1. Field of the Disclosure
The present disclosure relates generally to wireless communication, and more particularly, to a system and method for enabling small cell deployment and access in a low power (i.e., “green”) 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) System.
2. Description of the Related Art
Wireless communication systems are widely deployed to provide various types of communication contents such as, for example, voice, data, and so on. Typical wireless communication systems are multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, and the like. Additionally, the systems can conform to specifications such as 3rd Generation Partnership Project (3GPP), 3GPP Long Term Evolution (LTE), Ultra-Mobile Broadband (UMB), Evolution Data Optimized (EV-DO), etc.
Generally, wireless multiple-access communication systems simultaneously support communication for multiple mobile devices or User Equipments (UE). Each mobile device may communicate with one or more base stations via transmissions on a forward link and a reverse link. The forward link (or downlink) refers to a communication link from a base station to a mobile device, and the reverse link (or uplink) refers to a communication link from a mobile device to a base station. Further, communication between a mobile device and a base station may be established via Single-Input Single-Output (SISO) systems, Multiple-Input Single-Output (MISO) systems, Multiple-Input Multiple-Output (MIMO) systems, and so forth. In addition, mobile devices can communicate with other mobile devices (and/or base stations with other base stations) in peer-to-peer wireless network configurations.
To supplement conventional base stations, additional low power base stations can be deployed to provide more robust wireless coverage to mobile devices. For example, low power base stations (e.g., which can be commonly referred to as Home Node Bs or Home evolved Node Bs (eNBs), collectively referred to as H(e)NBs, femto nodes, femtocell nodes, pico nodes, micro nodes, etc.) can be deployed for incremental capacity growth, richer user experience, in-building or other specific geographic coverage, and/or the like. Due to their low power, these base stations create small area cells (also referred to herein as “small cells”). In some configurations, such low power base stations are connected to the Internet via a broadband connection (e.g., Digital Subscriber Line (DSL) router, cable or other modem, etc.), which can provide the backhaul link to the mobile operator's network. In this regard, low power base stations are often deployed in homes, offices, etc. without consideration of a current network environment.
The high geometry (high dB) experienced by UEs in some small cell deployments provides the possibility for introducing a higher order modulation scheme (i.e. 256 Quadrature Amplitude Modulation (QAM)) for the downlink transmission. The channel characteristics of a small cell include a low frequency-selective fading channel with a small delay spread and a low time-selective fading, when the UE mobility is low.
Small cells can provide a large portion of data traffic and are also energy efficient due to their lower transmission power. However, a macro cell, for a small portion of data, consumes a large amount of bandwidth and requires higher transmission power due to its larger coverage area for a given bandwidth. Hence it will require a higher power spectral density in a transmission band. Thus, the system becomes power inefficient from a transmission power perspective.
Thus, there is a need for a system and method that adds a small cell after a UE moves to a connected mode on a macro cell via measurement and handover. Further, there is a need for a system and method that triggers handover of a UE to small cells only due to signal strength criterion or due to traffic reasons. Thus, there is need for a system and method for small cell deployment and access in a low power (e.g. “green”) 3GPP LTE System.
The present disclosure has been made to address the above-mentioned problems and disadvantages, and to provide at least the advantages described below. Accordingly, an aspect of the present disclosure provides a method and system for providing small cell deployment and access in a green 3GPP LTE system.
The present disclosure provides methods for small cell deployment within a green 3GPP LTE system for efficient data traffic management and reduced power consumption by a User Equipment (UE). The present disclosure provides methods of establishing a connection between the UE and a macro cell within the green 3GPP LTE network, determining one of a small cell in the macro cell for data transfer, verifying a sleep mode of one of the small cells, establishing a connection with the small cell if the small cell is in a wake-up mode, sending a Sounding Reference Signal (SRS) for an initial uplink synchronization, and allocating uplink and downlink resources to the UE, such that the data transfer from the UE is conducted efficiently with reduced power consumption.
The above and other aspects, features and advantages of the present disclosure will be more apparent from the following description, taken in conjunction with the accompanying drawings, in which:
In the following detailed description of embodiments of the present disclosure, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration embodiments in which the present disclosure may be practiced. The embodiments of the present disclosure are described in sufficient detail to enable those skilled in the art to practice the present disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope and spirit of the present disclosure. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present disclosure is defined only by the appended claims and their equivalents.
The specification may refer to “an”, “one” or “some” embodiment(s) of the present disclosure in several locations. This does not necessarily imply that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments of the present disclosure may also be combined to provide other embodiments.
As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes”, “comprises”, “including” and/or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations and arrangements of one or more of the associated listed items.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Described herein are various aspects related to methods for small cell deployment within a green 3GPP LTE system for efficient data traffic management and reduced power consumption by a User Equipment (UE). The present disclosure describes effective methods for establishing a connection between the UE and a macro cell within the green 3GPP LTE network, determining one of a small cell in the macro cell for data transfer, verifying a sleep mode of one of the small cells, establishing a connection with the small cell if the small cell is in a wake-up mode, sending a Sounding Reference Signal (SRS) for an initial uplink synchronization, and allocating uplink and downlink resources to the UE, such that the data transfer from the UE is conducted efficiently with reduced power consumption.
The various embodiments of the present disclosure disclose methods of providing small cell deployment and access in a green 3GPP LTE system, wherein the active mode status of the small cells is checked before allocating the small cell to the UE for data transfer, and thereby reducing power consumption.
According to an embodiment of the present disclosure, a method of providing small cell deployment and access in a green 3GPP LTE system is provided. The method includes establishing, by a User Equipment (UE), a Radio Resource Control (RRC) connection with a macro cell, wherein the RRC connection manages control plane signaling that includes, but is not limited to, connection establishment and release, broadcasting system information, paging notification and release, and configuration of power control and the like. Further, the method comprises receiving an RRC connection establishment message from the UE by the macro cell, wherein the RRC connection establishment message comprises of an Information Element (IE) from the UE to the macro cell along with the identity of a list of small cells within the network of the macro cell on which the UE initiates connection establishment.
Further, the macro cell determines at least one small cell for data transfer. The small cell determined by the macro cell can be any one of the small cells identified by the UE and presented in a list of small cells received by the macro cell. Further, the macro cell verifies whether the at least one small cell is in a sleep mode. The macro cell identifies the at least one small cell which is not in sleep mode (e.g. in wake-up mode) for data transfer. Further, the macro cell triggers a connection setup message for initiating establishment of a connection with the small cell if the at least one small cell is in a wake-up mode. If the small cell is in sleep mode, then the macro cell searches for another small cell from the list received by the UE and verifies whether the cell is in sleep mode or not. The connection set up message is only triggered by the small cell which is in wake-up mode, because the connection between the UE and small cell which is in wake-up (e.g. active) mode is established to use the resources effectively, and thereby avoiding wasting resources as well as time for establishing a connection with small cells.
Further, the UE sends a Sounding Reference Signal (SRS) to the macro cell in an uplink direction. The macro cell can also use the SRS for uplink timing estimation as part of a timing alignment procedure. Further, the at least one small cell allocates an uplink/downlink resource to the UE for communication with the at least one small cell within the macro cell. As the macro cell identifies and verifies the small cell, which is in wake-up mode, before establishing a connection and synchronizing with the UE for data transfer, the time consumed for data transfer is reduced and thereby the power consumption within the macro cell during data transfer is reduced.
Various embodiments of the present disclosure are described for illustrating the various arrangements and set ups in the network architecture to describe the method mentioned above.
Referring to
In the first deployment, the UE 206 maintains the RRC signaling bearer with the macro cell 202. Therefore, whenever there is a requirement to send Layer-3 (L3) level processing signaling data for mobility and bearer establishment, security, session setup and management related procedures, the UE 206 sends such signals directly to the macro cell 202. The UE 206 directly sends and receives a signal bearer with the macro cell 206. Further in the first deployment, whenever the UE 206 must establish a bearer for data traffic, the UE 206 establishes a connection with the macro cell 202, notifies the macro cell 202 regarding its requirement of the bearer for the data transfer, and, based on the requirement of the UE 206, the macro cell 202 exchanges Access Stratum (AS) configuration parameters with a designated small cell 204 for a radio bearer to be setup for data traffic via the small cell 204.
Whenever there is simultaneous traffic on a signal bearer and a data bearer, the scenario will be treated like a carrier aggregation scenario but signaling traffic will be sent on the macro cell carrier, and data traffic will be sent on the small cell carrier. It is assumed that a signal bearer is active during the life-span of the data bearer. According to the first deployment, whenever the UE 206 wants to transfer data, the UE 206 sends a signal bearer to the macro cell 202. Upon receiving the signal bearer from the UE 206, the macro cell 202 sends the AS configuration parameters to the selected small cell 204 indicating to the small cell 204 that the UE 206 is in need of a carrier for data transfer. Once the small cell 204 receives the AS configuration parameters, the small cell 204 allocates small cell carriers to the UE 206 for data transfer, wherein the UE 206 uses the small cell carriers of the small cell 204 to transfer data to the S-GW 210.
In the second deployment, L3 level processing signaling data resides with the macro cell 202. In the second deployment, whenever the UE 206 must establish a bearer for data traffic, the UE 206 establishes a connection with the macro cell 202, and the macro cell 202 exchanges the AS configuration parameters with designated the small cell 204 for a radio bearer to be setup for data traffic via the small cell 204. Then, the signaling bearer with the macro cell 202 is merged with the small cell 204; thereby all traffic including the signal bearer along with the data bearer is sent to the small cell 204. Processing of the RLC and the PDCP is done at the small cell 204 and L3 level processing of signaling data is relayed to the macro cell 202 for mobility and bearer establishment, security, session setup and management related procedures. As the signal bearing and data bearing are done via the small cell 204, the second deployment requires a robust backhaul link between the macro cell 202 and the small cell 204.
Referring to
According to the network architecture described above and its two possible deployments, the UE 306i can encounter two cases, wherein the first small cell 304a and the second small cell 304b can be in a sleep state or in a wake-pp state. In this case, the small cell in the sleep state can only transmit discovery signals as defined in 3GPP LTE Release 12/13. A small cell cannot listen to any Random Access Channel (RACH) attempts while in a sleep state. If the UE 306i is measuring the first small cell 304a and the second small cell 304b, then as per the current 3GPP LTE Release 12/13 design, the UE 306i can easily identify if a small cell is in a sleep state or not by virtue of a Discovery Reference Signal (DRS) or Channel Reference Signal/Channel State Information Reference Signal (CRS/CSI-RS) measurements. The deployments described above can be applied to the network architecture, and therefore is not described herein to avoid repetition.
Referring to
Referring to
First, the UE 506 establishes an RRC connection with the macro cell 502 during a connection establishment procedure. Upon establishment of the connection, the macro cell 502 provides a Timing Advance (TA) in a Random Access Response (RAR) with respect to the macro cell 502. Further, the macro cell 502 provides a coarse level TA for the selected small cell 504 by the UE 506 in a TA Medium Access Control (MAC) Protocol Data Unit (PDU). Thus, the UE 506 can get a coarse level timing advance from the small cell 504 for the first transmission.
If the small cell 504 identifies that the coarse level TA for the UE 506 is within the limits of correctness, then the small cell 504 sends a TA MAC PDU to the UE 506 in response to the SRS sent by the UE 506 in order to conduct a fine adjustment of the TA PDU and an UpLink (UL)/DownLink (DL) resource allocation and communication. If the small cell 504 identifies that the coarse level TA for the UE 506 is out of the limits of correctness, then the small cell 504 sends a default TA to the UE 506 and the UE 506 initiates the RACH to continue the course of operation.
Referring to
The macro cell 602 identifies the small cell ID1604 as the suitable small cell for the UE 606 for data transfer, and sends a MAC PDU-coarse level TA for the small cell 604 in step 612 and, at the same time, the small cell ID1604 is awakened in step 614. Then, the macro cell 602 sends a connection setup CONN_SET_UP message to the UE 602 in step 616, wherein the configuration set up message includes the small cell's 604 information such as the name of the small cell 604, configuration details, and the like. Upon receiving the configuration set up message, the UE 606 sends an SRS with course level TA message to the small cell 604 to measure the TA in step 618, and then the small cell 604 can sends a MAC PDU TA to the UE 606 in step 620, If the TA is default TA, the small cell 604 sends the default TA to the UE 606 in step 622, upon which the UE 606 sends the RACH message again for a new small cell in step 624. If the TA is not default TA, the UE 606 makes a connection with the small cell 604 for UpLink (UL)/DownLink (DL) in step 626.
Referring to
The macro cell 702 identifies the first small cell ID 1704a as the suitable small cell for the UE 706 for data transfer, and sends a MAC PDU-coarse level TA for the first small cell ID1704a to the UE 706 in step 718. The macro cell 702 checks whether the first small cell ID1704a is in the sleep state in step 720. If the first small cell ID1704a is in the sleep state, then the macro cell 702 sends a wake up request message (e.g. WAKE_UP_REQ) to the first small cell ID1704a in step 722. If the first small cell ID1704a is in the sleep state, can receive the message and switch to active (e.g. awake) mode, the first small cell ID1704a sends a wake up response message (e.g. WAKE_UP_RES) to the macro cell 702 in step 724. If the macro cell 702 identifies that the first small cell ID1704a is not in the sleep state in step 720, then the macro cell 702 identifies that the first small cell ID1704a is active and ready for communication with the UE 706.
Upon identifying that the first small cell ID 704a is in the active mode, the macro cell 702 sends a connection set up message (e.g. CONN_SET_UP) to the UE 706 in step 726, wherein the configuration set up message includes first small cell ID1704a information such as the name of the first small cell ID1704a, configuration details, and the like. Further, the macro cell 702 sends “connection configuration message (CONN_CONFIG) to the small cell ID 1. Upon receiving the configuration set up message, the UE 706 sends an SRS with coarse level TA message to the first small cell ID1704a in step 728. If the first small cell ID1704a identifies that the coarse level TA is well within the correction level, then the small cell ID1704a sends a MAC PDU TA message to the UE 706 in step 730, and If TA is default TA, the first small cell ID1704a sends a default TA message to the UE 706 in step 732, upon which the UE 706 sends the RACH message again for new small cell in step 734. If TA is not default TA, the UE 706 makes a connection with the first small cell ID1704a for uplink (UL)/downlink (DL) in step 736. Upon establishing UL/DL, all L3 signaling is relayed to the macro cell 702 in steps 738, 740a, and 740b, in order to make a decision for all L3 control signaling.
Referring to
In the first deployment, the UE 806 maintains the RRC signal bearer with the macro cell 802 in order to send L3 level processing signaling data to the macro cell 802 when there is no data traffic. In the second deployment, the UE 206 connects to the small cell 804 for the data traffic, and when the data bearer is available from the small cell 804, L3 control signaling can be transmitted via the small cell 804 to the macro cell 802. As described above, the small cells 804 can have a backhaul connection with the macro cell 802 to process handover conditions.
Referring to
According to the network architecture and its two possible deployments described above, the UE 906i can encounter two cases, wherein the first small cell 904a and the second small cell 904b can be in a sleep state or in a wake-up state. In the sleep state, the sleeping cell can only transmit discovery signals as defined in 3GPP LTE Release 12/13. A small cell cannot listen to any RACH attempts during a sleep state. The UE 906i can connect to the macro cell 902 only for L3 control signaling when the UE 906 does not wish to transfer data. If the UE 906 wishes to transfer data using the first small cell 904a or the second small cell 904b, then, as per the current 3GPP LTE-Release 12/13 design, the UE 906i can connect to the first small cell 904a or the second small cell 904b for data traffic and when the bearer is available, then the L3 control signaling is transmitted via the first small cell 904a or the second small cell 904b to the macro cell 902. The rest of the process for processing data is performed as described in the aforementioned embodiment of the present disclosure.
Referring to
Referring to
Upon receiving the macro system information, the UE 1106 updates the neighbor small cell list in step 1110. The UE 1106 conducts idle mode DRX measurements for the macro cell 1102 and the small cells present within the macro cell 1102 in step 1112. The UE 1106 sends a RACH message to the macro cell 1102 in step 1114, wherein the RACH message includes information about the selected small cells with identifiers ID1 and ID2 present within the network area of the macro cell 1102 to which the UE 1106 wishes to associate with for data transfer. Upon receiving the RACH message from the UE 1106, the macro cell 1102 schedules the small cells to identify the suitable small cell for the UE 1106 to associate with for transferring data in step 1115.
The macro cell 1102 identifies the first small cell ID11104a as the suitable small cell for the UE 1106 for data transfer and sends a MAC PDU-coarse level TA for the first small cell ID11104a in step 1118. The macro cell 1102 checks whether the first small cell ID11104a is in a sleep state in step 1120. If the first small cell ID11104a is in the sleep state, then the macro cell 1102 sends a wake up request message (e.g. WAKE_UP_REQ) to the first small cell ID11104 in step 1122. If the first small cell ID11104a is in the sleep state, the first small cell ID11104a receives the message, switches to an active (e.g. awake) mode, and sends a wake up response message (e.g. WAKE_UP_RES) to the macro cell 1102 in step 1124. If the macro cell 1102 identifies that the first small cell ID11104a is not in the sleep state, then the macro cell 1102 identifies that the first small cell ID11104a is in the active mode and ready for communication with the UE 1106.
Upon identifying that the first small cell ID 1104a is in the active mode, the macro cell 1102 sends a connection set up message (e.g. CONN_SET_UP) to the UE 1102 in step 1126, wherein the configuration set up message includes small cell information such as a name of the small cell, configuration details, and the like. Upon receiving the configuration set up message, the UE 1106 sends a RACH access request message (e.g. RACH_ACCESS_REQ) to the first small cell ID11104a in step 1128. Upon receiving the RACH access request message, the first small cell ID11104a sends RACH access response message to the UE 1106 in step 1130, and the UE 1106 makes a connection with the first small cell ID11104a for UpLink (UL)/DownLink (DL) in step 1132. Upon establishing UL/DL, all L3 signaling is relayed to the first small cell ID11104a in step 1134, in order to make decisions for all L3 control signaling.
In the above mentioned embodiments of the present disclosure, the macro cell sends small cell selection and acquisition information in system information. In addition to Selection criteria (S-criteria), cell identifiers, frequency and other related information, the macro cell can also send the RACH configuration information for all the small cells in the macro cell system information. This can enable the UE to start measurements on the small cells, and can apply initial access on the small cells as per the procedure described above for all neighbor small cells and the macro cell. The procedure of sending system information is illustrated in
As soon as the UE triggers a connection request, either due to a Mobile Originated (MO) call, or paging for the Mobile Terminal (MT) call, the UE can trigger search on the given neighbor cell set in addition to optimizations to search small cells and the macro cell found during DRX measurement. The UE can make a list of the macro cells and the small cells as per their received signal strength on reference symbols. As per the current 3GPP design, the UE may need to achieve the acquisition on the best small cell as per the selection criterion, and then find the RACH information on the target small cell before triggering the random accesses request. However, the delay of reading system information can be minimized by sending primary small cell related information as an addition to macro cell System Information Block (SIB) information. This will help in achieving the acquisition without reading system information at the small cell. The UE will select the best cell and will make a RACH attempt to achieve initial RRC connection. It is possible to optimize the random access related parameters to reduce the load of the macro cell by means of transmitting common RACH information and specific RACH information separately, or implicit derivation of parameters from the macro cell's parameter using offset or delta information transmission.
Further, the additional points which are to be considered for RACH parameter optimization comprises:
In the embodiments of the present disclosure, measurement of small cells also plays an important role, as the information about the small cells present within the macro cell can be helpful for making the list and scheduling of the small cells before transferring data. When the UE decides to measure small cells, some small cells could be in the sleep state and some small cells could be in the awake state (e.g. wake up mode). Thus, for the UE to indicate the possible small cells to the macro cell during random access, it may need to apply some criteria when it ranks small cells based on DRS and CSI-RS measurement as both have different measurement quantities as follows:
i. Discovery Reference Signal (RS) is different from Channel State Information-Reference Signal (CSI-RS) (Primary Synchronization Signal/Secondary Synchronization Signal (PSS/SSS)) signals. A new measurement quantity can be defined called Discovery Reference Signal Received Power (RSRP), and used to maintain the best small cell in the sleep state.
ii. If the small cell is in the awake state, then the small cells can transmit CSI-RS like a normal cell, and the UE will maintain this small cell in the awake state, where the small cell identifiers must be indicated via the macro cell SIB, so that the UE can identify if the measure cell is a macro cell or a small cell.
The list arrived at during the RRC Idle State is described in Table 1 below.
Between small cell lists (Active vs. Sleeping), ranking can be merged like in Table 2 below based on a translation of Discovery RSRP to a normal RSRP, so that the UE can choose the small cell on which to attempt access when the need arises. The translation could be an absolute offset, a multiplication factor, or a combination of both which can be applied to Discovery RSRP to make it a normal RSRP.
The present disclosure has been described with reference to embodiments thereof, it will be evident that various modifications and changes may be made to these embodiments without departing from the scope and spirit of the present disclosure. Furthermore, the various devices, modules, and the like described herein may be enabled and operated using hardware circuitry, for example, Complementary Metal Oxide Semiconductor (CMOS) based logic circuitry, firmware, software and/or any combination of hardware, firmware, and/or software embodied in a machine readable medium.
Although the present disclosure is with various certain embodiments, it will be obvious for a person skilled in the art to practice the disclosure with modifications. However, all such modifications are deemed to be within the scope and spirit of the present disclosure, as defined by the appended claims and their equivalents.
Number | Date | Country | Kind |
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10-2015-0020898 | Feb 2015 | KR | national |
This application claims priority under 35 U.S.C. §119(e) to a U.S. Provisional Patent Application filed on Apr. 1, 2014 with the United States Patent and Trademark Office and assigned Ser. No. 61/973,535, and a Korean Patent Application, filed on Feb. 11, 2015 in the Korean Intellectual Property Office and assigned Serial No. 10-2015-0020898, the entire contents of which are incorporated herein by reference.
Number | Date | Country | |
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61973535 | Apr 2014 | US |