| 摘要 |
PROBLEM TO BE SOLVED: To maintain efficient communication between an interrogator and transponders, even if the number of transponders is increased or the amount of data changes in a communication area. SOLUTION: When several transponders 12 exist in the communication area 13 for one interrogator 11, the modulation level is changed, according to the amount of data. When communication is established between the interrogator 11 and the transponders 12 by using one carrier for each transponder 12, the modulation level is set higher, as the amount of data becomes larger. Alternatively, the modulation level is held constant and several subcarriers are used. The number of subcarriers to be used for each transponder 12 is changed, according to the amount of data. The number of subcarriers is set larger, as the amount of data becomes larger. Yet in another way, the modulation level and the number of subcarriers to be used is changed to each of the transponder 12 on a case-by-case basis, according to the amount of data. COPYRIGHT: (C)2006,JPO&NCIPI
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