![]() A Motorola XPR8300 repeater, providing DMR (digital mobile radio) coverage.A mast-mounted WiFi access point for 2.4 / 5 GHz WiFi coverage.Our software-defined LTE network that is band-agile.The van is currently outfitted to provide four access networks supported by three backhaul networks, undergirded by four power sources. Re-fitting the ambulance involved putting in a shock-mounted equipment rack where one of the paramedics used to sit (see the photo on the right), putting in a 42-foot pneumatic antenna mast where the oxygen bottle used to go, creating a full roof walk with ladder, making it easy to attach various fixtures to the top of the mast, and filling the rack with networking and computing equipment. We selected an ambulance as our vehicle of choice because it provides multiple power sources (alternator, shore power, battery), some natural places for equipment (more on that below), storage space for equipment, and decent creature comforts. Our van began its life as an honest-to-goodness ambulance for the City of Los Angeles. Drone-based data collection and real-time visualization use the same infrastructure as our Survivable Social Network (an emergency communications service). This integration and flexibility make it straightforward to configure the van for different applications. This same environment supports both virtualized network functions as well as service machines - a local computing cloud - that is integrated with the wireless network. All of the core computing, including the software-defined radios themselves, run within a unified virtualization environment in the van. Using the software-defined mobile network approach that we applied to our on-campus network, we built the mobile lab using software-defined radios and software-defined networking. We observed that many, if not most, were designed to house many traditional fixed-band radios. We created the concept for our mobile lab by studying emergency communications vehicles that other organization had assembled. This mobile lab also includes local compute servers, a satellite ground station and a stand-alone power plant that give us the opportunity to create a full mobile network wherever we go. In addition to this fixed network, we’ve designed and built a mobile RF laboratory that allows us to take this capability into the field - with the ability to create, run, instrument and study cellular, WiFi, and narrowband networks. The CROSSMobile project at CMU’s Silicon Valley campus includes an on-campus cellular network testbed, supporting experimentation at all levels of networks. Bridging the gap often involves extensive planning, logistics and setup to create a real network in the field. But even so, the more interesting studies involve real topographies, real antennas, and real user equipment with real users. Connecting theory to practice for wireless networks requires a substantial investment in lab facilities.
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