KR20000005014A - Method and apparatus for performing preferred system selection - Google Patents

Abstract

PURPOSE: A method and apparatus for selecting a communication system in accordance with the geographic region in which the subscriber station is located are disclosed. CONSTITUTION: Upon successful acquisition (26), a subscriber station examines the received system identification information to determine its geographical region (27). The subscriber station then determines whether the acquired system is the most desirable system for use in the geographical region (48). If it is the most desirable system for use in the geographical region, the subscriber station provides service using the acquired system (50). If it is not the most desirable system for use in the geographical region, the subscriber station attempts to acquire a more desirable system (54).

Description

Method and apparatus for first performing system selection

As mobile communication systems become widespread in society, there is a desire for larger and more sophisticated services. Techniques for multiple access to limited communication resources have been developed to meet the demand for capacity of mobile communication systems. The use of code division multiple access (CDMA) modulation technology is one of several techniques to facilitate communication when there are multiple system users. Other multiple access communication system techniques, such as time division multiple access (TDMA) and frequency division multiple access (FDMA), are also known in the art. However, the spread spectrum communication scheme of CDMA has significant advantages over these modulation techniques for multiple access communication systems.

The use of CDMA technology in a multiple access communication system is USP No. 13, 1990, entitled "SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS", assigned to the assignee of the present invention and referenced herein. 4,901,307. The use of CDMA technology in a multiple access communication system is also USP dated April 7, 1992 entitled “SYSTEM AND METHOD FOR GENERATING SIGNAL WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM”, which is assigned to the assignee of the present invention and referenced herein. No. 5,103,459.

When a user of a subscriber station moves from one geopolitical area to another geopolitical area, the subscriber station must select a communication system to serve. There are two ways a user can manipulate his subscriber station when changing a geopolitical area. The first method is for the user to subscribe to a communication service in various regions. Thus, the subscriber station can provide a service by using any of the service providers as long as the subscriber station searches for the communication system to which the user subscribes.

Alternatively, the user may communicate by roaming service. Mobile communication providers set up contracts between them to provide customers with a service known as "roaming." A "roamer" is a subscriber station that requires service in a system operated by a mobile communication service provider to which a user is not subscribed. In general, when the subscriber station is roaming, a signal is provided to the user indicating the roaming condition. Roaming is determined by comparing the system identification (SID) of the subscribed system or systems with the SID of the system providing the broadcasted service. This warns that services provided to users of subscriber stations incur roaming charges.

In general, since the subscriber station does not have information about the user's geopolitical location, the subscriber station (from among possible communication systems in a region) must select a system that provides the best service to the user in terms of service cost and quality. As the number of areas that a user wants to be able to operate increases, so does the number of communication systems that a subscriber station should attempt to acquire.

The present invention is disclosed in detail in co-pending US patent application Ser. No. 08 / 509,719 entitled "METHOD AND APPARATUS FOR SYSTEM DETERMINATION IN A MULTI-MODE SUBSCRIBER STATION", assigned to the assignee of the present invention and referred to herein. Disclosed is a multi-way subscriber station as described. An example embodiment is disclosed for a subscriber station capable of transmitting and receiving CDMA signals and capable of transmitting and receiving analog signals such as AMPS and NAMPS. The present invention is equally applicable to any digital communication system, including TDMA, FDMA, and GSM. In addition, the present invention is equally applicable to subscriber stations that can only operate in one way (eg analog or digital).

Summary of the Invention

In the present invention, the subscriber station maintains a list of systems, some of which are 'preferred' systems (systems available to subscriber stations), and some are 'negative' systems (subscriber stations are unavailable). System). Corresponding to each system in the list is the system identification (SID) and the corresponding acquisition variables (band, frequency, scheme, etc.). This list is referred to below as the universal system table.

The universal system table is maintained in such a way that it can easily determine which system (prior or negative) covers the common geopolitical area. Common geopolitical area is a common communication area. In addition, systems covering common geopolitical areas are prioritized (ie, ordered from the most desirable to the least desirable). The subscriber station's mission is to attempt to capture service on the most desirable system in the current geopolitical area of the subscriber station. Since systems typically provide services only within a limited geopolitical area, they cannot capture services from systems outside the subscriber's current geopolitical area.

The problem is that the subscriber station does not necessarily know where and when to turn on. Because of roaming, it may be a completely different area than before. Thus, it may not be obvious how to capture the system, not to mention the most desirable system. In an exemplary embodiment of the invention, the subscriber station maintains a list of the most recently used (MRU) systems. Attempting to capture one of these systems in the first way is very convincing. This is because the subscriber station is likely to be present somewhere in the past not too far away.

If the subscriber station cannot capture the MRU system, it may attempt to capture any preferred system in the universal system table using the appropriate acquisition variables. In an exemplary embodiment, the subscriber station first attempts to acquire at the 'easy' to obtain the system (eg, an AMPS system if there is any AMPS system in the universal system table). In an exemplary embodiment, if the subscriber station fails to capture one of these systems, it attempts to capture the 'most representative' system in the universal system table. In other words, a universal system may contain numerous systems that have the same acquisition parameters (eg channel number or frequency cutoff indicator), but only differ in their geopolitical region from the SID.

Once the subscriber station has acquired the system, the subscriber station can obtain the captured system's SID from the overhead message. The subscriber station uses the received SID to determine the geopolitical area in which it is located. In an exemplary embodiment, the subscriber station obtains geopolitical information from the universal system table as to whether the captured system is a preferred system or a negative system.

If the SID, in the universal system table, belongs to the preferred system, which is the most desirable system in the geopolitical area, the subscriber station uses that system to provide services. If the SID of the captured system belongs to a system in the universal system table that is not the most desirable system within that geopolitical region, the subscriber station uses the received SID to determine the geopolitical region in which it is located. The subscriber station attempts to capture the most desirable system in the geopolitical area by making successive acquisitions of systems in the geopolitical area from the most desirable system to the least desirable system.

If the SID belongs to a system that does not exist in the universal system table, the subscriber station attempts to acquire other systems. The subscriber station must first return to this system if it cannot capture the system.

The present invention relates to a communication system. More specifically, the present invention relates to a new and improved method and apparatus for selecting a preferred communication system at a subscriber station operable in multiple geopolitical regions.

1 is a block diagram of an exemplary multi-way subscriber station in accordance with the present invention.

2A, 2B and 2C are flow charts of an exemplary system selection method in accordance with the present invention.

The features, objects, and advantages of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings. Like reference numerals refer to like elements throughout the specification and drawings.

In Fig. 1, when the multi-method subscriber station (MMSS) 1 is in the system decision substate, the operation is performed by the system decision processor 8. In the system decision substate, the system decision processor 8 selects a communication system for the MMSS 1 to attempt to perform an acquisition and provide the necessary variables for the acquisition circuit. The system decision processor 8 may be implemented with a microprocessor that functions under the program control described with reference to FIG.

In an exemplary embodiment, the MMSS 1 is a dual capable of both analog transmission and reception using analog modulation and demodulation and processing circuits (analog circuits) 4 and digital transmission and reception using digital modulation and demodulation and processing circuits (digital circuits) 6. Method subscriber station. In an exemplary embodiment, the digital circuit 6 is a CDMA transmit and receive circuit. However, other forms of digital communication such as TDMA or GSM can also be used. The present invention is applicable to cellular communication systems, mobile communication systems (PCSs), and any other communication system capable of providing service to subscriber stations operable in a number of geopolitical regions.

The design of the analog circuit 4 is known in the art and is described in detail in Mobile Cellular Telecommunication Systems of William C. Y. Lee. An exemplary embodiment of the digital circuit 6 is described in USP Nos. 4,901,307 and 5,103,459.

The most recently used (MRU) system table 9 contains a list of the systems most recently used by the MMSS 1. In an exemplary embodiment, the MRU table 9 is implemented in a nonvolatile memory that can be maintained even after the MMSS 1 is powered off. The universal system table 11 contains system variables for all communication systems that the MMSS 1 "knows about" its existence. In the exemplary embodiment, the universal system table 11 first contains information about both systems and fraudulent systems, which systems are stored according to their geopolitical location. In the exemplary embodiment, the universal system table 11 is implemented in a nonvolatile memory that can be maintained even after the MMSS 1 is powered off. In an exemplary embodiment, the systems stored in the universal system table 11 are grouped according to geopolitical regions, with each system listed within one geopolitical group sequentially from the most desirable to the least desirable. Are arranged. Criteria for system sequencing may include, for example, service costs, quality of service, unique feature support, and the like. For each system, the universal system table 11 includes the necessary acquisition variables, including the system identification (SID), as well as the band, frequency, scheme, and other variables needed to perform the acquisition. In an exemplary embodiment, each system listed is labeled with whether the system is a subscriber station's available system (preferred system) or a subscriber station's unusable system (negative system).

2 is a flowchart illustrating an exemplary method of prioritizing system selection in accordance with the present invention. Upon powering up (20), the MMSS 1 enters the system decision substate and control passes to the system decision processor 8. In block 22, the system decision processor 8 selects an initial system to attempt to acquire, in an exemplary embodiment in accordance with the systems listed in the MRU table 9. In the exemplary embodiment, the system decision processor 8 selects the final system used to provide the service as the system for initial acquisition. In an alternative embodiment, the system decision processor 8 selects the system most often used by the MMSS 1. In another alternative embodiment, the system decision processor 8 selects the home system of the MMSS 1.

In block 22, the system decision processor 8 retrieves the necessary acquisition variables from the universal system table 11. If the system selected for initial acquisition is an analog system, the system decision processor 8 provides acquisition parameters to the analog circuit 4 and provides the required frequency information to the transceiver 3. In block 24, MMSS 1 attempts to capture the selected analog system. The transceiver 3 amplifies or downconverts the signal (if present) received via the antenna 5 in accordance with the frequency information provided by the system decision processor 8. The analog circuit 4 demodulates the signal in accordance with acquisition variables provided by the system decision processor 8.

In block 22, if the selected system is a digital system, the system decision processor 8 provides acquisition variables to the digital circuit 6 and provides the transceiver 3 with the necessary frequency information. In an exemplary embodiment, the digital system selected for acquisition is disclosed as a CDMA system. However, as mentioned above, the present invention is equally applicable to the acquisition of other digital communication systems. At block 24, MMSS 1 attempts to capture the selected CDMA system. The transceiver 3 down converts the signal (if present) received via the antenna 5 according to the frequency information provided by the system decision processor 8. The digital circuit 6 demodulates the signal in accordance with acquisition variables provided by the system decision processor 8. Demodulation of the CDMA signal is performed by the USP No. 5,103,459.

At block 26, if the acquisition attempt is successful, control is returned to the system decision processor 8 at block 25. In block 25, the system decision processor 8 selects the next system to be captured. In an exemplary embodiment, the MMSS 1 first attempts to capture the mode systems stored in the MRU table 9. If the MMSS 1 fails to capture one of the systems stored in the MRU table 9, the MMSS 1 attempts to capture a collection of systems that are identified as "easy" to capture. Easy-to-capture systems are chosen to provide quick and easy identification of geopolitical areas, although they are not the most desirable systems within each geopolitical area. In an alternative embodiment, since the availability of the AMPS system can be readily determined, the MMSS 1 will first attempt to capture the AMPS system before attempting to capture the system in the MRU table 9.

If the MMSS 1 cannot capture a system that is easy to capture, an attempt is made to the "representative" system. The representative system is a system having acquisition variables common to many other systems. Thus, by attempting to capture a representative system, the MMSS 1 is actually testing a set of geopolitical regional assumptions simultaneously. If none of these systems can be captured, the MMSS 1 attempts to capture the rest of the systems in the universal system table 11.

When the acquisition of the system selected by the system decision processor 8 fails, block 28 proceeds. Block 28 determines whether an acquisition was attempted for all systems in the MRU table 9. If there are systems in the MRU table 9 that have not been attempted to acquire, the system decision processor 8 selects a system from the MRU table 9 and, as described above, the analog circuit 4, the digital circuit 6 and the transceiver. Optionally provide system acquisition variables in (3). Next, an acquisition for the selected system is attempted as described above at block 24.

If a capture attempt has been made for all systems in the MRU table 9, then the MMSS 1 attempts to acquire a " fast capture " system. AMPS systems are typical examples of high speed capture systems. Although AMPS systems provide inferior services to those provided by CDMA systems in terms of service identity, it is possible to capture AMPS systems in a shorter time. In block 34, if the MMSS 1 has not attempted to capture all of the high speed acquisition systems, then in block 36, the system decision processor 8 selects the high speed acquisition system and acquires acquisition parameters from the universal system table 11; Search them. The system decision processor 9 optionally provides system acquisition variables to the analog circuit 6, the digital circuit 4 and the transceiver 3 as described above. At block 24, an acquisition is attempted for the selected system as described above.

If a capture attempt has been made for all " representative " systems in block 42, then MMSS 1 makes a successful attempt to capture the remaining systems in the universal system table 11. In block 44, if there is a preferred system in the universal system table 11 that no acquisition was attempted, proceed to block 40. In block 40, the system decision processor 8 selects the remaining preferred system for the acquisition attempt, retrieves acquisition variables from the universal system table 11 and stores the analog circuit 4, digital circuit 6 as described above. And optionally the system acquisition variables to the transceiver (3).

Next, an acquisition is attempted for the system selected at block 24 as described above. If acquisition attempts for all preferred systems have failed, MMSS 1 temporarily turns off at block 46 and resumes the preferred system selection process at block 20 at the next opportunity. The first possible alternative is that the MMSS 1 only powers off. A second possible alternative is for the MMSS 1 to immediately resume the priority system selection process. A third possible alternative is for the MMSS 1 to indicate a failure and to wait for user intervention.

If the acquisition is successful, the MMSS 1 receives a system identification (SID) that is broadcast by the system captured at block 27. The signal is received via the antenna 5 and provided to the transceiver 3 where the message signal is downconverted and amplified. If the captured system is analog, a message is provided to the analog circuit 4, which demodulates the signal according to the analog demodulation format and provides the system identification information to the system decision processor 8. If the captured system is CDMA, a message is provided to the digital circuit 6, which demodulates the signal according to the CDMA demodulation format and provides the system identification information to the system decision processor 8.

In block 35, the system decision processor 8 determines whether the received SID is one of the systems stored in the universal system table 11. If the captured system is unknown to the MMSS 1, the process returns to block 25 and the MMSS 1 attempts to capture another system. In an exemplary embodiment, acquisition variables of a captured but unknown system are retained by the system decision processor 8, and the system may be used if the system cannot be captured first.

If the received system identification (SID) is listed as a "negative" system in the universal system table 11, the system decision processor 8 passes control to block 25, and the MMSS 1 sends another system. Try to capture. In the preferred embodiment, the capture parameters of the captured system are held by the system decision processor 8 and the system is used if an emergency call occurs.

If the received system identification (SID) is listed in the universal system table 11, then at step 48 the system decision processor 8 determines if it is the most desirable system in that geopolitical area. It may be the case that more than one system is equally desirable for use by a subscriber station. If the captured system is the most desirable system for the geopolitical area in question, then service is provided using the captured system at block 50. When the service is terminated, the system decision processor 8 updates the MRU table 9 at block 52.

If the received system identification is not the most desirable system for that geopolitical region, then the system decision processor 8 selects the most preferred system for that geopolitical region at block 54, and the analog circuit 4 as described above. ), Optionally provide system acquisition parameters to the digital circuit 6 and the transceiver 3. In block 56, the MMSS 1 attempts to capture the most desirable system in its geopolitical area. If the acquisition is successful at block 58, then the captured system is the system the subscriber station expected to acquire, and MMSS 1 uses the system captured at block 60 to provide the service. In block 62, the system decision processor 8 updates the MRU table 9 at the end of the service.

If the acquisition fails, at block 64, the system decision processor 8 selects the next most desirable system for use in that geopolitical region. The system decision processor 8 selectively provides system acquisition variables to the analog circuit 4, the digital circuit 6 and the transceiver 3 as described above. This process is repeated until the acquisition is successful and in step 60 the MMSS 1 provides the service using the captured system. In an exemplary embodiment, if no system can be captured at block 66, the MMSS 1 temporarily turns off the power at step 68 and saves battery, then at system 20 the first opportunity at the next opportunity. Start the selection process again. There are several possible alternatives in the process. The first possible alternative is that the MMSS 1 only powers off. A second possible alternative is for the MMSS 1 to immediately resume the priority system selection process. A third possible alternative is for the MMSS 1 to indicate failure and to wait for user intervention.

In an alternative embodiment, in the event of a successful acquisition at block 48, the system decision processor 8 determines whether the system is a system first. If it is a preferred system, the MMSS 1 uses the captured system to provide services and immediately reenters the system decision substate to see if a more desirable system can be captured in that geopolitical domain.

In an exemplary embodiment, the information stored in the universal system table 11 is one that indicates whether the corresponding system is more desirable than the next system in the list (bit = 1) or has the same degree of desirability (bit = 0). To provide a bit. This allows for multiple priority systems within the same geopolitical area. Table 1 shows an exemplary method of indicating the degree of desirability of a system within a geopolitical area.

Table 1 SID Geopolitical local bit More desirable bits 1111 0 One 2222 0 0 3333 0 0 4444 0 One 5555 0 0 6666 One 0 7777 One 0 8888 One 0

In Table 1, there are two geopolitical regions. Note that systems of common geopolitical area are indicated by geopolitical area bits. Thus, systems covering the first geopolitical area are 1111, 2222, 3333, 4444, and 5555, and systems covering the second geopolitical area are 6666, 7777, and 8888. This is indicated by a flip in the polarity of the geopolitical local bit.

The desirability of the system within the geopolitical area is indicated by the more desirable polarity of the bit. Within the first geopolitical area, system 1111 is more preferred than system 2222. Systems 2222, 3333, and 4444 are equally preferred and all three are more preferred than 5555. Within the second geopolitical area, systems 6666, 7777, and 8888 are all equally preferred. It should be noted that the desired extent of indicating the geopolitical area served by a system and capturing service through the system is exemplary and other ways of storing this information are possible.

In Table 1 above, system 1111 is described as a subset of the most preferred SIDs in that geopolitical region. The systems 2222, 3333, and 4444 are equally preferred and are described as the second preferred subset of SIDs in that geopolitical region. Similarly, system 5555 may be described as a subset of the third preferred SIDs in that geopolitical region. As mentioned above, in the exemplary embodiment of the universal system table 11, the table consists first of both a system and a negative system. Thus, for example, system 5555 is a negative system and may not be described as the third preferred subset, but rather may be described as an element of a collection of negative systems for that geopolitical region.

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention.

Various modifications to these embodiments will be readily apparent to those skilled in the art, and the inventive conceptual principles defined herein may be applied to other embodiments without utilizing new capabilities. Accordingly, the invention is not limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (13)

In a method of selecting a system for acquisition in a subscriber system, (a) receiving a system identification (SID) from a central communication station; And (b) determining a geopolitical area from the received system identification. The method of claim 1, And determining the geopolitical area comprises determining a collection of central communication stations that provide a serviceable area for the geopolitical area. The method of claim 2, Determining the geopolitical region, (a) comparing the received SID with a list of SIDs stored at the subscriber station; And (b) identifying the set of central communication stations according to the comparison. The method of claim 3, wherein And wherein the list of SIDs stored at the subscriber station is sequentially sequenced according to a set of predetermined user preferences. The method of claim 1, (a) comparing the received SID with a first subset of preferred SIDs from a set of preferred SIDs for the geopolitical region; And (b) if the received SID belongs to the first subset of preferred SIDs, providing a service using the central communication station. The method of claim 5, (a) selecting an alternate system from the preferred subset of SIDs; And (b) if the received SID does not belong to the first subset of preferred SIDs, then attempting to capture the alternate system. The method of claim 6, If the acquisition attempt is successful, further comprising providing a service using the alternate system. The method of claim 7, wherein (a) if the acquisition attempt is unsuccessful, selecting a second alternate system from the set of preferred SIDs for the geopolitical region according to a predetermined selection format; And (b) attempting to capture the second alternative system. The method of claim 1, Receiving the SID from the central communication station, (a) selecting an initial system to capture; (b) attempting to capture the initial system; And (c) if the acquisition attempt is successful, receiving the SID from the central communication station. The method of claim 9, Receiving the SID from the central communication station, (a) if the acquisition attempt is unsuccessful, selecting an alternative system to attempt the acquisition attempt; And (b) further attempting to capture the alternate system. The method of claim 10, Selecting the alternate system to attempt the acquisition attempt is determined according to a set of the most recently used systems. The method of claim 10, Selecting the alternate system to attempt the acquisition attempt is determined in accordance with a set of systems that are readily captured. The method of claim 10, Selecting the alternate system to attempt the acquisition attempt is determined according to a set of systems having acquisition variables in common with a number of other systems.