Next-generation optical network architecture aimed at five directions

In the high-speed, large bandwidth demand driven by the telecommunications network has been developing rapidly, but the energy issues have been aroused widespread concern operators, telecommunications equipment manufacturers, service providers have forecast, if there are 1000 1.2P router, its energy consumption will reach 1.5 Gigabit power, the equivalent of a nuclear power plant. To this end the EU set up a green photoelectric networking groups dedicated to energy-saving light device research. Chinese Academy of Engineering Wu Hequan in 2010 China Internet Conference opening ceremony, mentioned: "Broadband Internet is the flow under the extraordinary development of the mobile Internet will increase the energy consumption of the network, the need in terms of system technology development efficient, energy-saving Internet. "As an important part of the telecommunications network, optical network plays an important role in the green, energy saving.

Construction of low-carbon green network imminent

With the progress of society and the economy continues to develop, contradiction between energy consumption and environmental protection become more prominent. On the one hand, the importance of the environment for sustainable human development, has been unprecedented attention; to improve the environment, reduce pollution, has become the urgent voice of the times. On the other hand, energy depletion looming, energy consumption doubled every year, the total energy consumption of excessive energy consumption and low efficiency is a major bottleneck to limit human development. Solve the energy problem, the protection of the living environment, have become formidable challenges to human development.

The rapid development of human society as a symbol of industry, communications industry to bear the brunt of the energy challenge. With the gradual improvement of people's communication needs, a rapid increase in ICT network coverage, ICT energy consumption is also rapid growth, but increasing consumption of network equipment and components. Data show that, ICT energy consumption in 2009 accounted for 8% of total world energy consumption. As an important part of the ICT infrastructure, energy-saving measures telecommunications networks also put on the agenda.

telecommunications network
Figure 1 telecommunications network

Telecommunications network structure shown in Figure 1, from the three components of the telecommunications network to start, namely core, metro and access networks, optical networks currently existing summary representation of energy-saving programs.

Promoting multi-core network

The core network is the main parts of the network with a wide coverage, long distance transmission, data volume, transfer rate is high. Backbone network energy consumption of the total energy consumption of about 12% is expected in 2020 will reach 20%.

First, the core network traffic in different sizes at different times of day. When the traffic load is low, the nodes and links suspended or the presence of a low utilization rate, resulting in a waste of energy. How to achieve maximum energy efficiency, namely, how to turn off as many free nodes and links, is key. This problem is NP-hard problem, usually MILP (Mixed Integer Linear Program) to resolve, but with the increase of network nodes, MILP calculation increases dramatically, and therefore only suitable for small networks MILP.

For large networks, heuristic algorithm can be used to complete the routing and wavelength assignment, network effective components is minimized. Now commonly use local search, multiple search and global search space to deal with NP-hard problems. Local search algorithm is a generic term for a class of approximation algorithms, which from an initial solution, every step to find a better solution in the current field, the objective function gradually optimized until no further improvement so far; multi-space search algorithm search space smoothing techniques to reduce the number of local minima; global search algorithm, it refers to the global search or global optimization using SAT question a special transformation model discrete Boolean space into a "continuous amount of space on the real SAT question "The global optimization method known steepest descent method, Newton method, quasi-Newton method, cutting plane method, ellipsoid method, homotopy method, Boolean difference method.

Second, the core network IP routing is the main energy-consuming equipment, its energy consumption accounts for about 90% of the total net energy consumption, how to reduce energy consumption is an important aspect of the core network routing saving to be considered.

Core routing line cards and chassis energy can not be ignored, line cards and chassis configurations different result in different power consumption. Generally the higher the level of the chassis is filled, saving more obvious, that is, high fill rate is less than the low filling factor chassis Chassis energy consumption per bit.

Third, the core network presents multi-layer network structure, so it should take into account the comprehensive energy saving multi-layer networks. Since most energy exchange and transmission equipment to some extent, depending on the traffic load, thus relates to multilayer traffic grooming to achieve network optimization business, so as to reduce the amount of use of the wavelength and ADM. Currently focused on traffic grooming WDM ring network under static business plan by establishing universal traffic grooming model, using heuristic algorithm to solve the traffic grooming to achieve network optimization. In addition, the transmission route of IP packet size affect its energy consumption there. When that is constant bit-service transmission, IP packets larger energy is smaller.

Fourth, the traditional best path selected on the basis of the minimum number of hops, but the minimum number of nodes hop path is the excessive use of the possibility of large, resulting in net energy increase and affect the network lifetime. Therefore, it is proposed energy-aware routing, it will route the remaining energy is selected as the best path indicators, thereby reducing the network energy consumption and prolong the network lifetime. Energy-aware routing in two designs: one is the power efficiency of the design, namely the integration of routing ASICs / FPGAs and propose a scalable central structure, making routing energy consumption reduced by 50%. Another power-saving design, namely to reduce the extra energy, including static and dynamic performance control performance of the control of both. Static performance control can achieve 10% to 20% energy saving, Dynamic Performance Control can be changed dynamically according to the arrival traffic routing performance, it is the next generation routing development.

MAN local conditions

MAN boundary between LAN and WAN, which covers the geographic scope of the city, connecting the user's device and service aggregation and core network directly connected. MAN used different network technologies are also different. In the main technology MAN has SONET, WDM ring, Ethernet. Metro WDM ring structure which is widely applied.

Consider three kinds of structure for unidirectional WDM ring network: FG (First-Generaion) optical network, SH (single-hop) networks, MH (multi-hop) networks. In FG optical network, each node inflow and outflow of business is electrical processing, including relay service; in SH network, when the node is the source node or the destination node only when the electrical processing; MH network between both of Room. When unidirectional WDM ring network with uniform service, the capacity and the connection rate approaching wavelength, MH network energy consumption is lower than FG. When the low connection rate, MH network better than SH network, because the network service multiplex MH more flexible terms.

Research priorities Ethernet energy savings, the main problem is to reduce the energy consumption of the Ethernet interface. IEEE 802.3az work of the Working Group, in order to reduce the energy consumption of Ethernet, Ethernet Working Group for efficient electronic interfaces including 1000BASE-T and 10GBASE-T, standardized process. The main idea of ​​this aspect of the study is: when the load is small, by reducing or even shut down the port speed port to reduce energy consumption. Research on the Ethernet energy issues will be further cut operating costs Ethernet, making Ethernet gradually become a green technology.

Access Network two-pronged approach

long-reach PON Chart
Figure 2 long-reach PON Chart

As a network infrastructure connection between the user terminal equipment and some service network nodes, the access network is the last one kilometer telecommunications network facilities, consisting of most of the telecommunications network. Modern access networks are characterized by integrated service access, particularly integrated access multimedia services and IP services. Studies have shown that the presence of a large number of active nodes, the access network consumes 70 percent of the energy of the whole network. Therefore, to reduce the energy consumption of the access network can significantly reduce the energy consumption of the whole network.

The current access network technologies there are two types of wired access and wireless access. Wired access technologies include xDSL, CM, FTTx and other wireless access technologies, including Wi-Fi, WiMAX and cellular data services (such as LTE, 2G, 3G, etc.).

Cable Access introduce FTTx currently widely used as the main technique of PON FTTx energy mainly from improvements in integrated circuit technology, energy-saving chip design, equipment improvement aspects to be considered. New long-distance network passive optical network LR-PON (Long-reach Passive Optical Network) proposed, shown in Figure 2, the transmission distance of the conventional PON extends from 20km to 100km, for a large number of access / metropolitan area provide broadband access customers, it is a promising future access network solution. Because between the central office and the customer using passive devices to achieve long distance transmission, so that the transmission energy consumption greatly reduced; and patients with multiple optical line terminal and the central office, simplifying the network and reducing equipment interfaces and network elements to achieve device energy saving.

Wireless access to cellular data services, for example, in a cellular data service, since the ad hoc network nodes to limit the source power and transmission power, so usually a perception cellular-based routing protocol, to achieve energy-aware and load balancing.

Imagine the future of energy-efficient network

green future optical network architecture
Figure 3 green future optical network architecture

As shown in Figure 3 green future optical network architecture, it should have five characteristics.

First, the entire network to all-optical networks, signal switching, routing, transport and recovery all functions in the form of light, not only broke through the bottleneck of electrical transmission rate, but without optical / electrical, electrical / optical conversion device, saving energy consumption.

Second, the use of dynamic energy-aware routing, dynamic routing performance vary depending on the volume of business, namely business volume adjustment transmitter power and selected according to the network nodes and links, the best path based on the residual energy, thereby reducing some of the network nodes excessive use, the data flow evenly distributed network nodes.

Third, take dynamic traffic grooming, without changing the number of wavelengths and ADM and ADM distributed by dynamically changing each wavelength carrying business, regulate distribution business in wavelengths, flexible achieve wavelength conversion, reached with the least ADM quantity to support dynamically changing business.

Fourth, according to the traffic volume of nodes and links, for unused and under-node and link thresholds into hibernation, the high utilization node set a lower threshold, low utilization node set a higher threshold, the business reach Threshold is open nodes below the threshold, select another link, the purpose of a dynamic and efficient use of nodes and links.

Fifth, the use of long-distance access network instead of the traditional metro and access networks, the optical line terminal to the local exchange of 90km feeder sections and the local exchange to the ONU under 10km transmission line are made of passive components, reducing the traditional program energy active devices. Since the burst-mode upstream information, so there are a lot of idle time ONU can design business trigger mechanism, that information transmission was started OUN, no information then goes into sleep mode, thereby reducing the idle time ONU power consumption.

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