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Enhanced Cellular Coverage and Capacity

Capacity & Coverage = Small Cells. It's Time.

It's projected that mobile data usage will outpace wireline data by 2015.

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I'm sure my daughter is to blame, as she uses 10 times more mobile data than anyone I know. Really, how many "selfies" can you post in a day? Ok, she is only one of the 91 percent of the world's population with a mobile phone, and like 50 percent of all cell phone users, her smartphone is her primary access to the Internet. But she and others like her add up fast. It's why the network infrastructure market is undergoing a transformation, a reinvention, of how our mobile devices access the Internet.

The emergence of the HetNet, a hybrid of access technologies including small cells, is slated to offload mobile data traffic from the macrosite network, increasing coverage and capacity of the mobile network. If you recall, 2013 was slated to be the year small cell deployments begin. It turns out that 2013 was the year of evaluation and planning with a couple of the big mobile network operators projecting actual numbers of deployments planned for 2014. Is this small cell thing going to kick off? It is. It's just happening a bit slower than most originally anticipated. Why? There are a lot of challenges and questions yet to be answered.

The ratio of small cells to macrocell sites is projected to swell to at least 10:1 to 15:1, with metrocells (cellular hotspots deployed in high-density outdoor metro areas) outnumbering macrosites very quickly. Forecasts are also indicating small cell traffic will surpass macrocell capacity within the next three years, so it's easy to see that the need to ramp quickly and get it right the first time would make anyone take pause. So here we are...paused? Hardly. The entire ecosystem is working for answers to the challenges, from small cell radio selection and street furniture considerations, to the installation, power and backhaul options. It's been said before...is it going to be easy? No. But it is going to be very interesting.

Metrocell site acquisition: finding the perfect location for a metrocell is the result of studying and forecasting capacity and coverage data from existing LTE or UMTS networks for both data and voice service to locate hotspots and mapping street-level assets (street furniture such as light poles, utility standards, and traffic lights) for acceptable mounting locations and assessing the availability of power and backhaul options. Throw in an RF analysis for interference and it's not hard to appreciate why things are moving slowly. Now take the power and backhaul requirements off the table for the time-being and explore what is taking place behind the scenes to secure the perfect site. Chances are the perfect location is owned by someone else, and securing the site is going to take some negotiation. Access to right-of-way and street furniture will require a legal agreement, followed by an engineering review, followed by receiving permission from local authorities and obtaining approvals from historic or urban aesthetics governing bodies.

There have been some interesting and creative solutions to the aesthetic objections to metrocell access points. First and somewhat obvious is to simply make the access point, well, really small. This might work for some locations but there is still going to be some objections to the antenna, the mounting hardware, or the exposed cabling. Next best thing would be to conceal the access point in an enclosure. It can be "camouflaged" to blend with the surrounding environment. The enclosure approach can also provide environmental protection for equipment and space for backup power options. Next, and what seems to be a very agreeable approach for all, is to conceal the access point within the street furniture itself. Bus stops, kiosks, benches...all have been explored and deployed in early tests.

Betting on the Small Cell / Metrocell Trifecta?

The perfect location should have a usable power source, and fiber to backhaul to the core. But the odds of hitting the metrocell "trifecta" (coverage & capacity, power, and backhaul) are slim and will require some creative approaches to overcome the obstacles. Locating and engineering power and backhaul requirements during the site acquisition process is critical. Additional agreements or partnerships may be required as well as engineering to make it all work. In fact, the perfect location from a capacity and coverage perspective may not be so perfect once the power and backhaul requirements are identified.

Power

Of course in the process of determining the perfect location for the small cell, power availability is one of the survey components. Depending on the solution, you will need power for the radio, and backhaul equipment. Either wireless or wired. Each site will require somewhere between 20-100 watts. Your options include working with the local electrical utility to including access to available power at the installation location or creating an off-the-grid power solution. Streetlights, traffic lights, and signage lighting are all viable power access points and all will be considered; however, the likelihood of having a meter to account for power consumption is unlikely, so working power into the site agreement is a more likely option.

Also remember that the power at the exact install location may be controlled by a timer or photocell, as with streetlights and signage, or may not meet the proper grounding requirements or voltage. Several of the market-leading wireless backhaul solutions require a DC power source, but thanks to today's power-efficient radios and green initiatives, our power options are considerable. There are renewable power solutions that utilize solar cells with battery reserves; however, most renewable power sources are intermittent by nature, and will most likely require an electrical grid source to maintain seamless operation. The good news is that in some applications, today's solar, battery and charging technology is capable of meeting small cell requirements and can be engineered to back feed the power grid with excess power generated, creating green credits or off-setting power for utility payment. Power consumption is also a consideration and can hit the bottom line hard. Self-optimized network (SON) technology will also play a role in managing power use by turning cells off during low-demand / off-peak hours to save on power consumption.

These are aspects often overlooked in the small cell / metrocell power discussion:

  • Requirements for AC versus DC (or both) impact your power solution
  • Proper grounding and surge protection against lightning to protect sensitive equipment
  • Where and how do you locate the power solution? Remote or co-located with the small cell?
  • Utility demarcation point; metered?
  • Autonomous or semi-autonomous power solutions
  • Backup power for grid failures or intermittent autonomous feeds
  • SON controls and remote monitoring of small cell equipment

Backhaul

Let's assume that a small cell / metrocell site has been iidentified and all hurdles have been passed. The site is perfect, providing both a capacity offload and increasing geographical coverage, creating a perfect hotspot. Power has been identified and agreements signed. There's only one thing left...backhauling the traffic. What's the best solution? That depends. The first and preferable option is fiber. Explore all your options to access fiber and be sure to consider the cost of installation and reoccurring lease expense. It may be that these expenses exceed other backhaul options or that the required site construction to access the fiber is blocked by the site owner or agreements. When you reach this point in your deployment, the next best option is a carrier-grade, street-level wireless backhaul solution.

Going wireless has been identified as the leading option for small cell / metrocell backhaul deployments based on the installation ease, capacity, and flexible architectures that solve multiple site constraints. Microwave and millimeter wave solutions are available and widespread use is anticipated. Both licensed and unlicensed solutions are deployable on a case-by-case basis with either line-of- sight or non-line-of-site. Of course there are tradeoffs. Licensed spectrum may or may not be available and there could be considerable expense associated with securing spectrum, and interference levels at the site may eliminate the unlicensed options.

Wireless backhaul's flexibility can offer multiple topology options to overcome line-of-sight impediments. The backhaul access can use a point-to-point (PTP) or point-to-multipoint (PTMP) configuration with PTP used to overcome line-of-site constraints and to increase capacity and PTMP helping with capacity by essential load balancing the traffic. Because of the proposed density and relatively short distances between small cell / metro- cell locations, it's possible to daisy chain, PTP, or create a PTMP or meshed network with each cell passing its traffic down the line where the final link to the macrosite or core handles the traffic from multiple small cell / metrocell access points. Additionally, this PTMP topology can be used to manage capacity, actively increasing load from path to path with demand.

There are of course other backhaul performance requirements and operational considerations including: QoS thresholds, timing and synchronization, capacity growth, RF and physical security, and possible operation administration and management functionality. Not enough can be said around the importance of getting the backhaul piece of the small cell / metrocell trifecta right. It is absolutely the critical component when identifying the site location. Low cost, ease of install, and robust capacity will spotlight the leading backhaul solutions along with their ability to deliver acceptable QoS and OAM functionality.

Selecting the best site location, and engineering the installation with power and backhaul requirements is only the beginning and prompts the need for partnerships, alliances and agreements between all parties in the small cell ecosystem. TESSCO is prepared to support your efforts in this complex process. Considering the scale, the vast installation variables, and complexity of each cell rollout, TESSCO's broad infrastructure, power, and backhaul offering, along with carrier-class program logistics, will be instrumental in meeting the forecasted demand. Each site will require accuracy and redundancy to ensure on-time installation and turn up. TESSCO will work with your project teams to engineer, kit, preassemble, stage and ship based on your exact specifications.

Small Cell / Metrocell Backhaul Spectrum Overview

6-42 GHz Microwave

LOS PTP

Typically licensed; the go-to-backhaul solution for macrocells. Expensive reoccurring license; high reliability; high CAPEX and OPEX.

60-80 GHz Millimeter Wave

LOS PTP

Unlicensed/registration licensed; short-range, high-capacity. Pure LOS requires expertise in alignment. Sensitive to movement requiring secure mounting. Narrow beam limits interference; susceptible to street-level interruptions from large vehicles and dynamic environment.

Sub-6 GHz

PTP/PTMP NLOS

Unlicensed and registered licensed; perfect for working in and around obstacles such as signage and architecture. Typically a PTMP solution; directional antennas can be used; PTP to increase capacity by sectoring the central site. Allows for great resilience in a dynamic environment; interference mitigated through network management; reduced OPEX with PTMP tree topology.

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