MXPA99008168A - A wireless communication device and method - Google Patents

Abstract

A wireless communication device (100) automatically and seamlessly switches to an alternate, available system when it is unable to complete a call origination attempt, without requiring the user to take any affirmative actions to select the alternate system or re-initiate a call origination. The wireless communication device (100) comprises a transceiver (104) and a processor (104). The transceiver (107) transmits and receives messages and signals. The processor (107) generates a first signaling message for transmission to a first communication system and generates a second signaling message for transmission to a second communication system if the transceiver does not receive an acknowledgement message from the first communication system. This decreases the percentage of call failures by providing a hold-over of pending call origination attempts until service is finally acquired. In the case of either exceeding the maximum number of access sequences (reverse link limited) or failure to acquire the forward link of the preferred communication system (forward link limited), the user is not required to re-initiate the call origination, thus turning a potential call failure into a success.

Description

DEVICE AND WIRELESS COMMUNICATION METHOD BACKGROUND OF THE INVENTION. I. Field of the Invention The present invention relates to a wireless communication device. More specifically, the present invention relates to a wireless communication device and a method of automatic switching between wireless communication systems. II. Description of the Related Art. The use of multiple access modulation techniques by code distribution (CDMA) is one of several techniques to facilitate communications in a wireless communication system in which a large number of users of the system are present. Other techniques of multiple access communication systems are known in the art, such as multiple time distribution access (TDMA) and multiple frequency distribution access (FDMA). An example of a TDMA communication system is the Pan-European Global System for Mobile Communications (GSM). An example of an analog FDMA system is the Advanced Mobile Telephony System (AMPS) currently used in the US. for cellular communications. However, the spread spectrum modulation technique of CDMA has significant advantages over these other techniques for multiple access communication systems. The use of CDMA techniques in a multiple access communication system is disclosed in the U.S. Patent. No. 4,901,307, issued February 13, 1990, entitled "MULTI ACCESS COMMUNICATION SYSTEM OF DIFFUSED SPECTRUM USING SATELLITE OR REPEATER REPEATER" ("SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS"), assigned to the transferee of the present invention, the disclosure of which is incorporated herein by reference. CDMA by its inherent nature of being a broadband signal offers a form of frequency diversity by spreading the signal energy over a broad bandwidth. Accordingly, selective frequency fading affects only a small part of the CDMA signal bandwidth. Path space or diversity is obtained by providing multiple signal paths through simultaneous links from a mobile user through two or more cell sites. In addition, path diversity can be obtained by exploiting the multiple path environment through spread spectrum processing by allowing a signal with different propagation delays to arrive upon receipt and processing separately. Examples of path diversity are illustrated in the U.S. Patent. No. 5,101,501, issued March 31, 1992, entitled "FLEXIBLE TRANSFER IN A CDMA CELLULAR TELEPHONE SYSTEM" ("SOFT HANDOFF IN A CDMA CELLULAR TELEPHONE SYSTEM"), and in the US Patent. No. 5,109,390 issued April 28, 1992, entitled "DIVERSITY RECEIVER IN A CDMA CELLULAR TELEPHONE SYSTEM" ("DIVERSITY RECEIVER IN A CDMA CELLULAR TELEPHONE SYSTEM"), both assigned to the assignee of the present invention and incorporated in the present for reference. The deleterious effects of fading can be better controlled to some degree in a CDMA system by controlling the power of the transmitter. A system for controlling the power of the cell site and the mobile unit is set forth in the U.S. patent. No. 5,056,109, issued October 8, 1991, entitled "METHOD AND APPARATUS FOR CONTROLLING THE TRANSMISSION POWER IN A CELLULAR MOBILE CDMA TELEPHONE SYSTEM" ("METHOD AND APPARATUS FOR CONTROLLING TRANSMISSION POWER INTO A CDMA CELLULAR MOBILE TELEPHONE SYSTEM" ), Serial No. 07 / 433,031, filed on November 7, 1989, also assigned to the assignee of the present invention. The use of CDMA techniques in a multiple access communication system is further described in the US patent. No. 5,103,459, issued April 7, 1992, entitled "SYSTEM AND METHOD FOR GENERATING FORMS OF SIGNAL WAVE IN A CDMA CELLULAR TELEPHONE SYSTEM" ("SYSTEM AND METHOD FOR GENERATING SIGNAL WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM"), assigned to the assignee of the present invention, whose disclosure thereof is incorporated herein by reference. In the field of wireless communications, such as cellular phones, wireless local circuit and Personal Communication Services (PCS), base stations communicate with remote subscriber units such as portable radiotelephones. For simplicity, the term "mobile station" will be used herein to refer to such remote subscriber units, although it is understood that some remote subscriber units, such as wireless local circuit telephones, do not move frequently through the environment wireless, but rather they are usually stationary. Typically, in any geographic service area, there will be more than one wireless communication service provider. For example, in cellular systems in the United States, there are usually two providers, one whose system is designated System "A" and the other whose system is designated System "B". For the PCS services currently planned in the United States, there are many more service providers, denoted by the "A" - "F" blocks, which cover the same geographic service area. The frequency spectrum available for each geographical service area is divided among these wireless telecommunication service providers. Each service provider typically operates its own base stations and other network equipment. In accordance with the various wireless communication standards, including the Provisional Standard IS-95 of the Electronic Industries Association (EIA) / Association of the Telecommunications Industry (TIA), entitled "Compatibility Standard Mobile Station - Base Station for Cellular Systems Broadband Dual-Mode Broadcast Spectrum "(" Mobile Station - Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System "), there are dual mode CDMA / AMPS radiotelephones which can communicate with either a station CDMA base or an AMPS base station. In addition, there are or are in development other industry standards with support for Dual Mode operation among other modulation and multiplexing schemes such as the CDMA dual-mode PCS band and the AMPS, the dual-band CDMA PCS band and the band CDMA cellular, dual-mode GSM and AMPS, and various other combinations of the known modulation and multiplexing schemes. As can easily be seen from the number of co-established service providers and the number of communication protocols that can be used, there is a large number of possible communication systems that can be operated in a single geographical area, each with varying coverage levels. For example, since AMPS was the first FM-based analogue cellular system to gain wide market acceptance in the United States, AMPS communication systems currently provide close to 100% coverage for all populated regions of the United States. However, as other competitive communication systems such as CDMA PCS and cellular systems are being deployed, their total coverage areas are expanding rapidly. In this way, it is anticipated that there will be many co-established communication systems with varying and overlapping coverage levels. Due to the advantages of the CDMA as summarized previously, many users of CDMA / AMPS dual-mode mobile stations prefer to use the CDMA service any time they are available and use the AMPS service only when the CDMA service is not available. is available In addition, a particular user of a portable dual-mode CDMA and CDMA PCS cellular radiotelephone may prefer to use PCS services to cellular services for a variety of reasons. For these reasons, the dual mode mobile stations designated in accordance with IS-95 generally allow the user to select the preferred mode of operation (i.e. CDMA or AMPS), and the mobile station will operate accordingly. Other standards may allow the same user preferences, or they may "code non-flexible" a particular priority of the system. In any case, at any time that the user of a dual-mode mobile station is in a geographical area where there is good coverage for one of the non-preferred communication systems, for example, the AMPS, but imperfect coverage for the preferred system For example, the CDMA, the user will generally want to make a "no suture" transmission between the two systems without requiring excessive attention to the portable radiotelephone. In the art, the forward link (base station to mobile station) is generally assumed to decrease along with the reverse link (mobile station to base station). However, due to the complexities of network planning, forward and reverse links may be somewhat unbalanced. That is, the forward link may not be admissible by the mobile station in some localized areas where a base station should otherwise be able to receive the reverse link. This first case is generally referred to as "limited forward link". A limited forward link condition could be caused by an obstruction or reflection in the path of the forward link that would not be so harmful to the reverse link due to the difference in frequency between forward and reverse links. Conversely, the forward link may be strong enough to be admissible by the mobile station in some localized areas where the base station is not capable of receiving the reverse link. The latter case is generally referred to as being in "limited reverse link". A limited reverse link condition may also be caused by differences in the propagation path, or perhaps because the service provider has increased the effective radiated power (ERP) of the base station to combat interference by other nearby base stations belonging to a system of the competition. To illustrate the undesirable effects of a limited forward link condition, consider the case where a CDMA / AMPS dual-mode mobile station is operating in the CDMA mode, and moves into a deep fading area for the link in advancement of the CDMA system, such as towards an abrupt valley, and with which, it loses the CDMA forward link (ie it may no longer receive and demodulate the pilot signal from the base station), but a forward link signal of a nearby AMPS system is still present. In a conventional dual-mode mobile station, if the user attempts to originate a call during this deep fading, the call will not succeed and the user will be prompted with an indication "No Service" and "Failed Call" while the dual mode mobile station attempts reacquire the service. After reacquiring the service, the user of the conventional dual-mode mobile station will be required to restart the call origin by highlighting the number. As regards the limited reverse link condition, consider the case where the CDMA / AMPS dual-mode mobile station is operating in the CDMA mode, and moves to a deep fading area for the reverse link of the CDMA / AMPS CDMA, such as the interior of a building or near the cell's coverage limit, and therefore unable to successfully transmit any message to the CDMA base station, but would be able to successfully transmit to an AMPS base station if it were operating in AMPS mode. Assume further that the CDMA forward link is still strong enough in this case to be successfully demodulated by the dual mode mobile station. In a conventional dual-mode mobile station, an indication of signal strength such as a number of signal bars on the visual display of the mobile station would be displayed due to the intensity of the forward link. Nevertheless, if the user tries to originate a call during this condition, the call will not be successful and a "Failed Call" indication will be displayed to the user. As a result, the user will see a satisfactory service indication on the screen due to the relative strength of the forward link, but will still be unable to communicate with the CDMA base station. In this limited reverse link situation, the dual mode mobile station would not be able to recognize a page, originate a call, or even register with the CDMA base station even though a satisfactory service indication is displayed. In addition, in a conventional dual mode mobile station, since the mobile station can successfully demodulate the preferred system (CDMA), it would not attempt to acquire the non-preferred system (AMPS), and therefore the user could not originate or receive any call to unless the user takes action manually to force the phone to acquire the non-preferred system, such as changing the mobile station to "AMPS only" mode and then redialing the outgoing telephone number. Also, the user would not be aware of the limited reverse link condition because the conventional dual mode mobile station would indicate a satisfactory service. Accordingly, the conventional dual-mode mobile station under both limited forward link and limited reverse link conditions requires the user to take at least some affirmative action to redial a telephone number due to an unsuccessful call attempt, and in the worst case it requires the user to access a menu of user preferences to manually switch the mobile station to an alternate system. What is needed is a mobile station that switches automatically and "without sutures" to an available system, alternately when it finds a limited forward link condition or a limited reverse link condition, without the user needing to take affirmative actions to select the alternate system or restart the call origin. SUMMARY OF THE INVENTION. In one aspect the invention provides a wireless communication device comprising: a processor for generating a first signaling message for transmission to a first communication system having a first pilot signal; and a transceiver, coupled to said processor, for transmitting the first signaling message to the first communication system and for receiving the first pilot signal and a first acknowledgment message from the first communication system; wherein the processor automatically generates a second signaling message for transmission to a second communication system having a second pilot signal if the transceiver does not receive the first acknowledgment message and receives the first pilot signal. In another aspect the invention provides a method for automatically switching between a first communication system having a first pilot signal and a second communication system having a second pilot signal, the method comprising the steps of: receiving the first pilot signal; generating a first signaling message for transmission to the first communication system;, transmitting the first signaling message to the first communication system; automatically generate a second signaling message for transmission to the second communication system if a first acknowledgment message is not received from the first communication system. In a further aspect the invention provides a mobile communication device arranged to monitor signals from various different communication systems, to transmit a signaling message to one of the communication systems when the device is connected to the system and to connect to the other of communication systems when the signaling message is not recognized by the system. Preferably, the wireless communication device comprises a processor for generating a first signaling message for transmission to a first communication system having a first pilot signal, and a transceiver for transmitting the first signaling message to the first communication system. In response to the first signaling message, the first communication system must generate a first acknowledgment message. The transceiver receives the first pilot signal and must also receive the first acknowledgment message from the first communication system. However, if the first acknowledgment message is not received, but the first pilot signal is being received (indicating that the wireless communication device is in a limited reverse link situation), the processor automatically generates a second signaling message for transmission to a second communication system having a second pilot signal. Accordingly, the wireless communication device automatically seeks to acquire the second communication system after the failure of the closing of the reverse link with the first communication system.

In the preferred embodiment, the wireless communication device further comprises a user interface, such as a keyboard and associated circuitry, for generating a first set of dialed digits, and a memory for storing the first set of digits dialed, with the first and second signaling messages that include both the first set of dialed digits. For example, the first set of dialed digits can be a desired destination telephone number. The destination telephone number is stored in the memory for later retrieval by the processor to generate the second signaling message. In such a case, the first and second signaling messages would be originating messages, and therefore the processor automatically "re-attempts" the call origin with the second communication system by retrieving the dialed digits from the memory without requiring the user Take some action To do this, in the preferred embodiment, the processor comprises a call processing module for generating the first and second signaling messages and for generating a source wait signal, and a user interface module for storing the first set of signals. digits dialed in memory and to provide the first set of digits dialed to the call processing module in response to the originating wait signal. The call processing module sets the originating wait signal to the logical value "TRUE" when the wireless communication device acquires the first or second communication system, and to the logical value "FALSE" when the wireless communication device has acquired the first or second communication system. Therefore, when the user interface module detects the change of the originating wait signal from TRUE to FALSE, it resets the pending call origin that was kept waiting during the acquisition attempt. Therefore, the wireless communication device automatically switches "without sutures" to an available system, alternately when it encounters a limited forward link condition or a limited reverse link condition, without requiring the user to take any affirmative action to select the alternate system or restart a call origin. BRIEF DESCRIPTION OF THE DRAWINGS. The features, objects and advantages of the present invention will become more apparent from the detailed description of an embodiment of the invention set forth below when taken in conjunction with the drawings, in which like reference characters are correspondingly identified through of the entire document and wherein: Figure 1 is a block diagram of the selected components of an exemplary mobile station of the present invention; and Figure 2 is a high level state diagram of the operation of the present invention. DETAILED DESCRIPTION OF THE PREFERRED MODALITY. Although the embodiment of the present invention as described herein will be set forth with reference to an exemplary CDMA / AMPS dual-mode mobile station, it should be noted that the present invention is applicable to any wireless communication device that can communicate with more than a communication system, whether or not the two communication systems employ the same modulation or multiplexing protocols. For example, the present invention is applicable to any wireless communication device that can "roam" between various communication systems. The selected components of an exemplary mobile station 100 for use with the present invention are illustrated in Figure 1. On the forward link (base station to mobile station), the antenna 102 captures and directs the RF energy to the transceiver (XCVR) 104. The XCVR 104 subverts and demodulates the received signal and passes it to the processor 107. The processor 107 receives the demodulated forward link signal from the XCVR 104 , and processes the signal according to conventional methods known in the art and described in greater detail in the aforementioned patents. With relevance to the present invention, the processor 107 also performs such tasks as determining which base station of which wireless communication system acquires in response to the user's preferences stored in the non-volatile memory 111, acquiring the forward link of the base station selected, and generating signaling messages for transmission to the base station. The processor 107 may be a conventional microprocessor as is known in the art, programmed to perform the tasks of the present invention described herein. Although the processor 107 includes many other processing modules, the call processing module 106 and the user interface module 108 are more relevant to the present invention and are therefore illustrated in Figure 1. The call processing module 106 receives and processes signaling messages from the base station, and on the other hand controls the actions taken by the mobile station 100 in response to signaling from the base station. For example, a call processing module 106 receives and acts after such signaling messages as the registration commands, general information messages such as paging channel assignments, pages, and transfer address messages. In response to the instructions of the call processing module 106, the user interface module 108 controls the various user interfaces such as the screen 110 and the keyboard 112 which may be a conventional display and keyboard as are known in the art. technique. For example, in response to the signaling of the base station indicating that the mobile station 100 is outside its "local" system, and therefore "roaming", the user interface module 108 may enable an indication of "roaming" "on the screen 110. As a further example, in response to the acquisition of the pilot channel of the base station, the user interface module 108 may enable a service indication on the display 110. The user interface module 108 may controlling other user interfaces which, for clarity and simplicity, have not been illustrated in Figure 1 due to their limited relevance to the present invention. In the reverse link (mobile station to base station), the user of the mobile station 100 can enter a destination telephone number using the keypad 112 to initiate a call origin. The user interface module 108 temporarily stores the dialed digits in the memory 109, and unless the "wait" instruction is given the dialed digits as will be explained hereafter, provides them to the call processing module 106 the which generates a source message for transmission to the base station by the XCVR 104 through the antenna 102. In the present invention, the call processing module 106 and the user interface module 108 act together to implement the method of the present invention as described hereinafter with reference to Figure 2. Specifically, the mobile station 100 automatically switches "without sutures" to an available system, alternately when it encounters a limited forward link condition or condition. of limited reverse link, without requiring the user to take any affirmative action to select the alternate system or and start a call origin. A high-level state diagram of the operation of an exemplary mobile station employing the present invention is shown in Figure 2. Although the diagram in Figure 2 corresponds to a compatible mobile station IS-95, its techniques are equally applicable to other wireless communication standards, whether they are cellular, mobile, PCS, or otherwise and independently of the modulation or multiplexing technology employed, i.e. Multiple Access for Distribution of Code (CDMA), Multiple Access for Time Distribution (TDMA), the Global System based on TDMA for Mobile Communications (GSM), or Analog Systems for Advanced Mobile Telephony. (AMPS). In Figure 2, five separate main operational states are illustrated: state without acquired system 200, initialization state of mobile station 202, inactive state of mobile station 204, access state of system 206 and control status of mobile station on the traffic channel 208. In addition, the various relevant transitions between these main operational states are represented. However, it should be noted that in any mobile station suitable for use with the present invention, there may be many more states and transitions which, for simplicity and clarity of exposure, are not shown in Figure 2. The mobile station starts in the state without acquired system 200. The state without acquired system 200 can be achieved in many ways such as the transition between "gaps" in the coverage areas of the wireless service, and also of any of the other states shown after the loss of the link in Advance.

While in the state without acquired system 200, screen 110 of Figure 1 may display a "NO SERVICE" indication. To obtain the service, the processor 107 (Figure 1) causes the mobile station 100 to enter the initialization state of the mobile station 202. The initialization status of the mobile station 202 consists of the following four sub-states, but for clarity only illustrates the first in Figure 2: 1) System Determination Substate; 2) Sub-State of Acquisition of the Pilot Channel; 3) Acquisition Substate of the Synchronization Channel; and 4) Synchronization Change Sub-State. Upon entering the initialization state of the mobile station 202, the call processing module 106 establishes a logical indicator, "HOLD_ORIG", which is the abbreviation of "origin originates", in the logical value "TRUE" . As long as the value of H0LD_0RIG is TRUE, the call origins initiated by the user (for example, dialing a telephone number on the keypad 112) and detected by the user interface module 108 are not activated immediately, but are "retained" "in temporary storage in the memory 109 awaiting the result of the initialization status of the mobile station 202. This is in contrast to a conventional mobile station in which the origin attempts occurring during the initialization of the mobile station immediately result in a "failed call" indication because the wireless service has not yet been reset. "In the system determination sub-station 214, the mobile station 100 selects which system, and which channel of that system is used. is typically influenced by a set of preferences (ie "CDMA only," "AMPS only," or "CDMA then AMPS") which may n be stored in a non-volatile memory 111. This determination of the system can generally be performed in accordance with the procedures described in detail in the co-pending US Patent Application. Serial No. 08 / 509,719 entitled, "METHOD AND DEVICE FOR THE DETERMINATION OF THE SYSTEM IN A MULTI MODE SUBSCRIBER STATION" ("METHOD AND APPARATUS FOR SYSTEM DETERMINATION IN A MULTI-MODE SUBSCRIBER STATION"), presented on July 31 of 1995, and assigned to the assignee of the present invention and incorporated herein by reference. In addition, the determination of the system can be performed generally according to the procedures described in the copending US Patent Application. Serial No. 08 / 626,744 entitled, "METHOD AND APPARATUS FOR PERFORMING SELECTION OF THE PREFERRED SYSTEM" ("METHOD AND APPARATUS FOR PERFORMING PREFERRED SYSTEM SELECTION"), filed on March 27, 1996, assigned to the assignee of the present invention and incorporated herein by reference. In the acquisition sub-state of the pilot channel (not shown), the mobile station 100 acquires the pilot channel of the selected system. In a system compatible with IS-95, the pilot channel is a broadcast spectrum signal of unmodulated direct sequence continuously transmitted by each CDMA base station. The pilot channel allows a mobile station to acquire CDMA forward channel synchronization, provide a phase reference for coherent demodulation, and provide a means for comparisons of signal strength between the base stations. In order to acquire the pilot channel, the mobile station 100, controlled by the processor 107, can execute the acquisition procedures described in detail in the copending U.S. Patent Application. Serial No. 08 / 687,694 titled, "METHOD AND APPARATUS FOR PERFORMING SEARCH ACQUISITION IN A CDMA COMMUNICATION SYSTEM" ("METHOD AND APPARATUS FOR PERFORMING SEARCH ACQUISITION IN A CDMA COMMUNICATION SYSTEM") filed July 26, 1996 , and assigned to the assignee of the present invention and incorporated herein by reference. Alternatively, the mobile station 100 can execute other acquisition procedures which are well known in the art, depending on what type of system is being acquired. However, if the mobile station 100 is not successful in acquiring the pilot channel of a preferred CDMA system when it is in the initialization state of the mobile station 202, it will reenter the system determination substate and try to acquire the pilot channel of the mobile station. an alternate communication system, according to the set of preferences stored in the non-volatile memory 111 as previously mentioned. Failure to initially acquire the pilot channel may be a case of the limited forward link situation previously described. After the successful acquisition of the pilot channel, the mobile station 100 enters the acquisition substate of the synchronization channel in which it receives and processes the synchronization channel messages. In a CDMA system compatible with IS-95, the synchronization channel uses the same PN sequence and phase shift as the pilot channel and can be demodulated any time the pilot channel is scanned. The synchronization channel carries, among other things, the identification of the base station and the System Time. In the Synchronization Change Substate, the mobile station synchronizes its system timing with that of the base station, based on the System Time received in the synchronization channel. Upon successful acquisition and initialization of the system, the call processing module 106 would set HOLD_ORIG back to FALSE, thus allowing any call origin already detected and stored by the user interface module 108 to proceed normally. This is in contrast to a conventional mobile station in which the origin attempts that occur during the initiation of the mobile station immediately result in a "failed call" indication because the wireless service has not yet been established. Accordingly, the dialed digits of an origin attempt occurring during the initialization state of the system 202 are temporarily stored in the memory 109 until a system is acquired, at which point it is directed to the call processing module 106 for its inclusion in the portion of the dialed digits of an origin message transmitted by the XCVR 104 (Figure 1). By temporarily storing the dialed digits in the memory 109 until a system is acquired, a user of the mobile station 100 would not require re-entering the digits dialed on the keypad 112, or taking any other action (such as pressing a "redial" key). ) in order to complete a premature call origin attempt that occurs before wireless communication has been established. In the idle state of the mobile station 204, the mobile station 100 monitors the paging channel. The paging channel is a forward channel used for the transmission of control information and pages from a base station to a mobile station. While the mobile station 204 is in the idle state, the mobile station 100 can receive general messages which communicate the specific base station as well as broad system information, receive an incoming call, initiate a call origin, initiate a registration, or start a transmission of a message. When the mobile station 100 initiates a call origin, register or other message transmission such as responding to an incoming page, the call processing module 106 generates an access channel message for transmission to the base station. When an access channel message has been generated as illustrated in decision diamond 218, mobile station 100 enters the access state of system 206 where it attempts to transmit one or more access channel messages over the access channel.

The access channel message may be, for example, a pending call origin attempt that was held during the system initialization substate 202, or it may be a call origin attempt that was first initiated during the inactive state of the system. mobile station 204, or it can be a general message such as a registration message. In a CDMA communication system, the access channel provides communications over the reverse link from the mobile station 100 to the base station when the mobile station 100 is not using the traffic channel. One or more access channels are paired with each paging channel. The base station responds to transmissions on a particular access channel by means of a message in the associated paging channel. Similarly, the mobile station 100 responds to a paging channel message when transmitting on one of the associated access channels. If the mobile station were to experience a deep fading of the paging channel, that would be another case of the previously described limited forward link situation and the mobile station would return to the system determination substate of the initialization state of the mobile station 202 and would attempt to reacquire the service either with the same CDMA communication system or an alternate system according to the set of system preferences stored in the non-volatile memory 111. In the access state of the system 206, the mobile station 100 transmits in the access channel using a random access procedure. The complete process of sending an access channel message and receiving (or failing to receive) an acknowledgment of that channel message from. Access is called an "access attempt". An access attempt comprises transmitting one or more "access test sequences". Each access test sequence comprises the transmission of one or more "access tests". Each access test comprises the access channel message and the mobile station transmits the same access channel message in each access test in an access attempt. Therefore, within an access attempt, the access tests are grouped into sequences of access tests. The first access test of each access test sequence is transmitted at a predetermined power level. Each subsequent access test in that access test sequence is transmitted at a power level which is a predetermined power increase greater than the previous access test in that access test sequence. For example, if the default power level for the first access test is 7 dB, and the default power increase is 2dB, then the first access test in each access test sequence will be transmitted at 7dB, the second Access test in each access test sequence will be transmitted at 9dB, the third at lldB, and so on until the access test sequence is completed. If an access test sequence is not successful in evoking an acknowledgment from the base station, another identical access test sequence will begin. The mobile station 100 stops transmitting the access test sequences, thereby terminating the access attempt, when it receives an acknowledgment from the base station, or when it has transmitted a predetermined maximum number of access test sequences. The termination of the access attempt due to the scope of the predetermined number of access test sequences would be a case of the limited reverse link situation previously described. It should be noted that access attempts can be made in other ways as is known in the art, depending of the nature of the system that provides the service. If the access attempt succeeds as determined by the decision diamond 220, and the access channel message is a source message indicating that the user of the mobile station is originating a call, the mobile station is directed towards a traffic channel by the base station, and the mobile station enters the control of the mobile station in the traffic channel state 208. When the use of the traffic channel has been completed, as when the call is completed as determined by the decision diamond 222, the mobile station returns to the inactive state of the mobile station 204. However, if the access attempt is unsuccessful because it does not evoke an acknowledgment of the base station in the diamond decision 220, then processor 107 determines, in decision diamond 224, whether this last unsuccessful access attempt was the nth access access failure for the same access channel message, where N is a larger integer than one. If it is not, then the call processing module 106 again sets HOLD_ORIG to TRUE and reenters the system determination substate 214. Instead of using a fixed number of retries as determined by decision diamond 224, it is also possible to use a timer that allows as many or as few attempts as can be attempted within a period of time, such as 20 seconds. In such a case, the decision diamond 224 would fail a call origin attempt after the expiration of the timer regardless of whether so many or so few attempts have been made. Alternatively, a combination of these techniques may be used. In the initialization state of the system 202, the mobile station 100 preferentially tries to acquire a communication channel or system different from that in which the access attempt recently failed. For example, assuming that there are two communication systems in the same geographical area - a CDMA PCS system and an analog AMPS system. Assuming further that the CDMA PCS system is operating on two different CDMA channels, channel number 400 and channel number 425, and the AMPS system is operating on the analog channel "B". If an access attempt failure for the source message was received while the service was being provided on the CDMA PCS channel 425, then the system determination substate 214 would preferably try to either acquire the analog system AMPS in the analog channel " B ", or the PCS CDMA system on channel number 400 of CDMA. If the analog channel AMPS "B" was acquired during the initialization state of the system 202, the call processing module 106 would again set HOLD_ORIG to FALSE. In response to detecting the change of HOLD_ORIG from TRUE and back to FALSE, the user interface module 108 would retrieve the dialed digits from memory 109 and restart the call origin. If the call origin was direct this time, meaning that the base station recognized the call origin on the decision diamond 220, the mobile station 100 would complete the call normally on a traffic channel and return to the idle state of the mobile station 204 Therefore, the user did not need to dial the telephone number even though the service was lost in one system and then recovered in another. In one embodiment, provisions are made to periodically re-track the service on the original preferred CDMA channel number 425 of PCS CDMA. For example, the processor 107 may set a timer to one minute and then return to the initialization state of the system 202 to reacquire the preferred system after the timer expires. Alternatively, the one minute timer can be reset after each origin in the analog AMPS system. However, if the analog channel "B" of AMPS is not acquired during the initialization state of the system 214, the mobile station 100 may continue to track and eventually acquire the acquisition service on the 400th alternate channel of PCS CDMA. Similar to the example already presented, in response to detecting the change of HOLD_ORIG from TRUE and back to FALSE, the user interface module 108 would recover the dialed digits of the memory 109 and restart the call origin.

Assume that the access attempt will fail as determined in decision diamond 220 in any alternate system that would have been first acquired (either analog channel "B" of AMPS or channel number 400 of PCS CDMA). This would be the second fault for the same call origin attempt, i.e. for the same digits marked once entered by the user. If N = 2 in the decision diamond 224, then the call origin would fail and the user interface module 108 would indicate an unsuccessful call on the screen 110 in block 226. Accordingly, the present invention provides N access attempts in different systems for the same call origin before the user is required to take any action to remedy the situation (ie highlight the phone number, go to an area with better coverage, etc.). The number N, and therefore the number of "retries", can be fixed or can be configured by the user. For example, the manufacturer of the mobile station 100 may decide that only a single retry of the originating message as described herein is suitable and may set the value of N to two. It should be noted again that the present invention is applicable beyond the specific examples of CDMA and analog AMPS presented herein, but rather is applicable to any mobile station that can operate in more than one communication system. For example, if there are two CDMA PCS systems in. In a given geographic area, the present invention can be used to provide a retry of CDMA to CDMA. Furthermore, it should be noted that the specific user preferences stored in a non-volatile memory 111 and used during the determination substate of the system 214 to determine which systems should be purchased, are not critical to the present invention. The user preferences in a non-volatile memory can be a table of preferred systems, or a classified table of systems in order of preference, or only a list of likely systems that may be available. As described herein, the present invention decreases the percentage of failed calls by providing a "hold" of pending call origin attempts until the service is finally acquired. In the case of exceeding either the maximum number of access sequences (limited reverse link) or failure to acquire the forward link of the preferred communication system (limited forward link), the user is not required to restart the call origin , thus making a potential failed call a success. In addition, the present invention is not limited to retrying the call origins. The present invention can also be used to perform an automatic, sutureless system switching in a limited reverse link situation for a failure of any access channel message, thereby allowing the mobile station 100 to quickly switch to, and register on. , an alternate system when it is unable to register in the preferred system. This would avoid the undesirable affectation of the mobile station 100 that omits an incoming call because it was unable to register in the preferred system. Even in the case where the mobile station 100 is unable to register in the preferred system before reaching the limited reverse link, the automatic switching of the system of the present invention can be used to make the telephone look for an alternate system for service when it is not able to receive an acknowledgment for any other general message transmitted on the access channel. The prior description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. The various modifications to these modalities will be readily apparent to those skilled in the art and the generic principles defined herein may be applied to other modalities without the use of the inventive faculty. Accordingly, the present invention is not intended to be limited to the embodiments shown herein but to be in accordance with the broadest scope consistent with the principles and novel features described herein.

Claims (15)

1. CLAIMS Having described the present invention is considered as a novelty and therefore claimed as property described in the following claims: 1. A wireless communication device comprising: a processor to generate a first signaling message for transmission to a first communication system that has a first pilot signal; and a transceiver, coupled to the processor, for transmitting the first signaling message to the first communication system and for receiving the first pilot signal and a first acknowledgment message from the first communication system; wherein the processor automatically generates a second signaling message for transmission to a second communication system having a second pilot signal only if the transceiver does not receive the first acknowledgment message and receives the first pilot signal. The wireless communication device according to claim 1 characterized in that it further comprises: a user interface, coupled to the processor, to generate a first set of dialed digits; and a memory, coupled to the processor, for storing the first set of dialed digits, including both first and second signaling messages, the first set of digits dialed. 3. The wireless communication device according to claim 2, characterized in that the processor recovers the first set of digits dialed from the memory to generate the second signaling message. 4. The wireless communication device according to claim 3, characterized in that the first and second signaling messages are call originating messages. The wireless communication device according to claim 3 or 4, characterized in that the processor comprises: a call processing module for generating the first and second signaling messages and for generating a source retention signal; and a user interface module for storing the first set of dialed digits in the memory and for providing the first set of dialed digits to the call processing module in response to the origin retention signal. 6. The wireless communication device according to claim 5, characterized in that the call processing module establishes the originating retention signal to a first logical value where the wireless communication device is acquiring the first or second communication system and a second one. logical value when the wireless communication device has acquired the first or second communication system. The wireless communication device according to any of the preceding claims, characterized in that the first and second signaling messages are registration messages. A method for automatically switching between a first communication system having a first pilot signal and a second communication system having a second pilot signal, the method comprising the steps of: receiving the first pilot signal; generating a first signaling message for transmission to the first communication system; transmitting the first signaling message to the first communication system; automatically generate a second signaling message for transmission to the second communication system only if a first acknowledgment message is not received from the first communication system. The method according to claim 8, characterized in that it also comprises the steps of: generating a first set of dialed digits; and storing the dialed digits in a memory, including both of the first and second signaling messages the first set of dialed digits. 10. The method according to claim 9 characterized in that the step of automatically generating the second signaling message includes the step of recovering from memory the first set of dialed digits. The method according to claim 10 characterized in that the first and second signaling messages are call originating messages. The method according to claim 10 or 11, characterized in that it also comprises the step of generating a retention signal of origin, wherein the step of recovering the first set of dialed digits from the memory is performed in response to the origin retention signal. 13. The method according to claim 12, characterized in that the step of generating the origin retention signal includes the steps of: establishing the origin retention signal to a first logical value when the wireless communication device is acquiring the first or second communication system; setting the source signal to a second logical value when the wireless communication device has acquired the first or second communication system. The method according to claims 8 to 13 characterized in that the first or second signaling messages are registration messages. 15. A mobile communication device configured to monitor signals from several different communication systems, to transmit a signaling message to one of the communication systems where the device is connected to a system and to connect to another of the communication systems when the signaling message is not recognized by the system. SUMMARY A wireless communication device (100) is automatically switched without sutures to an available system, alternative when it is not available to complete an attempt to originate a call without requiring the user to take any affirmative action to select the alternate system or re-start a call origin. The wireless communication device (100) comprises a transceiver (104) and a processor (104). The transceiver (107) transmits and receives messages and signals. The processor (106) generates a first signaling message for transmission to a first communication system and generates a second signaling message for transmission to a second communication system if the transceiver does not receive an acknowledgment message from the first communication system. This decreases the percentage of failed calls by providing a continuation of pending call origin attempts until the service is finally acquired. In the case of either exceeding the maximum number of access sequences (limited reverse link) or failing to acquire the forward link of the preferred communication system (link in limited advance), the user does not need to re-initiate the origin of so changing from a potential call failure to a successful one.