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Serially-concatenated low-density for transmission over AWGN generator matrix (SCLDGM) codes and Rayleigh fading channels

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2007年第8期6卷 2753-2758页

作者： Gonzalez-Lopez, Miguel Vazquez-Araujo, Francisco J. Castedo, Luis Garcia-Frias, Javier Univ A Coruna Dept Elect & Sistemas La Coruna 15071 Spain Univ Delaware Dept ECE Newark DE 19716 USA

Low Density Generator Matrix (LDGM) codes are a particular class of Low Density Parity Check (LDPC) codes with very low encoding complexity. Single LDGM codes present high error-floors, which can be substantially reduced with the serial concatenation of two LDGM (SCLDGM) codes. We propose a technique to obtain good SCLDGM codes using EXtrinsic Information Transfer (EXIT) functions in a novel way. Although the optimization is performed for AWGN channels with binary signaling, the resulting codes are also optimal for AWGN and perfectly-interleaved Rayleigh fading channels with non-binary signaling and perfect CSI at reception, provided that Gray mapping is utilized. Optimized regular and irregular SCLDGM codes outperform heuristically-designed LDGM codes existing in the literature, and have a performance similar to or better than that of Irregular Repeat Accumulate (IRA) codes.

关键词： code design Gaussian channels LDGM codes LDPC codes Rayleigh fading channels

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Optimal bandwidth allocation for multimedia mobile networks using particle swarm optimization 07

Optimal bandwidth allocation for multimedia mobile networks ...

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4th international Conference on Mobile Technology, Applications and Systems, Mobility 2007, Incorporating the 1st international symposium on Computer Human Interaction in Mobile Technology, IS-CHI 2007

作者： Karthikeyan, N.K. Narayanasamy, P. CSE Dept. Sri Krishna College of Engg. and Tech. Coimbatore - 641 008 Tamilnadu India Dept. of CSE Anna University Chennai-600 023 India

ISBN: (纸本)9781595938190

though significant improvement in communication infrastructure has been attained in the mobile network technology, the issues concerning the optimized bandwidth allocation to different applications in a reasonable time remain challenging and need to be solved. Also varying mobility and various service class requirements of present multimedia applications makes it more critical. It is mostly realized in the present third generation (3G) and Beyond 3G (B3G) mobile network system. Hence an effective and efficient bandwidth optimization schemes for a cellular mobile network system are needed. In this paper we propose an algorithm based upon the Particle Swarm optimization (PSO) approach to solve the bandwidth allocation problem. the PSO algorithm is an adaptive algorithm based on a social-psychological metaphor;a population of individuals adapts by returning stochastically toward previously successful regions. Although PSO is a population based evolutionary technique like Genetic Algorithm it differs in that each particle or solution contains a position, velocity and acceleration. We explore and analyze the behavior of particle by examining the computational results of our PSO algorithm under different parameter settings. the performance of the PSO algorithm is compared with metaheuristic technique namely Simulated annealing (SA). Experimental results shown that the proposed PSO algorithm is an efficient and competitive approach in composing fairly good results with respect to solution quality and execution time for the bandwidth optimization problem as compared with SA. Copyright 2007 ACM.

关键词： Simulated annealing

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Low-Complexity Blind Adaptive MIMO Receivers for CDMA Systems with Space-Time Block-codes in Multipath Channels

Low-Complexity Blind Adaptive MIMO Receivers for CDMA System...

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international symposium on Wireless Communication Systems (ISWCS)

作者： R. C. de Lamare R. Sampaio-Neto Communication Research Group Department of Electronics University of York UK CETUC/Pontifical Catholic University of Rio de Janeiro Brazil

In this paper we present low-complexity blind multi-input multi-output (MIMO) adaptive linear multiuser receivers for direct sequence code division multiple access (DS-CDMA) systems using multiple transmit antennas and space-time block codes (STBC) in multipath channels. A space-time code-constrained constant modulus (CCM) design criterion based on constrained optimization techniques and low-complexity stochastic gradient (SG) adaptive algorithms are developed for estimating the parameters of the space-time linear receivers. the receivers are designed by exploiting the unique structure imposed by both spreading codes and STBC. A blind space-time channel estimation scheme for STBC systems based on a subspace approach is also proposed along with an efficient SG algorithm. Simulation results for a downlink scenario assess the receiver structures and algorithms and show that the proposed schemes achieve excellent performance, outperforming existing methods.

关键词： MIMO Multiaccess communication Multipath channels Direct-sequence code-division multiple access Adaptive arrays Receiving antennas Block codes Algorithm design and analysis Constraint optimization Design optimization

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Acquisition of an Unknown Hopping code in an Ultra-Wideband FH-OFDM System

Acquisition of an Unknown Hopping Code in an Ultra-Wideband ...

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Fourth international symposium on Wireless Communication Systems (ISWCS'07), vol.2

作者： Paavo Hahtola Antti Anttonen Aame Mammela VTT Technical Research Center of Finland Oulu Finland

In this paper, we study methods for code acquisition in a burst-type ultra-wideband (UWB) frequency-hopped (FH) orthogonal frequency division multiplexing (OFDM) system. In the first scenario, the time-frequency code (TFC) that controls the frequency-hopping is assumed to be completely unknown to the receiver, while in the other scenario we make simplifying assumptions with regard to the TFC. Data-aided (DA) decision variable generation method is used, which aims at keeping the acquisition time and training data overhead to a minimum. Parallel and serial receiver algorithms are proposed for the scenarios, and an iterative serial method for acquiring the TFC is developed. While the parallel receiver enables fast detection, in some cases it is unfeasible due to its complexity. the receiver using the low-complexity serial approach needs more information about the TFC to ensure efficient operation. Simulation results prove that it achieves good performance when such conditions exist.

关键词： Timing synchronization Multi-carrier modulation Frequency-hopping Training signal Differential correlation

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Blind Adaptive Constrained Reduced-Rank Estimation Algorithms for Constant Modulus Signals Applied to CDMA Interference Suppression

Blind Adaptive Constrained Reduced-Rank Estimation Algorithm...

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Fourth international symposium on Wireless Communication Systems (ISWCS'07), vol.2

作者： Rodrigo C. de Lamare Martin Haardt Raimundo Sampaio-Neto Communication Research Group Department of Electronics University of York UK Communications Research Laboratory Ilmenau University of Technology Germany CETUC/Pontifical Catholic University of Rio de Janeiro Brazil

this work proposes a multistage decomposition for blind adaptive parameter estimation in the Krylov subspace with the code-constrained constant modulus (CCM) design criterion. Based on constrained optimization of the constant modulus cost function and utilizing the Lanczos algorithm and Arnoldi-like iterations, a multistage decomposition is developed for blind parameter estimation. A family of computationally efficient blind adaptive reduced-rank stochastic gradient (SG) and recursive least squares (RLS) type algorithms is also devised and evaluated against existing methods. Simulation results consider the application of the proposed techniques to the suppression of multi-access and intersymbol interference in DS-CDMA systems.

关键词： Interference constraints Multiaccess communication Interference suppression Parameter estimation Constraint optimization Cost function Stochastic processes Least squares methods Resonance light scattering Computational modeling

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On the Optimized Patent-Free LDPC code Design for Content Distribution Systems

On the Optimized Patent-Free LDPC Code Design for Content Di...

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international symposium on Wireless Communication Systems (ISWCS)

作者： Dejan Vukobratovic Vojin Senk Department of Communications and Signal Processing University of Novi Sad Yugoslavia

In this paper, we analyze the application of asymptotic and finite-length analysis and design of low-density parity-check (LDPC) codes for the large scale content distribution systems over packet based networks, such as MBMS or DVB-H. We show connections of the classical coding theory performance measure, the bit error rate (BER) performance, and the measure called the overhead factor which is of interest in the content distribution systems. We point out to LDPC codes design methods that can provide an excellent overhead factor performance. Particularly, we are interested in performance limits of the class of patent-free LDPC codes.

关键词： Design optimization Parity check codes Forward error correction Measurement Signal design Signal analysis Digital video broadcasting Bit error rate Iterative decoding Algorithm design and analysis

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A Hashing-based Anti-Collision Algorithm for RFID Tag Identification

A Hashing-based Anti-Collision Algorithm for RFID Tag Identi...

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international symposium on Wireless Communication Systems (ISWCS)

作者： G. Binetti G. Boggia P. Camarda L. A. Grieco Dipartimento di Elettrotecnica ed Elettronica Politecnico di Bari Bari Italy

Anti-collision algorithms are responsible for fast and energy efficient identification of RFID tags. they can be classified in Tree or Aloha based. To exploit benefits of both approaches, in this paper, we present a hybrid anti-collision algorithm. We assume that each tag stores a unique product identifier (ID) and the output of a hash function applied to that ID, which is shorter than the entire ID. With the proposed algorithm, in a first step, the reader, exploiting a Query Tree approach, queries the tags trying to identify each tag ID with the corresponding digest. When a hash collision is revealed, a second step, based on Framed Slotted Aloha Protocol, is used by the reader to identify only tag IDs with same digest. Numerical results have shown that the developed method, when using the most general Electronic Product code scheme for tags addressing, improves performance in terms of mean identification delay with respect to query based protocols. Moreover, it gets about the same performance of the Binary Tree protocol, but overcoming its principal drawbacks.

关键词： RFID tags Radiofrequency identification Protocols Intrusion detection Binary trees Product codes Random number generation Telephony Energy efficiency Classification tree analysis

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Post register allocation spill code optimization 06

Post register allocation spill code optimization

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4th international symposium on code generation and optimization

作者： Lupo, Christopher Wilken, Kent D. Univ Calif Davis Dept Elect & Comp Engn Davis CA 95616 USA

ISBN: (纸本)0769524990

A highly optimized register allocator should provide an efficient placement of save/restore code for procedures that contain calls. this paper presents a new approach to placing callee-saved save and restore instructions that generalizes Chow's shrink-wrapping technique[6]. An efficient, profile-guided, hierarchical spill code placement algorithm is used to analyze the structure of a procedure to calculate the minimum dynamic execution count locations to place callee-saved save and restore code. the algorithm is implemented in the Gnu Compiler Collection and has been tested on the SPEC CPU2000 Integer Benchmark suite. Results show that the technique reduces the number of dynamic load and store instructions by 15% compared to saving and restoring at procedure entry and exit while Chow's shrink-wrapping technique reduces dynamic load and store instructions by only 1% compared to saving and restoring at procedure entry and exit. the dynamic number of callee-saved save and restore instructions inserted with this new approach is never greater than the number produced by Chow's shrink-wrapping technique or the placement at procedure entry and exit.

关键词： Registers Algorithm design and analysis Benchmark testing Cost function

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Tailoring graph-coloring register allocation for runtime compilation 06

Tailoring graph-coloring register allocation for runtime com...

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4th international symposium on code generation and optimization

作者： Cooper, Keith D. Dasgupta, Anshurnan Rice Univ Houston TX 77251 USA

ISBN: (纸本)0769524990

Just-in-time compilers are invoked during application execution and therefore need to ensure fast compilation times. Consequently, runtime compiler designers are averse to implementing compile-time intensive optimization algorithms. Instead, they tend to select faster but less effective transformations. In this paper we explore this trade-off for an important optimization - global register allocation. We present a graph-coloring register allocator that has been redesigned for runtime compilation. Compared to Chaitin-Briggs [7], a standard graph-coloring technique, the reformulated algorithm requires considerably less allocation time and produces allocations that are only marginally worse than those of Chaitin-Briggs. Our experimental results indicate that the allocator performs better than the linear-scan and Chaitin-Briggs allocators on most benchmarks in a runtime compilation environment. By increasing allocation efficiency and preserving optimization quality, the presented algorithm increases the suitability and profitability of a graph-coloring register allocation strategy for a runtime compiler.

关键词： Optimizing compilers Runtime environment Design optimization Java Virtual machining Algorithm design and analysis Profitability Program processors Virtual manufacturing Costs

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Practical structure layout optimization and advice 06

Practical structure layout optimization and advice

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4th international symposium on code generation and optimization

作者： Hundt, Robert Mannarswamy, Sandya Chakrabarti, Dhruva Hewlett Packard Corp Java Compilers & Tools Lab Palo Alto CA 94304 USA

ISBN: (纸本)0769524990

With the delta between processor clock frequency and memory latency ever increasing and with the standard locality improving transformations maturing, compilers increasingly seek to modify an application's data layout to improve spatial and temporal locality and to reduce cache miss and page fault penalties. In this paper we describe a practical implementation of the data layout optimizations Structure Splitting, Structure Peeling, Structure Field Reordering and Dead Field Removal, both for profile and non-profile based compilations. We demonstrate significant performance gains, but find that automatic transformations fail for a relatively high number of record types because of legality violations or profitability constraints. Additionally, we find a class of desirable transformations for which the framework cannot provide satisfying results. To address this issue we complement the automatic transformations with an advisory tool. We reuse the compiler analysis done for automatic transformation and correlate its results with performance data collected during runtime for structure fields, such as data cache misses and latencies. We then use the compiler as a performance analysis and reporting tool and provide insight into how to layout structure types more efficiently.

关键词： Optimizing compilers Delay Runtime Clocks Profitability Performance analysis Java Laboratories Frequency Performance gain

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