Maximum Number Of Retransmissions Research Articles

Ensuring Data Freshness in Wireless Monitoring Networks: Age-of-Information-Sensitive Coverage and Energy Efficiency Perspectives

With the development of IoT, the sensor usage has been elevated to a new level, and it becomes more crucial to maintain reliable sensor networks. In this paper, we provide how to efficiently and reliably manage the sensor monitoring system for ensuring data freshness. A sensor transmits its sensing information regularly to the data center (DC), and the sensed information generally has the correlation over the space and the time. Hence, the accuracy of the estimated information from the sensed information decreases as the target location for information estimation is further away from the sensor or the AoI, the elapsed time from the information generation, increases. Therefore, by considering the effect of the AoI and the distance from the sensor on the estimation error, we newly define an error-tolerable sensing (ETS) coverage as the area that the estimated information at the DC is with smaller error than the target value. To analyze the impact of the AoI on the ETS coverage, we derive the η-coverage probability, which is the probability that the ETS coverage is greater than η ratio of the maximum sensor coverage, and the average ETS coverage. We also provide the optimal transmission power of the sensor, which minimizes the average energy consumption while guaranteeing certain level of the η-coverage probability. Numerical results validate the theoretical analysis and show the tendency of the optimal transmission power according to the maximum number of retransmissions. This paper can pave the way to efficient design of the AoI-sensitive sensor networks.

Performance Evaluation of an On-Body Wireless Body Network Based on an Ultra-Wideband Physical Layer under a Dynamic Channel Model

Wireless body area networks (WBANs) are attracting attention as an important technology for realizing the Internet of Medical Things (IoMT). In addition, ultra-wideband (UWB) is one of the wireless communication technologies suitable for the IoMT and WBANs. Our previous study investigated the feasibility of WBANs utilizing UWB under ideal and static wearable WBAN channel models. The present research applies a dynamic on-body UWB channel model to a WBAN as a more realistic channel model. The feasibility of a high-reliability UWB-WBAN is demonstrated by evaluating the physical layer performance. Numerical results reveal the maximum number of retransmissions needed to achieve the desired transmission failure ratio for each link type and the corresponding energy efficiency and average number of retransmissions. These findings contribute to the realization of a highly reliable IoMT utilizing UWB-WBANs in a practical environment.

ПРОГНОЗИРОВАНИЕ ВРЕМЕНИ РАБОТЫ БЕСПРОВОДНЫХ СЕНСОРНЫХ СЕТЕЙ НА ОСНОВЕ ТЕХНОЛОГИИ LORA С ИСПОЛЬЗОВАНИЕМ ВЕРОЯТНОСТНОЙ МОДЕЛИ МАРКОВСКИХ ЦЕПЕЙ

Real-time monitoring systems and sensors are not complete without wireless data transmission modules. Improving energy efficiency requires examining various system parameters that affect the power consumption of transmitting and receiving devices. The most important parameter of any autonomous wireless network is its uptime. In this work, we used LoRa wireless modules on the SX1278 chip manufactured by Semtech to determine their power consumption in various operating modes. The obtained data were used to build a consumption model of the device when connected to a receiver. Three operating modes are considered: transmit mode, receive mode and sleep mode. In an ideal communication channel, all transmitted data reaches the receiver with 100% probability. In a real situation, data reaches the receiver with a certain probability, depending on the communication channel, transmission power, distance to the addressee, and network parameters. In this work, the occurrence of an error is random. In this case, the occurrence of an error during reception entails a lack of confirmation of receipt or a request for re-sending data. Sending data again increases the power consumption of the device and, consequently, decreases the operating time of the wireless device. This paper shows the dependences of the operating time on various initial monitored parameters of the device, such as: confirmation timeout, packet length, time of one transmission cycle and the maximum number of retransmissions in one cycle. The developed model for predicting the consumption of the device can be used in the design of autonomous wireless sensor monitoring networks.

Improvement on Age of Information for Information Update Systems With HARQ Chase Combining and Sensor Harvesting-Transmitting Diversities

The age of information (AoI) has attracted increasing attentions as a new metric and tool to capture the timeliness of reception and freshness of data, which is different from the conventional metric such as outage, delay, and throughput. While most existing works focused on AoI analysis and optimizing method, the information update system design by utilizing diversity to reduce AoI is not fully exploited so far. Inspired by this fact, a novel information status update system is designed by jointing wireless energy harvesting diversity, status update transmitting diversity, and hybrid automatic repeat request (HARQ). Specially, the update system consists of two sensors that can be seen as an unified entity from the destination's perspective, and one destination. The two sensors, which have finite-size batteries and synchronously operate in half-duplex mode, harvest energy from a Bernoulli process source, and cooperatively deliver the status update to destination by sharing a common information source. To exploit the information of the unsuccessfully decoding update packet, the HARQ and chase combining (HARQ-CC) are jointly used at destination so that the HARQ-CC receiving diversity is also exploited. By using Bernoulli process energy arrival probability and sensor transmission probability, we first propose one novel sensor energy harvesting and update delivering model that can be represented by Markov Chain (MC) and develop one novel construction method of the transition matrix of sensor battery energy states. Considering the developed energy state transmission matrix column stochastic, irreducible, and aperiodic, we obtain the stationary distribution of sensor battery energy states so that the steady transmitting power is derived. Secondly, the average AoI of the dual-sensor status update system is derived in terms of a closed-form expression by accurately calculating the statistical descriptions of the maximum retransmission number (time) in HARQ-CC and the service time of one packet. The analytical results are validated by using the comparison from simulations. Moreover, compared with traditional single sensor system, the dual-sensor system not only harvests more energy, but also has smaller average AoI because of the joint exploitation of multi-diversity. Besides, the impact of the system parameters on harvested energy and average AoI is provided, which provides insights in terms of the optimal design of Internet of things system.

Reliability and Delay Trade-Off Analysis of Unslotted IEEE 802.15.4 Sensor Network for Shipboard Environment

Wireless sensor network technology has been widely studied and applied in different fields. The applications in shipborne wireless sensor networks face serious physical-layer packet loss problems due to the wireless signals blocking by steel structure and wireless channel interference. The MAC-layer retransmission mechanism can reduce the packet loss rate but increases latency. So it's necessary to analyze the performance of reliability and latency for different applications in shipborne wireless sensor networks. In this article, first, we analyze the distribution of the physical-layer packet loss rate for IEEE 802.15.4 sensor network in ship indoor environment. We also present an analysis model based on three-dimensional Markov chain for unslotted CSMA/CA of IEEE 802.15.4 sensor network considering physical-layer packet loss rate and MAC-layer retransmission. We evaluate the effects of three MAC parameters, macMinBE, macMaxCSMABackoffs, and macMaxFrameRetries, on average delay and reliability. The percentage error of the analytical model for delay and reliability are 2.09% and 1.37%, respectively. Our work provides trade-off analysis between average delay and average reliability using the maximum number of retransmission based on the measured data of physical-layer packet loss rate in shipboard environment for different QoS requirements.

Energy efficiency of five broadcast‐based ARQ protocols in multi‐hop wireless sensor networks

Achieving reliable and energy-saving broadcast is the main issue discussed in this study. Firstly, a multi-hop broadcast model is introduced, and the energy consumption and reliability of the network are defined in this study. Then five broadcast-based automatic repeat request (ARQ) protocols (automatic retransmission N times, stop-and-wait end-to-end-ARQ, stop-and-wait hop-by-hop-ARQ, stop-and-wait hop-by-hop oriented implicit ARQ, stop-and-wait hop-by-hop implicit and explicit ARQ) are proposed to realise the reliable transmission. Secondly, based on five protocols, the relationship between the system reliability and the number of retransmissions of the root node is established analytically, and the maximum number of retransmissions is solved under the required system reliability. Thirdly, the energy consumptions of the root node are calculated, and then the analytical expressions of the minimum system energy consumption are obtained separately according to five broadcast-based retransmission mechanisms. Finally, the relationships between the maximum number of retransmissions, energy consumption and reliability, the broadcast probability and feedback probability are discussed in the numerical analysis. Specially, for better energy-saving, the modulation technique should be adopted to choose suitable protocol based on a dynamic hop threshold.

Selective Dynamic Coded Cooperative Communications for Multi-Hop Underwater Acoustic Sensor Networks

Due to the limitation of acoustic velocity in underwater environments, propagation delay is a horrible problem in multi-hop underwater acoustic sensor networks (UW-ASNs). In this paper, we proposed an improved scheme of dynamic coded cooperation called selective dynamic coded cooperation (S-DCC) for the multi-hop UW-ASNs, aiming at reducing the end-to-end delay and improving the transmission efficiency. In S-DCC scheme, the cooperative node actively transmits blocks with limited redundancy; yet the receiver only selectively receives those cooperative blocks depending on its own decoding conditions. The S-DCC scheme can utilize the retransmission mechanism adequately to eliminate the waiting time and drastically shorten the overall transmission time, the gain of which increases linearly with the number of hops. Concerning the transmission delay and energy consumption, we evaluated the performances with the different maximum number of retransmissions and different data burst sizes for the proposed S-DCC scheme and other compared schemes. The simulation results showed that the proposed S-DCC scheme could achieve decent outage performance and reduce the end-to-end delay effectively without extra energy consumption compared with other existing schemes, especially for the cases with low transmission signal to noise ratio. Sea test data were also adopted to further verify the conclusions.

Channel Constrained Multiple Selective Retransmissions for OFDM System: BER and Throughput Analysis

Hybrid automatic repeat request (HARQ) retransmission is an effective method to combat time-variant channel fading. Conventional HARQ methods initiate retransmission of failed packet without exploiting channel knowledge. When a packet fails, retransmission of data corresponding to high gain sub-carriers of an orthogonal frequency division multiplexing (OFDM) modulation is not necessary and deteriorates the throughput of the communication system. In this paper, we propose accumulated channel norm constrained selective retransmission (CNSR) at physical layer (PHY) in conjunction with HARQ method, which enhances throughput of the transceiver without compromising latency. When a packet fails, medium access control (MAC) layer requests retransmission of the failed packet. The proposed CNSR method initiates retransmission of data at PHY layer transmitted over low signal-to-noise ratio sub-carriers using outdated channel information. The transceiver pair continues retransmission of the failed packet until target channel norm of the sub-carriers is achieved or maximum number of retransmissions are completed. We maximize throughput by optimizing threshold on channel norm for OFDM modulation. We also present an upper bound on bit error rate and throughput analysis of the proposed method. The proposed method achieves higher throughput as compared with the existing Chase combining with selective repeat and conventional Chase combining schemes with and without forward error correction codes.

Protocol for Energy-Efficiency in Networked Control Systems Based on WSN.

This paper proposes a new communication protocol for output-feedback control through multi-hop Wireless Sensor Network (WSN). The protocol is based on a Hop-by-Hop transport scheme and is especially devised to simultaneously fulfill two conflicting criteria: the network energy consumption and the stability/performance (in terms of norm) of the closed-loop system. The proposed protocol can be implemented by means of three heuristics, basically using distinct rules to control the maximum number of retransmissions allowed in terms of the voltage level of the batteries of the network nodes. As another contribution, a Markov jump based representation is proposed to model the packet loss in the communication channel, giving rise to a systematic procedure to determine the transition probability matrix and the Markov chain operation modes of a network with multiple information sources. The synthesis of the output-feedback controller is made in two steps (observer filter plus a state-feedback controller) for the Markov model assuming partial availability of the operation modes. The efficiency and applicability of the communication protocol is illustrated by means of a numerical experiment, based on a physical model of a coupled tanks plant. The features of each heuristic of implementation of the proposed protocol are presented in the numerical comparisons.

Rate selection for wireless multicast system adopting incremental redundancy type hybrid-ARQ

We propose a rate selection method in wireless multicast systems where an incremental redundancy type hybrid automatic repeat request (HARQ-IR) scheme is employed under Rayleigh block-fading channels. We aim at maximizing the long-term average transmission rate (LATR) while the maximum number of retransmissions is limited to L — 1 and the probability that at least one user fails to decode a message within L (re)transmissions is limited to e. We consider two user-distribution scenarios: 1) Receivers are located at the same distance from the source and 2) receivers are uniformly distributed in a circular cell. For the former scenario, we derive two closed-form approximations for the LATR. Among the two, the simpler one is expressed as $\mu - {{Q^{-1}(1-0.5^{1/U})\sigma}\over{\sqrt L}}$ for a large L value where U, μ, σ, Q denote the number of receivers, the ergodic capacity, and the deviation of the mutual information for one HARQ round, and the complementary Gaussian cumulative distribution function, respectively. We also analyze the second scenario using point mass approximation. We show that the HARQ-IR scheme outperforms the conventional fixed-length coding and Chase-combining type HARQ schemes in wireless multicast network for both scenarios.

Efficiency of Power Ramping During Random Access in LTE

In this paper, we examine the impact of power ramping, number of retransmission attempts, and limitations of the physical downlink control channel (PDCCH) on the performance of random access in Long Term Evolution/Long Term Evolution-Advanced networks. We demonstrate that positive feedback exists between the maximum number of retransmissions, age-based power ramping, and PDCCH deficiency. As the result, system capacity is decreased and performance deteriorates abruptly under moderate to high traffic intensity. We show that, under power ramping and default PDCCH capacity, increasing the number of retransmissions beyond 1 or at most 2 does not bring any benefits and, in fact, is detrimental to system capacity. Increasing PDCCH capacity would enable the benefits of power ramping and allow more retransmission attempts. However, increasing the number of retransmissions combined with power ramping, while helpful under moderate to high load, will decrease system capacity.

Adaptation for the retransmission in VoIP applications

An adaptive retransmission scheme can be used for voice over Internet protocol services to provide a certain level of quality of service. However, parameters used for adaptive retransmission must be selected carefully due to unintended frame loss in the channel and in the playout buffer. In this paper, we evaluate the frame loss rate (FLR) in the output of playout buffer for the adaptive retransmission. This paper also proposes a parameter selection algorithm based on the evaluation. The proposed algorithm controls the probability of starting the retransmission process and the maximum number of retransmissions considering a bursty channel model and the loss in the playout buffer. The evaluation results show that the proposed scheme can select the proper parameters to provide a desired FLR in the output of the playout buffer. In addition, the measured mean opinion score-listening quality objective, which is an expected objective quality score, also shows that the proposed algorithm has a potential to provide a desired level of quality score.

On HARQ-IR for Downlink NOMA Systems

Non-orthogonal multiple access (NOMA) can exploit the power difference between the users to achieve a higher spectral efficiency. Thus, the power allocation plays a crucial role in NOMA. In this paper, we study the power allocation for hybrid automatic repeat request (HARQ) in NOMA with two users. For the power allocation, we consider the error exponents of the outage probabilities in HARQ with incremental redundancy (IR) and derive them based on large deviations. While a closed-form expression for the error exponent (or rate function) without interference is available, there is no closed-form expression for the error exponent with interference. Thus, we focus on the derivation of a lower bound on the error exponent in this paper. Based on the error exponents, we formulate a power allocation problem for HARQ-IR in NOMA to guarantee a certain low outage probability for a given maximum number of retransmissions. From the simulation results, we can confirm that it is possible to guarantee a certain outage probability by the proposed power allocation method.

Efficient Image Transmission Schemes over Zigbee‐Based Image Sensor Networks

Image transmission is one of the biggest challenges in wireless sensor networks because of the limited resource on sensor nodes. We proposed two image transmission schemes driven by reliability and real time considerations in order to transfer JPEG images over Zigbee-based sensor networks. By adding two bytes counter in the header of data packet, we can easily solve the repeated data reception problem caused by retransmission mechanism in traditional Zigbees network layer. We proposed an efficient retransmission and acknowledgment mechanism in Zigbees application layer. By classifying different data reception response events, we can provide data packets with differential responses and ensure that image packets can be transferred quickly even with large maximum number of retransmission. Practical results show the effectiveness of our solutions to make image transmission over Zigbee-based sensor networks efficient.

Special issue on energy‐efficient wireless communication networks with QoS

Special issue on energy‐efficient wireless communication networks with QoS

ARS: An Adaptive Retransmission Scheme for Contention-Based MAC Protocols in Underwater Acoustic Sensor Networks

Due to the limited capacity and high propagation delay of underwater communication channels, contention-based media access control (MAC) protocols suffer from a low packet delivery ratio (PDR) and a high end-to-end (E2E) delay in underwater acoustic sensor networks due to the reliance on packet retransmission for reliable data delivery. In order to address the problem of low performance, we propose a novel adaptive retransmission scheme, named ARS, which dynamically selects an optimal value of the maximum number of retransmissions, such that the successful delivery probability of a packet is maximized for a given network load. ARS can be used for various contention-based protocols and hybrid MAC protocols that have contention periods. In this paper, ARS is applied to well-known contention-based protocols, Aloha and CSMA. Simulation results show that ARS can achieve significant performance improvement in terms of PDR and E2E delay over original MAC protocols.

Stability and Capacity of Regular Information Theory and Communication Networks

The problem of throughput optimization in decentralized wireless networks with spatial randomness under queue stability and packet loss constraints are investigated. Two key performance measures are analyzed, namely the effective link throughput and the network spatial throughput. Specifically, the double of medium access probability, coding rate, and maximum number of retransmissions that maximize each throughput metric is analytically derived for a class of Poisson networks, in which packets arrive at the transmitters following a geometrical distribution. Necessary conditions so that the effective link throughput and the network spatial throughput are stable and achievable under bounded packet loss are determined, as well as upper bounds for both cases by considering the unconstrained optimization problem. It results show in which system configuration stable achievable throughput capacity obtained as a function of the network density and the arrival rate. Finally the time delay has get reduced at high rate. The throughput for the two nodes has been found efficiently.

Timer‐based power management for infrastructure IEEE 802.11 WLAN with unreliable wireless links

SUMMARYEfficient power management is a critical requirement for the battery‐operated portable electronic devices incorporating wireless transceivers to have a longer runtime. The existing timer‐based power management (TPM) is able to balance energy saving and quality of service requirements by tuning the values of its idle and doze timers. In this paper, the TPM applied in the infrastructure IEEE 802.11 wireless local area network with unreliable wireless links, referred to as TPM‐UWL, is presented. A novel stochastic analysis model is developed for TPM‐UWL, based on which the probabilities that a mobile station (STA) is at active, dozing, and idle states are obtained. Additionally, the number of buffered frames at the access point and the sleeping STA, the STA's average power consumption, and a frame's average delay under TPM‐UWL are derived. Further, the optimization problem that minimizes power consumption under the constraints of delay and buffer size is presented, which enables an STA to set its maximum number of retransmissions and the values of the idle and doze timers in the medium access control layer such that power consumption is minimized, while the constraints of delay and buffer size are satisfied. Copyright © 2014 John Wiley & Sons, Ltd.

Throughput Optimization in Wireless Networks Under Stability and Packet Loss Constraints

The problem of throughput optimization in decentralized wireless networks with spatial randomness under queue stability and packet loss constraints is investigated in this paper. Two key performance measures are analyzed, namely the effective link throughput and the network spatial throughput. Specifically, the tuple of medium access probability, coding rate, and maximum number of retransmissions that maximize each throughput metric is analytically derived for a class of Poisson networks, in which packets arrive at the transmitters following a geometrical distribution. Necessary conditions so that the effective link throughput and the network spatial throughput are stable and achievable under bounded packet loss are determined, as well as upper bounds for both cases by considering the unconstrained optimization problem. Our results show in which system configuration stable achievable throughput can be obtained as a function of the network density and the arrival rate. They also evince conditions for which the per-link throughput-maximizing operating points coincide or not with the aggregate network throughput-maximizing operating regime.

Adaptive HARQ With Non-Binary Repetition Coding

We consider Incremental Redundancy Hybrid Automatic Repeat reQuest (IR-HARQ) in which the code rate and modulation of the initial transmission and all retransmissions are adjusted based on average channel statistics. In the absence of instantaneous channel state information at the transmitter (CSIT), we present a method which computes, prior to transmission, the optimum code rates and modulations and explicitly considers a given maximum number of retransmissions. For the case that additional feedback on CSI of previous transmission attempts is available, we present two heuristic schemes which exploit this knowledge and offer increased throughput at the cost of higher computational complexity. We employ a rate-adaptive non-binary LDPC coding scheme which makes use of non-binary repetitions. While this coding scheme is particularly well-suited for adaptive IR-HARQ, we note that the presented analysis can be applied to any other channel code which employs soft decoding.