Sharing perceptual data (e.g., camera and LiDAR data) with other vehicles enhances the traffic safety of autonomous vehicles because it helps vehicles locate other vehicles and pedestrians in their blind spots. Such safety applications require high throughput and short delay, which cannot be achieved by conventional microwave vehicular communication systems. Therefore, millimeter-wave (mmWave) communications are considered to be a key technology for sharing perceptual data because of their wide bandwidth. One of the challenges of data sharing in mmWave communications is broadcasting because narrow-beam directional antennas are used to obtain high gain. Because many vehicles should share their perceptual data to others within a short time frame in order to enlarge the areas that can be perceived based on shared perceptual data, an efficient scheduling for concurrent transmission that improves spatial reuse is required for perceptual data sharing. This paper proposes a data sharing algorithm that employs a graph-based concurrent transmission scheduling. The proposed algorithm realizes concurrent transmission to improve spatial reuse by designing a rule that is utilized to determine if the two pairs of transmitters and receivers interfere with each other by considering the radio propagation characteristics of narrow-beam antennas. A prioritization method that considers the geographical information in perceptual data is also designed to enlarge perceivable areas in situations where data sharing time is limited and not all data can be shared. Simulation results demonstrate that the proposed algorithm doubles the area of the cooperatively perceivable region compared with a conventional algorithm that does not consider mmWave communications because the proposed algorithm achieves high-throughput transmission by improving spatial reuse. The prioritization also enlarges the perceivable region by a maximum of 20%.

The safety applications for cooperative driving in VANETs, typically require the dissemination of safety-related information to all vehicles with high reliability and a strict timeline. However, due to the high vehicle mobility, dynamic traffic density, and a self-organized network, Safety message dissemination has a special challenge to efficiently use the limited network resources to satisfy its requirements. With this motivation, we propose a novel broadcasting protocol referred to as congestion awareness multi-hop broadcasting (CAMB) based loosely on a TDMA-like transmission scheduling scheme. The proposed protocol was evaluated using different traffic scenarios within both a realistic channel model and an 802.11p PHY/MAC model in our simulation. The simulation results showed that the performance of our CAMB protocol was better than those of the existing broadcasting protocols in terms of channel access delay, packet delivery ratio, end-to-end delay, and network overhead.

A cooperative relaying system with transmission scheduling is investigated. Cooperative relaying is composed of multiple links because the source sends the data to more than one receiver, and the destination receives multiple data transmitted by more than one transmitter. Therefore, if the source can transmit the data when the channel gains of the links are high, it is not clear which channel gains should be high in order to achieve high spectral efficiency. In the present letter, the spectral efficiency of a cooperative relaying system is theoretically derived under the assumption that the source transmits the data only when the channel gains of links are above certain threshold values. Numerical results reveal that a high spectral efficiency can be achieved by assuring a high channel gain for the link with the highest average received power among links to the destination.

In this paper, we consider the all-to-all broadcast problem in optical broadcast star networks using Wavelength Division Multiplexing. Our network model assumes that receivers are fixed-tuned and transmitters are tunable such that optical lasers assigned to transmitters have limited access to the network bandwidth; hence, each node must be equipped with multiple optical lasers and/or multiple optical filters in order to maintain a single-hop network. This paper is primarily concerned with single-hop networks, in which each node is assigned a single optical filter. Lower bounds are first established on the number of lasers per each node and the minimum schedule length, and a schedule achieving the minimum schedule length is presented. The results are applicable to arbitrary tuning delays, arbitrary numbers of wavelength channels, and optical lasers' arbitrary tuning ranges. Network models with optical devices having limited tuning ranges have not yet been considered in connection with transmission schedules, and this is the first work in this new direction.

A Wavelength Division Multiaccess (WDMA) network with buffer sharing among stations is studied. All stations in the network are connected to a passive optical star coupler and each station has a different fixed wavelength laser for transmitting packets. Each station in the network reports its packet backlog to a scheduler which computes and then broadcasts a transmission schedule to all the stations through a control channel in each time slot. A transmission schedule includes two types of assignments: 1) assign a maximum number of stations for conflict-free transmissions, and 2) assign the relocation of packets from congested stations to uncongested relaying stations through idling transceivers for distributed buffer sharing. The first assignment aims at maximizing throughput and the second assignment aims at minimizing packet loss. Simulation results show that as much as 75% of the buffers can be saved with the use of buffer sharing when 50% of the packets are of the non-sequenced type.