Abstract: The demand for 4G network construction is based on China Mobile’s goal of 4G construction in 2014, and plans to build 500000 TD-LTE base stations by the end of the year. As of now, the cities with mixed networks of China Unicom and China Telecom have developed from their initial 16 cities to 40 cities respectively. With the large-scale construction of 4G networks, the construction process is also facing more and more problems. On the one hand, considering the breadth of 4G network coverage, as the coverage range of 4G base stations is smaller than that of 3G base stations, LTE sites in 4G networks will be more dense. Among them, in order to meet the continuous coverage of 4G networks, it will be necessary to implement

4G network construction requirements

According to China Mobile’s goal for 4G construction in 2014, it is planned to build 500000 TD-LTE base stations by the end of the year. As of now, the cities with mixed networks of China Unicom and China Telecom have developed from their initial 16 cities to 40 cities respectively. With the large-scale construction of 4G networks, the construction process is also facing more and more problems.

On the one hand, considering the breadth of 4G network coverage, as the coverage range of 4G base stations is smaller than that of 3G base stations, LTE sites in 4G networks will be more dense. Among them, in order to meet the continuous coverage of 4G networks, it will be necessary to build new sites in the 4G coverage blind spots of existing sites, while in some new sites, fiber optic resources are scarce. Especially in mega cities such as Beijing, Shanghai, and Guangzhou, the progress and difficulty of fiber optic deployment cannot meet the requirements of network construction, and mobile backhaul network resources are facing enormous pressure and challenges. On the other hand, considering the depth of 4G network coverage, for data hotspot areas and coverage edge areas, in order to improve user perception and experience, Small Cell small stations based on macro base stations will be more widely deployed in the next stage of 4G construction. The deployment of Small Cell small stations will be more flexible, with smaller coverage and higher deployment density. The backhaul scheme based on Small Cell small stations also poses new challenges to network construction.

In the above situation, domestic operators have officially incorporated microwave transmission solutions into the construction plan of 4G networks. As an important solution for mobile backhaul, microwave transmission products are widely deployed in the networks of global operators due to their compact structure, flexible deployment, fast installation, and simple maintenance. With the widespread deployment of LTE networks worldwide in recent years and the development of microwave transmission technology, microwave transmission products have played a more important role in 4G networks.

Large capacity and bandwidth technology

With the development and evolution of mobile communication networks, the microwave products currently used in 3G and 4G networks are mainly packet microwave products. Thanks to the development of chip technology and system technology, as well as more open frequency policies and resources, the transmission capacity of grouped microwave products has greatly exceeded that of the previous generation TDM microwave products. At present, the modulation and demodulation mode of the most advanced microwave products can support up to 2048QAM, which is 40% more efficient than the traditional TDM microwave modulation mode with a maximum of 256QAM in terms of spectrum utilization. In addition, the open use of 56MHz or larger frequency bandwidth in the traditional frequency band and the recent attention of operators to the E-band frequency band (80GHz) further enhance the transmission capacity of microwave products. In traditional microwave systems, under 2048QAM modulation and 56MHz bandwidth conditions, XPIC technology can achieve an air port service transmission capacity of over 1Gbps at a single frequency point. In the E-band frequency band, due to its rich and clean spectrum resources, a larger bandwidth (such as 250MHz~1.25GHz) can be allocated to achieve ultra large air port service transmission capacity. For example, in the E-band frequency band, under 256QAM modulation and 500MHz bandwidth conditions, a maximum air port service transmission capacity of 3.2Gbps can be achieved.

Adaptive modulation and demodulation technology and QoS functionality

In response to the business characteristics of 4G mobile networks, microwave transmission equipment uses adaptive modulation and demodulation reception to combat various fading during the transmission process. When the transmission environment and conditions deteriorate, the performance of the microwave system is changed through changes in modulation and demodulation methods to ensure the normal transmission of services. The bandwidth change caused by modulation and demodulation changes can be classified and processed for different priority services through the QoS function of the microwave system. The eight levels of QoS mechanisms within microwave devices, including classification, scheduling, shaping, and conflict avoidance mechanisms, can achieve more precise and flexible processing of 4G services. By adjusting the length of each internal business queue, the delay and throughput of business transmission can be optimized according to the type and nature of different businesses.

Application of V-Band Microwave Products

According to the global deployment of V-Band (60GHz) microwave products, the main advantage is that this frequency band can be used for free, reducing spectrum usage costs; Under 256QAM modulation and demodulation mode, it can support a service throughput of over 400Mbps. In addition, due to the significant oxygen attenuation in the V-Band frequency band and the limited microwave transmission distance (up to approximately 300m), the frequency multiplexing efficiency of V-Band microwaves is very high, and the frequency interference between microwave transmission links is very limited. It is very suitable as a backhaul solution for densely deployed Smallcell small stations. At present, NEC’s commercially available V-Band microwave products have been deployed in multiple operator networks in five countries. This product has a very high integration level and adopts an all outdoor product structure with a built-in high gain flat antenna. The total weight of the microwave product is only 5kg, making it very suitable for deployment in various environmental conditions, including streets, walls, road poles, bus stops, newsstands, etc.

High integration, low power consumption

With the comprehensive deployment and rapid construction of 4G networks, power consumption has become one of the biggest problems in network construction. REF545KB133AAAA will incur huge network operation and maintenance costs due to device power consumption. On the basis of the development of RF technology and technology, the integration level of microwave systems is increasingly improving, and the structure is becoming simpler and smaller, in order to further reduce the power consumption of microwave products. Among them, NEC, with its leading RF technology and manufacturing process, released the world’s first ultra compact and miniaturized handheld microwave outdoor unit (IAG/IAP ODU) in 2013, surpassing similar products in terms of size, weight, and power consumption. Compared to the microwave products before NEC, this new outdoor unit (ODU) has reduced its volume by one-third and weight by half, only 2kg; Power consumption savings of at least 30%, with a minimum of only 18W.

Fronthaul Microwave Solution

At present, the new generation of microwave products can easily achieve a transmission capacity of gigabit rates. With the development of microwave technology and the opening of new spectrum resources, the transmission capacity of microwave products will be further improved, the variety of products will be more diverse, and the microwave application scenarios will also be more extensive. Relying on the stable and reliable performance and large capacity transmission capacity of microwave products, NEC released its first CPRI microwave product in the E-band frequency band in 2014, which is applied to wireless connections between baseband processing units (BBUs) and radio frequency remote modules (RRUs) of distributed base stations, providing a new outdoor solution for front-end backhaul in mobile networks. NEC’s CPRI microwave products have a transmission capacity of 2.5Gbps, which can meet the speed requirements of CPRI Ver5.0 Option-3 (2457.6 Mbps). They provide a standard CPRI service interface and can be used to solve multi-channel transmission solutions for BBU+RRU. The introduction of CPRI microwave products has made the mobile network construction of operators more diversified and the network structure more flexible.

Diversified products, advanced technology and functions, stable system performance, simple and compact structure with ultra-low power consumption, strong environmental adaptability, and fast and easy deployment and installation make microwave products an important transmission method in the construction process of mobile transmission networks, receiving widespread attention from operators. In the future construction of 4G networks in China, microwave products will also play an increasingly important role, providing more choices for network construction of various operators and improving the efficiency of network construction.