Have you ever seen a production set with cables everywhere? What if they all vanished?
That’s a true wireless video production setup, and the ultimate goal is to get there. This article goes into the basics of wireless video transmission, and how you can go about setting up a wireless video production set.
The advantages and disadvantages of wireless video
What are the advantages of wireless transmission? Here are a few:
- Increases mobility of camera and audio gear and crew.
- Nothing to trip over (though there are some individuals who can trip on air).
- Cables are also limited by distance, so the ‘traditional’ argument of range is moot. With the Internet, wireless can go where no cable has gone before.
- More than one device can ‘join the party’ and communicate.
- You can transmit different kinds of data (audio, video, metadata, photos, bad jokes) over the same wireless technology.
There are disadvantages too. Here are some major ones:
- It is easier and faster to connect a cable than set up a wireless system.
- Getting different kinds of devices to talk to each other over a wireless network is technologically challenging.
- There is the risk of data theft.
- If there are other wireless networks in the area, you have the problem of data interference. Commonly used Wi-Fi bands also compete with other wireless devices like security cameras, baby monitors, cordless phones, etc.
- ‘Overall’ speed over wireless is limited. E.g., you can string up two 3G-SDI connections to get 6G-SDI, but you can’t do that with wireless, yet.
- It adds to the production cost because you need a transmitter and receiver, or a device that has these built-in.
Overall, if we can protect the network from theft and set it up easily (Apple does wireless brilliantly, even a chimp can set it up), the advantages will far outweigh the disadvantages. When more people begin to use wireless devices, the cost will come down.
Finally, for those worrying about health issues, here’s what Wikipedia has to say:
The World Health Organization (WHO) says “there is no risk from low level, long-term exposure to wi-fi networks” and the United Kingdom’s Health Protection Agency reports that exposure to Wi-Fi for a year results in the “same amount of radiation from a 20-minute mobile phone call.”
Okay, let’s get our feet wet.
Understanding wireless technology
How does wireless work? I’m going to keep this as simple as I can. Let’s start with a large sports club with many swimming pools. There are small pools for the kids, ‘general’ pools for the low-paying members and Olympic-size pools for the elite.
As you can imagine, the size of the pool gives it its prestige. You want to be seen in the largest pool, even if you’re just a shrimp swimming with the sharks.
Due to physics and the nature of electromagnetic radiation, there are only limited swimming pools available in our airwaves. And these are all controlled by government and military bodies. Special ‘slices’ are allotted for consumers so they can enjoy radio, television, mobile, Internet, etc.
Such slices of the airwaves are called frequency bands. It’s nothing fancy, just a lower limit and upper limit that looks like: 2,412 MHz (lower) to 2,484 MHz (upper). If you subtract the smaller number from the bigger number, you get 72 MHz. This is the size of your pool.
Now, due to the nature of signals, we don’t want one signal to interfere with the other, so when we create frequency bands, we give them a slightly ‘wider berth’, like this:
Our signal needs room to move, so we create lanes in our pool. A lane in airwave terminology is called a channel. Each channel is about 5 MHz wide. In our example, the size of our pool is 72 MHz. If each channel is 5 MHz, how many channels can we have within this frequency range?
We can have 14 channels. What this means is, if the government says: ‘Though shalt use the 2,412 to 2,484 MHz band at this location’, it means only 14 channels can work on that network at that location. Which means, only 14 wi-fi networks can exist at that location. But it gets worse.
Now let’s enter a wireless technology (elephant in the pool) that wants a space of 20 MHz to swim. Each channel is only 5 MHz, but the elephant is an elite member of our club, so it will be allowed to swim in the 5 MHz channel-ized pool. Obviously, any poor soul who wants to go channel to channel with the elephant will be swiped hard. Signals have the same problem:
The three hard lines are three elephants in the pool. The dotted lines are the other 11 dudes who want to swim in the pool, but can’t. For this reason, only three elephants can set up a wireless network in the allotted frequency band in one location. From 14, we’re down to 3.
This above scenario is a real-world case. No, not the swimming pool, but the frequency band. 2,412 to 2,484 MHz is called the 2.4 GHz band. You’ll find it on common Wi-Fi routers used in your home. It can only hold about 14 channels. However, Wi-Fi technology needs 20 MHz to do its magic (20 MHz is called a band), so only three Wi-Fi networks can coexist in one place. When setting up a wireless network, you must choose a channel spaced 3 channels apart from any existing network. Luckily for us, the wireless routers do all this under the hood.
In densely populated areas (elephant convention) where everyone has a router and wants to play an MMORPG, the speeds must drop. Routers do this automatically as well, under the hood.
To counter this problem (what can the governments do? Wi-fi is popular and represents the vote-bank!), wi-fi technology was given another slice, the 5 GHz frequency range.
5 GHz is more popular because you have a frequency range from 4,915 to 5,825 MHz (910 MHz space, 182 channels). However, not all of these channels are usable because depending on which country you’re in, some are off-limits. The usable number of channels is about 42.
Wi-fi technology in the 5 GHz range uses two kinds of bands – 20 MHz and 40 MHz. With the former, you can have 10 connections in one location. With the latter, you can have 5. This is why it is popular, because more people can set up networks in the same spot.
Just to make things clearer, when I say ‘connections’ I don’t mean devices. I mean networks. A network can support multiple devices (television, computers, tablets, smartphones, etc.).
By the way, 5 GHz does not mean you get twice the speed of 2.4 GHz. Actually, the speeds are roughly the same, but slightly higher for 5 GHz. Don’t fall for the marketing on the box.
Comparing consumer wireless technology
The thing about wireless technology is that we will have to abandon traditional solutions like SDI, HDMI, XLR, etc.
Unfortunately, there’s more than one kind of wireless technology available. It’s a growing field, and new technologies are bound to come at regular intervals and replace the old. Let’s look at a chart comparing different wireless technologies as of 2013:
|Technology||Version||Frequency**||Maximum distance (feet)||Maximum bandwidth|
|Bluetooth||3.0||2.4 GHz||300||24 Mbps|
|Infrared||IrDA-FIR||33,000 GHz||20||4 Mbps|
|GigaIR||33,000 GHz||5||1 Gbps|
|Wi-Fi 802.11||b||2.4 GHz||120-300||11 Mbps|
|g||2.4 GHz||120-300||22 Mbps|
|n||2.4/5 GHz||240-600||450 Mbps|
|ac||5 GHz||n/a||1 Gbps^|
|ad||60 GHz||n/a||7 Gbps|
|Mobile||2G/2.5G||800 MHz to 2.7 GHz||Unlimited||In kbps|
|3G HSPA+||28 Mbps*|
|4G LTE||100 Mbps*|
*Typical speeds can reach 1 Gbps, but mobile users won’t be able to download at those rates.
**Anything between 300 MHz to 300 GHz is Microwave radiation. Anything under 300 MHz is Radio. Anything over 300 GHz till visible light is Infrared. Bottom line, for our purposes, everything except infrared is Microwave. Fun fact: Microwave ovens also run on 2.4 GHz. You cook your food with the same radiation that brought you your recipe!
***Bluetooth can be used to send data over Wi-Fi. It’s called High Speed (HS) Bluetooth.
^ac can go higher, up to 2.5 Gbps probably, and the theoretical maximum is 7 Gbps, but the products aren’t there yet.
The biggest drawback with infrared is that it can’t go through walls or objects – even a human being. Mobile technology is okay, but is nowhere near what Wi-Fi is capable of.
Wi-Fi is king, and for small video applications, you should squarely focus on versions 802.11 n and ac (We’ll talk about ad in a bit).
Important: The speeds given above for wi-fi are theoretical maximums. In the real world you can expect about 25-40% of that for practical use (40 MHz bandwidth mode is slightly higher than 20 MHz, but not by much). This is how many streams of video we can get over such a network in the real world:
|Data rate (Mbps)||802.11 n^^||802.11 ac^^^||802.11 ad|
At best we can squeeze in one stream of Prores HQ (220 Mbps) on current technology. As you can see, consumer wi-fi technology isn’t going to cut it for high-end productions.
^^The N speed is limited to 450 Mbps. Anything higher uses dual band (e.g., N750=N300+N450, N900=2xN450 and N600=3xN300). The maximum data rate per stream is always limited.
^^^ac also uses the 80 MHz band (dinosaur?)
Wireless technologies specific to video production
Basically you are limited by law (and physics) on the frequency at which you can operate in. This is why most consumer-grade microwave technologies operate in either the 2.4 GHz or 5 GHz band. Since neither will cut it for video, we are given an additional band to play with, 60 GHz.
In order to get greater speeds, for professionals who are ready to pay for it, there are special wireless standards (some proprietary). A few important ones are as follows:
|Data rate (Gbps)||Frequency||Range (feet)|
|Wireless USB||0.48||3.1- 10.6 GHz||10|
|Wi-Fi Direct||0.25||2.4/5 GHz||600|
WiGig is actually 802.11 ad, which we’ve seen earlier. Both WiGig and WirelessHD works in the 60 GHz band. Is that good or bad? In one way, it’s good, because you can achieve large data rates with less interference from other wireless technologies.
In another way, it is bad, because as the frequency increases, electromagnetic radiation finds it harder to bend around corners to avoid walls and humans, etc. This is why infrared needs a ‘line of sight’ to work. 60 GHz isn’t that bad, but it won’t work reliably without a straight line of sight.
However, to address the problem, those who use the 60 GHz band also include a technology called beamforming, that lets signals go around walls and opaque objects. Otherwise it wouldn’t be of much use.
How do these standards perform for video? Here’s a chart that shows how many streams of video we can get:
|HD-SDI||3G-SDI||6G-SDI||Prores HQ||50 Mbps|
The most promising technology is WirelessHD, which at present gives us about 3 Gbps and is able to go as high as 28 Gbps.
Okay, I think this is more than enough information to help you get a basic understanding of what’s possible with wireless technology. There’s tons of technical stuff I’ve left out, but they don’t concern us at this point.
Let’s see how all this affects our line of work.
The five kinds of wireless data transmissions on a video set
Let’s look at how data can be transferred on a production set. There are five major categories of data transfer:
- Video-Video (Video from one hardware device to another)
- Audio-Audio (Audio from one hardware device to another)
- AV-AV (Audio+Video from one hardware device to another)
- Device-Device (Communication between two devices directly)
- Device-Network-Device (Many devices communicate over a common network, a special case of which is Device-Internet-Device)
The first four choices are ‘special’ in a way. They don’t need computers or software or even a wireless network to exist. The primary goal is to maintain data integrity and speed over the connection. For this reason the number of devices talking to each other will be limited.
The last one is in a different league because you are no longer in the game of transmitting and receiving pure audio and video. It’s a community swimming pool. Here are some things you can transmit on a set to your crew:
- Photographs, images, and other forms of multimedia
- Social media updates (through a production collaboration tool – not Facebook or Twitter!)
- Schedule changes and status updates
- The latest score, crew jokes, wolfcrow.com links…
If you’re connected to the Internet, you have these additional options:
- Backup your data to a service like Backblaze, etc. Imagine not having to wait for software to load or hard drives to get up to speed.
- Weather information
- Communicate with the editorial team, producers, even fans!
In Part Two we’ll go into detail about the solutions available today in each category for professional video.