A Gateway 3 receives mobile station data corresponding to a mobile station 2 from a switching center in a mobile packet communication network 1. The mobile station data may be communicated with a communication protocol such as Network Management Protocol (NWMP). Mobile station 2 transmits and receives user data, such as Hypertext Transfer Protocol (HTTP) data, in a protocol, such as HTTP, via gateway 3. In transmitting user data from mobile station 2 to a server 5, gateway 3 may add the mobile station data corresponding to mobile station 2 to the data. Mobile station 2 cannot falsify the mobile station data because the added mobile station data corresponds to identification data used in establishing a wireless connection between mobile station 2 and mobile packet communication network 1. As a result, server 5 may trust mobile station data added by gateway 3 to the user data transmitted from mobile station 2.