Effect of Integrated Wiring System channels on Network Transmission Performance

In recent communications magazines and IT industry exhibitions, the impact of 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, the Avaya lab recently conducted experiments using three high-speed, highly intensive 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. And connect the same-sheath large-logarithm shared Cable
In the experiment, the interference network transmission environment of the near-end crosstalk under the worst condition is simulated.
The results of these experiments show that the cabling system with high performance and rich margin can significantly improve the network transmission speed as required by the standard. 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 cabling 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 the structured cabling system. 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 receiving 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 cabling 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 the effects of remote crosstalk are compared with that of near-end crosstalk, it is obviously small 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 transmission performance of the channel in the structured cabling system 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 cabling system. Like other damage factors that affect the channel of a structured cabling system, crosstalk can spread to an uncontrollable level and affect more applications.
Demo
Experiments conducted by Avaya lab show that near-end crosstalk NEXT is the primary cause of damage to Transmission Performance for three large high-bandwidth intensive applications. The experiment is based on two four-connector channels, one of which uses CAT5e CAT5e CAT5e-related products on the market, and the other uses the market-wide IMAX GigaSPEED? Cat6 cabling system.
1. 100BASE-TX LAN large data file transmission:
The bit error rate affects the time required to transmit large files on the LAN, and even affects the work efficiency.
Demo
A) 100BASE-TX large data file transmission over the LAN
B) 100BASE-TX local area network video signal transmission stream
C) serial digital video signal (SDV)
Using the Norton clone genie multi-point transfer server software, a 248 MB video file is transferred from the server to the client. Monitor the transmission speed and time used during transmission. The 8112A pulse generator of HP company is used to introduce interference signal pulses at the adjacent ends of the channel in four pairs.
Experiment results using 5e cable channels:
When the LAN connected to the client PC uses the CAT5e channel of the general manufacturer, the file transmission takes 129 seconds, and the average transmission rate per minute is 115 MB.
The following figure shows the experiment result of using GigaSPEED six-class cable channels:
Using GigaSPEED 6 channels, file transmission takes 72 seconds, and the average transmission rate per minute is 206 MB. Under the same crosstalk interference conditions, the same amount of information is transmitted over GigaSPEED 6 channels at 80% of the time transmitted over 5e channels.
2. 100BASE-TX LAN Video Signal Stream:
The ability to transmit multimedia content over a LAN must be sufficient. For users' real-time browsing, the ability to transmit large amounts of data from multimedia servers to end users and the ability to correct the error are all critical. You can evaluate the video and audio quality of the received digital signal or determine the number of bits.
A 56 MB, 40 seconds video file is transmitted between the server and the client through a pair of structured cabling channels with four connectors at a rate of 15 Gb/s/second, the channels use the 5e and GigaSPEED cables of other manufacturers. Generally, the transfer speed of a computer video is 15 Gb/s/second. Files are transmitted in Multi-Point broadcast mode using Microsoft multimedia devices. This file is an image of a boarding student skiing on a snowy hillside. The 8112A pulse generator is used to introduce interference pulses at the end of an adjacent pair of channel in four pairs. The size, cycle, rise/fall time of the introduced pulse are different, so as to simulate the worst near-end crosstalk environment. The unused end of the cable is terminated by the 100 ohm connector. Statistical software is used to measure sent and lost data packets, network utilization, and CRC bit codes.
Experiment results of CAT5e cable channels from other manufacturers:
In CAT5e cable channels, CRC bits cause deformation of the video image, for example, freezing. Each error will invalidate the data packet, resulting in the loss of the image swap, resulting in the receiving image jitter.
The following figure shows the experiment result of using GigaSPEED 6 cable channels:
In the same near-end crosstalk environment, using the GigaSPEED cable does not produce bits, so the received video image quality is quite good.
3. serial digital video SDV ):
SDV transmission is based on the SMPTE 259M standard. This standard is widely used in the field of animation production. It digitizes movies and transfers them at a non-compressed speed of 270 Mb/s. This system can also transmit important images at a compression speed of 45 Mb/s, and transmit TV images at a non-compressed video transmission speed of 143 Mb/s. Only 270 Mb/s uncompressed videos can be used to transmit high-quality movie images. The 270 Mbit/s bit stream is edited and transferred to the broadcast front end for live broadcast. The cable length is generally less than or equal to 100 meters.
SDV comes from analog baseband video and audio signals and requires an independent, digital, and composite bandwidth of 4.2MHz and 20 kHz. 270 Mb/sNRZI serial bit stream transmission on a single 75 ohm coaxial cable. The brightness and chromatic aberration elements in the video signal are separated. Embedded Digital Audio requires 3 MHz bandwidth. The unit interval is usually 0.2UI), which is about 0.5ns. The SMPTE 259M standard allows a return loss greater than 18 decibels. The peak-to-peak voltage of the synthesized SDV baseband signal is 0.8 V +/-10%), and the minimum bandwidth is 135 MHz, in the following line analysis diagram, the valid energy spectrum can be extended to 270 MHz.
The demo configuration of SDV can be used to measure the number of BITs and the number of BITs, as well as to assess the video and audio quality of received signals. The experiment consists of audio and video devices manufactured by Sony and Tektronix for subjective evaluation and independent quantitative measurement. It contains an adapter for transmitting/receiving SDV to UTP. the SDV signal is transmitted to 270 Mb/s over a non-balanced 75 ohm coaxial cable, exceeding the balanced 100 ohm 4-pair UTP cable. Two SDV signals are transmitted in relative directions, that is, two and three pairs of four pairs of cables, in order to produce crosstalk at each end of the channel. The standard adapter performs adaptive balancing and provides automatic compensation within the channel cable length range based on the deformation status and quantity. The standard adapter is designed as a connector with 15 pins connected to a plug-in/plug-in device. The function of the Multi-pin connector is similar to that of the current Cable Testing Device. It can minimize the connector crosstalk measured by any channel. The unused cables in the channel end with an adapter and set each adapter to "Y.
The one-to-four connector structured cabling channels are made up of CAT5e and CAT5e and GigaSPEED 6 components commonly used by other manufacturers on the market. Tektronix TSG601 SDV signal generator sets one of 16 optional SDV test samples at a rate of 270 Mb/s, transmits the embedded AES/EBU digital audio and CRC data to the Tektronix WFM601M SDV waveform monitor. The monitor performs real-time digital error detection and reports CRC errors according to the SMPTE standard RP-165.
When the CRC value between the previous and current video frames is detected, an error is reported immediately. Beating can be accurately measured and displayed as an eye-shaped image. This figure is formed by superposition of all the transmit pulse sequences that may reach the receiver of the channel. Like an eye. This eye chart is a method for evaluating the performance of baseband signals such as SDV. In the channel, when the noise, interference, or beating increases, the degree of eye opening will decrease. The height of opening indicates the degree of margin in the noisy environment. The Tektronix WFM601M SDV waveform Monitor also provides a passive closed loop that allows you to display received video signals on a high-resolution NTSC Sony 20 display. Sony DVW-510 Digital Betacam? Player uses an embedded AES/EBU Digital audio method to format a 3.5-minute Digital Betacam tape and transmit Digital videos to a high-resolution SDV Sony 20 display. Displays are specially equipped with video and audio serial digital interfaces for automatic evaluation of both.
Experiment results of CAT5e cable channels from other manufacturers:
There was no obvious problem when a single SDV signal was initially used to transmit video and audio in one way. However, when a second SDV signal is added to the channel to produce near-end crosstalk, the quality of the video and audio changes very poorly. There are a lot of white spots and snowflakes in the image ). The reason for this white spot is that the bitcode causes the loss of image elements, that is, pixel loss. The transmitted audio has obvious and unsatisfactory electrostatic interference. The Tektronix WFM601M waveform monitor displays a red alarm to indicate a CRC bit code. The heartbeat is displayed as an eye image with a measurement result of 962 microseconds. When the transmission Signal from Tektronix TSG601 Signal Generator or Sony Digital Betacam Player is canceled, all visible and audible interference is terminated, and the beat is reduced to 592 microseconds. CRC bit codes, white spots, or static electricity will no longer appear.
The following figure shows the experiment result of using GigaSPEED 6 cable channels:
No visible and audible interference was detected and no CRC bit code was recorded during bidirectional transmission through 6 types of GigaSPEED channels. The result of the heartbeat measurement is 592 microseconds, which is the same as the heartbeat record when only one SDV signal is transmitted in the 5e channel. Obviously, the near-end crosstalk margin design provides excellent Transmission Performance for 6 types of GigaSPEED channels.
Summary
Many interference factors affect the transmission performance of high-speed, high-bandwidth-intensive network applications when files are uploaded and transmitted through structured cabling channels. The experiment clearly reveals the serious impact of near-end crosstalk. Currently, two types of applications using CAT 5e cables from other manufacturers-file transmission and LAN Video Streams-are used in poor near-end crosstalk environments, the GigaSPEED 6-class cable has achieved remarkable operation performance. The 10 dB surplus attached to the near-end crosstalk greatly improves the data transmission performance of 6 types of channels. The extra margin improves the signal-to-noise ratio. In addition, when the crosstalk generated by the channel is reduced by an hour, more signals can be transmitted.
The final argument also pointed out that some applications such as 270 Mb/s serial digital videos far exceed the performance of 5e channels. The standard clearly states that the performance of 5e channels is as high as 100 MHz, which is obviously insufficient because the channel performance required by SDV applications must reach 250 MHz, this is only available for 6 types of channel GigaSPEED. Applications such as file transfer can allow occasional data packet loss and wait for the data packet to resend. However, applications such as video streams and 270 Mb/s SDV do not allow any latency at all. The video stream program only transmits and processes one data packet at a time.
Transmission Losses in structured cabling channels cannot be compensated. Because of the loss of the image watermark and pixels, the quality of the original transmitted image is significantly reduced. Therefore, channel loss restricts transmission performance to a large extent. With the increasing demand for high-speed applications and bandwidth in the future, this impact will become more and more obvious. The channel of the structured cabling system needs to provide sufficient margin to resist channel losses, so as to support the next generation data rate exceeding the current level and achieve good transmission performance.
1) CAT5e cable channel results from other manufacturers: many white spots are generated due to bit codes.
2) Avaya GigaSPEED 6-class cable channel result: pixel loss caused by no bit code