final wran
DESCRIPTION
PresentationTRANSCRIPT
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Group Members:
1.Maidha Shoukat
2.Asia Aman
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Background
Introduction
Why IEEE 802.22
Concept Of cognitive Radio
Basics Of IEEE 802.22 WRAN
Air Interface
Advantages and Disadvantages
Conclusion
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The IEEE 802.22 standard for a Wireless Regional Area
Network was formally approved on July 2011
In recent years there is a rapid growth in the field of wireless
services
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One particular technology that may bring better spectrum
utilization is that of cognitive radios technology
By using CR technique the radios can sense their
environment and adapt accordingly. The use of cognitive
radio technology is therefore key to the new IEEE 802.22
WRAN standard
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The IEEE 802.22 standard defines a system for a Wireless
Regional Area Network, WRAN that uses unused or white
spaces within the television bands
It utilizes cognitive radio technology to ensure that no
interference is caused to television services by using the
television bands
In this way 802.22 is the first standard to fully incorporate
the concept of cognitive radio
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This standard provides an efficient utilization of UHF and
VHF TV bands between 54 and 862 MHz
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Spectrum scarcity
Demand for higher data rates and coverage
It utilizes TV white spaces
IEEE 802.22 share the geographically unused TV spectrum
in a rural environment to provide broadband access
Use cognitive radio capabilities to avoid interference to
broadcast incumbents and other WRAN systems
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Vacant frequencies made available for unlicensed use at
locations where spectrum is not being used by licensed
services
This spectrum is located in the VHF(54-216 MHz) and UHF
(470-698MHz) frequency bands
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Cognitive radio (CR) is a form of wireless communication in
which a transceiver can intelligently detect which
communication channels are in use and which are not and
instantly move into vacant channels while avoiding occupied
ones
This optimizes the use of available radio-frequency (RF)
spectrum while minimizing interference to other users
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Cognitive radio uses a number of technologies including
Adaptive Radio and Software Defined Radio
In Adaptive Radio the communication system monitors and
modifies its own performance
Software Defined Radio (SDR) where traditional hardware
components including mixers, modulators and
amplifiers have been replaced with intelligent software
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Sensing
CR enables customer premises equipment to sense available channel
Selecting
Select best available channel
coordination
Coordinate spectrum access with other customer premises equipment
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Spectrum Sensing
Spectrum Sharing
Location Identification
Network/System Discovery
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Resource utilization
QoS (Quality of Service)
Incumbent monitoring
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The 802.22 standard includes the following parameters as the
basics of the system
System topology
Coverage area
System capacity
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The 802.22 system is intended
to be a fixed point-to-
multipoint wireless air
interface
In this topology base station
(BS) manages its own cell and
all associated Consumer
Premise Equipments (CPEs),
as shown in Figure
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BS also manages a unique feature of distributed sensing
This is needed to ensure proper incumbent protection and is
managed by the BS, which instructs the various CPEs to
perform distributed measurement of different TV channels
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The coverage area for the
IEEE 802.22 standard is much
greater than many other IEEE
802 standards
The BS coverage range is up
to 100km
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The system has been defined
to enable users to achieve a
level of performance similar
to that of DSL services
available
The downlink or download
speed is around 1.5 Mbps
and an uplink or upstream
speed of 384 kbps
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Base Station
Fixed Station
Decides Channel Availability
Makes Final decision if there is availability of TV channels
Client Station
Customer premises equipment
Fixed location
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The basic specification parameters of the IEEE 802.22
standard can be seen in the table below
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IEEE 802.22 WRAN is established to provide fixed wireless
broadband services using vacant TV channels without causing
harmful interference to incumbent TV broadcast signals
IEEE 802.22 is a standard for Wireless Regional Area
Network using white spaces in the TV frequency spectrum on
a non-interfering basis
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Tolerable level of interference is needed
Reason: In many countries not all available TV channels are
used as it is necessary to allow guard channels between
active high power transmitters to prevent mutual interference
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PHY layer is designed
To support a system that uses vacant TV channels
To provide wireless communication access over distances
of up to 100 km
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PHY specification is based on orthogonal frequency
division multiple access (OFDMA) for both
Upstream (US) access: from CPE to BS with rate 384 kb/s
Downstream (DS) access: from BS to CPE with rate 1.5 Mb/s
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MAC is one of two sub layers that make up the Data Link
Layer of the OSI model
It is responsible for moving data packets to and from one
NIC to another across a shared channel
It determines where one frame starts and other ends
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Frames are grouped into a super frame structure
Super frame allow for better incumbent protection and self-
coexistence
Super frame structure consists of 16 frames
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Each frame consists of:
Super frame preamble used for time synchronization
Frame preamble used for channel estimation
Super frame Control Header (SCH) which carries BS MAC
address along with the schedule of quiet periods for sensing,
as well as other information about the cell. Support the intra-
frame and inter-frame quiet periods management
mechanisms for sensing
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802.22 supports Time Division Duplex (TDD) frame structure
Each frame consists of downlink (DL) sub-frame, uplink (UL)
sub-frame, and the Co-existence Beacon Protocol (CBP)
burst
The UCS window can be used by CPEs to transmit an
indication that an incumbent has been detected on the channel
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A transmit-receive turnaround (TTG) gap is inserted between
the DS and US to allow the CPE to switch between the
receive mode and transmit mode
A receive-transmit turnaround (RTG) gap is inserted at the
end of each frame to allow the BS to switch between its
receiving mode and transmit mode
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The DS/US MAPs are broadcast messages that specify the
resource allocation in the DS and US sub frames, respectively
The SCW is used for execution of the coexistence beacon
protocol (CBP), which involves transmission of coexistence
beacons (or CBP packets) carrying information about the cell
and specific coexistence mechanisms
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Both the BS and CPE have the capability to detect the
presence of an incumbent user on a channel, but the channel
management decisions are made only by the BS
Different techniques used for it are:
Geo-allocation
Global Positioning System (GPS)
Spectrum sensing
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IEEE 802.22 uses lower frequencies
The coverage area for WRAN is much larger than that of other
IEEE 802 standards PAN, LAN & MAN
It provides various type of services like data, voice, audio &
video with appropriate (QOS) support
IEEE 802.22 users are unlicensed users in TV bands and this
decreases the cost of this standard in comparison to some other
standards
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Because the geographical coverage of this standard is in the
range up to 100 Km the propagation delay is more
considerable in this standard in comparison to the others.
Another disadvantage of this standard is the self-
coexistence and hidden incumbent problem.
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IEEE 802.22 is required to reuse the fallow TV spectrum without causing any harmful interference to incumbents (i.e., the TV receivers)
Cognitive radio techniques are of primary importance in order to sense and measure the spectrum and detect the presence/absence of incumbent signals
Base Station and Customer Premise Equipment has Master Slave N/w Architecture
Spectrum sensing is periodically done by BS and CPE CPE Reports spectrum sensing to Base Station (BS) BS makes the final decision
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