Max number of imps on sleep mode (most of the time) connecting to one 3g wifi router

Hi there - we are considering the imp for an application which requires a large number of imps connecting to one 3g Wireless Router once every 10 mins. Data packets are small and the imp sleeps for the rest of the time. Are there any considerations we should be aware of? Any recommendations for a router? Is there a possibility that it wont be able to handle the number of devices due to concurrency? Thank you.

3g wireless routers, especially the small ones, do have a limited number of simultaneous TCP connections. Just how many imps are you considering connecting to a single unit? The routers we use support a maximum of 16 connections. You could manage the diversity somewhat to spread them across the entire 10 minutes.

Coverdriven - thanks for your response. To start about 200, but would like to scale up to 2000. We have a solution that currently uses RF, but the intelligence of the imp is very tempting! I know I would need an industrial router - any suggestions?

At my work we use heaps of Cisco 819G hardened routers and a heap more Netcomm 3G routers but a guy at work prefers his home Dovado 4G router for reliability.

Are you thinking about using 3G for 2000 imps?

Yes rocketfire, is that feasible? How could i simulate it?

I try not to rely on 3G as a primary link in my job, it only takes one bus load of teenagers to drive past and there goes the bandwidth. It’s 2x 3G routers if I need to rely on 3G but I try to only use it on sites as a backup.

Take a look at the cradlepoint devices, these are a bit more industrial grade - and also have ethernet ports so you can daisy chain additional routers, eg on alternate SSIDs, to spread the load onto multiple channels and networks.

You should ensure the DHCP pool size is big enough, and the lease time is short enough, that you won’t run out of DHCP leases - that’s the most common problems seen at (eg) factories that build imp-based devices.

Thanks Hugo and Rocketfire