A Distributed Contention Vector Division Multiple Access (D-CVDMA) Protocol for Wireless Networks

Due to its fixed assignment nature, the well-known time division multiple access (TDMA) protocol suffers from poor performance when the offered traffic is bursty. In this paper, an adaptive TDMA protocol, which is capable of operating efficiently under bursty traffic conditions, is introduced. According to the proposed protocol, the station which is granted permission to transmit at each time slot is selected by means of learning automata (LA). The choice probability of the selected station is updated by taking into account the network feedback information. The system which consists of the LA and the network is analyzed and it is proven that the choice probability of each station asymptotically tends to be proportional to the probability that this station is not idle. Although there is no centralized control of the stations and the traffic characteristics are unknown and time-variable, each station tends to take a fraction of the bandwidth proportional to its needs. Furthermore, extensive simulation results are presented, which indicate that the proposed protocol achieves a significantly higher performance than other well-known TDMA protocols when operating under bursty traffic conditions.

Monitoring of water sources is a major concern worldwide. Wireless sensor networks (WSN) may be used for this monitoring. However, current systems employ mainly physical sensors for variables such as temperature, pressure, humidity and light. Wireless chemical sensors networks (WCSNs) for environmental monitoring are scarce due to the lack of autonomy of conventional sensors. This paper presents results of a WCSN for monitoring pH based on ion selective field effect transistors (ISFETs). Sensing nodes employ a human interface required for in situ calibration of chemical sensors. Unlike most studies, our work evaluates the network employing chemical measurements and wireless network metrics. Results show zero packet losses by using a time division multiple access (TDMA) protocol. The network allows wireless communication within 300m including attenuation from buildings and trees. Therefore, the system presented in this paper is suitable for long range applications with unobstructed line of sight. pH measurements present a standard deviation below 1%, showing high repeatability. When compared to a commercial pH meter, difference in measurements is below 5%. As a consequence, accuracy is adequate for the application. Measurements also presented high stability during 3 h of continuous measurement.

Information Technology has grown rapidly leading to challenges with communicating information with nodes at remote locations. There are many communication media, and certain varieties of wired links such as coaxial cables, where multiple nodes can all be linked to hear each other's transmissions either properly, correctly or with some non-zero probability. Generally, there are two rudimentary ways of sharing such stations or media, which can be the time-sharing, and frequency sharing. This paper tackles the rudimentary question of how such one common communication channel also called a shared medium can be distributed among the distinct nodes with maximum productivity. It analyzes wireless sensor networks and its accompanying technologies sighting their pros and cons. Focusing on time-sharing, we examine methodically two prevalent approaches used in obtaining this which are either by time division (split) multiple access (TDMA) or contention protocols of which both approaches are widely being used in today’s systems. It also shows that with proper time of selecting the likelihood exigency of Tame Division Multiple Access’s (TDMAs), utilization tends to 1/e (37%) but also tends to increase collision. To adapt the transmitted message likelihood, a format for calculation was adopted. The idea was to seek to gather to the favorable point of value. Slotted Aloha has twice the utilization of Unslotted-Aloha when the numbers of accumulated nodes grow. The Study also shows that each node will stake transmission within sprinkling fixed number of slots and this is guaranteed when using a related distribution in a finite window, but this is not the case with geometric distribution.

With the advent of self-driving cars, vehicular networking is gaining greater attention and the subject of extensive research. It is important to implement a more efficient and secure transportation system by enabling communication among objects on the road. Specifically, safety applications should be delivered in a reliable manner within a limited time period. Several time division multiple access (TDMA) protocols have been proposed to realize this. However, most of the existing research have proposed slot management approaches by taking into account the static topology; they have not sufficiently discussed research on “merging collision” arising from overlapping two or more collision domains due to vehicle mobility. In this study, we examine the effect of merging collision in terms of packet delivery ratio, overhead, and inter-basic safety message (inter-BSM) delay. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> Delay between BSMs received in succession. To mitigate the effect of merging collision, we also propose a lightweight distributed TDMA protocol, where the order of vehicles on the road and their relative distances are exploited to determine the dedicated slot. The collision is further resolved using in-band signaling from the surrounding vehicles. Simulation studies show that the proposed scheme improves the performance of the packet delivery ratio (PDR) 10% more than the comparative protocol, and consequently achieves 97% and 95% PDRs, in highway and urban environment, respectively. Furthermore, the overhead and inter-BSM delay are substantially reduced.

국제해사기구(International Maritime Organization, IMO)에서는 선박의 해상 충돌을 방지하기 위하여 SOLAS의 요구조건에 따라 모든 선박에 대하여 선박자동식별장치(Automatic Identification System, AIS)를 의무적으로 장착하도록 권고하고 있다. AIS를 사용하면 타선에 대한 제원 및 항행정보의 획득이 가능하여 충돌방지뿐만 아니라 광역관제, 조난 선박의 탐색구조 등 안전관리에도 활용이 가능하다. 본 논문에서는 AIS 장비를 사용하여 ADS-B (Automatic Dependent Surveillance - Broadcast) 개념 기반의 항공감시용 송수신기를 구현한 결과에 대하여 살펴보도록 한다. 기본적으로 AIS는 해상에서 사용되기 때문에 고도 정보를 사용하지 않지만, AIS 장비 내부에 사용하는 GPS (Global Positioning System) 칩셋에서 제공하는 고도 정보의 추출이 가능하다. 고도 정보를 포함한 감시 메시지 형식을 정의하고, SOTDMA (Self-Organizing Time Division Multiple Access) 방식을 개선하여 ADS-B 송수신기를 구현하였다. 적용 결과를 확인하기 위하여 지상시험 및 비행시험을 수행하였다. International Maritime Organization (IMO) recommends the installation of an Automatic Identification System (AIS) according to requirements by SOLAS to avoid maritime collision. AIS provides traffic information of other ships that may be used for maritime traffic control, SAR (Search and Rescue) and collision avoidance to apply safety management. In this paper, preliminary results to implement an aeronautical surveillance transceiver using AIS transceiver based on ADS-B concepts are described. Although altitude information is not required for AIS since the AIS is operated at MSL (Mean Sea Level), altitude information can be extracted by a GPS (Global Positioning System) chip-set in the AIS transceiver. ADS-B transceiver is implemented by defining a surveillance message format including the altitude information and modifying SOTDMA (Self-Organizing Time Division Multiple Access) protocol. Ground tests and flight tests are performed to validate the implementation results.

In this chapter we present an approach to mapping and scheduling for time-driven systems where processes are scheduled according to a non-preemptive static cyclic scheduling scheme, and communication uses a time division multiple access (TDMA) protocol. We accurately take into consideration the communication costs and consider, during the mapping and scheduling process, the particular requirements of the communication protocol.

The potential of exploiting large propagation delays in underwater acoustic (UWA) networks to maximize the network throughput is established in the recent past. Transmission scheduling strategies have been proposed to take advantage of large propagation delay. Super-TDMA is one among such Medium Access Control (MAC) strategies proposed. It is a form of Time Division Multiple Access (TDMA) protocol in which multiple transmissions are allowed in the same time slot and hence concurrently propagate in the medium. We present the implementation challenges of Super-TDMA on underwater acoustic modems and the experimental results demonstrating interference alignment, the crossing of simultaneously transmitted packets in water, and the time synchronization among the deployed nodes in the network.

We investigate opportunistic transmissions in a time-slotted wireless network, emphasizing constraints arising from finite durations allocated to various network operations and the availability of energy for these operations. Each time frame (time slot) comprises three sub-frames: sensing, reporting, and either transmission or energy harvesting based on the presence or absence of the primary user. We assume a fixed duration for the transmission sub-frame within each time frame. Utilizing a time division multiple access (TDMA) protocol, we manage local sensing data reporting within each time frame; consequently, the reporting time is contingent on the number of users. As a result, with the total time allocated for sensing and reporting being fixed, a trade-off arises between the number of collaborating users and the number of samples. Additionally, energy limitations and causality lead to two scenarios for wireless network operation: energy-deficit and energy-surplus regimes. To address this complexity, we formulate an optimization problem aimed at maximizing overall network throughput while considering constraints imposed by finite durations for various network operations and energy availability. We provide analytical evidence of the convexity of the optimization problem in both energy-deficit and energy-surplus scenarios. Furthermore, we propose two algorithms designed to achieve optimal throughput for each scenario. The accuracy of our analyses is validated through Monte Carlo simulations. Numerical results demonstrate the effectiveness of our proposed approach.

We discuss medium access control (MAC) issues related to the migration to the next generation on-demand mode for communication support of NASA missions in near Earth orbits. For this scenario, to meet the objective of bandwidth-efficient support while guaranteeing specific QoS requirements, a detailed investigation of the suitability of the MAC schemes is performed. Performance measures of interest include end-to-end delay and successful throughput. A reservation-based demand time division multiple access (RD-TDMA) protocol is proposed and its performance is analyzed. Using simulation, we compare the system's performance under this scheme with that obtained under a fixed-assignment scheme. Simulation results demonstrate that on-demand mode is a suitable strategy for future NASA space missions with an unpredictable traffic pattern, and can offer certain performance advantages.

Cooperation among heterogeneous marine vehicles can offer several benefits to underwater applications, such as supporting the navigation of submerged robots by leveraging the information available to a surface vehicle. Within such context, this paper describes an acoustic positioning and communication protocol developed for the localisation of multiple Autonomous Underwater Vehicles (AUVs) by means of an Autonomous Surface Vehicle (ASV) equipped with an Ultra-Short BaseLine (USBL) device. To avoid packet collisions, access to the acoustic channel is managed through a time slot division mechanism. Unlike a classical Time Division Multiple Access (TDMA) protocol, the approach considered in this work consists of a centralised scheduling handled by the ASV, in which AUVs are localised at regular time epoch but can transmit only when queried. This allows to prioritise the number of position measurements taken by the ASV and then relayed back to the submerged vehicles, with the final goal of improving the navigation accuracy of the latter. The solution is also designed to handle the latency of acoustic communication and to correctly associate each position measurement with the corresponding acquisition time. Furthermore, it does not require any a priori synchronisation between the clocks of the vehicles involved and ensures complete decoupling between their navigation algorithms. Experimental activities in very-shallow waters, involving an ASV and two target nodes, were carried out to validate the multi-AUVs positioning system and to provide a characterisation of its performance.

A multiple access protocol is a scheme to control the access to a shared communication medium (radio frequency) among various users. Although many access protocols have been proposed and each has its advantages and limitations, very few are suitable for integrated wireless communications. Access protocols can be grouped according to the bandwidth allocation mechanism, which can be static or dynamic, and according to the type of control mechanism implemented. Multiple access protocols can be categorized into three classes: fixed assignment, random assignment, and demand assignment.

We consider the problem of minimizing the energy needed for data fusion in a large scale sensor network by varying the transmission times assigned to different sensor nodes. The optimal scheduling protocol is derived, based on which, we develop a low-complexity inverse-log scheduling algorithm that achieves near-optimal energy efficiency. To eliminate the communication overhead required by centralized scheduling protocols, we also develop a distributed inverse-log protocol that is applicable to networks with a large number of nodes. Simulations demonstrate that this distributed scheduling protocol achieves substantial energy savings over uniform time division multiple access protocol.

Introduction. Traffic in modern telecommunication radio networks is self-similar, therefore, the use of methods for calculating the parameters of Carrier Sense Multiple Access (CSMA) protocols adopted in the classical theory of teletraffic, based on Poisson distribution models, leads to an underestimation of the load and stability of these protocols. Purpose. Build a mathematical model for the operation of synchronous CSMA protocols with flexible and rigid strategies in conditions of self-shaped traffic. Obtain average transmission rate equations and their comparative analysis of the results of studies of the same protocols for traffic with the Poisson distribution. Methods. The goal is achieved by creating and analyzing a mathematical model for the operation of synchronous CSMA protocols with flexible and rigid strategies under conditions of Pareto-distributing traffic. The model is described by the equations of the average protocol transfer rate, which are a function of traffic intensity and Pareto distribution parameters. Results. It has been proven that self-similar traffic has a significant impact on the stability limit of CSMA protocols and their throughput, which must be taken into account when using these protocols in radio networks with long-term dependence on traffic distribution. At the same time, there is a slight decrease in the maximum average transmission rate of CSMA protocols compared to the traffic model with the Poisson distribution. Conclusions. The proposed mathematical model of CSMA protocols with flexible and rigid strategies makes it possible to calculate the real values of the average speed, stability limit, and throughput of these protocols under conditions of self-similar traffic.

Long Range (LoRa) has become one of the most promising physical layer technologies for the Internet of Things (IoT) ecosystem. Although it manifests low-power consumption and long-distance communication, LoRa encounters a large number of collisions in the IoT environment, which severely affects the system’s throughput and delay performance. In this paper, a code division carrier sense multiple access (CD/CSMA) protocol that resolves the traditional channel collision problem and implements multi-channel transmission is proposed for the LoRa medium access control (MAC) layer. To reduce data transmission delay and maximize the throughput of the system, the adaptive p-persistent CSMA protocol divides the channel load into four states and dynamically adjusts the data transmission probability. Then, to reduce channel collisions significantly, the code division multiple access (CDMA) protocol is performed on different channel states. Moreover, the combination of the proposed adaptive p-persistent CSMA protocol and the CDMA successfully reduces the number of data retransmissions and makes LoRa more stable. The simulation results demonstrate that the proposed adaptive p-persistent CD/CSMA protocol can achieve near-optimal and occasionally even better performance than some conventional MAC protocols, especially in a heavy load channel.

In this paper, a novel multiple access scheme named DSAMA protocol is proposed for wireless ATM networks. DSAMA is the combination of reservation multiple access protocol and dynamic slot allocation algorithm. The orthogonal code is used for reservation in the DSAMA system. Hence, the packet collisions are prevented while several packets apply for reservation slot simultaneously. In addition, due to bandwidth limitation, the dynamic slot allocation algorithm with bound variable for bursty traffic is also proposed in this paper, so that the QoS of multimedia traffic is guaranteed in wireless ATM networks. A computer simulation is utilized to validate the DSAMA protocol. From the analysis and simulation results, we know that the slot utilization in the DSAMA system is higher than that of the other well-known integrated services multiple access (e.g., PRMA, PRMA++). Furthermore, the performance of bursty traffic in the DSAMA system outperforms the case without dynamic slot allocation. We are sure that DSAMA protocol is a competitive candidate to be adopted in the wireless ATM networks.