# State-Of-The-Art and Prospects for Peer-To-Peer Transaction-Based Energy System
## 4 Enabling Technologies for Transaction-Based Energy
### Information Communication Technologies
#### 4.3.1 Communication Technologies in the Microgrid  
Feasible communication technologies in MGs include wireless and wireline technologies. The rest of this section provides a brief summary of the communication technologies that can be adopted for  
Figure 2: Components of a microgrid [46] showing both energy and information flows. MG: micro-grid; DER: distributed energy resources. MG control and communication [23; 44; 45; 46; 50; 51]. In addition, Table 1 summarises the communication technologies and requirements in MGs. * Power line communication (PLC): PLC is the transmission of data over electric power cables, thus enabling utility companies to utilize a single infrastructure for data and power transmission. Since PLC operates on already established power line infrastructure, the cost of deployment is low, and it has been proposed for grid communication in the literature. However, grid communication over PLC will experience the same challenges faced by power cables such as signal attenuation and electromagnetic interference. PLC can be categorized into three types: broadband PLC (BB-PLC), narrowband PLC (NB-PLC) and ultra-narrowband PLC (UNB-PLC). The NB-PLC data rates can range from 1 bps up to 500 kbps, and it can cover a distance of about 150 km, while BB-PLC has higher bandwidth performance, but shorter coverage (up to 200 Mbps over a few tens of meters and about 10 Mbps over 8 km); thus, it is commonly found in home area network (HAN) applications such as home automation. The UNB-PLCs operate within 125 Hz and 3 kHz [52], supporting data transmissions coverage of up to 150 km with data rates from sub 1 bit/s to tens of bits/s [53]. * Optical fibre: data are transmitted over optical fibre through pulses of light. Optical fibre has a low interference and attenuation rat, which makes it suitable for long distance communication. Fibre optic communication has a coverage range of 62 miles before signal regeneration and provides a total bandwidth in order of Gbps. An optical fibre communication network is characterized by low latency, high data rate, reliability and immunity to electromagnetic interference. Suitable areas of deployment in MG are neighbourhood area networks (NAN), backhaul networks and wide area networks (WAN). Its main drawbacks are the high cost of installation and maintenance. * Digital subscriber line (DSL): DSL transmits digital data over telephone lines. Thus, the cost of deployment is low because the backbone is already in place. However, the electricity utilities pay a service charge to the telecommunication operators to maintain the communication network infrastructure within the power network. Typical data rate and coverage distance of DSL vary with the specification applied. For example, the asymmetric DSL (ADSL)data rate ranges from 8-24 Mbps for downlink and 1.3-3.3 Mbps for uplink, covering a distance of 4-7 km. Furthermore, the data rate of very-high-data rate DSL (VDSL) ranges from 52-85 Mbps for downlink and 16-85 Mbps for uplink, covering a distance of 300 m-1.2 km. DSL provides high throughput with reduced latency; hence, it is found to be applicable in MG applications like demand response and smart metering. * Wireless personal area network (WPAN): WPAN is based on the IEEE 802.15x series of standards. They are designed for information exchange over short distances to address a low to medium data rate for personal computer networks and local area networks (LANs). ZigBee/6 LowPAN and Bluetooth technology belong to this series. WPAN generally has a low coverage area and data rate. The ZigBee/6 LowPAN coverage range is up to 70 m with the data rate ranging from 20-250 kbps, while the Bluetooth coverage range is up to 10 m with a data rate of 712 kbps. ZigBee has low power consumption, and it is fully interoperable with IPv6-based networks. WPANs are low-cost systems with adequate security for short-range deployments. Some of the major weaknesses of WPANs are low bandwidth/data rate and low coverage area, and they do not scale to large networks.