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Space Time Block Code (STBC) schemes are widely used in MIMO systems for link performance improvement. For more than two transmit antenna systems, Quasi Orthogonal STBC (QOSTBC) and Constellation Rotation QOSTBC (CR-QOSTBC) is found to be appropriate. Various proposed STBC schemes are evaluated over Rayleigh fading channels, where there is no consideration for correlation between antennas. Inadequate...
It is well known that extremely long low-density parity-check (LDPC) codes perform exceptionally well for error correction applications, short-length codes are preferable in practical applications. However, short-length LDPC codes suffer from performance degradation owing to graph-based impairments such as short cycles, trapping sets and stopping sets and so on in the bipartite graph of the LDPC matrix...
A Wireless Sensor Network is a network of sensors that senses specified parameter(s) related to environment; processes data locally or in a distributed manner and wirelessly communicates information to central Base Station. The Base Station analyzes information and initiates suitable response if required. The complexities introduced by severely limited processing capabilities, memory and power supply...
The minimum distance of linear block codes is one of the important parameter that indicates the error performance of the code. When the code rate is less than 1/2, efficient algorithms are available for finding minimum distance using the concept of information sets. When the code rate is greater than 1/2, only one information set is available and efficiency suffers. In this paper, we investigate and...
The principles of distributed source coding or Slepian-Wolf coding, primarily employed for compression of correlated sources with side information, can also be used for reducing the encoder complexity of a single source. This effectively shifts the encoder complexity to the decoder. This exchange of computational complexities has opened up the door for many applications in wireless video and image...
TCP is the most common transport layer protocol used in Internet. It was designed primarily for wired networks, assuming reliability at lower layers and packet losses are considered as an indication of congestion. The characteristic of wireless links is very different from wired links, particularly in terms of loss behavior. In wireless networks, most packet losses are due to poor link quality and...
Because of increased design complexity and advanced fabrication technologies, the number of tests and corresponding data volume increases rapidly. As the large size of test data volume is becoming one of the major problems in testing System-on-a-Chip (SoC), several compression coding schemes have been proposed in past. Run length coding is one of the most familiar coding methodologies for compression...
Test data compression is a basic necessity for today's test methodology with reference to test cost and test time. This paper presents a compression/decompression scheme based on frequency dependant bit appending of test vector used with statistical codes. In the proposed scheme, the emphasis is not only on data compression but it aims the data compression with a smaller amount of silicon area overhead...
As a result of the emergence of new fabrication technologies and design complexities, standard stuck-at scan tests are no longer sufficient. The number of tests and corresponding data volume increase with each new fabrication process technology. The demand goes to well beyond 100X tester cycle reduction considering new fault models. The test data compression has been an emerging need of VLSI field...
Replay protection is one of the three vital security attributes, desirable in a link layer security protocol for a wireless sensor network (WSN). Whether to implement replay protection at the link layer or at the application layer, in the WSNs, remains a debatable issue. For, the popular WSN link security framework TinySec does not offer replay protection, whereas MiniSec at the other extreme, implements...
The Ka band regenerative payload is a transponder of GSAT-4 satellite. It provides Narrow Spot Beams, Wide Bandwidth and small size of antenna for both transmission and reception. The Signaling Demodulator is a one of the important subsystem of regenerative Payload. This Signaling Demodulator was developed in-house for providing signaling information to provide communication between one spot beam...
Raised Cosine (RC) type of digital FIR Pulse Shaping Filters (PSF) have been developed & implemented in the QPSK Modulators for GSAT-4 regenerative payload. These filters maintain stable spectrum against wide temperature variation across different panels of the satellite. They also ensure minimum Inter Symbol Interference (IST) and hence, provide excellent eye opening (= 90 %) at the sampling...
An opportunity has been proposed recently by the Space Applications Center (SAC) of the Indian Space Research Organization (ISRO) to carry out a propagation experiment at Ka-band over India. To this purpose, the GSAT-4 satellite will board two propagation beacons at 20.2 GHz and 30.5 GHz in linear polarization. The objective of this paper is to present the GSAT-4 propagation experiment. In a first...
In this paper we have studied and carried out performance evaluation of Peer-to-Peer (P2P) networking in context of satellite image processing. The application scenarios identified are sharing of satellite image data, P2P enabled nowcasting and forecasting and sharing of distributed computing resources using P2P. JXTA is used to setup a P2P based network and the peer discovery and peer bootup aspects...
This paper consists of design and analysis of direct digital frequency synthesizer (DDFS). Its key elements are: phase accumulator, a phase to amplitude converter (sine ROM) also called look-up table (LUT), a digital to analog converter (DAC) and a filter. The phase values are generated using modulo 2N overflowing property of a N-bit phase accumulator. Higher compression in ROM is achieved, by taking...
Mobile Wireless Broadband Access (MWBA) in latest WiMax versions (IEEE 802.16e onwards) has critical requirement of vehicular mobility. OFDM is a wideband multicarrier digital modulation scheme, very much suitable for applications like WiMax because of its features such as ISI elimination and high speed support due to parallel transmissions. Now, complexity in the WiMax system is because of fast varying...
In this paper, we carry out the performance evaluation of satellite image resampling software, which follows service-oriented architecture and the service executes on a distributed operating system. The parameters, which are used for performance evaluation, include load balancing under multiple instance execution, overheads of process migration, effect of file caching and replication and performance...
In this paper, we carry out the performance evaluation of satellite image resampling software, which follows service-oriented architecture and the service executes on a distributed operating system. The parameters, which are used for performance evaluation, include load balancing under multiple instance execution, overheads of process migration, effect of file caching and replication and performance...
The integration of wireless links (terrestrial and satellite) with terrestrial wired networks has been a subject of extensive research keeping in view the performance issues of TCP with wireless links. Performance improvement in SACK TCP has been shown earlier by delaying fast recovery. However, the technique of delayed fast recovery just avoids flow control in case of random loss. If congestion cannot...
Wireless links have been increasingly used in expanding Internet, making it possible to provide TCP/IP based services even in rural areas. The widely used TCP has been designed to operate efficiently over traditional almost error-free wired links with relatively low delay. Existing TCP suffers from channel delay and errors. No congestion control is needed for losses due to channel problems. In this...
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