Dina Katabi

Caraoke: An E-Toll Transponder Network for Smart Cities

By: 
Omid Abari, Deepak Vasisht, Dina Katabi, Anantha Chandrakasan
Appears in: 
CCR August 2015

Electronic toll collection transponders, e.g., E-ZPass, are a widely-used wireless technology. About 70% to 89% of the cars in US have these devices, and some states plan to make them mandatory. As wireless devices however, they lack a basic function: a MAC protocol that prevents collisions. Hence, today, they can be queried only with directional antennas in isolated spots. However, if one could interact with e-toll transponders anywhere in the city despite collisions, it would enable many smart applications.

A Real-time 802.11 Compatible Distributed MIMO System

By: 
Ezzeldin Hamed, Hariharan Rahul, Mohammed A. Abdelghany, Dina Katabi
Appears in: 
CCR August 2015

We present a demonstration of a real-time distributed MIMO system, DMIMO. DMIMO synchronizes transmissions from 4 distributed MIMO transmitters in time, frequency and phase, and performs distributed multi-user beamforming to independent clients. DMIMO is built on top of a Zynq hardware platform integrated with an FMCOMMS2 RF front end. The platform implements a custom 802.11n compatible MIMO PHY layer which is augmented with a lightweight distributed synchronization engine. The demonstration shows the received constellation points, channels, and effective data throughput at each client.

LTE radio analytics made easy and accessible

By: 
Swarun Kumar, Ezzeldin Hamed, Dina Katabi, Li Erran Li
Appears in: 
CCR August 2014

Despite the rapid growth of next-generation cellular networks, researchers and end-users today have limited visibility into the performance and problems of these networks. As LTE deployments move towards femto and pico cells, even operators struggle to fully understand the propagation and interference patterns affecting their service, particularly indoors. This paper introduces LTEye, the first open platform to monitor and analyze LTE radio performance at a fine temporal and spatial granularity. LTEye accesses the LTE PHY layer without requiring private user information or provider support.

RF-IDraw: virtual touch screen in the air using RF signals

By: 
Jue Wang, Deepak Vasisht, Dina Katabi
Appears in: 
CCR August 2014

Prior work in RF-based positioning has mainly focused on discovering the absolute location of an RF source, where state-of-theart systems can achieve an accuracy on the order of tens of centimeters using a large number of antennas. However, many applications in gaming and gesture based interface see more benefits in knowing the detailed shape of a motion. Such trajectory tracing requires a resolution several fold higher than what existing RF-based positioning systems can offer.

A light-weight wireless handshake

By: 
Kate Lin, Yung-Jen Chuang, Dina Katabi
Appears in: 
CCR April 2012

In many wireless systems, it is desirable to precede a data transmission with a handshake between the sender and the receiver. For example, RTS-CTS is a handshake that prevents collisions due to hidden terminals. Past work, however, has shown that the overhead of such handshake is too high for practical deployments. We present a new approach to wireless handshake that is almost overhead free.

Public Review By: 
Bhaskaran Raman

Wireless systems often face this trade-off: information exchange is necessary for performance enhancement, but such information exchange itself has a high cost. A classical example is that of RTS-CTS packet exchange in WiFi systems, which can help in various aspects such as hidden node detection, effective rate adaptation, channel estimation in MIMO systems, etc. However, prior work has shown the cost of RTS-CTS to be quite high. This paper proposes an interesting idea: separate the data header from the data, and ACK header from the ACK, and use the header exchange as an inexpensive proxy for RTS-CTS exchange. While an attractive idea on the surface, separating the header from the actual body raises questions about whether the packet's decodability will be affected. Through a software-radio based prototype, this paper demonstrates that the header separation has insignificant effect on packet reception ratio. Further, the paper experimentally shows that severe hidden terminal scenarios can be effectively avoided, with the header-exchange. Experimental results are also presented to indicate that rate adaptation can function about twice as effectively with such header-exchange, than without. The reviews agreed that the idea of separating the header from the body, is novel for wireless systems. Worthy of further exploration are issues such as: (1) Would the SIFS interval need to be lengthened in a real implementation, due to the extra computations necessary in the dataACK header exchange? (2) What benefits, if any, would accrue in practice for other systems requiring feedback, such as MIMO beamforming systems, if the data-ACK header exchange were to be used for this purpose?

SourceSync: A Distributed Wireless Architecture for Exploiting Sender Diversity

By: 
Hariharan Rahul, Haitham Hassanieh, and Dina Katabi
Appears in: 
CCR October 2010

Diversity is an intrinsic property of wireless networks. Recent years have witnessed the emergence of many distributed protocols like ExOR, MORE, SOAR, SOFT, and MIXIT that exploit receiver diversity in 802.11-like networks. In contrast, the dual of receiver diversity, sender diversity, has remained largely elusive to such networks.

Interference Alignment and Cancellation

By: 
Shyamnath Gollakota, Samuel David Perli, and Dina Katabi
Appears in: 
CCR October 2009

The throughput of existing MIMO LANs is limited by the number of antennas on the AP. This paper shows how to overcome this limita- tion. It presents interference alignment and cancellation (IAC), a new approach for decoding concurrent sender-receiver pairs in MIMO networks. IAC synthesizes two signal processing techniques, inter- ference alignment and interference cancellation, showing that the combination applies to scenarios where neither interference align- ment nor cancellation applies alone. We show analytically that IAC almost doubles the throughput of MIMO LANs.

Symbol-level Network Coding for Wireless Mesh Networks

By: 
Sachin Katti, Dina Katabi, Hari Balakrishnan, and Muriel Medard
Appears in: 
CCR October 2008

This paper describes MIXIT, a system that improves the throughput of wireless mesh networks. MIXIT exploits a basic property of mesh networks: even when no node receives a packet correctly, any given bit is likely to be received by some node correctly. Instead of insisting on forwarding only correct packets, MIXIT routers use physical layer hints to make their best guess about which bits in a corrupted packet are likely correct and forward them to the destination.

ZigZag Decoding: Combating Hidden Terminals in Wireless Networks

By: 
Shyamnath Gollakota and Dina Katabi
Appears in: 
CCR October 2008

This paper presents ZigZag, an 802.11 receiver design that combats hidden terminals. ZigZag’s core contribution is a new form of interference cancellation that exploits asynchrony across successive collisions. Specifically, 802.11 retransmissions, in the case of hidden terminals, cause successive collisions. These collisions have different interference-free stretches at their start, which ZigZag exploits to bootstrap its decoding.

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