Communications: electrical – Continuously variable indicating – With meter reading
Reexamination Certificate
1998-11-03
2001-11-27
Zimmerman, Brian (Department: 2735)
Communications: electrical
Continuously variable indicating
With meter reading
C340S007460, C340S870030, C455S502000, C455S524000, C370S332000, C370S333000
Reexamination Certificate
active
06323784
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radio selective call receiver and, more particularly, to a method for automatically selecting a reception channel from a plurality of channels.
2. Description of the Related Art
There has been disclosed an example of a radio selective call receiver having the function of automatically switching a reception area in Japanese Patent Application Laid-Open Publication No. 6-315001. This conventional example is used in a system which is composed of a plurality of radio areas (small zones) each having a different frequency. When the state of the receiver comes out of synchronization with a selective calling signal, the sweep of the frequency channels is performed a prescribed number of times in accordance with a scan list. Then, when no synchronization signal has been detected, the operation of the radio system is stopped and, after the lapse of a prescribed time period, the sweep of the frequency channels is performed again.
However, in the above-described conventional radio selective call receiver, even when the channel condition has become temporarily deteriorated, the sweep of the frequency channels is performed in accordance with the scan list. Therefore, the possibility that the receiver will become synchronized with a channel different from the previous channel becomes high. For this reason, in a case where adjacent radio areas are overlapped, it results that a changeover or handover from one area to another frequently occurs. Therefore, when area changeover is not in time, there is the possibility that the failure to receive the selective calling signal will occur.
Further, the above-described radio selective call receiver employs a channel selection method to prevent the frequent occurrences of such area changeover. More specifically, when detecting the failure of synchronization with a current reception channel, it is determined whether this failure of synchronization with the reception channel has been repeatedly detected a prescribed number of times. If the synchronization with the reception channel was not successfully established after the repetition of the channel synchronization check, then the channel sweep is started in accordance with the scan list.
In this method, however, an unnecessary period of time for determining the synchronization of the last synchronized channel is needed and therefore the average time length needed for achieving a re-synchronization becomes long. As a result, the battery life becomes inconveniently short. Further, in a case where the status of the electric field becomes bad at the point in time when determining the synchronization of the last synchronized channel, the receiver becomes synchronized with an available channel that has been first detected. For this reason, there is the possibility that area changeover will frequently occur.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a channel selecting method which enables efficient selection of a reception area without performing unnecessary changeover on the channels.
Another object of the present invention is to provide a radio selective call receiver which enables automatic selection of the channels with a lower power consumption.
According to an aspect of the present invention, a reception channel is selected from a plurality of radio channels in a radio selective call receiver as follows: a) when having lost synchronism with a first radio channel, scanning the radio channels in a predetermined sequential order to search for a second radio channel with which synchronization is established; b) when the second radio channel has been found, switching to the first radio channel to determine whether synchronization can be established with the first radio channel; c) when synchronization has been established with the first radio channel, selecting the first radio channel as the reception channel; and d) when synchronization fails to be established with the first radio channel, selecting the second radio channel as the reception channel.
As described above, it is again determined whether the previous sync established channel (the first radio channel) is now qualified for reception when switching to the second radio channel. If the first radio channel is available for sufficient reception, the first radio channel that was selected previously is again selected with making no channel change. Accordingly, it is possible to prevent execution of unnecessary area changeovers due to temporary deterioration in radio condition and to achieve an increase in the life of the battery and an increase in the efficiency with which the sync pull-in operation is performed.
According to another aspect of the present invention, a reception channel is selected from a plurality of radio channels as follows: a) when having lost synchronism with a first radio channel, scanning the radio channels in a predetermined sequential order to search for a second radio channel with which synchronization is established: b) when the second radio channel has been found, determining quality of the second radio channel; c) when the quality of the second radio channel has been determined, switching to the first radio channel to determine whether synchronization can be established with the first radio channel; d) when synchronization has been established with the first radio channel, determining quality of the first radio channel; and e) selecting one of the first radio channel and the second radio channel as the reception channel by comparing quality between the first radio channel and the second channel.
The step e) may be comprised of the steps of selecting the first radio channel as the reception channel when the quality of the first radio channel is not less than the quality of the second radio channel; and selecting the second radio channel as the reception channel when the quality of the first radio channel is less than the quality of the second radio channel.
Alternatively, the step e) may be comprised of the steps of relatively decreasing the quality of the second radio channel In a predetermined ratio with respect to the quality of the first radio channel to produce a decreased quality of the second radio channel; comparing the quality of the first radio channel to the decreased quality of the second radio channel; selecting the first radio channel as the reception channel when the quality of the first radio channel is not less than the decreased quality of the second radio channel; and selecting the second radio channel as the reception channel when the quality of the first radio channel is less than the decreased quality of the second radio channel.
When the second radio channel has been found through the channel scanning, the condition of the first radio channel that was a previously sync established channel is again checked. Therefore, under the circumstances wherein area changeover is properly needed, the area changeover can be performed smoothly.
Further, since the quality of the second radio channel is relatively decreased in a predetermined ratio with respect to the quality of the first radio channel and then the comparison is made, it is possible to prevent execution of unnecessary area changeovers due to temporary deterioration in radio condition and to achieve an increase in the life of the battery and an increase in the efficiency with which the sync pull-in operation is performed.
REFERENCES:
patent: 5187470 (1993-02-01), King et al.
patent: 5280541 (1994-01-01), Marko et al.
patent: 5787346 (1998-07-01), Iseyama
patent: 5793756 (1998-08-01), Ayerst et al.
patent: 5875179 (1999-02-01), Tikalsky
patent: 0 118 153 A1 (1984-09-01), None
patent: 0 593 027 A1 (1994-04-01), None
patent: 0 632 599 A1 (1995-01-01), None
patent: 6-315001 (1994-11-01), None
patent: WO 91/10300 (1991-07-01), None
Dalencourt Yves
NEC Corporation
Scully Scott Murphy & Presser
Zimmerman Brian
LandOfFree
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