AeroMACS: Impact of link symmetry on network capacity

Aeronautical Mobile Airport Communications System (AeroMACS) is a WiMAX-based cellular technology that enables the access of Subscriber Stations (SS) to support ATC, AOC and airport applications on the airport surface. SS can be fixed stations, aircraft or vehicle embedded radios, or handheld devices. The AeroMACS access service network is provided by a number of Base Stations (BS) that operate in dedicated 5 MHz bandwidth channels. The BS manages the access of the SS to the common channel by accessing configured channels in radio cells. The connectivity to the service network is enabled through an ASN gateway that establishes the data path between the SSs and the ground network. The RTCA/EUROCAE released an AeroMACS profile indicating mandated communication features that guarantee radio interoperability. One of these features is the Time Division Duplex (TDD) configuration of the AeroMACS frames, of which a number of options allow different share of resources between the downlink (DL) and the uplink (UL) directions of the BS-SS radio portion of the datalink. This paper raises awareness on the impact of the TDD frame configuration into application-level throughput. It provides an analysis on the outcome of previous studies to demonstrate the influence of this feature, and concludes on aspects that may drive the AeroMACS capacity of a network deployment into either optimal or sub-optimal levels. The particularly challenging use case of video surveillance as an airport surface application is presented here. The paper also provides recommendations to deployment managers, network service providers and regulators to achieve an optimal AeroMACS capacity and performance.