RF Network Optimization and RF Drive Test Basics

This page describes the basics of RF network planning, RF network optimization, and RF drive tests. It mentions the tools and equipment used for RF drive tests and RF network optimization. Let’s understand some of the terminologies related to the subject.

There are two basic components in a cellular network:

• BTS (Base Transceiver Station)
• Mobile Subscriber Station (MSS)

The location of the BTS will be referred to as the “network side.” We will refer to the MSS as the “user” of the network service.

Before network rollout, the complete region or area is divided into sectors known as cells. Each of the cells is served by one BTS. The 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’s RF frequency can be re-used in non-adjacent cells. This is referred to as frequency re-use. The frequency reuse factor depends on the average number of transceivers and the total number of frequencies.

There are mathematical empirical propagation models to predict the propagation path loss and other losses. Network planning tools utilize these models along with terrain data. Following are popular models:

• Okumura-Hata Model for macro cells
• Walfisch Ikegami model for micro cells

What is RF Network Planning and RF Network Optimization?

The following activities are carried out during the 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 information, while control channels carry signaling information required to establish and maintain the voice/data connection between mobile subscribers and the base station.
• Network Site Survey to check for any hindrances in the path of the RF signal for proper coverage to users.
• Frequency Allocation to cells
• Parameter planning
• The final radio network plan involves parameters such as power budget calculations, path loss calculations, etc.

The optimization process involves monitoring, verifying, and improving the performance of the radio network. There are four processes which include design, planning, implementation (i.e., network rollout), and optimization. Hence, optimization is a continuously 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 Indicators), 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: area level, cell level, and TRX level.

RF Drive Testing Equipments

The RF Drive testing process involves the following:

• A live region of the network is selected first.
• The drive test path is decided next.
• The RF drive test kit, including mobile equipment, drive test software, a scanner, a laptop PC, and a GPS module, are arranged.

During the RF drive tests, the 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 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, the 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 the 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 Equipment Used for RF Network Optimization and RF Drive Testing

Besides these, many companies develop software and applications for RF network optimization and drive tests. They have tools and equipment for network optimization and drive test needs.