Integrated Wireless-pon access Network Architectures Milos Milosavljevic

Chapter 3 Optical and Wireless PHY Integration
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Figure 3-3: PHY structure of emerging broadband wireless networks [25]
In recent years, efforts have been dedicated in defining a standardized format for the connection 
of remote radio heads to the baseband processing unit, the so-called CPRI specification 
(Common Public Radio Interface) [26]. CPRI represents a means to transport analogue 
baseband signals digitally. This would be realised in the figure by utilising reference point (f). 
Alternatively a RoF approach would exploit connection point (g) where the analogue radio 
signal gets transmitted via the xPON.
The various alternatives by means of interfacing the wireless and PON architectures would
offer the common infrastructure different functionality properties. The more processing 
functionalities are shifted into the CO for example, the higher the amount of data to be 
transmitted over the PON. Integration at point (a) would need the minimum amount of 
resources since only the payload is communicated. In point (b) the packet overhead starts 
increasing due to the application of forward error correction. If the physical mapping operation 
at point (e) is fully performed in a centralized manner within the CO the overhead increases as 
in this case further frame elements such as pilots, reference symbols and frequency guards have 
to be transmitted via the xPON. Finally, at points (f) and (g) the overhead would be at its 
maximum as the cyclic prefix consumes resources.
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