Welcome to our new WiFi Ninjas Podcast episode!
We’re lucky again to get a chance to speak with a true legend! This time around we chat with Andrew McHale discussing some juicy voice design tips.
A bit about Andy:
- Worked for Vocera for 8 years as an implementation engineer
- Assess Vocera Badge and smartphone performance on customer WLAN’s
- Part of Vocera’s internal Wireless Council
- Assessed hospitals, libraries, hotels, schools, offices, and a superyacht for VoWLAN quality
- Assessed in Asia, Middle East, Europe, UK and North America
- At least 1 access point at a minimum of -67dBm everywhere.
- Ideally 2 access points greater than -67dBm everywhere.
- Access points in corridors… Bad?
Avoid DFS Channels:
- DFS channels add a LOT of time to scanning
Advertise SSID in Beacons!
- We used to cope with 3 – 4 channels in a very crowded band
- 5GHz is a cleaner band
- Voice devices often scan all configured channels
- Europe/UK only has 4 non-DFS channels
- 36-64 if indoor only, 36-48 + 100-112 if supporting outdoors
- Sharing is Caring – use 11k.
- Use 20MHz Wide Channels
- Only using 8 channels (right…!), we can’t afford to bond them.
- Voice doesn’t need 20MHz, let alone 40MHz.
- 5 SNR everywhere is challenging, why take a 3-6dBm Noise hit because you’re bonding channels.
PSK, OKC or 11r:
- What do we want? FAST ROAMS! When do we want them? EVERYTIME!
- Pre-shared key 4 way handshake is quick and consistent
- What is quicker than PSK exchanges? No exchanges!
- OKC/11r can save the client performing the full re-auth
- DO NOT make a voice client perform RADIUS authentication every time.
No subnet roaming:
- 400ms is a quick DHCP exchange. No biggie right?
- Voice needs delay below 150ms.
- 400-800ms (DHCP) + 100-200ms (Roam) = sad faces!
- Ensure voice clients only perform DHCP at Association
- Set lease renewal to an entire shift (8hr in business, 12hr in Hospitality/Healthcare)
- End-to-End QoS is hard.
- Suck it up buttercup, this is why you get the big bucks!
- Peer-to-peer voice clients need it to avoid downstream voice packets casually skipping along holding hands with Facebook status updates…
AP Power Levels:
- 2011 – “Please turn your AP’s Down, they’re on Max power”
- Too much CCI
- 2019 – “Please turn your AP’s Up, they’re on Min power”
- Too much roaming
- Put a leash on RRM.
- Don’t leave -125dBm/30dBm defaults, we’re better than that.
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