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Mobile wireless services are in transition. Successful outdoor coverage has driven higher demand for mobile devices, and people now expect to use their phones everywhere. Many consumers are eliminating wireline phones from their homes, and enterprise workers are increasingly relying on cellular phones as their primary point of contact. At the same time, mobile carriers are offering new services such as video and GPS mapping in an effort to drive ARPU, but these new, bandwidth-hungry services are putting greater strain on cellular networks.

Carriers have spent tens of billions of dollars to build out their macro networks, but those networks don’t always adequately support new high-speed data services and richer applications, and they don’t consistently deliver coverage in buildings, subways, stadiums, and other locations. And when customers are frustrated by sporadic service, they switch carriers.
Enterprise and consumer subscribers have a different standard of quality for their cell phone service. Today’s users rely more heavily on cell phones to do more things in more locations, and carriers must step up to boost service quality.

Equipment vendors have begun to address these challenges, and carriers have many options for specific problems. They often use distributed antenna systems (DAS) for enterprises and public facilities, remote radio heads for filling coverage gaps in outdoor networks, and small base stations for covering remote areas. In addition, carriers are now testing femtocells for consumer/SoHo applications.

But with these new coverage and capacity concerns and a plethora of products that address them, how can carriers plot a sensible course for the future? In this article, we’ll look at the new challenges posed by emerging wireless services and applications, and review the requirements for a successful carrier strategy.

Moving Wireless Indoors

Since the first mobile networks, carriers have built macro networks that were designed to provide a blanket of outdoor coverage, covering the biggest areas possible with the fewest base stations and cellular towers. When mobile services primarily used 850MHz frequencies this strategy worked fairly well because such relatively low frequencies were pretty good at penetrating buildings. But three major shifts have caused this strategy to outlive its success:

Consumers whose mobile phone usage was primarily in cars or outdoor areas have now come to rely on them inside buildings and other structures.

Carrier roll out of 2.5 and 3G services, which generally operate at 1.9 or 2.1 GHz (with 2.5 and 3GHz WiMAX and LTE services in the wings). These higher frequencies don’t penetrate buildings nearly as well as lower frequencies.

The advent of 2.5 and 3G services is enabling users to watch video, check e-mail, play games, and do other things that primarily take place in buildings and also increase the demand for bandwidth.

Filling Macro Gaps

In-building coverage challenges aside, carriers are also facing stiffer pressures to fill holes in their macro networks. Wireless signals like to travel along lines of sight, and typical macro network towers can’t provide pervasive coverage in dense urban environments or in areas where the landscape or structures block or attenuate the signal from the nearest cell tower. Geographic features such as canyons, slopes, and dense forests are a challenge, as are urban centers with dense buildings that block signals.

Even in areas with an abundant supply of rooftop cell towers, users often find that signal strength tails off toward the lower floors of tall buildings. When on the upper floors of buildings, subscribers can experience poor service because signals from multiple towers may be visible to the phone and the phone constantly hunts from one signal to another.

Capacity is also a challenge outdoors. Macro networks that were designed to support an average user base five or ten years ago can’t support current call volumes or the need for higher-speed data support. Most of us have experienced an inability to make or sustain a call in stadiums, on bridges, or even on crowded freeways or urban sidewalks simply because the nearest macro towers are overloaded.

To resolve these issues, carriers must find scalable and cost-effective ways to extend coverage in these “shadow” areas, and to increase available network capacity to support current and future user densities and services. The question is: what’s the best way to do that?

Figure 1: Urban locations often have “shadow” areas where macro cellular coverage is weak or non-existent, especially when higher-frequency services like HSDPA or EV-DO are used.

No Shortage of Solutions

As these issues have become more prominent, the marketplace has responded with an ever-growing array of solutions. Here’s a quick review.

DAS – Distributed Antenna Systems (DAS) have been used for years to extend mobile coverage inside buildings, subways, and public facilities as well as in outdoor areas of stadiums, parking garages, university or enterprise campuses, and other structures. The idea behind DAS is to minimize the number of backhaul connections and the expense of BTS equipment by relying on centralized base stations and then distributing their signals with more cost-effective remote antennas.

Remote radio heads – Remote radio heads extend a base station’s coverage by broadcasting its signal in a new area. In effect, these operate as an outdoor DAS (relaying the signal from a base station), which is far more cost-effective than adding more base stations. Traffic from radio heads can be backhauled via terrestrial networks or microwave links.

Micro base stations – When remote or isolated areas require network coverage, it may not be cost-effective to extend a macro network out from its nearest edge. Islands, cruise ships, military bases, and other areas require dedicated networks, and micro base stations fill this need. Backhaul options include microwave and satellite links.

Picocells and femtocells – Within the past few years, vendors have begun offering smaller base stations that can provide cellular service for residences and smaller facilities. The advantage to these is that they provide coverage and capacity: rather than forcing carriers to use part of their macro network’s capacity for users inside a home or office, they can provide dedicated capacity within the facility through picocells or femtocells. Picocells can even be grouped to deliver more capacity, which is then distributed with a DAS. The advantage to these options (other than offloading the macro network of the job of providing capacity to indoor areas), is that traffic can be backhauled over existing cable, DSL, or other IP connections in the home or office, further saving carrier OPEX.

Infrastructure Requirements

So the good news is that the marketplace provides lots of solutions that solve the specific coverage and capacity challenges outlined earlier. The bad news is that none of them fits every situation. Wireless infrastructure is in a state of flux, and new services and protocols are emerging. Carriers must respond to market demand, but they can’t afford to bet the farm on the wrong technology.

Strategically, the best course is to think of the entire wireless network as a single infrastructure, and then use requirements dictated by that vision to qualify point solutions for inclusion within the infrastructure.

Figure 2: Solving macro network coverage problems requires multiple solutions.

Here are some key requirements that can help carriers select products that deliver maximum flexibility for an uncertain future while minimizing the cost of management and upgrades.

Completeness – Solutions must address any challenge, and they must fit within the overall architecture, ideally using similar backhaul technologies, requiring minimal integration, and supporting unified management.

Flexibility – Every in-building or macro gap deployment is slightly different, and different solutions can easily be required depending on the number of carriers or protocols to be supported, services delivered, location, facility use, budget, and other factors. Carriers should look at a range of options and choose the ones that best meet service and business needs.

Investment protection – As technology evolves, solutions within the architecture should accommodate upgrades with minimal cost or disruption. Carriers should be able to add WiMAX or LTE components without having to replace base stations or radio heads, for example, and these upgrades should not disrupt service or impact performance or manageability.

Support for prevailing standards – While one of the challenges in wireless networks is the constant appearance of new protocols, it is generally agreed that the future of network infrastructure is in IP. Any solution should integrate with IP networking and management systems.

Integration and support – Solutions should be broadly available in all service areas and should be well understood by service and support personnel.

Centralized management – All solutions should fit within a common management system to minimize OPEX and maximize network up-time.

The Holistic View

As carriers plan to address the myriad challenges of providing new services with adequate coverage and capacity, it’s easy to get caught up in one particular solution or another. But the best course is to take a step back and look at today’s mobile network evolution as an opportunity to unify the network infrastructure, to build for current capacity as well as tomorrow’s needs, and to choose solutions that offer the service flexibility to meet any market demand in any location.

John Spindler is vice President, Product Management, for ADC.

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© 2014 Penton Media Inc.

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