Simplified cross-polarized multi-antenna system for radio relay transmission in wireless backhaul Abstract Wireless backhaul systems have been considered as a promising candidate of beyond 3G wireless broadband system for mobile communications. The achievable transmission performance over radio relay channel depends on antenna directivity and radiation patterns of each antenna element. To improve the transmission performance and keep radio relay channel in an acceptable condition, it is effective to control the antenna directivity by employing multi-antenna signal transmission and reception. In this paper, we propose a simple method to extend the existing single antenna relay node based on IEEE802.11a to multi-antenna system, where a cross polarized multi-antenna is applied to the existing relay nodes as external equipment. The multi-antenna system is controlled by detecting the antenna control information assigned to the lengths of the packets transmitted from the existing node. The proposed method does not require special change of the existing system such as hardware design on multi-antenna configuration. We also developed a prototype base/relay node with optional multi-antenna equipment and confirmed the effectiveness of the proposed method by experiment. To clarify the effectiveness of the proposed multi-antenna system in wireless backhaul networks, we evaluate throughput performance by system level simulations. Simulation results ensure that the proposed multi-antenna system with highly efficient packet forwarding protocol, called Intermittent Periodic Transmit (IPT), improves throughput performance of the radio relay transmission in wireless backhaul as compared with conventional Omni-directional antenna system.
Compact switched and reconfigurable 4-ports beam antenna array for MIMO applications Abstract In this paper, we analyze and introduce a practical design for a switched beam planar antenna that can be implemented as a compact and low cost switched and/or reconfigurable beam antenna array. The antenna is composed of a four ports antenna array based on arranged eight L-shaped quarter-wavelength slot antenna elements. This type of antenna array is a planar structure and its maximum directional radiation beam pattern presents in azimuth plane with the covering of 360 degree. The operation of antenna array is based on the statuses of ON/OFF stage of PIN diodes in each individual slot antenna element and the combined signals from four ports. Consequently, by proper controlling the stage of PIN diodes, the antenna can exposes its characteristic of switchable and/or reconfigurable beam patterns in φ-plane. The antenna array size is about 56 mm in square with four ports. To prove the concept, a 2.5-2.8 GHz switched-beam antenna for WLAN applications in MIMO is simulated and fabricated.
Antennas and propagation for body centric wireless communications Abstract Body-centric wireless communications refer to human-self and human-to-human networking with the use of wearable and implantable wireless sensors. It is a subject area combining wireless body-area networks (WBANs), Wireless Sensor Networks (WSNs) and Wireless Personal Area Networks (WPANs). Body-centric wireless communications has abundant applications in personal healthcare, smart home, personal entertainment and identification systems, space exploration and military. The human body is an uninviting and often hostile environment for a wireless signal. In general, antennas suffer from reduced efficiency due to electromagnetic absorption in human tissues, radiation pattern fragmentation and variations in impedance at the feed. Typical geometries of wireless wearable and implantable devices vary from mill metric to cent metric sizes and, hence, compact yet efficient antennas need to be fully characterized and integrated with the RF transceiver. As well as size there are other significant challenges in the design of antennas for body-centric wireless communications. The objective of this talk is to highlight current and emerging research in antennas and propagation for body-centric wireless communications, as well as applications of this technology.
Efficient placement of directional antennas in infrastructure-based wireless networks Abstract
Over the past decade, the use of directional antennas has immensely proliferated in wireless networks. Methodically positioning and orienting directional antennas can help reduce the interference while saving energy. In an infrastructure-based wireless network, wireless devices communicate through base stations. In this setting, directional antennas placed on the base stations form the backbone of the communication network. The wireless devices distributed around the base stations have bandwidth requirements that have to be satisfied by the directional antennas, and antennas constrained by hardware limits can only serve a limited number of devices. This introduces an optimization problem and in this paper, we develop an integer linear program for placing and directing antennas on multiple base stations to minimize the number of antennas required to serve all the wireless bandwidth demands. Through this integer programming formulation, we analyze the performance of directional antennas under various settings. A simulation-based evaluation using Cplex's branch-and-bound algorithm demonstrates the efficacy of our approach and provides us further insights into these problems.
Indoor Wireless Planning Using Smart Antennas Abstract This paper considers the problem of indoor wireless planning using smart antennas. Smart antennas have gained much attention in wireless networking because of their capability in providing more spatial reuse and increased network capacity. Recent research has demonstrated their effectiveness in indoor environments where Omnidirectional antennas have been traditionally the dominant technology. Much of the work, however, assumes that a network is already deployed and focuses on scheduling antenna patterns. In this work, we investigate finding a wireless plan for an indoor environment where the wireless plan specifies minimum number of antennas required to provide complete coverage of the environment as well as the location, transmission power and beam pattern for each antenna. This problem is more challenging than radio planning using Omni-directional antennas because of the special shape of antenna beams. Both single-beam and multi-beam antenna patterns are considered and Integer Linear Programming formulations are provided for computing the minimum cost wireless plan. Moreover, to solve large-scale instances of the problem an efficient polynomial-time heuristic is proposed.
Slot Antennas with an Extended Ground for Multiple-Antenna Systems in Compact Wireless Devices Abstract In this letter, new slot antennas with an extended ground are proposed. They are easily built as internal antennas in a compact wireless device. Originated from lambda/4 slot antennas, an additional vertical L-shaped metallic sheet as an extended ground and a main radiator is added to reduce the antenna size. The sheet is designed close to a ground plane, and its height can be chosen according to the available space of a given device. These features offer more design flexibility for antenna and mechanical engineers. In this letter, antennas for WLAN are designed and implemented as examples, and a four-element antenna design using the resultant antennas is demonstrated, showing that the multiple-antenna design occupies only a small region in the system board. With these design examples the proposed structures can be a promising solution for multiple-antenna systems in compact wireless devices.
Simple design method of wireless power transfer system using 13.56MHz loop antennas Abstract In this paper, we propose a simple design method of a wireless power transfer system using 13.56MHz loop antennas. This method can simple design a wireless power transfer system by only using the measurements of coupling coefficients and the equations for equivalent circuit model about loop antennas without the complicated electromagnetic analysis. Using the proposed design method, a wireless power transfer system with a pair of loop antennas operating at the frequency of 13.56MHz, which have a dimension of 50×50 cm2, is designed and implemented. The input return loss, coupling coefficient, efficiency, and input impedance variation with respect to the distance between loop antennas were measured. The proposed design method provides good agreements between
measured and predicted results. Also, the wireless power transfer system with impedance matching circuits designed by the proposed design method shows two times higher efficiency characteristics than the case with the general 50 Ω impedance matching circuits. Therefore, we verified that our design method could be an effective tool to design a wireless power transfer system.
Upper Bounds on the Number of Channels to Ensure Collision-Free Communications in Multi-Channel Wireless Networks Using Directional Antennas Abstract Recent studies have found that using multiple channels can separate concurrent transmissions and significantly improve network throughput. However, these studies have only considered wireless nodes that are equipped with omni-directional antennas, which have high interference. On the other hand, other researchers have found that using directional antennas in wireless networks can reduce interference and improve the network performance. But their studies have only considered single channel to be used in wireless networks with directional antennas. Thus, integrating the two technologies of multiple channels and directional antennas together can potentially bring more benefits. Some previous works have studies the capacity on the multi-channel wireless networks using directional antennas. However, the channel assignment problem of such networks has not been well studied. In this paper, we study the channel assignment problem in the multi-channel wireless networks using directional antennas. In particular, we study the problem: given a set of wireless nodes equipped with directional antennas, how many channels are needed to ensure collision-free transmission? We derive the upper bounds on the number of channels, which depend on the node density. We also construct several scenarios to examine the tightness of the derived bounds. Our result can be used to estimate the number of channels required for a practical wireless network. Besides, our results can also be used to provide a suggestion on the proper node density in the node deployment when the number of channels is given for a wireless network.
Inexpensive fabric antenna for off-body wireless sensor communication Abstract Emerging trends in monitoring people (patients, soldiers, athletes, etc.) have led to numerous recent advances in body area communication networks (BAN). Wireless sensor communication opens up tremendous potential for wireless patient monitoring. Body centric wireless networks use RF sensor nodes in close proximity to the human body. Body networks include on body, body to body and off body communication. Antenna design and analysis plays an important part in the development of sensors for BAN. Antennas for on-body communication include the inverted F antenna, (IFA) and the planar inverted F antenna (PIFA), low profile microstrip patch antenna, sleeve dipole, printed-F antenna, wearable (fabric) antennas, broadband discone antennas etc.. In this paper we discuss a low cost, nearly circularly polarized truncated patch antenna design on Zelt fabric and Felt substrate for performing offbody communication centered at 915 MHz for monitoring patients after operation. This low cost antenna provides good return loss and high directivity and efficiency comparable to the fabric antennas designed in the literature. The antenna also has a 10-dB bandwidth of 75 MHz which accounts for the frequency shifting due to the bending of the antenna.
Wireless communication capability of a reconfigurable plasma antenna Abstract A 30 cm long plasma column is excited by a surface wave, which acts as a plasma antenna. Using plasma properties (pattern formation/striations in plasmas) single plasma antenna can be transformed into array, helical, and spiral plasma antenna. Experiments are carried out to study the power patterns, directivity, and half power beam width of such different plasma antennas. Moreover, field properties of plasma and copper antenna are studied. Further, wireless communication and jamming capability of plasma antenna are tested. Findings of this study suggest that directivity and communication range can be increased by converting single plasma antenna in to array/helical/spiral plasma antenna. Field frequencies of plasma antenna determine the communication and jamming of radio frequency waves. Therefore, this study invokes applications of pattern formation or striations of plasmas in plasma antenna technology.
Radiation Characteristics of Photonic Antenna for Optical Wireless Communication using Beam Propagation Method Abstract The optical wireless communication is the only solution to the emerging next generation wireless communication. The photonic antennas play major role in the development of optical wireless communications. This photonic antenna transfers light energy from optical waveguide to free-space with high directionality and act as a matching device between optical source and channel (atmosphere). The analysis of light propagation through waveguide structures is indispensable in designing complex photonic devices. The optical waveguide grating structures with multiple longitudinal reflecting interfaces are analyzed to form photonic antennas. The multilayer triangular grating structure is analyzed using beam propagation method for its ability and suitability to optical wireless communication. The beam propagation method (BPM), extensively used tool for computer simulation of light propagation in optical waveguide structures, has been developed for analyzing optical waveguides with discontinuities in transmission, reflection and radiations. The discontinuities comprise changes in core thickness and effective refractive index. The optical powers radiated and transmitted at an abrupt discontinuity in waveguide gratings are calculated numerically by means of BPM for TE modes, and applied to the eigen mode and propagating beam analysis of that structure. The current method achieves soaring precision and converging time is significantly abridged and it is proportional to the log of the total number of periods in the waveguide than that in the conventional time-domain method. This paper intends a novel integrated photonic antenna with snooty directional efficiency and radiation which can be tattered for protracted distance optical wireless communication. The consequences confirm that it is promising to curtail radiation loss under sturdy mode coupling conditions. This method can be used for modeling of laser beam propagation in non-homogeneous atmosphere.
Low cost DGPS wireless network Abstract This article depicts the development and test of a low cost wireless sensor network intended for use in severe environmental conditions. The test site is a serac located at 4100m above a populated area. It was needed to put in place a monitoring system able to trace displacement continuously and in all weather conditions. To achieve this goal starting from a professional but cheap single frequency GNSS module we developed the needed electronics to control it, log the data and transmit them over a long distance. The final board is working at 2.4 GHz and the network protocol is based on a proprietary implementation of a listen before talk approach. The high DGPS precision is obtained by using local GNSS permanent stations.
Verification of an OFDM-based range and Doppler estimation algorithm with ray-tracing Abstract In this paper, a simulation and validation method using ray-tracing for an OFDM joint radar and communication system is presented. The motivation is to verify the range and Doppler estimation algorithm and to observe the behaviour of the OFDM radar system in a real scenario where there are multipath and multiusers in its environment. The OFDM radar system has only been performance verified for a single user and since Doppler measurement is not easily repeatable, it is thus unreliable to use measurement verification for performance observation purposes of a real scenario. Hence a ray-tracing technique based on geometrical-optics is used where the wave propagation, material parameters and traffic are modeled according to realistic environments. The ray-tracing results are then exported into the OFDM radar system's model on MATLAB and the result is observed from the radar image where the set distance and velocity are compared to those processed with the novel range and Doppler estimation algorithm.
Channel characteristics analysis of the dual circular polarized land mobile satellite MIMO radio channel Abstract
This paper analyses the characteristics of the dual circular polarized land mobile satellite MIMO radio channel using measured and modeled channel data. To describe the small scale fading observed in the measured channel, the model makes use of three parameters, which respectively represent the mean LOS, specular reflected and diffuse multipath signals. The model is validated by comparing the CDF plots of the received signal power and eigenvalues with that of the measured channel. Furthermore, the effects of channel correlation on the capacities of equal power allocation MIMO and dual circular polarization multiplexing (DCPM) is investigated. It is found that only the capacity of the LOS-friendly DCPM is negatively affected by a reduction in channel correlation.
