Design of Multiuser Pre-Rake Systems for Reliable Ultra-Wideband Communications

1. Design of Multiuser Pre-Rake
Systems for Reliable
Ultra Wideband
Ultra-Wideband Communications
ZAHRA AHMADIAN
MICHAEL B. SHENOUDA
LUTZ LAMPE

2. Overview
 I t d ti
Introduction to P R k UWB
t Pre-Rake
 System Model
 Problem Formulation
 Convex Problem Formulation
 Results
 Conclusion

3. Introduction to Pre-Rake UWB 1/2
 Traditional Rake Receiver
 Pre-Rake Transmission
P E
Pre-Equalized P R k
li d Pre-Rake

4. Introduction to Pre-Rake UWB 2/2
 MISO Pre-Equalized Pre-Rake (Torabi et al. 2009)
 Multiuser MISO Pre-Equalized Pre-Rake

5. System Model
Transmitter Receiver
• Multiple Antenna Central transmitter • Single Antenna Receiver
• Pre-Equalizing Filter • De-Spreading Filter
• Up Sampler • Down Sampler
• Spreading Code • Equalizing Gain
• Pre-Rake Filter • Demodulator

6. System Model
 Channel impulse responses generated according to
802.15.4a
802 15 4a model
 Discrete time baseband channel impulse response
root-raised cosine pulse shaping filters
p p g

7. System Model
 Discrete-time complex base-band received signal
p g

8. Problem Formulation
Where, is the total transmit power and σu2 is the mean-square error.

9. Convex Problem Formulation
where .

10. Results 1/3
26
 = 0.08
24  = 0.1
22
20
18
 [dB]
16
14
12
10
8
5 10 15 20
Lq

11. Results 2/3
CM2 CM6
0.3 0.3
Lq = 10 Lq = 10
Lq = 20 Lq = 20
0.25 0.25
0.2 0.2
0.15 0.15


0.1 0.1
0.05 0.05
0 0
5 10 15 20 25 5 10 15 20 25
 [dB]  [dB]

12. Results 3/3
350
 = 0 08 CM2
0.08
300
 = 0.10 CM2
 = 0.08 CM6
 = 0.10 CM6
250
# of channels with  < X
200
150
f
100
50
0
5 10 15 20 25 30 35 40
X [dB]

13. Conclusion
 We have proposed the use of multiuser pre-equalization
filters to mitigate the effect of ISI and MUI.
 We have formulated the filter optimization problem
pertinent for the operation of such UWB systems
systems.
 We have shown that this problem is equivalent to a convex
QCQP problem
 The numerical results illustrated the efficacy of multiuser
pre-equalization to achieve quality of service constraints
with a minimal power budget
budget.
Future work
• Design of multiuser pre-equalization filters subject to
pre equalization
spectral mask constraints.

14. Thank you
QUESTIONS ?