Browse Prior Art Database

PREFERRED SITE CHANNEL SCAN METHOD FOR TRUNKED RADIO SYSTEMS

IP.com Disclosure Number: IPCOM000006252D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2001-Dec-19
Document File: 4 page(s) / 174K

Publishing Venue

Motorola

Related People

Robin Roberts: AUTHOR [+2]

Abstract

Trunked radio system designers have the ability to define transmitter site locations to provide optimum sys- tem operation. However, in the real world, the place- ment of transmitter sites in large multi-site trunked radio systems is often less than ideal. This is because the selec- tion of transmitter sites is often constrained by issues other than RF coverage: zoning regulations, site devel- opment costs, site access, etc. Often the result is non- ideal placement of sites, which can result in considerable RF overlap areas, as well as areas of weak signal strength. In these situations, large numbers of subscriber radios can cluster on the control channel of a single site even though a different distribution of radio subscriber units among the sites would be more desirable.

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MOTOROLA INC. Technical Developments Volume 14 December 1991

PREFERRED SITE CHANNEL SCAN METHOD FOR TRUNKED RADIO SYSTEMS

by Robin Roberts &Wilson Wiedenheft

  Trunked radio system designers have the ability to define transmitter site locations to provide optimum sys- tem operation. However, in the real world, the place- ment of transmitter sites in large multi-site trunked radio systems is often less than ideal. This is because the selec- tion of transmitter sites is often constrained by issues other than RF coverage: zoning regulations, site devel- opment costs, site access, etc. Often the result is non- ideal placement of sites, which can result in considerable RF overlap areas, as well as areas of weak signal strength. In these situations, large numbers of subscriber radios can cluster on the control channel of a single site even though a different distribution of radio subscriber units among the sites would be more desirable.

  Unless the overall radio system design specifically addresses this issue, subscribers will often be operating via sites which are not ideal to their area of operations. This has two important system level consequences. Fitly the clustering of so many radios (and talkgroups) at a single site can cause that site to be excessively busy while channels at other sites are under-utilized. Furthermore, systems need to maximize channel usage efftciency by minimizing the number of sites that a channel must be assigned at for any given talkgroup call. This will reduce the total number of channels required in the system. If subscriber units are scattered between more sites than is necessary, that channel efXciency will be impacted.

THE PREFERRED SITE CHANNEL SCAN METHOD

  This method involves the use of subscriber radio unit algorithm which, when used in conjunction with radio unit-to-site registration technique, will ensure that radios lock on to a predetermined preferred site and operate there as long as that site is able to provide an adequate level of service. Furthermore, if the need arises (due to geographic positioning) for the radio to use a non- preferred site, it will periodically re-scan its preferred site to determine whether it can return to that site.

The preferred site list needs to be defined on a talkgroup basis, since each talkgroup may have differ-

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ent operating requirements. The system manager must determine the preferred sites for each talkgroup. This will generally correspond to the sites closest to the "normal" operating area of members of the given talkgroup. The preferred site list is then loaded in the radio personality information.

  An important part of the implementation of this method involves the assignment of a signal quality rat- ing which is determined by the radio to each of the site control channels it detects upon power up and when scanning. This rating is made on the basis of either con- trol channel signal strength (RSSI) or data bit error rate (See figure 1.)

  The algorithm us...