To ensure reliable in-door wireless connectivity, industries across the board are turning to a distributed antenna system (DAS). A DAS typically comprises active electronics, usually a central hub connected to remote units, paired with antennas distributed throughout a building, all interconnected with cabling. The central hub is connected to an RF source supplying the cellular signal.
DAS is usually fed by its own RF signal source (except in rare instances where a repeater is used as the RF source) that is based on paid license spectrum and secured, providing added capacity with guaranteed reliability and performance. This is in contrast to Wi-Fi signals, which are based on unlicensed spectrum with more limited range, hampering VOIP and other data services.
But even after a business decides on a DAS, the decision-making isn’t over. Another one of the choices that will arise is whether to choose a high-power or low-power solution — and the answer depends on several factors.
Evaluating coverage needs vs capacity needs
Today, users require faster speed and more capacity. That is why most operators select low power as a primary option for the densification of the network. Low power is the ideal option for faster speed and more capacity, as the RF signal is easier to control, and it brings the user faster speed.
When considering performance, it’s critical that future technologies and frequency demands be part of the consideration set. Unlicensed frequency spectrum in 3.5GHz to 4.2GHz will be challenging or even impossible to efficiently support using high-power networks, and RF losses at those frequency bands over coaxial systems will be significant.
Additionally, future technologies — specifically 5G — will require network latency to be at a minimum, and coaxial cables used in high-power networks have higher latency than all fiber-optic networks used by low-power systems.
Future needs and TCO
To determine the total cost of ownership, post-deployment maintenance, operational costs and future upgradeability must be considered.
A wideband, low-power system will require few to no upgrades for future frequency bands, technology or operators. High-power systems will require installing a substantial amount of equipment in telco closets, whereas low-power systems will not. Space and power are at a premium in most venues, so DAS operational costs (both in terms of power needs and operational expenses related to the amount of space occupied) will typically be much higher for high-power systems.
Also, consider monitoring costs. Some low-power systems can be configured so that one can monitor the entire network all the way to the antennas. In high-power systems, and fiber/coaxial hybrid low-power systems, the passive parts of the system (anything after IDF closets) aren’t monitored. Once troubleshooting is required, field crews have to make educated guesses about where the problem is with the passive distribution — sometimes spending countless hours doing so — while in a properly configured low-power system, monitoring software will identify the exact point of failure within seconds.
Scaling for power
Another element to think about is sectorization — an especially important factor for higher-capacity solutions.
In a large public venue with significant numbers of users (e.g., a stadium, arena, convention center or airport), a DAS system has to support more sectors, or zones, than in a more contained installation (e.g., an office building). Low power makes sectorization easier by making it simpler to control and define the sector “boundary,” so that a sector isn’t significantly overlapping a neighboring sector. If overlap occurs, it can create interference, and devices that are in the overlapping area will “see” both sectors and likely ping-pong between the two, creating interference and using resources in each sector. In contrast, with a high-power system, it’s tough to control the RF signal from overlapping and keep the sector edge well defined.
Sectorization is becoming more important even for the systems that are coverage-driven at installation. It’s much easier to efficiently scale a low-power system for capacity as coverage needs shift because each remote covers a much smaller area. With a high-power system, where each remote unit covers a much larger area, you risk having too many people within that zone for a single network sector to support. That means the reliable cellular connectivity you were trying to provide by switching to DAS may not be significantly better than it was before.
Choosing the right power level
For businesses or facilities requiring higher capacity today or in the future (something there will continue to be more of, as the cell phone has become the communication tool of choice for the majority of people), a low-powered solution will deliver the best performance
