Source: I2C Keypad – Hackster.io

The Radio Resource Control (RRC) protocol is used in UMTS and LTE on the Air interface. It is a layer that exists between UE and eNB and exists at the IP level. This protocol is specified by 3GPP in TS 25.331 for UMTS and in TS 36.331 for LTE. RRC messages are transported via the PDCP-Protocol.
The major functions of the RRC protocol include connection establishment and release functions, broadcast of system information, radio bearer establishment,reconfiguration and release, RRC connection mobility procedures, paging notification and release and outer loop power control. By means of the signalling functions the RRC configures the user and control planes according to the network status and allows for Radio Resource Management strategies to be implemented.

The operation of the RRC is guided by a state machine which defines certain specific states that a UE may be present in. The different states in this state machine have different amounts of radio resources associated with them and these are the resources that the UE may use when it is present in a given specific state. Since different amounts of resources are available at different states the quality of the service that the user experiences and the energy consumption of the UE are influenced by this state machine.

Source: Radio Resource Control – Wikipedia

Orthogonal frequency-division multiplexing (OFDM) is a method of encoding digital data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital communication, used in applications such as digital television and audio broadcasting, DSL Internet access, wireless networks, powerline networks, and 4G mobile communications.
COFDM stands for Coded orthogonal frequency-division multiplexing. It differs from OFDM because in COFDM, forward error correction is applied to the signal before transmission. This is done to overcome errors. COFDM and OFDM are sometimes used as synonyms.
OFDM is a frequency-division multiplexing (FDM) scheme used as a digital multi-carrier modulation method. A large number of closely spaced orthogonal sub-carrier signals are used to carry data on several parallel data streams or channels. Each sub-carrier is modulated with a conventional modulation scheme (such as quadrature amplitude modulation or phase-shift keying) at a low symbol rate, maintaining total data rates similar to conventional single-carrier modulation schemes in the same bandwidth.
The primary advantage of OFDM over single-carrier schemes is its ability to cope with severe channel conditions (for example, attenuation of high frequencies in a long copper wire, narrowband interference and frequency-selective fading due to multipath) without complex equalization filters. Channel equalization is simplified because OFDM may be viewed as using many slowly modulated narrowband signals rather than one rapidly modulated wideband signal. The low symbol rate makes the use of a guard interval between symbols affordable, making it possible to eliminate intersymbol interference (ISI) and utilize echoes and time-spreading (on analogue TV these are visible as ghosting and blurring, respectively) to achieve a diversity gain, i.e. a signal-to-noise ratio improvement. This mechanism also facilitates the design of single frequency networks (SFNs), where several adjacent transmitters send the same signal simultaneously at the same frequency, as the signals from multiple distant transmitters may be combined constructively, rather than interfering as would typically occur in a traditional single-carrier system.

Source: Orthogonal frequency-division multiplexing – Wikipedia

A Radio Access Technology or (RAT) is the underlying physical connection method for a radio based communication network. Many modern phones support several RATs in one device such as Bluetooth, Wi-Fi, and 3G, 4G or LTE.
The term RAT was traditionally used in mobile communication network interoperability, for example, in Virtej et al.,[1] or in the example provided on the Wiki page for Radio access network.
More recently, the term RAT is used in discussions of heterogeneous wireless networks. The term is used when a user device selects between the type of RAT being used to connect to the Internet. This is often performed similar to access point selection in IEEE 802.11 (Wi-Fi) based networks.[2]

Source: Radio access technology – Wikipedia

Source: XLoader

bossac -e -w -v -b image.bin

Source: How can I upload a .bin to arduino due?