WIMAX Basics from PHY Layer to Scheduling and Multicasting Approaches

WiMAX (Worldwide Interoperability for Microwave Access) is an emerging broadband wireless technology for providing Last mile solutions for supporting higher bandwidth and multiple service classes with various quality of service requirement. The unique architecture of the WiMAX MAC and PHY layers that uses OFDMA to allocate multiple channels with different modulation schema and multiple time slots for each channel allows better adaptation of heterogeneous user’s requirements. The main architecture in WiMAX uses PMP (Point to Multipoint), Mesh mode or the new MMR (Mobile Multi hop Mode) deployments where scheduling and multicasting have different approaches. In PMP SS (Subscriber Station) connects directly to BS (Base Station) in a single hop route so channel conditions adaptations and supporting QoS for classes of services is the key points in scheduling, admission control or multicasting, while in Mesh networks SS connects to other SS Stations or to the BS in a multi hop routes, the MMR mode extends the PMP mode in which the SS connects to either a relay station (RS) or to Bs. Both MMR and Mesh uses centralized or distributed scheduling with multicasting schemas based on scheduling trees for routing. In this paper a broad study is conducted About WiMAX technology PMP and Mesh deployments from main physical layers features with differentiation of MAC layer features to scheduling and multicasting approaches in both modes of operations

A Survey on Efficient Routing Strategies For The Internet of Underwater Things (IoUT)

The Internet of Underwater Things (IoUT) is an emerging technology that promised to connect the underwater world to the land internet. It is enabled via the usage of the Underwater Acoustic Sensor Network (UASN). Therefore, it is affected by the challenges faced by UASNs such as the high dynamics of the underwater environment, the high transmission delays, low bandwidth, high-power consumption, and high bit error ratio. Due to these challenges, designing an efficient routing protocol for the IoUT is still a trade-off issue. In this paper, we discuss the specific challenges imposed by using UASN for enabling IoUT, we list and explain the general requirements for routing in the IoUT and we discuss how these challenges and requirements are addressed in literature routing protocols. Thus, the presented information lays a foundation for further investigations and futuristic proposals for efficient routing approaches in the IoUT

Performance Evaluation of Routing Protocols in Wireless Sensor Networks

The efficiency of sensor networks strongly depends on the routing protocol used. In this paper, we analyze three different types of routing protocols: LEACH, PEGASIS, and VGA. Sensor networks are simulated using Sensoria simulator. Several simulations are conducted to analyze the performance of these protocols including the power consumption and overall network performance. The simulation results, using same limited sensing range value, show that PEGASIS outperforms all other protocols while LEACH has better performance than VGA. Furthermore, the paper investigates the power consumption for all protocols. On the average, VGA has the worst power consumption when the sensing range is limited, while VGA is the best when the sensing range is increased

Adaptive Power Controlled Techniques for Routing and Sink Redeployment In Underwater Sensor Networks

Underwater Sensor Network (UWSN) is the enabling technology for a broad range of potential and evolving applications in scientific, industrial and military domains. To make these applications viable, acoustic waves are used as an alternative to the highly attenuated electromagnetic waves in water medium. However, acoustic channel introduces unique challenges that are absent in UWSNs counterpart, terrestrial Wireless Sensor Networks (WSNs). In this dissertation we tackle these challenges mainly by designing routing, single sink and multi-gateway redeployment strategies. Firstly, we have developed an Adaptive Power Controlled Routing (APCR) strategy that is location free, energy efficient and is robust to the mobility of underwater nodes. In our techniques, nodes assign themselves to concentric layers centered at the sink node and the routing paths are the determined on the fly. Nodes can adjust their transmission power to a finite set of values to adjust for the change in the network topology to maintain connectivity and reduce the energy consumption Secondly, we have opted to adaptively redeploy the surface sink to reduce the effect of mobility on the network performance metrics. In our adaptive dynamic sink redeployment strategy, the sink moves only if an actual reduction in energy consumption is expected. The redeployment decision is based on the routing information collected at the surface sink throughout the network\u27s operation. The surface sink finds and moves to the optimal new location that minimizes total energy consumption. Lastly, we have extended our redeployment strategy for multi-surface gateway architecture. In which underwater nodes communicate with one of the surface gateways that collectively form a virtual sink. For multi-surface gateway redeployment, we use APCR as the underlying routing protocol to determine when to redeploy. The redeployment problem is then reduced to find the optimal node to gateway assignment. The solution minimizes the total number of transmission power levels used by nodes communicating with surface gateways while enforcing a set of constraints on both surface gateways and underwater nodes. We solved for the optimal solution using exhaustive search and compared it with a near optimal solution obtained by a greedy algorithm to cater for processing limitation of surface gateways

A Dynamic Surface Gateway Placement Scheme for Mobile Underwater Networks

Deployment of surface-level gateways holds potential as an effective method to alleviate high-propagation delays and high-error probability in an underwater wireless sensor network (UWSN). This promise comes from reducing distances to underwater nodes and using radio waves to forward information to a control station. In an UWSN, a dynamic energy efficient surface-level gateway deployment is required to cope with the mobility of underwater nodes while considering the remote and three-dimensional nature of marine space. In general, deployment problems are usually modeled as an optimization problem to satisfy multiple constraints given a set of parameters. One previously published static deployment optimization framework makes assumptions about network workload, routing, medium access control performance, and node mobility. However, in real underwater environments, all these parameters are dynamic. Therefore, the accuracy of performance estimates calculated through static UWSN deployment optimization framework tends to be limited by nature. This paper presents the Prediction-Assisted Dynamic Surface Gateway Placement (PADP) algorithm to maximize the coverage and minimize the average end-to-end delay of a mobile underwater sensor network over a specified period. PADP implements the Interacting Multiple Model (IMM) tracking scheme to predict the positions of sensor nodes. The deployment is determined based on both current and predicted positions of sensor nodes, which enables better coverage and shorter end-to-end delay. PADP uses a branch-and-cut approach to solve the optimization problem efficiently, and employs a disjoint-set data structure to ensure connectivity. Simulation results illustrate that PADP significantly outperforms a static gateway deployment scheme