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A QoS-Based Channel Allocation and Power Control
Algorithm for Device-to-Device Communication
Underlaying Cellular Networks
Yu Baozhou1 and Zhu Qi
2
1 The Key Wireless Laboratory of Jiangsu Province, School of Telecommunication and Information Engineering,
Nanjing University of Posts and Telecommunications, Nanjing 210003, China 2 Key Laboratory on Wideband Wireless Communications and Sensor Network Technology of Ministry of Education,
Jiangsu Nanjing 210003, China
Email: [email protected]; [email protected]
Abstract—In device-to-device (D2D) communication system,
rational resource allocation can effectively reduce the
interference between cellular users and D2D users. In this paper,
based on the QoS requirement of cellular users and D2D users,
we propose a channel allocation and power control optimization
algorithm, which takes limit transmission power of each cellular
user and total D2D users into consideration when maximizing
the system capacity of total D2D users. We can achieve the
candidate cellular users set of D2D users according to the
minimum SINR requirement of D2D users. And then, the
transmission power of cellular users and D2D users are
optimized with Lagrange multiplier method, meanwhile we
calculate the capacity of each D2D user by optimal power and
allocate channel to the D2D pair, which has the maximum value
of capacity. However, the optimal algorithm has a high
complexity. We further propose a low complexity suboptimal
algorithm, which allocates channel and controls power in
different stages. Simulation results show that the proposed
algorithms effectively improve the capacity of D2D users under
the condition of guaranteeing the QoS of cellular users and the
suboptimal algorithm greatly reduces the complexity compared
with the optimal algorithm. Index Terms—D2D communication, Interference management,
Optimization theory, Resource allocation, Power control
I. INTRODUCTION
Device-to-Device (D2D) Communication [1] is a
promising communication technology, which can satisfy
the increasing data rate demand and provide better
services of users. The definition of D2D communication
underlaying cellular networks is that proximity users can
reuse radio resource to communicate directly without
going through the Base Station (BS) or core network [2].
D2D communication can improve resource reuse rate and
allow more users to access the network for its reuse of
cellular network resource.
Since D2D communication reusing resource will cause
interference to the cellular network, resource allocation of
D2D communication underlaying cellular network has
Manuscript received March 16, 2016; revised July 19, 2016. This work is supported by National Natural Science Foundation of
China (NO. 61571234.) Corresponding author email: [email protected].
doi:10.12720/jcm.11.7.624-631
been deeply studied. In [3], authors consider a system
model including one cellular user and one D2D pair, the
analysis focuses on the optimization total throughput by
resource allocation subject to QoS (Quality of Service) of
the cellular user and maximum transmission power
constraint. In [4], authors propose a criterion based on
distance constraint resource sharing, which can reduce
the interference between users and improve the system
capacity through obtaining the optimal distance between
cellular user and D2D pair that sharing the same resource.
A greedy heuristic algorithm has been proposed in [5] to
solve a Mixed Integer Nonlinear Programming (MINLP)
problem, which converts from the problem of D2D users’
radio resources allocation. And the proposed greedy
heuristic algorithm improves system performance in
terms of cell capacity without causing significance harm
between cellular users and D2D users. In [6] and [7],
combined game theory has been used to allocate
resources. A distributed merge-and-split coalition
algorithm has been proposed in [6], which achieves an
approaching preference in terms of network sum-rate
with the exhaustive search optimal resource allocation
scheme. In [7], authors formulate the resource allocation
problem as a reverse iterative combinatorial auction game.
In [8], authors propose a novel resource allocation
algorithm that D2D users can reuse more than one
resource of cellular users. After that, they discuss the
selection of resource allocation scheme through the
proposed algorithm, and the proposed algorithm can
increase the total system throughput to a large extent. The
above relevant references focus on researching the
resources allocation of users under the conditions of
determined power, while the literatures that optimizing
the transmission power and resource allocation of users
simultaneously are not much. Authors investigate the
joint resource block assignment and transmit power
allocation problem to optimize the network performance
in [9], which establishes the interference graph composed
of D2D communication links and cellular communication
links and proposes resource allocation scheme under the
interference graph. Meanwhile, they optimize the
transmission power of D2D pair, but the transmission
power of the cellular user is a certain value.
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Journal of Communications Vol. 11, No. 7, July 2016
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In this paper, we assume that the radio resource
allocation [10] of cellular users has been completed.
Based on QoS of cellular users and D2D users, a
channel allocation and power control algorithm in D2D
communication underlaying cellular networks is proposed.
Firstly, obtaining candidate cellular users set of D2D user
according to the minimum SINR demand of D2D user.
And then, taking communication quality of cellular users
and D2D users, limited transmit power of cellular user
and D2D user into consideration. We build an optimal
subjective function to maximize the capacity of total D2D
users. The transmit power of D2D users and cellular users
is optimized with Lagrange multiplier method and the
capacity of D2D users is calculated by optimal power.
Meanwhile, we allocate the channel to one D2D pair,
which has the maximum value of capacity. However, the
optimal algorithm has a high complexity. We further
propose a low complexity suboptimal algorithm, which
allocates channel and controls power in different stages.
Simulation results show that the capacity of D2D users is
improved with the proposed algorithms in a certain extent.
And the performance of suboptimal algorithm with low
complexity is close to the optimal algorithm.
The rest of the paper is organized as follows. We
describe the system model of D2D communications
underlaying the cellular networks in Section 2. Then, in
Section 3, the proposed resource allocation algorithm is
investigated. Simulation results are provided and
analyzed in Section 4 to show the performance of
proposed algorithms. Finally, conclusions are drawn in
Section 5.
CUEi
CUEm
CUE2
CUE1
DUE1 Rx
DUE1 Tx
BS
DUEi Tx
DUEi Rx
Fig. 1. System model of D2D communications sharing uplink resources
of cellular users
II. SYSTEM MODEL
We investigate resource allocation for D2D
communication sharing uplink (UL) resource of cellular
networks as in Fig. 1, where M cellular users coexist
with N D2D pairs. We use 1,2, ,C M and
1,2,...,D N to indicate the sets of cellular users and
D2D users. We assume that M cellular users occupy
the K independent orthogonal channels in the cell [11].
D2D pair reuse the channel that assigned to the cellular
users, but D2D pairs can’t reuse the same channel. Each
resource can be occupied by at most one cellular user and
one D2D pair simultaneously. That is to say, there is no
interference between cellular users and no interference
between D2D pairs, the interference only exists in the
cellular user and the D2D pair that sharing the same radio
resource.
On the channel k , we suppose that cellular user i sends
the signal,c ix to the BS, and
,d jx is the transmission
signal between D2D pair j .
So, we can achieve the received signal of BS and D2D
pair j as follows
, , , . , , , 1
c d
c i i k i B c i j k j B d jy p g x p h x n (1)
, , , , , . 2
d c
d j j k j d j i k i j c iy p g x p h x n (2)
where ,
c
i kp and ,
d
j kp are the transmission power of cellular
user i and the D2D pair j that sharing the channel k .
Channel gain consists of the slow fading [12] of
distanced based PathLoss (PL) and the fast fading of
selective Rayleigh Fading. Therefore, the channel gain
between BS and the cellular user i can be written as 2
, , 0i B i Bg d g , where ,i Bd is the distance between
the cellular user i and BS, and are the channel
fading constant and channel fading exponent, respectively.
0g indicates exponential distribution of fast fading gain.
Similarly, the channel gain between the transmitter and
receiver of D2D pair j is jg ,
,j Bh is the channel gain
between the BS and D2D pair j and the channel gain
from cellular user i to the receiver of D2D pair j is ,i jh .
1n and2n are the additive white Gaussian noise for BS
and the receiver of D2D pair, respectively. Without loss
of generality, we assume that all communication links
have the same noise power0N .
The SINR of cellular user i on channel k can be
expressed as
, ,
,
0 , ,
c
i k i Bc
i k d
j k j B
p g
N p h
(3)
The SINR of the receiver of D2D pair j on channel k
can be indicated as
,
,
0 , ,
d
j k jd
j k c
i k i j
p g
N p h
(4)
III. PROBLEM FORMULATION
A. Jonit Optimization Algorithm
In this section, we analyze transmission power of
cellular users, transmission power of D2D users and
channel allocation of D2D users. Taking the minimum
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Journal of Communications Vol. 11, No. 7, July 2016
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QoS demands of cellular users and D2D users, limit
transmission power of each cellular user and total D2D
users into consideration, we establish the following
optimization problems
, , ,
2 , ,, ,
max log 1c di k j k j k
d
j k j kp p k j D
(5)
Subject to:
, max0 ,c c
i kp P i C (6)
, ,c c
i k th i C (7)
, ,d d
j k th j D (8)
, , , 1,2,...,d
j k j k tot
k j D
p P k K
(9)
, ,1, 0,1 , 1,2,...,j k j k
j D
k K
(10)
where ,j k represents the channel occupancy situation of
D2D users, , 1j k represents channel k is occupied by
D2D user j and , 0j k means channel k is not occupied.
max
cP andtotP indicate the maximum transmit power
constraint of each cellular user and total D2D users. c
th and d
th represent the minimum Signal-to-Interference-
plus-Noise-Ratio (SINR) threshold of cellular users and
D2D users, respectively. Formula (5) means maximizing
the capacity of the objective function of D2D users.
Formula (6) indicates limited transmission power of
cellular user. Constraints (7) and (8) represent the QoS
requirements of cellular users and D2D users,
respectively. Constraint (9) represents the limit
transmission power of total D2D users. Formula (10)
ensures that the resource of cellular user can be shared by
at most one D2D pair.
Analyzes (5), the objective function has three unknown
parameters, transmit power of cellular user ,
c
i kp , transmit
power of D2D user ,
d
j kp and channel selection factor,j k .
The optimal problem is a mixed integer programming NP
hard problem [13], which is difficult to solve directly.
Therefore, we obtain the solutions of the power control
and channel assignment problem through the joint
iteration optimization.
B. Solving Joint Optimization Problem
According to the following inequality:
,
2
0 , , 0
d
j k j d
thc
i k i j
p g
N p L h
(11)
the expression (11) is converted from (4) and (8). We can
receive the following inequality
1
2
0
,
max 0
d totth
i j d d
j th
Ph
NLP g N
(12)
where ,i jL indicates the distance between cellular user
and the receiving terminal of D2D pair, D2D pair j reuse
the resource of cellular user, which falls outside the circle
that putting receiving terminal of D2D pair as the center
and putting ,i jL as the radius. Therefore, according to (12),
we can receive the set of reusable channel for D2D user
j and the set can be indicated as
, , , , 1,2,..., ,
1,2,...
j i j i j
j
k d L k i i M j D
j N
(13)
where k represents channel k occupied by cellular user i ,
,i jd means the distance between cellular user i and D2D
pair j , and the constraint (7) can be further translated into
the following expression
, ,
, , 0 0
c
i k i Bd
j k j B c
th
p gp h N
(14)
The Lagrange function of (5) with respect to (9)
,
, , , 2 ,
0 , ,
, ,
, , , log 1
d
j k jc d
i k j k j k j kck j D i k i j
d
j k j k tot
k j D
p gL p p
N p h
p P
(15)
where is the Lagrange multiplier, and Lagrange dual
function can be expressed as
, , ,
, , ,, ,
max , , ,c di k j k j k
c d
i k j k j kp p
k tot
k
G L p p
G P
(16)
where is defined as
, , ,, , : 6 , 10 , 14c d
i k j k j kp p
kG can be expressed as follows
, , ,
,
2 , ,, ,
0 , ,
max log 1c di k j k j k
d
j k j d
k j k j kcp p j D i k i j
p gG p
N p h
(17)
We observe that expression (16) can be decomposed
into M separate problems for a given , and each
problem corresponds to a given channel k , which is (17).
According to (10), for each channel, there is at most one
,j k nonzero for all 1,2,...,k K . Therefore, we
calculate the value of kG through traversal of N
D2D users, and then assign the channel k to the D2D
pair with maximum value of kG .
j
kG is defined as the value of kG with
allocating the channel k to D2D pair j , as this time
, 1j k . Therefore, j
kG can be obtained through the
following problem for a given
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Journal of Communications Vol. 11, No. 7, July 2016
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, ,
,
2 ,,
0 . ,
max log 1c di k j k
d
j k jj d
k j kcp p
i k i j
p gG p
N p h
(18)
Subject to:
, max0 c c
i kp P (19)
, ,
, , 0 0
c
i k i Bd
j k j B c
th
p gp h N
(20)
The variables ,
c
i kp and ,
d
j kp in above problem are
coupled, which can be divided into two aspects of
problem by the decomposition method [14]. In the low
layer problem, for a fixed ,
d
j kp , we can find the objective
function of the problem (18) is a monotone decreasing
function with regard to ,
c
i kp . This shows that the
objective function of the problem (18) can be acquired
maximum value with the minimum value of ,
c
i kp .
Constraints (19) and (20) can be rewritten as a more
compact form
, , 0 , max
,
c
d c cth
j k j B i k
i B
p h N p Pg
(21)
Therefore, the optimal value of ,
c
i kp can be written as
, , , 0
,
c
c dth
i k j k j B
i B
p p h Ng
(22)
In the upper layer problem, putting (22) into the
objective function of problem (18) to simplify the
problem (18)
,
,
2
, , ,
0 ,
, ,
,
max log 1
1
dj k
d
j k jj
k c cpth i j th j B i j d
j k
i B i B
d
j k
p gG
h h hN p
g g
p
(23)
Subject to:
,
d
j kp (24)
where
,
max 0
,
1 i B c
c
j B th
gP N
h
and max ,0 , the constraint (24) can be obtained
from (20). To prove the above problem as a convex
problem [15], we can get the following formula through
seeking the second derivative of (23) j
kG with ,
d
j kp
2,
2 2 2
, , , ,
2 2 djj j j j kk
d d d d
j k j k j j k j k
Ag A B g B B g pd G
d p A Bp g p A Bp
(25)
where we denote A and B as follows
,
0
,
1
c
th i j
i B
hA N
g
(26)
, ,
,
c
th j B i j
i B
h hB
g
(27)
The formula (25) is always less than zero, so j
kG is
a convex function of ,
d
j kp , the optimal solution can be
obtained by convex optimization method.
According to KKT (Karush-Kuhn-Tucker) conditions
[16], we can calculate the first derivative of j
kG with
,
d
j kp and make it to zero
2
,
, , ,, , ,
1 10
ln 2
j i B
ddi B i B j ki B i B j j k
g g A
g A g Bpg A g g B p
(28)
Obtaining the optimal value of ,
d
j kp according to (28)
, 2
,0
22 2
d
j k
i B j j
A Ap
Bg B g B g B
(29)
where [ ] min max( , ),y
x x y and can be written as
the following formula
2 2 2
, , ,
4
ln 2j i B j i B i B jg g A g g A g B g B
(30)
Putting (29) into (22) can obtain the optimal value of
,
c
i kp . j
kG can be translated into the following formula
after acquiring the optimal value of ,
c
i kp and ,
d
j kp
,
2 ,
, , ,
0 ,
, ,
log 1
1
d
j k jj d
k j kc c
th i j th j B i j d
j k
i B i B
p gG p
h h hN p
g g
(31)
We allocate channel k to D2D user with the maximum
value of j
kG through obtaining all of the value
j
kG of D2D users corresponding to channel k
arg max j
kj
j G and , 1j k (32)
It should be noted that on the channel k , for all D2D
users j j ,their values are , 0j k , , 0d
j kp .
Dual function G can be obtained by (16) after
acquiring sum of j
k kG G through traverse all
channels. Finally, we need to get the optimum
according to maximum G , and we use the second
gradient method to obtain the optimal .
Proposition 1: The second gradient of G is
,
d
tot j k
k j
P p .
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Journal of Communications Vol. 11, No. 7, July 2016
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Proposition 1 shows that can be updated according
to the following formula
,1 d
tot j k
k j
t t t P p
(33)
where 0t is a series of step sequence. Reference
[17] shows that as long as t is small enough, the
above iterative update of second gradient can converge to
the optimal value. Some popular selection rules of t
are tt
, t and t
t
, where is a
constant.
Detailed steps of optimal resource allocation algorithm
are summarized as Table I.
TABLE I: OPTIMAL RESOURCE ALLOCATION ALGORITHM
Algorithm Optimal Resource Allocation Algorithm
Input: The set of cellular users C
The set of D2D pairs D
The SINR of cellular user and D2D user c
th and d
th
Output: The optimal transmission power of cellular user and D2D
user ,
c
i kp and,
d
j kp
The resource k reuse indicator for cellular user and D2D
user j ,j k
1. Initialization
2. for all j D and channel resources
from 1k to k K do
3. calculate ,
d
j k
4. if ,
d d
j k th then
5. j j k and j j D
6. end if
7. end for
8. If 0 then
9. for the D2D user has no available channel resource
and the algorithm ends
10. end if
11. Initializes and set 1t
12. while 1t t do
13. for i C and j D
14. for all channels k do
15. calculate,
c
i kp and ,
d
j kp by (222) and (29).
16. calculate j
kG by formula (31) then
17. ,
arg max j
kk j D
j G
and then , 1j k
18. for all j j do
19. set , 0j k , , 0d
j kp
20. end for 21. end for
22. end for
23. update ,( 1) ( ) ( )( )d
tot j k
k j
t t t P p
24. 1t t
25. end while
C. Suboptimal Algorithm
We propose a two-stage suboptimal algorithm to
further reduce the computational complexity of the
proposed optimization algorithm, which has a high
computational complexity for joint optimizing the power
control and channel allocation. The two-stage method of
channel allocation and power control is performed
separately. In the first phase, each channel resource is
allocated to the D2D user, which has the maximum value
of 0 max ,( )c
j i jg N P h . In the second phase, power is
assigned to the above D2D users and cellular users with
the method that is similar to the power control of optimal
algorithm.
Detailed steps of the two-stage algorithm are presented
as Table II.
TABLE II: SUBOPTIMAL ALGORITHM
Algorithm Suboptimal Algorithm
Input: The set of cellular users C
The set of D2D pairs D
The SINR of cellular user and D2D user c
th and d
th
Output: The optimal transmission power of cellular user and
D2D user ,
c
i kp and,
d
j kp
The set of resources sharing between cellular user and
D2D pair S
1. Initialization S and
2. for all j D and channel resources from 1k to k K
do
3. calculate ,
d
j k
4. if ,
d d
j k th then
5. j j k and j j D
6. end if
7. end for
8. for all i C and j D do
9. calculate 0 max ,
j
c
i j
g
N P h
10. ,
0 max ,
arg maxj
ci C j D
i j
gj
N P h
then
11. &j j j jS S k k i k and S S j D
12. end for
13. if 0 then
14. for the D2D user has no available channel resource and
the algorithm ends
15. end if
16. Initializes and set 1t
17. while 1t t do
18. for k S and j D
19. calculate,
c
i kp and ,
d
j kp by (22) and (29).
20. end for
21. update ,( 1) ( ) ( )( )d
tot j k
k j
t t t P p
22. 1t t
23. end while
IV. SIMULATION RESULTS AND ANALYSIS
In this section, we evaluate the preference of the
proposed algorithms. Consider an isolated cellular cell,
where traditional cellular users and D2D users are
distributed randomly within the cell. The cell is a circular
area with the radius R , in which the Base Station locates
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Journal of Communications Vol. 11, No. 7, July 2016
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in the center and each D2D pair has a fixed distance
between the transmitter and the receiver. The list of
detailed simulation parameters is summarized in Table III.
TABLE III: SIMULATION PARAMETERS
Cell radius R (m) 500
Distance between D2D pairs Rd (m) 10,20,30,…,100
Number of CUs M 5,10,15,…,40
Number of D2D pairs N 10
Maximum CU transmit power max
cP (dBm) 24
Maximum D2D total transmit power totP (dBm) 30
Noise power 0N (dBm) -114
Cellular user SINR c
th (dBm) 0
D2D user SINR d
th (dB) 0
Pathloss exponent 4
Pathloss constant 0.01
5 10 15 20 25 30 35 400
100
200
300
400
500
600
700
The number of cellular users
Tota
l C
apacity o
f th
e D
2D
pairs(b
ps/H
z)
Proposed Optimal
Proposed Suboptimal
Algorithm in [8]
Greedy
Random
Fig. 2. D2D total capacity for different number of cellular users.
In Fig. 2, in terms of system capacity performance of
D2D users, we compare five resource allocation
algorithms for the D2D communications underlaying
cellular networks, i.e., the proposed joint optimization
scheme, the proposed suboptimal scheme, algorithm in
[8], a greedy algorithm and a random resource allocation
scheme. Algorithm in [8] calculates the ratio between the
channel gain of cellular users and BS and the channel
gain of D2D pairs, and then the resource is allocated to
D2D pair, which has the maximum value of gain ratio.
And the D2D pair can reuse more channels of different
cellular users. The greedy resource allocation algorithm
allocates some resources to the D2D pair who have
enough higher SNR on the corresponding resources and
the power of the D2D pair on the allocated resources are
fixed. It is seen that the performance of the five resource
allocation algorithms increases with the ascent number of
cellular users. The number of cellular users’ resources
that can be occupied by D2D user increases with the
increasing number of cellular users, and then the capacity
of D2D users also increases. From Fig. 2, it is clearly
shown that the proposed suboptimal resource allocation
scheme can acquire an approaching performance with the
proposed optimal algorithm. Besides, compared with the
algorithm in [8] and the Greedy algorithm, we can see
that the two proposed resource sharing schemes have a
significant performance gain in terms of capacity of D2D
users, which verifies the good performance of the
proposed algorithms.
10 20 30 40 50 60 70 80 90 10050
100
150
200
250
300
350
400
450
500
The distance between D2D pair(m)
Tota
l C
ap
acit
y o
f th
e D
2D
pa
irs(
bps/H
z)
Proposed Optimal
Proposed Suboptimal
Algorithm in [8]
Greedy
Random
Fig. 3. D2D total capacity for different distance between D2D pairs.
Fig. 3 shows D2D total capacity of five different
resource allocation schemes with different distance
between D2D pair. The channel gain of D2D link
decreases with the distance increasing between D2D pair,
which leads to the slight decrease of D2D total capacity.
Therefore, total capacities of D2D users decrease with the
increasing distance between D2D pair. From the Fig. 3,
we can see that the proposed algorithms have much
capacity gain compared with the algorithm in [8], the
Greedy algorithm and the Random resource allocation
algorithm with small distance between D2D pair. When
the distance between D2D pair is more than 90m, the
proposed algorithms have lower capacity gain of D2D
pairs according to the less number of candidates.
5 10 15 20 25 30 350
0.5
1
1.5
2
2.5
3
3.5x 10
4
The number of cellular users
Itera
tion t
imes
Proposed Optimal
Proposed Suboptimal
Fig. 4. Iteration times of proposed optimal and suboptimal for different
number of cellular users.
Fig. 4 demonstrates the computational complexity of
the proposed optimal algorithm and proposed two-stage
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Journal of Communications Vol. 11, No. 7, July 2016
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suboptimal algorithm. It is shown that iteration times of
the proposed suboptimal algorithm is less than the
proposed optimal algorithm. The difference of iteration
times between the optimal algorithm and suboptimal
algorithm becomes greater with the increasing number of
cellular users, which indicates that the computational
complexity of the proposed suboptimal algorithm is much
lower than the optimal algorithm. In summary, compared
with the proposed optimal algorithm, the suboptimal
algorithm can acquire approaching best performance with
lower computational complexity.
V. CONCLUSIONS
In this paper, we have proposed a resource allocation
and power control algorithm, which can obtain the
optimal system capacity of D2D users under the
conditions of QoS of cellular users and D2D users. The
candidate cellular users of each D2D pair can be received
through the SINR requirement of D2D users. We can
obtain optimal transmission power of cellular user, which
is represented by the transmission power of D2D user
through the SINR demand of cellular user. And then the
optimal transmission power of D2D users can be received
by Lagrange multiplier method. The algorithm solves the
resource allocation problem of D2D user and coordinates
the interference between cellular users and D2D users.
We also propose the suboptimal algorithm for the high
computational complexity of the proposed optimal
algorithm. Simulation results show that the proposed
algorithms outperform the algorithm in [8], the greedy
algorithm and the random resource allocation algorithm
in terms of capacity of D2D users. Meanwhile, the
capacity of D2D users of the suboptimal algorithm is
approaching to the optimal algorithm, but the
computational complexity of the proposed suboptimal
algorithm has much lower than the proposed algorithm.
APPENDIX A PROOF OF PROPOSITION 1
Proof: in [16], we know that if
1 2 1 2G G s is found for all 2 0 , so s
is the second gradient of G at 1 . Therefore, we can
get the following inequality
1 1 1k tot
k
G G P
,
2 1 , 1
0 , ,
log 1
d
j k j d
j k totck j D i k i j
p gp P
N p h
,
2 1 , 1
0 , ,
log 1
d
j k j d
j k totck j D i k i j
p gp P
N p h
,
2 1 , 1
0 , ,
log 1
d
j k j d
j k totck j D i k i j
p gp P
N p h
2 , 2 ,
d d
tot j k tot j k
k j D k j D
P p P p
,
2 2 , 2
0 , ,
1 2 ,
log 1
( )
d
j k j d
j k totck j D i k i j
d
tot j k
k j D
p gp P
N p h
P p
2 1 2 ,( ) ( ) d
tot j k
k j D
G P p
,
c
i kp and ,
d
j kp are the optimal solutions according to 1 ,
while ,
c
i kp and ,
d
j kp are the optimal solutions according to
2 , inequality is due to that ,
c
i kp and ,
d
j kp are the optimal
solutions with respect to1 . Thus, Proposition 1 is
proved.
ACKNOWLEDGMENT
This work is supported by National Natural Science
Foundation of China (61571234, 61401225), Jiangsu
Provincial National Science Foundation (BK20140894).
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Bao-Zhou Yu was born in Jiangsu Province, China, in 1991.
He received the B.E. degree in Communication Engineering
from Nantong University, Nantong, in 2014. He is now
pursuing master's degree in the department of Communication
and Information Engineering. He researches on the area of
resource management and power control of D2D
communication underlaying cellular networks
Zhu Qi (corresponding author) was born in Suzhou, Jiangsu,
China, in 1965. She received the M.S. degree in radio
engineering from Nanjing University of Posts and
Telecommunications in 1989. Now she is a professor in the
Department of Telecommunication and Information
Engineering, Nanjing University of Posts and
Telecommunications, Jiangsu, China. Her research interests
focus on technology of next generation communication,
broadband wireless access, OFDM, channel and source coding,
dynamic allocation of radio resources.
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