Optical Multistage Interconnection Networks Research Articles

A machine learning assisted optical multistage interconnection network: Performance analysis and hardware demonstration

AbstractIntegration of the machine learning (ML) technique in all‐optical networks can enhance the effectiveness of resource utilization, quality of service assurances, and scalability in optical networks. All‐optical multistage interconnection networks (MINs) are implicitly designed to withstand the increasing high‐volume traffic demands at data centers. However, the contention resolution mechanism in MINs becomes a bottleneck in handling such data traffic. In this paper, a select list of ML algorithms replaces the traditional electronic signal processing methods used to resolve contention in MIN. The suitability of these algorithms in improving the performance of the entire network is assessed in terms of injection rate, average latency, and latency distribution. Our findings showed that the ML module is recommended for improving the performance of the network. The improved performance and traffic grooming capabilities of the module are also validated by using a hardware testbed.

A GreedyZero algorithm to minimise the conflicts in an Optical Multistage Interconnection Network

An Optical Multistage Interconnection Network (OMIN) is an important class of Interconnection Network that has large transmission capacity in the communication networks. One of the severe problems is the conflict which is caused through coupling two signals within switching elements. In this paper, we have proposed a new algorithm to minimise the number of conflicts of OMINs using the greedy graph colouring and Zero algorithm. The greedy graph colouring approach employed the Zero algorithm to categorise inputs of the OMINs without conflict. The results showed that the number of passes reduced by approximately 30%. In addition, the average execution time of our proposed algorithm was less than the average execution time of the Zero algorithm.

On the Minimization of Crosstalk Conflicts in a Destination Based Modified Omega Network

In a parallel processing system, Multi-stage Interconnection Networks (MINs) play a vital role in making the network reliable and cost effective. The MIN is an important piece of architecture for a multiprocessor system, and it has a good impact in the field of communication. Optical Multi-stage Interconnection Networks (OMINs) are the advanced version of MINs. The main problem with OMINs is crosstalk. This paper, presents the (1) Destination Based Modified Omega Network (DBMON) and the (2) Destination Based Scheduling Algorithm (DBSA). DBSA does the scheduling for a source and their corresponding destination address for messages transmission and these scheduled addresses are passed through DBMON. Furthermore, the performance of DBMON is compared with the Crosstalk-Free Modified Omega Network (CFMON). CFMON also minimizes the crosstalk in a minimum number of passes. Results show that DBMON is better than CFMON in terms of the average number of passes and execution time. DBSA can transmit all the messages in only two passes from any source to any destination, through DBMON and without crosstalk. This network is the modified form of the original omega network. Crosstalk minimization is the main objective of the proposed algorithm and proposed network.

A Cost-Effective Architecture For Optical Multistage Interconnection Network

In this paper a new architecture for Optical Multistage Interconnection Networks (OMINs) has been proposed to avoid crosstalk problem. At the same time, the probablity of losing pass through an optical long connection path is reduced in this architecture. The new architecture is inherent form the standard OMIN by converting two switches of the network to one switch in each row. By reducing the number of switches in new architecture, the reduction in the execution time is considered. The modifying in the number of passes via the same low stage transformation is negligible. The ability of the new architecture to decrease cost and avoid crosstalk has been validated through simulations that show improvement in the network performance in terms of approximately 30% reduction in the execution time.

ZeroX Algorithms with Free crosstalk in Optical Multistage Interconnection Network

Multistage interconnection networks (MINs) have been proposed as interconnecting structures in various types of communication applications ranging from parallel systems, switching architectures, to multicore systems and advances. Optical technologies have drawn the interest for optical implementation in MINs to achieve high bandwidth capacity at the rate of terabits per second. Crosstalk is the major problem with optical interconnections; it not only degrades the performance of network but also disturbs the path of communication signals. To avoid crosstalk in Optical MINs many algorithms have been proposed by many researchers and some of the researchers suppose some solution to improve Zero Algorithm. This paper will be illustrated that is no any crosstalk appears in Zero based algorithms (ZeroX, ZeroY and ZeroXY) in using refine and unique case functions. Through simulation modeling, the Zero based algorithm approach yields the best performance in terms of minimal routing time in and number of passes comparison to the previous algorithms tested for comparison in this paper.

A Challenge for Routing Algorithms in Optical Multistage Interconnection Networks

Problem statement: A class of dynamic interconnection networks is Multistage Interconnection Networks (MINs) that connects input devices to output devices through a number of switch stages. MINs have assumed importance in recent years; because of their cost-effectiveness. Optical MINs are one type of MINs that have large transmission capacity in the communication networks. There is a major problem in Optical MIN that is crosstalk, which is caused by coupling two signals within a switching element. Approach: To avoid crosstalk in Optical MINs many algorithms have been proposed by many researchers that we review applying five routing algorithms and scheduling them in the Optical MINs. Results: The comparative results of routing algorithms show affective of avoiding crosstalk in number of passes and execution time for different algorithm. Conclusion: The challenge between these routing algorithms is thoroughly investigated, by applying them on Optical MIN and showing which algorithm has better performance to avoid crosstalk.

Component Reducing and Routing Algorithm of Double-Layer Network with Rearranging the Channel Allocation

Recently, there has been a growing demand for communication systems. The implementation of optical multistage interconnection networks (MINs) is more and more noticed. In our previous study, we have presented a modified version of holographic optical switches (HOSs). The double-layer network constructed by the modified version of HOSs and rearranged the channels allocation, the number of electro-optic halfwave plates (EOHWPs) could be significantly decreased from 2N^2-2N to 2Nlog2N. We propose a routing algorithm for the novel DLN and the time complexity of the routing algorithm is O (1).

Optical omega networks with centralized buffering and wavelength conversion

In this paper, we study the internal blocking problem in optical Multistage Interconnection Networks (MINs). We introduce algorithms to resolve internal blocking in optical MINs based on buffering and/or wavelength conversion. Since the computations involved in some of the introduced algorithms are so little, they can be implemented in real time effectively. A simulation program has been developed to verify the performance enhancement gained using the algorithms. Simulation results indicate that the developed algorithms effectively decreased the internal blocking and thus increased the network performance.

FAST ZEROX ALGORITHM FOR ROUTING IN OPTICAL MULTISTAGE INTERCONNECTION NETWORKS

Based on the ZeroX algorithm, a fast and efficient crosstalk-free time- domain algorithm called the Fast ZeroX or shortly FastZ_X algorithm is proposed for solving optical crosstalk problem in optical Omega multistage interconnection networks. A new pre-routing technique called the inverse Conflict Matrix (iCM) is also introduced to map all possible conflicts identified between each node in the network as another representation of the standard conflict matrix commonly used in previous Zero-based algorithms. It is shown that using the new iCM, the original ZeroX algorithm is simplified, thus improved the algorithm by reducing the time to complete routing process. Through simulation modeling, the new approach yields the best performance in terms of minimal routing time in comparison to the original ZeroX algorithm as well as previous algorithms tested for comparison in this paper.

On path dependent loss and switch crosstalk reduction in optical networks

Although optical multistage interconnection networks (OMINs) promise to meet the ever growing demands of communication networks and multiprocessor systems in fast communication, they suffer from challenges such as path dependent loss and switch crosstalk. In this paper, we propose an innovative approach for reducing not only the path dependent loss but also the number of switch crosstalks in OMINs. Our approach is centered upon modelling OMINs with Petri nets and using the P-invariants method to determine the minimum number of stages m min that is sufficient to establish requested communication patterns in variable-stage OMINs. Being composed of the smallest number of stages and consequently directional couplers (or photonic switches), m min -stage OMIN employs minimal structure and, therefore, path dependent loss and also number of switch crosstalks reach the least possible values in the realization of requested communication patterns. We prove that the size of Petri nets created in this work is in polynomial dependence on the problem size which alleviates memory consumption significantly and ascertains the fact that memory capacity and performance of modern computers are indeed sufficient to run our task. We also show that the complexity results obtained in this research improve similar results reported in our previous paper. We carry out a series of computer experiments to confirm the effectiveness of the proposed approach.

Clique‐partitioning connections‐scheduling with faulty switches in dilated benes network

In Dilated Optical Multistage Interconnection Networks constructed by 2 ×2 photonic switches, each input‐to‐output connection can be established along one path through the network. If two connections compete for the same switch, only one connection can be established at a time. For a given set of requested connections with/ without faulty switches, it is desirable to establish them in as few rounds as possible. Optical crosstalk is a problem in Optical Multistage Interconnection Networks and a switch is said to be faulty if it causes excessive crosstalk(s) above a given threshold, whose value can be determined according to certain criteria. In this paper, we study the problem of connections‐scheduling with faulty switches in a dilated re‐arrangeable photonic network, a Dilated Benes Network (DBN). We map the connections‐scheduling problem to a variant of the clique partitioning problem, and then use a heuristic algorithm for scheduling the connections. The simulation results show that the proposed method is efficient and it can maintain the reliability of the DBN network by tolerating some faulty switches.

Optimization of a Switching Node for Optical Multistage Interconnection Networks

In this letter, we demonstrate a 2 times 2 switching node optimized for optical multistage interconnection networks. The optical packet-switched node is improved by making use of comparators with dual-threshold action to regenerate the routing header signal. The switching node is shown to correctly route packets with the presence of glitches in the header information. We employ a hybrid integrated semiconductor optical amplifier in the switching node that reduces packet guard times enabling a 67% increase in the number of stages for large-scale multistage networks.

Analyzing the performance of optical multistage interconnection networks with limited crosstalk

Analytical modeling techniques can be used to study the performance of optical multistage interconnection network (OMIN) effectively. MINs have assumed importance in recent times, because of their cost-effectiveness. An N?N MIN consists of a mapping from N processors to N memories, with log??2 N stages of 2?2 switches with N/2 switches per stage. The interest is on the study of the performance of unbuffered optical multistage interconnection network using the banyan network. The uniform reference model approach is assumed for the purpose of analysis. In this paper the analytical modeling approach is applied to an N?N OMIN with limited crosstalk (conflicts between messages) up to (log??2 N?1). Messages with switch conflicts satisfying the constraint of (log??2 N?1) are allowed to pass in the same group, but in case of a link conflict, the message is routed in a different group. The analysis is performed by calculating the bandwidth and throughput of the network operating under a load l and allowing random traffic and using a greedy routing strategy. A number of equations are derived using the theory of probability and the performance curves are plotted. The results obtained show that the performance of the network improves by allowing limited crosstalk in the network.

The augmented data vortex switch fabric: An all-optical packet switched interconnection network with enhanced fault tolerance

Optical Multistage Interconnection Networks (OMINs) are capable of transmitting terabits of bandwidth per second, and they have been considered as possible solutions to the electronic communications bottleneck in interconnection networks. A novel architecture, the Data Vortex (DV) switch, has been proposed by Yang et al., as a scalable, ultra low latency, ultra high capacity, high throughput, low cross-talk and low BER, all-optical packet switching fabric that is a suitable candidate for use as an OMIN. For any interconnection network, its fault tolerance and reliability are crucial issues, which have lacked attention up to now in the case for a DV switch. In this paper we, therefore, present results of fault tolerance and reliability analysis of the primary DV switch, and propose (1) a new Augmented Data Vortex (ADV) switch fabric, to improve the fault tolerance of the primary DV switch. (2) The labelling and a numbering scheme, with detailed interconnections of nodes for the ADV switch is given. (3) A new self-routing procedure and a priority scheme for distributed control signalling in the ADV switch have been given. (4) For the first time, conversion of the 3-dimensional switch to an equivalent chained-MIN model, has been given, which is more suitable for later analysis of fault tolerance. (5) A multiplexing scheme at input ports and output ports which further enhances the fault tolerance of the ADV switch has been given. (6) Computation has been done of the reliability and fault tolerance of the new architecture via an analytical model. (7) Finally, comparison of the ADV switch architecture with the primary architecture (DV) in view of fault tolerance and reliability has been given, and hardware complexity and cost effectiveness have been studied.

Polarization-Dependent Gain in SOA-Based Optical Multistage Interconnection Networks

The small polarization dependence (< 1 dB) of optical components becomes significant in optical multistage interconnection networks. The cumulative effect can ultimately limit physical layer scalability by changing the maximum number of internal nodes that optical packets can traverse error free. It is shown that for nodes based on commercial semiconductor optical amplifier (SOA) switches with polarization-dependent gains of less than 0.35 dB, the maximum number of cascaded nodes changes by as much as 20 nodes, depending on both the packet wavelength and its state of polarization. This deviation in the number of nodes could correspond to a 100-fold decrease in the number of interconnected ports of an optical interconnection network such as the data vortex. This dramatic effect is explained in terms of optical signal-to-noise ratio degradation due to accumulated amplified spontaneous emission noise originating from the SOA device in the node

A Novel Multistage Network Architecture with Multicast and Broadcast Capability

In this paper, a new class of optical multistage interconnection network (MIN) architecture is presented, which is constructed utilizing a modularization approach rather than the traditional recursive or fixed exchange pattern methods. The modified architecture consists of an input module, an output module, two point-to-point (PTP) modules, and one modified multicast/broadcast (M/B) module(s). We also implement the multicast/broadcast module with WDM technique, which reduces the hardware cost required for multicast and the re-computation cost for a new connection. We show that it has the best application flexibility and provides multicast function without imposing significant negative impacts on the whole network. A new multicast connection pattern is also proposed in this paper, which makes it practical and economical to apply amplification in space-division networks. Compared with existing multicast architectures, this new architecture with Dilated Benes PTP modules has better performance in terms of system SNR, the number of switch elements, and system attenuation in point-to-point connections. Moreover, the multicast/broadcast module adopts wavelength division multiplexing (WDM) technique to increase its multicast/broadcast assignment. As a result, given m available distinguished wavelengths, one M/B module can support at most m M/B requests at the same time. The new proposed M/B module with WDM is more practical and economical to apply amplification in space-division networks.

A Class of Benes-Based Optical Multistage Interconnection Networks for Crosstalk-Free Realization of Permutations

Vertical stacking is a novel technique for creating nonblocking (crosstalk-free) optical multistage interconnection networks (MINs). In this paper, we propose a new class of optical MINs, the vertically stacked Benes (VSB) networks, for crosstalk-free realization of permutations in a single pass. An N x N VSB network requires at most O(N log N) switching elements, which is the same as the Benes network, and much lower overall hardware cost than that of the existing optical MINs built on the combination of horizontal expansion and vertical stacking of banyan networks, to provide the same crosstalk-free permutation capability. Furthermore, the structure of VSB networks provides a more flexible way for constructing optical MINs because they give more choices in terms of the number of stages used in an optical MIN. We also present efficient algorithms to realize crosstalk-free permutations in an N x N VSB network in time O(N log N), which matches the same bound as required by the reported schemes.

Design of Optical Rearrangeable Nonblocking MINs Under Various Crosstalk Constraints

Optical interconnection networks suffer from the intrinsic crosstalk problem that should be overcome to make them work properly. Vertical stacking of optical banyan networks is a novel scheme for constructing nonblocking optical multistage interconnection networks (MINs). Rearrangeable nonblocking optical MINs are feasible since they have lower complexity than their strictly nonblocking counterparts. In this paper, we determine the sufficient condition for these MINs to be rearrangeable nonblocking under various crosstalk constraints. We show how the crosstalk constraint affects the design of rearrangeable nonblocking MINs and demonstrate that these networks can tolerate a stricter crosstalk constraint without increasing their hardware complexity significantly. The results in the paper will be useful in designing optical MINs with reasonable hardware cost and crosstalk level.

ROUTING IN OPTICAL MULTISTAGE NETWORKS WITH LIMITED CROSSTALK USING ANT COLONY OPTIMIZATION

Ant Colony Optimization (ACO) techniques can be successfully implemented to solve many combinatorial optimization problems. After the traveling salesman problem was successfully solved using the ACO technique, other researchers have concentrated on solving other problems like the quadratic assignment and the job-shop scheduling problems using the same technique. In this paper we use the ACO technique to route messages through an N × N Optical Multistage Interconnection Network (OMIN) allowing upto ' C ' limited crosstalk's (conflicts between messages within a switch) where ' C ' is a technology driven parameter and is always less than log 2 N . Messages with switch conflicts satisfying the crosstalk constraint are allowed to pass in the same group, but if there is any link conflict, then messages have to be routed in a different group. The focus is to minimize the number of passes required for routing allowing upto ' C ' limited crosstalks in an N × N optical network. This routing problem is an NP-hard problem. In this paper we show how the ACO technique can be applied to the routing problem and compare the performance of the ACO technique to that of the degree-descending algorithm using simulation techniques. Finally the lower bound estimate on the minimum number of passes required is calculated and compared to the results obtained using the two algorithms discussed. The results obtained show that the ACO technique performs better than the degree-descending algorithm and is quite close to optimal algorithms to the problem.

Optimal all-to-all personalised exchange in a novel optical multistage interconnection network

An all-to-all personalised exchange is one of the most dense collective communication operations in parallel and distributed computing and communication applications. Each node in the network needs to send a different message to each of the other nodes. Advances in electro-optic switches have made optical communication a good networking choice that can satisfy the high channel bandwidth, low communication latency, low error rate, and gigabit transmission requirements of high performance computing and communication applications. Previously proposed optical multistage interconnection networks (MINs) require at least two passes to send a message from each node to a different node (to realise a permutation) in the network. In this paper, we propose an MIN that requires only one pass to realise a permutation. That is, the new MIN requires n 1 passes instead of 2n passes, the requirement for other optical MINs, for an all-to-all personalised exchange. The new network is optimal in terms of the number of passes that is required for an all-to-all personalised exchange.