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When cluster heads transmit their data to the sink via multi-hop communication, the cluster heads closer to the sink are burdened with heavy relay traffic and tend to die early. On the contrary, if all cluster heads transmit data's to the sink via single-hop communication, the cluster heads further from the sink will die much more quickly than those closer to the sink. In this paper, we first develop an analytical model to derive the optimal cluster radius. Then we propose a hybrid communication method where the nodes can transmit data to the sink in either single-hop or multi-hop. Finally, we conduct extensive experiments and show that our method outperforms LEACH and HEED in terms of network lifetime by balancing energy consumption. [ABSTRACT FROM AUTHOR]

Wireless Sensor Network technology is a kind of new data gathering and transmission technology, which combines with wireless communication, sensors, embedded computing and distributed information processing. It has the great potential with various applications in military defense, industrial automation and transportation. This paper mainly focuses on the developing present situation and trend of wireless sensor network routing protocol, its research hotspot and difficulty. It analyzes the application of wireless sensor network in various fields, pointing out the potential problems, and puts forward some improvement methods. Theoretical guidance is provided for further research and expanding the application range of wireless sensor network. [ABSTRACT FROM AUTHOR]

Remote Attestation is very importance in trusted computing, and the attestation evidence is foundation of the Remote Attestation. However, the existing technologies are not pay close attention on the protection of attestation evidence. In this paper, through research the main technologies of Remote Attestation, and analyze the attestation evidence in each method, providing a TPM-based protection mechanism for remote attestation evidence. The mechanism for Remote Attestation to ensure the secure transmission of the attestation's information, and designing a common communication protocol to guarantee the confidentiality and integrity of remote attestation's information in the course of transmission. [ABSTRACT FROM AUTHOR]

In the structure of distributed cluster server, web log data mining model based on data warehouse has the defects of bottlenecks in the network and computing, transmission errors caused by the large data transmission, the paper makes use of the advantages of cloud computing, distributed processing and virtualization technology, designs a type of Web log analysis platform based on cloud computing Hadoop cluster framework, finally, a new hybrid algorithm of distributed procession in the cloud computing environment is proposed. To further verify the efficiency of the platform, we use the improved data pretreatment algorithm on the platform of processing large number of Web logs, experimental results show that it can improve the efficiency of Web data mining. [ABSTRACT FROM AUTHOR]

WIMAX relay station mesh network has been approved by IEEE 802.16j as a standard to provide a highly data rate transmission , the RS was implemented to extend the coverage zone of the BS, for instance the MSs previously were out of the coverage of the BS they become in the coverage of the RS, therefore these MSs can have Admission control from the BS through the RS. This paper describe a problem in the mesh network Relay station, for instance the problem of how to serve the mobile stations (MSs) which are out of the Relay station coverage. This paper also proposed a solution for mobile stations out of the coverage of the WIMAX Relay stations mesh Network. Therefore Ad-hoc network defined as a solution by using its admission control schema and apply it on the mobiles inside and outside the Relay station coverage. [ABSTRACT FROM AUTHOR]

This paper mainly studies the data communication protocols of control area network (CAN) for the vehicle information systems. The objective is to create the environment of the line replaceable unit (LRU) in these systems. The data transmitted from CANBus are one of the valuable resources. There are 8 bytes of them in each transmission. If they are appropriately planned, the data communication protocol can improve the efficiency of the communication, e.g., arbitrations, masks, filters of nodes for CAN can be assigned arbitrarily on line. Even the software of CAN unit can be upgraded and downloaded on line, too. Upon the above concept, this paper will propose a feasible configuration of the vehicle information systems as well as a kind of possible data communication protocols. [ABSTRACT FROM AUTHOR]

As XML became an official recommendation of the World Wide Web Consortium (W3C) in 1998, it is increasingly being used to transmit data on networks but is a verbose format and needs an efficient encoding to send relatively large amounts of data efficiently, which is most attractive to wireless data communications. It is a common technical challenge for researchers in XML-driven networks to have good performance. There are many papers discussed this issues, such as one may employ a middleware to enhance performance by minimizing the impact of transmission time [1, 3]. Normally, to reduce the amount of data sent the XML documents are converted to a binary format using a compression routine such as Gzip. However while this would reduce the amount of data, it results in an increase in the CPU time as the XML document must be compressed before being sent and uncompressed when it is received. In this paper we extended our previous research results [2, 11-14] to an enabling technology, namely Dynamic Adaptive Threshold Transmission (DATT) for XML data on networks, in particularly focusing on "dynamic" nature. We also show the experimental results obtained from our technique and that from the Network Adaptable Middleware (NAM) established by Ghandeharizadeh et al [1]. Experimental results show that our method is superior to the NAM method [1], which supported by the fact that the time taken is 220.6 times better in the applied regions. [ABSTRACT FROM AUTHOR]

In the first part of this paper we present experimental evidence that the Mexican stock market has a fractal structure. We obtained the experimental results by using the Matsushita-Ouchi method, the box-counting method, and the fractal image compression technique of M. Barnsley. The results obtained by applying the Matsushita-Ouchi technique to the returns of the Indice de Precios y Cotizaciones (IPC) of the Mexican stock market support the assertion that the returns of the IPC behave like a fractional brownian motion. The box-counting method allows us to calculate the dimension of the graphs of the IPC, and its Hurst exponent H. The application of the fractal image compression technique produces attractors which are closed to the graphs of the returns of the IPC, and has permited us to estimate H. In the second part of the paper, we present two applications: first we study the efficiency graphs of the Mexican stock market, by plotting the Hurst exponent H as a funtion of time, and then we localize its structural changes by making use of a fractal attractor located in the phase space: H-IPC. We show that the fall of the IPC, that occurred between 1994 and 1995, corresponded to a rise of the value of H. We localize approximately the structural changes of the Mexican economy between 1987 and 1996. [ABSTRACT FROM AUTHOR]

The article reports that facsimile has become commonplace in the office since the mid-1980s, but its basic principles were invented prior to the invention of the telephone. In 1843, a Scottish physicist named Alexander Bain demonstrated the ability to record an image remotely on electrolytic paper. This invention had a pendulum scanner which made contact with raised metal characters, and at the receiver it had a stylus which passed over damp electrolytic paper. During the early part of the twentieth century, as telephone circuits became practical for long-distance communication, the use of telegraph circuits ceased.

This paper presents, provides justification for, and discusses the implications of a set of measures of information. In presenting these definitions, the paper discusses their relationship to colloquial use of the two terms and of other relevant terms, to the historical development of measurement theories related to them, and to the problems that have to this point been unresolved in reconciling colloquial and theoretical uses of them. The paper concludes with a characterization of three contexts within which the communication meta-process may be considered: (1) that of the channel (with the source and the recipient taken as external); (2) that of a single source, a single channel, and a single recipient; and (3) that of multiplicity of sources, channels, and/or recipients. The effects of each context upon the measurement of information are discussed. Information is defined as that property of data (i.e., recorded symbols) which represents (and measures) the effects of processing of those data. Communication is a meta-process involving a source of information (i.e., of data and associated processing), a channel for data transfer, and a recipient of information (again, with associated data processing). [ABSTRACT FROM AUTHOR]

Network coding is a novel technique that includes many applications in realistic networking era. Through network coding, intermediary nodes might send out packets that are combinations of incoming information. The basic theme behind network coding is the summation of incoming information traffic through simple XOR. There are many profits of network coding: improved throughput, less number of transmissions, better network management, less BER, minimum delay, less resource consumptions. In this paper we will prove how network coding improves and achieves the Qos of any network. We also discuss the Implementation aspects of network coding like how it may implemented on current infrastructure networks, we also discuss the theoretical and practical results on network coding for improving quality of service parameters using four basic approaches of network coding, Optimal, Deterministic, Random and Heuristic approach. [ABSTRACT FROM AUTHOR]

This paper aims at time-variant or uncertain network delay in the wireless networked control systems (WNCS), as well as Smith predictor models might be imprecise, a novel approach is proposed that new Smith predictor combined with generalized predictive control (GPC) for the WNCS. Because new Smith dynamic predictor hides predictor model of the network delay into real transmission process of the network data, further the network delay no longer need to be measured, identified or estimated on-line. It is applicable to some occasions that wireless network delays are random, time-variant or uncertain, possibly large compared to one, even tens sampling periods, meanwhile, there are some data dropouts in closed loop. Based on IEEE 802.11b/g (WLAN), the results of simulation show validity of the control scheme, and indicate that system has better dynamic performance and robustness. [ABSTRACT FROM AUTHOR]

In this paper, we propose the model of Scalable Joint Source/Channel Coding for wireless data transmission where channel is inherently time varying and subject to Rayleigh fading nature. We consider the problem of still image data transmission over time varying channels with two Channel State Information's (CSI) and three bit rates (1, ½ and ¼) for efficient transmission of data. Here, we analyze the effect of CSI availability on the optimal performance analysis of proposed scheme. Our source model is based on two level wavelet image decomposition using Haar mother wavelet with Set Partition In Hierarchical Tree (SPIHT) for significant coefficients for dynamic thresholding and channel coding will be Rate-Compatible Punctured Convolutional (RCPC) Codes. We simulated the new scheme of SJSCC and tried for optimal performance for wireless channels. Further, we show how our optimized SJSCC scheme out performs over Optimized Joint Source/Channel Coder (OJSCC) for channel states as well for various bit rates [2] [3]. In our optimization of SJSCC Scheme, marginal improvement in PSNR of 0.14dB is obtained for both average and worst channels and significant improvements of PSNR values in the order of 2dB is also obtained for all three bit rates over existing OJSCC system. Finally, our proposed SJSCC system performance is compared with RCPC and RCPT for wide range of SNRs and noticed marginal is noticed with RCPC channel coder or RCPT. [ABSTRACT FROM AUTHOR]

"Satellite Communication is one of the most impressive spin-offs from the space programmes and has made a major contribution to, indeed totally altered, the patterns of International communication. Communication by satellite evolved from the simple technology of "Early Bird" to the highly sophisticated present-day satellites" [1]. The potential of the outer space as a communication hub is great and at the heart of this is the satellite. This paper aims at developing a micro-satellite, which can be used for educational purposes as well as a stepping stone for further complex developments. Data from this satellite will be formatted on the basis of the CCSDS (Consultative Committee for Space Data Systems) standards before transmission. We will also highlight one of the simplest designs of the micro satellite CanSat (Satellite in a can) at university level with most cheaply and easily available resources ever highlighted for the Space Education in Asia. [ABSTRACT FROM AUTHOR]

In this paper, we propose an implementation neutral protocol, called Multiple Disjoint Path (MDP), for the determination of the min-cut in wireless ad hoc networks by summarizing the capacity of disjoint paths constructed from source node to sink nodes. Min-cut is essential in the formulation of data being sent using Linear network code in source node. MDP consists of virtual source routing and core heuristic. Virtual source routing is to resolve scalability, privacy and efficiency problems caused by long paths in large networks. Core heuristic is to ensure the efficiency of request packet propagation. Our simulation results reveal that MDP performs at a satisfactory level in dense networks in terms of connectivity and transmission efficiency. An opportunity for deployment of linear network code for data transmission in dynamic wireless environment can be created. [ABSTRACT FROM AUTHOR]

This paper proposes a novel and area efficient bit serial multiplier architecture in which both the multiplier and multiplicand are processed in real time. The major advantage of proposed multiplier is the bit serial data which results in reduced area and simple circuitry, the use of compressor enables us to get bit serial out put every clock cycle. The proposed architecture is best suited for bit serial communication system. The proposed bit serial multiplier is an integral part of bit serial digital down converter. The design uses a compressor algorithm for partial product addition which removes the dependency of each data bit from its previous one by using a triangular compressor. The complexity of our algorithm is 2n+1. [ABSTRACT FROM AUTHOR]

Massively parallel distributed-memory architectures are receiving increasing attention to meet the increasing demand on processing power. Many topologies have been proposed for interconnecting the processors of distributed computing systems. The hypercube topology has drawn considerable attention due to many of its attractive properties. The appealing properties of the hypercube topology such as vertex and edge symmetry, recursive structure, logarithmic diameter, maximally fault-tolerance, simple routing and broadcasting, and the ability to simulate other interconnection networks with minimum overhead have made it an excellent candidate for many parallel processing applications. Many variations of the hypercube topology have been reported in the literature, mainly to add to the computational power of the hypercube. One of the attractive versions of the hypercube that was introduced to enhance the performance is the twisted hypercube. A twisted hypercube has the same structural complexities of the hypercube. It preserves the attractive properties of the hypercube and improves on the communication time by reducing the diameter by a factor of two. This paper presents the basic communication and some of the basic operations usually needed in parallel computing on the twisted hypercube interconnection network. [ABSTRACT FROM AUTHOR]

The paper deals with the design and realization of a secure multicarrier modem on FPGA. The crypto-modem principle is adopted. An encryption block is integrated in the modem transmitter and a decryption block is integrated in the modem receiver. Different Encryption/Decryption IPs (Intellectual Properties) implementing DES (Data Encryption Standard), 3DES (Triple DES) and AES (Advanced Encryption Standard) algorithms are developed and/or adapted in order to estimate the feasibility as well as the time and area efficiency of the crypto-modem. The design language used is VHDL and the crypto-modem system is validated in ISE environment, using Xilinx development board with XC4VSX3S circuit from VIRTEX-4 family. [ABSTRACT FROM AUTHOR]

The use of discrete wavelet for image compression and a model of the scheme of verification of parallelizing the compression have been presented in this paper. It is well known that wavelet transform is especially useful to transform image. Here we apply it twice: first on rows, second on columns. Upon this, the image matrix is deinterleaved and recursively transformed each subband individually further for the compression. A model for parallelizing the compression technique has also been proposed here. [ABSTRACT FROM AUTHOR]

Interleave division multiple access (IDMA) and orthonogonal frequency division multiplexing - interleave division multiple access (OFDM-IDMA) have been proposed for beyond third generation (B3G) and fourth generation (4G) communication systems. These system are based on iterative multiuser detection (MUD) techniques. The efficiency of these systems is dependent on the generation of efficient user specific interleavers on the basis of which the users are differentiated as compared to signature code sequences in code division multiple access (CDMA). In this paper we discuss the impact of interleaver design on the efficient of IDMA system. [ABSTRACT FROM AUTHOR]

This paper is focused on the Relative Intensity Noise (RIN) aspect of a research project on development of a novel approach for accurate measurement of RIN and Frequency Excursion (Chirp) in Laser Diodes as Transmitters for Optical Communication Networks. The desired metrology capabilities have been developed and demonstrated, providing significantly improved sensitivity and accuracy than existing methods. RIN is a key parameter for laser components used in telecommunication systems due to the drive to reduce inherent noise, improve overall signal-to-noise ratio and thus increasing achievable communication link length and reduce required component specification. The novelty of our approach has resulted significant advantages, achieving improved sensitivity, improving measurement accuracy as low as ±1dB and simplifying the system calibration methodology thus improving flexibility. Laser RIN's of between 10 to 14dB below the Shot RIN have been shown (typically -170dB/Hz) which is a direct result of the improved system sensitivity. [ABSTRACT FROM AUTHOR]

This paper introduces a logic circuit of data buffer between higher speed ADC and lower speed DSP. While allowing dropping some frames, the circuit also realizes effective image rescale and image buffer transfers frame by frame. The realization of this design initially solves the problem of the video capture system, which is limited by the resolution of the image, and enables DVR system to get high-speed access to large-resolution image. [ABSTRACT FROM AUTHOR]

Advances in technology introduce new application areas for wireless sensor networks (WSNs). Foreseeable wide deployment of mission critical sensor networks creates concerns on security issues because they are more vulnerable to attacks due to broadcast nature of transmission medium, resource limitation on sensor nodes and uncontrolled environments where they are left unattended. The most critical security requirements in WSNs include authentication and confidentiality .These security requirements can be provided by a key management but it is difficult due to the adhoc nature, intermittent connectivity, and resource limitations of the sensor networks .In this paper we proposed a key management scheme for clustered wireless sensor networks based on the random key distribution. Our analysis of this scheme shows that it is more resilient to node capture as compared to other random key distribution schemes. It also provide global and continuous authentication of each entity in the network and multiple level of encryption. [ABSTRACT FROM AUTHOR]

In the ubiquitous personal area network based on MB-OFDM, huge amount of multimedia data and software components will be transmitted, and this huge data will require higher data rate, and reliability over various wireless channel. Therefore, in this paper, dynamic signal transmission with intelligent transmission scheme for MB-OFDM system is considered. The intelligent transmission technique is investigated for the most suitable adaptation in various channel environments. For this scheme, the proposed technique includes STBC, BLAST, and STBC-BLAST in all. By properly selecting their MIMO schemes using estimated SNR, the proposed technique has the advantage of each technique; diversity gain or high transmission rate relative to general scheme. [ABSTRACT FROM AUTHOR]

In this paper, we provide a new detection scheme for interference nulling and cancellation operation in a VBLAST system to reduce unexpected effects due to parallel transmission. This method can reduce the time delay and moderate the multipath fading effect. We have shown that the investigated VBLAST detection based on hybrid processing performs better than ordinary VBLAST detections based on sequential and parallel processing, respectively. [ABSTRACT FROM AUTHOR]

In this paper, two DUSTM-OFDM (differential unitary space-time modulation-orthogonal frequency division multiplexing) transmission schemes for two antennas in frequency selective fading channels are introduced. One is a serial scheme which send the input symbols into two different antennas separately first. The other is a parallel scheme in which the input symbols are first send into subcarriers separately. The influence on the two systems in different Doppler spread is compared and the performance of the parallel scheme is analyzed in different multipath channels, data transmission rate and Doppler spread. Simulation results show that the parallel system outperforms the serial-scheme system in terms of processing rate, hardware simplicity, multipath diversity and performance. It is concluded that the parallel DUSTM-OFDM is much more suited for frequency selective fading channels than the serial one. [ABSTRACT FROM AUTHOR]

In this paper, we present a receiver-driven congestion control mechanism for streaming video application, which is called RD-BCC. It applies BCC (Binomial Congestion Control) scheme to control rate at receivers and don't need to send feedback for each packet received. RD_BCC shifts most of rate control mechanism of BCC to receivers. In RD_BCC, the receivers directly estimate an appropriate rate by using the congestion signals and send the result to the sender instead of sending the congestion signals to the sender. RD_BCC consists of many algorithms. In the end, we use simulation to evaluate the RD_BCC performance. Result shows some algorithms have well TCP-friendliness and smoothness, which provide flexible choice for the transmission of streaming video application. RD_BCC is also appropriate for multicast flow, because it is not a per-packet acknowledgement mechanism and is implemented at receivers. [ABSTRACT FROM AUTHOR]

Space time block codes (STBC) provide transmit diversity by using multiple transmit antennas. We obtain a lattice representation of the STBC by converting the complex channel model into a real matrix without any effect on the orthogonality. In this paper, we propose a computationally efficient demapper in the coded STBC systems. Based on independently divided maximum likelihood (ML) decoding, we derive a simple equation for the soft bit metrics. With the efficient soft bit metrics, the computational complexity generally reduces more than 80%. By employing the proposed soft bit value generation, the computational complexity can be significantly decreased without any performance loss. [ABSTRACT FROM AUTHOR]

This paper proposes the Channel Hopping with Negotiated Pattern (CHNP) protocol, a MAC protocol specially designed for industrial Wireless Sensor Networks (WSN) applications. CHNP tries to achieve the reliable communication under the harsh industrial radio environment in an energy and bandwidth efficient way by fully take advantage of the multi-channel capability of radio chips. To the best of our knowledge, CHNP is the first multi-channel MAC protocol specially designed for industrial WSN applications, which pays special attention to the reliability performance, and makes comprehensive optimization on energy, delay, and throughput performance at the same time. The following contributions are made in CHNP: first, a novel MAC framework based on synchronized channel hopping mechanism is proposed, which provides a good platform to perform the comprehensive performance optimization; second, an effective interference domain division mechanism is designed to achieve higher performance; third, an adaptive transmission mechanism is designed, which can sidestep the bad channels and realize reliable communication even under harsh RF environment ; last, a sniffing mechanism is provided to achieve low energy operation. Simulation results show that the performance of CHNP achieves a significant improvement over the previous related work in the context of industrial WSN applications. [ABSTRACT FROM AUTHOR]

The enormous amount of multimedia data will be transmitted by various devices of the wireless personal area network, and this network environment will require very high transmission capacity. In this paper, we apply multiple antenna to MB-OFDM UWB system for high performance. With an emphasis on a preamble design for multi-channel separation, we address a channel estimation in MB-OFDM system with multiple antenna. By properly designing each preamble for multiple antenna to be orthogonal in time domain, the channel estimation can be applied to the MB-OFDM proposal for IEEE 802.15.3a standard in the case of more than 2 transmit antennas. By using the multiple antenna scheme and proposed channel estimation technique, the reliability and performance of MB-OFDM system can be improved. [ABSTRACT FROM AUTHOR]

Multiple-Input Multiple-Output (MIMO) system is composed of source and destination nodes with multiple antennas. But, when nodes cannot support multiple antennas due to size or other constraints, especially for mobiles, the MIMO cannot be used to provide diversity. Cooperative communication enables single antenna mobiles generate a virtual multiple antenna transmit diversity. To achieve high-performance by using Space-Time Block Codes (STBC), this paper applies pre-coding scheme to the transmit symbols. Even though pre-coding scheme has several shortcomings, it is possible to employ STBC with one transmit antenna, thereby it can achieve high gain, without loss of transmission rate. Simulation results reveal that it is possible to obtain higher error performance at the low SNR by using proposed scheme. [ABSTRACT FROM AUTHOR]

In this paper, we propose a bus encoding scheme to minimize coupling effects which cause significant power consumption in the on-chip interconnects. The proposed bus encoding scheme consist in silencing the middle two data lines of each subset which consists of 4-bit. We present a technique to eliminate correlated switching in the 4-bit data lines and also minimize self-transitions in these data lines. Experimental results indicate that the presented bus encoding scheme reduces the number of self-transitions by 20% and it also increases the number of silent lines by 9%. In addition, it reduces the power dissipation by 46% compared Bus-Invert method. [ABSTRACT FROM AUTHOR]

This paper justifies using explicit performance signaling in support of congestion control by means of a simple yet efficient scheme called “Congestion Avoidance with Distributed Proportional Control (CADPC)”. It thereby contradicts a common belief that no additional forward traffic should be sent by such mechanisms. CADPC, which solely relies on rare bandwidth feedback from routers, is shown to outperform several TCP-friendly mechanisms and TCP “flavors” in various aspects in simulations; its robustness against RTT fluctuations and loss from link noise makes it particularly well suited for heterogeneous network scenarios. [ABSTRACT FROM AUTHOR]

The article reports that the years since 1977 have witnessed widespread applications of Huffman coding in data compression, in sharp contrast with the first 25 years since the appearance of Huffman's groundbreaking paper. This phenomenon can be explained by the increasing affordability of computing power and the growing demand of data compression to save transmission time or storage space. Nowadays, Huffman coding competes with state-of-the-art coding schemes such as arithmetic coding and Lempel-Ziv coding in applications requiring data compression. Since each letter in a data sequence to be compressed must be encoded into an integer number of bits, the compression performance of Huffman coding is often worse than that of arithmetic coding or Lempel-Ziv coding.

Recently, much attention has been focused on digital TV broadcasting and broadcast-type information delivery systems. Notable features of the broadcast-type information delivery systems are that the same information is transmitted to anonymous users, and that users receive those information in a passive manner. The delivered contents is usually composed of multiple components, whose update timings may vary. This paper describes our recent research focussing on the above substantial aspects of broadcasting-type information systems. First, we will describe a version management mechanism to maintain the temporal consistency of delivered data in data broadcasting systems. Secondly, we will describe a way to view Web contents in a passive manner like TV-program contents. Finally, we will show our new information filtering mechanism for data broadcasting systems considering the time-series features of data, especially, the freshness and the popularity of data. [ABSTRACT FROM AUTHOR]

Chapter 18 surveys routing algorithms in communication networks, where nodes are aware of the geographic position of themselves and their neighboring nodes. Guaranteed delivery is a salient property of the algorithms, assuming destination location is accurate, all nodes have the same transmission radius, and there are no obstacles. [ABSTRACT FROM PUBLISHER]

Chapter 24 reviews broadcasting algorithms in radio networks, under different communication scenarios and different amounts of knowledge of the network. Broadcasting is the task of forwarding a message from a source (or central facility) to all the nodes in the network. The chapter primarily deals with the worst case analysis of algorithms. [ABSTRACT FROM PUBLISHER]

Transmission Control Protocol (TCP) includes eleven variants-Tahoe, FullTcp, TCP/Asym, Reno, Reno/Asym, Newreno, Newreno/Asym, Sack1, Fack, Vegas and VegasRBP as source and five-TCPSink, TCPSink/Asym, Sack1, DelAck and Sack1/DelAck as destination, implemented in Network Simulator (NS-2). Performance of TCP versions indicates how they respond to various network parameters-propagation delay, bandwidth, TTL (time to live), RTT (round trip time), rate of packet sending and so on. Such analysis is immensely in need to be aware of which TCP is better for a specific criterion, wherefrom an appropriate one will be selected in respective network to optimize traffic goal. But yet no complete summary is available as we've investigated hereby thoroughly. Recently published researches considered Congestion Window, Throughput, and Delay for five variants only. This paper covers all the supported variants to observe their nature regarding to five new perspectives in details. [ABSTRACT FROM AUTHOR]

Orthogonal frequency division multiplex (OFDM) modulation is being used more and more in telecommunication, wired and wireless. DVB and DAB already use this modulation technique and ADSL is based on it. The advantages of this modulation are the reason for its increasing usage. OFDM can be implemented easily, it is Spectraly efficient and can provide high data rates with sufficient robustness to channel imperfections. The purpose of this paper is to use a Matlab simulation of OFDM to see how the Bit Error Ratio (BER) of a transmission varies when Signal to Noise Ratio (S/N Ratio) and Multipropagation effects are changed on transmission channel. [ABSTRACT FROM AUTHOR]

Based on the characteristic that the signals of a direct sequence spread spectral (DSSS) communication system, before being transmitted, will be modulated by a periodical spread spectral pseudo-random sequence, the paper proposes to estimate the spread spectral pseudo-random sequence by chip-delay and eigenvalue analysis. By using the method, we can retrieve the spread spectral pseudo-random sequence of the direct sequence spread spectral signals only based on the one eigenvector corresponding to the maximum eigenvalue of the correlation matrix of the chip-delay-multiply signals, and can find the synchronization position quite easily. The computer simulations show that it can not only achieve the estimation of the spread spectral pseudo-random sequence in the context of low signal to noise ratio, but also does can give the synchronization information in a distinct way. And it is a good method for the blind detection of DSSS signals. [ABSTRACT FROM AUTHOR]

In the last years, the computers have increased their capacity of calculus and networks, for the interconnection of these machines, have improved until obtaining the actuals high rates of data transfering. The programs that nowadays try to take advantage of these new technologies cannot be written using the traditional techniques of programming, since most of the algorithms were designed for being executed in an only processor, in a nonconcurrent form instead of being executed concurrently in a set of processors working and communicating through a network. This paper aims to present the ongoing development of a new system for the reconfiguration of groupings of computers, taking into account these new technologies. [ABSTRACT FROM AUTHOR]

Recently, P2P's applications develop very fast and are becoming very important in the network. As gradually increasing, P2P applications definitely cause the network's immensely consuming and network congestion. Therefore this article gives a method of distinguishing P2P's flow based on flow and payload in order to improve this situation. At the same time, in order to establish a better campus network for sharing resources, this article also gives a model of PRNM data sharing based on P2P technique, which is using P2P half distributed architecture to put the resources on each peer. [ABSTRACT FROM AUTHOR]

A definition of the term "Facsimile Transmission" is presented. It refers to a system of communication or delivery for paper documents. Facsimile Transmission, which is also called Fax, scans the pages of the documents, compresses the scanned image, and transmits the digital signals by wire to a FAX received at a remote point.

Discusses wireless data networks. Concept of internetworking; Functions of the Open System Interconnection (OSI) reference model; Purposes of each layers of the OSI model.

The article focuses on electronic wave propagation. Wireless communication from one point to another requires a transmitter and an antenna electromagnetic waves. When the wave is not in free space or encounters objects, it can change amplitude, phase, and direction and may no longer be a uniform plane. In short, the plane wave characterization is just a temporary description of the wave at a given time and at a given location. Free-space transmission is a primary consideration in essentially all fixed broadband wireless communication systems.

The article presents information about the wideband Code Division Multiple Access (CDMA) network sensitivity. The approach provides a relatively simple way to specify the required quality of MAI canceller (decorrelator) and RAKE receiver in a CDMA system, taking into account all their imperfections. A flexible, complex signal format is used that enables to model all currently interesting wideband CDMA standards. For such a signal we first derive a complex decorrelator structure. This is the first time that a complete decorrelator is described for the CDMA signal with two independent data and two independent code streams. This type of the signal is used in all CDMA standards. In the next step all imperfections in the operation of such a system are modeled and analyzed by using the concept of a network sensitivity function.

The article presents information about the packet transmission in a Code Division Multiple Access (CDMA) radio network. The author starts with dual-class traffic and then extends the analysis to multimedia systems. These two classes are characterized by a set of parameters. The Class 2 mobiles must be capable of variable rate transmission, dependent on available residual capacity and the base station capable of the corresponding reception. The information transmission rate to be used by the Class 2 users will be decided by the base station, using information about the population distribution in the system, and in the constrained transmit power case, knowledge of the received power ratio parameter. In practice, the user-population distribution may be a slowly changing variable. This would imply that Class 2 information rate changes do not have to be effected too often.

The article presents information about the Code Division Multiple Access (CDMA) network capacity. The CDMA network capacity depends significantly on the so-called near-far effect. From the very beginning, theory and practice of CDMA were aware of this fact. All practical systems use Power control (PC) to reduce this effect. PC is more efficient in the system optimized for speech, such as IS-95. In a multimedia network such as Universal Mobile Telecommunication System in which different signals levels are used for different data rates, additional solutions like multi-user detectors are used. In IS-95, every mobile station attempts to adjust its transmission power so that signals received at a base station are at the same, minimum level at which good quality communication can still be provided.