Ericsson Counter: handovers between underlaid and overlaid subcell

HOAATOL : Number of handover attempts from underlaid to overlaid subcell. The corresponding counter for handover to underlaid subcell is called HOAATUL.

HOSUCOL : Number of successful assignment attempts to overlaid subcell. The corresponding counter for underlaid subcell is called HOSUCUL.

HOATTULMAXIHO : Number of handover attempts from overlaid to underlaid subcell due to maximum number of intra-cell handovers in overlaid subcell.

HOSUCULMAXIHO : Number of successful handover attempts from overlaid to underlaid subcell due to maximum number of intra-cell handovers in overlaid subcell.

HOATTOLMAXIHO :  Number of handover attempts from underlaid to overlaid subcell due to maximum number of intra-cell handovers in underlaid subcell.

HOSUCOLMAXIHO :  Number of successful handover attempts from underlaid to overlaid subcell due to maximum number of intra-cell handovers in underlaid subcell.

EBS (Event Based Statistics)

The data in this database will act as a complement to the STS database but it is of more detailed character than the STS statistics. The data can either be stored in the database or in a Bulk Copy format file that can be distributed to other postprocessing tools. The monitors (counters) that can be stored must be activated in the GUI by the user, the user must have the correct authority to perform this action. The user must also select if the counters are to be collected for all cells in a specific BSC or several/all BSCs. The user can schedule the start and stop of data storage. The aggregation time, i.e. how often data is accumulated, can be decided by the user.

The data can later be postprocessed and reports can be created from monitors stored as counters by using the Business Objects tool. EBS and STS data can preferrably be combined into the same Business Objects report.

Note:  In order to combine STS and EBS data in the same report, it is important that the data is stored with the same periodicity

R-PMO (Realtime Performance MOnitoring)

R-PMO was the first application that was introduced in the family. Its main purpose is to present data in real-time. Realtime is achieved by letting the event data stream continuously to the OSS from the BSCs,and updating the OSS GUI once every minute.

The performance data that can be evaluated in real-time includes traffic load, service quality, hand over, GPRS/EGPRS cell reselection performance, GPRS/EGPRS data throughput and more. The measures are called Monitors.

The monitors are combined into reports. Several pre-defined Ericsson Standard Reports for both circuit switched and packet switched traffic performance monitoring are available. The user can also assemble monitors into own reports by using drag and drop.

A wide range of filters can be used on monitors, depending on the nature of the monitor. As an example the performance information for circuit switched traffic can be filtered per MS manufacturer and type, and the dropped calls can be filtered per drop reason.

FFAX (Find Faulty Antenna eXpert)

The purpose of FFAX is to provide an efficient way to remotely identify RF paths and antenna installations that are not performing according to expectations.

This is done by monitoring the difference in received signal strength from different RX paths in the BTS.

FFAX in OSS is applicable for the uplink and requires the BSS feature Find Faulty Antenna Data (FFAD). FFAX enables managing of cell sets to monitor, presentation of results in real-time and database storage functionality. For each reported TRX, key values are presented representing the accumulated receiver signal strength difference, during the measurement period, and when relevant an indication of the most likely fault or no fault found. The report will be updated every minute, and can be viewed in table as well as graph format (sliding window displaying data for the last hour). This is ideal during site visits where results of changes to the RF paths can be immediately seen in OSS.

BTS Fault Alarm

Types of Fault Map
Internal Class 1A	Internal to BTS, affecting MO, within MO
Internal Class 1B	Internal to BTS, affecting MO, within MO environment
Internal Class 2A	Internal to BTS, not affecting MO, within MO
External Class 1	External to BTS and affecting MO
External Class 2	External to BTS not affecting MO

The alarm slogan is the description of the current alarm situation for an MO or TG. The alarm slogans 'BTS INTERNAL' and 'BTS EXTERNAL' each describe more than one alarm situation. The remaining alarm slogans each describe a unique alarm situation. This section describes how each alarm slogan should be interpreted.
TGC FAULT No active TGC application exists in the Transceiver Group.
PERMANENT FAULT A managed object is classified as being permanently faulty when fault situations have occurred, and have been cleared, a certain number of times within a certain period of time. Manual intervention is required to bring such equipment back into operation.
LOCAL MODE The BTS equipment is in Local Mode or the BTS equipment has changed from Local to Remote Mode and a fault exists in the communication link between the BSC and the BTS. Communication between the BSC and the BTS is not possible.
LMT INTERVENTION Local maintenance activities are being performed in the BTS.
LOOP TEST FAILED Test of the traffic carrying capabilities of the TS has failed.
BTS INTERNAL There is a fault internal to the BTS.
MAINS FAILURE There is a fault in the power supply to the BTS or one or more items of equipment within the BTS. Battery backup (where available) is in use. Escalation may occur if corrective action is not taken.
BTS EXTERNAL There is a fault external to the BTS.
OML FAULT There is a fault in the communications link between the BSC and BTS.
ABIS PATH UNAVAIL No transmission device exists between the BSC and BTS.
CON QUEUE CONGESTION At least one of the LAPD Concentrator concentration outlet queues has reached an unacceptable filling level.
TS SYNC FAULT Synchronization lost on uplink or downlink TRA or PCU channels.
FORLOPP RELEASE A fault has occurred within the BSC software leading to a Forlopp release. Automatic recovery procedures are taking place. Report to your Ericsson Support Office. Alternatively, this alarm is issued as an advisory following a command ordered Forlopp release of a TG. In either case, the alarm is automatically ceased following successful recovery.
OPERATOR CONDITION A condition has arisen due to operator intervention

 Abbreviations and acronyms

BSC	Base Station Controller
BTS	Base Transceiver Station
CF	Central Functions
CON	LAPD Concentrator
DP	Digital Path
IS	Interface Switch
LAPD	Link Access Protocol for the D channel
LMT	Local Maintenance Terminal
MO	Managed Object
OML	Operation and Maintenance Link
PCU	Packet Control Unit
RBS	Radio Base Station
RX	Receiver
TF	Timing Function
TG	Transceiver Group
TGC	Transceiver Group Controller
TRA	Transcoder Rate Adaptor
TRXC	Transceiver Controller
TS	Timeslot
TX	Transmitter

Antenna Hopping

During a call connection, a burst can easily be lost when the mobile station happens to be located in a fading dip for that particular frequency, or if it is subjected to interference. The coding and interleaving scheme in GSM is constructed so that loss of a single burst has minimal influence on the speech quality. The probability that several bursts within a speech frame have poor signal quality is reduced if the bursts are transmitted on different paths. This can be done by using antenna hopping. With antenna hopping, transmit diversity is introduced by changing transmit antenna between bursts.

                                                  Schematic picture of antenna hopping

This transmit diversity scheme mimics frequency hopping in the sense that the fading changes rapidly between bursts due to transmission through different paths.
From a subscriber point of view, antenna hopping gives an improved speech quality.
From an operator point of view, antenna hopping is a very attractive scheme in particular for traffic channels without frequency hopping, but also for traffic channels frequency hopping over a relatively low number of frequencies, where it can provide substantial diversity gains. What makes antenna hopping especially interesting as a transmit diversity scheme is the fact that it can be used without increasing the number of TRXs in a base station. Thus giving the operator the following benefits:

• a possibility to tighter frequency reuse and increase in capacity,
• a more robust radio environment,
• a possibility to give subscribers a more uniform speech quality. 

Antenna hopping can reduce the effect of multipath fading. With antenna hopping, a non-moving mobile will typically not remain in a specific fading dip longer than one TDMA frame. The low signal strength dips in multipath fading are thus leveled out, and the mobile will perceive a more constant radio environment.

Schematic picture of multipath fading at one frequency and antenna hopping between two antennas for a slow/non-moving mobile station 

Antenna Hopping Parameters 

AHOP		: Defines the wanted state for antenna hopping on a transceiver group. The wanted state can be either of ON, ONXC0 or OFF. : In state ONXC0, all channels except those on the BCCH frequency/frequencies will antenna hop.

Measurement Result Recording (MRR)

Measurement Result Recording (MRR) is a tool for measuring the radio characteristics of the connections between MSs and the network. MRR records information on the radio characteristics of the dedicated channels and calculates statistics on the data recorded.

MRR utilises the data that the BSC receives from the BTS in Measurement Results. These data include the results of the measurements performed by both the BTS and the MS.

The purpose of the feature is to provide the operator with a facility for compiling statistics on the radio interface. The feature makes it easier for the operator to supervise the radio network. It also makes it possible for the operator to determine correlations within the collected data.

The MRR application can be used for:

• Supervision of the network performance
• Troubleshooting of the network
• Comparison of the network performance before and after a change is made to the network

MRR is a feature in the Operation and Support System (OSS). Recordings can be defined, scheduled, ended, stored and processed in OSS. The user can generate a large number of reports that can be used to analyse each recording and make comparisons. MRR is based on a function in the BSC, where it is possible to initiate and to end a recording by command. All data are recorded initially by the BSC and stored in a binary file that can be output directly or forwarded to OSS for further processing.

The measured radio characteristics are:

• Signal strength in both Uplink (UL) and Downlink (DL).
• Signal Quality in both UL and DL.
• Timing Advance (TA).
• Power level used by the MS and Power reduction of the BTS.
• UL and DL Pathloss.
• Pathloss difference (Pathloss DL - Pathloss UL).

The radio characteristics can be recorded for one or more cell sets simultaneously by initiating one or more recordings. A cell set can comprise one or more cells.

The user can filter the data received from a Measurement Result by specifying recording thresholds. Recording thresholds can be specified for either one or two specified radio characteristics. The use of recording thresholds allows the user to determine: radio performance, the causes of poor radio performance and correlations between different radio characteristics. As a special filtering option, connections using Adaptive Multi Rate full rate (AMR FR) can be selected to be included or excluded from the results.