One of the biggest trends in the electronics market is adding wireless functionality and connectivity to products. Products as varied as electric, gas or water meters, home security systems, TV remote controls or exercise equipment have added wireless functionality.

This is partly due to convenience for the user such as a wireless remote control that can operate anywhere in a house as opposed to a line of sight (LOS) infrared remote.

Another driving factor is avoiding the expensive rewiring that would be required to retrofit a home with a security system. Other trends such as automated meter reading (AMR) or advanced metering infrastructure (AMI) rely on low power protocols where battery lifetime can be measured in years.

In this three part series we will provide an overview of wireless network protocols, but will focus on ZigBee, 802.15.4 and compare it with one example proprietary protocol, SimpliciTI, all designed for low power applications.

In Part 1, here, we will review network basics including common networking terminology, the Open Systems Interconnect (OSI) network model and considerations to keep in mind when deciding on a network for a particular application.

In Part 2, a set of network selection criteria will be presented upon which the comparison of the three protocols will be framed. Finally, in Part 3, the 802.15.4, ZigBee and the proprietary SimpliciTI protocols will be described in detail and some specific examples will be described,  using these selection criteria to determine the optimum network for particular applications.

The list of released wireless network protocols is a long one. The following is just a partial list of network protocols that are available:

* Standards-based protocols such as WiFi (802.11b), Bluetooth, ZigBee, ZigBee Pro, 802.15.4, RFID and Wireless USB

* Proprietary protocols from silicon vendors, third parties, or what this paper calls "do-it-yourself" networks, built and controlled completely by the company that uses the network in their own products.

Figure 1 below shows a table with various protocols, the applications these are focused on, typical resource requirements and so forth. When comparing the low power networks such as ZigBee/802.15.4 against other protocols, it is important to focus on the key features of a low power wireless network that distinguishes it from its peers: low data rates, reduced operating range, a low frame overhead, power management considerations built directly into the protocol, and low complexity.

Each design consideration serves as a basis for the end goal of reducing the power consumption per individual node on the network. As the figure shows, this is a perfect fit to the applications within environmental monitoring and control markets in which the devices would be optimally battery powered and be offered at price points considerably lower than hardware capable of supporting larger, more complex protocols.

Figure 1--Wireless protocols parameters and focus applications (courtesy of ZigBee Alliance)

Low power networks were designed chiefly to provide wireless connectivity between products with battery lifetime in months or years. In most low power wireless systems, the element that uses the most power is the radio transmitting and receiving data. It is, therefore, extremely important to minimize the power used by the radio to maximize battery life.

Since the distance a signal can be transmitted and received is a function of the power input to the antenna, the wireless network range between individual nodes is typically limited. Wireless protocols also tend to be less complex to reduce computational overhead and the need for larger memories, resulting in lower cost.