Editor's Note: With the development of economy and technology, people's demand for communication services is no longer a simple voice and one-way video, but a faster, richer and more interactive broadband multimedia service. The popularity of broadband communications and the Internet has greatly contributed to the development of digital media content. Nowadays, in addition to the digital innovation of home appliances, building a home network with broadband access, internal interconnection and content sharing has become increasingly prominent.
First, digital home network networking
From the trend of industrial development, technologies such as communication, information and entertainment have matured and merged. The trend of 3C integration has emerged. Information resources can be integrated on personal terminals. Individual users can directly operate on a virtual information platform. A seamless link between devices and information makes all the hot topic of "digital home networking" hotter and hotter.
1 Definition of digital home network and business applications
The digital home network refers to extending the functions and applications of the public network to the home through the home gateway, and based on the flexible configuration of the home intelligent wiring system or constructing a wireless environment, connecting various information terminals (such as home appliances, PCs, etc.) and providing Integrated voice, data, multimedia, control and management functions enable the circulation and sharing of information between home internal terminals and external public networks and home internal terminals.
Digital home network services are usually located in three areas: a. home audio and video entertainment, watching movies, listening to music, personal audio and video STudio.b. telecommunications and broadcasting services, VOD, VOIP, IPTV, online games, telecommuting/education/medical . c. Control and monitoring functions to achieve security, electrical control, meter reading, power management. The following services and applications can be realized through the digital home network: a. Interconnect with the Internet, VOD on demand through set-top boxes and TV sets or computers, and provide mass storage and personalized information services based on Active Server web pages (ASP) And interactive Internet entertainment games and other services. b. Realize high-speed information sharing of various information terminals within the home, such as data sharing between PDAs and PCs. c. Remote control, adjustment and monitoring of various household appliances through the home gateway, such as control of microwave ovens, washing machines, air conditioners, lights, electric curtains, temperature and humidity controllers, air volume regulators, etc. d. Realize automatic alarm of burglar alarm, automatic smoke detector and harmful gas detection device and send it to the user's mobile phone, E_mail mailbox or the management center of the community through the network. e. Through the home camera, using the home gateway as a video server, users can remotely monitor home security through the Internet.
2 Composition of digital home network
The digital home network structure is shown in Figure 1. It usually consists of three parts: a. Home gateway; b. Various information terminal equipment and smart home appliances; c. Construction of a home intelligent networking environment, which interconnects various terminals in the digital home. It is connected to the home gateway and realizes the self-organizing networking of the information terminal devices and the smart home appliances of the home network through the internal wired or wireless interconnection technology of the home and provides automatic discovery and configuration. The ResidenTIal Gateway (RG or Home Gateway, HG) is the core of the digital home network. It is a simple, intelligent, standardized and flexible personal home network interface unit that can receive communications from different external networks. A signal that passes a signal to a device. RG is also the bridge between the entire home network and the external network, and is the key to the various businesses and applications of the digital home. ITU-T has incorporated the home network as part of NGN (Next Generation Network), in which RG will play an important role. The location of RG in NGN and its connection to the outside is shown in Figure 2. MGC is the Media Gateway Controller. , MG is the media gateway.
The RG should have the following functions: a. Multiple or different types of access can be performed simultaneously, and the same family network can be constructed using multiple technologies; b. Can handle multiple types of access network technologies and multiple types of networks simultaneously Technology; c. can bridge the QoS of the access network and the QoS of the home network; d. can ensure that the accessed content does not depend on the hardware and transmission mechanism used to transmit the content; e. can flexibly support the latest technology; f. should be established in Flexible on the platform and easy to upgrade.
Figure 1 Structure of the digital home network
Figure 2 NGN and home gateway
3 Digital home network networking
3.1 Digital networking mode of digital home network
The home network aggregates the devices inside the home to form an RG-centric communication network. Therefore, the connection technology of the home network is mainly the access problem of each terminal in the home. The GRG access mode can be selected between the RG and the carrier. Various technologies can be used for the interconnection between the RG and each device. Each technology has its own characteristics and applicable scope.
The most common connection between RG and each device is Ethernet. All devices can be interconnected by Ethernet interface. However, wired networks are limited by wiring in some cases: wiring and rerouting are large, and the line is easy. Damaged, each node in the network cannot be moved. Therefore, it is also possible to use the wireless local area network as an access method.
The wireless LAN standard can be IEEE 802.1la/b/g, where the transmission rate of 802.1la/g is 54 Mb/s, the transmission rate of 802.11b is 11 Mb/s, and 802.11a and 802.11b work in two completely different. The frequency band, using completely different modulation techniques, is completely incompatible, but can coexist in the same area without interfering with each other.
The newly approved 802.11g has two main features: high-speed and 802.1lb.802.11g-compliant is the next mainstream wireless LAN standard that provides high-speed data communication bandwidth and provides the original cost at a more economical cost. Compatible with mainstream wireless LAN standards. In addition, the home intranet can also use PI T (Power Line Communication Technology), HomePNA (Home Phone Line Network Alliance, is a computer network standard for home network) technology, HomePNA on COAX (Coax-based HomePNA) Technology, Bluetooth, USB and DECT (Enhanced Digital Cordless Communications).
3.2 Connection of digital home network to external public network
With the diversification of broadband service applications and the increasing demand for bandwidth, the global boom in fiber optic access has been set in the past two years. Future-oriented broadband applications include voice (VoIP and video telephony), data (high-speed Internet services) and video (IPTV). Since the bandwidth requirements of each type of broadband application are different, it is necessary to select different broadband access methods. At present, the main application of most broadband access users in China is high-speed Internet access, and xDSL or LAN can meet the needs of most ordinary users. But if you need to use broadband to achieve other broadband applications, including various video services (broadcast TV, HDTV, VOD, etc.), video conferencing, video telephony, interactive online games, etc., the original access technology in the bandwidth It seems to be difficult to do. The GPON access method provides higher bandwidth and provides sufficient bandwidth for such high-end users to enjoy various broadband services.
Although the previous generation technology (BPON, EPON) can meet the needs of the current network, the interactive TV and HDTV based on the 1P protocol, and the telecom operators' requirements for the network after the transformation to the integrated information service are higher, only GPON can be more Satisfied well. First, GPON can support multiple rate levels, which can support uplink and downlink asymmetric rates. The uplink does not have to support more than 1 Gb/s, while EPON can only support symmetric 1 Gb/s single rate. Therefore, GPON optical device options Larger, which can reduce costs. Second, GPON supports oDN classes Class A, B, and C, while EPON only supports Class A and B, so GPON can support up to 128 split ratios and transmission distances up to 20 km. Furthermore, the GPON standard provides unprecedented high bandwidth, with a downlink rate of up to 2.5 Gb/s and an uplink rate of 1.2 Gb/s. Its asymmetric characteristics are more suitable for broadband data services. The supported service types include data services (Ethernet service, 1P). Service and MPEG video streaming), PSTN services (POTS, ISDN services), dedicated line services (T1, E1, DS-3, E3 and ATM) and video services (digital video); provide full service guarantee for QoS, and at the same time Multi-service mapping to ATM cells and/or GEM Encapsulation Methods (GEM) for transmission and good service level, supporting QoS guarantee and full service access capability; when carrying GEM frames, TDM services can be mapped To the GEM frame, the standard 8 kHz (125 s) frame can directly support the TDM service; as a carrier-class technical standard, GPON also specifies the protection mechanism and complete OAM function at the access network level; GPON technology It also allows operators to provide specific services that customers need in accordance with their respective market potential and specific regulatory environment.
Compared with the previous generation technology, GPON has the highest efficiency in both the transmission aggregation layer and the service adaptation layer, and has the highest total efficiency and the lowest equivalent system cost. Assuming that TDM services account for 10% and data services account for 9O, the total efficiency of GPON is 94, while APON and EPON are 72 and 49 respectively. GPON can provide not only 10 Mb/s, 100 Mb/s, 1 Gb/s services. VI AN services and voice services are also available to accommodate any existing service and future new service adaptation requirements.
GPON consists of an optical line termination (OLT), an optical network termination (oNT), and a ring (or tree) topology of PONs.
The OLT is located in the central office and provides WAN interfaces up to the top, including GbE, OC-3/STM-1, DS-3, etc., and provides 1.244 Gb/s or 2.488 Gb/s optical interfaces to the PON. The ONU/ONT is located on the user side and provides users with 10/100 BaseT, T1/E1, and DS-3 application interfaces. The optical interface rates of the PON are 155 Mb/s, 622 Mb/s, 1.244 Gb/s, and 2.488 Gb. /s and many other options. The direction from oLT to ONU/ONT is the downlink direction, and the data stream transmission mode of broadcast transmission is adopted; otherwise, the uplink direction is adopted, and the time division multiple access (TDMA) technology based on statistical multiplexing is adopted.
The PON implements full-duplex transmission of data streams through coarse wavelength division multiplexing (CWDM) coverage. The PON generally adopts a tree topology. When service protection and channel protection are required, the protection ring can be added to provide protection for some ONTs.
At present, FTTx based on GPON technology is the best technology for broadband access, and it is the guarantee for the integration of voice, data and video.
However, GPON technology equipment is relatively complex. GPON carries the advantages of QoS-guaranteed multi-service and strong OAM capability, which is largely at the expense of technology and equipment complexity, which makes the related equipment costly. With the development of GPON technology and large-scale application, the cost of GPON equipment will decline.
4 Summary
Today, with the rapid development of network and communication technologies, digital home networks have important research value. It is an extension of public network services to families, and an important market expansion space for telecom operators and network operators. High-speed home business requires high bandwidth, so the access technology of digital home network is also a hotspot research. GPON will undoubtedly become the best choice for future access network. Digital home network and GPON combination are future home broadband services. The inevitable result of development.
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