Kalyani Bogineni

Low-complexity multiple access protocols for wavelength-division multiplexed photonic networks

Media access control protocols for an optically interconnected star-coupled system with preallocated wavelength-division multiple-access channels are discussed. The photonic network is based on a passive star-coupled configuration in which high topological connectivity is achieved with low complexity and excellent fault tolerance. The channels are preallocated to the nodes with the proposed approach, and each node has a home channel it uses either for data packet transmission or data packet reception. The performance of a generalized random access protocol is compared to an approach based on interleaved time multiplexing. Semi-Markov analytic models are developed to investigate the performance of the two protocols. The analytic models are validated through extensive simulation. The performance is evaluated in terms of network throughput and packet delay with variations in the number of nodes, data channels, and packet generation rate. >

A collisionless multiple access protocol for a wavelength division multiplexed star-coupled configuration: architecture and performance analysis

A collisionless wavelength-division multiple-access (WDMA) protocol for a passive star-coupled photonic network is introduced and shown to possess significant performance and flexibility advantages. A performance modeling technique based on a semi-Markov analytic model, which eliminates many of the unrealistic assumptions of past approaches, is introduced. The performance of the protocol is analyzed using this model and discrete-event simulation. Control channel access arbitration is achieved through time-division multiplexing (TDM), enabling all active nodes to transmit once every control cycle. The long synchronization delays typical of TDM systems are significantly reduced, because the control cycle length is proportional to the control packet size rather than the data packet size. The protocol eliminates packet collision and variable-sized data packets are supported without utilization degradation. >

Pre-allocation media access control protocols for multiple access WDM photonic networks

Media access control protocols for an optically interconnected star-coupled system with pre-allocated WDMA channels are introduced and compared. The photonic network is based on a passive star-coupled WDM–based configuration with high topological connectivity and low complexity. The channels are pre-allocated to the nodes with this approach, where each node has a home channel that it uses either for all data packet transmissions or all data packet receptions. A home channel may be shared if the number of nodes exceeds the number of channels in the system. This approach does not require both tunable transmitters and tunable receivers. The performance of a generalized random access protocol is compared to a protocol based on interleaved time multiplexing. Both protocols are designed to operate in a multiple-channel multiple-access environment and require each node to possess a tunable transmitter and a fixed (or slow tunable) receiver. Semi-markov analytic models are developed to investigate the performance of the two protocols. The analytic models are validated through simulation and performance is evaluated in terms of network throughput and packet delay with variations in system parameters.

Design and performance analysis of preallocation protocols for WDM photonic networks

Wavelength Division Multiplexing (WDM) enables partitioning the enormous bandwidth of photonic networks into multiple smaller, more manageable, multiple access channels. These channels operate at a data rate which matches the electronic interface speed, viz. Gbps. Media access protocols for an optically interconnected star-coupled WDM network with no control channel are introduced and compared. The channels are preallocated to nodes where each node has a home channel that it uses for all data reception. If the number of nodes exceeds the number of channels, home channels are shared among nodes. This approach does not require both tunable transmitters and tunable receivers reducing system complexity and is not limited by the number of channels available. A generalized random access protocol and an interleaved time division multiplexed protocol are compared. Both protocols require a fast tunable transmitter and a slow (or fixed) tunable receiver per node. Each node has a set of queues of variable capacity -- one per data channel. The switching time of tunable transmitters has a significant impact on system performance and techniques are developed to reduce the impact. Detailed discrete-event simulation results are used to evaluate system performance in terms of network throughput and average packet delay with variation in the number of nodes and channels and transmitter switching latency.

Acm sigcomm: Acknowledgement techniques of random access based media access protocols for a WDM photonic environment

This paper evaluates acknowledgement schemes for random access based media access protocols for star-coupled WDM networks. Each node requires a fast wavelength tunable transmitter and a slow/fixed receiver. The multiple, multi-access channels are pre-allocated to the nodes for data reception. Each data packet has to be acknowledged by the destination node to indicate successful transmission since the channel cannot be sensed. One solution to providing acknowledgements is to extend the transmission slot: each transmission consists of a data transmission phase and an acknowledgement phase. At the end of the slot, the source node would know if transmission was successful if collisionless acknowledgement transmission is ensured. However, this approach degrades with increased propagation delay and processing latency. An alternative technique eliminates the acknowledgement phase by requiring explicit acknowledgements from the destination node. The relative advantages and drawbacks of the two schemes are studied, and the impact of the acknowledgement scheme on protocol performance is examined. Protocol performance, measured in terms of average packet delay and network throughput, is studied with respect to system scalability, sensitivity to propagation delay, packet processing latency and transmitter tuning latency.

Collisionless media access protocols for high-speed communication in optically interconnected parallel computers

This paper introduces a collisionless wavelength division multiple access protocol for a passive star-coupled parallel computer. A performance analysis is developed based on a semi-Markov model. This model, verified by extensive simulation, is then used to study the behavior of the protocol with varying system characteristics.

Performance analysis of two address space allocation schemes for an optically interconnected distributed shared memory system

An Optically Interconnected Distributed Shared Memory (OIDSM) system is introduced and analyzed. Distributed shared memory systems place a heavy traffic requirement on the interconnection network. Complex memory allocation schemes have been introduced to reduce the network load. The photonic network of the system introduced in this paper alleviates the traffic load concern, and enables the development of a fixed memory allocation scheme with a significant reduction in complexity. The photonic network employs wavelength division multiple access (WDMA), creating multiple channels on a single optical fiber. This paper analyzes the performance of two memory allocation schemes through mean value analysis of a closed queueing network. The performance model is validated through simulation.<<ETX>>

Switching latency overlap techniques for WDM star-coupled media access protocols

The impact of the wavelength-tunable device switching latency on the performance of media access protocols for star-coupled wavelength-division-multiplexed (WDM) photonic networks is investigated. The effects of a reservation-base protocol (TDMA-C) and two preallocation-based protocols (I-TDMA* and I-SA) are compared. TDMA-C is control-channel based, with one WDM channel allocated to reserve access for data packet transmission on the remaining data channels. I-SA and I-TDMA* are designed for a network where channels are preallocated to the nodes for reception, with each node having a home channel it uses for all data packet receptions. The performance of the protocols is evaluated through discrete-event simulation is terms of network throughput, packet delay, and data channel utilization, with variations in the number of nodes and data channels, packet generation rate, data packet length, optical device switching latencies, and propagation delay.<<ETX>>

Simulation analysis of a collisionless multiple access protocol for a wavelength division multiplexed star-coupled configuration

A collisionless wavelength division multiple access protocol is introduced for a passive star-coupled photonic network that possesses significant performance and flexibility advantages over alternative approaches. A detailed simulation analysis is developed to study the behavior of the protocol with varying system characteristics. The protocol is control channel based: one of the WDM channels is used to reserve access for data packet transmission on the remaining data channels. Control channel access arbitration is achieved through time-division multiplexing, enabling all active nodes to transmit once every control cycle. This approach significantly reduces the long synchronization delays typical of time-division multiplexing systems: the control cycle length is proportional to the control packet size rather than the data packet size. The proposed approach has the advantage that variable sized data packets in a collisionless environment are supported without utilization degradation. Furthermore, a mechanism is introduced that relaxes the constraints on the switching times of the optical components by decreasing the performance sensitivity. The performance is evaluated in terms of network throughput, packet delay, and control and data channel utilization. In particular, this paper examines the performance impact with variations in the number of nodes and data channels, packet generation rate, data packet length, and the optical device switching latencies.<<ETX>>

Switching Latency Impact on Star-Coupled WDM Photonic Network Pre-Allocation Protocol Performance

This paper evaluates the performance of two pre-allocation protocols when the switching latency of the wavelength tunable optical devices required for WDM networks is not negligible. The channels are pre-allocated to the nodes with the approach, where each node has a home channel that it uses either for all data packet transmissions or all data packet receptions. This approach reduces the resulting system complexity since both tunable transmitters and receivers are not required, and also has the advantage of being applicable to systems where there are many more nodes than wavelength channels. Switching latency is the time required by the tunable optical devices to tune to the required destination wavelength. The performance impact of switching latency on a generalized random access protocol is compared to an approach based on interleaved time multiplexing. Both protocols are designed to operate in a multiple-channel multiple-access environment and require each node to possess a tunable transmitter and a fixed (or slow tunable) receiver. Semi-markov analytic models are developed to investigate the performance of the two protocols. The analytic models are validated through extensive simulation. The performance is evaluated in terms of network throughput and packet delay with variations in the number of nodes, data channels, packet generation rate, and switching latency.