Patent Publication Number: US-8538337-B2

Title: Methods and apparatus for uplink and downlink inter-cell interference coordination

Description:
CLAIM OF PRIORITY UNDER 35 U.S.C. §119 
     This application for patent claims the benefit of U.S. Provisional Application Ser. No. 61/045,549, filed on Apr. 16, 2008, and entitled “INTERFERENCE MANAGEMENT FOR FEMTO CELLS.” The present Application is also a continuation application of, and claims priority to U.S. application Ser. No. 12/423,498, filed Apr. 14, 2009, “METHODS AND APPARATUS FOR UPLINK AND DOWNLINK INTER-CELL INTERFERENCE COORDINATION,” all assigned to the assignee hereof, the disclosures of which are hereby expressly incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to wireless communication systems. More specifically, the present disclosure relates to methods and apparatus for uplink and downlink inter-cell interference coordination. 
     BACKGROUND 
     Wireless communication systems have become an important means by which many people worldwide have come to communicate. A wireless communication system may provide communication for a number of mobile stations, each of which may be serviced by a base station. 
     As the number of mobile stations deployed increases, the need for proper bandwidth utilization becomes more important. Furthermore, the introduction of semi-autonomous base stations may create interference with existing base stations. Inter-cell interference coordination (ICIC) may provide for the reduction or elimination of interference due to the introduction of semi-autonomous base stations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a wireless communication system with multiple user equipments (UEs), a home evolved nodeB (HeNB), an evolved nodeB (eNB), a relay node, and a core network; 
         FIG. 2  is a wireless communication system with a macro-eNB and multiple HeNBs; 
         FIG. 3  illustrates transmission schemes between a UE and two or more eNBs for uplink ICIC; 
         FIG. 4  is a flow diagram illustrating a method of uplink ICIC by an HeNB; 
         FIG. 4A  illustrates means-plus-function blocks corresponding to the method of  FIG. 4 ; 
         FIG. 5  illustrates transmission schemes between a UE, a mobility management entity (MME) and two or more eNBs for downlink ICIC; 
         FIG. 6  is a flow diagram illustrating a method for downlink ICIC by an HeNB; 
         FIG. 6A  illustrates means-plus-function blocks corresponding to the method of  FIG. 6 ; 
         FIG. 7  is a flow diagram illustrating a method for downlink ICIC by a UE; 
         FIG. 7A  illustrates means-plus-function blocks corresponding to the method of  FIG. 7 ; 
         FIG. 8  is a flow diagram illustrating another method for downlink ICIC by a UE; 
         FIG. 8A  illustrates means-plus-function blocks corresponding to the method of  FIG. 8 ; 
         FIG. 9  illustrates transmission schemes between a UE, a restricted HeNB and one or more unrestricted eNBs for downlink ICIC; 
         FIG. 10  is a flow diagram illustrating a method for downlink ICIC by an eNB; 
         FIG. 10A  illustrates means-plus-function blocks corresponding to the method of  FIG. 10 ; 
         FIG. 11  illustrates transmission schemes between a UE, an HeNB and one or more unrestricted eNBs for downlink ICIC; 
         FIG. 12  is a block diagram illustrating the various components of a UE for use in the present methods and apparatus; 
         FIG. 13  is a block diagram illustrating the various components of an eNB for use in the present methods and apparatus; 
         FIG. 14  illustrates certain components that may be included within a UE; and 
         FIG. 15  illustrates certain components that may be included within an eNB. 
     
    
    
     DETAILED DESCRIPTION 
     A method for inter-cell interference coordination (ICIC) by a home evolved NodeB (HeNB) is disclosed. A portion of bandwidth is reserved for a user equipment (UE). Notification of the reserved portion of bandwidth is sent to at least one potentially interfering evolved NodeB (eNB). A data exchange is performed with the UE using the reserved portion of bandwidth. Notification is sent to the at least one potentially interfering eNB releasing the reserved portion of bandwidth. 
     The notification releasing the reserved portion of bandwidth may be sent when the data exchange with the UE has stopped or when the UE enters idle mode. 
     The at least one potentially interfering eNB may be identified through a self organizing network (SON) server. The HeNB may communicate with the at least one potentially interfering eNB through a backhaul connection and/or an X2 link. The at least one potentially interfering eNB may be another HeNB. 
     A method for downlink inter-cell interference coordination (ICIC) by a home evolved NodeB (HeNB) is also disclosed. A data exchange is performed with a user equipment (UE). A measurement report is received. A transmit power is reduced with a first slew rate. The transmit power is increased with a second slew rate. 
     A timer may be started. It may be determined whether the timer has elapsed, and the transmit power may be increased with the second slew rate when the timer has elapsed. 
     The HeNB may be a restricted HeNB. The UE may not belong to a closed subscriber group (CSG) for the HeNB. 
     The measurement report may be received from the UE. In another configuration, the measurement report may be received from an evolved NodeB (eNB). The eNB may be a potentially interfering eNB or a potentially interfering HeNB. 
     A method for downlink inter-cell interference coordination (ICIC) by a user equipment (UE) is disclosed. A received signal strength is measured for a home evolved NodeB (HeNB). A measurement report is prepared. The measurement report includes the received signal strength for the HeNB. The measurement report is sent to a first evolved NodeB (eNB). 
     The first eNB may be the HeNB. A reselection to the HeNB may be performed. Access procedures may be performed with the HeNB for a first time. A mobility management entity (MME) may be registered with. A page may be received from the MME. Access procedures may be performed with the HeNB for a second time. The UE may perform access procedures with the HeNB for the second time before sending the measurement report to the HeNB. Performing a reselection to the HeNB may occur because downlink signals from the HeNB are interfering with downlink signals from a second eNB. 
     A home evolved NodeB (HeNB) configured for inter-cell interference coordination (ICIC) is also disclosed. The HeNB includes a processor and memory in electronic communication with the processor. Executable instructions are stored in the memory. A portion of bandwidth is reserved for a user equipment (UE). Notification of the reserved portion of bandwidth is sent to at least one potentially interfering evolved NodeB (eNB). A data exchange is performed with the UE using the reserved portion of bandwidth. Notification is sent to the potentially interfering eNBs releasing the reserved portion of bandwidth. 
     A home evolved NodeB (HeNB) configured for downlink inter-cell interference coordination (ICIC) is further disclosed. The HeNB includes a processor and memory in electronic communication with the processor. Executable instructions are stored in the memory. A data exchange is performed with a user equipment (UE). A measurement report is received. A transmit power is reduced with a first slew rate. The transmit power is increased with a second slew rate. 
     A user equipment (UE) configured for downlink inter-cell interference coordination (ICIC) is also disclosed. The UE includes a processor and memory in electronic communication with the processor. Executable instructions are stored in the memory. A received signal strength is measured for a home evolved NodeB (HeNB). A measurement report is prepared. The measurement report includes the received signal strength for the HeNB. The measurement report is sent to a first evolved NodeB (eNB). 
     An apparatus for inter-cell interference coordination (ICIC) is also disclosed. The apparatus includes means for reserving a portion of bandwidth for a user equipment (UE). The apparatus includes means for sending notification of the reserved portion of bandwidth to at least one potentially interfering evolved NodeB (eNB). The apparatus also includes means for performing a data exchange with the UE using the reserved portion of bandwidth. The apparatus further includes means for sending notification to the at least one potentially interfering eNB releasing the reserved portion of bandwidth. 
     An apparatus for downlink inter-cell interference coordination (ICIC) is disclosed. The apparatus includes means for performing a data exchange with a user equipment (UE). The apparatus includes means for receiving a measurement report. The apparatus also includes means for reducing a transmit power with a first slew rate and means for increasing the transmit power with a second slew rate. 
     Another apparatus for downlink inter-cell interference coordination (ICIC) is disclosed. The apparatus includes means for measuring a received signal strength for a home evolved NodeB (HeNB). The apparatus includes means for preparing a measurement report. The measurement report includes the received signal strength for the HeNB. The apparatus also includes means for sending the measurement report to a first evolved NodeB (eNB). 
     A computer-program product for a wireless device configured for inter-cell interference coordination (ICIC) is disclosed. The computer-program product includes a computer-readable medium having instructions thereon. The instructions include code for reserving a portion of bandwidth for a user equipment (UE). The instructions include code for sending notification of the reserved portion of bandwidth to at least one potentially interfering evolved NodeB (eNB). The instructions include code for performing a data exchange with the UE using the reserved portion of bandwidth. The instructions include code for sending notification to the at least one potentially interfering eNB releasing the reserved portion of bandwidth. 
     Another computer-program product for a wireless device configured for downlink inter-cell interference coordination (ICIC) is disclosed. The computer-program product includes a computer-readable medium having instructions thereon. The instructions include code for performing a data exchange with a user equipment (UE). The instructions include code for receiving a measurement report. The instructions also include code for reducing a transmit power with a first slew rate and code for increasing the transmit power with a second slew rate. 
     Additionally, another computer-program product for a wireless device configured for downlink inter-cell interference coordination (ICIC) is disclosed. The computer-program product includes a computer-readable medium having instructions thereon. The instructions include code for measuring a received signal strength for a home evolved NodeB (HeNB). The instructions include code for preparing a measurement report. The measurement report includes the received signal strength for the HeNB. The instructions include code for sending the measurement report to a first evolved NodeB (eNB). 
     The 3 rd  Generation Partnership Project (3GPP) is a collaboration between groups of telecommunications associations that aims to define a globally applicable third generation (3G) mobile phone specification. 3GPP Long Term Evolution (LTE) is a 3GPP project aimed at improving the Universal Mobile Telecommunications System (UMTS) mobile phone standard. The 3GPP may define specifications for the next generation of mobile networks, mobile systems, and mobile devices. 
     In 3GPP LTE, a mobile station or device may be referred to as a “user equipment” (UE). A base station may be referred to as an evolved NodeB (eNB). A semi-autonomous base station may be referred to as a home eNB (HeNB). An HeNB may thus be one example of an eNB. The HeNB and/or the coverage area of an HeNB may be referred to as a femtocell, an HeNB cell or a closed subscriber group (CSG) cell. 
       FIG. 1  shows a wireless communication system  100  with multiple user equipments (UEs)  104 , a home evolved NodeB (HeNB)  110 , an evolved NodeB (eNB)  102 , a relay node  106 , and a core network  108 . The eNB  102  may be the central base station in a wireless communication system. A UE  104  may also be called, and may contain some or all of the functionality of, a terminal, a mobile station, an access terminal, a subscriber unit, a station, etc. A UE  104  may be a cellular phone, a personal digital assistant (PDA), a wireless device, a wireless modem, a handheld device, a laptop computer, etc. 
     The core network  108  may be the central piece of a telecommunications network. For example, the core network  108  may facilitate communications with the Internet, other UEs, etc. A UE  104  may communicate with the core network  108  through an eNB  102  or an HeNB  110 . Multiple UEs  104  may be in wireless communication with an eNB  102  or an HeNB  110 . 
     The term “eNB” may be used to refer to the eNB  102  or to the HeNB  110 , because the HeNB  110  may be considered to be one type of eNB. The eNB  102  may be referred to as a macro-eNB  102 . 
     A macro-eNB  102  may have a much larger range than an HeNB  110 . Furthermore, a macro-eNB  102  may provide unrestricted access to UEs  104   a  subscribing to the core network  108 . In contrast, an HeNB  110  may provide restricted access to UEs  104   b  belonging to a closed subscriber group (CSG). It may be assumed that a UE  104  may only communicate with a single eNB at a given time. Thus, a UE  104   b  communicating with an HeNB  110  may not simultaneously communicate with a macro-eNB  102 . 
     The coverage area of an eNB may be referred to as a cell. Depending on sectoring, one or more cells may be served by the eNB. The coverage area of a macro-eNB  102  may be referred to as a macro-cell  112  or an eNB cell. Likewise, the coverage area of an HeNB  110  may be referred to as an HeNB-cell  114  or a femtocell. 
     Multiple eNBs may have a backhaul connection with each other through the core network  108 . For example, a backhaul connection may exist between the HeNB  110  and the eNB  102 . In a backhaul connection, an eNB  102  may communicate  126  with the core network  108  and the core network  108  may correspondingly communicate  128  with the HeNB  110 . A direct connection may also exist between multiple eNBs. For example, a direct connection may exist between the HeNB  110  and the eNB  102 . The direct connection may be an X2 connection  120 . Details about an X2 interface may be found in 3GPP TS 36.423×2-AP. Multiple eNBs may also have a connection  122 ,  124  through use of a relay node  106 . In one configuration, the relay node  106  may be the core network  108 . 
     The coverage range for a macro-cell  112  may be much larger than the coverage range for an HeNB-cell  114 . In one configuration, the coverage range for a macro-cell  112  may include the entire coverage range for an HeNB-cell  114 . 
     A UE  104  may communicate with a base station (e.g., the eNB  102  or the HeNB  110 ) via transmissions on the uplink  116  and the downlink  118 . The uplink  116  (or reverse link) refers to the communication link from the UE  104  to a base station, and the downlink  118  (or forward link) refers to the communication link from the base station to the UE  104 . Thus, a UE  104   a  may communicate with the eNB  102  via the uplink  116   a  and downlink  118   a . Likewise, a UE  104   b  may communicate with the HeNB  110  via the uplink  116   b  and downlink  118   b.    
     The resources of the wireless communication system  100  (e.g., bandwidth and transmit power) may be shared among multiple UEs  104 . A variety of multiple access techniques are known, including code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), single-carrier frequency division multiple access (SC-FDMA), and so forth. 
     A UE  104   a  in wireless communication with a macro-cell  112  may be referred to as a macro-UE  104   a . A UE  104   b  in wireless communication with an HeNB-cell  114  may be referred to as an HeNB-UE  104   b . One or more macro-UEs  104   a  located within an HeNB-cell  114  may jam the HeNB-cell  114 . For example, a macro-UE  104   a  located within an HeNB-cell  114  may cause interference for communications between an HeNB-UE  104   b  and the HeNB  110 . Likewise, a macro-UE  104   a  within the HeNB-cell  114  may not have macro-cell  112  coverage due to interference. Both uplink interference  130  and downlink interference  132  may occur. 
     If there are no UEs  104  in the CSG cell (HeNB cell  114 ), there may be no interference issues. In order to allow a successful initial access by a UE  104  to the CSG cell, the CSG cell may dynamically bias the open loop power control algorithm to balance the effect of high interference. CSG cells may also add noise to balance the uplink  116  and the downlink  118 . 
     Inter-cell interference coordination (ICIC) may be used to prevent the uplink interference  130  and/or the downlink interference  132 . Frequency ICIC may be feasible for both synchronous and asynchronous deployments. Time ICIC may be feasible in synchronized deployments. However, asynchronous deployments may require UE  104  feedback. Antenna techniques such as nulling interference from macro-cell UEs  104   a  may be used to control uplink inter-cell interference  130 . 
       FIG. 2  is a wireless communication system  200  with a macro-eNB  202  and multiple HeNBs  210 . The wireless communication system  200  may include an HeNB gateway  234  for scalability reasons. The macro-eNB  202  and the HeNB gateway  234  may each communicate with a pool  240  of mobility management entities (MME)  242  and a pool  244  of serving gateways (SGW)  246 . The HeNB gateway  234  may appear as a C-plane and a U-plane relay for dedicated S1 connections  236 . An S1 connection  236  may be a logical interface specified as the boundary between an evolved packet core (EPC) and an Evolved Universal Terrestrial Access Network (EUTRAN). The HeNB gateway  234  may act as a macro-eNB  202  from an EPC point of view. The C-plane interface may be S1-MME and the U-plane interface may be S1-U. 
     The HeNB gateway  234  may act towards an HeNB  210  as a single EPC node. The HeNB gateway  234  may ensure S1-flex connectivity for an HeNB  210 . The HeNB gateway  234  may provide a 1:n relay functionality such that a single HeNB  210  may communicate with n MMEs  242 . The HeNB gateway  234  registers towards the pool  240  of MMEs  242  when put into operation via the S1 setup procedure. The HeNB gateway  234  may support setup of S1 interfaces  236  with the HeNBs  210 . 
     The wireless communication system  200  may also include a self organizing network (SON) server  238 . The SON server  238  may provide automated optimization of a 3GPP LTE network. The SON server  238  may be a key driver for improving operation and maintenance (O&amp;M) to the wireless communication system  200 . An X2 link  220  may exist between the macro-eNB  202  and the HeNB gateway  234 . X2 links  220  may also exist between each of the HeNBs  210  connected to a common HeNB gateway  234 . The X2 links  220  may be set up based on input from the SON server  238 . An X2 link  220  may convey ICIC information. If an X2 link  220  cannot be established, the S1 link  236  may be used to convey ICIC information. 
       FIG. 3  illustrates transmission schemes  300  between a UE  304  and two or more eNBs for uplink ICIC. One of the eNBs may be an HeNB  310 . The HeNB  310  may provide unrestricted access to the core network  108  for UEs  304 . The UE  304  and the HeNB  310  may perform  301  access procedures between each other. Access procedures comprise an exchange of messages between the UE  304  and an eNB or an HeNB  310 . The HeNB  310  may then identify  303  one or more interfering eNBs  302  through SON and/or O&amp;M. The one or more interfering eNBs  302  may be HeNBs and/or macro-eNBs. An interfering eNB  302  may be a nearby eNB whose communications with a UE interfere with communications between the HeNB  310  and the UE  304 . The one or more interfering eNBs  302  may be stored on the HeNB  310  in a neighboring cell list. The neighboring cell list is discussed in more detail below in relation to  FIG. 13 . 
     The HeNB  310  may determine load information for the UE  304 . Load information may include overload and/or protected bands for the UE  304 . For example the HeNB  310  may determine particular frequency resources for the UE  304  to use in uplink communications  116   b  with the HeNB  310 . The HeNB  310  may instruct the UE  304  to send uplink transmissions  116   b  over the particular frequency resources. In one configuration, the HeNB  310  may use a different frequency band than the interfering eNBs  302 . For example, the HeNB  310  and interfering eNBs  302  may each use fractional frequency reuse (FFR). In FFR, the HeNB  310  and interfering eNBs  302  use the same frequency band along with the same low power sub-channels but each uses only a fraction of the high power sub-channels. Bandwidth partitioning may be accomplished through the SON server  238 . The FFR may be managed dynamically. Dynamic FFR may be important for the early deployment of CSG cells. A relatively small number of CSG cells may not warrant static FFR or a separate carrier. FFR may also be coupled with hopping. 
     The HeNB  310  may use a High Interference Indicator (HII) to reserve the particular frequency resources. The HII may identify frequency resources that are sensitive to high interference levels. For example, the HeNB  310  may reserve the load information by sending the load information to the one or more interfering eNBs  302 . Alternatively, the load information may be sent to potentially interfering eNBs. In one configuration, a macro-eNB  302  may use HII to reserve part of the bandwidth for macro-UEs. The macro-eNB  302  may send the reserved bandwidth information to CSG cells within the coverage range of the macro-eNB  302 . HII is based on operators policy. In HII, a common bandwidth is used for all CSG cells. It may be impractical for the macro-eNB  302  to reserve resources, due to the potentially large number of HeNBs within a single macro-cell. Interference management may be simpler if all the control channels on a CSG cell are mapped to the Physical Uplink Shared Channel (PUSCH) and protected with ICIC. 
     Each macro-UE may know which CSG-cells it interferes with. However, as the number of CSG-cells increases within a wireless communication network, it may become much more likely that many macro-UEs interfere with at least one CSG-cell. An HeNB  310  may scan for all sounding reference signals (SRSs) and report any received signal to neighboring macro-cells. 
     In one configuration, the HeNB  310  may send  303  the load information to a relay node  306 . The relay node  306  may then send  307  the load information to the one or more interfering eNBs  302 . If an X2 interface  220  exists between the HeNB  310  and the one or more interfering eNBs  302 , the load information may be sent directly to the interfering eNBs  302  through the X2 interface  220 . 
     A data exchange  309  between the UE  304  and the HeNB  310  may then occur. The data exchange  309  may involve the UE  304  sending uplink transmissions  116   b  to the HeNB  310  using the reserved resources. The HeNB  310  may then send  311  an RRC_Connection release to the UE  304 . An RRC_Connection release may release the UE  304  from the data exchange  309  with the HeNB  310  using the reserved resources. After the HeNB  310  has sent  311  an RRC_Connection release to the UE  304 , the HeNB  310  may send load information to the interfering eNBs  302  releasing the reserved resources. In one configuration, the HeNB  310  may send  313  the load information to a relay node  306  and the relay node  306  may send  315  the load information to the interfering eNBs  302 . 
     The HeNB  310  may also send the load information releasing the reserved resources to the interfering eNBs  302  when the UE  304  has been inactive for a sufficient period of time. For example, the HeNB  310  may send the load information releasing the reserved resources if the HeNB  310  has not received an uplink transmission  116   b  from the UE  304  for a certain amount of time. As another example, the HeNB  310  may send the load information releasing the reserved resources if the UE  304  has indicated a switch from RRC_Connected mode to RRC_Idle mode. 
       FIG. 4  is a flow diagram illustrating a method  400  of uplink ICIC by an HeNB  110 . The HeNB  110  may perform  402  access procedures to allow a UE  104   b  access. The HeNB  110  may then reserve  404  a portion of the available bandwidth for UE  104   b  data exchange. Specifically, the HeNB  110  may reserve  404  a portion of the available bandwidth for the UE  104   b  to use for uplink data transmissions  116   b.    
     The HeNB  110  may send  406  a notification of the UE  104   b  in connected mode and the reserved portion of the bandwidth to potentially interfering eNBs. The potentially interfering eNBs may include HeNBs and/or macro-eNBs. The HeNB  110  may then perform  408  a data exchange with the UE  104   b . When the data exchange has stopped  410 , the HeNB  110  may send  412  a notification of the released portion of bandwidth to the potentially interfering eNBs. 
     The method  400  of  FIG. 4  described above may be performed by various hardware and/or software component(s) and/or module(s) corresponding to the means-plus-function blocks  400 A illustrated in  FIG. 4A . In other words, blocks  402  through  412  illustrated in  FIG. 4  correspond to means-plus-function blocks  402 A through  412 A illustrated in  FIG. 4A . 
       FIG. 5  illustrates transmission schemes  500  between a UE  504 , a mobility management entity (MME)  542  and two or more eNBs for downlink ICIC. The UE  504  may be a macro-UE. For example, the UE  504  may be communicating with a macro-cell  112 . One of the eNBs may be an HeNB  510 . The HeNB  510  may be a restricted HeNB. For example, the HeNB  510  may only allow data exchange with UEs  504  that are part of the CSG of the HeNB  510 . The UE  504  may communicate with an eNB  502 . The UE  504  may not be part of the CSG of the HeNB  510 . The UE  504  may perform  501   a  reselection to the restricted HeNB  510  even though the restricted HeNB  510  may not allow data exchange for the UE  504 . For example, if the link between the UE  504  and the macro-cell  112  fails, the UE  504  may access an interfering HeNB  510  even if the HeNB  510  is restricted, so that the UE  504  may send measurement reports. Alternatively, in order to prevent failure, the macro-eNB  502  may request gaps to power control CSG-cells if the reference signal received power (RSRP) corresponding to the HeNBs  510  for these cells exceeds a maximum threshold. A gap may be a period of time where the UE  504  is not required to monitor the serving cell. 
     The UE  504  and HeNB  510  may perform  503  access procedures. The UE  504  may then register  505  with the CSG-cell by registering with the MME  542 . The UE  504  may then have a new tracking area. Mobility based cell reselection parameters may scale as the UE  504  moves through dense CSG cell environments. 
     The MME  542  may page  507  the UE  504 . For UE  504  terminated calls, the UE  504  may be paged  507  on the last register CSG-cell and the macro network tracking area. When the UE  504  is in the RRC_Idle state, the UE  504  may register with the MME  542  so that in the case of a UE  504  terminated call, the network (MME  542 ) may locate the UE  504  and send a page. A UE  504  may perform one registration per tracking area. The UE  504  may be able to register with a CSG cell (the CSG cell also makes up a tracking area) even though that CSG cell may not serve data traffic to the UE  504 . After the UE  504  registers with the CSG cell, it  504  may be paged on a CSG cell, and after the UE  504  receives this page, the UE  504  may access the CSG cell and power it down so that the UE  504  may communicate with the macro network. If the UE  504  is not allowed to access the CSG cell, it may not be able to power it down and hence a macro UE would be in outage. 
     The UE  504  and HeNB  510  may again perform  509  access procedures. The UE  504  may then send  511   a  measurement report to the HeNB  510 . Upon receiving the measurement report, the HeNB  510  may adjust  513  the transmit power according to the measurement report. For example, the HeNB  510  may reduce the HeNB  510  transmit power for a time period. 
     The UE  504  and an HeNB or macro-eNB  502  may then perform  515  access procedures. For both UE  504  originated calls and UE  504  terminated calls, the UE  504  may access the macro-eNB  502  when radio conditions are sufficient for doing so. For example, the interfering HeNB  510  may adjust  513  the transmit power such that the radio conditions are sufficient for the UE  504  to access the macro-cell  112 . Upon completion of the access procedures, a data exchange  517  between the UE  504  and the HeNB or macro-eNB  502  may occur. 
     In case of partial co-channel deployment, rules may be needed for how the UE  504  takes into account measurements on the reference signal (RS) in resource blocks (RBs) where the HeNB  510  is transmitting. For example, if the UE  504  detects an HeNB cell  114  partially overlapping a macro-cell  112 , measurement gaps may be required. For overlapping RBs, the UE  504  may discount (i.e. assume there is no signal) RS measurements. The UE  504  may effectively report lower channel quality indicators (CQIs) in order to ensure that the eNB  102  properly controls the power of the Packet Data Control Channel (PDCCH). The UE  504  may be able to receive the CQI in case an HeNB  510  is causing interference on those RBs. 
       FIG. 6  is a flow diagram illustrating a method  600  for downlink ICIC by an HeNB  110 . The HeNB  110  may perform  602  a data exchange with a UE  104   b . The HeNB  110  may then receive  604  a measurement report. The HeNB  110  may receive  604  the measurement report from the UE  104   b . Alternatively, the HeNB  110  may receive  604  the measurement report from another UE  104 . Alternatively still, the HeNB  110  may receive  604  the measurement report from a macro-eNB  102  or another HeNB. The HeNB  110  may receive  604  the measurement report from a macro-eNB  102  via backhaul signaling. 
     The HeNB  110  may reduce  606  the transmit power with a first slew rate. The HeNB  110  may be required to reduce  606  the transmit power such that the reference signal received power (RSRP) received from the HeNB  110  by the UE  104   b  is below a maximum threshold if the macro-cell  112  RSRP is below a minimum threshold and the macro-cell reference signal received quality (RSRQ) is below a minimum threshold. The HeNB  110  may reduce  606  the transmit power to meet the maximum RSRP threshold using a first slew rate. The first slew rate may be in decibels (dB)/millisecond (ms). For example, the first slew rate may be 1 dB/ms. Generally, the power may be reduced until the macro UE can have good channel. 
     The HeNB  110  may then start  608  a timer. When the timer elapses  610 , the HeNB  110  may increase  612  the transmit power with a second slew rate. The second slew rate may also be in dB/ms. The HeNB  110  may be provisioned to not transmit more power than the maximum RSRQ after accounting for minimum coupling loss. This may require a receiver functionally at the HeNB  110 . In order to estimate the received quality in the vicinity of the HeNB  110 , the HeNB  110  may estimate the received signal (from other cells that make up interference for the home UE) and compute the RSRQ after it accounts for its transmit power and minimum coupling loss. 
     The method  600  of  FIG. 6  described above may be performed by various hardware and/or software component(s) and/or module(s) corresponding to the means-plus-function blocks  600 A illustrated in  FIG. 6A . In other words, blocks  602  through  612  illustrated in  FIG. 6  correspond to means-plus-function blocks  602 A through  612 A illustrated in  FIG. 6A . 
       FIG. 7  is a flow diagram illustrating a method  700  for downlink ICIC by a UE  104   b . The UE  104   b  may perform  702  data exchange with an eNB. In one configuration, the eNB may be a macro-eNB  102 . Alternatively, the eNB may be an HeNB  110 . The UE  104   b  may then measure  704  the received signal strength from an HeNB  110 . The UE  104   b  may measure  704  the received signal strength using a physical layer procedure. The UE  104   b  may detect the synchronization signal from the eNB, and then it may perform a signal strength measurement. The UE  104   b  may prepare the received signal strength into a measurement report. The UE  104   b  may then send  706  the measurement report to an eNB. The eNB may be the eNB that the UE  104   b  performed data exchange with. Alternatively, the eNB may be a different eNB. In one configuration, the UE  104   b  may send  706  the measurement report to an HeNB  110 . 
     The method  700  of  FIG. 7  described above may be performed by various hardware and/or software component(s) and/or module(s) corresponding to the means-plus-function blocks  700 A illustrated in  FIG. 7A . In other words, blocks  702  through  706  illustrated in  FIG. 7  correspond to means-plus-function blocks  702 A through  706 A illustrated in  FIG. 7A . 
       FIG. 8  is a flow diagram illustrating another method  800  for downlink ICIC by a UE  104   b . The UE  104   b  may perform  802  a reselection to a restricted HeNB  110  from an unrestricted eNB  102 . A UE  104   b  may be allowed to access a restricted HeNB  110  if the macro-cell  112  is not suitable and there are no other frequencies available. A UE  104   b  may also be allowed to access a restricted HeNB  110  if the connection with a macro-cell  112  fails and there are no other frequencies available. The UE  104   b  may then register  804  with an MME  242 . The UE  104   b  may receive  806  a page from the MME  242 . 
     The UE  104   b  may then measure  808  the received signal strength of the restricted HeNB  110 . The UE  104   b  may also measure  810  the received signal strength of other eNBs  102  that the UE  104   b  can detect. The UE  104   b  may prepare a measurement report that includes the received signal strength of the restricted HeNB  110 . The measurement report may also include the received signal strengths of any other eNBs  102  that the UE  104   b  could detect. 
     The UE  104   b  may again access  812  the restricted HeNB  110 . The UE  104   b  may then send  814  the measurement report to the restricted HeNB  110 . The UE  104   b  may next access  816  the unrestricted eNB  102 . The UE  104   b  may access  816  the unrestricted eNB  102  when radio conditions are sufficient. The UE  104   b  may then perform  818  a data exchange with the unrestricted eNB  102 . 
     The method  800  of  FIG. 8  described above may be performed by various hardware and/or software component(s) and/or module(s) corresponding to the means-plus-function blocks  800 A illustrated in  FIG. 8A . In other words, blocks  802  through  818  illustrated in  FIG. 8  correspond to means-plus-function blocks  802 A through  818 A illustrated in  FIG. 8A . 
       FIG. 9  illustrates transmission schemes  900  between a UE  904 , a restricted HeNB  910  and one or more unrestricted eNBs  902  for downlink ICIC. A data exchange  901  may occur between the UE  904  and an unrestricted eNB  902 . The UE  904  may then send  903  a measurement report corresponding to the HeNB  910  to the unrestricted eNB  902 . The unrestricted eNB  902  may send  905  the measurement report corresponding to the HeNB  910  to a relay node  906 . The relay node  906  may then send  907  the measurement report corresponding to the restricted HeNB  910  to the restricted HeNB  910 . 
     Upon receiving the measurement report, the restricted HeNB  910  may adjust  909  the transmit power. For example, the restricted HeNB  910  may reduce the transmit power by a reduction slew rate. The HeNB  910  may be required to adjust  909  the transmit power according to the received measurement report. For example, the HeNB  910  may be required to perform downlink power control. The downlink power control may be facilitated through backhaul signaling such as through an S1  236 . A data exchange  911  may then occur between the UE  904  and the unrestricted eNB  902 . 
       FIG. 10  is a flow diagram illustrating a method  1000  for downlink ICIC by an eNB. The eNB may be a macro-eNB  102 . Alternatively, the eNB may be an HeNB  110 . The eNB may be an unrestricted eNB. The eNB may perform  1002  a data exchange with a UE  104 . The eNB may receive  1004  the measured signal strength for a restricted HeNB  110  from the UE  104 . The eNB may next determine  1006  the restricted HeNB  110  transmits power such that the eNB RSRP and RSRQ are above minimum thresholds. The eNB may then send  1008  the determined power control requirements to the restricted HeNB  110 . 
     The method  1000  of  FIG. 10  described above may be performed by various hardware and/or software component(s) and/or module(s) corresponding to the means-plus-function blocks  1000 A illustrated in  FIG. 10A . In other words, blocks  1002  through  1008  illustrated in  FIG. 10  correspond to means-plus-function blocks  1002 A through  1008 A illustrated in  FIG. 10A . 
       FIG. 11  illustrates transmission schemes  1100  between a UE  1104 , an HeNB  1110  and one or more unrestricted eNBs  1102  for downlink ICIC. A data exchange  1101  may occur between the UE  1104  and the HeNB  1110 . The HeNB  1110  may then reserve portions of the frequency band for downlink transmission between the HeNB  1110  and the UE  1104 . The HeNB  1110  may then send  1103  load information such as the reserved portions of the frequency band to a relay node  1106 . The load information may include protected subbands. The relay node  1106  may send  1105  the load information to the one or more unrestricted eNBs  1102 . The one or more unrestricted eNBs  1102  may adjust  1107  scheduling according to the received load information. For example, the one or more unrestricted eNBs  1102  may adjust  1107  downlink scheduling to avoid inter-cell interference with the HeNB  1110 . A data exchange  1109  may then occur between the UE  1104  and the HeNB  1110 . 
       FIG. 12  is a block diagram illustrating the various components of a UE  1204  for use in the present methods and apparatus. The UE  1204  may include a measurement report  1248 . The measurement report  1248  may include a restricted HeNB received signal strength  1252 . The measurement report  1248  may also include one or more unrestricted eNB received signal strengths  1250 . The UE  1204  may prepare the measurement report  1248  to be sent to an HeNB  110  and/or an eNB  102 . The UE  1204  may also include the reserved resources  1274  for communication with an HeNB  110 . 
       FIG. 13  is a block diagram illustrating the various components of an eNB  1302  for use in the present methods and apparatus. The eNB  1302  may be a restricted HeNB  110 , an unrestricted HeNB  110 , or a macro-eNB  102 . The eNB  1302  may include a received measurement report  1354 . The eNB  1302  may receive the measurement report  1354  from a UE  104 . The received measurement report  1354  may include power measurements and/or power control for the eNB  1302 . Alternatively, the received measurement report  1354  may include power measurements and/or power control for an HeNB  110  which the eNB  1302  will forward the measurement report to. 
     The eNB  1302  may also include a neighboring cell list generation module  1356 . The neighboring cell list generation module  1356  may generate a neighboring cell list  1358 . The neighboring cell list  1358  may include a list of one or more interfering eNBs  102 . As discussed above, an interfering eNB may be a nearby eNB whose communications with a UE  104  interfere with communications between the eNB  1302  and a UE  104 . The neighboring cell list  1358  may also include a list of one or more potentially interfering eNBs  102 . 
     The neighboring cell list generation module  1356  may generate the neighboring cell list  1358 . The neighboring cell list generation module  1356  may generate the neighboring cell list  1358  based on CSG eNB measurements. CSG eNB measurements may be measurements by the HeNB of the received signal strength from eNBs. The neighboring cell list generation module  1356  may also generate the neighboring cell list  1358  based on UE  104  measurements. The UE  104  measurements may include SON functionality. 
     The eNB  1302  may also include load information  1366 . The load information  1366  may include overload and/or protected bands for the eNB  1302  and/or a UE  104 . For example, the load information  1366  may include reserved portions of the bandwidth for uplink and/or downlink communications with a UE  104 . The eNB  1302  may include the transmit power  1370  for the eNB  1302 . The transmit power  1370  may be the transmit power  1370  that the eNB  1302  uses when sending transmissions to a UE  104  over the downlink. 
     The eNB  1302  may include a power reduction module  1362 . The power reduction module  1362  may determine when to reduce or increase the transmit power  1370 . The power reduction module  1362  may also determine the rate and amount of change to the transmit power  1370 . The power reduction module  1362  may include a timer  1364   a . The power reduction module  1362  may use the timer  1364   a  to determine how long the transmit power  1370  should remain at a reduced level. 
     The power reduction module  1362  may also include a transmit power reduction slew rate  1366 . The transmit power reduction slew rate  1366  may define the rate of reduction of the transmit power  1370  for the eNB  1302  when the transmit power  1370  of the eNB  1302  needs to be reduced. The transmit power reduction slew rate  1366  may be in dB/ms. The power reduction module  1362  may also include a transmit power increase slew rate  1368 . The transmit power increase slew rate  1368  may define the rate at which the transmit power  1370  is increased after the timer  1364   a  has expired. The transmit power increase slew rate  1368  may also be in dB/ms. 
     The eNB  1302  may include a resource reservation module  1372 . The resource reservation module  1372  may schedule resources for communications with a UE  104 . For example, the resource reservation module  1372  may include a list of the reserved resources  1374  for communications with a UE  104 . The resource reservation module  1372  may also include a timer  1364   b . The resource reservation module  1372  may release reserved resources  1374  if the timer  1364   b  has elapsed before communications have been received from a UE  104 . 
       FIG. 14  illustrates certain components that may be included within a UE  1404 . The UE  1404  may be a mobile device/station. Examples of mobile stations include cellular phones, handheld wireless devices, wireless modems, laptop computers, personal computers, etc. A mobile station may alternatively be referred to as an access terminal, a mobile terminal, a subscriber station, a remote station, a user terminal, a terminal, a subscriber unit, user equipment, etc. 
     The UE  1404  includes a processor  1403 . The processor  1403  may be a general purpose single- or multi-chip microprocessor (e.g., an ARM), a special purpose microprocessor (e.g., a digital signal processor (DSP)), a microcontroller, a programmable gate array, etc. The processor  1403  may be referred to as a central processing unit (CPU). Although just a single processor  1403  is shown in the UE  1404  of  FIG. 14 , in an alternative configuration, a combination of processors (e.g., an ARM and DSP) could be used. 
     The UE  1404  also includes memory  1405 . The memory  1405  may be any electronic component capable of storing electronic information. The memory  1405  may be embodied as random access memory (RAM), read only memory (ROM), magnetic disk storage media, optical storage media, flash memory devices in RAM, on-board memory included with the processor, EPROM memory, EEPROM memory, registers, and so forth, including combinations thereof. 
     Data  1409  and instructions  1407  may be stored in the memory  1405 . The instructions  1407  may be executable by the processor  1403  to implement the methods disclosed herein. Executing the instructions  1407  may involve the use of the data  1409  that is stored in the memory  1405 . When the processor  1403  executes the instructions  1407 , various portions of the instructions  1407   a  may be loaded onto the processor  1403 , and various pieces of data  1409   a  may be loaded onto the processor  1403 . 
     The UE  1404  may also include a transmitter  1411  and a receiver  1413  to allow transmission and reception of signals to and from the UE  1404 . The transmitter  1411  and receiver  1413  may be collectively referred to as a transceiver  1415 . An antenna  1417  may be electrically coupled to the transceiver  1415 . The UE  1404  may also include (not shown) multiple transmitters, multiple receivers, multiple transceivers and/or multiple antennas. 
     The various components of the UE  1404  may be coupled together by one or more buses, which may include a power bus, a control signal bus, a status signal bus, a data bus, etc. For the sake of clarity, the various buses are illustrated in  FIG. 14  as a bus system  1419 . 
       FIG. 15  illustrates certain components that may be included within an eNB  1502 . An eNB  1502  may be a base station. For example, the eNB may be the central base station in a 3GPP LTE wireless communication system. As another example, the eNB  1502  may be an HeNB  110  for use in a 3GPP LTE wireless communication system. 
     The eNB  1502  includes a processor  1503 . The processor  1503  may be a general purpose single- or multi-chip microprocessor (e.g., an ARM), a special purpose microprocessor (e.g., a digital signal processor (DSP)), a microcontroller, a programmable gate array, etc. The processor  1503  may be referred to as a central processing unit (CPU). Although just a single processor  1503  is shown in the eNB  1502  of  FIG. 15 , in an alternative configuration, a combination of processors (e.g., an ARM and DSP) could be used. 
     The eNB  1502  also includes memory  1505 . The memory  1505  may be any electronic component capable of storing electronic information. The memory  1505  may be embodied as random access memory (RAM), read only memory (ROM), magnetic disk storage media, optical storage media, flash memory devices in RAM, on-board memory included with the processor, EPROM memory, EEPROM memory, registers, and so forth, including combinations thereof. 
     Data  1509  and instructions  1507  may be stored in the memory  1505 . The instructions  1507  may be executable by the processor  1503  to implement the methods disclosed herein. Executing the instructions  1507  may involve the use of the data  1509  that is stored in the memory  1505 . When the processor  1503  executes the instructions  1507 , various portions of the instructions  1507   a  may be loaded onto the processor  1503 , and various pieces of data  1509   a  may be loaded onto the processor  1503 . 
     The eNB  1502  may also include a transmitter  1511  and a receiver  1513  to allow transmission and reception of signals to and from the eNB  1502 . The transmitter  1511  and receiver  1513  may be collectively referred to as a transceiver  1515 . An antenna  1517  may be electrically coupled to the transceiver  1515 . The eNB  1502  may also include (not shown) multiple transmitters, multiple receivers, multiple transceivers and/or multiple antennas. 
     The various components of the eNB  1502  may be coupled together by one or more buses, which may include a power bus, a control signal bus, a status signal bus, a data bus, etc. For the sake of clarity, the various buses are illustrated in  FIG. 15  as a bus system  1519 . 
     The term “determining” encompasses a wide variety of actions and, therefore, “determining” can include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, “determining” can include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory) and the like. Also, “determining” can include resolving, selecting, choosing, establishing and the like. 
     The phrase “based on” does not mean “based only on,” unless expressly specified otherwise. In other words, the phrase “based on” describes both “based only on” and “based at least on.” 
     The term “processor” should be interpreted broadly to encompass a general purpose processor, a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a controller, a microcontroller, a state machine, and so forth. Under some circumstances, a “processor” may refer to an application specific integrated circuit (ASIC), a programmable logic device (PLD), a field programmable gate array (FPGA), etc. The term “processor” may refer to a combination of processing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     The term “memory” should be interpreted broadly to encompass any electronic component capable of storing electronic information. The term memory may refer to various types of processor-readable media such as random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), programmable read-only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable PROM (EEPROM), flash memory, magnetic or optical data storage, registers, etc. Memory is said to be in electronic communication with a processor if the processor can read information from and/or write information to the memory. Memory that is integral to a processor is in electronic communication with the processor. 
     The terms “instructions” and “code” should be interpreted broadly to include any type of computer-readable statement(s). For example, the terms “instructions” and “code” may refer to one or more programs, routines, sub-routines, functions, procedures, etc. “Instructions” and “code” may comprise a single computer-readable statement or many computer-readable statements. 
     The functions described herein may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions on a computer-readable medium. The terms “computer-readable medium” or “computer-program product” refers to any available medium that can be accessed by a computer. By way of example, and not limitation, a computer-readable medium may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray® disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. 
     Software or instructions may also be transmitted over a transmission medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of transmission medium. 
     The methods disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is required for proper operation of the method that is being described, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims. 
     Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein, such as those illustrated by  FIGS. 4 ,  6 ,  7 ,  8  and  10 , can be downloaded and/or otherwise obtained by a device. For example, a device may be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via a storage means (e.g., random access memory (RAM), read only memory (ROM), a physical storage medium such as a compact disc (CD) or floppy disk, etc.), such that a device may obtain the various methods upon coupling or providing the storage means to the device. Moreover, any other suitable technique for providing the methods and techniques described herein to a device can be utilized. 
     It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the systems, methods, and apparatus described herein without departing from the scope of the claims.