Time division multiplex

The new generation of "user-oriented'' satellites are conceived to involve a dramatic reduction in the earth station size and complexity. Frequency division multiple access (FDMA) and single channel per carrier (SCPC) in the uplink and time division multiplexing (TDM) in the downlink are employed in the system described here. To interface FDMA in the uplink and TDM in the downlink, multicarrier demodulation (MCD) is required on-board the satellite. The operation of the on-board MCD is the separation of each individual channel and subsequent demodulation. The results presented in this paper have been obtained under INTELSAT Contract INTEL-479, which has provided an analysis of the advanced technologies and techniques for on-board frequency demultiplexing and demodulation for low bit rate carriers. The study was constrained by the requirement that new-generation payloads could serve the stations already active in the INTELSAT Business System. A digital hardware design that implements an MCD that can process three channels at 4.4 Mb/s, or 12 channels at 1.1 Mb/s is described in this paper. The test results have confirmed the MCD feasibility, and further improvements are expected from a semicustom implementation.

Statistical multiplexing at the optical layer has been considered a critical requirement in order to build the next generation of ultra-high capacity optical transport networks in a cost-efficient manner. However, even today, the state of the art of commercially available optical core networks is based on mature wavelength switching and routing technologies, which lack a transport and control plane architecture that can support statistical traffic multiplexing with guaranteed Quality of Service (QoS) across a wide range of QoS parameters even if they can support fast reconfiguration at msec time scales. For several years, most research efforts have focused on the concepts of Optical Burst Switching (OBS) and Optical Packet Switching (OPS), which are based on the hybrid use of electronic nodes and optical switches to exploit Time Division Multiplexing (TDM) in order to achieve statistical multiplexing and dynamic resource reservation over optical networks. While burst switching has b...

Field experiments of 42.7 / 128.1 Gb/s WDM-OTDM transmultiplexing and all-optical dual-wavelength regeneration at the OTDM rate are presented. By using the asynchronous retiming scheme, we achieve error-free buffer-less data grooming with time-slot interchange (TSI) capability for OTDM meshed networking. We demonstrate excellent performance from the system, discuss scalability, applicability, and the potential reach of the asynchronous retiming scheme for transparent OTDMdomain interconnection.

Field experiments of 42.7 / 128.1 Gb/s WDM-OTDM transmultiplexing and all-optical dual-wavelength regeneration at the OTDM rate are presented. By using the asynchronous retiming scheme, we achieve error-free buffer-less data grooming with time-slot interchange (TSI) capability for OTDM meshed networking. We demonstrate excellent performance from the system, discuss scalability, applicability, and the potential reach of the asynchronous retiming scheme for transparent OTDMdomain interconnection.

The physical activities of a real wireless network are represented by events which are the main components of a discrete event simulation (DES) system and are produced by its event generator during simulation time. Each network service (e.g. voice, data and video) constitutes an event for a particular mobile user. A critical component within the simulation system, called scheduler, runs by selecting the next earliest event, executing it till completion, and returning to execute the next event. Calendar queue is the state of the art implementation of the scheduler among the most popular networking simulation tools such as ns-2. However, Calendar queue time-stamping mechanism presents drawbacks in the case of complex dynamical systems, like wireless networks, where probability of events concurrency is large. In such a case sequential time-stamping of calendar queue scheduling does not reflect real network events occurrence and generation. It should be remarked that there are very few reports if any in the literature concerning research on events scheduling mechanisms in such real time systems. On the other hand, multi-threading technology offers advanced capabilities for modelling concurrent events. The main goal of this paper is to illustrate that multithreading architectures provide the means for designing efficient schedulers in the simulation of wireless networks resource allocation but, also, several critical issues such as deadlocks, synchronization and scheduling must be effectively faced. In this paper, a stable simulation model is presented based on a novel layered thread architecture and on an alternative network event scheduling mechanism, called the Priority Queue (PQ) -Time Division Multiplexing (TDM) Layered Multithreading mechanism, which supports concurrent events as compared to the state of the art approach which supports only sequential events. Moreover, specific drawbacks of the JVM multi-threading platform such as thread execution unpredictability are also faced and presented.

In this paper we analyze the delay performance of an opportunistic multi-channel medium access control scheme and compare it to that of the corresponding single channel MAC scheme. In the opportunistic multi-channel MAC scheme, we assume that the pair of sender/receiver is able to evaluate the channel quality after a certain amount of channel sensing delay and to choose the

We propose a novel approach to QoS for real-time traffic over wireless mesh networks, in which application layer characteristics are exploited or shaped in the design of medium access control. Specifically, we consider the problem of efficiently supporting a mix of Voice over IP (VoIP) and delay-insensitive traffic, assuming a narrowband physical layer with CSMA/CA capabilities. The VoIP call carrying capacity of wireless mesh networks based on classical CSMA/CA (e.g., the IEEE 802.11 standard) is low compared to the raw available bandwidth, due to lack of bandwidth and delay guarantees. Time Division Multiplexing (TDM) could potentially provide such guarantees, but it requires fine-grained network-wide synchronization and scheduling, which are difficult to implement. In this paper, we introduce Sticky CSMA/CA, a new medium access mechanism that provides TDM-like performance to real-time flows without requiring explicit synchronization. We exploit the natural periodicity of VoIP flows to obtain implicit synchronization and multiplexing gains. Nodes monitor the medium using the standard CSMA/CA mechanism, except that they remember the recent history of activity in the medium. A newly arriving VoIP flow uses this information to grab the medium at the first available opportunity, and then sticks to a periodic schedule, providing delay and bandwidth guarantees. Delay-insensitive traffic fills the gaps left by the real-time flows using novel contention mechanisms to ensure efficient use of the leftover bandwidth. Large gains over IEEE 802.11 networks are demonstrated in terms of increased voice call carrying capacity (more than 100% in some cases). We briefly discuss extensions of these ideas to a broader class of real-time applications, in which artificially imposing periodicity (or some other form of regularity) at the application layer can lead to significant enhancements of QoS due to improved medium access.

This paper presents an on-chip network for a run-time reconfigurable System-on-Chip. The network uses packetswitching with virtual channels. It can provide guaranteed services as well as best effort services. The guaranteed services are based on virtual channel allocation, in contrast to other on-chip networks where guarantees are provided by time-division multiplexing. The network is particularly suitable for systems in which the traffic is dominated by streams. We model the data traffic in the system and simulate the behaviour of the network with this model. The results show that the network is capable of handling the system traffic and can provide the required guarantees. Advances in silicon technology bring, among others, two problems that chip designers have to face -a high design complexity and a signal integrity problem [1],[2], . The first problem is the concern that the complexity of a system that fits on a single chip is getting so high that the time needed to design a completely new system using the current design methods and tools is becoming impractical long. For that reason it is foreseen that future System-on-Chip (SoC) will be based mostly on pre-designed IP blocks relying on extensive IP reuse. To be practical, such a design methodology needs to be complemented with a unified and simple solution for interconnecting and integrating IP blocks in a system. Currently on-chip buses offer such a solution, but since the bus bandwidth does not scale with the number of IP cores on the chip it will soon become a system bottleneck. The second problem, the signal integrity problem, is due to the fact that with the technology scaling transistors get smaller and faster while wires get thinner and slower. Wire delay becomes proportional to the wire length and a few long wires on a chip can degrade the performance of the entire chip. Thus, the on-chip interconnects become a limiting factor for SoC performance and their physical parameters * This research is supported by the research program of the Dutch organisation for Scientific Research NWO (project number 612.064.103) and the EU-FP6 project 4S (IST 001908

We describe recent results of the Advanced Research Projects Agency (AFWA) sponsored Consortium on Wideband All-Optical Networks which is developing architectures, technology components, and applications for ultrafast 100 Gb/s timedivision multiplexing (TDM) optical networks. The shared-media ultrafast networks we envision are appropriate for providing low-access-delay bandwidth on demand to both future highburst rate (100 Gb/s) users as well aggregates of lower-rate users (i.e., a heterogeneous user population). To realize these goals we are developing ultrafast network architectures such as HLAN, described here, that operate well in high-latency environments and require only limited processing capability at the ultrafast bit rates. We also describe results on SO-Gb/s, 90-km soliton transmission, lOO-Gb/s soliton compression laser source technology, picosecond short-pulse fiber ring lasers, picosecondaccuracy optical bit-phase sensing and clock recovery, all-optical injection-locked fiber figure-eight laser clock recovery, shortpulse fiber loop storage, and all-optical pulse width and wavelength conversion. I sponsored Consortium made up of AT&T Bell Laboratories, Digital Equipment Corporation, and the Massachusetts Institute of Technology was formed to develop architectures and technologies for future high-speed high-capacity wavelengthdivision multiplexing (WDM) optical networks and to develop architecture and technology for ultrafast, 100 Gb/s, timedivision multiplexing (TDM) networks. This paper describes our optical TDM architecture and details key technology milestones toward realization of this system. A second separate paper in this special issue addresses Consortium work on WDM networks.

We propose a novel approach to QoS for real-time traffic over wireless mesh networks, in which application layer characteristics are exploited or shaped in the design of medium access control. Specifically, we consider the problem of efficiently supporting a mix of Voice over IP (VoIP) and delay-insensitive traffic, assuming a narrowband physical layer with CSMA/CA capabilities. The VoIP call carrying capacity of wireless mesh networks based on classical CSMA/CA (e.g., the IEEE 802.11 standard) is low compared to the raw available bandwidth, due to lack of bandwidth and delay guarantees. Time Division Multiplexing (TDM) could potentially provide such guarantees, but it requires fine-grained network-wide synchronization and scheduling, which are difficult to implement. In this paper, we introduce Sticky CSMA/CA, a new medium access mechanism that provides TDM-like performance to real-time flows without requiring explicit synchronization. We exploit the natural periodicity of VoIP flows to obtain implicit synchronization and multiplexing gains. Nodes monitor the medium using the standard CSMA/CA mechanism, except that they remember the recent history of activity in the medium. A newly arriving VoIP flow uses this information to grab the medium at the first available opportunity, and then sticks to a periodic schedule, providing delay and bandwidth guarantees. Delay-insensitive traffic fills the gaps left by the real-time flows using novel contention mechanisms to ensure efficient use of the leftover bandwidth. Large gains over IEEE 802.11 networks are demonstrated in terms of increased voice call carrying capacity (more than 100% in some cases). We briefly discuss extensions of these ideas to a broader class of real-time applications, in which artificially imposing periodicity (or some other form of regularity) at the application layer can lead to significant enhancements of QoS due to improved medium access.

General guidelines for high-speed time-division multiplexing (TDM) data-rate transmission are essential for the increase of the overall transmission capacity. In this paper, general theoretical investigations concerning fiber chromatic dispersion in optical TDM systems are performed. Recent experiments that confirm the theoretical predictions are presented. Nonzero dispersionshifted fiber and standard single-mode fiber are recommended for 40 and 160 Gb/s, respectively, independent of the chromatic dispersion compensation scheme.

In this article, a new dynamic bandwidth allocation algorithm for the upstream channel of Ethernet Passive Optical Networks, called DySLa, is proposed not only to provide service differentiation but also to offer subscriber differentiation. In contrast to previous methods in which the performance of each class of service is not insured, DySLa is continuously evaluating the mean packet delay and guarantees that the highest priority services fulfil the packet delay requirements in the access network for every type of client. Simulation results show that DySLa can maintain both the mean packet delay and packet loss ratio below the maximum upper bounds permitted for the most sensitive services of every class of customer. Moreover, DySLa outperforms other dynamic bandwidth allocation algorithms which provide service and client differentiation and it makes a fairer bandwidth distribution than those methods. Ethernet passive optical networks • Dynamic bandwidth allocation algorithms • Quality of service • Service level agreement • Class of service • Service and customer differentiation • Automatic weight adaptation

In this paper, we analyze the queueing performance in terms of loss rate of an OFDM (orthogonal frequency-division multiplexing)/TDMA (time division multiplexing access) based wireless system taking into account the multifractal behavior of the wireless traffic flows. To this end, first, we show evidences of multifractal characteristics on wireless traffic traces. These findings motivated us to propose a traffic policing and control scheme based on a multifractal envelope process in order to maintain the traffic flows well-behaved, i.e., in accordance to the desired QoS parameters. Furthermore, by assuming a multifractal traffic model, we derive a data loss probability equation for wireless traffic flows that was applied to the OFDM/TDMA based wireless system. Simulations and comparisons to other methods were carried out in order to verify the efficiency of the proposed traffic policing scheme as well as of the loss probability estimation approach.

We propose a hybrid wavelength-division-multiplexing/time-division-multiplexing architecture using reflective semiconductor optical amplifiers (RSOAs) for next-generation access solutions. We demonstrate that the use of a high gain and high output power RSOA as remote modulator enables a 36-dB optical budget for colorless operation at 2.5 Gb/s over 45-km single-mode fiber. This RSOA-based configuration provides a reasonable cost per user for this hybrid system and can be easily upgraded.

In this paper, we discuss different algorithms that can be used to encode channel state information (CSI) in realistic multiuser multiple-input multiple-output (MIMO) systems where there are only few users experiencing similar propagation conditions and the mobile user receivers do not necessarily have the same number of receive antennas. We divide systems with CSI encoding into four classes: time-division multiplexing (TDM) with and without linear pre-coding, and multiple user scheduling with and without linear pre-coding. The practical aspects such as system's complexity and approaches for transmitting the CSI feedback and rate information from the mobile receivers to the base station are discussed and compared for different bit rates in the feedback link. We show that significant increases of the mean throughput of the multiuser scheduling systems demand much higher feedback link bit rates than TDM solutions. We also demonstrate that, while optimum, the non-linear precoding systems may introduce unacceptable degree of complexity into the base station design while linear pre-coding offers a very good trade-off between performance and complexity. Keywords Multiuser MIMO systems • Channel state information feedback • Multiuser diversity • Vector quantization 1 Introduction Practically all state-of-the-art high-capacity wireless communication systems rely on some form of multiple-input multiple-output (MIMO) solutions to increase spectral efficiency on

We address the complete design flow from specification models of new automotive functions captured in Matlab-Simulink to their distributed execution on hierarchical bus-based electronic architectures hosting the release of already deployed automotive functions. We propose an automated design space exploration process resulting in a costoptimized extension of the existing target hardware and an allocation of balanced task structures automatically derived from the specification model on this modified target hardware which is sufficient to guarantee both system-level timing requirements and deadlines extracted from the Matlab-Simulink specification model.

The new generation of "user-oriented'' satellites are conceived to involve a dramatic reduction in the earth station size and complexity. Frequency division multiple access (FDMA) and single channel per carrier (SCPC) in the uplink and time division multiplexing (TDM) in the downlink are employed in the system described here. To interface FDMA in the uplink and TDM in the downlink, multicarrier demodulation (MCD) is required on-board the satellite. The operation of the on-board MCD is the separation of each individual channel and subsequent demodulation. The results presented in this paper have been obtained under INTELSAT Contract INTEL-479, which has provided an analysis of the advanced technologies and techniques for on-board frequency demultiplexing and demodulation for low bit rate carriers. The study was constrained by the requirement that new-generation payloads could serve the stations already active in the INTELSAT Business System. A digital hardware design that implements an MCD that can process three channels at 4.4 Mb/s, or 12 channels at 1.1 Mb/s is described in this paper. The test results have confirmed the MCD feasibility, and further improvements are expected from a semicustom implementation.

We present an analysis of linear in-band crosstalk in high split long reach wavelength/time-division-multiplexing passive optical networks (WDM-TDM PONs). In this letter, a mathematical model is deducted for the first time to calculate optical signal-to-noise ratio penalties due to in-band crosstalk in multipoint-to-point networks. The network performance can be perturbed by in-band crosstalk caused by power leakages from burst-mode optical network units (ONUs) in OFF-state. Our study results show that the leaked powers in upstream ONU transmitters can have an impact on the achievable split factor of WDM-TDM PONs. Furthermore, the performance limitations caused by aggregated interburst residual power are discussed.

The Terminal Access Control System (TACS) is designed to make efficient usage of 25-kHz-wide satellite transponder channels, such as those available on FLEETSAT, GAPSAT, LEASAT. It does so by applying time division multiple access and automated demand assignment techniques to these channels, allowing a significant increase in both data throughput and supportable user population, as compared to the initial, single network per transponder FLEETSAT operating mode. The Terminal Technology Group of Lincoln Laboratory Division 6 has built prototypes of all of the TACS ground segment equipment, as well as special-purpose test equipment used to demonstrate and quantify the performance of TACS. This report describes the implementation details of components of the TACS Central Control Facility as configured for testing at the Laboratory. The components described are: the Multiple access Controller, the Call Simulator, the System Operator's Console, and the Scenario Generator. All differe...

In optical time division multiplexed (OTDM) optical data streams are constructed time multiplexing a number of lower bit rate optical streams. The advances in OTDM systems and components research show the technique to be highly suited to the generation and transmission of high capacity data on a single optical carrier. In this work, Spectrum compression based on filters for improving bandwidth efficiency is presented and demonstrated experimentally in 40 GB/s OTDM system. Even after 100km transmission, de multiplexing and clock recovery can be implemented successfully, and the data rate-to-bandwidth ratio has been improved.

Recent advances in satellite communication technology have led to the deployment of very small aperture terminal (VSAT) networks supporting diverse applications. VSAT networks are characterized by their low cost per node, integrated network management facilities, and support of multiple applications and integrated communications services. Since its introduction into the communications marketplace in recent years, VSAT technology has advanced in a number of significant ways. The use of high-yield microwave monolithic integrated circuit technology in radio frequency components, volume production of radio and baseband systems, application of digital signal processing and satellite multiple access techniques, and support of many common data communications protocols have increased the performance and capabilities of VSAT networks, while at the same time reducing associated costs. A survey of available VSAT technology is provided, and new systems and services using VSAT technology are described. Future trends in VSAT technology and applications are also discussed.

The rapid surge in internet-driven smart devices and bandwidth-hungry multimedia applications demands high-capacity internet services and low latencies during connectivity. Cloud radio access networks (C-RANs) are considered the prominent solution to meet the stringent requirements of fifth-generation (5G) and beyond networks by deploying the fronthaul transport links between baseband units (BBUs) and remote radio heads (RRHs). High-capacity optical links could be conventional mainstream technology for deploying the fronthaul in C-RANs. But densification of optical links significantly increases the cost and imposes several design challenges on fronthaul architecture which makes them impractical. Contrary, Ethernet-based fronthaul links can be lucrative solutions for connecting the BBUs and RRHs but are inadequate to meet the rigorous end-to-end delays, jitter, and bandwidth requirements of fronthaul networks. This is because of the inefficient resource allocation and congestion control schemes for the capacity constraint Ethernet-based fronthaul links. In this research, a novel reinforcement learning-based optimal resource allocation scheme has been proposed which eradicates the congestion and improves the latencies to make the capacity-constraints low-cost Ethernet a suitable solution for the fronthaul networks. The experiment results verified a notable 50% improvement in reducing delay and jitter as compared to the existing schemes. Furthermore, the proposed scheme demonstrated an enhancement of up to 70% in addressing conflicting time slots and minimizing packet loss ratios. Hence, the proposed scheme outperforms the existing state-of-the-art resource allocation techniques to satisfy the stringent performance demands of fronthaul networks.

Hybrid optical and wireless technology integrations have been considered as one of the most promising candidates for the next generation broadband access networks for quite some time. The integration scheme provides the bandwidth advantages of the optical networks and mobility features of the wireless networks for Subscriber Stations (SSs). It also brings economic efficiency to the network providers particularly in rural area where the existing wired telecommunication infrastructures such as Digital Subscriber Line (DSL), Cable Modem (CM), T-l/E-I networks or fibre deployments are either costly or unreachable. For successful integration of the optical and wireless technologies there are some technical issues which need to be addressed efficiently in order to provide End-to-End (ETE) and diverse Quality of Service (QoS) for various service classes. This paper investigates the possible challenging issues for the integrated structure of the Time Division Multiplexing and Wavelength Division Multiplexing Ethernet Passive Optical Networks (TDM EPON and WDM EPON) with the Worldwide Interoperability for Microwave Access and Wireless Fidelity (WiMAX and Wi-Fi) networks. To reduce the ETE delay and provide the QoS for diverse service classes, we have compared six existing upstream scheduling mechanisms in two levels which are distributed on Access Points (APs) from Wi-Fi domain and Base Stations (BSs) from WiMAX domain. Performance evaluations of the existing scheduling techniques for three popular service classes (Quad-play) have been studied which show the strong impact of using the efficient up-link scheduler in converged scenario. We have also proposed a dynamic scheduling algorithm for optical and wireless integration scheme, which is under the implementation and evaluation process.

Security is a major challenge for "Active Networking," as accessible programmability creates numerous opportunities for mischief. The point at which programmability is exposed, e.g., through the loading and execution of code in network elements, must therefore be carefully crafted to ensure security. The SwitchWare active networking research project has studied the architectural implications of various tradeoffs between performance and security. Namespace protection and type safety were achieved with a module loader for active networks, ALIEN, which carefully delineated boundaries for privilege and dynamic updates. ALIEN supports two extensions, the Secure Active Network Environment (SANE), and the Resource Controlled Active Network Environment (RCANE). SANE extends ALIEN's node protection model into a distributed setting, and uses a secure bootstrap to guarantee integrity of the namespace protection system. RCANE provides resource isolation between active network node users, including separate heaps and robust time-division multiplexing of the node. The SANE and RCANE systems show that convincing active network security can be achieved. This paper contributes a measurement-based analysis of the costs of such security with an analysis of each system based on both execution traces and end-toend behavior.

Implicit local coordination of nodes in a wireless network using mechanisms such as Carrier Sense Multiple Access (CSMA) is conceptually attractive and relatively easy to implement, but often leads to performance that is far inferior to what is possible using explicit global coordination strategies such as Time Division Multiplexing (TDM). In this paper, we give two examples showing that appropriately designed implicit coordination strategies that employ learning and memory can provide performance competitive with that obtained using explicit strategies, while requiring minimal overhead. The first example is an algorithm for distributed timing synchronization maintenance using the timing information already present in ongoing communication in the network. The second example is a distributed medium access control protocol that achieves performance close to time division multiplexing (TDM) without requiring explicit resource allocation: nodes lock into communication patterns that have been found to work, with enough randomization to prevent locking into poor schedules. While the general philosophy of exploiting learning and memory in the design of network protocols is of broad applicability, our numerical results emphasize 60 GHz networks with highly directional links: effective coordination is particularly important for such networks, in view of the "deafness" caused by directionality.

Current optical networks are migrating to wavelength division multiplexing (WDM)-based fiber transport between traditional electronic multiplexers/demultiplexers, routers, and switches. Passive optical add-drop WDM networks have emerged but an optical data network that makes full use of the technologies of dynamic optical routing and switching exists only in experimental test-beds. This paper will discuss architecture and technology issues for the design of high performance optical data networks with two classes of technologies, WDM and time division multiplexing (TDM). The WDM network architecture presented will stress WDM aware internet protocol (IP), taking full advantage of optical reconfiguration, optical protection and restoration, traffic grooming to minimize electronics costs, and optical flow-switching for large transactions. Special attention is paid to the access network where innovative approaches to architecture may have a significant cost benefit. In the more distant future, ultrahigh-speed optical TDM networks, operating at single stream data rates of 100 Gb/s, may offer unique advantages over WDM networks. These advantages may include the ability to provide integrated services to high-end users, multiple qualityof-service (QoS) levels, and truly flexible bandwidth-on-demand. We will give an overview of an ultrahigh-speed TDM network architecture and describe recent key technology developments such as high-speed sources, switches, buffers, and rate converters. Index Terms-Optical data processing, optical fiber communication, optical fiber LAN, optical signal processing, time division multiaccess, time division multiplexing, wavelength division multiplexing.

The aim of this paper is to present an adaptable Fat Tree NoC architecture for Field Programmable Gate Array (FPGA) designed for image analysis applications. Traditional NoCs (Network on Chip) are not optimal for dataflow applications with large amount of data. On the opposite, point to point communications are designed from the algorithm requirements but they are expensives in terms of resource and wire. We propose a dedicated communication architecture for image analysis algorithms. This communication mechanism is a generic NoC infrastructure dedicated to dataflow image processing applications, mixing circuit-switching and packet-switching communications. The complete architecture integrates two dedicated communication architectures and reusable IP blocks. Communications are based on the NoC concept to support the high bandwidth required for a large number and type of data. For data communication inside the architecture, an efficient time-division multiplexed (TDM) architecture is proposed. This NoC uses a Fat Tree (FT) topology with Virtual Channels (VC) and flit packet-switching with fixed routes. Two versions of the NoC are presented in this paper. The results of their implementations and their Design Space Exploration (DSE) on Altera StratixII are analyzed and compared with a point to point communication and illustrated with a multispectral image application. Results show that a point-to-point communication scheme is not efficient for large amount of multispectral image data communications. A NoC architecture uses only 10% of the memory blocks required for a point to point architecture but seven times more logic elements. This resource allocation is more adapted to image analysis algorithms as memory elements are a critical point in embedded architectures. A FT NoC-based communication scheme for data transfers provides a more appropriate solution for resource allocation.

We consider all-optical TDM/WDM broadcast and select networks. We assume that each network node is equipped with one fixed transmitter and one tunable receiver; tuning times are assumed to be not negligible with respect to the slot time. We discuss efficient scheduling algorithms to assign TDM/WDM slots to multicast traffic in such networks. Given the problem complexity, heuristic algorithms based on the Tabu Search methodology are proposed, and their performance are assessed using randomly created request matrices based on two types of multicast traffic patterns: a video-conference, and a server distribution traffic pattern. The considered performance index is the frame length required to schedule a given traffic request matrix.

ccess networks are part of the telecommunications infrastructure that connect individual subscribers to the service provider's central office (CO) over public ground. They are cost prohibitive and have consistently been regarded as the bottleneck, primarily because the ever-growing demand for higher bandwidth is beyond the supported levels of the widely deployed access technologies. As illustrated in Table 1, the typical broadband access connections at home are composed of at least three phone lines, two high-definition television (HDTV) channels, and two PC connections for Internet access [1]. Neither digital subscriber line (DSL) nor cable modem can successfully meet the bandwidth requirements of this so-called "telhome" service. Therefore, upgrading access networks with a low-cost and high-capacity solution is necessary to provide broadband access. As an inexpensive, simple and scalable technology, passive optical networks (PONs) are considered a promising solution to provide various end users with broadband access [2]. As exemplified in Fig. 1, a PON system is composed of one optical line terminal (OLT) residing in the central office (CO), one passive optical splitter deployed in the remote node (RN), and multiple optical network units (ONUs) near subscribers' locations. Intermediate powering between the OLT and the ONUs is eliminated by the use of optical fibers and passive optical splitter. Great efforts to push the PON standardization progress have been made through both the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) and the IEEE Ethernet in the First Mile Task Force (IEEE EFM TF). The ratified PON standard and recommendations are tabulated in Table 2. Significant differences among diverse PON "flavors" include the supported line rates and type of bearer units. The ITU-T G.983.x Recommendation series were ratified to specify broadband PON (BPON) [3], which employs asynchronous transfer mode (ATM) cells to encapsulate the data transmitted between the OLT and ONUs. IEEE 802.3ah [4] specifies the physical and medium access control (MAC) layer characteristics of Ethernet PON (EPON). EPON carries Ethernet frames with 1 Gb/s symmetric transmission speed. The recently approved IEEE P802.3av Task Force is working on an enhanced version of EPON, 10 Gb/s EPON (10GEPON). 10GEPON upgrades the existing EPON with two solutions, a symmetric solution of 10 Gb/s upstream and 10 Gb/s downstream transmission, and an asymmetric solution of 10 Gb/s downstream and 1Gb/s upstream transmission [5]. Gigabit PON (GPON) [6] is the continuation and evolution of BPON. Besides ATM cells, GPON supports Ethernet frames as well as time-division multiplexing (TDM) units by mapping them into GPON encapsulation method (GEM) frames. The maximum transmission speed over GPON reaches 2.448 Gb/s symmetrically. BPONs, EPONs, and GPONs are also called TDM-PONs for their data transmission is divided into time slots. As shown in Fig. 1a, in the downstream from the OLT to the associated ONUs, one wavelength is employed, and TDM enables data transmission to different ONUs. This is a point-to-multipoint architecture, and data are broadcast to each ONU through the shared downstream trunk.

The new generation of "user-oriented'' satellites are conceived to involve a dramatic reduction in the earth station size and complexity. Frequency division multiple access (FDMA) and single channel per carrier (SCPC) in the uplink and time division multiplexing (TDM) in the downlink are employed in the system described here. To interface FDMA in the uplink and TDM in the downlink, multicarrier demodulation (MCD) is required on-board the satellite. The operation of the on-board MCD is the separation of each individual channel and subsequent demodulation. The results presented in this paper have been obtained under INTELSAT Contract INTEL-479, which has provided an analysis of the advanced technologies and techniques for on-board frequency demultiplexing and demodulation for low bit rate carriers. The study was constrained by the requirement that new-generation payloads could serve the stations already active in the INTELSAT Business System. A digital hardware design that implements an MCD that can process three channels at 4.4 Mb/s, or 12 channels at 1.1 Mb/s is described in this paper. The test results have confirmed the MCD feasibility, and further improvements are expected from a semicustom implementation.

The results of an investigation of the performance of a time-division-addressed fiber-optic gas-sensor array by means of wavelength modulation of a distributed-feedback ͑DFB͒ laser are reported. The system performance is found to be severely limited by the extinction ratio of the optical switch used for pulse amplitude modulation. Formulas that relate the cross-talk level to the extinction ratio of the switch, the modulation parameters of the DFB laser, and the optical path differences among sensing channels are derived. Computer simulation shows that an array of 20 methane gas sensors with a detection sensitivity of 2000 parts in 10 6 ͑ppm͒ ͑10-cm gas cell͒ for each sensor may be realized with a commercially available single Mach-Zehnder amplitude modulator ͑Ϫ35-dB extinction ratio͒. An array of 100 sensors with a 100-ppm detection sensitivity for each sensor may be realized if a double Mach-Zehnder amplitude modulator is used.

We consider all-optical TDM/WDM broadcast and select networks. We assume that each network node is equipped with one fixed transmitter and one tunable receiver; tuning times are assumed to be not negligible with respect to the slot time. We discuss efficient scheduling algorithms to assign TDM/WDM slots to multicast traffic in such networks. Given the problem complexity, heuristic algorithms based on the Tabu Search methodology are proposed, and their performance are assessed using randomly created request matrices based on two types of multicast traffic patterns: a video-conference, and a server distribution traffic pattern. The considered performance index is the frame length required to schedule a given traffic request matrix.

The large investments required for deploying passive optical networks (PONs) render the disposal of appropriate planning tools for designing such networks in a cost-effective way a necessity. This paper addresses the problem of finding the least costly tree topology time-division multiplexing PON (TDM-PON) deployment configurations considering equipment and installation costs (CAPEX) and operational exploration costs. With this purpose, an integer linear programing model is developed, which is capable of designing not only common single-stage PON configurations, but also PONs with multiple stages of optical splitting. In order to reduce the computation time for problems of larger size, a two-stage heuristic is also proposed. The simulation results for the cases studied reveal that an optimal multistage splitting strategy can lead to cost savings of up to 15% in CAPEX expenditures in comparison with the traditional single-stage approach. Furthermore, the heuristic procedure proposed is shown to obtain results within acceptable bounds relative to the optimum solutions, hence validating its use for larger sized networks. The results also show that the average CAPEX cost savings between the two-stage and single-stage approaches are quite dependent on the strategies used to choose candidate locations for the splitters, with values ranging from 5 to 12% depending on whether random candidate placement or k-means-based placement is used. Index Terms-Access networks; Integer linear programing; Multistage optical splitting; Passive optical network. I. INTRODUCTION T he bandwidth in access networks has been steadily increasing since the 1990s, with an average growth of about 50% per year [1,2]. If this growing trend continues, it is expected that, within eight years' time, connection speeds of 1 Gb/s will be available worldwide, with some authors indicating 2016 as the starting year for these services in the US [2]. Although the range of technologies available for the access part in telecommunication networks is quite diverse, only fiber-to-the-home (FTTH) solutions are capable of meeting the bandwidth requirements of the future services supported in those speeds. To meet these challenges, many network operators around the world have started to deploy optical fiber Manuscript

This paper demonstrates the use of software radio techniques in the context of sensing, rather than communications. It describes code-division multiplexing (CDMA) and time-division multiplexing (TDMA) of a receiver channel in an electric field sensing system. The only hardware used is a front-end gain stage consisting of two opamps and a microcontroller. The modulation and demodulation operations are implemented entirely in the microcontroller software. Multiple coded waveforms are transmitted simultaneously, and induce a combined signal on a single receive electrode. The combined signal, after passing through a single analog front end terminating in an analog-todigital converter, is separated into the four original component signals by a software demodulation operation. The signal-to-noise ratio (SNR) achieved by the code-division multiplexed system given a fixed measurement time is compared to the SNR achieved by a time-division multiplexed implementation given the same total measurement time. The paper also compares the scaling of TDMA and CDMA performance with the number of transmitted channels and the number of demodulated channels.

This paper demonstrates the use of software radio techniques in the context of sensing, rather than communications. It describes code-division multiplexing (CDMA) and time-division multiplexing (TDMA) of a receiver channel in an electric field sensing system. The only hardware used is a front-end gain stage consisting of two opamps and a microcontroller. The modulation and demodulation operations are implemented entirely in the microcontroller software. Multiple coded waveforms are transmitted simultaneously, and induce a combined signal on a single receive electrode. The combined signal, after passing through a single analog front end terminating in an analog-todigital converter, is separated into the four original component signals by a software demodulation operation. The signal-to-noise ratio (SNR) achieved by the code-division multiplexed system given a fixed measurement time is compared to the SNR achieved by a time-division multiplexed implementation given the same total measurement time. The paper also compares the scaling of TDMA and CDMA performance with the number of transmitted channels and the number of demodulated channels.

To ensure low power consumption while maintaining flexibility and performance, future Systems-on-Chip (SoC) will combine several types of processor cores and data memory units of widely different sizes. To interconnect the IPs of these heterogeneous platforms, Networks-on-Chip (NoC) have been proposed as an efficient and scalable alternative to shared buses. NoCs can provide throughput and latency guarantees by establishing virtual circuits between source and destination. State-of-the-art NoCs currently exploit Time-Division Multiplexing (TDM) to share network resources among virtual circuits, but this typically results in high network area and energy overhead with long circuit setup time. We propose an alternative solution based on Spatial Division Multiplexing (SDM). This paper describes our first design of an SDM-based network, discusses design alternatives for network implementation and shows why SDM should be better adapted to NoCs than TDM for a limited number of circuits. Our case study clearly illustrates the advantages of our technique over TDM in terms of energy consumption, area overhead, and flexibility. SDM thus deserves to be explored in more depth, and in particular in combination with TDM in a hybrid scheme.

Cloud-Radio Access Networks (Cloud-RANs) are separating the mobile network's base station functions into three units, the connection between the two of them is referred to as the fronthaul network. This work demonstrates the transmission of user data transport blocks between the distributed Medium Access Control (MAC) layer and local Physical (PHY) layer in the radio unit over a Passive Optical Network (PON). PON networks provide benefits in terms of economy and flexibility when used for Cloud-RAN fronthaul transport. However, the PON upstream scheduling can introduce additional latency that might not satisfy the requirements imposed by Cloud-RAN functional split. In this work we demonstrate how our virtual Dynamic Bandwidth Allocation (DBA) concept can be used to effectively communicate with the mobile Long Term Evolution (LTE) scheduler, adopting the well known cooperative DBA mechanism, to reduce the PON latency to satisfactory values. Thus, our results show the feasibility of using PON technology as transport medium of the fronthaul for the MAC/PHY functional split, in a fully virtualised environment. Further background traffic is added, so that measurements show a more realistic scenario. The obtained round trip times indicates that using PON at fronthaul might be limited to the distance of 11 km for a synchronised scenario, or no compliance for an non-synchronised scenario.

In order to address the challenges that have come with the exploding demand for higher speed, traffic growth and mobile wireless devices, Mobile network operators have decided to move to the notion of small cells based on cloud radio access network. The merits of cloud based RAN includes the ease of infrastructure deployment and network management as well as the fact that its performance are optimized and it is cost effective the merits of cloud based RAN includes the ease of infrastructure deployment and network management as well as the fact that its performance are optimized and it is cost effective. Notwithstanding, cloud radio access network comes with so many strict requirements to be fulfilled for its fronthaul network. In this paper, we have presented these requirements for a 5G fronthaul network. Particular interest on the time division multiplex passive optical network’s challenge of latency was treated by proposing an optimized version of the round robin dynamic bandwidth...

We address the complete design flow from specification models of new automotive functions captured in Matlab-Simulink to their distributed execution on hierarchical bus-based electronic architectures hosting the release of already deployed automotive functions. We propose an automated design space exploration process resulting in a costoptimized extension of the existing target hardware and an allocation of balanced task structures automatically derived from the specification model on this modified target hardware which is sufficient to guarantee both system-level timing requirements and deadlines extracted from the Matlab-Simulink specification model.

The mission of the GeneSat-1 technology demonstration spacecraft is to validate the use of researchquality instrumentation for in situ biological research and processing. GeneSat-1 is a "triple-CubeSat" vehicle currently being developed for launch as a secondary payload on a Minotaur launch vehicle in late 2006. Spacecraft and mission development is being led by the NASA Ames Research Center Astrobionics group. However, university participation is a crucial element of the program with significant contributions being made from a number of academic groups throughout the Silicon Valley region. This paper will review progress in the development of the GeneSat-1 mission. In addition, the role of each University partner will be discussed, the educational elements of the program will be described, and a discussion of technical and organization challenges will be presented. Finally, the paper will review the relevance of GeneSat-1's technology to advanced sensing concepts, biotechnology and pharmaceutical research, astrobiology, and human space flight research.

We have designed and tested a lead-insensitive ÿber optic pH sensor that is based on the absorption of an indicator dye immobilized in a polymer bead. The ÿber optic pH sensor uses two wavelengths; one senses the change in absorption of the indicator dye and the other provides a reference signal. In a view to desired time modulation and the dual wavelength time division multiplexing, we used light emitting diodes for sources, a phototransistor for the detector, and electronics process the detected signal. The sensor has demonstrated fast response, repeatable calibration, reversibility, and stability. This inexpensive device may also be used during bending of the optical ÿber for applications in the ÿeld.