DESC:FORM 2
THE PATENTS ACT, 1970
[39 of 1970]
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(Section 10; Rule 13)

A METHOD FOR REDUCING THE CONFLICT DURING CELL SEARCH PROCEDURE IN A MULTI SUBSCRIPTION DEVICE

SAMSUNG R&D INSTITUTE INDIA – BANGALORE PRIVATE LIMITED,
#2870, Orion Building, Bagmane Constellation Business Park,
Outer Ring Road, Doddanekundi Circle,
Marathahalli Post, Bangalore – 560037,
Karnataka, India,
an Indian Company

The following Specification particularly describes the invention and the manner in which it is to be performed

RELATED APPLICATION

The present invention claims benefit of the Indian Provisional Application No. 2052/CHE/2015 titled " A METHOD FOR REDUCING THE CONFLICT DURING CELL SEARCH PROCEDURE IN A MULTI SUBSCRIPTION DEVICE” by Samsung R&D Institute India – Bangalore Private Limited, filed on 22nd April 2015, which is herein incorporated in its entirety by reference for all purposes.

FIELD OF THE INVENTION

The present invention generally relates to Multi Subscription Device. The present invention more particularly relates to a method for reducing the conflict during cell search procedure in a multi subscription device.

BACKGROUND OF THE INVENTION

There is an increasing demand for devices that can support multiple subscriptions, thereby supporting simultaneous wireless, e.g., cellular, access with different networks, such as different public land mobile networks (PLMNs) and/or networks operated by different carriers and/or different network operators. In order to support multiple subscriptions, devices, such as mobile terminals, may include multiple SIMs. In this regard, devices that include two SIMS are often referred to as dual SIM devices. However, devices may include any number of SIMs for supporting three, four, five or more subscriptions.

In some wireless networks, a user equipment (UE) can have multiple subscriptions to one or more networks (e.g., by employing multiple subscriber identity module (SIM) cards or otherwise). Such a UE may include, but is not limited to, a dual-SIM, dual standby (DSDS) device.

In DSDS devices, the user may establish a call, such as a voice call, data call, data session, text messaging session, or any other data transfer session, via one of the two subscriptions. Because most DSDS devices contain a single radio resource, such as a transceiver, where a first subscription has established an ongoing call with a first subscription network, the UE must tune the transceiver away to a second subscription to receive necessary paging signals and to transmit, for example, message acknowledgement signals and/or measurement indication signals. Therefore, while the first subscription continues an ongoing call, the transceiver may periodically tune away from the first subscription to the second subscription to receive such necessary paging and/or control information.

In some situations, such as where the UE reselects a new cell for one of its subscription services, it needs to undertake a cell search procedure. The cell search procedure typically comprises a series of synchronization stages by which the mobile device determines parameters that are necessary to demodulate the downlink and to transmit uplink symbols with correct timing. In multi radio access technology systems, the cell search procedure is performed for a plurality of radio access technologies. For example, the multi radio access technology system may comprise GSM (Global System for Mobile communications), WCDMA (Wideband Code Division Multiple Access) and LTE (Long Term Evolution). The mobile device then undertakes the cell search for any radio access technology (RAT) it can operate and more in TDD systems where uplink and downlink switching is frequent.

In Further the cell search procedure is divided across multiple layers and the upper layers will not be able to know about the conflicts at the lower layers. The search time for one frequency can vary from technology to technology and also in time dependent upon the procedures at the lower layer.

In any DSDS device, where RF resources are shared across many SIM when Cell search procedure is initiated on one SIM, the other sim is required to perform periodic procedures like reading paging/measurements at the same time. During the scanning of frequencies, the RF may be taken away by the other SIM resulting in interruption, thereby causing a performance reduction. If multiple frequencies are being scanned during a cell search procedure, interruptions from the other SIM can cause the procedure to provide incomplete results, thus leading to a failure.

Figure 1 is a schematic flow diagram 100 illustrating periodic radio frequency (RF) interruptions during cell search, according to the existing art. According to the Figure 1, the flow diagram 100 comprises an upper layer 102, a lower layer 104 and other SIM 106. Initially, the resources are being assigned to a SIM (not shown in the figure) and the SIM can be performing any of the procedures, such as, but not limited to, a call, such as a voice call, data call, data session, text messaging session, any other data transfer session, and the like. The other SIM 106 which is idle needs RF resources to perform periodic paging searches and other related tasks. As the resources are with the other SIM 106 now, the upper layer 102 transmits a cell search request to the lower layer 104. Upon receiving the cell search request, the lower layer 104 receives periodic RF interruptions from the other SIM 106 too. Upon receiving the period RF interruptions, the lower layer 104 transmits cell search failure to the upper layer 102. The process of transmission of cell search request and cell search failure continues between the upper layer 102 and the lower 104 as the resources are with the other SIM 106.

Figure 2 is a schematic diagram 200 illustrating signaling information during cell search interruption of first SIM, according to the existing art. According to the Figure 2, initially, radio frequency (RF) resources are assigned to first SIM SIM1 and second SIM SIM2 is in idle state. During active state, the first SIM SIM1 initiates cell searching. During cell search of the SIM1, the second SIM SIM2 receives paging and measurement information and thus the resources assigned to the SIM1 are shared with SIM2. After certain period of time, the DRX cycle of SIM2 starts and thus the resources remain with the SIM2. As the resources are with SIM2, no conflict arises and the SIM1 continues to wait for the resources for performing cell search.

After particular time, a timer expires for the SIM1 as the SIM1 does not receive the resources and thus the cell search of the SIM1 gets interrupted. Again after particular time period, the SIM2 receives paging and management information, and continues accessing the resources for itself. After particular time interval, the SIM1 attempts to access the resources for cell search and identifies that the resources are still with the SIM2. Thus, the SIM1 continues to wait for the particular time period to receive the resources. Upon the expiry of the timer, the SIM1 identifies that the resources are unavailable and are with the SIM2, the cell search of the SIM1 is interrupted.

In view of the foregoing, there is a need for a system and method to reduce the conflict during cell search procedure in multi subscription devices, such as Dual SIM Dual Standby (DSDS) devices.

The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.

SUMMARY OF THE INVENTION

The various embodiments herein disclose a method for reducing the conflict during cell search procedure in a multi subscription device.

According to an embodiment of the present invention, a method of handling a cell search in a Multi-subscription device, the method comprises steps of estimating, by a first subscriber identity module (SIM) of multiple SIMs of a User Equipment (UE), a search time required for identifying one cell and a margin time for cell search, where the first SIM is associated with a first radio access technology, obtaining a Discontinuous Reception (DRX) period from a second subscriber identity module (SIM) associated with a second radio access technology in the user equipment, determining a number of cells to be searched within one DRX period, performing an Received Signal Strength Indication (RSSI) scan to determine a signal strength of one or more cells to be searched, ranking the one or more cells based on the RSSI scan, and initiating, by the first SIM, a cell search on one or more cells having a highest signal strength without any interruption from the second SIM.

According to an embodiment of the present invention, the method further comprises initiating cell search on a plurality of remaining cells within the one DRX period, and identifying the cell having the highest signal strength to complete the cell selection process.

According to an embodiment of the present invention, the one or more cells are ranked based on a Received Signal Strength Indication (RSSI) or any other available metric which indicates the quality of the received signal strength. According to an embodiment of the present invention, the one or more cells for cell searching is obtained from, but not limited to, preconfigured cell selection results, signal strength obtained by RRSI scan of a full frequency band, and the like.

According to an embodiment of the present invention, the first radio access technology and the second radio access technology are respectively selected from a group of Radio Access Technologies (RAT) comprising of Global System for Mobile Communications (GSM) and Code Division Multiple Access (CDMA), Long Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS).

According to yet another embodiment of the present invention, a method of handling a cell search in a Multi-subscription Device , the method comprises steps of estimating, by a first subscriber identity module (SIM) of multiple SIMs of a User Equipment (UE) and associated with a first radio access technology, a search time required for identifying one cell margin time , a Discontinuous Reception (DRX) cycle value and a DRX timing information from a second subscriber identity module (SIM) associated with a second radio access technology, determining a number of cells to be searched within one DRX cycle, performing a Received Signal Strength Indication (RSSI) scan to determine a signal strength associated with each of the one or more cells, ranking the one or more cells based on the RSSI scan, and initiating a cell search on one or more cells having a highest signal strength without any interruption from the second subscription.

According to an embodiment of the present invention, method further comprises transmitting, by the lower layer a message indicating a start time and a stop time of the DRX cycle an upper layer, and initiating the cell search with the received time information in case of conflict at a lower layer, wherein the time for start time and stop time of the DRX cycle is pre-stored in a reference table

The foregoing has outlined, in general, the various aspects of the invention and is to serve as an aid to better understanding the more complete detailed description which is to follow. In reference to such, there is to be a clear understanding that the present invention is not limited to the method or application of use described and illustrated herein. It is intended that any other advantages and objects of the present invention that become apparent or obvious from the detailed description or illustrations contained herein are within the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:

Figure 1 is a flow diagram representing cell search procedure, according to the prior art illustration.

Figure 2 is a schematic representation illustrating cell search procedure, according to the prior art illustration.

Figure 3 is a flow diagram representing a cell search procedure in Dual SIM Dual Standby (DSDS) devices, according to an embodiment of the present invention.

Figure 4 is a flow diagram representing cell search procedure in Dual SIM Dual Standby (DSDS) devices, according to another embodiment of the present invention.

Figure 5 is a schematic representation illustrating cell search procedure without conflicts, according to an embodiment of the present invention.

Figure 6 is an exemplary Dual SIM Dual Standby (DSDS) device, according to an embodiment of the present invention.

Although specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method for handling a cell search in a Multi-subscription Device. In the following detailed description of the embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.

The specification may refer to “an”, “one” or “some” embodiment(s) in several locations. This does not necessarily imply that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.

As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes”, “comprises”, “including” and/or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations and arrangements of one or more of the associated listed items.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The present invention discloses a method for handling a cell search in a Multi-subscription Device. The embodiments of the present invention are described with respect to dual subscriber information module (SIM) device, but the present method can be applied to any of the two, three or multiple SIM devices, without departing from the scope of the invention.

According to an embodiment of the present invention, a method for handling a cell search in a Multi-subscription Device, the method comprises step of estimating, by a first subscriber identity module (SIM) of multiple SIMs of the Multi-subscription Device, a search time required for identifying one cell and a margin time for cell search, where the first SIM is associated with a first radio access technology. The Multi-subscription Device can comprise of multiple subscriber identity modules (SIMs). The first SIM of multiple SIMs of the Multi-subscription Device can be associated with the radio access technology (RAT) of a service provider. The first SIM, associated with the first RAT, can estimate the time required for conducting search with respect to identifying one cell/ frequency and the margin time for conducting the cell search.

Further, the method comprises step of obtaining a Discontinuous Reception (DRX) period from a second subscriber identity module (SIM) associated with a second radio access technology in the Multi-subscription Device. The second SIM of the Multi-subscription Device can be associated with the second RAT and the Multi-subscription Device can receive DRX period from the second SIM. In an embodiment of the present invention, the Multi-subscription Device can receive DRX period of the second SIM after predetermined periodical intervals. In another embodiment of the present invention, the Multi-subscription Device can receive the DRX period of the second SIM dynamically as soon as the request is generated.

In another embodiment of the present invention, the first SIM and second SIM can be associated with two different RATs, first RAT and second RAT respectively. In another embodiment of the present invention, the first SIM and the second SIM can be associated with the same RAT, without departing from the scope of the invention. In an embodiment of the present invention, the first radio access technology (RAT) and the second radio access technology (RAT) are respectively selected from a group of Radio Access Technologies (RAT) comprising of Global System for Mobile Communications (GSM) and Code Division Multiple Access (CDMA), Universal Mobile Telecommunications System (UMTS), Long Term Evolution (LTE), or higher RATs, without departing from the scope of the invention.

Further, the method comprises step of determining a number of cells to be searched within one DRX period. Based on the received DRX period of the second SIM, the Multi-subscription Device can identify the number of cells to be searched.

Further, the method comprises the step of performing a Received Signal Strength Indication (RSSI) scan to determine signal strength of one or more cells to be searched. Based on the identified one or more cells, it is important to identify the cell with better signal strength among all. This can be identified based on the signal strength of the received signal from the one or more cells. Therefore, the Multi-subscription Device can perform RSSI scan on the one to more cells to determine signal strength of one or more cells to be searched. In an embodiment of the present invention, the one or more cells for cell searching can be obtained from at least one of, but not limited to, preconfigured cell selection results, signal strength obtained by RRSI scan of a full frequency band, and the like. The process of perfuming RSSI is already known to the person having ordinarily skilled in the art and hence not described in detail.

Further, the method comprises step of ranking the one or more cells based on the RSSI scan. Upon performing the RSSI scan, the Multi-subscription Device can obtain signal strengths of the cells to be searched for. Based on the obtained signal strengths, the multi-subscription device can rank the cells, wherein the one or more cells are ranked based on a Received Signal Strength Indication (RSSI) or any other available metric which indicates the quality of the received signal strength. In an embodiment of the present invention, the ranking can be given based on the cells with lowest to highest strength. In another embodiment of the present invention, the ranking can be given based on the cells with highest to lowest strength, without departing from the scope of the invention.

Further, the method comprises step of initiating, by the first SIM, a cell search on one or more cells having highest signal strength without any interruption from the second SIM. Based on the ranking of the cells, the first SIM can identify the one or more cells with highest strengths. Based on the identified cells with highest strengths, the first SIM can initiate cell search. In an embodiment of the present invention, the highest signal strengths of the one or more cells can be based on the RSSI value identified by the Multi-subscription Device, wherein the signal strength should be equal to the defined RSSI value. In another embodiment of the present invention, the Multi-subscription Device can set a threshold RSSI value and the first SIM can identify signal strengths of the one or more cells as highest signal strength if it is more than the set threshold RSSI value. In yet another embodiment of the present invention, the Multi-subscription Device can set upper and lower threshold value and the first SIM can identify and initiate cell search for the one or more cells for which the signal strength is within or equal to the upper and lower threshold RSSI values. The person having ordinarily skilled in the art can understand that cells with particular RSSI value can be selected using any of the known methods, without departing from the scope of the invention.

According to another embodiment of the present invention, the method further comprises step of initiating cell search on a plurality of remaining frequencies within the one DRX period. If the first SIM identifies cells which are not searched and still DRX period is not over, then the first SIM can initiate cell search on the remaining un-searched cells within the DRX period. Further, the method comprises step of identifying the cell having the highest signal strength to complete the cell selection process. Within the cells which were not searched, the first SIM can identify the cells with highest signal strength and can initiate cell search for the cells with highest signal strength, without departing from the scope of the invention.

According to another embodiment of the present invention, a method of handling a cell search in a Multi-subscription Device, the method comprises step of estimating, by a first subscriber identity module (SIM) of multiple SIMs of the Multi-Subscription Device and associated with a first radio access technology, a search time required for identifying one cell, a margin time, a Discontinuous Reception (DRX) cycle value and a DRX timing information from a from a second subscriber identity module (SIM) associated with a second radio access technology. The first SIM of the Multi-subscription Device can be associated with the first RAT and can estimate search time required for identifying one cell along with the margin time, the DRX cycle value, and the DRX timing information of the second SIM, wherein the second SIM can be associated with the second RAT. According to an embodiment described herein above, the first SIM and the second SIM can be associated with the first RAT and second RAT respectively or can be associated with the same RAT, without departing from the scope of the invention.

Further, the method comprises step of determining a number of cells to be searched within one DRX cycle. Further, the method comprises step of performing a Received Signal Strength Indication (RSSI) scan to determine signal strength associated with each of the one or more cells. The person having ordinarily skilled in the art can understand that any of the known methods can be used to perform RSSI and determine signal strengths of the one or more cells, without departing from the scope of the invention. Further, the method comprises step of ranking the one or more cells based on the RSSI scan. Further, the method comprises step of initiating a cell search on one or more cells having highest signal strength without any interruption from the second subscription.

According to an embodiment of the present invention, the method further comprises step of transmitting, by the lower layer a message indicating a start time and a stop time of the DRX cycle an upper layer. Further, the method comprises step of initiating the cell search with the received time information in case of conflict at a lower layer, wherein the time for start time and stop time of the DRX cycle is pre-stored in a reference table.

Figure 3 is a flow diagram 300 representing cell search procedure, according to an embodiment of the present invention. According to the Figure 3, the flow diagram comprises an upper layer 302, a lower layer 304 and other SIM 306. According to the flow diagram 300, the upper layer 302 can estimate search time for one frequency TFS and margin time. Based on the estimated search time and margin time, DRX Cycle value information can be obtained from the other SIM 306 and exchanged with the upper layer 302. The DRX cycle can vary based on the type of technology, country, network operator or any other parameter. The UE also may use a pre stored table with specific number of entries for the peer sim DRX cycle. In case there are more than two SIM, the UE may use the minimum of all the values of the DRX cycle of the peer SIMs. Once the DRX cycle value is available, the number of frequencies N that are to be searched in one DRX Period TDRX of the peer SIM can be estimated using the formula Estimate N = (TDRX .- Margin)/ TFS. In an embodiment of the present invention, the number N may also be pre-configured to restrict the search to a specific number of frequencies applicable to all possible DRX cycles.

Further, an initial received signal strength indication (RSSI) scan can be performed and the frequencies can be ranked according to a pre-specified metric. In another embodiment of the present invention, any of the known scanning method that provides frequencies with ranks as metric corresponding to the specific Radio access technology can be used, without departing from the scope of the invention. Once the ranking is done cell search on the N best frequencies is requested in order to perform the cell search without any interruption from the other SIM. If there are any RF interruptions in the other SIM 306, then the cell selection on the remaining frequencies can be repeated at the upper layer 302 to complete the cell selection process on the best cell. The upper layer 302 can transmits request to the lower layer 304 for cell search for N best remaining frequencies. If any RF interruptions are still observed at the other SIM 306, then the upper layer 302 can complete the cell selection process on the best cell from the results of all the frequencies. According to the proposed solution, when the DRX timing information is not available at the upper layer 302, the lower layer 304 will retry the request from the upper layer in case of RF conflict.

Figure 4 is a flow diagram 400 representing cell search procedure, according to another embodiment of the present invention. According to the present invention, the Figure 4 comprises of an upper layer 402, a lower layer 404, and other SIM 406. According to the flow diagram 400, the search time for one frequency TFS, margin time, DRX time and DRX timing information of the other SIM can be estimated by the upper layer 402 and also, the number of frequencies is estimated using the formula Estimate N = (TDRX .- Margin)/ TFS, which can be searched as mentioned in the first embodiment. Further, the initial RSSI scan can be performed to rank the frequencies obtained from the lower layer 404 according to the available metric. Once the ranking is done, the cell search on the N best frequencies is requested by the upper layer 402 to the lower layer 404 in order to perform the cell search without any interruption from the other SIM. If any RF interruptions are observed on the other SIM 406, then the cell selection on the remaining frequencies is repeated to complete the cell selection process on the best cell. Any cell search or scan procedure is synchronized with the timing information received from the peer SIM. This avoids any conflict at the lower layers when the cell search procedure is ongoing.

According to the present invention, the method for reducing conflicts during cell search in multi subscription devices is as follows. Firstly, search time for one frequency from the lower layer, margin time required for other L1 procedures is estimated. Based on the estimation, the DRX value of the other RAT is acquired after which the number of frequencies N to be searched is estimated within one DRX cycle. Further, the start of the cell search procedure is tuned to the DRX cycle of the other SIM at the upper layer.

Once the tuning is done, an Initial scan is performed on the frequencies to choose the best N frequencies. Frequencies can be acquired from previously stored cell selection results or from a full band scan. After choosing the best N frequencies, the cell search is repeated till all the frequencies are completed. In this method, the start and stop of the DRX cycle is indicated by exchanging messages and the mechanism is retried with time information in case of conflict at the lower layers. The time information is indicated by the lower layer to the upper layer, so that the cell search can be adjusted from the upper layer with the DRX cycle from the next cycle onwards. Once the frequencies searches are done, the selection procedure on the best cell is completed.

Figure 5 is a schematic representation 500 illustrating cell search procedure without conflicts, according to an embodiment of the present invention. According to the schematic representation 500, initially paging and measurement cycle of SIM 2 is ongoing while SIM1 is waiting for the resources. Upon completion of the paging and measurement cycle, the SIM2 will go into idle mode and DRX cycle SIM2 commences. After particular time period, cell search procedure for SIM1 commences, wherein the SIM1 searches for the cells with best strength based on the RSSI scan. The SIM1 identifies the best cell and completes the cell search within no conflict duration. As soon as the cell search is completed, the resources are free and again at the predetermined period, the SIM2 commences paging and measurement, without any hindrance. The same procedure follows for the fore coming cell searches from SIM1.

Figure 6 is an exemplary Dual SIM Dual Standby (DSDS) device 600, according to an embodiment of the present invention. According to the Figure 7, the Dual SIM Dual Standby (DSDS) device 600 comprises of a first SIM SIM1 602, a second SIM SIM2 604, a processor 606, and a storage unit 608. The first SIM SIM1 602 and the second SIM SIM2 604 can be dual SIMs which can be associated with same or same radio access technologies (RATs) and camped on same or different cells, without departing from the scope of the invention.

The processor 606 assists the first SIM SIM1 602 in estimating a search time required for identifying one cell and a margin time for cell search, where the first SIM is associated with a first radio access technology. Further, the processor 606 obtains a Discontinuous Reception (DRX) period from the second SIM SIM2 604 associated with a second radio access technology. Further, the processor 606 determines a number of cells to be searched within one DRX period. Further, the processor 606 performs a Received Signal Strength Indication (RSSI) scan to determine signal strength of one or more cells to be searched. Based on the RSSI scan performed, the processor 606 ranks the one or more cells based on the RSSI scan. Further, the processor 606 and assists the first SIM 602 for initiating a cell search on one or more cells having highest signal strength without any interruption from the second SIM. The storage unit 608 store instructions, which are executable by the processor 606 such that the Dual SIM Dual Standby (DSDS) device 600 is operable to perform handling cell search process, as described herein above with respect to Figures 3-5, without departing from the scope of the invention.

The present embodiments have been described with reference to specific example embodiments; it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the various embodiments. Furthermore, the various devices, modules, and the like described herein may be enabled and operated using hardware circuitry, for example, complementary metal oxide semiconductor based logic circuitry, firmware, software and/or any combination of hardware, firmware, and/or software embodied in a machine readable medium. For example, the various electrical structure and methods may be embodied using transistors, logic gates, and electrical circuits, such as application specific integrated circuit.

Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

,CLAIMS:CLAIMS

WE CLAIM:

1. A method of handling cell search in a Multi-subscription Device, the method comprises of:
estimating, by a first subscriber identity module (SIM) of multiple SIMs of the multi-subscription device, a search time required for identifying one cell and a margin time for cell search, where the first SIM is associated with a first radio access technology;
obtaininga Discontinuous Reception (DRX) period from a second subscriber identity module (SIM) associated with a second radio access technology in the multi-subscription device;
determininga number of cells to be searched within one DRX period;
performing , a Received Signal Strength Indication (RSSI) scan to determine a signal strength of one or more cells to be searched;
ranking the one or more cells based on the RSSI scan; and
initiatinga cell search on one or more cells having a highest signal strength without any interruption from the second SIM.

2. The method of claim 1, further comprising:
initiating cell search on a plurality of remaining cells within the one DRX period; and
identifying the cell having the highest signal strength to complete the cell selection process.

3. The method of claim 1, wherein the one or more cells are ranked based on a Received Signal Strength Indication (RSSI) or any other available metric which indicates the quality of the received signal strength.

4. The method of claim 1, wherein the one or more cells for cell searching is obtained from:
preconfigured cell selection results; or
signal strength obtained by RRSI scan of a full frequency band.

5. The method of claim I, wherein the first radio access technology and the second radio access technology are respectively selected from a group of Radio Access Technologies (RAT) comprising of Global System for Mobile Communications (GSM) and Code Division Multiple Access (CDMA), Long Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS).

6. A method of handling a cell search in a Multi-subscription Device, the method comprises of:
estimating, by a first subscriber identity module (SIM) of multiple SIMs of the multi-subscription device and associated with a first radio access technology, a search time required for identifying one cell, a margin time , a Discontinuous Reception (DRX) cycle value and a DRX timing information from a from a second subscriber identity module (SIM) associated with a second radio access technology;
determining a number of cells to be searched within one DRX cycle;
performing a Received Signal Strength Indication (RSSI) scan to determine a signal strength associated with each of the one or more cells;
ranking the one or more cells based on the RSSI scan; and
initiating a cell search on one or more cells having a highest signal strength without any interruption from the second subscription.

7. The method of claim 1 further comprising:
transmitting, by the lower layer, a message indicating a start time and a stop time of the DRX cycle an upper layer; and
initiating the cell search with the received time information in case of conflict at a lower layer, wherein a start time and a stop time of the DRX cycle is pre-stored in a reference table.

8. A Multi-subscription Device comprising:
a first subscriber identity module (SIM) of multiple SIMs of the Multi-subscription Device adapted for:
estimating a search time required for identifying one a cell, a margin time , a Discontinuous Reception (DRX) cycle value and a DRX timing information from a second subscriber identity module (SIM) associated with a second radio access technology;
determining a number of cells to be searched within one DRX cycle; and
initiating a cell search on one or more cells having a highest signal strength without any interruption from the second subscription;
a second subscriber identity module (SIM) of multiple SIMs of the Multi-subscription Device; and
a processor adapted for:
performing a Received Signal Strength Indication (RSSI) scan to determine a signal strength associated with each of the one or more cells; and
ranking the one or more cells based on the RSSI scan.

Dated this the 22nd day of March 2016
Signature

KEERTHI J S
Patent agent
Agent for the applicant