New technology is offering a lifeline for bandwidth pressed providers. A shift in the access architecture that will move some or all of the CMTS processing layers out to the plant and closer to the subscriber will increase capacity and expand the bandwidth operators can offer subscribers.

Today the most common architecture used by operators is Centralized Access Architecture or (CAA) and the vast majority of nodes are on this type of architecture. But as the demand for bandwidth services escalates, the distance limitation of the analog optical transport becomes the chief challenge of CAA.

Now that operators are transitioning to digital optics for FTTN, the traditional Centralized Access Architecture can convert to a Distributed Access Architecture (DAA). The idea behind DAA is to take or distribute some or all of the smart processing from the CMTS in the headend and put it out into the plant and closer to the subscriber. With DAA, the forward analog link from the headend is replaced with a digital fiber connection, extending the signals deep into the network before converting them to analog signals at the node.  Keeping the data signals in digital format as far out as possible produces less signal interference and improves the quality of the signal to the end subscriber. 

Embracing DAA allows for shorter coax distances, which is a necessity for making the network more reliable. With today’s extended networks, it’s crucial to improve the data path every step of the way. Making this change will offer:

•   Increased network capacity and simpler outside plant maintenance
•   Better SNR quality, higher modulation rates, higher bit-rates    
•   Reduced headend power, space and cooling requirements
•   The ability to extend the IP network to the node

There are various ways of deploying a Distributed Access Architecture but the two most popular options are Remote PHY and Remote MAC/PHY. The main difference between the two approaches is which functions of the network are moved out of the headend.

The Remote PHY approach moves the physical connection layer (PHY), out to the node or the MDU. This layer includes the optical fiber, coaxial cable, optical transmitters, optical receivers, RF amplifiers, RF modulators and RF demodulators that move the cable bits across the network.

The Remote MAC/PHY option removes the PHY layer and the Media Access Control (MAC) out of the headend and into the plant. The MAC layer provides addressing and channel access components that let network nodes communicate with each other.  

Each approach has advantages and disadvantages but both will require managing an expanded network of intelligent nodes but the result will be much higher bandwidth capacity and processing power and an overall improved network.

For more details into DAA and the Remote PHY and Remote MAC/PHY versions just click on  this link for a new white paper, “Distributed Access Architecture: Choices, Challenges, and Considerations” that highlights things you’ll want to consider before transitioning to DAA or choosing a version for your operation.