Method and apparatus for paging group handling

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PAGE GROUP MANIPULATION APPLIANCE

FIELD OF THE INVENTION

[001] The present application relates to wireless communications.

BACKGROUND

[002] One of the efforts for the long-term evolution program (LTE) of the third generation partnership project (3GPP) is to bring new technology, new architecture and new methods to the new adjustments and configurations of LTE. The LTE program is designed to provide greater spectrum efficiency, reduced latency and better utilization of radio resources to provide the user experiences faster speeds and richer applications and services with less associated cost.

[003] Regarding the reception of idle-mode paging by mobile terminals, the LTE system can use downlink layer 1 (L1) and layer 2 (L2) control signaling to signal paging indicators for groups of transmission units and wireless reception (WTRUs) with the same paging group identity. This may not be practical, however, when implementing certain aspects of paging group handling with respect to idle paging bases (such as full system paging capacity, system paging load distribution, and flexibility in assigning to the paging groups. WTRUs of different discontinuous receive (DRX) cycle lengths in a single paging group of WTRUs). [004] It would therefore be beneficial to provide a method and apparatus for handling paging groups.

SUMMARY OF THE INVENTION

[005] A method and apparatus for handling paging groups are described. The method includes grouping wireless transmit and receive units (WTRUs) into a paging group. The paging group is assigned a paging occasion and the existence of content is indicated for the WTRUs.

BRIEF DESCRIPTION OF THE FIGURES

[006] A more detailed understanding can be obtained from the following description, provided as an example and to be understood in conjunction with the attached Figures, in which:

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Figure 1 shows an example of a wireless communication system that includes a series of WTRUs and a base station;

Figure 2 is a functional block diagram of a WTRU and the base station in Figure 1;

Figure 3 is a flowchart of a method of manipulating paging groups;

- Figure 4 shows an example of base paging occasion;

- Figure 5 shows an example of bitmap representation of paging groups; and

Figure 6 is a diagram of an example LTE paging message. DETAILED DESCRIPTION

[007] Where indicated below, the terminology "wireless transmit and receive unit (WTRU)" includes, but is not limited to, a user equipment (UE), mobile station (STA), fixed or mobile subscriber unit , pager, cell phone, personal digital assistant (PDA), computer, or any other type of user device capable of operating in a wireless environment. As indicated below, the terminology “base station” includes, but is not limited to, a Node B, site controller, access point (AP) or any other type of interface device capable of operating in a wireless environment.

[008] Figure 1 shows a wireless communication system 100 that includes a series of WTRUs 110 and a base station 120. As shown in Figure 1, the WTRUs 110 are separated, for example purposes, into three called paging groups “A” which includes 110i WTRUs, “B” which includes HO2 WTRUs and “C” which includes 11O3 WTRUs. WTRUs 110 are in communication with base station 120. It should be noted that while an example configuration of WTRUs 110 and base station 120 is illustrated in Figure 1, any combination of wired and wireless devices can be included in wireless communication system 100.

[009] Figure 2 is a functional block diagram 200 of a WTRU 110 and base station 120 of the wireless communication system 100 of Figure 1. As shown in Figure 2, the WTRU 110 is in communication with the station base 120 and both are configured to perform a method of handling paging groups.

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[0010] In addition to the components that might be found in a typical WTRU, the WTRU 110 includes a processor 115, a receiver 116, a transmitter 117 and an antenna 118. The processor 115 is configured to perform a paging group handling procedure . Receiver 116 and transmitter 117 are in communication with processor 115. Antenna 118 is in communication with receiver 116 and transmitter 117 to facilitate wireless data transmission and reception.

[0011] In addition to the components that might be found in a typical base station, the base station 120 includes a processor 125, a receiver 126, a transmitter 127 and an antenna 128. The processor 125 is configured to perform a group handling procedure of paging. Receiver 126 and transmitter 127 are in communication with processor 125. Antenna 128 is in communication with receiver 126 and transmitter 127 to facilitate wireless data transmission and reception.

[0012] The arrival of content received in a WTRU 110 is a random event. This should be considered in light of the maintenance needs of the WTRU in idle mode for the maximum practicable time for energy savings. The WTRU 110 must “wake up” regularly to check for content arrival. It may be desirable, therefore, to address an appropriate number of paging groups of WTRUs 110, while allowing different WTRUs 110 in a paging group to have different DRX cycle lengths. In one example, a minimum paging occasion time unit is an LTE frame (or group).

[0013] Consequently, Figure 3 is a flowchart of a method 300 of manipulating paging groups. In step 310, the WTRUs 110 are grouped into paging groups. Referring again to Figure 1, for example, WTRUs 110i are placed in paging group A, WTRUs 1102 are placed in paging group B, and WTRUs 11O3 are placed in paging group C.

[0014] In an LTE network, a paging group that has a paging group identity (PG ID) can be defined in a number of ways. WTRUs can be grouped numerically, for example, by the WTRU entity, such as the

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4/12 international mobile subscriber identity (IMSI) or temporary mobile subscriber entity (TMSI). Due to the temporary nature of TMSI, however, IMSI can be a more stable identity to use in LTE for idle mode paging handling. Alternatively, the paging group can be logically grouped by network operators for the purpose of service distinction or classification, network service handling differential and paying customer prioritization.

[0015] When grouping is numeric, the following example methods can be used: PG ID = (IMSI mod DRX cycle length) or PG ID = (IMSI div DRX cycle length) + (IMSI mod DRX cycle length) ). The resulting paging group, ID PG, becomes the base paging occasion compensation frame number when all paging occasions for a specific WTRU are determined and a group of WTRUs with a similar numeric property of their IMSIs (or TMSI) with respect to the shortest DRX cycle length is defined by the LTE system. A WTRU 110 can derive its own PG ID by the IMSI to which it is assigned with one of the above equations. If the WTRU 110 is assigned an IMSI of 18922, for example, and the network DRX cycle length (as published in a system information broadcast) is 32, the PG ID for that WTRU would be ten (10) as per first equation (ie, 18922 mod 32 = 10).

[0016] When grouping is logical, network operators may wish to group WTRUs 110 into sets of WTRUs based on certain properties or those that require differential treatment. In this case, WTRUs are assigned to different local paging groups by the network/service provider in a specific service category, within a network source or using other properties. Examples of groupings may depend on the mobile network code (MNC) of the IMSI of the WTRU, the mobile country code (MCC) or certain attributes of the mobile station identification number (MSIN) of the IMSI of the WTRU. Network operators can use some of the following possible combinations to define the paging occasion group identity:

- PG ID = e-UTRAN prefix || MNC || suffix of e-UTRAN;

- PG ID = e-UTRAN prefix || MCC || suffix of e-UTRAN; and

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- PG ID = e-UTRAN prefix || (MSIN logical partition) || suffix of e-UTRAN;

where the e-UTRAN prefix and e-UTRAN suffix can be any value except one that is used for another PG ID in subsequent operations.

[0017] Alternatively, a PG ID with other desired properties can be assigned.

[0018] As the WTRUs in idle mode periodically wake up to check if the E-UTRAN network has sent or is sending a specific paging indication for it and its WTRU group, paging occasions are assigned to the paging groups (step 320). A paging occasion, which can occur at the beginning of an LTE frame, defines a specific time when a WTRU should wake up to check if it is receiving paging messages. The LTE system distributes three paging occasions in the time domain, so that the paging load at any time is equalized and the WTRU that received paging messages receives the paging messages with minimal delay relative to its sleep and activity cycle (ie DRX cycle).

[0019] In step 330, the WTRUs in a paging group can be assigned different DRX cycle lengths. Consequently, for a specific paging group, with respect to the PG ID, the system will need to determine a base paging occasion offset that would be equivalent to a frame number. The continuous and subsequent paging occasions are built on the base paging occasion offset. This base paging occasion compensation can be called PO-GP.

[0020] In distributing full paging occasions for different WTRUs that have different DRX cycle lengths, the PO-GP indicates, at the beginning of the system frame, a numerical scale which is used as the compensation frame number. This may be the shortest DRX cycle length by the LTE system due to the assignment of variable DRX cycle lengths that a WTRU can have, regardless of the paging group it belongs to. A specific WTRU 110 can have the shortest or longest DRX cycle. Figure 4 shows an example 400 base paging occasion. Figure 4 shows a group of WTRUs

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110 on a PG ID “A which also includes PO GP “1”. These WTRUs have different DRX cycle lengths that display as 8 or 16. Consequently, WTRUs can expect their corresponding paging occasions in the timescale of system frame numbers (SFNs). A WTRU with DRX cycle length = 8, for example, would expect its paging at SFN 1, 9, 17, 25, 33 and the like, while a WTRU with DRX cycle length = 16 might expect its paging at 1, 17 , 33 and the like. A selection between DRX cycle lengths can include performance versus energy savings considerations. A WTRU with a DRX cycle length of 8, for example, may consume more power, but may have more paging capability, which results in faster call reception, and the like.

[0021] Similar to the PG ID, the PO-PG can be determined numerically or logically. The PO-PG can be determined numerically, for example, following the equation: PO-PG = ID PG mod DRX cycle length, where the DRX cycle length is the minimum DRX cycle length defined by the system.

[0022] The PG-OP can also be organized logically, especially for the logically formed paging groups. In this case, the PG ID is converted to PO-GP by means of a mapping table if there is no short formula for numerical translation of PG ID into PO-GP where, for example, the PG IDs are not sequentially sequenced. The mapping table can also be used to achieve the desired PO-GP distribution or retain assignment flexibility such that, for example, the new assignment can be easily arranged. Table 1 below shows an example table mapping a PG ID to a PO-GP.

Table 1

<td>PG ID (Allocated WTRU Group ID)</td><td>PO-GP (Base Paging Occasion Compensation Group)</td>

<td>PGA ID</td><td> 0</td>

<td>PG ID Β</td><td> 1</td>

<td>ID PG C</td><td> 2</td>

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<td>ID PG D</td><td> 2</td>

<td>ID PG E</td><td> 3</td>

<td></td><td></td>

<td>ID PG Nid pg max</td><td>φ</td>

[0023] It should be noted that Nid pg Max is the maximum number of paging groups that the LTE system will be able to accommodate, φ is an absolute value less than or equal to the smallest DRX cycle length minus one (φ &lt; length of shorter DRX cycle - 1). Several paging groups can be assigned to the same PO-GP.

[0024] From the point of view of the system, the PO-GP needs to be distributed for all frame occasions covered in the shortest DRX cycle, in order to homogenize the paging load, as well as maintain the paging performance. In addition, more than one paging group can be assigned to the same PO-GP so that you can maintain DRX cycle length flexibility and maximize the system's paging capacity.

[0025] In a system and WTRU LTE, the overall continuous paging occasions (that is, the paging occasion frame numbers "PO-FN") with any DRX cycle lengths are calculated using PO-FN = PO -GP + n * DRX cycle length, where n = 0.1,2,..., such that the resulting PO-FN does not exceed the system's maximum frame number limit and the DRX cycle length is assigned by WTRU. In this way, the paging status for any specific WTRU 110 (step 340) is indicated.

[0026] On each paging occasion, PO-FN, a WTRU 110 in DRX cycle in idle mode, as well as WTRUs 110 in its paging occasion group or other groups with the same PO-GP, agree to read the indication of paging (step 350) based on the PO-GP it is in and the DRX cycle length to which it is assigned. Since more than one group of WTRUs 110 may be in the process of checking the paging indicator to find the paging state towards their group at the same time, the system may need to accommodate more paging groups in the limited space of the paging indicator and , at the same time, organize

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8/12 efficiently space for status indication of multiple paging groups.

[0027] One way to accommodate the needs is to use a bitmap method to indicate the paging position of paging groups belonging to a paging occasion (PO-GP). A bit in the paging situation map or bit would indicate whether a specific paging group is receiving content (such as bit value “1”) or not (such as bit value “0”). Figure 5 shows an example bitmap representation of paging groups 500. As shown in Figure 5, paging group ID “A” includes a PO-GP of 1, paging group ID “B” includes a PO-GP of 4, and paging group ID “C” includes a PO-GP of 1. Each WTRU in a paging group reads the paging status bit in the bitmap during the group's paging occasion and as per the WTRU's DRX cycle length, as indicated by the arrows shown in Figure 5 , in order to determine whether or not there is content for the WTRU.

[0028] The bitmap construction is essentially a line up to N bits where bit 0 represents the paging group with the smallest ID PG, bit 1 represents the group with the next value of ID PG and so on . Table 2 below shows an example bitmap for a PO-GP.

Table 2

<td>BitO</td><td>Bit 1</td><td>Bit 2</td><td></td><td>Bit n</td>

<td>PG ID a1</td><td>PG ID a2</td><td>PG ID a3</td><td></td><td>PG ID an</td>

where ID G a1 &lt; ID PG a2 &lt; ID PG a3 &lt; ... &lt; ID PG an.

[0029] There will be N (ie N = shortest length of DRX cycles - 1) bitmaps in the system, with one for each PO-GP position. The E-UTRAN system transmits this PG/PO-GP ID mapping in transmitting system information. Table 3 below shows a bitmap of PG ID mapping at paging time.

Table 3

<td></td><td>PO-GP 0</td><td>PO-GP 1</td><td>PO-GP 2</td><td></td><td>PO-GP N</td>

<td>BitO</td><td>PG ID</td><td>PG ID x1</td><td>PG ID y1</td><td></td><td>PG ID z1</td>

<td>Bit 1</td><td>PG ID b</td><td>PG ID x2</td><td>PG ID y2</td><td></td><td>PG ID z2</td>

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<td></td><td></td><td></td><td></td><td></td><td></td>

<td>Bit K</td><td>PG ID</td><td>PG ID xn</td><td>PG ID yn</td><td></td><td></td>

[0030] If the E-UTRAN system has adopted the approach described in Table 1 above and in published Table 1, however, the WTRU 110 can calculate the bit position of its paging group based on the rule specified in Table 2 above.

[0031] As previously described, a WTRU 110 in idle mode wakes up on the paging occasions indicated by the PO-FN and checks the paging indicator. Based on the assigned PG ID and the bit position in the bitmap, the WTRU 110 checks whether its paging group(s) has active content, which may include whether the bit position J in the paging group bitmap is defined or not.

[0032] If the bit position is set (that is, content is indicated), the WTRU 110 reads the LTE physical channel (PDSCH) (step 360), described by the radio carrier (RB) allocation part of the indicator paging message, where an upper layer paging message will list the exact IMSI/TMSI of each of the WTRUs 110 that receives the paging message. If the WTRU 110 finds an exact match of your IMSI/TMSI, it indicates that there is a page for the WTRU 110.

[0033] Furthermore, the bitmap is defined by the E-UTRAN and is transmitted to each of the PO-GPs in the system information when the PO-GP receives this information regarding PG IDs. Only one bitmap for each PO-GP needs to be transmitted. Consequently, although WTRUs in any specific group can have variable DRX cycles, they can use the same bitmap for all PG-FNs.

[0034] In an example, an LTE paging message can be used when a WTRU receives signaling from a defined page and the exact WTRU is addressed directly to restart paging. Figure 6 is an example diagram of an example LTE 600 paging message.

[0035] As shown in Figure 6, a WTRU in frame 9 receives a paging indicator (obtained), which contains a "Paging Situation Bitmap" and a "RB allocation information (LTE resource block)" for the WTRU to receive the actual paging message (such as the LTE paging message) from another

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10/12 channel leading to actual paging message. This provides time and physical channel information. If the bitmap status bit for your paging group is not set, the WTRU may not read the actual paging message in order to conserve power.

[0036] The LTE 600 paging message contains the paging records (that is, the actual WTRU IMSIs) for each WTRU that actually received paging content. A WTRU checks the bitmap to observe its set PG ID bit and uses the RB allocation information to read the LTE 600 paging message. A WTRU determines that it receives paging messages by confirming that its IMSI is found. in the paging logs.

[0037] The number of IMSIs that can be addressed in an LTE paging message represents the LTE paging capacity at its maximum and should be designed to account for peak paging loads. If the defined IMSI conduction capacity is not large enough, certain WTRUs 110 may be left out of the paging confirmation and may not receive incoming calls in time.

[0038] In addition, the LTE paging message record should contain as many WTRU IMSIs that received paging content as possible. If the allocated RB space is limited, extensions can be made to include all paging records/IMSIs. The extension may be performed in the RB allocation portion of the paging indicator, where a pointer may indicate another RB allocation or helper for the extension of LTE paging messages. Alternatively, the extended space can be resolved in the PCH domain, where additional space can be temporarily provided for the LTE paging message extension.

[0039] Additionally, to accommodate as many IMSIs in the message as possible, signaling compression can be applied. Duplicate MCCs and MNCs do not need to be included in the message, which results in a direct list of MSINs from IMSIs in most cases, in order to save message space. Formatting the IMSI can start with the MCC and then move to the MNC and finally the MSIN. The MCC is the front index and then the MNC. If the next MCC or MNC is not

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11/12 Unlike above, they do not need to be included. A WTRU search for an IMSI match can also make use of this formatting rule, disregarding unmatched MCCs and MNCs and going directly to the matching MCC and MNC to increase the efficiency of the matching process.

[0040] Although the features and elements are described above in specific combinations, each feature or element can be used alone, without the other features and elements or in various combinations with or without other features and elements. The methods or flowcharts provided herein may be implemented in a computer program, software or firmware embedded in a computer readable storage medium for execution by a processor or general purpose computer. Examples of computer readable storage media include read-only memory (ROM), random access memory (RAM), registry, cache memory, semiconductor memory devices, magnetic media such as internal hard drives and removable disks, magneto- optical and optical media such as CD-ROM discs and digital versatile discs (DVDs).

[0041] Suitable processors include, for example, a general purpose processor, special purpose processor, conventional processor, digital signal processor (DSP), an array of microprocessors, one or more microprocessors in association with a DSP core, controller , microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gateway Assemblies (FPGAs) circuits, any other type of integrated circuit (IC) and/or state machine.

[0042] A processor in association with software can be used to implement a radio frequency transceiver for use in a wireless transmit and receive unit (WTRU), user equipment (UE), terminal, base station, network controller. radio (RNC) or any host computer. The WTRU can be used in conjunction with modules, implemented in hardware and/or software, such as a camera, video camera module, videophone, headset, vibration device, speaker, microphone, television transceiver, headset. handsfree headset, keyboard, Bluetooth® module, frequency modulated (FM) radio unit,

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12/12 liquid crystal display unit (LCD), organic light emitting diode (OLED) display unit, digital music player, media player, video game module, Internet browser and/or any network module Wireless Local Area (WLAN) or Ultra Wide Band (UWB)

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