Time Slot Allocation Scheme Research Articles

A powerful adversary model and corresponding OTP time slot allocation scheme in RIS-assisted physical layer key generation

Physical layer key generation (PLKG) is a technique of information-theoretic security to tackle the problem of key distribution between resource-constrained legitimate users and is a promising candidate for the one time pad (OTP) technique. However, in quasi-static, the key rate is greatly limited due to low entropy. Reconfigurable intelligent surface (RIS) is introduced to adaptively reconfigure the radio environment. However, how to allocate time slots in the OTP to counter the increasingly powerful adversary model is an urgent problem to be solved. In this paper, we propose a very powerful adversary model and give an attack strategy called eavesdropping channel search, which allows Eve to use its search and eavesdropping capabilities to maximize the probability of successful attacks. Meanwhile, we propose a time slot allocation algorithm in the OTP to ensure the security of the key. Simulations validate that our proposed attack strategy is more powerful than any existing adversary model and our proposed time slot allocation algorithm does not have any security loss.

Delay Optimization for Cooperative Multi-Tier Computing in Integrated Satellite-Terrestrial Networks

The integrated satellite-terrestrial network is promising to provide global broadband communication service. However, the long propagation delay of satellite-terrestrial links will lead to high communication delay when users access the Internet via satellites. In this paper, we investigate the cooperative multi-tier computing in the integrated satellite-terrestrial network, in which the computation tasks of users are processed by leveraging the cooperation of devices, edge nodes, and cloud servers. Based on the proposed three-tier computing framework, we formulate the cooperative edge-cloud offloading problem to minimize the total delay of the network. Considering the computation task is dividable, we propose the optimal task splitting strategy based on the partial offloading model, in which the closed-form solution is derived for each computation task. With the optimal task splitting strategy obtained, the original optimization problem is reformulated as the problem of the time slot allocation strategy and the computation capacity allocation strategy. Then, we further propose the cooperative edge-cloud computing strategy to optimize the delay performance of the network. Finally, numerical results are presented to demonstrate the performance of the proposed three-tier computing architecture and the offloading strategies.

Age of Information in Energy Harvesting Aided Massive Multiple Access Networks

Given the proliferation of the massive machine type communication devices (MTCDs) in beyond 5G (B5G) wireless networks, energy harvesting (EH) aided next generation multiple access (NGMA) systems have drawn substantial attention in the context of energy-efficient data sensing and transmission. However, without adaptive time slot (TS) and power allocation schemes, NGMA systems relying on stochastic sampling instants might lead to tardy actions associated both with high age of information (AoI) as well as high power consumption. For mitigating the energy consumption, we exploit a pair of sleep-scheduling policies, namely the multiple vacation (MV) policy and start-up threshold (ST) policy, which are characterized in the context of three typical multiple access protocols, including time-division multiple access (TDMA), frequency-division multiple access (FDMA) and non-orthogonal multiple access (NOMA). Furthermore, we derive closed-form expressions for the MTCD system’s peak AoI, which are formulated as the optimization objective under the constraints of EH power, status update rate and stability conditions. An exact linear search based algorithm is proposed for finding the optimal solution by fixing the status update rate. As a design alternative, a low complexity concave-convex procedure (CCP) is also formulated for finding a near-optimal solution relying on the original problem’s transformation into a form represented by the difference of two convex problems. Our simulation results show that the proposed algorithms are beneficial in terms of yielding a lower peak AoI at a low power consumption in the context of the multiple access protocols considered.

An Energy-Efficient Clustering Routing for Wireless Sensor Networks Based on Energy Consumption Optimization

In order to alleviate energy consumption of wireless sensor networks (WSNs), energy consumption optimization-based clustering routing (ECOR) is proposed in this paper. In ECOR, network is gridding by hexagon. And there is only a cluster head (CH) in each hexagon, which makes the distribution of CHs more even. Residual energy of nodes and distance from the centroid of hexagon are used to elect CHs. For any a CH, dynamic time slot allocation strategy is adopted to allocate time slot for its cluster members. According to status of cluster members, the duration of time slot is dynamically adjusted. In intercluster communication, the Dijkstra algorithm is used to construct the shortest path between CHs in order to shorten the distance of transmitting data. Simulation results show that the ECOR algorithm outperforms the improved-Low Energy Adaptive Clustering Hierarchy (I-LEACH) algorithm in terms of distribution of CHs and energy consumption.

LoRaWAN ESL for Food Retail and Logistics

Electronic shelf labels (ESL, or electronic price tag) are used by retailers for displaying product pricing on shelves substituting printed price tags; each ESL can display not only the price, but also text, and images, and can be remotely updated, configured, and programmed from a central server. Additionally, the emerging IoT paradigm, allows to expand the application horizon. Firstly, this work presents an analysis on how the use of Cloud-connected, intelligent, ESLs can improve food logistics in the complex scenarios of medium and large cities. Then, a low-cost ESL device, using an electronic ink (e-ink) display and the LoRaWAN protocol to communicate with the central server, aimed at price display and innovative applications in food retail and logistics, is presented. Several current consumption and communication distance measurements are shown, and the design and configuration space are explored to optimize battery life and communication reliability in the different food distribution scenarios. The proposed ESL is powered with a 500mA ·h LiMnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> battery that can last for >8 years in a typical application, considering it communicates with a central server once per hour. The developed price tag can dynamically update the price and information for the customer, which in the case of food can be used to minimize spoilage and can easily upgraded to incorporate sensors or smartphone interaction to develop innovative food logistics and marketing practices. Finally, a LoRaWAN time-slot allocation strategy is presented, to minimize collisions when thousand nodes are connected to a single gateway, with a minimum power consumption overhead.

A Joint Optimization Scheme for Hybrid MAC Layer in LEO Satellite Supported IoT

The Internet of Things (IoT) aims to interconnect and converge the physical world and cyberspace. It represents the future of networking, and leads the wave of the third industrial revolution. As IoT applications evolve, more and more regions lacking infrastructures are also experiencing an urgent need to deploy and connect IoT devices into the network. Low earth orbit satellites, due to its wide coverage and relatively low latency, can provide network access for IoT system. In this article, we propose a low-latency heterogeneous network MAC approach for space-earth integrated IoT network, which can significantly reduce network latency, improve system scalability and balance total system load. Specifically, we design a geographic priority time slot allocation strategy which ensures optimal load and latency, besides, we also design a continuous forward time slot allocation strategy, which guarantees data timeliness while reducing the utilization of satellite resources. Then we design three algorithms based on above strategies, which can effectively reduce network latency and balance the satellite resources. The simulation experimental results are consistent with the theoretical results, which embodies the effectiveness of the algorithm.

Joint rate maximization of downlink and uplink in NOMA SWIPT systems

The combination of Non-orthogonal multiple access (NOMA) and Simultaneous wireless information and power transfer (SWIPT) is an emerging technology that can meet the requirements of spectral efficiency and energy efficiency. In this paper, we study the achievable rate maximization for jointly downlink and uplink network with power splitting-based SWIPT. We propose two different models. By using Single-Input Single-Output (SISO)-NOMA in conjunction with SWIPT, a joint uplink and downlink resource allocation scheme is proposed with the optimization objective to maximize the sum rate. We prove the objective function is strictly concave and found the optimal power splitting factor of each user. By using Multiple-Input Multiple-Output (MIMO)-NOMA in conjunction with SWIPT, we add timeslot allocation and propose a power splitting control and a timeslot allocation scheme. The optimization problem is divided into two subproblems to reduce solving complexity. In more detail, we first design the power splitting control scheme to maximize both the achievable rate and harvested energy in the downlink. Then timeslot optimization method is designed to improve the sum throughput. The simulation results show that a relatively high downlink rate can be achieved, while the required energy is simultaneously harvested by the users for the uplink.

Channel Resource Scheduling for Stringent Demand of Emergency Data Transmission in WBANs

Media access control (MAC) plays a pivotal role in ensuring proper operation in wireless body area networks (WBANs). However, current solutions still cannot satisfy the stringent requirements of low power and low delay for emergency data reporting. In this paper, we propose an energy-efficient and emergency-aware MAC (EEEA-MAC) protocol for meeting such a rigorous demand. First, we design a node-different channel access scheme, in which source nodes use the CSMA/CA pattern while relay nodes adopt the hybrid CSMA/CA-TDMA pattern. Second, we devise an emergency-first time-slot allocation scheme, in which channel sensing is performed and the emergency data is handled by relay nodes according to different cases. EEEA-MAC has two striking features. One is that, source nodes adopt the CSMA/CA scheme instead of the conventional CSMA/CA-TDMA scheme, ensuring the requirement because there are almost no collisions and no confirmation messages in this scheme. The other is that, relay nodes use a sensing-based emergency data handling mechanism instead of the traditional empty-slot occupying mechanism, further guaranteeing the requirement owing to the immediate handling of emergency data and the short time of channel sensing. Extensive simulations demonstrate the advantages of EEEA-MAC in terms of energy dissipation and latency.

Dynamic Spectrum Interaction of UAV Flight Formation Communication With Priority: A Deep Reinforcement Learning Approach

The formation flights of multiple unmanned aerial vehicles (UAV) can improve the success probability of single-machine. Dynamic spectrum interaction solves the problem of the ordered communication of multiple UAVs with limited bandwidth via spectrum interaction between UAVs. By introducing reinforcement learning algorithm, UAVs can continuously obtain the optimal strategy by continuously interacting with the environment. In this paper, two types of UAV formation communication methods are studied. One method allows for information sharing between two UAVs in the same time slot. The other method is the adoption of a dynamic time slot allocation scheme to complete the alternate use of time slots by the UAV to realize information sharing. The quality of experience (QoE) is introduced to evaluate the results of UAV sharing, and the M/G/1 queuing model is used for priority and to evaluate the packet loss of UAV. In terms of algorithms, a combination of deep reinforcement learning (DRL) and the long-short-term memory (LSTM) network is adopted to accelerate the convergence speed of the algorithm. The experimental results show that, compared with the Q-learning and deep Q-network (DQN) methods, the proposed method achieves faster convergence and better performance with respect to the throughput rate.

Joint optimization of power control and time slot allocation for wireless body area networks via deep reinforcement learning

E-healthcare system based on wireless body area network (WBAN) promises to produce potential benefits in health-care industry. A major issue of such an on-body networked system is the energy efficiency, that is, how to improve the reliability and effectiveness of physiological data transmission with the energy constraints of tiny wireless sensors. Motivated by this, we consider an individual WBAN scenario, focusing on finding an adaptive time slot allocation and power control scheme to maximize the average energy efficiency for implementing the task of health monitoring. We formulate the maximization problem with latency and sensors’ energy budget constraints as a markov decision process (MDP). As a solution, we propose a deep reinforcement learning-based scheme to make a sequence decision for the MDP, which jointly optimizes power control and slot allocation. Simulation results show that the proposed scheme is energy efficient and has a good convergence.

User Clustering and Power Allocation for Hybrid Non-Orthogonal Multiple Access Systems

In this article, a comprehensive strategy of user clustering and power allocation is investigated in downlink hybrid non-orthogonal multiple access (NOMA) networks. More particularly, users in the same cluster can receive signals simultaneously by using NOMA techniques, while time-division multiple access (TDMA) schemes are utilized among different clusters. By employing the weight factor, a weighted sum rate maximization problem is formulated and decoupled into user clustering and power allocation problems, where two different schemes for time slot allocation are proposed. The formulated user clustering problems with user-based and cluster-based time slot allocation schemes are respectively considered as coalitional games in characteristic and partition formations, and solved by two different algorithms, where both low-complexity and global optimal methods are proposed. The properties, including complexity, convergence, stability and optimality, are analyzed. To further improve the system performance, the formulated power allocation problem is solved by a successive convex approximation (SCA) based iterative algorithm. Simulation results reveal that: i) the proposed hybrid NOMA system is capable of achieving promising gains over centralized NOMA-based and conventional TDMA-based frameworks; and ii) the developed algorithms can significantly improve the weighted sum rate compared with the random user structure and the fixed power allocation.

A data fusion privacy protection strategy with low energy consumption based on time slot allocation and relay in WBAN

Wireless body area network (WBAN) can collect and analyze human health signs data of various modes in real time by virtue of low-energy consumption high-precision sensing technology, and it needs to protect health sensitive data related to personal privacy in the process of data transmission. In order to solve the important problem of reliable data transmission in wireless body area network, a new strategy is proposed in this paper. From the two levels of single-hop communication and two-hop communication, the channel characteristics and node data rate in WBAN are fully considered. The reliable data transmission in wireless body area network is realized by using time slot allocation and relay strategy. The introduction of TDMA mechanism of dynamic time slot allocation improves the energy efficiency of strategy and avoids the energy consumption caused by competition, while dynamic time slot allocation satisfies the change of node flow. Time slot allocation strategy based on channel condition and data traffic, exist some nodes in the practical use of the status of the data transmission reliability not guaranteed, we use the relay for this strategy to improve its, meet the requirements of the reliability of data transmission in the network, to bring the additional energy consumption, and strategy information dynamic relay selection depend on the channel information and energy, so that improve the energy efficiency, its energy consumption is reduced. Simulation results show that our transmission strategy can significantly improve the transmission success rate and reduce packet loss, and can adjust the channel changes to improve the reliability of data transmission.

Priority-Based Medium Access Control for Wireless Body Area Networks With High-Performance Design

The wireless body area network (WBAN) has attracted considerable attention. Two main problems exist in WBANs: 1) the quality of service (QoS) requirements and 2) the energy efficiency of data transmission. To solve the above problems, in this paper, we carefully design the sensor priority according to the importance degree, sampling rate, timeout condition, and remaining energy. Then, considering the priority of the node and the channel factors, a utility function is introduced to characterize the value of a node transmitting data frames in a specific time period. Next, we model the time slot allocation problem, where the objective is to maximize the total utility of the data transmission of all nodes in a specified period of time by adjusting the transmission time and the transmission duration of each node. Finally, according to the problem model, we propose a time slot allocation scheme based on a greedy strategy, which effectively reduces the time complexity of the direct solution to the problem. In this scheme, nodes with higher priority are arranged to transmit data frames in the time slots with better channel conditions. The experimental results show that the proposed scheme achieves substantial improvements in QoS and energy efficiency relative to the comparison schemes.

Fuzzy-Based Dynamic Time Slot Allocation forWireless Body Area Networks.

With the advancement in networking, information and communication technologies, wireless body area networks (WBANs) are becoming more popular in the field of medical and non-medical applications. Real-time patient monitoring applications generate periodic data in a short time period. In the case of life-critical applications, the data may be bursty. Hence the system needs a reliable energy efficient communication technique which has a limited delay. In such cases the fixed time slot assignment in medium access control standards results in low system performance. This paper deals with a dynamic time slot allocation scheme in a fog-assisted network for a real-time remote patient monitoring system. Fog computing is an extended version of the cloud computing paradigm, which is suitable for reliable, delay-sensitive life-critical applications. In addition, to enhance the performance of the network, an energy-efficient minimum cost parent selection algorithm has been proposed for routing data packets. The dynamic time slot allocation uses fuzzy logic with input variables as energy ratio, buffer ratio, and packet arrival rate. Dynamic slot allocation eliminates the time slot wastage, excess delay in the network and attributes a high level of reliability to the network with maximum channel utilization. The efficacy of the proposed scheme is proved in terms of packet delivery ratio, average end to end delay, and average energy consumption when compared with the conventional IEEE 802.15.4 standard and the tele-medicine protocol.

Time division multiple access scheduling strategies for emerging vehicular ad hoc network medium access control protocols: a survey

Vehicular ad hoc network (VANET) is an emerging and promising technology, which allows vehicles while moving on the road to communicate and share resources. These resources are aimed at improving traffic safety and providing comfort to drivers and passengers. The resources use applications that have to meet high reliability and delay constraints. However, to implement these applications, VANET relies on medium access control (MAC) protocol. Many approaches have been proposed in the literature using time division multiple access (TDMA) scheme to enhance the efficiency of MAC protocol. Nevertheless, this technique has encountered some challenges including access and merging collisions due to inefficient time slot allocation strategy and hidden terminal problem. Despite several attempts to study this class of protocol, issues such as channel access and time slot scheduling strategy have not been given much attention. In this paper, we have relatively examined the most prominent TDMA MAC protocols which were proposed in the literature from 2010 to 2018. These protocols were classified based on scheduling strategy and the technique adopted. Also, we have comparatively analyzed them based on different parameters and performance metrics used. Finally, some open issues are presented for future deployment.

Simultaneous Wireless Information and Power Transfer for Dynamic Cooperative Spectrum Sharing Networks

In this paper, we provide a comprehensive performance analysis of simultaneous wireless information and power transfer (SWIPT) for cognitive relay networks with different relay schemes. In the considered system, the energy-constrained secondary transmitter harvests the energy from the primary signal and then employs the harvested energy to forward the primary signal along with the secondary signal simultaneously. To improve the spectral efficiency, we propose a novel cooperative spectrum sharing protocol with dynamic time-slot allocation based on energy harvesting, namely, dynamic time-power-based cooperative spectrum sharing protocol. Considering the delay-limited transmission mode, we analytically derive the exact closed-form expressions of outage probabilities and achievable throughput for both the primary and secondary networks with amplify-and-forward and decode-and-forward relaying schemes, respectively. More importantly, different from the existing works, we take into account the power outage probability at the energy-constrained secondary transmitter to better match the reality. Finally, the numerical results are provided to evaluate the effect of different key parameters on the system performance, which demonstrate that the dynamic cooperative spectrum sharing protocol improves the outage performance compared with the uniform time-slot allocation scheme.

Adaptive multichannel MAC protocol based on SD‐TDMA mechanism for the vehicular ad hoc network

In this study, the design of an adaptive medium access control (MAC) protocol based on the space-division–time-division multiple access (SD-TDMA) mechanism is presented to improve the utilisation and fairness of the time-slot allocation scheme in the vehicular ad hoc network. The SD-TDMA mechanism dynamically allocates time-slots owing to a dynamic topology. This protocol reduces transmission collisions through user detection procedures. Most users can thus access the service channel (SCH) without conflict and acquire time slots according to the mapping between geographic locations and time slots. Users failing to access the channel in user detection procedures can send request access packets in security channels to again participate in SCH time-slot allocation during the SCH interval. Simulations are conducted to evaluate the performance of the proposed method in urban scenarios. The SD-TDMA mechanism is compared with an SDMA-based MAC protocol, the IEEE 802.11p distributed coordination function and an MAC protocol based on transmission sequences. Owing to the decreased rate of transmission collisions and the dynamic time-slot allocation scheme, it is shown that the SD-TDMA mechanism provides a significantly higher utilisation of time slots and better fairness of data transmission than existing approaches.

Dynamic time slot allocation and stream control for MIMO STDMA in ad hoc networks

Multiple-input multiple-output (MIMO) technologies have been shown to potentially improve the performance of network. Many traditional medium access control (MAC) protocols, such as spatial time division multiple access (STDMA), may not support MIMO technologies directly and not make full use of the feature of MIMO, which may be a limitation in the practical application in ad hoc networks. Therefore, in this paper, we propose a dynamic time slot allocation and stream control for MIMO STDMA (DTSMS) protocol to improve STDMA in performance. Utilizing stream control technology of MIMO and reservation scheme, DTSMS makes improvement on network throughput and avoids the mutual interference of neighbor links. Thus, DTSMS can support both unicast and multicast simultaneously. Moreover, we implement the dynamic time slot allocation scheme in DTSMS to guarantee the transmission efficiency of packets with high cross-layer transmission parameters, such as the packet priority, neighbor node density, or link quality. Utilizing the collected cross-layer information, the proposed scheme allocates time slots for all nodes dynamically according to the changes of network topology and nodes’ transmission parameters. Finally, the effectiveness of the protocol is demonstrated by numerical analysis and simulations. The results show that DTSMS outperforms STDMA in terms of network throughput and delay. Furthermore, compared to our previous TTS-MIMO, DTSMS can decrease the delay of packets with high transmission parameters and improve the quality of service (QoS).

Resource Allocation in Space Multiaccess Systems

Currently, most Landsat satellites are deployed in the low earth orbit (LEO) to obtain high-resolution data of the Earth surface and atmosphere. However, the return channels of LEO satellites are unstable and discontinuous intrinsically, resulting from the high orbital velocity, long revisit interval, and limited ranges of ground-based radar receivers. Space-based information networks, in which data can be delivered by the cooperative transmission of relay satellites, can greatly expand the spatial transport connection ranges of LEO satellites. While different types of these relay satellites deployed in orbits of different altitudes represent distinctive performances when they are participating in forwarding. In this paper, we consider the cooperative mechanism of relay satellites deployed in the geosynchronous orbit (GEO) and LEO according to their different transport performances and orbital characteristics. To take full advantage of the transmission resource of different kinds of cooperative relays, we propose a multiple access and bandwidth resource allocation strategy for GEO relay, in which the relay can receive and transmit simultaneously according to channel characteristics of space-based systems. Moreover, a time-slot allocation strategy that is based on the slotted time division multiple access is introduced for the system with LEO relays. Based on the queueing theoretic formulation, the stability of the proposed systems and protocols is analyzed and the maximum stable throughput region is derived as well, which provides the guidance for the design of the system optimal control. Simulation results exhibit multiple factors that affect the stable throughput and verify the theoretical analysis.

무인로봇체계에서 QoS 보장을 위한 트래픽 방향 기반 중앙집중식 TDMA 슬롯 할당 기법

This paper proposes a time slot allocation scheme for military patrol environments. This proposal comes from analysis of traffic properties in a military patrol environment. In the near future, robots are expected to explore enemy grounds and measure threat, taking the place of human patrol. In order to control such robots, control messages must be extremely accurate. One mistake from the control center could cause a tragedy. Thus, high reliability must be guaranteed. Another goal is to maintain a continual flow of multimedia data sent from patrol robots. That is, QoS (Quality of Service) must be guaranteed. In order to transmit data while fulfilling both attributes, the per-path based centralized TDMA slot allocation scheme is recommended. The control center allocates slots to robots allowing synchronization among robots. Slot allocation collisions can also be avoided. The proposed scheme was verified through the ns-3 simulator. The scheme showed a higher packet delivery ratio than the algorithm in comparison. It also performed with shorter delay time in the downlink traffic transmission scenario than the algorithm in comparison. 논문 16-41-05-08 The Journal of Korean Institute of Communications and Information Sciences '16-05 Vol.41 No.05 http://dx.doi.org/10.7840/kics.2016.41.5.555 555 ※ 본 논문은 국방과학연구소의 “그룹 무인로봇체계용 위치기반 전술 MANET 통신/제어 S/W 개발” 과제의 지원을 받아 수행된 연구임 First Author : Ajou University Department of Computer Engineering, jina@uns.ajou.ac.kr, 학생회원 ° Corresponding Author : Ajou University Department of Computer Engineering, youngko@ajou.ac.kr, 정회원 * Ajou University Department of Computer Engineering, dabin912@gmail.com ** Agency for Defense Development, Korea, dhkwon@add.re.kr 논문번호:KICS2015-12-397, Received December 16, 2015; Revised April 1, 2016; Accepted April 8, 2016 The Journal of Korean Institute of Communications and Information Sciences '16-05 Vol.41 No.05