Exclusive Use Spectrum Access Trading Models in Cognitive Radio Networks: A Survey

Spectrum frequency is a valuable resource for wireless communication but very limited in its availability. Due to the extensive use and ever increasing demand of spectrum bands by wireless devices and newer applications, unlicensed band is becoming congested, while licensed bands are found mostly underutilized. To solve this problem of spectrum scarcity, cognitive radio (CR) devices can share licensed bands opportunistically in several ways. We analyze the three main dynamic sharing models (commons, shared-use, and exclusive-use) proposed in literature with extensive analysis of the exclusive-use model, which is the most promising as it provides benefits to both licensed and unlicensed users. In this model, CR-enabled service providers, also known as secondary service providers, can buy or lease spectrum from licensed, known as primary service providers, for both short and long duration and gain exclusive rights to access the spectrum. In this survey paper, exclusive-use trading approaches, namely, game theory, market equilibrium, and classical, hybrid and other models are reviewed extensively and their characteristics and differences are highlighted and compared. We also propose possible future research directions on exclusive-use CR model.

I. Introduction

Wireless communication technology has become an integral part of our life and the number of wireless devices is increasing at an enormous rate due to recent technological advancements. The wireless devices and their applications, alongside emerging technologies and their demand for higher bandwidth and data rate, are continuously increasing and evolving. However, radio frequency is a limited and precious resource. According to the current spectrum policy, majority of the available spectrum has been allocated or licensed to wireless service providers such as cellular companies, TV/radio stations and satellite communications. These providers are called licensed service providers (or primary service providers) and bands are allocated on a long term basis for large geographical regions. Statistics show that these licensed spectrum bands are under-utilized or unoccupied in most places and for most of the time [1], [2] even in the most crowded region of big cities (e.g., Chicago, New York) [3], [4]. For example, according to the Federal Communications Commission (FCC) [5], [6], the average usage of the licensed bands ranges from 15% to 85%. The FCC also assessed that for the bands below 3 GHz, only 5.2% of the spectrum is utilized in the United States in any given location at any given time [7]. On the contrary, a small portion of the available spectrum, called unlicensed spectrum, is left to be used free by a large number and types of wireless devices which do not use licensed services, partly because of high cost involved. This presents a challenging scenario, even more so with the ever increasing number of services where the licensed spectrum is under-utilized while the unlicensed spectrum is becoming more and more congested [8]. This demands a pressing need for efficient utilization of licensed spectrum bands. As a result, researchers around the world, along with some major organizations such as FCC, DARPA (Defense Advanced Research Projects Agency) and IEEE (Institute of Electrical and Electronics Engineers), are investigating solutions to this spectrum scarcity problem for the emerging technologies and applications, and to utilize spectrum more efficiently and reliably.