Overview of legacy systems in L-band and its influence on the future aeronautical communication system LDACS1

L-band digital aeronautical communications system type 1 (LDACS1) is the broadband candidate technology for the future aeronautical communications system in the L-band. As unused spectrum is very scarce in the L-band, LDACS1 pursues the approach to make use of the gaps between adjacent channels used by the distance measuring equipment (DME) to meet the capacity requirements of a new aeronautical data link. This is a challenging approach as the power of DME signals is well above the LDACS1 received power in most cases. Moreover, additional legacy system operating in the L-band will interfere with LDACS1. Herein, we will first introduce LDACS1, focusing on the physical layer design. Next, the different systems operating in the L-band are briefly described, with a particular emphasis on their influence onto LDACS1. For comparison of the influence from the different systems, we will calculate an interference duty-cycle, specifying the fraction of time LDACS1 is exposed to interference from the different legacy systems