The optimisation of an in-building distributed antenna system (DAS) is a function of three main things: coverage, capacity and infrastructure. Good coverage brings efficient signal propagation. Plenty of capacity is required to achieve maximum throughput. And with the increased capacity demand created by new generation mobile technologies, a future-proof infrastructure is required early on in the installation phase.
In this series of three blogs, Moti Shalev, Director of Product Management at Axell Wireless, summarises a recently produced whitepaper, covering how combining high- and low-power remotes on the same DAS can provide flexible network designs which right-size the solution to the requirement, and reduce costs.
In this blog we’ll start with function number one: coverage.
Possibly as recently as eighteen months ago, operators were not optimising their indoor systems for next generation technologies, typified at the time by the arrival of 3G. Technology has moved fast. Mobile video traffic, for example, exceeded 50 per cent of mobile data for the first time in 2012.
Those same operators are now engaged in renewed capital expenditure as they go back to underserved locations to add base stations, or replace entire systems, in order to reduce noise levels in line with the requirements of new technologies and the demands of their users. Today, such situations can be avoided and nobody can be blamed for not having anticipated the pace at which the demands of the mobile world would change.
It’s a lesson from which the industry as a whole has learned – a flexible system enables operators to augment indoor coverage and capacity as required.
Design is crucial
The design stage has become more critical than ever before as operators now give high priority to future-proofing their indoor coverage systems. Delivering the highest achievable performance depends on maximising the desired factors; a relatively straightforward affair arising from rigorous RF design procedures.
High performance depends also on minimising the undesired factors; interference, or ‘noise’ comes at the very top of the agenda in this regard. Production of a robust architecture plan is now a well-established discipline –interactive apps are available that drive a comprehensive check-list approach to the process. This is the stage at which decisions need to be made regarding the relative power of the remote optical units, dictated by the requisite coverage sector, which then informs decisions on the number of units required together with the number of optical master units, which then propagate the signal from the remote and take it on to the BTS.
Mixing and matching
The selection of high power or low power remotes is decided at the design stage of any multi-band fibre optic system when the layout of the infrastructure is first specified, reflecting coverage requirements. A low power remote typically has a composite output power of 20dBm at the antenna port, compared to up to 37 to 43dBm for a high power remote. Given arguments for and against both types of remote, the optimal solution often involves both.
In the case of a high-rise building, for example, the use of low power remotes would typically involve at least one per floor; a configuration which necessitates the installation of more optical master units (OMUs) also known as head-ends, as well as the laying of more cable. In short, more effort and more costs are involved. From the points of view of an effective network, an optimised architecture and cost control, the higher powered remote is at the very least adequate for the requirement. It is capable of coping with present and future needs within a fixed space scenario, where demand can be confidently forecast.
The use of high power remotes facilitates a DAS architecture in which five, six or even seven floors, in the case of a high-rise building, can be covered from one unit. This approach can often be governed by cabling restrictions and access permitted to the systems integrator at the installation stage – factors which have to be accommodated for during the design process.
The implication of such restrictions, in the absence of any acceptable workaround could be that low power remotes are specified as logistically appropriate even if they are not the optimal solution. Though, technically-speaking, this may be viewed as a compromise, such a solution exemplifies the flexibility of the DAS – wherever wireless coverage is needed, a distributed antenna system can be designed to deliver it. It is important to be mindful of the flexibility of DAS in this regard; as a real world solution it can be configured in response to real world restraints whilst still delivering on its network promise of best-in-class coverage solutions. Additional sectors can be added as required, especially in large venues such as sports stadia, convention centres, and airports.
Product Marketing Manager, Axell WirelessMoti Shalev joined Axell Wireless in 2009 as Product Marketing Manager with the responsibility for defining the product management strategy. Moti has a B.S.C EE in Electrical Engineering and over 20 years of worldwide experience in the telecommunications industry.
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