Introduction & Outline
Introduction
- Aim
- Cognitive Radio
- Blockchain enabled CR
- Learning Objectives
- Understand the principles of CR
- Know how blockchain can help CR
- Assumed Previous Knowledge
- Wireless communication network
Outline
- Basics of cognitive radio network
- Blockchain-enabled CR
Basics of cognitive radio network
Communication Systems
Wireless- and wire-based communication systems with their data rates
Wireless Communication
Wireless signals are used to transfer data from one place to another. Like other natural resources, such as petrol, gas, and minerals, wireless radio spectrum is also a natural resource.
A small chunk of wireless radio spectrum band cost millions of dollars.
wireless radio spectrum
The figure shows the behavior of wireless radio spectrum from lower frequencies to higher frequencies in terms of “coverage area”, “transmit power”, “power consumption”, and “bandwidth”.
classified
- Licensed spectrum
- The licensed spectrum is managed by the respective governments and can only be used by buying it. Telecom operators buy these licensed bands and then provide communication services to their customers.
- Unlicensed spectrum
- Unlicensed spectrum is the one which can be used free of charge by anyone at any time. This unlicensed spectrum can also be called as Industrial, Scientific, and Medical (ISM) band.
CR
why CR
The utilization of wireless radio spectrum varies according to the time and geographic location.
The wireless radio spectrum is underutilized, and lot of licensed radio spectrum is not being utilized. The primary reason for this is the static allocation of the spectrum by the regulatory bodies.
In order to efficiently utilize the wireless radio spectrum, researchers and scientists proposed to use this wireless radio spectrum dynamically. Thus, a new paradigm was introduced known as Dynamic Spectrum Access (DSA).
Cognitive Radio (CR) is the technology that enables this DSA paradigm to efficiently utilize this unused wireless radio spectrum
Nodes in CR
Primary Radio (PR) nodes
Primary Radio (PR) nodes are the licensed users and can only use the licensed spectrum
Secondary Users (SU)
Secondary Users (SU), i.e., CR nodes can only use the licensed spectrum when it is not being utilized by the primary users and CR nodes do not cause harmful interference to the PR nodes. The CR nodes are also required to leave the frequency band when a primary radio node arrives over it.
CR Network
The primary network and the CR network.
Ad hoc CR network
Basic of CR
Collision-Free Communication
Collision-free communication (CFC) is desirable in wireless and wired networks and this has been a topic of research for several decades.
The role of those medium access protocols is to allow devices to access the medium (resource) without making a collision with other devices.
Numerous medium access protocols were proposed and standardized
Avoiding collision is necessary; otherwise, packets will be lost, re-transmission will be required and thus result in energy and time consumption.
Dynamic spectrum sharing in CR
Dynamic Spectrum Sharing (DSS)is an exemplary achievement in the technological field.
It is a new technology which is going to enable use of LTE and 5G simultaneously in the same frequency band.
The technology helps in determining the demand for different radios in real-time.
The available bandwidth of the network is divided into independent parts and dynamically assigns respective mobile communications standard it can be ideally used for available frequencies.
The DSS concept allows different radios coexistence in the same carrier using spectrum sharing.
Issues of DSS in CR
- Self-aware: it should be able to know what is happening inside; then according to what it knows to determine appropriate actions to achieve goals and to learn.
- Self-configuration: it can adapt immediately—and with minimal human intervention to configure itself in the dynamically network environment.
- Self-healing: Through self-healing, network state can be evaluated and corrective actions can be initiated without disrupting system operation. The network environment as a whole becomes more resilient as changes are made to reduce or help to eliminate the impact of failing components.
- Self-optimizing: This feature refers to the ability of the network environment to efficiently maximize resource allocation and utilization to achieve end-to-end goals with a minimal human intervention.
- Self-protecting: self-protecting can detect hostile or intrusive behavior as it occurs and take autonomous actions to make itself less vulnerable to unauthorized access and use, viruses, denial of service attacks and general failures.
Blockchain-enabled CR
How Blockchain Can Help CR
- The blockchain provides verification and validation schemes to ensure the security of the CR network.
- A decentralized validation algorithm of blockchain enables a medium access protocol of CR to be more accessible, and the implementation will be easier since there is no need for a central-authority node.
- By applying blockchain, lacking a centralized node for validating a transaction and monitoring the spectrum access makes the overall system robust against singlepoint failures
Avoid collision-free communication in CRNs
The following steps will be carried out to avoid collision-free communication in CRNs by using blockchain.
- Local consensus is reached to allocate resources in each group.
- Broadcast the information to all CR nodes in the network.
- CR nodes will not use these resources.
- Results in collision avoidance in channel hopping sequence based CRN.
The benefits of using blockchain in CR network:
- Lack of Central Entity
- Blockchain through its decentralization feature can remove the reliance of buying and selling spectrum without going to the central entity or spectrum regulator.
- This can enhance the spectrum assigning process by making the buying and selling more faster than getting permission from a centralized regulator.
- Immutability
- This feature of blockchain can help in keeping the spectrum management-related records safe and secure.
- Moreover, the records cannot be tampered easily in a blockchain system designed for spectrum management
- Availability
- This feature of blockchain makes the dynamic spectrum management distributed ledger more available as several copies of the ledger co-exist and it will be extremely difficult for the attacker to make modifications in the ledger.
- Additionally, there will be no need to contact regional or national spectrum regulator every time when evaluating white spaces and determining spectrum opportunities.
- DoS Resilient
- Blockchain-based dynamic spectrum management system makes the system denial of service attack resilient as the copy of the ledger is available at multiple nodes and a compromise to a single node or few nodes will not hinder the activities of the blockchain system.
- Non-repudiation
- This non-repudiation feature of blockchain makes the dynamic spectrum management more transparent and auditable since once the transactions related to dynamic system management is recorded into the ledger, a node cannot disown it, thus a completely transparent record of transaction can be managed and maintained.
- Smart Contract Integration
- Blockchain brings smart contract feature which will bring new business models and rule-based spectrum management and assignment policies.
Issues of Blockchain-Enabled CR
- Is it important to think about who will manage this blockchain? Will the spectrum broker own this ledger? How the nodes join and leave the blockchain network?
- How the consensus will be reached among the blockchain nodes? Which consensus protocol will be more feasible? Which blockchain system?
Answer
- As we already know, wireless channel has already capacity issues, thus it is not clear how blockchain-related communication will be carried out in such a scenario? Will new spectrum access methods be required, or the existing spectrum access methods will suffice?
- One unique feature of blockchain system is that the nodes keep their local copy of the ledger and this requires memory. However, the lack of these resources is important in the context of mobile devices. Thus, this aspect also needs to be considered when thinking about blockchainbased spectrum management systems.