Multi Channel Protocols In Cognitive Radio Networks

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Cognitive radio is a paradigm for wireless communication in which either a network or a wireless node changes its transmission or reception parameters to communicate efficiently avoiding interference …

Cognitive radio is a paradigm for wireless communication in which either a network or a wireless node changes its transmission or reception parameters to communicate efficiently avoiding interference with licensed or unlicensed users. This alteration of parameters is based on the active monitoring of several factors in the external and internal radio environment, such as radio frequency spectrum, user behaviour and network state. this presentation discusses main approaches and protocols of multichannel cognitive radio networks.

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  • 1. Multi-Channel MAC Protocols in Cognitive Radio Networks Prepared by: Mohammad J. Abdelhadi Muhammad K. Mustafa King Abdullah II School of Electrical Engineering Princess Sumaya University for Technology
  • 2. Outline Multi-channel MAC Multi-channel MAC Approaches What is Cognitive Radio(CR)? Overview of some Cognitive multi-channel MAC protocols. King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 1
  • 3. Multi-channel MAC  Multi-channel means that there are more than one channel available for communication in a system.  Why Multi-channel MAC? • Reducing collusion among users • Higher throughput • Less normalized propagation delay King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 2
  • 4. Multi-channel MAC King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 3
  • 5. Multi-channel MAC Approaches  There are three main approaches for Multi-channel MAC • Common Control Channel Approach(CCC). • Split Phase Approach(SP). • Common Hopping Approach(CH). King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 4
  • 6. Common Control Channel Approach  The CCC approach applies a single dedicated common control channel.  Usually uses more than one transceiver, one of them is tuned to the common control channel at all time.  Advantages: • Solves the hidden terminal problem( when using more than one transceiver). • Doesn't require time synchronization.  Disadvantages: • Congestion can occur. • Energy inefficient • Bandwidth inefficient. King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 5
  • 7. Common Control Channel Approach King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 6
  • 8. Split phase Approach  It splits all channels into two phases: • Control phase • Data phase.  During a control phase, all nodes tune to a common control channel.  During the data phase, nodes tune to negotiated channels for data transmission.  Advantages: • Uses Only one transceiver • Does not allow the hidden terminal problem • Energy Efficient  Disadvantages: • Precise time Synchronization is required • Data Channels are wasted during the control phase • Data Channel negotiation is only during the control phase King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 7
  • 9. Split phase Approach King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 8
  • 10. Common Hopping Approach  Every node hops through all available channels following a common hopping pattern.  After sending the control packets and agree to send data, a node pair stop hopping until the transmission is completed.  Advantages: • Using only one transceiver • No common Control channel • Data channel negotiation is performed simultaneously on different channels.  Disadvantages: • The hidden terminal problem • There is a high Channel switching delay • Time Synchronization King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 9
  • 11. Common Hopping Approach King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 10
  • 12. Default Hopping Sequence Approach  Every node determines its default hopping pattern using the seed of a pseudo random generator which is known by all nodes.  same communication procedure that used in CH but with a scheduled sequence.  Same advantages and disadvantages of CH. King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 11
  • 13. What is Cognitive Radio  The main aim behind CR is to utilize the unused spectrum at a given time and place, thereby creating virtual unlicensed band.  Two kinds of users in CR networks; primary users(PU) and secondary users(SU).  A great principle of CR is the using of the spectrum from SU must not affect the communication of PU.  Once the PU returns to a channel, the communication of the SU in that channel must stop immediately.  SUs can exchange spectrum information with each other. King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 13
  • 14. FCC: In most places, Over 70% of the allocated spectrum is not used ! King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 14
  • 15. Cognitive MAC protocols and its Fundamentals  Cognitive MAC protocols allow unlicensed users to share the licensed spectrum.  The presence of PU distinguishes cognitive MAC protocols from other multi-channel MAC protocols.  Sensing and distribution of channels is a major concern in CR MAC protocols.  Each Cognitive MAC protocol may use more than one approach of multi-channel MAC approaches.  Cognitive MAC protocols are in its infancy. King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 15
  • 16. Some Cognitive MAC protocols  Hang Su and Xi Zhang's MAC Protocol.  HC-MAC protocol.  Noun Choi et al protocol. King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 16
  • 17. Hang Su and Xi Zhang's MAC Protocol.  This protocol assumes that each SU is equipped with two transceivers  One is for a dedicated control channel and the other is for a data channel.  In the control channel the time is divided into time slots and each slot contains two phases; reporting phase and negotiation phase.  When a node wants to transmit data, it first senses the channels and reports the channel state.  If one channel is idle, it negotiates with the destination over the control channel on which channel to be used.  Two sensing policies are used: • Random Sensing Policy(RSP) • Negotiation-based sensing policy (NSP) King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 17
  • 18. Hang Su and Xi Zhang's MAC Protocol. King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 18
  • 19. HC-MAC protocol  Assumes that a control channel is available for secondary users at any time.  Each SU is equipped with single transceiver.  Time frame is divided into three time slots, each with three phases; contention phase, sensing phase, and transmission phase.  In contention phase, secondary users content the spectrum and reserve channels.  In sensing phase, they conduct sensing in each channel.  In transmission phase, secondary user will transmit data in channels sensed ideal. Contention Sensing Transmission Phase Phase Phase King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 19
  • 20. HC-MAC protocol King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 20
  • 21. Noun Choi et al MAC Protocol  This protocol assumes that there are two transceivers at least for each node.  One is used for transmitting data while the other is used for receiving data.  Each node chooses an available channel and keep it as its Home Channel (HCh) which its information are broadcasted into a common control channel to its neighbors.  If a node wants to transmit data to another one, it has to tune its transmitting radio to the HCh of the destination node.  Another HCh is selected in the following cases: o PU returns to use the same channel. o Any disagrees with the node's HCh. o The selected HCh is noisy. King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 21
  • 22. Noun Choi et al MAC Protocol King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 22
  • 23. A comparison between some Cognitive Radio MAC protocols King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 23
  • 24. Summary  The use of Multi-channel facilitates and improves many communication systems.  Multi-channel MAC protocols have many categories and ways to be established.  Cognitive Radio is a new idea aims to utilize the maximum bandwidth available.  Cognitive Radio MAC protocols are based on Multi-channel MAC protocols with a lot of concern in channel sensing and distribution. King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 24
  • 25. THANK YOU King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology