OFDM presents advantages of high spectrum efficiency, simple and efficient implementation by using the fast Fourier transform (FFT) and the inverse Fast Fourier Transform (IFFT), mitigation of intersymbol interference (ISI) by inserting cyclic prefix (CP), and robustness to frequency selective fading channel.
As one of the most popular technologies for wireless communications, orthogonal frequency division multiplexing (OFDM) [1], on the one hand, has attractive advantages such as high spectrum efficiency, robustness to multi-path fading and efficient implementation based on fast Fourier transform, which make it suitable for wide-band wireless communications.
In addition, OFDM has several favorable properties like high spectrum efficiency, robustness to channel fading, multipath delay spread tolerance, efficient digital signal processing implementation, and granular resource allocation, etc. (for example, in [4, 5]).
OFDM has several favorable properties like high spectrum efficiency, robustness to channel fading, multipath delay spread tolerance, efficient fast Fourier transform (FFT) implementation, etc. (for example, in [5 7]).
Relay-assisted Automatic Repeat reQuest (ARQ), which allows the relays instead of the source to carry out retransmissions of packets erroneously received at the destination, is an efficient cooperative transmission technique to improve link reliability with high spectrum efficiency in wireless networks.
high spectrum efficiency.
DWT-OFDM can also support much higher spectrum efficiency than discrete Fourier-based OFDM (DFT-OFDM).
Moreover, compared to the spectrum overlay sharing method, the spectrum underlay & overlay can provide substantial higher spectrum efficiency.
The simulation results have indicated that SEM can achieve higher spectrum efficiency while EEM may get higher energy efficiency.
Therefore, we allocate the spectrum resource based on the timed KSBS approach, and can maintain a higher spectrum efficiency.
The interference weighted selection policy achieves lower outage probability and higher spectrum efficiency than the equal selection policy.
