Analytical Throughput Model Research Articles

Performance of hybrid transmission in a reconfigurable intelligent surface assisted D2D using NOMA

Recent research on Reconfigurable Intelligent Surface (RIS) aided communication and Non-Orthogonal Multiple Access (NOMA) technology shows enhanced spectral efficiency for 5 G and beyond wireless network systems. This paper evaluates the performance of a Device-to-Device (D2D) network where RIS is deployed in a suitable position and NOMA is employed to accommodate more number of users in the spectrum simultaneously. The D2D users exploit cellular network resources. Analytical models for outage, throughput, and energy-efficiency are developed considering spectrum sensing and a transmit power constraint. This work investigates the network performance in underlay, overlay, as well as hybrid modes through extensive simulations. The simulation model is designed based on the analytical models. Outage probability, network throughput, and energy efficiency are analysed to evaluate the D2D network performance. The simulation results shows incorporation of RIS and NOMA, network performance improves substantially. Increase in number of RIS elements also improves the network performance.

Extreme power saving directional MAC protocol in IEEE 802.11ah networks

In this study, a novel directional medium access control scheme with an extreme power saving mechanism is developed for traffic indication map stations in the IEEE 802.11ah networks. To improve the aggregate throughput, stations are managed based on their geographical locations in combination with the employment of directional operation mode on the access point. In addition to the restricted access window mechanism used in the IEEE 802.11ah standard for power saving, an adaptive transmission power scheme is proposed for uplink transmission to leverage the power-saving efficiency. With the proposed access scheme, the network performance is significantly enhanced compared to the IEEE 802.11ah standard. The analytical models for throughput and energy consumption are formulated using Markov Chains under unsaturated conditions. The simulation results indicate the effectiveness of the proposed directional access scheme under various network scenarios.

Tuning Wi-Fi Traffic Differentiation by Combining Frame Aggregation with TXOP Limits

There are two IEEE 802.11 mechanisms which enhance Wi-Fi network efficiency by lowering communication overhead: the legacy transmission opportunity (TXOP) limit and frame aggregation. According to the IEEE 802.11 standard, frame aggregation has priority over TXOP duration settings, in some cases completely overriding legacy behavior. Therefore, Wi-Fi vendors and administrators may resign from enabling TXOP limit which, as we show in this letter, is not always a good choice. We base our findings on the presented analytical throughput model of 802.11ac (validated by ns-3 simulations), which allows measuring interactions between the two considered mechanisms and their impact on traffic differentiation in 802.11 networks.

Dynamic Channel Bonding Algorithm for Densely Deployed 802.11ac Networks

To meet the rising demand of mobile data, IEEE 802.11ac was recently developed to offer better network performance than previous IEEE 802.11 standards, representing the 5G Wi-Fi technology. One of the new technologies added to IEEE 802.11ac is a dynamic bandwidth channel access scheme that supports channel bonding (CB) with an up to 160 MHz bandwidth. However, the use of CB increases the number of stations sharing the same medium, resulting in an increased collision rate and severe interference caused by overlapping sub-channels. This problem is further aggravated in densely deployed wireless networks where the service ranges of access points (APs) are likely to be highly overlapping. To resolve these issues, we present an analytical throughput model that considers the effect of both collisions and interference. With this analytical model, we formulate the CB problem to optimize the throughput along with the traffic demand and propose a genetic algorithm for solving the problem. Further, a dynamic channel bonding algorithm (named DCB) is proposed to solve the problem with lower complexity. Extensive simulation results demonstrate that our proposed algorithm provides a higher performance than other recent dynamic CB algorithms with respect to the throughput achieved for the traffic demand.

A new analytical model of TCP Hybla for satellite IP networks

TCP Hybla is increasingly being recognized for yielding high throughput over satellite IP links. However, due to the difficulty in measuring the expected performance over such links, the deployment decision is not trivial. A good analytical model of TCP Hybla can help spread its deployment by allowing easy estimation of its performance using network parameters like packet loss probability and round trip time (RTT) over the target satellite connection. Also, it can lead to design of congestion control mechanisms based on Hybla friendly rate control. In this paper, we therefore propose new analytical models for (i) steady-state throughput and (ii) latency for TCP Hybla over satellite IP links. The new model for steady-state throughput results from a major overhaul of our previously devised model for the same. The latency model has been devised newly. Using the latency model, the throughput and the average transmission time can be estimated. We verify the accuracy of our model by comparing with simulation and emulation results. It is observed that for packet loss probability of 10−4 or below that correspond to real life packet loss probability over satellite link, our analytical models for throughput and latency closely match both the simulation and emulation outcomes. That is, our analytical models correctly represent the behavior of satellite links. Our new model leads to up to 3% more accuracy than our previously proposed model while calculating steady-state throughput.

Performance Optimization of Priority Assisted CSMA/CA Mechanism of 802.15.6 under Saturation Regime

Due to the recent development in the field of Wireless Sensor Networks (WSNs), the Wireless Body Area Networks (WBANs) have become a major area of interest for the developers and researchers. Human body exhibits postural mobility due to which distance variation occurs and the status of connections amongst sensors change time to time. One of the major requirements of WBAN is to prolong the network lifetime without compromising on other performance measures, i.e., delay, throughput and bandwidth efficiency. Node prioritization is one of the possible solutions to obtain optimum performance in WBAN. IEEE 802.15.6 CSMA/CA standard splits the nodes with different user priorities based on Contention Window (CW) size. Smaller CW size is assigned to higher priority nodes. This standard helps to reduce delay, however, it is not energy efficient. In this paper, we propose a hybrid node prioritization scheme based on IEEE 802.15.6 CSMA/CA to reduce energy consumption and maximize network lifetime. In this scheme, optimum performance is achieved by node prioritization based on CW size as well as power in respective user priority. Our proposed scheme reduces the average back off time for channel access due to CW based prioritization. Additionally, power based prioritization for a respective user priority helps to minimize required number of retransmissions. Furthermore, we also compare our scheme with IEEE 802.15.6 CSMA/CA standard (CW assisted node prioritization) and power assisted node prioritization under postural mobility in WBAN. Mathematical expressions are derived to determine the accurate analytical model for throughput, delay, bandwidth efficiency, energy consumption and life time for each node prioritization scheme. With the intention of analytical model validation, we have performed the simulations in OMNET++/MIXIM framework. Analytical and simulation results show that our proposed hybrid node prioritization scheme outperforms other node prioritization schemes in terms of average network delay, average throughput, average bandwidth efficiency and network lifetime.

High performance locks for multi-level NUMA systems

Efficient locking mechanisms are critically important for high performance computers. On highly-threaded systems with a deep memory hierarchy, the throughput of traditional queueing locks, e.g., MCS locks, falls off due to NUMA effects. Two-level cohort locks perform better on NUMA systems, but fail to deliver top performance for deep NUMA hierarchies. In this paper, we describe a hierarchical variant of the MCS lock that adapts the principles of cohort locking for architectures with deep NUMA hierarchies. We describe analytical models for throughput and fairness of Cohort-MCS (C-MCS) and Hierarchical MCS (HMCS) locks that enable us to tailor these locks for high performance on any target platform without empirical tuning. Using these models, one can select parameters such that an HMCS lock will deliver better fairness than a C-MCS lock for a given throughput, or deliver better throughput for a given fairness. Our experiments show that, under high contention, a three-level HMCS lock delivers up to 7.6x higher lock throughput than a C-MCS lock on a 128-thread IBM Power 755 and a five-level HMCS lock delivers up to 72x higher lock throughput on a 4096-thread SGI UV 1000. On the K-means clustering code from the MineBench suit, a three-level HMCS lock reduces the running time by up to 55% compared to the C-MCS lock on a IBM Power 755.

Towards a Realistic Primary Users' Behavior in Single Transceiver Cognitive Networks

Most of the models intended to describe the throughput of Primary (PUs) and Secondary (SUs) users of Cognitive Radio Networks (CRNs) assume that PUs only change their activity state (ON/OFF) in the beginning of each SU's operation cycle, admitting that PUs are synchronized with SU's operation cycle. This letter characterizes a more realistic scenario where PUs can randomly change their activity state during the SU's operation cycle. We derive an analytical model for the PU's throughput and its validation is assessed through simulation results. The analysis shows that assuming synchronized PUs leads to an undervaluation of the interference caused to PUs, and the interference decreases as more SU's operation cycles are performed per ON/OFF PU's activity state.

Opportunistic Random-Access Scheme Design for OFDMA-Based Indoor PLC Networks

Multiuser systems can benefit from multiuser diversity by assigning channels to users with better channel conditions at different time instants. In this paper, we present an opportunistic random-access scheme for orthogonal frequency-division multiple-access-based indoor power-line communication systems, based on time- and frequency-varying channel conditions, to exploit multiuser diversity. The proposed scheme dynamically adjusts the backoff time of each user according to its own channel-state variations in time and frequency domains during the contention procedure and, thus, “better” users have a higher priority to contend over their favorable subchannels. Moreover, subchannels are assigned to users with better channel conditions in order to further enhance the system throughput. In addition, an analytical throughput model for such a multiuser and multichannel system is derived to obtain the optimal parameter settings of the proposed access scheme. Simulation results show that the proposed scheme provides significant improvement in system throughput even in the case where the number of users highly exceeds that of subchannels.

IEEE 802.11 Saturation Throughput Analysis in the Presence of Hidden Terminals

Due to its usefulness and wide deployment, IEEE 802.11 has been the subject of numerous studies, but still lacks a complete analytical model. Hidden terminals are common in IEEE 802.11 and cause the degradation of throughput. Despite the importance of the hidden terminal problem, there have been a relatively small number of studies that consider the effect of hidden terminals on IEEE 802.11 throughput, and many are not accurate for a wide range of conditions. In this paper, we present an accurate new analytical saturation throughput model for the infrastructure case of IEEE 802.11 in the presence of hidden terminals. Simulation results show that our model is accurate in a wide variety of cases.

Improving TCP performance over optical burst-switched (OBS) networks using forward segment redundancy

Random contentions occur in optical burst-switched (OBS) networks because of one-way signaling and lack of optical buffers. These contentions can occur at low loads and are not necessarily an indication of congestion. The loss caused by them, however, causes TCP at the transport layer to reduce its send rate drastically, which is unnecessary and reduces overall performance. In this paper, we propose forward segment redundancy (FSR), a proactive technique to prevent data loss during random contentions in the optical core. With FSR, redundant TCP segments are appended to each burst at the edge and redundant burst segmentation is implemented in the core, so that when a contention occurs, primarily redundant data are dropped. We develop an analytical throughput model for TCP over OBS with FSR and perform extensive simulations. FSR is found to improve TCP's performance by an order of magnitude at high loads and by over two times at lower loads.

RaPTEX

Advances in microprocessors, memory, and radio technology have enabled the emergence of embedded systems that rely on communication systems to exchange information and coordinate their activities in spatially distributed applications. However, developing embedded communication systems that satisfy specific application requirements is a challenge due to the many tradeoffs imposed by different choices of underlying protocols and their parameters. Furthermore, evaluating the correctness and performance of the design and implementation before deploying it is a nontrivial task due to the complexity of the resulting system. This article presents the design and implementation of RaPTEX, a rapid prototyping tool for embedded communication systems, especially well suited for wireless sensor networks (WSNs), consisting of three major subsystems: a toolbox, an analytical performance estimation framework, and an emulation environment. We use a hierarchical approach in the design of the toolbox to facilitate the composition of the network stack. For fast exploration of the tradeoff space at design time, we build an analytical performance estimation model for energy consumption, delay, and throughput. For realistic performance evaluation, we design and implement a hybrid, accurate, yet scalable, emulation environment. Through three use cases, we study the tradeoff space for different protocols and topologies, and highlight the benefits of using RaPTEX for designing and evaluating embedded communication systems for WSNs.

Service differentiation mechanisms for WLANs

Designing a medium access control (MAC) protocol that simultaneously provides service differentiation and high throughput, and allows individual users to share limited spectrum resources fairly is a challenging problem for wireless LANs when applications have diverse performance requirements, such as high throughput, low delay, and delay jitter. In this paper, we propose efficient flow-based and class-based weighted fair queueing (WFQ) mechanisms with very simple-state information that considers only collisions, like the standard IEEE 802.11e MAC protocol. We utilize an analytical throughput model to obtain the optimal parameter settings for both mechanisms. Simulation results show that both mechanisms provide weighted throughput within 1% of the given throughput ratio. Additionally, we propose a novel and efficient priority mechanism. Our key technique involves each node changing its backoff counter based on both its own packet’s priority level and the priority level of the transmitted packet. Specifically, a node will increase its backoff counter linearly with a higher-priority packet transmission and decrease it exponentially with a lower-priority packet transmission. Simulation results show that our mechanism always protects high-priority traffic while still providing high throughput.

Analytical Model for the Throughput and Drive Power Calculation in the Melting Section of Single Screw Plasticizing Units considering Wall-Slippage

Abstract In single-screw extrusion the simulation of the plasticizing process by means of software tools becomes more and more important. These programs need mathematical models that have to be improved continuously to simulate the process values realistically. A two-part article presents an analytical approach to calculate the pressure/throughput and drive power behaviour of wall-slipping polymers in the melting section of single-screw plasticizing units. The investigations that are conducted are based on the notion commonly found in the literature of a melt film forming between the barrel and a compact solid bed, with the simultaneous development of a melt pool. As boundary condition for describing the wall slippage, a critical shear stress, as of which a slippage process commences, and also a slippage-velocity-dependent shear stress is assumed. In this first part of the publication, the investigations focus on the processes that take place in the melt film. A new model is developed for describing the process behaviour in this area.

Analytical TCP throughput model for high-speed downlink packet access

This study deals with the throughput analysis of data services over high-speed downlink packet access (HSDPA) systems. The achievable throughput is calculated with an approximate analytical method based on the Padhye model that has two input parameters: the packet loss probability and the transmission control protocol (TCP) round trip time. The proposed solution is to calculate these parameters with an equivalent queuing network model of the HSDPA system that takes into account the possible congestion points in the system and the protocol layers that have dominant impact on the delay and packet drop. The modelling considerations and the analysis method are described in detail. Finally, the model is validated with a performance study of the HSDPA system that is executed with detailed NS2- based simulations too. The proposed method is found to be reasonably accurate requiring less computational effort than the simulations.

Performance analysis of IEEE 802.11 DCF networks

This paper presents an analytical saturation throughput model of IEEE 802.11 DCF (distributed coordination function) with basic access in ad hoc mode. The model takes into account freezing of the backoff timer when a station senses busy channel. It is shown that taking into account this feature of DCF is important in modeling saturation throughput by yielding more accurate and realistic results than models known from literature. The proposed analytical model also takes into account the effect of transmission errors. All essential features of the proposed analytical approach are illustrated with numerical results. The presentation of the model is proceeded by an overview of approaches to IEEE 802.11 network performance evaluation presented in the literature.

Throughput-coverage tradeoff in a scalable wireless mesh network

The wireless mesh network (WMN) is an economical and low-power solution to support ubiquitous broadband services. However, mesh networks face scalability and throughput bottleneck issues as the coverage and the number of users increase. Specifically, if the coverage is extended by multiple hops, the repeatedly relayed traffic will exhaust the radio resource and degrade user throughput. Meanwhile, as the traffic increases because of more users, the throughput bottleneck will occur at the users close to the gateway. The contention collisions among these busy users near the gateway will further reduce user throughput. In this paper, a newly proposed scalable multi-channel ring-based WMN is employed. Under the ring-based cell structure, multi-channel frequency planning is used to reduce the number of contending users at each hop and overcome the throughput bottleneck issue, thereby making the system more scalable to accommodate more users and facilitate coverage extension. This paper mainly focuses on investigating the overall tradeoffs between user throughput and cell coverage in the ring-based WMN. An analytical throughput model is developed for the ring-based WMN using the carrier sense multiple access (CSMA) medium access control (MAC) protocol. In the analysis, we also develop a bulk-arrival semi-Markov queueing model to describe user behavior in a non-saturation condition. On top of the developed analytical model, a mixed-integer nonlinear optimization problem is formulated, aiming to maximize cell coverage and capacity. Applying this optimization approach, we can obtain the optimal number of rings and the associated ring widths of the ring-based WMN.

A short-term fair MAC protocol for WLANs

Designing a medium access control (MAC) protocol that simultaneously provides high throughput and allows individual users to share limited spectrum resources fairly, especially in the short-term time horizon, is a challenging problem for wireless LANs. In this paper, we propose an efficient cooperative MAC protocol with very simple state information that considers only collisions, like the standard IEEE 802.11 MAC protocol. However, contrary to the IEEE 802.11 MAC, the cooperative MAC gives collided users priority to access the channel by assigning them shorter backoff counters and interframe-spaces than users who did not participate in the collision event. In other words, collided users are the only ones allowed to transmit in the following contention period. For the cooperative MAC protocol, we utilize an analytical throughput model to obtain the optimal parameter settings. Simulation results show that the cooperative MAC provides significant improvement in short-term fairness and access delay, while still providing high network throughput.