| CPC H04B 11/00 (2013.01) | 20 Claims |

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1. A device, comprising:
one or more processors; and
a non-transitory computer-readable medium storing instructions that, when executed by the one or more processors, cause the device to:
segment data into a sequence of symbols, each of the symbols having a preset number of bits;
determine for each symbol of the sequence of symbols three or more tones based on a mapping between symbols and sets of tones selected from tones spread evenly over a frequency spectrum, wherein the mapping includes a mapping between the symbols and a multi-tone Frequency Shift Keying (FSK) signal including three or more tones; and
generate an audio signal based on the determined tones for each symbol of the sequence of symbols.
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