Optical WDM Ring Research Articles

Wide-Sense Nonblocking Multicast in WDM Optical Linear Array and Ring Networks with 2-Length Extension under Index Based Routing

Multicast communication is the concurrent transmission of data from one source node to many destination. It is widely deployed in high performance computing and communication networks.In this paper, a linear array and ring networks are extended by directly linking all nodes which are separated by one intermediate node with additional fibers which is referred as linear array and ring network with 2-length extension and wide sense nonblocking multicast is studied. The wavelength allotment methods are proposed to realize one-to-many communication over wavelength division multiplexing optical linear array and ring with 2-length extension under index-based routing and the minimum wavelength number needed is determined. The minimum wavelength number needed to support for the extended linear array and ring topologies is reduced approximately by half when compared with that of a linear array network and ring network.

All-to-all Broadcast in Optical WDM Ring with 2-length Extension and 3-length Extension

All-to-all broadcast communication is to transmit a distinctive data from each node to every other node available in the network. This is a fundamental prerequisite in high performance computing and telecommunication networks including enterprises operating datacenters which may spread across thousands of nodes by means of WDM optical networks. Wavelengths are scarce resources in WDM optical networks. Reducing the wavelengths usage is essential to decrease the price and complication of the network. In this article, a ring network is extended by additionally connecting alternate nodes in order to provide alternate paths so as to reduce the effective number of hops between the communicating nodes and also to reduce the wavelength requirements and this network is referred as a ring network with 2-length extension. Similarly, a ring network is extended by directly linking all nodes which are separated by two intermediate nodes with additional fibers and this network is referred as a ring network with 3-length extension. For the ring network with 2-length extension the optimum wavelength number necessary to establish all-to-all broadcast under unidirectional routing is derived by grouping nonoverlapping connections on a common wavelength. The wavelength number necessary atmost to establish all-to-all broadcast in a unidirectional ring with 3-length extension is derived using longest link first routing algorithm.

Wavelength Allotment for All-to-All Broadcast in WDM Optical Bidirectional ring with 3-Length Extension

All-to-all broadcast communication, distributing messages from each node to every other node, is a dense communication pattern and finds numerous applications in advanced computing and communication networks from the control plane to datacenters. A ring network topology is one of the important regular network topologies due to its simple structure, high speed, easy to extend and tolerant to link and node failures. Few researchers recommended connecting the alternate nodes of the ring with additional fibers in the ring network, to support increased call connection probability, higher tolerable to multiple link and node failures, enormous traffic handling capability and improved survivability. To reduce the complicatedness and cost of the network, it is essential to reduce the wavelength-number required to establish all-to-all broadcast in wavelength-division multiplexed ring network. In this paper, a ring network is extended by directly linking all nodes which are separated by two intermediate nodes with additional fibers and this network is referred as ring with 3-length extension. The wavelength allotment methods are proposed for realizing all-to-all broadcast over a WDM optical bi-directional ring with 3-length extension under multiple unicast routing model using a two-stage heuristic algorithm. The heuristic algorithm is developed to identify non-overlapping connections and an explicit wavelength allotment method based on the output of the heuristic technique is given. The result obtained shows that wavelength-number required atmost to establish all-to-all broadcast in a bi-directional ring with 3-length extension is reduced by a minimum of 57% and a maximum of 66% when compared to bi-directional primary ring. Similarly, the wavelength-number required atmost to establish all-to-all broadcast in a bi-directional ring with 3-length extension is reduced by a minimum of 20% and a maximum of 33% when compared to a bi-directional ring with 2-length extension.

Dimensioning Models of Optical WDM Rings in Xhaul Access Architectures for the Transport of Ethernet/CPRI Traffic

The Centralized Radio Access Network (C-RAN) provides a valid solution to overcome the problem of traditional RAN in scaling up to the needed processing resource and quality expected in 5G. The Common Public Rate Interface has been defined to transport traffic flows in C-RAN and recently some market solutions are available. Its disadvantage is to increase by at least 10 times the needed bandwidth and for this reason its introduction will be gradual and will coexist with traditional RAN solutions in which Ethernet traffic is carried towards the radio base stations. In this paper, we propose an Xhaul optical network architecture based on Optical Transport Network (OTN) and Dense Wavelength Division Multiplexing (DWDM) technologies. The network allows for a dynamic allocation of the bandwidth resources according to the current traffic demand. The network topology is composed of OTN/DWDM rings and the objective of the paper is to evaluate the best configuration (number of rings and number of wavelengths needed) to both to minimize the cost and to provide an implementable solution. We introduce an analytical model for the evaluation of the number of wavelengths needed in each optical ring and provide some results for 5G case studies. We show how, although the single ring configuration provides the least cost solution due to the high statistical multiplexing advantage, it is not implementable because it needs switching apparatus with a too high number of ports. For this reason, more than one ring is needed and its value depends on several parameters as the offered traffic, the number of Radio Remote Units (RRU), the percentage of business sub-area and so on. Finally, the analytical model allows us to evaluate the advantages of the proposed dynamic resource allocation solution with respect to the static one in which the network is provided with a number of wavelengths determined in the scenario in which the radio station works at full load. The bandwidth saving can be in the order of 90% in a 5G traffic scenario.

Wavelength assignment for all-to-all broadcast in bidirectional WDM optical ring with limited drops

All-to-all broadcast is to disseminate a unique message from each node to every other node in a network. This problem is significant in the context of control plane design as it relates to status information dissemination. In this paper, a wavelength assignment method to reduce the number of wavelengths is proposed to establish all-to-all broadcast in a bidirectional WDM ring network. The network model is an all-optical network, in which a message from source node can be dropped (or split) only at a limited number of destination nodes along a light path due to power loss of dropping optical signals. An expression for the upper bound on the number of wavelengths required to support all-to-all broadcast is derived for certain cases of WDM ring while for other cases, an attractive algorithm is given to identify the lengths of connection sets that can be grouped together with suitable wavelength assignment strategies. Numerical results are computed to show that the results obtained are close to the lower bound.

Optical Control Network for Avionics Applications Using a WDM Packet Ring

We propose aviation real-time adaptive ring (AVATAR) as a potential solution for the integrated communication infrastructure for future aero-engine control systems. AVATAR features an Ethernet-over-WDM (wavelength-division multiplexing) architecture. It employs reconfigurable optical add/drop multiplexer (ROADM) as node technology. Compared with existing serialized data bus, e.g., time-triggered protocol (TTP), AVATAR exploits multi-wavelength and spatial reuse properties of an optical WDM ring through sophisticated packet scheduling. To quantitatively evaluate the advantages over existing avionic networks, and to understand the architectural parameters of AVATAR, optimal scheduling methods using mixed integer linear programming (MILP), as well as a simple, near-optimal heuristic, are presented. Numerical results demonstrate the superiority of AVATAR, with a simple two-channel configuration more than doubling the capacity of TTP.

Performance evaluation of algorithms for wavelength assignment in optical ring network

In this paper, the performance evaluation of first-fit, random, most-used and wavelength conversion algorithms in WDM optical ring network are being proposed. The blocking probability of various algorithms has been compared. The blocking probability is maximum for first fit algorithm and least for wavelength conversion algorithm nearer to 0.01 and 0.0025 respectively. So the performance of the wavelength conversion algorithms is best but there is burden of using expensive hardware. Without the need of wavelength-convertor, the most-used algorithm performs better than the random and first-fit algorithms. These approaches are very effective for the minimization of blocking probability of optical WDM networks.

Optimal dimensioning of the WDM unidirectional ECOFRAME optical packet ring

To efficiently support the high rate and the high dynamicity of the traffic in metro networks, an optical packet-switched WDM ring, named ECOFRAME, is proposed. The key features of the proposed ring are optical transparency and statistical multiplexing of optical packets on parallel WDM channels. Such features can be exploited by properly allocating wavelengths and receivers. This paper aims to optimally dimension the unidirectional ECOFRAME rings. The dimensioning at minimum cost (i.e., for wavelengths and receivers) is modeled with an mixed-integer linear programming formulation. An heuristic algorithm is also proposed, and its performance is compared against the optimal solutions and bounds. When considering the receiver and wavelength cost, results indicate that trading the wavelengths for receivers allows cost saving of up to 75% with respect to WDM optical packet rings with a single dedicated wavelength per node (i.e., single receiver at each node).

On providing metro ethernet services over transparent WDM optical rings

The long list of benefits (especially cost and capacity) of Ethernet LANs has made the IEEE, the ITU-T, and the Metro Ethernet Forum define the requirements for taking Ethernet beyond the local area, toward the metropolitan region. In addition, the ever-increasing traffic demands of new applications and users can only be met by the huge bandwidth capacity provided by optical fibers. This work studies how to provide metro Ethernet services over transparent tunable-transmitter fixed-receiver WDM optical ring networks. A new adaptation layer of ME to WDM is proposed, and its benefits and drawbacks are studied. It is shown that such a transparent WDM ring network can be seen as a logical full-mesh topology by the upper ME layer, thus reducing to one the number of optical-electronic-optical conversions per unicast frame. Additionally, two different approaches are proposed in the case of broadcast/multicast traffic, since this may bring scalability difficulties in ring topologies.

Fair MAC protocol for optical ring network of wavelength-shared access nodes

In this paper, a WDM optical ring consisting of access nodes with fixed transmitter-n fixed receivers (FT—FR n ) is considered. As access nodes share a wavelength channel there is trade-off between node throughput and fairness among them. In order to abbreviate the transmission unfairness and to increase the throughput, we propose p-persistent medium access control (MAC) protocol. Each node uses the carrier sense multiple access with collision avoidance (CSMA/CA) protocol to transmit packets, and decides whether to use a local empty slot with probability p when a transferred packet based on source-stripping is dropped and emptied. Numerical prediction for the proposed MAC protocol is introduced to compute the maximum node throughput under uniform traffic condition. For more detail results, we use network simulation with self-similar traffic and introduce various results. The proposed MAC protocol gives better node throughput than non-persistent protocol and shows an improved fairness factor than 1-persistent protocol. Through simulation, we also find the reasonable probability of p-persistent protocol for a given architecture.

Shortest path routing in optical wdm ring networks under multicast traffic

We present an analytical model to investigate the mean hop distance of shortest path routing bidirectional optical WDM ring networks not only for multicast traffic with arbitrary fanout but also for unicast and broadcast traffic.

Shortest path routing in optical wdm ring networks under multicast traffic

We present an analytical model to investigate the mean hop distance of shortest path routing bidirectional optical WDM ring networks not only for multicast traffic with arbitrary fanout but also for unicast and broadcast traffic.

Optical WDM rings using a smart wavelength routing assignment

AbstractFunctionality is inserted into the physical layer of WDM optical networks in order to provide for an efficient carrier routing and packet‐addressing scheme. No optoelectronic conversions are needed along the network nodes, except at the source and destination nodes. Tuned transmitters or receivers are not used. The ancillary network routing management structure is dramatically reduced, together with the total network cost. Simple and efficient mechanisms to avoid optical carrier modulation inefficiency and data collision are introduced. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 121–125, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10392

Optimal mesh routing in four-fibre WDM rings

It is shown that in a four-fibre optical WDM ring with N nodes, the number of wavelengths required to accommodate a full mesh interconnection is (N2 – 1)/8, rounded up to the nearest integer. This result applies for all values of N, is the same with and without wavelength conversion, and represents the optimum value.

Wavelength reuse scheme in a WDM unidirectionalring network using a proper fibregrating add/drop multiplexer

An experimental optical WDM ring network is proposed. It uses a proper add/drop multiplexer based on a fibre grating filter. Both-way transmission using a wavelength reuse scheme is successfully demonstrated without any crosstalk.