Polymers for RF Apps

The explosive growth of the Internet over the last decade has led to an increasing demand for high-speed, ubiquitous Internet access. Broadband wireless technologies are increasingly gaining popularity by the successful global deployment of the wireless personal area networks (Bluetooth-IEEE 802.15.1), wireless local area networks (WiFi- IEEE 802.lln), and wireless metropolitan area networks (WiMAX- IEEE 802.16). New ICT and e-Learning strategies and advances in wireless standards and technologies- particularly in the areas of Bluetooth, WiFi (wireless fidelity), WiMAX (worldwide interoperability for microwave access) and mobile computing can help to bridge the digital divide in education and research. Using open broadband Wireless technologies and implementing mobile computing architectures, one can overcome the challenges of ground, infrastructure, and finance to increase access; deploy broadband quickly and cost-effectively to areas currently not served; and extend the benefits of digital revolution to previously unreachable populations. These technologies aim to provide low-cost, high-performance Wireless access to residential and business applications. As technology evolves to address portable and mobile applications, the required features and performance of the system will increase. Evolution toward the phase called "full mobility" provides incremental support for low latency, low packet loss and real-time handoff of subscriber terminals operating at high speeds. This paper presents the analogy of promising wireless technologies on different frequencies: Bluetooth, WiFi, and WiMAX. This paper is organised into four parts: part I describes the functionality and usage of Bluetooth in the wireless personal area networks, part II presents the WiFi- IEEE 802.1 In strategies for users considering higher-bandwidth alternatives to existing wireless personal area networks, part III discusses how the WiMAX is used as a current standard for Wireless data transmission technology, which is optimized to deliver high, bursty data rates to mobile subscribers, and to support real-time multimedia and Voice over IP (VoIP) applications, and part-TV explores how these emerging Wireless technologies differ from one another.

More and more devices, such as Bluetooth and IEEE 802.15.4 devices forming Wireless Personal Area Networks (WPANs) and IEEE 802.11 devices constituting Wireless Local Area Networks (WLANs), share the 2.4 GHz Industrial, Scientific and Medical (ISM) band in the realm of the Internet of Things (IoT) and Smart Cities. However, the coexistence of these devices could pose a real challenge—co-channel interference that would severely compromise network performances. Although the coexistence issues has been partially discussed elsewhere in some articles, there is no single review that fully summarises and compares recent research outcomes and challenges of IEEE 802.15.4 networks, Bluetooth and WLANs together. In this work, we revisit and provide a comprehensive review on the coexistence and interference mitigation for those three types of networks. We summarize the strengths and weaknesses of the current methodologies, analysis and simulation models in terms of numerous important metrics such as the packet reception ratio, latency, scalability and energy efficiency. We discover that although Bluetooth and IEEE 802.15.4 networks are both WPANs, they show quite different performances in the presence of WLANs. IEEE 802.15.4 networks are adversely impacted by WLANs, whereas WLANs are interfered by Bluetooth. When IEEE 802.15.4 networks and Bluetooth co-locate, they are unlikely to harm each other. Finally, we also discuss the future research trends and challenges especially Deep-Learning and Reinforcement-Learning-based approaches to detecting and mitigating the co-channel interference caused by WPANs and WLANs.

Problem statement: In universal networking environments; two or more heterogeneous communication systems coexisting in a single place. Especially, Wireless Local Area Networks (WLANs) based on IEEE 802.11b specifications and Wireless Personal Area Networks (WPANs) based on IEEE 802.15.4 specifications need to coexist in the same Industrial, Science and Medial (ISM) band. If the WPAN communication coverage is expanded using a cluster-tree network topology, then the 802.15.4 network is more susceptible to interference from neighboring WLANs. Approach: In this study, we propose an adaptive transmission power aware cluster scheduling algorithm using multiple channels in a WPAN in the presence of WLAN interference. Results: The algorithm includes node identification, channel allocation, clustering and time scheduling. To evaluate the performance of the proposed algorithm, the performance metrics such as Bit error, Packet Error Rate (PER), Throughput, Average End-End Delay and Average Jitter is measured through Qualnet simulation. PER is calculated from bit error rate. The simulation results are compared with the conventional TDMA scheme. Conclusion/Recommendations: The measurement result shows that the proposed algorithm is effective in an IEEE 802.15.4 cluster-tree network in the presence of multiple IEEE 802.11 interferers.

A frequency domain multiple-antenna and channel estimation approach for facilitation of UWB technologies coexistence in heterogeneous WPANs

An adaptive bluetooth packet selection and scheduling scheme in interference environments

Low proflle, light weight, easily mounted and broad bandwidth are the key charac- teristics for antennae designed for wireless applications. The microstrip antenna (MSA) suits the features mentioned except for its narrow bandwidth. The bandwidth of the microstrip antenna usually ranges from less than 1% to several percent. This paper experimentally investigates an alternative approach in enhancing the bandwidth of the microstrip antenna for the Wireless Lo- cal Area Network (WLAN) application operating at a frequency of 2.45GHz. The bandwidth enhancement technique which is studied is the Identical Dual Patch Microstrip Antenna with Air-Gap (IDMA). A bandwidth enhancement of more than 11% was achieved. Wireless applications have undergone rapid development in recent years. One particular wireless application that has experienced this trend is the Wireless Local Area Network (WLAN). The wireless application that is selected to be studied is the 2.4GHz to 2.5GHz frequency band which is based on the 802.11b WLAN standard. This frequency band is very popular due to its low cost. WLAN antenna requires being low proflle, light weight and broad bandwidth. The microstrip antenna suits the features very well except for its narrow bandwidth. The WLAN antenna should have a minimum bandwidth of 100MHz to fully utilize the WLAN band based on the 802.11b standard. The conventional microstrip antenna could not fulflll this requirement as its bandwidth usually ranges from less than 1% to several percent (1). Although the required operating frequency range is from 2.4GHz to 2.5GHz, at least double the bandwidth is required to avoid expensive tuning operations and to cause uncritical manufacturing. Therefore, there is a need to enhance the bandwidth of the microstrip antenna for WLAN applications. This paper investigates a technique which can enhance the bandwidth of the microstrip antenna without increasing the lateral size and the complexity of the microstrip antenna too much. The Identical Dual Patch Microstrip Antenna with Air-Gap (IDMA) bandwidth enhancement technique takes the advantage of using the air gap to lower the efiective permittivity and increase the total thickness of the microstrip antenna which is essential for bandwidth enhancement. This bandwidth enhanced microstrip antenna can be deployed for the WLAN application operating at a frequency of 2.45GHz. 2. SIMULATED AND MEASURED RESULTS OF THE SINGLE-LAYER MICROSTRIP ANTENNA

1.1 Impulse Radio (IR) Ultra Wideband (UWB) Communications Ultra wideband (UWB) communication is a fast emerging technology that offers new opportunities such as high data rates, low equipment cost, low power, precise positioning capability and extremely low interference Ghawami (2005). A wide range of possible UWB communication system applications includes radars due to UWB ultra high precision ranging at the centimeter level, wireless personal area networks (WPAN), sensor networks, imaging systems, UWB positioning systems, etc. Yang (2004), Kshetrimayum (2009). From a commercial point of view, the high data rates are the most attractive feature of UWB systems for which speeds of over 100Mb/s have been demonstrated Ghawami (2005). There exist three main types of UWB technologies: impulse radio (IR UWB), direct sequence (DS UWB), and multi-band orthogonal frequency division multiplexing (MB OFDM) Ran (2009). IR UWB communication technique is essentially different from all other communication techniques because it is carrier free and uses for communication between transmitters and receivers very narrow radio frequency (RF) pulses generated from the UWB pulse generator, while traditional transmission systems transmit information by varying the power, frequency, and/or phase of a sinusoidal wave in a modulation process Kshetrimayum (2009), Yao (2007). Consequently, complicated frequency mixers and local oscillators for carrier frequency up and down conversion are not necessary Yao (2007). IR UWB modulation techniques are especially important because the UWB spectrum has been made available by the Federal Communication Commission (FCC) and it can be used with IRs developed to date Lin (2005). Waveforms for IR UWB are designed to obtain a flat frequency response over the bandwidth of the pulse and to avoid a DC component. The large spectrum of a UWB signal may interfere with existing users. In order to keep this interference to the minimum, FCC specifies spectral masks for different applications, i.e. the allowed power output for specific frequencies Ghawami (2005). A contiguous bandwidth of 7.5GHz is available in the frequency interval of (3.1− 10.6)GHz at a maximum power output of −41.3dBm/MHz which is considered as extremely low Ghawami (2005). The power spectral density (PSD) of UWB systems defined as a ratio of the transmitted power P in watts and a signal bandwidth B in hertz is extremely low as compared to other communication systems due to the very wide bandwidth B of short pulses that are typically of nanosecond or picosecond order Ghawami (2005). The selection of the impulse signal type for IR UWB communication system is essential since it determines

In this paper a systematic model is used to find a closed-form formula for the channel capacity of ad hoc networks with line topology based on Ultra-Wideband (UWB) and Wireless Local Area Network (WLAN) technologies. As a result, it has been found that the interference level in this network topology is upper bounded and a formula to compute this limit is provided. Based on our computations, it is shown that UWB ad hoc networks have much larger channel capacity than WLAN ad hoc networks. With UWB technology the maximum throughput per node is limited by the transmission bit rate while it is limited by the low channel capacity when WLAN technology is used. As a minor advantage of our findings, a clue about routing algorithm optimization is also given.

Ultra-wideband (UWB) communications has emerged as a promising technology for high data rate wireless personal area networks (WPANs). In this paper, we address a key issue that impacts the performance of multi-hop, multi-rate UWB-based WPANs, namely joint routing and rate selection. Arbitrary selection of routes (including direct links) and transmission rates along these routes results in unnecessarily long channel reservation time and high blocking rate for prospective reservations, and leads to low network throughput. To remedy this situation, we propose a novel overhearing-aware joint routing and rate selection (ORRS) scheme, which improves the network throughput by exploiting the dependence between the channel reservation time and the multi-rate capability of an UWB system. At the same time, ORRS takes advantage of packet overhearing, a typical characteristic of broadcast communications. For a given source-destination pair, ORRS aims at selecting a path and its transmission rates that achieve the minimum reservation time, leading to low blocking rate for prospective reservations and high network throughput. We show that achieving this goal while simultaneously exploiting packet overhearing and satisfying a target packet delivery probability over the selected route leads to an NP-hard problem. Accordingly, ORRS resorts to approximate solutions (proactive and reactive) to find a near-optimal result with reasonable computational/communication overhead. We further propose other variants that exploit packet overhearing in different ways to improve ORRS performance.

Millimeter-wave (mmWave) communication standards in the unlicensed band—such as IEEE 802-based wireless personal area networks (WPANs), wireless local area networks (WLANs), and 3GPP-led cellular networks (CNs)—have faced challenges in achieving commercial acceptance for over a decade. To enable widespread adoption of mmWave communication systems, a concept called the mmWave virtual community network (VCN) has recently been proposed. In this architecture, a decentralized WPAN-style device-to-device (D2D) community coexists with centralized WLANs and CNs in the unlicensed mmWave band via multi-hop links. However, the current mmWave VCN concept lacks a clear definition of strategic and technical enablers to support large-scale commercial deployment. To address this gap, this paper proposes a strategic ecosystem that promotes mmWave VCN deployment for the mutual benefit of both decentralized and centralized entities. Specifically, the decentralized community—enabled by mmWave D2D communication—supports the coverage expansion of mmWave WLANs and CNs. In return, the CN operator incentivizes distributed communities through a reward mechanism, ensuring mutual growth and cooperation. Furthermore, we propose “New Radio Sidelink for mmWave Unlicensed (NR SL-mmW-U),” as a technical enabler of mmWave D2D communication, thereby materializing a sidelink-native mmWave VCN with concrete specifications. We evaluate the proposed sidelink-native mmWave VCN via a link-level simulation and initial incentive theory-based analytical model, thereby providing preliminary assessments of its feasibility in meeting the key requirements for realizing the envisioned ecosystem.

A novel method to generate ultra-wideband (UWB) signals based on two differential group delay modules and one Mach-Zehnder Modulator is proposed. Both simulation and experiments verified that the method could generate two kinds of UWB monocycles using low bit-rate non-return-to-zero data source (1Gbps). The monocycles have a fractional bandwidth of 127% at centre frequency 5.5GHz. Keywords: Ultra wideband (UWB), radio-over-fiber (RoF), differential group delay (DGD) 1. INTRODUCTION Ultra-wideband (UWB) is a fast emerging technology for short-range broadband wireless communication such as wireless personal area network and sensor network, etc. The UWB signal occupies wide bandwidth and has low power density, and it has immunity to multi-path fading [1]. As a carrier-free modulation scheme, direct-sequence impulse radio is more cost-effective and simpler compared with multi-band orthogonal frequency scheme. Since UWB is a room-scaled short range wireless communication technique, the wireless networks can operate mainly in indoor environment in standa lone mode. Considering the integration of UWB access networks and fixed wired networks, the combination of UWB-over-fiber technology and fiber-to-the-home (FTTH) technology is a competitive candidate for future wideband access networks [2]. So many all-optical schemes that fit for UWB-over-fiber technology to generate and distribute UWB impulses have been reported recently. Zeng et al. proposed two approaches to generate UWB impulses using one phase modulator (PM), and 25-km single mode fiber (SMF) or FBG to convert phase-modulated light to UWB pulses [3, 4]. Wang and Dong proposed UWB signal generation using cross-gain modulation or cross-phase modulation in semiconductor optical amplifier [5, 6], which requires two laser sources and may increase the system complexity. Chen proposed a scheme based on optical polarization time delay [7]. It is a simple method, but the elect rical signal source needs at least twice bit-rate compared to the carried data. Most of the schemes n eed an electrical Gaussian pulse source, which is comm only composed of a high-speed pulse pattern generator (PPG). This is an expensive construction, for which the PPG should work at least 10 Gbps. Furthermore, if data are carried on the UWB pulses, another modulator should be added to the systems, which increase the system cost and complexity. In this paper, we proposed and experimentally demonstrated a simple method to generate data-carried UWB monocycle pulses based on two differential group delay (DGD) modules and one Mach-Zehnder modulator (MZM). Instead of the data pattern “1000 0000 ”, which has one “1” followed by several “0”s to form the UWB signal, we use electrical non-return-to-zero (NRZ) data. The NRZ data modulate the optical signal in MZM to get an optical binary phase shift keying (BPSK) signal, which is then fed into two cascade DGD module s while the polarization of the light is carefully adjusted

A compact 5GHz WLAN notched Bluetooth/UWB antenna has been proposed, fabricated, and characterized. The rectangular UWB monopole antenna has gained the Bluetooth frequency band and the notched frequency band by using a coupling-fed meander line and inverted L-shaped strips, respectively. The proposed antenna is a good candidate for integrated Bluetooth and UWB systems.

A novel and compact planar ultra wide band (UWB) filter is presented. Stepped impedance resonator (SIR) is used as multi mode resonator (MMR). MMR is fed by inter digital coupled lines. Coupled lines are designed such that to ensure low insertion loss over a wide frequency range. SIR (i.e., MMR) produces three resonant modes in the UWB frequency range ensures wide pass band. To avoid the potential interference caused by the co-existing wireless services is mitigated by incorporating band notch characteristics. In addition to UWB pass band, GSM 1800 band for GSM mobile communication with center frequency at 1850MHz is also achieved. Filter exhibits narrow pass band from 1800MHz to 1950MHz and UWB pass band from 3.5 GHz to 10 GHz with reference to 3 dB. At band notch frequency filter exhibits high attenuation level up to 40 dB and ensures less interference caused by co-existing wireless local area network (WLAN) band from 5.6 GHz to 5.9 GHz. GSM 1800 Band is obtained by loading shorted stub to the MMR without disturbing the UWB pass band response. S-parameters of the filter depict good UWB characteristics along with GSM 1800 pass band. Proposed filter is designed based on RT/Duroid 5880 substrate with dielectric constant 2.2 and thickness 0.785 mm. Proposed filter design is aimed to be a compact over reported UWB filter (i.e., surface area of 0.24λ 0 × 0.14λ 0 (Where λ 0 is the free space wavelength at the 6.85 GHz)).

The wireless personal area network (WPAN) is an emerging wireless technology for future short range indoor and outdoor communication applications. The IEEE 802.15.3 medium access control (MAC) is proposed to coordinate the access to the wireless medium among the competing devices, especially for short range and high data rate applications in home networks. In this paper we use analytical modeling to study the performance analysis of WPAN (IEEE 802.15.3) MAC in terms of throughput, efficient bandwidth utilization, and delay with various ACK policies under error channel condition. This allows us to introduce a K-Dly-ACK-AGG policy, payload size adjustment mechanism, and Improved Backoff algorithm to improve the performance of the WPAN MAC. Performance evaluation results demonstrate the impact of our improvements on network capacity. Moreover, these results can be very useful to WPAN application designers and protocol architects to easily and correctly implement WPAN for home networking.

This paper presents frequency band-notched antenna to overcome electromagnetic interference (EMI) between UWB systems and Wireless Local Area Networks (WLANs) based on IEEE 802.11a standard for Ultra Wide-Band (UWB) communication. The proposed antenna is designed on FR4 substrate having a size of 12×18 mm2 with thickness of 1.6 mm and relative permittivity (er) of 4.4 which provides frequency notching from 4.9 to 6.2 GHz. This antenna consists of two conducting strips inside a rectangular slot printed on circular shaped patch. This antenna provides a wide band width from 4.4 to 11.2 GHz with single band frequency notch from 4.9 to 6.2 GHz to avoid interference of UWB band with the existing systems. The design parameters and the performance of the proposed antenna are analyzed by using HFSS. The antenna displays a good omnidirectional radiation pattern and gain.