Another Interframe Space: RIFS

Another Interframe Space: RIFS

By CWNP On 08/15/2007 - 9 Comments

RIFS (Reduced Interframe Spacing) is a means of reducing overhead and thereby increasing network efficiency.  RIFS may be used in place of SIFS to separate multiple HT format transmissions from a single transmitter when no SIFS-separated response transmission (like an ACK) is expected.  The RIFS is the time from the end of the last symbol of the previous frame to the beginning of the first symbol of the preamble of the subsequent frame as seen at the air interface.  The value of RIFS for the MIMO PHY is 2us.  

 

An AP must set the RIFS mode field of the HT information element to 0 (prohibited) if the Operating Mode is set to 3 (HT mixed mode).  If the Operating Mode is set to 1 (HT non-member protection mode), the AP may set the RIFS mode field to 0 according to implementation-specific criteria (i.e. such as to protect legacy overlapping BSSs in the primary or secondary channels).  Otherwise the RIFS mode field is set to 1 (permitted).  

A station that is associated with a BSS may protect RIFS sequences when the Operating Mode field of the HT Information element transmitted by its AP is set to 1 (there may be non-HT stations in either the primary or secondary channel or both).  A STA that is associated with a BSS must protect RIFS sequences when the Operating Mode field of the HT Information element transmitted by its AP is set to 3 (HT Mixed).  RIFS are only to be used when the RIFS Mode field of the HT Information element is set to 1.

0 Responses to Another Interframe Space: RIFS

Subscribe by Email
There are no comments yet.
<< prev - comments page 1 of 1 - next >>

Leave a Reply

Please login or sign-up to add your comment.
Success Stories

I literally just came out of the testing centre having taken the CWDP exam. The certification process opened my mind to different techniques and solutions. This knowledge can only broaden your perspective. Great job, CWNP, you have a great thing going on here.

-Darren
Read More

Working through the CWNP coursework and certifications helped not only to deepen my technical knowledge and understanding, but also it boosted my confidence. The hard work it took to earn my CWNE has been rewarding in so many ways.

-Ben
Read More

I want to commend you and all at CWNP for having a great organization. You really 'raise the bar' on knowing Wi-Fi well. I have learned a ton of information that is helping my job experience and personal career goals, because of my CWAP/CWDP/CWSP studies. Kudos to all at CWNP.

-Glenn
Read More