1) The document presents a dynamic subcarrier allocation (DSA) scheme called DSA-ESINR that uses estimated signal-to-interference-plus-noise ratio (ESINR) as a metric to allocate subcarriers in a correlated space-division multiple access (SM-OFDMA) system. 2) Simulation results show that DSA-ESINR can minimize the effect of self-interference and improves subcarrier allocation as signal-to-noise ratio increases compared to a baseline DSA scheme. 3) Future work is proposed to study different correlation scenarios, apply adaptive modulation and coding, and analyze self-interference between space-time block coding and spatial multiplexing

1. Dynamic Subcarrier Allocation
with ESINR Metric in
Correlated SM-OFDMA
APCC 2011
Dr. R. Nordin & Prof. Dr. M. Ismail
Universiti Kebangsaan Malaysia

2. Presentation Outline
 Self-interference
 DSA-ESINR
 Simulation Parameters
 Results & Analysis
 Conclusion

3. 3
Correlation in MIMO
 Occurs due to: 12
RBS=0.0,RMS=0.0
RBS=0.4,RMS=0.4
10
RBS=0.5,RMS=0.5
RBS=0.0,RMS=0.9
8 RBS=0.9,RMS=0.0
capacity (bps/Hz)
• antenna location/spacing
RBS=0.9,RMS=0.9
6 RBS=1.0,RMS=1.0
• lack of scatterers 4
• angular spread. 2
0
-10 -5 0 5 10 15 20
SNR (dB)
 Resulting in self-interference.
 Retransmissions and equalisation do not
improve the BER performance.

4. 4
Self-Interference
 MIMO only works when the channel is in
low correlation.
In practice:
h’
s0 h’ r0
r0=r1=h’(s0+s1)
BS h’ MS
Scenario: all spatial layers
`
h’ are fully correlated
s1 r1
Mathematically:
If h’ coefficients are correlated, then [H] is
[S] =[H]-1[R] ill-conditioned matrix and difficult to revert

5. 5
SINR Metric
 As the performance metric to determine the
subcarrier allocation.
MMSE filter
q= spatial layer Main spatial layer
2
Gk H k qq Es
q
ESINRk 2 2 2
Gk H k qj, j q Es Gk qq
Gk qj, j q
N
Knowledge of
self-interference
k= subcarrier index

6. 6
DSA-SINR
 Involves sorting, comparing and simple
arithmetic.
 Ranks users from lowest to highest SINR.
 Fairness: Allow poor users to have the next
‘best’ subcarriers.
 Prevents users from sharing the same
subcarrier with the adjacent layer (interferer).

7. 7
System Model X1 Tx1 Rx1
H1
X1 With Index 1
Transmitter at Base Station OFDM H3
X1
User k Input With Index 2
Data Scrambling/ FEC/ Symbol Serial to Parallel& DSA
H2 Rx2
X1X2 Puncturing/ Interleaving Mapping Spatial Multiplexing mapping X2 Tx2
With Index 3
H4
X2 X2 OFDM
With Index 4
Uplink process Index 1 2 3 4
Downlink process Index 4
ESINR and channel
Index 1 DSA
Index 2
} DSA-ESINR gain feedback from
other users
Scheme
Index 3
Index 2
Index 3 Index 1
Index 4 } DSA-Scheme 1
ESINR1
ESINR2
[ H3 ]
[ H4 ]
ESINR
calculation
Receiver at Mobile Station k [ H1 H3 ] [ H2 H4 ]
S1 Y1 DSA
OFDM
User k Deinterleaving/ S1 S2 Parallel to MMSE [ H1 H3 ] Demapping
Symbol
Output Depuncturing/ Viterbi Serial& De- Linear
Demapping
Data Decoding/ Descrambling Multiplexing Detection Y2 DSA
S2
[ H2 H4 ] Demapping OFDM

8. 8
Simulation Setup
 Nsub= 768, NFFT= 1024 for 16 users, 48
subcarriers per user
 3GPP-SCM ‘Urban Micro’:
1
Rms delay spread= 251 ns
0.9
0.8
0.7
Normalised power
 Excess delay= 1200 ns
0.6
0.5
0.4
0.3
 2000 i.i.d Rayleigh
0.2
0.1
200 300 400 500 600 700 800 900 1000
Excess delay (ns)
 Six MCS schemes, consists of BPSK,
QPSK, 16-QAM and 64-QAM with ½ or ¾
coding rate

9. 9
Correlation Model
 Kronecker product, RMIMO=RMS RBS
 ‘Default’ = generated by the channel model,
i.e. practical scenario
 ‘Forced’ = ideal channel environment
Correlation Coefficient
Correlation Modes
RBS RMS
‘Default’ 0.45 0.32
‘Forced’ 0.00 0.00

10. 10
BER Performance
0 0
10 10
DSA-ESINR M1 DSA-ESINR M1
Bit Error Rate (BER)
Bit Error Rate (BER)
-1 DSA-Sch1 M1 -1
10 10 DSA-Sch1 M1
DSA-ESINR M2
DSA-ESINR M2
DSA-Sch1 M2
DSA-Sch1 M2
DSA-ESINR M3
DSA-ESINR M3
DSA-Sch1 M3
DSA-Sch1 M3
-2 DSA-ESINR M4
10 -2 DSA-ESINR M4
DSA-Sch1 M4 10 DSA-Sch1 M4
DSA-ESINR M5
DSA-ESINR M5
DSA-Sch1 M5
DSA-Sch1 M5
DSA-ESINR M6
DSA-ESINR M6
-3 DSA-Sch1 M6
10 -3 DSA-Sch1 M6
-20 -10 0 10 20 30 10
Signal-to-Noise Ratio (SNR) in dB -20 -10 0 10 20 30
Signal-to-Noise Ratio (SNR) in dB
‘Forced’ ‘Default’

11. 11
Conclusions
 SINR with combination of DSA can minimise
the effect of self-interference.
 Allocation improves as SNR increase.
 Future works:
 Consider different case of correlation scenarios,
e.g. moderate, full correlation
 Apply adaptive MCS on the BS Tx antenna
 Study the effect of self-interference between STBC
and SM

12. Thank You!