Wireless Labs

Service and Facilities - Wireless Laboratory

Dynamic Frequency Selection (DFS)

BACL performs Dynamic Frequency Selection (DFS) testing for 802.11a wireless devices with the latest upgraded Radar Generator testing system according to the current standards (including the latest weather radar at 5.6-5.65 GHz):

EN 301 893 v1.4.1 and v1.5.1
FCC 15.407;
Japan DFS

BACL’s test capabilities are major benefits for WLAN manufacturers who are now able to test for compliance to multiple DFS regulatory domain requirements at one facility.

Dynamic Frequency Selection was designed to instruct “master” devices to monitor, detect and respond to aircraft, military, weather and civil radar operation within certain selected frequency ranges in the 5 to 6 GHz band. When the user system is impinged by a radar signal, detection and response is required and the operating channel must cease operation and proceed to vacate this channel frequency. Those instructions are provided from the master to the “client” device to switch to another channel.

BACL continues offer its customer with quality services which meet the test and certification needs.

Updates:

Dynamic Frequency Selection (DFS) requirements change for Europe’s EN 301 893.

In November 2008 the European Union’s Official Journal (OJ) published a list of standards for the Radio and Telecommunications Terminal Equipment Directive (R&TTED). The list indicated that the radio spectrum standards for devices using the 5150-5350MHz and 5470-5725MHz unlicensed bands (e.g. Wi-Fi 802.11a/n devices) remain as previously published - this is EN 301 893 V1.4.1 and EN 301 893 V1.3.1, with EN 301 489 V1.3.1 superseded by v1.4.1 on March 31st 2009.

The previous listing OJ listing had indicated that the V1.3.1 and V1.4.1 standards did not adequately address protection for meteorological radars using the 5600-5650 MHz band and added the following requirements for that sub-band:

Detection of interleaved radar waveforms (no previous requirement to detect non-constant pulse periods);
Detection of pulse widths of 0.8us (previously minimum width was 1.0us);
A 10-minute Channel Availability Check (CAC)

The requirements only applied in the sub-band and as an alternative, devices could be configured to not use the sub-band (e.g. blocking out channels 120 through 130 for 802.11an devices).

The most recent listing updates the footnote to EN 301 893 V1.4.1. This new note requires that devices subject to the radar detection requirements1 in the 5250 – 5350MHz and 5470-5725MHz bands will need to be evaluated for their capability to detect interleaved radars across all DFS bands if they are to be placed on the market after April 1, 2009. The requirements for using the 5600-5650 MHz band remain unchanged (10-minute Channel Availability Check and ability to detect 0.8us pulse widths).

Following is the comparison of EN 301 893 V1.4.1 and EN 301 893 V1.5.1:

Table 1: EN 301 893 V1.4.1 vs EN 301 893 V1.5.1 DFS Requirements
Parameter	EN 301 893 V1.4.1 Requirement	EN 301 893 V1.5.1 Requirement
Minimum channel availability check time (CAC time)	60s	60s outside 5600-5650MHz 10 minutes for 5600-5650MHz sub-band
Off-channel channel availability check time	Off-channel CAC not implemented in this standard.	4 hours outside 5600-5650MHz 24 hours for 5600-5650MHz sub-band
Channel Move time	10s (maximum)	10s (maximum)
Channel Closing Time	260ms (maximum)	1s (maximum)
Interference Detection Threshold	-64dBm Transmit power ³ 200mW -62dBm Transmit power < 200mW	DFS Detection Threshold (dBm) = -62 + 10 - EIRP Spectral Density (dBm/MHz) + G (dBi)Shall not be lower than -64 dBm assuming a 0 dBi receive antenna gain.
Non-occupancy period	30 minutes (minimum)	30 minutes (minimum)
Note – Slave devices (aka client devices) do not need radar detection capabilities unless they have an output power (eirp) that exceeds 200mW. All devices need to demonstrate compliance with the channel move and channel closing times. The off-channel CAC mechanism allows for non-continuous monitoring of one channel while operating on another channel in order for a device to be able to quickly move from one channel to another.

BACL has updated their software version for DFS testing to meet both V1.4.1 and V1.5.1 requirements. It can generate the 0.8us pulse width radar signals according to V1.5.1, and still keep the requirement for the V1.4.1 version.

Please contact our Compliance Experts for technical inquiries or our friendly Sales Team to schedule testing or a tour of our facilities.