This work introduces a non-orthogonal multiple access (NOMA) scheme suitable for low-rate ultra-reliable low-latency communication (URLLC) and enhanced mobile broadband (eMBB) services multiplexing in downlink communication. Tailored to minimize mutual interference, URLLC information is conveyed via a modified index modulation (IM) scheme on top of quadrature amplitude modulation (QAM) transferring eMBB traffic. Aiming at providing a proof of concept of the proposed scheme, we calculate the bit error rate of both services over Rayleigh fading with diversity, as well as the eMBB service achievable rate with typical multi-input multi-output (MIMO) configuration when the URLLC service utilizes space–time coding or diversity. The proposed scheme achieves a low bit error rate for the URLLC IM signal, at the cost of a lower information rate, while affecting the performance of the eMBB user mainly due to power sharing among the IM and QAM signals. To further investigate the feasibility of the proposed scheme, we calculate the transmission energy required by the base station to support both services over a typical cellular channel model, for various service requirements and user distances, in comparison to an orthogonal multiple access (OMA) puncturing scheme utilizing time-multiplexing of QAM for the eMBB traffic and BPSK for the URLLC traffic. Overall, our results show that the proposed scheme attains better performance compared to the puncturing scheme and offers a robust solution with easy user pairing for low-rate URLLC and typical eMBB downlink service multiplexing for 5G communications and beyond.

Random access (RA) has recently been revisited and considered as a key technology for the medium access control layer of the Internet of Things applications. Compared to other RA protocols, slotted ALOHA (SA) has the advantages of low complexity and elimination of partially overlapping transmissions, reducing the number of collisions, however it may suffer from congestion as the traffic load and the number of devices increase. To this end, two RA protocols based on SA and uplink non-orthogonal multiple access are proposed and applied to wireless sensor networks and wireless powered sensor networks. More specifically, to reduce the number of collisions and increase the throughput of SA, while maintaining low complexity, two detection techniques are used to mitigate the interference, when two sources transmit information in the same time slot, namely successive interference cancellation (SIC) with optimal decoding order policy and joint decoding (JD). To evaluate the performance of the proposed protocols, the outage probability of SIC and JD is derived, which is used to express the average throughput attained by each protocol in closed-form. Finally, both the analytical results and the simulations verify that the proposed protocols substantially increase the throughput and the number of connected devices compared to SA.

One challenging requirement of the Internet of Things (IoTs) is related to the capability of the wireless access network to be able to provide internet connectivity to a very large number of devices, compared to conventional cellular use cases. With the WiFi technology being the spearhead of the wireless local area networks (WLANs), the exploitation of already deployed WLANs has gained ground as a practical and efficient approach towards increasing the spectral efficiency of wireless networks. Based on the coordinated tethering concept, we introduce a purely wireless heterogeneous network deployment, where cellular and WLAN radio resources are optimally coordinated towards the universal maximization of the user’s throughput. The wireless users (smartphones, IoT devices, etc.) are coordinated by the evolved node B (eNB) about their role in the network (access point (AP) or normal user) and the access technology they have to employ. The performance of the new approach has been investigated based on a theoretical framework that has been developed. In this context, closed-form expressions are derived for important statistical characteristics of the system’s output signal-to-interference plus noise ratio (SINR) for the single-user case with multiple interferers. Then, this approach is extended to a multi-user multi-cellular system and a greedy algorithm is proposed for optimizing the system performance. Various numerical and simulation results have presented, which show that the proposed multi-cellular multi-radio access technology (RAT) scheme with coordinated tethering may increase spectral efficiency.

The energy consumption of Data Centers (DCs) is a very important figure for the telecommunications operators, not only in terms of cost, but also in terms of operational reliability. A relation between the energy consumption and the weather conditions would indicate that weather forecast models could be used for predicting energy consumption of DCs. A reliable forecast would result in a more efficient management of the available energy and would make it easier to take advantage of the modern types of power-grid based on renewable energy resources. In this ,paper, we exploit the capabilities provided by the FIESTA-IoT platform in order to investigate the correlation between the weather conditions and the energy consumption in DCs. Then, by using multi-variable linear regression process, we model this correlation between the energy consumption and the dominant weather conditions parameters in order to effectively forecast the energy consumption based on the weather forecast. We have validated our results through live measurements from the RealDC testbed. Results from our proposed approach indicate that forecasting of energy consumption based on weather conditions could help not only DC operators in managing their cooling systems and power usage, but also electricity companies in optimizing their power distribution systems.

Resource allocation and traffic aggregation is becoming a significant part of the network deployment as it is expected that operators will offer advanced services through 5G systems. Scheduling procedures need to be fair but also to handle requirements set for diverse groups of users forming network slices. Heterogeneous networks will need to be controlled locally and the traffic could be split between the macro cell LTE nodes and small cell WiFi distributed access points (APs). In this work, we examine the performance of a novel optimal resource allocation algorithm while adding a new process aiming in achieving predefined throughput and delay performance for selected groups/slices of users. From the optimal resource allocation algorithm, we derive an algorithmic solution which can be applied to determine a number of network slices. The 3GPP-WLAN interworking setup evaluation shows that our proposal can be used for allocating resources to slices of users fulfilling throughput and delay requirements set by their subscription.

Distributed-Multiple Input Multiple Output (D-MIMO) communication systems consist an attractive solution for networks with increased capacity demands. In these systems, the required information that needs to be exchanged among the network elements increases the data overhead and hence decreases the effective sum-rate (or throughput). Recently, it was shown that the total required overhead for D-MIMO networks can be reduced through its partitioning into smaller orthogonal D-MIMO segments. In this paper, a new scheme is proposed for further improving the effective sum-rate of D-MIMO networks by means of exploiting the spatial channels correlation within the D-MIMO network. Such effects can be observed in dense networks and the scope of the proposed correlation exploitation techniques is to avoid sending redundant feedback information. Numerical results indicate that important savings can be achieved when this novel method is applied under different wireless environments.

The exploitation of already deployed wireless local area networks (WLAN)s access points (AP)s has attracted considerable attention, as an efficient and practical method to improve the performance of wireless networks. In this paper, we adopt a hybrid accessing approach, where the WLAN APs share their wireless cellular broadband connection with other users. These users will select their serving node based on a certain selection criterion. Thus a challenging research field is originated, where interfering effects and wireless resources limitations play a dominant role. Important performance metrics of the proposed hybrid scheme, including the bit error probability and the ergodic capacity, are theoretically studied and closed form expressions are derived. Numerical results and simulations show that the proposed wireless architecture may offer significant performance gains in the presence of multiple interferers, compared to a conventional cellular network.

In wireless networks, the transmission medium poses several challenges in preserving the Quality-of-Service due to its random nature especially in operational environments with mobility and absence of line-of-sight links between the receiver and the transmitter. On the other hand, confronting the effects of fading channels requires the employment of complex but necessary mechanisms, such as channel equalization and diversity reception and/or transmission, which utilize hardware and channel resources. A common practice, which compromises between resources consumption and performance improvement, is to employ adaptive diversity mechanisms, such as the selection diversity (SD), which represents an attractive solution in various wireless communication scenarios, since it offers relatively low complexity and improved performance. In many practical situations, though, the continuous monitoring of all the available diversity paths, which is mandatory in SD schemes, leads to unnecessary resources consumption (e.g., control channels). In order to alleviate this complexity, we adopt a new adaptive threshold-based SD (t-SD) receiver, where only the current diversity path is used for signal reception as long as its signal-to-noise ratio is above a predefined threshold, otherwise the receiver becomes a pure SD. To this aim a new analytical performance evaluation framework is presented in terms of important statistical metrics, along with a complexity analysis. Numerical evaluated results illustrate how the proposed scheme outperforms other well known schemes in terms of performance and complexity trade-off.

Implant devices are used to measure biological parameters and transmit their results to remote off-body devices. As implants are characterized by strict requirements on size, reliability, and power consumption, applying the concept of cooperative communications to wireless body area networks offers several benefits. In this paper, we aim to minimize the power consumption of the implant device by utilizing on-body wearable devices, while providing the necessary reliability in terms of outage probability and bit error rate. Taking into account realistic power considerations and wireless propagation environments based on the IEEE P802.l5 channel model, an exact theoretical analysis is conducted for evaluating several communication scenarios with respect to the position of the wearable device and the motion of the human body. The derived closed-form expressions are employed toward minimizing the required transmission power, subject to a minimum quality-of-service requirement. In this way, the complexity and power consumption are transferred from the implant device to the on-body relay, which is an efficient approach since they can be easily replaced, in contrast to the in-body implants.

The exploitation of already deployed wireless local area networks (WLAN)s (e.g., WiFi access points (AP)s) has attracted considerable attention, as an efficient and pract ical method to improve the performance of wireless networks. In t his paper, we propose a novel communication paradigm to satisfy the performance demands of the future wireless networks:a hybrid Cellular-WLAN network architecture with wireless offloadi ng. In contrast to the commonly adopted practice of the WiFi offloading, where the WLAN APs have a wired backhaul (e.g., Digital Subscriber Line), we propose a wireless offloading approach, wh ere the WLAN APs will share their wireless cellular broadband connection with other users. These users will select their s erving node, i.e., the macro-cell base station or a WLAN AP, based on a certain selection criterion, originating a challenging research field, where interfering effects and wireless resources limitations play a dominant role. Important performance metrics of the proposed hybrid scheme -as the outage probability and the avera ge signal-to-interference-plus noise ratio (SINR)are theo retically studied and closed form expressions are derived for the sing leuser case with multiple interferers, considering both identical and non-identical fading channels. Furthermore, consideringa multicell network scenario the proposed hybrid scheme is optimiz ed for minimizing the intercell interference. Moreover, based on the general multi-cellular hybrid WLAN/Celullar concept, we present a novel scheme for achieving frequency reuse one wit hin a single macro-cell, under specific performance criteria an d constraints, that guarantee the overall cell’s or the individual user’s quality-of-service requirements. We consider two optimization problems that aim at the overall cell’s SINR maximization or at the minimum user’s SINR maximization and we propose a fast greedy solution for both of them. Numerical results and simulations showed that the proposed wireless architectur e may offer significant performance gains in the presence of multi ple interferers, compared to a conventional cellular network.

The exploitation of already deployed wireless local area networks (WLAN)s (e.g., WiFi access points (AP)s) has attracted considerable attention, as an efficient and practical method to improve the performance of beyond 4G wireless networks. In this paper, we propose a novel communication paradigm to satisfy the performance demands of future wireless networks: a hybrid Cellular/WLAN network architecture with wireless offloading. In contrast to the commonly adopted practice of WiFi offloading, where the WLAN APs have a wired backhaul (e.g., Digital Subscriber Line), we propose a wireless offloading approach, where the WLAN APs will share their wireless cellular broadband connection with other users. These users will select their serving node, i.e., the macro-cell eNodeB or a WLAN AP, based on a certain selection criterion. Thus a challenging research field is originated, where interfering effects and wireless resources limitations play a dominant role. Important performance metrics of the proposed hybrid scheme, including the bit error probability, the ergodic capacity and the average signal-to-interference-plus noise ratio, are theoretically studied and closed form expressions are derived for the single-user case with multiple interferers, for both identical and non-identical fading conditions. Also, based on the general multi-cellular hybrid WLAN-Cellular concept, we first propose a intercell interference minimization approach. Then we present a novel scheme for achieving frequency reuse equal to one within a single macro-cell, under specific performance criteria and constraints, that guarantee the overall cell or the individual user QoS requirements.

The exploitation of already deployed wireless local area networks (WLAN)s (e.g., WiFi access points (AP)s) has attracted considerable attention, as an efficient and practical method to improve the performance of beyond 4G wireless networks. In this paper, we propose a novel communication paradigm to satisfy the performance demands of future wireless networks: a hybrid Cellular/WLAN network architecture with wireless offloading. In contrast to the commonly adopted practice of WiFi offloading, where the WLAN APs have a wired backhaul (e.g., Digital Subscriber Line), we propose a wireless offloading approach, where the WLAN APs will share their wireless cellular broadband connection with other users. These users will select their serving node, i.e., the macro-cell eNodeB or a WLAN AP, based on a certain selection criterion. Thus a challenging research field is originated, where interfering effects and wireless resources limitations play a dominant role. Important performance metrics of the proposed hybrid scheme, including the bit error probability, the ergodic capacity and the average signal-to-interference-plus noise ratio, are theoretically studied and closed form expressions are derived for the single-user case with multiple interferers, for both identical and non-identical fading conditions. Also, based on the general multi-cellular hybrid WLAN-Cellular concept, we first propose a intercell interference minimization approach. Then we present a novel scheme for achieving frequency reuse equal to one within a single macro-cell, under specific performance criteria and constraints, that guarantee the overall cell or the individual user QoS requirements.

In many situations the performance of wireless communication systems decreases especially when they operate over multipath fading channels subject also to shadowing. In this sense, cluster‐based networks have been introduced as an efficient solution, offering coverage extension and energy saving. In this study, the authors investigate new cluster‐head (CH) selection algorithms, where the nodes can select different CHs, according to the corresponding signal strength. In addition, it is shown that if CHs are equipped with multiple antennas, the negative consequences of fading/shadowing can be further reduced. The performance of this scheme is theoretically investigated over correlated Nakagami‐ m fading channels, which are also subject to shadow fading, modelled by gamma distribution. The derived statistical metrics are used to obtain numerical evaluated results for the outage and the average bit error probabilities. These results are complemented by computer simulated ones, which validate the accuracy of the proposed analysis.

Distributed-Multiple Input Multiple Output (D-MIMO) networks is a promising enabler to address the challenges of high traffic demand in future wireless networks. A limiting factor that is directly related to the performance of these systems is the overhead signaling required for distributing data and control information among the network elements. In this paper, the concept of orthogonal partitioning is extended to D-MIMO networks employing joint multi-user beamforming, aiming to maximize the effective sum-rate, i.e., the actual transmitted information data. Furthermore, in order to comply with practical requirements, the overhead subframe size is considered to be constrained. In this context, a novel formulation of constrained orthogonal partitioning is introduced as an elegant Knapsack optimization problem, which allows the derivation of quick and accurate solutions. Several numerical results give insight into the capabilities of D-MIMO networks and the actual sum-rate scaling under overhead constraints.

ABSTRACTSupporting emerging machine‐to‐machine (M2M) communications over Long‐term Evolution (LTE)/LTE Advanced cellular networks in an efficient way will be beneficial for both telecommunication communities. The first step to migrate to an M2M‐enabled cellular standard is to provide these new services through the existing architectures and protocols, while maintaining seamless backward compatibility. To this end, we thoroughly examined a key LTE Medium Access Control entity, which is the packet scheduler, and proposed solutions based on the time‐controlled M2M feature, to deal with the diverse M2M traffic characteristics and quality‐of‐service requirements. Starting from the single M2M class case, we extended our study to more realistic scenarios, involving more M2M classes with diverse quality‐of‐service requirements. We defined analytical models for predicting the system performance on the basis of queueing theory concepts and considered the interaction between classes with different priorities. The proposed analytical models are validated through extensive system‐level simulations. On the basis of the insight obtained from our analytical approach, we modified an existing scheduling algorithm to improve the performance of low‐priority M2M device groups, and we demonstrated its superior performance both experimentally and analytically. Copyright © 2013 John Wiley & Sons, Ltd.

Machine-to-machine (M2M) communications over cellular networks pose significant challenges as a result of the large number of devices, small data transmissions, and vast applications range. Current solutions based on general packet radio service (GPRS) access proved to be inadequate for supporting the M2M ecosystem. Therefore, advanced cellular network releases, such as long-term evolution (LTE) and LTE-Advanced (LTE-A), should efficiently cater to M2M communications. However, the increase in signaling overhead and diverse quality-of-service (QoS) requirements calls for the development of novel flexible scheduling algorithms. In this article, we present the challenges in facilitating M2M scheduling over existing and future cellular infrastructures, review the related proposals, provide some initial solutions, and identify new perspectives, which pave the way for efficient and smooth migration to M2M-enabled broadband cellular systems.

In this paper, we present a Machine to Machine (M2M) communication scheme, where the source communicates with the corresponding destination with the help of multiple relays. Relays that participate into the communication process are selected according to three alternative selection criteria, while the non selected relays sleep for periods of fixed length. Thus, the proposed method combines cooperative communication techniques and sleep wake mechanisms. In order to enhance further energy efficiency and prolong network lifetime, we seek to determine the optimal energy allocated at each active relay, according to the minimization of the total energy consumed at the relays, under specific error performance constraints. Simulation results are provided to illustrate the performance of the proposed method.

achine-to-machine (M2M) communications overcellular networks pose significant challenges asa result of the large number of devices, smalldata transmissions, andvast applications range.Current solutions based on general packet radio service(GPRS)accessprovedtobeinadequateforsupportingtheM2M ecosystem. Therefore, advanced cellular networkreleases, such as long-term evolution (LTE) and LTE-Advanced (LTE-A), should efficiently cater to M2M com-munications. However, the increase in signaling overheadand diverse quality-of-service (QoS) requirements callsfor the development of novel flexible scheduling algo-rithms. In this article, we present the challenges in facili-tating M2M scheduling over existing and future cellularinfrastructures, review the related proposals, providesome initial solutions, and identify new perspectives,which pave the way for efficient and smooth migration toM2M-enabledbroadbandcellularsystems.