The impact of redundant channels on the transmission performance of the integrated wiring system is described.

The total amount of data transmitted or transmitted by a channel per unit of time is called the channel transmission volume. However, in actual application environments, all channels will suffer different losses, we call this loss a channel surplus. In our Integrated Wiring System, effective use of channel surplus can greatly improve network transmission performance. Based on the experimental results, the impact of the channel rich margin on the network transmission performance in the Integrated Wiring System is presented and the causes are analyzed.

At many recent communications magazines and IT industry exhibitions, the impact of structured cabling system transmission performance on bit/error rates in data network transmission has become a major concern. In general, the channel Return Loss Caused by impedance mismatch is the main cause of high bit error rate, and the return loss has a certain impact on all the system performance, the effect of the decline of the near-end crosstalk is more serious.

The design and testing requirements stipulated by the standard require that channels must meet application performance, but these channels may not be able to provide sufficient surplus to meet the needs of many high-bandwidth networks in the future. In order to compare and verify that the six types of cabling solutions provide better transmission quality and faster network speeds than the recently released 5e standards, recently, the American lab conducted a channel surplus experiment using three high-speed, high-density information transmission application systems. The selected application system is a 270 Mbit/s serial digital video signal, 100BASE-TX video stream and 100BASE-TX data file transmission. In addition, the shared cables with the same sheath are connected to the experiment to simulate the interference network transmission environment with the near-end crosstalk under the worst conditions.

The results of these experiments show that, under the requirements of the standard, the use of efficient and high-performance channel surplus structured Integrated Wiring System can significantly improve the network transmission speed. In addition, experiments show that the use of six types of cabling systems can provide better transmission and use performance for existing application systems in the market.

Background

The definition of Channel Transmission Volume refers to the total amount of data transmitted through or over a channel within a certain period of time. The maximum Channel Transmission volume can only be achieved under the ideal channel conditions, but cannot be achieved in the real environment. All channels have different losses, so the channel can only work under conditions lower than the maximum working capacity or transmission volume. In a communication system or a specific LAN, the channel design must be considered to compensate for these losses.

System components and the surrounding environment bring some damage to the channel transmission characteristics, thus affecting the transmission performance of the structured Integrated Wiring System. Some interference factors have a negative impact on the Channel Transmission Performance of the structured cabling system. These interference factors are recorded in the 1000BASE-T IEEE 802.3ab Gigabit Ethernet standard and are listed as follows:

Scattering
External interference
Latency Deviation
Attenuation
Impedance mismatch/ripple loss
Near-end crosstalk and remote Crosstalk

All these potential interference factors may lead to channel bit codes, thus reducing the channel transmission volume of structured cabling systems. Bit Error Rate refers to the ratio of the received error bits to the total transmitted bits. In high-speed network bandwidth and intensive information transmission applications, the lowest Bit Error code is required to ensure the highest transmission performance. In data applications, high bit error rates and poor network performance may lead to signal retransmission. In video applications, a higher bit rate leads to image interruptions, loss of seek, or white spot snowflake ). In any application field, high bit error rates can lead to unsatisfactory performance. The following sections will discuss some factors that affect bit/error rates and post-transmission volumes.

Scattering:

Scattering is the diffusion of a bit pulse when it passes through a channel. It is caused by the superposition of each bit and the adjacent bit, which leads to an error in the transport bit received by the channel terminal. The effect of scattering is usually called Inner Disturbance, which can be reflected by visible graphs and measured by beats. Matching of channel cables and connection lines is the main cause of scattering. For digital transmission applications such as 270 Mbit/s serial digital videos, scattering will increase bit error rates and reduce channel performance, resulting in reduced image resolution at the receiver end. The adaptive balancing circuit is usually added to the circuit interface of the Communication hardware system to compensate for the effect of scattering.

External interference:

Noise enters the channel through the external electric field and magnetic field near the channel, which is external interference. The non-targeted launch of ESD or EFT is a source of external interference. It should be noted that, even if the channel of the structured Integrated Wiring System is designed and installed perfectly, the conversion of external electromagnetic fields will still work on it, affecting bit error rate, in addition, the original imbalance causes the communication hardware circuit and the cable interface to intrude into the channel, resulting in poor system performance.

Latency deviation:

Latency deviation is the transmission rate difference between different pairs of cables in multiple pairs of cable covers. The variation of the twisting rate and the insulation structure of the line pair limit the deviation, in seconds. Some application systems need to transmit signals on composite twisted pair wires and reach the receiver at the end of the channel at the same time. Therefore, it is very important to minimize the latency deviation.

A typical case of on-site transmission using twisted pair wires is to send financial information to a high-resolution display screen on the stock exchange. This type of display requires an available bandwidth of more than 100 MHz and an RGB synchronous analog video signal. Excessive delay deviation may lead to Pigment Dispersion, which may be duplicated as the channel length increases. 1000BASE-T Gigabit Ethernet) is another case where UTP twisted pair wires are used for transmission. Latency deviation is defined in the IEEE 802.3ab protocol as between 2 MHz and MHz. The deviation between all pairs of duplex channels cannot exceed 50ns. Attenuation:

Attenuation reduces the energy when the signal amplitude passes through the channel. Similar to scattering, cables and connection plug-ins are the main cause of attenuation. In IEEE 802.3, The 1000BASE-T Standard specifies that attenuation is access loss. The maximum attenuation of duplex channels is calculated using the following formula:

Access loss (f) = 2.1 f (0.529) + 0.4/f (dB) [f = 1 MHz to 100 MHz]

The negative effects of channel attenuation can be demonstrated by examining the transmission Effect of analog video signals. Excessive attenuation causes the intensity of the low-frequency Brightness Signal in the video stream to be lower than that of the high-frequency color signal, which makes the received image gray and the contrast is too low.

Impedance mismatch/ripple loss:

Impedance mismatch/ripple loss occurs when the load impedance is not balanced with the internal impedance of the device. For structured cabling systems, such losses often occur when the components that constitute the channel do not properly match. This will affect the maximum transmission power between energy and load. For systems that use the hybrid function interface circuit, it is very important to minimize the imbalance of impedance matching. Hybrid functions are often used to realize full duplex transmission of data information.

The hybrid circuit provides four pairs of terminals. After the signal enters from one terminal pair, it is distributed from two adjacent pairs, but it cannot reach the corresponding terminal line pair. The impedance matching between the device circuit and the channel is very important. Otherwise, the echo, that is, the reflected transmission energy, will appear at the receiving end in the form of noise. The echo compensation circuit is incorporated into the 1000BASE-T interface circuit to effectively resist the echo effects produced by the hybrid function.

1000BASE-T, IEEE 802.3ab standard, indicates that the impedance mismatch is represented by a forward packet loss, that is, the correlation impedance of each specific frequency segment is 100 ohm ). The return loss is the application signal reflection produced by impedance mismatch and is the ratio of a fractional value. The IEEE 802.3ab standard records the impact of impedance mismatch on the channel, and uses the following formula to indicate the range of impedance mismatch.

Return Loss (f) = 15 (dB) {f = 1 MHz to 20 MHz}
Return Loss (f) = 15-10log (f/20) (dB)
{F = 20 MHz to 100 MHz}

The second formula allows a wide margin in the return loss fit value. For example, this limitation is the return loss of 8 dB at a standard 100 MHz frequency. The return loss is equal to the impedance mismatch between 100 ohm-57 ohm to 133 ohm. Applications such as 1000BASE-T can tolerate wide range of impedance misfit. This shows that such damage has not compromised cabling performance as other factors do.

Near-end crosstalk and remote crosstalk:

Signal coupling from one or more pairs of cables to other adjacent lines is called crosstalk. The near-end crosstalk loss is defined as the ratio of the transmission signal size to the coupling signal size when the coupling signal is measured from the same channel end. Remote crosstalk loss is defined as the ratio of the transmission signal to the coupling signal size when the original transmission signal is measured relative to the other end. The loss of near-end crosstalk and remote crosstalk is also expressed in dB.

For multi-line transmission systems such as 1000BASE-T, it is critical to minimize the crosstalk at the end of the transmission system. Each 1000BASE-T full-duplex channel receiver senses near-end crosstalk from three adjacent channels connected to four pairs of channels. Therefore, in the 1000BASE-T transmission system, compensation for near-end crosstalk is introduced to reduce interference of near-end crosstalk. In the same way, introducing the remote crosstalk compensation into the 1000BASE-T transmission system can also reduce the interference of remote crosstalk. However, if we compare the effects of remote crosstalk with that of near-end crosstalk, it will be much smaller and negligible. In addition, near-end crosstalk interference occurs between adjacent cables, which are not in the same jacket. Near-end crosstalk generally refers to external near-end crosstalk interference, which is generated when the cables are tightly bundled. External near-end crosstalk is generally considered as external interference.

All in all, the channel transmission performance of structured cabling systems is affected by some potential interference factors. Whether it is near-end crosstalk, remote crosstalk, or crosstalk produced by external noise, it has a very important impact on bit error rates, which also affect the transmission performance of the channel in the structured Integrated Wiring System. Just like other damage factors that affect the channel of a structured cabling system, crosstalk can spread to an uncontrollable level and affect more applications.

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