On the Performance of Interference Cancellation in D2D...

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1 On the Performance of Interference Cancellation in D2D-enabled Cellular Networks Chuan Ma, Weijie Wu, Ying Cui, Xinbing Wang Abstract—Device-to-device (D2D) communication underlaying cellular networks is a promising technology to improve network resource utilization. In D2D-enabled cellular networks, the inter- ference among spectrum-sharing links is more severer than that in traditional cellular networks, which motivates the adoption of interference cancellation (IC) techniques at the receivers. However, to date, how IC can affect the performance of D2D- enabled cellular networks is still unknown. In this paper, we present an analytical framework for studying the performance of two IC methods, unconditional interference cancellation (UIC) and successive interference cancellation (SIC), in large-scale D2D-enabled cellular networks using the tools from stochastic geometry. To facilitate the interference analysis, we propose the approach of stochastic equivalence of the interference, which converts the two-tier interference (interference from the cellular tier and D2D tier) to an equivalent single-tier interference. Based on the proposed stochastic equivalence models, we derive the general expressions for the successful transmission probabilities of both cellular uplinks and D2D links in the networks where UIC and SIC are respectively applied. We demonstrate how these IC methods affect the network performance by both analytical and numerical results. Index Terms—D2D communication, cellular network, interfer- ence cancellation, stochastic equivalence, stochastic geometry. I. I NTRODUCTION Recently, there has been a rapid increase in the demand of local area services and proximity services (ProSe) among the highly-capable user equipments (UEs) in cellular networks. In this context, a new technology called device-to-device (D2D) communication, which enables direct communication between UEs that are in proximity, has been proposed and has strongly appealed to both academia [2], [3] and industry [4], [5]. The integration of D2D communication to cellular networks holds the promise of many types of advantages [3]: allowing for high-rate low-delay low-power transmission for proximity ser- vices, increasing frequency reuse factor and network capacity, facilitating new types of peer-to-peer services, etc. However, the introduction of D2D communication also brings a number of technical challenges, such as peer de- vice discovery, mode selection and interference management. Interference management is a major issue in D2D-enabled cellular networks, since D2D links share the same spectrum resource with regular cellular links and the interference among the spectrum-sharing links severely hampers the performance of the network. To guarantee reliable communications in The authors are with the School of Electronic Info. & Electrical Eng., Shanghai Jiao Tong University, China, e-mail: {oknewkimi, weijiewu, cuiying, xwang8}@sjtu.edu.cn. Part of this paper is accepted by 2015 IEEE Conference on Computer Communications (INFOCOM 2015) [1]. D2D-enabled cellular networks, extensive research has been undertaken on the design of effective interference manage- ment schemes. Most proposed schemes can be classified into three categories: (1) Interference avoidance: orthogonal time-frequency resource allocation schemes are adopted to avoid interference between D2D and cellular links [6]; (2) Interference coordination: intelligent power control and link scheduling schemes are employed to mitigate the interference between D2D and cellular links [7]–[9]; and (3) Interference cancellation: advanced signal processing techniques are ap- plied at cellular and/or D2D links to cancel interfering signals [10], [11]. In this paper, we focus on the topic of interference cancellation in D2D-enabled cellular networks. Interference cancellation (IC) is regarded as a promising technique to reduce interference and improve network ca- pacity. In interference cancellation techniques, the interfering signals can be regenerated and subsequently canceled from the desired signal [12]. In this paper, we focus on the performance of two interference cancellation methods. One is unconditional interference cancellation (UIC), which is a simplified IC method with the assumption that the interference from the strong interferers whose received powers are greater than a certain threshold can be completely (unconditionally) canceled. The other is successive interference cancellation (SIC), which is one of the best known IC techniques. The key advantage of SIC compared to other IC techniques is that the SIC receiver is architecturally similar to traditional non-SIC receivers in terms of hardware complexity and cost [13], as it uses the same decoder to decode the composite signal at different stages and neither complicated decoders nor multiple antennas are required. It is also known that SIC can achieve the Shannon capacity region boundaries for both the broadcast and multiple access networks. As such, SIC has been widely studied and recently implemented in commercial wireless systems such as IEEE 802.15.4. A. Contributions and Organization To date, most analytical results on IC are for ad hoc and cellular networks. It is still unknown how IC can improve the performance of large-scale D2D-enabled cellular networks, in which the interference among spectrum-sharing links is more severer than that in traditional ad hoc and cellular networks. In this paper, we present an analytical framework via stochastic geometry to quantify the benefit of IC in large-scale D2D- enabled cellular networks. The main contributions of this paper are summarized as follows. (1) We first provide an analytical framework to model a large-scale D2D-enabled cellular network without IC capa-

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On the Performance of Interference Cancellation inD2D-enabled Cellular Networks

Chuan Ma, Weijie Wu, Ying Cui, Xinbing Wang

Abstract—Device-to-device (D2D) communication underlayingcellular networks is a promising technology to improve networkresource utilization. In D2D-enabled cellular networks, the inter-ference among spectrum-sharing links is more severer than thatin traditional cellular networks, which motivates the adoptionof interference cancellation (IC) techniques at the receivers.However, to date, how IC can affect the performance of D2D-enabled cellular networks is still unknown. In this paper, wepresent an analytical framework for studying the performanceof two IC methods, unconditional interference cancellation (UIC)and successive interference cancellation (SIC), in large-scaleD2D-enabled cellular networks using the tools from stochasticgeometry. To facilitate the interference analysis, we propose theapproach of stochastic equivalence of the interference, whichconverts the two-tier interference (interference from the cellulartier and D2D tier) to an equivalent single-tier interference. Basedon the proposed stochastic equivalence models, we derive thegeneral expressions for the successful transmission probabilitiesof both cellular uplinks and D2D links in the networks whereUIC and SIC are respectively applied. We demonstrate how theseIC methods affect the network performance by both analyticaland numerical results.

Index Terms—D2D communication, cellular network, interfer-ence cancellation, stochastic equivalence, stochastic geometry.

I. INTRODUCTION

Recently, there has been a rapid increase in the demand oflocal area services and proximity services (ProSe) among thehighly-capable user equipments (UEs) in cellular networks. Inthis context, a new technology called device-to-device (D2D)communication, which enables direct communication betweenUEs that are in proximity, has been proposed and has stronglyappealed to both academia [2], [3] and industry [4], [5]. Theintegration of D2D communication to cellular networks holdsthe promise of many types of advantages [3]: allowing forhigh-rate low-delay low-power transmission for proximity ser-vices, increasing frequency reuse factor and network capacity,facilitating new types of peer-to-peer services, etc.

However, the introduction of D2D communication alsobrings a number of technical challenges, such as peer de-vice discovery, mode selection and interference management.Interference management is a major issue in D2D-enabledcellular networks, since D2D links share the same spectrumresource with regular cellular links and the interference amongthe spectrum-sharing links severely hampers the performanceof the network. To guarantee reliable communications in

The authors are with the School of Electronic Info. & Electrical Eng.,Shanghai Jiao Tong University, China, e-mail: {oknewkimi, weijiewu, cuiying,xwang8}@sjtu.edu.cn.

Part of this paper is accepted by 2015 IEEE Conference on ComputerCommunications (INFOCOM 2015) [1].

D2D-enabled cellular networks, extensive research has beenundertaken on the design of effective interference manage-ment schemes. Most proposed schemes can be classifiedinto three categories: (1) Interference avoidance: orthogonaltime-frequency resource allocation schemes are adopted toavoid interference between D2D and cellular links [6]; (2)Interference coordination: intelligent power control and linkscheduling schemes are employed to mitigate the interferencebetween D2D and cellular links [7]–[9]; and (3) Interferencecancellation: advanced signal processing techniques are ap-plied at cellular and/or D2D links to cancel interfering signals[10], [11]. In this paper, we focus on the topic of interferencecancellation in D2D-enabled cellular networks.

Interference cancellation (IC) is regarded as a promisingtechnique to reduce interference and improve network ca-pacity. In interference cancellation techniques, the interferingsignals can be regenerated and subsequently canceled fromthe desired signal [12]. In this paper, we focus on theperformance of two interference cancellation methods. Oneis unconditional interference cancellation (UIC), which is asimplified IC method with the assumption that the interferencefrom the strong interferers whose received powers are greaterthan a certain threshold can be completely (unconditionally)canceled. The other is successive interference cancellation(SIC), which is one of the best known IC techniques. Thekey advantage of SIC compared to other IC techniques isthat the SIC receiver is architecturally similar to traditionalnon-SIC receivers in terms of hardware complexity and cost[13], as it uses the same decoder to decode the compositesignal at different stages and neither complicated decodersnor multiple antennas are required. It is also known that SICcan achieve the Shannon capacity region boundaries for boththe broadcast and multiple access networks. As such, SIC hasbeen widely studied and recently implemented in commercialwireless systems such as IEEE 802.15.4.

A. Contributions and OrganizationTo date, most analytical results on IC are for ad hoc and

cellular networks. It is still unknown how IC can improve theperformance of large-scale D2D-enabled cellular networks, inwhich the interference among spectrum-sharing links is moreseverer than that in traditional ad hoc and cellular networks. Inthis paper, we present an analytical framework via stochasticgeometry to quantify the benefit of IC in large-scale D2D-enabled cellular networks. The main contributions of this paperare summarized as follows.

(1) We first provide an analytical framework to model alarge-scale D2D-enabled cellular network without IC capa-

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bilities, and derive the general expressions for the successfultransmission probabilities of cellular uplinks and D2D links.The derived results are the baseline for evaluating the perfor-mances of IC methods.

(2) To simplify the interference analysis in the network, wepropose the approach of stochastic equivalence of the interfer-ence. By this approach, the two-tier interference (interferencefrom the cellular tier and D2D tier) can be represented byan equivalent single-tier interference that maintains the samestochastic characteristics as the two-tier interference.

(3) Based on the stochastic equivalence models, we derivethe general expressions for the successful transmission prob-abilities of cellular uplinks and D2D links in the networkswhere UIC and SIC are respectively applied. We demonstratethe effect of these two IC methods by both analytical andnumerical results.

The rest of this paper is organized as follows. Section IIdescribes the system model. Sections III analyze the networkperformance without IC capabilities and propose the approachof stochastic equivalence of the interference. Section IV and Vrespectively analyze the network performances with UIC andSIC capabilities and present the numerical results. Section VIconcludes the paper. A summary of the notations used in thispaper is given in Table I.

B. Related Work

Interference cancellation for wireless networks. Very re-cently, there is a growing interest to exploit IC, especially SIC,at the physical layer to improve network performances at upperlayers. In [10], Min et al. designed an interference cancellationscheme that exploits a retransmission of the interference fromthe base station to reduce the outage probability. In [14], Gelalet al. proposed a topology control framework for exploiting thebenefits of multi-packet reception using IC. In [15], Jiang et al.combines interference cancellation and interference avoidanceto improve the throughput of a multi-hop network. In [16], Xuet al. developed a decentralized power allocation scheme toachieve the maximum throughput for random access systemswith SIC receivers. In [17], Lv et al. presented optimal linkscheduling schemes for ad hoc networks with SIC capabilities.In [18], Mollanoori and Ghaderi derived the optimal decodingorder of the concurrent transmissions in networks supportingSIC. These works do not take into account the spatial distri-bution of users and the results apply to fixed networks (or asnapshot of networks). However, in this paper, we consider astochastic network and analyze the IC performance in such anetwork using tools from stochastic geometry.

Stochastic geometry for wireless networks. As a mathemat-ical tool to study random spatial patterns, stochastic geometrycan be used to model and analyze the interference, connectivityand coverage in large-scale wireless networks [19]. Most ofthe literature in the area of modeling networks via stochasticgeometry focus on ad hoc [20], [21] and cellular [22], [23]networks. Recently, stochastic geometry has also been em-ployed to model D2D-enabled cellular networks [24]–[26]. In[24]–[26], the cellular and D2D networks were modeled byindependent PPPs, and their SINR distributions were derived

Table I: Notations used in the paper

Notation DescriptionΦc Poisson point process of cellular users (density λc)Φd Poisson point process of D2D transmitters (density λd)

Φeqc−intf

Equivalent Poisson point process ofthe interferers for cellular links (density λeq

c−intf )

Φeqd−intf

Equivalent Poisson point process ofthe interference for D2D links (density λeq

d−intf )Pc Transmission power of cellular usersPd Transmission power of D2D usersα Path loss exponent

(δ = 2

α

)T SIR threshold for successful transmissionpc Successful transmission prob. of cellular links without ICpd Successful transmission prob. of D2D links without ICpUICc Successful transmission prob. of cellular links with UICpUICd Successful transmission prob. of D2D links with UIC

pSICc , pN−SIC

cSuccessful transmission prob. of cellular links

with infinite and (finite) N -level SIC

pSICd , pM−SIC

d

Successful transmission prob. of D2D linkswith infinite and (finite) M -level SIC

without considering interference cancellation techniques. Thestochastic geometry-based analysis of IC has been presented inliterature [27]–[31]. In [27], [28], simplified IC models weregiven by assuming that all signals from transmitters withina specific radius can all be completely canceled. Exact SICmodels were investigated for ad hoc network in [29], [30] andfor cellular networks in [31]. Different from [27]–[31], in thispaper, we focus on the analysis of the effect of IC for D2D-enabled cellular networks. Since the stochastic characteristicsof heterogeneous networks (comprising D2D users and cellularusers) are much more complex than those of homogeneousnetworks (comprising only ad hoc users or cellular users), theanalysis of IC performance in this paper is more challengingthan that in [27]–[31].

II. SYSTEM MODEL

In this section, we elaborate on the network model anddescribe the IC methods.

A. Network Model

We consider a spectrum-sharing D2D-enabled cellular net-work consisting of both cellular users and D2D users over alarge two-dimensional space, and focus on the uplink trans-mission for cellular users. The cellular users are assumedto be spatially distributed as a homogene [16]ous Poissonpoint process (PPP) Φc with density λc, and an independentcollection of base stations (BSs) is assumed to be locatedaccording to some independent stationary point process Φb.We assume that each cellular user is associated with its nearestbase station, and each base station has only one active uplinkcellular user scheduled. Under such assumptions, each basestation can be considered to be uniformly distributed in theVoronoi cell of its associated cellular user, as shown in Fig.1.It is noted that the orthogonal scheduling policy leads tocoupling between the locations of cellular users and thoseof base stations. Nevertheless, it has been shown that thedependence introduced by coupling has negligible effects onthe performance analysis [23], [31]. Therefore, for analytical

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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Base station

Cellular user

D2D user

Figure 1: Network model.

tractability, we assume that the point processes of cellular usersand base stations are independent.

The D2D transmitters in the network are assumed to bedistributed according to a homogeneous PPP Φd with densityλd. For a given D2D transmitter, its associated receiver isassumed to be located at a distance l away with isotropicdirection, where l is Rayleigh distributed:

fl (l) = 2πλdle−πλdl2 . (1)

This Rayleigh distribution assumption is of practical interestand is employed in many works [24]–[26]. Other distributionsof l can be easily incorporated into the framework.

The transmission powers are assumed to be Pc at uplinkcellular users and Pd at D2D transmitters respectively. Weadopt a unified channel model that comprises standard pathloss and Rayleigh fading for both cellular and D2D links:given transmission power P of the transmitter located at xi, thereceived power at the receiver located at xj can be expressedas Ph ‖xi − xj‖−α, where h is the fading factor followingan exponential distribution with unit mean, i.e., h ∼ exp (1),and α > 2 is the path loss exponent. In this paper we use δ todenote 2

α for brevity of expressions. As interference dominatesnoise in most modern cellular networks, we consider thenetwork to be interference-limited.

B. IC Methods

In this paper, we focus on the performance of two ICmethods, unconditional interference cancellation (UIC) andsuccessive interference cancellation (SIC).

Unconditional interference cancellation (UIC) is simpli-fied interference cancellation method with the assumption thatthe interference from the strong interferers whose receivedpowers are greater than a certain threshold can be completely(unconditionally) canceled [28]. UIC does not refer to aspecific IC technique, but rather uses a cancellation-power-threshold based approximation to model the effect of ICtechniques. This model allows for analytical tractability andprovides a general insights on IC performance.

Decode strongest

interfering signal

Regenerate

strongest

interfering signal

Decode k-th

strongest

interfering signal

Regenerate k-th

strongest

interfering signal

+

+

-

-

Received

composite

signal

Decode desired

signal Desired signal

Figure 2: Schematic diagram of SIC process.

Successive interference cancellation (SIC) is a promis-ing interference cancellation technique that has been widelystudied for wireless networks. The basic concept of SIC is toregenerate the interfering signals and subsequently cancel themfrom the received composite signal to improve the signal-to-interference ratio (SIR) of the desired signal. Specifically, theSIC receiver first decodes the strongest interfering signal bytreating other signals as noise. Then it regenerates the analogsignal from the decoded signal and cancels it from the receivedsignal. After this stage, the remaining signal is free from theinterference of the strongest interfering signal. Then, the SICreceiver proceeds to decode, regenerate and cancel the secondstrongest interfering signaling from the remaining signal andso forth, until the desired signal can be decoded. The schematicdiagram of SIC process is shown in Fig.2.

In the following part of this paper, we first analyze theperformance of the network without IC capabilities as baselineresults, and then study how UIC and SIC affect the networkperformance.

III. NETWORK PERFORMANCE WITHOUT ICIn this section, we consider the scenario that neither the

cellular receivers (BSs) nor the D2D receivers have IC ca-pabilities, and derive the successful transmission probabilitiesof both cellular and D2D links. We also propose a stochasticequivalence model of the interference in the network, whichis essential for analyzing the performance of IC techniques inlater sections.

A. Successful Transmission Probability of Cellular Links

Without loss of generality, we conduct the analysis on atypical cellular link that comprises a typical BS located atthe origin and its associated cellular user located at a randomdistance r away. Under the nearest-BS association policy, therandom variable r can be shown to be Rayleigh distributedand its probability density function (pdf) follows [23]:

fr (r) = 2πλcre−πλcr2

. (2)

Denote the fading factor of the typical cellular link by g0,which is i.i.d exponential with g0 ∼ exp (1). Then, the received

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SIR of the typical cellular link, i.e., the received SIR at thetypical BS, can be expressed as

SIRc =Pcg0r

−α

Ic, (3)

where

Ic =∑

xi∈Φc\{x0}

Pcgi ‖xi‖−α +∑yi∈Φd

Pdhi ‖yi‖−α (4)

is the cumulative interference from all other cellular users(except the typical cellular user x0) that are located at xi withfading factor gi and D2D transmitters that are located at yiwith fading factor hi1.

The successful transmission probability of cellular links canbe defined as

pc4= P [SIRc > T ] , (5)

where T is the SIR threshold. The expression of pc is givenby the following theorem.

Theorem 1. The successful transmission probability of cellu-lar links without IC capability is

pc =λc

λc (µ+ 1) + λd

(PdPc

)δν

, (6)

where

µ =δ

1− δT · 2F1 (1, 1− δ; 2− δ;−T ) , (7)

ν = T δΓ (1− δ) Γ (1 + δ) , (8)

and 2F1 (·) ,Γ (·) are respectively the Hypergeometric functionand Gamma function.

Proof: Starting from the definitions of pc, we have

pc4= P [SIRc > T ]

= Er,Ic [Pg0 [SIRc > T ]]

= Er,Ic[Pg0

[g0 > P−1

c TrαIc]]

(a)= Er,Ic

[exp

(−P−1

c TrαIc)]

(b)= Er

[LIc

(P−1c Trα

)]=

ˆ ∞0

LIc(P−1c Trα

)· fr (r) dr. (9)

(a) follows from the Rayleigh distribution assumption ofchannel fading. In (b), LIc (·) denotes the Laplace trans-form of Ic. Let Ic = Ic−c + Ic−d, where Ic−c =∑xi∈Φc\{x0} Pcgi ‖xi‖

−α and Ic−d =∑yi∈Φd

Pdhi ‖yi‖−αdenote the interference from cellular links and D2D linksrespectively. Then it is straightforward to get

LIc (s) = LIc−c (s) · LIc−d (s) . (10)

The Laplace transform of Ic−c is given by

LIc−c (s) = E

exp

−s ∑xi∈Φc\{x0}

Pcgi ‖xi‖−α

1To distinguish different links, in this paper we use g ∼ exp (1) , h ∼exp (1) to represent the fading factors of links related to cellular transmitters(cellular users) and D2D transmitters respectively. It is noted that there is noessential distinction between these two symbols.

= EΦc

∏xi∈Φc\{x0}

Eg[exp

(−sPcgi ‖xi‖−α

)](c)= exp

(−λcˆ

Φc∩B(o,r)

(1− Eg

[e−sPcgi‖xi‖

−α])

dxi

)

= exp

(−λcˆ

Φc∩B(o,r)

(1− 1

1 + sPc ‖xi‖−α

)dxi

)(d)= exp

(−λc · 2π

ˆ ∞r

v

1 + s−1P−1c vα

dv

)(e)= exp

(−λcπ

δ

1− δsPcr

2−α2F1

(1, 1− δ; 2− δ;−sPc

)).

(11)

(c) follows from the probability generating functional (PGFL)of PPP [32]: E

[∏x∈Φ f (x)

]= exp

(−λ´R2 (1− f (x)) dx

).

(d) follows from the double integral in polar coordi-nates. (e) follows from the definite integral [33, 3.194.2]:´∞b

x1+axα dx = 1

α ·b2−α

a(1− 2α ) 2F1

(1, 1− 2

α ; 2− 2α ;− 1

abα

).

Similarly, we have

LIc−d (s) = E

exp

−s ∑yi∈Φd

Pdhi ‖yi‖−α

= exp

(−λdˆR2

(1− Eh

[exp

(−sPdhi ‖yi‖−α

)])dyi

)= exp

(−λdˆR2

(1− 1

1 + sPd ‖yi‖−α

)dyi

)= exp

(−λd · 2π

ˆ ∞0

u

1 + s−1P−1d uα

du

)(f)= exp

(−λdπ (sPd)

δΓ (1− δ) Γ (1 + δ)

). (12)

(f) follows from the definite integral [33, 3.241.4]:´∞0

x1+axα dx = 1

2

(1a

) 2α Γ

(1 + 2

α

)Γ(1− 2

α

). By plugging

(11) (12) into (10) and letting s = P−1c Trα, we get

LIc(P−1c Trα

)= exp

(−π

[λcµ+ λd

(PdPc

)δν

]r2

),

(13)where µ = δ

1−δT · 2F1 (1, 1− δ; 2− δ;−T ) , ν = T δ ·Γ (1− δ) Γ (1 + δ). Then by plugging (2) (13) into (9), wecomplete the proof.

B. Successful Transmission Probability of D2D Links

We conduct the analysis on a typical D2D link that com-prises a typical D2D transmitter located at some point inthe network and a typical D2D receiver located at a randomdistance l away. Shift the coordinates such that the typicalD2D receiver is located at the origin2, and denote the fadingfactor of the typical D2D link by h0, h0 ∼ exp (1). Then, thereceived SIR of the typical D2D link can be expressed as

SIRd =Pdh0l

−α

Id, (14)

2It is noted that the translations do not change the distribution of PPP [34].

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where

Id =∑

yi∈Φd\{y0}

Pdhi ‖yi‖−α +∑xi∈Φc

Pcgi ‖xi‖−α (15)

is the cumulative interference from all other D2D transmitters(except the typical D2D transmitter located at y0) that arelocated at yi with fading factor hi and cellular users that arelocated at xi with fading factor gi.

The successful transmission probability of D2D links canbe defined as

pd4= P [SIRd > T ] , (16)

where T is the SIR threshold. Note that the same SIR thresholdT is assumed for cellular and D2D links. The expression ofpd is given by the following theorem.

Theorem 2. The successful transmission probability of D2Dlinks without IC capability is

pd =λd

λd (ν + 1) + λc

(PcPd

)δν

, (17)

where ν is given in (8).

Proof: Starting from the definitions of pd, we have

pd4= P [SIRd > T ]

= El,Id [Ph0[SIRd > T ]]

= El[LId

(P−1d T lα

)]=

ˆ ∞0

LId(P−1d T lα

)· fl (l) dl. (18)

Following approaches similar to those in previous proofs andSlivnyak’s theorem [32]: P!x = P, we have

LId (s) = EId [exp (−sId)]

= E

exp

−s ∑yi∈Φd\{y0}

Pdhi ‖yi‖−α

× E

[exp

(−s

∑xi∈Φc

Pcgi ‖xi‖−α)]

= exp(−λdπ (sPd)

δΓ (1− δ) Γ (1 + δ)

)× exp

(−λcπ (sPc)

δΓ (1− δ) Γ (1 + δ)

). (19)

Therefore,

LId(P−1d T lα

)= exp

(−π

[λd + λc

(PcPd

)δ]νl2

), (20)

where ν is given in (8). Then by plugging (1) (20) into (18),we complete the proof.

Remark 1. Via the expressions of pc and pd shown in Theorem1 and 2, we can observe that µ, ν represent the effect of theinterference from the cellular links and D2D links respectively,and (Pd/Pc)

δ, (Pc/Pd)

δ can be regarded as the conversionfactors of powers.

C. Stochastic Equivalence of Interference

By (4) (15), the cumulative interference at each link isgenerated by two-tier interferers, i.e., cellular-tier and D2D-tier interferers. The analysis of such two-tier interference is te-dious, as shown in the derivations of Theorem 1 and 2. There-fore, to simplify the analysis and facilitate the performanceevaluation of IC techniques in later sections, we propose anapproach to equate the two-tier interference by a single-tierinterference that has the same stochastic characteristics (interms of successful transmission probability) as the two-tierinterference.

We first study the stochastic equivalence of the interferencefor cellular links. By (4), the interferers for the typical cellularlink constitute Φc−intf = (Φc \ {x0})

⋃Φd. We represent

Φc−intf by an equivalent PPP Φeqc−intf \ {x0} with density

λeqc−intf and transmission power Pc. Then, the equivalent

interference at the typical cellular link can be expressed as

Ieqc =

∑xi∈Φeq

c−intf\{x0}

Pcgi ‖xi‖−α , (21)

which has the same stochastic characteristics as Ic. Theequivalent interferer density for the typical cellular link canbe obtained from the following lemma.

Lemma 1. The density of the equivalent interferers for cellu-lar links is

λeqc−intf = λc + λd

(PdPc

)δν

µ, (22)

where µ, ν are given in (7) , (8) respectively.

Proof: Considering Ieqc has the same stochastic charac-

teristics as Ic, we have

LIc(P−1c Trα

)= LIeq

c

(P−1c Trα

). (23)

The Laplace transform of Ieqc is obtained as

LIeqc

(s) = EIeqc

[exp (−sIeqc )]

= E

exp

−s ∑xi∈Φeq

c−intf\{x0}

Pcgi ‖xi‖−α

= exp

(−λeq

c−intfπδ

1− δsPcr

2−α2F1

(1, 1− δ; 2− δ;−sPc

)).

(24)

Therefore,

LIeqc

(P−1c Trα

)= exp

(−λeq

c−intfπµr2), (25)

where µ is given in (7). Then by plugging (13) (25) into (23),we complete the proof.

It is noted that pc can be obtained as´∞

0LIeq

c

(P−1c Trα

fr (r) dr, and by (24), we have

pc =λc

λeqc−intfµ+ λc

, (26)

which is consistent with the result of Theorem 1.We next study the stochastic equivalence of the interference

for D2D links. By (15), the interferers for the typical D2D

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6

link constitute Φd−intf = (Φd \ {y0})⋃

Φc. We representΦd−intf by an equivalent PPP Φeq

d−intf \ {y0} with densityλeqd−intf and transmission power Pd. Then, the equivalent

interference at the typical D2D link can be expressed as

Ieqd =

∑yi∈Φeq

d−intf\{y0}

Pdhi ‖yi‖−α . (27)

The equivalent interferer density for the typical D2D link canbe obtained from the following lemma.

Lemma 2. The density of the equivalent interferers for D2Dlinks is

λeqd−intf = λd + λc

(PcPd

)δ. (28)

Proof: Starting from the Laplace transform of Ieqd ,

LIeqd

(s) = EIeqd

[exp

(−sIeq

d

)]= E

exp

−s ∑yi∈Φeq

d−intf\{y0}

Pdhi ‖yi‖−α

= exp(−λeq

d−intfπ (sPd)δ

Γ (1− δ) Γ (1 + δ)). (29)

Therefore,

LIeqd

(P−1d T lα

)= exp

(−λeq

d−intfπνl2), (30)

where ν is given in (8). Then by letting LIeqd

(P−1d T lα

)=

LId(P−1d T lα

), we complete the proof.

It is noted that pd can be obtained as´∞

0LIeq

d

(P−1d T lα

fl (l) dl, and by (30), we have

pd =λd

λeqd−intfν + λd

, (31)

which is consistent with the result of Theorem 2.

D. Numerical ResultsHere we provide some numerical results to validate the

proposed stochastic equivalence models and correspondinganalytical results. The system parameters are set as α =4, Pc = Pd = 1, λc = 0.01.

Fig.3 shows the successful transmission probabilities ofcellular and D2D links without IC capabilities. As can beobserved from the figure, the analytical results of the proposedstochastic equivalence models are in quite good agreementwith the corresponding simulation results. This fact confirmsthat the proposed models closely match the practical D2D-enabled cellular networks. In addition, as shown in the figure,when λc = λd, cellular links have a higher successfultransmission probability than D2D links. The reason is asfollows: when λc = λd, both the mean signal powers and meaninter-type (cellular-D2D) interference powers of cellular andD2D links are equal; however, the mean intra-type (cellular-cellular or D2D-D2D) interference power of cellular links issmaller that of D2D links, since for each cellular receiver(BS), the cellular interferers are located at farther distancesaway than the associated cellular user (due to the nearest-BSassociation policy), while for each D2D receiver, the D2Dinterferers can be located at any distances away (due to therandom distribution of D2D users).

-10 -7.5 -5 -2.5 0 2.5 5 7.5 100

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

T (dB)

Su

ccessfu

l tr

an

sm

issio

n p

rob

ab

ilit

y

Cellular (Simulation)

Cellular (Analysis)

D2D (Simulation)

D2D (Analysis)

d=0.002

d=0.05

d=0.01

Figure 3: Successful transmission probabilities of cellular andD2D links without IC. The system parameters are set as α =4, Pc = Pd = 1, λc = 0.01.

IV. NETWORK PERFORMANCE WITH UIC

In this section, we analyze how UIC affects the successfultransmission probabilities in D2D-enabled cellular networks.The analysis is based on the stochastic equivalence modelsproposed in subsection III.C.

A. Successful Transmission Probability of Cellular Links

We conduct the analysis on a typical cellular link thatcomprises a typical UIC-capable BS located at the origin andits associated cellular user located at x0, where ‖x0‖ = r.According to Lemma 1, the interferers for the typical cellularlink constitute an equivalent PPP Φeq

c−intf \ {x0} with densityλeqc−intf and transmission power Pc. By applying UIC, the

typical BS can completely cancel the interference from thestrong interferers whose received powers are greater than athreshold χ. Hence, the equivalent cumulative interference atthe typical cellular link can be expressed as

Ieq(χ)c =

∑xi∈Φeq

c−intf\{x0}

Pcgi ‖xi‖−α ·∆xi , (32)

where

∆xi =

{0, if Pcgi ‖xi‖−α > χ.

1, else.(33)

Then, the received SIR of the typical cellular link is

SIRUICc =

Pcg0r−α

Ieq(χ)c

, (34)

and the successful transmission probability of the typicalcellular links is defined as

pUICc4= P

[SIRUIC

c > T]. (35)

The expression of pUICc is given by the following theorem.

Page 7: On the Performance of Interference Cancellation in D2D ...iwct.sjtu.edu.cn/Personal/xwang8/paper/INFOCOM2015_D2D...of interference cancellation (IC) techniques at the receivers. However,

7

Theorem 3. The successful transmission probability of cellu-lar links with UIC is

pUICc =

ˆ ∞0

e−λeqc−intfπ·[κ1(r)+κ2(r)−κ3(r)] · fr (r) dr, (36)

where fr (r) is given in (2) and

κ1 (r) =δ

1− δTr2

2F1 (1, 1− δ; 2− δ;−T ) , (37)

κ2 (r) = e−P−1c Trαχ ·

∞∑n=0

(−1)n+1 (

χP−1c

)nn!

· r2+nα

1 + nα2

× 2F1 (1,−δ − n;−δ − n+ 1;−T ) , (38)

κ3 (r) = δ(χ−1Pc

)δΓ(δ, rαχP−1

c

). (39)

Proof: Starting from the definitions of pUICc , we have

pUICc4= P

[SIRUIC

c > T]

= Er[LI

eq(χ)c

(P−1c Trα

)]=

ˆ ∞0

LI

eq(χ)c

(P−1c Trα

)· fr (r) dr. (40)

The Laplace transform of Ieq(χ)c is given by

LI

eq(χ)c

(s) = EI

eq(χ)c

[exp

(−sIeq(χ)

c

)]= EΦeq

c−intf

∏xi∈Φeq

c−intf\{x0}

Eg[e−sPcgi‖xi‖

−α·∆xi

]= e−λeq

c−intf´Φ

eqc−intf∩B(o,r)

(1−Eg

[e−sPcgi‖xi‖

−α·∆xi

])dxi.

(41)

Since g ∼ exp (1), the expectation term in (41) is obtained as

Eg[e−sPcgi‖xi‖

−α·∆xi

]=

ˆ ∞0

e−sPcgi‖xi‖−α·∆xi · e−gi dgi

=

ˆ χP−1c ‖xi‖

α

0

e−sPcgi‖xi‖−α· e−gi dgi +

ˆ ∞χP−1

c ‖xi‖αe−gi dgi

=1− e−(sχ+χP−1

c ‖xi‖α)

sPc ‖xi‖−α + 1+ e−χP

−1c ‖xi‖

α

. (42)

Substituting (42) in (41), we get

LI

eq(χ)c

(s) =

e−λeq

c−intf´Φ

eqc−intf∩B(o,r)

1− 1−e−(sχ+χP−1

c ‖xi‖α)sPc‖xi‖−α+1

−e−χP−1c ‖xi‖α

dxi

= e−λeq

c−intf2π´∞r

(sPcv

−α

sPcv−α+1+ e−(sχ+χP−1

c vα)sPcv−α+1

−e−χP−1c vα

)v dv

.(43)

In (43), the first integral term is obtained using the definiteintegral [33, 3.194.2]:ˆ ∞r

sPcv−α

sPcv−α + 1v dv =

1

α

ˆ ∞rα

x2α−1

1 + s−1P−1c x

dx

=1

2

δ

1− δsPcr

2−α2F1

(1, 1− δ; 2− δ;−sPc

), (44)

the second integral term is obtained using the definite integral[33, 3.194.2] and Taylor series expansions of exponentialfunctions:ˆ ∞

r

e−(sχ+χP−1c vα)

sPcv−α + 1v dv =

1

αe−sχ

ˆ ∞rα

x2α e−χP

−1c x

sPc + xdx

= e−sχ ·∞∑n=0

(−1)n+1 (

χP−1c

)nn!

· r2+nα

2 + nα

× 2F1

(1,−δ − n;−δ − n+ 1;−sPc

), (45)

and the third integral term is obtained asˆ ∞r

e−χP−1c vαv dv =

1

α

ˆ ∞rα

x2α−1e−χP

−1c x dx

2

(χ−1Pc

)δΓ(δ, rαχP−1

c

). (46)

Then by plugging (44) − (46) into (43) and letting s =P−1c Trα, we complete the proof.In Theorem 3, κ1 (r) , κ2 (r) represent the effect of the weak

(uncanceled) interference and κ3 (r) represents the effect ofthe strong (canceled) interference.

B. Successful Transmission Probability of D2D Links

We conduct the analysis on a typical D2D link that com-prises a typical UIC-capable D2D receiver located at the originand a typical D2D transmitter located at y0, where ‖y0‖ = l.According to Lemma 2, the interferers for the typical D2Dlink constitute an equivalent PPP Φeq

d−intf \ {y0} with densityλeqd−intf and transmission power Pd. The equivalent cumula-

tive interference at the typical D2D link can be expressed as

Ieq(χ)d =

∑yi∈Φeq

d−intf\{y0}

Pdhi ‖yi‖−α ·∆yi , (47)

where

∆yi =

{0, if Pdhi ‖yi‖−α > χ,

1, else.(48)

Then, the received SIR of the typical D2D link is

SIRUICd =

Pdh0l−α

Ieq(χ)d

, (49)

and the successful transmission probability of the typical D2Dlink is defined as

pUICd4= P

[SIRUIC

d > T]. (50)

The expression of pUICd is given by the following theorem.

Theorem 4. The successful transmission probability of D2Dlinks with UIC is

pUICd =

ˆ ∞0

e−λeqd−intfπ·[τ1(l)+τ2(l)−τ3] · fl (l) dl, (51)

where fl (l) is given in (1) and

τ1 (l) = δT δl2Γ (δ) Γ (1− δ) , (52)

τ2 (l) = δT δl2Γ (1 + δ) Γ(−δ, P−1

d lαTχ), (53)

τ3 = δ(χ−1Pd

)δΓ (δ) . (54)

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8

Proof: Starting from the definitions of pUICd , we have

pUICd4= P

[SIRUIC

d > T]

= El[LI

eq(χ)d

(P−1d T lα

)]=

ˆ ∞0

LI

eq(χ)d

(P−1d T lα

)· fl (l) dl. (55)

The Laplace transform of Ieq(χ)d is given by

LI

eq(χ)d

(s) = EI

eq(χ)d

[exp

(−sIeq(χ)

d

)]= EΦeq

d−intf

∏yi∈Φeq

d−intf\{y0}

Eh[e−sPdhi‖yi‖

−α·∆yi

]= e−λeq

d−intf´R2

(1−Eh

[e−sPdhi‖yi‖

−α·∆yi

])dyi. (56)

Since h ∼ exp (1), the expectation term in (56) is obtained as

Eh[e−sPdhi‖yi‖

−α·∆yi

]=

ˆ ∞0

e−sPdhi‖yi‖−α·∆yi · e−hi dhi

=

ˆ χP−1d ‖yi‖

α

0

e−sPdhi‖yi‖−αe−hi dhi +

ˆ ∞χP−1

d ‖yi‖α

e−hi dhi

=1− e−(sPd‖yi‖−α+1)χP−1

d ‖yi‖α

sPd ‖yi‖−α + 1+ e−χP

−1d ‖yi‖

α

. (57)

Substituting (57) in (56), we get

LI

eq(χ)d

(s) =

e−λeq

d−intf´R2

1− 1−e−(sPd‖yi‖−α+1)χP−1

d ‖yi‖α

sPd‖yi‖−α+1−e−χP

−1d ‖yi‖

α

dyi

= e−λeq

d−intf2π´∞0

(sPdv

−α

sPdv−α+1

+ e−(sχ+χP

−1d

vα)sPdv

−α+1−e−χP

−1d

)v dv

.(58)

In (58), the first integral term is obtained using the definiteintegral [33, 3.241.4]:ˆ ∞

0

sPdv−α

sPdv−α + 1v dv =

ˆ ∞0

v

1 + s−1P−1d vα

dv

2(sPd)

δΓ (δ) Γ (1− δ) , (59)

the second integral term is obtained using the definite integral[33, 3.383.10]:ˆ ∞

0

e−(sχ+χP−1d vα)

sPdv−α + 1v dv =

1

αe−sχ

ˆ ∞0

x2α e−χP

−1d x

sPd + xdx

2(sPd)

δΓ (1 + δ) Γ (−δ, sχ) ,

(60)

and the third integral term is obtained asˆ ∞0

e−χP−1d vαv dv =

1

α

ˆ ∞0

x2α−1e−χP

−1d x dx

2

(χ−1Pd

)δΓ (δ) . (61)

Then by plugging (59) − (61) into (58) and letting s =P−1d T lα, we complete the proof.In Theorem 4, τ1 (l) , τ2 (l) represent the effect of the weak

(uncanceled) interference and τ3 represents the effect of thestrong (canceled) interference.

0 2 4 6 8 10 12 14 16 18 200.26

0.28

0.3

0.32

0.34

0.36

0.38

0.4

0.42

0.44

0.46

(dB)

Su

ccessfu

l tr

an

sm

issio

n p

rob

ab

ilit

y

Cellular (Simulation)

Cellular (Analysis)

D2D (Simulation)

D2D (Analysis)

+ 0

Figure 4: Successful transmission probabilities of cellular andD2D links with UIC. The system parameters are set as α =4, Pc = Pd = 1, λc = λd = 0.01, T = 1 (0 dB).

C. Discussions and Numerical Results

Now that we have developed expressions for the successfultransmission probabilities of cellular and D2D links withUIC capabilities, based on the stochastic equivalence modelsproposed in subsection III.C. It is noted that the stochasticequivalence models are obtained based on the non-IC scenario,and thus when applied to UIC networks, these models do notnecessarily produce exact results of the successful transmis-sion probabilities. Revisiting the UIC process, we can make thefollowing observations: for D2D links, the UIC process doesnot change the equivalent density of cellular interferers, andthus the stochastic equivalence model can produce exact valuesof the successful transmission probability of D2D links withUIC; however, for cellular links, the UIC process changes theequivalent density of D2D interferers, and thus the stochasticequivalence model can only produce approximated values ofthe successful transmission probability of cellular links withUIC. Here we provide some numerical results to compare theanalytical results based on the stochastic equivalence modelswith the actual (simulation) results. The system parameters areset as α = 4, Pc = Pd = 1, λc = λd = 0.01, T = 1.

Fig.4 shows the successful transmission probabilities ofcellular and D2D links with UIC capabilities, where χ0 =−27.96 dB is the reference power threshold that equals thereceived power from a transmitter located at a distance of5 m away. As expected, the analytical results of pUIC

d are inquite good agreement with corresponding simulation results,but there exist gaps between the analytical results of pUIC

c

and corresponding simulation results. Meanwhile, the gapsbetween the analytical and simulation results of pUIC

c are verysmall, which implies that the stochastic equivalence modelscan provide a good approximation for the interference in UICnetworks. An interesting observation from the figure is thatthe increasing rate of pUIC

d is larger than that of pUICc (as χ

decreases), which means UIC is more effective to improving

Page 9: On the Performance of Interference Cancellation in D2D ...iwct.sjtu.edu.cn/Personal/xwang8/paper/INFOCOM2015_D2D...of interference cancellation (IC) techniques at the receivers. However,

9

0

5

10

15

20

0

5

10

1

1.1

1.2

1.3

1.4

1.5

(dB)r

cUIC

+ 0

cUIC(r=5)

(a) UIC coefficient for cellular links

0

5

10

15

20

0

5

10

1

2

3

4

5

(dB)l

dUIC

+ 0

dUIC(l=5)

(b) UIC coefficient for D2D links

Figure 5: UIC coefficients for cellular and D2D links. The system parameters are set as α = 4, Pc = Pd = 1, λc = λd =0.01, T = 1 (0 dB).

the performance of D2D links than that of cellular links.This is because, the mean interferer-receiver distance of D2Dlinks is shorter than that of cellular links (as is analyzed insubsection III.D) and thus UIC can cancel more interferencefor D2D links.

To measure the effect of UIC on the successful transmissionprobabilities, we define a new metric called UIC coefficientsas follows: ρUIC

c (r) = LI

eq(χ)c

(P−1c Trα

)/LIc

(P−1c Trα

)and ρUIC

d (l) = LI

eq(χ)d

(P−1d T lα

)/LId

(P−1d T lα

). The UIC

coefficients ρUICc (r) and ρUIC

d (l) quantify how much pUICc

and pUICd are improved by UIC with given r and l. Ac-

cording to the definitions, pUICc and pUIC

d can be obtained aspUICc =

´∞0ρUICc (r) · LIc

(P−1c Trα

)fr (r) dr and pUIC

d (l) =´∞0ρUICd (l) · LId

(P−1d T lα

)fl (l) dl, and when ρUIC

c (r) =ρUICd (l) = 1, pUIC

c and pUICd reduce to pc and pd (see (9) and

(18)) respectively. Fig.5 shows numerical results of the UICcoefficients. As expected, ρUIC

d is larger than ρUICc when l = r,

which is consistent with the foregoing analysis on Fig.4.

V. NETWORK PERFORMANCE WITH SIC

In this section, we study how SIC affects the successfultransmission probabilities in D2D-enabled cellular networks.The analysis is based on the stochastic equivalence modelsproposed in subsection III.C.

A. Successful Transmission Probability of Cellular Links

We conduct the analysis on a typical cellular link thatcomprises a typical SIC-capable BS located at the origin andits associated cellular user located at x0, where ‖x0‖ = r.According to Lemma 1, the interferers for the typical cellularlink constitute an equivalent PPP Φeq

c−intf \ {x0} with densityλeqc−intf and transmission power Pc. We assume the equivalent

interferers are ordered by their received power at the typicalBS such that Pcgi ‖xi‖−α > Pcgj ‖xj‖−α ,∀ 0 < i < j.Before deriving the successful transmission probability of thetypical cellular link, we first present two useful lemmas.

First, we study the successful transmission probability ofthe typical cellular link after canceling n strongest equivalentinterferers. Given that n strongest equivalent interferers havebeen canceled, the received SIR of the typical cellular link canbe expressed as

SIR(n)c =

Pcg0r−α

Ieq(n)c

, (62)

where

Ieq(n)c =

∑xi∈Φeq

c−intf\{x0,x1,...xn}

Pcgi ‖xi‖−α (63)

is the cumulative interference for the typical cellular link.Then, the successful transmission probability of the typicalcellular link given that n strongest equivalent interferers havebeen canceled can be defined as

p(n)c4= P

[SIR(n)

c > T]. (64)

The expression of p(n)c is given by the following lemma.

Lemma 3. Given that n strongest equivalent interferers havebeen canceled, the successful transmission probability of thetypical cellular link is

p(n)c =

ˆ ∞0

ˆ ∞0

2(λeqc−intfπd

2n

)ndnΓ (n)

e−λeqc−intfπξ(r,dn)·fr (r) ddndr,

(65)where fr (r) is given in (2) and

ξ (r, dn) =δ

1− δTrαd2−α

n 2F1

(1, 1− δ; 2− δ;−Tr

α

dαn

)+d2

n.

(66)

Proof: Starting from the definitions of p(n)c , we have

p(n)c4= P

[SIR(n)

c > T]

= Er[LI

eq(n)c

(P−1c Trα

)]=

ˆ ∞0

LI

eq(n)c

(P−1c Trα

)· fr (r) dr. (67)

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10

The calculation of LI

eq(n)c

requires the distribution of the sumof the order statistics of interfering powers, which is difficultto obtain in the SIC scenario. However, it has been shown thatthe order statistics of received powers in modern networks aredominated by the distance [31]. Therefore, we can calculateLI

eq(n)c

by relaxing the ordering of interfering powers to that ofinterfering distances. Denote the distance from n-th equivalentinterferer to the origin by dn, then we have

LI

eq(n)c

(s) = EI

eq(n)c

[exp

(−sIeq(n)

c

)]= Edn,Φeq

c−intf ,g

∏xi∈Φeq

c−intf\{x0,x1,...xn}

e−sPcgi‖xi‖−α

= Edn

[e−λeq

c−intf´Φ

eqc−intf∩B(o,dn)

(1−Eg

[e−sPcgi‖xi‖

−α])dxi

]

=

ˆ ∞0

e−λeq

c−intf´Φ

eqc−intf∩B(o,dn)

sPc‖xi‖−α1+sPc‖xi‖−α

dxifdn (dn) ddn

=

ˆ ∞0

e−λeq

c−intf ·2π´∞dn

v

1+s−1P−1c vα

dvfdn (dn) ddn

=

ˆ ∞0

e−λeq

c−intfπδ

1−δ sPcd2−αn 2F1

(1,1−δ;2−δ;− sPcdαn

)fdn (dn) ddn.

(68)

From [32], the probability density function of dn is given by

fdn (dn) = e−λeqc−intfπd

2n ·

2(λeqc−intfπd

2n

)ndnΓ (n)

. (69)

By plugging (69) into (68) and letting s = P−1c Trα, we get

LI

eq(n)c

(P−1c Trα

)=

ˆ ∞0

e−λeqc−intfπξ(r,dn) ·

2(λeqc−intfπd

2n

)ndnΓ (n)

ddn, (70)

where ξ (r, dn) = δ1−δTr

αd2−αn 2F1

(1, 1− δ; 2− δ;−Tr

α

dαn

)+

d2n. Then by plugging (2) (70) into (67), we complete the

proof.A possible approach for simplifying the expression of p(n)

c

is to approximate dn by a fixed value d̃n, which equals theexpectation of dn, i.e.,

d̃n = E [dn] =Γ(n+ 1

2

)√πλeq

c−intfΓ (n). (71)

Then, p(n)c can be approximated by

p(n)c ≈

ˆ ∞0

e−λeqc−intfπξ̃(r,d̃n) · fr (r) dr, (72)

where fr (r) is given in (2) and

ξ̃(r, d̃n

)=

δ

1− δTrαd̃n

2−α2F1

(1, 1− δ; 2− δ;−Tr

α

d̃nα

).

(73)Next, we study the probability of canceling n-th strongest

equivalent interferer. Given that all n− 1 strongest equivalent

interferers have been canceled, the received SIR of n-thstrongest interferer at the typical BS can be expressed as

SIR(n)c−intf =

Pcgn ‖xn‖−α

Ieq(n)c−intf

, (74)

where

Ieq(n)c−intf =

∑xi∈Φeq

c−intf\{xn,x1,...xn−1}

Pcgi ‖xi‖−α (75)

is the cumulative interference for n-th strongest equivalentinterferer. Then, the probability of canceling n-th strongestequivalent interferer given that all n − 1 strongest equivalentinterferers have been canceled can be defined as

p(n)c−intf

4= P

[SIR

(n)c−intf > T

]. (76)

The expression of p(n)c−intf is given by the following lemma.

Lemma 4. Given that all n−1 strongest equivalent interferershave been canceled, the probability of canceling n-th strongestequivalent interferer for the typical cellular link is

p(n)c−intf =

1

(µ+ 1)n , (77)

where µ is given in (7).

Proof: Following the relaxation approach for the orderstatistics of interfering powers in the proof of Lemma 3, wecan rewrite SIR

(n)c−intf as

SIR(n)c−intf =

Pcgnd−αn

Ieq(n)c−intf

. (78)

Then, we have

p(n)c−intf

4= P

[SIR

(n)c−intf > T

]= E

dn,Ieq(n)c−intf

[exp

(−P−1

c TdαnIeq(n)c−intf

)]= Edn

[LI

eq(n)c−intf

(P−1c Tdαn

)]=

ˆ ∞0

LI

eq(n)c−intf

(P−1c Tdαn

)· fdn (dn) ddn. (79)

The Laplace transform of Ieq(n)c−intf is obtained as

LI

eq(n)c−intf

(s) = e−λeq

c−intfπδ

1−δ sPcd2−αn 2F1

(1,1−δ;2−δ;− sPcdαn

).

(80)Hence,

LI

eq(n)c−intf

(P−1c Tdαn

)= exp

(−λeq

c−intfπµd2n

), (81)

where µ is given in (7). Then by plugging (69) (81) into (79),we complete the proof.

Based on Lemma 3 and 4, we can derive the successfultransmission probability of the typical cellular link.

Theorem 5. The successful transmission probability of cellu-lar links with infinite SIC capability is

pSICc = pc+

∞∑n=1

(n∏i=1

p(i)c−intf

)(n−1∏i=0

(1− p(i)

c

))p(n)c , (82)

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11

where pc, p(n)c , p

(i)c−intf are given in (6) , (65) , (77) respec-

tively.

Proof: For the typical cellular link, we define the eventof its successful transmission without SIC as

E0 : SIR(0)c > T, (83)

and the event of its successful transmission with n-level(n ≥ 1) SIC as

En :

(n⋂i=1

SIR(i)c−intf > T

)∩

(n−1⋂i=0

SIR(i)c < T

)∩(SIR(n)

c > T).

(84)Using the assumption that the interference to each user isindependent, we get

P [En] =

{p

(0)c = pc, n = 0,(∏ni=1 p

(i)c−intf

)(∏n−1i=0

(1− p(i)

c

))p

(n)c , n ≥ 1.

(85)Therefore, the successful transmission probability of cellularlinks can be obtained as pSIC

c =∑∞n=0 P [En].

Corollary 1. The successful transmission probability of cel-lular links with (finite) N -level (N ≥ 1) SIC capability is

pN−SICc = pc +

N∑n=1

(n∏i=1

p(i)c−intf

)(n−1∏i=0

(1− p(i)

c

))p(n)c ,

(86)where pc, p

(n)c , p

(i)c−intf are given in (6) , (65) , (77) respec-

tively.

B. Successful Transmission Probability of D2D Links

We consider a typical D2D link with M -level SIC receivers.The assumption of finite-level SIC receiver is motivated bythe limited computational capabilities of D2D users. Thederivation of the successful transmission probability of D2Dlinks is quite similar to that of cellular links, and hence wedirectly present the results and omit their proofs.

Lemma 5. Given that n strongest equivalent interferers havebeen canceled, the successful transmission probability of thetypical D2D link is

p(n)d =

ˆ ∞0

ˆ ∞0

2(λeqd−intfπk

2n

)nknΓ (n)

e−λeqd−intfπ$(l,kn)fl (l) dkndl,

(87)

where fl (l) is given in (1) and

$ (l, kn) =δ

1− δT lαk2−α

n 2F1

(1, 1− δ; 2− δ;−T l

α

kαn

)+k2

n.

(88)

Lemma 6. Given that all n−1 strongest equivalent interferershave been canceled, the probability of canceling n-th strongestequivalent interferer for the typical D2D link is

p(n)d−intf =

1

(µ+ 1)n , (89)

0 1 2 3 4 5 6 7 8 9 100.2

0.25

0.3

0.35

0.4

0.45

0.5

SIC level

Su

ccessfu

l tr

an

sm

issio

n p

rob

ab

ilit

y

Cellular (Simulation)

Cellular (Analysis)

Cellular (Analysis, approx dn)

D2D (Simulation)

D2D (Analysis)

D2D (Analysis, approx kn)

Figure 6: Successful transmission probabilities of cellular andD2D links with SIC. The system parameters are set as α =4, Pc = Pd = 1, λc = λd = 0.01, T = 1 (0 dB).

where µ is given in (7).

Theorem 6. The successful transmission probability of D2Dlinks with (finite) M -level (M ≥ 1) SIC capability is

pM−SICd = pd +

M∑n=1

(n∏i=1

p(i)d−intf

)(n−1∏i=0

(1− p(i)

d

))p

(n)d ,

(90)where pd, p

(n)d , p

(n)d−intf are given in (17) , (87) , (89) respec-

tively.

C. Discussions and Numerical Results

Now that we have developed expressions for the successfultransmission probabilities of cellular and D2D links with SICcapabilities, based on the stochastic equivalence models. It isnoted that the derived analytical expressions are not the exactresults of corresponding successful transmission probabilities,since approximated models are used in the derivation. We pro-vide some numerical results to compare the analytical resultswith the actual (simulation) results. The system parameters areset as α = 4, Pc = Pd = 1, λc = λd = 0.01, T = 1.

Fig.6 shows the successful transmission probabilities of cel-lular and D2D links with SIC capabilities. As can be observedfrom the figure, there exist gaps between the analytical resultsof pN−SIC

c , pM−SICd and corresponding simulation results. The

analytical results can be regarded as lower bounds on thesuccessful transmission probabilities. The analytical resultsbased on approximated dn (see (71) (72)) and kn (similarto (71) (72)) are also plotted in the figure, through whichwe can find that the results of the approximated analyticalexpressions are in quite good agreement with those of the exactanalytical expressions. Therefore, the approximated analyticalexpressions can be employed to simplify the calculation of thesuccessful transmission probabilities. In addition, as shown inthe figure, 2-level SIC can provide almost 50% performance

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12

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02

0.2

0.3

0.4

0.5

0.6

0.7

0.8

d

Su

ccessfu

l tr

an

sm

issio

n p

rob

ab

ilit

yCellular, N=0

Cellular, N=1

Cellular, N=2

Cellular, N=3A B

C

Figure 7: Successful transmission probability of cellular linkswith SIC vs. density of D2D links. The system parameters areset as α = 4, Pc = Pd = 1, λc = 0.01, T = 1 (0 dB).

improvement for the network; however, when the SIC levelis larger than 2, SIC cannot further improve the networkperformance. Considering the hardware complexity and costof multi-level SIC, in practical networks, 1-level and 2-levelSIC can be adopted in the receivers.

Fig.7 shows the successful transmission probability of cel-lular links with SIC vs. the density of D2D links. As expected,increasing the density of D2D links leads to a decrease in thesuccessful transmission probability of cellular links. However,from this figure we can observe that SIC can compensate partof the performance loss of cellular links. For example, 1-levelSIC at the cellular receiver can compensate the performanceloss generated by D2D interferers of density λd = 0.0035(see point A), and 2-level SIC corresponds to λd = 0.0045(see point B). Moreover, the fact that point C is very closeto point B also indicates that more SIC levels (> 2) cannotprovide extra performance gains for the network.

VI. CONCLUSION

In this paper, we study the performance of IC techniquesin large-scale D2D-enabled cellular networks using the toolsfrom stochastic geometry. We first derive the successfultransmission probabilities of cellular and D2D links in thenetwork without IC capabilities as the baseline results. Then,to simplify the interference analysis, we propose the approachof stochastic equivalence of the interference, through whichthe two-tier interference can be represented by an equivalentsingle-tier interference. Based on the proposed stochasticequivalence models, we derive the successful transmissionprobabilities of cellular and D2D links in the networks whereUIC and SIC are respectively applied. The effectiveness ofthese two IC techniques for improving the performance ofD2D-enabled cellular networks is validated by both analyticand numerical results. Future work will extend the analysis tothe maximum transmission capacity of the network.

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