In this paper we consider a link, characterized by specific capacity, that services multi-rate random or quasirandom traffic. Random traffic is generated by an infinite number of traffic sources, while ...quasi-random traffic is generated by a finite population of traffic sources. The link is modeled as a multi-rate loss system. Handover and new calls are distinguished. New calls compete for the available bandwidth under a threshold call admission policy. In that policy, a new call of a particular service-class is not allowed to enter the system if the in-service handover and new calls of the same service-class plus the new call, exceed a predefined threshold (which can be different for each service-class). On the other hand, handover calls compete for the available bandwidth based on the complete sharing policy. We show that the steady state probabilities in the proposed models have a product form solution (PFS). The PFS leads to a convolution algorithm for accurate calculation of congestion probabilities and link utilization.
In this paper, first we review two multirate loss models, whereby we can assess the call-level QoS of the Long Term Evolution X2 link supporting calls of different service-classes with fixed ...bandwidth requirements. The X2 interface directly connects two neighboring evolved NodeBs and is mainly responsible for the transfer of user-plane and control-plane data during a handover. In both models, the X2 interface is modelled as a link of fixed capacity. Handover calls are accepted in the X2 link whenever there exists available bandwidth, i.e., no QoS guarantee is achieved for high-speed calls. Secondly, we propose three multirate loss models where calls arrive in the X2 link according to a quasi-random process and compete for the available bandwidth under the Multiple Fractional Channel Reservation (MFCR) policy, the Bandwidth Reservation (BR) policy and the Complete Sharing (CS) policy. The MFCR/BR policies allow the reservation of real/integer number of channels, respectively, in order to benefit high-speed calls. The CS policy allows calls to enter the system when there exists available bandwidth (no reservation is allowed). We propose approximate but recursive formulas for the calculation of time and call congestion probabilities as well as link utilization for all three policies. The accuracy of the proposed formulas is verified through simulation and found to be highly satisfactory.
The authors study the downlink of an orthogonal frequency division multiplexing (OFDM) based cell that services calls from different service-classes with various resource requirements. They assume ...that calls arrive in the cell as batches according to a compound Poisson process. They consider that the batch size is generally distributed while each call of a batch is treated separately from the other calls of the same batch, according to the complete sharing policy. To determine the most important performance metrics, i.e. congestion probabilities and resource utilisation in this OFDM-based cell, they model it as a multirate loss model, show that the steady-state probabilities can be determined via a product form solution (PFS) and propose recursive formulas which reduce the complexity of the calculations. In addition, they study the bandwidth reservation (BR) policy which can be used for the reservation of subcarriers in order to favour service-classes whose calls have high subcarrier requirements. The existence of the BR policy destroys the PFS of the steady-state probabilities. However, they show that there exist recursive formulas for the determination of the various performance measures. Simulation verifies the accuracy of the proposed formulas.
We consider the downlink of an orthogonal frequency division multiplexing (OFDM)-based cell that services calls from many service-classes. The call arrival process is random (Poisson) or ...quasi-random, i.e., calls are generated by an infinite or a finite number of sources, respectively. In order to determine congestion probabilities and resource utilization, we model the cell as a multirate loss model. Regarding the call admission, we consider the restricted accessibility, the bandwidth reservation (BR), and the complete sharing (CS) policies. In a system of restricted accessibility, a new call may be blocked even if resources do exist. In a BR system, subcarriers can be reserved in favor of calls of high subcarrier requirements. Finally, in a CS system, a new call is blocked due to resource unavailability. In all three policies, we show that there exist recursive formulas for the determination of the various performance measures. Based on simulation, the accuracy of the proposed formulas is found to be quite satisfactory.
In this paper we consider the downlink of an Orthogonal Frequency Division Multiplexing (OFDM) based cell that accommodates Poisson arriving calls generated from different service-classes and having ...different traffic description parameters. The system is modelled as a multirate loss model. To determine Call Blocking Probabilities (CBP) and resource utilization in this system, we propose a recursive formula which reduces substantially the complexity of the calculations. This fact makes the formula attractive for network planning and dimensioning procedures. Besides, as we show in this paper, the proposed formula can be used as the springboard for the analysis of more complicated subcarrier sharing policies, such as the Multiple Fractional Channel Reservation (MFCR) policy. The MFCR policy can be used for the reservation of subcarriers in order to reduce CBP and therefore favor calls of high subcarrier requirements.
In this paper we study a single link, modelled as a loss system, that accommodates Poisson traffic originated from different service-classes. Calls of a service-class are distinguished to new and ...handover calls. New calls compete for the available link bandwidth under a threshold call admission policy. In this policy, new calls of a service-class are not allowed to enter the system if the number of in-service new and handover calls of the same service-class plus the new call, exceeds a threshold (different for each service-class). On the other hand, handover calls compete for the available link bandwidth under the complete sharing policy. The steady state probabilities in this model have a Product Form Solution (PFS). Due to the existence of a PFS, a convolution algorithm is proposed for the accurate calculation of call blocking probabilities and link utilization.
Czech.J.Phys.55:B659-B666,2005 The discovery potential of the ATLAS detector for scalar leptoquark pair
production at the LHC is discussed in this paper. The study is performed using
a parameterized ...yet realistic simulation of the ATLAS detector response for the
signal and the background. The channel LQLQ->(lq)(lq),where l=e,mu, is
investigated for the first two generations and the decay mode LQLQ->(nu_tau
b)(nu_tau b) for the third one. In both cases, a preliminary mass reach is
found to be ~1.3 TeV for three years of LHC running at low luminosity.
The discovery potential of the ATLAS detector for scalar leptoquark pair production at the LHC is discussed in this paper. The study is performed using a parameterized yet realistic simulation of the ...ATLAS detector response for the signal and the background. The channel LQLQ->(lq)(lq),where l=e,mu, is investigated for the first two generations and the decay mode LQLQ->(nu_tau b)(nu_tau b) for the third one. In both cases, a preliminary mass reach is found to be ~1.3 TeV for three years of LHC running at low luminosity.
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