Hidden Terminal Problem Research Articles

IRI-MAC: An Improved Receiver Initiated MAC Protocol for Wireless Sensor Network

Now a day's wireless sensor network takes much attention to researcher. A lot of Medium Access Control (MAC) protocol has been proposed to improve the efficiency in case of increase throughput and energy preservation. ReceiverInitiated MAC(RI-MAC) is one of the most popular MAC protocol due to its ultra-low duty cycle and good throughput. But RI-MAC major disadvantages are exposed terminal collision problem and hidden terminal collision problem. In this paper we only addressed exposed terminal problem using an unique time Clear Channel Assessment(CCA).According to Improved Receiver-Initiated MAC(IRI-MAC) protocol the receiver beacon is not respond immediately but wait a random time and perform a CCA either the channel is clear. If channel clear then transmit its data immediately. More precisely, we provide such an equation that generate an unique CCA time for each node in order to avoid collision for exposed terminal problem. Our proposed system is implemented in omnet/Mixim platform and result shows that IRI-MAC perform better than that of RC-MAC and RI-MAC.

Performance Analysis of CSMA/CA based Medium Access in Full Duplex Wireless Communications

Full duplex communication promises a paradigm shift in wireless networks by allowing simultaneous packet transmission and reception within the same channel. While recent prototypes indicate the feasibility of this concept, there is a lack of rigorous theoretical development on how full duplex impacts medium access control (MAC) protocols in practical wireless networks. In this paper, we formulate the first analytical model of a CSMA/CA based full duplex MAC protocol for a wireless LAN network composed of an access point serving mobile clients. There are two major contributions of our work: First, our Markov chain-based approach results in closed form expressions of throughput for both the access point and the clients for this new class of networks. Second, our study provides quantitative insights on how much of the classical hidden terminal problem can be mitigated through full duplex. We specifically demonstrate that the improvement in the network throughput is up to 35-40\% over the half duplex case. Our analytical models are verified through packet level simulations in ns-2. Our results also reveal the benefit of full duplex under varying network configuration parameters, such as number of hidden terminals, client density, and contention window size.

On Demand Stable Routing with Channel Allocation and Backoff Countdown Optimization in Wireless Mesh Networks

The multi-channel and multi-interface wireless mesh networks (WMNs) allow multiple orthogonal channels simultaneously to facilitate increased broadband connectivity to the end-users. Many efforts have been devoted to allocate the channels to the interfaces in a multi-channel multi-interface setting. Recently, the hybrid channel allocation mechanism jointly optimizes the routing and channel assignment, by utilizing the queuing traffic. It is essential to map the optimization of traffic distribution on each channel along with channel switching in such an order that it adapts to the changing traffic. However, the contention in medium access and channel switching delay are the key issues in a multi-channel hidden terminal problem. The proposed optimized stable path- channel allocation and routing (OSCAR) protocol is a hybrid multi-channel protocol that reduces the communication delay without degrading the network performance. The proposed work, OSCAR determines a highly stable path that increases mesh routers to improve the routing efficiency. The channel allocation mechanism mainly promotes queue dynamics based probabilistic channel selection (QDPCS), and backoff countdown optimization (BCO). An essential component of the QDPCS scheme is the factor of queuing utilization, and this strategy selects a least congested channel. The BCO mechanism creates the logical order among contending nodes based on the remaining backoff value. It reduces the medium access delay and enables the feasibility of scheduled transmissions without degrading the network throughput. Finally, the performance evaluation results show that the OSCAR protocol outperforms the existing protocol over WMNs.

Solving hidden terminal problem in MU-MIMO WLANs with fairness and throughput-aware precoding and a degrees-of-freedom-based MAC design

We generally emphasize that the zeroforcing (ZF) technique backed by an appropriate medium access control (MAC) protocol can be used to address the inevitable hidden terminal (HT) problem in multi-user multiple input multiple output (MU-MIMO) wireless local area network (WLAN) settings. However, to address the implementation-specific requirements of MU-MIMO WLANs, such as fairness in client access and throughput of the network, we propose a fairness and a throughput-aware ZF precoding in our design at the physical layer (PHY). This precoding scheme not only solves the HT problem but also meets the fairness and the throughput requirements of MU-MIMO WLANs. Besides, we design a MAC layer protocol, supportive to PHY, which decides transmission opportunities (TXOPs) among access points (APs) based on the available degrees of freedom (DoF). We make a mandatory provision in our design that APs should have a sufficient DoF. This can ensure collision-free transmission whenever APs/transmitters transmit in the HT scenario. Additionally, we design an improved channel sounding process for MU-MIMO WLANs with a less signaling overhead than IEEE802.11ac. We demonstrate the feasibility of our PHY in a USRP2/GNU Radio testbed prototype in the lab settings. It is found that our PHY improves the SNR and effective SNR of the received signal from about 5 to 11 dB in the HT scenario. The performance of our MAC design is checked with simulation studies in a typical six-antenna AP and clients scenario. We observe that our MAC protocol has a slightly higher signaling overhead than traditional ready to send/clear to send (RTS/CTS) due to design constraints; however, the signaling time overheads are reduced by 98.67 μs compared to IEEE802.11ac. Another interesting aspect to highlight is the constant Throughput gain of four to five times that of the traditional RTS/CTS. Our MAC protocol obtains this gain as early as 98.67 μs compared to IEEE802.11ac.

Q-BT: Queue-Based Burst Transmission Over an Asynchronous Duty-Cycle MAC Protocol

In this letter, we tackle the channel contention and hidden terminal problems of asynchronous duty-cycle MAC protocols under heavy traffic scenario. To resolve the problems, we design a queue-based burst transmission MAC protocol (Q-BT), which couples burst (and fast) transmission and asynchronous duty-cycle features together by using queue length information. We evaluate its performance in a multihop testbed, which shows that our proposal improves packet reception ratio and duty-cycle performance by 70.2% and 59.1%, respectively, at a maximum compared to BoX-MAC (i.e., the default MAC in TinyOS).

Random Access or Scheduling: Optimum LTE Licensed-Assisted Access to Unlicensed Spectrum

To deploy long-term evolution advanced (LTE-A) networks on unlicensed bands, licensed-assisted access (LAA) has been regarded as an unprecedented technology in the third generation partnership project (3GPP) Rel-13. However, due to uncontrollable interference from collocated WiFi networks, a particular LAA-WiFi hidden terminal problem may occur, thus degrading the performance of the existing scheduling-based radio access in LTE-A. To provide foundations for LAA standardization, we analytically derive the optimum radio access for LAA, which reveals a dynamic switch between scheduling-based and random access schemes. The switching condition derived in this letter thus suggests the optimum design for LAA networks.

Full-Duplex Wireless Communications: Challenges, Solutions, and Future Research Directions

The family of conventional half-duplex (HD) wireless systems relied on transmitting and receiving in different time slots or frequency subbands. Hence, the wireless research community aspires to conceive full-duplex (FD) operation for supporting concurrent transmission and reception in a single time/frequency channel, which would improve the attainable spectral efficiency by a factor of two. The main challenge encountered in implementing an FD wireless device is the large power difference between the self-interference (SI) imposed by the device’s own transmissions and the signal of interest received from a remote source. In this survey, we present a comprehensive list of the potential FD techniques and highlight their pros and cons. We classify the SI cancellation techniques into three categories, namely passive suppression, analog cancellation and digital cancellation, with the advantages and disadvantages of each technique compared. Specifically, we analyze the main impairments (e.g., phase noise, power amplifier nonlinearity, as well as in-phase and quadrature-phase (I/Q) imbalance, etc.) that degrading the SI cancellation. We then discuss the FD-based media access control (MAC)-layer protocol design for the sake of addressing some of the critical issues, such as the problem of hidden terminals, the resultant end-to-end delay and the high packet loss ratio (PLR) due to network congestion. After elaborating on a variety of physical/MAC-layer techniques, we discuss potential solutions conceived for meeting the challenges imposed by the aforementioned techniques. Furthermore, we also discuss a range of critical issues related to the implementation, performance enhancement and optimization of FD systems, including important topics such as hybrid FD/HD scheme, optimal relay selection and optimal power allocation, etc. Finally, a variety of new directions and open problems associated with FD technology are pointed out. Our hope is that this treatise will stimulate future research efforts in the emerging field of FD communications.

Allocation of Spectrum using ADCSO for Collision Avoidance and Cooperative Spectrum Sensing with MIMO

This paper investigates the problem of allocation of spectrum for the Secondary Users (SUs) based on Adaptive Dynamic Cat Swarm Optimization (ADCSO) which follows certain priorities that allows SU to access the spectrum without collision and it also details the cooperative spectrum sensing using Multiple Input Multiple Output (MIMO). Cooperative spectrum sensing shares the sensed information obtained using MIMO to the peer SUs which avoids the Hidden Terminal Problem. In Wireless Communication the avoidance of interference and delay are the major issues. In recent times the number of users have been increased that lead to the concern on quality of spectrum to the quantity of spectrum. Hence it is necessary to find the free spectrum from the available spectrum nearby. However, this need may result in collision among the SUs trying to find free spectrum in the Primary User (PU) region. To avoid this, method based on Swarm Intelligence (SI) is used. There can be certain nodes that remain hidden due to the presence of obstacles in between them causing Hidden Terminal Problem. This can be overcome by sharing the sensed information to the peer nodes which acts as a relay node for the communication. Hence, this proposed method collectively solves the above mentioned problems effectively.

Power-Controlled Data Transmission in Wireless Ad-Hoc Networks: Challenges and Solutions

Energy scarcity and interference are two important factors determining the performance of wireless ad-hoc networks that should be considered in depth. A promising method of achieving energy conservation is the transmission power control. Transmission power control also contributes to the mitigation of interference thereby promotes throughput by means of rendering multiple hosts to communicate in the same neighborhood simultaneously without impairing each other’s transmissions. However, as identified previously in the literature, traditional hidden terminal problem gets deteriorated when transmission power control mechanism is intended to be applied. In this article, we discuss the primary details about the power usage and throughput deficiency of the traditional 802.11 RTS/CTS mechanism. Improvements by means of power control are introduced as well as the solutions to the challenges likely to emerge because of the usage of diverse power levels throughout the network.

Performance Evaluation of Dynamic CCA-ED Threshold Control Scheme for WLAN

An effort has been made to achieve and maintain a high data rate, which is actually experienced by the users and less affected by the nearby devices even in a Wi-Fi dense area. An IEEE 802.11ax TG (task group) was formed to standardize these efforts, so called HEW (high efficiency WLAN). As a way of alleviating the effect of nearby devices, the IEEE 802.11ax TG is considering a scheme which changes the CCA (clear channel assessment) threshold dynamically. In this paper we explain how the scheme tries to resolve the hidden terminal problem and the exposed terminal problem at the same time. We also analyze the performance of the dynamic CCA threshold control scheme in various density of APs/STAs through simulation.

Least Channel Variation Multi-Channel MAC (LCV-MMAC) under Mobile Random Topologies in Mobile Adhoc Networks

The use of multiple channels for transmissions has raised several challenges, for example, multi-channel hidden terminal problem, channel switching delay, and control channel saturation problem. Dedicated control channel techniques simplify channel coordination by eliminating the need for synchronization, however the control channel may become the bottleneck for the performance of the network. A better trade off which can solve the coordination problem, and can mitigate the control channel bottleneck is desirable. Least Channel Variant Multi-channel MAC (LCV-MMAC) is a multi-channel MAC based on IEEE 802.11 MAC. The novel part of this protocol is the channel assignment technique, where a mechanism to avoid unnecessary channel assignment and thus channel switching is used. Further, LCV-MMAC avoids channel contention when the control channel is highly saturated. In this paper, we explore the properties of LCV-MMAC through extensive simulations with the help of ns-2, and compare it with popular existing multi-channel MAC protocols in different mobile and static random topologies. Experimental results validate that LCV-MMAC achieves significantly better aggregated throughput, and fairness index than other multi-channel MAC protocols in different random network scenarios.

Load-aware channel hopping protocol design for mobile ad hoc networks

Using multiple channels in wireless networks improves spatial reuse and reduces collision probability and thus enhances network throughput. Designing a multi-channel MAC protocol is challenging because multi-channel-specific issues such as channel assignment, the multi-channel hidden terminal problem, and the missing receiver problem, must be solved. Most existing multi-channel MAC protocols suffer from either higher hardware cost or poor throughput. Some channel hopping multi-channel protocols achieve pretty good performance in certain situations but fail to adjust their channel hopping mechanisms according to varied traffic loads. In this paper, we propose a load-aware channel hopping MAC protocol (LACH) that solves all the multi-channel-specific problems mentioned above. LACH enables nodes to dynamically adjust their schedules based on their traffic loads. In addition to load awareness, LACH has several other attractive features: (1) Each node is equipped with a single half-duplex transceiver. (2) Each node's initial hopping sequence is generated by its ID. Knowing the neighbor nodes' IDs, a node can calculate its neighbors' initial channel hopping sequences without control packet exchanges. (3) Nodes can be evenly distributed among available channels. Through performance analysis, simulations, and real system implementation, we verify that LACH is a promising protocol suitable for a network with time-varied traffic loads.

Reliability and performance of general two-dimensional broadcast wireless network

In this paper, an analytic model is built to study the medium access control (MAC) performance and reliability of general two-dimensional (2-D) IEEE 802.11 based wireless networks for one-hop broadcast communications. First, a semi-Markov process (SMP) model is introduced to capture the medium contention and backoff behavior and the impact of hidden terminal problem in IEEE 802.11 broadcast wireless networks in a more precise way. An M/G/1/K queue is used to model arrival and service of messages in an individual mobile terminal. To the contention for the shared medium, the SMP model interacts with the M/G/1/K queue through fixed-point iteration. Furthermore, based on the fixed-point solution, performance metrics including packet delivery probability (PDP), MAC-level and Application-level transmission delay, and MAC-level and Application-level packet reception ratio (PRR) are derived. The 2-D PDPs are derived through a coverage area computation for the impact of hidden terminal problem and concurrent transmissions to evaluate point-to-point reception probability, and then through integration of the reception probabilities over the circular intended range of the sending node. The analytical model takes into account IEEE 802.11 backoff counter process, hidden terminal problem, message inter-arrival interval, distinct transmission range, carrier sensing and interference ranges, and Nakagami fading channel with distance dependent path loss. Finally, as an example, the proposed analytic model is applied to a 2-D ad hoc network. The new model is validated through extensive simulations and new observations about the effects of network parameters on the performance and reliability are obtained.

A Hybrid Lifetime Extended Directional Approach for WBANs.

Wireless Body Area Networks (WBANs) can provide real-time and reliable health monitoring, attributing to the human-centered and sensor interoperability properties. WBANs have become a key component of the ubiquitous eHealth (electronic health) revolution that prospers on the basis of information and communication technologies. The prime consideration in WBAN is how to maximize the network lifetime with battery-powered sensor nodes in energy constraint. Novel solutions in Medium Access Control (MAC) protocols are imperative to satisfy the particular BAN scenario and the need of excellent energy efficiency in healthcare applications. In this paper, we propose a hybrid Lifetime Extended Directional Approach (LEDA) MAC protocol based on IEEE 802.15.6 to reduce energy consumption and prolong network lifetime. The LEDA MAC protocol takes full advantages of directional superiority in energy saving that employs multi-beam directional mode in Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) and single-beam directional mode in Time Division Multiple Access (TDMA) for alternative in data reservation and transmission according to the traffic varieties. Moreover, the impacts of some inherent problems of directional antennas such as deafness and hidden terminal problem can be decreased owing to that all nodes generate individual beam according to user priorities designated. Furthermore, LEDA MAC employs a Dynamic Polled Allocation Period (DPAP) for burst data transmissions to increase the network reliability and adaptability. Extensive analysis and simulation results show that the proposed LEDA MAC protocol achieves extended network lifetime with improved performance compared with IEEE 802.15.6.

Highly Efficient Multi-Hop Packet Transmission Using Intra-Flow Interference Cancellation and Maximal-Ratio Combining

Conventional Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) multi-hop transmission suffers severely from intra-flow interference (IFI) in dense traffic, due to the hidden terminal (HT) problem. We propose a non-CSMA/CA multi-hop transmission scheme with IFI-canceler (IFIC) that can efficiently relay packets under high traffic loads in fading environments. This interference cancellation technique employs adaptive equalization with a normalized least mean square (NLMS) algorithm for channel estimation and has good BER/PER performance under a wide range of SNR and SIR conditions. It is also capable of canceling multiple interference sources. A multi-hop packet transmission frame format dedicated to the IFIC proposal is designed. An analysis model is created that considers possible outage events in multi-hop traffic flows. Simulations of multi-hop transmission indicate that IFIC throughput under slow Rayleigh fading linearly increases with traffic load and is 3.5 times higher than that of current CSMA/CA systems at the highest normalized traffic load. When 2-branch maximal-ratio combining (MRC) reception is added after IC, the throughput is further improved to a level very close to the theoretical maximum for additive white Gaussian noise (AWGN) channels. We also assess the impact of maximum Doppler frequency, and show that the best performance is maintained if the frequency is less than 10 Hz and the performance under higher Doppler frequencies can be effectively improved by retransmission.

Channel measurement-based access point selection in IEEE 802.11 WLANs

With the wide deployment of IEEE 802.11 Wireless Local Area Networks, it has become common for mobile nodes (MNs) to have multiple access points (APs) to associate with. With the Received Signal Strength Indicator (RSSI)-based AP selection algorithm, which is implemented in most commercial IEEE 802.11 clients, the AP with the best signal strength is selected regardless of the candidate AP’s available throughput, resulting in unbalanced distribution of clients among the APs in the network. Several studies have shown performance improvement in not just the new MN (nMN), but also the network as a whole when the selection process considers the current load status of candidate APs. However, the proposed algorithms in these studies assume that there are no hidden terminal problems that severely affect the performance of the network. Hidden terminal problems frequently occur in wireless networks with unlicensed frequencies, like IEEE 802.11 in the 2.4 GHz band. Moreover, none of the previous studies have considered frame aggregation, a major improvement in transmission efficiency introduced and widely deployed with the IEEE 802.11n standard. In this paper, we propose a new AP selection algorithm based on the estimation of available throughput calculated with a model based on the IEEE 802.11 distributed coordination function in consideration of hidden terminal problems and frame aggregation. The proposed algorithm is evaluated through extensive simulation, and the results show that the nMN with the proposed AP selection algorithm can achieve up to 55.84% and 22.31% higher throughput compared to the traditional RSSI-based approach and the selection algorithm solely based on the network load, respectively.

Cooperative Interference Game in cognitive radio hidden terminal scenario

Hidden terminal problem in spectrum sensing is one of the most challenging problems in cognitive radio network (CRN). To tackle this problem, we propose a novel Cooperative Interference Game scheme in this paper. The scheme adopted full duplex (FD) mode to sense over multiple sub-bands in an iterative manner without extra sensing devices. The implementation algorithm of the proposed scheme is consisted of three modules: the formulation of the maximum transmit power limitation of second user (SU); the self-interference cancellation coefficient; and the optimal location of SU for an optimized low collision probability. Monte Carlo simulation proved that compared with cooperative spectrum sensing, the proposed scheme significantly improves the performance of spectrum detection and mitigates hidden terminal problem to a large extent with less energy consumption.

Addressing Hidden Terminal Problem in Heterogeneous Wireless Networks

Addressing Hidden Terminal Problem in Heterogeneous Wireless Networks

A Low Latency, Energy Efficient MAC Protocol for Wireless Sensor Networks

Reducing unnecessary and redundant handshake frame is considered as a promising way to reduce the end-to-end delay and energy consumption. Here, a protocol named compressed handshake media access control (CH-MAC) is presented. CH-MAC introduces a new handshake mechanism with implicit RTS to achieve the object of low delivery latency and an initiative sleeping mechanism to settle the hidden terminal problem. Simulation results show that the proposed protocol outperforms SMAC protocol in both energy consumption and packet latency.

Implementation of Smart Home with Multi-Channel Technology

In this paper, we propose a Smart-Home system with ZigBee Wireless Sensor Networks (WSNs) technology. The system provides automation system in the House. The monitor system uses Andriod NDK and SDK to write application interface for an Android embedded platform. In this system, we provide access control system to obtain sensor data and inquiry into node status. We use multi-channel architecture to reduce a hidden terminal problem and upgrade packet delivery ratio.