Browse Prior Art Database

BEAM LIST DETERMINATION FOR RING ALERT IN A MOBILE SATELLITE SYSTEM

IP.com Disclosure Number: IPCOM000008895D
Original Publication Date: 1998-Sep-01
Included in the Prior Art Database: 2002-Jul-22
Document File: 3 page(s) / 178K

Publishing Venue

Motorola

Related People

Scott Blanchard: AUTHOR [+3]

Abstract

For a Mobile Satellite System (MSS) to operate, portable and mobile radio users must be notified of an incoming call. This is done using a ring alert sig- nal which is broadcast on various beams on various satellites that each of the radio users are listening to. This paper describes an approach for the calculation of the beams and satellites which should be used to ensure that the user will hear the ring alert message. This calculation is based upon the stored location area that the user is known to be operating in called a "Location Area Code" (LAC).

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MOTOROLA Technical Developments

BEAM LIST DETERMINATION FOR RING ALERT

IN A MOBILE SATELLITE SYSTEM

by Scott Blanchard, Joseph Lester and Dean Vanden Heuval

ABSTRACT

   For a Mobile Satellite System (MSS) to operate, portable and mobile radio users must be notified of an incoming call. This is done using a ring alert sig- nal which is broadcast on various beams on various satellites that each of the radio users are listening to. This paper describes an approach for the calculation of the beams and satellites which should be used to ensure that the user will hear the ring alert message. This calculation is based upon the stored location area that the user is known to be operating in called a "Location Area Code" (LAC).

  Thus an apparatus is needed to determine the smallest (or near smallest) subset of the antenna beams that the ring alert message can be sent on with a high probability of contacting the subscriber. The time required for this apparatus to compute the set of beams is relatively small. Since the beam set is computed every time a subscriber is called, the number of calls per second in the telecommunica- tion system sets the time available for the apparatus to compute the beam set. In a typical system the time available is on the order of 10 milliseconds. This invention provides an apparatus for computing a near optimum set of beams in a small amount of time and requiring a small amount of data to describe the telecommunication system antenna beams.

PROBLEMS ENCOUNTERED BY THE MSS

  A global satellite telecommunication system is able to establish a wireless communication link with subscribers located anywhere in the world. To accomplish this the antennas on the satellites must cover the entire earth with sufficient antenna gain to establish the communication link. When contact is required with a subscriber, the telecommunication system sends the subscriber a message to alert the subscriber of an incoming call. This process is referred to as 'ring alerting' the subscriber. If the ring alert message is sent out over all antenna beams in the system then the message is guaranteed to reach the subscriber, since the system antenna foot- prints cover the entire earth. Sending the message in all antenna beams, however, makes inefficient use of system resources such as the bandwidth available for the ring alert messages and system DC power.

METHOD OF OPERATION

  This approach, referred to as the Ring Alert Apparatus, accepts as an input a message containing the location of the subscriber on or near the surface of the earth. The subscriber's location is in the form of a Location Area Code (LAC), which is an area on or near the surface of the earth. It responds with the set of beams which intersect the ring alert area, i.e. those beams required to ring alert the subscriber. To compute the beam list the apparatus requires the fol- lowing data:

I. The orbital elements of each of the satellites,

2. Data to describe the satellite antenna b...