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Large wireless deployments at stadiums and in other dense areas demand high capacity and high performance, but it’s not always easy to provide these when a venue may need 18 to 20 sectors of capacity and need to support four mobile operators. Mobile operators envision pulling miles of fiber with thousands of costly splices to deploy distributed antenna systems in these venues with costs running into the hundreds of thousands of dollars, but recent DAS and fiber innovations are making it easier to transport DAS traffic around large venues without breaking the bank
Challenges
The main challenges in using DAS in large venues are cost, efficiency and capacity.
Cost: Much of the cost of deploying a DAS in a large venue doesn’t come from the cost of the DAS equipment, but the cost of installation. Traditional analog DAS systems require one fiber pair between each head-end and remote antenna. This one-to-one requirement in a venue that may need dozens of remote antennas means that a lot of fiber must be deployed. In many stadiums, for example, it is not uncommon for such a system to require 192 fiber pairs. Pulling fiber and splicing it in the field is extremely expensive, running as much as $250,000 for this part of the deployment alone.
Efficiency: A traditional analog DAS requires the use of a separate base station for each remote radio head. In an 18-sector stadium, for example, the mobile operator must deploy18 RF sources for that DAS. Base station shelters at arenas and stadiums were not built to accommodate so much communication equipment, so they must be enlarged, leading to an extra expense and added time to the deployment.
Capacity: An analog DAS requires an inordinate amount of traffic engineering before deployment because the signal attenuates more the farther the radio head is from the head-end. To achieve the required capacity for a large venue, an analog system will require more radio heads than a digital system.
Solutions
Advanced fiber and DAS solutions mitigate the challenges of large venue deployment. The best DAS products feature all-digital transport, which enables a single head-end to simulcast a signal to many remote antennas or radio heads and to deliver the same, high-capacity signal at each antenna. In addition, these head-ends can aggregate the capacity from two or more base stations, so the mobile operator can increase capacity by simply adding another base station (no additional head-ends, antennas, or radio heads are required). Finally, advanced fiber solutions offer optional fiber-saving technologies such as coarse wave division multiplexing and dense wave division multiplexing, which reduce the amount of fiber needed by 80% or more.
All-digital transport: Digital DAS solutions transport RF signals in digital format from the head-end to the radio head or remote antenna unit. This means that the signal does not attenuate between the head-end and antenna, and that the head-end can simulcast the digital signal to all of the remote antennas in the system.
Capacity aggregation: Modern DAS solutions can simulcast the capacity from the connected base station(s) to all of the remote antennas or radio heads in the system. Capacity aggregation saves on base stations and head-end units and simplifies network design and management.
Fiber-saving technologies: There are several fiber-saving technologies that can be used to minimize the amount of fiber that needs to be pulled and spliced. The first option is to use CWDM and DWDM to expand the data-carrying capacity of individual fibers and fiber pairs by multiplexing eight (CWDM) or 80 (DWDM) wavelengths on a single fiber.
Another option is to use a serial link combiner to slash the amount of fiber needed in a DAS network. A serial link combiner can support up to 225 megahertz of spectrum over a single fiber pair. The SLC combines up to three 3.072 gigabits per second fiber links to a single 9.8304 Gbps (10 Gbps) single-mode or multi-mode fiber pair.
Another alternative is to use 12-fiber micro-cable with push-on connectors to eliminate the need for field splicing of fiber. Fiber splicing specialists are expensive, so reducing the number of splices saves time and money.
As we can see, there are plenty of ways to reduce fiber counts and installation costs tied to mobile network builds in stadiums and other large venues. By taking advantage of advances in optical networking, service providers can deliver optimum capacity and coverage at a reasonable cost.
