Signal generating method, signal generating unit, and non-transitory recording medium storing computer program

1. A signal generating method for generating a visible light signal transmitted by way of a luminance change of a light source included in a transmitter, the method comprising:

determining, by a processor and as a method for transmitting the visible light signal from the transmitter, one of a single-frame transmitting method for transmitting data as one frame and a multiple-frame transmitting method for transmitting the data while dividing the data into a plurality of frames;

when the multiple-frame transmitting method is determined to be the method for transmitting the visible light signal, generating, by the processor, partition type information indicating a type of data to be transmitted, and generating, by the processor, combination data by adding the partition type information to the data to be transmitted;

generating, by the processor, the plurality of frames, each of which includes each of a plurality of data parts, by dividing the combination data into the plurality of data parts;

generating, by the processor, the visible light signal by adding a preamble, being data indicating a head of a frame, to the head of each of the plurality of frames; and

outputting, by the processor, the visible light signal to the transmitter,

wherein

in the generation of the visible light signal, a first preamble is added to the head of the frame located at a last position in an array of the plurality of frames as the preamble, and

a second preamble different from the first preamble is added to the head of the frame located at a position that is not the last position in the array as the preamble.

2. The signal generating method according to claim 1 , wherein

in the generation of the visible light signal, when a plurality of frames located at positions that are not the last position are present in the array of the plurality of frames, the second preamble is added to the head of each of the plurality of frames located at the positions that are not the last position.

3. The signal generating method according to claim 1 , wherein

each of the first and second preambles is constructed with an N-bit (N is an integer of 2 or more) bit string, and

the bit string indicates a number previously correlated with a bit length of a data part included in each of the plurality of frames.

4. The signal generating method according to claim 3 , wherein

each of the first and second preambles is constructed with an M-bit (M is an integer that is greater than or equal to 2 and less than N) first bit string indicating an identical number greater than or equal to 1 and a K-bit (K=N−M) second bit string indicating 0, and

the first preamble differs from the second preamble in order in which the first bit string and the second bit string are disposed.

5. The signal generating method according to claim 4 , wherein

the partition type information indicates, as the type of the data to be transmitted, a first type or a second type in which a restriction of a data configuration is different from that of the first type, and

when the partition type information indicating the second type is added in the generation of the combination data, length information indicating the bit length of the data to be transmitted and ID type information indicating a type of identification information expressed by the data to be transmitted are further added to the data to be transmitted.

6. A signal generating unit that generates a visible light signal to be transmitted by way of a luminance change of a light source included in a transmitter, the signal generating unit comprising:

a processor; and

a memory storing thereon a computer program, which when executed by the processor, causes the processor to perform operations including:

determining, as a method for transmitting the visible light signal from the transmitter, one of a single-frame transmitting method for transmitting data as one frame and a multiple-frame transmitting method for transmitting the data while dividing the data into a plurality of frames;

when the multiple-frame transmitting method is determined to be the method for transmitting visible light signal, generating partition type information indicating a type of data to be transmitted, and generating combination data by adding the partition type information to the data to be transmitted;

generating the plurality of frames, each of which includes each of a plurality of data parts, by dividing the combination data into the plurality of data parts;

generating the visible light signal by adding a preamble that is data indicating a head of a frame to the head of each of the plurality of frames; and

outputting the visible light signal to the transmitter,

wherein

in the generation of the visible light signal, a first preamble is added to the head of the frame located at a last position in an array of the plurality of frames as the preamble, and

a second preamble different from the first preamble is added to the head of the frame located at a position that is not the last position in the array as the preamble.

7. A non-transitory recording medium having a computer program stored thereon, the computer program causing a processor which is included in a transmitter having a light source which transmits a visible light signal by change in luminance, to execute operations comprising:

determining, as a method for transmitting the visible light signal from the transmitter, one of a single-frame transmitting method for transmitting data as one frame and a multiple-frame transmitting method for transmitting the data while dividing the data into a plurality of frames;

when the multiple-frame transmitting method is determined to be the method for transmitting visible light signal, generating partition type information indicating a type of data to be transmitted, and generating combination data by adding the partition type information to the data to be transmitted;

generating the plurality of frames each of which includes each of a plurality of data parts by dividing the combination data into the plurality of data parts;

generating the visible light signal by adding a preamble, which is data indicating a head of a frame, to the head of each of the plurality of frames; and

outputting the visible light signal to the transmitter,

wherein

in the generation of the visible light signal, a first preamble is added to the head of the frame located at a last position in an array of the plurality of frames as the preamble, and

a second preamble different from the first preamble is added to the head of the frame located at a position that is not the last position in the array as the preamble.