Energy efficient optical-wireless in-building networks [electronic resource]
Keywords: Electrical Engineering.

Energy efficiency has become an important paradigm in the operation of modern telecommunication systems. As will be shown in this thesis, the energy consumption of in-building networks in the U.S. alone is higher than the energy consumption of both global optical transport and of the core and metro area networks worldwide. Residential and office buildings are significant contributors to this energy consumption. This is mainly caused by the large number of office and residential buildings in the US. The design of current in-building networks aims to meet capacity and performance requirements with little regard to their energy consumption. Thus as demand increases and energy performance requirements become more stringent, in-building network design requires more complex technologies. This situation is similar to the early days of the automotive industry, when the main performance measure of a car was its speed. However, as cars became a household item and gas became more expensive, the energy efficiency measured in miles per gallon became an important (and sometimes the primary) performance metric. Similarly, for current network devices and architectures, speed is the primary performance indicator. However, as the energy is fast becoming an expensive resource for network operators, energy efficiency is becoming important as well. Thus, we envision that for future network devices and architectures, bits transmitted per joule (or, inversely, joules per bit) will be an important efficiency-rating metric, just like miles per gallon for cars. This work envisions future high throughput in-building networks will consist of two segments --- optical and wireless; wireless alone at the network edge and optical links as the backbone. An important challenge in their design is how to accommodate a rapidly increasing data traffic while reducing or at least containing the energy consumption. In this work, the physical mechanisms and design principles contributing to the energy consumption of wireless and optical systems is discussed. Also demonstrated is the existence of an optimum cell size to realize green in-building optical/wireless networks. The major factors that affect the energy consumption of Radio-over-Fiber (RoF) links, such as Electrical-Optical-Electrical (EOE) conversion loss, optical link loss, and bandpass sampling frequency, that affect the energy consumption of Radio-over-Fiber (RoF) links are analyzed. Further, methods to mitigate their adverse effect on energy consumption are shown. Finally, the energy consumption of several in-building optical-wireless architectures based on the RoF technology is compared. Results illustrate that centralized architectures based on RoF links can be more energy efficient when designed keenly. The architectures are "rated" according to their energy-efficiency using the metric of "joules per bit". The practical issues of using the optical-wireless architectures in outdoor access networks is also studied. The possibility of multiplexing of wireless-over-optical data, referred to as "fronthaul", and the traditional backhaul data in transport networks and in Passive Optical Networks (PONs) is analyzed. Future mobile technologies, such as Massive MIMO, and their impact on future indoor network infrastructure and energy consumption is discussed.