Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W74/00—Wireless channel access
  • H04W74/08—Non-scheduled access, e.g. ALOHA
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/20—Control channels or signalling for resource management
  • H04W72/21—Control channels or signalling for resource management in the uplink direction of a wireless link, i.e. towards the network
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/20—Control channels or signalling for resource management
  • H04W72/23—Control channels or signalling for resource management in the downlink direction of a wireless link, i.e. towards a terminal
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W74/00—Wireless channel access
  • H04W74/08—Non-scheduled access, e.g. ALOHA
  • H04W74/0833—Random access procedures, e.g. with 4-step access
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W74/00—Wireless channel access
  • H04W74/08—Non-scheduled access, e.g. ALOHA
  • H04W74/0833—Random access procedures, e.g. with 4-step access
  • H04W74/0838—Random access procedures, e.g. with 4-step access using contention-free random access [CFRA]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W84/00—Network topologies
  • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
  • H04W84/04—Large scale networks; Deep hierarchical networks
  • H04W84/042—Public Land Mobile systems, e.g. cellular systems
  • H04W84/045—Public Land Mobile systems, e.g. cellular systems using private Base Stations, e.g. femto Base Stations, home Node B
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
  • Y02D30/00—Reducing energy consumption in communication networks
  • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

• Certain exemplary embodiments of the present invention relate generally to random access procedures, and more particularly, to a method, a user equipment, and base stations for performing random access procedures in a heterogeneous network.
• ePDCCH enhanced Physical Downlink Control Channel ePHICH enhanced Physical Hybrid ARQ Indicator Channel
• the heterogeneous network 100 comprises a high power BS 101, a low power BS 102 and a UE 103, wherein a coverage area of the high power BS 101 is depicted with a large ellipse and a coverage area of the low power BS 102 is depicted with a relatively small ellipse according to different power levels.
• the coverage area of the high power BS 101 e.g., a macro BS
• the coverage area of the low power BS 102 e.g., a pico BS
• the received DL signals from the macro cell are generally stronger than those from the Pico cell.
• the UE is associated with the macro cell and receives DL signals from the macro cell.
• the UE would connect with the high power BS 101 in the DL direction and connect with the low power BS 102 in the UL direction, which in turn may probably form various backhaul links to a core network (not shown).
• the high power BS 101 would manage or schedule the DL transmission possibly with a DL scheduler and the low power BS 102 may be in charge of the UL transmission possibly with a UL scheduler, leading to a decoupled DL UL scenario as noted before.
• reception points e.g., low power BSs
• transmission points e.g., high power BSs
• separations of DL and UL modules/components have been widely investigated to enable the decoupling scenario to support all sorts of the backhaul connections possibly dependent on different lengths of latency (e.g., good, less than ⁇ 0.5ms latency; medium, ⁇ 5ms latency; any, -50-100ms latency, the symbol " ⁇ " denoting "approximately"), the MAC RLC separation, scheduling, power control, and ePDCCH/ePHICH.
• the decoupled DL UL scenario as discussed above may be beneficial for heterogeneous communications, it is likely to engender potential problems when implemented in an LTE system.
• LTE system there is a strict delay requirement for DL/UL coordination in RA procedures, which may cause problems in the decoupled DL/UL scenario that aims to support "any backhaul" ( ⁇ 50- 100ms latency), as will be discussed in detail below.
• the RA procedures can be divided into a contention based RA procedure and a non-contention based RA procedure. Such division depends upon whether the RA preamble used during the RA procedure is selected by the UE itself or selected by the BS.
• an RA preamble transmitted from the UE should be received by the low power BS, which manages the UL transmission from the UE, as discussed previously.
• Msg 2 of the RA procedure i.e., an RAR, which may include a TA command, a UL grant and a temporary C-RNTI, should be sent by the high power BS, which is in charge of the DL transmission to UE, also as discussed previously.
• the maximum delay between the RA preamble Tx and the RAR Rx is 13 ms at most (the largest value of ResponseWindowSize is 10 ms), which is apparently less than the latency of "'any' backhaul connections" (-50- 100ms).
• the latency of the backhaul link so as to satisfy the strict delay requirement between the RA preamble Tx and RAR Rx would be a critical factor in performing the contention based RA procedure in the heterogeneous network, as illustrated in Fig. 1.
• the BS uses a "PDCCH order" to initiate the RA procedure for delivery of new DL data. Since the largest periodicity of a PRACH is 20ms according to the current the 3 GPP specification, it is requested that the delay between the BS's transmission of the PDCCH order in the DL and the UE's transmission of the dedicated RA preamble in the UL as a response takes no longer than 20ms.
• certain embodiments of the present invention would provide for an efficient way of performing an RA procedure in a heterogeneous network, thereby shortening the latency of the RA procedure due to the backhaul link and accelerating performance of the RA procedure.
• a method for performing an RA procedure in a network including a high power BS, a low power BS and a UE, wherein the UE is in connection with the high power BS in a DL direction and is in connection with the low power BS in a UL direction.
• the method comprises performing, by the UE, the RA procedure with the low power BS if the RA procedure is initiated by the UE.
• the method further comprises performing, by the UE, the RA procedure with the high power BS if the RA procedure is initiated by the high power BS.
• a UE for performing an RA procedure in a network including a high power BS, a low power BS and the UE, wherein the UE is in connection with the high power BS in a DL direction and is in connection with the low power BS in a UL direction.
• the UE comprises a transmitting module, adapted to transmit messages in relation to the RA procedure.
• the UE further comprises a receiving module, adapted to receive messages in relation to the RA procedure, wherein if the RA procedure is initiated by the UE, the transmitting module is adapted to transmit to the low power BS the messages in relation to the RA procedure therebetween and the receiving module is adapted to receive from the low power BS the messages in relation to the RA procedure therebetween, and wherein if the RA procedure is initiated by the high power BS, the transmitting module is adapted to transmit to the high power BS the messages in relation to the RA procedure therebetween and the receiving module is adapted to receive from the high power BS the messages in relation to the RA procedure therebetween.
• a low power BS for performing an RA procedure in a network including a high power BS, the low power BS and a UE, wherein the UE is in connection with the high power BS in a DL direction and is in connection with the low power BS in a UL direction.
• the low power BS comprises a transmitting module, adapted to transmit messages in relation to the RA procedure.
• the low power BS further comprises a receiving module, adapted to receive messages in relation to the RA procedure, wherein if the RA procedure is initiated by the UE, the transmitting module is adapted to transmit to the UE the messages in relation to the RA procedure between the UE and the low power BS and the receiving module is adapted to receive from the UE the messages in relation to the RA procedure between the UE and the low power BS.
• a high power BS for performing an RA procedure in a network including the high power BS, a low power BS and a UE, wherein the UE is in connection with the high power BS in a DL direction and is in connection with the low power BS in a UL direction.
• the high power BS comprises a transmitting module, adapted to transmit messages in relation to the RA procedure.
• the high power BS further comprises a receiving module, adapted to receive messages in relation to the RA procedure, wherein if the RA procedure is initiated by the high power BS, the transmitting module is adapted to transmit to the UE the messages in relation to the RA procedure between the UE and the high power BS and the receiving module is adapted to receive from the UE the messages in relation to the RA procedure between the UE and the high power BS.
• the UE-initiated RA procedure is carried out between the UE and the low power BS and the high power BS-mitiated RA procedure is carried out between the high power BS and the UE.
• the duration of the RA procedure conducted under the decoupled DL UL scenario can be significantly shortened and thereby the delay needs as specified under the LTE system or other possible systems could be well met.
• interference that might take place among multiple UEs performing the RAs simultaneously can be alleviated or mitigated since the messages in relation to the RAs, such as the RAR and the preambles, are transmitted on respective different resources.
• FIG. 1 illustrates a simplified and exemplary heterogeneous network in which certain embodiments of the present invention can be practiced
• FIG. 2 schematically illustrates performing RA procedures in the heterogeneous network as illustrated in Fig. 1 according to an embodiment of the present invention
• FIG. 3 schematically illustrates a signaling diagram for performing a UE-initiated RA procedure according to an embodiment of the present invention
• FIG. 4 schematically illustrates another signaling diagram for performing a high power BS-initiated RA procedure according to an embodiment of the present invention
• FIG. 5 is a simplified schematic block diagram illustrating a UE according to one embodiment of the present invention.
• Fig. 6 is a simplified schematic block diagram illustrating a BS, which may be embodied as a low power BS or high power BS, according to another embodiment of the present invention.
• Embodiments of the invention may be applied in various wireless networks, including but not being limited to the 3GPP LTE network. Given the rapid development in communications, there will of course also be future type wireless communication technologies and systems with which the present invention may be embodied. It should not be seen as limiting the scope of the invention to only the aforementioned system.
• the term "high power BS,” as implied by its name, may refer to any BSs that have relatively high transmission power and thereby cover a relatively large coverage area. Examples of such a high power BS is a macro BS or macro eNB.
• the term “low power BS” may refer to any BSs that have relatively low transmission power and thereby cover a relatively smaller coverage area as compared to the high power BS . Examples of such a low power BS is a pico BS, a femto BS, and a relay node, as widly employed in the current various communication system.
• resources according to embodiments of the present invention may include but are not limited to a time domain, a frequency domain, a code domain, a spatial domain, or a combination of such domains.
• the embodiments of the present invention propose that the RA initiated by the high power BS be performed directly between the high power BS and the UE without involvement of the low power BS and that the RA initiated by the UE be performed directly between the low power BS and the UE without involvement of the high power BS.
• the RA procedure under the decouple DL/UL scenario could be carried out in a more efficient and straightforward manner.
• the embodiments of the present invention also propose allocating different resources for delivery of different RARs and RA preambles.
• FIG. 1 illustrates a simplified and exemplary heterogeneous network 100 in which certain embodiments of the present invention can be practiced. Details regarding the network 100 have been described previously and thus further description is omitted herein for simplicity's sake.
• FIG. 2 schematically illustrates performing RA procedures in the heterogeneous network as illustrated in Fig. 1 according to an embodiment of the present invention. Shown at the left part of the Fig. 2 are some steps of an ongoing RA procedure initiated by the high power BS 101 and corresponding resource allocation for PDCCH, as exemplarily depicted by a block diagram.
• the UE 103 may send, among other things, its dedicated preamble to the high power BS 101 in the UL direction and as a response, the high power BS 101 sends to the UE 103 an RAR together with pertinent DL data in the DL direction.
• the UE 103 may initiate an RA procedure by sending a preamble to the low power BS 102 together with some UL data and then, as a response, may receive an RAR from the low power BS 102.
• resource allocated for PDCCH As exemplarily depicted by a block diagram. It can be noted from the two resource allocation block diagrams that the resource as reserved at the high power BS 101 side is exactly used at the low power BS 102 side for RAR delivery. Thereby, different resources would be used to transmit the RARs from the high power BS 101 and low power BS 103 on the PDCCHs, respectively.
• Fig. 2 Although the high power BS-initiated and the UE-initiated procedures are both shown in Fig, 2, it is to be understood that the UE may only initiate or participate in a single RA procedure at a time. Further, some other messages or steps, such as those illustrated in Figs. 3 and 4, are not shown in Fig. 2 merely for a simplifying purpose.
• Fig. 3 schematically illustrates a signaling diagram 300 for perfonning a UE-initiated RA procedure (i.e., a contention based RA procedure) according to an embodiment of the present invention.
• the signaling diagram 300 begins with step S301, at which the UE 103 is informed, by the high power BS 101, low power BS 102 or a potential third party, of information regarding PRACH resource allocation. The reason for this PRACH resource allocation or partition is discussed as below.
• the UE may need higher power to send an RA preamble aiming at the high power BS than an RA preamble aiming at the low power BS. If both types of RA preambles are sent using the same PRACH resource, the preamble aiming at the high power BS would impose large interference on the preambles sent by other potential UEs and aiming at the low power BS. Therefore, a resource partition method is necessary to separate PRACH resources for the high power BS and for the low power BS, and the signaling of the resource allocation information to the UEs can be implemented in different ways.
• the information regarding the PRACH resource partition could be sent to the UEs beforehand, e.g., via a broadcasted SIB or dedicated RRC signaling, such that the UEs could have knowledge of which PRACH can be applied to perform RA attempts directed to the low power BS and which PRACH can be applied to send the preamble directed to the high power BS once RA commands, i.e., PDCCH orders, have been received from the high power BS.
• RA commands i.e., PDCCH orders
• the information regarding the PRACH resource partition could be sent to the UEs when necessary.
• the PRACH configuration information broadcasted in the SIB is actually only for PRACH reception at the low power BS.
• the PRACH resources allocated for the high power BS reception would be delivered to UEs along with the RA attempt commands sent by the network, in the form of the RRC, MAC CE, DCI or the like.
• the embodiments of the present invention propose transmitting respective RA preambles on respective different resources with respect to the high power BS and the low power BS, thereby mitigating or alleviating the interference as discussed before.
• the UE 103 in order to send UL data or to re-establish an RRC connection, the UE 103 would send an RA preamble, also referred to as RACH Msg 1 , to the low power BS 102 to initiate an RA procedure.
• RACH Msg 1 an RA preamble
• this RA attempt including the RA preamble should be sent to the low power BS 102 using the PRACH resources as notified at step S301.
• the low power BS 102 instead of the high power BS 103, may send an RAR, also referred to as RACH Msg 2, to the UE 103 at step S303.
• the RAR may include a preamble identifier, a UL grant, a temporary C-RNTI and a time alignment command, and the like. It may be easy for the low power BS 102 to do so since a UL grant included in the RAR could be simplified.
• the embodiments of the present invention also propose using a resource partition scheme to implement transmission of RARs with respect to the high power BS 101 and low power BS 102 on respective different resources. Because details regarding the RAR resource partition have been described in connection with Fig, 2, a further discussion thereof is omitted herein for a brief purpose.
• the UE may form an RACH Msg 3 based upon the RAR received from the low power BS 102 and send it to the low power BS 102 through the UL grant at step S304.
• the Msg 3 may include a BSR of a UL buffer in the UE.
• a new UL grant may be formed at the low power BS 102 and sent to the UE 103 as a Msg 4. Based upon the new UL grant, UL transmission from the UE 103 commences (not shown).
• the UE-initiated RA procedure as illustrated in Fig. 3 can be completed in a straightforward and time-saving way, thereby meeting the strict delay requirement as specified by the LTE system towards the RA procedure.
• Fig. 4 schematically illustrates another signaling diagram 400 for performing a high power BS-initiated RA procedure (i.e., a non-contention based RA procedure) according to an embodiment of the present invention.
• the signaling diagram 400 also begins with transmitting information regarding the PRACH resource allocation to the UE 103, as performed by step S401.
• a high power BS-initiated RA procedure may commence by sending a PDCCH order on a PDCCH or ePDCCH to the UE 103 at ste S402.
• the UE 103 has already been allocated a dedicated preamble by the high power BS 101.
• the high power BS 101 is able to identify the US 103 through the RA preamble as sent by the UE 103 at step S403 for acquiring UL synchronization. Similar to those discussed in Fig. 3, the dedicated preamble should be sent using the PRACH resources as previously partitioned so as not to cause harmful interference to other UEs.
• the high power BS 101 Upon receipt of the dedicated preamble, the high power BS 101 sends an RAR to the UE 103 at step S404. Thereafter, the high power BS 101 may, at step S405 , send to the UE 103 a DL assignment which may also be a UL grant, as a non-limiting example.
• Fig. 5 is a simplified schematic block diagram illustrating a UE 500 according to one embodiment of the present invention.
• the UE 500 may include a transmitting module 501 adapted to transmit messages in relation to the RA procedure and a receiving module 502 adapted to receive messages in relation to the RA procedure.
• the message may be Msgs 1-4, including the RA preamble and the RAR, as discussed with reference with Figs. 3 and 4.
• the transmitting module 501 is adapted to transmit to the low power BS the messages (e.g., including the preamble or Msg 3) in relation to the RA procedure therebetween and the receiving module 502 is adapted to receive from the low power BS 102 the messages (e.g., including the RAR or UL grant) in relation to the RA procedure therebetween.
• the messages e.g., including the preamble or Msg 3
• the receiving module 502 is adapted to receive from the low power BS 102 the messages (e.g., including the RAR or UL grant) in relation to the RA procedure therebetween.
• the transmitting module 501 is adapted to transmit to the high power BS the messages in relation to the RA procedure therebetween and the receiving module 502 is adapted to receive from the high power BS the messages in relation to the RA procedure therebetween.
• the message may relate to Msgs 1-4, including the RA preamble and the RAR, as discussed with reference with Fig. 4.
• the transmitting module 501 is adapted to transmit respective RA preambles on respective different resources to the low power BS and high power BS so as to mitigate or eliminate the potential interference.
• the receiving module 502 is adapted to receive, on respective different resources, respective RARs from the low power BS and the high power BS.
• Fig. 6 is a simplified schematic block diagram illustrating a BS 600 according to another embodiment of the present invention.
• the BS 600 may include a transmitting module 601 adapted to transmit messages in relation to the RA procedure.
• the BS 600 may further include a receiving module 602 adapted to receive messages in relation to the RA procedure.
• the transmitting module 601 is adapted to transmit to the UE the messages (e.g., PDCCH order, RAR or DL assignment) in relation to the RA procedure between the UE and the high power BS and the receiving module 602 is adapted to receive from the UE the messages (e.g., the dedicated preamble) in relation to the RA procedure between the UE and the high power BS, as is the case in the Fig. 4.
• the messages e.g., PDCCH order, RAR or DL assignment
• the receiving module 602 is adapted to receive from the UE the messages (e.g., the dedicated preamble) in relation to the RA procedure between the UE and the high power BS, as is the case in the Fig. 4.
• the transmitting module 601 is adapted to transmit an RAR on a different resource from a resource allocated for transmission of an RAR in a RA procedure initiated by the UE with the low power BS.
• the high power BS may be a macro BS.
• the transmitting module 601 is adapted to transmit to the UE the messages (e.g., the RAR or UL grant) in relation to the RA procedure between the UE and the low power BS and the receiving module 602 is adapted to receive from the UE the messages (e.g., the RA preamble or Msg 3) in relation to the RA procedure between the UE and the low power BS, as is the case in Fig. 3.
• the messages e.g., the RAR or UL grant
• the receiving module 602 is adapted to receive from the UE the messages (e.g., the RA preamble or Msg 3) in relation to the RA procedure between the UE and the low power BS, as is the case in Fig. 3.
• the transmitting module 601 is adapted to transmit an RAR on a different resource from a resource allocated for transmission of an RAR in a RA procedure initiated by the high power BS with the UE.
• the low power BS may be one of a pico base station, a femto base station, and a relay node.
• the invention may be implemented in any suitable form including hardware, software, firmware or any combination of these.
• the invention may optionally be implemented at least partly as computer software running on one or more data processors and/or digital signal processors.
• the elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the invention may be implemented in a single unit or may be physically and functionally distributed between different units and processors.

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• 2012
  • 2012-10-23 IN IN1919DEN2015 patent/IN2015DN01919A/en unknown
  • 2012-10-23 US US14/435,634 patent/US20150237655A1/en not_active Abandoned
  • 2012-10-23 WO PCT/CN2012/083342 patent/WO2014063298A1/en not_active Ceased
  • 2012-10-23 EP EP12886989.8A patent/EP2912915B1/en not_active Not-in-force

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