GSM/GPRS Erlang capacity analyses and simulations under air traffic loading conditions

This paper looks at the general packet radio system (GPRS) technology as an alternative communications technology for the air traffic users within a managed air space. This technology can compliment, or back up the more conventional links such as VHF digital link modes VDL 2,3,4. Theoretical maximum speeds of up to 171 kilobits per second (kbps) are achievable with GPRS. In addition, it is a widely accepted migration step toward Third generation universal mobile telecommunication system (3G UMTS) which will provide even more capabilities through the use of wideband code division multiple access (W-CDMA). This study involved the computation of availability/blockage of voice and controller pilot data link communications (CPDLC) data over GSM/GPRS. The Erlang B was used for the voice, while the Erlang C was used for the data services to compute the availability of each. Traffic loads are obtained for the airport, terminal, and enroute airspace domains. Several parameters that effect the availability results were studied including the outage definition time, range of service data, number of available TDMA logical channels, and buffer size. The results show very good availability for busiest airspace demand rates for year 2015. Overall, the voice communications will reduce the system availability the most, followed by the data applications. The most significant reduction of ideal maximum capacity is probably the limitation of the controller's human capability to handle a large group of aircraft within a sector. Nonetheless, automation advancements may improve that limitation in the future