BTS

Cell Health Check Description

Authors Mika Peltonen & Teemu Karhima

Revision 1 (2008-06-25)Yasir Ikram

Cell Health Check Description1. IntroductionThe Cell Health Check facility is provided for the 3GIS Network Operations to check the BTS status and performance for a defined period of time. It is a web based program created by Performance Management (PM) Group. The program acquires the Network performance data and presents it in form of graphs and tables.

This document intends to present the features available on the Cell Health Check, how to access it and how to interpret the results.

2. Accessing Cell Health Check

In the NOC Domain open the Internet Explorer and type in the following address.

http://10.15.144.9/rap/3GISOperations/Default_Frame.htmOn the left column menu click on Tools & Info and then select Cell Health Check.3. Information Provided by Cell Health Check

3.1. Site Entry & Feature Selection Table

In this box the user can enters the Site Name, Site Id and Cell Id for which the performance data is required. User can also specify the Time Period for the KPIs, the Graph Scaling and Graph Size. Once the selection of features is made and the Site Id etc. is entered, user presses Get Report to extract the performance data for the specified time duration.

Some important points which a user should keep in mind while making selections are listed below:Time Period: User can access site data ranging from 6 hours to 180 Days. Hourly Graphs give more details about recent performance. For longer time periods data can only be seen for Daily Summarization.

Graph Scaling: It is better to use Automatic Graph Scaling so that everything fits in a graph. Fixed Graph Scaling can also be used if one wants to compare graphs between different cells.

Graph Size: It is better to use Normal.3.2. WBTS Table

The table provides information about the site.

WBTSNAMESite Name

AddressSite Location (RNC Name/Interface No./Site Priority)

Integrated DateDate Site was integrated into the Network

TPName of the Transmission Planner

CPName of the Cell (Radio) Planner

IP-AddressSites IP Address (Used for direct coupling to WBTS from user PC)

ClutterRegional information where the site is located

PrioritySite Priority

Ent StatusRepresents sites rollout phase. If site is implemented & accepted then it is either working or working_rfl.

WBTS IDSite Identity

MRSites Maintenance Region (South of Sweden: On_air_S, North of Sweden: On_air_N)

SW VersionSoftware version active on site

TTProvides a list of all Open and Closed TTs on site (as shown in figure below this table)

OpenProvides information about how many TTs are in Open Status on the site

ClosedNumber of TTs that were Closed on site for the time period selected

AlarmsProvides a list of all alarms arrived on site during the time period selected

WSPDescribes the Number and Type of WSP cards installed on site along with the usage profile of WSP Resources (WSP Resources are discussed in detail after this discussion)

TT List Table

The TT table is provided from the time site is integrated into the Network. It describes the TT Creation date, TT number and its Status. A number of other TT parameters are also shown in the list.

Alarm List Table

The Alarm list is provided for the time period; that is selected by the user. The table shows the alarm details in various columns.

NAME: Name of the BTS part alarm is related to; e.g. Cell, AXC or BTS etc.

ALARM TIME: Alarm arrival time on the Network Element

CANCEL TIME: Shows the time when the alarm is removed from site (if it is still not active)

Etc.3.2.1. WSP Resources Graph

The WSP Resource Graph shows WSP usage and its capacity. In case the WSP is overloaded the customer will get a low throughput and he might not be able to access to the service (BTS fails). In order to have a clearer view, one need to press Detailed Graph button, shown below the main graph. Most accurate data for WSP usage can be seen by pressing Click for detailed data for . This will give hourly breakdown of the WSP Resource Usage.WSP Resources Graph

The graph lines are interpreted as follows:

LineMeaningDescriptionNotes

Black LineMax avail CEMaximum Channel Element Capacity on siteThe line should be at a constant level. If it jumps up, more WSP-card (s) are added. If it goes down, one of the WSP cards is faulty or has been removed. In such case check site and its alarm history to see if the WSP card is really faulty.

Red LineMax used CE dlMaximum Channel Elements used in downlink operationsIf the line hits the Max avail CE (Black line) there will be a WSP blocking on the site. In such a case the site should be searched in the Blocking report. If it is not present there; the TT is sent to PM Engineer who will create a Blocking Ticket on it.

Green Line Min used CE ulMinimum Channel Elements used in uplink operationsThere is always fixed amount of CEs used for common channels and HSDPA.

Dark Blue LineBTS FaultsIf WSP resources run out of the CE capacity, it will be indicated as a BTS fault.If this is the case one need to check the existence of a Blocking Ticket on the site. If no BT is found and the site is seen in blocking; the TT is sent to PM Engineer who creates a BT on site.

Purple LineMin avail CEMinimum Channel Element available on siteThe line should follow Max Avail CE (Black line). If it drops below black line then the site has limited CE availability. If the line is dropping below Black line many a times then there might be some HW fault on site. One needs to check all alarms on site.

Turkous LineMax used CE ulMaximum used Channel Elements in uplink operationIf the line hits the Max avail CE (Black line) there will be a WSP blocking on the site. In such a case the site should be searched in the Blocking report. If it is not present there; the TT is sent to PM Engineer who will create a Blocking Ticket on it.

Dark Grey LineAvg used CE dlAverage used Channel Elements in downlink operation

Light Grey LineAvg avail CE Average available Channel Elements on site

Orange LineMin used CE dlMinimum used Channel Elements in downlink operationThis line can be used to identify WSP hanging resources.

Light Black LineAvg used CE ul

3.2.2. WSP Capacity on Site

There are normally two types of cards installed on BTS, namely WSPA & WSPC. WSPA card has a maximum CE (channel Element) capacity of 32 while the WSPC card has a maximum CE (channel Element) capacity of 64. A channel element supports transmission of user data on air interface communication channels e.g., air interface channels, whether traffic channels or control channels. Table below shows the usage of CE for different types of services in 3G system.

ServiceCE Usage

Voice Call1

Data: 322

Data: 64 1284

Data: 38416

Depending upon the traffic needs a variety of different WSP cards combinations can be used. In such a case it is important to determine the total WSP capacity for the site. Table below shows the total WSP capacity for different card configurations:

Number of WSP cardsMax CE capacity

1 WSPA32

2 WSPA64

2 WSPA + 1 WSPC128

2 WSPA + 2 WSPC192

Please note that as the number of WSP cards on site increases beyond 3, special configuration changes (in commissioning file) on site are required. Failing to do so will cause the 4th WSP card to be non-recognizable by site and the CEs for this card will not be counted in Maximum CE count for the site. While checking the availability of WSP resources on a site, the engineer needs to calculate the total number of CEs by counting WSP cards along with their types and then comparing it with the Max. avail CE (Black Line) shown on the WSP Resources graph. If a difference is found between the two then it might be the case that there is some problem with the site configuration.3.2.3. WSP Capacity Utilized for SignallingPlease note that not all the CEs for all WSP cards on site are available for user call (voice, video, etc.) processing. Some WSP Resources (CEs) are dedicated for the signalling between the BTS and the User Equipments (UE) [Air interface].In case of a WSPA card 24 out of 32 CEs while in case of a WSPC card 16 out of 64 CEs are used for signalling purposes. In case of mixed WSP card configuration (Both WSPA and WSPC cards present on site) the higher figure is used (i.e. 24). Signalling capacity is reserved just from one WSP card per WAM card. Second WAM card is required if BTS have 4 or more WSP cards.In case the site is HSDPA capable, then the following holds:

For HSDPA Site level Packet Scheduler activation (normal case): 32 CEs

For HSDPA Cell level Packet Scheduler activation (normal case): 32 CEs per cellThe table below shows the CE utilization for different WSP card configuration for different types of services available in 3G systems: WSP configurationRel 99 onlyHSDPAHSDPA with Cell Scheduler*

1 WSPA2424 + 32 = 56

2 WSPA2424 + 32 = 56

1 WSPC1616 + 32 = 48

1 WSPA + 1 WSPC2424 + 32 = 5624 + (3*32) = 120

2 WSPA + 2 WSPC4848 + 32 = 8048 + (3*32) = 144

4 WSPC3232 + 32 = 6432 + (3*32) = 128

* For cell scheduler case it is assumed that the site has 3 cells in it.

3.3. CELLS Table

The CELLS table provides information about the cells on the site.

CELL: Name of the Cell

CELL_ID: Cell identity

STATE: Defines the state of the cell. It should be WO; if the cell is up. By clicking on the box, user can see the working states of the cells for 10 minute intervals.

3.4. AXC Table

The AXC table provides details about the transmission parameters for the site.

COCO: Connection Configuration Object (Same number as the BTS ID). It defines among other things the capacity reserved for Control plane signalling and for user plane traffic.

ATM IF ID: ATM interface ID for the site. The parameter is required to define the traffic routing towards RNC. VPI: Virtual Path Identifier Number

SW: Defines the SW version active on the AXC

3.5. RNC Table

The RNC table provides details about the Radio Network Controller for the site. There are totally 18 RNC available in the 3GIS Network in Sweden. Each RNC has a name and unique ID.

3.6. Comments

In this section a Radio Planner or a Cell (Transmission) Planner can enter comments related to some problems or future plans for the site.

3.7. Transmission Hierarchy

This section shows how the sites are connected by transmission link up to RNC. Note that only upstream sites are shown; not the downstream sites.

3.8. Transmission Capacity Usage between Node-B and RNC The two watch like graphs describe the total available and currently used transmission capacity (defined in cells/s) for both Release 99 (VC 36 and VC41) and HSDPA (VC 37) traffic. The boxes shown below the graphs Click for detailed data for cell are used to show how much and traffic (common channel, CS or PS) the cell has. By pressing the button the user can open/save the traffic data file which is provided as an Excel sheet.

VC 36 IUB = Transmission between Node-B and RNC (Release 99) If we click on the watch symbol under title VC 36, the detailed graph for Release 99 traffic is shown.

VC36

LineMeaningDescriptionNotes

Red LineIUB CAPACITYMaximum IUB CapacityDefines the maximum link capacity.

Blue LineIUB MAX USAGEIUB Maximum UsageDefines the maximum usage of link capacity under certain time periods.

Green Line IUB AVG USAGEIUB Average UsageDefines the average link usage. As a thumb rule if the average link usage (green line) often goes beyond 60% of the max. link capacity (red line), one can assume that customer will have a low throughput and might have problems to access to the service.

VC 37 IUB = Transmission between Node-B and RNC (HSDPA)

If we click on the watch symbol under title VC 37, the detailed graph for HSDPA traffic is shown.

VC37

3.9. Graphs

There are various graphs shown on cell health check which narrates the site performance during the time period selected by the user. 3.9.1. Availability

This graph shows the availability of the cells marked by the green line. The cells should be available 100% all the time, if not then one need to find the reasons why the cell is down. The best way to do that is to first check the alarm history for the time cell is down and so on.

3.9.2. R99 Traffic Minutes

This graph shows amount of all traffic (in minutes) running through the cell except the HSDPA traffic. The voice, video and PS traffic is marked by Blue, Red and yellow curves. The graph most importantly shows if the cell is taking traffic or not. Following should be kept in mind while interpreting this graph:

a. The traffic should follow a constant pattern e.g. most of the sites have more traffic during the weekdays and some might have more during the weekends. b. Some sites might have some strange traffic patternsc. It is therefore advisable to check 30 days traffic minutes graph before drawing conclusions.

d. If Traffic deviates from normal pattern, one needs to check the following things:

i. Alarms: Cell out of useii. TTs and CRs: Related to the site/cell

iii. Changes done by Radio Planner: Mostly to the antenna configurationiv. New site(s) in the area: They can cause a change in the traffic behavior of site/cell3.9.3. HSDPA Traffic Volume

The graph shows HSDPA traffic pattern. A similar kind of HSDPA traffic deviation can be expected as with R99 traffic patterns, however, variation is normally larger than with R99 traffic and busiest hours are during the evenings.

One might find that there is no HSDPA traffic at all on a site/cell. In such a situation one need to check the followings: a. Most likely this is because site is not yet HSDPA capable. The HSDPA capability for a site/cell can be checked from WSP graph. One need to count the minimum CE required for signalling to RNC without HSDPA. This is done as described in section 3.2.2. WSP Capacity on Site. If counted value is equal to Min Used CE dl (Orange line), then there is no HSDPA activated on the site. If Orange line shows counted values + 32, there is HSDPA activated with Site Level Packet Scheduler. If orange line shows counted value + 96 (for 3 cells site), there is HSDPA activated with cell packet scheduler.b. It might be the case that although HSDPA is activated, but still there is no HSDPA traffic on some or all of the cells. In this kind of case one needs to check HSDPA Accessibility graph (discussed under section 3.9.6). If there are no HSDPA attempts then there is no problem on site anyhow if there are attempts visible in a graph, there is something wrong with the site. A deep analysis is required which might be performed by either RAN Expert or the Radio Planner. 3.9.4. HSDPA Simultaneous Users

The maximum number of simultaneous HSDPA users is 16 per cell or site, depending upon activation of Cell or Packet specific HSDPA Scheduler type respectively. The average amount of users in low traffic site is normally 1,5 = grey line. Color coded bars will indicate the number of HSDPA users. If a certain time has average users reaching the limit (16 per site or Cell), no more HSDPA users cant get a connection. Many simultaneous HSDPA users in a cell might be a cause for a low throughput. In such a situation one need to check Blocking Ticket report to find site in it. If not then the TT is sent to PM engineer for the creation of a Blocking Ticket. 3.9.5. R99 Accessibility

The graph shows the amount of attempts made by customers to access the network during the time period selected by the user. The call attempts can be made for Voice, Video or Packet data (Release 99). By default the graph displays the details of all call attempts (Total: Voice, Video and Packet data). One can click on the individual entity e.g. Voice to check the call attempt details for it. The graph parameters are described by the table below:Graph ParameterBar ColorExplanation

CSSRLight BlueCall Setup Success Rate

RRC SETUP AND ACCGreenAbsolute value for successful RRC attempts

RAB STP COMPYellowAbsolute value for successful RAB attempts

RRC STP ATTDark BlueAbsolute value for RRC attempts, which were not successful

RAB STP ATTRedAbsolute value for RAB attempts, which were not successful

RRC RRC stands for Radio Resource Control. It belongs to the UMTS WCDMA protocol stack and handles the control plane signalling of Layer 3 between the UEs (User Equipments) and RAN and perform functions for connection establishment and release, broadcast of system information, Radio Bearer establishment/ reconfiguration and releases, RRC Connection mobility procedures, paging notification and release, outer loop power control.RABRAB stands for Radio Access Bearer and it represents the bearer service that the access stratum provides to the non-access stratum for transfer of user data between mobile station [MS] and the core network.RRC_DetailsThe button is used to view the reasons for failing RRC attempts. There can be many reasons for RRC attempt failures which are described in the table below.

RRC_DetailsGraph ParameterColorReasonExplanation

RRC_CONN_STP_FAIL_HCPinkDue to Handover ControlOne can check the reasons in R99 Hand Over graph ( 3.9.9). Normally these problems are dealt by RAN Engineers.

RRC_CONN_STP_FAIL_BTSGreyDue to Site itselfThis is normally the case when there are problems with WSP resources on site. One need to check the WSP graphs.

RRC_CONN_STP_FAIL_RNCBrownDue to RNCThis indicates setup problems at RNC. Normally any of these problems are dealt by RAN Experts.

RRC_CONN_ACC_FAIL_MSDark BlueDue to MobileThis indicates that there are faulty Mobile Stations (MS) under the cell. The problem is not important and can be neglected provided the performance of the site is ok.

RRC_CONN_STP_FAIL_ACLight GreenAdmission ControlThere are two reasons for this fault: 1. Cell Overloaded: Admission control is checking radio resources (Ptx and Prx power). If there are no enough radio resources, AC will block the call. This cannot be seen from WSP graph, but from cell resource tables. 2. Site Restart (Reset): There will be no admission possible. One need to check the site reset from alarm history and TT history. If such a reason is found there are no further actions required.

RRC_CONN_STP_FAIL_TRANSYellowDue to transmissionThis indicates that the connection is not possible due to transmission problems. In such a case check IUB graphs. If problem is found then a Blocking Ticket is to be created.

RRC_CONN_STP_FAIL_FROZBSBlackDue to Frozen BSThis problem should not exist, but if so then the case is sent to RAN expert.

RRC_CONN_ACC_FAIL_RADIORedDue to Radio reasonsThis indicates problems with radio link connection between UE and Site. It might be due to Bad Coverage or Radio Interference etc. The case is sent to Radio Planner for further investigation if there are too many failures due to this reason.

RAB_DetailsThe button is used to view the reasons for failing RAB attempts. There can be many reasons for RAB attempt failures which are described in the table below.

RAB_DetailsGraph ParameterColorReasonExplanation

RAB_STP_FAIL_xx_AC

PinkDue to Admission controlThere are two reasons for this fault:

1. Cell Overloaded: In such a case IUB graphs and WSP graphs are to be checked. One may need to check/create a BT ion site. 2. Site Restart (reset): There will be no admission possible. One need to check the site reset from alarm history and TT history. If such a reason is found there are no further actions required.

RAB_STP_FAIL_ xx_TRANSGreyDue to transmission during RAB reconfiguration (up-down grade).This indicates that the connection is not possible due to transmission capacity. Small amounts of failures are acceptable. If the failures are large; check IUB graphs. If problem is found then a Blocking Ticket is to be created.

RAB_STP_FAIL_ xx_FROZBS

BrownDue to Frozen BSThis indicates that the BTS is frozen and is not taking traffic. The reason should not be seen, but if so, then the case should be sent to RAN Engineer.

RAB_ACC_FAIL_ xx_MSGreenDue to MobileRAB access is failing due to Mobile Station. These problems might exist in country borders.

RAB_STP_FAIL_ xx_BTS

Light GreenDue to Site itselfThis is normally the case when there are problems with WSP resources on site. One need to check the WSP graphs.

RAB_STP_FAIL_ xx_RNC YellowDue to RNCThis indicates setup problems at RNC. Normally any of these problems are dealt by RAN Experts.

RAB_ACC_FAIL_ xx_RNC BlackDue to RNCThis indicates problems at RNC. Normally any of these problems are dealt by RAN Experts.

RAB_STP_FAIL_PS-BACKG_ANCHRedFailure due to anchoringThis should not happen, but if it does -> contact RAN.

It is always good to check fault causes for a longer period of time. For example there might be a small amount of Radio failures all the time, but still site is performing well. The small errors might be due to coverage limitations. If however some of the fault causes are increasing suddenly, there should be an explanation for that, and then more investigation is needed.3.9.6. HSDPA Accessibility

The graphs show HSDPA accessibility percentage and absolute numbers of HSDPA Attempts. Accessibility is shown by Grey line and number of attempts is indicated by bars. If the accessibility is not 100%, one can see reasons for it by selecting the Faults button.

Faults GraphGraph ParameterColorReasonExplanation

REJ_HS_DSCH_RET PinkLack of radio resource (power)The case represents lack of UL radio resources. Such a case should be sent to the Radio Planner.

SETUP_FAIL_RNC_HS_DSCH GreyDue to RNCIn such a case the case should be sent to the RAN Engineer.

SETUP_FAIL_UE_HS_DSCHRedDue to UENot an important cause because it indicates that UE is not HSDPA capable.

DCH_SEL_MAX_HSDPA_USERS Dark Blue16 user limit reach in cell / siteOne needs to check if a BT exists on site; if not then the case should be sent to the Radio Planner.

REJ_HS_DSCH_AMRLight GreenDue to admission controlIn such a case one need to check BT. If a BT exist but not complete, then the case is sent to Radio Planner.

SETUP_FAIL_IUB_HS_TOTAL

YellowDue to transmissionIn such a case one need to check Iub graph and BTs. Case might be sent to Transmission Planner.

SETUP_FAIL_BTS_HS_DSCH

Dark GreenDue to Node-BIn such a case one need to check WSP graph and BT. If no blocking can be seen, case can be sent to RAN Engineer.

Accessibility thresholds have not been defined yet. Small amount of faults can be accepted, if retainability stays close to 100%. If there is one reason causing most of the problems, then problem should be forwarded accordingly. Also in cases where a certain cause is related to RP actions, those can be forwarded right away. Those are capacity related issues and RP should be aware of those even if no further actions are taken right away.

3.9.7. R99 Retainability

The graphs show the R99 call retainability. A call can be dropped after a successful setup (during its active phase). By default the graph displays the details of R99 retainability for all calls (Total: Voice, Video and Packet data). One can click on the individual entity e.g. Voice to check the Retainability details for it. The graph parameters are defined as follows:

Graph ParameterBar ColorExplanation

DCRGreyDCR stands for Drop Call Rate and is shown by the Grey line in the graph. It shows how many calls as a percentage are dropped during their active phase.

DROPSRedRepresents the actual total number of drop calls, and is shown by Red line in the graph.

RAB ACT COMPYellowIt shows the total number of calls which are completed in the Active RAB phase.

More detailed information about drops can be seen by selecting RAB_Details.

RAB_DetailsGraph ParameterColorReasonExplanation

RAB_ACT_FAIL_ xx_BTSPinkDue to BTS reasonOne need to check WSP graph and possible BTs.

RAB_ACT_FAIL_ xx_RADIORedDue to Radio reasonsIt might be due to bad coverage, Interference etc. If this is a major cause, one needs to send case to Radio Planner.

RAB_ACT_FAIL_xx_IUR

BrownDue to interface between two RNCsIn case of HO problem between two RNCs. If this starts to be a major issue, then the RAN team first needs to check how Iur is working. If it is working properly then they need to send the case to Radio Planner.

RAB_ACT_FAIL_ xx_UE Dark GreenDue to mobile reasonThe problem may be due to a faulty mobile or a faulty WSP. If this error reason is significant for many days, the case should be sent to RAN Engineer.

RAB_ACT_FAIL_ xx_RNCLight GreenDue to RNCThe case should always be sent to the RAN Engineer.

RAB_ACT_FAIL_ xx_IUYellowDue to Iu interface (RNC-Core Network)The case should always be sent to the Core Team.

RAB_ACT_FAIL_ xx_I_CHECKBlackNot important issue as Mobile dont support requested service. Error can be ignored.

3.9.8. HSDPA Retainability

The graphs show the HSDPA call retainability for each cell. The graph parameters are defined as follows:

Graph ParameterBar ColorExplanation

RetainabilityGrey LineShows HSDPA Drop call rate in percentage (inverted way). 100% is ok and everything below means reduced performance.

AttemptsYellow BarsAbsolute number of active HSDPA connections.

If Retainability is decreased from 100%, more details can be seen by selecting Faults.

Graph ParameterColorReasonExplanation

REL_ALLO_OTH_FAIL_HSDSCH_INTPinkOther than radio failOne needs to send case to RAN Engineer.

REL_ALLO_OTH_FAIL_HSDSCH_BGRLight GreenOther than radio failOne needs to send case to RAN Engineer.

REL_ALLO_RL_FAIL_HS_DSCH_INTGreyOne needs to check customer UE type. If it is Huawei 220, the CC TT can be sent back to Customer Help Desk (Tre/Telenor in 3GIS case). Otherwise if the fault is occurring on daily basis it is a potential coverage problem. The case should be forwarded to Radio Planner.

REL_ALLO_RL_FAIL_HS_DSCH_BGRYellowOne needs to check customer UE type. If it is Huawei 220, the CC TT can be sent back to Customer Help Desk (Tre/Telenor in 3GIS case). Otherwise if the fault is occurring on daily basis it is a potential coverage problem. The case should be forwarded to Radio Planner.

3.9.9. R99 Hand Over

R99 Hand Over

In 3G the customer is connected with more than one cell = Soft Handover

Active set of connections, maximum 3 cells = Active Set

Graph ParameterBar ColorExplanation

SHO_SSR%Grey LineSuccess rate for Soft Handover. Normally better than 95 %

SHO_Overhead%Turquoise LineSoft handover Overhead. Overhead is normally 40-60 %. If the value is higher than this figure, then there might be too much overlapping of the cells. In such a case, the issue must be sent to the Radio Planner, as there might be a need of a new site(s) or need for cell optimization.

IFHO_ATTRedInter frequency HO attempts. Handover attempts between 2 different carriers, for example Home Network and 3GIS

IFHO_SUCCYellowNumber of successful Inter frequency HOs.

ISHO_ATTBlackIntersystem HO (handover attempt from 3G to 2G).

ISHO_SUCCGreen Number of successful Intersystem HOs.

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