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<ul><li><p> 2016 Incognito Software Systems, Inc. All rights reserved. </p><p>Are You Ready for DOCSIS 3.1? The Future of Cable Technology and How to </p><p>Prepare Your Network </p><p> An Incognito White Paper </p></li><li><p> 2016 Incognito Software Systems, Inc. All rights reserved. Page 2 of 13 </p><p>Are You Ready for DOCSIS 3.1? ContentsIntroduction ........................................................................................................................ 3Bandwidth Capacity: The Driver for 3.1 ....................................................................................... 3</p><p>What Does this Mean for Service Providers? ............................................................................. 4DOCSIS 3.1 Technical Advantages ............................................................................................ 4</p><p>Error Correction ................................................................................................................ 4Modulation ...................................................................................................................... 5Variable Modulation Profiles ................................................................................................. 5Multicarrier Transmission ..................................................................................................... 6Increased Spectrum Utilization .............................................................................................. 7</p><p>The Future of DOCSIS ........................................................................................................... 7Immediate Challenges ........................................................................................................ 7Improving the Standard ...................................................................................................... 8</p><p>DOCSIS 3.1 and the Race to Fiber ............................................................................................ 9Greenfield Deployments ...................................................................................................... 9Brownfield Deployments ................................................................................................... 10</p><p>Conclusion ....................................................................................................................... 10Glossary of Terms .............................................................................................................. 11 </p></li><li><p>Are You Ready for DOCSIS 3.1? </p><p> 2016 Incognito. All rights reserved. Page 3 of 13 </p><p>Introduction A decade after DOCSIS 3.0 launched, CableLabs has extended the specification with a massive capacity boost to support next-generation applications and usage needs. The Data Over Cable Service Interface Specification (DOCSIS) version 3.1 will provide more bandwidth capacity and clear technical advantages to network operators and broadband users alike; however, there will also be challenges. Making DOCSIS 3.1 part of the procurement process is essential for cable MSOs to stay ahead of the curve and remain competitive. This will become even more essential as operators shift to access technologies that provide Gbps service for their customers as the capacity demand continues to grow with the adoption of OTT services and IoT deployments within the customer's home or office. </p><p>Bandwidth Capacity: The Driver for 3.1 In the decade since the CableLabs DOCSIS 3.0 specification was released, bandwidth demand has continued to grow unabated. The rise of over-the-top (OTT) content, along with an explosion of WiFi services, cloud applications, and the burgeoning Internet of Things (IoT) has meant an even greater reliance on Internet networks than ever before. Butters Law states that optical transmission speeds are doubling every nine months. But how does that compare to the latest specification of DOCSIS? Is it keeping up? From 1997 to 2006, downstream capacity grew from 38Mbps of DOCSIS 1.x to up to 1Gbps of DOCSIS 3.0 with 32 bonded downstreams. With the latest DOCSIS 3.1 specification, this capacity has reached 10Gbps. </p><p> What has CableLabs provided in the latest revision of the DOCSIS specification, and are these capabilities sufficient motivators for operators to upgrade today? At the most basic level, DOCSIS 3.1 has boosted bandwidth capacities from 1Gbps downstream to 10Gbps and allows 100Mbps upstream to 1Gbps. The standard is backwards-compatible with the previous generation and even coexists with networks running DOCSIS 3.0. </p></li><li><p>Are You Ready for DOCSIS 3.1? </p><p> 2016 Incognito. All rights reserved. Page 4 of 13 </p><p> Although this is a significant improvement over the previous iteration, the bandwidth growth rate is roughly half of the prediction from the aforementioned Butters Law. However, using a DOCSIS 3.1 modulation of 4096-QAM allows for just north of 64.32Mbps while the previous capped modulation of 256-QAM is only able to achieve a theoretical rate of 42.88Mbps. This has a theoretical advantage of 50% increase of data capacity using the same 6Mhz channel. In reality, the two numbers end up being 54Mbps and 38.81Mbps respectively due to DOCSIS overhead and spectral efficiencies (the information rate that can be transmitted over a given bandwidth). How is this all achieved? Spectral efficiencies of higher order modulations. Using 256-QAM as a benchmark the highest modulation available in DOCSIS 3.0 the spectral efficiencies can be compared using this formula: </p><p>bandwidth = rate* x log2(modulation) (*where 256-QAM rate as defined by the ITU-T standard J.83 (12/07) at 5.361 Msym/s.) </p><p>What Does this Mean for Service Providers? DOCSIS 3.1 has the potential to enable a 10x bandwidth capacity increase over DOCSIS 3.0. Given the insatiable appetite that subscribers are showing for bandwidth consumption, this increased capacity is essential for cable operators to continue to provide a high quality of service in the future. Clearly, enabling a 50% increase of data capacity is no minor feat for a service provider. The advantages include faster, more reliable service speed and an increased capacity to add additional users to networks. While many operators still use DOCSIS 2.0 equipment, an upgrade to DOCSIS 3.1 will extend the life of the outside plant and deliver a better quality of experience (QoE) for customers. Essentially, although there are other technical advantages to DOCSIS 3.1 (which will be explored later in this white paper), it is the increased throughput that should spur network operators into action and is the reason why DOCSIS 3.1 spectrum planning and plant upgrades should be part of the MSO roadmap. </p><p>DOCSIS 3.1 Technical Advantages DOCSIS 3.1 has the potential to enable technological advantages, such as a 10x capacity increase over DOCSIS 3.0; however, upgrading does present some challenges. It is therefore necessary to consider potential impacts while examining the technical aspects and benefits of DOCSIS 3.1. </p><p>Error Correction All previous versions of DOCSIS used forward error correction (FEC) to deal with the bit error rate (BER), the rate at which errors occur in the signal due to degradation. However, DOCSIS 3.1 increases efficiency with additional error correction methods. In DOCSIS 3.0, the FEC algorithm used was Reed Solomon (RS). This provided a decent coding gain of approximately 6dB compared to the un-encoded stream and in North America, this was coupled with Trellis Coded Modulation (TCM), for an extra 2dB gain. </p></li><li><p>Are You Ready for DOCSIS 3.1? </p><p> 2016 Incognito. All rights reserved. Page 5 of 13 </p><p>During the development of the DOCSIS 3.1 standard, the CableLabs committee evaluated additional error correction methods as a means to improve the overall efficiencies. One of the additional FEC technologies explored currently used in WiMax, WiFi (802.11n), and Digital Video Broadcasting was Low Density Parity Check (LDPC). Although LDPC is more computationally expensive (though less intensive as Turbo Codes), modern application-specific integrated circuit and DSP/SoC are sufficiently powerful to easily add this as the FEC mechanism, providing options at both the headend and CPE. If the DSP or FPGA is sufficiently powerful, this LDPC could be enabled via a software upgrade and several CCAP vendors have already taken advantage of this. CableLabs choice of LDPC has yielded approximately a 6dB gain over DOCSIS 3.0 Reed Solomon (RS) method, shrinking the gap to the theoretical Shannon Limit at only 1dB for the spectral efficiency vs. signal-to-noise ratio. As a result, LDPC provides near optimal FEC method with marginal increase in complexity and the efficiencies provided by LDPC saves about 2bps/Hz. Essentially, this means that a 6MHz downstream channel can effectively transmit an additional 12Mbps. </p><p>Modulation Before DOCSIS 3.1, the maximum modulation available was 64-QAM and 256-QAM for upstream and downstream respectively. With the introduction of LDPC FEC (see the above section), what used to require a 27dB signal-to-noise ratio now only requires a 22.5dB signal-to-noise ratio. With these increased efficiencies comes the availability to add some higher order modulation. An alternative way to look at the impact of the FEC is using the following example: the required signal-to-noise ratio (SNR) for 1024-QAM using LDPC is the same as 256-QAM using RS when combined with TCM. This has enabled the existing plant to support higher order modules. As such, DOCSIS 3.1 has added support for up to 4096-QAM with future optional 8192-QAM and 16384-QAM in the downstream while the standard now supports 1024-QAM and future optional 2048-QAM and 4096-QAM in the upstream. As discussed earlier in this paper when investigating spectral efficiencies, the overall bandwidth is tied to the modulation. The important factor is that with LDPC and OFDM (Orthogonal Frequency Division Multiplexing; which will be discussed in detail in the Multicarrier Transmission section of this document) combined, the required signal budget can be lowered at higher order modulations to fit within where the cable plant commonly reaches most modems. Essentially, this makes 4096-QAM quite attainable as the SNR threshold is only 36dB, capturing the majority of devices in todays plant. </p><p>Variable Modulation Profiles In addition to supporting higher order modulations in DOCSIS 3.1, the standard now allows for an outside plant operating with multiple modulation profiles. Previously, operators were required to choose a modulation profile that would provide service to all the cable modems in the plant, which usually meant choosing a modulation based on the cable modems who had the lowest SNR. Even if the outside plant could support a higher modulation, operators would still have been limited to 256-QAM as defined by the standard. With DOCSIS 3.1, it is possible to use multiple modulation profiles, providing lower QAM modulation for those with modems with a lower SNR and higher order modulations for modems with a higher SNR. Assuming a typical gaussian or uniform distribution with a mean of 36dB </p></li><li><p>Are You Ready for DOCSIS 3.1? </p><p> 2016 Incognito. All rights reserved. Page 6 of 13 </p><p>and 2dB deviation, we would see an improvement of 35.8% network efficiency improvement when using multiple modulation profiles with DOCSIS 3.1. </p><p> Given a uniform distribution of devices in your network, the SNR through DOCSIS 3.1 is able to use higher order modulations for higher throughput. This model has been validated in a production environment with 20mm CMs, courtesy of Dave Urban of Comcast. </p><p>Multicarrier Transmission One of the most important contributions in DOCSIS 3.1 was the introduction of Orthogonal Frequency Division Multiplexing (OFDM). OFDM is based on the idea of frequency-division multiplexing, but the multiplexed streams are considered parts of a single stream. The bitstream is split into parallel data streams that are each transferred over its own sub-carrier; which are summed to form an OFDM signal. OFDM may be new to DOCSIS, however it has been used for many applications including PLC, WiFi, and cell networks. What this means for DOCSIS is that subcarrier spacing could potentially be 25kHz wide instead of 6MHz. This equates to a 960-QAM sub-carrier only requiring 24MHz of bandwidth. In DOCSIS, an adaptive equalizer with 24 taps covers 4.5 s per 6Mhz channel. OFDM is simpler: a single guard interval is added which is generally set as the longest expected echo. Assuming as high as 2% bandwidth per guard band pair, this change will save approximately 6% per 24Mhz of OFDM space. Additionally, the OFDM subcarriers can be bonded inside a block spectrum that could be as large as 192MHz, which theoretically supports 1.99Gbps. This has the added benefit of being able to leverage up to 10% efficiencies at the band edge on digital channel. By combining OFDM and multiple modulation profiles, the channel bandwidths can be assigned to match exact real-time subscriber demand and/or channel conditions. There is more to the new standard than just the spectral efficiencies of OFDM being combined with an </p></li><li><p>Are You Ready for DOCSIS 3.1? </p><p> 2016 Incognito. All rights reserved. Page 7 of 13 </p><p>LDPC FEC (also referred to as COFDM). Rather than mapping 6 or 8 bits to a symbol (as occurred with the earlier standard), DOCSIS 3.1 at 4096-QAM maps 12 bits to each data subcarrier in the OFDM symbol highlighting the increased capacity the standard affords. </p><p>Increased Spectrum Utilization In addition to higher order and variable modulation profiles, improvements in forward error correction, and spectrum efficiency, DOCSIS 3.1 also has increased the RF domain, resulting in additional capacity. The upstream frequency range is from 5MHz to 204MHz, increased from the prior limit of 42MHz. Likewise, the downstream has also increased, starting at 258MHz and spanning to 1218MHz, optionally growing to 1794MHz. This increased spectrum utilization does affect MoCA, which previously operated at frequencies higher than DOCSIS used. As a result, operators will need to ensure that filters in the range of 860MHz to 1.7GHz are properly in place at the customer premises, otherwise the MoCA signal will interfere with DOCSIS 3.1 service in the tap if the operator is using that frequency range. Some have even suggested that two F-connectors might be in the future for the gateway to enable full capacity for the respective frequency bands. One of the tenets of DOCSIS 3.1 is to provide a backwards-compatible framework. As a result, CableLabs has chosen to preserve downstream channels below 258MHz for legacy mode. This provides a mechanism for operators to deploy a hybrid SC-QAM and OFDM without having to service to an all OFDM deployment in one step. </p><p>The Future of DOCSIS What does the future hold for DOCSIS and what will the outside plant of tomorrow look like? There have been significant i...</p></li></ul>

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