8188037
Performance evaluation of distributed-antenna communications systems using beam-hopping
Digital beamforming (DBF) techniques are capable of improving the performance of communications systems significantly. However, if the transmitted signals are conflicted with strong interference, especially, in the direction of the transmitted beams , these directional jamming signalswill severely degrade the system performance. In order to efficiently mitigate the interference of the directional jammers, in this contribution a beam-hopping (BH) communications scheme is proposed. In the proposed BH communications scheme, only one pair of the beams is used for transmission and it hops from one to the next according to an assigned BH pattern. In this contribution a range of expressions in terms of the average SINR performance have been derived, when both the uplink and downlink are considered. The average SINR performance of the proposed BH scheme and that of the conventional single-beam (SB) as well as multiple-beam (MB) assisted beam-processing schemes have been investigated. Our analysis and results show that the proposed BH scheme is capable of efficiently combating the directional jamming, with the aid of utilizing the directional gain of the beams generated by both the transmitter and the receiver. Furthermore, the BH scheme is capable of reducing the intercept probability of the communications. Therefore, the proposed BH scheme is suitable for communications, when several distributed antenna arrays are available around a mobile.
17529460
Systematic redundant residue number system codes: analytical upper bound and iterative decoding performance over AWGN and Rayleigh channels
The novel family of redundant residue number system (RRNS) codes is studied. RRNS codes constitute maximum-minimum distance block codes, exhibiting identical distance properties to Reed-Solomon codes. Binary to RRNS symbol-mapping methods are proposed, in order to implement both systematic and nonsystematic RRNS codes. Furthermore, the upper-bound performance of systematic RRNS codes is investigated, when maximum-likelihood (ML) soft decoding is invoked. The classic Chase algorithm achieving near-ML soft decoding is introduced for the first time for RRNS codes, in order to decrease the complexity of the ML soft decoding. Furthermore, the modified Chase algorithm is employed to accept soft inputs, as well as to provide soft outputs, assisting in the turbo decoding of RRNS codes by using the soft-input/soft-output Chase algorithm
21840466
Acquisition of$m$-Sequences Using Recursive Soft Sequential Estimation
A novel sequential estimation method is proposed for the initial synchronization of pseudonoise (PN) signals derived from m-sequences. This sequential estimation method is designed based on the principle of recursive soft-in/soft-out (SISO) decoding, and we refer to it as the recursive soft sequential estimation (RSSE) acquisition scheme. The RSSE acquisition scheme exhibits a complexity similar to that of a conventional m-sequence generator, which increases only linearly with the number of stages in the m-sequence generator. Our simulation results also show that the acquisition time of the proposed RSSE acquisition scheme is also linearly dependent on the number of stages in the m-sequence generator. Owing to the above properties, the employment of the proposed RSSE acquisition scheme is beneficial for the acquisition of long m-sequences.
974543
A framework for sensor management in wireless and heterogeneous sensor network
This paper proposes a framework for sensor configuration and management in wireless multi sensor network system, which is responsible for taking decisions in order to coordinate the assignment and scheduling of sensors best suited for the application. A sensor manager operates over a heterogeneous sensor network, which provides sensory data from multiple types of sensors. The application of this work is tracking the movement of objects in a moderately occupied confined space. Simulations were run to study the operations of the proposed sensor manage in such application. The simulation results are compared to other published results to show the effectiveness of this work.
3869043
XQuery Translation to Sem-SQL
XML query translation is an inevitable step involved in using non-XML databases storing XML data. In this paper, we address the XQuery to Sem-SQL translation issue, part of the XML storage and retrieval using the Semantic Binary Object-Oriented Database System (Sem-ODB) project, by providing a high-level description of the translation scheme between XQuery and Sem-SQL. Our translation scheme utilizes the navigation-oriented paradigm of Sem-SQL in translating XQuery path expressions to avoid excessive joins. Our approach can deal with all recursive path expressions without requiring the underlying database system to support recursive queries. We also extend the sorted outer union approach with consideration on user-defined orderings.
2470832
Statistical data reduction for efficient application performance monitoring
There is a growing need for systems that can monitor and analyze application performance data automatically in order to deliver reliable and sustained performance to applications. However, the continuously growing complexity of high performance computer systems and applications makes this process difficult. We introduce a statistical data reduction method that can be used to guide the selection of system metrics that are both necessary and sufficient to describe observed application behavior, thus reducing the instrumentation perturbation and data volume to be managed. To evaluate our strategy, we applied it to one CPU-bound grid application using cluster machines and GridFTP data transfer in a wide area testbed. A comparative study shows that our strategy produces better results than other techniques. It can reduce the number of system metrics to be managed by about 80%, while still capturing enough information for performance predictions.
15362390
Transforming Sem-ODM semantic schemas to DTDs
Exporting data in traditional databases as XML documents so that non-XML data can be accessed and exchanged seamlessly among applications has been studied in a number of projects. In this paper, we present an algorithm that automatically derives a Document Type Definition (DTD) from a Semantic Schema of the Semantic Binary Object-Oriented Data Model (Sem-ODM) based on the formal definitions of DTDs and Semantic Schemas. The structure and semantic information of a Semantic Schema is captured and expressed naturally in a DTD without applying any complicated operators or scanning the actual data stored in the database. Furthermore, the formalization of the two schemas connects the two data models and helps us better understand the capabilities brought about by publishing Sem-ODB data as XML.
11280884
A novel cache design for vector processing
This paper introduces an innovative cache design for vector computers, called prime-mapped cache. By utilizing the special properties of a Mersenne prime, the new design does not increase the critical path length of a processor, nor does it increase the cache access time as compared to a direct-mapped cache. The prime-mapped cache minimizes cache miss ratio caused by line interferences that have been shown to be critical for numerical applications by previous investigators. We show that significant performance gains are possible by adding the proposed cache memory into an existing vector computer provided that application programs can be blocked. The performance gain will increase with the increase of the speed gap between processors and memories. We develop an analytical performance model based on a generic vector computation model to study the performance of the design. Our preliminary performance analysis on various vector access patterns shows that the prime-mapped cache can provide as much as a factor of 2 to 3 performance improvement over the conventional direct-mapped cache in the vector processing environment. Moreover, the additional hardware cost introduced by the new mapping scheme is negligible.