Testing LTE Connectivity in Cars

Ensuring Optimal End-User Experience

Testing LTE Connectivity in Cars

LTE-advanced (LTE-A) technology implemented into new cars is becoming a commodity within the industry. Due to the long development cycle and the fact that cars live a long life in the market, it is imperative to ensure the functionality of LTE during the development cycle. LTE-A uses MIMO antenna technology (multiple-input and multiple-output) to exploit multipath propagation, multiplying the capacity of a radio link.

There are multiple factors influencing LTE Quality-of-Service (QoS) in a car, including:

• Device RF front-end performance
• Car antenna gain and sensitivity
• Car antenna performance, placement, and housing
• Modem interoperability with different cellular networks
• Cellular network conditions, settings, and configuration

There are basic test cases that need to be performed to collect data on LTE performance, to verify the QoS, and to secure the time-to-market of the vehicle:

• Antenna performance field verification, including MIMO
• Modem and antenna field testing

Antenna Performance Field Verification

The car antenna design and the placement of the antenna impact the cellular coverage perceived in the car. With modern MIMO antennas, the antenna design and placement also have a direct impact on the achievable maximum bitrate.

Challenge:

• What antenna location gives optimal LTE performance?
• Does my MIMO antenna deliver what it should?

Solution:

• Perform throughput performance and quality measurements comparing various locations
• Confirm that the chosen location delivers the expected level of quality

With Nemo Outdoor, antenna performance can be measured and compared in the field, both in terms of coverage and MIMO (throughput) performance. The Nemo solution enables side-by-side benchmarking of commercial smartphone antennas and car antennas.

In the Nemo test solution, Nemo Outdoor controls the measurements, a scanner connected to the car antenna is assessing coverage, and a smartphone with external antenna connectors is connected to the car antenna for active testing, indicating throughput and coverage. The real-time measurements can be saved for later postprocessing and analysis.

There are three ways Nemo Outdoor can perform antenna performance verification measurements:

• with a scanner
• with a test handset connected to the car antenna
• with a car’s internal modem with diagnostics

With a Nemo Outdoor + scanner setup, you can measure MIMO condition number which indicates the performance of a MIMO channel in the environment and is not impacted by the network load. Using a scanner for antenna performance verification enables equal comparison of drive tests made at different times, which is not possible with a test handset or car’s internal modem due to different network loads. With a scanner you can also try to estimate the MIMO performance of each channel.

When performing antenna performance verification with a test handset or a car’s internal modem, you can measure the actual MIMO usage and data throughput, which is not possible with a scanner. Using a test handset/modem enables real QoE benchmarking provided the measurements are done at the same time and with the same device while network impact has been normalized out. Furthermore, with a test handset/modem, you can measure both RANK requested by the mobile and configured by the network.

In other words, all three options have their benefits and challenges and can be used to measure and verify different things.