Digital Signal Processing Reference
In-Depth Information
Fig. 7.3
Different types of
starvation mechanism and the
way they are detected
transmitting during our transmission. This means that this node was not listening
to our transmission, but we are listening to his transmission. Hence, this is a clear
case of asymmetric starvation (see Fig.
7.3
).
•
Neighborhood starvation is detected by long busy times (see Fig.
7.3
). Using
this detection mechanism, we cannot distinguish between slow neighbors and
neighborhood starvation. However, as the recommendation for this situation is
the same (you want to increase
T
CS
), this does not really matter.
•
The starvation-free scenario occurs when the above three scenarios are not iden-
tified.
7.3.4 Design-Time Procedures
The optimal operating point cannot be known at DT. However, for each scenario we
can identify possible escape procedures that may lead to better performance. We rely
on the learner to identify at RT the best actions among those possible. However, we
can already at DT devise procedures, also called heuristic recommendations here-
after, that are used as a seed for the learning engine.
In Fig.
7.4
, we see the system scenario diagram. As the system scenario diagram
is based on the scenario identification techniques presented in Sect.
7.3.3
, it differs
from the state space presented in Sect.
7.3.2
. The heuristic recommendations are
also shown and explained below.
Hidden Terminal Starvation
The hidden terminal starvation occurs when a large amount of packets fail (see
Sect.
7.3.3
). This implies that the SINR at the receiver is too low for successful
packet transmission. Hence, the heuristic recommendation would be to either to
increase the SINR at the receiver or to lower the required SINR for successful packet
reception. This can be done by:
•
increasing the transmission power: this increases the received power and, hence,
increases the SINR at the receiver,
