This paper presents, FastForward (FF), a novel full duplex relay that constructively forwards signals such that wireless network throughput and coverage is significantly enhanced. FF is a Layer 1 in-band full duplex device, it receives and transmits signals directly and simultaneously on the same frequency. It cleanly integrates into existing networks (both WiFi and LTE) as a separate device and does not require changes to the clients. FF’s key invention is a constructive filtering algorithm that transforms the signal at the relay such that when it reaches the destination, it constructively combines with the direct signals from the source and provides a significant throughput gain. We prototype FF using off-the-shelf software radios running a stock WiFi PHY and show experimentally that it provides a 3× median throughput increase and nearly a 4× gain at the edge of the coverage area.
Dinesh Bharadia, Sachin Katti
This paper presents demonstration of a real-time full duplex point-to-point link, where transmission and reception occurs in the same spectrum band simultaneously between a pair of full-duplex radios. This demo first builds a full duplex radio by implementing self-interference cancellation technique on top of a traditional half duplex radio architecture. We then establish a point-to-point link using a pair of these radios that can transmit and receive OFDM packets. By changing the environmental conditions around the full-duplex radios we then demonstrate the robustness of the self-interference cancellation to adapt to the changing environment.
Dinesh Bharadia, Kiran Joshi, Sachin Katti
This paper presents the design and implementation of the first in-band full duplex WiFi-PHY based MIMO radios that practically achieve the theoretical doubling of throughput. Our design solves two fundamental challenges associated with MIMO full duplex: complexity and performance. Our design achieves full duplex with a cancellation design whose complexity scales almost linearly with the number of antennas, this complexity is close to the optimal possible. Further we also design novel digital estimation and cancellation algorithms that eliminate almost all interference and achieves the same performance as a single antenna full duplex SISO system, which is again the best possible performance. We prototype our design by building our own analog circuit boards and integrating them with a WiFi-PHY compatible standard WARP software radio implementation. We show experimentally that our design works robustly in noisy indoor environments, and provides close to the expected theoretical doubling of throughput in practice.
Dinesh Bharadia, Sachin Katti
This paper asks the following question: could we transform the radios found in our personal gadgets into powerful multipurpose scanning devices that can detect and locate tumors, guns, buried human bodies, a la the Star Trek Tricoder? Our key insight is that if radios could measure the backscatter of their own transmissions (i.e. reflections from the environment of their transmissions), then Tricorder-style powerful object detection and localization algorithms could be realized. In this paper we focus specifically on backscatter measurement, we describe novel circuits and algorithms that can be added to existing radios to enable them to accurately and concurrently receive and disentangle their own transmissions’ reflections and infer its properties.
Dinesh Bharadia, Kiran Raj Joshi, Sachin Katti
This paper presents the design and implementation of the first in-band full duplex WiFi radios that can simultaneously transmit and receive on the same channel using standard WiFi 802.11ac PHYs and achieves close to the theoretical doubling of throughput in all practical deployment scenarios. Our design uses a single antenna for simultaneous TX/RX (i.e., the same resources as a standard half duplex system). We also propose novel analog and digital cancellation techniques that cancel the self interference to the receiver noise floor, and therefore ensure that there is no degradation to the received signal. We prototype our design by building our own analog circuit boards and integrating them with a fully WiFi-PHY compatible software radio implementation. We show experimentally that our design works robustly in noisy indoor environments, and provides close to the expected theoretical doubling of throughput in practice.
Dinesh Bharadia, Emily McMilin, Sachin Katti
Citation count > 1700
This paper presents a full duplex radio design using signal inversion and adaptive cancellation. Signal inversion uses a simple design based on a balanced/unbalanced (Balun) transformer. This new design, unlike prior work, supports wideband and high power systems. In theory, this new design has no limitation on bandwidth or power. In practice, we find that the signal inversion technique alone can cancel at least 45dB across a 40MHz bandwidth. Further, combining signal inversion cancellation with cancellation in the digital domain can reduce self-interference by up to 73dB for a 10MHz OFDM signal.
Mayank Jain, Jung Il Choi, Taemin Kim, Dinesh Bharadia, Siddharth Seth, Kannan Srinivasan, Philip Levis, Sachin Katti, Prasun Sinha