Method to steer audio on a frequency restricted RF channel
Original Publication Date: 2014-Jun-24
Included in the Prior Art Database: 2014-Jun-24
Britton, Richard: INVENTOR [+4]
The customer/field is provided a means to associate a voted subsite (inbound audio) to a zero, one, or many transmit subsites as part of configuring the comparator product which functions as the voter and simulcast controller. Additionally, the customer/field may associate a group of transmitters to console commands to allow a dispatcher to manually steer console audio. During repeat audio scenarios, the comparator will vote which results in a specific inbound subsite being selected as the voted port. The comparator will then use the previously mentioned user configuration to map the voted port to a group of transmitters. The comparator will then transmit simulcasted audio to this group, and only this group of transmitters. For call continuity, the comparator will "latch" this voted port such that follow-on console transmissions will also be routed to this same group of transmitters. If the voted port changes, then the comparator will automatically change the group of transmitters involved in the call based upon user configuration. In the event that the dispatcher wishes to manually override automatic steering, the dispatch issues a dispatcher invokes a control command which the comparator receives and uses to determine the group of transmitters (based on user configuration) in which to use for the corresponding call.
Richard Britton, Eran Agmon, Kamel Chaker, Deganit Margalit
Motorola Solutions, Inc.
A method at a comparator (or voting Unit) of steering audio on a frequency restricted RF channel, by using existing simulcast technology for coverage benefits beyond single transmitter coverage, but limiting the quantity of transmitters so that undue audio distortion is eliminated. The method combines steering and simulcast technology to meet the outbound coverage objective. The method further includes a means, to associate a voted subsite (inbound audio) to zero, one, or many transmits as part of configuring the comparator product which functions as the voter and simulcast controller and to associate a group of transmitters to console commands to allow a dispatcher to manually steer console audio. This method will provide superior outbound coverage and enhance audio quality.
Simulcast is a technique used to provide large area coverage from a radio system to subscriber radios. In a simulcast communication system, the same radio signal is transmitted by two or more base stations on the same frequency from different locations (see Simulcast System Topology figure 1 below). The intent of simulcast is to extend the radio coverage to an area larger than a single transmitter can cover, while utilizing a single frequency. Simulcast technology is typically used across urban areas to provide adequate coverage given terrain and structure obstacles commonly occurring in urban areas.
In some overlap areas, use of simulcast across the entire area results in a coverage violation, since unacceptable audio distortion occurs because timing differences with that quantity of transmitters cannot be neutralized.
Figure 1 Simulcast System Topology
The standard method for manual audio steering used today by the operators (i.e. use of a single active transmitter) will not meet operators/customer coverage needs. The mixture of a very large geographic area and simulcast technology results in the need to sub-divide the coverage area into multiple cells to avoid phasing and distortion issues. The figure below attempts to graphically depict how the transmit RF coverage area of the one channel is sub-divided into 6 cells. Receive BRs(Base Repeater) are associated to transmit BRs (which may be the same BR in some instances) such that a subscriber transmission with the shaded area results in transmit activity in that same shaded area which is sufficient to satisfy contractual outbound coverage obligations. In this manner, only one shaded region is transmitting at any given time.
Figure 2 Graphical Representation of Regional Mutual Aid Channel
Further, the majority of the steering decisions must be made automatically by the system to avoid overwhelming the dispatcher operator with steering decisions. Therefore, a need exists for an automatic site steering method in a simulcast communication system which can...