# A Multi-Carrier Waveform Design for 5G and beyond Communication Systems
## 2 Related Work
The FBMC waveform is one of the most investigated waveforms that offers a good frequency domain localization. This technique extends the pulse duration in the time domain along with optimally designed pulse shaping filters to achieve good frequency domain localization. The filters are designed to be applied at the sub-carrier level. This increases the flexibility of the filters and they can be used in various channel conditions and in different use cases. The FBMC can be used in different ways such as filtered multitoned FBMC and cosine modulated multitoned. However, the preferred method to implement FBMC is by using staggered modulated multitoned (SMT). SMT is also known as offset quadrature amplitude modulation FBMC (OQAM-FBMC) [18]. The ability of SMT to handle interference while handling dense symbol placement in frequency-time lattice makes it a very strong candidate for 5G networks. In OQAM-FBMC, the orthogonality between different sub-carriers is ensured through OQAM, which leads to better spectral efficiency when compared to CP-OFDM. Moreover, this technique is very suitable for mobile carriers as its well localized sub-carriers makes it very much immune to Doppler effects. On the other hand, similar to other techniques, this technique is also countered by various challenges. Some of these challenges include poor integration with MIMOs and high intrinsic interference that results from OQAM signaling [19]. The multi-carrier based non orthogonal multiple access (MC-NOMA) waveform is also one of the finest waveforms proposed in the literature to support a massive number of different users and application classes for 5G communication networks. The MC-NOMA allows overlaps in times and frequency between signals from different users. In order to eliminate the undesired interference, signals are transmitted with different power levels and a successive interference cancellation (SIC) is carried out at the receiver [20]. The MC-NOMA waveform offers significant benefits as compared to the conventional CP-OFDM waveform and is considered to be more powerful due to their reduced spectral side-lobe levels. Nevertheless, the MC-NOMA also has some implementation issues such as error propagation, channel estimation errors, complexity and nonsupport for short packet burst [21]. The UFMC is the most promising waveform proposed for the 5G communication network due to its short packet burst communication support. The UFMC waveform inherits all the advantages from FBMC and OFDM, respectively, while avoiding their drawbacks [5]. The UFMC is a technique that uses the sub-band filtering technique, where filtering is performed with a fixed granularity of frequency domain. Likewise, the filtering process reduces the out-of-band (OOB) emissions [22]. If we look at the side lobe, compared to OFDM, UFMC has a much lower side lobe. Therefore, UFMC is comparatively more resilient than OFDM, when it comes to interferences between sub-carriers that arise from the frequency shift in the channel. It is worth mentioning that although UFMC is much better at suppressing OOB emission compared to OFDM, it has high computational complexity. However, if the UFMC is based on a Finite Impulse Response (FIR) filter rather than the conventional method, it has lower computational complexity and at the same time the impact of OOB emissions is also very low [23]. In UFMC, the use of CP depends upon the desired ISI. With the use of CP, the ISI goes down and vice versa. Normally, CP is not used in standard UFMC systems as the transition regions provide protection against ISI. To achieve orthogonality in the frequency domain, the signals are sent one after the other in time domain. However, the absence of CP in UFMC waveform requires more complicated receiver designs as compared to the CP-OFDM waveform [24]. Moreover, the use of sub-bands in the UFMC waveform gives better time localization.