International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 05 | May -2017
p-ISSN: 2395-0072
www.irjet.net
Waveform Contenders of 5G Technology PRAMITI PARASHAR1, MODI RISHABHKUMAR N2 1ME-CSE, 2ME-CSE,
L D COLLEGE OF ENGINEERING L D COLLEGE OF ENGINEERING
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Abstract - There are different multiplexing techniques
which are used in different mobile networks and wireless technologies. The most emergent and used wireless technologies now-a- days are 3G and 4G, also termed as LTE (Long Term Evolution). The most efficient multiple access technique for wireless technologies is OFDM, which has been adopted for 3G and also 4G-LTE. Now as the technology is being advanced to 5G, there are some drawbacks of OFDM so the new different filtering techniques are the emerging waveform contenders for 5G wireless technology which are FBMC, UFMC & GFDM. All the three techniques have been discussed here in this paper.
Fig.1:Orthogonality in OFDM
Key Words: OFDM, FBMC, UFMC, GFDM
The advantages of OFDM are as follows:
1.INTRODUCTION
1.
The different multiplexing techniques which are very efficient are OFDM and CP-OFDM (Cyclic Prefix OFDM). Cyclic Prefix is the copy of tail of the given data symbol which works as the guard band. This Cyclic Prefix is applied to the OFDM symbol and creates redundancy in the symbol, due to which the bandwidth requirement increases which is a drawback. So, to use less bandwidth new different techniques for filtering and processing have been adopted for 5G wireless technology. These different filtering techniques are FBMC, UFMC, GFDM. In this paper all the three techniques have been discussed and the reasons why OFDM is not used as the access technique for 5G has also been discussed.
2. 3.
4.
1.2 LIMITATIONS OF OFDM The limitations of OFDM are as follows: 1.
2.
1.1 OFDM(ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING) 3.
OFDM is an access technique which is considered the most efficient access technique for the wireless technologies. It is a multicarrier transmission scheme which divides the bandwidth into different sub-channels known as subcarriers so as to multiplex in both time and frequency domain. In OFDM the sub-carriers are spaced at Δđ?‘“=1/đ?‘‡đ?‘†đ?‘Śđ?‘šđ?‘?đ?‘œđ?‘™ which is known as orthogonality. The fig 1 shows the orthogonality in OFDM.
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The spectrum efficiency of OFDM based system is considerably good. It is robust against multipath propagation. It has a less complex receiver. Multiple user scheduling advantage
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Cyclic Prefix Overhead: The added Cyclic Prefix adds redundancy to the transmission scheme which needs more bandwidth. Sensitivity to Frequency and Timing Offsets: In OFDM it is considered that the transmitting and receiving frequencies are the same. So the orthogonality looses with the change in frequencies which leads to ICI. High Peak To-Average Power Ratio (PAPR): When multiple subcarriers are summed up, the PAPR increases which leads to crest factor which is a big challenge.
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