Although the i-MIMO concept and the methodological approach of this work are still valid, the PI and thus the [[sigma].sub.p] will play a different role in that case.
In this section, considerations and guidelines for the planning and the deployment of i-MIMO DAS systems in reference, regular 1D (corridor), 2D (single floor), and 3D (multifloor) layouts are provided on the base of both the throughput plots of Section 2.2 and the following path-loss formula, introduced and parameterized in :
Therefore i-MIMO DAS planning can be based on a two-step procedure.
In addition, since high-order i-MIMO DAS deployments and/or high [beta] values in (5) lead to high PI between the different branch-signals, then MIMO order should be matched to the propagation characteristics in order for [[sigma].sub.P] to remain low enough.
There is therefore affinity between i-MIMO DAS planning and traditional cellular planning, where radio coverage must be provided in the first step and then the cluster-size must be chosen so as to satisfy signal-to-interference (SIR) requirements.
It is worth noticing that hereafter the performance of the i-MIMO solutions will not be evaluated in terms of absolute throughput, but rather in terms of "average (relative) gain with respect to the SISO case" ([n.sub.G]), which is of course defined as the ratio between the actual system throughput (evaluated through the previously described procedure) and the SISO maximum throughput:
This is due to the above-mentioned problem: when the MIMO order n is overdimensioned, then the i-MIMO "cluster" is too big and power imbalance is too high to effectively exploit all MIMO branches.
(i) different i-MIMO DAS deployment solutions are evaluated to identify the best one, especially in 2D and 3D cases where different, apparently equivalent solutions are possible, as highlighted in Section 2.1;
Low [bar.[n.sub.G]] values in Figure 7 should be pursued when planning a linear i-MIMO DAS system.
The combined effects of SNR and [[sigma].sub.p] on the performance of an i-MIMO DAS system are further explained in Figures 8 and 9, which represent two examples of 2D spatial distribution of the [n.sub.G] values over the cluster area in the 2- and the 4-branch arrangement, respectively.
For the sake of brevity, the analyses of the 3D case are here limited to the solution represented in Figure 13, where a 4th order i-MIMO DAS system is deployed over 3 different floors.