18-04-2011, 10:38 AM
Presented By,
Manoj Sudharshan J
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Wireless Interrupt: Inter-Device Signaling in Next Generation Wireless Networks
ABSTRACT
Recent advances in wireless technique which has led to the rapid reproduction of wireless devices.
Even greater increase in number of wireless services.
FLEXIBILITY and INTEROPERABILITY are the main factors for the success of future wireless networks
Main aim of this is to investigate the Technical issues that must be overcome in dealing with flexibility and interoperability
Device discovery is the main issue
Therefore Wireless Interrupt has been proposed to solve the problem of Device discovery
INTRODUCTION TO NEXT GENERATION WIRELESS NETWORK
The prediction of future wireless technology is difficult but the trends in which it has emerged and developed is unalterable
There are severable aspects of this trend
First, there will be lots of wireless of all kinds
Second, the demand for mobility and portability will keep increasing
Third, there will be greater demand for integrated services
For wireless success to continue necessary features should be provided to keep the trend characterized
RELATED WORK
Flexibility and Interoperable Wireless Networks
In Wireless different technologies have been developed each supporting a specific use
Eg: Recent ipods have come with 3G, Wifi and Bluetooth interfaces.
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
A device is Flexible if it can support multiple wireless modes in a single hardware configuration
Two or more devices are Interoperable if it can communicate with another device that employs a different protocol
Software Defined Radios(SDR’s) can be reconfigured to enable the flexible transformation of device from one mode to another
But putting SDR’s into a practical use is a challenging task due to performance and cost reasons
Software Defined Radio Model
Device Discovery
First step in constructing the interoperable networks is to enable heterogeneous devices to discover each other
Device discovery is not an easy task since a device should discover another device without any a priori information such as protocols, carrier frequency and existence of other devices
There are 2 approaches to solve this problem
To actively send alert messages
To passively listen to other signals and analyze them
WIRELESS INTERRUPT: CONCEPT
• Overview of Wireless Interrupt
To solve the problem of device discovery, explicit signaling is used which we call Wireless Interrupt
• Establishing the Interrupt-Request Line Over the Air
Since there is no dedicated Interrupt request line in Wireless Interrupt it proves to be a great challenge
A solution to this problem is to create a Control channel which is a frequency band dedicated to control message signal
ASYNCHRONOUS RENDEZVOUS SCHEMES
Synchronization between Tx and Rx is not possible in heterogeneous wireless environment
Following 2 properties should be satisfied for ARS
The interrupt signal must be transmitted over N channels with equal probabilities
Two devices make a rendezvous in N channels with equal probabilities
Time should be assumed to be divided into slots of length ‘μ’
Scanning
A concept Expected overlap is introduced here
In simple scanning Tx transmits its interrupt signal in one channel at a time while the receiver uniformly picks a channel and monitors it
Expected Overlap for Simple Scanning is given by
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
Expected Overlap for Enhanced Scanning is given by
Drawback of Scanning
The drawback of Scanning is that 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 and Scheme
PRELIMINARY TESTS
• TTR - Time to rendezvous
• CBR - Constant bit rate
WIRELESS SERVICES
Common examples of wireless equipment in use today include:
Professional LMR (Land Mobile Radio) and SMR (Specialized Mobile Radio)
Consumer Two way radio
The Amateur Radio Service
Consumer and professional Marine VHF radios
Cellular telephones and pagers
Global Positioning System (GPS)
Cordless telephone sets
Satellite television
APPLICATIONS
Security systems
Cellular telephone (phones and modems)
Wi-Fi
Computer interface devices
MERITS AND 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 AND FUTURE WORK
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
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