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In wireless sensor networks (WSNs), many applications require a high reliability for the sensing data forwarding to sink. Due to the lossy nature of wireless channels, achieving reliable communication through multihop forwarding can be very challenging. Broadcast technology is an effective way to improve the communication reliability so that the data can be received by multiple receiver nodes. As long as the data of any one of the receiver nodes is transmitted to the sink, the data can be transmitted successfully. In this paper, a cross-layer optimization protocol named Adaptive transmission Power control based Reliable data Forwarding (APRF) scheme by using broadcast technology is proposed to improve the reliability of network and reduce communication delay. The main contributions of this paper are as follows: (1) for general data aggregation sensor networks, through the theoretical analysis, the energy consumption characteristics of the network are obtained. (2) According to the case that the energy consumption of nearsink area is high and that in far-sink area is low, a cross-layer optimization method is adopted, which can effectively improve the data communication by increasing the transmission power of the remaining energy nodes. (3) Since the reliability of communication is improved by increasing the transmission power of the node, the number of retransmissions of the data packet is reduced, so that the delay of the packet reaching the sink node is reduced. The theoretical and experimental results show that, applying APRF scheme under initial transmission power of 0 dBm, although the lifetime dropped by 13.77%, delay could be reduced by 40.37%, network reliability could be reduced by 10.08%, and volume of data arriving at sink increased by 10.08% compared with retransmission-only mechanism.

Recently, the vehicle-to-everything (V2X) paradigm is attracting more attention from both academia and industry. In the smart city, there are a huge number of roadside smart devices (RSDs) undertaking various sensing and monitoring tasks, and they collect information among V2X devices for various applications. With the software-defined technology applying into RSDs, one of the challenging issues is how to update the software of RSDs in a fast and low-cost way. We argue that recruiting a large number of vehicles to disseminate the update code for such RSDs through vehicle-to-sensing devices communications technology is an effective method. A cost-efficient greedy code mules selection scheme (CGCSS) is proposed to disseminate code to a huge number of RSDs in the smart city. In CGCSS, a task is defined as the process of transmitting the update code from the mobile code station (MCS) to RSD. So, the goal of CGCSS is to recruit an appropriate number of vehicles to finish the tasks with low cost and high coverage. A measure function is proposed to take the historical trajectories and cost into account. Therefore, the vehicles with high task completion possibility and low price will be selected as code mules (CMs). Then, a high-performance MCS deploy scheme (HMDS) is proposed to select the optimized MCS positions according to the movement and frequency of the CMs to optimize the performance of the system. Finally, extensive experiments using the real trajectory dataset have been done. The results show the better performance of CGCSS than the basic greedy code mule select scheme and the random code mules select scheme in terms of completion rate, average price, and cost-performance ratio, and the results confirm the validity of the proposed HMDS as well. INDEX TERMS Vehicle to everything, code dissemination, vehicles as code mules, recruit vehicles, low cost.

An Adaptive Transmission Range Based Topology Control (ATRTC) scheme is proposed to reduce delay and improve reliability for data collection in delay and loss sensitive wireless sensor network. The core idea of the ATRTC scheme is to extend the transmission range to speed up data collection and improve the reliability of data collection. The main innovations of our work are as follows:(1) an adaptive transmission range adjustment method is proposed to improve data collection reliability and reduce data collection delay. The expansion of the transmission range will allow the data packet to be received by more receivers, thus improving the reliability of data transmission. On the other hand, by extending the transmission range, data packets can be transmitted to the sink with fewer hops. Thereby the delay of data collection is reduced and the reliability of data transmission is improved. Extending the transmission range will consume more energy. Fortunately, we found the imbalanced energy consumption of the network. There is a large amount of energy remains when the network died. ATRTC scheme proposed in this paper can make full use of the residual energy to extend the transmission range of nodes. Because of the expansion of transmission range, nodes in the network form multiple paths for data collection to the sink node. Therefore, the volume of data received and sent by the near-sink nodes is reduced, the energy consumption of the near-sink nodes is reduced, and the network lifetime is increased as well. (2) According to the analysis in this paper, compared with the CTPR scheme, the ATRTC scheme reduces the maximum energy consumption by 9%, increases the network lifetime by 10%, increases the data collection reliability by 7.3%, and reduces the network data collection time by 23%.

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Urban computing creates novel solutions for smart city systems by integrating with ubiquitous sensing, cooperative communication, and data/code collection or dissemination technologies. In this paper, a collaborative code dissemination (CCD) approach with two-way vehicle to everything (V2X) paradigm is proposed by using vehicles act as code mules to disseminate code with fast and low cost style for urban Computing. The main innovation of the CCD-V2X scheme, which is different from the previous code dissemination method, is the use of three cooperative communication methods to speed up the dissemination of code. They are Roadside Smart Devices (RSDs) to vehicle (R2V), vehicle to vehicle (V2V) and R2V combined V2V (R2V-V2V) communications method. The corresponding three code dissemination schemes are proposed as follow: (1) The Code Dissemination with Roadside Smart Device Assisted (short as CDRSDA) scheme is proposed for vehicles to fast disseminate code in which the vehicles can receive code from RSDs that have get update code. (2) A Code Dissemination with V2V Transmission Assisted (short as CDVVA) scheme is proposed to improve the performance of code dissemination by enabling the transmission from code mules that have update code to the code mules that have no update code. (3) The R2V combined V2V (R2V-V2V) scheme is proposed which can further improve the performance by using both R2V and V2V communication method. The CCD scheme has been extensively experimentally verified by using real vehicle trajectory data. The experimental results show that: Compared with the Traditional Scheme, the CDRSDA scheme, CDVVA scheme, R2V-V2V scheme can be increased by up to 35.42%, 35.42%, 34.72%, respectively from the code diffusion coverage performance index, and from the speed performance indicators, the three schemes increased by at least 68.4%, 89.3% and 90.3%. INDEX TERMS Urban computing, vehicle to everything, collaborative code dissemination, vehicles as code mules.

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