DAS 3.0 - the next generation DAS and its core architecture
DAS 1.0 was all coax DAS, DAS 2.0 was a mix of fiber and coax. DAS 3.0 is all fiber DAS, and this is the next generation of DAS.
We will discuss core architecture of a typical DAS 3.0 platform – I say ‘core’, because this architecture will be common to most of the DAS 3.0 or all fiber DAS. I have used generic names for the electronics, because names of electronics may change from vendor to vendor – but essentially if you understand this core architecture you will be able to easily and quickly understand any DAS 3.0 platform.
Core Architecture of DAS 3.0
On the diagram above, we start with signal source – which can be a base station from an Operator or Carrier. We will feed signal via short coaxial jumpers into the head-end electronics. Head-end electronics will be located in the MDF. Usually there will be a cluster of cards or components in these head-end electronics.
Head-end electronics usually have 2 major functions:
Preparing the RF signal for distribution throughout the system
Convert the RF Signal to optical signal to distribute via fiber
From head-end electronics, fiber will fan out to multiple remotes – usually mounted on a ceiling tile or above ceiling grid. In this line diagram, I am showing only 1 remote, but in most cases there will be multiple remotes. Fiber will be single mode fiber in pretty much all DAS 3.0 platforms.
If you have another building that you will have to cover, you can run 1 or 2 strands of single mode fiber from the head-end electronics to a Network Expansion Unit – which may be rack mounted in this building’s MDF closet. Now you can replicate the architecture of the 1st building – basically run fiber to multiple remotes throughout the building to achieve your coverage goal.
Note that ALL of the electronics shown here will need electrical power source. Often times, remotes are fed power via copper wire or CAT5 from an IDF closet from power supply unit or PSU. Instead of running separate copper for power, DAS OEMs offer hybrid fiber, which will have fiber strands and copper for power within the same jacket.
Let's review the summary of the features of DAS 3.0 architecture:
1 head-end equipment supports multiple remotes
1 network extension unit supports multiple remotes
1 system can support a large building or multiple buildings in a campus
Remotes are usually ceiling mounted
Remotes may be connected to optional antennas via coax jumper
Power to remote can be supplied via copper (e.g. CAT5) from IDF closets
Let’s review a scenario of poor signal in a building, and find out how DAS 3.0 would solve this problem. We have 2 buildings and there are subscribers from 4 different carriers. Buildings have little to no cell signal indoor. Users are obviously very frustrated.
2 buildings with poor cell signal inside from all 4 carriers
We will install a DAS 3.0 in the building.
Solving the problem of poor cell signal with DAS 3.0
Blue boxes on the first floor are the DAS head-end. You can see remotes (i.e., blue boxes) on each floor. These remotes will be connected to the head-end through 1 or 2 strands of fiber. These remotes will also get power through 2 copper conductors.
For the 2nd building we will link the DAS head-end from 1st building to a Network Extension Unit placed in the second building. We will then install the rest of the DAS in the second building.
We add 4 sets of signal sources from 4 carriers to the DAS head-end in the first building, and turn the whole system on.
Every body is now receiving the signal, they can make calls and they are all happy.
In the next post, let’s look at an all-fiber DAS from Corning. It will help us understand this core architecture we just discussed.
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