The figure shows that though the BCPPM system multiple access mode is simple, it still has low BER performance when using the LDPC codes.
We envision that data can be transmitted from the BS to multiple users over MIMO links employing either of the two schemes: (1) time division multiple access mode with spatial multiplexing, which is interference-free, and (2) space division multiple access mode with superposition coding employed for interference cancellation (i.e., multi-user MIMO).
The Frame Allocation Algorithm (FAA) exploits spatial multiplexing of MIMO communication, as the BS communicates with one user at a time over a point-to-point MIMO link in time division multiple access mode, hence, interference is avoided.
In addition to that in the multiple access mode, the available relay node sends the network coded bits of the information received from the cooperating users to the destination.
Based on the 802.15.6 standard [3], a multiple access mode known as 'improvised access' is supported in the WBAN standard, whereby the coordinator can inform nodes that they have been granted one-off exclusive time slots to transmit or receive information.
In the first time slot t (normalized), known as broadcast mode (BC), S transmits to both R and D. In the second time slot t ̄ = 1 − t, known as multiple access mode (MAC), either only R or both R and S transmit to D as shown in Figure 2. In this paper, only R transmits to D in MAC mode. Figure 2 Half-duplex relay network operations in BC and MAC modes.
Therefore, the channel is time-shared by broadcast (BC) mode and multiple access (MAC) mode as depicted in Figure 1.
The users are multiplexed by partitioning the tones in a frequency division multiple access (FDMA) mode.
In order to avoid possible interferences in the network, we design the system in time division multiple access (TDMA) mode.
