Filter Bank MultiCarrier, FBMC is a form of multi-carrier modulation that has its origins within OFDM. It is a development of OFDM and aims to overcome some of the issues, although this comes at the cost of increased signal processing.
FBMC has a much better usage of the available channel capacity and is able to offer higher data rates within a given radio spectrum bandwidth, i.e. it has a higher level of spectrum efficiency.
FBMC Filter Bank MultiCarrier basics
Filter bank multicarrier aims to overcome some of the shortcomings that were encountered with OFDM, orthogonal frequency division multiplexing.
One of the main shortcomings arises from the fact that OFDM requires the use of what is termed a cyclic prefix. The cyclic prefix is essentially a copy of part of a transmitted symbol in OFDM that is appended at the beginning of the next.
This redundancy reduces the throughput of the transmission and also wastes power.
A further disadvantage of OFDM is that spectral localisation of the subcarriers is weak and this results in spectral leakage and interference issues with unsynchronised signals.
Filter bank multicarrier is a development of OFDM. Using banks of filters that are implemented, typically using digital signal processing techniques, FBMC.
When carriers were modulated in an OFDM system, sidelobes spread out either side. With a filter bank system, the filters are used to remove these and therefore a much cleaner carrier results.
Systems using FBMC modulation are more complicated than OFDM. This results from the exchange of FFT/IFFT modules by the filter banks.
FBMC advantages & disadvantages
- FBMC is able to provide a spectrum efficient and more selective system.
- The cyclic prefix, CP required for OFDM is not needed thereby freeing up more space for real data.
- Provide robust narrowband jammers
- The use of MIMO with FBMC is very complcated and as a result few systems have investigated the use of these two techniques together.
- The design of wide bandwidth and high dynamic range systems with FBMC provides soem signiicant RF developemnt challenges.
- FBMC is more complicated than OFDM - it introduces an overhead in overlapping symbols in the filter bank in the time domain.
Although FBMC, Filter Bank Multicarrier is not in real use yet, it has been considered for use in some developing technologies, although it is still probably some years off being used for many applications.