Impact of DME Interference on LDACS Channel Estimation in En-route Phase

L-band Digital Aeronautical Communications System (LDACS) is an air-to- ground digital communication system operating at 960-1164 MHz, which is going to play an important role in the future communication infrastructure. Considering that aeronautical channel makes significant impact on LDACS signal transmission, channel estimation and compensation are necessary for LDACS signal processing. Since LDACS and DME systems are in the same frequency band, the existence of DME signal brings challenges for LDACS channel estimation. In the case of using the Inverse Distance Weighting (IDW) algorithm to calculate distance factors, it is necessary to optimize the time-frequency weights. This paper conducts separate optimizations of the weights under both interference-free and DME background signal conditions and compares the results. Besides, we proposed a new pilot pattern, which is much simpler compared with the existing one. The performance of these two pilot patterns is analyzed in detail. The result shows that DME signals makes little impact on the weights optimization. And the proposed pilot pattern has a shortfall of only 1 dB in the performance to meet the BER compared to the existing pilot pattern. The performance difference is acceptable in relation to the system margin of the implementation.