Patent Publication Number: US-9420605-B2

Title: Method and apparatus for cell coordination in heterogeneous cellular networks

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates to heterogeneous cellular networks and in particular relates to a method of cell coordination in heterogeneous cellular networks. 
     BACKGROUND 
     A clustered cell deployment where a large number of low-power cells (deployed in an unplanned manner) within a macro cell coverage is considered. Pico cells and femto or small cell clusters may be situated within the coverage of a macro cell. When a user equipment (‘UE’) moves through a path which crosses some of these pico or small cells, it may undergo many handovers. For example, a UE which traverses between two pico cells will undergo two handovers: one from the first pico cell to the macro cell, and from the macro cell to the next pico cell. 
     The above mentioned handovers result in data interruption for each handover. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will be better understood with reference to the drawings, in which: 
         FIG. 1  is a block diagram illustrating one example of a macro cell comprising pico cells and femto cells; 
         FIG. 2  is a data flow diagram illustrating current handover procedures; 
         FIG. 3A  is a block diagram illustrating a UE served by a macro cell; 
         FIG. 3B  is a block diagram illustrating a UE receiving control signaling from a macro cell but receiving data from a low power cell; 
         FIG. 3C  is a block diagram illustrating a UE served by a low power cell; 
         FIG. 3D  is a block diagram illustrating a UE receiving control signaling from a macro cell but receiving data from a low power cell; 
         FIG. 4  is a data flow diagram illustrating a procedure for data/control offloading; 
         FIG. 5  is a diagram illustrating radio resource scheduling for a UE according to at least one embodiment of the present disclosure; 
         FIG. 6  is a data flow diagram illustrating how coordinating cells and a UE are configured according to at least one embodiment of the present disclosure; 
         FIG. 7  is a block diagram illustrating a MAC control element according to at least one embodiment of the present disclosure; 
         FIG. 8  is a data flow diagram illustrating how a serving cell requests and receives subframe offset information for the coordinating cells from a UE; 
         FIG. 9  is a block diagram of an example user equipment; and 
         FIG. 10  is a block diagram showing a simplified example network element. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure provides a method for radio resource scheduling for a user equipment (‘UE’) in a heterogeneous network, comprising receiving at the UE, scheduling parameters including a first value and a second value; listening, at the UE, to a serving cell for a number of consecutive subframes corresponding with the first value; and listening, at the UE, to at least one coordinating cell for a number of consecutive subframes corresponding with the second value. 
     The present disclosure further provides a user equipment (‘UE’), comprising a processor and a communication subsystem; wherein the processor and the communication subsystem cooperate to receive scheduling parameters including a first value and a second value; listen to a serving cell for a number of consecutive subframes corresponding with the first value; and listen to at least one coordinating cell for a number of consecutive subframes corresponding with the second value. 
     The present disclosure further provides a method for radio resource scheduling for a user equipment (‘UE’) in a heterogeneous network, comprising sending, from a serving cell, scheduling parameters to the UE, the scheduling parameters indicating subframes associated to the serving cell and subframes associated to a plurality of coordinating cells; and establishing, at the eNB of the serving cell, a connection with the UE during the subframes associated to the serving cell. 
     The present disclosure further provides an enhanced Node B (‘eNB’) of a serving cell, configured for radio resource scheduling of a user equipment (‘UE’) in a heterogeneous network, comprising a processor and a communication subsystem; wherein the processor and the communication subsystem cooperate to send scheduling parameters to the UE, the scheduling parameters indicating subframes associated to the serving cell and subframes associated to a plurality of coordinating cells; and establish a connection with the UE during the subframes associated to the serving cell. 
     The present disclosure further provides a method for synchronizing a serving cell and at least one coordinating cell, comprising sending, from the serving cell, a request to a UE to measure a subframe offset for each of the at least one coordinating cell; receiving, at the serving cell, from the UE, the subframe offset for each of the at least one coordinating cell; and determining, at the serving cell, subframe numbers for each of the at least one coordinating cell based on the subframe offset for each of the at least one coordinating cell. 
     The present disclosure further provides an enhanced Node B (‘eNB’) of a serving cell, configured for synchronizing the serving cell and at least one coordinating cell, comprising a processor and a communication subsystem; wherein the processor and the communication subsystem cooperate to send a request to a UE to measure a subframe offset for each of the at least one coordinating cell; receive from the UE the subframe offset for each of the at least one coordinating cell; and determine subframe numbers for each of the at least one coordinating cell based on the subframe offset for each of the at least one coordinating cell. 
     The present disclosure further provides a method for synchronizing a serving cell and at least one coordinating cell, comprising receiving, at a UE, a request to measure a subframe offset for each of the at least one coordinating cell; computing, a the UE, the subframe offset for each of the at least one coordinating cell; and sending, from the UE to the serving cell, the subframe offset for each of the at least one coordinating cell. 
     The present disclosure further provides a user equipment (‘UE’) comprising a processor and a communication subsystem; wherein the processor and the communication subsystem cooperate to receive a request to measure a subframe offset for each of the at least one coordinating cell; compute the subframe offset for each of the at least one coordinating cell; and send to the serving cell, the subframe offset for each of the at least one coordinating cell. 
     Reference is now made to  FIG. 1 .  FIG. 1  illustrates a macro cell  10 , served by eNB  20 . Macro cell  10  includes pico cells  30   a  and  30   b . As illustrated by arrows, pico cells  30   a  and  30   b  communicate with the core network  60  directly, as does macro cell  10 . Macro cell  10  further includes femto cells  40   a ,  40   b  and  40   c , who are connected to the core network  60  via Home eNB Gateway (‘HeNB-GW’)  50 . 
     As seen in  FIG. 1 , a UE moving in the trajectories indicated by arrows A or B will undergo many handovers. 
     Reference is now made to  FIG. 2 , showing a handover procedure between a serving eNB and a target eNB in a Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) architecture. While the present disclosure relates to the 3GPP LTE architecture, the present disclosure is not so limited and concepts described therein are applicable to other types of network architecture. 
     At message  230 , the UE  210  sends a measurement report to the serving eNB  212 . The serving eNB  212  makes a handover decision based on the measurement report, and in the event the serving eNB  212  decides that a handover is required, a handover request is sent to target eNB  214 , at message  232 . In response, a handover request ACK is provided to the serving eNB at  234  and the target eNB  214  decides if it has sufficient resources to accept UE  210 . 
     At message  236 , the serving eNB  212  transmits an RRC reconfiguration message to the UE  210 , for assisting the UE in configuring itself for communication with the target eNB  214 . 
     At message  238 , the serving eNB  212  transmits unacknowledged data packets intended for UE  210  to target eNB  214 . 
     At message  240 , the UE indicates to target eNB  214  that its RRC reconfiguration is complete. 
     At block  242 , path switch messages are exchanged between the target eNB  214 , the Mobility Management Entity (‘MME’)  216 , the Serving Gateway (‘S-GW’)  218 , and the serving eNB  212 . The path switch procedure informs the network of the handover. 
     Once the target eNB  214  receives an acknowledgement of the path switch messages from MME  216 , target eNB  214  sends a UE Context Release message to the serving eNB  212 , indicating that the handover is successfully completed. 
     Importantly, during a successful handover procedure as described above, the UE may not send uplink data during the period indicated by bracket  250 , and the UE may not receive downlink data during the period indicated by bracket  260 . 
     Reference is now made to  FIGS. 3A, 3B, 3C, and 3D  showing a UE at different positions within a macro cell comprising a low power cell. 
     Low power cells may be stand-alone or non-stand-alone. A stand-alone cell is a cell through which the UE can attach to the LTE network. A non-stand-alone cell is a cell through which the UE may not attach directly to the LTE network. When the low power cell is a stand-alone cell, a UE can perform a cell search and find a cell on a frequency and attach itself to the LTE network by connecting to that cell. 
     Since the macro cells are typically planned for large coverage areas, generally control messages such as Radio Resource Control (‘RRC’) and Non Access Stratum (‘NAS’) signals are transmitted and received through the macro cell. In some cases, the data may be routed through the low power cell if there is a dearth of radio resources at the macro cell. 
     In  FIG. 3A , the UE  310  is served by macro cell  312 , as it is outside the coverage area of low power cell  314 . Control signaling from MME  316  (represented by short-dashed line) is routed to the UE  310  through macro cell  312 , as is data from S-GW  318  (represented by long-dashed lines). 
     In  FIG. 3B , UE  320  is within Cell Range Expansion (‘CRE’) region  325  of low power cell  324 . In the scenario of  FIG. 3B , the UE is arriving in CRE  325  from the macro cell. As shown in  FIG. 3B , data from S-GW is routed to the macro cell  322 , to low power cell  324 , and then to the UE  320 . Control signaling from MME  326  is routed from the macro cell  322  directly to the UE  325 . 
     In  FIG. 3C , UE  330  is within the coverage area of low power cell  334 , and both data from S-GW  338  and control signaling from MME  336  are routed through low power cell  334  to the UE  330 . However, UE  330  could also connect to both macro cell  332  and low power cell  334 , particularly if low power cell  334  is a non-stand-alone cell. 
     In  FIG. 3D , UE  340  is within CRE  345  of low power cell  344 , as in the case of  FIG. 3B . However, in  FIG. 3D , the UE was previously connected to low power cell  344  and is moving towards macro cell  342 . As shown in  FIG. 3D , data from S-GW is routed through low power cell  344 , and control signaling from MME  346  is routed through low power cell  344 , to macro cell  342 , and then to the UE  340 . 
     Therefore, a serving cell may offload data or control signaling to a near-by cell. A procedure for data offloading is shown with reference to  FIG. 4 . In  FIG. 4 , a UE  410  communicates with macro eNB  412  and can also see low power eNB  414 . Both macro eNB  412  and low power eNB  414  can communicate with MME  416  and S-GW  418 . 
     As seen in  FIG. 4 , at message  430  a measurement report is sent from the UE  410  to the macro eNB  412 . At block  432 , the data offloading procedure is performed. Then, at block  434 , data is forwarded between the macro eNB  412  and the low power eNB  414 . 
     At block  436 , the UE performs an uplink synchronization with the low power eNB  414 , and indicates that RRC Reconfiguration is complete at message  438 . Notably, the path switch procedure  242  shown in  FIG. 2  is not performed. 
     After the data offloading procedure of  FIG. 4 , uplink messages travel as illustrated by dashed line  440 . Specifically, an uplink message goes from UE  410  to low power eNB  414 , to macro eNB  412 , and to S-GW  418 . Similarly, downlink messages go from S-GW  418  to macro eNB  412 , to low power eNB  414 , to UE  410 . 
     In a typical heterogeneous cellular deployment, low-power cells, such as pico cells or femto cells are deployed as an overlay to the existing planned homogeneous deployments. Normally the overlay deployment is done in an unplanned manner. The overlay deployment is intended to meet the demand for ever-increasing mobile data applications or to improve coverage. As seen above, the serving eNB may offload data or control plane traffic for a UE via a near-by low power cell. During data offloading, the UE is in an RRC_connected state with both the serving cell and the coordinating cell, at the same time. Therefore, the resources assigned by each of the serving cell and the coordinating cells should be coordinated properly to avoid conflicts. Proper coordination may require accurate knowledge of the subframe timing differences between the serving eNB and the coordinating eNB. 
     Furthermore, low power eNBs may be installed independently and powered on and off as needed. 
     Resource Allocation Between Macro and Low-Power eNBs 
     Static Scheduling 
     According to one embodiment, UEs may be pre-scheduled to listen to the serving cell and the coordinating cell intermittently.  FIG. 5  illustrates the tuning of a radio on the UE, and in particular, the tuning to the frequency of the macro cell, small cell and transition periods. As illustrated in  FIG. 5 , the UE is scheduled to be in communication with the macro eNB for N M  subframes (or milliseconds) and with the low power cell for N L  subframes in every L consecutive subframes. For every transition from the macro cell to the low power cell and vice versa, N R  subframes are allotted to the UE to allow the UE to prepare for the transition. In some implementation, the N R  subframes may include a number of extra subframes beyond the subframes needed for UE transition. During the extra subframes, the UE may listen to neither the macro cell nor the low power cell. In at least some embodiments, the UE prepares for the transition by retuning its transceiver to a different frequency or adjusting its transmission power. 
     In at least some embodiments, the parameters N M , N L , and N R  are exchanged between the serving cell and the coordinating cells before the data offloading commences. The serving cell, whether it is the macro cell or the low power cell, may decide the bandwidth sharing between control and data transmissions and set appropriate values for N M , N L , and N R , and inform the coordinating cells and the UE. In at least some embodiments, initial bandwidth estimates for data offloading may be based on quality of service (‘QoS’) requirements of an application. Similarly, an estimate of the bandwidth is required for the control signal offloading. In at least some embodiments, the bandwidths are further adjusted when data transmission commences. 
     As seen in  FIG. 5 , the UE may listen to a macro cell or a low power cell intermittently, based on the values of N M , N L , and N R . In  FIG. 5 , a bolded line indicates that the UE listens to the corresponding cell for the period represented by the length of the line. Thus, at  520  the UE listens to the low power cell. At  530 , the UE transitions between the low power cell and the macro cell, and at  540  the UE listens to the macro cell. 
     Also as seen in  FIG. 5 , the UE listens to the low power cell for N L  subframes, to the macro cell for N M  subframes, and uses N R  subframes for transitioning between the low power cell and the macro cell. The length of the cycle is L, such that L=N M +N L +2*N R . In some implementation, the length of the cycle L could be more than N M +N L +2*N R  and the UE listens to neither the macro cell nor the small cell during the last L−(N M +N L +2*N R ) subframes. 
     In at least some embodiments, the UE communicates with the macro cell during subframes n to (n+N M −1), when n satisfies the condition mod(n, L)=p, where p is a number between 0 and L−1. 
     If the UE starts communicating with the macro cell at subframe n, it will start transitioning to the macro cell at subframe n−N R . 
     In cases where there are two coordinating cells, the UE will communicate with the serving cell and first coordinating cell during the subframes (n+N R , n+N R +N M −1) and (n+N M +2N R , n+N M +2N R +N L1 −1) respectively, where n is the subframe at which the UE starts transitioning to the serving cell, and N L1  is the number of subframes reserved for listening to the first coordinating cell. 
     Generally, if there are C coordinating cells, the UE will communicate with the i-th coordinating cell starting at subframe A and ending at subframe B, such that: 
     
       
         
           
             
               
                 
                   A 
                   + 
                   n 
                   + 
                   
                     N 
                     m 
                   
                   + 
                   
                     
                       ( 
                       
                         i 
                         + 
                         1 
                       
                       ) 
                     
                     ⁢ 
                     
                       N 
                       R 
                     
                   
                   + 
                   
                     
                       ∑ 
                       
                         j 
                         = 
                         1 
                       
                       
                         i 
                         - 
                         1 
                       
                     
                     ⁢ 
                     
                       N 
                       Lj 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     and, 
     
       
         
           
             
               
                 
                   B 
                   = 
                   
                     n 
                     + 
                     
                       N 
                       M 
                     
                     + 
                     
                       
                         ( 
                         
                           i 
                           + 
                           1 
                         
                         ) 
                       
                       ⁢ 
                       
                         N 
                         R 
                       
                     
                     + 
                     
                       
                         ∑ 
                         
                           j 
                           = 
                           1 
                         
                         
                           i 
                           - 
                           1 
                         
                       
                       ⁢ 
                       
                         N 
                         Lj 
                       
                     
                     + 
                     
                       N 
                       Li 
                     
                     - 
                     1. 
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
     Where N Lj  is the number of subframes during which the UE communicates with the j-th coordinating cell. According to this convention, the length of the cycle, L is computed by: 
     
       
         
           
             
               
                 
                   L 
                   = 
                   
                     
                       N 
                       M 
                     
                     + 
                     
                       
                         ( 
                         
                           C 
                           + 
                           1 
                         
                         ) 
                       
                       ⁢ 
                       
                         N 
                         R 
                       
                     
                     + 
                     
                       
                         ∑ 
                         
                           j 
                           = 
                           1 
                         
                         C 
                       
                       ⁢ 
                       
                         N 
                         Lj 
                       
                     
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
     Reference is now made to  FIG. 6 .  FIG. 6  shows a message flow diagram as shown in  FIG. 4  but with additional steps to configure the serving cells and the low power cells with the coordination parameters. Notably,  FIG. 6  depicts a scenario in which the macro cell is the serving cell. 
     The procedure starts with message  630  in which a measurement report is sent from the UE  610  to the macro cell  612 . At block  632 , the data offloading procedure is performed, and at block  634  data is forwarded between the macro cell and the low power cell or cells. 
     As shown with message  636 , the macro cell  612  sends a Coordination Configuration Request message to the low power cell or cells. In at least one embodiment, the Coordination Configuration Request is included in an RRC Connection Reconfiguration message. In at least some embodiments, the message includes some or all of the following parameters:
         the coordination cell list (including Physical Cell Identifier (‘PCI’) and carrier frequency;   the cell association time for each coordinating cell N L ;   serving cell association time N M ;   switching time N R ;   cyclic parameter p.       

     Using message  638 , the low power cell responds with an acknowledgement of the Coordination Configuration Request message. In at least some embodiments, the low power cell&#39;s response may include changes to the parameters provided in the Coordination Configuration Request message. If there is more than one low power cell, each low power cell may provide proposed changes to the parameters with respect to itself. 
     In some embodiments, messages  636  and  638  are sent after the uplink synchronization  640 . In other embodiments, messages  636  and  638  can be sent as part of Data Offloading Procedure  632 . For example, coordination configuration messages may be piggybacked onto a handover request and a handover request acknowledgement. One example of the coordination configuration message is shown in Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Coordination Configuration Message 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 IE/Group 
                   
                   
                 IE type and 
                 Semantics 
                   
                 Assigned 
               
               
                 Name 
                 Presence 
                 Range 
                 reference 
                 description 
                 Criticality 
                 Criticality 
               
               
                   
               
               
                 Message 
                 M 
                   
                 9.2.13 
                   
                 Yes 
                 reject 
               
               
                 Type 
               
               
                 Serving eNB 
                 M 
                   
                 eNB UE 
                 Allocated at 
                 Yes 
                 reject 
               
               
                 UE X2AP ID 
                   
                   
                 X2AP ID 
                 the source 
               
               
                   
                   
                   
                 9.2.24 
                 eNB 
               
               
                 Cause 
                 M 
                   
                 9.2.6a 
                   
                 Yes 
                 ignore 
               
               
                 Coordinating 
                 M 
                   
                 eNB UE 
                 Allocated at 
                 Yes 
                 reject 
               
               
                 eNB UE 
                   
                   
                 X2AP ID 
                 the 
               
               
                 X2AP ID 
                   
                   
                 9.2.24 
                 coordinating 
               
               
                   
                   
                   
                   
                 eNB 
               
               
                 UE Context 
                   
                 1 
                   
                   
                 Yes 
                 reject 
               
               
                 Information 
               
               
                 &gt;Association 
                 M 
                   
                 OCTET 
                 Includes the 
                 — 
                 — 
               
               
                 Context 
                   
                   
                 STRING 
                 RRC 
               
               
                   
                   
                   
                   
                 message 
               
               
                   
                   
                   
                   
                 with the UE 
               
               
                   
                   
                   
                   
                 association 
               
               
                   
                   
                   
                   
                 information 
               
               
                   
               
            
           
         
       
     
     An example of the coordination configuration message response is shown in Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Coordination Configuration Message Response 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 IE type 
                   
                   
                   
               
               
                 IE/Group 
                   
                   
                 and 
                 Semantics 
                   
                 Assigned 
               
               
                 Name 
                 Presence 
                 Range 
                 reference 
                 description 
                 Criticality 
                 Criticality 
               
               
                   
               
               
                 Message 
                 M 
                   
                 9.2.13 
                   
                 Yes 
                 reject 
               
               
                 Type 
               
               
                 Coordinating 
                 M 
                   
                 eNB UE 
                 Allocated at 
                 Yes 
                 reject 
               
               
                 eNB UE 
                   
                   
                 X2AP ID 
                 the 
               
               
                 X2AP ID 
                   
                   
                 9.2.24 
                 coordinating 
               
               
                   
                   
                   
                   
                 eNB 
               
               
                 Cause 
                 M 
                   
                 9.2.6a 
                   
                 Yes 
                 ignore 
               
               
                 Serving eNB 
                 M 
                   
                 eNB UE 
                 Allocated at 
                 Yes 
                 reject 
               
               
                 UE X2AP ID 
                   
                   
                 X2AP ID 
                 the source 
               
               
                   
                   
                   
                 9.2.24 
                 eNB 
               
               
                 UE Context 
                   
                 1 
                   
                   
                 — 
                 ignore 
               
               
                 Information 
               
               
                 &gt;Association 
                 M 
                   
                 OCTET 
                 Includes the 
                 — 
                 — 
               
               
                 Context 
                   
                   
                 STRING 
                 RRC 
               
               
                   
                   
                   
                   
                 message 
               
               
                   
                   
                   
                   
                 with the UE 
               
               
                   
                   
                   
                   
                 association 
               
               
                   
                   
                   
                   
                 information 
               
               
                   
                   
                   
                   
                 with 
               
               
                   
                   
                   
                   
                 suggested 
               
               
                   
                   
                   
                   
                 changes. 
               
               
                   
               
            
           
         
       
     
     After the UL synchronization  640 , the serving cell  612  transmits the coordination parameters to the UE  610  with message  644 . 
     Optionally, the coordination parameters are also provided to the UE by each of the low power cells  614  with message  646 . 
     By multicasting the coordination parameters from multiple cells, the probability of correct detection at the UE can be increased. Further improvements in reception can be achieved if the identical messages transmitted by all the coordinating cells can be soft combined by the UE during the reception. However, the UE should know the transmission timing of these messages from each of the coordinating cells. 
     The value of L, the length of a full cycle in which the UE listens to the serving cell and each of the coordinating cells, can be network specific, or can be cell specific. When L is configured as a cell specific parameter, its value may be broadcast by the serving cell. For example, such broadcast may be in System Information Block Type 2 (‘SIB2’) as shown below with regards to Table 3. 
     
       
         
           
               
             
               
                 TABLE 3  
               
               
                   
               
               
                 SystemInformationBlockType2 information element 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 -- ASN1START 
                   
                   
               
               
                 SystemInformationBlockType2 ::= 
                  SEQUENCE { 
               
               
                  ac-BarringInfo 
                 SEQUENCE { 
               
               
                   ac-BarringForEmergency 
                   BOOLEAN, 
               
               
                   ac-BarringForMO-Signalling 
                   AC-BarringConfig 
               
               
                  OPTIONAL, -- Need OP 
               
               
                   ac-BarringForMO-Data 
                   AC-BarringConfig 
                 OPTIONAL - 
               
               
                  } 
               
               
                  OPTIONAL, -- Need OP 
               
            
           
           
               
               
            
               
                  radioResourceConfigCommon 
                  RadioResourceConfigCommonSIB, 
               
               
                  ue-TimersAndConstants 
                  UE-TimersAndConstants, 
               
               
                  freqInfo 
                 SEQUENCE { 
               
               
                   ul-CarrierFreq 
                  ARFCN-ValueEUTRA 
               
               
                  OPTIONAL, -- Need OP 
               
               
                   ul-Bandwidth 
                  ENUMERATED {n6, n15, n25, n50, n75, n100} 
               
               
                  OPTIONAL, -- Need OP 
               
               
                   additionalSpectrumEmission 
                   AdditionalSpectrumEmission 
               
               
                  }, 
               
               
                  mbsfn-SubframeConfigList 
                 MBSFN-SubframeConfigList 
               
               
                  OPTIONAL, -- Need OR 
               
               
                  timeAlignmentTimerCommon 
                  TimeAlignmentTimer, 
               
               
                  ..., 
               
               
                  lateNonCriticalExtension 
                 OCTET STRING 
               
               
                  OPTIONAL, -- Need OP 
               
            
           
           
               
               
               
            
               
                  [[ ssac-Barring ForMMTEL-Voice-r9 
                 AC-BarringConfig 
                   
               
               
                  OPTIONAL, -- Need OP 
               
               
                       ssac-Barring ForMMTEL-Video-r9 
                 AC-BarringConfig 
               
               
                  OPTIONAL-- Need OP 
               
               
                  ]], 
               
               
                  [[ ac-BarringForCSFB-r10 
                 AC-BarringConfig 
                 OPTIONAL - 
               
               
                  ]], 
               
            
           
           
               
               
            
               
                  [[ UEAssociationConfig-rxxxx  
                 UEAssociationConfig 
               
            
           
           
               
               
            
               
                  OPTIONAL-- Need OP 
                   
               
               
                  ]] 
               
               
                 } 
               
               
                 AC-BarringConfig ::= 
                 SEQUENCE { 
               
               
                  ac-BarringFactor 
                  ENUMERATED { 
               
               
                   
                   p00, p05, p10, p15, p20, p25, p30, p40, 
               
               
                   
                   p50, p60, p70, p75, p80, p85, p90, p95}, 
               
               
                  ac-BarringTime 
                  ENUMERATED {s4, s8, s16, s32, s64, s128, 
               
               
                 s256, s512}, 
               
               
                  ac-BarringForSpecialAC 
                   BIT STRING (SIZE(5)) 
               
               
                 } 
               
               
                 UEAssociationConfig-rxxxx ::= 
                    SEQUENCE { 
               
               
                  L-typical 
               
               
                  N_R-inter-frequency 
               
               
                  N_R-intra-frequency 
               
               
                  N_L-typical 
               
               
                 } 
               
               
                 MBSFN-SubframeConfigList ::= 
                  SEQUENCE (SIZE (1..maxMBSFN- 
               
            
           
           
               
            
               
                 Allocations)) OF MBSFN-SubframeConfig 
               
               
                 -- ASN1STOP 
               
               
                   
               
            
           
         
       
     
     Typical values for L, N L , N R  for intra and inter-frequency may also be provided with SIB2. When the serving cell intends to change these values or make these values UE-specific, the new parameter values or the UE-specific values may be included within an information element of an RRC message. For example, a UEAssociationInfo information element, as shown in Table 4 below, may be used. According to some embodiments, if the UE receives different parameter values in SIB2 and the UEAssociationInfo information element, the UE may use the parameters from the UEAssociationInfo information element. In another alternative, the values for L, N L , N R  may also be provided in other SIB signaling or other broadcast messages. 
     
       
         
           
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 UEAssociationInfo information element 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 -- ASN1START 
                   
               
               
                 UEAssociationInfo ::= 
                 SEQUENCE { 
               
               
                   coordinatingCellList 
                     CoordinatingCellList    OPTIONAL,  -- Need 
               
               
                 OR 
               
               
                   N_M 
                         ENUMERATED{ }, 
               
               
                   N_R 
                         ENUMERATED{ } 
               
            
           
           
               
            
               
                   OPTIONAL,  -- Need OP 
               
            
           
           
               
               
            
               
                   p 
                       ENUMERATED{ } 
               
               
                   ... 
               
               
                 } 
               
               
                 CoordinatingCellList ::= 
                 SEQUENCE (SIZE (1..maxCellIntra)) OF 
               
               
                 IntraFreqNeighCellInfo 
               
            
           
           
               
               
            
               
                 IntraFreqNeighCellInfo ::= 
                 SEQUENCE { 
               
            
           
           
               
               
            
               
                   physCellId 
                         PhysCellId, 
               
               
                   carrierFrequency 
                         CarrierFrequency, 
               
               
                   N_L 
                           ENUMERATED{ } 
               
               
                 } 
               
               
                 -- ASN1STOP 
               
               
                   
               
            
           
         
       
     
     The serving cell may optimize L such that there is no conflict between the DRX cycle and the resource sharing cycle. Alternatively, the serving cell and the coordinating cells should be aware of both these cycles so that there is no conflict. 
     Dynamic Scheduling 
     As presented above, static resource partitioning for control signaling and data may be effective. However, based on the value of L, data transmission interruptions or loss of data may be more or less frequent. For example, while the UE is communicating with a low power cell, the UE may be required to send a measurement report to the macro cell. In order to send the measurement report, the UE must wait until the next opportunity to communicate with the macro cell, causing a delay in the measurement report reporting. This problem can be partially alleviated by selecting a small value of L. However, a small value of L may reduce the system and spectrum usage efficiency, η, defined in equation 4 below. 
     
       
         
           
             
               
                 
                   η 
                   = 
                   
                     
                       N 
                       R 
                     
                     L 
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
     To improve the spectrum usage efficiency, resource sharing can be fully or partially dynamic. For example, a large value for L can be configured and if there is a need for RRC or NAS signaling, a low power cell may direct the UE to listen to the macro cell for RRC messages. Similarly, on the uplink, the UE may indicate to the low power cell a need for communications with the macro cell during a data transmission. 
     During downlink communications, the need for sending an RRC message to an RRC_connected UE is decided either by the macro cell or the low power cell, depending on how the RRC functionality is split between the macro cell and the low power cells. If a low power cell makes a decision to send an RRC message and the UE is associated with the low power cell at that time and for the next ζ subframes, the low power cell can include a Medium Access Control (‘MAC’) element to indicate that the UE should listen to the macro cell after β subframes, where ζ&gt;β+T, and T represents the expected delay incurred by coordination signaling over a backhaul link between eNBs. 
     On the other hand, if the macro cell makes the decision to send an RRC message, the macro cell may inform the low power cell to inform the UE of its decision. 
     On the uplink, if the UE intends to send an RRC or NAS message, the UE may indicate its intentions on the Physical Uplink Shared Channel (‘PUSCH’) on a MAC control element. In another alternative, a new layer 1 control signaling may be designed for this purpose, or the current scheduling request (SR) channel may be extended to achieve this, by for example, providing another SR channel but with lower rate. But generally, for the simplicity, MAC control element alternative is slightly preferred. 
     Specifically, one of the reserved values for the Logical Channel Identifier (‘LCID’) of a MAC Control Element may be used to indicate a request for an RRC message to a coordinating cell, or an indication that an RRC message was scheduled by a coordinating cell, as shown in bold in Tables 5 and 6 below. While Tables 5 and 6 indicate the value ‘01011’, those skilled in the art will appreciate that any of the reserved values may be used for this purpose. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Values of LCID for Downlink MAC CE 
               
            
           
           
               
               
            
               
                 Index 
                 LCID values 
               
               
                   
               
               
                 00000 
                 CCCH 
               
               
                 00001-01010 
                 Identity of the logical channel 
               
               
                 01011 
                 
                   Indication of RRC message 
                 
               
               
                   
                 
                   scheduled by a coordinating cell 
                 
               
               
                 01100-11010 
                 Reserved 
               
               
                 11011 
                 Activation/Deactivation 
               
               
                 11100 
                 UE Contention Resolution Identity 
               
               
                 11101 
                 Timing Advance Command 
               
               
                 11110 
                 DRX Command 
               
               
                 11111 
                 Padding 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Values of LCID for Uplink MAC CE 
               
            
           
           
               
               
            
               
                 Index 
                 LCID values 
               
               
                   
               
               
                 00000 
                 CCCH 
               
               
                 00001-01010 
                 Identity of the logical channel 
               
               
                 01011 
                 
                   Grant Request for RRC message 
                 
               
               
                   
                 
                   to a coordinating cell 
                 
               
               
                 01100-11000 
                 Reserved 
               
               
                 11001 
                 Extended Power Headroom Report 
               
               
                 11010 
                 Power Headroom Report 
               
               
                 11011 
                 C-RNTI 
               
               
                 11100 
                 Truncated BSR 
               
               
                 11101 
                 Short BSR 
               
               
                 11110 
                 Long BSR 
               
               
                 11111 
                 Padding 
               
               
                   
               
            
           
         
       
     
     The MAC control element is identified by a MAC PDU subheader with the LCID field as specified in Tables 5 and 6 above. 
     An example of a MAC control element is shown with respect to  FIG. 7 . As seen in  FIG. 7 , the MAC control element includes a first portion (not shown) represented at  710 . The MAC control element further includes a value  720  for β, a value  730  for β1, and a value  740  for the CellID. 
     The MAC control element has a fixed size and comprises the following fields:
         β: This field contains the subframe offset. The length of the field is 8 bits.   β1: This field contains the subframe range. The length of this field is 8 bits.   CellID: This field contains the coordinating cell ID. The cell ID may be a temporary ID assigned by the serving cell during the coordination configuration.       

     In some embodiments, the UE receives the RRC or NAS message between subframe (n+β) and subframe (n+β+β1), where n is the current subframe number. 
     UE Assisted Subframe-Number-Offset Determination 
     As outlined above, when the UE is initially attached to the macro cell and moving towards a low power cell, the data traffic may be offloaded by the macro cell to the low power cell. During the initiation of this offloading procedure, the macro eNB should configure the coordination parameters and inform the UE of these parameters. These parameters may include pre-scheduling information, so that the UE may be aware of the time during which it has the opportunity to communicate with the macro cell or the MME. 
     For example, the UE may be configured to listen to the macro cell if the subframe number n meets the following criterion: mod(n, L)=p; where n is the macro cell&#39;s subframe number. L and p are communicated to the UE by the macro cell during the coordination configuration setup, as is the value of N R . These values are also communicated to the low power cells over the backhaul interface. Low power cells may schedule data packets for the UE during the subframes assigned to them as described in  FIG. 5 . Low power cells should be aware of the relative subframe numbering of the macro cell to schedule transmission of data packets. However, subframe numbers between two eNBs may not be synchronized. If the eNBs try to synchronize their subframe numbers by exchanging information over the backhaul interface, the unpredictability of the backhaul delay means that synchronization may fail. 
     This issue may be resolved by involving the UE. For example, the UE may be asked by the serving cell to read the system frame number (SFN) and the subframe number of coordinating cells, and the difference may be reported to the serving cell. 
     Normally, this measurement may take some time if the UE is not already synchronized with the coordinating cells. The serving cell may provide a fixed time for uplink resources in which the UE may send the SFN delta report. 
     In at least some embodiments, the SFN delta report is sent as an RRC message or in a MAC payload. 
     In at least some embodiments, the UE computes the subframe number delta for a coordinating cell as follows. 
     The UE obtains the radio frame number for the serving cell, n R  and the subframe number within the radio frame, n s . Similarly, the UE obtains the radio frame number for the coordinating cell m R , and the subframe number within the radio frame, m s . 
     The subframe number for the serving cell is computed as n=10n r +n s . and the subframe number for the coordinating cell is computed as m=10 m r +m s , assuming there are 10 subframes per radio frame. Accordingly, values n and m represent the subframe number independently of a radio frame. 
     The delta value is then computed as the cyclic difference of values n and m, wherein the cyclic difference is defined by the function f of (n−m) and K, as follows: 
     
       
         
           
             
               
                 
                   
                     
                       
                         
                           f 
                           ⁡ 
                           
                             ( 
                             
                               
                                 n 
                                 - 
                                 m 
                               
                               , 
                               K 
                             
                             ) 
                           
                         
                         = 
                         
                           n 
                           - 
                           m 
                         
                       
                     
                     
                       
                         
                           if 
                           ⁢ 
                           
                               
                           
                           - 
                           
                             K 
                             2 
                           
                         
                         ≤ 
                         
                           ( 
                           
                             n 
                             - 
                             m 
                           
                           ) 
                         
                         &lt; 
                         
                           K 
                           2 
                         
                       
                     
                   
                   
                     
                       
                         
                           f 
                           ⁡ 
                           
                             ( 
                             
                               
                                 n 
                                 - 
                                 m 
                               
                               , 
                               K 
                             
                             ) 
                           
                         
                         = 
                         
                           n 
                           - 
                           m 
                           + 
                           K 
                         
                       
                     
                     
                       
                         
                           if 
                           - 
                           K 
                         
                         &lt; 
                         
                           ( 
                           
                             n 
                             - 
                             m 
                           
                           ) 
                         
                         &lt; 
                         
                           
                             - 
                             K 
                           
                           2 
                         
                       
                     
                   
                   
                     
                       
                         
                           f 
                           ⁡ 
                           
                             ( 
                             
                               
                                 n 
                                 - 
                                 m 
                               
                               , 
                               k 
                             
                             ) 
                           
                         
                         = 
                         
                           n 
                           - 
                           m 
                           - 
                           K 
                         
                       
                     
                     
                       
                         
                           if 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           
                             K 
                             2 
                           
                         
                         ≤ 
                         
                           ( 
                           
                             n 
                             - 
                             m 
                           
                           ) 
                         
                         &lt; 
                         K 
                       
                     
                   
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
     In at least some embodiments, the delta value is computed as:
 
Δ=mod(| n−m|,K )  (6)
 
     In some embodiments, the value of K is 10240 (10 subframes for 1024 radio frames), however other values for K may be configured and the present disclosure is not so limited. 
     Alternatively, the differences in SFN and subframe number within a radio frame may be reported separately. The difference in SFN is provided as Δ 1 =f (n r −m r , 1024) where f is as defined above, and n r , and m r  are the SFN numbers of the serving cell and the coordinating cell. In at least one embodiment, Δ 1  is represented by 10 bits, including one bit to indicate whether the difference is an advance or a delay. 
     The difference in subframe number within the radio frame is provided as Δ 2 =f(n s −m s , 10), where f is as defined above, and n s  and m s  are the subframe numbers within the radio frame of the serving cell and the coordinating cell. In at least one embodiment, Δ 2  is represented by 4 bits, including one bit to indicate whether the difference is an advance or a delay. 
     Since these subframe numbers are static, the serving cell may request this measurement from some of the UEs in the RRC_connected state, a first time when the eNB is powered on, and whenever the eNB or a coordinating cell&#39;s eNB configuration is updated. 
     Alternatively, the serving cell may request the UE and/or the coordinating cells to measure the relative subframe offset by listening to an uplink transmission from some of the UEs connected to the serving cell. For example, coordinating cells may listen to an UL synchronization sequence, such as SRS, to measure the relative subframe offset. UE specific SRS configuration may be sent to the surrounding cells. The neighboring cells may measure the timing of these transmitted sequences relative to their own uplink timing. 
     The value of L may be determined by the serving cell. L may be network specific or UE specific. 
     Reference is now made to  FIG. 8  which shows the data flow for a serving cell (in this case macro cell  812 ) requesting subframe offsets from a UE  810 . A coordinating cell (in this case low power eNB  814 ) can further communicate with UE  810  and macro eNB  812 . 
     The process starts with message  830 , where the UE  810  sends a measurement report to the macro (or serving) cell  812 . After receiving the measurement report from the UE  810 , the macro cell  812  may send a Time Difference (‘TD’) Report Request with message  832  to the UE  810 . 
     The TD Report Request message may include the Cell IDs of cells with respect to which the serving cell wishes to know the subframe offset. Based on the measurement report, the macro cell  812  would know which cells the UE is close to, and may select from these cells a subset for which the UE may determine the subframe offset. 
     If the macro cell  812  receives measurement reports from multiple UEs, the macro cell  812  may select a UE that is closest to the cell or cells that need to be measured. This may help ensure that the subframe offset will be measured with low latency and high accuracy. 
     Upon receiving the TD Report Request message, the UE may perform subframe number offset determination at block  834  with respect to the cells identified in the message. The macro (or serving) cell  812  should then allow the UE enough time to access downlink message from the identified cells. For example, if the macro cell and the low power cells are on different frequencies, the macro cell  812  may give the UE  810  a 40 milliseconds gap for receiving 4 consecutive Physical Broadcast Channel (‘PBCH’) transmissions to determine the 2 least significant bits of the SFN, in one approach. In other cases, for example if the UE is close to the cell that needs to be measured and the Signal to Interference Noise Ratio (‘SNIR’) is sufficient, a 10 milliseconds gap may be enough. In some approaches, the macro cell  812  may also provide an uplink grant in advance for the UE to send the report. 
     Using message  836 , the UE  810  responds to the macro cell  812  with the TD Report. In at least one embodiment, the TD Report is provided in an RRC message. In at least one embodiment, the UE includes a confidence measure in the TD Report. The confidence measure indicates the accuracy of the measurement (i.e., an estimate of the measurement error) which depends on factors such as the measurement time, the measurement algorithm, and the like. 
     UE  810  may obtain the subframe number of the coordinating cell with the coordinating cell&#39;s PCI. First, the UE tries to acquire the subframe synchronization by correlating samples of a received signal with a locally generated Cell-specific Reference Signal (‘CRS’) sequence. The CRS sequence is generated based on the PCI and a selected slot number within a radio frame and a selected Orthogonal Frequency Division Multiplexing (‘OFDM’) symbol number within the slot. Then, the UE reads the Master Information Block (‘MIB’) transmitted by the cell. 
     After the TD Report is transmitted by the UE  810 , the macro cell  812  optionally responds with an ACK with message  838 . The above data offloading procedure may then be performed, as shown at block  840 . 
     The above procedure for measuring the subframe offset number of coordinating cells may be performed after receiving the measurement report from a UE, as depicted in  FIG. 8 . Alternatively, the above procedure may be triggered across the network, e.g., by a newly installed eNB, when a eNB is powered on or reset, when a neighboring eNB is reset, or when a eNB receives a message to the effect that a eNB was turned on. 
     In at least some embodiments, the TD Report Request, the TD Report and the TD Report ACK are new messages. In at least some other embodiments, the TD Report Request may be provided over a MAC control element. 
     The above may be implemented by changing section 5.5.3.1 of the 3GPP Technical Specification (TS) 36.331 V10.3.0 (2011-09) “Technical Specification: Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol Specification (Release 10)” incorporated herein by reference, as shown by the bold portions in the example of Table 7. Further, changes may be made to information elements to convey the information. For example, the ReportConfigEUTRA information element may be amended, as shown by the bold portions in Table 8. Other or different changes are possible. 
     
       
         
           
               
             
               
                 TABLE 7 
               
               
                   
               
               
                 Performance Measurement Changes 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 
                   5.5.3 Performing measurements 
                 
               
               
                 5.5.3.1 General 
               
               
                 For all measurements the UE applies the layer 3 filtering as specified in 5.5.3.2, before 
               
               
                 using the measured results for evaluation of reporting criteria or for measurement 
               
               
                 reporting. 
               
               
                 The UE shall: 
               
               
                  1&gt; whenever the UE has a measConfig, perform RSRP and RSRQ measurements for 
               
               
                    each serving cell, applying for the Pcell the time domain measurement resource 
               
               
                    restriction in accordance with measSubframePatternPCell, if configured; 
               
               
                  1&gt; for each measId included in the measIdList within VarMeasConfig: 
               
               
                    2&gt; if the purpose for the associated reportConfig is set to reportCGI: 
               
               
                      ... ... ... 
               
               
                    2&gt; else 
               
               
                    3&gt; if a measurement gap configuration is setup, or 
               
               
                    3&gt; if the UE does not require measurement gaps to perform the concerned 
               
               
                 measurements: 
               
               
                       4&gt; if s-Measure is not configured; or 
               
               
                       4&gt; if s-Measure is configured and the Pcell RSRP, after layer 3 filtering, is 
               
               
                 lower than this value: 
               
               
                        5&gt; perform the corresponding measurements of neighbouring cells 
               
               
                 on the frequencies and RATs indicated in the concerned measObject, applying for 
               
               
                 neighboring cells on the primary frequency the time domain measurement resource 
               
               
                 restriction in accordance with measSubframePatternConfigNeigh, if configured in the 
               
               
                 concerned measObject; 
               
               
                       4&gt; if the ue-RxTxTimeDiffPeriodical is configured in the associated 
               
               
                 reportConfig: 
               
               
                        5&gt; perform the UE Rx-Tx time difference measurements on the 
               
               
                 Pcell; 
               
               
                        4&gt; if the ue-RxTimeDiff-CoordinatingCell is configured in the   
               
               
                 
                   associated reportConfig: 
                 
               
               
                         5&gt; perform the UE Rx time difference measurements on the   
               
               
                 
                   Serving Pcell and the coordinating cell; 
                 
               
               
                    2&gt; perform the evaluation of reporting criteria as specified in 5.5.4 
               
               
                 NOTE 3: The s-Measure defines when the UE is required to perform measurements. 
               
               
                 The UE is however allowed to perform measurements also when the Pcell RSRP 
               
               
                 exceeds s-Measure, e.g., to measure cells broadcasting a CSG identity following use of 
               
               
                 the autonomous search function as defined in TS 36.304[4] 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 8 
               
               
                   
               
               
                 ReportConfigEUTRA information element 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 -- ASN1START 
                   
               
               
                 ReportConfigEUTRA ::= 
                  SEQUENCE { 
               
               
                  triggerType 
                 CHOICE { 
               
               
                   event 
                 SEQUENCE { 
               
               
                    eventId 
                  CHOICE { 
               
               
                     eventA1 
                   SEQUENCE { 
               
               
                      a1-Threshold 
                    ThresholdEUTRA 
               
               
                     }, 
               
               
                     eventA2 
                   SEQUENCE { 
               
               
                      a2-Threshold 
                    ThresholdEUTRA 
               
               
                    }, 
               
               
                    eventA3 
                   SEQUENCE { 
               
               
                      a3-Offset 
                   INTEGER (−30..30), 
               
               
                      reportOnLeave 
                    BOOLEAN 
               
               
                     }, 
               
               
                     eventA4 
                   SEQUENCE { 
               
               
                      a4-Threshold 
                    ThresholdEUTRA 
               
               
                     }, 
               
               
                     eventA5 
                   SEQUENCE { 
               
               
                      a5-Threshold1 
                    ThresholdEUTRA, 
               
               
                      a5-Threshold2 
                    ThresholdEUTRA 
               
               
                     }, 
               
               
                     ..., 
               
               
                     eventA6-r10 
                    SEQUENCE { 
               
               
                      a6-Offset-r10 
                    INTEGER (−30..30), 
               
            
           
           
               
               
            
               
                      a6-ReportLeave-r10 
                 BOOLEAN 
               
            
           
           
               
               
            
               
                     }, 
                   
               
               
                    }, 
               
               
                    hysteresis 
                   Hysteresis, 
               
               
                    timeToTrigger 
                   TimeToTrigger 
               
               
                   }, 
               
               
                   periodical 
                   SEQUENCE { 
               
               
                    purpose 
                    ENUMERATED { 
               
               
                   
                   reportStrongestCells, reportCGI} 
               
               
                   } 
               
               
                  }, 
               
               
                  triggerQuantity 
                  ENUMERATED {rsrp, rsrq} 
               
               
                  reportQuantity 
                  ENUMERATED {sameAsTriggerQuantity, both}, 
               
               
                  maxReportCells 
                   INTEGER (1..maxCellReport), 
               
               
                  reportInterval 
                  ReportInterval, 
               
               
                  reportAmount 
                 ENUMERATED {r1, r2, r4, r8, r16, r32, r64, infinity}, 
               
               
                  ..., 
               
               
                  [[ si-RequestForHO-r9 
                   ENUMERATED {setup} OPTIONAL,-- Cond 
               
               
                 reportCGI 
               
            
           
           
               
               
            
               
                   ue-RxTxTimeDiffPeriodical-r9 
                  ENUMERATED {setup} OPTIONAL -- Need OR 
               
               
                  ]], 
               
               
                  [[ includeLocationInfo-r10 
                  ENUMERATED {true} OPTIONAL, -- Cond 
               
               
                 reportMDT 
               
               
                   reportAddNeighMeas-r10 
                 ENUMERATED {setup} OPTIONAL -- Need OR 
               
               
                  ]] 
               
            
           
           
               
               
            
               
                  [[  RequestForSubFrameNoDiff-rxx   
                 
                   ENUMERATED OPTIONAL, 
                 
               
            
           
           
               
               
            
               
                    ue-RxTimeDiff -rxx   
                    ENUMERATED OPTIONAL   
               
               
                   ]]   
               
               
                 } 
               
               
                 TresholdEUTRA ::= 
                   CHOICE{ 
               
               
                  threshold-RSRP 
                 RSRP-Range, 
               
               
                  threshold-RSRQ 
                 RSRQ-Range 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     The above may be implemented by any UE. One exemplary device is described below with regard to  FIG. 9 . 
     UE  900  is typically a two-way wireless communication device having voice and data communication capabilities. Depending on the exact functionality provided, the UE may be referred to as a data messaging device, a two-way pager, a wireless e-mail device, a cellular telephone with data messaging capabilities, a wireless Internet appliance, a wireless device, a mobile device, or a data communication device, as examples. 
     Where UE  900  is enabled for two-way communication, it may incorporate a communication subsystem  911 , including both a receiver  912  and a transmitter  914 , as well as associated components such as one or more antenna elements  916  and  918 , local oscillators (LOs)  913 , and a processing module such as a digital signal processor (DSP)  920 . As will be apparent to those skilled in the field of communications, the particular design of the communication subsystem  911  will be dependent upon the communication network in which the device is intended to operate. The radio frequency front end of communication subsystem  911  can be any of the embodiments described above. 
     Network access requirements will also vary depending upon the type of network  919 . In some networks network access is associated with a subscriber or user of UE  900 . A UE may require a removable user identity module (RUIM) or a subscriber identity module (SIM) card in order to operate on a network. The SIM/RUIM interface  944  is normally similar to a card-slot into which a SIM/RUIM card can be inserted and ejected. The SIM/RUIM card can have memory and hold many key configurations  951 , and other information  953  such as identification, and subscriber related information. 
     When required network registration or activation procedures have been completed, UE  900  may send and receive communication signals over the network  919 . As illustrated in  FIG. 9 , network  919  can consist of multiple base stations communicating with the UE. 
     Signals received by antenna  916  through communication network  919  are input to receiver  912 , which may perform such common receiver functions as signal amplification, frequency down conversion, filtering, channel selection and the like. A/D conversion of a received signal allows more complex communication functions such as demodulation and decoding to be performed in the DSP  920 . In a similar manner, signals to be transmitted are processed, including modulation and encoding for example, by DSP  920  and input to transmitter  914  for digital to analog conversion, frequency up conversion, filtering, amplification and transmission over the communication network  919  via antenna  918 . DSP  920  not only processes communication signals, but also provides for receiver and transmitter control. For example, the gains applied to communication signals in receiver  912  and transmitter  914  may be adaptively controlled through automatic gain control algorithms implemented in DSP  920 . 
     UE  900  generally includes a processor  938  which controls the overall operation of the device. Communication functions, including data and voice communications, are performed through communication subsystem  911 . Processor  938  also interacts with further device subsystems such as the display  922 , flash memory  924 , random access memory (RAM)  926 , auxiliary input/output (I/O) subsystems  928 , serial port  930 , one or more keyboards or keypads  932 , speaker  934 , microphone  936 , other communication subsystem  940  such as a short-range communications subsystem and any other device subsystems generally designated as  942 . Serial port  930  could include a USB port or other port known to those in the art. 
     Some of the subsystems shown in  FIG. 9  perform communication-related functions, whereas other subsystems may provide “resident” or on-device functions. Notably, some subsystems, such as keyboard  932  and display  922 , for example, may be used for both communication-related functions, such as entering a text message for transmission over a communication network, and device-resident functions such as a calculator or task list. 
     Operating system software used by the processor  938  may be stored in a persistent store such as flash memory  924 , which may instead be a read-only memory (ROM) or similar storage element (not shown). Those skilled in the art will appreciate that the operating system, specific device applications, or parts thereof, may be temporarily loaded into a volatile memory such as RAM  926 . Received communication signals may also be stored in RAM  926 . 
     As shown, flash memory  924  can be segregated into different areas for both computer programs  958  and program data storage  950 ,  952 ,  954  and  956 . These different storage types indicate that each program can allocate a portion of flash memory  924  for their own data storage requirements. Processor  938 , in addition to its operating system functions, may enable execution of software applications on the UE. A predetermined set of applications that control basic operations, including at least data and voice communication applications for example, will normally be installed on UE  900  during manufacturing. Other applications could be installed subsequently or dynamically. 
     Applications and software may be stored on any computer readable storage medium. The computer readable storage medium may be a tangible or in transitory/non-transitory medium such as optical (e.g., CD, DVD, etc.), magnetic (e.g., tape) or other memory known in the art. 
     One software application may be a personal information manager (PIM) application having the ability to organize and manage data items relating to the user of the UE such as, but not limited to, e-mail, calendar events, voice mails, appointments, and task items. Naturally, one or more memory stores would be available on the UE to facilitate storage of PIM data items. Such PIM application may have the ability to send and receive data items, via the wireless network  919 . Further applications may also be loaded onto the UE  900  through the network  919 , an auxiliary I/O subsystem  928 , serial port  930 , short-range communications subsystem  940  or any other suitable subsystem  942 , and installed by a user in the RAM  926  or a non-volatile store (not shown) for execution by the processor  938 . Such flexibility in application installation increases the functionality of the device and may provide enhanced on-device functions, communication-related functions, or both. For example, secure communication applications may enable electronic commerce functions and other such financial transactions to be performed using the UE  900 . 
     In a data communication mode, a received signal such as a text message or web page download will be processed by the communication subsystem  911  and input to the processor  938 , which may further process the received signal for output to the display  922 , or alternatively to an auxiliary I/O device  928 . 
     A user of UE  900  may also compose data items such as email messages for example, using the keyboard  932 , which may be a complete alphanumeric keyboard or telephone-type keypad, among others, in conjunction with the display  922  and possibly an auxiliary I/O device  928 . Such composed items may then be transmitted over a communication network through the communication subsystem  911 . 
     For voice communications, overall operation of UE  900  is similar, except that received signals would typically be output to a speaker  934  and signals for transmission would be generated by a microphone  936 . Alternative voice or audio I/O subsystems, such as a voice message recording subsystem, may also be implemented on UE  900 . Although voice or audio signal output is generally accomplished primarily through the speaker  934 , display  922  may also be used to provide an indication of the identity of a calling party, the duration of a voice call, or other voice call related information for example. 
     Serial port  930  in  FIG. 9  would normally be implemented in a personal digital assistant (PDA)-type UE for which synchronization with a user&#39;s desktop computer (not shown) may be desirable, but is an optional device component. Such a port  930  would enable a user to set preferences through an external device or software application and would extend the capabilities of UE  900  by providing for information or software downloads to UE  900  other than through a wireless communication network. The alternate download path may for example be used to load an encryption key onto the device through a direct and thus reliable and trusted connection to thereby enable secure device communication. As will be appreciated by those skilled in the art, serial port  930  can further be used to connect the UE to a computer to act as a modem. 
     Other communications subsystems  940 , such as a short-range communications subsystem, is a further optional component which may provide for communication between UE  900  and different systems or devices, which need not necessarily be similar devices. For example, the subsystem  940  may include an infrared device and associated circuits and components or a Bluetooth™ communication module to provide for communication with similarly enabled systems and devices. Subsystem  940  may further include non-cellular communications such as WiFi or WiMAX. 
     The above may be implemented by any network element. A simplified network element is shown with regard to  FIG. 10 . The network element of  FIG. 10  shows an architecture which may, for example, be used for the base stations or eNBs described in the embodiments of  FIGS. 1 to 8 . 
     In  FIG. 10 , network element  1010  includes a processor  1020  and a communications subsystem  1030 , where the processor  1020  and communications subsystem  1030  cooperate to perform the methods of the embodiments described above. 
     Processor  1020  is configured to execute programmable logic, which may be stored, along with data, on network element  1010 , and shown in the example of  FIG. 10  as memory  1040 . Memory  1040  can be any tangible storage medium. 
     Alternatively, or in addition to memory  1040 , network element  1010  may access data or programmable logic from an external storage medium, for example through communications subsystem  1030 . 
     Communications subsystem  1030  allows network element  1010  to communicate with other network elements. 
     Communications between the various elements of network element  1010  may be through an internal bus  1050  in one embodiment. However, other forms of communication are possible. 
     The embodiments described herein are examples of structures, systems or methods having elements corresponding to elements of the techniques of this application. This written description may enable those skilled in the art to make and use embodiments having alternative elements that likewise correspond to the elements of the techniques of this application. The intended scope of the techniques of this application thus includes other structures, systems or methods that do not differ from the techniques of this application as described herein, and further includes other structures, systems or methods with insubstantial differences from the techniques of this application as described herein.