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Terahertz (THz) communication is envisioned as one of the key technologies to satisfy the high data rate demand of intelligent 6G networks. However, directional transmissions, as well as the peculiarities of the THz band, pose challenges on medium access control (MAC) design. In this paper, a dual-radio-assisted MAC protocol supporting concurrent transmission is proposed, in which 2.4/5 GHz omnidirectional radio is utilized for control signaling, while THz beamforming is adopted for data transmissions. The request-to-send (RTS-GHz)/test-to-transmit (TTT-THz) handshake is adopted for initial link establishment. Furthermore, the network table is constructed at each node recording receiver-oriented network allocation vector (RNAV) value, angle-of-departure (AoD) of DATA, and angle-of-arrival (AoA) of RTS-GHz. The RNAV record enables concurrent transmission without collision. The record of the first two dominant AoA paths alleviates the LoS blockage problem. The AoD record further decreases the link association delay by replacing RTS-THz with RTS-GHz. Network performances on the protocol are analytically and numerically investigated. Results indicate that the proposed DRA-MAC protocol with AoD memory can achieve 88.2%, 51.6%, and 50% improvement in average link delay, throughput, and LoS blockage alleviation respectively, compared with existing THz MAC protocols.

In this book chapter, a flexible and contention-free point-to-point direct communication (PDC) approach is proposed to achieve direct transmission between SSs within IEEE 802.16 PMP networks. With the considerations of both relative locations and channel conditions among the BS and SSs, a two-tiered admission control scheme is proposed to determine the establishment of direct link between the SSs in the PDC approach. While adapting the PDC approach, the

Device-to-device (D2D) communication is such a paradigm that anticipated to play a cabalistic role for the next-generation cellular networks especially for the 5G cellular network as it promises to extend the network coverage and offload some traffics from the cellular transceiver’s side to the user devices’ side and it may operate in both licensed and unlicensed spectra simultaneously. D2D communication in the unlicensed spectrum may facilitate the purpose of D2D communication as the licensed spectrum almost possessed. Interference is the main drawback of the unlicensed spectrum. In this paper, we propose the request-to-send/clear-to-send (RTS/CTS) mechanism with the free-to-receive (FTR)-MNAV technique to improve the performance of the D2D communication in the unlicensed spectrum. Deployment of the carrier sense multiple access with collision avoidance (CSMA/CA) protocol can alleviate interference, but collisions occur due to the hidden node problem. The integration of the RTS/CTS mechanism with the CSMA/CA protocol can minimize the hidden node problem, but the blocking and false blocking problems are introduced. The proposed scheme can reduce the blocking and false blocking problems, which improves the performance of the D2D communication in the unlicensed spectrum where neighbor nodes maintain Multiple Network Allocation Vector (MNAV) to resolve the blocking problem and broadcast the FTR control packet to the respective neighbor nodes if the transmission is completed prior to the expiration of the timer or actual communication does not take place due to any reason, thus solving the false blocking problem and improving the performance of the D2D communication in the unlicensed spectrum.

Motivated by the shared spectrum paradigm, we address the problem of implicit coordination between coexisting wireless systems that do not share a common control plane. We consider the coexistence of LTE and Wi-Fi and study mechanisms for conserving energy when the wireless channel is occupied. In a Wi-Fi only system, the network allocation vector (NAV) included in the header of IEEE 802.11 frames advertises the duration of an imminent transmission. Nearby Wi-Fi terminals decode the frame header and transition to sleep mode to conserve energy. However, when heterogeneous systems coexist (e.g., LTE and Wi-Fi), frames that belong to other systems are not decodable. This leads to continuous channel sensing even when the channel is to be occupied for a long duration. We design two implicit mechanisms to play the role of the NAV. Our mechanisms predict the duration of an imminent LTE transmission by predicting the frame's traffic class. The prediction is based on the elapsed idle slots between successive transmissions and the transmission history. We show that our methods achieve significant energy savings without stifling transmission opportunities.

Medium access control (MAC) protocol is an important link for achieving networks function in any wireless networks, an efficient and reliable MAC protocol is crucial for an effective underwater acoustic sensor networks (UASNs). Significant differences between UASNs and terrestrial sensor networks (TSNs) render the traditional MAC protocols applied on land inapplicable underwater. Existing MAC protocols for UASNs use the omnidirectional antenna, which wastes energy, restricts the network&rsquo, s coverage range, and brings about unnecessary interferences in neighbor nodes. This paper proposes a dual channel MAC protocol for UASNs based on directional antenna (DADC-MAC), which increases the network coverage range, efficiently utilizes space, and reduces node interference compared to the omnidirectional antenna. The DADC-MAC protocol divides the channel into a data transmission channel and busy prompt message channel, the node uses the former to transmit the control frame and DATA package while the sending node and receiving node use the latter channel to inform the neighbor nodes of on-going communications to prevent DATA package collision. A neighbor discovery mechanism and directional network allocation vector are applied to resolve hidden terminal and deafness problems. Simulation results show that the DADC-MAC protocol could improve network throughput and reduce end-to-end delay, is efficient, performs well, and is well suited to both symmetrical and asymmetrical UASNs topology.

Drone networks are playing a significant role in a wide variety of applications such as the delivery of goods, surveillance, search and rescue missions, etc. The development of the drone to drone (D2D) networks can increase the success of these applications. One way of improving D2D network performance is the monitoring of the channel utilization of the link between drones. There are many works about monitoring channel utility; however, either they sense channel physically, which is not reliable and effective due to noise in the channel and miss-sense of signals, or they have protocol-based solutions with high time-complexity. Hence, we propose a less time and power-consuming MAC layer protocol based monitoring model, which works on the IEEE 802.11 RTS/CTS protocol for D2D communication. We work on this protocol because it solves the hidden terminal problem, which can be seen widely in drone communication due to the characteristics of wireless networks and mobility of drones. Our model consists of Searching & Finding and Functional Sub-layers. In the Searching & Finding Sub-layer, we locate the other drones in the air with a specific flying pattern; we also sense and collect frame information on the channel. With a Functional Sub-layer, we calculate channel utilization with Network Allocation Vector (NAV) vector sizes, showing the duration of the drone about how long it must defer from accessing the link. Also, we create a visualization map with Voronoi Diagram. In that diagram, according to drone coordinates, each region is generated after the k-means clustering algorithm, which is one of the simplest and popular unsupervised machine learning algorithms. Hence, each Voronoi section shows channel utility in terms of percentage in a more precise and discretized way. Furthermore, with our model, we decrease the sensing time of the channel by about 25%, and we reduce the power consumption of sensing drone approximately 26%. Also, our model uses about 57% less area during the calculation phase.

Energy transfer (ET) and energy harvesting (EH) through radio frequency (RF) signals are a promising technology that can reduce the dependency on batteries in wireless sensor networks. However, there is a tradeoff between the RF-based ET and data communication when they operate in the same frequency band. Therefore, a proper medium access control (MAC) protocol is needed in wireless powered sensor networks (WPSNs). However, a utilization degradation problem occurs when the distributed coordination function (DCF) MAC protocol of the IEEE 802.11 is applied to WPSNs. In order to overcome this problem, this paper extends the IEEE 802.11e enhanced DCF (EDCF) into a harvest-then-transmit-based modified EDCF MAC (HE-MAC) protocol. In addition, the HE-MAC’s Markov chain model and steady-state probabilities are derived and used in the performance analysis. Next, based on the steady-state conditions, optimization is conducted to maximize the EH rate, which satisfies the frame generation rate and transfers additional energy to achieve a self-sustained energy consumption profile. Finally, the simulation performance of EH protocols HE-MAC, RF-MAC, and DOS are compared, where the results show that HE-MAC provides in a superior performance for the range of interest.

The IEEE 802.15.4 standard is the most widely used for the realization of Wireless Sensor Networks (WSN) and Internet of Things (IoT) applications. The effects of various disturbances on IEEE 802.15.4 wireless transmissions in the 2.4 GHz band have been studied previously for background noise, multipath fading, wideband and narrowband interference caused by WiFi and Bluetooth networks. The influence of co-channel interference, which originates from collisions between IEEE 802.15.4 devices which perform simultaneous radio transmission, has not been investigated previously. The IEEE 802.15.4 standard uses the Carrier Sense Medium Access with Collision Avoidance (CSMA/CA) channel access mechanism to prevent collisions between devices, but this mechanism does not provide protection from a hidden node problem, which is the primary source of co-channel interference. Hidden node collision in the CSMA/CA channel access mechanism occurs because of the time-spatial relation between nodes located inside the radio range of the recipient device. In our paper, we determined the spatial probability for k -tuple of mutually hidden nodes using the Monte Carlo simulation method. Furthermore, we analyzed the influence of co-channel interference on the error probability of IEEE 802.15.4 communication, and derived accurate analytical models by considering the non-ideal features of the used spreading sequences. The accuracy of the derived mathematical models was tested by numerical Monte Carlo simulation of the IEEE 802.15.4 communication and in a real-world experiment using IEEE 802.15.4 compliant wireless transceivers for creating co-channel interference. The presented simulation and real world experiment results show consistency with the proposed analytical error probability models.

The internet of things (IoT) requires connecting various physical devices, including computing and mechanical devices to the internet. IPv6 over low power wireless personal area networks (6LoWPAN) is the great option for realizing IoT. IEEE 802.15.4 defines the physical and medium access control (MAC) layers of 6LoWPAN. MAC layer of 6LoWPAN plays an important role in the efficient utilization of resources and energy consumption of 6LoWPAN devices. The contribution of this paper is the improvement of resource utilization of 6LoWPAN devices including energy consumption and delay using Lamport’s algorithm in the MAC layer instead of the conventional carrier sense multiple access with collision avoidance approach. The proposed Lamport’s algorithm protocol shows a significant improvement in energy consumption and throughput of 6LoWPAN devices.

High throughput wireless standards based on IEEE 802.11n and IEEE 802.11ac have been developed and released within the last few years as new amendments over the commercially popular IEEE 802.11. IEEE 802.11n and IEEE 802.11ac support a large pool of parameter set such as increased number of spatial streams via multiple input multiple output (MIMO) communications, channel bonding, guard intervals, different modulation and coding schemes, several levels of frame aggregation, block acknowledgement etc. As a consequence, they boost up physical data rate in the order of Gigabits per second. However, all these enhancements have their internal trade-offs with the channel quality, as explored in the existing literature. For example, higher channel bonding levels result in poor performance under high bit error rate. In a free wireless environment, multiple heterogeneous stations share the wireless channel which is again a time-varying system. Consequently, none of these link level parameters provide an optimal performance for all channel quality instances. Therefore, to practically meet the theoretical high throughput, each wireless device should adapt its physical data transmission rate dynamically by an appropriate tuning of different link parameters. Otherwise, high transmission failure may arise. In this paper, we design an adaptive automated on-line learning mechanism, called “Smart Link Adaptation” (SmartLA), for dynamic selection of link parameters, motivated by “State-Action-Reward-State-Action” (SARSA) model, a variant of reinforcement learning. SmartLA can make a wireless station quite intelligent to cope up with various network conditions by exploiting the best suited data rate observed so far for various channel conditions from the past experience as well as by exploring different possible set of parameters. We analyze the performance of SmartLA in both from simulation analysis and over a 26 nodes IEEE 802.11ac testbed (6 access points and 20 client devices). We observe that the proposed link adaptation mechanism performs significantly better compared to other competing mechanisms mentioned in the literature.

IEEE 802.11ad specifies a hybrid medium access control (MAC) protocol consisting of contention as well as noncontention-based channel access mechanisms. Further, it also employs directional antennas to compensate for the high freespace path loss observed in 60GHz frequency band. Therefore, it significantly differs from other IEEE 802.11(b/g/n/ac) MAC protocols and thus requires new methods to analyze its performance. In this paper, we propose a new analytical model for performance analysis of IEEE 802.11ad employing a threedimensional Markov chain considering all the features of IEEE 802.11ad medium access mechanisms including the presence of non-contention access and the different number of sectors due to the use of directional antennas. We show that the number of sectors has a high impact on the network throughput. We also show that the MAC packet delay is significantly affected by the duration of the contention period. Our results indicate that a suitable choice of the number of sectors and contention period can illustriously improve the channel utilization and MAC delay performance.

In a wireless body area network (WBAN), high data reliability and long operating time are important requirements. The retransmission process of the default Automatic Repeat reQuest (ARQ) mechanism in IEEE 802.15.4 is a suitable method to ensure the data reliability of WBAN communications, where frame loss can occur frequently. However, retransmitting the entire DATA frame is energy inefficient due to the fact that the most of payload data within lost frames are only partially corrupted. Therefore, this paper proposes the automatic segment repeat request scheme for the IEEE 802.15.4-based WBANs. The proposed scheme partitions the data payload into segments when the channel condition is bad, and retransmits only the corrupted segment(s). This reduces the size of the retransmitted frames, which improves frame reception rate and decreases the amount of transmitted traffic, and thus energy consumption. Our experiments using a real IEEE 802.15.4-based WBAN test bed show that the proposed method provides higher transmission reliability and lower power consumption than the default IEEE 802.15.4 ARQ mechanism.

In this paper we provide a model for analyzing the saturation throughput of the ieee 802.15.4 mac protocol, which is the de-facto standard for wireless sensor networks, ensuring fair access to the channel. To this end, we introduce the concept of a natural layer, which reflects the time that a sensor node typically has to wait prior to sending a packet. The model is simple and provides new insight how the throughput depends on the protocol parameters and the number of nodes in the network. Validation experiments with simulations demonstrate that the model is highly accurate for a wide range of parameter settings of the mac protocol, and applicable to both large and small networks. As a byproduct, we discuss fundamental differences in the protocol stack and corresponding throughput models of the popular 802.11 standard.

In this paper, a new communication mechanism for IEEE 802.15.4 based Wireless Sensor Networks (WSNs) is designed to reduce the collisions and to prevent simultaneous data transmission by the nodes. Analytical models are designed for the uplink traffic in beacon-enabled slotted CSMA/CA with acknowledgements. In order to avoid the collisions and thereby the number of retransmissions, a new medium access control (MAC) protocol is designed. Beside, the current mechanism of IEEE 802.15.4 CSMA/CA is extended to develop the analytical models by including retransmission limits of the nodes with packet collision probability. Taking uplink traffic of the sensors, a Markov chain model is developed to analyze the energy consumption and throughput of the nodes and to study the impact of various network parameters such as the data rate, packet size and node numbers. The proposed models show that the throughput of the system is reduced and energy consumption is increased due to data retransmissions irrespective of the data rates.

IEEE 1609.4 suite in WAVE is responsible for the multi-channel operation in VANET. This layer supports better QoS but requires synchronization. They follow a fixed duration for control and service channels that may result in inefficient utilization of channels. In this paper, an asynchronous multi-channel MAC scheme allowing simultaneous transmission on different service channels is proposed. The proposed scheme allows those nodes to dynamically access control channel and also allows them to listen and utilize the control channel while not associated with the service channel. The scheme is compared with IEEE 1609.4 in terms of throughput and channel utilization

Frame resolution and physical layer (PHY) protocol type detection are the basis of research and development of intrusion prevention systems for IEEE 802.11 wireless network. Aiming at the problems which cannot be solved by the specifications export, this paper proposed a MAC frame analytical method and a PHY protocol type detection algorithm based on parsing the IEEE 802.11packets captured by the library Libpcap. The packet structure and the length of the frame preamble (18 or 26 bytes) are presented. Then the methods of transforming byte-order and resolving sub-fields are given. A detection algorithm of PHY protocol type is proposed based on the experiments and examples are given to verify these methods. This work can be a reference for the R & D related to link layer frame analysis.

Fairness, low latency, and high throughput with low energy consumption are desired attributes for medium access control (MAC) protocols. The IEEE 802.15.4 standard defines the MAC and physical layers standard for IPv6 over low power personal area network (6LoWPAN). When a non-appropriate parameter setting is used, the default MAC parameters generate excessive collisions, packet losses, and high latency under high traffic when a large number of 6LoWPAN nodes being deployed. A search of the literature revealed few studies that investigate the impact of optimizing these parameters to achieve high throughput with minimum latency. This paper proposes a new intelligent approach to selecting the optimal 6LoWPAN MAC layer parameters set; the introduced mechanism depends on artificial neural networks, genetic algorithm, or particles swarm optimization to select and validate the optimized MAC parameters. The obtained simulation results showed that utilizing the optimal MAC parameters improved 6LoWPAN network throughput by 52-63% and reduced the end-to-end delay by 54-65% in which the enhancement percentage depends on the number of deployed sensor nodes in the network.

Security of any wireless network is always an important issue due to its serious impacts on network performance. Practically, the IEEE 802.11 medium access control can be violated by several native or smart attacks that result in downgrading network performance. In recent years, there are several studies using analytical model to analyze medium access control (MAC) layer misbehavior issue to explore this problem but they have focused on binary exponential backoff only. Moreover, a practical condition such as the freezing backoff issue is not included in the previous models. Hence, this paper presents a novel analytical model of the IEEE 802.11 MAC to thoroughly understand impacts of misbehaving node on network throughput and delay parameters. Particularly, the model can express detailed backoff algorithms so that the evaluation of the network performance under some typical attacks through numerical simulation results would be easy.

This paper proposes a unified medium access control (MAC) design methodology and presents the implementation of the IEEE 802.11ac down-link multi-user multi-input and multi-output wireless local area network MAC using the proposed design methodology. The proposed methodology employs unified code for both network simulation and system implementation. Because the unified code closely relates these two processes, the performance of the implemented MAC system can be estimated before implementation. The MAC architecture for an access point implemented using the proposed design methodology is verified on an ARM-based platform, and it is applied to a 65 nm CMOS library.

Wireless local area networks (WLANs) are widely deployed for internet-centric data applications. It is predicted that by 2018, about two-thirds of the world's internet traffic will be video, and mo...

In this paper, we propose an adaptive medium access control (MAC) solution for a fully connected mobile ad hoc network (MANET), supporting homogeneous best-effort data traffic. The MAC scheme achieves consistently high network performance by adapting to the ever-varying network traffic load. Based on the detection of a current network load condition, nodes can make a switching decision between IEEE 802.11 distributed coordination function (DCF) and dynamic time-division multiple access (D-TDMA), when the network traffic load reaches a threshold, referred to as MAC switching point. The adaptive MAC solution determines the MAC switching point to maximize network performance. Approximate and closed-form performance analytical models for both MAC protocols are established, which facilitate the computation of MAC switching point in a tractable way. Extensive analytical and simulation results demonstrate that the adaptive MAC solution provides consistently maximal network performance in the presence of traffic load dynamics.

The major challenge pertaining to single-hop wireless networks is to design a medium access control (MAC) scheme to efficiently utilize the scarce wireless bandwidth; whereas the most popular solution, IEEE 802.11 distributed coordination function, achieves only limited performance because of the considerable idle time and the high rate of transmission collisions caused by the backoff procedure at high loads. In this paper, we propose a novel contention/reservation MAC scheme, which aims at ensuring low control overheads and collision-free data transmission to maximize system performance. Our scheme provides an efficient control contention resolution algorithm which resolve one or at least one successful reservation in a time frame, thus only a few numbers of control minislots are necessary for a number of active mobile stations contending for reservations. Moreover, with the help of the broadcast messages from the Access Point, all mobile stations determine a nearly-round-robin and collision-free data transmission schedule in a distributed manner, and also implicitly resolves the well-known hidden terminal problem. Extensive simulation results demonstrate that the proposed MAC scheme achieves exceptional system performance under a wide range of traffic loads and various system parameters, and also shown to be robust even when under attack by malicious mobile stations.

Sensors cooperate and coordinate with each other to disseminate sensed data in the network. In establishing coordination among sensors such that they can access the shared wireless medium, Medium Access Control (MAC) protocol plays an important role. In this article, we presented an analytical study on some popular MAC protocols for Wireless Sensor Networks (WSNs). Based on the design techniques, MAC protocols for WSNs are classified into two main categories: single-layer and cross-layer. MAC protocols such as S-MAC, T-MAC, B-MAC and X-MAC are selected to study the design approaches of single-layer genre. BoX-MAC-1 and BoX-MAC-2 are selected to analyze cross-layer design approaches. This survey paper aims at reporting an implementation viewpoint of different design approaches of MAC protocols in WSN. We have considered mixed WSNs that exhibits node movement (e.g., static, mobile) and changes in communication medium (e.g., air, water). Representative protocols are implemented in Castalia simulator and evaluated on the basis of important performance metrics such as energy consumption, network lifetime, throughput and end-to-end delay. The merits and demerits of different protocols are also compared.

According to the amendment 5 of the IEEE 802.11 standard, 802.11n still uses the distributed coordination function (DCF) access method as mandatory function in access points and wireless stations (essentially to assure compatibility with previous 802.11 versions). This article provides an accurate two dimensional Markov chain model to investigate the throughput performance of IEEE 802.11n networks when frame aggregation and block acknowledgements (Block-ACK) schemes are adopted. Our proposed model considered packet loss either from collisions or channel errors. Further, it took anomalous slots and the freezing of backoff counter into account. The contribution of this work was the analysis of the DCF performance under error-prone channels considering both 802.11n MAC schemes and the anomalous slot in the backoff process. To validate the accuracy of our proposed model, we compared its mathematical simulation results with those obtained using the 802.11n DCF in the network simulator (NS-2) and with other analytical models investigating the performance of 802.11n DCF. Simulation results proved the accuracy of our model.

In next generation wireless communication, cognitive radio technology facilitates to utilize underutilized licensed frequency bands that help to enhance the spectrum utilization. Cognitive radio wireless mesh network CRWMN is a promising and reliable technology to experience high throughput with low cost. Existing IEEE 802.11 based medium access control MAC protocols offer high data rates with decreasing efficiency at the MAC layer. Hence, most of the researchers applied aggregation mechanisms to provide the solution to bandwidth craving applications. In CRWMN, MAC design is significant because stability, efficient resource utilization, and scalability are predominating problems; however, the specified MAC issues are not yet resolved. The proposed MAC is novel, which aims to ensure reliability and scalability for CRWMN. The common control channel is used to exchange handshaking frames between the transmitter and receiver. It helps us to schedule the data transmission as well as reserve the channel in a discrete time interval. It introduces a token-based channel accessing mechanism with resource-aware channel assignment, which resolves the problems of efficiency and stability. The proposed MAC simulated using the network simulator ns-2, and the simulation results demonstrate that the proposed protocol improved the performance compared with the existing protocols.

IEEE 802.11-based wireless networks are becoming more popular, and a lot of research is done to enhance the performance of the distributed control function (DCF) found in the IEEE 802.11 standard. Many researchers utilized jamming to further enhance the performance of the contention resolution in DCF. However, jamming-based protocols follow elimination schemes based on the use of jam signals which add to the complexity of wireless devices, add new types of errors like falsely detecting noise as a jam, and are not compatible with the IEEE 802.11 standard. In this paper we propose a self-elimination MAC protocol, called SEMP, for wireless networks to achieve a high performance like that of jamming-based protocols but without the use of jamming signals. SEMP requires no changes to the IEEE 802.11 physical layer, is fully compatible with the IEEE 802.11 wireless devices, and is designed to work without any prior knowledge of the number of nodes. Through extensive simulation, we evaluate SEMP and compare it to the IEEE 802.11 DCF and CONTI (a jamming-based protocol that was shown to highly improve the performance of the IEEE 802.11 wireless networks). Simulation results demonstrate that SEMP outperforms the IEEE 802.11 DCF in terms of the throughput, delay, fairness, and jitter. In addition, results show that SEMP provides throughput and delay gains over CONTI, and that both schemes have comparable fairness and jitter measures. Hence, results reveal that SEMP actually does achieve a high performance like CONTI even though no jamming is used.

IEEE 802.11 MAC is designed for single channel and based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). The throughput of network is limited by the bandwidth of the single channel and the CSMA-based MAC protocol with omnidirectional antennas can cause the serious unfairness or flow starvation. By exploiting the multiple channels and using the directional antennas, nodes located in each other's vicinity may communicate simultaneously. This helps to increase the spatial reuse of the wireless channel and thus increase the network performance. In this paper, we propose a Multi-channel MAC protocol with Directional Antennas (MMAC-DA) that adopts IEEE 802.11 Power Saving Mechanism (PSM) and exploits multiple channel resources and directional antennas. Nodes have to exchange control packets during the Announcement Traffic Indication Message (ATIM) window to select data channels and determine the beam directions which are used to exchange data packets during the data window. The simulation results show that MMAC-DA can improve the network performance in terms of aggregate throughput, packet delivery ratio, energy efficiency and fairness index.

This paper proposes a particle filter framework to perform an online estimation of the unsaturated buffers of the stations in the IEEE 802.11 distributed coordination function (DCF) network. Using this framework, an access point can adapt flow control to its serving stations and configure related parameters dynamically, thus improving the system throughput and reducing the packet latency. Current research analyzing the unsaturated condition in the IEEE 802.11 DCF network is based on the steady-state model, whereas this proposed method is devoted to the dynamic estimation for the probability distribution of the unsaturated buffer in the stations, in either homogeneous or heterogeneous networks. This study also employs theoretical support from Bayesian inference to the particle-filtering algorithm. The estimation accuracy and effectiveness were evaluated via root mean square error (RMSE) and time complexity. Furthermore, we considered different network loads and convergence speeds in our analysis. Our analysis demonstrated that the proposed dynamic estimation scheme has greater awareness of the traffic changes in the varying wireless network when compared with the traditional static traffic model.

IEEE 802.15.4 targets low data rate communication with limited power devices and cheap wireless networking solutions. In recent years both industry and academia are attracted to IEEE 802.15.4 because of its applicability in wireless sensor networks and wireless body area networks. An important feature of IEEE 802.15.4 is its very low duty cycle operation for conserving energy consumption of sensor device. Super-frame structure of IEEE 802.15.4 defines the duty cycle of nodes. The super-frame structure is based on two parameters: beacon order (BO) and super-frame order (SO). The performance of an IEEE 802.15.4 network depends on the values of BO and SO. These values depict the energy consumption, throughput, node discovery and latency of communication. IEEE 802.15.4 uses fixed BO and SO values which can be carefully chosen to meet the network requirements. In this paper, an extensive survey of dynamic super-frame adjustment algorithms is presented. The survey focuses on beacon-enabled star topology of IEEE 802.15.4 and studies the impact of aforementioned algorithms for various applications. Also, the survey categorizes common IEEE 802.15.4 applications based on their requirements for super-frame adjustment. A brief simulation analysis is included in this survey to highlight the impact of BO and SO on the network performance.

Relay technology is one of the key technologies for long-term evolution advanced (LTE-A) project. The introduction of relay will not only bring a wider coverage and higher capacity to the system but also lower the cost of network building. Multihop wireless relay technology plays an important role in next-generation mobile and wireless communication systems. Nowadays, we are witnessing the formation of a new technological marvel: Internet of Things (IoT). This formation is able to combine in a particular operational entity, all the bits and pieces of the world around us. In this paper, we perform queuing modeling of a two-hop wireless relay network and carry out performance analysis of end-to-end packet delay. In the two-hop wireless relay network, two groups of wireless nodes (WNs) and a single relay node (RN) are considered. A Poisson packet arrival process and IEEE 802.11 distributed coordination function are assumed in the network for the network traffic model and for regulating the nodes’ access to the shared channel, respectively. We model a node as a single-server queuing system, whose service time of a packet is unknown and dependent on the probabilistic parameters of IEEE 802.11 DCF medium access control (MAC). A system of equations is then obtained for numerically computing the probabilistic parameters of IEEE 802.11 DCF MAC through discretization of the continuous-time network operations, based on which we construct semi-Markov processes and derive an analytic result for the expectation of the end-to-end packet delay. As a key performance indicator in evaluation of wireless networks, the packet delay result helps measure the efficiency of IEEE 802.11 MAC in two-hop wireless relay networks.

Wireless Sensor Networks (WSNs) are more popular due to the use of low cost sensors with their interfaces. In designing of WSNs, energy conservation is a main issue. The nodes available in WSNs use battery as limited energy source. Various techniques have been proposed to improve the energy efficiency in WSNs. Energy efficient Medium Access Control (MAC) protocol is required for obtaining higher energy efficiency during difficult operating conditions, where node failure and link failures are common. Cross layer approach between data link and network layer is adapted in the proposed work. In the proposed work, the MAC protocols such as Correlation based Collaborative MAC (CC-MAC), CC-MAC combined with Hybrid MAC, Hybrid MAC, Hybrid MAC combined with sensor MAC have been considered for analysis. Two popular routing protocols such as Ad hoc On-demand Distance Vector, Ad hoc On-demand Multipath Distance Vector are also considered to identify the routing performance of the network. The Parameters such as end-to-end delay, packet drop, packet delivery ratio, throughput, energy efficiency are considered to measure the network performance. These parameters are acting as a primary and secondary attributes to design an efficient MAC protocols for WSNs.

In wireless local area network, all transmissions are preceded by clear channel assessment (CCA), which determines the availability of wireless medium. Ideally, CCA should enable concurrent transmissions, whenever possible, to improve network capacity via spatial reuse. However, current CCA method is inherently limited in exploiting spatial reuse. Only the received signal strength of an incoming frame is utilized for CCA, and hence, the feasibility of a concurrent transmission should be determined without the knowledge of the frame’s transmitter, the corresponding receiver, etc. In this letter, we propose a novel CCA method which utilizes additional information delivered in the physical layer header to properly determine the feasibility of concurrent transmissions. Simulation results show that the proposed method increases network throughput by up to 54% by promoting spatial reuse.

As one of the most widely used wireless network technologies, IEEE 802.11 wireless local area networks (WLANs) have found a dramatically increasing number of applications in soft real-time networked control systems (NCSs). To fulfill the real-time requirements in such NCSs, most of the bandwidth of the wireless networks need to be allocated to high-priority data for periodic measurements and control with deadline requirements. However, existing QoS-enabled 802.11 medium access control (MAC) protocols do not consider the deadline requirements explicitly, leading to unpredictable deadline performance of NCS networks. Consequentially, the soft real-time requirements of the periodic traffic may not be satisfied, particularly under congested network conditions. This paper makes two main contributions to address this problem in wireless NCSs. Firstly, a deadline-constrained MAC protocol with QoS differentiation is presented for IEEE 802.11 soft real-time NCSs. It handles periodic traffic by developing two specific mechanisms: a contention-sensitive backoff mechanism, and an intra-traffic-class QoS differentiation mechanism. Secondly, a theoretical model is established to describe the deadline-constrained MAC protocol and evaluate its performance of throughput, delay and packet-loss ratio in wireless NCSs. Numerical studies are conducted to validate the accuracy of the theoretical model and to demonstrate the effectiveness of the new MAC protocol.

This paper proposes an opportunistic approach to mitigating the hidden and exposed node problem in a high-throughput mesh network, by exploiting the frame aggregation and block acknowledgment (BACK) capabilities of IEEE 802.11n/ac wireless networking standard. Hidden nodes significantly drop down the throughput of a wireless mesh network by increasing data loss due to collision, whereas exposed nodes cause under-utilization of the achievable network capacity. The problem becomes worse in IEEE 802.11n/ac supported high-throughput mesh networks, due to the large physical layer frame size and prolonged channel reservation from frame aggregation. The proposed approach uses the standard carrier sense multiple access (CSMA) technology along with an opportunistic collision avoidance (OCA) method that blocks the communication for hidden nodes and opportunistically allows exposed nodes to communicate with the peers. The performance of the proposed CSMA/OCA mechanism for high throughput mesh networks is studied using the results from an IEEE 802.11n+s wireless mesh networking testbed, and the scalability of the scheme has been analyzed using simulation results.

Energy efficiency has become a regular hot topic in the research on wireless communications networks. However, existing proposals leave room for improvement when multi-hop wireless broadband networks are used to provide on-demand connectivity under low traffic load conditions. For this kind of networks, the capability of bringing the network up and down on demand wirelessly would help significantly to design energy-efficient, compact and low-cost network nodes. This paper presents a new approach for multi-hop energy-efficient networks based on a dual network architecture called dualWireless. Each node belongs to two parallel wireless multi-hop networks, an on-demand IEEE 802.11n network for data communications and a permanent IEEE 802.15-4 network for control purposes. The paper explains the proposal, the development of prototypes and the empirical validation with a testbed. In addition, a power consumption analytical model is used to measure the energy savings achieved by dualWireless and for comparison with other authors proposals. The dualWireless approach is shown to be more energy efficient than other alternatives as long as the occupation time of the network is under 40%, which is the case for many particular applications.

In this paper, we propose a technique for making IEEE 802.15.4 standard suitable for low-latency deterministic networks for wireless control applications where the cyclic update time of sensor’s information is not more than 10 ms. The IEEE 802.15.4 has shown good characteristics for deterministic networks in beacon-enabled mode, but with minimum cyclic update time for personal area network devices not less than 15.36 ms. Moreover, it is unsuitable for hard real-time systems when used in nonbeacon-enabled mode due to the random nature of channel access protocol. The proposed technique employs time-division multiple access (TDMA)-based protocol that works on slightly modified IEEE 802.15.4 in star topology. Each end device in the network transmits its data frame after certain time delay in response to periodic requests from the coordinator. This time delay is optimized for better channel bandwidth utilization and reliable data exchange. While this TDMA-based protocol eliminates the risk of frame collisions to a great extent, medium-access control sublayer modifications reduce the nondeterminism of the network and increase the bandwidth efficiency. A mathematical model is proposed to design and develop a practical communication network with commercial off-the-shelf radios that can predict worst case arrival time of data frames. Experiments were conducted to evaluate the model for the proposed protocol.

The flexible use of sensors has made them an attractive device to be deployed in almost every field of life such as health, military and home. Recent advancement in electronics and wireless communications has witnessed the development of low cost-sensor devices. While wireless sensor networks (WSNs) are flexible to use and less costly, they need to be more energy-efficient as they are operated by the battery. Mostly they are deployed in harsh environments where it is very difficult to change the batteries frequently. Several medium access control (MAC) algorithms have been developed for the energy-efficient acquisition of the wireless channel, however, none of them are satisfactory. In this paper, we proposed a medium access control algorithm called MAC-PE. MAC-PE is based on the concept of prioritized frames where prioritized frames are transmitted urgently. In addition, it uses scheduled-based MAC instead of accessing channel randomly. We found MAC-PE (Power-Efficient MAC) was efficient in terms of power consumption without sacrificing on the performance using NS-2.

In this paper, we investigate the throughput capacity of physical-layer network coding (PNC) in a non-all-inclusive carrier-sensing network with IEEE 802.11 distributed coordination function (DCF). In particular, we consider the many-to/from-one bidirectional networks in which a common center node exchanges packets with many other nodes through multihop transmissions. We first analyze the canonical networks with equal-link-length (ELL) and variable-link-length (VLL), respectively, and derive the corresponding analytical network capacity. Simulations show that the throughput capacities are reasonably tight. We further maximize the network capacity by properly selecting the signal-to-interference-plus-noise ratio (SINR) threshold/transmission rate through numerical calculation. Last but not least, we identify the optimal number of hops that has the maximum network throughput. In particular, the four-hop canonical networks have the maximum network throughput, which indicates that in a many-to/from-one network with five or more hops, it is preferable to transmit the packets across the four-hop nodes to make full use of the PNC scheme. Simulation results show that the throughput gain of PNC scheme with and without considering the synchronization cost can, respectively, reach upto 291.7% and 340.6%, compared with the traditional IEEE 802.11 multihop networks without network coding.

The wireless sensor network (WSN) has a wide range of uses. It can be used, for example, as a powerful tool for gathering several kinds of environmental information. This type of monitoring fits in the concept of Internet of Things (IoT), which aims to optimize the real world processes by monitoring their variables. In this study, a WSN developed in the IEEE 802.15.4 standard was used with the objective of measuring the local temperature. The access to the data was available through a WLAN network in the IEEE 802.11 standard (also known as Wi-Fi), an already existing network or a solution's dedicated network were used. Quality tests of signal and maximum range of communication of the WSN were made, as well as the network's battery lifetime usage estimates. Finally, the study also shows the monitoring of the temperature of some environments.

In this paper, we study two schemes for the fair resource allocation in wireless powered communication networks (WPCNs): a non-orthogonal multiple access (NOMA) scheme, and a proportional fair (PF) scheduling scheme. The considered WPCN consists of a base station (BS) that broadcast radio frequency (RF) energy over the downlink, and N energy harvesting users (EHUs). If NOMA is employed, all EHUs concurrently transmit information over the uplink with successive interference cancellation employed at the BS. If PF scheduling is employed, a single EHU is selected for uplink transmission in each frame. For both schemes, we arrive at optimal allocations for the BS transmit power and the time sharing between uplink and downlink transmissions that maximize the uplink sum-rate, while maintaining high level of system fairness. For the PF scheme, we also derive the optimal scheduling policy. Compared to the state-of-the art schemes based upon time division multiple access (TDMA), both schemes significantly improve the system fairness at the expense of minor (or nonexistent) rate degradation. Key words: energy harvesting; wireless powered communication networks; non-orthogonal multiple access; successive interference cancelation; proportional fair scheduling REFERENCES: [1] P. Grover, A. Sahai: Shannon meets Tesla: wireless information and power transfer, Proc. IEEE ISIT 2010, pp. 2363–2367, Austin, USA, June 2010. [2] D. Gunduz, K. Stamatiou, N. Michelusi, M. Zorzi: Designing intelligent energy harvesting communication systems, IEEE Commun. Magazine, 52, 1, 210–216 (Jan.2014). [3] C. K. Ho, R. Zhang: Optimal energy allocation for wireless communications with energy harvesting constraints, IEEE Trans. Signal Proccessing, 60, 9, 4808–4818 (May 2012). [4] H. Ju, R. Zhang: Throughput maximization in wireless powered communication networks, IEEE Trans. Wireless Commun., 13, 1, 418–428 (Jan. 2014). [5] X. Kang, C. Ho Keong, S. Sun: Optimal time allocation for dynamic-TDMA-based wireless powered communication networks, Proc. IEEE Globecom 2014, Austin, USA, Dec. 2014. [6] H. Ju, R. Zhang: Optimal resource allocation in full-duplex wireless-powered communication network, IEEE Trans. on Commun., 62, 10, 3528–3540 (Oct. 2014). [7] T. Takeda, K. Higuchi: Enhanced user fairness using non-orthogonal access with SIC in cellular uplink, VTC 2011, San Francisco, USA, pp. 1–5, 2011. [8] Z. Ding, Z. Yang, P. Fan, H. V. Poor: On the performance of non-orthogonal multiple access in 5G systems with randomly deployed users, IEEE Signal Process. Lett., 21, 12, 1501–1505 (2014). [9] S. Timotheou, I. Krikidis: Fairness for non-orthogonal multiple access in 5G systems, IEEE Signal Process. Lett., 22, 10, 1462–1465 (2015). [10] H. Chingoska, Z. Hadzi-Velkov, I. Nikoloska, N. Zlatanov: Resource Allocation in Wireless Powered Communication Networks with Non-Orthogonal Multiple Access, IEEE Wireless Communications Letters, 5 (6), 684–687 (2016). [11] P. Viswanath, D. N. Tse, R. Laroia: Opportunistic beamforming using dumb antennas, IEEE Trans. Information Theory, 46, 6, 1277–1294 (June 2002). [12] N. Tekbiyik, T. Girici, E. Uysal-Biyikoglu, K. Leblebicioglu: Proportional fair resource allocation on an energy harvesting downlink, IEEE Trans. Wireless Communications, 12, 4, 1699–1711 (April 2013). [13] H. Chingoska, I. Nikoloska, Z. Hadzi-Velkov, N. Zlatanov: Proportional fair scheduling in wireless powered communication networks, 23rd International Conference on Telecommunications (ICT), May 2013. [14] Z. Hadzi-Velkov, I. Nikoloska, H. Chingoska, N. Zlatanov, Proportional fair scheduling in wireless networks with RF energy harvesting and processing cost, IEEE Comm. Letters, 20, 10, 2107–2110 (2016). [15] T.-D. Nguyen, Y. Han: A Proportional Fairness Algorithm with QoS Provision in Downlink OFDMA Systems, IEEE Comm. Letters, 10, 11 (Nov. 2006). [16] Z. Hadzi-Velkov, I. Nikoloska, G. K. Karagiannidis, T. Q. Duong: Wireless networks with energy harvesting and power transfer: joint power and time allocation, IEEE Signal Process. Letters, 23, 1, 50–54 (Jan. 2016). [17] R. Jain, D. Chiu, W. Hawe: A Quantitative measure of fairness and discrimination for resource allocation in shared computer systems, Tech. Rep. TR-301, DEC, September 1984. [18] W. Yu, R. Lui: Dual methods for nonconvex spectrum optimization of multicarrier systems, IEEE Trans. Commun., 54, 7, 1310–1322 (Jul. 2006). [19] L. Liu, R. Zhang, K.-C. Chua: Wireless information transfer with opportunistic energy harvesting, IEEE Trans. Wireless. Commun., 12, 1, 288–300 (Jan. 2013).

Summary Wireless body sensor networks are offered to meet the requirements of a diverse set of applications such as health-related and well-being applications. For instance, they are deployed to measure, fetch and collect human body vital signs. Such information could be further used for diagnosis and monitoring of medical conditions. IEEE 802.15.4 is arguably considered as a well-designed standard protocol to address the need for low-rate, low-power and low-cost wireless body sensor networks. Apart from the vast deployment of this technology, there are still some challenges and issues related to the performance of the medium access control (MAC) protocol of this standard that are required to be addressed. This paper comprises two main parts. In the first part, the survey has provided a thorough assessment of IEEE 802.15.4 MAC protocol performance where its functionality is evaluated considering a range of effective system parameters, that is, some of the MAC and application parameters and the impact of mutual interference. The second part of this paper is about conducting a simulation study to determine the influence of varying values of the system parameters on IEEE 802.15.4 performance gains. More specifically, we explore the dependability level of IEEE 802.5.4 performance gains on a candidate set of system parameters. Finally, this paper highlights the tangible needs to conduct more investigations on particular aspect(s) of IEEE 802.15.4 MAC protocol. Copyright © 2015 John Wiley & Sons, Ltd.

IEEE 802.11n defines a significant two-level frame aggregation scheme aimed at improving the transmission efficiency of MAC layer. However, the performance of the two-level frame aggregation scheme does not meet the user expectation due to the inevitable aggregation and retransmission overheads. To overcome this problem, an enhanced two-level frame aggregation with the optimized aggregation level is proposed in this letter for IEEE 802.11n wireless local area networks (WLANs). In the proposed scheme, in order to maximize the throughput of the two-level frame aggregation, the aggregation level (i.e., sub-MPDUs, the number of the aggregated sub-MAC protocol data units) used for the two-level frame aggregation is optimized and adjusted dynamically according to the subframe size, the maximum aggregation level (MAL) allowed by the current two-level frame aggregation and the real-time channel bit-error-rate (BER). Results from the simulation show the superiority of the proposed enhanced two-level aggregation in respect of throughput performance.