In the context of fully distributed systems, we consider a scenario densely populated with wireless nodes which are equipped with simultaneous wireless information and power transfer (SWIPT) capabilities and can act as relays between a source and a destination. In this scenario, the probability of finding a node able to provide a useful contribution to the quality of the link tends to be high and can be exploited adopting a suitable relay selection scheme. Assuming nodes distributed following a Poisson point process and communicating only with source and destination to ensure the scalability of the system, we consider two well-known relay selection schemes, which are typically used as performance benchmarks, and derive an analytical framework to investigate the performance of the source-destination link in terms of outage probability. In our analysis we include, through the use of a simple but effective model, the non-linear effects of the energy harvesting circuitry of the devices and introduce a simple signaling mechanism between source, SWIPT nodes and destination to identify the most suitable relay among the various SWIPT devices. The impact of multiple access during the phase of relay selection is also modeled and investigated.

Emerging scenarios envision a widespread deployment of reconfigurable intelligent surfaces (RISs) across structures and objects to manage wave propagation and create smart radio environments (SREs). While numerous studies have explored indoor and outdoor integration of large-scale RIS, many of these analyses oversimplify channel characteristics and assume ideal or random phase profiles for RISs, which may not align with realistic situations. Thus, this paper introduces a comprehensive communication outage analysis that, unlike existing literature, accounts for practical phase profiles on the cascaded double Rician fading channel BS-RIS-UE. We validate our model through extensive numerical simulations, discussing the trade-offs between the number of RIS antennas and quantization bits per RIS.

Future scenarios foresee the deployment of a large amount of reconfigurable intelligent surfaces (RISs) covering buildings and objects to control the propagation of waves and to realize smart radio environments (SREs). Several works have already investigated the possibility to have a large-scale deployment of RISs indoors and outdoors, providing insightful considerations about the coverage and outage probability, especially in the absence of a direct base station (BS)-user (UE) link. Unfortunately, such works typically consider simplified propagation channels and assume ideal or random phase profiles at the RIS, which do not always fit real scenarios. This paper proposes a communication outage analysis that accounts for realistic RIS selection mechanisms and phase shift profiles. Differently from the literature, we first discuss some RIS association mechanisms and provide a general outage analysis, which is then specialized to the cascaded double Rician fading channel BS-RIS-UE. Finally, we provide extensive numerical evaluation, validated through simulations, to corroborate the proposed model to allow discussing the trade-off in terms of the number of employable RIS antennas and the number of quantization bits for each RIS element, which should be accounted for in the system design.

Most of the applications envisaged for the forthcoming connected vehicles are based on the broadcasting by each vehicle of periodic messages describing its characteristics, state, and actions. Such messages are denoted as cooperative awareness messages (CAMs) in the ETSI standardization. From a communication perspective, the success of CAM delivery is thus a particularly important aspect to evaluate and the obvious method to address large scale scenarios consists in performing simulations. Normally, given that the relevance of the information is related to the distance between communicating vehicles, output metrics are restricted to a given range. However, no attention is typically posed on the relative positions and movements of the vehicles, which could be, for example, on parallel roads. In this work, we propose a novel method to identify and neglect those transmissions that are not really meaningful, based only on the position and direction of the vehicles. Particular emphasis is laid on the efficiency of the methodology for possible large-scale simulations. The described approach is evaluated in a complex urban scenario, where hundreds of vehicles are equipped with either LTE-V2V or IEEE 802.11p. Results show that, in the considered cases, even less than half of the transmissions could be meaningful and that neglecting those that are not relevant significantly impacts on the quality of the investigated application.

We investigate a dual-user scenario where sources transmit their messages to the destinations by means of relays in an amplify-and-forward two-hop mechanism. In this scenario, the presence of co- channel interference requires the design of a suitable relay selection algorithm to minimize outage events. To this aim, we present a relay selection algorithm specifically tailored for amplify-and-forward relaying. The performance of the relay selection mechanism is evaluated analytically, in terms of outage probability, under the assumption that relay nodes are distributed according to a homogeneous Poisson point process. Numerical results show that the proposed algorithm outperforms a conventional one, based only on the measurement of the power received from the desired transmitters.

On the path to zero fatalities on the roadways, all vehicles have to periodically broadcast cooperative awareness messages (CAMs) in a timely and reliable manner, even in areas of high traffic density. The carrier senses multiple access with collision avoidance (CSMA/CA) scheme of IEEE 802.11, the de-facto standard for vehicular communications, is known to offer no reliability to broadcast packets that cannot be acknowledged, and to poorly perform at high network load due to collisions and interference. In this paper, an enhanced CSMA/CA protocol is analyzed for vehicular networks, which improves the CAM timeliness and reliability by leveraging full-duplex (FD) transceivers on board. FD devices can listen to the channel while transmitting, thus making collision detection viable. A FD vehicle can detect a CAM collision while sending, promptly abort the packet and retransmit it later. Results achieved through an analytical model under mathematically tractable assumptions, and through extensive system-level simulations in a complex urban environment, show the effectiveness of the protocol to cope with direct collisions, especially in high traffic areas, paving the way towards the realization of cooperative automated driving.

Vehicle-to-everything (V2X) communications may radically change the transportation system allowing a real-time and highly reliable exchange of information, which can be processed by vehicles in the neighborhood or by the road-side infrastructure to enable safety, mobility and environmental applications. In this context, 3GPP-based cellular networks, and especially long term evolution (LTE), are offering progressively higher performance and enabling a wider set of operations. To this aim, vehicle-to-vehicle (V2V) has been recently added as a new feature to LTE, but the usage of radio resources still needs to be optimized and is subject of extensive research activities. In this work, we focus on autonomous V2V resource reselection schemes, which allow communications also in out-of-coverage areas, we propose MAP-RP, a reselection procedure based on the embedding of a map of resources, as detected by each receiving vehicle, in the broadcasted packet, and we compare it to two sensing-based benchmark algorithms found in the literature. Results are achieved through simulations performed on a realistic highway scenario and demonstrate that the proposed solution guarantees a lower update delay and allows to achieve up to 20% of improvement in terms of packet reception ratio, with respect to the best-performing benchmark algorithm.

In this paper, we consider a multi-user scenario where an arbitrary number of sources transmit their messages to the intended destinations by means of relays in a decode-and-forward two-hop mechanism. To minimize the interference generated in the scenario, two opportunistic relay selection mechanisms are proposed and investigated. The performance of the two selection mechanisms is analytically evaluated, in terms of outage probability and average achievable rate, under the assumption that relay nodes are distributed according to a Poisson point process. Asymptotical analysis is also presented for infinite node density. Numerical results show that the selection of the relays has a significant impact on the amount of interference generated and a suitable choice can improve the overall performance.

In a near future, vehicles will be equipped with wireless communications technologies to periodically broadcast information to their neighbors on their position and speed. The messages carrying such information, normally denoted as beacons, will reduce the probability of accidents and improve the safety of drivers and passengers. The main candidate technologies for this scope today are IEEE 802.11p and LTE-Advanced with device-to-device communications (LTE-D2D), which is now evolving into vehicle-to-vehicle communications features (LTE-V2V). The aim of this paper is thus to compare the performance in terms of scalability of these two technologies when used for beacon transmission. The comparison is made analytically, through the definition of common scenario and metrics.

We consider a multi-user scenario where sources transmit their messages to the destinations by means of a two-hop mechanism. To minimize the interference generated in the scenario, a simple opportunistic relay selection mechanism is investigated. The performance of the scenario is evaluated using some results of the stochastic geometry under the assumption that relay nodes are distributed according to a Poisson point process. Results show that, when the relay density is sufficiently high, a suitable choice of the relay leads to a limited amount of interference generated during source-relay and relay-destination transmissions.

Vehicular ad hoc networks (VANETs) based on IEEE 802.11p are moving new safety and traffic applications beyond the present limitations given by infrastructures. However, due to the high variability in time and position of nodes, the medium access control layer of IEEE 802.11p, which is based on carrier sensing multiple access with collision avoidance (CSMA/CA), could lead to severe performance degradation in terms of delivery delay and delivery ratio as the node density increases. Because of its higher efficiency, we propose the use of orthogonal frequency division multiple access (OFDMA) as access technique in VANETs, discussing and evaluating i) its feasibility, ii) the challenges posed by the distributed allocation of resources, and iii) its performance in terms of resource allocation efficiency (specifically, delivery rate and delivery delay) when compared to CSMA/CA. Results, obtained by means of simulations that jointly take into account realistic road maps, vehicular traffic, and the whole network architecture from the application down to the physical layer, show that OFDMA allows up to four times higher delivery rate and that it also guarantees lower delivery delay in heavy loaded network conditions.

When energy is harnessed by wireless nodes from renewable sources, its availability becomes uncertain and its use for communications must be carefully designed. While the optimal power allocation has been derived in previous works when energy availability is fully (a priori) known, practical algorithms are needed when only causal and statistical information is available. In this paper, we study the optimal transmission policy when only the statistical distribution of the energy arrival intervals is known and no information is available on the amount of energy that will be harnessed. We firstly obtain an exact solution for the case of a step-wise transmission power profile. This result is then extended to the time-continuous case. Within energy arrival intervals, the obtained power profile is shown to be non increasing as a function of time and non decreasing as a function of the residual energy. Numerical results are finally provided focusing on an exponentially distributed energy arrival process as a case study.

Routing strategies deeply affect the performance of wireless ad hoc networks, in terms of coverage, interference, and delay. In this work, we investigate the impact of different routing strategies on the overall amount of interference generated in a distributed ad hoc network with power control. To this end, we derive an analytical model for the evaluation of the performance in terms of mean value and variance of the interference when signal level power control is adopted and different routing strategies, based on long-hop and short-hop relay selections schemes, are considered. This model allows us to quantify the performance of the overall network in terms of interference, average number of hops and path efficiency. Numerical results have been also verified by simulations.

In this paper we consider a multi-hop ad hoc network where nodes are distributed according to a Poisson point process (PPP) over a line. A slotted Carrier Sense Multiple Access protocol is used to transmit data from a source to a destination node, through multiple relays. Due to the hidden terminal node problem interferences are present and reduce the network capacity. Performance is evaluated in terms of mean ergodic capacity of the generic link. Results show that there exists an optimum value of nodes' density maximizing the performance and this value changes when varying the source-destination distance.

The high flexibility of ad hoc wireless networks plays an important role in the design of future wireless generation. In this work, we consider an ad hoc network with nodes communicating the one with each other using multi-hop. Nodes use signal level power control to adjust the amount of transmitted power. The objective of this work is to quantity the amount of interference generated in the network as a function of the relay selection scheme considered. The effectiveness of the power control in reducing the level of interference is also investigated.

We investigate high spectral efficiency wireless multiple-input multiple-output (MIMO) systems in fading environments. We assume frequency flat fading, channel state information at both the transmitter and receiver sides, and linear preceding based on singular value decomposition (SVD). For this MIMO SVD scenario, the optimal solution in terms of achievable rate requires water-filling to optimally allocate the power to the different channel eigenmodes. Alternatively, reduced complexity power allocation methods can be employed, where the allocation is based on statistical expectations of functions related to the singular values of the channel gain matrix. In this paper we study these power allocation methods, by using the exact distribution of an arbitrary (ordered) eigenvalue of Wishart matrices, with the probability density function of the ¿thlargest eigenvalue given as a sum of terms xße-x¿. We derive expressions for the achievable rate for both zero-outage and non-zero-outage strategies. We show that, often, the low-complexity methods have performance very similar to water-filling methods.

In this paper we investigate the performance of two-hop virtual multiple-input-multiple-output systems with random location of nodes. In the scenario we consider the communication between source and destination through the use (following a decode-and-forward approach) of a relay node. A number of ancillary nodes, distributed according to a Poisson point process, are supposed to be distributed around source, relay and destination, with the possibility to create clusters of cooperating nodes. Random fluctuations are accounted for in the channel model which considers both slow and fast fading. Performance is evaluated in terms of outage probability, defined as the probability that the achieved capacity between source and destination is smaller than a given threshold. Finally, the total power consumed by the network for delivering the data is evaluated. Results obtained in the two-hop communication protocol are compared with the single-hop case.

This paper considers the analysis of optimum combining systems in the presence of both co-channel interference and thermal noise. We address the cases where either the desired-user or the interferers undergo Rician fading. Exact expressions are derived for the moment generating function of the SINR which apply for arbitrary numbers of antennas and interferers. Based on these, we obtain expressions for the symbol error probability with M-PSK. For the case where the desired-user undergoes Rician fading, we also derive exact closed-form expressions for the moments of the SINR. We show that these moments are directly related to the corresponding moments of a Rayleigh system via a simple scaling parameter, which is investigated in detail. Numerical results are presented to validate the analysis and to examine the impact of Rician fading on performance.

Random matrices play a crucial role in the design and analysis of multiple-input multiple-output (MIMO) systems. In particular, performance of MIMO systems depends on the statistical properties of a subclass of random matrices known as Wishart when the propagation environment is characterized by Rayleigh or Rician fading. This paper focuses on the stochastic analysis of this class of matrices and proposes a general methodology to evaluate some multiple nested integrals of interest. With this methodology we obtain a closed-form expression for the joint probability density function of k consecutive ordered eigenvalues and, as a special case, the PDF of the lscrthordered eigenvalue of Wishart matrices. The distribution of the largest eigenvalue can be used to analyze the performance of MIMO maximal ratio combining systems. The PDF of the smallest eigenvalue can be used for MIMO antenna selection techniques. Finally, the PDF the kthlargest eigenvalue finds applications in the performance analysis of MIMO singular value decomposition systems.

We discuss the correctness of one of the main results of about the probability density function of the distance between two audible nodes in an infinite 2-dimensional scenario. We prove that result is wrong and derive a more general expression, which is valid for an infinite d-dimensional area. It is worth noting that, although the results on the distribution of the distance between two nodes are wrong, the other results and in particular the fact that the number of audible nodes in an arbitrary area is a Poisson r.v. is correct.

The research of closed form expressions for the PDF of the lscrthordered eigenvalue of a Wishart matrix has received a great attention in the past years owing to its applications in the performance analysis of multiple input multiple output (MIMO) systems in fading environments. Although several closed form expressions for this PDF were obtained in the past years, to the authors' knowledge, no one was very friendly for further analysis. We propose a methodology to obtain the PDF for the lscrthlargest eigenvalue whose expression is given as a sum of termsxbetae-xdelta. This expression is easily usable to obtain closed form results for the performance of many MIMO systems, such as, for instance, MIMO beamforming, and MIMO with singular value decomposition (SVD). The methodology is valid for both uncorrelated and correlated central Wishart, allowing the investigation of MIMO systems with uncorrelated and correlated Rayleigh fading.

This paper focuses on the stochastic analysis of Wishart matrices, which appear in many problems related to the performance analysis multiple-input-multiple-output (MIMO). We propose a general methodology to evaluate some multiple nested integrals of interest With this methodology we obtain a closed-form expression for the joint probability density function (pdf) of k consecutive ordered eigenvalues and, as a special case, the pdf of the lthordered eigenvalue of Wishart matrices.

The distribution of the eigenvalues of Wishart matrices and Gaussian quadratic forms is of great interest in communication theory, especially in relation to multiple-input multiple-output (MIMO) systems. In this paper we present some new results on the joint distribution of an arbitrary subset of the ordered eigenvalues of Wishart matrices, using the tensor operator T (.), which was first introduced in . We obtain both the joint probability distribution function (p.d.f.) of the eigenvalues and the expectation of arbitrary functions of the eigenvalues, including the moments, for the case of both ordered and unordered eigenvalues. These expressions are extremely compact and easy to handle. Application to MIMO systems are discussed.

The research for analytical models able to estimate the amount of interference, which is the most important cause of performance degradation in wireless networks, has received a lot of attention in the past years. In this paper we propose an analytical framework for the evaluation of any statistical moment of the interference provided by a Poisson field of nodes located on a given region of limited area. The propagation environment we consider is characterized by a deterministic distance-dependent path-loss and log-normal shadowing. Exact closed form expressions are given for some specific regions.

This paper analyzes the performance of optimum combining systems in the presence of both co-channel interference and thermal noise, addressing the case where the desired- user undergoes Rician fading. Exact expressions are derived for the moment generating function of the SINR which apply for arbitrary numbers of antennas and interferers. Based on these, we obtain expressions for the symbol error probability with M-PSK. We also derive exact closed-form expressions for the moments of the SINR, and show that they are directly related to the corresponding moments of a Rayleigh system via a simple scaling parameter. Numerical results are presented to validate the analysis, and to examine the impact of Rician fading.

This paper proposes a connectivity model for nodes which are spatially distributed according to a Poisson Point Process in a bounded (circular) area. The propagation environment is characterized by distance-dependent loss and log-normal shadowing. We consider nodes that communicate with a terminal located in the center of the circular area and derive an expression for the distribution of the power received by this terminal. We also obtain an expression for the moments of the co-channel interference received by the terminal located in the center of the area.

This paper investigates wireless sensor networks where nodes, which are uniformly and randomly distributed in a given area, transmit information to a sink that is equipped with smart antennas. The framework proposed herein, which considers a propagation environment composed by a distance-dependent loss, shadowing and Rayleigh fading permits an analytical evaluation of the achievable rate.

In this paper, we investigate the performance of optimum combining multiple antenna systems in the presence of Rician-faded interferers. We assume that the desired user is subjected to Rayleigh fading but interferers undergo Rician fading. Unlike other approaches addressing optimum combining with Rician fading, we consider the effect of both interference and thermal noise. Our methodology is based on the evaluation of the moment generating function of the signal-to-interference-plus-noise (SINR) ratio at the output of the combiner. Our results are exact, and allow the calculation of the symbol error probability (SEP) for M-PSK signals with arbitrary number of antennas and interferers.

In this paper we consider a scenario composed by nodes which are uniformly and randomly distributed in a given area and derive the distribution of the power received by a given terminal. The model, which takes a propagation environment characterized by distance-dependent loss and log-normally distributed shadowing into account, can be used to evaluate the distribution of the received power in wireless ad hoc and sensor networks. In particular, the model is suited to investigate the distribution of the received useful and the interference power in a scenario where all the terminals can communicate with each other using the same radio resource

The investigation of both link and network level aspects is fundamental when a thorough analysis of mobile radio systems is required. The conventional approach, based on a complete separation between the two levels, adopted in the past for the performance evaluation of second generation systems, is not enough accurate for third generation ones, characterized by the presence of both voice and data services as well as circuit and packet switched applications. Here we describe a methodology on how to interface link and network level tools and finally show an example of application

In this letter, we derive a closed-form symbol-error probability expression for adaptive antenna array with optimum (or, equivalently, linear minimum mean-square error) combining. We consider coherent detection of M-ary phase-shift keying signals in the presence of unequal-power interferers and thermal noise. The analysis is based on our new results on the eigenvalues distribution of central Wishart matrices with correlation.

A frequency- and time-division multiple-access (F-TDMA)-based mobile radio system using both dynamic channel allocation (DCA) and frequency hopping (FH) is investigated. We propose a new interference adaptive DCA (IA-DCA) algorithm that is suitably designed for a network implementing FH. The role played by the power control algorithm in this DCA-FH context is also investigated. We compare the performance of our proposal to that of fixed channel allocation (FCA) with and without FH and the well-known IA-DCA schemes investigated in the literature in the absence of FH. The performance results show that interesting synergic effects can be obtained in terms of forced termination and user satisfaction probability by using both DCA and FH. The results we show in the paper have been achieved by means of a system-level simulation tool which takes propagation, user mobility, interference, traffic, and channel allocation into account. The advantages of using FH are accounted for by using a suitable analytical model that gives the frame error rate as a function of the carrier-to-interference ratio and the number of hopping frequencies, at link level; this model is taken from the literature where it was presented for FCA, and here it is modified in order to be applicable to the DCA case.

In this paper, we investigate the performance in terms of symbol error probability (SEP) of multiple-input-multiple-output (MIMO) systems with high spectral efficiency. In particular, we consider the coherent detection of M-PSK signals in a flat Rayleigh-fading environment. We focus on spectrally efficient MIMO systems where, after serial-to-parallel conversion, several substreams of symbols are simultaneously transmitted by using an antenna array, thereby increasing the spectral efficiency. The reception is based on linear minimum mean-square-error (MMSE) combining, eventually followed by successive interference cancellation. Exact and approximate expressions are derived for an arbitrary number of transmitting and receiving antenna elements. Simulation results confirm the validity of our analytical methodology.

We investigate convergence properties of both the steepest descent (SD) and least mean-square (LMS) algorithms applied to a multiple-input-multiple-output system in a Rayleigh fading environment with correlated fading. For a given value of the adaptation step, we evaluate the probability that the algorithms are stable. Then, we compare two stable strategies to choose the adaptation step of SD and analyze their speed of convergence. Our results are valid for an arbitrary number of transmit and receive antennas for the uncorrelated fading, and for an arbitrary number of receive antennas less or equal to the number of transmit antennas for the case of correlated fading.

This work deals with the problem of cellular network reconfiguration. In particular, we focus on the development of a very complete simulation tool that allows an accurate performance analysis of realistic mobile radio systems. The results we show in the paper have been achieved by means of an integrated approach taking both the system and link level aspects into account. Since the accuracy of the simulation results depends strongly on the mobility model considered, we propose a methodology to assign a given class of mobility to the cells. Finally, to validate the simulation tool we have compared the results with those obtained in a realistic network The results show that the agreement between simulation and the measured values is very good.

This paper investigates the effects of directed retry (DR) in cellular networks characterized by a nonuniform environment, that is, with unequal distribution of users and/or radio resources. We propose an analytical model able to take both propagation and network aspects into account. The nonuniform environment is modeled assuming the superposition on a uniform scenario of a circular area characterized by different offered load or radio capacity. The case of a hot spot of users is included. Path loss and lognormal shadowing have been considered. This is done through a statistical approach which is very general, and provides an expression for the probability of receiving a suitable power level from a given number of base stations within a fixed distance from the mobile. A comparison to simulation results is performed to validate the model. We show that the impact of DR on the blocking probability depends largely on the propagation parameters considered.

We derive a simple closed-form upper bound on the symbol error probability for coherent detection of M-ary phase-shift keying using antenna arrays with optimum combining, in the presence of multiple uncorrelated equal-power cochannel interferers and thermal noise in a Rayleigh fading environment. The new bound, based on Laguerre polynomials, is valid for an arbitrary number of antenna elements as well as arbitrary number of interferers, and it is proven to be asymptotically tight. Comparisons with Monte Carlo simulation are also provided, showing that our bound is useful in many cases of interest.

We derive an exact bit-error probability (BEP) expression for coherent detection of binary signals with optimum combining in wireless systems in the presence of multiple cochannel interferers and thermal noise. A flat Rayleigh fading environment with space diversity, uncorrelated equal-power interferers, and additive white Gaussian noise is considered. The approach is to use the chain rule of conditional expectation together with the joint probability density function (pdf) of the eigenvalues of the interference correlation matrix. This joint pdf is related to the Vandermonde determinant. Let N/sub A/ denote the number of antennas and N/sub I/ the number of interferers. We consider both the cases of an overloaded system, in which N/sub I//spl ges/N/sub A/, and an underloaded system, in which N/sub I/

We investigate the capacity distribution of spatially correlated MIMO channels. In particular, we consider MIMO systems with arbitrary correlation among the transmitting antennas or among the receiving antennas in frequency-flat Rayleigh fading environments. We derive a simple expression for the distribution of the eigenvalues of a Wishart matrix including correlation, and then a closed-form expression for the characteristic function (CF) of MIMO system capacity. Using the exact expression of the CF, the probability density function and the cumulative distribution function can be easily obtained, thus enabling the exact evaluation of the outage and mean capacity of spatially correlated MIMO channels.

We investigate the performance, in terms of symbol error probability (SEP), of multiple-input-multiple-output (MIMO) systems in a flat Rayleigh fading environment with coherent detection of M-PSK signals. The reception is based on linear minimum mean square error (MMSE) combining, followed by successive interference cancellation. Compared to conventional vertical-Bell Laboratories layered space-time (V-BLAST) MIMO systems, we assume a low complexity strategy that does not include the ordering phase. To reduce the difference in terms of SEP on the sub-streams, we consider a MIMO scheme where the symbols transmitted by the different antennas have different energy. Our methodology is completely analytical, is valid for an arbitrary number of receive and transmit antennas (provided that N/sub R//spl ges/N/sub T/) and provides a very fast evaluation of MIMO performance. Results show that the unequal power transmission scheme gains about 3-4 dB over the conventional equal-power transmission case.

We derive a closed form expression of the symbol error probability (SEP) for coherent detection of M-ary PSK signals using an array of antennas with optimum (or, equivalently, linear MMSE) combining in the presence of unequal power interferers and thermal noise. This result is based on a new expression for the eigenvalues distribution of central Wishart matrices with correlation.

An exact expression for the symbol-error probability (SEP) for coherent detection of M-ary phase-shift keying using an array of antennas with optimum combining in a Rayleigh fading environment is derived, based on the theory of orthogonal polynomials. In particular, performance analysis in the presence of multiple uncorrelated equal-power cochannel interferers and thermal noise is considered, starting from problems related to the eigenvalues distribution of complex Wishart matrices. We give an effective technique to derive the SEP involving only one integral with finite integration limits. The result is general and valid for an arbitrary number of receiving antennas and/or cochannel interferers. Based on our efficient method, new results that are useful for the design of wireless systems are obtained.

We derive an upper bound and investigate some approximations on the symbol error probability (SEP) for coherent detection of M-ary phase-shift keying, using an array of antennas with optimum combining in wireless systems in the presence of multiple uncorrelated equal-power cochannel interferers and thermal noise in a Rayleigh fading environment. Our results are general and valid for an arbitrary number of antenna elements as well as an arbitrary number of interferers. In particular, the exact SEP is derived for an arbitrary number of antennas and interferers; the computational complexity of the exact solution depends on the minimum number of antennas and interferers. Moreover, closed-form approximations are provided for the cases of dual optimum combining with an arbitrary number of interferers, and of two interferers with an arbitrary number of antenna elements. We show that our bounds and approximations are close to Monte Carlo simulation results for all cases considered in this paper.

In this paper, we investigate the capacity distribution of spatially correlated, multiple-input-multiple-output (MIMO) channels. In particular, we derive a concise closed-form expression for the characteristic function (c.f.) of MIMO system capacity with arbitrary correlation among the transmitting antennas or among the receiving antennas in frequency-flat Rayleigh-fading environments. Using the exact expression of the c.f., the probability density function (pdf) and the cumulative distribution function (CDF) can be easily obtained, thus enabling the exact evaluation of the outage and mean capacity of spatially correlated MIMO channels. Our results are valid for scenarios with the number of transmitting antennas greater than or equal to that of receiving antennas with arbitrary correlation among them. Moreover, the results are valid for an arbitrary number of transmitting and receiving antennas in uncorrelated MIMO channels. It is shown that the capacity loss is negligible even with a correlation coefficient between two adjacent antennas as large as 0.5 for exponential correlation model. Finally, we derive an exact expression for the mean value of the capacity for arbitrary correlation matrices.

In this paper, we derive an exact expression for the symbol error probability (SEP) for coherent detection of M-ary PSK signals using array of antennas with optimum combining in a Rayleigh fading environment. The proposed analytical framework is based on the theory of orthogonal polynomials and we give an effective technique to derive the SEP involving only one integral with finite integration limits. The result is general and valid for an arbitrary number of receiving antennas or co-channel interferers.

We derive a simple closed-form upper bound on the symbol error probability for coherent detection of M-ary PSK using an array of antennas with optimum combining. We assume multiple equal-power cochannel interferers and thermal noise in a Rayleigh fading environment. The new bound applies for an arbitrary number of antenna elements as well as arbitrary number of interferers, and it is proved to be asymptotically tight. Based on the simplicity of the bound, the signal-to-noise ratio penalty due to cochannel interference is evaluated. Comparisons with simulation is also provided, showing that our bound is useful in a large number of practical interesting cases.

This paper deals with intersystem handover between third and second generation mobile radio systems. Here, we propose an efficient monitoring strategy for acquisition of both frequency correction channels (FCCH) and synchronization channels (SCH) of a GSM system by user equipment (UE) connected to a time division-synchronous code division multiple access (TD-SCDMA) network. The proposed strategy, which is based on a discontinuous search, exploits the properties of periodicity of TD-SCDMA and GSM radio frames. The proposed strategy proves to be very efficient in the utilization of the monitoring windows and allows us to acquire a number of FCCH/SCH bursts which is comparable with that achievable by adopting a continuous (unrealistic) monitoring strategy taken as reference.

This paper considers two sets of points which can communicate with one another and which are uniformly and randomly distributed, one set within a confined area, a hot spot, on the plane, and the other with a different density over the rest of the plane: an inverse power law with lognormal shadowing is assumed for attenuation. Communication is assumed to be possible if the attenuation of a signal transmitted from one point, say a mobile telephone, does not exceed some specified value by the time it reaches the other, say a base station. The probability distribution of the number of base stations which can hear such a signal from a given mobile is found, taking account of the effect of the hot spot. The conditional distribution of the number of such base stations within the hot spot, given the total number over the whole plane, is deduced, and this result is applied in an example to finding the blocking probability for a directed retry algorithm. The results also apply to the number of mobiles within range of a base station and, in an ad hoc network, to the number of nodes within range of a given node.

In this paper we present an analytical model for the estimation of the blocking probability as a function of the offered traffic per user in a cellular environment, where capacity is determined by hard blocking and the average number of users per cell is small. By the term "hard" capacity we mean the maximum number of users that can be served by a base station. Using a statistical model, the paper shows that the number of mobiles audible to a base that have that base as the strongest one has a Poisson distribution whose mean is given in terms of the mean densities of mobiles and base stations and the parameters of the attenuation law. The model proposed here does not represent a tool for detailed network planning, but it is a helpful (and from the computational viewpoint simple) means for network dimensioning.

An F-TDMA (frequency and time division multiple access) based mobile radio system using both dynamic channel allocation (DCA) and frequency hopping (FH) is investigated in this work. This paper follows the work of Verdone, Zanella and Zuliani (see IEEE PIMRC'01, San Diego, CA, September 2001), where the same authors proposed a new interference adaptive DCA algorithm that is suitably designed for a network implementing FH. The role played jointly by the power control and handover algorithm in this mixed DCA-FH context is investigated in this paper. We compare the performance of our proposal to that of fixed channel allocation with FH. The performance results show that interesting synergic effects can be obtained in terms of user satisfaction probability by using both DCA and FH. The results we show in the paper have been achieved by means of an integrated approach taking both system level and link level aspects into account.

In this paper a F-TDMA based mobile radio system using both dynamic channel allocation (DCA) and frequency hopping (FH) is investigated. We propose and evaluate the performance of a new interference adaptive DCA (IA-DCA) algorithm that is suitably designed for a network implementing FH. The results we show in the paper have been achieved by means of a simulation tool which takes propagation, mobility, interference, traffic and channel allocation into account. Moreover, the advantages of using FH are accounted for by using suitable analytical models that give the frame error rate as a function of the carrier-to-interference ratio and the number of hopping frequencies. We compare the performance of our proposal to that of fixed channel allocation (FCA) with and without FH, and the well known IA-DCA schemes investigated in the literature in the absence of FH. The performance results show that interesting synergic effects can be obtained in terms of forced termination and user satisfaction probability by using both DCA and FH in a F-TDMA based mobile radio network.

We derive the exact symbol error probability for coherent detection of MPSK signals with optimum combining in the presence of multiple uncorrelated equal power co-channel interferers and thermal noise in a Rayleigh fading environment. The expression is general and valid for arbitrary numbers of receiving antennas or co-channel interferers. The complexity of the analytical model depends on the smaller of the number of antennas and the number of interferers.

The blocking probability in a cellular network implementing directed retry (DR) is analyzed as a function of the main characteristics of the scenario (the density of base stations), the propagation model (path loss and shadowing), and the speed of mobiles. The analytical approach allows the evaluation of the blocking probability as a function of the maximum number of cells that can be considered at call setup by the DR algorithm. It is shown that the effectiveness of the DR strategy depends on the values of the variance of shadowing and the path loss model. Moreover, the blocking probability is found to be approximately independent from the mobile speed. The analytical results are compared to those obtained by means of simulation: a good agreement has been found, and the analytical model has been shown to be able to reflect the main effects of propagation and mobility on the advantages of DR in a real cellular network.

In this paper, the investigation of the effects of directed retry (DR) in cellular radio networks is carried out through an analytical model which takes both propagation and network aspects into account. In this model, path loss as well as lognormal shadowing have been considered. The paper shows that the impact of DR on the blocking probability depends largely on the number of cells which can be considered by the mobile during the call set-up procedure; this number depends on the propagation environment considered. The analytical results have been compared with those obtained through a simulation tool and the results have shown a good agreement. Moreover, with the aim to take non-uniform scenarios into account, a generalization of the analytical method, through a statistical approach, has been proposed.

The combined use of adaptive antennas and decision feedback equalization (DFE) is analyzed in a realistic propagation scenario at millimeter waves, taking the direction of arrivals (DOA's) of the received paths into account. The joint antennas and DFE scheme, with one forward filter for each antenna and a single feedback filter (FBF), can be viewed as a spatial and temporal DFE (ST-DFE). The performance of this solution is compared with the cascade of adaptive antenna used for beamforming and DFE. It is found that ST-DFE achieves better performance since it combines the beamforming capability of the antenna array with the equalization properties of the DFE, with great advantages especially when rays arrive from similar angles. The mean square error (MSE) is analytically derived for infinitely long filters in a quasi-static environment with multiple rays having different DOAs, and compared (for the two-path model) with simulation results assuming filters with a small number of taps. Finally, service availability through coverage evaluation is developed and compared with that of a coded-orthogonal frequency division multiplexing (C-OFDM) system.