EVERYTHING ABOUT SPECTRUM ACCESS IN COGNITIVE RADIO

1. BY
SANJANA PRASAD
Research scholar
PSG COLLEGE OF TECHNOLOGY
1601RL01

2.  New spectrum sharing paradigm that allows
secondary users to access the abundant
spectrum holes or white spaces
 Promising technology to alleviate the
spectrum scarcity problem
 Increase spectrum utilization
 Overcomes two types of interference
◦ Harmful interference caused by device
malfunctioning
◦ Harmful interference caused by malicious user

3.  Secondary users dynamically search for idle
spectrum bands and temporarily access them
for wireless communications
 To avoid interference to primary users (PU)’s
secondary users continuously monitor the
spectrum bands and yield to PU’s whenever
PU start using a band .
 Dsa-made possible-cr technology

4.  Functions of DSA :
◦ Spectrum awareness
◦ Cognitive processing
◦ Spectrum access
 COMPONENTS OF A COGNITIVE RADIO:
◦ Analog RF front end
◦ A digital processing engine
◦ Digital signal processor
◦ Customized FPGA

5.  Dynamic exclusive use
 Open sharing model
 Hierarchial access model
 Dynamic Exclusive Use model:
◦ Basic structure of the current spectrum regulation
policy are maintained in this model
◦ Spectrum bands licensed to services for exclusive
use
◦ Improves spectrum efficiency by introducing
flexibility

7. 2 approaches:
 Spectrum property rights
 Dynamic spectrum allocation
Spectrum property rights:
Allows licensees to sell and trade spectrum and
to choose technology freely
Economy,profit- play important role with the
most profitable use of this limited resource

8.  Dynamic spectrum allocation
◦ Improve efficiency through spectrum assignment by
using spatial / temporal traffic statistics of different
services

9.  Open sharing model:
 Spectrum commons model
 Every user has equal rights to use the
spectrum
 Applied for wireless services which operates
in unlicensed ISM radio bands(WLAN)
 3 TYPES:
 Uncontrolled commons
 Managed commons
 Private commons

10.  Uncontrolled commons
 No entity has exclusive license to the
spectrum band
 Managed – commons
◦ Imposes a limited form of structure of spectrum
access
◦ Resource which is owned or controlled by a group
of individuals or entities
◦ Characterized by restrictions on when and how the
resource is used.

11.  Private commons:
◦ Introduced by FCC.
◦ allows advanced technologies which enable multiple
users to access the spectrum
Hierarchial access models :
 Interweave
 Underlay
 Overlay

12.  Different from overlay and underlay DSA
models
 SU cannot access a licensed spectrum band
as long as PU is active on the band
 PU-absolute priority on the spectrum band
 SU accessing the spectrum band must yield to
PU whenever PU starts to access the band
 Also called oppurtunistic spectrum access.

13.  SU’ s are constrained to oppurtunistically
utilise spectrum holes or white spaces in the
temporary ,spatial,and/or frequency domain.
 SU uses SR –sense the sorounding
environment
 Selects one or more idle spectrum bands
 Switches the cognitive radio to the selected
bands to transmit

15.  Allows SU to transmit on a licensed spectrum
band regardless of the PU accessing the band
or not, subject to a constraint that the
accumulated interference from all SU’s is
tolerable by the PU ie. below some threshold
 2 approaches
◦ UWB TECHNOLOGY
◦ INTERFERENCE TEMPERATURE

16.  UWB Technology
◦ SU transmit power
◦ Interference < threshold
 Interference temperature
◦ SU transmit with higher power as long as the total
interference from all SU’s on the band is below a
threshold.

17.  SU transmit on the licensed spectrum band
even when the PU is accessing the band.
 Targets maintaining the PU performance
 SU are allowed to transmit simultaneously
with PU s as long as there is no performance
degradation
 2 approaches:
◦ Channel coding
◦ Network coding

18. Channel coding Network coding
 Used when a PU
transmitter is
transmitting a PU packet
that is known to a SU
transmitter
 Su transmitter- can split
into two parts-
◦ One to transmit its own SU
packet
◦ Transmit PU packet to
enhance the total power
received such that SINR not
degrade
 Su-relay – between
disconnected or weakly
connected nodes.
 While relaying a PU
packet:
◦ SU may encode an SU
packet onto the PU packet
through network coding
◦ transport of the SU packet
does not incur separate
spectrum access ,without
degrading the PU
performance .

20.  Accurate spectrum sensing
 Uncertainity of noise
 PUE attacks

21. [1]Min Song,Chunsheng Xin,Yanxiao
Zhao,Xiuzhen Cheng “Dynamic Spectrum
Access: From Cognitive Radio To Network
Radio”,IEEE Wireless Communications,Feb 2012.
[2]Goutam Ghosh,Prasun Das,Subhajit
Chatterjee ,“Cognitive Radio And Dynamic
Spectrum Access-a Study”,International Journal
Of Next Generation Networks,Vol 6,No 1 ,March
2014