The activity considered three architectural options for the satellite backhaul in an LTE network, following the new architectural blueprints considered within the software network community:
A) The ground system maintains only the eNB;
B) The ground system maintains local mobility and resource management;
C) The ground system maintains a full EPC network.
The integrated architecture is a composition of Option B and Option C. The main reason to exclude Option A is the delay of the communication over the S1-MME interface which results in large delays for the handover and activation procedures leading to very large buffering, requiring significant modifications to the 3GPP standards. Additionally, option A requires non-standard modifications of the eNBs and MMEs which will (especially because of the eNBs) highly increase the price of such a system.
The architecture includes apart from the convergence layer, also the different deployed network functions. Two different PGWs are deployed, one local PGW on the UE-side and one remote on the hub side for covering the communication mechanisms of both Option B and Option C.
The Local GW (which represents a merge of a small SGW and a small PGW) is responsible for routing all local network access and terminates the local voice calls. By that the local data traffic is kept from using the satellite link. All other traffic is routed via the SGW through the convergence layer to the hub side.