multi channel protocols in cognitive radio networks

Multi-Channel MAC Protocols in Cognitive Radio Networks

Prepared by:Mohammad J. AbdelhadiMuhammad K. Mustafa

King Abdullah II School of Electrical Engineering Princess Sumaya University for Technology

King Abdullah II School of Electrical Engineering - Princess Sumaya University for Technology

Multi-channel MACMulti-channel MAC ApproachesWhat is Cognitive Radio(CR)?Overview of some Cognitive multi-channel

MAC protocols.

Outline

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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

Multi-channel MAC

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Multi-channel MAC

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There are three main approaches for Multi-channel MAC

• Common Control Channel Approach(CCC).• Split Phase Approach(SP).• Common Hopping Approach(CH).

Multi-channel MAC Approaches

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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.

Common Control Channel Approach

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Common Control Channel Approach

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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

Split phase Approach

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Split phase Approach

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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

Common Hopping Approach

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Common Hopping Approach

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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.

Default Hopping Sequence Approach

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The main aim behind CR is to utilize the unused spectrum ata 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.

What is Cognitive Radio

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FCC: In most places, Over 70% of the allocated spectrum is not used !

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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.

Cognitive MAC protocols and its Fundamentals

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Hang Su and Xi Zhang's MAC Protocol.

HC-MAC protocol.

Noun Choi et al protocol.

Some Cognitive MAC protocols

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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)


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Assumes that a control channel is available for secondary usersat 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.

HC-MAC protocol

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Contention Phase

Sensing Phase

Transmission Phase


HC-MAC protocol

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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.

Noun Choi et al MAC Protocol

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Noun Choi et al MAC Protocol

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A comparison between some Cognitive Radio MAC protocols

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The use of Multi-channel facilitates and improves many communication systems.

Multi-channel MAC protocols have many categories and ways tobe 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.

Summary

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THANK YOU

King Abdullah II School of Electrical Engineering - Princess Sumaya University

for Technology

multi channel protocols in cognitive radio networks

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