Even if you had the most advanced wiring installed into your new home, you’d still appreciate the benefits of wireless networks. The biggest benefit comes with mobility – and the ability to use your notebook PC, touch screen tablet, or other device from anywhere in the house or yard, and without being tied to a wall outlet.
Do your taxes on the dining table; it’s that time again. Surf sports websites while sitting on the couch and watching the big game. Access auto repair information from the garage, or a gardening site from â€¦ the garden. That flexibility gets more important as battery powered Internet devices get smaller and more portable.
The cost of connecting PCs with radio waves instead of wires is now as low as $99 per system, and there are several technologies to choose from. But that’s the problem – too many to choose from. Since a confused market doesn’t buy, I’m dedicating this second HomeToys.com “mentor” article to positioning the three emerging wireless standards – Bluetooth, IEEE 802.11b, and HomeRF.
In my first article, “Future Proofing Your Home: Is It Possible?” I concluded that no-new-wires network technologies will rescue those of us who can’t retrofit our homes. Wireless networks may be the ultimate in these new technologies, but they cost more. Still, there are good reasons to use other networks in the same home.
Many home appliances are heavy and not at all portable. They don’t need wireless networks, and their metal cabinets would keep radio signals trapped inside anyway. Since there’s no phone line next to the refrigerator or dish washer, they can’t use phoneline networking, so appliances will probably network using power lines, while handheld devices will be wireless.
Unlicensed Wireless Frequencies
Starting in 1985, the Federal Communication Commission (FCC) let users operate wireless products without first requiring a license, as long as the products used the Industrial, Scientific and Medical (ISM) frequency bands. As shown below, more bandwidth (and performance potential) is available at higher frequency bands.
Â· 902 â€“ 928 MHz (26 MHz available)
Â· 2.4 â€“ 2.4835 GHz (83.5 MHz available, over 3 times as much)
Â· 5.725 â€“ 5.850 GHz (125 MHz available, nearly 5 times as much)
Frequency Modulation Terms
You may have noticed that new cordless phones use digital spread spectrum technology. This makes them less susceptible to electronic eavesdropping and interference. For data networks, these characteristics result in fewer errors that would otherwise cause retransmissions and degrade performance.
Spread spectrum is a signal modulation technique that “spreads” a signals power over a wide frequency band.
Frequency hopping spread spectrum (FHSS) works much like the name implies. The data is modulated with a carrier signal that hops between different frequencies in a specific sequence. Because all devices on FHSS networks must know the hopping pattern and register with the network, FHSS is quite secure and less prone to interference from devices like microwave ovens. FHSS is the modulation scheme used by three popular wireless networking standards: Bluetooth, HomeRF and OpenAir.
Direct sequence spread spectrum (DSSS) is another modulation scheme used by the IEEE 802.11b standard.
Design Trade-offs of Emerging Wireless Standards
When comparing these standards, let’s contrast their design points with the primary focus on the range, but realize that designers have to deal with other trade-offs too.
1. Cost â€“ Addressing Range and other features can add cost, although everyone wants to keep costs low.
2. Data Rate â€“ Raw speed of the physical transport is a function of frequency bandwidth and modulation efficiency.
3. Aggregate Capacity â€“ Actual performance is affected by network protocol overhead and architecture.
4. Interference â€“ Tolerance to electrical noise from other devices emitting RF signals in the same frequency range improves performance and security.
5. Security â€“ Protection against eavesdropping can be inherent in the modulation scheme and/or added with encryption software.
6. Power Consumption â€“ Low power improves battery life and generates less heat.
7. Signal Strength â€“ The amount of energy emitted effects the range, but since too much power can be unhealthy to humans, limits are set.
8. Range â€“ A small coverage area is ideal for wearables and proximity detection, but a much larger area is needed for enterprise office or campus settings.
Mobile Cell Phone
Voice & Data
~1 Mbps (1.6Mbps raw)
~4 Mbps (11Mbps raw)
Personal Area (<30 ft.) House & Yard (150 ft.) Office Bldg/Campus Power Low Power Mode Low Power Mode More Power Required Topology Multi point-to-point Peer-Peer Distributed Ctrl. Points Phone support 3 lines 4+ Lines (DECT) Requires IP Telephony Phy. Interface 2.4 GHz FHSS radio 1600 hops/sec 2.4 GHz 802.11 FHSS 50 hops/sec 2.4 GHz DSSS MAC Layer Non-IP base OpenAir & DECT IEEE 802.11 Certification Various Purdue's PlugLab WECA For Info: www.bluetooth.com HomeRF Resource www.wirelessethernet.com Bluetooth Bluetooth is a low power, short-range, Wire Replacement designed for wearable devices like Ericsson's wireless headset. In Europe it's against the law to drive while holding a cellular phone, so with Ericsson's headset and a Bluetooth phone, you only need to say "answer" or "call home" to make the connection, even though your phone is still in a briefcase or purse. Bluetooth will also let your phone access a large contact list in a PDA. And your notebook PC will access the Internet through a cellular phone that's still on your belt. Bluetooth is optimized for the low power radio transceivers that are ideal for personal devices. The resulting small range is good for proximity detection, but since the signals aren't strong enough to penetrate walls and floors or cover an entire house, Bluetooth is not well suited for wireless LANs. Although it is possible to design Bluetooth devices with more powerful transceivers to cover more distance, I'm not in favor of extending the technology in that manner since using a phone with such high power might be unsafe, and there are other technology better suited for that purpose. With over 1,000 members of the Bluetooth SIG, it seems obvious that the standard will be wildly successful and included in all kinds of personal devices. Contributing to the high membership, however, is the fact that there's no fee to join. IEEE 802.11b 802.11 is a subcommittee of the relatively slow and arduous IEEE standards process. There are actually three 802.11 standards, covering FHSS, DSSS and infrared technologies. These standards are now being extended with 802.11b (a higher data rate version at 2.4 GHz) and 802.11a (a future high rate version in the 5 GHz band). Home wireless networking products based on 802.11b are just now coming to market, with the most notable example being Apple's AirPort, which uses radio technology from Lucent. The FHSS and DSSS versions of 802.11 were designed for large enterprise multi-story office buildings or multi-building campus settings, with the ability to roam between wireless "control points" that are wired into an Ethernet network forming overlapping "micro-cells." Robust 802.11 technologies let workers freely roam between offices, meeting rooms, and public spaces while remaining connected. But this increased network function and complexity adds to the cost. 802.11b is an enhancement that is advertised as having 11 Mbps performance that matches that of wired Ethernet. But that claim is a bit misleading, since the real throughput closer to 4-5 Mbps -- half the speed of 10baseT Ethernet and far slower than 100baseT or Gigabit Ethernet networks where companies may use a switch for dedicated performance instead of a shared network hub. Still, 802.11b provides an important speed improvement over previous generations, and this is especially important in the office environment where dozens of employees must share the network. The home environment is quite different, with fewer PC users, a need for consumer price points of about $100 (or less) per system, and with no need for roaming if the range of a single transmitter can cover the whole house. Lucent eliminated the ability to roam, thus simplifying the design for Apple's Airport, thus helping to get costs into the $99 price range. At the same time, Apple designed its radio antenna into their PC systems, thus hiding some of the cost. Even with these efforts, it's not clear if Apple is making a profit at the $99 price point. But they've surely sent a clear message - that wireless networking is getting affordable. HomeRF Rather than force-fit a particular wireless technology into the home environment, the HomeRF Working Group took a different approach. They started with a keen understanding of the market requirements, including consumer price points, home-sized coverage area, high security for dense multi-dwelling units, and the need for interference immunity from microwave ovens. There was one more important requirement - the ability to integrate cordless phones with computers. A PC could significantly enhance the capabilities of phones, acting as answering machine and home PBX. And phones could become speech I/O peripherals for running PC and Internet applications. But possibly more important is the potential of bringing worldwide standards to the cordless phone market, which already outsells wired phones two to one, even though they cost twice as much. Europe already has the Digitally Enhanced Cordless Telephone (DECT) standard, but it uses a 1.9 GHz frequency band that's not available in the rest of the world. So think of HomeRF as combining a wireless LAN with a 2.4 GHz version of DECT which can be used anywhere in the world. With a worldwide standard, Siemens phones might interoperate with Sony phones, Panasonic phones, or models made by specialty companies (motorcycle phone, Mickey Mouse, etc.). Faster 2.4 GHz Networks HomeRF is the organization. SWAP (Shared Wireless Access Protocol) is the technical specification that has become the emerging standard for home wireless networking. At 1.6 Mbps, SWAP is not as fast as the latest version of 802.11, but don't let that deter you. This industry has a history of leapfrog technologies, so wait until the next hop. Just as 802.11b is faster than previous generations and is backwards compatible, a future version of HomeRF's SWAP could add similar performance improvements for the home market. A proposed rule change by the FCC (docket No. 99-231) will effect some cordless phones and nearly all wireless LAN equipment. The change would let FHSS radios take longer hops. In typical "leap frog" fashion, SWAP would then be able to operate at speeds up to 11 Mbps, although actual throughput would be more like 6-7 Mbps. In exchange for the added speed that might otherwise interfere with other wireless networks, manufacturers would be required to cut transceiver power. This might normally decrease the effective range, but improved semiconductor technology should compensate. A second FCC rule change would put pressure on makers of 2.4 GHz DSSS hardware that could require some 802.11b equipment to be retested or replaced. Understandably, the 802.11b camp objects to the ruling. They suggest that it will cause interference problems, but the HomeRF group argues that the lower power levels would mitigate any interference problem. Wireless Multimedia Networks Even while SWAP is getting established, the 100+ member HomeRF group is looking further into the future, by defining market requirements for advanced multimedia. The fairly near term (1-2 years) need is for simultaneous distribution of multiple channels of standard definition Digital TV signals throughout the home. A longer-term need is for high definition DTV, and both of these objectives may take the group into new modulation schemes and the 5 GHz frequency bands that are not compatible with SWAP. That would be a market driven design trade-off. To date, no HomeRF decisions on a wireless multimedia have been made, and the group has seen working demonstrations and expects to hear many technology proposals before selecting anything. It's good to see that they are not wedded to a specific technology. Ultra Cheap Wireless Networks Both the Bluetooth SIG and the HomeRF Working Group expect radio component costs to fall to $5 within a few years, down from $20-30 today. But that's not good enough for a $5 computer mouse, a $7 smoke alarm, home appliances or kid's toys. So HomeRF is working with the Bluetooth SIG and companies like Lego, Mattel Toys, Frigidaire, and Whirlpool to drive costs well below $5 with radio technology that again may not be compatible with SWAP. Conclusion Many industry leaders are participating in all three wireless networking initiatives, and not just because they are hedging their bets. The market development guys understand the proper fit and positioning of each technology and know they must all coexist. Since a wide variety of portable devices will move around and into each other's space, the network standards must interoperate, so these companies are working on ways to allow this. In contrast is the myopic vision of a few engineers in narrowly focused companies who are so wedded to their own inventions that they are blind to alternatives. When they force-fit their products and technologies where they don't belong, they cause religious standards wars and unwittingly confuse the market, possibly offering new meaning to Disconnected Connectivity. The first, and Bigger Picture, view is better for the industry and leads to a very positive overall outlook for all.