Reducing international call costs for roamer to roamer calls

Existing mobile telecom operators allow subscribers to receive mobile phone services when they roam in other countries. However, call setup to an international roaming subscriber is indirectly routed through the home network of the subscriber, which results in the usage of two expensive international telephone trunks. In this paper, we propose a plug-in roaming gateway to avoid the international trunk connections. Our solution is especially attractive when both call parties are roamers.