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To design an energy-efficient Medium Access Control (MAC) protocol for the Underwater Wireless Sensor Networks (UWSNs) is an urgent research issue since depleted batteries cannot be recharged or replaced in the underwater environment. Moreover, the underwater acoustic channels are affected by hindrances such as long propagation delay and limited bandwidth, which appear in the design of the MAC protocol for the UWSNs. The available MAC protocols for the terrestrial wireless sensor networks exhibit low performance in energy efficiency, throughput and reliability in the UWSNs, and cannot be used in the UWSNs directly because of their unique characteristics. This paper proposes a synchronous duty-cycled reservation-based MAC protocol named Ordered Contention MAC (OCMAC) protocol. The basic mechanism of this protocol is to schedule data transmission by transmitters through the scheduling of Ready To Send (RTS) frames. The protocol eliminates the possible collision during data transmission and improves communication efficiency. The paper analyzes the performance in energy efficiency, throughput and reliability of the protocol by modeling the queuing behavior of OCMAC with a Markov Chain process. Furthermore, the analytical model is validated through a simulation study. The analysis results demonstrated that while providing good throughput and reliability, OCMAC can achieve energy saving.

Underwater communication (UWC) growing over the past few decades is the major tool for exploring the vast underwater space. Research and development of UWC networks are dominantly acoustic (Ac) wave based due to its long coverage capability. However, the demand of low latency and high throughput applications, and the emergence of short-range UWCs in modern times has drawn attention towards the development of electromagnetic (EM) wave based underwater sensor networks (UWSNs). In light of this, this paper proposes novel medium access control (MAC) protocols by integrating EM-based communications in UWSNs. Proposed protocols use one TDMA-based control channel and one or multiple data channel(s) for control and data packet transmissions respectively. The control channel uses EM wave, while the data channels use either EM or Ac wave for communications. Proposed MAC protocols are developed considering both protocol interference model and physical interference model by taking both propagation delay and underwater channel impairments into account. Performance of the protocols is evaluated through extensive simulations in terms of throughput, packet collision rate, waiting time, energy requirement and network coverage. Impact of system parameters including offered load, network size, data packet size, control packet power, water conductivity and channel bandwidth are analyzed thoroughly. A comprehensive feasibility study by comparing the proposed MAC protocols with the traditional protocols as well as with the full Ac-wave based counterpart is also presented for further validations.

This paper presents the design and analysis of directional random access MAC protocols for cognitive radio wireless mesh network (CRWMN). We have proposed three directional random access MAC protocols for CRWMNs using three different access mechanisms called Directional CSMA/CA MAC protocols for Cognitive Radio (DCR-MAC). An event driven simulator is used to make performance comparison for the three MAC protocols. Moreover, the performances of the DCR-MAC protocol for the three access mechanisms are also compared with an omni-directional CRMAC protocol in terms of average throughput and average packet delay. The performances of the proposed directional protocols show better performance for CRWMN.

IEEE 802.15.7 Visible Light Communication (VLC) networks suffer from performance degradation caused by the hidden device collisions due to the directional transmission with narrow beamwidth. One of the solutions for mitigating the hidden device collisions is to employ a full-duplex transmission technique. As a side effect of the full-duplex transmission in the VLC networks, however, the data-packet discard due to the retransmission limitation occurs frequently in the networks. This paper proposes an improved backoff scheme and its performance analysis to suppress the packet discard. The proposed backoff scheme increases the Backoff Exponent (BE) and the Number of Backoff stage (NB) in IEEE 802.15.7 only when the data packet transmission fails. To evaluate the system performance theoretically, this paper also provides the Markov-chain model for channel access with the proposed scheme. The performance evaluations through simulation and theoretical analysis show the effectiveness of the proposed scheme.

Multiuser access is a critical issue in distributed cognitive radio networks (DCRNs), as the collisions among the competing secondary users (SUs) may decrease the network throughput significantly. In order to reduce the collisions, we propose a dynamic backoff algorithm to find an optimal backoff contention window to maximize the network throughput and reduce the channel access delay. Based on the proposed algorithm, a multichannel medium access control (MAC) protocol with dynamic backoff contention (MMAC-DB) is designed. In this protocol, the time duration of each channel is divided into four phases: idle, sensing-sharing, contention, and data transmission. The dynamic backoff algorithm is implemented in the contention phase. Moreover, a duration tradeoff is made between the data transmission phase and the contention phase. The effectiveness of the proposed protocol is examined by extensive simulations, which shows that the proposed protocol can enhance the throughput and reduce the channel access delay.

We consider an hoc network where nodes are assumed to be distributed uniformly in space, according to a 2-D Poisson point process (PPP), and packets arrive at each transmitter according to a 1-D temporal PPP. The system bandwidth is divided into multiple subbands, and each transmitter selects one subband to transmit over. The channel access is governed by ALOHA or carrier sensing multiple access (CSMA) MAC protocols, in their various incarnations. The main system objective is correct reception of packets, and thus the analysis is performed in terms of outage probability, which is defined as the probability that the transmission rate required for correct reception of a packet exceeds the channel capacity, and in terms of throughput, that is the amount of information correctly received at the receivers. The performance of these protocols is derived both in the absence and presence of fading, and used to compare the different MAC protocols. The optimal number of subbands maximizing the throughput is obtained analytically for ALOHA and through simulations for CSMA, illustrating how the ’right’ number of subbands can improve the performance, compared to a random number of subbands. Furthermore, in the case of CSMA, sensing across all subbands is introduced and shown to provide additional performance gain.

In order to solve the problem of redundant time slot allocation for single node sectors, too large overhead and excessively long time spent for beamforming training under mobile scenarios in existing directional MAC protocols, this paper proposes high slot utilization rate and fast directional MAC protocol(HUFD-MAC) for Terahertz wireless personal area networks. The HUFD-MAC protocol uses redundant single node sectors to transmit downlink data and reduces the number of transmitted beam training frames based on time information. This effectively improves the utilization of time slots, reduces network overhead, and decreases the time required for beamforming. The simulation results show that compared with the IEEE 802.15.3c and ACAP-MAC protocols, the network overhead of HUFD-MAC is reduced by about 3.23%, and the MAC layer throughput is increased by about 8.50%.

In underwater wireless sensor networks (UWSNs), media access control (MAC) is important because it may have a significant impact on network performance; however, the complex and changeable underwater communication environment is a great challenge for the MAC protocol. In flowing water, the network nodes are constantly moving, and the number of competitors in the network also varies. The existing hybrid MAC protocol neither can adapt to the dynamic network load nor can switch the access control protocols with changing network loads, which may result in poor network performance. In order to solve the above problems, this paper proposes a load-based time slot allocation (LBTSA) protocol. The LBTSA selects the slot allocation scheme, from a set of possible schemes, according to the instantaneous network load. Then, based on the relative priority of the nodes and the optimal number of backoff stages, the host node selects the optimal access control protocol. This not only adapts well to changing network loads but also maximizes network throughput. By assuming that the number of competitors obeys a universal Poisson distribution, the LBSTA protocol and the HCR (a hybrid MAC protocol using channel reservation) protocol are compared. As the results show, the throughput of the LBTSA is higher than that of the HCR protocol, and the end-to-end delay of the LBTSA is lower than that of the HCR protocol.

Packet collisions caused by the standard Distributed Coordination Function (DCF) protocol in wireless local area networks (WLANs) have been a challenging problem leading to congestion and reduced throughput. To solve this problem, we propose a novel backoff state generation algorithm, called adaptive virtual backoff algorithm (AVBA), operating in an access point. The virtual contention window size in the algorithm is automatically adjusted based on the number of synchronized active nodes in a cell. Backoff counts generated by AVBA operating in the access point are sent by the access point to each active node in the cell to try to synchronize transmissions and minimize packet collisions. The evaluation results show that the AVBA improves the throughput performance compared to the existing collision resolution techniques, such as the deterministic backoff and centralized random backoff (CRB), when the number of active nodes is large. Moreover, the results show that it maintains a high level of fairness in terms of channel access opportunities between nodes using AVBA and nodes using the DCF protocol when they coexist in a mixed wireless network scenario.

Network lifetime maximization is the primary challenge in the wireless sensor network (WSN) due to its resource limitations. E2R2 routing algorithm uses a hierarchical WSN model to minimize energy consumption in the WSN. However, it increases complexity, time consumption, and energy consumption due to the hierarchical model. To resolve these problems, this paper proposes a novel ring partitioned based MAC (RP-MAC) protocol for the energy-efficient WSN with a mobile sink node. Energy efficiency is achieved by the following phases: clustering phase, MAC scheduling phase, data aggregation phase, and routing phase. Clustering phase is initiated by a weighted Voronoi diagram (WVD) algorithm by assigning a weight value for each node. Energy consumption due to idle listening is minimized by enabling novel RP-MAC scheduling in each cluster. Involvement of RP-MAC protocol also achieves collision-free data transmission in the network. A two-fold data aggregation (TFDA) scheme is proposed for the data aggregation phase to minimize energy consumption by reducing the number of transmissions. Routing phase supports both intra-cluster routing and inter-cluster routing. For intra-cluster routing, a hybrid chicken swarm optimization algorithm is proposed. For inter-cluster routing, position-based routing tree is constructed based on the sink node’s position. Our proposed RP-MAC protocol minimizes energy consumption in all possible ways for improving the network lifetime. Extensive simulation in ns-3 shows that the RP-MAC protocol achieves promising results in the following performance metrics: the number of dead nodes, average energy consumption, network lifetime, and throughput.

Merging mobile edge computing (MEC) service with the wireless local area networks (WLANs) provides enormous benefits such as intensive computation capabilities. Access to high-speed WLANs has become an urgent challenge due to the fast rate of application development and user adoption. Providing increased wireless resources is one solution, but millimeter (mmWave) multi-user massive Multiple-Input Multiple-Output (MIMO) technology has also attracted attention due to a series of features such as high throughput, strong anti-interference ability, and small fading. Hence, exploring the potential of mmWave MIMO systems for WLAN could play a significant role in improving network performance, especially throughput. In this paper, we introduce mmWave and massive MIMO into traditional WLAN with MEC, which enables a large portion of spatial resources to be allocated among users, and mitigates inter-user interference. Moreover, we propose a novel media access control (MAC) protocol, named as LSMWN-MAC, to adapt to a series of unique characteristics of mmWave and massive MIMO, which adopts space division multiple access (SDMA) as one of the resource methods, taking full advantage of spatial resources. In addition, we modify the protocol and propose the MLSMWN-MAC protocol to allocate resources dynamically, a solution that is particularly suitable for scenes with 30-50 users. Simulation results show that compared to 802.11ad, the proposed two protocols can increase the saturated throughput by 4.7Gb/s and 5.4Gb/s respectively, which are close to the throughput upper limit of the mmWave MIMO system. Meanwhile, we observe that when the number of users exceeds the threshold, the performance of the LSMWN-MAC protocol using a static allocation method is superior to the MLSMWN-MAC protocol using a dynamic method. In other cases, the dynamic protocol has better performances.

Vehicular Ad-hoc Networks (VANETs) can improve the road safety by transmitting safety-critical messages such as beacons and emergency messages. IEEE 802.11p VANETs have adopted the carrier sense multiple access with collision avoidance (CSMA/CA) mechanism for the multiple access control. The 802.11p media access control (MAC) protocol, however, can not guarantee the reliability of broadcasting data, since the reception of transmitted messages are not acknowledged. Moreover, the backoff scheme of the 802.11p MAC utilizes a fixed-size contention window for safety message broadcasting, which causes high collision probabilities especially in dense environments. In order to improve such drawbacks, we propose a hybrid access method as follows: Nodes are equipped to reserve time slots for the next round of broadcasting, while unoccupied time slots are preserved for those which have emergency needs. In addition, implicit feedbacks are enabled for detecting collisions incurred during random channel accesses in preserved time slots. We devise a mathematical model which optimally controls the parameters of our scheme while minimizes the cost caused by idle channels and collisions. Extensive simulations show that our mechanism can remarkably improve the performance of VANETs in broadcasting of the safety messages.

In wireless local area networks (WLANs), the effect of interference signals between neighboring nodes increases as the number of wireless nodes using limited radio frequency resources in a limited space increases, which can significantly degrade the reliability of data transmission. In high-density WLANs, there can be several neighboring access points (APs) that can receive uplink transmission from a station. In conventional medium access control (MAC) protocols, uplink data frames containing errors or transmitted from a non-associated station are discarded at APs. Alternatively, we propose a MAC protocol using redundant wireless links between neighboring APs and the non-associated stations. In the proposed MAC protocol, we consider a centralized WLAN with a control node that performs error corrections of erroneous uplink data frames via a majority voting algorithm-based link-layer diversity scheme using uplink data received from multiple APs to increase the reliability of data transmission. In addition, we propose an adaptive carrier sensing ranging mechanism to improve the uplink network throughput in the proposed centralized WLAN system. Further, we conduct simulation studies and software-defined radio-based experiments to evaluate the performance of the proposed MAC protocol in various WLAN scenarios.

Medium access control (MAC) protocol operations for in-band full duplex multi-hop networks play an important role in efficient data relaying and throughput enhancement. Knowledge of the relationship between essential operations in MAC protocol for full duplex MAC (FD MAC) networks and network performance is important and useful in terms of the protocol and network design. FD MAC protocols often require exchanging control frames, e.g., request to send/clear to send (RTS/CTS). However, the conventional model cannot analyze the performance of wireless multi-hop networks with RTS/CTS-based FD MAC. Thus, this paper proposes a throughput analysis model for wireless multi-hop networks with RTS/CTS-based FD MAC. The proposed model includes novel “airtime expressions”, which allows us to handle RTS/CTS operations under FD MAC. The proposed model provides the end-to-end throughput of multi-hop networks with RTS/CTS-based FD MAC for any number of hops and any payload size. The validity of the analytical expressions is confirmed through comparisons with simulation results.

Networking protocols are used by each networking host (e.g., end device) to communicate with one another. These hosts Before can exchange data bit with the central node (e.g., Base Station (BS) or Access Point (AP)), should first negotiate the communication protocol, conditions and parameters for that transmission which is supported at the protocol stack. Estimating these parameters in an intelligent way is much needed desired. Could machine learning estimate the parameters on their own without human in the loop? In this paper, we investigate the medium access control protocol in cellular networks. We demonstrate that reinforcement learning.

Wireless sensor networks employ duty-cycles to save energy, with the cost of enlargement of end-to-end latency. Cross-layer protocols that use anycast medium access control achieve latency reduction in asynchronous duty-cycled wireless sensor networks (WSNs). A series of strobed preambles is sent in order to achieve rendezvous with the next relay, selected from a forwarding candidate set (FCS). This paper proposes PAX-MAC: Pramble Ahead Cross-layer Medium Access Control. It is a novel anycast protocol for low latency packet propagation in duty-cycled WSNs. In PAX-MAC, preambles propagate ahead of data packet, prospecting the route towards sink node, while the message is sent some hops later. Simultaneous propagation of preambles and data packets provides latency reduction. The cardinality of FCS determines the average preamble propagation speed, which is lower bounded by data packet propagation speed. Differently from other approaches, our protocol takes the data packet size into account in order to maintain an optimal distance between preamble and data to minimize latency. For determining this distance, a detailed mathematical model is introduced. The performance of several state-of-the-art asynchronous protocols was appraised and compared with PAX-MAC. Our protocol outperforms in latency all other protocols for the simulated scenarios. Its energy expenditure was compatible with the best result among the other protocols. In the worst case, PAX-MAC spent 6 % more energy than the best one for a gain of 20 % in latency.

Wireless communication has become a core part of modern communication technology. The Infrastructure less wireless network, commonly referred to as Ad Hoc networks, has attracted extensive research interest for past 30 years. In this work, the focus is on IEEE 802.11 network performance analysis of Multihop hop Ad Hoc networks under non saturated network conditions. To meet the increasing demand of multimedia, it is necessary to provide the quality of service in such networks. The current work presents the development of an analytical model for network performance analysis. The medium access mechanism in multihop wireless networks should minimize collisions, and take care of the hidden and exposed node problems. The IEEE 802.11 MAC with Distributed Coordination Function DCF does not scale well in such networks. We introduce Point Coordination Function PCF in the region of high traffic areas, and discuss its effect on network performance. To improve network scalability and throughput, we propose the design of a new MAC called Dual MAC. This work discusses architecture and working of the dual MAC in detail. Performance results of the network using dual MAC are presented, and compared with that of pure DCF operation. Prince Kumar | Rashmi Raj "Design and Evaluation of MAC Protocol Strategies Techniques in Wireless Ad Hoc Network" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-6 , October 2018, URL: https://www.ijtsrd.com/papers/ijtsrd18446.pdf

This study aims to solve time-space uncertainties due to the narrow network channel bandwidth and long transmission delay of an underwater acoustic sensor network when a node is using a channel. This study proposes a MAC protocol (BSPMDP-MAC) for an underwater acoustic sensor network based on the belief state space. This protocol can averagely divide the time axis of a sensor’s receiving nodes into n slots. The action state information of a sensor’s transmission node was divided by the grades of link quality and the residual energy of each node. The receiving nodes would obtain the decision strategy sequence of the usage rights of the competitive channels of the sensor’s transmission nodes according to the joint probability distributions of historical observations and action information of channel occupancy. The transmission nodes will transmit data packets to the receiving nodes in turns in allocated slots, according to the decision strategy sequence, and the receiving nodes will predict the channel occupancy and perceive the belief states and access actions in the next cycle, according to the present belief states and actions. These experimental simulation results show that this protocol can reduce the collision rate of data packets, improve the network throughput and transmission success rate of data packets, and reduce the energy overhead of the network.

The mixture of full-duplex (FD) and half-duplex (HD) wireless networks and its solutions have been studied to improve the medium access control (MAC) performance. Especially, the header snooping is one of the most effective solutions to achieve the high throughput. Besides, one of the solutions that can significantly enhance the throughput is network coding. The effectiveness of network coding has been extensively studied in many research. Accordingly, the paper aims to propose a new MAC scheme for the mixture of HD and FD wireless network using network coding. This paper investigates the node combination from a network topology and evaluates the performance of the proposed MAC scheme in terms of saturation throughput and the effectiveness of network topology.

Recent advances in self-interference cancellation techniques have enabled in-band full-duplex (IBFD) transmission, which can double ergodic capacity and reduce end-to-end delay. However, how to solve the channel contention problem in IBFD radios with inter-node interference and asymmetric traffic is still a challenge. This paper presents pFD-MAC, a novel polling-based traffic-aware medium access control (MAC) protocol for centralized full-duplex wireless networks. To solve the channel contention problem and fully utilize the channel resources under full-duplex mode, we first design a novel polling-based transmission mechanism and make comprehensive investigations on the effect of polling profile in full-duplex communication. By characterizing the inter-node interference into a directed non-conflict graph, we study the polling profile generation problem in which our objective is to minimize the packet transmission time. The problem is then theoretically formulated and proved to be NP-hard, which means it cannot be solved in polynomial time. Thus, we develop a heuristic traffic-aware algorithm and apply it to work with the packet transmission procedure in parallel. Full-duplex communication opportunities are highly exploited by parallelly organizing per-node upstream/downstream traffic according to the generated polling profile. Moreover, to achieve fairness without sacrificing throughput, deficit round robin algorithm has been applied with respect to the access time considering concurrent transmission time. Simulation results reveal that our proposed protocol can achieve improved performance in terms of throughput and transmission delay while maintaining fairness, compared with two state-of-the-art centralized MAC protocols.

This paper proposes a spectRum Aware cRoss-layEr (RARE) medium access control protocol for cognitive radio ad-hoc networks. The RARE protocol initially splits the network into clusters, where cluster formation is defined as maximum edge biclique problem. Besides, in order to maintain the integrity of the cluster-based network, super-frame structure, and topology maintenance protocols are also presented in this paper. Moreover, RARE also integrates a delay-aware routing protocol, where the routing protocol is defined as a weighted graph problem. It is anticipated that clusters in RARE adapt themselves dynamically with respect to spectrum availability and nodes mobility. Furthermore, the routing protocol in RARE is expected to select stable paths while ensuring faster data delivery from a source node to the destination. Simulation is conducted to evaluate the performance of the proposed RARE protocol, where it is found that RARE outperforms existing approaches by maintaining a lesser number of clusters and a steady number of common channels. The simulation results also show that route selection in RARE proves to be more stable with the lowest packet transmission delay compared with the other approaches.

A sensor-based wearable system is a promising platform to monitor the health and movement of human in real time to improve the quality of life. However, it places stringent requirements on communication delay, energy efficiency, and throughput. In this paper, an adaptive beaconing medium access control (AB-MAC) protocol is proposed to reduce communication delay and improve throughput and energy efficiency for duty cycle-based wearable system. AB-MAC protocol belongs to receiver initiated (RI) MAC protocol, where the sender keeps listening the channel to send data while the receiver sends beacons actively for the preparation of receiving data when it becomes awake. AB-MAC protocol exploits the unbalance energy consumption in the network, where the nodes near the sink (or hub) consume more energy than that of nodes far away from the hub. AB-MAC protocol makes efficient use of the remaining energy of the nodes far away from the hub to send more beacons during the sleep time, which can decrease the sleep delay and improves the energy efficiency and throughput. In addition, the number of beacons that can be sent for the nodes is also obtained based on the remaining energy level. The theoretical analysis is conducted for analyzing the performance of AB-MAC protocol. Furthermore, experimental results are provided, which demonstrate that compared with RI-MAC protocol, AB-MAC protocol can reduce the delay by 32%-51%, increase the throughput by 45%-116%, and improve the energy efficiency by 12%-21% without sacrificing the network lifetime.

Underwater glider is a cost-effective underwater unmanned vehicle with high endurance for applications in both civilian and military fields. Mobile underwater acoustic sensor networks are consisted of underwater gliders confront with several unique challenges, including high spatial–temporal uncertainty and long propagation delay of acoustic signal. In this paper, we propose an OFDMA-based MAC protocol named G-MAC for an underwater glider network, which leverages dynamic sub-channel allocation and transmission power adjustment. G-MAC is a multichannel MAC protocol dedicated for using in underwater centralized networks, which aims to maximize the network’s goodput. To solve the optimal problem, G-MAC allows for concurrent data transmissions by applying Nash equilibrium to allocate transmission subchannel and related power adjustment. In addition, to reduce the negative impact from spatial uncertainty, a motion prediction method based on the characteristic of underwater glider is applied. Simulation results document that G-MAC outperforms the existing solutions in terms of network goodput and energy consumption in the representative network scenario.

Cooperative spectrum sensing (CSS) is widely investigated in cognitive radio networks (CRNs) to improve the spectrum sensing performance. To realize CSS, how to collect sensing data from the secondary users (SUs) is one of the major problems. To solve the problem, in this paper, we propose a contention-free reporting scheme-based MAC protocol for CSS in the CRNs. With the proposed the MAC protocol, the SUs can report the sensing data to the fusion center without any reporting collisions, therefore increasing the reporting channel efficiency. Moreover, two admission control schemes are designed for throughput optimization and energy efficiency optimization, which further improve the performance of the proposed MAC protocol. Simulation results show that the proposed MAC protocol outperforms existing protocols.

In a cloud-based network architecture, the central unit (CU) at the cloud coordinates wireless nodes such as the remote access units (RAUs) at the edges of the network and manages most functions for providing wireless connectivity services to clients. The CU facilitates efficient communication resource management such as radio frequency or transmission power of RAUs by global resource coordination. In this paper, we propose a cloud-based Wi-Fi network architecture consisting of a CU and RAUs as an improvement on the conventional Wi-Fi architecture with traditional access points (APs). We then propose a method for uplink data transmission in a cloud-based Wi-Fi network. In a conventional Wi-Fi network with independently operating APs, APs close to each other may not be able to utilize the same frequency band efficiently because of significant amounts of interference. However, in a cloud-based Wi-Fi network, the CU coordinates RAUs so that they can operate in the same frequency band by transmitting or receiving signals through the shared wireless medium to improve spectral efficiency. For each frequency band, the proposed system utilizes a diversity combining that combines multiple signals and introduces a single improved signal with high signal-to-noise ratio for uplink transmission in the cloud-based Wi-Fi network. In our proposed uplink transmission method for a cloud-based Wi-Fi network, we utilize diversity combining with the immediate acknowledgement (ACK) transmission method that transmits the ACK frame to the client immediately before decoding. The proposed uplink data transmission method mitigates the performance degradation caused by the fronthaul propagation delay between the CU and RAUs, without significant modification of the IEEE 802.11 standard. Using an IEEE 802.11n standard-compliant simulation and experiments with software-defined radio equipment, we verify the goodput performance of the proposed method for a cloud-based Wi-Fi network architecture.

Localization plays a more and more important role in underwater wireless sensor networks (UWSNs). But in the large-scale UWSNs, the localization algorithm can’t be realized for the continuous packet collision. Therefore, we need to consider the impact of MAC protocol on the positioning algorithm. First, this paper proposes a multi-layer positioning model based on the underwater network architecture. Then according to the non-synchronous localization scheme, we analyze the reason of packet collisions and propose the variable interval ALOHA (VI-ALOHA) protocol based on the Poisson distribution. The VI-ALOHA protocol reduces the collision by adding random space–time. Through the comparison of localization coverage, packet loss, and localization time, this paper evaluates the impact on the localization result in equal interval ALOHA (EI-ALOHA) and VI-ALOHA. Our simulation results show that the MAC protocol has a significant influence on localization; besides, the localization coverage and the packet loss of VI-ALOHA protocol are above 20% better than the EI-ALOHA.

With the boosting of mobile services, licensed spectrum for wireless networks becomes more and more crowded. To explore new spectrum for cellular users, more and more mobile operators are interested in deploying the long-term evolution in unlicensed spectrum (LTE-U), which utilizes the unlicensed spectrum occupied by Wi-Fi. Because the medium access control (MAC) protocols of LTE-U and Wi-Fi are different, the synchronization between the LTE-U users and Wi-Fi users cannot be guaranteed for LTE-U/Wi-Fi coexisting networks, thus resulting in the throughput deterioration of LTE-U and Wi-Fi users. In this paper, we propose the full-duplex two-threshold spectrum sensing (FDTT-SS) algorithm for LTE-U/Wi-Fi coexisting networks, where both LTE-U and Wi-Fi users adopt the listen-before-talk mechanism, with adaptive priority for LTE-U. Using our proposed FDTT-SS scheme, the LTE-U/Wi-Fi average transmission time can be guaranteed by avoiding the collisions among LTE-U/Wi-Fi users. We further develop the FDTT-MAC protocol that can significantly increase the sum throughput while guaranteeing the fairness for LTE-U/Wi-Fi coexisting networks. Numerical results show that our proposed fair FDTT-MAC protocol can improve the channel utilization in unlicensed spectrum and can increase the throughput of Wi-Fi without greatly degrading the throughput of LTE-U for coexisting wireless networks as compared with existing schemes.

International audience; This paper addresses a wireless sensor network dedicated to monitor a large mechanical system. The chosen system for the scenario is a chairlift. In this case the wireless sensor network special feature is the mobility of nodes following an invariant path traveled repeatedly. A sensor node is put on each chair and a sink node is at ground at the upper end of the chairlift. A new protocol called TOMAC-WSN is designed in order to schedule frames transmission using token concept. This avoids collision at the medium access. The second concept used by TOMAC-WSN is frame aggregation. This new protocol has been modelled using Finite State Automata. An experimental implementation on Arduino boards shows the correct operation of the network. Network performance in terms of delivery time and packet loss rate is evaluated using simulation. The results show that the proposed TOMAC-WSN protocol delivers the appropriate quality of service for the monitoring of large physical systems.

Wi-Fi devices operate following the 802.11 distributed coordination function in order to fairly use the channel that the devices share. However, the throughput performance of the Wi-Fi networks is known to be degraded due to packet collisions. So, we propose a novel multiple access protocol, called centralized random backoff (CRB) for collision-free Wi-Fi networks. In CRB, after a successful reception of a data frame from a station, the access point allocates a unique backoff state to the station by means of the ACK frame. We evaluate its performance by comparing to that of a deterministic backoff mechanism. Evaluation results show that CRB significantly improves the throughput performance by reducing collisions, and it allows a larger number of nodes to operate in a collision-free state without dynamic parameter adjustment.

The full-duplex (FD) wireless is one of the key drivers for realizing the 5G cellular systems, which can initiate the mixture of FD and half-duplex (HD) wireless networks simultaneously. Many research works have been studied to improve the medium access control (MAC) performance of the mixture of HD and FD wireless networks. However, the hidden terminal problem still remains unsolved today. Therefore, the paper aims to revisit and evaluate this problem explicitly. This paper depicts the numerical evaluations of HD, FD and mixture of HD and FD wireless networks in terms of conditional collision probability, transmission probability and saturation throughput.

Nano-networks are composed of interconnected nano-nodes and can enable unprecedented applications in various fields. Due to the peculiarities of nano-networks, such as high density, extremely limited energy and computational resources, traditional carrier-sensing based Media Access Control (MAC) protocols are not suitable for nano-networks. In this paper, a Slot Self-Allocation based MAC protocol (SSA-MAC) is proposed for energy harvesting nano-networks. Two transmission schemes for centralized and distributed nano-networks are designed, respectively. In centralized nano-networks, nano-nodes can only send packets to the nano-controller in their Self-Allocation Slots (SASs), while, in distributed nano-networks, nano-nodes can only receive packets from surrounding nano-nodes in their SASs. Extensive simulations were conducted to compare the proposed SSA-MAC with PHysical LAyer aware MAC (PHLAME), Receiver-Initiated Harvesting-aware MAC (RIH-MAC) and Energy Efficient Wireless NanoSensor Network MAC (EEWNSN). From the results, it can be concluded that the proposed SSA-MAC achieves better performance and can reduce the collision probability, while improving the energy efficiency of nano-networks.

Full-duplex (FD) communication provides new opportunities for improving the throughputs of networks. However, this condition means that the number of senders increases from one to two within a certain range. We have to arrange the two nodes to send frames simultaneously in the media access control (MAC) layer. For the single-hop network model, using the FD features of the nodes and the cut-through mechanism, we propose an FD MAC protocol. The protocol improves the throughput of the network from the following two aspects. On the one hand, during the transmission of each node, based on the information of the received frame&rsquo, s header, the protocol can detect collisions in the network, preventing the channel from being ineffectively occupied for a long time. On the other hand, the protocol can provide the FD with as many opportunities as possible for the nodes. According to the working process of the protocol, we modeled the states (&ldquo, active&rdquo, and &ldquo, passive&rdquo, transmission, back-off) of each node and their transitions to a Markov chain. We solved the &ldquo, transmission probability of the node and further modeled the analytical performance of the protocol. The simulation results showed that the system throughput produced by our protocol was at least twice that of the conventional CSMA/CA protocol used in the half-duplex networks.

Packet collisions caused by the standard Distributed Coordination Function (DCF) protocol in wireless local area networks (WLANs) have been a challenging problem leading to congestion and reduced throughput. To solve this problem,we propose a novel backoff state generation algorithm, called adaptive virtual backoff algorithm (AVBA), operating in an access point. The virtual contention window size in the algorithm is automatically adjusted based on the number of synchronized active nodes in a cell. Backoff counts generated by AVBA operating in the access point are sent by the access point to each active node in the cell to try to synchronise transmissions and minimize packet collisions. Evaluation results show that AVBA improves the throughput performance compared to existing collision resolution techniques, such as deterministic backoff andcentralized random backoff (CRB), when the number of active nodes is large. Moreover, the results show that it maintains a high level of fairness in terms of channel access opportunities between nodes using AVBA and nodes using the DCF protocol when they coexist in a mixed wireless network scenario.

International audience; Wireless sensor networks (WSNs) with energy harvesting capabilities have drawn increasing attention in the last few years, as they enable long-term monitoring applications. However, the level of power harvested is usually limited to few mW. To improve the energy efficiency of WSNs, many power management techniques have been proposed to adjust the quality of service according to the harvested energy fluctuations. As wireless communications consume a major fraction of the available energy, numerous medium access control (MAC) protocols have been proposed to minimize energy consumption, latency, and data collisions. In this paper, we present an innovative MAC protocol for energy-harvesting based WSNs exploiting ultralow-power wake-up radios. To overcome the limited range typical of wake-up radios, a multi-hop wake-up scheme based on a dual radio system is proposed enabling asynchronous communications between a base station and any node of the network while maintaining a low latency and a high energy efficiency. To reduce energy consumption, wake-up calls and data packets are transmitted using two distinct data rates. Combined with destination address decoding, using a higher data rate for data transmission also minimizes the risk of collisions. Our approach has been applied to monitoring applications composed of autonomous sensor nodes powered by indoor light energy. OMNeT++ simulation results demonstrate the benefits of our wake-up radio-based approach in terms of energy, latency, and collisions when compared with the state-of-the-art duty-cycled MAC protocols. Experiments performed with real WSN platforms equipped with a wake-up radio prototype confirm the efficiency of our approach.

Wireless Sensor Networks (WSNs) consist of a large number of small interconnected devices. The aim of such networks is the monitoring of some types of area. This work is done by collaboration between these devices. All of them must sense and send information to the sink. These devices are characterized by limited memory, limited computing resource and they are usually powered by an irreplaceable battery, which limits their lifetime. Therefore it is essential to design an effective and energy aware protocols in order to extend the network lifetime by reducing the energy consumption. In this article, a new communication mechanism for IEEE 802.15.4 based WSNs called "Kalman based MAC (K-MAC) protocol" is proposed. K-MAC is designed to maximize the efficiency of the energy consumption. Therefore, the network nodes lifetime will extend through a predicting filter. The objectif of this filter is to optimize the sleep interval time of nodes between consecutive wake-ups. The network node be awake only if it have to receive or to send data. In other words, there will be an adaptation between the activation of the transceivers and the node traffic load. The simulation results show that K-MAC obtains better performance in terms of energy efficiency, Packet Delivery Ratio (PDR), the whole without affecting negatively the latency.

Bayrakdar, M. Enes/0000-0001-9446-0988; CICIOGLU, MURTAZA/0000-0002-5657-7402; Calhan, Ali/0000-0002-5798-3103 WOS: 000480604600005 In this study, network performance analysis of a newly proposed cognitive radio wireless network (CRWN) medium access control (MAC) protocol is investigated in order to improve the performance of wireless cognitive radio networks (CRNs). Several MAC protocols have been used in the literature in order to increase the performance of wireless CRNs. In this context, a cognitive radio based MAC protocol is proposed, which is also a solution to the needs of wireless CRNs with high performance results. We propose an autonomous control strategy that recognizes both the primary network and the CRN environment considering the service quality requirements of the wireless CRN environment. Simulation of the network environment is performed with Riverbed Modeler software for more realistic performance evaluation. By selecting various workloads for secondary users, the analysis of different network performance parameters such as throughput ratios, end-to-end delays, packet loss ratios, bit error rates, and energy consumptions reveal the originality of our study. In addition, Slotted Aloha, TDMA, and CSMA/CA based MAC protocols for CRNs used in different studies in the literature are compared with CRWN. As a result, proposed protocol is given about 40% higher performance than Slotted Aloha in terms of throughput and about 36% higher performance than TDMA in terms of delay. Moreover, the proposed CRWN consumes less energy than CSMA/CA.

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.

Devices used in Internet of Things (IoT) networks continue to perform sensing, gathering, modifying, and forwarding data. Since IoT networks have a lot of participants, mitigating and reducing collisions among the participants becomes an essential requirement for the Medium Access Control (MAC) protocols to increase system performance. A collision occurs in wireless channel when two or more nodes try to access the channel at the same time. In this paper, a reinforcement learning-based MAC protocol was proposed to provide high throughput and alleviate the collision problem. A collaboratively predicted Q-value was proposed for nodes to update their value functions by using communications trial information of other nodes. Our proposed protocol was confirmed by intensive system level simulations that it can reduce convergence time in 34.1% compared to the conventional Q-learning-based MAC protocol.

A hybrid optical-acoustic underwater wireless sensor network (OA-UWSN) was proposed to solve the problem of high-speed transmission of real-time video and images in marine information detection. This paper proposes a novel energy-efficient contention-based media access control (MAC) protocol (OA-CMAC) for the OA-UWSN. Based on optical-acoustic fusion technology, our proposed OA-CMAC combines the postponed access mechanism in carrier sense multiple access with collision avoidance (CSMA/CA) and multiplexing-based spatial division multiple access (SDMA) technology to achieve high-speed and real-time data transmission. The protocol first performs an acoustic handshake to obtain the location information of a transceiver node, ensuring that the channel is idle. Otherwise, it performs postponed access and waits for the next time slot to contend for the channel again. Then, an optical handshake is performed to detect whether the channel condition satisfies the optical transmission, and beam alignment is performed at the same time. Finally, the nodes transmit data using optical communication. If the channel conditions do not meet the requirements for optical communication, a small amount of data with high priority is transmitted through acoustic communication. An evaluation of the proposed MAC protocol was performed with OMNeT++ simulations. The results showed that when the optical handshaking success ratio was greater than 50%, compared to the O-A handshake protocol in the literature, our protocol could result in doubled throughput. Due to the low energy consumption of optical communication, the node&rsquo, s lifetime is 30% longer than that of pure acoustic communication, greatly reducing the network operation cost. Therefore, it is suitable for large-scale underwater sensor networks with high loads.

26th IEEE Signal Processing and Communications Applications Conference (SIU) -- MAY 02-05, 2018 -- Izmir, TURKEY Bayrakdar, M. Enes/0000-0001-9446-0988 WOS: 000511448500600 Cognitive radio is a new network approach that enables effectively and efficient use of limited spectrum bands. In this study, network performance analysis of a newly proposed cognitive radio wireless network (CRWN) medium access control (MAC) are investigated in order to improve the performance of wireless cognitive radio networks. Instead of proposing a new MAC technique, exist MAC techniques have been used in the literature in order to increase the performance of wireless cognitive radio networks. In this context, cognitive radio based a new MAC technique which can be a solution to the needs of wireless cognitive radio networks is proposed. Simulation of the network environment was performed with Riverbed Modeler (OPNET) software. By selecting different workloads for secondary users, the analysis of different network performance criteria such as throughput ratio and end-to-end delays has been examined. IEEE, Huawei, Aselsan, NETAS, IEEE Turkey Sect, IEEE Signal Proc Soc, IEEE Commun Soc, ViSRATEK, Adresgezgini, Rohde & Schwarz, Integrated Syst & Syst Design, Atilim Univ, Havelsan, Izmir Katip Celebi Univ

Targeting the medical monitoring applications of wireless body area networks (WBANs), a hybrid medium access control protocol using an interrupt mechanism (I-MAC) is proposed to improve the energy and time slot utilization efficiency and to meet the data delivery delay requirement at the same time. Unlike existing hybrid MAC protocols, a superframe structure with a longer length is adopted to avoid unnecessary beacons. The time slots are mostly allocated to nodes with periodic data sources. Short interruption slots are inserted into the superframe to convey the urgent data and to guarantee the real-time requirements of these data. During these interruption slots, the coordinator can break the running superframe and start a new superframe. A contention access period (CAP) is only activated when there are more data that need to be delivered. Experimental results show the effectiveness of the proposed MAC protocol in WBANs with low urgent traffic.

A wireless sensor network is a large number of sensor nodes deployed in a fixed or random manner over a wide area for environmental monitoring applications. Wireless sensors communicate via wireless links and are powered by batteries. They collect and provide information to the base station usually called sink. The information collected is generally physical, chemical or biological nature. For some of these applications, as pipeline or road monitoring, wireless sensor nodes have to be deployed in a linear manner. We refer to these WSNs as Linear Sensor Networks (LSNs). Due to specificity of LSNs, MAC protocol designed for WSNs, as contention or TDMA based protocols, are often not suitable. Furthermore, wireless node deployment can provide a certain form of redundancy to prevent link or node failures. In this paper, we propose a token based MAC protocol for linear sensor networks in order to improve the network performance. We evaluate the effect of the redundancy on the throughput and on the end-to-end delay.

In this paper, we propose a medium access control (MAC) protocol to allow a radio over fiber-based wireless local area network (RoF-based WLAN) to coexist with legacy carrier sense multiple access with collision avoidance (CSMA/CA)-based WLANs. In RoF-based WLANs, there are long propagation delays between access points (APs) and stations (STAs). When an RoF-based WLAN uses the conventional CSMA/CA protocol and coexists with legacy WLANs, the propagation delay causes unexpected frame collisions and unfairness between the RoF-based WLAN and legacy WLANs. The proposed protocol reduces unexpected frame collisions and improves fairness between the RoF-based WLAN and legacy WLANs in environments where they coexist. It is only necessary to apply the proposed protocol to the AP in the RoF-based WLAN (RoF AP); there is no need to modify STAs, which is an advantage of the protocol. In the proposed scheme, the RoF AP transmits frames during the transmission and reception of frames in the legacy WLAN, such that the frame transmitted by the AP arrives at a destination STA one short interframe space (SIFS) period after the channel became idle, and thus the RoF AP’s frames do not collide with other frames. As a result, the proposed method decreases the likelihood of frame collisions and increases the throughput of the RoF-based WLAN. In addition, the proposed method provides adaptive adjustment of the transmission probability, which enables the RoF-based WLAN and the legacy WLANs to fairly share wireless channels. The proposed protocol has been investigated for IEEE 802.11a/b/g WLANs. Numerical analysis and simulation evaluations show that the proposed scheme increases the TCP throughput of the RoF-based WLAN up to the same level as that in legacy WLANs.

Wireless body area networks (WBANs) are severely energy constrained, and how to improve the energy efficiency so as to prolong the network lifetime as long as possible is one of the most important goals of WBAN research. Low data-rate WBANs are promising to cut down the energy consumption and extend the network lifetime. Considering the characteristics and demands of low data-rate WBANs, a low duty-cycling medium access control (MAC) protocol is specially designed for this kind of WBAN in this paper. Longer superframes are exploited to cut down the energy consumed on the transmissions and receptions of redundant beacon frames. Insertion time slots are embedded into the inactive part of a superframe to deliver the frames and satisfy the quality of service (QoS) requirements. The number of the data subsections in an insertion time slot can be adaptively adjusted so as to accommodate low data-rate WBANs with different traffic. Simulation results show that the proposed MAC protocol performs well under the condition of low data-rate monitoring traffic.

Full-duplex (FD) wireless communication is evolving into a practical technique, and many studies are being conducting in this area, especially regarding the physical layer. However, to exploit FD benefit successfully, efficient medium access control (MAC) protocols are crucial as well as physical layer advances. Numerous FD-MAC protocols have been proposed, but these MAC protocols cannot address all the issues encountered in this area. In addition, many half-duplex (HD) capable devices are present in existing wireless local area networks (WLANs), so there is an urgent need to integrate FD clients and HD clients in the same WLAN. We refer to this type of WLAN as a heterogeneous WLAN (Het-WLAN). In this paper, we propose an FD-MAC for Het-WLAN, which considers all possible types of FD transmissions. Our proposed FD-MAC protocol suppresses inter-user interference. Simulation results demonstrated that a significant throughput gain (about 96%) could be achieved by using our proposed FD-MAC compared with traditional HD communications. Moreover, our proposed MAC obtained better performance (average throughput gain of about 11%) compared with another existing FD-MAC design. In addition, probability analysis suggested that the total probability of FD transmissions increased rapidly as the WLAN approached saturation conditions.

This doctoral dissertation comprises a novel contention resolution mechanism for wireless sensor networks, based on the exchange of short radio-frequency (RF) tones among sensor nodes. Originality of the proposed mechanism comes from the new algorithm for successive elimination of nodes during the contention resolution phase. The algorithm is based on binary countdown mechanism and guaranties collision-free communication with minimum number of RF tones transmitted. The proposed technique, called TONE, has better performances in terms of energy efficiency and communication throughput, compared to existing binary countdown based contention resolution mechanisms. The application area of the TONE are Medium Access Control (MAC) protocols for wireless sensor networks. In this dissertation, the proposed TONE is applied in intracluster MAC protocol for star topologies, where reduces the average energy consumption during contention period for up to 44.5% compared to the baseline countdown mechanism. When aplied in receiver-driven TDMA MAC protocol, the proposed TONE achieves the same troughput as transmitter-driven TDMA MAC protocol with 3 times smaller energy consumption, and even 4.5 smaller energy consumption than receiver-driven TDMA MAC protocol with CSMA-based contention resolution mechanism. The proposed TONE is also applied in active period MAC protocols, where it increases normalized data troughput for more than 100% compared to existing active-tone MAC protocols, with reduction of energy consumption of up to 500%.

International audience; A wireless sensor network is a large number of sensor nodes deployed in a fixed or random manner over a wide area for environmental monitoring applications. Wireless sensors communicate via wireless links and are powered by batteries. They collect and provide information to the base station usually called sink. The information collected is generally physical, chemical or biological nature. For some of these applications, as pipeline or road monitoring, wireless sensor nodes have to be deployed in a linear manner. We refer to these WSNs as Linear Sensor Networks (LSNs). Suitable MAC protocols for LSN must take account the linearity in order to ensure reliability and optimize parameters such as the end-to-end delay, the delivery ratio, the throughput, etc. In this paper, we present LTB-MAC a Linear Token Based Mac Protocol designed for linear sensor networks. In this paper we present a comparative study in terms of throughput, delivery ration, end-to-end delay between a Linear Token Based MAC protocol and the unslotted CSMA/CA of 802.15.4.; Un réseau de capteurs sans fil est un grand nombre de nœuds de capteurs déployés de façon fixe ou aléatoire sur une vaste zone pour des applications de surveillance environnementales. Les capteurs sans fil communiquent via des liaisons sans fil et sont alimentés par des piles. Ils recueillent et fournissent des informations à la station de base habituellement appelée puits. Les informations recueillies sont généralement de nature physique, chimique ou biologique. Pour certaines de ces applications, comme la surveillance de pipeline ou la surveillance routière, les nœuds de capteurs sans fil doivent être déployés de manière linéaire. De tels type de réseaux sont appelés réseaux de capteurs linéaires (LSN (Linear Sensor Networks)). Les protocoles MAC appropriés pour réseaux de capteurs sans fil linéaires doivent tenir compte de la linéarité afin d'assurer la fiabilité et d'optimiser des paramètres tels que le délai de bout-en-bout, le débit, le débit, le ratio, etc. Dans cet article, nous présentons présentons une étude comparative entre un protocole MAC basé sur des jetons circulants et un protocole MAC basé sur la contention. Nous effectuons cette comparaison en terme de délai, débit au puits, taux de délivrance.

Wireless body sensor networks (WBSNs) constitute a key technology for closing the loop between patients and healthcare providers, as WBSNs provide sensing ability, as well as mobility and portability, essential characteristics for wide acceptance of wireless healthcare technology. However, one important and difficult aspect of WBSNs is to provide data transmissions with quality of service, among other factors due to the antennas being small size and placed close to the body. Such transmissions cannot be fully provided without the assumption of a MAC protocol that solves the problems of the medium sharing. A vast number of MAC protocols conceived for wireless networks are based on random or scheduled schemes. This paper studies firstly the suitability of two MAC protocols, one using CSMA and the other TDMA, to transmit directly to the base station the signals collected continuously from multiple sensor nodes placed on the human body. Tests in a real scenario show that the beaconed TDMA MAC protocol presents an average packet loss ratio lower than CSMA. However, the average packet loss ratio is above 1.0 %. To improve this performance, which is of vital importance in areas such as e-health and ambient assisted living, a hybrid TDMA/CSMA scheme is proposed and tested in a real scenario with two WBSNs and four sensor nodes per WBSN. An average packet loss ratio lower than 0.2 % was obtained with the hybrid scheme. To achieve this significant improvement, the hybrid scheme uses a lightweight algorithm to control dynamically the start of the superframes. Scalability and traffic rate variation tests show that this strategy allows approximately ten WBSNs operating simultaneously without significant performance degradation., Project "AAL4ALL", co-financed by the European Community Fund FEDER through COMPETE-Programa Operacional Factores de Competitividade (POFC). Foundation for Science and Technology, Lisbon, through project PEst-C/CTM/LA0025/2013.

Landslides during heavy rainfall cause a great amount of damage in terms of both property and human life. To predict landslide disasters, we designed and implemented a wireless sensor network using our existing highly fault tolerant ad-hoc network. Since many sensors must be used, we propose a new MAC protocol that allows the network to support more sensor terminals. Our protocol is a hybrid CSMA/Psuedo-TDMA scheme which allows the terminals to decide their transmission timing independently in a random fashion. A timing beacon is not required, so power consumption can be reduced. Simulation results show that the number of terminals supported by the network can be greatly increased., Article, IEICE TRANSACTIONS ON COMMUNICATIONS. E97B(7):1449-1456 (2014)

Vehicular ad-hoc networks (VANETs) technology has been emerged as a critical research area. Being ad-hoc in nature, VANET is a type of networks that is created from the concept of establishing a network of cars for a specific need or situation. Communication via routing packets over the high- speed vehicles is a challenging task. Vehicles mobility, speed can vary depending on the road specification. However, on highway, the speed can be increase up to 120–200 Km/H. Moving at high speed can affect the efficiency of data delivery. In particular V2I traffic where moving car trying to deliver data to fixed space units which are designed to collect and process data from vehicles. Different protocols have been proposed to be implemented for VANET infrastructure, including 802.11 and 802.11p. The performance of these proposed protocols has not been compared and investigated to find out the robust mechanism for handling high speed VANETs. In this paper, the performance of the most widely deployed MAC protocols for handling wireless communication which is 802.11 and the 802.11p have been compared, which is a customized version for high speed modes. Performance is investigated in term of data delivery evaluation metrics including network throughput, delay and packet delivery ration. Results show that 802.11p has efficiently enhanced the network performance where network throughput is increased, delay is decreased, and packet delivery ratio is increased as well.