Reader Forum: Reconfigurable beam antennas address exploding data traffic

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Wireless data traffic is growing exponentially in all global markets because of the growing number of data service subscribers and the increased traffic per subscriber.
Smart phones add to the growing wireless traffic thanks to enhanced capabilities, user-friendly applications, convenient Internet access, frequent synchronization between applications and network servers, and high bandwidth requirements of some applications such as video. To deal with this data traffic explosion, wireless operators are increasing network capacity with 3G technologies and beyond, but cutting-edge infrastructure solutions are also available for capacity optimization. Reconfigurable beam base station antennas help meet capacity demands through load balancing, interference mitigation, and better coverage patterns.
Did you know that downloading a typical two-minute video to a smart phone requires the same capacity as sending 500,000 simultaneous text messages? And that a typical Apple Inc. iPhone user generates about 500 megabytes of data traffic per month, which is around 10 times more than the data traffic generated by users of any other smart phone types (around 50 MB)? It is no wonder that wireless operators are challenged in ensuring enough capacity is available to their subscribers. All industry reports point to the continued massive surge in data traffic on broadband wireless networks.
Operators, however, face significant pressure to keep costs low even while trying to add the network capacity needed to handle high traffic volume. Costs for adding capacity have two aspects: the initial cost of deployment (capital expenditures) and the total cost of ownership (operating expenditures). Both are equally important because ongoing expensive optimization could cause high operational expenses in the mid- and long-term. At many cell sites, the operational costs exceed the initial capex due to expensive site visits for antenna optimization. Wireless service providers have to provide additional capacity to support demand, but should do so with the least total cost and as efficiently as possible.
Meeting the capacity challenge efficiently
Often when faced with capacity challenges, operators will simply add more base stations to overbuild the network. Just adding more sites or more radios to accommodate peak traffic during the day in a business area adds to inefficiency during the off-peak times (e.g. at night, when everyone is back at home). Such networks are static, providing the same capacity per sector at all times of the day, which is an inefficient use of expensive radio capacity. Subscribers are mobile, and unless subscriber movements are taken into account, there is misalignment between capacity and demand.
Fortunately, subscriber movements are not chaotic, but predictable. During the work week, the majority of traffic usually moves in the morning from residential areas to business areas, stays there during the day, and moves back to residential areas for the late afternoon and evening. Typical traffic patterns can easily be captured from the switch, and new radio plans can be generated; for example:
–A radio plan for business hours, focusing on business areas during the day;
–A radio plan for rush hour, to cover commuters and workers;
–A plan for night time or weekends when subscribers are typically at their residences;
–Each plan can have different network configurations.
Reconfigurable beam antennas are capable of making real-time adjustments to changing traffic patterns. Reconfigurable beam antennas can dynamically load balance capacity across all sectors of a site cluster by tilting the beam, changing the horizontal azimuth direction of the beam by +/-30 degrees and also changing the width of the beam from 35 degrees to 105 degrees, all at the same time. Because traffic often appears in hot spots, some sectors become overloaded and reject new calls, while adjacent sectors remain under-utilized. With agile beam shaping in three dimensions, traffic is more evenly distributed between the whole network, off-loading traffic across all sectors to ensure efficient use of capacity. These three degrees of freedom also change the gain of the antenna, which means that a reconfigurable antenna can change its performance from a 105 degree antenna with 14 dBi of gain to a 65 degree antenna with 18 dBi of gain or to a 35 degree antenna with 20 dBi of gain, which helps increase the signal power in areas with high interference and the signal-to-noise ratio.
Load balancing can be done with the click of a mouse as advanced reconfigurable beam antennas can be managed over a network connection. That means no expensive site visits and the ability to execute different radio plans throughout the day and night. Overloaded sectors can be aided by under-utilized ones for even distribution of traffic across site sectors. The addition of more radios or more sites can be delayed or even prevented, saving on capex and reducing the need to acquire more channels, which are difficult to obtain and very expensive. The unique three degrees of freedom of reconfigurable beam antennas also have benefits for reducing interference in sensitive 3G and 4G networks and providing the best coverage patterns possible.
Limiting interference for optimal performance
The containment of downlink interference from neighboring sectors and uplink interference from mobile devices is a crucial requirement in all wireless data networks. But 3G and 4G technology standards such as UMTS, WiMAX and LTE are much more sensitive to interference than 2G systems. In data networks, interference has a huge impact not only on network quality but also on the service area, capacity, and data rate. Higher interference actually reduces the service area in 3G and 4G networks, whereas reducing interference will increase the service area. A key objective when planning 3G and 4G networks is to optimize and reduce interference.
Limiting interference results in an improved signal-to-noise ratio in the wireless network – one of the key parameters affecting data rate, capacity and, ultimately, service quality. When interference is not compensated for well, a mobile phone will increase its power to improve the uplink signal, helping this specific mobile phone maintain its connection. However, the network and all the other mobiles connected to it experience an increased noise level, more interference, and lower signal-to-noise, triggering the other mobiles to increase their power in compensation. This ripple effect has a significant combined negative impact on the service quality, capacity, and data rate of the wireless network, especially for users on the cell edges.
Two things are critical for running low interference wireless data networks: initial containment and ongoing optimization for continued containment. Reconfigurable antennas offer unique abilities to meet both requirements.
Reconfiguring beams for better service
Network planning engineers attempt to pick the best antenna for initial interference containment, but often need to compromise with antennas that have either a horizontal beamwidth of 65 degrees or 90 degrees. A 90 degree antenna offers a wide beam that is great for signal levels inside the sector and has a very low sector-to-sector null (around 6 dBi). But a 90 degree antenna is disadvantaged with a wider sector overlap (around 90 degree overlap) because its pattern roll-off is not as good as a 65 degree antenna. In order to reduce sector overlap, 65 degree antennas are wi
dely used because they provide a much better roll-off, which means less interference. But their coverage inside the sector is not as wide and the sector-to-sector null is not as good as a 90 degree antenna.
A reconfigurable beam antenna with three degrees of freedom utilizes a multi-column design that generates superior pattern shaping and more enhanced roll-off than a standard 90 degree antenna. Set to 90 degree horizontal beamwidth, a reconfigurable beam antenna essentially combines the advantages of both a 65 degree and 90 degree antenna into one superior pattern. It has the wide coverage of a 90 degree antenna with the roll-off of a 65 degree antenna. The result is less interference, wider coverage area, improved SNR, better network quality, and higher data rates, even when the three-way reconfigurable beam antenna is used statically (i.e. not adjusted routinely). When combined with the agility to change the tilt, azimuth direction and beamwidth in a matter of a few minutes with no costs, three-way reconfigurable beam antennas are the key solution for superior, cost efficient data networks.
Reconfigurable beam antennas with three degrees of freedom are setting a new RF planning parameter, enabling RF engineers to design wireless data networks with reduced interference and superior signal performance. RF planners can optimize the horizontal beamwidth of each sector based on the needs of each sector. No longer will engineers have to settle for fixed beamwidths.
The increase in data traffic is not going away or slowing down. Reconfigurable base station antennas with three degrees of freedom are one solution to the challenges of wireless data networks. These antennas have the ability to change the tilt, azimuth direction and horizontal beamwidth remotely to balance the load across sectors. Load balancing offers the highest capacity efficiency and can reduce capex by delaying or preventing the addition of new sites or radios. Reconfigurable antennas also reduce the opex by eliminating site visits for optimization, which instead can be executed from the office. With improved performance, better roll-off and better shape, three-way reconfigurable antennas also provide better signal-to-noise ratio even when used statically. This means less interference, wider coverage area, and better network performance.