Patent ID: 8190891

Claim:
A transmitter, comprising: a network interface unit connected to a wireless network capable of transmitting contents for which copyright protection is necessary; an encryption processing unit configured to encrypt contents for which copyright protection is necessary; an RTT measuring unit configured to measure a round trip time after a predetermined packet is transmitted to a receiver, until a response corresponding to the predetermined packet is received; a communication permission determination unit configured to permit transmission of the contents for which copyright protection is necessary when the round trip time measured by the RTT measuring unit is within a predetermined time; and a parameter modification unit configured to change parameters of the wireless network, before the RTT measuring unit measures the round trip time, the parameters improving accuracy of the round trip time when the RTT measuring unit measures the round trip time, wherein the wireless network is Bluetooth; and the parameter modification unit changes at least one of a sniff interval expressing transmission and reception interval, a polling interval, transmission power and master-slave exchange prescribed by a standard of Bluetooth as parameters.