Data Over Cable Service Interface Specification Research Articles

360 8K Viewport-Independent VR

Over the past few years 360 virtual reality (VR) has been deployed using different techniques. Viewport-independent technology has been used on 4K content for delivery to 4K-capable head-mounted displays (HMDs) and smartphone devices, resulting in a disappointing experience. The alternative is using viewport-dependent technology with 8K content on 4K-capable HMDs and smartphones devices, which enables a good experience, but with complexities and limitations in terms of the integration into existing over-the-top (OTT) workflows. The 8K viewport-independent technology presented uses off-the-shelf encoding techniques to compress 8K 360 VR content as a single file and to distribute it in a common media application framework (CMAF) low-latency Dynamic Adaptive Streaming over HTTP (DASH) mode to 8K-capable devices such as the Oculus Quest 2 or Galaxy S20. This article presents an end-to-end 8K VR workflow, which is entirely cloud-based and capable of delivering high-quality 8K VR digital rights management (DRM)-protected content compared with 4K content on different devices. We present the initial results of the trial performed by the VR Study Group of the Streaming Video Alliance (SVA) in collaboration with the VR Industry Forum (VRIF), where 8K VR content was encoded and streamed on different very-high-speed (fiber and data over cable service interface specification (DOCSIS)) networks.

Novel PAPR Reduction Algorithms for OFDM Signals

This paper proposes two efficient peak-to-average power ratio (PAPR) reduction algorithms for OFDM signals based on the principle of tone reservation. The first algorithm is performed in the time domain, whereas the second algorithm is a new clipping-and-filtering method. Both algorithms consist of two stages. The first stage, which is done off-line, precomputes a set of canceling signals based on the settings of the OFDM system. In particular, these signals are constructed to cancel signals at different levels of maximum instantaneous power that are above a predefined threshold. The second stage, which is online and iterative, reduces the signal peaks using modified versions of the canceling signals constructed in the first stage. When the reserved tones are distributed among the data tones, analysis and simulation results obtained with Data Over Cable Service Interface Specifications (DOCSIS) parameters show that the proposed algorithms achieve slightly better PAPR reduction performance and with significantly lower complexity when compared to the conventional algorithms.

Self-Interference Cancellation in Time-Domain for DOCSIS 3.1 Uplink System With Full Duplex

This paper introduces a self-interference cancellation (SIC) technique for data over cable service interface specification (DOCSIS) 3.1 uplink system with full duplex. At DOCSIS 3.1 uplink environment with full duplex, cable modems (CMs) transmit their request information (upstream) to CM termination system (CMTS), and CMTS transmits its broadcasting data (downstream) through the same frequency band at the same time. Therefore, the upstream becomes a signal of interest (SoI), and consequently the high-power feedback downstream causes self-interference (SI) signal against SoI. However, under the practical DOCSIS 3.1 uplink environment, achieving time and frequency synchronization between upstream and downstream is a challenging problem and additional signal processing technique should be applied. Therefore, in order to improve the processing efficiency and to reflect practical communication environment, the time-domain SIC technique, which does not require any synchronization between upstream and downstream is proposed. Furthermore, since the proposed scheme can consider various practical signal processing aspects, such as multi-path fading channel estimation and nonlinear element estimation of SI signal, it can be efficiently applied for the practical DOCSIS 3.1 uplink system. Test results indicate that the uplink system with 1024QAM (mandatory maximum constellation) can be operated in the case that there is SI estimation interval with two OFDM symbols.

Zero-CP OFDM for DOCSIS-Based CATV Networks

The current version of the data over cable service interface specification (DOCSIS), which is DOCSIS 3.1, is markedly different from previous versions in that orthogonal frequency-division multiplexing (OFDM) is used together with high-density QAM constellations (up to 4096-QAM) in both the downstream and upstream directions to facilitate high data rates. This is in a sharp contrast with the single-carrier modulation techniques used in prior versions of DOCSIS. Despite many advantages, a drawback of OFDM is the insertion of a cyclic prefix (CP) at the beginning of each transmitted OFDM symbol to mitigate inter-symbol interference (ISI). The CP, which is configurable, but can be as large as 25% of the symbol time for DOCSIS 3.1 downstream transmission, does not carry useful data and therefore reduces the overall transmission throughput. In general, not only the channel but also the transceivers’ digital filters determine the ISI and therefore the length of the CP. In this paper, the aspects that determine the CP length are thoroughly addressed. A novel technique to eliminate the CP is introduced and analyzed. It is demonstrated that the CP can be completely removed with a negligible effect on the transmission performance using this technique. Moreover, the proposed technique requires only a modest amount of hardware, making it a promising candidate to be included in the a future version of DOCSIS.

A Novel Approach for Profile Optimization in DOCSIS 3.1 Networks Exploiting Traffic Information

The latest release of the data over cable service interface specification (DOCSIS), namely DOCSIS 3.1, has introduced the use of adaptive bit loading profiles. The design of these profiles is critical for the overall performance of a hybrid fiber coaxial (HFC) cable system. Previous works on profile optimization for DOCSIS networks have mainly focused on grouping cable modems (CMs) based on their signal-to-noise ratio (SNR) similarity to maximize the system’s capacity. However, this approach can be inefficient due to effect of data demand and traffic variations that can highly affect the overall system performance. In this paper, we introduce a profile design approach to maximize the average throughput of an HFC system while considering the effect of both CMs’ traffic and channels SNRs on the system’s performance. Moreover, the profile optimization should not require knowledge of future instantaneous data arrival rates, which is not possible to obtain in practice. Thus, our proposed approach uses only average information which can be easily predicted using learning techniques. We show that the proposed approach yields significantly high performance, particularly for scenarios with high degree of heterogeneity in the CMs’ traffic.

Principal Component-Based Approach for Profile Optimization Algorithms in DOCSIS 3.1

Data over cable service interface specification (DOCSIS) introduced the possibility of a variable bit-loading over the subcarriers within a channel in its release DOCSIS 3.1. This variable bit-loading will improve the data rates. However, to limit the encoding processing overhead, the concept of profiles was introduced. Each profile defines the modulation per subcarrier for a given channel while the number of allowed profiles is limited. Thus, an efficient profile assignment scheme, which determines the best set of profiles based on the users’ channel conditions, is needed. Although various profile assignment algorithms have been proposed in the literature, realistic evaluation of these schemes has been difficult, as channel quality measurements of real DOCSIS 3.1 systems has not previously been available. In this paper, we exploit DOCSIS 3.1 measurement data to evaluate performance of the proposed algorithms. We propose to employ principal component analysis to derive low-dimensional clustering variables in order to ensure efficient profile optimization. We show how this technique can be employed with different clustering algorithms to improve the spectrum efficiency of the profiles by extracting the most important information of the channels in low-dimensional vectors. This not only reduces the complexity of the clustering, but also ensures better throughput. Moreover, we adapt the clustering algorithms to tailor them to the profile optimization problem. Finally, we present an exhaustive simulation-based performance analysis to compare the different algorithms for various scenarios using extrapolation of the measurements data.

Performance Comparison of R-PHY and R-MACPHY Modular Cable Access Network Architectures

Emerging modular cable network architectures distribute some cable headend functions to remote nodes that are located close to the broadcast cable links reaching the cable modems (CMs) in the subscriber homes and businesses. In the remote-PHY (R-PHY) architecture, an R-PHY device conducts the physical layer processing for the analog cable transmissions, while the headend runs the data over cable service interface specification (DOCSIS) medium access control (MAC) for the upstream transmissions of the distributed CMs over the shared cable link. In contrast, in the remote MACPHY (R-MACPHY) architecture, an R-MACPHY device (RMD) conducts both the physical and MAC layer processing. In this paper, we conduct a comprehensive performance comparison of the R-PHY and R-MACPHY architectures. We first develop analytical delay models for the polling-based MAC with gated bandwidth allocation of Poisson traffic in the R-PHY and R-MACPHY architectures. We then conduct extensive simulations to assess the accuracy of the analytical model and to evaluate the delay-throughput performance of the R-PHY and R-MACPHY architectures for a wide range of deployment and operating scenarios. Our evaluations include long converged interconnect network (CIN) distances between remote nodes and headend, bursty self-similar traffic, and double-phase polling to mask long CIN propagation distances. We find that for long CIN distances above 100 miles, the R-MACPHY architecture achieves significantly shorter mean upstream packet delays than the R-PHY architecture, especially for bursty traffic. Our extensive comparative R-PHY and R-MACPHY evaluation can serve as a basis for the planning of modular broadcast cable based access networks.

R-FFT: Function Split at IFFT/FFT in Unified LTE CRAN and Cable Access Network

The Remote-PHY (R-PHY) modular cable network for Data over Cable Service Interface Specification (DOCSIS) service conducts the physical layer processing for the transmissions over the broadcast cable in a remote node. In contrast, the cloud radio access network (CRAN) for Long-Term Evolution (LTE) cellular wireless services conducts all baseband physical layer processing in a central baseband unit and the remaining physical layer processing steps towards radio frequency (RF) transmission in remote nodes. Both DOCSIS and LTE are based on Orthogonal Frequency Division Multiplexing (OFDM) physical layer processing. We propose to unify cable and wireless cellular access networks by utilizing the hybrid fiber-coax (HFC) cable network infrastructure as fiber fronthaul network for cellular wireless services. For efficient operation of such a unified access network, we propose a novel Remote-FFT (R-FFT) node that conducts the physical layer processing from the Fast-Fourier Transform (FFT) module towards the RF transmission, whereby DOCSIS and LTE share a common FFT module. The frequency domain in-phase and quadrature (I/Q) symbols for both DOCSIS and LTE are transmitted over the fiber between remote node and cable headend, where the remaining physical layer processing is conducted. We further propose to cache repetitive quadrature amplitude modulation (QAM) symbols in the R-FFT node to reduce the fronthaul bitrate requirements and enable statistical multiplexing. We evaluate the fronthaul bitrate reductions achieved by R-FFT node caching, the fronthaul transmission bitrates arising from the unified DOCSIS and LTE service, and illustrate the delay implications of moving part of the cable R-PHY remote node physical layer processing to the headend.

Future Broadband Access Networks [Point of View

Since the development of practical optical fiber, people have been predicting the widespread introduction of broadband access. The original vision was to replace the copper telephone lines with fiber, but that has not happened. Instead, we see a wide variety of fiberdeeper architectures (where the fiber network is taken closer to the end customer), including very high speed digital subscriber line (VDSL)-based fiber to the node, data over cable service interface specification (DOCSIS)-based hybrid fiber coax (HFC), and passive optical network (PON)-based fiber to the premise. Why such a diversity? And why hasn't the best technology won? The answers to these questions may help us to understand why we have gotten to the present situation, and give us clues to what may come next.

A 2.7 mW/Channel 48–1000 MHz Direct Sampling Full-Band Cable Receiver

A direct sampling full-band capture (FBC) receiver for cable and digital TV applications is presented. It consists of a 0.18 μm BiCMOS low-noise amplifier (LNA) and a 28 nm CMOS direct RF sampling receiver based on a 2.7 GS/s analog-to-digital converter (ADC) embedded in a system-on-chip (SoC). Digital signal processing (DSP) plays critical roles to assist analog circuits in providing functionalities and enhancing performances, including digital automatic gain control (AGC), digital phase-locked loop (PLL), and digital ADC compensation. The receiver is capable of receiving 158 256 QAM channels from 48 to 1000 MHz simultaneously, achieving up to 10 Gb/s data throughput for data and video while exceeding Data over cable service interface specification (DOCSIS) and Society of Cable Telecommunications Engineers (SCTE) requirements. The CMOS receiver occupies $1 \text{ mm}^{2}$ area while consuming 300 mW. The LNA consumes 130 mW and occupies $3 \text{ mm}^{2}$ area. The total power dissipation from the receiver is 2.7 mW per 6 MHz channel when capturing the entire cable spectrum.

DOCSIS provisioning of ethernet PON (DPoE)

The tremendous demand on carriers for bandwidth in the access network, as well as demands on carriers to manage that bandwidth, continues to drive the technical evolution of access networks. As one approach to satisfy these demands, DOCSIS® Provisioning of EPON (DPoE), combines two access technologies: Ethernet passive optical network (EPON) and Data Over Cable Service Interface Specification ( DOCSIS). DOCSIS makes possible mature service provisioning mechanisms based on centralized back-office automation. EPON provides a transport layer between the DPoE System and a number of connected DPoE optical network units (D-ONUs) for distances of 20 km and more. The completely passive interconnection structure of EPON also reduces capital expenditures (CAPEX) and operational expenditures (OPEX) by requiring no electrical power outside of the hub.

Design of Energy-Saving Algorithms for Hybrid Fiber Coaxial Networks Based on the DOCSIS 30 Standard

We propose energy-saving algorithms to improve the energy efficiency of hybrid fiber coaxial (HFC) networks that support DOCSIS (Data Over Cable Service Interface Specification) 3.0 standard. The algorithms incorporate a traffic-aware approach and modify the operation statuses of the two primary network elements, the cable modem (CM) and the cable modem termination system (CMTS), dynamically. For the CM-side operation, we first propose a basic algorithm that can optimize the CMs’ energy efficiency, regardless of significant increase of the packet delay and the number of operation changes (NoOC). We then propose two modified approaches to reduce the packet delay and NoOC while saving energy. Simulations with these algorithms show 37.5%–42.2% energy saving on the CM side, compared to the traditional case where the CMs’ operation statuses are static. Next, we propose a CMTS-side energy-saving algorithm to find the actual connection mapping between the CM channels and CMTS ports. The proposed algorithm tries to support CM connections with minimal numbers of CMTS ports. To further improve the energy efficiency of the CMTS, we design a readjustment approach that can reorganize CM connections on CMTS ports based on their loads. Simulation results show that 31.08%–32.61% energy saving can be achieved on the CMTS in total. Hence, the proposed algorithms achieve effective energy saving on both the CM and CMTS sides.

A cable modem receiver supporting four upstream channels

A receiver of upstream cable modem (CM) for data over cable service interface specifications (DOCSIS) 3.0 is proposed and implemented in field programmable gate arrays (FPGAs). The receiver, which can demodulate four upstream channels simultaneously, consists of a digital down converter (DDC), a pre-forward error correction (FEC) and a FEC decoder. In DDC, fixed decimation and variable decimation with respect to symbol rate are used to remove adjacent channel images. An automatic gain control (AGC) uses a power calculation in a packet detection (PD) to reduce hardware complexity. Coefficients of symbol timing estimation (STE) use the sign of preamble symbols for eliminating multipliers. In addition, STE operates only for some parts of preamble to save power consumption. We simulate estimated AGC values, success probability of STE, estimated frequency offsets. In addition, it is found that when the bit error rate (BER) of the pre-FEC of 64QAM is 10-5, the required Eb/N0 is 19.5 dB under the conditions of additive white Gaussian noise (AWGN), a frequency offset, and echo channel. We measure the spectrum of DDC output, an estimated AGC value, and an estimated frequency offset, and experiment on FEC decoder. Measured results show the maximum transmitted error vector magnitude (EVM) of 1.54 % and the maximum received EVM of 2.67%.

Statistical Multiplexing of Upstream Transmissions in DOCSIS Cable Networks

The appearance of increased-bandwidth applications with quality-of-service (QoS) requirements has brought about the emergence of multi-service access networks. Data Over Cable Service Interface Specification (DOCSIS) networks are intended to support high quality audio, video, and interactive services over Internet protocol (IP) flows within a Hybrid Fiber/Coax (HFC) network context. In order to support large amount of users and demanded QoS for such applications, a careful management of resources is needed. In this paper we propose a centralized bandwidth allocation scheme for the return path of DOCSIS networks. The proposed scheme takes advantage of the application's traffic characteristics to minimize the bandwidth dedicated to control signals and achieve high bandwidth utilization. At the same time, the proposed approach complies with the QoS requirements of the serviced applications. The performance of our bandwidth allocation approach was evaluated using computer simulation. The performance metrics used are the average packet delay, data throughput, and number of users supported. Results are obtained for networks with a single service as well as for a mixed service scenario. As shown by the results, our approach achieves high bandwidth utilization, and still complies with the delay constraints imposed by the user applications. It increases the system capacity as compared to reference approaches.

Guest editorial

Emerging technologies bring very high-speed connectivity for residential users through both fixed and mobile access: fiber to the home/curb/... (FTTx), Data Over Cable Service Interface Specification (DOCSIS) 3.0, WiMAX, Long Term Evolution (LTE), satellite. Typical speeds are reaching 100 Mb/s, even 1 Gb/s. Furthermore, symmetrical channels are offered (as opposed to asymmetrical digital subscriber line [ADSL]). Already in 2008 (source: FTTH Council) almost 3 million consumers used direct fiber optic connections in the United States, more than 10 million in Japan, and about 15 million worldwide. This enhanced capacity certainly removes the barriers and constraints of limited broadband offers, paving the way to future digital services for the home.

Efficient Traffic Scheduling for Real Time VBR MPEG Video Transmission Over DOCSIS-Based HFC Networks

Data-over-cable service interface specifications (DOCSIS), the de facto standard in the cable industry, defines a scheduling service called real-time polling service (rtPS) to provision quality of service (QoS) transmission of real-time variable bit rate (VBR) videos. However, the rtPS service intrinsically has high latency, which makes it not applicable to real-time traffic transport. In this paper, we present a novel traffic scheduling algorithm for hybrid fiber coax (HFC) networks based on DOCSIS that aims to provide QoS for real-time VBR video transmissions. The novel characteristics of this algorithm, as compared to those described in published literatures, include 1) it predicts the bandwidth requirements for future traffic using a novel traffic predictor designed to provide simple yet accurate online prediction; and 2) it takes the attributes of physical (PHY) layer, media access control (MAC) layer and application layer into consideration. In addition, the proposed traffic scheduling algorithm is completely compatible with the DOCSIS specification and does not require any protocol changes. We analyze the performance of the proposed traffic predictor and traffic scheduling algorithm using real-life MPEG video traces. Simulation results indicate that 1) the proposed traffic predictor significantly outperforms previously published techniques with respect to the prediction error and 2) compared with several existing scheduling algorithms, the proposed traffic scheduling algorithm surpasses other mechanisms in terms of channel utilization, buffer usage, packet delay, and packet loss rate.

Faster than Smoke? More Blinding than Mirrors?

Version 3.0 of the cable television industry's data transport standard, Data over Cable Service Interface Specifications (DOCSIS), might speed the time to download anything from a text file to a movie to 160 megabits per second. Even if the technology's theoretical maximum speed isn't commercially realistic, its demonstration at the May 2007 annual Cable Show in Las Vegas has network strategists and analysts wondering how users and competitors will react.

Full-Duplex DOCSIS/WirelessDOCSIS Fiber–Radio Network Employing Packaged AFPMs as Optical/Electrical Transducers

A hybrid fiber-radio access network architecture for simultaneous wireline and wireless transmissions of data-over-cable service interface specification (DOCSIS) signals is presented. An all-optical harmonic up-conversion technique using a dual-drive Mach-Zehnder modulator provides the downstream optical signal modulated not only at the intermediate frequency in the 600- to 900-MHz band for wireline transmission but also at the up-converted frequency in the 5.45- to 5.75-GHz band for wireless transmission. An InGaAsP/InGaAsP multiple-quantum-well asymmetric Fabry-Perot modulator/detector has been designed, fabricated, and packaged and has been employed in the base station (BS) as an optical/electrical transducer, simultaneously providing the functions of optical intensity modulation and photodetection. At the BS, the DOCSIS signals are recovered at the wireline and wireless frequencies for the respective feeding of a cable access network or a fixed wireless access network in a highly flexible approach. Full-duplex operation has been demonstrated for both access types in an indoor laboratory environment. In a subsequent small-scale field trial, real-life Internet traffic provided by a local community antenna television system operator has been transported over the present hybrid fiber-radio access network architecture, and simultaneous transmission of both DOCSIS and digital television signals has also been performed.

A Simulation Model of the DOCSIS Protocol

The number of households and businesses using hybrid fiber coaxial cable networks for Internet access is rapidly approaching 40 million in the United States. The cable industry has standardized on a single medium access control (MAC) and physical layer standard, the Data Over Cable Service Interface Specification (DOCSIS). The MAC layer of the emerging IEEE 802.16 broadband wireless access standard is also based upon DOCSIS. Thus, the performance of DOCSIS is now and will remain a critical element in the overall performance of shared medium broadband access networks. Despite this fact, public domain tools that may be used to assess and improve the performance of DOCSIS have been slow to emerge. To address this problem, we have implemented a simulation model of the DOCSIS MAC layer for the ` ns' network simulation tool. Due to the complexity of DOCSIS and because the specifications are purposely incomplete, developing an accurate simulation is quite challenging. In this paper we present analytic and live network evidence that the simulation accurately reflects the behavior of a DOCSIS network under a limited set of workloads.

An adaptive fast expansion, loading statistics with dynamic swapping algorithm to support real time services over CATV networks

As the community antenna television (CATV) networks becomes ubiquitous, instead of constructing an entirely new broadband network infrastructure, it has emerged as one of the rapid and economic technologies to interconnecting heterogeneous network to provide broadband access to subscribers. How to support ubiquitous real-time multimedia applications, especially in a heavy traffic environment, becomes a critical issue in modern CATV networks. In this paper, we propose a time guaranteed and efficient upstream minislots allocation algorithm for supporting quality-of-service (QoS) traffic over data over cable service interface specification (DOCSIS) CATV networks to fulfill the needs of realtime interactive services, such as video telephony, video on demand (VOD), distance learning, and so on. The proposed adaptive fast expansion algorithm and the loading statistics with dynamic swapping algorithm have been shown to perform better than that of the multimedia cable network system (MCNS) DOCSIS.