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In 1987 it was becoming apparent that computer systems would need to communicate at data rates beyond the capabilities of then current approaches. To take on this challenge, the IEEE Futurebus group formed a new group dedicated to building a fast, coherent interface, scalable from the smallest computer to the largest mainframe. The IEEE officially established the SCI (Scalable Coherent Interface) working group, referenced as IEEE P1596, in 1988. Today the SCI is IEEE Std 1596. It has several derivatives that enhance its operation and meet additional needs such as real-time operations: a differential voltage specification (IEEE 1536.3), a point-to-point memory interface (IEEE 1596.4), and SyncLink (IEEE P1596.7). SyncLink is a new, high-speed memory interface that combines synchronous dynamic RAM (SDRAM), developed in the late 1980s, and the IEEE's RamLink interface, developed in 1990. SyncLink uses the earlier interface's packet protocol as a base but eliminates its point-to-point link to reduce latency. The new interface uses SDRAM's internal pipelining and control for efficient bus utilization. It allows access in the lowest latency possible for a very high bandwidth DRAM. Future plans include data rates of 800 Mbits per pin per second in 1998, to double in the early 2000s. This rate will allow systems to operate at full capability, even when running 3D graphics.

The voice service through IEEE 802.11 wireless LANs is considered and the maximum voice sessions are analysed and simulated for different patterns of voice packet generation based on IEEE 802.11b and 802.11a physical layer characteristics.

The IEEE-802.15.4 standard utilizes the CSMA-CA mechanism to control nodes access to the channel communication. It is becoming the popular choice for various applications of surveillance and control used in wireless sensor network (WSN). The benefit of this standard is evaluated regarding of the packet loss probability that depends on the configuration of IEEE 802.15.4 MAC parameters and the traffic load. Our exigency is to evaluate the effects of various configurable MAC parameters on the performance of beaconless IEEE 802.15.4 networks, under different traffic loads. Static values of IEEE 802.15.4 MAC parameters (macMinBE, macMaxCSMABackoffs, CW, and macMaxFrame Retries) will be evaluated. To evaluate the performance of the protocol, we use ns-2 network simulator.

IEEE 802.11p is an improved edition of the IEEE 802.11 protocol which serves specifically for vehicle to infrastructure (V2I) communication. It can realize a fast V2I wireless communication connection in the urban road environment and ensure transportation safety and communication reliability for moving vehicles. However, the effectiveness and reliability for vehicle wireless access based on IEEE 802.11p in the highway environment still need to be verified even if this protocol could work in the complicated urban road condition. In this paper, an IEEE 802.11p based V2I wireless communication simulation system in the highway environment is built by NS-2 simulation, and several key indices that reflect the system performance including average transfer delay, packet loss rate and throughput are analyzed.

IEEE 802.15.4 Wireless Sensor Networks (WSNs) and IEEE 802.11b/g Wireless Local Area Networks (WLANs) are often collocated, causing a coexistence issue since these networks share the same 2.4GHz Industrial, Scientific, and Medical band. In our previous work, we built a coexistence model of IEEE 802.15.4 WSNs and IEEE 802.11b/g WLANs. By identifying three distinct coexistence regions, the model explained the coexistence behavior of IEEE 802.15.4 WSNs and IEEE 802.11b/g WLANs, and the model was experimentally validated. In this paper, we improve the model by introducing two important implementation factors: the transceiver's Rx-to-Tx turnaround time and the Clear Channel Assessment partial detection effect. The enhanced model significantly improves the accuracy on explaining and predicting the coexistence performance of IEEE 802.15.4 WSNs in the real-life environment. Furthermore, under the guidance of the model, the coexistence performance of IEEE 802.15.4 WSNs is extensively investigated in various coexistence scenarios by analysis, simulation and experiments, respectively. The simulation and experimental results agree with our analysis. The coexistence model is believed to be helpful in resolving the coexistence issue.

Handover performance is critical to support multimedia services that are becoming increasingly available over the wireless devices. The high transition delay can be unaccepted for such services or can be a source of disruption on the session. On the other side, IEEE 802.11 standard is being extended with new functionalities. Security and QoS features, included in recent IEEE 802.11-2007 standard, add management frames that are exchanged during the transition process. In consequence the handover delay is increased. IEEE 802.11r-2008 amendment introduces Fast BSS Transition (FT) that simplifies the handover process. The authors propose the new handover algorithms based on FT protocol and compare them with existing solution. Additionally, simulation experiments are conducted to answer the question if multimedia services can be properly supported in IEEE 802.11r networks. The authors prove that handover delay can be reduced to 13 ms in the average case.

The emerging IEEE 802.11ah is a promising communication standard that supports a massive number of heterogeneous devices in the Internet of Things (IoT). It provides attractive features like improved scalability, low energy consumption, and coverage of large area. In this paper, we analyze the performance of IEEE 802.11ah, and compare it with a prominent alternative, the IEEE 802.15.4. The simulation results show that the new 802.11ah standard performs better than the 802.15.4 in terms of association time, throughput, delay, and coverage range.

The IEEE 802.11s standard specifies a mesh technology to be supported by IEEE 802.11 devices. Among the limitations caused by this heritage, we focus on the low scalability of the current IEEE 802.11s standard mechanisms. As a main contribution to the related research field, this article presents the DHT-based Cluster Routing Protocol (DCRP). DCRP addresses IEEE 802.11s’ scalability issues by exploiting both Distributed Hash Tables and Clustering schemes, which have proved to be effective in scaling wireless (e.g., MANETs) and wired (e.g., P2P) networking systems. DCRP was implemented and compared with the HWMP through simulation for different scalability parameters and performance metrics. Simulation results indicate that the proposed scheme improves performance in terms of packet delivery ratio, end-to-end delay, throughput, and overhead.

This work examines the IEEE 802.11, used in WLANs (Wireless Local Area Network), and IEEE 802.15.4, for WPANs (Wireless Personal Area Network), along with the Agent-based Rate Adaptive Scheme. The paper presents the Agent-based Rate Adaptive Scheme, which allows each channel to adaptively set the rate for serving a specific transfer. To this, end Agents are being utilized on each node in order to enable efficient monitoring of the requirements of each transfer and adjust the rate accordingly. Results were extracted by conducting simulation experimentation, and comparing the behavior and performance of a WLAN and a ZigBee network, in a short distance environment such as an office or a house, in order to determine the optimal protocol to be used in applications such as home/building automation. The experiment showed that while the 802.11 protocol performs better when it comes to delay, ZigBee has the upper hand in reliability, as more packets were successfully delivered in the WPAN, rather than the WLAN. Furthermore, this paper takes into consideration parameters such as queuing delay and transmission rate adaptivity, investigates them in a more calculative manner, and presents the findings of our evaluations.

According to the ongoing IEEE 802.11ac amendment, the wireless network is about to embrace the gigabit-per-second raw data rate. Compared with previous IEEE standards, this significant performance improvement can be attributed to the novel physical and medium access control (MAC) features, such as multi-user multiple-input multiple-output transmissions, the frame aggregation, and the channel bonding. In this paper, we first briefly survey the main features of IEEE 802.11ac, and then, we evaluate these new features in a fully connected wireless mesh network using an analytic model and simulations. More specifically, the performance of the MAC scheme defined by IEEE 802.11ac, which employs the explicit compressed feedback (ECFB) mechanism for the channel sounding, is evaluated. In addition, we propose an extended request-to-send/clear-to-send scheme that integrates the ECFB operation to compare with the IEEE 802.11ac-defined one in saturated conditions. The comparison of the two MAC schemes is conducted through three spatial stream allocation algorithms. A simple but accurate analytical model is derived for the two MAC schemes, the results of which are validated with simulations. The observations of the results not only reveal the importance of spatial stream allocations but also provide insight into how the newly introduced features could affect the performance of IEEE 802.11ac-based wireless mesh networks. This work was partially supported by the Spanish and the Catalan governments, through the projects CISNETS (TEC2012-32354) and AGAUR SGR2009-617, respectively.

Problem statement: IEEE 802.11 Medium Access Control (MAC) protocol is one of the most implemented protocols in this network. The IEEE 802.11 controls the access to the share wireless channel within competing stations. The IEEE 802.11 DCF doubles the Contention Window (CW) size for decreasing the collision within contending stations and to improve the network performances but it is not good for error prone channel because the sudden CW rest to CWmin may cause several collisions. Approach: The research to date has tended to focus on the current number of active stations that needs complex computations. A novel backoff algorithm is presented that optimizes the CW size with take into account the history of packet lost. Results: Finally, we compare the HBCWC with IEEE 802.11 DCF. The simulation results have shown 24.14, 56.71 and 25.33% improvement in Packet Delivery Ratio (PDR), average end to end delay and throughput compared to the IEEE 802.11 DCF. Conclusion: This study showed that monitoring the last three channel status achieve better delay and throughput that can be used for multimedia communications.

The IEEE 802.11p standard has been optimized for low-delay small-bandwidth wireless communications to provide vehicular safety services. However, IEEE 802.11p transceivers can considerably improve their robustness by incorporating MIMO transmission methods. Moreover, multiple antennas can also be used to increase the data transfer rate of IEEE 802.11p transceivers, a requirement necessary to implement, for instance, non-critical safety applications. In this article we describe the design and development of a multiple-antenna IEEE 802.11p performance evaluation system made of two IEEE 802.11p software-based transceivers and two different, flexible low-cost FPGA-based multi-antenna channel emulators. Our channel emulators are able to recreate seven vehicular communication environments including highways, urban canyons and suburban areas. Using our performance evaluation system, we obtained performance curves showing that IEEE 802.11p can dramatically improve its performance by using multiple transmit and receive antennas. In addition, our channel emulators accelerated the performance evaluation task between 6 and 209 times compared to that of conventional software-based simulation approaches.

More and more devices are becoming wirelessly connected. Many of these devices are operating in crowded unlicensed bands, where different wireless technologies compete for the same spectrum. A typical example is the unlicensed ISM band at 2.4 GHz, which is used by IEEE 802.11bgn, IEEE 802.15.4, and IEEE 802.15.1, among others. Each of these technologies implements appropriate Media Access Control (MAC) mechanisms to avoid packet collisions and optimize Quality of Service. Although different technologies use similar MAC mechanisms, they are not always compatible. For example, all CSMA/CA-based technologies use Clear Channel Assessment (CCA) to detect when the channel is free; however, in each case it is specifically designed to improve detection reliability of the specific technology. Unfortunately, this approach decreases the detection probability of other technologies, increasing the amount of cross-technology collisions. In this article, we introduce the concept of coexistence aware CCA (CACCA), which enables a node operating in one technology to backoff for other coexisting technologies as well. As a proof of concept, we analyze the Packet Error Rate(PER) incurred by an IEEE 802.15.4 network in the presence of IEEE 802.11bg interference, and assess the PER reduction that is achieved by using CACCA.

We demonstrate BIGAP, a novel architecture providing both high network performance as well as seamless handover in Enterprise IEEE 802.11 networks. The former is achieved by assigning different channels to co-located APs to fully utilize the available radio spectrum. The latter is achieved by providing a mechanism for below MAC-layer handover through exploiting the Dynamic Frequency Selection (DFS) capability in IEEE 802.11. In essence BigAP forces clients to change AP whilst they ‘believe’ they are simply changing channel. BIGAP is fully compatible with 802.11 and requires no modifications to the wireless clients.

In this paper we conduct a delay analysis of IEEE 802.16 wireless metropolitan area network. In particular, we address the overall message delay, which consists of the reservation and scheduling components. Unicast polling is used for bandwidth reservation and round-robin scheduling is applied at the base station. A discrete-time analytical model is developed with general independent and identically distributed arrivals during a time slot. The model enables asymmetric traffic flows and different message sizes at the subscriber stations. The exact mean overall delay is obtained for the nrtPS service flow in the scenario when the base station splits the subscriber stations into individually polled groups. The analytical model is verified by means of simulation.

Wireless systems operating in the ISM frequency bands and sharing the same environment are likely to interfere with each other. We address the problem of coexistence between IEEE 802.11 and IEEE 802.15 devices, and we present a mechanism that mitigates the interference between these devices when IEEE 802.15 supports voice traffic. The proposed scheme can work when 802.11 and 802.15 devices operate in non-collaborative mode, ie, independently of one another. The performance of the proposed algorithm is compared to the results obtained through the so-called MEHTA scheme, which is a collaborative mechanism recently presented to the IEEE 802.15 Working Group. Simulation results show that the proposed algorithm gives good performance relative to the MEHTA scheme when colocated interfering devices only are considered, while it outperforms the MEHTA scheme when non-colocated interfering devices are present.

In WLAN the medium access control (MAC) protocol is the main element for determining the efficiency in sharing the limited communication bandwidth of the wireless channel. This paper focuses on the efficiency of the IEEE 802.11 standard for wireless LANs. Specifically, we derive an analytical formula for the protocol capacity. From this analysis we found (i) the theoretical upper bound of the IEEE 802.11 protocol capacity; (ii) that the standard can operate very far from the theoretical limits depending on the network configuration; (iii) that an appropriate tuning of the backoff algorithm can drive the IEEE 802.11 protocol close to its theoretical limits. Hence we propose a distributed algorithm which enables each station to tune its backoff algorithm at run-time. The performances of the IEEE 802.11 protocol, enhanced with our algorithm, are investigated via simulation. The results indicate that the enhanced protocol is very close to the maximum theoretical efficiency.

The popularity and wider acceptance of IEEE 802.11 based WLANs has resulted in their dense deployments in diverse environments. While this massive deployment can potentially increase capacity and coverage, the current physical carrier sensing of IEEE 802.11 cannot limit the overall interference induced and also cannot insure high concurrency among transmissions. Recently, the IEEE 802.11 working group has continued efforts on developing WLAN technology through the creation of the TGax, which aims to improve efficiency of densely deployed IEEE 802.11 networks. In this paper, we propose a Dynamic Sensitivity Control for Access Point (DSC-AP) algorithm for IEEE 802.11ax. This algorithm dynamically adjusts the Carrier Sensing Threshold (CST) of an AP based on received signal strength from its associated stations and interfering APs. We show that the aggregate throughput of a dense network (under asymmetric traffic conditions) utilizing DSC (both at the stations and AP) is considerably improved (i.e. up to 32%) when compared with legacy IEEE 802.11. © 2016 IEEE.

The popularity of IEEE 802.11 based wireless local area networks (WLANs) has increased significantly in recent years because of their ability to provide increased mobility, flexibility, and ease of use, with reduced cost of installation and maintenance. This has resulted in massive WLAN deployment in geographically limited environments that encompass multiple overlapping basic service sets (OBSSs). In this article, we introduce IEEE 802.11ax, a new standard being developed by the IEEE 802.11 Working Group, which will enable efficient usage of spectrum along with an enhanced user experience. We expose advanced technological enhancements proposed to improve the efficiency within high density WLAN networks and explore the key challenges to the upcoming amendment.

The IEEE 802.11e technology is receiving much interest due to the promising enhancements it offers to wireless local area networks in terms of QoS support. Until now, research has focused on single hop, access point based environments, which are the most common. We review the enhancements proposed in the last IEEE 802.11e draft (version 8.0). We analyze the performance of the IEEE 802.11e protocol on ad-hoc networks (multi-hop) in terms of throughput and end-to-end delay. We also measure the effectiveness for static and fully dynamic networks with a variable number of source stations. Finally, we analyze the performance of IEEE 802.11e when legacy IEEE 802.11 stations (no IEEE 802.11e support) are present in the network. Simulation results show that IEEE 802.11e does not lose effectiveness in multi-hop mobile environments, though the existence of legacy stations in the MANET provokes a severe performance drop.

This paper proposes a model for the IEEE 802.11 infrared physical layer that includes the effect of multiuser interference through a detailed consideration of the modulation and detection techniques. The model was designed to be integrated into a discrete-event simulator of medium access protocols and allows the calculation of the frame error rate without any constraints on the length of the captured and interfering packets and on the joint distribution of the interference. With the purpose of studying the impact of the interference in the IEEE 802.11 medium access protocol, the model was integrated into the discrete-event simulator RFMACSIM, which was initially developed to study the performance of the IEEE 802.11 medium access mechanisms with a radio physical layer. Several simulation studies on the efficiency of the immediate priority acknowledgement and reservation mechanisms embedded in the IEEE 802.11 protocol are presented.

IEEE 802.11a is a new high-speed physical layer (PHY) defined for the 5 GHz U-NII bands as a supplement to the existing IEEE 802.11 wireless LAN (WLAN) standard. We give an overview of the IEEE 802.11a orthogonal frequency domain multiplexing (OFDM) PHY with eight different PHY rates as well as the distributed coordination function (DCF) of the IEEE 802.11 MAC, then derive the goodput performance analytically for peer-to-peer communication under the DCF. Based on the numerical results, we claim that link adaptation, which performs both dynamic fragmentation and PHY rate selection depending on the wireless channel condition between the transmitter and receiver, is an attractive way to improve the goodput performance of an IEEE 802.11a wireless LAN. Finally, we propose a system architecture to perform link adaptation.

The IEEE 802.11 wireless LAN (WLAN) is the most widely used standard nowadays for wireless LAN technology. However, the current standard does not provide the QoS support required by the wide range of end applications. Thus, a large number of enhancements to the standard are being proposed. The paper presents a survey of the on-going research activities. We also overview the upcoming IEEE 802.11e standard being introduced. The IEEE 802.11e standard is a proposal defining the mechanisms for wireless LANs aiming to provide QoS support to bandwidth-sensitive applications such as voice and video communications.

International audience; Wireless Mesh Networks have the potential to serve as an all-wireless backbone. They represent a key building block of the new Internet of Things to collect all the traffic. However, IEEE 802.11 performs very poorly in multi-hop topologies leading to unfairness and a poor throughput. Thus, the standard IEEE 802.11s proposes to re-use the IEEE 802.11 medium access in a mesh multi-hop topology while using a routing protocol to create routes at the layer 2. IEEE 802.11s may exploit multi-channel multi-interface wireless routers to increase the through-put. In particular, the routing protocol must select carefully the forwarders to limit inter-and intra-flow interference. In this paper, we propose to fully characterize the performance of IEEE 802.11s when using multi-interface nodes, and to isolate some key performance issues. We also propose some key mechanisms that must be implemented to solve these pathological cases and to improve the throughput.

The challenge of the IEEE 802.15.4 beacon-enabled mode is how to improve throughput and bandwidth utilization in contention access period (CAP) and contention free period (CFP), respectively. This article proposes a scheme to improve IEEE 802.15.4 medium access control, called superframe duration adjustment scheme (SUDAS), which analyzes the overall of the IEEE 802.15.4 not only CAP but also CFP. SUDAS is expected to effectively allocate guaranteed time slot to the requested devices, it adjusts the length of the slot in superframe duration based on the length of the packet data. This article also presents a comprehensive Markov chain analysis for SUDAS, especially for star topology, to predict the probability of successful transmission, network goodput, average bandwidth utilization, as well as total network energy consumption. The validity of the analytical model is proven by closely matching the simulation experiments. SUDAS performs better than other algorithms in terms of the probability of successful packet transmission, network goodput, average bandwidth utilization, and total energy consumption.

In this paper an innovative simulation study of five IEEE 802.11e network configurations is presented. The conducted analysis is crucial for understanding how a theoretically simple and, most of all, popular line topology network can be degraded by the presence of hidden and exposed nodes. The discussion of the obtained results helps to understand how and why the behavior of IEEE 802.11e based line topologies changes when the number of nodes increases. Furthermore, the usefulness of the four-way handshake mechanism is argued. Finally, the need for a better MAC protocol is stressed and a number of novel conclusions about the IEEE 802.11e nature is provided.

The IEEE 802.11 WLAN legacy standard cannot provide QoS support for multimedia applications. Thus, considerable research efforts have been carried out to enhance QoS support for 802.11. Among them, 802.11e is the upcoming QoS-enhanced standard proposed by the IEEE working group. This article describes in detail the new QoS features of 802.11e based on the latest version of the standard draft. We investigate the performance of 802.11e through computer simulations. Using simple examples, we show the effectiveness of adaptive schemes under the 802.11e framework.

IEEE 802.11p is one of the most promising future wireless standards due to the increasing demand of vehicular communication applications. At the time of writing, the document of the standard is in draft and much research is still required to study and improve the performance of transceivers in common vehicular scenarios. In this paper, we present a framework to evaluate the PHY layer of IEEE 802.11p systems in realistic situations. We detail the design and implementation of an FPGA-based real-time vehicular channel emulator. Contrarily to commercial emulators, ours is cheap, very flexible, and reconfigurable. We show its capabilities by evaluating performance in different high-speed scenarios. We also study the importance of coding and the benefits of using IEEE 802.11p instead of IEEE 802.11a in vehicular environments. Towards this aim, we developed a reference IEEE 802.11p PHY transceiver software model that can be taken as a convenient starting point for transceiver design.