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Wiring is a key factor when designing a network system. With the rapid development of the Internet and the improvement of computer desktop applications, the new wiring technology connected to the desktop has broad prospects and provides unlimited business opportunities for Category 5E and Category 6 cabling.
Integrated wiring technology
1, wiring standards
The LAN specifications described in this paper refer to TIA/EIA-568-A (Commercial Building Telecommunications Cabling Standard) and ISO/IEC11801:1995 (E) standards. The cabling standards include cabling network topology, performance, components, installation practices, and field testing. There are many telecommunication standards related to it, such as ATMForum, CC99vT, CENELEC, IEEEANSI802 and so on.
2, wiring topology
The TIA/EIA-568-A and ISO/IEC11801 cabling standards are based on the same basic cabling system architecture, and the system architecture is strictly and clearly defined in the standards. Cabling systems include cables, patch cords, and connectors for horizontal cabling, trunk wiring within buildings, and trunk wiring for buildings. Structured cabling supports cabling terminations, and plug-in cords are easily connected or cross-connected to the device.
3, the wiring distance
In the standard, the wiring distance is strictly regulated (horizontal wiring <90 m, building trunk <500 m, park trunk <1500 m), and the wiring distance mainly depends on the actual working area (ie, the building floor area). The trunk wiring distance is based on the distance defined by the actual application.
4, wiring performance
In the two standards of TIA/EIA-568-A and ISO/IEC11801, 100-ohm twisted pairs are classified according to their performance:
Category 3: specified as 16MHz;
Category 4: specified as 20MHz;
Category 5/5E: specified as 100MHz;
Category 6: specified as 250MHz.
5, cable electrical transmission performance parameters
DC resistance is unbalanced;
DC Resistance;
Working capacitor
Unbalanced capacitance to the ground;
Characteristic impedance
Structural return loss (SRL);
attenuation;
Near-end crosstalk attenuation (NEXT).
6, connector electrical transmission performance parameters
DC Resistance;
Return loss
attenuation;
Near-end crosstalk attenuation.
7, horizontal wiring link performance
The transmission characteristics of the TIA/EIA-568-A standard for horizontal wiring are based on its constituent components, while ISO/IEC 11801 is application dependent. In addition, the ISO/IEC 11801 specification is based on a link (ie, does not include work area cables and equipment cables), while TIA/EIA-568A is based on a channel. The TIA/EIA568-A minimum channel near-end crosstalk attenuation can be derived from the characteristics of the constituent elements (eg, the channel near-end loss is the sum of the phase-to-phase losses of the components it uses), and the maximum attenuation is the attenuation of each component in the channel. Sum. For ISO/IEC 11801 links, the minimum near-end attenuation and maximum attenuation are based on the standard applications listed in Appendix G. ISO links are classified by performance (Class A to Class E), where Class E is equivalent to Class 6 performance.
8, the crosstalk attenuation ratio
ACR is associated with a letter-to-string ratio (SCR) defined in LAN technology (usually more precisely defined as crosstalk and insertion loss ratio NIR). ACR is not affected by transceiver changes, as is SCR and NIR.
Since there is no technology supporting 4dBACR above 100MHz, there is no specific application associated with ACR above 100MHz. In addition, with the development of network technology and the elimination of crosstalk methods, the wiring selection will no longer depend on the ACR value (that is, after the ACR is fixed, the attenuation associated with the cable length and the near-end crosstalk can compensate each other).
9, 100-ohm wiring performance field test
The transmission performance of a cabling system depends on both the performance of its constituent components and the installation process. The TIA/EIA Technical System Bulletin (TSB-67) specifies the parameters of a field test tool used to test the performance of 100 ohms twisted pair cabling after installation.
10, TIA / EIA-TSB-67 test parameters
Wiring diagram: Check the cable to the connector and plug termination to find the connection error.
Attenuation: Signal loss in a channel or link.
Length: The maximum length of the wiring.
Near-string attenuation: Signal coupling between adjacent transmit and receive line pairs.
11, MHz and MBps comparison
Cable attenuation and NEXT can be derived from sweep measurements with specified test ranges from 0.1MHz to 100MHz. The attenuation and NEXT values represent sinusoidal voltage losses at a particular frequency and are not to be confused with bandwidth limits, bit rates or baud (ie 622 MBps does not mean limiting the wiring to 622 MHz). Depending on the design goal, modulation and signal processing with amplitude, frequency, or phase changes is typically used to change the desired bit rate to an acceptable signal transmission rate (baud).
12, data transmission
Design goals dictate modulation techniques, signal shaping, and the complexity of eliminating crosstalk. The most challenging and attractive are 1000BASE-T based on Category 5E cabling and 100BASE-T2 based on Class 3 cabling. These recommendations require extremely complex compensation for cable defects. For example, 100BASE-T2 requires digital signal processing and mixed-signal processing techniques in two pairs of Class 3 (Class A of ISO/IEC11801) wiring. Moreover, 100BASE-T2 is operated under the environment of near-end crosstalk and only conforms to FCCA or B and CISPR.022A or B.
13, crosstalk environment
Since multi-pair cables can be used in a variety of applications, applications based on parallel data transmission and multimedia technology have been implemented (eg 1000BASE-T uses 4 pairs of lines to simultaneously transmit data), so other sources of crosstalk and their own near-end crosstalk must be caused. Emphasis is placed on the addition of new performance parameters for Category 5E and Category 6 cabling, such as RSL (Return Loss) and ELFEXT (Equivalent Far End Crosstalk).
Near-end crosstalk (NEXT) or far-end crosstalk (FEXT) coupling referred to by alien crosstalk cannot be eliminated in a manner that eliminates near-end crosstalk (ie, crosstalk from external connections). When crosstalk is related to two possible sources of alien interference, it is defined as a multi-interference source NEXT (MID NEXT) and a multi-interference source ELFEXT (MDELFEXT).
Far End Crosstalk (FEXT) describes the crosstalk coupling from the transmitter (source) at one end of the cable to the loop at the other end.
The equivalent far-end crosstalk (ELFEXT) describes the crosstalk coupling from the transmitter (source) at one end of the cable to the loop at the other end, which is obtained by subtracting the pair attenuation from FEXT (distal crosstalk), thereby eliminating the cable length. influences.
The return loss (RSL) is determined by the degree of mutual matching of the components in the transmission channel. For 1000BASE-T, only the matching connections can be used to meet the demanding RSL requirements.
14, shared and switched LAN
In a local area network (LAN), workstations can share a single channel using the Medium Access Control Protocol (MAC) or can connect to a switch. In a shared LAN, each workstation is connected to a repeater or concentrator and forms a broadcast channel between the stations. So the workstation can receive the information sent from any station. Workstations operate in half-duplex mode, and only one can send information on the LAN at a time, as determined by the MAC protocol.
The workstation mentioned above can also be connected to the switch. Only one activation source is allowed per switch at any single time. The switch copies packets from one input to a specific output that is required, while other ports can send and receive different packets. When the working terminal is directly connected to the switch, it is in full-duplex mode, so access control is not necessary.
15, transmission delay and delay distortion
In shared 1000BASE-TLAN, the round trip delay including the routing transmission delay is a key parameter. In addition, for applications such as 100BASE-T4 (half-duplex) and 1000BASE-T (full-duplex) that use synchronous transmitters, delay distortion (ie, the difference in transmission delay between pairs) is also important.
Under any conditions, the fastest and slowest simplex link segments in a link have a difference in propagation delay or delay of more than 50 ns (with a frequency range of 2 MHz to 100 MHz) and a travel delay of no more than 570 ns. As a further functional requirement, once 1000BASE-T is installed, the delay distortion between all pairs of pairs caused by environmental conditions will not exceed ±10 ns under the conditions that meet the above requirements.
