Sheet140#TopicQuestionAnswerExample1RNPWhat is GSM and frequency bandsU:890-915, D:935-960; U:1710-1785, D1805-18802RNPWhat is RNPRadio Network Planning3RNPHow it is done (in short)Using some inputs(area in Sq. Km and cell radius for coverage site count, subscribers & traffic(miliErlang per sub), and # of GSM channels for capacity site count) calculate how many sites will required to offer service (coverage & capacity).1. For example, to cover 100 sq. km. with 4 sq. km. per site would require around 25 coverage sites.2. For 15000 subs with 30miliErlang per subs will be a total of 450 Erlang. The number of sites with traffic capacity of 20 Erlang per sites would be apprx. 22. 3. As we have to take the maximum of both coverage and capacity sites, the final number of sites will be 25.4. Nominal cell planning is done and site survey is started. After the site survey, final site location is fixed.4RNPWhat is called clutterIt is the nature of the area, density of buidlings. Based on this penetration loss is considered. There are mainly four types of clutters - Dense urban, urban, Sub urban and rural. Penetraiton loss in Dense urban is highest and is around 25dB.5RNPWhat is Freq planning1. Using a certain spectrum allocation, reusing the GSM channel over the number of sites in a geographic area to offer GSM comminication services with reduced interference. 2.Base band hopping the reuse pattern is - 4/12, 9/27 and total of 36 frequencies(7.5MHz band) will be divided as 3 channels per cell in a 4/12 cluster resue pattern. 3. In Synthesized Frequency hopping some channels are allocated for BCCH(for example 12 channels in 4/12 cluster) and the rest 24 channels can be put in all cells in 1:1 pattern or 8 channels for each cell in 1:3 pattern6RNPWhy hexagonal pattern is followed in GSM site planningIn order to make the frequency planning easier and null filling. Null fill means the small gap between two sectors of a site will be covered by a sector of an adjacent site.7RNPWhat is interferenceDisturbance created by an unwanted signal on the channel used for communication. Normally it is two types - Co-channel interference and Adjacent channel interfernce.8What is the thresholds of Co and adjacent chennel interference?Co-channel: C/I>=9dB and Adjacent channel: C/I>=-9dB9RNPHow can be interference controlledIt can be controlled through frequency tunning, power control, maintaining proper handover border, controlling coverage through antenna tilting, azimuth change etc.10RNPWhat is the typical cell rangeIn metro area with rooftop site is 500~1500meter and in rural area with green field site 6000~8000meter11RNPWhat is the typical o/p power and Rx Sensitivity46dBm(40 watt) and -113dBm12RNOWhat is RNORadio Network Optimization13RNOWhy RNO is needed1. Improve the perforfmance of a site after it has been put on air. The traffic and radio conditions are always changing. So to imcrease capacity, improve quality and reduce coverage gaps, optimization is required.2. Planning is based on assumption thus not always 100% accurate. So optimization is done to reduce the errors coming after implementation.14RNOWhat are the kinds of RNOThere basically two kinds of optimization - Site physical optimization and site performance optimization.Site physical optimization includes antenna tilting, azimuth change, antenna type and height change etc. The detection is done through drive testing and recommendations impleneted in the field.Site performance optimization includes frequency tunning, neighbor tunning, KPI moniotring and parameter modifications etc. The detection is done through OMC data and KPIs and changes implemented in the OMC parameter database. However, Frequency tunning and neighbor tunning can also be done through drive testing and analysis15RNOWhat are the ways of physical tunningSite physical optimization includes antenna tilting, azimuth change, antenna type and height change etc. The detection is done through drive testing and recommendations impleneted in the field.16RNOWhat is tilting and which one is betterTwo kinds - Electrical and mechanical.Urban areas: Both mechanical and eletricalRural areas: Mainly mechnical17RNOWhich antenna is better in which areaUrban areas: Low and mid gainRural areas: High gain antenna18RNOWhat is frequency tunningFrequecny tunning is changing the frequency(BCCH, TCH) of a cell after the initial frequency planning has been done and sites are on air. Typically it is done when DT done or quarterly for global network19RNOWhat is neighbor tunning1. Neighbor tunning is addition/deletion of neighbors in the live network(after initial neighbor setting is done and sites are on air). This is detected either through DT(drive test) or performance KPIs. 2. In DT it can be found when the position is close to a site with strong RxLevel but handover doesn;t take place. This is also called a missing neighbor. It can also be chacked from KPI if any cell has low handover success rate becasue the propoer cell is not in the nehbor list for handover and distant cells are takeing the handover. 3. If a cell is in the neighbor list but handover attempt doesn;t take place, it is deleted.20RNOHow can you detect the interfernce in TEMS1. In TEMS if we find that RxQual becomes worse 6 or 7 but Rxlevel is stong -50 to -80dBm, then it is an interfernce situation. Then neighbor cells' BCCH and TCH has to be checked whther there is any possible interfer and then frequency retunning has to be done and DT has to be done again to ensure that RxQual becomes good (0 to 5). 2. It can also be detected if the C/I in TEMS go below 9dB21RNOWhat are the cuases of interference and what are solutions1. The causes of interfernce is mainly Co- channel and it happens even if the RxLevel if good(-50 to -80dBm). Sol: Frequency tunning.2. It can also happen when the handover doesn;t take place properly to adjacent cells and the adjacent channel RxLevel becomes very strong. Sol: Neigbor tunning and physical optimization for propoer HO border.3. However, the interfernce can also happen in low coverage areas(-95 to -110dBm) and this comes due to thermal noise in the signal. Sol: Physical optimization to improve coverage or new sites.22RNOHow can you detect a missing neighbor1. In DT it can be found when the DT position is close to a site or cell with strong RxLevel but handover doesn;t take place. This is also called a missing neighbor. It can also be chacked from KPI if any cell has low handover success rate becasue the propoer cell is not in the nehbor list for handover. 2. TEMS can also identify the missing neighbor automatically in the EVENTS window23RNOWhat is handover1. While moving in deidicated mode, maintaining the communication from one cell to its neghbor cell is called HO (handover)2. From entity aspects it can be many types: Intra-cell, Inter-cell, Intra-BSC inter-cell, Inter-BSC inter-cell etc.3. From causes it can be many types: Level(due to RxLevel), Quality (RxQual), TA(due to distance), Load(due to hgih traffic load), PBGT(due to pathloss), layer(due to priority setting of cells) HOs.24RNOWhat is power control1. It is controlling the transmit power of the MS and BTS dynamically based on the RxLevel or RxQual condition. The purpose is to transmit only minimum power required for good communication but not transmiting excessive power and thus create interference.2. it works on TCH channels only. It is applied on the BCCH as it is the coverage channel and reducing BCCH power will reduce cell coverage25TEMSHow can you monior the singal strength, quality and C/I, speech QualityPlease refer to TEMS software26TEMSWhat are the typical test setupPlease refer to TEMS DT process27TEMSWhy idle mode and dedicated mode DT is needed?What are modes of a GSM mobile?1. Idle mode mobile shows real coverage as it monitors BCCH and BCCH doesnt have any power control. It also shows Location updates and LAC borders. 2. Dedicated mode mobile shows other things like Quality, TA, handover success or fails, Call successful or unsuccessful or dropped.3. GSM mobile has three states - Idle mode(no communication), Dedicated mode (In communication) and Emergency mode (when no coverage it goes into emergency state)28TEMSHow can you check whether the cell supports Edge, GPRS, Hopping, Channel, TS etcPlease refer to TEMS software29TEMSHow can you collect log of a single operator with AMR FR codec onlyLock PLMN and AMR FR codec in TEMS30TEMSHow can you check the maximum coverage of a cellLock the BCCH of the cell and drive to the point where call drops and no further calls can be established31TEMSHow to export a logfilePlease refer to TEMS software32TEMSHow to generate TEMS reportPlease refer to TEMS software33TEMSHow can you do the indoor drive testPlease refer to TEMS DT process34TEMSWhat is GSM, GPRS, EDGEGlobal System for Mobile, General Packet Radio Service, Enhanced Data for Global Evolution35TEMSWhat are the KPIs that can be found from TEMS report generationCall attemts, Call blcoked, Call failed, Call dropped, Handpver attenpts, Handover success, handover fails, Rxlevel distribution, Rxqual distribtuion, TA distribution, SQI distribution, C/I distribution etc.Please refer to TEMS software36RNOWhat is a dropped call and why it happens and how it is improved1. When a successfully established call gets abnormal(not by users) disconnection, it is dropped.2. It normally happens in bad quality areas. Bad quality might be found in good rxLevel with high interfence situation. Sol: frequency tune and remove interfernce.3. It might happen in low Rxlevel condition(in cell edge) with thermal noise and some interfence as well. Sol: Physical optimization to improve coverage or new sites.4. It can also happen when handover doesn;t take place properly and call dragged to far distance from the cell and get dropped. Sol: Define neigbors properly and physical tune to make proper cell borders37RNOWhat is a handover fail and why it happens and how it is improved1. When attempt to move a running GSM communication from one cell to its neighbor cell fails, it is called a handpevr fail.2. Case when the neighbor is define: The neighbor can be interfered and handpver fails take place. Sol: Frequency tunning or physical optimization for proper cell border.3. Case when neighbor is not defined: The propoer neighbor is not defined as neighbor and thus hadnover takes place to a distant cell. So handover might fail in that case as well. Sol: Define neighbors and if required do physical optimiztion.38GPRSWhat is the speed of GPRS/Edge channel. How can be the speed of the mobile becomes high?How can the users share the GPRS speed?1. For GPRS and a single TS it is 10kbps. For edge and a single TS it is 59.2kbps. 2. Mobile can combine a max of 4 or 5 TS at the same time and thus speed becomes 4 times 59.2 or 5 time 59.2kbps3. In contrast to GSM voice, in GPRS many users share a single TS and then speed per single TS (59.2kbps) is divided equally among the number of users.39GPRSWhat are the states of a GPRS mobile?What is the cell change event called in GPRS?1. First the mobile can be attached(when we put the mobile in always online mode in the GPRS settings) or detached state( when we put the mobile in when needed mode in the GPRS settings) 2. For data transfer scenario, it can be Idle state or data transfer state(when it download or uploads) 3. The cell change event in GPRS is called "Cell Update" which is similar to handover in GSM40GPRSWhat are the network HW needed for GPRS service?How is the data transferred in the GPRS network1. TS(TRX) in BTS, Abis TS or E1 and PCU(Packet control unit) card in BSC.2. From MS to BTS(through air interface), from BTS to BSC/PCU(through Abis), from BSC/PCU to SGSN(thorugh Gb interface) and from SGSN to GGSN and internet cloud.

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