A low-cost test platform to estimate the LTE timing advance procedure

The LTE Base Station (BS) testing process requires a large amount of investment, time and skilled resources. One important feature of LTE BS physical layer is the timing advance (TA) procedure, which is responsible for aligning the signal received from multiple User Equipment (UEs) at different cell distances. The BS informs the UE of the correct time to send the uplink frame in order to synchronize all UE frames and mitigate the interference between the terminals. Some vendors provide test platforms to emulate multiple UEs combined in a single box test system. These platforms are very sophisticated and allow the emulation of more than 500 UEs connected simultaneously, with different channels and at different distance conditions, handover, etc. Related costs can easily reach some hundreds of thousands of dollars, which are usually outside the project's budget. Besides, some features, including timing advance procedures cannot be obtained separately. Therefore, in order to test the LTE timing advance procedure with an affordable investment of less than five thousand dollars, a creative test environment was built with fiber optics and electrical/optical transceivers to emulate geographic distances inserting a delay on the RF uplink signal. This work describes the low-cost test environment and presents some lab results compared with field tests.