A Cross-Layer Admission Control Framework for Wireless Ad-Hoc Networks using Multiple Antennas

Unlike single omnidirectional antennas, multiple antennas offer wireless ad-hoc networks potential increases in their achievable throughput and capacity. Due to recent advances in antenna technology, it is now affordable to build wireless devices with more than one antenna. As a result, multiple antennas are expected to be an essential part of next-generation wireless networks to support the rapidly emerging multimedia applications characterized by their high and diverse QoS needs. This paper develops an admission control framework that exploits the benefits of multiple antennas to better support applications with QoS requirements in wireless ad-hoc networks. The developed theory provides wireless ad-hoc networks with flow-level admission control capabilities while accounting for cross-layer effects between the PHY and the MAC layers. Based on the developed theory, we propose a mechanism that multiple antenna equipped nodes can use to control flows' admissibility into the network. Through simulation studies, we show that the proposed mechanism results in high flow acceptance rates and high network throughput utilization.     

D-STAR MAC Protocol: A Cross Layer Solution for Wireless Sensor Networks Endowed with Directive Antennas

This paper deals with a novel MAC layer protocol, namely Directive synchronous transmission asynchronous reception (D-STAR), which is able to logically synchronize a Wireless sensor network (WSN). In this case both sleep and active states together with integrating directional antennas within the communications framework can be managed, according to a cross-layer design. D-STAR protocol has been characterized in terms of functional characteristics and the overall performance is presented in terms of network lifetime gain, set-up latency and collision probability. A remarkable gain is shown with respect to the basic approach endowed with omnidirectional antennas without increasing the signaling overhead nor affecting the set up latency, but achieving energy consumption reduction.

Congestion Control Framework for Ad-Hoc Wireless Networks

During the last few years, bandwidth and traffic control have immerged as issues of great importance in ad-hoc wireless networks, requiring sophisticated managing techniques. Moreover, due to the increasing variety of applications and consequently respective need for bandwidth control, such issues are expected to become even more critical in the near future. Main characteristics of MANETs such as multi-hop communication and supporting dynamically varying topologies rapidly and unpredictably change or remain static over long periods of time augments the complexity of the problem as well as the need to efficiently handle it. In order to circumvent those problems, many researchers turn their attention to cross-layer design which provides the possibility to create lightweight and flexible substrate for the demanding ad-hoc wireless networks. This design approach provides critical features that suit the characteristics of ad-hoc wireless networks. This paper proposes a novel, lightweight and efficient cross-layer architecture for congestion control at wireless ad-hoc networks. The performance of this framework is evaluated considering characteristic ad-hoc routing protocols, such as AODV and DSR, in static as well as mobile network topologies using the well known network simulator NS2.     

一种新的有效支持智能天线应用的多址接入协议

本文研究将智能天线应用于分组无线网络中,提出了支持智能天线应用的自适应时隙分配多址接入协议(ASAMA).该协议采用时分双工(TDD)方式,每一帧开始时用户节点依次发送训练序列,基站的智能天线据此计算出各用户节点的空间特征(Spatial Signature).基于波束形成的信干噪比最大化准则,设计了逐点优化与全局优化两种不同复杂度的时隙分配算法.由基站对上下行业务的时隙进行动态分配,在保证通信质量的前提下,使每个时隙容纳多个数据分组,以充分实现信道的空分复用(SDMA).对该协议的信道利用率进行了近似分析,并利用仿真方法考察其性能.结果表明,ASAMA协议能有效支持智能天线应用并具有很高的信道利用率与良好的时延性能.     

基于智能天线的Ad Hoc网络MAC协议

天线Ad Hoc网络已经广泛应用于各种无基础架构的环境中。阐述了基于智能天线的Ad Hoc网络MAC协议研究领域的最新进展。对Ad Hoc网络中的隐节点和暴露节点问题作了分析,并对智能天线技术的实现机制进行了简要的概括。在介绍典型MAC协议的基础上,指出了未来MAC协议设计的研究方向,指出基于智能天线的MAC协议研究具有很好的发展前景。     

MAQF:一种新的移动Ad-Hoc网络自适应QoS结构框架

链路的时变特性及节点移动的无规则性是造成移动Ad-Hoc网络QoS保障难以实现的根本原因，针对这一难题，本文在对INSIGNIA结构框架进行个性的基础上，通过增加动态资源调整、QoS路由及MAC层QoS保障等组件和机制，提出了一种新的自适应QoS结构框架MAQF。此外，本文还涉及及移动接入时的QoS保障问题，并对动态资源调整算法进行了详细阐述。仿真结果表明，MAQF可以更好地适应网络环境的动态变化。     

A Unified Cross-Layer Framework for Resource Allocation in Cooperative Networks

Node cooperation is an emerging and powerful solution that can overcome the limitation of wireless systems as well as improve the capacity of the next generation wireless networks. By forming a virtual antenna array, node cooperation can achieve high antenna and diversity gains by using several partners to relay the transmitted signals. There has been a lot of work on improving the link performance in cooperative networks by using advanced signal processing or power allocation methods among a single source node and its relays. However, the resource allocation among multiple nodes has not received much attention yet. In this paper, we present a unified crosslayer framework for resource allocation in cooperative networks, which considers the physical and network layers jointly and can be applied for any cooperative transmission scheme. It is found that the fairness and energy constraint cannot be satisfied simultaneously if each node uses a fixed set of relays. To solve this problem, a multi-state cooperation methodology is proposed, where the energy is allocated among the nodes state-by-state via a geometric and network decomposition approach. Given the energy allocation, the duration of each state is then optimized so as to maximize the nodes utility. Numerical results will compare the performance of cooperative networks with and without resource allocation for cooperative beamforming and selection relaying. It is shown that without resource allocation, cooperation will result in a poor lifetime of the heavily-used nodes. In contrast, the proposed framework will not only guarantee fairness, but will also provide significant throughput and diversity gain over conventional cooperation schemes.     

On Busy-Tone Based MAC Protocol for Wireless Networks with Directional Antennas

The application of directional antennas in wireless ad hoc networks offers numerous benefits, such as the extended communication range, the increased spatial reuse, the improved capacity and the suppressed interference. However, directional antennas can cause new location-dependent carrier sensing problems, such as new hidden terminal and deafness problems, which can severely degrade the network performance. Recently, a few schemes have been proposed to address these problems. However, most of these existing methods can only partially solve the hidden terminal and deafness problems. Some of them even bring significant performance overhead. In this paper, we propose a novel MAC protocol, in terms of the busy-tone based directional medium access control (BT-DMAC) protocol. In BT-DMAC, when the transmission is in progress, the sender and the receiver will turn on their omni-directional busy tones to protect the on-going transmission. Integrating with the directional network allocation vector (DNAV), the scheme can almost mitigate the hidden terminal problem and the deafness problem completely. We then propose an analytical model to investigate the throughput performance of BT-DMAC. The numerical results show that BT-DMAC outperforms other existing directional MAC schemes. We next evaluate the performance of BT-DMAC through extensive simulation experiments. The results show that our proposed BT-DMAC scheme has superior performance to other existing solutions, in terms of higher throughput.     

The Design and Evaluation of Unified Cellular and Ad-Hoc Networks

In third-generation (3G) wireless data networks, providing service to low data-rate users is required for maintaining fairness, but at the cost of reducing the cell's aggregate throughput. In this paper, we propose the unified cellular and ad hoc network (UCAN) architecture for enhancing cell throughput while maintaining fairness. In UCAN, a mobile client has both 3G interface and IEEE 802.11 -based peer-to-peer links. The 3G base station forwards packets for destination clients with poor channel quality to proxy clients with better channel quality. The proxy clients then use an ad hoc network composed of other mobile clients and IEEE 802.11 wireless links to forward the packets to the appropriate destinations, thereby improving cell throughput. We refine the 3G base station scheduling algorithm so that the throughput gains are distributed in proportion to users' average channel rates, thereby maintaining fairness. With the UCAN architecture in place, we propose novel greedy and on-demand protocols for proxy discovery and ad hoc routing that explicitly leverage the existence of the 3G infrastructure to reduce complexity and improve reliability. We further propose secure crediting mechanisms to motivate users that are not actively receiving to participate in relaying packets for others. Through both analysis and extensive simulations with HDR and IEEE 802.11b, we show that the UCAN architecture can increase individual user's throughput by more than 100 percent and the aggregate throughput of the HDR downlink by up to 50 percent.     

MAC Layer Resource Allocation for Wireless Body Area Networks

Wireless body area networks(WBANs) can provide low-cost, timely healthcare services and are expected to be widely used for ehealthcare in hospitals. In a hospital, space is often limited and multiple WBANs have to coexist in an area and share the same channel in order to provide healthcare services to different patients. This causes severe interference between WBANs that could significantly reduce the network throughput and increase the amount of power consumed by sensors placed on the body. Therefore, an efficient channel-resource allocation scheme in the medium access control(MAC) layer is crucial. In this paper, we develop a centralized MAC layer resource allocation scheme for a WBAN. We focus on mitigating the interference between WBANs and reducing the power consumed by sensors. Channel and buffer state are reported by smartphones deployed in each WBAN,and channel access allocation is performed by a central controller to maximize network throughput. Sensors have strict limitations in terms of energy consumption and computing capability and cannot provide all the necessary information for channel allocation in a timely manner. This deteriorates network performance. We exploit the temporal correlation of the body area channel in order to minimize the number of channel state reports necessary. We view the network design as a partly observable optimization problem and develop a myopic policy, which we then simulate in Matlab.     

Improving the MAC Layer of Multi-Hop Networks

Ad hoc and multi-hop networks will probably be a part of the fourth generation of wireless networks, which will integrate networks of several sizes and capacities with heterogeneous coverage: cellular networks (3G), WLAN hot spots, wireless personal area networks (WPAN) and wireless body area networks (WBAN). In this context, MAC protocols play a deciding role for a high utilization of the wireless channel. In this paper, several issues of the MAC layer and concepts for the definition of a new MAC protocol are presented. These concepts include synchronization, multi-user diversity, and multi-packet reception. It is shown that all these techniques can drastically increase the capacity of the MAC layer for multi-hop networks.     

A Generic Framework for Modeling MAC Protocols in Wireless Broadband Access Networks

In this article we present a simple yet accurate generic analytical model for a family of slotted CSMA/CA-based MAC protocols widely used in various wireless broadband access networks. The proposed model is based on a hierarchical three-level renewal process concept, which leads directly to some important MAC protocol performance metrics, such as throughput and average frame service time. The applicability of the model is demonstrated by extensive simulation results.     

Performance Analysis of a Flexible MAC Protocol for Real-Time Services in Vehicular Ad-Hoc Networks

Several MAC protocols for ad-hoc networks have been proposed in the literature for topologies with a large number of nodes. In particular, the MAC protocols based on 802.11 cannot guarantee the delays needed by real-time traffic, as they are mainly based on the CSMA/CA random access scheme, which inserts significant random inter-frame delay components, strongly dependent on network load. Other MAC protocols assign dynamically a dedicated channel to each connected node. In this way, it is possible to guarantee a strictly controlled delay for real-time traffic at the expense of a greater bandwidth waste. The goal of this paper is to evaluate the performance of a MAC protocol of this latter family. Our analysis is focused on scenarios with fast moving users, while in the literature most of the proposed MACs, also for mobile ad-hoc networks, are studied in the case of stationary users. Our study shows that the system performance strongly depends on the users’ speed and provides an accurate analysis of the performance degradation registered as speed grows.     

定向Ad hoc网络MAC组网技术研究

定向天线利用数字信号处理技术产生空间定向波束,将发射信号能量集中在某一个或者某些特定的方向上进行辐射,其应用于传统的Ad hoc网络中能够有效减少相邻节点间的互干扰,并能通过增加同时传输的节点对数达到显著提升网络空间复用率和容量的目的。首先简单介绍了定向天线和定向通信特点,然后对定向Ad hoc网络MAC层组网关键技术进行了综述,并对定向邻居发现协议、空分TDMA动态时隙分配机制、定向波束对准与跟踪技术等进行介绍和梳理,最后总结现有研究不足并指出未来重点研究方向。     

Cross Layer Security MAC Aware Routing Protocol for IoT Networks

Wireless Personal Communications - Proliferation Internet of Things (IoT) devices is increasing security vulnerabilities across the enterprise besides its intrinsic constraints such as processing...     

Data Transmission Using IoT in Vehicular Ad-Hoc Networks in Smart City Congestion

Development of Internet of Things (IoT) enables smart city advancement throughout the world. Increasing number of vehicles has brought focus on road safety precautions and in-vehicle communication. This is the right time to focus on the development of new applications and services for vehicular environments. The Vehicular Ad-hoc Networks (VANETs) are an interesting range of Mobile Ad-hoc Networks (MANETs) where the Vehicle to Vehicle (V2V) and vehicle roadways transmission is possible. The V2V scheme is fresh by combining Wireless Fidelity (Wi-Fi), Bluetooth and other all sorts of communication standards. An immense number of nodes working with these networks and due to their immense displacements, the analysis is prevailing regarding the possibility of routing standards. The estimation of conventional routing standards for MANETs illustrates that their behaviors are minimal in VANETs. The intention is to make use of mediators for routing with an effort to address the before described issues. The mediators are accountable for gathering data related to routing and identifying the optimal paths for forwarding information packets. The routing scheme is based on group routing standards and data cluster framework for locating the best possible routes. In this paper, we analyze smart cities vehicle communication development by implementing IoT. We also discuss the ways to minimize the limitations connected to IoT deployment and implementation in smart city environment using multi mediator scheme.

     

A Framework for Unified Spectrum Management (USM) in Heterogeneous Wireless Networks

In the information age, spectrum is a valuable natural resource. Currently, there is a great deal of ongoing research into architectures for spectrum (or more generally, radio resource) management for next generation wireless communications systems. This article proposes a framework for unified spectrum management (USM), where both licensed and license-exempt bands are managed by a hierarchical band management method. An outline for developing the required entities in this architecture is introduced, as well as the protocols that are required for USM operation. We also discuss spatial and temporal coordination of resource usage in such a heterogeneous wireless environment. Finally, a number of open research issues for future study are outlined.     

Analysis of a Cooperative Beacon-Free MAC Layer for Body Area Networks

This paper discusses medium access control (MAC) issues for body area networks (BANs), relying on an Ultrawide Band Impulse radio (UWB-IR) physical layer. BANs are bound to be coordinated by a powerful device like a smart-phone, which manage the access of the nodes on a beaconed fashion. But in some particular situations, the coordinator may disappear and/or be not yet available. These transient situations shall be addressed and a beacon-free medium access control is desirable. We propose a beacon-free MAC layer, based on a collaborative version of the preamble sampling approach. This is designed to address the European regulatory low duty cycle (LDC) constraint, which UWB devices must comply to. A Markov chain model is given to describe the protocol. By means of simulations, we first show that the model is accurate and secondly that this protocol looks able to manage various BANs configurations.     

Delay-Aware MAC Protocol for Wireless Sensor and Actor Networks in Smart Grid

Wireless Personal Communications - The conventional electric grid is converting in to the new emerging smart grid by utilizing information and communication technologies. The smart grid...     

An Opportunistic Directional MAC Protocol with Pulse/Tone Exchange in Wireless Ad-Hoc Networks

Wireless Personal Communications - This paper proposes a Medium Access Control (MAC) protocol using directional antennas in wireless ad-hoc networks, which achieves frame-collision reduction,...