Indoor distributed antenna systems and NEC class 2

An indoor distributed antenna system (DAS) is a network of small antennas that prevents isolated spots of poor coverage inside densely populated indoor spaces. In addition to an antenna, a DAS node can include equipment such as amplifiers, remote radio heads, signal converters and power supplies that propagate, process or control the communications signals transmitted and received through the DAS node. Providing power to these remote nodes can be a challenge. This paper describes two options for powering the remote nodes - either locally at the nodes or from a centralized location at the head end. The local power approach has issues with access to AC power, space allocation and aesthetics of equipment cabinets as well as ongoing maintenance of batteries. On the other hand, deploying a centralized power solution incurs cabling costs to the individual remote sites. To be compliant with local and national standards, armored cable or conduits may be necessary; both require the assistance and cost of a licensed electrician. The paper then describes an alternative centralized power solution, using NEC Class 2 circuits to power the remote nodes. NEC class 2 circuits provide the added advantage of running standard composite fiber cables, reducing the capital expenditure incurred with deploying and installing conduits or armoured cabled. In addition, the assistance of a certified electrical personnel is not required thereby eliminating the associated costs. The pros and cons of this line powered technique are provided. Finally, the paper concludes with a summary of the requirements for NEC class 2 circuit compliance.