RF OPTIMIZATIONNetwork Analysis and Tuning

RF Optimization Objective - Reach the optimal configuration of each cell site in the wireless network (height, tilt, orientation) - Maximise RF QoS (coverage improvement, interference reduction) and capacity of the network - Define neighbouring plan according to drive test

Method - Use of drive tests - Identify a list of optimization recommendations aiming to achieve the optimization targets in all the identified problematic areas - Prioritise the optimisation recommendations according to the input received from the regions regarding the details of each area - Highlight the expected improvements or degradations

Data Analysis FlowchartScanner and UE drive logsCompare scanner measurements with planned quality and coverage thresholdsCPICH RSCP => thresholdCPICH Ec/No => thresholdDominance Area OKAmount of SC > XAggregated to Peak > 3 dBYesYesYesNoNoNoYesYesBad Ec/IoMulti-path problemPilot PollutionLow CPICH Ec/No

RF Performance Measurements

What To Do If1. High Interference Area (High RSCP and low Ec/No e.g. Pilot Pollution): Reduce interference by reducing too high number of strong pilots Solution: adjust antenna down tilts of involved Scrambling Codes

2. Excellent Area (High RSCP and high Ec/No): Good RSCP and good Ec/No Good quality

3. Poor Coverage Area (Low RSCP and high Ec/No): Improve coverage by adjusting antenna azimuths towards coverage gap Check calculated site-to-site distance from link budget: if not sufficient in network, additional Sites are needed

4. Non-dominant Server Area (Low RSCP and low Ec/No): Increase the signal strength of the most probably serving sector that can provide sufficient RSCP coverage quality Solution: create one dominant pilot by adjusting antenna azimuths

RF TuningTuning Methods for Coverage Problem Area Up tilt of serving cells antenna to extend coverage radius and to improve unsatisfied coverage area

Increase CPICH Tx Power of serving cell

Change antenna bearing angle: Focus the main beam of antenna to coverage holes and low RSCP area

Change antenna pattern: Displace with higher antenna gain antenna with adequate antenna tilting

Increase serving cells antenna height to get higher effective antenna gain but there is risk to make undesirable inter-cell interference to adjacent cellsHigh PriorityTuning Methods for Dominance Problem Area Down tilt of serving cells antenna which generate pilot pollution

Change CPICH Tx Power: Increase serving cells Tx power but decrease interfering cells Tx power

Change antenna bearing angles of cells involved in pilot pollution

Change antenna patterns of cells involved in pilot pollution. Smaller gains for interfering cells and higher gain for victim cell

Decrease antenna height of interfering cells and increase antenna height of victim cell with adequate tilting angle

Pilot Pollution Basic Definition - Any cell that provides an Ec/No level higher than the Pilot Pollution Threshold, but is not in the UEs active set, is a pilot polluter for the UE

Indication for Pilot Pollution - More than 3 CPICHs (Ec/No or RSCP) are decoded within a sliding window of 6...8dB size, but not all can be used in the active set - Window should be above Reporting Range and above minimum design criterion - CPICH Ec/No very low (High interference)

Effects - Decreased connection quality (low throughput / bad speech quality) - Rise of UE Tx power due to high interference - increase of SHO - increase of signaling traffic

No Dominant Server

No Dominant Server Area: - All detected CPICH are below minimum design criteria (targets) - All detected CPICHs are within same level, interfering each other - Low RSCP, low Ec/No

Effects - Low RSCP, low Ec/No poor signal - Rise of UE Tx power due to high interference - Decreased connection quality (low throughput / poor speech quality) - Increase of call drop rate - Increase of signaling traffic capacity loss

Electrical vs Mechanical Tilt Mechanical - The down tilt angle varies over the horizontal beamwidth. Patterns measure +-90 from the center of the beam have decreasing tilt angle until there is no tilt 90 from the main beam - The horizontal half-power beam width increases with greater down tilt - The resulting gain reduction depends on azimuth direction

Electrical - There is uniform down tilt over the whole azimuth range - The horizontal half-power beamwidth is independent of the down tilt angle - There is identical gain reduction in all azimuth directions

Mechanical vs Electrical - The largest advantage of electrical antenna down tilt is that the horizontal beam width is not affected. - High mechanical tilt, the cells become shorter and wider

Calculation of Pre-optimized down tilt