Multi-Channel MAC Protocols in Cognitive Radio Networks

1. Multi-Channel MAC Protocols in Cognitive Radio Networks Prepared by: Muhammad K. Mustafa Mohammad J. Abdelhadi 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 Interference among users • Higher throughput • Less normalized propagation delay per channel 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 four main approaches for Multi-channel MAC • Common Control Channel Approach(CCC). • Split Phase Approach(SP). • Common Hopping Approach(CH). • Default Hopping Sequence Approach(DHS). 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 schedule sequence. • Same advantages and disadvantages of CH. King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 11

13. Default Hopping Sequence Approach King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 12

14. 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

15. 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

16. 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

17. 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

18. 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

19. Hang Su and Xi Zhang's MAC Protocol. King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 18

20. 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 Phase Sensing Phase Transmission Phase King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 19

21. HC-MAC protocol King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 20

22. 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: • PU returns to use the same channel. • Any disagrees with the node's HCh. • The selected HCh is noisy. King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 21

23. Noun Choi et al MAC Protocol King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 22

24. A comparison between some Cognitive Radio MAC protocols King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology 23

25. 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

26. THANK YOU King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology