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The Narrowband Internet of Things (NB-IoT) has been introduced in the 3rd Generation Partnership Project (3GPP) Rel-13 with the aim to provide low-cost, low-power, wide-area cellular connectivity for the Internet of Things. With the exponentially increasing number of connected wireless devices in the order of 100 billion, it has become crucial that researchers develop efficient resource management techniques to meet the 5th Generation (5G) quality of service (QoS) requirements. Recently, several research challenges including the low modulation data rates, energy-expensive channel coding techniques, and the fast-growing number of connected devices have been identified as some of the main issues encountered in the design and deployment of NB-IoT systems. In addition, several techniques have emerged in the literature to resolve some of these challenges of NB-IoT systems. However, the research activities towards the enhancement of the NB-IoT resource management are yet to continue in the next half-decade before, high data rates, energy-efficient, and scalable NB-IoT specifications can be released for the standardisation and commercialisation. Considering the limited number of existing surveys of such technical enhancement approaches in a broader perspective (i.e. energy efficiency, data rate performance and scalability) and also the non-existence, to the best of our knowledge, of a comparative survey, this paper seeks to elaborate, describe and compare the performances of such resources management approaches. Of the multiple NB-IoT resources, the focus of this paper is on the data rate, energy efficiency, and scalability enhancement schemes that have been proposed for the last three years. The contribution of the paper lies in the analysis, synthesis, comparison and summarised alignments of some of the major existing schemes towards identifying challenges faced by the NB-IoT development. Finally, this work seeks to identify research challenges, open questions, and opportunities that could arise from the existing techniques analysed.

A novel modulation technique termed as orthogonal frequency division multiplexing with subcarrier power modulation (OFDM-SPM) has been proposed for achieving spectral-efficient data transmission in wireless communication systems. OFDM-SPM utilizes the power of each subcarrier in an OFDM block as an extra degree of freedom to convey extra information bits besides the bits transmitted by conventional signal modulation. OFDM-SPM has originally been introduced with binary phase shift keying (BPSK) symbol modulation, and was shown to provide great gains and various merits such as doubling the spectral efficiency, reducing transmission power and transmission times by half. Displaying its capabilities as a scheme to be adopted for future wireless communication systems, a question detrimental to the adoption of OFDM-SPM has yet to be answered. This is whether the gains that OFDM-SPM brings persist when paired with higher order modulation schemes, especially two dimensional signal constellation schemes such as M-ary PSK. In this paper, OFDM-SPM is paired with quadrature phase shift keying (QPSK) symbol modulation as an example of a higher order two dimensional modulation scheme. The performance analysis of this scheme along with its numerical simulations are carried out where the bit error rate (BER) and throughput performances of the scheme are given in both an additive white Gaussian noise (AWGN), and multipath Rayleigh fading channels. These simulations are done for different power allocation policies. Unlike other 3D modulation methods, the results show that OFDM-SPM can be used with higher order modulation schemes while maintaining all the gains exhibited in OFDM-SPM with BPSK. This gives OFDM-SPM a unique advantage when compared to other 3D modulation schemes such as OFDM-IM and OFDM-SNM, which lose the gain in spectral efficiency as the modulation order becomes higher. Furthermore, the results of OFDM-SPM with QPSK were compared to that of conventional OFDM with 16-QAM symbol modulation. OFDM-SPM displayed superiority both in terms of BER and throughput achieving a gain of approximately 2.5-3 dB. These findings clearly point out that OFDM-SPM is a promising modulation scheme, which should be investigated more vigorously and considered as a strong candidate for adoption in future 6G and beyond wireless communication systems. This research was partly funded by TUBITAK under Grant/Award Number: 119E408.

IEEE 802.15.4 standard defines both media access control (MAC) and physical (PHY) layer protocols for low power consumption, low peak data rate, and low cost applications. Nowadays the most important feature of IEEE 802.15.4 is maximizing battery life. This paper is focusing how to achieve low average power consumption through assuming that the amount of data transmitted is short and that it is transmitted infrequently so as to keep a low duty cycle. The outcomes demonstrate that the phase shift estimation of Offset quadrature phase-shift keying (OQPSK) modulation has no impact on bit error rate (BER) if it is identical in the transmitter as same as in the receiver.

Most of the current research work on the Narrowband Internet of Things (NB-IoT) is focused on enhancing its network coverage. Many of the existing NB-IoT channel coding techniques are based on repeating transmission data and control signals as a way of enhancing the network&rsquo, s reliability and therefore, enabling long-distance transmissions. Although most of these efforts are made at the expense of reducing the energy consumption of the NB-IoT network, they do not always consider the channel conditions. Therefore, this work proposes a novel NB-IoT Energy-Efficient Adaptive Channel Coding (EEACC) scheme. The EEACC approach is a two-dimensional (2D) approach which not only selects an appropriate channel coding scheme based on the estimated channel conditions (dynamically classified as bad, medium or good from initial based on a periodically assessed BLER performance outcome) but also minimizes the transmission repetition number under a pre-assessed probability of successful transmission (based on the ratio of previous successful transmissions over the total number of transmissions). This results in creating a single mixed gradient based on which a higher or lower Modulating Coding Scheme (MCS) is selected on each transmission. It is aimed at enhancing the overall energy efficiency of the network by dynamically selecting the appropriate Modulation Coding Scheme (MCS) number and efficiently minimizing the transmission repetition number. Link-level simulations are performed under different channel conditions (good, medium, or bad) considerations to assess the performance of the proposed up-link adaptation technique for NB-IoT. The obtained results demonstrate that the proposed technique outperforms the existing Narrowband Link Adaptation (NBLA) as well as the traditional repetition schemes in terms of the achieved energy efficiency as well as network reliability, latency, and scalability.

We experimentally demonstrate a 28-Gbaud 16-QAM self-homodyne digital radio-over- 33.6km-7-core-fiber system with entropy coding for mobile fronthaul, achieving error-free carrier aggregation of 330 100-MHz 4096-QAM 5G-new-radio channels and 921 100-MHz QPSK 5G-new-radio channels with CPRI-equivalent data rate up to 3.73-Tbit/s., Comment: 3 pages, 44th European Conference on Optical Communication (ECOC 2018), Rome, Italy, 2018

We address in this paper the challenge of coping with asymmetric data rates in two-way relay channels. We consider a relay network comprising two sources and one relay. The sources communicate at different rates through the relay. That is, we assume that one source uses M 1 -QAM (quadrature amplitude modulation) and the other uses M 1 /M 2 -QAM hierarchical modulation where M 1 ≠ M 2 . For the underlying network, we consider two decode-and-forward (DF) relaying schemes. One scheme combines hierarchical zero padding and network coding (HZPNC) at the relay. The novelty of this scheme lies in the way the two signals (that have different lengths) are network-coded at the relay. The other scheme is referred to as opportunistic user selection (OUS) where the user with a better end-to-end channel quality is given priority for transmission. We analyze both schemes where we derive closedform expressions for the end-to-end (E2E) bit error rate (BER). Since the two schemes offer a trade-off between performance and throughput, we analyze and compare both schemes in terms of channel access probability and average throughput. We show that HZPNC offers better throughput and fairness for both users, whereas OUS offers better performance. We also compare the performance of HZPNC with existing schemes including the original zero padding, nesting constellation modulation and superposition modulation. We show through examples the superiority of the proposed HZPNC scheme in terms of performance and/or reduced complexity. Scopus

In this paper we present two resource allocations techniques in a visible light communication network with overlapping coverage areas due to the use of access points. Particularly, the first approach exploits the rate maximization criteria, and then aims at maximizing the network rate under constraints on minimum and maximum rates, while the other procedure focuses on achieving fairness in the rate of each user accessing the network. The proposed system relays on optical code division multiple access mechanism, and resource allocation is intended in terms of codes assigned to a given user. Simulation results have been addressed in terms of achievable data rates, outage probability and percentage of accessing users.

The dynamic growth of mobile communications technology is creating opportunities for economic growth, social empowerment, and grassroots innovation in developing countries. One of the areas with the greatest potential impact is in the contribution that mobile applications can make to agricultural and rural development (ARD), by providing access to information, markets, and services to millions of rural inhabitants. For both agricultural supply and demand, mobile phones can reduce waste, make delivery more efficient, and forge closer links between farmers and consumers. This report provides policymakers and development practitioners with a guide that facilitates the development and deployment of mobile applications for ARD. It also informs their understanding of the key drivers for promoting such applications and services in their countries. Using James Moore’s (1996) revised definition of ecosystems: economic communities based on interacting organizations and individuals the report identifies a wide range of players in the ecosystem for m-ARD apps, such as mobile network operators, m-app (mobile applications) providers, content providers, and various types of users. M-apps are software designed to take advantage of mobile technology and can be developed for technology besides mobile phones. But mobile phones have many key advantages: affordability, wide ownership, voice communications, and instant and convenient service delivery. As a result, there has been a global explosion in the number of m-apps, facilitated by the rapid evolution of mobile networks and by the increasing functions and falling prices of mobile handsets. M-apps are markedly different in developing countries because they typically run on second-generation (2G) phones rather than smartphones, which are far more common in developed countries. The report reviews country examples and extracts policy lessons and good practices. It also presents detailed studies of cases from Kenya, Philippines, and Sri Lanka, as well as summarizes 92 case studies from Africa, Asia, and Latin America. The goal is to provide a comprehensive understanding of the development impact, ecosystem, and business models for mobile applications in ARD. The report is intended to complement the recent ICT in Agriculture eSourcebook. One of the main findings is that an enabling platform (or platforms) is probably the most important factor for the development of m-ARD apps. Platforms can facilitate interactions among ecosystem players, increase access to users, provide technical standards, and incorporate payment mechanisms.

Cooperative communication is shown to be an efficient method of combating fading in wireless networks. By "sharing" their antennas cooperating single-antenna nodes create a virtual multi-antenna system and therefore, benefit from spatial diversity. Network coding being a particular cooperative communication technique provides substantial gains in data rate, especially in networks with many sink nodes. By allowing intermediate nodes of a network to mix the incoming data streams, one can achieve the multicast capacity. Recently, Xiao and Skoglund showed that binary network coding (BNC) is not optimal for multi-user multi-relay networks in terms of diversity and proposed diversity network coding (DNC) scheme that outperforms BNC approach. Following this approach we examine potential diversity gains of using the DNC scheme for multi-source line networks. We show that the DNC technique outperforms both conventional time-orthogonal transmission and the BNC scheme. Further, the problem of optimal scheduling of the transmission is explored. We formulate the optimization problem and propose efficient solutions. Numerical results are presented to support theoretical findings. Refereed/Peer-reviewed

In this paper, we investigate the effects of asymmetric frequency-dependent joint transmit-receive I/Q imbalance on the performance of multiple beamforming MIMO OFDM systems. We derive the throughput-maximizing TX/RX beamforming coefficients taking into account I/Q imbalance effects. In addition, we propose a low-complexity pilot-aided scheme for the estimation of the channel and I/Q imbalance parameters. Our simulation results demonstrate that the proposed generalized multiple beamforming scheme is effective in mitigating I/Q imbalance effects and by using multiple beamforming data rate can be increased at the expense of increased error rate. 2012 IEEE. Scopus

To optimize performance of ad hoc networks, the contradicting objectives: energy conservation and high data rate realization need to be jointly considered. In such a case, network interference need to be controlled in a manner that users transmit at minimum power enough to sustain the transmission. This paper proposes a joint power and rate adaptation in ad hoc network based on coupled interference minimization (PRIM) where the formulated network utility maximization (NUM) is solved using reverse engineering based on Karush-Kuhn-Tucker (KKT) conditions. In that way, users determine their transmit power and data rate based on their local observations (coupled interference). Pricing mechanism is employed in PRIM to restrict users from self-interest behaviours. It is demonstrated theoretically that PRIM satisfies the conditions of the super-modular games such that the local optimality is always the global optimality. Simulation results have shown that adapting transmits power and data rates based on the coupled interference (i.e. link dynamics) can improve the performance of ad hoc networks.

The wide range of wireless body area network (WBAN) applications gives rise to different system requirements for the carrier frequencies and data rates. In order to accommodate various standards in WBAN applications, a universal receiver system with good performance and low power is highly desirable. The subsampling receiver architecture is one of the promising receiver architectures that might fulfill the features of low power consumption and reconfigurability. However, there are two main concerns, namely the frequency stability and noise performance. In order to overcome these problems, a novel subsampling receiver architecture with two sampling branches as well as a new compensation algorithm are proposed and analyzed in this paper. The frequency stability and noise performance of the receivers can be greatly improved using this architecture. Simulation in different scenarios is carried out, and the results verify the effectiveness of the proposed architecture. © 2011 IEEE.

We investigate an outage optimal adaptive resource allocation scheme for the upstream of two-hop OFDMA based decode-and-forward cooperative relay systems. The objective of this work is to design resource allocation strategy, which addresses the needs of the users minimizing their outage probability. This scheme utilizes the subchannel-pairing and proportional fairness in two-hop multiuser multirelay network to achieve the user required percentage throughput ( i.e., if the user's application can tolerate 5% outage then guaranteeing the 100% availability is actually a wastage of scarce radio resources). Using outage optimal resource allocation scheme, we achieve the complimentary fairness along with the required data rate on each node. Simulation results show that the proposed scheme achieve better throughput-fairness trade-off compared to proportional fair scheduling (PFS) and MaxMin resource allocation schemes. 2011 IEEE. Scopus

During the last few years, several authors have studied the performance of many different types of channel codes for cooperative communication systems. Some of these codes include Low Density Parity Check (LDPC), Turbo and convolutional codes. Published results show that these codes effectively improve both the data rate and system performance in cooperative schemes such as the decode and forward (DF). Reed-Solomon (RS) codes are one of the most widely used channel codes in wireless communication systems today. These codes have also been adopted by several 3G standards including several digital video broadcasting (DVB) standards and also by worldwide interoperability for microwave access (WiMAX) which is based on the IEEE 802.16 standard. However, published literature shows no specific study to investigate their performance for the cooperative communication environment. Using the component codes adopted in the IEEE 802.16 standard, this paper investigates the performance of the concatenated RS coding schemes for cooperative communication. This paper first analyses the standard RS-coded DF cooperative system. The results obtained for the standard RS-coded scheme show huge gains over the non-cooperative system. Some of the problems of the standard DF relay protocol is then discussed and an improved RS-coded DF cooperative scheme is proposed. The performance of the proposed scheme shows significant gains over the standard RS-coded DF system. Qatar National Research Fund Scopus

We propose a data precoded relay-assisted scheme, for a system cooperating with L relays, each one equipped with a single antenna. The use of relays is of significant interest to allow radio access in situations where either the direct path is not available or has poor quality. However because of the half duplex constraint at the relays, transmission of a data rate that would be possible using a modulation technique with m bits per symbol in the case a continuous link was available from the BS to the UT, requires the use of a constellation with 2m bits per symbol. This implies a penalty in the power efficiency. In this communication we propose a simple precoding scheme that exploits the relation between QPSK and 4L-QAM, by alternately transmitting through the L relays, keeping the diversity of order L. Numerical results are presented for the case where 2 relay nodes are used, for realistic scenarios with LTE parameters and using turbo coding, showing significant performance improvements relatively to the case of a relay based distributed Alamouti employing 16-QAM. ©2010 IEEE. European project CODIV - FP7-ICT-2007-215477 CADWIN - PTDC/EEATEL/ 099241/2008 Portuguese Foundation for Science and Technology (FCT) grant

Multiview video is increasingly getting attention due to emerging applications such as 3DTV and immersive teleconferencing. In this paper, we present a non-stationary Hidden Markov Model (HMM) for characterizing the data rate of compressed multiview content. The states of the model correspond to different video activity levels and exhibit a Poisson state duration distribution. We derive a stable maximum likelihood algorithm for estimating the parameters of our multiview traffic model. Synthetic data generated by the model exhibits statistics that closely match those of actual multiview data. In addition, we demonstrate the high accuracy of the model in two multiview streaming applications by evaluating the frame loss rate of a constrained network buffer fed by actual and synthetic data.

In this paper we discuss the performance of different profiles of VDSL2 systems in a frequency range up to 12 MHz (bandplan 998 and 997, corresponding to the European region) using two different noise scenarios: VDSL2 Mix and VDSL2 only. The use of different power levels at the downstream is evaluated in these scenarios and it is found that there is no need to use maximum power. As operators are commonly interested to achieve higher data rates, we have selected profile 12a as the most suitable when dealing with frequencies up to 12MHz while consuming 4 times less power at the downstream than profile 8b and leading to similar performance in the scenarios herein described. The impact of using different cables has been evaluated for both the downstream and upstream direction. An analysis on boosted and non-boosted masks is also provided. A method to evaluate the upstream performance per band has been used in order to obtain the contribution of each upstream band versus the loop length. With this approach and keeping in mind the dependency of the cable when evaluating performance (e.g. TP150 0.5mm cable), it has been shown that US2 dies out after 700m, US1 after 1600m and USO provides more or less a constant performance contribution in the VDSL2 only scenario for band-plan 998. The same behavior for these upstream bands but in different ranges is expected for other type of cables (also for other bandplans, i.e. 997, which is presented in annex B). © 2007 IEEE.