Multiple-access Communication Networks Research Articles

On the time complexity of achieving optimal throughput in time division multiple access communication networks

<abstract><p>The fundamental problem of finding transmission schedules for achieving optimal throughput in time division multiple access (TDMA) communication networks is known to be NP-hard. Let $ \mathcal{N} $ be a scheduled $ k $-time slot TDMA network with $ n $ stations and $ m $ links. We showed that an optimal link schedule for $ \mathcal{N} $ can be computed recursively with a recursion tree of logarithmic depth $ \mathcal{O}(\ln m) $ in expectation. Additionally, we showed that optimal link schedules for those TDMA networks, with recursion trees of depth meeting the expectation, can be found in time $ \mathcal{O}(m^{2+\ln k}) $. Likewise, we discuss analogous results for computing optimal station schedules of TDMA networks.</p></abstract>

Multi-users different rates visible light communication system for sixth-generation multimedia applications

The two most significant issues that communication engineers have been confronting since the development of fifth-generation wireless networks are bandwidth increase and energy-saving techniques in data transmission. We present an innovative solution for utilizing a multi-user different-rates visible light communication (VLC) system for sixth-generation applications. Such a solution takes advantage of orthogonal frequency division multiple access (OFDMA) with orthogonal codes as multiple access communication networks. For the achievement of energy-saving and wide beam width of the optical source, the light emitting diode is often used as a transmitter. Furthermore, one of the most popular orthogonal codes in use is the double length modified prime code, which has been utilized for enhancing communication network security and network capacity. Most importantly, the performance of the network is evaluated versus the number of users, taking into consideration the amount of noise resulting from the multiple access interference, shot noise, and thermal noise. The error vector magnitude has also been considered for performance analysis and results. Significantly, the obtained results show the possibility of accommodating 110 users at an error rate of no more than 10 − 9 and a data rate per user of 50 Gbps.

Experimental Study of Multiband Acousto-Optic Filtering by Decoding of Spectrally Encoded Signals in Noncoherent OCDMA Systems

The possibility of using acousto-optic multiband filters for construction of code division multiple-access communication networks has been experimentally proved. Correlation interference has been studied for a set of bands with a spectrum close to sin(x)/x function which are used for encoding/decoding. For the case of several transmitters, a special technology was developed and realized that made it possible to perform studies on a transmission line based on two filters. The key component of this technology lies in emulating the sum signal from two to five transmitters on the first filter. The measured signal-to-interference ratio was more than 11 dB and decreased by less than 3 dB due to correlation interference from the network neighborhood and the emulation error of the sum signal.

Application of Asynchronous Weak Commitment Search in Self Organized Cognitive Radio Networks

This article presents a distributed solution to autonomous quality of service provision. This method paves the way for decentralized and autonomous quality of service (QoS) provision in capillary networks that reach end nodes at Internet of Things, when, due to any reason, central management is either unavailable or not efficient. As case studies, cognitive spatial reuse time division access and code division multiple access communication networks are investigated. Based on asynchronous weak commitment search the task of QoS provision is distributed among different network nodes. This application of artificial intelligence in wireless and mobile communications can be used in home automation and networking, and vehicular technology. Extensions of this approach can be used in self organizing networks, specifically for machine to machine communications.

Alocação de Potência em Redes de Comunicação Móveis de Múltiplo Acesso: Aspectos de Implementação via Modelos de Verhulst e Perron-Frobenius

In this work, the Verhulst model and the Perron-Frobenius theorem are applied on the power control problem which is a concern in multiple access communication networks due to the multiple access interference. This paper deals with the performance versus complexity tradeoff of both power control algorithm (PCA), as well as highlights the computational cost aspects regarding the implementability of distributed PCA (DPCA) version for both algorithms. As a proof-of-concept the DPCA implementation is carried out deploying a commercial point-floating DSP platform. Numerical results in terms of DSP cycles and computational time as well indicate a) feasibility of implementing the PCA-Verhulst model in 2G and 3G cellular systems; b) high computational cost for the PCA-Perron-Frobenius model.

Analysis of a Communication Network Governed by an Adaptive Random Multiple Access Protocol in Critical Load

A mathematical model of an adaptive random multiple access communication network is investigated. The value of the network critical load is found; in the critical load, asymptotic probability distributions for states of the information transmission channel and for the number of requests in the source of repeated calls are found. It is proved that distributions of the normalized number of requests belong to the class of normal and exponential distributions, and it is shown how conditional normal distributions pass in the limit to the class of exponential ones.

Investigation of the Markov Models of h2-Persistent Random-Access Communication Networks with Conflict Messages

The h2-persistent multiple-access communication networks with discrete and continuous strategy of control of conflict messages are investigated.

Ergodicity of Band Graph Markov Chains and Their Application to Problems of the Analysis of Existence of a Stationary Regime in a Dynamic Random Multiple Access Communication Network

A concept of the class of band graph Markov chains is introduced. Simple ergodicity criteria for this class of stochastic processes are found. We show how these criteria can be applied to prove the existence of a stationary operation regime in a dynamic access communication network with conflict warning.

Multichannel processing of broad-band multiuser communication signals in shallow water acoustic channels

High-throughout multiple-access communication networks are being considered for use in underwater acoustic channels. Bandwidth limitations of underwater acoustic channels require receivers to process broad-band communications signals in the presence of several active users. To deal with the resulting multiple-access interference in addition to high intersymbol interference, the spatial variability of ocean multipath is exploited in a multichannel multiuser receiver. Two configurations of such a receiver, a centralized and a decentralized one, are presented in fully adaptive modes of operations. While greatly reducing intersymbol and multiple-access interference, spatial diversity implies high increase in adaptive multiuser receiver complexity. To reduce the complexity of the optimal multichannel combiner, spatial structure of multipath is exploited. The complexity of resulting adaptive decentralized multichannel multiuser receiver is reduced at almost no cost in performance. Comparison of proposed multichannel receivers in an experimental shallow water channel demonstrates superior performance of spatial signal combining. The use of multiple input channels is shown to provide high level of tolerance for the near-far effect in both centralized and decentralized receivers. Decentralized receiver with reduced-complexity combining is found to satisfy the performance/complexity trade-off required for practical receiver realization in shallow water networks.

Performance management of multiple access communication networks

This paper focuses on conceptual design, development, and implementation of a performance management tool for computer communication networks to serve large-scale integrated systems. The objective is to improve the network performance in handling various types of messages by on-line adjustment of protocol parameters. The techniques of perturbation analysis of Discrete Event Dynamic Systems (DEDS), stochastic approximation (SA), and learning automata have been used in formulating the algorithm of performance management. The efficacy of the performance management tool has been demonstrated on a network testbed. The conceptual design presented offers a step forward to bridging the gap between management standards and users' demands for efficient network operations since most standards such as ISO (International Standards Organization) and IEEE address only the architecture, services, and interfaces for network management. The proposed concept for performance management can also be used as a general framework to assist design, operation, and management of various DEDS such as computer integrated manufacturing and battlefield C/sup 3/ (Command, Control, and Communications).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Simulation of multiple access protocols for real-time control

The simulation activity described in this paper was undertaken for the design of a hierarchical multiple access communication network for a distributed real-time control system. The network consisted of multiple busses hierarchically connected by bridges. High bandwidth control loops were closed over local busses. Lower rate loops and status information were shared between busses. Multiple simulation methodologies were employed to design and valdate the communications protocol for the network. The methodologies included mathematical analysis, functional simulation, and physical simulation. Each method elucidated a separate aspect of the protocol's behavior. The unique contribution of each method yielded a comprehensive understanding of the proposed design and perrnitted model validation by cross-checking the results. The ortginal traffic load for this study included messages with maximurn acceptable delays between 0.001 and 1.0 seconds. The speed of the network was limited to less than 1.0 megabit per second (Mbps) for electrical reasons. The results demonstrated an unacceptable probability of delay for the highest rate messages, even at the muximum bus speed. A separate dedicated link was therefore added to the control system for the highest rate messages.

Stability of multiple access communication networks

The problem of stability of different multiple access schemes in computer networks is discussed. The results for the main multiple access schemes — slottedaloha, controlledaloha, csma, csma/cd, polling systems and collision resolution algorithms are surveyed. The techniques used for the stability of these systems have been emphasized.

An adaptive canceller of cochannel interference for spread-spectrum multiple-access communication networks in a power line

The authors propose and investigate an adaptive canceller of intersymbol and cochannel interference due to channel distortion and cross-correlation among pseudonoise sequences assigned to individual users of a DS-SSMA (direct-sequence spread-spectrum multiple-access) system. In order to implement a local area network (LAN) by using a power line installed in a building wall as a transmission channel, the authors have investigated utilization of DS-SSMA which has advantages such as robustness against narrow-band interference and noise and realization of asynchronous code division multiple access. In a power line, however, restriction of transmission bandwidth for communications makes it difficult to suppress cochannel interference and the channel is also time-varying due to fluctuation of loads. Since the proposed canceller adaptively eliminates cochannel interference as well as intersymbol interference, it can facilitate synchronization and increase the number of the simultaneously accessing users on a power line with restricted processing gain. The error probability in the output of the canceller is theoretically calculated for the steady-state case by using a Markov model. Computer simulations illustrate stable convergence properties of the canceller.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

On retransmission control policies in multiple-access communication networks

We focus on an earlier proposed class of ALOHA-type retransmission policies intended to control the random accessing of a single-channel communication network by a large number of packet-transmitting, bursty users. These control policies use channel feedback information to adaptively adjust the level of the traffic intensity, and can maintain any input rate less than e-1, for an infinite-population Poisson arrival model. Our analysis focuses on a simplified recursive model for describing locally the dynamics of the traffic intensity. The convergence analysis of this local model is reduced to stability analysis of a deterministic differential equation, and reveals a speed of convergence versus steady-state accuracy tradeoff. We introduce measures for evaluating this tradeoff. We use the proposed measures to show how certain parameter choices might best be made, and to study the effect of feedback limitations and channel errors on the performance of the random-access system. Our results show that with proper parameter choices the considered policies can be made extremely insensitive to channel errors.

Outline of a Multiple-Access Communication Network Based on Adaptive Arrays

We propose here a single-frequency communication system consisting of K mobile users simultaneously communicating with a central station equipped with a computationally adapted array consisting of n \geq K antennas. The array employs K sets of n weights to segregate the signals received from the K users. The weights are determined by direct computation based on position information transmitted by the users. Currently known techniques require (for n = K ) about (4/3)K^{4} computer operations (multiply and add). We develop here an improved technique that accomplishes that in 8K^{3} operations, yielding a reduction by a factor of K/6 .