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Resource Allocation and Power Control Scheme for Cellular Network

Based D2D (Device-to-Device) Communication

1Tae-Sub Kim,

2Suk-Ho Yoon,

3Seungwan Ryu,

4Choong-Ho Cho

1, First AuthorDepartment of Computer and Information Science, Korea University, Korea,[email protected]

2,Department of Computer and Information Science, Korea University, Korea,

[email protected],Department of Information Systems, Chung-Aug University, Korea, [email protected]

*4,Corresponding AuthorDepartment of Computer and Information Science, Korea University, Korea,

[email protected]

Abstract

In this paper, we propose a resource allocation and Tx power control scheme, called resource

allocation and power control (RAPC), in LTE Advanced device-to-device (D2D) network. In the

proposed scheme, the macro base station (mBS) and D2D senders (D2DSs) service macro user

equipments (mUEs) and D2D receivers (D2DRs) use the different frequency bands and Tx powerchosen as D2D links locations in inner and outer zones to reduce interference substantially.

Simulations show the proposed scheme outperforms D2D networks with soft frequency reuse (SFR)

systems in terms of the signal to interference and noise ratio (SINR) and system throughput for mUEs

and D2DRs.

Keywords: LTE-Advanced, Interference Mitigation, Device-to-Device Communication, ResourceAllocation, Power Control

1. Introduction

Recently, the amounts of traffic to be treated by cellular networks have increased as mobile

multimedia services have become popular. In particular, the macro base station (mBS) handles more

traffic than in the past years because of the fast-growing needs of high data rate services. However, theradio resources in cellular networks are limited and the installation cost of mBS is high. In [1] it has

been proposed to handle the local peer-to-peer traffic in a reliable, scalable, and cost-efficient mannerby enabling direct device-to-device (D2D) communication as an underlay to the IMT Advanced

cellular network.

D2D communication is the technology enabling mUEs to directly communicate with each other

without the help of mBS. D2D communication can offload the traffic handled by mBS and reduce end-to-end transmission delay since end users are able to directly exchange data without the intervention of

mBS. However, D2D links may generate high interference to mUEs located in their communication

areas if they use the same spectrum with the mUEs for data transmission [2][3].

As shown in Figure 1, we initially conducted an experiment in order to examine the interferenceeffect between D2D communication and cellular system. The experiment environment was set as a

single-cell, and the experiment was conducted in the 200 D2D links environment with 20W for mBS'

Tx power, and 6.3mW and 251mW for D2DS's Tx power. Experiment results showed that the signal tointerference and noise ratio (SINR) value received by mUE decreased and that mUE of the cell edge

region receives almost no service. (outage ratio, below -6dB, [4])

To solve this problem, research on reducing interference between D2DRs and mUEs in cellularnetwork supporting D2D communication was conducted. When earlier studies are examined, in [2],

they suggested the technique of using D2D links' channels first if frequency bands were not already

being utilized in the mBS, and observing the D2DRs' channel status if all frequency bands are used and

getting assigned the best channel from mBS. Also, in [5], the technique of measuring one's ownchannel gain and the channel gain till mUE that uses an applicable channel, and assigns the lowest

gaining channel to the D2D terminal, was suggested, but such studies focus on the cell center

interference control and do not improve the performance of mUEs for the cell edge. Also, they are not

designed to respond to strong signals that are received from the cell center for D2DRs. Lastly, in [6],

Resource Allocation and Power Control Scheme for Cellular Network Based D2D (Device-to-Device) Communication

Tae-Sub Kim, Suk-Ho Yoon, Seungwan Ryu, Choong-Ho Cho

Journal of Convergence Information Technology(JCIT)

Volume8, Number7,April 2013

doi:10.4156/jcit.vol8.issue7.7

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resource allocation that considers the interference and power optimization technique was studied.

However, in this case, there was a high possibility of heavy collisions occurring between the two linksby due to random allocation of frequency resources regardless of the cellular link and D2D link.

mBS

D2D linkmUE

INTERFERENCE

500m

0 100 200 300 400 500-40

-20

0

20

40

60

X is SINR value less th an -6dB

Received SINR of mUE(mBS pow er 15W)

mUE locations form mB S of a given cel l (m)

Avg.S

INR

(dB)

w/oD2D

wD2D(#50/6.3mW)

wD2D(#200/6.3mW)

wD2D(#50/251mW)

wD2D(#200/251mW)

Figure 1. Received SINR of mUE

Therefore, we can consider the resource allocation and power control methods that reduce the

interference of the cellular link and D2D link by using the frequency reuse scheme, so that the

performance at the cell-edge of cellular links can be improved and the D2D link can respond to astrong signal at the cell center.

(a) FRF1 (b) Reuse3

(d) SFR(c) FFR

F3

F2

F1

power

Frequency

F3

F2

F1

power

Frequency

F3

F2

F1

power

Frequency

InnerOuter

F3

F2

F1

power

Frequency

F2

F1

F3

F2

F1

F3

F2

F1

F3

F2

F1

F3

Figure 2. Reuse 1 and other static partition based schemes (Omni-antenna)

As shown in Figure 2, several schemes of inter-cell interference mitigation are being considered in

OFDMA networks, such as fractional frequency reuse (FFR) [7] and soft frequency reuse (SFR) [8].Partial reuse adopts different reuse factors for the cell center and cell edge. Thus, partial reuse schemes

can achieve a much higher network capacity compared to traditional frequency reuse schemes and can

simultaneously reduce inter-cell interference compared to a frequency reuse factor (FRF) of 1.However, since the cell edges use a higher reuse factor, the cell edge spectral efficiency may be

significantly degraded compared to the cell center.

In this paper, we propose a resource allocation and Tx power control scheme, called resourceallocation and power control (RAPC), in LTE Advanced D2D network. Simulations show the proposed



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scheme outperforms D2D networks with soft frequency reuse (SFR) [8] systems in terms of the signal

to interference and noise ratio (SINR) and system throughput for mUEs and D2DRs.

6

7

2

1

5

4

3

site1

site3site2

Inner zone

Outer zone

mBS D2D link

mUE

mBS1

D2D Communication

Sender

(D2DS)Receiver

(D2DR)

Figure 3.System topology

2. System Model

2.1. System Topology and Path Loss Model

As shown in Figure 3, we consider a system topology with 7 hexagonal macrocells and the inter-site

distance is D in meter (m) to analyze the performance. We assume that each mBS is located at thecenter of each macrocell and has cell identification (ID). For example, an mBS with cell ID = i is

described as mBS. mUEs and D2DSs are randomly deployed in the macrocell coverage and stationary.In each cell, D2DSs are distributed in grid pattern with distance of 50m in each cell, and D2DRs are

apart from their corresponding D2DSs with distance q, where q is uniform random variable in [1 20] m.

The target cell is the center macrocell, mBS, and interfering neighbor mBSs to mUEs and D2DSs ineach cell site of mBS.

We consider a path loss model for mUE and D2DR [9] [10], PL,is the link between the mBS

and the m-th mUE, mUE,, in the coverage of mBSand PL,,is the link between the j-th D2DS

and the h-th D2DR, D2DR,,, in the j-th D2DS coverage of mBS, as shown in (1) and (2).

The path-loss is modeled according to micro-urban models ITU-R report [11]. We apply different

path-loss models to D2DRs and mUEs as given in Eqs. (1) and (2). The path-losses of the micro-urban

models for D2DRs (PL,,)and mUEs (PL,)are expressed as

, ,2 10 1040log [ ] 30log [ ] 49

i j hD DR cPL d km f MHz

(1)

, 10 1036.7log [ ] 40.9 26log ( [ ] / 5)

i mmUE cPL d m f GHz

(2)

Where d represents distance between a sender and a receiver, and fmeans carrier frequency of thesystem. The azimuth antenna pattern, G,, between the mBSand mUE,is as shown in (3).

,

3

min 12 , , 180 180i mdB

G G

(3)

where, G= 4dBiis the maximum antenna gain, = 70is the 3dB bandwidth, and = 20dBis

the maximum attenuation.

2.2. Physical Frame Structure and Signal to Interference and Noise Ratio (SINR) Model



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The physical frame structure in our D2D network is orthogonal frequency division multiple access(OFDMA)-frequency division duplex (FDD). The length of each frame is 10ms and a frame consists of

10 sub-frames. Also, each sub-frame has two slots (a slot is 0.5ms) and each sub channel per slot is the

unit of resource block (RB) [12] but we name a sub-channel per symbols RB is this paper. Thenumbers of sub-channels and symbols are S and Z, respectively.

The SINR model is defined as the ratio of a signal power to the interference power for the b-th RB

in the a-th sub-channel, RB,. We assume that X mBSs are placed in a given area and Y D2DSs are

deployed in each macrocells coverage. Also, L mUEs are serviced by each mBS and F D2DRs are

serviced by each D2DS.

Under these assumptions, let R,

,and R

,,

,be strengths of received signal for the b-th RB

(1 b Z) in the a-th sub-channel (1 a S) from the i-th mBS (1 i X) to the m-th mUE(1 m L) in the i-th macrocell coverage and from the j-th D2DS (1 j Y) to the h-th D2DR(1 h F)in the j-th D2DS coverage in the i-th macrocell coverage, respectively. The SINR of the

mUE, for the RB, , ,,

, can be expressed as (4). N is the white noise power. I,,

and

I,,

, are the strengths of interfering signal from the x-th mBS and from the y-th D2DS in the x-th

macrocell coverage to the mUE,for the RB,. ,and ,which are binary values are 1 else 0 ifmBS is in the group of interfering neighbor mBSs for the m-th mUE and the RB, is used by the

neighbor mBSs or D2DSs, respectively. The SINR of the D2DR,,for the RB,,,,,

, can be

expressed as (5).

,

,,

,

, ,

, , ,0 , , 2 ,

1, 1 1

a b

i ma b

i m

a b a b

x m x y m

RB

mBSRB

mUE X X YRB RB

mBS x m a b D DS a b

x x i x y

R

N I I

(4)

,

, ,,

, ,

, ,

, , ,

2

2

0 , 2 ,

11 1

1,

a b

i j ha b

i j h

a b a b

x h x y h

RB

D DSRBD DR X X Y

RB RB

mBS a b D DS a byx x

x y j

R

N I I

(5)

3. Proposed Resource Allocation and Power Control Scheme

As shown in Figure 4, D2DSs allocate randomly RBs in DL subframe (RBand RB) forD2DRs in conventional D2DS networks with SFR system. Thus, D2DSs cause substantial interference

for mUEs in the outer zone and D2DRs in the inner zone are affected by substantial interference from

the mBS.

In the proposed scheme, mBSs and D2DSs service mUEs and D2DRs using different RBs inRB to reduce strong interference of outer zone, as shown in Figure 5 D2DSs in the outer zoneservice their D2DRs using RBs in RB, except the same sub-channel group for mUEs in the samesite, because D2DRs in the outer zone are affected by substantial interference from the mBS. In

addition mBSs and D2DSss powers are controlled. We increase powers of mBS and D2DS for mUE

and D2DR in the outer zone, and increase D2Ds power for D2D resource used in inner zone and mUEresource used outer zone which has interference.



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,

, ,, , 2

1 1

( ) log (1 )s zi m i m

S ZRB

mUE s z s z mUE

s z

T RB

(6)

,

, , , ,2 , , 2 2

1 1( ) log (1 )

s z

i j h i j h

S ZRB

D DR s z s z D DR

s zT RB

(7)Where, , is a binary value and , = 1 else ,= 0 if the , is used by the , and

2,,. The system throughputs for mBS and all D2DS, ,and ,, in the i-th macrocell are

calculated by (8) and (9).

,,

1i l

L

mBS i mUE

l

T T

(8)

, ,2 , 2

1 1i y f

Y F

D DS i D DR

y f

T T

(9)

4. Performance Evaluation

We investigated the DL performance of the proposed frequency planning and power management

scheme in terms of the system throughput and outage probability of mUEs and D2DRs for D2D

networks using a Monte Carlo simulation. We performed 30,000 independent simulations andevaluated system performance according to the number of D2DSs in the analysis. The values of X, S, Z,

Y, L, and F are 7, 5, 10, 200(dense distribution), 30, and 1, respectively. We assume that the mBS and

D2DSs allocate only one RB for each mUE and D2DR, respectively. The mBS does not allocate the

same RBs to mUEs in the same cell but D2DSs allocate randomly an RB in allocated channel groups

for each D2DR. Log-normal shadow fading is considered with zero mean and standard deviations of

8dB for the link between the mBS and mUEs, and 9dB for the link between the D2DS and D2DRs but

multi-path fading is not considered. Table 1 gives the key parameters.

Table 1.System parameters

Parameter Value

Carrier Frequency 2GHz

Bandwidth for DL 10MHz

D 866m / 500m(radius)

D 300m

mBS Tx power ()Inner zone 41.76dBm(15W)

Outer zone 43.42dBm(22W)

D2DS Tx power ()High Power 24dBm(251mW)

Low Power 10, 15, 20dBm (10,32,100mW)

Noise power density (N) -174dBm/Hz

Figure 6 illustrates SINR CDF of mUEs. As shown in Figure 6, the SINR of mUEs in networkwithout D2D network is higher than the others because the mUEs are not interfered by D2DSs. In the

network supporting D2D communication, SINR of mUEs is degraded due to interference from D2D

communication. The mUEs in the proposed scheme achieve higher SINR than those in SFR scheme.

This is because mUEs in cell outer region use different radio resource, and increase mBSs power for

mUEs in outer zone.Figure 7 shows the SINR CDF of the D2DRs. SINR of D2DRs in the proposed scheme is higher

than the other scheme. This is because two reasons as follows. First, D2DSs in cell outer region use

different radio resource. Second, BSs and D2DSss powers are controlled. We increase powers of mBS



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and D2DS for mUE and D2DR in the outer zone, and increase D2Ds power for D2D resource used in

inner zone and mUE resource used outer zone which has interference.Figure 8 shows the system throughput using other D2D power. RAPC schemes performance in

outer zone (edge) is higher than SFR schemes when increase D2DSs power. This is because we

allocate to mUE and D2D different radio frequency in outer zone, and we control each power. Theresults of the proposed scheme with mUEs in outer zone are approximately increased by 5%, 6%, and

11% compared to those of the SFR system when the Pare 10, 15, and 20dBm, respectively.Figure 9 describes the results of C,that increase linearly, as the Pincreases. RAPC scheme

has approximately same performance in outer zone than SFR scheme. The results of the proposedscheme with D2DSs in outer zone are approximately increased by 24%, 9% compared to those of the

SFR system when Pare 10, 15dBm, respectively.

-40 -20 0 20 40 600

0.2

0.4

0.6

0.8

1

SINR (dB)

CDF

w/oD2D

SFR(10dBm)

SFR(15dBm)

SFR(20dBm)

RAPC(10dBm)

RAPC(15dBm)

RAPC(20dBm)

10 12 14

0.52

0.53

0.54

0.55

0.56

0.57

Figure 6. Outage probability for mUEs.

-40 -20 0 20 40 600

0.2

0.4

0.6

0.8

1

SINR (dB)

CDF

SFR(10dBm)

SFR(15dBm)

SFR(20dBm)

RAPC(10dBm)

RAPC(15dBm)

RAPC(20dBm)

30 35 40

0.58

0.6

0.62

0.64

0.66

0.68

Figure 7. Outage probability for D2DRs.

Figure 8. System throughput for mUEs. Figure 9. System throughput for D2DRs.

5. Conclusion

In this paper, we proposed a novel resource allocation and Tx power control scheme to enhance the

DL system performance for D2D networks. In the proposed scheme, the mBS and D2DSs service

mUEs and D2DRs in the inner and outer zones in different frequency bands and Tx power, to reducesubstantial interference. Simulations showed the proposed scheme outperforms D2D networks with

SFR systems in terms of system throughput and SINR for mUEs and D2DRs. We know that Pisone of the key parameters for D2D networks. Thus, we plan to study the improved resource allocation

scheme considering Tx power control of D2DSs to enhance system performance in future work.

w/oD2D SFR(10) SFR(15) SFR(20) RAPC(10) RAPC(15) RAPC(20)0

5

10

15

20

25

30

Throughput(Mbps)formUEs

Edge

Center

SFR( 10 ) SFR( 15 ) SFR( 20) RA PC (10 ) RA PC (1 5) RA PC (2 0)0

50

100

150

200

250

300

350

400

450

Throughput(Mbps)forD2DRs

Edge

Center



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6. Acknowledgement

This research was supported by Basic Science Research Program through the National Research

Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010-

0025125)

7. References

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[2] K. Doppler, M. P. Rinne, C. Wijting, C. Ribeiro, and K. Hugl, "Device-to-Device Communication

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[3] G. Fodor, E. Dahlman, G. Muldh, S. Parkvall, N. Reider, G. Miklo and Z. Turanyi, DesignAspects of Network Assisted Device-to-Device Communications, IEEE Communication

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[5] P. Janis, V. Koivunen, C. Ribeiro, J. Korhonen, K. Doppler and K. Hugl, "Interference-Aware

Resource Allocation for Device-to-Device Radio Underlaying Cellular Networks," in Proc.IEEEVehicular Technology Conference (VTC), pp. 1-5, Apr. 2009.

[6] O. Tirkkonen, K. Doppler, and C. Ribeiro, Power Optimization of device-to-device

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[7] G. Boudreau, J. Panicker, N. Guo, R. Chang, N. Wang, and S. Vrzic, Interference coordination

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Apr. 2009.[8] 3GPP; Huawei, Soft frequency reuse scheme for UTRAN LTE, R1-050507, May 2005.

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[12]3GPP TS 36.211 v10.0.0, Evolved universal terrestrial radio access (E-UTRA); Physicalchannels and modulation, Jan. 2011.

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[14]Zhenglei Huang, Zhimin Zeng, Hailun Xia, "Improving Energy Efficiency of Two-tier OFDMA

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