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XRA-31 5.0 Changelog
Posted by Dieter Dobbelaere, Last modified by Dieter Dobbelaere on 15 February 2021 03:19 PM

Welcome 

We are very excited to announce this release of the XRA-31!

This version supports up to 2 OFDM, 2 OFDMA, 32 SC-QAM and 8 A-TDMA channels simultaneously, in real time at line-rate speeds!

Improved OFDM equalization, faster and more robust OFDM locking and significantly reduced power consumption are other notable enhancements.

Furthermore this release has several other improvements and bug fixes.

Check out the details below.

New since 5.0!

  • General

    • Lower power consumption.

  • OFDM

    • Up to 2 channels.
    • Improved equalization.
    • Improved locking.

  • SC-QAM

    • Up to 32 channels.

Changelog 5.0.4-1638 (2020-12-07) 

Fixes 

  • [Firmware] More robust reset sequence of inter-FPGA serial links (fixes long-standing known issue of occasionally having to reboot after powering on the XRA-31 due to selftest errors).
  • [System] Trailing padding is now stripped from upstream MAC frames data bursts without segment header (this also fixes a packet loss issue).
  • [System] Fixed issue leading to upstream data burst loss.
  • [System] Fixed issue in OFDMA data burst handler to prevent segmentation fault.
  • [System] Fixed issue where incomplete support archive could be downloaded.

Changelog 5.0.2-1624 (2020-08-10) 

Fixes 

  • [System] Fixed incorrect handling of OFDMA data bursts for SIDs higher than 255 (critical bug introduced in v4.0).
  • [Firmware] Don't try to demodulate A-TDMA grants for the NULL SID.

Changelog 5.0-1618 (2020-08-03) 

Enhancements 

  • [System] Up to 2 OFDM channels supported.
  • [System] Up to 32 SC-QAM channels supported.
  • [Firmware] Optimized FPGA power consumption.
  • [Firmware] Improved OFDM equalizer leading to significantly higher MER.
  • [Firmware] Completely revised OFDM locking, faster and more robust than ever, which fixes several locking issues caused by neighboring channel interference.
  • [Firmware] More robust OFDM power level estimate (especially during locking).
  • [Firmware] Minimized OFDM DC offset.
  • [GUI] Added "delete all" button for easier upstream/downstream channel configuration.
  • [GUI] Moved channel connector information from configure page to status panel.
  • [GUI] Also show PLC-only lock state in status panel.
  • [GUI] Multiple layout improvements.
  • [GUI/API] Roll-off period is no longer required to configure an OFDM channel.
  • [API] Print the client API version without XRA-31 connection.
  • [API] Introduced paths (click here for more details).
  • [System] Reduced total system update time to about 7 minutes.

Fixes

  • [Firmware] Fixed incorrect parsing of MMMs defragmented over multiple PLC MC-MBs, leading to OFDM locking or data demodulation failures.
  • [GUI] Fixed missing suffix in status panel OFDM(A) reported input power level.
  • [GUI] Fixed OFDM MER reporting for PLC-only lock.
  • [GUI] Fixed slow update of status panel after channel configuration change.
  • [GUI] Fixed issue where downstream and upstream channels could be edited simultaneously.
  • [API] Fixed issue where CLI commands overwrite JSON file with empty file on error.
  • [API] Fixed multiple issues related to downloading latest captured file via xra31-analyse.
  • [System] Fixed issue with firmware flashing during system update.

Features 

OFDM

  • Real-time demodulation and decoding 
  • Full line rate
  • All FFT sizes, cyclic prefixes and roll-off periods defined by [CM-SP-PHYv3.1] 
  • Data demodulation and decoding 
    • All interleaver settings defined by [CM-SP-PHYv3.1] 
    • All modulations from zero-bit-loading up to 4096-QAM defined by [CM-SP-PHYv3.1] 
    • All possible configurations of exclusion bands defined by [CM-SP-PHYv3.1] 
    • Multiple concurrent data profiles (from A up to P) 
    • Mixed-modulation profiles 
    • Dynamic data profile changes 
    • Timestamp precision of DOCSIS frames is equal to one OFDM symbol (between 21 and 45 microseconds depending on FFT size and cyclic prefix) 
  • PLC and NCP demodulation and decoding 
    • Including MER statistics 
    • Timestamp precision is on the order of a few nanoseconds 

OFDMA

  • Real-time demodulation and decoding 
  • Full line rate
  • All FFT sizes, cyclic prefixes and roll-off periods defined by [CM-SP-PHYv3.1] 
  • Dynamic UCD changes (including data profile IUC changes) 
  • Data demodulation and decoding 
    • All interleaver settings defined by [CM-SP-PHYv3.1] 
    • All modulations from zero-valued up to 4096-QAM defined by [CM-SP-PHYv3.1] 
    • All possible configurations of exclusion bands and unused sub-carriers defined by [CM-SP-PHYv3.1] 
    • All data profile IUCs defined by [CM-SP-MULPIv3.1] concurrently 
    • Supported pilot patterns: 1-4, 8-11 
    • Timestamp precision of DOCSIS frames is equal to one OFDMA frame (between 126 and 1665 microseconds depending on OFDMA frame size, cyclic prefix and FFT size) 
  • Real-time full line rate bandwidth request (REQ) message demodulation and decoding 
    • Timestamp precision is on the order of a few nanoseconds 
  • Initial Ranging and Fine Ranging demodulation and decoding 
    • Including MER statistics and time offset estimations 
    • Timestamp precision is on the order of a few nanoseconds

Downstream SC-QAM 

  • Real-time demodulation and decoding 
  • Full line rate
  • Hardware timestamping of packets using reference channel clock (nanosecond resolution) 
  • 64/256-QAM, independently configurable per channel 
  • Dynamically configurable annex 
    • Annex A (EuroDOCSIS)  
    • Annex B (US DOCSIS)  
      • All interleaving parameters (control words) defined in [ITU-T Rec. J.83] supported 
      • Viterbi decoding for increased reliability. 
  • Extended downstream frequency range support 
    • Channel frequencies can be any multiple of 62.5 kHz between 108 and 1006 MHz, complying with all CM requirements in [CM-SP-PHYv3.1]. 
  • Two independent 248 MHz wide receive modules 
    • All channel frequency configurations that can be grouped evenly into the two receive module bands are valid, e.g. a channel configuration consisting of three channels at 200 MHz, 440 MHz and 1000 MHz is valid, but a configuration with frequencies 200 MHz, 600 MHz and 1000 MHz is not. 
  • Data MER and Reed-Solomon decoder statistics 
  • Timestamp precision of DOCSIS frames is equal to one MPEG frame (between 29 and 56 microseconds depending on annex and modulation)

A-TDMA 

  • Real-time demodulation and decoding 
  • Full line rate
  • Full A-TDMA UCD type 29 and 35 support (with the sole exceptions of differential encoding, zero-length preambles and IUC 2 Request_2 demodulation). 
    • All channel bandwidths (from 200 kHz to 6.4 MHz) defined in [CM-SP-PHYv3.0] 
    • All upstream center frequencies allowed by [CM-SP-PHYv3.0] 
    • All modulation types (from QPSK to 64-QAM) defined in [CM-SP-PHYv3.0] 
    • All preamble patterns, types (QPSK0/QSPK1) and lengths from 2 to 1536 bits defined in [CM-SP-PHYv3.0] (Hence, the minimum allowed preamble length is one QPSK symbol) 
    • Scrambler on/off 
    • Fixed/shortened last codeword 
    • All interleaving parameters allowed by [CM-SP-PHYv3.0] 
    • All Reed-Solomon FEC parameters allowed by [CM-SP-PHYv3.0] 
    • Supported IUCs: 1 (Request), 3 (Initial Maintenance), 4 (Station Maintenance), 5 (Short Data Grant), 6 (Long Data Grant), 9 (Advanced PHY Short Data Grant), 10 (Long PHY Short Data Grant), 11 (Advanced PHY Unsollicited Grant) 
    • Dynamic UCD changes 
  • Detailed statistics per demodulated burst 
    • Data MER 
    • Time offset 
    • Reed-Solomon decoder statistics 
    • Start minislot ID

References 

  • [CM-SP-PHYv3.0] DOCSIS® 3.0 Physical Layer Specification (December 2017, http://www.cablelabs.com/specs/) 
  • [CM-SP-PHYv3.1] DOCSIS® 3.1 Physical Layer Specification (September 2019, http://www.cablelabs.com/specs/) 
  • [CM-SP-MULPIv3.1] DOCSIS® 3.1 MAC and Upper Layer Protocols Interface Specification (September 2019, http://www.cablelabs.com/specs/) 
  • [ITU-T Rec J.83] ITU-T J.83: Digital multi-programme systems for television, sound and data services for cable distribution  (December 2007, Telecommunication Standardization Sector of ITU)

Known limitations

Firmware

  • OFDM

    • Possible temporary data loss during dynamic NCP updates
    • Zero-bit-loading of NCP subcarriers not supported
    • No data MER statistics

  • OFDMA

    • Unsupported pilot patterns: 5-7, 12-14
    • No probing sequences
    • No data MER statistics

  • A-TDMA

    • UCD type 2 (DOCSIS 1.x PHY channel and mixed DOCSIS 1.x/2.0 TDMA PHY channel) channels not supported
    • Differential encoding not supported
    • Zero preamble length not supported
    • IUC 2 (Request_2) not supported

Environment and system tools

  • xra31-admin: It is not possible to follow the system/service logs

Analysis

  • Captured packets are not ordered by timestamp

Known Issues

Firmware

  • General

    • [Fixed in version 5.0.4] After a system (re)boot, e.g. as part of a system update, it's possible that the inter-FPGA serial links are stuck in a non-operational state. This is signaled in the GUI by error messages on connector US-1. We have taken several measures to improve resilience against this behavior, but are still working on a more pertinent solution. In the meantime, please reset the system via the GUI system page until the serial links are fully operational.

  • OFDM

    • The first channel locking step after a system reset or a CMTS change can take considerably longer than subsequent locking steps. This is because internal frequency offset has to be reliably estimated (after which it is cached).

System and services

  • The reported upstream channel MER is the average over all fine ranging requests (for OFDMA) or all data bursts excluding initial ranging requests and bandwidth requests (for A-TDMA) over an elapsed interval of at most 30s. As such, it is possible that N/A (not available) is shown on low-load channels with T4 timeout multiplier higher than 1.
  • Captured Wireshark traces might contain invalid (malformed) packets corresponding to collisions (or possible RF interference) on A-TDMA IUC 1 (bandwidth request) grants. In a future release we plan to filter out these spurious bursts.
  • Inverse upstream Concatenation and Fragmentation (ICCF) of "segment header on" service flows is now performed for each channel independently. Hence, for CMs in MTCM (multi transmit channel mode), MAC frames that are fragmented over multiple upstream channels are not detected and consequently absent in the Wireshark trace. A future release will support ICCF over multiple channels.
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