Optical transmission solution of 5G mobile network
Background
The fifth generation mobile phone mobile communication standard, also known as the fifth generation mobile communication technology, English abbreviation: 5G.According to the schedule organized by 3GPP, R14 standard mainly carries out research on 5G system framework and key technologies;R15 meets the 5G demand in some scenarios and starts the commercial process;R16 will do all the standardization.The three standards are expected to be completed in March 2017, June 2018 and December 2019, and the final complete 5G standard will be submitted to the International Telecommunication Union (ITU) for commercial use in early 2020.
According to the 3GPP plan, 5G standards are divided into NSA and SA (Standalone networking).Among them, 5GNSA networking requires 4G base stations and 4G core network, and 4G is used as the anchor point of the control plane to meet radical operators' requirements of utilizing existing LTE network resources and realizing the rapid deployment of 5GNR (NewRatio).
On June 14, 2018, 3GPP held a plenary meeting in the United States and formally approved the freezing of the 5th Generation mobile Communication Technology Standard (5GNR) Independent Networking (SA) function.The 5GNR non-independent networking (NSA) standard has been frozen since December last year, so the first phase of fully functional and complete 5G standard has been officially released, and 5G commercial use has entered the full sprint stage.
The main features of 5G network to provide services include large bandwidth (maximum user experience rate of 1Gbps), low delay (1ns) and massive connection (connection density of 106/km2), thus putting forward new requirements for bearer network in terms of bandwidth, capacity, delay and networking flexibility.The baseband signal of 5G base station AAU adopts digital transmission, and the air interface adopts eCPRI protocol interface, with a typical rate of 25.165824Gbps. Considering the scenario of co-station with 4G, it needs to be compatible with CPRIoption10 at a rate of 24.33024Gbps.
5G has come. As a member of the optical communication device industry, here we will talk about the optical devices that will be used in 5G network. They all meet the massive demand of tens of millions of levels.Optical communication devices are the core components of optical transmission network, carrying the key network physical layer functions such as photoelectric conversion, optical wavelength multiplexing and demultiplexing, and optical power distribution.Compared with the current 3G4G network, the biggest change of 5G in the wireless bearer network lies in the field of the forward and intermediate transmission. The forward transmission is the connection between the base station and the DU(DistributeUnit, responsible for handling the physical layer protocol and real-time service), and the intermediate transmission is the connection between the DU and the CU(CentralizedUnit, centralized unit, centralized unit).Handles non-real-time protocols and services).
The wireless base station is usually installed on the communication tower or the roof of the building, which is in the sun and the wind, so the optical devices used in the forward transmission need to meet the outdoor scene. The most important thing is that the operating temperature of the devices should meet the industrial requirements, -40℃~85℃.By the way, another indoor scene is generally the requirement of commercial grade temperature, 0~70℃.
In the prequel scenario, most transmission distances are required to be less than 10kmLR, of which 80% are less than 5km and 20% are between 5 and 10km.Of course, there will be a gap between the theoretical value and the practical application of the live network. There will certainly be problems such as increased attenuation of the optical fiber aging link and the critical distance of the coverage area. Therefore, the transmission distance specification above 10km, such as 20kmER, is still needed.In the medium transmission scenario, the transmission distance is required to be between 10 and 40km, and there are two operating temperature requirements, industrial and commercial.Currently, leading active manufacturers in the industry have launched or are launching a series of optical module solutions for pretransmission and intermediate transmission applications, including pretransmission 25GLR/ER, 25GLR/ERBIDI, 25GCWDM/DWDMER, 25GSFP28TUNABLE,In the transmission of 100GQSFP28LR4/4WDM40, 200GQSFP56LR4 and other industrial optical module products.We also offer industrial passive products such as 5GOMUX,CCWDM,AAWG, etc.
Figure 1: Speed and distance of 5g forward pass
Optical module is photoelectric conversion, the intermediate transmission medium is optical fiber, the largest investment in optical network is always optical fiber resources, so the choice of equipment and devices should first consider the optical fiber.Due to the factors of policy and population, optical fiber resources are abundant in China's cities and most regions, but they are very scarce in rural China and most regions abroad.Fiber is precious, so save it with optical modules, so there are three options for 5G pretransmission.
1.Scenarios where optical fibers are abundant
In the scenario with abundant optical resources, use optical fibers for direct connection, one fiber for each sector, and 25GLR/ERBIDI for optical modules.Generally, a base station has three sectors, so the BIDI scheme only needs three optical fibers to meet the traffic forward of a base station, and is conducive to high precision clock synchronization.Whether the descending wavelength is 1310nm or 1330nm is unclear.OPTICO offers a full range of 25GLR/ER, 25GLR/ERBIDI, 25GCWDM/DWDMER, 25GSFP28, with proven manufacturing processes and ultra-high cost efficiencies to save customers fiber resources and wiring costs.
Figure 2:5G forward optical fiber direct connection scheme
2.Scenarios where optical fiber resources are scarce
When optical fiber resources are scarce, the WDM scheme is needed. All service wavelengths of a Base station are multiplexed into one or a pair of optical fibers for backtransmission to save optical fiber resources from the base station to DU, which is called OneFiberOneSite(one optical fiber for one base station).A large number of colored optical modules are required, which may cause inconvenience in installation, spare parts, and maintenance. Tunable optical modules are designed for use.Therefore, in this scenario, OPTICO can provide customers with 25GCWDM/DWDMLR/ER, 25GSFP28TUNABLELR/ER, the wavelength can be O band and C band, as well as industrial passive WDM products 5GOMUX, CCWDM and other modules.
Of course, the more efficient way to return the network is to sink the wave division equipment directly to the base station and DU, namely, the active WDM scheme, which can be compatible with 2G/3G/4G services of the live network, and can realize more L3 layer service management and optimization functions, of course, which will increase the CAPEX.
3.The extreme shortage of backpropagation backbone fiber resources
In case of extreme shortage of back-up backbone fiber resources, traffic from multiple Base stations should be aggregated into one DU for back-up, which is called OneFiberNSites(base-station) (one backbone fiber for N base stations). This is a point-to-multipoint passive WDM scheme.For example, the commonly used AAWG40 wavelength can cover 6 base stations (each base station has 3 sectors, a total of 18 AAU, 20 waves up /20 waves down).This topology structure conforms to PON based optical passive network and maximizes the advantage of the old and present network ODN network.
At present, there are only mature commercial grade AWGs in the industry, with the operating temperature range of 0℃~75℃. In the future WDM-PON network and 5G pretransmission solution, the AWG operating temperature range needs to be further increased to the industrial grade -40℃~85℃, which puts forward more stringent requirements for hot and non-hot packaging, and further increases the requirements for chip-level non-heat AWGs.Still need the industry colleagues to work hard to break.If the industrial AWG is still immature and the installation environment is not suitable to meet the commercial operating temperature, PLCsplitter can be considered when the link optical power budget can meet the requirements. Splitter products can fully meet the requirements of industrial operating temperature at present.
In the P2MP scenario, optical modules 25G CWDM/DWDM LR/ER, 25G SFP28 TUNABLE LR/ER are mainly used. The wavelength can be O band and C band, and industrial passive WDM products 5G OMUX, CCWDM, etc.AWG or PLC Splitter.OPTICO is the largest PLC Splitter/FBT Coupler manufacturer in Shenzhen, offering a full range and a variety of customized PLC Splitter/FBT Coupler/WDM Devices.
Figure 4:5 G forward point-to-multipoint passive WDM scheme
Conclusion
5G is a key milestone in the history of communications. The market is large and challenging, and OPTICO will continue to provide customers with innovative design and solutions for optical interconnection.