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When a GSM user travels to a foreign country, it is anticipated that a call delivery from a caller in that country to the GSM roamer should be a local phone call. Unfortunately, under the current GSM implementation, the call delivery results in two international calls! In this article we explain why current GSM implementation is expensive for this kind of call delivery, and then propose four solutions to reduce the two international calls into one local phone call. Our solutions may significantly reduce the nonnecessary usage of international circuits as well as customer costs.
Cho et al. (Wed,) studied this question.