Efficient RTS and CTS Mechanism Which Save Time and System Resources

It is a well-known fact that the forthcoming names are distinctively different: interference range, career sense, and transmission. The given paper reveals the underlying study of disengagement of a request to send (RTS)/ clear to send (CTS) dialog. It was basically adopted under the influence of both; the presence of distributed coordination function of IEEE 802.11 and a sub-layer protocol which is called media access control (MAC) protocol. The demonstration was seen when applying a type of traffic flows such as Constant Bit Rate (CBR), Transmission Control Protocol (TCP), and besides User Datagram Protocol (UDP). When these are applied the output performance in term of throughput shows a very linear topology configuration of the network. To sum up, a new RTS /CTS mechanism was proposed based on the results obtained from the above suggestions. The detailing for the new mechanism showed that a terminal node will be responsible for deciding if it is authorized to use an RTS/CTS protocol dialog to send one of its packets or not. Needless to say, this process will be dynamic in nature.

Mobility Aware Duty Cycling Algorithm (MADCAL) A Dynamic Communication Threshold for Mobile Sink in Wireless Sensor Network

The hotspot issue in wireless sensor networks, with nodes nearest the sink node losing energy fastest and degrading network lifetime, is a well-referenced problem. Mobile sink nodes have been proposed as a solution to this. They do not completely remove the hotspot problem though, with nodes the sink passes most closely still expending more energy than others. This study proposes a lightweight algorithm, located in the media access control (MAC) layer of static nodes and utilising knowledge of predictable sink node mobility. This is in order to create a dynamic communication threshold between static nodes and the sink, within which static nodes awaken, lessening competition for sink communication between nodes. In utilising predictable mobility and factors already known to the static node, such as location and interference range, there is no need for energy-consuming messaging. Analysis and simulation results, tested on a lightweight implementation of a carrier-sense multiple-access-based MAC protocol, show a significant improvement in energy consumption in both controlled and random environments, with frame delivery improved to the point where sink speed is negated. This is when compared to the existing duty cycling approach.

Optimal interference range for minimum Bayes risk in binomial and Poisson wireless networks

Interference is the main performance-limiting factor in most wireless networks. Protocol interference model is extensively used in the design of wireless networks. However, the setting of interference range, a crucial part of the protocol interference model, is rather heuristic and remains an open problem. In this paper, we use the stochastic geometry and the direct approach to obtain the associated feasibility distributions. After that, we use the binary hypothesis testing to achieve the Bayes risk under binomial point process (BPP) and Poisson point process (PPP), respectively. According to the first derivative of the Bayes risk, we provide the equation to achieve the optimal interference range for minimum Bayes risk. We extend the method proposed by Wildman et al. to a more general situation. Furthermore, we show that for infinite PPP, those two methods converge to the same results. Several numerical results for wireless networks under BPP, finite PPP, and infinite PPP are given. Simulation results show that in the finite wireless network, the BPP method performs better than the PPP method.

Interference Range-Reduced Cooperative Multiple Access with Optimal Relay Selection for Large Scale Wireless Networks

Cooperative communication improves the link throughput of wireless networks through spatial diversity. However, it reduces the frequency reuse of the entire network due to the enlarged link interference range introduced by each helper. In this paper, we propose a cooperative medium access control (MAC) protocol with optimal relay selection (ORS-CMAC) for multihop, multirate large scale networks, which can reduce the interference range and improve the network throughput. Then, we investigate the performance gain achieved by these two competitive factors, i.e., the spatial frequency reuse gain and spatial diversity gain, in large scale wireless networks. The expressions of maximum network throughput for direct transmissions and cooperative transmissions in the whole network are derived as a function of the number of concurrent transmission links, data packet length, and average packet transmission time. Simulation results validate the effectiveness of the theoretical results. The theoretical and simulation results show that the helper can reduce the spatial frequency reuse slightly, and spatial diversity gain can compensate for the decrease of the spatial frequency reuse, thereby improving the network throughput from the viewpoint of the whole network.

Connectivity Analysis of Cognitive Radio Ad-Hoc Networks with Multi-Pair Primary Networks

In this paper, we study the connectivity of cognitive radio ad-hoc networks (CRAHNs) where primary users (PUs) and secondary users (SUs) are randomly distributed in a given area following a homogeneous Poisson process. Moreover, for the sake of more realistic CRAHNs, contrary to previous works in the literature, we consider the case that primary network is comprised of multiple communication pairs which are spatial-temporal distributed in the network area. We also take into consideration the differences in transmission range and interference range of both PUs and SUs. The connectivity of such CRAHN is studied from three viewpoints. First, we mathematically analyze the probability of isolated secondary transmitter and secondary receiver. Second, we derive the approximation expression of the link probability between two adjacent SUs. Third, we investigate the path connectivity between two arbitrary SUs by using the simulation analysis approach. The correctness of our mathematical expressions is confirmed by comparing analytical results with simulation results. The results in this paper provide insights into how multiple communication pairs in primary network affect the connectivity of secondary network, which can be useful guidelines for the design of CRAHNs.

Design and Fabrication of Laser-Machined Hinge Joints on Miniature Tubes for Steerable Medical Devices

With the proliferation of successful minimally invasive surgical techniques, comes the challenge of shrinking the size of surgical instruments further to facilitate use in applications such as neurosurgery, pediatric surgery, and needle procedures. This paper introduces laser machined, multi-degree-of-freedom (DOF) hinge joints embedded on tubes, as a possible means to realize such miniature instruments without the need for any assembly. A method to design such a joint for an estimated range of motion was explored. The effects of design and machining parameters on the mechanical interference, range of motion, and joint dislocation were analyzed. The extent of interference between the moving parts of the joint can be used to predict the range of motion of the joint for rigid tubes and future design optimization. The total usable workspace was also estimated using kinematic principles for a joint in series and for two sets of orthogonal joints. Our work can open up avenues to a new class of miniature robotic medical devices with hinge joints and a usable channel for drug delivery.

On Carrier Sensing Accuracy and Range Scaling Laws in Nakagami Fading Channels

We make a detailed study on carrier sensing of 802.11 in Nakagami fading channels. We prove that to maximize sensing accuracy, the optimal channel accessing probability is solely determined by the path-loss SIR (Signal to Interference Ratio). We define pfail-interference range and pbusy-carrier sensing range for fading channels and prove that their scaling laws in Nakagami fading channels are similar to those in the static channel. The newly derived theoretical results show a unified property between the static and fading channels. By extensive simulations, we reveal that fading depresses the probability of a dominating transmission state, and therefore it can mitigate severe hidden and exposed terminal problems, but fading harms the average sensing accuracy for an optimally adjusted carrier sensing threshold.