Finally, today each small cell can support one or at most two frequencies, so in an environment where multiple frequencies and/or mobile operators must be supported, it will be necessary to deploy multiple small cells in each coverage area.
DAS and small cell use cases
Small cells are being deployed in smaller buildings with low user density, where multi-operator support may not be desired. In these situations, the small cells’ capacity and frequency-carrying capabilities are well matched to the needs of the users. Typically, indoor small cell deployments have been limited to buildings of less than 100,000 square feet.
DAS deployments typically involve larger buildings where the main requirements are to support hundreds or thousands of users, and to support multiple operator frequencies. Simply put, there is no other way to simply and economically cover a large space requiring multi-frequency/multi-operator support than with a DAS.
So it isn’t a question of replacing DAS with small cells, but rather finding the best environments where the strengths of each type of solution can be best applied. As with many things, you should always use the right tool for the job.
How small cells and DAS can work together
In fact, it’s possible to use small cells and DAS together to overcome the limitations of using either alone. You can use small cells to provide the RF signal, and DAS to distribute that signal throughout the building. In those instances where a building requires more capacity than can be provided by a single small cell, or when more than one or two frequencies must be supported, multiple small cells can be centrally located and easily fed into the DAS head-end.
Here’s how this combination solves the problems of using small cells or DAS alone:
* Small cells are far less expensive than base stations. Mobile operator base stations cost $30,000 or more, and make up a significant part of the cost of a DAS head-end deployment. Small cells cost a couple of thousand dollars each.
* Small cell power doesn’t need to be attenuated. Since they output .5 Watts of power, small cells eliminate the need for racks of attenuation equipment at the head-end of a DAS, saving on space, power, and cooling. Instead, small cells can be plugged directly into a DAS head-end.
* DAS overcomes small cell frequency limitations. A DAS can distribute a range of cellular frequencies to serve more than one mobile operator, so just one set of remote antennas is required, rather than multiple small cells in each location. The user would simply deploy a series of small cells at the DAS head-end to supply the needed frequencies.
* Interference concerns are mitigated. Since the DAS simulcasts radio channels throughout the building, multi-cell interference issues are eliminated along with the need to hand off from one cell to the next as the user moves around the building.
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