Battery life is a very precious resource in sensor networks to provide high-quality multimedia communications among wireless nodes. For reducing power consumption and satisfying QoS requirements, we propose a routing scheme with efficient power management and on-demand quality control for wireless sensor networks. Two cost functions are developed to minimize the transmitting power and maximize the link quality under the constraint that an end-to-end frame error probability should be met. The heuristic problem on minimizing power consumption under frame error constraints can be derived as a closed-form solution in this paper. Therefore, an optimal route can be rapidly determined by accurately calculating the power requirement for each sensor node. Finally, our analytical results indicate that the proposed scheme is superior to a previous work with the same constraint and is also comparable to the results obtained from a heuristic simulation.
Power consumption is a critical issue in multimedia streaming over a heterogeneous network, where wired and wireless links are interoperated together. To effectively reduce power consumption in this type of networks, we propose an effective power control method that can determine the optimal transmit powers for multimedia traffic with QoS constraints. Optimal transmit power of a network node can be characterized by a cost function, which jointly takes into account the transmit power and link quality under an end-to-end frame-error constraint. Two proposed methods, namely, route-based power management and link-associated power management, are developed to solve the power cost problem. Experiments are conducted through simulation in a heterogeneous network. The results demonstrate the relative superiority and effectiveness of the link-associated approach in power saving.
In this paper, we present a cluster-based slot allocation (SLA) algorithm for vehicle communications in VANETs. The proposed CSA uses a simple transmit-and- listen scheme to fast elect a VC (VANET Coordinator). Additionally, without restricting the number of nodes, CSA allows a VN (VANET node) to randomly choose a time slot for bandwidth requests. To evaluate the proposed CSA, we derive mathematical equations using probabilities. The analytical results are validated through a simulation. Both the analytical and simulation results show that the proposed CSA can effectively improve the performance of inter-vehicle communications, particularly when the number of VNs is increased.
RSVP bandwidth reservation mechanism using one-pass with advertising may encounter killer reservation problems, when more than two reservation requests are merged from different receivers. We present a two-pass with advertising (TPWA) mechanism to inherently avoid the killer reservation problems. TPWA requests pre-engaged bandwidth at the first pass before actually reserving bandwidth at the second pass. The pre-engaged bandwidth is a tagged bandwidth which may be used to deliver non-QoS traffic using the resources that QoS traffic may later request for reservation. Hence, the percentage of pre-engaged bandwidth to be allocated at a router under a receiver's request may significantly affect the transmission quality of QoS traffic. We develop algorithms for RSVP modules at a router to dynamically convert the free bandwidth to the pre-engaged bandwidth and finally to the reserved bandwidth.
IEEE 802.11ah can support machine-to-machine (M2M) communications among many sensor devices, which is rapidly increasing with the Internet of Things (IoT). In 802.11ah, a restricted access window (RAW) is designed for a beacon interval (BI). RAW is divided into many slots that allow sensor devices to contend for transmission. This paper proposes a dynamic slot allocation scheme (DSAS) in 802.11ah networks. To alleviate the contention in crowded M2M environments, the DSAS defines two sets of thresholds, high and low, to determine the sleeping-time level of a machine and the contention level for a slot, respectively. The innovative aspect of the DSAS is that machines with short sleeping time are allocated to less congested slots whereas machines with long sleeping time are allocated to more congested slots. To avoid unnecessary slot reallocation, machines with sleeping-time levels or contention levels between the high and low thresholds continue to use their original transmission contention slots. Simulations performed on NS-3 show the DSAS can significantly improve average backoff time and packet delay and increase the overall system throughput by 30%.
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