Andreas Ziller

Reliable Broadcast Mechanism for the IEEE 802.16 Mesh Extension

The simultaneous transmission of data messages to a group of neighbors forms the basis for many essential services in wireless ad hoc and mesh networks, for example to communicate link status information or to assist route discovery. Despite the fact that communication on a wireless medium is inherently of broadcast nature, there exist situations, where data broadcasting is non-trivial. In particular, reservation-based medium access control (MAC) schemes such as employed in the optional mesh mode of the IEEE 802.16 standard are optimized with respect to maximizing the number of concurrent unicast transmissions. While broadcast control messages are supported in the standard, no mechanisms are specified to efficiently and reliably schedule broadcast data messages. We present an extension to the IEEE 802.16 standard, which enables a reliable, reservation-based broadcast method for usage within the mesh mode. We thoroughly analyze the performance of our mechanism vs. broadcast as unicast - currently the only feasible method to deliver broadcast data according to the standard. Our results indicate the superior performance of our scheme, i.e. a significant gain in broadcast efficiency as well as in broadcast reliability.

A packet-level adaptive forward error correction scheme for wireless networks

Especially for synchronization-critical wireless networks like ultrawideband impulse radio (UWB-IR), data packets are lost not only due to single bit errors in the payload but also to a large degree because of synchronization errors or preamble failures. Current FEC codes only address bit errors inside a packet. Packets that are lost because of errors in preambles or headers can only be recovered on packet level. In this Paper we propose a low-complexity adaptive packet-level FEC and prove by simulation that it can reduce packet loss with very small overhead.