Browse Prior Art Database

Group Call Simultaneously Sourcing Narrowband and Broadband Audio

IP.com Disclosure Number: IPCOM000238348D
Original Publication Date: 2014-Aug-19
Included in the Prior Art Database: 2014-Aug-19
Document File: 4 page(s) / 147K

Publishing Venue

Motorola

Related People

Kuehner, Nate: INVENTOR [+2]

Abstract

A method of group call setup that, depending on the capabilities and coverage conditions of the call's source and destination devices: -assigns the call's sourcing device or devices to transmit the call's source audio at either: -- (i) a narrowband (i.e. low) bitrate (such as a P25 or TETRA vocoder), or -- (ii) a broadband (i.e. high) bitrate (such as a high-quality, low compression vocoder), or -- (iii) at two different bitrates simultaneously, a low, narrowband bitrate and a high, broadband bitrate, and -assigns the call's destination devices to receive call audio via narrowband, broadband, or both. See attached slides for more details.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 50% of the total text.

GROUP CALL SIMULTANEOUSLY SOURCING  NARROWBAND AND BROADBAND AUDIO STREAMS

By Nathanael Kuehner, Robert Horvath

Motorola Solutions, Inc.

 

ABSTRACT

This publication describes a method of group call setup within  the field of Land Mobile Radio (LMR) systems. Depending on the capabilities and coverage conditions of the call’s source and destination devices, this method (1) assigns the call’s sourcing device or devices to transmit the call’s source audio at either (i) a narrowband (NB) (i.e. low) bitrate (such as a P25 or TETRA vocoder), or (ii) a broadband (BB) (i.e. high) bitrate (such as a high-quality, low compression vocoder), or (iii) at two different bitrates simultaneously, a low, narrowband bitrate and a high, broadband bitrate, and (2) assigns the call’s destination devices to receive call audio via narrowband, broadband, or both.

PROBLEM

In traditional Land Mobile Radio (LMR) systems, audio is heavily compressed to economize bitrate to fit within a narrow air interface bandwidth.  In broadband wireless systems (e.g. LTE), higher bitrate ‘high-definition’ audio compression is feasible and desirable.  In a group call with a mixture of narrowband-connected and broadband-connected devices, users are best-served if they receive high-definition audio whenever possible, while still gaining the benefits of highly-compressed narrowband audio when nothing better is available. While it is possible to transcode between audio bitrates, it typically impacts audio quality, and it also requires decrypting and re-encrypting, which is objectionable to customers who want full end-to-end encryption.

SOLUTION

This problem is solved by setting up a group call’s audio source and destination(s) in a manner consistent with the capabilities and coverage conditions of the call’s source and destination devices.  This method (1) assigns the call’s sourcing device or devices to transmit the call’s source audio at either (i) a narrowband bitrate, or (ii) a broadband bitrate, or (iii) at two different bitrates simultaneously, a low, narrowband bitrate and a high, broadband bitrate, and (2) assigns the call’s destination devices to receive call audio via narrowband, broadband, or both.

In addition to this basic method, the following optional elements are possible:

·         When a NB+BB-capable sourcing device is in weak/unreliable coverage, as defined by either signal quality metrics or certain regions of a coverage map, then assign the sourcing device to transmit via both BB and NB and combine audio streams in the infrastructure to combat fading/outage from either RAN individually.

·         Similarly, when a NB+BB-capable destination device is in weak coverage, assign it to receive via both BB and NB RANs, and combine the (potentially different bit-rate) audio streams internally before playing out to user.

·         A device’s BB capability may come from (i) its own BB RAN radio, or (ii) from a collaborating BB device paired (e.g. via Bluetooth) with it, or...