# 6G Mobile Networks: Key Technologies, Directions, and Advances
### Outline of the Survey
\begin{table}
\begin{tabular}{l l l l} \hline \hline
**Abbreviations** & **Full Forms** & **Abbreviations** & **Full Forms** \\ \hline
**D-OMA** & Delta-Orthogonal Multiple Access & **ORAN** & Open Radio Access Network \\ \hline
**DoS** & Denial-of-Service & **OWC** & Optical wireless communication \\ \hline
**DRL** & Deep Reinforcement Learning & **PKI** & Public Key Infrastructure \\ \hline
**DRM** & Digital Rights Management & **RAN** & Radio access network \\ \hline
**DSCM** & Digital Sub-Carrier Multiplexing & **QOS** & Quality of Service \\ \hline
**DT CCM** & Distributed Turbo Trellis Coded Modulation & **RF** & Radio Frequency \\ \hline
**E2E** & End to End & **RIS** & Reconfigurable intelligent surfaces \\ \hline
**ECC** & Elliptic Curve Encryption & **RL** & Reinforcement Learning \\ \hline
**eMBB** & Enhanced Mobile Broadband & **RSMA** & Resource Spread Multiple Access \\ \hline
**eMTC** & Enhanced Machine Type Communication & **RTD** & Real Time Difference \\ \hline
**ETSI** & European Telecommunications Standards Institute & **RTIE** & Real-time intelligent edge \\ \hline
**eURLLC** & Enhanced Ultra-Reliable Low Latency Communications & **SDN** & Software-Defined Networking \\ \hline
**FBMC** & Filterbank Multicarrier & **SLA** & Service-Level Agreement \\ \hline
**FDMA** & Frequency Division Multiplex Access & **TDMA** & Time Division Multiple Access \\ \hline
**feUMBB** & Further Enhance Ultra-Mobile Broadband & **THz** & Terahertz \\ \hline
**FSO** & Free-space optical communication & **TLS** & Transport Layer Security \\ \hline
**FTN** & Faster-than-Nyquist & **TPG** & Test Pattern Generator \\ \hline
**HAP** & High-Altitude Platform & **TTCM** & Turbo Trellis enCiphered Modulation \\ \hline
**IIoT** & Industrial Internet of things & **UAV** & Unmanned Aerial Vehicle \\ \hline
**IoE** & Internet of Everything & **UHDD** & ultra-High Density Data services \\ \hline
**IoT** & Internet of Things & **uHEE** & ultra-High Energy Efficiency \\ \hline
**IPsec** & Internet Protocol Security & **uHRS** & ultra-High Reliability and Sensing \\ \hline
**IR** & Infrared radiation & **uHRUx** & ultra-High Reliability and User experience \\ \hline
**JWT** & JSON Web Token & **uHS** & ultra-High Security \\ \hline
**KPIs** & Key Programmable Interface & **uHSLLC** & ultra High Sensing Low Latency Communications \\ \hline
**LAP** & Link Access Protocol & **uHSLo** & ultra-High Sensing and Localization \\ \hline
**LDPC** & Low-Density Parity-Check & **uLLRS** & ultra-Low Latency Reliability and Secure \\ \hline
**LiFi** & Light-Fidelity & **UMTS** & Universal Mobile Telecommunications Service \\ \hline
**LMDS** & Local Multipoint Distribution Service & **uRLLC** & Ultra-Reliable Low Latency Communication \\ \hline
**LoS** & Line of sight & **V2X** & Vehicle to Everything \\ \hline
**LTE-A** & Long Term Evolution-Advance & **VLC** & Visible light communication \\ \hline
**MIMO** & Multiple-Input Multiple-Output & **VNF** & Virtualized Network Functions \\ \hline
**MITM** & Man In The Middle Attack & **VR** & Virtual Reality \\ \hline
**ML** & Machine Learning & **WCDMA** & Wideband Code Division Multiple Access \\ \hline
**mMTC** & Massive Machine Type Communication & **WiMAX** & Worldwide Interoperability for \\  & & Microwave Access \\ \hline
**mmWave** & millimeter Wave & **XR** & Extended Reality \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._