1 / 5

CCA- and slot-time relations

CCA- and slot-time relations. Jan Boer Agere Systems. IEEE Std 802.11g/D2.8, May 2002 clause 19.4.5 CCA.

damali
Télécharger la présentation

CCA- and slot-time relations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CCA- and slot-time relations Jan Boer Agere Systems Jan Boer, Agere Systems

  2. IEEE Std 802.11g/D2.8, May 2002clause 19.4.5 CCA b) With a valid signal (according to the CCA mode of operation) present at the receiver antenna within 5 µs of the start of a MAC slot boundary, the CCA indicator shall report channel busy before the end of the slot time. Refer to Figure 47 (should be 58)of IEEE Std 802.11, 1999 Edition for a slot time boundary definition. d) The start of a valid OFDM transmission at a receive level equal to or greater than the minimum 6 Mbit/s sensitivity (-82 dBm) shall cause CCA to indicate busy with a probability >90% within 4 µs. • b) is copied out of 11b, d) is copied out of 11a • Looks inconsistent, d) is overspecified for the 11b (or 11g) slottime (20µs) Jan Boer, Agere Systems

  3. Jan Boer, Agere Systems

  4. Slottime relations n n+1 n+2 Slottime 20µs CCA del RX/TX CCA del RX/TX CCA del RX/TX MAC slot boundery Station A (wants to transmit at slot n+1, performs CCA in slot n) CCA idle Transmit Station B (wants to transmit at slot n+2, performs CCA in slot n+1) CCA active Defer At a slottime of 20µs the CCA time can be 15µs independent on the modulation received Jan Boer, Agere Systems

  5. Proposed change • In 11b the CCA time is specified to be 15µs (minus the MAC proc. delay), with a slottime of 20µs • To copy the 11a CCA time to 11g is overspecifying. Also for OFDM the CCA time can be 15µs at a 20µs slottime. This longer time can be used to make the the probability of the CCA indicator more reliable. • Proposal: b) With a valid signal (according to the CCA mode of operation) present at the receiver antenna within 5 µs of the start of a MAC slot boundary, the CCA indicator shall report channel busy before the end of the slot time. In case of a valid OFDM signal at a receive level equal or greater than –82dBm the probability of the CCA indicator to report channel busy shall be > 90%. Refer to Figure 58of IEEE Std 802.11, 1999 Edition for a slot time boundary definition. Delete d) Jan Boer, Agere Systems

More Related