Resource Allocation for Underlay Cognitive Radio Networks: A Survey

Dynamic Spectrum Sharing in 5G Wireless Networks With Full-Duplex Technology: Recent Advances and Research Challenges

“…Several survey papers exist in the literature in the context of dynamic spectrum sharing and spectral coexistence covering a wide range of areas such as spectrum occupancy modeling and measurements [29,30], interweave DSS [31,32,34], underlay DSS [35][36][37], overlay DSS [38], MAC protocols for DSS [39], spectrum decision [43], spectrum assignment [44], security for DSS [40], learning for DSS [41,42], DSS under practical imperfections [13], licensed spectrum sharing [61][62][63] IoT, M2M and D2D [64][65][66][67] techniques [45], and the coexistence of LTE and WiFi [46]. Furthermore, the contribution in [37] provided a comprehensive review of radio resource allocation techniques for efficient spectrum sharing based on different design techniques such as transmission power-based versus SINRbased, and centralized versus distributed method, and further provided various requirements for the efficient resource allocation techniques.…”

“…On the other hand, spectrum exploitation techniques can be broadly classified into interweave, underlay and overlay based on the access mechanisms employed by the SUs [12]. Interweave paradigm allows the opportunistic secondary transmission in the frequency channels in which the primary transmission is absent [97] while the underlay paradigm enables the concurrent operation of primary and secondary systems while guaranteeing sufficient protection to the PUs [98,99]. On the contrary, the overlay paradigm utilizes advanced coding and transmission strategies and requires a very high degree of coordination between spectrum sharing systems, which might be complex in practice [100,101].…”

“…4. Application of Physical Layer Network Coding (PLNC) on decode and forward FD relaying to enable simultaneous transmissions from two sources to two destination nodes [98,133,134] 1. Implementation of packet fragmentation at the MAC layer in order to improve the performance of the FD-based CR networks.…”

Sum Utilization of Spectrum with Spectrum Handoff and Imperfect Sensing in Interweave Multi-Channel Cognitive Radio Networks

“…Spectrum allocation is considered one of the major problems among the mentioned requirements [1,9]. The static spectrum allocation policies are inefficient for meeting the ever-growing demand of spectrum resources, which are needed for high-speed wireless access in 5G cellular networks [10]. Radio resources have become increasingly scarce because of the static spectrum allocation approaches.…”

“…Radio resources have become increasingly scarce because of the static spectrum allocation approaches. The unlicensed users cannot access the licensed bands, making the bands under-utilized [6,10]. Spectrum allocation flexibility and spectrum utilization efficiency can be achieved with different proposed technologies, such as LTE-WiFi aggregation (LWA) [11], operations in millimeter-wave band [12], LTE over the unlicensed band (LTE-U) [13], multicasting [14,15], layer-division multiplexing [14,16], ultra-dense small cells in Sustainability 2018, 10, 1764 3 of 18 5G architecture [17], non-orthogonal multiple access (NOMA) [18][19][20], and software-defined cognitive radio network (SD-CRN) [21][22][23][24][25].…”