In this chapter, CRSN based SG architecture and applications vis-a-vis communications access technologies are explored, and a conceptual framework for a CRSN in a SG, in- cluding challenges of a CRSN based SG, are highlighted. Overall, the CRSN based SG communication network architecture together with implementation of a design model, and associated communication access technologies, are presented. The NIST Framework for SG Interoperability standard is discussed.
Recommendations are made with regards to a CRSN based SG communication network ar- chitecture and implementation design model. This includes a discussion on the suitability and utilization of a LPWAN infrastructure for successful SG integration and deployment. Finally, future work is discussed and this includes: utilization of hybrid communication access systems and a LPWAN infrastructure in a CRSN SG, communication network protocols, radio resource allocation, and energy harvesting in a SG. These are presented as open research issues.
Some of the open research problems are addressed in the subsequent chapters in this thesis.
RRA Improvements in CRSN
based Smart Grid
3.1
Introduction
This chapter investigates and surveys the perspective of radio resource allocation (RRA) in CRSNs based SG including the overview and unique characteristics as well as functionali- ties of CRSNs. Also, the various resource allocation schemes vis-a-vis RRA architecture in a CRSN SG environment are highlighted. The work reported in this chapter, includes performance analysis of RRA based on throughput improvement criteria in CRSNs for SGs. The analysis assists in establishing suitable spectrum band operation of CRSNs in RRA for SGs. Finally, future research direction in contributing to knowledge such as energy efficiency, hybrid energy harvesting schemes for perpetual power supply to the battery power constraints sensor node have also been presented.
Traditional power grids use a top-down layer approach where the communication flow is only in one direction from the utility to the consumers. A SG has a bidirectional communica- tion and information flow between utility and consumers. There are several communication technologies such as wired or wireless technologies which can be used to realize the bidirec- tional communication in SG. Wireless communication is a good communication technology option to drive SG due to the extensive coverage area required in SG. However, the wireless channels in the wireless communication undergo wide range of impediments such as fading, path losses and interference caused by other wireless devices operating in the same ISM free band. There is also spectrum limitation and spectrum efficiency issues due to the high cost of acquiring a spectrum channel and poor spectrum utilization (only about 15 %) of the allocated spectrum is utilized.
To this end, to address the impairments and spectrum issues, a CRSN which is the combi- nation of CR and WSN is proposed as adequate communication technology in SG which will enable power generation, transmission, distribution, utilities and customers to transfer,
monitor, predict, control and manage energy usage effectively and in cost efficient means. The realization of CRSNs for smart grid mainly requires efficient radio resource al- location strategies to manage the DSA of cognitive radio sensor nodes in harsh SGs environmental condition. To meet the requirement of data rate and power constraints of the CRSN users, as well as to avoid interference, researchers all over the world are working hard to develop RRA scheme that will effectively manage radio resources. CRSN has the potential advantages of reconfigurability and DSA capabilities; to exploit these potential advantages of CRSN, a dynamic efficient RRA among the sensor nodes is essential. The RRA has been well studied for various wireless networks, though not in the perspective of SG. Numerous surveys on RRA for different wireless networks such as cellular/LTE net- works, cognitive radio networks (CRN), and WSN can be found in literature [112]–[116]. These works are not in the context of SG; they do not involve the integration of the wireless network into SG in their surveys. Only very few studies survey RRA in CRSN perspective. Yet, their emphasis is not on the intersection of CRSN in SG for the RRA. This chapter presents investigative and survey approach that focused on RRA in CRSN application in smart grids.
Surveys on RRA in CRSN for SG environments have been rarely conducted. References [117]–[119] conducted a survey on resource allocation in WSN. The study in [19] ] surveyed works on RRA in CRSN. In their work, CRSN resource allocation scheme were categorized some optimization criteria for CRSN highlighted outside the context of SG consideration. Other studies which are not mainly on the survey of resource allocation but on some aspects of resource allocation strategies are found in [21], [120]-[126]. Reference [120] presented a survey of spectrum sensing methodologies for cognitive radio which was centered on spectrum sensing strategy. [121] conducted a research showing that resources in cognitive radio networks (CRNs) should dynamically be allocated according to the sensed radio environment.
Another work by Le and Hossain is in [122],which presented a RRA framework specifically for spectrum underlay in cognitive wireless networks. [123] studied resource allocation in Orthogonal Frequency Division Multiplexing (OFDM)-based cognitive radio network (CRN), under the consideration of many practical limitations such as imperfect spectrum sensing, limited transmission power, different traffic demands of secondary users.
Table 3.1 presents a comparative table on RRA survey in CRN, CRSN and CRSN based SG. It helps to exemplify whether surveys on radio resource allocation have been considered in CRSN based SG
Also, [124] studied the energy efficiency aspect of spectrum sharing including power allocation in heterogeneous cognitive radio networks with femtocells. [125], [117] - [119] presented a generalized survey works on WSNs. Resource allocation was generally dis-
Table 3.1: Comparison table on radio resource allocation in CRSN based SG Survey References
for resource allocation CRN CRSN CRN based SG CRSN based SG
Resource allocation Tragos et al. [111] Yes No No No Yes Ahmad et al. [18] No Yes No No Yes Ireyuwa et al. [118] Yes No No No No Xie et al. [122] Yes No No No No Le et al. [101] Yes No No No No Yu et al. [133] Yes No No No No Khan et al. [29] No No Yes No No Akan et al. [20] No Yes No No No Gungor et al. [40] No No Yes No No Faheem et al. [12] No No No Yes No
cussed in these works but the survey of resource allocation strategies was not their major target. [21] discussed issues regarding dynamic spectrum management in CRSN which does not provide any survey on resource allocation strategies. The authors in [126], [127] discussed CRN but radio resource allocation was not the main objective of their papers. Works reflecting survey in SG that highlight some aspect of resource allocation are found in [30], [41], [13]. They discussed spectrum sensing, they did not highlight resource alloca- tion extensively such as including spectrum, QoS, fairness, priority, and power allocation scheme, and so on. Also, resource allocation scheme was not their main focus.
Some of the works focused on radio resource allocation in only CRN or CRSN or other aspects of wireless network without intersecting with the SG domain. None surveyed the integration of RRA in CRSN into SG. The studies which involve SG domain discussed some aspects of RRA without delving into full details of resource allocation schemes; and RRA was not the main aim of their studies. This chapter articulates the extension of works on radio resource allocation into SG domain. Hence, the focus here is to explore radio resource allocation in CRSN based SG, thus leading to the following contributions:
• A comprehensive survey of RRA in CRSN based SG is presented.
• The overview, functionalities, unique characteristics and challenges of CRSN in SG are discussed.
• Radio resources optimization criteria in CRSN based SG are also discussed in this chapter.
• Also, RRA scheme in CRSN based SG including its architecture are presented. Suggestions and future research directions concerning RRA in CRSNs based SG are high- lighted. The remainder of this chapter is structured in subsections as follows: Description
of the overview, functionalities and unique characteristics of CRSN in a SG; radio re- source allocation in CRSN based SG; recommendations and future research direction are discussed. Finally, the chapter is summarized.