The Andrew CDX723A series of diplexers has been added to multiband combiner solution from Commscope that offers DC automatic switching, which enables standardization for most low band and high band feeder sharing applications. Available twin modularity and an integrated AISG modem facilitate handling and deployment by consolidating hardware and eliminating interconnections. A special tower top version separates the AISG signals feeding into the antennas. The CDX723A is the first product family to feature convertible mounting brackets for increased efficiency. This stacking and mounting system quickly installs equipment on poles, walls, framing channels, suspension rods and even in racks. Covering extended 698-894 MHz and 1710-2360 MHz bandwidths, the CDX723A compliments any LTE deployment on the horizon. www.commscope.com
Antenna performance is critical to the capacity and data throughput gains sought by the industry’s deployment of LTE Releases 10 and beyond, Ray Butler, vice president active wireless products engineering, Commscope, told AGL Bulletin at PCIA’s Wireless Infrastructure Show last month in Hollywood, Fla. He spoke on the “LTE Evolution” panel.
“We have done some analysis on antenna performance and what we are seeing is how well the pattern is shaped is very important for LTE in the macro-layer of the network and it is also true for the small cells,” he said.
Butler said there was a tendency in early deployments to use whip antennas in outdoor metro small cell sites, with a plan to place them on every street corner of the coverage area without performing the RF optimization. But this approach leads to system performance issues, because the radio issues that are present in the macro-cellular networks, – for example, carrier-to-interference ratio, containing the radio signal to the desired coverage area– also apply in small cells, according to his analysis.
“As operators get into the deployment, we are seeing a more practical approach being used, where a 2-foot to 4-foot antenna with electrical tilt capability is being specified instead of a whip antenna. You are better off using a high-performance antenna. It makes a huge difference in the network,” Butler said.
Small cells should be deployed with the same care and precision as a macrocell, according to Butler. “Many small cells will operate on the same frequencies as the umbrella macrocell, so you need to contain the radio signal and minimize the interference between the layers,” he said.
While the self-optimizing networks’ algorithms are powerful, Butler said that RF engineering is critical to unleashing maximum system throughput and capacity gains.
“You are never going to achieve full throughput and meet your capacity goals if there is too much overlap of coverage in each sector. If the signals overlap too much, you are going to have trouble with interference.”
In the area of high performance antennas, there are many considerations: MIMO versus beam forming and single-user MIMO versus multi-user MIMO for optimizing the antenna and the antenna configuration for the different LTE transmission modes.
“If you have a high mobility user, transmission diversity works the best. There is less dependence upon feedback,” Butler said. “If you have pedestrian traffic close to the site with a scattering environment where there are a lot of radio signal reflections, single- or multi-user MIMO is the best, because the traffic speed is slower and there is better signal-to-interference ratio.”
A user moving slowly close in to the antenna utilizes closed-loop feedback to maximize performance, so the antenna can be switched back and forth between beam forming and MIMO as needed to optimize the radio link, which creates the throughput gains.
The question arises, according to Butler, as to how antennas can be configured to maximize the throughput—either side by side or stacked vertically one on top of the other, for example. “The answer is rather intuitive: side by side, if users are spread horizontally and vertically for coverage down a corridor,” he said.
Butler discussed the various ways that high-performance antennas can increase the spectral efficiency of a wireless network.
“With single-user MIMO, the bit stream can be split into two paths for 2-way MIMO, which roughly doubles the spectral efficiency,” he said. “Multi-user MIMO sends multiple bit streams using the same spectrum to geographically separated users. Beam forming, on the other hand, sends a bit stream that focuses on or follows the user as he travels through the sector, which decreases interference and increases the signal-to-interference ratio.”
Commscope has removed the complexity out of integrating a DAS into a macro wireless network by upgrading its unified indoor-outdoor, low- and high-power single master unit ION platform. The upgrade reduces space requirements and the number of cable runs while maximizing design flexibility into a simple-to-use plug-and-play solution. The platform features integrated guidance and intelligence, enabling wireless network operators to design, plan, deploy and optimize a DAS more quickly and efficiently and at a lower total cost of ownership. The platform contains built-in intelligence that greatly simplifies installation. The embedded intelligence intuitively guides the design, planning, installation, set up, commissioning and optimization with virtually foolproof simplicity. The remote configuration tools enable operators to re-sectorize and access auto-leveling functions from anywhere in the world or right at the head end, and the built-in monitoring measures network quality and monitors interference and passive intermodulation (PIM). It also conducts detailed uplink/downlink spectrum analysis. www.commscope.com
LTE equipment is not only a heavier weight for the tower to bear than its 3G predecessors, but it presents more surface area for increased wind loading. Additionally, new demands for fiber to the antenna (FTTA) are increasing the complexity of tower deployments and network upgrades.
The good news is new mounts are entering the market to accommodate the heft and complexity of the LTE era equipment.
One example of the next generation of mounts is the V-Frame Boom Gate, from Connect-It Wireless, which was engineered to handle today’s heavier loads. At 181 MPH winds, the maximum combined load area for the new V-Frame is 7,945 square inches, according to Jim Schultz, founder and president of Connect-It Wireless.
“As the amount of material added to the tower increases, a mount is required that’s tough enough to handle the wind area loading,” he said. “And considering the max combined load weight is a solid 650 lbs., it’s a durable, heavy duty application that the new upgrades demand.”
The V-Frame adheres to building codes across the nation, such as the 2010 Florida Building Code, TIA-EIA-222-G-2, and A.S.C.E. 7-10.
Also in response to the rollout of 4G remote radio heads, Valmont/Site Pro 1 released the Ultra-Low Profile (ULP) Ridged T-Frame monopole mount.
The size and weight of the LTE equipment has led to a 25 percent increase in wind loading on the mounts, according Brandon Chapman, Valmont/Site Pro 1.
“A lot of T-arms were being sold for LTE systems, because they are economical compared with a platform mount,” Chapman said. “Through analysis of these mounts, I found that they were pushing their boundaries in terms of strength.”
T-arms are popular because of their price, but Chapman believed that what was needed for LTE antennas was the strength of a platform mount. He then set out to create a mount that would be economical like a T-arm and strong like a platform.
“I designed the ULP to have the cost of a T-arm with the strength of a platform. Twice the strength of a T-arm,” he said.
Valmont/Site Pro 1 analyzed the ULP for a 200-foot tower with a 90 MPH wind, using ANSI/TIA-222-G-2005. Four antenna loads were evenly spaced across each face of the mount, centered on the centerline of the mount. Based on the design criteria, the mount capacity is 5,400 pounds (170 square-feet).
The maximum normal force per antenna pipe is 450 pounds (14.1 square-feet) with a maximum tangential force of 450 pounds (14.1 square feet). The weight of each antenna was considered to be a maximum of 200 pounds. The mount will also support a nominal load of 250 pounds at two locations simultaneously (500 pounds total) to provide access for climbers.
Limiting the weight and wind loading of the mount itself were also factored into its design.
Remote Radio Deployments Present Fiber Optics Challenge
As carriers opt to deploy remote radio units, fiber-optic cables typically run up to the top of the tower to connect baseband equipment. This brings a new level of complexity for tower technicians. And the challenge strikes cell tower sites worldwide.
“It has become increasingly complex, time-consuming and expensive for operators to maintain existing cellular sites. Typically, the infrastructure had to be assembled on-site at the top of the tower, and the lack of a single tower top design standard has made each upgrade a challenging process,” Bill Walters, Commscope spokesman, told AGL Bulletin.
In Doha, Qatar, Commscope collaborated with an international communications provider, Ooredoo, to develop a factory-assembled tower-top base station remote radio, which was made according to a single global design standard.
“The aim of the tower top development is to create and maintain a network that is radio vendor agnostic and does not require significant on-site remote radio modifications for future upgrades,” Walters said.
The tower top solution will become Ooredoo’s standard cell site design across its markets in the Middle East, North Africa and Asia, in line with the company’s network modernization strategy of upgrading or replacing 15,000 of its base stations.
Building on its partnership with Ooredoo in standardizing tower tops for cellular sites, CommScope is bringing a solution for enabling fiber-to-the-antenna site deployments to America.
“FTTA installation needs to be standardized, because when you have electronics at the tower top plus fiber optics, it gets more complicated, difficult to install and there is more chance for error for the installer,” Walters said. “So we started using a pre-assembly of the whole unit that goes on the tower top, including the base station antenna, mounting, the remote radio unit and the cabling.”
The FTTA Turnkey Solution, part of the Andrew portfolio of wireless solutions, is designed to standardize and simplify remote radio unit (RRU) installation, as well as accommodate multiple RF technologies and frequencies. The solution includes the Argus UltraBand multiport antennas; HELIAX FiberFeed hybrid fiber and power trunk cables; HELIAX SureFlex RF cable assemblies, cabinets, structural supports, connectors and assemblies.
The optional Andrew SiteRise offers pre-assembly and pre-testing of all RF equipment prior to hoisting up the tower.