Minimizing Spatial and Time Reservation With Collision-Aware DCF in Mobile Ad Hoc Networks

Carrier sensing is widely adopted in wireless communication to protect data transfers from collisions. For example, distributed coordination function (DCF) in IEEE 802.11 standard renders a node to defer its communication if it senses the medium busy. For the duration of deferment, each frame carries, in its MAC header, a 16-bit number in microseconds during which any overhearing node must defer. However, even if the carrier signal is detected, both ongoing and a new communication can be simultaneously successful depending on their relative positions in the network or equivalently, their mutual interference level. Supporting multiple concurrent communications is important in multihop ad hoc networks in order to maximize the network performance. However, it is largely ignored in DCF of the 802.11 standards because it is primarily targeted at single-hop wireless LANs. In addition, in DCF, the time duration information mentioned above is not delivered to all potential interferers, particularly those in the distance. This paper proposes Collision-Aware DCF (CAD) that efficiently utilizes the available channel resource along with the spatial as well as time dimension. First, each node makes its deferment decision adaptively based on the feedback from the communication counterpart and the status of the medium rather than on a simple, fixed carrier sense threshold as DCF. Second, CAD embeds the spatial and time reservation requirements in the PHY header, which is transmitted at the lowest data rate, so that a larger group of neighbors become aware of the ongoing communication and thus avoid collisions. Extensive experiments based on ns-2 network simulator show that CAD consistently outperforms DCF regardless of node mobility, traffic intensity, and channel randomness. For practicality, this paper discusses the implementation of CAD based on the DCF specification

A survey on wireless ad hoc networks

A wireless ad hoc network is a collection of wireless nodes that can dynamically self-organize into an arbitrary and temporary topology to form a network without necessarily using any pre-existing infrastructure. These characteristics make ad hoc networks well suited for military activities, emergency operations, and disaster recoveries. Nevertheless, as electronic devices are getting smaller, cheaper, and more powerful, the mobile market is rapidly growing and, as a consequence, the need of seamlessly internetworking people and devices becomes mandatory. New wireless technologies enable easy deployment of commercial applications for ad hoc networks. The design of an ad hoc network has to take into account several interesting and difficult problems due to noisy, limited-range, and insecure wireless transmissions added to mobility and energy constraints. This paper presents an overview of issues related to medium access control (MAC), routing, and transport in wireless ad hoc networks and techniques proposed to improve the performance of protocols. Research activities and problems requiring further work are also presented. Finally, the paper presents a project concerning an ad hoc network to easily deploy Internet services on low-income habitations fostering digital inclusion8th IFIP/IEEE International conference on Mobile and Wireless CommunicationRed de Universidades con Carreras en Informática (RedUNCI

MAC Protocols for Wireless Mesh Networks with Multi-beam Antennas: A Survey

Multi-beam antenna technologies have provided lots of promising solutions to many current challenges faced in wireless mesh networks. The antenna can establish several beamformings simultaneously and initiate concurrent transmissions or receptions using multiple beams, thereby increasing the overall throughput of the network transmission. Multi-beam antenna has the ability to increase the spatial reuse, extend the transmission range, improve the transmission reliability, as well as save the power consumption. Traditional Medium Access Control (MAC) protocols for wireless network largely relied on the IEEE 802.11 Distributed Coordination Function(DCF) mechanism, however, IEEE 802.11 DCF cannot take the advantages of these unique capabilities provided by multi-beam antennas. This paper surveys the MAC protocols for wireless mesh networks with multi-beam antennas. The paper first discusses some basic information in designing multi-beam antenna system and MAC protocols, and then presents the main challenges for the MAC protocols in wireless mesh networks compared with the traditional MAC protocols. A qualitative comparison of the existing MAC protocols is provided to highlight their novel features, which provides a reference for designing the new MAC protocols. To provide some insights on future research, several open issues of MAC protocols are discussed for wireless mesh networks using multi-beam antennas.Comment: 22 pages, 6 figures, Future of Information and Communication Conference (FICC) 2019, https://doi.org/10.1007/978-3-030-12388-8_

Design of a Power Control MAC Protocol for Mobile Ad Hoc Networks

Power conservation is a major issue in Mobile Ad Hoc networks, as most of the nodes are battery powered. Power control is not related to any particular layer, since we can apply power conservation methods in all layers. But most of the power control mechanisms are working in MAC layer. Here we designed a Power Control MAC protocol for MANET. Our first aim was to control the overall power consumption and the second was improve the throughput of the network. Thus our protocol includes two phases; in the first phase we reduce the power consumption and in the second phase we improve the aggregate throughput of the network. Our work is based on the IEEE 802.11 MAC protocol. We added an additional field to the RTS and CTS control packets (PRTS in RTS packet to indicate the power used to send RTS packet and PData in the CTS packet to indicate the power with which sender can send DATA packet) for the design purpose. For reducing the power consumption we used the following method: We send the RTS packet with maximum or default power. The receiver after receiving the RTS packet calculate the data transmission power PData using the received power Pr , RTS transmission power PRTS and the receiving threshold Rth. After calculating the PData that power is assigned to the PData field of the CTS frame and then the CTS frame will send with the same power PData. Then after receiving the CTS frame the sender will send the DATA frame using the power PData and the receiver will send the ACK packet with the same power. In the second phase we have to improve the throughput of the network. For that purpose we made some modifications in the virtual carrier sensing mechanism. We used a NAVR with NAV to make the VCS scheme suitable for our protocol. It make more nodes to send packets at a time and thus improves the spatial reusability. The improvement in spatial reusability increases the aggregate throughput of the network

Cognitive Adaptive Mac Based on Knowledge Based Reasoning For Cognitive Radio Computer Networks

In this paper we are proposing a new concept in MAC layer protocol design for Cognitive radio by combining information held by physical layer and MAC layer with analytical engine based on knowledge based reasoning approach. In the proposed system a cross layer information regarding signal to interference and noise ratio (SINR) and received power are analyzed with help of knowledge based reasoning system to determine minimum power to transmit and size of contention window, to minimize backoff, collision, save power and drop packets. The performance analysis of the proposed protocol indicates improvement in power saving ,lowering backoff and significant decrease in number of drop packets. The simulation environment was implement using OMNET++ discrete simulation tool with Mobilty framework and MiXiM simulation library

Virtual sensing directional hub MAC (VSDH-MAC) protocol with power control

Medium access control (MAC) protocols play a vital role in making effective use of a multiple access channel as it governs the achievable performance such as channel utilization and corresponding quality of service of wireless sensor networks (WSNs). In this paper, a virtual carrier sensing directional hub (VSDH) MAC protocol incorporating realistic directional antenna patterns is proposed for directional single hub centralized WSNs. While in most instances, MAC protocols assume idealized directional antenna patterns, the proposed VSDH-MAC protocol incorporates realistic directional antenna patterns to deliver enhanced link performance. We demonstrate that the use of directional antennas with a suitable MAC protocol can provide enhanced communication range and increased throughput with reduced energy consumption at each node, compared to the case when only omnidirectional antennas are used. For the scenarios considered in this study, results show that the average transmit power of the sensor nodes can be reduced by a factor of two, and at the same time offer significantly extended lifetime

A stochastic model for optimizing physical carrier sensing and spatial reuse in wireless ad hoc networks

threshold is key to the trade-off between the amount of spatial reuse and probability of packet collisions in a wireless ad hoc network. In this paper, we present a new analytical approach for optimizing the PCS threshold as measured by probability of packet collisions and the aggregate one-hop throughput. Our model simultaneously incorporates the impact of PCS threshold and the backoff mechanism via a suitable Markov chain model for saturation (i.e. all nodes always have a packet to send in their queues). Elaborate OPNET simulation results show the effectiveness of the analytical model. Keywords-spatial reuse; physical carrier sensing; MAC; ad hoc network; IEEE 802.11; analytical modeling; simulatio

Spectrum and Energy Efficient Medium Access Control for Wireless Ad Hoc Networks

The increasingly growing number of mobile devices and volume of mobile data traffic necessitate establishing an effective self-organizing wireless ad hoc network to efficiently utilize radio spectrum and energy. The transmissions time and bandwidth should be dynamically coordinated based on instantaneous traffic load of the links in the network. Energy consumption in a mobile device can be reduced by putting the radio interface into a sleep mode. However, the mobile device cannot receive incoming data packets in the sleep mode. Thus, awake and sleep times of radio interfaces should be carefully planned to avoid missing incoming packets. In a wireless network, links that are far apart in distance can simultaneously transmit using the same bandwidth without interfering reception at destination nodes. Concurrent transmissions should be properly scheduled to maximize spatial spectrum utilization. Also, the transmission power level of each link should be optimized to enhance spectrum and energy efficiencies. First, we present a new energy-efficient medium access control (MAC) scheme for a fully connected wireless ad hoc network. Energy consumption is reduced by periodically putting radio interfaces in the sleep mode and by reducing transmission collisions. The network throughput and average packet transmission delay are also improved because of lower collision and contention overhead. The proposed MAC scheme can achieve energy saving for realtime traffic which requires a low packet transmission delay. An analytical model is established to evaluate the performance of the proposed MAC scheme. Analytical and simulation results demonstrate that the proposed scheme has a significantly lower energy consumption, achieves higher throughput, and has a lower packet transmission delay in comparison with existing power saving MAC protocols. Second, we present a novel distributed MAC scheme based on dynamic space-reservation to effectively coordinate transmissions in a wireless ad hoc network. A set of coordinator nodes distributed over the network area are employed to collect and exchange local network information and to periodically schedule links for transmission in a distributed manner. For each scheduled transmission, a proper space area around the receiver node is reserved to enhance spatial spectrum reuse. Also, the data transmission times are deterministic to minimize idle-listening radio interface energy consumption. Simulation results demonstrate that the proposed scheme achieves substantially higher throughput and has significantly lower energy consumption in comparison with existing schemes. We study joint scheduling and transmission power control in a wireless ad hoc network. We analyze the asymptotic joint optimal scheduling and transmission power control, and determine the maximum spectrum and energy efficiencies in a wireless network. Based on the asymptotic analysis, we propose a novel scheduling and transmission power control scheme to approach the maximum spectrum efficiency, subject to an energy consumption constraint. Simulation results show that the proposed distributed scheme achieves 40% higher throughput than existing schemes. Indeed, the scheduling efficiency of our proposed scheme is about 70% of the asymptotic optimal scheduling and transmission power control. Also, the energy consumption of the proposed scheme is about 20% of the energy consumed using existing MAC protocols. The proposed MAC, scheduling and transmission power control schemes provide effective spectrum sharing and energy management for future wireless hotspot and peer-to-peer communication networks. The presented asymptotic analysis determines the maximum spectrum and energy efficiencies in a wireless network and provides an effective means to efficiently utilize spectrum and energy resources based on network traffic load and energy consumption constrains

Performance issues in cellular wireless mesh networks

This thesis proposes a potential solution for future ubiquitous broadband wireless access networks, called a cellular wireless mesh network (CMESH), and investigates a number of its performance issues. A CMESH is organized in multi-radio, multi-channel, multi-rate and multi-hop radio cells. It can operate on abundant high radio frequencies, such as 5-50 GHz, and thus may satisfy the bandwidth requirements of future ubiquitous wireless applications. Each CMESH cell has a single Internet-connected gateway and serves up to hundreds of mesh nodes within its coverage area. This thesis studies performance issues in a CMESH, focusing on cell capacity, expressed in terms of the max-min throughput. In addition to introducing the concept of a CMESH, this thesis makes the following contributions. The first contribution is a new method for analyzing theoretical cell capacity. This new method is based on a new concept called Channel Transport Capacity (CTC), and derives new analytic expressions for capacity bounds for carrier-sense-based CMESH cells. The second contribution is a new algorithm called the Maximum Channel Collision Time (MCCT) algorithm and an expression for the nominal capacity of CMESH cells. This thesis proves that the nominal cell capacity is achievable and is the exact cell capacity for small cells within the abstract models. Finally, based on the MCCT algorithm, this thesis proposes a series of greedy algorithms for channel assignment and routing in CMESH cells. Simulation results show that these greedy algorithms can significantly improve the capacity of CMESH cells, compared with algorithms proposed by other researchers

1 On the Physical Carrier Sense in Wireless Ad Hoc Networks

Abstract — The aggregate throughput of a wireless ad hoc network depends on the channel capacity, channel utilization (i.e., the fraction of channel capacity used for generating goodput), and the concurrent transmissions allowed in the network. While channel utilization is determined by MAC overhead, physical carrier sense has been used as an effective way to avoid interference and exploit spatial reuse. Prior research has attempted to identify the optimal carrier sense range that can maximize the aggregate throughput. However, the impact of MAC overhead has been ignored. In this paper, we use both an analytical model and simulation results to show that MAC overhead has significant impact on the choice of optimal carrier sense range. If MAC overhead is not taken into account properly in determining the optimal carrier sense range, the aggregate throughput can suffer a significant loss