Concurrent Detection Mode Description#

Concurrent mode is a dual detection of Wi-SUN FSK and Wi-SUN OFDM frames at the receiver side.

This feature can be considered as an advanced mode switch case without signaling, which improves network performance. This feature requires that the receiver listens to both FSK and OFDM frames simultaneously. The first detected preamble selects the demodulator used for frame reception, FSK or OFDM. As such, only one frame can be received (no concurrent reception).

Given concurrent detection is an extension of mode switch, it is based on Wi-SUN PHY Technical Profile Specification 2V00 and uses all its definitions, in particular:

  • The base PHY is the FSK PHY

  • The alternate PHY is the OFDM PHY

Concurrent mode could be used by the stack as the Wi-SUN FAN 1.1 mode switch. The channel numbering re-uses the same rules as for Wi-SUN FAN 1.1 as listed below:

  • The channel of the new operating mode must be a valid channel as specified by the ChanPlanID and the respective ChanMask in Wi-SUN PHY Technical Profile Specification 2V00.

  • The channel of the new mode must be the one with a center frequency closest to that of the original channel used in base mode. If two channels are equally distant from the original channel, the higher channel must be used.

Note that Wi-SUN mode switch and thus the channel selection scheme differ from the one defined in IEEE802.15.4-2020.

The same RF signal is used to do the dual detection. The base (FSK PHY) channel number automatically selects the alternate (OFDM PHY) channel number as shown below for FSK mode XX and OFDM option XX.

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  • Base channel number 0 up to 7 selects alternate channel number 0.

  • Base channel number 8 up to 13 selects alternate channel number 1.

Depending on the selected base channel number the Intermediate Frequency (IF) in the receiver is dynamically computed for the base and the alternate PHY. Therefore, the user cannot modify the IF in concurrent mode.