WiSA & Dynamic Frequency Selection Channels in the 5GHz U-NII Band
When I mention WiSA compliant wireless home theater speakers to my friends, they often think I’m talking about WiFi or Bluetooth speakers. WiSA is different, because it uses a robust set of frequencies that have been recently opened up within the international unlicensed (U-NII) 5 GHz radio band. These frequency channels require Dynamic Frequency Selection (DFS) procedures.
Traditionally reserved for weather and military radar applications, these channels are now available as long as conflicts with these important functions are avoided. A WiSA compliant transmitter and speaker system will scan the 5 GHZ band and find a totally unoccupied channel.
Further, it also looks ahead for another unoccupied channel, so in case of interference, it can jump directly to that channel without losing any of the audio stream. If the channel jumps in the middle of a movie or your favorite TV show, you can rest assured there will be no breaks in the audio stream.
The U-NII Band
The DFS channels from 52-140 go mostly unused, leaving plenty of quality space for wireless audio shown on DFS channel 56. 5GHz 802.11nWiFi traffic is shown on channels 40-48 and 153-161. The transmitter is looking ahead to find the next DFS channel for it to occupy.
The 5GHz U-NII band has up to 24 of these Dynamic Frequency Selection channels. Due to the strict DFS requirements, and the nature of 5GHz radio (it doesn’t pass well through concrete or brick walls, not an issue with home theater), the DFS frequencies are seldom used, leaving plenty of room for all of the neighbors.
The extra bandwidth and fewer errors due to interference mean that the system is more reliable. When wireless conflicts do happen, the system falls back on tried-and-true recovery methods, such as those used on CDs:
- Forward error correction – extra data is sent to make 100% repairs
- Error concealment – missing (uncorrected) data is filled in a way that is unnoticeable.
- Play-out buffer – allows longer concealment ability
- Silence – avoid noisy artifacts at all cost
All WiSA compliant components are all tested in to ensure clean communications within a 30x30 foot (10x10m) area even when interference is present. We actually have tried our demo system in rooms larger than 30x30 without having any issues. The obvious target market for WiSA certified components is home theater, but we feel strongly that the WiSA DFS technology will eventually grow and be adaptable to larger commercial installations and live events.