WIRELESS NETWORKS
Shared Infrastructure for LTE Services Playing Nicely By Tony LeFebvre, Director of Product Management, TE Connectivity
Carriers will need many more base stations to
support LTE. Tony LeFebvre argues in favour of shared infrastructure as a way of keeping costs in check.
Carriers are accustomed to providing their own, discrete infrastructure for mobile services, but the need to increase the number of base stations by 300-500 percent to support LTE is causing them to rethink infrastructure deployment choices. Macro base stations (BTS) are expensive and they can’t be deployed everywhere signals are needed because of space or zoning considerations. As a result, alternative infrastructure choices are being used. Not only is it expensive to build an LTE network on top of their existing network of technologies that are still in service, but infrastructure is limited and municipalities do not have the willingness to stomach additional construction and visual pollution. Solutions to minimise infrastructure use and practices to cooperate with municipalities and other carriers need to be explored. The primary reason for sharing
infrastructure is to keep costs down. Carriers share antenna towers, base station enclosures, and even fi bre assets. The challenge is to fi nd ways to share infrastructure that fi t in with service needs. For example, the infrastructure requirements for LTE service are very different than they are for GSM service.
Residential DAS Remotes
Sharing Signal Distribution The only part of carrier infrastructure that can’t be shared is the base station itself, which provides the carrier’s service. In models where the base station is also the distribution point for the service, carriers must deploy additional BTS whenever they need additional coverage or capacity. A DAS uses a system of hubs and
remote antennas to distribute the signal from a central source to the antenna points. In addition, it permits multiple wireless carriers to share the means of signal distribution. In a stadium, for example, several carriers can share a single DAS; each carrier provides a base station to deliver its service through the DAS. Dozens of stadiums and large buildings throughout the world use shared DAS infrastructure.
Sharing Fibre Assets Another way to share infrastructure is for the DAS to leverage existing FTTx assets to distribute the signal between a head-end and the remote antenna units that actually provide the signal to subscribers. Wireline carriers have invested billions in bringing fi bre to the node and fi bre to the premises in cities and suburban neighborhoods, and they can improve payback from these assets by leasing capacity to DAS operators who need to connect remote antennas in neighborhoods. It is less costly for DAS operators to lease capacity on these FTTx networks than it is to run new fi bre specifi cally for their own purposes. DAS overlays nicely onto a FTTx
CENTRAL OFFICE/ BTS HOTEL
network. The fi bre origination in a FTTx network is typically in a serving offi ce with great access to necessary facilities to host or ‘hotel’ BTS resources. Access to electrical, backhaul, HVAC and importantly fi bre to the remote nodes creates an environment where the wireline operator can lease space, eliminating the need for the wireless operator to develop a new site to locate the BTS resources. The wireline operator then has the fi bre from this serving offi ce running deep into the network serving their FTTx investment. By either leasing spare dark fi bres or
A DAS uses a system of hubs and remote antennas. 22 NETCOMMS europe Volume II Issue 3 2012
offering wavelength services, the wireline carrier can recognise recurring revenues leasing these fi bres to the wireless
www.netcommseurope.com
operators for their use to distribute the BTS capacity to remote DAS nodes. By sharing FTTx assets in a
neighborhood or business park, the operators save the cost of running their own fi bre to link head-end equipment with remote antennas.
For Example Four Las Vegas Hotels (Bellagio, MGM Grand, Mirage, and New York New York) use a shared DAS system that runs between hotels over existing fi bre under the street. The base stations for four major cellular carriers are located in a base station ‘hotel’ at the Mirage Hotel. In many cases where a shared DAS
is used, the DAS itself is deployed and maintained either by the facility itself or by a neutral host carrier. This offl oads responsibility for maintenance from the carriers, and allows them to share the cost of deployment and maintenance. Carriers are responsible only to maintain their own base stations at the DAS head-end. Another advantage is that the shared
DAS and base station hotel centralise the location of carrier infrastructure. It is easier and more cost-effective to maintain equipment in one location than it is to travel to several different locations for maintenance. Cost is the major factor driving use
of shared DAS infrastructure. It can cost half as much to deploy a DAS as it does to deploy microcells to cover a given space, and the carrier splits the cost of equipment, deployment, and maintenance among several other carriers sharing the system. A shared DAS can cost carriers as little as one-fi fth as much as using discrete infrastructure. By leveraging shared DAS, wireless
carriers can extend their coverage and capacity into areas that they normally couldn’t reach, and they can do so at far lower cost than deploying microcells. Shared infrastructure makes operational and economic sense, and with new services like LTE demanding higher bandwidth and capacity, it is likely to become a key strategy for wireless carrier infrastructure deployments.
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