CN1628482A - Method and apparatus for efficient selection and acquisition of a wireless communications system - Google Patents

Abstract

A mobile station includes processing circuitry and a memory. A group of wireless communications systems is selected in accordance with a predetermined system acquisition procedure. A received signal corresponding to each selected system is analyzed to determine a likelihood that the selected system would be acquired by the mobile station. The group of selected systems is reprioritized based on the results of the analysis to produce a more efficient system acquisition sequence. The mobile station then attempts to acquire a selected wireless communications system in accordance with the system acquisition sequence.

Description

Method and apparatus for efficient selection and acquisition of a wireless communication system

technical field

The present invention relates generally to wireless communication, and in particular to a method and apparatus for efficiently selecting and acquiring a wireless communication system.

Background technique

This application claims priority to US Provisional Application No. 60/355,742, filed February 5,2002.

A mobile device often has access to more than one wireless communication system within its geographic location. The quality of wireless service available to a mobile device may vary from system to system, depending on the instrumentation used by each system, the characteristics of the mobile device, the distance between the mobile device and the local base station, factors such as buildings and hills physical obstacles such as , and the communication traffic capacity of each system. The local wireless communication system can also support different multiple access wireless communication protocols, such as: Code Division Multiple Access (CDMA), Wideband CDMA (WCDMA), Advanced Mobile Phone Service (AMPS), Global System for Mobile Communications (GSM), General Packet Wireless business (GPRS) or high data rate (HDR) technology (such as 1xEV technology). Additionally, charges to mobile device users vary depending on the time of day, duration of connectivity to the wireless communication system, and whether the mobile device is listed as a user of the wireless communication system.

In order to select the desired wireless communication system, conventional mobile devices store data describing known systems in a Preferred Roaming List (PRL). The PRL usually includes a system store and an acquisition store, the system store stores the system identifier (SID) and the network identifier (NID) for each known wireless communication system, and the acquisition store stores the acquisition parameters of the known wireless communication systems including the frequency band , frequency and mode. In systems storage, wireless communication systems are often grouped by geographic region and ordered within each region from most desirable to least desirable systems. The most ideal system in a particular geographic area is usually a subscriber system, but could also be a roaming system that provides a good combination of low-cost, high-quality service to mobile devices. Roaming systems typically provide wireless service to non-subscriber mobile devices at a much higher cost than subscription service, but when the mobile device enters a geographic area outside the coverage of the mobile device's subscription service, when the subscription service is blocked or unavailable, Or roaming systems may be ideal when subscription services are only available at an unacceptably low quality.

During the mobile device power sequence, an attempt is made to acquire and register the mobile device with the most optimal wireless communication system available in its current geographic area. In one method, the mobile device identifies its current geographic area and then steps through the entries in the system table from the most desirable system in the identified geographic area to the least desirable system in the identified geographic area until a system Capture and registration attempts are successful. The mobile device may also attempt to acquire and register with a new wireless communication system during operation. For example, the connection between the mobile device and the current wireless communication system may be lost and the mobile device needs to acquire a new system. For example, when the connection between the mobile device and the current wireless communication system may be lost, the mobile device needs to acquire a new system. Additionally, the wireless communication systems available to a mobile device may change as the location of the mobile device and its surroundings change. In order to provide mobile device users with the best combination of high quality and low cost, many mobile devices periodically attempt to acquire and register with a wireless communication system that is more desirable than the current wireless communication system used by the mobile device. The mobile device searches a system table of wireless communication systems in its geographic area that are more desirable than the current system used by the mobile device, and if a more desirable system is found in the system table, the mobile device switches off the current communication channel and attempts to acquire And sign up for one of the more desirable systems.

A system acquisition sequence, such as that described above, typically includes a series of failed attempts to acquire a signal and register with a corresponding wireless communication system before a single successful system acquisition and registration. A preferred roaming list typically includes more than 50 systems, and in some cases, a mobile device may take more than 60 seconds to step through the systems in the preferred roaming list before a capture attempt is successful. These failed capture attempts are common and can be caused by various factors. For example, a mobile device may not be able to detect a pilot signal transmitted from a system base station if the pilot signal is blocked or impaired by physical obstructions, or if the mobile device is outside the coverage area of the base station. Registration to the system may fail if the mobile device and system use incompatible protocol revisions and hardware, or if the system rejects the mobile device's registration attempt.

In view of this, there is a need in the art for a method and apparatus for efficiently selecting and acquiring a wireless communication system.

Contents of the invention

The present invention is a method and apparatus for efficiently selecting and acquiring a wireless communication system. In a preferred embodiment, a mobile station selects a set of wireless communication systems according to a determined system acquisition procedure. The selected set of systems has a priority order, such as a preference order determined by the wireless service provider, that can be used by the mobile station during system acquisition and registration attempts. Next, the corresponding received signal for each selected system is analyzed to determine the likelihood that each corresponding system will be acquired by the mobile station. The group of wireless communication systems is then re-prioritized based on the analysis results to produce a more efficient system acquisition order. The mobile station attempts to acquire and register with one of the systems in the re-prioritized set of wireless communication systems in the set-specified acquisition order.

Preferably, the mobile station includes processing circuitry, memory, a communication transceiver and an antenna. The processing circuitry includes a control processor for controlling the operation of the mobile station, signal processor, searcher and system determination unit. In a preferred embodiment, the mobile station is a multi-mode device and the processing circuitry is adapted to operate in CDMA or AMPS mode. Preferably, the memory comprises volatile and non-volatile random access memory storing a preferred roaming list comprising a system table and an acquisition table, and one or more look-up tables such as candidate lists . The system determination unit is adapted to select one or more wireless communication systems from the system table according to the system acquisition procedure. In a preferred embodiment, the system determination unit stores the selected systems in the candidate list, and instructs the searcher to analyze the received signal corresponding to each system in the candidate list. For each system listed, the searcher commands the transceiver to switch to the corresponding channel for that system and a received signal is analyzed. Analysis of the received signal may include: measuring the received signal strength (Rx) of each system, measuring the signal-to-noise ratio Ec/Io, or other tests in determining whether a candidate system is likely to be acquired - provided the test takes longer than the full There are fewer system capture and registration attempts.

After each system is analyzed, the selected group of systems is re-prioritized based on the analysis results. In a preferred embodiment, all systems are ordered such that those with the greatest likelihood of being acquired are selected first. In a first alternative embodiment, the desirability order is maintained, and at each desirability level, the analysis results are used to rank the selected systems. In a second alternative embodiment, the desirability information for each selected system is adjusted based on the results of the analysis, and then the selected group of systems is ranked using the adjusted desirability information. In a third alternative embodiment, each system whose corresponding analysis result is below a threshold value is deleted from the selected group of systems.

The mobile station next attempts to acquire and register with a wireless communication system. The system with the highest priority level is selected first from the re-prioritized candidate list, and an attempt is made to acquire and register the selected system. Any system capture method may be used including conventional system capture methods well known in the art. If the acquisition/registration attempt is unsuccessful, the next highest priority wireless communication system is selected from the candidate list and another acquisition/registration is attempted. This process continues until one system capture/registration attempt succeeds, or until there are no more candidate systems. In a preferred embodiment, if the acquisition/registration attempt is successful, the wireless communication system is used for future wireless communication services. In an alternate embodiment, the acquired wireless communication system has a known geographic area and a reattempt is made to acquire and register a more preferred wireless communication system within said geographic area.

In the first alternate system acquisition sequence, the first system is selected according to the system acquisition procedure. Any system acquisition procedure may be used, including selecting the system most recently used by the mobile station. The signal quality of the selected system is measured, and if this system is not likely to be acquired, the next system is selected following the system acquisition procedure. If a selected system is likely to be acquired, an attempt is made to acquire and register the selected system. If the acquisition/registration attempt is successful, then the wireless communication system is used for future wireless communication services. Otherwise, follow the system capture procedure to select the next system.

A more complete understanding of the method and apparatus for efficient selection and acquisition of a wireless communication system, as well as the realization of its other advantages and objectives, will be presented to those skilled in the art by considering the following detailed description of preferred embodiments. The description will be made with reference to the accompanying drawings, which will first be briefly described.

Description of drawings

The features, objects and advantages of the present invention will become more apparent from the following detailed description set forth in conjunction with the accompanying drawings, in which like reference numerals identify corresponding places throughout, in which:

Figure 1 illustrates a preferred embodiment of the present invention;

Figure 2 is a mobile station according to a preferred embodiment of the present invention;

Figure 3a is a system table according to a preferred embodiment of the present invention;

Figure 3b is a capture table according to a preferred embodiment of the present invention;

Figure 4 illustrates a look-up table used by a mobile station according to a preferred embodiment of the present invention;

Figure 5 is a flowchart illustrating a preferred system selection and acquisition procedure; and

Figure 6 is a flow chart illustrating an alternative system selection and acquisition procedure.

Detailed ways

A preferred embodiment of the present invention will now be described with reference to FIG. 1 . Mobile station 2 operates in a geographical area 4 served by at least one base station 6 . Each base station 6 is connected to a network 8, which is part of a larger wireless communication system supporting at least one multiple-access wireless communication protocol, including Code Division Multiple Access (CDMA), Wideband CDMA (WCDMA ), Advanced Mobile Phone Service (AMPS), Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), or High Data Rate (HDR) technology (eg, 1xEV technology). Mobile station 2 may be any wireless device, whether fixed or mobile, adapted to communicate wirelessly with at least one base station 6, such as a cellular telephone, pager, personal digital assistant (PDA), vehicle navigation system or portable computer. In a preferred embodiment, the mobile station is a multimode device adapted to operate in both CDMA and AMPS modes.

The mobile station 2 includes a list of known wireless communication systems such as a Preferred Roaming List (PRL) 10 . PRL 10 is stored in non-volatile memory of mobile station 2 and includes a list of wireless communication systems and corresponding acquisition parameters used by mobile station 2 during an attempt to acquire and register with one wireless communication system. In a preferred embodiment, the wireless communication systems listed in PRL 10 are grouped by geographic region and ordered within each region from most desirable to least desirable. As is known in the art, the PRL 10 may be maintained by the mobile station's service provider and includes information available to the mobile station 2 through its wireless service provider or other wireless service providers that have agreed to provide roaming services to the mobile station 2. List of wireless communication systems.

In operation, the mobile station 2 attempts to acquire and register with an available wireless communication system that provides wireless service to the mobile station 2 . First, a set of wireless communication systems is selected from the PRL 10 according to a predetermined system acquisition procedure. The system group has a priority order that can be used by the mobile station 2 during system acquisition and registration attempts. For example, in a preferred embodiment, the wireless communication systems in the mobile station's geographic area 4 are selected and ordered from most desirable to least desirable systems in each area. Next, the received signals corresponding to each selected system are analyzed to determine a relative likelihood of each corresponding system being acquired by the mobile station 2 . The group of wireless communication systems is then re-prioritized based on the analysis results to produce a more efficient system acquisition order. The mobile station 2 selects the system with the highest relative priority from the re-prioritized group, and attempts to acquire and register with the selected system. If the acquisition/registration attempt is successful, the selected system is used by the mobile station 2 for wireless communications. Otherwise, try to acquire/register the system with the next highest priority from the group.

A preferred embodiment of the mobile station 2 will now be described with reference to FIG. 2 . Mobile station 2 includes processing circuitry 80 , memory 82 , communication transceiver 84 and antenna 86 . Preferably, the processing circuit 80 includes a control processor 90 for controlling the operation of the mobile station 2 , a signal processor 92 , a searcher 94 and a system determination unit 96 . Memory 82 preferably includes volatile and non-volatile random access memory that stores a preferred roaming list, including system table 100 and capture table 102 . Memory 82 may also store one or more look-up tables, such as a list of recently used systems 106 and program instructions for execution by processing circuitry 80 .

Searcher 94 is adapted to identify valid signals received by transceiver 84 via antenna 86, such as pilot signals, synchronization channels and paging channels. The design and apparatus of the searcher hardware for CDMA acquisition is described in U.S. Patent No. 5,109,390 entitled "DIVERSITY RECEIVERIN A CDMA CELLULAR TELEPHONE SYSTEM" assigned to the assignee of the present invention , and said reference is used here. Searcher 94 is also adapted to perform pre-acquisition analysis of one or more candidate communication systems.

The system determining unit 96 is adapted to select one or more wireless communication systems from the system table 100 and extract corresponding acquisition parameters from the search table 102 . The system determination unit 96 is also adapted to forward the acquisition parameters to the searcher 94 which attempts to acquire a selected system. In an alternative embodiment, the system determination unit 96 determines whether the current wireless communication system is the most desirable system in the current geographic area of the mobile unit, and attempts are made by the mobile station 2 to acquire a more desirable system when a more desirable system is available. system. A method and apparatus for performing preferred system selection operable in a mobile station in multiple geographic areas is disclosed in assigned to the assignee entitled "Method and Apparatus for Performing Preferred System Selection" (METHOD AND APPARATUS FOR PERFORMING PREFERRED SYSTEM SELECTION) is disclosed in US Patent No. 6,085,085 and is used by reference herein.

It should be understood that the mobile station 2 shown in FIG. 2 is schematic only and that alternative configurations and additional features are contemplated within the scope and spirit of the invention. For example, the components of mobile station 2 may be implemented in various hardware configurations using conventional circuit elements such as one or more processors, memory, and application specific integrated circuits (ASICs). The mobile station 2 may also be suitable for voice communications, high speed data communications, video communications, Internet applications such as e-mail and World Wide Web access, position location (such as gpsOne™ developed by the present assignee), personal navigation, voice recognition , integrated removable storage, and short-range wireless connectivity to local peripherals and devices. In a preferred embodiment, processing circuitry 80 includes a mobile station modem chipset developed by the assignee that integrates digital and analog functions with GPS-based position location.

Referring now to Figures 2 and 3a, a preferred embodiment of the system table 100 will be described. System table 100 includes a list of wireless communication systems used by mobile station 2 during an attempt to acquire and register with a wireless communication system. As shown, each record in the system table 100 includes a system identifier (SID) 100a, network identifier (NID) 100b, an indication that the system is or is not preferred (P/N) 100c, covered by the system An identifier 100d of a geographical area (area), desired information 100e, and a pointer (AT pointer) 100f pointing to a record in the acquisition table 102. Each wireless communication system listed in the system table 100 is identified by a unique pair of SID 100a, NID 100b, and is designated by a P/N 100c as a preferred system that can be used by the mobile station 2 during roaming, or as not. An unselected system that should be used by the mobile device 2 during roaming. In alternative embodiments, other system identifiers such as unique frequency bands, modes and frequencies, Internet Protocol Version 6 (IPV6) addresses, or public land mobile network (PLMN) identifiers may be used to identify the devices listed in system table 100. wireless communication system. Preferably, the wireless communication systems are grouped by geographical area 100d and stored in the system table 100 in order from most desirable system to least desirable system within each area utilizing expectation information 100e.

A preferred embodiment of capture table 102 is now described with reference to FIG. 3b. Acquisition table 102 includes a list of parameters required to acquire the wireless communication systems listed in system table 100 . As shown, each record in capture table 102 preferably includes a mode 102a, frequency band 102b and frequency 102c. Preferably, the system table 100 and the acquisition table 102 are stored in non-volatile memory and are provided by an external source such as the mobile station's wireless service provider via a wireless connection or other data transfer method supported by the mobile station 2 Download to periodically update. It should be understood that alternative configurations of the PRL, system table 100 and capture table 102, and alternative identification and capture parameters may be employed in accordance with the present invention.

As shown in FIG. 4 , the memory also includes one or more look-up tables 104 . In a preferred embodiment, the lookup tables include: a Most Recently Used (MRU) system table 104a storing a list of systems most recently used by the mobile station 2; a candidate list including a list of systems that have been selected as acquisition candidates 104b; and a preference table 104c maintaining the mobile station 2's local preference settings. Other information can also be stored in the lookup table, including historical information that tracks usage of each system. Preferably, the look-up tables are stored in a volatile portion of memory 24 , but in alternative embodiments one or more look-up tables may be stored in a non-volatile portion of memory 24 .

A preferred system acquisition sequence for mobile station 2 will now be described with reference to the flowcharts of FIGS. 2 and 5 . Preferably, the system acquisition sequence is performed by the system determination unit 96 . In step 200, a set of wireless communication systems is selected from a stored list of systems according to a predetermined system acquisition procedure. In a preferred embodiment, wireless communication systems in the geographic area 4 of the mobile station are selected from the system table 100 and the corresponding system identifiers are stored in the candidate list 104b in the memory 24 . In alternative embodiments, candidate list 104b may include other data such as corresponding acquisition parameters and selected system desired information. Preferably, the candidate list 104b is ordered in an initial order of priority (eg, from most desirable to least desirable systems) as determined by the pre-system acquisition procedure. Although illustrated using the system selection of PRL, it should be understood that other system capture procedures may be used in accordance with the preferred embodiment of the present invention. For example, in an alternate embodiment, the system capture procedure may include selecting a set of systems from the MRU 104a or other stored list of systems.

As is known in the art, system table 100 specifies a preferred system acquisition order to be used by mobile station 2 during acquisition/registration attempts. However, this system acquisition order is not always the most efficient system selection order for acquiring and registering wireless communication systems. The order of selection specified by the system table 100 is typically determined by the mobile station's wireless service provider based on a factor that is irrelevant to the likelihood that each listed system is acquired by the mobile station 2 . For example, criteria such as system usage cost, quality of communication service provided by the system, protocols used by the system, support of unique features, and whether the mobile station 2 is listed as a user of the wireless communication system, etc., may be used to determine each system expectations.

To improve the efficiency of the system acquisition/registration process, the mobile station 2 analyzes the received signal corresponding to each system in the candidate list 104b (step 202), and adjusts the system acquisition order based on the analysis result (step 204). In a first preferred embodiment, the analysis of the received signal includes measuring the received signal strength (Rx) of each system. In operation, the searcher 94 steps through the systems identified in the candidate list 104 b stored in the memory 24 . In an alternative embodiment, the candidate list may be sent from the system determination unit 96 to the searcher 94 . For each system listed, the searcher 94 commands the transceiver 84 to switch to the corresponding channel for the system. The received signal strength is then measured and stored in the candidate list 104b. If the received signal strength measurement is relatively low, the probability that the candidate system will be available for acquisition will be low. If the received signal strength measurement is relatively high, the probability that the candidate system can be acquired may be higher. It should be appreciated that signal strength measurements of a group of systems can typically be accomplished in a much shorter time than attempting to acquire and register each system in the group. In alternative embodiments, other tests to help determine whether a candidate system is likely to be acquired may be performed on the received signal.

In a first alternative embodiment, the analysis of the received signal includes determining whether the received signal is likely to be a CDMA signal. In this embodiment, the system determination unit 96 commands the searcher 94 to measure the signal-to-noise ratio Ec/Io, where Ec is the strength of the received signal and Io is the total thermal noise received on the channel. In a CDMA system, this measurement provides an indication of the portion of the received signal available. If the ratio Ec/Io is relatively large, the probability that the candidate system can be acquired can be greater. The ratio Ee/Io provides a more reliable indication of whether the signal is likely to be acquired than the measured raw strength of the signal.

In a second alternative embodiment, the system determination unit 96 and the searcher 94 provide multiple acquisition testing methods and methods, and may be adapted to use more than one type of analysis alone or in combination. The test pattern may be determined by user preferences, mobile station configuration, current operating state of the mobile station, or other criteria. Preferably, searcher 94 operates in accordance with instructions received from system determination unit 96, and system determination unit 96 is adapted to issue a candidate system test instruction and a system acquisition instruction. The candidate system testing instructions include parameters identifying the candidate list, an identifier to perform the test on each candidate system, and minimum thresholds to be met by each system. The searcher 94 executes the received instructions and returns candidate systems that meet the test requirements. In a preferred embodiment, searcher 94 modifies a candidate list stored in memory. The system determination unit 96 is also adapted to analyze the test results and transmit to the searcher 94 a system capture command including parameters identifying the candidate list.

At step 204, the selected group of systems is reprioritized based on the analysis results to produce a more efficient system acquisition order. In a preferred embodiment, all systems are ordered such that those with the greatest likelihood of being acquired are selected first. In a first alternative embodiment, multiple selected systems have the same desirability level. At each desirability level, the measured signal strength is used to rank the selected systems from the most likely to be acquired to the least likely to be acquired. In a second alternative embodiment, the desired information for each selected system is adjusted based on test measurements. For example, the relative desirability of systems with signal strength measurements greater than a first threshold may be adjusted upwards, while the relative desirability of systems with signal strengths below a second threshold may be adjusted downward. The selected system groups are then sorted using the adjusted desired information. In a third alternative embodiment, each system whose test signal quality is below a threshold is removed from the selected set of systems. For example, candidate systems with corresponding measured signal strengths below -90 db can be eliminated from the candidate list. Candidate systems can also be eliminated and ranked using other criteria. For example, a weighting factor may be used that takes into account measured signal strength, whether the system has been used recently, desirability parameters, and other information.

After the selected system group is re-prioritized, the mobile station 2 attempts to acquire and register with one of the wireless communication systems in the group. At step 206, the system with the highest priority level is selected from the candidate list 104b. In a preferred embodiment, based on measured signal quality, such as signal strength measurements, the system has a relatively high level of desirability and a high probability of success for acquisition/registration attempts. At step 208, an attempt is made to acquire and register the selected system. Any system capture method may be used including conventional system capture methods well known in the art. In a preferred embodiment, the mobile station 2 is adapted to acquire a CDMA system. To acquire a CDMA system, the searcher 94 commands the transceiver 84 to switch to the communication channel of the selected CDMA system and listen for the pilot signal. Searcher 94 attempts to verify the received pilot signal by testing for various pseudorandom noise (PN) offsets in the received signal until a match is found. When acquiring the pilot signal, processing circuit 80 receives the information of the forward CDMA channel and the phase reference for signal demodulation. Next, processing circuit 80 attempts to acquire a synchronization channel associated with the identified pilot channel. The synchronization channel transmits basic system information such as the unique SID/NID of the transmitting wireless communication system and network, as well as synchronization information. The processing circuit 80 adjusts its timing according to the received information, and then switches to the paging channel of the base station. The paging channel is used by the local base station of the current communication system to communicate with the mobile station 2 when the mobile station 2 is not assigned to a traffic channel. Through the paging channel, the base station notifies the mobile station 2 of an incoming message, such as an incoming telephone call or received voicemail message.

If the acquisition/registration attempt is successful (step 210), then the selected system is used by the mobile station 2 for wireless communications. If the acquisition/registration attempt was unsuccessful, then (at step 212), the wireless communication system with the next highest priority is selected from the candidate list and control is returned to step 208 for the next acquisition/registration attempt. If the searcher 94 cannot acquire the selected system (step 210), the searcher 94 will try to acquire each of the remaining systems in the order of selection until either a wireless communication is acquired or the candidate systems are exhausted. In an alternate embodiment, if the acquisition/registration attempt is successful at step 210, then the process returns to step 200 to select a more desirable set of systems than the selected system in the current geographic area.

An alternative system acquisition sequence is shown in the flowchart of FIG. 6 . At step 250, a first system is selected according to a predetermined system acquisition procedure. Any system acquisition procedure may be used, including selecting the system most recently used by the mobile station 2 . In step 252 the signal quality of the selected system is measured. If the system is likely to be acquired (step 254), then at step 256 an attempt is made to acquire and register the selected system. In a preferred embodiment, the system is likely to be acquired if the measured signal quality exceeds a predetermined threshold. If the system is not likely to be acquired, then at step 260 the next system is selected according to the system acquisition procedure. If the acquisition/registration attempt is successful (step 258), then the mobile station 2 uses the selected system for future wireless communication services. If the acquisition/registration attempt is unsuccessful, then at step 260 the next wireless communication system is selected and control returns to step 252 .

Having thus described preferred embodiments of methods and apparatus for efficient selection and acquisition of a wireless communication system, it will be apparent to those skilled in the art that certain advantages within said system have been achieved. It should also be understood that various modifications thereof, and applicable alternative embodiments may be made within the scope and spirit of the invention.

The scope of the invention is defined by the following claims.

Claims (23)

1. In a mobile station storing a list of wireless communication systems, a system acquisition procedure comprising the steps of: selecting a group of wireless communication systems from the list according to a predetermined system acquisition procedure, the group of wireless communication systems having a first system acquisition order; Measure the signal quality of each selected system; re-prioritizing the group of wireless communication systems according to the measured signal quality, the re-prioritized group of wireless communication systems having a second system acquisition order; and An attempt is made to acquire the wireless communication system with the highest priority in the second system acquisition order. 2. The method of claim 1, wherein the wireless communication system list is a preferred roaming list comprising geographic area identifiers, and the step of selecting a group of wireless communication systems includes: determining the current geographic area of the mobile station, and selecting a listed wireless communication system for a geographic area identifier corresponding to the mobile station's current geographic area, and Wherein, the first system acquisition order is based on the relative order of the selected wireless communication systems in the preferred roaming list. 3. The method of claim 2, wherein each wireless communication system identified in the preferred roaming list has a corresponding desirability level, at least two selected systems share the same desirability level, and Wherein the reprioritizing step includes locating selected systems that share the same desirability level, and ordering the located systems by measured signal strength. 4. The method of claim 3, wherein each wireless communication system identified in the preferred roaming list has a corresponding desirability level, and the step of reprioritizing comprises the steps of: For each selected system, adjusting the corresponding desirability level based on the corresponding measured signal strength, the adjusted desirability criteria being stored in the set of wireless communication systems; and The wireless communication system group is sorted by the adjusted desirability level. 5. The method of claim 1, wherein the step of reprioritizing includes removing a selected system from said group if its corresponding measured signal quality does not satisfy a minimum threshold. 6. The method of claim 1, wherein the step of measuring signal quality includes calculating a ratio Ec/Io of the received signal. 7. A mobile station comprising: a memory storing a preferred roaming list comprising a first plurality of system identifiers and corresponding acquisition parameters; and a processing circuit adapted to select a wireless communication system from the preferred roaming list according to a predetermined system acquisition procedure, the selected wireless communication system having a corresponding system acquisition order, Wherein: the processing circuit is further adapted to measure the signal quality of each selected system based on the measured signal quality and to modify the system acquisition order, the modified system acquisition order increasing the efficiency of the system acquisition process. 8. The mobile station of claim 7, wherein the selected wireless communication system includes a corresponding desirability criterion, and Wherein, if the corresponding signal strength measurement exceeds the first threshold, the processing circuit is further adapted to adjust the desirability criteria of the selected systems, and rank the selected wireless communication systems using the adjusted desirability criteria. 9. The mobile station of claim 7, wherein the measured signal quality for each system includes a signal-to-noise ratio of the received signal corresponding to a likelihood that the corresponding system will acquire. 10. A method for acquiring a wireless communication system in a multi-mode mobile station adapted to operate in CDMA and AMPS modes, comprising the steps of: analyzing signals received on a channel associated with a candidate communication system; determining whether the candidate communication system is likely to be acquired by the mobile station based on an analysis of the received signal; and An attempt is made to acquire a candidate communication system only if the candidate communication system is likely to be used for acquisition. 11. The method of claim 10, wherein the step of analyzing includes switching to a channel associated with said candidate communication system and testing the signal quality of the received signal. 12. The method of claim 11, wherein the mobile station includes a list of known communication systems, each known communication system having a relative degree of desirability, and wherein candidates are selected from the list of known communication systems according to a predetermined system acquisition procedure Communication Systems. 13. The method of claim 1, wherein the test signal quality is a received signal strength measurement. 14. The method of claim 11, wherein the test signal quality is a signal-to-noise ratio of a received signal. 15. The method of claim 11, wherein the communication system is likely to be selected if the measured signal quality exceeds a predetermined threshold. 16. The method of claim 11, further comprising the step of selecting a set of candidate communication systems, wherein the steps of analyzing and deciding are repeated for each candidate communication system in the set, and the step of trying is performed on the candidate communication system most likely to be acquired . 17. The method of claim 16, further comprising ranking the candidate communication systems in order of measured signal quality, the ranking order defining an acquisition order for the set of candidate communication systems. 18. In a radio device, an integrated circuit comprising: a system determination unit adapted to identify candidate communication systems in the radio's current geographic area; and A searcher coupled to the system determination unit, said searcher being adapted to analyze signal quality in at least one of the identified wireless communication systems to determine a likelihood that the wireless communication system will be acquired. 19. The integrated circuit of claim 18, wherein the searcher measures received signal strength corresponding to each identified wireless communication system. 20. The integrated circuit of claim 18, wherein the searcher calculates a signal-to-noise ratio Ec/Io of the received signal for each identified wireless communication system. 21. The integrated circuit of claim 18, further comprising a memory coupled to the system determination unit, said memory storing a list of known communication systems, each known communication system having an associated geographic area and relative degree of desirability , wherein the system determining unit selects the system analyzed by the searcher from the system table. 22. The integrated circuit of claim 18, wherein the system determination unit is adapted to transmit an instruction to the searcher, said instruction including a test identifier; and Wherein responsive to a received command, the searcher analyzes signal quality in at least one identified wireless communication system using a test method identified by the test identifier. 23. The integrated circuit of claim 18, wherein the transmitted instructions further include a threshold value, and wherein the searcher transmits a notification message to the system determination unit when at least one of the analyzed signal qualities exceeds the threshold value.

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