This post is by Kevin Linehan, VP and CTO Antenna Systems, CommScope
According to a GSMA Intelligence study, global LTE connections will hit the 1-billion mark by 2017 and Asia will account for almost half, or 47 percent of that. The demand for high speed connections and rich media experience is keeping operators on their toes and constantly upgrading and building more efficient LTE networks. As operators work towards keeping high levels of subscriber satisfaction, network coverage and capacity becomes utmost concern.
I have been in the telecommunications industry for nearly three decades and these developments are extremely exciting. At the LTE Asia Conference, which took place from September 24-25 in Singapore, I was happy to share a presentation titled “Antennas Solutions for Capacity Improvement” in which I addressed concerns related to maximizing network capacity and developing unified industry standards for base-station antennas.
Antenna Evolutions to Increase Network Capacity
First of all, it’s important to highlight the fact that antennas have gone through several evolutions over the years, from the omni-directional antenna to today’s LTE & MIMO antennas. MIMO improves capacity and other aspects of network performance by using multiple antennas at both the cell site and the user’s handset. Currently one dual-polar array is prevalently used as a base station antenna to provide two-way transmit and receive signals; operators worldwide now are examining the mechanics and benefits of adding a second dual-polar array to enable four-way.
In the last 50 years, thanks to various new technologies, wireless capacity has increased by around 1,000,000. Better spectral efficiency and addition of spectrum has contributed to this but the addition of cells/sectors has been by far, the biggest contributor. To achieve maximum throughput, operators need to ensure a good signal-to-interference-plus-noise ratio (SINR). This can be achieved in a few ways like noise suppression in the RF path and sector sculpting.
Sector Sculpting, Beam Tilting and Multi-Beam BSAs
Sector sculpting describes superior antenna beam pattern shaping that enables operators to shape each sector precisely to minimize interference with neighbouring cells.
The measurement of the signal power registered outside and inside a desired receiving area as a consequence of an antenna’s radiation pattern is known as the sector power ratio and this is a key metric. In cellular network applications, higher sector power ratios indicate a higher amount of interference between antennas in adjacent coverage areas, which consequently reduces performance, such as dropped calls.
Since sector sculpting results in the improved containment of interference, operators can then reuse the same frequencies or codes in cells that are closer to each other. This then leads to increased spectral efficiency, cell edge throughput, and overall network performance.
Beam tilting can also be employed to good effect. Operators can tilt the vertical pattern of the antenna downwards to reduce the coverage on the horizon where interference to neighbouring cell sites takes place.
Advanced networks now deploy a more elegant method of tilting the sector antenna’s vertical pattern using electrical downtilt, as it offers greater control and precision in shaping the antenna’s horizontal radiation patterns. This method ensures a consistent tilt over the entire 360 degrees, generating consistent reduction of the entire cell coverage. In addition, electrical downtilt can be accomplished remotely in advanced antenna systems, a feature becoming more and more indispensable as technologies like LTE mature, where self-organizing network (SON) re-optimizes itself on demand.
One of the best investments an operator can make today is to go with twin-beam or other multi-beam antennas. The twin beam antenna, for example, allows operators to change their existing three-sector site into six sectors. This has an added advantage over simply adding more antennas in terms of tower leasing costs and reduced tower load.
Base Station Antenna Standardization and Benefits
Previously, there existed no comprehensive, global, standards focusing on the base station antenna and this made it difficult for operators to compare antennas and make a decision on what would work best for their needs. The benefits from enacting such industry-wide standards include the reduction of ambiguity and miscommunications between antenna vendors and operator, facilitating cost/benefit decisions and driving higher quality and performance.
That’s what the BASTA recommendations from the NGMN (Next Generation Mobile Networks) Alliance, an industry group founded by leading international mobile network operators, are all about. The BASTA standards define radio frequency parameters common to all antenna models, making it possible for operators to accurately compare the antenna technology that is necessary for implementing high quality wireless networks. CommScope continues to adopt and promote the BASTA standards in our antenna models. We encourage all operators to request that antenna data sheets comply with the BASTA recommended standards.
I recently authored a whitepaper, Time to Raise the Bar on Base Station Antennas: Evolving Technology Drives Adoption of Recommended Standards, where you can find more detail on this topic.
The NGMN’s recommendations on base station antenna standards are also available for download.
About the Author
Kevin Linehan is vice president and chief technology officer of Antenna Systems for CommScope. Kevin’s responsibilities include the monitoring of wireless industry trends, technologies and standards as they relate to antenna technology and product development. Kevin is also responsible for the scouting, evaluation and introduction of emerging antenna systems technologies through collaborative innovation and strategic alliances.
Prior to assuming a strategic role at CommScope, his responsibilities have included management and design positions for base station antennas, terrestrial microwave antennas and earth station antennas.
He received a bachelor’s degree in electrical engineering from the University of Illinois at Champaign-Urbana, where he was a research assistant in the Electromagnetics Research Laboratory. He holds eleven patents for antenna design in the United States.