Investigation and Technological Comparison of 4G and 5G Networks

Mobile cellular data networks have allowed users to access the Internet whilst on the move. Many companies use this technology in their products. Exam-ples of this would be Smart Meters in the home and Tesla cars having their “over the air updates”. Both of these two companies use the 4G and 5G technology. So this report will include a technical overview of the technology and protocols (LTE Advanced) used in 4G and 5G networks and how they provide services to the user and how data is transferred within the networks. And there are lots of different parts about the network architecture between the 4G and 5G systems. This report will talk about some different parts between these two systems and some challenges in them.

great convenience for the masses in communication, entertainment and business. Compared with previous generations of communication technologies, 4G has incomparable advantages, mainly in that 4G can be deployed in places not covered by DSL and CATV modems, and then extended to the whole region. In fact: 4G is the same as LTE technology, and they are both evolved from the existing 3G wireless communication technology. In other words, 4G is an advanced form of 3G [1].
As the most important protocol of 4G communication technology, LTE Advanced has two different standards: TD-LTE and FDD-LTE. These two modes correspond to two different duplex modes: TDD and FDD. TDD is what we call time division duplex. It means that uplink and downlink are crossed in the same frequency band according to time allocation, which can make better use of spectrum resources and facilitate layout; in addition, FDD is called frequency division duplex, which means that uplink and downlink are carried out simultaneously in different frequency bands. The advantage of FDD mode lies in its stronger data transmission capability. In fact, 4G uses OFDM to modulate downlink, while SC-OFDM to modulate uplink is quite different from 3G [2].

Development and Formulation Organization of 5G Protocol
The official name of 5G is IMT-2020, which is the fifth generation mobile communication standard formulated by the International Telecommunication Union. As for the formation of 5G protocol, there is a unified standard in the industry field, instead of the multi-standard parallel standard in previous times. It can be said that the formation of 5G is the result of joint efforts of many organizations, among which 3GPP is the most important organization in standardization work. As a matter of fact, the reason why 3GPP was originally established was to customize technical reports and specifications for the third generation mobile communication system, and then it gradually evolved into the leading institution for formulation. As a standard, Release specified by 3GPP can complete the specification of one version in 1 -2 years on average, and the first standard version of 5G is called R15 [3].

5G Protocol Framework
As the first 5G standard of 3GPP, R15 is mainly used to study the Phase1 phase of 5G. At this stage, we mainly study the definition of NR (the new global 5G standard based on OFDM is also the foundation of the next generation cellular will be studied, and the framework of NR protocol will be further improved on the basis of R15. In addition to optimizing uRLLC on the basis of R15, R16 will also play its unique competitiveness in other vertical industries. The following is a chart to introduce it ( Figure 1).
5G is committed to research in eMBB, mMTC, uRLLC to provide services for people. EMBB refers to enhanced mobile broadband, which can provide users with larger system capacity and faster wireless access rate, so that users can enjoy a better ultra-clear experience. MMTC refers to mass Internet of Things, which is mainly to prepare for the wide popularization of Internet of Things in the future. This research can be applied to intelligent logistics, smart cities and even people's daily fitness. URLLC refers to high reliability and low delay. This research has been used in industrial production precision control, UAV (Refers to drone driving technology) remote monitoring and emergency personnel tracking, and it is believed that it will have a great impact on human life in the future [4].

4G Network Architecture
The architecture of 4G network system consists of three parts, namely EPC, eNB and UE. Among them, EPS is composed of EPC and radio access network E-UTRAN, which is often called 4G network system. The core network EPC is mainly responsible for verifying user identity, transmitting user data and managing user data. The radio part (E-UTRAN) of 4G system mainly includes some functions of eNB and NodeB and some functions of core network. The specific framework is shown in Figure 2.  is the evolution of system architecture, and IMS mainly solves the problem of carrying multimedia services such as voice to 4G network. The 4G basic architecture defined by GPP includes the following key points: First, MME is the control core of 4G network architecture, which is mainly responsible for handling control signaling such as user access control, service bearer control and handover control. Serving Gateway, as the anchor point when switching between local base stations, is mainly responsible for transmitting data information between base stations and public data gateways, and providing buffer for downlink data packets. Then PDN Gateway, as the anchor point of data bearer, can carry out packet forwarding, packet parsing, billing of basic related services, commercial QoS control, and so on. The full name of HSS is Home Subscriber Server. It is a database for storing contracts signed by users, and the stored information includes user security control information, user policy control information, user location information, user identification information and so on. Then, the full name of PCRF is Policy and Charging Rules Function. It mainly carries out policy control and charging control. It means that according to the contract selected and signed by the user, the user's service usage and charging strategy is determined and transmitted to the policy executor in the gateway, and finally the strategy is implemented.

5G Network Architecture
The 5G network architecture adopts SBA architecture, which is called Service Based Architecture. In fact, 5G network is a user-centered intelligent elastic network, which splits the original whole into several individuals with independent functions, and these individuals play their own roles. Next, we analyze the 5G network in particular. First, we look at the unlimited network components of 5G network, which are CU, DU and AAU. CU is used to handle non-real-time services. DU is used to handle real-time business and physical requirements. The AAU is composed of RRU, passive wireless and a part of BBU physical layer. The architecture diagram of 5G unlimited network is shown in Figure 3.

Challenges of Terminal Technology
In order to meet the market demand, the terminal technology of 5G will be di-

Conclusion
This report is a technical overview of the technology and protocols used in 4G and 5G networks and how they provide services to the user and how data is transferred within the networks. Then, we make a comparison of the network architecture between the systems. Next, there is a description of the technical challenges in implementing mobile data communications and a table that compares technical properties of 4G and 5G. Finally, we make a conclusion on your findings and description of where you feel that the technology will progress.
With the development of science and technology, 4G can no longer meet people's needs, while the research of 5G solves the problems of network delay and insufficient storage space. It can be seen that the performance of 5G is better than the previous network system. And I think that in the future, 5G will develop towards virtual industries like VR. Finally, it makes human life more convenient.

Conflicts of Interest
The author declares no conflicts of interest regarding the publication of this paper.