Title of Invention	A METHOD OF IMPLEMENTING A REDUCED SLOTTED MODE IN A MOBILE STATION"
Abstract	The present invention provides an apparatus and method for operating in reduced slotted made. Fllowing the releas of the traffic channel, a mobile nation (102) and base station (103) oparate with a shooter slot cycle govermed by a reduced slot cycle Index value. The mobile station and base station operate using the reducced slot cycle index value until a particular time occurs governed by a reduecd sloted timer value or for a period of time governed by the reduced sloted timer value, The invention provides faster call setup for mobile station terminated calls, without requiring registration with a MSC (110) to change between the reduced slot cycle index value and the registred slot cycle index value.

Title of Invention

A METHOD OF IMPLEMENTING A REDUCED SLOTTED MODE IN A MOBILE STATION"

Abstract

The present invention provides an apparatus and method for operating in reduced slotted made. Fllowing the releas of the traffic channel, a mobile nation (102) and base station (103) oparate with a shooter slot cycle govermed by a reduced slot cycle Index value. The mobile station and base station operate using the reducced slot cycle index value until a particular time occurs governed by a reduecd sloted timer value or for a period of time governed by the reduced sloted timer value, The invention provides faster call setup for mobile station terminated calls, without requiring registration with a MSC (110) to change between the reduced slot cycle index value and the registred slot cycle index value.

Full Text	The present application claims priority from provisional application, Serial No. 60/448343, entitled "APPARATUS AND METHOD FOR IMPLEMENTING A REDUCED SLOTTED MODE IN A COMMUNICATION SYSTEM,* filed February 13,2003, which is commonly owned and incorporated herein by reference in its entirety. Field of the Invention The present invention relates generally to the field of communication systems, and more particularly, to an apparatus and method for implementing a reduced slotted mode in a communication system. Background of the Invention Call setup for a mobile station terminated call can take several seconds or more to complete. Although this length of time may be acceptable for voice calls, it has a significant negative impact on the user's perception of call quality for data calls. Therefore, in typical deployments, the traffic channel is maintained during a period of data inactivity before the data call is released to the dormant state. Such prolonged maintenance of the data call during periods of data inactivity results in inefficient use of RF and channel element resources, The desirable reduction or elimination of hold overtime, while preserving acceptable service for the end user, requires fast call setup time. One of the most significant components of call setup For mobile station terminated calls is the paging delay. White in the idle State, the mobile station typically operates in the Slotted Mode in order to conserve battery life. in the Slotted Mode, the mobile station monitors the forward common control channel for pages only during certain assigned time slots. The Slot Cycle Index (SCI) governs how often the mobile station checks for a page. The lowest currently standardized SCI value (i.e. 0) corresponds to 1.28 seconds. WO 20004/075416 PCT/US 2004/005759 Thus, a page for a mobile station using the shortest slot cycle in the Slotted Mode can be delayed up to 1.23 seconds, even when the lowest SCl value is used. As previously described, the cdma2000 standard currently supports the concept of Slotted Mode. Slotted Mode is described in the TIA/EIA 15- 2000.5 standard, section 2.6.2.1,1.3, However, Slotted Mode as currently defined has a significant impact to call setup delay because the shortest slot cycle is 1.23 seconds, The cdma2000 standard also currently supports a Slotted Timer feature. in accordance with this feature, the mobile station operates in Non-Slotted Mode, i.e., continuously monitors the forward common control channel, following its release from the traffic channel for a duration of time specified by the Slotted Timer (provided by the base station). A significant drawback to this feature is thet continuously monitoring the forward common control channel has a significant impact on the battery life of the mobile station. Also, the feature is controlled entirely by the base station. The mobile station is unable to request being put in Non-Slotted Mode. One proposed solution thet has been introduced for standards body consideration is to allow reduced SCl values. If accepted, the proposal would reduce the shortest slot cycle down to 80 ms. However, under the solution, the only way for a mobile station to change its SCI is via mobile registration. Therefore, in order to effectively make use of the reduced SCI without wasting mobile station battery life, the mobile station must register each time it changes between a reduced SCl value (i.e. while a packet data session is dormant) and a higher SCl value (i.e. while there is no dormant packet data session). This results in increased loading on the air and IOS interfaces, Thus, a need exists for an apparatus and method for implementing a reduced slotted mode, with minimal impact on the air and IOS interfaces. Brief Description of the Drawings FIG. 1 is a block diagram of a system thet can be used to implement the apparatus and method of the present invention. WO 20004/075416 PCT/US 2004/005759 FIG. 2 is a flow chart of a first embodiment of the method in accordance with the present invention. FIG. 3 is a flow chart of a second embodiment of the method in accordance with the present invention. FIG, 4 is a flow chart of a third embodiment of the method in accordance with the present invention. FIG. 5 is a flaw chart of a fourth embodiment of the method in accordance with the present invention. Detailed Description of the Drawings The present Invention provides an apparatus and method for implementing a reduced slotted mode in a communication system. in a first embodiment a method, of implementing a reduced slotted mode in a mobile station includes transmitting a request for reduced slotted mode, wherein the request comprises a desired reduced slotted timer value and a desired reduced slot cycle index value: determining whether the request is granted; and when the request is granted, operating in reduced slotted mode until a time corresponding to the reduced slotted timer value occurs (in the case of an absolute time, e.g., 2:30 pm on a given date) or until a period of time corresponding to the reduced slotted timer value elapses (such as 30 minutes), wherein a frequency at which the mobile station checks for a page is governed by the reduced slot cycle index value. in a second embodiment of the present invention, a method of implementing a reduced slatted mode in a mobile station includes receiving a first message from a base station, the first message indicating whether the base station supports reduced slotted mode; when the base station supports reduced slotted mode, determining whether the first message specifies a maximum reduced slotted timer value; when the firat message does not specify a maximum reduced slotted timer value, sending a second message to the base station requesting reduced slotted mode, wherein the second message specifies a reduced slotted timer value and a desired reduced slot WO 20004/075416 PCT/US 2004/005759 cycle index value; when the first message specifies a maximum reduced slotted timer value, sending a second message to the base station requesting reduced slotted rnode. wherein the second message specifies a reduced slot cycle Index and a reduced slotted timer value thet is earlier in time (in the case of an absolute time) then the maximum reduced slotted timer value specified in ihs first message, less then the maximum reduced slotted timer value specified in the first message (in the case of a time period), or equal to the maximum reduced slotted timer value specified in the first message; and operating in reduced slotted mods until a time corresponding to the reduced slotted timer value occurs or until a period of time corresponding to the reduced slotted timer value elapses, wherein a frequency at which the mobile station checks for a page is governed by the reduced slot cycle index value. in a third embodiment of the present invention, a method of implementing a reduced slotted mode in a base station includes sending a message to a mobile station, the message indicating whether the base station supports reduced slotted mode; receiving a request for reduced slotted mode, the request comprising a desired reduced slot cycle index value and a desired reduced slotted timer value; and operating in reduced slotted mode until a time corresponding to the reduced slotted timer value occurs or until a period of time corresponding to the reduced slotted timer value elapses, wherein a slot in which the base station pagas the mobile station is governed by the reduced slot cycle index value. in a fourth embodiment of the present invention a method of implementing a reduced slotted mode in a base station includes receiving a request for reduced slotted mode, the request comprising a desired reduced slot cycle index value and a desired reduced slotted timer value; determining whether the desired reduced slotted timer value is earlier in time then a maximum reduced slotted timer value or less then a maximum reduced slotted timer value; when the desired value is earlier in time then the maximum or less then the maximum, setting a reduced slatted timer value equal to the desired reduced slotted timer value; and operating in reduced slotled mode until a time corresponding to a reduced slotted timer value WO 20004/075416 PCT/US 2004/005759 occurs or until a period of time corresponding to the reduced slotted timer value elapses, wherein a slot in which the base station pages the mobile station is governed by the reduced slot cycle index value. in a fifth embodiment of the invention, a storage medium having stored thereon a set of instructions which, when loaded into a processor of a mobile station, causes the mobile station to transmit a request for raduced slotted mode, wherein this request comprises a desired reduced slotted timer value and a desired reduced slot cycle index value; determine whether the request is granted; and whan the request is granted, operate in reduced slotted mode until a time corresponding to the reduced slotted tinner value occurs or until a period of time corresponding to the reduced slotted timer value elapses, wharein a frequency at which the rnobile station checks for a page is governed by the reduced slot cycle index value. Referring now to FlG.1, a fanctional block diagram of a system thet can be used with the present invention is shown. It is assumed thet the reader is familiar with cellular telephone systems and the manner in which messages are transmitted between a Base Transceiver Station (BTS) serving a particuler service cell and a mobile station (MS) located within thet cell. To simplify the present description, only the portion of a cellular telephone system relevant to the present invention is discussed. FIG. 1 shows, a MS 102 in communication with a BTS 104 aver an air interface. The MS 102 may be but is not limited to a radiotelephone, internet appliance, Iaplop computer, or other suitable communication device. The STS 104 is coupled to a Base Station Controller (BSC) 106. The BTS 104 and BSC 106 are collectively referred to herein as the Base Station (BS) 103. The BS 105 is coupled to a Mobile Switching Center (MSC) 110 over an JOS interface (as specified in 36PP2 A-S0001-A, "3GPP2 Access Network Interfaces Interoperability Specification", and subsequent versions). Any commercially available US 102 can be used with the present invention. A BS 108 commercially available from Motorola, Inc., Schaumburg, 1L and a MSC 110 commercially available from Nortel Networks, Inc., can be used with the present invention. WO 20004/075416 PCT/US 2004/005759 As commonly known in the art, the Paging Channel or the Forward Common Control Channel protocol provides for scheduling the transmission of messages for a specific MS in certain assigned slots. A MS thet monitors The Paging Channel or the Forward Common Control Channel only during certain assigned slots, typically one or two slots per slot cycle, is referred to as operating in the Slatted Mods. During the slats in which the Paging Channel or the Forward Common Control Channel is not being monitored, the MS can stop or reduce processing for power conservation. A MS may not operate in the slotted mode in any state except the Mobile Station Idle State. Currently, when the MSC 110 has data to transmit to ths MS 102, it instructs the BS 108 to page the MS 102 using the SCI thet the MS 102 provided during registration. The MIS 102 also uses toe SCI to determiner how often to check for a page from the BS 103, The present invention provides an apparatus and method for operating in reduced slotted mode, wherein the MS 102 can change the SCI without registering the new SCI with the MSC 110. While implementing reduced slotted mode, the BS 103 overrides ths SCI communicated by the MSC 110 and uses an SCI requested by ths MS 102. Ths MS 102 also requests to operate in reduced slotted mode fora period of time. The MS 102 selects the reduced SCI and the period of time for operating in reduced slotted mode based on its knowledge of the application, the MS's capabilities, battery status and possibly information from the BS 108. in first and second embodiments of the invention, methods of implementing reduced slotted mode in the MS 102 are described. in the first embodimerit, US initiated reduced stotted mode is described. in the second embodiment, BS initiated reduced slotted mode is described. Turning now to the first embodiment, the MS 102 initiates reduced slotted mode by sending a request to the BS 108, The request includes a desired reduced SCI and a desired reduced Slotted timer value corresponding to a time period spent operating in reduced slotted mode; The timer value may define a period of time (e.g., 30 seconds) or may define an absolute time limit (3:30 pm on February 3). The MS 102 waits for the BS 103 to acknowledge whether it WO 20004/075416 PCT/US 2004/005759 supports reduced slotted made. If the BS 108 response is thet it supports reduced slotted mode or if the MS 102 does not receive a response, the M.S 102 sets the reduced Slotted timer according to the desired reduced Slotted timer value and begins operating in reduced slotted mode using its desired reduced SCI, As described in more detail below, the MS 102 may use a different reduced slotted timer value if the BS 108 so dictates. The MS 102 operates in reduced slotted mode until the timer expires and then reverts back to Normal operation. The MS 102 also reverts back to Normal operation when the MS 102 acquires the traffic channel as a result of an origination or termination while the timer is running. Normal operation in the Idle State typically means Normal Slotted Mode operation, white Normal operation in the Traffic State typically means traffic channel processing, BS Initiated reduced slotted mode in the MS 102 will now be described. After a predetermined period of inactivity over the traffic channel occurs during a packet data session, the MS 102 receives a message from the BS 108 releasing the MS 102 from the traffic channel. The MS determines from the message whether the BS 108 supports reduced shotted mods, and if so, whether the BS 108 specified a maximum reduced slotted timer value. When a maximum reduced slotted timer value is specified, the MS 102 requests reduced slotted mode specifying a reduced SCI and a reduced slotted timer value thet is no greater then the maximum value specified by the BS 108. This informs the BS 108 thet the MS 102 desires to operate in reduced slotted mode using the reduced SCI for a period of time corresponding to the reduced slotted timer value. The MS 102 then releases the traffic channel and operates in reduced slotted mods until art event occurs to causa the MS 102 to revert back to Normal operation. in third and fourth embodimerits of the invention, methods of implementing reduced sfotted mode fn the BS 106 are described. in the third embodiment, BS Initiated reduced slotted mode is described, in the fourth embodiment, MS initiated reduced slotted mode is described. Turning now to the third embodiment, the BS 108 initiates reduced slotted mode by sending a message to the MS 102 releasing the MS 102 from the traffic channel and -7- WO 20004/075416 PCT/US 2004/005759 indicating thet the BS 106 supports reduced slotted mode. Optionally, the message may specify a maximum time period during which the BS 108 wilI support reduced slotted mode (maximum reduced slotted timer value). when the 8S 108 receives a reduced slotted mode request from the MS 102, the request including a desired reduced SCl and a desired reduced slotted timer value, the BS 108 enables a reduced slotted timer using a timer value thet does rot exceed a maximum value as determined by the BS 108, and begins operating in reduced slotted mode using the desired reduced SCI to page the MS 102 when a page request is received. When the timer expires of when any other event occurs to cease reduced slotted mode operation, such as acquiring MS 102 on the traffic channel, the BS 108 reverts back to Normal operation. Normal operation with the MS 102 in the idle Slate typically means Normal Slotted Mode operation using the registered SCI to page the MS 102 when a page request arrives, while Normal operation with the MS 102 in the Traffic State- typically maans traffic channel processing. MS initiated reduced slotted mode operation in. the BS 108 will now bs described. The BS 108 receives a reduced slotted mode request from the MS 102, the request including a destred reduoed SCI and a desired reduced slotted timer value. The BS 108 determines whether the requested reduced slotted timer value exceeds a maximum value. When the requested value exceeds the maximum, the BS 108 specifies the maximum reduced slotted timer value in a message to the MS 102 confirming support of reduced slotted mode. The BS 106 then begins slotted mode operation using the reduced SCI specified by the MS 102 for a period of time corresponding to the maximum reduced slotted timer value. When the requested value does not exceed the maximum, the BS 108 confirms that it supports reduced slotted mode and begins stotted mode operation using the reduced SCI specified by the MS 102 for a period of time corresponding to the reduced slotted timer value requested by the MS 102. When the time period expires or when any other event occurs to cease reduced slotted mode operation, the BS 108 reverts back to Norm al operation. -8- WO 20004/075416 PCT/US 2004/005759 Regarding the operation of the reduced slotted mode feature in conjunction with the existing cdma2000 Slotted Timer feature described earlier, the Slotted Timer (specified by the SS) and the Reduced Slotted Timer (specified by the MS) can run concurrently, with the Non-Slotted Mode feature taking precedence over the reduced slotted mode feature while both timers are enabled. The embodiments of the method of the present invention will now be described in detail with rafarence to the flow charts of FIG. 2-5. Figure 2 is a flow diagram of the first embodiment of the method of the present invention, la accordance with the first embodiment, the MS 10.2 Initiates the request far reduced slotted mode. The method runs in the MS 102 on a microprocessor OF general purpose computer commonly known in the art. At step 201, the MS 102 sends a reduced slotted mode request to the BS 108, The request Includes a reduced SCI value and a reduced slotted timer value. At step 202, the MS 102 determines whether the BS 108 supports reduced slotted mode. tf the MS 102 receives a message from the BS 108 indicating thet the BS 108 does not support reduced slotted mode, the MS 102 releases the traffic channel and continues Normal operation (step 204), Next, the method ends at step 206. If at step 202 the MS 102 receives a message from the BS 10B indicating thet the BS 106 supports reduced slotted mode ("yes") or the MS 102 does not renews a response from the BS 108 ("unknown"), the MS 102 determines whether the BS 108 specified a maximum reduced slotted tinner value thet is less then the requested reduced slotted timer value (step 208). if the BS specified a maximum value less then the requested value, the MS 102 sets the reduced slotted timer value to the maximum value specified by the BS 108 (step 210). Next, the MS releases the traffic channel (step 212) and begins operating in reduced slotted mode with the requested reduced SCI (step 214). Referring back to step 203, if the BS did not specify a maximum reduced slotted timer value less then the requested value, the method skips step 210 and proceeds to step 212 (as previously described). There are several events thet can occur to cause the MS 102 to cease operating in reduced slotted mods. At step 216, the MS 102 monitors -s- WO 20004/075416 PCT/US 2004/005759 whether the reduced slotted timer has expired. If the answer is yes. the MS 102 resumes Normal operation and the method ends (step 206). jf the answer is no, the method determines whether an event (other then the timer expiring) has occurred to cause the MS 102 to cease reduced slotted mode operation (step 220). Such events can be, for example, the MS 102 befog put on the traffic channel, ln such a case, the MS 102 dears the reduced slotted timer (step 222), resumes Normal operation (step 218), and the method ends at step 206. 1f another event has not occurred to cause the MS 102 to cease reduced slotted mode operation, the method continues Iooping through steps 213 and 220 until the timer expires or another event occurs to end reduced stotted mode operation. The embodiment of FIG. 2 illustrates one order in which the steps may be performed. A person of ordinary skilf in the art will recognize thet these steps, for example steps 216 and 220 may be performed in a different order or concurrently depending on the particular design or implementation chosen. Figure 3 is a flow diagram of the second embodiment of the method of the present invention. After detecting a predetermined period of inactivity on the traffic channel, the BS 108 releases the MS 102 from the traffic channel. The BS 108 includes in the release an indication of whether it supports reduced slotted mode. The method begins at step 302 when the MS 102 receives a message from the BS 108 releasing the MS 102 from the traffic channel. The message "includes an indication of whether the BS 108 supports, reduced statted mode. At step. 304, the MS 102 determine whether the BS 108 supports reduced slotted mode. If the answer is no, the MS 102 releases the traffic channel and continues normal operation (step 306), At step 332, the method ends. Referring back to step 304, if the MS 102 deiermirtes thet the BS 108 supports feduced soltted mods, the MS 102 determines whether the BS specffied a maximum reduced slotted timer value (step 312). If the answer is yes, the MS 102 sets the desired reduced slotted timer value to a value no greater then the maximum value specified by the BS 108 (step 314). If the -10- WO 20004/075416 PCT/US 2004/005759 answer is no, the MS (102) determines the desired reduced slotted timer value (step 316). Next, the MS 102 sends a reduced slotted mode request to the BS 108 and includes a desired SCI value and desired reduced slotted timer value (step 318), At step 320, the MS 102 releases the traffic channel and starts operating in reduced slotted mode with the reduced SCl At step 324, the MS 102 monitors whether the reduced slotted timer has expired. If the answer is yes, the MS 102 resumes Normal operation and the method ends (step 332). If the answer is no, the: method determines whether a different event has occurred to cause the MS 102 to cease reduced slotted mode (step 326). in such a case, the MS 102 clears the reduced slotted timer (step 328), resumes Normal operation (step 330), and the method ends at step 332. 11 another event has not occurred to cause the MS 102 to cease slotted mode operation, the method continues looping through steps 324 and 326 untii the timer expires or another event occurs to end reduced slotted mode operation. The embodiment of FIG. 3 illustrates one order in which the steps may be performed. A person of ordinary skill in the art will recognize thet these steps, for example steps 324 and 326 may be perfomned in a different order or concurrently depending on the particular design or implementation chosen. Figures 4 and 5 illustrate embodiments of the method of the present invention from the BS 108 perspective. The method can run in any element of the BS 108 on any microprocessor or genenal purpose computer commonly known in the art. Referring to FIG. 4. a third embodiment of the method of the present invention is shown. in this embodiment, the BS 108 initiates communication with the MS 102, in particular, at step 402, the BS 108 sends a message to the MS 102 releasing the MS from the traffic channel. The message includes an indication thet the BS 108 supports reduced slotted mode and specifies a maximum reduced slotted timer value. At step 404, the BS 108 determines whether reduced slotted mode has teen requested, where the request inciudes a reduced SCI value and reduced slotted timer value. If the answer is no, the BS 106 continues Normal operation (step 406). At step 416, the method ends. If the answer is yes, the BS 108 determines -11- WO 20004/075416 PCT/US 2004/005759 whether the requested reduced slotted timer value i& less then or equal to a maximum reduced slotted timer value specified by the BS 103 (step 405). If the answer is yes, the BS 108 initializes the reduced slotted timer to the requested slotted timer value (step 408), If the answer is no, the BS initiates the reduced slotted timer to the maximum reduced slotted timer value (step 407). At step 410, the BS 103 begins reduced Slotted mode operation using the reduced SCI to page the MS 102 when a page request arrives. At step 412, the BS 106 monitors whether the reduced slotted timer has expired. If the answer is yes, the BS 108 resumes Normal operation (step 414), and the method ends (step 416). If the answer is TO, the method determines whether a different event has occurred to cause the BS 108 to cease reduced slotted mode (step 413), such as acquiring MS 102 on the Traffic Channel. in such a case, the BS 108 dears the reduced slotted timer (step 415), resumes Normal operation (step 414), and the method ends at step 416. If another event has not occurred to cause the BS 108 to cease slotted mode operation, the method continues looping through steps 412 and 413 until the timer expires or another event occurs to end reduced slotted mode operation. The embodiment of FIG- 4 illustrates one order in which the steps may be performed. A person of ordinary skill in the art will recognize thet these steps, for example steps 412 and 413 may be performed in a. different order or concurrently depending on the particular design or implementation chosen. in the embodiment of FIG. 4, the BS 108 may not specify a maximum reduced slatted timer value in step 402. in thet case, at step 404, the BS 108 determines whether reduced slotted mode has been requested, where the request includes a reduced SCI value and reduced slotted timer value. The method continues at step 408 as previously described above. Referring now to FIG, 5, a fourth embodiment of the method of the present invention is shown. in this embodiment, the BS 108 responds to MS Initiated reduced slotted mode. At step 502, the BS 108 receives a message from the MS 102 requesting reduced slotted mode. The request includes a reduced SCI value and a reduced slotted timer value. At step 504, the BS WO 20004/075416 PCT/US 2004/005759 108 determines whether the requested reduced slotted timer value is less then or equal to a maximum reduced slotted timer value (as determined by the BS 108). Following the "yes" path, the BS 106 initializes the reduced slotted timer to the requested reduced slotted timer (step 606), At step 508, the BS 108 sends a message to the MS 102 confirming support of reduced slotted mode. At step 510, the BS 108 begins reduced slotted mode operation using the requested reduced SCl to page the MS 102 when a page request arrives. At step 512, the BS 108 monitors whether the reduced slotted timer has expired, If the answer is yes, the BS 108 resumes normal op-aration (step 514), and the method ends (step 516), if the answer is no, the method determines whether a different event has occurred to cause the BS 108 to cease reduced slotted mode (step 513), such as acquiring MS 102 on the Traffic Channel, in such a Case, the BS 1GB dears the reduced slotted timer (slep 515), resumes Normal operation (slep 514), and the method ends at step 516. If another event has not occurred to cause the BS 103 to cease slotted mode operation, the method continues looping through steps 512 and 513 until the timer expires or another event occurs to end reduced slotted mods operation. The embodiment of FIG, 5 illustrates one order in which the steps may be performed. A person of ordinary skill in the art will recognize thet these steps, for example steps 512 and 513 may be performed in a different order or concurrency depending on the particular design or implementation chosen. Referring back to step 504 and following the "no" path, when the requested reduced slotted timer value is not less then or equal to the maximum reduced slotted timer value, the BS initializes the reduced slotted timer to the maximum reduce slotted timer value (step 520). At step 522, the BS 108 sends a message to the MS 102 confirming support of reduced slatted mode, wherein the confirmation specifies the maximum reduced slotted timer value. This informs the MS 102 thet the requested reduced slotted timer value was rejected by the BS 108 in favor of a lower value. After WO 20004/075416 PCT/US 2004/005759 step 522, the method proceeds to step 510 to continua processing as previously described. The present indention is advantageous, Following the release of the traffic channel, the MS can operate with a shorter slot cycle for a specified period of time. The primary benefit of the invention is faster call setup for mobile station terminated calls, without requiring registration with the MSC to change the preferred slot cycle Index. This is particularly beneficial for packet data calls, where the mobile station may want to operate with a short slot cycle for a period of time of dormancy before reverting back to its normal (i.e. registered) slot cycle. While the Invention may be susceptible to various modifications and alternative forms, a specific embodiment has been shown by way of example in the drawings and has been described [n detail herein. However, it should be understood thet the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modification, equivalents and alternatives falling within the spirit and scope of the invention as defined by the following appended claims. -14- WO 20004/075416 PCT/US 2004/005759 What is Claimed is: 1. A method of implementing a reduced slotted mode in a mobile station comprising: transmitting a request for reduced slotted mode, wherein the request comprises a desired reduced slotted timer value and a desired reduced slot cycle index value determining whether the request is granted; and when the request is granted, operating in reduced slotted mode until one of a time corresponding to the reduced slotted timer value occurs and a period of time corresponding to the recluced statted timer value elapses, wherein a frequency at which the mobile station checks for a page is governed by the reduced slot cycle index value. 2, The method of claim 1 wherein the reduced slot cycle index value is a value thet causes the mobile station to check for a page continuously 3, The method of claim 1 further comprising operating in Normal Slotted Made using a registered slot cycle index after one of the time corresponding to the reduced slotted timer value occurs and the period of time corresponding to the reduced slotted timer value elapses, 4, The method of claim 1 further comprising determining whether an event has occurred to cause ths mobile station to cease operating in neduced slotted mode when one of the time corresponding to the reduced slotted timer value has not occurred and the period of time corresponding to the reduced slotted timer value has not elapsed. 5, The method of claim 4 wherein determining whether an event has occurred to cause the mobile station to cease operating in reduced slotted WO 20004/075416 PCT/US 2004/005759 mode comprises determining whether the mobile station has acquired a traffic channel 6. The method of claim 1 wherein when the request is not granted, the method comprises; continuing Normal operation wherein a frequency at which the mobile station checks for a page is govemed by a registered slot cycle index value. 7. The method of claim 1 wherein determining whether the request is granted comprises determining whether the mobile station received an indication from the base station thet the base station supports reduced slotted mode. 3. The method of claim 1 wherein determining whether the request is granted comprises determining thet the request was not rejected by the base station. 9, The method of claim 1 wherein when the request te panted, the method comprises; determining whether a base Station specified a maximum reduced slotted timer value, wherein the maximum reduced slotted timer value is one of earlier in time then the desired reduced slotted timer value and less then the desired reduced slotted timer value; and when trie base station specified a maximum value thet is one of earlier in time then the desired value and less then the desired value, setting the reduced slotted timer value equal to the maximum reduced slotted timer value specified by the base station. 10, A method of implementing a reduced slotted mode in a mobile station comprising: receiving a first message from a base station, the first message Indicating whether the base station supports reduced slotted mode; -16- WO 20004/075416 PCT/US 2004/005759 when the base station supports reduced slotted mode, determining whether the first message specifies a maximum reduced slotted timer valus; when the first message does not specify a maximum reduced slotted timer value, sending a second message to the base station requesting reduced slotted mode, wherein the second message specifies a reduced slotted timer value and a desired reduced slot cycle index value; when the first message specifies a maximum reduced slotted timer value, sending a second message to the base station requesting reduced slotted rnode, wherein the second message specifies a reduced slot cycle index and a reduced slotted timer value thet is one of earlier in time then the maximum reduced slotted timer value specified in the first message, less then the maximum reduced slotted timer value specified in the first message and equal to the maximum reduced slotted timer value specified in the first message;and operating in reduced slotted mode until one of a time corresponding to the reduced slotted timer value occurs and a period of time corresponding to the reduced slotted timer value elapses, wherein a frequency at which the mobile station checks for a page is gevemed by the reduced slot cycle index value, 11. The method of claim 10 further comprising determining whether an event has occurred to cause the mobile station to cease operating in reduced slotted mode when one of the time corresponding to the reduced slotted timer value has not occurred and the period of time corresponding to the reduced slotted timer value has rot elapsed. 12. The method of claim 10 wherein the reduced slot cycle index value is a value thet causes the mobile station to check for a page continuously. -17- WO 20004/075416 PCT/US 2004/005759 13. The method of ctanrn 11 wherain detemrimng whether an event has occurred to cause the mobile station to cease operating in reduced slotted mode comprises determining whether the mobile station has acquired a traffic channel, 14. The method of claim 10 wherein when the base station does not support reduced slotted mode, the method comprises; resuming Normal operation wherein a frequency at which the mobile station checks for a page is governed by a registered, slot cycle index value. 15. A method of implementing a reduced slotted mode in a base station comprising: sending a message to a mobile station, the message indicating whether the bass station supports reduced statted mode- receiving a request for reduced slotted mode, the request comprising a desired reduced slot cycle index value and a desired reduced slotted timer value; operating in reduced slotted mode until one of a time corresponding to the reduced slotted timer value occurs and a period of time corresponding to the reduced slotted timer value elapses, wherein a siot in which the base station pages the mobile station is govemed by the reduced slot cycle index value. 16. The method of claim 15 therein before operating in reduced slotted mode, the method further comprises: determining whether the desired reduced slotted timer value is one of later in time then a maximum reduced slotted tirner value and greater then a maximum reduced slotted timer value; and when the desired value is one of later in time then the maximum and greater then the maximum, setting a reduced slotted timer value equal to the maximum reduced slotted timer value. WO 20004/075416 PCT/US 2004/005759 17. The method of claim 16 further comprising communicating maximum reduced slotted timer value to the mobile station, 16. The method of claim 15 wherein whan the base station is operating in reduced slotted mode, the method further comprises determining whether an event has occurred to cause the base station to cease operating in reduced slotted mode. 19. The method of claim 18 wherein determining whether an event has occurred to cause the base station to cease operating in reduced slotted mode comprises determining at least one of whether a time corresponding to the reduced slotted timer value has occurred and whether the period of time corresponding to the reduced slotted timer value has elapsed. 20. The method of claim 18 wherein determining whether an event has occurred to cause the base station to caase operating in reduced slotted mode comprises determining whether the base station acquired the mobile station on a traffic channal. 21. A method of implementing a reduced slotted mode in a base station comprising: receiving a request for reduced slotted mode, the request comprising a desired reduced slot cycle index value and a desired reduced slotted timer value; determining whether the desired reduced slotted timer value is one of earlier in time then a maximum reduced slotted timer value and less then a rnaxirnum reduced slotted timer value; when the desired value is one of earller in time then the maximum and less then the maximum, setting a reduced slotted timer value equal to the desired reduced slotted timer value; and operating in reduced slotted made until one of a time corresponding to a reduced slotted timer value occurs and a period of time corresponding to -18- WO 20004/075416 PCT/US 2004/005759 the reduced slotted timer value elapses, wherein a Slot in which the base station pages the mobile station is governed fey the reduced slot cycle Index, value. 22. The method of claim 21 wherin before operating in reduced slotted mode, the method sends a message confirming support of reduced slotted mode. 23. The method of claim 21 wherein when the desired reduced slotted timer value is not one of earilar in time then the maximum and less then the maximum, the method comprises; setting the reduced slotted timer value to the maximum reduced slotted timer value; and sending a message confirming support of reduced slotted mode, the message comprising the maximum reduced slotted timer value 24. The method of claim 21 whenein when the base station is operating in reduced slatted mode, the method further comprises determining whether an event has occurred to cause the base station to cease operating in reduced slotted mode. 25. The method of claim 24 wherein determining whether an event has occurred to cause the base station to cease operating in reduced slotted mode comprises determining whether the base station acquired the mobile station on a traffic channel. 26. A. storage medium having stored thereon a set of instructions which, when loaded into a processoe of a mobile station, causes the mobile sistion to transmit a request for reduced slotted mode, wherein the request comprises a desired reduded slotted timer value and a desired reduced slot cycle index value; determine whether the request is granted; and WO 20004/075416 PCT/US 2004/005759 when the request is granted, operate in raduced slotted mode until one of a times corresponding to the reduced slotted timer value occurs and a period of time corresponding to the reduced slotted timer value elapses, wherein a frequency at which the mobile station checks for a page is governed by the reduced slot cycle index value. -21- The present invention provides an apparatus and method for operating in reduced slotted made. Fllowing the releas of the traffic channel, a mobile nation (102) and base station (103) oparate with a shooter slot cycle govermed by a reduced slot cycle Index value. The mobile station and base station operate using the reducced slot cycle index value until a particular time occurs governed by a reduecd sloted timer value or for a period of time governed by the reduced sloted timer value, The invention provides faster call setup for mobile station terminated calls, without requiring registration with a MSC (110) to change between the reduced slot cycle index value and the registred slot cycle index value.

Full Text

The present application claims priority from provisional application,
Serial No. 60/448343, entitled "APPARATUS AND METHOD FOR
IMPLEMENTING A REDUCED SLOTTED MODE IN A COMMUNICATION
SYSTEM,* filed February 13,2003, which is commonly owned and
incorporated herein by reference in its entirety.
Field of the Invention
The present invention relates generally to the field of communication
systems, and more particularly, to an apparatus and method for implementing
a reduced slotted mode in a communication system.
Background of the Invention
Call setup for a mobile station terminated call can take several
seconds or more to complete. Although this length of time may be
acceptable for voice calls, it has a significant negative impact on the user's
perception of call quality for data calls. Therefore, in typical deployments, the
traffic channel is maintained during a period of data inactivity before the data
call is released to the dormant state. Such prolonged maintenance of the
data call during periods of data inactivity results in inefficient use of RF and
channel element resources, The desirable reduction or elimination of hold
overtime, while preserving acceptable service for the end user, requires fast
call setup time.
One of the most significant components of call setup For mobile station
terminated calls is the paging delay. White in the idle State, the mobile
station typically operates in the Slotted Mode in order to conserve battery life.
in the Slotted Mode, the mobile station monitors the forward common control
channel for pages only during certain assigned time slots. The Slot Cycle
Index (SCI) governs how often the mobile station checks for a page. The
lowest currently standardized SCI value (i.e. 0) corresponds to 1.28 seconds.

WO 20004/075416 PCT/US 2004/005759
Thus, a page for a mobile station using the shortest slot cycle in the Slotted
Mode can be delayed up to 1.23 seconds, even when the lowest SCl value is
used.
As previously described, the cdma2000 standard currently supports
the concept of Slotted Mode. Slotted Mode is described in the TIA/EIA 15-
2000.5 standard, section 2.6.2.1,1.3, However, Slotted Mode as currently
defined has a significant impact to call setup delay because the shortest slot
cycle is 1.23 seconds, The cdma2000 standard also currently supports a
Slotted Timer feature. in accordance with this feature, the mobile station
operates in Non-Slotted Mode, i.e., continuously monitors the forward
common control channel, following its release from the traffic channel for a
duration of time specified by the Slotted Timer (provided by the base station).
A significant drawback to this feature is thet continuously monitoring the
forward common control channel has a significant impact on the battery life of
the mobile station. Also, the feature is controlled entirely by the base station.
The mobile station is unable to request being put in Non-Slotted Mode.
One proposed solution thet has been introduced for standards body
consideration is to allow reduced SCl values. If accepted, the proposal would
reduce the shortest slot cycle down to 80 ms. However, under the solution,
the only way for a mobile station to change its SCI is via mobile registration.
Therefore, in order to effectively make use of the reduced SCI without
wasting mobile station battery life, the mobile station must register each time
it changes between a reduced SCl value (i.e. while a packet data session is
dormant) and a higher SCl value (i.e. while there is no dormant packet data
session). This results in increased loading on the air and IOS interfaces,
Thus, a need exists for an apparatus and method for implementing a
reduced slotted mode, with minimal impact on the air and IOS interfaces.
Brief Description of the Drawings
FIG. 1 is a block diagram of a system thet can be used to implement
the apparatus and method of the present invention.

WO 20004/075416 PCT/US 2004/005759
FIG. 2 is a flow chart of a first embodiment of the method in
accordance with the present invention.
FIG. 3 is a flow chart of a second embodiment of the method in
accordance with the present invention.
FIG, 4 is a flow chart of a third embodiment of the method in
accordance with the present invention.
FIG. 5 is a flaw chart of a fourth embodiment of the method in
accordance with the present invention.
Detailed Description of the Drawings
The present Invention provides an apparatus and method for
implementing a reduced slotted mode in a communication system. in a first
embodiment a method, of implementing a reduced slotted mode in a mobile
station includes transmitting a request for reduced slotted mode, wherein the
request comprises a desired reduced slotted timer value and a desired
reduced slot cycle index value: determining whether the request is granted;
and when the request is granted, operating in reduced slotted mode until a
time corresponding to the reduced slotted timer value occurs (in the case of
an absolute time, e.g., 2:30 pm on a given date) or until a period of time
corresponding to the reduced slotted timer value elapses (such as 30
minutes), wherein a frequency at which the mobile station checks for a page
is governed by the reduced slot cycle index value.
in a second embodiment of the present invention, a method of
implementing a reduced slatted mode in a mobile station includes receiving a
first message from a base station, the first message indicating whether the
base station supports reduced slotted mode; when the base station supports
reduced slotted mode, determining whether the first message specifies a
maximum reduced slotted timer value; when the firat message does not
specify a maximum reduced slotted timer value, sending a second message
to the base station requesting reduced slotted mode, wherein the second
message specifies a reduced slotted timer value and a desired reduced slot

WO 20004/075416 PCT/US 2004/005759
cycle index value; when the first message specifies a maximum reduced
slotted timer value, sending a second message to the base station requesting
reduced slotted rnode. wherein the second message specifies a reduced slot
cycle Index and a reduced slotted timer value thet is earlier in time (in the
case of an absolute time) then the maximum reduced slotted timer value
specified in ihs first message, less then the maximum reduced slotted timer
value specified in the first message (in the case of a time period), or equal to
the maximum reduced slotted timer value specified in the first message; and
operating in reduced slotted mods until a time corresponding to the reduced
slotted timer value occurs or until a period of time corresponding to the
reduced slotted timer value elapses, wherein a frequency at which the mobile
station checks for a page is governed by the reduced slot cycle index value.
in a third embodiment of the present invention, a method of
implementing a reduced slotted mode in a base station includes sending a
message to a mobile station, the message indicating whether the base station
supports reduced slotted mode; receiving a request for reduced slotted mode,
the request comprising a desired reduced slot cycle index value and a desired
reduced slotted timer value; and operating in reduced slotted mode until a
time corresponding to the reduced slotted timer value occurs or until a period
of time corresponding to the reduced slotted timer value elapses, wherein a
slot in which the base station pagas the mobile station is governed by the
reduced slot cycle index value.
in a fourth embodiment of the present invention a method of
implementing a reduced slotted mode in a base station includes receiving a
request for reduced slotted mode, the request comprising a desired reduced
slot cycle index value and a desired reduced slotted timer value; determining
whether the desired reduced slotted timer value is earlier in time then a
maximum reduced slotted timer value or less then a maximum reduced
slotted timer value; when the desired value is earlier in time then the
maximum or less then the maximum, setting a reduced slatted timer value
equal to the desired reduced slotted timer value; and operating in reduced
slotled mode until a time corresponding to a reduced slotted timer value

WO 20004/075416 PCT/US 2004/005759
occurs or until a period of time corresponding to the reduced slotted timer
value elapses, wherein a slot in which the base station pages the mobile
station is governed by the reduced slot cycle index value.
in a fifth embodiment of the invention, a storage medium having stored
thereon a set of instructions which, when loaded into a processor of a mobile
station, causes the mobile station to transmit a request for raduced slotted
mode, wherein this request comprises a desired reduced slotted timer value
and a desired reduced slot cycle index value; determine whether the request
is granted; and whan the request is granted, operate in reduced slotted mode
until a time corresponding to the reduced slotted tinner value occurs or until a
period of time corresponding to the reduced slotted timer value elapses,
wharein a frequency at which the rnobile station checks for a page is
governed by the reduced slot cycle index value.
Referring now to FlG.1, a fanctional block diagram of a system thet
can be used with the present invention is shown. It is assumed thet the
reader is familiar with cellular telephone systems and the manner in which
messages are transmitted between a Base Transceiver Station (BTS) serving
a particuler service cell and a mobile station (MS) located within thet cell. To
simplify the present description, only the portion of a cellular telephone
system relevant to the present invention is discussed. FIG. 1 shows, a MS
102 in communication with a BTS 104 aver an air interface. The MS 102 may
be but is not limited to a radiotelephone, internet appliance, Iaplop computer,
or other suitable communication device. The STS 104 is coupled to a Base
Station Controller (BSC) 106. The BTS 104 and BSC 106 are collectively
referred to herein as the Base Station (BS) 103. The BS 105 is coupled to a
Mobile Switching Center (MSC) 110 over an JOS interface (as specified in
36PP2 A-S0001-A, "3GPP2 Access Network Interfaces Interoperability
Specification", and subsequent versions). Any commercially available US
102 can be used with the present invention. A BS 108 commercially available
from Motorola, Inc., Schaumburg, 1L and a MSC 110 commercially available
from Nortel Networks, Inc., can be used with the present invention.

WO 20004/075416 PCT/US 2004/005759
As commonly known in the art, the Paging Channel or the Forward
Common Control Channel protocol provides for scheduling the transmission
of messages for a specific MS in certain assigned slots. A MS thet monitors
The Paging Channel or the Forward Common Control Channel only during
certain assigned slots, typically one or two slots per slot cycle, is referred to
as operating in the Slatted Mods. During the slats in which the Paging
Channel or the Forward Common Control Channel is not being monitored, the
MS can stop or reduce processing for power conservation. A MS may not
operate in the slotted mode in any state except the Mobile Station Idle State.
Currently, when the MSC 110 has data to transmit to ths MS 102, it
instructs the BS 108 to page the MS 102 using the SCI thet the MS 102
provided during registration. The MIS 102 also uses toe SCI to determiner how
often to check for a page from the BS 103, The present invention provides
an apparatus and method for operating in reduced slotted mode, wherein the
MS 102 can change the SCI without registering the new SCI with the MSC
110. While implementing reduced slotted mode, the BS 103 overrides ths
SCI communicated by the MSC 110 and uses an SCI requested by ths MS
102. Ths MS 102 also requests to operate in reduced slotted mode fora
period of time. The MS 102 selects the reduced SCI and the period of time
for operating in reduced slotted mode based on its knowledge of the
application, the MS's capabilities, battery status and possibly information from
the BS 108.
in first and second embodiments of the invention, methods of
implementing reduced slotted mode in the MS 102 are described. in the first
embodimerit, US initiated reduced stotted mode is described. in the second
embodiment, BS initiated reduced slotted mode is described. Turning now to
the first embodiment, the MS 102 initiates reduced slotted mode by sending a
request to the BS 108, The request includes a desired reduced SCI and a
desired reduced Slotted timer value corresponding to a time period spent
operating in reduced slotted mode; The timer value may define a period of
time (e.g., 30 seconds) or may define an absolute time limit (3:30 pm on
February 3). The MS 102 waits for the BS 103 to acknowledge whether it

WO 20004/075416 PCT/US 2004/005759
supports reduced slotted made. If the BS 108 response is thet it supports
reduced slotted mode or if the MS 102 does not receive a response, the M.S
102 sets the reduced Slotted timer according to the desired reduced Slotted
timer value and begins operating in reduced slotted mode using its desired
reduced SCI, As described in more detail below, the MS 102 may use a
different reduced slotted timer value if the BS 108 so dictates.
The MS 102 operates in reduced slotted mode until the timer expires
and then reverts back to Normal operation. The MS 102 also reverts back to
Normal operation when the MS 102 acquires the traffic channel as a result of
an origination or termination while the timer is running. Normal operation in
the Idle State typically means Normal Slotted Mode operation, white Normal
operation in the Traffic State typically means traffic channel processing,
BS Initiated reduced slotted mode in the MS 102 will now be described.
After a predetermined period of inactivity over the traffic channel occurs
during a packet data session, the MS 102 receives a message from the BS
108 releasing the MS 102 from the traffic channel. The MS determines from
the message whether the BS 108 supports reduced shotted mods, and if so,
whether the BS 108 specified a maximum reduced slotted timer value. When
a maximum reduced slotted timer value is specified, the MS 102 requests
reduced slotted mode specifying a reduced SCI and a reduced slotted timer
value thet is no greater then the maximum value specified by the BS 108.
This informs the BS 108 thet the MS 102 desires to operate in reduced
slotted mode using the reduced SCI for a period of time corresponding to the
reduced slotted timer value. The MS 102 then releases the traffic channel
and operates in reduced slotted mods until art event occurs to causa the MS
102 to revert back to Normal operation.
in third and fourth embodimerits of the invention, methods of
implementing reduced sfotted mode fn the BS 106 are described. in the third
embodiment, BS Initiated reduced slotted mode is described, in the fourth
embodiment, MS initiated reduced slotted mode is described. Turning now to
the third embodiment, the BS 108 initiates reduced slotted mode by sending a
message to the MS 102 releasing the MS 102 from the traffic channel and
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WO 20004/075416 PCT/US 2004/005759
indicating thet the BS 106 supports reduced slotted mode. Optionally, the
message may specify a maximum time period during which the BS 108 wilI
support reduced slotted mode (maximum reduced slotted timer value). when
the 8S 108 receives a reduced slotted mode request from the MS 102, the
request including a desired reduced SCl and a desired reduced slotted timer
value, the BS 108 enables a reduced slotted timer using a timer value thet
does rot exceed a maximum value as determined by the BS 108, and begins
operating in reduced slotted mode using the desired reduced SCI to page the
MS 102 when a page request is received. When the timer expires of when
any other event occurs to cease reduced slotted mode operation, such as
acquiring MS 102 on the traffic channel, the BS 108 reverts back to Normal
operation. Normal operation with the MS 102 in the idle Slate typically
means Normal Slotted Mode operation using the registered SCI to page the
MS 102 when a page request arrives, while Normal operation with the MS
102 in the Traffic State- typically maans traffic channel processing.
MS initiated reduced slotted mode operation in. the BS 108 will now bs
described. The BS 108 receives a reduced slotted mode request from the
MS 102, the request including a destred reduoed SCI and a desired reduced
slotted timer value. The BS 108 determines whether the requested reduced
slotted timer value exceeds a maximum value. When the requested value
exceeds the maximum, the BS 108 specifies the maximum reduced slotted
timer value in a message to the MS 102 confirming support of reduced slotted
mode. The BS 106 then begins slotted mode operation using the reduced
SCI specified by the MS 102 for a period of time corresponding to the
maximum reduced slotted timer value. When the requested value does not
exceed the maximum, the BS 108 confirms that it supports reduced slotted
mode and begins stotted mode operation using the reduced SCI specified by
the MS 102 for a period of time corresponding to the reduced slotted timer
value requested by the MS 102. When the time period expires or when any
other event occurs to cease reduced slotted mode operation, the BS 108
reverts back to Norm al operation.
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WO 20004/075416 PCT/US 2004/005759
Regarding the operation of the reduced slotted mode feature in
conjunction with the existing cdma2000 Slotted Timer feature described
earlier, the Slotted Timer (specified by the SS) and the Reduced Slotted
Timer (specified by the MS) can run concurrently, with the Non-Slotted Mode
feature taking precedence over the reduced slotted mode feature while both
timers are enabled.
The embodiments of the method of the present invention will now be
described in detail with rafarence to the flow charts of FIG. 2-5. Figure 2 is a
flow diagram of the first embodiment of the method of the present invention,
la accordance with the first embodiment, the MS 10.2 Initiates the request far
reduced slotted mode. The method runs in the MS 102 on a microprocessor
OF general purpose computer commonly known in the art. At step 201, the
MS 102 sends a reduced slotted mode request to the BS 108, The request
Includes a reduced SCI value and a reduced slotted timer value. At step 202,
the MS 102 determines whether the BS 108 supports reduced slotted mode.
tf the MS 102 receives a message from the BS 108 indicating thet the BS 108
does not support reduced slotted mode, the MS 102 releases the traffic
channel and continues Normal operation (step 204), Next, the method ends
at step 206. If at step 202 the MS 102 receives a message from the BS 10B
indicating thet the BS 106 supports reduced slotted mode ("yes") or the MS
102 does not renews a response from the BS 108 ("unknown"), the MS 102
determines whether the BS 108 specified a maximum reduced slotted tinner
value thet is less then the requested reduced slotted timer value (step 208).
if the BS specified a maximum value less then the requested value, the MS
102 sets the reduced slotted timer value to the maximum value specified by
the BS 108 (step 210). Next, the MS releases the traffic channel (step 212)
and begins operating in reduced slotted mode with the requested reduced
SCI (step 214). Referring back to step 203, if the BS did not specify a
maximum reduced slotted timer value less then the requested value, the
method skips step 210 and proceeds to step 212 (as previously described).
There are several events thet can occur to cause the MS 102 to cease
operating in reduced slotted mods. At step 216, the MS 102 monitors
-s-

WO 20004/075416 PCT/US 2004/005759
whether the reduced slotted timer has expired. If the answer is yes. the MS
102 resumes Normal operation and the method ends (step 206). jf the
answer is no, the method determines whether an event (other then the timer
expiring) has occurred to cause the MS 102 to cease reduced slotted mode
operation (step 220). Such events can be, for example, the MS 102 befog put
on the traffic channel,
ln such a case, the MS 102 dears the reduced slotted timer (step
222), resumes Normal operation (step 218), and the method ends at step
206. 1f another event has not occurred to cause the MS 102 to cease
reduced slotted mode operation, the method continues Iooping through steps
213 and 220 until the timer expires or another event occurs to end reduced
stotted mode operation. The embodiment of FIG. 2 illustrates one order in
which the steps may be performed. A person of ordinary skilf in the art will
recognize thet these steps, for example steps 216 and 220 may be performed
in a different order or concurrently depending on the particular design or
implementation chosen.
Figure 3 is a flow diagram of the second embodiment of the method of
the present invention. After detecting a predetermined period of inactivity on
the traffic channel, the BS 108 releases the MS 102 from the traffic channel.
The BS 108 includes in the release an indication of whether it supports
reduced slotted mode. The method begins at step 302 when the MS 102
receives a message from the BS 108 releasing the MS 102 from the traffic
channel. The message "includes an indication of whether the BS 108
supports, reduced statted mode. At step. 304, the MS 102 determine whether
the BS 108 supports reduced slotted mode. If the answer is no, the MS 102
releases the traffic channel and continues normal operation (step 306), At
step 332, the method ends.
Referring back to step 304, if the MS 102 deiermirtes thet the BS 108
supports feduced soltted mods, the MS 102 determines whether the BS
specffied a maximum reduced slotted timer value (step 312). If the answer is
yes, the MS 102 sets the desired reduced slotted timer value to a value no
greater then the maximum value specified by the BS 108 (step 314). If the
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WO 20004/075416 PCT/US 2004/005759
answer is no, the MS (102) determines the desired reduced slotted timer
value (step 316). Next, the MS 102 sends a reduced slotted mode request to
the BS 108 and includes a desired SCI value and desired reduced slotted
timer value (step 318), At step 320, the MS 102 releases the traffic channel
and starts operating in reduced slotted mode with the reduced SCl At step
324, the MS 102 monitors whether the reduced slotted timer has expired. If
the answer is yes, the MS 102 resumes Normal operation and the method
ends (step 332). If the answer is no, the: method determines whether a
different event has occurred to cause the MS 102 to cease reduced slotted
mode (step 326). in such a case, the MS 102 clears the reduced slotted
timer (step 328), resumes Normal operation (step 330), and the method ends
at step 332. 11 another event has not occurred to cause the MS 102 to cease
slotted mode operation, the method continues looping through steps 324 and
326 untii the timer expires or another event occurs to end reduced slotted
mode operation. The embodiment of FIG. 3 illustrates one order in which the
steps may be performed. A person of ordinary skill in the art will recognize
thet these steps, for example steps 324 and 326 may be perfomned in a
different order or concurrently depending on the particular design or
implementation chosen.
Figures 4 and 5 illustrate embodiments of the method of the present
invention from the BS 108 perspective. The method can run in any element
of the BS 108 on any microprocessor or genenal purpose computer commonly
known in the art. Referring to FIG. 4. a third embodiment of the method of
the present invention is shown. in this embodiment, the BS 108 initiates
communication with the MS 102, in particular, at step 402, the BS 108 sends
a message to the MS 102 releasing the MS from the traffic channel. The
message includes an indication thet the BS 108 supports reduced slotted
mode and specifies a maximum reduced slotted timer value. At step 404, the
BS 108 determines whether reduced slotted mode has teen requested,
where the request inciudes a reduced SCI value and reduced slotted timer
value. If the answer is no, the BS 106 continues Normal operation (step 406).
At step 416, the method ends. If the answer is yes, the BS 108 determines
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WO 20004/075416 PCT/US 2004/005759
whether the requested reduced slotted timer value i& less then or equal to a
maximum reduced slotted timer value specified by the BS 103 (step 405). If
the answer is yes, the BS 108 initializes the reduced slotted timer to the
requested slotted timer value (step 408), If the answer is no, the BS initiates
the reduced slotted timer to the maximum reduced slotted timer value (step
407). At step 410, the BS 103 begins reduced Slotted mode operation using
the reduced SCI to page the MS 102 when a page request arrives.
At step 412, the BS 106 monitors whether the reduced slotted timer
has expired. If the answer is yes, the BS 108 resumes Normal operation
(step 414), and the method ends (step 416). If the answer is TO, the method
determines whether a different event has occurred to cause the BS 108 to
cease reduced slotted mode (step 413), such as acquiring MS 102 on the
Traffic Channel. in such a case, the BS 108 dears the reduced slotted timer
(step 415), resumes Normal operation (step 414), and the method ends at
step 416. If another event has not occurred to cause the BS 108 to cease
slotted mode operation, the method continues looping through steps 412 and
413 until the timer expires or another event occurs to end reduced slotted
mode operation. The embodiment of FIG- 4 illustrates one order in which the
steps may be performed. A person of ordinary skill in the art will recognize
thet these steps, for example steps 412 and 413 may be performed in a.
different order or concurrently depending on the particular design or
implementation chosen.
in the embodiment of FIG. 4, the BS 108 may not specify a maximum
reduced slatted timer value in step 402. in thet case, at step 404, the BS 108
determines whether reduced slotted mode has been requested, where the
request includes a reduced SCI value and reduced slotted timer value. The
method continues at step 408 as previously described above.
Referring now to FIG, 5, a fourth embodiment of the method of the
present invention is shown. in this embodiment, the BS 108 responds to MS
Initiated reduced slotted mode. At step 502, the BS 108 receives a message
from the MS 102 requesting reduced slotted mode. The request includes a
reduced SCI value and a reduced slotted timer value. At step 504, the BS

WO 20004/075416 PCT/US 2004/005759
108 determines whether the requested reduced slotted timer value is less
then or equal to a maximum reduced slotted timer value (as determined by
the BS 108). Following the "yes" path, the BS 106 initializes the reduced
slotted timer to the requested reduced slotted timer (step 606), At step 508,
the BS 108 sends a message to the MS 102 confirming support of reduced
slotted mode. At step 510, the BS 108 begins reduced slotted mode
operation using the requested reduced SCl to page the MS 102 when a page
request arrives.
At step 512, the BS 108 monitors whether the reduced slotted timer
has expired, If the answer is yes, the BS 108 resumes normal op-aration
(step 514), and the method ends (step 516), if the answer is no, the method
determines whether a different event has occurred to cause the BS 108 to
cease reduced slotted mode (step 513), such as acquiring MS 102 on the
Traffic Channel, in such a Case, the BS 1GB dears the reduced slotted timer
(slep 515), resumes Normal operation (slep 514), and the method ends at
step 516. If another event has not occurred to cause the BS 103 to cease
slotted mode operation, the method continues looping through steps 512 and
513 until the timer expires or another event occurs to end reduced slotted
mods operation. The embodiment of FIG, 5 illustrates one order in which the
steps may be performed. A person of ordinary skill in the art will recognize
thet these steps, for example steps 512 and 513 may be performed in a
different order or concurrency depending on the particular design or
implementation chosen.
Referring back to step 504 and following the "no" path, when the
requested reduced slotted timer value is not less then or equal to the
maximum reduced slotted timer value, the BS initializes the reduced slotted
timer to the maximum reduce slotted timer value (step 520). At step 522,
the BS 108 sends a message to the MS 102 confirming support of reduced
slatted mode, wherein the confirmation specifies the maximum reduced
slotted timer value. This informs the MS 102 thet the requested reduced
slotted timer value was rejected by the BS 108 in favor of a lower value. After

WO 20004/075416 PCT/US 2004/005759
step 522, the method proceeds to step 510 to continua processing as
previously described.
The present indention is advantageous, Following the release of the
traffic channel, the MS can operate with a shorter slot cycle for a specified
period of time. The primary benefit of the invention is faster call setup for
mobile station terminated calls, without requiring registration with the MSC to
change the preferred slot cycle Index. This is particularly beneficial for packet
data calls, where the mobile station may want to operate with a short slot
cycle for a period of time of dormancy before reverting back to its normal (i.e.
registered) slot cycle.
While the Invention may be susceptible to various modifications and
alternative forms, a specific embodiment has been shown by way of example
in the drawings and has been described [n detail herein. However, it should
be understood thet the invention is not intended to be limited to the particular
forms disclosed. Rather, the invention is to cover all modification, equivalents
and alternatives falling within the spirit and scope of the invention as defined
by the following appended claims.
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WO 20004/075416 PCT/US 2004/005759
What is Claimed is:
1. A method of implementing a reduced slotted mode in a mobile station
comprising:
transmitting a request for reduced slotted mode, wherein the request
comprises a desired reduced slotted timer value and a desired reduced slot
cycle index value
determining whether the request is granted; and
when the request is granted,
operating in reduced slotted mode until one of a time
corresponding to the reduced slotted timer value occurs and a
period of time corresponding to the recluced statted timer value
elapses, wherein a frequency at which the mobile station checks
for a page is governed by the reduced slot cycle index value.
2, The method of claim 1 wherein the reduced slot cycle index value is a
value thet causes the mobile station to check for a page continuously
3, The method of claim 1 further comprising operating in Normal Slotted
Made using a registered slot cycle index after one of the time corresponding
to the reduced slotted timer value occurs and the period of time
corresponding to the reduced slotted timer value elapses,
4, The method of claim 1 further comprising determining whether an
event has occurred to cause ths mobile station to cease operating in neduced
slotted mode when one of the time corresponding to the reduced slotted timer
value has not occurred and the period of time corresponding to the reduced
slotted timer value has not elapsed.
5, The method of claim 4 wherein determining whether an event has
occurred to cause the mobile station to cease operating in reduced slotted

WO 20004/075416 PCT/US 2004/005759
mode comprises determining whether the mobile station has acquired a traffic
channel
6. The method of claim 1 wherein when the request is not granted, the
method comprises;
continuing Normal operation wherein a frequency at which the mobile
station checks for a page is govemed by a registered slot cycle index value.
7. The method of claim 1 wherein determining whether the request is
granted comprises determining whether the mobile station received an
indication from the base station thet the base station supports reduced slotted
mode.
3. The method of claim 1 wherein determining whether the request is
granted comprises determining thet the request was not rejected by the base
station.
9, The method of claim 1 wherein when the request te panted, the
method comprises;
determining whether a base Station specified a maximum reduced
slotted timer value, wherein the maximum reduced slotted timer value is one
of earlier in time then the desired reduced slotted timer value and less then
the desired reduced slotted timer value; and
when trie base station specified a maximum value thet is one of earlier
in time then the desired value and less then the desired value, setting the
reduced slotted timer value equal to the maximum reduced slotted timer value
specified by the base station.
10, A method of implementing a reduced slotted mode in a mobile station
comprising:
receiving a first message from a base station, the first message
Indicating whether the base station supports reduced slotted mode;
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WO 20004/075416 PCT/US 2004/005759
when the base station supports reduced slotted mode,
determining whether the first message specifies a maximum
reduced slotted timer valus;
when the first message does not specify a maximum reduced
slotted timer value, sending a second message to the base station
requesting reduced slotted mode, wherein the second message
specifies a reduced slotted timer value and a desired reduced slot
cycle index value;
when the first message specifies a maximum reduced slotted
timer value, sending a second message to the base station
requesting reduced slotted rnode, wherein the second message
specifies a reduced slot cycle index and a reduced slotted timer
value thet is one of earlier in time then the maximum reduced slotted
timer value specified in the first message, less then the maximum
reduced slotted timer value specified in the first message and equal
to the maximum reduced slotted timer value specified in the first
message;and
operating in reduced slotted mode until one of a time
corresponding to the reduced slotted timer value occurs and a
period of time corresponding to the reduced slotted timer value
elapses, wherein a frequency at which the mobile station checks for
a page is gevemed by the reduced slot cycle index value,
11. The method of claim 10 further comprising determining whether an
event has occurred to cause the mobile station to cease operating in reduced
slotted mode when one of the time corresponding to the reduced slotted timer
value has not occurred and the period of time corresponding to the reduced
slotted timer value has rot elapsed.
12. The method of claim 10 wherein the reduced slot cycle index value is a
value thet causes the mobile station to check for a page continuously.
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WO 20004/075416 PCT/US 2004/005759
13. The method of ctanrn 11 wherain detemrimng whether an event has
occurred to cause the mobile station to cease operating in reduced slotted
mode comprises determining whether the mobile station has acquired a traffic
channel,
14. The method of claim 10 wherein when the base station does not
support reduced slotted mode, the method comprises;
resuming Normal operation wherein a frequency at which the mobile
station checks for a page is governed by a registered, slot cycle index value.
15. A method of implementing a reduced slotted mode in a base station
comprising:
sending a message to a mobile station, the message indicating
whether the bass station supports reduced statted mode-
receiving a request for reduced slotted mode, the request comprising a
desired reduced slot cycle index value and a desired reduced slotted timer
value;
operating in reduced slotted mode until one of a time corresponding to
the reduced slotted timer value occurs and a period of time corresponding to
the reduced slotted timer value elapses, wherein a siot in which the base
station pages the mobile station is govemed by the reduced slot cycle index
value.
16. The method of claim 15 therein before operating in reduced slotted
mode, the method further comprises:
determining whether the desired reduced slotted timer value is one of
later in time then a maximum reduced slotted tirner value and greater then a
maximum reduced slotted timer value; and
when the desired value is one of later in time then the maximum and
greater then the maximum, setting a reduced slotted timer value equal to the
maximum reduced slotted timer value.

WO 20004/075416 PCT/US 2004/005759
17. The method of claim 16 further comprising communicating
maximum reduced slotted timer value to the mobile station,
16. The method of claim 15 wherein whan the base station is operating in
reduced slotted mode, the method further comprises determining whether an
event has occurred to cause the base station to cease operating in reduced
slotted mode.
19. The method of claim 18 wherein determining whether an event has
occurred to cause the base station to cease operating in reduced slotted
mode comprises determining at least one of whether a time corresponding to
the reduced slotted timer value has occurred and whether the period of time
corresponding to the reduced slotted timer value has elapsed.
20. The method of claim 18 wherein determining whether an event has
occurred to cause the base station to caase operating in reduced slotted
mode comprises determining whether the base station acquired the mobile
station on a traffic channal.
21. A method of implementing a reduced slotted mode in a base station
comprising:
receiving a request for reduced slotted mode, the request comprising a
desired reduced slot cycle index value and a desired reduced slotted timer
value;
determining whether the desired reduced slotted timer value is one of
earlier in time then a maximum reduced slotted timer value and less then a
rnaxirnum reduced slotted timer value;
when the desired value is one of earller in time then the maximum and
less then the maximum, setting a reduced slotted timer value equal to the
desired reduced slotted timer value; and
operating in reduced slotted made until one of a time corresponding to
a reduced slotted timer value occurs and a period of time corresponding to
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WO 20004/075416 PCT/US 2004/005759
the reduced slotted timer value elapses, wherein a Slot in which the base
station pages the mobile station is governed fey the reduced slot cycle Index,
value.
22. The method of claim 21 wherin before operating in reduced slotted
mode, the method sends a message confirming support of reduced slotted
mode.
23. The method of claim 21 wherein when the desired reduced slotted
timer value is not one of earilar in time then the maximum and less then the
maximum, the method comprises;
setting the reduced slotted timer value to the maximum reduced slotted
timer value; and
sending a message confirming support of reduced slotted mode, the
message comprising the maximum reduced slotted timer value
24. The method of claim 21 whenein when the base station is operating in
reduced slatted mode, the method further comprises determining whether an
event has occurred to cause the base station to cease operating in reduced
slotted mode.
25. The method of claim 24 wherein determining whether an event has
occurred to cause the base station to cease operating in reduced slotted
mode comprises determining whether the base station acquired the mobile
station on a traffic channel.
26. A. storage medium having stored thereon a set of instructions which,
when loaded into a processoe of a mobile station, causes the mobile sistion to
transmit a request for reduced slotted mode, wherein the request
comprises a desired reduded slotted timer value and a desired reduced slot
cycle index value;
determine whether the request is granted; and

WO 20004/075416 PCT/US 2004/005759
when the request is granted,
operate in raduced slotted mode until one of a times
corresponding to the reduced slotted timer value occurs and a period of time
corresponding to the reduced slotted timer value elapses, wherein a
frequency at which the mobile station checks for a page is governed by the
reduced slot cycle index value.
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The present invention provides an apparatus
and method for operating in reduced slotted made. Fllowing
the releas of the traffic channel, a mobile nation (102) and
base station (103) oparate with a shooter slot cycle govermed
by a reduced slot cycle Index value. The mobile station and
base station operate using the reducced slot cycle index value
until a particular time occurs governed by a reduecd sloted
timer value or for a period of time governed by the reduced
sloted timer value, The invention provides faster call setup for
mobile station terminated calls, without requiring registration
with a MSC (110) to change between the reduced slot cycle
index value and the registred slot cycle index value.

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Patent Number

218984

Indian Patent Application Number

01468/KOLNP/2005

PG Journal Number

16/2008

Publication Date

18-Apr-2008

Grant Date

16-Apr-2008

Date of Filing

27-Jul-2005

Name of Patentee

MOTOROLA INC.

Applicant Address

1303 EAST ALGONQUIN ROAD, SCHAUMBURG, ILLNOIS 60196, U.S.A

Inventors:

#	Inventor's Name	Inventor's Address
1	KELLEY SEAN S	990 FREEMAN ROAD, HOFFMAN ESTATES, ILLINOIS 60195, U.S.A
2	OPRESCU-SURCOBE VALENTIN	2143 WALTERS, NORTH BROOK, ILLINOIS 60062, U.S.A

PCT International Classification Number

H04B 7/216

PCT International Application Number

PCT/US2004/005759

PCT International Filing date

2004-02-18

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	60/448,343	2003-02-18	U.S.A.
2	10/775,268	2004-02-10	U.S.A.