The csi is assumed to be available at S. When the csi is available at the transmitter, the optimal transmission scheme is maximal ratio transmission (MRT) [24], hence, S uses MRT as the transmission scheme and destination uses MRC.
In this section, we present the achievable sum-rate for the MARC model that we study using the OFDMA transmission scheme [10].
The data bits x ∈ (0,1) from the source encoder are encoded by the channel encoder, and the coded bits are then sent through the atmospheric turbulent channel using the OOK transmission scheme.
The earliest emergence of relay networks can be traced back to the late 1970s in [5, 6], Cover and others indicate that the transmission scheme using relays can effectively increase the capacity and coverage of system by ensuring credible communications between users from the viewpoint of information theory.
Figure 6 Transmission scheme of Lemma 2. Illustration of the transmission scheme used in proof of Lemma 2. We will show that keeping the total consumed energy constant, and transferring some amount of energy Δ E from the first slot to the second such that power levels are reallocated closer to each other, the sender can transmit at least the same number of bits within the same duration.
Cognitive radios offer the possibility to improve the spectrum use and to adapt the transmission scheme to optimize the sharing of the available bandwidth, which leads to important constraints on the hardware components, located on the physical layer [1].
In Table 1, the optimum values for to antennas have been given for systems with equal numbers of Tx and Rx antennas along with the percentage sum rate increase achieved by using the proposed scheme over the transmission schemes using ZF receiver processing and TDM, when there are users available in the system and at dB SNR.
Then the transmission scheme becomes fully distributed.
The transmission scheme is as follows.
This can be explained as follows: when higher order modulation schemes are used, the transmission time given by (4) and (9) is reduced by a factor log2M.
