1

PRESENTS

RADIO FREQUENCY SYSTEMS ENGINEERING

2

COURSE CONTENT

1. Introduction to Telecommunication.2. Second Generation Mobile Network.3. Radio Network Planning Process.4. Coverage Planning.5. Capacity Planning.6. Interference Theory: Frequency Planning.7. Network Systems Information Parameters Planning.8. Special Network Solutions.9. Radio Network Optimization: Quality of Service.10.Mirroring Advance Technologies.

3

Module 1: Introduction to Telecommunication.

Evolution of Mobile Communication. Information Theory: Multiple Access. Modulation & OSI model.

4

Evolution of Mobile Communication

1. First Generation System-Analogue

Started in early 1980 Based on Analogue Transmission Nordic Countries deployed NMT while Europe deployed

TAC Roaming was not possible No efficient use of frequency

2. Second Generation Networks-Digital

Started in mid 1980s Product of ESTI standardization Gave birth to GSM and other variants Roaming available

5

Evolution of Mobile Communication

3. Third Generation System-WCDMA in UTMS

High data transfer; still packet transfer on the air interface behaves like a circuit switched call.

Called UMTS in Europe; CDMA2000 in America WCDMA is the air interface technology for the UMTS Offers many internet based services, along with video

phoning, imaging, etc

4. Fourth Generation Networks-All IP

Provides the common platform for all the technologies that have been developed.

The functinalities of the RNC and BSC is now distributed to the BTS and a set of servers and gateways.

Data transfer is faster, and overall system setup is cheaper.

6

MULTIPLE ACCESSThe basic concept of Multiple Access is to permit transmitting

station to transmit to receiving station without any interference. 3 different modes are explored: Frequency, Time, and Code.

1. FDMA: Frequency Division Multiple Access.

• Each user is assigned a discreet slice of the frequency spectrum.

• Permit only one user per channel since it allows the user to use the channel 100% of the time.

• Use for analog cellular mobile system like AMPs, TACs, etc.

7

2. TDMA: Time Division Multiple Access.

• Multiple users share RF carrier on a time slot basis.• Carriers are sub divided into time slots.• Information flow is not continuous for a user; it is sent

and received in “burst”.

8

3. CDMA: Code Division Multiple Access.•Multiple access spread spectrum technique.•Each user is assigned a sequence code during a call.•No time division, all users use the entire carrier.

9

MODULATION SCHEMES1. Gaussian Minimum Phase-shift Keying

• Modulation scheme for GSM.• Frequency modulation

2. Octagonal Phase-shift keying (8-PSR)

• Employed for data handling in 2.5G

3. Quadrature Phase-shift keying (QPSK)

• The wavelength is changed instead of the frequency.• Utilized for WCDMA.

10

OSI ModelThe basic idea behind development of the OSI reference model

by the ITU was to separate the various parts that form a communication system. This was possible by layering and modularization of the function that were performing by various layers. Although initially developed for communication between computers, this model is being extensively used in the telecom field, especially mobile communication.

1. Physical Layer

• Physical in nature: Copper wire, optical fiber, radio transmitter or satellite connection.

• Does actual transmission of data.

2. Data Link Layer

• Combines data into frames• Error detection and correction; forms part protocol

testing.• Pack data based on High Level Link Control protocol.

11

3. Network Layer

• Gives routing information.

4. Transport Layer

• Boundary between the physical and the logical elements.• Checks data consistency end-to-end• Flow control and Error detection.

5. Session Layer

• Application identification and synchronization.

6. Presentation Layer

• Defines and prepares data• Compression and decompression

12

7. Application Layer

• Acts as interface between the processes• Application dependent

13

Module 2: Second Generation Mobile Networks

GSM Network Architecture and functions. Radio Channel Management. Frequency Spectrum. Digital Signal Processing.

14

GSM System Architecture and Function.

A mobile network system has two major components:-

(a) The Fixed installed networkRadio networks.Mobile switching networks.Management networks

(b) Mobile subscribers.

15

SECOND GENERATION NETWORKSSecond generation networks are networks based on the digital transmission technology. Types of second generation networks;(1) D-AMPS ( Digital Advance Mobile Phone System)(2) CDMA ( Code Division Multiple Access).(3) GSM ( Global System for Mobile Communication).

GSM-Global System for Mobile Communication.•First developed in the 1980s.•Digital system and a narrow band TDMA.•Modulation scheme is Gaussian Minimum Shift Keying, GMSK.•First commercially launched in Finland in 1991.•More than a billion people using GSM by 2005.•Added services such as prepaid calling, international roaming, SMS, voice mail, call waiting, etc.•GSM operates on various radio frequencies, with most operating at 900MHz and/ or 1800MHz.•Downlink band for 900M is 935-900MHz and the Uplink band is 890-915MHz

16

GSM System Architecture

17

Radio Network-Base Station Subsystem (BSS).

• On the MS side is air, MSC side is 2mbits.• Provides the link between the MS and the M SC.• Made up of Base Station Controller & Base Transceiver Station.

Base Station Control• Frequency administration• Control of the BTS• Exchange function between BTS and MSC.

Base Transceiver Station

• Usually located in the centre of a cell.• Contains the RF components that provides the air

interface/channels for signaling and user data traffic in the cell.

18

Mobile Switching System

The mobile switching system consist of the mobile switching centre and databases, which stores data required for routing and service provisions.

Components of MSS

(a) Mobile Switching Centre.(b) Gateway Mobile Switching Centre.(c) Home Location Register.(d) Visitor Location Register.(e) Authentication Centre.

Mobile switching centre (MSC)

•That is the switching node for mobile network.•Route path search and signal routing.•BSCs are subordinate to a single MSC.

19

(2) Dedicated Gateway MSC (GMSC)

Passes traffic between fixed networks and mobile networks.

(3)Home Location Register

Synchronization of registration of subscribers and their current location.Stores the identity and user data of all subscribers belonging to the related GMSC.

These includes both Permanent and Temporary data.

Permanent data:

(a) International mobile subscribers identity, IMSI.(b) Phone number from the public network (different from IMSI)(c) Authentication keys.(d) Subscribers permitted supplementary service.

20

Temporary data:

(a) Address of the current HLR.(b) The number to which the calls may be forwarded.(c) Some transit parameters for authentication and ciphering.

*In general , there is one HLR per PLMN, but…

(4)Visitor Location Register

•Synchronization of registration of subscribers and current location.•Stores the data of all mobile stations within the administrative area (LA) of the associated MSC.•Can be responsible for one or more MSC.

21

Operation and Maintenance Subsystem.

(1) Control and maintains the network.

(2) Network control functions are monitored and initiated from the Operation and Maintenance centre (OMC).

(3) The OMC has access to both MSC and BSC and the functions are;- i. Administration and commercial operations (subscribers, end terminals, charging) ii. Security management. iii. Network configuration, operation, performance management. iv. Maintenance task.

(4) The OMC configures the BTS via the BSC and allows the operator to check the components of the system.

22

MOBILE SYSTEMThe mobile system/ station are a set of equipment used by the mobile subscribers to access the services consist of two major components:-

(1) Mobile Equipment ME-(handset)(2) Subscribers Identity Module, SIM- (defines the users)

23

IDENTIFIERS

Location Area Identity – LAI

• Identifies every location area in the network.• LAI= MCC+MNC+LAC

(1) IMSI = International mobile Subscribers Identity

• Identify each subscribers uniquely in the network.• Stored in the SIM.• IMSI= MCC + MNC+ MSIN• MCC= Mobile country code: 3 decimal places (internal standard).• MNC= Mobile Network Code: 2 decimal places, for unique

identification of mobile network across the country.• MSIN= Mobile Subscriber Identification Number:- identify the

subscriber in the mobile network

24

IMEI= International mobile equipment identity

•Uniquely identifies each mobile station internationally.•Allocated by the equipment manufacturer and registered by the network operators in the EIR.

(3)MSISDN:- Mobile Subscriber ISDN number.

•The real telephone number of the MS.•Assigned to the subscriber, such that MS can have several MSISDN depending on the SIM.

(4) TMSI:- Temporary Mobile Subscriber Identity.

•Assign by the VLR to the MS.•Significant only in the area handled by the VLR.•Used in place of the TMSI for identification and addressing of the MS.•Serves a identity hopping means, since nobody can listen to the radio channel and identify the correct IMSI •TMSI changes from one VLR to another.

25

INTERFACE

(1) Air Interface

•The central and most important in every mobile system.•The only interface exposed to the mobile station.•Interface between the MS and the BTS.

(2) ABIS Interface

•Interface between BTS and the BSC.•It is a PCM interface that means it is defined by the 2Mbps PCM link. Thus a transmission rate of 2.048Mbps, having 32 channels of 64kpbs each.•Multiplexing and transcoding functions from 64kpbs on the Abis to 13kbps on the air.

26

(3) A interface

•Physical interface between the MSC and the BSC.•Consist of one or more PCM, each of capacity 2.048mbps.•There are two parts of the A interface – one from the BSC to the TRAU where transmission is compressed, and one between the TRAU and the MSC, where the data is uncompressed.

27

SIGNALLING

LAPDm

LAPDm stands for modified link access protocol for D-channel.This is the modified optimization version of the LAPDm signaling for the GSM air interface.

SS7

•SS7 stands for Signaling System No 7.•Forms the basis of all signaling traffic on all the NSS interface.•Developed by the ITU.•Provides the protocol by which the network elements in the mobile (telephone) network can exchange information.•Used between BSC and MSC, and used for call setup and call management.•It is also Known as CCS7•It is not allocated permanently, requires only for call setup and call release functions.

28

X.25

•X.25 links the BSC to the O and M centre.•ITU developed signaling protocol, allowing communication between remote devices.•Utilizes connection –oriented protocol.•It is a packet switched data network protocol that allows both data and control information flow between the host and the network.

29

RADIO CHANNEL MANAGEMENT

In the mobile network MS is connected to the network via the radio channel. In this way the subscribers can access the network and obtain communication services. To achieve the inter-working between the MS and BTS, a set of standard are set for signal transmission through the radio channel. This set of specifications is aimed at Um interface.The Um interface is a kind of radio interface. It is responsible for the communication between the MS and the BTS and provides the inter-working link between the MS and the GSM system. Channel types.(1) Physical channels.(2) Logical channels.

30

Physical channels.

Physical channels is all the TS of the BTS, either full rate (13kbps) or half rate(6.5kbps).

Logical channels

Logical channels refers to the specific type of information that is carried by the physical channel.

Logical channel can also be divided into two types : Traffic channels (TCH) and control channels.

(1) Broadcast control channel- BCCH•Broadcast system information to the MS.•Configured in every cell.•Enable MS to identify and access network at the idle mode.

31

(2) Frequency Correction channel-FCCH

•Provides information for carrier synchronization

(3) Synchronous channel –SCH

•Decodes the BSIC and MS frame synchronization..

(4) Paging Channel-PCH

•The BTS/BSC uses PCH to page the MS using the TMSI or IMSI.

(5) Access Grant Channel-AGCH

•Used in answering network access request by the MS.•Allocation of SDCCH or TCH directly.

6) Random Access Channel-RACH

•Used by MS to randomly access the network by requesting for SDCCH.

32

7) Stand-alone Dedicated Control Channel-SDCCH

•Used for signaling messages, concerned with call setup, location update message, SMS, etc.

(8) Slow Associated Control Channel-SACCH

•Used with the traffic channel or SDCCH.•It carries specific information while transmitting the subscribed information.•In uplink, it transmits the measurement report.•In down link, it transmits some system information messages.

(9) Fast Associated control Channel- FACCH

•Provides signaling messages who speed and timeliness are much higher than SACCH.•Used together with TCH

33

Traffic channel carries voice or data, which are full rate TCH/F or half rate TCH/H. (13kbps or 6.5kbps).

The control channel are used to transmit signaling or synchronous data.

There are three main types of control channels:(1) Broadcast Channel, BCCH(2) Common Control channel.(3) Dedicated Control channel.

Physical combination of logical channel

There are two multi-frame types of combination:(1) 26- frame multi-frame.(2) 51-frames Multi-frame.

34

(1) 26 – frame multi-frame.

TCH/F+FACCH/F+SACCH/TF (Full rate)TCH/H+FACCH/H+SACCH/TH (Hall rate)

(2) 51-frame multi-frame

FCCH+ SCH+BCCH+CCCH-Main BCCHFCCH+SCH BCCH CCCH +SDCCH/4+SACCH/C4(combined BCCH)BCCH+CCCH (Extended BCCH)SDCCH/8+SACCH/8 (Main SDCCH)

As shown above CCCH =PCH+RACH+AGCH.

35

36

Digital Signal Processing

The radio channel is quite different from the wired channel. The radio channel has a distinct time change characteristics and is also exposed to air. So it is vulnerable to the interferences in the air. To solve the problems mentioned above a series of forward and backward (uplink and downlink) transmission techniques are applied.

The original subscribers data or signaling data are transformed before being carried by the radio waves. And at the other end of the transmission a reverse transformation is done.

The transformation processes includes:(a) Channel coding /decoding.(b) Interleaving / de-interleaving(c) Burst formatting(d) Encryption/ Decryption(e) Modulation/ Demodulation.

37

Digital Signal Processing

The radio channel is quite different from the wired channel. The radio channel has a distinct time change characteristics and is also exposed to air. So it is vulnerable to the interferences in the air. To solve the problems mentioned above a series of forward and backward (uplink and downlink) transmission techniques are applied.

The original subscribers data or signaling data are transformed before being carried by the radio waves. And at the other end of the transmission a reverse transformation is done.

The transformation processes includes:Voice codingChannel coding /decoding.Interleaving / de-interleavingBurst formattingEncryption/ DecryptionModulation/ Demodulation.

38

Module 3: Radio Network Planning Process

Definition of Radio Network RequirementsPreliminary Network DesignProject Setup and ManagementSite Planning: Site Simulation and ModellingCoverage and Capacity PlanningSite AcquisitionTechnical Site Survey and ValidationParameter PlanningSite IntegrationSite Verification and drive testHardware/Software checkNetwork Optimization and Site Acceptance

39

DEFINITION OF RADIO NETWORK REQUIREMENTS.

This defines the customer request to the vendor equipment supplier through the request for quote:

Coverage

•Definition of coverage probability: percentage of measurement above level threshold.•Definition of covered area.

Traffic

•Definition of erlang by subscribers.•Number of subscribers .•Definition of number of TRX per cell.•Definition of mixture of cell configurations.•Half rate ratio.•Mixture of circuit switch and packet switched traffic

40

•Quality of service

Key performance indices benchmark definitions: call setup success rate , call drop rate, hand over success rate, channel congestion rate.Rx-Qual, Voice Quality (SQI), throughput rates, ping time.

•Frequency Resources Licensed

41

PRELIMINARY NETWORK DESIGN

The output is the bill of quality (BOQ) of all the needed network elements.

Geo data procurement.

• Digital elevation model/topographic map.• Clutter map.

Definition of standard equipment configurations.

• Clutter type.• Traffic density.

Coverage plot

• Expected receiving level at different points.

42

Definition of roll out phases.

•Areas to be covered.•Number of sites to be installed.•Project take off date.

Network architecture design•BSC dimensioning•BSC/MSC parenting.

•Frequency Multiplexing pattern.

43

SITE PLANNING:SITE SIMULATION AND MODELING

(1) Area survey: check the correctness of the geo-data.

(2) Simulation tool calibration for different morpho classes:(a) Performing of CW measurement (b) Calibration of correction factor and standard deviation by comparison of measurement to predicted received power values of the tool.

(3) Site simulation and modeling : site is modeled in the tool and a hypothetical position is taken and this defines the numerical search area map.

(4)A team consisting of RF, TX and SAQ searches for the location based on some agreed conditions .

(5) Selection of number of TRX/sectors per sites.

(6) Frequency spectrum planning and design.

(7) Final output: cell design coverage & Prediction plot.

44

COVERAGE PLANNING.

Definition of coverage area.Expected area coverage probability.Expected Signal receiving level at different points: Outdoor, Indoor, Incar.

CAPACITY PLANNING

Number of subscribers Traffic Plan per subscribersNumber of BTS/BSCHalf Rate Ratio

45

SITE ACQUISITION

Site acquisition procedures involves the following:

1. Identify several locations within the Search Area Map, SAM.

2. Redefinition of SAM if no good candidate exist within the pre-determined area.

3. Identify possible candidate and produce a report bearing the following information;• Location information- latitude, longitude, altitude.• Land usage.• Object (rooftop pylon, grassland)

46

SITE ACQUISITION

Site plan.

If the reported location are candidates then it is ranked according to its quality in terms of the following:

1. Structural engineering suitability.

2. Feasibility of Site Acquisition.

3. Availability of Line of sight

4. Subscribers base potential

5. Statutory restrictions.

6. Material handling

7. RF Engineering conditions.

47

TECHNICAL SITE SURVEY AND VALIDATION

The stakeholders here are:

(1) RF engineer.(2) Transmission engineer.(3) Civil /site engineer.(4) Property officer.(5) Site owner.

Technical site survey report defines:

(1) Antenna type, position, height, bearing / orientation and tilt.(2) Mast/pole or wall mounting position of antenna.(3) EMC rules are observed.(4) BTS location(5) Power and feeder cable mount.(6) Transmission equipment location and installation.(7) Final Line of Site (LoS) confirmation for microwave link planning.(8) Accessibility for maintenance use.

48

If the site is not acceptable based on the condition above or the owner disagrees with all suggested solutions, the site rejected and process starts all over.

PARAMETER PLANNING

After installation of equipment the basic parameter setting are used for commissioning and functional testing of BTS. The following cell design parameters are defined:

(1) CGI/LAC/BSIC(2) Frequencies(3) Neighbor/cell handover relationships.(4) Transmit power of radios.(5) Cell type (macro, micro, umbrella)(6) Cell band e.g. 900M, 1800M or 900/1800M.(7) Layer threshold, etc.

49

SITE INTEGRATION

•Provision of site support elements.•Confirming the site commissioning checklist.•Powering up and system pre-check.•Commissioning•Inspection and Alarm testing•Integration of elements.

50

SITE VERIFICATION AND DRIVE TEST

RF engineer performs the site verification and drive test to compare the real coverage with the predicted coverage of the cells.

If coverage holes or area of high interference are detected; Adjust the antenna tilt and direction.

HW/SW Problem Detection•During the functional testing and drive testing, we can detect the following:•Defective equipment.•Soft ware bugs,•Incorrect parameter settings.•Faulty antenna installation.

51

Network OptimizationProcedures

•Drive testing•KPI evaluation•Network parameter audit.

Network Acceptance

Procedures

•Acceptance drive test•Calculation of KPI according to acceptance requirement in contract.•Presentation of KPI to customers.•Comparison of KPI with the accepted target in the contract.•Network acceptance: part or whole•Commercial launch.

52

Module 4: Coverage Planning.

Geo Databases Radio Elements. Radio Cell and Wave Propagation. Path loss prediction. Link budget. Antenna System Engineering. Coverage improvement solutions.

53

GEO DATABASES.

Geo data is required for radio planning because propagation models depends on the characteristics of geographical data.

Geographical information for site acquisition include:

Longitude and Latitude.Rectangular Coordinates.

Map Projection.

Different map projections.Geodetic Datum eg WGS 84Transverse Mercator Projection, UTM

54

Geospatial Data for Network Planning

1. DEM-Digital Elevation Model Raster dataset that shows terrain features such as hills and

valleys. Each element or pixel in the DEM image represents the

terrain elevation at the location. Resolution in most cases: 20m for urban areas; 50-100m for

other areas. DEM are typically generated from topographic maps,

satellite images or aerial photography.

2. Morpho-structure/Land Usage/Clutter.

Land usage classification according to the impact on wave propagation eg buildings, forest, plain land, rivers, etc

Resolution for urban areas is 20m; 50-100m for other areas.

55

3. Background Data.

• All kinds of information data like streets, borders, coastlines etc.

• Necessary for orientationin plots of calculation results

• The background data arenot needed for the calculationof the field strength, power etc.

56

4. Scanned Map

•Mainly used asbackground data

•Not used for calculationbut for localization

•Has to be geo-codedto put it into a GIS (Geographic Information System) e.g. a Radio Network Planning Tool

57

5. Buildings• Outlines of single buildings

and building blocks

• Building heights

• Material code

58

Coverage Planning

The target for coverage planning is to find optimal locations for base station to build continuous coverage according to the planning requirements.Coverage planning is performed with a planning tool including a digital map with topography information.

Steps in Coverage Planning

•Create a preliminary plan base on the calculated number of base station from the dimensioning phase agreed with the operator.

•Find the actual base station location during site survey and validation

59

Radio Elements.

•Radios: 900M/1800M TRX•Combiners •Feeders•Antenna

Radio cell and wave propagation.Coverage in cell is dependent upon the area covered by the signal. The distance traveled by the signal is dependent upon radio propagation characteristics in the given area.

The whole land area is divided into three major classes – urban, suburban and rural, based on human made structure and natural terrains.The cell sites that are constructed are also classified as outdoor or indoor cells.Outdoor cells can be further classified as:

60

Macro cell•When base station antennas are placed above the average root top level•The area to be covered is wide•Cell range up to 35Km depending on terrain type and propagation condition.

Micro cell•Base station antennas are placed below the average roof top.•The area to be covered is small.•Cell range within 1km.

Pico cell•Define in the cell layer as micro cell•Used as indoor.

Umbrella Cell•Antenna height is placed above 50m•Used for road coverage sites

61

Radio Propagation Environment

The radio frequency from 3Hz to 3000GHz are separated into 12 bands, as shown in the table below. Frequency in different frequency spectrum has different propagation characteristics. For mobile communication, we only pay attention to the UHF spectrum.

62

Radio Propagation Model.

Propagation is the basis for mobile communication in cell planning. A good model should have good recognition and acceptability. Models predict path loss in radio propagation path.

Propagation environment plays an important role in radio propagation model. Main factors are:

• Natural (mountains, hills, plains and water.• Quantity, height, distribution and material of man made

buildings.• Characteristics of vegetation in the area.• Climatic conditions.• Condition of natural and man made electromagnetic noise.

63

In addition, radio propagation model is affected by the system working at the frequency. E.g. stationary and moving MS.

Types of propagation models• Outdoor• Indoor

Radio wave propagation conceptsPropagation of the radio wave in free space depends heavily on the frequency of the signal and obstacle in its path.

Major effects on signal behavior are

• Reflection and Multi-path• Diffraction or Shadowing• Building and vehicle penetration.• Propagation of signal over water.• Foliage loss.

64

Fading of the signalSignal looses strength from transmitting antenna to the receiving

antenna. This may be due to• Path loss: loss in free space• Rayleigh effect.

Rayleigh Effect• Multi-path fading• Frequency- selective fading.

65

Antenna System Engineering

Basis of Antenna

In the wireless communication system, antenna is the interface between the transceiver and outside transmission medium.

Antenna can serve two functions at the same time:

1. Transmit Radio waves: converts high frequency current in radio waves.

2. Receive Radio waves: converts radio waves into high frequency current.

66

ANTENNA SELECTION PRINCIPLE

When selecting GSM Base station antennas, two parameters are considered, namely:

1. Electric parameters2. Mechanical parameters.

ELECTRIC PARAMETERS 1. Working frequency 2. Gains 3. Polarization mode 4. Lobe width: Horizontal and Vertical 5. Down tilt 6. Adjusting range of down tilt 7. Power capacity

67

MECHANICAL PERFORMANCES

1. Dimension2. weight3. Wind Load4. Antenna input interface

SELECTION BASED ON RADIATION DIRECTION

Omni directionalDirectional

SELECTION BASED ON POLARIZATION MODE

1. vertical polarization-Single polarization 2. Cross polarization –Dual polarization

68

ANTENNA GAIN

Gains is one of important indicator of antenna, which shows the capacity of an antenna to concentrate energy in a certain direction.

There are two units designated to antenna gain, namely Dbi and dbd.

The relationship between them is:

Dbi = dbd + 2.15

Dbd: Defined to be the relative capacity of an actual directional antenna to concentrate energy in relation to dipole.

Dbi: Defined to be the relative capacity of an actual directional antenna to concentrate energy in relation to isotropic antenna.

69

ISOTROPIC ANTENNA

Isotropic Antenna is a kind of theoretical model, not existing in reality, which presumed the antenna is to be a radiating point source energy radiating around evenly from the center of this point in the form of electromagnetic field to form a spherical wave.

70

ANTENNA RADIATION PATTERN

Antenna radiation pattern is the shape of the electromagnetic field radiating by antenna distributed with angular coordinates within a fixed distance. We have three kinds of patterns: 1. Field strength 2. power density 3. Phase pattern

The radiation lobe required in the maximum radiation direction in the directional diagram is called antenna major lobe-Antenna beam. Other lobes are secondary or side lobes.

71

Radiation Pattern

Omni-directional Antenna

72

Directional Antenna

73

Antenna Tilt.The angle of inclination given to the antenna when installed.Depends on antenna height, azimuth, gain, vertical beam power and cell range expected.

Two type exist:

Mechanical TiltElectrical Tilt

74

Antenna Selection.

In mobile communication, it is very important to select the right antenna for the deregulation. We make a choice in the light of practical conditions such as the requirement on coverage, traffic, interface and network service quality of the network.

The major antenna parameters considered are the gain, beam width, tilt. A proper antenna will enlarge the coverage, reduce interference and improve service quality.

Antenna selection is closely related to coverage requirements, antenna selection can be divided types of land forms and traffic distribution.

1. Urban 2. Suburban 3. Rural 4. Highway

75

Module 5: Capacity Planning.

Traffic theory. Erlang B Table. Traffic capacity and channel planning. Carrier types.

Control Channel planning.BTS/BSC DimensioningLocation Area PlanningCell structures and network evolution.

76

gtt

77

Link BudgetAlso known as Power Budget. Link budget calculations give the loss in the signal strenght on the path between the mobile station antenna and base station antenna.

Defines the cell rangeCoverage threshold.

Link budget calculations are done for both uplink and downlink. Since the power transmitted by the MS antenna is less than the power transmitted by the BTS antenna, the BTS Power budget is the most critical.

Important component of Link Budget Calculation.

MS sensitivity.BTS sensitivityFade MarginConnector and Cable lossesMS and BTS antenna gain

78

Module 5: Capacity Planning.

Traffic theory. Erlang B Table. Traffic capacity and channel planning. Carrier types.

Control Channel planning.BTS/BSC DimensioningLocation Area PlanningCell structures and network evolution.

79

TRAFFIC THEORY

Cellular system capacity depends on a number of different factors. These include:

1. The number of channels available for voice and or data

2. The grade of service (GOS) the subscribers are encountering in the system.

Traffic refers to the usage of channels and is usually taken to be the holding time per time unit (or number of “call hours “per hour) for one or several circuits (trunks or channels).

The unit of traffic is Erlang (E)

For example, if one subscriber spends all his/her time on the phone he/ she can generate one call per hour or 1E of traffic.

80

Erlang B table

Erlang B table named after the Danish traffic theorist is based on most common assumptions, namely

• No queues• Number of subscribers much higher than number of traffic

channels• No dedicated traffic channels• Blocked calls, abandon call attempt• Poisson distributed (random) traffic.

Erlang B traffic model is used to work out the traffic density a network is capable of bearing. GoS or call loss may be 2% or 5%. Erlang B table is shown below.

81

ERLANG B TABLE

82

Traffic capacity and channel planningThese are three major channels during capacity planning namely

•BCCH—Carries the systems information•TCH---- carries voice/data•SDCCH--- carries signaling information.

Rule of thumb

•Every cell bears a BCCH channel•Every cell contains a certain number of SDCCH channel depending on anticipated TCH traffic and signaling activities•The remaining channels are TCH channels

For exampleA cell has 2 TRX there are 1 BCCH, 1SDCCH, & TCH channels

From erlang B table, 14TCH channels at 2% GoS is equal to 8.2erlang

83

SDCCH PLANNINGThe table below shows a simple guideline on how to utilize SDCCH

channelsActivities that use the SDCCH channels are• location updating• periodic registration• IMSI attach/detach• Call setup• SMS• FAX

CARRIER TYPES

1. 900M--- 40W-60W2. 1800M--- 40W-60W

84

Control channel planning

1. combined CCCH2. uncombined CCCH

BTS/BSC Dimensioning

• Sharing the BTS across the BSC• Available TX resources• Available radio resources in the BSC

• MSC/ transcoder resources available

85

Location Area Planning

Under the GSM protocol, the entire mobile communication network is divided into service areas in light of different area codes.

Paging messages are delivered in terms of location areas, with the paging of one MS in the location area delivered to all the cells.The location area may include one or more BSC, but it must belong to a single MSC

The principles of designing Location Area Code includes:

•Location area must not be too large or too small•Location area division is performed in terms of geographical distribution and behavior of mobile users, so as to achieve fewer location updates at the edge of area.

86

Module 6: Interference Theory: Frequency Planning.

Theory of Interference. Frequency Spectrum Allocation. Frequency Planning & Reuse Pattern. Frequency Hopping.

87

FREQUENCY RESOURCE OF GSM SYSTEM

GSM 900 :

GSM 1800 :

1710 1785 1805 1880

Duplex distance : 95 MHz

890 915 935 960

Duplex distance : 45 MHz

88

FREQUENCY BAND CONFIGURATION

GSM900:

BTS receiver (uplink ): f1 (n) =890.2+ (n-1)*0.2 MHzBTS transmitter (downlink ): f2 (n) =f1 (n) +45 MHz

GSM1800:

BTS receiver (uplink ): f1 (n) =1710.2 + (n-512) * 0.2 MHzBTS transmitter (downlink ): f2 (n) =f1 (n) +95 MHz

89

INTERFERENCE THEORY

GSM is an interference restricted system.

Carrier-to-interference ratio, also called interference protection ratio, CI C/I = All useful signals = _ carrier All useless signals Interference

GSM standard: C / I >= 9 dBIn practical projects: C / I >= 12dB

Useful signal Noise from environment

Other signals

90

EFFECTS OF INTERFERENCE

Decrease of signal quality

• Bit errorRecoverable: channel coding, error

correctionIrrecoverable: phase distortion

System interference model

• Unbalanced: uplink interference ≠ downlink interference• Asymmetrical: the interference is different at the MS and BTS ends

91

SIGNAL QUALITY•Receiving quality (RXQUAL parameter)•Level of receiving quality (0 ... 7)

•Bit error rate before decoding and error correction

RXQUAL Mean BER BER rangeclass (%) from... to0 0.14 < 0.2%1 0.28 0.2 ... 0.4 %2 0.57 0.4 ... 0.8 %3 1.13 0.8 ... 1.6 %4 2.26 1.6 ... 3.2 %5 4.53 3.2 ... 6.4 %6 9.05 6.4 ... 12.8 %7 18.1 > 12.8 %

92

CONCEPT OF FREQUENCY REUSE

Frequency resource is limited. If there is 8MHz frequency resource, 8 MHz = 40 channels * 8 timeslots = 320 ==> max. 320 users can access the network at the same time.

{fi,fj..fk}

{fi,fj..fk} {fi,fj..fk} {fi,fj..fk}.. ..

Macro-cell system

dMicro-cell system

93

FREQUENCY REUSE CLUSTER

Reuse density is the number of cells in a basic reuse cluster.4*3 ： 12n*m ： n*m

n: BTS number in a basic reuse clusterm: Frequency group number in a BTS

4*3 Reuse PatternA1

C1

B1D1

A2A3

B2B3

C2C3

D2D3

A1C1

B1D1

A2A3

B2B3

C2C3

D2D3

A1C1

B1D1

A2A3

B2B3

C2C3

D2D3 A1

C1

B1D1

A2A3

B2B3

C2C3

D2D3

A1C1

B1D1

A2A3

B2B3

C2C3

D2D3

A1C1

B1D1

A2A3

B2B3

C2C3

D2D3

94

4*3A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3

34 34 35 36 37 38 39

40 41 42 43 44 45 46 47 48 49 50 51

52 53 54 55 56 57 58 59 60 61 62 63

64 65 66 67 68 69 70 71 72 73 74 75

76 77 78 79 80 81 82 83 84 85 86 87

88 89 90 91 92 93 94 95

95

TIGHT REUSE PATTERN

Multi-layer reuse patternUnderlaid and overlaid cell1*31*1

MULTI-LAYER REUSE PATTERN

96

Suppose that the available frequency carrier is 10MHZ, channel number is 46 ～ 94, the Multi-layer reuse pattern should be:

RC type Allocated frequencies

Number of available

frequencies

BCCH 46~57 12

TCH1 58~66 9

TCH2 67~74 8

TCH3 75~82 8

TCH4 83~88 6

TCH5 89~94 6

97

1*3 REUSE PATTERN

1*1 REUSE PATTERN

FREQUENCY PLANNING PRINCIPLE

•There should be no co-channel frequency carriers in one BTS.•The frequency separation between BCCH and TCH in the same cell should be not less than 400K.•When frequency hopping is not used, the separation of TCH in the same cell should be not less than 400K.•In non-1*3 reuse mode, co-channel should be avoided between the immediately neighbor BTS. •Neighbor BTS should not have co-channels facing each other directly. •Normally, with 1*3 reuse, the number of the hopping frequencies should be not less than twice of the number of frequency hopping TRX in the same cell.•Pay close attention to co-channel reuse, avoiding the situation that the same BCCH has the same BSIC in adjacent area.

98

EXAMPLES OF FREQUENCY PLANNING

An example network in a specific place, BTS are densely located. The topography is plain. The maximum BTS configuration is S3/3/2.

INITIAL PLANNING

99

FINAL PLAN

100

FREQUENCY HOPPING

Frequency hopping is a technique that basically improves the channel to interference C/I ratio by utilizing many frequency channels.

BENEFITS.

•Get an agreeable radio environment.

•Provide a similar communication quality for every user.

•Tighter reuse patterns are possible to be used for larger capacity.

101

TYPES OF FREQUENCY HOPPING

1. Base band Hopping2. RF Hopping

102

HOPPING PARAMETERS

•At the Um interface, the ARFCN on a specific burst is an element in MA set. MAI is used for indication, referring to a specific element in the MA set.

•When 0< MAI<n-1MAI is the function of TDMA FN, HSN and MAIO.

HSN

HOPPING SEQUENCE NUMBER,

Used to define the actual rule for hopping.

•HSN ： hopping sequence number （ 0 ～ 63 ） .•HSN=0 ： cycle hopping.•HSN≠0 ： random hopping. Every sequence number corresponds a pseudo random sequence.

103

MA

Mobile Allocation set: Set of available frequency during hopping. Must not contain the BCCH frequency for RF hopping.

MAIO

Mobile Allocation Index Offset: Used to define the initial frequency of the hopping. The MAIO of all channels of one hopping TRX must be identical. The MAIO of different channels of the different hopping TRX in the same cell must be different.

TSC

Training Sequence Code: Used for delay equalization at the receiver end. TSC must be the same as the BCC.

104

Module 7: Network System Information Parameters

Network Identity Parameters System Control Parameters. Cell Data Parameters. Network Function Parameters.

105

NETWORK PARAMETERS

Network parameters are those parameters that govern the behavior of the MS as it access the network, setup call, and conclude communication appropriately.

Network parameters are actually system information sent to the MS through the air interface, and this include network identity parameters, cell selection parameters, system control and network function parameters. By reading this system information, the MS can access the network, perform cell selection and reselection, fully utilize various services provided by the network, and achieve favorable cooperation with the network.

These network parameters can be sent to the MS on two different channels:BCCH, usually on idle mode: CCCH information.SACCH, usually on dedicated mode: TRX management.

106

Network parameters are divided into four parts:

•Network identity parameter.•System control parameter.•Cell selection parameter.•Network function parameters.

NETWORK IDENTITY PARAMETERS

Network identity parameters includes :•CGI•BSIC

•CGI = Cell Global Identity consist of location, Area identity and Cell identity, and LAI consist of ; Mobile Country Code (MCC), Mobile Network Code (MNC), and Location Area Code (LAC).

CGI= MCC+MNC+LAC+CI

107

MCC:•Consist of 3 decimal numbers.•Indicates home country of the mobile subscriber.•Coding range is decimal 000-999.

MNC:•Uniquely identify a specific OSM PLMN network in a certain country.•Consist of two decimal numbers. •The coding range is 00-99.

LAC:•Locate the location of the MS based on the local area demarcation•Contains Hexadecimal coding.•Available range is 000IH to FFFEH.

CI•Cell ID of individual cell.•Uniquely identifies a cell in a network.

108

BSIC: Base Station Identity Code.

This is a color code allocated to each base station. MS can identify two cells with the same BCCH with the help of a

BSIC. BSIC = NCC+BCCNCC-:•MS uses it to distinguish adjacent BTS that belong to different GSM PLMN.•The coding range is 0-7.

BCC-:•Used to identify different cells with the same BCCH in the same GSM system.•BCC is always configured the same value as TSC•Coding range is 0-7.

109

SYSTEM CONTROL PARAMETERS

System Control Parameters are meant for favorable cooperation between MS and BTS. On the other hand, the values of these parameters affect the traffic load and signaling flow of each part of the system.

ATT Value range: Yes, No.

Content: Referred to as attach- detach is allowed in a cell.

Yes means, network should not process the connection to the subscriber called when MS is switched off. Thus network processing time and resources are saved.

Recommended value : Yes.

)

110

CCCH – CONF.

This is the Common Control Channel Configuration and determines the capacity of PCH, AGCH and RACH.

It is either a combined CCCH or uncombined CCCH, and value is determined by the number of TRX configured.

NOTE: When you have 1TRX configured, use combined CCCH, otherwise use uncombined CCCH.

BS-AG-BLKS-RES

This is called Access Granted Blocks Reserved,

Assigned the proportion of AGCH and PCH on CCCH. It affects the MS response to paging.

Recommended value is 2.

111

T3212

•It is periodic Location Update Timer- Defines periodic length of location updating.

•MS makes periodic location update controlled by T3212. MS reads T3212 and stores it in the SIM, when the time expires, the location area update would be triggered.

•The shorter the time, the better the system performance but it would increase the signaling load of the system.

112

Radio Link Timeout

•This parameter is used by MS to decide down link disconnection in case of SACCH decoding failures.

•MS starts a counter S, from then S decreases by 1 once SACCH fails to decode its message, and increases by two when SACCH decodes correctly. When S drops to O, the call would drop.

•Recommended configuration is dependent on the area (high traffic, low traffic and medium traffic).

Neighbor Cell Description

•There are BA1 and BA2 tables.

•BA1 describes BCCH frequencies of the adjacent cell to be measured when MS is in idle mode. BA2 describes BCCH frequencies of the adjacent cells to be measured when MS is in dedicated mode.

113

MS MAX Re-trans

•The number of times MS is allowed to send ‘channel request’ in one immediate assignment procedure.•Setting dependent on traffic situation and area.

MBR.

•Multi-band Reporting: used to inform MS to report the adjacent cells in a controllable way.•Applicable for a dual band network.•Value is from 0-3.•When the value is ‘0’, MS will report MR of six strongest adjacent cells no matter which band its in.

114

Cell Selection Parameters.

•Normal Cell Selection•Stored List Cell Selection.

NORMAL SELECTION.

SIM card of MS does not store any BCCH.

Cell Reselection Process.

•Cell reselection in same Location Area.•Cell selection in different Location Area. C2=C1+CRO-TO*H(PT-T)

115

MS _ TXPWR _ MAX _ CCH

•This parameter determines the maximum allowed output power of the MS when it begin to access a cell, and has not yet received power control.•Recommended value 900M(5), 1800M(0).

RXLEV_ACCESS_MIN

•The minimum receives signal level required for MS to access a cell.•Recommended is -102dBm.

CRO

Cell Reselection Offset: Manual adjustment of the value of C2 to motivate MS cell reselection.

CRH

Cell Reselection Hysteresis: Parameter utilize when cell reselection is between two location areas.

116

Network Functions Parameters

•Uplink Discontinuous Transmission•Call- Re-establishment Allowed.•EC Allowed.

117

MODULE 8: SPECIAL NETWORK SOLUTION

•Dual Band Network Topology•Speech codec•Multi-band Cell Network•Concentric Circle•Adaptive Multi-rate and Speech optimization.

118

1) Types of Frequency band

•900M•1800M

900M•124 channels available.•Limited capacity; •maximum number of subscribers is 40 million on 900M macro cells.•Suffers less fading and losses when compared to 1800M, hence utilized as coverage band.

1800M•374 channels available.•More capacity than 900M, about 3 times that of 900M, hence utilized as capacity band.•Suffers more fading and losses

119

Types of dual band technology: Topology

1. Independent MSC networking.

2. MSC-sharing / independent BSC networking.

3. BSC sharing networking.

120

) Independent MSC networking.

•Explicit network planning.

•Clear network data configuration.

•Easy implementation and engineering.

•Meets long term network expansion.

•Convenient for whole network management and new service

development.

•It needs large volume of initial investment in network building.

121

MSC sharing/ BSC independent networking

•Exert great significance upon original network.

•Has limited expansion space.

•Slight difficulty in implementation and engineering.

122

BSC – sharing (Hybrid)

•Exert great influence upon the original network.

•Requires re-planning of the NSS.

•Difficult to implement.

•Small volume of initial investment

123

Traffic Control Management Policy

To implement flexible and effective dual band traffic guidance and control, various control policies are used ;

•Idle mode MS selects 1800M.

•In stand by state, MS selects 1800M.

•In communication state, MS utilizes cell layer and priorities based on the HCS, to choose cell.

•Various dual-band traffic handover methods can be used to implement reasonable traffic load.

124

Traffic balancing between 900M and 1800M

Idle mode. Active mode.

Idle mode;CRO: Cell Reselection Offset.

C2 = C1+CRO

Active ModeInter-Layer Handover Threshold

125

SPEECH CODEC

Full Rate

Data transmit rate is 13kpbs.

Half Rate

Data transmit rate is 6.5kbps

Enhanced Full Rate

Data transmit rate is between 13kbps and 16kbps

126

Multiband Cell Network Structure

Multiband Cell structure defines

•One frequency band per cell.

•Handling of propagation differences between high and low bands

•Channel selection based on existing channel allocation and MS capability.

•Improves the radio performance and the traffic capacity.

•The number of cells and the neighbour relations are significantly reduced.

•One more timeslot for traffic in the non-BCCH frequency band.

•Dynamic overlaid-underlaid is a prerequisite for MBC

127

Overlaid-Underlaid

1. The traffic capacity of a cellular network can be increased by adding more frequencies or reducing the frequency re-use distance.

2. One approcah is to aply a second frequency re-use pattern, using the existing sites, with a tighter frequency re-use as overlaid on the existing pattern.

128

Adaptive Multi Rate

Possible to change speech codec during a call, depending on the interference conditions.

Improves speech quality at low C/I

Apply tighter frequency re-use in a network high AMR capable MS penetration.

Provides enhanced speech quality for AMR mobiles in the network.

The enhanced speech quality also provides better coverage at the edge of the cell, thus making it possible to increase the coverage area.

AMR tolerates more interference than the old speech codecs.

AMR enables higher traffic loads which leads to higher capacity.

129

The speech quality enhancement is divided in two parts:

1. Robust FR channel2. Audible FR Channel

AMR Transcoders

There are 8 different codec modes available in AMR, namely:

1. 12.2kbps2. 10.2kbps3. 7.95kbps4. 7.40kbps5. 6.70kbps6. 5.90kbps7. 5.15kbps8. 4.75kbps

130

An active codec set may contain up to 4 coec modes; all using the same channel rate

12.2kbps and 10.2kbps can only be used in FR channels and the other six can be used in both FR and HR.

131

Module 9: Radio Network Optimization: Quality of Service.

RNO process flow. KPI definitions: Interference, Call Drop, Call Setup, Handover, & Congestion. RNO methods: Drive test & Call Quality Test.

RNO Case studies.

132

RADIO NETWORK OPTIMIZATION: QUALITY OF SERVICE.

Network Optimization refers to reasonable modification to planning and designing of communication networks according to certain principles so that a more reliable, more economic network operation, a higher QOS, and a higher utilization of radio for network resources can be achieved.

Mobile communication network is divided into three parts:

•Mobile switching.•Transport network.•Radio network.

Radio network is the most decisive factor in quality of service because of mobility of subscribers and the complexity of radio waves in propagation.

133

Radio Network Optimization Process Flow

134

Preparatory work

•Knowledge of progressive slates in network construction•Analyzing the operation states of network•Preparing for optimization test equipment•Network planning report•Collection of engineering and designing information

Basic network information gathering•Further inspection on local radio environment•Hot spots of traffic•Confirmation of engineering parameters and network indices for practical installation•Customer complaint gathering

135

Data Collection•Subjective reflection of mobile subscribers•Drive test data.•OMC/ Traffic statistics data

Data Analysis

•Back analysis of optimization of software•OMC traffic statistic analysis•Drive test log analysis

136

Network parameter modification

•Network engineering parameters•Network function parameters

Network optimization report

•Methods utilized in the process.•Network performance indices expected.•Positive suggestions for network development

137

KEY PERFORMANCE INDICATORSRadio network optimization means network performance improvement utilizing existing network resources. The purpose is increasing the utilization of network resources solving the existing and potential problem on the network, identifying solution for future network planning.

Three main elements of any mobile network is capacity, quality and coverage. These forms the basis of definition of the Key Performance indicators.

Typical KPI

•Call drop•Interference•Call setup•Handover•Congestion

138

CALL DROP

Call drop here refers to call drop after distribution of traffic channels. It has been the hot spot of complaint from subscribers. There are two types of call drop: TCH call drop and SDCCH call drop.

Call drop is caused by:1. Coverage hole2. Interference 3. Handover failure4. Imbalance of uplink and downlink5. Inappropriate parameter configuration6. Equipment failure

Call drop is measured as call drop rate.Measurement benchmark varies from operator to operator, but the

standard is 2%. TCH call drop rate = TCH call drop x 100% Successful TCH seizure

139

INTERFERENCE

Mobile networks make use of frequency multiplexing to improve application efficiency of spectrum and increase system capacity. Mean while it also brings forth co-channel and adjacent channel interference (internal interference). There are also other interference caused as a result of multi-path effect and external factors like repeaters.

Downlink interference is measured by voice quality level, which is a factor of the bit error rate.

Uplink interference can be measured with certain interference band definition in the OMC.

Also measurement reports for both uplink and downlink can be viewed with a Signaling Analyzer connected to the Abis interface. In this way uplink and downlink interference can be measured.

140

HANDOVER

When a mobile subscriber moves from one cell into another, handover must be implemented. Otherwise voice quality maybe greatly reduced. In some cases even call drop may occur.

Causes of Handover Failure

•Congestion in adjacent cells•Missing neighbor relation •Equipment failure•Interference•Coverage hole

141

CONGESTION.

Inadequate resources causes congestion.

Types of congestion.

•Radio Resources congestion: TCH, SDCCH congestion•Non Radio Resources congestion: A interface circuit congestion.

142

RADIO NETWORK OPTIMIZATION

Drive testCall Quality Test •Traffic Statistics Measurement.

Drive Test

The quality of the network is ultimately determined by the satisfaction of the users of the network, the subscribers. Drive tests give the feel of the designed network as it is experienced in the field.

The following are frequently used drive test tools:

•TEMS INVESTIGATION•ANTPILOT•NEMO•AGILENT•NEPTUNE

143

The test can be cell selection, cell reselection, frequency scanning in idle mode, regular dial test and continuous conversation test in dedicated mode.

The data received include:

•Rx-Level•Rx-Quality•TA•BER•FER•SQI

A typical drive test tool setup is made up of:

•Laptop•Drive test software•GPS•Test MS

Drive test also benchmarks the performance of other operators.

144

Traffic Statistics Measurements.

Network traffic statistics are monitored from the OMC daily by the operator with the help of a counter. The OMC usually measures the functionalities such as call setup failures, dropped calls, and handovers. It also gives data related to traffic and blocking in the radio network, apart from giving data related to quality such as FER, BER, field strength and frequency hopping functionalities such as:

•Data related to traffic and blocking rate. •Data related to quality such as FER.•Network Performance Assessment.

Network Performance Assessment Measurement

•Amount of traffic and blocking •Resource availability and access•Handover related parameters•Receive level and quality•Power control

145

RNO CASE STUDIES

Coverage •Coverage Hole

Coverage hole may exist when coverage areas of two BTS do not overlap accordingly, or there are some big obstacles in the coverage area and this leads to no signal or very poor signal level.

Solution

To improve the coverage of BTS at the area, add a new BTS, or extend the coverage of the site if proper frequency planning with the neighboring sites has been taken care of. Coverage holes in valleys and shops can be covered with new BTS or repeaters.

While for underground garage and high building coverage, a repeater, leaking cable technology and micro-cell technology can be used.

146

Over shooting

This is when a BTS with high antenna propagates beyond its prescribed boundary, which results in a phenomena called “Isolate Island”.

Solution

•Adjust the antenna down tilt and output power of TRX.•Change the azimuth•Add missing adjacent cells.

147

CONGESTION

Traffic congestion

With OMC traffic statistics data, TCH congestion rate can be obtained (with occupation at all busy). It is possible to judge the traffic congestion status by comparing the busy hour traffic volume against calculations capacity of each base station cell.

Solution

•Add more carriers•Cell splits•Construction of new base station•Adopt dual frequency networks where necessary.•Add micro cells.

148

Traffic Balance

•Traffic balance can be implemented between •Two cells in a sector or sectors in a site•Sites in a common area.

Solution

•Modify antenna height, down tilt, transmission power of base station.•Modify the traffic related parameters.•Start load handover.

149

Module 10: Mirroring Advance Technologies.

GPRS. EDGE. 3G/UMTS/WCDMA.

150

GPRS – General Packet Radio Services.

GPRS is a non voice service; i.e data; a value added service to the GSM network. This done by overlaying a packet based air interface on the existing circuit switched GSM network.

Theoretically, GPRS carries a, maximum speed data rate of 171.2kbps while using all the eight timeslots.

GPRS SYSTEM

The GPRS system is oriented towards providing a data service, and to upgrade a GSM system to a GPRS system, new hardware and software solutions are implemented mainly

(1) SGSN GGSN and PCU are major hardware overlaid on the existing GSM.(2) Relevant software upgrades.(3) High level coding schemes utilized

151

152

(1) SGSN – Serving GPRS support node

•This is the service access point for the mobile station.•Functions include mobility management, registration and authentication.•Interacts with mobile, with packet data flow and functions related to compression and ciphering.•Most important element of the GPRS network.

(2) GGSN- Gateway GPRS Support Node

Serves as the gateway between the SGSN (network sides) and the outside external networks such as the internet and X.25.

(3) PCU –Packet Control Unit

Incorporated in the GSM BSC to manage GPRS traffics.

153

GPRS MOBILESGPRS mobiles are different from GSM mobiles due to their ability to handle packet data at a higher speed.

There are three classes of GPRS mobiles.Class A -Handles both GPRS and GSM simultaneously.Class B –Handles both GPRS and GSM, but one at a time.Class C – Handles only GPRS or GSM.

GPRS CODING SCHEMES

In GPRS there are four coding schemes that are used for packet data, namely CS-1, CS-2, CS-3 and CS_4.

154

GPRS INTERFACES

Interfaces in GPRS networks are called G interface. There are number of G interfaces namely,

•Gb = Between BSS and SGSN.•Gn = Between SGSN and SGSN/GGSN of same network.•Gd = Between SMS-GMSN/SMS-INMSC and SGSN.•Gp = Between SGSN and GGSN of other networks.•Gs = Between SGSN and MSC/VLR.•Gr = Between SGSN and HIR.•Gf = Between SGSN and EIR.•Gi = Between GGSN and external networks (internet).

155

EDGE – Enhanced Data Rate for GSM Evolution.

GPRS networks are able to handle higher bit rate than GSM networks, but the data rate still fall short of what is required to make existing GSM network deliver services at a speed comparable to that promised by third generation networks. The delay in the deployment of third generation systems led to the emergence of a technology known as EDGE. This was capable of delivering services similar to those of third generation networks, yet with implementation on the existing 2nd generation network (GSM).

EDGE stands for Enhanced Data Rate for GSM Evolution. The enhancement from GSM is in two phases: first from GSM to GPRS, and from GPRS to EDGE

156

EDGE SYSTEM

Edge system is quite similar to the GPRS system, but has capability for higher, data rates. The data rate can go up as much as 500kbps (theoretically).

A major change in the EDGE is the modulation scheme used. Octagonal phase-shift keying (8-PSK) modulation is used which enables a three fold higher gross data rate of 59.2kbps per radio time slot.

157

EDGE Coding Scheme.

EDGE system is an enhancement to the existing GPRS system.Here are 9 modulation and coding scheme (MSC-1-MCS-9) that provides different throughput.

The table below illustrate the coding scheme.

158

3G- THIRD GENERATIONS NETWORK

Third generation UMTS (Universal Terrestrial Mobile System) network have a predominance of data traffic, unlike GSM networks. The rate at which this data traffic is delivered is higher than that offered by GSM/GPRS/EDGE networks.

3G networks serves a different purpose to earlier networks, and major changes from previous network types are:

( i ) Maximum user bits rates up to 354kbps.( ii) Efficient handover between different operators and technologies.(iii) Ability to deliver requested bandwidth.(iv) Ability to deliver different services (CS & PS) at the same time, at required quality.

159

WCDMA – Radio Fundamentals

WCDMA is known as Wide-Band Code Division Multiple Access. It has emerged as the most preferred and most adopted technology for the third generation air interface.

The table below illustrate the difference between WCDMA and GSM

160

SERVICE CLASSES IN 3G

• Ability to maintain multiple connections simultaneously.• Allows efficient cooperation between applications with diverse

quality of service.• Allows adaptive application that will function within a wide

range of QoS setting.• Quality can be defined by two main parameters:

1. Guaranteed and maximum bit rate (kbps) possible.2. Permissible delays.

• Both single media and multi media service will be handled in the 3rd generation networks.

Based on QoS criteria, multi-media services have been further classified as

(a) Conversational(b) Streaming.(c) Interactive.(d) Background.

161

Radio Network Controller (RNC)

Radio Network Controller, is similar to the BSC in GSM/GPRS networks, but is rather more complicated and has more interface to handle.

Its functions includes:”Radio resources managementMobility management.