Communication device, method and communication system

A method that is to be executed using a communication device including a receiving circuit configured to receive a plurality of signals transmitted at time intervals, the method comprising:

• changing the receiving circuit from a sleep state to an active state at a first time earlier than a second time when a first signal among the plurality of signals is input to the communication device;
• receiving the first signal with the receiving circuit in the active state;
• changing, after the first signal is received by the receiving circuit, the receiving circuit from the active state to the sleep state;
• measuring a first time difference between the second time of the first signal and the first time;
• determining, based on the first time difference, a third time that is a time after the receiving circuit is changed from the sleep state to the active state;
• and
• changing the receiving circuit from the sleep state to the active state at the second time, wherein the receiving circuit is configured to detect the reception of the first signal based on at least one of a frame synchronization signal obtained by modulating the plurality of signals, an output signal of a reception signal strength detector provided in the communication device, and an output signal of an energy detector provided in the communication device.

A communication system comprising:

• a transmitting device configured to transmit a plurality of signals at time intervals;
• and
• a receiving device configured to receive the plurality of signals,
• wherein the receiving device includes:
• a receiving circuit configured to receive the plurality of signals, and
• a start-up time adjustment circuit configured to transmit, to the receiving circuit, a start signal that instructs a change from a sleep state to an active state, and
• wherein:
• a first start signal that instructs a change from the sleep state to the active state is transmitted to the receiving circuit at a first time earlier than a second time when a first signal among the plurality of signals is input to the receiving device,
• a first time difference between the second time and the first time is measured,
• a third time that is a time after the receiving circuit is changed from the active state to the sleep state is determined based on the first time difference,
• a second start signal that instructs a change from the sleep state to the active state is transmitted to the receiving circuit at the second time,
• the transmitting device receives data from the receiving device and processes the data, and
• the receiving circuit is configured to detect the reception of the plurality of signals based on at least one of a frame synchronization signal obtained by modulating the plurality of signals, an output signal of a reception signal strength detector provided in the communication device, and an output signal of an energy detector provided in the communication device.

A communication device configured to receive a plurality of signals transmitted at time intervals, the communication device comprising:

• a receiving circuit configured to receive the plurality of signals;
• and
• a start-up time adjustment circuit configured to transmit, to the receiving circuit, a start signal that instructs a change from a sleep state to an active state,
• wherein the start-up time adjustment circuit is configured to:
• transmit, to the receiving circuit, a first start signal that instructs a change from the sleep state to the active state at a first time earlier than a second time when a first signal among the plurality of signals reaches the communication device;
• measure a first time difference between the second time and the first time;
• determine, based on the first time difference, a third time that is a time after a time when the receiving circuit is changed from the active state to the sleep state;
• and
• transmit a second start signal that instructs a change from the sleep state to the active state to the receiving circuit at the third time, and
• wherein the start-up time adjustment circuit includes:
• a timer unit configured to count a reference clock, based on a timer setting value, and output the start signal;
• a first latch configured to hold, based on the start signal, the timer setting value or a counter value of the timer unit;
• a second latch configured to hold, based on the plurality of signals, the counter value of the timer unit;
• a subtractor configured to subtract a value held by the first latch from a value held by the second latch;
• an integrator configured to integrate an operation result of the subtractor;
• a first adder configured to add the operation result of the integrator and the timer setting value;
• and
• a multiplier inserted between the first adder and the timer unit and configured to multiply an output value of the adder by an intermittent temporal scaling factor, and wherein an output value of the multiplier is set as the timer setting value.