Integrated Wireless-pon access Network Architectures Milos Milosavljevic

Chapter 8 Project Achievements and Future Work 
161 
Figure 8-1: Long reach optical/wireless integration (MO: middle office, eNB: enhanced Node B, UE: user 
interface) [22] 
To that extent, the delay associated with 100 km fibre transmission is reduced since the time 
sensitive wireless data is transmitted only over 20 km (between eNB
p1
and eNB
p2
). It is 
important to note that the centralised wireless processing is performed in the MO instead of CO. 
Such a configuration would contribute massively towards the business plans of network 
operators in increasing bandwidth to support emerging media-rich services with mobility to 
potentially offer significant CAPEX and OPEX savings in an incorporate access/metro 
infrastructure. 
The efficiency of the architecture should be further explored by investigating the benefits 
gained by centralised processing, considered also as an important aspect of the integrated 
optical/wireless networks. In particular, multi-site transmission schemes, such as co-ordinated 
scheduling with beamforming antennas and joint processing, could be simplified with the 
application of RoF, as detailed below [22]. These two schemes are important features in order to 
reduce interference and increase capacity respectively.
In standard wireless network deployments exchange of interference measurements is typically 
performed by X2 logical interfaces, as shown in Figure 8-2 [13]. Therefore, this imposes 
stringent requirements on the backhauling links (mainly the maximum distance and capacity) 
supporting these base stations.

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Chapter 8 Project Achievements and Future Work 
162 
Figure 8-2: LTE network architecture (P-GW: packet gateway, S-GW: service getaway, MME: mobility 
management unit) [22]
However, with the application of centralised processing the X2 logical interface could be 
shifted at the CO, as shown in the Figure 8-3. Therefore, inter eNB communication is limited in 
CO which could result in decreased delay and higher capacity on the wireless links.