Filippo Giannetti

Mobile and Personal Communications in the 60 GHz Band: A Survey

This paper intends to present a summary of the technical issues arising in the exploitation of the 60 GHz mm-wave band for mobile and personal communications. The most significant applications proposed so far are surveyed, with particular emphasis placed on recent experimentation about millimeter-wave propagation for road/railway transportation as well as indoor scenarios. As a case study, the capacity of a (micro-)cellular Code Division Multiple Access (CDMA) network in the 60-GHz band is also evaluated in detail.

Advances in satellite CDMA transmission for mobile and personal communications

An ubiquitous network for multimedia personal communications (Personal Communications Network (PCN)) with small, individual low-cost terminals is one of the most ambitious worldwide projects for the 21st century that are being pursued nowadays. In the development of such PCN, Geostationary, Medium, and Low Earth Orbiting (GEO, MEO, LEO) satellite constellations will play a fundamental role to provide worldwide coverage for most services required by the end-user. The characteristics of efficiency and flexibility inherently required by that scenario suggest, amidst other possibilities, to take into special consideration a radio interface based on code division multiple access (CDMA) to ensure, in addition to the features mentioned above, a sufficient grade of power and spectral efficiency of the relevant satellite radio link. The aim of this paper is a review of the current status of those issues in the field of satellite CDMA transmission systems design that, in our opinion, appear fundamental to the successful operation of an efficient PCN. In particular, we survey the techniques for multiplexing, coding and transmission of direct-sequence spread spectrum (DS/SS) signals, and we touch upon the techniques for the minimization of the self-noise effect, and the related topics of power-control and multiuser detection. We also shortly address in this respect some technological aspects related to an efficient modem design via digital signal processing techniques. The final part of the paper deals more specifically with some typical issues of satellite transmission, namely the minimization of the detrimental effects of the nonlinear satellite transponder and of multipath propagation; the applicability of diversity reception to a multisatellite network is also addressed as possible means of performance boost.

DS-CDMA satellite diversity reception for personal satellite communication: satellite-to-mobile link performance analysis

The satellite-to-mobile link of a mobile personal satellite communication system employing power-controlled direct-sequence code-division multiple access (DS-CDMA) and exploiting satellite diversity is analyzed and its performance compared with a more traditional communication system utilizing single-satellite reception. The semianalytical model developed has been thoroughly validated by means of extensive Monte Carlo computer simulations. System capacity and performance have been numerically evaluated in the presence of a realistic operating scenario, including antenna radiation pattern, imperfect power control, shadowing, and cross-polarization effects. It is shown how the capacity gain provided by diversity reception considerably shrinks in the presence of increasing traffic or in the case of mild shadowing conditions. Moreover, the quantitative results tend to indicate that to combat system capacity reduction due to the intrasystem interference, no more than two satellites sharing the same frequency slot must be active over the same region.

Signal recognition and signature code acquisition in CDMA mobile packet communications

Fast and reliable signal sense and signature code synchronization for direct-sequence spread-spectrum (DS-SS) signals are key issues in the design of the receiver for modern packet code-division multiple-access (CDMA) radio networks for mobile communications; this motivates the study of the signal recognition and code-acquisition (SR/CA) scheme we describe in this paper. Specifically, starting from elementary estimation and detection theory criteria, we work out a noncoherent parallel SR/CA algorithm that is suited to a full-digital implementation in a single application-specific integrated circuit (ASIC). The results of a theoretical analysis of such a scheme, encompassing additive white Gaussian noise (AWGN) and multiple-access interference (MAI), are integrated and validated by an overall time-domain system simulation. We also evaluate through a simplified approach the impact of some degradation factors on the overall circuit performance, namely, sampling epoch and carrier frequency offset and 1-b signal quantization, to allow optimization of the design parameters as a function of the characteristics of the received signal.

Chip-level differential encoding/detection of spread-spectrum signals for CDMA radio transmission over fading channels

This paper is concerned with the design and performance evaluation of a direct-sequence spread-spectrum transmission and signal-detection technique for application to code-division multiple-access mobile radio networks. Unlike the conventional differential encoding/detection of data symbols, such a technique envisages differential encoding/detection of the spreading code chips to counteract the fast time-selective fading encountered in mobile radio transmissions. Binary PSK modulation on a Rician frequency-flat-fading channel is assumed, with Gaussian and Rayleigh channels as particular cases. The bit-error rate performance of the receiver is analytically evaluated as a function of the relevant system parameters, and the impact on the receiver performance of a carrier frequency offset is also investigated.

A novel single base station location technique for microcellular wireless networks: description and validation by a deterministic propagation model

Positioning algorithms in cellular networks has become increasingly important as a means of supporting emerging services that require a sufficiently precise estimation of the position of the mobile terminal (MT) associated with a given base station (BS). Currently, even the most sophisticated positioning algorithms require at least three BSs to achieve satisfactory precision. This paper presents a novel algorithm that makes use of a single-BS antenna array to locate MTs in cellular networks. A triangulation technique is utilized and supported by some minimal information about the environment in the BS neighborhood. This algorithm is shown to perform well when operating in a microcellular environment with perfect channel-parameter estimation. The effect of finite resolution of the input parameters is also investigated. The performance is analyzed for a universal mobile telecommunications system microcellular scenario through a three-dimensional deterministic channel model. Finally, the performance of the proposed positioning technique is compared to the well-known location method based on the time-of-arrival measurements at three different BSs.

Design of an all-digital receiver for narrowband continuous-phase asynchronous CDMA systems

The authors analyze a full-digital receiver for band-limited spread-spectrum signals in a radio communication network employing asynchronous code-division multiplexing and constant-envelope continuous-phase modulation (CPM). They present a detailed analysis of the code synchronization strategy, both in the acquisition and in the tracking mode. They also consider the issue of chip timing recovery, discussing first the impact of chip timing errors on code acquisition, and then evaluating the performance of three different code tracking loops. In particular, the acquisition performance is assessed in terms of false alarm and miss probabilities as well as average lock-in time, while in the analysis of the tracking behavior the root mean square chip timing jitter is assumed as the quality factor. A special subset of CPM, known as generalized minimum shift keying (GenMSK), encompassing Gaussian-filtered MSK modulation as well as traditional MSK, has been emphasized.<<ETX>>

Analysis of an advanced satellite digital audio broadcasting system and complementary terrestrial gap-filler single frequency network

Digital audio broadcasting (DAB) to mobile and fixed users exploiting the latest advances in compression coding, and transmission techniques represents an appealing application for future satellite systems. This paper introduces coded quasi-orthogonal code division multiplexing (CQO-CDM) as a transmission technique for digital audio broadcasting. The proposed technique performs well over both the L-band satellite fading channel and the terrestrial gap-filler type of transmission. Preliminary link budgets based on extensive computer simulation results are provided. Numerical results show that remarkable overall capacity can be achieved by using a constellation of satellites in highly elliptical orbit (HEO) complemented by a terrestrial gap-filler network. A variety of transmission rates and hence broadcasting services can be realized with the proposed transmission technique. It is shown that a geostationary orbit (GEO) satellite can provide limited service availability to the mobile user, but can also be used for experimental purposes. >

A Novel Link Performance Prediction Method for Coded MIMO-OFDM Systems

Coded multi-antenna and multi-carrier techniques combined together with link resources adaptation algorithms are the key technologies toward efficient high-data-rate communications over wireless fading channels. The practicability of this concept, however, requires that the transmitter can perform accurate and simple evaluation of the actual link performance. This paper contributes with a novel method specifically developed to predict the link performance of bit-interleaved coded MIMO-OFDM links, which offers improved accuracy at the price of lower complexity when compared with conventional techniques. Its effectiveness is confirmed through extensive simulation results obtained over typical wireless channel environments.

Simple carrier frequency rate-of-change estimators

This paper is concerned with the estimation of the rate-of-change of the instantaneous frequency of an unmodulated carrier. Such an issue arises, for instance, in satellite communication systems based on a low-Earth-orbit constellation, wherein the speed of each satellite relative to earth is rapidly time-varying, and consequently, the received carrier is affected by nonnegligible Doppler shift and Doppler rate. First, we present simple yet efficient estimators of the Doppler rate derived from maximum-likelihood estimation theory. Next, we investigate their performance in terms of bias and estimation error variance. Finally, we compare our variance results with the relevant modified Cramer-Rao bound.