ANSI SCTE 55-1-2019 pdf free download – Digital Broadband Delivery System: Out of Band Transport Part 1: Mode A.
6.2.6. RF RETURN-PATH DEMODULATOR SPECIFICATION
The return-path differentially-encoded QPSK demodulator uses the same FEC code as the modulator. The required C/(N+I) of the input signal, which includes interference effect (I) due to ingress and impulse noise in the return-path channels, is equal or greater than 20 dB at packet error rate (PER) less than 1⋅10 -7 (corresponds to one packet loss every 5 hours). The required C/(N+I) assumes the simultaneous presence of multiple impairments in the upstream channel. PER is the ratio of the number of error packets to the total number of transmitted packets. The return-path demodulator specifications are summarized in Table 8.
6.3.EXTENDED PRACTICE FOR RETURN-PATH TRANSMISSION This section provides the specifications of the extended practice for return-path transmission systems. The higher upstream transmission rates are optional for new decoder boxes and cable modems applications. The return-path modulator output specifications are summarized in Table 9. It references to DOCSIS RFI specifications: Radio Frequency Interface Specification SP-RFIv1.1-I01-990311 [3]. As DOCSIS is still evolving with extended practices for more enhanced data features, the current implementation may be upgraded as future needs arise. The maximum channel bandwidth (measured at -30 dB) is 25% larger than the symbol rate (in kHz), except for the lowest symbol rate case, which has a bandwidth of 192 kHz.
7.DATA LINK LAYER
This section describes the Data Link Layer of the Out-Of-Band downstream and upstream channels. Itspecifies the communication between Network Related Control (NRC), for example the Network Controllerat the headend, and the Digital ‘Terminal. It is largely based on General Instrument’s past contributions toDAVIC and MCNS. The Medium Access Control sublayer is comprised of control messages, describedwithin this section, and is independent of the physical layer; hence it may reside above any different rate ofthe physical layer , as well as In-Band or Out-OF-Band, without any loss of functionality. Another MACcharacteristic is that it can be tailored to accommodate different traffic characteristics dynamically or perconfiguration.The need for this adaptability would largely depend on how interactive services will bereceived by consumers and at what growth-rate. At present, only contention-mode access(Aloha, non-TDMA) is considered as a requirement. Therefore, any TDMA related consideration is strickly optional.
The Data Link Layer, along with its MAC (Media Access Control) sublayer, are responsible for transportingNetwork Layer PDUs between the Digital Terminal and the headend. The layer also provides segmentingand re-assembly of higher layer PDUs, e.g.network layer, as well as routing to the corresponding protocolstack. Additional information about general DLL and MAC functionality may be found in IEEE Std 802-1990, Local and Metropolitan Area Networks: Overview and Architecture and ISO/IEC 10039:1991
Information Technology, Open Systems Interconnection, Local Area Networks,Medium Access Control(MAC) Service Definition [1].
To maximize the synergy on the In-Band and Out-Of-Band, the link layer syntax is MPEG-2 TS based.Thisis described further in the following sections. Additional detail may be found in ITU-T RecommendationH.222.0 |ISO/IEC 13818-1:2007, Information Technology — Generic Coding of Moving Pictures andAssociated Audio Information Systems [2].
7.1.APPLICATION PDU PROCESSING
Figures 6 and 7 show the packetization schemes for upstream and downstream, respectively.
For the upstream direction, the higher protocol layers hand off the SDU to the data link layer. The data linklayer adds the Upstream Link Layer Header and Upstream Link Layer Trailer.Padding may also be necessary so that the entire Data Link Layer PDU(i.e.Upstream Link Layer Header +Higher Layer PDU +Padding + Upstream Link Layer Trailer) is a multiple of 48 bytes. The pad character is Ox00. The CRC inthe Link Layer Trailer is computed over the entire Data Link PDU.
In the downstream direction,MPEG-2 transport packets are received and filtered based on PID values.Following this, Data Link Layer messages are re-assembled, address filtered, and CRC checked. From anMPEG-2 point of view, Data Link Layer messages form an MPEG-2 private stream. The re-assembly ofthose messages from the underlying MPEG-2 transport packets is as per the MPEG-2 specification, usingthe Payload Unit Start Indicator bit in the MPEG-2 transport packet header. Those messages addressed tothe Digital Terminal are processed by the Digital Terminal.For packets containing higher layer applicationPDUs, the PDU is extracted, reassembled and routed based on the Protocol lD field.ANSI SCTE 55-1 pdf download.