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Research on WDM-PON Bearer 5G Application Scenarios and Technologies From ZKTEL

- May 25, 2018 -

    The 5G market can be described as the biggest hot spot in 2017. The industrial chain has eager expectations for 5G at all levels. In the 5G era, carrying bearers has become the consensus of the industry. Therefore, it is expected that bearer networks will be placed on 5G networks. Since 2017, international operators have also taken WDM-PON as a key program for 5G forward transmission. This article analyzes the application scenarios of the WDM-PON bearer in the 5G market through the 5G pre-transmitting bearer scheme, the 5G bearer network architecture, and the carrier's requirements for the bearer network. The latest technology research. ZKTEL produces 5G products like GPON ONU/OLT, EPON ONU/OLT, QSFP+,QSFP28,SFP+. Welcome to connect with ZKTEL, we will provide yours good services.

  1. WDM-PON bears 5G application scenarios

1.1 Forward Network Architecture Definition

      With the rapid development of the mobile Internet and the emergence of many new applications such as the Internet of Things, the fifth-generation mobile communication (5G) technology has emerged as a response to the explosive growth of mobile data traffic and the connection of massive devices.

      In 2015, ITU-R formally defined 5G three typical application scenarios: eMBB, mMTC, and URLLC. eMBB corresponds to high-volume mobile broadband services such as 3D/Ultra-HD video, mMTC corresponds to large-scale IoT services, and URLLC corresponds to services that require low latency, high reliability, and connections such as unmanned and industrial automation.

     November 28, 2016 China Mobile issued a white paper on requirements, architecture, and challenges for 5G C-RAN.

The 5G BBU function will be reconstructed into two functional entities, CU and DU (see Figure 1). The CU mainly includes non-real-time wireless high-layer protocol stack functions, and supports the deployment of some core network function sinking and edge application services. The layer 2 function mainly deals with physical layer functions and real-time requirements. The pre-post is divided into two levels, one-level pre-transmission and two-stage pre-transmission.

    The existence of the CU realizes the partial function concentration of the original BBU, that is, it is compatible with a completely centralized deployment and also supports distributed DU deployment.

    The two-stage forward C-RAN architecture provides network support for DU pooling or CU pooling. The first-level forward is Fronthaul, which supports eCPRI and other forward protocols. The second-level forward is also known as Midhaul. Fronthaul and Midhaul have different delay and bandwidth requirements for different 5G services.

    The large-bandwidth requirements of 5G forward and return transmissions drive the large-interface requirements of the transmission network, mainly including high-speed Ethernet interfaces or OTN/DWDM transmission interfaces. At the same time, with the introduction of eCPRI's new forward interface, the network architecture has evolved into a new architecture supporting DU and CU pooling. It presents new opportunities and challenges for wireless access and 5G bearers.

1.2 WDM-PON Bearer 5G Application Scenarios

When operators have base station site selection pressure, or need to release the BBU room, or need to deploy DU pools in dense urban areas, DU locations can be moved upwards and deployed in these scenarios. In particular, new scenarios for operators with existing wired services and wireless services are very suitable for the use of WDM-PON for bearer forwarding. The OLT can take advantage of the access room to centrally deploy the DU, DU pool and OLT co-sites. For the 5G URLLC service, it is recommended that the CU also co-locate with the OLT, DU. The DU pooling common station will make the user plane data transmission path of cooperative demand (such as CoMP) closer between DUs; DU and CU co-station will make Midhaul disappear and the 5G RAN user plane transmission delay is smaller.

2. The realization of WDM-PON technology and the significance of 5G bearer

The key technology of WDM-PON currently focuses on: colorless ONU technology, that is, clear and adjustable technology of ITU-T G.989.2 and CCSA WR WDM-PON standards to realize colorless ONU; and the other is the auxiliary management channel (AMCC) technology. RF Pilot-tone and Baseband Overmodulation.

In the WDM-PON solution, the development of key technologies such as optical module technology, OAM management, and protection switching plays an important role in the WDM-PON 5G bearer planning. Related agreements are being discussed and developed in the standards organization.

2.1 Forward Bearer Plan

The unified optical access platform for WDM-PON OLT equipment is used for 5G mobile forward transmission and supports wired optical access services. The 5G DU or BBU pool and the RRU are connected through a WDM-PON passive optical network to implement mobile service forwarding.

    WDM-PON as a 5G pre-transmission scheme embodies the following technical features:

1. The WDM-PON technology has a small delay, which can provide separate networking and service performance guarantee for 5G, government and enterprise services;

2. Large bandwidth, supporting 10G and 25G per channel, meeting the bandwidth requirements of 25G eCPRI forward signals;

3. High transmission efficiency. Embodied in two aspects, one is exclusive bandwidth without DBA scheduling, logical point-to-point. The other is management, using the AMCC signal-tuning technology, the management channel is superimposed on each wavelength, there is no OMCC reservation, there is no waste caused by GEMPORT resource reservation.

WDM-PON as a 5G pre-transmission solution will also reflect the value in engineering applications:

1. The WDM-PON solution is suitable for densely populated urban residential areas. Because of the "natural tree-shaped cable topology", "fixed convergence business", "intensive coverage."

2. You can share existing fiber infrastructure settings. The deployment of 5G networks requires a large amount of fiber resources. The network architecture is based on a point-to-multipoint tree topology of passive optical networks, which can greatly save fiber cabling resources. At present, FTTx fiber optic networks cover a wide range of areas and are rich in line and port resources. They can be fully utilized to reduce the deployment cost of 5G networks, reduce duplication of investment, improve the utilization of existing network resources, and quickly complete the intensive coverage of 5G networks.

3. After a plurality of wavelengths are converged on the AWG and branched to the branch fiber, a large amount of trunk fiber resources are saved.

4. AWG has less loss than POWER SPLITER. In the case of the same ODN networking, the replacement of SPLITER with AWG means farther transmission distance.

5. 5G and wired access can share room resources, such as Local PoP access points. In particular, the computer room based on AO reconstruction can play a more comprehensive role in network construction and balance the investment.

6. The OLT can be shared, and access to home users, government-enterprise users and 5G base stations can be integrated. Further improve equipment utilization, save network equipment deployment costs, and reduce resource requirements such as the engine room.

7. After the DU pooling, it helps to realize the co-construction and sharing of wireless and wireline access resources and build a future-oriented mobile convergence network. Including the control surface fusion of the fixed, to achieve certification, billing and user information, etc.; to achieve the fixed transfer surface fusion UPF fixed common platform equipment; can also achieve solid storage resource integration, such as CDN, MEC resources.

2.2 WDM-PON Standard Progress and Operators' Appeal

    Currently, the WDM-PON standard mainly studies WDM-PON systems with single-wavelength 10G rates (1.25G/2.5G/10G). When the single-wave rate reaches 10G, the mainstream technology of the WDM-PON colorless ONU is an adjustable technology. Standards organizations began to focus on the application of WDM-PON in 5G forward transmission, especially single-wave 25G WDM-PON systems. The ITU-T G.sup.5GP discussion group is advancing and discussing 25G WDM-PON.

    Since 2017, international operators have studied WDM-PON as a key solution for 5G forward transmission. Acting Orange, the current network is mostly D-RAN, C-RAN is not much, 5G C-RAN, consider CU on NG-POP, 5G pre-transmission to pay close attention to and study WDM-PON. DT, considering C-RAN, CU/DU separation, CU focused on the convergence layer. WDM-PON prequel is of interest. Telstra Australia, for C-RAN prequel, compares active DWDM and WDM-PON solutions. The three major operators in China, the China Telecom Research Institute, are actively promoting the testing and commercial trials of WDM-PON; China Unicom is mainly promoting G.metro and WDM-PON technologies for 5G bearers, which can be used as a simplified version of G.metro; China Mobile For 5G bearers, FlexE, WDM-PON can be integrated with it.

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