Getting LTE Device Design Right

By Michael Keeley On January 1, 2011

The current large-scale rollout of commercial non-proprietary LTE is our industry’s most ambitious initiative since the first cellular networks were launched years ago. Designing mobile devices for LTE is very different from previous mobile design efforts, mainly due to three key factors:

  1. Complexity – LTE brings major changes to every link in the network from the core to the mobile device.
  2. Multi-technology support – Subscribers expect voice and data applications to run seamlessly as they move between networks or service areas. As a global standard, LTE demands devices that simultaneously support CDMA, UMTS and, of course, LTE.
  3. The popularity of data applications and the demand for faster data rates.

Multiple-In Multiple-Out (MIMO) technology will significantly impact the success of LTE. It is a “game-changer’ with the potential to multiply data rates without incurring additional spectrum costs.

But when MIMO is used, the device’s physical orientation directly affects the system’s capability. The system must quickly adjust as the device moves. Over-the-air (OTA) testing of device designs ensures that the system adjusts properly and quickly enough to realize the “headline” data rates promised by LTE.

Next, what happens when a subscriber launches a data application using LTE service, then moves out of range into a CDMA-only area? Finding out requires mobility or Inter-RAT (Inter-Radio Access Technology) testing, which involves multiple emulated radio networks working in concert to provide realistic repeatable scenarios.

Data testing must be done with realistic network conditions. This includes not only Inter-RAT, RF fading, and MIMO scenarios, but adverse-condition (e.g. overloaded network) scenarios as well. In addition to throughput testing, data testing requires “data retry” or “device aggression management” testing, which ensures that a network won’t be overrun by service-connection requests when, for example, a network-based server goes down.

LTE is one of the few large-scale technologies to be deployed before the device certification process is finalized. Because of this and because of the new pitfalls outlined above, network operators and mobile device manufacturers alike are adding whole new areas of interest to their device test plans. Base largely on lessons learned from other large-scale wireless deployments, these new test plan philosophies are here to ensure that LTE delivers on its promise.


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