Methods and apparatus to support paging with less interference in multi-tier communication systems

A first base station and mobile station are capable of mitigating interference resulting from communications from a second base station. The base station can determine if at least a portion of a paging slot overlaps with an available interval (AI) of the second base station in which the second base station transmits. The first base station adjusts an occurrence of the paging slot such that the paging slot overlaps and/or occurs within an unavailable interval (UAI) of the second base station wherein the base station does not transmit or transmits with limited resources.The mobile station also can determine if at least a portion of a listening slot overlaps with the AI and, using the same procedure that the first base station uses to recalculate the paging slot, recalculates the listening slot such that the listening slot overlaps and/or occurs within the UAI of the LDC mode.

TECHNICAL FIELD OF THE INVENTION

The present application relates generally to mobile communication devices and, more specifically, to paging with less interference in multi-tier communications systems that include different types and sizes of the base stations such as macro, pico, femto base stations, and the like.

BACKGROUND OF THE INVENTION

The demand of wireless data traffic is explosively increasing. To meet such demand, the cellular systems are evolving into multi-tier networks with base stations with diverse sizes, types, use cases, and so forth. To have more and multi-tier base stations, such as femtocells, picocells, relay, and the like, in cellular system gains the momentum in wireless networks. Small-sized low-power base stations, such as picocell, femtocell, and the like, become heated topics, because of their potential advantages of low cost, offloading the traffic from macrocells, providing large amount of wireless data traffic to mobile stations, and the like.

Femtocell devices are small base stations designed for home or small business use. Femtocell devices operate in a small range and are designed to provide cellular coverage in the home or office. The typical femtocell device connects to a Security Gateway or Softswitch over an Interent Protocol (IP) connection, such as a Digital Subscriber Line (DSL) or broadband cable connection. The Security Gateway or Softswitch is intended to plug into the DSL or cable modem using a standard Ethernet cable.

Femto Base Stations (FBSs) can be open or closed. An open FBS accepts any compatible mobile device (e.g., accepts communications to and from any compatible cell phone, PDA, and the like). A closed FBS requires that the mobile device be authorized to access through the FBS.

SUMMARY OF THE INVENTION

A first base station capable of delivering a paging message is provided. The paging message is broadcast in a paging slot to at least one of a plurality of mobile stations. The base station can determine if at least a portion of the paging slot overlaps with an available interval (AI) of a second base station in which the second base station transmits. The base station further can adjust an occurrence of the paging slot such that the paging slot overlaps and/or occurs within an unavailable interval (UAI) of the LDC mode.

A method for delivering a paging message, in a paging slot, to at least one of a plurality of mobile stations, is provided. The method includes obtaining the patterns of the occurrence of an available interval (AI) of at least one base station in which the at least one base station transmits, and an unavailable interval (UAI) of the at least one base station in which the at least one base station transmits over limited resources or does not transmit. The method also includes comparing the paging slot to the patterns of the occurrence of AI and/or UAI of the base station. If it is determined that at least a portion of the paging slot overlaps with an available interval (AI) of the base station, an occurrence of the paging slot is adjusted such that the paging slot overlaps and/or occurs within an UAI of the base station.

A mobile station capable of receiving a paging message is provided. The mobile station includes a plurality of antennas configured to receive the paging message, in a paging listening slot, from at least one base station. The mobile station also includes a main processor coupled to the antennas. The main processor can determine if at least a portion of the paging listening slot overlaps with an available interval (AI) of a second base station in which the second base station transmits. The main processor also can adjust an occurrence of the paging listening slot such that the paging listening slot overlaps and/or occurs within an unavailable interval (UAI) of the second base station in which the base station transmits over limited resources or does not transmit.

A method for receiving a paging message in a listening slot is provided. The method includes obtaining the patterns of the occurrence of an available interval (AI) of at least one base station in which the at least one base station transmits, and an unavailable interval (UAI) of the at least one base station in which the at least one base station transmits over limited resources or does not transmit. The method also includes receiving paging slot information from a serving base station. The paging slot information is configured to identify the occurrence of a paging slot such that the listening slot can be calculated. The method further includes comparing the paging slot to the patterns of the occurrence of the at least one of the AI and UAI of the at least one base station; determining if at least a portion of the paging slot overlaps with the AI of the at least one base station; and adjusting an occurrence of the paging slot such that the paging slot at least one of overlaps and occurs within an UAI of the at least one base station.

A base station capable of broadcasting a paging message is provided. The paging message is broadcast in a paging slot to at least one of a plurality of mobile stations. The base station can operate in a low duty cycle (LDC) mode. The LDC mode includes an available interval (AI) and an unavailable interval (UAI). The base station can transmit and receive in the AI and is configured to not transmit or transmit with limited resources during the UAI. The base station can determine if at least a portion of the paging slot overlaps with the UAI and adjust an occurrence of the paging slot such that the paging slot overlaps and/or occurs within the AI.

A method for broadcasting a paging message, in a paging slot, to at least one of a plurality of mobile stations, is provided. The method includes operating a base station in a low duty cycle (LDC) mode. The LDC mode includes an available interval (AI) and an unavailable interval (UAI). The base station can transmit and receive in the AI and is configured to not transmit or transmit with limited resources during the UAI. The method also includes comparing the paging slot to a LDC mode pattern for the base station; determining if at least a portion of the paging slot overlaps with the UAI; and adjusting an occurrence of the paging slot such that the paging slot overlaps and/or occurs within the AI.

A mobile station capable of receiving a paging message is provided. The mobile station includes a plurality of antennas configured to receive the paging message, in a listening slot, from a base station. The mobile station also includes a main processor coupled to the antennas. The main processor can determine if at least a portion of the paging listening slot overlaps with an unavailable interval (UAI) of a low duty cycle (LDC) mode of the base station. The main processor adjusts an occurrence of the paging listening slot such that the paging listening slot overlaps and/or occurs within an available interval (AI) of the LDC mode.

A method for receiving a paging message in a listening slot is provided. The method includes obtaining a low duty cycle (LDC) mode pattern for a base station operating in an LDC mode. The LDC mode includes an available interval (AI) and an unavailable interval (UAI). The base station can transmit and receive in the AI and is configured to not transmit or transmit with limited resources during the UAI. The method also includes determining if at least a portion of a paging slot overlaps with the UAI of the LDC mode; and recalculating an occurrence of the listening slot such that the listening slot overlaps and/or occurs within the AI of the LDC mode.

DETAILED DESCRIPTION OF THE INVENTION

As described in IEEE 802.16m System Requirements, a Femtocell is a low power Base Station (BS). Femtocells are typically installed by a subscriber in a home or small office/home office to provide access to closed or open group of users as configured by the subscriber and/or the access provider. Femtocell BS's typically operate in licensed spectrum and may use the same or different frequency as macro-cells and use broadband connection such as cable or DSL for backhaul. The mobile station (MS)'s using access in a femtocell are typically stationary or moving at low (i.e., pedestrian) speed.

The present application is to support the coexistence of small-sized low-power base stations and larger base stations such as macro, which may overlay the low-power small-sized base stations. Throughout the application, femtocell is used as an example of the low-power small-sized base stations, and macrocell is used as an example of the large-sized base stations which may overlay the smaller base stations. All the embodiments are applicable to any type or size of the base stations in multi-tier networks, where some larger cell may overlay some smaller cells.

Low-power small-sized cells, such as femtocells, are different from larger cells, such as macro cells. The multi-tier network, with base stations of various types and sizes, may have the capability to identify femto base stations as well as to distinguish femtocells from macro cells. Further, the multi-tier network may have the capability to distinguish open-access femtocell (which allow any compatible MS to access) from the Closed Subscriber Group (CSG) femtocell (which allows only authorized MS's, i.e., the MS's belonging to this femtocell, to access), since some operations, such as, but not limited to, handover, paging, and the like, will be different for femtocells and macro cells, and for open-access and CSG femtocells. For example, the MS with high speed may not need to handover to any femtocells, the open-access femto base stations may accept the handover requests from MS while the MS that does not belong to a CSG femtocell may not need to send handover request to that femtocell, and so forth. When there is no mobile station in its cell (that is, coverage area), the femto base station may enter a low duty cycle (LDC) mode, which has a limited active frequency, time, or both. The LDC mode can be referenced differently in various examples such as a power saving mode and the like.

The LDC mode is a new attribute for base stations. LDC mode is may not be needed for macrocells because, as discussed in IEEE 802.16, Rev2_D9a, March 2009, the contents of which are hereby incorporated by reference, it is very rare that a macrocell does not have any active or prospective user within its coverage. In addition, the macrocell may include the LDC mode in the future as well, such as during a nighttime in the area where there may be no or very few residences. However, a smaller sized base station, such as a femto BS, can have no active user in its coverage, such as a home femto after the residence leaves home without any active session setup. In this example, the LDC mode can reduce power consumption of the femto BS and can reduce the interference the femto BS generates to macrocells.

The embodiments of the present disclosure are not limited to femtocells, although femtocells are illustrated as examples of the low-power, small-sized cells. Other low-power small-sized cells can include picocells, hot zone cells, small relay cells, and the like. In addition, the embodiments are not limited to the macrocells, although macrocells are illustrated as examples of the larger cells that can cover or overlay the smaller cells within the coverage are of the large cell. The embodiments can be used with any type or sized base station with some level of accessibility differentiation such as open to all mobile stations (e.g., open BS), or open to limited/authorized/subscribed mobile stations (e.g., CSG BS), or open to all mobile station but with limited/authorized/subscribed mobile stations having higher priority and other mobile stations having lower priority (e.g., hybrid BS), and so forth. The concept of the CSG is not limited to femtocells only, but also can be applicable to other BSs, such as microcells, picocells, relays, and the like.

The femtocell base station is configured to inform a mobile station regarding an identification of CSG with the CSG ID. Therefore, even if the MS knows the femtocell is of a CSG type, the MS also is informed whether this femtocell is closed for or authorized for the MS to access, i.e., the MS knows whether the MS can access this CSG or not. The MS can be configured to store a list (such as a white-list) of the CSG femtocells that the MS can access. As such when the MS receives the CSG ID of a CSG femtocell, the MS checks the received CSG ID with the list of the accessible femtocells. If the received CSG ID is in the list of the MS's list of accessible femtocells, the MS knows the CSG is accessible. Hence, a CSG ID of the CSG femtocell is sent to MS's via wireless communication signaling. To make the list of accessible CSG femtocells of a MS short, multiple CSG femtocells share a common CSG ID if these CSG femtocells have the same set of MS's allowed to access them. For example, if a user subscribes via a chain of coffee shops to access the closed femtocells at each coffee shop, the CSG femtocells for the coffee shops will share the common CSG ID.

In some examples, different groups of preambles are used to distinguish femtocells from macro cells. The preambles are divided into two groups, one for femtocells, and another for macro cells. In the case of a large number of femtocells and insufficient preambles, the preambles are dynamically allocated. In some examples, one bit in least significant bit (LSB) that is a24programmable bit segment of the base station ID is used to distinguish femtocell and macro cell, and to use another bit in LSB to distinguish femtocell open-access mode and CSG mode. This approach will increase the overhead of Broadcast Channel (BCH), which is very expensive. In additional and alternative examples, different scrambling sequences and/or different CRCs (cyclic redundancy check) to differentiate femto BS from macro BS's, and to differentiate open-access femto BS and CSG femto BS.

FIG. 1illustrates exemplary wireless network100according to embodiments of the present disclosure. The embodiment of wireless network100illustrated inFIG. 1is for illustration only. Other embodiments of the wireless network100could be used without departing from the scope of this disclosure.

Wireless network100comprises a plurality of cells121-126, each containing one of the Base Stations (BS), BS101, BS102, or BS103or Femto Base Stations (FBS), FBS104, FBS105or FBS106. Base stations101-103can be larger sizes, while base stations104-106can be small sizes. Base stations101-106communicate with a plurality of mobile stations (MS)111-116over code division multiple access (CDMA) channels), Orthogonal Frequency Division Multiple Access (OFDMA), or any other communications standard as is known in the art. In some embodiments, mobile stations111-116are capable of receiving data traffic and/or voice traffic on two or more CDMA channels simultaneously. Mobile stations111-116may be any suitable wireless devices (e.g., conventional cell phones, PCS handsets, personal digital assistant (PDA) handsets, portable computers, telemetry devices) that are capable of communicating with base stations101-106via wireless links.

Dotted lines show the approximate boundaries of cells121-123in which base stations101-103are located. The cells are shown approximately circular for the purposes of illustration and explanation only. It should be clearly understood that the cells may have other irregular shapes, depending on the cell configuration selected and natural and man-made obstructions.

As is well known in the art, each of cells121-123is comprised of a plurality of sectors, where a directional antenna coupled to the base station illuminates each sector. The embodiment ofFIG. 1illustrates the base station in the center of the cell. Alternate embodiments may position the directional antennas in corners of the sectors. The system of the present disclosure is not limited to any particular cell configuration.

In one embodiment of the present disclosure, each of BS101, BS102and BS103comprises a base station controller (BSC) and one or more base transceiver subsystem(s) (BTS). Base station controllers and base transceiver subsystems are well known to those skilled in the art. A base station controller is a device that manages wireless communications resources, including the base transceiver subsystems, for specified cells within a wireless communications network. A base transceiver subsystem comprises the RF transceivers, antennas, and other electrical equipment located in each cell site. This equipment may include air conditioning units, heating units, electrical supplies, telephone line interfaces and RF transmitters and RF receivers. For the purpose of simplicity and clarity in explaining the operation of the present disclosure, the base transceiver subsystems in each of cells121,122,123and the base station controller associated with each base transceiver subsystem are collectively represented by BS101, BS102, and BS103, respectively.

In some embodiments, BS101, BS102and BS103transfer voice and data signals between each other and the public switched telephone network (PSTN) (not shown), or any IS-41 communication network as is known in the art, via communication line (not shown) and mobile switching center (MSC) (not shown). The communication line may be any suitable connection means, including a T1 line, a T3 line, a fiber optic link, a network packet data backbone connection, or any other type of data connection. The communication line links each vocoder in the BSC with switch elements in the MSC. The connections on communication line may transmit analog voice signals or digital voice signals in pulse code modulated (PCM) format, Internet Protocol (IP) format, asynchronous transfer mode (ATM) format, or the like.

The MSC is a switching device that provides services and coordination between the subscribers in a wireless network and external networks, such as the IS-41, PSTN, or Internet. The MSC is well known to those skilled in the art. In some embodiments of the present disclosure, communications line may be several different data links where each data link couples one of BS101, BS102, or BS103to the MSC.

The wireless network100includes a femto-cell base station124-126. Each FBS124-126includes components analogous to those found in macro base stations BS101, BS102and BS103. As such, FBS124, FBS125and FBS126each comprises a femto base station controller (FBSC) and one or more femto base transceiver subsystem(s) (FBTS). Each of FBS124, FBS125and FBS126communicates with mobile stations in its served area using wireless fidelity, IS-95, CDMA or any other cellular communications standard.

Voice and data signals are transferred between the FBS104, FBS105and FBS106and the IS-41 network (e.g., PSTN) via communications lines, wireless gateway and wireless soft switches. For example, Voice signals are transferred between the FBS105and the IS-41 network via communication line130, Wireless Gateway (WGW)132. Data signals are transferred between the FBS105and the IS-41 network via communication line134and Wireless Soft Switch (WSS)136. The WGW132and WSS136are coupled via a backhaul connection (not shown), e.g., the IS-41, to the MSC. The WGW132provides a bearer path between FBS105and the MSC via the IS-41. The WSS136provides a signaling path FBS105and WGW132as well as to the MSC via the IS-41.

A dotted line shows the approximate boundaries of cells124-126in which FBS104, FBS105and FBS106are located. The cell is shown approximately circular for the purposes of illustration and explanation only. It should be clearly understood that the cell may have an irregular shape, depending on the cell configuration selected and natural and man-made obstructions.

In the exemplary wireless network100, MS111is located in cell121and is in communication with BS101. MS112is located in cell121and cell124and is in communication with BS102. MS113is located in cell126, is in communication with FBS106. MS114is located in cell123, is in communication with BS103and is moving in the direction of cell126, as indicated by the direction arrow proximate MS114. At some point, as MS114moves into cell126and MS114will detect signals from FBS106. MS115is located in cell122and is in communication with BS102. MS115also is located close to the edge of cell123. MS116is located in cell123, is in communication with BS103and is moving in the direction of cell121and cell125. At some point, as MS116moves into area covered by cell121and cell125, MS116will detect signals from BS101and FBS105and a handoff will occur.

The handoff procedure transfers control of a call from a first cell to a second cell. A handoff may be either a “soft handoff” or a “hard handoff.” In a “soft handoff” a connection is made between the mobile station and the base station in the second cell before the existing connection is broken between the mobile station and the base station in the first cell. In a “hard handoff” the existing connection between the mobile station and the base station in the first cell is broken before a new connection is made between the mobile station and the base station in the second cell.

As shown inFIG. 1, MS112is located in both cell122and cell124. FBS104is a CSG FBS. Furthermore, MS112has not subscribed to FBS104. Therefore, MS112is not authorized to access FBS104. Accordingly, MS112is not in communication with FBS104and is only in communication with BS102.

Additionally, MS114is moving from BS103towards FBS106. FBS106is an open-access FBS. As MS114enters cell126, MS114becomes aware of FBS106as MS114receives signaling from FBS106. The signaling contains a base station identifier (e.g., base station identity, or some other value) for FBS106indicating that FBS106is an open FAP. Since FBS106is an open FAP, all compatible wireless devices, including MS114, are authorized to access FBS106. In some embodiments, a handoff occurs wherein communications between MS114and BS103are terminated and communications between MS114and FBS106are established. MS114may still be located within cell123and in communication with FBS104.

Furthermore, MS116is moving from BS103towards FBS105. FBS105is a closed FBS. Therefore, only authorized wireless devices are allowed to access FBS105. For example, FBS105may be located in a Starbucks® and only individuals who have subscribed for access a FBS through Starbucks® are allowed to access FBS105. A subscriber with MS116enters cell125. MS116receives signaling from FBS105. The signaling includes a Closed Subscriber Group (CSG) Identification (ID) for FBS105. MS116recognizes the CSG ID for FBS105and a handoff of MS116from BS103to FBS105occurs.

FIG. 2is a high-level diagram of an orthogonal frequency division multiple access (OFDMA) transmit path.FIG. 3is a high-level diagram of an orthogonal frequency division multiple access (OFDMA) receive path. InFIGS. 2 and 3, the OFDMA transmit path is implemented in base station (BS)102or femto base station (FBS)104and the OFDMA receive path is implemented in mobile station (MS)112for the purposes of illustration and explanation only. However, it will be understood by those skilled in the art that the OFDMA receive path may also be implemented in BS102and/or FBS104and the OFDMA transmit path may be implemented in MS112.

In BS102, channel coding and modulation block205receives a set of information bits, applies coding (e.g., Turbo coding) and modulates (e.g., QPSK, QAM) the input bits to produce a sequence of frequency-domain modulation symbols. Serial-to-parallel block210converts (i.e., de-multiplexes) the serial modulated symbols to parallel data to produce N parallel symbol streams where N is the IFFT/FFT size used in BS102and MS116. Size N IFFT block215then performs an IFFT operation on the N parallel symbol streams to produce time-domain output signals. Parallel-to-serial block220converts (i.e., multiplexes) the parallel time-domain output symbols from Size N IFFT block215to produce a serial time-domain signal. Add cyclic prefix block225then inserts a cyclic prefix to the time-domain signal. Finally, up-converter230modulates (i.e., up-converts) the output of add cyclic prefix block225to RF frequency for transmission via a wireless channel. The signal may also be filtered at baseband before conversion to RF frequency.

Each of base stations101-106may implement a transmit path that is analogous to transmitting in the downlink to mobile stations111-116and may implement a receive path that is analogous to receiving in the uplink from mobile stations111-116. Similarly, each one of mobile stations111-116may implement a transmit path corresponding to the architecture for transmitting in the uplink to base stations101-106and may implement a receive path corresponding to the architecture for receiving in the downlink from base stations101-106.

FIG. 4illustrates wireless mobile station112according to embodiments of the present disclosure. The embodiment of wireless mobile station112illustrated inFIG. 4is for illustration only. Other embodiments of the wireless mobile station112could be used without departing from the scope of this disclosure. It will be understood that although MS112is described for illustration and example only, descriptions can apply to MS112-116equally.

Wireless mobile station112includes antenna405, radio frequency (RF) transceiver410, transmit (TX) processing circuitry415, microphone420, and receive (RX) processing circuitry425. MS112also includes speaker430, main processor440, input/output (I/O) interface (IF)445, keypad450, display455, and memory460. Memory460further includes basic operating system (OS) program461, a white-list including a plurality of CSG IDs462, and instructions for interference mitigation464that can include functions or algorithms for changing a paging listening interval and/or a paging listening slot.

Radio frequency (RF) transceiver410receives from antenna405an incoming RF signal transmitted by a base station (e.g., either a base station or femto base station) of wireless network100. Radio frequency (RF) transceiver410down-converts the incoming RF signal to produce an intermediate frequency (IF) or a baseband signal. The IF or baseband signal is sent to receiver (RX) processing circuitry425that produces a processed baseband signal by filtering, decoding, and/or digitizing the baseband or IF signal. Receiver (RX) processing circuitry425transmits the processed baseband signal to speaker430(i.e., voice data) or to main processor440for further processing (e.g., web browsing).

Transmitter (TX) processing circuitry415receives analog or digital voice data from microphone420or other outgoing baseband data (e.g., web data, e-mail, interactive video game data) from main processor440. Transmitter (TX) processing circuitry415encodes, multiplexes, and/or digitizes the outgoing baseband data to produce a processed baseband or IF signal. Radio frequency (RF) transceiver410receives the outgoing processed baseband or IF signal from transmitter (TX) processing circuitry415. Radio frequency (RF) transceiver410up-converts the baseband or IF signal to a radio frequency (RF) signal that is transmitted via antenna405.

In some embodiments of the present disclosure, main processor440is a microprocessor or microcontroller. Memory460is coupled to main processor440. According to some embodiments, part of memory460comprises a random access memory (RAM) and another part of memory460comprises a Flash memory, which acts as a read-only memory (ROM).

Main processor440executes basic operating system (OS) program461stored in memory460in order to control the overall operation of wireless mobile station112. In one such operation, main processor440controls the reception of forward channel signals and the transmission of reverse channel signals by radio frequency (RF) transceiver410, receiver (RX) processing circuitry425, and transmitter (TX) processing circuitry415, in accordance with well-known principles.

Main processor440is capable of executing other processes and programs resident in memory460. Main processor340can move data into or out of memory460, as required by an executing process. Main processor440is also coupled to I/O interface445. I/O interface445provides mobile station112with the ability to connect to other devices such as laptop computers and handheld computers. I/O interface445is the communication path between these accessories and main controller440.

Main processor440is also coupled to keypad450and display unit455. The operator of mobile station112uses keypad450to enter data into mobile station112. Display455may be a liquid crystal display capable of rendering text and/or at least limited graphics from web sites. Alternate embodiments may use other types of displays.

Main processor440is configured to store one or more CSG IDs462for use in accessing closed FAPs. When a user (e.g., subscriber) subscribes to a FAP service, the user is provided with one or more CSG IDs462in order to access one or more respective FBSs. In some embodiments, the user's wireless device (e.g., MS112) receives the CSG TDs462wirelessly via one or more of the wireless connections between the MS and a BS and the MS and another FBS. In some embodiments, the user enters the CSG IDs462into the wireless device (e.g., MS112) using one or more of I/O IF445, keypad450and display455. Furthermore, the user can subscribe to multiple closed FAPs and, thus, receive and store multiple CSG ID's462corresponding to the various closed FAPs to which subscriptions have been obtained.

In some embodiments, main processor440is configured to recalculate a paging listening interval and/or a paging listening slot. The main processor440is configured to determine whether a recalculation is necessary. The main processor440can use the same process utilized by a femto base station, such as FBS104, or a macro base station, such as BS102, to recalculate the position for the paging listening interval or paging listening slot.

Embodiments of the present disclosure provide a system and method to support paging with less interference in communication systems with femtocells. When femtocells send paging messages to idle mobile stations, which can be non-subscribers or subscribers of the CSG femtocell, the paging messages can cause a lot of overhead for paging because the CSG femtocell also is sending the paging to those mobile stations that do not subscribe the CSG of the femtocell. IEEE 802.16m-08/003r8 and its latest version, IEEE 802.16m System Description Document (SDD), 2009, the contents of which are incorporated by reference, states that femtocells may not send paging messages to non-subscribers in order to save paging overhead. However, a CSG femtocell may still interfere with a non-subscriber MS. For example, if a non-subscriber MS that is in idle mode passes by the CSG femtocell and receives strong interference from the CSG femtocell, then the paging message from the macrocells may not be heard by the MS.

IEEE 802.16, Rev2_D9a, discloses a procedure for paging a subscriber station. However, since the femtocell is not considered in IEEE 802.16, Rev2D9a, the macrocell mobile station may not be able to receive the paging message when near a femtocell. For example, when MS112is in idle mode and it is very close to FBS104, which is a CSG femto base station operating in regular mode (not in low duty mode) to which MS112is not a subscriber; or if the paging message happens to be allocated in the active interval of the low duty mode of such CSG femtocell104, and if the femtocell104is not paging MS112, then the paging message to MS112from BS102can be overwhelmed by the FBS104, hence MS112may not be able to receive the paging message. Here, the interference scenario is that the macrocell MS is interfered by the nearby inaccessible femtocell, however, the interference scenario is not limited to this example. There can be other interference scenarios, such as femto MS interfered by the macro BS, femto MS interfered by other femto BS, macro MS interfered by pico BS, and so forth. The embodiments in this disclosure apply to any interference scenario, for the coordination of interference mitigation and reliable paging delivery in multi-tier networks.

For the femtocells and macrocells operating at the same frequency allocation, when a non-subscriber mobile station, such as MS112, comes near to a CSG femtocell, such as FBS104, the connection in-between MS112and the macrocell may be lost because it may be overwhelmed by the large interference from FBS104. MS112may lose the connection with BS102because of the strong interference from the FBS104. Further, MS112cannot access FBS104because MS112is not a subscriber to FBS104. Therefore, FBS104may not page MS112if MS112in idle mode.

FIG. 5illustrates a low duty cycle mode for a base station according to embodiments of the present disclosure. The embodiment of the LDC mode pattern500shown inFIG. 5is for illustration only. Other embodiments could be used without departing from the scope of this disclosure

For interference mitigation, FBS104can be in the low duty cycle mode. IEEE 802.16m-08/003r8 and its latest version, IEEE 802.16m System Description Document (SDD), 2009, the contents of which are hereby incorporated by reference, further discusses a LDC mode. In the LDC mode, a base station is active only on limited time and frequency resources in the air interface. When there is no MS in its coverage, to reduce the interference to others and save its transmission energy or power, femtocells may enter low duty cycle (LDC) mode, which has a limited active resource such as frequency/time.

In the example shown inFIG. 5, the LDC mode pattern500includes an available interval (AI)505and an unavailable interval (UAI)510. The LDC mode pattern500can include a pattern of AI's505and UAI's510occurring at periodic or aperiodic intervals. The relative sizes of the AI's505and UAI's510can vary. For example, a first AI505can be larger than a first UAI510and a second AI can be smaller than the first UAI510or a differently sized second UAI510. In AI505, FBS104has an active resource in the air interface and FBS104can transmit and receive. That is, during AI505, FBS104may be transmitting or receiving signals. In UAI510, FBS104may not transmit in the air interface or may transmit minimized signals such as the synchronization channel or the preambles; rather FBS104may receive from the air interface. That is, during the UAI510, FBS104may be silent or almost silent. In addition, in the UAI510, FBS104may have backhaul communication with core network. If no active user exists in the coverage area for FBS104, FBS104can operate in LDC mode500such that FBS104can reduce the interference to other base stations. Additionally, operating in LDC mode500enables FBS104to save energy as well. The LDC patterns can be provided to the MS by the network so that the MS can memorize the LDC patterns and use them to scan or search for the base stations in LDC mode. For example, if the MS knows that the BS in LDC mode would not transmit anything in certain interval, then the MS would not try to scan for such BS in the interval where the BS may not transmit because nothing from the BS would be in the air.

In LDC mode, the AI505and UAI510may be periodical or may not be periodical. For example, the base station may include one UAI510when needed; then there can be UAIs510located in different positions (e.g., here and there) regularly or irregularly and/or periodically or non-periodically, based on the base station configuration. Such scenario can be regarded as a regular mode of a base station including some UAIs from time to time or it could also be regarded as a separate configuration of the LDC mode. The LDC mode and/or LDC patterns throughout this disclosure are meant to refer to their general meaning, which refers to any transmission configuration pattern which may have some UAI from time to time regularly or irregularly, where in the UAI510the base station may not transmit, or transmit with limited or less resource such as in limited or less time, frequency, power, space angle, and so forth, comparing with the transmission in AI505. The LDC mode, or LDC patterns, can be referred by other names in different systems. The base station can be in LDC mode when there are no active mobile users, or no active sessions, or mobile users are active but they are in sleep mode, and so forth.

The network entity, such as BS102, can send (e.g., by broadcasting, multicasting, unicasting, and so forth) the LDC mode pattern500to MS112. As such, both BS102and MS112are aware of the LDC mode pattern500.

In some embodiments, to detect the femtocells operating in LDC mode, all of the femtocells operate at the same frequency allocation and use the same LDC pattern. For example, BS102can send to the MSs in its coverage such as MS112the same LDC mode pattern500to be used by FES104, FBS144and FBS154. The same LDC mode pattern500may be used so that MS112can synchronize (sync) and detect the femtocells operating in LDC mode more efficiently, that is, the MS can detect the sync channel for multiple BSs in LDC mode in one common interval, rather than in multiple intervals.

In some embodiments, one or more femtocells use one of a number of multiple (countable) LDC patterns. For example, FBS104and FBS144may be operating using different LDC mode patterns500while FBS154uses the same pattern500as FBS104. In another example, FBS104, FBS144and FBS154each operate using different LDC mode patterns500.

In some embodiments, all the femtocells and macrocells are operating at the same frequency allocation.

FIGS. 6A through 6Cillustrate an exemplary process for paging mobile stations in idle mode. In the example shown inFIG. 6A, a paging controller (not shown) tells BS102which mobile stations are to be paged. It will be understood that the paging controller can instruct more than one base station to page respective mobile stations. In some embodiments, the paging controller instructs one or more femto base stations, such as FBS144and FBS154, which mobile stations are to be paged. Then, during a paging cycle605, BS102broadcasts one or more paging messages610,615in paging slots612and617respectively. The paging messages,610,615can include the mobile station identifiers to be paged and some other assisting information. The paging slots can be similar to or longer than the time needed for transmitting the paging message. If the paging slot is shorter than the time needed for the paging message, the paging slot may be extended. The mobile stations, such as MS112, which are in idle mode wake up at a certain time to listen to the paging message610,615. When MS112determines that its identifier (MSID) is included in the paging message610, then MS112determines that it is paged and MS112performs further action such as exiting idle mode and performing network re-entry. If the paging message610does not include an MSID for MS112, MS112proceeds to a paging unavailable interval in which MS112is not listening and remains in idle mode.

When in idle mode, MS112can have a period of paging listening time and paging listening unavailable time periodically within the paging cycle605. The paging cycle605occurs periodically such that multiple paging cycles605exist although only one paging cycle605is illustrated inFIGS. 6A through 6C. In the paging cycle605, the paging messages610,615can be sent by BS102at a time that is offset within the paging cycle605. The timing for BS102to broadcast paging messages610,615to MS112and MS115should be aligned to the timing for a listening period (“slot”)620for MS112and listening slot630for MS115to listen to the paging messages. For example, paging slot612should align with listening slot620and paging slot617should align with listening slot630. The timing alignment may already take into account the delays such as propagation delay from the BS to the MS. The timing alignment for BS102and MS112can be achieved by explicit signaling or by the same predefined algorithm at both BS102and MS112to calculate the timing information for paging message. For example, the predefined algorithm can be a function (such as a hash function) of the paging cycle605and desired timing offset625for the paging message (or paging slot and listening slot) within the paging cycle605.

In a paging cycle605, different MSs112,115may be paged in different paging slots612,617, so that the paging message can be shortened. For example, MSs112,115are divided into groups with different groups of MSs being paged in different time offsets. In some embodiments, a predefined process (such as a predefined algorithm) executed at both BS102and MS112to calculate the timing information for the paging message610can include a function (such as a hash function) of MS identifiers. Therefore, MS112is able to know which listening interval slot620,630contains the possible message for MS112and, as such, MS112does not need to listen when the other listening interval slots620,630, which is associated with another group of MS's. For example, using the predefined function, MS112can determine that listening interval slot620contains the paging message610for MS112and, as such, MS112does not need to listen to listening interval slot630. The predefined process can hash the MS identifiers to the index of paging slots, such as, letting MSs with identifiers ending with ‘00’, ‘01’, ‘10’, ‘11’ be in the first, second, third, and fourth slot, respectively. In some embodiments, explicit signaling can be alternatively used wherein BS102explicitly notifies MS112which slots to listen. In some embodiments, to make the paging message shorter, the globally unique MS identifier (MSID) can be hashed into a shorter identifier.

FIG. 6Billustrates a paging interval and a paging listening interval according to the present disclosure. Within a paging cycle605, the BS102can define one or multiple paging intervals635, within which BS102pages MSs112,115. A paging interval offset625identifies the beginning time of the paging interval635. The interval offset625can be an attribute of BS102. In some embodiments, the paging interval offset625can be determined by a paging area identifier, or a base station paging group ID (BSPG ID), where all the base stations with the same BSPG ID can have the same paging interval offset625. A paging area can include many base stations and all the base stations can share a BSPG ID. A base station may be involved in multiple paging areas, and therefore, a BS can include multiple BSPG IDs. In some embodiments, BS102broadcasts its BSPG ID to MS112and MS115. MS112and MS115each include a respective paging listening interval offset626,627according to the paging interval offset625of BS102. Within one paging interval635, BS102can page multiple groups of MSs. Each group can include a different paging listening offset626,627and a common paging listening interval offset628, which also is related to MS identifiers. The paging listening offsets626-627also can be defined relative to the beginning of the paging listening interval640as shown inFIG. 6C. For example, the paging interval offset625aidentifies the beginning time of the paging interval635, the first paging slot offset625bidentifies the beginning of the first paging slot612and the second paging slot625cidentifies the beginning of the second paging slot617. In addition, the paging listening offset628aidentifies the beginning of the paging listening interval640, a first listening slot offset628bidentifies the beginning of the first listening slot620and the second listening slot628cidentifies the beginning of the second listening slot630. In one listening interval640, MS112and MS115do not need to listen all the time, but only listen when the message possibly relevant to them is transmitted. In some embodiments, the timing offsets625-629can be determined by explicit signaling. In some embodiments, the timing offsets625-629can be determined by predefined algorithms at BS102and MSs111,115.

Embodiments of the present disclosure mitigate the interference from femtocell to macrocell, so as to ensure the paging message to MS112, which is located very close to FBS104, which is a CSG femtocell to which MS112does not have the right, or has limited or low priority, to access because MS112is not a subscriber to FBS104.

For ease of illustration, the time slot in which BS102transmits a paging message is referred to as the paging slot, and the listening interval slot (that is, the time slot) in which MS112listens to the paging message is referred to as the listening slot. However, each slot can be referred to by other names without departing from the scope of this disclosure.

FIG. 7illustrates a process for paging in an unavailable interval according to embodiments of the present disclosure. The embodiment of the paging process shown inFIG. 7is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

In some embodiments, the network entity, such as BS102, checks whether any of the paging messages610,615in a paging cycle605will be broadcasted in the AI505of the LDC for the femtocells, FBS104, FBS144, FBS154. As shown in the example illustrated inFIG. 7, the first paging message610is broadcasted in a paging slot612, which occurs in the AI505. Using a predefined process, such as a predefined function or algorithm BS102recalculates a paging offset725such that the paging message610can be transmitted in the UAI510bof the LDC of FBS104, FBS144and FBS154. Then BS102broadcasts the paging message610in the paging slot712at the new paging offset725.

MS112checks whether its expected paging message610will be in the AI505. When MS112determines that the paging message610will occur in a paging listening slot620, which occurs in the AI505, MS112uses the same predefined process used by BS102to recalculate a paging listening offset726such that the listening slot720occurs within the UAI510. Then, MS112listens to the paging message610at the new listening slot720based on the new paging listening offset725b.

In addition, MS115checks whether its expected paging message615will be in the AI505. If MS115determines that the paging message615will occur in the AI505, MS115uses the same predefined process used by BS102to recalculate a paging listening offset such that MS115will listen for the paging message615in a listening slot within the UAI510. However, if MS115determines that the paging message615occurs in the UAI510, MS115does not recalculate the paging offset. MS115listens to the paging message615at the previous listening interval slot630based on the previous paging listening offset627.

The process for determining AI and paging conflicts as well as for adjusting the paging message by recalculating the paging offsets may be performed repeatedly, or periodically, because the pattern of paging slots in the AI505can vary over time and since periodicity of the paging cycle605and the femto low duty cycle mode500may not be the same. In addition, it will be understood that although one MS is paged once within one paging cycle605in the example, multiple paging slots for one MS can occur without departing from the scope of this disclosure.

Accordingly, BS102, MS112and MS115can opportunistically utilize the UAI510of the femtocells in LDC mode, to mitigate the interferences from femtocells to macrocells. Therefore, MS112can have a larger chance to receive the paging message610, even when MS112is very close to FBS104. In addition, overhead and latency in notifying/updating MS112regarding the timing of the recalculated paging intervals of the macrocells can be reduced because the MS uses predefined algorithm to determine the paging listening timing, rather than extracting such timing via the signaling from the BS.

FIG. 8illustrates a process for changing paging timing according to embodiments of the present disclosure. The embodiment of the process800shown inFIG. 8is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

In block805, BS102identifies the femtocell low duty mode pattern500. BS102may receive the femtocell LDC pattern500, such as via a backhaul connection. In some embodiments, the LDC pattern500is predefined. BS102compares the paging slots612,617with the femtocell LDC mode pattern500in block810. In block815, BS102determines if any of the paging slots612,617overlap with the AI505of the LDC mode pattern500. If any of the paging slots612,617overlaps with the AI505, BS102recalculates one or more new paging offsets725in block820. BS102recalculates the paging slot offset725such that the new paging slot712occurs within the UAI510of femtocells. In block825, BS102transmits the paging message610in the new paging slot712. If BS102determines that the paging slots612,617do not overlap with the AI505in block815, BS102transmits the respective paging messages610,615during the original paging slots612,617in block830.

FIG. 9illustrates a process for changing listening interval timing according to embodiments of the present disclosure. The embodiment of the process900shown inFIG. 9is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

In block905, MS112is in active mode. MS112identifies the femtocell LDC mode pattern500and macrocell paging slot612in block910. MS112may receive the femtocell LDC pattern500via signalling. In some embodiments, the LDC pattern500is predefined. MS112enters idle mode in block915. MS112, in idle mode, is assigned to a paging group. Additionally, MS112may be in idle mode as it enters a cell124in block920. In block920, MS112identifies the femtocell LDC mode pattern500. The LDC pattern500can be predefined or received via signaling. MS112compares the AI's505in the femtocell LDC mode pattern500with the paging slot612in block925. In block930, MS112determines if the paging slot612occurs within the AI505of the LDC mode pattern500. If the paging slot612occurs within the AI505, MS112recalculates a new paging listening slot720in block930. MS112recalculates the listening offset726such that the new paging listening slot720occurs within the UAI510of FBS104. In block940, MS112listens for the paging message610in the new paging listening slot720. Alternatively, if MS112determines that the paging slot612does not overlap with the AI505in block930, MS112listens for the paging message610during the original paging listening slot620in block945.

The adjustment of the paging slot612, listening slot620, paging offset625and/or paging interval offset625bmay be done per paging cycle605in order to avoid the overlapping of a new paging slot720and AI505. In other words, this adjustment can be performed per paging cycle605. If the next paging slot612based on the regular idle mode operation does not overlap with the AI505in the next paging cycle605, both BS102and MS112can use the timing of the paging slot612and listening slot620as determined by the regular method. This will ensure that MS112knows where to locate a paging message610no matter whether MS112has just entered a cell124or has been in the cell124for a long period of time.

However, if BS102explicitly signals the usage of the new paging offset725and other parameters for calculating the timing of the paging slot712, all the MSs, such as MS112and MS115, that are affected use the new parameters.

In some embodiments, the predefined process for recalculating the paging and paging-listening offsets is a predefined algorithm. The predefined algorithm to recalculate the paging/paging-listening offset can be a function (such as a hash function) of a low duty cycle patterns of femtocells and one or more of: MSIDs or some sequences derived from MSIDs, macro base station identifiers, paging cycle, paging area identifiers, BSPG IDs, and the like.

For example, in one paging cycle, there are M paging offsets (0,1, . . . , M-1) and M associated paging slots (0,1, . . . , M-1), with each paging slot associating with one paging offset. In systems that do not include the femtocells LDC pattern, the algorithm to calculate the paging/paging-listening offsets may be a function of the MS IDs. The paging offset/slot I for MS112with identifier MS_ID can be determined by Equation 1:
Paging_Offset I=MS_ID modulo M.  [Eqn. 1]

However, in embodiments of the present disclosure, the algorithm includes the femtocell LDC mode pattern. For example, in one paging cycle, among M available paging slots (0,1, . . . , M-1), there are L paging slots that occur within the UAI of femtocell LDC. These L paging slots are placed in UAI of LDC in a new set S=(s0, s1, . . . , sL-1). For MS112with identifier MS_ID, if its paging slot I is not in set S, the paging slot is recalculated and a new slot I is calculated according to Equation 2:
NEW_Paging_offset I=s1, where s1is in S, and l=MS_ID modulo L.  [Eqn. 2]

In Equation 2, S is the set of paging offsets in UAI of femocell LDC in one paging cycle.

In some embodiments, both MS112and BS102shift a paging listening slot620out of the AI505. For example, the paging listening slot620could be shifted from the AI505such that the new listening slot720occurs at the beginning of the immediately next UAI510b, the middle of the immediately next UAI510b, or a pre-determined place of the immediately next UAI510b. Similarly, the paging listening slot730could be shifted to the beginning of the immediately previous UAI510a, the middle of the immediately previous UAI510a, or a pre-determined place of the immediately previous UAI510a.

In addition, the algorithm can be configured to randomly choose one slot from set S. Alternatively, the hash function can use the some part of MS_ID as the input (for example, the first 8 most significant bits (MSB) of MS_ID; some function of MS_ID; and the like). The hash function can also consider other parameters as the input, such as the macro base station ID, the paging area ID, paging group ID, and the like. For example, for different paging area ID, the paging offsets can be further shifted differently.

In some embodiments, the network entity, such as BS102, recalculates a paging offset725for the paging message610that occurs within the AI505of the LDC of femtocells such that the resulting new listening slot720occurs within the UAI510of the LDC of femtocells. In addition, BS102signals MS112regarding the recalculated paging offset. MS112receives the new paging offset725from the signaling from BS102and listens to the paging message610in the listening slot720.

FIG. 10illustrates a process for paging interval offset changes according to embodiments of the present disclosure. The embodiment of the paging interval offset change shown inFIG. 10is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

In some embodiments, the network entity, such as BS102, checks whether some of or the entire paging interval635overlaps with the AI505in the same paging cycle605. BS102recalculates the paging interval offset625for the paging interval635, such that the resulting new the paging offset1025can reduce or remove the overlapping of the new paging interval1035and the AI505. BS102broadcasts the paging message610in the paging interval1035at the new paging interval offset1025. MS112checks whether its expected paging listening interval640overlaps the AI505. If the paging listening interval640overlaps the AI505, MS112uses the same process used by BS102to recalculate a new paging listening interval offset1028. MS112then listens to the paging message610in the new paging listening interval1040. Additionally, MS115checks whether its expected paging listening interval640overlaps the AI505. If the paging listening interval640overlaps the AI505, MS115uses the same process used by BS102to recalculate the new paging listening interval offset1028. MS115then listens to the paging message615in the new paging listening interval1040.

Here, the offset625of the paging interval635and the offset628for the paging listening interval640are recalculated. Since the paging interval635, which can contain one or multiple paging slots612,617for paging messages610,615, is being adjusted, the multiple paging slots612,617and listening slots620,630are adjusted as opposed to the adjustment of individual paging slots612,617and listening slots620,630as shown inFIG. 7or individual paging slot offset. Therefore, the embodiment can have a larger granularity.

In some embodiments, the predefined process to recalculate the paging/paging-listening interval offset can be a function (such as a hash function) of low duty cycle patterns of femtocells, and one or more of: MSIDs or some sequences derived from MSIDs, macro base station identifiers, paging cycle, paging area identifiers, BSPG IDs, and the like.

For example, assuming in one paging cycle, there are M possible paging interval offsets (0,1, . . . , K-1) and the femtocells LDC pattern is not considered, the function to calculate the paging/paging-listening interval offset may be a function (such as a hash function) of the BSPG IDs. Multiple base stations can be grouped into one paging group, and they can share a paging group ID. The paging interval offset J macro BS with BSPG_ID can be calculated according to Equation 3:
Paging_Interval_Offset J=BSPG_ID modulo K.  [Eqn. 3]

However, when the femtocells LDC pattern is considered to recalculate the paging offset, the function will be adjusted to take into account of femtocell LDC. For example, assuming in one paging cycle, among K paging interval starting with offsets (0,1, . . . , K-1), there are (Q0, Q1, . . . , QN) paging intervals have (0,1, . . . , N) units overlap with AI of femtocell LDC, where N-unit is the minimum of the length of the AI and the paging cycle. Note that the unit can be different in different systems, such as frame, subframe, and so forth. Suppose Q0=Q1= . . . =Qi−1=0, Qi>0, that is, Qiis the first non-zero element in (Q0, Q1, . . . , QN).

R denotes the set of all these Qioffsets associated with the paging intervals that include the least units of overlapping with AI as illustrated in Equation 4:
R=(r0, r1, . . . , rQi−1)  [Eqn. 4]

For BS with BSPG_ID, if its paging interval starting with offset J includes more than Qiunits overlapping with AI, the paging interval is recalculated and a new slot I is produced by Equation 5:
NEW_Paging_Interval_offset J=rl, where rlis in R, and l=BSPG_ID modulo Qi.  [Eqn. 5]

It will be understood that the functions shown by Equations 4 and 5 illustrate one example function. Other processes could be used without departing from the scope of this disclosure, such as randomly choosing one offset from set R, or the hash function can use the some part of BSPG_ID as the input (for example, the first 3 most significant bits (MSB) of BSPG_ID; some function of BSPG_ID; and the like). The hash function can also consider other parameters as the input, such as the macro base station ID, the paging area ID, MSID, and the like. Therefore, the paging interval timing will be a function of Low Duty Cycle patterns of femtos.

In some embodiments, when the network entity, such as BS102, recalculates a paging interval offset625for the paging interval635that overlaps the AI505such that the resulting new the paging interval1040includes less or no overlapping with the AI505. BS102also signals MS112regarding the recalculated paging offset1025. MS112receives the new paging interval offset1025from the signaling from BS102and listens to the paging message610.

BS102can use explicit signaling to notify MS112regarding the new paging interval offset1025. The explicit signaling may introduce overhead because of the signaling, but it can be used to make the paging interval offset1025assignment more flexible and reduce the complexity for (re-)calculating the listening slot720by MS112.

In some embodiments, the recalculation of the paging interval offset1025as shown inFIG. 10and paging slot626,627offset as shown inFIG. 7can be jointly performed. For example, the recalculation of paging interval offset625(and listening interval offset628) can be performed first. If the new intervals1035,1040that do not overlap with the AI505can be found, then the process ends. Otherwise, BS102and MS112each recalculate the paging offset625and listening offset626respectively to determine the new paging slot712and listening slot720.

In some embodiments, a plurality of femtocells, such as FBS104, FBS144and FBS154, in the same paging area reserve a common interval and make the common interval part of the unavailable interval510, macrocells, such as BS102, in the same paging area use the common interval to broadcast paging messages. The timing information of the common interval can be fixed or signaled to MS112so that MS112listens to the paging message in the common interval when MS112is in idle mode.

Therefore, the timing for the paging interval1035can be fixed or signaled so that there is no need for BS102or MS112to judge whether the paging interval1035will overlap with the AI505or not.

In some embodiments, FBS104can reserve a particular interval for macrocells paging messages and/or for other purposes such as for interference mitigation. The reserved interval does not need to be associated with the unavailable interval510. The timing information of the reserved interval can be fixed or signaled to MS112. In some embodiments, the timing information of the reserved interval can be sent or signaled (e.g., by broadcasting, unicasting, multicasting, and so forth) to the network entity such as MS by the other network entity, such as BS102or FBS104as part of the system configuration. The additional signaling, such as broadcast of the timing information of the reserved interval, can make the resource allocation more configurable if needed. The signaling, such as broadcast of the timing information of the reserved interval, can be made in advance before the reserved interval being effective.

In some embodiments, before MS112enters idle mode, the network configures the paging cycle, paging listening offset and paging listening interval such that all the paging slots always fall in the UAI510, or the overlapping of the number paging slots and the AIs505are minimized. Therefore the network may also need to configure the low duty cycle mode at the same time such that the paging slots and the AI505are configured to avoid each other (that is, not overlap) as much as possible. In some embodiments, the network may modify an existing low duty mode and/or existing idle mode parameters in order to minimize the overlapping between the paging slots and the AIs505. The parameters, such as the timing information of the existing/modified LDM and/or existing/modified idle mode parameters, can be sent or signaled (e.g., by broadcasting, unicasting, multicasting, and so forth) to the network entity, such as MS, by the other network entity, such as BS102or FBS104, as part of the system configuration or reconfiguration. The additional signaling can make the resource allocation more configurable if needed. The signaling such as broadcast of the (re)configured LDM pattern parameters, such as the timing information and/or idle mode parameters, such as those timing offsets mentioned above, can be made in advance before the parameters being effective.

In some embodiments, one or more (or all) of FES104, FES144and FBS154, can adjust their transmission so that no transmission from a FBS104, FBS144and FBS154occurs when BS102is broadcasting a paging message. This applies equally for each femtocell BS operating in either normal operation mode or in low duty operation mode. Through the network and/or through BS102(that is, the overlapped macro BS), FBS104knows when the BS102may broadcast paging messages. FBS104in normal operation mode halts any transmission in those paging slots, or minimizes the transmission in those paging slots. FBS104in low duty operation mode halts or minimizes any transmission in those paging slots if those periods happen in the AI505. In this example, neither BS102nor MS112needs to adjust the operation in idle mode. Either in regular mode or in low duty mode, the parameters such as the timing of the paging slots where the transmission would be halted or minimized can be sent or signaled (e.g., by broadcasting, unicasting, multicasting, and so forth) to the network entity, such as MS by the other network entity, such as BS102or FBS104, as part of the system configuration or reconfiguration. The additional signaling can make the resource allocation more configurable if needed. The signaling such as broadcast of the parameters such as the timing of the paging slots where the transmission would be halted or minimized mentioned above can be made in advance before the parameters being effective.

In some embodiments, the adjustment of paging slots or the adjustment of transmissions from FBS104leaves enough room for MS112to be paged to complete the network re-entry. For example, the paging slot can be moved from the AI505enough such that a MS112(a paged MS) can finish network re-entry without suffering serious interference from FBS104. Similarly, if FBS104tries to avoid transmission when BS102is broadcasting a paging message, FBS104can minimize the usage of the resource scheduled by BS102for any paged MS to complete network re-entry.

FIG. 11illustrates a process for paging interval offset changes for a femtocell to page a mobile station according to embodiments of the present disclosure. The embodiment of the paging interval offset change shown inFIG. 11is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

In some embodiments, FBS104, operating in low duty mode, can page MS115in idle mode. FBS104can broadcast paging messages in the active interval505. When MS115listens to FBS104for paging messages, MS115aligns the paging listening offset with the available interval for FBS104. If needed, the recalculation of the timing using a predefined process similar to the embodiment described hereinabove with respect toFIGS. 5 through 10, to reduce or minimize or remove the overlap of the time for paging message and the UAI of the LDC, to make the time for paging message to overlap with the AI of the LDC as much as possible, to reduce the total transmission time of femto so as to reduce the interference to other BSs. For example, if the original paging slot1105, based upon the original paging offset1110, for MS115, when FBS104is in the regular mode, overlaps with the unavailable interval510, FBS104recalculates a new paging offset1125to overlap with the active interval505as much as possible using a predefined process. When MS115detects that the original paging slot1105overlaps with the unavailable interval510, MS115uses the same predefined process to recalculate the new paging listening offset1135and paging listening slot1130to listen to the paging messages. The predefined process can be a function (such as, a hash function) of the LDC patterns of the femtocells, the identifiers of the MSs, the paging cycle, the required paging offsets, and so forth. In addition, MS112detects that the original paging slot1140occurs within the AI505, therefore MS115does not recalculate offsets; rather MS115listens for the paging messages in the original paging slot1140.

In some embodiments, the offsets1125,1135that are recalculated are the paging/paging-listening interval offsets. Therefore, the embodiment can have a larger granularity.

FIG. 12illustrates paging/paging-listening interval timings changes according to the femtocells LDC pattern for a femtocell to page its member MS according to embodiments of the present disclosure. The embodiment of the paging/paging-listening interval timings changes shown inFIG. 12is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

The paging interval1205overlaps with the UAI510. Therefore, FBS104recalculates a new paging interval offset with which a new paging interval1210will overlap with AI505as much as possible, to reduce the total transmission time of femto so as to reduce the interference to other BSs. In the example shown inFIG. 12, only one paging message is shown; however, multiple paging messages for different groups of MSs can be broadcasted in the paging interval1210. In addition, MS112can recalculate the paging listening interval offset such that the paging listening interval1215overlaps with the AI505as much as possible. Therefore, instead of listening for the paging messages in the original paging listening interval1220, which overlaps with in the UAI510, MS112listens for the paging messages within the new paging listening interval1215.

In some embodiments, FBS104, operating in low duty cycle mode, can broadcast a paging message in the UAI510. If the timing of a paging message for MS112, when FBS104is in the regular mode, overlaps the UAI510, then FBS104performs an exceptional transmission over the air in its UAI510to send a paging message to MS112. Therefore, MS112does not need to change its paging listening interval or slot.

In some embodiments, when a paging message needs to be delivered by FBS104, operating in low duty cycle mode, to MS112, the network (or the paging controller) sends a message to the FBS104to wake up FBS104. In response, FBS104exits the low duty cycle mode (that is, enters the regular mode) and delivers the paging message to MS112.

In some embodiments, MS112is a member mobile station and in idle mode. FBS104is a CSG femto in LDC mode. When the paging controller has updated MS112's location, and MS112is to be paged, all the femtos in the same CSG page MS112. To avoid waking up all the femtos that are in LDC in the same CSG, MS paging listening timing is configured to occur within the available interval of femtocell LDC. If needed, a recalculation of the BS102paging timing and MS112paging listening timing using a predefined process similar to the embodiment disclosed herein above. In some embodiments, all the femtos in the same CSG go back to regular mode (that is, exit LDC mode) and page MS112.

In some embodiments, the transmitting time of the femto is reduced. More particularly, embodiments of the present disclosure can reduce the total length of the AI505to further improve interference mitigation.

FIG. 13illustrates coordinating available and paging intervals by adjusting the available interval start time according to embodiments of the present disclosure. The embodiment of the coordinating process shown inFIG. 13is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

In the example shown inFIG. 13, FBS104is operating in LDC mode500aand the AI505ais longer than the paging interval slot1305. If the start time of an AI505a, which does not include the femto paging interval slot1305, is within a certain distance from the femto paging interval slot1305start time, FES104changes the AI505astart time using a predefined process. For example, FBS104adjusts the start time of505asuch that the paging interval slot1305overlaps with a synchronized AI505bas shown in the LDC mode500b. FBS104can adjust the start time of the newly positioned synchronized AI505bforward (earlier) or backward (later). In one example, FBS104adds AI for paging505cto the AI505asuch that the two AI's505a,505coccur as illustrated in the LDC mode500c. The AI for paging505ccan be created such that it is substantially the same size as the femto paging interval slot1305.

FBS104informs MS112, in advance, the timing for the AI505aand the paging intervals slot1305. Thereafter, MS112uses the same process to determine how the AI505ais moved.

In some embodiments, the predefined process can be based on a function as illustrated in Equation 6:
|PG_OFFSET−AI_OFFSET|≦PARAMETER  [Eqn. 6]

Therefore, if the distance of the FBS paging interval slot1305starting time (PG_OFFSET1310) and an AI505astarting time (AI_OFFSET) is less than a given parameter (PARAMETER), then FBS104will move the AI505ato match the offset1310for the paging interval slot1305, which matches the paging message1315.

PG_OFFSET and AI_SC_OFFSET can be configured in units of a metric of the frame, such as, superframe, frame, subframe, and the like.

In the example shown inFIG. 13,500breduces transmission time of the femto as compared with500c.

FIG. 14illustrates coordinating available and paging intervals by adjusting the available interval start time and size according to embodiments of the present disclosure. The embodiment of the coordinating process shown inFIG. 14is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

In the example shown inFIG. 14, the AI505adoes not include, i.e., overlap, the paging intervals1405of FBS104, which is operating in LDC mode (LDM)500. FBS104can extend the interval length of the AI505ais the AI505ainterval length is smaller than the one of the paging interval slots1405. The AI505ainterval length is extended so that the available interval505acontains the paging interval slot1405of PBS104.

The AI505athat does not include the paging interval slot1405can be used for assisting MS112to scan femto in LDM, or it can be used for other purposes. Adjusting the size and start time of the AI505acan reduce the total time for AI505, so that the interference to other cells can be reduced.

If FBS104determines that AI505ais shorter than the paging interval slot1405, FBS104extends the size of the AI505ato assist MS112to detect FBS104. If necessary, FBS104can adjust the start time of AI505as illustrated inFIG. 13. Therefore, FBS104can adjust the start time such that the paging interval slot1405overlaps with a synchronized AI505bas shown in the LDC mode500b. FBS104can adjust the size of the newly positioned synchronized AI505bto match the size of the paging interval slot1405.

In some embodiments, the starting time of an AI505can be a pre-defined function of system information such as frequency allocation, paging group ID, types of femtos, and the like. MS112knows the pre-defined function and MS112can calculate the timing for AI505based on the received system information.

FIG. 15another example for coordinating available and paging intervals by adjusting the available interval start time and size according to embodiments of the present disclosure. The embodiment of the coordinating process shown inFIG. 15is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

In the example shown inFIG. 15, the coordinating of the AI505and paging interval slot1505by adjusting the AI505starting time based on a frequency allocation is shown. FBS104coordinates the starting of the synchronized AI505bto assist MS112to detect FBS104in LDM as a function of frequency allocation (FA) of the FBS104. In this example, the frequency allocation and paging interval slot1505, which may be decided by paging group ID, can be the inputs of the functions. The timing for the synchronized AI505bto assist MS112to detect femto can be decided based on the FA. For example, for a first FA, a sync AI1510can be included in a first portion of the synchronized AI505band for a second FA, a sync AI1515can be included in a second portion of the synchronized AI505b. Then to coordinate paging further, the processes defined in the embodiments above can be used.

In some embodiments, the change of the starting time of an AI505can be signaled to MS112by FBS104.

In some embodiments, the time for AI505is shortened when there are multiple MSs in sleep mode.

FIG. 16illustrates coordinating of mobile station sleep cycles according to embodiments of the present disclosure. The embodiment of the coordination shown inFIG. 16is for illustration only. Other embodiments could be used without departing from the scope of this disclosure.

In some embodiments, FBS104coordinates the sleeping cycles for the mobile stations in sleep mode. In the example shown inFIG. 16, MS112includes listening intervals (LI)1610aand sleep intervals (SI)1615aand MS115includes LIs1620aand SIs1625a. FBS104can adjust and expand AI505ato be the modified AI505d. FBS104also can add an additional modified AI505das necessary. Modified AI505dis configured to start at least as soon as the first LI1610a,1620aand last until at least the end of the last LI1610a,1620a. As a result, at least a portion of the SIs1615a,1625aoverlap with the UAI510. Therefore, FBS104can use as much as the resource available in the basic low duty500pattern to reduce the total time for available interval taking into account both the AI in basic low duty pattern and the AI to assist the mobile stations in sleep mode, that is the modified AI505d.

In some embodiments, FBS104can signal the adjusted low duty cycle patterns to mobile stations.

In some embodiments, MS112and MS115coordinate the start times of their LIs. femto base station can follow predefined rules to adjust the low duty cycle patterns, and mobile stations will use the same predefined rules to know the pattern. The MSs can coordinate their sleep mode based on the rules and received signals about some other MSs sleep mode

The predefined rules can be, for example, the starting time of the listening interval of an MS can be changed to be the nearest starting time of the AI which assists MS to detect femto, and the said listening interval shifts accordingly. Or the listening interval of an MS can be shifted in a minimum distance such that it will contain nearby AI which assists MS to detect femto.

For example, LI1610bfor MS112can start at substantially the same time as LI1620bfor MS112. IN addition, FBS104can adjust and expand AI505ato be the modified AI505e. FBS104also can add an additional modified AI505eas necessary. Modified AI505eis configured to start as soon as the first LI1610a,1620astarts and last until the end of the last LI1610a,1620a. As a result, at least a portion of the SIs1615a,1625aoverlap with the UAI510. However, the modified AI505euses only those resources necessary to overlap with the LI's1610b,1620b.