Showing papers on "IEEE 802.11e-2005 published in 2012"

Analytical Study of the IEEE 802.11p MAC Sublayer in Vehicular Networks

Abstract: This paper proposes an analytical model for the throughput of the enhanced distributed channel access (EDCA) mechanism in the IEEE 802.11p medium-access control (MAC) sublayer. Features in EDCA such as different contention windows (CW) and arbitration interframe space (AIFS) for each access category (AC) and internal collisions are taken into account. The analytical model is suitable for both basic access and the request-to-send/clear-to-send (RTS/CTS) access mode. Different from most of existing 3-D or 4-D Markov-chain-based analytical models for IEEE 802.11e EDCA, without computation complexity, the proposed analytical model is explicitly solvable and applies to four access categories of traffic in the IEEE 802.11p. The proposed model can be used for large-scale network analysis and validation of network simulators under saturated traffic conditions. Simulation results are given to demonstrate the accuracy of the analytical model. In addition, we investigate service differentiation capabilities of the IEEE 802.11p MAC sublayer.

Enhancing IEEE 802.11p/WAVE to provide infotainment applications in VANETs

Abstract: IEEE 80211p/WAVE (Wireless Access for Vehicular Environment) is the emerging standard to enable wireless access in the vehicular environment Most of the research contributions in this area has focused on safety-related applications, while comfort and information/entertainment applications (such as on board Internet access, point-of-interest notification, e-map download) have been considered only recently Notwithstanding, the user interest in this kind of applications is expected to become a big market driver in a near future In this paper, an extension to IEEE 80211p is proposed that is compliant with the multi-channel operation of the WAVE architecture and targets at the support of non-safety applications, while preserving the delivery of safety services The proposed W-HCF (WAVE-based Hybrid Coordination Function) protocol leverages controlled access capabilities on top of the basic contention-based access of the IEEE 80211p; it exploits vehicles' position information and coordination among WAVE providers in order to improve performances of delay-constrained and loss-sensitive non-safety applications

IEEE 802.11ah: Advantages in standards and further challenges for sub 1 GHz Wi-Fi

Abstract: The rapid developments in Internet-of-Things (IoT) and Machine-to-Machine (M2M) communication make it necessary to design communication systems operating in different wireless spectrum as an alternative to highly congested wireless access systems. In addition, the deployment of wireless smart meter devices is ramping up and it is expected that such devices will flood the market in the near future competing for the same wireless spectrum. The IEEE 802.11ah standardization task group is developing a global Wireless LAN (WLAN) standard that will allow wireless access using carrier frequencies below 1 GHz in the ISM (Industrial, Scientific, and Medical) band and will help Wi-Fi-enabled devices to get guaranteed access for short-burst data transmissions, such as meter data. In addition to exploiting the underutilized sub 1 GHz spectrum the improved coverage range allows new applications to emerge such as wide area based sensor networks, sensor backhaul systems and potential Wi-Fi off-loading functions. This paper summarizes the IEEE 802.11ah standardization activities in progress and discusses advantages and challenges in the design of physical layer (PHY) and media access control (MAC) schemes in the sub 1 GHz band.

Throughput and Delay Analysis of IEEE 802.15.6-based CSMA/CA Protocol

Abstract: The IEEE 802.15.6 is a new communication standard on Wireless Body Area Network (WBAN) that focuses on a variety of medical, Consumer Electronics (CE) and entertainment applications. In this paper, the throughput and delay performance of the IEEE 802.15.6 is presented. Numerical formulas are derived to determine the maximum throughput and minimum delay limits of the IEEE 802.15.6 for an ideal channel with no transmission errors. These limits are derived for different frequency bands and data rates. Our analysis is validated by extensive simulations using a custom C+?+ simulator. Based on analytical and simulation results, useful conclusions are derived for network provisioning and packet size optimization for different applications.

Throughput, energy consumption, and energy efficiency of IEEE 802.15.6 body area network (BAN) MAC protocol

Abstract: Low-powered and light-weight sensor nodes will be deployed for e-health services in wireless body area networks (WBANs). Recently, the Institute of Electrical and Electronic Engineering (IEEE) introduced a new standard, IEEE 802.15.6 for wireless body area communications. The goal of this standard is to specify several physical layers (PHY) and medium access control (MAC) layer protocols for variety of applications with various QoS requirements. In this paper, we evaluate the performance of the IEEE 802.15.6 WBAN MAC protocol in terms of throughput, power consumption, and energy efficiency under unsaturated conditions. We develop a discrete-time Markov chain based analytical model to evaluate the performance of CSMA/CA based WBAN MAC protocol during contention access phases. To verify the numerical results obtained from analytical model, we performed simulations and compared the results.

On the Necessity of Accurate IEEE 802.11P Models for IVC Protocol Simulation

Abstract: In the scientific community, Inter-Vehicle Communication (IVC) protocols are frequently evaluated using simulation techniques, often using variants of WiFi stacks instead of IEEE 802.11p, which constitutes the basis for the new DSRC/WAVE standard. We discuss the necessity of using accurate WAVE models based on an extensive set of simulation experiments using: an IEEE 802.11b model, an IEEE 802.11b model tweaked to work in the same frequency range and using similar timings like IEEE 802.11p, as well as a fully featured channel hopping WAVE model. Even though, intuitively, the use of the different protocols will lead to a different network behavior, to the best of our knowledge, there has been no qualitative and quantitative evaluation or comparison of both worlds. According to our results, we can conclude that the simple WiFi model may indeed be used, but only for extremely sparse scenarios - this is exactly what has been validated using field tests. In denser traffic scenarios there is a significant deviation of the protocol behavior between WiFi (and its adapted variant) compared to WAVE. Thus, especially in dense scenarios, the application behavior is strongly influenced if simulated with the wrong model - leading to unrealistic results.

Avoiding collisions between IEEE 802.11 and IEEE 802.15.4 through coexistence aware clear channel assessment

Abstract: 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.

Performance Analysis of IEEE 802.11ac DCF with Hidden Nodes

Abstract: Recently, the IEEE 802.11 standard based Wireless Local Area Networks (WLAN) have become more popular and are widely deployed. It is anticipated that WLAN will play an important rule in the future wireless communication systems in order to provide several gigabits data rate. IEEE 802.11ac is one of the ongoing WLAN standard aiming to support very high throughput (VHT) with data rate of up to 6 Gbps below the 6 GHz band. In the development of IEEE 802.11ac standard, several new physical layer (PHY) and medium access control layer (MAC) features are taken into consideration, such as employing wider bandwidth in PHY and incrementing the limits of frame aggregation in MAC. However, due to the newly introduced features, some traditional techniques used in previous standards could face some problems. This paper presents a performance analysis of 802.11ac Distributed Coordination Function (DCF) in presence of hidden nodes in overlapping BSS (OBSS) environment. The effectiveness of DCF in IEEE 802.11ac WLAN when using different primary channels and different frequency bandwidth has also been discussed. Our results indicate that the traditional RTS/CTS handshake mechanism faces shortcomings and needs to be modified in order to support the newly defined 802.11ac amendment.

An Accuracy Enhanced IEEE 1588 Synchronization Protocol for Dynamically Changing and Asymmetric Wireless Links

Abstract: IEEE 1588 is the clock synchronization protocol for networked measurement and control system, and widely used for both wire-line and wireless network environments. IEEE 1588 was initially considered for wire-line networks, but its application is extended to wireless network especially for indoor wireless networks which can not use Global Positioning System (GPS) technology. However, the conventional IEEE 1588 assumes symmetric/asymmetric fixed data rate links, and time accuracy errors are caused for dynamically changing wireless links. We propose an enhanced synchronization algorithm for IEEE 1588 in order to compensate the offset error due to the dynamically changing data rate of the wireless link and to enhance the accuracy of time.

IEEE 802.11aa: Improvements on video transmission over wireless LANs

Abstract: Transmitting multimedia streams over IEEE 802.11 Wireless Local Area Networks (WLANs) with high performance and reliability is a challenging task. In the current paper, we study the basic problems that video transmission encounters in wireless LANs and we present some of the proposed solutions. In particular, we will outline the solutions that were selected for the 802.11aa amendment to the IEEE 802.11 standard in order to provide reliable and robust transport of video streams in IEEE 802.11 wireless LANs.

Impact of IEEE 1609.4 channel switching on the IEEE 802.11p beaconing performance

Abstract: The IEEE 802.11p Wireless Access in Vehicular Environment (WAVE) protocol can only transmit packets on one channel. To support multi-channel operations, channel switching procedures have been proposed in IEEE 1609.4. This paper provides an analysis of the beaconing performance of IEEE 802.11p when these channel switching procedures are used. To analyse the performance of beaconing, simulation experiments are conducted using the simulation tool OMNeT++. An overview is given of existing solutions which can be applied to minimise the impact of channel switching on IEEE 802.11p performance. An interesting observation is that present solutions focus on optimising for use of the Service Channels, and some even deteriorate the performance of the Control Channel.

Adaptive two-level frame aggregation in IEEE 802.11n WLAN

Abstract: In order to reduce the overhead of legacy WLANs, the IEEE 802.11n standard defines two aggregation schemes, i.e., A-MSDU and A-MPDU. In general, A-MPDU outperforms A-MSDU due to its selective retransmission capability. However, A-MPDU has a fundamental restriction on the minimum separation in time between the start of two consecutive subframes carried on the same A-MPDU. If such a gap is smaller than the minimum MPDU start spacing of the receiver, the sender should insert additional padding, thus resulting in throughput degradation. The main contribution of this paper is that we provide an adaptive aggregation scheme in which the sender conveys A-MSDUs within A-MPDUs in an adaptive manner, in order to resolve this potential problem in A-MPDU. Our analytical and simulation results demonstrate that the proposed scheme improves throughput performance over A-MPDU and A-MSDU by up to 280% and 19%, respectively.

Performance evaluation of wireless mesh networks using IEEE 802.11s and IEEE 802.11n

Abstract: With the recent approval of IEEE 802.11n standard and progress on IEEE 802.11s mesh standardization efforts, performance evaluation of such standards has gained acceleration. In particular, several wireless testbeds have been created to form wireless mesh networks (WMNs) in order to test various aspects of these new standards. However, none of these considered multi-hop performance of WMNs when 802.11n based nodes are employed. While IEEE 802.11s is geared for implementing multi-hopping capability among the nodes, current studies still assume IEEE 802.11a/g based nodes. This paper presents a performance evaluation of WMNs using both 802.11s (in conjunction with 802.11a/g) and 802.11n on a real academic testbed. While a draft version of 802.11s has been used for creating a linear WMN using 802.11a/g based routers, the same linear WMN using 802.11n has been created using virtualized interfaces at the IP layer. Using such WMNs, throughput performance of TCP and UDP at both the 2.4 GHz and 5 GHz spectrums with different number of hops has been examined. The experiment results have shown that multi-hopping significantly degrades the expected performance of IEEE 802.11n.

Evaluation of the IEEE 802.11aa group addressed service for robust audio-video streaming

Abstract: With the deployment of Audio-Video (AV) services and the flexibility offered by wireless networks, there is more and more an increasing interest on defining more reliable multicast mechanisms. Towards this end, the IEEE Task Group aa (TGaa) is currently working on the definition of the IEEE802.11aa amendment. The standardization efforts in this area aim to develop efficient QoS mechanisms by keeping in mind that any new mechanism should: 1) properly interoperate with the already existing unicast mechanisms; and 2) provide the robustness required by AV applications. In order to meet the former, the efforts are focusing on amending the existing multicast standard while to meet the latter there is a need of better understanding the stringent requirements of AV streaming applications. In this work, after reviewing the amendments introduced by the IEEE 802.11aa, we carried out an evaluation of the proposed multicast mechanisms when supporting video streaming applications. The main contribution of this work focuses therefore on evaluating the QoS parameters that the TGaa has taken into account to define the proposed mechanisms.

A frame aggregation scheduler for QoS-sensitive applications in IEEE 802.11n WLANs

Abstract: The IEEE 802.11n standard promises to extend todays most popular WLAN standard by significantly increasing reach, reliability, and throughput. Ratified on september 2009, this standard defines many new physical and medium access control (MAC) layer enhancements. These enhancements aim to provide a data transmission rate of up to 600 Mbps. The frame aggregation mechanism of 802.11n MAC layer can improve the efficiency of channel utilization by reducing the protocol overheads. In this paper we investigate the effect of frame aggregation on the support of voice and video applications in wireless networks. We also propose a new frame aggregation scheduler that considers specific QoS requirements for multimedia applications. We dynamically adjust the aggregated frame size based on frame's access category defined in 802.11e standard.

Practical Message Manipulation Attacks in IEEE 802.15.4 Wireless Networks

Abstract: We assess the ability of adversaries to modify the content of messages on the physical layer of wireless networks. In contrast to related work, we consider signal overshadowing to achieve such manipulations during transmission. We present preliminary experimental results, which suggest that our approach enables deterministic message manipulations, even in unpredictable radio environments.

A comparison of PHY layer on the Ecma-392 and IEEE 802.1 laf standards

Abstract: Cognitive radio is widely expected to be a promising technology to efficiently exploit underutilized spectrum. Regulatory committees in many countries are taking into account the spectrum policy of dynamic spectrum access using this technology. The TV band is under consideration as a first step to share the spectrum resource. As a result, many activities to specify a standard using this band have been shown. In this paper, an overview on the physical layer of Ecma-392 standard and IEEE 802.11af draft standard is presented together with software simulated performance results. Furthermore, the effect of the frequency diversity on different number of subcarriers and channel bandwidth is analyzed and discussed.

Enhanced Superframe Structure of the IEEE802. 15. 4 Standard for Real-time Data Transmission in Star Network

Abstract: The IEEE 802.15.4 standard is one of the main communication protocols proposed for wireless sensor networks, IoT ‘Internet of Things’ and WoT ‘Web of Things’. This protocol provides a flexible MAC layer designed to meet a variety of applications. Since WSN is application-specific, it’s very difficult to provide a generic solution for all types of applications and topologies. In this work we focus on delay sensitive applications in star networks. This topology is used in wireless sensor networks for monitoring and control applications. The IEEE 802.15.4 standard provides some quality of service features for real-time data transmission. We identified some limitations of this standard and we proposed an improvement to provide a lower end-to-end delay with respect to energy consumption constraint by optimizing MAC layer. The experimentations are done using the NS-2 simulator. The results show the improvements expected by our approach among the IEEE 802.15.4 MAC standard.

A distributed load balancing approach for industrial IEEE 802.11 wireless networks

Abstract: Advantages provided by the use of wireless technologies in industrial scenarios, like reduced costs of installation, better flexibility, the ability to easily realize temporary deployments (e.g. for monitoring purposes), etc. are discussed by researchers in literature. In these contexts, time-critical transmissions have to be supported by automation networks. In IEEE 802.11 standard protocol, one of most popular technologies for process control networks, Access Points (APs) are responsible for nodes connection. Timeliness of communications can be compromised by transmission of wireless nodes through overloaded APs. This paper shows a new dynamic Load Balancing approach that distributes network load in order to ensure, for each station, best possible performances in terms of soft real-time constraints, in an industrial process control scenario.

Performance Modeling of a Two-Tier Primary-Secondary Network Operated with IEEE 802.11 DCF Mechanism

Abstract: In this paper, we present an analytical study for the performance of a two-tier primary-secondary network based on IEEE 802.11 DCF mechanism. It is assumed that multiple primary users (PUs) and secondary users (SUs) coexist in the radio environment and share a single band such that the SUs are allowed to contend only if they sense the channel idle for a certain period of time. First, we derive the PUs' medium access delay in the presence of SUs. Then, assuming an exponential packet inter-arrival time for the primary network, and using M/G/1 queue modeling, we determine the collision probability and throughput for the primary and secondary networks, as well as the PUs' average total delay including the queuing delay. Numerical along with simulation results show how the performance in the primary network, with given packet arrival rate, can be affected as functions of the sensing time, packet payload size and population size of the SUs. The findings of this work can be used effectively to study the performance of any IEEE 802.11 based primary-secondary network, such as cognitive radio networks where SUs may exploit a primary channel opportunistically based on a predefined policy, as well as to optimize the performance of distributed cognitive radio MAC protocols.

IEEE 802.15.4m: The first low rate wireless personal area networks operating in TV white space

Abstract: This paper provides an overview on motivations and process behind the forming of the first low rate (LR) wireless personal area networks (WPAN) operating in the TV white space (TVWS), IEEE 802.15.4m. There are three main forces driving the LR-WPAN community to expand its operational band to the TVWS. First, the change in TVWS-related regulations that opens up new spectrum resources is the key triggering factor. Secondly, there are many potential applications addressed by LR-WPAN systems that are anticipated to benefit from the expansion of the spectrum. Thirdly, the emergence of multiple standardizations targeting on the same types of applications in the same conventional frequency bands, indicating potential congestion and heterogeneous coexistence issues, is also one of the main pushing factor. In this paper, a comprehensive summary of different regulations, list of potential usage models and interactions among conventional LR-WPAN system are presented. A general discussion on how these factors fall in place to realize the forming of IEEE 802.15.4m is given. Finally, the paper concludes with expected functional requirements for the IEEE 802.15.4m system.

Upcoming WLANs MAC access mechanisms: An overview

Abstract: This paper gives an overview of the recent medium access control (MAC) mechanisms which are rising today. We focus on the already existing IEEE 802.11 and IEEE 802.11e MAC mechanisms, as well as those which are under development such as IEEE 802.11ac, IEEE 802.11ad, and IEEE 802.11aa. We describe the 802.11ac access mechanisms which support the multi-user access techniques in the form of sharing the transmit opportunity TXOP period. For the 802.11ad, we explain protocols that enable up to 7 Gigabit. We detail 802.11aa access mechanisms that guarantee more reliable multicast transport for video streaming.

Analyzing the Impact of Security Protocols on Wireless LAN with Multimedia Applications

Abstract: The availability and reasonable cost of broadband Internet made it an attractive and favorable option to billions of users worldwide. Being a fast service also encourages its users to use multimedia applications. The performance of such applications in wireless LAN may be highly affected by security protocols. This paper examines the effect of different security protocols on the performance of wireless LAN with multimedia applications. Experiments were performed on a wireless test-bed and the results were analyzed for throughput, delay and jitter for four security settings: disabled security, WEP, WPA1, and WAP2. The experiments were performed under two different scenarios and using multimedia traffic streams. The results revealed a significant degradation in performance when security protocols were enabled in wireless LAN. Specifically, delay and jitter, were significantly increased, both of which are key metrics for multimedia applications. The increase is clearer when a larger number of hosts exist in the network. We finally propose an outline for a solution to obtain strong security in wireless LAN without significant performance degradation. The solution proposes that the security processing at the hosts be conducted by the powerful host processor rather than by the radio card processor. As for the wireless access point, adding ASIC or FPGA processor is suggested for performing the heavy security processing. Keywords-WLAN; WEP; WPA1; WPA2; delay; jitter; multimedia traffic.

Rate adaptation with loss diagnosis on IEEE 802.11 networks

Abstract: Rate adaptation in wireless networking aims to seek the optimal data transmission rate most appropriate for current wireless channel conditions to make full use of the channel potentials. It is important in wireless networks because (1) most of them support multiple data rates, and (2) wireless channel is unstable with fast changes on which a single rate thereby may not be proper for long. Based on a comprehensive survey of the rate adaptation for IEEE 802.1 networks in literature, this work proposes a rate adaptation scheme, dubbed effective rate adaptation (ERA), for IEEE 802.11 networks. ERA takes advantage of the fragmentation technique in IEEE 802.11 standard and utilizes the lowest rate retransmission in diagnosing frame loss cause (collision or channel degradation), diffusing collision, and promptly recovering frame losses. It also adopts an adaptive rate increase threshold concept to exploit channel potentials. Different from other rate adaptation schemes, ERA effectively addresses two challenges in rate adaptation on IEEE 802.11 networks: (1) it does not require RTS/CTS for loss diagnosis purpose; the use of RTS/CTS that are optional in IEEE standard results in inefficiency on channel utilization; (2) it promptly responds to frame failure due to channel degradation, unlike others waiting till the end of a transmission window or cycle. With extensive simulation, ERA shows its unique strength in different lossy environments, especially in collision-prone environments. Copyright © 2011 John Wiley & Sons, Ltd. (This work was presented in part at the IFIP Networking08, Singapore.)

Delay and throughput performance of IEEE 802.16 WiMax mesh networks

Abstract: IEEE 802.16 can provide wireless broadband access with its support to both single-hop and multi-hop mesh modes. It defines several traffic/service categories and offers differentiated quality of service assurance through scheduling algorithms. However, it is not quite clear how well an IEEE 802.16 network could support real-time services such as video streaming and voice over Internet protocol services, especially in its mesh-mode operation. This study aims to analyse delay and throughput properties of an IEEE 802.16 mesh network for evaluating the performance of various real-time applications. The authors establish an analytical model to calculate delay and throughput of IEEE 802.16 distributed scheduling schemes. The proposed model helps to investigate how delay and throughput vary in terms of network parameters in order to optimise the system design via proper parameter configuration. Extensive simulations have been conducted to demonstrate the accuracy of the model.

Performance evaluation of PTPd, a IEEE 1588 implementation, on the x86 Linux platform for typical application scenarios

Abstract: The paper introduces the results of performance evaluation of IEEE 1588 Clock Synchronization technology implementation on the x86 (Intel) Linux platform. First, the typical application scenarios of IEEE 1588 in modern distributed measurement systems are listed, and based on that test systems are derived for testing with different configurations. These test systems are 1) a full software implementation in which no hardware elements support IEEE 1588, 2) a partial IEEE 1588 aware system in which end nodes synchronizing clocks support hardware time stamping but network elements do not, and 3) a full IEEE 1588 aware solution in which both end nodes and network elements support the standard. The hardware assisted PTP implementation utilized for evaluation has been developed by the authors of the paper, and available from http://home.mit.bme.hu/~khazy/ptpd/. The hardware assisted implementation is based on the Linux operating kernel infrastructure specifically developed for high precision network time keeping available from the kernel version of 2.6.30, and uses Network Interface Cards with IEEE 1588 hardware time stamping available on the market. The initial results show that clock accuracy (master-slave clock difference) less than one microsecond is achievable with using a full IEEE 1588 implementation even in the case of high network traffic and slave node (a node that synchronizes its clock to a master clock) load in standard Linux. The paper also details how the implementation of the clock servo realized by fixed point arithmetic computations (quantization) effect the achievable clock accuracy and proposes enhancements to the current solution.