Hidden Terminal Problem Research Articles

Transmission power adaptations for data collision avoidance in wireless ad hoc networks

The paper proposes a fragmentation-based MAC protocol with power control, named F-RCRC MAC protocol, for wireless ad hoc networks to avoid the Large Interference Range Collision LIRC problem, which is a kind of hidden terminal problem. F-RCRC designs a new interframe space, called FIFS, to reduce the overhead caused by the fragmentation scheme. Taking advantage of fragmentation, the design of FIFS can effectively avoid the hidden STAs from interfering with the receiver's reception. F-RCRC can reduce the energy consumption and increase the spatial reuse due to the controlled transmission power. Simulation results show that F-RCRC performs much better than the related work in terms of network throughput as well as energy efficiency.

医学设备的抗干扰无线接入方案

无线网络中的射频传输往往会对敏感的电子医学设备造成电磁干扰，影响其正常运行。而传统的无线接入方案并没有考虑电磁干扰问题。为了解决该问题本文提出了一种新的抗干扰无线接入方案。所提方案在能解决隐藏终端的RTS/CTS协议基础上引入功率控制，通过限制医疗环境中无线非医疗设备的发送功率来避免其对医学设备造成的电磁干扰。仿真结果表明：同传统的IEEE802.11无线接入方式相比较，本文提出的方案在牺牲一部分通信性能的情况下，可以有效的降低对医学设备的干扰概率。根据对结果的分析，本文还会进一步地优化所提方案。 Radio frequence (RF) transmission in wireless network tends to cause electromagnetic interference (EMI) to sensitive electronic medical equipments, affecting their normal operation. The traditional wireless access schemes do not consider the electromagnetic interference. In order to solve this problem, this paper proposed a new anti-interfer- ence wireless access scheme. The proposed scheme introduces the power control based on RTS/CTS agreement which can solve the hidden terminal problem. It limits the transmission power of wireless non-medical equipments in medical environment to avoid its electromagnetic interference to medical equipments. Simulation results show that, compared with traditional IEEE 802.11 wireless access scheme,the proposed scheme can effectively avoid electromagnetic interference to electronic equipments by sacrificing some performance of communication system. According to the analysis of the results, this paper can further optimize the proposed scheme.

Solution of the Hidden Terminal Problem using Random Length Signals for Wireless LANs

Solution of the Hidden Terminal Problem using Random Length Signals for Wireless LANs

The New Approach to provide Trusted Platform in MANET

In distributed operation, we uses different key management schemes, authentication and many trust models, but in wireless medium having reliability problem, hidden terminal problem etc. To provide authenticated nodes and secured environment is the important issue in MANET. Frequent path breaking, multihop wireless link between mobile nodes, self organization and maintenance are such properties that makes difficult to provide trust in MANET. This paper proposes the new trust scheme, which provides malicious free atmosphere for mobile ad-hoc network. This model first check the authenticity of nodes through challenge response method and then PKI certificate will be given to only authenticated nodes so as to enable the trusted communication platform. At last this paper give the comparisons of ACTP model with other existing trust model.

The New Approach to Provide Trusted Platform in MANET

In distributed operation, we uses different key management schemes, authentication and many trust models, but in wireless medium having reliability problem, hidden terminal problem etc. To provide authenticated nodes and secured environment is the important issue in MANET. Frequent path breaking, multihop wireless link between mobile nodes, self organization and maintenance are such properties that makes difficult to provide trust in MANET. This paper proposes the new trust scheme, which provides malicious free atmosphere for mobile ad-hoc network. This model first check the authenticity of nodes through challenge response method and then PKI certificate will be given to only authenticated nodes so as to enable the trusted communication platform. At last this paper give the comparisons of ACTP model with other existing trust model.

Energy-efficient cooperative spectrum sensing in sensor-aided cognitive radio networks

Cognitive radio has been proposed to make full use of the limited spectrum resources, where spectrum sensing plays an important role to detect the channel state for opportunistic utilization. To address the hidden terminal problem, cooperative spectrum sensing is employed to improve the detection performance. Due to the energy constraint of battery-powered sensor nodes, energy efficiency emerges as a critical issue in sensor-aided cognitive radio networks. By exploiting the abundant sensor nodes and multiuser diversity, a cooperative schedule of each sensor node's on/off can effectively extend the network lifetime. However, frequent on/off switching of sensor nodes will generate an adverse impact and make the network vulnerable and unreliable. We consider the problem of optimizing the schedule order to reduce the switch frequency. Greedy Heuristic is proposed to approach the minimum node switch with low computational complexity. Simulation results are presented to verify the performance of the proposed algorithm.

Energy efficient smart-relay-based cooperative MAC for wireless networks

An enormous number of papers investigated wireless cooperative networks over the last few years. Almost all have shown that cooperative transmission improves network performance significantly. However, none of these studies have considered the hidden and exposed terminal problems which appear due to the cooperative mechanisms of relay selection and transmission processes. The hidden terminal problems increase collisions and the exposed terminal problems increase bandwidth wastage, degrading the expected performance of cooperative networks. This paper addresses these problems of traditional wireless cooperative networks. We also propose a protocol called smart-relay-based-cooperative (SRcoop) MAC to optimally reduce the impacts of hidden and exposed terminal problems. We also illustrate an efficient relay selection mechanism that uses a back-up relay to increase transmission reliability. Our innovative model significantly improves the network throughput, end-to-end delay and energy efficiency over traditional cooperative MAC, 2rcMAC, LC-MAC, C-ARQ and Adere et al. protocols.

Combating Hidden and Exposed Terminal Problems in Wireless Networks

The hidden terminal problem is known to degrade the throughput of wireless networks due to collisions, while the exposed terminal problem results in poor performance by wasting valuable transmission opportunities. As a result, extensive research has been conducted to solve these two problems, such as Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). However, CSMA-like protocols cannot solve both of these two problems at once. The fundamental reason lies in the fact that they cannot obtain accurate Channel Usage Information (CUI, who is transmitting or receiving nearby) with a low cost. To obtain additional CUI in a cost-efficient way, we propose a cross layer design, FAST (Full-duplex Attachment System). FAST contains a PHY layer Attachment Coding, which transmits control information independently on the air, without degrading the effective throughput of the original data traffic, and a MAC layer Attachment Sense, which utilizes the PHY layer control information to identify the hidden and exposed nodes in real time. We theoretically analyze the feasibility of the Attachment Coding, and then implement it on a GNU Radio testbed consisting of eight USRP2 nodes. We also conduct extensive simulations to evaluate the performance of FAST, and the experimental results show that FAST can effectively solve both the hidden and the exposed terminal problems, and improve the average throughput by up to 200% over CSMA in practical ad-hoc networks.

RSBP: A Reliable Slotted Broadcast Protocol in Wireless Sensor Networks

In wireless sensor networks for monitoring and control applications, a sink node needs to disseminate messages to all nodes to acquire monitoring data or to control the operation of sensor nodes. The basic flooding protocol suffers from low transmission reliability in broadcasting messages due to the hidden terminal problem. Besides, it can cause the broadcast storm problem by having many nodes rebroadcast the received message simultaneously. In order to resolve these problems while minimizing energy consumption in delivery of broadcast messages, we propose a reliable slotted broadcast protocol (RSBP) that allocates broadcast time slots to nodes based on their slot demands and then allows every node to transmit its broadcast message within the allocated slots. Then, every node can broadcast messages safely in a contention-free manner. Moreover, RSBP can be deployed easily since it does not have any specific requirements such as GPS, multi-channels and directional antennas that may not be always available in real scenarios. We show by experimental study that RSBP significantly outperforms other broadcast protocols in terms of safety-critical packet delivery and energy consumption.

Hierarchical Range Sectoring and Bidirectional Link Quality Estimation for on-demand collections in WSNs

The paper presents two mechanisms for designing an on-demand, reliable and efficient collection protocol for Wireless Sensor Networks. The former is the Bidirectional Link Quality Estimation, which allows nodes to easily and quickly compute the quality of a link between a pair of nodes. The latter, Hierarchical Range Sectoring, organizes sensors in different sectors based on their location within the network. Based on this organization, nodes from each sector are coordinated to transmit in specific periods of time to reduce the hidden terminal problem. To evaluate these two mechanisms, a protocol called HBCP (Hierarchical-Based Collection Protocol), that implements both mechanisms, has been implemented in TinyOS 2.1, and evaluated in a testbed using TelosB motes. The results show that the HBCP protocol is able to achieve a very high reliability, especially in large networks and in scenarios with bottlenecks.

ASO-TDMA: ad-hoc self-organizing TDMA protocol for shipborne ad-hoc networks

A shipborne ad-hoc network (SANET), a maritime counterpart of the terrestrial vehicle ad-hoc network, can provide ships with diverse multimedia services by substituting digital maritime VHF communications for expensive satellite communications. This article proposes ad-hoc self-organizing TDMA (ASO-TDMA), a medium access control (MAC) protocol targeting SANETs. Frames in ASO-TDMA are divided into several sub-frames, and based on the proposed rules for assigning time slots, ships can only reserve time slots for data transfers through their available sub-frames. Accordingly, ASO-TDMA provides better performance in terms of reducing receiver collisions from hidden terminal problems compared to self-organizing TDMA (SO-TDMA) and carrier-sensing TDMA (CS-TDMA), two existing MAC protocols for maritime VHF communications. In addition, the article compares the performance of the three MAC protocols in terms of delays and collision rates (CRs). The results suggest that, given the same delay, ASO-TDMA can reduce the CR by as much as 30% in comparison with SO-TDMA and CS-TDMA. Similarly, given the same CR, ASO-TDMA can reduce delays by as much as 26% in comparison with SO-TDMA and CS-TDMA.

A Novel Distributed Asynchronous Multichannel MAC Scheme for Large-Scale Vehicular Ad Hoc Networks

This paper proposes a novel distributed asynchronous multichannel medium access control (MAC) scheme for large-scale vehicular ad hoc networks (VANETs), i.e., asynchronous multichannel medium access control with a distributed time-division multiple-access mechanism (AMCMAC-D). The proposed scheme supports simultaneous transmissions on different service channels while allowing rendezvous and broadcast of emergency messages on the control channel. The scheme is distributed, because it handles access to the shared control channel for different access categories without relying on the beacon frames from roadside units. This condition eliminates the overhead that is associated with channel allocation, making the proposed scheme suitable for large-scale networks in terms of the number of active nodes. Service differentiation in the proposed scheme is enhanced by allocating different numbers of time slots for different access categories. We compare the performance of the proposed scheme with the IEEE 1609.4 standard and the asynchronous multichannel Coordination Protocol (AMCP) in terms of throughput, packet delivery rate, collision rate, utilization of service channels, service differentiation, and the penetration rate of noncollided emergency messages. The results show that AMCMAC-D outperforms the IEEE 1609.4 standard and AMCP in terms of system throughput by increasing the utilization of the control channel and service channels. The proposed scheme also demonstrates better performance in terms of packet delivery rate, collision rate on a service channel, load balancing, and service differentiation. Finally, AMCMAC-D mitigates the multichannel hidden terminal and missing receiver problems, which occur in asynchronous multichannel MAC schemes.

A joint solution for the hidden and exposed terminal problems in CSMA/CA wireless networks

It is well-known that the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)-based wireless networks suffer seriously from the hidden terminal problem and the exposed terminal problem. So far, no satisfactory solutions that can resolve both problems simultaneously have been found. In this paper, we present a joint solution to the two problems. Our approach avoids the drawback of lessening one problem but aggregating the other. It is compatible with the IEEE 802.11 MAC and requires no protocol change. Analysis and simulations show that the proposed scheme can significantly reduce the hidden and exposed terminal problems. Not only it can significantly improve the throughput of the network and the fairness among different flows, it can also provide a much more stable link layer. In simulated scenarios under heavy traffic conditions, compared to the conventional IEEE 802.11 MAC, the new method can achieve up to 1.8 times gain in network throughput for single-hop flows and up to 2.6 times gain for multihop flows.

Spectrum Sensing Methods and RF Architectures for Cognitive Radios

In this paper, we review some of the recent patents on spectrum sensing techniques for cognitive radio (CR) applications. The presented patents are categorized under: 1) spectrum sensing algorithms and architectures, 2) spectrum sensing and data communication and 3) cooperative spectrum sensing. The presented patents include special sensing algorithms that are based on the multi-resolution spectrum sensing (MRSS) approach, which ensures reliability of the spectrum sensing in wireless RF environments. We also discuss a CR patent that includes multiple RF chains to perform simultaneous cognitive tasks. Several patents that consider cooperative sensing are also presented as a solution to the hidden terminal problem inherent in wireless networks. We review the advantages and disadvantages of the presented patents and propose future directions for developing spectrum sensing techniques for CR’s. Keywords: Cognitive radio, cooperative spectrum sensing, dynamic spectrum access, energy detection, multi-resolution spectrum sensing, opportunistic spectrum access, spectrum sensing

A multi-path QoS multicast routing protocol with slot assignment for mobile ad hoc networks

Mobile multimedia applications have recently generated much interest in mobile ad hoc networks (MANETs) supporting quality-of-service (QoS) communications. Due to the limited bandwidth of a wireless node, a QoS multicast routing is often blocked if there is not a single multicast tree with the requested bandwidth, even when there is sufficient bandwidth in the network to support the call. In this paper, a multi-path QoS multicast routing (MQMR) protocol for MANETs is proposed. The scheme offers dynamic time slot control using a multi-path tree (or a uni-path tree) to meet the bandwidth requirements of a call. The final multi-path QoS multicast tree meets the QoS requirements, and the aggregate bandwidth of the paths meets the bandwidth requirements of a call. To avoid the hidden terminal problem or insufficient bandwidth in the bandwidth reservation process, each destination uses a decision rule. Moreover, a bandwidth reservation scheme is used for selecting the reserved time slots on each node in the multi-path QoS multicast tree. Simulation results demonstrate the effectiveness of MQMR in reducing network blocking and improving the call success ratio.

Asynchronous Multi-Channel MAC Protocol for WSNs

To tackle control channel saturation and triple hidden terminal problems,this paper proposes RIM,a receiver-initiated multi-channel MAC protocol with duty cycling for WSNs.By adopting a receiver-initiated transmission scheme and probability-based random channel selection,RIM effectively alleviates,if not completely eliminates,control channel saturation and triple hidden terminal problems.In addition,RIM exploits a simple but reliable asynchronous broadcast scheme to solve the problem of broadcast data loss with reliable broadcast-intensive applications.More importantly,RIM is fully distributed with no requirements of time synchronization or multi-radio.Therefore,RIM is very easily implemented in resource-constrained sensor nodes.Via the theoretical analysis,the optimal duty cycle are obtained,respectively.The simulation and real testbed experimental results show that RIM achieves significant improvement in energy efficiency with increasing benefit when the number of channels and traffic loads increase,while maintaining higher throughput.Moreover,RIM exhibits a prominent ability to enhance its broadcast reliability.

An efficient reliable one-hop broadcast in mobile ad hoc networks

A reliable one-hop broadcast is a fundamental communication primitive in mobile ad hoc networks in which a message from the source node is guaranteed to be delivered to all nodes within the source node’s transmission range. Despite the importance of it, reliable one-hop broadcast is not easy to accomplish due to collisions in wireless networks known as Hidden Terminal Problem. This paper presents a MAC protocol that not only guarantees reliable one-hop broadcast but also achieves it efficiently by exploring as many simultaneous executions of the communication as possible. In addition to the data packets, the proposed algorithm utilizes the control packets that prevent packet collisions, and at the same time, make the simultaneous communications possible to improve the network throughput. Simulation results show the effectiveness of the proposed algorithm.

IEEE 802.11 Saturation Throughput Analysis in the Presence of Hidden Terminals

Due to its usefulness and wide deployment, IEEE 802.11 has been the subject of numerous studies, but still lacks a complete analytical model. Hidden terminals are common in IEEE 802.11 and cause the degradation of throughput. Despite the importance of the hidden terminal problem, there have been a relatively small number of studies that consider the effect of hidden terminals on IEEE 802.11 throughput, and many are not accurate for a wide range of conditions. In this paper, we present an accurate new analytical saturation throughput model for the infrastructure case of IEEE 802.11 in the presence of hidden terminals. Simulation results show that our model is accurate in a wide variety of cases.

DSDMAC: Dual Sensing Directional MAC Protocol for Ad Hoc Networks with Directional Antennas

Applying directional antennas in wireless ad hoc networks can theoretically achieve higher spatial multiplexing gain and, thus, higher network throughput. However, in practice, deafness, hidden-terminal, and exposed terminal problems are exaggerated with directional antennas, and they cause the degradation of the overall network performance. Although there are several random-access-based medium-access control (MAC) protocols being proposed in the literature for networks with directional antennas, the deafness, hidden-terminal, and exposed terminal problems have yet to be fully solved. In this paper, we present a new MAC protocol called the dual-sensing directional MAC (DSDMAC) protocol for wireless ad hoc networks with directional antennas. Different from existing protocols, the DSDMAC protocol relies on the dual-sensing strategy to identify deafness, resolve the hidden-terminal problem, and avoid unnecessary blocking. The integrity of the DSDMAC protocol is verified and validated using , which is a formal protocol verification and validation tool. We further develop an analytical framework to quantify the performance of the DSDMAC protocol and conduct extensive simulations, which verify the accuracy of the analysis. The protocol verification, analysis, and simulation results show the robustness and superior performance of the DSDMAC protocol, which can achieve a much higher network throughput and lower delay utilizing the spatial multiplexing gain of the directional antennas. The results presented in this paper show that the proposed DSDMAC protocol can substantially outperform the state-of-the-art protocols.

Handling Triple Hidden Terminal Problems for Multichannel MAC in Long-Delay Underwater Sensor Networks

In this paper, we investigate the multichannel MAC problem in underwater acoustic sensor networks. To reduce hardware cost, only one acoustic transceiver is often preferred on every node. In a single-transceiver multichannel long-delay underwater network, new hidden terminal problems, namely, multichannel hidden terminal and long-delay hidden terminal (together with the traditional multihop hidden terminal problem, we refer to them as hidden terminal problems”), are identified and studied in this paper. Based on our findings, we propose a new MAC protocol, called CUMAC, for long-delay multichannel underwater sensor networks. CUMAC utilizes the cooperation of neighboring nodes for collision detection, and a simple tone device is designed for distributed collision notification, providing better system efficiency while keeping overall cost low. Analytical and simulation results show that CUMAC can greatly improve the system throughput and energy efficiency by effectively solving the complicated triple hidden terminal problems.