What is a Distributed Antenna System? The Basics

Distributed Antenna System (DAS) in Australia

Wireless Coverage Solutions is a Sydney, Australia based company in the Distributed Antenna System (DAS) industry and have been providing In-Building Coverage (IBC) throughout Australia for some time. As a company we are are experts in Distributed Antenna System Design, DAS Installation and Commissioning.

What is a Distributed Antenna System?

A Distributed Antenna System, known as a DAS, is a dedicated antenna infrastructure deployed throughout a site/building to improve cellular In-Building Coverage (IBC), i.e. mobile phone reception. A Distributed Antenna System is typically only evident to the occupants of the building as the antennas mounted below the ceiling, which vary in appearance but usually resemble a circular smoke detector in shape and size and radiate the mobile phone signal to the targeted areas indoors.

Distributed Antenna Systems are deployed all around Australia in all sorts of high-traffic buildings and are largely taken for granted. Distributed Antenna System sites aim to provide a seamless end to end mobile reception and connectivity across a variety of sites types including: road tunnels and bridges, rail tunnels, hotels, hospitals, universities, stadiums, carparks, shopping centres, airports, commercial office space and everything in between.

The Wireless Coverage Solutions team have experience in all of the above indoor environments Australia wide, please don’t hesitate to contact us to discuss your cellular coverage requirements.

Distributed Antenna System, What is a Distributed Antenna System? The Basics

Distributed Antenna System systems can vary in size and strictly speaking even the smallest system comprising of a few antennas upwards to systems with 500+ antennas are all a type of Distributed Antenna System. The size of the system typically dictates the topology and type of Distributed Antenna System deployed, and the appropriate RF source to provide connectivity into the various carrier cellular networks.

Distributed Antenna Systems within Australia are typically multi-operator and shared by the likes of Telstra, Optus and Vodafone. There are some exceptions when systems are small and designed for use with Signal Boosters (Repeaters) for one carrier only. But even these can be shared by all 3 operators when designed properly from the outset.

You may have heard of terms such as Passive DAS, Active DAS, Hybrid DAS, iDAS, oDAS, SISO, MIMO, iMIMO and many more weird and wonderful combinations. This article will discuss the high level need for Distributed Antenna Systems. If you are more interested in the technical detail perhaps our article on Passive Vs Active DAS would be of interest or the difference between SISO and MIMO DAS.

Why do you need a Distributed Antenna System?

There are a few key reasons as to why a Distributed Antenna System is becoming a necessity to improve indoor mobile coverage. These are largely driven by technology change, rising consumer expectations and the lack of penetration from the outdoors as a result of dense building materials, especially as the use of higher cellular frequencies is becoming prevalent.

Higher spectrum allocations

Cellular coverage is delivered over RF spectrum which is leased to the mobile operators by the Australian Federal Government. Over the years the spectrum being used for this has gradually increased in frequency through the generations (2G to 4G and onwards to 5G). The higher the frequency the less it propagates and the less it penetrates through different kinds of building materials.

For example, in the diagram below, a 2G signal of 900MHz would penetrate the exact same building much farther than a modern 4G 2600MHz signal. The major issue associated with higher frequencies is that the Carrier Network preferences will direct modern smartphones to connect to as high a frequency as possible to maximise their utility in as many locations where viable.

Distributed Antenna System, What is a Distributed Antenna System? The Basics

When the 4G network was originally launched, the 4G service was initially used for data only, with calls falling back to the farther propagating lower frequency 3G services. In recent years, 4G technology has matured and so now modern smartphones prefer to make calls also over the 4G network (Voice over LTE or VoLTE).

This presents additional challenges where 4G does not have the same coverage footprint as 3G previously had in the same location. This has caused a recent surge in consumer complaints of dropped calls. Consequently, getting enough 4G coverage to complete basic tasks such as phone calls has become a challenge without a Distributed Antenna System.

Distributed Antenna System, What is a Distributed Antenna System? The Basics

Limited RF Signal Penetration

Building materials all to a degree impact the penetration of mobile phone signal into a structure, some more so than others. Typically, metal attenuates signal the most, followed by concrete and then plaster wall in descending order of impact. A solid concrete wall will easily take 20dB off a mobile signal (that means the signal is 1/100th the strength on the other side of the wall). Consequently, one can see how being in an underground car park or within a lift (a metal box surrounded by a concrete shaft) can be a particularly challenging place to receive a mobile signal.

A more recent challenge, particularly in commercial buildings, has been the extensive use of Low E-Glass film, designed to reflect UV rays to improve the buildings thermal efficiency. Unfortunately, blocking UV energy also largely blocks cellular RF waves which limit the penetration of cellular signals from the outdoors.

Evolving user Connectivity expectations

Even in situations where there is RF penetration from the outside presenting a viable mobile phone signal, the performance, particularly around data throughput, can be largely unpredictable. The user essentially shares capacity with the outdoor network, so during peak times, it’s likely they will experience a deterioration in throughput due to network congestion.

Distributed Antenna System, What is a Distributed Antenna System? The Basics

Advantages of a Distributed Antenna System

 

We’ll caveat the below with a dependency that the Distributed Antenna System was well designed, deployed and integrated by industry experts. Unfortunately, we see a lot of systems that are not. Particularly with repeaters, we come across a variety of solutions which are not implemented to a high standard, at no fault of the product itself. More often these are design or installation issues.

Distributed Antenna System, What is a Distributed Antenna System? The Basics

Improved mobile coverage

This is probably the most self-explanatory (and most important!) as we have all become accustomed to glancing at the number of bars on our mobile devices. While different phones often measure this differently and it can vary somewhat, the biggest difference a Distributed Antenna System will make is a significant improvement in the mobile/cellular coverage throughout the premises allowing for voice and data-based activities to be made seamlessly across the property.

To take it a step further, a Distributed Antenna System can provide coverage into places where it would otherwise be extremely unlikely to have any connectivity, such as basements or lifts. Coverage in basements and lifts is typically not possible (or very consistent) without a Distributed Antenna System. A well-deployed system should provide absolute mobility around the building where one could be on a call as they drive into the carpark, up the lifts to the café, up to the office and around the floor.

Signal to Interference Noise Ratio (SINR)

We’ve touched on the idea of coverage but less known to most people is the idea that that coverage can have ranging quality. In a nutshell, SINR is a measurement of how clear the signal you are using is with respect to those around it. A Distributed Antenna System provides a strong dominant source of coverage, and since the outdoor network struggles to penetrate the building its typical to see much higher SINR indoors than outdoors with a Distributed Antenna System Installation.

A strong SINR is the primary requirement for all high-speed data and allows for you to get the most out of your data connection to consume all the 4K video you desire.

Distributed Antenna System, What is a Distributed Antenna System? The Basics
Distributed Antenna System, What is a Distributed Antenna System? The Basics

Dedicated Capacity

When one relies on the outdoor macro network to provide connectivity, they are sharing cell capacity with many other buildings around them, streets, retail shops and the general public. As demand on the network increases, the total available capacity decreases (especially during peak traffic times) resulting in an inferior experience.

When a Distributed Antenna System is deployed within a building it essentially creates a dedicated capacity zone for that building which is not shared with any other users and consequently less susceptible to congestion.

Minimise Radiation from your device

This benefit is often glanced over and misunderstood. Your phone is one of the largest emitters of EME you always have on you , and unfortunately, we often store it in our jeans, or hold it up to our ears. However, a Distributed Antenna System is a sure-fire way to reduce the EME emitted by your mobile device.

It sounds somewhat counterintuitive but here’s how it works. Your phone is constantly trying to talk back to the mobile base station, in the case of the outdoors this is a long way away, with a variety of concrete and other obstructions in between. Think of it like trying to talk to your friend who is at the other end of a football field. But because he can’t hear you, you have to bust out your handy megaphone and turn things up to 11.

When a Distributed Antenna System is in the building, all of a sudden, it’s like you and your friend are next to each other on a park bench, and you can just talk at a normal volume now. The phones turn down their ‘volume’ to match the distance the signal needs to travel and consequently will emit significantly less EME when near an Antenna.

Distributed Antenna System, What is a Distributed Antenna System? The Basics
Distributed Antenna System, What is a Distributed Antenna System? The Basics

Improved Battery Life

Following on from the above, if your phone doesn’t have to yell as loud it is able to conserve battery life, you may have noticed before when you have a weak signal on a bushwalk or the like your battery will deteriorate fairly rapidly.

What are the Australian standards for a Distributed Antenna System?

 

The Multi-Carrier Forum (MCF) produces a Distributed Antenna System specification agreed by the three mobile operators Telstra, Optus and Vodafone which provides a recommended set of guidelines for the deployment of Distributed Antenna System. It dictates things such as coverage areas, equipment types, performance criteria as well as electrical/space/cooling considerations. The most recent version is MCF2018  at the time of writing, and these are usually reviewed every few years with mobile technology standards constantly evolving.

The Australian Distributed Antenna System MCF Specification provides for the minimum specifications required to deploy a Distributed Antenna System acceptable to the operators, however, it does leave open opportunities to go above and beyond, particularly in forward planning to create a future proof system ready for 5G and other upgrade paths. There is a lot of confusion in the industry around how Distributed Antenna System will support 5G, we have provided a dedicated article on the topic for consideration.

Installation best practise does receive some input from the MCF, but these also fall under more broad telecommunications cabling standards and installation practises.

The MCF defines ‘lead’ operator who will be the first operator to connect to the system and who will maintain the Distributed Antenna System henceforth. During the Distributed Antenna System design and throughout the installation process, complete integration and consultation with the lead operator is necessary to ensure they are across all the site considerations and changes. This ensures no surprises arise at the end of the project and connection doesn’t get delayed.

The engineers at Wireless Coverage Solutions have designed Distributed Antenna Systems for some of the most prestigious buildings throughout Sydney, Melbourne, Brisbane and all around. Our designs take into account a variety of future upgrade paths, installation logistics, long term maintenance and tenant impacts along the way. Do not accept a 2nd rate Distributed Antenna System design today which will create problems tomorrow and contact us now. All our Distributed Antenna System designs are MCF2018 approved by an Australian Tier 1 mobile operator prior to construction and we are one of the few companies who completes all our work in house.