SIP with Cradlepoint MBR95 and AT&T Mobile Broadband

We wanted to build a network that would allow our team to move from location to location without being dependent on potentially subpar network service.
Published: May 31, 2013

VoIP Resources VoIP Reviews VoIP Hardware

Written by Eric Phipps, Software Engineer at OnSIP, and edited by Kevin Bartley, member of the marketing team.

Walking around with a Polycom desk phone in your pocket? We've got the perfect solution for you! We started testing the mobile network and devices for our sales people looking to demonstrate hosted PBX with desk phones on the road (for conferences and expos). SIP phones are very dependent on a stable network, but many networks block everything except world wide web and email traffic. We wanted to build a network that would allow our team to move from location to location without being dependent on potentially subpar network service. In this article, we deployed a wired SIP phone that runs off of a cellular network to create this kind of network.

Our dream device is a router that utilizes either a cellular modem or a WiFi-as-Wan device (WISP), and The Cradlepoint MBR95 was exactly what we were searching for. Cradlepoint produces routers that are designed to hook into the existing cellular network using either a USB modem or WISP. We tested it on AT&T’s network with a directly wired T-Mobile Jet Modem and an iPhone 5 in Personal Hotspot mode.

Cradlepoint MBR95
Cradlepoint MBR95

The set up was equally easy regardless of how we decided to connect to the Internet. The T-Mobile Jet modem plugs directly into the router, and when the router is turned on, it activates the modem and connects to the cellular network very quickly. Aside from the aforementioned issues with T-Mobile's network for SIP, we didn't have any new issues by introducing new equipment. We also connected the MBR95 directly to our Verizon FiOS handoff and found that the router had no issues associated with trying to use the router as a traditional router.

We finally found what we were looking for when we used an iPhone 5 in Personal Hotspot mode with WISP functionality. Empirically, we found that AT&T's network to perform better than T-Mobile's network from our location in downtown Manhattan. Our ping times to sip.onsip.com were excellent. They went to about 200ms. Not perfect, but we were able to hold many good HD voice phone calls on Polycom devices. We were able to do transfers and BLF functioned perfectly.

What really surprised us was the fact that we were able to maintain a stable connection between the Cradlepoint and the iPhone at about a distance of 40 feet. The iPhone was even able to place calls while serving as a Mobile Hotspot causing no interruption in service on either device. With this testing in mind, we are looking to provide our field agents with a Cradlepoint MBR95 and an AT&T iPhone for their jaunts to the field.