With the development of science and technology and the advancement of society, mobile communication technology is undergoing rapid changes. While people are still researching and deploying third-generation mobile communication systems, in order to meet the requirements of future communication, the international communication community has begun to study a new generation of mobile communication systems. At present, the new generation of mobile systems cannot be precisely defined, but this new generation mobile communication system is conceptually and technically similar to the 4G system and the Beyond 3G system, so the communication system discussed in this paper is based on 4G and Beyond. 3G's next-generation mobile communication system. The new generation of mobile communication systems is not only a smooth evolution on existing communication systems, but also has its own distinctive features. These features include: (1) The new generation communication system supports higher rate communication with a bit rate of up to 100 Mb/s. In this way, we can better adapt to the needs of users for broadband services. (2) The new generation communication system supports richer mobile services and is more closely integrated with the Internet, including not only existing voice services, but also high-definition image services, online banking, wireless positioning and virtual reality services. Users can get any information service they need, anytime, anywhere. This is also the future direction of mobile communication services. (3) The new generation mobile communication system has an open structure, which will be more fully integrated with wireless LAN, Bluetooth, Ad hoc, WiMAX and UWB networks, and can better support the mobile phone mutual help function and realize wearable radio. (4) The new mobile system will be a highly autonomous adaptive network, which can adaptively manage its structure. It can adopt distributed management and multi-hop structure to meet the changes and evolution of users in service and capacity. (5) In order to meet the requirements for specific data services, the new generation of mobile communication systems will use more advanced algorithms to improve the security of the network. (6) The new generation mobile communication system can be well compatible with the previous wireless communication network, so that the existing network investment can be well used, which is also an important guarantee for the commercialization of the new generation mobile communication system. 3. Spectrum allocation of a new generation mobile communication system Since the new generation of mobile communication systems is still in the stage of exploration and research, there is no very precise division of the spectrum allocation for the new generation of mobile communication systems. At present, with the operation of wireless communication systems such as GSM, PHS, CDMA, WCDMA, WLAN, satellite and microwave communication, effective spectrum resources have become very scarce. For the 3G system, the World Radiocommunication Conference WRC-2000 specifies that the 1900MHz to 2025MHz and 2110MHz to 2200MHz bands are allocated to 3G systems and satellite communications, and the 806 MHz to 960 MHz, 1710 MHz to 1815 MHz, and 2500 MHz to 2690 MHz bands are used as 3G development. Alternate spectrum. For the new generation of mobile communication systems, because it combines multiple wireless networks and mobile communication systems, in order to meet the higher communication rate, the rapid growth of mobile data and video services and the goal of facilitating global roaming, more needs Bandwidth. Therefore, further research is needed on how to effectively integrate existing spectrum resources and provide frequency bands that can meet the requirements of the new generation mobile communication system. The new generation mobile communication system is a stage and goal in the evolution of mobile communication systems. It not only adopts new wireless transmission technology to improve the performance of communication systems, but also integrates with various existing wired and wireless networks; it not only includes the present Some mobile cellular network structures, and in some environments, may also use Ad hoc mode for networking, or a combination of two structures to form a two-hop or multi-hop network structure in a cellular network. In general, a cellular network is a widely-covered network networking method, and its goal is to achieve wide-area wireless coverage with limited frequency and power resources. Compared with the cellular network structure, the Ad hoc mobile network structure is more flexible. It adopts distributed management technology, and a group of autonomous wireless nodes cooperate with each other to form a mobile communication network. The wireless node is a mobile terminal in a general sense. It can also be used as a wireless relay and routing device to forward data of other users. Therefore, it has the functions of dynamic search, rapid network construction and network self-recovery, and has broad application prospects. In view of the importance of Ad hoc in wireless networking and next-generation wireless networks, the Internet Engineering Task Force (IETF) has established a MANET working group to conduct research on Ad hoc networks. In addition, in recent years, with the development and application of UWB (Ultra Wide Band) technology, nodes in wireless networks can transmit a large number of very short and fast energy pulses while working, and their transmitted signal power spectral density is low, very It is suitable as an implementation technology of a personal domain network in a new generation mobile communication system. With the continuous development and maturity of softswitch technology based on the separation of control and bearer, and the wide application of intelligent network technologies that can quickly realize various value-added services based on the separation of switching and service control, they are in the new generation mobile communication system. Lieutenant will play a bigger role. In addition, with the wide application of IP technology, the industry generally believes that the development trend of communication network structure based on next-generation mobile communication is based on IP network, and its framework structure can be represented by Figure 1, where each system uses IP-based packet transmission. The data flow reflects the network structure of the next generation network with IP as the core. At the same time, with the rapid development of network capacity and users, IPv6 technology will become the core protocol of the next generation network. Figure 1 Network architecture of a new generation mobile communication system and its access method From the perspective of the coverage and implementation technology of the wireless access network of the new generation mobile communication system, the industry generally believes that the future wireless network based on the new generation mobile communication system will be mainly realized by three levels of networks: wireless personal area network, wireless local area network and Cellular structure based mobile communication network. It can be seen that the wireless side of the new generation mobile communication system will be a heterogeneous fusion of different wireless access networks. These systems can achieve horizontal switching between the same layer, and vertical switching between different layers to implement the network. Inter-communication, in which the wireless personal area network is mainly used for short-range wireless communication in the personal and family range. Today's cordless telephone system and the future wearable wireless system are typical applications; wireless local area network refers to IEEE802. The wireless network of 11 international standards has a larger coverage and capacity than the personal area network; the mobile communication network based on the cellular structure refers to the existing 2G, the 3G to be deployed, and various cellular mobile network systems that will appear in the future ( It includes WiMAX networks that are now one of the 3G standards. These systems are wide-area communication networks that enable cross-regional roaming and mobility management. From the perspective of the user or the wireless terminal, in some areas, the wireless terminal may be covered by only one network. At this time, the terminal device has no choice to access the system; and in many places, the wireless terminal may be composed of multiple layers. The network is jointly covered. At this time, the terminal can not only select the optimal network access according to the user's requirements for service, network load and QoS, but also can effectively perform in a specific network layer according to the change of the wireless channel and the movement of the user. Horizontal switching and seamless vertical switching between different network levels, which shows that the new mobile communication system can achieve seamlessness in many aspects such as system, service and coverage, and is a seamless communication network in the true sense. . Of course, in order to achieve such an ideal network performance, the processing power of the mobile terminal is also highly demanded, and this is directly related to the electronic device process and its processing speed and capability, so in a sense The realization of a new generation of mobile communication systems is the support of all-round technological development in the entire communication electronics field. In mobile communication systems, due to the unpredictability of a large number of wireless channels, and the uneven traffic between different services and different users in a new generation mobile communication system, the network structure changes caused by mobile node mobility, and the high rate of broadband The requirements of communication and the seamless interconnection between different heterogeneous networks place high demands on the new generation of mobile systems. Therefore, in order to realize the requirements of the new generation mobile communication system, more advanced wireless transmission technology is needed. (1) OFDM technology OFDM is a multi-carrier modulation technique. Its core idea is to divide the channel into several orthogonal sub-channels, convert high-speed data signals into parallel low-speed data streams, and modulation is transmitted on each sub-channel. The advantage of this modulation transmission technology is that on the one hand, the transmission rate of the signal can be increased, and on the other hand, the inter-symbol interference (ISI) caused by the wireless channel can be reduced; at the same time, since each subcarrier is orthogonal, Mutual interference (ICI) between subchannels is avoided. However, as a multi-carrier transmission system, OFDM is sensitive to frequency deviation and has a high peak-to-average power ratio. This is a key issue that needs to be solved in the industry. (2) Software radio technology Software radio is one of the hotspots of current academic and industrial circles. Its basic idea is to use software to define and implement the functions of each module of the radio station on the general hardware platform of programmable control. Specifically, the A/D and D/A transforms are placed as close as possible to the RF front end, and the entire RF segment or the middle band is subjected to A/D conversion by using a wideband antenna or a multi-band antenna, and the subsequent processing is performed by a general-purpose processor or a DSP. The device is complete. Therefore, the software radio technology has the characteristics of flexible design and open structure. It can enable flexible network and service selection for mobile terminals in different frequency bands, different networks and different services, effectively realize network reselection, intelligent spectrum allocation and horizontal and vertical. Switching to achieve true personal mobile communications. At present, while effectively implementing the design of multi-band conversion, high-speed parallel DSP processing and high openness and expansive bus structure in software radio, how to further reduce the power consumption, volume and cost of software-based radio equipment is also its Key factors for practical and commercialization. (3) Smart antenna Smart antennas are one of the key technologies for future mobile communications. It has an intelligent function of automatically tracking the target signal and suppressing unwanted interference signals. Through its use, it can increase system capacity and increase coverage, and effectively save the transmission power of wireless devices. Therefore, it is widely recognized as one of the key technologies for improving the performance of mobile communication systems. The smart antenna is mainly implemented in two parts: an antenna array and an adaptive algorithm. The antenna array is a wireless signal transmitting (receiving) device composed of a plurality of antenna elements, and by performing space-time processing on the transmitting (receiving) signals on different array elements, the gain generated in the effective signal direction can be enhanced. The "trapping point" occurs in the direction of the interference signal; the adaptive algorithm is the core of the smart antenna, and the adaptive algorithm under the constraints of different beamforming criteria (such as minimum mean square error criterion, least squares criterion and minimum variance criterion) can be dynamic Track the useful signals to effectively realize the intelligence of the antenna. At present, how to reduce the implementation complexity of the smart antenna adaptive algorithm and improve the number of tracking and system capacity of smart antenna users is the focus of its research. (4) Channel coding technology Channel coding technology is an important method for mobile communication systems to resist multipath fading. In the 3G communication system, channel coding techniques such as convolutional codes and Turbo codes are employed. A new generation of mobile communication systems will adopt higher-level channel coding schemes based on these, such as Turbo code-based improved coding and decoding algorithms and LDPC, which are all close to the Shannon limit and can be used in lower Eb. /No guarantees sufficient decoding performance. Among them, LDPC codes have received extensive attention in the industry due to their relatively simple decoding. (5) Source coding technology The source coding in the mobile communication system includes speech coding and image coding. For speech coding, 3G mobile communication system adopts AMR coding method. In order to improve system capacity, the new generation mobile communication system also adopts hybrid coding method based on waveform and parameter coding. With the improvement of parametric coding technology, pure adoption cannot be ruled out. Parameter-coded vocoders enable speech coding. With the application of video-based data services in mobile communication systems, the role of image and video coding techniques in a new generation of mobile communication systems is particularly important. At present, encoding technologies such as H.263, MPEG4 and H.264 are important standards for achieving low bit rate compression coding. In addition, in the multipath fading environment of mobile communication, it is also the research direction of video coding to study the error concealment technique with better anti-fading effect. (6) MIMO technology MIMO (Multiple Input Multiple Output) technology is a wireless transmission technology that has attracted extensive research and attention in recent years. It uses multiple antennas at the transmitting end and the receiving end to resist wireless channel fading, thereby effectively increasing the capacity of the wireless system. A communication signal processing method based on spatial domain and time domain joint diversity. Theoretical and computer simulations show that the channel capacity of MIMO-based wireless systems increases linearly with the increase of the number of antennas, so it has a wide application value. A current research hotspot in the field of MIMO technology is space-time coding. Common coding methods mainly include space time block code, space time block code and BLAST code. (7) Adaptive wireless transmission technology Realizing the intelligence of communication networks is the constant pursuit of communication technology development. Adaptive technology is an embodiment of system intelligence. The so-called adaptive wireless transmission technology means that the mobile communication device can select different transmission modes according to different situations of the wireless network to obtain the best wireless transmission effect. In a new generation of mobile communication systems, this adaptive wireless transmission technology will be widely adopted. Among them, the source channel joint coding technology and the OFDM subcarrier adaptive modulation technology are good examples of adaptive technology. (8) Iterative receiving technology Reliability is the basic requirement of communication, and iterative technology can greatly improve the reliability of the receiving system. Iterative reception means that the detection and decoding performance of the receiver is optimized by multiple loop iterations at the receiving end. In general, the result of the previous iteration is always part of the input of this iteration, and the more the number of iterations, the better the decoding performance of the receiver, but the system complexity is correspondingly increased, so in actual implementation, it should be in performance and A compromise between complexity. Iterative techniques have evolved from the iterative decoding techniques of Turbo codes and are now more widely used. At present, Turbo iterative channel estimation and decoding, joint iterative reception of beamforming and decoding, and MIMO-oriented iterative receiving techniques are all examples of specific applications of iterative receiving techniques. With the rapid development of hardware devices and digital signal processing technologies, these iterative techniques will be widely used in later generations of communication technologies. (9) Intelligent spectrum allocation technology With the development of mobile and wireless communication systems, wireless spectrum resources are increasingly becoming the bottleneck for the development of these systems. The effective use of wireless spectrum resources can not only improve the communication quality of mobile communication systems, but also effectively improve the capacity of communication systems. Intelligent spectrum allocation technology based on spectrum adaptive detection is an effective method to achieve these advantages. First, in the future, when multiple wireless communication systems coexist, the mobile terminal can automatically access the idle wireless communication system through spectrum detection, so as to achieve effective load balancing and QoS guarantee between different systems. Secondly, through intelligent spectrum allocation technology. The channel can be dynamically selected between the mobile terminal and the access device, thereby improving the communication quality of the wireless communication system. At present, the main research fields based on intelligent spectrum allocation technology include spectrum-aware MAC layer access technology and spectrum-aware multi-network resource management. The new generation of mobile communication system is still only a concept and outline. This paper combines the development trend of the industry and comprehensively expounds the understanding and understanding of the new generation mobile communication system based on the related technical literature reports. With the development and drive of technology and market, the concepts and standards of new mobile communication systems will become clearer and clearer. At the same time, as the key technology to realize the next-generation mobile communication system will gradually mature, and finally realize the effective integration of different mobile and wireless networks to achieve a beautiful blueprint for ideal personal communication. Hydrogel Screen Protector Sheets Universal Screen Protector, TPU Screen Protector, Hydrogel Protective Film, Mobile Phone Screen Protector, Hydrogel Screen Protector, TPU Protective Film Shenzhen Jianjiantong Technology Co., Ltd. , https://www.jjthydrogelmachine.com