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FASTER SIGNALING OF DYNAMIC FREQUENCY SELECTION (DFS) TO CLIENTS

IP.com Disclosure Number: IPCOM000242970D
Publication Date: 2015-Sep-03

Publishing Venue

The IP.com Prior Art Database

Related People

David Kloper: AUTHOR

Abstract

The Network Allocation Vector (NAV) of Wi-Fi® systems can be used after Dynamic Frequency Selection (DFS) detection to speed Clients to go quiet, resulting in less interference to the primary channel owner (radar). Faster response and reduced impact to radar can be achieved. This makes spectrum sharing more practical, so as to allow Wi-Fi to enter other shared frequency bands.

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FASTER SIGNALING OF DYNAMIC FREQUENCY SELECTION (DFS) TO CLIENTS

AUTHORS:

David Kloper

CISCO SYSTEMS, INC.

ABSTRACT

    The Network Allocation Vector (NAV) of Wi-Fi® systems can be used after Dynamic Frequency Selection (DFS) detection to speed Clients to go quiet, resulting in less interference to the primary channel owner (radar). Faster response and reduced impact to radar can be achieved. This makes spectrum sharing more practical, so as to allow Wi-Fi to enter other shared frequency bands.

DETAILED DESCRIPTION

     In wireless networks that use unlicensed spectrum, there is a push for more unlicensed ("open") spectrum. One solution involves reducing the emissions profiles after Dynamic Frequency Selection (DFS) detection. The access point (AP) needs to flush any downstream traffic from its hardware queues, and stop generating new downstream traffic, including Beacons + Probe Responses. There is also concern with upstream traffic that might be multiplied due to repeatedly retried frames resulting from the AP moving onto another channel, and possibly using decreasing data rates. This residual upstream traffic may be due to latency in processing the announcement, flushing data already in hardware queues, and from missing the announcement when Clients are in Power Save state.

    It has been suggested that the AP remain on channel for some closing duration, and continue to generate Acknowledgment/Block Acknowledgment (ACK/BA) response control frames to minimize harm, but additional ways of minimizing upstream traffic are being investigated.

    A different solution is presented herein. Suppose when in this channel quiescence mode the AP sets the Network Allocation Vector (NAV) for all ACK/BA it generates to

Copyright 2015 Cisco Systems, Inc.

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0x8000, indicating a Contention Free Period (CFP). Since the ACK/BA is sent at legacy rates, requiring minimal Signal-to-Noise Ratio (SNR), there is a good probability that any other awake Wi-Fi® device on channel would honor the NAV and go silent, including Clients in a co-channel Basic Service Set (BSS). This can be further enhanced by limiting the AP in this mode to always sending the ACK/BA at 6 Mbps. Clients that wish to support these new channels would be required to recognize the CFP on a DFS channel from any device, and stop all transmissions excluding immediate ACK/BA control response frames, until re-enabled by their Master (AP) sending a Beacon or Contention Free (CF)-end. Clients would still respond normally to downstream traffic, but the pause in upstream may help a neighboring AP to improve its chance of detecting the radar, when visible to several co-channel APs.

    Another usage of t...