Design of a tunable multi-band differential LC VCO using 0.35 mu m SiGe BiCMOS technology for multi-standard wireless communication systems

In this paper, an integrated 2.2-5.7GHz multi-band differential LC VCO for multi-standard wireless communication systems was designed utilizing 0.35 mu m SiGe BiCMOS technology. The topology, which combines the switching inductors and capacitors together in the same circuit, is a novel approach for wideband VCOs. Based on the post-layout simulation results, the VCO can be tuned using a DC voltage of 0 to 3.3 V for 5 different frequency bands (2.27-2.51 GHz, 2.48-2.78 GHz, 3.22-3.53 GHz, 3.48-3.91 GHz and 4.528-5.7 GHz) with a maximum bandwidth of 1.36 GHz and a minimum bandwidth of 300 MHz. The designed and simulated VCO can generate a differential output power between 0.992 and -6.087 dBm with an average power consumption of 44.21 mW including the buffers. The average second and third harmonics level were obtained as -37.21 and -47.6 dBm, respectively. The phase noise between -110.45 and -122.5 dBc/Hz, that was simulated at 1 MHz offset, can be obtained through the frequency of interest. Additionally, the figure of merit (FOM), that includes all important parameters such as the phase noise, the power consumption and the ratio of the operating frequency to the offset frequency, is between -176.48 and -181.16 and comparable or better than the ones with the other current VCOs. The main advantage of this study in comparison with the other VCOs, is covering 5 frequency bands starting from 2.27 up to 5.76 GHz without FOM and area abandonment. Output power of the fundamental frequency changes between -6.087 and 0.992 dBm, depending on the bias conditions (operating bands). Based on the post-layout simulation results, the core VCO circuit draws a current between 2.4-6.3 mA and between 11.4 and 15.3 mA with the buffer circuit from 3.3 V supply. The circuit occupies an area of 1.477 mm(2) on Si substrate, including DC, digital and RF pads

CHARACTERIZATION OF HOTSPOT COVERAGE PLAN IN 2.4/ 5GHZ FREQUENCY BAND (NNAMDI AZIKIWE UNIVERSITY, NIGERIA, AS A CASE STUDY)

Research and tertiary institutions today uses wireless connectivity owing to the benefits of mobility flow-awarecommunication and flexibility advantages generally. In this case, mobility computing involving the use of smartdevices, laptops, wifi-desktops, etc, largely depends on a deployed hotspot infrastructure. In particular, the physicalposition of the mobile system (and hence of the user) and the hotspot infrastructure design layout are fundamentalconsiderations for service efficiency. While previous works have focused on user position estimation, signal strengthquality and network QoS, this work leverages the contemporary challenges of network connectivity in tertiaryinstitutions in Nigeria with respect to optimal coverage and cost minimization. Using Nnamdi Azikiwe University-Unizik, Awka as testbed, we carried out a study on hotspot/WLAN IEEE 802.11 deployments while devising a costeffective coverage plan in 2,4/5GHz frequency band. A mathematical model on cost optimization for WLANHotpot project processes was developed using Linear programming, the installation procedure, coverage plan basedon specifications of the deployment hardware, and data security were covered in this work. Consequently, from themodel, we argue that with careful selection of optimization criteria in the deployment, an efficient design cost plan,and QoS, could eliminate possible trade-offs in the deployment contexts by over 95%.Keywords: Mobility, Flow-aware, Hotspot, Infrastructure, Optimization, Design, Minimizatio

Performance Study of Hybrid Spread Spectrum Techniques

This thesis focuses on the performance analysis of hybrid direct sequence/slow frequency hopping (DS/SFH) and hybrid direct sequence/fast frequency hopping (DS/FFH) systems under multi-user interference and Rayleigh fading. First, we analyze the performance of direct sequence spread spectrum (DSSS), slow frequency hopping (SFH) and fast frequency hopping (FFH) systems for varying processing gains under interference environment assuming equal bandwidth constraint with Binary Phase Shift Keying (BPSK) modulation and synchronous system. After thorough literature survey, we show that hybrid DS/FFH systems outperform both SFH and hybrid DS/SFH systems under Rayleigh fading and multi-user interference. Also, both hybrid DS/SFH and hybrid DS/FFH show performance improvement with increasing spreading factor and decreasing number of hopping frequencies

A General Framework for Analyzing, Characterizing, and Implementing Spectrally Modulated, Spectrally Encoded Signals

Fourth generation (4G) communications will support many capabilities while providing universal, high speed access. One potential enabler for these capabilities is software defined radio (SDR). When controlled by cognitive radio (CR) principles, the required waveform diversity is achieved via a synergistic union called CR-based SDR. Research is rapidly progressing in SDR hardware and software venues, but current CR-based SDR research lacks the theoretical foundation and analytic framework to permit efficient implementation. This limitation is addressed here by introducing a general framework for analyzing, characterizing, and implementing spectrally modulated, spectrally encoded (SMSE) signals within CR-based SDR architectures. Given orthogonal frequency division multiplexing (OFDM) is a 4G candidate signal, OFDM-based signals are collectively classified as SMSE since modulation and encoding are spectrally applied. The proposed framework provides analytic commonality and unification of SMSE signals. Applicability is first shown for candidate 4G signals, and resultant analytic expressions agree with published results. Implementability is then demonstrated in multiple coexistence scenarios via modeling and simulation to reinforce practical utility

Realization of a voltage controlled oscillator using 0.35 um sige-bicmos technology for multi-band applications

The stable growth in wireless communications market has engendered the interoperability of various standards in a single broadband frequency range from hundred MHz up to several GHz. This frequency range consists of various wireless applications such as GSM, Bluetooth and WLAN. Therefore, an agile wireless system needs smart RF front-ends for functioning properly in such a crowded spectrum. As a result, the demand for multi-standard RF transceivers which put various wireless and cordless phone standards together in one structure was increased. The demand for multi-standard RF transceivers gives a key role to reconfigurable wideband VCO operation with low-power and low-phase noise characteristics. Besides agility and intelligence, such a communication system (GSM, WLAN, Global Positioning Systems, etc. ) required meeting the requirements of several standards in a cost-effective way. This, when cost and integration are the major concerns, leads to the exploitation of Si-based technologies. In this thesis, an integrated 2.2-5.7GHz Multi-band differential LC VCO for Multi-standard Wireless Communication systems was designed utilizing 0.35μm SiGe BiCMOS technology. The topology, which combines the switching inductors and capacitors together in the same circuit, is a novel approach for wideband VCOs. Based on the post layout simulation results, the VCO can be tuned using a DC voltage of 0 to 3.3V for 5 different frequency bands (2.27-2.51 GHz, 2.48-2.78GHz, 3.22-3.53GHz, 3.48-3.91GHz and 4.528-5.7GHz) with a maximum bandwidth of 1.36GHz and a minimum bandwidth of 300MHz. The designed and simulated VCO can generate a differential output power between 0.992 dBm and -6.087 dBm with an average power consumption of 44.21mW including the buffers. The average second and third harmonics level were obtained as -37.21 dBm and -47.6 dBm, respectively. The phase noise between -110.45 and -122.5 dBc/Hz, that was simulated at 1 MHz offset, can be obtained through the frequency of interest. Additionally, the figure of merit (FOM), that includes all important parameters such as the phase noise, the power consumption and the ratio of the operating frequency to the offset frequency, is between -176.48 and -181.16 and comparable or better than the ones with the other current VCOs. The main advantage of this study in comparison with the other VCOs, is covering 5 frequency bands starting from 2.27 up to 5.76 GHz without FOM and area abandonment

Cross-layer analysis for video transmission over COFDM-based wireless local area networks

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Multi-gigabit CMOS analog-to-digital converter and mixed-signal demodulator for low-power millimeter-wave communication systems

The objective of the research is to develop high-speed ADCs and mixed-signal demodulator for multi-gigabit communication systems using millimeter-wave frequency bands in standard CMOS technology. With rapid advancements in semiconductor technologies, mobile communication devices have become more versatile, portable, and inexpensive over the last few decades. However, plagued by the short lifetime of batteries, low power consumption has become an extremely important specification in developing mobile communication devices. The ever-expanding demand of consumers to access and share information ubiquitously at faster speeds requires higher throughputs, increased signal-processing functionalities at lower power and lower costs. In today’s technology, high-speed signal processing and data converters are incorporated in almost all modern multi-gigabit communication systems. They are key enabling technologies for scalable digital design and implementation of baseband signal processors. Ultimately, the merits of a high performance mixed-signal receiver, such as data rate, sensitivity, signal dynamic range, bit-error rate, and power consumption, are directly related to the quality of the embedded ADCs. Therefore, this dissertation focuses on the analysis and design of high-speed ADCs and a novel broadband mixed-signal demodulator with a fully-integrated DSP composed of low-cost CMOS circuitry. The proposed system features a novel dual-mode solution to demodulate multi-gigabit BPSK and ASK signals. This approach reduces the resolution requirement of high-speed ADCs, while dramatically reducing its power consumption for multi-gigabit wireless communication systems.PhDGee-Kung Chang - Committee Chair; Chang-Ho Lee - Committee Member; Geoffrey Ye Li - Committee Member; Paul A. Kohl - Committee Member; Shyh-Chiang Shen - Committee Membe

Modeling and analysis of OFDM with adaptive clipping technique for PAPR reduction

Orthogonal Frequency Division Multiplexing (OFDM) systems are better than single-carrier systems in multipath fading channel environment. OFDM systems are being adapted in many wire-line and wireless high data rate transmission systems of digital video broadcasting (DVB), IEEE 802.11, IEEE 802.16, HIPERLAN Type II, Digital Subscriber Line (DSL), and Home networking etc. There is also strong interest to use OFDM systems in 4G wireless systems. OFDM has recently received increased attention due to its capability of supporting high data rate communication in frequency selective fading environments which cause Inter symbol Interference(ISI). In order to take advantage of the diversity provided by the multi-path fading, appropriate frequency interleaving and coding is necessary. Therefore, coding becomes an inseparable part in most OFDM applications and a considerable amount of research has focused on optimum encoder and decoder design for information transmission through OFDM over fading environments. The OFDM systems use multiple orthogonal subcarriers. Transmission data is loaded on each subcarrier and transmitted after summation. When all subcarriers have same phase than instantaneous power of transmitted signal is very high. The peak power of OFDM scheme is higher than average power. This phenomenon is called PAPR problem. This is one of the main disadvantages of the OFDM system. Power amplifier characteristics are linear until some input value, so for higher peak powers the amplifier characteristic may be nonlinear. If peak powers are not handled in linear part, OFDM signals will get distorted. A definition of PAPR is log-scale of peak power over average power, and PAPR problem appears in all multicarrier systems. Traditionally several techniques are used for reducing PAPR instead of catering for higher peak powers in amplifiers. First, clipping technique is the most famous and simple technique. But it has BER(Bit Error Rate) performance degradation. Second, peak power avoidance precoding technique is used. It has some coding gain but it decrease data rate or increase bandwidth. Third, scrambling technique is used. With the scrambling technique, probability of peak power occurrence goes low, but hardware architecture is more complex. In this thesis, a joint solution is proposed with RS coding, OFDM, and PAPR clipping. We implemented the hybrid method which consists of RS coding and adaptive clipping technique over an additive white Gaussian noise (AWGN) channel. Reed Solomon RS (255, 239) coding can correct 8 symbol errors from 239 symbols data. This capability can effectively compensate for the performance degradation resulted by setting PAPR threshold to 5 in case of 256 QAM, and RS (63, 47) and threshold of 4 incase of 64 QAM. Binary data are grouped into ‘x’ bits and encoded by RS (255, 239) encoder and then modulated by 256 QAM. For 64 QAM, RS (63, 47) is used. In a typical OFDM system consists of N = 52 subcarriers and 64 point IFFT is used. The adaptive clipping technique is used with clipping ratio of 5 for 256 QAM, and clipping ratio of 4 for 64 QAM is used. The symbols are transmitted through AWGN channel. The receiver structure has reciprocal to the transmitter architecture. The implemented hybrid technique based on RS coding and adaptive clipping technique method to compensate the performance degradation caused by clipping. From the simulation results, by using hybrid technique the clipping distortion can be removed when CR = 5 and SNR = 26.5 dB for 256 QAM, and CR = 4 and SNR = 20.5 dB for 64 QAM. The simulation results show that the hybrid method is an effective technique to mitigate the clipping distortions

Investigación en tecnologías de inteligencia ambiental para la salud del futuro

El concepto de Inteligencia Ambiental que fue desarrollado en el documento ISTAG presenta una visión de la Sociedad de la Información futura enfatizando en la proximidad al usuario, eficiencia y soporte a servicios distribuidos, potenciación del usuario y en la facilidad de interacción humana con el entorno

Energy-efficient design and implementation of turbo codes for wireless sensor network

The objective of this thesis is to apply near Shannon limit Error-Correcting Codes (ECCs), particularly the turbo-like codes, to energy-constrained wireless devices, for the purpose of extending their lifetime. Conventionally, sophisticated ECCs are applied to applications, such as mobile telephone networks or satellite television networks, to facilitate long range and high throughput wireless communication. For low power applications, such as Wireless Sensor Networks (WSNs), these ECCs were considered due to their high decoder complexities. In particular, the energy efficiency of the sensor nodes in WSNs is one of the most important factors in their design. The processing energy consumption required by high complexity ECCs decoders is a significant drawback, which impacts upon the overall energy consumption of the system. However, as Integrated Circuit (IC) processing technology is scaled down, the processing energy consumed by hardware resources reduces exponentially. As a result, near Shannon limit ECCs have recently begun to be considered for use in WSNs to reduce the transmission energy consumption [1,2]. However, to ensure that the transmission energy consumption reduction granted by the employed ECC makes a positive improvement on the overall energy efficiency of the system, the processing energy consumption must still be carefully considered.The main subject of this thesis is to optimise the design of turbo codes at both an algorithmic and a hardware implementation level for WSN scenarios. The communication requirements of the target WSN applications, such as communication distance, channel throughput, network scale, transmission frequency, network topology, etc, are investigated. Those requirements are important factors for designing a channel coding system. Especially when energy resources are limited, the trade-off between the requirements placed on different parameters must be carefully considered, in order to minimise the overall energy consumption. Moreover, based on this investigation, the advantages of employing near Shannon limit ECCs in WSNs are discussed. Low complexity and energy-efficient hardware implementations of the ECC decoders are essential for the target applications