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Making it all Wireless

As you’ve probably noticed, wireless products are extremely popular. Cordless phones and wireless remote controls have been around for decades, but now it seems that anyone over 12 years old has a mobile phone or wireless laptop hanging around. So many products have become wireless that the battery manufacturers must be jumping for joy and landing in piles of money. So, what is the difference between one wireless technology and another? Here’s a really rough breakdown.

Wireless Protocols

Wi-Fi / 802.11 a, b, g, n / Wireless Ethernet

802.11x uses unregulated radio signals to transmit large amounts of data quickly. It is very popular for home and business computer networks and can be secured using various techniques including complex encryption, making it a very good method for portable devices to reach the internet. The protocol is mesh-networking capable (messages hopping along several intermediate nodes to reach a destination as opposed to point-to-point). The radio signals utilized for this technology penetrate walls, which is useful when line-of-sight communication is not possible.

From a design standpoint, however, this is a more complicated solution than other wireless protocols. The associated electronics are complex and draw a lot of power, so wi-fi can be expensive and battery intensive for a handheld device.

Table 1 Different flavors of the 802.11 wireless protocol

802.11a 54 Mbps 5 Mhz High cost, low range
802.11b 11 Mbps 2.4 Mhz Good range, cheap, and popular
802.11g 54 Mbps 2.4 Mhz Great range, faster
802.11n 100 Mbps 2.4 & 5 Mhz Best range, fastest, lowest signal interference

Proprietary (e.g. Radiotronix Wi232)

Some companies create their own radio-frequency (RF) wireless protocols. Lots of point-to-point “garage door” protocols, for example. This is because it is very easy from a design standpoint.

  • Point-to-point, not mesh
  • Low power
  • Long range
  • Low data rate

ZigBee

ZigBee is an open protocol used to create a network of devices that can communicate with each other. The premise is similar to wi-fi, but it has optimized performance for different applications such as battery-powered handhelds. Example products are building controls and sensors. Performance features include

  • Extremely low data rate (for individual sensors or switches)
  • Low power
  • Long range (~100 yards)
  • Mesh networking capable (transmitting data through various nodes to the central control unit which greatly extends the range of a network)

Bluetooth

Bluetooth is an open radio-frequency protocol for transmitting data over short distances, generally less than 30 feet, although the protocol can be used for longer ranges with higher power output. It is most useful for connecting multiple devices together such as laptops with mice, remote controls, and mobile phones.   Bluetooth is designed as a low configuration, easy to use option.  The newest revisions of Bluetooth are also opening much higher speed data transmissions and even lower power usage.

900Mhz, 2.4Ghz

These are just frequencies, but people might call their protocol as such to identify that they use RF signals instead of infrared or that they are not part of the wi-fi platform.

  • 900 Mhz is old school, longer range / lower data rate.
  • 2.4 Ghz is new school, shorter range / higher data rate / may interfere with nearby wi-fi networks

Infrared (IR or IrDA)

IR is most popular with remote controls because it is cheap and easy to implement. This is a line-of-sight technology, meaning that the infrared light emitted from the remote must travel to the sensor to transmit the command. It can be reflected around a room, but not from room to room. For this reason, it is also used in security systems, position sensors, and level switches to detect localized movement via interference with the line of sight.

IrDA was once used to transmit data on Palm Pilots and laptops for a time, but it has a very low data rate compared to current competitive technologies and a very short range.

What makes wireless cheap or expensive?

Cheap to develop

  • Point-to-point, one-way, garage door opener.
  • Messages sent are simple, and all of the same type and purpose. A layman could easily define each message in English in a spec.
  • A network that doesn’t need to be “managed” (think about devices joining and leaving, think about multiple networks in same air space, think about distinguishing IDs of senders and receivers)

Expensive

  • Mesh networking
  • Network reconfigurable (by user or automatic – both a pain.)
  • Variety of message types and purposes
  • Two-way communication or authentication
  • Pushing the limits of range or power. Or, lack of line-of-sight.
  • Application is sensitive to interference or garbled messages
  • High speed data access, or continuous network access


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