Exploiting platform diversity for GoS improvement for users with different High Altitude Platform availability

This paper investigates the ways of improving the Grade-of-Service (GoS) in a coexistence scenario with different user types in a multiple High Altitude Platforms (HAPs) system with shared coverage area and radio spectrum. It is achieved through the exploitation of HAP diversity. An analytical model based on a two-dimensional state-transition-rate diagram is developed to describe system behaviour of a coexistence scenario containing two user groups, which have full and limited HAP availability. On the basis of the analytical model, a novel restriction mechanism is implemented in order to achieve a fair balance of GoS to the two user groups using connection admission control (CAC). The mechanism restricts access to the channel resource for users with full HAP choice in order to give more chance of access to users with a more limited HAP selection. Different types of restriction function are analysed and the paper shows that a step restriction function is the most suitable mechanism to provide a balanced low blocking probability performance to both user groups simultaneously. Furthermore, the mechanism can potentially provide a certain level of GoS guarantee for the users if adequate flexibility is available within the whole system.