Sixth Generation (6G) Cognitive Radio Network (CRN) Application, Requirements, Security Issues, and Key Challenges

Table 1

Used abbreviations and explanation.

Serial no.	Abbreviation	Explanation
1	4G	Fourth generation
2	5G	Fifth generation
3	6G	Sixth generation
4	CRNs	Cognitive radio networks
5	CR	Cognitive radio
6	THz	Terahertz
7	MIMO	Multiple-input multiple-output
8	VRAN	Virtualized radio access network
9	UAV	Unmanned aerial vehicle
10	uRLLC	Ultrareliable low latency communication
11	CRAN	Cloud radio access network
12	BBU	Base band unit
13	O-RAN	Open access radio network
14	RRHS	Remote radio heads
15	ML	Machine learning
16	DL	Deep learning
17	NNs	Neural networks
18	UE	User equipment
19	WSN	Wireless sensor network
20	IoT	Internet of things
21	PUs	Primary users
22	SUs	Secondary users
23	SSaaS	Spectrum sensing as a service
24	u/mMTC	Ultra/massive machine type communication
25	eMBB	Enhanced mobile broadband
26	feMBB	Further enhanced mobile broadband
27	LDHMC	Long-distance and high-mobility communications
28	ELPC	Extremely low-power communications
29	uHSLLC	Ultrahigh speed with low latency communication
30	uMUB	Ubiquitous mobile ultrabroadband
31	uHDD	Ultrahigh data density
32	ITU	International telecommunication union
33	ITU-T	International telecommunication union-technology
34	MR	Mixed reality
35	AR	Augmented reality
36	XR	Extended reality
37	M2M	Machine to machine
38	M2H	Machine to human
39	H2M	Human to machine
40	BCI	Brain computer interface
41	ORT	Optical radio technology
42	RF	Radio frequency
43	FSO	Free-space optical communication
44	LiDAR	Light detection and ranging
45	ITU-R	International telecommunication union-radio communication
46	OF	Optical fiber
47	LPWAN	Low-power wide-area network
48	SRS	Smart reflecting surface
49	IoE	Internet of everything
50	SS	Spectrum sensing
51	QoS	Quality of service
52	VR	Virtual reality
53	CPS	Cyber physical systems
54	E2E	Everything to everything
55	AI	Artificial intelligence