Milica Pejanovic

Impact of scheduling algorithms on performances of buffered crossbar switch fabrics

In this paper, the impacts of different scheduling algorithms on buffered crossbar switch (BCS) performances are analyzed. Four BCSs are considered: combined input- and crosspoint-queued (CICQ) switch, output-queued with speed-up N (OQ-N) switch virtual ouput-queued with iterative longest input part first (VOQ) switch and virtual output-queued with longest input port first and with throughput maximization (VOQL) switch. As solutions for input buffers and crosspoint buffers scheduling procedures, longest queue first (LQF), oldest cell first (OCF) and round robin (RR) algorithms are implemented. The simulation results show that different BCSs have very close performances, irrespective which scheduling algorithm is implemented, for both uniform and bursty traffic. Also simulations indicate that CICQ switches an very close to OQ-N. Taking into account cost-effectiveness it is proved that the RR scheduling algorithm has great perspective as an easy solution for CICQ high speed switch implementation.

Performance Analysis of a New OFDM-CDMA System with Pilot Tone for Multimedia Communications

In this letter, we analyze a solution for multiple access technique based on OFDM-CDMA with pilot tone. The proposed system is designed to provide higher data rates in multimedia wireless communications. Primarily, it is achieved by introducing a serial to parallel converter with a pilot tone implemented in each of its output branches. The bit error rates (BER) performance of the proposed scheme are evaluated using computer simulations. The results show that the presented OFDM-CDMA system provides high data rates and low BER and, for the same bandwidth, it performs better than its competitive solution.

OFDM system performance over time-selective fading channels

The paper deals with transmission of OFDM-BPSK signals over time-selective fading channels. The carrier frequency offset due to Doppler shifts is taken to be the main reason for the channel time-selectivity. Closed form analytical relation for bit error rate (BER) determination is derived enabling efficient evaluation of the inter-carrier-interference (ICI) effects introduced by the channel time-selectivity.

Evaluation of trellis coded modulation effects in time-selective fading mobile radio channel

In this paper effects of trellis coded modulation in mobile radio systems are evaluated. The specific channel with timeselective fading process is considered. The complete descriptions of such channel and an appropriate receiver is given. General model for bit error rate calculations is presented. That model enables error determination for every type of fading encountered in mobile radio systems as well as for different TCM schemes. Here we chose to analyse trellis encoding in combination with PSK, PSK with pilot tone and DPSK.

A New Technique for Performance Improvement of Mobile Radio Systems

In this paper a new technique for improving quality of signal transmission over mobile radio channels with flat fading of Rayleigh statistics, is suggested. It is the technique based on implementation of 16QAM trellis modulation. After an original analytical model for such signal processing scheme is defined, the mobile radio system performance are determined through calculation of bit error rate at the system output. It is shown that the technique proposed in this paper enables better received signal quality in comparison with other known techniques such as diversity reception with various combination methods or trellis coding with phase- shift keying modulations.

A new analytical model for the dual-banyan ATM switch throughput calculation

Dual-banyan is a buffered banyan asynchronous transfer mode (ATM) switch encompassing multiple input-queueing (bifurcated queueing) as its buffering strategy. This paper describes a new analytical model for a throughput evaluation of the dual-banyan switch under different traffic patterns. the model developed and presented enables the computation of buffer state probability and the switch normalized throughput by iterative calculations. The efficiency of the given model is verified through a comparison with simulation results.

On performance evaluation of trellis coded PSK modulation in Rician-fading mobile radio channel

This paper analyses the impact of trellis coded modulation (TCM) on the performance of mobile radio communication systems subjected to Rician fading. Since the system output bit error rate could be regarded as a reliable parameter for that purpose, a mathematical model for error probability calculations is presented. Such a model is characterized by the fact that it could be implemented for any type of multi-level PSK or QAM modulation combined with trellis coding in the system transmitter. Numerical results for various Rice distribution parameter K are given together with adequate comments. Also, it is shown that the presented analytical model can be used for error rate calculations in a special case when a trellis coded mobile radio signal is corrupted by Rayleigh fading.

On the optimization of 3G cellular systems deployment

This paper presents a combined analytical and practical approach in considering the third-generation mobile systems implementation. Starting from the characteristics of the second-generation cellular systems and the required next-generation features, different possible migration paths towards next-generation systems are analysed. Thus, two basic scenarios - evolutionary and innovative - are described. However, it is shown that considerable modifications in this basic approach can be introduced. A full scale of possible third-generation deployment possibilities is identified. The presented analyses are then used for defining an algorithm for the choice of an optimized solution.

An ILPF cell scheduling algorithm for ATM input-queued switch with service class priority

Input-queued switch with service class priority is becoming attractive solution for a high-bandwidth ATM switches. In previous related works, it has been proved that throughput achieve almost 100% for up to 92% of the offered load when a random access buffers and round robin scheduling algorithm are used. In this paper we introduce a modification through a scheduling algorithm called iterative longest port first proposed to overcome the complexity of the previous solutions regarding its hardware implementation at high speed. A performance analysis is carried out by simulation and the results show a better performance in comparison with the recent ATM input-queued switch with round robin schedulers and service class priority.

Performance of the Dual‐Banyan ATM switch under arbitrary traffic patterns

Dual-Banyan (DB) is a buffered banyan asynchronous transfer mode (ATM) switch encompassing multiple input-queueing (bifurcated queueing) as its buffering strategy. This paper describes a new analytical model for a performance evaluation of the DB switch under arbitrary traffic patterns. The model developed and presented enables the computation of the switch normalized throughput and the average packet delay by iterative calculations. The efficiency of the given model is verified through a comparison with simulation results, too. We compare throughputs of DB switch and input buffer banyan, and show that DB switch has significantly better performance levels. Copyright