Hybrid-clustering game Algorithm for Resource Allocation in Macro-Femto HetNet

Transcription

1 KSII TRANSACTIONS ON INTERNET AND INFORMATION SYSTEMS VOL. 12, NO. 4, Apr Copyrght c 2018 KSII Hybrd-clusterng game Algorthm for Resource Allocaton n Macro-Femto HetNet Fang Ye 1, Jng Da 1 and Ybng L 1 1 College of nformaton and communcaton engneerng, Harbn Engneerng Unversty, Harbn, Chna [e-mal: yefang0923@126.com, ng d@163.com, lybng0920@126.com] *Correspondng author: Ybng L Receved June 15, 2017; revsed September 23, 2017; accepted October 8, 2017; Publshed Aprl 30, 2018 Abstract The heterogeneous networ (HetNet) has been one of the ey technologes n Long Term Evoluton-Advanced (LTE-A) wth growng capacty and coverage demands. However, the ntroducton of femtocells has brought serous co-layer nterference and cross-layer nterference, whch has been a maor factor affectng system throughput. It s generally acnowledged that the resource allocaton has sgnfcant mpact on suppressng nterference and mprovng the system performance. In ths paper, we propose a hybrd-clusterng algorthm based on the Matérn hard-core process (MHP) to restran two nds of co-channel nterference n the HetNet. As the mpractcalty of the hexagonal grd model and the homogeneous Posson pont process model whose ponts dstrbute completely randomly to establsh the system model. The HetNet model based on the MHP s adopted to satsfy the negatve correlaton dstrbuton of base statons n ths paper. Base on the system model, the spectrum sharng problem wth restrcted spectrum resources s further analyzed. On the bass of locaton nformaton and the nterference relaton of base statons, a hybrd clusterng method, whch taes nto accounts the farness of two types of base statons s frstly proposed. Then, aucton mechansm s dscussed to acheve the spectrum sharng nsde each cluster, avodng the spectrum resource waste. Through combnng the clusterng theory and aucton mechansm, the proposed novel algorthm can be appled to restran the cross-layer nterference and co-layer nterference of HetNet, whch has a hgh densty of base statons. Smulaton results show that spectral effcency and system throughput ncrease to a certan degree. Keywords: Game theory, Clusterng, Heterogeneous networ, Co-channel nterference, Spectrum resource allocaton Ths paper ncludes a hybrd-clusterng game algorthm based on a Matérn Hard-core Process (MHP) system model. Ths research was supported by the Natonal Natural Scence Foundaton of Chna (Grant No ), the Natural Scence Foundaton of Helongang Provnce, Chna (Grant No. F201345), the Fundamental Research Funds for the Central Unverstes of Chna (Grant No. GK ), the Natonal Key Foundaton for Explorng Scentfc Instrument of Chna (Grant No. 2016YFF ) and the Provncal Foundaton of Natural Scence (Grant No. F ). ISSN :

2 KSII TRANSACTIONS ON INTERNET AND INFORMATION SYSTEMS VOL. 12, NO. 4, Aprl Introducton Wth the wdespread applcaton of 4G technology worldwde, user data demands have wtnessed further ncreases, causng explosve ncreases n data quantty n wreless communcaton systems. Accordng to the 3GPP research report, t s expected that both of the average rate of moble data busness and ndoor moble data transmsson busness n the followng year wll exponentally ncrease [1-3], whch becomes a huge challenge for current cellular communcaton technology to mantan. Femtocells have also been ntroduced n current cellular networs [4-5] due to ther hgh flexblty and commercalzaton capablty, whch can provde better data rates and coverage for ndoor users. However, the co-exstance of femtocells and macro base statons may create severe co-layer and cross-layer nterference. Furthermore, the random nature of femtocells deployment turns the nterference nto a much more complex ssue. In recent years, resource allocaton algorthm s one of the man solutons for the nterference suppresson problem based on the heterogeneous networ (HetNet). For the research of ths type of problem, modelng nterference for the networ s the prmary purpose. As the establshment of the nterference model needs the locaton nformaton of the base statons and the users, we frstly adopt a system model, whch accurately reflect spatal dstrbuton feature of the base statons. Several lterature has dscussed ths queston. System networ models of most exstng algorthms adopt a regular networ model. However, n an actual envronment, due to nconsstent capacty demands, nstead of beng deployed completely based on a regular networ model, base statons wll dsplay randomness. In terms of modelng cellular networs wth rregular base staton deployment, Andrews J G. et al. [6] used a homogeneous Posson pont process (HPPP) to model base staton dstrbutons n cellular networs, and analyzed two performance ndces for coverage and reachable rate. On ths bass, Dhllon H S. et al. [7] proposed one type of K-layer cellular networ model for heterogeneous cellular networ modelng. In ths model, each layer of the networ conssted of the same type of base staton, and each base staton layer formed an ndependent HPPP wth ther own densty. Both of the above references demonstrated that the Posson pont process (PPP) and a typcal lattce networ could accurately represent the curve of coverage. However, for cellular networ staton dstrbuton modelng, the homogeneous Posson pont process s not an deal model because actual base staton deployment typcally dsplays a certan repulson feature. The Matérn hard-core process (MHP) whose ponts attempt to repel each other actng as a spatal pont process can better reflect the characterstc of the actual base staton deployment. So, n ths paper, consderng the repulson feature of base staton deployment n actual networ, HetNet model based on MHP s adopted. Furthermore, the postonal nformaton of the base statons can be obtaned after the system modeled. In terms of the postonal nformaton of the base statons, the nterference model can be constructed base on the nterference relatonshps. Necer M C. et al. [8] ntroduced the nterference graph nto LTE (Long Term Evoluton) macro cellular nter-cell nterference coordnaton, n whch the vertex represented users and the edge showed nterference between two users. By utlzng a vertex colorng heurstc algorthm, frequency resource blocs were allocated, and two vertces connected by edges could not be allocated to the same bloc. Based on above, [9-10] presented graph theory to suppress the co-channel nterference for downln transmsson n small cell networs. Qu J. et al. [9] presented a novel clusterng approach to establsh the nterference graph amng at suppressng nterference of ultra-dense small cell

3 1640 Fang et al.: Hybrd-clusterng game Algorthm for Resource Allocaton n Macro-Femto HetNet networs. However, they assumed that some of the vertces, who are named splt messengers (SMs), have the hgh prorty to gan the resource n the networ. The hypothess cannot guarantee the farness of all the users. To ensure the equalty of both nd of users, Uygungelen S. et al. [10] adopted both macro users and femto users as the vertces to establsh the nterference graph. Then used a hybrd vertex colorng algorthm adaptvely matched the frequency reuse. However, there s an edge between two vertces s smply defned as a 0, 1 problem, that s, there s an edge as long as there s nterference. At the same tme, each vertex could been assgned only one channel. It caused the waste of the spectrum resource to a certan extent. Meanwhle, n hgh-densty networs, the sgnalng overhead for updatng the graph s too hgh due to a complcated nterference graph, whch then tends to lower overall system throughput capacty. Thus, n ths paper, we study the nterference modelng based on the system model to solve the questons above. The followng part wll dscuss the nterference suppresson approach. Currently, the method of nterference suppresson based on resource allocaton can be dvded nto three types whch ncludes statc, sem statc and dynamc. For the statc nterference suppresson method, the wreless resources used by each cell are completely n accordance wth the planned dstrbuton scheme. The sgnalng cost s small but ths method s not flexble enough. The sem statc nterference suppresson method s used to adust the wreless resource of each cell accordng to the change of load. However, the blocng rate of the edge users s too hgh to suffer. Compared wth the statc and sem statc nterference suppresson methods, the dynamc nterference suppresson method can adust the user equpment rapdly, therefore the system can acheve the optmal performance [11]. Many scholars use the theory of game to study the dynamc nterference suppresson based on resource allocaton [12-21]. Spectrum resource leasng has become an effectve method for mprovng band and spectrum utlzaton rate, and s an mportant techncal aspect of heterogeneous networ spectrum sharng [12-13]. Frequency spectrum leasng mechansms that combne economc models such as the aucton model have been appled to spectrum sharng n heterogeneous networs [14-17]. Xnbng W. et al. [14] used the aucton mechansm for analyzng the dvson of spectrum resources n cogntve wreless networs. Each cogntve user offered a prce for requred spectrum resources, and a responsble authorzed user networ for the spectrum aucton decded on spectrum resources to be shared wthout affectng self-communcaton qualty. The teratons of solutons for cogntve user prcng n dstrbuted cogntve networs s dscussed as well. Lang Q. et al. [15] analyzed aucton agency based spectrum sharng. In the networ, there was a specal agency responsble for spectrum resource allocaton, whch would apply for spectrum resources n a unfed manner and then allocate resources at a certan prce. Usng ths type of spectrum resource sharng, nformaton transmsson among users s reduced, hence realzng effectve sharng of spectrum resources. Hasan N U. et al. [16] presented a novel approach to mnmze the nterference caused by all secondary users by applyng game theory. Furthermore, the method could be found a near-optmal soluton wth the genetc algorthm. However, the farness of all the users has not been consdered. Hossan E. et al. [17] studed spectrum sharng among cogntve users based on the aucton mechansm, and proposed sgnal-to-nterference rato and power based on the aucton mechansm, as well as a Nash equlbrum prcng strategy applcable for teratons of user solutons. However, the above aucton mechansm based spectrum sharng model studed centralzed spectrum sharng aganst sngle or multple bdders. Besdes, maorty of studes have focused on the problems, whch are based on cogntve wreless networs. Qu J. et al. [18] ntroduced a ont power control and frequency resource allocaton algorthm. However, only co-ter nterference n extremely dense small

4 KSII TRANSACTIONS ON INTERNET AND INFORMATION SYSTEMS VOL. 12, NO. 4, Aprl cell networs has been consdered. As for a heterogeneous networ wth relatvely large base staton densty, t s dffcult for centralzed spectrum resource allocaton schemes to realze effectve spectrum allocaton. As for the resource allocaton ssue n hgh-densty system networs, clusterng theory s typcally adopted. Reference [19-20] consdered sub channel allocaton for co-channel nterference mtgaton. For hgh-densty femtocell systems, L W. et al. [19] used a weghted nterference graph to classfy each femtocell nto dsontng femtocell groups, and then reled on maxmal femtocell group capacty to allocate sub-channels for all femtocells. However, ths algorthm dd not consder the performance mprovement of macro base staton users. Tang H. et al. [20] proposed one type of hybrd-clusterng algorthm, whch utlzed graph modelng to buld an nterference graph, and turned channel resource allocaton nto a hybrd-clusterng ssue, n whch each cluster represented one channel. Dfferent from the conventonal colorng algorthm that mnmzes color use number to save channel resources, a hybrd-clusterng algorthm uses all usable channel resources, wth the goal of mnmzng system nterference to mprove user throughput capacty. However, the above method used smple random allocaton n reusng spectrum resources, rather than combnng effectve allocaton methods le game theory. Therefore, the ey s to buld a more reasonable heterogeneous mode, as well as a reasonable system nterference gram, and a resource allocaton method that reduces cross-layer and co-layer nterference. In ths paper, consderng the repulson feature of base statons deployment n the femto ter, we frst adopt a heterogeneous networ model by applyng the Posson pont process wth repulson functon. Then, n order to solve the problems n resource allocaton algorthms based on game theory, ths paper proposes one type of hybrd-clusterng game (HCG) algorthm that ncorporates equalty and mproves throughput capacty. The algorthm frstly bult a regonal average channel state (RACS) based on base staton poston nformaton to estmate the nfluence of nterference. Sgnal-to-nterference rato (SINR) s used to udge whether there s a strong nterference ln. Then consderng as well as the nterference relatonshp, an nterference graph G( V, E ) s bult. Accordng to the weghts measured by RACS, the problem of optmal clusterng partton s evolved nto the maxmum K-cuttng problem n graph theory. Fnally, combned wth the aucton model of game theory, a spectrum sharng model wth a sngle auctoneer and a pluralty of bdders s establshed to allocate the spectrum resources to the users n the same cluster. It maes up for the shortcomngs of the tradtonal clusterng algorthm, such as low ntermedate frequency band reuse rate and low femtocell throughput. At the same tme, t changes the problem of the game theory n the hgh-densty networ model, whch s dffcult to realze the spectrum allocaton by usng the centralzed spectrum resource allocaton scheme. The smulaton analyss s conducted, and results show that ths algorthm can mprove spectrum effcency by ntroducng a clusterng approach to mprove resource allocaton. The rest of ths paper s organzed as follows. Secton 2 presents the novel system model. Secton 3 ntroduces the hybrd-clusterng game algorthm. In Secton 4, smulatons are used to evaluate the performance of the proposed algorthm. Fnally, we provde a concluson for the paper 2.1 System Model 2. System Model

5 1642 Fang et al.: Hybrd-clusterng game Algorthm for Resource Allocaton n Macro-Femto HetNet Consder a blayer downln HetNet that conssts of a macro base staton MBS M and several femtocells FBS, {1,2,..., N}, as shown n Fg. 1, the sold lne represents the usable sgnal, whle the dashed lne represents the nterference sgnal. The usual method for modelng cellular networs s HPPP, whch reflect the random nature of base staton dstrbuton to a certan extent. However, usng HPPP to model the base staton poston n a cellular networ means that all deployed base statons are completely ndependent. Actually, each base staton has a certan coverage scope and overlappng coverage brngng complex nterference. Thus, base staton placement wll dsplay a certan repulson feature. In order to reflect the negatve correlaton of the base staton locaton more accurately, n ths paper, spatal ponts wth a repulson functon among nodes are adopted to model the heterogeneous networ. MUE 2 Femto C FUE 3 MUE 4 MUE 1 M MUE 3 Femto B FUE 1 FUE 2 Femto A Fg. 1. Downln transmsson lns n HetNet We assume that base statons of the same type be n the same layer and have the same transmsson power. Moreover, the same layer base staton dstrbuton conforms to one HPPP wth a densty (see Fg. 2(a)). Then, based on the repulson radus r h, we thn to obtan ˆ. Frstly, we assgn a random value unformly dstrbuted n [0,1] to each pont n. Then we tae any pont n and tae the pont as the center of the crcle r h radus. We delete all ponts n the crcle that coexst wthn a dstance less than r h from the pont wth a lower value. Hence, only ponts wth the lowest value n ther r h neghborhood dstance are retaned. The repulson radus r h s the actual radus of the base staton [22]. In ths manner, terate through every pont n on ths account. After beng thnned, the obtaned spatal pont process ˆ becomes a Matérn Hard-core Process (MHP) and the ponts n ˆ are the centers of hard balls of radus r h /2. The densty ˆ of ths spatal pont process can be obtaned by equaton (1). 2 ˆ 1exp( rh ) 2 rh (1)

6 KSII TRANSACTIONS ON INTERNET AND INFORMATION SYSTEMS VOL. 12, NO. 4, Aprl Fg. 2(b) s a HetNet model bult n ths paper based on MHP. The coverage of each base staton does not overlap, and the locaton relatonshp among base statons s negatvely correlated. Meanwhle, due to the dluton of the femtocell dstrbuton, the nterference between the base staton and the user s smplfed, and the complexty of the system s reduced. (a) Posson pont process wth densty (b) MHP ˆ wth densty ˆ thnned from Fg. 2. The locaton of femtocells based on PPP 2.2 Interference Model Based on the base staton poston nformaton n Fg. 2(b) and the system nterference relatonshp, the nterference graph G( V, E ) s developed as shown n Fg. 3, where V { V1, V2..}. represents vertces (shown as crcles) and E { E, E...} 1 2 represents edges (shown as straght lnes). M FUE 3 MUE 4 FUE 2 Femto C FUE 2 Femto A Fg. 3. Schematc plot of nterference graph In a tradtonal nterference graph, the vertex normally only contans femtocell users or macro base staton users. Besdes, whether there s an edge exst between two vertces s smply defned as a 0, 1 model. That s, the edge exsts s dentfed 1 as long as the transmsson ln s an nterference ln. Otherwse, the edge does not exst and s dentfed as 0. Ths type of nterference graph cannot ensure equalty. Meanwhle, n hgh-densty networs, the sgnalng overhead for updatng the graph s too hgh due to the complcated nterference graph, whch then tends to lower overall system throughput capacty. In order to ensure equalty among dfferent base staton users, we choose all femtocell and macro base staton communty users as vertces n the graph and manage femtocells at an equal level.

7 1644 Fang et al.: Hybrd-clusterng game Algorthm for Resource Allocaton n Macro-Femto HetNet Moreover, we propose the strong nterference ndcaton matrx {, } to C C C mprove the method for udgng the exstence of edge. Only f there s a strong nterference ln between two vertces based on sgnal-to-nterference rato, can the edges of the two vertces be consdered to exst. That s, when C 1, the nterference between vertces s udged large enough, and t s consdered as a strong nterference ln. For better assessment of nterference, a regonal average channel state ( RACS ) s bult to estmate the nfluence of nterference. RACS s the threshold used to determne whether the value of C s defned as C 1. When C 1, the vertex nterference s large and there exsts a strong nterference ln; That s, when RACS SINRth cth, there should be an edge representng the nterference between two vertces. c th s a predefned threshold [23]. RACS of regon m served by F and nterfered by F ( V, V ) represents the average sgnal-to-nterference plus nose rato, whch s calculated based on the locaton nformaton of the base staton:,, /,, r, r, 0 SINR x y P x y P x y N (2) 01 RACS(,, A ) SINR ( x, y) dxdy / S( A ) (3) A, m where V, V, ; P r, s the sgnal power sent from base staton user r ; N 0 s nose power; SA ( ) s the sze of staton BS. A, and BS and receved by A s the coverage area of base Three dfferent nterference scenaros are analyzed wth the use of regonal average channel state, and three types of nterference between the vertces dscussed above are as follows. 1. Interference between dfferent femtocells. Choose femtocells FBS and FBS located at 0,0 and d,0, respectvely, wth base staton rad R and R. P and P represent the transmt power of FBS and FBS, respectvely. RACS (,, A ) ndcates the average channel qualty of the FBS coverage area under the nterference FBS. r, RACS(,, A ) dxdy S A A Pr, x, y N0 P x, y (4) Path loss mode uses the ndoor transmsson formula L ds ds c log 10, where ds ndcates the dstance between the FBS user and base staton. Ignorng bacground nose, RACS (,, A ) can be approxmated as follows:

8 KSII TRANSACTIONS ON INTERNET AND INFORMATION SYSTEMS VOL. 12, NO. 4, Aprl where RACS 2 cos 2 2 P 2 R r d rd (,, A ) 2 P R R rdrd Rmn mn (5) r R mn s the shortest dstance between the femtocell user and femtocell. 2. Interference of macro base staton on femtocell. The same schematc detals as provded n 1 are used. Assumng one base staton MBS M located at D,0 wth transmsson power P M. Snce the macro base staton covers the whole communty, FBS femtocell users wll be nterfered by macro base staton MBS M. Smlar to scenaro one, n the path loss model, the nfluence of the macro base staton on the femtocell L ds, and users from the femtocell to the base uses the urban space transmsson formula c staton coverage area use the ndoor transmsson formula log 10( ds). Ignorng bacground nose, we can approxmate obtan: P D 2 RACS(, M, A ) mn mn 4 R R R R D PM R Rmn 3 R Rmn (6) 3. Interference of femtocell on macro base staton users. In ths scenaro, assumng one macro base staton MBS M wth transmsson power P and M one femtocell FBS located at xf, y f wth transmsson power P F. When macro base staton user MUE s located at xy,, gnorng nose power and usng the urban space transmsson formula L c ds, we can approxmate as follows: RACS r r 2rr f rdrd (7) 2 2 P 2 RM f ( M,, A ) 2 0 R 2 P mn M D r 1.88 Dstngushng the exstence of strong nterference between two vertces by RACS, we buld strong nterference ndcaton matrx C { C C 01, }. When the exstence of the edge of all vertces s determned, we obtan an accurate nterference graph. RACS s also used to analyze nterference weght n the clusterng scheme whch s elaborated n the next secton. In the next secton, we transform the problem of channel resource allocaton nto the problem of hybrd clusterng accordng to the nterference graph. The obectve s to mnmze the nterference n order to mprove throughput. The aucton mechansm s used to allocate the spectrum resources to the users n the same cluster n order to acheve the reasonable allocaton of the spectrum.

9 1646 Fang et al.: Hybrd-clusterng game Algorthm for Resource Allocaton n Macro-Femto HetNet 3.1 Hybrd Clusterng Algorthm 3. Game Model and Problem Statement The HCG algorthm s dvded nto two parts. Frst, we propose a hybrd-dsatur clusterng algorthm to mnmze co-channel nterference. We assume that the number of sub-bands s K, the same node can be assgned to dfferent clusters, and each node can reuse multple channels. In order to mprove throughput, the problem s formulated as follows: K N 11 arg max B log (1 SINR ), 2, subect to : 1 or 0, V 1, K B log ( 1SINR ) R 2, mn (8) where N s the total number of vertces N V, B s a sub-band mared, 1, K, and mn sub-band wll assgn to node, V when, 1, otherwse, 0. R s the mnmum rate requrement of users. To determne the possblty that vertces belong to the same cluster, the nterference weghts between vertce and vertce s defned as cc. The graph nterference weghts matrx CC cc, V, V can be constructed. Snce two macro users cannot be NN assgned to the same sub-band, weght between whch can be set as cc 0 (a very large value). Meanwhle, we consder a macro user wth hgher prorty than the femto user. cc 0 s also assgned to denote nterference from the femtocell to the macro user n order to ensure the performance of the macro user. For other types of nterference, 1/ RACS s used to express the amount of nterference. The purpose of ths algorthm s to assgn all the elements of the vertce set V to S orthogonal sets by usng the nterference weght matrx. Hence, the channel assgnment problem can be descrbed as a clusterng process. In regular clusterng schemes, the common target s to mnmze the number of clusters. However, our proposed clusterng scheme uses all avalable channels and ams to mnmze nterference n order to mprove throughput. The K resource blocs are dvded nto S segments, and each segment contans R resource blocs. Each spectrum resource represents a cluster, whch defnes the user cluster number group S as [1,2,..., S ]. Vertces are dvded nto the same cluster and share spectrum resources. In order to partton the vertces nto S clusters, we frst calculate the sum nterference sum _ cc, whch expresses the total nterference of node suffered from others. the parameter s calculated as follows: N 1 sum _ cc cc, [1, N] (9)

10 KSII TRANSACTIONS ON INTERNET AND INFORMATION SYSTEMS VOL. 12, NO. 4, Aprl Then, we mar the nodes ordered by the value of sum _ cc. The node wth the lowest value of sum _ cc wll frst be assgned nto clusters so that we mnmze nterference on the graph. In order to mprove spectrum effcency, the process of assgnng nodes nto clusters s expressed as three steps: Step 1: In order to ensure the communcaton qualty of macro users, S macro users wth the hghest level of spectrum requrements are assgned to the clusters at frst. These users wth hgher communcaton qualty requrements become cluster heads. Each cluster s traversed untl each cluster has a cluster head. Then proceedng to allocate other clusters. Step 2: Dvdng the remanng users nto dfferent clusters as far as possble to meet the mnmum servce guarantee requrements. We udge whether node can be assgned nto th cluster ( S ) accordng to the n number of the cluster. Three condtons must be satsfed: a. All nodes of c,, meet c 0,, where s the current node set of cluster. b. cc _ ls 1 SINRth, where cc _ ls s the sum nterference of node as suffered from all current nodes n cluster. cc _ ls s calculated as:. n cc _ ls cc ; n (10) 1 cluster, c. prce _ cc 1 SINRth,, where prce _ cc s the sum nterference of current node f node s assgned nto cluster. prce_ cc s calculated as: n prce _ cc cc, ; n clusterm, (11) 1 Once beng assgned nto a cluster, node wll traverse all clusters untl all condtons are met. We then allocate the node nto cluster, whch has the mnmum cc _ ls : mn cc _ ls, f there s no approprate cluster for a node. Ths wll ensure networ farness.the second step assgns nodes nto dfferent clusters n order to guarantee that each node can reuse a sub-band. Step 3: In order to mprove throughput and spectrum effcency, the same node can be assgned to dfferent clusters. In the thrd step, we repeat the second step for each node. The clusterng process stops when no node can be assgned nto a cluster. Snce the number of clusters s guaranteed to be the same as the number of sub spectrum band. therefore, one band s allocated for each cluster, and the same frequency band s used by all users n the same cluster. Based on the clusterng results, S secton spectrum resources wll be randomly allocated to clusters. Spectral effcency wll be enhanced because the same user can reuse multple channels. By usng the aucton mechansm, spectrum resources obtaned by the cluster are dstrbuted to each cluster node based on spectrum bddng of nodes n the cluster.

11 1648 Fang et al.: Hybrd-clusterng game Algorthm for Resource Allocaton n Macro-Femto HetNet 3.2 Aucton Mechansm Based Spectrum Sharng An aucton mechansm based spectrum sharng model can solve spectrum resource sharng ssues n the case of one sngle clusterng node or multple clusterng nodes. A clusterng node has prorty for spectrum resources and the prcng rght for spectrum resource leasng and allocaton. In order to ensure the communcaton speed of clusterng node user, a clusterng node can lease out and allocate spectrum resources to nodes nsde the cluster, hence meetng the communcaton requrements of clusterng nodes and obtanng economc revenue. Therefore, spectrum resource sharng can be consdered as a spectrum resource auctonng model. We consder the aucton model has one prmary user and a group of secondary users. The prmary user s the cluster head who wll share the frequency resource wth the other nodes n the cluster who actng as secondary users. As all the nodes are selfshly to maxmze ts own utlty, we consder the aucton s a non-cooperatve game. Nodes n the cluster can apply for spectrum resources from cluster head nodes through spectrum resource bdng. The cluster head node s the auctoneer of spectrum resources and s responsble for collectng offers from nodes and determnng the sze of spectrum resources to be allocated. Assumng that the revenue obtaned by a unt occupyng spectrum resources s nown for nodes n the cluster, and the maxmal transmsson speed obtaned by nodes n the cluster s regarded as the revenue obtaned by nodes n obtanng the use rght [24]. For that reason, we defne the utlty functon as the transmsson speed obtaned by nodes. Nodes n the cluster submt spectrum resource prces based on self-communcaton demand. Assumng that b b 1, b 2,, b Nc s the prce offered by nodes n the cluster and that N c s the number of nodes n the cluster. Reference [24] regarded spectrum resource prces as the tot w resource szes applyng to be occuped. 0 b B, where B s the spectrum resource bandwdth of nodes n the cluster. As the spectrum auctoneer, cluster head nodes collect spectrum resource prces b from cluster nodes and determne the shared szes B B1, B2,, B Nc based on cluster nodes possessed spectrum resources and the condton of ensurng suffcent resources for tself, B b B Nc b 1 w (12) where s the rato of spectrum resources retaned by the cluster head node. In addton, gven that the cluster head node needs to ensure ts own communcaton qualty, shared spectrum resources B provded to cluster nodes have to satsfy N c w r B B B 1, where are the spectrum resources requred by the cluster head node to ensure self communcaton qualty. The cluster head node wll lease out remanng dle spectrum resources to cluster nodes at unt prce u. The earnngs R obtaned by node n the cluster due to shared spectrum resources provded by the cluster head node are: r B R r B (13)

12 KSII TRANSACTIONS ON INTERNET AND INFORMATION SYSTEMS VOL. 12, NO. 4, Aprl where r s the revenue obtaned through unt transmsson speed. The cost C for node n the cluster to obtan shared spectrum resources where l s the prorty factor of the cluster node. C B s: ul b (14) Therefore, the revenue functon for node to apply for spectrum resources at the offered prce b s:, b,, b, U b u R B b C b u b r B ul b w N c b 1 (15) b [ b, b,, b, b,, b ] s the prce offered by each node except node. where N c 1 Nodes n the cluster choose a spectrum offer prce b that maxmzes ther revenue functon accordng to ther own communcaton parameters to acheve Nash equlbrum. Nodes n the cluster cannot obtan a hgher spectrum revenue by changng the prcng strategy; namely, the spectrum offer prce for each node has to satsfy b : where b b arg max U b,, u w 0b B b (16) b, b. In order to fnd the spectrum prce offer strategy that U b, b, u b 0. Then, maxmzes the shared spectrum revenue for cluster nodes, let the followng can be obtaned: r B w Nc 1, Nc 1 b ul 2 b 0 (17) Snce node does not now the offer prce of other nodes, the soluton s smlar to the sharng spectrum prce n the compettve prce game model through obtanng the spectrum offer prce of nodes through multple teratons t Nc b 1 1, t t t w t 2 Nc b 1 b b b r B b ul where b s the spectrum offer prce of node at moment t. (18)

13 1650 Fang et al.: Hybrd-clusterng game Algorthm for Resource Allocaton n Macro-Femto HetNet 4. Smulaton Results and Analyss In ths secton, we conduct smulatons n order to assess algorthm performance. Frst, we analyze the aucton mechansm based spectrum sharng model n one cluster. Then, we smulate and analyze throughput of the HCG algorthm. Smulaton parameters are shown n table 1. Table 1. Smulaton parameters Parameter Macrocell Femtocell System Bandwdth 20MHz 20MHz Cell Radus 500 m 50 m Antenna Gan 14 db 0 db Transmt Power 46 dbm 21 dbm User Dstrbuton 90 per cell 2 per cell cc th 0 c 10 db 10 db Assumng that the cluster head node possesses a secton of spectrum resource, we consder that the same type of vertces rent the spectrum at the same prce. Nodes n the cluster share spectrum resources of the cluster head node to obtan a certan transmsson speed; per unt of transmsson speed can obtan the spectrum revenue r 10 ; per unt prce for the cluster head node provdes bandwdth for sharng u 10. Fg. 4 shows a smulaton analyss where nodes n the cluster qucly obtan a stable spectrum offer prce strategy by an teratve soluton through adoptng the aucton mechansm based spectrum sharng model. Clusterng theory based spectrum allocaton models do not analyze how to further allocate spectrum resources to nodes n the cluster. Whle aucton mechansm based spectrum leasng models manly dscuss the spectrum sharng ssue between sngle spectrum resource provders and multple nodes n the cluster, and the determnaton of spectrum resources to be shared by the auctoneer through collecton of spectrum offer prces. Therefore, frst we use clusterng theory to smplfy the complcated nterference topologcal structure, treat cluster head nodes as the spectrum auctoneers, and use the aucton mechansm to complete spectrum resource sharng among cluster nodes. Fg. 4. Spectrum offer prce strategy Fg. 5. Revenue obtaned for dfferent requrement levels

14 KSII TRANSACTIONS ON INTERNET AND INFORMATION SYSTEMS VOL. 12, NO. 4, Aprl Fg. 5 shows the revenue obtaned by each cluster head node by provdng nodes n the cluster wth spectrum resources for dfferent requrements. Smulaton results show that wth the ncrease of requrement level, nodes n the cluster tend to apply for more shared spectrum resources from cluster head through the requrement level factor, and generate hgher sharng spectrum revenue for cluster head. When ths spectrum leasng mechansm, whch consders the requrement of nodes n the cluster, s appled to clusterng game spectrum sharng, all cluster heads consder the nfluence of spectrum resource requrements at each node whle conductng resource leasng and sharng, whch s more smlar to an actual applcaton. Fg. 6 (a) shows channel average multplexng curves for varous algorthms wth dfferent macro user densty. Smulaton results show that the proposed algorthm s more effcent than other algorthms. In addton, wth an ncrease n the number of macro users, the average number of HCG channels decreases. HCIG allocates only one channel for users n the networ, as well as the networ channel number reuse tme suffcent for all users, so, wth an ncrease n the number of macro users, the number of the correspondng channel multplexng s also ncreased. Fg. 6 (b) shows channel average multplexng curves for varous algorthms wth dfferent femtocell densty. Smulaton results show that HCG s more effcent than exstng algorthms. Wth the ncrease of the number of femtocells, the average number of channel multplexng for HCG ncreases because HCG s based on the prncple of maxmzng throughput allocaton and s bound to allocate more channels for the femtocell. Ths reduces total networ throughput for macro user servces and result n an ncrease n the number of channel multplexng. At the same tme, HCG ensures the communcaton qualty requrements of users, and n ths macro set the macro users are unchanged. The number of multplexed channels does not change much, meanng that the nfluence of the macro base staton on allocaton of networ spectrum resources remans bascally unchanged. Therefore, users wth hgher communcaton qualty requrements are generally macro users. Fg. 7 shows average throughput curves for dfferent algorthms as the ncrease of femto users. The overall performance of the proposed algorthm s better than other algorthms due to the ncrease n HCG channel multplexng ntensty, whch enables users to get more channels for communcaton. Wth an ncrease n macro staton users, the channel number assgned to the femtocell decreased, so the overall trend s downward. (a) all users as macro users ncreases (b) all users as femtocell ncreases Fg. 6. Channel average curves

15 1652 Fang et al.: Hybrd-clusterng game Algorthm for Resource Allocaton n Macro-Femto HetNet (a) Average throughput curves of all users as (b) Average throughput curves of femto users as femto users ncreases femto users ncreases Fg. 7. Average throughput curves 5. Concluson In ths paper, a networ model wth random characterstcs and a negatve correlaton between base statons s establshed by MHP to solve the problem of heterogeneous networs wth a hgh densty of base statons. The mproved system model can be used to accurately model nterference n heterogeneous networs. We ntroduce Regonal Average Channel State based on the locaton nterference of base statons to mnmze nterference. Cluster theory s ntroduced to mae small nterferng peas n the nterference graph share the same spectrum resources. In order to suppress cross-layer and co-layer nterference, femtocells and macro users are treated on the same level. Combned wth the aucton model of game theory, the spectrum leasng mechansm s an effectve method to mprove frequency spectrum utlzaton. In order to resolve ths problem, exstng algorthms manly study the spectrum sharng model wth a sngle auctoneer and a pluralty of bdders. The proposed algorthm mproves spectral effcency by ntroducng an mproved aucton mechansm as well as a new clusterng scheme. Acnowledgement Ths paper was supported by the Natonal Natural Scence Foundaton of Chna (Grant No ), the Natural Scence Foundaton of Helongang Provnce, Chna (Grant No. F201345), the Fundamental Research Funds for the Central Unverstes of Chna (Grant No. GK ), the Natonal Key Foundaton for Explorng Scentfc Instrument of Chna (Grant No. 2016YFF ), and the Provncal Foundaton of Natural Scence (Grant No. F ). References [1] 3GPP, 3rd Generaton Partnershp Proect; Techncal Specfcaton Group Servces and System Aspects; Feasblty study for proxmty servces (ProSe) (Release 12), TR , V12.2.0, Jun Artcle (CrossRef Ln)

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17 1654 Fang et al.: Hybrd-clusterng game Algorthm for Resource Allocaton n Macro-Femto HetNet [18] Qu J, Dng G, Wu Q, et al. Herarchcal Resource Allocaton Framewor for Hyper-Dense Small Cell Networs, IEEE Access, vol.4, no.99, pp , Artcle (CrossRef Ln) [19] L W, Su T, Zheng W, Dynamc Clusterng Based Sub-Band Allocaton n Dense Femtocell Envronments, n Proc. of IEEE Vehcular Technology Conference (VTC Sprng), pp.1-5, Artcle (CrossRef Ln) [20] Tang H, Hong P, Xue K, Peng J, Cluster-Based Resource Allocaton for Interference Mtgaton n LTE Heterogeneous Networs, n Proc. of IEEE Vehcular Technology Conference (VTC Sprng), pp.3-6, Artcle (CrossRef Ln) [21] Han S, L X, Lu Z, Herarchcal-game-based algorthm for downln ont subchannel and power allocaton n OFDMA femtocell networs, Journal of Networ and Computer Applcatons, vol.73, pp , [22] Dhllon H S, Gant R K, Andrews J G, Load-Aware Modelng and Analyss of Heterogeneous Cellular Networs, IEEE Transactons on Wreless Communcatons, vol.12, no.4, pp , Artcle (CrossRef Ln) [23] Cho S, Cho W, Coverage and Load Balancng n Heterogeneous Cellular Networs wth Mnmum Cell Separaton, IEEE Transactons on Moble Computng, vol.13, no.9, pp , Artcle (CrossRef Ln) [24] Parvn S, Hussan F K, Hussan O K, et al. Cogntve rado networ securty: A survey, Journal of Networ & Computer Applcatons, vol.35, no.6, pp , Artcle (CrossRef Ln) Fang Ye receved the B.S. and Ph.D degrees n Electrcal Informaton Engneerng from Harbn Engneerng Unversty n 2002 and 2006, respectvely. She has been a teacher n Harbn Engneerng Unversty of Chna snce 2002, and became an assocate professor n Durng , she stayed n School of Electroncs and Computer Scence from Unversty of Southampton as a vstng scholar. Now she s a member of Chna Insttute of Communcatons and a member of Chna Computer Federaton. Jng Da receved the B.S. degrees n Northeast Agrcultural Unversty n Now she s studyng as a master course student n Electrcal Informaton Engneerng from Harbn Engneerng Unversty. She study on the resource allocaton algorthms and nterference suppresson. Ybng L receved the B.S., M.S. and Ph.D degrees n Harbn Marne engneerng college, Harbn engneerng unversty n 1989, 1997 and 2003, respectvely. He has been a teacher n Harbn Engneerng Unversty of Chna snce 1989, and became a professor n Durng , he stayed n the Unversty of Hong Kong Electronc Engneerng lab as a vstng scholar. Now he s a senor member of Chna Insttute of Communcatons and a senor member of Chna Computer Federaton.