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Achieving Full Duplex Relay by Exploiting Multi-antenna Technology in Cooperative Communications

IP.com Disclosure Number: IPCOM000219202D
Publication Date: 2012-Jun-26
Document File: 9 page(s) / 167K

Publishing Venue

The IP.com Prior Art Database

Abstract

The full duplex relay, which can receive and transmit in the same wireless channel simultaneously, is a promising apparatus in cooperative communication system. However, in such relay system, since the transmit antenna is so close to the receive antenna, the received signal will be submerged or strongly interfered by such strong transmit signal. In order to overcome this weakness, in this invention, we propose a method and apparatus that utilizes multi-antenna technique to suppress such strong interference to a reasonable level. We deliberately generate a null (or deep fading) point in the position of the receive antenna through weighting different coefficients in the transmit antennas based on the real-time channel estimation between the transmit antenna and the receive antenna. This invention is also applicable for multi-carrier system or wideband wireless system.

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Page 01 of 9

Achieving Full Duplex Relay by Exploiting Multi-antenna Technology in Cooperative Communications

Cooperative diversity has recently received wide recognition as a promising technique to improve the performance of wireless systems. Within the framework of cooperative diversity, there are two basic cooperative protocols: amplify-and-forward (AF) and decoded-and-forward (DF). In AF mode, the relay forwards the received signal with an amplified version. In DF mode, it first decodes the received signal, then regenerates transmitted data and forwards to the destination. In IoT related applications, relay is an essential part for systems with long distance transmission requirements. For example, in oil pipe monitoring or grid transmission power line monitoring system, the wireless relay is the key component to transfer the original sensor data to the destination with multi-hop. The design of relay is vital for the whole system's performance, whether from the delay side or from the interference resistance side.

Base Station

Relay

Mobile User

1


Page 02 of 9

The cooperative communication can be generally divided into two phases. In the first phase, the source transmits the message to the relay. In second phase, the relay will retransmit the received signal to the destination in another orthogonal wireless channel.

Here the orthogonal wireless channel means that the relay can not receive and transmit in the same wireless channel simultaneously because such a full duplex relay is really difficult to implement in real system. Since the transmit antenna is so close to the receive antenna, the received signal will be submerged or strongly interfered by such strong transmit signal, which will make the relay unworkable.

Reference [1] proposed the interference suppression method by using two transmit antennas, where the receive antenna is located in a proper position. However, this mechanism can only applicable to the scenario with limited transmit power and less scatters (LOS), and it is also sensitive to working frequency and bandwidth.

To overcome the weakness of the prior works, in this invention, we propose a novel mechanism to achieve a fully duplex relay by exploiting multi-antenna technology based on real-time channel estimation.


[1] Jung II Choi, Mayank Jain, etl . Achieving single channel, full duplex wireless communication. Mobicom2010.

In this invention, we propose a full duplex relay system with utilizing multi-antenna technique to suppress such strong interference to a reasonable level. As we all know, with adopting multi-antenna technique, we can change the power spectrum in the space domain. The more antennas, the more degree of freedom we can derive.

2


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Relay

Tx

Rx

Relay Rx/Tx

Relay Tx/Rx

Figure: Illustration of Relay System with Interference Suppression Function

In this invention, we deliberately generate a null (or deep fading) point in the position of the receive antenna through weighting different coefficients in t...