Faculty of Electrical Engineering

In this paper, performance analysis of 16x16 crosspoint queued crossbar switch, under admissible multicast traffic, is presented. Switches with various buffer lengths are analyzed under bursty multicast traffic, using two scheduling algorithms: longest-queue-first and round-robin. Multicast traffic is modeled with multicast probability, which is one of the input parameters in the simulations. The results of the simulations are compared with theoretically superior output queued switch. The results show that, for particular output load, CQ switch has almost identical performance regardless of multicast probability. This property of a CQ switch distinguishes it from other switch architectures as an ideal solution for supporting multicast traffic.

Achievement of desired performance levels (quality of service-QoS) in switches and routers is one of the most important tasks in switching systems. This implies providing guaranteed throughput, cell loss probability, average and maximal latency within the required bounds. To achieve this task in crosspoint queued switch, we implemented the weighted round robin (WRR) algorithm. We showed that WRR algorithm can achieve very good performance levels regarding the throughput and latency, but had major drawback because it require knowledge of arrival traffic. To overcome this problem, we implemented and presented in this paper the dynamic weighted round robin (DWRR) algorithm that can work with unknown arrival traffic. We showed that DWRR can achieve same performance as WRR, without the need for incoming traffic information, which makes it suitable for practical implementation.

In this paper analysis of Quality of Service (QoS) performance of Crosspoint Queued (CQ) crossbar switch is performed. In order to achieve performance guarantees, priority flow separation was done. To separate different flows, we modified CQ crossbar switch, by adding two buffers in each crosspoint. Scheduling algorithms with QoS support for the CQ crossbar switch are presented and analysed. With the particular attention on the cell delay and cell loss, results of simulation show that this crossbar architecture with proposed scheduling algorithms can achieve QoS performance guarantees.

U ovom radu je predstavljena analiza uticaja veličine frejma WRR (Weighted Round Robin) algoritma raspoređivanja na performanse CQ (Crosspoint Queued) komutatora. Performanse 32x32 CQ komutatora paketa sa WRR algoritmom raspoređivanja su analizirane za različite veličine frejma WRR algoritma i poređene sa performansama drugih algoritama u uslovima nebalansiranog sporadičnog dolaznog saobraćaja. Rezultati simulacija pokazuju da za male dužine frejma WRR algoritama, CQ komutator postiže izuzetno dobru propusnost, dok se za velike dužine frejma kašnjenje koje on unosi značajno smanjuje. Ovi rezultati pokazuju da WRR algoritam ima veliki potencijal za implementaciju CQ komutatora paketa koji će garantovati kvalitet servisa.

U ovom radu je ispitivana mogućnost obezbjeđivanja kvaliteta servisa u komutatoru sa baferima u ukrsnim tačkama. Jedan od najznačajnijih parametara u današnjim mrežama predstavlja kašnjenje, te je stoga u ovom radu ispitivano kašnjenje koje unosi CQ (Crosspoint Queued) komutator pri bursty (sporadičnom) dolaznom saobraćaju, pri velikom ulaznom opterećenju i odsustvu gubitaka. Pored srednjeg kašnjenja, ispitivano je i maksimalno kašnjenje koje unosi CQ komutator.

The possibility of enabling Quality of Service (QoS) in crosspoint-queued packet switches has been presented in this paper. For this purpose, the weighted round robin algorithm was simulated and analyzed. The packet delay represents one of the most important parameters in modern networks. Therefore, besides the throughput, we have been investigating the delay that crosspoint queued switch introduce, under bursty unbalanced traffic. Along with the average delay, the truncated maximum cell delay is analyzed. Results show that the weighted round robin scheduling algorithm achieves throughput similar to output-queued switch, under unbalanced bursty traffic, while maintaining low cell delay.

Recently, an L-statistics based method for the micro-Doppler effects removal has been proposed by the authors. Order statistics is performed on the spectrogram, while the rigid body signal synthesis is done by using the remaining STFT samples, after micro-Doppler removal. By the proposed method, the Fourier transform is recovered with a concentration close to the original one. However, during the procedure of the micro-Doppler removal, the STFT samples that correspond to the rigid body are retracted, as well. Consequently, in the reconstructed Fourier transform of the rigid body, we get one very highly concentrated pulse, as in the original Fourier transform, and a number of low-concentrated components, being spread around the peak. These low concentrated components are summed up by different random phases. In this paper, we propose a genetic algorithm for the estimation of the removed STFT samples corresponding to the rigid body. Each individual in the genetic algorithm contains possible estimation of the phases of the missing STFT samples, whereas fitness function forces individuals (combination of phases) for which a minimal energy of the side lobs is obtained. The individual with the highest fitness is considered as the final phases' estimation of the missing STFT values, and then used for the reconstruction of the original Fourier transform. The amplitude of a STFT sample is estimated as median of the amplitudes of the remaining samples at the same frequency. Performance of the proposed genetic algorithm is illustrated by examples.

In this paper, implementation of a Crosspoint-Queued switch output controller on the NetFPGA development platform is presented. The output controller is a part of design that implements functionality of Crosspoint Queued Ethernet switch and it performs a scheduling algorithm on the crosspoint buffers. Round robin algorithm is chosen as a scheduling algorithm in this implementation. The basic principle of output controller implementation is presented here, as well as its sub-modules with detailed description of tasks that they perform. Apart from the basic scheduling function, output controller presented in this paper performs the other functions such as de-segmentation and error detection, which are needed in order to make a device fully functional in the real network environment.

In this letter we propose a new analytical iterative method for calculating the throughput and average cell latency of the crosspoint queued switch with random scheduling algorithm under the bursty traffic model. This method is verified by comparing it with simulation results, which shows a very good match. To the authors' knowledge, this is the first analytical method for performance analysis of such a switch under the bursty traffic model. key words: crosspoint queued switch, throughput, average cell latency, bursty traffic

In this paper we study the influence of Weighted Round Robin (WRR) scheduling algorithm frame size to the performance of Crosspoint Queued (CQ) crossbar switch. In order to show that throughput and cell delay can be adjusted with appropriate WRR frame size, we analyzed switch for different values of frame size and under the unbalanced bursty traffic. We show that WRR scheduling algorithm achieve throughput similar to Output Queued switch when frame size is low. Also, with an increase of the frame size, the delay decreases.