No reason a startup would need YOUR internet hardware to do their work. They should only need square footage and maybe power to install equipment - not your internet access, or your devices.... sounds really dodgy.

Who is this startup?

"rent my roof" for a new wireless start up in my area.

Looks suspicious already

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they are installing an antenna on my roof and it will be hardwired to my router..

It smells not very good

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.they have assured me that my personal network would be at no risk

If they are wired their access point (I suppose this "antenna" is one) to a LAN port of your router, I am suspecting you are exposing all your network to the wireless network this access point creates.

Sounds strange. Do you have link to this service so we can look them up?

If they’re installing an antenna to your router, that means that it creates a “rogue wireless” often used by mobile devices signed to that company when they’re on the road.

• Though this type of setup tends to be segregated from your network, it still creates an attack vector and also means that any third party could use your network/IP as a launchpad for a nefarious act.

• Simple advice, disconnect the antenna from your router, and demand that they disable the ‘rogue network’ preconfigured in the router.

“bringing the sharing economy to telecom”

no thanks

Really is connecting a LTE eNodeB in your network. That device is creating an IPsec vpn tunnel directly from the device to their datacenters and then broadcasting a LTE signal out.

All traffic between the radio and datacenter is tunneled and encrypted.

They won't just plug in to your network and share access with anyone as some other commenter is suggesting. They want to protect their customers from you as much as you want to be protected from them.

You really need to ask them, we don't know what they are fitting or how they are doing it. Surprised they are sharing your internet, I started a WISP and when we did this we'd have our own connection, we wouldn't just share the homeowners internet.