Tessco Wireless Journal December January 2014 Page 8 Systems & Applications

Product information and performance claims are provided by manufacturers. 8 Product information and performance claims are provided by manufacturers. 8 Product information and performance claims are provided by manufacturers. 8 SYSTEMS & APPLICATIONS December 2013 January 2014 Cellular Coverage/Capacity the Small Cell Revolution By Scott Gregory, TESSCO Technologies If you're reading this, I'm sure you're like me in that you enjoy following the development of wireless technology. I'm also sure that you take all that you read with a grain of salt too. The fun part for me is to watch the devel- opment unfold in an environment of exploding technology that is balanced by a need for a healthy ROI and impressive marketing bud- gets - providing enough confusion to make it interesting. It's clear that the wireless sector is invest- ing time and dollars to develop solutions to tackle the projected increase in mobile broad- band capacity and coverage. There is a lot written on the growth of cellular data and the demand for capacity and coverage. There are two data points that reinforce the discussion - more mobile devices requiring more data. The direction is clear a slowdown in macro site deployment and an increase in distributed antenna systems (DAS) and small cell archi- tectures is a way to provide an effective data offloading. Sounds easy, but it's not. In fact, it can be absolutely confusing. There are a lot of ways to offload data traffic from the macro site - including DAS, Wi-Fi and small cells - and each have a specific use case and drivers associated. To provide and promote clarity, admittedly at a high level, consider the following guide: Distributed Antenna Systems First things first - DAS networks and small cells, while they are both to solve capacity and coverage challenges, they differ greatly and are not interchangeable. DAS networks are deployed indoors and outdoors by distributing RF signals from a central hub to areas that require enhanced signal or increased capac- ity. They then aggregate the signals and inter- connect or backhaul the traffic to the mobile operators network. The network is comprised of three basic elements: (1) DAS nodes (antennas and possibly amplifiers, radios, signal convertors, and power supplies); (2) transport medium (fiber optic cable connect- ing nodes to the central hub); and (3) head end / hub components (comprised of radio transceivers that convert process and control signals from the nodes). Today's DAS solutions follow a standard configuration of RF to optical to RF for which the head end converts the RF signals from the carrier's radio transceiver and transports them via fiber optic cable to the DAS nodes where the signal is converted back to RF and transmitted to the cellular users via a remote antenna(s). DAS deployments may be owned by a single wireless carrier or a third-party, neutral host such as a DAS network owner or a building /venue owner. DAS networks usually cover larger outdoor or indoor venues with high user concentration. The use of 50 (or more) nodes is common in stadiums or small municipalities that cover many square miles. DAS network deployments require a significant upfront ef- fort in design, configuration, and carrier coordination, but they are very robust and flexible, en- abling multiple carrier frequen- cies to be delivered over a single architecture covering latest LTE spectrum (including commercial 700-2500 MHz and UHF VHF Public Safety bands). With sig- nificant upfront cost, carriers/ owners are careful in forecast- ing and design as it can take years to recognize profitability. In contrast, small cells are deployed indoors and outdoors, in single-node scenarios to small areas requiring coverage or increased capacity, or both. They have almost identical in- frastructure requirements as a DAS node, including transport link and backhaul with an interconnection to the mobile provider's network. They can be quickly deployed to provide temporary or per- manent coverage to remote locations. Small Cells The term small cell has been adopted to refer to a group of cellular nodes designed to fill gaps in the macrocell network where either capacity or coverage, or both, are challenges. Acting as an underlay or an extension to the macro network, small cells are essentially low- power macrocells and as their name implies, they are physically smaller. Small cells emulate the macro cell by providing coverage and ca- pacity to a smaller or focused area. They also have limitations on the number of simul- taneous users and capacity limitations based on the type of node and the backhaul connection. This is where it can get complicated. Microcells, picocells, metrocells and femto- cells are all considered small cells. However, each one has unique use cases, specific equipment, and performance limitations. To clear things up, let's look at each and define their role in the small cell world. single-node, outdoor, short-range radio transceiver deployed to enhance existing macrocell site cover- age. Microcells are installed indoors and outdoors to fill gaps in both capacity and coverage. Their com- pact size enables them to be mounted on buildings and PROW (public right of way) infrastructure. Carriers use microcells to enhance the user ex- perience in high user density venues or where macro coverage is impeded or impossible (think rush hour in Manhattan). Each microcell can support 200 users - supporting a single carrier - over two frequencies. With a range of up to two miles, they can quickly fill coverage gaps and capacity issues created by peak usage demand that would outpace the supporting macrocell site. These solutions require trained technicians to install, con- figure, and maintain optimal performance. A common challenge for all small cells is one of backhaul capacity and availability. We'll cover this a bit later. than a microcell, a picocell is used both indoors and outdoors, and solves a unique challenge for mobile carriers. Think small, even more focused than a microcell. Areas of use are typically less than 30,000 square feet, but see high traffic with a lot of turnover. Each node can typically support up to 80 users. While the nodes cannot be intercon- nected in a distributed architecture, multiple picocells can be deployed to meet capacity and coverage requirements. Transportation terminals and busy downtown intersections are perfect outdoor locations with the later being coined a metrocell. This class of small cell has also been deployed as a rural solu- tion that can provide coverage to remote locations, cruise ships, and commercial airliners. These solutions are often supported by satellite backhaul. Like microcells, pico- cells can be mounted on utility and traffic infrastructure. Indoor applications such as airports, hotel lobbies, campus venues, and office settings with limited users are very attractive for picocells. These solutions also require trained technicians to install, con- figure, and maintain optimal performance, which is expected for a carrier-owned solu- tion. The equipment is physically smaller than microcells. With a footprint of only 1.5' x .25' x 1.0', it's easier to find a mounting point that is acceptable to the property owner and can be easily concealed. Picocell nodes support only one wireless carrier and offer only a few frequencies, although LTE versions are emerging. sion down yet another level and you have the femtocell which provides enhanced cellular service to residential and SOHO applications. Typically these solutions sup- port as few as two and enterprise solutions as high as 25. The small, easy-to-install femtocell has a significant impact on the wireless carrier's macro site load, as well as increasing customer satisfaction, with one caveat. Femtocells can handoff to a macrocell but typically do not take a handoff from a macrocell. Other limitations include a 5,000 square foot coverage foot- print and the ability to support only one technology (for example: 3G/4G per device and the service from a single provider). This brings us to backhaul. Femtocells, like all small cell applications, require a back- haul connection - typically the resident's/ SOHO's Internet connection. This backhaul connection can drastically affect the ser- vice QoE. 4G LTE will require the resident to have a fiber connection to maintain service quality. Small Cell Backhaul While the small cell players have been suc- cessful in addressing the connectivity of devices to the network, there are still a few hurdles to clear. These impediments, when combined, can create a very complicated and messy playing field. To keep it simple, let's break them out as follows: backhauling traffic to the core network, coordinating site acquisi- tion, optimizing small cell locations, and con- trolling OPEX associated with installing and managing small cell sites. for a small cell node has been determined, it will be like winning the lottery to find that fiber is available or easily installed at that location. When fiber is not an option, wire- less backhaul via microwave is the option. Microwave is very attractive given its multi- gigabit capacity, narrow beam, great at- tenuation, and reasonable cost. Depending on the critical nature of the small cell - is it an overflow capacity for a macro site versus a primary access point for cover- age and capacity - the exact microwave By 2015, wireless data traffic will surpass wired data - fueled by smartphone and tablet adoption and world- wide growth of Internet users. will overtake macrocell capacity. conducted by Informa found that 98 percent of operators think small cells are essential to the future of their networks .

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