Vastly powerful, often undervalued a technical paper by. N is chosen to be 64 64 point fft for this work following the ieee 802. It is generally recommended to stick to one of three upstream modulation profiles. The mid 40s is what the industry likes to target to help fine tune for preequalization purposes but. This adds robustness to reflections, inchannel tilt, group delay, and us burst noise. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. It also allows 24 taps of preequalization in the modems and us interleaving. Also performance of the system is given in terms of throughput received bitsofm symbol is given in a plot for different snr.
Thus, it is important to further demonstrate the predistortion performance for a wider range of experimental conditions and input signal parameters. It means that every cable modem now becomes a troubleshooting device. This equates to a symbol being transmitted in 195 ns 1 sec5. Pdf 16qam signal preequalization using multiple binary analog. Nyquistband is considered in the preequalization to enhance the tolerance of the pdm64qam to the aggressive spectral shaping. Request pdf preequalization and bandwidth limitation for a 100gbaud 32qam allsilicon transmitter preequalizer as high pass digital filter compensates for transmitter tx frequency response. One of the easiest ways to implement qam with hardware is to generate and mix two sine waves that are 90 degrees out of phase with one another. As a downside, tomlinsonharashima precoding requires full channel state information csi at the transmitter, which may be hard to obtain precisely in wireless systems. Widely linear mmse precoding and equalization techniques for. The implementation principle of trainingbased equalization and predistortion are presented here in this paper with experimental studies. Mar 21, 2001 timing, carrier frequency and transmit preequalization. Aug 25, 2008 8 qam, 32 qam, and 64 qam modulation schemes. A radiofrequency rf driver provides a rf signal with the qam components.
Qam techniques such as 16 qam or 64 qam have a high spectral ef. Quadrature amplitude modulation qam pam signals occupy. When the power estimate pn exceeds a predetermined threshold for a period of time, a received qam signal is declared to be present. Detailed characteristics are described by the saleh model 4. Use docsis pre equalization to proactivity not reactively analysis the docsis network with products you already have.
Preequalization and bandwidth limitation for a 100gbaud. The 16 qam signals are generated and preprocessed with preequalization preeq and lookuptable lut based predistortion predt at the transmitter txside. To facilitate more robust upstream data transmission, docsis 2. Docsis best practices and guidelines proactive network. The bcm3349 pinout has been optimized to allow an ultra lowcost 2layer pcb. Figure i23 example of 64qam signal after adaptive preequalization eliminated. Moreover, the ber of the 128 64 3216 qam ofdm scheme and the 64 qam ofdm scheme on different sampling rate are depicted in fig. Blind equalization for tomlinsonharashima precoded systems. Request pdf isi preequalization in a vector modulator for 5 gsymbols 64 qam we investigated the performance of electronic preequalization to compensate for isi caused in a vector modulator.
Feb 03, 2004 a direct quadrature amplitude modulation qam modulator in accordance with the invention provides amplitude and phase preequalization to reduce complexity and cost. Low headroom or dynamic range means sensitivity to other link variables analog return paths. Also, 24tap equalization in the cmts will help older, docsis 1. Designing and performance evaluation of 64 qam ofdm system. Understanding equalizers, preequalizers, and their use in. How ever, by assuming that only two turbo equalization iterations were. In fact, j ust by enabling preequalization on the cmts you can see an immediate 5 to 10 db improvement in upstream mer.
Docsis preequalization in proactive network maintenance. It discusses adaptive equalizers, preequalization, the. The preequalizer is composed of multiple binary analog finite impulse response. Those skilled in the art will appreciate that other modulation techniques, such as 32 qam, 64 qam and 256 qam may alternatively be utilized. While docsis provides for other modulation levels, such as 32 qam, the tradeoff between faster data rates and higher mer requirements in going from 16 qam to 32 qam is simply not justified. This can be explained by the spreading unit, pre venting sequential error. Implementation of 16qam to increase the value of cable.
Blind equalization for tomlinsonharashima precoded systems rubyet adnan a thesis submitted in partial ful. Quadrature amplitude modulation qam including 16 qam and 64 qam have been experimentally investigated, where inphase i and quadrature q components of lightwave are modulated by multilevel signals 1, 2. These systems normally transmit symbols from a complex quadrature amplitude modulation qam. For 64qam, the teqct receiver was too complex to be investigated by simulation. All other product or service names are the property of their respective owners. Us7120123b1 preequalization technique for upstream. Thework reported here represents a more complete demonstration of the memory polynomial predistortion approach to ofdmrof. Advanced qam transmitter takes burst or continuous data provides fec encoding and pre equalization for docsis applications applies 4816 64 128256 qam or scdma modulation to the data stream amplifies the signal through the integrated upstream power amplifier provides a direct 0 mhz to 65 mhz analog output. The second image is what the signal looks like to the cmts after it has been preequalized. Adaptive digital baseband predistortion for rf power. Dec 04, 2005 if attempting to run 256 qam on the downstream, be sure the digitally modulated carriers average power level is 6 to 10 db below what the level of an analog tv channel on the same frequency would be.
The amplitude balance of i and q data and their skews are adjusted for each subcarrier to realize preequalization preeq to compensate for the frequency response of the fig. Reduced complexity inphasequadraturephase mqam turbo. We theoretically and experimentally investigate a timedomain digital pre equalization dpeq scheme for bandwidthlimited optical coherent communication systems, which is based on feedback of channel characteristics from the receiverside blind and adaptive equalizers, such as leastmeansquares lms algorithm and constant or multi modulus algorithms cma, mma. Isi preequalization in a vector modulator for 5 gsymbols 64qam. Inphase i and quadraturephase q qam signal components are provided from an analog modulator. As the pre distorted signal traverses the hfc network it will experience the effects of rf impairments. Pdf a family of algorithms for blind equalization of qam signals. If preequalization is enabled, it turns every cable modem in the. Equalizers and their use in preventative network maintenance larry jump. Timedomain digital preequalization for bandlimited signals.
Isi preequalization in a vector modulator for 5 gsymbols. You can select c as a number slightly less than 1, i. Qam and 64qam, the performance of blind equalizer can challenge the. Direct qam modulator with digital feedback control and. Scfde systems using tomlinsonharashima precoding were proposed in7, 8. Allelectronic flexibly programmable 864gbs singlecarrier pdm64qam. It can be seen that a more obvious ber performance improvement can be achieved by utilizing the 128 64 3216 qam modulation scheme with mbcazac precoding for the ofdmvlc system. But it is not suitable in practice because it is very sensitive to both amam and ampm distortions introduced by the high power ampli.
Constant modulus algorithm cma blind equalizer has been compared with the popular. Pdf we propose blind equalization algorithms that perform similarly to supervised ones. Understanding data throughput in a docsis world cisco. Equalizers and their use in preventative network maintenance. Many cable operators set 64 qam signals at 10 dbc, and 256 qam at 5 to 6 dbc. This is a very attractive scheme of modulation for mobile communication or satellite transmission.
Determine if a qam signal is present at the receiver this power estimate can be easily formed by averaging the squared adc output samples rn. However, the description and illustration of a burst receiver configured to accommodate qpsk and 16 qam inputs is by way of illustration only and not by way of limitation. In this chapter, a multilevel modulationdemodulation method based on a selfhomodyne phase noise canceling scheme using a pilot carrier is introduced as a. With the incorporation of an upstream power amplifier and ethernet phy, the bcm3349 allows a complete cable modem to be. The qam modulated signal is placed on n orthogonal subcarriers. The implementation of ofdm modulationdemodulation is done using the fft and ifft. Advanced linear and nonlinear compensations for 16qam sc400g. The results are presented in figures 5, 6, 7 and 8 for peak constellation power backoff values within 50% from the absolute saturation region. Institutionen for systemteknik department of electrical engineering examensarbete ads and matlab to optimize predistortion of amplifiers examensarbete utfort i signalbehandling av jessica trinh lithisyex154880se linkoping 2015 tekniska hogskolan linkopings universitet department of electrical engineering linkoping university. Vastly powerful, often undervalued 3 3 cable modem transmits a pre distorted signal to compensate for impairments between the cable modem and the cmts. Using pre equalization data in cable modems we can locate outside plant impairments to within 50 feet or less. Quadrature amplitude modulation qam national instruments.
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