Broadcast Communication Channel Research Articles

Проблемы организации вычислений в многомашинных вычислительных системах с программно-управляемой сбое- и отказоустойчивостью. Часть III

This three-part paper analyzes existing approaches and methods of organizing failure- and fault-tolerant computing in distributed multicomputer systems (DMCS), identifies and provides rationale for a list of issues to be solved. We review the application areas of failure- and fault- tolerant control systems for complex network and distributed objects. The third part proceeds with the study of the problems of organizing failure- and fault-tolerant computing in distributed multicomputer systems (DMCS), carried out in parts I and II of this work, and deals with the issues related to the diagnosis of multiple faults. The paper describes the main differences in ensuring fault tolerance in systems with broadcast communication channels and point-to-point communication channels.

Проблемы организации вычислений в многомашинных вычислительных системах с программно-управляемой сбое- и отказоустойчивостью. Часть I

This three-part paper analyzes existing approaches and methods of organizing failure- and fault-tolerant computing in distributed multicomputer systems (DMCS), identifies and provides rationale for a list of issues to be solved. We present the concept of fault tolerance proposed by A. Avizienis, explicate its dissimilarity from the modern concept and the reason for its inapplicability with regard to modern distributed multicomputer systems. We justify the necessity to refine the definition of fault tolerance approved by the State Standards, as well as the necessity to specify three input parameters to be taken into account in the DMCS design methods: permitted fault models, permitted multiplicity of faults, permitted fault sequence capabilities. We formulate the questions that must be answered in order to design a truly reliable, fault-tolerant system and consider the application areas of the failure- and fault-tolerant control systems for complex network and distributed objects. System, functional, and test diagnostics serve as the basis for building unattended failure- and fault-tolerant systems. The concept of self-managed degradation (with the DMCS eventually proceeding to a safe shutdown at a critical level of degradation) is a means to increase the DMCS active life. We consider the issues related to the diagnosis of multiple faults and present the main differences in ensuring fault tolerance between systems with broadcast communication channels and systems with point-to-point communication channels. The first part of the work mainly deals with the analysis of existing approaches and methods of organizing failure- and fault-tolerant computing in DMCS and the definition of the concept of fault-tolerance.

BROADCAST CHANNEL TRANSMISSION CAPACITY

The most important studies of well-known Broadcast Communication Channels (BCC) models are associated with obtaining accurate information efficiency estimates(IE). Earlier, the coding problem was stated, the joint information measure (JI) of the proposed BCC model was introduced and investigated. Then the information capacity (IC) was introduced and the conditions for maximizing the average JI were defined, the uncertainty concept was defined, and an evidence-based adjustment of the Feinstein inequality for the channel model under study was made. In the present paper, the general information accurate estimate transmitted via the BCC by proving the fundamental coding theorems is obtained. On the basis of the previously obtained results, the inverse coding theorem for BCC was proved, which determines the condition for the code error average probability striving to one, which consists in choosing a code with a speed exceeding IE BCC. The Feinstein inequality role on the basis of which the direct coding theorem roof is carried out is determined. The theorem states that there are codes with a low error probability, provided that the code rate does not exceed the channel's IE. The coding theorems cumulative result proves that the IE and the throughput (BC) coincide. An accurate estimate of BC BCC is obtained. The results obtained do not contradict and extend the well-known IE studies of various BCC models and can be used by designers to assess the synthesized communication systems potential capabilities, including BCC channels. The purpose of further research is the gain estimate through IE channel transmission in comparison with the successive transmission through the component channels, which will outline the conditions for the preferred use of the BCC.

Hybrid FLUTE/DASH video delivery over mobile wireless networks

ABSTRACTThis paper describes how File Delivery over Unidirectional Transport (FLUTE) and Dynamic Adaptive Streaming over Hypertext Transfer Protocol (DASH) can be used to provide mobile video streaming services over broadcast wireless networks. FLUTE is a multicast protocol for multimedia file download. In this proposal, the protocol is adapted to provide video streaming services in crowded environments. Thus, video is delivered over a single connection to all viewers, reducing the traffic in the network. FLUTE incorporates an application‐layer forward error correction (AL‐FEC) mechanism in order to improve the reliability of the broadcast communication channel. For streaming applications, AL‐FEC improves the relationship between the peak signal‐to‐noise ratio (PSNR) of the received video and the bandwidth allocated to the broadcast connection. The AL‐FEC hereby presented applies simple unequal error protection schemes to favour the download of key frames. Furthermore, the proposal is based on the same video segmentation mechanism as DASH, and therefore, clients can connect to a DASH repository to repair errors in the segments. This paper shows that FLUTE and DASH can be seamlessly integrated into a hybrid broadcast/unicast streaming technology, providing flexibility to trade off PSNR and bandwidth depending on the conditions of the mobile network. Copyright © 2014 John Wiley & Sons, Ltd.

Random multiple access of broadcast channels with Pareto distributed packet interarrival times

We consider the random multiple access of a slotted broadcast communication channel. Packet arrivals for such channels are often modeled as Poisson processes because the latter have attractive theoretical properties and are well understood, even though a number of traffic studies have shown that packet interarrival times are not always exponentially distributed. For example, some studies argue convincingly that traffic from a variety of working packet networks (LANs, WANs, etc.) is much better modeled using statistically self-similar processes to characterize the packet interarrival times of the aggregate traffic, which have much different properties than Poisson processes. Because of the great influence multiple access algorithms (used in the channel access subsystem) will have on the performance of third-generation digital wireless mobile communication systems, we study the problem of random multiple access under packet traffic generated by interactive data applications (e.g., reading/composing short e-mail messages, responding to paging type messages, transferring files between the mobile and a fixed computer, and querying of a database). We examine and demonstrate the performance robustness of the random access algorithms (RAAs) when they are driven by a strongly bursty packet arrival process, commonly found in interactive data applications.

Performance Analysis of Finite Nonhomogeneous Population Tree Conflict Resolution Algorithms Using Constant Size Window Access

Multiple-access protocols control access to a broadcast communication channel. Tree conflict resolution algorithms are the heart of some distributed multiple-access protocols with nice properties like stability, high capacity, and low delay under light load. We consider a random access protocol based on a tree conflict resolution algorithm similar to one first proposed by Capetanakis, but in which constant size windows on the arrival time axis are used to admit packets into the algorithm instead of the more common "free" or "blocked" access methods. We obtain exact recursive relationships for the (steady-state) distribution of packet delay, and thus, the exact throughput-delay curve for any finite (in general, nonhomogeneous) configuration under a Bernoulli-per-window arrival model. Then, we consider the address assignment problem. We show that by choosing an appropriate addressing scheme, we can improve the performance of the algorithm with respect to both mean delay and maximum throughput.

Performance Analysis for a Terminal-Priority Contentionless Access Algorithm for Multiple-Access Communications

We consider a multiple-access broadcast communication channel which serves a network of terminals, each characterized by a distinct priority level. Higher priority terminals require, on the average, faster access across the communication channel than lower priority ones. We present a terminal priority contentionless access (TPCA) control scheme for sharing such a channel on a conflict-free basis. A ready terminal wishing to access the channel will wait for the channel to become idle, and then defer its access untill after higher priority terminals are given the opportunity to transmit. The model accounts for acquisition delays (including propagation and timearound delay components), idle detection times, multipacket message structures and different arrival intensities at different terminals, Analytical results are derived for the moments and transform of the message waiting-time distribution at each network terminal by relating the waiting times in our model to those in an appropriate M/G/1 queue with HOL (head of the line) priorities. Performance curves are presented under varirous system parameter conditions which correspond to applications involving digital radio local distribution systems and metropolitan-area, packet radio, and local-area communicatiton networks.

An Analysis of a TDMA Channel Using Stop-and-Wait, Block, and Select-and-Repeat ARQ Error Control

In this paper, the multiaccess broadcast communication channel operating under a TDMA control discipline and employing an ARQ scheme is examined. The generating function of the message delay distribution is derived. The effects of nonzero bit error rates on multipacket messages under several stop-and-wait and block ARQ systems are incorporated. Numerical results for the steady-state mean and variance of the message delay are presented for a stationary transmission error process model in which errors occur as independent events. Results for this channel under a select-and-repeat ARQ system are developed for single packet messages. Stability requirements are stated, useful bounds on the average message delay at steady state are derived, and numerical examples are presented.

Tree algorithms for packet broadcast channels

The multiaccessing of a broadcast communication channel by independent sources is considered. Previous accessing techniques suffer from long message delays, low throughput, and/or congestion instabilities. A new class of high-speed, high-throughput, stable, multiaccessing algorithms is presented. Contentions resolving tree algorithms are introduced, and they are analyzed for specific probabilistic source models. It is shown that these algorithms are stable (in that all moments of delay exist) and are optimal in a certain sense. Furthermore, they have a maximum throughput of 0.430 packets/slut and have good delay properties. It is also shown that, under heavy traffic, the optimally controlled tree algorithm adaptively changes to the conventional time-division multiple access protocol.