Design Article
MoCA and DBS Channel Stacking Switch technology
Jon Iwanaga and Troy Brandon,
Entropic Communications
2/27/2009 2:30 PM EST
The Multimedia over Coax Alliance or MoCA and Channel Stacking Switch (CSS) solutions are key tools for DBS operators to generate new lines of revenue while providing significant infrastructure savings. These technologies, whether used in a combined or stand-alone fashion, improve the customer experience, reduce churn and offer a conduit to deliver new services to drive average revenue per user (ARPU) -- all of which can create a positive position in the highly competitive Pay-TV market.
According to Parks Associates in their recent report Home Networks for Consumer Electronics, home networking will reach 167 million households worldwide by the end of 2008 and is forecasted to reach 250 million households by year-end 2013. The home entertainment networking segment is expected to grow even faster. Parks Associates forecasts home entertainment networking penetration to grow from 6.4 million at year-end 2008 to 52 million by year-end 2013-- a compound annual growth rate of over 50%.
Traditionally, DBS set-top boxes (STB) function as independent receivers with no need for connectivity between STBs within the home. However, with the introduction of digital video recording (DVR) capability integrated into DBS set-top boxes (STB), streaming content recorded on one DVR STB to another STB in another room becomes an attractive feature that consumers will soon come to demand. With multi-room DVR capabilities, family members are no longer forced to watch their favorite programs on the same television to which the DVR STB is attached. MoCA can provide this capability today. In fact, a MoCA home network allows DBS operators to not only gain the ability to provide multi-room DVR, but also to converge their DVR STBs with the subscriber's broadband access networks for HD video-on-demand downloads, remote DVR programming and other interactive services.
If a DBS Operator combined a MoCA home networking solution with CSS technology, they would gain the opportunity to offer new services while reducing the capital costs associated with new subscriber installations and current customer upgrades. Further, CSS provides a flexible way to allocate spectrum on the subscriber's coax wiring so that it is future proof against any potential bandwidth expansion required for the home network.
Next: MoCA 101
MoCA 101
The Multimedia over Coax Alliance (MoCA) has defined a network MAC/PHY standard that can establish a full-mesh communications network using existing coax cables found in typical residential dwellings. From its very beginnings, the targeted application for a MoCA home network was to provide access to and liberate multimedia content from the confines of a single room or device, providing the ability to stream multiple high-definition video, audio and data traffic throughout the home to provide access to entertainment content in any room with a coax outlet.
Figure 1: Illustrative MoCA whole home entertainment network
Coax cabling provides an ideal physical medium for a high-speed network since it offers wide bandwidth, a shielded and relatively low noise environment and is typically conveniently co-located next to televisions. Unlike other network technologies that focused primarily on transferring non-time critical data, MoCA focused on achieving the key performance specifications critical to support streaming multiple streams of HD video around the home.
- High reliability to assure operators MoCA works at virtually any coax outlet in any subscriber's home -- without rewiring
- Throughput to support real-time streaming of multiple HD/SD video programs
- Low error rates and low latency to ensure a good subscriber viewing experience
- Frequency coexistence with established operator services to avoid contention
Low packet error rates (PER) and low latency are achieved through a fully-coordinated and collision-free MAC. When sending UDP video packets over a home network, the technology must provide low packet error rates at the PHY layer since retransmission of packets above the MAC layer is not supported. Since the MAC is fully coordinated with no retransmissions necessary to achieve low PER, latency remains low and is more deterministic than technologies that use multiple access protocols. These key attributes help ensure that video glitches due to dropped packets or starved data buffers are kept acceptably low to provide a high quality consumer experience.
The Channel Stacking Switch
Coax cabling within the home provides plenty of bandwidth, however for a home network technology to be accepted by operators, coexistence with existing coax services must be supported. MoCA already provides spectrum flexibility with channels available from 875 MHz to 1500 MHz. To provide even greater flexibility for DBS operators, Channel Stacking Switch technology can be used to re-allocate IF video to another portion of the coax cable to free-up channels for a MoCA home network. It is this frequency agility that allows the performance of a MoCA network to be combined with the cost and customer advantages provided by CSS technology to build competitive positions for DBS operators worldwide.
Next: Channel Stacking Switch 101
Channel Stacking Switch 101
Changes to the television viewing experience and the adoption of DVRs, sometimes multiple DVRs per household, have created an increasingly complex, difficult and expensive installation for DBS service providers. Traditional DBS installations consist of 1 or more dishes with an applicable low noise block (LNB) converter. The output(s) of the LNB is run directly to either each satellite set top box (STB) in the home or to a multi-switch with its outputs run to the STB. An individual cable run is required from either the LNB or multi-switch to each tuner in the STB. A typical DVR/PVR has at least two tuners to support watch and record functionality. For a traditional DBS installation, this DVR would require two unique cable runs to the STB. A home with 3 DVR STBs requires 6 cable runs. One can see how this complex cabling architecture would be a significant cost driver for the DBS Operator and an area of concern for homeowner.
Figure 2: CSS technology enables a single cable to drive multiple STBs and tuners.
These cost and complexity issues are addressed through the use of channel stacking systems. CSS solutions create a channel-stacking architecture where multiple channels can be transmitted on a single cable based on the demands from multiple STBs and tuners connected to that cable. A single cable drop from the outdoor unit (ODU) provides each STB tuner with dedicated channels, eliminating the need for multiple cables. (See Figure 2)
In-home receivers communicate with a CSS-enabled ODU to request specific channels. The CSS translates a particular satellite channel of interest and passes through a dedicated surface acoustic wave (SAW) filter. The desired channels are then combined, or in other words, 'stacked', onto the single cable. The ODU tells each receiver where a requested channel is located.
These DBS systems typically transport programming from the ODU to STB using a frequency range of 950 to 2150 MHz, which provides a useable bandwidth of 1.2 GHz. Individual transponders are typically only 20 to 36 MHz wide, depending on satellite transmission symbol rates. For example, a CSS system can convert and pass desired channels with a typical SAW bandpass filter to allow 12 individual channels to be stacked on a single cable. This translates into the ability to support 12 separate, active STBs or tuners on a single cable drop.
Next: MoCA and CSS combination single cable solution
MoCA and CSS combination single cable solution
In most US homes, there is a cabling network already in place. This usually consists of a single point of entry at the curb or garage with splitters used as required to support multi-room outlets. This preexisting network goes largely unused during a traditional DBS installation, resulting in a lost opportunity to leverage the existing cabling and extra labor and material costs to the Operator.
Figure 3: CSS--single cable solution
A single cable network allows video-on-demand (VOD) and pay-per view (PPV) support with only a central, conveniently located phone line or broadband connection versus a connection at each STB location. Additionally, with the CSS frequency agility, a DBS Operator is able to create large chunks of BW within the 950MHz -2150MHz band. This entire band is reserved for DBS service which provides the Operator means to incorporate a whole home entertainment network system like MoCA.
Figure 4: DBS channel stacking switch frequency plan ensures co-existence with other services on the same cable
MoCA & CSS Coexistence
For DBS operators, MoCA provides a network channel with a center frequency of 875 MHz that can coexist with the 950 MHz to 2150 MHz range of a typical DBS system. Currently, MoCA operates with channel bandwidth of 50 MHz. Operating a MoCA home network at 875 MHz provides 50 MHz of transition bandwidth between the home network and DBS video -- easily meeting the filter requirements.
Looking into the future, it is foreseeable that the bandwidth needs of the home network and DBS operator will continue to grow as more HD broadcast channels and HD VOD programming becomes available. To support this growth, the home network's bandwidth requirement is expected to double. Under this scenario, if an operator were using the existing DBS MoCA channel, there would not be any room available for a transition band. However, by using CSS technology to shift the operating range of the video, the cost impact of filtering between the future home network and DBS video delivery can be kept in check.
As detailed above, the vast majority of DBS operators utilize the 950MHz to 2150MHz band for video broadcast use. With the CSS technology an Operator has the option of only using the amount of BW needed to support the specific numbers of tuners within the home. If a home has four DVRs (eight tuners) the Operator only needs ~800MHz to support this home from a broadcast video standpoint. This leaves ~400MHz free for other uses by the Operator.
Next: MoCA and CSS future bandwidth requirements
MoCA and CSS future bandwidth requirements
Future-looking home networking needs to support multiple streams of HD Video and Data that are in the +100MHz BW range. While DBS operators can utilize BW outside of their traditional 950MHz to 2150MHz band, there can be interference issues, especially when attempting to coexist with Cable and Terrestrial TV signals. It is much simpler and in some instances technically necessary, for the DBS Operator to utilize the BW reserved for their use. The frequency agility of both MoCA and CSS technology enables simultaneous DBS video delivery and high data rate home networking solutions to coexist within the same home on the same coax cable.
For the first time, CSS technology enables DBS operators to support multiple viewing locations within the home via a single cable network. MoCA technology not only enables home networking capabilities between all DBS viewing locations, it also connects with any pre-existing PC network. Combining the two technologies allows a DBS Operator to provide industry leading HD content via Direct Broadcast Satellite and home networking services such as multi-room DVR, media centers, and server-based VOD/PPV. Additionally, with MoCA, the customer can access their personal content over this network and stream music, view a slideshow of family photos or watch stored or downloaded video from the NAS or PC to any viewing location in the network.
Summary
For service operators the benefits of a MoCA home network are clear. MoCA provides the most reliable, flexible and highest throughput network technology available with a true "no new wires" approach enabling operators to expand their service offerings. For subscribers, the benefits include a whole home entertainment network enabling any-room access to all of their multimedia content -- all from a technology that already exists in their home and is completely transparent to them.
Channel Stacking Switch technology has revolutionized the way DBS operators run their businesses. Not only are installation and subscriber acquisition costs reduced, but so are the rates of service installation rejections and subscriber churn. CSS technology also enables plug and play upgrades and the opportunity to easily deploy new services without truck rolls to drive ARPU gains. The benefits of CSS taken collectively translate into higher customer satisfaction levels.
In conclusion, by combining MoCA and CSS, DBS operators can deliver programming from a single cable structure that also supports whole home entertainment networking to expand the service offerings to subscribers. Coexistence of CSS and MoCA technology enables competitive customer service advantages and monetization of revenue generating system technology solutions. Together MoCA and CSS offer DBS operators proven, ready-to-deploy technology solutions that are future proof, reliable, cost efficient and can help drive the operator's bottom line.
About the author
Jon Iwanaga has over 15 years of experience in the development of semiconductors for graphics, video and communications systems. Early on at Brooktree Corp., Jon worked on graphics chips that first brought color to personal computers and workstations. At Conexant Systems, he worked on cable modem ICs along with video and tuner chips that enabled the capture of video signals on personal computers. Currently, as product marketing manager at Entropic Communications, he manages the company's c.LINK products for home networking. Jon Iwanaga holds a B.S. Degree in Electrical Engineering from UC San Diego and Masters Degree in Business Administration from UC Irvine. He can be reached at jon.iwanaga@entropic.com.
Troy Brandon has over 18 years of experience in the RF Industry. Troy retired from the Navy in 1995 where he maintained and integrated various Radar, Communications, and GPS systems. At Space Systems Loral, Troy ran the RF Products Microwave division. Using advanced techniques Troy's team enabled complex and tightly specified MIC and MMIC designs for >15yr on orbit guaranteed performance. From Loral, Troy transitioned to REMEC Wireless and Defense where he managed the ODU product line. The group developed and manufactured highly integrated RF Microwave Outdoor Unit point to point and point to multi-point radios used in the cellular and data backbone market. Troy made the transition to the RF on a chip sector when he joined RF Magic, which was later acquired by Entropic Communications. Troy currently manages all Marketing aspects of the DBS ODU Product Line from New Product Proposal to End of Life. He can be reached at troy.brandon@entropic.com.
