There have been several studies that have discussed and derived MAC protocols for UWASNs. In [7], the authors summarize some of the MAC protocols thereby that have been proposed for UWASNs. The multiple access control including Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA) and the medium access control including ALOHA, Carrier Sense Multiple Access (CSMA), Multiple Access with Collision Avoidance (MACA), and Floor Acquisition Multiple Access (FAMA), which use in terrestrial sensor network, have been modified in order to adapt to the nature of acoustic transmission in an underwater environment.Slotted FAMA [8] uses time slotting over floor acquisition multiple access (FAMA) discipline where the time line is divided into fixed-length slots.
It combines both carrier sensing (CS) and a dialogue between the source and destination Inhibitors,Modulators,Libraries prior to data transmission. Although time slotting eliminates the asynchronous nature of the protocol and the need for excessively long control packets, guard times should be used in the Inhibitors,Modulators,Libraries slot duration. Moreover, Slotted FAMA assumes an infinite local buffer at each node which is unrealistic in resource limited sensor nodes. Finally, Slotted FAMA assumes that the clocks of the sensor nodes are fully synchronized.In [9,10], the authors use contention instead of Request To Send/Clear To Send (RTS/CTS) packets to acquire the channel in a distributive manner. Inhibitors,Modulators,Libraries This algorithm, namely T-Lohi, divides time into slots, but uses tones instead of control packet exchanges to contend for the channel.
However, T-Lohi ignores the Inhibitors,Modulators,Libraries hidden terminal and the exposed terminal problems. Furthermore, the use of tones requires the Entinostat use special hardware which increases the cost and the complexity of the sensor nodes.In [11], the authors propose a MAC protocol for dense networks. The used performance metric is energy consumption rather than the bandwidth. The algorithm selleck bio is designed to achieve a locally synchronized schedule even in the presence of long propagation delays. The authors assume synchronized node clocks. However, it is not clear how nodes go about reselecting transmission cycles when there is an overlap between two nodes. Moreover, the strategy for resolving hidden terminal problem was not clarified. In addi
Hyperspectral sensors, because of their high spectral detail over contiguous narrow bands, have proven to be a valuable tool for discriminating plants species [1�C4] compared to multispectral resolution sensors [5]. However, due to high dimensionality, working with hyperspectral data poses challenging problems such as redundancy, intensive computation, and singularity of covariance matrix inversion [6�C10].