Interference Cancellation and Detection for MAC with Two Users - Interference Cancellation Using Space-Time Processing and Precoding Design - page 28

tion, while the MUD method using QOSTBC with no channel information can only
achieve a diversity of 4.
Further, we show the results for 2 users each with 2 transmit antennas and one
receiver with 2 or 3 receive antennas in Fig. 2.6 . By increasing the number of receive
antennas from 2 to 3, the diversity increases from 4 to 6. Therefore, extra receive
antennas will provide extra diversity and the resulting diversity of the system is NM
which confirms our theoretical analysis.
2.8 Conclusions
We have considered interference cancellation for a systemwith two users when users
know each other channels. The goal is to utilize the channel information to cancel
the interference without sacrificing the diversity or the complexity of the system. We
have proposed a system to achieve the maximum possible diversity of NM with low
complexity for 2 users eachwith N transmit antennas and one receiver with M receive
antennas. To the best of our knowledge, this is the first multiuser detection scheme
that achieves full diversity while providing a linear low complexity decoding. Our
main idea is to design precoders, using the channel information, to make it possible
for different users to transmit over orthogonal spaces. Then, using the orthogonality
of the transmitted signals, the receiver can separate them and decode the signals
independently. We have analytically proved that the system provides full diversity
to both users. In addition, we provide simulation results that confirm our analytical
results.
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