Interference Cancellation and Detection for MAC with Two Users - Interference Cancellation Using Space-Time Processing and Precoding Design - page 27

Multi−User, 2 bits/sec/Hz

10 −1

Our scheme with 2 receive antennas
Our scheme with 3 receive antennas
3 receive antennas and no interference

10 −2

10 −3

10 −4

10 −5

10 −6

8 10 12 14 16 18 20 22 24

Signal to Noise Ratio (dB)

Fig. 2.6 Comparison of our scheme for 2 users each with 2 transmit antennas and different number
of receive antennas

2.7 Simulation Results

In this section, we provide simulation results that confirm our analysis in the previ-
ous sections. We assume a quasi-static Rayleigh channel. The performance of our
proposed scheme is shown in Figs. 2.4 , 2.5 and 2.6 . In each figure, the curves for
Users 1 and 2 are identical. In Fig. 2.4 , we consider 2 users each equipped with 2
transmit antennas and a receiver with 2 receive antennas. We compare our results
using QPSK with the results in [ 5 ] for the same configuration without channel infor-
mation at the transmitter. With 2 receive antennas, the multi-user detection (MUD)
method offered in [ 5 ] can cancel the interference and provides a diversity of 2. Our
scheme can also cancel the interference completely but provides a diversity of 4 by
utilizing the channel information at the transmitter. We also present the results for a
system with no interference. This is the same system when User 2 does not exist and
can be easily achieved by G

0. Simulation results confirm that we have achieved
interference cancellation completely.
Next, we present results for 2 users each with 4 transmit antennas and one receiver
with 2 receive antennas in Fig. 2.5 . We compare the performance of our method with
the multiuser detection method in [ 5 ] using QOSTBC. As shown in Fig. 2.5 , our
scheme can achieve a diversity of 8, i.e., full diversity, by using channel informa-

=