Patent ID: 9166856
Filing Date: 2015-10-20
Classification: H04L

Abstract:
1. A method for initial ranging in a wireless communication system, comprising the steps of: receiving at a base station a plurality of OFDM blocks transmitted to the base station from a plurality of remote user devices in wireless communication with the base station; processing the plurality of OFDM blocks to extract a ranging subchannel from the plurality of OFDM blocks; identifying a total number K of active codes in the ranging subchannel by applying an information-theoretic criterion to the ranging subchannel; determining active devices of the plurality of remote user devices by: (i) evaluating frequency estimates for codes corresponding to the plurality of remote user devices, (ii) searching for K largest frequency estimates, (iii) declaring corresponding codes of the plurality of remote user devices having the K largest frequency estimates as the active codes, and (iv) declaring corresponding ones of the plurality of remote user devices having the active codes as the active devices; estimating carrier frequency offsets for the active devices among the plurality of remote user devices using the active codes; estimating timing delays and power levels for the active devices of the plurality of remote user devices using the active codes; broadcasting the estimated carrier frequency offsets, timing delays, and power levels to the plurality of remote user devices; and synchronizing the plurality of remote user devices with the base station based on the broadcasted estimated carrier frequency offsets, timing delays, and power levels by adjusting transmission parameters.