Scaling Laws for Infrastructure Single and Multihop Wireless Networks in Wideband Regimes

With millimeter wave bands emerging as a strong candidate for 5G cellular networks, next-generation systems may be in a unique position where spectrum is plentiful. To assess the potential value of this spectrum, this paper derives scaling laws on the per mobile downlink feasible rate with large bandwidth and number of nodes, for both Infrastructure Single Hop (ISH) and Infrastructure Multi-Hop (IMH) architectures. It is shown that, for both cases, there exist \emph{critical bandwidth scalings} above which increasing the bandwidth no longer increases the feasible rate per node. These critical thresholds coincide exactly with the bandwidths where, for each architecture, the network transitions from being degrees-of-freedom-limited to power-limited. For ISH, this critical bandwidth threshold is lower than IMH when the number of users per base station grows with network size. This result suggests that multi-hop transmissions may be necessary to fully exploit large bandwidth degrees of freedom in deployments with growing number of users per cell.Comment: 5 pages, 3 figure

Dynamic Time-domain Duplexing for Self-backhauled Millimeter Wave Cellular Networks

Millimeter wave (mmW) bands between 30 and 300 GHz have attracted considerable attention for next-generation cellular networks due to vast quantities of available spectrum and the possibility of very high-dimensional antenna ar-rays. However, a key issue in these systems is range: mmW signals are extremely vulnerable to shadowing and poor high-frequency propagation. Multi-hop relaying is therefore a natural technology for such systems to improve cell range and cell edge rates without the addition of wired access points. This paper studies the problem of scheduling for a simple infrastructure cellular relay system where communication between wired base stations and User Equipment follow a hierarchical tree structure through fixed relay nodes. Such a systems builds naturally on existing cellular mmW backhaul by adding mmW in the access links. A key feature of the proposed system is that TDD duplexing selections can be made on a link-by-link basis due to directional isolation from other links. We devise an efficient, greedy algorithm for centralized scheduling that maximizes network utility by jointly optimizing the duplexing schedule and resources allocation for dense, relay-enhanced OFDMA/TDD mmW networks. The proposed algorithm can dynamically adapt to loading, channel conditions and traffic demands. Significant throughput gains and improved resource utilization offered by our algorithm over the static, globally-synchronized TDD patterns are demonstrated through simulations based on empirically-derived channel models at 28 GHz.Comment: IEEE Workshop on Next Generation Backhaul/Fronthaul Networks - BackNets 201

Scaling Laws for Vehicular Networks

Equipping automobiles with wireless communications and networking capabilities is becoming the frontier in the evolution to the next generation intelligent transportation systems (ITS). By means of vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications, information generated by the vehicle-borne computer, vehicle control system, on-board sensors, or roadside infrastructure, can be effectively disseminated among vehicles/infrastructure in proximity or to vehicles/infrastructure multiple hops away, known as vehicular networks (VANETs), to enhance the situational awareness of vehicles and provide motorist/passengers with an information-rich travel environment. Scaling law for throughput capacity and delay in wireless networks has been considered as one of the most fundamental issues, which characterizes the trend of throughput/delay behavior when the network size increases. The study of scaling laws can lead to a better understanding of intrinsic properties of wireless networks and theoretical guidance on network design and deployment. Moreover, the results could also be applied to predict network performance, especially for the large-scale vehicular networks. However, map-restricted mobility and spatio-temporal dynamics of vehicle density dramatically complicate scaling laws studies for VANETs. As an effort to lay a scientific foundation of vehicular networking, my thesis investigates capacity scaling laws for vehicular networks with and without infrastructure, respectively. Firstly, the thesis studies scaling law of throughput capacity and end-to-end delay for a social-proximity vehicular network, where each vehicle has a restricted mobility region around a specific social spot and services are delivered in a store-carry-and-forward paradigm. It has been shown that although the throughput and delay may degrade in a high vehicle density area, it is still possible to achieve almost constant scaling for per vehicle throughput and end-to-end delay. Secondly, in addition to pure ad hoc vehicular networks, the thesis derives the capacity scaling laws for networks with wireless infrastructure, where services are delivered uniformly from infrastructure to all vehicles in the network. The V2V communication is also required to relay the downlink traffic to the vehicles outside the coverage of infrastructure. Three kinds of infrastructures have been considered, i.e., cellular base stations, wireless mesh backbones (a network of mesh nodes, including one mesh gateway), and roadside access points. The downlink capacity scaling is derived for each kind of infrastructure. Considering that the deployment/operation costs of different infrastructure are highly variable, the capacity-cost tradeoffs of different deployments are examined. The results from the thesis demonstrate the feasibility of deploying non-cellular infrastructure for supporting high-bandwidth vehicular applications. Thirdly, the fundamental impact of traffic signals at road intersection on drive-thru Internet access is particularly studied. The thesis analyzes the time-average throughput capacity of a typical vehicle driving through randomly deployed roadside Wi-Fi networks. Interestingly, we show a significant throughput gain for vehicles stopping at intersections due to red signals. The results provide a quick and efficient way of determining the Wi-Fi deployment scale according to required quality of services. In summary, the analysis developed and the scaling laws derived in the thesis provide should be very useful for understanding the fundamental performance of vehicular networks

Achieving Scalable Capacity in Wireless Mesh Networks

Wireless mesh networks play a critical role in enabling key networking scenarios in beyond-5G (B5G) and 6G networks, including integrated access and backhaul (IAB), multi-hop sidelinks, and V2X. However, it still poses a challenge to deliver scalable per-node throughput via mesh networking, which significantly limits the potential of large-scale deployment of wireless mesh networks. Existing research has achieved $O(1)$ per-node throughput in a dense network, but how to achieve scalability remains an unresolved issue for an extended wireless network where the network size increases with a constant node density. This issue prevents a wireless mesh network from large-scale deployment. To this end, this paper aims to develop a theoretical approach to achieving scalable per-node throughput in wireless mesh networks. First, the key factors that limit the per-node throughput of wireless mesh networks are analyzed, through which two major ones are identified, i.e., link sharing and interference. Next, a multi-tier hierarchical architecture is proposed to overcome the link-sharing issue. The inter-tier interference under this architecture is then mitigated by utilizing orthogonal frequency allocation between adjacent tiers, while the intra-tier interference is reduced by considering two specific transmission schemes, one is MIMO spatial multiplexing with time-division, the other is MIMO beamforming. Theoretical analysis shows that the multi-tier mesh networking architecture can achieve a per-node throughput of $\Theta(1)$ in both schemes, as long as certain conditions on network parameters including bandwidth, antenna numbers, and node numbers of each tier are satisfied. A case study on a realistic deployment of 10,000 nodes is then carried out, which demonstrates that a scalable throughput of $\Theta(1)$ is achievable with a reasonable assumption on bandwidth and antenna numbers.Comment: ~12pages, 4 figures, submitted to IEEE TIT, part of this work has been published in IEEE MASS 202

Hybrid Spectrum Sharing in mmWave Cellular Networks

While spectrum at millimeter wave (mmWave) frequencies is less scarce than at traditional frequencies below 6 GHz, still it is not unlimited, in particular if we consider the requirements from other services using the same band and the need to license mmWave bands to multiple mobile operators. Therefore, an efficient spectrum access scheme is critical to harvest the maximum benefit from emerging mmWave technologies. In this paper, we introduce a new hybrid spectrum access scheme for mmWave networks, where data is aggregated through two mmWave carriers with different characteristics. In particular, we consider the case of a hybrid spectrum scheme between a mmWave band with exclusive access and a mmWave band where spectrum is pooled between multiple operators. To the best of our knowledge, this is the first study proposing hybrid spectrum access for mmWave networks and providing a quantitative assessment of its benefits. Our results show that this approach provides major advantages with respect to traditional fully licensed or fully unlicensed spectrum access schemes, though further work is needed to achieve a more complete understanding of both technical and non technical implications

KUNCI TEKNOLOGI 5G

[Id] Proses kelengkapan standarisasi teknologi 5G diharapkan akan selesai sebelum Oktober 2020. Resminya standarisasi ini akan menjadi hal penting untuk komersialisasi jaringan 5G. Teknologi 5G diprediksi akan membutuhkan transformasi akan kebutuhan frekuensi carrier yang sangat tinggi dengan bandwidth yang sangat lebar, densitas ekstrim untuk berbagai divais dan base station, serta sejumlah besar antena. 5G tidak akan menjadi antarmuka udara tunggal sebagaimana pada model generasi sebelumnya. 5G diprediksi akan sangat integratif: jalinan koneksi antarmuka udara dan spektrum 5G bersama-sama dengan teknologi nirkabel yang sudah ada (misalnya: LTE dan WiFi) akan memberikan layanan dengan pesat data tinggi dan cakupan luas, serta menjamin terwujudnya pengalaman pengguna tanpa hambatan. Untuk mendukung hal tersebut, di bagian core network harus berevolusi untuk mencapai tingkat belum pernah terjadi sebelumnya dalam hal fleksibilitas dan kecerdasan, regulasi spektrum perlu dikaji kembali dan direvisi, masalah energi dan efisiensi biaya juga akan menjadi pertimbangan yang penting. Berdasarkan studi literatur yang telah dilakukan, artikel ini akan mengidentifikasi dan merumuskan empat kunci penting implementasi teknologi 5G. Kata kunci : implementasi 5G, massive MIMO, jaringan hybrid, mmWave, unified air interface [En] 5G standardization process is expected to be finished before October 2020. This standardization is essential for making 5G network commercial deployment. The 5G technology is forecasted to demand a transformation in the need for very high carrier frequencies with very extensive bandwidth, extreme density for devices and base stations, as well as large numbers of antennas. 5G will not be a distinct air interface based on Radio Access Technology as in former generation models. 5G is predicted to be immensely collaborative: the linkage of air interface and 5G spectrum together with existing wireless technologies (for example: LTE and WiFi) will provide services with universal high-rates coverage and ensure seamless user experience. To support this, the core network must also evolve to achieve an extraordinary level of adjustability and intelligence, spectral standardization needs to be reviewed and revised, energy issues and cost efficiency will also be an important attention. Based on studies that had been done, this article will discuss and identify the four significant keys to the implementation of 5G technology

Asymptotic Analysis of Random Wireless Networks: Broadcasting, Secrecy, and Hybrid Networks

This thesis work is concerned with communication in large random wireless ad hoc networks. We mathematically model the wireless network as a collection of randomly located nodes, and explore how its performance scales as the network size increases. In particular, we study three important properties: broadcasting ability, rate of information exchange, and secret communication capability. In addition, we study connectivity properties of large random graphs in a more general context, where the graph does not necessarily represent a wireless communication network. Broadcasting, i.e., delivering a message from a single node to the entire network in a wireless ad hoc network can be achieved by nodes acting as relays. However, due to the random placement of nodes, broadcasting gets more difficult as the network size increases. We study how a stronger form of cooperation where nodes coordinate and transmit at the same time to increase their collective transmit range can improve broadcast ability. We show that, in this case, broadcast performance strongly depends on the type of wireless medium, in particular how fast the signal strength decays with distance. Specifically, we establish that, with increasing network size, broadcast probability goes to zero unless the attenuation in the medium is lower than a certain critical threshold. We consider the case of a wireless ad hoc network that is supported by base stations to improve data rate, which is referred to as a hybrid network. Although the availability of base stations may improve the throughput between the wireless nodes by providing access to an overlaid high-speed wired network, this improvement does not necessarily bring a scaling advantage as the network gets larger. Motivated by work which suggests the capacity increase depends on at what rate the number of base stations scales in comparison to the number of wireless nodes, we study the ultimate constraints on the capacity of hybrid networks. In particular, we prove upper bounds on the capacity scaling benefit the base stations can provide and also show constructions that achieve these bounds in some cases. We study secret communication capabilities of nodes in a large wireless ad hoc network that also includes eavesdropper nodes. Under an information-theoretic secrecy framework, we investigate whether nodes can exchange data while keeping bits secret from eavesdropper nodes without sacrificing on the data rate, and, most importantly, without location information about the eavesdroppers. We show that this is indeed possible by employing a combination of secret sharing, two-way communications and network coding, where nodes perform simple coding operations on messages instead of simply forwarding them. Finally, motivated by the results in the theory of random graphs that facilitate the understanding of the behavior of large wireless networks, we study connectivity in general random graphs in more detail. In particular, we study the percolation phenomenon, which refers to the abrupt transition of connectivity in large random graphs from a combination of disconnected islands to a large cluster spanning the whole graph when a critical threshold on the randomness parameter is exceeded. We study the extension of this percolation behavior to the case of a multilayer graph, which is formed by merging different graphs on the same vertex set, each representing a different type of connection between vertices. A multilayer graph, in general, is better connected than its individual layers, as vertices can be connected through paths traversing many layers. We numerically calculate the critical connectivity level on each layer such that the multilayer graph transitions to a well-connected state, i.e., percolates. Furthermore, we study the exact asymptotic behavior of this critical percolation threshold as the number of layers increases