Single-hop Wavelength Division Multiplexing Network Research Articles

Using Dynamic Control Frames to Reduce Packet Delays in Transceiver Array-Based Single-Hop WDM Networks

This paper considers transceiver array-based single-hop wavelength division multiplexing (WDM) networks with reservation-based packet scheduling algorithms. In reservation-based packet scheduling algorithms for single-hop WDM networks, one or more of the wavelengths are used as control channels for transmitting reservation information. Time on a control channel is divided into control frames and each control frame is further divided into control slots. Each node is usually assigned a dedicated control slot in each control frame. Before transmitting a data packet, a node sends a control packet in a control slot to all other nodes to reserve a data slot. This paper proposes to adjust the lengths of the control frames dynamically according to the loads of the nodes by removing unused control slots. A dynamic control frame structure with variable number of control slots is proposed. A method is devised to enable the nodes in the network to dynamically acquire and release control slots depending on their loads such that the control frames include only necessary control slots for those nodes that have or potentially have data packets to send. Therefore, the delays for transmitting control packets and data packets can be reduced. Dynamically adjusting the lengths of the control frames is able to reduce the delays for transmitting control packets and data packets when the network load is light to medium or the traffic pattern is moderately or highly nonuniform; however, it introduces extra overhead in each control frame such that the length of the control frame may become larger than the size of the control frame in the fixed control frame structure resulting in higher mean packet delay when the load of the network is heavy and the traffic pattern is uniform or nearly uniform. Therefore, this paper further proposes a hybrid fixed and dynamic scheme that dynamically employs the fixed control frame scheme or the dynamic control frame scheme depending on the loads of the nodes. The performance of the proposed hybrid scheme is studied via simulations. Our simulation results show that the hybrid scheme is able to dynamically choose the better of the fixed and dynamic control frame schemes such that it yields the lowest mean packet delay for the entire range of network loads and traffic patterns.

A large-scale AWG-based single-hop WDM network using couplers with collision avoidance

Single-hop wavelength division multiplexing (WDM) networks based on a central arrayed waveguide grating (AWG) have attracted a great deal of attention as a solution for metropolitan area network applications because they can achieve high throughput with reduced cost due to the periodic wavelength-routing property of the AWG. Unfortunately, scalability is a significant problem in an AWG-based single-hop WDM network because the number of transceivers required at each node is equal to the total number of nodes. This problem can be solved by providing optical couplers between the AWG and the nodes and by aggregating multiple nodes before connecting to the AWG. In this case, however, packet collisions at the couplers will seriously increase the packet network delay. Therefore, we propose a novel AWG-based single-hop WDM network in which an autonomic collision avoidance mechanism is introduced in the couplers. We derive the optimum number of couplers for this architecture. Through numerical study, we clarify that the proposed network architecture can reduce the total network cost dramatically.

Performance evaluation of a scalable media access control protocol for single hop WDM networks

We propose a new media access protocol for single hop Wavelength Division Multiplexing (WDM) networks with a passive star topology. In the conventional protocols, in the case of packets collision or when the packets did not get a data channel from the reservation mechanism, these packets should be retransmitted. But, when transmission distance becomes long, the propagation delay time will be long. Our protocol can allocate data channels without retransmitting control packets except the collided ones. Thus, it is possible to reduce the transmission delay time and to get high throughput by reducing the number of retransmitted control packets.

The AWG<tex>$parallel$</tex>PSC Network: A Performance-Enhanced Single-Hop WDM Network With Heterogeneous Protection

Single-hop wavelength-division-multiplexing (WDM) networks based on a central passive star coupler (PSC) or arrayed-waveguide grating (AWG) hub have received a great deal of attention as promising solutions for the quickly increasing traffic in metropolitan and local area networks. These single-hop networks suffer from a single point of failure: if the central hub fails, then all network connectivity is lost. To address this single point of failure in an efficient manner, we propose a novel single-hop WDM network, the AWG/spl par/PSC network. The AWG/spl par/PSC network consists of an AWG in parallel with a PSC. The AWG and PSC provide heterogeneous protection for each other; the AWG/spl par/PSC network remains functional when either the AWG or the PSC fails. If both AWG and PSC are functional, the AWG/spl par/PSC network uniquely combines the respective strengths of the two devices. By means of analysis and verifying simulations we find that the throughput of the AWG/spl par/PSC network is significantly larger than the total throughput obtained by combining the throughput of a stand-alone AWG network with the throughput of a stand-alone PSC network. We also find that the AWG/spl par/PSC network gives over a wide operating range a better throughput-delay performance than a network consisting of either two load sharing PSCs in parallel or two load sharing AWGs in parallel.

The arrayed-waveguide grating-based single-hop WDM network: an architecture for efficient multicasting

Research on multicasting in single-hop wavelength-division-multiplexing (WDM) networks has so far focused on networks based on the passive star coupler (PSC), a broadcast device. It has been shown that multicasting performance is improved by partitioning multicast transmissions into multiple multicast copies. However, the channel bottleneck of the PSC, which does not allow for spatial wavelength reuse, restricts the multicast performance. We investigate multicasting in a single-hop WDM network that is based on an arrayed-waveguide grating (AWG), a wavelength routing device that allows for spatial wavelength reuse. In our network, optical multicasting is enabled by wavelength-insensitive splitters that are attached to the AWG output ports. Multicasts are partitioned among the splitters and each multicast copy is routed to a different splitter by sending it on a different wavelength. We demonstrate that the spatial wavelength reuse in our network significantly improves the throughput-delay performance for multicast traffic. By means of analysis and simulations, we also demonstrate that, for a typical mix of unicast and multicast traffic, the throughput-delay performance is dramatically increased by transmitting multicast packets concurrently with control information in the reservation medium access control protocol of our AWG-based network.

Minimizing the Number of Multicast Transmissions in Single-Hop WDM Networks

The problem of minimizing the number of transmissions for a multicast transmission under the condition that the packet delay is minimum in single-hop wavelength division multiplexing (WDM) networks is studied in this paper. This problem is proved to be NP-complete. A heuristic multicast scheduling algorithm is proposed for this problem. Extensive simulations are performed to compare the performance of the proposed heuristic algorithm with two other multicast scheduling algorithms, namely, the greedy and no-partition scheduling algorithms. The greedy algorithm schedules as many destination nodes as possible in the earliest data slot. The no-partition algorithm schedules the destination nodes of a multicast packet to receive the packet in the same data slot without partitioning the multicast transmission into multiple unicast or multicast transmissions. Our simulation results show that (i) an algorithm which partitions a multicast transmission into multiple unicast or multicast transmissions may not always produce lower mean packet delay than the no-partition algorithm when the number of data channels in the system is limited and (ii) the proposed heuristic algorithm always produces lower mean packet delay than the greedy and the no-partition algorithms because this algorithm not only partitions a multicast transmission into multiple unicast or multicast transmissions to keep the packet delay low but also reduces the number of transmissions to conserve resources.

In single-hop WDM networks, a data packet can be transmitted from one node to another only when one of the transmitters of the source node and one of the receivers of the destination node are tuned to the same wavelength, i.e., a data packet is transmitted from one node to another without going through intermediate nodes. A hybrid multicast scheduling

This paper shows that, for single-hop wavelength division multiplexing (WDM) networks, a multicast scheduling algorithm which always tries to partition a multicast transmission into multiple unicast or multicast transmissions may not always produce lower mean packet delay than a multicast scheduling algorithm that does not partition multicast transmissions. The performance of a multicast scheduling algorithm may depend on the traffic conditions and the availability of the channel resource in the network. A hybrid multicast scheduling algorithm that can be used in single-hop WDM networks.

Performance of Single-Hop WDM LANs Supporting Real-Time Services

Optical wavelength division multiplexing (WDM) local area networks are capable of fulfilling the enormous bandwidth demands of present and future applications. Up to now, the WDM LAN world is primarily dominated by the passive-star coupler (PSC) based architectures, for which many medium access control (MAC) protocols have been proposed. However, an arrayed waveguide grating multiplexer (AWGM)-based single-hop WDM network seems to be a very promising alternative. One of the most critical issues in designing next generation photonic LANs is the support of real-time services for applications with different time constraints. In this paper, different basic access protocols for the PSC as well as AWGM-based single-hop WDM LANs are considered and their performance in supporting real-time traffic is analyzed by means of extensive computer simulations. For evaluation of real-time performance, packet drop rates and deadline missing rates are taken as performance measures. Furthermore, new real-time message scheduling schemes are proposed which improve the performance of protocols accommodating mixed traffic. They can be differentiated between message scheduling at the source nodes’ transmit queues and scheduling based upon control information from a control channel. It is shown that both types of priority scheduling significantly improve the overall real-time performance.

Multidestination communication over tunable-receiver single-hop WDM networks

We address the issue of providing efficient mechanisms for multidestination communication over one class of lightwave wavelength division multiplexing (WDM) architectures, namely, single-hop networks with tunability provided only at the receiving side. We distinguish a number of multicast traffic types, we present a number of alternative broadcast/multicast time-division multiple-access (TDMA) schedules for each type, and we develop heuristics to obtain schedules that result in low average packet delay. One of our major contributions is the development of a suite of adaptive multicast protocols which are simple to implement, and have good performance under changing multicast traffic conditions.