Cognitive Mesh Network Under Interference from Primary User

Abstract

In a commonly accepted usage scenario, a cognitive radio appears as a secondary user of certain spectrum which is licensed to another, primary system. A prominent example of cognitive system is a mesh network operating under the interference from primary system. For such a scenario, we propose techniques for efficient secondary usage of spectrum, which rely on the adaptive array antenna in order to reduce the interference between the primary and the cognitive system. In order to keep the hardware complexity as small as possible, the number of antennas at each cognitive node should be small. However, with the simplest 2-element linear adaptive array, the created antenna pattern can result in non-optimized pattern between cognitive nodes in the mesh network. In order to solve such a problem, this paper introduces a simple antenna pattern switching where each cognitive node is equipped with three antennas, and tries to select the antenna configuration constituting 2-element linear array with the best antenna pattern for each link. The proposed configuration requires three antennas but only two transceiver chains, which can reduce the hardware complexity. We also introduce 3-element linear array and design a simple procedure to heuristically select the pattern. Our numerical results show that the proposed techniques can significantly increase the available bandwidth and networking connectivity with small complexity when a cognitive mesh network is located inside the communication area of the primary system.

Underlay MIMO Cognitive Radio Downlink Scheduling with Multiple Primary Users and No CSI

“…In this paper, best-effort interference mitigation is adopted in the sense that no hard IT constraint is assumed, even if the primary CSIT is available, which is similar to [7], [15], [16]. This is justifiable, for example, when the CBS lies outside a primary exclusion area or guard zone, or the maximum CBS transmit power is designed based on a worst-case PU interference scenario.…”

Cognitive Radio Operation under Directional Primary Interference and Practical Path Loss Models

“…Therefore, before starting their communication, the secondary transmitters can estimate their interference toward the primary receivers by using the received power (detected during primary transmission) from a primary transmitter toward the secondary receivers. The actual method for the estimation of the interference power from the secondary transmitters toward a primary receiver is detailed in [12]. The method introduced in [12] counts on the channel reciprocity which can be violated when considering mobility as well as different interference conditions at two end-points.…”

“…The actual method for the estimation of the interference power from the secondary transmitters toward a primary receiver is detailed in [12]. The method introduced in [12] counts on the channel reciprocity which can be violated when considering mobility as well as different interference conditions at two end-points. The lack of channel reciprocity results in the degradation of spatial opportunity as the secondary transmitter underestimates the interference and starts transmission, which consequently violates the target quality at primary receiver or overestimates the interference and does not start transmission itself.…”

Heuristic Algorithm Based on MAXDCP and GEOCP in Grid Network

“…The WIMAX network increases relays in the propagation path, forming a access link (Access Link) from users to the relay and the relay access link (Relay Link) from users to the base station, which has advantages with low cost, high bandwidth, wide coverage, and it is a new direction in technical aspects of the 802.16 standard [5][6][7].…”