Channel Access Method Research Articles

Delay–Accuracy Tradeoff in Opportunistic Time-of-Arrival Localization

While designing a positioning network, the localization performance is traditionally the main concern. However, collection of measurements together with channel access methods require a nonzero time, causing a delay experienced by network nodes. This fact is usually neglected in the positioning-related literature. In terms of the delay-accuracy tradeoff, broadcast schemes have an advantage over unicast, provided nodes can be properly synchronized. In this letter, we analyze the delay-accuracy tradeoff for localization schemes in which the position estimates are obtained based on broadcasted ranging signals. We find that for dense networks, the tradeoff is the same for cooperative and noncooperative networks, and cannot exceed a certain threshold value.

Performance Evaluation of Wireless 802.11n Using Level 2 and Level 3 Mobility

Objectives: To present a performance evaluation of a WI-FI network under the impact of mobility. It alsomakes the study and the evaluation cover for level 2 and level 3 mobility. Methods/Statistical Analysis: The OPNET simulator was used for simulating the scenarios of proposed architectures. For performance evaluations, the different parameter has considered, such as mobility speed, number of connected users and channel access methods. Findings: The main interest of this paper is to reveal the mobility schema that ensures a better continuity of providing services to mobile users moving between different Wi-Fi access points while considering a number of constraints related to the quality of service. Application/Improvements: Deploying level 2 roaming gives better results compared with level three roaming using MIPv4, while increasing the speed of mobility and the number of clients. Keywords: Level 2 Mobility, Level 3 Mobility, Performance Evaluation, MIPv4, 802.11 n

Channel Access Method Classification for Cognitive Radio Applications

Motivated by improved detection and prediction of temporal holes, we propose a two stage algorithm to classify the channel access method used by a primary network. The first stage extends an existing fourth-order cumulant-based modulation classifier to distinguish between TDMA, OFDMA, and CDMA. The second stage proposes a novel collision detector using the sample variance of the same cumulant to detect contention-based channel access methods. Our proposed method is blind and independent of the received SNR. Simulations show that our classification of TDMA, OFDMA, and CDMA is robust to network load while detection of contention outperforms existing methods.

Advanced Approximation of Channel Quality in a VLC CDM System

Expanding the functionality of LED indoor lighting with visible light communication (VLC) allows an additional communication channel beside wireless radio in buildings. This service may be based on various channel access methods and modulation types. Code division multiplexing (CDM) is a suitable method to such an application, but it is complicated to measure the signal quality which is essential to compare different codes and settings, and necessary for some applications like position-dependent information services. Computing crest factor is a suitable method to estimate quality, but it may be inaccurate in some cases. This paper presents novel methods to approximate the quality of received CDM signals along with the crest factor, aiding the more accurate investigation of the VLC CDM technique.

A Hybrid Channel Access Scheme for Coexistence Mitigation in IEEE 802.15.4-Based WBAN

Wireless body area network (WBAN) is a communication technology, which aims providing both medical and consumer electronics services through sensor devices in, on, or around a human body. Due to the absence of the IEEE 802.15.6-based RF modules, the IEEE 802.15.4, a typical low-power communication technology of which requirements are similar, is considered to implement WBANs. In the case where a lot of WBANs coexist, meanwhile, collisions and signal attenuations may lead to their communication performance degradation. However, the IEEE 802.15.4 does not provide any solutions to solve coexistence problems, and thus, coexistence mitigation schemes for the IEEE 802.15.4-based WBANs are necessary. In this paper, we perform preliminary experiments to identify aspects of coexistence problem among the coexisting IEEE 802.15.4-based WBANs. Based on the results of preliminary experiments, we also propose a hybrid channel access scheme to mitigate coexistence problems in WBANs. The proposed scheme can be classified into two phases. In the first phase, the proposed scheme provides probabilistic collision avoidance on the contention-free period. When the pre-defined requirements of reliability cannot be satisfied with performing the first phase, the proposed scheme performs the second phase, which helps to mitigate collision or interference through changing channel access method. To evaluate the performance of the proposed scheme, we implement our scheme and perform experiments by comparing with an IEEE 802.15.4-based WBAN.

Database-Assisted Distributed and Cloud-Based Access Methods for Unlicensed and Radar Bands

This paper focuses on the design of methods which enable unlicensed devices to use the frequency spectrum already allocated to rotating radar systems without causing interference to those radars. We first present a database-assisted spectrum sharing/co-existence mechanism for radar spectrum bands. This mechanism takes into account the real spectrum usage behavior of different radars, and is also implemented by prototyping a real-time rotating radar beam emulator, a radar spectrum database using MySQL software, and spectrum access algorithm on wireless open access research platform. Then we propose a cloud-based unified channel access (UCA) method and a distributed UCA method for co-existence of multiple competing users in unlicensed and rotating radar spectrum bands. We model the UCA problem as a game and propose iterative methods (i.e., algorithms) to obtain the solution of the game. We study the stability of the proposed methods under several different scenarios. We show that the proposed UCA game is a potential game, and also show that the proposed methods guarantee convergence to a Nash equilibrium. Our results show that the cloud-based method allows fast convergence and can achieve performance that is close to optimal solution.

Uncoordinated Access Schemes for the IoT: Approaches, Regulations, and Performance

Internet of Things (IoT) devices communicate using a variety of protocols, differing in many aspects, with the channel access method being one of the most important. Most of the transmission technologies explicitly designed for IoT and Machine-to-Machine (M2M) communication use either an ALOHA-based channel access or some type of Listen Before Talk (LBT) strategy, based on carrier sensing. In this paper, we provide a comparative overview of the uncoordinated channel access methods for IoT technologies, namely ALOHA-based and LBT schemes, in relation with the ETSI and FCC regulatory frameworks. Furthermore, we provide a performance comparison of these access schemes, both in terms of successful transmissions and energy efficiency, in a typical IoT deployment. Results show that LBT is effective in reducing inter-node interference even for long-range transmissions, though the energy efficiency can be lower than that provided by ALOHA methods. The adoption of rate-adaptation schemes, furthermore, lowers the energy consumption while improving the fairness among nodes at different distances from the receiver. Coexistence issues are also investigated, showing that in massive deployments LBT is severely affected by the presence of ALOHA devices in the same area.

Implementation of Advanced Routing Technique for Cognitive Radio

One of the most developing technologies for future wireless communication is Cognitive Radios (CR) networks. The Cognitive Radios are fully programmable wireless devices for supporting dynamic spectrum access, the policy that addresses the channel access method, spectrum use and spectrum scarcity problem. In this a transceiver is designed to use the best wireless channels in its vicinity thereby intelligently detecting which communication channels are available and instantly move into vacant channels while avoiding the occupied ones. Thus the use of RF spectrum is optimized while minimizing interference to end users. To establish a route between source and destination nodes in CRAHN, a routing technique is needed. Various routing methods have been proposed based on performance metrics such as propagation delay, transmitted power, number of intermediate nodes between source and destination (hop count) and spectrum awareness. This paper implements a new routing technique incorporating all the above metrics. The routing strategy can be implemented in MATLAB which may improve metrics like distance, number of intermediate nodes between source and destination (hop count), transmitted power, propagation delay in comparison with shortest path and the MTPR routing technique.

Adaptive Blind CDMA Receivers Based on ICA Filtered Structures

Code division multiple access (CDMA) is a channel access method adopted by various radio technologies worldwide. In particular, CDMA is used as an access method in many mobile standards such as CDMA2000 and WCDMA. We address the problem of blind multiuser equalization in the wideband CDMA systems in the noisy multipath propagation environment. Herein, we propose three new blind receiver schemes based on variations of independent component analysis within several filtering structures. These adaptive blind CDMA receivers do not require knowledge of the propagation parameters or spreading code sequences of the users--they primarily exploit the natural assumption of statistical independence among the symbol signals. We also develop three semi-blind adaptive detectors by incorporating new adaptive methods into the standard Rake receiver structure. Extensive comparative case studies based on bit error rate performance are carried out as a function of (i) the number of users, (ii) the number of symbols per user, and (iii) the signal-to-noise ratio. The conventional detectors include the baseline linear minimum mean squared error detector. The results show that the proposed methods outperform other detectors in estimating the symbol signals from the received mixed CDMA signals. Moreover, the new blind detectors mitigate the multiaccess interference in CDMA.

User Assignment Algorithms for Energy-Efficiency-Aware Multiple Access Systems

An energy-efficiency-aware multiple access (EMA) system selects an energy-efficient channel access method, either time-division multiple access or space-division multiple access, for each frequency subband. We propose polynomial-complex and greedy-based user assignment algorithms for the EMA system. By conducting complexity analysis and energy efficiency comparison, we verify that the proposed algorithms can significantly improve energy efficiency with practically tractable complexity.

V2V QoS Guaranteed Channel Access in IEEE 802.11p VANETs

IEEE 802.11p Wireless Access in the Vehicular Environment (WAVE) has been serving as the de facto wireless protocol for a Vehicular Ad hoc Network (VANET) with the explosive growth of vehicular applications. These applications require guaranteed Quality-of-Service (QoS). However, the fundamental channel access mechanism of WAVE, Enhanced Distributed Channel Access (EDCA), is not able to provide guaranteed QoS due to the unpredictable random access. To remedy this problem, we propose a novel channel access scheme, called Earliest Deadline First based Carrier Sense Multiple Access (EDF-CSMA). EDF-CSMA based on EDCA dynamically adjusts the priority of real-time streaming to avoid collision and introduces an admission control policy according to time constraints to provide guaranteed QoS in multi-channel environments. An analytical model is carried out to study and compare the channel utilization of EDF-CSMA and QoS-aware Hybrid Coordination Function (HCF) controlled channel access (HCCA) method. The result shows that 60 percent of channel utilization is improved by EDF-CSMA. Additionally, real video-based simulations are conducted to evaluate the performance of EDF-CSMA and the existing EDCA method. The results show that EDF-CSMA reaches better QoS support than EDCA while maintaining efficient channel utilization.

Cognitive spectrum access in device-to-device-enabled cellular networks

Cognitive spectrum access (CSA) in in-band D2D-enabled cellular networks is a potential feature that can promote efficient resource utilization and interference management among coexisting cellular and D2D users. In this article, we first outline the challenges in resource allocation posed by the coexistence of cellular and D2D users. Next, we provide a qualitative overview of the existing resource allocation and interference management policies for in-band D2D-enabled cellular networks. We then demonstrate how cognition along with limited information exchange between D2D users and the core network can be used to mitigate interference and enhance spectral efficiency of both cellular and D2D users. In particular, we propose a CSA scheme that exploits channel sensing and interference- aware decision making at the D2D terminals. This CSA scheme at the D2D terminals is complemented by a D2D-aware channel access method at the cellular BSs. The performance gains of the proposed CSA scheme are characterized in terms of channel access probability for a typical D2D transmitter and spectral efficiencies for both cellular and D2D transmissions. Finally, potential research issues that require further investigation are highlighted.

IEEE 802.15.4 기반 WBAN의 공존 문제 완화 기법

ABSTRACT WBAN(Wireless Body Area Network) operating around the human body aims at medical and non-medical service at the same time. and it is the short-range communication technology requiring lo w-power, various data rate and high reliability. Various studie s is performing for IEEE 802.15.4, because IEEE 802.15.4 can provide high compatibility for operate WBAN among communication standa rd satisfiable these requirements. Meanwhile, in the case of coexi sting many IEEE 802.15.4-based WBAN, signal interference and co llision are the main cause that is decreasing data reliability. but IEE E 802.15.4 Standard does not consider about coexistence of many networks. so it needs improvement. In this paper, To solve abou t this problem, identify coexistence problem of IEEE 802.15.4-b ased WBAN by preliminary experiments. and propose a scheme to mitiga te the reliability decrease at multiple coexistence WBAN. The proposed scheme can be classified in two steps. The first step is avoidance to collision on the CFP through improving data tra nsmission. The second step is mitigation collision through converting chan nel access method. Proposed scheme is verified the performance by performing comparison experiment with Standard-based WBAN.

Evaluation of Analog Joint Source-Channel Coding Systems for Multiple Access Channels

We address the evaluation of low-complexity analog Joint Source Channel Coding (JSCC) methods for the transmission of discrete-time analog symbols over Multiple-Input Multiple-Output (MIMO) Multiple Access Channels (MAC). Analog JSCC is employed to encode the source information at each transmitter prior to be directly input to the MAC access scheme. Three channel access methods are considered to ensure the receiver is able to recover the user information: Code Division Multiple Access (CDMA), linear MMSE access codes and opportunistic access. CDMA allows the orthogonal transmission of the user data requiring only Channel State Information (CSI) at reception. On the other hand, linear MMSE access codes exploit CSI knowledge at transmission and exhibit better performance. Finally, opportunistic access also exploits CSI at transmission and allocates all MAC resources to the user with the strongest channel. This latter access scheme exhibits the best performance in terms of sum distortion although it may lead to unfair rate distributions among users.

Examination of Energy Efficiency for MAC Protocol in Wireless Body Area Networks

Wireless body area networks are widely used for applications such as health care system, where wireless sensors (nodes) monitor the parameter(s) of interest. Sensors play a critical role in many sensor network applications. Mac layer operates on non-beacon and beacon enabled mode. The IEEE 802.15.4 standard provide two modes of connections: beacon enabled mode and non-offer transmission determinism. The nonbeacon enabled mode does not suggest any assurance on traffic determinism. In this network an unslotted CSMA/CA channel access method is used beacon mode. In beaconenabled networks, the extraordinary network nodes called ZigBee Routers transmit episodic beacons to verify their existence to other network nodes i.e. it can. Opposing to the non-beacon enabled mode, the beacon analyze delay, packet loss ratio, network life time, throughput of the wireless body area network. There will be three states nodes, sleep, awake, idle, which will be used to do transmission of data packets.AR-MAC protocol is based upon TDMA technique to reduce energy utilization. AR-MAC assigns Guaranteed Times Slot (GTS) to every sensor node for communication based upon the necessities of sensor node. Analysis of this parameter is performed on TDMA and CSMA/CA techniques that will be used to do the comparison on MAC layer. The performance will be judged on beacon and nonbeacon enabled mode. Enabled mode does not permit us to shape mesh topology in order to interrelate numerous beacon networks.

Rendezvous Issues in AD Hoc Cognitive Radio Networks

Rendezvous is a process of two or more cognitive radio nodes gathering on the same channel at the same time for a negotiation to establish data communications. This paper discusses rendezvous issues in cognitive radio networks. It details why rendezvous is an issue in cognitive radio networks and how rendezvous works. It classifies channel access methods, and details sequence-based channel-hopping methods. It surveys existing works on blind rendezvous and compares the proposed algorithms in terms of the maximum time to rendezvous. This paper discusses the properties that an efficient channel-hopping rendezvous algorithm should have and illustrates common issues in the existing rendezvous methods. It also explains open research issues in the rendezvous area.

Adaptive and Autonomous Channel Access Methods for Distributed Cognitive Radios

In distributed multichannel cognitive radio (CR) networks, autonomous CRs face competition from one another to access the potentially available channels. Efficient resource allocation in such scenarios can be achieved by carrying out negotiation among distributed CRs via a coordinator (base station) or with the help of a common control channel. While the use of a coordinator or a common control channel simplifies the problem, it may create significant signaling overhead or potential contention under heavy load. Opportunistic channel selection strategies that require no centralized coordination among the autonomous CRs are surveyed in this paper and also novel results related to our own proposed $$\gamma $$?-persistent adaptive strategy are provided. Unlike our previous work in Khan et al. (IEEE Trans Mob Comput 12(2): 2013), we evaluate the performance of the proposed $$\gamma $$?-persistent strategy in terms of different performance metrics such as: (1) Average throughput of an individual CR; (2) Probability of finding a channel free in first step (given that the channel is free) for an autonomous CR; and (3) Average number of unsuccessful transmissions experienced by a CR. Using these performance metrics, we compare the performance of the proposed strategy with two other distributed strategies and also with a centralized strategy. We show that the proposed strategy allows the CRs to find a free channel with high probability in the first sensing step (given that the channel is free). This reduces the overhead of multiple sensing steps incurred by an autonomous CR. The reduced number of sensing steps required to find a channel free in turn improves throughput per time slot of a CR. Moreover, the proposed strategy reduces the likelihood of unsuccessful transmissions by CRs which in turn improves throughput and also reduces the transmission attempt costs of an autonomous CR.

Three-dimensional light positioning algorithm with filtering techniques for indoor environments

This paper introduces an indoor positioning system based on visible light communication technology with three-dimensional positioning capability. Light-emitting diodes are employed as transmitters, with photodiodes as receivers to obtain the received signal strength (RSS) information. Based on the trilateration technique, the proposed algorithm is able to calculate horizontal coordinates of the receiver with RSS information, after which the height of the receiver is estimated. The system does not require other measurements such as time-of-arrival or angle-of-arrival, thus system design and costs are simplified and minimized. Basic framed slotted ALOHA is applied as the channel access method to enable asynchronous transmissions. In addition, Kalman and particle filters are used in order to realize target tracking. Results show that both filters help to increase the positioning accuracy and the particle filter exhibits a better performance than the Kalman filter, with a higher computational complexity.

Performance Analysis of Channel Access Model for MAC in Randomly Distributed Wireless Sensor Networks

Medium Access control (MAC) is one of the fundamental problems in wireless sensor networks. The performance of wireless sensor network depends on it. The main objective of a medium access control method is to provide high throughput, minimize the delay, and conservers the energy consumption by avoiding the collisions. In this paper, a general model for MAC protocol to reduce the delay, maximize throughput and conserve the energy consumption in channel accessing in high density randomly distributed wireless sensor network is presented. The proposed model is simulated using MATLAB. The simulation results show that the average delay for sensors with sufficient memory is lower than sensors without memory. Further, the throughput of the channel access method with memory is better than without memory.

Stability and Delay Analysis of EPON Registration Protocol

The Ethernet passive optical network (EPON) has recently emerged as the mainstream of broadband access networks. The registration process of EPON, which is defined by the IEEE 802.3av standard, is a multi-point control protocol within the media access control layer. As with other contention-based channel access methods, such as ALOHA and CSMA, stability and delay are critical issues concerning the performances of implementing the protocol on systems with finite channel capacity. In this paper, the registration process of an EPON subscriber, called optical network units (ONUs), is modeled as a discrete-time Markov chain, from which we derive the fundamental throughput equation of EPON that characterizes the registration processes. The solutions of this characteristic equation depend on the maximum waiting time. The aim of our stability analysis is to pinpoint the region of the maximum waiting time that can guarantee a stable registration throughput and a bounded registration delay. For a maximum waiting time selected from the stable region, we obtain the expression of registration delay experienced by an ONU attempting to register. All analytic results presented in this paper were verified by simulations.