1. A New Differential Space-Time Modulation Scheme based on Weyl Group
11th International Symposium on Signals, Circuits and Systems (ISSCS 2013)
, July, 2013, Iasi, Romania
A New Differential Space-Time Modulation Scheme based on Weyl Group
JI Hui, Gheorghe Zaharia and Jean-François Hélard
Institute of Electronics and Telecommunications of Rennes (IETR)
Institut National des Sciences Appliquées (INSA), France

2. Outline Differential Space-Time Modulation (DSTM)
New scheme for MIMO systems
Simulation and comparison
Conclusions 1

3. Outline Differential Space-Time Modulation (DSTM)
New scheme for MIMO systems
Simulation and comparison
Conclusions 1

4. Differential Space-Time Modulation
Advantage: not require channel state information
Used for MIMO systems with large number of antennas
Used for MIMO systems when the propagation channel changes rapidly
Existing differential space-time modulation schemes:
Differential space-time block codes (DSTBC)
Differential unitary space-time modulation (DUSTM) … 2

5. Differential Space-Time Modulation
System model:
Fundamental differential transmission relation:
where
is a unitary matrix which carries information
The relation between two successively received signals:
The maximum likelihood demodulation : 3

6. Outline Differential Space-Time Modulation (DSTM)
New scheme for MIMO systems
Simulation and comparison
Conclusions 4

7. The constellation of the new scheme
For MIMO systems with 2 transmit antennas, the transmitted information matrices are selected from the Weyl group Gw (192 unitary matrices, 2×2).
The Weyl group is a set that contains 12 cosets.
with
where the matrices are: 5

8. The constellation of the new scheme
The distance between two matrices Ma and Mb:
The distance spectrum of the Weyl group: 6

9. The scheme with 2 transmit antennas
Fundamental differential transmission relation: …
There are 192 matrices in the Weyl group, the maximum spectral efficiency is 7

10. The scheme with 4 transmit antennas
Kronecker product is used to expand the Weyl group
For example, for R = 1 system
where
Actually, there are 4608 distinct matrices in the new group Gw4. The maximum spectral efficiency is 8

11. The scheme with 4 transmit antennas
The performance can also be improved considering the distance spectrum
For example, for R = 2 system, we select the first 16 matrices from every successive 192 matrices of the group Gw4, i.e., the set is
This set has a better distance spectrum than the original one. Simulation results show the advantage of using this set. 9

12. Outline Differential Space-Time Modulation (DSTM)
New scheme for MIMO systems
Simulation and comparison
Conclusions 10

13. Comparisons
Performance comparison for 2 transmit antennas of different schemes (R=2) 11

14. Performance comparison for 4 transmit antennas of different schemes
Comparisons
Performance comparison for 4 transmit antennas of different schemes 12

15. Simulation results for different spectral efficiencies
Performance for 4 transmit antennas with different spectral efficiencies 13

16. Outline Distributed MIMO broadcasting
Space-Time codes for distributed MIMO broadcasting
Simulation and comparison
Conclusions 14

17. Conclusions The new 4×4 MIMO scheme
higher spectral efficiency than Tarokh’s Differential STBC scheme
the BER performance can be improved by selecting the set of transmission matrices having the best distance spectrum
Can be expanded to MIMO systems with 8 transmit antennas 15

18. Thank you!