Abstract: Abstract In this communication design and performance of a novel single-layer assembly of gap coupled elements in elliptical shape is proposed to achieve broadband performance with circular polarization. Out of five patches considered in this assembly, two pairs of patches having different patch areas are arranged close to an edge truncated elliptical patch. The central edge truncated elliptical patch is fed through inset feed arrangement and the other patches are parasitically gap coupled to the central patch. With such an arrangement, an improved impedance bandwidth of 1.58 GHz or 18.5% with respect to central frequency 8.5 GHz is achieved. Three resonant modes are excited with this arrangement giving improved bandwidth and gain in comparison to a conventional elliptical patch antenna with same semi-major and semi-minor axes. In the entire bandwidth, the simulated radiation patterns of proposed arrangement of patches are more or less identical in shape.

Abstract: Abstract. Diffraction problem of the TE1nand TM0nmodes by a system of annular slots in the hollow inner conductor of a coaxial waveguide is considered. Inner conductor is of finite thickness. The waveguide is filled with dielectrics with different permittivities. As a key problem the diffraction problem by a circular-to-coaxial waveguide step discontinuity is solved with the mode-matching technique. The obtained solution is used in the analysis of structures with a finite and semiinfinite number of discontinuities. Dependences of the transmission and reflection coefficients of the dominant mode of a circular and coaxial waveguides as functions of wavenumber and distance between slots are analyzed.

Abstract: Abstract The aim of this study was to considered possible discrepancy in electromagnetic (EM) fascination in the human head. Commercially available software CST Microwave Studio based on the finite-difference time-domain (FDTD) method was adopted in this study. In this calculation, the conductivity and permittivity of all tissues were increased from 10 to 20% except using if not the same revelation conditions. Familiar cellular phone frequencies of 835, 900, and 1900 MHz were investigated in this research. The rise of up to 20% in conductivity, permittivity and varied substrate material always caused a SAR variation of 30.42% for SAR 1 g and 23.75% for SAR 10 g at 835 MHz, variation of 22.41% for SAR 1 g and 21.96% for SAR 10 g at 900 MHz and variation of 11.96% for SAR 1 g and 14.29% for SAR 10 g at 1900 MHz respectively.

Abstract: This paper is about a Spectrum Sensing Network (SSN) which generates an accurate radio environment map (e.g. power over frequency, time, and location) from a given application area. It is intended to be used in combination with cognitive Program Making and Special Events (PMSE) devices (e.g. wireless microphones). It consists of a distributed network of multiple scanning radio receivers and a central data management and storage unit. The parts of the SSN are presented in detail and the advantages and the use cases of such a sensing network structure are outlined.

Abstract: Abstract Software defined radios are increasingly used in modern communication systems, especially in cognitive radio. Since this technology has been commercially available, more and more practical deployments are emerging and its challenges and realistic limitations are being revealed. One of the main problems is the RF performance of the front-end over a wide bandwidth. This paper presents an analysis and mitigation of RF impairments in wideband front-ends for software defined radios, focussing on non-linear distortions in the receiver. We discuss the effects of non-linear distortions upon spectrum sensing in cognitive radio and analyse the performance of a typical wideband software-defined receiver. Digital signal processing techniques are used to alleviate non-linear distortions in the baseband signal. A feed-forward mitigation algorithm with an adaptive filter is implemented and applied to real measurement data. The results obtained show that distortions can be suppressed significantly and thus increasing the reliability of spectrum sensing.

Abstract: In this article, we propose a flexible CSMA based MAC protocol which facilitates research and experimenta- tion using software define radios. The modular architec- ture allows to employ the protocol on platforms with het- erogeneous hardware capabilities and provides the freedom to exchange or adapt the spectrum sensing mech- anism without modifying the MAC protocol internals. We discuss the architecture of the protocol and provide structural details of its main components. F urthermore, we present throughput measurements that have been obtained on an example system using host-based spec- trum sensing.

Abstract: We analyze the signal-signal beating interference (SSBI) when optical orthogonal frequency division multiplexing (OOFDM) signal is directly detected by photodiode at the receiver. We propose a novel training sequence configuration to reduce SSBI. The experimental results show that the receiver sensitivity of the OFDM signal with the new training sequence at the BER of 1 10 3 is 2.4 dB better than that with standard training sequence after transmission over 100 km standard single mode fiber (SSMF) at a bit rate of 2.5 Gbit=s.

Abstract: This paper presents simulation environment that includes transmission channel models from the ETSI standard EN 300 744 (DVB-T system) and channel models based on real measured parameters. Our simulation includes transmitter and receiver, supports different system parameters (modulation, code rate, guard interval) and channel models. It is adaptive and reconfigurable environment that allows incorporation of hardware generated channel matrix in channel model and provides accurate estimation of system constraints. The model offers evaluation of channel models and can be used for testing and educational purposes.

Abstract: Abstract The objective of this paper is to investigate methods to guarantee the network performance of industrial Ethernet networks by an optimized topology design. The proposed approach differs from former works on network design by taking into account the specific requirements of industrial applications, the Quality of Service (QoS) related features of industrial Ethernet protocols, and the increasing network complexity in the industrial field. A multi-objective variable neighbourhood search algorithm (MOVNS) is presented offering a co-design method of physical topology and logical topology to satisfy the requirements of real-time capability, high reliability, and fast recovery time. The result analysis on simulation test cases shows the proposed algorithm can greatly improve the performance of industrial Ethernet networks at a moderate computational complexity.

Abstract: Abstract Over the last years ongoing advances in ADC technology have enabled RF signals to be sampled at IF frequencies. Undersampling is nowadays employed in software-defined radio or radar receivers and offers the possibility to relieve requirements in the analog receiver partition. Unfortunately, when moving to higher IF concepts, this becomes demanding for the ADC itself, because of inherent spurious-free dynamic range (SFDR) roll-off that increases with input frequency. This fact often limits the receiver's IF placement to Nyquist zone (NZ) 2. In this work the emerging concept of Digital Assistance is pursued to give the receiver access to higher NZs while making no compromise on the SFDR. We will present and discuss post-correction results for two 16-bit high-speed converters from two different vendors at 120 and 125 MSPS, respectively. The proposed system-level post-correction decomposes nonlinearity into a static and a dynamic part. For both ADCs under investigation the degraded SFDR in higher NZs could be improved by up to 15 dB using purely digital linearization technologies, thus increasing the detectability of small signals in the presence of very strong signals or interferers. Near-identical results for both ADCs confirm the general validity of the system-level correction approach.

Abstract: Abstract In this paper, we introduce a precise real-time 3D indoor localization concept using a combination of the MISAS (multilateral inverse synthetic aperture secondary radar) approach and SMCM (sequential Monte Carlo method). The synthetic aperture approach is a promising locating technique with effective multipath suppression. However, its practical use is restricted by the huge computational load of the reconstruction algorithms. We use a weighted-particle set – which we reduce subsequently by resampling – to represent the PDF (probability density function) instead of the highly complex, standard, grid-based approach. Simulation runs and experiments, carried out with a 5.8 GHz FMCW secondary radar system with a bandwidth of only 140 MHz, show that a robot TCP (tool center point) can be localized in 3D in the mm-range using a few hundred particles and operating in a dense multipath environment. This novel extension is a promising solution for real-time, 3D MISAS localization applications.

Abstract: Abstract A highly integrated 24 GHz radar sensor is presented, based on a Radio Frequency Integrated Circuit (RFIC) which was specifically developed for a Frequency Modulated Shift Keying (FMSK) based Radar system design. Antenna, waveform, the Radio Frequency (RF) and Digital Signal Processor (DSP) module, the software design, cost and performance aspects will be described. The significant technical and economical advantages of the implemented Silicon-Germanium (SiGe) Bipolar CMOS (BiCMOS) transceiver are demonstrated. Some automotive and other applications based on this technology and new radar system design will be explained.

Abstract: The capacity of multiple-input multiple-output (MIMO) wireless communication channels is affected by the multipath angle spread and relative multiple signal strength (RMSS) at both sides of the transmitter and the receiver. In this paper, we study analytically how these two factors emerge in the MIMO capacity equation when the channel state information (CSI) is unknown at the trans- mitter and perfectly known at the receiver. Mathematical expression for the channel capacity is carried out for2 � 2 MIMO system and two propagation paths between the base station (BS) and the mobile terminal (MS) are considered. The proposed analytical model is verified through numeri- cal results, which show that channel capacity increases with increasing angle spread. Also, as the relative strength of multipaths becomes larger, the better channel capacity is obtained.

Abstract: Software-Defined radio (SDR) is a future-proof solution for designing flexible and adaptable wireless networks and equipments. It replaces conventional radio hardware with reconfigurable, reprogrammable radios. A graphical approach for designing flexible SDR multi-standard systems is proposed, which provides all the possible alternatives of implementation capable of realizing the multi-standard design. However, a cost function which evaluates the cost of any one of these options is proposed in previous work. All these ideas are briefly mentioned in this paper but however, our goal is to help finding the option of implementation which has the minimum cost. Graph theory is adopted and particularly the study of directed hypergraphs, to present a new idea algorithm capable of solving this optimization problem. This algorithm provides an exact-optimal solution, unlike the previously applied heuristic methods which give a near-optimal solution. Furthermore in this work, we analyze the computational complexity of our algorithm.

Abstract: Abstract In this paper, a novel current-mode differential transconductance low noise amplifier (LNA) designed in the chartered 0.18 μm CMOS technology is proposed to realize the receiver front-end. The proposed LNA frequency ranges from 4.7 GHz to 6 GHz,mainly targeting at IEEE802.11a application. It utilizes two stage structure, with a PMOS current-mirrorr using inductive series peaking technique to achieve optimized current output. The noise performance is improved through the use of a gm-boosting technique, while the gain performance is improved and power consumption is saved by using current-reused technique. Measured results demonstrate that the circuit provides flat transconductance gain higher than 17.0 dB, noise figure lower than 2.31 dB and low operating voltage of 0.85 V in frequency band. A comparison with other LNAs in similar and nearby frequency bands shows the proposed LNA has advantages of higher gain, lower noise figure and better other performances.

Abstract: An investigation of GaN-HEMT based switching stages in hybrid switching amplifiers (HSA) for wide-bandwidth supply modulation of RF power amplifiers is presented. The HSA is designed for maximum 15 ...

Abstract: Abstract In this letter, a broadband coupler is presented that makes use of a half mode substrate integrated waveguide (HMSIW) technique using a printed circuit board process. The coupler is realized by a parallel HMSIW line which couples energy by magnetic field. Compared with microstrip coupler and conventional HMSIW coupler it has lower loss and better Electromagnetic Compatibility owning to the closed field structure. Compared with SIW coupler, it has smaller size and lower cost owing to the half TE10 model. Based on coupler, a two-way balanced power combining amplifier is designed and measured. The measured results show a good agreement with simulation and a combining efficiency of 88% is achieved at 9.7 GHz.

Abstract: Abstract To improve the sensing performance, cooperation among secondary users can be utilized to collect space diversity. We focus on the optimization of cooperative spectrum sensing in which multiple secondary users efficiently cooperate to achieve superior detection accuracy with minimum sensing error probability in heterogeneous cognitive radio (CR) networks. Rayleigh fading and Nakagami fading are considered respectively in cognitive network I and cognitive network II. For each cognitive network, we derive the optimal randomized rule for different decision threshold. Then, the optimal decision threshold is derived according to the rule of minimum sensing error (MSE). MSE rule shows better performance on improving the final false alarm and detection probability simultaneously. By simulations, our proposed strategy optimizes the sensing performance for each secondary user which is randomly distributed in the heterogeneous cognitive radio networks.

Abstract: Abstract This paper presents a computationally effective approach for including dense multipath components in ray tracing simulations of ultra wideband (UWB) channels. Through a combination of a standard ray tracing model with a simple geometric-stochastic model realistic scenario-specific simulations are possible. The frequency and direction selectivity of the channel are reproduced accurately by the model. The structure and parameters of the stochastic part of the model are derived from measurements in the FCC-UWB frequency range. Compared to conventional ray tracing simulations the proposed model reduces considerably the differences between simulated and measured channel characteristics.

Abstract: Abstract According to the current IEEE 802.11 wireless LAN standards, IEEE 802.11 ad hoc networks have the limitation that all STAs (Stations) are in the one-hop transmission range of each other. In this paper, to alleviate the limitation of IEEE 802.11 ad hoc networks we propose the efficient method for selecting the most appropriate pseudo AP (Access Point) from among the set of ad hoc STAs and extending the service area of IEEE 802.11 ad hoc networks by the pseudo AP’s relaying the internal traffic of IEEE 802.11 ad hoc networks. Numerical examples show that the proposed method significantly extends the service area of IEEE 802.11 ad hoc networks.

Abstract: Conventional workshop-grade aluminum milling is a feasible and rapid way to make good connectorized microwave stripline bandpass filters with air dielectric for system prototyping purposes up to 40 GHz. Insertion loss is typically 1–3 dB in wide band units. Filters with 0.5 per cent fractional bandwidth are well within reach and have an insertion loss of 4–8 dB, depending on center frequency. The benefits when compared to typical substrate designs include rapid in-house prototyping without information leaks, easy integration with other connectorized commercial modules and avoidance of expensive and complicated semiconductor substrate or chemical processes. Resonator foreshortening remains problematic and the first resonator coupling gap shows a strong tendency of shrinkage at K-band and above. Waveguide propagation should be prevented by choosing a small enough stripline height.

Abstract: Abstract A kind of three dimensional Low Temperature Co-fired Ceramic (LTCC)-System in Package (SIP) transition was proposed in this paper. The basic design of SIP with LTCC technology was done by vertical transitions which transmit the microwave signal from the bottom to the surface of the substrate. The measured insertion loss did not exceed 1.5 dB, which contains the insertion loss of the test board about 0.6 dB at 18 GHz and the return loss was better than-15 dB up to 18 GHz. Then this technology was applied to a kind of phase shifting and amplifier module with two output ports. Basing on this module, a miniature Ku-band active phase array antenna was realized. The design results in a small size(84.8 mm×84.8 mm×55 mm). The measured performance of systems radiation pattern was also given.

Abstract: Abstract Software defined radio (SDR) clouds centralize the computing resources of base stations. The computing resource pool is shared between radio operators and dynamically loads and unloads digital signal processing chains for providing wireless communications services on demand. Each new user session request particularly requires the allocation of computing resources for executing the corresponding SDR transceivers. The huge amount of computing resources of SDR cloud data centers and the numerous session requests at certain hours of a day require an efficient computing resource management. We propose a hierarchical approach, where the data center is divided in clusters that are managed in a distributed way. This paper presents a set of computing resource management tools for analyzing computing resource management strategies and algorithms for SDR clouds. We use the tools for evaluating a different strategies and algorithms. The results show that more sophisticated algorithms can achieve higher resource occupations and that a tradeoff exists between cluster size and algorithm complexity.

Abstract: Abstract Low Density Parity Check Codes (LDPC) give groundbreaking performance which is known to approach Shannon’s limits for sufficiently large block length. Historically and recently, LDPC have been known to give superior performance than concatenated coding. In the following paper, a proposal to modify the standard Min-Sum (MS) algorithm for decoding LDPC codes is presented. This is done by introduction of a factor, intensity reflection coefficient (IRC),κ in the check to bit node updating process. Simulation results demonstrate that the proposed algorithms are effective in imparting a better performance in terms of a lower bit error rate (BER) at low to medium signal to noise ratio (SNR) when compared to the traditional MS or Belief Propagation (BP) algorithm while adding a minimum amount of complexity. The proposed algorithm results in a reduced hardware complexity when implemented in VLSI.

Abstract: Abstract An accurate electromagnetic optimization tool for designing rectangular and circular microstrip antennas is proposed. This optimization method is based on the improved cavity model analysis in conjunction with the well-known genetic algorithm, which is employed to optimize the dimensions and feed point location of rectangular and circular microstrip antennas. Results obtained by this technique agree quite well with the measured data and the data obtained by the FEM based software HFSS by ANSOFT. This technique can be fruitfully used in microwave CAD applications.

Abstract: Abstract An innovative method to achieve temperature-insensitive Optical Differential Phase Shift Keying demodulation is presented The demodulation is realized with a Mach–Zehnder-Interferometer-based-DPSK with direct intensity detection at the output using photodiodes followed by a trans-impedance amplifier. The output amplifier voltages thermal-drift are automatically compensated using a differential2 ×2 matrix voltage-control where amplifier voltages are taken as input vector. Matrix elements are calculated by a microcontroller using a predefined algorithm in correlation with MZI time delay and ambient temperature. Experimental Eye diagram amplitudes are reported for both compensated and uncompensated 100 ps MZI-based DPSK. We show theoretically and experimentally stable demodulation performances over a wide temperature range from 290 K to 390 K.

Abstract: Abstract Cyclostationary signatures have been shown to be an effective method for OFDM network synchronization and Cognitive Radio coordination. In this article, an extended method that utilizes cyclostationary signatures for signal parameter identification of OFDM-based Cognitive Radio nodes is presented. The scenario, implemented on a GNU Radio based evaluation platform, shows how different signal parameters, e.g. carrier frequency, occupied bandwidth and the used modulation scheme can be identified at the receiver side using the described approach. A major drawback of cyclostationary detection in OFDM systems is its sensitivity to frequency offset and sampling rate mismatches between oscillators at the transmitter and the receiver. An analytical model that characterizes this impairments is derived, followed by a discussion of implementation issues and the performance evaluation of proposed cyclostationary signature detection, both in a simulation environment and through RF experiments.

Abstract: Abstract For more than ten years, car-2-x communication has been a major topic of research in the scientific community and an important development focus for the automotive industry. First, this article takes a retrospective look at the evolution of car-2-x and the two different communication paradigms: decentralized car-2-car communication and centralized cellular solutions. Afterwards, a comparison of their technical advantages and limitations is presented, respectively. The result shows that in order to implement safety-relevant applications, car-2-car communication has strong advantages compared to cellular technologies but requires high market penetration. However, its introduction solely for safety applications is difficult since the required penetration will not be achieved until several years after initial deployment. Therefore, car-2-car communication must provide a benefit to the customer, even in the phase of market introduction. For this purpose, the article outlines an approach called SODAD (Segment-Oriented Data Abstraction and Dissemination). It offers a possibility to introduce decentralized vehicular applications with early customer benefit, in order to enable safety applications based on car-2-car communication on a long term.

Abstract: This paper presents a low noise amplifier (LNA) with differential output using a passive frequency selective feedback. The introduced feedback stabilizes the amplifier at lower frequencies and improves the gain in the desired frequency band. The LNA consists of two stages. Additionally, a buffer at the output is added for measurements. The amplifier was implemented in a 0.35 μm SiGe technology. For measurements the LNA was bonded to a substrate. A peak gain of 28.1 dB and a minimum noise figure of 2.2 dB at a supply voltage of 3 V were achieved.