565 research outputs found
Turbo Packet Combining for Broadband Space-Time BICM Hybrid-ARQ Systems with Co-Channel Interference
In this paper, efficient turbo packet combining for single carrier (SC)
broadband multiple-input--multiple-output (MIMO) hybrid--automatic repeat
request (ARQ) transmission with unknown co-channel interference (CCI) is
studied. We propose a new frequency domain soft minimum mean square error
(MMSE)-based signal level combining technique where received signals and
channel frequency responses (CFR)s corresponding to all retransmissions are
used to decode the data packet. We provide a recursive implementation algorithm
for the introduced scheme, and show that both its computational complexity and
memory requirements are quite insensitive to the ARQ delay, i.e., maximum
number of ARQ rounds. Furthermore, we analyze the asymptotic performance, and
show that under a sum-rank condition on the CCI MIMO ARQ channel, the proposed
packet combining scheme is not interference-limited. Simulation results are
provided to demonstrate the gains offered by the proposed technique.Comment: 12 pages, 7 figures, and 2 table
Turbo Packet Combining Strategies for the MIMO-ISI ARQ Channel
This paper addresses the issue of efficient turbo packet combining techniques
for coded transmission with a Chase-type automatic repeat request (ARQ)
protocol operating over a multiple-input--multiple-output (MIMO) channel with
intersymbol interference (ISI). First of all, we investigate the outage
probability and the outage-based power loss of the MIMO-ISI ARQ channel when
optimal maximum a posteriori (MAP) turbo packet combining is used at the
receiver. We show that the ARQ delay (i.e., the maximum number of ARQ rounds)
does not completely translate into a diversity gain. We then introduce two
efficient turbo packet combining algorithms that are inspired by minimum mean
square error (MMSE)-based turbo equalization techniques. Both schemes can be
viewed as low-complexity versions of the optimal MAP turbo combiner. The first
scheme is called signal-level turbo combining and performs packet combining and
multiple transmission ISI cancellation jointly at the signal-level. The second
scheme, called symbol-level turbo combining, allows ARQ rounds to be separately
turbo equalized, while combining is performed at the filter output. We conduct
a complexity analysis where we demonstrate that both algorithms have almost the
same computational cost as the conventional log-likelihood ratio (LLR)-level
combiner. Simulation results show that both proposed techniques outperform
LLR-level combining, while for some representative MIMO configurations,
signal-level combining has better ISI cancellation capability and achievable
diversity order than that of symbol-level combining.Comment: 13 pages, 7 figures, and 2 table
- âŠ