We analyze this hard non-convex optimization problem, and obtain a dual form consisting of a series of sub-problems. The sub-problem demonstrates the functionalities of the protocol layers and their interaction. We show that the routing problem may be solved by a shortest path algorithm. In the case of Ultra Wide Band (UWB) networks, the power adaptation & scheduling problem is simplified and may be solved. Thus, an algorithmic solution to the joint problem, in the UWB case, is developed. Comparison of results with the previous information theoretic capacity results on UWB networks [1], demonstrates the importance of this cross-layer optimization framework. For more information, please see the following papers. In particular, [4] validates the interesting claim made in [1], that the capacity of UWB networks increases with node density.

[2] R. Negi, and A. Rajeswaran, "Scheduling and power adaptation for networks in the Ultra Wide Band regime," Proc. IEEE Globecom, pp. 139-145, Dallas, USA, Dec. 2004.

[3] A. Rajeswaran, Gyouhwan Kim, and R. Negi, "A scheduling framework for UWB and cellular networks," in Proc. IEEE/ACM Broadband Networks, pp. 386-395, San Jose, Oct. 2004.

[4] Gyouhwan Kim, A. Rajeswaran, and R. Negi, "Joint power adaptation, scheduling and routing framework for wireless ad-hoc networks," IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), June 2005.

For more information, please visit: Yaron Rachlin's home page

In [1], we considered a joint queuing/coding system (a queue + server followed by an encoder) that operates on a wireless link. The application of interest was a delay sensitive application which has a hard constraint on the delay. A bit error occurs if either the bit was decoded incorrectly (error due to channel noise) or the bit experienced excessive delay (error due to delay violation). Formally, the problem statement was, given the joint queuing/coding system and a certain maximum tolerable delay, design the system such that the probability of error is minimized. For simplicity, the paper considered a memoryless server model, i.e. the instantaneous server capacity was chosen to be the function of only the current CSI. Thus, the design of the system involved finding the right server capacity function. It was shown through simulations that the joint queuing/coding system performed better than the pure coding system in a variety of scenarios.

For more information, please visit: Satashu Goel's home page

[2] R. Negi and S. Goel, "Secret Communication using Artificial Noise," to appear in Proc. IEEE Vehicular Tech. Conf, Dallas, Fall 2005.

[3] S. Goel and R. Negi, "Secret Communication in Presence of Colluding Eavesdroppers," to appear in Proc. IEEE Military Communication (MILCOM), Atlantic City, Fall 2005.