In-band full-duplex (IBFD) operation has emerged as an attractive solution for increasing the throughput of wireless communication systems and networks. With IBFD, a wireless terminal is allowed to transmit and receive simultaneously in the same frequency band. This tutorial paper reviews the main concepts of IBFD wireless. One of the biggest practical impediments to IBFD operation is the presence of self-interference, i.e., the interference that the modem's transmitter causes to its own receiver. This tutorial surveys a wide range of IBFD self-interference mitigation techniques. Also discussed are numerous other research challenges and opportunities in the design and analysis of IBFD wireless systems.

/pdf/in-band-full-duplex-wireless-challenges-and-opportunities-djlyhtrciu.pdf

In-Band Full-Duplex Wireless: Challenges and Opportunities

In-band full-duplex (IBFD) operation has emerged as an attractive solution for increasing the throughput of wireless communication systems and networks. With IBFD, a wireless terminal is allowed to transmit and receive simultaneously in the same frequency band. This tutorial paper reviews the main concepts of IBFD wireless. Because one the biggest practical impediments to IBFD operation is the presence of self-interference, i.e., the interference caused by an IBFD node's own transmissions to its desired receptions, this tutorial surveys a wide range of IBFD self-interference mitigation techniques. Also discussed are numerous other research challenges and opportunities in the design and analysis of IBFD wireless systems.

We present an experiment-based characterization of passive suppression and active self-interference cancellation mechanisms in full-duplex wireless communication systems. In particular, we consider passive suppression due to antenna separation at the same node, and active cancellation in analog and/or digital domain. First, we show that the average amount of cancellation increases for active cancellation techniques as the received self-interference power increases. Our characterization of the average cancellation as a function of the self-interference power allows us to show that for a constant signal-to-interference ratio at the receiver antenna (before any active cancellation is applied), the rate of a full-duplex link increases as the self-interference power increases. Second, we show that applying digital cancellation after analog cancellation can sometimes increase the self-interference, and thus digital cancellation is more effective when applied selectively based on measured suppression values. Third, we complete our study of the impact of self-interference cancellation mechanisms by characterizing the probability distribution of the self-interference channel before and after cancellation.

/pdf/experiment-driven-characterization-of-full-duplex-wireless-3u33o8w3q1.pdf

Experiment-Driven Characterization of Full-Duplex Wireless Systems

We study full-duplex wireless communication systems where same band simultaneous bidirectional communication is achieved via cancellation of the self-interfering signal Using off-the-shelf MIMO radios, we present experimental results that characterize the suppression performance of three self-interference cancellation mechanisms, which combine a different mix of analog and digital cancellation Our experimental results show that while the amount of self-interference increases linearly with the transmitted power, the self-interference can be sufficiently cancelled to make full-duplex wireless communication feasible in many cases Our experimental results further show that if the self-interference is cancelled in the analog domain before the interfering signal reaches the receiver front end, then the resulting full-duplex system can achieve rates higher than the rates achieved by a half-duplex system with identical analog resources

/pdf/full-duplex-wireless-communications-using-off-the-shelf-1c51cbc7l0.pdf

Full-duplex wireless communications using off-the-shelf radios: Feasibility and first results

In this paper, we present an experiment- and simulation-based study to evaluate the use of full duplex (FD) as a potential mode in practical IEEE 802.11 networks. To enable the study, we designed a 20-MHz multiantenna orthogonal frequency-division-multiplexing (OFDM) FD physical layer and an FD media access control (MAC) protocol, which is backward compatible with current 802.11. Our extensive over-the-air experiments, simulations, and analysis demonstrate the following two results. First, the use of multiple antennas at the physical layer leads to a higher ergodic throughput than its hardware-equivalent multiantenna half-duplex (HD) counterparts for SNRs above the median SNR encountered in practical WiFi deployments. Second, the proposed MAC translates the physical layer rate gain into near doubling of throughput for multinode single-AP networks. The two results allow us to conclude that there are potentially significant benefits gained from including an FD mode in future WiFi standards.

Design and Characterization of a Full-Duplex Multiantenna System for WiFi Networks

Division-free duplex is proposed for future wireless systems, thus providing simultaneous duplex radio transmission on a division-free basis. The required duplex isolation can be achieved by electronic interference cancellation operating at both RF and baseband, with results from an experimental RF system yielding some 72 dB duplex isolation at 1.8 GHz for 200 kHz channelisation.

S. Chen

Papers

Division-free duplex for wireless applications