Phil HIppensteel on 802.11 Wireless (Wi-Fi) and Video - Sound & Video Contractor

Phil HIppensteel on 802.11 Wireless (Wi-Fi) and Video

Author:
Publish date:
AVOVERIP_HEAD_01.jpg

Customers who are implementing IP video systems often ponder the role wireless might play. It seems to offer some significant advantages. Two of the most promising are mobility and avoiding new cabling. But, can wireless provide the required level of video quality and security? That’s the contention we’ll investigate in this newsletter.

First, a primer on 802.11 wireless. Commonly referred to as Wi-Fi or wireless Ethernet, neither term is really accurate. The first is a trade-mark of the Wi-Fi Alliance and the second is used because 802.11 wireless nearly always extends a wired Ethernet network. I’ll consistently refer to this technology as 802.11 wireless because it is specified by the IEEE as the 802.11 series of specifications.

By now, most of us have learned that there are several versions of 802.11 wireless. 802.11 b came first and had a nominal speed of 11 Mb/sec. 802.11g came next and operated at a nominal speed of 55 Mb/sec. This was followed by 802.11n with a nominal speed of 100 Mb/sec and variations that advertised 150, 300 and 600 Mb/sec. The latest version to be ratified is 802.11 ac, nominally operating at 1 Gb/sec. Currently the most widely deployed wireless is probably a mixture of g, n, and ac.   The devices used by consumers tend to be mostly n or ac.

However, these are theoretical maximum speeds and should never be considered a real and practical operating speed for your application. Table 1 shows the results of a small test I conducted with my own 802.11n router/access point (AP). It’s nominal speed is 100 Mb/sec . I merely moved my notebook computer to different positions in the office.

There are several lessons we can learn from this table. But an explanation of the terms is necessary. The signal level is measured relative to 0 dB, which is 1 mW. Each 10 dB the signal is lowered, the power level is cut to 1/10 of the previous level. So, the table shows that moving the computer by five feet to a position 10 feet away decreased the signal strength to nearly a tenth of the previous level.

Table  1

Distance  to    AP     (feet)  

Resulting  Speed     (Mb/s)  

Received    Signal    level     (dBi)  

5     

72  

-­‐32  

10  

72  

-­‐40  

15  

58  

-­‐52  

20  

58  

-­‐57  

30  

43  

-­‐62  

At 30 feet from the AP, the signal level was 1/1000 the level when it was five feet away. So, the distance between the device and the access point is very significant. You can also see, moving the computer to a distance of thirty feet away from the AP decreased the operating speed (bandwidth) to less than half the nominal speed of the access point.

I had no other wireless devices in operation, no competing neighbor devices, and I chose the best position for the antenna in my computer. These are ideal results, not what you would typically expect in a classroom, workspace, or restaurant. The air is a shared medium. So, if there are five people simultaneously using the wireless AP, cut the speed rates in the table by approximately a factor of 1/5. If there is competing web traffic using HTTP/TCP, it will burst in spurts to using 60% or more of the available bandwidth.

Featured

Related

Lighthouse Create Impact copy

Lighthouse Direct View LED

Lighthouse Technologies Limited, a leading global brand in direct view LED video display solutions with a 20-year history in the USA, debuted its new Quantum q-Series fine pitch direct-view LED indoor display solutions for the North American commercial AV market during InfoComm ...read more

LG inglass copy

LG In-glass OLED

At InfoComm 2018, LG introduced slimmer-bezel versions of the 65-inch Ultra HD “Wallpaper,” 55-inch Full HD “In-Glass Wallpaper,” and 65-inch Ultra HD video wall LG OLED displays with a new super-slim bezel overlap seam. LG also showcased the highly-acclaimed LG OLED Canyon, ...read more

Epson InfoComm2018

Epson 12,000 lumen native 4K

Epson showcased its laser projector solutions at this year’s InfoComm, including the world’s first 12,000 lumen native 4K (shown in photo). The Pro L12000Q is a 12,000 lumen native 4K 3LCD laser projector and the Pro L20000U boasts 20,000 lumens of color and white brightness2 ...read more

Leyard VVR series indoor outdoor LED

Leyard and Planar LED

Leyard and Planar demonstrated their growing portfolio of fine pitch LED display solutions at InfoComm 2018. These high resolution LED video wall solutions offer customers a wide array of choices to fit almost any need. The fine pitch LED displays showcased included: Leyard ...read more