Practical application of Broadband Access Network

Broadband access networks are quite common. So I studied the basic knowledge of broadband access networks and the practical cases of comprehensive applications. I would like to share with you here, hoping to be useful to you. The optical fiber access network has been widely used in communication networks, and the comprehensive service access capability is one of the advantages of high hopes. In addition to voice, ISDN, and DDN Services, how to achieve broadband and evolution to NGN has become the focus of the industry, and has a great impact on its position in the future network.

The broadband access network of the optical fiber access network is facing the problem of transmission networking. At present, most of the bottom layer of the man uses SDH as the transmission platform. This SDH fixed bandwidth designed for Circuit Switching businesses is not only inefficient in transmitting burst data services, in addition, changing the bandwidth often means changing the physical interface and even the business type, and thus having to redesign and rebuild the network. At present, most of the common ADSL and LAN construction uses bare fiber direct connections. Although this method solves the difficulty of SDH carrying broadband at the access layer, however, the direct connection of bare fiber consumes large optical fibers, which leads to problems in the long-term development. It can be seen that the Broadband Network of the optical fiber access network must solve a lot of service transmission problems.

Currently, the most popular multi-service transmission methods in the industry use the MSTP solution based on the SDH Transmission Platform. According to national conditions, although the Internet data traffic has exceeded the voice service, the revenue of the voice service is still the main revenue of the telecom service, therefore, the MSTP platform must have a good TDM Service Transmission QoS guarantee. However, traditional SDH transmission devices are naturally based on the requirements of TDM services, regardless of their maturity or technical applicability, therefore, adding certain data transfer capabilities to the SDH platform is also a logical solution.

There are three ways to develop MSTP devices:
The first is the traditional early MSTP, which features the use of branch board resources on the SDH platform to provide data service interfaces. It features a point-to-point passthrough service with large granularity, mostly STS-1 VC cascade or E1 bundle mode. This type of device simply adds some data service interfaces to the functions of the original SDH transmission device to provide Internet bandwidth, it does not have the operation capabilities required by traditional services to provide devices, such as flexible billing policies such as ports, durations, and traffic, and user authentication, it can only be used for monthly subscription port leasing, Metro enterprise interconnection, and other solutions. Meanwhile, SDH is a point-to-point connection. The resource exclusive Technology System Based on bandwidth allocation by fixed time slot is incapable of providing a small amount of data service passthrough capability in case of burst bandwidth demands.

The second is to solve the disadvantages of exclusive bandwidth and low utilization efficiency of network resources. MSTP provides the built-in ATM and IP address exchange aggregation functions on the SDH platform, in this case, some functions such as bandwidth sharing and Statistical Multiplexing are available, and a small amount of network bandwidth is used to achieve multi-point access and bandwidth sharing. This solution involves multi-layer frame ing, resulting in low bandwidth efficiency, complicated overhead processing, and high device costs. It is difficult to apply the scale of the access layer. This solution is applicable to scenarios where TDM business is the main business and shaojing data business, saving the overall investment. In the long run, this solution is not an effective solution, especially when data services become the dominant business type of the network,

The third is to increase the transmission Networking capability on the service provision devices. The business exchange and transmission networking functions are organically unified to provide the comprehensive service transmission capability, this device form is also known as the next seven-segmented MSTP device. This solution has good broadband service carrying capacity and smooth evolution capability, and can adapt to the upgrade capability from shaojing broadband users to almost all broadband users, at the same time, it can well carry TDM services that account for the majority of current operating income sources, and ensure their service quality, network security, and operation and maintenance costs, in addition, it can well adapt to the broadband services that occupy the mainstream business volume in the future, such as video services, network TVs, multicast, and so on ), provide necessary controllable bandwidth and operation control capabilities for these businesses, and have the ability to evolve to the next generation of business. Considering the competitive landscape of broadband access networks and resident networks, such devices must have a low-cost, low-power, and compact structure space, and maintain a unified control signaling with business configuration management, maintain the consistency of the Operation Support Platform.

At present, the ATM technology is a good solution to solve the transmission load of Broadband Integrated Services in the broadband access network. The reason is that in addition to pure IP access or distribution network of pure broadcast programs, the Integrated Access Network should support both data, multimedia and voice services, real-time services are usually sensitive to QoS, so the broadband access network must provide QoS Assurance. Another condition that facilitates the application of ATM technology in the access layer is that, with the development of large-scale ASIC Technology and the improvement of design capabilities, the cost of commercial Chips Based on ATM Adaptation and switching has been decreasing. ATM is often selected as the link layer protocol between access nodes and networks that support QoS. For example, ADSL, APON, HFCs, and LMDS all adopt the ATM link layer protocol.

Currently, the Service bearer devices of various manufacturers are using the ATM technology to integrate TDM services. There are two solutions:
One solution is to integrate the data into SDH, encapsulate the grouped data into E1 through the IMA interface, and then map the data to SDH frames or map the ATM cells to SDH frames through the STM-1 interface; another solution is to integrate the E1 circuit signal into an ATM Cell. From the perspective of development, the data business volume will gradually become the mainstream of the telecom business. Using the IMA technology to transmit ATM services on SDH devices, the existing idle bandwidth resources can be fully utilized, however, its long-term development scalability and economics are not as simple as simulating E1 directly on an ATM Transmission Device.

In recent years, devices with certain ATM switching functions have become a trend in the development of broadband access networks in the form of Optical Fiber Ring Connection. The line interface of the ATM switching equipment is SDH frame, however, instead of using SDH to automatically replace K1 and K2 bytes, it relies on the switch matrix's ability to reselect routes during external line faults to achieve self-healing. Due to the SDH frame, this ATM ring can also be seen as a special case of SDH ring, but it saves sdh adm, instead of VP/vc adm of ATM, make the user-side interface finer. Because the ATM layer is introduced, the bandwidth dynamic allocation and management capabilities are strong. This technology effectively protects broadband services. QoS and security issues, combined with the TDM simulation feature of ATM, should be a group MSTP access transmission technology that meets the requirements of Integrated Access networking.

Due to technical complexity and cost-effectiveness, ATM has never become an end-to-end service solution. However, because it can centralize different services in one pipeline and provide classification management, establish an explicit path for traffic monitoring of PVC and VP to provide different connections for traffic load, digest congestion points on the network, and achieve efficient transmission, therefore, as a wide variety of broadband access network and service bearer technology, more and more Telecom experts are paying attention to it, in particular, in the case that the man's multiple business networks are relatively mature and widely covered, and that the user's resident networks and terminal devices are diversified, ATM can be used to adapt these businesses to access them, after that, it is a feasible technical approach that deserves further research and discussion to solve the problem of distributing broadband access networks to their respective metropolitan networks. ATM has a relatively high internal overhead when transmitting IP services, but this problem is not prominent in broadband access networks. The development of optical communication technology has brought a lot of low-cost original bandwidth to modern communication networks, how to use these bandwidths to provide customers with comprehensive and differentiated services with guaranteed service quality is the most confusing and worth considering for operators.

In addition, the full IP mode is used to provide a converged solution, that is, the TDMoIP or VoIP method is used to transmit voice and data services on the IP network. From the current situation, it is not a good choice to use the IP network to carry end-to-end real-time services, because the IP address, QoS, security, and management issues are not well resolved, more seriously, communication can only be completed through two sets of address encoding methods. To become the basic network of the future information network, the broadband IP network must first solve the problems of voice transmission and the quality of service (QoS) of real-time services such as video.

DPT is a packet-optimized optical transmission solution proposed by CISCO. It combines the bandwidth efficiency, service capability, and the rich bandwidth and self-healing capabilities of the optical fiber ring, supports multiple business types and low-cost applications based on LAN, MAN, and WAN. Because DPT adopts a dedicated method to achieve the rapid recovery of Layer 2, it is not yet an international standard and only exclusive product support, so it can only be used for controllable networks such as man ), it cannot be used for a large network across autonomous domains, and the future of development is unclear. For the operating broadband MAN, the openness of the network must be fully considered considering the future development.

Specific to the access layer, considering its unique high network construction cost pressure and small network scale, operators mostly adopt an integrated solution from one equipment vendor to facilitate management and reduce maintenance costs, the requirement for interconnectivity is lower than that for man or backbone networks. If the RPR standard, similar to DPT or IEEE developed on this basis, can solve the problems of cost and TDM real-time service QoS protection, it is also an option to consider when creating a network at the access layer.

At present, operators emphasize the pursuit of profit and return maximization business model, "market-oriented, customer-centric, and Benefit-Oriented ". In addition to using careful prediction and planning methods to guide the construction of backbone networks, man, and other fields, in the access layer construction, due to wide coverage, large investment, and fierce competition, the development of users is unpredictable. Therefore, access devices must be highly adaptive and provide various services flexibly as needed. In this case, MSTP with multi-service transmission capabilities built into the broadband access network device can achieve a kind of management is an ideal choice for the network of the integrated optical fiber access network.

1. Quick Access Network Management
2. Discussion on the Development Trend of Wireless Network Access Technology
3. Detailed description of the optimal residential broadband access solution
4. Development of Fixed Wireless Access Networks
5. Detailed description of the development history of Broadband Access Networks