Busy-tone Channel Research Articles

A CS-Based Grant-Free Media Access Scheme for NOMA-Based Industrial IoTs with Location Awareness

Grant-free media access is vital for applications in Industrial IoTs (IIoTs), where stringent delays are required. Recently, due to the capability of supporting parallel receptions, Non-Orthogonal Multiple Access (NOMA) has gained research interests in IIoTs. Obviously, combining them organically is beneficial for enhancing the delay performances. In this paper, for a typical convergecast wireless network where its data sink is NOMA-based, we propose a grant-free MAC (Media Access Contention) scheme based on Compressive Sensing in Busy Tone Channel (CSiBTC), by exploiting the transmission sparsity in IIoTs. First, a to-be transmitter acquires the identities of active transmitters with the proposed CSiBTC scheme completely by itself. Two construction methods for CSiBTC are proposed for two distinct application scenarios respectively. Then, given the locations of all wireless sensors and the data sink in the network, the to-be transmitter can find out if it is eligible for starting its transmission without impairing the on-going transmissions. The scheme is grant-free and makes the most use of the parallel reception capability of NOMA, and therefore both the delay performance and throughput performance can be improved with respect to the general CS-based MAC. Performance evaluations also strongly support the above conclusions.

MONET Special Half-Issue “Recent Advances on Communications and Networking in China”

Editorial: This special issue features extended versions of six of the best papers selected from the conference Chinacom 2011, which was held in Harbin, China, on August 17– 19, 2011. The emerging vehicular networks are targeted to provide efficient communications between mobile vehicles and fixed roadside units (RSU), and support mobile multimedia applications and safety services with diverse quality of service (QoS) requirements. In the paper titled “Medium Access Control for QoS Provisioning in Vehicle-to-Infrastructure Communication Networks”, Bi, Cai, Shen and Zhao propose a busy tone based medium access control (MAC) protocol with enhanced QoS provisioning for life critical safety services. By using busy tone signals for efficient channel preemption in both contention period (CP) and contention free period (CFP), emergency users can access the wireless channel with strict priority when they compete with multimedia users, and thus achieve the minimal access delay. Furthermore, through efficient transmission coordination on the busy tone channel, contention level can be effectively reduced, and the overall network resource utilization can be improved accordingly. The authors develop an analytical model to quantify the medium access delay of emergency messages. Extensive simulations with Network Simulator (NS)-2 validate the analysis and demonstrate that the proposed MAC can guarantee reliable and timely emergency message dissemination in a vehicular network. Delay tolerant networks (DTNs) rely on the mobility of nodes and sequences of their contacts to compensate for lack of continuous connectivity and thus enable messages to be delivered from end to end in a “store-carryforward” way, where multiple relay nodes are usually employed in the message delivery process. In the paper “Performance Modeling for Relay Cooperation in Delay Tolerant Networks Layered Fault”, Liu, Jiang, Nishiyama and Kato focus on such relay cooperation and analytically explore its impact on the delivery performance in DTNs. Specifically, the authors first develop a continuous time Markov chain-based theoretical framework to model the complicated message delivery process in delay tolerant networks adopting the two-hop relay algorithm. They then derive closed-form expressions for both the expected V. C. M. Leung (*) Department of Electrical and Computer Engineering, University of British Columbia (UBC), Vancouver, Canada e-mail: vleung@ece.ubc.ca

Medium Access Control for QoS Provisioning in Vehicle-to-Infrastructure Communication Networks

The emerging vehicular networks are targeted to provide efficient communications between mobile vehicles and fixed roadside units (RSU), and support mobile multimedia applications and safety services with diverse quality of service (QoS) requirements. In this paper, we propose a busy tone based medium access control (MAC) protocol with enhanced QoS provisioning for life critical safety services. By using busy tone signals for efficient channel preemption in both contention period (CP) and contention free period (CFP), emergency users can access the wireless channel with strict priority when they compete with multimedia users, and thus achieve the minimal access delay. Furthermore, through efficient transmission coordination on the busy tone channel, contention level can be effectively reduced, and the overall network resource utilization can be improved accordingly. We then develop an analytical model to quantify the medium access delay of emergency messages. Extensive simulations with Network Simulator (NS)-2 validate the analysis and demonstrate that the proposed MAC can guarantee reliable and timely emergency message dissemination in a vehicular network.

A New MAC Scheme Supporting Voice/Data Traffic in Wireless Ad Hoc Networks

In wireless ad hoc networks, in addition to the well-known hidden terminal and exposed terminal problems, the location-dependent contention may cause serious unfairness and priority reversal problems. These problems can severely degrade network performance. To the best of our knowledge, so far there is no comprehensive study to fully address all these problems. In this paper, a new busy-tone based medium access control (MAC) scheme supporting voice/data traffic is proposed to address these problems. Via two separated narrow-band busy-tone channels with different carrier sense ranges, the proposed scheme completely resolves the hidden terminal and exposed terminal problems. Furthermore, with the use of transmitter busy-tones in the node backoff procedure, the proposed scheme ensures guaranteed priority access for delay-sensitive voice traffic over data traffic. The priority is also independent of the user locations, thus solving the priority reversal problem. The fairness performance for data traffic in a non-fully-connected environment is also greatly improved (as compared with the popular IEEE 802.11e MAC scheme) without the need for extra information exchanges among the nodes.

Quality of Service in Mobile Ad Hoc Networks

Mobile ad hoc networking is a challenging task due to thelack of resources residing in the network as well as the fre-quentchangesinnetworktopology.Althoughmuchresearchhas been directed to supporting quality of service (QoS) inthe Internet and traditional wireless networks, present re-sults are not suitable for mobile ad hoc network (MANET).QoS support for mobile ad hoc networks remains an openproblem, drawing interest from both academia and indus-try under military and commercial sponsorship. MANETshave certain unique characteristics that pose several diffi-culties in provisioning QoS, such as dynamically varyingnetwork topology, lack of precise state information, lack ofcentral control, error-prone shared radio channels, limitedresource availability, hidden terminal problems, and inse-cure media, and little consensus yet exists on which ap-proaches may be optimal. Future MANETs are likely to be“multimode” or heterogeneous in nature. Thus, the routerscomprising a MANET will employ multiple, physical-layerwireless technologies, with each new technology requiring amultiple access (MAC) protocol for supporting QoS. Abovethe MAC layer, forwarding, routing, signaling, and admis-sion control policies are required, and the best combinationofthesepolicieswillchangeastheunderlyinghardwaretech-nology evolves.In response to the above demand for mobile ad hocnetworks, this special issue aims at providing a timely andconcise reference of the current activities and findings in therelevant technical fields, and focuses as well on the state-of-the-art and up-to-date efforts in design, performance anal-ysis, implementation and experimental results for variousQoS issues in MANETs.Webelievethatallofthesepapersnotonlyprovidenovelideas, new analytical models, simulation and experimentalresults, and handful experience in this field, but also simu-late the future research activities in the area of the quality ofserviceformobileadhocnetworks.Abriefsummaryofeachpaper is listed as follows.The first paper by Qi He et al. first identifies two criti-cal issues leading to the TCP performance degradation: (1)unreliable broadcast, since broadcast frames are transmittedwithout the request-to-send and clear-to-send (RTS/CTS)dialog and Data/ACK handshake, so they are vulnerable tothehiddenterminalproblem;and(2)falselinkfailurewhichoccurs when a node cannot successfully transmit data tem-porarily due to medium contention. Secondly, the authorspropose a scheme to use a narrow-bandwidth, out-of-bandbusy-tonechanneltomakereservationforbroadcastandlinkerror detection frames only. The proposed scheme is sim-ple and power efficient, because only the sender needs totransmit two short messages in the busy tone channel beforesending broadcast or link error detection frames in the datachannel. Analytical results show that the proposed schemecan dramatically reduce the collision probability of broad-cast and link error detection frames. Extensive simulationswith different network topologies further demonstrate thatthe proposed scheme can improve TCP throughput by 23%to150%,dependingonusermobility,andeffectivelyenhanceboth short-term and long-term fairness among coexistingTCP flows in multi-hop wireless ad hoc networks.The second paper by Deying Li et al. discusses the en-ergy efficient QoS topology control problem for nonhomo-geneous ad hoc wireless networks. Given a set of nodes withdifferent energy and bandwidth capacities in a plane, andgiven the end-to-end traffic demands and delay bounds be-tween node pairs, the problem is to find a network topol-ogy that can meet the QoS requirements, and the maximumenergy utilization of nodes is minimized. Achieving this ob-jective is vital to the increase of network lifetime. We con-sider two cases of the problem: (1) the traffic demands arenot splittable, and (2) the traffic demands are splittable. For

Improving TCP Performance over Wireless Ad Hoc Networks with Busy Tone Assisted Scheme

It is well known that transmission control protocol (TCP) performance degrades severely in IEEE 802.11-based wireless ad hoc networks. We first identify two critical issues leading to the TCP performance degradation: (1) unreliable broadcast, since broadcast frames are transmitted without the request-to-send and clear-to-send (RTS/CTS) dialog and Data/ACK handshake, so they are vulnerable to the hidden terminal problem; and (2) false link failure which occurs when a node cannot successfully transmit data temporarily due to medium contention. We then propose a scheme to use a narrow-bandwidth, out-of-band busy tone channel to make reservation for broadcast and link error detection frames only. The proposed scheme is simple and power efficient, because only the sender needs to transmit two short messages in the busy tone channel before sending broadcast or link error detection frames in the data channel. Analytical results show that the proposed scheme can dramatically reduce the collision probability of broadcast and link error detection frames. Extensive simulations with different network topologies further demonstrate that the proposed scheme can improve TCP throughput by 23% to 150%, depending on user mobility, and effectively enhance both short-term and long-term fairness among coexisting TCP flows in multihop wireless ad hoc networks.

Design of an Optimum Channel Utilisation Multiaccess Protocol for Packet Radio Networks

Design and throughput performance of an Optimum Channel Utilisation Multiaccess (OCUM) protocol applicable to Packet Radio Networks (PRN) is presented in this paper. The OCUM protocol utilizes a slotted message channel for data transmission and a busytone channel for sensing and acknowledgement functions. The messages constitute multiple data packets where each packet length is equal to one slot size. The OCUM protocol design results in effective utilisation of the message channel by achieving minimum channel idle rate and collision rate. The throughput performance of the protocol has been analyzed for a finite population model with Bernoulli arrivals at cach node, geometric distribution of message lengths (measured in number of packets) and with no buffer assumption. Both the analytical and simulation results show that the protocol enjoys better throughput characteristics at high values of average message lengths making it ideally suited for file transfer type applications.

Performance evaluation of the R-BTMA protocol in a distributed mobile radio network context

A reservation multiple-access protocol for mobile communication in a decentralized environment is proposed and investigated both analytically and by simulation. The reservation-busy-tone multiple access (R-BTMA) is a fully distributed and reservation-based protocol. It is a medium access control (MAC) protocol designed for short-range communications between vehicles in a decentralized context (i.e., without a base station). The specificity of this protocol relies on the utilization of two different characteristic channels. Information is transmitted on the data channel (DC), whereas the busy-tone channel (BTC) is used for signalling traffic. The range of the BTC is typically longer than the DC one. The throughput and access delay performance are studied in the particular context of two cells sharing a common BTC. The traffic between the vehicles is supposed to be regular and is parameter sharing. The comparison of the model analysis results to those obtained by the simulative approach shows a satisfactory matching.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>