The signaling protocols, methods, and apparatus described herein relate to Satellite communications systems in U.S. patent No. 5,613,194, entitled "Satellite-Based cellular information System and Method of Operation Thereof," to Olds et al, 1997, 3, 18, and assigned to the assignee of the present invention, which is hereby incorporated by reference.
The specific embodiment is as follows:
fig. 1 shows a general diagram of a wireless communication system 5 according to the invention. For simplicity, the wireless communication system 5 is simply referred to as "system 5". The system 5 is preferably a satellite communication system comprising at least one controller 6 connected to a transmitting unit comprising at least one satellite 1 with a transmitter. It will be appreciated, however, that the invention is also applicable to a terrestrial-based wireless communication system in which the transmitting unit is at least one terrestrial-based conventional radio transmitter. In view of the substantially identical operation of each embodiment of the present invention, the following discussion will focus on one embodiment of a satellite communication system.
According to fig. 1, several satellites 1 are located in a lower orbit around the earth 4. These satellites 1 are preferably placed in orbit so that the entire constellation of satellites 1 provides continuous coverage over the entire earth 4. In addition to the satellites 1, the system 5 includes one or more controllers 6 disposed on the earth 4. Each controller 6 functionally corresponds to a central switching office 6 (or a gateway). For simplicity, each controller 6 is referred to simply as a "office 6". The office 6 is set up on the surface of the earth 4 and communicates with nearby satellites 1 via radio frequency communication links 8. The satellites 1 also communicate with each other via a data communication link 3. The station 6 provides communication coverage for an area of arbitrary size on the earth 4 by means of the constellation of satellites 1. The office 6 is connected to a public switched telephone network (not shown) through which requests for "calls to subscribers of the system 5" can be received. Each office 6 receives a request to place a call to a subscriber believed to be located in an area of the earth 4 associated with that office 6. For convenience, only one office 6 is shown in fig. 1.
However, it should be clear to those skilled in the art that any number of offices 6 are possible for use in connection with any number of regions on the earth 4. It should also be understood that all offices 6 are capable of operating in a distributed or collective manner to communicate with a given office 6, which given office 6 forwards messages from all offices 6 to the constellation of satellites 1 in the system 5.
The system 5 also includes any number of potentially millions of Selective Call Receivers (SCRs) 2, such as pagers or other one-way portable units. The SCRs 2 are arranged to receive communications from the overhead satellite 1 via a communications link 7. These communication links 7 preferably employ Radio Frequency (RF) frequencies which are substantially suitable for line-of-sight communication, and the links 7 are simplex links. That is, communications are only transmitted unidirectionally from the satellite 1 to the SCRs 2. Simplex communication allows each SCR2 to be made into a low-consumption unit that consumes a small amount of energy. Simplex communication is not limited to links 3 or 8. Specifically, these links are used for "satellite-to-satellite" and "office-to-satellite" communications, respectively.
Fig. 2 shows a timing diagram depicting a communication protocol 200 according to the present invention, this communication protocol 200 being applied by the system 5 for communication with the SCRs 2. During one communication cycle 202 (preferably having a duration of 194.4 seconds), the communication protocol 200 contains 9 block time periods 204 (each preferably having a duration of 21.6 seconds). Each block time period 204 is subdivided into a probe group message time period 206 followed by a message reception time period 203 which includes four message time periods 208. Preferably, each of the SCRs 2 is assigned to one of the 9 block time periods 204 for monitoring messages 218. It will be appreciated that alternatively each SCR2 may be assigned to one or more of the 9 block time periods 204.
The office 6 typically controls communications to a large area on earth 4. Specifically, the station 6 controls the transmission of the satellite 1 to a plurality of cell areas. Each cell area is part of a large territory associated with an office 6. In order to track the location of the SCRs 2 on the earth 4, users of the SCRs 2 must log onto their portable units when traversing between cell areas (e.g., cities) associated with different offices 6, or when traversing between large areas (e.g., countries) associated with different offices 6. Since the cell area associated with an office 6 is relatively large, users are not typically required to log on to the SCR2 during a particular regional stay.
Since a block period 204 is allocated to an SCR2, this SCR2 is only activated during the allocated block period 204, which, as will be seen hereinafter, will hierarchically provide a first level of battery saving capability to the totality of those SCRs 2 and satellites operating in the system 5. The probe group message time limit 206 is used by the system 5 to send at least one probe group message 213. In this example, the system 5 preferably sends a plurality of probe group messages 213, as shown in fig. 2, and during a selected one of the 48 frames 210, sends out one probe group message 213, as shown in fig. 2. Each probe group message 213 includes a group level information field 212 and an access period table field 214. These fields provide information to the SCRs 2 to determine in what way to monitor the message during the message reception time period 203. It should be appreciated that an additional field may be used for the probe group message time limit 206, such as a field to indicate to the SCRs that a particular channel selected from a plurality of possible channels is to be used for receiving messages 218. Further, it should be understood that the order of the fields 212, 214 is not critical and may be changed without affecting the operation of the communication protocol 200.
The same is true. Each of the plurality of message time periods 208 contains a plurality of message frames 216 (preferably 48 frames). During each message frame 216, the system 5 may send one or more messages 218 to one or more targeted SCRs 2. The access schedule field 214 contains digital data that directs the targeted SCR2 to monitor messages in selected numbered ones of the 48 message frames 216 during each of the plurality of message time periods 208.
To accomplish this, access schedule field 214 contains 48 bits of data. Each bit position in the access schedule field 214 has a direct correspondence to the 48 message frames 216 contained in each message time period 208. A logic "1" in any one of the 48 bit positions in the access schedule field 214 indicates that an SCR2 must monitor messages during a particular one of the 48 message frames 216 during each of the 4 message time periods 208. For example, one logical "1" found at bit positions 16, 19, 40 and 43 and one logical "0" found at all other bit positions indicates that one SCR2 must monitor messages during message frames numbered 16, 19, 40 and 43 (representing fig. 2) of the message frames 216 during each of the 4 message time periods 208. During each of the 4 message time periods 208, the SCRs 2 enter a power saving state during all other message frames 216 (i.e., frames 1-15, 17-18, 20-39, 41-42, and 44-48).
As will be apparent from this description, the access schedule field 214 also provides a second level of battery saving capability among the SCRs 2. While considerable battery saving capability may be achieved in SCRs 2 by hierarchically combining the allocation of block time periods 204 with the dynamic allocation of one or more message frames 216 by means of the access schedule field 214, additional battery saving capability is also desirable.
To achieve this flexibility, communication protocol 200 employs a group level information field 212, as shown in fig. 2. Similar to the access schedule field 214, the group level information field 212 contains digital data that directs targeted SCRs 2 to monitor messages during selected numbered ones of the plurality of message frames 216 and the message time period 208. Tables 1 and 2 below illustrate by way of example the operation of two alternative embodiments of the group level information field 212. For convenience, the group level information field 212 is abbreviated as "GH field".
TABLE 1
| Message frames 1-48 |
| GH field | 1-12 | 13-24 | 25-36 | 37-48 |
| 00 | A，B | A，B | C，D | C，D |
| 01 | A | B | C | D |
| 10 | A，B，C，D | A，B，C，D | A，B，C，D | A，B，C，D |
TABLE 2
| Message time limit 1-4 |
| GH field | 1 | 2 | 3 | 4 |
| 00 | A，B | A，B | C，D | C，D |
| 01 | A | B | C | D |
| 10 | A，B，C，D | A，B，C，D | A，B，C，D | A，B，C，D |
Table 1 shows a first embodiment of the group level information field 212. The first column of table 1 corresponds to the group level information field 212, which in this example comprises a two-bit code, so that SCRs 2 can be provided with one of four possible commands (one of which is not used in this example). The remaining four columns contain selected numbered message frames 216 that are assigned to one or more SCR groups. In this example, there are four SCR groups (shown in the example as SCR groups A, B, C and D). The SCR group requires a subdivision of the population of SCRs 2 around the satellite communication system 5. Preferably, the SCRs 2 are subdivided into SCR groups according to the address ranges of SCR 2.
For example, assume that there are one million SCRs 2 worldwide, and further assume that the SCRs are numbered in order. In such a case, SCR2 with address range of 1-250,000 will be assigned to SCR group A, SCR2 with address range of 250,001-500,000 will be assigned to SCR group B, SCR2 with address range of 500,001-750,000 will be assigned to SCR group C, and SCR2 with address range of 750,001-1,000,000 will be assigned to SCR group D. It will be apparent to those skilled in the art that countless distribution methods can be employed to break down the universe of SCR's 2 around the world into different groups of SCR populations. Although table 1 shows an example containing 4 SCR groups, it will be appreciated that the population of SCRs may be subdivided into more or fewer SCR groups without altering the operation of the invention.
As shown in Table 1, each row in the table represents a supergroup. For the present embodiment, each supergroup is assigned to a number of SCR groups, with a unique set of message frames 216 assigned to the SCR groups. For example, the binary code "00" represents a super group in which SCR groups A and B are assigned to message frames 216 numbered 1-24 and SCR groups C and D are assigned to message frames 216 numbered 25-48. The binary code "01" represents another supergroup, wherein SCR group a is assigned to message frames 216 numbered 1-12, SCR group B is assigned to message frames 216 numbered 13-24, SCR group C is assigned to message frames 216 numbered 25-36, and SCR group D is assigned to message frames 216 numbered 37-48. The third supergroup is represented by the binary code "10" where SCR groups a-D are allocated to all 48 message frames 216.
In the embodiment shown in table 1, the SCR groups a-D are assigned to all 4 message time periods 208 during the message reception time period 203. The operation of this embodiment is briefly explained immediately below after discussing table 2.
In contrast to table 1, table 2 assigns a combined message time limit 208 to SCR groups a-D for each supergroup. For example, the binary code "00" represents a super group, wherein SCR groups a and B are assigned to the first and second message time periods 208 and SCR groups C and D are assigned to the third and fourth message time periods 208. The binary code "01" represents another super group, SCR group a being assigned to the first message time period 208, SCR group B being assigned to the second message time period 208, SCR group C being assigned to the third message time period 208, and SCR group D being assigned to the fourth message time period 208. The third supergroup is represented by the binary code "10" and the SCR groups a-D are assigned to all 4 message time periods 208. Please note that: in the embodiment of table 2, SCR groups a-D are assigned to all 48 message frames 216 of a selected numbered message time period of the message time periods 208.
One of ordinary skill in the art will appreciate that more or less supergroups may be used for each table. In addition, the bit code used by the group level information field 212 may be conveyed using unused bit states in other fields sent during the probe group message time limit 206.
The result of the combination of the functions of the group level information field 212 and the access schedule field 214 results in an advanced method for conserving power in the SCRs 2. Fig. 4 and 5 provide illustrative examples of the integrated utilization of the group level information field 212 and the access schedule field 214 in two alternative embodiments.
The three examples shown in fig. 3 represent one embodiment of the group level information field 212 according to the example shown in table 1. For convenience, the first example is subdivided into two timing portions (e.g., 1A and 1B). In this example, the access schedule field 214 directs SCRs 2 to monitor data in message frames 216 numbered 16, 19, 40, and 43. The example begins with SCR's 2 receiving the sounding group messages 213 (48 sounding group messages 213 are sent by system 5, which is illustrated by timing portion 324). The probe group message 213 contains a group level information field 212 with the binary code "00".
This code directs SCR groups a and B to monitor messages during any one of message frames 216 numbered 1-24 and during all message time periods 208. In addition, this code directs SCR groups C and D to monitor messages during any of the message frames 216 and during all of the message time periods 208, numbered 25-48. Since SCR groups a and B can only monitor message frames 216 numbered 1-24, message frames 216 numbered 40 and 43 assigned by the access schedule field 216 are ignored. Similarly, because SCR groups C and D can only monitor message frames 216 numbered 25-48, message frames 216 numbered 16 and 19 are also ignored. These allocations are illustrated by timing portions 326, 328.
Example 1 is suitable for SCR groups a and B and SCR groups C and D having messages that can be distributed by capacity among two message frames 216 of each message time period 208. Distributing the messages in this manner, the battery life of the SCRs 2 in each SCR group is substantially optimized, in contrast to the case where all SCRs 2 monitor the messages "often" during all message time periods 208 and all message frames 216 specified by the access schedule field 214.
In example 2, a probe group message 213 is received by SCR's 2 (48 probe group messages 213 sent from system 5, as illustrated by timing portion 331), and this probe group message 213 includes: an access schedule field 214 to direct SCRs 2 to monitor messages only during message frames 216 numbered 16 and 19; further comprising: a group level information field 212 having a binary code of "01". This code directs SCR group a to monitor for messages during any of message frames 216 numbered 1-12, SCR group B to monitor for messages during any of message frames 216 numbered 13-24, SCR group C to monitor for messages during any of message frames 216 numbered 25-36, and SCR group D to monitor for messages during any of message frames 216 numbered 37-48. This allocation is illustrated by timing portion 330.
Since the access schedule field 214 directs many SCR groups to monitor only message frames 216 numbered 16 and 19, the SCR groups A, C and D ignore this instruction and are therefore in a power saving state during all message frames 216 and message time periods 208, thereby saving a significant amount of power, except that SCR group B monitors messages during message frames 216 numbered 16 and 19 during all message time periods 208. Example 2 illustrates a situation where messages are directed only to a group of SCRs. It will be apparent to those of ordinary skill in the art that a collective of all SCR groups A, B, C and D may be targeted to receive messages, with each individual SCR group monitoring only the messages of the particular SCR group targeted for it.
Finally, in example 3, a probe group message 213 is received by the SCRs 2 (48 probe group messages 213 sent from the system 5, as illustrated by timing portion 333), and the probe group message 213 includes: an access schedule field 214 for directing SCRs 2 to monitor messages during message frames 216 numbered 16, 19, 40, and 43; further comprising: a group level information field 212 having a binary code of "10". This code directs SCR groups a-D to monitor for messages in any of message frames 216 numbered 1-48. To this end, the SCR groups a-D monitor for messages during message frames 216 numbered 16, 19, 40 and 43 during each message time period 208, as directed by the access schedule field 214. Example 3 considers the case where maximum flexibility is required for each frame and SCR group assignment message.
The three examples shown in fig. 4 represent other embodiments of the group level information field 212 according to the examples shown in table 2. For each example in fig. 4, the access schedule field 214 directs the SCRs 2 to monitor data during message frames 216 numbered 16, 19, 40, and 43.
In the first example shown in fig. 4, a probe group message 213 is received by the SCRs 2 (48 probe group messages sent from the system 5, as illustrated by timing portion 304). This probe group message 213 includes: a group level information field 212 having the binary code "00". This code directs the SCR groups a and B to monitor messages during either of the first two message time periods 208 and during message frames 216 numbered 16, 19, 40 and 43. This code also directs SCR groups C and D to monitor messages during either of the last two message time periods 208 and during message frames 216 numbered 16, 19, 40 and 43. The allocation for SCR groups a and B is illustrated by timing portion 306. Likewise, the allocation for SCR groups C and D is illustrated by timing section 308.
This supergroup is appropriate when SCR groups a and B and SCR groups C and D have messages and the messages can only be distributed in two message slots 208 by capacity. Distributing the messages in this manner, the battery life performance of the SCRs 2 in each SCR group is significantly optimized, as opposed to the case where all SCRs 2 monitor the messages "always" during all message time periods 208 and during all message frames 216 as specified by the access schedule field 214.
The supergroup shown in example 2 indicates why the battery life performance optimization of the SCRs 2 is higher than that provided by the supergroup of ratio 1. In example 2, one probe group message 213 is received by the SCRs 2 (48 probe group messages sent from the system 5, illustrated by the timing portion 310). This probe group message 213 includes: a group level information field 212 with a binary code of "01". This code directs SCR group a to monitor messages during a first message time period 208, group B to monitor messages during a second message time period 208, SCR group C to monitor messages during a third message time period 208, and SCR group D to monitor messages during a fourth message time period 208. The SCR groups a-D monitor messages during their assigned message time period 208 during message frames 216 numbered 16, 19, 40 and 43. These allocations are illustrated by timing portion 312 and 318.
It is clear that this supergroup requires that the energy consumed by the SCRs 2 is minimal, since each SCR2 is only active during one message frame 208.
Finally, in example 3, one probe group message 213 is received by the SCRs 2 (48 probe group messages sent from system 5, as illustrated by timing portion 320). This probe group message 213 includes: a group level information field 212 with binary code "10". This code directs the SCR groups a-D to monitor messages during all message time periods 208 during message frames 216 numbered 16, 19, 40 and 43. This allocation is illustrated by timing portion 322. This super-group is useful when it is desirable to have maximum flexibility in assigning messages to the message frame 216 and SCR groups.
The reader at this point will clearly see that the embodiment of the group level information field 212, as exemplified in tables 1 and 2, provides a flexible means in which each office 6 of the system 5 can be used to optimize the battery life performance of the SCRs 2. Those skilled in the art will appreciate that those embodiments presented for the group level information field 212 may be combined to form more complex battery saving schemes.
Fig. 6 to 8 show electrical schematic block diagrams of the SCR2, the controller 6 and the satellite 1 according to the invention, respectively.
According to fig. 5, the SCR2 comprises: a receiver 404 coupled to a conventional antenna 402; a power switch 408; a processor 410; and a user interface 421. The receiver 404 and the antenna 402 (via which the communication link 7 is established) are used to receive radio signals containing messages transmitted by the satellite communication system 5. The receiver 404 preferably recovers the Binary Phase Shift Keyed (BPSK) and Quadrature Phase Shift Keyed (QPSK) encoded data contained in the transmission from the link 7. The receiver 404 recovers the digital data and then processes the data by the processor 410. Based on the data provided by the receiver 404, the processor 410 is programmed to reject or accept the received data.
The power switch 408 is a conventional switch, such as a MOS (metal oxide semiconductor) switch, for controlling the power supply to the receiver 404 under the direction of the processor 410, thereby providing battery saving functionality.
Processor 410 is used to control the operation of SCR 2. Its basic function is typically to decode and process demodulated messages provided by the receiver 404, store the demodulated messages and alert the user of the received message. The demodulated message is preferably decoded by the processor 410 in accordance with the communication protocol 200 shown in fig. 2. To perform the decoding function, the processor 410 includes a conventional microprocessor 416 coupled to a conventional memory 418, the memory 418 having non-volatile and volatile memory portions, such as ROM (read only memory) and RAM (random access memory). One of the purposes of the memory 418 is to store messages received from the system 5 and the other is to store one or more selective call addresses identifying the incoming individual or group of messages received by the SCR 2.
Once a message is decoded and stored in the memory 418, the processor 410 activates an alert device 422 (included in the user interface 421), which alert device 422 generates a tactile and/or audible alert signal to the user. The user interface 421 also includes, for example, a conventional Liquid Crystal Display (LCD)424 and conventional user controls 420 for the user to process the received messages. This interface provides options such as read, delete, lock messages.
It will be appreciated that alternatively more than one processor 410 may be used, if additional processing capabilities are required to perform the functions of the present invention and other common operational functions such as message processing and user message interface functions.
Fig. 6 shows a block diagram of a controller 6 (also called "central exchange" or "gateway") according to the invention. The controller 6 includes: a processor 432, the processor 432 may be implemented with a single processor or a network of processors; a modulator/demodulator 428 operative to couple the processor 432 through to an antenna 426; an antenna 426 for establishing the communication link 8. The modulator/demodulator 428 converts the digital data generated by the processor 432 into a modulated RF communication signal compatible with the link 8.
The controller 6 further includes: a memory 434 for storing permanent and temporary data, including computer programs, and for storing data that has not changed and data that has changed after being operated by the controller 6; a timer 433 coupled to the processor 432, the timer 433 allowing the controller 6 to maintain a current system duration and action for transmitting transmissions from the controller 6 according to real-time requirements; a processor 432 is coupled to a Public Switched Telephone Network (PSTN) 436 via a PSTN interface 430, and may receive requests to send calls to the SCR2 via the PSTN436 and interface 430. In addition, a request for a SCR2 to send a call may also be received via the network of the satellite 1 (see fig. 1) and the link 8.
Fig. 7 shows a block diagram of a satellite 1 according to the invention. All satellites 1 (see fig. 1) in the system 5 are best illustrated with reference to the block diagram of fig. 7. The satellite 1 includes: cross-linked transceiver 440 and cross-linked antenna 438, transceiver 440 and antenna 438 supporting cross-link 3 (fig. 1) for interfacing with other satellites 1 in the vicinity; the gateway link transceiver 444 and the gateway link antenna 442 support the gateway link 8 (fig. 1) in communication with the gateway 6.
Also, subscriber unit transceiver 448 and subscriber unit link antenna 446 support SCRs 2 (fig. 1). Each satellite 1 may preferably support many thousands or more SCR2 links simultaneously (fig. 1). Of course, those skilled in the art will appreciate that antennas 438, 442, and 446 may be implemented with a single multidirectional antenna or a group of discrete antennas. It is desirable that subscriber unit antenna 446 be a phased array antenna that can access many cell areas simultaneously. In a preferred embodiment, up to 48 individual spot beams simultaneously access an equal number of cell regions.
Processor 452 is coupled to each of transceivers 440, 444, and 448 and is also coupled to memory 454 and timer 450. Processor 452 may be implemented with one or more microprocessors. The processor 452 utilizes the timer 450 to maintain the current date and period. The memory 454 stores data as instructions for the processor 452 and, when executed by the processor 452, causes the satellite 1 to perform the processes discussed below in describing the controller 6 flow diagram (see fig. 8). In addition, the memory 454 stores variables, tables, and databases to be processed due to the operation of the satellite 1.
The subscriber unit transceiver 448 is desirably a multi-channel frequency division multiple access/time division multiple access (FDMA/TDMA) transceiver that can transmit and receive on all of the different, selectable frequencies during a particular selectable time slot under the direction of the processor 452. Subscriber unit transceiver 448 has a sufficient number of channels to provide a desired number of transmit and receive frequencies for communication. It is desirable that the subscriber unit transceivers 448 provide for transmission and reception on any set of frequency channels such that each subscriber unit transceiver 448 has the ability to process all frequency and time slot assignments, if necessary, to utilize the full spectrum capacity of all sets of frequency channels.
Subscriber unit transceiver 448 transmits the SCR signal at a higher power than the duplex carrier for ordinary traffic. This additional power provides improved link margin over the normal traffic channel. This additional link margin enhances the ability of the SCR signal to traverse obstacles such as vehicles and buildings. It also allows less sensitive, less expensive SCRs 2 to be used with the system 5.
Fig. 8 and 9 show flowcharts 500, 600 for describing the operation of the controller 6 and the SCR2, respectively, according to the invention. The flow charts 500, 600 describe programming instructions for the controller 6 and SCR2, which are stored in their respective memories 434, 418, respectively.
The steps shown in the flowchart 500 are operations performed by the controller 6 during the single block time period 204. As will be discussed below, such operations are repeated by the controller 6 for each of the remaining block time periods 204.
The flow chart 500 begins at step 502, where the controller 6 generates a plurality of supergroups at step 502. To accomplish this, the controller 6 subdivides or divides the SCRs into a plurality of SCR groups and assigns the SCR groups to a plurality of supergroups. The controller 6 also assigns a number of selected numbered message frames 216 and message time periods 208 to each SCR group in each supergroup. Examples of such allocations are shown in tables 1 and 2 (see above). At step 506, the controller 6 generates a plurality of probe group messages 213 (preferably 48 frame messages, see fig. 2-5). Each of the probe group messages 213 is designated for transmission during a selected one of the frames 210 of the probe group message time period 206.
To generate the probe group message 213, the controller 6 selects a super group from a plurality of super groups and includes group level information corresponding to the super group in the probe group message 213. This group level information is contained in group level information field 212. This super-group is used to direct targeted SCRs 2 to receive selected probe group messages 213 for monitoring one or more messages during the message reception time period 203 according to the selected number of message frames 216 and message time periods 208 contained within the super-group.
Once the plurality of sounding group messages 213 have been generated, the controller 6 begins to perform step 508, and at step 508, the controller 6 causes the satellite 1 to activate the transceiver 448 to transmit the plurality of sounding group messages 213 during the sounding group message time limit 206. At step 510, the controller 6 generates one or more messages corresponding to one or more SCRs 2 assigned to the current block time limit 204. Once these SCR messages have been generated, the controller 6 starts to execute step 514, in which step 514 it causes the satellite 1 to activate the transceiver 448 to transmit said one or more messages during the message reception time period 203 in accordance with the selected super-cluster for each SCR 2. Please note that: communication between the controller 6 and the satellite 1 is effected by a communication link 8.
Referring to fig. 9, the flowchart 600 begins at step 602, where the SCR2 monitors a probe group message 213 transmitted from satellite 1 with the receiver 404 at step 602. As described above, this probe group message 213 includes group level information for directing the SCR2 to a number of selected numbered message frames 216 and message time periods 208. In step 604, SCR2 causes the receiver 404 to monitor one or more messages during the message reception time period 203 based on the received group level information (corresponding to a selected supergroup) and the supergroup to which the SCR belongs. Once one or more messages are detected during the message receipt period 203, the SCR2 processes the messages as described above with respect to figure 5 at step 606 and then begins to perform step 608. At step 608, the SCR2 alerts its user that a pending message has been received.
Although not shown in fig. 9, the processor 410 of the SCR2 is programmed to place the receiver 404 and portions of the processor 410 in a power saving state during the message reception time period 203 in accordance with the selected numbered message time period 208 and message frames 216 as directed by the probe group message 213. This operation corresponds to a battery saving mode of the SCR2 based on a selected supergroup sent with the sounding group message 213. The combined instructions received from the group level information field 212 and the access schedule field 214 provide a flexible means for optimizing the battery life of the SCRs 2 under various message traffic conditions.
In summary, the present invention provides an advanced method and apparatus for optimizing battery life performance of the satellite 1 and SCRs 2. This is due to the combined application of the group level information field 212 and the access schedule field 214. Combining these fields provides the controller 6 with the ability to optimize the battery life performance of the satellite 1 and SCRs 2 under the present conditions of information traffic.
While the invention has been described in terms of a preferred embodiment, it will be apparent to those skilled in the art that many modifications and variations can be made within the scope of the invention. Accordingly, it is intended that such changes and variations be considered as within the spirit and scope of the invention as defined by the appended claims.