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Understanding Japan's 4ms Rule for Radio Law Compliance

Learn about Japan's 4ms rule in the Radio Law, requiring stations to sense the carrier wave every 4ms to comply with regulations. Sharp Corporation's solution ensures compliance through proper channel sensing. Stay updated on regulatory requirements for HC and ESTAs in Japan.

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Understanding Japan's 4ms Rule for Radio Law Compliance

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  1. Japan local 4ms rule Yoshihiro Ohtani Srinivas Kandala Sharp Corporation November 12, 2001 Yoshihiro Ohtani, Sharp

  2. HC or Sender station have to make the carrier sense at least every 4ms. • Else Non-compliant vendors cannot sell HC-related products in Japan at all. Japan-local Radio Law in 5GHz band ( 4ms rule ) Japan-local Radio Law ( 4ms rule ) Any sending station shall make the carrier sense before sending packets. If it detects radio power (*), it should not send packet at that radio channel. (*) An electric field intensity ( in the maximum gain direction ) greater than 100mV/m, which is equivalent to -50dBm. However, it can omit the carrier sense under either of the following condition. (a) In case that the sender STA is controlled by another STA to send packet. ( However, the controlling STA has to make the carrier sense, in this case. ) (b) In case that the sender STA sends a packet again within 4ms after it made the carrier sense. Yoshihiro Ohtani, Sharp

  3. Solution for Japanese 4ms rule • HC should provide a long TXOP for this STA, and the polled TXOP holder shall ensure that the channel is sensed at least once per 4ms. • A MIB parameter “aMediumOccupancyLimit” set to 3[TU] can be used for this purpose. Time for A + Time for B + n x aSlotTime SIFS PIFS A A A A A A A B B B B B SIFS PIFS B B B B B A A A A A A A aMediumOccupancyLimit Yoshihiro Ohtani, Sharp

  4. Proposed Text for 4 ms Rule Add the following informative note in clause 9.10.2 immediately below the Note below the second paragraph: • Note: In certain regulatory domains, channel sensing should be done at periodic intervals (for example, in Japan, this period is 4 ms). This means that the duration of a TXOP in these regulatory domains should not be more than this periodic interval. If longer durations are desired then the TXOP holder shall sense the channel at least once in aMediumOccupancyLimit TU by waiting for at least for the duration of one PIFS during which it will sense the channel. If it does not detect any energy, it shall send the next frame. Implementers of HC and ESTAs should be mindful of these regulations and shall ensure that they are compliant with the regulations. This means that the total TXOP size assigned will include an extra time allocated (i.e., n x aSlotTime, where n is the number of times the ESTA needs to sense the channel and is given by floor(TXOP limit/aMediumOccupancyLimit) for the channel sensing. Yoshihiro Ohtani, Sharp

  5. Motion • Move to instruct the editor to incorporate the text in document 01/640r2 Yoshihiro Ohtani, Sharp

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