The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
The following topics were dealt with: properties of codes; feedback and cooperation in networks; channel coding, communication techniques and estimation methods; construction, analysis and decoding of LDPC codes; sequences and permutations; universal lossless compression; capacity and coding for fading channels; network theory; statistical mechanics; turbo and turbo-like code constructions; communication...
This paper considers networks where nodes are connected randomly and can fail at random times. It provides scaling laws that allow to find the critical time at which isolated nodes begin to appear in the system as its size tends to infinity. Applications are in the areas of sensor and ad-hoc networks where nodes are subject to battery drainage and 'blind spots' formation becomes a primary concern...
Fidelity is one of the key considerations in data collection schemes for sensor networks. A second important consideration is the energy expense of achieving that fidelity. Data from multiple correlated sensors is collected over multi-hop routes and fused to reproduce the phenomenon. However, the same distortion may be achieved using multiple rate allocations among the correlated sensors. These rate...
We define the routing capacity of a network to be the supremum of all possible fractional message throughputs achievable by routing. We prove that the routing capacity of every network is achievable and rational, we present an algorithm for its computation, and we prove that every non-negative rational number is the routing capacity of some network. We also determine the routing capacity for various...
In a sensor network, the data collected by different sensors are often correlated because they are observations of related phenomena. This property has prompted many researchers to propose data centric routing to reduce the communication cost. In this paper, we design heuristic algorithms for combined routing and source coding with explicit side information. We build a data rate model upon the observation...
An analytical approach to a search process is a mathematical prerequisite for digital synchronization acquisition analysis and optimization. A search is performed for an arbitrary set of sequences within random but not equiprobable L-ary data. This paper derives in detail an expression for probability distribution function, from which other statistical parameters - expected value and variance - can...
T-decomposition maps a finite string into a series of parameters for a recursive string construction algorithm. Initially developed for the communication of coding trees (M. R. Titchener, June 1996), (U. Guenther, Feb. 2001), T-decomposition has since been studied within the context of information measures. This involves the parsing of potentially very large strings, which in turn requires algorithms...
Recently we presented information-theoretic bounds for the achievable rates of pattern recognition systems operating under data compression constraints. In this paper we improve on our previous inner bound, and report progress toward finding formulas for the achievable rate region boundaries in the special cases where the pattern data is either binary or Gaussian
Pattern recognition systems may be designed to recognize an exponentially large number of objects from potentially noisy measurements. We propose a design based on storing compressed representations of binary patterns corresponding to objects of interest. Sensor measurements are similarly compressed and recognition proceeds by comparing the compressed sensor measurements to the compressed representations...
We consider coset LDPC codes over GF(q), designed for use over arbitrary channels (particularly nonbinary and asymmetric channels). We show that the random selection of the nonzero elements of the GF(q) parity-check matrix induces a permutation-invariance property on the densities of the messages produced by the decoder. We use this property to show that under a Gaussian approximation, the entire...
We consider the ensemble of regular LDPC codes and obtain an expression for the second moment of the distance spectrum. We show how this expression can be used to derive a lower bound on the probability that the growth rate of a randomly chosen code from the ensemble is equal to the growth rate of the average distance spectrum, when the block length is sufficiently large. In particular, when the connectivity...
New upper bounds on the rate of low-density parity-check (LDPC) codes as a function of the minimum distance of the code are derived. These bounds are based on combinatorial arguments and linear programming. They improve on the previous bounds due to Burshtein et al. It is proved that at least for high rate LDPC codes have worse relative minimum distance than the one guaranteed by the Gilbert-Varshamov...
We show for a large class of LDPC ensembles, including RA and IRA codes, that the bit iterative decoding threshold is essentially identical to the block iterative decoding threshold
A cognitive radio can sense the transmission of other users in its environment and possibly extract the corresponding messages. It can use this information to transmit over the same channel while reducing interference from, and to other users. In this paper, we define inter/intra-cluster competitive, cooperative, and cognitive behavior in wireless networks. We define intercluster cognitive behavior...
We analyze a distributed M-user multiple-access problem in both the additive white Gaussian noise channel and the discrete memoryless channel. A system where each user independently chooses a transmission rate according to a probability distribution function is considered. Under the assumption of symmetric capacity regions, we show that the optimal transmission rate distribution is a point mass for...
We consider a multiple access channel shared by two sources. The channel is noiseless but there is interference between the transmissions of the sources. Because of applications to distributed control we are interested in the real-time version of this problem, in which the receiver must act immediately upon received information. Block coding is therefore not possible, and error probability cannot...
We extend Shannon's result on the capacity of channels with state information to multiple user channels. More specifically, we characterize the capacity (region) of degraded broadcast channels and physically degraded relay channels where the channel state information is causally available at the transmitters. We also obtain inner and outer bounds on the capacity region for multiple access channels...
We introduce a new problem of broadcast source coding with a discrimination requirement - there is an eavesdropping user from whom we wish to withhold the true message in an entropic sense. Binning can achieve the Slepian-Wolf rate, but at the cost of full information leakage to the eavesdropper. Our main result is a lower bound that implies that any entropically efficient broadcast scheme must be...
Designing a communication system using joint source-channel coding in general makes it possible to achieve a better performance than when the source and channel codes are designed separately, especially under strict delay-constraints. The majority of work done in joint source-channel coding uses a discrete channel model, corresponding to an analog channel in conjunction with a hard decision modulation...
Motivated by the sensor network setting, we consider lossless storage of correlated discrete memoryless sources. The underlying tradeoff is between exploitation of inter-source correlation for low rate storage and efficient (low rate) selective retrieval from the fusion storage. We define the problem of shared descriptions (SD) source coding and relate it to the storage and retrieval problem. We present...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.