Battery powered network for skiing

[Coach]

Hello,

What a great resource! I hope the collective expertise of this forum can suggest equipment and configuration for an outdoor battery powered network.

I coach alpine skiing with a team of athletes that travel around the world training and racing. I’m trying to develop a battery powered portable wireless network that would allow coaches to film at multiple points on the hill and wirelessly transmit the footage to an iPad located at the bottom of the training course. The network solution would need to be battery powered and yet strong enough to transmit and collect footage over a long distance.

Size of the network would need to be rather large, if you’re not familiar with alpine skiing, courses can range form a third of a mile (500m) to 1.5 miles (3km) in length. Although typically our training environments would not exceed 1 mile in length.
Overall the network would need to be relatively easy to set up and provide continuous coverage for approximately 4 hours per charge. If necessary a secondary wireless repeater could be set up to improve the network coverage.

I'd planned on using the following:

Camcorders: JVC GC-PX100B, wifi enabled filming in iFrame mode.
Wireless Router: TP-Link TL-MR3040
Wireless Repeater(s): Haven’t found a battery powered version so I’ll likely need to retrofit something. Suggestions?
iPad: ideally one iPad air located at the bottom of the training course mounted on a tripod with a sun shield and a life proof case.

Any suggestions would be greatly appreciated.

Thanks!

 

[stevech]

Hello,

What a great resource! I hope the collective expertise of this forum can suggest equipment and configuration for an outdoor battery powered network.

I coach alpine skiing with a team of athletes that travel around the world training and racing. I’m trying to develop a battery powered portable wireless network that would allow coaches to film at multiple points on the hill and wirelessly transmit the footage to an iPad located at the bottom of the training course. The network solution would need to be battery powered and yet strong enough to transmit and collect footage over a long distance.

Size of the network would need to be rather large, if you’re not familiar with alpine skiing, courses can range form a third of a mile (500m) to 1.5 miles (3km) in length. Although typically our training environments would not exceed 1 mile in length.
Overall the network would need to be relatively easy to set up and provide continuous coverage for approximately 4 hours per charge. If necessary a secondary wireless repeater could be set up to improve the network coverage.

I'd planned on using the following:

Camcorders: JVC GC-PX100B, wifi enabled filming in iFrame mode.
Wireless Router: TP-Link TL-MR3040
Wireless Repeater(s): Haven’t found a battery powered version so I’ll likely need to retrofit something. Suggestions?
iPad: ideally one iPad air located at the bottom of the training course mounted on a tripod with a sun shield and a life proof case.

Any suggestions would be greatly appreciated.

Thanks!

I'd put a high gain antenna/Access Point at the bottom.
WiFi reliablity at 500' or so is poor unless you have antennas at one or both ends with 14dBi gain or more. And 100% clear line of sight.

http://www.newegg.com/Product/Produ...168089&cm_re=engenious-_-33-168-089-_-Product

If you wish to, you can use a travel-sized router that connects to the AP as above, and also can take a USB dongle Cellular modem. Cradlepoint is a good choice for these, or get one off eBay. Like the MBR95. The USB cellular modem can plug into the router or later, into your laptop. In the US, Verizon has the best remote-area coverage.

 

[azazel1024]

Is it a fixed filming point or just need to travel with the one coach? If so then what you'll want for the portable wifi end is a pair of routers. One in bridge mode with a directional antenna pointed back at the base station and another one with regular antennas. Then you'll need a 12v power pack that has a pair of DC barrel plugs and can supply something on the order of 50whr of power at a 4hr rate (most medium/low end routers use 4-7w of power, times 2, times 4 hours).

If this is something where you want the ENTIRE moutain covered, that is going to probably be too much of a pain in the butt. You'll need the above times the length of the course in feet divided by about 800. Maybe 1,000 if you have some very high gain omni directional antennas on the router used to connect the wifi video camera with (9dBi minimum, probably more like 14dBi).

Since you are talking probably 10-15 to cover a course...I'd think that is not feasible between time to position and cost.

For the "goes with the coach" setup I'd suggest something like a portable travel router that has a RJ45 plug on it that you can then plug in to maybe something like an Engenius N150 outdoor bridge. Battery pack, dunno. I'd look in to something like a 12v lithium Ion battery pack that also had a USB output on it (for the travel router). Issue here is I assume you'll want/need to package it all up in a weatherized covering and probably also some amount of padding plus figure out a way to point the antenna while filming (maybe a collapsable monopod with the wireless bridge/antenna on the end that you can stick in to the snow pointed down the mountain at the base station).

 

[Coach]

Thanks for the detailed replies azazel1024 and stevech.

Setup time and ease of use can’t be overstated, if it’s too complicated to set up or cumbersome to carry around the benefit likely won’t outweigh the hassle. I’d envisioned, placing the battery powered router in a sealed pelican case connected to a weatherproof directional antenna with a 35 degree beam facing up the hill collecting video camera footage. Typically there will be two coaches filming at any given moment. Keep in mind most alpine training courses are linear, top to bottom, with less then 100' of lateral movement across the hill. Let’s assume the coaches filming are less then 1000’ away and can see the directional antenna at the bottom of the hill next to the iPad, would it work? Or would each of the coaches need to carry a bridge router in their bags?

I've included a link to a PDF to better visualize what I'm train to attain.
https://www.dropbox.com/s/ip8pv6nhxen6gdi/Ski%20WiFI.pdf

 

[stevech]

Will it work? I can answer that if you tell me what the camera site arrangement is in terms of WiFi. Hardware and antenna. If the answer is simply choose what's easy.. then we can do that too.

Also, the easiest way to do this is without WiFi. Analog. Standard Def camera (not HD), RCA jack composite video out. Goes to a low cost analog transmitter with a decent antenna. Might be 900MHz, not 2.4GHz. Receiver with decent antenna on other end. Output of that is analog video. You can view that and/or record it with video gear, not WiFi. If it were me, I'd do this, not WiFi, unless there's something I don't know.

Scan the catalogs of companies like
http://www.supercircuits.com/wirele...2-4-ghz-wireless-transmitter-receiver-dvl24wr
http://www.supercircuits.com/wirele...less-link-kit-with-transmitter-receiver-dvl24

Power this with a small 110VAC inverter connected to a rechargable 12V battery - small motorcycle battery or one as used in small UPSes.
Or maybe the gear runs on 12V itself.


They have a zillion alternatives.

 

[azazel1024]

35 degree beam indicates a pretty low gain antenna. I think you'd need something narrower beam if you want sufficient gain on both sides to possibly stretch something like 1.5km near the top of a slope.

A 14dBi directional is around 30 degrees HPBW, which means ideally you really want to be more like within 15 degrees or so on target (because at 30 degrees you are at half power and rapidly drop off after that).

A pair of 14dBi directionals with true LOS (IE no trees in the way) should be roughly sufficient to setup around a 11Mbps link, give or take a little.

Without a listed radio power or sensitivity I am looking at a TP-Link 14dBi directional outdoor antenna and it lists 1/11/54Mbps range as 5km/3km/440m. No idea if the assumption is a 14dBi on both ends or a isometric antenna on one end and the 14dBi on the other (which if that is the case, a single 14dBi and modest omni's on the other should easily be good for 54Mbps at 1.5km. If not and it implies a 14dBi on both ends...you might actually need an even higher gain on one of the ends to get up around something like a 1080p compressed (like 22-24Mbps bit rate) capable connection over wifi.

I have little long range experience with wifi links/bridges.

 

[sfx2000]

I'm with Steve on this one...

Analog in the 900MHz space is a better solution perhaps.

If you want to try an interesting experiment - go to an office park on the weekend - put the AP on one end, and walk directly away from it - one will get to a point where the Link is still up, but throughput falls thru the floor as frame timing starts to overlap. This can be tweaked to some extent, but this would be specific to a given layout...

The camera that the OP (Coach) is using generates a 36Mbps HD stream over wifi - that'll be a challenge in and of itself...

 

[azazel1024]

Oh, ouch. 36Mbps. I was thinking it was in the low 20 range.

Yeah, I forget what it is, but I think it is somewhere in the 500m range that you have to start dealing with long link packet delay issues and the changes are dependent upon how long the link is, so you'd have to tinker as you go down the hill.

 

[stevech]

Antenna narrower than about 30 degrees on the horizontal will be too hard to aim/keep aimed if not hard-mounted.
Note too that all panel or sector antennas are directional on both H and V.

Some are very narrow on V by their intended use.

Standard Def. analog RF will not need as much antenna gain as the required signal to noise is much less than with IP video.

 

[chadster766]

The only way I can see this working is to use 4G cellular modems (Ex: Sierra) with higher gain antennas for your communications.

The core components should be put in a plastic outdoor rated electrical box. Antenna and camera mounted to the outside of the box. Box mounted to a spike stand or tripod.

Each camera system would be independent and could be recorded and view together in a NVR\DVR with it's software (Ex: WatchNet).

 

[Coach]

Oh, ouch. 36Mbps. I was thinking it was in the low 20 range.

Yeah, I forget what it is, but I think it is somewhere in the 500m range that you have to start dealing with long link packet delay issues and the changes are dependent upon how long the link is, so you'd have to tinker as you go down the hill.

I believe the JVC PX100 iFrame 720p footage is 24-26Mbps, which is also optimized to play back on an iPad. Also, the footage doesn't need to be instantaneously available the moment an athlete reaches the bottom of a run. Even if it took a minute or two to upload that would be satisfactory, and athletes are typically only coming down the course once ever 3 minutes. The iPad would operate as a repository for all the footage collected from the cameras over the course of a training session.

 

[azazel1024]

So its less streaming and its more wireless transmission? That may work, but you might still run in to a lot of long link issues. Really not sure. My experience is much more in the couple of hundred meter or less range.