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Home-networking systems should co-evolve with standards

Posted: 16 Apr 2007 ?? ?Print Version ?Bookmark and Share

Keywords:Digital home systems? Digital home networking? home-networking solution?

By Tam Do
Altera Corp.

The home network is becoming the "grand central station" for faster video, voice and data traffic. Demand for a higher data rate is expected to increase as more video changes from standard to high definition. This means that new home-networking systems must evolve along with the standards that will undoubtedly emerge in the foreseeable future.

Various interface standards for both wired and wireless networking have typically been used to implement home networking for multimedia. But none of the current standards guarantees quality-of-service (QoS) for live multimedia transmission within the home.

The first challenge is to design a reliable multimedia home-networking platform that is able to deliver Internet Protocol (IP) packets with sufficient QoS and also with no visible or audible distortion.

For the second challenge, designers must figure out how to do this cost-effectively, keeping the consumer application affordable.

Several techniques have already been deployed in the professional broadcast arena to address the first challenge. Designers can implement those techniques in a consumer-type, low-cost FPGA in order to meet the second challenge.

Whenever data is routed through a wired or wireless network, it is subjected to corruption due to noise, clock jitter and saturated network link, which translates into packet loss or video pixel loss. This is more obvious for a compressed video stream vs. an uncompressed video stream.

One method for ensuring a minimum level of data integrity in an IP network environment is to use payload-aware processing. Payload-aware processing involves IP encapsulation, timing correction and application layer forward error correction (FEC). Live video transmission cannot use the packet resent method. Therefore, by using FEC, the receiver reconstructs missing or corrupted data on the fly without having to request a retransmission. Various types of FEC schemes have been used in cable, satellite and terrestrial digital video transmission.

For IP video networks, the Pro-MPEG Forum had proposed a FEC algorithm that mainly uses an exclusive-OR method to generate the redundant data for error correction. This standard is called the Pro-MPEG Code of Practice #3 release 2. This FEC is used primarily for compressed video streams such as MPEG-2 or H.264. The code of practice recommends transmission protocols such as Real Time Protocol (RTP), User Datagram Protocol (UDP) and Internal Protocol, mapping and a FEC scheme. It also discusses issues such as timing recovery, jitter tolerance and latency. RTP is used to deliver audio and video packets. UDP is one of the cores in the IP suite for sending short messages. Therefore RTP, UDP and IP are the combined total protocol for audio/video transmission.

Most of the key building blocks are readily available and can be downloaded for reuse into an FPGA system design. The design can also be built by using existing building blocks in the FPGA design tool. Most design tools contain blocks such as FIFO, internal memories, external memory controllers, counters, phase-locked loops and other simple logic blocks.

Low-cost FPGAs can be used to implement a complete design, giving the system flexibility and upgradeability to fit future requirements.

About the author
Tam Do
is senior technical marketing manager at Altera Corp.'s Broadcast/Automotive/Consumer Business Unit. Do holds a BeE from the University of Nevada, Reno. Comments may be sent to TAMO@altern.com.




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