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Since the birth of mobile communication networks in the late 1970s, mobile base stations have been with mankind for 40 years, bringing unprecedented changes to human society, but do you know its story? 1G: The Origin of Base Stations The deployment of mobile communication networks began in the late 1970s, which we call the 1G era. At that time, the full English name of the base station was Base Station, abbreviated as BS, which literally means "base station", and this name has continued to this day. In the 1G era, there were many standards, but there were two main mainstream standards: AMPS and TACS. TACS base station (Ericsson 1G analog base station RBS883) [color=rgb(51, 51, In 1987, my country established the first generation of analog mobile communication systems in Qinhuangdao, Hebei and Guangdong, marking the beginning of China's mobile communication industry. From the comparison of the pictures, we can see that the 1G base station at that time used Ericsson's TACS system. AMPS base station and antenna 1G is an analog system, which not only has low capacity and poor call quality, but also has extremely poor confidentiality. When I was maintaining a base station, I accidentally heard the conversation between users clearly. You may not believe it today. 2G: Integrated BTS The base station in the 2G era is not called "Base Station", but BTS, which stands for Base Transceiver Station. GSM network architecture Compared to the 1G base station called Base Station, BTS adds a "Transceiver" in the middle of Base Station, which is a more accurate name. Because Transceiver is the transceiver unit, it is an important part of BTS. Let’s take a look at the composition of the 2G base station... Ericsson RBS2206 BTS mainly includes public unit, transceiver unit and combining and splitting unit. The public unit includes power supply unit, transmission interface unit and clock distribution unit. The transceiver unit, full name Transmission Receiver Unit, abbreviated as TRX or TRU, refers to the collective name of the receiver and the transmitter. We in communications usually call it "carrier frequency". The functions of the earliest BTS transceiver unit include the transmission and reception, amplification, modulation/demodulation, encoding and decoding, and DSP digital processing of wireless signals, which is actually the integration of the baseband unit (BBU) and the radio frequency unit (RRU). The transceiver unit is a key component of the 2G base station, which is why the 2G base station is called Base Transceiver Station. The former Motorola and Nortel 2G base stations have now disappeared with the wind. Early 2G base stations were large and heavy, making expansion and operation and maintenance very troublesome. Each transceiver unit can only process one carrier signal, and one carrier frequency can accommodate up to 8 users at the same time. Every time the base station is congested and expanded, it is necessary to increase the carrier frequency and combiner, etc. The operation and maintenance engineers have to carry the heavy carrier frequency and shuttle up and down the base station on the roof every day. If the congestion continues, the cabinets will have to be expanded, which will increase the workload. Looking back, many buildings didn’t have elevators, and the base stations were on the rooftops. You had to go up when you looked up. The brothers held a carrier in their left hand, a combiner in their right hand, a computer bag on their shoulders, and a toolbox on their heads. They went up and down more than ten floors without any back pain or breathlessness. It was great to be young! To summarize, the 2G base station is an integrated BTS. The baseband processing, RF processing, power supply unit, etc. are all placed in a cabinet, which looks like a big refrigerator. The construction and expansion costs are high, and the operation and maintenance are also very troublesome. In the 3G era, base stations must develop in a simpler and lower-cost direction. 3G: Separation of BBU and RRU In order to distinguish it from 2G, the base station in the 3G era is no longer BTS, but NodeB. The "B" may be derived from the "B" in BTS. Basic architecture of 3G network Compared with the 2G era, the biggest change in base stations in the 3G era is the separation of BBU and RRU. Why should BBU and RRU be separated? As mentioned earlier, the BBU and RRU of 2G BTS are integrated into one, which is not only large and heavy, but also very troublesome to expand. Entering the 3G data era, facing the future, the baseband part must introduce technologies such as adaptive modulation and coding and MIMO multi-antenna to support the ever-increasing data rate requirements. If the baseband and RF are still not separated, it means that each expansion will require a separate channel from baseband processing, DAC conversion, RF power amplifier to feeder, which will undoubtedly greatly increase the construction cost. This is somewhat similar to the situation where our traditional indoor distribution systems today are facing MIMO technology and cannot adapt to future upgrades. Traditional 2G base stations are large and bulky, and now we need to build new 3G base stations in the computer room. The space in the computer room is limited, which requires further simplification of the 3G equipment in the computer room. What to do? The industry fell into deep thought. At this point, the popular software-defined radio opened a window for base stations. Can we use software defined radio technology to integrate baseband signal generation, modulation/demodulation, encoding and decoding functions into a "central base station hub" and transmit the modulated signal to a remote RF unit through a unified interface? Good idea. Add chicken legs tonight. Thus, there is a structure with separate BBU and RRU. BBU and RRU are connected through Common Public Radio Interface (CPRI) and Open Base Station Standard Initiative (OBSAI). One BBU can provide baseband resource pool for multiple RRUs.This modular base station architecture not only reduces the cost of network construction and improves the flexibility of network expansion and upgrade, but also avoids the high loss caused by long-distance transmission of traditional feeder lines by connecting BBU and RRU through optical fiber. 51, 51)] 3G distributed base station (ZTE) In addition, the operators have quietly set an ambush, because the power amplifier and RF module usually account for nearly 50% of the total cost of the base station. If the BBU and RRU are separated and then connected through a standard interface, it means that the operators can purchase BBU and RRU separately from different manufacturers, thereby removing the equipment lock binding, improving bargaining power, and further reducing procurement costs. However, this wishful thinking has not been realized to this day. 4G: The Legendary SingleRAN 4G LTE will evolve over the long term, emphasizing evolution. Therefore, the name of the 4G base station adds an "Evolved" in front of NodeB, i.e., eNodeB, evolved Node B. 4G: The Legendary SingleRAN 4G LTE will evolve over the long term, emphasizing evolution. Therefore, the name of the 4G base station adds an "Evolved" in front of NodeB, i.e., eNodeB, evolved Node B. 4G: The Legendary SingleRAN 4G LTE will evolve over the long term, emphasizing evolution. 4G LTE will evolve over the long term, emphasizing evolution. Therefore, the name of the 4G base station adds an "Evolved" in front of NodeB, i.e., eNodeB, evolved Node B. "]The basic structure of 4G network Entering the 4G era, software radio not only opens a window for base stations, this time it opens a door. The most significant feature of base stations in the 4G era is SingleRAN, which means that one set of equipment integrates multiple standards of 2G/3G/4G. SingleRAN also applies software-defined radio technology. It is another major change in mobile base stations after the separation of BBU and RRU. It further reduces the complexity and construction cost of base stations. SingleRAN was first launched by Huawei. As early as 2008, before the 4G era, Huawei and Vodafone deployed the world's first SingleRAN base station integrating 2G and 3G. Subsequently, Latin American operators such as AméricaMóvil, Finland's TeliaSonera, Sweden's Net4Mobility, and Aero2 all purchased Huawei's SingleRAN products. The reason is that Huawei's SingleRAN fully utilizes the flexibility of software and standards, is oriented towards future 2G/3G/4G integration, and can provide operators with a smooth evolution channel to 4G at a lower cost. The picture comes from Vodafone's SingleRAN report in the early years SingleRAN helped Huawei win many orders and laid a solid foundation for Huawei to open the door to the 4G market. At that time, overseas media reported that SingleRAN had become a star in the industry. The Economist reported that after America Móvil deployed Huawei's SingleRAN, its base station power consumption was reduced by 50% and the number of equipment required was reduced by 70%. Fortune magazine said in a report that Huawei's SingleRAN equipment can handle multiple types of signals such as 2G, 3G, WiMax, CDMA, GSM, etc. in one "box". The new technology is making the Chinese equipment manufacturer a more powerful competitor because the product can help operators save a lot of costs. SingleRAN is a legendary product in Huawei's wireless history. It has helped Huawei expand its overseas territory unprecedentedly. Since entering the 4G era, Huawei's wireless equipment share has climbed from fourth place to first in the industry. 5G: Base Station Reconstruction Now we are entering the 5G era. 5G supports ultra-high speed, ultra-low latency and ultra-large connections, and its services are diversified, which puts forward new requirements for base stations: 1) The fronthaul bandwidth of 5G base stations is as high as hundreds of G to Tbps. The pressure on the CPRI optical interface between the traditional BBU and RRU is too great, and some functions need to be separated to reduce the fronthaul bandwidth. 2) 5G is oriented towards multiple services. Low-latency applications need to be closer to users. Ultra-large-scale IoT applications require efficient processing capabilities. 5G base stations should have flexible expansion capabilities. Different from the BBU+RRU architecture of 4G base stations, 5G base stations are reconstructed into three parts: CU (central unit), DU (distributed unit) and AAU/RRU (remote radio unit). The network between RRU/AAU and DU is called fronthaul, the network between CU and DU is called midhaul, and the network between CU and core network is called backhaul. Such an architecture design can better promote RAN virtualization, reduce fronthaul bandwidth, and meet low latency requirements. There are four main deployment methods for future 5G base stations: 1) RRU/AAU, CU and DU are deployed independently The distance between RRU and DU is in the range of 0-20 kilometers, while the distance between DU and CU can reach tens of kilometers. 2) CU and DU are co-located CU and DU are together, without mid-transmission. Currently, most 5G base stations are deployed in this way. AAU of 5G base station [color= rgb(51, 51, 51)] 3) RRU/AAU and DU are deployed close to each other RRU and DU are deployed close to each other, which may be hundreds of meters, for example, to achieve coverage on different floors within a building. 4) Integrated deployment of RRU/AAU, DU and CU This situation is usually applied to micro-station coverage hotspots, in which only backhaul is available. I almost forgot to mention that the 5G base station is called gNB. Why is it called gNB? The full name of gNB is next Generation Node B. The abbreviation should be ngNB, but only one letter can be kept in front. What if it is called nNB? Grandma B? It seems that this name is not very nice, so let's just call it gNB.In fact, when naming 5G base stations in the early days, various manufacturers proposed different names. For example, ZTE called it NB BS, AT&T called it fNB, NEC called it 5NB, Intel called it gNB... Finally, 3GPP unified it as gNB. However, can a gNB represent a 5G base station? No. As we all know, there are multiple options for early 5G deployment, including independent deployment and non-independent deployment. Therefore, the names of 5G base stations under various combinations have also changed. For example, option 3 (non-independent deployment) is anchored to the existing 4G base station and core network. At this time, the 5G base station is called en-gNB; if option 7 is adopted in the future, the 4G base station under the 5G core network will no longer be called eNB, but ng-eNB. Does it belong to 5G base station or 4G base station? Also, as mentioned earlier, 5G base stations are separated into DU, CU and AAU/RRU. Therefore, there should also be gNB DU, gNB CU, plus various fronthaul function separation solutions, there will also be lls-gNB-DU, lls-gNB-CU... (lls, underlying function separation) Finally, use a picture to describe the development history of mobile base stations in the past 40 years. It should be like this...
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