Resource Allocation Algorithm with Dynamic Subcarrier Assignment in OFDMA-based Wireless Networks

Abstract

AbstractThe allocation of available resources is one of the main issues in multi-user systems. Dependence of system capacity on radio link quality is an additional obstacle of efficient resource allocation in wireless networks. Combinations of two opposite approaches—fair resource allocation and system capacity maximization are used to solve this problem in practice.This paper proposes a resource allocation method that is primarily based on assigning almost an equal bandwidth to all users. System capacity maximization is achieved by selecting the subcarriers with the best SNR values. This algorithm was developed for orthogonal frequency division multiple access (OFDMA) wireless systems. Resource allocation is done at the subcarrier level according to the weight factor that had been calculated for each user. Frequency hopping was used to increase frequency diversity and to make the system more robust to disturbance. Frequency hopping pattern is determined dynamically on the basis of SNR value of each subcarrier.The results of the proposed algorithm are compared with the water filling (WF) and proportional fairness (PF) methods. The influence of various data traffic classes on system throughput and resource allocation is also described.U sustavima s više korisnika jedno od glavnih pitanja je kako podijeliti raspoložive resurse. Kod radio mreža dodatni otežavajući faktor predstavlja promjenjivost kapaciteta sustava ovisno o kvaliteti radio veze. U praksi se za raspodjelu resursa obično koriste algoritmi koji su kombinacija dvaju oprečnih pristupa, fer raspodjele resursa i maksimizacije kapaciteta sustava.U ovom radu predložena je metoda primarno bazirana na fer raspodjeli resursa. Maksimizacija kapaciteta sustava ostvarena je odabirom podnosilaca s najboljim mogućim SNR-om. Algoritam je razvijen za sustave bazirane na OFDMA. Dodjela resursa korisnicima vrši se na razini pojedinog podnosioca prema izračunatom težinskom faktoru za svakog korisnika posebno. Kako bi se povećao frekvencijski diverziti i sustav učinio otpornijim na smetnje, uvedeno je frekvencijsko skakanje prema dinamički određenom predlošku. Predložak se formira na osnovu SNR vrijednosti određene po svakom podnosiocu.Rezultati predloženog algoritma uspoređeni su s WF (water filling) i PF (proportional fairness) algoritmima. Prikazan je utjecaj različitih klasa prometa na prijenosni kapacitet i raspodjelu resursa sustava.Key words: OFDMAQoSResource allocationSubcarrier schedulingKljučne riječi: OFDMAQoSraspodjela resursaraspoređivanje podnosilaca Additional informationNotes on contributorsVitomir ŠebaVitomir Šeba received B.Sc. in electrical engineering from the Faculty of Electrical Engineering, University of Zagreb, Croatia in 1997. He is now a doctoral student with the same academic institution. His research interests include resource allocation, QoS, modulation techniques and next generation wireless communication systems.Borivoj ModlicBorivoj Modlic was born in Zagreb, Croatia in 1950. He received B.Sc., M.Sc. and Ph.D. in Electrical Engineering in 1972, 1974 and 1976 respectively from University of Zagreb, Croatia. He started his professional career at Department of Radio-frequency Engineering (presently Department of Wireless Communications), Faculty of Electrical Engineering and Computing, University of Zagreb where he has worked ever since, now as full professor in wireless communications. He is the co-author of six university textbooks and editor of the Engineering Handbook. His research interests are: signal processing in communications, especially modulation methods, wireless access systems and electromagnetic compatibility.Gordan ŠišulGordan Šišul received B.Sc., M. Sc. and Ph.D. in electrical engineering from the Faculty of Electrical Engineering, University of Zagreb, Croatia in 1996, 2000 and 2004 respectively. He is currently employed as an Associate Professor at the same Faculty. His academic interests include wireless communications, signal processing applications in communications, modulation techniques and radio propagation.