Abstract
In this study, we propose a new Amplify-and-Forward (AF) amplification factor to improve the error performances of the current AF schemes and thus enhance the total capacity at the destination terminal. The proposed scheme has two degrees of freedom, meaning that it contains two variable parameters that can simultaneously vary the amplification factor instead of one as in traditional variable-gain or semi-blind relaying. The numerical results show that the proposed AF scheme outperforms some current ones with which it is compared in terms of average capacity and probability of outage and thus brings AF relaying performances closer to that of Decode-and Forward (DF) strategy which hitherto outperforms it. The results also show that by increasing or decreasing the power share of the relay, the optimal location of the relay is not only moved closer to or farther away from the destination, the total average capacity at that location is also correspondingly increased or decreased.
Highlights
Relaying has been considered a promising solution in extending service coverage, especially where multiple antennas are not deployable at the terminal
The relay amplification factor in the AF relaying plays a major role in the resource allocation to the active users in the Orthogonal Frequency Division Multiplexing (OFDM) relaying system (Rasouli, 2012)
It is evident that the proposed scheme achieves the highest capacity because it uses additional variable parameter which increases its average signal-to-noise ratio (SNR)
Summary
Relaying has been considered a promising solution in extending service coverage, especially where multiple antennas are not deployable at the terminal. The main function of the amplification factor is ideally to equalize the effect of the channel fading between the source and the relay and to achieve that it uses a variable channel gain parameter, i.e., channel variance or channel coefficient in its denominator; while in its numerator some fixed scaling constant, which can further affect amplification, is specified. The relay amplification factor D2 as seen in the first term of Equation 3 is expected to provide proper amplification to the relay while equalizing the effect of the channel fading and prevents the relay gain from saturating when the S-R channel undergoes deep fade This gain amplifies the effective noise term, by a margin which depends on the choices of the scaling parameters. Because α2 is non-fading path gain, its average power gain α 2 = α 2 is assumed for the proposed AF amplification factor in Equation 13 and so its outage probability can be derived as:
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