It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

On the capacity of a cellular CDMA system

Device-to-device (D2D) communication enables the user equipments (UEs) located in close proximity to bypass the cellular base stations (BSs) and directly connect to each other, and thereby, offload traffic from the cellular infrastructure. D2D communication can improve spatial frequency reuse and energy efficiency in cellular networks. This paper presents a comprehensive and tractable analytical framework for D2D-enabled uplink cellular networks with a flexible mode selection scheme along with truncated channel inversion power control. Different from the existing mode selection schemes where the decision on mode selection is made based only on the D2D link distance (i.e., distance between two UEs using D2D mode of communication), the proposed mode selection scheme for a UE accounts for both the D2D link distance and cellular link distance (i.e., distance between the UE and the BS). The developed framework is used to analyze and understand how the underlaying D2D communication affects the cellular network performance. Through comprehensive numerical analysis, we investigate the expected performance gains and provide guidelines for selecting the network parameters.

Analytical Modeling of Mode Selection and Power Control for Underlay D2D Communication in Cellular Networks

Modeling, Analysis, and Design of 5G Networks using Stochastic Geometry Konpal Shaukat Ali Improving spectral-utilization is a core focus to cater the ever-increasing demand in data rate and system capacity required for the development of 5G. This dissertation focuses on three spectrum-reuse technologies that are envisioned to play an important role in 5G networks: device-to-device (D2D), full-duplex (FD), and nonorthogonal multiple access (NOMA). D2D allows proximal user-equipments (UEs) to bypass the cellular base-station and communicate with their intended receiver directly. In underlay D2D, the D2D UEs utilize the same spectral resources as the cellular UEs. FD communication allows a transmit-receive pair to transmit simultaneously on the same frequency channel. Due to the overwhelming self-interference encountered, FD was not possible until very recently courtesy of advances in transceiver design. NOMA allows multiple receivers (transmitters) to communicate with one transmitter (receiver) in one time-frequency resource-block by multiplexing in the power domain. Successive-interference cancellation is used for NOMA decoding. Each of these techniques significantly improves spectral efficiency and consequently data rate and throughput; however, the price paid is increased interference. Since each of these technologies allow multiple transmissions within a cell on a time-frequency resource-block, they result in interference within the cell (i.e., intracell interference). Additionally, due to the increased communication, they increase network interference from outside the cell under consideration as well (i.e., increased intercell interference). Real networks are becoming very dense; as a result, the impact of intercell interference coming from the entire network is significant. As such, using models that 5 consider a single-cell/few-cell scenarios result in misleading conclusions. Hence, accurate modeling requires considering a large network. In this context, stochastic geometry is a powerful tool for analyzing random patterns of points such as those found in wireless networks. In this dissertation, stochastic geometry is used to model and analyze the different technologies that are to be deployed in 5G networks. This gives us insight into the network performance, showing us the impacts of deploying a certain technology into real 5G networks. Additionally, it allows us to propose schemes for integrating such technologies, mode-selection, parameter-selection, and resource-allocation that enhance the parameters of interest in the network such as data rate, coverage, and secure communication.

Modeling, Analysis, and Design of 5G Networks using Stochastic Geometry

Protocols and Algorithms for Harmonious Coexistence Over Unlicensed Bands in Next-Generation Wireless Networks

Licensed shared access (LSA) is one of the emerging modes of regulation for dynamic spectrum sharing management among incumbent wireless networks and secondary networks such as LTE mobile networks. This proof- of-concept demonstration of LSA exploits the Virtually Shared Spectrum Access (ViSSA) platform among various wireless networks and management entities. The ViSSA platform is an innovative integration of five parts by combining LTE small cells, emulators and management servers: i) a monitoring and management center with a spectrum repository that extends a license-exempt mode compliant geo-location database (GLDB/SR); ii) emulated incumbents that may register to GLDB/SR or directly access their spectrum; iii) a few LTE small cell networks of secondary accesses, each network having an LSA controller to communicate between GLDB/SR and its own network management; iv) feature-based sensing of incumbent signals emulated by a USRP; and v) implementation of LSRAI- and http-based communications among i) - iv) via Internet. On-site exhibition of ViSSA platform will demonstrate the novel LSA management of database-guided and sensing-based evacuation yielding to the incumbent. Demonstrations of re-activation of secondary LTE small cells in other available spectrum bands show the feasibility of completing evacuation and re-activation in 60 to 70 seconds.

Licensed shared access by mobile networks: Proof-of-concept demonstration over ViSSA platform

Opportunistic Spectrum Access has recently become the most desirable solution for greatly improving the performance of telecommunication systems. It has proven to be a viable solution to cope with the challenging problem of spectrum scarcity and also it has been widely explored in 5G networks, so that multiple random access technologies can coexist in a cognitive setup. In 5G networks, such secondary technology candidates like Device-to-Device (D2D) communications, and Licensed-Assisted Access are envisioned to opportunistically exploit spectrum opportunities and coexist with primary technologies like LTE or WiFi. Moreover, Full Duplex (FD) technology is envisioned to play a significant role in 5G networks by allowing a user to transmit and receive on the same frequency band.
In this thesis, we present a comparative performance analysis of the spectral efficiency in a heterogeneous system where a cellular network allows the FD-Enabled D2D network to use opportunistically its spectrum while ensuring protection for its transmission/reception through guard zones. The main contributions and emphasis of this work are to explore the spectrum opportunities for secondary users by: firstly, deriving their probability of successful transmissions, deciding the feasible mode of operation (half-duplex, full-duplex or silent); and secondly, incorporating the protection zone for primary users. We assess the overall system performance, analyze the impact of different access mechanisms and propose an efficient mode selection for secondary users.
Such a systematic analysis of the integrated technologies requires a rigorous and critical evaluation of the performance gains and the costs incurred in terms of increased interference. Also, ultra-dense and random network models are envisioned in future networks especially in the urban scenario, hence, pre-deployment average system performance over various deployment scenarios can in fact be advantageous. In this thesis, we use stochastic geometry to model and analyze different coexistence scenarios and spectrum sharing frameworks in 5G networks for multiple radio access technologies. We also assess different coexistence methodologies for secondary users to fairly and peacefully coexist with primary users while ensuring the interference protection for primary users.
In summary, FD enabled heterogeneous networks have not been critically studied in previous literature, and for this reason a comprehensive study on the use of FD to existing systems is needed. This thesis proposes an innovative FD enabled D2D cognitive setup and carefully studies the improvement in system performance while taking into account the cost of these gains in 5G networks, using stochastic geometry tools.

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Noman Haider

Papers

Dynamic spectrum sharing and coexistence with full-duplex device-to-device communications in 5G networks