Introduction â€“ Networking Consumer Devices
The consumer world is buzzing with news and standards to network home appliances, PCs, peripherals and other consumer devices. Several technologies are vying to be the next technology to network all appliances in the home. Some of these 22 technologies include HomeRF, Bluetooth, HiperLAN2, IEEE 802.11, Ethernet, HomePNA, USB 2.0 and IEEE 1394. While each one presents unique pros and cons, technologies that require adding cables provide one unique capability â€“ the ability to provide high-speed and reliable voice, data and video transfer. Home networking is incomplete without the ability to transfer voice, data and video together. Some of these â€œnew wires” technologies include Ethernet, USB 1.1/2.0 and IEEE 1394. Ethernet is a low-cost technology, which uses a protocol ideal for data traffic. USB 1.1 and its more recent specification USB 2.0 are primarily PC-centric, and network PCs and PC peripherals. IEEE 1394 is the technology that holds the promise to be the perfect home networking technology that will network audio-video and PC equipment.
IEEE 1394 Backgrounder
The move from analog to digital technology has enabled the sharing of video, Internet, data, and audio. Consumers are constantly searching for faster, cheaper, more reliable, and easier ways of transferring and sharing such information. While this has been happening in the enterprise for the last few years, the home is just seeing its introduction. This phenomenon, known as home networking, allows the interconnection of PCs, consumer equipment, and communications, and the distribution of infotainment between these appliances. The convergence of voice, data and video will happen only when seamless, high-speed communication becomes readily available. IEEE 1394 is one such interconnection technology that will enable connection of these devices across home. IEEE 1394, also known as 1394, FireWire™ or iLink™, is a versatile, high-speed, and inexpensive method of interconnecting a variety of consumer electronic devices (such as digital TV, set-top boxes and home theatre equipment), PCs and PC peripherals (such as, scanners and printers).
Origins of IEEE 1394
The FireWire bus standard, originally created by Apple Computer was born out of the need for a low-cost, consumer-oriented connection between digital-video recorders and PCs. It grew into a standard called the IEEE 1394 for low-cost, high data rate connections. In 1994, the 1394-trade association (1394ta) was formed to support and promote the adoption of the IEEE 1394 standard. In 1995, the 1394ta formally released the 1394 specification, and further revisions like 1394a in 1998 and 1394b in 1999 were introduced. The 1394b is fully backward compatible with the current 1394 and 1394a specifications. Each revision of 1394 has added features, performance, and capabilities.
USB (Universal Serial Bus) vs. IEEE 1394
The computer industry has been promising users the ability to easily connect electronics devices such as digital TVs, cameras, set-top boxes, and stereo equipment to each other and to PCs for several years. USB and IEEE 1394 interconnection technologies are the two solutions that have been developed specifically to meet commitments to their customer base. USB and 1394 are complementary technologies, differing in their application focus. USB is the preferred connection for most PCs and PC peripherals such as keyboards, digital cameras, and scanners. IEEE 1394 targets consumer electronic devices such as digital camcorders, digital VCRs, DVD players, and digital televisions. Both technologies are ideal for advanced entertainment networks, but require additional special wiring.
While IEEE 1394 and USB are very different in the underlying technology and algorithms used, they are also quite similar. Both are emerging technologies that offer a new method of connecting multiple peripherals to a PC. Both permit peripherals to be added to or disconnected from a computer without the need to reboot, i.e., hot pluggable. Both use thin, flexible cables and employ simple, durable connectors. But this is where the similarities end. Although 1394 and USB cables may look similar, the amount of data transfer is quite different.
Today, 1394 offers data transfer rates that are over 16 times faster than USB 1.1. In addition, 1394 has a well-defined bandwidth roadmap, with speeds increasing to over 1Gbps in the next couple of years. Such dramatic improvements in data transfer capacity will be required to keep pace with devices such as HDTV, gaming consoles, and set-top boxes which require high-bandwidth. USB 1.1 in comparison supports data rates of 12Mbps, which are ideal for low-bandwidth peripherals. It does not suffice as the ultimate home networking technology. However, the recently released USB 2.0 has data rates up to 480Mbps, which are ideal for voice, data, and several data streams.
IEEE 1394 has a more complex protocol and signaling rate, allowing more data transfer in a given amount of time. Also, 1394 is considerably more expensive than USB 1.1. Industry analysts expect 1394 and USB to coexist peacefully. IEEE 1394 and USB connectors will replace the myriad of connectors found on the back of today’s PCs and information appliances. USB 1.1 will be reserved for low-bandwidth peripherals (mice, keyboards, and modems), while 1394 will be used to connect to the new generation of high-bandwidth computer and consumer electronics products. Meanwhile, analysts predict that USB 2.0 will be used for data transfer between multiple PCs and PC peripherals such as external drives, CD writers and DVD-ROMs.
IEEE 1394 Architecture
The components that form a 1394-based home network include the actual protocol itself, the cabling system, and the architectural design of the network. Similar to other high-speed networking systems, IEEE 1394 adopts a layered approach to transmitting data across a physical medium. The four layers used by the IEEE 1394 protocol are shown in Figure 1.
Figure 1: IEEE 1394 Protocol Stack
Physical Layer â€“ The physical layer provides the electrical and mechanical connection between the 1394 appliance (connector) and the cable itself. Besides the actual data transmission and reception tasks, the physical layer also provides arbitration to insure all devices have fair access to the bus. As its physical media, 1394 requires optical fiber or high-grade copper wiring between the appliances. The 1394 physical layer is physically point to point and logically a bus (each node is a repeater). The physical layer transmits the unstructured raw bit stream over a physical medium, and describes the electrical, mechanical, and functional interface to the carrier. It provides the linking to the upper sessions via signaling and the initialization and arbitration services necessary to assure that only one node at a time is sending data. The physical layer of the 1394 protocol includes:
The electrical signaling
The mechanical connectors and cabling
The arbitration mechanisms
The serial coding and decoding of the data being transferred or received
Transfer Speed detection
Link Layer â€“ The link layer takes the raw data from the physical layer and formats it into two types of recognizable 1394 packets â€“ Isochronous and Asynchronous. Asynchronous data transfer is the conventional transmit-acknowledgment protocol and puts the emphasis on guaranteed delivery of data, with less emphasis on guaranteed timing. Isochronous data transfer is a real-time guaranteed-bandwidth protocol for just-in-time delivery of information. It puts the emphasis on the guaranteed timing of the data and less emphasis on delivery. Isochronous transfers are always broadcast in a one-to-one or one-to-many fashion. No error correction or retransmission is available for isochronous transfers.
Transaction Layer â€“ The third layer in the IEEE 1394 protocol is called the transaction layer and is responsible for managing the commands that are executed across the home network. It supports the asynchronous protocol write, read, and lock commands. A write sends data from the originator to the receiver and a read returns the data to the originator.
Serial Bus Management â€“ The fourth and final logical grouping of functions is responsible for the overall configuration control of the serial bus. It provides overall configuration control of the serial bus in the form of optimizing arbitration timing, guarantee of adequate electrical power for all devices on the bus, assignment of which 1394 device is the cycle master, assignment of Isochronous channel ID, and basic notification of errors. The bus management is built upon IEEE 1212 standard register architecture.
Benefits of IEEE 1394
Â§ Broad support: Due to its high data rates and support for real-time data (such as voice), 1394 has been adopted by consumer electronics manufacturers such as Sony, Panasonic, Philips, Matsushita, Hitachi and Grundig.
Â§ Low cost: 1394 is a low-cost digital interface for audio/video applications.
Â§ Endorsed by international standards bodies: The European Digital Video Broadcasters (DVB) have endorsed IEEE 1394 as their digital television interface.
Â§ Speed: Multimedia entertainment is the most frequently used application in today’s homes. A high-quality distribution of video for entertainment applications requires larger bandwidth than audio and data. IEEE 1394 is capable of transporting data at 100, 200, 400, or 800Mbps. The next version of the standard will be capable of transporting data at 3.2Gbps.
Â§ Plug and play: Consumers can add or remove 1394 devices and there is no need to reset the home network.
Â§ Non-proprietary: Like all IEEE standards, IEEE 1394 is an open, royalty-free standard.
Â§ Different applications: Almost all of the consumer electronic, office automation, industrial, biomedical, and networking devices can benefit from 1394 features and capabilities.
IEEE 1394 is an enabling technology for connecting multimedia devices, such as digital camcorders and VCRs, satellite modems, set-top boxes, digital TV, PCs, DVD players, gaming consoles, home theater, musical synthesizers/samplers with digital audio capabilities, and digital audio tape (DAT) recorders, mixers, hard-disk recorders, and video editors. Market research firm, IDC forecasts that by the year 2003, over 50 million different types of informational and entertainment appliances will support the IEEE 1394 interface.
HAVi (Home Audio/Video Interoperability) is an industry initiative, started by Sony and Philips in 1996. Since then six other companies have joined â€“ Thomson, Hitachi, Toshiba, Matsushita, Sharp, and Grundig. HAVi adopted the IEEE1394 bus standard as the underlying network technology for the HAVi protocols and for the transport of real-time audio/video (A/V) streams. Using 1394 as the bus standard (shown in figure 2) provides benefits such as high-speed, flexible connectivity, and the ability to link up to 63 appliances together. No other interconnection technologies such as wireless, HomePlug, HomePNA, and USB are capable of distributing high-speed video applications.
Figure 2: Simplistic figure showing HAVi using IEEE 1394 bus standard
The HAVi middleware architecture is an open (non-proprietary), lightweight, and platform independent specification that allows development of home networking applications. It specifically focuses on the transfer of digital A/V content between in-home digital appliances as well as the processing (rendering, recording, and play back) of this content by HAVi enabled appliances. It does not, however, address home networking functions such as controlling the lights or monitoring the climate within the house. The HAVi middleware system is independent of any particular operating system or CPU and can be implemented on a range of hardware platforms including: digital products such as cable modems, set-top boxes, integrated TVs, internet-TVs, or intelligent storage appliances for AV content.
Today in the world of analog consumer electronic appliances, there exists a number of proprietary solutions for interoperability between appliances from one brand or vendor. In the upcoming world of digital technologies, HAVi extends this networking model by allowing communication between consumer electronic appliances from multiple brands in the home. The HAVi middleware architecture specifies a set of APIs (Application Programming Interfaces) that allow consumer electronic manufacturers and software engineering companies to develop applications for IEEE 1394 based home networks. One of the main reasons HAVi selected IEEE 1394 over other transmission protocols is because of its support for isochronous communications. HAVi comprises of software elements that facilitate the interoperability between different brands of entertainment appliances within the house. Interoperability is an industry term that refers to the ability of an application running on an in-home appliance to detect and use the functionality of other appliances that are connected to the home network.
The underlying structure for a home network based on HAVi technologies is a peer-to-peer network, where all appliances can talk to and interact with each other. HAVi has been designed to allow the incremental addition of new appliances, which will most likely result in a number of interconnected clusters of appliances. Typically, there will be several clusters of networks in the home, with one per floor or per room. Over time these clusters will be connected with technologies such as 1394 long or wireless 1394.
Benefits of HAVi
A HAVi compliant appliance offers a number of advantages, which include:
Â§ Automatic detection: It can automatically detect other information appliances on the home network.
Â§ Automatic registration: Each added appliance to the HAVi network is automatically registered so that other appliances know its capabilities. This level of functionality helps other appliances utilize the useful resources of this appliance without a need to own the same resources themselves.
Â§ Automatic software upgrades: Some HAVi compliant appliances are capable of installing new software on all appliances connected to the same home network. For instance, a HAVi Panasonic VCR can install the necessary application on a Sony TV in order to make two appliances interoperable. This greatly reduces the need for network administration.
Â§ Manageability: HAVi software takes advantage of the powerful resources of silicon chips built into modern A/V appliances to give the consumer the management function of a dedicated audio-video networking system.
Â§ Brand independence: Entertainment products from different manufactures will communicate with each other when connected into a HAVi network. For example, a Panasonic VCR can work and share its resources with a Sony amplifier and be controlled by a Mitsubishi TV remote control as long as all of these devices are HAVi compliance.
Â§ Hot Plug and Play capabilities: This allows HAVi compliant appliances to configure themselves and integrate within the home network without user intervention.
Â§ Legacy appliances: The HAVi architecture supports legacy appliances, which is important because the transition to networked devices is gradual. Manufacturers are not producing networked appliances alone, and consumers are not immediately replacing their existing appliances.
Xilinx Programmable Solutions Enable IEEE 1394/HAVi Products
The IEEE 1394 technology consists of a physical layer for encoding-decoding, arbitration, a medium interface, and provides an electrical signal and mechanical interface. The link layer provides cycle control, packet transmit, packet receive, CRC and provides the host and application interface. As shown in figure 3, programmable logic solutions provide complete link layer functionality with the ability to connect to multiple interfaces such as PCI, USB, and proprietary audio-video buses, etc. The advantage of programmability is realized when there is a proprietary application interface. However, in an IEEE 1394 system, the Spartan-II FPGA provides system interface and other ASSP functionalities.
Figure 3: The IEEE 1394 Physical Layer and Link Layer Controller with a Host Interface
With the 1394 specification still continuing to evolve, having the link layer controller programmed in a FPGA provides the ability to reprogram the FPGA with the latest 1394 revision. Supporting different products requires the support and interface to different interfaces. For example, using 1394 in a PC requires an interface to PCI, PCMCIA, and other proprietary interfaces. Programmable solutions are ideal for providing this interface because developing ASSPs for these applications is relatively expensive. Also, the decreasing cost of programmable logic solutions makes them ideal for IEEE 1394 and HAVi-based products.
The digital home continues to evolve and smarter appliances continuing to perpetrate the home. These smarter appliances and the need for sharing broadband data, voice, and video is pushing the need for home networking. While several technologies exist the technology that provides high-speed and reliable delivery of voice, data and video will win. IEEE 1394 is one such home networking technology that provides both high-speed and reliable delivery. The proliferation of 1394 as the A/V standard will be accelerated through the use of HAVi as its middleware solution to connect disparate devices, thus providing a complete solution to the consumer.
However the specification continues to evolve and 1394 products need to coexist with other home networking and system interface technologies, thus requiring products that interface between these technologies. With the continuing reduction in prices of programmable logic solutions, these are ideal solutions to provide interfaces between 1394 and other technologies such as PCI, USB, PCI-X, SCSI, HomePNA, etc.