Exploring the effects of physical layer parameters in WDM based fixed and flexible-grid networks

Service differentiation-based spectrum defragmentation in mixed grid optical networks

The metro section of telecom networks is currently pressured by a strong increase of traffic required by end users. Especially mobile end users are adopting new media-rich services that require high bandwidth. These users are characterized by a geographical mobility this mobility induces significant changes in the traffic pattern at metro level. So future metro networks are expected not only to provide very large capacities but also to support sudden (dynamic) changes of the traffic pattern. An optical metro network based on the concept of flexible spectrum grid can address such requirements in terms of bandwidth and flexibility. In this paper we show the benefits of employing a flexible grid in metro ring networks compared to a fixed-grid WDM case, under dynamic (changing) traffic. The adoption of flexible grid enables an effective spectrum utilization resulting in network blocking a few orders of magnitude lower with respect to fixed grid case.

Elastic optical networks (EONs) have provision long transmission reach (TR) and high spectral-efficiency (SE). Hence, compared to fixed-grid optical networks, in EONs, managing resources and addressing network design poses complex challenges. In this work, we formulate a link-based mixed integer linear program (MILP) model which considers quality of transmission (QoT) while determining the route, modulation format/level (MF/ML) and spectrum allocation (SA) for every request. To improve SE, model chooses the highest ML; however, when QoT is considered, TR of path with highest ML is very limited. Hence, model finds trade-off between ML, number of required frequency slots (FSs), and TR, with the objective of minimising required amount of network FSs so as to admit all requests. Finally, we evaluate and analyse model's performance and show that for simplicity, existing schemes impractically assume single MF (i.e., higher SE and ML) compared to fixed-grid networks, thereby ignoring the flexible nature of EONs.

We propose a quasi-dynamic network design algorithm considering traffic growth in multi-layered photonic networks that consist of electrical paths and optical paths. The quasi-dynamic network design proposed herein leaves existing paths unchanged in order to minimize service disruption due to path rerouting as well as human error. Simulations verify that the network cost strongly depends on the network design algorithms adopted and the holding terms of service traffic. We, then, introduce a new parameter that represents expected service holding terms. The parameter is shown to represent effectively the network cost trend versus the number of the incremental designs. Furthermore, lower network cost is obtained by taking advantage of the network design algorithms that consider service holding times. This study is the first to address the criteria in designing future multi-layered photonic networks that offer cost-effective expansion while accommodating different services.

In this paper, we propose a novel adaptive carrier sense multiple access scheme with collision avoidance (CSMA/CA) to perform efficient and reliable data transfer with increased throughput across multiple coexisting wireless body area networks (BANs) in a tiered architecture. We investigate the proposed scheme using two distributed cross-layer optimized dynamic routing techniques, i.e., shortest path routing (SPR) and cooperative multi-path routing (CMR). The channel state information from the physical layer is passed on to the network layer using an adaptive cross-layer carrier sensing mechanism between the physical and MAC layer, which adjusts the carrier sense threshold (e.g., RSSI) periodically based on the slowly-varying channel condition. An open-access experimental dataset of 'everyday' mixed-activities is used for analyzing the cross-layer optimization. Our proposed optimization using adaptive carrier sensing performs better than static carrier sensing with CSMA/CA as it reduces the continuous back-off duration and latency as well as significantly increases the throughput (in successful packets/s) by more than 50%. Adaptive CSMA/CA also shows 20% and 6% improvement over a coordinated TDMA approach with higher duty cycle for throughput and spectral efficiency, respectively, and provides acceptable packet delivery ratio and outage probability with respect to SINR.

ABSTRACTThis paper offers the different type transmission schemes used in wireless sensor networks. The wireless sensor network used in a number of applications such as Agriculture, Military, Medical, Multimedia etc. According to the applications there are different quality of service parameters and designing requirements for different layers in network design. While designing any ad hoc network or sensor network many designing principals and challenges are taken into consideration. For the designing of protocols layering in ad hoc sensor network basically a five layer model is taken into consideration. These layers are application, transport, network, Medium access control and physical layer. In this paper different types of designing constraints associated with physical and medium access layer has been introduced for different applications in sensor networks. In that manner this paper helps us to select the designing of a link for particular application.

The main challenges of cognitive radio include spectrum sensing at the physical (PHY) layer to detect the activity of primary users and spectrum sharing at the medium access control (MAC) layer to coordinate access among coexisting secondary users. In this paper, we consider a cognitive radio network in which a primary user shares a channel with secondary users that cannot distinguish the signals of the primary user from those of a secondary user. We propose a class of distributed cognitive MAC protocols to achieve efficient spectrum sharing among the secondary users while protecting the primary user from potential interference by the secondary users. By using a MAC protocol with one-slot memory, we can obtain high channel utilization by the secondary users while limiting interference to the primary user at a low level. The results of this paper suggest the possibility of utilizing MAC protocol design in cognitive radio networks to overcome limitations in spectrum sensing at the PHY layer as well as to achieve spectrum sharing at the MAC layer.

Most of the proposed communication protocols exploiting the collaborative nature of WSNs and its correlation characteristics improve energy efficiency. However, they follow the traditional layered protocol architectures; specifically, the majority of these communication protocols are individually developed for different networking layers, i.e., transport, network, medium access control (MAC), and physical layers. While they may realize high performance in terms of the metrics related to each of these individual layers, they are not jointly optimized to maximize the overall network performance while minimizing the energy expenditure. Considering the scarce energy and processing resources of WSNs, joint optimization, and design of networking layers, i.e., cross-layer design, stands as the most promising alternative to inefficient traditional layered protocol architectures.The basic principle of cross-layer design is to make information available to all levels of the protocol stack. It allows the definition of protocols or mechanisms that do not meet the isolation layers of the OSI model (van der Schaar M, Shankar NS, Wirels Commun 12(4):50–58, 2005; Srivastava V, Motani M, Commun Mag 43(12):112–119, 2005). In fact, cross-layer integration and design techniques result in significant improvement in terms of energy conservation in WSNs (van Hoesel L, Nieberg T, Wu J, Havinga PJM, Wirel Commun 11(6):78–86, 2004; Yetgin H, Cheung KTK, El-Hajjar M, Hanzo L, Trans Veh Technol 64(8):3795–3803, 2015). Several researches started by focusing on the cross-layer interaction and design to develop new communication protocols (Melodia T, Vuran MC, Pompili D, The state of the art in cross-layer design for wireless sensor networks. Vol 3883, in Lecture Notes in Computer Science-Wireless Systems and Network Architectures in Next Generation Internet (EuroNGI), by M Cesana and L Fratta, Berlin/Heidelberg: Springer, pp 78–92, 2005). Yet, these works either provide analytical results without communication protocol design or perform pairwise cross-layer design within limited scope, e.g., only MAC and network layers, which do not consider all of the networking layers involved in WSNs communication, such as transport, network, MAC, and physical layers.Considering the scarce energy and processing resources of WSNs, joint optimization, and design of networking layers, i.e., cross-layer design, stands as the most promising alternative to inefficient traditional layered protocol architectures. There are considerable benefits of rethinking the protocol functions of networking layers in a unified way so as to provide a single communication module for efficient communication in WSNs.KeywordsCross-layering approachesLayers interactionsSingle-layer integrated moduleHeuristic approachCross-layering MAC and network layersCross-layering physical and MAC and network layers PANELCLBTPGFPlusXLPCross-layer design for WSNs security

We propose a network segmentation and design algorithm based on traffic distribution information. Numerical experiments demonstrated that the proposed algorithm can greatly reduce network cost.

In this paper, we developed a joint AMC-ARQ design combining adaptive modulation and coding at the physical layer with automatic repeat request protocol at the data link layer in multiple-input multiple-output(MIMO) orthogonal frequency division multiplexing(OFDM) systems which is converted into a series of parallel and independent flat sub-channels based on channel matrix singular value decomposition(SVD) at the physical layer. Theoretical derivation supports that our proposed design maximizes the spectral efficiency under prescribed delay and error performance constrains. Simulation results show that this cross-layer design based on channel matrix singular decomposition for MIMO-OFDM obtains more than 2 dB gain in spectral efficiency comparing the traditional SISO cross-layer design.

In order to tackle the increasing heterogeneous global Internet traffic, mixed-line-rate (MLR) optical wavelength division multiplexed (WDM) networks have emerged as the cost- and power-efficient solution. In MLR WDM networks, channels are structured as sub-bands, each of which consists of wavelengths operating at a similar data rate. By reducing the (1) spacing within a sub-band, or (2) spacing between sub-bands operating at different data rates, spectral efficiency can be improved. However, owing to high physical layer impairment levels, decrease in sub-band spacing adversely affects transmission reach of the channels, which results in higher power consumption due to requirement of increased signal regeneration. In this work, we compare power efficiency of various MLR and single-line-rate (SLR) solutions, and also investigate the trade-off that exists between spectral and power efficiency in a WDM network. Simulation results indicate that (1) for high transmission capacities, a combination of 100 Gbps transponders and 40 Gbps regenerators will obtain the highest power efficiency; (2) for long connection distances, a point ofmerging occurs for various SLR and MLR designs, where power consumption is independent of the frequency band distribution; and (3) for MLR systems, both spectral and power efficiency can be improved by using either shorter links with higher bandwidth assignment to 100 Gbps wavelengths, or longer links with higher bandwidth assignment to 40 Gbps wavelengths. Finally, the results indicate that focusing on spectral efficiency alone results in extra power consumption, since high quality of transmission and spectral efficiency leads to increased regeneration.

The North-East Corridor (NEC) Testbed project is the 3rd of three NIST (National Institute of Standards and Technology) greenhouse gas emissions testbeds designed to advance greenhouse gas measurements capabilities. A design approach for a dense observing network combined with atmospheric inversion methodologies is described. The Advanced Research Weather Research and Forecasting Model with the Stochastic Time-Inverted Lagrangian Transport model were used to derive the sensitivity of hypothetical observations to surface greenhouse gas emissions (footprints). Unlike other network design algorithms, an iterative selection algorithm, based on a k-means clustering method, was applied to minimize the similarities between the temporal response of each site and maximize sensitivity to the urban emissions contribution. Once a network was selected, a synthetic inversion Bayesian Kalman filter was used to evaluate observing system performance. We present the performances of various measurement network configurations consisting of differing numbers of towers and tower locations. Results show that an overly spatially compact network has decreased spatial coverage, as the spatial information added per site is then suboptimal as to cover the largest possible area, whilst networks dispersed too broadly lose capabilities of constraining flux uncertainties. In addition, we explore the possibility of using a very high density network of lower cost and performance sensors characterized by larger uncertainties and temporal drift. Analysis convergence is faster with a large number of observing locations, reducing the response time of the filter. Larger uncertainties in the observations implies lower values of uncertainty reduction. On the other hand, the drift is a bias in nature, which is added to the observations and, therefore, biasing the retrieved fluxes.

In this paper, we propose a cross-layer design which combines adaptive modulation and coding (AMC) at the physical layer with a hybrid automatic repeat request (HARQ) protocol at the data link layer to minimize the packet error rate (PER) and maximize the spectral efficiency. By using Markov model to predict the channel condition of next frame according to the second order statistics characteristics of the former frame, we calculate the conditional probability density function and joint probability density function of signal to noise ratio (SNR). Further, we derive the packet error rate and average spectral efficiency in closed-form for transmission over Nakagami-m fading channels. Numerical results show that the proposed scheme can obtain lower PER and higher spectral efficiency c ompared with traditional HARQ protocol s. The cross-layer design scheme combing type-III HARQ with AMC can achieve the highest spectral efficiency and the lowest PER than type-I HARQ and type-II HARQ.

Recent advancement in technology fosters the emergence of Body Area Nanonetworks (BANs) as a new communication paradigm. BANs foreshadow its gleaming applications in diversified fields more specifically in health-care applications such as recognizing and destroying tumors cells via penetration of sensitive body sites. Such applications bolster amalgamation of both molecular and electromagnetic communication leading to the emergence of a hybrid communication leveraging perks of both types of communication. Even though most of the existing studies in the literature mainly focus on lower layers of the protocol stack, i.e., Physical and MAC layers for BANs addressing either type of communication, the design of protocols for upper layers such as Transport layer deploying hybrid communication still remains unexplored to the best of our knowledge. Therefore, in this paper, we focus on developing an energy-efficient transport layer protocol in BANs deploying hybrid communication. Here, we introduce a congestion control mechanism with limited complexity and overhead. Our endeavor is to ensure a delicate balance among different network-level performance metrics such as throughput, end-to-end delay, and energy consumption. We evaluate the efficacy of our proposed protocol in comparison to several state-of-the-art approaches through ns-2 simulation.

In wireless sensor networks (WSN), the nodes have limited energy resource. So power conservation in individual node is of significant importance. In this paper we derive a cross-layer design method that combines adaptive modulation and coding (AMC) at the physical layer and two sleep modes according to monitoring type at the medium access layer (MAC) in healthcare monitoring WSN, judiciously to maximize spectral efficiency, and to minimize energy consumption, under prescribed error performance constraints. To achieve maximum spectral efficiency in the entire SNR (signal-to-noise ratio) range, we advise a combined transmission mode switching between convolutionally code and unconvolutionally code mode, based which we analyze the energy consumption of the system with multi mobile nodes and a sink node and verify that it is energy efficient to adopt AMC instead of single modulation at physical layer in healthcare monitoring WSN.