Spectrum sharing systems for improving spectral efficiency in cognitive
      cellular network
Creators: name: G C, Deepak
Publisher: name: Lancaster University
Year: 2017
Subjects: spectrum sensing
COGNITIVE RADIO NETWORKS
ENERGY EFFICIENCY
Spectral energy

description: Since spectrum is the invisible infrastructure that powers the wireless
      communication, the demand has been exceptionally increasing in recent
      years after the implementation of 4G and immense data requirements of 5G
      due to the applications, such as Internet-of-Things (IoT). Therefore, the
      effective optimization of the use of spectrum is immediately needed than
      ever before. 
      
      
      The spectrum sensing is the prerequisite for optimal resource allocation
      in cognitive radio networks (CRN). Therefore, the spectrum sensing in
      wireless system with lower latency requirements is proposed first. In such
      systems with high spatial density of the base stations and users/objects,
      spectrum sharing enables spectrum reuse across very small regions. The
      proposed method in this Thesis is a multi-channel cooperative spectrum
      sensing technique, in which an independent network of sensors, namely,
      spectrum monitoring network, detects the spectrum availability. The
      locally aggregated decision in each zone associated with the zone
      aggregator (ZA) location is then passed to a decision fusion centre (DFC).
      The secondary base station (SBS) accordingly allocates the available
      channels to secondary users to maximize the spectral efficiency. The
      function of the DFC is formulated as an optimization problem with the
      objective of maximizing the spectral efficiency. The optimal detection
      threshold is obtained for different cases with various spatial densities
      of ZAs and SBSs. It is further shown that the proposed method reduces the
      spectrum sensing latency and results in a higher spectrum efficiency. 
      
      
      Furthermore, a novel power allocation scheme for multicell CRN is proposed
      where the subchannel power allocation is performed by incorporating
      network-wide primary system communication activity. A collaborative
      subchannel monitoring scheme is proposed to evaluate the aggregated
      subchannel activity index (ASAI) to indicate the activity levels of
      primary users. Two utility functions are then defined to characterize the
      spectral efficiency (SE) and energy efficiency (EE) as a function of ASAI
      to formulate a utility maximization problem. The optimal transmit power
      allocation is then obtained with the objective of maximizing the total
      utility at the SBS, subject to maximum SBS transmit power and collision
      probability constraint at the primary receivers. Since optimal EE and SE
      are two contradicting objectives to obtain the transmit power allocation,
      the design approach to handle both EE and SE as a function of common
      network parameter, i.e., ASAI, is provided which ultimately proves the
      quantitative insights on efficient system design. Extensive simulation
      results confirm the analytical results and indicate a significant
      improvement in sensing latency and accuracy and a significant gain against
      the benchmark models on the rate performance, despite the proposed methods
      perform with lower signalling overhead.