Digital Signal Processing Reference
In-Depth Information
Chapter 3
Interference Cancellation and Detection for
More than Two Users
3.1 Interference Cancellation for Four Users Each with Four
Transmit Antennas
In this chapter, we assume a quasi-static flat Rayleigh fading channel model. The
path gains are independent complex Gaussian random variables and are fixed during
the transmission of one block. In addition, a short-term power constraint is assumed.
For the sake of simplicity, we only present the scheme for four users each with
four transmit antennas and one receiver with four receive antennas. By adjusting the
dimensions of channel matrices, our proposed scheme can be easily applied to
J
users with
J
transmit antennas and one receiver with
J
receive antennas.
The block diagram of the system is shown in Fig.
3.1
. We assume the channel
matrices for Users 1, 2, 3, 4 are
H
1
=[
h
1
(
i
,
j
)
]
4
×
4
,
H
2
=[
h
2
(
i
,
j
)
]
4
×
4
,
H
3
=[
h
3
(
i
,
j
)
]
4
×
4
,
H
4
=[
h
4
(
i
,
j
)
]
4
×
4
(3.1)
respectively. At the
l
th time slot,
l
=
1
,
2
,
3
,
4, the precoders for Users 1, 2, 3, 4 are
A
l
1
=[
a
l
1
(
i
,
j
)
]
4
×
4
,
A
l
2
=[
a
l
2
(
i
,
j
)
]
4
×
4
,
A
l
3
=[
a
l
3
(
i
,
j
)
]
4
×
4
,
A
l
4
=[
a
i
4
(
i
,
j
)
]
4
×
4
(3.2)
respectively. In every four time slots, Users 1, 2, 3, 4 send Quasi Orthogonal Space-
Time Block Codes (QOSTBCs) [
1
]
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