RF network optimization and RF drive test basics

This page describes basics of RF network planning,RF network optimization and RF drive tests. It mentions tools and equipments used for RF drive tests and RF network optimization.

Let us understand some of the terminologies related to the subject. There are two basic components in a cellular network viz. BTS (Base Tranceiver Station) and Mobile Subscriber station(MSS). The place where BTS is located we will refer as network side. We will refer MSS as user of the network service. Before the network roll out, the complete region or area is divided into sectors known as cells. Each of the cells are served by one BTS.

Total number of cells required depends on the following:
• Capacity (Erlang per subscriber during busy hour, QoS)
• Coverage (penetration loss and other factors)

One cell RF frequency can be re-used in non adjacent cells. This is referred as frequency re-use. The frequency reuse factor depends on average number of transceivers and total number of frequencies.

There are mathematical empirical propagation models to predict the propagation path loss and other losses. The network planning tools utilize these models along with terrain data. Following are the popular models.
• Okumura-Hata Model for macro cell
• Walfisch ikegami model for micro cell

What is RF Network Planning and RF network optimization

Following activities are carried out during RF network planning process:
• Collection of input parameters required to have smooth network rollout.
• Pre-planning of data channels and control channels, data channels carry data or voice informations while control channels carry signalling information required to establish and maintain the voice/data connection between the mobile subscribers and base station.
• Network Site Survey to check for any hindrances if any in the path of RF signal for proper coverage to users.
• Frequency Allocation to cells
• Parameter planning
• Final radio network plan involves parameters such as power budget calculations, path loss calculations etc.

Optimization process involves monitoring, verifying and improving performance of the radio network. There are four processes as shown in figure-2 which include design, planning, implementation (i.e. network roll-out) and optimization. Hence optimization is continuous evolving process.

RF Network optimization takes feedback from various tests conducted on the site, during field trials and during drive testing. Based on the feedback of data collected (i.e. logs) and continuous monitoring of parameters against set KPIs (Key Performance Parameters), suggestions and improvements are planned. Based on this, fine network parameter tuning is applied to achieve the desired performance. KPIs typically fall into three functional categories viz. area level, cell level and TRX level.

RF Drive testing Equipments

RF Drive testing process involves following:
• Live region of the network is selected first.
• Drive test path is decided next.
• RF drive test kit including mobile equipment, drive test software, Scanner, laptop PC, GPS module are arranged.

During the RF drive tests following typical tests are performed and in case of test failures, data logs are collected for further analysis by experts.
• Continuous CS (Circuit Switched) or voice call
• Continuous PS (Packet Switched) or data call
• Handover tests between two cells of the same RAT (Radio Access Technology i.e. GSM)
• Handover tests between cells of the two different RATs (i.e. between GSM and CDMA or between GSM and LTE etc.)
• Cell selection and re-selection etc.

After the drive tests are completed and data logs are available following typical suggestions are given by the RF optimization experts to the field team or to the software team.
• Antenna locations have been moved
• Antenna height from ground is altered.
• serving ARFCNs are being changed.
• Antenna orientation is being adjusted and if needed polarization is changed.
• Software or firmware is being upgraded as per PHY (layer-1) and RF parameters

Tools or Equipments used for RF network optimization and RF Drive Testing

Other these there are many companies who develop software and applications for RF network optimization and drive tests. They have tools and equipments for network optimization and drive test need.

RF test and measurement equipments

RF Vector Signal Generator
Keysight vs Tektronix vs Rigol Spectrum Analyzers
Waveguide Mixer
Sound Level Meter
PIM Analyzer
Noise Figure Meter
Near Field Probe Set