With current IEEE 802.11 WLANs two problems arise
- The physical layer data rates of up to 54MBit/s are not reached on higher layers.
- Unbounded latencies complicate the transmission of high-quality video streams.
Simulations have shown that crosslayer optimization is a promising approach to deal with these problems [3, 4]. Following this approach the focus of this student research project is to extend 802.11a WLANs with a cross-layer oriented optimization scheme. To show the realizability and evaluate the performance the scheme is implemented on the SORBAS real time wireless testbed.
This student project group, consisting of 11 students, is tackling these problems in the academic year 2005/2006.
The development of the 802.11a extention is done by the following working groups:
- 802.11a PHY extension:
The task of this group is to provide channel state information and per OFDM subcarrier adaptive rate selection.
- 802.11a MAC extension:
The 802.11a MAC is extended by functions to signalize channel state information and channel allocation.
- Cross-layer algorithm:
This group is focussed on the implementation and evaluation of cross-layer optimization algorithms.
- SDR integration:
The integration of the SORBAS test bed, e.g. by developing a Linux driver, and the provision of a developement workflow is the task of this group.
Publications and released material
 S. Simoens, P. Pellati, J. Gosteau, K. Gosse, and C. Ware. The evolution of 5GHz WLAN toward higher throughputs. IEEE Wireless Communications, 10(6):1536-1284, December 2003.
 Y. Xiao and J. Rosdahl. Throughput and delay limits of IEEE 802.11. IEEE Communications Letters, 6(8):355357, August 2002.
 J. Gross, H. Karl, F. Fitzek, and A. Wolisz. Comparison of heuristic and optimal subcarrier assignment algorithms. In Proc. of the 2003 International Conference on Wireless Networks, June 2003.
[ S. Valentin, J. Gross, H. Karl, and A. Wolisz, "Adaptive scheduling for heterogeneous traffic flows in cellular wireless OFDM-FDMA systems", In Proc. of the 10th IFIP international conference on Personal Wireless Communications, August 2005. PDF
 Signalion GmbH. SORBAS 101: signalion software radio based prototyping system, 2005.