Transmission method, reception method, transmission device, and reception device
View Patent ↗A transmission method includes: in a first period, causing a light source to emit light having a first luminance; and in a second period, causing the light source to transmit an optical signal by causing the light source to alternately emit light having a second luminance and light having a third luminance lower than the second luminance.
1. A transmission device comprising:
a light source that, in operation, emits a light; and
a processor that, in operation, controls the light source to perform:
transmitting an optical signal frame in a data transmission period, the optical signal frame including a reference symbol and a data symbol, a luminance of the data symbol being modulated by transmitted data, data transmission periods being provided intermittently;
emitting an illumination light in a first illumination period, the first illumination period being provided between two consecutive data transmission periods;
providing a guard period immediately before the data transmission period, a first luminance in the guard period being lower than a second luminance in the first illumination period; and
emitting light while changing a direction in which the light is emitted in a second illumination period,
wherein the second luminance is variable, wherein
a time ratio between the data transmission period and the first illumination period is changed based on an ambient light condition.
2. The transmission device according to claim 1 , wherein
the first luminance monotonously decreases within the guard period.
3. The transmission device according to claim 1 , wherein
the second luminance is changed based on time length of the data transmission period.
4. The transmission device according to claim 1 ,
wherein in the transmitting, the processor transmits the optical signal frame by controlling the light source to emit the light while alternating between a third luminance lower than the second luminance and a fourth luminance lower than the third luminance in the data transmission period.
5. The transmission device according to claim 1 , wherein the time ratio is changed according to whether a time of day is daytime or nighttime.
6. A method performed by a transmission device having a light source, the method comprising:
transmitting an optical signal frame in a data transmission period, the optical signal frame including a reference symbol and a data symbol, a luminance of the data symbol being modulated by transmitted data, data transmission periods being provided intermittently;
emitting an illumination light in a first illumination period, the first illumination period being provided between two consecutive data transmission periods; and
providing a guard period immediately before the data transmission period, a first luminance in the guard period being lower than a second luminance in the first illumination period; and
emitting light while changing a direction in which the light is emitted in a second illumination period,
wherein the second luminance is variable, wherein
a time ratio between the data transmission period and the first illumination period is changed based on an ambient light condition.