CN1494240A

CN1494240A - Method of optical fiber coaxial mixed cut in network back transmission noise inhibition

Info

Publication number: CN1494240A
Application number: CNA021377979A
Authority: CN
Inventors: 晏祥彪; 沈瑞武; 臧洪兴
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2002-10-31
Filing date: 2002-10-31
Publication date: 2004-05-05
Anticipated expiration: 2022-10-31
Also published as: CN100472986C

Abstract

The method includes following steps. Digital reversing amplifier is setup at junction of optical fiber coaxial hybrid access network. Up loading data at user's node passing through optical fiber coaxial hybrid access network are transferred to a junction at upper level. Digital amplifier at junction terminates up loading data from user's node as wel as blocks up noise in up loading data. Then, the said terminated data are up loaded to up junction sequentially. Data termination and noise blocking is carried out by digital reversing amplifiers stage by stage till the root node. The invention solves intrinsic funnel noise of HFC network, and provides perfect broadband access mode for building metropolitan area network.

Description

A kind of method of optical fiber coaxial mixed cut in network back transmission noise suppressed

Technical field

The present invention relates to the method that a kind of HFC (hybred fiber-coax) Access Network return noise suppresses, particularly relate to a kind of return noise inhibition method that the two-way broadband data cut-in method is provided to the user by the Hybrid Fiber and Coax Network HFC of cable TV.

Background technology

Broadband metropolitan area network claims metropolitan area, broadband data communication network mainly to be meant all kinds of data communication networks that broadband access is provided of covering whole city again.Along with China various places development of urban informationization paces quickening in recent years, the construction of broadband metropolitan area network has become the important component part of a urban informationization capital construction.The appearance of broadband metropolitan area network will make the information communication in city organically be incorporated on the same platform, this has comprised that the call voice business that provides, the TV programme that cable television network provides transmit, and business such as the shopping online that can realize of computer network institute, online medical treatment, stock market's transaction on the net, web-based teaching, VOD video request program, video conference.Everything has promoted the enforcement of engineerings such as " ecommerce ", " enterprise online ", " e-government implementation ".

Utilize cable TV catv network wide coverage, the abundant characteristics of band resource, with the present one-way transmission network rebuilding is the bidirectional data communication network, not only can transmit outside traditional CATV cable TV, but also transmission of digital audio frequency and video and data service realizes cable TV Hybrid Fiber and Coax Network HFC and The interconnection between data networks intercommunication, provides Broadband Internet to insert and the interactive audiovisual business.Broadband metropolitan area network based on hybred fiber-coax HFC (being called for short HFC hereinafter) network is the Hybrid Fiber and Coax Network HFC that has catv network based on cable TV now, make full use of conventional network resources, do not need rewiring, small investment, network coverage face are big, can insert the user fast, the investment return repayment is fast, and therefore such data metropolitan area network has a extensive future.

But, because the construction of hfc plant is the purpose that broadcasts as with cable TV, the hfc plant structure belongs to tree topology, down going channel is fit to radio network very much, satisfy the needs of television network broadcast, simultaneously like this tree causes from the up channel of user-to-network as a huge antenna of accepting, can accept the noise of each tributary circuit, produce the gathering of noise, i.e. " funneling effect ", the coaxial cable of hfc plant disturbs responsive especially to low-frequency range in addition, cause the noise of return path serious, signal to noise ratio is low, and such passage is used for the data network transmission, the error rate is too high, does not reach the requirement of broadband metropolitan area network.For this reason, for many years, the construction department of hfc plant has proposed the multiple technologies measure from engineering and transmission technology angle and has solved reverse return noise problem.Relatively typical method has three kinds, and the one, existing coaxial cable is transformed, all change four layers of shielded cable into, improve the shield effectiveness of network; The 2nd, with the breath of delivering a letter under the wire cable, upload information with telephone line; The 3rd, adopt the S-CDMA technology.This several method all has application in present hfc plant bidirectional rebuilding, but does not all have comprehensively to solve the problem of backward channel return noise, and still difficulty makes good.For first kind of scheme, the cable TV network in domestic most of area is not four layers of shielding conductor, transform and must lay cable again, adds expensive track remodelling and terminal access device expense, the improvement expenses costliness, huge like this investment can't be born by networking unit.For second kind of scheme, involve the use telephone line again, need with other rivals' collaborative problem, wired network can become the accessory of other communication networks, does not make full use of the Internet resources of HFC, does not reach the purpose of building the bi-directional data access network.For the third situation, use spread spectrum, be the noise immunity that cost improves system to sacrifice bandwidth and transmission rate, the bandwidth of restriction upstream data passage.

Summary of the invention

The present invention proposes a kind of method of optical fiber coaxial mixed cut in network back transmission noise suppressed, solve the intrinsic funnel noise of hfc plant, utilize the resource of cable TV HFC network, for the construction of metropolitan area network provides perfect broadband access method.

The method of optical fiber coaxial mixed cut in network back transmission noise suppressed of the present invention comprises following treatment step:

The first step is provided with the digit reverse amplifier on the convergence point of hybrid fiber coax access network;

In second step, the upstream data on the user node uploads to higher level's convergence point by hybrid fiber coax access network;

In the 3rd step, the data termination that the digital amplifier on the described convergence point is uploaded user node, and the noise of uploading in the data cut off continues the data after a convergence point is upwards uploaded described termination then;

In the 4th step, described digit reverse amplifier carries out the data termination step by step and noise cuts off processing, up to root node.

The method that a kind of HFC Access Network return noise of the present invention suppresses, changed traditional noise suppressed processing mode, the reason of compiling according to noise, transform new cellular logic topological structure as, structure digit reverse amplifier solves the funnel noise problem of hfc plant, the bi-directional data of realizing hfc plant inserts, and can use hfc plant to build broadband metropolitan area network, promotes the development of informatization.

Description of drawings

Fig. 1 is the tree of hfc plant.

Fig. 2 is the logical construction schematic diagram of prior art hfc plant uploading channel.

Fig. 3 is the logical construction schematic diagram that adopts the hfc plant uploading channel of the method for the invention.

Fig. 4 is the network application schematic diagram of the digit reverse amplifier that adopts among the present invention.

Embodiment

Below in conjunction with accompanying drawing the specific embodiment of the present invention is further described

Tradition hfc plant coaxial cable tree is the design of one-way CATV broadcast service, provides high speed, bidirectional data communication by data feedback channel now, makes up the wideband data metropolitan area network.At first, data feedback channel occupies (5～65) MHz of frequency spectrum, has been full of invasion noise, impulsive noise, HAM interference, wideband Gaussian noise, imbalance and non-linear infringement, makes very difficulty of high speed data transfer.Secondly, limited (5～65) MHz wave band has seriously limited the ability of uplink, and two-way, the high-speed communication that realize HFC are faced the challenge.The generation of following surface analysis hfc plant return noise and inhibition method.

According to the generation approach of hfc plant return noise, return noise is made up of construct noise and invasion noise two parts.

Construct noise is produced by device self, mainly is made up of thermal noise and shot noise, wherein based on thermal noise.The thermal noise source in cable TV back transmission loop is active devices such as subscriber terminal equipment, sign-changing amplifier, backlight emission (reception) machine.

Invasion noise (promptly disturbing) is caused by the residing environment of cable television network, it is a kind of at random, unpredictalbe radio frequency interference, it enters cable system by electromagnetic field at cableport and feeder line, mainly contain following several: 1. impact and disturb: produce when mainly being started by thunder and lightning, car engine, industrial electrical equipment and household electrical appliances, its form of expression is spike at random.2. narrow-band continuous wave interference: mainly by radio communication such as various shortwave broadcastings and multiple harmonic that day aerial each electric wave beat produces, the form of expression of its frequency spectrum is the relatively-stationary impulse disturbances on a frequency.

In adopting the distribute type CATV net of branch type structure, the noise that each branch road produces will produce the effect of converging at optical node and front end, form so-called noise " funneling effect ", be referred to as the funnel noise, coaxial network on the hfc plant optical node admits number of users many more, the noise power that is pooled to root node is just big more, and the signal to noise ratio of return path is just low more.

With reference to the tree of hfc plant shown in Figure 1, in Fig. 1 hfc plant with head end as root node, from forming the tree network structure below the optical node of hfc plant, the user node of least significant end begins, and noise compiles step by step, for example A, B, C compiles to D, E, F, G compiles to H, D, H, K compiles to upper level M, up to root node, forms the funnel noise like this.

Because the root that the funnel noise produces is a hfc plant coaxial cable net is tree property structure, tree property structure is suitable for descending cable tv broadcast and data broadcasting, but such tree is complicated to up uploading channel, introduces the funnel noise easily.This uploading channel is tree physically, but be hub-and-spoke configuration in logic, it all is to unify termination at root node that all users upload data, concentrates all users' of termination uploading channel information as the headend of Cable Modem Terminal System CMTS commonly used in the HFC Access Network.Shown in Figure 2 is logical construction signal on the basis of the physical structure of Fig. 1.Solid line represents that the tree type of physics connects the star-like connection of dotted line presentation logic, A, B, C, E, F, the upstream data of user nodes such as G are not the tandem node D at physics, the H termination, but directly terminate to root node, such hub-and-spoke configuration is the root that forms the funnel noise.

At Fig. 3 is to adopt the logical construction signal of method of the present invention on the basis of the physical structure of Fig. 1.Shown in multi-thread the walking abreast among the figure, A, B, the upstream data of C user node terminates at the tandem node D of physics, rather than directly delivers to root node and terminate E, F, the upstream data of G user node terminates at the tandem node H of physics, rather than directly delivers to root node and terminate, such tree, near the tandem node D of user side, H finishes the termination of user data, make the scope of noise limit in the part, avoid A, B, the noise that user nodes such as C are introduced is uploaded, D then, H, the K data are finished the tandem of data step by step in convergence point M termination, the segment processing noise solves the funnel noise problem.Wherein convergence points such as D, H, K, M are placed digital amplifier.With reference to shown in Figure 4, the relay structure of the tree of above-mentioned digital amplifier support hfc plant node, hub-and-spoke configuration, a branch is realized the multiplexing of user data and management, and multiplexing logical channel is isolated mutually, guarantees user's data safety.This amplifier is not the processing and amplifying of simply carrying out analog signal, but utilizes ripe IP network agreement, and as the IEEE802 protocol family, IP routing protocol etc. are handled data, reaches the purpose of cutting off network noise.The noise that suppresses data feedback channel like this by the digit reverse amplifier uses the digit reverse amplifier to replace HFC simulated inverse amplifier commonly used to realize the passback of backward channel signal, solves the inverse noise problem of hfc plant completely.

Return noise inhibition method of the present invention causes the characteristics of funnel noise at the tree of up return path, propose to keep the tree of down going channel, satisfy the needs of one-way broadcast systems, the physics that the changes traditional up return path type of climbing the tree, hub-and-spoke configuration in logic, with data feedback channel from also becoming tree in logic, Rendezvous Point in each branch of data feedback channel carries out the processing that compiles of data, sending into the upper level Rendezvous Point then terminates again, up to root node, the trunking scheme that this processing mode is equivalent to act on behalf of step by step, the transmission channel that block noise is up, thoroughly solve compiling of data feedback channel return noise, make it to form the funnel noise.

Claims

1. the method for an optical fiber coaxial mixed cut in network back transmission noise suppressed is characterized in that, comprises following treatment step:

2. the method for optical fiber coaxial mixed cut in network back transmission noise suppressed according to claim 1 is characterized in that described digit reverse amplifier can be set on the convergence point of hybrid fiber coax access network of relay structure that network topology is tree, hub-and-spoke configuration or a branch.