Hybrid time slot allocation algorithm based on LoRa Internet of things

To improve the efficiency and stability of data transmission in the long-range (LoRa) Internet of things (IoT),a hybrid time slot allocation algorithm is proposed, which implements a priority mechanism with high-priority nodes sending data in fixed time slots and low-priority nodes using the carrier sense multiple access (CSMA) algorithm to compete for shared time slots to transmit data. To improve network efficiency, a gateway is used to adjust the time slot allocation policy according to network status and balance the number of fixed and shared time slots. And more, a retransmission time slot is added to the time slot allocation algorithm, which redesigns the time frame structure, and adopts a retransmission mechanism to improve communication reliability. Simulation and measurement results show that the packet loss rate and transmission delay of the proposed hybrid algorithm are smaller than those of the fixed slot allocation algorithm, making the proposed algorithm more suitable for LoRa IoT.     

Energy-efficient cluster-based cooperative FEC in wireless networks

In this article, we introduce a novel link layer cooperation technique in noisy wireless networks to improve overall system throughput and reliability, and to reduce the cost of retransmission and energy consumption. Under a cluster-based network design, Chase combining (Chase, IEEE Transactions on Communications 33(5):385–393, 1985) is used together with FEC to improve the link layer reliability. This approach is different from how combining is used in the conventional hybrid ARQ, which is in a sequential way. The analytical results and the simulations show that with the cooperation of nodes in a clustering network, the link reliability will be greatly improved with the same power consumption. We also show that not only transmission power is greatly reduced, but also the aggregate power consumption for a successful transmission and reception.     

Energy Efficient and Reliable ARQ Scheme (E^2R-ACK) for Mission Critical M2M/IoT Services

Wireless sensor networks (WSNs) are the main infrastructure for machine to machine (M2M) and Internet of thing (IoT). Since various sophisticated M2M/IoT services have their own quality-of-service (QoS) requirements, reliable data transmission in WSNs is becoming more important. However, WSNs have strict constraints on resources due to the crowded wireless frequency, which results in high collision probability. Therefore a more efficient data delivering scheme that minimizes both the transmission delay and energy consumption is required. This paper proposes energy efficient and reliable data transmission ARQ scheme, called energy efficient and reliable ACK (E \(^2\) R-ACK), to minimize transmission delay and energy consumption at the same time. The proposed scheme has three aspects of advantages compared to the legacy ARQ schemes such as ACK, NACK and implicit-ACK (I-ACK). It consumes smaller energy than ACK, has smaller transmission delay than NACK, and prevents the duplicated retransmission problem of I-ACK. In addition, resource considered reliability (RCR) is suggested to quantify the improvement of the proposed scheme, and mathematical analysis of the transmission delay and energy consumption are also presented. The simulation results show that the E \(^2\) R-ACK scheme achieves high RCR by significantly reducing transmission delay and energy consumption.     

Performance Modeling of the Fast and Reliable Two-Layer Retransmission for CDMA Systems

1　Introduction　With the proliferation of the World Wide Web (WWW)in our daily life, a number of wireless data services[1] suchas voice, audio, video streaming, file and web downloadingalso need to be supported in the wireless access networks.To bring the WWW traffic to the wireless mobile devices, itis important that a suitable protocol or standard is chosen tocater to the growing demands of data services over wirelesschannels which could handle a wide variety of multimediatraffic with …     

Design of MAC-defined aggregated ARQ schemes for IEEE 802.11n networks

Based on the IEEE 802.11n standard, frame aggregation is considered one of the major factors to improve system performance of wireless local area networks (WLANs) from the medium access control (MAC) perspective. In order to fulfill the requirements of high throughput performance, feasible design of automatic repeat request (ARQ) mechanisms becomes important for providing reliable data transmission. In this paper, two MAC-defined ARQ schemes are proposed to consider the effect of frame aggregation for the enhancement of network throughput. An aggregated selective repeat ARQ (ASR-ARQ) algorithm is proposed, which incorporates the conventional selective repeat ARQ scheme with the consideration of frame aggregation. On the other hand, the aggregated hybrid ARQ (AH-ARQ) protocol is proposed to further enhance throughput performance by adopting the Reed-Solomon block code as the forward error correction (FEC) scheme. Novel analytical models based on the signal flow graph are established in order to realize the retransmission behaviors of both schemes. Simulations are conducted to validate and compare the proposed ARQ mechanisms with existing schemes based on service time distribution. Numerical results show that the proposed AH-ARQ protocol outperforms the other retransmission schemes owing to its effective utilization of FEC mechanism.     

Energy consumption optimization for self‐powered IoT networks with non‐orthogonal multiple access

Energy harvesting (EH) has been considered as one of the promising technologies to power Internet of Things (IoT) devices in self‐powered IoT networks. By adopting a typical harvest‐then‐transmit mode, IoT devices with the EH technology first harvest energy by using wireless power transfer (WPT) and then carry out wireless information transmission (WIT), which leads to the coordination between WPT and WIT. In this paper, we consider optimizing energy consumption of periodical data collection in a self‐powered IoT network with non‐orthogonal multiple access (NOMA). Particularly, we take into account time allocation for the WPT and WIT stages, node deployment, and constraints for data transmission. Moreover, to thoroughly explore the impact of different multiple access methods, we theoretically analyse and compare the performance achieved by employing NOMA, frequency division multiple access (FDMA), and time division multiple access (TDMA) in the considered IoT network. To validate the performance of the proposed method, we conduct extensive simulations and show that the NOMA outperforms the FDMA and TDMA in terms of energy consumption and transmission power.     

RESIDENT: a reliable residue number system-based data transmission mechanism for wireless sensor networks

Retransmission is the most common data transmission mechanism in wireless sensor networks, and can improve data transmission reliability via the acknowledgement mechanism. However, the simple acknowledgement retransmission is associated with some negative factors such as data delay, low throughput among others. To overcome the shortcomings of the retransmission mechanism, redundancy coding is introduced to wireless communications, which has been widely applied in 4G communication. Unfortunately, not all redundant erasure codes are suitable for wireless sensor networks, as nodes’ energy, processing power, and storage capacity are all limited. Moreover, we also need to consider data transmission delay. Therefore, to improve data transmission reliability, we must take into account the complexity of algorithm, data transmission delay, node energy consumption, and other factors. In this article, we propose a REliable reSIDuE number system-based data transmission mechanism (RESIDENT) for WSNs, which can improve data transmission reliability via hybrid automatic repeat requests in hop-by-hop scenarios. In order to decrease the complexity of decoding, we present our algorithm and the proof of correctness, and report the performance using extensive set of simulation experiments. Our simulation results show that RESIDENT exhibits a good performance when compared to the previous studies, not only in terms of reliable data transmission, but also in end-to-end delay and energy consumption.     

An Efficient FIR Filter Based on Hardware Sharing Architecture Using CSD Coefficient Grouping for Wireless Application

Current research emphasis on IoT (Internet-of-Things) to enable physical objects to connect, co-ordinate among themselves in a ubiquitous manner. Specifically, for this type of applications, the quality of wireless communication is indeed considered vital to enhance the reliability of battery operated IoT devices. Moreover, these devices operate on unlicensed bands creating heavy congestion on spectrum. Interestingly operating these devices on Cognitive Radio band avoids the spectrum shortage problem by exploiting the dynamic spectrum access capabilities. Cognitive relaying for IoT applications ensures reliable communication through interference mitigation among co-existing IoT devices. In this paper, we therefore propose spectrally efficient two-path decode and amplify relaying technique in three time slots through network-coded co-operation of Primary user and Secondary User. To address the interference issues, optimum power allocation is formulated as a convex optimization problem solved through a modeling system named CVX. Thereby we achieve co-operative diversity without the need for additional antennas for IoT networks. Performance evaluation compares the Bit Error Rate for different relaying schemes with and without optimum power allocation. Our simulation results ensure that the probability of error is minimized and rate is maximized by our proposed algorithm.

     

一种基于网络编码的重传算法研究

无线网络中,节点发送的数据分组传输失败后,执行重传机制。传统的重传机制ARQ由于在一次重传中只能发送一个丢失的数据分组,因此传输效率比较低。利用网络编码技术和AQR重传机制,我们可以在重传中使用网络编码,广播发送由多个丢失数据分组编码得到的编码分组,从而提高重传效率。本文中我们提出一种将网络编码应用于多个发送方多个接收方(MSMR)无线网络中的算法RMBNC。理论推导和仿真分析验证了我们提出的算法的有效性。     

A collision detection method for multicast transmissions in CSMA/CA networks

Compared to unicast traffic, multicast is not protected by any ARQ mechanism in 802.11 networks: collisions with other multicast and unicast transmissions are not detected and senders will not adapt to the contention situation by backing off. This results in an unreliable service for multicast transmissions. We propose early multicast collision detection (EMCD), an algorithm with the purpose of increasing the reliability of multicast transmissions in the MAC layer of an IEEE 802.11 network. A multicast sender using it will introduce an early pause in a transmission, perform a clear channel assessment (CCA), and if a collision is detected abort the transmission after a fixed time and schedule a retransmission. This allows for detecting collisions with both multicast and unicast transmissions but also adapting to the contention situation. A probabilistic analysis is provided showing that EMCD is more efficient than ordinary multicast and can be made even more efficient by tuning parameters. Simulations show that EMCD leads to increased reliability for multicast transmissions. Copyright © 2006 John Wiley & Sons, Ltd.     

Cross-layered retransmission schemes for TCP-based services

Various retransmission schemes for wireless communication systems have been used to improve performance such as reliability and throughput. Each retransmission scheme is designed to improve the performance according to characteristics of each layer of protocol stacks, such as delay components and error control. Especially, a cross-layered retransmission scheme has been proposed to maximize the spectral efficiency by combining a retransmission scheme and adaptive modulation and coding (AMC). However, the cross-layered retransmission scheme is designed for performance improvement at the wireless access networks. The end-to-end performance is not taken into account for modeling of the cross-layered retransmission schemes. It is difficult to design retransmission schemes for the end-to-end performance improvement. In this paper, we analyze the delay and the throughput at the transport layer for the end-to-end performance when a system uses a cross-layered retransmission scheme and the transmission control protocol as the reliable transmission protocols. We also propose a cross-layered retransmission strategy, AMC combined with automatic repeat request (ARQ) and hybrid ARQ (HARQ), to improve end-to-end throughput. From the evaluation results, it is shown that the proposed cross-layered retransmission strategy is suitable for delay insensitive services that require high throughput.     

基于无线电波广播特性的多用户自动请求重传

提出了一种多用户自动请求重传的方法.采用网络编码基站将多个用户的重传数据包线性组合在一起后广播;用户利用置信传播算法从中检测出基站发给本用户的重传数据包,并和以前传输的数据包软合并后译码.分析表明:多用户自动请求重传能够将无线通信系统的频谱效率提高10%左右,并且复杂度和单用户自动请求重传相近.另外,该方法适用于所有类...     

Power control and capacity analysis for a packetized indoormultimedia DS-CDMA network

This paper proposes a packetized indoor wireless system using direct-sequence code-division multiple-access (DS-CDMA) protocol. The indoor radio environment is characterized by slow Rayleigh fading with or without lognormal shadowing. The system supports multimedia services with various transmission rates and quality of service (QoS) requirements and allows for seamless interfacing to asynchronous transfer mode (ATM) broadband networks. All packets are transmitted with forward error correction (FEC) using convolutional code for voice packets and Bose-Chaudhuri-Hocquenghem (BCH) code for data packets with an automatic retransmission request (ARQ) protocol and for video packets without ARQ. A queueing model is used for servicing data transmission requests. A power control algorithm is proposed for the system, which combines closed-loop power control with channel estimation to give the best performance. The cell capacity of each traffic type and various multimedia traffic configurations in both single-cell and multiple-cell networks are evaluated theoretically under the assumption of perfect power control. The effect of power control imperfection on the capacity using the proposed power control algorithm is investigated by computer simulation     

The MIMO ARQ Channel: Diversity–Multiplexing–Delay Tradeoff

In this paper, the fundamental performance tradeoff of the delay-limited multiple-input multiple-output (MIMO) automatic retransmission request (ARQ) channel is explored. In particular, we extend the diversity-multiplexing tradeoff investigated by Zheng and Tse in standard delay-limited MIMO channels with coherent detection to the ARQ scenario. We establish the three-dimensional tradeoff between reliability (i.e., diversity), throughput (i.e., multiplexing gain), and delay (i.e., maximum number of retransmissions). This tradeoff quantifies the ARQ diversity gain obtained by leveraging the retransmission delay to enhance the reliability for a given multiplexing gain. Interestingly, ARQ diversity appears even in long-term static channels where all the retransmissions take place in the same channel state. Furthermore, by relaxing the input power constraint allowing variable power levels in different retransmissions, we show that power control can be used to dramatically increase the diversity advantage. Our analysis reveals some important insights on the benefits of ARQ in slow-fading MIMO channels. In particular, we show that 1) allowing for a sufficiently large retransmission delay results in an almost flat diversity-multiplexing tradeoff, and hence, renders operating at high multiplexing gain more advantageous; 2) MIMO ARQ channels quickly approach the ergodic limit when power control is employed. Finally, we complement our information-theoretic analysis with an incremental redundancy lattice space-time (IR-LAST) coding scheme which is shown, through a random coding argument, to achieve the optimal tradeoff(s). An integral component of the optimal IR-LAST coding scheme is a list decoder, based on the minimum mean-square error (MMSE) lattice decoding principle, for joint error detection and correction. Throughout the paper, our theoretical claims are validated by numerical results     

Adaptive link layer strategies for energy efficient wireless networking

Low power consumption is a key design metric for portable wireless network devices where battery energy is a limited resource. The resultant energy efficient design problem can be addressed at various levels of system design, and indeed much research has been done for hardware power optimization and power management within a wireless device. However, with the increasing trend towards thin client type wireless devices that rely more and more on network based services, a high fraction of power consumption is being accounted for by the transport of packet data over wireless links [28]. This offers an opportunity to optimize for low power in higher layer network protocols responsible for data communication among multiple wireless devices. Consider the data link protocols that transport bits across the wireless link. While traditionally designed around the conventional metrics of throughput and latency, a proper design offers many opportunities for optimizing the metric most relevant to battery operated devices: the amount of battery energy consumed per useful user level bit transmitted across the wireless link. This includes energy spent in the physical radio transmission process, as well as in computation such as signal processing and error coding. This paper describes how energy efficiency in the wireless data link can be enhanced via adaptive frame length control in concert with adaptive error control based on hybrid FEC (forward error correction) and ARQ (automatic repeat request). Key to this approach is a high degree of adaptivity. The length and error coding of the atomic data unit (frame) going over the air, and the retransmission protocol are (a) selected for each application stream (ATM virtual circuit or IP/RSVP flow) based on quality of service (QoS) requirements, and (b) continually adapted as a function of varying radio channel conditions due to fading and other impairments. We present analysis and simulation results on the battery energy efficiency achieved for user traffic of different QoS requirements, and describe hardware and software implementations.     

On the average rate performance of hybrid-ARQ in quasi-static fading channels

The problem of efficient communication over a scalar quasi-static fading channel is considered. The single-layer transmission (SLT) and multi-layer transmission (MLT) schemes do not require any knowledge of the channel state information (CSI) at the transmitter, but their performance is also limited. It is shown that using Hybrid-ARQ (HARQ) can significantly improve the average rate performance, provided that the rate assignment between different ARQ rounds is carefully chosen. The average rate performance of several HARQ schemes is optimized and compared. In addition, optimal power allocation among retransmissions is derived and shown to further increase the average rate. This power allocation gain is remarkable at low signal-to-noise ratio (SNR), but becomes negligible at high SNR. Comparison of two different types of limited feedback, sequential feedback (ARQ) and one-shot feedback (quantized CSI), is made from several perspectives. Although the optimization problem is formed with respect to the average rate, simulation results give a comprehensive comparison under different metrics, including average rate, outage probability, and the combination of both. Substantial performance improvement is observed with even one ARQ retransmission in all simulations. More importantly, this gain appears to be robust with respect to the fading distributions.     

MBC中的Ⅰ型HARQ改进方案

在流星突发通信中,为确保数据有效可靠地传输,通常采用前向纠错与自动重传请求相结合的方法,即HARQ。传统I型HARQ效率较低,难以满足大数据量通信。为了有效利用流星信道,建立了流星突发通信模型,提出了一种基于分集合并的Ⅰ型HARQ方案,推导出了有效信噪比公式,讨论了信噪比改善系数和最大重传次数,并进行了仿真。仿真结果表明,该方案可有效提高可靠性,增加吞吐量。     

NOMA物联网下多UAV辅助MEC系统的资源分配

为解决偏远地区或突发灾害等场景中的物联网(Internet of Things, IoT)设备的任务计算问题,构建了一个非正交多址接入(Non-orthogonal Multiple Access, NOMA)-IoT(NOMA-IoT)下多无人机(Unmanned Aerial Vehicle, UAV)辅助的NOMA多址边缘计算(Multiple Access Edge Computing, MEC)系统。该系统中设备的计算能耗、卸载能耗和MEC服务器计算能耗直接受同信道干扰、计算资源和发射功率的影响,可通过联合优化卸载策略、计算资源和发射功率最小化系统加权总能耗。根据优化问题的非凸性和复杂性,提出了一种有效的迭代算法解决：首先,对固定卸载策略,计算资源和发射功率分配问题可通过连续凸逼近转化为可解的凸问题;其次,对固定计算资源和发射功率,利用联盟形成博弈解决卸载策略问题,以最小化IoT设备之间的同信道干扰。仿真结果表明,较OMA接入方式,NOMA接入方式减少本地计算能耗、卸载能耗及计算能耗约20%;较无卸载策略方法,包含卸载策略方法在减少系统加权总能耗方面效果较为明显。     

RIS辅助卫星物联网中基于压缩感知的SCMA信号重构

卫星物联网是未来6G网络重要组成部分,在地面部署可重构智能反射面（Reconfigurable Intelligence Surface, RIS）则能进一步增强天地之间信号的传输能力;然而海量设备的接入和检测,以及RIS的引入带来的较高复杂度,给系统设计与实现带来挑战。针对卫星物联网设备和业务稀疏特性,本文提出了一种基于压缩感知的信号重构算法,旨在提高系统的接入用户数和检测成功率,同时降低检测的复杂度。首先,介绍了RIS辅助的卫星物联网系统架构,构建了天地信道模型和星上接收信号模型。然后考虑到卫星物联网地面终端的稀疏性和业务的稀疏性,结合稀疏码分多址（Sparse Code Multiple Access,SCMA）和压缩感知的信号处理方法,通过合理设计SCMA中的稀疏码字,将多用户检测转化为压缩感知理论中的信号重构。最后提出了一种演进的近似消息传播算法（Evolved Approximate Message-Passing,EAMP）来实现压缩感知中的信号重构。仿真结果表明,RIS辅助的SCMA系统与功率域的非正交多址接入技术相比可以提高系统的吞吐量性能,同时EAMP算法相比传统的SIC算法具有更高的正确检测概率和更低的算法复杂度。      

A Modified Selective-Repeat Type-II Hybrid ARQ System and Its Performance Analysis

The hybrid ARQ scheme with parity retransmission for error control, recently proposed by Lin and Yu [1], [2], is quite robust. This scheme provides both high system throughput and high system reliability. In this paper, a modified Lin-Yu hybrid ARQ scheme is presented. The modified scheme provides a slightly better throughput performance than the original Lin-Yu scheme; however, it is more flexible in utilizing the error-correction power of a code. The modified scheme can be incorporated with a rate 1/2 convolutional code using Viterbi decoding. Furthermore, the pure selectiverepeat ARQ is a degenerated case of the modified scheme in selective mode. Lin and Yu analyzed their scheme only for a receiver buffer of sizeNwhereNis the number of data blocks that can be transmitted in a round-trip delay interval. No analysis for other buffer sizes was given. In this paper, the throughput performance of the modified Lin-Yu scheme is analyzed for any size of receiver buffer. Consequently, the throughput efficiency of the pure selective-repeat ARQ for any receiver buffer size can be obtained. We also show that the modified scheme achieves the same order of reliability as a pure ARQ scheme.