Ok, so 802.11ad, previously known as WiGig, promises speeds up to 7GB, which should be enough to stream 4K video w/o problems. So, can I use it for the surveillance system and other video streaming applications?
- According to Wiki, the minimal Rx sensitivity for minimal datarate (that is 385Mbps PHY mind you!) is -68dBm.
- According to this source (read it for more details on 802.11ad it’s good, despite the website design), max output power in 60GHz range is limited to 10dBm. You got it right – that’s 10 times less than your normal Wi-Fi.
- The FSPL for mere 10m in 60GHz is (according to numerous calculators on the Internet) is 88dB. Plus, there are adverse effects due to oxygen molecules resonating at around 60GHz (with peak at 63GHz), absorbing even more energy. But let’s ignore that for now.
Let’s see what we can get at 10m from the AP:
- Building the link budget : TXpower + TX/Rxgains – FSPL >= Rxmin. (that’s w/o any other losses due to attenuation, reflection, the aforementioned oxygen absorbtion, etc)
- In our case: 10dBm + Gains – 88dB >= -68dBm
- Or, Gains >= 88-68-10 = 10dB
So, in order to establish minimal 802.11ad connectivity at 10m we need 10dB extra gain in the link. We can get it on the Rx (antenna, MRC, etc) or Tx (antenna, beamforming) side. Let’s take another look:
- Rx Antenna gain for many Wi-Fi mobile devices is <=0 (can be actually negative due to losses and overall small size), is there a reason to believe that things will be better with 802.11ad? Don’t see any gains here.
- 802.11n/ac utilize MRC that may provide extra 3-5dB gain, but 802.11ad seems to not use it (there is not a single occurence of MIMO or MRC in the standard). Nothing to gain here as well.
- Tx beamforming: 802.11ad can use TxBf, which is good. However, the results of 802.11ac showed that the gains are not that big: 3-5dB. No reason to believe that 60GHz TxBf will be any better.
- This leaves us with Tx antennas, that should provide at least 5dB gain. While it is perfectly possible to have 5dB omni antennas, their beamwidth in vertical plane will be around 15deg, which doesn’t seem very useful. Alternatively, you end up with directional antennas, which may be OK for some applications, but imposes limits on mobility, alignment, etc.
Summary: in my opinion (which may be wrong, BTW, will be glad to hear back), 802.11ad will unliely work even at 10m with standard Omni antennas. So:
- Wireless replacement for my monitor cable? Yes, but think of the power cable…
- Wireless streaming of HD/4K from my mobile device to a TV (so I don’t have to plug a cable) – maybe (if your counch is not too far from the TV)
- Wireless 4K camera streaming to something nearby – yes, but why?
- Wireless backup / video dump to my external/portable hard drive – likely.
- Wireless giga-speed “USB stick” – hey, why not? 🙂
- 60GHz wireless mouse/headset – be my guest, I’ll only be happy to see all BT stuff to get out of Wi-Fi band 🙂 Alas…
- 60GHz SOHO wireless bridges – why not, you can get dish antennas with huge gain, and go even beyind 100m! 🙂
- Wireless video surveillance – unlikely, unless in SOHO setting (small distances) and both camera has a decent, properly pointed directional antenna. I.e. unlikely.
- Would be interesting to see 802.11ad mesh network 🙂
So this is it – very fast, very limited in range. Perfect for SOHO (high density w/o interference effects that every WI-Fi user now experiences), but do not try using it where it does not belong. Also keep in mind that WirelessHD technology (which is also used for display streaming) is using the same 60GHz band. Now you will appreciate the shorteffective range 🙂
As a homework, try calculating required gain for MAX datarate, or required range assuming, say, 6dB overall gain.
Do you know something about 802.11ad 60GHz antennas? Share!