## 2 Descriptive Analysis of the Maritime Communication Network on Medium Frequency  
The leap of AVISOMEF from conducting remote identification of vessels to constituting a Maritime Communication Network on Medium Frequency will be due to the achievement of the objective of the already stated Automatic Vessel Identification System on Medium Frequency: the verification of the existence of a continuous linkage along the maritime traffic routes in which it has been implemented. The forward phase will consist in mounting a new \"chain\" on those routes that allows communication to be established between any two of the previously identified vessels. The information will leap forward from ship to ship from origin to destination, so that the communication can flow in this new chain in a similar way to the process used in AVISOMEF. A new channel that is different for each cell, called the \"listening/calling (channel L/C)\", will have to be implemented in AVISOMEF. Therefore, each ship that aims to establish a communication process with another ship must express said intention by making use of this new channel. In this request, it must also include the MMSI of both the call recipient and itself. The rest of the ships located in the same AVISOMEF cell as her will take note of her intention, so that the first of them that is required by AVISOMEF to make one of the periodic identifications will include with the information to be transmitted to the TCC the request of initiating a communication process on the part of her cellmate. Once the corresponding TCC is aware of the mentioned request, it will do a search in a communal database of all the TCCs involved in the Maritime Communication Network on Medium Frequency. In this way, it will verify if the contacted ship is within it. If so, it will determine the proper routing [20]. During the routing phase, once a TCC involves a certain vessel in a communication process, this will be visible to all the remaining TCCs. Consequently, if a vessel takes part in a communication process, as a repeater of a chain for communication to flow or as an interlocutor with a ship, and it is requested by another vessel to initiate a communication, the TCC in charge of the process will take notes of the fact and will manage the communication the moment it becomes available [21]. The chain will begin to materialize once the responsible TCC of a communication process has determined the necessary chain that is able to establish a channel between two vessels. The channel will be registered it in a common TCC database so that no one else can make use of the resources that are intended to be employed, placing it within the grid belonging to the Maritime Communication Network on Medium Frequency (elevated with respect to AVISOMEF, Figure 3). The initial step will consist in the promotion of a call made by the corresponding TCC to the first linkage, using the listening/calling (channel L/C) of its cell, providing the vessel with the constitutive list of the chain. This first member of the chain will proceed to communicate its membership to the second member, again making use of the listening/calling channel in which this second member operates, and so on, until all the members are notified of their belonging to this communication chain. Subsequently, each one of them will begin to operate on the different operating frequencies that the Maritime Communication Network on Medium Frequency imposes to each cell of its grid (upper grid of Figure 3), leaving the listening/calling channel free as soon as possible. In order to materialize this process, it is necessary to modify the hardware architecture of the primitive AVISOMEF as shown in Figure 4. Two new receivers with digital selective calling (E and F) will be implemented in the system. Figure 3: Subject area covered by an AVISOMEF grid on which a Maritime Communication Network on Medium Frequency is established. The channels that are underlined in each cell are listening channels and those that are not underlined are broadcast channels.