Browse Prior Art Database

EFFICIENT MSU LOCATION TRACKING FOR DATA SITE STEERING

IP.com Disclosure Number: IPCOM000011396D
Original Publication Date: 2003-Feb-18
Included in the Prior Art Database: 2003-Feb-18
Document File: 5 page(s) / 133K

Publishing Venue

Motorola

Related People

John Suh: AUTHOR [+3]

Abstract

This paper describes a method for a set of simulcast channel controllers in a trunked mobile radio communications system to efficiently track mobile subscriber unit (MSU) locations among multiple simulcast RF sites for the purpose of site steering packet data transmissions to individual MSUs. The method is efficient because only the subset of MSUs that are currently using or preparing to use a packet data channel (PDCH) are tracked from among the entire set of MSUs using a simulcast subsystem.

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Efficient MSU Location TRACKING for Data Site Steering

By John Suh, Nathanael Kuehner, and Robert Biggs

ABSTRACT

This paper describes a method for a set of simulcast channel controllers in a trunked mobile radio communications system to efficiently track mobile subscriber unit (MSU) locations among multiple simulcast RF sites for the purpose of site steering packet data transmissions to individual MSUs. The method is efficient because only the subset of MSUs that are currently using or preparing to use a packet data channel (PDCH) are tracked from among the entire set of MSUs using a simulcast subsystem.

PROBLEM

In order to site steer packet data in a trunked simulcast subsystem, the radio network infrastructure must track MSU locations among the subsystem’s RF sites and between its channels. Furthermore, the tracking method must be efficient because of the preference to place all site steering functionality within the simulcast channel controller, an embedded real-time device with limited processing and memory resources.

 

The prior art has a method of tracking MSU locations in the central data controller of a single channel conventional system. There are several drawbacks with extending this approach to large multi-channel trunked systems:

1.       It places simulcast-specific requirements on central data controllers that would not otherwise need to know about simulcast and site steering.� This compromises the design goal of making these controllers generic for use in many different system types.

2.       Once the central data controller has begun transferring outbound payload to the simulcast subsystem, it is too late for it to apply MSU location updates to this payload.

3.       Location updates may be delayed as they traverse extra network hops between the simulcast subsystem and the central data controller.

SOLUTION

Overview

Simulcast channel controllers determine MSU location by comparing the signal quality of inbound transmissions received from the MSU via different RF receiver sites. The site with the best quality signal is deemed to be the site nearest to the MSU.

The need for dedicated ‘radio-finder’ messages is eliminated by leveraging off of inbound trunking control messages.� Specific control channel messages (those that indicate that the MSU is preparing to use a PDCH) activate the location determination algorithm to locate the MSU.� Such MSUs are called ‘pending users’, since they will soon be on a PDCH pending successful completion of the necessary steps. Accordingly, their locations are stored by all of the subsystem’s simulcast channel controllers in their Pending Users Databases. In addition, each PDCH simulcast controller maintains a separate database of the MSUs that it knows to be active on its channel, called an Active Users Database.

The combination of these two databases ensures that every PDCH simulcast controller has the particular MSU location information it needs at any given time, even though it is only tracking a small...