Integrated Wireless-pon access Network Architectures Milos Milosavljevic

Chapter 2 Next Generation Access Networks 
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LTE, since it can incorporate many access points efficiently as it can residential FTTH users 
[19]. 
Figure 2-6: NG-PON use cases [2, 19]
A range of possible scenarios, in particular between EPON and WiMAX, are reviewed in [55, 
56]. What is common in these architectures is the employment of the complete WiMAX base 
station functionalities at common ONU/BSs. However, this would require significant 
modifications at the MAC layers of both networks to achieve fine bandwidth granularity. In 
addition, the benefits of the optical network as the backbone are not efficiently utilised since all 
WiMAX modulation is still performed at the ONU/BSs.
Instead, to achieve smaller radio cells, considered as a prerequisite for higher spectral efficiency 
than the currently standardised and deployed wireless networks, the application of RoF could 
deliver radio signals through the high-capacity fibre to densely spaced remote BSs [57-60]. 
Among these initiatives, [61] presents a scheme developed throughout this research programme. 
Its merits will be discussed and evaluated in detail in following chapters. 

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Chapter 2 Next Generation Access Networks 
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In view of RoF application complex equipment and processing is kept at the centralised head-
end allowing for easy installation and maintenance of the network. Consequently, low power 
consumption is achieved due to the passive nature of these base stations (BSs). In addition to 
the above, due to the signal transparency, a RoF approach could be used to distribute multi-
operator and multi-service traffic resulting in high economic savings [62]. Finally, as it will be 
described in proceeding chapters, RoF networks allow for dynamic resource allocation due to 
the centralised processing and control. For instance, in view of FDM transmission additional 
sub-carriers could be dropped to a base station increasing its capacity.
The application of RoF techniques alone would not be sufficient to exploit all benefits of optical 
backhauling to wireless standards. Although optical fibres, compared to copper and free space 
media, can provide superior transmission of radio frequency (RF) signals for long distances, 
their utilisation is however hampered by the limitation in bandwidth of electrical systems. 
Efficient multiplexing techniques, such as FDM, are therefore required to increase the optical 
bandwidth utilisation.
The presented challenges have very recently drawn the attention of research consortia 
worldwide, on establishing the critical aspects associated with the integration and 
implementation of optical and radio standards, the pros and cons of which will be analysed in 
the following chapter against the network developed in this work. 

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