We focus on the problem of modulating a parameter onto a power-limited signal transmitted over a discrete-time Gaussian channel and estimating this parameter at the receiver. Considering the well-known threshold effec...
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We focus on the problem of modulating a parameter onto a power-limited signal transmitted over a discrete-time Gaussian channel and estimating this parameter at the receiver. Considering the well-known threshold effect in the non-linear modulation systems, our approach is the following: instead of deriving upper and lower bounds on the total estimation error, which weighs both weak-noise errors and anomalous errors beyond the threshold, we separate the two kinds of errors. In particular, we derive upper and lower bounds on the best achievable tradeoff between the exponential decay rate of the weak-noise expected error cost and the exponential decay rate of the probability of the anomalous error event, also referred to as the outage event. This outage event is left to be defined as a part of the communication system design problem. Our achievability scheme, which is based on lattice codes, meets the lower bound at the high signal-to-noise limit and for a certain range of tradeoffs between the weak-noise error cost and the outage exponent.
Mobile video traffic is expected to increase explosively because of the proliferating number of Wi-Fi terminals. An overloaded multiple-input multiple-output (MIMO) technique allows the receiver to implement smaller n...
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Mobile video traffic is expected to increase explosively because of the proliferating number of Wi-Fi terminals. An overloaded multiple-input multiple-output (MIMO) technique allows the receiver to implement smaller number of antennas than the transmitter in exchange for degradation in video quality and a large amount of computational complexity for postcoding at the receiver side. This paper proposes a novel linear precoder for high-quality video streaming in overloaded multiuser MIMO systems, which protects visually significant portions of a video stream. A low complexity postcoder is also proposed, which detects some of data symbols by linear detection and the others by a prevoting vector cancellation (PVC) approach. It is shown from simulation results that the combination use of the proposed precoder and postcoder achieves higher-quality video streaming to multiple users in a wider range of signal-to-noise ratio (SNR) than a conventional unequal error protection scheme. The proposed precoder attains 40 dB in peak signal-to-noise ratio even in poor channel conditions such as the SNR of 12 dB. In addition, due to the stepwise acquisition of data symbols by means of linear detection and PVC, the proposed postcoder reduces the number of complex additions by 76% and that of multiplications by 64% compared to the conventional PVC.
Degraded K-user broadcast channels (BCs) are studied when the receivers are facilitated with cache memories. Lower and upper bounds are derived on the capacity-memory tradeoff, i.e., on the largest rate of reliable co...
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Degraded K-user broadcast channels (BCs) are studied when the receivers are facilitated with cache memories. Lower and upper bounds are derived on the capacity-memory tradeoff, i.e., on the largest rate of reliable communication over the BC as a function of the receivers' cache sizes, and the bounds are shown to match for interesting special cases. The lower bounds are achieved by two new coding schemes that benefit from 'nonuniform cache assignments'. Lower and upper bounds are also established on the global capacity-memory tradeoff, i.e., on the largest capacity-memory tradeoff that can be attained by optimizing the receivers' cache sizes subject to a total cache memory budget. The bounds coincide when the total cache memory budget is sufficiently small or sufficiently large, where the thresholds depend on the BC statistics. For small cache memories, it is optimal to assign all the cache memory to the weakest receiver. In this regime, the global capacity-memory tradeoff grows by the total cache memory budget divided by the number of files in the system. In other words, a 'perfect global caching gain' is achievable in this regime and the performance corresponds to a system where all the cache contents in the network are available to all receivers. For large cache memories, it is optimal to assign a positive cache memory to every receiver, such that the weaker receivers are assigned larger cache memories compared to the stronger receivers. In this regime, the growth rate of the global capacity-memory tradeoff is further divided by the number of users, which corresponds to a local caching gain. It is observed numerically that a uniform assignment of the total cache memory is suboptimal in all regimes, unless the BC is completely symmetric. For erasure BCs, this claim is proved analytically in the regime of small cache sizes.
This paper considers the problem of simultaneous information and energy transmission, where the energy harvesting function is only known experimentally at sample points, e.g., due to nonlinearities and parameter uncer...
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This paper considers the problem of simultaneous information and energy transmission, where the energy harvesting function is only known experimentally at sample points, e.g., due to nonlinearities and parameter uncertainties in harvesting circuits. We investigate the performance loss due to this partial knowledge of the harvesting function in terms of transmitted energy and information. In particular, we assume that the harvesting function is a subclass of the Sobolev space and consider two cases, where the experimental samples are either taken noiselessly or in the presence of noise. Using constructive function approximation and regression methods for noiseless and noisy samples, respectively, we show that the worst loss in energy transmission vanishes asymptotically as the number of samples increase. Similarly, the loss in information rate vanishes in the interior of the energy domain;however, it does not always vanish at maximal energy. We further show that the same principle applies in multicast settings, such as medium access in the Wi-Fi protocol. We also consider the end-to-end source-channel communication problem under source distortion constraint and channel energy requirement, where both distortion and harvesting functions are known only at samples.
We introduce a definition of perfect and quasi-perfect codes for discrete symmetric channels based on the packing and covering properties of generalized spheres whose shape is tilted using an auxiliary probability mea...
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We introduce a definition of perfect and quasi-perfect codes for discrete symmetric channels based on the packing and covering properties of generalized spheres whose shape is tilted using an auxiliary probability measure. This notion generalizes previous definitions of perfect and quasi-perfect codes and encompasses maximum distance separable codes. The error probability of these codes, whenever they exist, is shown to coincide with the estimate provided by the meta-converse lower bound. We illustrate how the proposed definition naturally extends to cover almost-lossless source-channelcoding and lossy compression.
We consider the broadcasting of a scalar memoryless Gaussian source over a two-user Gaussian broadcast channel with bandwidth expansion. In concurrent with the source description, a message that should be decoded reli...
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We consider the broadcasting of a scalar memoryless Gaussian source over a two-user Gaussian broadcast channel with bandwidth expansion. In concurrent with the source description, a message that should be decoded reliably just by the "higher quality" user is sent. Conditioned on the message rate, we derive a necessary condition for the achievability of a mean-squared-error distortion pair at the two receivers, which extends the Reznic-Feder-Zamir bound. This necessary condition and a sufficient condition that we derive establish the set of achievable energy-distortion exponents for this setting.
A distributed joint source-channel coding scheme based on a unity-rate code (URC) assisted trellis coded modulation (TCM) is proposed, which exploits the spatiotemporal correlation of symbol-based sources. More specif...
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A distributed joint source-channel coding scheme based on a unity-rate code (URC) assisted trellis coded modulation (TCM) is proposed, which exploits the spatiotemporal correlation of symbol-based sources. More specifically, asymmetric distributed sourcecoding of two spatially correlated Markov sources is considered, where one of the sources is assumed to be perfectly decoded and to be available at the receiver of the other source as side information. In order to exploit the temporal correlation statistics, an iterative decoding process exchanging extrinsic information between the amalgamated URC-assisted TCM and a soft-symbol source decoder employing a modified symbol-based maximum a posteriori algorithm is invoked. Furthermore, the Slepian-Wolf (SW) bound of symbol-based sources having spatiotemporal correlation is derived and the benefits of exploiting the spatiotemporal correlation using the proposed coding scheme are demonstrated by our extrinsic information transfer chart analysis. It is shown from our simulation results that upon exploiting the spatiotemporal correlation of the sources, the proposed coding scheme is capable of operating within 0.02 b of the SW bound.
The high cost and power consumption of millimeter wave (mmWave) radio frequency (RF) hardware elements demands for advanced signal processing techniques to design MIMO transceivers. Hybrid analog-digital architectures...
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ISBN:
(纸本)9789082797039
The high cost and power consumption of millimeter wave (mmWave) radio frequency (RF) hardware elements demands for advanced signal processing techniques to design MIMO transceivers. Hybrid analog-digital architectures for MIMO transceivers have become an attractive strategy to reduce the number of RF chains of the transceivers. In the uplink of a multiuser mmWave MIMO system, this hardware reduction is limited by the number of users to be handled, which can be rather large. In this work, we propose to use distributed quantizer linear coding (DQLC) in order to superimpose correlated sources in a cluster-based uplink multiuser mmWave MIMO system and reduce the number of RF chains at the receiver. The scheduling policy to cluster the transmitters is also analyzed by considering the correlation of the sources and channel state information (CSI). Numerical results show the advantage of employing the proposed scheme to reduce hardware complexity.
We consider the Gaussian multiple-access interference relay channel (MAIRC), where a relay aids the communication of two two-user multiple-access channels that transmit over a shared medium and thus interfere mutually...
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ISBN:
(纸本)9781728109541
We consider the Gaussian multiple-access interference relay channel (MAIRC), where a relay aids the communication of two two-user multiple-access channels that transmit over a shared medium and thus interfere mutually. We study the problem of transmitting four correlated memoryless sources, one each for the four transmitters, over the phase incoherent MAIRCs (PI-MAIRC) where transmissions are subject to fixed non-ergodic phase shifts that change across blocks. For a class of PI-MAIRCs where the phase-shifts are assumed to be unknown at the transmitters and known at the receivers, necessary and sufficient channel conditions are derived under which separate source and channelcoding proves optimal. We then extend this result to (i) the N-user PI-MAIRC as well as (ii) MAIRCs with general ergodic phase fading.
Asymptotic energy-distortion performance of zero-delay communication under Gaussian broadcasting is investigated. The analysis can be motivated by the scenario where the same internet of things (IoT) device is transmi...
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ISBN:
(纸本)9781538692912
Asymptotic energy-distortion performance of zero-delay communication under Gaussian broadcasting is investigated. The analysis can be motivated by the scenario where the same internet of things (IoT) device is transmitting its measurements to multiple control units that are experiencing varying noise levels. Using high-resolution analysis for quantizer design coupled with orthogonal signaling, the higher-order term in the negative logarithm of the distortion, termed the energy-distortion dispersion, is optimized while keeping the leading term, the energy-distortion exponent, at its optimal value for the zero-delay regime.
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