Although it has been somewhat ignored in the past, base transceiver station-to-DAS headend connectivity is now getting a lot of attention from manufacturers.
“Given the prevalence of DAS deployments, and multi-operator DAS installations in particular, BTS-to-DAS solutions are critical,” John Spindler, TE Connectivity director, product management, in-building DAS, told AGL Small Cell Link.
Historically, integrating base transceiver stations into DAS headends was done in a couple of ways. One was to take a hodgepodge of attenuators, splitters and combiners from different sources and assemble the cables and components on-site. Later the packaging was improved when manufacturers began assembling the parts and delivering them to integrators in a box, which made it easier because it reduced the installation time.
But both methods were passive. Any attenuation had to be made by manually turning the knobs, and there was no effective way to monitor it remotely.
The development of active integration panels (AIP) provides a new era of connectivity between mobile operator base stations and DAS with features such as remote monitoring and software configurable controls that improve system management, according to Spindler.
“In a multi-operator scenario, monitoring the downlink allows you to make sure that a single operator does not take more of the composite power than the other operators,” he said. “With a user- configurable automatic limit control on the downlink, you can avoid overdriving the DAS headend.”
With remote monitoring, in the case of a problem, the system may be fixed without sending a service tech. Diagnostics may be performed over the Internet, and adjustments may be made to the systems, Spindler said.
“If you cannot monitor these systems remotely and diagnose the problems, they are hard to maintain. This is a big step forward,” he said.
Active integration panels offer space savings, which may reduce the footprint in the headend by as much as 75 percent compared with traditional, passive attenuation panels. This solves the problem of space, which can be both expensive and scarce.
“You’ll see racks and racks of attenuation panels in large venues,” Splindler said. “Space is huge. Getting enough space for the DAS headend can be problematic in some places. With an AIP you get real estate savings from an opex standpoint plus the reduction in installation time and cost.
Active integration technology also reduces passive intermod by eliminating cabling and connectors and using components are low PIM, which is essential for LTE operations.
“With the advent of 4G and LTE, performance has really come to the forefront. Eliminating PIM is imperative so that DAS performs at its best,” Spindler said.
Amid the hype surrounding small cells, Phillip Sorrells, CommScope vice president of strategic marketing, stands out as someone who questions the rush to the new technology.
The problem that needs to be solved is getting capacity into places that are hard to cover with the kind of data throughput and performance that consumers expect today, Sorrells said. “Our answer often is DAS, especially inside buildings, venues and arenas. It provides multi-operator, multi-technology and dynamic high-capacity solutions.”
There is a place for a pico/remote radio head solution, such as the Ericsson Dot, for smaller buildings or even larger buildings that need a single-operator, single-frequency indoor system, according to Sorrells.
But for other indoor coverage and capacity needs, Sorrells maintains that an outside-in strategy is viable. By outside-in he means splitting the 65-degree beam in a nearby cell tower. A twin-beam antenna results in two 33-degree beams, which doubles the capacity of that sector, increases the gain by 3 dB and improves building penetration.
“Take a college dormitory, for example. One approach is to take an antenna sector that faces the dormitory and do some beam-splitting techniques on that sector to enhance the capacity and efficiency of the coverage going into that dormitory from the outside in,” Sorrells said.
Multi-beam antenna technology can also add capacity for an outdoor system. An existing tower can be “densified” by using beam-splitting antenna technology, which divides one beam into five beams. The technique provides a “tremendous uplift in radio capacity and a 6 dB gain in each beam,” Sorrells said.
Contradicting the Small Cell Conversation
Conventional wisdom these days says that 60 small cells will equal the coverage of 10 macrocells, but Sorrells questions that logic. “Where are you going to get those sites? People answer they will use telephone poles and streetlights. It is not that easy,” he said. “I see several viable paths for wireless operators to explore for expanding wireless capacity.”
One answer to the need for densification is a concept Sorrells calls the mini-macro whereby a remote radio unit, antenna and other RF path equipment are concealed in one monopole-type structure. In fact, three mini-macros will provide the coverage of six small cells.
“We are exploring different ways to interface the radios and the antennas to make the overall size small and easier to implement,” he said. “We think using fewer sites is almost always going to be preferred.”
A mini-macro would be a 20-watt radio, 10-watt radio or 5-watt radio, and it would look like a macrocell to the operator, with all the usual radio/handoff management parameters.
“All the radio parameter complexities of the picocell, which cloud its introduction into the radio architecture, are eliminated,” he said. “With the concept of the mini-macro, you use the same well-known radio technologies. What you are really doing is packaging it so that it is easier to implement it.”
The other theory Sorrells is advancing is that capacity can be improved by using a more sophisticated antenna than is available with a picocell.
“Down-tilt and pattern management capabilities, we believe, allow you to build half the number of new small cell sites,” Sorrells said. “The question becomes one of economics. The math will prove that building three mini-macros, which are a little bigger, will make more economic sense than six small cells.”
In the world of network optimization, down-tilting an antenna’s beam is about 60 percent of the techniques. “It is a very important to tool for optimizing any network antenna,” Sorrells said. “When compared with one-element dipole omni, a quasi-omni with three sectors and a 16-degree tilt offers a 36 percent improvement in network capacity.”
Antenna OEMs are seeing the fruits of the growth in in-building wireless, small cells and outdoor DAS and are responding with new products and increased distribution. For example, Radio Frequency Systems (RFS) experienced double-digit growth for several of its North American product lines in 2013, following a record-breaking year in 2012. The vendor responded by expanding its product line and doubling its nationwide distribution capability.
RFS booked 45 percent growth in 2013 for its in-building broadband wireless communications products, and has invested in product development in anticipation of additional growth in 2014, adding the LTE-ready I-ATO2-698/2700JPL PIM-certified omnidirectional antenna and the ICA LITE (ICA12-50JPLLW) ½-inch aluminum plenum-rated wideband coaxial cable.
Another rapidly growing segment for RFS in 2013 was the in-tunnel market, which included large deployments of RFS technology into major projects such as Phase 2 of Transit Wireless’ extensive Distributed Antenna System for the New York City subway (RFS announced its successful deployment during Phase 1 in 2012) and Phase 1 of BAI Canada’s project to build a shared wireless Wi-Fi and cellular infrastructure for Toronto Transit Commission (TTC) underground subway stations.
To support this growth, RFS has doubled its distribution centers nationwide with a new distribution center in Ontario, Calif., and expanded distribution via its partnership with KGP Logistics in Warsaw, Ind. Furthermore, RFS has expanded its installation services to support increasing deployments of HYBRIFLEX.
Wireless Sales Up at CommScope
CommScope, which completed an IPO last fall, also reported growth. Its wireless segment net sales increased 3 percent year over year to $553 million in the third quarter. The net sales increase was primarily driven by ongoing capital spending by U.S. wireless operators at macro base stations as well as robust deployment of small cell DAS solutions that support capacity and densification of the wireless network. The company reported lower wireless sales in the Asia Pacific region, which were offset by higher sales to a major Middle Eastern wireless operator. Wireless adjusted operating income rose 16 percent year over year to $116 million, or 21 percent of net sales.
Sales of tablets and smart phones, as well as the impact of BYOD, have created a greater need for a mobile Internet, according to President and CEO Eddie Edwards.
“Operators are deploying more cell sites and new technologies globally to meet this demand,” Edwards said. “We believe we are in the early innings of a long-term, global growth cycle in LTE, which includes coverage, capacity, optimization, small cell DAS solutions, backhaul and seamless in-building cellular.”
To help speed the deployment of DAS, CommScope launched the ION platform, which 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.
Late last fall, CommScope’s technical support team helped a U.S. carrier complete the first customer installation of the ION-U in a congested downtown area of Dallas as part of an outdoor coverage and capacity upgrade.
CommScope also branched into the concealment business with a family of equipment-integrated, modular solutions called Metro Cell Concealment Solutions, which hide the key RF path equipment in a structure that more easily meets zoning restrictions.
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.”