APN - Access Point Name

1. A network access technology that is a required parameter for terminal access.
2. It determines the access method for the terminal to access the network.
3. All operators use specific APNs.
4. APN usually pre-configured on SIM card.
5. For regular SIM card (public network cards), APNs are publicly available and can be found online or by contacting the corresponding operator.
6. For IoT SIM card or other specialized network cards, we need to contact the corresponding operator to confirm which APN to use.

CFUN - Cellular Functionality
1. Functional mode of a mobile terminal.
2. Generally refer to the APIs of "net" feature or the AT command "AT+CFUN" to set or get the functional mode of the mobile terminal.
3. Mobile terminals usually have the following functional modes:
	a. Minimum functionality mode:
		In this mode the entire radio frequency network protocol stack is turned off, and the SIM card is powered off. The power consumption of the terminal device is at the lowest while it is not turned off.
	b. Full functionality mode:
		In this mode, all wireless radio frequency functions of the terminal device are enabled, and the device can perform network-related operations.
	c. Airplane mode:
		In this mode, wireless radio frequency functions of the terminal device are disabled, the device is prohibited from sending and receiving RF signals, but the SIM card is still powered on and can be recognized.

MCC - Mobile Country Code
MNC - Mobile Network Code
1. MCC and MNC are used to distinguish a mobile network operator in a mobile communication network.
2. MCC is a 3 digit number used to identify the country or region where the mobile device is located.
3. MNC is a 2 digit or 3 digit number used to identify a specific mobile network operator within a particular country or region.
4. The combination of MCC and MNC forms a globally unique code used to identify every mobile network operator in the world.
5. The identifier consisting of MCC and MNC is called PLMN(Public Land Mobile Network).

Cell
1. In a mobile network, a cell represents a specific geographical area covered by a base station.
2. Each cell is covered by a base station and receives network services from the base station.
3. Cells are divided into:
	a. Serving Cell:
		The cell currently providing services to the mobile device.
	b. Neighboring Cell:
		The cell adjacent to the serving cell and may become new serving cell when the mobile device moves.

Signal Quality
Factors:
	a. Distance.
	b. Obstacles.
	c. Antenna performance.
	d. Interference.
	e. Multipath effects.
	f. Weather conditions.
	g. Network congestion.
	h. Base station load.
	i. Power control.
Some common measurement:
	a. RSSI(dBm) - Received Signal Strength Indicator
		Poor - less than -100
		Fair - -100 ~ -90
		Good - -90 ~ -80
		Very good - -80 ~ -70
		Excellent - more than -70

	b. CSQ - Carrier Signal Quality
		0 - RSSI -113
		1 - RSSI -111
		2~30 - RSSI -109 ~ -53
		31 - RSSI >= -51
		99 - Unknown/undetectable

	c. RSRP(dBm) - Reference Signal Received Power
		Very poor - less or equal to -105
		Poor - -105 ~ -95
		Fair - -95 ~ -85
		Good - -85 ~ -75
		Very good - -75 ~ -65
		Excellent - more th

	d. RSRQ(dB) - Reference Signal Received Quality
		Poor - -20 ~ -15
		Fair - -15 ~ -10
		Good - -10 ~ -7
		Excellent - -7 ~ -3

	e. RSCP(dBm) - Received Signal Code Power
		Very poor - less than -110
		Poor - -110 ~ -100
		Fair - -100 ~ -85
		Good - -85 ~ -75
		Excellent - more than -75

	f. SINR(dB) - Signal to Interference plus Noise Ratio
		Very poor - less than 3
		Poor - 3 ~ 10
		Fair - 11 ~ 15
		Good - 16 ~ 25
		Excellent more than 25


Band
1. In mobile communication, a band refers to a frequency band, which is a specific range of frequencies in the radio spectrum.


Network Mode / RAT - Radio Access Technology
1. Refers to the wireless technology for devices to connect to the network.
2. Technologies like GSM, GPRS, WCDMA, CDMA2000 and LTE are network modes.


Network Technology
1. Network technology refers to a set of technologies or protocols used to establish and manage connections between devices and network.
2. Example:
	a. COMPACT is an optimization technology for GSM network. It improves the spectrum efficiency and capacity of the network by changing the processing of control channels.
	b. EMTC(Enhanced Machine-Type Communication) is an LTE technology for improving network support for a large number of low-power devices.


Default Bearer
1. A bearer, also known as an EPS bearer, it is a concept introduced in LTE.
2. It refers to the channel through which information is transmitted in an LTE wireless network.
3. In LTE network, bearers are divided into:
	a. Default bearer:
		A bearer created during the initial UE attachment according to the default QoS Level in the user subscription is a default bearer. This default bearer is maintained throughout the existence of the PDN connection, providing an "always-on" IP connection to the UE. It can be understood as a bearer that provides a best-effort IP connection.
	b. Dedicated bearer
		Other EPS bearers connected to the same PDN are called dedicated bearers. Dedicated bearers are established to provide specific QoS transmission requirements. For example, a dedicated bearer for VoLTE.


Base Station Time
1. Base station time usually refers to the internal clock of a wireless base station, which provides an accurate time reference for the mobile communication network.
2. In a wireless communication system, sending and receiving data needs to be done within precise time windows. For example, data transmission needs to be synchronized with the base station's time accurately, otherwise, data loss or errors may occur. Therefore, base stations need a precise internal clock to control these time-sensitive operations.
3. In addition, base station time is commonly used for automatic time calibration of mobile devices, especially when devices move between different time zones. This process is achieved through Network Identity and Time Zone (NITZ).


NIC - Network Interface Card

DTU - Data Transfer Unit
1. DTU is a wireless terminal device specially used to convert serial port data into network data or convert network data into serial port data for wireless communication through networks.



SIM

APDU - Application Protocol Data Unit