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Future Aeronautical Communications Part 16

Tham khảo tài liệu 'future aeronautical communications part 16', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | The Airborne Internet 363 6.2 GLSR handover strategy In order to increase per-aircraft bandwidth an inflight connectivity provider will likely deploy an A2G access network composed of geographically distributed ground stations along the coast at appropriate locations dictated by the expected transoceanic air traffic patterns of its customer airlines. The total data traffic demand in the airborne mesh network can then be better accommodated by sharing the load among multiple IGWs. A trivial approach to the Internet Gateway assignment problem is shown in Fig. 12. Nodes are assigned to the geographically closest topologically reachable IGW. The dotted lines represent the Voronoi diagram corresponding to the set of points where the IGWs are located. Each Voronoi cell Vi represents the area formed by all points on the sphere whose geographically closest IGW is i. All aircraft within Vi are served by IGW i. Whenever an aircraft crosses a cell boundary say from Vi to Vj a handover procedure is performed between the aircraft and the access network to transfer all A2G communications for that aircraft from IGW i to IGW j. Fig. 12. Internet Gateway assignment based on geographic proximity Voronoi diagram . The proximity criterion ignores two important aspects The spatiotemporal distribution of traffic demand in the airborne mesh network. At any given time the aggregate traffic demand from all airborne nodes in a Voronoi cell may vary greatly among different cells e.g. the number of nodes Vk flying within each Voronoi cell Vk can be very different. The total A2G capacity Ck cu at each IGW k. A richly connected IGW may be able to serve a larger number of users e.g. by performing load sharing among A2G links. Compare the IGWs in Ireland over forty A2G links and Iceland just two A2G links in Fig. 12. A simple way to address these two important aspects together is to consider the impact of an imbalance between A2G demand and A2G capacity on an IGW s transmission buffers. 364 .