Resource Allocation for Device-to-Device Communications in Multi-Cell Multi-Band Heterogeneous Cellular Networks

Heterogeneous cellular networks (HCNs) with millimeter wave (mm-wave) communications are considered as a promising technology for the fifth generation mobile networks. Mm-wave has the potential to provide multiple gigabit data rate due to the broad spectrum. Unfortunately, additional free space path loss is also caused by the high carrier frequency. On the other hand, mm-wave signals are sensitive to obstacles and more vulnerable to blocking effects. To address this issue, highly directional narrow beams are utilized in mm-wave networks. Additionally, device-to-device (D2D) users make full use of their proximity and share uplink spectrum resources in HCNs to increase the spectrum efficiency and network capacity. Towards the caused complex interferences, the combination of D2D-enabled HCNs with small cells densely deployed and mm-wave communications poses a big challenge to the resource allocation problems. In this paper, we formulate the optimization problem of D2D communication spectrum resource allocation among multiple micro-wave bands and multiple mm-wave bands in HCNs. Then, considering the totally different propagation conditions on the two bands, a heuristic algorithm is proposed to maximize the system transmission rate and approximate the solutions with sufficient accuracies. Compared with other practical schemes, we carry out extensive simulations with different system parameters, and demonstrate the superior performance of the proposed scheme. In addition, the optimality and complexity are simulated to further verify effectiveness and efficiency.Comment: 13 pages, 11 figures, IEEE Transactions on Vehicular Technolog

Performance Analysis of Relay-Assisted Device-to-Device Communication

Outage and Success performances of an amplify-and-forward relay-assisted D2D communication system over a κ-μ shadowed fading wireless link are presented here. Co-channel interference (CCI) is assumed to affect the D2D signals at relay and destination nodes. The system is analyzed with two scenarios, namely, with diversity combining and without diversity combining. Selection combining (SC) based diversity scheme is incorporated at the D2D receiver to combat fading conditions. The expressions for success and outage probabilities are presented by using the characteristic function approach. The expressions are functions of path-loss exponents, wireless link length between relay and D2D source node, wireless link length between the receiver node and relay, distances between interferers and the relay node, CCI distances from various devices of the system, fading channel. The numerical analysis for various scenarios is presented and analyzed

Performance Analysis of Relay-Assisted Device-to-Device Communication

Outage and Success performances of an amplify-and-forward relay-assisted D2D communication system over a κ-μ shadowed fading wireless link are presented here. Co-channel interference (CCI) is assumed to affect the D2D signals at relay and destination nodes. The system is analyzed with two scenarios, namely, with diversity combining and without diversity combining. Selection combining (SC) based diversity scheme is incorporated at the D2D receiver to combat fading conditions. The expressions for success and outage probabilities are presented by using the characteristic function approach. The expressions are functions of path-loss exponents, wireless link length between relay and D2D source node, wireless link length between the receiver node and relay, distances between interferers and the relay node, CCI distances from various devices of the system, fading channel. The numerical analysis for various scenarios is presented and analyzed

Frequency reconfigurable rectangular patch antenna for cognitive radio applications

A frequency reconfigurable microstrip transformed rectangular patch antenna consisting of two slots able to radiate in S-band and C-band is proposed. Spectrum occupancy is first analyzed using the data from literature and internet sources and hence spectrum holes are identified. A rectangular radiating patch is then designed for 5.8 GHz resonant frequency. A coaxial feed is used in the bottom by a suitable feed point. Two slots at an angle of +45 degree are made at the two corners. The electrical length of the patch is changed by using two varactor diodes in the slots. The varactors enable frequency reconfiguration in the band of frequencies that are unused or the spectral occupancy is very less. The return loss, voltage standing wave ratio (VSWR), and 2D-radiation patterns are analyzed for various values of the capacitances. high-frequency structure simulator (HFSS) is used for simulation. FR4 substrate which is economical, is used with height, h=1.6 mm, width W=25.33 mm, and length L=21.34 mm. On the substrate the rectangular patch is of width 15.73 mm and length 11.74 mm. The return loss and radiation patterns for different values of capacitances is presented. The tunability ratio obtained is 1.93. The results obtained agree with the standards

AI-based resource management in future mobile networks

Η υποστίριξη και ενίσχυση των δίκτυων 5ης γενιάς και πέρα από αλγόριθμους Τεχνητής Νοημοσύνης για την επίλυση προβλημάτων βελτιστοποίησης δικτύου, μελετάται πρόσφατα προκειμένου η νέα γενιά των δικτύων να ανταποκριθεί στις απαιτήσεις ποιότητας υπηρεσίας σχετικά με την κάλυψη, τη χωρητικότητα των χρηστών και το κόστος εγκατάστασης. Μία από τις βασικές ανάγκες είναι η βελτιστοποίηση στην διαδικασία της εγκατάστασης σταθμών βάσης δικτύου. Σε αυτή την εργασία προτείνεται μια μετα-ευριστική μέθοδος, με όνομα «Γενετικός Αλγόριθμός» (Genetic Algorithm) για την επίλυση προβλημάτων βελτιστοποίησης λαμβάνοντας υπόψη τους περιορισμούς ζήτησης. Ο κύριος στόχος είναι η παρουσίαση της εναλλακτικής αυτής λύσης, η οποία είναι η χρήση του Γενετικού Αλγόριθμου, για τη βελτιστοποίηση της διαδικασίας εγκατάστασης των σταθμών βάσης του δικτύου. Με την χρήση του αλγορίθμου για την εγκατάσταση σταθμών βάσης παρέχονται οι ίδιες υπηρεσίες με πριν και ελαχιστοποιείται την κατανάλωση ενέργειας της υποδομής του δικτύου, λαμβάνοντας υπόψιν ομοιογενή και ετερογενή σενάρια σταθμών βάσης. Οι προσομοιώσεις πραγματοποιήθηκαν σε γλώσσα προγραμματισμού Python και τα καλύτερα αποτελέσματα εγκατάστασης παρουσιάστηκαν και αποθηκεύτηκαν. Έγινε σύγκριση της εγκατάστασης αποκλειστικά μακρο-σταθμών βάσης με μικρότερου μεγέθους (σε κάλυψη) σταθμών βάσης πάνω από την υπάρχουσα. Με την χρήση των μικρότερων σταθμών βάσης, η εγκατάσταση του δικτύου θα επιτρέψει βελτιώσεις στην κάλυψη των χρηστών και θα μειώσει το κόστος, την κατανάλωση ενέργειας και τις παρεμβολές μεταξύ των κυψελών. Όλα τα σενάρια μελετήθηκαν σε 3 περιοχές με διαφορετική πυκνότητα χρηστών (A, B και C). Ως προς την ικανοποίηση των απαιτήσεων αναφορικά με την ποιότητα υπηρεσιών και των κινητών συσκευών, η ανάπτυξη μικρών σταθμών βάσης είναι επωφελής, συγκεκριμένα σε περιοχές hotspot.The 5G and beyond networks supported by Artificial Intelligence algorithms in solving network optimization problems are recently studied to meet the quality-of-service requirements regarding coverage, capacity, and cost. One of the essential necessities is the optimized deployment of network base stations. This work proposes the meta-heuristic algorithm Genetic Algorithm to solve optimization problems considering the demand constraints. The main goal is present the alternative solution, which is using the Genetic Algorithm to optimize BSs network deployment. This deployment provides the same services as existing deployments and minimizes the network infrastructure's energy consumption, including using homogenous and heterogenous scenarios of base stations. The simulations were performed in Python programming language, and the results as the best plans for each generation were presented and saved. A comparison of the macro base station deployment and small base station deployment was made on top of the existing one. By applying the small base stations, the network deployment will enable user coverage enhancements and reduce the deployment cost, energy consumption, and inter-cell interference. All the scenarios were assembled in user density area A, user density area B, and user density area C areas of interest. In meeting the requirements for QoS and UE, the small base station deployment is beneficial, namely in hotspot areas

Resource Allocation for Device-to-Device Communications in Multi-Cell Multi-Band Heterogeneous Cellular Networks

Heterogeneous cellular networks (HCNs) with millimeter wave (mm-wave) communications are considered as a promising technology for the fifth-generation mobile networks. Mm-wave has the potential to provide multiple gigabit data rate due to the broad spectrum. Unfortunately, additional free space path loss is also caused by the high carrier frequency. On the other hand, mm-wave signals are sensitive to obstacles and more vulnerable to blocking effects. To address this issue, highly directional narrow beams are utilized in mm-wave networks. Additionally, device-to-device (D2D) users make full use of their proximity and share uplink spectrum resources in HCNs to increase the spectrum efficiency and network capacity. Toward the caused complex interferences, the combination of D2D-enabled HCNs with small cells densely deployed and mm-wave communications poses a big challenge to the resource allocation problems. In this paper, we formulate the optimization problem of D2D communication spectrum resource allocation among multiple micro-wave bands and multiple mm-wave bands in HCNs. Then, considering the totally different propagation conditions on the two bands, a heuristic algorithm is proposed to maximize the system transmission rate and approximate the solutions with sufficient accuracies. Compared with other practical schemes, we carry out extensive simulations with different system parameters, and demonstrate the superior performance of the proposed scheme. In addition, the optimality and complexity are simulated to further verify effectiveness and efficiency

Delay and energy efficiency optimizations in smart grid neighbourhood area networks

Smart grids play a significant role in addressing climate change and growing energy demand. The role of smart grids includes reducing greenhouse gas emission reduction by providing alternative energy resources to the traditional grid. Smart grids exploit renewable energy resources into the power grid and provide effective two-way communications between smart grid domains for efficient grid control. The smart grid communication plays a pivotal role in coordinating energy generation, energy transmission, and energy distribution. Cellular technology with long term evolution (LTE)-based standards has been a preference for smart grid communication networks. However, integrating the cellular technology and the smart grid communication network puts forth a significant challenge for the LTE because LTE was initially invented for human centric broadband purpose. Delay and energy efficiency are two critical parameters in smart grid communication networks. Some data in smart grids are real-time delay-sensitive data which is crucial in ensuring stability of the grid. On the other hand, when abnormal events occur, most communication devices in smart grids are powered by local energy sources with limited power supply, therefore energy-efficient communications are required. This thesis studies energy-efficient and delay-optimization schemes in smart grid communication networks to make the grid more efficient and reliable. A joint power control and mode selection in device-to-device communications underlying cellular networks is proposed for energy management in the Future Renewable Electric Energy Delivery and Managements system. Moreover, a joint resource allocation and power control in heterogeneous cellular networks is proposed for phasor measurement units to achieve efficient grid control. Simulation results are presented to show the effectiveness of the proposed schemes

Performance Limits of Microwave and Dual Microwave/Millimeter Wave Band Networks

Traditionally, wireless networks communicate over the conventional microwave band (sub-6 GHz) as it supports reliable communication over a large geographic area. The ever increasing demand for bandwidth to support the rising number of consumers and services, however, is fast depleting the available microwave spectrum. As such, complementing the microwave spectrum with additional bandwidth from the millimeter-wave (mm-wave) band has been envisioned as a promising solution to this problem. Since transmissions in the mm-wave band are typically achieved with highly directional steerable antenna arrays to counter the severe path-loss in mm-wave frequencies, the resulting mm-wave links are typically rendered highly directional, which can often be modeled as directional point-to-point links. However, mm-wave transmissions are inherently unreliable compared to those in the microwave band. Hence, communicating simultaneously over both bands in an integrated mm-wave/microwave dual-band setup is emerging as a promising new technology. In this dual-band setting, high-rate data traffic can be carried by relatively unreliable high-bandwidth mm-wave links, while control signals and moderate-bandwidth traffic can be communicated over the relatively reliable microwave band. In this thesis, we first study two dual-band multi-user networks that model two important aspects of wireless communication: inter-user interference and relay-cooperation. The broad goal of this study is to characterize information-theoretical performance limits of such networks, which can then be used to obtain insights on the optimal encoding/decoding strategy, effective resource allocation schemes, etc. In the first part of this thesis, we study a two-transmitter two-receiver dual-band Gaussian interference channel (IC) operating over an integrated mm-wave/microwave dual-band. This channel models a setting where a pair of single-transmitter single-receiver links communicate simultaneously, and thus mutually interfere. Here, transmissions in the underlying microwave band are modeled as a two-user conventional Gaussian IC (GIC). In contrast, a transmitter in the mm-wave band is assumed to be capable of communicating to either the desired destination or the interfered destination via a point-to-point direct-link or a cross-link, respectively. The dual-band IC is first classified into 3 classes according to the interference level in the underlying microwave GIC, and then sufficient channel conditions are obtained under which the capacity region of the 3 classes are characterized. For cases in which the sufficient conditions do not necessarily hold, approximate capacity results are obtained that characterizes the capacity region to within 1/2 bit per channel use per user. The performance of the dual-band IC is likely to be impacted significantly by the point-to-point nature and large bandwidth of the mm-wave links, and specifically by whether the mm-wave spectrum is used as direct-links or cross-links. Transmitting in either the direct-links only or the cross-links only is not optimal for all channel conditions, and there exists a non-trivial trade-off between the two modes. To understand the impact of this trade-off on the performance of the dual-band IC, we study the power allocation scheme over the mm-wave direct and cross-links that maximizes the sum-rate of the channel. The resulting power allocation strategy is characterized in closed form, which possesses rich properties and reveals useful insights into the trade-offs in such networks. In the second part of this thesis, we study a fading Gaussian multiple-access relay channel (MARC) over an integrated mm-wave/microwave dual-band, where two sources communicate to a destination with the help of a relay. In the dual-band MARC, transmission in the underlying microwave band is modeled as a conventional Gaussian MARC. However, similar to that in the dual-band IC, a mm-wave transmitter in this channel is modeled as being able to communicate to either the destination or the relay by creating a direct-link or a relay-link, respectively. For dual-band MARC, we characterize an achievable region and a set of rate upper bounds, and then obtain sufficient channel conditions under which its capacity region is characterized. Similar to the dual-band IC, the performance of the dual-band MARC will likely be significantly affected by whether the mm-wave band is used as direct-links or relay-links, and a non-trivial trade-off between the two modes exists in this case as well. To understand this trade-off, we study the transmission power allocation scheme over the mm-wave direct and relay-links that maximizes the sum-rate of the dual-band MARC. The resulting power allocation scheme, characterized in closed form, is observed to have rich structural properties, which reveal insights into the trade-offs in relay cooperation in dual-band networks. While dual-band communication is a promising technology, currently the bulk of the connectivity is still supported by the microwave band. However, the problem of interference mitigation for conventional microwave bands is still open even for the basic case of a two-user IC. Motivated by this, in the third part of the thesis, we study the performance limits of the multiple-access interference channel (MAIC) which models the interference during cellular uplink over the conventional single band. Focusing on the weak interference case, which provides a more realistic model of the inter-cell interference, we characterize an achievable strategy and 3 novel upper bounds on the sum-rate in the partially symmetric case, thereby providing improved sum-rate upper and lower bounds in these cases