UNIVERSAL FILTERED MULTI CARRIER TECHNIQUE FOR 5G COMMUNICATION SYSTEMS
Sonam Rathore M. Tech Scholar, BTIRT Sagar
Mr. Naveen Khare
Asstt. Prof. EC Deptt, BTIRT Sagar
Abstract - This paper describes the merits of Universal Filtered Multi Carrier (UFMC). It is a multi- carrier modulation technique in fifth generation network (5G). Orthogonal Frequency division Multiplexing (OFDM), a modulation technique in 4G, have some drawbacks like side band leakages and high Peak to Average Power ratio (PAPR) issues. With the advent of Internet of Things (IOT) and the move towards user-centric processing makes the OFDM technique more unfeasible. Filter Bank Multi carrier (FBMC) is another multi carrier technique, which is better than OFDM, have some issues in practical aspects. So, an another multi carrier technique is proposed to fulfill all necessary requirements of 5G communication systems, which is Universal Filtered Multi Carrier (UFMC). This paper describes the aspects of Universal Filtered Multi-Carrier system and highlights the merits of new modulation method for emerging fifth generation Wireless Communication Systems.
Orthogonal Frequency Division Multiplexing is an excellent choice for fourth generation.
Side band leakage is another problem in OFDM. Our current 4G systems rely on the OFDM waveform, which is not capable of supporting the diverse applications 5G will offer. The traffic generated by 5G is expected to have very different characteristics and requirements when compared to current wireless technology. As result other multiple access schemes are being investigated. The way to overcome the known limitations of OFDM is UFMC technique. In this proposed work performance of OFDM and UFMC is compared in several aspects. Performance is judge on the basis of simulated results. Simulation is done in MATLAB environment. From the simulation results it is noted that UFMC performs better than OFDM in 5G spectrum. The OOBE is lesser in UFMC. The PAPR value is 8.62 for UFMC when 64QAM is employed and The PAPR value is 9.92 for OFDM in the same scenario.
1 INTRODUCTION
OFDM is a multicarrier modulation technology which is used in broadband wireless communication systems. OFDM was the dominant technology used in 4G networks since it has high spectral efficiency because it uses orthogonal subcarrier signals. OFDM is easily implemented by using IFFT and FFT at the transmitter and receiver respectively.
OFDM mitigates inter symbol interference (ISI) and combats the effect of multipath reception. However OFDM cannot meet the 5G wireless communication demand because it has high out of band emission (OOBE).
OOBE in OFDM is because of the use of rectangular window in time domain, which leads to sinc pulses in frequency domain. Subcarriers in OFDM remain orthogonal only in case of perfect synchronization conditions.
Strict synchronization is required in OFDM to avoid interference between the users since it is very sensitive to time and carrier frequency offsets (CFO). The
frequency offset may be because of oscillator frequency mismatch between transmitter and a receiver or due to the Doppler shift resulting from the mobility.
Performance degradation in OFDM occurs because of inter carrier interference (ICI). ICI occurs because of CFOs which destroy the orthogonality between subcarriers. To reduce OOBE of OFDM and to meet the requirement of 5G network scenario filter based waveforms were proposed in the literature. Another drawback of OFDM is that it has high PAPR.
Figure 1 shows the block diagram of OFDM transmitter and receiver system. It uses only band pass filter which is less efficient to mitigate side lobe losses. In UFMC frequency side lobe losses are less.
Fig.1: Block representation of OFDM Trans-receiver system
Orthogonal frequency division multiplexing is a mix of adjustment and multiplexing. In balances information or data is mapped on to changes in adequacy or stage, recurrence of a bearer flag. Multiplexing manages distribution/convenience of clients in a given data transfer capacity and that is manages portion of accessible data. In this procedure, the given transfer speed is shared among individual tweaked information sources. Basic modulation techniques are like Amplitude modulation, Phase modulation, Frequency modulation, Binary phase shift keying, quadrature phase shift keying and so on. These are single transporter regulation procedures, in which the approaching data is adjusted over a solitary bearer. OFDM is a multicarrier balance procedure, which utilizes a few transporters, inside the designated data transmission, to pass on the data from source to goal.
UFMC is a generalization of Filtered OFDM and FBMC multi-carrier modulation technique. Generally in filtered OFDM, entire band is filtered where as in FBMC individual sub carriers are filtered. But in UFMC group of sub carriers are filtered [6]. This is the main difference in Filtered OFDM, FBMC and UFMC multi-carrier.
Grouping of sub carriers helps in reducing the filter length in UFMC. IN UFMC, to retain the complex orthogonality, QAM is used which works with existing MIMO. The whole UFMC transmitter section is shown in chapter 4. In UFMC the full band of „N‟ sub- carriers is partitioned into several sub bands. Each sub band has a fixed number of sub carriers. In transmitter section no need of employing all sub bands for a transmission. To get rid of
from the sub band carrier interfere, Inverse Fast Fourier Transform (IFFT) is used. At each N-point IFFT, sub bands are computed and zeros are allocated for unallocated carriers. IFFT converts frequency domain (Xi) to time domain (xi). After the N-point IFFT, the output can be written as:
Yi = IFFT {xi}
2 WORK STUDY
Mohammad R. Abou Yassin et Al [1]
explains that in the telecommunications field, multicarrier modulations attract a lot of attention among researchers and engineers, especially specialists in 5G domain. Several candidate waveforms have been proposed to be used in 5G systems. In this paper, Universal Filter Multi Carrier (UFMC) is recommended for 5G communications. UFMC is recommended because of its many advantages such as significant reduction of Out Of Band emissions OOB and support for data bursts. Nevertheless, UFMC is a multicarrier communication system, so it also suffers from high Peak to Average Power Ratio PAPR problem, which every multicarrier technique suffers from. In order to reduce the PAPR, many PAPR reduction techniques were proposed over the last few decades.
Asia Hazareena et al [2] discuss about OFDM. Orthogonal frequency division multiplexing (OFDM) is a multicarrier modulation technique, which is used as a dominant waveform for the 4G communication systems. But OFDM cannot meet the demands in 5G.
Universal filtered multicarrier (UFMC) has been paid more attention in the 5G communication system because of its low out of band emission (OOBE) and compatibility for multiple input multiple output (MIMO) communication. In this paper performance of UFMC is analyzed in terms of power spectral density (PSD), Bit error rate (BER) and peak to average power ratio (PAPR).
Asia Hazareena et al [3] explained that UFMC has brought down out-of-band outflow and is likewise perfect with the various info different yield procedure. Be that as it may, as other multicarrier waveforms, it suffers from phase noise of imperfect oscillator. In contrast to the rich literature on phase noise impact on MIMO- OFDM (where the radio wire
shared coupling impact is generally overlooked however), there is little work investigating the phase noise effect on MIMO-UFMC.
P. Naga Rani and Shanti Rani [4]
discussed about UFMC. It is generalization of Filtered OFDM and FBMC multi-carrier modulation technique. Generally in filtered OFDM, entire band is filtered where as in FBMC individual sub carriers are filtered. But in UFMC group of sub carriers are filtered [6]. This is the main difference in Filtered OFDM, FBMC and UFMC multi-carrier.
Grouping of sub carriers helps in reducing the filter length in UFMC. IN UFMC, to retain the complex orthogonality, QAM is used which works with existing MIMO. Here the full band of
„N‟ sub carriers is partitioned into several sub bands. Each sub band has a fixed number of sub carriers. In transmitter section no need of employing all sub bands for a transmission.
3 PROPOSED WORK
In current growing world, faster data communication is the basic need of a big population. To achieve higher data transfer and faster digital communication 5G communications system is a better option. 5G technology requires higher data rate, lower latency and efficient usage of frequency spectrum. For such requirements UFMC (Universal Filtered Multi-carrier) modulation technique is proposed here, which overcomes the drawbacks of OFDM system and achieves 5G technology requirements. OFDM is best suited for 4G communication and UFMC is best for 5G communication.
UFMC is considered as a generalization of Filtered OFDM and FBMC (Filter Bank Multi-carrier) modulations. The entire band is filtered in filtered OFDM and individual subcarriers are filtered in FBMC, while groups of subcarriers (sub- bands) are filtered in UFMC. This subcarrier grouping allows one to reduce the filter length (when compared with FBMC). The full band of subcarriers (N) is divided into sub-bands. Each sub-band has a fixed number of subcarriers and not all sub-bands need to be employed for a given transmission. An N-point IFFT for each sub-band is computed, inserting zeros for the unallocated carriers. Each sub-band is filtered by a filter of length L,
and the responses from the different sub- bands are summed. The filtering is done to reduce the out-of-band spectral emissions. Different filters per sub-band can be applied, in this proposed work the same filter is used for each sub-band. A Chebyshev window with parameterized side-lobe attenuation is employed to filter the IFFT output per sub-band. The transmission process of UFMC is shown with help of block diagram in figure 2.
The proposed 5G scheme using UFMC modulation is simulated in MATLAB.
Simulation Algorithm is as follows:
i. Define basic parameters.
ii. Define Dolph-Chebyshev window design parameters.
iii. Initiate loop over each sub-band.
iv. Filter for each sub-band.
v. Compute PAPR.
vi. Plot PSD plot for each sub-band for UFMC.
vii. Sum the filtered sub-band to transmit signal.
viii. Receive the signal using FFT.
ix. Compute BER and SNR.
x. Plot PSD for OFDM.
Fig. 2: Block diagram of UFMC Transmitter
4 RESULTS
On the basis of proposed algorithm simulation is done in MATLAB. The simulated results are obtained in graphical form and analyzed. It is very clear from figure 3 and 4 that when 64 QAM is applied to UFMC and OFDM, side bands leakage is higher in OFDM. On the other hand frequency spectrum utilization is better in UFMC.
Figure 5 shows the PAPR comparison between UFMC and OFDM. It is known that less PAPR is required for better communication. In this result for
16QAM and 64QAM PAPR for UFMC is less than OFDM. It implies that for 16QAM and 64QAM UFMC performs better.
Fig. 3: PSD analysis for UFMC (64QAM)
Fig. 4: PSD analysis for OFDM (64QAM)
Fig. 5: PAPR comparison between UFMC and OFDM
5 COCLUSION
The proposed work presents the basic characteristics of the UFMC modulation
scheme at both transmit and receive ends of a communication system. Explore different system parameter values for the number of sub-bands, number of subcarriers per sub-band, filter length, side-lobe attenuation, and PAPR. UFMC is considered advantageous in comparison to OFDM by offering higher spectral efficiency. Sub-band filtering has the benefit of reducing the guards between sub-bands and also reducing the filter length, which makes this scheme attractive for short bursts. The latter property also makes it attractive in comparison to FBMC, which suffers from much longer filter length. From the simulated results it is very clear that OOBE is lesser in UFMC in comparison to OFDM. From the simulation results it is noted that UFMC performs better than OFDM in 5G spectrum. The OOBE is lesser in UFMC. The PAPR value is 8.62 for UFMC when 64QAM is employed and The PAPR value is 9.92 for OFDM in the same scenario. The small value of PAPR implies that the transmitted signals are more efficient.
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