The progression in thefield of mobile communication is easily determinable by looking at theproliferation of data rate due to rapid growth in wireless technology .Thereare new applications arising whose requirement go beyond the throughput. Theevolution of each generation has its own advantage and limitation. Thephenomenal growth in wireless technology has contributed towards thedevelopment of next generation (5G), which provides higher data service formore number of user simultaneously.5G deals with the challenges such as veryhigh data rate, very low latency, mobility, very dense crowds of users, verylow energy and cost.
These challenges need not to be addressed simultaneously,it varies depending on the application, for instances Tactile internet requirelow latency, Machine Type Communication (MTC) require lower side lobe andhigher throughput for bit pipe communication. In order to achieve thesechallenges the primary requirement relies on the physical layer.Multicarrier modulationtechnique has a greatest influence in wireless communication in terms ofperformance. The ultimate challenge of wireless communication is to providehigher data rate with better user mobility and low latency. A few solutionshave been proposed to meet these challenges such as small cell, channelprediction, multicell channel estimation, distributed synchronization andmulticarrier modulations. In particular multicarrier modulation technique isconsidered to be promising solution to overwhelm these challenges.Traditional (singlecarrier) modulation technique fails to support these issues. Thus multicarriermodulation is adopted for current wireless technology.
Orthogonal frequencydivision Multiplexing (OFDM) is most widely adopted for current wirelesstechnology due to its attractive features like Immunity to selective fading,resilience to interference and low complexity, these features has made OFDM ascandidate for 4G. Despite of its advantages, it possess certain drawbacks suchas requirement of guard band in order to avoid ISI, use of CP (Cyclic Prefix)limits the spectrum efficiency. Addition to this PAPR is one of the biggest hindrancesthat affect the performance. With the aim of achieving the future wirelessrequirement researches are contributing their work on modulation techniquesthat has explored to the development of some of new modulation technique like FBMC(Filtered Bank Multi Carrier), UFMC (Universal Filtered Multi Carrier) and GFDM(Generalized Frequency Division Multiplexing).In FBMC pulse shaping operationis performed per subcarrier in individual manner which helps in reduction of OOB(Out Of Band), with cost of long filter length. Whereas in UFMC pulse shapingis performed per subcarrier which reduces OOB in addition with reduced filterlength. GFDM generalizes the OFDM, modulation is performed in block structurethat consists of K subcarrier and M subsymbol.
It offers good spectralefficiency compared to OFDM since single CP is utilized for entire block,obviously it also provide reduced OOB. On consideringthe future wireless communication (5G), it becomes necessary to find the systemwith flexible physical layer that solves the challenges that 5G possess. Onesuch solution is OFDM alternatives, which has been discussed above. Instead ofselecting one specific alternative for each requirement, it will be desirableto use single multicarrier modulation technique that can be easily reconfigureddepending on needs. In this case GFDM can be considered as a general solutionto future wireless communication (5G) which offers the flexibility ofreconfiguration. Similar to OFDM, GFDM also suffers from few drawbacks such asself-induced interference due to subcarrier based pulse shaping this may alsoaffect the BER performance, constructiveaddition of subcarrier may lead to produce high amplitudes which results inPAPR.
So as to overcome these drawbacks few solution has been adopted. Forreducing the interference some of the techniques like channel estimation,self-interference cancellation technique at receiver and use of pilot symbolsare being employed .Whereas techniques like SLM,PTS, clipping, filtering and precoding are aimed at reducing PAPR. Among thesetechniques precoding technique is considered to be a promising way to resolvePAPR as well as interference issue, and also it preserves the originality of signal.In general precoding technique is classified as linear and nonlinear precoding.Linear precoding technique is capable of yielding reasonable performance andnonlinear precoding technique yields considerably better performance. Linearprecoding techniques include channel inversion, block diagonalization andtransformed based precoding.
Nonlinear precoding includes dirty paper codingand Tomlinson-Harashima (TH) precoding. With regard to the future wirelesscommunication requirement it is preferable to employ transform based precoding,since it involves the process of transforming the data before transmissionwhich in turn provides high speed transmission. Some of the transformed basedprecoding is as follows (i) Discrete Fourier Transform (DFT) (ii) WalshHadamard Transform (WHT) (iii)CAZAC transform (iv) Discrete Hartley Transform (DHT) and (v) Zadoff-chu MatrixTransform (ZCMT). Added to precoding techniques, variation in filter parametersmay also influence the PAPR.