DOCSIS 3.1 Upstream Signal Analysis - Keysight Upstream and Downstream DOCSIS 3.1 Devices April 2015 Steve Hall DOCSIS 3.1 Business Development Manager

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

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