Tight approximation algorithms for maximum general assignment problems
SODA '06 Proceedings of the seventeenth annual ACM-SIAM symposium on Discrete algorithm
MobiSteer: using steerable beam directional antenna for vehicular network access
Proceedings of the 5th international conference on Mobile systems, applications and services
Scheduling algorithms for multi-carrier wireless data systems
Proceedings of the 13th annual ACM international conference on Mobile computing and networking
Maximizing a Submodular Set Function Subject to a Matroid Constraint (Extended Abstract)
IPCO '07 Proceedings of the 12th international conference on Integer Programming and Combinatorial Optimization
Cross-layer wireless bit rate adaptation
Proceedings of the ACM SIGCOMM 2009 conference on Data communication
On the effectiveness of switched beam antennas in indoor environments
PAM'08 Proceedings of the 9th international conference on Passive and active network measurement
Uplink cross-layer scheduling with differential QoS requirements in OFDMA systems
EURASIP Journal on Wireless Communications and Networking - Special issue on adaptive cross-layer strategies for fourth generation wireless communications
FERMI: a femtocell resource management system forinterference mitigation in OFDMA networks
MobiCom '11 Proceedings of the 17th annual international conference on Mobile computing and networking
Cross-layer optimization for OFDM wireless networks-part I: theoretical framework
IEEE Transactions on Wireless Communications
Grassmannian beamforming for multiple-input multiple-output wireless systems
IEEE Transactions on Information Theory
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Beamforming is a signal processing technique with numerous benefits. Unlike with omni-directional communications, it focuses the energy of the transmitted and/or the received signal in a particular direction. Although beamforming has been extensively studied on conventional systems such as WiFi, little is known about its practical impact on OFDMA femtocell deployments. Since OFDMA schedules multiple clients (users) in the same frame (in contrast to WiFi), designing intelligent scheduling mechanisms and at the same time leveraging beamforming, is a challenging task. Unlike downlink, we show that the integration of beamforming with uplink scheduling projects an interesting trade-off between beamforming gain on the one hand, and the power pooling gain resulting from joint multi-user scheduling on the other hand. This, in turn, makes the uplink scheduling problem even hard to approximate. To address this, we propose algorithms that are simple to implement, yet provably efficient with a worst case guarantee of half. We implement our solutions on a real WiMAX femtocell platform integrated with an eight-element phased array beamforming antenna. Evaluations from both prototype implementation and trace-driven simulations show that our solution delivers throughput gains of over 40% compared to an omni-directional scheme.