Image Processing Reference
In-Depth Information
Universal Mobile Telecommunications System (UMTS) to improve the network
capacity, the SE at cell edges and the coverage at hotspots. Relay technology has
also been standardized by 3GPP in Release 9 and Release 10 of the Long Term
Evolution-Advanced (LTE-A) [
44
-
46
], where relays are deployed either at fixed
locations or on mobile vehicles (e.g., trains, buses, etc.) to extend the coverage and
enhance the spectral- and the energy-efficiency. A relay node is attached to an eNB
through a wireless backhaul link either using the same frequency as the one used in
the access part (inband relaying or self-backhauling) or using a different frequency
band (outband relaying). 3GPP also defines different types of relays functioning in
different network layers varying from layer 1 (PHY layer) to layer 3 (Network
layer) [
47
]. Layer 1 relay is the simplest form of the LTE relay functioning in AF
mode. Layer 2 and Layer 3 relays operate in DF mode. A Layer 3 relay is indeed a
small eNB with the full functionality such as transmitting control signaling or
performing mobility management. As for the academic activities on the MCN, in
[
48
], the authors proposed the integration of the Mobile Ad-hoc Network (MANET)
and the Global System for Mobile (GSM) and introduced a so called Ad-hoc GSM
(A-GSM) platform, addressing practical issues for evolutionary changes of the
GSM system in order to support the relaying functionality for the voice calls.
Additionally, in [
49
], the authors overview several contributions to Working
Group 4 of the Wireless World Research Forum (WWRF) and present several
relay-based deployment concepts such as multihop relaying, cooperative relaying,
virtual antenna arrays and so on.
Recently, cooperative communication has been exploited to extend the battery
lifetime of UEs. C2POWER [
50
] and Green-T [
51
] are two European research
projects aiming at exploiting cooperative and cognitive communication to reduce
the power consumption of the multi-mode UEs. In [
52
,
53
], the authors study the
energy saving performance of cooperative communication exploiting short range
(SR) interfaces of the multi-mode UEs. Interacting as independent agents while
cooperating or competing for efficient resource utilization, conflict of interest
naturally occurs among the mobile users. Game theory is a mathematical tool that
can be applied to analyse strategic interaction among rational players [
54
-
63
]. Spe-
cifically, with the adoption of cooperative communication in wireless networks,
coalitional game theory (a.k.a. cooperative game theory) can be applied to incen-
tivize UEs to cooperate with each other [
56
-
59
]. Solution of a non-cooperative
game—which is given by the well-known Nash Equilibrium—basically predicts the
equilibrium strategy profile where no player wants to change its strategy. On the
other hand, solving a cooperative game means incentivizing all players by dividing
the common payoff that the players obtain by their cooperation in a fair way where
all players are satisfied and no one has incentive to leave the cooperation. Further
detail about cooperative game theory is out of the scope of this chapter. The
interested is referred to [
59
].
Another important issue related to the cooperation of UEs is detecting and
isolating selfish nodes from the cooperative ones. There are two main techniques
for this purpose, namely credit-based schemes [
64
-
67
] and reputation-based
schemes [
68
-
73
]. In the former, there is a central trustworthy entity that maintains
a credit account for each UE, where the cooperation of the UEs is fully recorded and
