Multi-mode Metrocells to Aid AT&T in Densification

January 8, 2014

While the metrocells that AT&T is currently deploying support UMTS and HSPA+, the carrier plans to push forward with more advanced technology in the future. Later this year the carrier expects to deploy units that will also support Wi-Fi and LTE, but it has not released the name of the vendor yet.

Jim Parker, AT&T spokesman, told AGL Small Cell Link, “Metrocells are largely in their infancy. They support a single technology, a single frequency band and a single sector. It is extremely limited.”

AT&T requested a neutral host metrocell last summer from the OEMs through the Metrocell Forum, which created a requirements document and distributed it around the world. “We expect metrocells to evolve into a neutral hosting ability, but not for a few years,” Parker said.

The carrier is in the second year of its three-year Project Velocity IP, which will deploy 40,000 metrocells.

AT&T is deploying metrocells through three separate divisions, the Antenna Solutions Group, which targets large public venues, the Advanced Enterprise Mobility Solutions Group, which targets enterprises, and local RAN organizations, which are deploying them outdoors.

Expansion of the Addressable In-building Wireless Markets

AT&T is seeing significant growth in metrocell deployments in retail outlets, such as Best Buy and Walmart, because of the large number of customers, but also because they are retail outlets for the carrier’s phones. Metrocells can be economically deployed in places where a DAS network would be too expensive.

“The total number of addressable markets for wireless in-building systems has now significantly expanded with the advent of metrocells,” he said. “Now with metrocells at a much lower cost, we are able to go after markets that were previously unattainable, like multiple-dwelling units, retail and smaller hotel chains. We will even drop metrocells into the basement of a building that otherwise has good in-building coverage. In the past we would simply walk away from those opportunities.”

The carrier has negotiated master lease agreements with several nationwide chains of hotels and retail stores. Big box chain stores, with cinder block walls and metal roofs don’t always have the best macrocell penetration. An in-building metrocell helps facilitate the salesperson’s ability to activate the handset, according to Parker.

The decision to deploy metrocells versus DAS is also guided by capacity needs. Current metrocell technologies support up to 32 users. Compare that to a DAS. The DAS antenna can support multiple wireless operators, multiple wireless technologies, multiple frequency allocations, and the system can be expanded through sectorization.

Don’t expect to see a lot of metrocells in stadiums where capacity is king. Metrocells can be used where capacity needs are not as great, such as Marriott Courtyards.

“We are deploying metrocells in corporate America where the employees are encouraged to bring their own devices, but they don’t have adequate coverage,” Parker said.

Project Velocity IP, which includes macrocells, DAS and metrocells, had its first metrocells field application in the fourth quarter 2012, with wide-area deployments commencing the first quarter of last year. By 2015, metrocells will be the dominant technology of choice used in AT&T’s densification program, according to Parker.

“We are very much in the early stages of deployment and currently utilize specially trained personnel to deploy the metrocells, but due to their plug-and-play architecture, simple IP-connectivity and self-organizing architecture, we envision a day when we will be able to simply ship them to our enterprise customers and have their IT technicians deploy them,” Parker said.

The RF output of each metrocell varies from 39 milliwatts to 250 milliwatts, which is comparable to the power output of other indoor wireless solutions. The metrocell has a Fast Ethernet interface, which can use the building’s existing Internet access for backhaul and can be either shared or dedicated. The self-configuring architecture reduces the time and cost of installation.

Each metrocell can support 16 or 32 devices and can support simultaneous voice and high-speed data sessions. Each metrocell covers from 7,000 to 15,000 square feet depending on building layout and construction. Multiple metrocells can be deployed within a facility, allowing for seamless call handoff within the premises.

Each metrocell has a Fast Ethernet interface and can use the building’s existing Internet infrastructure, which offers less cost, simplified site acquisition and faster deployment. However, the quality and performance of the system is dependent upon the customer’s infrastructure, routers, switches and the cables that are maintained by the customer. The operator has restricted visibility into the network, making it more difficult to manage and maintain.

A metrocell can also be deployed with a dedicated network and backhaul, which provides additional network control for the operator, more network visibility and the ability to maintain the system end to end. The disadvantages of this approach are: more site acquisition requirements, running cable to each metrocell, increased capex and opex, and longer deployment time. More control over a network is always preferred by the carrier.

“We have been deploying our own LAN infrastructure to be able to manage and monitor end-to-end performance,” Parker said.

Metrocells Pass the Test

In the first field applications that took place in 2012, AT&T wanted to evaluate the performance of metrocells across a wide range of environments, including an outdoor residential area, an office campus and an urban high-rise in New York City.

For the outdoor environment, AT&T deployed 14 metrocells in the residential area of Crystal Lake Park, Mo., a small town located west of St. Louis. The system resolved spotty coverage caused by hilly topography. After deploying the metrocells, the macrocell performance improved with a 40 percent reduction in dropped calls.

To test the technology in the office campus environment, AT&T deployed 12 metrocells in an office building in Waukesha, Wis. “We realized a 15 percent increase in network traffic and a reduction in the call drop rates,” Parker said. “With ubiquitous wireless coverage throughout the facility, we have seen a significant increase in data traffic with more than 50,000 data sessions per day.”

AT&T deployed 20 metrocells for multiple enterprise customers in New York City. In order to reduce the amount of time to deploy the system, the carrier used the customers’ existing Internet wiring or a shared network to backhaul the metrocells.