732 research outputs found
Space-Time Signal Design for Multilevel Polar Coding in Slow Fading Broadcast Channels
Slow fading broadcast channels can model a wide range of applications in
wireless networks. Due to delay requirements and the unavailability of the
channel state information at the transmitter (CSIT), these channels for many
applications are non-ergodic. The appropriate measure for designing signals in
non-ergodic channels is the outage probability. In this paper, we provide a
method to optimize STBCs based on the outage probability at moderate SNRs.
Multilevel polar coded-modulation is a new class of coded-modulation techniques
that benefits from low complexity decoders and simple rate matching. In this
paper, we derive the outage optimality condition for multistage decoding and
propose a rule for determining component code rates. We also derive an upper
bound on the outage probability of STBCs for designing the
set-partitioning-based labelling. Finally, due to the optimality of the
outage-minimized STBCs for long codes, we introduce a novel method for the
joint optimization of short-to-moderate length polar codes and STBCs
Design and optimization of joint iterative detection and decoding receiver for uplink polar coded SCMA system
SCMA and polar coding are possible candidates for 5G systems. In this paper, we firstly propose the joint iterative detection and decoding (JIDD) receiver for the uplink polar coded sparse code multiple access (PC-SCMA) system. Then, the EXIT chart is used to investigate the performance of the JIDD receiver. Additionally, we optimize the system design and polar code construction based on the EXIT chart analysis. The proposed receiver integrates the factor graph of SCMA detector and polar soft-output decoder into a joint factor graph, which enables the exchange of messages between SCMA detector and polar decoder iteratively. Simulation results demonstrate that the JIDD receiver has better BER performance and lower complexity than the separate scheme. Specifically, when polar code length N=256 and code rate R=1/2 , JIDD outperforms the separate scheme 4.8 and 6 dB over AWGN channel and Rayleigh fading channel, respectively. It also shows that, under 150% system loading, the JIDD receiver only has 0.3 dB performance loss compared to the single user uplink PC-SCMA over AWGN channel and 0.6 dB performance loss over Rayleigh fading channel
Bridging the complexity gap in Tbps-achieving THz-band baseband processing
Recent advances in electronic and photonic technologies have allowed
efficient signal generation and transmission at terahertz (THz) frequencies.
However, as the gap in THz-operating devices narrows, the demand for
terabit-per-second (Tbps)-achieving circuits is increasing. Translating the
available hundreds of gigahertz (GHz) of bandwidth into a Tbps data rate
requires processing thousands of information bits per clock cycle at
state-of-the-art clock frequencies of digital baseband processing circuitry of
a few GHz. This paper addresses these constraints and emphasizes the importance
of parallelization in signal processing, particularly for channel code
decoding. By leveraging structured sub-spaces of THz channels, we propose
mapping bits to transmission resources using shorter code words, extending
parallelizability across all baseband processing blocks. THz channels exhibit
quasi-deterministic frequency, time, and space structures that enable efficient
parallel bit mapping at the source and provide pseudo-soft bit reliability
information for efficient detection and decoding at the receiver
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