Antenna technologies are crucial to increasing LTE capacity
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Operators’ Capacity Challenge
Globally, operators are experiencing ever-growing demands for reliable communication, fast speed and stable cellular services from their users. The key to resolving this conundrum lies in increasing the network capacity.
Historically speaking, operators have been carving out additional capacity from three major resources: increasing spectral efficiency, expanding spectrum, and adding cells or sectors to existing network infrastructure.
As capacity is determined by signal-to-interference-plus-noise ratio (SINR), to achieve maximum throughput requires technologies for minimizing noise and maximizing interference suppression in the RF path. In the following paragraphs, I will be shedding some light on the most-deployed antenna technologies that tackle issues in those areas.
Antenna Solutions to increase Capacity
For operators who have deployed LTE networks, they realized LTE is much more sensitive to interference. For this reason, RF engineers have to pay extra attention when it comes to designing cells for LTE and in the specifications of antennas selected.
When an operator deploys an LTE network in a new band, they typically replace the old antennas with new ones having more antenna arrays in the same radome thereby providing additional ports for the new LTE band. Increasing the capacity of a site without out adding new radomes has the benefit of minimal impact to site leasing costs, wind loading and aesthetics.
However, that addition of more antenna arrays in the same radomes is challenging as the interaction of the arrays can degrade beam pattern performance impacting the service quality of the existing network. Therefore, it is critical that an operator assure any new multi-band antennas deployed in a network have equivalent or better performance than the antenna being replaced.
Operators should keep two things in mind when choosing new antennas, that the antenna performance is characterized using a data sheet conforming to the BASTA antenna standards and that the antenna exhibit good sector sculpting performance. An antenna that exhibits good sector sculpting is one that maximizes the energy radiated inside the cell covering users and minimizes the energy radiated outside the cell creating interference to other users. The beam of such an antenna will have superior sector-edge roll-off, front –to-back (F/B) and front-to-side (F/S) ratios.
Increasing the number of sectors at a site is a cost effective way to increase capacity. Capacity can nearly be doubled by taking a 120 degree sector served by a single 65° beam and splitting into two sectors by using a multi-beam antenna radiating a pair of 33° beams. These two beams are radiated from a single BSA and are pointed +/- 30° from boresite so the twin beam antenna can simply take the place of the existing BSA without any repositioning or re-pointing.
At CommScope, we offer a slew of multi-beam solutions including 5-beam antenna systems with low and high band options, the industry’s first 18-beam antennas, and Cell on Wheels (CoW).
Increasing Capacity of Metro Sites in Heterogeneous Networks
A HetNet is a diverse combination of both macro and outdoor small/metro cell sites that collectively provide both wide area coverage and targeted areas of high capacity data. Metro cells, which are typically installed on lamp poles and street furniture, have been envisioned to use simple omni-directional whip antennas.
CommScope has shown in studies conducted with RF planning companies and University of Texas, that higher performance antennas deployed on the metro site layer have can significantly increase capacity. CommScope has designed several models of MetroCell antennas which have smaller elevation beamwidths, suppressed upper sidelobes and beam-tilting capability which provides the higher performance needed to realize the value of Metro Sitel investments.
Operators will inevitably experience even greater demand and pressure on speed and quality from users in future. Operators should look to continuously modernizing their networks and deploying advanced technologies in their wireless infrastructure and delivery of services, so as to be well-poised for the capacity challenge.
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