Provision of guaranteed services in broadband LEO satellite networks
The provision of guaranteed services in low earth orbit (LEO) satellite networks is rather complicated due to the mobility of satellites. Users may be handed-off from one spot beam to another and/or from one satellite to another frequently during the lifetime of their calls. Traffic on inter-satellite links (ISLs) incident on a particular satellite change as the user traffic served by the satellite changes due to satellite mobility. The variation of user traffic over the ISLs may cause violation of quality of service (QoS) requirements of ongoing connections. We propose a novel protocol which we call the predictive routing protocol (PRP), which exploits the deterministic nature of the LEO satellite topology to maximize the total number of users served by the system, while maintaining each user's QoS requirements. PRP predicts the traffic load on the ISLs up to a short time in the future by using the deterministic knowledge of the LEO satellite topology and user location information. PRP determines multiple paths for a particular connection that effectively help avoid possible future bottlenecks as predicted by estimated future traffic on the ISLs. The protocol is compared with other non-predictive routing protocols such as IP routing by simulations and it is shown that PRP can deliver deterministic QoS guarantees (such as delay or delay jitter), without over-reserving channel bandwidth. An admission control curve has also been obtained which may be used to limit the number of users in order to ensure that the desired QoS metrics may be guaranteed.