Exploiting Multi-Antennas for Opportunistic Spectrum Sharing in Cognitive Radio Networks

Abstract

In cognitive radio (CR) networks, there are scenarios where the secondary (lower priority) users intend to communicate with each other by opportunistically utilizing the transmit spectrum originally allocated to the existing primary (higher priority) users. For such a scenario, a secondary user usually has to trade off between two conflicting goals at the same time: one is to maximize its own transmit throughput; and the other is to minimize the amount of interference it produces at each primary receiver.In this paper, we study this fundamental tradeoff from an information-theoretic perspective by characterizing the secondary user's channel capacity under both its own transmit-power constraint as well as a set of interferencepower constraints each imposed at one of the primary receivers. In particular, this paper exploits multi-antennas at the secondary transmitter to effectively balance between spatial multiplexing for the secondary transmission and interference avoidance at the primary receivers. Convex optimization techniques are used to design algorithms for the optimal secondary transmit spatial spectrum that achieves the capacity of the secondary transmission.Suboptimal solutions for ease of implementation are also presented and their performances are compared with the optimal solution. Furthermore, algorithms developed for the single-channel transmission are also extended to the case of multi-channel transmission whereby the secondary user is able to achieve opportunistic spectrum sharing via transmit adaptations not only in space, but in time and frequency domains as well. Simulation results show that even under stringent interference-power constraints, substantial capacity gains are achievable for the secondary transmission by employing multi-antennas at the secondary transmitter. This is true even when the number of primary receivers exceeds that of secondary transmit antennas in a CR network, where an interesting "interference diversity" effect can be exploited. Index TermsCognitive radio (CR), opportunistic spectrum sharing, multiple-input multiple-output (MIMO), channel capacity, dynamic resource allocation, interference diversity, convex optimization.

Optimal power allocation for fading channels in cognitive radio networks: Ergodic capacity and outage capacity

“…In [10], the authors considered the outage capacity under both the peak and the average interference power constraints. It is noted that optimal design of SU transmission strategy under interference-power constraints at PU receivers has also been studied in [11] for multi-antenna CR transmitters, and in [12] for multiple CR transmitters in a multiple-access channel (MAC).…”

Power Control in Cognitive Radio Networks Using Cooperative Modulation and Coding Classification

“…One critical modification is the knowledge of the interference channels from the CR transmitters to the PU receivers. Previous work has considered perfect CR-to-PU channel knowledge [15], [16], limited-rate feedback from the PUs on CR-to-PU channel gains [17], imperfect CR-to-PU channel knowledge [18] and CR-to-PU channel uncertainty knowledge attained through SS or channel gain cartography [19].…”

An interference-aware distributed transmission technique for dense small cell networks

“…Minimum mean squared error (MMSE) receivers can improve the spectral efficiency (SE) by suppressing parts of the received interference [4]. The SE can also be enhanced via transmitter centric interference management techniques, such as interference aware transmission schemes [5], [6].…”

“…Distributed transmission techniques as a MU interference management tool has been studied in [5]- [7], among others. Reference [5] proposes precoding schemes that exploit multiple transmit antennas to either enhance the spatial multiplexing gain for the desired transmission, or avoid interference generated at the interfered receivers.…”