Akihiro Fujiwara

Multipath interference canceller for high-speed packet transmission with adaptive modulation and coding scheme in W-CDMA forward link

This paper proposes a multipath interference canceller (MPIC) associated with orthogonal code-multiplexing that achieves much higher peak throughput than 2 Mbit/s with adaptive data modulation for high-speed packet transmission in the wideband direct sequence-code division multiple access (W-CDMA) forward link, and evaluates its throughput performance by computer simulation. The simulation results elucidate that sufficient multipath interference (MPI) suppression is achieved by a four-stage MPIC with 6-12 orthogonal code-multiplexing using one iterative channel estimation with pilot and decision feedback data symbols and further that the interference rejection weight control according to the number of observed multipaths is effective in improving the throughput. It is also demonstrated that MPIC exhibits a superior MPI suppression effect to a chip equalizer in the lower received signal energy per bit-to-background noise spectrum density (E/sub b//N/sub 0/) channel around 0-3 dB owing to the successive channel estimation at each stage. We show that the maximum peak throughput using MPIC is approximately 2.1 fold that without MPIC in a two-path and three-path Rayleigh fading channel and that the peak throughput of 8.0 Mbit/s is achieved using 64 QAM data modulation in a two-path fading channel within a 5 MHz bandwidth. Furthermore, the required average E/sub b//N/sub 0/ for satisfying the same throughput with MPIC is decreased by more than 2.0 dB.

An optimal parallel algorithm for the Euclidean distance maps of 2-D binary images

Abstract This paper presents a PRAM algorithm for computing the n × n Euclidean distance map. This algorithm can be performed in O(log n) time using n 2 log n processors on the EREW PRAM and in O ( log n log log n ) time using n 2 log log n log n processors on the common CRCW PRAM, respectively. This algorithm is also applicable to many distance maps, for example, cityblock, chessboard, octagonal and chamfer distance maps.

PROCEDURES FOR LOGIC AND ARITHMETIC OPERATIONS WITH DNA MOLECULES

In this paper, we consider procedures for logic and arithmetic operations with DNA molecules. We first show a DNA representation of n binary numbers of m bits, and propose a procedure to assign the...

An optimal parallel algorithm for the Euclidean distance maps of binary images

The Euclidean distance map (EDM) of a black and white n/spl times/n binary image is the n/spl times/n map where each element has the Euclidean distance between the corresponding pixel and the nearest black pixel. The EDM plays an important role in machine vision, pattern recognition and robotics. Many algorithms have been proposed for computing the EDM. In recent years, O(n/sup 2/) time sequential algorithms were presented for computing the EDM. Hirata and Kato (1994) showed that their algorithm can be parallelized to run in O(n/sup 2//p) time using p processors (1/spl les/p/spl les/n) on the EREW PRAM. We present a parallel algorithm for computing the EDM. The algorithm runs in O(log n) time using n/sup 2//log n processors on the EREW PRAM and in O(log n/log log n) time using n/sup 2/ log log n/log n processors on the common CRCW PRAM, respectively. The algorithm is optimal in the sense that the product of the time and the number of processors is equal to the lower bound of the sequential time for computing the EDM.<<ETX>>

Access point selection algorithms for maximizing throughputs in wireless LAN environment

In wireless LAN technology, access point selection at each station is a critical problem in order to obtain satisfactory throughputs. The current protocol for access point selection is based on the received signal strength, and a concentration of stations causes a degradation of the entire wireless network. In the present paper, we propose two access point selection algorithms for maximizing two types of throughputs. The first algorithm is proposed for maximizing the average throughput of stations, and the second algorithm is proposed for maximizing the minimum throughput of stations. The experimental results of the proposed algorithms indicate that the proposed algorithms achieve a number of performance improvements compared with previous algorithms.

Addressable procedures for logic and arithmetic operations with DNA strands

In this paper, we consider addressable procedures with DNA strands for logic and arithmetic operations. Using a theoretical model for DNA computing, we first show a DNA representation of n binary numbers of m bits, and propose a procedure to assign values for the representation. The procedure is applicable to n binary numbers of m bits in O(1) lab steps in parallel. Next, we propose a procedure for logic operations. The procedure enables any Boolean operation whose input and output are defined by a truth table, and executes different kinds of Boolean operations simultaneously for any pair of n binary numbers of m bits in O(1) lab steps using O(mn) DNA strands. Finally, we propose a procedure for additions of pairs of two binary numbers. The procedure works in O(1) lab steps using O(mn) DNA strands for O(n) additions of two m-bit binary numbers.

LOGIC AND ARITHMETIC OPERATIONS WITH A CONSTANT NUMBER OF STEPS IN MEMBRANE COMPUTING

In the present paper, we propose P systems that work in a constant number of steps. We first propose two P systems for computing multiple input logic functions. An input of the logic functions is a set of n binary numbers of m bits, and an output is a binary number defined by the logic functions. The first and second P systems compute AND and EX-OR functions for the input, and both of the P systems work in a constant number of steps by using O(mn) types of objects, a constant number of membranes, and evolution rules of size O(mn). Next, we propose a P system for the addition of two binary numbers of m bits. The P system works in a constant number of steps by using O(m) types of objects, a constant number of membranes and evolution rules of size O(m2). We also introduce a P system that computes the addition of two vectors of n binary numbers of m bits by using the above P system as a sub-system. The P system for vector addition works in a constant number of steps by using O(mn) types of objects, a constant number of membranes, and evolution rules of size O(m2n).

A Cost Optimal Parallel Algorithm for Patience Sorting

In this paper, we consider a parallel algorithm for the patience sorting. The problem is not known to be in the class NC or P-complete. We propose two algorithms for the patience sorting of n distinct integers. The first algorithm runs in time using p processors on the EREW PRAM, where m is the number of decreasing subsequences in a solution of the patience sorting. The second algorithm runs in time using p processors on the EREW PRAM. If is satisfied, the second algorithm becomes cost optimal.

Parallelizability of Some P-Complete Problems

In this paper, we consider parallelizability of some P-complete problems. First we propose a parameter which indicates parallelizability for a convex layers problem. We prove P-completeness of the problem and propose a cost optimal parallel algorithm, according to the parameter. Second we consider a lexicographically first maximal 3 sums problem. We prove P-completeness of the problem by reducing a lexicographically first maximal independent set problem, and propose two cost optimal parallel algorithms for related problems. The above results show that some P-complete problems have efficient cost optimal parallel algorithms.

A simple parallel algorithm for the medial axis transform of binary images

The medial axis transform (MAT) is an image representation scheme. For a binary image, the MAT is defined as a set of upright maximal squares which consist of pixels of value 1 entirely. The MAT plays an important role in image understanding. The paper presents a parallel algorithm for computing the MAT of an n/spl times/n binary image. We show that the algorithm can be performed in O(log n) time using n2/log n processors on the EREW PRAM and in O(log log n) time using n/sup 2//log log n processors on the common CRCW PRAM. We also show that the algorithm can be performed in O(n/sup 2//p/sup 2/+n) time on a p/spl times/p mesh and in O(n/sup 2//p/sup 2/+(n log p)/p) time on a p/sup 2/ processor hypercube (for 1/spl les/p/spl les/n). The algorithm is cost optimal on the PRAMs, on the mesh (for 1/spl les/p/spl les//spl radic/n) and on the hypercube (for 1/spl les/p/spl les/n/log n).