f-OFDM: Advantages and Disadvantages

This page discusses the advantages and disadvantages of f-OFDM (Filtered OFDM). It details the benefits and drawbacks of this technique.

What is f-OFDM?

f-OFDM stands for Filtered OFDM (Orthogonal Frequency Division Multiplexing). It’s a variation of the conventional OFDM technique.

Introduction

As mentioned, f-OFDM is short for Filtered Orthogonal Frequency Division Multiplexing.

Figure 1: f-OFDM Transmitter and Receiver

Figure 1 depicts the use of a filtering algorithm after the IFFT/CP module in a normal OFDM transmit chain.

Benefits or Advantages of f-OFDM | Filtered OFDM

f-OFDM offers all the advantages of OFDM, such as flexible frequency multiplexing, simple channel equalization, and easy combination with multi-antenna transmission.

Following are the specific benefits or advantages of f-OFDM (Filtered OFDM):

• Efficient utilization of spectrum: f-OFDM makes better use of the available frequency spectrum.
• Suppressed Out-Of-Band Emission: It reduces Out-Of-Band Emission, minimizing the need for large guard bands.
• Optimized Numerology: Different numerologies can be applied to suit the needs of specific services within each sub-band. This allows for optimized performance for various applications.
• Incorporation of other Waveforms: It’s possible to integrate other waveforms such as GFDM, FBMC, UFMC, etc.
• Backward and forward compatibility: Supports compatibility with both older and newer technologies.
• Relaxed Synchronization Requirements: Using sub-band based filtering relaxes the global synchronization requirement, enabling inter-sub-band asynchronous transmission.

Drawbacks or Disadvantages of f-OFDM | Filtered OFDM

Following are the disadvantages of f-OFDM (Filtered OFDM):

• Additional Filters: f-OFDM requires an additional pair of transmit and receive filters in the transmitter and receiver chains compared to conventional OFDM, adding to complexity and cost.
• CP Requirement: Like OFDM, Cyclic Prefix (CP) is still needed in filter-based waveforms like UFMC and F-OFDM to protect the signal from Inter-Symbol Interference (ISI).
• ICI Presence: Full-band filtering cannot remove Inter-Carrier Interference (ICI), meaning it still exists in f-OFDM, similar to standard OFDM.

Conclusion

f-OFDM can overcome the drawbacks of the OFDM technique while retaining its benefits. It is used in 5G technology due to its overall performance, associated moderate complexity, cost, and smoothness.