As data traffic continues to grow exponentially, DAS networks are extremely crucial for Communication Service Providers (CSPs) to assist in providing better coverage & capacity indoors & outdoors for Enterprises, Hotels, Campuses and Stadia.
Modern DAS systems can alleviate problems of capacity and coverage through a deployment of nodes that split the transmitted power among several antenna elements, separated in space so as to provide coverage over the same area as a single antenna but with reduced total power and improved reliability.
What are Distributed Antenna Systems (DAS)?
A Distributed Antenna Systems or DAS involves a clustered installation of set of antennas that’re used to boost mobile network coverage within local areas that have poor coverage or capacity.
A DAS system distributes a wireless signal but does not generate the mobile signal itself. The source could be fed by operators 4G LTE or 5G networks from a passive donor antenna (repeater) on the roof, a BTS/NodeB/eNodeB or several variations of small cells including femtocells, picocells, nanocells, and metrocells. The signal is carried through the building via, passive, active, hybrid or digital distributions systems.
Passive DAS
A passive DAS uses passive RF components such as coaxial cable, splitters and couplers to distribute signal inside a building. The farther the antenna is from the signal source and any amplifiers, the more attenuation (loss) there will be in the power broadcast from that antenna. Designing a passive DAS correctly requires calculating precise link budgets to make sure the outputted power at each antenna is equal.
Active DAS
An Active DAS converts radio frequency transmissions from the signal source signal so they can be distributed via an optical or ethernet cable. A “master unit” combines the signals from multiple carriers and performs this conversion. Some Active DAS systems also “digitize” this signal which adds cost but improves performance . Once converted, an Active DAS transmits the digital signal over fiber optic or ethernet cables to remote radio units (RRUs) that convert the signal back to an RF signal. These RRUs are also sometimes called “nodes” or even “active antennas” depending on the vendor and the architecture of the system.
Unlike their Passive DAS counterparts, Active DAS deployments minimize the use of coaxial cable used to distribute signal. In some cases there is no coaxial at all; this is called a “fiber to the antenna” or “fiber to the node” system.
Digital DAS
A Digital DAS converts each carrier’s signal to zeros and ones before combining them and transmitting over fiber optic or ethernet cable. This conversion and combination process is computationally expensive, which makes digital DAS systems considerably more expensive than their analog counterparts.
One of the biggest benefits of deploying a Digital DAS is that they are much less susceptible to interference, and thus more performant. A second benefit is that Digital DAS platforms allow the capacity of the signal sources to be directed to different areas of a venue. This is particularly important when the capacity of a building shifts dynamically – think for example of a large cafeteria or event space on a school, university, or office space.
If both the signal source and Digital DAS platform support the “Common Public Radio Interface” (CPRI) specification, it’s possible for a signal source’s Baseband Unit (BBU) to communicate directly with the DAS master unit and through to the remote units without any conversion to an analog RF signal.
DAS systems are widely used in offices, suburbs, stadiums, & other venues where the coverage or network capacity of a specific service provider is required to be enhanced.
Genesis Technology Services provide full end-to-end survey, design, build & maintenance of DAS systems for its customers.
DAS Use Cases
There are two main categories of Distributed Antenna Systems (DAS), each with a distinct purpose. They are as follows:
Cellular
Cellular DAS, also known as ‘in-building wireless systems (IBS)’, are an ideal solution to tackle poor cellular reception inside an office building. With the help of this system, a network of small antennas is installed to serve as cellular signal repeaters which boost the full-strength cellular signal picked up outside the office building. These distributed antennas are physically connected to a central head-end controller which is then integrated with the wireless carrier’s network.
Public Safety
Emergency communications are imperative in the event of a fire, any natural disaster, security threat, or any other emergencies. A Public Safety Distributed Antenna System guarantees that emergency personnel can maintain the radio communication in an emergency throughout an entire building. Emergency first responders & government employees must have access to dependable coverage in the event of any emergency.
Advantages of different DAS deployments
Each Type of DAS system has its own advantages:
Advantages of a Passive DAS system
A Passive system using repeaters presents a lower cost than other types of DAS and is quicker to install and deploy. It requires a strong outdoor signal for the donor antenna
Advantages of a Passive Combined with small cells
A Passive system combined with small cells connected by diplexers to the venue’s backhaul Internet is a good option where the donor signal quality is poor or nearby congestion is an issue.
Advantages of a Hybrid DAS
A hybrid DAS combines the functionality of an active DAS to cover larger areas with some of the cost advantages of a passive system. This type of system can be advantageous when dealing with long cable runs or where coverage of a large area is a priority over capacity.
Advantages of a BTS-fed Active/Hybrid DAS
BTS-Fed Active/Hybrid DAS is advantageous in large buildings with many users and where capacity and performance is a priority over coverage. These systems can be expensive, require leased line backhaul (often for each carrier) and full cooperation from the carrier to connect into your DAS system.
How DAS Improves Communications in Business, Education & Health Care
DAS in Business
Densification in urban areas causes congestion. Distributed Antenna Systems (DAS) are a great help to Enterprise businesses where they can provides seamless wireless coverage to employees & customers.
DAS in Education
The use of laptops, smartphones & iPads are now more prevalent in learning. There are times that wireless devices have larger number than people within a campus. Students & staff at universities and colleges need a stable network that will support learning needs and provide mobile coverage during emergencies.
DAS in Health Care
Many of the materials used for insulation in hospitals have side effects that obstruct mobile phone signals. Cladding materials used on the outer walls, with metal bases to keep heat in, combined with reflective double or triple glazed windows act as unintended communication barriers. Additionally, the excessive quantity of steel in the building frame can create ‘faraday cage’ effects, stopping phone signals.
All NHS institutions have an obligation to enable patients to stay in touch with friends and family, as stipulated in Government guidelines on mobile usage in NHS facilities, published by the Department of Health.
By working with local NHS Trusts, MNOs and vendors to provide coverage survey, design, install and maintenance services, Genesis Technology Services is able to provide mobile coverage for patients and improve patient safety by providing mobile phone coverage for consultants & critical care staff.
Genesis Technology Services are able to provide end-to-end DAS services, so if you’re looking to install DAS as a solution, please contact us and we’ll be happy to assist and advise.