49 research outputs found
Multiterminal Source-Channel Coding
Cooperative communication is seen as a key concept to achieve ultra-reliable communication in upcoming fifth-generation mobile networks (5G). A promising cooperative communication concept is multiterminal source-channel coding, which attracted recent attention in the research community.
This thesis lays theoretical foundations for understanding the performance of multiterminal source-channel codes in a vast variety of cooperative communication networks. To this end, we decouple the multiterminal source-channel code into a multiterminal source code and multiple point-to-point channel codes. This way, we are able to adjust the multiterminal source code to any cooperative communication network without modification of the channel codes. We analyse the performance in terms of the outage probability in two steps: at first, we evaluate the instantaneous performance of the multiterminal source-channel codes for fixed channel realizations; and secondly, we average the instantaneous performance over the fading process. Based on the performance analysis, we evaluate the performance of multiterminal source-channel codes in three cooperative communication networks, namely relay, wireless sensor, and multi-connectivity networks. For all three networks, we identify the corresponding multiterminal source code and analyse its performance by the rate region for binary memoryless sources. Based on the rate region, we derive the outage probability for additive white Gaussian noise channels with quasi-static Rayleigh fading. We find results for the exact outage probability in integral form and closed-form solutions for the asymptotic outage probability at high signal-to-noise ratio.
The importance of our results is fourfold: (i) we give the ultimate performance limits of the cooperative communication networks under investigation; (ii) the optimality of practical schemes can be evaluated with respect to our results, (iii) our results are suitable for link-level abstraction which reduces complexity in network-level simulation; and (iv) our results demonstrate that all three cooperative communication networks are key technologies to enable 5G applications, such as device to device and machine to machine communications, internet of things, and internet of vehicles.
In addition, we evaluate the performance improvement of multiterminal source-channel codes over other (non-)cooperative communications concepts in terms of the transmit power reduction given a certain outage probability level. Moreover, we compare our theoretical results to simulated frame-error-rates of practical coding schemes. Our results manifest the superiority of multiterminal source-channel codes over other (non-)cooperative communications concepts
Differential Modulation for Short Packet Transmission in URLLC
One key feature of ultra-reliable low-latency communications (URLLC) in 5G is
to support short packet transmission (SPT). However, the pilot overhead in SPT
for channel estimation is relatively high, especially in high Doppler
environments. In this paper, we advocate the adoption of differential
modulation to support ultra-low latency services, which can ease the channel
estimation burden and reduce the power and bandwidth overhead incurred in
traditional coherent modulation schemes. Specifically, we consider a
multi-connectivity (MC) scheme employing differential modulation to enable
URLLC services. The popular selection combining and maximal ratio combining
schemes are respectively applied to explore the diversity gain in the MC
scheme. A first-order autoregressive model is further utilized to characterize
the time-varying nature of the channel. Theoretically, the maximum achievable
rate and minimum achievable block error rate under ergodic fading channels with
PSK inputs and perfect CSI are first derived by using the non-asymptotic
information-theoretic bounds. The performance of SPT with differential
modulation and MC schemes is then analysed by characterizing the effect of
differential modulation and time-varying channels as a reduction in the
effective SNR. Simulation results show that differential modulation does offer
a significant advantage over the pilot-assisted coherent scheme for SPT,
especially in high Doppler environments.Comment: 15 pages, 9 figure
Decoding Across the Quantum LDPC Code Landscape
We show that belief propagation combined with ordered statistics
post-processing is a general decoder for quantum low density parity check codes
constructed from the hypergraph product. To this end, we run numerical
simulations of the decoder applied to three families of hypergraph product
code: topological codes, fixed-rate random codes and a new class of codes that
we call semi-topological codes. Our new code families share properties of both
topological and random hypergraph product codes, with a construction that
allows for a finely-controlled trade-off between code threshold and stabilizer
locality. Our results indicate thresholds across all three families of
hypergraph product code, and provide evidence of exponential suppression in the
low error regime. For the Toric code, we observe a threshold in the range
. This result improves upon previous quantum decoders based on
belief propagation, and approaches the performance of the minimum weight
perfect matching algorithm. We expect semi-topological codes to have the same
threshold as Toric codes, as they are identical in the bulk, and we present
numerical evidence supporting this observation.Comment: The code for the BP+OSD decoder used in this work can be found on
Github: https://github.com/quantumgizmos/bp_os
Extreme Value Theory Based Rate Selection for Ultra-Reliable Communications
Ultra-reliable low latency communication (URLLC) requires the packet error
rate to be on the order of -. Determining the appropriate
transmission rate to satisfy this ultra-reliability constraint requires
deriving the statistics of the channel in the ultra-reliable region and then
incorporating these statistics into the rate selection. In this paper, we
propose a framework for determining the rate selection for ultra-reliable
communications based on the extreme value theory (EVT). We first model the
wireless channel at URLLC by estimating the parameters of the generalized
Pareto distribution (GPD) best fitting to the tail distribution of the received
powers, i.e., the power values below a certain threshold. Then, we determine
the maximum transmission rate by incorporating the Pareto distribution into the
rate selection function. Finally, we validate the selected rate by computing
the resulting error probability. Based on the data collected within the engine
compartment of Fiat Linea, we demonstrate the superior performance of the
proposed methodology in determining the maximum transmission rate compared to
the traditional extrapolation-based approaches.Comment: 6 pages, 4 figures including 7 subfigure
Covert Wireless Communication with a Poisson Field of Interferers
In this paper, we study covert communication in wireless networks consisting
of a transmitter, Alice, an intended receiver, Bob, a warden, Willie, and a
Poisson field of interferers. Bob and Willie are subject to uncertain shot
noise due to the ambient signals from interferers in the network. With the aid
of stochastic geometry, we analyze the throughput of the covert communication
between Alice and Bob subject to given requirements on the covertness against
Willie and the reliability of decoding at Bob. We consider non-fading and
fading channels. We analytically obtain interesting findings on the impacts of
the density and the transmit power of the concurrent interferers on the covert
throughput. That is, the density and the transmit power of the interferers have
no impact on the covert throughput as long as the network stays in the
interference-limited regime, for both the non-fading and the fading cases. When
the interference is sufficiently small and comparable with the receiver noise,
the covert throughput increases as the density or the transmit power of the
concurrent interferers increases