Transcript IEEE C802.16m-08/230

SCvsOFDM Throughput
Document Number:
IEEE C802.16m-08/230
Date Submitted:
2008-03-13
Source:
Mohammed Nafie
Ahmed Shalash
Cairo University and WiCreo
3 Mosadaq St #9-2
Dokki, Giza, 12311
Egypt
Re:
TGm Call for Contribution on SDD, Rapporteur Chairs report
([email protected])
([email protected])
Abstract :
Simulations showing throughput of Single Carrier vs OFDMA
Purpose:
To help the TGm group make a decision regarding uplink multiple access scheme
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OFDM vs. SC-FDE

We present figures showing throughput of
both OFDM and SC-FDE
under the
following assumptions:


SISO system
FFT size 1024


Numbered 1,2, to 1024
Uses 128 subcarriers


Distributed: uses subcarriers 81,85,89,…589
Localized: uses subcarriers 449,450,451,…576
Assumptions (cont.)

ITU VehA channel model





Extended as in Table 23 of EMD
Sampled every 5ms to produce 100 realizations
The 100 realizations are normalized such that
the average energy is 1
OFDM: MMSE receiver
SC-FDE:
Frequency
domain
MMSE,
sometimes followed by time domain DFE
of length 10
Throughput

We calculate the SNR after the MMSE receiver of the OFDM or the SC-FDE

Then, throughput scaled by subcarrier spacing is:
ThroughputOFDMA 
 log( 1  SNR
subcarrieri
)
subcarriers
Throughput SC  FDE  log( 1  SNR)

Note that SNR of SC-FDE is related to SNR of OFDMA as
UL_MA_(freq_selective_scheduling)C802.16m_08_085r1_clarification
or C80216m-08_045r1
in
Localized
Distributed
Frequency Selective Scheduling


Similar
to
UL_MA_(freq_selective_scheduling)C802.1
6m_08_085r1_clarification
OFDMA: choose best 16 subbands of 8
subcarriers each


Total = 128 subcarriers
Choose best 128 contiguous subcarriers

16 contiguous subbands of 8 subcarriers each
Frequency Selective Throughput
Conclusion


For distributed and localized, OFDM has
higher throughput than SC-FDE in SISO
systems if a linear MMSE receiver is used
However, using a DFE in SC-FDE leads to
the same throughput
Conclusion

For
frequency
selective
scheduling,
OFDMA and SC-FDE achieve similar
performance