Home Media Alternatives

In many types of media, bits flow among terminal devices in the home. Due to the interest in residential broadband, new companies and technologies are emerging constantly. Among the more promising approaches are these:

• Phone wire, standardized as HomePNA

• Coaxial cable, now used to distribute cable TV in the home

• Home electrical circuits or powerline

• Firewire, or IEEE 1394b

• Category 5 wiring, used for Fast Ethernet in business locations

• Wireless, standardized as IEEE 802.11a, 802.11b, HomeRF, and Bluetooth

Phone Wire

Telephone wire is used today to distribute voice service from the NID to the individual telephone handsets in the home in a bus topology. A study by [Kerpez] characterized the performance of home phone wire for data purposes and concluded that, given proper precautions, telephone wire could be used for high-speed data even though it wasn't engineered for that purpose. Recent innovations have enabled the use of this legacy wiring for high-speed service. One standard for developing phone wire is promoted by the Home Phone Networking Alliance, or HomePNA .

The current version of HomePNA is 1.0, which is based on technology from Tut Systems. Because it passes analog voice, it must modulate above the analog telephone frequencies. Accordingly, it is very much like xDSL, but the modulation scheme is different. Version 1 provides only 1 Mbps. However, in July 1999, the HomePNA announced that technology from a startup company called Epigram was chosen as the basis for a Version 2 standard for 10 Mbps. Seeing a good thing in process, Broadcom acquired Epigram in April 1999.

The ITU is getting in on the act by chartering a committee, called G.pnt., to study phone wire networking. The scope of the committee is to develop interoperable home-networked transceivers for point-to-point and multipoint data communications using existing home wiring. Its goal is to extend xDSL access technologies. This effort is being strongly driven by telephone operators, and currently the goal is to achieve a recommendation by October 2000.

HPNA has already begun discussions of the next generation of the specification and has targeted 30 to 33 Mbps as the logical next step. Broadcom, among others, believes that phone line networking is capable of 100 Mbps.

HomePNA has the support of more than 90 companies, including Advanced Micro Devices, Broadcom, Conexant, Intel, Lucent, and National Semiconductors.

Phone Wire Issues

Phone wire has the advantage of being in place today in virtually all homes. Incremental costs, therefore, are minimal. However, some problems persist.

• VDSL spectral compatibility— HomePNA and VDSL are feared to have spectral incompatibility problems. Therefore, care must be taken to be sure that modulation schemes or other techniques are used to prevent interference.

• Connectivity— All the networked PCs must be plugged into jacks on the same phone line. If you have multiple lines in the home, the devices cannot broadcast to each other because they are on a different bus. A bridge (or router) connects the extensions.

• Japan— As of this writing, home phone line networking is not legal in Japan. This is an oddity, a remnant of when regulators worried about telephone crosstalk. However, not having Japan's consumer electronics companies involved slows the pace of cost reduction.

• Home noise sources— Proximity to refrigerator or air conditioning motors (or other high-power wideband sources) can cause excessive interference.

Coaxial Cable

Coaxial cable is a high-speed bus normally installed by the cable operator but owned by the homeowner. The physical problems of coaxial cables are similar to those of twisted-pair wires, but home cable is generally newer and often can be used for high-speed networking without upgrading. However, if the consumer has installed a splitter or an unauthorized set-top box, the chance exists that the wiring is sufficiently disturbed to render it unusable for data.

A final problem with both twisted-pair wiring obtained from the phone company and coaxial cable obtained from the cable operator is that they don't go to all rooms in the house. For example, if you want to leverage your in-home coax for telephone use, you might need to string extra cabling to the kitchen, where you have a telephone handset on twisted-pair wires but no cable TV. In this case, you would need to rewire your kitchen.

Powerline

For ubiquitous service in the home, nothing surpasses electrical circuits, also called powerline service. All devices need electricity. If you can use the same plug for electricity and connectivity, you have cost savings and convenience. Because of the advantages of ubiquity, powerline has been pursued as a home networking solution for years. Many systems in deployment are using low bit rate modulation for everything from baby monitors to electric meter reading and power management. Most are below 10 Kbps.

However, technical advances have accomplished trial versions of multimegabit powerline. Work is organized by a trade association called International Powerline Forum (IPF, London). Companies working on a solution include Enikia, Intellon (partly owned by Microsoft), Interlogis (an offshoot of Novell), and Northern Telecom.

IEEE 1394b (Firewire)

Because of our view that digital TV is a significant market driver for RBB, and because IEEE 1394 is not widely available, this section discusses IEEE 1394b, or Firewire, in a little more detail.

IEEE 1394 is a new form of cabling and software architecture for consumer electronics and personal computing. It originally was developed by Apple under the name Firewire as an interface for multimedia peripherals to Apple PowerPCs. After its submission to IEEE for standardization, the product was given the designation of IEEE 1394, but it is often still referred to as Firewire. Apple and Thomson continue to hold the intellectual property rights, which apply primarily to firms devising integrated circuits to implement the protocol, not to downstream manufacturers of adapter cards and end users. The original 1394 specification had a limit of only 5 meters in distance. A successor, IEEE 1394b, extends the range to 50 meters.

Firewire has garnered the support of CE manufacturers as a high-speed, daisy-chained network for the attachment of consumer entertainment equipment such as stereo sound equipment, digital cameras, digital video discs (DVD), and digital television sets. Firewire supports the speeds necessary to accommodate multiple streams of digital video and is the medium of choice for CE vendors. Additionally, PC NICs will be available. Apple is the holder of the original intellectual property and intends to ship Firewire on Powerbook and desktop computers in 1999. Sony currently is shipping a digital camera with a Firewire port. Japanese manufacturers such as Sony and Toshiba are shipping DVDs and digital decoders with Firewire. There is considerable momentum from the CE industry behind Firewire, if not the computer and telecommunications industries.

The following list details the attributes of Firewire:

• Speeds of 98.304 Mbps, 196.608 Mbps, and 393.216 Mbps, commonly referred to as 100 Mbps, 200 Mbps, and 400 Mbps. Work is under way to define an 800 Mbps capability.

• Single-wire cabling for all devices, such as no more separate video cables for audio and video.

• Combined isochronous and asynchronous modes.

• Hot-pluggable devices, which are devices that can be added to or removed from the network without interfering with working devices.

• Optional power-passing capability from an IEEE 1394 hub to various pieces of terminal equipment.

• Plug-and-play capability for PC and TV connections.

• Strong support among consumer equipment manufacturers.

• Support for digital TV and IP protocols.

Firewire Architecture

Figure 7-4 shows the elements of Firewire's RG. The home-use IP router function defines the address translation of IP to and from Firewire, which has its own numbering plan. The MPEG-2 stream-handling function is concerned with MPEG interaction with Firewire. In particular, this function maps MPEG programs to Firewire channels.

Firewire Principles of Operation

A Firewire network supports daisy-chained and star topologies. Each Home Network consists of a root node, which contains a global view of all devices attached in the home and discerns the topology from control traffic crossing the network. The root node can be any Firewire device, but an RG is a logical place for this function.

The software standard specifies a protocol stack encompassing addressing, timing, bandwidth reservation, and Media Access Control.

Each Firewire-compliant device contains a configuration read-only memory (ROM) that is embedded in digital set-top units, NICs, and consumer electronic devices. This ROM contains the equivalent of an Ethernet MAC address, the speed requirement of the device, and information on whether it operates in asynchronous or synchronous mode. The configuration ROM provides the plug-and-play capability of Firewire. Enough intelligence exists in this ROM to enable it to participate in the configuration process. The result is that the consumer plugs in the Firewire connector, and the device is fully capable of participating in the local network.

When devices power on to the network, an event called the bus reset occurs. In the bus reset, each device broadcasts the contents of its configuration ROM. The root node listens to all the traffic, distills it, and develops a topology. After the bus reset, the root has a global picture of who is attached to the network, their speed requirements, their requirements for isochronous support, and their identifier.

This protocol has both asynchronous and synchronous support. This is achieved by using a slotted protocol reminiscent of some HFC media-control protocols.

An important function of the RG in the Firewire model is to bind the 1394 channel identifier to an MPEG PID or IP address.

Firewire Issues

Firewire represents a very high-end Home Network architecture that is particularly well-suited for video transmission, including broadcast TV. Nonetheless, despite the plug-and-play feature, simplified cabling, speed, and support of the CE industry, Firewire faces hurdles.

The following list details some of the challenges for Firewire:

• Rewiring in the home is required. Firewire does not run over legacy wiring.

• Firewire requires some form of RG. The root device is an inherent part of the architecture.

• The cost is significant compared to that of legacy systems. The Firewire cables are new, the interfaces are new, and there is a requirement for new devices such as set-top units, the root processor, and home rewiring.

• Little support exists for Firewire apart from the consumer electronics industry and Apple. Further information can be obtained from the 1394 Trade Association Web page at www.firewire.org .

Category 5 Wiring

Those familiar with internetworking recognize that home networking presents roughly the same problem as local-area networking for business use. A natural consideration would be to install some form of commercially implemented local-area network (LAN) technology, particularly Fast Ethernet (100 Mbps), which is enough to support multiple TV streams and even HDTV. It would be possible to have three or four concurrent HDTV NTSC programs, with multimegabit data service and telephony over a broadcast Fast Ethernet in the home. Given the familiarity of FE at work, this seems to be a logical home medium. Business Ethernets are configured as a star or bus topology, and either can be used in the home. However, to combat congestion problems, Ethernets are increasingly configured in star topologies.

Home networking differs in several ways from the LAN model. First is the requirement to accommodate broadcast digital TV. No LAN protocol is designed specifically for this role. It is widely believed that video services require isochronous networking. Isochronous networking provides bits at a fixed rate over time. Ethernet and its higher-speed brethren do not explicitly provide for isochronous service. ATM is being considered for point-to-point video, but no economic architecture exists for the broadcast case.

Second, the Home Network must be easier to use than a business LAN because there won't be a system administrator to help you configure your IP address or program your access list. Plug-and-play is a requirement.

Third is cost. The Home Network probably won't be paid for by the boss. Consumer electronics is highly cost-sensitive, and vendors are accustomed to small margins, which is a bit of a rude awakening for networking companies accustomed to 50-percent-plus margins.

Wireless

The regulatory and technical changes facilitating the development of wireless access networks are having a beneficial effect on the introduction of wireless home networks. New frequencies are being considered, and technology is addressing previous issues of robustness and cost. Several new standards are emerging with different design assumptions and supporters. The ones discussed herein are IEEE 802.11b, HomeRF, Bluetooth, and HIPERLAN (for High Performance Radio LAN) because of our view that these have lead positions as of this writing. Other standards exist, and others will no doubt emerge. But these illustrate technical and commercial issues and solutions that can be applied to contemplate other wireless technologies as they emerge.

IEEE 802.11a and IEEE 802.11b

In July 1997, the IEEE adopted the 802.11 standard supporting 1 and 2 Mbps data rates in the 2.4 GHz band with frequency-hopping spread-spectrum (FHSS), direct-sequence spread-spectrum (DSSS), and infrared physical layers ( grouper.ieee.org/groups/802/11/main.html ).

However, the 2.4 GHz ISM band is getting crowded, and there is not a lot of spectrum anyway. Also, because 2 Mbps is insufficient to handle large amounts of video, the 802.11 committee created two extensions, called Task Group A (TgA) and Task Group B (TgB), to work in a different frequency location and to offer more bit rate. TgA is creating 802.11a, which requires mandatory support of 6, 12, and 24 Mbps data rate service in the U-NII band (5 GHz). TgB is creating 802.11b, which provides 11 Mbps service in the 2.4 GHz band. Additionally, Task Group A has set a goal of making the physical layer the same as the European Standards Telecommunications Institute broadband radio-access network, to allow both standards to use the same radio and to drive down costs.

802.11a and 802.11b will use the same MAC layer as the original 802.11 but will use different modulation. 802.11a uses orthogonal frequency-division multiplexing (OFDM, similar to the modulation used by European digital TV transmission). 802.11b uses a complementary code-keying waveform (CCK), using technology from Harris and Lucent. 802.11b specifies a negotiable bit rate from 1 or 2 Mbps at 400 feet up to 11 Mbps at 150 feet (see Table 7-1).

Major challenges for designs operating at 11 Mbps include modularizing and shrinking the radio. However, Apple Computers made a surprising announcement with its introduction of the Airport module for its new iBook series of laptop personal computers ( www.apple.com/airport/faq2.html ). It announced an 802.11b implementation using Lucent technology that allowed an iBook to connect at 11 Mbps to a central home wireless hub. The initial list price was $99 per iBook and $299 for the hub. This was an aggressive move and one that surprised many because it established 802.11 as a contending home network solution.

Table 7-1. A Comparison of the 802.11 Standards

	802.11	802.11a	802.11b
Frequency range	2.4 GHz ISM	5.3 GHz U-NII	2.4 GHz ISM
Bit rate	1 to 2 Mbps	6, 12, and 24 Mbps	11 Mbps
Modulation scheme	Phase shift keying (PSK) in ISM band; baseband coding for infrared	OFDM	CCK
Vendors	Proxim, Harris	NTT, Breezecom, NEC, Lucent, Aironet, Symbol	Apple, Alantro, Symbol, Harris, Lucent, Aironet

HomeRF

HomeRF supporters view the 802.11 family of standards as too expensive for consumer use. In particular, there seemed to be no need to support direct sequence or infrared for high-speed home use. So a consortium of companies sought to modify 802.11 by mandating only frequency hopping to accommodate a consumer market.

Version 1.0 specifies a protocol called Shared Wireless Access Protocol (SWAP). SWAP specifies the carriage of voice and data over the 2.4 GHz ISM band. It also specifies voice support for six telephone conversations using the European Digital Enhanced Cordless Telephone (DECT) protocol. DECT provides a 32 Kbps voice service using ADPCM coding. Thus, it attempts to be a more integrated solution than 802.11 or Bluetooth (discussed later), which are focussed on data. It remains to be seen whether an integrated cordless phone and data solution can meet the cost requirements needed for home use and for which HomeRF has criticized 802.11. The 802.11 and Bluetooth camps assert that DECT is not an economic way to handle voice. Their approach is to use a packet voice approach, such as Voice Over IP.

SWAP specifies frequency-hopping spread spectrum transceiver in the 2.4 GHz ISM band. It achieves 2 Mbps service using frequency shift keying (FSK) modulation, a well-known (some would say ancient) line-coding scheme that also is very low in cost. Because it handles voice, SWAP supports both isochronous service (for voice) and asynchronous service (for data). It does so by mixing both voice and data packets into a common frame. Each frame is stuffed with voice and data bits, and then the transmitter hops to another frequency. Each frame is 20 milliseconds, so SWAP hops at 50 hops per second. It hops in the same manner as 802.11, but with what is claimed to be a lower-cost radio.

FHSS has issues with respect to speed in that it takes time to settle on a new frequency. Therefore, it remains to be seen whether it can be made to exceed 1 to 3 Mbps to be competitive with 802.11b. On the other hand, FHSS technology is well known, and it may be that HomeRF and Bluetooth can keep a niche in the low-end, low-cost segment of the wireless LAN market. On the other hand, HomeRF is specifying a second version to operate at 10 Mbps.

Further information can be found at www.homerf.org

Bluetooth

Bluetooth is another attempt at using 2.4 GHz ISM spectrum for home use. Like HomeRF, it is based on the FHSS specification for 802.11, but it does not require the DSSS—nor does it provide telephone support. As a result, Bluetooth is positioned as a very low-end, low-cost wireless home solution.

Bluetooth was originally developed in Scandinavia by Ericsson (Nasdaq: ERICY) www.ericsson.se ), and Nokia (NYSE: NOK, www.nokia.com ; www.nokia.fi ) to provide a low-cost point-to-point peripheral attachment solution for computers, telemetry, and metering. However, as the interest in high-speed networking grew, Bluetooth and its adherents positioned themselves as home media protocols as well. Bluetooth specifies a single-chip solution for a frequency-hopping spread spectrum transceiver. It hops over 100 channels and thereby provides a secure medium. Further information can be found at www.bluetooth.com .

HIPERLAN

Bluetooth was developed in Europe primarily for low cost. HIPERLAN (High Performance Radio LAN) was developed in Europe for speed. Version 1.0 was specified in 1996, but not much happened in the market after the initial introduction. However, the move to home LANs has stimulated this technology, as it has other technologies. As of this writing, HIPERLAN has the high ground among wireless LANs in terms of speed. HIPERLAN uses 100 MHz of bandwidth in the low end of the U-NII band, between 5.15 and 5.25 GHz, with a maximum transmission power of 1 watt to achieve 23.5294 Mbps of service. Although the usable bandwidth to the user is more like 18 Mbps, HIPERLAN alone among the wireless LAN protocols has the reach (35 to 50 meters indoors) and speed to handle multichannel television.

As with 802.11a, the use of the U-NII band by HIPERLAN makes sense because of the cacophony of wireless devices already in the home at 2.4 GHz ISM. Those devices include toys, garage door openers, cordless phones, microwave ovens, and other consumer devices not intended for communications use.

Version 1 supports Ethernet, and Version 2 supports ATM. The specification work is the responsibility of the Broadband Radio Access Network (BRAN) group of ETSI . As a cost-reduction measure, HIPERLAN uses the same modulation scheme as GSM telephones, called for Gaussian minimum shift keying (GMSK).

Further information can be found at www. hiperlan.com .

For a comparison of the wireless LAN technologies, see Table 7-2.

Table 7-2. A Comparison of Wireless LAN Technologies

	802.11b	HomeRF	Bluetooth	HIPERLAN
Frequency range	2.4 GHz ISM	2.4 GHz ISM	2.4 GHz ISM	5.15 to 5.25 GHz U-NII
Bit rate	11 Mbps	2 Mbps, version 1.0; 10 Mbps, version 2.0	2 Mbps; 20 Mbps demonstrated	23.5294 Mbps
Modulation scheme	CCK	FSK	—	GMSK
Vendor Sampling	Apple Airport, Lucent, Harris	Intel, Motorola, Proxim, Sharewave, Compaq	Nokia, Ericsson, Intel, IBM, Toshiba	Thomson, ST Microelectronics, Nokia, Harris
Web site	grouper.ieee.org/groups/802/11/	www.homerf.org	www.bluetooth.com	www.hiperlan.com , www.etsi.org/bran/bran.htm