DoPa (DoCoMo Packet Transmission) is a packet-switched network service developed by NTT DoCoMo in Japan for Internet connection from mobile devices. NTT DoCoMo, Japan's leading wireless technology company, created their popular i-Mode service by adding features to DoPa that made it easier to use and allowed a wider range of content to be delivered. The transmission of packets allows the service to charge by the number of packets transmitted, so the customer pays for the volume of data, rather than according to call duration and distance, as is almost always tbe case with circuit-switched services.