This paper proposes a model to detect and solve coverage holes in 5G Radio Access Network (RAN) deployments operating with millimeter waves. The proposed model utilizes a DBSCAN-based detector to identify coverage constrained areas and then proposes the use of Relay User Equipment (RUE) capabilities to extend the RAN coverage. To optimize the activation and deactivation of RUEs, a Deep-Q-Network-based algorithm is proposed, aiming to improve spectral efficiency and decrease the outage probability experienced by network users. The obtained results demonstrate the effectiveness of the model in accurately detecting coverage constrained areas and efficiently solving these issues by means of an effective RUE activation, leading to significant improvements in network performance while minimizing the time that RUEs remain in active mode, which implies potential benefits for MNOs and UE holders and significant energy savings.

Multi-connectivity emerges as a useful feature to handle the traffic in heterogeneous cellular scenarios and fulfill the demanding requirements in terms of data rate and reliability. It allows a device to be simultaneously connected to multiple cells belonging to different radio access network nodes from a single or multiple radio access technologies. This paper addresses the problem of optimally splitting the traffic among cells when multi-connectivity is used. For this purpose, it proposes the use of deep learning to determine the optimum amount of traffic of a device that needs to be sent through one or another cell depending on the current traffic and radio conditions. Obtained results reveal a promising capability of the proposed Deep Q Network solution to select quasi optimum traffic splits in the considered scenario.

Network slicing is a fundamental feature of 5G systems to partition a single network into a number of segregated logical networks, each optimized for a particular type of service or dedicated to a particular customer or application. The realization of network slicing is particularly challenging in the Radio Access Network (RAN) part, where multiple slices can be multiplexed over the same radio channel and Radio Resource Management (RRM) functions shall be used to split the cell radio resources and achieve the expected behaviour per slice. In this context, this paper describes the key design and implementation aspects of a Software-Defined RAN (SD-RAN) experimental testbed with slicing support. The testbed has been designed consistently with the slicing capabilities and related management framework established by 3GPP in Release 15. The testbed is used to demonstrate the provisioning of RAN slices (e.g., preparation, commissioning, and activation phases) and the operation of the implemented RRM functionality for slice-aware admission control and scheduling.

Radio Access Network (RAN) slicing is a key technology, based on Software Defined Networks (SDN) and Network Function Virtualization (NFV), which aims at providing a more efficient utilization of the available network resources and the reduction of the operational costs. On that respect, in this demo a Wireless LAN hypervisor is presented that is based on a time variant scheduling mechanism and that is able to follow the dynamicity of the traffic variations seen by the different tenants in the network Access Points (APs). The work builds upon the 5G-EmPOWER tool kit, which is provided with SDN and NFV capabilities. During this demo it will be shown that the proposed hypervisor is able to dynamically assign, in every AP of the network, the appropriate resources per tenant according to their traffic requirements.

Femtocell networks have gained momentum due to their important benefits, such as improved indoor coverage, higher areal spectral efficiency, enhanced signal quality, among others. Those benefits are only achievable if adequate deployment decisions and efficient resource allocation techniques are able to assure the seamless co-existence among Femtocell Access Points (FAPs) within the femtocell tier and between FAPs and macrocell users. In this work, we study the frequency planning problem on the femtocell tier deployed on a closed access mode and using a dedicated spectrum. A novel radio resource allocation technique that performs a mid/long-term frequency planning for the FAPs in the femtocell tier is proposed. It is concluded in this paper that the Dynamic Frequency Planning (DFP) algorithm based on the Branch and Bound technique is able to find the optimal frequency planning according to any desired criterion and that the proposed algorithm is suitable for implementation in a distributed 4G femtocell network regarding signaling overhead and latency aspects.

The inability to perfectly know the system noise properties to infinite precision, referred to as noise uncertainty, results in noise power calibration errors that have been proven to impose fundamental limitations on the detection performance of any spectrum sensing (signal detection) method in cognitive radio networks. In this work we argue that the inability of cognitive radio users to perfectly know beforehand the primary signals that might be present in the sensed band and their properties, referred to as signal uncertainty in this work, also results in an additional detection performance degradation. The noise uncertainty consequences have widely been studied, verified experimentally and distilled into tractable mathematical models. However, the potential effects of the particular primary signal properties on the resulting detection probability of generic spectrum sensing algorithms, such as energy detection, have not been taken into account in the analysis and performance evaluation of spectrum sensing in cognitive radio networks. In this context, this work develops a mathematical model for signal uncertainty and, based on such model, analyzes the impact of signal uncertainty on the resulting detection performance of spectrum sensing, with and without noise uncertainty, and compares the practical consequences of both degrading effects.

Energy detection constitutes a preferred approach for spectrum sensing in cognitive radio owing to its simplicity and applicability (it works irrespective of the signal format to be detected) as well as its low computational and implementation costs. The main drawback, however, is its well-known detection performance limitations. Various alternative detection methods have been shown to outperform energy detection, but at the expense of increased complexity and confined field of applicability. In this context, this work proposes and evaluates an improved version of the energy detection algorithm that is able to outperform the classical energy detection scheme while preserving a similar level of algorithm complexity as well as its general applicability regardless of the particular signal format or structure to be detected. The performance improvement is evaluated analytically and corroborated with the experimental results.

Cognitive radio nodes of a dynamic spectrum access network monitor the spectrum around them in order to detect and opportunistically exploit temporarily unoccupied spectrum gaps. The overall behavior of the whole network depends on the spectrum occupancy perceived by each node at its local environment. An appropriate understanding of the local perception of cognitive radio nodes in various scenarios and locations as well as its dependence on the propagation environment can provide valuable information for the design, dimensioning and performance evaluation of dynamic spectrum access networks. In this context, this work presents a novel and practical approach to predict the spectrum occupancy that would be perceived by cognitive radio nodes in realistic scenarios. Based on such approach, we explore the dependence of the spectrum occupancy perception with the considered scenario and location as well as the impact of particular parameters of the radio environment.

The existing approximations for the Gaussian Q-function have been developed bearing in mind applications that require high estimation accuracies (e.g., derivation of the error probability for digital modulation schemes). Unfortunately, the associated mathematical expressions are too complex to be easily employed in many other analytical studies, even if they do not require such a high accuracy. This letter proposes a simple, yet accurate mathematical approximation to the Gaussian Q-function. When compared to other existing approximations, the proposed model provides an adequate balance between accuracy and analytical tractability. Its simplicity enables its application over a wider range of analytical studies at reasonable accuracy levels. As an illustrative example, the proposed approximation is employed to obtain a new and simple closed-form expression for the probability of detection of an energy detector under Rayleigh fading channels.

Spectrum occupancy modeling in the context of Dynamic Spectrum Access/Cognitive Radio (DSA/CR) constitutes a rather unexplored research area that still requires much more effort. This paper addresses the problem of modeling spectrum occupancy in the spatial domain by proposing a novel theoretical approach that enables modeling the occupancy level perceived at any geographical location based on the knowledge of some simple primary signal parameters. The validity of the theoretical model is verified with extensive empirical measurement results. Some examples of its potential applicability are discussed as well.

Handling mobility at the transport layer is a promising approach to achieve seamless handover in the context of heterogeneous wireless access networks. In particular, features such as multihoming and dynamic address reconfiguration provided by mobile SCTP (mSCTP) protocol are among the key enablers for handover support at the transport layer. This paper investigates the applicability of concurrent multipath transfer (CMT) to distribute data among two end-to-end paths of an mSCTP association during the handover transition process. To that end, the principles of the mSCTP-CMT design are given, emphasizing the consequences of a sender-introduced reordering and its effect on congestion control. The proposed mSCTP-CMT handover scheme is benchmarked with two other handover schemes, namely mSCTP and SCTP failover-based. Provided analysis indicates the possible application area of mSCTP-CMT, taking into account not only handover scenario parameters (dwelling time, available bandwidth ratio and round-trip time), but also an important design constraint: receiver buffer (rbuf) size. Rbuf size proves to be a major limiting factor shrinking significantly, yet not excluding mSCTP-CMT's application scope.

This paper details the current work status of the ETSI Reconfigurable Radio Systems (RRS) Technical Committee (TC) and gives an outlook on the future evolution. In particular, Software Defined Radio (SDR) related study results are presented with a focus on SDR architectures for Mobile Devices (MD), such as mobile phones, etc., as well as for Reconfigurable Base Stations (RBS). For MDs, a novel architecture is presented enabling the usage of SDR principles in a mass market context. Cognitive Radio (CR) principles within ETSI RRS are concentrated on two topics, a Cognitive Pilot Channel (CPC) proposal and a Functional Architecture (FA) for Management and Control of Reconfigurable Radio Systems, including Dynamic Self-Organising Planning and Management, Dynamic Spectrum Management, Joint Radio Resource Management, etc. Finally, study results are indicated which are targeting a SDR/CR security framework

Handling mobility at the transport layer is a promising approach to achieve seamless handover in the context of heterogeneous wireless access networks. In particular, features such as multihoming and dynamic address reconfiguration provided by mobile SCTP (mSCTP) protocol are among the key enablers for handover support at the transport layer. This paper investigates the applicability of Concurrent Multipath Transfer (CMT) to distribute data among two end-to-end paths of a mSCTP association during handover transition process. To that end, the principles of the mSCTP-CMT design are given, emphasizing the consequences of such a sender-introduced reordering and its congestion control implications in a handover scenario. The proposed mSCTP-CMT handover scheme is benchmarked with a pure mSCTP handover scheme. Provided analysis indicates the possible application area of mSCTP-CMT, taking into account not only handover scenario parameters (dwelling time, available bandwidth ratio and round-trip time), but also the most important constraint of such a design: receiver buffer (rbuf) size. Rbuf size proves to be the major limiting factor shrinking significantly possible mSCTP-CMT application scope, yet not excluding definitively the proposed idea.

Cognitive radio (CR) has been identified as a promising solution to the so-called spectrum scarcity problem. The basic idea of this paradigm is to allow unlicensed users to access in an opportunistic and non-interfering manner some licensed bands that are temporarily unoccupied by licensed users. CR is expected to significantly increase current spectrum usage. However, before this paradigm can turn into reality, a full understanding of the dynamic usage of spectrum is required. Current spectrum utilization has already been evaluated in some measurement campaigns. However, most of them were performed in USA and therefore evaluated the American spectrum regulation and utilization. Few studies have been carried out in other places. In this context, this paper presents spectrum occupancy measurements conducted in the frequency range from 75 MHz to 3 GHz in an outdoor environment in urban Barcelona, Spain. The measurements are analyzed and compared to the official spectrum regulations. The obtained results demonstrate the existence of a significant amount of spectrum available for the deployment of future CR networks.

Spectral efficiency, fairness and user satisfaction are crucial aspects for resource allocation in multi-user Orthogonal Frequency Division Multiplexing (OFDM)-based cellular networks. Classical Radio Resource Allocation (RRA) strategies, such as Max-Rate (MR), Proportional Fairness (PF) and Max- Min Fairness (MMF), show different performances regarding the three aforementioned aspects. In this work, we present an adaptive RRA framework that joins the criteria of the three classical strategies in a unified manner and can be dynamically configured according to the cellular operator's objectives. We exemplify the flexible use of this general framework by proposing two adaptive RRA algorithms that provide strict fairness among users and maximizes the users' satisfaction, respectively. Simulation results show that the two proposed algorithms can efficiently achieve their respective objectives by means of the adaptation of the general RRA framework. I.

This paper analyzes the complexity-performance trade-off of three heuristic approaches applied to synchronous multicarrier multiuser detection (MUD) of single/multiple transmit antennas and multiple receive antennas code division multiple access (S/MIMO MC-CDMA) systems. Weighting particle swarm optimization (WOPSO) and unitary Hamming distance search-based strategies, specifically 1-opt local search (1-LS) and simulation annealing (SA) multiuser detection algorithms, were analyzed in details using a single-objective antenna-diversity-aided optimization approach. Monte-Carlo simulations show that, after convergence, the performances reached by the three heuristic MUD (HEUR-MUD) S/MIMO MC-CDMA algorithms are identical, with computational complexities remarkably smaller than the optimum multiuser detector (OMUD). However, the computational complexities could differ substantially depending on the operation system conditions. The complexities of the HEUR-MUDs were carefully analyzed in order to demonstrate that 1-LS scheme provides the best trade-off between implementation complexity aspects and bit error rate (BER) performance when applied to multiuser detection of S/MIMO MC-CDMA systems with low order modulation.

This paper analyzes the particle swarm optimization multiuser detector (PSO-MUD) under high-order modulation schemes, (particularly for M-QAM), in DS/CDMA systems single-input-single-output (SISO) multipath channels. In order to avoid the computation of complex-valued variables in high-order squared modulation, the optimization problem is reformulated as a real-valued problem. Considering previous results on literature for low-order modulation formats (usually binary/quadrature phase shift keying - BPSK/QPSK), a performancetimescomplexity trade-off comparison is carried out between PSO-MUD and local search multiuser detector (LS-MUD). Performance is evaluated by the symbol error rate (SER), and complexity by necessary number of cost function calculations for convergence. If the background for BPSK heuristic multiuser detection (HEURMUD) problem indicates that the 1-opt local search method is enough to achieve excellent performancetimescomplexity trade-offs, our Monte-Carlo simulation results and analysis show herein indicate the LS-MUD presents a lack of search diversity under high-order modulation formats, while the PSO-MUD is efficient to solve the MUD problem for high-order modulation schemes.

The motivation behind this paper is a need to have a more accurate estimation of the failover time in SCTP. The traditional one, commonly used in the literature, is based on the sum of the consecutive retransmission timeouts. This is not always appropriate, especially when using the SCTP multihoming feature as a basis for achieving transport layer mobility in wireless networking scenarios, where the transition time between available paths becomes a key aspect for the optimisation. Two new factors are introduced into the proposed estimation formula to reflect the influence of the network parameters and the behaviour of the most common protocol implementations. For the proposed model, we perform a best-worst case analysis, and then illustrate it with an example of a detailed estimation. Finally, we perform simulations comparing our proposal with the traditional estimation in a typical transport layer mobility scenario including long thin networks.

This paper presents a novel end-to-end quality of service (QoS) architecture for wireless networks. The focus is placed in the coordination of QoS management between common radio resource management (CRRM), for heterogeneous radio access technologies, and the QoS enabled IP-based network segments. A functional reference QoS framework is introduced and the envisaged QoS management functions are described. The innovations proposed in the presented QoS framework arise mainly from the study of cross effects between the radio and fixed transport resources management. The proposed QoS framework has been designed considering the current 3GPP R6 networks as well as their long-term evolution (LTE) scenario. Some illustrative results for a coordinated admission control algorithm are given as a proof of concept, to show the advantages of CRRM and IP QoS management coordination.

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.

Transport layer mobility is becoming a serious candidate for implementing seamless handover in a heterogeneous radio access network scenario. In this context, the stream control transmission protocol (SCTP) is in the core of most relevant transport layer mobility schemes being currently studied. Most of these proposals inherit multihoming and congestion control rules specified in the standard SCTP. However, standard SCTP's design was not targeted to cope with the variable nature of wireless channels. In this paper we analyse the performance of the SCTP failover mechanism when used as a handover solution in multihoming scenarios. In particular, the performance of the protocol is assessed under different radio channel variation patterns and different degrees of link level reliability. Obtained results are claimed to be a reference point for further investigation related to new proposals for handover schemes handled at the transport layer.

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

The transmission opportunity (TXOP) is a novel mechanism, proposed by Task Group "e", for burst packet transmission within IEEE 802.11 wireless networks. However, its use is not optimized. In this paper an Enhanced TXOP scheme is proposed to exploit more effectively TXOP limits and increase system efficiency. The performance of ETXOP is evaluated from simulation based studies realized by means of simulator developed in OPNET platform.

In the third generation wireless system UMTS, radio resource management (RRM) functions should encompass scheduling algorithms. In particular, scheduling mechanisms play a key role in resource allocation for UMTS shared channels. These shared channels are mostly used in UMTS to support services such as web browsing and e-mail that work with the transport protocol TCP. So, performance achieved by TCP users in shared channels is closely related to RRM scheduling. In this letter, we study the cross-layer interaction between TCP and two main sets of RRM scheduling strategies: rate-oriented and delay- oriented. Both strategies can be considered as the basic pillars behind more complex scheduling algorithms. We found that the low delay jitter achieved by rate-oriented scheduling is the reason for having a better TCP throughput in comparison with the delay-oriented scheduling algorithm. Results have been obtained with the aid of a real-time UMTS emulator.

This paper focuses on the analysis of 3G mobile communications systems in scenarios with non-uniformly distributed traffic. Special attention is paid to the impact of hot spots on uplink BLER and admission control. Load balance is carried out by dynamically varying common pilot power. Results reveal that the performance of the system in the uplink may be improved when applying such technique

Common radio resource management strategies are devoted to achieve an efficient usage of the pool of radio resources available in a heterogeneous radio access network context. This paper describes the functionalities associated with the common vision of radio access technologies, the different possibilities in the functional model split and the corresponding implementation considerations.

Prioritisation based on traffic class is widely used within radio resource control strategies to provide quality of service (QoS) assurances in 3G wireless systems. Under high load conditions, traffic prioritisation can lead to situations where, momentarily, most of the radio resources are assigned to delay-constrained connections (e.g. conversational users) and, consequently, the available bandwidth for less priority users (e.g. interactive traffic) is significantly reduced. In This work we analyse the impact of this bandwidth oscillation phenomenon on TCP connections over a downlink UMTS channel. Experimental results have been obtained using legacy TCP connections over a real-time UMTS testbed.

Packet transmission combined with WCDMA (wideband code division multiple access) access technique defined in the Universal Mobile Telecommunication System (UMTS) provides high flexibility in resource allocation in order to integrate multimedia services with different requirements. However, this flexibility requires designing an efficient call admission control (CAC) able to control the number of active users in a system where capacity varies according with the level of interference. Taking into account the stochastic nature of multimedia traffic and the changes in the available capacity in the CDMA system, an effective capacity request is derived and used to characterize the resources required by each mobile user in order to meet its respective quality of service requirements. These requirements are expressed in terms of rate and delay constraints in addition to the signal to interference ratio. After setting an effective capacity threshold for the system, a linear approximation is used to find the total amount of resource required by all the mobile users already admitted in the system and the new connection request. Packet transmission is considered for both real time and non real time services while a centralized demand assignment algorithm has been implemented in order to provide QoS in the packet level. Performance in a multicell scenario and in time variant wireless channel conditions has been evaluated considering channel-stated scheduling algorithms. Computer simulation results are given to demonstrate the performance of the proposed method.

The general packet radio service (GPRS) system provides a packet switched data service with quality of service (QoS) over a GSM infrastructure. In order to cope with the QoS requirements, packet scheduling strategies are used. On the other hand, GPRS introduces four coding schemes with different degrees of data protection according to the radio channel conditions. The selection of an appropriate coding scheme according to the time variant channel conditions can lead to a substantial increment of the QoS. Two scheduling policies, namely MED (modified earliest deadline) and MLT (minimum laxity threshold) are evaluated, assuming both link adaptation (LA) strategy, based on BLER (block erasure rate) estimation, and heterogeneous traffic. Web browsing, fleet management, SMS (short message service) and e-mail services are assumed. The performance of the proposed scheduling policies is evaluated in terms of throughput and delay. For urban environments with high load conditions, the obtained results show that a simple LA enhances QoS system performances, even though there is a trade-off with respect to the network packet loss.

In this paper, we present a capacity analysis in order to set an effective threshold for connection admission control associated to the reverse link of a multimedia wireless communication system using CDMA. The analysis has been associated to the WCDMA concept defined in UMTS, where packet transmission has been considered for both real time and non real time services. A centralized demand assignment algorithm has been considered in the packet level in order to provide QoS, in terms of lost packet and delay constraints.

This paper presents some packet transmission mechanisms dealing with the provision of quality of service (QoS) over the radio interface in a TDD-TD/CDMA scenario such as the one considered for the UTRA TDD proposal in the UMTS system. To this extent, two different multiple access protocols are proposed for such an environment, based on the ISMA and DSA++ approaches, and they are complemented by a polling mechanism that allows a reduction in the access time. A scheduling algorithm is also considered in order to prioritise transmissions to guarantee the specific QoS requirements for the different services.

The General Packet Radio Service (GPRS) system will offer to the users an easy access to Internet applications which work with the TCP protocol. We analyse by means of simulations the performance in the GPRS network of the following wireless TCP proposals that use a proxy server: the Snoop protocol and the Split mechanism. We also describe the impact of the GPRS LLC layer in acknowledged mode in the TCP end-to-end throughput. Unlike previous research we consider two scenarios for the GPRS radio interface: one with several users present in the system, and the other with only one user in it.

Software radio will have an important role in future terminal and base station definition. Although the ideal software radio architecture is highly restricted by technology, at present it is possible to build complex systems completely customised and reconfigurable using FPGA devices. They provide the designer with the possibility of modifying the hardware functional qualities without giving up high performance or using resources poorly. To check how important is this affirmation considering future wideband systems, a representative DS-CDMA subsystem has been built over an FPGA platform that allows fast reconfiguration of internal system blocks.

This paper presents the performance analysis of different scheduling strategies suitable for transmission of real time and nonreal-time services in packetized form in the FDD mode of UMTS. A centralized demand assignment protocol is implemented to transmit over the dedicated physical channel. Given that in CDMA the capacity is not fixed and varies with the interference, the arrangement of transmissions is combined with a distributed power control that allows one to maximize the throughput by adjusting the transmitted power of terminals in order to minimize the interference. The scheduling strategies analyzed are based on the establishment of static priorities between classes of traffic combined with the assignment of dynamic priorities, associated with time stamps, to the individual packets belonging to a connection. Although scheduling based in time stamps offers differentiated quality of service to multimedia users, we have shown that the maintenance of the control channel (DPCCH) associated with data channel (DPDDH), when mobile stations MS are waiting their permit to transmit, is an important factor in the reduction of the capacity of system. So, this paper also considers that DPCCH are only present if mobiles are transmitting on DPDCH. In this case, the impact of imperfections in the power control mechanism is evaluated. Although results improve, simulations show that the mean and variance of the ratio between intercell and intracell interference grows, decreasing the global capacity. A new scheduling mechanism is proposed in order to improve the performance. The main idea is to limit the number of changes in the assignment of permits to transmit maintaining the permits to the same users as long as the delay tolerance of the waiting users allows it. A complementary priority is associated to the packets.

GPRS defines four coding schemes named from CS-1 to CS-4 with different degrees of data protection against transmission errors in the air interface. The former coding scheme is already used in GSM and the others sequentially offer higher throughput rates but less protection. The selection of the best suited coding scheme could be based on link quality estimators but also on more deterministic system parameters such as time advance (TA) information. This paper analyses this latter option and provides results in order to quantify the feasibility of such allocation based on the time advance information. Aspects such as TA resolution, cell coverage, power control policies and system load are taken into consideration.

Cellular packet systems such as GPRS rely on cell update (CU)/routing area update (RAU) mechanisms to provide continuous connectivity within the service area. This paper is aimed to evaluate the impact that these mechanisms have on system performance. We show that the CU/RAU procedure could cause the loss of user data packets that, in case of reliable data services, can increase the amount of retransmission signaling to cope with such packet losses. In any case, it should be useful to characterize the amount of user data traffic affected in order to take into account this effect when QoS criteria are pursued.

In the context of third-generation (3G) systems a mix of services with different requirements are expected. Consequently, packet scheduling mechanisms for quality of service (QoS) guarantees will play a key role. This paper proposes a new scheduling strategy that makes consistent the target quality in the radio link with the priority level assigned to each user. The performance of such a strategy is assessed by system level simulations and, in order to gain more insight into the difficulties of this optimization problem, it is compared to other alternatives. This work is part of the Wineglass project, within the Fifth Framework Program of the European Commission (IST), where a real time demonstrator including the radio resource management tasks is being developed. Thus, an implementation approach of the proposed scheduling is also described. The implementation is based on lookup tables and this approach is validated by simulation.

An overview of the main characteristics of the real time emulator (RTE) to be implemented in the context of the Rainbow project is presented. First of all, the RTE functional description is shown in order to justify the rationality of the envisaged approach. Next, a description of the emulation and simulation models used in the RTE for CoDiT is provided. Off-line simulation models are used to estimate the parameters to be employed in the emulation of the different scenarios, while the use of emulation models allows for a reduction of the RTE complexity.

This paper presents an analysis of soft-output equalization and coding techniques applied to 4 and 16-QAM TDMA radio systems for frequency selective fading channels. In particular, typical urban and hilly terrain environments have been considered. The use of the soft information provided by the equalizer enhances the system performance considerably. Specifically, an improvement of more than 4 dB can be achieved in relation to hard decoding techniques. The necessity of introducing some interleaving in order to destroy the channel memory has also been stated. The actual investigated equalizers have been a soft-output decision-feedback equalizer (SODFE) and a soft-decision M-algorithm (SDMA) jointly with convolutional coding and both ideal and finite interleaving.

Presents an investigation of diversity and/or equalization techniques applied to 4 and 16-QAM TDMA radio systems for rapid fading dispersive channels. In particular, typical urban (TU) environments have been considered. A least sum of squared errors (LSSE) channel estimator has been introduced in order to allow the analytic calculation of the equalizer coefficients. By means of simulation methods the authors have found that a degradation of 4 dB can be expected in relation to ideal estimation. Furthermore, the degrading effects of non-linear power amplifiers have been analyzed and a degradation of 2 dB has been found.>

This paper presents a comparative study of 16-QAM, 32QAM, 64-QAM, and 128-QAM 140 Mbit/s digital radio in the presence of multipath fading. ConventionalT-spaced and fractional tapspaced equalizers have been considered to compensate for the ISI-induced symbols. The performance measure used is the bit error ratio (BER); thus, upper and lower bounds on BER have been developed. Based on this calculation procedure, results showing the net fade margin versus the gross fade margin have been obtained in a variety of cases that include the presence of both nonlinear and linear equalizer structures.

This paper presents the performance of a pseudoerror monitoring technique for a 16 QAM 140 Mbit/s digital radio in presence of multipath dispersive fading. The so-called pseudoerrors, generated by means of a threshold modification of two, namely, secondary receivers are entered into an extrapolating function to obtain a fast bit error ratio (BER) calculation. A counting time of 10 ms was retained in order to follow fading depth changes up to 100 dB/s and fading notch speeds up to 300 MHz/s approximately. We have considered three structures for the receiver: without equalization, with IF amplitude equalization, and decision feedback equalization (DFE). The results obtained show the estimated and real BER within a margin that includes the two recommended CCIR values: 10-3and10-6. In particular, the estimated signature obtained in the case of using IF equalization reveals that this fast BER calculation could be an effective choice to control a frequency diversity switch, even in the presence of a fading activity with rapid variations.