Radio Network Optimisation Process for umts 2nd phần 8 pot

Counters and Network Resources The defined physical measurements must always represent a collection of counters in relation to a network resource (Section 7.1.1.3). The most common example of a network resource is the UtranCell. Others are the RNC or a defined interface (Iub, Iur, Iu). Before collecting the counters from the network and using them in making the right measurements, one characteristic of the radio access network must be noted and also shown in the measurements. This is the role of an RNC, which can act as an Serving RNC (SRNC), Drift RNC (DRNC) or Controlling RNC (CRNC). Some measure- ments are carried out in a CRNC and the counters are also separated for SRNC and DRNC. These measurements are currently: . L3 signalling at Iub/Iur; . soft handover/intra-system handover; . traffic. Other measurements are also carried out in a CRNC but counter separation into SRNC or DRNC is not needed. These measurements are currently: . L3 signalling at Iu; . RRC signalling; . cell resource. Some measurement s are carried out in an SRNC. These are currently service level measurements. Figure 7.22 presents a view of the radio network measurements obtained from a radio access network. Naming of the Counters Every measurement must have a unique identifier – e.g., M1000C1. This means that only one object in the network can own the measurement in question and only one measurement type under that object can have that name. Other relevant information depen ds on the ‘usage’ of the measurement. Information common to all counters is the counter name, reason for update, and dependences on other counters. For fast and network-wide follow-up/optimisation, counter names should correspond to standardised names and terms – one naming conventio n is introduced in [16]. Reason for Counter Triggering All measurement descriptions should include a sufficiently detailed description of the reason or con dition for the update – e.g., signalling-related, failure, policy decision, together with dependences on other measurements, if any. For QoS and control- and signalling-related measurements the triggering point is essential information. This tells at what stage of a signalling sequence the counter was triggered. For example, for a mobile-terminated call a successful RRC connection setup can be triggered as in Figure 7.23. Radio Network Optimisation Process 429 7.3.3.3 Measurement Storing and Post-processing Storing of Raw Measurements It is necessary for the network element to retain the measurement result data it has produced until they have been sent to, or retrieved by, the destination OSs. The storage capacity and the duration for which the data will be retained at the network element will be operator- and implementation-dependent. If the measurement result data are routed to a network manager via the element manager, then it is necessary for the element manager to retain the data at least until they have been successfully transferred to the network manager. Typically the measurement results produced by network elements are transferred to an external network management system for storage, post-processing and presentation to the system operator for further evaluation. In a network with more than one network management system the data may be required by several OSs in order to handle the regional border areas. It is therefore necessary to support the possibility for multiple destinations for the transfer of measurement result data. From the network element to the element manager, the results of the measurement jobs can be forwarded in either of two standard ways: either as notification or as files. In the first case the scheduled result reports are sent to the element manager as soon as they are available. In the latter case the reports are stored in the network element (files) and transferred to or retrieved by the element manager when required. 430 Radio Network Planning and Optimisation for UMTS ATM MODULE RNC AXC BTS L3 Signalling Radio Network Monitoring in RNC SGSN Iu-CS Iu-PS Iur Iub AXC Iub RRC RRC RNC CRNC CRNCSRNC CRNC CRNC CRNC CRNC TrafficHandover CRNC /DRNC CRNC /SRNC BTS Cell Resource BTS Cell Resource RAN /(SRNC) /(DRNC) /DRNC /SRNC UE Service Level Figure 7.22 Radio network monitoring in a radio access network. Radio Network Optimisation Process 431 RRC Setup success counter triggered here RRC Setup attempt counter triggered here RNC CNMS BTS RRC Setup attempt counter triggered here RRC Setup success counter triggered here RRC:RRC CONNECTION SETUP NBAP:SYNCHRONIZATION INDICATION NBAP:RADIO LINK SETUP NBAP:RADIO LINK SETUP RESPONSE RRC:CONNECTION SETUP COMPLETE RRC:INITIAL DIRECT TRANSFER RRC:RRC CONNECTION REQUEST RANAP:INITIAL UE MESSAGE Connection established AAL2 Setup L1 synch RANAP:COMMON ID MS-CN signalling RANAP:RAB ASSIGNMENT REQUEST NBAP:RADIO LINK RECONFIGURATION PREPARE NBAP:RADIO LINK RECONFIGURATION READY AAL2 Setup AAL2 Setup NBAP:RADIO LINK RECONFIGURATION COMMIT RRC:RADIO BEARER SETUP RRC:RADIO BEARER SETUP COMPLETE RANAP:RAB ASSIGNMENT RESPONSE RANAP:PAGING RRC:PAGING TYPE 1 Figure 7.23 Triggering a successful radio resource control connection setup. From the network to the network manager, measurement results can be forwarded via a bulk transfer (i.e., file-based) interface. It is an implementation option whether this inter face to the network manager resides in the element manager or in the network elements. There are several different users (e.g., network planners, operations engineers, business managers) for the measured data. Therefore, the collected data should be stored in databases where these users can access it easily. Because of the large number of users, data should be collected frequently and in the short term. For essential measurements, data collection and storage every hour is recomm ended. The amount of data collected can vary greatly, depending on the measurement activated. Usually a measurement includes between 50 and 300 counters. The sizes of the collected measurements together with their collecting frequencies should be taken into consideration when reserving storage capacity in a network element). Post-processing of Raw Measurements To obtain optimal benefit from the collected information, a network management system should have good post-processing facilities for the raw measurements. Usually it is very hard to notice problems in the network just by looking at the counter values; some graphical presentation is needed. With graphical views where a user can compare counters and other measurements with each other on a screen, problem solving is fast and more extens ive. More about data processing and advanced visualisation and analysis methods for measured performance data is in Chapter 9. 7.3.3.4 Radio Access Network Key Performance Indicators Operators have historically reported the performance of their networks against a set of KPIs. These KPIs are inherently network focused and they provide an indication of the end-to-end service delivery that the network supports. Nevertheless KPIs are an important measurement for network operations and will continue to be so for the foreseeable future. By definition a PI is a measure that gives information about the performance of a network element, a process or a function in an NE or in a network subsystem. A KPI is considered an important performance measure to be followed. Later in this chapter, the term ‘KPI’ is used for both cases. In a radio network operator’s organisation, different groups (management, marketing, operations) are interested in slightly different sets of KPIs in their reports – i.e., there is a need for several KPI sets to fulfil all parties’ needs – and the definition of a ‘KPI set’ is always a subjective matter. The move towards service-focused management leads to a requirement for a new ‘breed’ of indicators that are focused on service quality rather than network performance. These KQIs are discussed in more detail in Chapter 8. 432 Radio Network Planning and Optimisation for UMTS Radio Access Network Measurements to Key Performance Indicators Most KPIs are composed of several raw counters or other measurements collected from the network, mainly because a single raw measurement is at too detailed a level to be used as a KPI as such. However, there are exceptions where a collection of single raw measurement values can be used as a KPI. Also, the excessive number of raw counters would cause problems in understanding the real status of the network. Raw counters can be compiled to meaningful KPIs by using various equations – i.e., logical counters. In a WCDMA radio access network there are tens of differen t KPIs to be followed, and there might be several different formulas to calculate a measure which may depend on object level, features used in network elements, etc. To define a formula for RAN calculations, a deep knowledge is required of the interest group’s needs, the WCDMA system, vendor-specific counter implementation, basic mathematics, statistical methods and the statistics tools in use. 3GPP has done extensive work to define a uniform set of measurements that should be collected from the network elements of any vendor [16]. These KPIs include RAB management KPIs, like attempted RAB establishments for the CS/PS domain, successful RAB establishments wi thout queuing for the CS/PS domain, failed RAB establishments without queuing for the CS/PS dom ain, successful RAB establishmen ts with queuing for the CS/PS domain and failed RAB establishments with queuing for the CS/PS domain. In addition to RAB-related measurements numerous RRC-related measurements are defined. These include RRC connection establishment and release related-measurements. In the handover area numerous soft handover and hard handover measurements are proposed. Reference [16] also contains definitions for measurements in SGSN, GGSN, Iu and Gn interfaces. In addition to these standardised measurements vendor-specific KPIs are needed in order to monitor RRM performance and its impact on the network and service quality. The first sample equation is presented in Equation (7.1): the RAB setup and access complete ratio for CS voice calls (i.e., a subset of CS domain measurements). The formula is based on cell-level measurements and related counters. The numerator is the sum of all successfully completed RAB setups (RAB setup and access phases included), and the denominator is the sum of all setup attempts. This formula could also be used, as such, for area levels covering several cells: 100 Ã Sum(RABSetupAccCompforCSVoiceCall) Sum(RABSetupAttforCSVoiceCall) % ð7:1Þ Equation (7.2) gives a sample formula for calculating a RAB setup complete ratio, including all traffic classes. When using a formula the study period may be different from case to case. One might be interested in busy hour (or busy period) averages from the previous week, while others might want to analyse 24 hr averages from the previous month. The formula itself does not change when the study period changes, but there might be a need to define several templates in the reporting tools used: Radio Network Optimisation Process 433 Sum(RABSetupAccCompforCSVoiceCall þRABSetupAccCompforCSDataCallConvClass þRABSetupAccCompforCSDataCallStreamClass þRABSetupAccCompforPSDataCallConvClass þRABSetupAccCompforPSDataCallStreamClass þRABSetupAccCompforPSDataCallInteraClass 100 Ã þRABSetupAccCompforPSDataCallBackgClass) Sum(RABSetupAttforCSVoiceCall % ð7:2Þ þRABSetupAttforCSDataConvClass þRABSetupAttforCSDataStreamClass þRABSetupAttforPSCallswithConvClass þRABSetupAttforPSCallswithStreamClass þRABSetupAttforPSCallswithInteraClass þRABSetupAttforPSCallswithBackgClass) KPI documentation plays a very important role, especially since terms such as Drop Call Ratio (DCR) are heavily overloaded – i.e., different parties use the same names when referring to slightly or even totally different things. Typically, each formula has a unique reference code, name, description and calculati on formula. Alarms collected from the WCDMA RAN can also be used as KPIs. Some typical KPIs are listed in Table 7.1. 434 Radio Network Planning and Optimisation for UMTS Table 7.1 Typical WCDMA key performance indicators. Note that some of the measurements are vendor-specific. Object Metrics Capacity Average uplink loading [dBm] Average downlink loading [dBm] Average random access channel throughput [kbps] Average forward access channel throughput [kbps] Average paging channel throughput [kbps] Uplink dedicated channel throughput [kbps] Downlink dedicated channel throughput [kbps] Access Radio resource control setup and access complete ratio [%] Radio access bearer setup and access complete ratio, for each traffic class [%] Success Radio resource control drop ratio [%] Radio access bearer drop ratio, for each traffic class [%] Handover Soft handover overhead [%] Hard handover failure ratio [%] The KPI-reporting environment from raw measurement to KPIs is depicted in Figure 7.24. Before analysing the network’s performance, special attention should be paid to how the KPI formula has been implemented in the reporting tool and how the tool has been used: the measurement period, the number of measurement samples during the study period and the averaging method used. In addition the user group plays an important role. Management needs are different from planning engineers’ needs. At worst, one may end up with totally wrong conclusions when analysing the reported PIs if the items listed above are not co nsidered and understood. Reference [16] contains an extensive list of KPIs as defined by 3GPP. 7.3.3.5 Radio Access Network Optimisation Process and Key Performance Indicators The radio access network optimisation process can be defined in very many ways depending on the focus. In Figure 7.25 a simplified WCDMA radio access network optimisation process is describ ed. An operator’s master/business plan sets the framework for both short- and long-term performance criteria in terms of planned service area, call blocking and service mix used in dimensioning, soft handover overhead, etc. The process in Figure 7.25 can be divided into three different areas – namely, preparations, measurements and optimisation. During the process it is important to support the rollback functionality in order to return to the previous configuration if needed (see Section 7.3.2). The starting point for the preparation phase is related to short- and long-term planning related to new services, capacity expansion needs, service area expansions and additional tasks related to new features in network elements or network element upgrades. During the preparations phase the performance targets are defined for Radio Network Optimisation Process 435 OPERATOR’S USER GROUPS MANAGEMENT MARKETING PLANNING O&M CUSTOMER CARE PI zz KPI ac a b c KPI ab KPI xx . . . . . . PI KPI REPORTS DISTRIBUTION GENERATION WORK PROCESS KNOW - HOW TOOLS KNOW - HOW FORMULAE KNOW - HOW PERFORMANCE STATISTICS SERVICE . . . . . . PI PI PI Figure 7.24 Reporting environment. short- and long-term acti ons. KPI targets are defined for capacity-, coverage- and quality-related measures. Once those measures are defined the method to collect the information is chosen. Two main sources of measurements can be identified: statistics using the management system and the field measurement tool. For management system measurements the following items are defined: . resources and their availability; . list of KPIs to be followed; . measurement schedules (start and stop time); . summarisation level; . scope (the objects to be followed); . reporting. In the case of the field measurement tool the measured indicators and their post- processing, measurement routes, services to be used (voice, CS/PS data) and number of calls to be generated are addressed. During the measurement phase, measurements are collected either by storing the counters and other raw measurements in the performance management database or by collecting the information with the field measurement tool. In (signalling) trouble- shooting cases, measurements can be appended with information from a protocol analyser. During the optimisation phase, measurements are post-processed an d the acquired information is utilised in optimisation or troubleshooting activities. The alarm history 436 Radio Network Planning and Optimisation for UMTS Report actions, progress Preparations Measurement plan QoS criteria Tool guidelines Master Plan: general operating process definitions Business plan Update long/short term quality targets Set taargets Plan measurement Define tools Define reporting practises and templates Customer feedback Customer view of the NW Measurement service platform Warehouse Warehouse Active measurements Conduct measurement Store data Field meas. data OMC meas. data Store data Service platform NW configiguration Alarm history Service optimisation platform Identify problem Plan Action Track changes Analyze and verify performance Resolution database Action plan/ request Change history Record actionImplement action Service development platform Long term planning: new features, new services, capacity/coverage expansion Reports NW configuration Set targets Define reporting practices and templates Figure 7.25 A simplified WCDMA radio access network optimisation process chart. and customer complaints can help the optimisation personnel to find and solve problems. For optimisation tasks, configuration information is also essential – as indicated in Figure 7.2. During the optimisation phase, measurement data/reports are analysed together with the configuration information, alarm history and feedback from customer care. Possible problems are identified and an action plan is derived with the support of a resolution database. Two main types of resolutions can be introduced: hard ones and soft ones. Hard ones are associated with hardware-related changes, meaning antenna bearing, antenna type or antenna tilt change, site additions, network element hardware changes, etc. Soft changes are parameter changes that can be done centrally using management system capabilities. During the optimisation phase, cost and benefit con- siderations are made when deciding what type of change to make and in which order to perform the changes. After the planned action has been implemented, the measurement results are analysed again to find out whether the taken action caused positive changes in the performance metrics. Service optimisation can be considered a never-ending task, aiming to maximise the amount of traffic without sacrificing quality. 7.3.4 Measurement Applications in Network Elements and in the Network Management System In this section measurement support in the RNC and network-wide measuremen t support at the network management service level are introduced. 7.3.4.1 Real Time Monitoring in the Radio Network Controller In addition to earlier described and presented measurements – which are processed with a delay and thus the results cannot be utilise d immediately – there should also be real time tools providing monitoring possibilities for looking more deeply at the radio network. The one presented here is online monitoring, in which the user selects a specific monitored item – e.g., monitoring type – and according to parameters – e.g., cell-by-cell – tells from which pa rt of the radio network the detailed information should be obtained. In Figure 7.26 the administration window is shown. Two different screenshots are chosen as examples: 1. The monitoring of load behaviour in a cell. 2. The monitoring of handovers in a cell. The result of (1) can be presented as in Figure 7.27 and (2) in Figure 7.28, respectively. The first screenshot shows the load behaviour in the uplink of a selected cell in relation to basic admission control parameters. Uplink total interference is presented as PrxTotal and the own-cell real time user and non-real time user loads are seen as L_RT and L_NRT. The admission control parameters are presented as PrxNoise (noise floor), PrxTarget (planned uplink interference) and PrxOffset. The second screenshot shows the distribution of different handover types in a cell and the relation of successful and unsuccessful handovers per handover type. There can also Radio Network Optimisation Process 437 be other possibilities to be monitored real time like the distribution of differen t handover-triggering causes received from the UE (User Equipment) (handover reasons are shown in the screenshot). 7.3.4.2 Mobile Tracing Functionality Measurements and online monitoring tell about service usage, traffic amounts, radio link characteristics and all kinds of errors detected in the radio network. But for locating problems for individual users/mobiles the operator must also have a means to pinpoint a specific user (IMSI) or a specific mobile (IMEI) from the network. This is done by the tracing functionality. Trace is a network-wide tool to collect all kinds of information for a user/mobile from all the network elements (BTS, RNC, MSC, etc.) and all the interfaces (RRC, Iub, Iur, etc.). Figure 7.29 depicts the trace activation mechanism. Trace Activation The activation of trace is not possible from any part of the network. Only the HLR and the Visitor Location Registers (VLRs) know if and when a certain UE is registered to 438 Radio Network Planning and Optimisation for UMTS Figure 7.26 Cell-level online monitoring administration. [...]... verification of adjacency definitions for location and routing areas This visualisation function can be used in the scope selection of the optimisation case For example, the KPIs are sorted according to the performance level Objects (or network elements) whose performance is below a set target are selected for further analysis and optimisation Radio Network Optimisation Process •Performance Analysis •Scope Selection... 7.37 7.3.6 Field Measurement Tool The optimisation process of a network is easily understood as something conducted purely in a centralised manner – e.g., by utilising network management systems that allow control of the network by, say, parameter adjustment In many cases, however, a Radio Network Planning and Optimisation for UMTS 4 48 Navigator view Navigation view Network topology topology Multi-technologyview... (DPCH) SIR 7.3.6.3 Field Measurement Sub -process of the Network Optimisation Process In general, network optimisation is the part of the WCDMA network planning process that enables the availability of various network services and provides a defined service quality and performance During the network launch period, however, troubleshooting is the main focus of pre-launch optimisation This concentrates on locating... related to service quality is provided Further sources for information about protocol interactions in IP (Internet Protocol) stacks are [8] , [11], [15] and [19] The classification is necessarily only a rough guide to IP-based services and may need to be applied in a modified form for special services Radio Network Planning and Optimisation for UMTS 4 58 8.3.1 Generic Issues There are certain issues that... of the route, resulting in highly variable measurement–vehicle speeds along the route (from 0 to 50 km/h) Radio Network Planning and Optimisation for UMTS 452 GSM MSC GSM A-interface MS for MS for Functional Functio tests: tests: Speech Speech + data up data up to 384 kbit/ 384 4,8W kbit/s 4 .8 W BS in Suosaarenkallio ATM BSS transmission BS in Upseerinkatu MCC-SIM Connection to LAN A router or a bridge... thresholds per probe This information is sent to the network management system where several applications can use these data to conclude both network and service performance Radio Network Planning and Optimisation for UMTS 446 1 Verify QoE, e2e via MT connected to probe 2 Verify Mobile Network only (GPRS or 3G) 3 Verify IP Backbone (between Core Sites) 4 Verify Service Platform (services offered via... Planning and Optimisation for UMTS 462 UMTS UTRAN/ GERAN MT TE CN Iu edge node TE CN Gateway End-to-End Service TE/MT Bearer Service External Bearer Service UMTS Bearer Service Radio Access Bearer Service Radio Bearer Service Iu Bearer Service BB Service Physical Radio Service Figure 8. 2 CN Bearer Service Physical Bearer Service An illustration of 3GPP bearers for UMTS [1] UMTS part as well as parts... vehicle On Radio Network Planning and Optimisation for UMTS 450 GPS or DGPS • Computer running the field measurement tool software location and time information • UMTS Terminal (UE) • 3GPP compliant measurement abilities real-time map display Terminal I/F GPS I/F File I/F File (input/output) map data, network configuration • measurement data storage with • location and time information Figure 7. 38 Typical... operator organisation Proper element management and network management are prerequisites for effective service management and service assurance and optimisation 454 Radio Network Planning and Optimisation for UMTS References [1] C Willard, T Rochefolle, C.C.E Baden, J.C.S Cheung, S.G Chard, M.A Beach, P Constantinou and L Cupido, Planning tools for mobile networks Electronics & Communication Engineering... Heitzer, Mobile radio network management supported by a planning tool Network Operations and Management Symp., NOMS 98, Vol 2, 19 98, pp 483 –492 [8] G Riva, M Frullone, C Passerini and G Falciasecca, Impact of the multiple access scheme on optimal site positioning Proc of International Conf on Universal Personal Communications, Vol 1, 19 98, pp 547–551 [9] T Binzer and F.M Landstorfer, Radio network planning . rather than network performance. These KQIs are discussed in more detail in Chapter 8. 432 Radio Network Planning and Optimisation for UMTS Radio Access Network Measurements to Key Performance Indicators Most. Objects (or network elements) whose performance is below a set target are selected for further analysis and optimisation. 446 Radio Network Planning and Optimisation for UMTS Radio Access Network Packet. most out of your network. Monitoring services 444 Radio Network Planning and Optimisation for UMTS Radio Access IP Backbone Service Platform ContentAccess Transport Passive Network Monitoring Active