Bridging two Wifi networks to enable Car Network

[wayner]

I am working on implementing a media server in my car. The server will be a laptop running Win7 with Plex Media Server that can serve up content to clients on mobile devices like tablets or phones. It can also connect into the video screens installed on the headrests and the car's audio system.

I want to create a LAN within my car (a CAN - Car Area Network) which will interconnect the devices in the car. I also want this CAN to occasionally be able to bridge into an external (to the car) network that comes from either: (1) my house LAN (while in the garage to do maintenance on the server, transfer files, etc) or (2) a mobile device acting as a wifi hotspot to provide internet access while travelling away from home.

What is the best way to do this? I have tried adding a second Wifi adapter to my laptop and setting it up as an ad-hoc network that then uses ICS to connect to the built-in wifi on the laptop. I followed these instructions but I couldn't get it to work. Googling seems to bring up lots of people with issues so perhaps a recent Windows update has broken this functionality? Can anyone confirm that they can get this working? When I try to connect into my ad-hoc network with an iPhone or iPad it is never able to complete the connection it says something like "Unable to Join Network". Therefore I can't even create the CAN, never mind bridge into another connection.

Alternatively I could use a small travel router, like the TP-Link Nano router, to provide the CAN and then bridge that to the otyher networks. If I do this what mode should I use for my pocket router? Router mode? AP mode? Repeater mode? Bridge mode? Do I need a mode that is running a DHCP server that can give out IP addresses to the mobile devices connecting? Do I still need a second wifi adapter or can I use the ethernet port to connect to the router in such a configuration.

And how do I configure it so that I can connect to multiple external networks (house LAN, mobile wifi hotspot)? Do I need to have a fixed number as the gateway?

I guess in some ways this is similar to bridging together two wifi networks - let's say you wanted to share internet with your neighbour and you each had LANs in your house. The slight wrinkle here is that the other network may change between home LAN and Wifi hotspot and I want to make it as seemless as possible to switch between the two.

 

[azazel1024]

My suggestion on the "cleanest" way to set this up...

get that nano router. Set that up to provide the wireless network. Hardwire that to the laptop through the WAN port (or whatever router through it's WAN port).

The nano/travel router provides DHCP and routing + wireless for all devices connecting in the car. The laptop's wireless is then setup to connect to whatever wireless network you want it connecting to, to provide wireless bridging services for the car. Use ICS to bridge the hardwired and wireless adpaters in the laptop.

You may need to set a static IP on both the router's WAN port as well as the laptops ethernet port. Ensure they are on the same subnet and you may also need to set static DNS on the router.

What might be easier is getting a router that supports WISP/WWAN for one stop shopping and then hang the laptop off a LAN port to provide the PLEX server support to reduce complication.

I've considered doing something similar at some point, but I mostly come back to just using a lightweight router with WISP/WWAN support and hanging a HDD off the router's USB port, or using a very low power NAS to host things. I don't have any built in video equipment, but sometimes having "everything" with me is nice, plus the ability to let the kids/wife (rare times me when I am a passenger) stream whatever they want to their phone/tablet would be nice. I still come back to, as much fun as it would be, I don't have the time/money to set it up.

 

[wayner]

Thanks for the advice. I have a 6 yr old spare laptop that has a wonky screen so that will act as the server. All I have had to buy is a 2TB external HD, which I need anyhow, and a $15 VGA to composite adapter to drive the car's AV input which is only composite. Plus the nano travel router for about $18. This will also make a good mobile media server for when we go on vacation, etc.

 

[azazel1024]

What are you doing for power? I can think of several suggestions, but possibly one of the easier ones might be to disconnect the battery in the laptop, setup in BIOS to restart after power failure and then connect it to a relay that is only on when the key is only in the ON position.

That way you don't drain the vehicle battery with that stuff running and you don't have to worry about manually turning it on and off.

The travel router continuing to get power wouldn't be a big deal. It should only draw 2w most likely, and most vehicle batteries at that low a power draw work out to around 600-800whr of juice in them (most auto batteries are 80-100 minutes reserve capacity, which is measured at a 20amp draw, base on lead acid battery characteristics, at something like a .5amp draw, you are going to get double or better the capacity you would at a 20amp draw)...which means so long as you don't plan on leaving your car unattended for several days the battery drain isn't going to be very significant.

What I had considered doing to power it all is installing a secondary deep cycle battery around 30ah of capacity (works out to around 300whr). I figure with a drive spun up in a small single disk NAS, with a low power drive in there (maybe a high capacity 2.5" model to reduce power consumption to the bone) and a light weight WISP/WWLAN router, total consumption should be 15w or less, and with the drive spun down and the NAS/router idle it might be more like 5-8w. Setup a charge controller that is powered only when the vehicle is on to charge/supply power, so it doesn't draw anything from the main vehicle battery. Setup a voltage regulator that'll kick off once the battery voltage drops below the right threshold (to keep from too deeply discharging the deep cycle battery) and should be good to go.

It should give a good solid day of power during active use if the car is off and maybe two or possibly three days of idle time with the car off. Run the car every day and things should stay nice and charged. Hopefull the NAS (and I'd think certainly the router) should be fairly "power interuptable" tolerant and just turn back on when the power comes back on and it would also allow me to use the CAN and streaming with the vehicle off for a number of hours.

I don't think I'll ever end up implementing that (c'est la vie), but I do have a MUCH more ambitious project planned for a trailer/camper. Looking to build a tear drop trailer from scratch (I hope, or at worst, buying a used one and completely reconditioning it). I plan to integrate WLAN, as well as wired LAN on the thing, a small TV in back (like a 27") hanging from the lift gate and probably something like an Intel NUC to supply storage and HTPC duties to it all. Maybe go with an Apple TV to supply the 27" in back (because it uses ridiculously little power and I frankly like the setup of them and easy to grab over my iTunes library and video library to load up on the NUC), have LAN ports for the Apple TV, a spare in back and probably a LAN port in the sleeper section to in case I want to wire in a laptop or something inside. Probably supply all 4 of these LAN ports through the router's built in LAN ports (1 for NUC, 1 for Apple TV, 1 in the back/kitchen section, 1 in the sleeper section).

Power I am thinking solar on the roof of the tear drop trailer, as well as setting it up to be able to plug in a portable solar panel/tripod to expand the power for moderate term camping (probably something like a pair of 65W, one on the roof, one I can pull out and setup on a tripod). Something like a 100ah battery, or maybe even somewhat more if I can budget/pull off a Lithium Ion battery pack.

Also being powered in addition to the electronics would be a couple of lights (LED, probably 20-40w equivelent) to provide light in the sleeper area as well as the kitchenette/cooking section. Probably a small fan in the sleeping section for those hot days/nights and lastly I am thinking ambitious and going with a minifridge, though depending on power, that might end up just having to be a very well insulated icebox to avoid the power drain that a minifridge has (or if I get in the kludging mode, because I LOVE to kludge, I might try to do an ice box with something like a little 10-20w peltier cooler to extend out how long the ice box can keep things cold...if I wrap the ice box in insulation before installing in top of what it already has, I'd imagine a bag of ice could probably realistically keep things like milk, eggs and meat cold enough for a couple of days...a little peltier might extend that to double the amount of time if the ice box isn't opened much).

Also setup the power system so that it can be connected back to 12/14v vehicle power through the trailer hitch as well as to 120v mains for when being left unattended in a garage.

Pie in the sky and everything might change, because this isn't a project I can take on for at least 3-4 years, since I have house addition I have to get through first in 1.5-2 years. It is fun to think about though.

 

[wayner]

Power shouldn't be an issue although I haven't actually tried it in my car yet.

I have ordered a DC laptop power supply to plug into a cig lighter. The cig lighter in my car only provides power when the car is on. In the BIOS of the laptop (a Dell E6400) I have turned on the Wake on AC setting. And in power management I have set the laptop to hibernate after 15 minutes.

So here is how it should work. The laptop will be in hibernzte mode. The car is powered on which will cause the laptop to resume from hibernate. That takes about 17 seconds. When the car shuts off the laptop will hibernate after 15 minutes of no activity. There is no worry about draining the car battery since the cig lighter has no power when the car isn't running.

Ideally I would use Hybrid sleep mode rather than hibernate but so far I can't get the laptop to come out of sleep mode when power resumes to the power supply. The resume from sleep is much faster, about only 2 seconds, and even if the car wasn't used for a while which drained the laptop battery then you would get the resume from hibernate when power was restored.

The BIOS also has a Wake on WLAN setting - I have turned this on but haven't tried it yet. Theoretically that should allow me to send a magic Wireless packet and wake up the PC if I want to do maintenance and/or transfer files.

The laptop has three USB ports plus an eSATA port (which may also function as an eSATA port). To the USB ports I will connect the router, the 2.5" 2TB external hard drive (which is also powered via USB) and the VGA-composite adapter.

It would be nice to be able to use a NUC, Brik or a Zotac Pico PC but I can't figure out how to do the proper power management when using a "desktop" PC rather than a laptop with an integrated battery. It would probably require a UPS so that the PC didn't shut down when you shut the car off. But then how does it get turned back on when power is restored? I know that most UPS' can shut down a PC after a few minutes but can they also have the PC hibernate or sleep rather than do a full power down? And are they smart enough to have the PC boot up when "AC" power is restored?

And can you get a UPS that is relatively small. Even the smallest UPS that I have seen are about 8"x12"x5" - bigger than most laptops. The other thing is that I had this laptop and it wasn't that functional due to a bad screen so this is a good way to recycle an unloved old laptop.

Anyone have any ideas on how to use a battery/UPS with a "desktop" PC so that it functions similarly to a laptop.

Note that there are some small UPS' designed specifically for the RPi.

 

[azazel1024]

It'll deffinitely be bigger, but you can stow it in the trunk, or under the front seats. Some are relatively small.

Granted, not all UPS will communicate the proper battery level, but it will work exactly like a laptop will (as far as windows is considered, a laptop is simply a desktop with a battery, and all desktops with windows and various UPS I have used, if they are connected to the desktop over USB, windows knows there is a battery there).

So windows will know when it is on "ac" versus "on battery" and can respond accordingly. Have it set to hibernate on battery after 15 minutes, the NUC or what not will do that still if connected to a UPS. Also a lot of UPS software does allow hibernate instead of shutdown (I think the Cyberpower one I am using for my server allows that as an option instead of straight shutdown).

In a lot of ways, a laptop would be the best way to do things, especially the way you are looking at setting it up. To me a NUC and making a battery pack would be cheaper...the downside is getting it to respond appropriately when actually on battery power and the extra complication of the charge circuitry. Also, some of those UPS draw quite a bit of power when recharging. You'd really need to look carefully at the draw (that said, the "low end" little UPS you'd probably ever consider using for anything like this generally have 6-10hr recharge times...and based on their itty bitty batteries, that is probably only a 5-15w draw above and beyond whatever is connect to it, so you won't fry the lighter fuse).

 

[sfx2000]

FWIW - get a high-end "MiFi" type of device to act as the network hub - I'm holding in my grubby little hands one such device...

It's an AT&T Unite Pro - it's co-branded with NetGear, but designed by Sierra Wireless - it's a simultaneous dual band 802.11n 2 stream router that uses ATT LTE/4G/3G as the WAN connection - supports up to 15 clients...

One can find them on eBay and Amazon for around 100USD - they're pretty amazing...

Verizon also has their JetPack line - there are equivalents to the Unite Pro there.

For the media server - Asus X200CA is interesting, as it runs linux just fine, and you can find them at a very reasonable price online - alternately, MSI has the WindBox DC-111, which is a "net top" - runs off DC power, no panel/keyboard, but runs nicely headless... and a fair amount of storage there...

Sounds like a fun project!

 

[azazel1024]

The possible issue there is with that the OP may not be looking to have a cellular WAN connection, they might only be looking for a WWAN setup and also the ability to wireless connect their CAN to their LAN/WLAN to update files and such forth..

My possible future, it would be both WWAN and cellular WAN, that I'd be looking for which is going to take some planning and careful device selection.

 

[sfx2000]

True... and in that case, one can pull the SIM card out, it'll still act as an AP for the other clients.

Having Wireless/Cellular WAN in the car is something that folks might like to do - I keep a pay-as-you-go MiFi in the mini-van so when we do road-trips, the passengers can occupy their time

Also since it's not a hard mount, we take it to the hotel room with us, as a MiFi is cheaper and most likely better internet than what many hotels these days offer...

Alternately, one could do hotspot on a smartphone, but generally speaking in my experience, the MiFi type devices are better at it, and can usually handle more clients.

 

[wayner]

I actually do have a Sierra Wireless Wifi Hotspot that I use occasionally when travelling - I live in Canada and I have an ATT LTE SIM that I use to give mobile access when in the US. But at home in Canada I don't have a SIM card for it and I figured it is just easier to occasionally use my iPhone or iPad to provide the LTE access when required. I am also not sure how easy it is to get proper pay as you go access to the SIM card as the carrier (Rogers) really likes to tie you into contracts.

I will still need to surmount the technical challenge of bridging into another Wifi LAN when I want to connect to the CarPC while at home to transfer files, etc.

 

[sfx2000]

Pre-paid SIM cards up in Canada - last time I checked, fido wasn't too terribly expensive, cheaper than Koodo... and don't forget the MVNO's like PetroCanada and 7-Eleven.

If you're in the Wind Mobile footprint, they've got one of the better deals for data packages for pay as you go..

 

[wayner]

Thanks - I will look into that, especially Wind since I am in Toronto. Fido looks pretty much like Rogers as it is 150MB for $10, 1gb for $25 and 5GB for $35 so if you use it at all you will be paying at least $25/month.

Wind is $15 for 1GB, $25 for 3GB and $35/month for unlimited with fair usage.

 

[sfx2000]

I will still need to surmount the technical challenge of bridging into another Wifi LAN when I want to connect to the CarPC while at home to transfer files, etc.

Have you considered using connection priority? Let the CarPC attach to the home WiFi, and then attach to the MiFi device... go into the advanced settings and make the home WiFi network higher priority - what should happen, and I've tested this with Windows 7, Mac OSX, and Ubuntu 14.04LTS, is that it will prefer the home WiFi, and then when that network is lost, it will attach to the MiFi...

Did a quick starbucks run, and it actually worked ok - and then drove back to the house - it took a couple of minutes, but it did hand back over to the home WiFi network (wish there were some rescan variables that could be tweaked a bit)...

Anyways - plenty of ways to skin that cat - sounds like a fun project for the holidays

 

[wayner]

Good idea. The only potential wrinkle that I can think of with that is that the mobile devices won't be able to connect to the CarPC until the CarPC drops the home Wifi and connects into the Mifi. But I think my Mifi can use a tethered USB connection for its LTE connection. That would make things even easier unless it insists on using the Mifi's internet connection even if it is connected to the Home Wifi LAN.

One more question - my Mifi device has a battery. It will be powered via the USB port on the laptop. Once the laptop shuts down I assume the Mifi will keep going until it runs out of battery. Is there any reason why this would be problematic?

FYI - my Mifi is an Elevate 4G - here is the manual.

 

[sfx2000]

Thanks - I will look into that, especially Wind since I am in Toronto. Fido looks pretty much like Rogers as it is 150MB for $10, 1gb for $25 and 5GB for $35 so if you use it at all you will be paying at least $25/month.

Wind is $15 for 1GB, $25 for 3GB and $35/month for unlimited with fair usage.

One caveat - Wind gets pretty spendy once off foot-print, so if possible, you might consider putting it to home-only...

I have a friend that learned that lesson the hard way

(unrelated perhaps, I was up in Washington last summer, just south of the border, and my iPhone locked on to Bell - only for a couple of minutes, but those were very expensive minutes data roaming - I've since disabled data roaming on my devices when I go up there, and where I live in San Diego, if I'm not careful, the devices can hop on to Telcel, which again, very spendy)

 

[wayner]

This is getting rather OT but I don't understand how wireless companies cna justify the roaming fees that they charge. Why is data about 1000X more expensive when you are roaming vs. when you are home? My company has a special deal for roaming yet I pay about $1.25/MB when in Hong Kong. Here in Canada I pay about $11/GB.

 

[azazel1024]

This is getting rather OT but I don't understand how wireless companies cna justify the roaming fees that they charge. Why is data about 1000X more expensive when you are roaming vs. when you are home? My company has a special deal for roaming yet I pay about $1.25/MB when in Hong Kong. Here in Canada I pay about $11/GB.

On the Mifi, the only issue is that it'll kill the battery in it at a lot faster. Most Lithium Ion batteries have around 500 charge/discharge cycles for their battery before you start cutting WAY in to their capacity (most after 500 cycles are going to only have around 50-70% of their original capacity left). If you generally tend to discharge down to only ~20% and charge up to only around 90%, you can preserve this MUCH longer (the equivelent of probably 700-1000 FULL discharge and charge cycle equivelents).

However, if it is only ever going to live tethered, the fact that you might be knocking the realistic battery life span from maybe 5-8 years of use if you were turning the Mifi off everytime the laptop powered down down to maybe only a couple of years might not matter. It should still be able to live off the laptop USB power even once the battery in the Mifi is effectively toast.

As for data roaming, companies like making money and when they have you in a bind is the best time for them to make money.

Even with THEIR data costs that they have to pay to the network owner when you roam to their network, they are making HUGE profits. FCC and FTC in the US and other regulatory bodies in other countries let them get away with it. Most places in the world, at worst, the telecom is possibly paying in the 20-50 cents per gigabyte range for the data (as opposed to on their own network, even if they have to transport the data to other networks for its final resting place, they are likely only paying a couple of cents per GB).

Heck, just look at general costs to telecoms on their own infrastructure. You are already paying some kind of minimum cost just for your cell/data plan. The actual incremental costs between you using 500MB of data and 10GB of data over wireless are TINY for the telecom. Yes, huge data plans would likely encourage more wireless use, which would mean they'd need to building things out even more for the capacity, but the fact that a 500MB plan and a 10GB plan in the US might be $50-70 a month, or that most US plans the data overage charges are ~$15 per GB (or fraction there of) are ridiculous. It costs the telecoms very little for that data.

The worst are the wireline guys who have data caps, as capacity and network management are deffinitely not excuses to limit how much data you can use. 250GB of data for a wireline guy is likely costing them $2-5 in actual data transport costs if it is all leaving their network (in they have to do paid peering on all of the data). Charging ~$10-20 per 50GB of overage in a lot of cases is highway robbery when the actual 50GB of extra data is costing less than a single dollar, in a lot of cases less than a quarter.

 

[sfx2000]

We've had some good discussions, but I'll try to get the thread back on topic if I can...

I am working on implementing a media server in my car. The server will be a laptop running Win7 with Plex Media Server that can serve up content to clients on mobile devices like tablets or phones. It can also connect into the video screens installed on the headrests and the car's audio system.

Win7 is one option, but also consider Linux, as it can provide options via it's network stack, and most importantly, the bonding driver, where you can do some interesting things with WLAN/WWAN and failover...

I want to create a LAN within my car (a CAN - Car Area Network) which will interconnect the devices in the car. I also want this CAN to occasionally be able to bridge into an external (to the car) network that comes from either: (1) my house LAN (while in the garage to do maintenance on the server, transfer files, etc) or (2) a mobile device acting as a wifi hotspot to provide internet access while travelling away from home.

So perhaps the approach here is to use both WLAN and WWAN as the WAN connection into the CAN - this can be done...

What is the best way to do this? I have tried adding a second Wifi adapter to my laptop and setting it up as an ad-hoc network that then uses ICS to connect to the built-in wifi on the laptop. I followed these instructions but I couldn't get it to work. Googling seems to bring up lots of people with issues so perhaps a recent Windows update has broken this functionality? Can anyone confirm that they can get this working? When I try to connect into my ad-hoc network with an iPhone or iPad it is never able to complete the connection it says something like "Unable to Join Network". Therefore I can't even create the CAN, never mind bridge into another connection.

Treat the CAN as a standalone NAT'ed WLAN - then you can use the Home WiFi and the Cellular network as WAN's

Review Linux Ethernet Bonding Driver mini-howto - this is not new technology - Linux bonding has been around for at least 15 years now...

In a nutshell - you bond if0 (WLAN) and if1 (WWAN) to bond0 - and bond0 is the WAN interface into the car WiFi network. For the WWAN, use a 3G/4G USB dongle...

You can do this on a netbook - I suggest looking into the Asus X200CA serious, as it's reasonably fast, and very cheap, has a decent amount of RAM/HardDisk (which can be swapped out for an SSD perhaps), and a lot of interfaces on the USB and Ethernet side (and it has VGA and HDMI to boot) - and boots fine into Ubuntu and Debian... So the netbook running linux could be the hub of the CAN - otherwise, go with what I suggested earlier with a MiFi device...

End of the day, the MiFi might be a better approach - depends on how much effort/time you want to spend to maintain things :|

I guess in some ways this is similar to bridging together two wifi networks - let's say you wanted to share internet with your neighbour and you each had LANs in your house. The slight wrinkle here is that the other network may change between home LAN and Wifi hotspot and I want to make it as seemless as possible to switch between the two.

Like I mentioned earlier - it's entirely doable, just takes some planning and effort to test things out.

sfx

 

[AcostaJA]

Wrong approach:

Notwithstanding you are working with currently available parts and devices you have, the main error it's to do it with window and Plesk.

I've done an similar setup with an Nano pc but running Ubuntu server, under Linux you can have two wifi adapters (one as Hotspot and other as client) concurrent bridged to a gb lan and running a variety of services for media sharing (there are tons of Plesk equivalent solutions).

The other error it's using spinners hdd on a car, my experience is that it's an no-no unless you have something like an Cadillac or an Mercedes with ultra soft suspension and you always drive on AAA carpet.

Right now I've seen very similar setups done with less than 100$ (w/o External storage or display ) using an raspberry Pi as CarPC media server two cheap wifi adapters an SD card and an usb pendrive or hard drive (latest raspberry Pi required since the original raspi only have 2usb).

Of course this approach means you have to try Linux and learn how to, I recognize it's intimidating but believe me actually not as complicated as seem, of course isn't a plug and play solution, you need to invest some time researching what to do and how to do, the prize it's optimal stable solution and virus proof with 100% free and legal software.

 

[AcostaJA]

Another approach it's with some capable wireless router with DD-WRT, configured as wireless repeater with lan bridged and running miniDLNA for media sharing (and some pendrive or ssd with the media loaded). Not as perfect as a raspi carpc but by far lesser complicated than dealing with Linux.

Buffalo's wzr-1750dhp it's one good choice since you can power supply it from an DC power source has lots of ram and 2 usb, and performs very good as repeater.

This is the approach I'll use on my hypothetic TEOTWAWKI bugout camper/SUV... [emoji12] [emoji3] [emoji1] [emoji2] [emoji2]