Wireless Sensor Networks (WSNs) provide a valuable capability to autonomously monitor remote activities. Their limited resources challenge WSN medium access control (MAC) layer designers to adequately support network services while conserving limited battery power. This paper presents an energyadaptive WSN MAC protocol, Gateway MAC (G-MAC), which implements a new cluster-centric paradigm to effectively distribute cluster energy resources and extend network lifetime. G-MAC's centralized cluster management function offers significant energy savings by leveraging the advantages of both contention and contention-free protocols. A centralized gateway node collects all transmission requirements during a contention period and then schedules their distributions during a reservation-based, contention-free period.With minimal overhead, the gateway duties are efficiently rotated based upon available resources to distribute the increased network management energy requirements among all of the nodes.

With the progression of computer networks extending boundaries and joining distant locations, wireless sensor networks (WSNs) emerge as the new frontier in developing opportunities to collect and process data from remote locations. WSNs rely on hardware simplicity to make sensor field deployments both affordable and long-lasting without maintenance support. WSN designers strive to extend network lifetimes while meeting application-specific throughput and latency requirements. Effective power management places sensor nodes into one of the available energy-saving modes based upon the sleep period duration and the current state of the radio. The newest generation of sensor platform radios with a 250 kbps data rate does not provide adequate time to completely power off the radio during overheard 128-byte constrained IEEE 802.15.4 transmissions. This paper proposes a new radio power management (RPM) algorithm which optimizes radio sleep capabilities by transitioning nodes to intermediate power level states. Additionally, the experimental work characterizes the radio power levels, state transition times, and state transition energy costs of an IEEE 802.15.4 compliant sensor platform for improved accuracy in simulating WSN energy consumption.

This paper introduces the Virginia Tech Center for Wireless Telecommunications' Vehicular Public Safety Cognitive Radio (VPSCR), a vehicle-based extension to our previously fielded cognitive radio prototype for the public safety community. Specifically, the VPSCR can scan the radio spectrum over multiple public safety frequency bands, classify commonly used public safety waveforms and networks, and reconfigure itself for network interoperation. The VPSCR is designed for vehicular assembly, powering itself from the onboard car battery. Such a platform, however, has a significant power requirement, which prevents it from being easily downsized into a handheld mobile device, thereby limiting its mobility. We introduce a new architecture which uses a personal digital assistant (PDA) to remotely control and access services from the VPSCR. Following a modular approach, we designed a remote agent on the VPSCR to advertise services that a PDA can discover and subscribe. This provides a PDA with the capability to remotely control the VPSCR according to a public safety officers own needs. The data link between the PDA and the VPSCR utilizes existing fixed infrastructures such as the 802.11 Wi-Fi or Bluetooth standards, enabling the PDA to extend its operational range.

Cognitive Radios (CRs) and Software Defined Radios (SDRs) have ubiquitous applications ranging from handheld to base station devices. In order to meet the computational requirements of such radios, computing heterogeneity, the mixed usage of General Purpose Processors (GPPs), Digital Signal Processors (DSPs), and Field-Programmable Gate Arrays (FPGAs), is attractive. Developing SDR and CR applications already requires a diverse set of skills, and computing heterogeneity further complicates the process. This paper presents a developmental workflow used successfully by the authors for SDR and CR application running on a platform combining DSP and GPP based processors. The paper discusses tools used to set up the platform, create compilation environment, develop code for GPP/DSP communication, integrate the DSP into GNU Radio, and use the environment to develop SDR/CR applications. It presents a case study showing how computing heterogeneity can be used to address diverse application needs.

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