The GFDM generalizes the OFDM, modulation is performed in

The progression in the
field of mobile communication is easily determinable by looking at the
proliferation of data rate due to rapid growth in wireless technology .There
are new applications arising whose requirement go beyond the throughput. The
evolution of each generation has its own advantage and limitation. The
phenomenal growth in wireless technology has contributed towards the
development of next generation (5G), which provides higher data service for
more number of user simultaneously.5G deals with the challenges such as very
high data rate, very low latency, mobility, very dense crowds of users, very
low energy and cost. These challenges need not to be addressed simultaneously,
it varies depending on the application, for instances Tactile internet require
low latency, Machine Type Communication (MTC) require lower side lobe and
higher throughput for bit pipe communication. In order to achieve these
challenges the primary requirement relies on the physical layer.

Multicarrier modulation
technique has a greatest influence in wireless communication in terms of
performance. The ultimate challenge of wireless communication is to provide
higher data rate with better user mobility and low latency. A few solutions
have been proposed to meet these challenges such as small cell, channel
prediction, multicell channel estimation, distributed synchronization and
multicarrier modulations. In particular multicarrier modulation technique is
considered to be promising solution to overwhelm these challenges.

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Traditional (single
carrier) modulation technique fails to support these issues. Thus multicarrier
modulation is adopted for current wireless technology. Orthogonal frequency
division Multiplexing (OFDM) is most widely adopted for current wireless
technology due to its attractive features like Immunity to selective fading,
resilience to interference and low complexity, these features has made OFDM as
candidate for 4G. Despite of its advantages, it possess certain drawbacks such
as 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 hindrances
that affect the performance. With the aim of achieving the future wireless
requirement researches are contributing their work on modulation techniques
that 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 operation
is 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 shaping
is performed per subcarrier which reduces OOB in addition with reduced filter
length. GFDM generalizes the OFDM, modulation is performed in block structure
that consists of K subcarrier and M subsymbol. It offers good spectral
efficiency compared to OFDM since single CP is utilized for entire block,
obviously it also provide reduced OOB.

On considering
the future wireless communication (5G), it becomes necessary to find the system
with flexible physical layer that solves the challenges that 5G possess. One
such solution is OFDM alternatives, which has been discussed above. Instead of
selecting one specific alternative for each requirement, it will be desirable
to use single multicarrier modulation technique that can be easily reconfigured
depending on needs. In this case GFDM can be considered as a general solution
to future wireless communication (5G) which offers the flexibility of
reconfiguration. Similar to OFDM, GFDM also suffers from few drawbacks such as
self-induced interference due to subcarrier based pulse shaping this may also
affect the BER performance, constructive
addition of subcarrier may lead to produce high amplitudes which results in
PAPR.So as to overcome these drawbacks few solution has been adopted. For
reducing the interference some of the techniques like channel estimation,
self-interference cancellation technique at receiver and use of pilot symbols
are being employed .Whereas techniques like SLM,
PTS, clipping, filtering and precoding are aimed at reducing PAPR. Among these
techniques precoding technique is considered to be a promising way to resolve
PAPR 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 and
nonlinear precoding technique yields considerably better performance. Linear
precoding techniques include channel inversion, block diagonalization and
transformed based precoding. Nonlinear precoding includes dirty paper coding
and Tomlinson-Harashima (TH) precoding. With regard to the future wireless
communication requirement it is preferable to employ transform based precoding,
since it involves the process of transforming the data before transmission
which in turn provides high speed transmission. Some of the transformed based
precoding is as follows (i) Discrete Fourier Transform (DFT) (ii) Walsh
Hadamard Transform (WHT) (iii)
CAZAC transform (iv) Discrete Hartley Transform (DHT) and (v) Zadoff-chu Matrix
Transform (ZCMT). Added to precoding techniques, variation in filter parameters
may also influence the PAPR.