Random subcarrier allocation in OFDM-based cognitive radio networks

Abstract

Abstract-This paper investigates the performance of an orthogonal frequency-division multiplexing (OFDM)-based cognitive radio (CR) spectrum sharing communication system that assumes random allocation and absence of the primary user's (PU) channel occupation information, i.e., no spectrum sensing is employed to acquire information about the availability of unused subcarriers. In case of a single secondary user (SU) in the secondary network, due to the lack of information of PUs' activities, the SU randomly allocates the subcarriers of the primary network and collide with the PUs' subcarriers with a certain probability. To maintain the quality of service (QoS) requirement of PUs, the interference that SU causes onto PUs is controlled by adjusting SU's transmit power below a predefined threshold, referred to as interference temperature. In this work, the average capacity of SU with subcarrier collisions is employed as performance measure to investigate the proposed random allocation scheme for both general and Rayleigh channel fading models. Bounds and scaling laws of average capacity with respect to the number of SU's, PUs' and available subcarriers are derived. In addition, in the presence of multiple SUs, the multiuser diversity gain of SUs assuming an opportunistic scheduling is also investigated. To avoid the interference at the SUs that might be caused by the random allocation scheme and obtain the maximum sum rate for SUs based on the available subcarriers, an efficient centralized sequential algorithm based on the opportunistic scheduling and random allocation (utilization) methods is proposed to ensure the orthogonality of assigned subcarriers.

Resource allocation for OFDM-based multiuser cooperative underlay cognitive systems

“…In [14], the authors maximized the secondary achievable rate under a new criterion referred to as rate-loss constraint. The authors in [15] investigated the problem of random subcarrier allocation in OFDM-based CR networks without any spectrum-sensing information at the SU. The SU's transmit power was adjusted in order to maintain the interference on the primary receiver under a predefined threshold.…”

Interference-aware spectrum sensing mechanisms in cognitive radio networks

“…Over the last decades, much work focused on improving the spectrum utilization of communication networks [18][19][20][21][22]. The authors in [19] utilized the average capacity of SU as the performance metric to investigate the random allocation scheme for both general and Rayleigh channel fading models.…”

“…The authors in [19] utilized the average capacity of SU as the performance metric to investigate the random allocation scheme for both general and Rayleigh channel fading models. In [20], the authors studied the opportunistic spectrum sharing problem through the joint optimization of spectrum detection and transmission power control, and adopted a multi-state spectrum sensing model for detection decision.…”

Resource allocation for SC‐FDMA based cognitive radio systems

“…Almost all of the previous work on resource optimization in the context of multi-carrier and multiuser CR systems has focused on OFDMA-based CR systems [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. However, none of these works can be used for SC-FDMA-based CR systems.…”