Cooperation and cognition in MIMO cognitive networks
Ying Chang, Andrea Goldsmith
ACHIEVEMENT DESCRIPTION
MAIN ACHIEVEMENT:
Single-primary-user
cognitive network
Pp=5
7
3.4
IMPACT
SVD
P-SVD
D-SVD
6
3.6
5
3.2
Rs
3
3
2.8
2.6
2
2.4
1
• In literature, achievable rates of
single-antenna secondary user is
well studied
• How to do cooperation and
cognition with multiple antennas and
multiple primary users is our main
focus
2.2
2
0.4
0
0
0.6
0.8
1
1.2
Rp
1.4
1.6
1.8
2
4
6
8
10
Ps
2
12
14
16
18
20
• Proposes practical strategy
for cognition and cooperation
in MIMO system
1.3
1.2
MISO , single primary user
1
SVD
P-SVD
D-SVD
0.8
5
0.7
4
0.6
0.5
3
0
0
2
4
6
16
18
20
HOW IT WORKS:
Secondary user has non causal knowledge of primary
users’ transmission and performs cognition together with
cooperation to compensate the interference to primary
receiver.
We study the cases with MISO and MIMO secondary
transmission system and multiple primary receivers.
ASSUMPTIONS AND LIMITATIONS:
•
Primary users’ transmission rate is unchanged
0.8
Rp1
1
1.2
1.4
• Study multiple primary receivers
with multiple antennas
• Information theoretical bounds on
MIMO cognitive networks
7
SVD
P-SVD
D-SVD
SVD
P-SVD
D-SVD
6
Interestingly, we find out the
relation between primary users’
sum rate and cognitive user’s
transmission rate is non
monotonic.
Pp=15
Pp=5
6
5
5
4
4
3
3
2
• Direct Channel SVD (D-SVD)
0.14
2
1
0.13
1
0
0
The precoding matrix is obtained from the SVD of the cognitive
user’s channel
1.6
When the capacity region of
primary broadcast channel is
achieved the transmission
rate for cognitive user is
illustrated as follows:
7
In this case, we have a MIMO cognitive transmission pair. We
propose a two sub-optimal transmission strategies for
cognitive user:
• Projected Channel SVD (P-SVD)
3.8
0.6
In MIMO networks, we are more flexible to deal with interference
2
4
6
8
10
Ps
12
14
16
18
20
0.12
0
0
2
4
6
8
10
Ps
12
14
16
18
20
0.11
0.1
Pp=15
Pp=5
7
7
SVD
P-SVD
D-SVD
SVD
P-SVD
D-SVD
0.09
6
6
4
0.4
To maintain the capacity
region of primary users, the
cognitive user cooperate with
each primary receiver. Power
allocation scheme is
developed for MISO and
MIMO cognitive user.
Rs
In this case, we have a MISO cognitive
transmission pair. We propose a optimal
transmission strategy for cognitive user
through project the beamforming vector onto
orthogonal and aligned channel components.
The relation between primary user’s rate and
cognitive user’s rate is illustrated as follows:
14
0.2
Single primary user
MIMO cognitive user
MISO cognitive user
12
NEXT-PHASE GOALS
NEW INSIGHTS
Encoding rule for the cognitive
user: The cognitive encoder acts in
two stages. For every message pair
(mp, mc), the cognitive encoder first
generates a codeword for the
primary message mp. In the second
stage, the cognitive encoder
generates a codeword for mc using
Costa pre-coding. The two
codewords are superimposed to
form the cognitive codeword.
• Decompose the MIMO
channel into orthogonal
components and leverage
secondary user’s
beneficial and
deteriorative impact to the
primary user.
• Introduce cooperation to
broadcast system
10
Ps
MIMO
MISO
multiple primary users
8
0
• Finds out the relation between
secondary user’s achievable
rate and primary user’s power
allocation scheme
1
To not impact the transmission rate
of primary (licensed) user, the
cognitive user performs cooperation
to compensate its interference to
the primary user.
0.9
6
2
How to utilize new
degrees of freedom
brought by MIMO
technique?
In this case, the primary
transmitter broadcasts to
several primary receivers.
1.1
Pp=5
7
Rs
We consider a MIMO cognitive
network as in the following picture.
The cognitive transmitter determines
its codeword as a function of the
messages mp and mc .
STATUS QUO
4
System model
Multi-primary-user
cognitive networks
• Derives the optimal
achievable rate for MISO
secondary users under
coexistence constraints
4
3.8
0.08
5
5
4
4
3
3
2
2
1
1
0.07
3.6
The cognitive user’s channel is projected onto the null space of
the channel between cognitive transmitter and primary
receiver. Than SVD is performed on the projection.
3.4
Rs
3.2
3
2.8
2.6
2.4
2.2
2
0.4
0.6
0.8
1
1.2
Rp
1.4
1.6
1.8
2
Under different power constraint, the performances of the two
strategies are compared with the MIMO channel capacity.
0
0
2
4
6
8
10
Ps
12
14
16
18
20
0
0
0.06
0.05
0.04
2
4
6
8
10
Ps
12
14
16
18
20
1.3
1.4
1.5
1.6
Rps
1.7
1.8
1.9
2