13,747 research outputs found
Communication Beyond Transmitting Bits: Semantics-Guided Source and Channel Coding
Classical communication paradigms focus on accurately transmitting bits over
a noisy channel, and Shannon theory provides a fundamental theoretical limit on
the rate of reliable communications. In this approach, bits are treated
equally, and the communication system is oblivious to what meaning these bits
convey or how they would be used. Future communications towards intelligence
and conciseness will predictably play a dominant role, and the proliferation of
connected intelligent agents requires a radical rethinking of coded
transmission paradigm to support the new communication morphology on the
horizon. The recent concept of "semantic communications" offers a promising
research direction. Injecting semantic guidance into the coded transmission
design to achieve semantics-aware communications shows great potential for
further breakthrough in effectiveness and reliability. This article sheds light
on semantics-guided source and channel coding as a transmission paradigm of
semantic communications, which exploits both data semantics diversity and
wireless channel diversity together to boost the whole system performance. We
present the general system architecture and key techniques, and indicate some
open issues on this topic.Comment: IEEE Wireless Communications, text overlap with arXiv:2112.0309
Joint Coding and Scheduling Optimization in Wireless Systems with Varying Delay Sensitivities
Throughput and per-packet delay can present strong trade-offs that are
important in the cases of delay sensitive applications.We investigate such
trade-offs using a random linear network coding scheme for one or more
receivers in single hop wireless packet erasure broadcast channels. We capture
the delay sensitivities across different types of network applications using a
class of delay metrics based on the norms of packet arrival times. With these
delay metrics, we establish a unified framework to characterize the rate and
delay requirements of applications and optimize system parameters. In the
single receiver case, we demonstrate the trade-off between average packet
delay, which we view as the inverse of throughput, and maximum ordered
inter-arrival delay for various system parameters. For a single broadcast
channel with multiple receivers having different delay constraints and feedback
delays, we jointly optimize the coding parameters and time-division scheduling
parameters at the transmitters. We formulate the optimization problem as a
Generalized Geometric Program (GGP). This approach allows the transmitters to
adjust adaptively the coding and scheduling parameters for efficient allocation
of network resources under varying delay constraints. In the case where the
receivers are served by multiple non-interfering wireless broadcast channels,
the same optimization problem is formulated as a Signomial Program, which is
NP-hard in general. We provide approximation methods using successive
formulation of geometric programs and show the convergence of approximations.Comment: 9 pages, 10 figure
A General Framework for Analyzing, Characterizing, and Implementing Spectrally Modulated, Spectrally Encoded Signals
Fourth generation (4G) communications will support many capabilities while providing universal, high speed access. One potential enabler for these capabilities is software defined radio (SDR). When controlled by cognitive radio (CR) principles, the required waveform diversity is achieved via a synergistic union called CR-based SDR. Research is rapidly progressing in SDR hardware and software venues, but current CR-based SDR research lacks the theoretical foundation and analytic framework to permit efficient implementation. This limitation is addressed here by introducing a general framework for analyzing, characterizing, and implementing spectrally modulated, spectrally encoded (SMSE) signals within CR-based SDR architectures. Given orthogonal frequency division multiplexing (OFDM) is a 4G candidate signal, OFDM-based signals are collectively classified as SMSE since modulation and encoding are spectrally applied. The proposed framework provides analytic commonality and unification of SMSE signals. Applicability is first shown for candidate 4G signals, and resultant analytic expressions agree with published results. Implementability is then demonstrated in multiple coexistence scenarios via modeling and simulation to reinforce practical utility
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