Random Access Method Research Articles

Modeling of Real-Time Multimedia Streaming in Wi-Fi Networks With Periodic Reservations

An important problem of modern Wi-Fis is the interferences caused by hidden stations active in the same area, or in multihop communications. All these issues significantly degrade the efficiency of the random channel access methods. Recent standardization and research activities are focused on solving coordination problems between various Wi-Fi devices. For example, the ongoing development of Wi-Fi 7 includes a coordinated schedule between the access points as a candidate solution. Consequently, Wi-Fi has many deterministic channel access mechanisms, which schedule channel time in a periodic manner well in advance and, thus, are utilized for streaming QoS sensitive data. However, both random traffic intensity and error-prone nature of the wireless channel complicate choosing such reservation parameters, i.e., the duration and the period of the reserved time intervals, that satisfy QoS requirements while minimizing channel time consumption. This paper introduces a general mathematical framework to solve the problem of choosing appropriate reservations parameters. The comparison of the analytical and simulation results show the high accuracy of the proposed framework. Finally, the paper gives an example of how to use the developed framework to maximize the network capacity.

Software Defined Network architecture model and cognitive control method for organizing multiple access in the Internet of Things

The study has the method of random multiple wireless access in the networks of the Internet of Things and the control architecture, similar to a software-configured network, examined. The models of collision description, network parameters selection and their initial values, which provide target values for the probability of the delivery in the considered networks, are analyzed. The paper proposes a method the novelty of which lies in the usage of cognitive control of network parameters, taking into account the heterogeneity of conditions for different users with a given probability of data delivery. The proposed method and model of random multiple access and cognitive selection of network parameters are relevant and can be applied when building the access level of the Internet of Things in networks with allowable losses when managing large volumes of heterogeneous traffic and ensuring the required quality of service.

Simulation model of local computer network with channel aggregation and random access method at redundant transfer

Simulation model of local computer network with channel aggregation and random access method at redundant transfer

On the performance of UNB for machine‐to‐machine low earth orbit (LEO) satellite communications

SummaryUltra narrow band (UNB) is a widely used technology for machine‐to‐machine and low‐power wide‐area communications. Its properties, long range with small RF power, make it naturally attractive for satellite communications but also draw new challenges compared with terrestrial systems where this technology is already deployed. Indeed, the main advantage of UNB signals, their small bandwidth, makes them more sensitive to frequency drifts that are particularly present in the case of LEO satellite systems. It also implies the use of a random access method in which the carrier frequency is a parameter unknown by the receiver. In this paper, we propose a general semianalytical model to evaluate the performance of a terrestrial or satellite system using UNB technology, taking into account the multiuser interference and the frequency drift. This model is then used to assess the performance (packet loss ratio and throughput) on the return link medium access control (MAC) of a representative LEO satellite system. With our model, we analyze the effect of frequency drift on the system performance. This paper also proposes to investigate more deeply the multiuser interference modeling in order to estimate accurately the performances of a UNB system in terms of bit error rate (BER). We propose a semianalytical approach to study the interference in presence of arbitrary power imbalance that includes the effect of frequency offset and frequency drift and applicable for any linear modulation and any pulse‐shaping filter. The expression of the multiuser interference is established in the general case. We then propose a methodology to compare this exact model to the Gaussian interference approximation (mainly used through the central limit theorem) in order to assess its accuracy.

Historical evolution of magnetic data storage devices and related conferences

Telegraphic invention by Danish engineer Valdemar Poulson in 1898 was the first demonstration that a magnetic recording medium could be used to record information and for playback. It was not until 1947, that 3 M shipped the first commercial oxide tape coated on paper backing, and in 1953, IBM shipped the first magnetic tape drive, IBM 727, for data storage. IBM invented the first hard disk drive, IBM 305, called the random access method of accounting and control (RAMAC) for data storage. The RAMAC stored 5 MB of data and used fifty 24-in. diameter disks. The drive could be housed in a room of about 9 m × 15 m. It weighed over a ton and had to be moved around by forklifts. The cost was USD $250,000 at the time (a whopping $50,000 per MB!). In 2018, one could buy a 30 TB tape cartridge or 1 TB portable hard disk drives (with a 2.5-in. diameter disk), for about USD $100. Since the late 1970s, the tribology of head-medium interface has been considered a limiting technology for development of reliable drives with ever increasing recording densities. Given the importance of tribology, a first ever symposium on Tribology and Mechanics of Magnetic Storage Systems was held in 1984 at the ASME/STLE Tribology Conference, co-organized by B. Bhushan, D. Bogy, N. Eiss and F. Talke, and annually thereafter by Bhushan and Eiss. Many electromechanical, materials science, design and manufacturing issues also became important. In order to broaden the scope to include mechanical issues, the first International Symposium on Advances in Information Storage Systems was organized at the ASME Winter Annual Meeting in 1989 by B. Bhushan, and annually thereafter. B. Bhushan led the founding of Information Storage and Processing Systems (ISPS) Sub-division in ASME in 1992 which was elevated to a Division level in 1996. In 1993, the conference was renamed as the Annual Conference on ISPS. In 2018, the 27th Annual Conference on ISPS was held after 30th year of its inception, and the ISPS division celebrated its silver jubilee in 2017. The research papers continue to be published in a dedicated journal. This paper provides an overview of historical evolution of magnetic data storage devices and related conferences and publications with a focus on tribology and electromechanical, materials science, design and manufacturing issues.

Random-Access Control Method for MTC in an LTE System Inspired by the Minority Game

To support machine-type communications in an LTE system, we propose a contention control method that regulates the number of devices competing simultaneously for the random-access channel in a distributed manner. We modeled the decision problem of a device—whether to participate in a random-access contention—as the minority game. Using inductive reasoning from observing the collective behavior of all devices, a device adapts access strategies so as to increase the probability of access success. We analyze the average number of successfully decoded preambles by deriving the average number of devices competing simultaneously. Through simulation studies, we also show that our method reduces the probability of random-access failure, the access delay, and the energy consumption of a device compared with other conventional methods.

Improved Method of Contention-Based Random Access in LTE System

Random access is the necessary process to establish the wireless link between the user equipment (UE) and network. The performance of the random access directly affects the performance of the network. In this work, we propose a method on the basis of the existing alternatives. In this method, we estimate the system load in advance to adjust the number of terminals. An access threshold is set to control the number of terminals which want to access the base station at an acceptable level. At the same time, we have an improvement on the existing power climbing strategy. We suppose that the power ramping is not always necessary for the re-access. And the selection of power ramping steps is studied in this paper. Simulations based on MATLAB are employed to evaluate the effectiveness of the proposed solution and to make comparisons with existing alternatives.

Structural Healthcare Services for Personal Area Networks in Multi-hop Cognitive Radio Networks

In recent years, the research on structural healthcare services for personal area networks in multi-hop cognitive radio networks has attracted much attention. The way people enjoy health care has been changed by networks and information technology (i.e., electronic-healthcare and mobile-healthcare). With the increase in people’s demand and the development of information technology, the construction of people’s digital healthcare becomes a trend, such as real-time monitoring by video or audio. However, this requires the use of fixed spectrum resources. User experience will be greatly reduced. In this work, an effective method can be proposed to improve the quality of service. Numerical simulation demonstrates that the method of random access can improve resource utilization and throughput of healthcare system effectively.

Horizontal Localization in Simulated Unilateral Hearing Loss.

Background and ObjectivesThe ability to localize a sound source is one of the binaural hearing benefits in a horizontal plane based on interaural time difference and interaural intensity difference. Unilateral or bilateral asymmetric hearing loss will affect binaural hearing and lead to sound locating errors. In this cross sectional analytical descriptive study, the localization error was investigated when participants turned their heads to the sound source with closed eyes and after simulating unilateral hearing loss by placing earplugs inside the right ear canal. Subjects and MethodsThis cross sectional analytical descriptive study was carried out on 30 right-handed adults, 22 female and 8 male (average: 25 years, standard deviation: 3.16). They were selected with the available random access method. Horizontal localization was evaluated with five speakers located at 0, ±30, and ±60 degree azimuths at a 1-meter distance from the examinee. Narrow-band noise signals were delivered at 35 dB SL in two “without earplug” and “with earplug” situations and the results were compared. The study was performed between September and December 2016 in Tehran, Iran. ResultsSignificant differences were observed in localization errors between the “with earplug” and “without earplug” situations. The localization differences were greater for left-side speakers (-30 and -60 degrees) compared with right-side speakers (+30 and +60 degrees). The differences were more apparent at 4,000 and 6,000 Hz, which confirmed the effect of unilateral simulated hearing loss on interaural latency differences. ConclusionsSimulating hearing loss by using an earplug in one ear (right) increased localization errors at all frequencies. The errors increased at higher frequencies.

A Novel Random Access Mechanism for Timely Reliable Communications for Smart Meters

Smart meter (SM) is a key component of the smart grid, which reports power consumption to a centralized control center at regular intervals. The long term evolution (LTE) network has gained much attention as an attractive communication platform for SM traffic due to its high bandwidth, low latency, and coverage. However, when a large number of SMs simultaneously access the LTE network, it is very likely to result in preamble congestion. This eventually becomes a contributing factor for prolonged delays at the eNode-B, which would eventually degrade the performance of the LTE network. Hence, a random access mechanism is desirable for preamble signatures to occupy resource blocks for SMs. In this paper, we introduce a novel technique that combines contention- and noncontention-based random access methods. Our proposed method does not require a backoff time and regeneration of a new preamble if the first attempt is unsuccessful. Although SMs have fixed periodic communications, under the proposed random access mechanism preamble signatures do not need to be reserved. We analyze the proposed mechanism's efficiency in terms of metrics collision probability and packet delay. The simulation results are validated against the 3GPP standard.

A random multi-user access method with unequal protection

A random multi-user access method with unequal protection

Sparse Signal Aloha: A Compressive Sensing-Based Method for Uncoordinated Multiple Access

We investigate the problem of sparse signal medium access control in the wireless sensor networks. The proposed sparse signal Aloha (SSA) transmits sampled compressive data to the fusion center using Aloha random access protocol. In order to maximize the overall data transmission rate in the presence of packet collision, redundant data are randomly subsampled at individual sensor nodes according to an optimal subsampling rate before transmission. Data loss due to random subsampling and collision in the wireless channel are compensated using compressive sensing recovery method at the fusion center. Simulation results verify the theoretical analysis and show the significant improvement of SSA compared with existing CS-based random access method.

Effects of LTE Random Access Methods on Healthcare M2M Applications

In recent years, the communication between machines, known as Machine-to-Machine (M2M) communication, has become a dynamic research area. M2M refers to networks, which connect devices together and enable them to make a smart decision. The most viable option of implementing M2M communication is over the Long Term Evolution (LTE) network. A key challenge for M2M communication over the Long Term Evolution (LTE) is the performance of Random Access Channel (RACH) because its operation was not designed with the enormous number of M2M devices in mind. To deal with the situation reduces network access success rate, several major access control methods were adopted. However, the suggested methods generally increase the access success rate regardless of delay requirements. On the other hand, access delay is crucial for many M2M applications such as healthcare. This paper investigates the effects of LTE Random Access Methods on healthcare M2M applications when enormous number of devices are introduced. The study clearly shows that to meet the requirements for delay sensitive M2M applications, the random access (RA) resources should be very strictly and carefully allocated.

A multiple power level random access method for M2M communications in LTE‐A network

AbstractAccess control is an effective way to protect the radio access part of Long‐Term Evolution–Advanced (LTE‐A) network from the overload caused by a huge number of Machine‐Type Communication Devices (MTCDs). A class of access control mechanisms is the Access Class Barring (ACB), which regulates the Machine‐to‐Machine (M2M) traffic in accordance with the available Random Access (RA) resources. In this paper, we extend the single power level ACB scheme to a multiple power level method to increase the number of successfully transmitted requests in the case of overload. Our analysis is based on the capture effect in the third step of RA procedure of the LTE‐A system in which one of the transmitted requests by 2 or more co‐tagged MTCDs, MTCDs which use the same preamble in the first step, can be decoded by the evolved–Node B (eNB). We first formulate the power level selection as an optimization problem assuming the perfect capture model without considering MTCDs' energy budget. Then, to take into account MTCDs' energy consumption, the scenario is extended for the signal‐to‐interference ratio–based capture model. In addition, we investigate the advantages of the proposed multiple power level RA method on discriminating the access of MTCDs with different priorities. The numerical results show that using the optimal parameters, the RA throughput can be improved in comparison with the single power level system at the cost of slightly increasing MTCDs' energy consumption and the complexity of RA procedure.

Multiple-antenna systems and multiuser communications: Fundamentals and an overview of software-based modeling techniques

In this paper, advanced contemporary multiple communication techniques, including multiple-antenna systems and multiuser communications are introduced and analyzed in details. Moreover, their supportive software-based modeling techniques are also detailed with appropriate mathematical derivations and simulations. Additionally, random access methods, as a promising and efficient implementation of multiuser communications are also briefly introduced for industrial use purposes. By reading this paper, the readers are expected to have a broad understanding of these advanced contemporary multiple communication techniques and acquire the technical know-hows of software-based simulation and industrial implementation of these techniques. Meanwhile, this paper is also expected to play the role of a solid reference for the relevant technicians which might require the introduced modeling techniques in this paper.

A Low Collision and High Throughput Data Collection Mechanism for Large-Scale Super Dense Wireless Sensor Networks.

Super dense wireless sensor networks (WSNs) have become popular with the development of Internet of Things (IoT), Machine-to-Machine (M2M) communications and Vehicular-to-Vehicular (V2V) networks. While highly-dense wireless networks provide efficient and sustainable solutions to collect precise environmental information, a new channel access scheme is needed to solve the channel collision problem caused by the large number of competing nodes accessing the channel simultaneously. In this paper, we propose a space-time random access method based on a directional data transmission strategy, by which collisions in the wireless channel are significantly decreased and channel utility efficiency is greatly enhanced. Simulation results show that our proposed method can decrease the packet loss rate to less than in large scale WSNs and in comparison with other channel access schemes for WSNs, the average network throughput can be doubled.

A prospective study of two isothermal amplification assays compared with real-time PCR, CCNA and toxigenic culture for the diagnosis of Clostridium difficile infection.

BackgroundNew molecular methods of detecting Clostridium difficile infection (CDI) provide the routine lab with a sensitive random access method to produce results that are available in a shorter time than traditional methods.MethodsIn this prospective study a total of 989 stool specimens were tested over a period of 16 months in parallel using two isothermal amplification assays, AmpliVue® (Quidel) and Illumigene® (Meridian) and the results compared to those from toxigenic culture. In addition all specimens were tested using a cytotoxic cell neutralisation assay (CCNA) and three different Real-time PCR targeting a C. difficile-specific 16S rDNA sequence or the toxin genes tcdA, tcdB/tcdB027 or cdtB.ResultsAmpliVue® was positive in 242 (24.5 %) and Illumigene® in 228 (23.1 %) specimens. 167 (16.9 %) specimens were positive in toxigenic culture. Real-time-tcdA and -tcdB PCR was positive in 211 (21.3 %) specimens, Real-time-cdtB PCR was positive in 101 (10.2 %) specimens and C. difficile-PCR (16S rDNA) in 267 (27.0 %) specimens.ConclusionsThe respective sensitivity, specificity, positive predictive value and negative predictive value compared to toxigenic culture were 91, 89, 62 and 98 % for AmpliVue® and 91, 91, 67 and 98 % for Illumigene®.

On the Adaptive Determination of the Number of Preambles in RACH for MTC

Recently, in the Long Term Evolution-Advanced (LTE-A) system, a random access method, called random access (RACH) procedure, has been proposed for machine-type communications (MTC) to support a number of devices. Since the RACH procedure is similar to multichannel ALOHA, the fast retrial can be employed. In this letter, when the fast retrial is used for the RACH procedure, we propose an adaptive approach that can adaptively decide the number of preambles to maximize the throughput without knowing the number of devices and the access probability.

Improving web experience on DVB-RCS2 links

The specifications of digital video broadcasting—return channel via satellite (DVB-RCS2) state that the satellite gateway could introduce both random and dedicated access methods to distribute the capacity among the different home users. Before starting an engineering process to design an algorithm allowing to combine both methods, it seems necessary to assess the performance of each. This paper compares random and dedicated access methods by measuring their impact on the performance of transmission control protocol (TCP) sessions when the home users exploit the DVB-RCS2 link for regular use (e.g., web browsing or email transmission). In this paper, we detail the implementation of an NS-2 module emulating physical channel access (PCA). This module fills a gap in terms of random and deterministic access methods and allows to model various satellite channel access strategies. Based on NS-2 simulations using realistic system parameters of the DVB-RCS2 link, we demonstrate that, compared to dedicated access methods, which generally result in higher levels of transmitted data, random access methods enable faster transmission for short flows. We propose to combine random and dedicated access methods, with the selection of a specific method dependent on the dynamic load of the network and the sequence number of the TCP segments.

A Distributed TDMA Slot Scheduling Algorithm for Spatially Correlated Contention in WSNs

In WSNs the communication traffic is often time and space correlated, where multiple nodes in a proximity start transmitting simultaneously. Such a situation is known asspatially correlated contention. The random access method to resolve such contention suffers from high collision rate, whereas the traditional distributed TDMA scheduling techniques primarily try to improve the network capacity by reducing the schedule length. Usually, the situation ofspatially correlated contentionpersists only for a short duration, and therefore generating an optimal or suboptimal schedule is not very useful. Additionally, if an algorithm takes very long time to schedule, it will not only introduce additional delay in the data transfer but also consume more energy. In this paper, we present a distributed TDMA slot scheduling (DTSS) algorithm, which considerably reduces the time required to perform scheduling, while restricting the schedule length to the maximum degree of interference graph. The DTSS algorithm supports unicast, multicast, and broadcast scheduling, simultaneously without any modification in the protocol. We have analyzed the protocol for average case performance and also simulated it using Castalia simulator to evaluate its runtime performance. Both analytical and simulation results show that our protocol is able to considerably reduce the time required for scheduling.