Title of Invention	A METHOD AND SYSTEM FOR ENABLING A MOBILE COMMUNICATIONS DEVICE TO TRANSITION FROM A FIRST NETWORK TO A SECOND NETWORK
Abstract	A communications system (10) includes a wireless telephony network (12) and a wireless Local Area Network (LAN) (14), both accessible by a mobile communications device (16). To facilitate transitioning of the mobile communications device to the wireless LAN from the wireless telephony network, the wireless LAN includes a beacon transmitter (30), which generates a synchronization channel having a pattern unique to the wireless LAN. The Wireless LAN synchronization channel is received at a first receiver in the mobile communications device together with a synchronization channel from the wireless telephony. The wireless LAN synchronization channel enables the mobile communication device to synchronize with, for transitioning to, the wireless LAN.

Title of Invention

A METHOD AND SYSTEM FOR ENABLING A MOBILE COMMUNICATIONS DEVICE TO TRANSITION FROM A FIRST NETWORK TO A SECOND NETWORK

Abstract

A communications system (10) includes a wireless telephony network (12) and a wireless Local Area Network (LAN) (14), both accessible by a mobile communications device (16). To facilitate transitioning of the mobile communications device to the wireless LAN from the wireless telephony network, the wireless LAN includes a beacon transmitter (30), which generates a synchronization channel having a pattern unique to the wireless LAN. The Wireless LAN synchronization channel is received at a first receiver in the mobile communications device together with a synchronization channel from the wireless telephony. The wireless LAN synchronization channel enables the mobile communication device to synchronize with, for transitioning to, the wireless LAN.

Full Text	TECHNICAL FIELD This invention relates to a technique for enabling a mobile communications device to transition from a first wireless communications network to a second network. BACKGROUND ART Wireless telephony technology continues to evolve over time. Most recently, the European Telecommunications Standards Institute (ETSI) has promulgated a new standard for mobile telephony service, known as "Universal Mobile Telecommunications Service" or UMTS which offers broadband, packet-based transmission of voice, text, video and multimedia information at rates as high as 2 Mbs. The proposed UMTS standard describes a wireless network that includes one or more radio access nodes, each typically referred to as a "Node B." One or more Radio Network Controllers (RNC) exist within the UMTS network to manage the radio access nodes. Each RNC has a broadband connection, typically in the form of an Asynchronous Transport Mode (ATM) Link, to a UMTS core network that provides Authorization, Authentication and Accounting (AAA) Functions. Advances in the field of wireless LAN technology have resulted in the emergence of publicly accessible wireless LANs (e.g., "hot spots") at rest stops, cafes, libraries and similar public facilities. Presently, wireless LANs offer mobile communications device users access to a private data network, such as a Corporate Intranet, or a public data network such as the Internet. The relatively low cost to implement and operate a wireless LAN, as well as the available high bandwidth (usually in excess of 10 Megabits/second) makes the wireless LAN an ideal access mechanism through which the mobile communications device user can exchange packets with an external entity. Given the lower access cost and higher bandwidth afforded by wireless LANs, users of mobile communications devices often find it advantageous to transition from a wireless telephony network, such as the UMTS network, to a wireless LAN. To that end, many present day wireless LAN operators provide coverage areas that overlap the coverage area of a UMTS network. Also, many mobile communication device manufacturers will include a dual protocol stack within the device to enable the device user to transition between networks. Ideallj, transitioning from the wireless telephone network to the wireless LAN (and vice versa) should'occur seamlessly, i.e., without any loss of communications. To achieve a seamless transition from a UMTS network to the wireless LAN, the mobile communications device must i ! j first detect entry into the coverage area of the wireless LAN before undertaking a handoff from i: t the wireless telephony network to the wireless LAN, Presently, the mobile communications device undertakes detection of a wireless LAN by operating a second receiver tuned to the wireless LAN while a first receiver remains tuned to the wireless telephony network. Continuously operating both the first and second receivers concurrently consumes battery resources in the mobile communications device, often a precious commodity. Thus, there is a need for a technique for enabling a mobile communications device to seamlessly transition from one wireless network to another while overcoming the aforementioned disadvantage of the prior art. v t BRIEF SUMMARY OF THE INVENTION Briefly, in accordance with the present principles, there is provided a technique for ! • enabling a mobile communications device to transition from a first wireless communications network, such as a wireless telephony network, to a second wireless network, such as a wireless LAN. To enable such a transition, a synchronization signal (hereinafter referred to as the "second network synchronization signal") is generated in the second wireless network with a synchronization pattern that is unique to that network. In other words, the second network synchronization signal is readily distinguishable from a first network synchronization signal generated by the first network. The second wireless network broadcasts the second network synchronization signal for receipt by a common receiver in the mobile communications device that also receives the first network synchronization .signal. Upon receipt of the second network synchronization signal, the mobile communications device can establish a cornmunicationsession with the second wireless network to enable a transition thereto from the first wireless communications network. Transmitting the second network synchronization signal for receipt at the same receiver in the mobile communications device that receives the first network synchronization signal obviates the need to continuously operate two separate receivers, thus reducing the consumption of battery resources. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 depicts a block schematic diagram of a first wireless communications network interworked with a second wireless communications network; FIGURE 2 depicts a block schematic diagram of the details of the second wireless communications network modified in accordance with the present principles; FIGURE 3 depicts a first embodiment of a synchronizing signal for synchronizing a mobile communications device with the second wireless communications network of FIGS. 1 and 2; and FIGURE 4 depicts a second embodiment of a synchronizing signal for synchronizing a mobile communications device with the second wireless communications network of FIGS. 1 and 2. DETAILED DESCRIPTION FIGURE 1 depicts a block schematic diagram of a communications system 10 that includes a first wireless communication network 1.2 interworked with a second wireless communication network 14 for providing communications services to one or more mobile communications devices, exemplified by device 16. In practice, the mobile communications device 16 can comprise a wireless telephony handset, a wireless Personal Data Assistant (PDA) or a personal computer having a wireless modem. In the illustrated embodiment, the first wireless communications network 12 comprises a wireless telephony network having an architecture in conformance with the well-known Universal Mobile Telephone (i.e., 3G) standard. To that end, the wireless telephony network 12 includes at least one, and preferably, a plurality of radio access nodes 18 (each typically referred to as a "node B"), each node providing wireless telephony service within a corresponding area (cell) 20. The wireless telephony network 12 of FIG. 1 also includes at least one Radio Node Controller (RNC) 22 for controlling one or more of the plurality of radio access nodes 18. Depending on the number cells 20 and hence, the number of radio access nodes 18, the wireless telephony network 12 could include a plurality of RNCs 22. Each RNC 22 is controlled by a core network 24 that typically includes at least a Serving Gateway Service Node (SGSN) (not shown) that provides Authentication, Authorization and Accounting (AAA) functions within the core network. The second wireless network 14 may be partially or fully overlaid by a first one of the cells 20, with FIG. 1 depicting a fully overlaid cell 20. Referring to FIG. 2, the second wireless communications network 14 typically takes the form of a wireless LAN that includes one or more access points 26. Each access point 26 within the wireless LAN 14 includes a radio transceiver (not shown) for transmitting RF signals to, and for receiving"RF"signals from'the mobile communications device 16. In practice, one or more of the access points 26 of the wireless LAN 14 reside within one of the cells 20 of the wireless telephony network 12 of FIG. 1. Thus, the mobile communications device 16, while resident in a cell 20, will enter the coverage area of one of the access points 26 of the wireless LAN 14 and can initiate a communications session with the wireless LAN. Ideally, the transition (hand off) of the mobile communications device 16 from the wireless telephony network 12 of FIG. 1 to the wireless LAN 14 illustrated in FIG. 2 should occur seamlessly. In other words, the capability should exist for the mobile communications device 16 to establish a communications session with the wireless LAN 16 while the device remains in communications with the wireless telephony network 12 of FIG. 1. In order for the mobile communications device 16 to establish a communications session with the wireless LAN 14, the device must have the ability to detect the presence of the wireless LAN. Traditionally, the mobile communications device 16 has continuously operated two protocol stacks, and two receivers (not shown), one tuned to the wireless telephony network 12, and the other tuned to the wireless LAN 14, In this way, the mobile communications device can detect the presence of the wireless LAN while still in communications with the wireless telephone network. This approach to achieving seamless transitioning between networks, while effective, nonetheless requires the continuous use of two separate receivers, and the attendant consumption of precious battery power. In accordance with the present principles, seamless transitioning can be effected without the need to operate two separate receivers simultaneously within the mobile communications device 16. To enable the communications device 16 to detect the presence of the wireless LAN 14 by means of a first receiver (not shown) .in the device, the wireless LAN 14 includes a basic transmitter 30 that transmits an identifying signal at the same frequency as a synchronizing signal transmitted by the wireless telephony network 12. The identifying signal transmitted by the transmitter 30 of FIG. 2 has a format compatible with the wireless telephony network 12 but is unique to the wireless LAN 14, thereby avoiding interference with the synchronizing signal from the wireless telephony network 12. In practice, the identifying signal transmitted by the transmitter 30 of FIG. 2 has a signal strength corresponding to the coverage of the wireless LAN 14, The identifying signal transmitted by the transmitter 30 of FIG. 2 can take one of several lorms. Referring to FIG. 3, the signal from the transmitter 30 of FIG. 2 can take the form of a Primary Synchronization Channel (P-SCH) corresponding to a downlink signal transmitted in the wireless telepTioriy network I2"for effecting synchronization at the outset of a cell search. The P- SCH signal depicted in FIG. 3 comprises a periodic synchronizing code having fifteen slots per frame, each frame being typically 10 ms in length. The synchronizing code is the same for each slot and has a format unique to the wireless LAN 14 so that the mobile communications device, upon receiving the code can specifically identify the wireless LAN 14 of FIG. 2. In practice, the mobile communications device 16 establishes the identity of the wireless LAN 14 by matching the characteristics of the received P-SCH channel to one of a plurality of stored patterns in memory, each pattern corresponds to a particular wireless network technology. Once the mobile communications device 16 establishes the identity of the wireless LAN 14, the device stops the search for a match. Thereafter, the mobile communications device 16 initiates operation of a second receiver dedicated to the associated wireless LAN radio technology to effect the transition from the wireless telephony network 12 of FIG. 1. In the illustrated embodiment, the Frequency Division Duplex (FDD) mode is assumed when the wireless telephony network 12 embodies WCDMA technology. In a wireless telephony network embodying TDMA technology, the Time Division Duplex (TDD) mode or a similar mechanism would apply. As an alternative solution, the transmitter 30 could transmit a Secondary Synchronization Channel (S-SCH) as seen in FIG. 4 which is comparable to the downlink signal transmitted by the wireless telephony network 12 of FIG. 1 to effect frame synchronization and scrambling code detection as part of the cell search operation. In practice, the S-SCH channel corresponds to the repetition of a sequence of fifteen Secondary Synchronization codes (SSCs). Each code is chosen among sixteen such codes and is modulated within a given time slot. There exist sixty-four different possible combinations (or SSC sequences), each sequence corresponding to a separate scrambling code group and each having the same duration as the collective fifteen slots of a radio frame. Upon receipt of the SSC sequence, the first receiver in the mobile communications device 16 matches the sequence to a corresponding stored value indicative of the scrambling code group. Thereafter, the first receiver in the mobile communications device 16 finds the scrambling code group and becomes frame synchronized to the basic transmitter 30. After finding the scrambling code group, the first receiver within the mobile communications device 16 looks for a primary CPICH (Common Pilot Channel) channel that carries a well-specified bit sequence that is the same for all cells. From knowledge of the scrambling code group, the receiver will attempt a match to the CPICH channel bit sequence to .;(.'• the stored value (1 among 8 possible sequences). In this way, the first receiver will detect the wireless LAN 14. The wireless LAN detection mechanism is based on the reservation of a scumbling code (the combination of a scrambling code group and a scrambling code in that group) allocated for inter-working of the wireless LAN 14 of FIG. 2 with the wireless telephony network 12 of FIG. 1. In case the'operator of jhe wireless LAN 14 implements more than one wireless LAN technology, the above-described detection mechanism requires enhancement in one of the two ways: First Solution- -! • Each new wireless LAN inter-working technology receives its own scrambling code. Standardization of this'Solution could prove potentially problematic since the number of downlink primary scrambling codes is limited. Second Solution: • After recognition of this wireless LAN scrambling code, the mobile communication device 16 will go through an extra step to identify the radio technology of the wireless LAN by looking for the Primary Common Control Physical Channel (P-CCPCH) that carries system information. The P-CCPCH channel has a well-specified channelization code and thus can bring a new type of system message that will allow the mobile communications device 16 to discover the type of wireless LAN cell it is entering. t\In order to implement the second solution, the following are required: • The mobile communications device 16 must monitor listed cells (including the wireless LAN 14). To identify a cell, the mobile communications device 16 must identify its primary scrambling code (one among 512). This solution works as long as the cell belongs to the monitored list. Typically, the mobile communications device 16 is constrained in terms of the maximum numbers of cells the device can measure in parallel. - ' ' i , i ; , :. • Once it detects the wireless LAN 14, the mobile communications device 16 stops searching for cells and no longer performs any measurement, nor does it signal the presence of any subsequently detected cell to its corresponding cell controller. After being detected, the wireless LAN 14 manages future communication with the mobile communications device 16. Ideally, there should be standardization of the scrambling codes dedicated to wireless LAN technology by the 3GPP standardization body or the like. In addition, there should also be standardization of the message format and content. Although standardization of the message format and content isn't mandatory, such standardization will assure that all mobile terminals will be compliant regardless of the network operator. ,i The foregoing describes a technique for enabling a mobile communications device to seamlessly transition-from a wireless telephony network to a wireless LAN without unnecessary consumption of battery resources. We claim:- 1. A recording medium including recorded data, comprising: a control data area comprising pits formed along tracks, with data recorded therein, wherein pits in some portions of the tracks are formed as wobbled pits, pits in other portions of the tracks of the control data area are formed as straight pits, and the wobbled pits are formed intermittently and alternately with the straight pits within the control data area, wherein control information is encoded along the wobbled pits in such a way that data bit "0" and "1" comprising the control information are represented by a transition within a predetermined period of the wobbled pits and each data bit is distinguished from each other by the transition direction within the predetermined period, and wherein the control data area comprises a plurality of data units, and the wobbled pits are formed in at least one data unit preceded by the straight pits or followed by the straight pits. 2. The recording medium as claimed in claim 1, wherein the control information comprises protection information used for controlling at least one of reproduction and recording of main data. 3. The recording medium as claimed in claim 2, wherein the protection information is repeatedly encoded in plural arrays of the wobbled pits. 4. The recording medium as claimed in claim 1, wherein the control information in the control data area is recorded along the wobbled pits while being encoded by bi-phased modulation. 5. The recording medium as claimed in claim 1, wherein the control data area comprises arrays of the wobbled pits and arrays of the strait pits periodically. 6. The recording medium as claimed in claim 1, wherein arrays of the wobbled pits and arrays of the straight pits in the control data area are of different length. 7. The recording medium as claimed in claim 1, comprising: a main data area comprising main data recorded with modulation in straight pits formed along tracks. 8. The recording medium as claimed in claim 1, wherein the wobbled pits are formed in more than two data units different from a first data unit. 9. The recording medium as claimed in claim 8, wherein the plurality of data units comprise one address unit, and the wobbled pits are formed in more than two data units different from the first data unit within the address unit. 10. The recording medium as claimed in claim 9, wherein the wobbled pits are formed in a plurality of address units. 11. A method of forming a recording medium, comprising: forming pits in a control data area along tracks, with data recorded therein, wherein pits in some portions of the tracks are formed as wobbled pits, pits in other portions of the tracks of the control data area are formed as straight pits, and the wobbled pits are formed intermittently and alternately with the straight pits within the control data area, wherein the step of forming pits comprises encoding control information along the wobbled pits in such a way that data bit "0" and "1" comprising the control information are represented by a transition within a predetermined period of the wobbled pits and each data bit is distinguished from each other by the transition direction within the predetermined period, and wherein the control data area comprises a plurality of data units, and the step of forming pits comprises forming the wobbled pit in at least one data unit preceded by the straight pits or followed by the straight pits. 12. The method as claimed in claim 11, wherein the control information comprises protection information used for controlling at least one of reproduction and recording of main data. 13. The method as claimed in claim 12, wherein the step of encoding control information repeatedly encodes the same protection information in plural arrays of the wobbled pits. 14. The method as claimed in claim 11, wherein the step of encoding control information encodes the wobbled pits by bi-phased modulation. 15. The method as claimed in claim 11, wherein the control data area comprises arrays of the wobbled pits arid arrays of the strait pits periodically. 16. The method as claimed in claim 11, wherein the step of forming pits forms arrays of the wobbled pits and arrays of the straight pits having different lengths respectively in the control data area. 17. The method as claimed in claim 11, wherein the step of forming pits forms the wobbled pits in more than two data units different from a first data unit. 18. The method as claimed in claim 17, wherein the step of forming pits comprises comprising the plurality of data units into one address unit, and wherein the wobbled pits are formed in more than two data units different from the first data unit within the address unit. 19. The method as claimed in claim 18, wherein the wobbled pits are formed in a plurality of address units. 20. A method of reproducing data from are recording medium, comprising: detecting data recorded in pits formed along tracks in a control data area, wherein pits in some portions of the tracks are formed as wobbled pits, pits in other portions of the tracks of the control data area are formed as straight pits, and the wobbled pits are formed intermittently and alternately with the straight pits within the control data area, wherein the step of detecting data comprises detecting control information encoded along the wobbled pits, data bit "0" and "1" comprising the control information are represented by a transition within a predetermined period of the wobbled pits and each data bit is distinguished from each other by the transition direction within the predetermined period, and wherein the control data area comprises a plurality of data units, and the step of detecting control information comprises detecting the wobbled pits from at least one data unit preceded by the straight pits or followed by the straight pits; and utilizing the control information to reproduce main data recorded with modulation in straight pits formed along tracks of a main data area of the recording medium. 21. The method as claimed in claim 20, wherein the step of detecting data comprises: converting signals reflected from the wobbled pits into electrical signals; and extracting the control information by applying the electrical signals to a logic circuit. 22. The method as claimed in claim 21, comprising: reproducing the main data using the control information, and outputting the reproduced main data. 23. The method as claimed in claim 20, wherein the step of detecting control information detects the control information recorded in pits from a difference signal between a right and a left electric signals, generated by a beam reflected from the pits formed along the tracks. 24. The method as claimed in claim 23, wherein the step of detecting data detects the main data from a high-frequency electric signal generated by a beam reflected from the straight pits. 25. The method as claimed in claim 20, wherein the control information comprises protection information for controlling at least one of reproduction and recording of main data, and wherein the step of detecting control information detects the protection information. 26. The method as claimed in claim 20, wherein the step of detecting control information detects the control information recorded in the wobbled pits by bi-phased modulation, in the control data area. 27. The method as claimed in claim 20, wherein the step of detecting pits detects arrays of the wobbled pits and arrays of the straight pits having different lengths respectively in the control data area. 28. The method as claimed in claim 20, wherein the step of detecting control information comprises detecting the wobbled pits formed in more than two data units different from a first data unit. 29. The method as claimed in claim 28, wherein the plurality of data units comprise one address unit, and wherein the step of detecting control information comprises detecting the wobbled pits formed in more than two data units different from the first data unit within the address unit. 30. The method as claimed in claim 29, wherein the wobbled pits are formed in a plurality of address units, and wherein the step of detecting control information comprises detecting the wobbled pits formed in the plurality of address units. 31. An apparatus for reproducing data from a recording medium, said apparatus comprising: a detection unit configured to detect data recorded in pits formed along tracks in a control data area, with data recorded therein, wherein pits in some portions of the tracks are formed as wobbled pits, pits in other portions of the tracks of the control data area are formed as straight pits, and the wobbled pits are recorded intermittently and alternately with the straight pits, wherein control information is encoded along the wobbled pits in such a way that data bit "0" and "1" comprising the control information are represented by a transition within a predetermined period of the wobble pits and each data bit is distinguished from each other by the transition direction within the predetermined period, wherein the control data area comprises a plurality of data units, and the wobbled pits are formed in at least one data unit preceded by the straight pits or followed by the straight pits, and wherein the detection unit converts signals reflected from the pits into electric signals; and a signal processor, coupled to the detection unit, configured to process the electric signals to generate the control information and to process main data recorded with modulation in straight pits formed along tracks of a main data area of the recording medium. 32. The apparatus as claimed in claim 31, wherein the signal processor is configured to generate the control information from low-frequency components and generate the main data from high-frequency components. 33. The apparatus as claimed in claim 31, comprising: a controller, coupled to said detection unit and said signal processor, configured to control the detection of the control information and the processing of the main data, wherein the controller is configured to control said signal processor to output the main data based on the control information. 34. The apparatus as claimed in claim 33, wherein the controller is configured to control said detection unit to detect the control information by a push-pull method. 35. The apparatus as claimed in claim 33, wherein the control information comprises protection information used for controlling at least one of reproduction and recording of the main data, and wherein the controller is configured to control the reproduction of the main data in response to the protection information. 36. The apparatus as claimed in claim 31, wherein the detection unit is configured to detect the wobbled pits formed in more than two data units different from a first data unit. 37. The apparatus as claimed in claim 36, wherein the plurality of data units comprise one address unit, and wherein the detection unit is configured to detect the wobbled pits formed in more than two data units different from the first data unit within the address unit. 38. The apparatus as claimed in claim 37, wherein the wobbled pits are formed in a plurality of address units, and wherein the detection unit is configured to detect the wobbled pits formed in the plurality of address units.

Full Text

TECHNICAL FIELD
This invention relates to a technique for enabling a mobile communications device to transition from a first wireless communications network to a second network.
BACKGROUND ART
Wireless telephony technology continues to evolve over time. Most recently, the European Telecommunications Standards Institute (ETSI) has promulgated a new standard for mobile telephony service, known as "Universal Mobile Telecommunications Service" or UMTS which offers broadband, packet-based transmission of voice, text, video and multimedia information at rates as high as 2 Mbs. The proposed UMTS standard describes a wireless network that includes one or more radio access nodes, each typically referred to as a "Node B." One or more Radio Network Controllers (RNC) exist within the UMTS network to manage the radio access nodes. Each RNC has a broadband connection, typically in the form of an Asynchronous Transport Mode (ATM) Link, to a UMTS core network that provides Authorization, Authentication and Accounting (AAA) Functions.
Advances in the field of wireless LAN technology have resulted in the emergence of publicly accessible wireless LANs (e.g., "hot spots") at rest stops, cafes, libraries and similar public facilities. Presently, wireless LANs offer mobile communications device users access to a private data network, such as a Corporate Intranet, or a public data network such as the Internet. The relatively low cost to implement and operate a wireless LAN, as well as the available high bandwidth (usually in excess of 10 Megabits/second) makes the wireless LAN an ideal access mechanism through which the mobile communications device user can exchange packets with an external entity.
Given the lower access cost and higher bandwidth afforded by wireless LANs, users of mobile communications devices often find it advantageous to transition from a wireless telephony network, such as the UMTS network, to a wireless LAN. To that end, many present day wireless LAN operators provide coverage areas that overlap the coverage area of a UMTS network. Also, many mobile communication device manufacturers will include a dual protocol stack within the device to enable the device user to transition between networks.
Ideallj, transitioning from the wireless telephone network to the wireless LAN (and vice versa) should'occur seamlessly, i.e., without any loss of communications. To achieve a seamless
transition from a UMTS network to the wireless LAN, the mobile communications device must
i ! j
first detect entry into the coverage area of the wireless LAN before undertaking a handoff from
i: t
the wireless telephony network to the wireless LAN, Presently, the mobile communications device undertakes detection of a wireless LAN by operating a second receiver tuned to the wireless LAN while a first receiver remains tuned to the wireless telephony network. Continuously operating both the first and second receivers concurrently consumes battery resources in the mobile communications device, often a precious commodity.
Thus, there is a need for a technique for enabling a mobile communications device to seamlessly transition from one wireless network to another while overcoming the aforementioned disadvantage of the prior art.
v t
BRIEF SUMMARY OF THE INVENTION
Briefly, in accordance with the present principles, there is provided a technique for
! •
enabling a mobile communications device to transition from a first wireless communications network, such as a wireless telephony network, to a second wireless network, such as a wireless LAN. To enable such a transition, a synchronization signal (hereinafter referred to as the "second network synchronization signal") is generated in the second wireless network with a synchronization pattern that is unique to that network. In other words, the second network synchronization signal is readily distinguishable from a first network synchronization signal generated by the first network. The second wireless network broadcasts the second network synchronization signal for receipt by a common receiver in the mobile communications device that also receives the first network synchronization .signal. Upon receipt of the second network synchronization signal, the mobile communications device can establish a cornmunicationsession with the second wireless network to enable a transition thereto from the first wireless communications network. Transmitting the second network synchronization signal for receipt at the same receiver in the mobile communications device that receives the first network synchronization signal obviates the need to continuously operate two separate receivers, thus reducing the consumption of battery resources.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 depicts a block schematic diagram of a first wireless communications network interworked with a second wireless communications network;
FIGURE 2 depicts a block schematic diagram of the details of the second wireless communications network modified in accordance with the present principles;
FIGURE 3 depicts a first embodiment of a synchronizing signal for synchronizing a mobile communications device with the second wireless communications network of FIGS. 1 and 2; and
FIGURE 4 depicts a second embodiment of a synchronizing signal for synchronizing a mobile communications device with the second wireless communications network of FIGS. 1 and 2.
DETAILED DESCRIPTION
FIGURE 1 depicts a block schematic diagram of a communications system 10 that includes a first wireless communication network 1.2 interworked with a second wireless communication network 14 for providing communications services to one or more mobile communications devices, exemplified by device 16. In practice, the mobile communications device 16 can comprise a wireless telephony handset, a wireless Personal Data Assistant (PDA) or a personal computer having a wireless modem. In the illustrated embodiment, the first wireless communications network 12 comprises a wireless telephony network having an architecture in conformance with the well-known Universal Mobile Telephone (i.e., 3G) standard. To that end, the wireless telephony network 12 includes at least one, and preferably, a plurality of radio access nodes 18 (each typically referred to as a "node B"), each node providing wireless telephony service within a corresponding area (cell) 20.
The wireless telephony network 12 of FIG. 1 also includes at least one Radio Node Controller (RNC) 22 for controlling one or more of the plurality of radio access nodes 18. Depending on the number cells 20 and hence, the number of radio access nodes 18, the wireless telephony network 12 could include a plurality of RNCs 22. Each RNC 22 is controlled by a core network 24 that typically includes at least a Serving Gateway Service Node (SGSN) (not shown) that provides Authentication, Authorization and Accounting (AAA) functions within the core network. The second wireless network 14 may be partially or fully overlaid by a first one of the cells 20, with FIG. 1 depicting a fully overlaid cell 20.
Referring to FIG. 2, the second wireless communications network 14 typically takes the form of a wireless LAN that includes one or more access points 26. Each access point 26 within the wireless LAN 14 includes a radio transceiver (not shown) for transmitting RF signals to, and for receiving"RF"signals from'the mobile communications device 16. In practice, one or more of
the access points 26 of the wireless LAN 14 reside within one of the cells 20 of the wireless telephony network 12 of FIG. 1. Thus, the mobile communications device 16, while resident in a cell 20, will enter the coverage area of one of the access points 26 of the wireless LAN 14 and can initiate a communications session with the wireless LAN.
Ideally, the transition (hand off) of the mobile communications device 16 from the wireless telephony network 12 of FIG. 1 to the wireless LAN 14 illustrated in FIG. 2 should occur seamlessly. In other words, the capability should exist for the mobile communications device 16 to establish a communications session with the wireless LAN 16 while the device remains in communications with the wireless telephony network 12 of FIG. 1. In order for the mobile communications device 16 to establish a communications session with the wireless LAN 14, the device must have the ability to detect the presence of the wireless LAN.
Traditionally, the mobile communications device 16 has continuously operated two protocol stacks, and two receivers (not shown), one tuned to the wireless telephony network 12, and the other tuned to the wireless LAN 14, In this way, the mobile communications device can detect the presence of the wireless LAN while still in communications with the wireless telephone network. This approach to achieving seamless transitioning between networks, while effective, nonetheless requires the continuous use of two separate receivers, and the attendant consumption of precious battery power.
In accordance with the present principles, seamless transitioning can be effected without the need to operate two separate receivers simultaneously within the mobile communications device 16. To enable the communications device 16 to detect the presence of the wireless LAN 14 by means of a first receiver (not shown) .in the device, the wireless LAN 14 includes a basic transmitter 30 that transmits an identifying signal at the same frequency as a synchronizing signal transmitted by the wireless telephony network 12. The identifying signal transmitted by the transmitter 30 of FIG. 2 has a format compatible with the wireless telephony network 12 but is unique to the wireless LAN 14, thereby avoiding interference with the synchronizing signal from the wireless telephony network 12. In practice, the identifying signal transmitted by the transmitter 30 of FIG. 2 has a signal strength corresponding to the coverage of the wireless LAN 14,
The identifying signal transmitted by the transmitter 30 of FIG. 2 can take one of several lorms. Referring to FIG. 3, the signal from the transmitter 30 of FIG. 2 can take the form of a Primary Synchronization Channel (P-SCH) corresponding to a downlink signal transmitted in the wireless telepTioriy network I2"for effecting synchronization at the outset of a cell search. The P-
SCH signal depicted in FIG. 3 comprises a periodic synchronizing code having fifteen slots per frame, each frame being typically 10 ms in length. The synchronizing code is the same for each slot and has a format unique to the wireless LAN 14 so that the mobile communications device, upon receiving the code can specifically identify the wireless LAN 14 of FIG. 2.
In practice, the mobile communications device 16 establishes the identity of the wireless LAN 14 by matching the characteristics of the received P-SCH channel to one of a plurality of stored patterns in memory, each pattern corresponds to a particular wireless network technology. Once the mobile communications device 16 establishes the identity of the wireless LAN 14, the device stops the search for a match. Thereafter, the mobile communications device 16 initiates operation of a second receiver dedicated to the associated wireless LAN radio technology to effect the transition from the wireless telephony network 12 of FIG. 1. In the illustrated embodiment, the Frequency Division Duplex (FDD) mode is assumed when the wireless telephony network 12 embodies WCDMA technology. In a wireless telephony network embodying TDMA technology, the Time Division Duplex (TDD) mode or a similar mechanism would apply.
As an alternative solution, the transmitter 30 could transmit a Secondary Synchronization Channel (S-SCH) as seen in FIG. 4 which is comparable to the downlink signal transmitted by
the wireless telephony network 12 of FIG. 1 to effect frame synchronization and scrambling code detection as part of the cell search operation. In practice, the S-SCH channel corresponds to the repetition of a sequence of fifteen Secondary Synchronization codes (SSCs). Each code is chosen among sixteen such codes and is modulated within a given time slot. There exist sixty-four different possible combinations (or SSC sequences), each sequence corresponding to a separate scrambling code group and each having the same duration as the collective fifteen slots of a radio frame. Upon receipt of the SSC sequence, the first receiver in the mobile communications device 16 matches the sequence to a corresponding stored value indicative of the scrambling code group. Thereafter, the first receiver in the mobile communications device 16 finds the scrambling code group and becomes frame synchronized to the basic transmitter 30.
After finding the scrambling code group, the first receiver within the mobile communications device 16 looks for a primary CPICH (Common Pilot Channel) channel that carries a well-specified bit sequence that is the same for all cells. From knowledge of the
scrambling code group, the receiver will attempt a match to the CPICH channel bit sequence to
.;(.'•
the stored value (1 among 8 possible sequences). In this way, the first receiver will detect the wireless LAN 14. The wireless LAN detection mechanism is based on the reservation of a
scumbling code (the combination of a scrambling code group and a scrambling code in that group) allocated for inter-working of the wireless LAN 14 of FIG. 2 with the wireless telephony
network 12 of FIG. 1.
In case the'operator of jhe wireless LAN 14 implements more than one wireless LAN technology, the above-described detection mechanism requires enhancement in one of the two ways:
First Solution-
-!
• Each new wireless LAN inter-working technology receives its own scrambling code.
Standardization of this'Solution could prove potentially problematic since the number of
downlink primary scrambling codes is limited.
Second Solution:
• After recognition of this wireless LAN scrambling code, the mobile communication
device 16 will go through an extra step to identify the radio technology of the wireless
LAN by looking for the Primary Common Control Physical Channel (P-CCPCH) that
carries system information. The P-CCPCH channel has a well-specified channelization
code and thus can bring a new type of system message that will allow the mobile
communications device 16 to discover the type of wireless LAN cell it is entering.
t\In order to implement the second solution, the following are required:
• The mobile communications device 16 must monitor listed cells (including the wireless
LAN 14). To identify a cell, the mobile communications device 16 must identify its
primary scrambling code (one among 512). This solution works as long as the cell
belongs to the monitored list. Typically, the mobile communications device 16 is
constrained in terms of the maximum numbers of cells the device can measure in parallel.
- ' ' i
, i ; , :.
• Once it detects the wireless LAN 14, the mobile communications device 16 stops
searching for cells and no longer performs any measurement, nor does it signal the
presence of any subsequently detected cell to its corresponding cell controller. After
being detected, the wireless LAN 14 manages future communication with the mobile
communications device 16.
Ideally, there should be standardization of the scrambling codes dedicated to wireless LAN technology by the 3GPP standardization body or the like. In addition, there should also be standardization of the message format and content. Although standardization of the message format and content isn't mandatory, such standardization will assure that all mobile terminals
will be compliant regardless of the network operator.
,i The foregoing describes a technique for enabling a mobile communications device to
seamlessly transition-from a wireless telephony network to a wireless LAN without unnecessary consumption of battery resources.

We claim:-
1. A recording medium including recorded data, comprising:
a control data area comprising pits formed along tracks, with data recorded therein, wherein pits in some portions of the tracks are formed as wobbled pits, pits in other portions of the tracks of the control data area are formed as straight pits, and the wobbled pits are formed intermittently and alternately with the straight pits within the control data area,
wherein control information is encoded along the wobbled pits in such a way that data bit "0" and "1" comprising the control information are represented by a transition within a predetermined period of the wobbled pits and each data bit is distinguished from each other by the transition direction within the predetermined period, and
wherein the control data area comprises a plurality of data units, and the wobbled pits are formed in at least one data unit preceded by the straight pits or followed by the straight pits.
2. The recording medium as claimed in claim 1, wherein the control information comprises protection information used for controlling at least one of reproduction and recording of main data.
3. The recording medium as claimed in claim 2, wherein the protection information is repeatedly encoded in plural arrays of the wobbled pits.
4. The recording medium as claimed in claim 1, wherein the control information in the control data area is recorded along the wobbled pits while being encoded by bi-phased modulation.
5. The recording medium as claimed in claim 1, wherein the control data area comprises arrays of the wobbled pits and arrays of the strait pits periodically.
6. The recording medium as claimed in claim 1, wherein arrays of the wobbled pits and arrays of the straight pits in the control data area are of different length.
7. The recording medium as claimed in claim 1, comprising: a main data area comprising main data recorded with modulation in straight pits formed along tracks.
8. The recording medium as claimed in claim 1, wherein the wobbled pits are formed in more than two data units different from a first data unit.
9. The recording medium as claimed in claim 8, wherein the plurality of data units comprise one address unit, and the wobbled pits are formed in more than two data units different from the first data unit within the address unit.

10. The recording medium as claimed in claim 9, wherein the wobbled pits are formed in a plurality of address units.
11. A method of forming a recording medium, comprising:
forming pits in a control data area along tracks, with data recorded therein, wherein pits in some portions of the tracks are formed as wobbled pits, pits in other portions of the tracks of the control data area are formed as straight pits, and the wobbled pits are formed intermittently and alternately with the straight pits within the control data area,
wherein the step of forming pits comprises encoding control information along the wobbled pits in such a way that data bit "0" and "1" comprising the control information are represented by a transition within a predetermined period of the wobbled pits and each data bit is distinguished from each other by the transition direction within the predetermined period, and
wherein the control data area comprises a plurality of data units, and the step of forming pits comprises forming the wobbled pit in at least one data unit preceded by the straight pits or followed by the straight pits.
12. The method as claimed in claim 11, wherein the control information comprises
protection information used for controlling at least one of reproduction and recording of main data.
13. The method as claimed in claim 12, wherein the step of encoding control information repeatedly encodes the same protection information in plural arrays of the wobbled pits.
14. The method as claimed in claim 11, wherein the step of encoding control information encodes the wobbled pits by bi-phased modulation.
15. The method as claimed in claim 11, wherein the control data area comprises arrays of the wobbled pits arid arrays of the strait pits periodically.
16. The method as claimed in claim 11, wherein the step of forming pits forms arrays of the wobbled pits and arrays of the straight pits having different lengths respectively in the control data area.
17. The method as claimed in claim 11, wherein the step of forming pits forms the wobbled pits in more than two data units different from a first data unit.
18. The method as claimed in claim 17, wherein the step of forming pits comprises comprising the plurality of data units into one address unit, and wherein the wobbled pits are formed in more than two data units different from the first data unit within the address unit.
19. The method as claimed in claim 18, wherein the wobbled pits are formed in a plurality of address units.
20. A method of reproducing data from are recording medium, comprising:
detecting data recorded in pits formed along tracks in a control data area, wherein pits in some portions of the tracks are formed as wobbled pits, pits in other portions of the tracks of the control data area are formed as straight pits, and the wobbled pits are formed intermittently and alternately with the straight pits within the control data area,
wherein the step of detecting data comprises detecting control information encoded along
the wobbled pits, data bit "0" and "1" comprising the control information are represented by a transition within a predetermined period of the wobbled pits and each data bit is distinguished from each other by the transition direction within the predetermined period, and
wherein the control data area comprises a plurality of data units, and the step of detecting control information comprises detecting the wobbled pits from at least one data unit preceded by the straight pits or followed by the straight pits; and
utilizing the control information to reproduce main data recorded with modulation in straight pits formed along tracks of a main data area of the recording medium.
21. The method as claimed in claim 20, wherein the step of detecting data comprises: converting signals reflected from the wobbled pits into electrical signals; and extracting the control information by applying the electrical signals to a logic circuit.
22. The method as claimed in claim 21, comprising: reproducing the main data using the control information, and outputting the reproduced main data.
23. The method as claimed in claim 20, wherein the step of detecting control information detects the control information recorded in pits from a difference signal between a right and a left electric signals, generated by a beam reflected from the pits formed along the tracks.
24. The method as claimed in claim 23, wherein the step of detecting data detects the main data from a high-frequency electric signal generated by a beam reflected from the straight pits.
25. The method as claimed in claim 20, wherein the control information comprises protection information for controlling at least one of reproduction and recording of main data, and wherein the step of detecting control information detects the protection information.
26. The method as claimed in claim 20, wherein the step of detecting control information
detects the control information recorded in the wobbled pits by bi-phased modulation, in the control data area.
27. The method as claimed in claim 20, wherein the step of detecting pits detects arrays of the wobbled pits and arrays of the straight pits having different lengths respectively in the control data area.
28. The method as claimed in claim 20, wherein the step of detecting control information comprises detecting the wobbled pits formed in more than two data units different from a first data unit.
29. The method as claimed in claim 28, wherein the plurality of data units comprise one address unit, and wherein the step of detecting control information comprises detecting the wobbled pits formed in more than two data units different from the first data unit within the address unit.
30. The method as claimed in claim 29, wherein the wobbled pits are formed in a plurality of address units, and wherein the step of detecting control information comprises detecting the wobbled pits formed in the plurality of address units.
31. An apparatus for reproducing data from a recording medium, said apparatus
comprising:
a detection unit configured to detect data recorded in pits formed along tracks in a control data area, with data recorded therein, wherein pits in some portions of the tracks are formed as wobbled pits, pits in other portions of the tracks of the control data area are formed as straight pits, and the wobbled pits are recorded intermittently and alternately with the straight pits, wherein control information is encoded along the wobbled pits in such a way that data bit "0" and "1" comprising the control information are represented by a transition within a predetermined period of the wobble pits and each data bit is distinguished from each other by the transition direction within
the predetermined period, wherein the control data area comprises a plurality of data units, and the wobbled pits are formed in at least one data unit preceded by the straight pits or followed by the straight pits, and wherein the detection unit converts signals reflected from the pits into electric signals; and
a signal processor, coupled to the detection unit, configured to process the electric signals to generate the control information and to process main data recorded with modulation in straight pits formed along tracks of a main data area of the recording medium.
32. The apparatus as claimed in claim 31, wherein the signal processor is configured to generate the control information from low-frequency components and generate the main data from high-frequency components.
33. The apparatus as claimed in claim 31, comprising:
a controller, coupled to said detection unit and said signal processor, configured to control the detection of the control information and the processing of the main data, wherein the controller is configured to control said signal processor to output the main data based on the control information.
34. The apparatus as claimed in claim 33, wherein the controller is configured to control said detection unit to detect the control information by a push-pull method.
35. The apparatus as claimed in claim 33, wherein the control information comprises protection information used for controlling at least one of reproduction and recording of the main data, and wherein the controller is configured to control the reproduction of the main data in response to the protection information.
36. The apparatus as claimed in claim 31, wherein the detection unit is configured to detect the wobbled pits formed in more than two data units different from a first data unit.
37. The apparatus as claimed in claim 36, wherein the plurality of data units comprise one
address unit, and wherein the detection unit is configured to detect the wobbled pits formed in
more than two data units different from the first data unit within the address unit.
38. The apparatus as claimed in claim 37, wherein the wobbled pits are formed in a plurality of address units, and wherein the detection unit is configured to detect the wobbled pits formed in the plurality of address units.

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Patent Number

259911

Indian Patent Application Number

1566/DELNP/2006

PG Journal Number

14/2014

Publication Date

04-Apr-2014

Grant Date

29-Mar-2014

Date of Filing

23-Mar-2006

Name of Patentee

THOMSON LICENSING

Applicant Address

46, QUAI A.LE GALLO, F-92100 BOULOGNE-BILLANCOURT, FRANCE.

Inventors:

#	Inventor's Name	Inventor's Address
1	LI, JUN	26 ORCHID DRIVE, PLAINSBORO, NJ 08536 (US).
2	GAO, WEN	21-21 QUAIL RIDGE DRIVE, PLAINSBORO, NJ 08536 (US).
3	GILBERTON, PHILIPPE	24 STONEWALL CIRCLE, PRINCETON, NJ 08540 (US).
4	BICHOT, GUILLAUME	26 RUE DE MONTMURAN, F-35630 LA CHAPELLE CHAUSSEE (FR).

PCT International Classification Number

H04M 1/00

PCT International Application Number

PCT/US2003/031536

PCT International Filing date

2003-10-03

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA