 20
  21. 21. MSC VLR LA 2LA 1Figure 3.4 : Location UpdateEvery time the mobile receives data through the control channels, it reads the LAI and compares it with the LAI stored in its SIM card.A generic location update is performed if they are different. The mobile starts a Location Update process by accessing theMSC/VLR that sent the location data .A channel request message is sent that contains the subscriber identity (i.e. IMSI/TMSI) andthe LAI stored in the SIM card. When the target MSC/VLR receives the request, it reads the old LAI which identifies the MSC/VLRthat has served the mobile phone up to this point. A signalling connection is established between the two MSC/VLRs and thesubscriber’s IMSI is transferred from the old MSC to the new MSC. Using this IMSI, the new MSC requests the subscriber data fromthe HLR and then updates the VLR and HLR after successful authentication. 21
  22. 22. MS BSS M SC VLR new V L R o ld HLR 1 . c h a n n e l a s s ig n m e n t 2 . lo c a tio n u p d a te re q u e s t 3 . re q u e s t s u b s c rib e r id e n tity 4 . re q u e s t s u b s c rib e r id e n tity 5 . re q u e s t s u b s c rib e r d a ta 6 . re q u e s t s u b s c rib e r d a ta 7 . s e c u rity p ro c e d u re s 8 . u p d a te lo c a tio n 9 . u p d a te H L R 1 0 . u p d a te a c k n o w le d g e m e n t 1 1 . c a n c e l o ld lo c a tio n 1 2 . lo c a tio n c a n c e llin g a c c e p te dFigure 3.5: location update procedure3.3 HandoverIn a mobile communications network, the subscriber can move around. How can we maintain the connection in such cases? Tounderstand this, we must study the process of handing over the calls.Maintaining the traffic connection with a moving subscriber ismade possible with the help of the handover function. The basic concept is simple: when the subscriber moves from the coverage areaof one cell to another, a new connection with the target cell has to be set up and the connection with the old cell has to be released.There are two reasons for performing a handover: 22
  23. 23. 1. Handover due to measurements occurs when the quality or the strength of the radio signal falls below certain parameters specified in the BSC. The deterioration of the signal is detected by the constant signal measurements carried out by both the mobile station and the BTS. As a consequence, the connection is handed over to a cell with a stronger signal. 2. Handover due to traffic reasons occurs when the traffic capacity of a cell has reached its maximum or is approaching it. In such a case, the mobile stations near the edges of the cell may be handed over to neighbouring cells with less traffic load.The decision to perform a handover is always made by the BSC that is currently serving the subscriber, except for the handover fortraffic reasons. In the latter case the MSC makes the decision. There are four different types of handover and the best way to analyzethem is to follow the subscriber as he moves:Intra cell - Intra BSC handoverThe smallest of the handovers is the intra cell handover where the subscriber is handed over toanother traffic channel (generally in another frequency) within the same cell. In this case the BSC controlling the cell makes thedecision to perform hanover. 23
  24. 24. Air A BSC TC BTS el hann O ld C n el Ch an N ewFigure: 3.6 Intra Cell - Intra BSC HandoverInter cell - Intra BSC handoverThe subscriber moves from cell 1 to cell 2. In this case the handover process is controlled by BSC. The traffic connection with cell 1 isreleased when the connection with cell 2 is set up successfully. 24
  25. 25. A ir A BTS B SC TC BTS O ld C ell / B TS N ew C ell / B TSFigure 3.7: Inter Cell - Intra BSC handoverInter cell - Inter BSC handoverThe subscriber moves from cell 2 to cell 3, which is served by another BSC. In this case the handover process is carried out by theMSC, but, the decision to make the handover is still done by the first BSC. The connection with the first BSC (and BTS) is releasedwhen the connection with the new BSC (and BTS) is set up successfully. 25
  26. 26. N ew C ell / B T S A ir A B SC TC B TS M SC VL R B SC TC B TS Old C ell / B TSFigure3.8: InterCell-InterBSCHandoverInter MSC handoverThe subscriber moves from a cell controlled by one MSC/VLR to a cell in the domain of another MSC/VLR. This case is a bit morecomplicated. Considering that the first MSC/VLR is connected to the GMSC via a link that passes through PSTN lines, it is evidentthat the second MSC/VLR can not take over the first one just like that.The MSC/VLR currently serving the subscriber (also known as the anchor MSC), contacts the target MSC/VLR and the trafficconnection is transferred to the target MSC/VLR. As both MSCs are part of the same network, the connection is established smoothly. 26
  27. 27. It is important to notice, however, that the target MSC and the source MSC are two telephone exchanges. The call can be transferredbetween two exchanges only if there is a telephone number identifying the target MSC. N ew C ell / B T S A ir A B SC TC B TS M SC VL R B SC TC B TS M SC VLR Old C ell / B TSFig 3.9: Inter Cell - Inter MSC HandoverSuch a situation makes it necessary to generate a new number, the Handover Number (HON). The generation and function of theHON are explained in the following text.The anchor MSC/VLR receives the handover information from the BSS. It recognises that the destination is within the domain ofanother MSC and sends a Handover Request to the target MSC via the signaling network. The target MSC answers by generating aHON and sends it to the anchor MSC/VLR, which performs a digit analysis in order to obtain the necessary routing information. 27
  28. 28. This information allows the serving MSC/VLR to connect the target MSC/VLR. When the two MSCs are connected, the call istransferred to a new route.In practice, the handover number is similar to the roaming number. Moreover, the roaming number and the handover number have asimilar purpose, that is connecting two MSCs. The structure of the handover number is shown below: HON = CC + NDC + SN  CC= Country Code  NDC= National Destination Code (of the serving network)  SN= Subscriber NumberThe call will not last forever and the connection has to be released sooner or later. To understand the process of releasing theconnection, we must consider a few things such as: Who pays for the call, which exchange takes care of the charging operation andwhere is the subscriber data stored. 28
  29. 29. Chapter 4 RF PLANNING4.1 ObjectiveThe overall objectives of any RF Design depend on a number of factors that are determined by the needs and expectations of theoperator, the resources made available by the operator, any service levels determined by the contract between operator and Vendor butonly as they affect the RF Design, and the resources that are available at the Technical Centre or Business Unit that is responsible forthe RF Design.Generally speaking the RF Design should satisfy the following criteria:- Maximizing coverage Providing sufficient capacity Providing an acceptable quality of service Minimizing cost 29
  30. 30. 4.2 RF DesignThe RF design engineer for that particular region would then decide the type of antenna to be used, the antenna height above groundlevel, Frequency Re Use pattern; the antenna orientation, the antenna mechanical or electrical down tilt if required and the base stationmaximum transmit power. RF Design includes the following: Antenna Selection LAC Design Grid Design Morphology Definition Link Budget Frequency Re Use Technique 30
  31. 31. The Cell Planning Process System Growth Traffic Analysis System Tuning Nominal Cell Plan System Installation Coverage & Interference Prediction 31
  32. 32. Cell planning begins with traffic and coverage analysis. The analysis should produce information about the geographical area and theexpected capacity (traffic load). The types of data collected are: Cost Capacity Coverage Grade Of Service (GOS) Available frequencies Speech quality System growth capabilityThe basis for all cell planning is the traffic demand, i.e. how many subscribers use the network and how much traffic they generate.The Erlang (E) is a unit of measurement of traffic intensity. 32
  33. 33. It can be calculated with the following formula:A = n x T / 3600 ErlangWhere,A = offered traffic from one or more users in the systemn = number of calls per hourT = average call time in secondsThe geographical distribution of traffic demand can be calculated by the use of demographic data such as: Population distribution Car usage distribution Income level distribution Land usage data Telephone usage statistics Other factors, like subscription/call charge and price of MSs 33
  34. 34. 4.3 RF Drive TestEvery good RF design, after its implantation should be evaluated. There are few ways to do this, for example through analysis of KPI(Key Performance Indicator) or through prediction tools and signal interference. Other very common and efficient way to evaluate thenetwork is conducting a Drive Test. But what is it?The name is intuitive: take a drive test. The Drive Test is a test performed in cellular networks regardless of technology (GSM,CDMA, UMTS, LTE, etc. ...). Means collecting data on vehicle movement. Its variation has also intuitive: Walk Test, ie, collect databy walking areas of interest.The analysis of drive test is fundamental for the work of any professional in the field of IT and Telecom comprising two phases: datacollection and data analysis. 34
  35. 35. Figure 4.1 : Drive Test SetupTypes of Drive TestThe main types of Drive Test are : Performance Analysis Integration of New Sites and change parameters of Existing Sites Marketing 35
  36. 36. Benchmarking 36
  37. 37. Figure 4.2 : Drive Test Result 37
  38. 38. Chapter 5 TRANSMISSION AND PLANNING5.1 Introduction The propagation of radio waves is generally affected by several factors, irrespective of the radio communication service or the specified purpose of telecommunication. These factors are described below.5.2 Propagation Mechanisms Depending on topography and meteorological conditions,radio wave can be propagated in different ways,normally,but not always,causing attenuation.One of the main tasks of radio engineering is to evaluate the attenuation of radio signals between transmitters and receivers. In order to do this,it is helpful to categorize propagation mechanisms: Free Space Propagation Refraction Diffraction Reflection and Scattering 38
  39. 39. AbsorptionLine Of SightThe earth atmosphere influences the propagation of radion waves in different ways.The radio waves travel with differentvelocities in different parts of the atmosphere,due to the variations in the electrical characteristics,which cause refaction.Due to the atmospheric refraction the radio waves are usually bent slightly downwards,which allows a somewhat longer pathlength than the straight line With the bending effect in mind it is customary to speak about a radio optic line of sight,rather than ageometricalline of sight.Under normal conditions the radio optic line of sight reaches further than a geometrical line of sight.The standard atmosphere and the other atmospheric conditions affecting the refraction factor and which occurs at a given site isdescribed by the earth radius factor k.The k value depending on the climatic conditions is 4/3 when applied to a standardatmosphere.Figure:5.1 : Line of Sight 39
  40. 40. The First Fresnel ZoneThe radio optical Earth radius can be described using the effective Earth radius factor.ClearanceEven if free line of sight is available on the entire path,close-by obstacles might have an attenuating effect if they ae loacated closeenough to the path .It is customary to define a fresnel zone around the centerline of the path.the first Fresnel zone is defined as azonesshaped as an eellipsoid with its focal points at the antennas on both ends of the path.The fresnel zone decreases with increasingfrequency.Provided that there is no obstacle within the first Fresnel zone the obstacle attenuation can be ignored,the clearance requirement issatisfied . 40
  41. 41. Figure:5.2:The first Fresnel zone5.3 Path ProfilesThe purpose of the path profile is to provide information concerning free line of sight between the selected station sites, and to decidewhether there is sufficient clearance to avoid obstacle attenuation.The path profile will also be used when determining the fading ofthe received signal.The path profile is essentially a plot of the elevation of the arth as a function of the distance along the path between the transmittingand receiving sites.The data is derived by locating the two terminals on an elevation contour map,drawing a straight linebetween thetwo points,and reading the elevation contours at suitable distance intervals.The topographical information used to design a path profile can also be derived from topographical map databases,which include analtitude databse and a land use database. 41
  42. 42. 5.4 Path and Site SurveyDuring the planning microwave radio link paths it is often necessary to closely survey the intended Hop on the location in order toevaluate the Obstacles by sight.Also the intended site and antenna carrier site should bechecked concerning space,power availabilityand strength.The following checked list covers the important items to be investigated. The geometrical position of the intended site. The antenna carrier height above groun level. The antenna carrier type,strength and torsion strength. The site altitude above mean sea level. The possibility of installing antennas required height. All obstacles in path directions,including their heights and widths. Potential reflecting surfaces. The radio environment.other radio installations or interfering signals. The distance between indoor and outdoor equipment. The main power availability. The battery backup possibilities. 42
  43. 43. The possibilities to install antenna feeders or multi-conductors cables between indoor and outdoor equipment regardingavailable space,grounding,wall entrance,bending radii etc.For new sites,access to roads and to power transformer stations must be considered. 43
  44. 44. REFERENCE Study training material at Vodafone,Ranchi www.google.com 44
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