In this paper, an L-DACS1 physical layer laboratory demonstrator is presented which has been implemented recently in FPGA technology by the German Aerospace Center (DLR). The main goal of this lab demonstrator is to perform first compatibility measurements between L-DACS1 and legacy L-band systems where interference from L-DACS1 towards the legacy systems as well as interference from the legacy systems onto the L-DACS1 receiver is considered. The lab demonstrator is already implemented up to the first intermediate frequency at 10.7 MHz. The radio frontend for up-/down-conversion to/from the Lband is scheduled to be delivered in May this year. First compatibility tests are planned to take place in the labs of the German ATC authority DFS this summer. Using real hardware equipment, these tests will give valuable insight into the L-band coexistence issue and possible deployment scenarios.
In this paper, a new access scheme for an aeronautical mobile ad-hoc network (MANET) is presented. The access scheme combines the ideas of nested cellular reuse patterns and variable guard times. The nested cellular reuse patterns solve the hidden station and the near-far problem whereas variable guard times ensure the efficiency of this particular access scheme. Conventional approaches for coordinated, consecutive transmissions require fixed guard times. Considering aeronautical MANETs with their large dimensions together with typical aeronautical applications having short message durations, fixed guard times are inefficient, since the ratio between massage duration and guard time becomes too small. An algorithm for calculating the variable guard times in a MANET is presented and a lower bound for the mean required guard time is derived. In addition, the question of message collisions that might influence the stability of the algorithm is addressed.
In this paper, the L-DACS1 physical layer laboratory demonstrator development is described which has been recently carried out by the German Aerospace Center (DLR). The main goal of the lab demonstrator is to perform first compatibility measurements between L-DACS1 and legacy L-band systems where interference from L-DACS1 towards the legacy systems as well as interference from the legacy systems onto the L-DACS1 receiver is considered. In addition to the demonstrator description, results from functional tests of the lab demonstrator as well as the measurement scenarios foreseen for compatibility testing are presented. The compatibility measurements will take place at the labs of the Deutsche Flugsicherung GmbH (DFS) -the German ATC provider -in fall this year.
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