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Optimising distributed antenna system installation

Posted: 03 May 2016     Print Version  Bookmark and Share

Keywords:distributed antenna system  DAS  cable  fibre optic  coax systems 

A truly wideband DAS is different; it uses a single amplifier that covers every frequency. Because of the high-power nature of this amplifier, it allows you to spread the amp's power across multiple frequencies – as well as operators using those frequencies – while being able to balance the power output at the end of the remote so that coverage is consistent for each and every frequency.

Facilities use
When deploying a DAS, space for the needed equipment is always an issue. Equipment uses space, power, and cooling resources, so the size of the overall system impacts TCO.

There's a difference in size between types of DAS systems. Hybrid fibre coax systems, in particular, can be fairly large. Most hybrid fibre coax systems have a head-end hub which is rack mounted and can easily be accommodated in a standard telecom or IT room, but the remotes, which are typically 4-6U high rack- or wall-mounted units, go in the tight confines of a wiring closet. Finding the necessary space and power for these units can often be a challenge. You should also consider the amount of space the cabling takes – it spreads from the remote unit to 4-8 antenna points, and that's a pretty heavy footprint caused by the cable infrastructure when you are using heavy coax.

Figure 3: A ceiling-mounted RAU.

The head-end is also a space consideration. Space is precious in equipment rooms and data centres, and, while the head-end hub of a DAS solution may not be a space issue, most DAS systems require attenuation panels between the carrier base station and the DAS head-end to condition the carrier base station's signal. This is necessary to ensure that the signal is of an appropriate strength so it can be fed to the DAS head-end without damaging the equipment. Most DAS manufacturers now use active integration panels to reduce the amount of such "plumbing" required, and some even use direct digital interfaces so the base station can talk directly to the head-end without a lot of intermediate "plumbing." But even with these improvements, the space requirements – as well as power and HVAC – can be significant, particularly for larger buildings supporting multiple wireless operators.

Recommendations
While Cat 5/6 Ethernet may be a tempting DAS system cabling option because of its ubiquity, its distance and capacity constraints make it suitable only for smaller buildings and applications requiring support of only one or two wireless frequencies. As we've seen, while the use of coax cabling provides more available bandwidth, even hybrid fibre coax systems have their drawbacks in terms of cost, reach and performance. A pure fibre cabling infrastructure offers the most advantages, particularly in terms of key attributes such as cost, performance, and flexibility.

Ultimately, given the relative characteristics of cable types and DAS architectures, it seems clear that a DAS which uses end-to-end fibre connectivity and a truly wideband amplification architecture will deliver the lowest TCO. This type of system will deliver a genuinely future proof solution, which is critical in today's rapidly changing wireless landscape.

About the author
John Spindler joined Zinwave as VP marketing and product management in November 2015 and has over 30 years of product management and marketing experience in the wireless and telecommunications industries. His most recent role as director of product management was with TE/CommScope, and prior to this as VP marketing at ADC Telecommunications. John holds a BA degree in Psychology from UCLA and has an MBA from the Marshall School of Business at USC.


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