# Web-Based Toolkit for Performance Simulation and Analysis of Power Line Communication Networks
## 2 PLC Technologies
### Iee 1901  
SimBPL is based on IEEE 1901 [27], which is currently being used by Spanish DSOs, such as Iberdrola orUnion Fenosa. The IEEE 1901 standard considers two different specifications for Medium Access Control (MAC)/Physical (PHY): the first is based on Fast Fourier Transform (FFT) and the second on wavelet. It also describes both broadband communications over MV and indoor broadband communications over LV. In detail, SimBPL implements the MAC /PHY specification based on FFT for MV distribution infrastructures. In the PHY layer, IEEE 1901 uses Orthogonal Frequency Division Multiplexing (OFDM) as a modulation technique. The standard considers the frequency band between 2 to 30 MHz. However, most real implementations use two sub-bands within the 2 to 30 MHz band. The first, called Mode 1, varies operates in the sub-band from 2 to 7 MHz, and the second, called Mode 2, operates in the sub-band from 8 to 18 MHz. Mode 2 allows higher data rates but is also more sensitive to attenuation. In this type of communication, data rates in MV links are asymmetric because they are affected by background noise between two substations. Currently, a performance requirement of at least 100 kbps applies to medium-voltage networks. However, raw data rates of around Mbps can be achieved in practice [14]. IEEE 1901 defines three different kinds of nodes, namely the Network Termination Units (NTUs), the Head-End (HE), and the Repeating stations (RSs). Although the underlying physical topology of MV networks fits a ringed-mesh topology, the communications overlay on top of it forms a tree-wise logical topology. As defined in the standard, such a tree may be different for data traffic and signaling, since faster data rates are targeted for the former, while more robust modulations are used for the latter [28]. In practice, however, the topology is defined manually. NTUs represent the leaves of such a tree-like topology and work as gateways to networks located at lower levels of the hierarchical power distribution infrastructure (in this caseLV), RSs work as communication relays, and the HE coordinates intra-cell communication and also works as a gateway for backhaul communication. In practice, however, the role of HE is split into two nodes: the master, which coordinates communication within the cell, and the gateway, which provides such backhaul communication capability. This division is due to the fact that, in practice, different criteria are used to select the master and the gateway. In principle, the node that has the smallest average distance to all other nodes in the cell is the perfect candidate for the role of master, while the selection of the gateway depends heavily on the communication equipment installed in the SSs. Nevertheless, it may happen that the roles of master and gateway are assigned to the same SS. 1. At the MAC level, two periods are defined: a Contention Period (CP), where Carrier Sense Multiple Access is used with Collision Avoidance (CSMA/CA) as the multiple access method, and a Contention Free Period (CFP), where Time Division Multiple Access (TDMA) is used as the multiple access method. The CFP is used for data transmission and three TDMA variants are considered [28]: Centralized TDMA, the Master allocates time slots for every path between the Gateway and a given node;
2. Dynamic TDMA Polling: the master fixes the slots at the beginning of each transmission period using the result of polling all the nodes in the cell;3. Distributed TDMA: the master only allocates time slots to its neighbors and delegates the responsibility of allocating time slots to their corresponding neighbors. SimBPL assumes centralized TDMA as a multiple access method. TDMA is also used for planning MV -BPL networks by defining TDMA domains that operate in one of the aforementioned frequency bands and can coexist with neighboring TDMA domains that operate in another frequency band [14].