134 research outputs found
Unified turbo/LDPC code decoder architecture for deep-space communications
Deep-space communications are characterized by extremely
critical conditions; current standards foresee the usage of both turbo
and low-density-parity-check (LDPC) codes to ensure recovery from
received errors, but each of them displays consistent drawbacks.
Code concatenation is widely used in all kinds of communication to
boost the error correction capabilities of single codes; serial
concatenation of turbo and LDPC codes has been recently proven
effective enough for deep space communications, being able to
overcome the shortcomings of both code types. This work extends
the performance analysis of this scheme and proposes a novel
hardware decoder architecture for concatenated turbo and LDPC
codes based on the same decoding algorithm. This choice leads to a
high degree of datapath and memory sharing; postlayout
implementation results obtained with complementary metal-oxide
semiconductor (CMOS) 90 nm technology show small area
occupation (0.98 mm
2
) and very low power consumption (2.1 mW)
One and Two Bit Message Passing for SC-LDPC Codes with Higher-Order Modulation
Low complexity decoding algorithms are necessary to meet data rate
requirements in excess of 1 Tbps. In this paper, we study one and two bit
message passing algorithms for belief propagation decoding of low-density
parity-check (LDPC) codes and analyze them by density evolution. The variable
nodes (VNs) exploit soft information from the channel output. To decrease the
data flow, the messages exchanged between check nodes (CNs) and VNs are
represented by one or two bits. The newly proposed quaternary message passing
(QMP) algorithm is compared asymptotically and in finite length simulations to
binary message passing (BMP) and ternary message passing (TMP) for spectrally
efficient communication with higher-order modulation and probabilistic
amplitude shaping (PAS). To showcase the potential for high throughput forward
error correction, spatially coupled LDPC codes and a target spectral efficiency
(SE) of 3 bits/QAM symbol are considered. Gains of about 0.7 dB and 0.1 dB are
observed compared to BMP and TMP, respectively. The gap to unquantized belief
propagation (BP) decoding is reduced to about 0.75 dB. For smaller code rates,
the gain of QMP compared to TMP is more pronounced and amounts to 0.24 dB in
the considered example.Comment: Accepted for IEEE/OSA Journal on Lightwave Technolog
Cellular, Wide-Area, and Non-Terrestrial IoT: A Survey on 5G Advances and the Road Towards 6G
The next wave of wireless technologies is proliferating in connecting things
among themselves as well as to humans. In the era of the Internet of things
(IoT), billions of sensors, machines, vehicles, drones, and robots will be
connected, making the world around us smarter. The IoT will encompass devices
that must wirelessly communicate a diverse set of data gathered from the
environment for myriad new applications. The ultimate goal is to extract
insights from this data and develop solutions that improve quality of life and
generate new revenue. Providing large-scale, long-lasting, reliable, and near
real-time connectivity is the major challenge in enabling a smart connected
world. This paper provides a comprehensive survey on existing and emerging
communication solutions for serving IoT applications in the context of
cellular, wide-area, as well as non-terrestrial networks. Specifically,
wireless technology enhancements for providing IoT access in fifth-generation
(5G) and beyond cellular networks, and communication networks over the
unlicensed spectrum are presented. Aligned with the main key performance
indicators of 5G and beyond 5G networks, we investigate solutions and standards
that enable energy efficiency, reliability, low latency, and scalability
(connection density) of current and future IoT networks. The solutions include
grant-free access and channel coding for short-packet communications,
non-orthogonal multiple access, and on-device intelligence. Further, a vision
of new paradigm shifts in communication networks in the 2030s is provided, and
the integration of the associated new technologies like artificial
intelligence, non-terrestrial networks, and new spectra is elaborated. Finally,
future research directions toward beyond 5G IoT networks are pointed out.Comment: Submitted for review to IEEE CS&
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