Viewing the Gigabix system from the development of six kinds of wiring

The advent of the information age means that we have more and more requirements for the speed of the network, we have to transfer files through the network, but also through the network to hold video conferencing; We not only need to send and receive mail, but also quickly download a variety of video, audio files. And with the speed of the network from the original one trillion, 10 trillion, a few years ago, hundreds of trillion, developed to today's gigabit, cabling system as the network infrastructure is facing higher challenges.

The challenge of Gigabit transmission technology

The development of the Gigabit Ethernet protocol began after the IEEE 802.3 completed the development of the Hundred Gigabit Ethernet protocol. At that time 5 types of wiring is beginning to be widely used, so the copper Gigabit Ethernet development goal is to be in a large number of 5 types of wiring can achieve Gigabit Ethernet transmission, This copper Gigabit Ethernet (1000BASE-T) is determined to be in the form of a protocol compatible with Gigabit Ethernet (100BASE-TX) (same frame structure, same signal rate-125 trillion signals per second). To achieve the gigabit data transmission rate under this condition, more efficient encoding and multiple-line parallel transmission must be adopted. 1000BASE-T uses the pulse amplitude modulation 5 level level (PAM5) encoding method, namely each signal has 5 level level, may carry 2.5 bit information, among them 2 bits is the useful information, other is the control information. This allows the available data rate of 125M signal/sec x 2 bit/signal = 250M bit/sec to be transmitted on a single line pair, and 4 pair simultaneous transmission must be used for the gigabit duplex transmission rate, while two-way simultaneous transmission is required on each pair. ---http://bianceng.cn (computer science)

Several main parameters that affect transmission performance

Copper Gigabit Ethernet due to the use of complex transmission mode, the traditional 5-class cabling is a huge challenge.

According to Shannon's theory of information transmission, the transmitted signals are always accompanied by noise to reach the receiver side. To be able to identify useful signals at the receiving end, required to receive the strength of the useful signal must be greater than the received noise signal intensity, and the signal and noise intensity is equal to receive the critical point, at this time the signal and noise ratio is equal to 1, and we usually use logarithmic form to express the signal noise ratio, the results are expressed in decibels (db), The signal and noise ratio is equal to 1 of the place is 0dB point, signal and noise ratio of more than 1 of the place its decibel is greater than 0, which is what we often say signal-to-noise ratio is greater than 0.

The transmission of signals on twisted-pair wires is affected by several factors, one of which is the attenuation of the cable (attenuation). The attenuation is mainly due to the effect of the skin effect on the transmission of high-frequency signals on copper wires. Skin effect is a kind of physical phenomenon that the transmission area of the signal tends to the outer part of the conductor when the high frequency signal is transmitted on the wire. The higher the signal frequency, the thinner the surface of the conductor can transmit the signal, the greater the attenuation of the signal, and thus the attenuation of the signal on the wire increases with the increase of the frequency.

Another factor that affects the transmission of the twisted pair is called crosstalk (Cross Talk), which is a line pair that generates electromagnetic coupling with other lines, and the other lines are coupled to this line to the transmitted signal, which constitutes the main source of noise for the transmission. The degree of electromagnetic coupling also increases with increasing frequency, so crosstalk is increased with increasing frequency.

In general, the signal-to-noise ratio becomes the attenuation crosstalk ratio after the specific performance parameters of the wiring system are used, and the English abbreviation is ACR. The attenuation of cabling system increases with frequency, that is, signal strength decreases with frequency, crosstalk increases, two curves have intersection point, acr=0 or signal-to-noise ratio equals 0, this frequency is acr>0 below. This acr=0 point determines the upper bound of the useful transmission frequency, which defines the transmission bandwidth of the wiring system.

In various transmission conditions will produce different forms of crosstalk,
The crosstalk of a receiving line at one end of the line to the effect of a signal being sent by another wire at the end of the cable is called a near-end crosstalk (NEXT).
A crosstalk called a remote crosstalk (fext) is caused by the influence of another transmission line on the other end of the cable.


In the case of multiple pairs of parallel transmissions, a line pair is not only affected by another linear pair, but is affected by multiple line pairs, at which point the effect is superimposed on multiple line pairs, respectively for power and near-end crosstalk (the power sum NEXT), and for powers and remote crosstalk (fext).

Gigabit Ethernet is used in bidirectional transmission on every line pair, therefore, a new reflection noise------due to cable, connectors and jumpers and other components of the impedance mismatch, in one Direction transmitted signals due to different impedance of the reflection generated by the other side to the transmission signal constitutes a noise. The intensity of this noise is expressed by return loss (Loss).

Gigabit Transmission requirements for wiring

Because of the five types of wiring wiring standards appear, there is no such complex as Gigabit Ethernet transmission protocol, the five types of cabling system of the main performance requirements only to measure attenuation and near-end crosstalk, there is no power and near-end crosstalk, remote crosstalk, return loss and other parameters to make demands, Therefore, the traditional five kinds of system indicators can not meet the requirements of Gigabit Ethernet transmission.

To this end, the Wiring standards committee for gigabit transmission of the wiring system has developed two documents, respectively, TSB-95 and Tia/eia 568-a5. TSB-95 contains engineering guidelines for verifying that the five installed cabling systems are capable of gigabit transmission, as well as for upgrading the five types of cabling systems that do not meet the gigabit requirements in order to enhance their transmission capabilities. Tia/eia 568-a5 as Tia/eia 568-a standard 5th attachment file defines a cabling system with Gigabit capability------enhanced five-Class cabling system (Cat 5e). These two files relative to the original five standards increased the power and near-end crosstalk, line pairs of remote crosstalk, power and remote crosstalk, return loss and other parameters of the performance requirements of the original line to the near-end crosstalk also improved the requirements. TSB-95 and Tia/eia 568-a5 two files are based on the same gigabit transmission performance requirements, but only two of the files are applied in different environments and differ in performance requirements. Tia/eia 568-a5 is applied to the newly built and enhanced five-class cabling system, and its performance requirements are based on the worst channel model (90 meters horizontal line, 10 m jump plug, 4 connectors). The TSB-95 is applied to the five installed systems where most of the channels are not in the worst channel conditions, whereas a significant portion of the network connection channel is connected by an interconnected (direct) approach. The TSB-95 validated channel parameters are calculated in the case of 2 connectors, which is slightly looser than the Tia/eia 568-a5 requirements.

In the future, the wiring standard will no longer use five categories of standards, all data port cabling requirements are enhanced five types of wiring, in the upcoming release of the new wiring standard Tia/eia 568-b, will no longer appear five types of performance indicators.

Six class, Super Six cabling system
With the development of network technology, in five or enhanced five types of wiring has been unable to meet the transmission of gigabit network, and Gigabit Ethernet in order to 100MHz bandwidth cabling system transmission, the use of complex transmission mode, bringing more noise impact. For this Gigabit Ethernet transceiver uses a much more complex line design than hundred Gigabit Ethernet, using more digital signal processor (DSP) to abate noise, increase signal-to-noise ratio, the result is gigabit network equipment is expensive. The reduction of the margin between the performance of cabling system and the requirement of network transmission performance means that once the environment is deviated from the wiring system, the error rate of the network increases and the transmission performance decreases.

Six-class cabling provides a higher transmission bandwidth than the five-class cabling system, for the future use of simpler transmission mode of LOW-COST gigabit network equipment applications to provide the basic conditions for the ordinary gigabit network equipment, six types of cabling provides greater performance margin, In the worse environment, the error rate of network transmission can still be guaranteed, and the performance of network transmission will remain unchanged.

Gigabix Product Series
High-speed wiring system to the high speed wiring to the distribution rack put forward higher requirements. Gigabit wiring, six types of wiring because of the design, manufacturing more complex, more stringent quality control, more expensive than the previous wiring, and a large number of use of fast-frame way, it increased the cost. And the wiring of the telephone network versatility in this configuration is difficult to achieve. The traditional IDC type wiring frame supports the universality of wiring, and the price is moderate, but with the increase of the network application, the traditional wiring frame developed by telephone wiring frame has been unable to be qualified for this work.

In this regard, NORDX/CDT has made a new breakthrough, January 15, 2001, at the Orlando (Orlando, FL) BICSI Winter conference in Montreal, Lit (NORDX/CDT) Limited liability company for the first time to display a new Gigabix cross-link system. This new data transmission crossover system delivers unmatched performance beyond the current six-class standard of high-density.

The newly introduced Gigabix wiring frame is a new generation of IDC type distribution frame, it is made of transparent textured material, has a high-tech appearance, and is equipped with a complete set of cable management components, and supports up to 300MHz of bandwidth, is today's most high-performance and highest end-density of the wiring rack system. In addition to support cabling versatility, but also has a reliable connection, easy to install and management, cabinets, walls, such as general features, and can be used Low-cost Gigabix crossover and Gigabix jump plug line two configuration forms. The price of Gigabix distribution frame is moderate, which provides the optimal cost-performance configuration for high-performance cabling system.