Paolo Grazioso

On the performance of packet reservation multiple access with fixed and dynamic channel allocation

The evaluation of packet reservation multiple access (PRMA) is extended from a single cell case, investigated in several previous papers, to a cellular environment characterized by user mobility and by the interference from other cells. The analysis is based on a comparison of PRMA performances with those of classical circuit switching schemes. The comparison methodology is defined, and the comparison, performed by means of a simulation program based on a dynamic traffic model, is discussed. >

PRMA performance in cellular environments with self-adaptive channel allocation strategies

The personal communication systems envisaged for next years will have to accommodate a wide range of services with different quality requirements (on delays, bit error rates, etc.), and will often be characterized by a high burstiness (i.e., with relatively short traffic bursts, alternating with comparatively long silence periods). Therefore, an extension of packet communications to the cellular scenario is appealing for its inherent flexibility. The packet reservation multiple access (PRMA) protocol is considered. On the other hand, the current trend in reducing cell sizes poses major planning problems, which cannot be properly coped with by the usual fixed channel allocation methods; therefore, adaptive allocation schemes, which are able to avoid any frequency planning, are currently studied. A review of adaptive channel allocation strategies in view of application to packet switching is carried out. Then, a self-adaptive assignment method (channel segregation) originally developed for circuit switched systems is selected and conveniently adapted for PRMA operations. Simulations show good performance, provided that values of some system variables are correctly chosen.

Comparisons of multiple access schemes for personal communication systems in a mixed cellular environment

The paper deals with the evaluation of performances of packet reservation multiple access (PRMA) and code division multiple access (CDMA) in a mixed cellular environment, composed by a regular grid of macrocells plus microcells deployed in the most congested areas. The investigation aims at evaluating the impact of the different interference mechanisms on traffic performance and bases on the comparison between two technical solutions proposed in literature. The approach is quite innovative since the analysis is carried out considering realistic spatial traffic statistics, which are characterized, even with a nominally uniform user distribution, by fluctuations resulting in uneven traffic loads on different cells. Different propagation models for macrocells and microcells have been adopted. >

Advanced planning criteria for cellular systems

This article provides a review of the most up-to-date frequency planning techniques suitable for current digital cellular systems. Frequency planning is becoming a key issue in the current scenario, with exceedingly high growth rates in many countries which compel operators to re-configure networks virtually on a monthly basis. Therefore, the search for smart techniques, which may considerably alleviate planning efforts (and associated costs) becomes extremely important for operators in a competitive market. Although reference is made particularly to a market leader (GSM and its offspring), the considerations reported are quite general, and can be applied to any TDMA/FDMA system. The article examines such well-known concepts as fractional loading, frequency hopping, and intelligent antennas in order to elaborate on them and show how they may impact conventional planning methodology and deprive complex dynamic channel allocation methods of any practical interest. The evaluation of this impact is extended to mixed cellular architectures, starting from a real case for the city of Munich and finally identifying some basic guidelines for cell planning.

The Italian national electromagnetic field monitoring network

The paper describes the Italian national electromagnetic field monitoring network that the Italian Ministry of Communications established with the technical support of Fondazione Ugo Bordoni and in collaboration with the local Environmental Protection Agencies of all Italian regions.

A new statistical approach for urban environment propagation modeling

Field prediction is an essential component of the planning process of cellular radio systems. This task is particularly time- and money-consuming in the urban environment, where cell size is of the order of a few hundred meters, and the influence of the city structure (building size and dimension, street width, orientation, etc.) cannot be neglected in the field prediction. For this reason, traditional statistical models such as the well-known Okumura-Hata, cannot be used in this environment, and the prediction is accomplished by means of accurate but time-consuming methods, such as ray-tracing, which require detailed and very expensive databases of the building and street layout of the city under investigation. In this correspondence, we propose a new methodology, which is based on the decomposition of propagation in its basic mechanisms, corresponding to different propagation planes, which can be treated independently from each other. This allows us to build a model which is as simple, fast, and easy to use as the traditional statistical models, with the advantage that it requires only a few statistical parameters thus realizing the need of high-resolution databases.

Analysis of optimum resource management strategies in layered cellular structures

The paper deals with the identification of channel allotment criteria in a multilayered cellular environment composed by a regular grid of macrocells, plus a number of microcells deployed in the most congested areas. The optimum resource allotment between microcells and macrocells cannot be simply worked out by considering the expected traffic densities for each cell type, but it has to take into account their different functionalities, After a quick overview of the main working principles of such a multilayered architecture, the paper introduces some basic planning criteria. The analysis is carried out considering realistic traffic statistics and different propagation models for macrocells and microcells have been adopted.<<ETX>>

Investigation on dynamic channel allocation strategies suitable for PRMA schemes

Among the various packet multiple access schemes proposed for mobile radio operation, packet reservation multiple access (PRMA) method is discussed. The performance of a PRMA scheme in a cellular layout depends heavily on the adopted resource allocation scheme, which is required to keep the mutual interference below the desired limit. Due to its discontinuous transmission and to the high variability of the interference patterns, PRMA cannot control the interference level by simply monitoring the link quality. This evidence makes PRMA operations with dynamic channel allocation (DCA) really difficult to achieve. However, DCA seems to be necessary in microcellular environments, where traditional planning algorithms may fail due to the high complexity of propagation phenomena. The issue of compatibility between PRMA and DCA compatibility are proposed.<<ETX>>

Usage of adaptive arrays to solve resource planning problems

The usage of adaptive antenna arrays in cellular systems is currently being investigated by many researchers. In this paper we show by means of simulation that adaptive antenna arrays allow to reduce the reuse distance, and hence to increase spectrum efficiency. Furthermore, it is shown that, by adopting a fractional loading factor, it is possible to adopt a cluster size equal to 1, which avoids the need of frequency planning altogether, and allows a further improvement in spectrum efficiency.

Packet reservation multiple access in cellular environments

Some different packet protocols, based on a Reservation ALOHA protocol, have been proposed in literature for use in mobile radio systems, even though their performance have been fully evaluated only in interference free environments. The paper focuses on Packet Reservation Multiple Access (PRMA) and extends the evaluation of its performance to a cellular environment, first by characterising its performance when loaded by a Poisson traffic distribution and then assessing the impact of interference from other cells.