Anthony Plummer

A Cognitive Spectrum Assignment Protocol using Distributed Conflict Graph Construction

The availability of multiple interfaces and channels in wireless devices is expected to alleviate the capacity limitations that exist in traditional single channel wireless mesh networks. Although having multiple radio interfaces and available channels can generally increase the effective throughput, a problem arises as to what is the best strategy to dynamically assign available channels to multiple radio interfaces for maximizing effective network throughput by minimizing the interference. This paper presents a distributed and localized interference-aware channel assignment framework for multi-radio wireless mesh networks in a cognitive network environment. The proposed framework uses a novel interference estimation method by utilizing distributed conflict graphs at each network interface to model the interference. Extensive simulation studies in 802.11 based multi-radio mesh networks have been performed. The results indicate that for both local and multi-hop traffic, the proposed protocol can facilitate a large increase in network throughput in comparison with a Common Channel Assignment mechanism that is used as a benchmark in the literature.

Distributed spectrum assignment for cognitive networks with heterogeneous spectrum opportunities

This paper presents a distributed and localized interference-aware channel assignment framework for multi-radio wireless mesh networks in a cognitive network environment. The availability of multiple interfaces and channels in wireless devices is expected to enhance network throughput in wireless mesh networks. A notable design issue in such networks is how to dynamically assign available channels to multiple radio interfaces for maximizing effective network throughput by minimizing interference. The proposed framework uses a novel interference estimation method by utilizing distributed conflict graphs on a per-interface basis. Presented results obtained via simulation studies in 802.11 based multi-radio mesh networks indicate that for both homogeneous and heterogeneous primary networks, the proposed protocol can facilitate a large increase in network throughput in comparison with a Common Channel Assignment mechanism that is used as a benchmark in the literature. Copyright

Measurement-Based Bandwidth Scavenging in Wireless Networks

Dynamic Spectrum Access can enable a secondary user in a cognitive network to access unused spectrum, or whitespace, found between primary user transmissions in a wireless network. The key design objective for a secondary user access strategy is to scavenge” the maximum amount of spatio-temporally fragmented whitespace while limiting the amount of disruption caused to the primary users. In this paper, we first measure and analyze the whitespace profiles of an 802.11 network (using ns-2 simulation) and a non-802.11 (CSMA)-based network (developed on TelosB Motes). Then we propose two novel secondary user access strategies, which are based on measurement and statistical modeling of the whitespace as perceived by the secondary users. Afterward, we perform simulation experiments to validate the effectiveness of the proposed access strategies under single and multiple secondary user scenarios, and evaluate their performance numerically using the developed analytical expressions. The results show that the proposed access strategies are able to consistently scavenge between 90 and 96 percent of the available whitespace capacity, while keeping the primary users disruption less than 5 percent.

A localized and distributed channel assignment framework for cognitive radio networks

The availability of multiple interfaces and channels in wireless devices is expected to alleviate the capacity limitations that exist in traditional single channel wireless mesh networks. Although having multiple radio interfaces and available channels can generally increase the effective throughput, a problem arises as to what is the best strategy to dynamically assign available channels to multiple radio interfaces for maximizing effective network throughput by minimizing the interference. This paper presents a distributed and localized interference-aware channel assignment framework for multi-radio wireless mesh networks in a cognitive network environment. The proposed framework uses a novel interference estimation method by utilizing distributed conflict graphs at each network interface to model the interference. Extensive simulation studies in 802.11 based multi-radio mesh networks have been performed. The results indicate that for both local and multi-hop traffic, the proposed protocol can facilitate a large increase in network throughput in comparison with a Common Channel Assignment mechanism that is used as a benchmark in the literature.

Ultra wide band impulse switching protocols for event and target tracking applications

This paper presents a novel energy-efficient pulse switching protocol for ultra light-weight wireless network applications. The key idea is to abstract a single pulse, as opposed to multi-bit packets, as the information exchange mechanism. Pulse switching is shown to be sufficient for event and target tracking applications with binary sensing. Target tracking with conventional packet transport can be prohibitively energy-inefficient due to the communication, processing, and buffering overheads of the large number of bits within a packets data, header, and preambles. The paper presents a joint MAC and Routing architecture for pulse switching with a novel hop-angular event localization. Through analytical modeling and simulation experiments, it is shown that pulse switching can be an effective means for event based networking, which can potentially replace the packet transport when the information to be transported is binary in nature.

Cooperative caching for improving availability in Social Wireless Networks

This paper presents a cooperative object caching mechanism for maintaining high content availability in Social Wireless Networks. Most of the existing cooperative caching schemes in wireless networks provide either high network level availability or high node level availability, but not both at the same time. The first one ensures object availability in isolated network partitions and the second one ensures object availability in individual nodes when they are completely detached from the rest of the network. In this paper, we propose a novel cache partitioning mechanism that is able to provide high network level and high node level availabilities at the same time. This scheme reduces the generated network traffic compared to the prevalent schemes in the literature. In addition to computing theoretical bounds for the availabilities and generated traffic, caching performance is evaluated using a detailed ns2 simulation model under static and mobile networks with realistic mobility patterns.

Capacity scavenging in wireless networks: A comparative study

Dynamic Spectrum Access can enable secondary network users to access unused spectrum, or whitespace, which is found between the transmissions of primary users in a wireless network. The main design objectives for secondary user access strategy are to be able to “scavenge” spatio-temporally fragmented whitespace opportunities while limiting the amount of interference caused to the primary users. In this paper, we propose a novel secondary user access strategy which is based on measurement and modeling of the whitespace as perceived by the secondary network users. A secondary user continually monitors its surrounding whitespace, models it, and then attempts to access the available spectrum holes so that the effective secondary throughput is maximized while the resulting interference to the primary users is limited to a pre-defined bound. We first develop analytical expressions for the secondary throughput and primary interference, and then perform ns2 based simulation experiments to validate the effectiveness of the proposed access strategy, and evaluate its performance against two other access schemes from the cognitive network literature.

Traffic Protection via Bandwidth Scavenging in Heterogeneous Sensor Networks

This paper presents a history based statistical channel access mechanism for enabling traffic prioritization in wireless sensor networks. Prioritized access is realized such that low priority non-real-time sensors can access channel bandwidth that is unused by high priority real-time traffic. The key idea is for the low priority sensor nodes to first observe and statistically model the channel usage pattern by the high priority traffic. Then make probabilistic transmissions depending on the amount of time elapsed after the most recent high priority packet transmission ends. The objective is to dimension such probabilities based on the channel utilization statistics so that the non-priority traffic throughput is maximized while protecting the high-priority traffic from disruptions. The proposed access mechanism is implemented in a TelosB mote based sensor testbed in which the non-priority motes continually measures the RSSI to infer the channel usage pattern and probabilistically access the channel while different types of traffic is sent by high-priority TelosB motes. Experimental results from the testbed demonstrates that the proposed mechanism can improve non-priority traffic throughput by up to approximately 70% over compared protocols, while limiting the disruptions to high-priority traffic to pre-specified bounds of 3% to 5%.

Pulse Switching for Static Event Sensing in Sensor Networks

This paper presents a novel energy-efficient pulse switching protocol for ultra light-weight wireless network applications. The key idea is to abstract a single pulse, as opposed to multi-bit packets, as the information exchange mechanism. Pulse switching is shown to be sufficient for event sensing applications with binary sensing. Event sensing with conventional packet transport can be prohibitively energy-inefficient due to the communication, processing, and buffering overheads of the large number of bits within a packets data, header, and preambles. The paper presents a joint MAC-Routing architecture for pulse switching with a novel hop-angular event localization. Through simulation experiments, it is shown that pulse switching can be an effective means for event based networking, which can potentially replace the packet transport when the information to be transported is binary in nature.