Radio selective pager

Details Radio selective pager Radio selective pager

1998-06-05

2001-04-10

Horabik, Michael (Department: 2735)

Communications: electrical

Continuously variable indicating

With meter reading

C340S870030, C340S870030, C375S368000

Reexamination Certificate

active

06215414

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a radio selective pager for indicating a calling on receiving a general radio selective paging wave, and more particularly to a radio selective pager capable of preventing a malfunction caused by an erroneous synchronism on receiving a general radio selective paging wave of a different transmission rate.
DESCRIPTION OF THE RELATED ART
As a conventional transmission mode of a radio selective paging for indicating a calling on receiving a general radio selective paging wave, a POCSAG system at a transmission rate (bit rate) of 512 bps, 1200 bps, or 2400 bps has been known.
In a radio selective pager of this POCSAG system, when a received field strength is changed by fading due to a change of mobile position or multipath amid receiving a general radio selective paging wave, its synchronism can often break off. In such a case, the synchronism is restored by isolating bit data or a noise. In the case of the bit data cut off in this judgement, even when no preamble is received, the synchronism is restored from the remaining bit data of the demodulation data.
On this occasion, a contrivance is made so as not to invite an erroneous synchronism with a different transmission rate. Besides a protocol processing with this POCSAG system, a new protocol processing with a FLEX/ERMES system has been developed and is used in combination with the POCSAG system.
Accordingly, the radio selective pager of the POCSAG system can synchronize with a received wave of the FLEX/ERMES system except the POCSAG system. In the radio selective pager of this kind, a power saving for an internal battery is intended to prolong operation time and its life. For example, an intermittent power supply to a receiver is carried out in the absence of signal from a detection state of the preamble from the demodulation data, or a continuous power supply is executed in the presence of signals, processing the operation of a frame detection addressed to itself or an address collation. Thus, if the operation caused by the erroneous synchronism often occurs, the power saving efficiency for the internal battery is reduced, resulting in shortening its life.
The operation of the erroneous synchronization will be described as follows.
FIG. 1
shows a detection operation of a transmission rate (bit rate) in the POCSAG system and the FLEX/ERMES system. In this example, the bit rate is 2400 bps in the POCSAG system and 1600 bps in the FLEX/ERMES system. FIG.
1
(
a
) shows a set (position) state of change point detection windows (data) against the demodulation data of 2400 bps in the POCSAG system, and the change point detection windows are set at every leading change point from a low (L) level to a high (H) level every bit and at every trailing change point from the H level to the L level.
FIG.
1
(
b
) shows bit string data “1101001” of the demodulation data at 2400 bps in the POCSAG system, and FIG.
1
(
c
) a discrimination result against the bit string data “1101001” of the demodulation data at 2400 bps shown in FIG.
1
(
b
). In other words, the discrimination result shows whether or not the leading and trailing change points of the bit string data “1101001” of the demodulation data are positioned within the change point detection windows shown in FIG.
1
(
a
), and shows that all the leading change points are within the change point detection windows.
Moreover, FIG.
1
(
d
) shows bit string data “10101” of the demodulation data at 1600 bps in the FLEX/ERMES system, and FIG.
1
(
e
) shows a discrimination result against the bit string data “10101” of the demodulation data at 1600 bps shown in FIG.
1
(
d
). That is, the discrimination result shows whether or not the leading change points from the low level to the high level are positioned within the change point detection windows shown in FIG.
1
(
a
), and similarly to the case shown in FIG.
1
(
c
), shows that all the leading change points are within the change point detection windows.
As described above, in the conventional radio selective pager, at both 2400 bps in the POCSAG system and 1600 bps in the FLEX/ERMES system, the leading change points of the bit string of the demodulation data are positioned within the change point detection windows, and the pager cannot distinguish between the transmission rates of 2400 bps and 1600 bps.
Hence, when receiving a general radio paging wave at 1600 bps in the FLEX/ERMES system, the radio selective pager at 2400 bps in the POCSAG system synchronizes erroneously, and vice versa. As a result, the pager switches from the power saving (battery saving) mode to the continuous receive mode to transfer to a synchronism signal detection operation, and the continuous operation increases much, thereby reducing the power saving efficiency for the internal battery. Thus, in the conventional radio selective pager, the power supply time increases, and the life of the internal battery is reduced.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a radio selective pager in view of the aforementioned problems of the prior art, which is capable of preventing an erroneous synchronization with received signals of different transmission rates to avoid an erroneous switch operation from a power saving mode to a continuous receiving mode on receiving a general radio selective paging wave of a different transmission rate (bit rate), saving unnecessary continuous operations, improving power saving efficiency, and prolonging life of an internal battery.
In accordance with one aspect of the present invention, there is provided a radio selective pager which receives a general radio selection paging wave and indicates a selective paging to a user, comprising receiving means which inputs a received signal of a general radio selection paging wave and outputs demodulation data; and selective paging processing means which detects leading change points, rising from a low level to a high level, and trailing change points, falling from the high level to the low level, of bits of the demodulation data, counts a detection number of at least ones of the leading and the trailing change points, recognizes the received signal to be of a predetermined transmission rate when a count number of the detection number is coincident with a predetermined value, and indicates a selection paging to a user.
In a radio selective pager of the present invention, the selective paging processing means can detect the leading and the trailing change points of the bits of the demodulation data using change point detection windows having a time spacing.
In a radio selective pager of the present invention, preferably, a time spacing and a position of the change point detection windows for holding the trailing change points are determined so that the change point detection windows for holding the trailing change points may be not overlapped with any of the change point detection windows of different transmission rates.
In a radio selective pager of the present invention, the selective paging processing means includes bit synchronizing means for synchronizing the demodulation data output from the receiving means with an internal reference clock to output synchronized demodulation data; preamble detecting means for detecting a preamble from the demodulation data output from the bit synchronizing means; bit rate detecting means which detects the leading and the trailing change points of the bits of the demodulation data, counts the detection number of at least ones of the leading and the trailing change points, and recognizes the received signal to be of a predetermined transmission rate when the count number of the detection number is coincident with a predetermined value; frame signal detecting means for detecting a frame synchronizing signal from the demodulation data output from the bit synchronizing means; address collating means for collating address numbers of the demodulation data output from the bit synchronizing means with individual address numbers stored previously, and outputs an indi

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