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MWEE MARAPR 2014

Emerging Wireless Cloud RAN – emergence in heterogeneity By Harpinder Matharu, Xilinx Inc. Wireless infrastructure network is going through a critical phase of technology evolution where a slew of different equipment form factors are being rolled out to meet perpetual growth in demand for capacity. All these solutions are gravitating towards maximising the potential of precious and limited spectrum resource. While 3gpp standardisation efforts are devising ways to pack more and more bits into available spectrum within the capacity constraints governed by Shannon’s law, wireless radio network is on the move to create topologies that allow less and less number of users to share more and more of the available spectrum. There are two major macro trends that are splitting the network into completely opposite directions. The first macro trend is pushing the network to deploy an underlay of 10’s of small cells per macro base station to add micro cells within a macro cell to initially improve coverage and then deliver capacity by serving fewer numbers of users. This trend simplifies radio access but creates complexity and scale challenges in the backhaul network. The second macro trend is splitting the base station into a network. This trend simplifies backhaul but adds complexity to the radio access. Cloud RAN and high density base stations are other names of this trend. The move to distributed base stations in terms of remote radio heads has been happening long before the days of cloud. Success of a distributed wireless network depends not only on a framework that allows adaptation and growth of distributed intelligence within the network via continuous self-learning but also on a solid foundation that allows coordination among the distributed intelligence to launch new services and profitable monetization of the network. Timing and synchronization is a key element of this foundation aside from self-healing, selfoptimizing and software defined network functionality. Timing and synchronization dictates the network performance while software defined network eases effective network sharing and virtualization, service deployment and maintenance. Figure 1 shows a traditional base station architecture. Due to pros and cons of the above stated trends and ongoing deployments, there will be no clear winner resulting in coexistence and eventual coopetition of Cloud RAN technologies and small cells. However, it is author’s view that network evolution would favor the fundamental precept of successful network monetization that builds upon continuously growing intelligence within the network to launch new and better services. Given the proliferation of distributed base station and remote radio head technologies, it is likely that the wireless network evolution will tilt more towards cloud RAN in coming time (Figure 2). This path is not going to be easy. Operators and system vendors would need to work collectively in standardizing some critical elements of cloud RAN to bring about cohesive framework that eases adoption and guides a series of future innovations to this cause. In order to delve into standardization needs for timing and synchronization, it is important to understand the present state of the wireless infrastructure network. Base stations and associated access connectivity has been a closed network where both proprietary and Figure 1: Traditional base station architecture. Figure 2: Distributed base station and remote radio heads. 14 Microwave Engineering Europe March-April 2014 www.microwave-eetimes.com


MWEE MARAPR 2014
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