A dynamic distributed multi-channel TDMA slot management protocol for ad hoc networks

With the emergence of new technologies and standards for wireless communications and an increase in application and user requirements, the number and density of deployed wireless ad hoc networks is increasing. For deterministic ad hoc networks, Time-Division Multiple Access (TDMA) is a popular medium access scheme, with many distributed TDMA scheduling algorithms being proposed. However, with increasing traffic demands and the number of wireless devices, proposed protocols are facing scalability issues. Besides, these protocols are achieving suboptimal spatial spectrum reuse as a result of the unsolved exposed node problem. Due to a shortage of available spectrum, a shift from fixed spectrum allocation to more dynamic spectrum sharing is anticipated. For dynamic spectrum sharing, improved distributed scheduling protocols are needed to increase spectral efficiency and support the coexistence of multiple co-located networks. Hence, in this paper, we propose a dynamic distributed multi-channel TDMA (DDMC-TDMA) slot management protocol based on control messages exchanged between one-hop network neighbors and execution of slot allocation and removal procedures between sender and receiver nodes. DDMC-TDMA is a topology-agnostic slot management protocol suitable for large-scale and high-density ad hoc networks. The performance of DDMC-TDMA has been evaluated for various topologies and scenarios in the ns-3 simulator. Simulation results indicate that DDMC-TDMA offers near-optimal spectrum utilization by solving both hidden and exposed node problems. Moreover, it proves to be a highly scalable protocol, showing no performance degradation for large-scale and high-density networks and achieving coexistence with unknown wireless networks operating in the same wireless domain

An Adaptive Common Control Channel MAC with Transmission Opportunity in IEEE 802.11ac

Spectral utilization is a major challenge in wireless ad hoc networks due in part to using limited network resources. For ad hoc networks, the bandwidth is shared among stations that can transmit data at any point in time. It  is important to maximize the throughput to enhance the network service. In this paper, we propose an adaptive multi-channel access with transmission opportunity protocol for multi-channel ad hoc networks, called AMCA-TXOP. For the purpose of coordination, the proposed protocol uses an adaptive common control channel over which the stations negotiate their channel selection based on the entire available bandwidth and then switch to the negotiated channel. AMCA-TXOP requires a single radio interface so that each station can listen to the control channel, which can overhear all agreements made by the other stations. This allows parallel transmission to multiple stations over various channels, prioritizing data traffic to achieve the quality-of-service requirements. The proposed approach can work with the 802.11ac protocol, which has expanded the bandwidth to 160 MHz by channel bonding. Simulations were conducted to demonstrate the throughput gains that can be achieved using the AMCA-TXOP protocol. Moreover, we compared our protocol with  the IEEE 802.11ac standard protocols

A Q-Learning approach with collective contention estimation for bandwidth-efficient and fair access control in IEEE 802.11p vehicular networks

Vehicular Ad hoc Networks (VANETs) are wireless networks formed of moving vehicle-stations, that enable safety-related packet exchanges among them. Their infrastructure-less, unbounded nature allows the formation of dense networks that present a channel sharing issue, which is harder to tackle than in conventional WLANs, due to fundamental differences of the protocol stack. Optimising channel access strategies is important for the efficient usage of the available wireless bandwidth and the successful deployment of VANETs. We present a Q-Learning-based approach to wirelessly network a big number of vehicles and enable the efficient exchange of data packets among them. More specifically, this work focuses on a IEEE 802.11p-compatible contention-based Medium Access Control (MAC) protocol for efficiently sharing the wireless channel among multiple vehicular stations. The stations feature algorithms that "learn" how to act optimally in a network in order to maximise their achieved packet delivery and minimise bandwidth wastage. Additionally, via a Collective Contention Estimation (CCE) mechanism which we embed on the Q-Learning agent, faster convergence, higher throughput and short-term fairness are achieved

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

An Energy Efficient Multichannel MAC Protocol for Cognitive Radio Ad Hoc Networks

This paper presents a TDMA based energy efficient cognitive radio multichannel medium access control (MAC) protocol called ECR-MAC for wireless Ad Hoc Networks. ECR-MAC requires only a single half-duplex radio transceiver on each node that integrates the spectrum sensing at physical (PHY) layer and the packet scheduling at MAC layer. In addition to explicit frequency negotiation which is adopted by conventional multichannel MAC protocols, ECR-MAC introduces lightweight explicit time negotiation. This two-dimensional negotiation enables ECR-MAC to exploit the advantage of both multiple channels and TDMA, and achieve aggressive power savings by allowing nodes that are not involved in communication to go into doze mode. The IEEE 802.11 standard allows for the use of multiple channels available at the PHY layer, but its MAC protocol is designed only for a single channel. A single channel MAC protocol does not work well in a multichannel environment, because of the multichannel hidden terminal problem. The proposed energy efficient ECR-MAC protocol allows SUs to identify and use the unused frequency spectrum in a way that constrains the level of interference to the primary users (PUs). Extensive simulation results show that our proposed ECR-MAC protocol successfully exploits multiple channels and significantly improves network performance by using the licensed spectrum band opportunistically and protects QoS provisioning over cognitive radio ad hoc networks.Comment: 8 Pages, International Journa

Efficient two windows MAC algorithm in wireless ad-hoc networks

In this thesis, a Two Windows MAC Algorithm (TWMA) is proposed and extensive simulation studies compare the proposed medium access algorithm and IEEE 802.11 standard. TWMA is introduced to solve the fairness problem in medium access and improve the utilization of the channel i.e. throughput, traffic delay, and fairness of medium access algorithm mainly in wireless ad hoc networks using Carrier-Sense Multiple Access with Collision Avoidance (CSMA/CA). The media access control (MAC) protocol plays a critical role in providing fairness, efficiency, and robustness in wireless networks. IEEE 802.11 MAC using exponential random backoff algorithm can not solve such fairness problem, i.e. stations cannot gain fair access to the shared wireless medium, due to non-homogeneous traffic load distribution, location dependent contention for medium access, and lack of central administration in ad hoc networks. The proposed MAC algorithm uses a variable Channel Status Indicator (CSI) to represent adjacent traffic status and two windows contention algorithm in order to achieve better throughput, latency, and a degree of fairness. Simulation results show the performance characteristics and functionalities of the algorithm that includes throughput, latency, buffer overflow, and etc. The simulation results reveal that the proposed TWMA achieve higher throughput and lower latency than that of the IEEE 802.11 standards MAC algorithm

CR-MAC: A multichannel MAC protocol for cognitive radio ad hoc networks

This paper proposes a cross-layer based cognitive radio multichannel medium access control (MAC) protocol with TDMA, which integrate the spectrum sensing at physical (PHY) layer and the packet scheduling at MAC layer, for the ad hoc wireless networks. The IEEE 802.11 standard allows for the use of multiple channels available at the PHY layer, but its MAC protocol is designed only for a single channel. A single channel MAC protocol does not work well in a multichannel environment, because of the multichannel hidden terminal problem. Our proposed protocol enables secondary users (SUs) to utilize multiple channels by switching channels dynamically, thus increasing network throughput. In our proposed protocol, each SU is equipped with only one spectrum agile transceiver, but solves the multichannel hidden terminal problem using temporal synchronization. The proposed cognitive radio MAC (CR-MAC) protocol allows SUs to identify and use the unused frequency spectrum in a way that constrains the level of interference to the primary users (PUs). Our scheme improves network throughput significantly, especially when the network is highly congested. The simulation results show that our proposed CR-MAC protocol successfully exploits multiple channels and significantly improves network performance by using the licensed spectrum band opportunistically and protects PUs from interference, even in hidden terminal situations.Comment: 14 Pages, International Journa

CROSS-LAYER SCHEDULING PROTOCOLS FOR MOBILE AD HOC NETWORKS USING ADAPTIVE DIRECT-SEQUENCE SPREAD-SPECTRUM MODULATION

We investigate strategies to improve the performance of transmission schedules for mobile ad hoc networks (MANETs) employing adaptive direct-sequence spread-spectrum (DSSS) modulation. Previously, scheduling protocols for MANETs have been designed under the assumption of an idealized, narrowband wireless channel. These protocols perform poorly when the channel model incorporates distance-based path loss and co-channel interference. Wideband communication systems, such as DSSS systems, are more robust in the presence of co-channel interference; however, DSSS also provides multiple-access capability that cannot be properly leveraged with a protocol designed for narrowband systems. We present a new transmission scheduling protocol that incorporates link characteristics, spreading factor adaptation, and packet capture capability into scheduling and routing decisions. This provides greater spatial reuse of the channel and better adaptability in mobile environments. Simulation results demonstrate the merits of this approach in terms of end-to-end packet throughput, delay, and completion rate for unicast traffic. We also discuss two variations of the protocol: one provides a method for enhancing the network topology through exchange of local information, and the other leverages multi-packet reception (MPR) capability to enhance the network topology. We show that each approach is useful in networks with sparse connectivity. We conclude by studying the capacity of the networks used in previous sections, providing insight on methods for realizing further performance gains

Routing performance in ad hoc networks.

Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.An ad hoc network is a multi-hop wireless network in which mobile nodes communicate over a shared wireless channel. The network is formed cooperatively without specific user administration or configuration and is characterised by a distributed network management system and the absence of a wired backbone. Military, law enforcement, and disaster relief operations are often carried out in situations with no pre-existing network infrastructure and can benefit from such networks because base stations, which are single points of failure, are undesirable from a reliability standpoint. The rising popularity of mobile computing has also created a potentially large commercial market for multimedia applications applied over wireless ad hoc networks. This dissertation focuses on the routing aspects of ad hoc networking. The multi-hop routes between nodes constantly change as the mobile nodes migrate. Ad hoc network routing algorithms must therefore adapt to the dynamic and unpredictable topology changes, the random radio propagation conditions and portable power sources. Various routing protocols have been proposed in the literature for ad hoc networks. These protocols together with comparative simulations are discussed and a new protocol based on load balancing and signal quality determination is proposed . and the simulation results are presented. Currently the proposed routing protocols are compared using simulation packages which are often time consuming. This dissertation proposes a mathematical model for evaluating the routing protocols and the resultant end-to-end blocking probabilities. The mathematical model is based on a derivation of the reduced load approximation for analysing networks modelled as loss networks and the evaluation incorporates and adapts models that have been used for the analysis of cellular Code Division Multiple Access (CDMA) systems. While analytical methods of solving blocking probability can potentially generate results orders of magnitude faster than simulation, they are more importantly essential to network sensitivity analysis, design and optimisation