Cognitive Radio for Dynamic Spectrum Allocation Systems

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Cognitive Radio for Dynamic Spectrum Allocation
Systems
Xiaohua (Edward) Li and Juite Hwu Department of
Electrical and Computer Engineering State
University of New York at Binghamton xli,jhuw1_at_b
inghamton.edu
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1. Introduction

• DSA (Dynamic Spectrum Allocation)
• What is this?
• New spectrum management rules.
• Why do we need it?
• For efficiently utilizing spectrum
• How to apply it?
• Two primary methods to approach

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1. Introduction (cont)

• Basic idea
• Licensed and unlicensed users access the spectrum
  at different time period.
• Licensed and unlicensed users access the spectrum
  simultaneous with proper power.

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1. Introduction (cont)

• Our task
• The 2nd method will be applied.
• We use two different analysis approaches, one is
  theoretical and the other is simulation.
• If allowed, find the maximum capacity that
  unlicensed user can obtain.

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1. Introduction (cont)

• Access protocol
• Give a very small power for the secondary
  transmitter.
• Check the SINR of primary receivers.
• Adjust the power of secondary transmitter
  according to the ACK.
• Repeat step 2 and 3, find the maximum power of
  secondary transmitter which is allowed.

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2. System Model

• Structure
• T0 primary transmitter
• T1,T2 secondary transmitters
• Circles the coverage range of different antennas

• Channel access protocol

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2. System Model (cont)
For successful transmissions, the power of
transmitter has to satisfy the equation
N noise power (include AWGN and other
transmitters power) a path-loss exponent K
constant ?0 SINR G0 minimum required SINR of T0
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2. System Model (cont)
Fig. 1
Fig. 2
Here, we separate our scheme into two different
cases. If we can find a receiver that has the
minimum SINR, the threshold can be examined
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2. System Model (cont)

• At Fig.1 Rx0 has the smallest SINR., For Fig.2,
  Rx0 and Rx1 have the minimum SINR.
• Why do we need the smallest SINR?
• Its our threshold and the worst case!!
• Capacity calculation

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3. Capacity of a single secondary transmitter
One secondary transmitter only (Tx1), and primary
receivers are distributed uniformly in a circle
made by Tx0
r0
Receivers with density ß
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3. Capacity of a single secondary transmitter
(cont)
x
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3. Capacity of a single secondary transmitter
(cont)
P0 power of primary transmitter P1(x) power of
secondary transmitter N very small noise power
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3. Capacity of a single secondary transmitter
(cont)

• Take the expect

• Why do we need this?
• We have to consider all locations that primary
  receivers may be placed.

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3. Capacity of a single secondary transmitter
(cont)
For convenience, we use polar coordinate system
instead of Cartesian
SINR of Rx is
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3. Capacity of a single secondary transmitter
(cont)

• The capacity of the transmission is

• So the average capacity is written as

The discussion above is based on one fixed
receiver, how about the receiver is moving?
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3. Capacity of a single secondary transmitter
(cont)
Best case
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3. Capacity of a single secondary transmitter
(cont)
Worst case
Fig. 1
Fig. 2
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3. Capacity of a single secondary transmitter
(cont)

• Why do we need the range?
• This range gives us the best and worst case that
  we can calculate the capacity gain

• Compare it with the loss of primary transmitter
  capacity
• Secondary access protocol provide large capacity
  when y is small

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4. Capacity of multiple secondary transmitters

• The scheme
• The primary spectrum access is keeping stable
• No interference between any two secondary
  receiver

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4. Capacity of multiple secondary transmitters

• Consider a special case

A(y,x) is the area of the cross section between
the circle of radius y and the circle of radius r1
Fs(y,x) is the cumulative distribution that all
secondary transmitters are inside a circle of
radius x centered around T0
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4. Capacity of multiple secondary transmitters
Consider R0 with a distance x from T0, and to
which all secondary transmitters have distance at
most y. The upper bound is obtained with the
equality sign
According to this bound, we can find the maximum
capacity
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5. Simulation

• One secondary transmitter
• Multiple primary receivers
• Two approach methods

Parameters PT0100 watts
PAWGN N510-10 GTGR1 (transmitter
and receiver gain) r01000 (m)
a3 (urban area) G020dB
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6. Conclusion

• d increase, the power from Tx0 decrease, P1
  decrease, but the capacity raise still.
• Our scheme provide a large capacity
• (GSM cellular provides 1.35bps/Hz)

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• Thank you
• and

Any question?