Essay: Cognitive Radio: 'Channel allocation in cognitive radio network'

Table of Contents
1. Introduction
I. What actually is Cognitive radio?
II. Definition
III. Why do we need of it?
IV. Components of cognitive radio
V. Functions of cognitive radio
2. Literature Review
I. History
II. Issues in cognitive radio networks
III. Challenges in cognitive radio networks
IV. Current research areas
3. Problem Statement
4. References
Introduction:
1. What actually Cognitive Radio is?
Cognitive radio is a new wireless technology for improving spectrum utilization in wireless computer networks. It is not a hardware device or a name of any specific network but actually it is a new concept or we can say an abstract idea to handle the problem of the scarcity of the radio spectrum. In last decade, cognitive radio has emerged as a major next generation wireless technology, which is the most promising candidate solution to solve the spectrum scarcity and improve the utilization.
2. Definition:
Cognitive radio is a wireless communication system which is aware of environment and its changes and can adapt its transmission parameters accordingly. Cognitive radio (CR) is a form of wireless communication in which a transceiver can intelligently detect which communication channels are in use and which are not, and instantly move into vacant channels while avoiding occupied ones. This optimizes the use of available radio-frequency (RF) spectrum while minimizing interference to other users.
Cognitive Capability: The ability to sense the unused spectrum at a specific time and location (spectrum hole)
Reconfigurability: The ability to receive and transmit at different frequency band enables the cognitive radio to reconfigure its parameters and select the best band.
In most basic form, CR is a hybrid technology involving software defined radio (SDR) as applied to spread spectrum communications. Possible functions of cognitive radio include the ability of a transceiver to determine its geographic location, identify and authorize its user, encrypt or decrypt signals, sense neighboring wireless devices in operation, and adjust output power and modulation characteristics.
There are two main types of cognitive radio, full cognitive radio and spectrum-sensing cognitive radio. Full cognitive radio takes into account all parameters that a wireless node or network can be aware of. Spectrum-sensing cognitive radio is used to detect channels in the radio frequency spectrum.
3. Why do we need of it?
Over the last few years, significant developments in wireless technologies have made mobile devices, such as laptops, mobile phones, smart phones, and personal digital assistants, an essential part of the human life. According to the SiliconIndia Magazine’s report , the number of cell phone subscriptions are estimated to increase from 6 billion in January 2013 to 7.3 billion in 2014, which is, interestingly enough, more than the world’s current population. Similarly, mobile-broadband subscriptions have increased from 268 million in 2007 to 2.1 billion in 2013, with an average annual growth rate of 40%. The increase in wireless network deployment has saturated the spectrum and has led to spectrum scarcity. Another fundamental reason for the scarcity of the spectrum and the saturation of unlicensed spectrum is inefficient spectrum assignment, in which a wireless spectrum is assigned to a licensee, also known as the primary user (PU), on a long-term basis using a fixed spectrum assignment policy. According to the Federal Communication commission (FCC), the utilization of the assigned spectrum varies temporally and geographically between 15% to 85% . This fixed spectrum assignment policy and the usage pattern cause over-utilization of the unlicensed spectrum and underutilization of the licensed spectrum.
The current fixed spectrum management approach is inefficient since it leaves many unused portions on it. New and more efficient management techniques are needed to make use of these free portions of the spectrum, also known as ‘Spectrum holes’ or ‘white spaces’, in order to solve the problem of the cognitive devices, as they are able to evaluate the electromagnetic spectrum availability make possible an improved spectrum utilization offering more flexibility, opportunity and efficiency in spectrum management.
Spectrum Hole
The Federal Communications Commission (FCC) ruled in November 2008 that unused portions of the RF spectrum (known as white spaces) be made available for public use. White space devices must include technologies to prevent interference, such as spectrum sensing and geolocation capabilities.
The main idea behind a cognitive network is to allow the coexistence of licensed (primary) users and unlicensed (secondary) users sharing opportunistically the same bandwidth. And one of the main requirements of cognitive devices is that they must be able to guarantee its ability to share spectrum without causing harmful interference.
4. Components of CRN
I. Primary network
‘ Primary users: Primary users have the license to operate in certain spectrum bands
‘ Primary base station: Controls the access of primary users to spectrum
II. Secondary network
‘ Secondary users: Secondary users have no licensed bands assigned to them.
‘ Secondary base-station: A fixed infrastructure component with cognitive radio capabilities and provides single hop connection to secondary users.
‘ Spectrum broker : Scheduling server shares the spectrum resources between different cognitive radio networks.
5. Cognitive radio architecture
Network access types
‘ CR Network Access: CRs can access their own base station on both licensed and unlicensed spectrum bands
‘ CR Ad Hoc Access: CRs can communicate with other CRs through an ad hoc connection on both licensed and unlicensed spectrum bands.
‘ Primary Network Access : CRs can access primary base station through the licensed bands
Functionalities of a CRN
i. Spectrum sensing: Cognitive radio user has the ability to sense the unused spectrum at any time and location.
ii. Spectrum management: Based on the availability of the spectrum and other policies, CR user allocates the best available spectrum band.
iii. Spectrum mobility: CR user shall vacate the spectrum in the presence of any primary user and move to next best available spectrum band.
iv. Spectrum sharing: CR network has to provide a fair and optimal spectrum allocation method among multiple CR users.
2. Literature Review
i. History:
‘ The concept of cognitive radio was first proposed by Joseph Mitola III in a seminar at KTH (the Royal Institute of Technology in Stockholm) in 1998 and published in an article by Mitola and Gerald Q. Maguire, Jr. in 1999. Mitola submitted his Ph.D Thesis, ‘Cognitive radio: integrated agent architecture for software defined radio’ in 2000.
‘ DSA(Dynamic Spectrum Access) concept was firstly implemented by DARPA(Defence ) in 2003.
‘ Simon Haykin described Radio’scene analysis, Channel’state estimation, predictive modeling, transmit’power control Transmit control, dynamic spectrum management in Feb. 2005.
‘ Dynamic Shared Spectrum access concept is described by I.F. Akyildiz in 2006 and also introduced concept of Cognitive Radio Ad Hoc Network (CRAHN) which is infrastrureless cognitive radio network in July 2009.
‘ Wireless Regional Area Network g (WRAN), also known as IEEE 802.22 Working Group on Wireless Regional Area Networks.
ii. Issues in cognitive radio networks
There are various issues in cognitive radio networks related with the functions of the cognitive radio networks.
Implementation issues
‘ Readiness of the CRN backbone
‘ Defining points of interconnect and interface.
‘ Definition of Uniform service based priorities.
‘ Default service and routing requirement.
‘ Service authentication and authorization.
Regulatory issues
‘ Migration from service based licensing to service neutral licensing regime.
‘ Issues related with converged licensing.
‘ Re’classification of the licenses.
‘ Pricing issues to end users.
‘ Migration from service based pricing to service neutral pricing.
‘ Revenue settlement of the operators in CRN environment.
QoS issues
‘ Need to define Quality of services parameters in CRN environment.
‘ Monitoring QoS in various networks and ensuring compliance to defined
‘ QoS parameters in CRN environment.
‘ Ensuring End to End QoS across the networks.
‘ Need to define unique service based priorities.
‘ Reliability across diverse applications.
Security issues
‘ Protection from various protocol attacks.
‘ Application attacks.
‘ Unauthorized user introduction.
‘ Unauthorized access to system data.
‘ Denial of services (DOS) and Distributed Denial of services attacks(DDOS).
To address the issues of cognitive radio networks, numbers of researcher has given various algorithms for them which are following:
‘ ‘Channel Assignment Algorithms in Cognitive Radio Networks: Taxonomy, Open Issues, and Challenges’ by Ejaz Ahmed, Student Member, IEEE; Abdullah Gani,
‘ A Channel Assignment Algorithm for Cognitive Radio Wireless Sensor Networks’ by Mehdi Askari*, YousefS. Kavian*, Hooman Kaabi*, Habib F. Rashvandt
‘ ‘Channel Assignment in Cognitive Wireless Sensor Networks’ by Mihaela Cardei and Amalya Mihnea
‘ ‘A Survey of Security Issues in Cognitive Radio Networks’ by Li Jianwu1*, Feng Zebing2, Feng Zhiyong2, Zhang Ping1
‘ ‘A New Wireless TCP Issue in Cognitive Radio Networks’ by Yu-Chun Cheng
‘ ‘Energy Efficient Cognitive Radio MAC Protocols for Adhoc Network’ by Muhammad Talha Zia ,Faisal Fayyaz Qureshi
‘ ‘QoS Routing for Cognitive Radio Ad-Hoc Networks:Challenges & Issues’ by Tauqeer Safdar Malik, Dr. Halabi B. Hasbulah
‘ ‘Channel Allocation in Cognitive Radios’ by Shridhar Mubaraq Mishra, Member, IEEE,
‘ ‘Segment-Based Channel Assignment in Cognitive Radio Ad Hoc Networks’ by Kaigui Bian and Jung-Min Park
‘ ‘Channel Assignment for Throughput Maximization in Cognitive Radio Networks’ by Le Thanh Tan and Long Bao Le
‘ ‘Cluster-Based Control Channel Allocation in Opportunistic Cognitive Radio Networks’ by Sisi Liu, Student Member, IEEE, Loukas Lazos, Member, IEEE, and Marwan Krunz, Fellow, IEEE
iii. Challenges of cognitive radio
Challenges in spectrum sensing
‘ Interference temperature measurement
‘ Spectrum sensing in multi’user networks
‘ Detection capability
Spectrum management challenges
‘ Decision model.
‘ Multiple spectrum band decision.
‘ Cooperation with reconfiguration.
‘ Spectrum decision over heterogeneous
‘ Spectrum bands.
Challenges of spectrum mobility
‘ Spectrum handoff.
‘ Spectrum mobility in multiple users.
Spectrum sharing challenges
‘ Common control channel (CCC).
‘ Dynamic radio range.
‘ Spectrum unit.
3. Problem statement:
The cognitive radio is an emerging technology that enables dynamic spectrum access in wireless networks. The cognitive radio is capable of opportunistically using the available ortions of a licensed spectrum to improve the application performance for unlicensed users. The opportunistic use of the available channels in the wireless environment requires dynamic channel assignment to efficiently utilize the available resources while minimizing the interference in the network. A challenging aspect of such algorithms is the incorporation of the channels’ diverse characteristics, highly dynamic network conditions with respect to primary users’ activity, and different fragmented sizes of the available channels.