Wireless ATM plays a key role in the realization of broadband wireless networks. The transmission of various classes of traffic and the provision of bandwidth on demand over a wireless channel poses a number of new technical challenges. This thesis addresses the design of a low cost adaptive transmitter for fixed wireless ATM/B-ISDN systems with emphasis on optimum use of wireless network resources. A new architecture for a direct microwave wireless ATM transmitter is proposed. The transmitter capacity adaptation is implemented by using an admission control metric and an M-QAM modulator. The two main components of the transmitter are: an M-QAM control unit and a direct microwave QAM modulator unit. The M-QAM control unit is used to select an optimum modulation level for the QAM modulator. The modulation level is adjusted based on the bandwidth demand, QoS requirements, and outage conditions of the wireless ATM link. The direct microwave QAM modulator unit transforms the broadband traffic to a modulated microwave signal that is suitable for transmission over a wireless network. The required bandwidth of the broadband traffic is estimated using an effective bandwidth metric. An analytical relation, called the capacity reduction factor, is derived to represent the performance degradation due to the wireless channel and channel fading in a B-ISDN network. Using the effective bandwidth metric and the capacity reduction factor, a QoS metric for the wireless broadband network is introduced. This metric is termed as, modified effective bandwidth. This metric is used to adapt the M-QAM modulator. Another significant contribution of this research work is a new architecture for the direct QAM modulator. This is based on use of PIN diode reflection attenuators. The PIN diodes operate in forward bias condition thereby overcoming the speed limitation problem due to charge storage. Using residue theory, analytical results to model the large signal forward bias operation of PIN diodes are presented. This theory also examines the transition time of a PIN diode with bias changes from a reverse bias to a forward bias. The direct microwave QAM modulator implementation using MIC and silicon MMIC technologies is examined. While a realization using MIC is simple and straightforward, a silicon MMIC realization offers a very cost effective solution. A system study was conducted to examine the operation of the adaptive direct microwave M-QAM modulator in the wireless channel with ATM traffic. The operation has been examined for different wireless channels and for various classes of traffic. The call acceptance and outage performance are compared with those for a fixed QAM modulator. The results show that the proposed system can be used for implementation of cost effective adaptive transmitters for broadband wireless applications.

Analytic models for the performance of the forward link of 3G CDMA systems using different maximum ratio combining (MRC) RAKE finger weight assignments are presented. The spreading modulations under investigation are the balanced QPSK and the complex-spreading QPSK. The models are computationally efficient, accurate, and applicable to Root Raised Cosine (RRC) pulse shaping with any roll-off factor, variable processing gain, chip rate, and data rate for orthogonal codes, random codes, quasi-orthogonal codes, Gaussian noise, and realistic channel models. The expressions derived are then used to obtain the so-called orthogonality factor, which is commonly used in system-level simulations. Next, closed-form mathematical expressions for the variance due to infinite chips interfering in systems using arbitrary Nyquist pulses are derived. These expressions are applicable to both the forward link and the reverse link. For the latter, the existing knowledge on the accurate and efficient estimation of the performance of CDMA systems is extended by presenting closed mathematical expressions for bandlimited systems using arbitrary Nyquist pulses for both BPSK and Offset-QPSK (OQPSK) modulation. The impact of adjacent channel interference in bandlimited systems is subsequently considered. Finally, mathematical expressions for the accurate and efficient estimation of a CDMA system using RRC pulse-shaping and a RAKE receiver in the presence of multipath interference are presented.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 143-150). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S. in Computer Science and M.S. in Electrical Engineering)--Naval Postgraduate School, March 2004. / Thesis advisor(s): Gilbert M. Lundy, Roberto Cristi. Includes bibliographical references (p. 95-97). Also available online.

Thesis (M.Eng.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves 111-113.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: indoor geolocation; TOA. Includes bibliographical references (p. 97).

The wide bandwidth employed in the UWB system allows for high data-rate communications, while its broadband nature requires it to coexist with other systems. For instance, several communication systems, such as digital TV, wireless LANs, WiMAX, and satellite receivers, utilize spectrum that is in the UWB band. According to Federal Communications Commission (FCC) regulations, the power spectral density (PSD) of UWB devices for communication applications is limited to less than -41.25dBm/MHz in the 3.1-10.6GHz frequency band, to minimize the impact of UWB on other systems. The impact of narrowband signals on UWB systems can also be significant, even though these signals may occupy a small part of the UWB spectrum, due to their much larger power. The performance and capacity of UWB systems can be significantly degraded by these narrowband interferers. In-band interference can be tolerated by increasing the dynamic-range of the receiver such that the interferers are accommodated within the linear range of the receiver. Alternatively, if the interferers can be avoided altogether, the excessive linearity requirements imposed by the interferers can be relaxed. Such an avoidance mechanism requires the ability to detect interferers. This work presents a low-power and low-cost detector for this purpose that can be employed in multi-band approaches to UWB, including pulse-based schemes, and those employing OFDM. The UWB band is divided into narrower sub-bands in these schemes. During transmission, the carrier hops to a new sub-band every symbol. The detector is designed to provide a profile of interference over the entire UWB spectrum, during each symbol period. This information would be available to the main-path UWB receiver to decide a frequency sequence of sub-band hopping, in order to avoid sub-bands occupied by large interferers. This relaxes the dynamic-range requirement, and hence the power dissipation of the main-path receiver, thus compensating for the extra power dissipation of the detector. The detector is based on a cascade of image-reject downconverter stages. An implementation of the architecture is demonstrated in a 0.13[mu]m CMOS process. / text

WiFi can be used to provide cost-effective last-mile IP connectivity to rural users. In initial rollout, hotspots or hotzones can be positioned at community centres such as schools, clinics, hospitals or call-centres. The research will investigate maximizing coverage using physical and higher layer techniques. The study will consider a typical South African rural region, with telecommunications services traffic estimates. The study will compare several IEEE 802.11 deployment options based on the requirements of the South African case in order to recommend options that improve performance. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007.

Technologies such as WiFi and WiMAX, can be a powerful driving force for increasing rural / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007.

Thesis (Ph.D.) - Swinburne University of Technology, School of Biophysical Sciences and Electrical Engineering, 2000. / Submitted for the degree of Doctor of Philosophy, School of Biophysical Science & Electrical Engineering, 2000. Typescript. Includes bibliographical references (p. 133-145).