47 research outputs found
Sub-6GHz Assisted MAC for Millimeter Wave Vehicular Communications
Sub-6GHz vehicular communications (using DSRC, ITS-G5 or C-V2X) have been
developed to support active safety applications. Future connected and automated
driving applications can require larger bandwidth and higher data rates than
currently supported by sub-6GHz V2X technologies. This has triggered the
interest in developing mmWave vehicular communications. However, solutions are
necessary to solve the challenges resulting from the use of high-frequency
bands and the high mobility of vehicles. This paper contributes to this active
research area by proposing a sub-6GHz assisted mmWave MAC that decouples the
mmWave data and control planes. The proposal offloads mmWave MAC control
functions (beam alignment, neighbor identification and scheduling) to a
sub-6GHz V2X technology, and reserves the mmWave channel for the data plane.
This approach improves the operation of the MAC as the control functions
benefit from the longer range, and the broadcast and omnidirectional
transmissions of sub-6GHz V2X technologies. This simulation study demonstrates
that the proposed sub-6GHz assisted mmWave MAC reduces the control overhead and
delay, and increases the spatial sharing compared to a mmWave-only
configuration (IEEE 802.11ad tailored to vehicular networks). The proposed MAC
is here evaluated for V2V communications using 802.11p for the control plane
and 802.11ad for the data plane. However, the proposal is not restricted to
these technologies, and can be adapted to other technologies such as C-V2X and
5G NR.Comment: 8 pages, 5 figure
Content- and Context-Aware Opportunistic Cellular Communications in Device-Centric Wireless Networks
Device-centric wireless networks, including Deviceto-
Device communications and Multi-hop Cellular Networks, are
expected to be a relevant component of future 5G wireless
networks. Traditionally, opportunistic networking has been
proposed for disconnected networks that cannot always reliably
ensure real-time end-to-end connections. However, previous
studies have demonstrated that opportunistic schemes can also be
utilized in connected networks to improve their efficiency by
intelligently exploiting context- and content-awareness. In this
context, this paper proposes and evaluates a mechanism to select
the adequate configuration of opportunistic cellular
communications in single-hop and multi-hop cellular networks.
To this aim, the mechanism probabilistically identifies for each
communications mode the adequate times for cellular
transmissions to take place in order to reduce the cellular
channel occupancy and improve its capacity. The obtained
results show that the proposed scheme reduces the channel
occupancy of cellular transmissions for delay-tolerant
information by up to 70% compared to conventional single-hop
cellular communication
Evaluation of IEEE 802.11ad for mmWave V2V Communications
Autonomous vehicles can construct a more accurate perception of their
surrounding environment by exchanging rich sensor data with nearby vehicles.
Such exchange can require larger bandwidths than currently provided by
ITS-G5/DSRC and Cellular V2X. Millimeter wave (mmWave) communications can
provide higher bandwidth and could complement current V2X standards. Recent
studies have started investigating the potential of IEEE 802.11ad to support
high bandwidth vehicular communications. This paper introduces the first
performance evaluation of the IEEE 802.11ad MAC (Medium Access Control) and
beamforming mechanism for mmWave V2V communications. The study highlights
existing opportunities and shortcomings that should guide the development of
mmWave communications for V2V communications.Comment: 6 pages, 5 figures, 1 tabl
Store, carry and forward for energy efficiency in multi-hop cellular networks with mobile relays
Abstract The wide scale adoption of smartphones is
boosting cellular data traffic with the consequent capacity
constraints of cellular systems and increase in energy
consumption. A significant portion of cellular data traffic can be
deemed as delay tolerant. Such tolerance offers possibilities for
designing novel communications and networking solutions that
can accommodate the delay tolerant cellular data traffic while
reducing their impact on the overall cellular capacity and energy
consumption. In this context, this work studies the use of
opportunistic store, carry and forward techniques in Multi-Hop
Cellular Networks (MCN) to reduce energy consumption for
delay tolerant traffic. The study focuses on two-hop MCN
networks using mobile relays (MCN-MR), and identifies the
optimum mobile relay location and the location from which the
relay should start forwarding the information to the cellular base
station in order to minimize the overall energy consumption. The
study shows that the use of opportunistic store, carry and
forward techniques in MCN-MR can significantly reduce energy
consumption compared to other solutions, including traditional
single-hop cellular systems or direct contact store, carry and
forward solutions.This work is supported in part by the Spanish Ministry of Economy and Competitiveness and FEDER funds (TEC2011–26109)and the Local Government of Valencia with reference ACIF/2010/161 and BEFPI/2012/06
Opportunistic Networking for Improving the Energy Efficiency of Multi-Hop Cellular Networks
Relaying technologies can help address the capacity
and energy-efficiency challenges faced by cellular networks as a
result of the rapid increase in mobile data consumption. A nonnegligible
portion of such consumption corresponds to delay
tolerant services. This delay tolerance offers the possibility for
opportunistic networking to exploit contact opportunities
between mobile devices in order to reduce the impact of data
traffic on the cellular capacity and energy-efficiency without
sacrificing the end-user quality of service. In this context, this
paper investigates the use of opportunistic forwarding in MCNMR
(Multi-hop Cellular Networks with Mobile Relays) to reduce
energy consumption in the case of delay tolerant services. The
study proposes to exploit context information provided at a low
cost by the cellular infrastructure to efficiently select the
forwarding node in a two-hop MCN-MR scenario. The proposed
solution results in significant energy savings compared to
traditional single-hop cellular communications and other
forwarding solutions reported in the literatureThis work is supported in part by the Spanish Ministry of
Economy and Competitiveness and FEDER funds (TEC201126109),and the Local Government of Valencia with reference
ACIF/2010/161 and BEFPI/2012/06
Context-based Broadcast Acknowledgement for Enhanced Reliability of Cooperative V2X Messages
Most V2X applications/services are supported by
the continuous exchange of broadcast messages. One of the main
challenges is to increase the reliability of broadcast transmissions
that lack of mechanisms to assure the correct delivery of the
messages. To address this issue, one option is the use of
acknowledgments. However, this option has scalability issues
when applied to broadcast transmissions because multiple
vehicles can transmit acknowledgments simultaneously. To
control scalability while addressing reliability of broadcast
messages, this paper proposes and evaluates a context-based
broadcast acknowledgement mechanism where the transmitting
vehicles selectively request the acknowledgment of
specific/critical broadcast messages, and performs
retransmissions if they are not correctly received. In addition, the
V2X applications/services identify the situations/conditions that
trigger the execution of the broadcast acknowledgment
mechanism, and the receiver(s) that should acknowledge the
broadcast messages. The paper evaluates the performance of the
context-based broadcast acknowledgment mechanism for a
Collective Perception Service. The obtained results show the
proposed mechanism can contribute to improve the awareness of
crossing pedestrians at intersections by increasing the reliability
in the exchange of CPM messages between vehicles approaching
the intersection. This solution is being discussed under IEEE
802.11bd, and thus can be relevant for the standardization
process.10.13039/501100000780-European Commission;10.13039/501100007170-Ministry of Econom
Next Generation Opportunistic Networking in Beyond 5G Networks
Beyond 5G networks are expected to support massive traffic through decentralized solutions and advanced networking mechanisms. This paper aims at contributing towards this vision through the integration of device-centric wireless networks, including Device-to-Device (D2D) communications, and the Next Generation of Opportunistic networking (NGO). This integration offers multiple communication modes such as opportunistic cellular and opportunistic D2D-aided communications. Previous studies have demonstrated the potential and benefits of this integration in terms of energy efficiency, spectral efficiency and traffic offloading. We propose an integration of device-centric wireless networks and NGO that is not driven by a precise knowledge of the presence of the links. The proposed technique utilizes a novel concept of graph to model the evolution of the networking conditions and network connectivity. Uncertainties and future conditions are included in the proposed graph model through anticipatory mobile networking to estimate the transmission energy cost of the different communication modes. Based on these estimates, the devices schedule their transmissions using the most efficient communication mode. These decisions are later revisited in real-time using more precise knowledge about the network state. The conducted evaluation shows that the proposed technique significantly reduces the energy consumption (from 60% to 90% depending on the scenario) compared to traditional single-hop cellular communications and performs closely to an ideal “oracle based” system with full knowledge of present and future events. The transmission and computational overheads of the proposed technique show small impact on such energy gains.This work has been partially funded by the Spanish Ministry of Science, Innovation and Universities, AEI, and FEDER funds (TEC2017-88612-R)the Ministry of Science, Innovation and Universities (IJC2018-036862-I)the UMH (‘Ayudas a la Investigación e Innovación de la Universidad Miguel Hernández de Elche 2018’)and by the European Commission under the H2020 REPLICATE (691735), SoBigData (654024) and AUTOWARE (723909) project
How Does 5G NR V2X Mode 2 Handle Aperiodic Packets and Variable Packet Sizes?
—5G NR V2X complements LTE V2X to support
advanced V2X services for connected and automated driving.
5G NR V2X introduces novel features at the MAC layer that are
designed to cope with potential packet collisions, and that could
help address the LTE V2X MAC inefficiencies observed under
aperiodic traffic of variable size. This is the case of the reevaluation mechanism that is a mandatory MAC feature of 5G
NR V2X, and that seeks avoiding possible packet collisions
detected before a vehicle transmits in selected resources.
Evaluations conducted to date of 5G NR V2X do not consider
the re-evaluation mechanism, and have focused on traffic
patterns that do not fully account for the traffic variability of
advanced V2X services. This paper extends the current state of
the art with the first evaluation of a fully standard compliant 5G
NR V2X implementation under the traffic patterns
recommended by 3GPP for advanced V2X services. Our study
shows that 5G NR V2X Mode 2 still faces MAC challenges when
using semi-persistent scheduling (SPS) to efficiently support
aperiodic traffic of variable size
A comparative analysis of the semi-persistent and dynamic scheduling schemes in NR-V2X mode 2
Over the last years, the evolution of Vehicle-to-Everything (V2X) services from basic safety-related to enhanced V2X (eV2X) applications prompted the development of the 5G New Radio (NR)-V2X technology. Standardized by the Third Generation Partnership Project (3GPP) in Release 16, NR-V2X features a distributed resource allocation mode, known as Mode 2, that allows vehicles to autonomously select their transmission resources employing a Semi-Persistent Scheduling (SPS) or a Dynamic Scheduling (DS) scheme. The SPS approach relies on the periodic reservation of resources, whereas the DS scheme is a reservation-less solution that forces the selection of new transmission resources for every generated message. 3GPP standards do not indicate under which conditions each scheduling scheme should be used. In this context, this study analyzes and compares the performance of SPS and DS under different traffic types and Packet Delay Budget (PDB) requirements. Simulation results demonstrate that the SPS scheme represents the best solution for serving fixed size periodic traffic, whereas DS is more adequate for aperiodic traffic (of fixed or variable size). The study shows that the superiority of DS over SPS becomes more evident when tighter PDB requirements are considered, and that the performance of the DS scheme is independent of the PDB. It is also demonstrated that an adaptive scheduling strategy, which allows vehicles to select the scheduling scheme that best suits the type of generated traffic, is the best solution in mixed traffic scenarios where fixed size periodic traffic and variable size aperiodic traffic sources coexist
Analytical Models of the Performance of IEEE 802.11p Vehicle to Vehicle Communications
The critical nature of vehicular communications requires their extensive testing and evaluation. Analytical models can represent an attractive and cost-effective approach for such evaluation if they can adequately model all underlying effects that impact the performance of vehicular communications. Several analytical models have been proposed to date to model vehicular communications based on the IEEE 802.11p (or DSRC) standard. However, existing models normally model in detail the MAC (Medium Access Control), and generally simplify the propagation and interference effects. This reduces their value as an alternative to evaluate the performance of vehicular communications. This paper addresses this gap, and presents new analytical models that accurately model the performance of vehicle-to-vehicle communications based on the IEEE 802.11p standard. The models jointly account for a detailed modeling of the propagation and interference effects, as well as the impact of the hidden terminal problem. The model quantifies the PDR (Packet Delivery Ratio) as a function of the distance between transmitter and receiver. The paper also presents new analytical models to quantify the probability of the four different types of packet errors in IEEE 802.11p. In addition, the paper presents the first analytical model capable to accurately estimate the Channel Busy Ratio (CBR) metric even under high channel load levels. All the analytical models are validated by means of simulation for a wide range of parameters, including traffic densities, packet transmission frequencies, transmission power levels, data rates and packet sizes. An implementation of the models is provided openly to facilitate their use by the community