Image Processing Reference
In-Depth Information
A nice property of this approach is that the cooperative UEs receive credit based on
their contribution to the achieved energy saving, satisfying all the UEs and incen-
tivizing all of them to keep the cooperation on. Last but not least, when a UE acts as
a relay, it consumes its energy to forward packets for the other UEs. Unless this
energy consumption is reimbursed, the relay will have no motivation to keep on
acting cooperatively. To this end, we provide the relay some additional credit, the
amount of which is equal to its consumed energy for the packet forwarding.
Obviously, this is apart from the credit that it receives from the distribution of the
achieved energy saving (determined by the
core solution
) explained previously.
Similarly, we charge the source nodes for receiving packet-forwarding service from
the other UEs. Therefore, our proposed credit scheme serves not only to ensure a
sustainable cooperation of the UEs, but also to detect and isolate the selfish UEs
from the cooperative ones.
In order to evaluate the effectiveness of the proposed credit scheme to detect and
isolate the selfish players, we conduct another simulation with a coalition size of
50 UEs and 50 % relay density (25 sources and 25 relays). Among them, 5 UEs are
selfish, while the rest 45 UEs are cooperative. The simulation starts with all the UEs
having equal initial battery of 2 Joules and an initial credit level of 0.1. Similar to
the previous simulation, every source UE generates a CBR traffic with the rate
10 packets per second and the packet size of 1024 bytes. Similar to the previous
simulation, every 10s, the sources and the relays change their roles, giving chance
to every UE to act both as a relay and as a source equally likely. The simulation lasts
until all UEs run out of battery. Figure
8.7
compares the average credit level of the
cooperative and the selfish UEs. As seen from the figure, all the UEs start with an
equal initial credit level of 0.1. The cooperative UEs gain credit and increase their
credit level, while the selfish ones lose their initial credit soon. As soon as a UE is
left without credit, other UEs avoid cooperating with it, which leads to its isolation
from other UEs. Further discussion on this topic is out of the scope of this chapter.
The interested reader is referred to [
75
].
Fig. 8.7 Comparing credit level of the cooperative and the selfish UEs [
75
]
