OFDM-TDMA Systems Research Articles

Estimação de Probabilidade de Transbordo do Buffer em Redes OFDM-TDMA utilizando Cadeias de Markov e Curva de Serviço

This paper presents two approaches for estimating buffer overflow probability in OFDM-TDMA networks. The first approach is based on Queuing Theory and Markov Chains and is used to evaluate the performance of the transmission link in OFDM-TDMA systems. The second approach is based on Network Service Curve and Envelope Processes of the traffic flows. More specifically, it is proposed an equation to estimate the probability of buffer overflow in OFDM-TDMA systems. To this end, an equation for the Service Curve of the considered system, is also proposed. The results show that the estimates are very close to those obtained by simulations and that the computational complexity to obtain them are significantly reduced due to the absence of matrix computation.

Estimation of quality of service parameters for OFDM–TDMA networks using Markov chains and service curve

SummaryThis paper presents a model based on Queueing Theory for Orthogonal Frequency‐Division Multiplexing–Time‐Division Multiple Access (OFDM–TDMA) networks. This network model requires a Markovian model to the traffic processes. Thus, we present a Markov Modulated Fluid Model (MMFM) with autocorrelation function fitting for the network traffic, in order to evaluate the performance of the transmission link in OFDM–TDMA systems. That is, we deduce equations for estimating QoS parameters of OFDM–TDMA systems. The obtained results confirm that the proposed network model is efficient in describing the OFDM based link performance. A novel equation is also introduced for estimating the buffer overflow probability in OFDM–TDMA systems using a proposed network service curve. The computational effort is reduced compared to the Queueing Theory based method of overflow probability estimation. Besides, the results show that the estimates are very close to those obtained by simulations.

Performance Analysis and Modeling of OFDM-TDMA Systems Using Queueing Theory and a Markov Modulated Fluid Model

This paper presents a model based on Queuing Theory, Markov Chains and MMFM in order to evaluate the performance of the transmission link in OFDM-TDMA systems. To this end, a MMFM traffic model with autocorrelation function fitting is proposed. From the Queueing model, it is derived multiple QoS parameter estimators. The obtained results confirm that the proposed model is efficient in describing the link performance indicators. The use of MMFM to model the arrival process improves the QoS parameter estimates of the queueing model making their values very close to those of the simulation results.

Performance of an OFDM Based Downlink Multiple Access System for Indoor Wireless Communications

We have analyzed the downlink performance of a multiuser Orthogonal Frequency Division Multiplexing based multiple access system for indoor wireless communications. The optimization problem for minimizing the total transmit power from a base station while satisfying the bit-rate and bit-error rate criterion of the various portable users in the system has been outlined. The analytical solution obtained cannot be realized in a simple manner and we present a realizable method for the combined allocation of subcarriers, modulation mode, and power to the signals transmitted to the different users. Simulation results are used to compare the performance of the analytical solution with that using the new method under various channel conditions. Performance comparisons between the new method and an OFDM-TDMA system clearly indicate the advantages of the new algorithm under most conditions. The correlation of the frequency-domain channel strengths among the various users is shown to have an influence on the performance of the new algorithm.