Algorithms that jointly allocate resources across different layers are envisioned to boost the performance of wireless systems. Recent results have revealed that two of the most important parameters that critically affect the resulting cross-layer designs are channel- and queue-state information (QSI). Motivated by these results, this paper relies on stochastic convex optimization to develop optimal algorithms that use instantaneous fading and queue length information to allocate resources at the transport (flow-control), link, and physical layers. Focus is placed on a cellular system, where an access point exchanges information with different users over flat-fading orthogonal channels. Both uplink and downlink setups are considered. The allocation strategies are obtained as the solution of a constrained utility maximization problem that involves average performance metrics. It turns out that the optimal allocation at a given instant depends on the instantaneous channel-state information (CSI) and Lagrange multipliers, which are associated with the quality-of-service (QoS) requirements and the operating conditions of the system. The multipliers are estimated online using stochastic approximation tools and are linked with the window-averaged length of the queues. Capitalizing on those links, queue stability and average queuing delay of the developed algorithms are characterized, and a simple mechanism is devised to effect delay priorities among users.
Bibliographical noteFunding Information:
Manuscript received June 10, 2011; revised November 2, 2011, January 17, 2012, and March 25, 2012; accepted April 4, 2012. Date of publication April 20, 2012; date of current version July 10, 2012. This work was supported in part by the Spanish Ministry of Science and Innovation under Grant TEC2009-12098, by the Spanish Ministry of Education, under FPU Grant AP2010-1050, and by the National Science Foundation under Grant 0830480, Grant 1016605, Grant 0824007, and Grant 1002180. This paper was presented in part at the 2010 IEEE Global Telecommunications Conference, Miami, FL. The review of this paper was coordinated by Prof. Y. Cheng.
- Congestion control
- cross-layer design
- dynamic resource management
- network optimization
- stochastic optimization