Cellular

New angles on control
The use of tilting is crucial. By directing the main beam of the antenna pattern at a specified angle below the horizon, less radiation travels into areas beyond the extent of the cell. The Optimizer is available with a wide selection of fixed, variable mechanical and variable electrical tilt combinations. Significantly, it features an extended tilt range from 0 to 10 degrees and enhanced null-fill that dramatically reduces the impact of the first and second lower null. The effect of these is to enable close-in coverage that is essential in urban areas, obviating the need to lower the mounting height of antennas in order to cover the streets below.
It is important to note that tilting the antenna beam can sometimes exacerbate interference, with side and rear lobes pushed in the direction of neighbouring cells. To avoid this, the radiation profile of RFS Optimizer antennas has been designed to minimize emissions in unwanted directions, employing front-to-back ratio above 30 dB, and reduced side lobe suppression of typically better than 20 dB across the entire tilt and frequency range.
The Optimizer series complements greater maximum down-tilt angle with greater electrical tilt control. Specifically, the‘Remote Tilt’ cellular antenna solution, the Optimizer RT provides the optional capacity to adjust the electrical tilt of each antenna without riggers, extending the flexibility of tilt control to the tower base, the network management system or, via the power of the Internet, from anywhere in the world. As a result, network engineers can quickly and easily optimize their networks as call density changes.
The principle innovation offered by Remote Tilt is flexibility. Traditionally, when network managers set out to optimize network performance, it is not always obvious what the exact angle of tilt should be. By contrast, the advent of Remote Tilt means that it is possible to vary the tilt of multiple sites and measure their performance in real time, allowing the optimum angle to be established. Because of this, the Optimizer RT is an indispensible tool for lowering the total cost of system optimization, and hence maximizing the performance of base station infrastructure.

Discriminating tastes
At the heart of the Optimizer design philosophy has been the need to address limitations in available base station space and access. With growing public demand for unobtrusive site installations, the value of a compact antenna shape and ease of implementation, without compromised performance, is extremely high.
For this reason, the Optimizer antenna family comes complete with a range of features and options to streamline site acquisition and deployment. These include: camouflage radomes with a selection of digitally camouflaged antenna surface treatments to blend in with walls, forest or sky; ‘cluster’ assemblies for mounting three panel antenna arrays in a low visual impact arrangement; and, via the advanced RFS Global Mount System mechanical mounting technology, one-hand tilt and azimuth adjustment.
The low-profile, high-performance philosophy is also at the heart of the Optimizer diversity system (used to discriminate between reflected signals and background noise in the uplink). The drive towards economy of space has led to a growing preference for polarization diversity over spatial diversity schemes, but the successor technology is difficult to master. The RFS Optimizer takes this a step further—its enhanced cross-polarization technology is able to discriminate signals from different polarizations with unusually high efficiency. Consequently, the antennas provide excellent signal diversity, maximizing capacity while maintaining a compact, efficient design.

Broad horizons
Restrictions on tower space are also affecting the way new services are introduced and, in particular, are driving the need for antennas to operate in different frequency bands. Not only does the Optimizer family support all the major cellular bands used in the world today, but these bands are accommodated in a wide selection of single-band, dual-band, multi-band and broadband antenna variants—including the RFS world-first Optimizer triple-band GSM 900/GSM 1800/UMTS 2100 antenna with independent fixed electrical tilt in each band.
It is also incumbent on operators to ensure that the introduction of new services, especially emerging third generation (3G) systems, do not cause degradation in the performance of existing second generation (2G) networks. Optimizer multi-band and ‘side-by-side’ format antennas can easily be substituted for older single-band antennas, without disrupting network planning and quality of service. They offer, therefore, a cost-effective means to overlay the latest wireless systems over a well-established, revenue-generating network.
Complementing the multi-band options, Optimizer broadband antennas operate across a wide range of frequencies, offering a flexible solution amid uncertainties surrounding new services and spectrum allocation. Together with enhanced coverage performance and real-time footprint control, the Optimizer series promises to shape the many and diverse future patterns in mobile communications.