
Physical Communication 25 (2017) 298–303
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Physical Communication
journal homepage: www.elsevier.com/locate/phycom
Full length article
Transport capacity of cooperative cognitive radio ad hoc networks
Jing Gao
a
, Yinghui Zhang
b,∗
, Yang Liu
b
a
Tianjin Key Laboratory of Wireless Mobile Communications and Power Transmission, Tianjin Normal University, 300387, China
b
College of Electronic Information Engineering, Inner Mongolia University, Hohhot, 010020, China
a r t i c l e i n f o
Article history:
Received 17 December 2016
Received in revised form
12 January 2017
Accepted 15 January 2017
Available online 18 January 2017
Keywords:
Transport capacity
Cognitive radio
Ad hoc
Cooperative
a b s t r a c t
It is more challenging for improving the traditional performance metrics for the 5-th generation network
(5G) because of more congestible frequency spectrum. How to improve the network capacity without
using more spectrum has become one of important studies in 5G. In this paper, the transport capacity of
cooperative cognitive radio ad hoc networks is studied. In order to characterize the transport capacity,
a half-slotted ALOHA multiple access protocol is introduced. In each slot, secondary users are divided
into cooperative secondary users and ordinary users dependent on the positional relationship between
them and primary transmitters. Primary transmitters send their packets in the first half slot while keep
silence in the second half slot. Ordinary secondary users send their packets at a probability p in the whole
slot. Cooperative secondary users receive the packets from their corresponding primary transmitters in
the first half slot and forward them to the primary receivers in the second half slot. The closed-form
expressions of the bounds of primary transport capacity and mean secondary transport capacity are
derived based on the protocol. Furtherly, the optimal problem of the performance is analyzed about two
important parameters: primary and secondary coverage radius. Theoretical results show that an optimal
primary coverage radius could be found to maximize the transport capacity of primary network. While
the transport capacity of secondary network increases with the increasing secondary coverage radius.
The analysis reveals that the transport capacity could be improved by secondary cooperation because of
higher successful transmission probability.
© 2017 Elsevier B.V. All rights reserved.
1. Introduction
It is well known that frequency spectrum will be more and
more tense with the rapid development of mobile communications
for 5G. Heterogeneous network and millimeter wave (mmWave)
technology are two established effective methods to solve this
problem. Cognitive radio (CR) networks is considered to be one
of the typical heterogeneous networks which could release the
conflict between spectrum scarcity and the inefficient use of
most licensed spectrum bands [1]. In CR networks, unlicensed or
secondary users (SU) are allowed to access the licensed spectra
when they do not cause unacceptable levels of interference to
licensed or primary users (PU). The framework of CR networks also
∗
Corresponding author.
E-mail addresses: jing401@126.com (J. Gao), zhangyinghuiimu@163.com
(Y. Zhang), yangliuimu@163.com (Y. Liu).
poses many new challenges in research despite its superiorities in
broad applying prospect.
The capacity of CR networks has been a hot spot all the time
because of its importance in analyzing the network performance.
Since the seminal work of Gupta and Kumar [2], the capacity of ad
hoc networks has been extensively explored. In [2], they present
the transport capacity of ad hoc networks in the order sense based
on signal to interference plus noise ratio (SINR) model. As λ being
the density of transmitters in the network, they certified that the
transport capacity scales as Θ
√
λ
. Based on the results, the
scaling law of CR networks are widely studied in [3–5]. In [3],
a tradeoff was testified to exist between throughput and delay
in a overlaid wireless network. In [4], the scaling law Θ
√
n
is achievable for both the primary network and the secondary
network by using percolation theory [6], where n is the number
of nodes in the network. In [5], the throughput of coexist two
networks could achieve the same scaling law in a two-tier network
which is same to that of single network.
The other primary concern of the capacity of CR network is
the closed-form expression which is first derived for the capacity
of ad hoc networks in [7,8]. In [7], Weber et al. analyze the
http://dx.doi.org/10.1016/j.phycom.2017.01.001
1874-4907/© 2017 Elsevier B.V. All rights reserved.