Technology Update /
802.15 aims to secure wireless PANs
 
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Wireless network standards such as IEEE 802.11b and Bluetooth traditionally have focused on quality of service and security, but they either lack sufficient industry support or impose requirements that are too costly to satisfy emerging demand for wireless communication.
The IEEE 802.15 Working Group is defining new standards for use in wireless personal-area networks (PAN). In addition to the traditional concerns of QoS and security, it is addressing power consumption, complexity, size and cost constraints. The result will be specifically tailored for short-range, low-cost wireless devices.
How it works
The working group is attempting to overcome three primary challenges: balancing cost with range and bandwidth, offering coexistence with other wireless devices and providing security in roaming environments.
802.15 wireless PAN solutions
The 802.15 standard defines specifications for media access control (MAC) and physical layers for wireless devices in a wireless PAN. The physical layer transmits in one of several channels in the 2.4-GHz range. The MAC specifications define the format of messages and the procedure for secure establishment of wireless PANs.
A wireless PAN consists of a dynamic group of less than 255 devices that communicate within about a 33-foot range. Unlike with wireless LANs, only devices within this limited area typically participate in the network, and no online connection with external devices is defined.
One device is selected to assume the role of the controller during wireless PAN initialization, and this controller device mediates communication within the WPAN. The controller broadcasts a beacon that lets all devices synchronize with each other and allocates time slots for the devices.
Each device attempts to join the wireless PAN by requesting a time slot from the controller. The controller authenticates the devices and assigns time slots for each device to transmit data. The data may be sent to the entire wireless PAN using the wireless PAN destination address, or it may be directed to a particular device.
The 802.15 working group is defining different versions for devices that have different requirements. 802.15.3 focuses on high-bandwidth (about 55M bit/sec), low-power MAC and physical layers, while 802.15.4 deals with low-bandwidth (about 250K bit/sec), extra-low power MAC and physical layers.
The emphasis on minimizing cost, complexity and chip size is permeating all aspects of the standardization process. The selection criteria for power management, security algorithms and QoS all include consideration of these features. The short-range nature of communication in a wireless PAN also means reduced transmission power and cost.
The security requirements for 802.15 networks are different from more static networks because of the dynamic nature of wireless PANs. As a result, the working group is looking into specifying public-key solutions for authentication and key exchange, letting devices that have not been in contact previously establish secure communications without revealing any secret keying material.
Once the devices have been authenticated, each device in the wireless PAN shares common group (symmetric) payload protection keys for encryption and data integrity. Devices also may use the authentication mechanism to establish two-party secure subnetworks.
Another issue still facing the working group before completion of the standards is coexistence with other types of wireless devices and among the different types of 802.15 devices. There are several wireless standards that specify transmission in the 2.4-GHz range, and in some cases they interfere with each other.
Despite the remaining challenges, the working group expects to resolve the outstanding issues and provide complete, cost-effective, low-power solutions in the wireless device market.
The standards are scheduled to be completed in the third quarter of this year.
Related Links
Related links
Singer is principal engineer for NTRU Cryptosystems. He can be reached at asinger@ntru.com.
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