Page 135 - ITU Journal Future and evolving technologies – Volume 2 (2021), Issue 2
P. 135
ITU Journal on Future and Evolving Technologies, Volume 2 (2021), Issue 2
(a) Multi‑tap architecture. (b) Multi‑AUX TX architecture.
Fig. 5 – Average value for the proposed FD MIMO design versus DL TX power and for UL TX power = [dBm] − 20 [dB] for = = 4.
(a) = = 1. (b) = = 4.
Fig. 6 – Average FD rates versus DL TX power and for UL TX power = [dBm] − 20 [dB] for = = 4.
in order to maximize the FD rate. Thus, our FD MIMO de‑ design having = 16 taps. As seen from both Figs. 6a
sign chooses the small = 1 so that the FD node can put and 6b with = = 1 and = = 4, respec‑
more effort into SI mitigation. Serving less streams in DL, tively, the multi‑tap design with = 4 and = 8 taps
by choosing a lower , allows to devote more TX spatial (i.e ., 75%and less 50%less taps than SotA) yields sim‑
directions at the FD node for SI mitigation. This show‑ ilar or better performance to SotA. Fig. 6 also showcases
cases the recon igurability of the TX digital BF design to the superiority of the proposed multi‑AUX TX design
satisfy the FD rate maximization objective, while meeting with respect to the SotA one having = 16 taps.
hardware and SI constraints.
In Fig. 7 we focus on the achievable DL and UL rates with
6.4 Achievable rates the proposed multi‑tap and multi‑AUX TX designs with
= 8 taps and = 3 AUX TXs, respectively, and with
We plot the ergodic DL, UL, and FD rates in bps/Hz as the SotA design with = 16 taps. It is shown that our
functions of the TX powers for the FD MIMO systems con‑ proposed TX digital precoder results in a larger DL rate
sidered in Figs. 4 and 5, using the algorithmic designs sat‑ for = = {1, 4}. The same trend holds for the UL
isfying the constraint of having residual SI power level af‑ rate with the proposed joint design of analog cancellation
ter analog cancellation lower than = −60dBm. We do and RX digital combining. This behavior witnesses the re‑
A
the same for the SotA algorithm with = 16 taps, which con igurability of the proposed joint design, which results
is the only considered design from the previous art meet‑ in both larger UL and DL gains compared to SotA, as the
ingthe latterSIconstraint. StartingwithFig.6, the FDrate number of antennas at nodes and increase.
performance of the proposed multi‑tap and multi‑AUX TX
designs with = {4, 8} taps and = {2, 3} AUX TXs,
respectively, is illustrated in comparison with the SotA
© International Telecommunication Union, 2021 121
