The gap between academic theory and the performance demands of a multi-billion pound network is where real engineering begins. Before my 8-week placement at BT’s Adastral Park, Pembroke’s LEAP events provided a crucial runway for my internship. A trip to BT’s labs allowed me to discuss telecommunications with researchers, making a placement with a major network operator an ideal fit for my interests. With the LEAP team’s help, I connected with my industrial supervisor, Dr. Keith Briggs, and on the 4th of August 2025, my project began. I was tasked with writing Python code for the Cellular Radio Reference Model (CRRM), an open-source 5G simulator designed to benefit the entire research community.
My work centred on a significant challenge in wireless network research: established, high-fidelity simulators are built on C++, which creates a major usability barrier for ML researching where Python is the dominant language. CRRM’s core design confronts this by avoiding the redundant calculations common in traditional simulators. We engineered a ‘compute-on-demand’ architecture, a form of lazy evaluation. When a network state changes, such as a user moving, computation is confined only to the minimal set of affected network parameters. This architectural choice wasn’t just theoretical. In our final timing tests on a typical mobility scenario with 10% of users moving, this ‘smart update’ mechanism delivered a measured speed-up factor of 1.84 over a full system recalculation.
A core part of the internship was the process of translating dense, abstract 3GPP industry standards into functional code. I spent a considerable amount of time implementing standard 3GPP TR 38.901 pathloss models to allow the simulator to represent real-world environments. The impact of selecting the right model is substantial; my simulations showed that for a user 2000 metres from a base station, the Rural Macrocell (RMa) model predicts a throughput of approximately 67 Mb/s, while the more obstructive Urban Macrocell (UMa) model predicts a throughput of less than 10 Mb/s under the same conditions. I also implemented 3-sector base station antennas using the exact 3GPP specifications of a 65.0-degree half-power beamwidth and 30.0 dB maximum attenuation. In one demonstration of the model’s precision, a worst-case scenario was configured where a user placed between two interfering cells experienced a Signal-to-Interference-plus-Noise Ratio (SINR) of 0.00 dB. Reconfiguring the cells in the simulator to use two separate subbands entirely eliminated this interference, improving the user’s SINR to 20.00 dB.
The internship was based at Adastral Park near Ipswich, with my accommodation in the town centre. The role offered flexibility, and I used my free time to explore the Suffolk coastline. This flexibility also taught me a lesson in discipline; the feeling that more could always be done helped me appreciate the need to strike a deliberate work-life balance. The project’s complexity meant certain technical hurdles required an iterative approach. Regular meetings with Dr. Briggs evolved into deep-dive technical reviews, where we would methodically analyse a problem and use modelling to reach a solution. This collaborative process consistently led to breakthroughs, allowing me to share the resulting findings with renewed enthusiasm.
By the end of the 8 weeks, I understood the project’s direct value to BT. CRRM provides a safe, offline environment to test new automation algorithms before deployment, with the potential to support network changes that lead to multi-million pound reductions in operational expenditure.
Looking back, the experience clarified my potential career pathways. I gained hard skills, from implementing 3GPP propagation models in Python to validating interference calculations against analytical theory from stochastic geometry. I also developed soft skills, such as discussing complex ideas with a mentor and being resilient when facing difficult problems. I am still exploring my options for after graduation, but this internship gave me a tangible appreciation for how a career in technology can drive personal and professional growth. I am deeply grateful to Dr. Keith Briggs for his guidance and to the Pembroke LEAP programme for facilitating an experience that allowed me to build real skills in a high-impact setting.
