7. Routing
Static
Operate on the basis of some static tables of input and
output data, where the configuration of
endpoints is either static, or a proposed for change, ie adding
or deleting a route planned in advance and be a new way
to distribute the routing table all the necessary nodes. One of
the representatives is the DNS .
Dynamic
The class of protocols that are capable of
independently transmit information about changes dynamically,
in real time, depending on the network, topology,
bandwight and load. This class is the
main protocols in LAN and in all other forms of
communication. only those that can be effective in the case
of radio communications
8. Graph theory
program shortest path {for process i >0};
define D, S : distance;
{S denotes the shortest distance received through a message}
parent : process deficit : integer;
N: set of neighbors of process i;
initially D= ∞ , parent = i, deficit = 0
{for process 0}
send (w(0,i), 0) to each neighbor i;
deficit := |N(0)|;
do ack ’ deficit := deficit – 1 od;
{deficit = 0 signals termination}
{for process i > 0}
do message = (S ,k) Ÿ S < D ’ if parent ≠ k or i ’ send ack to
parent fi;
parent := k; D := S;
send (D + w(i,j), i) to each neighbor j ≠ parent;
deficit := deficit + |N(i)| -1
0 message (S,k) Ÿ S ≥ D ’ send ack to sender
0 ack ’ deficit := deficit – 1
0 deficit = 0 Ÿ parent ≠ i ’ send ack to the parent
od
9. RSSI
• Received Signal Strength Indicator (RSSI): RSSI measures the
power of the signal at the receiver and based on the known transmit
power, the effective propagation loss can be calculated. Next by
using theoretical and empirical models we can translate this
loss into a distance estimate. This method has been used mainly
for RF signals. RSSI is a relatively cheap solution without any extra
devices, as all sensor nodes are likely to have radios
• Accordingly, the stronger the signal, the closer the location of the
receiver to the transmitter, so as to to the respective inverse-square
law
10. FRESNEL ZONE
• we have such a thing as a Fresnel zone,
which according to which each point of
the medium to which comes perturbation
itself becomes a source of secondary
waves, and the radiation field can be
considered as the superposition of all
the secondary waves. On the basis of
this principle can be shown that the
objects lying within the concentric circle
drawn around the line of sight of the two
transceivers, may affect the quality of
both positively and negatively. All
obstacles that fall inside the first circle,
the first Fresnel zone, have the most
negative impact...
11. TIME METHOD
• Time based methods (ToA, TDoA): These methods
record the time-of-arrival (ToA) or time-difference-
of-arrival (TDoA). The propagation time can be
directly translated into distance, based on the
known signal propagation speed. These methods
can be applied to many different signals, such as
RF, acoustic, infrared and ultrasound. TDoA
methods are impressively accurate under line-of-
sight conditions. But this line-of-sight condition is
difficult to meet in some environments.
•
15. MULTILATERATION IN GPS
Navigation technique based on the measurement
of the difference in distance to two stations at
known locations that broadcast signals at known
times
We can to generate the four constants Am,Bm,Cm,Dm from
measured distances and time for each receiver 2 ≤ m ≤ N. This
will be a set of N-1 inhomogeneous linear equations.
The distance in equation is the wave speed
times transit time . A TDOA multilateration
system measures the time difference of a
wavefront touching each receiver. The TDOA
equation for receivers m and 0 is
16. ANGLE METHOD
• Angle-of-Arrival (AoA): AoA estimates the angle at
which signals are received and use simple
geometric relationships to calculate node
positions. Generally, AoA techniques provide more
accurate localization result than RSSI based
techniques but the cost of hardware of very high in
AoA.
20. POPULAR TECHNIQUES
• RSSI- measures stronger signal , possibility to
estimate position by triangulation and directional
antenna.
• TODA- measures distance to sensor, with
multilateration and beacons can detect position of
sensor node, 3 beacons at least
• AoA- Angle to signal, good with directional
antennas, need to be bounded to some
coordinates
23. SRT
• Reference system is a material body, chosen as the origin of this system, a method for
determining the position of objects with respect to the reference system and method for
measuring time. Usually distinguish between reference systems and coordinate systems.
Adding measurement procedure time to the coordinate system "converts" it into a the frame
of reference.
• . Watches are considered synchronized if the relation
•
24. SRT POSTULATES
zero time calculated from as
start of initiating sensor with
coordinates 0.0.0
1) The initiating object is at
the origin
2) All the calculated values of
the distance and relative to
initiator by time reference.
3) The initiator provides the
starting point of time and in
space
4) Moving initiator in space,
does not occur changes of
his coordinates and does not
affect to cell units.
RSSI, is logarithmic value expressing
strength of the received signal, thus when
moving the source around, we have values
changing over time
ToA - time pinpoint from start the
transmission and to receive feedback.
Does not depend on the coordinates, using
only time period, which pinpoint the
beginning of the transmission.
Distance has been associated with the
speed of light and ToA (1) , that is also a
valid value in this context