A Research on Spectrum Allocation Using Optimal Power in Downlink Wireless system

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1 Iteratioal Research Joural of Egieerig ad Techology (IRJET) e-iss: Volume: 03 Issue: 04 Apr p-iss: A Research o Spectrum Allocatio Usig Optimal Power i Dowli Wireless system Hariom Patel, S.D.Gadhi 2, Dhairya Vyas 3 Master of Egieer,Dept. of Elect. & Comm. Eg., SPCE,Visagar,Gujarat,Idia 2 Assistace Professor, Dept. of Elect.SPCE,Visagar,Gujarat,Idia 3 Master of Egieer,Dept. of Elect. & Comm. Eg., PIET,Vadodara,Gujarat,Idia *** Abstract- A resource Allocatio Problem for spectrum sharig i wireless commuicatio system. Usig multiiput multi-output orthogoal frequecy divisio multiple ( MIMO-OFDM) is a very promisig techology for ehacig the flexibility ad efficiecy of cellular ad future commuicatio systems. A joit optimizatio problem for resource allocatio is solved by a combie scheme of multiple-iput multiple-output with orthogoal frequecy divisio multiple (MIMO-OFDM) ad used for broadbad wireless applicatios. The eergy efficiecy is also ey parameter i desigig ad evaluatig commuicatio system. we ca address the assigmet of subcarriers ad power allocatio to all users to optimize the sum of user average data rates, total available trasmitted power, ad proportioality amog users, subcarriers. We propose a algorithm that process subcarrier ad power allocatio simultaeously uder data rate costrait. Computatioally efficiet water fillig algorithm for multiuser OFDM. This algorithm is based o the multiuser water fillig theorem ad determies the subcarrier allocatio for a multiple access OFDM system, The preseted iterative algorithm performs well, also with a high umber of sub chaels. Key Words: Multiple-iput multipleoutput(mimo),power allocatio, water-fillig algorithm, Resource allocatio..itroductio ext geeratio wireless etwor target ubiquitous high data rates, efficiet resource (eg. Spectrum ad Power) usage ad ecoomical etwor deploymet give the fact that radio spectrum becomig a scare resource i wireless commuicatio system. With the ever icreasig demad for higher reliable data trasmissio ad various qualityof-service requiremets for emergig mobile services ad applicatios such as cotet sharig ad video streamig, mobile multimedia commuicatios are expected to be provided i a more effective ad efficiet way. From the wireless commuicatios perspective, chael variatio ad iterferece also challege system robustess. The Orthogoal Frequecy Divisio Multiple Access (OFDMA)has bee Proposed as a state of the art air iterferece techology to eable high spectrum efficiecy ad effectively combat Frequecy selective fadig. First the subcarrier allocatio algorithms assig the assig the subcarrier to the users, We cocetrate o the subcarrier allocatio based o the multiuser water fillig theorem. This maximizes the total bit rat uder the costrait of a maximum trasmissio power per user. The fudametal challege of resource allocatio lies i the scarcity of the available spectrum, the expasive servicig area, ad the large user umber. As a result, the same frequecy spectrum eeds to ofte be reused i multiple geographical areas or cells []. 2. THEORY OF BACKGROUD I[2]. eergy-efficiet ad fair resource allocatio is ivestigated i a dowli OFDM-based mobile commuicatio system. Give a subcarrier assigmet, the bisectio-based optimal power allocatio (BOPA) is proposed at first, which achieves the maximum EE ad guaratees proportioal data rates for users. The, a twostep subcarrier assigmet is desiged to avoid uaffordable computatioal complexity of exhaustive search. I the first step, the estimated eergy-efficiet trasmit power is foud via the assumptios o flat fadig ad subcarrier sharig. I the secod step, the traditioal spectral-efficiet subcarrier assigmet (SESA) is itroduced to complete the badwidth resource allocatio amog users. Although the two-step subcarrier assigmet is suboptimal due to the fact that the optimizatio is doe idepedetly i two separate steps, umerical results demostrate that its performace is very close to the optimum. This paper eergy-efficiet solutio ad the traditioal spectral-efficiet policy ad observes that they are similar with each other i the low chael-gai-to-oise ratio (CR) regime. 206, IRJET Impact Factor value: 4.45 ISO 900:2008 Certified Joural Page 255

2 Iteratioal Research Joural of Egieerig ad Techology (IRJET) e-iss: Volume: 03 Issue: 04 Apr p-iss: I[3] this paper, we address the assigmet of subcarriers ad power to all users to optimize the sum of user average data rates subject to costraits o sigal to oise ratio, total available trasmitted power, ad proportioality amog users, subcarriers. We compare the proposed rate adaptive scheme that maximizes the average data rate of multiuser multi iput multi output orthogoal frequecy divisio multiplexig (MU MIMO-OFDM) systems with others coversioal schemes. The total power allocatio scheme for MU OFDM system is proposed o covex optimizatio eviromet. I a rate adaptive resource-allocatio scheme, which icludes adaptive power distributio, subcarrier allocatio accordig to istataeous chael coditios, is proposed for multiuser MIMO-OFDM system.simulatio results show the large performace improvemet of proposed rate adaptive scheme over other adaptive ad fixed allocatio schemes. The wor i [4], a adaptive resource allocatio methodology is proposed for cellular orthogoal frequecy divisio multiplexig systems i a multiuser eviromet. The proposed method is featured as a low-complexity algorithm that ivolves ot oly adaptive modulatio, but also adaptive multiple-access cotrol ad cell selectio. Specifically, a multiuser subcarrier-ad-bit loadig scheme is developed to maximize the spectral efficiecy. Besides, a dyamic cell selectio scheme is proposed to deal with the problem of overloadig ad o uiform traffic desity. umerical results show that the preseted algorithm offers sigificat improvemet i spectral efficiecy due to the successful exploitatio of chael variatio, multiuser diversity, ad iter-cell diversity. I[5], a comprehesive resource allocatio scheme has bee proposed for dowli multi-cell OFDMA etwors. The scheme icludes radio resource ad power allocatios, which are implemeted separately to address the formulated problem with reduced complexity. The optimal solutio is obtaied by the Lagrage method ad The simulatio results show that the proposed scheme ca achieve sigificat performace improvemet for cell-edge users ad desirable performace for cell-cetre users compared with the referece schemes Problems i above methods Preseted wireless commuicatio system are required to support a variety of high speed data commuicatio services for its uses, such as video streamig ad cloud based services. A limited amout of resources,i.e,power ad badwidth are available at the trasmitter, Rate adaptio achieves higher goodput by combatig chael variability, which is commo to all wireless commuicatio system due to factors such as fadig mobility ad multiuser iterferece due to umber of user icreases system also scalable. I some of the paper they use complex algorithm for cellular wireless system which is hard to uderstad ad implemet. 3.. PROPOSED METHOD Step-.Water Fillig Algorithm Model: The process of water fillig algorithm is similar to pourig the water i the vessel. The ushaded portio of the graph represets the iverse of the power gai of a specific chael. The Shadow portio represets the power allocated or the water. The total amout o water filled (power allocated) is proportioal to the Sigal to oise Ratio of chael As show i the followig formula Power allocated Pt i Hi Chael Hi () Where Pt is the power udget of MIMO system which is allocated amog the differet chaels ad H is the chael matrix of system. The capacity of a MIMO is the algebraic sum of the capacities of all chaels ad give by the formula below. Capacity= i log ( Powerallocated * H ) 0 (2) We have to maximize the total umber of bits to be trasported.as per the scheme followig steps are followed to carry out the water fillig algorithm. Algorithm Steps:-. Tae the iverse of the chael gais. 2. Water fillig has o uiform step structure due to the iverse of the chael gai. 3. Iitially tae the sum of the total power Pt ad the iverse of the chael gai. It gives the complete area i the water fillig ad iverse power gai Pt i Hi (3) 4. Decide the iitial water level by the formul give below by taig the average power allocated Pt i Hi Chael (4) 5. The power values of each subchael are calculated by subtractig the iverse chael gai of each chael. Pt i Hi Chael Hi (5) 206, IRJET Impact Factor value: 4.45 ISO 900:2008 Certified Joural Page 256

3 Iteratioal Research Joural of Egieerig ad Techology (IRJET) e-iss: Volume: 03 Issue: 04 Apr p-iss: I case the power allocated value become egative stop iteratio. Step-2 Subcarrier Reallocatio: The subcarrier allocatio solutio from Step does ot guaratee the fulfillmet of every user s rate costraits i(5). Therefore, the iitial solutio eeds to be adjusted so that more subcarriers are allocated to the users whose miimum rate costraits have ot bee satisfied yet. To achieve a optimum feasible solutio i the ed, the followig coditios must be satisfied durig the reallocatio process. ) A subcarrier that was origially assiged to user caot be reallocated too their users if there allocatio will cause the violatio of user s data rate requiremet. That is, if.. 2) Each subcarrier reallocatio should cause the least reductio i the overall throughput. W={,...,} = p c r Calculate,, ( c * c, ) e. W c, =+ Y umber of satisfied costraits icreases mootoically i the subcarrier reallocatio process, so that the umber of reallocatio operatios is fiite ad divergece is avoided. Coditios 2 ad 3 ca be realized by lettig e K, ( c * c,, ) c, (6) Be the cost fuctio of reallocatig subcarrier to user istead of the origially assiged user.such fuctio is proportioal to the decrease i the overall throughput, ad iversely proportioal to the icrease of the data rate of user which affects the umber of reallocatio operatios. Subcarrier reallocatio is carried out o a user-by-user basis for all users whose rate costraits have ot bee satisfied i Step. Cosider user for example. I each stage, the subcarrier with the lowest cost fuctio, deoted by, is selected. will be allocated to user, if this reallocatio does ot cause,otherwise, it will ot be reallocated, ad a ew will the be idetified from the rest of the subcarriers. This subcarrier reallocatio process repeats for user util its data rate requiremet is satisfied. The detailed algorithm is depicted i Fig. 2. I the figure, A-B deotes the set differece operatio of set A ad B, which produces a ew set { } Liewise, W deotes the set of subcarriers that ca be selected for reallocatio. Subcarrier reallocatio is equally importat i Power Allocatio So usig Proposed algorithm for allocatio. =argmie e, W R c r * ', ' * * ' W=W-{ } 3. Simulatio Results I this sectio, the performace of the power allocatio as show i fig.first of all, we assume some parameters after that we allocated spectrum usig Proposed algorithm due to optimal spectrum allocatio we fid capacity,hear we assume system for user =5 Table -:Simulatio Parameters Multiuser Dyamic Allocatio Y Target BER oise Spectral Desity 0-4 P, = p 0 *, W=W-{ } umber of Users umber of Subchaels 6 5 Fig. : Subcarrier reallocatio 3) The umber of reallocatio operatios should be ept as low as possible. The first coditio esures that the Rate Reuiremet Fadig eviromet 23bits/sec/Hz Rayleigh Fadig 206, IRJET Impact Factor value: 4.45 ISO 900:2008 Certified Joural Page 257

4 Iteratioal Research Joural of Egieerig ad Techology (IRJET) e-iss: Volume: 03 Issue: 04 Apr p-iss: Total Power W Badwidhth MHz Fig -5: Amout of power required by subchael after reallocatio. Fig.2: Water Fillig Algorithm Model Fig -6: Reallocated Chael respose i differet sub chaels Fig -3: Resultig bit allocatio after subcarrier ad bit allocatio. Fig -4: Resultig SR i Differet sub chae Fig -4: Resultig SR i Differet sub chael. Fig -7 Usig MIMO-OFDM we get optimized capacity of = 6 subchael ad U = 5 users. 206, IRJET Impact Factor value: 4.45 ISO 900:2008 Certified Joural Page 258

5 Iteratioal Research Joural of Egieerig ad Techology (IRJET) e-iss: Volume: 03 Issue: 04 Apr p-iss: COCLUSIOS I this paper, we have preseted the MIMO OFDM model usig MATLAB. The results of simulatio form the model will eable the researches to choose water fillig algorithm for their requiremets. MIMO has helped to ISI problem. The Results idicates that the Capacity is ehaced sigificatly by trasmittig the differet stream of data through differet ateas at same frequecy. The water fillig algorithm allocates the more power to subcarrier for that oise level is high. Capacity is icreased with icrease i umber of atea also we get result from power allocatio we assig subchael for efficiet spectrum by usig Proposed Algorithm which allocate more subchael ad remove oise. [7] A. Gorohov, et al., "Receive atea selectio for MIMO spatial multiplexig: theory ad algorithms,"sigal Processig, IEEE Trasactios o, vol. 5, pp , 2005 [8] H. Bolcsei, "MIMO-OFDM wireless systems: basics, perspectives, ad challeges," Wireless Commuicatios,IEEE, vol. 3, pp. 3-37, [9]C.Y.Wog,R.S.Cheg,K.B.Letaief,adR.D.Murch, Multiuse r OFDM with adaptive subcarrier,bit, ad power allocatio, IEEE J.Sel. Areas commu. vol.7, o.0 pp ,oct. 999 ACKOWLEDGEMET I feel it my boude duty to express my hearty thafuless to the etire staff of Electroics & Commuicatio Departmet for their utirig cosistet cooperatio. REFERECES [] Roald Y. Chag ad Zhifeg Tao Multicell OFDMA Dowli Resource Allocatio Usig a Graphic Framewor IEEE Tras. Vehicular Techo,vol. 58, o. 7, pp , Sep [2] Zhayag Re, Shazhi Che, Bo Hu, ad Weiguo Ma Eergy-Efficiet Resource Allocatio i Dowli OFDM Wireless Systems With Proportioal Rate Costraits IEEE Tras. Vehicular Techo, vol. 63, o. 5, pp Jue 204. [3] Dushyat Kumar Tiwari ad Maish Trivedi A Efficiet Subcarrier ad Power Allocatio Scheme for Multiuser MIMO-OFDM System Iteratioal Joural of Recet Developmet i Egg. ad Techo. vol. 2, pp32-39, March 204. [4] Yig Ju Zhag ad Khaled Be Multiuser Adaptive Subcarrier-ad-Bit Allocatio With Adaptive Cell Selectio for OFDM Systems IEEE Tras. Wireless Commuicatios, vol. 3, o. 5, pp ,sept [5] Yiwei Yu, Ery Dutiewicz, Xiaojig Huag, ad Marus Muec Dowli Resource Allocatio for ext Geeratio Wireless etwors with Iter-Cell Iterferece IEEE Tras. O Wireless commuicatio, vol. 2, o. 4, pp , April 203 [6] W. Rhee ad J.M. Cioffi, Icrease i capacity of multiuser OFDM system usig dyamic Subchael allocatio, i Proc. IEEE Vehicular Techology Cof., Toyo, Japa, May 2000, pp , IRJET Impact Factor value: 4.45 ISO 900:2008 Certified Joural Page 259