2 research outputs found
Large-System Analysis of Joint Channel and Data Estimation for MIMO DS-CDMA Systems
This paper presents a large-system analysis of the performance of joint
channel estimation, multiuser detection, and per-user decoding (CE-MUDD) for
randomly-spread multiple-input multiple-output (MIMO) direct-sequence
code-division multiple-access (DS-CDMA) systems. A suboptimal receiver based on
successive decoding in conjunction with linear minimum mean-squared error
(LMMSE) channel estimation is investigated. The replica method, developed in
statistical mechanics, is used to evaluate the performance in the large-system
limit, where the number of users and the spreading factor tend to infinity
while their ratio and the number of transmit and receive antennas are kept
constant. The performance of the joint CE-MUDD based on LMMSE channel
estimation is compared to the spectral efficiencies of several receivers based
on one-shot LMMSE channel estimation, in which the decoded data symbols are not
utilized to refine the initial channel estimates. The results imply that the
use of joint CE-MUDD significantly reduces rate loss due to transmission of
pilot signals, especially for multiple-antenna systems. As a result, joint
CE-MUDD can provide significant performance gains, compared to the receivers
based on one-shot channel estimation.Comment: The paper was resubmitted to IEEE Trans. Inf. Theor
On an Achievable Rate of Large Rayleigh Block-Fading MIMO Channels with No CSI
Training-based transmission over Rayleigh block-fading multiple-input
multiple-output (MIMO) channels is investigated. As a training method a
combination of a pilot-assisted scheme and a biased signaling scheme is
considered. The achievable rates of successive decoding (SD) receivers based on
the linear minimum mean-squared error (LMMSE) channel estimation are analyzed
in the large-system limit, by using the replica method under the assumption of
replica symmetry. It is shown that negligible pilot information is best in
terms of the achievable rates of the SD receivers in the large-system limit.
The obtained analytical formulas of the achievable rates can improve the
existing lower bound on the capacity of the MIMO channel with no channel state
information (CSI), derived by Hassibi and Hochwald, for all signal-to-noise
ratios (SNRs). The comparison between the obtained bound and a high SNR
approximation of the channel capacity, derived by Zheng and Tse, implies that
the high SNR approximation is unreliable unless quite high SNR is considered.
Energy efficiency in the low SNR regime is also investigated in terms of the
power per information bit required for reliable communication. The required
minimum power is shown to be achieved at a positive rate for the SD receiver
with no CSI, whereas it is achieved in the zero-rate limit for the case of
perfect CSI available at the receiver. Moreover, numerical simulations imply
that the presented large-system analysis can provide a good approximation for
not so large systems. The results in this paper imply that SD schemes can
provide a significant performance gain in the low-to-moderate SNR regimes,
compared to conventional receivers based on one-shot channel estimation.Comment: re-submitted to IEEE Trans. Inf. Theor