This paper proposes an automatic anomaly detection and root cause analysis model that combines Density-based Spatial Clustering of Applications with Noise (DBSCAN) and Long Short-Term Memory (LSTM) Auto-Encoder (AE). The model is trained and tested using unlabelled real-world 4G network data from a Portuguese operator. The study demonstrates the promise of DBSCAN in separating normal network traffic patterns from abnormal ones, as well as the ability of LSTM-AE to learn daily network Key Performance Indicator (KPI) behaviour and detect anomalies and their probable root causes based on reconstruction errors. Results indicate that anomalies in available network KPIs do not always result in abnormal traffic patterns, and vice versa. Consequently, it can be inferred that relying solely on traffic volumes for DBSCAN is not an ideal method to separate normal network data from abnormal data for detecting network anomalies. Additionally, the results emphasize the importance of high-quality data in terms of sampling rate and the number of KPIs, as well as the significance of data analysis in identifying patterns across different levels of mobile networks.

A system loss model for body-to-body networks in indoor and outdoor environments is proposed in this paper, based on measurements taken at 2.45 GHz. The influence of the type of environment, antenna visibility and user mobility on model parameters has been investigated. A significant impact of mutual antennas' placement and their visibility is shown. The proposed model fits well to empirical data, with the average root mean square error being 2.1 dB and the coefficient of determination being above 0.6 in the majority of cases. For designing purposes in generalised cases, it is recommended that the system loss exponent is set to 1.5, and the system loss at the reference distance is equal to 55.9 dB.

This paper presents an analysis of system loss in Body Area Networks for room scenarios, based on a wideband measurement campaign at 5.8 GHz. The measurements were performed with a fixed antenna transmitting vertically and horizontally polarised signals, while the user wears dual-polarised antennas. The average system losses in co- and cross-polarised channels are 41.4 and 42.6 dB for vertically polarised transmitted signals and 41.8 and 45.0 dB for horizontally ones, showing that polarisation plays a role in the radio channel. Analytical models for the average and standard deviation of system loss are presented, with a linear dependence on user mobility, on transmitted/received polarisation, and on link visibility and dynamics. Overall, a good fit between model and measurements is obtained, with a mean square error of 2.3 and 0.12 dB for the average and standard deviation, respectively.

Cardiovascular events occurring in the bloodstream are responsible for about 40% of human deaths in developed countries. Motivated by this fact, we present a new global network architecture for a system for the diagnosis and treatment of cardiovascular events, focusing on problems related to pulmonary artery occlusion, i.e., situations of artery blockage by a blood clot. The proposed system is based on bio-sensors for detection of artery blockage and bio-actuators for releasing appropriate medicines, both types of devices being implanted in pulmonary arteries. The system can be used by a person leading an active life and provides bidirectional communication with medical personnel via nano-nodes circulating in the bloodstream constituting an in-body area network. We derive an analytical model for calculating the required number of nano-nodes to detect artery blockage and the probability of activating a bio-actuator. We also analyze the performance of the body area component of the system in terms of path loss and of wireless links budget. Results show that the system can diagnose a blocked artery in about 3 h and that after another 3-h medicines can be released in the exact spot of the artery occlusion, while with current medical practices the average time for diagnosis varies between 5 and 9 days.

This paper considers second-order statistics of non-stationary channels with arbitrary mobile antenna motion, by relaxing the constant velocity assumption inherent to stationary channel models. By assuming obstructed Line-of-Sight and horizontal signal propagation, analytical expressions for the Level-Crossing Rate (LCR) and Average Fade Duration are derived for non-isotropic scattering scenarios with Von Mises Distribution of angles of arrival. To demonstrate the non-stationary effects arising from non-linear motion, the obtained expressions are employed to investigate an off-body communications scenario with the user walking and the wearable antennas placed on the torso, wrist and lower leg. While the torso antenna yields an essentially stationary channel, for the latter two antenna locations the fading dynamics change periodically over the walking cycle. Two distinct phases with faster and slower signal variations are observed, with the former yielding 4.64 times higher LCR for the lower leg antenna.

Network slicing is a promising technique to enable multi-tenant operation in fifth generation (5G) cellular systems. However, efficient implementation of this technique at the air interface requires an adequate resource allocation policy that provides slice isolation and takes into account the heterogeneity of services and their performance requirements. We propose a new slicing scheme aimed at slice performance isolation, efficient capacity utilization, and fair resource allocation among all users. The policy ensures a slice-specific minimum data rate to all slice users as long as their number remains within a contracted limit, yet provides higher data rates whenever capacity is available. Specifically, we incorporate the best features of the complete partitioning and complete sharing policies, while ensuring flexibility and customization for network operators. The proposed scheme is based on an iterative solution of a convex programming problem characterized by polynomial complexity, which makes it suitable for on-line implementation. Associated algorithms are also proposed. Our numerical results demonstrate that the proposed slicing scheme is capable to accommodate heterogeneous traffic and provides performance isolation of slices while maintaining resource utilization at the level of complete sharing. Depending on the system parameters, the proposed scheme allows to improve session loss probability by an order of magnitude as compared to static slicing, while keeping the user data rates comparable to that of the complete sharing scheme and improving the average user satisfaction index by up to 90%. Overall, the proposed scheme results in efficient resource utilization compared to slicing policies in which slice isolation is provided via reservation by setting fixed upper or lower capacity bounds.

In this paper, Body-to-Body communications in indoor and outdoor environments for different on-body antenna configurations and different mobility scenarios were studied, based on system loss measurements at 2.45 GHz. The main objective is to properly characterise the influence of the Transmitter-Receiver configuration on system loss and fast fading behaviour, the latter being modelled by the Rice Distribution. Globally, it is observed that there is no significant difference on the measured average system loss between indoor and outdoor environments, but a strong dependence is seen on the configuration of the antennas and on the mobility scenario. Concerning the Rice Factor, as expected, higher values were obtained in outdoor environments, due to the lower level of multipath, the difference to the indoor case being below 4 dB, depending on the mobility environment and on the positioning of the antennas.

This paper addresses the performance evaluation of an off-body path loss model, based on measurements at 2.45 GHz, which has been developed with the use of the Generalised Additive Model, allowing to model a non-linear dependence on different predictor variables. The model formulates path loss as a function of distance, antennas’ heights, antenna orientation angle and polarisation, results showing that performance is very sensitive to the orientation angle and to the polarisation of the transmitting and receiving antennas. Considering the model’s global performance, the obtained overall value of the adjusted coefficient of determination equals 0.60, while the mean error and the root mean square error equal 0 dB and 5.6 dB, respectively, which can be considered quite good for such a large diversity of addressed scenarios. One can then conclude that, regardless of the low performance of the method for some particular cases, the overall model accuracy may be considered good.

This paper investigates the influence of user dynamics on small-scale fading characteristics in off-body channels. A statistical channel model employing a mobility model for wearable antennas on dynamic users is presented. The model is used to analyze the effects of both user's linear forward motion and periodic wearable antenna displacement due to changes in posture, for walking and running. The time-variant Doppler shift exhibited by signals arriving from different directions is considered for wearable antennas on the chest, wrist and lower leg. A strong influence of the on-body placement is observed, with antennas on the arms and legs yielding up to a 2.2 times higher maximum Doppler frequency than with the antenna on the torso. Furthermore, the small-scale fading dynamics for these antennas vary considerably during the motion cycle, where one can distinguish between slow and fast phases. The latter is found to yield up to 4 times as high root-mean-square level-crossing rates than the former, in the case of the antenna on the lower leg. These findings imply an important effect of the periodic antenna displacement on fading dynamics in off-body channels, which is typically neglected in literature.

In this paper, one proposes an approach to optimize the computational resource utilization of baseband unit pools in a Cloud Radio Access Network. The problem of resource allocation is formulated and solved as a constrained nonlinear optimization one, based on the concept of bargaining in cooperative game theory. The goal is to minimize resource usage by on-demand resource allocation, per instantaneous requirements of base stations, whilst taking Quality of Service into account. In the event of a shortage of resources, implying that not all demand can be served at the same time, baseband units are prioritized with a weighting policy. Real-time requirements and the priority of services being run on a baseband unit are the two contributors in calculating the weight in a timeslot. Lower prior baseband units, however, are always guaranteed to receive a minimum of resources to prevent them from crashes. Simulation results in a heterogeneous services environment show a minimum 83% improvement in allocation efficiency, compared to a fixed resource allocation scheme based on peak-hour traffic demands. Results also confirm that, in case of a resource shortage, 100% of the resources are fairly distributed among baseband units, fairness being governed by the weight of the baseband units in the pool.

This paper presents an analysis of the depolarization effect in off-body channels, based on a previously developed geometry-based channel model for polarized communications with dynamic users. The model considers Line-of-Sight propagation and components reflected from scatterers distributed on cylinders centered around the user. A mobility model for wearable antennas based on Fourier series is employed to take the effects of user's motion into account. The focus is on scattered signal components, where the impact of a scatter's position, its material properties, and the influence of user dynamics on signal depolarization are investigated. It is observed that the wearable antenna motion has a strong impact on the channel's polarization characteristics, particularly for dynamic on-body placements, such as arms and legs. If the antenna motion is neglected, the error in cross-polarization ratio is greater than 23dB compared to a static approach. The antenna rotation during motion is found to be the dominant factor, while the corresponding displacement can be neglected, with the error not exceeding 1dB. This result justifies the channel model simplification proposed in this paper.

One of the major potential benefits in wireless network virtualisation is enabling on-demand sharing of resources among different tenants in an isolated manner. This paper aims to propose a model for Radio Resource Management (RRM) among multiple Virtual Network Operators (VNOs) to address all their Service Level Agreements (SLAs) independently, as well as satisfying their customised service requirements to the highest achievable level. Performance isolation is attained by realising a centralised virtualisation platform called Virtual-RRM. This entity is responsible for sharing the total capacity obtained by aggregation of all the radio resource units from different access technologies, according to the service demands of the VNOs and considering service priorities. In order to evaluate model performance, a practical scenario with 3 types of SLA contracts is proposed, while all VNOs are in charge of providing the 4 service classes to their users. Results under different traffic loads and network parameters show that all VNOs' SLAs are satisfied to the maximum feasible point, 100% of the available capacity is utilised independently from the variation of network parameters, and when possible capacity is shared among the different services according to the concept of proportional fairness.

Virtualization as a promising technology for future mobile communications enables the principle of customized services and multi-tenancy by providing a shared resource platform to all the involved tenants in an isolated manner. This paper proposes a model of radio resource management in virtualized heterogeneous mobile networks comprised of different access technologies. To realize the concept of virtualization, the roles of Infrastructure Providers (InPs) and network operators are separated. A virtualization platform is responsible for aggregating and vitalizing all the radio resources from different access technologies owned by InPs, and distributing the total capacity among various Virtual Network Operators (VNOs) in the role of tenants, according to service priorities and some fairness criteria, with the aim of satisfying their Service Level Agreements (SLAs). The model considers two VNOs with the capability of providing different service classes and SLAs in a multi access technology environment. Results under different channel conditions and traffic loads confirm a level of isolation in the performance of each VNO, while the SLAs are addressed to the highest possible level. Furthermore, almost always 100% of the aggregated capacity is utilized independently of the variation of different network parameters.

This paper presents a radio propagation model for the UHF band that is designed for an outdoor scenario in the Amazon region of Brazil and comprises city, water, and forest environments. The model is designed for the Mobile and Home Digital Television (M‐DTV and H‐DTV) services. In the case of M‐DTV, the electric field is calculated at user height, while for H‐DTV it considers a fixed antenna on houses roofs. The field calculation is based on Geometrical Optics (GO) and the Uniform Theory of Diffraction (UTD). The results for M‐DTV show a good agreement with measurement data in an Amazonian city (Belém) for 521 MHz. Different parameters of the proposed model are analyzed: the transition zone city‐water, the level of water, the incidence angle in the forest, and electrical parameters for forest. Finally, the comparison that was made between the electric fields for H‐DTV and M‐DTV shows a difference of up to 19 dB.

Virtualisation, as a key role player of future mobile communications, promotes the idea of service‐oriented architectures. This paper proposes a model of Radio Resource Management (RRM) for emerging Virtual Radio Access Networks, based on the interaction between two separated management entities: Common‐RRM (CRRM) to coordinate the radio resources among the Radio Access Technologies (RATs) and a centralised virtualisation platform on top of it, called Virtual‐RRM (VRRM), which is responsible for service orchestration among Virtual Network Operators, enabling the definition of various services and policies, separately from vendors and underlying RATs. The main objective of VRRM is to satisfy the Service Level Agreements associated with different service classes to the highest possible level, within the framework of proportional fairness. On the other hand, CRRM is in charge of mapping the demanded capacity of each service onto the most suitable RATs. The model is further extended to deal with extreme situations of resource shortage, resulting from high traffic loads, by introducing delay to lower priority services. The performance of the proposed model is evaluated in a practical multi‐RAT scenario. Results confirm that the isolation of service classes is consistent with the introduced serving weights, while all the demanded capacities from different services are responded by the most suitable RATs. Finally, independent of the variation of traffic load, 100% of the aggregated capacity is used.

Wireless network virtualisation is a promising technology for future mobile communications, providing efficient and convergent mechanisms of resource management for emerging heterogeneous wireless networks. This paper proposes a model of virtual radio resource management in wireless heterogeneous networks, which can address the data rate requirements of different service classes provided by a virtual network operator, while implementing an efficient algorithm for fairness to satisfy all users based on their service priorities. The model is further extended to deal with the high traffic load, resulting from situations when there is not enough capacity to serve all users. A practical scenario is implemented to evaluate model performance, and results show that the maximum utilisation of the available capacity is achieved independent of the traffic load, while service level agreements are satisfied. Moreover, when possible, the proposed algorithm can keep a level of fairness among users from different service classes according to the predefined serving weights. Numerical results confirm that almost always 100% of the aggregated capacity is used.

The main objective of this work was to analyse different strategies for the implementation of Cloud Radio Access Networks (C-RAN) in an existing LTE-A network, by taking advantage of the functional split of a base station into Remote Radio Head and Baseband Unit, with the centralisation of the processing power in standard data centres. Four different strategies are compared: Minimise Delay, Load Balancing, Maximise Multiplexing Gain, and Minimise Number of Pools. The location of existing base station and possible data centres is taken as input. The metrics taken for the analysis are fronthaul latency, pool capacity of hourly traffic, processing power capacity, and multiplexing gain. The total cost of ownership model is also presented, to estimate possible cost savings. The model was implemented in a tool that enables the study of any scenario. The results obtained for the city of Oporto prove that a C-RAN implementation with 19 pools is possible without introducing latency problems; the operator can combine different traffic profiles, and achieve a multiplexing gain up to 1.31 that can be translated into capacity savings, and cost reductions of 63 % in capital investment and 31 % in operational expenditure can be achieved.

This paper proposes a model for the management of virtual radio resources, considering different assumptions on terminals' Signal-to-Interference- plus-Noise Ratio. The model has two main components: estimation and allocation of the available resources. In the former, a technique for obtaining probability functions for the network throughput based on the available radio resources is introduced; in addition, three approaches for estimating the network capacity, other than a general one, are proposed, i.e., optimistic, realistic, and pessimistic. In the latter, a portion of the estimated network capacity is allocated to each of the services of Virtual Network Operators (VNOs). Meeting the Service Level Agreements (SLAs) in addition to increasing the efficiency of resource usage are the key objectives in resource allocation. The results for practical scenarios show that the cellular network capacity can vary from 0.9 Gbps in the pessimistic approach up to 5.5 Gbps in the optimistic one. Moreover, the effect of this capacity variation on the allocation of the virtual radio resources to the VNOs with different SLAs is also studied. Finally, the isolation of the service classes and the VNOs by means of virtualisation of radio resources are clearly demonstrated through numeric results.

This paper proposes a model for the management of virtual radio resources. The virtualisation of radio resources is based on aggregating and managing all the available physical radio resources in a set of infrastructures. In this approach, Virtual Network Operators (VNOs) use wireless connectivity in the form of capacity per service, and do not have to deal with physical radio resources at all. Due to the isolation among instances and network elements abstraction, this virtualisation approach leads to a more efficient and flexible Radio Access Network. VNOs' services are provided by virtual resources, based on contracts and defined SLAs (Service Level Agreements). The details of the proposed model for the management of virtual radio resources, its relationship with physical resources managers, the estimation of network capacity, and the allocation procedure of data rate to the service of each VNO are described. A practical heterogeneous cellular network is considered as a case study. Results show an increase of resource usage efficiency up to 6%, presenting how the virtual radio resource management allocates capacity to services of different VNOs, when they have different SLAs and priorities.

This paper presents a statistical model for off-body radio channels in an indoor multipath environment. The model considers the distance dependent mean path loss, and describes body shadowing and fast fading components in a statistical way. The modelling of wearable antennas in Body Area Networks (BANs) has been separated into antennas in the vicinity of the body (full wave simulations), including body dynamics (taken from motion capture analysis), and the multipath environment (clusters of scatterers). A Geometrically Based Statistical Channel model adapted to the body environment is used. Several body postures and orientations, and 8 different antenna placements, are analysed for a BAN operating in 2.45 GHz. The body shadowing component is described by an average standard deviation equal to 4.6 dB, being 0.9 dB higher than the fast fading one.

The actual internet traffic growth is challenging the sustainability of mobile networks, therefore, the energy efficiency of the mobile communication infrastructure becomes a topic of particular relevance. Decreasing CO2emissions and energy demands while expanding the mobile infrastructure to satisfy traffic demands is essential. In this paper the energy efficient use of beamforming techniques and active antennas, in which an advanced antenna is utilized to direct the transmitted signal in a narrow direction, is evaluated. Slow beamforming based on reconfigurable antennas, exploits medium/long term variations of traffic in order to save energy. Fast beamforming, on the contrary, is immediately following the traffic distribution and can even allow saving more energy. From simulations it is observed that, when compared to existing state-of-art bases base stations, in a dense urban environment reconfigurable beamforming allows a maximum gain of about 8%. Adaptive beamforming, allows an additional consumed power reduction of up to 40%. Hence, the overall power consumption reduction that can be achieved by combining these techniques can be as high as 50%.

This paper presents an analysis of the capacity of a 2×2 MIMO system in off-body communications in a multipath environment. The modelling of wearable antennas in Body Area Networks has been separated into antennas in the vicinity of the body (full wave simulations), including body dynamics (taken from motion capture analysis), and street environment (clusters of scatterers). Multi-Path Components are calculated using a Geometrically Based Statistical Channel model. A street scenario is simulated, for a running body, and for 9 on-body antenna placements. The results allow one to identify 3 classes of antennas, i.e., co-directed (CD), cross-directed (XD) and opposite-directed (OD). The capacity depends strongly on power imbalance, and varies a lot in the case of antenna placement on the left hand (the difference in a single Run period is 6 bps/Hz). The average capacity is similar for all classes, and is lower when one antenna is on the right side of the body (i.e., constantly in NLoS). The CD class is characterised by the highest standard deviation, equal to 5.7 bps/Hz, whereas XD and OD present values of 4.1 and 2.9 bps/Hz, respectively.

Body Area Networks (BANs) are part of the incoming future in wireless communications. A full wave simulator is used to analyse the propagation channel between nine on-body antennas, at 2.45 GHz, in dynamic scenarios (walk and run). The movement is generated by an animation software, using a realistic shaped homogeneous phantom. The correlations between channels and their power distributions are investigated when the user is moving. Transmitter locations on the sides (for instance, on the arms), combined with non Line-of-Sight (NLOS) or quasi- LOS receiving links, were found to be the theoretically most favourable for MIMO.

This paper considers gray-space spectrum sharing when rotating radars are primary spectrum users, and multiple cells from one or more cellular networks are secondary users. A cellular network may share spectrum to supplement its dedicated spectrum, or provide a broadband hotspot service. A secondary device is allowed to transmit as long as cumulative interference is not harmful to nearby radars, probably because no radar is pointing its directional antenna at the device at this moment. This paper presents mechanisms that would support such sharing, and quantifies performance when spectrum is considered 100% utilized under traditional spectrum management. It is shown that the sharing allows cells to sustain significant mean data rates. For example, if 5% of a cellular network's cells need more capacity than dedicated spectrum can provide, a cell can get almost 1.2 bps/Hz on average from shared spectrum. By evaluating quality of service, it is found that shared spectrum could be used efficiently for applications such as non-interactive video streaming, peer-to-peer file sharing, large file transfers, and web browsing, but not for applications such as real-time transfers of small files, and VoIP.

This paper presents an analysis of the correlation between various links in off-body communications in a multipath environment. The modelling of wearable antennas in Body Area Networks has been separated into antennas in the vicinity of the body (full wave simulations), including body dynamics (taken from motion capture analysis), and street environment (clusters of scatterers). Multi-Path Components are calculated using a Geometrically Based Statistical Channel model. A street scenario is simulated, for a running or walking body, and for 9 on-body antenna placements. The results allow to identify 3 classes of antennas, i.e., co-directed (CD), cross-directed (XD) and opposite-directed (OD). The CD class is characterised by the highest average correlation, equal to 0.56, whereas XD and OD present values of 0.40 and 0.28, respectively.

Full wave simulations with realistic models of the human body are a powerful tool to study Body Area Networks. Usually, some simplifications are introduced in simulation models to speed up computation routines, and to save memory resources. This paper analyses the use of truncated voxel models, and discusses the option of using homogeneous or voxel phantoms. The metric used for the assessment is the performance of a patch antenna placed near the body (human or phantom). The statistical behaviour of the patch radiation pattern (over distance to the body) is compared via measurements and simulations. A pattern average difference of 0.9 dB is found, in the area of interest for on-body communications. The performance of the patch when using homogeneous or voxel models is very similar (12% difference), and a reduction of 5 times in the simulation time is obtained when using homogeneous models.

Current 3GPP specifications for LTE include the use of MIMO as a key technology. MIMO can be seen from two different perspectives: if increased data rates are targeted, for a given value of SNR, one gets improved data transmission; however, from an energy efficiency viewpoint, lower values of SNR are needed for the same reference data rate, therefore, allowing the reduction of the transmitted power, while providing the same data rate as the one for SISO. In this paper, a framework for evaluating the possible benefit of using MIMO instead of SISO, from the expected SNR improvement viewpoint is proposed, and results for different environments are presented and discussed. The proposed evaluation methodology allows one to properly assess the expected benefits of MIMO, therefore, providing guidelines to enable a proper SISO/MIMO mode selection according to the required service data rate. The analysis being presented is based on existing 3GPP models for data rate versus SNR in LTE. Simulation results for the ETU70 3GPP channel model are provided. It is observed that, for given reference data rates, significant SNR improvements can be obtained. Maximum values of 7.1, 15.7 and 18.0 dB SNR reduction are obtained for 2×2, 4×4 and 8×8 MIMO configurations, compared to the SISO case, therefore, allowing a significant reduction of the transmitted power, while providing the same target data rate as the one for SISO.

This paper considers opportunistic gray-space primary-secondary spectrum sharing when the primary is a rotating radar. We assume that a secondary device is allowed to transmit when its interference does not exceed the radar's tolerable level, probably because the radar's directional antenna is pointing elsewhere, in contrast to current approaches that prohibit secondary transmissions if radar signals are detected at any time. The secondary system is a cellular system using the shared spectrum in some but not all of its cells; this may occur when the cellular system needs the shared spectrum to supplement its dedicated spectrum, or for a broadband hotspot service. It is shown that, even fairly close to the radar, extensive secondary transmissions are possible, although subject to interruptions as the radar rotates. For example, with 20% of the cells transmitting in the shared spectrum, on average the cellular system can achieve a data rate close to the one obtained in dedicated spectrum, even at less than 9% of the distance that secondary transmissions will not cause harmful interference in the radar's main beam. By evaluating quality of service, it is shown that spectrum shared with radar is attractive for applications that generate much of the traffic on the Internet, including video streaming, peer-to-peer file sharing, downloads of large files, and web browsing, but not for an application sensitive to interruptions, like VoIP.

This paper considers opportunistic primary-secondary spectrum sharing when the primary is a rotating radar. A secondary device is allowed to transmit when its resulting interference will not exceed the radar's tolerable level, in contrast to current approaches that prohibit secondary transmissions if radar signals are detected at any time. We consider the case where an OFDMA based secondary system operates in non-contiguous cells, as might occur with a broadband hotspot service, or a cellular system that uses spectrum shared with radar to supplement its dedicated spectrum. It is shown that even fairly close to a radar, extensive secondary transmissions are possible, although with some interruptions and fluctuations as the radar rotates. For example, at 27% of the distance at which secondary transmissions will not affect the radar, on average, the achievable secondary data rates in down- and upstreams are around 100% and 63% of the one that will be achieved in dedicated spectrum, respectively. Moreover, extensive secondary transmissions are still possible even at different values of key system parameters, including cell radius, transmit power, tolerable interference level, and radar rotating period. By evaluating quality of service, it is found that spectrum shared with radar could be used efficiently for applications such as non-interactive video on demand, peer-to-peer file sharing, file transfers, automatic meter reading, and web browsing, but not for applications such as real-time transfers of small files and VoIP.

Wireless mesh networks are an efficient and low-cost solution for providing last-mile broadband Internet access. They face numerous challenges related to intrinsic characteristics of the multi-hop environment and flow of traffic. An energy-efficient and load-aware strategy is proposed for the unified management of radio resources of multi-radio nodes, combining channel assignment, rate adaptation, power control and max-min fairness mechanisms. It exploits 100% of the network capacity, achieving the maximum throughput, minimising spectrum and power usage. For a network of 13 dual-radio mesh nodes based on IEEE 802.11a, by using OPNET Modeler, one concludes that 4 channels and a total transmitted power of 34.5 dBm are sufficient to achieve an aggregated throughput of 4.8 Mbps per mesh point.

This paper introduces a statistical approach for modelling antennas behaviour in the vicinity of the human body. The statistics of radiation patterns, i.e., average and standard deviation, have been calculated for Uniform and Rayleigh antenna to body distance distributions. The coupling between the body and the antenna and reduction of antenna efficiency leads to the distortion of the antenna radiation pattern, which depends on the distance as well as on the location on the body. A patch antenna operating at 2.45 GHz was simulated in CST, near to regions of a voxel human model, i.e., Head, Chest, Arm and Leg. Results show that the relative change of the average radiation pattern for an antenna located on the Chest can reach 24%.

The goal of this paper is to introduce a statistical approach for modelling antennas behaviour in the vicinity of the human body. A very preliminary model based on geometrical optics has been developed, and calculations have been performed for parallel and perpendicular polarisations, for 0.915, 2.45 and 5.8 GHz, for various human body tissues, and for several antenna locations on the body. The statistics of radiation patterns, i.e., average, minimum, maximum and standard deviation, have been calculated for Uniform and Rayleigh antenna to body distance distributions. The results show a much higher variation of changes among various frequencies of average radiation patterns for the Rayleigh distribution, which can reach 60%, while for the Uniform one, it can go up to 30%. When modelling various tissues, the results show that the average radiation pattern is changing no more than 15%, but the change of standard deviation can reach 70%.

In a heterogeneous cellular networks environment, users behaviour and network deployment configuration parameters have an impact on the overall Quality of Service. This paper proposes a new and simple model that, on the one hand, explores the users behaviour impact on the network by having mobility, multi-service usage and traffic generation profiles as inputs, and on the other, enables the network setup configuration evaluation impact on the Joint Radio Resource Management (JRRM), assessing some basic JRRM performance indicators, like Vertical Handover (VHO) probabilities, average bit rates, and number of active users, among others. VHO plays an important role in fulfilling seamless users sessions transfer when mobile terminals cross different Radio Access Technologies (RATs) boundaries. Results show that high bit rate RATs suffer and generate more influence from/on other RATs, by producing additional signalling traffic to a JRRM entity. Results also show that the VHOs probability can range from 5 up to 65 %, depending on RATs cluster radius and users mobility profile.

The main goal of this work is to characterize user's influence in Body Area Networks, endeavoring to provide useful statistical values for channel models. Well-known theoretical models are used to obtain the fields produced by a plane wave or a point source near a circular dielectric cylinder (as a simple approach for the human body). A statistical analysis on the impact of the body for the source located at different distances is done. Modifications in the radiation patterns are found, ranging up to 30 dB, for instance, for a source located from 0 to 10 cm off the body.

The aim of this paper is the estimation of exclusion zones around typical installations of base station antennas. A classification of installation types is first presented, and essential parameters are identified. A discussion around biological effects from radiation and existing recommendations on exposure levels to electromagnetic radiation is then addressed. A literature overview is made, and an approach for the estimation of exclusion zones is presented. Then, for the most usual antennas and using the typical parameters for each system supplied by the Portuguese mobile operators, the exclusion zones were estimated. Values up to 6 m in front of the antenna were obtained depending on the configuration. A worst case situation was also considered (co-location of multiple systems and multiple carriers per system), values up to around 7 m being obtained.

This paper analyses and compares HSDPA and HSUPA capacity and coverage. For this purpose, a single user model is developed for the estimation of the maximum cell radius, which is then adapted to a multiple users and services scenario. The results from the single user model show that, in an indoor scenario, HSUPA can serve 1.22 Mbps up to 0.19 km, while HSDPA with 10 HS-PDSCH codes can serve 6.0 Mbps up to 0.17 km. In a pedestrian environment, HSUPA can offer 1 Mbps up to 0.7 km, while at the same distance HSDPA can offer almost 3.0 Mbps. The results from the multiple users simulator show an average cell radius of 0.28 km and 0.25 km for HSDPA and HSUPA, respectively. The HSDPA BS throughput is 2.39 Mbps, with an average throughput per user of 0.55 Mbps, while for HSUPA, the BS throughput is 0.62 Mbps with an average user throughput of 0.21 Mbps.

This paper studies performance optimisation in WLANs, by means of Quality of Service (QoS) algorithms. The 802.11e standard for QoS is analysed, compared to legacy ones, new algorithms being developed in order to improve it. All this was done in multi-service, multi-profile scenarios, with a varying number of users, in order to emulate the behaviour of real networks. QoS mechanisms manage to increase performance in all analysed scenarios, e.g., up to 7 times less delay, but these values are fixed. New algorithms for the QoS mechanisms were tested, i.e., changing channel access parameters to see if better performance can be achieved. It can be seen that better performance may be achieved by fine-tuning up the network "on the fly", i.e., by varying the parameters and adapting them according to the network location and usage profile at a given instant. All the performance analyses were done by using the OPNET Modeler simulation tool with its wireless module.

In general, modern networks are analysed by taking several key performance indicators (KPIs) into account, their proper balance being required in order to guarantee a desired quality of service (QoS), particularly, cellular wireless heterogeneous networks. A model to integrate a set of KPIs into a single one is presented, by using a cost function that includes these KPIs, providing for each network node a single evaluation parameter as output, and reflecting network conditions and common radio resource management strategies performance. The proposed model enables the implementation of different network management policies, by manipulating KPIs according to userspsila or operatorspsila perspectives, allowing for a better QoS. Results show that different policies can in fact be established, with a different impact on the network, e.g., with median values ranging by a factor higher than two.

The relative MIMO gain (RMG) is introduced as the ratio of the multiple input/multiple output capacity of a radio channel over its single input/single output one. In this paper, a statistical model is developed to approximate the distribution of the RMG, so that it can easily be incorporated into system-level simulators. A set of scenarios has been defined with different antenna configurations, for distances between 10 and 2400 m. The different antenna configurations range between 2 and 16 transmit and/or receive elements. The distribution of the RMG, presented here, is extracted from simulation results. The distribution of the RMG is modelled by an inverse Sigmoid function, which is determined by its mean value and standard deviation. The obtained model is assessed by simulation results, which shows a good fit for most of the cases. The model has a relative mean error of less than 6%, and a relative mean square error of less than 7.5%, for all antenna configurations and distances, compared to the simulation results.

In this paper, we describe the approaches taken in the 4WARD project to address the challenges of the network of the future. Our main hypothesis is that the Future Internet must allow for the fast creation of diverse network designs and paradigms, and must also support their co-existence at run-time. We observe that a pure evolutionary path from the current Internet design will not be able to address, in a satisfactory manner, major issues like the handling of mobile users, information access and delivery, wide area sensor network applications, high management complexity, and malicious traffic that hamper network performance already today. Moreover, the Internet’s focus on interconnecting hosts and delivering bits has to be replaced by a more holistic vision of a network of information and content. This is a natural evolution of scope requiring nonetheless a re-design of the architecture. We describe how 4WARD directs research on network virtualisation, novel InNetworkManagement, a generic path concept, and an information centric approach, into a single framework for a diversified, but interoperable, network of the future.

This study establishes a set of basic requirements for the network architecture of an all-wireless Internet, implemented using mesh network concepts. An implementation model to evaluate network performance at single hop level is defined, and a detailed analysis of the results obtained from several simulation runs with OPNET modeler reveals that: the standard for backbone network with better performance is 802.11a; the number of clients associated to each mesh access point must be lower than 30; the distance between mesh access points must be lower than 140 m; and that the minimum nominal data rate at the backbone is 5.5 Mbps. Using these requirements, the maximum throughput obtained at the backbone network is 5.35 Mbps. This value can be used as a figure of merit of the network in order to measure the relative gain of future network architectures and protocol enhancements.

This paper presents electromagnetic field measurements performed in Portugal by the monIT Project, a Portuguese risk communication project, which has the objective of providing the general public with relevant information on electromagnetic fields produced by mobile communication systems. The project team performed extensive measurement campaigns in public places, over the country, over the past 5 years. Two types of measurements are performed: localised and continuous ones. Localised measurements are 6 minutes spot ones, having been performed until now more than 430 measurements, with a total of 2 290 points. Continuous measurements are performed by using a network of autonomous remote probing stations. Until now, 22 different networks have been installed, with a total of 121 stations, for an average period of about 3 months each. Results from measurements show that all analysed locations are in compliance with exposure thresholds. Also, the temporal and spatial measurements parameters influence on the results is studied, e.g., in indoor locations values are about 4 times higher than in outdoor ones.

The impact of MIMO systems on common radio resource management (CRRM) in heterogeneous cellular networks is analysed, by taking some key performance indicators (KPIs) into account. A recent method used to integrate MIMO effects/gains into system level simulation is presented. User mobility profiles are mapped onto MIMO terminal capabilities, and their impact is analysed. CRRM algorithms are based on a integrated set of KPIs, by using a cost function (CF) that includes these KPIs, providing a single evaluation parameter as output, and reflecting network conditions and strategies performance. Results show that different mobility profiles and mobile terminals capabilities have different impacts on the network performance, e.g., with median CRRM QoS values ranging by a factor higher than two, when MIMO systems are present.

Wireless Communications Systems are at the centre of a new and passionate era for telecommunications characterised, in industrial terms, by the convergence of systems and technologies, a transition towards all-IP networks, and the development of technologies with a user-centric focus. On the other hand, in terms of Research and Development, researchers are already considering other, more futuristic, aspects beyond those just mentioned, and these days hot topics include things like the Internet of the Future, and all the Post-IP perspectives that come with it. In both grounds, that is the more industrial related one and the one nearer an academic perspective, there is still a long way to go, before many of the ideas being discussed today can see the light of day as a commercial product. In this context, the International Symposium on Wireless Communication Systems (ISWCS) has positioned itself as a dynamic forum for researchers and technologists to present and discuss original ideas and contributions in all fields related to mobile and wireless communication systems. ISWSC'06, the 3rd edition, held in Valencia, Spain, on September 2006, brought together leading and enthusiastic researchers and technologists, willing to identify and discuss the future technical challenges and business opportunities arising in the path towards the realisation of ambient wireless communication networks. Besides this, it was a good forum for Ph.D. students to present their work, and exchange their ideas. The idea of setting up a special issue of a journal with the very best papers of the conference was brought up by the excellent quality of some papers presented at the conference. The objective of a special issue of this kind is always to put together, beyond the conference proceedings, the best papers in an enhanced and revised version, enabling the journal to publish good papers with timely updated information in a very short time. This special issue of Wireless Communications and Mobile Computing contains the very best papers presented at ISWCS'06. An invitation was sent to a restricted number of papers, and an additional review procedure was held, beyond the conference one. At the end, this set of six papers was accepted. The papers in this issue address some of the hot topics being investigated these days, ranging from localisation and frequency sharing to multi carrier-code division multiple access (MC-CDMA) and multiple input multiple output (MIMO). This shows that the physical layer still attracts a lot of attention, and that it still has a lot of topics to be explored. The first two papers address MIMO channels, in modelling or measurement perspectives. Matthias Pätzold and Bjørn Olav Hogstad present a model for a wideband MIMO channel based on the geometric elliptical scattering one, which can be used as a starting point for the derivation of a frequency-selective space–time channel simulator, being also useful for studying MIMO channel capacity under various propagation conditions. Michail Matthaiou et al. bring a paper on dual frequency MIMO measurements around the ISM 2.4 GHz band, in indoor environments, with initial results being promising enough, as the joint spectra seem to be remarkably similar, implying that the underlying propagation mechanisms at the considered bands are also similar. Farrukh Rashid and Athanassios Manikas present one of the papers dealing with MC-CDMA, namely on arrayed reception in space-time diffused multipath vector channels; results show that the use of a diffused channel modelling in arrayed receivers yields better bit error rate (BER) and signal to noise plus interference ratio (SNIR) performance than receivers that ignore the presence of spatial and/or temporal diffusion. The other paper on MC-CDMA, from Nguyen Tran Khoa et al., addresses frequency sharing in hotspot communications for cellular networks; it proposes an overlap in the uplink of an OFDM hotspot system to an MC-CDMA cellular one, in the same frequency band, beam-forming being applied to eliminate inter-system interference. The paper for Barbara Mavì Masini et al. also deals with the coexistence of different systems, in particular on the benefits of diversity schemes for Bluetooth coverage extension in the presence of IEEE 802.11g interference, analysing packet error and coverage probabilities, among other parameters. Finally, Joseph Shmuel Picard and Anthony Joseph Weiss present a paper addressing localisation of networks using various ranging bias models, presenting a set of iterative algorithms that cope successfully with the various bias models and provide Maximum Likelihood position estimates.

Heterogeneous cellular networks are analysed by taking several Key Performance Indicators (KPIs) into account, their proper balance being required in order to guarantee a desired Quality of Service (QoS). An approach to integrate a set of KPIs into a single one is presented, by using a Cost Function that includes these KPIs, providing a single evaluation parameter as output, and reflecting network conditions and Common Radio Resource Management (CRRM) strategies performance. The proposed model enables the implementation of different CRRM policies, by manipulating KPIs according to user's or operator's perspectives, allowing for a better QoS. Results show that different policies can in fact be established, with a different impact on the network, e.g., with median values ranging by a factor higher than two.

A model for the estimation of exclusion zones around base station antennas in wireless communication systems, taking the actual surrounding environment into account, is presented. Numerical methods are applied to a GSM900 antenna installed in five common scenarios. Results show that the exclusion zone calculated in free space conditions must be redefined, due to the presence of surrounding objects, as its extension might need to be doubled when considering the installation scenario. In the case of metallic corner configurations at the back of the antenna, the exclusion zone may increase by a factor of 5. The main conclusions are valid for other wireless technologies.

This paper addresses the analysis of WCDMA systems with repeaters deployment. A generic and compact expression for up- and downlinks evaluation has been mathematically derived so that transmission powers and other radio resource management parameters can be calculated without simplifications. In particular, the real different path delays, taking into account the repeaters presence and the finite nature of the time window of Rake receivers are considered. This allows an enhanced analysis with respect to classical approaches from a system level viewpoint. Furthermore, higher reliable and accurate predictions on network performance can be obtained, which can be remarkably useful for network planning and management. By using these expressions, relevant network parameters have been evaluated and compared with the ones obtained using the classical approximations. The differences in the obtained metrics are highlighted, putting in evidence the improvement provided by the proposed analysis.

This paper presents an algorithm that improves the coverage of an initial radio network by adding new base stations, taking traffic information into account. These base stations are placed in a non-uniform way, according to the uncovered surfaces in the network and the multi-service non-uniform traffic distribution. Some results regarding the automatic placement of base stations were obtained for different scenarios in Lisbon, both with and without an initial UMTS-FDD network. For the case with an initial network, one sees that the network performance is improved, e.g., for a 128 kbps/vehicular scenario, since the uncovered traffic and uncovered area decrease (the uncovered traffic from 11.7 to 7.4 %, and the uncovered area from 28.1 to 21.4 %). Besides, each new placed sector processes 210 MB/h that were not covered yet in the initial network, compared to each initial sector processing on average 543 MB/h

This paper addresses the analysis of WCDMA systems with repeaters deployment. The real different path delays, taking into account the repeaters presence and the finite nature of the time window of Rake receivers are considered. This allows an enhanced analysis with respect to classical approaches from a system level viewpoint. Results show that not taking into account these effects imply erroneous metrics. Indeed, some of the most relevant parameters in network performance evaluation are clearly affected

This study analyses the performance of a UTRAN FDD network for multiservice users with distinct mobility profiles (pedestrian and vehicular). A set of 9 distinct services is considered with appropriate source models. Four test areas are defined in Lisbon, as an example, and non-uniform geographic users' distributions are generated in each one. Vehicular users are restricted to the city streets. Network performance is assessed by modeling the radio interface at frame level, and implementing power control, load control and admission control mechanisms. Applications' performance is assessed through the analysis of dropped and blocked call rates (for circuit switched services), delays and normalized throughputs (for packet switched ones). Downlink transmitted power is also analyzed for a more complete system characterization. System's response dependency on users* average speed and location is analyzed, trends being identified. Increasing average users* speed (up to 35 km/h) increased, as expected, drop call rate (up to 2 %) and the number of handover per call (up to 3.5)

This work presents a framework for the evaluation of converged mobile and wireless communication systems, focusing mainly on the capacity performance of the radio interface. The developed framework enables the analysis of issues such as the possible benefits of convergence and the evaluation of different convergence strategies, radio interface capacity performance, and the impact of different user traffic distributions in a converged network scenario. This framework allows one to observe that, e.g., for 700 users, HIPERLAN/2 combined with a second access technology (2G or 3G) provides sufficient capacity and performance.

The use of directional antennas at the mobile terminal or the base station, and its influence on the observed values of short-term fading depth, is addressed. This influence is modelled through the variation of the Rice factor and the maximum difference in propagation path length among different arriving components, relative to the case when omnidirectional antennas are used. Expressions for the dependence of these parameters on the antenna beamwidth, for different statistical distributions for the angle-of-arrival of arriving waves, and different types of antennas are presented. For illustration, results on the fading depth observed by UMTS and HIPERLAN/2 in different environments are presented and discussed. Globally, when using directional antennas, fading depth reduction is observed in micro-cellular environments; in macro- and pico-cellular ones, fading depth degradation can occur depending on the environment and system characteristics.

This paper presents the emerging requirements users are imposing upon the evolving world of heterogeneous 4G mobile/wireless networks through their perception of final services. The mapping proposed in this paper groups together these user requirements in three main and distinguishable categories: service provision, connectivity, and adaptability and reconfigurability, by describing system concepts for each category from user terminal to network and services/applications.

It is important to study the fundamental wideband and directional factors in order to establish how the channel properties affect adaptive beamforming, regarding intra-cell interference reduction. With such aim, a comparative set of micro- and macro-cell propagation scenarios is generated, allowing for the systematic analysis of the involved factors. A non-blind adaptive beamforming algorithm is applied, the conjugate gradient at the base station in the up-link makes use of the mobile terminal identifying the UMTS codes. Performance is measured through the gain in SINR relative to that obtained with a single omnidirectional antenna. The scenarios involve the variation of the grouping and angular displacement of mobile terminals, their distances to the base station, their number, and the number of array elements. It is found that the angular and temporal densities of incoming signals are the fundamental roots behind the differences in performances between macro- and micro-cells. For macro-cells, involving much larger angular densities, the effect of having common angles-of-arrival among links is much more critical than for micro-cells; in the case that terminals are grouped, beamforming gains are close to 0 dB. In such case, for micro-cells, values range from 0.9 to 9.6 dB, for 16 users, with a monotonous dependency on distance and on the number of array elements. Micro-cell environments not only allow for the application of simpler beamforming adaptive implementations, but also render larger performance increases by improving such implementations.

A traffic model for GSM/GPRS, the hybrid radio resource allocation (HRRA) algorithm is evaluated. A dedicated number of GPRS channels plus idle periods between GSM voice calls are used for GPRS data packet transfers. A simulator was developed in order to evaluate the HRRA algorithm, which provides a reasonable forecast on the voice blocking probability and on packet delay for a single cell system. Since the major issue is the correct resource allocation, results are shown for the influence of some choices and assumptions on the overall performance. As expected, blocking probability can reach very high values if the number of dedicated channels increases too much. For the specific case of 4 carries and traffic of 20 Erl, 4 channels dedicated to GPRS still enable an affordable blocking probability, leading to a mean packet delay of 15 s. The results can be used to illustrate the fundamental options that need to be taken by an operator, when implementing GPRS.

The performance of various cellular planning methods that decrease co-channel interference in GSM without sacrificing traffic capacity is evaluated. The advantages of each method are measured by calculating the carrier-to-interference ratio, C/I, the use of different clusters and the benefits of sectorisation being studied. An evaluation of the influence of frequency hopping on C/I is also done. The multiple re-use patterns method (MRP) is investigated as well, and a comparison is performed with previous results. The results show that changing the cluster size from 4 to 3 leads to a decreases in C/I of 2.6 dB. Several real antennas are studied for sectorisation, the best results being obtained for the 90/spl deg/ beamwidth one. The use of sectorisation, together with MRP, allows an increase in network performance, without visible additional costs.

A technique for fading depth characterisation in wideband mobile communications systems is described. The approach, based on the eigenvalue decomposition technique, allows deriving the cumulative distribution functions of the received power for Rayleigh and Ricean fading channels. Application examples for different systems, namely GSM, UNITS, HIPERLAN and MBS, working within different environments, as proposed by standard-setting bodies, are shown in detail, and the results are discussed, giving a general insight into the fading depth behaviour. In the considered environments, the fading depth experienced by GSM is between 9.4 and 18.4 dB. The fading depth observed by UNITS is below the one for GSM by 2.1 to 10.3 dB. Regarding HIPERLAN, the observed fading depth is 2.6 to 4.9 dB below the one for UNITS. MBS experiences fading depths that are usually below 9.7 dB (a worst case of 10.6 dB is observed in city streets under NLoS). Since the observed fading depth depends on the system and environment characteristics, different fading margins should be considered for each system and working environment.

A beamforming algorithm, the conjugate gradient, is applied to a base station array, in the uplink, for UTRA-TDD. Street-type, micro-cell propagation scenarios are considered, using a wideband directional channel model. Groups of mobile users are placed at different distances from the base station, along the street axis. The average beamforming gain is analysed, varying the number of array elements, the distance of users from the base station, their number and grouping. The desired signal and interference-plus-noise powers evolve differently towards optimisation, due to the composition of the correlation matrix and the algorithm's cost function. Allied to the high number of arriving correlated signals, this implies that a solution other than the MMSE one can lead to better interference suppression, for the tested scenarios. Among the tested scenarios, their influence highly depends on the number of users and their distances to the base station, the time-of-arrival spread overruling the importance of angle-of-arrival spread for larger numbers of users, closer to the base station, e.g., from 4 to 16 mobile users at 50 m or 1000 m from the base station, the beamforming gain can be degraded by nearly 4 dB or 2.3 dB, respectively, for 12 array elements.

The conjugate gradient algorithm is applied to antenna beamforming at the base-station, in the uplink, for UTRA-TDD. Specific microcell, street type propagation scenarios are used, applying a wideband directional channel model, based on the elliptical single bounce model. The scenarios are also characterised by the placement of a variable number of mobile interfering terminals, at different positions and groupings. Simulation average results mainly cover final beamforming processing gain and signal-to-noise ratio, focusing on their relation to propagation conditions. Algorithm convergence evolution and complexity are summarily addressed. The high dependency of the algorithm's performance on the propagation channel and on the number and positioning of the several mobile terminals has been confirmed, establishing such relationships. The average gain values present a minimum value of 7.3 dB, for all scenarios. It has also been concluded that a power control procedure highly improves the beamforming gain, in scenarios where the near-far effect is critical, rising up to 6.9 dB.

The development of a planar wideband directional channel model applicable to UMTS microcells is addressed. The model, a statistical one based on geometrical considerations, is implemented and simulated, its assessment being based on global parameters of channel impulse responses obtained from measurement results. Exemplifying results for the directional channel impulse response are depicted for streets based on the city of Lisbon. For longer distances, system performance improvement is expected when using adaptive antennas.

Multi-service traffic has a strong impact in mobile broadband systems (MBS) revenues, allowing one to obtain merit functions for optimisation purposes. A 'net cost' model is presented for the design trade-offs between re-use pattern, K, the coverage distance, R, and the spectral efficiency, S/sub ef/(R). It allows for the determination of the revenue per basic channel, R/sub 384/, that achieves a given value for the annual profit per kilometre. Comparing the urban with the roads scenarios for R=100 in and K=2, whereas (S/sub ef/)/sub TOT/=32.2 and 15.2%, R/sub 384/ has to be 0.005 and 0.045 #/min, respectively, i.e., the prices in the roads scenario (with higher terminal mobility) have to be around one order of magnitude higher than in the urban one.

Multi-service traffic engineering has a strong impact in mobile broadband systems (MBS) revenues, and it will allow one to obtain merit functions for optimisation purposes, a key aspect in cellular planning. MBS applications have access to different service components, with different data rates and average durations. Fast mobility has an important impact in handover failure probability, hence, in system capacity. While in the business city centre and other urban scenarios mobility has no significant effect, it affects the supported traffic in main roads. A reduction of up to 54% may come as a consequence.

The multi-service traffic analysis of a mobile broadband system (MBS), with a given mixture of applications, requires the definition of their main operation environments, corresponding to the residential, the mixed (half business/half residential), the business and the industrial markets. In this work, the respective deployment scenarios are defined by the values for the usage of a set of 26 applications. The usage of broadband applications (>2 Mb/s) increases from the residential market (17%) to the business one (25%), corresponding to a decrease in the usage of wideband (<2 Mb/s) ones (from 50 down to 42%), and to a constant value for the usage of low-MBS ([128, 384] kb/s) ones (33%); slight differences exist from the business to the industrial market. The actual number of users also depends on the density factor, varying from 0.004 users/m/sup 2/ in the industrial scenario to 0.150 users/m/sup 2/ in hotspots, e.g., offices.

This paper presents a new propagation model for urban environments, which takes into account propagation over buildings and inside streets. The formulation for multiple diffraction loss over rooftops results from the combination of Vogler's (1982) and Xia and Bertoni's (1992) models, which enables its application to profiles of buildings with non uniform heights and spacings keeping the calculation time low. A ray-tracing tool, based on the image method and UTD, has been developed to estimate the attenuation inside streets; attenuation introduced by vegetation is also accounted for by a new method. The results obtained with the application of the model to two areas of Lisbon show the importance of rays conducted by transversal streets and diffracted by vertical edges when predicting the signal near crossroads. Average values of 3.5 dB, -0.07 dB and 2.6 dB were obtained for the mean absolute and relative errors and for the standard deviation error, respectively.

An optimisation model for cellular planning by establishing the radius of micro-cells, and the border of their region in a macro-cell structure is presented. It uses a criterion based on the minimisation of the number of base stations for a specified maximum blocking probability. In a first stage, approximate analytic traffic density functions, obtained from real data for the city of Lisbon, are used. After explaining the structure of the mixed micro-/macro-cells regions, the evaluation of the average blocking probability is discussed. An application example of the optimisation algorithm is presented.

A cellular planning optimisation algorithm-the algorithm of coverage iteration with traffic partition-is presented, proposing, through a mixed structure of micro and macro cells, an optimum cellular planning for the coverage of an urban environment with a real (non-uniform) traffic distribution. The results of the algorithm, micro and macro cells radii and estimation of cells location, are obtained in order to minimise the number of base stations, guaranteeing a maximum blocking probability in every cell. A cellular planning tool that implements the algorithm, Nebmin, is described, and used to propose an optimum planning for Lisbon, by evaluating different criteria of real GSM traffic data.

Models allowing the study of the influence of coverage distance and mobile velocity on the supported traffic and on the new calls traffic linear density are examined, and results are obtained for typical scenarios in a mobile broadband system (MBS) with a linear coverage geometry. In order to cope with handover failure probability requirements, the use of guard channels for handover is assumed, mainly for high mobility scenarios. For these scenarios one concludes that there is a degradation in system capacity because, for the typical coverage distances foreseen for MBS, the new calls traffic linear density is one order of magnitude bellow the values obtained for the pedestrian scenario (where it is approximately 15 Erlang/km), decreasing from 2.47 Erlang/km, in the urban scenario, down to 0.84 Erlang/km, in the highway scenario, when two guard channels are used.

This article presents a model the analysis of the propagation channel mobile communications in urban streets at the millimetrewave band. A ray-tracing tool, based on geometrical optics, is used to calculate the impulse response at the mobile, when it moves along the street; the scenario is defined by the ground and walls surfaces, and may have obstructing objects within it. A comparison of the statistical distributions of the usual impulse response parameters resulting from the simulations with measured ones shows a good agreement. Further simulations show that the dimensions of the street and the roughness of its walls, the existence of trees, and others factors, influence the average impulse response.

The RACE-MBS (Mobile Broadband System) project deals with the development of a mobile communications system at the 60 GHz band, which means that its propagation models, both for indoor and outdoor environments, have to be developed for that specific frequency band. The article presents estimated values, at 60 GHz, for the electrical characteristics of several building materials (only for flat surfaces), namely the relative dielectric constant, the loss tangent, and the attenuation coefficient. The estimations are based on power reflection and transmission measurements of the material samples, and the multiple internal reflections in a dielectric slab are used as a model. A least-square approach is used to obtain the numerical values of the parameters from the measurements. The attenuation coefficient ranges from 1 dB/cm to 8 dB/cm.

This communication presents a model for the average received power in an outdoor environment in the millimetre waveband, similar to those used in the UHF band based on the average slope of the power decay with distance. Additional terms are included to account for the oxygen absorption and the rain attenuation. The model is intended for the specific band of MBS services [60, 66] GHz.>