METHOD AND APPARATUS FOR REGISTERING A PORTABLE MESSAGING UNIT IN A COMMUNICATION SYSTEM

Abstract: A portable messaging unit (130) roams within zones (105, 110, 115) of a communication system (100). The portable messaging unit (130) includes a processor (220) that determines whether the portable messaging unit (130) is registered in a current zone and a registration manager (235) for attempting to register at a time indicated by a retry algorithm when the portable messaging unit (130) is not registered in the current zone. An event detector (240) monitors unit operations to detect occurrence of a registration event, in response to which registration is attempted regardless of whether the time indicated by the retry algorithm has arrived.

Description: METHOD AND APPARATUS FOR REGISTERING A PORTABLE MESSAGING UNIT IN A COMMUNICATION SYSTEM Field of the Invention This invention relates in general to messaging systems, and more specifically to a communication system in which portable messaging units register for service. Background of the Invention In conventional radio communication systems, messages are transmitted to portable messaging units carried by system subscribers. When a communication system supports two-way communications, messages are provided to portable messaging units over a forward communication channel, and inbound messages, such as acknowledgments and registration requests, from the portable messaging units are transmitted over a reverse communication channel and processed by a radio frequency controller that controls operations of the communication system. A registration request is generally transmitted by a portable messaging unit to indicate its presence within a particular region, or zone, of the system so that messages can be provided to the portable messaging unit solely within that region. However, inbound registration requests are not always received by system receivers and forwarded to the radio frequency controller, usually because a relatively low power portable messaging unit is outside the range of the system receivers. When registration is unsuccessful, the portable messaging unit may be unable to transmit inbound messages. Furthermore, messages intended for reception by the unregistered portable messaging unit often have to be transmitted in multiple zones since the location of the portable messaging unit cannot be pinpointed. Continuous transmission of registration requests until registration is achieved would enable the portable messaging unit to become registered as quickly as possible, thereby enabling transmission of inbound messages and efficient outbound message transmission. However, transmission of numerous registration requests from the portable messaging unit would also crowd the inbound channel and rapidly deplete the battery, which is undesirable in small portable messaging units in which battery capacity is already at a premium. Thus, what is needed is a way to efficiently manage the transmission of registration requests by a portable messaging unit. Brief Description of the Drawings FIG. 1 is a block diagram of a communication system including zones into which portable messaging units can roam according to the present invention. FIG. 2 is an electrical block diagram of a portable messaging unit for registering in the communication system of FIG. 1 according to the present invention. FIG. 3 is a flowchart illustrating an operation of an event detector included in the portable messaging unit of FIG. 2 according to the present invention. Description of a Preferred Embodiment FIG. 1 is a block diagram of a radio communication system 100 that provides outbound communications, such as messages, to portable messaging units (PMUs) 130 over an outbound, or forward, communication channel. Inbound communications, such as registration requests or message acknowledgments, can also be transmitted by the PMUs 130 over an inbound, or reverse, communication channel. The communication system 100 comprises different geographic regions of service referred to as zones 105, 110, 115, and each zone includes one or more transmitters 120 for transmitting the outbound messages. When inbound communications are supported by a particular zone, the zone also comprises one or more receivers 125 for receiving the inbound communications. A radio frequency controller (RFC) 135 is coupled to stationary system devices, e.g., the transmitters 120 and the receivers 125, in the different zones 105, 110, 115 for controlling operations of the communication system 100. Two-way PMUs 130 preferably are registered in the respective zones in which they are located. Once a particular PMU 130 has registered, messages intended for the PMU 130 can be transmitted solely within the associated zone, rather than throughout the entire system 100. Additionally, inbound messages received from the PMU 130 registered in the associated zone can be processed by the RFC 135. When, on the other hand, a PMU 130 is not registered in the zone in which it is located, inbound messages are not always recognized or processed. In some cases, inbound messages may not even be transmitted by an unregistered PMU 130. Furthermore, because the location of the unregistered PMU 130 cannot be verified, outbound messages for the PMU 130 are transmitted throughout the system 100, thereby resulting in inefficient use of system resources. When the PMU 130 moves into a different zone, it receives a zone identifier indicative of the new zone, in response to which the PMU 130 transmits a conventional registration request to register in the new zone. When registration has been successful, the PMU 130 receives a registration acknowledgment indicating that the PMU 130 is registered within its current zone. The PMU's registration request, however, can sometimes be missed by receivers 125 within the current zone, such as when the PMU 130 is out of range of the receivers 125, when the PMU 130 is in a fringe area, or when interference is present. In such a case, the PMU 130 will subsequently attempt to register at times indicated by a retry algorithm programmed into the PMU 130. The retry algorithm can, for instance, indicate that registration is to be attempted at fixed intervals, e.g., thirty- minute time periods, at variable intervals, e.g., once a minute for the first ten minutes and once every ten minutes thereafter, or according to any other computation that does not result in inordinate depletion of the battery powering the PMU 130. The PMU 130 monitors internal PMU operations and also attempts to register in response to the occurrence of specified registration events, such as reception of a ^ message over the outbound channel or reception of information that is to be transmitted by the PMU 130 over the inbound channel. Unsuccessful attempted registration in response to occurrence of a registration event preferably does not interfere with attempts made in accordance with the retry algorithm. According to the present invention, the PMU 130 will attempt to register at scheduled times, per the retry algorithm, and will also attempt to register when necessary, i.e., when a particular event occurs that makes registration desirable. For instance, attempting registration is desirable in response to reception of a message because the PMU 130 often transmits an acknowledgment of a received message. Attempting registration is also desirable prior to transmission of an inbound message since inbound transmissions from unregistered PMUs 130 are not always processed, or even sent. In this manner, registration attempts are advantageously managed to balance battery life, system resources, and the need of the PMU 130 to operate in a registered mode. Referring next to FIG. 2, an electrical block diagram of a PMU 130 is shown. The PMU 130 can, for instance, be a pager or any other portable two-way radio device. The PMU 130 comprises a transceiver 205 for transmitting and receiving radio signals in a conventional manner and a processor 220 for processing the radio signals and for controlling operations of the PMU 130. The PMU 130 can additionally include a message memory 225 for storing received messages, an alert mechanism 215 for generating an alert to announce message reception, a display 210 for displaying information to a user, and controls 245 for receiving user inputs to operate or program the PMU 130. A data entry device (not shown) could be included for entering information, such as programming information, into the PMU 130. A device memory 230 is included in the PMU 130 for storing information used in operating the PMU 130. Such information preferably comprises zone identifiers used by the processor 220 in a conventional manner to identify a current zone and to determine whether the PMU 130 is registered in the current zone. The device memory 230 preferably also stores registration status information conventionally set by the processor 220 and registration information in accordance with which registration requests are transmitted. Registration event information is stored in the device memory 230 to indicate one or more registration events that trigger the transmission of a registration request. Registration event information can be programmable by a service operator or by the user via the controls 245, another data entry device, or over the air. Examples of registration events include reception of a message over the outbound channel, user entry of information to be transmitted over the inbound channel, or a specific user request for registration by manipulation of the controls 245. It will be appreciated that different or additional registration events could be programmed into the device memory 230 in accordance with the present invention. The PMU 130 also comprises a registration manager 235 for managing registration requests that are not linked to occurrences of registration events. The registration manager 235 can initiate a registration attempt for many reasons, such as in response to determining that the PMU 130 has entered a new zone or in response to reception of a "where are you" command from the system 100. The PMU 130 can, for example, determine that it has entered a new zone by determining that the zone identifier included in a received radio signal is not equivalent to the zone identifier associated with a zone in which the PMU 130 last registered. This information is preferably indicated by the stored registration status information. When the registration attempt is unsuccessful, e.g., when a registration acknowledgment is not received in response to a registration request, the registration manager 235 sets the registration status information to indicate that the PMU 130 is unregistered. Additionally, the registration manager 235 preferably keeps a log indicating times of registration attempts. Thereafter, the registration manager 235 attempts to register at times indicated by the stored retry algorithm for as long as the PMU 130 remains unregistered. As mentioned, the retry algorithm, which could be programmable via the controls 245, is preferably set to maximize the likelihood of successfully registering while, at the same time, avoiding undue depletion of the battery (not shown). Once the PMU 130 has successfully registered, the registration manager 235 changes the registration status information to indicate that the PMU 130 is registered and to indicate the current zone, such as by storing the zone identifier of the current zone. According to the present invention, an event detector 240 is included in the PMU 130 for monitoring internal PMU operations to detecF an occurrence of a registration event. In response to occurrence of a registration event, the event detector 240 initiates a registration attempt regardless of whether a time indicated by the retry algorithm has arrived. The registration manager 235 and the event detector 240 preferably comprise firmware stored in the device memory 230 and executed by the processor 220 during operation of the PMU 130. The retry algorithm can be stored as a part of the firmware used to implement the registration manager 235. Alternatively, the registration manager 235 and the event detector 240 can be implemented using hardware capable of performing equivalent operations, and the retry algorithm can be stored in a memory device, such as the device memory 230, in the form of an equation or formula that yields registration times. Use of the event detector 240 according to the present invention is advantageous because registration requests can be transmitted when necessary, as defined by programmed registration event information. Consequently, an unregistered PMU 130 will attempt registration at specified times, pursuant to the retry algorithm, and also when a registration event, such as message reception, occurs. Registration attempts are therefore managed in a way that prevents crowding of the inbound channel with repeated registration requests while ensuring that an attempt will be made in situations in which the PMU 130 needs to be registered for inbound communication, such as when the PMU 130 needs to transmit an acknowledgment of a received message or when the PMU 130 needs to send an inbound message to the RFC 135 or another PMU 130. As mentioned, the times at which the registration manager 235 initiates transmission of a registration request are set to avoid inordinate battery depletion, which could occur if continual registration attempts were made. However, use of the registration manager 235 alone could result in situations in which the PMU 130 moves into range of system receivers 125 (FIG. 1) very soon after an attempt to register has been unsuccessfully made. As a result, in the absence of the event detector 240, an in-range PMU 130 could operate in an unregistered mode for the entire remaining length of an interval or time period specified by the retry algorithm, even though the PMU 130 was capable of successfully registering and then sending inbound transmissions. The event detector 240 conveniently solves this problem by operating in conjunction with the registration manager 235 to request registration in response to programmed events regardless of whether a specified time has arrived. FIG. 3 is a flowchart showing an operation of the event detector 240, which monitors operations internal to the PMU 130. When, at step 305, information intended for the PMU 130 has been received over the forward channel or when, at step 310, information to be transmitted by the PMU 130 over the reverse channel has been received, the event detector 240 determines, in a conventional manner, whether the PMU 130 is already registered in the current zone, at step 320. It will be appreciated that message reception and message transmission are merely examples of registration events, and that occurrence of any other registration event, at step 315, also results in the event detector 240 determining, at step 320, whether the PMU 130 is registered in the current zone. Detection of occurrences of the registration events can be performed in numerous ways, as will be understood by one of ordinary skill in the art. For example, message reception could be detected by referencing the message memory 225 or by receiving an "incoming message" signal generated by the processor 220. Detection of information to be transmitted could be performed by monitoring user inputs received via the controls 245. When, at step 320, the PMU 130 is determined to be registered in the current zone, no specific actions are taken by the event detector 240 since inbound communication is already enabled. When the PMU 130 is not registered in the current zone, the event detector 240 activates, at step 325, the registration manager 235 to initiate a registration attempt by conventionally transmitting a registration request. In summary, the communication system described above includes different zones into which a PMU can roam. In response to entering a zone, the PMU attempts to register in that zone. Successful registration enables the PMU to send inbound communications that are processed by the system in a conventional manner. Registration is not always successful, though, because the relatively low-power transmissions from the PMU are not always received properly by system receivers in the zone. The PMU can, for instance, be out of range, in a fringe area, or in an area of high interference. In such a situation, the PMU can still operate in a one- way mode to receive the higher-power outbound transmissions over the forward channel. However, inbound communications from the PMU within a particular zone are not necessarily enabled until the PMU has registered within the zone. Therefore, registration requests are transmitted by the PMU in accordance with a programmable retry algorithm so that registration can be attempted at specified times without draining the battery too much. According to the present invention, registration requests are also made in response to occurrences of registration events, regardless of whether it is time to register. Registration events are programmable and preferably include events that trigger actions requiring inbound communications. For instance, message reception will usually be a registration event because the PMU sends an inbound acknowledgment in response to reception of a message. Additionally, user entry of information to be transmitted comprises a registration event since the information is sent by the PMU over the reverse channel for system processing. Other events, such as a simple user request, could also be set as registration events. Since the PMU as described above makes registration attempts in response to specified events as well as at specified times, registration attempts are conveniently managed to balance the necessity of sending inbound transmissions with the desirability of maintaining battery capacity and efficiently utilizing system channel capacity. It will be appreciated by now that there has been provided a way to better manage the transmission of registration requests by a portable messaging unit in a radio communication system. What is claimed is:

Claims: CLAIMS 1. A portable messaging unit (PMU) for roaming within zones of a communication system, the PMU comprising: a processor that determines whether the PMU is registered in a current zone; a registration manager coupled to the processor for attempting, when the PMU is not registered in the current zone, to register at a time indicated by a retry algorithm; and an event detector coupled to the processor, wherein the event detector monitors PMU operations to detect occurrence of a registration event in response to which registration is attempted regardless of whether the time indicated by the retry algorithm has arrived. 2. The PMU of claim 1, wherein the registration event comprises receiving a message intended for the PMU. 3. The PMU of claim 1, wherein the registration event comprises receiving information to be transmitted by the PMU. 4. The PMU of claim 1, further comprising: a transceiver, coupled to the processor, that transmits a registration request when registration is to be attempted. 5. The PMU of claim 1, further comprising: controls coupled to the processor for receiving user inputs; a display coupled to the processor for displaying information; an alert mechanism coupled to the processor for announcing reception of messages; and a message memory coupled to the processor for storing received messages. 6. The PMU of claim 1, further comprising: a device memory that stores zone identifiers associated with the zones of the communication system, wherein the zone identifiers are used by the processor to determine whether the PMU is registered in the current zone. 7. The PMU of claim 6, wherein the device memory further stores a registration status of the PMU, registration information used in making a registration request, and registration event information indicative of registration events, occurrence of which results in a registration attempt. 8. A communication system for providing information, the communication system comprising: a plurality of zones within which portable messaging units (PMUs) can register; and a PMU that roams within the plurality of zones, the PMU comprising: a processor that determines whether the PMU is registered in a current zone in which the PMU is located; a registration manager coupled to the processor for attempting, when the PMU is not registered in the current zone, to register at a time indicated by a retry algorithm; and an event detector coupled to the processor, wherein the event detector monitors PMU operations to detect occurrence of a registration event in response to which registration is attempted regardless of whether the time indicated by the retry algorithm has arrived. 9. The communication system of claim 8, further comprising: transmitters .for transmitting messages to the PMUs; and receivers for receiving information transmitted by the PMUs, wherein information transmitted by unregistered PMUs is not always processed by the communication system. 10. The communication system of claim 8, wherein the registration event comprises receiving a message intended for the PMU. 11. The communication system of claim 8, wherein the registration event comprises receiving information to be transmitted by the PMU. 12. The communication system of claim 8, wherein the PMU further comprises: a transceiver, coupled to the processor, that transmits a registration request when registration is to be attempted. 13. The communication system of claim 8, wherein the PMU further comprises: controls coupled to the processor for receiving user inputs; a display coupled to the processor for displaying information; an alert mechanism coupled to the processor for announcing reception of messages; and a message memory coupled to the processor for storing received messages. 14. The communication system of claim 8, wherein the PMU further comprises: a device memory that stores zone identifiers associated with zones of the communication system, wherein the zone identifiers are used by the processor to determine whether the PMU is registered in the current zone. 15. The communication system of claim 14, wherein the device memory of the PMU further stores a registration status of the PMU, registration information used in making a registration request, and registration event information indicative of registration events, occurrence of which results in a registration attempt. 16. A method, in a portable messaging unit (PMU), for registering within zones of a communication system, the method comprising the steps of: determining whether the PMU is registered in a current zone; attempting, when the PMU is not registered within the current zone, to register at a time indicated by a retry algorithm; monitoring PMU operations for occurrence of a registration event; and attempting, in response to occurrence of a registration event, to register regardless of whether the time indicated by the retry algorithm has arrived. 17. The method of claim 16, wherein each of the steps of attempting to register comprise the step of: transmitting a registration request in accordance with registration information stored by the PMU. 18. The method of claim 16, wherein the monitoring step comprises: detecting reception of a message intended for the PMU. 19. The method of claim 16, wherein the monitoring step comprises: detecting reception of information to be transmitted by the PMU.

Inventors: MOORE MORRIS A, ORLEN NOAH P, ROBERTSON KAREN S, MOORE, MORRIS, A., ORLEN, NOAH, P., ROBERTSON, KAREN, S.
Applicants: MOTOROLA INC, MOTOROLA INC.
Application year: 1997
Main classification: H04Q7
IPC codes: C07D501, H04W48, H04W60