Slot Switching Research Articles

Tuneman: Customizing Networks to Guarantee Application Bandwidth and Latency

We examine how to provide applications with dedicated bandwidth and guaranteed latency in a programmable mission-critical network. Unlike other SDN approaches such as B4 or SWAN, our system Tuneman optimizes both routes and packet schedules at each node to provide flows with sub-second bandwidth changes. Tuneman uses node-level optimization to compute node schedules in a slotted switch and does dynamic routing using a search procedure with Quality of Service– (QoS) based weights. This allows Tuneman to provide an efficient solution for mission-critical networks that have stringent QoS requirements. We evaluate Tuneman on a telesurgery network using a switch prototype built using FPGAs and also via simulations on India’s Tata Network. For mission-critical networks with multiple QoS levels, Tuneman has comparable or better utilization than SWAN while providing delay bounds guarantees.

Robust Sampling Clock Recovery Algorithm for Wideband Networking Waveform of SDR

A novel technique for sampling clock recovery in a wideband networking waveform of a software defined radio is proposed. Sampling clock recovery is very important in wideband networking radio operation as it directly affects the Medium Access adaptive time slot switching rate. The proposed Sampling clock recovery algorithm consists of three stages. In the first stage, Sampling Clock Offset (SCO) is estimated at chip level. In the second stage, the SCO estimates are post-filtered to improve the tracking performance. We present a new post-filtering method namely Steady-State State-Space Recursive Least Squares with Adaptive Memory (S4RLSWAM). For the third stage of SCO compensation, a feedforward Lagrange interpolation based algorithm is proposed. Real-time hardware results have been presented to demonstrate the effectiveness of the proposed algorithms and architecture for systems requiring high data throughput. It is shown that both the proposed algorithms achieve better performance as compared to existing algorithms.

Design, Simulation and Analysis of a Slotted RF MEMS Switch

Design, Simulation and Analysis of a Slotted RF MEMS Switch

Resource Allocation for SWIPT Systems with Nonlinear Energy Harvesting Model

In this paper, we study the resource allocation for simultaneous wireless information and power transfer (SWIPT) systems with the nonlinear energy harvesting (EH) model. A simple optimal resource allocation scheme based on the time slot switching is proposed to maximize the average achievable rate for the SWIPT systems. The optimal resource allocation is formulated as a nonconvex optimization problem, which is the combination of a series of nonconvex problems due to the binary feature of the time slot‐switching ratio. The optimal problem is then solved by using the time‐sharing strong duality theorem and Lagrange dual method. It is found that with the proposed optimal resource allocation scheme, the receiver should perform EH in the region of medium signal‐to‐noise ratio (SNR), whereas switching to information decoding (ID) is performed when the SNR is larger or smaller. The proposed resource allocation scheme is compared with the traditional time switching (TS) resource allocation scheme for the SWIPT systems with the nonlinear EH model. Numerical results show that the proposed resource allocation scheme significantly improves the system performance in energy efficiency.

5G Wireless Networking Connection and Playback Technology Assist the Low‐Latency Propagation of New Media

This article conducts an indepth study on the delay caused by time division multiple access (TDMA) technology and theoretically analyzes some methods that can reduce the TDMA delay. Traditional dynamic time slot allocation algorithms usually only consider the completion of conflict‐free time slot allocation in distributed scenarios, but they do not clearly specify the order of time slot allocation. The order of time slots allocated to each node is ultimately consistent with the new data flow. The order of media dissemination is not the same. Aiming at the scheduling delay problem caused by the inconsistency of the new media low‐latency propagation time slot allocation sequence and the data stream sequence, a protocol using the master time slot adaptive time slot exchange technology is proposed. The protocol designs the corresponding super frame structure and realizes the neighbor node discovery strategy and the time slot allocation based on the priority list. At the same time, the time slot switching technology is used to adjust the time slot sequence so that it tends to the data flow sequence. The exchange criterion based on the low‐latency propagation data stream value of the new media is designed to solve the problem of optimizing the time slot of multiple data streams in the network. Through the simulation results and analysis, it can be seen that the architecture design proposed in this paper can fulfill the expected requirements of the wireless Mesh network and can achieve good low‐latency performance for the highly dynamic network topology. It can also achieve good performance in terms of network throughput and data flow delivery rate, and it has adaptability to high dynamic topologies. By comparing with the traditional algorithm design, the design proposed in this paper has a large improvement in low latency and high submission rate. Therefore, it can be considered that the low‐latency architecture design proposed in this article has better performance for new media’s low‐latency propagation and highly dynamic network topology.

Online parameter tuning of the flow classification method in the energy-efficient data center network “HOLST”

An online parameter-tuning method for the energy-efficient data center network (DCN) named HOLST (high-speed optical layer 1 switch system for time-slot-switching-based optical data center networks) is proposed. HOLST comprises an optical circuit switching network, optical slot switching network, and electrical packet switching network for the spine layer. It requires flows to be assigned to optimal switches to achieve high power savings. In this study, first we experimentally confirm that the change in the DCN characteristics in the short term of actual data center traffic downgrades the accuracy of flow classification. Subsequently, we propose a procedure for reconfiguring a flow classification function and a method for online parameter tuning for this function. Finally, the accuracy of the flow classification method using the proposed tuning and estimated switching energy consumption in the spine layer are evaluated. The proposed online parameter-tuning function increases the accuracy of flow classification and reduces switching energy consumption relative to the conventional flow classification function.

Monolithic Integrated Slot-Blocker for High Datarate Coherent Optical Slot Switched Networks

Recent progresses on monolithic SOI-based integration are presented for achieving high-performance slot-blocker for cost-sensitive metropolitan and datacenter networks. We review several nodes architectures for such optical slot switching ring networks. Such devices integrate up to 65 functional elements, allowing complex operations such as polarization and wavelength (de)multiplexing with sub-wavelength switching capability. Compact footprint, fast switching time (below 10 ns) as well as high extinction ratio (more than 20 dB) are demonstrated. We demonstrate the fast add/drop operation of advanced modulation formats (56/80 Gbit/s SP-QPSK, 128 Gbit/s PDM-QPSK, 256 Gbit/s PDM-16QAM, and 320 Gbit/s PDM-32QAM) using three generations of integrated slot-blockers.

Transport Mechanisms for Mobility Support in Optical Slot Switching-Based Next-Generation Mobile Backhaul Networks

In order to implement the next-generation (e.g., LTE-A) mobile backhaul networking segment, an optical slot switching solution called packet optical add/drop multiplexer (POADM) was previously proposed. Optical slot switching is at the same time a high capacity, energy-efficient, and low-latency optical transport network technology that relies on the direct transmission of data from base station to base station without resorting to time-consuming electronic processing and energy-hungry optoelectronic conversions. Low latency is an important requirement of mobile backhaul networks for real-time traffic such as Coordinated MultiPoint (CoMP) and POADM was shown to be compatible with the strict latency requirement of CoMP—1 ms end-to-end—even for very high network loads of 80% and above. However, user mobility was not taken into account. The traffic of users moving from one cell to another cell during handovers should also meet this strict requirement. In this paper, we propose and evaluate several transport mechanisms to support User Element mobility at the optical layer in a next-generation mobile backhaul network implemented using our previously proposed optical slot switching technology. We show with simulations that with smart introduction of additional electronic processing for handover traffic only (traffic of user elements that have moved from one cell to another), very strict latency constraints (sub-ms) can be met even for the time-sensitive mobile traffic.

Capacity-enhanced receivers for low-latency Burst Optical Slot Switching rings

We propose a new receiver architecture for coherent detection in slotted optical packet switching rings with elastic (rate adaptive) optical transponders. Such rings are a candidate solution for future datacenter and metropolitan networks. The new receiver can detect more than a single packet per time slot and consequently has higher flexibility (translating into higher supported capacity, or, equivalently, lower end-to-end latency, or a combination or both), at the cost of a moderate increase in the transponder complexity and energy consumption (less than 10 %). We apply network planning and traffic engineering simulation tools (which we validate on small examples using theoretical models) to quantify the increase in network capacity and latency reduction that can be achieved thanks to the use of the new receivers. Finally, we identify the stability problem of the insertion process in the rings with the coherent receivers and propose a polynomial network planning algorithm, for the case of fast-tunable transmitters. We evaluate the cost of enforcing the stability, in terms of the additional transponders needed, for the mentioned case.

High data rate coherent optical slot switched networks: a practical and technological perspective

We review several node architectures for optical slot switching ring networks, which can be used in metropolitan or datacenter applications, and compare them for their networking aspects. The dimensioning, quality of service, latency, and protection issues are discussed for the different approaches. The main devices, i.e. fast wavelength-tunable laser, burst-mode coherent receiver (which is required to enable high data rate transmission at 100 Gb/s and above), and a slot blocker for improved wavelength usage efficiency are described, and available technologies for each key building block are reviewed.

Impact of the Electronic Architecture of Optical Slot Switching Nodes on Latency in Ring Networks

Optical slot switching has formerly been proposed as a flexible solution for metropolitan ring networks to carry data traffic with a subwavelength switching granularity and with good energy efficiency, which is enabled by optical transparency. In this paper, we propose for the first time, to the best of our knowledge, several architectures for the electronic side of optical slot switching nodes to increase flexibility through the addition of electronic switches, working either at client packet granularity or at slot granularity. Such electronic switches can be located at either the transmitter side or receiver side, or at both sides of a node, thereby decreasing traffic latency, at the expense of increased node cost and/or energy consumption. This paper focuses on the latency aspect. We investigate the impact of a timer that can be used to upper bound the slot insertion time on the medium. We also propose a novel client packet queuing model in an optical slot switching ring and assess and compare the latency of these node architectures analytically and with simulations.

A Comparison of Elastic and Mixed Line Rate Optical Slot Switching WDM Metro Rings

We propose optimal resource allocation techniques for two kinds of optical slot switching metro rings: 1) fixed mixed line rate (fMLR), where the rate of each transponder (TRX) is fixed and set at network planning time; and 2) elastic TRX, where the rate may adjust dynamically on a per-slot basis during network operation. We then numerically compare the cost (CAPEX or energy) of fMLR and elastic networks, and investigate the suitability of each of the two considered network technologies for several ring topologies, TRX cost models, and traffic distributions and loads.

Robust Sampling Clock Recovery Algorithm for Wideband Networking Waveform of SDR

A novel technique for sampling clock recovery in a wideband networking waveform of a software defined radio is proposed. Sampling clock recovery is very important in wideband networking radio operation as it directly affects the Medium Access adaptive time slot switching rate. The proposed Sampling clock recovery algorithm consists of three stages. In the first stage, Sampling Clock Offset (SCO) is estimated at chip level. In the second stage, the SCO estimates are post-filtered to improve the tracking performance. We present a new post-filtering method namely Steady-State State-Space Recursive Least Squares with Adaptive Memory (S4RLSWAM). For the third stage of SCO compensation, a feedforward Lagrange interpolation based algorithm is proposed. Real-time hardware results have been presented to demonstrate the effectiveness of the proposed algorithms and architecture for systems requiring high data throughput. It is shown that both the proposed algorithms achieve better performance as compared to existing algorithms.

Wavelength-reuse in optical time-slotted networks

An all-optical approach to achieve finer bandwidth granularity is to time division multiplex low capacity circuits on each wavelength channel and switch time–wavelength slots optically within the network. One such time-slotted network proposed in the literature is the Time Domain Wavelength Interleaved Network (TWIN), which eliminates slot switching within the network by using a non-reconfigurable core and an intelligent edge utilizing a fast tunable laser to emulate fast switching. In contrast to the TWIN, an optical time-slotted network which incorporates slot-switching within the network is the Time Wavelength Switched Network (TWSN), wherein the Time Wavelength Space Routers (TWSRs) are configured to change their routing pattern on a time-slot basis. The TWIN network assigns a unique wavelength to each node in the network and thus requires a total of W = N wavelengths for an N -node network. We call such a TWIN network as an unconstrained TWIN network. In this paper, we first provide integer linear programs and heuristic algorithms to solve the scheduling problem for a static traffic matrix (of connections) for both, the unconstrained TWIN and the TWSN networks and also compare their performances under a dynamic traffic scenario. To address the problem of scalability of the unconstrained TWIN network, we propose to design a wavelength-constrained (i.e., W < N ) TWIN network with no switching (TWIN-NS) by using a multicasting strategy. We also propose a variant of the TWIN network which possesses switching capabilities only at the edge nodes (TWIN-ES). Overall, this paper compares both versions of the TWIN networks to the TWSN network and investigates the benefits of having a reconfigurable core as opposed to a non-reconfigurable one.

Burst transmission algorithm to improve packet level performance in contention-free slotted OBS networks

In contention-free slotted optical burst switching (SOBS) networks, controllers are utilized in order to manage the time-slot assignment, avoiding congestions among multiple burst transmissions. In this network, bursts are never lost at intermediate nodes but packets are lost at an ingress edge node due to a burst transmission algorithm. In addition, packet transmission delay increases depending on the algorithm. In order to improve packet level performance, in this paper, we propose a new burst transmission algorithm. In this method, two different thresholds are used; one is used to send a control packet to a controller and the other is used to assemble a burst. With these thresholds, a time slot can be assigned to a burst in advance and packet level performance can be improved. In order to evaluate its packet level performance and investigate the impact of thresholds, we also propose a queueing model of a finite buffer where a batch of packets are served in a slot of a constant length. Numerical results show that our proposed method can decrease packet loss probability and transmission delay with two thresholds. In addition, we show that our analysis results are effective to investigate the performance of the proposed method when the number of wavelengths is large.

Advanced Information Technology of Slot-Switching Network Schemes for on All-Optical Variable-Length Packet

Problem statement: The purpose of this paper was to investigate all op tical packet switching, because it was the key to the success of the future Internet. It can meet the stringent bandwidth requirement of future Internet applicatio ns, such as real-time video streaming. Due to the lack of optical Random Access Memory (RAM), however, the all-optical schemes studied in the literature were either not flexible enough to accom modate Internet packets, which were variable-length in nature, or fail to schedule packets at switches to achieve low loss rate. Approach: The aim of this paper was thus to tackle the flexibility and utiliz ation issues in all-optical packet switches, even a t the absence of optical RAM. We approached this paper by first studied a new slotted model for all-optical variable-length packet switching, which was called Variable-length-Packet Fixed-Length Slot (VPFS) switching. Results: We proved by mathematical analysis the theoretical maximum utilizations that can be achieved by the model in two variant schemes. Then we proposed a new scheduling algorithm for shared-fiber-delay-line switches in order to achiev e low loss rate when the utilization approaches the maximum. We justified our design by simulation. In our finding, through mathematical analysis and computer simulation, our proposed switching model and scheduling algorithm can be coupled well to achieve good performance for all-optical packet swi tches. We also found that the selection of the slot size in the network was very critical as it determi ned the transmission overhead and hence the utilization of the all-optical network. Our resear ch limitation depended on slot size. Although a sma ll slot size was critical for high utilization with ou r model, it was not always preferable. It was becau se a small slot size increased the switching and schedul ing complexity at the switch. Thus the selection of an optimum slot size for the network was a compromise between utilization and complexity. Conclusion/Recommendations: A fast scheduling algorithm has been studied in ord er to reduce the scheduling complexity so as to increase the utiliza tion without much penalty. In regard to the practic al implications, the VPFS was a promising model to ful ly utilize the huge capacity of all-optical network s and to accommodate variable-length packets for futu re Internet traffic. With VPFS, the selection of th e slot size was critical, and it was a compromise bet ween the network utilization and scheduling complexity.

GMPLS-based optical slot switching access-distribution network with a 10 ns high-speed PLZT optical switch

We design and implement an optical slot switching network for bulk content transfer. To realize the slot switching network, we employ the generalized multiprotocol label switching (GMPLS) extension protocol to reserve and release slots dynamically according to the application. We use optical switches as relay points in the slot switching network, and we employ a 10ns high-speed (Pb,La)(Zr,Ti)O&lt;sub&gt;3&lt;/sub&gt; (PLZT) optical switch. We extend the resource reservation protocol-traffic engineering (RSVP-TE) and realize optical slot reservation. In the slot reservation, the proposed scheme allocates a slot in a frame for clients in order to guarantee the minimum bandwidth. The scheme considers the accelerated and tentative slot reservation. In the slot switching network, we use the PLZT optical switch. The PLZT switch can improve the bandwidth utilization by reducing the guard time between slots unlike the microelectromechanical system (MEMS) switch. To realize the slot switching network, we develop a PLZT optical switch system with a GMPLS-based controller. By experiment based on the experimental network, we confirm that we can realize the slot switching network. We consider the application of the proposed network as an access network for content distribution.

Performance Analysis of Slotted Optical Switching Scheme using Non-uniform Traffic Pattern

In this paper, we present the performance analysis of bufferless slotted optical packet switching using non uniform traffic pattern. The mathematical analysis has been done to evaluate the packet loss rate and also compared with the existing uniform traffic pattern. In addition to this, we have also studied the performance of the non uniform traffic pattern with the uniform traffic pattern of various packet sizes. Under non-uniform traffic pattern, packet loss rate is very much reduced compared to the uniform traffic pattern and more number of packets has been transmitted for the same period of time.

Packet contention resolution in slotted optical packet switch using ant-colony based algorithm

An ant-based contention resolution scheme for the slotted optical packet switched networks has been proposed, and the optimal number of fibre delay lines (FDLs) used in the switch under various traffic loads is investigated. The proposed algorithm can makes FDLs and output port assignment so as to improve the cell-loss rate under various traffic loads. It is found for traffic loads 0.9, 0.6, 0.3, the optimum value for FDL is 64 128 and 128.

Contention resolution in slotted WDM optical packet switching networks using cascaded auxiliary switch

A contention resolution scheme for slotted optical packet switching networks is proposed. The optical switch is augmented using auxiliary output ports connected to an auxiliary switch through fibre delay lines. The node architecture is illustrated and the results of the model show that packet blocking probability is improved using the proposed scheme.