If you are an engineer within the mobile communications industry, drive testing is arguably one of the most fun things you can do. It is like taking a crash course in mobile communications which allows you to learn how your mobile phone talks to the network when you are using mobile services such as making/receiving voice calls, sending/receiving messages, browsing, and video streaming etc. While it can be a lot of fun driving around with like-minded colleagues and learning on the go, the real purpose of drive testing is to monitor, tune, optimise, and troubleshoot the mobile network. Drive testing has been in the industry for a long time and mobile operators around the world have used market-leading tools to make sure that their customers get mobile services of the best quality. There are lots of specialised tools that mobile operators use to conduct drive tests. These tools typically use a combination of hardware and software where you have special phones that can be connected to laptops running radio network testing software. These tools are able to provide a snapshot of the mobile network performance by identifying any problem areas and allowing mobile operators to address these issues to improve service quality.
What is an RF Drive Test?
An RF (Radio Frequency) Drive Test is a test carried out by RF engineers to monitor a mobile network, perform necessary troubleshooting and come up with recommendations on how to improve network quality (Quality of Service – QoS). The captured data is assembled, processed and analysed to identify any potential issues so that they can be addressed by the relevant RF teams within a mobile operator. When mobile operators do drive tests, they try to look at the performance of the mobile network from a customer viewpoint. They connect mobile phones to specific software applications and then use mobile services as normal while driving around different locations. They record everything so that they can look into the details when they go back to the office.
What is an RF Drive Test Engineer?
A drive test engineer’s role is to perform necessary network tests by driving around a specific cell or a group of cells to monitor and troubleshoot a mobile radio network. There are two types of input that are essential to deciding on when and where to do the tests. The first input is network measurement from Operations Support Subsystems – OSS which gives regular snapshots of the health of a mobile network both for radio as well as the mobile core parts. The other source can be customer support (complaints) and even test logs (log files) from drive tests performed by other teams. The key here is to identify where the network issues are and then troubleshoot to get to the bottom of the problem. Drive Test engineers use specialised tools that are usually a combination of laptop software, phone hardware/software, RF scanners, and DSP (Digital Signal Processors) etc. One of the examples of such tools is TEMS Investigation.
What is a cluster drive test?
A cluster drive test is when a drive-test is performed for a cluster of cells within a radio network. A cluster in mobile networks is a group of cells that are adjacent to each other and share network resources in a way that minimises interference. If any network issues do take place e.g. interference, that’s when trouble-shooting may be required by the RF engineers.
What is the LTE drive test?
Drive-testing can be performed for any mobile network including GSM, UMTS, LTE, 5G NR etc. So, an LTE drive test simply means a drive test that is carried out for an LTE network. For example, it could be that a certain LTE cell is not enabling the Voice over LTE calls and the RF team wants to identify where the problem is. An RF test within the cell can show what happens when the call is initiated and how the call flow looks like. The ideal scenario for any mobile operator is to not have network issues and rely on system-based measurements e.g. OSS to identify any issues, but the combination of OSS and drive test allows a mobile operator to detect and troubleshoot the issues more closely.
How do you do RF Drive Testing?
The set-up involves mobile phones and devices connected to a laptop inside a car. The laptop has specialised software that is able to record all the communication between the mobile and the network. The laptop is also connected to a GPS which allows mobile operators to record location information. That way, they are able to find out how the network is performing in certain locations. They usually also have chargers for the phones and laptops properly installed in the car because the drive tests can take a lot of time when testing various mobile services in different locations.
At a high level, the drive-testing process is broken down into the following key steps:
- Data capture or data collection
- Data processing & analysis
- Reports and recommendations
The first step is to capture the network information that you will be analysing later. The information you are looking for is how a certain mobile network is performing in a certain area. For example, if you are tasked with identifying any network issues on behalf of a mobile operator, say, XYZ Comms, you will need a mobile phone with a SIM card from XYZ Comms, a laptop with a radio network testing software installed, a GPS, and possibly other additional devices like an RF (Radio Frequency) scanner or similar devices. Once everything is connected and all powered up, you are ready to make a start. Your aim could be, for example, to check the quality of voice calls within a mile radius of Oxford railway station.
For this example, you would start the recording and then initiate a voice call by dialling a test number through the mobile phones connected to the laptop. Depending on the test software you use, you may need specialised mobile phones that are compatible with the software. It is a good idea to have one person driving the car and other people sitting in the car with mobile phones connected to their laptops. Once you have driven around as per your plan, you should have recorded enough data for your analysis.
The recorded files that contain all this network information are referred to as log files. These log files can either be recorded locally on the laptop or can be sent to an online network drive. Irrespective of where you store the log files, it is important to make sure that they can be easily accessed by those who will carry out the analysis.
Data processing & analysis
When you finish a drive test and get back to the office, it is easier to recall any network issues that you may have encountered during the drive test. As a result, it can be intriguing to just start analysing those files first. But, it is better to do the analysis in a more organised way. It may be that you and other colleagues encountered a whole bunch of problems in different locations so it is important to be selective and to prioritise what you want to analyse first. Sometimes during the recording, the phone or laptop can freeze which means you are not able to record properly or at all.
Therefore, it is important to first select which files you want to analyse and in what order. Once you have sorted all the files, you can start your analysis. For that, you need to have a certain skill set and an understanding of how mobile networks communicate. For example, if you were analysing a voice call on a 2G GSM network, you would need an understanding of the call flow for GSM networks. That knowledge allows you to detect any issues or risks by analysing the communication flow through the different network layers.
Reports and recommendations
Once the analysis has been carried out either by yourself or another team, you may have a list of issues and risks. The results of the analysis can be used to go into the details of the problem areas and provide recommendations on what can be done to fix the issues. You can also create formal reports with all the issues and recommendations.
As you can imagine, drive testing takes a lot of time and requires dedicated resources to carry out specific tests. Mobile operators also use another option which is to get performance reports directly from the network (e.g. OSS). The network-based reports allow operators to study the information collected from the actual customers as opposed to the test phones.
Here are some helpful downloads
Thank you for reading this post, I hope it helped you in developing a better understanding of cellular networks. But sometimes, we need some extra support especially when preparing for a new job, or studying a new topic, or maybe just buying a new phone. Whatever you are trying to do, here are some downloads that can help you:
Students & fresh graduates: If you are just starting, the complexity of the cellular industry can be a bit overwhelming. But don’t worry, I have created this FREE ebook so you can familiarise yourself with the basics like 3G, 4G etc. As a next step, check out the latest edition of the same ebook with more details on 4G & 5G networks with diagrams. You can then read Mobile Networks Made Easy which explains the network nodes e.g. BTS, MSC, GGSN etc.
Professionals: If you are an experienced professional but new to mobile communications, it may seem hard to compete with someone who has a decade of experience in the cellular industry. But not everyone who works in this industry is always up to date on the bigger picture and challenges given how quickly the industry evolves. The bigger picture comes from experience which is why I’ve carefully put together a few slides to get you started in no time. So if work in sales, marketing, product, project or any other area of business where you need a high-level view, Introduction to Mobile Communications can give you a quick start. Also, here are some templates to help you prepare your own slides on product overview and product roadmap.