1,721,146 research outputs found
Channel adaptive scheduling of real time and non real time traffic for TDD/TCDMA systems
No full textA channel adaptive scheduling algorithm for TDD/TCDMA radio interfaces was proposed by the Authors in [1]. This algorithm is investigated in this paper in order to assess its ability to improve the performance of the radio interface in the presence of fading and both Real Time and Non Real Time traffic. More precisely, we estimate the maximum fading rate which gives performance improvements
Outage domains for digital transmission systems with an arbitrary number of interferers, noise and fading
No full textThis paper deals with performance characterization of digital transmission systems in the presence of co-channel interference and fading: the problem of evaluating outage and average bit error probability in the presence of any number of interferers is addressed. To this end, a new methodology with six different approaches is proposed and applied, as an example, to QPSK. The concept of outage domain for co-channel interference is introduced. It is shown in the paper that simplified bidimensional domains depending on mo-demodulation structure allow a simple and sufficiently accurate performance evaluation as a function of signal-to-noise ratio, carrier-to-interference ratio and interferers number. The same approach can also be utilized to evaluate average bit error probability. Finally, an application example is proposed to show the usefulness of this new approach
Bit error and outage probability for digital cellular systems with a small number of interferers
No full textThis paper proposes a semi-analytical approach to characterise the performance of digital cellular systems when cochannel interference is determined by a small number of interferers. Linearly modulated signals (such as BPSK, QPSK, M-ASK, M-QAM, MSK, O-QPSK, etc.) with linear receivers are investigated by considering the probability density function of the interference at the input of the decision device. Non-linear (Continuous Phase) modulation signals (such as GMSK) and non coherent detection are also investigated by means of simulation. As a consequence, a general approach to outage probability definition considering the protection ratio as a function of the interferers number and useful signal-to-noise ratio is introduced
Channel based adaptive resource allocation at the MAC layer in UMTS TD-CDMA systems
No full textIn this paper we propose a scheduling strategy at MAC level for the TDD/TCDMA UMTS Third Generation air interface. More precisely, we consider the uplink of a single-cell pedestrian outdoor scenario. Within this context we investigate the advantage of scheduling the different services that can be offered to the system, characterized by different quality and delay requirements, taking both the service priority and the channel state into account. The characteristics of the TDD/TCDMA transmission system, the power control algorithm and a frequency selective fading channel are considered in our approach, which is semi-analytical and allows the evaluation of the statistics of the Frame Error Rate and the average transmitted power per data unit, which is a measure of efficiency from the energy management point of view. The performance of the scheduling algorithm we propose is compared to a more traditional scheduling approach which takes only the priority of services into account
Outage and spectrum efficiency analysis in microcellular systems
No full textOutage probability due to interference and spectrum efficiency for a microcellular mobile radio system, are considered. A new general expression to evaluate outage probability in the presence of a Rician channel for the useful signal and an Rayleigh channel for the interferers, is presented. Traffic distribution and power control techniques are taken into account by means of a Monte Carlo simulation methods. The protection ratio for coherent and non-coherent demodulation of continuous phase-modulated signals and its impact on overall performance are estimated and discussed
The Impact of Edge Effects on the Performance of MAC Protocols in Ad Hoc Networks With Fading
No full textIn this paper, the impact of edge effects on the performance of MAC protocols is evaluated. We consider a network where packets are distributed in finite space according to a 2-D PPP, while packets arrive in time according to a 1-D PPP. Each transmitter communicates with its own receiver a fixed distance away using either the ALOHA or CSMA protocol. The metric used for analysis is outage probability, which is the probability that the measured SINR falls below a predefined threshold for the duration of a packet. Approximate analytical expressions are derived for the outage probability of the different MAC protocols assuming a fading channel. Compared to unbounded regions, ALOHA and CSMA are shown to yield lower outage probabilities in finite regions, since the boundedness can be regarded as spatial filtering. Furthermore, the benefit seems to be greater for small outage probabilities, i.e., in the region of practical interest
Impact of cochannel interference on vehicle-to-vehicle communications at millimeter waves
No full textIn order to assess a vehicle-to-vehicle millimeter wave mobile radio network the evaluation of co-channel interference effects is of great importance. In fact the definition of a coverage strategy requires suitable frequency reuse thus producing the above-mentioned interference effects. As regards vehicle-to-vehicle communication, a scenario oriented to highways is considered; in this situation, a first step in estimating the transmission performance has to be done when the link between two communicating vehicles is affected by a single co-channel interferer. This analysis is carried out by considering anomalous propagation conditions both for the useful and the interference signals: to describe the system performance the authors not only consider their power levels, but evaluate the interfered system outage probability. Moreover, in order to counteract the effects of anomalous propagation some kind of diversity techniques are investigated. Finally, rain effects will be evaluated at different carrier frequencie
On the Parameters Optimization in Handover Algorithms
No full textThis paper investigates the performance of handover algorithms used in microcellular F-TDMA radio networks such as GSM. A very general simulation tool has been developed within the framework of a cooperation between the University of Bologna and Italtel SpA. The tool allows the evaluation of network performance in the context of a multicell scenario taking log-normal shadowing, Co-Channel Interference, user mobility, uplink and downlink power levels, cell sectorization and proper frequency planning into account; different handover algorithms can be investigated by considering not only power levels, but also several quantities related to the grade of service and transmission quality. In this paper, handover algorithms based on measured power levels and timing constraints are addressed; the average number of handovers per call is considered as performance measure in order to stress the impact of Co-Channel Interference on the efficiency of the algorithm. Moreover, the concept of outage p..
Last Mile Wireless Broadband Access to Interactive Services using a C-OFDM System at 30 GHz
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