Scheme In IEEE Research Articles

Effects Investigation of MAC and PHY Layer Parameters on the Performance of IEEE 802.15.6 CSMA/CA

The recently released IEEE 802.15.6 standard specifies several physical (PHY) layer and medium access control (MAC) layer protocols for variety of medical and non-medical applications of Wireless Body Area Networks (WBAN). The most suitable way for enhancing network performance is to be the choice of different MAC and PHY parameters based on quality of service (QoS) requirements of different applications. The impact of different MAC and PHY parameters on the network performance and the tradeoff relationship between the parameters are essential to overcome the limitations of exiting carrier sense multiple access with collision avoidance (CSMA/CA) scheme of IEEE 802.15.6 standard. To address this issue, we develop a Markov chain-based analytical model of IEEE 802.15.6 CSMA/CA for all user priorities (UPs) and apply this general model to different network scenarios to investigate the effects of the packet arrival rate, channel condition, payload size, access phase length, access mechanism and number of nodes on the performance parameters viz. reliability, normalized throughput, energy consumption and average access delay. Moreover, we conclude the effectiveness of different access phases, access mechanisms and user priorities of intra-WBAN.

Markov-Chain Analysis Model based Active Period Adaptation Scheme for IEEE 802.15.4 Network

Markov-Chain Analysis Model based Active Period Adaptation Scheme for IEEE 802.15.4 Network

AP-based CW Synchronization Scheme in IEEE 802.11 WLANs

In this paper, an optimal CW (Contention Window) synchronization scheme is proposed in IEEE 802.11 WLANs. IEEE 802.11 WLANs operates with DCF (Distributed Coordination Function) mode for the MAC (Medium Access Control). In DCF, CW becomes the minimum CW according to the success of data transmissions and increases exponentially due to the collisions. In this situation, the smaller value of the minimum CW can increase the collision probability because stations have higher opportunity to access the medium. On the other hand, the higher value of the minimum CW will delay the transmission, which can result in the network performance degradation. In IEEE 802.11, since the base minimum CW value is a fixed value depending on the hardware or standard, it is difficult to provide the optimal network performance that can be determined by the flexible CW value according to the number of active stations. In addition, the synchronization of optimal CW is required among mobile stations to adapt the network parameters. Especially for the newly joined stations such as moving or turning on stations, they need to adapt the minimum CW value to get the optimal network performance. The shorter the adaptation time is, the better the network performance can maintain. Therefore, in this paper, AP (Access Point) calculates the optimal CW and shares it with mobile stations using beacon and probe response messages for the fast CW synchronization. Extensive simulation results show that the proposed scheme outperforms the previous schemes in terms of the network throughput and adaptation time. Â

Context-aware Hybrid Adaptive Beaconing for Driver Behavior Dissemination in VANETs

VANET is a special paradigm of high mobility ad hoc network that promotes communication among the vehicles to enhance traffic safety. Cooperative awareness is the basic principle of VANETs that is accomplished by periodic exchange of beacons/ WSMs between vehicles. Due to highly dynamic topology and irregular distribution of vehicles, there is a necessity of a flexible beaconing mechanism that maintains a balance between the required level of cooperative awareness and network load and overcomes the limitations of periodic beaconing scheme of IEEE 802.11p. We proposed a context-aware hybrid beaconing algorithm that piggybacks driver status in beacon and disseminates it to the neighboring vehicles to enhance safety. The complete context has been considered to get the value of driver status and initial network status using SBN. The proposed technique considers real-time network congestion status and dynamically adapts the transmission range and power parameters at PHY layer, and beacon interval and CW at MAC layer using EDCA mechanism. The performance of the proposed algorithm has been evaluated using SUMO and NS-3 based on PDR, WSM PDR, goodput, and EED. The proposed algorithm demonstrates comparable WSM PDR to the benchmark scheme of LIMERIC and outperforms periodic beaconing scheme by exhibiting 35% improvement in WSM PDR on CCH and 15% improvement in PDR on SCH. Further, our proposed approach depicts more realistic scenario by considering the complete context; and maintains balance between transmission of safety and non-safety messages, thus, preventing starvation of non-safety applications as compared to the techniques in the existing literature.

Multiple-Symbol Detection Scheme for IEEE 802.15.4c MPSK Receivers over Slow Rayleigh Fading Channels

Although the full multiple-symbol detection (MSD) for IEEE 802.15.4c multiple phase shift keying (MPSK) receivers gives much better performance than the symbol-by-symbol detection (SBSD), its implementation complexity is extremely heavy. We propose a simple MSD scheme based on two implementation-friendly but powerful strategies. First, we find the best and second-best decisions in each symbol position with the standard SBSD procedure, and the global best decision is frozen. Second, for the remaining symbol positions, only the best and second-best symbol decisions, not all the candidates, are jointly searched by the standard MSD procedure. The simulation results indicate that the packet error rate (PER) performance of the simplified MSD scheme is almost the same as that of the full scheme. In particular, at PER of 1 × 10 − 3 , no more than 0.2 dB performance gap is observed if we just increase the observation window length N to 2. However, the number of decision metrics needed to be calculated is reduced from 256 to 2. Thus, much balance gain between implementation complexity and detection performance is achieved.

An enhanced frequency-domain contention scheme for IEEE 802.11 WLANs

Frequency-domain contention is a new paradigm of contention that has been proposed to enhance the performance of OFDM wireless networks. In this paper, we demonstrate how frequency-domain contention schemes would fail in a wireless local area network (WLAN) due to the existence of nodes that are hidden from each other. In addition, we propose a new MAC protocol, which is called EFDC (enhanced frequency-domain contention), that solves the failure problem without sacrificing performance in a WLAN. Simulation is used to evaluate and compare EFDC to the T2F (time-to-frequency) protocol and IEEE 802.11 contention method. The results show that EFDC achieves higher performance in terms of throughput and delay.

SAMU: design and implementation of frequency selectivity-aware multi-user MIMO for WLANs

The traffic demand of wireless networks is expected to increase 1000-fold over the next decade. In anticipation of such increasing data demand for dense networks with a large number of stations, IEEE 802.11ax has introduced key technologies for capacity improvement including Orthogonal Frequency-Division Multiple Access (OFDMA), multi-user multi-input multi-output (MU-MIMO), and greater bandwidth. However, IEEE 802.11ax has yet to fully define a specific scheduling framework, on which the throughput improvement of networks significantly depends. Even within a 20 MHz of bandwidth, users experience heterogeneous channel orthogonality characteristics across sub-carriers, which prevents access points (APs) from achieving the ideal multi-user gain. Moreover, frequency selectivity increases as bandwidth scales and correspondingly severely deteriorates multi-user MIMO performance. In this work, we develop a novel channel adaptation scheme, named selectivity-aware multi-user MIMO (SAMU), to combat the issue of frequency selectivity and support coexistence among users in the network by jointly assigning subsets of sub-carriers to selected users and implementing downlink MU-MIMO. To do so, we first investigate the channel characteristics of an indoor environment. We then consider the frequency selectivity of current and emerging WiFi channel bandwidths to optimize multi-user MIMO by dividing the occupied sub-carrier resources into equally sized sub-channels according to the level of frequency selectivity. In our design, each sub-channel is allocated according to the largest bandwidth that can be considered frequency-flat, and an optimal subset of users is chosen to serve in each sub-channel according to spatial orthogonality. As a result, we support more simultaneous users than current 802.11 designs and achieve a significant performance improvement for all users in the network. Additionally, we propose a selectivity-aware high efficiency (SA-HE) mode, which is based on and fully backward compatible with the existing IEEE 802.11ax standard. Finally, over emulated and real indoor channels, we show that SAMU can achieve as much as 84.8% throughput improvement compared to existing multi-user MIMO schemes in IEEE 802.11ax.

Enhancing Cooperative Driving in IEEE 802.11 Vehicular Networks Through Full-Duplex Radios

On the path to zero fatalities on the roadways, all vehicles have to periodically broadcast cooperative awareness messages (CAMs) in a timely and reliable manner, even in areas of high traffic density. The carrier senses multiple access with collision avoidance (CSMA/CA) scheme of IEEE 802.11, the de-facto standard for vehicular communications, is known to offer no reliability to broadcast packets that cannot be acknowledged, and to poorly perform at high network load due to collisions and interference. In this paper, an enhanced CSMA/CA protocol is analyzed for vehicular networks, which improves the CAM timeliness and reliability by leveraging full-duplex (FD) transceivers on board. FD devices can listen to the channel while transmitting, thus making collision detection viable. A FD vehicle can detect a CAM collision while sending, promptly abort the packet and retransmit it later. Results achieved through an analytical model under mathematically tractable assumptions, and through extensive system-level simulations in a complex urban environment, show the effectiveness of the protocol to cope with direct collisions , especially in high traffic areas, paving the way towards the realization of cooperative automated driving.

A novel formation scheme for IEEE 802.15.4 WSN

A novel formation scheme for IEEE 802.15.4 WSN

A novel formation scheme for IEEE 802.15.4 WSN

This paper proposes a novel formation scheme for an IEEE 802.15.4 wireless sensor network which is organised into a tree topology. This scheme consists of the network formation initialisation algorithm and the network formation maintenance algorithm. In the initialisation algorithm, each node first calculate the lengths of routing paths reaching all other nodes in the network, and then the node with the minimum path length is elected as a root. In this way, the average length of the routing paths is reduced and accordingly the routing delay is also shortened. After the initialisation algorithm is executed, the maintenance algorithm is performed to maintain the tree topology. When the tree topology changes, the maintenance algorithm can dynamically adjust the root in order to reduce the average length of the routing paths and shorten the routing delay. This scheme employs beacons to achieve the initialisation algorithm and the maintenance algorithm, so the extra costs and delays are avoided. This scheme is analysed and evaluated, and the data results show that this scheme effectively reduces the average length of the routing paths and shortens the routing delay.

Sounding Node Set and Sounding Interval Determination for IEEE 802.11ac MU-MIMO

In this paper, we propose a sounding control scheme for IEEE 802.11ac multiuser multiple-input multiple-output (MU-MIMO). The proposed scheme comprehensively considers the long-term characteristics of a network environment, including the downlink traffic loads and channel coherence times of wireless links, and jointly determines the sounding node set and sounding interval to maximize the long-term expected MU-MIMO throughput gain in consideration of sounding overhead. To this end, we analytically formulate an MU-MIMO throughput gain maximization problem, considering the network environment and sounding overhead. We conduct MIMO channel measurement in practical wireless local area network (WLAN) environments and evaluate the performance of the proposed scheme by employing the real channel data traces. Simulation results verify that the proposed scheme adaptively determines the sounding node set and sounding interval, according to the network environment, and outperforms the existing scheme, which considers the channel coherence times only.

Energy consumption analysis of modulation schemes in IEEE 802.15.6-based wireless body area networks

Selection of the most energy-efficient modulation scheme is vital for wireless body area networks (WBANs) for improving the network lifetime. In this paper, we investigate the performance of various modulation schemes specified by IEEE 802.15.6 WBAN standard, in terms of energy consumed for successfully transferring one packet from the sensor node to the hub. Assuming a contention-free MAC protocol, we present an analytical model for computing the energy consumption for a given modulation scheme both for uncoded transmission as well as transmission using Bose-Chaudhuri-Hocquengham (BCH) codes; the coding scheme specified by IEEE 802.15.6 for WBAN. The following communication scenarios specific to a WBAN are considered: (i) in-body communication between invasive devices and hub and (ii) on-body communication among non-invasive devices and hub with line-of-sight (LOS) and non-LOS (NLOS) channels. The results show that the use of higher order differential phase shift keying (D8PSK)-based modulation schemes results in significant reduction of total energy consumption. When BCH codes with various code rate specifications are used, total energy consumption remains lower for the higher order modulation schemes. The energy consumption is further reduced when non-coherent frequency shift keying (NC-MFSK) is employed as an alternate modulation scheme instead of differential PSK schemes.

Enabling Validation of IEEE 802.15.4 Performance through a New Dual-Radio Omnet++ Model

Internet of Things (IoT) presents a promising technology concept for a wide range of applications due to the possibility of interconnecting any device with connection to Internet in order to improve the daily life of human beings. This fact, along with the increasing use of devices with wireless capabilities has created a saturation problem in the use of the radio-electric spectrum, which decreases the performance of wireless communications. A way to solve this problem is to develop policies for communicating nodes in different spectrum channels by means of the use of a dual radio scheme, which permits the communication in the same network using several channels. In this paper, we evaluate the performance of a dual-radio scheme in IEEE 802.15.4 networks for the Ad-Hoc On-demand Distance Vector routing protocol (AODV). The evaluation of our proposal has been done by developing a new IEEE 802.15.4 dual-radio module for OMNeT++ Network Simulator. Our simulation results show up to 36 % increase of network throughput when dual-radio schemes are used in the nodes, reaching a maximum of 20 % increase in the energy consumption. DOI: http://dx.doi.org/10.5755/j01.eie.22.3.15321

A New Aggregation Based Scheduling Method for Rapidly Changing IEEE 802.11ac Wireless Channels

In this paper we suggest a novel idea to improve the Throughput of a rapidly changing WiFi channel by exploiting the standard aggregation schemes in IEEE 802.11ac networks. The idea is based on blindly transmitting several copies of the first 4 MAC Protocol Data Units (MPDU) in the Transmission Window. This increases the probability that the window moves forward, enabling the transmission of new MPDUs and resulting in increased Throughput. It turns out that transmitting 2 copies of each of the first 4 MPDUs yields the best Throughput gain, in the order of 50% - 60% in PHY rates of 1.3 - 3.5 Gbps and few hundreds of bytes MPDUs. The proposed idea has advantage over Link Adaptation since it reduces the actual PHY rate only for the transmission of few MPDUs while Link Adaptation reduces the PHY rate for all the transmissions.

AFLAS: An Adaptive Frame Length Aggregation Scheme in Vehicular Networks

Vehicular ad hoc networks (VANETs) experience large-scale high-speed mobility and volatile topology. VANETs may therefore experience intermittent connections and may occasionally be unable to guarantee end-to-end connections. This gives the medium access control (MAC) layer the opportunity to adapt its transmission strategy to the current unstable wireless connections to improve transmission efficiency. In this paper, we propose an adaptive frame length aggregation scheme (AFLAS) for VANETs, which is designed to improve transmission efficiency and increase data throughput. In our scheme, the incoming data packets from higher layers are queued separately in the MAC layer to wait for transmission opportunities. Suitable aggregation frame lengths are calculated according to the current wireless status and applied in the MAC layer at the onset of data transmissions. In this paper, we analyze and apply our AFLAS strategy to two current frame aggregation schemes in IEEE 802.11. We also report on the performance evaluation of our scheme. Our results exhibit significant improvement results in data throughput, retransmissions, overheads, and transmission efficiency in comparison with nonadaptive aggregation schemes.

Special issue on energy‐efficient wireless communication networks with QoS

Special issue on energy‐efficient wireless communication networks with QoS

Compressed SNR-and-channel estimation for beam tracking in 60-GHz WLAN

Signal-to-noise ratio (SNR) and channel estimations are critical for 60-GHz communications to track the optimal transmission and reception beam pairs. However, the excessive pilot overhead for the estimations severely reduces system throughput in fast-rotation scenarios. In order to address this problem, we firstly demonstrate the potential sparseness property of 60-GHz channel in beam tracking; subsequently, via exploiting this property, we propose a novel compressed SNR-and-channel estimation. The estimation is conducted in a three-stage fashion, including the unstructured estimation, nonzero-tap detection, and structured estimation with nonzero- tap location. Numerical simulations show that, in the case of substantial reduction of the pilot overhead, the proposed estimator still reveals a significant improvement in terms of estimation performance over the scheme in IEEE 802.11ad. Furthermore, it is also demonstrated that the proposed SNR and channel estimators can approach the lower bounds in sparse channels so long as SNR exceeds 8 dB.

An enhanced authentication protocol for WRANs in TV white space

Cognitive radio technique has been recognized as an effective solution to the dilemma introduced by the rapid growth of wireless communications and the scarcity of spectrum resources. One example of the cognitive radio systems is the wireless regional area network operating in television white space TVWS spectrum, which has been specified by IEEE 802.22 standard. The wireless regional area networks in TVWS face not only the traditional security threats but also cognitive security challenges. Especially, the authentication between the base station and the customer premises equipment is vital for secure communication. We discovered that the authentication protocol specified in IEEE 802.22 is vulnerable to the interleaving attacks and cannot achieve mutual key confirmation. In this paper, an Enhanced Certificate-based Authentication scheme ECA has been proposed to overcome the vulnerability of the authentication scheme in IEEE 802.22 standard with much less requirements on the computation and communication resources. The drawbacks of the authentication protocol in IEEE 802.22 standard has been explored followed by the presentation of the proposed enhanced authentication protocol, ECA. The ECA protocol has been evaluated in terms of security functionality and the performance. The correctness of the Enhanced Certificate-based Authentication scheme is analyzed by the Burrows, Abadi, and Needham logic. Copyright © 2015 John Wiley & Sons, Ltd.

A routing scheme for IEEE 802.15.4 wireless sensor networks

This paper proposes a routing scheme for IEEE 802.15.4 wireless sensor networks in order to improve the routing performance. This routing scheme is achieved in the link layer, and is made up of the neighbour algorithm and the routing algorithm. The neighbour algorithm is used to achieve the two-hop routing and it is achieved by employing beacon frames. The routing algorithm is based on the neighbour algorithm and is used to achieve the n-hop n ≥ 3 routing. The performance of this scheme is evaluated, and the simulation results show that this routing scheme substantial reduces the routing establishment delay and cost, and also lowers the energy consumption.

A QoS‐aware green cooperative compressed sensing scheme in IEEE 802.22 WRAN

SUMMARYDistributed antennas (DAs) are introduced into IEEE 802.22 wireless regional area network (WRAN) in order to improve consumer premise equipment (CPE) access in high density or large scale network scenario. However, guaranteeing the CPEs' QoS in DA‐WRAN in the process of spectrum sensing is largely ignored. In this paper, we introduce compressed sensing theory into DA‐WRAN and propose a QoS‐Aware Green Cooperative Compressed Sensing scheme, which aims to maximize energy efficiency of DA‐WRAN under its basic QoS constraints of packet drop probability, sensing delay and total throughput. In the proposed scheme, the expression for accuracy of compressed signal recovery under certain sparsity is fitted into exponential function, and the number of compressed samples number is taken into account during the energy efficiency optimization for the first time. To solve the formulated nonlinear multivariate optimal problem, a sub‐optimal algorithm based on particle swarm optimization is presented. At last, the performances of the proposed scheme are simulated and discussed. The simulation results show that the performance on energy efficiency of proposed scheme is better than contrasting algorithms without compromising CPEs' QoS. Copyright © 2014 John Wiley & Sons, Ltd.