Figure 1 The Home Networking Scenario
There is a lot of literature on this hot topic. Here we will have a brief overview of keypoints summearized from these web pages, reports, news analyses and technical papers. First, we will go over the market and technology potential, then we will list the keypoints further in five possible networking technologies, traditional LAN, phoneline networking, powerline networking, wireless networking(including RF and wireless LAN) and infra-red digital access(IrDA). Then there is a discussion on the service and requirement issues for home networking. Finally an overview of current market players is given.
A home network can consist of multiple PCs and peripherals linking together by certain networking wires/wireless channels. It can be used for shared Internet access, peripheral sharing, and file and application sharing. Future visions of the home network also include consumer electronics devices such as televisions, VCRs, and CD players, as well as traditional home appliances such as a refrigerators, microwave ovens, washers and dryers, heating and air conditioning thermostats, home security systems, and home automation controls. Home automation and security functions can be implemented by linking consumer electronics, appliances, and system controls. For example, the television, VCR, stereo, and lights could be linked together and controlled from a PC or from several PCs connected to the network to form a surveillance system and can be expanded to an alarm system.
Currently, the near applications of home networking could be,
Figure 2 Home Networking Applications(Source: Intel's Anypoint Webpage)
In some industrial research articles ,  and , the behavior of current home PC users and how they use their home PCs to connect to Internet are investigated. They also point out some potential problems in the future home networking market, like the cost-effectiveness, the possible security and data integrity holes. With the technologies' progress, the problem of scalability and interoperatibility is also very important.
Interoperability, Privacy, Regulation and Oligopoly, Reliability and Ubiquitous Marketing could all become the future obstacles in the way of makeing home networking the backbones of home computing. Meanwhile, the development of home-aware community information infrastructure is also very important. The history of the telephony has showed the early trends could easily mislead analysts and industry representatvies. So the detailed market and technologies potential should be clearly addressed before the future failure or loss.
Carnagie Mellon University has conducted a pioneerig research project called HomeNet , they have a trial residential Internet environment with different kinds of users, including both adults and teenagers. Now the project is supervised by telerama.com, an ISP in Pittsburgh area. In that project, systematic data collection and user pattern analysis have been conducted. Also they made some demographical analysis for all future Internet usage in the typical American families. Their study reveals some interesting facts, like the teenagers are always the central to Internet use at home and motivate their parents invest and surf on the Internet. The race, gender and education do have some impact of the usage pattern. These study and facts would provide good background for future home networking development. Detailed report could be found in .
They also introduce a future vista of technology development directions. From the existed infrastructure like phoneline or powerline to wirless solutions like IrDA or Radio Freqency, there are some possible cost-effective solutions. Many pioneering vendors have done reasearch and development with some products. Also, some industrial organization or forums are formed or engaged to establish the standards, service and interoperability environment for these technologies. Typical organizations are Home Phone Networking Alliance, Home RF working group ( www.wca.org) and Home Applications Programming Interface(Home API) ( www.homeapi.org
As a well-established and extremely stable networking solution, Ethernet has long been used by businesses to link employees, systems, and network devices and forms a Local Area Network (LAN). Now, Ethernet is becoming popular in the home environment. The primary advantage of Ethernet is its reliability and reasonably high speed. At 10 to 100 megabits per second (Mbps), Ethernet is sufficient for most data networking needs. And the price of Ethernet devices is relatively reasonable. However, some issues have stagged its wide acceptance into home networking market. The first is separate wiring using Category 5 unshielded twist pair (Cat 5, UTP) which requires extra cost. And this networking technology is somewhat too complicated for a home networking. In near future, while Ethernet is still a very important connectivity solution in corporate networking, its market share in home networking is not significant.
The existing twisted pair plain old telephony system (POTS) wiring in the home is probably the first home connectivity solution coming to our mind. Home Phoneline Networking Alliance (HomePNA) is the leader of development and standization efforts in this field. It is an industrial consortium of 11 companies working toward a single, unified telephone line networking standard. The HomePNA standardization effort is well ahead of the AC power-line and wireless/RF efforts. The first version of the specification has been submitted to standards bodies like IEEE and ITU-T for future acceptance. And the first generation of products based on this standard is also available, including internal PCI-based HomePNA adapter cards that connect to an external RJ11 jack. External HomePNA adapters that connect to the PC via a Universal Serial Bus (USB) or parallel port are also available soon.
The HomePNA 1.0 specification is generally based on the HomeRun technology developed by Tut Systems ( www.tutsystem.com). It supports data rates of 1 Mbps over the existing in-home telephone wiring. Without extra wiring, it enables every RJ11 telephone jack to serve as LAN port. No hubs, routers, splitters, filters, or terminations are required for a network. HomeRun supports up to 25 nodes, with a maximum of 500 feet between devices. HomeRun operates concurrently with voice and fax service. Currently HomePNA is also developing a 10 Mbps specification which is said to be fully backward-compatible and interoperable with current 1-Mbps devices. It is based on Lucent and Epigram’s proposals.
In whole, HomePNA technology offers a technically easy and affordable transition for home networking. It is based on Ethernet and uses well-known modulation techniques. As the HomePNA specification includes higher speeds and as it expands its interoperability by supporting wireless protocols such as Bluetooth, HomePNA may be poised to become a de facto home-networking standard. Some other key enablers will be HomePNA's ease of use, as well as operating system and independent software vendor (ISV) support. Microsoft supports HomePNA in its Windows 98, Second Edition and Windows 2000 Professional will include native support for HomePNA.
Home automation vendors like X10 ( www.x10.com) and control networking companies like Echelon (www.echeolon.com), Intelogis (www.intelogis.com) are trying to utilize their powerline control networking technologies to the home networking market. In their technical white papers , ,  and , they give the prospects of powerline networking. With their properitary protocols like LonWorks or PLUG-IN, and the control chips from major IC vendors, the powerline networking are now an affordable solution for home pc users.
As a power-line carrier protocol, X10 allows compatible devices to communicate over home power supply electrical wiring. X10 enables control over lights and virtually any other electrical device from anywhere in the house with no additional wiring. A controller/transmitter is plugged into a standard electrical outlet, or is installed as a replacement to a current switch. Then each appliance that you want to control is plugged into an X10 module which is connected to a standarad electrical outlet. Then the controller/transmitter could use the electrical wiring as the transmission media to communicate with those modules.
X-10 powerline technology employes an Amplitude Modulation (AM) technique to transmit binary data. In order to differentiate the data symbols, the carrier uses the zero-voltage crossing point of the 60 Hz AC sine wave on the cycle’s positive or negative transition. Synchronized receivers accept the carrier at each zero-crossing point. X-10 uses two zero crossings to transmit a binary digit so as to reduce errors. So every bit requires a full 60 hertz cycle and thus the X-10 transmission rate is limited to only 60 bits per second (bps). Usually a complete X-10 command consists of two packets with a 3 cycle gap between each packet. Each packet contains two identical messages of 11 bits (or 11 cycles) each. Therefore, a complete X-10 command consumes 47 cycles that yields a transmission time of about .8 seconds. This technology is a bit slow to connect home PCs, but would be a potential technology for later connectivity between home electrical applicances.
Data packets are transmitted by the transceiver at about 10 Kilobits per second (Kbps), using spread spectrum technology. The CEBus protocol uses a peer-to-peer communications model so that any node on the network has access to the media at any time. Similar to Ethernet, it uses a Carrier Sense Multiple Access/Collision Detection and Resolution (CSMA/CDCR) protocol to avoid data collisions,. Basically, this Media Access Control (MAC) protocol requires a network node to wait until the line is clear, which means that no other packet is being transmitted before it can send a packet.
In the upper layer, CEBus includes a common application language (CAL) that allows devices to exchange commands and status requests. It defines a common command syntax and vocabulary to do this. CAL defines various electronic device functional sub-units called contexts. And each context is further divided into objects, which represent various control functions of the context. Objects are furtherly defined by a set of instance variablesthat specify the operation of the function of the object. By utilizing the CAL specification, Intellon ensures their products can communicate with other CAL compliant devices.
Intellon offers products ranging from chip sets to board solutions, depending on the level of integration the manufacturer wants to perform on their own. But the cost issues have made Intellon chips less affordable and thus they are not widely used as X10 devices.
In LONWORKS, control networking technology goes beyond simply being a communication protocol. It provides a complete platform on which to build control systems. The LonTalk protocol, an open and international standard designed specifically for the needs of control, is at the heart of LONWORKS networks. Neuron Chip in LONWorks family includes an implementation of the LonTalk protocol along with other built-in features to provide a complete system-on-a-chip solution for control devices. Inside this chip, LonTalk protocol support many communication media including, twisted pair, power line, fiber optics, coaxial cable, radio frequency, and infrared. Good news is that Echelon’s proprietary protocol strategy changed recently when they opened up their Neuron protocol, allowing it to interface with third-party power line transceivers.
Above these, LONWORKS Network Services (LNS) architecture is a powerful network operating system, which provides an object-oriented method to connect networked control devices. It provides a unified API system for developing tools for installing, configuring, and maintaining, monitoring and controlling LONWORKS control networks. LNS clients can run on any platform (PC, MAC, UNIX, embedded, etc.). And LNS Server supports both LONTALK and TCP/IP protocols at the transport layer.
At the physical layer, DPL protocol uses a modulation methodology called Frequency Shift Keying (FSK) to send digital signals over the power line. FSK modulation sends digital signals over the power line by using two or more separate frequencies that are in a fairly narrow band. PLUG-IN DPL single channel solution boasts line speeds of up to 350 Kilobits (Kbps) per second (Mbps). Using multiple channels and carrier signals, the future versions of PLUG-IN DPL will be capable of speeds up to 1 Mbps and beyond. Furthermore, the PLUG-IN FSK modulation scheme delivers bit error rates in the range of 10 -9 with 80 dB of dynamic range.
There are also other home automation technologies like Adaptive Networks, VESA and HAVi, etc. But most of them are targeted at low-speed automation controls.
Figure 3 Sample IEEE 802.11 topology
IEEE 802.11 provides for two variations of the PHY. These include two RF technologies namely Direct Sequence Spread Spectrum (DSSS), and Frequency Hopped Spread Spectrum (FHSS). The DSSS and FHSS PHY options were designed specifically to conform to FCC regulations for operation in the 2.4 GHz ISM band, which has worldwide allocation for unlicensed operation.
|US||2.4000 2.4835 GHz|
|Europe||2.4000 2.4835 GHz|
|Japan||2.471 - 2.497 GHz|
|France||2.4465 - 2.4835 GHz|
|Spain||2.445 - 2.475 GHz|
Both FHSS and DSSS PHYs currently support 1 and 2 Mbps. And all 11 Mbps radios are DSSS. Operating principles of DSSS radios are described in the following paragraphs. DSSS systems use technology similar to GPS satellites and some types of cell phones. Each information bit is combined via an XOR function with a longer Pseudo-random Numerical (PN) sequence as shown in Figure 3. The result is a high speed digital stream which is then modulated onto a carrier frequency using Differential Phase Shift Keying (DPSK).
For more information of IEEE 802.11 works, please refer to related standards and , , .
The Bluetooth technology is based on a short-range radio link built into small application-specific integrated circuits (ASICs). It can support both stationary and mobile communications and use frequency hopping (up to 1,600 hops per second) to reduce noise impact. Bluetooth supports data transmissions between devices of up to 721 Kbps and up to three voice channels. Operating in the unlicensed and globally available industrial, scientific, and medical (ISM) band at 2.45 gigahertz (GHz), it uses spread spectrum to connect devices as much as 30 feet apart. Bluetooth technology can enable a user to replace the various cables between devices with a universal short-range radio link. And they could interoperate with similarly equipped devices such as printers, fax machines, desktop computers and peripherals, and a host of other digital devices. Futhermore, Bluetooth technology can provide a connection between the ad hoc network and existing data networks.
As claimed, Bluetooth technology is designed for wireless personal area networks (WPANs), which are networks of personal electronic devices in close proximity to each other. Bluetooth technology is expected to become a major player in the wireless data communications market because of simplicity and its support from large companies. And Bluetooth members are encouraging vendors to incorporate the technology into their products by waiving intellectual property royalty fees.
The HomeRF Working Group also is developing the Shared Wireless Access Protocol (SWAP), which operates in the 2.4-GHz range of the spectrum and employs frequency hopping at 50 hops per second. SWAP is also expected to support as many as 127 devices per network at up to 50 meters apart.
SWAP system is designed to carry both voice and data traffic and to interoperate with the Public Switched Telephone Network (PSTN) and the Internet; it operates in the 2400MHz band and uses a digital frequency hopping spread spectrum radio. It is derived from extensions of existing cordless telephone (Digital Enhanced Cordless Telephone or DECT) and wireless LAN technology to enable a new class of home cordless services. In SWAP, a TDMA (Time Division Multiple Access) service is supported to provide delivery of interactive voice and other time-critical services, and a CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) service for delivery of high speed packet data.
The main features of SWAP are,
Now IrDA has a set of protocols covering all layers of data transportation, it also has some network management, security and interoperability designs., ,  Also, now IrDA is a standard on the Palm devices so its role in home networking would be essential in the future. IrDA protocols have IrDA DATA for data delivery and IrDA CONTROL for the controling aspect.
Figure 4 IrDA DATA – Hardware/Protocol Stacks
"IrDA DATA" defines a standard for an interoperable universal two way cordless infrared light transmission data port. Adapters now include the traditional upgrades to serial and parallel ports, plus Universal Serial Bus (USB) and Ethernet/Token Ring LAN point to point access.
IrDA Data Protocols consist of a mandatory set of protocols and a set of optional protocols. The mandatory protocols are listed below.
1) Physical IrDA Data Signaling,
- Range: Continuous operation from contact to at least 1 meter (typically 2 meters can be reached). A low power version relaxes the range objective for operation from contact through at least 20 cm between low power devices and 30 cm between low power and standard power devices. This implementation affords 10 times less power consumption. These parameters are termed the required maximum ranges by certain classes of IrDA featured devices and sets the end user expectation for discovery, recognition and performance.
- Bi-directional communication is the basis of all specifications
- Data transmission from 9600 b/s with primary speed/cost steps of 115 kb/s and maximum speed up to 4 Mb/s
- Data packets are protected using a CRC (CRC-16 for speeds up to 1.152Mb/s and CRC-32 at 4 Mb/s).
2) IrDA Link Access Protocol (IrLAP)
- Provides a device-to-device connection for the reliable, ordered transfer of data.
- Device discover procedures.
- Handles hidden nodes.
3) IrDA Link Management Protocol (IrLMP)
The optional IrDA Data Protocols are,
- Provides multiplexing of the IrLAP layer. Multiple channels above an IrLAP connection.
- Provides protocol and service discovery via the Information Access Service (IAS).
IrDA Control Protocols consist of a mandatory set of protocols.
1) IrDA Control Physical Signaling
2) IrDA Control MAC
- Distance and range equivalent current uni-directional infrared remote control units (minimum 5 meter range).
- Bi-directional communication is the basis of all specs.
- Data transmission at 75 kb/s at the top end
- The data is coded using a 16-Pulse Sequence multiplied by a 1.5 MHz subcarrier which is allocated for high speed remote control in IEC 1603-1 although this base band scheme has harmonics which can intrude upon other IEC bands.
- Data packets are protected with a CRC (CRC-8 for short packets and CRC-16 for long packets). The physical layer is optimized for low power usage and can be implemented with low-cost hardware.
- Enables a host device to communicate with multiple peripheral devices (1:n) and up to 8 peripherals simultaneously.
- Ensures fast response time (13.8 ms basic polling rate) and low latency.For Asymmetric MAC
3) IrDA Control LLC:
- Provides for dynamic assignment and re-use of peripheral addresses.
- Scheduling of media access is actually embeded in the HID LLC.
- Provides reliability features that provides data sequencing and retransmission when errors are detected.
- Works with an HID-IrDA Control Bridge to enable the link control functions of USB-HID.
In general, the following requirements need to be paid attention to during the design of NITS including home networks, "
In order to faciliate the developing of software applications over home network, HomeAPI is now setting up to simplify and reduce the efforts in both migration and interoperation.  The unified API would be an efficient way to establish a uniform communication across the home network. Combining the latest home networking technology and object model together, it will bring a new generation of sevice definition and application development. It uses a property-based OLE automation object model and extensible home device models to support run-time autonomous operation. The key features of HomeAPI are,"
Nortel's DPL-1000 is targeted at telecommunication service companies like ISP. X-10 is now a de facto standard for home automation, so it is now trying to push into home networking sector. Lucent puts much attention to WaveLAN and RF products. Traditonal control networking companies are quickly tranfering their products into home networking market. Echelon and Intelogis are now presenting into this market. Wireless vendors like Sharewave, Enikia and SOHOWare are starting to sell Home RF based products. The IrDA market is still primarily in the peripheral interconnection stage, hopefully there will be some products for home networking in near future.
The Universal Plug and Play, USB technologies are also essential technologies to support home networking.
Overall, home networking market is still in its early age. Considerate user education and solution development needs some time. ~
AM - Amplitude Modulation
API - Application Programming Interface
CAL - Common Application Language
CSMA - Carrier Sense Multiple Access
DPSK - Differential Phase Shift Keying
DSSS - Direct Sequence Spread Spectrum
FHSS - Frquency Hopping Spread Spectrum
FSK - Frequency Shift Keying
HomePNA - Home Phone Networking Alliance
HomeRF - Home Radio Frequency Working Groupd
IrDA - Infra-red Data Association
ISM - Industrial, Scientific and Medical
MAC - Media Access Control
NITS - Networks In The Small
OLE - Object Linking and Embedment
PHY - Physical
POTS - Plain Old Telephony System
PSTN - Public Switched Telephone Network
RF - Radio Frequency
SWAP - Shared Wireless Access Protocol
TDMA - Time Division Multiple Access
UTP - Unshielded Twisted Pair
USB - Universal Serial Bus
WLAN - Wireless Local Area Network
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Last Modified @ 11/14/1999