Ioannis E. Pountourakis

Analysis, stability and optimization of Aloha-type protocols for multichannel networks

Abstract In this paper we propose a protocol appropriate for multiple access in a multichannel environment. All free stations contend in one channel, while the busy stations construct one queue belonging to all retransmission channels for collision resolution. Thus asymmetric access methods, such as pre-selection or sequential selection of retransission channels. A queueing model appropriate for the analysis and performance evaluation of the proposed protocol is derived. Analytic solutions are developed for a system with a finite number of stations using discrete time Markov chains. Numerical results indicate the dependence of normalized performance (normalized throughput and normalized delay) on the number of channels. The cases in which the multichannel system is superior to the single channel protocol are found. The stability of the multichannel system with infinite population is studied. Pakess Lemma criteria are applied to specify regions in which the multichannel system is stable. The control parameters are the retransmission probabilities. Optimization rules are derived which show that the optimal retransmission probabilities are a function of the number of busy stations.

Slotted optical switching with pipelined two-way reservations

Optical burst switching is a core architecture designed to reconcile the available optical technology with the increasing burstiness of traffic. However, disappointing performance in terms of high packet loss and/or low system utilization discouraged broader experimental implementations. A method to avoid these losses by first sending over the control channel a short scout packet that simulates the events that the actual burst will experience is proposed in this paper. Once the scout message detects a drop at any intermediate node, it returns back to the source to avert the payload emission and repeat the process. The way the control works results in essential service quality features, i.e., no loss of bursts, no out-of-order emissions, increased efficiency, much reduced delay variation, and graceful throttling of the load respecting the contracted rates

A multiwavelength control architecture for electronic processing bottleneck reduction in WDMA lightwave networks

In this paper we propose a new network architecture which uses several wavelengths as control channels for coordination of packet transmissions on data channels for single-hop WDMA networks and passive star topology. The distribution of control information over a number of control channels in conjunction with a suitable network interface reduces the electronic processing bottleneck at one of the end stations. Time is divided into fixed size cycles. The proposed schemes adopt the slotted ALOHA protocol for the access to control and data multichannel systems and differ in the adopted policy for data packet transmission. Analytic model is developed and analyzed for performance measures evaluation based on Poisson approximation statistics of both the infinite and finite population. Numerical results are discussed for various numbers of control and data channels. The effect of receiver collisions is analyzed and estimated by the average rejection probabilities at destination. Also simulation results are presented for comparison with the results obtained by performance analysis.

Efficient burst aggregation for QoS‐aware slotted OBS systems

A crucial issue in slotted OBS systems is the slot-generating traffic aggregation strategy as it impacts heavily on efficiency. The longer the assembly time, the better the fill level, at the penalty of delay, which may affect sensitive services. To fulfil the QoS requirements of demanding traffic and achieve high efficiency whenever possible, two traffic priorities are employed and two different bounds on the aggregation delay are enforced. A slot aggregation strategy that creates a composite slot, improving utilisation gain while respecting service guarantees, is presented and evaluated in this paper. Under this approach a slot is launched whenever high-priority traffic cannot wait any longer but any low-priority traffic is accommodated as well, producing an efficiency gain in the sense that more traffic can be sent using the same number of slots. Copyright

Throughput evaluation of multichannel slotted Aloha-type protocols with receiver collisions

The problem of receiver collisions in multichannel multiaccess communication systems is studied in this paper. A rigorous method is developed for the analytic solution of throughput performance assuming receiver buffer with a capacity of one packet. We calculate the average rejection probability at the destination of a packet in order to estimate the effect of receiver collisions. The evaluations are carried out for multichannel slotted Aloha-type protocols with Poisson arrivals and finite population. Also numerical results are showing the throughput reduction as it compared with the protocol case without receiver collisions.

Performance optimization with propagation delay analysis in WDM networks

In this study we attempt to analyze a synchronous transmission WDMA protocol for passive star topology based on the propagation delay latency effect. The introduction of propagation delay constitutes a serious parameter for WDM networks performance behavior and a realistic basis for the analysis. The proposed WDM network uses a Multi-channel Control Architecture (MCA) for two reasons: First to reduce the electronic processing bottleneck and second to optimize the performance measures by dynamically dividing the control channels into two groups according to the knowledge of the stations status (free or backlogged). In this way we develop a Markovian model for finite population with receiver collisions evaluation.

A WDM control architecture and destination conflicts analysis

The well-known Single-hop Wavelength division multiplexing (WDM) networks using passive star topology, provide direct connection between the source and the destination of a data packet but require some pretransmission coordination between the stations over a control channel. Since the electronic processing bottleneck that the single control channel architecture introduces is high, we propose a new WDM control architecture to overcome this problem. Also, we develop and analyse a queueing model of the network in order to obtain the queue length distribution and loss probabilities at the receiving sides of the stations. A rigourous method is developed to examine the receiver collision phenomenon and to evaluate the performance reduction due to the finite number of tuneable receivers at each station and finite population. Copyright

On Multi-λ Packet Labeling for Metropolitan and Wide-Area Optical Networks

Bit-asynchronous optical packet-switched networks are seen as viable candidates for Metropolitan areas. For such networks we are proposing labeling of the optical packets based on multidimensional headers constructed by using a combination of two or more physical properties like time, wavelength, sub-carried frequency, or polarization state. The resulting header can be processed using slower electronics than the line rate without any sacrifice of the information transfer rate and with higher immunity with respect to degradation of the optical signal-to-noise ratio (OSNR). Packet identification as well as header-payload separation is achieved using passive devices. This method for constructing and switching information as well as transporting frames offers potential speed processing gains over the binary case as well as improvements on bit-error rate versus OSNR. The feasibility of using headers constructed by combination of wavelength and in terms of dispersion and spectral efficiency is established as a function of bit-rate and distance. Finally a generic architecture for a suitable optical packet add/drop node is described.

Asynchronous transmission protocols for WDM LANs using multichannel control architecture

In this paper we study a single-hop WDM network for passive star topology, based on a new network architecture which uses several wavelengths as control channels with an appropriate Network Interface Unit at each station for coordination of packet transmissions on the data channels referred to as Multichannel Control Architecture (MCA). With MCA, control informations are distributed over the total control channels and in conjunction with the suitable NIU reduces the headers electronic processing bottleneck at each end station. We propose a multiple access protocol which operates asynchronously, i.e data channels are not slotted. The proposed scheme adopts the ALOHA protocol for the access to MCA and data channels. Analytic model is developed and analysed for performance measures evaluation based on Poisson approximations statistics of both the infinite and finite population. Numerical results are discussed for various number of control and data channels. The effect of receiver collisions is analysed and estimated by the average rejection probabilities at destination.

Design and Analysis of a Synchronous Transmission WDMA Protocol

In this paper, we propose a synchronous WDMA protocol for a passive star topology and suggest a new architecture for the network interface of each station. The multichannel nature of WDM networks involves receiver collision phenomena at the destination. We develop an analytical model based on a finite number of tunable receivers and a finite number of stations to investigate the performance of the proposed protocol. Numerical results are showing the performance behaviour for various number of channels, stations, and tunable receivers. Also simulation results are presented for comparison with the results obtained by the performance analysis.