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The increasing number of low power communication devices in the era of Internet of Things (IoT) has resulted in challenges in maintenance and continuous energy supply. In this paper, the ambient energy harvesting is integrated with wireless local area network (WLAN), where low-power users adopt a distributed coordination strategy for their random access, namely ambient energy harvesting carrier-sense-multiple-access with collision avoidance (AEH-CSMA/CA). All users harvest ambient energy to power their data uploading. In order to increase the uplink throughput and to reduce the energy outage probability, a classic deep reinforcement learning (DRL) algorithm, namely deep Q-learning (DQL), is adopted by a smart user for intelligently adjusting its initial backoff window size during the backoff process. Simulation results demonstrate that the proposed DQL algorithm is capable of substantially improving the throughput performance, while gauranteeing the energy outage probability of the smart user lower than a certain threshold. [ABSTRACT FROM AUTHOR]

Conventional design of wireless transmissions mainly focuses on manipulating end devices to better adapt to the transmission environments, such as channel coding and modulation techniques, whose performance is significantly affected by the quality of the transmission environments. In this paper, we propose an innovative idea to proactively manipulate, reconfigure, and augment wireless transmission environments to better support end-to-end services. Specifically, we implement this idea into the commercialized millimeter-wave (mmWave) wireless local area networks (WLANs) to address the vulnerability to blockages in mmWave bands. Without damaging the aesthetic nature of environments, we deploy multiple small-piece highly-reflective metallic reflecting surfaces as tunable reflectors, where alternative indirect line-of-sight links are created by tuning the orientations of the reflecting surfaces. To demonstrate our idea, we devise a novel adaptive mechanism, mmRef, to enable the implementation of tunable reflectors in mmWave WLANs, where the system architecture, operational procedures, and the signaling process are developed, respectively. To theoretically quantify the expected benefits, we characterize the outage probability and system throughput of mmRef mechanism based on stochastic geometry theory. Simulation and numerical results demonstrate the effectiveness of implementing mmRef and the significantly improved system performance. [ABSTRACT FROM AUTHOR]

This letter proposes a circular patch antenna with dual-band circular polarization at the UHF-RFID and WLAN bands. Two perpendicular slots are etched on the patch to down-shift the first resonance to 915 MHz (UHF-RFID band) and introduce a new resonance at 2.45 GHz (WLAN band). Four slits are etched on the ground plane to improve axial ratio (AR) mainly in the first band. A dual-band AMC reflector having 25 unit cells is placed a small distance below the patch to reduce the backlobe level and improve the gain at both bands. Measured 3 dB AR bandwidths of 5.25% and 2% are achieved at UHF-RFID and WLAN bands respectively with gains of 3.1 dBi (UHF-RFID) and 6.25 dBi (WLAN). The antenna system can be used with RFID readers for detecting tags and sending information via the WLAN band. [ABSTRACT FROM AUTHOR]

Recently, we experience the increasing prevalence of wearable cameras, some of which feature Wireless Local Area Network (WLAN) connectivity, and the abundance of mobile devices equipped with on-board camera and WLAN modules. Motivated by this fact, this work presents an indoor localization system that leverages both imagery and WLAN data for enabling and supporting a wide variety of envisaged location-aware applications ranging from ambient and assisted living to indoor mobile gaming and retail analytics. The proposed solution integrates two complementary localization approaches, i.e., one based on WLAN and another one based on image location-dependent data, using a fusion engine. Two fusion strategies are developed and investigated to meet different requirements in terms of accuracy, run time, and power consumption. The one is a light-weight threshold-based approach that combines the location outputs of two localization algorithms, namely a WLAN-based algorithm that processes signal strength readings from the surrounding wireless infrastructure using an extended Naive Bayes approach and an image-based algorithm that follows a novel approach based on hierarchical vocabulary tree of SURF (Speeded Up Robust Features) descriptors. The second fusion strategy employs a particle filter algorithm that operates directly on the WLAN and image readings and also includes prior position estimation information in the localization process. Extensive experimental results using real-life data from an indoor office environment indicate that the proposed fusion strategies perform well and are competitive against standalone WLAN and imaged-based algorithms, as well as alternative fusion localization solutions. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the effects on throughput and fairness of dynamic channel bonding (DCB) in spatially distributed high-density wireless local area networks (WLANs). First, we present an analytical framework based on continuous-time Markov networks (CTMNs) for depicting the behavior of different DCB policies in spatially distributed scenarios, where nodes are not required to be within the carrier sense range of each other. Then, we assess the performance of DCB in high-density IEEE 802.11ac/ax WLANs by means of simulations. We show that there may be critical interrelations among nodes in the spatial domain–even if they are located outside the carrier sense range of each other–in a chain reaction manner. Results also reveal that, while always selecting the widest available channel normally maximizes the individual long-term throughput, it often generates unfair situations where other WLANs starve. Moreover, we show that there are scenarios where DCB with stochastic channel width selection improves the latter approach both in terms of individual throughput and fairness. It follows that there is not a unique optimal DCB policy for every case. Instead, smarter bandwidth adaptation is required in the challenging scenarios of next-generation WLANs. [ABSTRACT FROM AUTHOR]

This paper reports on a dual-band, polarization-insensitive frequency-selective surface (FSS) directly realized on window glass for Wi-Fi and WLAN shielding applications. The design incorporates an annular ring and modified flower-shaped geometry to suppress 2.45 and 5.5 GHz bands, respectively, while acting ineffective to the rest of the frequency spectrum. The proposed design is completely insensitive to incoming wave polarization owing to its symmetry. The FSS also offers excellent incident wave angular stability up to 45°. Additionally, a wide rejection bandwidth (−10 dB) of more than 630 and 1430 MHz for lower and higher bands, respectively, is obtained suffice to cover the WLAN spectrum. Unlike conventional screen-printed FSS for glass applications, the conducting patterns of the proposed FSS are realized with copper foil directly laminated and etched on the glass substrate while maintaining 86% transparency for sufficient light passage. The detailed analysis of all parameters has been carried out, and their effect on the performance of FSS is reported. An equivalent lumped circuit model is also generated for the proposed design to better understand the physical phenomena of electromagnetic (EM) wave suppression. A finite prototype containing 13 × 10 elements is fabricated and tested. The measured results are in good agreement with the simulated ones. The FSS offers measured suppression of 43 and 40 dB at 2.45 and 5.5 GHz bands, respectively. The design has excellent potential for EM field suppression, WLAN isolation, and security applications in indoor environments. [ABSTRACT FROM AUTHOR]

Rate adaptation (RA) is an essential mechanism in 802.11 WLAN. In the latest 802.11ac protocol, there are two emerging problems that need to be addressed for the RA. First, 802.11ac supporting more rate selections requires more efforts to find the optimal rate. Finally, 802.11ac supports higher rate. The difference between optimal rate and non-optimal rate can be so great that non-optimal rate would severely deteriorate the throughput of the WLAN. In order to tackle these problems, we develop a novel RA algorithm termed rate adaptation with Thompson sampling (RATS) for stationary and non-stationary channel environments. In this algorithm, we first consider compacting the search space by removing some rates to accelerate the convergence of the algorithm. Moreover, inspired by multi-armed bandit problem, we design RA algorithm based on Thompson sampling. Simulation results demonstrate that the performance of the proposed RATS outperforms the existing method. [ABSTRACT FROM AUTHOR]

With dramatically increased data traffic, the traditional low-frequency (LF) wireless local area networks (WLAN) are facing several difficulties, particularly, limited available spectrum resources and low network efficiency. While the use of millimeter-wave (mmWave) could bring more spectrum, WLAN in high-frequency (HF) suffers poor reliability. In addition, the current distributed WLAN architecture and the coupled data and control planes lead to inefficient management and poor performance with increased network scale, which cannot meet the stringent requirements from diverse applications. In overcoming these difficulties, the control plane and data plane decoupled network architecture and sub-6 GHz and mmWave dual-band cooperation are considered to be the critical solutions to improve the system performance in 5th-Generation (5G) and beyond networks. Therefore, to improve the throughput and reliability of the future WLAN, we propose a control plane and data plane decoupled WLAN architecture in this paper that supports both sub-6 GHz and mmWave based on the existing control plane and data plane decoupled WLAN concept. Furthermore, new multi-beam transmission and sub-6 GHz and mmWave dual-band cooperation mechanisms are developed to improve the throughput and reliability in our proposed WLAN architecture. Performance analysis and simulation show that with the multi-beam transmission and sub-6 GHz and mmWave dual-band cooperation mechanisms in our proposed WLAN architecture, throughput and reliability are both significantly improved when compared with the traditional distributed WLAN architecture and operation mechanism. [ABSTRACT FROM AUTHOR]

To improve spectrum sharing between long-term evolution license-assisted access (LAA) and incumbent systems such as wireless local area networks (WLANs) in unlicensed spectrum, listen before talk (LBT) has been proposed as a candidate for LAA channel access. To allow for a robust spectrum sensing performance, LBT may use a backoff-slot duration that is substantially larger than its WLAN counterpart. There is a potential for an unknown backoff slot-jamming (SJ) effect, which may significantly decrease the channel access probability (CAP) and throughput of LAA-LBT links. In this paper, we study the SJ effect and propose an effective anti-SJ (ASJ) LBT scheme. To gain theoretical insight, we develop a new performance analysis approach on coexisting systems with different slot durations. We model the LAA backoff process with super-counters, provide an in-depth analysis of the backoff process, and derive key performance indicator (KPI) statistics. These KPIs include backoff hold time, successful transmission probability, CAP, and throughput. The simulation results thoroughly validate our analytical results and show that the ASJ-LBT scheme is effective in mitigating the SJ effect. These results fill a major technical gap in spectrum sharing research and may be extended to support system optimization and coexistence analysis of other heterogeneous systems. [ABSTRACT FROM AUTHOR]

Cooperative content delivery using multiple air interfaces (CCDMI) is a powerful solution to mitigate congestion in cellular networks. In CCDMI, the operator distributes content to selected users that further distribute it locally among its nearby users. However, a user that is capable of contributing to CCDMI might act selfishly and refuse to participate. Although the operator can encourage user participation by offering incentives, it has incomplete information about the users’ willingness to participate. In order to overcome this problem of adverse selection in CCDMI, we propose two contract-based methods under information asymmetry. In both methods, the operator designs a performance-based contract set for the users that are capable of local content distribution. Using a mathematical analysis, we show that the optimal contract under information asymmetry achieves close to optimal utility for the users and the operator, compared with the information symmetry case. Moreover, the users with high willingness to participate get positive utility and the users with low willingness get zero utility. Hence, by assigning contracts, the operator can motivate user participation, despite the information asymmetry between them. Our results verify that the proposed methods improve the system performance in terms of the utility of the operator and the users. [ABSTRACT FROM AUTHOR]

Multicasting is an efficient mechanism to disseminate popular multimedia content to multiple interested third generation partnership project (3GPP) cellular users. To further enhance the multicast cellular capacity, non-3GPP WLAN networks can be leveraged to relieve the load of the 3GPP cellular networks. In this paper, we propose the distributed procedure of de-touring the multicast traffic to WLAN in the current LTE and WLAN heterogeneous network architecture. We also propose promising software-defined networking (SDN)-based centralized approach that facilitates multicast content dissemination, bringing efficiency and flexibility to the network. We analyze both the distributed and centralized approaches based on the multicast content popularity. Our analysis reveals that the SDN-based approach in heterogeneous cellular communication and multicasting brings significant radio resource savings. We also conduct packet-level simulation with a real SDN controller and smartphones to confirm the feasibility of the proposed SDN-based approach. [ABSTRACT FROM AUTHOR]

The coexistence problem of different wireless protocols that share a common frequency spectrum has attracted much attention owing to the proliferation of heterogeneous wireless networks in the research community. Recently, Bluetooth (BT) and Wireless LAN (WLAN) protocol stacks have been integrated as a single-chip communication module, and they now even share the antenna as well as the spectrum. In this paper, we show that this integration provides new opportunity for one protocol to better understand the other and to operate in harmony to avoid mutual interference. We develop an Opportunistic Bluetooth Transmission (OBT) scheme that enables a dual stack device having an integrated module to exploit previously-unused deferring times of the WLAN protocol. We evaluate its performance through not only model-based analysis but also practical implementation in a prototype testbed. The results show that the OBT scheme can significantly improve throughput of the dual-stack device. [ABSTRACT FROM AUTHOR]

Wireless local area network (WLAN) fingerprinting has been extensively studied for indoor localization due to the formidable deployability of WLAN in indoor environment, but one major bottleneck of its practical implementation is the extensive calibration effort required to construct the radio map through the fingerprinting which is time consuming and labor intensive. In response to this compelling problem, we newly design the graph-based semi-supervised manifold alignment approach which relies on the concept of graph construction to construct a cost-efficient radio map with a small number of labeled fingerprints. In addition, the unlabeled user traces are also considered to compensate for the sparsity of the raw radio map as well as enhance its robustness to the environmental change. The extensive experiments conducted in an actual indoor WLAN environment demonstrate the performance improvement (by 27.48% at most with respect to the confidence probability of errors within 3 m) by our system compared with the existing ones using the fingerprints solely. [ABSTRACT FROM PUBLISHER]

This paper describes the first dual-band MIMO 802.11a/b/g/n/ac WLAN RF transceiver capable of simultaneous dual-band operation. The measured receiver sensitivity of 2 GHz at 54 Mbps is −78.3 dBm and of 5 GHz for VHT80 is −66 dBm. The 802.11ac $2 \times 2$ MIMO 20-MHz MCS0 2 and 5 GHz receiver sensitivity levels are −96 and −95.5 dBm, respectively. Integrated power amplifiers with P_{\mathrm{sat}} of +29 dBm enable the 2-GHz transmitters to achieve TX output power of +23.5 dBm at 54-Mbps 64-quadratic-amplitude modulation (QAM). The 5-GHz transmitters achieve +17 dBm output for VHT80 256-QAM. This WLAN-BT connectivity system-on-chip is implemented in 40-nm CMOS technology. [ABSTRACT FROM AUTHOR]

Just like Ethernet before, IEEE 802.11 is now transcending the borders of its usage from the office environment toward real-time communication on the factory floor. However, similar to Ethernet, the availability of synchronized clocks to coordinate and control communication and distributed real-time services is not a built-in feature in WLAN. Over the years, this has led to the design and use of a wide variety of customized protocols with varying complexity and precision, both for wired and wireless networks, in accordance with the increasingly demanding requirements from real-time applications. This survey looks into the details of synchronization over IEEE 802.11 with a particular focus on the infrastructure mode which is most relevant for industrial use cases. It highlights the different parameters which affect the performance of clock synchronization over WLAN and compares the performance of existing synchronization methods to analyze their shortcomings. Finally, it identifies new trends and directions for future research as well as features for wireless clock synchronization which will be required by the applications in the near future. [ABSTRACT FROM PUBLISHER]

In this letter, we propose an access point (AP) sleeping and user offloading optimization scheme to improve energy efficiency in densely deployed WLANs. Through real trace analysis, we investigate AP energy efficiency to obtain the sleep-awake threshold, which is used to select sleep or awake APs according to real-time status information monitored on controller. Moreover, we formulate the user offloading problem as a reverse auction process to optimize energy efficiency of APs involved in offloading. Simulation results demonstrate that, comparing to traditional methods, our scheme can achieve up to 20% energy saving while maintaining effective system coverage and throughput. [ABSTRACT FROM PUBLISHER]

In this paper, we analyze the saturation throughput of a cognitive WLAN overlaid on a primary OFDMA TDD network (e.g., LTE or WiMAX). In this scenario, after the contention among the secondary nodes, the winner node transmits its data packet in the empty resource blocks (RBs) of downlink and uplink subframes of the primary network. Regarding the OFDMA structure as well as time-scheduled resources in the primary network, the time duration of opportunities for the secondary network does not follow simple exponential on-off pattern. To model the dynamic behavior of opportunities for secondary nodes as well as contentions to exploit the opportunities, we propose an analytical model comprised of a discrete-time Markov chain and two inter-related open multi-class queueing networks (QNs). The effects of the random number of empty resource blocks at different frames as the result of random amount of download and upload data, random packet transmission time at WLAN, the dependency of the number of empty RBs at consecutive frames, and the details of 802.11 MAC protocol are included in our analytical approach. We include different resource allocations in the primary network in our analysis. Simulation results confirm the accuracy of our analytical approach in different conditions. [ABSTRACT FROM AUTHOR]

Collisions are a main cause of throughput degradation in wireless local area networks. The current contention mechanism used in the IEEE 802.11 networks is called carrier sense multiple access with collision avoidance (CSMA/CA). It uses a binary exponential backoff technique to randomize each contender attempt of transmitting, effectively reducing the collision probability. Nevertheless, CSMA/CA relies on a random backoff that while effective and fully decentralized, in principle is unable to completely eliminate collisions, therefore degrading the network throughput as more contenders attempt to share the channel. To overcome these situations, carrier sense multiple access with enhanced collision avoidance (CSMA/ECA) is able to create a collision-free schedule in a fully decentralized manner using a deterministic backoff after successful transmissions. Hysteresis and fair share are two extensions of CSMA/ECA to support a large number of contenders in a collision-free schedule. CSMA/ECA offers better throughput than CSMA/CA and short-term throughput fairness. This paper describes CSMA/ECA and its extensions. In addition, it provides the first evaluation results of CSMA/ECA with non-saturated traffic, channel errors, and its performance when coexisting with CSMA/CA nodes. Furthermore, it describes the effects of imperfect clocks over CSMA/ECA and presents a mechanism to leverage the impact of channel errors and the addition/withdrawal of nodes over collision-free schedules. Finally, the experimental results on throughput and lost frames from a CSMA/ECA implementation using commercial hardware and open-source firmware are presented. [ABSTRACT FROM PUBLISHER]

Network traffic classification is the process of analyzing traffic flows and associating them to different categories of network applications. Network traffic classification represents an essential task in the whole chain of network security. Some of the most important and widely spread applications of traffic classification are the ability to classify encrypted traffic, the identification of malicious traffic flows, and the enforcement of security policies on the use of different applications. Passively monitoring a network utilizing low-cost and low-complexity wireless local area network (WLAN) devices is desirable. Mobile devices can be used or existing office desktops can be temporarily utilized when their computational load is low. This reduces the burden on existing network hardware. The aim of this paper is to investigate traffic classification techniques for wireless communications. To aid with intrusion detection, the key goal is to passively monitor and classify different traffic types over WLAN to ensure that network security policies are adhered to. The classification of encrypted WLAN data poses some unique challenges not normally encountered in wired traffic. WLAN traffic is analyzed for features that are then used as an input to six different machine learning (ML) algorithms for traffic classification. One of these algorithms (a Gaussian mixture model incorporating a universal background model) has not been applied to wired or wireless network classification before. The authors also propose a ML algorithm that makes use of the well-known vector quantization algorithm in conjunction with a decision tree-referred to as a TRee Adaptive Parallel Vector Quantiser. This algorithm has a number of advantages over the other ML algorithms tested and is suited to wireless traffic classification. An average F-score (harmonic mean of precision and recall) > 0.84 was achieved when training and testing on the same day across six distinct traffic types. [ABSTRACT FROM PUBLISHER]

Increasing the density of access points is one of the most effective mechanisms to cope with the growing traffic demand in wireless networks. To prevent energy wastage at low loads, a resource-on-demand (RoD) scheme is required to opportunistically (de)activate access points as network traffic varies. While previous publications have analytically modeled these schemes in the past, they have assumed that resources are immediately available when activated, an assumption that leads to inaccurate results and might result in inappropriate configurations of the RoD scheme. In this paper, we analyze a general RoD scenario with $N$ access points and non-zero start-up times. We first present an exact analytical model that accurately predicts performance but has a high computational complexity, and then derive a simplified analysis that sacrifices some accuracy in exchange for a much lower computational cost. To illustrate the practicality of this model, we present the design of a simple configuration algorithm for RoD. Simulation results confirm the validity of the analyses, and the effectiveness of the configuration algorithm. [ABSTRACT FROM PUBLISHER]

In uplink wireless local area networks (WLANs) with multi-packet reception (MPR) which can be implementable with multi-user multiple-input multiple-output techniques, partial successes among simultaneous transmissions may frequently occur due to frame errors. This causes an increase in the contention window size only for the failed stations (STAs) under the binary exponential backoff algorithm, and a severe unfairness problem in terms of channel access opportunity may occur among the STAs with different frame error rates. In this letter, we propose a novel medium access control (MAC) protocol to support fair channel access in uplink WLANs with MPR. Analysis and simulation results show that our proposed MAC protocol can significantly improve the fairness in terms of both channel access opportunity and throughput. [ABSTRACT FROM PUBLISHER]

We propose a channel access mechanism that allows Long Term Evolution (LTE) to operate in the 5-GHz unlicensed band (LTE-U/LAA) and fairly coexist with 802.11 Wireless Local Area Networks (WLANs). The proposed mechanism is compliant with listen before talk, and it can be configured to maximize the channel time used by the LTE-U stations while fairly coexisting with the 802.11 WLANs. That is, an LTE-U station will not affect the throughput of a WLAN more than if it were an 802.11 station. [ABSTRACT FROM PUBLISHER]

This letter investigates the problem associated with retransmission timeout (RTO) that is used in transport layer protocols. The current RTO algorithm is designed for wired networks, and is not properly prepared for IEEE 802.11-based wireless local area networks (WLANs). In this letter, a WLAN RTO (WRTO) algorithm, which can be applied to TCP and MPTCP is proposed. The experiments show that at poor channel conditions the proposed scheme results in a 18%, 29%, and 68% faster recovery time when compared to CMT-PF, cWPTCP, and CMT-QA, respectively, and also results in less spurious retransmission when compared to CMT-PF, which has the shortest recovery time among the existing schemes. [ABSTRACT FROM PUBLISHER]

This paper proposes an improved particle swarm optimization (PSO) process to design a high-performance compact ultrawideband (UWB) filter. The filter consists of one-cell composite right- and left-handed-transmission line (CRLH-TL) resonator, a stepped impedance (SI), and two spurlines. The one-cell CRLH-TL resonator has compact size but performs wide passband filtering. One SI and two spurlines are employed to reject both the harmonics outside the UWB and the wireless local area network (WLAN) (5.15–5.825 GHz) band. The improved PSO consists of the conventional PSO with the sensitivity analysis, and the process for checking the ripple. The improved PSO suppresses the ripple and accelerates the optimization. During the improved PSO, the objective function converges from the 116th iteration. In addition, the characteristic of the filter is optimized to get acceptable results. The proposed filter has the overall size of 14 \times 15 mm2 ( 0.63\lambda _{g} \times 0.53\lambda _{g}) only, a 105% bandwidth for a return loss >10 dB, a flat insertion loss <1.4 dB, and stopbands on 11.5\sim 22$ GHz and WLAN band. In particular, the ripple in the passband is minimized significantly by the improved PSO. [ABSTRACT FROM AUTHOR]

A novel compact asymmetric coplanar strip (ACS)-fed printed antenna using dual edge resonators for tri-band operation is presented. The proposed tri-band antenna is based on an ACS-fed beveled monopole, to which an E-shaped coupled resonator and an L-shaped slot resonator are introduced for achieving two new independent resonances and miniaturization of size. The antenna has a small overall dimensions of only 12 × 23 × 1 mm3. The experimental results demonstrate the proposed antenna is capable of operating over the frequency ranges 2.37-2.52, 3.38-3.71, and 4.92-5.96 GHz, suitable for 2.4/5.2/5.8-GHz WLAN and 3.5/5.5-GHz WiMAX applications. [ABSTRACT FROM PUBLISHER]

This letter presents a low-cost printed circuit board (PCB)-based dual-band antenna for future wireless local area network (WLAN) applications. The antenna is designed to fully cover both WiFi channels (2.4/5.2/5.8 GHz) and Wireless Gigabit Alliance (WiGig) channels (57-64 GHz). At the WiFi frequency bands, the antenna is based on a printed monopole, while at the WiGig frequency band, a wideband higher-order-mode patch antenna is adopted. A compact microstrip resonance cell (CMRC) low-pass filter is also designed to allow feeding the monopole antenna at WiFi frequency bands while isolating the monopole from the patch for WiGig operation. The design is fabricated by standard PCB and plated-through-hole technologies, and its performance is validated by measurement. [ABSTRACT FROM PUBLISHER]

We propose an energy-efficient L2 transmission scheme using the protocol property of Non-Real-Time (NRT) traffic in IEEE 802.11 WLANs. Typically, the collision probability at the Access Point (AP) and the retransmission probability at the Mobile Terminals (MTs) may increase significantly when the number of served MTs constantly increases. As these probabilities are increasead, energy efficiency in WLANs is decreased. In order to reduce the retransmission attempts, the proposed scheme allocates the maximum backoff count to an MT which is using NRT traffic. Thus, we propose a new energy consumption metric for retransmission while comparing it to the Distributed Coordination Function (DCF) by numerical analysis in a saturated network situation. [ABSTRACT FROM PUBLISHER]

The design of a four-band slot antenna for the global positioning system (GPS), worldwide interoperability for microwave access (WiMAX), and wireless area network (WLAN) is presented. The antenna consists of a rectangular slot with an area of \mathbf0.\mathbf37\lambda _g \times \mathbf0.\mathbf14\lambda _g = \mathbf48 \times \mathbf18\;\bf m\bf m^\mathbf2 (where \lambda _g is the guide wavelength), a $T$-shaped feed patch, an inverted $T$-shaped stub, and two $E$-shaped stubs to generate four frequency bands. The radiating portion and total size of the antenna are less than those of the tri-band antennas studied in literature. Parametric study on the parameters for setting the four frequency bands is presented and hence the methodology of using the design for other frequency bands is proposed. The multiband slot antenna is studied and designed using computer simulation. For verification of simulation results, the antenna is fabricated and measured. The simulated and measured return losses, radiation patterns, realized peak gains, and efficiencies of the antenna are presented. Measured results show that the antenna can be designed to cover the frequency bands from 1.575 to 1.665 GHz for the GPS system, 2.4–2.545 GHz for the IEEE 802.11b&g WLAN systems, 3.27–3.97 GHz for the WiMAX system, and 5.17–5.93 GHz for the IEEE 802.11a WLAN system. The effects of the feeding cable used in measurement and of the cover are also investigated. [ABSTRACT FROM PUBLISHER]