Cellular Vehicle-to-Everything (C-V2X) is a frontier in the evolution of distributed communication introduced in 3GPP release 14 towards advanced use cases. While research efforts continue to optimize the accessible bandwidth for transportation ecosystem, analysis of the network from the application layer perspective is essential prior to deployment, as it can help identify potential issues that end-users may encounter in a dynamic road environment. This emphasizes on assessing the network using application-oriented metrics to evaluate its capacity of providing advanced vehicular services with stringent latency and throughput requirements. C-V2X facilitates advanced applications like autonomous driving and on-the-go transaction services that necessitate consecutive exchange of messages. For such services, the network level metrics fails to capture the edge case service quality as they express an average measure of performance. In this paper, we present an application-oriented analysis of a transaction service built on C-V2X protocol. We analyze different design choices that affects quality of service both from network-oriented and user-centric metrics, and highlight issues regarding packet dissemination from infrastructures for vehicle-to-infrastructure (V2I) based service applications. We also present our study on the impact of batching in disseminating acknowledgement packets (ACK) and its consequences on both the service reliability and network congestion. Our results show that time-sensitive and mission-sensitive vehicular applications should aim for a balance between achieving the mission utility in shortest duration possible while maintaining minimal impact on the system-wide stability.

In this paper, we focus on the performance analysis of a semi-persistent scheduling scheme for vehicular safety communications, motivated by the Mode 4 medium access control protocol in 3GPP Release 14 for Cellular-V2X. An analytical model is built and a fixed point method is used to calculate the collision probability and average delay in both fully connected and partially connected cases under the assumption of perfect PHY performance. We use Monte Carlo simulation to verify the results obtained in the analytical model. The simulation results show that our analytical model can give a good estimation of the collision probability and average delay. We verify that a trade-off between delay and collision probability can be achieved with a flexible resource block selection. Monte Carlo simulation results show that with the flexible resource selection scheme average delay can be shortened significantly with only a small compromise in collision probability.

The first wave of sensor network deployments from the early 2000s relied on aggregation-a strategy in which readings are combined locally using low-power radio links before they are communicated to the gateway. Aggregation reduced dependence on battery-draining, long-distance radio links, and reduced redundancy among reported data. We are now experiencing a second wave of sensor network research driven by ubiquitous smartphone usage. In this paper, we study the application of aggregation to the new smartphone sensor network setting, arguing that it can help reduce costs in contexts where existing cost-reduction strategies, such as opportunistic use of Wi-Fi and data piggybacking, do not apply. In more detail, we propose two new aggregation protocols, designed for the challenges of high mobility, that offer trade-offs in terms of bandwidth and energy savings. We then evaluate these protocols using both test bed experimentation (using a collection of 11 Samsung Galaxy Nexus smartphones running a Noise Tube-like application) and trace based simulation (using a large collection of mobility traces from taxi cabs in Singapore). Our experiments demonstrate that our aggregation protocols reduce cellular bandwidth usage by up to 95% while losing less than 5% of the data. Moreover, in many common cases, our protocols also yield significant energy savings.

This paper presents a novel pulse switching protocol framework for ultra light-weight wireless network applications. The key idea is to abstract a single Ultra Wide Band (UWB) pulse as the information switching granularity. Pulse switching is shown to be sufficient for on-off style event monitoring applications for which a monitored parameter can be modeled using a binary variable. Monitoring such events 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 packet's data, header, and preambles for synchronization. The paper presents a joint MAC-routing protocol architecture for pulse switching with a novel hop-angular event localization strategy. Through analytical modeling and simulation-based experiments it is shown that pulse switching can be an effective means for event networking, which can potentially replace the traditional packet transport when the information to be transported is binary in nature.

This article presents a novel transmission power assignment mechanism for on-body wireless links formed between severely energy-constrained wearable and implanted sensors. The key idea is to develop a measurement-based framework in which the postural position as it pertains to a given wireless link is first inferred based on the measured RF signal strength and packet drops. Then optimal power assignment is done by fitting those measurement results into a model describing the relationship between the assigned power and the resulting signal strength. A closed loop power control mechanism is then added for iterative convergence to the optimal power level as a response to both intra-and-inter posture body movements. This provides a practical paradigm for on-body power assignment, which cannot leverage the existing mechanisms in the literature that rely on localization, which is not realistic for on-body sensors. Extensive experimental results are provided to demonstrate the model building and algorithm performance on a prototype body area network. The proposed mechanism has also been compared with a number of other closed loop mechanisms and an experimental benchmark.

This paper proposes a neighborhood route diffusion (NRD) mechanism in which certain selected entries from a node's routing table are selectively diffused to its neighbor nodes. When done efficiently, this selective route diffusion can create a temporary envelope of emergency route information to a destination around all nodes that are actively forwarding packets to that specific destination. When a link on a route fails due to mobility, the intermediate node on the failed link can forward packets to one of its neighbors which has already been diffused with the route information for the corresponding destination. It is shown that in most such occurrences, the packets can be successfully forwarded all the way to the destination using such pre-diffused routing information. This mechanism for salvaging packets during mobility-initiated link breaks can avoid packet drops which are usually prevalent in regular mobility aware routing protocols such as AODV. This paper presents strategies and network protocols for the selective NRD process and its associated routing mechanisms.

This paper presents an integrated sink navigation and data routing framework called network-assisted data collection (NADC) in which optimum trajectories for a mobile data harvester (MDH) are computed such that a desired balance between energy-efficiency and collection delay is achieved. We have formulated the problem of mobile sink based data collection using a configurable knob (k) to find the desired balance. The key concept is to appropriately adjust the data routing and mobile sink trajectory by varying parameter k. The paper introduces a large slew of application scenarios with their unique optimization objectives, and demonstrates the relevance of the proposed framework in each such scenario. The notable solution components of NADC include a fully distributed and network assisted MDH navigation mechanism that does not rely on sensor localization services, and a multi-hop routing mechanism which works with the underlying sink navigation so that the sensor data can be aggregated and uploaded through dynamically chosen gateway nodes located around the sink trajectory.

This paper presents a network-assisted sink navigation mechanism in which mobile sink trajectories are computed by a sensor network for energy-efficient data collection. The key idea is that for data collection, a mobile sink (referred to as Mobile Data Harvester MDH) should visit all network nodes in order to avoid energy- intensive multi-hop routing. While incurring higher data collection delays compared to the traditional static sink based collection, the proposed harvesting framework can deliver the maximum achievable lifetime for delay non-critical sensor applications. The main issue in this approach is to compute MDH trajectories that can reduce the average data collection delay while traversing through the radio ranges of all nodes, but not necessarily pass through the close proximity of each node. Our primary contribution is the design of a fully distributed and network assisted MDH navigation mechanism where MDH trajectories are cooperatively computed by the nodes without sensor localization services. Performance results obtained from an ns2 simulator indicate that the distributed algorithms and network assisted navigation framework can achieve low average delay, low delay variation and complete collection coverage of the network. Further, the performance of the distributed algorithms was found to be comparable to that of centrally computed solution.

This paper presents a mechanism for extending network life by introducing energy-aware mobility in wireless sensor networks. The concept of controlled mobility for energy saving has been motivated by a natural grouping behavior that is observed in Emperor penguins in the Antarctic region. As a survival strategy during the winters, large groups of Emperor penguins form a closely huddled group to improve their collective heat insulation. Individual penguins within a group exhibit a local mobility pattern that ensures that each individual spends equal amount of time at the periphery of the group, where the heat loss is the maximum. In this paper, we first draw a parallel between the heat loss of a penguin at the group periphery, and the routing energy burden of a sensor node near base stations. Then we develop a distributed and fully localized mobility control algorithm for collective extension of the network life. Experimental results demonstrate that the proposed controlled mobility can significantly extend a sensor network's operating life even in situations where the energy cost of physical node movement is modeled as high as up to four orders of magnitude larger than the energy cost for packet communication.

This paper presents a carrier-sense based transmission power control protocol, CSNE-PC, which addresses the energy inefficiency of basic power control protocols (BPC) for IEEE 802.11 based networks. In BPC, RTS and CTS packets are exchanged at full power while data and acknowledgement transmissions are carried out at low power. While being intuitive and simple to implement, BPC's energy efficiency is significantly degraded by a unique hidden collision problem, which is removed by the approach in this paper. In CSNE-PC, a node measures and analyses its carrier-sense activities for detecting 802.11 CTS packets in the extended neighborhood of carrier sense range. Upon detecting a CTS packet, the node sets or extends its MAC layer NAV and enters into a silence mode for the data packet duration. Unlike BPC, this enables CSNE-PC to control transmission power without having to suffer from additional data collisions. Evaluation of CSNE-PC through simulation demonstrates that under sustainable loading conditions, reduction in combined transmit and receive energy for CSNE-PC can be as high as 38%, and that is while retaining the throughput and delay characteristics of the regular 802.11 protocol