Intermedia Synchronization Protocol for Continuous Media Using MPEG-4 in Mobile Distributed Systems

While dealing with Mobile Distributed systems, we come across some issues like: mobility, low bandwidth of wireless channels and dearth of stable storage on mobile nodes, disconnections, inadequate battery power and high failure rate of mobile nodes. Minimum-process coordinated checkpointing is considered an attractive methodology to introduce fault tolerance in mobile systems transparently. In this paper, we propose a non-blocking coordinated global state compilation algorithm for mobile computing systems, which requires only a minimum number of processes to take permanent recovery points. We reduce the communication complexity as compared to the Cao-Singhal algorithm [4], while keeping the number of useless recovery points unchanged. Finally, the paper presents an optimization technique, which significantly reduces the number of useless recovery points at the cost of minor increase in the communication complexity. In coordinated global state compilation, if a single process fails to take its tentative recovery point; all the recovery point effort is aborted. We try to reduce this effort by taking soft recovery points in the first phase at Mobile Hosts.

The Joint Photographic Experts Group (JPEG) standard is widely used for coding still images. The JPEG standard includes two basic compression methods. A DCT-based method is specified for `lossy' compression, and a predictive method for `lossless' compression. JPEG features a simple lossy technique known as the Baseline method which has been by far the most widely implemented method for large number of applications. It is very sensitive to transmission errors and can be employed successfully only when the transmission channel is nearly error free. Wireless communication channels are characterized by long bursts of data errors, and average bit error rates (BERs) of 10-3 to 10-4. This paper presents an efficient scheme to transmit JPEG coded images over wireless channels. The compressed image is protected against various channel effects of wireless channel using Reed Solomon block code and transmitted over wireless channel.

This paper studies a fundamental problem, the termination detection problem, in distributed systems. Under a wireless network environment, we show how to handle the host mobility and disconnection problems. In particular, when some distributed processes are temporarily disconnected, we show how to capture a weakly terminated state where silence has been reached only by those currently connected processes. A user may desire to know such a state to tell whether the mobile distributed system is still running or is silent because some processes are disconnected. Our protocol tries to exploit the network hierarchy by combining two existing protocols together. It employs the weight-throwing scheme on the wired network side, and the diffusion-based scheme on each wireless cell. Such a hybrid protocol can better pave the gaps of computation and communication capability between static and mobile hosts, thus more scalable to larger distributed systems. Analysis and simulation results are also presented.

Coordinated checkpointing is an effective fault tolerant technique in distributed system as it avoids the domino effect and require minimum storage requirement. Most of the earlier coordinated checkpoint algorithms block their computation during checkpointing and forces minimum-process or non-blocking but forces all nodes to takes checkpoint even though many of them may not be necessary or non-blocking minimum-process but takes useless checkpoints or reduced useless checkpoint but has higher synchronization message overhead or has high checkpoint request propagation time. Hence in mobile distributed systems there is a great need of minimizing the number of communication message and checkpointing overhead as it raise new issues such as mobility, low bandwidth of wireless channels, frequently disconnections, limited battery power and lack of reliable stable storage on mobile nodes. In this paper, we propose a minimum-process coordinated checkpointing algorithm for mobile distributed system where no useless checkpoints are taken, no blocking of processes takes place and enforces a minimum-number of processes to take checkpoints. Our algorithm imposes low memory and computation overheads on MH's and low communication overheads on wireless channels. It avoids awakening of an MH if it is not required to take its checkpoint and has reduced latency time as each process involved in a global checkpoint can forward its own decision directly to the checkpoint initiator.

The mitigation of random effects in a wireless communication channel is a problem considered for many years. In the present day context, given the ever increasing need for, and growth of, bandwidth intensive applications like streaming wireless HD video on fast moving user equipment (UEs, i.e., user communication devices), this issue has intensified from being a theoretical pursuit to a must-be-solved practical endeavor. In that regard, the ability to accurately model the outdoor (or indoor) propagation conditions in a laboratory setting becomes vital to validating state-of-the-art wireless standards and the devices that derive from them. Laboratory-based analysis is a significant catalyst in reducing the time-to-market for telecom equipment manufacturers. Modeling a wireless channel has been a topic under quite a bit of study. This has progressed from the Jakes model developed for single antenna systems to the correlation and ray-based models used for multiple antenna systems. The models prescribed by the 3rd Generation Partnership Project (3GPP) in its standards, like the ray-based model, aim to realistically reproduce channel environments in software and hardware, by incorporating all the variables that characterize any particular fading scenario. In this thesis, the technical report produced by 3GPP detailing the Spatial Channel Modeling (SCM) for multiple input multiple output (MIMO) simulations is followed closely as a basis for developing a real-time channel emulator on a National Instruments (NI) based Real Time (RT) Platform. First, a general purpose channel emulator is described in terms of its structure and functionality and currently known channel models are briefly investigated. Next, the spatial channel model in the standard is described in detail along with the reasons for choosing to use it in the thesis. All the parameters involved are defined, and the formula for constructing the channel is carefully investigated. Next, the channel emulator built on the National Instruments LabVIEW platform is described along with both the changes and modifications made to the design parameters so as to adapt it to the operating constraints of the RT platform. The spatial and temporal characteristics of the model are also described and plotted. Finally, the model is tested for reliability by methodically changing the various channel parameters and observing their effects on an Orthogonal Frequency Division Multiplexing (OFDM) test vector by generating BER performance plots in MATLAB. Diversity schemes are also employed to improve rate performance.

Vehicular networked systems consist of numerous vehicles exchanging information over a wireless communication channel. These wireless communication channels are often subject to limited bandwidth and deep fading. Prior work shows that event triggering can generate, on average, larger transmission time interval than periodic scheme by triggering the transmission as a function of the sampled state. However, it is unclear whether this state-dependent transmission approach still outperforms the periodic scheme in vehicular networked system where the communication channel often fails to reliably deliver the sampled state due to deep fades. By adopting a bursty fading channel model, this paper presents a new event triggering scheme under which the vehicular system assures a larger transmission time interval than that of periodic scheme while preserving almost sure asymptotic stability in the absence of disturbance, and practical stability in probability with bounded disturbance. In the disturbance free case, the triggering law guarantees increasing transmission time interval as system approaches its equilibrium. In the bounded disturbance case, the probability of system state leaving a bounded set is a function of the transmission time interval, disturbance amplitude, and system's convergence rate. The simulation results of a leader follower example verify the theoretical findings in this paper.

How to provide reliable, cost-effective wireless services for high-speed railway (HSR) users attracts increasing attention due to the fast deployment of HSRs worldwide. A key issue is to develop reasonably accurate and mathematically tractable models for HSR wireless communication channels. Finite-state Markov chains (FSMCs) have been extensively investigated to describe wireless channels. However, different from traditional wireless communication channels, HSR communication channels have the unique features such as very high speed, deterministic mobility pattern and frequent handoff events, which are not described by the existing FSMC models. In this paper, based on the Winner II physical layer channel model parameters, we propose a novel FSMC channel model for HSR communication systems, considering the path loss, fast fading and shadowing with high mobility. Extensive simulation results are given, which validate the accuracy of the proposed FSMC channel model. The model is not only ready for performance analysis, protocol design and optimization for HSR communication systems, but also provides an effective tool for faster HSR communication network simulation.

A method, measurement system, and hardware and software facilities are developed for studying the reliability of data reception and signal level in radio channels. This method can be used to test the wireless communication channels employed in smart devices for data measurement and transmission during manufacture. Studies are made of the wireless communication channels of batches of commercially produced smart devices. The dependence of the loss probability for a packet of data on the radio signal level is determined.

Propagation Effects in Optical and Wireless Communications Channels, Noise Sources, and Channel Impairments

A distributed mobile system consists of a group of heterogeneous mobile devices connected by wireless network. Due to the fact that most of the mobile devices are battery based, the lifetime of a mobile system depends on both the battery behavior and the energy consumption characteristics of tasks. In this paper, we present a set of models for task scheduling in mobile systems equipped with Dynamic Voltage Scaling (DVS) processors. We propose battery-aware algorithms to obtain task schedules satisfying the battery lifetime constraints. The simulations with randomly generated Directed Acyclic Graphs (DAG) show that our proposed algorithms generate better schedules that can satisfy the battery lifetime constraints.

The most frustrating and troublesome issue in wireless communication is fading. Estimating the fading occurrence for the design of greatly reliable communication link is crucial. In this paper, we present a novel mathematical method for predicting the future signal fading on the basis of current and past data. The application of a Semi Markov Model as a generalization of the Markov Model is discussed for predicting the deep fading occurrence probabilities of the received envelope in wireless communications channels. This flexible model is given for assessing the system performance with the envelope correlation. 142 deep fading data whose amplitudes are lower than a mean of the amplitudes which occurred in a typical wireless system with the Jakes filtering are considered. The transition probability matrix and the holding time mass functions are calculated for the next 1 to 21 unit times. One unit time is regarded as the inverse of sampling frequency; moreover, the core matrix and the cumulative probability distribution of the waiting time are obtained. Calculating the interval transition probabilities for Amplitude to Amplitude transition for these deep fades demonstrates the forecasting occurrence probabilities in the future and the possibility of forecasting the fading occurrences in dimensions of time and amplitude.

Wireless communication channels experience high variability in channel quality due to a variety of phenomenon, including multipath, fading, atmospheric effects, and obstacles. Due to this different wireless communication channels have different capacity for transferring the data. This paper studies the movements of nodes within channel environments using Ricean, Rayleigh and Free space channel models. Three performance metrics are used for this purpose. These metrics are throughput, end to end delay and link ratio. It is discovered that free space channel model performed better than Ricean channel which in turn perform better than Rayleigh channel model.

Recently, the importance of a water resource is highly concerned. Therefore, Underwater Wireless Sensor Networks (UASNs) technologies are vigorously studied for monitoring underwater environment. The UASNs gather various underwater environmental data that should be delivered to a Monitoring Center where nearby or far from UASNs are deployed. To deliver data form underwater to the Monitoring Center or vice versa, a surface gateway should change acoustic signal to RF (Radio Frequency) signal. Depends on the service requirement, the surface gateway can adopt various wireless communication channels such as Cellular network, Zigbee and so on. In this paper, we propose the architecture of surface gateway that has several wireless communication channels and communication protocol.

Comparative link-level analysis and performance estimation of channel models for IIoT (Industrial-IoT) wireless communications

Wavelet packets (WP) have been found a promising candidate for user signature waveforms in code division multiple access communication systems. They have better orthogonality properties, and are capable of effectively suppressing certain types of noise/interferences. In this paper we present a method to model wireless communication channels using wavelet packets as bases. Modeling of wireless communication channels using WP has the advantage of more efficiency in wideband modulation. In addition, time-varying channel modeling can also be relatively easily accommodated. To evaluate the effectiveness of the proposed modeling method, we have tested it on indoor multipath fading channels. The results show promising features of the proposed model.