Modules

Modules – Communications Control Software with Wi-Fi/LTE/5G

The  communications and control software with Wi-Fi/LTE/5G consists of five major modules: Radio Firmware, Mobile Application (Android/iOS), Tower Base Stations , Communications Controller, and Dispatch Center. They perform as a hybrid communication network that support both trunked radio and broadband technologies for emergency situations.

Radio Firmware

The radio firmware module is to handle main functionality of Push-to-Talk (PTT) radio communication through trunked control channels. It is used to send and receive voice transmissions to and from the tower and account for RF interference (RFI) , signal strength and determines the channel frequency to communicate on based on the control channel. It also has an emergency function that overrides the control channel to transmit emergencies immediately. The radio firmware mainly interact with Tower Base Stations for channel updates.

The radio firmware which is a monolithic style architecture coupled with event-driven. The event-driven sections of the software monitor the push to talk, emergency, and antenna for input such as button press events and the detection of an incoming message. Inside the Prioritizer, it monitors for PTT and emergency events,  and listens to the control channel for instructions about which channel it should broadcast on. The radio software should override all incoming and outgoing traffic in the event of an emergency button press, and to ensure the emergency broadcast cannot be used to disable the network, only allow a simple transmission to notify the dispatch that an emergency event has occurred with the radio identification. Location can be determined by triangulation methods based on signal strength between the user and nearby towers whether they are 5G, LTE, or radio communications towers.  The Prioritizer also determines when the microphone can be enabled and should be shut off when the PTT is not engaged. The multiplexer and mixer are hardware components that can be software controlled based on the radio model and would have minimal functionality. The Prioritizer must also account for RF interference, and have the capacity to add encryption to the messages if enabled in the firmware.  Finally, it also stores all groups and available frequencies, and can be updated from dispatch over the air using a transmit message to the radio.

Android/iOS App

The Android/iOS app is to provide smartphone users with same functionality of PTT and status as radio devices. It basically does the same as the radio, but uses the App's buttons to transmit messages. The function include initiate PTT calls over LTE/5G/Wi-Fi. This module mainly interact with Tower Base Stations which can connect to the controller and dispatcher for sync call logs and alerts. The advantage of the phone is its simplicity, and the ability to provide a low cost option that can be installed on any smart phone with the purchase of a valid license. It can transmit by connecting to a nearby radio via bluetooth, or can be used to transmit and receive messages via a Wi-Fi connection to the internet and thus the dispatch. All messages sent and received by the phone are encrypted. The architecture here is a combination of Model-View-Controller, and a layered architecture (presentation, domain, data) to handle business logic and network communications.

Tower Base Stations

The two tower base stations is to relay communications between radio and controller. It has RF repeaters for 5G/LTE and radio communication frequency channels that re-transmit received messages to the appropriate devices based on the settings loaded into the base station software. The base station, like the radios have to account for RFI, signal strength, and channel frequencies. In addition, the base stations must account for multi-path interface, call priority, and to delay non-emergency calls if an emergency signal is detected. It acts as a central hub that converts analog RF signals into digital data to be sent to the network. This module mainly interacts with communication controller for routing and frequency assignment, and dispatch to provide usage logs. 

The base stations consists of an antenna system, transceiver units, control equipment, power supply, RF repeaters, and a back-haul network. The antenna system,  power supply, and RF power modules are hardware only devices, providing power and receiving/transmitting modulated RF. The control equipment is what manages communications protocols like P25 between devices and ensures data is correctly routed. The back-haul network connects the base station to the rest of the network , through a wired connection like high-speed fiber. The main part of the system which is the control equipment, uses a software defined radio architecture that functions like a hardware radio to define functions like modulation and demodulation, a process control architecture to monitor power for outages so it can be rerouted to a backup generator, and a layered architecture for communications with the dispatch via fiber.

Communications Controller

The communications controller is the brains of the system, determining where to retransmit incomming messages and handles not only the 5G/LTE and radio frequency communications signals, but must also handle input from the internet for any calls made over W-iFi. That capability is important in situations like a building that may have a working Wi-Fi system, but a call via RF or 5G/LTE cannot be made because of the building material that the building is constructed with, or the user is in a location such as a basement where the signals are too weak.  This module directly connected to Dispatch for monitoring and control. It communicates with Tower Base Stations to manage calls. The communications controller uses a layered architecture for network communications, and an event-driven architecture for message monitoring.

Dispatch

The dispatch is where scenario-based usability engineering would be extremely useful. The dispatch is composed of monitors, receivers from the communications controller, and a Push To Talk microphone for direct communications within all groups. They also have the ability to change the channel frequencies, groups, and add or remove groups. These changes are then sent to the towers so they can also implement any changes. Dispatchers can override and cancel any call.  This module mainly interact with Communications Controller to receive all data and control messages and Tower Base Stations (Software System as Repeater) for sending new configuration or frequency assignments.
The figure below is the sequence diagram of dispatch. When there is a message received and the dispatcher initiate the communication. The dispatcher send controlMessage to communications controller to determines which communication protocol that user use (e.g., RF, LTE/Wi-Fi). The controller receive this message and determine routing or priority level and may respond with updated settings (e.g., new frequency allocations). Dispatch updates the new configuration to maintain the communication. The dispatcher may send overides or cancel message to communications controller to manage and interrupt for preventing unpredicted conditions and human-sight flexibility. The controller immediately stops the ongoing connection when it receive overrideCall and update the setting. The controller pushes configuration changes to all connected tower stations. These changes ensure network synchronization between RF and broadband gateways. When tower receives the acknowledgeUpdate message towers confirm receipt and successfull application of new settings. The  communications controller sends an acknowledgement or error message back to dispatch with statusUpdate message. The dispatch uses a layered architecture for network communications, an event-driven architecture for transmitting and sending messages, and a fault tolerant architecture for maintaining constant availability and switching to alternate consoles when necessary.