Method and apparatus for paging a concentrated subscriber system for wireless local loop

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

I. Field of the Invention

The present invention relates to wireless telephone systems. More particularly, the present invention relates to a method and apparatus for paging a concentrated subscriber system for wireless local loop that allows for simplified construction of the concentrated subscriber system while maintaining maximum compatibility with prior art cellular telephone systems.

II. Description of the Related Art

Wire based or wire line telephone systems are the traditional method of providing non-mobile telephone service. Wire based telephone systems are well suited for this task because they provide high quality connections at a low operating cost and can accommodate increased demand for telephone service by the introduction of new telephone wires into the existing network. A disadvantage of wire base telephone systems is the substantial infrastructure and capital necessary for their implementation. These requirements can make wire based telephone systems uneconomical in areas that are remote or less populated, or in less developed areas where the required capital is unavailable. The result is that these less populated and remote areas often lack adequate telephone service which is detrimental to the to the economic well being of the people who live in those areas. Also, the time necessary to put the required infrastructure in place makes wire based telephone systems less desirable in areas where new telephone service must be provided quickly.

Wireless cellular telephone systems require substantially less capital and infrastructure than wire based telephone systems and therefore provide a possible alternative for providing primary telephone service. The degree to which cellular telephone systems can provide primary telephone service is limited, however, by their higher operating cost as compared to wire based telephone system which translates into a higher usage cost for the cellular telephone system subscriber. This higher usage cost limits the number of subscribers that can afford to use a cellular telephone system as their primary telephone service provider within a given area and therefore reduces the number of markets in which the use of cellular telephone systems is economical.

A cellular telephone system that provides simple telephone service at a reduced cost when compared to previous cellular telephone systems is described in co-pending U.S. patent application Ser. No. 08/384,291 entitled "Concentrated Subscriber System for Wireless Local Loop" filed concurrently herewith on Jan. 10, 1994 and assigned to the assignee of the present invention. The concentrated subscriber system described in that application includes a set of subscriber units that share a control and interface system which in the preferred embodiment incorporates code division multiple access (CDMA) digital technology because of its high bandwidth efficiency and high quality communication capability. Such a system reduces the cost of cellular telephone service incurred by each cellular telephone subscriber by spreading the cost of the control and interface system over a larger number of subscribers. This increases the number of markets in which it is economical to use cellular telephone systems as a primary provider of telephone service and therefore increases overall access to telephone service.

Many cellular telephone systems, including those using the preferred CDMA technology, page or "ring" the various subscriber units that are part of the cellular telephone system using a unique paging method for each subscriber unit or sub-set of subscriber units that are part of the cellular telephone system. This is done so that page messages can be directed to single one or a sub-set of the total number of subscriber units thereby simplifying the page monitoring process for each subscriber unit. In the case of the concentrated subscriber system, however, using multiple paging methods for paging makes the control and interface system described more complex. This is because the control and interface system must be capable of interacting in accordance with multiple different paging methods in order to monitor for paging messages directed to any one of the multiple subscriber units that are part of the concentrated subscriber system. Higher complexity is contrary the goal of the concentrated subscriber system, however, which is providing basic cellular telephone service at a reduced cost. Therefore, the use of the standard method of paging a subscriber unit in combination with a concentrated subscriber system cellular telephone system is undesirable.

SUMMARY OF THE INVENTION

Based on the forgoing a method and apparatus for paging a concentrated subscriber system for wireless local loop within a cellular telephone system is described. Within a mobile telephone switching office (MTSO) a visitor location register is generated in which a subscriber unit identification number (SUIN) for every subscriber unit registered within the area of coverage is stored along with corresponding telephone number, last cell site identification code, and concentrated subscriber system (CSS) status information. The SUIN can correspond to the electronic serial number (ESN), mobile identification number (MIN), or other unique identification code assigned to each subscriber unit. When a call directed to a subscriber unit having a particular telephone number is received the corresponding SUN, CSS status information, and last cell site information of that subscriber unit are determined using the visitor location directory.

In response to this determination, a paging code is calculated in various manners depending on the resulting CSS status information of the subscriber unit being paged. If the subscriber unit being addressed is part of a CSS the paging code used to generate the paging message is calculated in a first manner such that it is the same for each subscriber unit within a particular CSS. If the CSS status information indicates that the subscriber unit being paged is not part of a CSS the paging code is calculated in a second manner such that it is different for each subscriber unit. A set of paging parameter are then calculated using the paging code which in the preferred embodiment include a CDMA channel, a paging channel, and a paging slot. The page message is then transmitted in accordance with those paging parameters. In the preferred embodiment the page message generation process using the paging parameters is the same as that of the prior art cellular system in order to maintain maximum compatibility with those prior art systems.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, objects, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout and wherein:

FIG. 1 is a diagram of a cellular telephone system consistent with the use of CDMA radio and modulation techniques;

FIG. 2 is a diagram of a cellular telephone system configured in accordance with one embodiment of the invention;

FIG. 3 is a block diagram of the mobile telephone switching office configured in accordance with one embodiment on the invention; and

FIG. 4 is a block diagram of a base station transceiver configured in accordance with the described embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A method and apparatus for paging subscriber unit within a concentrated subscriber system for wireless local loop is described. In the following description various variables, procedures, and arraignments are described in detail. In particular, the invention is described in the context of a code division multiple access (CDMA) cellular telephone system which incorporates a method of paging having paging parameters including a CDMA channel, paging channel, and paging slot. It will be apparent to one skilled in the art that these details and specifics are not required to practice the present invention and that the present invention can be implemented within alternative cellular telephone systems or other radio wave based means of communication including satellite based systems. In other instances, various well known structures and systems are provided in block form. This is done in order to avoid unnecessarily obscuring the disclosure of the present invention.

FIG. 1 is an illustration of a cellular telephone system configured in a manner consistent with the use of Code Division Multiple Access (CDMA) radio wave modulation techniques. One implementation for such a CDMA cellular telephone system is described in U.S. Pat. No. 4,901,307 ('307) entitled "Spread Spectrum Multiple Access Communication System Using a Satellite or Terrestrial Repeater" and U.S. Pat. No. 5,103,459 ('459) entitled "System and Method for Generating Signal Wave forms in a CDMA Cellular Telephone System" both assigned to the assignee of the present invention, as well as in specification IS-95 from the Telecommunication Industry Association (2001 Pennsylvania Avenue, Suite 800, Wash., D.C. 20006) entitled "Mobile Station-Base Station Compatibility Standard for Dual Mode Wideband Spread Spectrum Cellular System" (IS-95). Radio Frequency (RF) signals generated in response to both incoming and outgoing phone calls in accordance with above referenced patents '459 and '307 and specification IS-95 are exchanged between subscriber units 10 and 12 and base station transceivers 14, 16 and 18. Additional subscriber units will normally also exchange such RF signals, but are not shown for ease of drawing. Base station transceivers 14, 16 and 18 communicate in various ways including ground base wires or microwave link with mobile telephone switching office (MTSO) 20 which routes the calls to public switching telephone network (PSTN) 22 and which interacts similarly with other cell sites 24. In general, subscriber units 10 and 12 do not communicate directly with one another.

As described in patents '459 and '307 and specification IS-95 the "forward link" communication that takes place from base station transceivers 14, 16, and 18 to subscriber units 10 and 12 is performed over various forward CDMA channels each of which occupies 1.23 MHz of radio frequency bandwidth. Each of these forward CDMA channels is divided into various additional channels that are separated and distinguished via the use of unique pseudo-random spreading codes that are applied to the data being transmitted. For channels that carry signals to be received by both subscriber units 10 and 12 a predetermined spreading code is used that is known by every communication unit including both subscriber units 10 and 12. For channels that carry data intended for only one subscriber units 10 or 12 a spreading code only known to that particular communication unit is used which is generally determined as a function of a unique thirty-two bit electronic serial number (ESN) stored in each subscriber unit. In addition to the ESN each subscriber unit may also be associated with a mobile identification number (MIN) which in the preferred embodiment is also 32 bits, as well as other additional unique identification codes.

The various channels within a given forward CDMA channel include a set of data channels, a synchronization channel, a pilot channel, and a set of paging channels, all transmitted from base station transceivers 14, 16 and 18 to subscriber units 10 and 12. The pilot channel carries a pilot signal that is a regularly repeated pattern phase offset slightly for each cell site in a local area which is received by every subscriber unit including subscriber units 10 and 12. The pilot signal allows subscriber units 10 and 12 to identify and become synchronized with the various base station transceiver that are within range of their communication capability. The synchronization channel carries additional synchronization information for use by both subscriber units 10 and 12. The set of data channels carry the data associated with the various communication sessions (usually phone calls) and are directed to a specific subscriber unit. The paging channels are used by the base station transceivers to notify a particular subscriber unit that a request to communicate has been received.

As also described in patents '459 and '307 and specification IS-95, the protocol for paging a subscriber unit is defined so as to evenly distribute background noise, and to reduce power consumption. This is done by dividing each paging channel into a set of paging "slots" or time windows during which paging signals directed to either subscriber units 10 and 12 may be generated, and by assigning a particular CDMA channel, paging channel and paging slot to each subscriber unit in an evenly distributed fashion. This assignment is performed via the use of a hashing function applied to the ESN of each subscriber unit under the established protocol although other unique numbers could be utilized. The hashing function yields a value that corresponds to a particular set of paging parameters including a CDMA channel, paging channel, and paging slot. The subscriber units are then configured to "listen" for a paging message over the corresponding CDMA channel and paging channel during the corresponding paging slot. Since listening for a page requires a certain amount of power, limiting the time a subscriber unit performs the listening function to a particular paging slot reduces the overall power consumption of that subscriber unit and therefore increases the life of any battery or other power storage system utilized by that subscriber unit. In general the page message itself will contain the ESN of the subscriber unit being paged in encoded form so that it can identify itself when the page is received, although other identification codes could theoretically be used.

FIG. 2 is a block diagram of a cellular telephone system configured in accordance with one embodiment of the present invention. Base station transceiver 102 transmits and receives radio waves modulated in accordance with the CDMA spread spectrum techniques described in above referenced patents '459 and '307 and specification IS-95 to and from subscriber units 100 and 112. Additionally, base station transceiver 102 interfaces with mobile telephone switching office (MTSO) 104 in any one of a variety of manners including microwave link, ground based T1 or E1 wire connections, or a combination thereof. MTSO 104 interfaces with public telephone switching network (PSTN) 106 allowing various communication sessions or telephone calls to be delivered between base station transceiver 102, base station transceiver 110, and other cell sites 108. Both subscriber units 100 and 112 have a unique thirty-two bit electronic serial number (ESN) as well as other unique identification codes as described above.

Base station transceiver 110 interfaces with MTSO 104 in a similar manner to base station transceiver 102 and communicates with subscriber unit 112 and concentrated subscriber system (CSS) 113 via radio waves modulated in accordance with above referenced patents '459 and '307 and specification IS-95. Within CSS 113 subscriber units 116(1) through (50) are coupled to CSS controller 114 which performs the interface function with base station transceiver 110. Subscriber units 116(1) through (50) each are also assigned a unique ESN and can be used in a manner similar to a standard telephone to initiate and receive telephone calls. While CSS controller 114 is shown coupled directly to subscriber units 116, alternative methods for exchanging information are contemplated including a simplified form of radio wave based communication. The configuration and operation of CSS controller 114 is described in further detail in the previously mentioned co-pending U.S. patent application Ser. No. 08/384,291 entitled "Concentrated Subscriber System for Wireless Local Loop."

During operation base station transceiver 110 receives requests to communicate with subscriber unit 112 and subscriber units 116 as well as other subscriber units not shown for ease of drawing from MTSO 104. In response to each request base station transceiver 110 generates a paging message directed to the corresponding cellular communication system a CDMA channel, paging channel, and paging slot determined using a paging code provided in the request. The paging code is calculated in one of two ways depending on whether the subscriber unit being paged is part of a concentrated subscriber system. If the communication unit being paged is not part of a CSS the paging code is set to a subscriber unit identification number (SUIN) associated with the subscriber unit being paged which in the preferred embodiment is the ESN of that subscriber unit, although any other unique identification code associated with the subscriber unit could be used as the SUIN including the MIN or the SUIN could be an additional unique code associated with each subscriber unit 116. If the subscriber unit being paged is a subscriber unit 116 and therefore part of a CSS the paging code is calculated in an alternative manner that will cause the page message to be generated using the same CDMA channel, paging channel and paging slot to for each subscriber unit 116.

FIG. 3 is a block diagram of MTSO 104 when configured in accordance with the described embodiment. Processor subsystem 129 receives and transmits data to and from PSTN 106 of FIG. 2, as well as receives and transmits data to and from base stations transceivers 102 and 110 also of FIG. 2. Memory subsystem 130 is coupled to processor subsystem 129 and provides data storage functionality. In the preferred embodiment processor subsystem 129 incorporates the use of at least one microprocessor and memory subsystem 130 incorporates the use of either integrated circuit, optical, magnetic or hard disk memory, or a combination thereof. Various additional circuits and systems are included within MTSO including interface systems located between processor subsystem 129 and PSTN 106 and base station transceivers 102 and 110 that are well known in the art, but that are not shown for ease of drawing and so as not to unnecessarily obscure disclosure of the present invention.

During operation communication requests including a telephone number of the subscriber unit with which communication is being requested are received by processor subsystem 129 Processor subsystem 129 performs a look up with the telephone number provided using a visitor location register (VLR) generated and maintained within memory subsystem 130 by processor subsystem 129. The VLR is a table containing information extracted from a home location registry (HLR) also stored with memory subsystem 130 that contains information for all the active ("turned on") subscriber units that have registered with the MTSO 104. The HLR is a table containing information associated with the all subscribers having accounts with the cellular telephone operator of MTSO 104 and the associated services to which they have subscribed. While the VLR and HLR are shown located within the same memory subsystem 130 and controlled by processor subsystem 129 both of which are located within MTSO 104, it is contemplated that the two table may be maintained separately by different systems and at different locations. In the preferred embodiment VLR table contains a subscriber unit identification number (SUIN), the telephone number or numbers, the CSS status, and the last base station identification number (BID) of each subscriber unit that has registered as being activated and within the coverage area of MTSO 104. The SUIN is generally the ESN of the subscriber unit although other unique identification codes may also be substituted. This information is constantly updated as subscriber units enter and leave the area of coverage or are activated and deactivated.

The CSS status is stored in different ways in different embodiments of the invention. In one embodiment the CSS status includes a CSS status bit (CSB) indicating whether a particular subscriber unit is part of a CSS and therefore is a subscriber unit 116. Generally, a "one" indicates a positive status and a "zero" indicates a negative status although this, of course, could be switched. In an alternative embodiment the CSS status may be indicated by a concentrated subscriber system identification code (CSSIC) stored within the HLR and the VLR in lieu of or in addition to this CSS status bit. The CSSIC is a number indicating the particular CSS with which the subscriber unit is associated. A zero CSSIC generally indicates a negative CSS status, however, other values may easily be use to indicate negative CSS status. The preferred length for the CSSIC is thirty-two bits. Table I lists a set of exemplary entries stored in the VLR.

TABLE I ______________________________________ SUIN Phone number CSB CSSIC Last BID ______________________________________ A16F 2051 619.555.1000 0 0000 0000 04F1 A16F 4051 619.555.1221 0 0000 0000 0539 A156 7151 619.555.1800 1 0751 64F3 2CF1 B34A 1F35 619.555.1801 1 2C41 0551 03A7 946D 3B74 619.555.1805 1 04A5 2CF1 57F6 3578 2041 619.555.1900 1 6493 9DA7 B4F1 A16F 2051 619.555.1903 1 87F6 57F9 14A1 ______________________________________

All numbers are in shown hex format except for the phone number which is shown in decimal format for ease of understanding although it may actually be stored in binary format like the other values. After the look up is performed a paging request is generated based on the resulting SUIN and CSS status information by processor system 129 and transmitted to the base station transceiver associated with the last BID in which the subscriber unit was located. The paging request is generally also transmitted to other base station transceivers located in adjacent cells in case the subscriber unit has moved, a practice well known in the art.

In the preferred embodiment a page request includes the MIN of the subscriber unit being paged and a paging code, which is also referred to as a paging-ESN. Other identification number may be included in the page request in lieu of or in addition to the MIN including the ESN in other embodiments of the invention. The paging code is calculated in a variety of manners depending on the CSS status of the subscriber unit being paged. If the CSS status information is negative indicating the subscriber unit being paged is not part of a CSS, the paging code is set to the SUIN, which as noted above is the ESN of the subscriber unit being paged in the preferred embodiment. This process is consistent with paging parameter calculation process of the IS-95 standard. If the CSS status information is positive, indicating the subscriber unit being paged is part of a CSS, the paging code is set to an alternative number that simplifies the page monitoring process of CSS controller 114 of FIG. 2. While in the described embodiment the paging code calculatio