Receiver-initiated medium access control protocols for wireless sensor networks

One of the fundamental building blocks of a Wireless Sensor Network (WSN) is the Medium Access Control (MAC) protocol, that part of the system governing when and how two independent neighboring nodes activate their respective transceivers to directly interact. Historically, data exchange has always been initiated by the node willing to relay data, i.e. the sender. However, the Receiver-Initiated paradigm introduced by Lin et al. in 2004 with RICER and made popular by Sun et al. in 2008 with RI-MAC, has spawned a whole new stream of research, yielding tens of new MAC protocols. Within such paradigm, the receiver is the one in charge of starting a direct communication with an eligible sender. This allows for new useful properties to be satisfied, novel schemes to be introduced and new challenges to be tackled. In this paper, we present a survey comprising of all the MAC protocols released since the year 2004 that fall under the receiver-initiated category. In particular, keeping in mind the key challenges that receiver-initiated MAC protocols are meant to deal with, we analyze and discuss the different protocols according to common features and design goals. The aim of this paper is to provide a comprehensive and self-contained introduction to the fundamentals of the receiver-initiated paradigm, providing newcomers with a quick-start guide on the state of the art of this field and a palette of options, essential for implementing applications or designing new protocols.     

Adaptive listen for energy-efficient medium access control in wireless sensor networks

Wireless Sensor Networks (WSN) have nodes that are small in size and are powered by small batteries having very limited amount of energy. In most applications of WSN, the nodes in the network remain inactive for long periods of time, and intermittently they become active on sensing any change in the environment. The data sensed by the different nodes are sent to the sink node. In contrast to other infrastructure-based wireless networks, higher throughput, lower latency and per-node fairness in WSN are imperative, but their importance is subdued when compared to energy consumption. In this work, we have regarded the amount of energy consumption in the nodes to be of primary concern, while throughput and latency in the network to be secondary. We have proposed a protocol for energy-efficient adaptive listen for medium access control in WSN. Our protocol adaptively changes the slot-time, which is the time of each slot in the contention window. This correspondingly changes the cycle-time, which is the sum of the listen-time and the sleep-time of the sensors, while keeping the duty-cycle, which is the ratio between the listen-time and the cycle-time, constant. Using simulation experiments, we evaluated the performance of the proposed protocol, compared with the popular Sensor Medium Access Control (SMAC) (Ye et al. IEEE/ACM Trans Netw 12(3):493–506, 39) protocol. The results we obtained show a prominent decrease in the energy consumption at the nodes in the proposed protocol over the existing SMAC protocol, at the cost of decreasing the throughput and increasing the latency in the network. Although such an observation is not perfectly what is ideally desired, given the very limited amount of energy with which the nodes in a WSN operate, we advocate that increasing the energy efficiency of the nodes, thereby increasing the network lifetime in WSN, is a more important concern compared to throughput and latency. Additionally, similar observations relating energy efficiency, network lifetime, throughput and latency exist in many other existing protocols, including the popular SMAC protocol (Ye et al. IEEE/ACM Trans Netw 12(3):493–506, 39).     

基于动态p-坚持的无线媒质访问控制算法

针对无线网络中的媒质访问控制存在的不足,提出了一种新的算法。该算法基于动态p-坚持算法,其核心思想采用虚拟传输或虚拟线程,目标是为动态p-坚持算法提供更多的信息以获得最佳传输概率,提高无线带宽的利用效率。仿真表明,新算法平均提高吞吐量约27%,平均降低碰撞率约28%。     

Opportunistic scheduling for streaming multimedia users in high-speed downlink packet access (HSDPA)

High-speed downlink packet access (HSDPA) achieves high data rates and high spectral efficiency by using adaptive modulation and coding schemes and employing multicode CDMA. In this paper, we present opportunistic algorithms for scheduling HSDPA users and selecting modulation/coding and multicode schemes that exploit channel and buffer variations to increase the probability of uninterrupted media play-out. First, we introduce a stochastic discrete event model for a HSDPA system. By employing the discrete event model, we transform the scheduling problem of providing uninterrupted play-out to a feasibility problem that considers two sets of stochastic quality-of-service (QoS) constraints: stability constraints and robustness constraints. A methodology for obtaining a feasible solution is then proposed by starting with a so-called stable algorithm that satisfies the stability QoS constraints. Next, we present stochastic approximation algorithms that adapt the parameters of the stable algorithm in a way that a feasible point for the robustness QoS is reached within the feasibility region of the stability QoS.     

Fairness of medium access control protocols for multi-hop ad hoc wireless networks

It is an undisputed fact that fairness is an important element of a well-designed medium access control (MAC) protocol for multi-hop ad hoc networks. However, most popular MAC protocols still fail to attain an acceptable level of fairness in media access although several enhancements have been proposed in the past. These proposed enhancements are effective only in limited scenarios. It is our objective in this paper to do the following: (i) analyze the fairness problem; (ii) identify and analyze the three main causes leading to the fairness problem, namely, the lack of synchronization problem (LSP), the double contention areas problem (DCP) and the lack of coordination problem (LCP); (iii) based on the analysis, propose a new MAC protocol named the extended hybrid asynchronous time division multiple access (EHATDMA) as a solution. For better assessment of fairness, we have designed an index named max–min fairness index, which is scenario-independent and reflects the difference between the fair sharing provided by a protocol and the ideal max–min fair sharing. Comprehensive simulations have been carried out to compare the fairness of our protocol with the existing ones. Simulation results show that although the existing protocols employ various enhancements meant to improve the fairness property, most of them are still strongly biased towards throughput when a conflict between throughput and fairness arises. In addition, the fairness performance of these protocols varies widely from one scenario to another. On the other hand, EHATDMA strikes a good balance between throughput and fairness. It delivers a consistently high level of fairness regardless of network topology, traffic load and radio parameters, yet maintains high throughput whenever possible. Our simulation results also reveal that the most important mechanism affecting the fair sharing of radio channels among flows is the non-work-conserving mechanism.     

A detailed review of energy-efficient medium access control protocols for mobile sensor networks

This article reviews the state-of-the-art energy-efficient contention-based and scheduled-based medium access control (MAC) protocols for mobile sensor networks (MSNs) by first examining access schemes for wireless sensor networks (WSNs). Efficient and proper mobility handling in sensor networks provides a window of opportunity for new applications. Protocols, such as S-MAC, reduce energy consumption by putting nodes to sleep after losing to channel contention or to prevent idling. Sleeping is a common method for energy-efficient MAC protocols, but delay depends on sleep duration or frame time, and longer delays lead to higher packet lost rate when nodes are unsynchronized due to network mobility. MS-MAC extends S-MAC to include mobility-awareness by decreasing this sleep duration when mobility is detected. S-MAC with extended Kalman filter (EKF) reduces mobility-incurred losses by predicting the optimal data frame size for each transmission. MMAC utilizes a dynamic mobility-adaptive frame time to enhance TRAMA, a scheduled-based protocol, with mobility prediction. Likewise, G-MAC utilizes TDMA for cluster-based WSNs by combining the advantages of contention and contention-free MACs. Z-MAC also combines both methods but without clustering and allows time slot re-assignments during significant topology changes. All of the above MAC protocols are reviewed in detail.     

Maximum lifetime rate control and random access in multi-hop wireless networks

Network lifetime and transmission quality are of paramount importance for rate control in an energy constrained multi-hop wireless network. It is known that they depend on mechanisms that span several protocol layers due to the existing interference across collision links and the energy constrained nature of wireless nodes. Although separate consideration of these issues simplifies the system design, it is often insufficient for wireless networks when the overall system performance is required. In this paper, we present a framework for cross-layer rate control towards maximum network lifetime and collision avoidance. The main contributions of this paper are twofold. First, although the link attainable rate is typically a non-convex and non-separable function of persistent probabilities, we prove the convergence of this cross-layer algorithm to the global optimum of joint congestion control and random access algorithm under the framework of nonlinear programming. Second, by adjusting a parameter in the objective function, we achieve the tradeoff between transmission quality and network lifetime. Simulations illustrate the desirable properties of the proposed algorithm, including convergence to the global optimum, better performance than the layered scheme, desirable tradeoff between transmission quality and network lifetime.     

An adaptive medium access control scheme for mobile ad hoc networks under self-similar traffic

An important function of wireless networks is to support mobile computing. Mobile Ad hoc NETworks (MANETs) consist of a collection of mobile stations communicating with each other without the use of any pre-existent infrastructure. The self-organization characteristic of MANETs makes them suitable for many real-world applications where network topology changes frequently. As a result, the development of efficient MAC (Medium Access Control) protocols in MANETs is extremely challenging. Self-similar traffic with scale-invariant burstiness can generate bursty network loads and thus seriously degrade the system performance. This paper presents an adaptive MAC scheme which dynamically adjusts the increasing function and resetting mechanism of contention window based on the status of network loads. The performance of this scheme is investigated in comparison with the legacy DCF (Distributed Coordination Function) under self-similar traffic and different mobility models. The performance results reveal that the proposed scheme is able to achieve the higher throughput and energy efficiency as well as lower end-to-end delay and packet drop probability than the legacy DCF.     

P2P网络动态精细粒度访问控制研究*

分析了现有P2P系统中访问控制的不足,结合RBAC(角色访问控制)和TBAC (基于任务访问控制),加入环境约束条件,提出了一种精细粒度的动态访问控制模型——ETRBAC。该模型对角色、权限、子任务进行层次划分,角色分为本地角色和协作角色,由子任务选择必要的角色和权限并进行合理配置。多个子任务协作构成一个会话。最后详细描述了ETRBAC模型的结构及实施流程。对比分析表明,本模型可以很好地应用到动态协作环境中。     

From versatility to auto-adaptation of the medium access control in wireless sensor networks

Recent deployments of wireless sensor networks have targeted challenging monitoring and surveillance applications. The medium access control being the main source of energy wastage, energy-efficiency has always been kept in mind while designing the communication stack embedded in spread sensors. Especially, versatile protocols have emerged to offer a suitable solution over multiple deployment characteristics. In this study, we observe to what extent versatility applies to dynamic scenarios in which communications do not respect specific communication paradigms. We first provide a performance evaluation of two well-reputed versatile protocols (B-MAC (Polastre et al., 2004 [17]) and X-MAC (Buettner et al., 2006 [4])) under the conditions of such a scenario. The obtained results convinced us to propose more than versatility and pre-configured solutions, that is auto-adaptation. We then introduce the main contribution of this paper, an auto-adaptive algorithm that allows one to adjust the previously mentioned protocols while the network is operating. We analyze to what extent it outperforms the previously obtained results.     

Lifetime maximizing dynamic energy efficient routing protocol for multi hop wireless networks

Energy efficiency is recognized as a critical problem in wireless networks. Many routing schemes have been proposed for finding energy efficient routing paths with a view to extend lifetime of the networks – however it has been observed that the energy efficient path depletes quickly. Further, an unbalanced distribution of energy among the nodes may cause early death of nodes as well as network. Hence, balancing the energy distribution is a challenging area of research in wireless networks. In this paper we propose an energy efficient scheme that considers the node cost of nodes for relaying the data packets to the sink. The node cost considers both the remaining energy of the node as well as energy efficiency. Using this parameter, an energy efficient routing algorithm is proposed which balances the data traffic among the nodes and also prolongs the network lifetime. Simulation shows that proposed routing scheme improves energy efficiency and network lifetime than widely used methods viz., Shortest Path Tree (SPT) and Minimum Spanning Tree (MST) based PEDAP, Distributed Energy Balanced Routing (DEBR) and Shortest Path Aggregation Tree Based Routing Protocol.     

A medium access control protocol that supports a seamless handover in wireless sensor networks

This paper introduces a mobility-aware medium access control protocol for multi-hop wireless sensor networks (MA-MAC). The protocol evaluates the RSSI values of acknowledgement packets and determines whether a gradual deterioration in the RSSI values eventually leads to a disconnection. If it does, it initiates a handover by switching transmission from a unicast to a broadcast mode and by embedding neighbour discovery requests in the broadcast data packets. While the mobile node continues transmitting data packets via the existing link, the neighbour discovery requests enable it to discover new nodes that can serve as intermediate nodes. Once an intermediate node is found, the mobile node establishes a link with it and switches transmission back to unicast. Conceptually, MA-MAC's handover feature can be implemented by extending any of the existing transmitter initiated, energy-efficient protocols such as XMAC or BMAC. Our present implementation is based on the XMAC protocol. The paper reports how the protocol performs as the speed of mobility, handover threshold, and sending interval vary.     

认知无线网络中基于信誉度管理的动态频谱接入研究

随着无线服务和相关设备的飞速发展,认知无线网络中特有频谱稀缺问题越来越引起研究者的重视。在集中式认知无线网络中,次级用户基站SUBS作为融合中心,通过收到周围的次级用户的感知信息来分配频谱资源。然而,环境的易变性使次级用户容易受到攻击从而影响次级用户感知信息,导致网络频谱资源分配错误。引入信誉度模型来表现次级用户在认知循环中的行为规范,在分配频谱阶段将信誉度作为评定标准,鼓励次级用户积极感知及规范运行。在感知阶段,次级用户感知信道数越多,感知信息越正确,其信誉度越高。在运行阶段,次级用户行为越符合网络规范,则信誉度越高。仿真结果表明,论文模型可以很好地减少次级用户基站的错误决策次数,提高其抗攻击性,同时使得网络在很好地分配资源的同时鼓励整个网络行为积极化。     

Policy-based spectrum access control for dynamic spectrum access network radios

We describe the design of a policy-based spectrum access control system for the Defense Advanced Research Projects Agency (DARPA) NeXt Generation (XG) communications program to overcome harmful interference caused by a malfunctioning device or a malicious user. In tandem with signal-detection-based interference-avoidance algorithms employed by cognitive software-defined radios (SDR), we design a set of policy-based components, tightly integrated with the accredited kernel on the radio device. The policy conformance and enforcement components ensure that a radio does not violate machine understandable policies, which are encoded in a declarative language and which define stakeholders’ goals and requirements. We report on our framework experimentation, illustrating the capability offered to radios for enforcing policies and the capability for managing radios and securing access control to interfaces changing the radios’ policies.     

A rate control video dissemination solution for extremely dynamic vehicular ad hoc networks

Video dissemination to a group of vehicles is one of the many fundamental services envisioned for Vehicular Ad hoc Networks, especially as a building block for entertainment applications. For this purpose, in this paper we describe VoV, a video dissemination protocol that operates under extremely dynamic road traffic conditions. Contrary to most existing approaches that focus exclusively on always-connected networks and tackle the broadcast storm problem inherent to them, VoV is designed to operate under any kind of road traffic condition. We propose a new geographic-based broadcast suppression mechanism that gives a higher priority to rebroadcast to vehicles inside especial forwarding zones. Furthermore, vehicles store and carry received messages in a local buffer in order to forward them to vehicles that were not covered by the first dissemination process, probably as a result of collisions or intermittent disconnections. Finally, VoV employs a rate control mechanism that sets the pace at which messages must be transmitted according to the perceived network data traffic, thus avoiding channel overloading. Therefore, VoV adapts not only to the perceived road traffic condition, but also to the perceived channel quality. When compared to two related and well-accepted solutions–ABSM and AID–under Manhattan grid and real city scenarios, we show that, overall, our proposal is more efficient in terms of message delivery, delay and overhead.     

Enforcing in-order packet delivery in system area networks with adaptive routing

Adaptive routing, which dynamically selects the route of packets, has been widely studied for interconnection networks in massively parallel computers and system area networks. Although adaptive routing has the advantage of providing high bandwidth, it may deliver packets out-of-order, which some message passing libraries do not accept. In this paper, we propose two mechanisms called (1) FIFO transmission and (2) couple limitation to guarantee in-order packet delivery in adaptive routing. Both of them limit packet injection at source hosts. The FIFO transmission completely avoids packet sorting at destination hosts, while the couple limitation uses a few buffers to sort packets at destination hosts. Evaluation results show that the FIFO transmission and the couple limitation achieve a similar throughput to that of a method equipped with huge (infinite) buffers enough to store all out-of-order packets at destination hosts under both synthetic traffic and NAS Parallel Benchmarks.     

Opportunistic forwarding for user-provided networks

Abstract

We study opportunistic forwarding in a community-based networking paradigm where mobile users and shared access points (SAPs) collectively provide Internet access to users (mobile or not), including those in areas where other connectivity options are not available. Our approach is based on an efficient interoperation of two challenging network types: the opportunistic and the user-provided networks (UPNs). This requires a re-evaluation of the existing assumptions regarding inter-contact patterns and their alignment to this hybrid environment. We confirm our arguments with numerical results from a stochastic model as well as experimental scenarios with realistic parameters using the ONE simulator. Our experiments are based on a reference routing algorithm we designed and implemented that extends the spray ’n focus protocol and exhibits the following characteristics: (i) is oriented to this integrated environment; (ii) employs delay-tolerant networking (DTN) technologies along with contact prediction; and (iii) is independent of the deployed UPN approach. According our results, the proposed methodological approach achieves lower communication overhead, latency and storage requirements compared to representative opportunistic routing algorithms.     

Uplink access control for machine-type communications in LTE-A networks

Internet of things (IoT) has been considered as one of the most promising technologies over the next decade. One of the basic requirements of IoT is the global communication connectivity between smart objects. LTE-A has been considered as the main communication channel for connecting devices. For this reason, the machine-type communication (MTC) has been defined in the 3GPP LTE-A specification. With the rapid growth of the IoT devices, MTC in LTE-A faces many challenges. The primary design of a LTE-A network is to support the human-type communication (HTC). However, MTC and HTC have different characteristics, such as packet size, traffic arrival rate, and delay tolerance. How to accommodate a large amount of MTC traffic without affecting the grade of service of the HTC is challenging. More specifically, before accessing the LTE-A network, a random access (RA) procedure needs to be performed by a device to synchronize in the uplink of an eNB. Since the number of MTC devices is expected to be much greater than the HTC devices, without suitable access control, the success rate of the RA requests from the HTC devices can be significantly degraded. Therefore, this research aims to design an appropriate RA procedure to relieve this problem. The authors propose an Adaptive RACH Resource Allocation (ARRA) which integrates several control schemes, including a Resource Allocation scheme, an Access Class Barring scheme, and a Priority Device Setting scheme. Simulation results show that the proposed ARRA is able to achieve a higher access success rate and a lower latency for HTC devices while providing a different quality of service to different types of MTC devices.     

Revealing the problems with 802.11 medium access control protocol in multi-hop wireless ad hoc networks

The IEEE 802.11 medium access control (MAC) protocol is a standard for wireless LANs, it is also widely used in almost all test beds and simulations for the research in wireless mobile multi-hop ad hoc networks. However, this protocol was not designed for multi-hop networks. Although it can support some ad hoc network architecture, it is not intended to support the wireless mobile ad hoc network, in which multi-hop connectivity is one of the most prominent features. In this paper, we focus on the following question: can IEEE 802.11 MAC protocol function well in multi-hop networks? By presenting several serious problems encountered in transmission control protocol (TCP) connections in an IEEE 802.11 based multi-hop network, we show that the current TCP protocol does not work well above the current 802.11 MAC layer. The relevant problems include the TCP instability problem found in this kind of network, the severe unfairness problem, and the incompatibility problem. We illustrate that all these problems are rooted in the MAC layer. Furthermore, by revealing the in-depth cause of these problems, we conclude that the current version of this wireless LAN protocol does not function well in multi-hop ad hoc networks. We thus doubt whether the current WaveLAN based system is workable as a mobile multi-hop ad hoc test bed. All the results shown in this paper are based on NS2 simulations, and are compatible with the results from the OPNET simulations.