HomePNA Chipsets Forge “No New Wires” Home Entertainment Networks

ITU Standard Leads the Digital Home Revolution

Connected Homes

If you’re still thinking of TVs, computers, and phones in your home as separate devices, think again. The era of home entertainment networking is here, which means these appliances can “talk” to each other and share – not only data – but voice and video too.

As evidenced by the popularity of IPTV offerings (like AT&T’s U-verse), the demand for speedy and reliable delivery of data, voice and video throughout the home is rising quickly. A recent report from ABI Research¹ states that IPTV service will increase by an estimated 32% annually over the next six years, to nearly 79 million subscribers globally by the end of 2014.

Digital Superhighway in the Home

Here’s how it works: Service providers bring ample broadband access to the home. However, to successfully transmit data, voice, and video inside the home, there must also be plenty of bandwidth from room to room – a digital superhighway from device to device – along with a modem that can assure that signals are delivered with high efficiency, low latency, minimal jitter and very little packet loss. These parameters become even more stringent with video streaming. The signals must be delivered reliably and constantly without interruptions or glitches that could seriously compromise the viewing experience.

Figure 1: The ideal approach to home entertainment networking uses existing infrastructure.

Ethernet wiring (CAT-5) is one way to deliver signals throughout the home, but it is expensive, requires laying new wires, and necessitates drilling unsightly holes into walls. Wireless distribution is another route, but often results in spotty transmission. The ideal solution uses existing infrastructure with technology that streams data, voice and video without a hitch. Sometimes called a “no new wires” approach, this solution is the proven, cost-effective alternative to both CAT-5 and WiFi (see Figure 1).

No New Wires

In 2001, the International Telecommunication Union (ITU) adopted the first “no new wires” home networking standard. Today, HomePNA 3.1 (ITU standard G.9954) is the latest and most current standard. It is supported by the HomePNA Alliance, a consortium of leading technology companies working together for a single existing wire home networking standard. While the HomePNA Alliance is not a standards body like the ITU, it contributes to standards by developing protocol specifications for networking over existing wires. The Alliance also determines certification testing standards for products to be HomePNA-certified.

The “no new wires” approach uses existing infrastructure – both coax and phone line – to stream digital signals from the residential gateway (RG) to other devices on the home network. The challenges of doing this successfully are multifold. First, coaxial cables and phone lines (like all existing wires) have signaldistorting noise, and conditions on these lines change quickly. Furthermore, IPTV must coexist with other applications, like VDSL and TV channels. To insure optimum results, interference must be avoided at all costs. Attenuation poses yet another challenge to delivering data, voice, and video consistently throughout the home. Indeed, running a home entertainment network over existing wires requires a modem robust enough for the job.

Attacking Noise: PHY and MAC

All of these challenges have been successfully addressed on both the Physical (PHY) and Media Access Control (MAC) layers of HomePNA chips. On the PHY layer, (the first level in the Open Systems Interconnection (OSI) Seven Layer Model), HomePNA uses a very robust modulation scheme that supports multiple PHY rates of up to 320 Mbps. This affords high flexibility and granularity in various line conditions.

Figure 2: This diagram depicts the HomePNA Frame Format.

The HomePNA standard uses burst (or frame) transmission, typical of the industry (see Figure 2). To increase robustness in noisy and constantly changing line conditions (a situation particularly true of phone lines), the HomePNA receiver re-adapts per frame. It has no memory; it performs instead an acquisition of channel characteristics on each individual frame by using a preamble that is attached to every frame. This preamble is used for channel estimation, Automatic Gain Control (AGC) adjustment, clock frequency offset estimation, and more. Using per-frame acquisition enables the receiver to quickly adapt to dynamic channel characteristics.

On a multi-node HomePNA network, transmission can occur at different rates between different nodes. If the line between two particular nodes is noisy, the rate will be reduced to maintain robustness. This flexibility is achieved by an advanced rate adaptation technique, which sets an optimal line rate between any two nodes. (In other words, it sets the highest line rate that channel conditions allow while still meeting a certain target error rate.) Each pair of transmitters and receivers automatically adjusts to the optimal line rate. Adaptation is based on a “negotiation” between the receiver and transmitter.

The MAC, a data communications protocol sub-layer of the OSI’s data link layer, provides addressing and channel access control mechanisms to allow several network nodes to communicate within a multipoint network. It also plays an important role in overcoming noise and maximizing robustness. The MAC uses a protocol called Limited Automatic Repeat Request (LARQ). Mainly for phone lines, LARQ retransmits frames that are received incorrectly by the receiver. This technique is very useful for environments with high impulse noise, which is known to cause frequent frame damage.

The MAC is very efficient, enabling optimal usage of the available PHY rate. It also is designed to maintain high efficiency and low latency, and guarantees a significant amount of bandwidth for data, voice, and video delivery, all essential qualities for home networking.

Embedded Ecosystem

The HomePNA chips that are the foundation of the truly digital home are embedded in an entire ecosystem of home networking devices (see Figure 3). Nearly 10 million HomePNA chips have been shipped to date. They’re found in network interface devices (NIDs), residential gateways, set-top boxes, Ethernet bridges, optical network terminals (ONTs), testers and more, making it easy for service providers to deploy inside the home. The chipsets co-exist with other services on the same wires, such as POTS, dial-up modems, ISDN, ADSL, VDSL, broadcast TV, and related technologies.

Figure 3: Nearly 10 million HomePNA chips have shipped in a full ecosystem of devices, like this IPN330HD from Cisco.

Today, four out of the top five largest telecommunications carriers in North America deploying IPTV have selected HomePNA as the base technology for its cost-effectiveness, reliability, and high performance. HomePNA lowers the cost and time required to deploy IPTV and other broadband services inside the home, helping service providers become more competitive and more profitable.

Conclusion

As the demand for home entertainment networks continues to grow, the technology behind features like IPTV, triple play, and whole-home DVR is becoming more robust. HomePNA has played a significant role in making this market viable and affordable. By developing chips that reliably stream data, voice, and video over existing wires, HomePNA has overcome the challenges of noise, changing line conditions, coexistence, and attenuation. It has turned those plain old telephone lines and coaxial cables into IP superhighways, connecting your home with future-proof features and keeping your home entertainment network moving forward in the fast lane.

References: ¹ ABI Research, At 32%, Telco TV Tops Pay-TV Platform Growth, http://www.abiresearch.com/press/1346- %20At+32%25,+Telco+TV+Tops+Pay-%20TV+Platform+Growth, January 14, 2009

Eran Gureshnik is the product line manager of HomePNA products at CopperGate Communications and has also worked for Marvell, Intel, and DSPC. He is an expert in communication semiconductors with experience in design engineering, chip and platform architecture, platform and product management, and technical customer support. Eran received his bachelor’s and master’s degrees from the Technion - Israel Institute of Technology. eran_g@copper-gate.com