New Cellular Architecture Offers Major Capacity Gains, Cost Cuts

Thomas Gruba, senior director, 3GPP product marketing, Alcatel-Lucent

Thomas Gruba, senior director, 3GPP product marketing, Alcatel-Lucent

February 17, 2011 – Alcatel-Lucent has found a way to meet a China Mobile-led consortium’s demand for a new cellular access architecture that will reduce deployment costs, increase capacity, cut back on real estate and power requirements and otherwise streamline the evolution and expansion of mobile networks.

While the innovations surrounding Alcatel-Lucent’s lightRadio architecture are targeted to China Mobile’s requirements, carriers elsewhere are expressing strong interest in the effort as a potential breakthrough that could have important implications for the pace of 3G and 4G deployments worldwide, says Thomas Gruba, senior director of 3GPP product marketing at Alcatel-Lucent. “What keeps people up at night is the explosion in data consumption,” Gruba says. “They realize there’s only so much capacity available even with deploying LTE Advance [release 10 of the 3GPP standard]. They know they’re going to hit a wall at some point.”

Indeed, researchers at Bell Labs have determined that the cellular network architecture as it currently exists is unsustainable. By 2015 they project that in urban areas there will be 30 times more smartphones per square kilometer than there were in 2010. They expect worldwide downloads of mobile applications to surpass 21.6 billion by 2013.

European mobile giant Orange is one of the carriers expressing support for the new architecture, which Alcatel-Lucent says will be fully ready for deployment by 2014 with various components entering the market between now and then, including a new Wideband Active Array Antenna that will be ready for trials later this year. “Alcatel-Lucent’s new vision and strategy of mobile broadband is quite exciting,” says Alain Maloberti, senior vice president for network architecture and design at France Telecom/Orange.

“The new wireless network architecture and innovative radio proposal will potentially help us to achieve significant operating cost savings and be better prepared for future challenges,” Maloberti adds. “We look forward to working closely with Alcatel-Lucent to explore and test this new approach.”

Verizon is going to be looking at the new architecture as well, says Tom Sawanobori, vice president of technology planning at Verizon Wireless. “Verizon looks forward to learning more about the benefits of lightRadio technology and how they could be applied as we continue to expand and evolve our LTE network,” Sawanobori says.

The cellular industry definitely needs a new architecture after more than two decades of reliance on the same basic digital RAN (Radio Access Network) infrastructure, asserts Phil Marshall, chief research officer at Tolaga Research. “The day has finally come when service providers need to take a serious look at the road ahead in terms of technology and their economic models,” Marshall says. “They must evolve network designs, embrace small cell sites and all-IP architectures and replace traditional network designs with flexible cloud-like architectures that can truly meet the data demands of the future.”

As described by Gruba, this is precisely what lightRadio is designed to accomplish. Essentially, the company, leveraging technology developed by its Bell Labs unit, has done away with the old one-to-one relationship of base stations to cell towers by breaking the base station into its component elements and then distributing those components into the antenna and throughout a cloud-like network. The clutter of antennas serving 2G, 3G and LTE systems are combined into the single multi-frequency, multi-standard Wideband Active Array Antenna, which can be mounted on poles, sides of buildings or anywhere there is power and a broadband connection.

“This is advancing LTE Advance beyond where it otherwise would go,” Gruba says. “Our solution will double access network capacity and reduce the cost per bit by 50 percent.”

In the classic RAN architecture, each base station controller (BSC) manages radio channel setup and handovers across a cluster of access cells, each of which is comprised of the BTS (base transceiver station) or base station and one or more passive antennas positioned on a cell tower to deliver various generations of signals. Signals are transported to and from the base stations over a coaxial link to the antennas, which requires use of a large amplifier to boost the signal. In some cases amplifiers have been compacted into weather-proof housing and placed next to the antennas in what are known as “remote radio heads.”

In the new lightRadio architecture a single system-on-a-chip (SOC) module, developed by chip maker FreeScale in cooperation with Bell Labs, compacts the base station functions to where they can be mounted virtually anywhere with antennas in small spaces or centralized in a clustered BST unit that serves anywhere from five to ten cell sites. In the latter case Alcatel-Lucent envisions that each of these new base station locations will be connected to the cell sites via fiber or microwave, using new compression techniques developed by Bell Labs that will compress the CPRI (Common Public Radio Interface) signals by a margin of three to one compared to today’s CPRI systems. This will allow carriers to more easily leverage existing fiber and microwave capacity in their metro networks to support the new architecture, the company says.

The new SOC Baseband Units can be software programmed to run any generation of GSM-based mobile service, from 2G to LTE Advance, which allows operators to support multiple generations of service from the same base station across all cells. “Today you can put different line cards supporting different generations into a single 19-inch cabinet, but you’re operating three electrically separate layers,” Gruba notes. “We’ve created a single scalable platform that can do all three Gs in a single block. And when it comes time to eliminate an older generation on one of the [SOC] modules you can alter the mix with a software download.”

Complementing the miniaturization of the base station is a dramatic shrinkage of the antenna into a 2.5-inch lightRadio Cube, the new Active Array Wideband Antenna which combines the radio, amplifier and passive cooling functions with a vertical beam-forming active antenna technology that can transmit over multiple frequency bands. “The lightRadio Cubes come with different power levels so that they can be used in a variety of deployment arrays,” Gubra notes. “You can put them on light poles or on signs and use them for different types of cells such as metro [pico] cells or even femtocells.”

Along with this Wideband Active Array Antenna, Alcatel-Lucent is also introducing a new Multiband Remote Radio Head antenna, which can be deployed with existing cell sites to support dual-band operations at, say, 3G and 4G, thereby eliminating the need to add separate antennas when moving to 4G. “Now you only need to attach one unit to the tower and hook it up to the antennas as opposed to having one radio head for each antenna,” Gubra says.

But the overarching gains in higher capacity, reduced power costs, flexibility of deployments and elimination of real estate hassles and tower eye sores come with the centralization of base station clusters used in conjunction with the lightRadio Cubes. “When I pull these Baseband Units together I only need one truck roll to serve five to ten cell sites in one location,” Gubra notes. “And now with these units working together from one site to serve multiple towers, I can coordinate load balancing across all those cells to allocate resources where traffic is highest at different times of day.”

Another advantage to pooling Baseband Units comes with implementation of a Bell Labs invention known as Coordinated MultiPoint or COMP, which is also called Network MIMO (multiple input-multiple output). This software-based technology can be used to coordinate signal propagation among towers so as to eliminate the RF interference that occurs when a user is moving at the edges between cell coverage areas. “By coordinating what each user sees at the cell edges you can achieve a 2x improvement in capacity performance at the edges,” Gubra says.

Another major component of the new architecture is the virtualized processing platform which Alcatel-Lucent is developing with HP and other partners to create a cloud-like wireless architecture for controllers and gateways. These efforts will incorporate application of Alcatel-Lucent’s 5620 Service Aware Manager (SAM), which enables unified, end-to-end management of services delivered over IP/MPLS and Carrier Ethernet networks.