Time Division Multiple Access Method Research Articles

Joint optimization of UAV-IRS placement and resource allocation for wireless powered mobile edge computing networks

The rapid evolution of communication systems towards the next generation has led to an increased deployment of Internet of Things (IoT) devices for various real-time applications. However, these devices often face limitations in terms of processing power and battery life, which can hinder overall system performance. Additionally, applications such as augmented reality and surveillance require intensive computations within tight timeframes. This research focuses on investigating a mobile edge computing (MEC) network empowered by unmanned aerial vehicle intelligent reflecting surfaces (UAV-IRS) to enhance the computational energy efficiency of the system through optimized resource allocation. The MEC infrastructure incorporates the energy transfer circuit (ETC) and edge server (ES), co-located with the intelligent access point (AP). To eliminate interference between energy transfer and data transmission, a time-division multiple access method is utilized. In the first phase, the ETC wirelessly transfers power to low-power IoT devices, which efficiently harvest and store the received energy in their batteries. In the second phase, IoT devices employ the stored energy for local computing or offloading tasks. Furthermore, the presence of tall buildings may obstruct communication routes, impacting system functionality. To address these challenges, we propose an optimization framework that simultaneously considers time, power, phase shift design, and local computational resources. This joint optimization problem is non-convex and non-linear, making it NP-hard. To tackle this complexity, we decompose the problem into subproblems and solve them iteratively using a convex optimization toolbox like CVX. Through simulations, we demonstrate that our proposed optimization framework significantly improves 40.7% system performance compared to alternative approaches.

Multi-Access Communication Technique Based on Joint Time-Frequency Increment Index Modulation for IoT Networks

Different classes of index modulation (IM) based on multi-access techniques have been investigated for Internet of Things (IoT) devices, especially, non-time sensitive applications (i.e., telemetry, smart metering). This paper proposes a joint time-frequency increment IM (TFIIM) by considering time and frequency increment domains for multi-access communication. Specifically, we activate the indices of frequency diverse array (FDA) antennas with their corresponding frequency increments f across the elements and the modulated complex symbol to radiate information bits at a specific time slot. The proposed scheme utilized the time slot to convey extra bits. The implementation of time slots depends on the incoming bits which is different from time division multiple access (TDMA) method. The proposed TFIIM transmitter allows concurrent transmissions to different IoT devices along the angle-range position since the time slot can be selected individually by the activated FDA antennas. Furthermore, the average bit error rate (ABER), green saving, probability of collision (PoC), throughput and system capacity are derived and evaluated. With the simulation results disclosed in this paper, the proposed TFIIM would constitute an excellent nominee for IoT device applications where high spectral efficiency, energy-efficiency, low-complexity, angle-range information beamspace, and data security are paramount.

Multilayer Joint Optimization of Packet Size and Adaptive Transmission Scheduling of Wireless Sensor Networks for Mechanical Vibration Monitoring

Limitations pertaining to the storage capacity and bandwidth of wireless sensor networks (WSNs) for mechanical vibration monitoring (MVM) pose difficulties in the realization of reliable and energy-efficient communication of big data. To prolong the lifetime of battery-limited WSNs, this paper proposes a multi-layer joint optimization of packet size and adaptive transmission scheduling (ATS) to jointly optimize the energy consumption of acquisition nodes from the storage and transmission layers. First, owing to the frequent storage and transmission of massive mechanical vibration data in WSNs, the packet size significantly affects the energy consumption during storage and transmission. The proposed packet size optimization based on the lowest energy consumption (PSO-LEC) model optimizes the energy consumption of acquisition nodes from three aspects: writing, reading, and transmission of data. Second, when transmitting massive vibration data frequently, the direct beacon frame conflict and indirect beacon frame conflict markedly induce data conflict and delay problems. Therefore, adaptive transmission scheduling based on the time division multiple access (TDMA/ATS) method is proposed to optimize the errors in data collision and transmission delay. Thus, the packet size and ATS are considered jointly to improve the network lifetime for MVM. Comprehensive experimental results indicate that the transmission reliability and energy-efficiency of the proposed scheme are significantly improved, and the network life is effectively prolonged for MVM.

A Digitally Assisted Multiplexed Neural Recording System With Dynamic Electrode Offset Cancellation via an LMS Interference-Canceling Filter

This article presents a low-power (LP) area-efficient implantable neural recording system that supports high-density neural implant (HDNI) applications. The system uses a time-division multiple access method to record from 16-neural electrodes simultaneously. A least mean squares (LMSs) algorithm is used to cancel the slowly varying electrode offsets from all channels simultaneously by using a single-tap digital adaptive filter (AF). The presented technique is fabricated in 65-nm CMOS technology and achieves a per-channel area of 0.00248 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ; 68% of which is digital circuitry (and is thus scalable with technology). The overall system consumes 3.38 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> per channel while achieving 2.6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{V}_{\mathrm {rms}}$ </tex-math></inline-formula> of input referred noise (IRN) in 10 kHz of bandwidth. The proposed system has a noise efficiency factor (NEF) of 1.83 and is fully integrated on-chip.

Security-Aware Routing Protocol Based on Artificial Neural Network Algorithm and 6LoWPAN in the Internet of Things

Today, with increasing information technology such as the Internet of Things (IoT) in human life, interconnection and routing protocols need to find optimal solution for safe data transformation with various smart devices. Therefore, it is necessary to provide an enhanced solution to address routing issues with respect to new interconnection methodologies such as the 6LoWPAN protocol. The artificial neural network (ANN) is based on the structure of intelligent systems as a branch of machine interference, has shown magnificent results in previous studies to optimize security-aware routing protocols. In addition, IoT devices generate large amounts of data with variety and accuracy. Therefore, higher performance and better data handling can be achieved when this technology incorporates data for sending and receiving nodes in the environment. Therefore, this study presents a security-aware routing mechanism for IoT technologies. In addition, a comparative analysis of the relationship between previous approaches discusses with quality of service (QoS) factors such as throughput and accuracy for improving routing mechanism. Experimental results show that the use of time-division multiple access (TDMA) method to schedule the sending and receiving of data and the use of the 6LoWPAN protocol when routing the sending and receiving of data can carry out attacks with high accuracy.

Static and dynamic evaluations of acoustic positioning system using TDMA and FDMA for robots operating in a greenhouse

Acoustic positioning system has great potential to be applied in a greenhouse due to its centimeter-level accuracy, low cost, and ability of extensive greenhouse coverage. Spread Spectrum Sound-based local positioning system (SSSLPS) was proposed to be a navigation tool for multiple agricultural robots by the authors' research team. However, to increase the system capacity for positioning multiple robots in a greenhouse, the near-far problem caused by the interference between speakers needs to be overcome. The use of different access methods, Time Division Multiple Access (TDMA) or Frequency Division Multiple Access (FDMA), is essential in the SSSLPS system for solving the near-far problem. The static positioning in a greenhouse was first evaluated by setting different parameters to determine the optimal signal setting for a dynamic experiment. From that, the moving robot tests were added with a motion capture system and tested the performance of TDMA and FDMA. The results demonstrated that TDMA can be used in a stationary sound-based positioning system with 12.2 mm accuracy, but it has a time delay problem in dynamic positioning. A simulation was designed to mimic the position error increases with different moving speeds. Although FDMA has the sound damping problem in high-frequency regions creating a peak detection issue, it achieved a higher accuracy with an average position error of 62.1 mm compared to 180.3 mm of TDMA. This study shows that the TDMA method is suitable for static measurements, while the FDMA method is suitable for measuring dynamic objects and controlling mobile robots. Keywords: greenhouse robots, positioning system, near-far problem, TDMA, FDMA DOI: 10.25165/j.ijabe.20221505.6796 Citation: Tsay L W J, Shiigi T, Zhao X Y, Huang Z C, Shiraga K, Suzuki T, et al. Static and dynamic evaluations of acoustic positioning system using TDMA & FDMA for robots operating in a greenhouse. Int J Agric & Biol Eng, 2022; 15(5): 28–33.

Enhanced overloaded code division multiple access for network on chip

The Code-division multiple access (CDMA) method is commonly used as the network infrastructure in multi-core chips. One of its advantages is the simultaneous connection of all network components. Another advantage is the constant delay of this method. On the other hand, one drawback is that the number of transmitters is limited to the number of encoding bits. In this study, the authors used the combination of Walsh codes and their inverses, as well as the simultaneous application of the time-division multiple access (TDMA) method, to increase the transmission capacity of this protocol more than four times the standard mode. In the proposed design, although the circuit area does not increase significantly, a fourfold increase in the throughput of the CDMA network is seen. Using the method proposed in this study, it will be possible to increase the capacity further.

A new medium access control mechanism for energy optimization in WSN: traffic control and data priority scheme

Over the last few years, energy optimization in wireless sensor networks (WSNs) has drawn the attention of both the research community and actual users. Sensor nodes are powered by attached batteries that are considered as a critical aspect of sensor nodes design. Besides, the constraint of the limited battery capacity is associated with the concern on how to reduce the energy consumption of nodes to extend the network lifetime. In this context, the purpose of this study is to implement an adaptive medium access control (MAC) for energy saving and traffic control enhancement. This program was designed to arrange nodes into two priority groups according to their traffic rate and data transmission packet delay. This fuzzy algorithm depends on their queue length where it is implemented into the carrier sense multiple access with collision avoidance (CSMA/CA) algorithm. However, other types of nodes should send their data during the contention-free period with a GTS reallocation scheme. Those nodes are classified as low priority access to the medium, and their data transmission is scheduled using time division multiple access methods. Moreover, this proposed scheme dynamically adjusts the contention access period length to ensure that nodes can complete their data transmission during the same super-frame. Simulation results are done using the network simulator tool (NS-2), and it has improved efficiency regarding the IEEE-802.15.4 standard.

On the issues of selective jamming in IEEE 802.15.4-based wireless body area networks

The beacon-enabled mode of IEEE 802.15.4 provides a Time Division Multiple Access (TDMA) method for low power devices by adopting Guaranteed Time Slots (GTS). GTS communication is a potential target for selective jammers where they perform GTS attacks. In GTS attacks, the adversary selectively picks one of the reserved device slots to corrupt its incoming communication. Considering countermeasures, most existing solutions rely on slot position randomization to distribute the harm of the attack over the other GTS slots. These solutions may be effective in the case of full-slot jamming. However, the introduced GTS attacks consider only TDMA property of GTS communication and ignore other important properties like the protocol behavior and the superframe structure effect on the traffic. Considering these properties while performing GTS attacks exempts the adversary from full-slot jamming and renders the existing solutions with no effect. In this paper, we introduce a new efficient version of GTS attacks that benefits from both the standard behavior and the superframe effect on the periodic traffic to conserve the adversary’s resources for the longest period. Additionally, we provide a solution specially developed to mitigate the harm from this detrimental attack. From extensive simulations conducted in this work, it follows that the attack is economic in terms of jamming duration and jamming packets ratio and the solution is efficient in terms of packet delivery ratio, energy consumption and delay overhead.

Distributed Reliable and Energy-Efficient Scheduling for LR-WPANs

Pervasiveness of wireless networks drives the heterogeneity and density of devices in a vast diversity of environments. To achieve high reliability and low energy consumption while enabling pervasiveness is inherently a resource allocation problem. In low-rate wireless personal area networks, multi-frequency time-division multiple access methods are identified as compelling solutions to resource allocation via scheduling transmissions in time and frequency. This work presents the TREE (TRaffic-aware Energy Efficient) algorithm, an adaptive and distributed scheduling algorithm, designed to provide high reliability in terms of packet reception ratio while optimizing the energy consumption of each device. This algorithm schedules communications according to the packets in the queue and short-memory performance. Decisions are made locally, and low-interference scheduling emerges at the network level. TREE is an adaptive threshold-based model that allocates more network resources (e.g., timeslots) when the communication queue size crosses a threshold and frees resources if the resource was underutilized. Implemented over IEEE-802.15.4-TSCH and extensively tested in simulation and on real deployments up to 81 devices, the algorithm is compared to MSF, Alice, and Orchestra, the state of the art in time-slotted channel hopping scheduling. Results highlight a high reliability regarding packet reception ratio and a lower energy consumption compared to the state of the art.

Reference broadcast synchronization and time division multiple access implementation on WSN

Various kinds of technology have been developed to assist obtain information. One of them is a Wireless Sensor Network (WSN). WSN is a wireless network consisting of multiple nodes connected wirelessly. WSN nodes on a device have small resources in the form of batteries. The main problem which owned by WSN was in the data collection process possible collisions data, there are nodes that transmit data at the same time. Time Division Multiple Access (TDMA) was able to provide data on the delivery schedule of each node. So no nodes that transmit data at the same time. But in order to apply the system each node should have equal time. One method that able to provide equalization time was Reference Broadcast Synchronization (RBS). This method synchronizes multiple nodes that have different local time (on the receiver) with the help of node that provides synchronization marks (beacons). Hence this each node was able to transmit data in accordance with the TDMA method that has been implemented. In addition time synchronization performed using RBS give equal time with accuracy up to microseconds. That case certainly makes the WSN node able to provide accurate information to guarantee the absence of errors due to data collisions. This research succesfully sending data delivery schedule by time slots that provided by RBS and time synchronization by TDMA average time delay 2285.9 microseconds.

TDMA in Adaptive Resonant Beam Charging for IoT Devices

Resonant beam charging (RBC) can realize wireless power transfer (WPT) from a transmitter to multiple receivers via resonant beams. The adaptive RBC (ARBC) can effectively improve its energy utilization. In order to support multi-user WPT in the ARBC system, we propose the time-division multiple access (TDMA) method and design the TDMA-based WPT scheduling algorithm. Our TDMA WPT method has the features of concurrently charging, continuous charging current, individual user power control, constant driving power and flexible driving power control. The simulation shows that the TDMA scheduling algorithm has high efficiency, as the total charging time is roughly half (46.9% when charging 50 receivers) of that of the alternative scheduling algorithm. Furthermore, the TDMA for WPT inspires the ideas of enhancing the ARBC system, such as flow control and quality of service (QoS).

Robust gateway placement in wireless mesh networks

Wireless mesh networks (WMNs) are communication networks that provide wireless Internet access over areas with limited infrastructure. Each node in a WMN serves several clients in its coverage area and transfers their traffic over wireless media to a few gateway nodes that have wired connections to the Internet. In this paper, we consider the Internet gateway placement (IGP) problem along with operational problems such as routing and wireless transmission capacity allocation. To eliminate wireless interference, we adopt the spatial reuse time division multiple access (TDMA) method, in which wireless transmissions are scheduled to occur at different time slots. We also employ destination-based single path routing for its ease of implementation. We present two mixed integer linear programming (MILP) formulations, both of which jointly determine the minimum number of gateway nodes needed to support forecasted demand, the locations of these gateway nodes, the routing trees, and the time slot allocations to wireless links. These formulations differ in the flow constraints. We also present a set of valid inequalities for the formulation with the multi-commodity flow constraints. In most cases, the solution to the IGP problem is not unique. Therefore, we also introduce a local search algorithm to select the most robust solution against any demand forecast errors. On example networks, we compare the proposed formulations with and without the valid inequalities in terms of the exact solution performances and the linear programming (LP) relaxations. We also demonstrate our local search algorithm to improve robustness against forecast errors on these example networks.

Block Precoding for Peak-Limited MISO Broadcast VLC: Constellation-Optimal Structure and Addition-Unique Designs

In this paper, we investigate the design of energy-efficient space-time modulation for peak-limited MISO broadcast visible light communication (VLC) systems by cooperatively managing the non-negative multiuser interference. We first characterize a constellation-optimal structure that maximizes the worst-case minimum Euclidean distance of all users for a general space-time modulation design. It turns out that the optimal space-time constellation can be constructed via the spatial repetition of the optimal multidimensional constellation in time dimension over ideal additive white Gaussian noise channels. Then, based on this structure, we specifically design two classes of energy-efficient time-dimensional constellations: 1) for the integer overall bit rate, we design the optimal linear precoded block design, which admits fast maximum likelihood demodulation algorithms. 2) for the non-integer case, we propose a nonlinear precoding scheme called block coded modulation , which sums the code word sets of the optimal linear design and a block channel code. In addition, we show that these two classes of designs are addition-unique, thus, generating an energy-efficient mapping from users’ data to the transmitted constellations. This property enables the efficient demodulation of the sum signal from a noisy received signal as well as the decoding of individual signal from the estimated sum signal. Extensive computer simulations indicate that our addition-unique designs have remarkable performance gains over the currently available zero-forcing, minimum mean square error and time-division multiple access methods for the multiuser multi-input-single-output VLC broadcast systems.

Efficient coding techniques algorithm for cluster-heads communication in wireless sensor networks

Random network coding (RNC) for Error Correction have been the subject of intense research lately. However, in wireless sensor networks (WSNs) the correlation between the received symbols, from the same cluster head (CH), provoke the column correlation on the generator matrix of array Low-Density Parity-Check (LDPC) codes, whereby many columns of this matrix do not offer any additional information, thus the most important properties are lost despite the fact that the generator matrices are more easily dispersed. In this paper, the authors describe each step of the problem-solving algorithm employing efficient coding techniques focusing on improvement planning at Bit-error rsate (BER) vs signal-to-noise ratio (SNR) curves, in dense WSN, between CHs and the base station (BS) node. They use efficient coding techniques approach based on RNC and LDPC codes using the Time Division Multiple Access (TDMA) method. They generalize the notion of RNC-LDPC, study their properties and formulate the main steps of the proposed algorithm reconstruction method. The simulation results demonstrate that this approach is more effective in improving the BER using the proposed algorithm. Moreover, subsequently ameliorate the technical properties offered by this codification type.

Investigation of Smart Meter Data Reporting Strategies for Optimized Performance in Smart Grid AMI Networks

Designing efficient and reliable wireless mesh-based advanced metering infrastructure (AMI) networks is challenging. In AMI networks, fine-grained regular data collections from smart meters (SMs) create a lot of traffic and interference. The location of the gateway that collects data from SMs may also add to this interference by impacting the length of routes. Furthermore, TCP-like protocols that are employed for reliability may bring additional overhead. Therefore, it is critical to pick the suitable data collection strategy and gateway location to meet some smart grid performance requirements. In this paper, we proposed three novel data collection mechanisms to set the periodic reporting time of each SM to improve TCP performance in IEEE 802.11s-based wireless mesh AMI networks. The first idea was based on the nature of IEEE 802.11s routing protocol. Each SM is assigned a reporting time based on its location in the spanning tree network. The second idea was inspired by the time division multiple access methods where each meter is given a separate slot. The third idea was based on both previous ideas and clustering to increase the number of meters that can send at the same slot. For the gateway location, we also proposed a novel mechanism based on ${p}$ -center facility problem to minimize data delivery delay. The simulation results indicate that the packet delay can be improved significantly without any negative impact on the other performance metrics.

A bandwidth-efficient and fair CSMA/TDMA based multichannel MAC scheme for V2V communications

Designing QoS-aware medium access control (MAC) scheme is a challenging issue in vehicular ad hoc networks. Proportional fairness and bandwidth utilization are among the significant requirements that should be taken into account by a MAC scheme. In this paper, a bandwidth-efficient and fair multichannel MAC protocol is proposed to address these two requirements, specifically in vehicle-to-vehicle communications. The proposed scheme is based on clustering of vehicles and exploits time division multiple access (TDMA) method alongside the carrier sense multiple access with collision avoidance mechanism to allocate DSRC-based resources in a different manner from IEEE 802.11p/IEEE 1609.4 protocols. It divides each channel into aligned dynamic-sized time frames. In each time frame, in a fully TDMA-based period, transmission opportunities are assigned to vehicles letting them have dedicated transmissions on the service and control channels. The maximum number of transmission opportunities per each frame is determined by the cluster head (CH) based on a defined optimization problem which aims at maximizing both proportional fairness and bandwidth utilization. Furthermore, the bandwidth utilization is assumed to be enhanced more through reallocation of unused transmission opportunities in each time frame, using a proposed reallocation algorithm. The proposed MAC protocol is treated as a lightweight scheme such that various types of unicast, multicast and broadcast communications are possible within the cluster without involving the CH. Evaluation results show that the proposed scheme has more than 90 % achievement in terms of proportional fairness and bandwidth utilization simultaneously, and in this case, has a considerable superiority over TC-MAC. In addition, using the proposed scheme, the satisfaction level of vehicles is preserved appropriately.

Superposition network coded cooperation for wireless networks

AbstractCooperative diversity is an innovative approach to improve the reliability of communication. Although this technique is considered in the next‐generation mobile communication standards, it has its own challenges in practice. For example, in simultaneous transmission‐based cooperative protocols, perfect synchronisation of nodes is very hard to realise. The traditional time division multiple access method can simplify the synchronisation problems but leads to long transmission delays. In this paper, a low‐delay cooperative strategy is proposed for a network with multiple sources and a single destination, which requires only a simple type of synchronisation. In this technique, we use a combination of superposition coding and network coding; hence the name superposition network coded cooperation. For this strategy, good bounds are obtained for the probability of correct detection for general M‐PSK and M‐QAM modulation and are compared with simulation results. The results demonstrate improvement in error performance compared with other transmission schemes requiring the same transmission time as superposition network coded cooperation. Copyright © 2016 John Wiley &amp; Sons, Ltd.

An Ultrasonic and Vision-Based Relative Positioning Sensor for Multirobot Localization

This paper proposes a novel 3D sensor node to establish relative measurements within a robot network. The developed sensor nodes employ ultrasonic-based range measurement and infrared-based bearing measurement for spatial localization of robots. The sensor is low power, lightweight, low cost, and designed to be applicable across many robotic platforms, including microaerial vehicles. The proposed sensor design requires only two robots to perform relative measurements of each other and achieves a measurement accuracy of 0.96-cm Root-Mean-Square Error (RMSE) for range and 0.3° RMSE for bearing. The sensor nodes are scalable and can be configured using either Star or Mesh protocols with a maximum of 10-Hz update rates over a detection range of 9 m. The correspondence issue of having multiple robots is resolved using time division multiple access methods where different time slots are used by each sensor node. These features are verified by multiple experimental evaluations on a multirobot team with both ground and aerial agents. The proposed approach allows multirobot localization in scenarios where supportive positioning services such as GPS are unavailable. As a result, even basic robots, which lack powerful simultaneous localization and mapping capabilities, will be capable of autonomous navigation by accessing the positional information provided by the sensor network.

Variable-rate transmission method with coordinator election for wireless body area networks

Wearable computing technologies are becoming widely used in healthcare and for tracking various human work and leisure activities. The collection and transmission of sensor data are fundamental functions of these technologies. A wireless body area network (WBAN) helps these wearable devices to continuously acquire ambulatory and physiological signals in real time with multiple sensor nodes attached or implanted into a human body. Sensor nodes transmit data to a sink node with wireless connections can enable mobility of human bodies. Since the data transmission rate of each sensor node is different, we proposed a variable-rate transmission MAC protocol (VTMAC) with coordinator election based on the time division multiple access method. This adaptive coordinator election scheme can balance the sensor nodes' power consumption to extend the lifetime of WBAN as possible. It can also flexibly allocate time slots for each sensor node according to their different data transmission rates to enhance the efficiency of networks. The proposed method has been implemented and demonstrated on a hardware wireless communication platform with multiple wearable sensor nodes. Simulations show the VTMAC can achieve less power consumption and higher throughput performance compared with conventional protocols especially in high data transmission rate situation for the body area networks we simulated.