3M Solves Fiber to the Antenna Issues

3M Solves Fiber to the Antenna Issues

In the evolution to advanced 3G and 4G services, wireless carriers are taking fiber to the top ofthe tower. Next-generation, fiber-fed architectures are quickly becoming the new norm for towerbuilds and retrofits. These new fiber-to-the-antenna (FTTA) architectures leveragetower-mounted radios to deliver a number of benefits over traditional coaxial-based systems. Telecom Review North America recently received a demonstration of 3Ms new technologiesthat they developed to address fiber to the antenna issues, that we felt would be of interest toour readers. 3M spends quite a bit of time and money to develop the right products for the rightapplications and they seem to be on track with their new 3M Slim Lock Closure and their NoPolish fiber connectors. Todays more complex cell site designs demand a new type of weatherproofing solution toprotect vulnerable connection points at the antenna and the remote radio unit (RRU). Suppliershave responded with products to meet the needs of these next-generation cell sitearchitectures. The result is a wide range of commercially available weatherproofing solutions,ranging from traditional tapes and mastics to closures designed specifically for the latestfiber-to-the-antenna (FTTA) architectures. However, when it comes to installing fiber networks with an operation geared toward hard-linecoax, operators face a new set of challenges, particularly in terms of connectivity. They mustweigh the pros and cons of factory-terminated versus field-terminated fiber cable. They have toconsider the skill sets of their field technicians. And they should address the increased need forweatherproofing required by many new antenna designs in order to provide advanced services.New solutions from connectivity suppliers are helping operators meet these challenges. Many operators around the globe have chosen to invest in fiber networks for new builds andretrofits of cell towers. They see it as the best architecture to meet current and future demand,reduce energy consumption and minimize footprint. Among the advantages of FTTA:

1 / 5


Better signal integrity: Conventional systems use coaxial corrugated cables to transmithigh-frequency radio signals from the base station on the ground to a passive antenna on thetower. As much as 50 percent of the signal can be lost along the way, according to manyindustry estimates. These losses increase the signal-to noise ratio, degrading the quality of thereceived signal. Signal loss in not a concern when fiber is used. FTTA systems usetower-mounted remote radio units (RRUs) to generate the signal at the top of the tower, nearthe antenna, with a coaxial jumper cable connecting the two. With a short distance to travel overcoax, signal loss is minimal. Increased energy efficiency: Reducing the carbon footprint (and energy costs) has becomea ubiquitous goal in the communications industry. In a traditional base station design,transmitted radio signal power travels up the coaxial feeder cable to the antenna. As thefrequency of the radio signal rises, the corresponding signal losses in the coaxial feederincrease. In the worst cases, twice as much signal must be injected into the feeder coax as isneeded to propagate out from the antenna. The radio frequency (RF) power amplifier in thebase station is one of the least efficient components of the system, and much of the extraenergy required to drive RF power up hard-line coax is simply wasted as heat. This, in turndrives up the energy costs even more because active cooling systems such as A/C are neededto keep the equipment within its operating temperature ranges. Cooling typically accounts for 25percent of a towers energy use, according to the ATIS report. With a remote radio system, theRF power amplifier is located in the RRU. The tower-mounted RRU is cooled by ambient airflow, eliminating or decreasing the need for active cooling in the base station and savingenergy. Increased capacity and coverage: Remote radio units often support advanced antennatechniques such as multiple In multiple Out (MIMO) and remote electrical tilt (RET), whichenable denser, more flexible coverage with fewer service gaps and higher capacity. Smaller footprint: FTTA systems consume less space because the fiber cable is many timesthinner and carries more signal than coaxial feeder cable. A fiber-fed system lessens or atleast doesnt add to coaxial congestion and tower loading issues, saving tower real estate,reducing physical complexity and minimizing visual impact. Also, the removal of the inefficientRF power amplifier and its associated cooling systems decreases the need for a shelter or alarge equipment storage unit to house the base band unit. Operators realize that fiber is generally better suited than coax to achieve advanced 3G and 4G

2 / 5


data rates and to prepare their networks to meet future demand. However, a number ofstumbling blocks stand in the way of implementation. 3M No Polish Connectors Fiber is relatively fragile and requires some care during installation. But the real reluctance toswitch from coax to fiber is steeped in fundamental unfamiliarity with the media. Indeed,installing fiber requires a new skill set. That means retraining technicians or hiring new ones, atime-consuming and costly proposition. Companies can sidestep the training issue bypurchasing factory terminated fiber. However, factory-termination adds to the cost of the cableand requires various lengths to be stocked. Additionally, because it comes in pre-definedlengths, factory-terminated cable may create either a slack storage situation or turn-up delayswhen the cable is too short, adding cost. Those issues have fueled the emergence of fieldterminated fiber connectors in the FTTA space. Field termination fits well with the prevailingpractices used for hard-line coax. Specifically, hard-line coax is always cut and terminated on-site to ensure a proper fit. Newfield-mount fiber connectivity solutions allow the same paradigm to be used for fiberdeployments simply roll out a spool of fiber, field terminate at the site, and you have a custominstallation every time with no messy slack storage or missed deadlines due to inadequatecable lengths. To make fiber more technician friendly, 3M has developed solutions to help mitigate the costand complexity of installing fiber in the field. The 3M No Polish Connector (NPC) allows quickand easy termination of fiber cables at the site. For the small fiber counts used in FTTAinstallations, the NPC connector is faster than fusion splicing because only one end of the fiberneeds to be prepped and the installation tool requires no power or care. For installationsrequiring integrated strain relief, the 3M Tool Less Connector (TLC) series makes the processeven simpler with an innovative fiber cable strength member capture mechanism. Provensolutions, NPC and TLC connectors are currently deployed in environmentally demandingapplications around the world. Wireless carriers must also address new weatherproofing challenges when installing next-gentower networks. Emerging designs, such as MIMO, incorporate multiple connection points andhigher density connections than traditional two port antenna designs. These connection pointsrequire effective weatherproofing to ensure reliability. However, traditional solutions for

3 / 5


weatherproofing, such as tapes and mastics, are often too cumbersome to apply on tightlyspaced connectors. Proper weatherproofing of RF connections tops the list of essentials toensure network reliability. A small investment in weatherproofing can help safeguard againstexpensive service interruptions. The importance of weatherproofing cannot be overstated. Evenconnectors with internal gaskets/weatherproofing are not fail-safe. Moisture build up around theconnector can cause corrosion, allowing RF signals to mix and generate passiveintermodulation (PIM) distortion. PIM can interfere with neighboring frequencies, prompting ahost of legal and regulatory headaches for the operator. Its no small wonder that major cellularantenna manufacturers recommend external weatherproofing around their sealed RFconnectors. The security in performance and reliability for minimal spend is simply too high toignore. Fiber-fed tower architectures that incorporate multiple in, multiple out (MIMO) or multibandantenna configurations, for example, have resulted in crowded connection points on theantenna and RRU. Very often, a grown mans hand wont fit between these connections in orderto wrap tape. Similarly, first-generation closures may often be too bulky for congested areas.Newly developed, second-generation closures sport a smaller footprint and are specificallydesigned to fit into crowded spaces. The closures retain all the features of earlier closures butare better suited for crowded connection points. 3M Slim Locktm Water is the enemy of coax. It can intrude into coaxial cable through connectors and causedamage. One tiny droplet of rain can attenuate the high frequency RF signal, resulting in aservice outage. Wireless carriers dont need to be reminded that even a short serviceinterruption can result in a loss of subscribers. Moisture build up within the cable can also wreakhavoc on a systems performance. The coaxial cables dielectric is typically made of open-cellfoam, which can act like a sponge, absorbing and retaining moisture. Moisture encouragescorrosion around the connector, potentially leading to a scenario where RF signals inadvertentlymix and generate passive intermodulation (PIM) distortion. PIM can interfere with neighboringfrequencies, prompting a host of legal and regulatory headaches for the operator. One new, innovative closure with a small form factor from 3M offers an added feature. The3M Slim Lock Closure contains a highly compliant sealing gel inside that conforms to theentire connection rather than a perimeter seal, displacing air. In the absence of air,condensation cannot occur, so the connection is further protected from corrosive moisture. Thenew 3M Slim Lock Closure for wireless weatherproofing applications is a compact closurethat protects RF connections at the cell site, even when those connections are close together.

4 / 5


As a result of Multiple In, Multiple Out (MIMO) antenna requirements for LTE and the trendtoward multiband multiservice antennas, RF connector density on the antenna is becomingproblematic for older, bulkier weatherproofing solutions. Tapes and mastics, for instance, canbe less reliable and difficult to use in these congested areas. The 3M Slim Lock Closure isreusable, re-enterable and tool-less, making it a timesaving, cost-effective, easy-to-use solutionfor the wireless industry. It can be used at the RF connection points on both the antenna andRemote Radio Unit (RRU) in an FTTA installation. RF connections need to be protected so thatmoisture cannot intrude, which can lead to signal integrity issues. Air is displaced aroundprotected interconnections using a highly compliant sealing gel technology providing a robustsealing interface. This closure can be opened and reused without disconnection of the network,thereby avoiding signal interruptions and additional replacement costs. Next-generation, fiber-fed architectures are quickly becoming the new norm for tower builds andretrofits, and 3M seems to be in the forefront of these next generation installations.

5 / 5

Documents

3M Solves Fiber to the Antenna Issues