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In the framework of prediction with expert advice we consider prediction algorithms that compete against a class of switching strategies that can segment a given sequence into several blocks and follow the advice of a different “base” expert in each block. The performance is measured by the regret defined as the excess loss relative to the best switching strategy selected in hindsight. Our goal is...
This paper derives a tight asymptotic upper bound on the maximum volume M∗cc(n, ∊) of length-n constant-composition codes subject to an average decoding error probability ∊: Mbb(n, ∊) = exp{nC − √nV Φ− (1 − ∊) + 1/2 log n + An, ∊ + o(1)} where Φ is the cdf of the standard normal distribution, and An, ∊ is a bounded sequence that can be explicitly identified and reduces to a constant in the nonlattice...
Energy efficiency in wireless fading channels is studied in the presence of statistical quality of service (QoS) constraints. Energy per bit is employed as the performance metric. Minimum energy per bit and wideband slope expressions are determined to quantify the energy efficiency in the low signal-to-noise ratio (SNR) regime. In particular, the impact of channel and source variations is investigated...
We consider the problem of joint link scheduling and power control for wireless networks with average transmission power constraints. Due to the high computational complexity of the optimal policies, we extend the class of greedy link scheduling policies to handle average power constraints. We develop a greedy link scheduling and power control scheme GECS, with provable performance guarantees. We...
This work focuses on the multi-terminal source coding problem and presents conditions when a rate point achievable with asymptotically zero-rate messages over a subset of network links, is also achievable with no communication over links in that subset. We show that when there exist block codes that are robust to small changes in the source distribution, zero-rate encoders can be ignored, i.e., their...
The multi-way relay channel (MWRC) models cooperative communication networks in which many users exchange messages via a relay. In this paper, we consider the finite field MWRC with correlated messages. The problem is to find all achievable rates, defined as the number of channel uses required per reliable exchange of message tuple. For the case of three users, we have previously established that...
We consider the two-encoder multiterminal source coding problem subject to distortion constraints computed under logarithmic loss. We provide a single-letter description of the achievable rate distortion region for arbitrarily correlated sources with finite alphabets. In doing so, we also give the rate distortion region for the CEO problem under logarithmic loss. Notably, the Berger-Tung inner bound...
The upper bound on the capacity of a 3-node discrete memoryless relay channel is considered, where a source X wants to send information to destination Y with the help of a relay Z. Y and Z are independent given X, and the channel is statistically degraded in the sense that XY Z or XZY can be re-described statistically as a Markov chain. The link from Z to Y is lossless with rate R0. A new method is...
We study the moderate-deviations (MD) setting for lossy source coding of stationary memoryless sources. More specifically, we derive fundamental compression limits of source codes whose rates are R(D) ± εn, where R(D) is the rate-distortion function and εn is a sequence that dominates √1/n. This MD setting is complementary to the large-deviations and central limit settings and was studied by Altug...
This paper considers the multi-way relay channel (MWRC) where multiple users exchange messages via a single relay. The capacity region is derived for a special class of MWRCs where (i) the uplink and the downlink are separated in the sense that there is no direct user-to-user links, (ii) the channel is restricted in the sense that each user's transmitted channel symbols can depend on only its own...
A network code is said to be reliable when all transmissions in the network are (deterministic) functions of the source messages; well-known examples include decode-forward for relay networks. It is said to be unreliable when transmissions depend on the noise realization at nodes; examples include compress-forward and amplify-forward. The deterministic capacity of a network is defined as the supremum...
We propose a buffer-aided relaying protocol for a three node relay network comprised of a source, a half-duplex relay with buffer, and a destination. We assume a direct source-destination link is available and all links undergo fading. The proposed protocol enables the half-duplex relay to choose its reception and transmission time slots adaptively and based on the quality of the involved links. We...
We give a polar coding scheme that achieves the full admissible rate region in the Slepian-Wolf problem without time-sharing. The method is based on a source polarization result using monotone chain rule expansions.
We consider a fading AWGN 2-user 2-hop network in which the channel coefficients are independently and identically distributed (i.i.d.) drawn from a continuous distribution and vary over time. For a broad class of channel distributions, we characterize the ergodic sum capacity within a constant number of bits/sec/Hz, independent of signal-to-noise ratio. The achievability follows from the analysis...
In this paper, we propose a distributed rateless coding (DRC) scheme for a two-user cooperative system. In DRC, the overall transmission is divided into two phases, a broadcast phase and a cooperation phase. In the broadcast phase, each user keeps transmitting its rateless coded symbols to the other user and the destination until its message has been successfully decoded by the destination or the...
Motivated by the study of deletion channels, this work presents improved bounds on the number of subsequences obtained from a binary sting X of length n under t deletions. It is known that the number of subsequences in this setting strongly depends on the number of runs in the string X; where a run is a maximal sequence of the same character. Our improved bounds are obtained by a structural analysis...
In this paper we study the two unicast information flow problem over layered Gaussian networks with arbitrary number of nodes and connectivity, under the model of delayed channel state information (CSI) at transmitters and instantaneous CSI at receivers. We show that similar to the case with instantaneous CSI at transmitters (CSIT), the degrees of freedom (DoF) region is strictly larger than the time-sharing...
The combination of low-density parity-check (LDPC) codes and higher-order modulation does usually neither require an interleaver in between nor elaborated signal mapping design rules. However, as the constellation size increases, a matching interleaver can be employed to compensate performance losses, especially in case of structured codes. This interleaver can be generally described by mapping distributions...
An important practical open question has been to design explicit, structured optical receivers that achieve the Holevo limit in the contexts of optical communication and “quantum reading.” The Holevo limit is an achievable rate that is higher than the Shannon limit of any known optical receiver. We demonstrate how a sequential decoding approach can achieve the Holevo limit for both of these settings...
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