Drive Test Optimization Process of 3G/UTRAN.

There are following processes of 3G/UTRAN drive test optimization.

1. Perform site readiness checks.
2. Plan optimization.
3. PerformRF optimization execution.

1. Perform site readiness checks.

The Site Readiness procedures are health checks that ensure all cells are operating
as required. Site readiness checks are usually performed after a new network or new cells are deployed and before the network goes operational. These checks do not need to be
re-performed. Site readiness checks include:

1. Spectrum clearance.
2. Antenna check.
3. Sector verification.

1. Spectrum clearance checks.

Spectrum clearance assures that no external interference is present and sufficient
guard bands are obeyed.

Detection of interference can be time-consuming once the UMTS system is up and running. It is desirable to have a very high degree of confidence that the spectrum is cleared prior to any testing.

2. Antenna check.

This phase involves a series of quality checks to ensure proper installation of the antenna system. There is a recommended audit minimum of 25% of cell sites in a cluster.

If more than 50% of the audited antennas uncover installation errors, the remaining antennas in the cluster must also be audited. Based on the results and the confidence level of the antenna installations, the percentage of cell sites to be audited may vary for successive clusters.

The audit process consists of various inspections on:

1. Antenna height.
2. Antenna azimuth.
3. Antenna type.
4. Antenna mechanical down-tilt.
5. Cable length etc.

3. Sector verification.

The sector tests include verification of basic call processing functions including:

1. Origination.
2. Termination and
3. Handover tests.

Measurements are made on UMTS signal levels to verify each sector is transmitting with the appropriate power levels and the correct scrambling code. These basic functional tests are intended to detect:

1. Hardware.
2. Software.
3. Configuration.
4. and parameter errors.

for each cell site in the cluster prior to further drive testing.

Sector drives should be executed for each sector in the system.

The sector tests are performed using the measurement system a CDMA AIR Interface Tracer and a UMTS test terminal. Once all data from the sector tests are collected the measurement data can be post-processed.

If sector problems persist, corrections must be made and the sector test should be repeated until all tests succeed.

2. Plan optimization.

The Optimization Planning phase ensures system and tool readiness for RF Optimization before beginning the actual drive testing, this includes:

1. Checking RF parameter settings.
2. Checking initial neighboring cell list settings.
3. Checking availability of tools, equipment and personnel.
4. Defining clusters.
5. Planning routes for drive testing.

Checking RF parameter settings.

At the beginning of the RF Optimization process, RF parameters must be inspected for consistency with the UMTS parameter catalogue (ParCat).

Checking initial neighboring cell list settings.

The complete neighbor lists in the UMTS network are required to compare the neighbor relations with network design plots.

Neighbor relations need to be verified for recent updates, validity and appropriateness.

The recommended strategy is to have a minimum number of neighbor relations in the neighbor lists.

Checking availability of tools& equipment.

Appropriate drive test tools and post-processing tools need to be prepared for optimization.

Defining clusters.

Approx. 15-19 cell sites should be combined into one cluster. The actual number used is based on the network expansion as well as on topographical environment. The clusters are selected to provide a center cell site with two rings of surrounding cell sites as shown below.

It may be worthwhile to utilize natural barriers such as hills, water bodies, etc. for cluster separation to minimize overlap and influence between the clusters. A little cell site overlap should remain between each cluster to ensure continuity across the boundaries.

Planning routes for drive testing.

Drive routes need to be defined for Sector Verification, Cluster Optimization and System Verification. Coverage prediction plots, morphology and clusters can define all drive test routes.

1. Planning Drive Routes for Sector Verification.
2. Planning Drive Routes for Cluster Optimization.
3. Planning Drive Routes for System Verification.

Drive Routes for Sector Verification.

Planning Drive Routes for Sector Verification: Each cell site is driven approximately around the entire cell site. The selected drive route should maintain a distance equal to 1/2 of the cell site radius.

Drive Routes for Cluster Optimization.

The routes for Cluster Optimization consist of major roads, highways and hotspots. Total time to drive all routes in a typical cluster should be approximately 6 to 8 hours.

One control route per cluster is chosen to verify system performance. A control route is a subset of the optimization route and should be limited to about 1 to 2 hours. Additional border routes are chosen to verify system performance on overlapping cluster regions. A border route is chosen by the way it crosses the cluster borders without going into the cluster areas.

Drive Routes for System Verification.

The System Verification drive routes are used to collect the metrics for the Exit Criteria. The routes are a combination of the cluster control routes and routes between the individual clusters.

3. RF Optimization Execution.

The RF Optimization Execution consists of:

1. Cluster optimization.
2. System verification.

The core activity is to provide system tuning, as well as data collection and reporting. Design changes relating to cell site layout modifications or adding a new cell site may be considered if critical coverage holes are discovered.

Cluster optimization.

Several factors make it worthwhile to optimize the system in manageable sized clusters.

1. Better focus on the area optimized easier to track the parameter changes and the impact of their performance.
2. Multiple teams can optimize different clusters simultaneously.
3. Smaller cluster optimization aids in speeding up the system tests for commercial operation.
4. Cluster Optimization should be performed for network sections that are fully deployed.
5. All cell sites in the network are switched on.
6. Each cluster is tested under unloaded and loaded conditions.
7. If live traffic exists, cells in the tested clusters must be barred for all users except for the test users (optimization team).

Perform cluster optimization using drive tests, this includes:

1. Unloaded cluster optimization to identify RF coverage holes, handover regions and
   pilot coverage areas.
2. Loaded cluster optimization to measure effects of cell breathing.
3. Cluster performance verification to prove network meets customer criteria.

Unloaded cluster optimization.

A measurement drive is performed under unloaded network conditions. The first pass highlights fundamental flaws in the RF design under best-case conditions:

1. Transmit powers.
2. Antenna azimuths.
3. Antenna tilts.

Loaded cluster optimization.

The second Cluster Optimization phase is performed under loaded conditions. Loaded testing = a rise in the noise floor (cell breathing), resulting in:

1. Negative Ec/Io values.
2. Coverage holes.
3. Higher BLER.
4. Lower mobility throughput, and more dropped calls.

Aim is to fix the problems by RF fine-tuning. Problem areas may be re-driven after fine-tuning. If the problem cannot be solved after three test drives, either a root cause analysis or Cluster Optimization proceeds with the next cluster.

In the third phase, the cluster performance is measured against the cluster Exit Criteria. The exit drive’s purpose is to verify and to confirm specific Exit Criteria.

Perform system verification.

System verification is designed to prove the entire network (all clusters) meets customer exit criteria. At the end of the system-wide drive test phase, the RF Optimization procedure is considered complete.

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