Coordinated Dynamic Spectrum Management of LTE-U and Wi-Fi Networks

This paper investigates the co-existence of Wi-Fi and LTE in emerging unlicensed frequency bands which are intended to accommodate multiple radio access technologies. Wi-Fi and LTE are the two most prominent access technologies being deployed today, motivating further study of the inter-system interference arising in such shared spectrum scenarios as well as possible techniques for enabling improved co-existence. An analytical model for evaluating the baseline performance of co-existing Wi-Fi and LTE is developed and used to obtain baseline performance measures. The results show that both Wi-Fi and LTE networks cause significant interference to each other and that the degradation is dependent on a number of factors such as power levels and physical topology. The model-based results are partially validated via experimental evaluations using USRP based SDR platforms on the ORBIT testbed. Further, inter-network coordination with logically centralized radio resource management across Wi-Fi and LTE systems is proposed as a possible solution for improved co-existence. Numerical results are presented showing significant gains in both Wi-Fi and LTE performance with the proposed inter-network coordination approach.Comment: Accepted paper at IEEE DySPAN 201

MAC-PHY Cross-layer Techniques for Simultaneous Multiuser Communication in Wireless Networks

Layering in wireless networks provide clear abstractions to how various resources are managed for a particular communication link. However, the unpredictability of the wireless channel presents great challenge to these clear abstractions. Often, optimizations in these layers are not transparent to others. This creates a necessity to violate the modular approach and share crosslayer information to modify each layer\u27s functionalities, which eventually improves the overall performance of the network. In this thesis, novel MAC-PHY crosslayer protocols have been designed, implemented and evaluated. These protocols provide unprecedented gain in various aspects of a wireless network, by facilitating simultaneous multiuser communication. By harnessing the untapped potential of the various signal processing subsystems in the physical layer, these protocols are able to increase network throughput, make certain group communications faster and enable covert communication. Using reconfigurable hardware to expose physical layer information, improvement is achieved in higher layers. Furthermore, it is also important to modify the physical layer based on the feedback from higher layers. The two-way handshaking changes the conventional modular approach and allows implementation of simultaneous communication in wireless domain. To make the crosslayer techniques practical, this thesis presents clear implementation steps to embed these concepts as an extension to common wireless network protocols and evaluate those using practical experiments and radio measurements. Through these techniques we are able to show practical benefits from a mutable radio and a crosslayer approach to protocol design for next generation, high bandwidth wireless networks

A network-aware MAC and routing protocol for effective load balancing in ad hoc wireless networks with directional antenna

Use of directional antenna in the context of ad hoc wireless networks can largely reduce radio interference, thereby improving the utilization of wireless medium. Our major contribution in this paper is to devise a routing strategy, along with a MAC protocol, that exploits the advantages of directional antenna in ad hoc networks for improved system performance. In this paper, we have illustrated a MAC and routing protocol for ad hoc networks using directional antenna with the objective of effective load balancing through the selection of maximally zone disjoint routes. Zone-disjoint routes would minimize the effect of route coupling by selecting routes in such a manner that data communication over one route will minimally interfere with data communication over the others. In our MAC protocol, each node keeps certain neighborhood status information dynamically in order that each node is aware of its neighborhood and communications going on in its neighborhood at that instant of time. This status information from each node is propagated periodically throughout the network. This would help each node to capture the approximate network status periodically that helps each node to become topology-aware and aware of communications going on in the network, although in an approximate manner. With this status information, each intermediate node adaptively computes routes towards destination. The performance of the proposed framework has been evaluated on QualNet Network Simulator with DSR (as in QualNet) as a benchmark. Our proposed mechanism shows four to five times performance improvement over DSR, thus demonstrating the effectiveness of this proposal