We propose a hybrid approach for conference applications for Named-Date Networks (NDN). This hybrid approach combines a participant-driven, distributed server-based approach for conference control and management with a server-less approach for media forwarding. The participant-driven, distributed server-based approach provides robust and efficient conference control and management that is resilient to single point of failure and can scale dynamically with any conference size. The server-less media forwarding eliminates traffic concentration and congestion in the network. We have carried out experiments using XMPP-based conference tools over CCNx and have successfully built the media forwarding for two conference tools (audio and whiteboard) on Android platform. This hybrid approach leverages NDN to support robust and efficient conference applications.

Multi-antenna systems can provide greater throughput and range coverage than traditional single antenna systems. A key aspect of exploiting this new physical layer (PHY) is rate adaptation, which consists of finding the best rate for sending data packets. Unlike rate adaptation in single antenna systems, nodes have many choices apart from adapting different modulation types, and these choices include using spatial multiplexing or transmit diversity, types of guard intervals, and channel width. We present an evaluation and implementation of a new rate adaptation scheme for multi-antenna systems applicable to off-the-shelf wireless cards. Our rate adaptation scheme, rate adaptation for multi-antenna systems (RAMAS), is simple and practical, and eliminates the complexity of the rate adaptation approaches proposed for IEEE 802.11n in the recent past. Extensive experimental evaluation is used to show that RAMAS performs consistently better than many current IEEE 802.11n rate adaptation schemes with much less complexity, and that RAMAS is especially efficient in multi-user and interference-laden environments.

Rate adaptation plays a central role in the efficiency of data transmissions in wireless networks. Due to the complex physical-layer effects of wireless links, including interference, attenuation, and multi-path fading, designing a rate adaptation algorithm that performs well in most scenarios is a challenging problem. We present the Multi-rate Adaptation with Interference and Congestion Awareness (MAICA) scheme, which is compatible with existing 802.11 implementations and relies only on acknowledgment packets for its operation. Extensive simulations, analytical model, and real-world experiments are used to show that MAICA consistently performs better than prior rate adaptation schemes used to date, especially in dense and congested wireless networks.

In this paper, we present a collision-free asynchronous multi-channel access protocol for Ad Hoc wireless networks using a single transceiver. Our protocol, dubbed AMMAC for Asynchronous Multi-channel Medium Access Control, targets low-cost and low-power deployments where nodes are equipped with a single transceiver. Other distinguishing features of AM-MAC include its simplicity and the fact that it does not require temporal synchronization among nodes. This is accomplished through an asynchronous split phase together with an observation phase as well as an unique handshake. Nodes observe the control channel for a period of time before asynchronously switching to the negotiated channel. Protocol correctness and collision-freedom in a multi-channel environment are verified. We also provide an analytical throughput assessment for our multi-channel approach. Simulation results show that AM-MAC improves performance significantly when compared to IEEE 802.11 and exhibits comparable performance to MMAC, one of the well-known multi-channel medium access control protocols, without the need for temporal synchronization.