International Journal of Recent Technology and Engineering (IJRTE) ISSN: 2277-3878, Volume-7, Issue-6, March 2019 1682 Published By: Blue Eyes Intelligence Engineering & Sciences Publication Retrieval Number: E2087017519/19©BEIESP Spectral Efficiency Analysis of Multicarrier Scheme for 5G Communications Patteti Krishna Abstract: Filter bank multicarrier (FBMC) system is the one of the favorable waveform candidates to satisfy the demands of future cellular and wireless communication networks. FBMC use prototype filters with lower side lobe and faster spectral decay, which enables it to have the advantages of reduced out-of-band energy and theoretically higher spectral efficiency (SE) compared to conventional multicarrier scheme i.e., orthogonal frequency division multiplexing (OFDM). These systems also have the ability to facilitate aggregation of non-adjacent bands to acquire higher bandwidths for data transmission. They also support asynchronous transmissions to reduce signaling overhead to meet the ever increasing demand of high data rate transmission in future wireless networks. In this paper, we discuss the fundamental difference between multicarrier scheme such as FBMC and conventional OFDM system along with a comparison between the two techniques and also evaluated the computational complexity of OFDM and FBMC systems. Key words: FBMC, OFDM, computational complexity and SE. I. INTRODUCTION 4G wireless communication network is currently massively rolled-out but it is also known that it will quickly reach its limits. The higher peak data rates have been increasing extremely over the past few years. To achieve this requirement is to use wide bandwidth but wideband signals are susceptible to frequency selective fading from the multipath fading channels. Single carrier transmission systems are not well suitable for this case. The multicarrier modulation(MCM) techniques is the one of most important techniques that can vanish the fading effect by converting wideband signals into number of narrowband signals, so frequency selective fading very effectively handled[1,7]. Orthogonal Frequency Division Multiplexing (OFDM) is MCM techniques used n various existing systems, such as WiFi, IEEE 802.11 standards, Wimax (Worldwide Interoperability for Microwave Access), Long Term Evolution (LTE), and LTE-advanced etc [2-3]. OFDM is more popular due to robustness to multipath fading, its high spectral efficiency (SE) due to the closely spaced orthogonal subcarriers and its ability to avoid both inter symbol interference (ISI) by using sufficient guard time and inter- carrier interference (ICI) by appending a cyclic prefix (CP) in the guard interval. OFDM suffers from remarkable Revised Manuscript Received on March 25, 2019. Patteti Krishna, Professor, Department of Electronics and Communication Engineering, Jayamukhi Institute of Technological Sciences, Narsampet, Warangal, Telangana, India spectral leakage due to rectangular pulses uses and it has poor frequency localization techniques. Therefore, OFDM requires a large guard bands to preserve nearby channels and also decay in SE of the system. FBMC system is one of the promising candidate waveforms to satisfy the requirements of future wireless communication and networks. FBMC system employ prototype filter and it is well localized both in time and frequency that enables to increasing SE and better spectral containment [5-8]. In this paper, we discuss the fundamental difference between multicarrier scheme such as FBMC and conventional OFDM system along with a comparison between the two techniques and also evaluated the computational complexity of OFDM and FBMC systems. Despite various advantages over conventional OFDM systems, there are also some open challenges in FBMC that needs attention to make it viable for practical applications. In this work, the primary research objective is to address some of the critical challenges in FBMC systems to make it a strong waveform candidate for future wireless networks. The first challenge is related to the SE of the FBMC system. Although, FBMC has higher SE compared to conventional OFDM system is use prototype filter that ensures ISI and ICI are avoided without the use of CP. However, FBMC systems suffers from long filter tails which may reduce the SE of the system. These long tails results from the fact that transmit filtering affect the localization of FBMC system in time domain. This reduces the actual efficiency of the system due to the filter transients when passing the transmit signal through the polyphase filter. The transmission efficiency η can be dropped by the following proportion. 1 M M K     where M is the number of symbols per transmission block and K is the length of each prototype filter. Although, this overhead can be negligible for long transmission blocks. However, this overhead can be significant when the transmitted data is divided into shorter blocks. II. OFDM vs. FBMC FBMC is an OFDM based multicarrier scheme that uses offset QAM for modulating each sub-carrier and utilizes a specially designed filter in time and frequency domain. The ability to achieve superior SE and robustness against multipath frequency selective fading channels without CP,