Decentralised multi-access MAC protocol for ad-hoc networks

In ad-hoc radio networks, mechanisms on how to access the radio channel are extremely important in order to improve network efficiency and, when needed, to guarantee QoS. Traditionally, Medium Access Control (MAC) protocols in ad hoc networks have been designed to face off the well known collision resolution problem. However, when using advanced signal processing techniques, general assumptions on collisions and packet loss are no longer valid. Besides, little has been reported about MAC algorithms dealing with multiaccess channels in ad hoc networks. In this paper, we present a novel decentralized multiaccess MAC protocol for Ad Hoc networks. This MAC protocol is an hybrid CDMA-TDMA in which a cross layer approach has been followed to dinamically adapt to the traffic load. Closed expressions for the throughput and delay of the network are presented as a function of the multipacket reception capability of the receiver, the number of codes and the packet retransmission probability.Postprint (published version

Analysis and evaluation of decentralized multiaccess Mac for ad-hoc networks

In mobile ad-hoc radio networks, terminals are mobile and heterogeneous, the architecture of the network is continuously changing, communication links are packet oriented and radio resources are scarce. Therefore, mechanisms on how to access the radio channel are extremely important in order to improve network efficiency and, when needed, to guarantee QoS. However, due to these network harsh conditions, decentralized Medium Access Control (MAC) protocols designed specifically for ad hoc networks are scarce. In this paper we present a novel decentralized multiaccess MAC protocol for Ad Hoc networks. This MAC protocol is an hybrid CDMATDMA in which a cross layer approach has been followed in order to maximize network throughput. A theoretical analysis of the system is presented ending up with closed expressions for the throughput and delay of the network and some simulations are presented to evaluate the performance of the system.Postprint (published version

RECOMAC: a cross-layer cooperative network protocol for wireless ad hoc networks

A novel decentralized cross-layer multi-hop cooperative protocol, namely, Routing Enabled Cooperative Medium Access Control (RECOMAC) is proposed for wireless ad hoc networks. The protocol architecture makes use of cooperative forwarding methods, in which coded packets are forwarded via opportunistically formed cooperative sets within a region, as RECOMAC spans the physical, medium access control (MAC) and routing layers. Randomized coding is exploited at the physical layer to realize cooperative transmissions, and cooperative forwarding is implemented for routing functionality, which is submerged into the MAC layer, while the overhead for MAC and route set up is minimized. RECOMAC is shown to provide dramatic performance improvements of eight times higher throughput and one tenth of end-to-end delay than that of the conventional architecture in practical wireless mesh networks

A Media Access Control Protocol for Wireless Adhoc Networks with Misbehaviour Avoidance

The most common wireless Medium Access Control (MAC) protocol is IEEE 802.11. Currently IEEE 802.11 standard protocol is not resilient for many identified MAC layer attacks, because the protocol is designed without intention for providing security and with the assumption that all the nodes in the wireless network adhere to the protocol. However, nodes may purposefully show misbehaviours at the MAC layer in order to obtain extra bandwidth con-serve resources and degrade or disrupt the network performance. This research proposes a secure MAC protocol for MAC layer which has integrated with a novel misbehaviour detection and avoidance mechanism for Mobile Ad Hoc Networks (MANETs). The proposed secure MAC protocol the sender and receiver work collaboratively together to handshakes prior to deciding the back-off values. Common neighbours of the sender and receiver contributes effectively to misbehaviours detection and avoidance process at MAC layer. In addition the proposed solution introduces a new trust distribution model in the network by assuming none of the wireless nodes need to trust each other. The secure MAC protocol also assumes that misbehaving nodes have significant levels of intelligence to avoid the detectio

Queue utilization with hop based enhanced arbitrary inter frame spacing MAC for saturated ad HOC networks

© 2015 IEEE. Path length of a multi hop Ad Hoc networks has an adverse impact on the end-to-end throughput especially during network saturation. The success rate of forwarding packets towards destination is limited due to interference, contention, limited buffer space, and bandwidth. Real time applications streaming data fill the buffer space at a faster rate at the source and its nearby forwarding nodes since the channel is shared. The aim of this paper is to increase the success rate of forwarding the packets to yield a higher end-to-end throughput. In order to reduce loss of packets due to buffer overflow and enhance the performance of the network for a saturated network, a novel MAC protocol named Queue Utilization with Hop Based Enhanced Arbitrary Inter Frame Spacing based (QU-EAIFS) MAC is proposed for alleviating the problems in saturated Ad Hoc networks. The protocol prioritises the nodes based on its queue utilization and hops travelled by the packet and it helps achieving higher end-toend performance by forwarding the packets with higher rate towards the destination during network saturation. The proposed MAC enhances the end-to-end performance by approximately 40% and 34% for a 5hop and 6hop communication respectively in a chain topology as compared to the standard IEEE802.11b. The performance of the new MAC also outperforms the performance of IEEE 802.11e MAC. In order to validate the protocol, it is also tested with short hops and varying packet sizes and more realistic random topologies

Scalable Lunar Surface Networks and Adaptive Orbit Access

Teranovi Technologies, Inc., has developed innovative network architecture, protocols, and algorithms for both lunar surface and orbit access networks. A key component of the overall architecture is a medium access control (MAC) protocol that includes a novel mechanism of overlaying time division multiple access (TDMA) and carrier sense multiple access with collision avoidance (CSMA/CA), ensuring scalable throughput and quality of service. The new MAC protocol is compatible with legacy Institute of Electrical and Electronics Engineers (IEEE) 802.11 networks. Advanced features include efficiency power management, adaptive channel width adjustment, and error control capability. A hybrid routing protocol combines the advantages of ad hoc on-demand distance vector (AODV) routing and disruption/delay-tolerant network (DTN) routing. Performance is significantly better than AODV or DTN and will be particularly effective for wireless networks with intermittent links, such as lunar and planetary surface networks and orbit access networks

A density-based contention window control scheme for unicast communications in vehicular ad hoc networks

[EN] Achieving a well-designed medium access control (MAC) protocol is a challenging issue to improve communications efficiency due to the dynamic nature of vehicular ad hoc networks (VANETs). IEEE 802.11p standard was selected as the best choice for vehicular environments considering its availability, maturity, and cost. The common problem in all IEEE 802.11 based protocols is scalability, exhibiting performance degradation in highly variable network scenarios. Experimental results for the IEEE 802.11-based MAC protocol show the importance of contention window adjustment on communications performance; However the vehicular communications community has not yet addressed this issue in unicast communication environments. This paper proposes a novel contention window control scheme for VANET environments based on estimating the network density, which is then used to dynamically adapt the CW size. Analysis and simulation results showthat our proposal provides better overall performance compared with previous proposals, even in high network density scenarios.This work was supported by the Ministerio de Economía y Competitividad, Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad, Proyectos I+D+I 2014, Spain, under Grant TEC2014-52690-R.Balador, A.; Tavares De Araujo Cesariny Calafate, CM.; Cano, J.; Manzoni, P. (2017). A density-based contention window control scheme for unicast communications in vehicular ad hoc networks. International Journal of Ad Hoc and Ubiquitous Computing. 24(1-2):65-75. doi:10.1504/IJAHUC.2017.080913S6575241-

Decentralized Time-Synchronized Channel Swapping for Ad Hoc Wireless Networks

International audienceTime-synchronized channel hopping (TSCH) is currently the most efficient solution for collision-free, interferenceavoiding communications in ad hoc wireless networks, such as wireless sensor networks, vehicular networks, and networks of robots or drones. However, all variants of TSCH require some form of centralized coordination to maintain the time-frequency slotting mechanism. This leads to slow convergence to steady state and moderate time-frequency slot utilization, especially under node churn or mobility. We propose decentralized timesynchronized channel swapping (DT-SCS), a novel protocol for medium access control (MAC) in ad hoc wireless networks. Under the proposed protocol, nodes first converge to synchronous beacon packet transmissions across all available channels at the physical layer, with balanced number of nodes in each channel. This is done by the novel coupling of distributed synchronization and desynchronization mechanisms—which are based on the concept of pulse-coupled oscillators—at the MAC layer. Decentralized channel swapping can then take place via peer-to-peer swap requests/acknowledgments made between concurrent transmitters in neighboring channels. We benchmark the convergence and network throughput of DT-SCS, TSCH and the Efficient Multichannel MAC (EM-MAC) protocol (seen as the state-of-the-art in decentralized, interference-avoiding, multichannel MAC protocols) under simulated packet losses at the MAC layer. Moreover, performance results via a Contikibased deployment on TelosB motes reveal that DT-SCS comprises an excellent candidate for decentralized multichannel MAC layer coordination by providing for: quick convergence to steady state,high bandwidth utilization under interference and hidden nodes,and high connectivity

Cross-layer optimizations in multi-hop ad hoc networks

Unlike traditional wireless networks, characterized by the presence of last-mile, static and reliable infrastructures, Mobile ad Hoc Networks (MANETs) are dynamically formed by collections of mobile and static terminals that exchange data by enabling each other's communication. Supporting multi-hop communication in a MANET is a challenging research area because it requires cooperation between different protocol layers (MAC, routing, transport). In particular, MAC and routing protocols could be considered mutually cooperative protocol layers. When a route is established, the exposed and hidden terminal problems at MAC layer may decrease the end-to-end performance proportionally with the length of each route. Conversely, the contention at MAC layer may cause a routing protocol to respond by initiating new routes queries and routing table updates. Multi-hop communication may also benefit the presence of pseudo-centralized virtual infrastructures obtained by grouping nodes into clusters. Clustering structures may facilitate the spatial reuse of resources by increasing the system capacity: at the same time, the clustering hierarchy may be used to coordinate transmissions events inside the network and to support intra-cluster routing schemes. Again, MAC and clustering protocols could be considered mutually cooperative protocol layers: the clustering scheme could support MAC layer coordination among nodes, by shifting the distributed MAC paradigm towards a pseudo-centralized MAC paradigm. On the other hand, the system benefits of the clustering scheme could be emphasized by the pseudo-centralized MAC layer with the support for differentiated access priorities and controlled contention. In this thesis, we propose cross-layer solutions involving joint design of MAC, clustering and routing protocols in MANETs. As main contribution, we study and analyze the integration of MAC and clustering schemes to support multi-hop communication in large-scale ad hoc networks. A novel clustering protocol, named Availability Clustering (AC), is defined under general nodes' heterogeneity assumptions in terms of connectivity, available energy and relative mobility. On this basis, we design and analyze a distributed and adaptive MAC protocol, named Differentiated Distributed Coordination Function (DDCF), whose focus is to implement adaptive access differentiation based on the node roles, which have been assigned by the upper-layer's clustering scheme. We extensively simulate the proposed clustering scheme by showing its effectiveness in dominating the network dynamics, under some stressing mobility models and different mobility rates. Based on these results, we propose a possible application of the cross-layer MAC+Clustering scheme to support the fast propagation of alert messages in a vehicular environment. At the same time, we investigate the integration of MAC and routing protocols in large scale multi-hop ad-hoc networks. A novel multipath routing scheme is proposed, by extending the AOMDV protocol with a novel load-balancing approach to concurrently distribute the traffic among the multiple paths. We also study the composition effect of a IEEE 802.11-based enhanced MAC forwarding mechanism called Fast Forward (FF), used to reduce the effects of self-contention among frames at the MAC layer. The protocol framework is modelled and extensively simulated for a large set of metrics and scenarios. For both the schemes, the simulation results reveal the benefits of the cross-layer MAC+routing and MAC+clustering approaches over single-layer solutions

Multi-hop Clock Synchronization in Wireless Ad-Hoc Networks

In this paper, we introduce Black Burst Clock Synchronization (BBCS), a novel protocol for multi-hop time synchronization in wireless ad-hoc networks, located at MAC level. BBCS is based on the exchange of synchronized tick and time frames, which are protected against collisions by a special encoding using black bursts. It provides a deterministic upper bound for clock offset that only depends on maximum network diameter, and on the used transceiver hardware. BBCS has low complexity in terms of communication, computation, storage, structure, and energy consumption. It provides low and deterministic convergence delay, and is robust against node movements and node failures. In this work, we introduce BBCS, provide a formal analysis of its properties, and evaluate the required overhead for clock-synchronizing a multi-hop wireless ad-hoc network