airtechy
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Wi-Fi Streaming Limits

Mon Jul 22, 2013 8:58 pm

Talk of going to Wi-Fi streaming of IFE rather that seatback displays brings up a question of bandwidth. Does the current Wi-Fi specification really have the bandwidth to stream movies to over 400 people on a large jet from an onboard server. For this to work, the server will have to use the existing spec as peoples devices will require it. Seems like that would be pushing it.  

AT
 
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1337Delta764
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RE: Wi-Fi Streaming Limits

Mon Jul 22, 2013 11:53 pm

Quoting airtechy (Thread starter):
Talk of going to Wi-Fi streaming of IFE rather that seatback displays brings up a question of bandwidth. Does the current Wi-Fi specification really have the bandwidth to stream movies to over 400 people on a large jet from an onboard server. For this to work, the server will have to use the existing spec as peoples devices will require it. Seems like that would be pushing it.

AT

Don't listen to anyone who claims this. Fact is, far more people use the IFE system than their own personal devices, and this was confirmed by an airline crew member in another thread (whose post was unfortunately deleted).

As for bandwidth, that is a good question. I can guarantee that streaming video would never have the usage rate that in-seat IFE does, so perhaps bandwidth isn't too much of a concern.
The Pink Delta 767-400ER - The most beautiful aircraft in the sky
 
airtechy
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RE: Wi-Fi Streaming Limits

Tue Jul 23, 2013 1:54 am

I started this discussion here in techops to avoid "personal" observations of usage as I want to understand the technical aspects of it. Could we keep such "observations" out of the discussions. Thanks.  

AT
 
JHwk
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RE: Wi-Fi Streaming Limits

Tue Jul 23, 2013 3:14 am

Any access point is limited to about 50 users. (You can have one device with up to three access points.) There are (3) non-overlapping bands at 2.5GHz, not sure about 5GHz. The lowest common denominator effectively limits capacity-- if someone is using 802.11g, the network can really operate well at up to 54Mbit. If you go for a lowest common denominator of dual-band 802.11n, you have nearly 10 times that. Practical throughput is about 50% of ideal, due to collisions and interference.

If a movie is 1GB/hour, you need 2.5Mbit per user, so a 54Mbit access point would be able to support 10 users, or 1.5 rows on a narrowbody. Likewise, a dual-band 802.11n access point would be limited by concurrent connections, so you would be at 6-7 rows per access point. Your three non-overlapping bands would alternate through the length of the aircraft, giving a spacing of non-overlapping access points of 21 rows or about 55' in economy.

This is where the problems start. Tuning systems to this short of a range is quite difficult, as all devices need to cooperate.

The systems will work fine with 802.11ac, but it is likely 8 years before you can count on all devices supporting it. Likewise, if the subscription rate is a more realistic 50%, tuning the system is an order of magnitude easier.

You see the same problems in convention center meeting halls; serving a large number of users in a confined space wirelessly is difficult. The current standards really were not geared for it.
 
airtechy
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RE: Wi-Fi Streaming Limits

Tue Jul 23, 2013 3:46 am

JHwk.....Thanks! I thought it would be difficult but maybe not impossible. I know "cells" for cell phones don't expect all users to be "on" at the same time. This is clear after disasters when everyone tries to call at the same time.

I guess they could control the number of users by the cost.  

AT
 
mandala499
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RE: Wi-Fi Streaming Limits

Thu Jul 25, 2013 10:17 pm

Quoting airtechy (Thread starter):
Does the current Wi-Fi specification really have the bandwidth to stream movies to over 400 people on a large jet from an onboard server.

From tests of a carrier that does WiFi streaming to embedded IFE (not bring your own device), it's about 50 passengers per wireless access point. That's the limit for reliable movie streaming I've heard of in an aircraft... sure there are higher ones in tests but they were not reliable enough I am told...

If you're meant for "bring your own device"... well... I dunno   
When losing situational awareness, pray Cumulus Granitus isn't nearby !
 
blueflyer
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RE: Wi-Fi Streaming Limits

Fri Jul 26, 2013 7:03 am

Quoting mandala499 (Reply 5):
From tests of a carrier that does WiFi streaming to embedded IFE (not bring your own device), it's about 50 passengers per wireless access point

Implementation for WiFi streaming to embedded devices is much easier, mainly because there are none of the issues brought up by JHwk since the system does not need to support a multitude of devices running different standards.

Quoting JHwk (Reply 3):
You see the same problems in convention center meeting halls; serving a large number of users in a confined space wirelessly is difficult.

In our experience, most of the problems convention halls and similar facilities have come from the fact they still see wireless networks as an expense that is forced on them, and therefore invest as little as possible. A couple of years ago, you could take a peek above the ceiling tile at a few of them and find a Netgear AP sitting next to the 240 volts cable powering the A/C equipment...

That said, it is true that the most costly wireless implementation is a public network covering a large, crowded facility due to the variety of end-user devices.
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nomadd22
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RE: Wi-Fi Streaming Limits

Fri Jul 26, 2013 10:56 am

I'm thinking that the APs might be limited to 802.11n & 802.11a. And, maybe not a. The 5ghz band isn't for wi-fi in some countries and is more like Bluetooth.
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faz777
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RE: Wi-Fi Streaming Limits

Tue Aug 13, 2013 3:23 am

Quoting airtechy (Thread starter):
Talk of going to Wi-Fi streaming of IFE rather that seatback displays brings up a question of bandwidth. Does the current Wi-Fi specification really have the bandwidth to stream movies to over 400 people on a large jet from an onboard server. For this to work, the server will have to use the existing spec as peoples devices will require it. Seems like that would be pushing it.

AT

Qantas are using Ipads in 767's at the moment. I think they call it Q-streaming. They all access the onboard server wirelessly. Works perfectly (have used it twice). They picked the 767's, as they didn't want to fit out newer entertainment, but improve the passenger experience.

If they can do 767's, im guessing larger aircraft wouldn't be too much of a problem, perhaps just a few more points available.
 
apfpilot
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RE: Wi-Fi Streaming Limits

Tue Aug 13, 2013 3:36 am

If you are talking about gogo vision the wifi access point is a a/b/g device called a CWAP. Each can support 75 i.p addresses and usually 3 are installed on the domestic aircraft that have gogo.
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