29-07-2011, 04:47 PM
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Wireless Interrupt: Inter-Device Signaling in Next Generation Wireless Networks
INTRODUCTION
Advanced Technology-Increase in wireless devices & wireless services
Demand for mobility , portability & integrated services
For success to continue-devices should support flexibility & interoperability
Heterogeneous devices should communicate with each other
Problem-Device Discovery-
Introduce Wireless Interrupt in SDRs
EXISTING SYSTEM
In Wireless different technologies have been developed each supporting a specific use
Portable wireless devices are now common
Multiple services are now seen in devices
Eg: Recent ipods & mobiles have come with 3G, Wi-fi and Bluetooth interfaces.
LIMITATIONS
Such parallel brewing of technologies will hinder further innovations mainly due to two limitations
A separate radio hardware architecture
Devices using different protocols cannot directly communicate with each other
Flexibility & Interoperability
flexibility-Can support multiple wireless modes with a single hardware configuration and can switch from one mode to another seamlessly
Deals with device design
Interoperability-Devices are interoperable if they can communicate with another device that employs a different protocol
Deals with networking the devices
Existing eg:-SDR
Issue with performance & cost
Software Defined Radio Model(SDR)
First Step : Inter Device Signaling & Device Discovery
Enabling heterogeneous devices to discover each other
Not an easy task
Device discovery problem-How can a device discover another if it does not have any priori information such as
What protocol(PHY or MAC) the other device is using
What carrier frequency the other device is operating in &
Whether there exist any other device to begin with
While allowing each device to implement its own local policies without changing existing protocols
Proposed Solutions
2 solutions proposed
1-Actively send alert messages
2-Passively listen to signals from other devices and analyzing them(looking for a known pattern)
Latter –difficult-requires detector-hurts scalability
preferred-Wireless Interrupt
HRDWARE INTERRUPT
HWI : Features
Has an interrupt request line
Provides many desired features of our purpose
1-we are interested in making a device alert another
2-Alerting is a rare event-
3-Each device must be able to enforce its own set of policies in handling these alerts
WIRELESS INTERRUPT:-CONCEPT
Features
Controller receives the interrupt signal
Choices-
ignore the signal
Reconfigure itself to another mode
Respond to originator
No interrupt request line-great challenge
Share with all devices-
Same transceiver for both interrupt and data signals-challenge-2
OVERVIEW OF WI PROCESS
ESTABLISHING INTERRUPT REQUEST LINE OVER THE AIR
Quick and dirty solution-Control channel-frequency band dedicated to contr0l message exchanges
Control channel saturation problem
Adopt TDMA like scheme
Controller of SDR periodically changes to interrupt mode
Tp (monitor interval)-receiver halts normal operation
Tm (monitor duration)-monitor for interrupt signals
In Tm –Tx and Rx-channel –rendezvous-MTTR
In heterogeneous system-Ts ≥ Tp+Tm –Ts-Signal duration(practical)
EXAMPLE
PROBLEM LIMITED TO-
How can two nodes make a rendezvous in a finite and possibly short time assuming no synchronization
How can transmitter encounter as many receivers as possible in a finite time
ASYNCHRONOUS RENDEZVOUS SCHEMES
Synchronization between Tx and Rx is not possible in heterogeneous wireless environment
Time is divided into slots of duration μ
Whole spectrum range is divided into N equally sized channels
2 properties
The interrupt signal must be transmitted over N channels with equal probabilities
Two devices make a rendezvous in N channels with equal probabilities
SCANNING
A concept Expected overlap is introduced here
Round Robin fashion
In simple scanning Tx transmits its interrupt signal in one channel at a time while the receiver uniformly picks a channel and monitors it
Limitation-Chance of complete overlap
EXAMPLE
ENHANCED SCANNING
Enhanced Scanning can be done by Scrambling the order of channel hops by defining (N-1) sequences
Tx then selects one of the (N-1) hopping sequences to transmit the interrupt signals
Exactly one overlap after every N slots
DRAWBACKS
The receiver sits in one channel to monitor signals.
If that channel is bad (e.g. interference) for the monitor duration of the receiver, then it cannot pick up any of the signals.
It is, therefore, preferred to make the receiver channel-hop along with the transmitter to add a degree of channel diversity, and it must be done carefully to not break the rendezvous guarantee, leading to the next scheme
QUORUM BASED
A quorum system is a set S = {S1, S2, ..., SN}, where Si is a subset of some universe U, such that ∀Si, Sj ∈ S, Si∩Sj ̸= ϕ
Given a quorum system S over U, a transmitter and a receiver pick quorums Si and Sj , respectively
The transmitter transmits an interrupt signal via the channels in Si in a certain order, repeatedly
The receiver visits the channels in Sj in a certain order, repeatedly, each time circularly shifting the order by one.
Quorum System Table & Scheme
MERITS & DEMERITS
MERITS
Mobility
Neat and easy Installation
Less cost
More user supported
Flexible
DEMERITS
Lower speed
Less secure
More complex
Attenuation(Affected by surrounding environment)
CONCLUSION
In this paper, the research authors has examined the issue of networking flexible wireless devices, such as software defined radios (SDRs), by proposing a signaling mechanism called Wireless Interrupt
The challenges were
No priori information about neighboring devices at the transmitter end
To guarantee a quick delivery of the message when there are multiple channels
They have proposed two channel rendezvous schemes and analyzed their characteristics
They argued that such inter-device signaling and device discovery is the first step towards the construction of Next Generation Wireless networks
Wireless Interrupt: Inter-Device Signaling in Next Generation Wireless Networks
INTRODUCTION
Advanced Technology-Increase in wireless devices & wireless services
Demand for mobility , portability & integrated services
For success to continue-devices should support flexibility & interoperability
Heterogeneous devices should communicate with each other
Problem-Device Discovery-
Introduce Wireless Interrupt in SDRs
EXISTING SYSTEM
In Wireless different technologies have been developed each supporting a specific use
Portable wireless devices are now common
Multiple services are now seen in devices
Eg: Recent ipods & mobiles have come with 3G, Wi-fi and Bluetooth interfaces.
LIMITATIONS
Such parallel brewing of technologies will hinder further innovations mainly due to two limitations
A separate radio hardware architecture
Devices using different protocols cannot directly communicate with each other
Flexibility & Interoperability
flexibility-Can support multiple wireless modes with a single hardware configuration and can switch from one mode to another seamlessly
Deals with device design
Interoperability-Devices are interoperable if they can communicate with another device that employs a different protocol
Deals with networking the devices
Existing eg:-SDR
Issue with performance & cost
Software Defined Radio Model(SDR)
First Step : Inter Device Signaling & Device Discovery
Enabling heterogeneous devices to discover each other
Not an easy task
Device discovery problem-How can a device discover another if it does not have any priori information such as
What protocol(PHY or MAC) the other device is using
What carrier frequency the other device is operating in &
Whether there exist any other device to begin with
While allowing each device to implement its own local policies without changing existing protocols
Proposed Solutions
2 solutions proposed
1-Actively send alert messages
2-Passively listen to signals from other devices and analyzing them(looking for a known pattern)
Latter –difficult-requires detector-hurts scalability
preferred-Wireless Interrupt
HRDWARE INTERRUPT
HWI : Features
Has an interrupt request line
Provides many desired features of our purpose
1-we are interested in making a device alert another
2-Alerting is a rare event-
3-Each device must be able to enforce its own set of policies in handling these alerts
WIRELESS INTERRUPT:-CONCEPT
Features
Controller receives the interrupt signal
Choices-
ignore the signal
Reconfigure itself to another mode
Respond to originator
No interrupt request line-great challenge
Share with all devices-
Same transceiver for both interrupt and data signals-challenge-2
OVERVIEW OF WI PROCESS
ESTABLISHING INTERRUPT REQUEST LINE OVER THE AIR
Quick and dirty solution-Control channel-frequency band dedicated to contr0l message exchanges
Control channel saturation problem
Adopt TDMA like scheme
Controller of SDR periodically changes to interrupt mode
Tp (monitor interval)-receiver halts normal operation
Tm (monitor duration)-monitor for interrupt signals
In Tm –Tx and Rx-channel –rendezvous-MTTR
In heterogeneous system-Ts ≥ Tp+Tm –Ts-Signal duration(practical)
EXAMPLE
PROBLEM LIMITED TO-
How can two nodes make a rendezvous in a finite and possibly short time assuming no synchronization
How can transmitter encounter as many receivers as possible in a finite time
ASYNCHRONOUS RENDEZVOUS SCHEMES
Synchronization between Tx and Rx is not possible in heterogeneous wireless environment
Time is divided into slots of duration μ
Whole spectrum range is divided into N equally sized channels
2 properties
The interrupt signal must be transmitted over N channels with equal probabilities
Two devices make a rendezvous in N channels with equal probabilities
SCANNING
A concept Expected overlap is introduced here
Round Robin fashion
In simple scanning Tx transmits its interrupt signal in one channel at a time while the receiver uniformly picks a channel and monitors it
Limitation-Chance of complete overlap
EXAMPLE
ENHANCED SCANNING
Enhanced Scanning can be done by Scrambling the order of channel hops by defining (N-1) sequences
Tx then selects one of the (N-1) hopping sequences to transmit the interrupt signals
Exactly one overlap after every N slots
DRAWBACKS
The receiver sits in one channel to monitor signals.
If that channel is bad (e.g. interference) for the monitor duration of the receiver, then it cannot pick up any of the signals.
It is, therefore, preferred to make the receiver channel-hop along with the transmitter to add a degree of channel diversity, and it must be done carefully to not break the rendezvous guarantee, leading to the next scheme
QUORUM BASED
A quorum system is a set S = {S1, S2, ..., SN}, where Si is a subset of some universe U, such that ∀Si, Sj ∈ S, Si∩Sj ̸= ϕ
Given a quorum system S over U, a transmitter and a receiver pick quorums Si and Sj , respectively
The transmitter transmits an interrupt signal via the channels in Si in a certain order, repeatedly
The receiver visits the channels in Sj in a certain order, repeatedly, each time circularly shifting the order by one.
Quorum System Table & Scheme
MERITS & DEMERITS
MERITS
Mobility
Neat and easy Installation
Less cost
More user supported
Flexible
DEMERITS
Lower speed
Less secure
More complex
Attenuation(Affected by surrounding environment)
CONCLUSION
In this paper, the research authors has examined the issue of networking flexible wireless devices, such as software defined radios (SDRs), by proposing a signaling mechanism called Wireless Interrupt
The challenges were
No priori information about neighboring devices at the transmitter end
To guarantee a quick delivery of the message when there are multiple channels
They have proposed two channel rendezvous schemes and analyzed their characteristics
They argued that such inter-device signaling and device discovery is the first step towards the construction of Next Generation Wireless networks
