SWAP defines a common interface specification that supports wireless voice and data services in the home. It was designed to operate with the Public Switched Telephone Network (PSTN) and the Internet.

HomeRF Wireless

Steven Totolo

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By Steven Totolo

SWAP defines a common interface specification that supports wireless voice and data services in the home. It was designed to operate with the Public Switched Telephone Network (PSTN) and the Internet.

Steven Totolo is President of Total Voice Control, a manufacturer of CEBus products and a member of the CABA Standards Committee. He can be reached at (613) 795-7117; fax (613) 737-3523;
email: steven.totolo@home.com

On July 20, 1998, the HomeRF™ Working Group (HRFWG) announced to the world the completion of the first phase of its wireless communication specification for the home called SWAP. The Shared Wireless Access Protocol, version 0.5 will be updated to a final version by the end of 1998 with products to be presented in the Fall of 1999.

Currently, there are in excess of 44 companies in the HRFWG that manufacture consumer electronics (CE), PCs and communications equipment. Core members are Compaq, Ericsson Enterprise Networks, Hewlett-Packard, IBM, Intel, Microsoft, Motorola, Philips Consumer Communications, Proxim and Symbionics. Other members include Cisco Systems, Harris Semiconductor, Intellon, National Semiconductor, Nortel, Rockwell Semiconductor and Samsung. HRFWG has defined the following mission:

"To bring about the existence of a broad range of interoperable consumer devices by establishing open industry specifications for unlicensed RF digital communications between PCs and CE devices anywhere in and around the home"

A Japanese working group was also established to address Japanese regulations. Known as the HRFWG-J, it includes most electronics manufacturers in Japan such as Casio Computer, Panasonic, NEC and Sharp Corporation to name a few.

The HRFWG expects the specifications will advance homeowners from around the world into a future seen only on the Jetsons. " For example", says Ben Manny, chairman of the HRFWG and engineering manager for residential networking at Intel Architecture Labs, "with HomeRF technology, users will be able to spontaneously access their PCs from anywhere in the house or yard". By using HomeRF, PC users will have the mobility to roam around their own home without the limitations of where the next LAN connection may be.

This could also lead to many other possible uses:

  • accessing the Internet from anywhere in the home or yard from PCs or portable display devices;
  • sharing computer peripherals such as modems and printers in multi-PC homes;
  • sending incoming telephone calls to multiple cordless handsets, FAX machines and voice mailboxes;
  • playing multi-player games from multiple locations; and,
  • controlling home security systems, and heating and air conditioning systems from anywhere in and around the home.

Ben continues, "we believe that by establishing a wireless communications specification for the home, a new industry will be created that results in unprecedented interoperability between intelligent devices in the home."

SWAP defines a common interface specification that supports wireless voice and data services in the home. It was designed to operate with the Public Switched Telephone Network (PSTN) and the Internet. Operating in the 2.4 GHz band available worldwide, SWAP uses digital frequency hopping spread spectrum radio technology with extensions of the existing cordless telephone (Digital Enhanced Cordless Telephone or DECT) and wireless Ethernet (IEEE 802.11) protocols. It supports both a Time Division Multiple Access (TDMA) service to provide real-time voice and other time critical services, and Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) service for high speed packet data such as TCP/IP.

Here is a summary of the system parameters:

  • Frequency Hopping : 50 hops/second
  • Frequency range:2.4 GHz ISM band
  • Transmission power:100mW
  • Data Rate:1 Mbps using 2FSK modulation (2 Mbps using 4FSK modulation)
  • Range:Covers typical home and yard
  • Support stations:Up to 127 devices/network
  • Voice connections:Up to 6 conversations
  • Data security:Blowfish encryption algorithm (1 trillion codes)
  • Data compression:LZRW3-A algorithm
  • 48-bit Network IDEnables concurrent operation of multiple co-located networks

The network can operate in two modes, as an ad hoc network or as a managed network. In the ad hoc mode, all devices have equal access controlling the network, providing data communications among themselves. Such devices could include home automation products such as light switches and load control centres. The managed mode provides time critical and interactive voice communication controlled by a Connection Point (Internet access, cordless phones). This Connection Point could be a PC that provides a gateway to the PSTN and connects to devices through interfaces such as Universal Serial Bus (USB) or a HomeRF interface card/modem. The Connection Point could also be used to support power management to prolong the battery life of devices by scheduling wakeup and polling.

In the future, the group is planning to form committees to plan a version of SWAP to address wireless multimedia (SWAP-MM) and a lower cost option (SWAP-LITE).

This protocol and others are documented and updated regularly in the CABA Quarterly and in the CABA Standards Committee that meets quarterly to discuss issues that affect the business of members in the automation industry. The committee is open to all CABA members interested in up-to-date issues involving communications standards, wiring practices, and regulations.

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