Wireless Internet. 7th International ICST Conference, WICON 2013, Shanghai, China, April 11-12, 2013, Revised Selected Papers

Research Article

A Scalable Feedback-Based Approach to Distributed Nullforming

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  • @INPROCEEDINGS{10.1007/978-3-642-41773-3_9,
        author={Muhammad Rahman and Soura Dasgupta and Raghuraman Mudumbai},
        title={A Scalable Feedback-Based Approach to Distributed Nullforming},
        proceedings={Wireless Internet. 7th International ICST Conference, WICON 2013, Shanghai, China, April 11-12, 2013, Revised Selected Papers},
        proceedings_a={WICON},
        year={2013},
        month={10},
        keywords={distributed nullforming cooperative transmission virtual antenna arrays},
        doi={10.1007/978-3-642-41773-3_9}
    }
    
  • Muhammad Rahman
    Soura Dasgupta
    Raghuraman Mudumbai
    Year: 2013
    A Scalable Feedback-Based Approach to Distributed Nullforming
    WICON
    Springer
    DOI: 10.1007/978-3-642-41773-3_9
Muhammad Rahman1,*, Soura Dasgupta1,*, Raghuraman Mudumbai1,*
  • 1: University of Iowa
*Contact email: mrahmn@engineering.uiowa.edu, dasgupta@engineering.uiowa.edu, rmudumbai@engineering.uiowa.edu

Abstract

We present a novel approach to the problem of distributed nullforming where a set of transmitters cooperatively transmit a common message signal in such a way that their individual transmissions precisely cancel each other at a designated receiver. Under our approach, each transmitter iteratively makes an adjustment to the phase of its transmitted RF signal, by effectively implementing a gradient descent algorithm to reduce the amplitude of the overall received signal to zero. We show that this gradient search can be implemented in a purely distributed fashion at each transmitter assuming only that each transmitter has an estimate of its own channel gain to the receiver. This is an important advantage of our approach and assures its scalability; in contrast any non-iterative approach to the nullforming problem requires centralized knowledge of the channel gain of every transmitter. We prove analytically that the gradient search algorithm converges to a null at the designated receiver. We also present numerical simulations to illustrate the robustness of this approach.