Time Division Multiple Address Research Articles

Outage performance and energy efficiency optimization of wireless-powered millimeter-wave sensor networks

AbstractWith the widespread use of wireless sensor networks, one of the most pressing concerns is extending the lifetime of the sensors. By deploying directional antenna arrays, millimeter wave (mmWave) is a possible candidate for wireless energy transfer (WPT). This paper investigates a beneficial combination of WPT and data transmission in a typical mmWave sensor network with Rayleigh channels, where a transmission interval can be divided into two sub-intervals. During the first sub-interval, one hybrid access point (HAP) employs beamforming techniques to transfer energy for serving multiple sensors within the service sector. The sensors then transmit their individual signal in turn to the HAP based on time division multiple address (TDMA) strategy by using the whole harvested energy. According to stochastic geometry, the exact and approximate expressions of beam outage probability for the considered system are determined, respectively. The optimal time allocation of energy harvesting and data transmission for sensors is examined in order to maximize the energy efficiency of the system. The optimization problem can be translated into corresponding parametric form, and the resulting optimization problem can be solved using the Lagrange dual method with Karush–Kuhn–Tucker (KKT) conditions. The numerical results show the variation trend of the beam outage probability under various parameters and verify the accuracy of the theoretical analyses. Furthermore, the simulation results illustrate that the proposed optimal time allocation strategy can significantly enhance the overall energy efficiency of the system compared with a similar scheme.

A Novel Method Locating Pedestrian With Smartphone Indoors Using Acoustic Fingerprints

Acoustic-based positioning method have high accuracy and good compatibility with commercial-off-the-shelf consumer devices. However, the traditional acoustic-based method, which utilizes the time-of-arrival (TOA) and time difference of arrival (TDOA), is highly affected by occlusion and non-line-of-sight (NLOS); limited signal transmitting stations can only support a small range of positioning; the first path of the acoustic signal is difficult to accurately detect in corridors and remote locations from the stations. To solve these situations, in this paper, a novel indoor localization method for smartphones based on acoustic fingerprinting is presented, which utilizes the difference of characteristics in the frequency domain of a predefined acoustic chirp signal at different positions. The innovations of this method include the design of a signal transmission scheme, detection of the first path according to the time-division-multiple-address (TDMA), and use of the PSD of signals in the frequency domain as the fingerprint feature. To verify the effectiveness, universality and performance of this method, three experiments were implemented in different environments, including a comparison experiment with Wi-Fi-based fingerprinting. The experimental results demonstrate that the proposed method can achieve accurate positioning performance, and the mean error is within 1 m in the mix of LOS and NLOS indoor environments.

TDMA Datalink Cooperative Navigation Algorithm Based on INS/JTIDS/BA

Position information is very important tactical information in large-scale joint military operations. Positioning with datalink time of arrival (TOA) measurements is a primary choice when a global navigation satellite system (GNSS) is not available, datalink members are randomly distributed, only estimates with measurements between navigation sources and positioning users may lead to a unsatisfactory accuracy, and positioning geometry of altitude is poor. A time division multiple address (TDMA) datalink cooperative navigation algorithm based on INS/JTIDS/BA is presented in this paper. The proposed algorithm is used to revise the errors of the inertial navigation system (INS), clock bias is calibrated via round-trip timing (RTT), and altitude is located with height filter. The TDMA datalink cooperative navigation algorithm estimate errors are stated with general navigation measurements, cooperative navigation measurements, and predicted states. Weighted horizontal geometric dilution of precision (WHDOP) of the proposed algorithm and the effect of the cooperative measurements on positioning accuracy is analyzed in theory. We simulate a joint tactical information distribution system (JTIDS) network with multiple members to evaluate the performance of the proposed algorithm. The simulation results show that compared to an extended Kalman filter (EKF) that processes TOA measurements sequentially and a TDMA datalink navigation algorithm without cooperative measurements, the TDMA datalink cooperative navigation algorithm performs better.

Performance analysis of NOMA-based mobile edge computing with imperfect CSI

In this paper, a non-orthogonal multiple access (NOMA)-based mobile edge computing (MEC) system is proposed, where paired users (the mth user and the nth user) offload tasks to the MEC server under imperfect channel state information (ipCSI) condition. To evaluate the effect on performance under ipCSI condition in NOMA-MEC system, this study derives new exact and asymptotic expressions of the offloading outage probability for two users under ipCSI and perfect channel state information (pCSI) conditions. On the basis of the theoretical derivation, the diversity orders of the nth user under ipCSI and pCSI conditions are zero and n, respectively, while those for the distant user are all zeros. In addition, we also investigate the system throughput and energy efficiency of NOMA-MEC in delay-limited transmission. Numerical results show that (1) the offloading outage behaviors of NOMA-MEC are better than those of time division multiple address (TDMA), (2) the offloading outage performance of paired users under ipCSI is worse than that under pCSI, and (3) the NOMA-MEC system achieves higher throughput and energy efficiency than does the TDMA-MEC system.

A multi-user joint constellation design of color-shift keying for VLC downlink broadcast channels

While creating a required illumination, LED luminaries can be used as wireless access points by visible light communication (VLC) technology. Under normal conditions, there is more than one user who needs to be connected to the VLC network. Consequently, multiple access technique, e.g., time division multiple address (TDMA), is required to enable multiple users to share the network without interfering each other. To achieve a more efficient multi-user communication, we propose a multi-user joint constellation (JC) design for color-shift keying (CSK) by utilizing multiple LED luminaries equipped with multi-color LEDs. Unlike traditional multiple-input–multiple-output (MIMO) researches in which the symbols of different transmitters are independently generated from the constellations, the transmitted symbols are jointly generated in our design which takes the advantage of both multi-color and spacial resources in VLC systems. Considering the signal constraints in both optical and electric domains, the JC design is formulated with the objective function of maximizing the minimum Euclidean distance (MED) between different receiving constellation points. To make it easy to solve the non-convex optimization problem, we propose an iterative algorithm with the help of slack variable and Taylor expansion. Afterwards, a method of constellation mapping for the system is provided. In order to analyze the performance of the JC design, conventional TDMA and non-orthogonal multiple access (NOMA) scheme are introduced as comparisons and the simulation results illustrate that JC owns a better performance than both of them.

Cooperative Spectrum Sensing in Cognitive Radio Using Bayesian Updating with Multiple Observations

We study cooperative spectrum sensing in cognitive radio (CR) networks using the hidden Markov model (HMM) for opportunistic spectrum access (OSA). We assume that the primary channel operates in a time division multiple address (TDMA) manner. Thus, spectrum sensing is operating in a slot-by-slot basis. In contrast to the conventional Bayesian updating using only one observation, in this work, we propose to perform the update in a concatenated fashion with all the observations available from the secondary users (SUs). In the proposed scheme, a predefined threshold on the belief is used for determining the channel activity. With the threshold, the proposed scheme is more flexible in the system operation than the simple majority vote scheme, in which no such threshold is available. We compare, by simulations, the performance of the proposed concatenated update scheme with that of the majority vote scheme and show that the probabilities of correctly detecting a busy state and an idle state are about 1 as the number of SUs is as large as 15, so the effects of the further increase in the number of SUs are limited.

Heterogeneous slot scheduling for real-time industrial wireless sensor networks

Real-time performance and reliability are two critical indicators in an industrial wireless sensor network (IWSN). Several time-division multiple-address (TDMA)-based industrial standards such as WirelessHART and ISA100 are widely used in IWSNs. However, to simplify the analysis, standard TDMA supports only one or two slot types in each frame, and each slot is usually 10 ms, which severely limits transmissibility and real-time responses in TDMA-based IWSNs where the number of transmissions is large but the length of most packets is small. In this paper, we propose a TDMA frame containing slots of different lengths to address this issue. The key ideas are to waste fewer slot resources and achieve on-demand slot allocation. First, we study the matching problem in a TDMA frame; then, we propose two scheduling methods, the split scheduling algorithm (SSA) and the double plug-in algorithm (DPA), under our TDMA frame. Extensive simulations and real testbed results show that the proposed solution DPA can significantly improve network performance and reliability. Real-time comparisons with other existing scheduling schemes show that the proposed solution improves the acceptance ratio by 48.8% compared to the rate-monotonic scheme.

A distributed decision method for missiles autonomous formation based on potential game

The distributed cooperative decision problems of missiles autonomous formation with network packet loss are investigated by using the potential game based on formation principles. In particular, a dynamic target allocation method for missiles formation is provided based on the potential game and formation principles, after the introduction of cooperative guidance and control system of the missiles formation. Then we seek the optimization of a global utility function through autonomous missiles that are capable of making individually rational decisions to optimize their own utility functions. The first important aspect of the problem is to design an individual utility function considering the characteristics of the missiles formation, with which the objective of the missiles are localized to each missile yet aligned with the global utility function. The second is to equip the missiles with an appropriate coordination mechanism with each missile pursuing the optimization of its own utility function. We present the design procedure for the utility, and present a coordination mechanism based on spatial adaptive play and then introduce the idea of “cyclical selected spatial adaptive play” and “negotiation based on time division multiple address (TDMA) protocol formation support network”. Finally, we present simulations for the distributed dynamic target allocation on the comprehensive digital simulation system, and the results illustrate the effectiveness and engineering applicability of the method.

Superposition constellation design for multi-user multi-chip visible light communication systems

In this paper, we study a multi-user multi-chip visible light communication (VLC) system. The superposition constellation is proposed for the system to achieve an efficient multi-user communication. Specifically, the constellation design is formulated to maximize the minimum Euclidean distance between users’ symbols with the constraint of illuminance, chromaticity and the dynamic range of light-emitting diodes (LEDs). It is proved the users’ performance is determined by the minimum Euclidean distance of the constellation. We then transform the constellation design into a convex optimization problem by Taylor series and get an iterative algorithm. In addition, a kind of modulation and demodulation methods is provided for the system. Simulation results illustrate that the proposed method outperforms the conventional time division multiple address (TDMA) scheme.

Design and Application of the Efficient Time-Division Multiple Address Protocol for Hybrid Server

The protocol of the hybrid server was designed based on the Internet of things for the realization of the intelligent management with the different equipments under the Internet of things. The Internet of things had large number of nodes, and the net topology was easy to change, it also had high requirements for the reliability. According to the properties of these properties, an efficient time-division multiple address protocol that was called E-TDMA protocol was proposed based on the improvement of the time division multiple address protocol. A power management system was designed based on the Internet of things, and the Internet of things was applied in the intelligent power management system, the indexes of the E-TDMA protocol based on the Internet of things such as throughput capacity, network stability were tested with the simulation. Test result shows that the number of the data packets in the buffer cache is much less than the traditional TDMA protocol and the dynamical TDMA protocol. It is because that the E-TDMA can make all the units can send data in the same time through CDMS coding. The result shows that the proposed E-TDMA protocol has efficient performance of accessing to the information channel and stability of network transmission in the application of the power management system.

A Weighed Least Square TDOA Location Algorithm for TDMA Multi-target

In order to improve the location precision of multiple targets in a time division multiple address (TDMA) system, a new weighed least square algorithm is presented for multi-target ranging and locating. According to the time synchronization of the TDMA system, the range difference model between multiple targets is built using the time relations among the slot signals. Thus, the range of one target can be estimated by the other one’s, and a group of estimated value can be acquired for every target. Then, the weighed least square algorithm is used to estimate the range of every target. Due to the time differences of arrival (TDOA) of all targets are used in one target’s location, the location precision is improved. The ambiguity and non-solution problems in the traditional TDOA location algorithm are avoided also in the presented algorithm. At the end, the simulation results illustrate the validity of the proposed algorithm.

Mobility-based clustering protocol for wireless sensor networks with mobile nodes

In this study, the authors propose a mobility-based clustering (MBC) protocol for wireless sensor networks with mobile nodes. In the proposed clustering protocol, a sensor node elects itself as a cluster-head based on its residual energy and mobility. A non-cluster-head node aims at its link stability with a cluster head during clustering according to the estimated connection time. Each non-cluster-head node is allocated a timeslot for data transmission in ascending order in a time division multiple address (TDMA) schedule based on the estimated connection time. In the steady-state phase, a sensor node transmits its sensed data in its timeslot and broadcasts a joint request message to join in a new cluster and avoid more packet loss when it has lost or is going to lose its connection with its cluster head. Simulation results show that the MBC protocol can reduce the packet loss by 25% compared with the cluster-based routing (CBR) protocol and 50% compared with the low-energy adaptive clustering hierarchy-mobile (LEACH-mobile) protocol. Moreover, it outperforms both the CBR protocol and the LEACH-mobile protocol in terms of average energy consumption and average control overhead, and can better adapt to a highly mobile environment.