## 4 Network Planning and Optimization
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Requirement** & **Description** & **Indicative Related Works** \\ \hline Network configuration should vary according to traffic and channel conditions & Unlike 3G/4G cellular systems where network configuration is predefined, in the 5G network case nodes may be added dynamically according to traffic conditions and overall requested bit rate. & [41, 42] \\ \hline Accurate channel modeling that incorporates not only BS-MS link but also D2D link and intermediate relay nodes. V2X communications should be supported as well (Section 5) & In order to support requested QoS, MSs with improved channel gain may act as intermediate relay nodes for content caching. In the physical layer, all possible channel links should be embedded at the simulator & [26, 27, 28, 29, 30, 68] \\ \hline Adaptive RRM techniques for 5G networks with dynamic configuration & Compared to current RRM approaches, followed by traditional mobile networks, 5G’s RRM is quite different, since resource allocation is not bounded to spatially and function-wise static nodes and thus the problem, especially when trying to jointly optimize a number of variables, becomes more complex. A key problem is that, depending on the fronthaul capacity of different links, the network might be forced to have a functional split according to the current link characteristics. & [22, 60, 64] \\ \hline Heterogeneous network infrastructure & Coexistence of 4G/5G networks in the same geographical area, as well as handover management to preserve QoS when network switching takes place. & [60, 64, 66] \\ \hline MU-Massive MIMO beamforming techniques for data rate maximization & Appropriate beamforming techniques are required in order to support user separation and provision of acceptable QoS to all MSs. Moreover, beamforming techniques should be computationally efficient in order to minimize post-processing complexity & [16, 17] \\ \hline Support of the increased complexity of MC simulations & 5G networks may have hundreds of nodes and increased number of MSs per serving node. Hence, in order to shorten the simulation time without sacrificing the simulation accuracy, parallel processing using multiple cores, hardware acceleration with graphic processing units, and distributed processing using cloud computing should be considered. & [48, 50] \\ \hline Reusability, scalability, and flexibility & The developed code for the 5G simulators should be highly reusable in various computational environments to allow scientific community to test and verify all developed features. High scalability and flexibility is also needed to support various scenarios and technologies in a single simulator. & [57, 58, 59, 61, 68, 69, 70, 71, 72] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Main requirements for 5G simulators. In this context, the work in [74] focused on providing a generic analysis for this problem, emphasizing the need for dense standalone small-cell networks in the mmWave band of 28 GHz, in order to achieve the capacity goals of 5G. The three main constraints of coverage, capacity, and cost were studied for a range of cases that reflected scenarios from dense to ultra-dense network deployments in order to achieve high capacity. In [75], a joint optimization algorithm is proposed of a multi-cell massive MIMO network towards three objectives: the power consumption, the downlink (DL) Electromagnetic (EMF) exposure, and the uplink (UL) EMF exposure. Both the DL and UL EMF exposure have been addressed in a different context. In a first step, the DL and UL EMF exposure are studied separately (E-field for the DL exposure and SAR for the UL exposure), while in a second step, the two objectives are jointly expressed in terms of the dose metric. In [76], the problem of planning a 5G network (and in particular BS sites) under EMF exposure limits has been studied. In this context, two real-world case-studies of currently deployed cellular networks have been examined.