scope:

Introduction

Recommendation ITU-R M.1652 recommends that, in order to facilitate sharing with radars, mitigation techniques be implemented by wireless access systems including radio local area networks (RLANs) (WAS) in the bands used by radars at 5 GHz. It describes a mitigation technique, named dynamic frequency selection (DFS), which requires a radar detection mechanism to be implemented. In addition, the Recommendation also gives the detection and response requirements with which the DFS should comply with.

This Report considers how radars operating in the 5 GHz band can be detected by WAS without extreme constraints on the RF front-end design or on the system capacity of the WAS.

Radar detection may only be possible during the time there is no active transmission in the WAS cell. During channel availability check time, there is no transmission for a significant time (e.g. 60 s). During in-service monitoring the detection can take place during moments of no uplink or downlink traffic.

The detection of a radar pulse of power above the so-called DFS threshold triggers a DFS procedure, and the access point must leave the channel within a short delay. In this Report the interplay of DFS threshold TDFS, WAS false alarm rate and radar detection failure rate by WAS are presented and discussed from the point of view of implementation of radar detection in a WAS receiver.