Coalition Formation Based Energy Efficient
Spectrum Leasing in Doubtful Inband Cooperative
D2D Communications
Hualiang Chen
∗
, Dan Wu
∗
, Yueming Cai
∗
and Xinrong Guan
∗
∗
College of Communications Engineering, PLA University of Science and Technology, Nanjing, China
Email: {chenhualiang2005, wujing1958728}@126.com, caiym@vip.sina.com, ywygxr_@aliyun.com
Abstract—In this paper, we investigate an inband cooperative
device-to-device (D2D) communication system in cellular net-
works. Cellular users and D2D pairs help each other to improve
their respective performance. Specifically, via coalition formation,
cellular users release some of their spectrum to D2D pairs so as to
start the communications of the D2D pairs; at the same time, D2D
pairs help to relay the messages of the cellular users. The D2D
pairs are thought to be socially untrusted to the cellular users, as
thus, a secrecy problem for cellular users comes into being due
to the relaying. Then we address this problem from a physical
layer security perspective. A coalition formation algorithm is
designed to solve the spectrum management problem in this
cooperative system. Numerical results show the validity of the
proposed scheme.
Index Terms—D2D communication, untrusted relay, physical
layer security, energy efficiency, coalition formation.
I. INTRODUCTION
With the rapid development of wireless networks, the perfor-
mance metrics of wireless communications are becoming more
and more multifarious. Wireless communications nowadays
require higher data rate, lower communication delay, higher
energy efficiency, et al. The demands for these performances
are especially booming, as it can be seen in the R&D of the
5G communication systems. To meet these challenges, device-
to-device (D2D) technique is proposed as one of the most
promising techniques. Having been added into the 3GPP LTE
Release 13 standard, D2D communications take advantage of
the physical proximity of communicating devices, so as to
improve spectrum utilization, system throughput, and energy
efficiency, enlarge cellular coverage, and enable new types of
service paradigms [1]- [5].
In particular, D2D communications can facilitate coopera-
tive relaying between ordinary cellular users. Cooperative D2D
communications organically integrate D2D Communications
and cooperative communications in cellular networks. And it
gains the advantages of the two techniques. The devices can
either cooperate with each other and form some local area
network, or be the relays of some cellular link and help the
cellular user in bad channel conditions to communicate with
the eNB [6]- [10]. However, cooperative D2D communica-
tions, while benefiting the system performance, can incur two
aspects of problems: incentive and confidentiality. Considering
the rareness of wireless resorces and the openness of the
cooperative communications, these two problems must be well
addressed.
By enabling the idle cellular users to act as relays for
D2D communication, [6] proposes a relay selection scheme
to minimize the sum transmit power of the communication.
After introducing the concept of D2D cluster, [7] performs
resource allocation and relay selection to increase the sum
rate of the D2D communication. However in [6] and [7] no
incentive mechanisms are taken account of for the cooperation.
[8] and [9] introduce incentives to inspire the cooperation
communications. [8] proposes a bandwidth exchange incentive
mechanism where a node can delegate a portion of its band-
width to another node in exchange for relay cooperation. Sim-
ilarly, a framework for macro-femto cooperation is designed
where both cooperative parties benefit from the cooperation
in term of throughput and delay in [9]. The cooperation there
is also inspired by spectrum leasing from macrocell users to
femtocell users. The problem is that the issue of confidentiality
in cooperation is not addressed because the cooperation is
based on the completely mutual trust among all parties.
With the above consideration, we investigate ajoint spectrum
and power allocation problem in a cooperative inband D2D
communication system in [10], where the confidentiality of
messages is addressed from the perspective of physical layer
security perspective. However, we just analyze the scenario
with single cellular user and single D2D pair in [10]. What
is more, there are neither incentives for the cellular user to
cooperate, nor any quality of service (QoS) requirements from
the D2D communication. And this is illogical in realistic
scenarios.
In this paper, a much more generalized scenario with
multiple cellular users and multiple D2D pairs is investigated.
The D2D pairs are assumed to be untrusted to the cellular
users. The cellular users and the D2D pairs are supposed to co-
operate with each other to improve their self-interests through
doubtful spectrum leasing. The word “doubtful” here means
each D2D pair eavesdrops each cellular user with a specified
probability.We propose a coalition formation game framework
to deal with this doubtful spectrum leasing problem. More
specifically:
• We regard energy efficiency as the performance metric
for both cellular users and D2D pairs. Each cellular user
would like to cooperate to improve its energy efficiency,
at the same time, all the D2D pairs want to obtain higher
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