Cable Network Impact

Existing Network Description

Looking at the downstream only, the cable plant divides the RF passband into legacy slices of 6MHz-wide channels. North America uses 6MHz, Europe uses up to 8MHz. The description here will be based on 6MHz channel sizes.

For each digitally modulated 6MHz channel, there is a series of pieces of rack-mount equipment or functions, the last two of which are a QAM modulator and an upconverter. The QAM modulator contains a function that takes MPEG2 Transport Stream packets as input and produces MPEG2-TS packets over the cable industry standard Intermediate Frequency (IF). The upconverter takes the IF as input and produces tunable RF to place the channel in its assigned place in the downstream passband.

The backend network of the headend can connect to a Metropolitan Area Network (MAN) capable of switching multi-gigabits per second of information. Those speeds must be signficantly dropped down via an Add/Drop Multiplexer (ADM). The slower rates are fed to a MPEG switch, which assigns MPEG program streams to their assigned downstream digital channels.

On the home side, there is a function within the set top box or cable modem which takes the RF from a single channel and converts it to an MPEG2-TS packet stream. Set top boxes enjoy downstream peak raw speeds of 30Mbps (64QAM) or 42Mbps (256QAM). Cable modems are typically configured for 30Mbps speeds.

Cable modems typically have an upstream peak rate maximum of 3-4Mbps.

The subscriber side digital processing capability of the modulator and demodulator is 30 + 3 = 33+Mbps.

Broadband Physics Enabled Headend and Subsriber

Broadband Physics enabled headend products are similar in function in that digital MPEG-TS packets are taken as input and modulated IF is produced as output. The key difference is that the data capcity of the SDM enabled downstream channel is 179.8Mbps withing an 18MHz channel.

 

 

These new function may be provided as a new box or as a blade upgrade to an existing box. In either case, the Broadband Physics enabled product provides 2x the digital capacity over 64QAM at the price of once box versus three boxes.

Broadband Physics plans to produce in the future a ~719Mbps in 72MHz downstream channel product, which will be composed of four 179.8Mbps channels. This configuration provides 2x data capacity over 12 64QAM channels.

Over time, the continued application of SDM channels will allow for the replacement or retirement of groups of 3x to 12x QAM channels.

The data capacity sizes of the SDM channels are designed to be large enought take the Synchronous Payload Envelope (SPE) payload from a SONET OC3 (155Mbps) port or SONET OC12 (620Mbps) port and directly move that packet data at fiber speed over the HFC plant. That is, if SONET is used. Otherwise, the backend transport is likely to be GiGE Ethernet, or IP over Resilient Packet Ring (RPR).

Fiber speed into the headend
Fiber speed over the HFC plant

This approach simplies the equipment in the headend and also directly supports the architectural move of program origination from the distribution headend to the regional hub or super hub.

The subscriber side of the SDM enabled plant enjoys a downstream peak raw speed of 179.8Mbps and an upstream peak rate of 150-170Mbps conditions permiting. The subscriber side digital processing capability is 170 + 150+ = 320+Mbps. This is 10x the existing performance and will be provided at comparable cost.

10x the subscriber side performance at comparable cost

The cable subscriber sees more digital choice and lower delay. The cable operator sees more digital capacity at the lowest cost of transport.; i.e. lowest $ per Mbps.

SDM enabled services will not interfere with existing services. By essentially changing the endpoints, the cable operator has access to additional free digital capacity in the plant.