# Information and Communication Technology Solutions for the Circular Economy
## 2 Information and Communication Technology Solutions for the Circular Economy
### Communication Technologies  
The use of most, if not all, ICT solutions towards a CE would be impossible without a proper telecommunication infrastructure. Furthermore, more energy-efficient communications can lead to important resource savings. This is demonstrated in the solutions presented below in the form of novel communication protocols (e.g., link-layer or routing protocols) or techniques (e.g., cognitive radio, software-defined networking, virtualization, etc.) that are more eco-friendly and energy-efficient and, thus, more suitable for serving a circular model of economy.  
Cellular mobile technologies all the way from 2 nd Generation (2G) up to the current 5 th Generation (5G) are being utilized as key building blocks for CE applications. [PERSON] et al. analyze a holistic solution for the integration of the discharges of small food companies into the urban sanitation system, leading to a reduction of water pollution as well as to a better quality of river and marine waters. The proposed solution makes use of the General Packet Radio Service (GPRS) network infrastructure as well as of Supervisory Control and Data Acquisition (SCADA) and Simulation Technologies [11]. [PERSON] et al. examine energy harvesting techniques in 5G mobile technologies. Such techniques offer controlled energy replenishment and subsequent energy and resources saving. They also assist in satisfying the Quality of Service (QoS) requirements of machine-to-machine (M2M) communications [12].  
In order to strengthen their potential as CE enablers, communication technologies evolve to reduce their own environmental footprint, taking advantage of novel techniques such as virtualization, adaptive transmission, or caches. [PERSON] et al. propose a novel industrial internet of things (IIoT) protocol. This protocol was evaluated on a wind park's 5G industrial network, which utilized Software-Defined Networking (SDN) and Network Function Virtualization (NFV) technologies. The proposed solution was found to be substantially faster and more efficient, as compared to the existing standardized solutions [13]. The use of Adaptive Link Rate (ALR) technology is investigated by [PERSON] et al. as a way of achieving energy savings in the operation of an Ethernet link [14]. Cache-based networks coupled with SDN features represent a promising solution, offering higher data rates and energy efficiency, in comparison to the Long-Term Evolution (LTE) network [15].  
Other advanced communication techniques and networking concepts, such as cognitive radio and peer-to-peer (P2P) communication, also serve well the advancement towards CE models. Cognitive radio is a type of wireless access programmed and configured dynamically, aiming at providing reliable communication whenever and wherever needed, as well as at efficiently utilizing the radio spectrum [16]. [PERSON] et al. analyze the role that cognitive radio could play in more power-efficient and generally \"greener\" communications [17]. [PERSON] et al. describe a case study, in which a P2P energy market, backed by Blockchain technology, is driving the growth of community microgrids, which present benefits in terms of resilience, robustness and renewable energy utilization, compared to the traditional utility grid infrastructure [18].  
Novel communication protocols and signal processing techniques are also being researched to relieve power consumption needs and facilitate the transition to CE models. [PERSON] et al. describe how the design of algorithms and the exploitation of distributed computing can be leveraged to achieve more efficient communication protocols (such as routing protocols), leading to greater energy efficiency in the M2M communications domain [19]. [PERSON] et al. analyze the Time-Reversal Wireless Signal Transmission technology and stress its contribution to the reduction of power consumption and interference alleviation [20].