Inter national J our nal of Electrical and Computer Engineering (IJECE) V ol. 9, No. 3, June 2019, pp. 2057 2063 ISSN: 2088-8708, DOI: 10.11591/ijece.v9i3.pp2057-2063 r 2057 Equity-based fr ee channels assignment f or secondary users in a cogniti v e radio netw ork Said Lakhal 1 , Zouhair Guennoun 2 1 Mohammadia School of Engineering, Mohammed 5 Uni v ersity in Rabat, Morocco 2 ERSC formerly kno wn as LEC, research Center E3S, Morocco Article Inf o Article history: Recei v ed May 31, 2018 Re vised No v 15, 2018 Accepted No v 23, 2018 K eyw ords: Cogniti v e radio netw ork Jain’s equity inde x Scheduler Channels allocation ABSTRA CT The present paper addresses the equity issue among the secondary users in a cogniti v e radio netw ork. After using a multi scheduler algorithm and a f airness metric namely Jain’ s Equity Inde x; we enhance the equity between the secondary users’ transfer rates by 0.64 in a v erage, relati v e to a pre vious w ork. Copyright c 2019 Institute of Advanced Engineering and Science . All rights r eserved. Corresponding A uthor: Said Lakhal, Mohammadia School of Engineering, Mohammed 5 Uni v ersity in Rabat, ERSC formerly kno wn as LEC, research Center E3S, Mohammadia School of Engineering, Ibn Sina A v enue, B.P 765, Agdal, Rabat, Morocco. Email: said.lakhal.rech@gmail.com 1. INTR ODUCTION In a cogniti v e radio netw ork (CRN) [1], the primary users (PUs) ha v e priority to use the s pectra, without pri v atization; while the secondary users (SUs), w ait the cessation of acti vities of some PUs, for trans- mitting data. The design of CRN e x ecutes four functions, by using one of four techniques, in the aims to reach at some objecti v es. These functions are called in the follo wing order [2, 3, 4]: spectrum sensing, spectrum management, spectrum mobility and spectrum sharing [5, 6, 7]. The Auctions, Game theory , Mark o vian queu- ing model and Multi-agent systems (MAS) represent the f amous used techniques for modeling a CRN [8, 9], all to achie v e some objecti v es, characterizing the performance of a CRN. These aims are e xpressed in terms of some quantities to maximize [10, 11, 12], such as: the equity , transfer rate and the spectrum use. These requirements are also e xpressed in terms of other quantities to minimize, lik e: the ener gy consumption [13], to e xtend the lifetime of electrical de vices; the interference [14, 15], to enhance the quality and quantity of transmission [8, 9]. The Figure 1 illustrates altogether the CRN functions, techniques, and objecti v es. The SUs’ pack et transmission phase be gins as soon as some channels are released by the PUs. Each of these SUs seeks to be the first to transmit. As a result, conflicts are created and the netw ork can be block ed, as well as no licensed user will be able to send their data. In front of this situation, the installation of a scheduler becomes essential, to manage the channel allocation for dif ferent SUs, based on performance criteria whose the equity represents an important component. This scheduler must tak e into consi deration the w ay of pack et transmission and the properties of the used equity metric. The w ay is e xplicit by the distrib ution of SUs on the free channels according to the time slots, and the properties of the metric are four: population and Scale independence, boundedness as well as Continuity . The authors of [6, 13] addressed the equity issues, based on a metric measurement. In the tw o w orks, the abo v e properties are not mentioned as well as the w ay of the pack et forw arding w as not clarified. In [5], the authors studied the equity by using the JEI as a metric, which satisfied the four properties, b ut J ournal homepage: http://iaescor e .com/journals/inde x.php/IJECE Evaluation Warning : The document was created with Spire.PDF for Python.
2058 r ISSN: 2088-8708 the y did not mak e a com parison with another w ork also the y treated the groups of SUs rather than the SUs themselv es. In [7, 16], the authors used one channel transmission. In [7], the standard de viation is adopted as metric, which not satisfies the abo v e four properties. In [16], the single channel transmission decreases the equity , despite the consideration of the JEI as a metric. In our present w ork, we tak e adv antage of the benefits of these w orks, and we impro v e them to remo v e their limit ations. Explicitl y , on one hand, we implement the multi scheduler algorithm in a multi channel netw ork, to produce the scheduling chain. On the other hand, we use JEI as a metric, since it satisfies the four properties. As a result, we impro v e equity by an a v erage of 0.64 for pre vious w ork. Figure 1. The functions, objecti v es and techniques of CRN The rest of this paper is structured as follo ws: Section 2 discusses some related w orks and our contri- b utions. Section 3 e xposes our approach. W e present the e xperimental results in section 4, and we conclude in section 5. 2. SCHEDULING AND EQ UITY CONCEPT : A LITERA TURE REVIEW 2.1. Scheduling The SUs and their pack ets appear randomly on the CRN. The y require the installation of a sched- uler , able to managing this flo w . This scheduler can be implemented in softw are or hardw are platform. It tar gets multiple purposes, depending on the priorities and constraints. F or e xample: the priorities can be e xpressed by the maximization of throughput or equity , while the constraints can be represented by the netw ork infrastructure and architecture. Se v eral pre vious w orks treated the throughput maximization problem [11, 17]. Based on constant input and output rates of queues [11], the authors e xposed an opportunistic scheduler to enhance the SUs’ transmission rates. By referring to the first-dif ference filt er clustering and correlation based PU modeling [17], the authors e xposed a QoS-based spectrum coordinator for the CR user cohabitation in or - der to achie v e high throughput and f airness. In addition, the equity criterion between the SUs transfer rates attracted much attention of researchers [13, 18, 5, 7]. So, by taking into account: the current and prior history of user e xperience, as well as the respect of QoS [13], the authors proposed a f airness approach, by using the JEI. Their aims are to determine the optimal po wer and rate distrib ution choices for each SU, while maintaining the f airness across all SUs. In other equity study [18], the authors presented a resource allocation algorithm, in order to m aximize the f airness. The y used a proportional f airness constraint, to assure that each SU can achie v e a required data rate, with QOS guarantees. Certainly , the adopted architecture af fects the netw ork performance. In this re g ard, we can distin- guish between tw o major architectures: distrib uted [19, 20, 21] and centralized [22, 7, 5, 19]. Both architec- tures are considered in [19]. The authors proposed an incenti v e-a w are spectrum sharing scheme, for taking in IJECE, V ol. 9, No. 3, June 2019 : 2057 2063 Evaluation Warning : The document was created with Spire.PDF for Python.
IJECE ISSN: 2088-8708 r 2059 the adv antages of these tw o architectures, and o v ercoming their weaknesses. The distrib uted aspect requires no central control entities, which can independently be implemented within a distrib uted spectrum mark et. By cons, the centralized aspect assigns the socially optimal contracts for all PUs and SUs, for attaining the eco- nomic rob ustness. In [20], the authors proposed a distrib uted clustering algorithm based on the soft-constraint af finity propag ation message passing model (DCSCAP). So, without depending on predefined common control channel (CCC), DCSCAP relies on the distrib uted message passing among the SUs, through their a v ailable channels, for applying the algorithm on lar ge scale of netw orks. In a centralized architecture, the authors of [22] proposed a h ybrid spectrum sensing method, after creating one of t h e most trusted spectrums sensing mechanism. The suggested model sho wed an impro v ement after comparison with v arious spectrum sensing methodologies. Figure 2. The operating of the mono-scheduler and multi-scheduler algorithms 2.2. Principles of the mono and multi scheduler algorithms In [7], the authors implemented a first algorithm, namely mono-scheduler, to assign the only free channel to dif ferent SUs. This algorithm produced a Scheduling String ( SS ) and used the standard de viation as a metric for e v aluating the f airness among the groups of SUs. Its comple xity is of order 2, in terms of the total number of pack ets. The same authors proposed in [5] another algorithm, as an e xtension of the first, namely multi-scheduler , with a comple xity of order 3. This second v ersion impro v ed the mono-scheduler in terms of the number of the free used channels. In the same paper , the y used the SS , the States matrix noted S , and the JEI to af fect the free channels to the SUs, based on the equity measure, between the groups of SUs. Both [5, 7], considered the f airness among the groups of SUs, b ut not between the SUs themselv es. Because of the importance of these tw o algorithms, i.e. mono-scheduler and multi-scheduler , in the present w ork; we propose to e xplain the operating principles. T o do this, we consider an e xample of CRN containing: (i) T w o groups of SUs: G 1 and G 2 , such as: G 1 has tw o SUs: S U 11 and S U 12 , each one has three pack ets; while G 2 has four SUs: S U 21 , S U 22 , S U 23 and S U 24 ; with tw o pack ets for each one as sho wn in Figure 2; (ii) Eight for both: number of PUs and that of channels; After the application of the mono-scheduler algorithm, we obtained: SS = ( G 1 ; 1)( G 2 ; 1)( G 1 ; 2)( G 2 ; 1) . The first component ( G 1 ; 1) of SS signifies that G 1 transmits one line of pack ets. This line cont ains tw o pack ets, because G 1 has tw o SUs. The second component ( G 2 ; 1) indicates that after the transmission of the first line of G 1 , G 2 transmits one line, which contains four pack ets, since G 2 has four SUs, and so on. On the other hand, the application of the multi-scheduler algorithm took tw o ar guments: SS and S . This last indicates the state of each channel, during each time slot. T o simplify the study , we considered that, the channels ha v e the same capacity . In this case, we were interested only , in the number of the free channels during each time slot, while all channels operated in the same manner . Therefore, S becomes a ro w v ector , containing in each component, the number of the free channels, during a gi v en time slot. Then, for the e xample illustrated in Figure 2, we can write: S = (3 ; 2 ; 3 ; 4 ; 3 ; 2 ; 1 ; 5) T . After applying the multi-scheduler algorithm for such e xample, we c o ul d distrib ute the pack ets, on the free channels, as sho wn in Figure 2. In [16], the authors treated the f airness between the transfer rates of SUs, rather than that betwe en the transfer rates of groups [5, 7]. The y are tw o Contrib utions of the present paper: Equity-based fr ee c hannels assignment for secondary ... (Said Lakhal) Evaluation Warning : The document was created with Spire.PDF for Python.
2060 r ISSN: 2088-8708 (i) Application of the multi-scheduler algorithm [5], for treating the SUs’ transfer rates rather than that of groups. (ii) Enhancement of the SUs’ f airness by 0.65, relati v e to [16]. 2.3. Equity concept In this w ork, we are interested in calculating the equity between the transfer rates of the SUs, after the application of a scheduler algorithm. In the literature, se v eral w orks ha v e treated the f airness c omputation, i.e. f airness metric, among the components of a v ector . These w orks ha v e also studied the properties of this metric. Let x = ( x 1 ; :; x i ; :; x n ) T be a v ector in R n + , with homogeneous components in terms of measurement unit. In [23], the authors distinguished between four properties of the f airness metric: P1, P2, P3 and P4. P1: Population size independence: The inde x should be applicable to an y number of components of x , finite or infinite. P2: Scale and metric independence: The metric should be independent of the scale of all components. P3: Boundedness: The inde x should be bounded by tw o finite v alues. P4: Continuity: An y slight change in this metric v alue, should sho w a change of at least one component v alue. The y proposed a ne w f airness metric namely JEI, which v erifies together these four properties: J E I ( x ) = " n X i =1 x i # 2 " n n X i =1 x 2 i # 1 . A v alue of J E I ( x ) close to 1 e xpresses that most of x components are close to their a v erage. By cons, if the y are dispersed around their a v erage, J E I ( x ) will be close to 0. 3. MODELING THE EQ UITY The y are man y parameters, which define the modeling of equity . Before be ginning this formulation, we prefer to e xpose these parameters in T able 2. T able 1. Symbols and Their Meanings Symbols Meanings m, n Number of PUs or channels, and number of current SUs, resp. MaxSUs, q j , MaxP ack Max number of SUs, size queue of S U j , Max number of pack ets in a queue, resp. P , Q , e V ector containing the size queue of each SU, v ector defined based on P , size of Q , resp. g j , G , S if Number of SUs in group G j , v ector of all g j , state of channel i during time slot f, resp. u f , u , s Number of free channels during time slot f, v ector of all v alues of u f , size of u , resp. QG i , t i , r i Number of pack ets of G i , time for sending all pack ets of G i , transfer rate of G i , resp. t ij , r ij T ime spent to transmit all pack ets of S U ij , transfer rate of S U ij , resp. P = ( q 1 ; :; q j ; :; q n ) T (1) W e note that during a time fraction, a SU may send one pack et or not. W e or g anize the SUs by groups [7], according to the number of pack ets; such as, a gi v en group, contains all SUs who ha v e the same number of pack ets. T o do this, we define a ne w v ector Q based on v ector P : Q = ( q 1 ; :; q j ; :; q e ) T ; q i 6 = q j ; 8 ( i 6 = j ; j ) 2 f 1 ; :; e g 2 ; ( e n ) ; G = ( g 1 ; :; g j ; :; g e ) T (2) W e ha v e m channels, and during each time slot, we can find a certain number of free channels. Lik e that, the state of the CRN is defined by the states of all channels. These states are or g anized in the matrix S : S if = 8 > < > : 1 if channel i is free ; during time slot f ; 0 if not : (3) The number of free channels during a time slot is stored in v ector: u = ( u 1 ; :; u f ; :; u s ) T (4) IJECE, V ol. 9, No. 3, June 2019 : 2057 2063 Evaluation Warning : The document was created with Spire.PDF for Python.
IJECE ISSN: 2088-8708 r 2061 During the time slot f, we ha v e u f free channels: u f = m X i =1 S if ; f 2 f 1 ; :; s g (5) The total number of pack ets of the group G i in noted QG i . It is obtained by summing the number of pack ets of all SUs form group G i . By using (2), we can write: QG i = q i g i (6) T o calculate the transfer rates of groups and those of SUs, we must kno w the necessary number of passing time slots, for sending all pack ets. Let t i and r i be the necessary number of passing time slots for sending all pack ets and the transfer rate of G i , resp. r i = QG i t 1 i = ( q i g i ) t 1 i (7) Let S U ij be the j th SU of G i . W e consider that S U ij needs t ij time slots, for sending all his pack ets. So, the transfer rate r ij of S U ij , will be gi v en by: r ij = q i t 1 ij (8) Since S U ij is a member of G i . Then, this last completes the transmission of his pack ets, only after the trans- mission of all pack ets of his SUs. Thus, we ha v e the follo wing inequality: t i ( g i 1) t ij t i ; 8 j 2 f 1 ; :; g i g (9) Let r and r be the v ectors containing all transfer rates, of all groups and SUs, respecti v ely . r = ( r 1 ; :; r i ; :; r e ) T ; r = ( r 11 ; :; r 1 g 1 ; : ; r i 1 ; :; r ig i ; : ; r e 1 ; :; r eg e ) T (10) J E I ( q ) = " n X i =1 q i # 2 " n n X i =1 q 2 i # 1 ; J E I ( QG ) = " e X i =1 QG i # 2 " e e X i =1 QG 2 i # 1 (11) J E I ( r ) = " e X i =1 r i # 2 " e e X i =1 r 2 i # 1 ; J E I ( r ) = " e X i =1 g i X k =1 r ik # 2 " n e X i =1 g i X k =1 r ik 2 # 1 : (12) 4. EXPERIMENT A TIONS W e consider four scenarios, containing tw o, three, four and v e groups of SUs, respecti v ely . After , we apply the mono and multi-scheduler algorithms. As a result, we deduct the JEI of the users’ rates, which are e xposed in Figures 3 and 4. In all the Figures, we can easily notice that the equities obtained by using our model are v ery important compared to those of the model [16]. On a v erage, this dif ference reaches 0.64, which is e xplained by the parallel transmission of se v eral pack ets via se v eral channels in our model. As a result, the users’ transfer rates are v ery close and the equities are v ery important. By cons, the model of [16] used a single transmission channel, therefore, the standard de viation of the users’ transfer rates is v ery important; then, the equities are v ery lo w . Figure 3. Groups’ equities, obtained by using the tw o models Equity-based fr ee c hannels assignment for secondary ... (Said Lakhal) Evaluation Warning : The document was created with Spire.PDF for Python.
2062 r ISSN: 2088-8708 Figure 4. SUs’ equities, obtained by using the tw o models 5. CONCLUSION In this w ork, we ha v e impro v ed the equity of a pre vious w ork, by using a ne w model. The performance impro v ement can be e xplained by the increase of the number of used channels processed by the multi scheduler algorithm. W ithout for getting the importa nce of the monoscheduler , which resides in the establishment of the scheduling chain. REFERENCES [1] Mitola J., ”Cogniti v e radio: an inte grated a gent architecture for softw are defined radio, Ph. D. dissertation, Ro yal Institute of T echnology (KTH), Sweden, pp. 8-13, 2000. [2] I.Ak yildiz et, al., ”NeXt generation/ dynamic spectrum access/ cogniti v e radio wireless netw orks A surv e y , Computer Netw orks, v ol. 50, pp. 2127-2159, 2006. [3] A.Khan et, al., ”Research Challenges of Cogniti v e Radio, IJER T , v ol. 1, 2012. [4] P .Bhattacharya et, al., ”Smart Radio Spectrum Management for Cogniti v e Radio, arXi v:1109.0257 [cs], 2011. [5] A.Idrissi and S.Lakhal, ”Equity between secondary users in a cogniti v e radio netw ork, Wseas, v ol. 13, pp. 90-98, 2014. [6] Y .Z.S.Maharjan et, al., ”Distrib uted spectrum sensing in cogniti v e radio netw orks with f airness considera- tion: Ef ficienc y of correlated equilibrium, Mobile Adhoc and Sensor Systems, pp. 540-549, 2011. [7] A.Idrissi and S.Lakhal, ”An algorithm for f airness between secondary users in cogniti v e radio netw ork, J A TIT , v ol. 8, 2013. [8] A.Garhw al and P .Bhattacharya, ”A suerv e y on dynamic spectrum acces techniques for cogniti v e ra- dio, ”arXi v preprint arXi v , pp. 1201-1964, 2012. [9] B.Benmammar et, al. ”A surv e y on dynamic spectrum acces techniques in cogniti v e radio net- w orks, ”IJCNIS, v ol. 5, pp. 68-79, 2013. [10] HT .Cheng and W .Zhuang, ”Simple channel sensing order in cogniti v e radio netw orks, ”IEEE JSA C, v ol. 29, pp. 676-688, 2011. [11] R.Ur g aonkar and M.Neely , ”Opportunistic Scheduling with Reliability Guar antees in Cogniti v e Radio Netw orks, IEEE transactions on mobile computing”, v ol. 8, pp. 766-777, 2009. [12] S.Li et, al., ”Maximizing System Throughput by Cooperati v e Sensing in Cogniti v e Radio Netw orks, IEEE/A CM T ransactions on Netw orking, v ol. 22, pp. 1245-1256, 2014. [13] L.Akter and B.Natarajan, ”Modeling F airness in Resource Allocation for Secondary Users in a Competi- ti v e Cogniti v e Radio Netw ork, W ireless T elecommunications Symposium IEEE, pp. 1-6, 2010. [14] D.Damodaram and T .V enkatesw arlu, ”Ef ficient Hardw are Architecture for Cyclostationary Detec- tor , ”Bulletin of Electrical Engineering and Informatics, v ol.5, no.3, pp. 340-346, 2016. [15] E.A.S.Kang and R.V ig, ”Impact of Ne xt Generation Cogniti v e Radio Netw ork on the W ireless Green Eco system through Signal and Interference Le v el based K Co v erage Probability , ”Indonesian Journal of Electrical Engineering and Informatics (IJEEI), v ol. 5, no.1, pp. 69-76, 2017. [16] S.Lakhal and A.Idrissi., ”Queues management of secondary users in a cogniti v e radio netw ork, in NGNS14, pp. 302-307,2014. [17] C.Berk et, al., ”QoS-A w are User Cohabitation Coordinator in Cogniti v e Radio Netw orks, IEEE Globe- com, pp. 1356-1361, 2012. [18] Y .Ma et, al., ”A Subcarrier -P air Based Resource Allocation Scheme Using Proportional F airness for Co- IJECE, V ol. 9, No. 3, June 2019 : 2057 2063 Evaluation Warning : The document was created with Spire.PDF for Python.
IJECE ISSN: 2088-8708 r 2063 operati v e OFDM-Based Cogniti v e Radio Netw orks, Sensors, v ol. 13, pp. 10306-10332, 2013. [19] Q.Liang et, al., ”A distrib uted centralized scheme for Short and Long T erm Spectrum Sharing with a Random Leader in Cogniti v e Radio Netw orks, ”IEEE JSA C, v ol. 30, pp. 2274-2284, 2012; [20] F .Y ao et, al., ”Distrib uted Clustering in Cogniti v e Radio Ad Hoc Netw orks Using Soft-Constraint Af finity Propag ation, Radioengineering, 2012. [21] S.Maharjan et, al., ”Distrib uted Spectrum Sensing in Cogniti v e Radio Netw orks with F airness Consid- eration, Ef ficienc y of Correlated Equilibrium, In IEEE International Conference on Mobile Ad-Hoc and Sensor Systems, pp. 540-549, 2011: [22] A.S.Khobrag ade and R.D.Raut, ”Hybrid Spectrum Sensing Method for Cogniti v e Radio, International Journal of Electrical and Computer Engineering (IJECE), v ol.7, no. 5, pp. 2683-269551, 2017. [23] Jain R et, al., ”A Quantiti v e Measure of F airness and Discrimination for Resource Allocation in Shared Computer Systems, Eastern Research Laboratory , Digital Equipment Corporation Hudson, v ol. 38, 1984. BIOGRAPHIES OF A UTHORS S. Lakhal obtained the diploma of application engineer in computer sciences in 1998, from the Uni v ersity Sidi Mohamed Ben Abdelah, Fes, Morocco, M.Sc. de gree in modelization in 2006, from Moha mmadia School of Engine ering. He is currently a researcher at the Labora- tory of Electronics and T elecommunications, Mohammadia School of Engineers (EMI), Rabat, Morocco. His current research interests are Computing, Radio cogniti v e, Algorithmic and com- ple xity , Modelization. Z. Guennoun recei v ed his engineering de gree in Electronics and T elecommunications from the Electronics and Electrical Montefiore Institute, ULG Lie ge, Belgium in 1987; his M.Sc. de gree in Communication Systems from the EMI School of Engineering, Rabat, Morocco in 1993; and his PhD de gree from the same school in 1996. He visited the Centr e for Communication Research (CCR) in Bristol Uni v ersity , UK, during the period of 1990-1994 to prepare a split PhD. Dur - ing 1988-1996 he w ork ed as an Assistant Lecturer in the EMI School of engineering, and from 1996 he is w orking in the same school as a Professor Lecturer . His fields of interest are digital signal processing, error control coding, speech and image processing. Currently in char ge of the laboratory of Electronics and T elecommunications (LEC) at EMI. IEEE member since 1990; and member of the Moroccan IEEE section e x ecuti v e committee. Equity-based fr ee c hannels assignment for secondary ... (Said Lakhal) Evaluation Warning : The document was created with Spire.PDF for Python.