Full-Duplex Bidirectional MIMO: Achievable Rates Under Limited Dynamic Range

Abstract

Abstract-In this paper, we consider the problem of full-duplex bidirectional communication between a pair of modems, each with multiple transmit and receive antennas. The principal difficulty in implementing such a system is that, due to the close proximity of each modem's transmit antennas to its receive antennas, each modem's outgoing signal can exceed the dynamic range of its input circuitry, making it difficult-if not impossible-to recover the desired incoming signal. To address these challenges, we consider systems that use pilot-aided channel estimates to perform transmit beamforming, receive beamforming, and interference cancellation. Modeling transmitter/receiver dynamic-range limitations explicitly, we derive tight upper and lower bounds on the achievable sum-rate, and propose a transmission scheme based on maximization of the lower bound, which requires us to (numerically) solve a nonconvex optimization problem. In addition, we derive an analytic approximation to the achievable sum-rate, and show, numerically, that it is quite accurate. We then study the behavior of the sum-rate as a function of signal-to-noise ratio, interference-to-noise ratio, transmitter/receiver dynamic range, number of antennas, and training length, using optimized half-duplex signaling as a baseline.

Full-duplex in large-scale wireless systems

“…, y u N ul ] T , H u ∈ C N ul ×U is the (tall and skinny) uplink channel matrix, H s ∈ C N ul ×N dl is the self-interference channel from the BS transmitters to the BS receivers, and n u ∈ C N ul models additive noise; H u is generated from the WINNER-Phase-2 model [16]; the entries of H s are assumed to be i.i.d. ZMCG with variance β [7]; the entries of n u are assumed to be i.i.d. ZMCG with variance N u 0 .…”

“…Another promising technology that is believed to increase the spectral efficiency (compared to conventional half-duplex systems) is full-duplex wireless communication; this approach aims at transmitting and receiving data at the same time and within the same frequency band [7]. In theory, fullduplex data transmission is capable of doubling the spectral efficiency compared to that of half-duplex systems.…”

“…In practice, however, the benefits promised by full-duplex technology is limited by the so-called self-interference, which refers to the transmitted signals that are directly received at the terminal's receive chain (in addition to the data signals received from other transmitters). To combat the fundamental problem of self-interference, a variety of solutions have been proposed in the literature [7]- [13]. The schemes of [8], [9] rely on RF-level and analog-level cancellation methods.…”

“…In [10], selfinterference is cancelled by careful placement of the transmit and receive antennas at each terminal. Another approach is to cancel interference via baseband processing techniques, e.g., using sophisticated transmit and receive filters (see [7], [11]- [13]). More recently, multi-user interference cancellation schemes have been proposed in, e.g., [14], [15].…”

Channel Estimation for Self-Interference Cancellation in Full-Duplex Wireless Systems

“…Full-duplex wireless systems have attracted considerable attention owing to their advantages in nearly doubling the physical layer capability and solving open problems in wireless systems [1][2][3][4][5][6]. A full-duplex radio can simultaneously transmit and receive on the same frequency band, whereas a conventional half-duplex radio can only perform either transmission or reception at one time.…”