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SHARING ANTENNAS IN MULTI-INPUT MULTI-OUTPUT (MIMO) MULTI-USER ENVIRONMENTS

IP.com Disclosure Number: IPCOM000237588D
Publication Date: 2014-Jun-25
Document File: 6 page(s) / 142K

Publishing Venue

The IP.com Prior Art Database

Related People

Leo Dumov: AUTHOR [+2]

Abstract

The proposed innovation entails sharing an antenna array between two cellular modems, each supporting Diversity or Multiple-Input Multiple-Output (MIMO) antennas. The proposal utilizes, in one embodiment, miniature, surface-mount splitters, along with low-cost U.FL cabling or printed-circuit board (PCB) traces for their interconnection into a unique topology which saves the cost of two antennas, and more importantly, the cost of material and installation for two low-loss radio frequency (RF) cables used to connect the antenna to the modems. The described methodology is particularly appropriate in situations where external antennas are deployed, as for example, is the case for mobile routers.

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SHARING ANTENNAS IN MULTI-INPUT MULTI-OUTPUT (MIMO) MULTI-USER ENVIRONMENTS

AUTHORS:

Leo Dumov David Doak

CISCO SYSTEMS, INC.

ABSTRACT

    The proposed innovation entails sharing an antenna array between two cellular modems, each supporting Diversity or Multiple-Input Multiple-Output (MIMO) antennas. The proposal utilizes, in one embodiment, miniature, surface-mount splitters, along with low-cost U.FL cabling or printed-circuit board (PCB) traces for their interconnection into a unique topology which saves the cost of two antennas, and more importantly, the cost of material and installation for two low-loss radio frequency (RF) cables used to connect the antenna to the modems. The described methodology is particularly appropriate in situations where external antennas are deployed, as for example, is the case for mobile routers.

DETAILED DESCRIPTION

    The use of MIMO antenna arrays to increase spectral efficiency (bits per second per Hz of bandwidth) is well-documented in the literature. A MIMO implementation normally entails increasing the number of input (transmit, "MI") and/or output (receive, "MO") antennas in a particular direction of transmission. For example, a cellular provider may transmit over four antennas to a subscriber who receives the signal with two antennas. This is known as 4x2 MIMO. (In the opposite direction, this is 2x4 MIMO.) If the provider uses two transmit antennas for the same user with two receive antennas, this is known as 2x2 MIMO. MIMO is a requirement of Long Term Evolution (LTE) in 3GPP Release 8, Category 2 and higher (50Mbps downlink).

    In some implementations of cellular user equipment, it may be advantageous to co-locate equipment for more than one user, or for more than one carrier. With advances in radio miniaturization technology, the co-location of the components can be done

Copyright 2014 Cisco Systems, Inc.
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relatively easily, with the exception of the antennas. Antennas must be sized and spacedaccording to the wavelengths of interest for best efficiency and utilization of the signal. This can create challenges with physical limitations of the equipment, which can otherwise be expensive to overcome. For example, an enclosure containing two user equipment radios, each with two antennas, must be larger than would be needed to house only the radios, simply because of the physical limitations of the antennas. Furthermore, spacing and signal reception requirements of the antennas may necessitate that they be moved to a remote location, which requires the use of expensive, low-loss, RF cabling.

    Thus, a method to reduce the number of required antennas and low-loss cables in MIMO configurations with multiple users (or "radios," or "modems") is desirable, provided any adverse effects on the signals can be overcome.

    A key (and valid) assumption for the innovation presented herein is that cellular service providers (SPs) use unique frequency bands for their services. This is based on the fact...