Los corresponsales de Laredo

This chapter comprised two major contributions. In the first part, we explained more than ten of the most important CR based applications by citing recent overview papers published about each application. We then summarised QoS objectives in CRNs. After an extensive search, we found that most of the previous surveys had highlighted the advantages and the disadvantages of the existing techniques, algorithms and schemes to improve QoS objectives. To the best of our knowledge, no survey has presented the approaches adopted to improve QoS objectives in CRN's components. Therefore, we presented the adopted QoS provisioning approaches in each of CRN’s components. To avoid confusing the reader with our main research problem, and due to the extensive nature of the topic, the main part of the surveys is found in [10], [47] and [48].

In the second part, we investigated the impact of CRNs coexisting (intentionally and unintentionally) that may force any CRN to lose utilising spectrum opportunities. We studied the merits and demerits of the studies done to mitigate our research problems.

Cognitive Knowledge Base Decision and Evaluation Learning and Reasoning Data Fusion Multi-Domain Cognitive Predictable Information Base Cooperative Information Base Local Information Base Cognitive Engine

Cognitive Information Base

Control Restructure

44

While the existing solutions are able to some extent to mitigate these challenges, they are unable completely to prevent them. We, therefore, conclude this section with six remarks, each one for a research problem:

1) Missed spectrum detection: Despite proposing significant spectrum sensing approaches, algorithms, cooperative strategies, and Fusion center rules, the probability of missed spectrum detection is still significant and can reach 0.1, and hence the possibility of interference always exists.

2) Primary User Emulation Attack: While the existing schemes are promising on detecting PUEA, they are not able to provide details of the commission of the PUEA including offender CRNs and attacks’ time and bandwidth. Consequently, they are not able to prevent CRNs from performing attacks.

3) Inter-cell Interference: Several ideas have been proposed in the literature, all with the primary assumption that all CRNs are willing to exchange their resource information. However, no internetwork spectrum sharing has been proposed to administer the exchanging among all CRN types.

4) Overcrowded CRNs situation: There is no doubt that the QoS in any CRN will deteriorate through increasing and fluctuating PUs activities. Furthermore, a rapid growth in the number of CRNs is anticipated, which will lead to a decrease in the available useful spectrum opportunities. Moreover, in the literature, so far no rule has been adopted to assign number of CRNs.

5) Inability to model SUs activity: Similar to point 3, with the expected increasing in the number of CRNs, it is necessary for each CRN to be aware of other CRNs’ behaviour to devise reliable models for the spectrum. This is very important for CRNs to be able to compete for spectrum opportunities among themselves. However, CRNs are so far still incapable of modelling SUs activity.

6) CRN administration: Lastly, while the Geolocation and SAS databases are useful to coordinate CRNs, they are restricted to a particular band which makes them useless in other bands where CRNs may be eligible to operate. Furthermore, these systems are available in only popular countries (e.g. USA).

Finally, after all these studies we have reasons to coordinate all CRNs by certain rules that can contribute to tackling our challenges. Therefore, the next chapter will be our start with a new framework of new managing method for CRNs spectrum sharing.

3

Chapter Three: CogMnet Framework

3.1

Introduction

Considering the challenges identified, there are good reasons to propose an Internetwork framework capable of regulating the CRNs spectrum sharing. By regulating is meant only coordinating their spectrum sharing rather than licensing spectrum bands to them, because CRNs have no dedicated spectrum bands. Therefore, in this chapter, we present a new internetwork framework called CogMnet. CogMnet is proposed to regulate and coordinate the operation of infrastructure CRNs using real time databases. Unlike conventional frameworks, CogMnet records in real time the transmission parameters of utilised channels of each CRN in a particular database. Each database includes three storage units: Networks Locations storage; Real Time storage; and Historical storage unit. As will be explained later, CogMnet aims to tackle and prevent a number of the self-coexistence issues identified in chapter 2. The content of this chapter has appeared in an international conference in Google Portfolio Event (Wlnn Comm ‘16) [181].

The remainder of this chapter is organised as follows: Section 3.2 presents the architecture of CogMnet, including a description of the system model and the rules that must be followed by each CRN. Section 3.3 gives a general overview of the

Knowing where you are going is the first step to getting there.

45

requirements that the regulator should prepare for designing CogMnet. In Section 3.4, we summarises both main and emerging merits of CogMnet respectively. Some useful databases for CogMnet are summarised in Section 3.5. Chapter discussion for comparing CogMnet with existing frameworks is explained in Section 3.6. Finally, section 3.7 concludes the chapter.