To advance digitalisation in public transport, ever faster data connections to and from vehicles are required. Although mobile technologies such as 5G theoretically provide higher bandwidths, they also need more powerful antennas, especially at high speeds. On behalf of Huber+Suhner, Prof. Beat Stettler and the Institute for Communication Systems (ICOM) at the University of Applied Sciences of Eastern Switzerland (OST) performed and compared antenna measurements in the greater Zurich area. Two 4×4 MIMO* and one 2×2 MIMO antenna were compared in terms of their MIMO performance and data throughput in urban areas, the suburbs and on motorways. The measurements were taken using ICOM’s Wireless Research Vehicle, which was specially converted for this purpose.

* MIMO (Multiple Input Multiple Output) is a method with which different data streams can be transmitted simultaneously via several antennas in WLAN. MIMO increases the stability and data throughput of WLAN.

In November 2022, in-depth tests were conducted over two days in the greater Zurich city and lake region. For all measurements, the modems installed in the measurement vehicle automatically selected the best band and technology. To reflect populated areas, a route through the city of Zurich was chosen for the throughput measurements. On the road from Zurich to Wädenswil through the villages along the lake, 5G coverage is still very patchy (e.g. due to many objections), which is why this route was chosen to reflect a rather poorly covered measurement route. The route back to Zurich along the motorway was chosen to represent data throughput in a vehicle moving at high speed.

The report based on these measurements provides an insight into the performance and data throughput capacities for three different roof-mounted railway antennas, which depend primarily on MIMO performance for modern mobile radio technologies. A difference between the cross-polarised and vertically polarised antennas is clearly visible in both the conversion-factor and throughput measurements. In high-speed environments in particular, the cross-polarised antenna showed better results.

“To achieve true 5G speeds, i.e. over 500 Mbps, 4×4 MIMO is absolutely necessary. The 2×2 MIMO antenna is slower by a factor of 2.5,” Beat Stettler explains after the measurements. “Both 4×4 antennas tested achieved a high average bandwidth of around 400 Mbps even at high speeds, with peaks exceeding 900 Mbps. However, the cross-polarised version still performed better by just over ten percent. Interestingly, the highest stable bandwidths were achieved on the motorway rather than in the city. This is probably because the mobile cells in cities are busier than along motorways.”