rf optimization and log file analysis in gsm
DESCRIPTION
RF Optimization and Log File AnalysisTRANSCRIPT
RF Optimization and Log File Analysis in GSMOptimization and Log File Analysis in GSM
1. INTRODUCTIONEvery alive Network needs to be under continues control to maintain/improve theperformance. Optimization is basically the only way to keep track of the network bylooking deep into statistics and collecting/analyzing drive test data. It is keeping an eyeon its growth and modifying it for the future capacity enhancements. It also helpsoperation and maintenance for troubleshooting purposes.Successful Optimization requires:• Recognition and understanding of common reasons for call failure• Capture of RF and digital parameters of the call prior to drop• Analysis of call flow, checking messages on both forward and reverselinks to establish “what happened”, where, and why.Optimization will be more effective and successful if you are aware of what you aredoing. The point is that you should now where to start, what to do and how to do.1.1. Purpose and Scope of OptimizationThe optimization is to intend providing the best network quality using availablespectrum as efficiently as possible. The scope will consist all below;• Finding and correcting any existing problems after site implementation andintegration.• Meeting the network quality criteria agreed in the contract.• Optimization will be continuous and iterative process of improving overallnetwork quality.• Optimization can not reduce the performance of the rest of the network.• Area of interest is divided in smaller areas called clusters to make optimizationand follow up processes easier to handle.51.2. Optimization ProcessOptimization process can be explained by below step by step description:1.2.1. Problem AnalysisAnalyzing performance retrieve tool reports and statistics for the worstperforming BSCs and/or SitesViewing ARQ Reports for BSC/Site performance trendsExamining Planning tool Coverage predictionsAnalyzing previous drive test dataDiscussions with local engineers to prioritize problemsChecking Customer Complaints reported to local engineers1.2.2. Checks Prior to ActionCluster definitions by investigating BSC borders, main cities, freeways,major roadsInvestigating customer distribution, customer habits (voice/data usage)Running specific traces on Network to categorize problemsChecking trouble ticket history for previous problemsChecking any fault reports to limit possible hardware problems prior totest1.2.3. Drive TestingPreparing Action PlanDefining drive test routes6Collecting RSSI Log filesScanning frequency spectrum for possible interference sourcesRe–driving questionable data
1.2.4. Subjects to InvestigateNon–working sites/sectors or TRXsIn–active Radio network features like frequency hoppingDisabled GPRSOvershooting sites – coverage overlapsCoverage holesC/I, C/A analysisHigh Interference SpotsDrop CallsCapacity ProblemsOther Interference SourcesMissing NeighborsOne–way neighborsPing–Pong HandoversNot happening handoversAccessibility and Retainability of the NetworkEquipment PerformanceFaulty Installations71.2.5. After the TestPost processing of dataPlotting RX Level and Quality Information for overall picture of the drivenareaInitial Discussions on drive test with Local engineersReporting urgent problems for immediate actionAnalyzing Network feature performance after new implementationsTransferring comments on parameter implementations after new changes1.2.6. RecommendationsDefining missing neighbor relationsProposing new sites or sector additions with Before & After coverage plotsProposing antenna azimuth changesProposing antenna tilt changesProposing antenna type changesBTS Equipment/Filter changeRe–tuning of interfered frequenciesBSIC changesAdjusting Handover margins (Power Budget, Level, Quality, UmbrellaHOs)Adjusting accessibility parameters (RX Lev Acc Min, etc..)Changing power parametersAttenuation Adds/RemovalsMHA/TMA adds81.2.7. TrackingRe–driving areas after implementing recommendationsCreate a tracking file to follow–up implementation of recommendations1.2.8. Other Optimization TopicsVerifying performance of new sitesVerifying handoversVerifying data after Re–HomesInvestigating GPRS performanceVerifying SectorizationsCollecting DTI Scan filesVerifying coverageVerifying propagation model by importing DTI scan files to PlanetPeriodic Consistency Checks
Frequency Planning CheckAnalyzing cell access parametersAnalyzing Handover parametersAnalyzing Power control parametersAnalyzing Frequency Hopping parameters (HSN, MAIO)Implementing/analyzing optional featuresKeep helping local engineers with emergency casesBenchmarking91.3. Before StartingThis document was prepared with TEMS screen shots from live examples of previousexperiences to guide RF Engineers on how to define/analyze problems or cases and optimizenetwork. After each case/problem demonstration, specific step to be taken will be defined andappropriate recommendation will be given.The document will be focusing on Drive Testing part of the Optimization Process and givedefinitions on basic GSM principals, features and parameters when needed.The readers of this document are considered to have basic knowledge of cell planning and TEMSInvestigation usage. Only little information will be given just to remember TEMS interface.102. DRIVE TESTINGDrive testing is the most common and maybe the best way to analyze Network performance bymeans of coverage evaluation, system availability, network capacity, network retainibility andcall quality. Although it gives idea only on downlink side of the process, it provides hugeperspective to the service provider about what’s happening with a subscriber point of view.The drive testing is basically collecting measurement data with a TEMS phone, but the mainconcern is the analysis and evaluation part that is done after completition of the test. Rememberthat you are always asked to perform a drive test for not only showing the problems, but alsoexplaining them and providing useful recommendations to correct them. Please note that asuccessful analysis should be supported by handling of network statistics from a statistics tool(Metrica/NetDoc–NMS/SRP–OSS, etc..) and careful evaluation of coverage predictions from acell planning tool (Planet, DB–Planner, TEMs Cell Planner, etc..). Please see Figure 1 for a usualview from TEMS.F
Test Types and Parameters for LTE Driving Testing
LTE drive tests are an important part of how wireless carriers determine whether their networks are performing well — and get a glimpse into their competitors’ network performance. There are multiple types of LTE drive tests, as well as specific parameters and requirements that should be met for drive tests.
LTE drive tests consist of two basic types: UE or user equipment based, and benchmark testing. UE tests consist of hooking up multiple, live end-user devices such as smartphones and tablets in order for a carrier to get a good look at how devices perform on its networks. Benchmark testing also includes UE devices that run on other operators’ networks, with some running voice calls and some making data connections, for perhaps 4-5 of the largest carriers in a given area in order to determine how an operator’s network measures up to the competition in a geographic area. Benchmark testing usually involves more devices than UE testing.
Equipment for LTE drive tests, according to Emilio Franchy, senior product manager at test and measurement company Anritsu, generally includes a scanning receiver and multiple UEs, plus a laptop that is running software to record the data from the drive testing that can later be analyzed in a laboratory. Anritsu’s Link Master ML 87110A is the company’s multiband receiver or scanning receiver, with the 10 model designed for use in North America and the 20 model for international use. The UEs provide data on performance and interactions with the network, while the scanning receiver can pick up sources of interference that can hamper network performance. Franchy said that some sources of interference can include repeaters inside businesses meant to improve cellular network signals that actually interfere with the network; and more prosaic sources such as certain fluorescent lights that can generate strong interference signals.
According to Franchy, the network trend toward small cell and distributed antenna system deployments has also meant an uptick in a new type of “drive” testing: walking, in order to best simulate a user’s experience in areas with heterogeneous network coverage such as stadiums, large convention centers, and major metropolitan pedestrian areas such as Times Square or downtown San Francisco, where a significant percentage of mobile users will be on foot rather than in vehicles.
Franchy said that Anritsu has also received requests for walking “drive” tests of railways and subways. Major new DAS installations were recently installed in New York City.
Among the major LTE drive test parameters are:
RSSI: Received Signal Strength Indicator, or the strength of the reference signal. SINR: Signal-to-Noise Ratio, which compares the strength of the signal to
background noise. RSRP: Reference Signal Received Power, the power of the reference signal. This is
an LTE-specific drive test parameter and is used by devices to help determine handover points.
RSRQ: Reference Signal Received Quality, or the quality of the reference signal; this is in part, a ratio of RSSI to RSRP
Transmission power between the UE and the base station, both uplink and downlink
Uplink and downlink throughput between the base station and the UE, in order to test the performance of MIMO antennas
For now, Franchy noted, LTE drive testing is mostly related to data performance, as Voice over LTE is not yet widely deployed. However, with larger deployments of VoLTE expected by the end of this year, LTE drive testing will soon come to include the testing of voice calls made on the LTE networks.
Although some of the LTE drive test data can be analyzed during the drive test process as it is displayed on a laptop screen, much of the details can best be examined in a lab. Software in the PC communicates with the devices’ chipsets in order to record and display the data.
Drive testing is required by the Global Certification Forum as part of its process to certify devices for wireless networks.
riday, January 11, 2013
LTE DRIVE TEST PARAMETERSRSRP :- Reference signal receive power.
• RSRP (dBm) = RSSI (dBm) -10*log (12*N)
where RSSI = Received Signal Strength Indicator
N: number of RBs across the RSSI is measured and depends on the BW
Significance :RSRP is the most basic of the UE physical layer measurements and is the linear average power (in watts) of the downlink reference signals (RS) across the channel bandwidth for the Resource elements that carry cell specific Reference Signals.
Knowledge of absolute RSRP provides the UE with essential information about the strength of cells from which path loss can be calculated and used in the algorithms for determining the optimum power settings for operating the network. Reference signal receive power is used both in idle and connected statesRange :- -44 to -140 dBm
• RSRP term is used for coverage same as RSCP in 3G
RSRQ :Reference signal receive quality
RSRQ = RSRP / (RSSI / N)
N is the number of resource blocks over which the RSSI is measured
RSSI is wide band power, including intra cell power, interference and noise.
Significance :- It provides the Indication of Signal Quality . Measuring RSRQ becomes particularly important near the cell edge when decisions need to be made, regardless of absolute RSRP, to perform a handover to the next cell. Reference signal receive quality is used only during connected states
Range :- -3 to -19.5 dB• RSRQ term is used for Quality same as Ec/No in 3G.
• SINR :- Signal to Noise Ratio.
SINR = S / I + N
S -- Average Received Signal Power
I -- Average Interference power
N -- Noise Power
Significance : Is a way to measure the Quality of LTE Wireless Connections. As the energy of signal fades with distance i.e Path Loss due to environmental parameters ( e.g. background noise , interfering strength of other simultaneous transmission)
• RSSI :- Received Signal Strength Indicator.
•
• RSSI = wideband power = noise + serving cell power + interference power
• RSSI=12*N*RSRP
• RSSI per resource block is measured over 12 resource elements.
N: number of RBs across the RSSI is measured and depends on the BW
Based on the above:
RSRP (dBm) = RSSI (dBm) -10*log (12*N)
• Significance :– Is the parameter represents the entire received power
including the wanted power from the serving cell as well as all the co channel power & other sources of noise
• CQI :- Channel Quality Indicator• Range :- 1 to 15
Significance: CQI is a measurement of the communication quality of wireless channels i.e. it indicates the downlink mobile radio channel quality as experienced by the UE .CQI can be a value representing a measure of channel quality for a given channel. Typically, a high value CQI is indicative of a channel with high quality and vice versa.
• CQI is measured in the Dedicated mode only.
•
• CQI depends on the RF conditions.
•
• Better the CQI better the throughput will get and vice versa.
• PCI :- Physical Cell Id
Range :- 0 to 503
• Significance - PCI used to identify the cell & is used to transmit the data
•
• PCI = PSS + 3*SSS
PSS is Primary Synchronization Signal ( Identifies Cell Id ).
PSS value can be 0, 1 & 2
SSS is Secondary Synchronization Signal ( identifies Cell Id
group).
SSS value can be 0 to 167.
• BLER :- Block Error Rate
• Block Error Ratio is defined as the ratio of the number of erroneous blocks received to the total number of blocks transmitted
•
Significance - A simple method by which a UE can choose an appropriate CQI value could be based on a set of Block Error Rate (BLER) thresholds . The UE would report the CQI value corresponding to the Modulation Coding Schemes that ensures BLER ≤ 10% based on the measured received signal quality
•
• BLER is Calculated using Cyclic Redundancy error Checking method
High BLER leads to loss of Peak rates & efficiency
BLER threshold should be low i.e. ≤ 10%
DDownlink Throughput
-I n E-UTRAN may use a maximum of 2 Tx antennas at the ENodeB and
2 Rx antennas at the UE ( MIMO ).
Significance - Target for averaged user throughput per MHz, 3 to 4 times
Release 6 HSDPA i.e Higher user throughput as compared to 3G ( Over 300 Mbps downlink as compared to 14 Mbps in UMTS)
- The supported user throughput should scale with the spectrum
bandwidth.
Uplink Throughput
-I n E-UTRAN uses a maximum of a single Tx antenna at the UE and 2 Rx
antennas at the E Node B.
- Greater user throughput should be achievable using multiple Tx
antennas at the UE ( MIMO )
.
- Significance- Target for averaged user throughput per MHz, 2 to 3 times Release 6 Enhanced Uplink i.e Higher user throughput as compared to 3G (Over 50 Mbps Uplink as compared to 5.76 Mbps in UMTS).The user throughput should scale with the spectrum bandwidth provided that the maximum transmit power is also scaled.
SINGLE SITE VERIFICATION SSVPosted by rizaza za on 01:08 with No comments
Single site verification SSVSingle site verification (SSV) is an audit method, where we need to check the entire KPI (Key performance indicator), coverage and quality for a single radio base station site. For GSM (Global System for Mobile Communications) network a single site has more
than twenty KPI (Key performance indicator), on the other hand for WCDMA(Wideband Code Division Multiple Access) including HSPA plus a single site has more than forty five Key
performance indicators (KPI). But all the KPI doesn’t carries the same morals, on the other hand less
significant KPI values depends on the major KPIs. So, we often check major Key performance
indicators for single site verification (SSV). The entire single site verification (SSV) can be categorized into three subcategory.
These are:
Radio frequency parameter verification (RF verification).
Radio frequency (RF) functionality test. Drive test and RNO (Radio network optimizer) verification.
Radio frequency parameter audit (RF audit):RF audit may be classified into parts:
1.General parameter audit.2.Radio parameter audit.
General parameter audit:
In general parameter audit, we have to check the coordinate(latitude and longitude) of radio base station, address, BTS/RBS information (BTS/RBS name, model or version, vendor etc.), Cluster name and type, transceiver configuration (TRX conf), business region name and type, BSC (Base station controller) name, MSC (Main switching center) name, radio base station security guard or gate keeper contract or house owner contract details.
An example of general parameter audit is given bellow:
Figure: General radio parameter audit information.
Radio parameter audit:
In a radio parameter audit, we need to check entire RF parameter such as antenna height, cell azimuth, electrical tilt, mechanical tilt, feeder cable type, feeder cable length, antenna information (model with vendor information), Base station identity
code (BSIC), allocated ARFCN (absolute radio frequency channel number) in BCCH (broadcasting control channel), Location area code (LAC) etc.
An example of RF (Radio Frequency) parameters audit is given bellow:
Figure: Radio frequency (RF) parameter audit information.
Tools and software for RF parameters audit:
Digital or magnetic compass. Digital camera. Tilting meter. Fifty meter measuring tape. Safety tools for rigger. Google Earth (Software)
Drive test and Radio network optimizer (RNO) verification:
Drive test and Radio network optimizer (RNO) verification is the final step for single site verification (SSV). For SSV drive test we need to unique arrangement for testing terminals.
Tools and Software for single site verification (SSV) drive test (DT):
TEMS Investigation data collection software.Or
Genex probeOr
Nemo outdoor. Mapinfo professional (minimum version 8.5scp) Microsoft excel (as a SSV template)
Or
Microsoft Power point (As a SSV template) Mobile Station (MS) Inverter (as a power source for laptop) GPS (Global positioning system) receiver.
An example of Drive test equipment arrangement is given bellow:
Figure: Drive Test equipment arrangement.
Drive test (DT) procedure:Drive test is the most significant event in entire verification process. For single site
verification (SSV) drive test (DT); we use three mobile stations (MS) as a testing terminal. This Mobile station (MS) are designated as MS1, MS2 and MS3 respectively. Also we use GPS receiver (global positioning system) as a testing terminal.
SSV Mobile station (MS) configuration:Mobile station-1 (MS1):
typically MS1 configured in idle mode and locked with the site. For locking Mobile station (MS), actually we have to lock Broadcasting Control Channel (BCCH) for all cell.
Mobile station-2 (MS2):
Typically MS2 configured in dedicated mode short call and unlocked. Usually short call duration is thirty seconds. There is no limit of number of test call. Test call will be continued entire test period with ten seconds as a frequent call interval period. Redial triggers should be Time out, blocked call and dropped call.
Mobile station-3 (MS3):
Typically MS3 configured in dedicated mode long call and unlocked. Usually, there is no limit for long call duration. Redial triggers should be Time out, blocked call and dropped call.
Figure: Command sequence for MS2 and MS3.
Drive Test (DT) Log collection method: Start collecting log files from the site access road of SSV (Single site verification) radio
base site to neighbor site access road, collect the log files in both way, that means from the SSV (Single site verification) radio base site to neighbor radio base site and neighbor radio base site to SSV (Single site verification) radio base site.
Run the command sequence for mobile station-2 (MS2) and mobile station-3 (MS3), cover the entire car accessible road surrounding (360 degree) of radio base SSV site. Please check the figure in bellow:
Figure: Single site verification (SSV) drive test (DT) route.
Drive Test (DT) data presentation System:Event Analysis:
All the mobile station is significant to check performance of radio base site through Drive Test (DT). We have to present major drive test (DT) event in reporting templates. The major Drive Test (DT) events comprises of number of call attempts, number of call established, call setup success rate (CSSR), number of handover attempt, number of successful handover, Handover success rate (HOSR), number of dropped call and dropped call rate (CDR). The presentation of drive test major event analysis is given bellow:
Figure: Drive Test (DT) event analysis
From Mobile Station-1 (Idle mode) SSV data presentation:
From mobile station-1 (MS1), we collect total coverage area of a radio base site and received signal strength (RxLevel) , also we check cell mismatch (feeder cable swap). An example of total coverage area and received signal strength (Rxlevel) of radio base site is given bellow:
Figure: Total coverage area of SSV radio base site.
From Mobile Station-2_MS2 (dedicated mode) SSV data presentation:
Form mobile station (MS2), we check basic functionality test, events, handover sequence number (HSN), mobile allocation index offset (MAIO) of radio base site. MS2 functionality test include call setup,call setup time, Inter Site handover, Intra site handover (handover between radio base sites own cell). We have already discussed about event analysis of Drive Test.
From Mobile Station-3_MS3 (dedicated mode) SSV data presentation:
From mobile station-3, we check received signal quality (RxQual), handover relation status (inter cell and intra cell), call continuity, serving cell footprint of SSV drive test route, overshooting of neighbor cell, planning parameter such as ARFCN (Absolute Radio Frequency Channel number) of BCCH (broadcasting control channel).An example of serving cell footprint diagram is given bellow:
Figure: Serving cell footprint of SSV DT route.
RNO (Radio network optimizer) and RNP (Radio network planner) Remarks:
RNP remarks: There is no mismatch found within planned and implemented radio frequency parameter, radio base site coverage footprint is satisfactory. RNO Remarks: Site performance is satisfactory, Key performance indicator (KPI) monitoring will be continued on daily basis.
Abstract:
ARFCN : "ARFCN means for Absolute Radio Frequency Channel number. There are 124 ARFCN in P-GSM, 175 in E-GSM, 375 in DCS 1800.
BCCH:
BCCH means for broadcasting control channel, it's a down link channel of GSM air interface. BCCH carries system information of radio base station including available features, configuration and identity.
Call setup success rate (CSSR):
"Call setup success rate is the ration between the number of handover attempts and number of successful handover. CSSR is presented in percentage."
Cell ID:
"Every individual cell of mobile network has a unique cell ID for own network, also there is a cell global identity (CGI). CGI = Mobile country code (MCC) + Mobile network code (MNC) + Location area code (LAC) + cell Id (CI)."
Drive Test (DT):
"Drive test (DT) is a network log collection procedure in vehicular mode."
Drive test (DT) Logs:
" Drive test log files include network signaling and event information; which is collected in real time through Drive Test (DT). Also we can collect logs from the BSC (Base station controller) end through IMEI(International Mobile station Equipment Identity) tracing."
Intra site Handover:
"Intra site handover is the handover between two cell of same radio base site.
Inter site Handover:
"Inter site handover is the handover between two adjacent or neighbor sites cell.
Handover Success rate (HOSR):
"Handover success rate (HOSR) is the radio between number of handover attempts and number of successful handover. HOSR is presented in percentage."
Radio frequency (RF) functionality test:“Radio frequency functionality test means for checking the various functionality of a single radio base site such as general call test (both long call and short call), call continuity test (long call only), network accessibility test (short call), data throughput test, call setup time etc."
Radio frequency parameter verification (RF verification): “Radio frequency parameter verification (RF verification) means for verifications of installed radio parameter with the previously planned radio parameter.”
