Academic literature on the topic '100510 Wireless Communications'

The use of neural-network computational modules for radio frequency and microwave modelling and design has lately gained popularity as an uncommon but useful technique for this type of modelling and design. It is possible to train neural networks to study the behaviour of active and passive mechanisms and circuits. In this study, technologists will learn about what neural networks are and how they can be used to model microstrip patch antennas. An artificial neural network is used in this work to investigate in depth several designs and analysis methodologies for microstrip patch antennas. Various network structures are also discussed in this study for wireless communications. Microstrip antenna design has been presented and the use of ANN in microstrip antenna design are also shown in this article.

Mobile communication technology is continuously evolving. Early Fifth generation (5G) products, due 2020, should support high capacity, higher data rates, lower la- tency, lower energy consumption and should be cost effective. High data rates will require wider bandwidths, which are available in the higher frequency millimetre wave (mmWave) bands. Millimetre waves have much shorter wavelengths compared to to- day’s microwave mobile systems. Understanding mmWave propagation characteristics is important in the physical layer design of future wireless systems. Statistical Channel models are required in the standardization process to evaluate implementation proposals without the expense of building costly hardware test-beds. Statistical channel models are described by a few key parameters and a variance. For example, transmission path loss is a function of environment, range, path loss exponent (PLE) and the standard deviation (σ) of a statistical (shadowing) component. These parameters are generated by fitting an equation, in a minimum mean square error (MMSE) fashion, to a collated measurement database from a number of research organizations in different countries. Considering this, a number of channel sounding empirical measurements at mmWave frequencies were conducted to characterize, model and evaluate the propagation chan- nel properties in different 3rd Generation Partnership Projects (3GPP) scenarios (envi- ronments) under Australian conditions. Particular outdoor areas of interest were Rural Macro (RMa), Urban Macro (UMa) and Urban Micro (UMi) while indoor areas (InH) of interest included office and shopping malls. An in-house channel sounder was modified to obtain signal strengths with respect to (wrt) location and angle of arrival (AoA). Angular resolution was nominally 10°, 20° and 55° depending upon the size of the horn antenna. The equipment covered frequencies between 24 GHz to 40 GHz and was capable of measuring path losses up to 160 dB with the appropriate antenna. The experimental work involved performing measurements in different scenarios and then comparing to existing channel models (if such exist) and suggesting improvements where appropriate. The thesis focuses on outdoor and out- door to indoor mmWave wireless propagation channels and contains contributions in each of the key scenarios as follows: Rural Macro (RMa) channel measurements were performed at 24 GHz. Average path loss and Angle of Arrival (AOA) spread were close to 3GPP predictions limited to sub 7 GHz frequencies. The results were submitted to the Third Generation Partnership Project (3GPP) enabling the extension of the existing RMa model to 30 GHz. Urban Macro (UMa) have base station (BS) antennas above roof-top height. Measure- ments at 27.1 GHz were performed in two environments; dense urban and light urban, both classified as NLOS UMa. The results were compared against two competing 3GPP path loss models; the alpha beta (AB) model and the close-in free space reference dis- tance (CI) model. The AB model had the lower RMS error. The AB model required input parameters such as average building height and street width etc. which made it sensitive to the choice of input parameters, whereas the CI model required no input pa- rameters and was preferred if the cell consists of wide variety of dense and light urban regions. Urban Micro (UMi) have BS antennas below roof-top height. Measurements were con- ducted at 39.5 GHz in Open Square (OS) and Street Canyon (SC) scenarios. Results showed that the extracted parameters are in close agreement with 3GPP specifications, particularly for the CI model. Additionally, we reported 31 dB for 100 m down the SC side streets out of which 18 dB loss occurs just around the corner. We further analysed the base station (BS) height gain effect in OS and found a marginal benefit of 0.5 dB for a 4 m height change. Cross polar discrimination were also reported in SC which reduced by 2.5 dB per 10 dB increase in path loss using directional antennas while correlation disappeared on a omnidirectional basis. We presented a double-directional measurements for an UMi OS environment. Results showed that multiple Angles of Departure from a given user equipment (UE) position often result in few (often one) Angles of Arrival at the BS. Similarly different UE lo- cations can often share a common angle of arrival at the BS. This could cause rank reduction in some MIMO system. An outdoor to indoor measurement campaign at 24 GHz emulating the satellite to in- door propagation channel was presented. The results are applicable to the satellite/mo- bile co-existence problem as well as in-building coverage from high altitude platform. The mean building entry loss increased by 0.43 dB per degree of (satellite) slant eleva- tion angle, almost twice the ITU recommendation. Further we showed that the signal linearly decays with distance with a slope that increases with slant angle. Additionally, we showed that high gain narrow beam antenna outperformed low gain wide beam an- tenna both in terms of signal maximization to high altitude platform as well as signal minimization to a co-existing satellite uplink channel. Further, there is an antenna gain reduction in this type of environment due to internally generated multipath.

This thesis focuses on the implementation of high resolution phase shifter devices for adaptive cancelling applications. Cancelling is a potential replacement for filtering in wireless handsets, where the area allocated to filtering is becoming excessive due to the growing numbers of transmission frequencies. Cancelling circuits have the potential to be integrated directly in silicon as part of the radio circuit. Adaptive cancelling requires precise adjustments of the gain and phase of the reference RF signal.

Intrabody communications (IBC) is a novel physical layer outlined in the recently ratified IEEE 802.15.6 Wireless Body Area Network (WBAN) standard. This data communication method uses the human body itself as the signal propagation medium.

The current trend in healthcare is the move towards proactive health monitoring and making health one’s responsibility. This has seen a proliferation of wearable devices that monitor physical and physiological parameters in real time. However, there is an increasing need to monitor internal body parameters, detect risks and act on them in a timely manner. Implanted medical devices (IMDs) are gaining recent attention due to their capability to provide diagnostic, therapeutic and assistive functionalities. With a projected annual growth of 7.1 % (2016- 2022) the global market share of IMDs is expected to reach 116.3 billion USD by year 2022. In Australia alone, the clinical use of remotely monitored IMDs has risen sharply from 987 (2013-14) to 2269 in just two fiscal years. The increasing demand for ubiquitous and minimally invasive implants is due to the prevalence of chronic disease and growing aging population. While bio-sensing and implant drug delivery techniques have improved tremendously, implant communication technology has advanced at a slower rate. This poses problems for the new generation of implants such as brain computer interfaces (BCI), controllers for artificial prostheses and bionics which will require higher data rates. Existing IMD communications are mainly enabled through antenna based radio frequency links that rely on electromagnetic (EM) wave propagation at ultra high frequencies (UHF). The Medical Device Radio Communication Services (MedRadio) band (401-406 MHz) and Industrial Scientific and Medical radio (ISM) band (2.4 GHz) are most commonly used. However, the human body has a high attenuation to signals at these high radio frequencies; as a result, transceivers tend to consume high power and require complex circuitry to mitigate channel attenuation effects. Lower RF frequencies (lower attenuation through the body) require larger antenna sizes resulting in larger implant sizes. On the other hand, while inductively coupled techniques use lower frequencies (lower path loss), they generally have a narrow transmission band and lower data rates. Thus, the race is on to develop new implant data transmission techniques that consume less power yet provide high (acceptably high) data rates. The thesis addresses this challenge by investigating an alternative implant communication technique using intrabody communication (IBC) mechanisms, specifically galvanically coupled IBC (gc-IBC). This communication method utilises the human tissue as a volume conductor for data communications. In this thesis we began by critically reviewing existing and emerging implant communications technologies. We then proposed and investigated gc-IBC as a new alternative implant communication technology. A novel analytical framework that modeled the human body as a communication channel was proposed. Simulation results were experimentally confirmed by measurements on phantom body solutions. The framework was then extended to analyse a hybrid communication scheme for cortical implants that utilised gc-IBC and the popular inductively coupled data transfer (ic-DT). It was found that for the same frequency range, gc-IBC offers a wider bandwidth for data transmission compared to ic-DT while ic-DT was better for wireless power transfer due to its narrow band characteristic and lower path loss at the resonant frequency. It was also shown that gc-IBC provided 20 dB lower path loss than antenna based RF schemes for the same transmit power. Then, an integrated sensor gc-IBC implant transceiver prototype was designed and developed to characterise and demonstrate the feasibility of implant communication using gc-IBC mechanism. The integration of the sensor into the transmitter was made in a way that minimises transmitter complexity which was crucial to achieve high degree of miniaturisation and low power consumption. Transceiver characterisation experiments were conducted using an automated mechatronic rig that is specifically designed and built for this work. The rig moves the receiver inside the phantom solution in the three axes with respect to the transmitter and is capable of computing the bit error rate (BER) of the reception. The transceiver demonstrated the feasibility of gc-IBC scheme for implants with a BER of 1.1 ×10−4 at signal to noise ratio (SNR) of 8 dB which is better compared to existing uncoded schemes. The gc-IBC channel noise was characterised for the first time as a function of transmission distance and was found to be -118 dB/Watt on average. Future work will focus on extending the framework to model more complex parts e.g., organs, channel capacity estimation under different setting, testing different coding schemes to improve transceiver performance and miniaturisation.

The popularity of smart phones, cloud computing and the growing market for machineto- machine communications is fuelling the growth of mobile broadband. More frequency bands are therefore being allocated to mobile services. Unfortunately, for historical reasons, these band allocations are fragmented, poorly harmonised between different countries and no longer large enough for the ever-increasing broadband data rates. Carrier aggregation, the operation on two or more bands at once, will be necessary. A future wireless terminal capable of global roaming would therefore have to handle 35 bands, and be capable of carrier aggregation. This is the research challenge. Duplexing is a technique to simultaneously transmit and receive information from the same antenna. Frequency Division Duplex uses two frequency bands for uplink and downlink communications, enabling the transmitter and receiver to operate continuously. Duplexing filters are essential for isolating the receiver from the strong self transmitted signal. Unfortunately the filters are expensive, non tunable and not suitable for integration into silicon. Each new frequency band requires its own duplexing filter and a complex array of switches and filters is required for multi-band operation This work presents an adaptive duplexer architecture compatible with silicon integration. It is tunable over a wide frequency range and capable of carrier aggregation. The structure uses a combination of a low isolation device with multiple analog cancelling loops controlled by a normalised least mean square algorithm to track changes in signal leakage. The control is a multi-input multi-output problem. However the use of the ”inverse plant control technique” enables orthogonalisation into multi single-input single-output problems, simplifying the structure and reducing convergence time over previous search algorithms. Convergence takes 10ms from ’cold’ and tracking has a latency of 1.5ms. Low power pseudo noise pilot signals placed in the receive bands measure the cancelling error residues used as feedback to the controller. The pilot generator is integrated into silicon using the Peregrine UltraCMOSr GC process. The generator was programmable to four sequence lengths and 8 delays for correlation purposes. The maximum chip rate of 100Mchip/s was more than the 10Mchip/s required for an LTE channel.

Increasing interest in self health monitoring and performance analysis has resulted in a growing number of human health sensor devices. Such devices usually take the form of small, wearable and battery powered electronic systems that emphasise low power consumption and minimum discomfort to the user. While such sensors may be helpful on their own, increased benefits can be realised though the implementation of an integrated sensor network around the human body. In 2012, the IEEE 802.15.6 standard was introduced to provide a common communications protocol that may be adopted by sensor devices using three types of physical layer communications methods: ultra wideband radio frequency, narrow band radio frequency and human body communications. While narrow band and ultra wideband communications utilise traditional electromagnetic wave propagation, human body communications relies on electrostatic coupling between the transmitter and receiver. Electrostatic coupling has the benefit of reduced attenuation when used in body area networking applications. This thesis presents an implementation of an IEEE 802.15.6 compliant transceiver using the human body communications physical layer. The thesis covers the design and implementation of the digital and analogue electronics necessary to meet the requirements of the standard, as well as describing a prototype transceiver that was developed to confirm correct operation of the design. The transceiver design has been developed in full for the purpose of this thesis. The prototype transceiver is capable of sustaining up to 763Kbps at a bit error rate of 0.21 at the maximum data date, or for improved quality of service, lower data rates may be used with a minimum bit error rate of 0.06. Complete FPGA proven hardware descriptions of the digital system are provided in addition to a mixed signal testbench, allowing end-to-end simulation of the entire communications channel.

The evolution of new telecommunication standards is increasingly leaning towards higher data transmission rates. The boundaries between digital and analog signal processing is impending closer to the antenna, therefore aiming for a software-defined radio solution. In terms of analog-to-digital converters (ADCs) of mobile terminal receivers, this indicates higher sample rate, lower power consumption and higher resolution. With comparison to other ADCs, the pipelined ADC architecture has most successfiilly covered the wide resolution limits and data rate requirements of these terminal receiver architectures. However, even though fix word-length pipeline ADC architecture could be a suitable device for the mobile receiver, it still has a distinct disadvantage when it comes to power consumption. In this thesis, the requirements of ADC of the mobile receiver architecture are studied and analysed using the system specifications of the 3rd Generation (3G) Wideband Code Division Multiple Access (WCDMA) standard.

This thesis considers the incorporation of cooperative relays into a cognitive radio network. Cognitive radio is a potential solution to the growing scarcity of radio spectrum and the increased demand for wireless services. Cooperative relay networks can help cognitive radios to improve their utilisation by reducing their transmit power. This allows a reduction in their interference footprint and increases their probability of accessing licensed spectrum, improving throughput, and/or coverage. A cognitive relay network model has been analysed to derive the closed-form outage probability expressions for the repetition-based and selection-based protocols. Both decode-and-forward and amplify-and-forward relaying schemes have been employed for these protocols. When the probability of spectrum availability is unity, the cognitive relay behaves as a conventional cooperative relay. An identical and independently distributed slow fading Rayleigh channel model has been assumed in the analysis. The outage probability expressions are valid for arbitrary signal-tonoise ratios. This is an improvement on the previously published work which was limited to high signal-to-noise ratio regimes.

The placement of base station transceivers at close proximity to one another is a major challenge for RF engineers. In a colocated setting, the base station receivers have to receive weak desired signals in the presence of high-power transmit/jamming signals from colocated base station transmitters; resulting in major interference issues. The thesis identifies two major mechanism of interference for the colocated victim receiver. First, the strong jamming signals mix within the victim receiver front-end to produce intermodulation products that may fall on its desired receive channel and cause interference. The strong signals may also saturate the receiver circuits and cause desensitization. Second, large jamming signals from one colocated transmitter can radiate into the antenna system of a second colocated transmitter. The signals enter the second transmitter in the reverse direction and mix in the output stage of its power amplifier to produce intermodulation products. These ‘reverse’ intermodulation products get radiated from the antenna system and may fall on the victim receiver’s desired channel.

Adaptive antenna arrays have recently been introduced to cope with the high capacity required by the 3rd generation (3G) wireless communications systems. As adaptive antenna arrays focus narrow high gain beams towards the desired user and nulls towards interferers, both coverage and capacity of the network can be improved. To establish the performance gain that a smart antenna can deliver in a 3G environment (i.e., with mixed traffic), the implementation of adaptive antenna arrays for the uplink of a Wideband Code Division Multiple Access (WCDMA) system in the Frequency Division Duplex (FDD) mode is addressed in this thesis. The beam-forming is implemented with a LS - DRMTA algorithm and a Lagrange multiplier based algorithm using the Q channel only. The results show that the adaptive antenna arrays offer significant performance enhancement over switched beam and single antennas in a 3G environment (i.e., with mixed traffic).

AbstractThe current stochastic model in GNSS processing is constructed based on the prior experience, for example the ratio of the weight of the pseudorange and phase observations is generally determined as 1:10000. These methods ignore the precision differences of the different GNSS receivers and observation space. In this paper, the standard deviation of differenced ionosphere-free pseudorange and phase observations is computed with dual-frequency observations and then the weight ratio of the pseudorange and phase observations is obtained using the computed standard deviation. This method is introduced in satellite clock estimating and the data is processed. The results show that the presented method is feasible, with which the accuracy of the estimated satellite clock results is improved. The estimated satellite clock results are further adopted in PPP and the positioning results of the 10 users validate that the estimated satellite clock, which uses the presented method, can accelerate the convergence of PPP compared with the traditional method.

Terahertz electromagnetic wave is one of the hottest research topics in nowadays scientific world thanks to its broad applications in material characterization, medical imaging, wireless communication, and security checking etc. Using free-electron beams to interact with periodic structures via the famous Smith-Purcell effect is an efficient way of generating high-power terahertz radiation. In this chapter, we introduce the basic theory and latest developments of the terahertz radiation schemes using a free-electron beam (including continuous electron beam, a single electron bunch, and a train of electron bunches, etc.) to interact with periodic electromagnetic structures, including grating, surface plasmonics, and subwavelength hole arrays, via a special Smith-Purcell effect or Cherenkov-like effect. A kind of free-electron lasers based on the special Smith-Purcell radiation in the terahertz region is proposed and investigated, which can be developed as high-power terahertz wave sources for practical applications.

In this chapter the authors present an overview and an evaluation of ICT policy in Brussels based on an analysis of policy documents and interviews with 12 policy experts. They discuss two types of policies enhancing structural participation (digital education policy for youngsters and digital adult education policy) and two types of policies enhancing socio-cultural participation (wireless networks in Brussels and E-government of Brussels) To contextualize this presentation of policies some results from a survey among youngsters (N=1005) and from exploratory focus groups will be used as well. These policies are evaluated as policies with a well-intended access approach, but the necessity to focus more on digital education and not only on digital access is stressed.

In this research, the aim is to design and implement a new low noise amplifier (LNA) for a multi-standard mobile receiver based on reconfigurability concept. The LNA design is based on the inductively-degenerated common-source (IDCS) topology as it has been proven to be a good choice in designing multi-standard multi-band LNA. The design is using 0.18 µm CMOS technology. The reconfigurable LNA has been designed to operate in two bands of standards consisting the bands range from 800 to 1000-MHz (lower band) and 1800 to 2200-MHz (upper band). The simulation results exhibit gain S21 of 12.9-dB for lower band and 12.4-dB for upper band, input reflection S11 of -14.5-dB and -17.2-dB for both bands, and output return loss S22 of -14.7-dB and -26-dB for lower and upper band making the LNA suitable for most of the mobile communication applications. The LNA also exhibits the noise of figure of 2.55-dB and 2.3-dB for lower and upper band respectively. The circuit consumes 26.5 mW when operating in lower band mode and uses 18.8 mW of power when operating in upper band mode.

In order to increase the higher competition in low-power wireless network communication market, a high-performance and low-cost product is necessary to distinguish the difference with others. Through integrating the system performance with suitable L-shape impedance-match circuit assisting with some network analyzer, this target with a 2.4 GHz radio-frequency (RF) product in long-distance data transportation seems to be promisingly implemented. In short-distance data transportation, the ideal output-link transportation rate (∼ max. 54 Mb/sec) is slightly influenced by impedance mismatch between power amplifier (PA) and antenna port. However, it is tremendously reduced at long-distance condition and the transportation rate is decreased to ∼ 24 Mb/sec. Using the attenuator to attenuate the real input signal to –70dB to simulate the real signal transportation, the packet error rate (PER) is less than 10% at a physical sublayer service data unit (PSDU) length of 1000 bytes under the communication 802.11g spec. as the real transmission rate is 20 Mb/sec. If the impedance of the transmission line is shifted, the long-distance transportation rate will be reduced to, almost, 20 × 24 / 54 = 8.8 Mb/sec. The transportation performance is greatly deducted. With the delicate design and the feasible component arrangement, the impedance mismatch influencing the long-distance (∼ 100 m) data transportation is overcome and reduced to the acceptable range. In this investigation using 3.3 V power supply, we observe that the selection of electronic components with miniaturization is also an art to reduce the radiation side-effect.