Space debris simulations show that if current space launches continue unchanged, spacecraft operations might become difficult in the congested space environment. It has been suggested that Active Debris Removal (ADR) might be necessary in order to prevent such a situation. Selection of objects to be targeted by ADR is considered important because removal of non-relevant objects will unnecessari...

Here, we present the collision probability of the IEEE 802.15.4 slotted Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) mechanism over a real-time wireless sensor network (RT-WSN), also called a synchronous network system. The “backoff,” the random delay of CSMA/CA, can be used to create a probability model and to determine the average packet delay over RT-WSN. The proposed theoreti...

The orbital evolution of Jupiter-family comets (JFCs), resonant asteroids, and asteroidal, trans-Neptunian, and cometary dust particles under the gravitational influence of planets was integrated. For dust particles we also considered radiation pressure, Poynting-Robertson drag, and solar wind drag. The probability of a collision of one former JFC with a terrestrial planet can be greater than a...

Random-access mechanisms play an important role in wireless networks, and have been extensively studied in recent years. Although many previous studies have proposed enhanced algorithms, each one has only considered either throughput or fairness. In this paper, we propose an efficient random-access mechanism called Multi-round Collision Avoidance (MrCA) that considers throughput and fairness to...

One of the most promising applications of cognitive radio networks (CRNs)is the efficient exploitation of TV white spaces (TVWSs) for enhancing the performance of wireless networks. In this paper, we propose a cross-layer design (CLD) of carrier sense multiple access with collision avoidance (CSMA/CA) mechanism at the medium access control (MAC) layer with spectrum sensing (SpSe) at the physica...

Free flight is an effective way to solve the congestions of air traffic flow. In order to guarantee the flight security, there is great significance to study on collision risk assessment in free flight. This paper applies the idea of collision risk of fixed route based on conflict area for reference, firstly designs a conflict area and establishes the collision risk model in free flight on the ...

most accidents happens because of lack of visibility and not driver’s reaction on time whenan accident occurs. increasing required time for driver’s reaction caused to decreasingaccidents on roadways .intelligent vehicle networks brings enough time for reaction by sendingalert and alternate messages to vehicles on roadway. main propose in this paper is aroundmodulation on reception interval saf...

Initial ranging is the primary and important process in wireless networks for the customer premise equipments (CPEs) to access the network and establish their connections with the base station. Contention may occur during the initial ranging process. To avoid contention, the mandatory solution defined in the standards is based on a truncated binary exponential random backoff (TBERB) algorithm w...

Binary Exponential Backoff (BEB) is the De-facto mechanism for contention control in IEEE 802.11 Wireless LAN. The exponential growth of Contention Window (CW) in all BackOff (BO) stages and randomness in BO selection causes unnecessary waiting time, high collision rate and unfairness in accessing the channel among the nodes. To overcome these anomalies, this paper proposes Hashing Based Distri...

In this work we study the collision probability, saturation throughput and statistical delay for the carrier sense multiple access collision avoidance (CSMA/CA) protocol with request to send and clear to send (RTS/CTS) mechanism in the case of frequency channel division. We propose in this paper a modified version of CSMA/CA-RTS/CTS to be compatible with the channel repartition technique and we...