DOCSIS 3.1 Upstream Signal Analysis

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<ul><li><p>Testing Upstream and Downstream DOCSIS 3.1 Devices April 2015 </p><p>Steve Hall </p><p>DOCSIS 3.1 Business Development Manager </p></li><li><p>Page </p><p> Keysight </p><p>Technologies 2015 </p><p>Agenda </p><p>1. Decoding and demodulating a real downstream DOCSIS 3.1 signal and reporting key metrics </p><p>such as MER and BER. </p><p>2. Combining powerful trigger and recording techniques to detect, identify and repair issues that </p><p>cause BER. </p><p>3. Understanding the complexities of demodulating and measuring low frequency, small grant </p><p>upstream signals. </p><p>4. Generating in-channel and out-of-channel upstream and downstream DOCSIS 3.1 signals. </p><p>2 </p></li><li><p>Page </p><p> Keysight </p><p>Technologies 2015 </p><p>1. Decoding and demodulating a real downstream DOCSIS 3.1 signal and reporting key </p><p>metrics such as MER and BER. </p><p>2. Combining powerful trigger and recording techniques to detect, identify and repair issues that </p><p>cause BER. </p><p>3. Understanding the complexities of demodulating and measuring low frequency, small grant </p><p>upstream signals. </p><p>4. Generating in-channel and out-of-channel upstream and downstream DOCSIS 3.1 signals. </p><p>3 </p><p>Agenda </p></li><li><p>Page </p><p> Keysight </p><p>Technologies 2015 </p><p>Physical Layer Link Channel (PLC) OFDM Channel Descriptor (OCD) </p><p>Downstream Profile Descriptor (DPD) messages </p><p>DOCSIS 3.1 Signal Format </p><p>4 </p></li><li><p>Page </p><p> Keysight </p><p>Technologies 2015 </p><p>NCP </p><p>Fields </p><p>Data </p><p>Fields </p><p>DOCSIS 3.1 Signal Format </p><p>5 </p></li><li><p>Page </p><p>Automatic Demodulation of Downstream signals in VSA </p><p>- New DOCSIS3.1 Downstream measurement option BHM for 89601B VSA </p><p>(BHM)Key features: </p><p>- Automatic setup for downstream configuration by demodulating and </p><p>decoding: </p><p> Physical Layer Link Channel (PLC) </p><p> OFDM Channel Descriptor (OCD) </p><p> Downstream Profile Descriptor (DPD) messages </p><p>- Decode the NCP and locate the codewords for each profile </p><p>- Demod the data for each profile - MER </p><p>- Post-process MER &amp; BER/PER measurements to accumulate over </p><p>successive acquisition. </p><p> Keysight </p><p>Technologies 2015 6 </p></li><li><p>Page </p><p>Result Traces DOCSIS3.1 Downstream </p><p>Step 1 detect and decode PLC Physical Layer Link Channel </p><p>Step 2 detect and decode OCD OFDM Channel Descriptor </p><p> (not necessarily sent every frame as per standard) </p><p>Step 3 detect and decode DPD Downstream Profile Descriptor </p><p> Keysight </p><p>Technologies 2015 7 </p></li><li><p>Page </p><p>Result Traces DOCSIS3.1 Downstream </p><p>Initial performance results </p><p> Keysight </p><p>Technologies 2015 8 </p></li><li><p>Page </p><p>Result Traces DOCSIS3.1 Downstream </p><p>Report Profile Results </p><p>Report NCP Results </p><p>De</p><p>sc</p><p>rip</p><p>tio</p><p>n o</p><p>f R</p><p>es</p><p>ult</p><p>s </p><p> Keysight </p><p>Technologies 2015 9 </p></li><li><p>Page </p><p>Result Traces DOCSIS3.1 Downstream </p><p> Keysight </p><p>Technologies 2015 10 </p></li><li><p>Page </p><p>Result Traces DOCSIS3.1 Downstream </p><p> Keysight </p><p>Technologies 2015 11 </p></li><li><p>Page </p><p>MER Measurement </p><p>Hardware Positioning </p><p>$ </p><p>Max 160MHz </p><p>Demod BW + RF Measurements </p><p>Max 750 MHz </p><p>Demod BW </p><p>Max 510 MHz </p><p>Demod BW + RF Measurements </p><p>MER </p><p>12 </p><p> Keysight </p><p>Technologies 2015 </p></li><li><p>Page </p><p>Introducing the N9040B UXA Signal Analyzer </p><p>8.4/13.6/26.5 </p><p>GHz </p><p>Streamlined </p><p>touch driven </p><p>interface </p><p>Full BW RTSA </p><p>Up to 510 </p><p>MHz analysis </p><p>BW </p><p>89600 VSA &amp; </p><p>N9068C </p><p>Phase Noise </p><p>App </p><p>Industry </p><p>Leading </p><p>Phase noise Keysight Technologies 2015 13 </p></li><li><p>Page </p><p> U5303A PCIe High-Speed </p><p>Digitizer </p><p> PCIe rack mount expansion </p><p>chassis </p><p> Desktop PC </p><p> UXA N9040B Signal Analyzer </p><p> Install 89600 VSA software on </p><p>Windows 7 OS or on an </p><p>external PC </p><p> Keysight </p><p>Technologies 2015 </p><p>89601B Vector Signal Analyzer </p><p>OR </p><p>Hardware Platforms: U5303A digitizer or X-Series Spectrum Analyzer </p><p>http://www.magma.com/sites/default/files/EB3TX_5a.jpg</p></li><li><p>Page </p><p>Hardware Platforms: U5303A digitizer and X-Series Spectrum Analyzer </p><p>Preserve your X-Series investment! </p><p>Combine the power of the PCIe Digitizer Modulation Measurements </p><p>with the power of the PXA/UXA RF Measurememts. </p><p>Personal Cpmputer </p><p> Keysight </p><p>Technologies 2015 15 </p></li><li><p>Page </p><p> Keysight </p><p>Technologies 2015 </p><p>Agenda </p><p>1. Decoding and demodulating a real downstream DOCSIS 3.1 signal and reporting key metrics </p><p>such as MER and BER. </p><p>2. Combining powerful trigger and recording techniques to detect, identify and repair issues </p><p>that cause BER. </p><p>3. Understanding the complexities of demodulating and measuring low frequency, small grant </p><p>upstream signals. </p><p>4. Generating in-channel and out-of-channel upstream and downstream DOCSIS 3.1 signals. </p><p>16 </p></li><li><p>Page </p><p>Device Under </p><p>Test </p><p>DOCSIS </p><p>Frame </p><p>Generator </p><p>M8190A </p><p> To BER or not to BER: </p><p> BER says everything is working nicely or that it is NOT! </p><p> Hours of testing complete yet BER fails! </p><p> How do you determine WHY your Bit Error Rate is failing? </p><p>Golden Receiver Cable Modem </p><p> CMTS (single ended) </p><p> Optical Transport </p><p> Amplifier </p><p>BER </p><p>What causes bit errors? </p><p> Clipping? </p><p> Noise? </p><p> Compression? </p><p> Interference? </p><p>How and where do they show up other than in an </p><p>accumulated over-time BER test? </p><p> Rapid fire in-channel and adjacent-channel energy </p><p>spikes? </p><p> Increased unexpected signal amplitude? </p><p> Spurious emissions? </p><p> Reduced Adjacent Channel Power performance? Keysight </p><p>Technologies 2015 17 </p></li><li><p>Page </p><p> How do DOWNSTREAM events manifest themselves? </p><p>These events show up at various times and places </p><p>and are distinguishable as perturbations in the </p><p>frequency domain! </p><p>By building a very flexible mask around the spectrum, </p><p>these perturbations can be trapped, recorded, </p><p>analyzed and subsequently questions answered! Keysight Technologies 2015 18 </p></li><li><p>Page </p><p> Keysight </p><p>Technologies 2015 </p><p> The test steps </p><p>Monitor Transient Spectral Behavior </p><p>in Real Time </p><p>Trigger on Transient Spectral Behavior in </p><p>Real Time </p><p>Record Transient Spectral Behavior Including Behavior </p><p>Leading up to the event </p><p>Determine if the Transient Spectral </p><p>Behavior Caused Bit Errors </p><p>Determine Root Cause and Repair </p><p>Issue </p><p>19 </p></li><li><p>Page </p><p> Keysight </p><p>Technologies 2015 </p><p> The Tools: How are transients found? </p><p> Real Time Spectrum Analysis </p><p>Watch for the transient event </p><p>20 </p></li><li><p>Page </p><p> Keysight </p><p>Technologies 2015 </p><p> The Tools: How are transients found? </p><p> Real Time Spectrum Analysis </p><p>Watch for the transient event </p><p>21 </p></li><li><p>Page </p><p> Keysight </p><p>Technologies 2015 </p><p>Frequency Mask trigger </p><p>Catches the transient </p><p> The Tools: How are transients found? </p><p> Real Time Spectrum Analysis </p><p>Watch for the transient event </p><p>22 </p></li><li><p>Page </p><p> Keysight </p><p>Technologies 2015 </p><p>Set up frequency Mask Trgger in VSA </p><p> The Tools: How are transients found? </p><p> Real Time Spectrum Analysis + Vector Signal Analysis </p><p>Watch for the transient event </p><p>23 </p></li><li><p>Page </p><p> Keysight </p><p>Technologies 2015 </p><p> Multiple Domain Insight </p><p>Watch for the transient event </p><p>24 </p></li><li><p>Page </p><p> Keysight </p><p>Technologies 2015 </p><p>Note spectral behavior of transient event </p><p> Multiple Domain Insight </p><p>Watch for the transient event </p><p>25 </p></li><li><p>Page </p><p> Keysight </p><p>Technologies 2015 </p><p>Transient Event Impact on Constellation </p><p>Impact on MER </p><p> The Tools: How are transients found? </p><p>26 </p></li><li><p>Page </p><p>DUT (Amplifier/Optical </p><p>Transport or CMTS) </p><p>M8190A (DOCSIS 3.1 Frame </p><p>Generator) </p><p>Real Time Spectrum </p><p>Analyzer uses </p><p>frequency Mask </p><p>Trigger to detect </p><p>unwanted energy in </p><p>and around the </p><p>desired signals. </p><p>Vector Signal Analyzer begins recording triggered by a violation detected by </p><p>the Real Time Spectrum Analyzer including a pre-trigger window </p><p>Monitor Transient Spectral Behavior </p><p>in Real Time </p><p>Trigger on Transient Spectral Behavior in </p><p>Real Time </p><p>Record Transient Spectral Behavior Including Behavior </p><p>Leading up to the event </p><p> The test steps </p><p> Keysight </p><p>Technologies 2015 27 </p></li><li><p>Page </p><p>Study demodulation test results for the gap </p><p>free recording to answer questions like: </p><p>Was signal quality impacted buy the event </p><p>that caused the recording to be triggered? </p><p>Calculate and </p><p>analyze BER </p><p>results for the </p><p>entire gap-free </p><p>recorded frames in </p><p>order to answer the </p><p>question: Did THIS </p><p>event cause bit </p><p>errors? </p><p>Determine if the Transient Spectral </p><p>Behavior Caused Bit Errors </p><p>Determine Root Cause and Repair </p><p>Issue </p><p> Keysight </p><p>Technologies 2015 28 </p></li><li><p>Page </p><p> Automating the process </p><p>Test Controller </p><p>Create scripts to automate and record </p><p>events. </p><p>Monitor Transient Spectral Behavior </p><p>in Real Time </p><p>Trigger on Transient Spectral Behavior in </p><p>Real Time </p><p>Record Transient Spectral Behavior Including Behavior </p><p>Leading up to the event </p><p>Determine if the Transient Spectral </p><p>Behavior Caused Bit Errors </p><p>Determine Root Cause and Repair </p><p>Issue </p><p> Keysight </p><p>Technologies 2015 29 </p></li><li><p>Page </p><p>Testing for the Real Upstream Environment </p><p>CM 1 </p><p>CM 2 </p><p>CM 3 </p><p>CM n </p><p>Node Node FIBER </p><p>CMTS </p><p>Environmental </p><p>Interference </p><p>How tolerant is this system of this signal? </p><p> Keysight </p><p>Technologies 2015 30 </p></li><li><p>Page </p><p>Testing for the Real Upstream Environment </p><p>Node Node FIBER </p><p>Environmental </p><p>Interference </p><p>How tolerant is this system of this signal? </p><p>Upstream </p><p>Generator </p><p>Plus </p><p>Impairments </p><p>Real Time </p><p>Spectrum </p><p>Analyzer </p><p>Plus </p><p>VSA </p><p> Keysight </p><p>Technologies 2015 31 </p></li><li><p>Page </p><p>Real Time Spectrum Analysis and Event recording </p><p>Step 2: Initiate Signal recording! </p><p>Step 3: Post-process using Multi-</p><p>measurements to show impact during </p><p>the event Step 4: Post-process Multimeasurements </p><p>Show recovery after the event the event </p><p>Step 1: RTSA Trigger Mask </p><p> Keysight </p><p>Technologies 2015 32 </p></li><li><p>Page </p><p> Keysight </p><p>Technologies 2015 </p><p>Agenda </p><p>1. Decoding and demodulating a real downstream DOCSIS 3.1 signal and reporting key metrics </p><p>such as MER and BER. </p><p>2. Combining powerful trigger and recording techniques to detect, identify and repair issues that </p><p>cause BER. </p><p>3. Understanding the complexities of demodulating and measuring low frequency, small </p><p>grant upstream signals. </p><p>4. Generating in-channel and out-of-channel upstream and downstream DOCSIS 3.1 signals. </p><p>33 </p></li><li><p>Page </p><p>Hybrid Fiber </p><p>Coax (HFC) </p><p>Network </p><p>Stability of MER Measurements at Low Grant % </p><p>CMTS </p><p>1 </p><p>96MHz Channel </p><p>Spectrum </p><p>3 </p><p>4 </p><p>5 </p><p>2 </p><p>OFDMA </p><p>96MHz Channel </p><p>Cable </p><p>Modems </p><p>OFDMA: Low-grant signals are those where less </p><p>than about half of the subcarriers are active, and the </p><p>remainder are transmitted as nulls. </p><p>1 2 3 4 5 </p><p> Keysight </p><p>Technologies 2015 34 </p></li><li><p>Page </p><p>Stability of MER Measurements at Low Grant % </p><p>Measurement Challenge: Vector Signal Analysis synchronization algorithms are </p><p>optimized for signals with a relatively high grant percentage. </p><p>5% grant </p><p>96 subcarriers </p><p>96 MHz Acquisition BW </p><p>DC </p><p>Sample Freq. 102.4 MHz </p><p>Center Freq. 53 MHz </p><p>2048 point FFT </p><p> Keysight </p><p>Technologies 2015 35 </p></li><li><p>Page </p><p>Stability of MER Measurements at Low Grant % </p><p>5% grant </p><p>96 subcarriers </p><p>96 MHz Acquisition BW </p><p>DC </p><p>Sample Freq. 102.4 MHz </p><p>Center Freq. 53 MHz </p><p>2048 point FFT </p><p>Mathematically </p><p>equivalent to: </p><p>Sample Freq. 6.4 MHz </p><p>Center Freq. 8 MHz </p><p>128 point FFT </p><p>100% grant </p><p>96 subcarriers </p><p>~5 MHz Acquisition BW </p><p>Measurement Approach: Reconfigure existing measurements to zoom in on the active </p><p>subcarriers only. Thus, rather than analyzing a small percentage of a large FFT block, </p><p>the demodulator processes a smaller FFT block that is almost fully-populated! </p><p> Smaller acquisition BW improves SNR to the sync algorithms, stabilizes MER readings. Mathematically, the two </p><p>approaches are identical there is no effect on the calculation of MER, carrier frequency error, symbol clock error, </p><p>or other measurement results. </p><p>Automatic Bandwidth Translation </p><p>Compliments of Optimizer Macro! </p><p> Keysight </p><p>Technologies 2015 36 </p></li><li><p>Page </p><p>Stability of MER Measurements at Low Grant % </p><p>Optimize VSA Macro </p><p> Keysight </p><p>Technologies 2015 37 </p></li><li><p>Page </p><p>Results Comparison </p><p>Demod config: 2K FFT 5% grant Demod config: 128 FFT 100% grant </p><p>Avg. MER: ~37 dB </p><p>Variance: 5 dB </p><p>Sync stability: 50% </p><p>Avg. MER: 53.8 dB </p><p>Variance: 1 dB </p><p>Sync stability: 100% </p><p>Identical hardware, identical input signal: </p><p> Keysight </p><p>Technologies 2015 38 </p></li><li><p>Page </p><p>Stability of MER Measurements at Low Grant % </p><p>Small Grant 1 Small Grant 2 </p><p>Setting the grants side by </p><p>side creates a challenging </p><p>measurement scenario. </p><p>Hybrid Fiber </p><p>Coax (HFC) </p><p>Network </p><p>CMTS </p><p>1 </p><p>96MHz Channel </p><p>Spectrum </p><p>3 </p><p>4 </p><p>5 </p><p>2 </p><p>OFDMA </p><p>96MHz Channel </p><p>Cable </p><p>Modems </p><p>1 2 3 4 5 </p><p> Keysight </p><p>Technologies 2015 39 </p></li><li><p>Page </p><p>Reconfiguring OFDM for Synchronized ACP </p><p> The DOCSIS 3.1 PHY specification requires that Adjacent Channel </p><p>Power be measured in the spectrum regions directly adjacent to </p><p>the transmitted signal, starting at one subcarrier spacing (25 or 50 </p><p>kHz) from the outermost active subcarriers. </p><p> However, even well-windowed OFDM signals will have significant </p><p>sinX/X modulation sidebands that extend into this region which are </p><p>visible when viewed on a traditional swept spectrum analyzer. </p><p> Keysight </p><p>Technologies 2015 40 </p></li><li><p>Page </p><p>Reconfiguring OFDM for Synchronized ACP </p><p> The ACP specification is not meant to include these sidebands, but </p><p>rather to measure only the unwanted noise and distortion that may </p><p>accompany them. </p><p> In order to separate these components, the spec requires that ACP </p><p>measurements at offsets of 2 MHz or less be performed </p><p>synchronously - that is, sampled at the same frequency and in </p><p>phase with the underlying OFDM modulation clock. </p><p> This suppresses all orthogonal (modulation-related) energy, </p><p>leaving only the non-linear distortion to be summed. </p><p> Keysight </p><p>Technologies 2015 41 </p></li><li><p>Page </p><p>Reconfiguring OFDM for Synchronized ACP </p><p>Adds extra null subcarriers to the OFDM </p><p>demod configuration. </p><p>Configure analyzer to display the null </p><p>subcarriers. </p><p>Read ACP from VSA spectrum display </p><p>using band power markers. </p><p>Optimizer </p><p>VSA </p><p> Keysight </p><p>Technologies 2015 42 </p></li><li><p>Page </p><p>Agenda </p><p>1. Decoding and demodulating a real downstream DOCSIS 3.1 signal and reporting key metrics </p><p>such as MER and BER. </p><p>2. Combining powerful trigger and recording techniques to detect, identify and repair issues that </p><p>cause BER. </p><p>3. Understanding the complexities of demodulating and measuring low frequency, small grant </p><p>upstream signals. </p><p>4. Generating in-channel and out-of-channel upstream and downstream DOCSIS 3.1 signals. </p><p> Keysight </p><p>Technologies 2015 43 </p></li><li><p>Page </p><p>M8190A Main Features </p><p>Breakthrough performance </p><p>Up to 90 dBc SFDR for </p><p>Reliable and repeatable measurements </p><p>14 bit 8 Gsa/s or 12 bit 12 Gsa/s </p><p>Variable sample rate from 125 Msa/s to 8/12 Gsa/s </p><p>2 GSa memory for </p><p>Long play time </p><p>5 GHz analog bandwidth </p><p>For todays and tomorrows apps </p><p>Operation with leading </p><p>software platforms </p><p> Keysight </p><p>Technologies 2015 44 </p></li><li><p>Page </p><p>M9099T Waveform Creator - Downstream </p></li><li><p>Page </p><p>M9099T Waveform Creator - Upstream </p></li><li><p>Page </p><p>SystemVue Libraries </p><p> Keysight </p><p>Technologies 2015 47 </p></li><li><p>Page </p><p>ATP PHY 31 Spectrum Loading </p><p>Cable Load </p><p>Signals </p><p>Notch </p><p>Cable Load </p><p>Signals </p><p> Keysight </p><p>Technologies 2015 48 </p></li><li><p>Page </p><p>ATP PHY 31 Interfering spectrum </p><p> Keysight </p><p>Technologies 2015 49 </p></li><li><p>Page </p><p> Keysight </p><p>Technologies 2015 50 </p><p>Output of M8190A as per settings described above </p><p>DOCSIS 3.0 = 158 </p><p>channels, 6 MHz spacing </p><p>DOCSIS 3.1, 1901 </p><p>active subcarriers </p></li><li><p>Page </p><p> Keysight </p><p>Technologies 2015 </p><p>Questions? </p><p>1. Decoding and demodulating a real downstream DOCSIS 3.1 signal and </p><p>reporting key metrics such as MER and BER. </p><p>2. Combining powerful trigger and recording techniques to detect, identify and </p><p>repair issues that cause BER. </p><p>3. Understanding the complexities of demodulating and measuring low frequency, </p><p>small grant upstream signals. </p><p>4. Generating in-channel and out-of-channel upstream and downstream DOCSIS </p><p>3.1 signals. </p><p>51 </p></li></ul>

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