Search

In mobile radio communications, inter-cell handover algorithms represent a critical issue for future pico and micro cellular systems. Two conflicting criteria must be optimized: the number of unnecessary handovers between two adjacent base-stations and the number of lost calls. A handover algorithm is proposed which utilizes a decision criterion such as signal strength. It allows for optimal trade-off between the number of unnecessary handovers and the number of lost calls. It is based on Bayes criterion which is commonly used in detection and estimation techniques. An optimal threshold q is derived using this criterion, which depends on the decision criterion and is dynamically adjusted by taking into account the observations. The decision of handover is made by comparing the distance d between the mobile station and the current base-station to this threshold q., This is a DSP application to hand-over procedures in mobile communications. (The most recent upgrade of the original software package that calculates Time-Frequency Distributions and Instantaneous Frequency estimators can be downloaded from the web site: www.time-frequency.net. This was the first software developed in the field, and it was first released publicly in 1987 at the 1st ISSPA conference held in Brisbane, Australia., and then continuously updated). A companion is the comprehensive book on Time-Frequency Signal Analysis and Processing available at: http://www.elsevier.com/locate/isbn/0080443354

Radio resource management (RRM) across multiple, potentially competing, wireless networks has emerged as a salient feature for future generation system. Besides increased overhead, it will incur more complicated architectures and the question then becomes whether the gains of cooperative RRM (increased throughput, reliability, etc.) can justify these disadvantages. Herein we study potential gains that can be achieved by utilizing sophisticated algorithms in a scenario with two cooperating IEEE 802.11a networks, limited by either the wireless or wired link. Both best-effort (BE) and minimum bitrate (MBR) are treated and throughout the paper we use the rudimentary minimum path-loss (MPL) allocation as reference. Our results indicate that sophisticated access selection methods that besides path-loss, also account for AP load and potential constraints in the wired connection, can increase performance significantly. The maximum gain varies between 30-60% and 100-150% for BE and MBR traffic respectively and is typically obtained when there, on average, is one user per AP. We also studied the case where APs with constrained wired capacity connected (using the MPL criteria) to high-capacity APs in order to reroute traffic. Contrary to the approach in which advanced allocation principles is used, "loose" network integration is sufficient and even though it gave lower gains for BE data, the achievable rates for MBR data could be improved substantially., QC 20101108

An efficient combination of radio access technologies, integrated in a multi-access network, will be a key enabler in future provisioning of mobile data services. This paper addresses a scenario where an incumbent mobile network operator, with an existing 2G and 3G infrastructure, has deployed a dense WCDMA/HSPA macro-cell network in an urban area. With this high capacity network deployed, upgrading previous 2G and 3G systems with EDGE and HSPA respectively may seem obsolete. However, even though these systems may not support the intended data rates alone, they could, thanks to favorable propagation characteristics and the additional spectrum available, be useful as complements. Simulation results indicate that upgrading GPRS base stations with EDGE, or a sparse WCDMA macro cell layer with HSPA, mainly would benefit uplink transmission. For this case, the data rate that can be guaranteed with 95 % area availability (coverage) can be increased with approximately 40-100 %. In the downlink, though, the dense WCDMA/HSPA system alone supports user data rates of 500 kpbs for all relevant user densities. Thus, upgrading legacy infrastructure would be obsolete., QC 20101108, SRA - Informations- och kommunikationsteknik

This paper presents an analytical framework for the theoretical characterization and performance evaluation of an MC-CDMA forward-link in the presence of nonlinear distortions induced by transmitter's high-power amplifiers. The analytical characterization of the signal features, both in the time and frequency domains, is carried out through the application of the Bussgang theorem. Simulation results are derived to validate the accuracy of the proposed method under typical operating conditions 1. © 2006 IEEE.

Demand for small and low-profile antennas has greatly increased due to the desire for miniaturisation of modern-day mobile radio electronic terminals. Such an antenna is often integrated into the dielectric casing of a terminal, or independently enclosed within a dielectric radome to provide a protection from operating environments and keep the system more compact. However, the dielectric casing or radome may interact strongly with the antenna and result in losses in performance. The primary focus of this dissertation is to investigate and enhance the performance of Planar Inverted-F Antennas (PIFAs) when enclosed in dielectric casings or radomes for applications in mobile radio communications. PIFAs have attracted much interest due to their small volume, low profile structures and electrical characteristics compatible with existing specifications, making it a promising candidate for mobile radio applications. Therefore, the design of a single band PIFA on a finite ground plane, operating in the 900 MHz band is first presented. It is found that the effect of the finite ground plane must be considered to achieve an optimum performance of the PIFA. Then the performance of this antenna in the presence of a dielectric cover layer is investigated and evaluated in terms of resonant frequency, bandwidth and efficiency. In this study, the dielectric layer represents the dielectric casing of a device where the antenna is much closer to the top part of the casing than to the other side parts whose effect can then be ignored. Computer simulations of performance are based on the Method of Moments (MOM) and have been validated by measurements. This study shows that a dielectric cover layer will strongly interact with the antenna with the result that the antenna performance may move outside the design specifications.Therefore, it is concluded that the dielectric cover layer must always be taken into account in the design stage. In addition, the input and radiation characteristics

In this paper we present an adaptive Block-Based EigenVector Algorithm (BBEVA) for blind equalization of time-varying multipath fading channels. In addition we assess the performance of the new algorithm for different configurations and compare the results with the least mean squares (LMS) algorithm. The new algorithm is evaluated in terms of intersymbol interference (ISI) suppression, mean squared error (MSE) and by examining the signal constellation at the output of the equalizer. Simulation results show that the BBEVA performs better than the non-blind LMS algorithm.

In this paper we present an adaptive Block-Based EigenVector Algorithm (BBEVA) for blind equalization of time-varying multipath fading channels. In addition we assess the performance of the new algorithm for different configurations and compare the results with the least mean squares (LMS) algorithm. The new algorithm is evaluated in terms of intersymbol interference (ISI) suppression, mean squared error (MSE) and by examining the signal constellation at the output of the equalizer. Simulation results show that the BBEVA performs better than the non-blind LMS algorithm.

In this paper we present an adaptive Block-Based EigenVector Algorithm (BBEVA) for blind equalization of time-varying multipath fading channels. In addition we assess the performance of the new algorithm for different configurations and compare the results with the least mean squares (LMS) algorithm. The new algorithm is evaluated in terms of intersymbol interference (ISI) suppression, mean squared error (MSE) and by examining the signal constellation at the output of the equalizer. Simulation results show that the BBEVA performs better than the non-blind LMS algorithm.

Spatial diversity is an attractive technology to cope with the fading channel encountered in mobile communications. This paper presents novel closed analytical expressions of the bit-error rate (BER) achievable in a coherent binary phase-shift-keying (CBPSK) direct-sequence code-division multiple-access (DS/CDMA) system for any power delay profile and for either postdetection selection or maximal ratio combining (MRC). In particular, expressions for the cutoff rate Ro and for its related parameter D are also formulated in order to assess the system performance under the consideration of some channel coding schemes. Finally, an exemplary study is carried out in order to illustrate the behavior of a realistic space-diversity code-division multiple-access (CDMA) system according to the analytical expressions that have been derived, Peer Reviewed