Medium access control protocol design for wireless communications and networks review

<p><span>Medium access control (MAC) protocol design plays a crucial role to increase the performance of wireless communications and networks. The channel access mechanism is provided by MAC layer to share the medium by multiple stations. Different types of wireless networks have different design requirements such as throughput, delay, power consumption, fairness, reliability, and network density, therefore, MAC protocol for these networks must satisfy their requirements. In this work, we proposed two multiplexing methods for modern wireless networks: Massive multiple-input-multiple-output (MIMO) and power domain non-orthogonal multiple access (PD-NOMA). The first research method namely Massive MIMO uses a massive number of antenna elements to improve both spectral efficiency and energy efficiency. On the other hand, the second research method (PD-NOMA) allows multiple non-orthogonal signals to share the same orthogonal resources by allocating different power level for each station. PD-NOMA has a better spectral efficiency over the orthogonal multiple access methods. A review of previous works regarding the MAC design for different wireless networks is classified based on different categories. The main contribution of this research work is to show the importance of the MAC design with added optimal functionalities to improve the spectral and energy efficiencies of the wireless networks.</span></p>

Blockchain networks as constitutional and competitive polycentric orders

Institutional economists have analyzed permissionless blockchains as a novel institutional building block for voluntary economic exchange and distributed governance, with their unique protocol features such as automated contract execution, high levels of network and process transparency, and uniquely distributed governance. But such institutional analysis needs to be complemented by polycentric analysis of how blockchains change. We characterize such change as resulting from internal sources and external sources. Internal sources include constitutional (protocol) design and collective-choice processes for updating protocols, which help coordinate network participants and users. External sources include competitive pressure from other cryptocurrency networks. By studying two leading networks, Bitcoin and Ethereum, we illustrate how conceptualizing blockchains as competing and constitutional polycentric enterprises clarifies their processes of change.

SARS-CoV-2 Positivity in a Combat Sports Bubble

ObjectiveThe objective of this report is to describe a SARS-CoV-2 protocol and subsequent positivity rate for athletes and staff participating in combat sports events.BackgroundCombat sports are among the most challenging to protect against the transmission of communicable diseases. Sports neurologists are often called on to take a leadership role in the safe management of these events. Our team was asked to provide a plan for pre-fight SARS-CoV-2 testing during the recent pandemic. As a result, we were able to successfully host 28 major combat sports events at a single venue with minimal exposure for staff and participants.Design/MethodsAthletes and staff were tested for the SARS-CoV-2 virus with a PCR method. Samples were obtained via nasal swab upon arrival at the host hotel. All participants were then quarantined until the results were available. Those with negative tests were allowed to resume training in isolated pods. All participants were retested within 72 hours of the event. Those who were positive were quarantined off site for up to 2 weeks. Consultation was provided with an infectious disease specialist via telemedicine.ResultsA total of 8,135 tests were performed from July 1, 2020 until April 30, 2021 for the purpose of maintaining a safe venue. A total of 1,649 subjects were tested. There were 42 positive tests that resulted in an overall SARS-CoV-2 positivity rate of 0.516% for these events.ConclusionsOur sports neurology team was able to design and implement an effective plan to protect combat sports athletes and staff during the SARS-CoV-2 pandemic. This allowed the safe continuation of 28 events. This protocol design can be implemented when dealing with future outbreaks of communicable diseases.

An Analysis on Contemporary MAC Layer Protocols in Vehicular Networks: State-of-the-Art and Future Directions

Traffic density around the globe is increasing on a day-to-day basis, resulting in more accidents, congestion, and pollution. The dynamic vehicular environment induces challenges in designing an efficient and reliable protocol for communication. Timely delivery of safety and non-safety messages is necessary for traffic congestion control and for avoiding road mishaps. For efficient resource sharing and optimized channel utilization, the media access control (MAC) protocol plays a vital role. An efficient MAC protocol design can provide fair channel access and can delay constraint safety message dissemination, improving road safety. This paper reviews the applications, characteristics, and challenges faced in the design of MAC protocols. A classification of the MAC protocol is presented based on contention mechanisms and channel access. The classification based on contention is oriented as contention-based, contention-free, and hybrid, whereas the classification based on channel access is categorized as distributed, centralized, cluster-based, cooperative, token-based, and random access. These are further sub-classified as single-channel and multi-channel, based on the type of channel resources they utilize. This paper gives an analysis of the objectives, mechanisms, advantages/disadvantages, and simulators used in specified protocols. Finally, the paper concludes with a discussion on the future scope and open challenges for improving the MAC protocol design.

Poster on SSS-Sms Communication Protocol Design

This is to show a complete communication architecture and software architecture of SSS-SMS communication protocol design and conference presentation details.

Feasibility of Data-Driven, Model-Free Quantitative MRI Protocol Design: Application to Brain and Prostate Diffusion-Relaxation Imaging

Purpose: We investigate the feasibility of data-driven, model-free quantitative MRI (qMRI) protocol design on in vivo brain and prostate diffusion-relaxation imaging (DRI).Methods: We select subsets of measurements within lengthy pilot scans, without identifying tissue parameters for which to optimise for. We use the “select and retrieve via direct upsampling” (SARDU-Net) algorithm, made of a selector, identifying measurement subsets, and a predictor, estimating fully-sampled signals from the subsets. We implement both using artificial neural networks, which are trained jointly end-to-end. We deploy the algorithm on brain (32 diffusion-/T1-weightings) and prostate (16 diffusion-/T2-weightings) DRI scans acquired on three healthy volunteers on two separate 3T Philips systems each. We used SARDU-Net to identify sub-protocols of fixed size, assessing reproducibility and testing sub-protocols for their potential to inform multi-contrast analyses via the T1-weighted spherical mean diffusion tensor (T1-SMDT, brain) and hybrid multi-dimensional MRI (HM-MRI, prostate) models, for which sub-protocol selection was not optimised explicitly.Results: In both brain and prostate, SARDU-Net identifies sub-protocols that maximise information content in a reproducible manner across training instantiations using a small number of pilot scans. The sub-protocols support T1-SMDT and HM-MRI multi-contrast modelling for which they were not optimised explicitly, providing signal quality-of-fit in the top 5% against extensive sub-protocol comparisons.Conclusions: Identifying economical but informative qMRI protocols from subsets of rich pilot scans is feasible and potentially useful in acquisition-time-sensitive applications in which there is not a qMRI model of choice. SARDU-Net is demonstrated to be a robust algorithm for data-driven, model-free protocol design.