Patent Application
20150079989
The present disclosure relates to wireless communication, and more specifically, to aspects of search and measurement scheduling in a cell reselection procedure executed a user equipment (UE) when camping on a small cell.
Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple UEs by sharing the available network resources. One example of such a network is the UMTS Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), Time Division-Synchronous Code Division Multiple Access (TD-SCDMA), High Speed Packet Access (HSPA), and Long Term Evolution (LTE), which uses orthogonal frequency division multiple access (OFDMA) on the downlink (DL), single-carrier frequency division multiple access (SC-FDMA) on the uplink (UL), and multiple-input multiple-output (MIMO) antenna technology.
Further, to supplement conventional wireless network base stations, referred to as macro base stations or macro cells, a network operator may deploy or allow users to deploy additional base stations to provide more robust wireless coverage to UEs. For example, wireless relay stations and small-coverage or closed subscriber group (CSG) base stations or cells (commonly referred to as access point base stations, Home NodeBs, femto access points, femto cells, or pico cells) may be deployed for incremental capacity growth, richer user experience, and in-building coverage. Typically, such small-coverage base stations are connected to the Internet and the network of the mobile network operator via a digital subscriber line (DSL) router or cable modem.
Additionally, in UMTS, the user equipment (UE) shall regularly search for a better cell to camp on according to the cell reselection criterion provided by the network, for example, as defined by 3GPP Technical Specification TS 25.304, “User Equipment (UE) procedures in idle mode and procedures for cells reselection in connected mode,” hereby incorporated by reference herein. This mechanism is used to ensure an acceptable quality of the camping cell, and therefore to achieve a desired call setup performance. A very reactive cell reselection mechanism can guarantee an adequate quality of the camping cell, however, this gain is achieved at the expense of stand-by time, which is decreased by frequent reselections.
Moreover, while the standards define the cell reselection criteria and some rules for performing a cell reselection evaluation when camping on the small coverage base station, the implementation of small coverage cell search and measurement scheduling in a cell reselection procedure may include many searches and measurements that adversely affect UE standby time and user experience.
Thus, improvements in performing a cell reselection evaluation when camping on the small coverage base station are desired.
The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.
In accordance with an aspect, methods and apparatus for cell reselection when camped on a small cell comprises determining, by a user equipment (UE), whether to perform a cell reselection evaluation after camping on the small cell communicating with the UE in a serving frequency and according to a serving radio access technology (RAT). Further, the methods and apparatus include performing a measurement of a signal transmitted by the small cell in response to determining whether the cell reselection evaluation should be performed. Moreover, the methods and apparatus include determining that a signal characteristic based on the measurement of the signal of the small cell falls below a cell reselection measurement triggering threshold. Additionally, the methods and apparatus include performing a measurement of a respective signal transmitted by one or more other cells in only the serving frequency in response to the signal characteristic of the small cell falling below the measurement triggering threshold. Further, the methods and apparatus include ranking the small cell relative to the one or more other cells based on the signal characteristic of the small cell and a respective signal characteristic of the one or more other cells determined from the measurement of the respective signal transmitted by the one or more other cells. Moreover, the methods and apparatus include remaining camped on the small cell when the small cell is ranked higher than the one or more other cells.
Further aspects provide a computer program product for cell reselection when camped on a small cell comprising a computer-readable medium includes at least one instruction for determining, by a user equipment (UE), whether to perform a cell reselection evaluation after camping on the small cell communicating with the UE in a serving frequency and according to a serving radio access technology (RAT). Further, the computer program product further comprises at least one instruction for performing a measurement of a signal transmitted by the small cell in response to determining whether the cell reselection evaluation should be performed. Moreover, the computer program product further comprises at least one instruction for determining that a signal characteristic based on the measurement of the signal of the small cell falls below a cell reselection measurement triggering threshold. Additionally, the computer program product further comprises at least one instruction for performing a measurement of a respective signal transmitted by one or more other cells in only the serving frequency in response to the signal characteristic of the small cell falling below the measurement triggering threshold. Further, the computer program product further comprises at least one instruction for ranking the small cell relative to the one or more other cells based on the signal characteristic of the small cell and a respective signal characteristic of the one or more other cells determined from the measurement of the respective signal transmitted by the one or more other cells. Moreover, the computer program product further comprises at least one instruction for remaining camped on the small cell when the small cell is ranked higher than the one or more other cells.
Additional aspects provide an apparatus for communication comprises means for determining whether to perform a cell reselection evaluation after camping on the small cell communicating with the UE in a serving frequency and according to a serving radio access technology (RAT). The apparatus further comprises means for performing a measurement of a signal transmitted by the small cell in response to determining whether the cell reselection evaluation should be performed. Moreover, the apparatus comprises means for determining that a signal characteristic based on the measurement of the signal of the small cell falls below a cell reselection measurement triggering threshold. Additionally, the apparatus comprises means for performing a measurement of a respective signal transmitted by one or more other cells in only the serving frequency in response to the signal characteristic of the small cell falling below the measurement triggering threshold. Further, the apparatus comprises means for ranking the small cell relative to the one or more other cells based on the signal characteristic of the small cell and a respective signal characteristic of the one or more other cells determined from the measurement of the respective signal transmitted by the one or more other cells. Moreover, the apparatus comprises means for remaining camped on the small cell when the small cell is ranked higher than the one or more other cells.
In an additional aspect, an apparatus for communication comprises a memory storing executable instructions and a processor in communication with the memory, wherein the processor is configured to execute the instructions to determine, by a user equipment (UE), whether to perform a cell reselection evaluation after camping on the small cell communicating with the UE in a serving frequency and according to a serving radio access technology (RAT). The processor is further configured to perform a measurement of a signal transmitted by the small cell in response to determining whether the cell reselection evaluation should be performed. Moreover, the methods and apparatus include determining that a signal characteristic based on the measurement of the signal of the small cell falls below a cell reselection measurement triggering threshold. Additionally, the processor is configured to perform a measurement of a respective signal transmitted by one or more other cells in only the serving frequency in response to the signal characteristic of the small cell falling below the measurement triggering threshold. Further, the processor is configured to rank the small cell relative to the one or more other cells based on the signal characteristic of the small cell and a respective signal characteristic of the one or more other cells determined from the measurement of the respective signal transmitted by the one or more other cells. Moreover, the processor is configured to remain camped on the small cell when the small cell is ranked higher than the one or more other cells.
To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.
The disclosed aspects will hereinafter be described in conjunction with the appended drawings, provided to illustrate and not to limit the disclosed aspects, wherein like designations denote like elements, and in which:
Various aspects are now described with reference to the drawings. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects. It may be understood, however, that the present aspects may be practiced without these specific details.
According to the present apparatus and methods, a user equipment (UE) that is camped on a small coverage cell and triggered to perform a cell reselection evaluation is configured to avoid making cell measurements, even when a quality of the small coverage cell is below a cell reselection measurement triggering threshold of one more networks, based on determining that the small coverage cell is the best ranked cell in a serving frequency of the small coverage cell. In other words, although the quality of the small coverage cell is below one or more cell reselection measurement triggering thresholds, the UE will not perform certain measurements and searches, or reselect to a cell, when the small coverage cell is the best ranked cell on its serving frequency. Thus, even in the presence of strong cell candidates for reselection, e.g., cells having high received signal strengths at the UE, the present apparatus and methods may enable the UE to remain camped on the small coverage cell, and may enable avoiding unnecessary cell measurements and searches.
As a result, the present apparatus and methods may enable the UE to save power and processing resources, and thereby improve standby time and improve the user experience.
The term “small cell” (or “small coverage cell”), as used herein, may refer to an access point or to a corresponding coverage area of the access point, where the access point in this case has a relatively low transmit power or relatively small coverage as compared to, for example, the transmit power or coverage area of a macro network access point or macro cell. For instance, a macro cell may cover a relatively large geographic area, such as, but not limited to, several kilometers in radius. In contrast, a small cell may cover a relatively small geographic area, such as, but not limited to, a home, a building, or a floor of a building. As such, a small cell may include, but is not limited to, an apparatus such as a base station (BS), an access point, a femto node, a femtocell, a pico node, a micro node, a Node B, evolved Node B (eNB), home Node B (HNB) or home evolved Node B (HeNB). Therefore, the term “small cell,” as used herein, refers to a relatively low transmit power and/or a relatively small coverage area cell as compared to a macro cell.
In some aspects, the one or more cells in the telecommunications network system 100 may communicate according to at least one technology such as, but not limited to, long term evolution (LTE), universal mobile telecommunications system (UMTS), code division multiple access (CDMA) 2000, wireless local area network (WLAN) (e.g., WiFi). Further, the transmission-related parameters associated with each of the one or more network entities, such as the foregoing non-limiting example network entities may include, but are not limited to, physical cell identity (PCI), primary synchronization code (PSC), pseudo-random noise code (PN), channel numbers and/or beacon patterns.
Moreover, for example, the wireless network system 10 may be an LTE network or some other wide wireless area network (WWAN). As such, the wireless communication system 10 may include a UE 12 having a communication manager component 14 configured to efficiently perform cell reselection evaluations when UE 12 is camped on a small cell 16.
In certain aspects, communication manager component 14 may include reselection component 24, which may be configured to determine whether to perform a cell reselection evaluation after camping on a small cell (e.g., small cell 16) communicating with UE 12 in a serving frequency and according to a serving RAT. The communication manager component 14 may further include measurement component 26, which may be configured to perform a measurement of a signal (e.g., signal 28) transmitted by the small cell (e.g., small cell 16) in response to determining whether to perform the cell reselection evaluation. Moreover, communication manager component 14 may include evaluation component 30 which may be configured to determine that a signal characteristic based on the measurement of the signal (e.g., signal 28) of the small cell (e.g., small cell 16) falls below a cell reselection measurement triggering threshold. Additionally, measurement component 26 may be configured to perform a measurement of a respective signal (e.g., signals 35, 37, and/or 39) transmitted by one or more other cells (e.g., cells 18, 20, and/or 22) in only the serving frequency in response to the signal characteristic of the small cell (e.g., small cell 16) falling below the measurement triggering threshold. Further, communication manager component 14 may include ranking component 32 which may be configured to rank the small cell (e.g., small cell 16) relative to the one or more other cells (e.g., cells 18, 20, and/or 22) based on the signal characteristic of the small cell and a respective signal characteristic of the one or more other cells determined from the measurement of the respective signal (e.g., signals 35, 37, and/or 39) transmitted by the one or more other cells. Moreover, communication manager component 14 may include determination component 34 which may be configured to remain camped on the small cell (e.g., small cell 16) when the small cell is ranked higher than the one or more other cells (e.g., cells 18, 20, and/or 22).
An eNodeB may be an example of a station that communicates with one or more UEs (e.g., UE 12) and may also be referred to as a base station, an access point, etc. Each eNodeB (e.g., cells 16, 18, 20, and/or 22) may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to a coverage area of an eNodeB 110 and/or an eNodeB subsystem serving the coverage area, depending on the context in which the term is used.
An eNodeB may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cell. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by one or more UEs (e.g., UE 12) with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by one or more UEs (e.g., UE 12) with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by one or more UEs (e.g., UE 12) having association with the femto cell (e.g., UE 12 may be subscribed to a Closed Subscriber Group (CSG), UE 12 for users in the home, etc.).
An eNodeB for a macro cell may be referred to as a macro eNodeB. An eNodeB for a pico cell may be referred to as a pico eNodeB. An eNodeB for a femto cell may be referred to as a femto eNodeB or a home eNodeB. In the example shown in
The wireless network system 10 may be a heterogeneous network that includes eNodeBs of different types, e.g., macro eNodeBs, pico eNodeBs, femto eNodeBs, relays, etc. These different types of eNodeBs may have different transmit power levels, different coverage areas, and different impact on interference in the wireless network system 10. For example, macro eNodeBs (e.g., cells 18, 20, and/or 22) may have a high transmit power level (e.g., 20 Watts) whereas pico eNodeBs, femto eNodeBs (e.g., small cell 16) and relays may have a lower transmit power level (e.g., 1 Watt).
The wireless network system 10 may support synchronous or asynchronous operation. For synchronous operation, the eNodeBs may have similar frame timing, and transmissions from different eNodeBs and may be approximately aligned in time. For asynchronous operation, the eNodeBs may have different frame timing, and transmissions from different eNodeBs and may not be aligned in time. The techniques described herein may be used for both synchronous and asynchronous operation.
The one or more UEs (e.g., UE 12) may be dispersed throughout the wireless network system 10, and each UE may be stationary or mobile. For example, the UE 12 may be referred to as a terminal, a mobile station, a subscriber unit, a station, etc. In another example, the UE 12 may be a cellular phone, a Smartphone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a netbook, a smart book, etc. The UE 12 may be able to communicate with macro eNodeBs, pico eNodeBs, femto eNodeBs, relays, etc.
LTE may utilize orthogonal frequency division multiplexing (OFDM) on the downlink and single-carrier frequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM may partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. In general, modulation symbols may be sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may be dependent on the system bandwidth. For example, the spacing of the subcarriers may be 15 kHz and the minimum resource allocation (called a ‘resource block’) may be 12 subcarriers (or 180 kHz). Consequently, the nominal Fast Fourier Transform (FFT) size may be equal to 128, 256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5, 5, 10 or 20 megahertz (MHz), respectively. The system bandwidth may be partitioned into subbands. For example, a subband may cover 1.08 MHz (i.e., 6 resource blocks), and there may be 1, 2, 4, 8 or 16 subbands for system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively.
Referring to
In an aspect, communication manager component 14 may include reselection component 24. For instance, reselection component 24 may be configured to determine whether to perform a cell reselection evaluation after camping on small cell 16 (
Further, communication manager component 14 may include measurement component 26. For instance, measurement component 26 may be configured to perform a measurement of a signal (e.g., pilot signal 43) transmitted by small cell 16 (
In a further aspect, communication manager component 14 may include evaluation component 30. In some instances, evaluation component 30 may be configured to determine whether small cell 16 (
Squat=Qqualmeas−Qqualmin
Srxlev=Qrxlevmeas−Qrxlevmin−Pcompensation
where:
In an aspect, when small cell 16 (
Further, evaluation component 30 may be configured to determine that a signal character 45 based on the measurement of the pilot signal 43 of small cell 16 (
When one or more respective cell reselection measurement triggering thresholds 47 are met, conventionally, measurements and searches are performed on intra-frequency cells and inter-frequency cells and inter-RAT cells. Based on the present aspects, however, UE 12 may be able to avoid performing at least a part of such measurements and/or searches.
For example, measurement component 26 may be configured to perform a measurement of a respective signal 44 transmitted by one or more other cells (e.g., cells 18, 20, and/or 22 in
In a further aspect, communication manager component 14 may include ranking component 32. For instance, ranking component 32 may be configured to rank the small cell 16 (
In another aspect, communication manager component 14 may include determination component 34. For instance, determination component 34 may be configured to remain camped on the small cell 16 (
Furthermore, UE 12 and/or communication manager component 14 may execute determination component 34 to initiate a sleep mode of operation based on the determination that UE 12 can remain camped on small cell 16. For example, in an aspect, communication manager component 14 may execute determination component 34 to shut down use of communication resources, e.g., all or part of transceiver or receiver, for a remainder of the current DRX time period until a next wake-up time corresponding to the occurrence of a next DRX time period.
Moreover, in an aspect, UE 12 and/or communication manager component 14 may execute measurement component 26 to detect and measure respective intra-frequency signals 35, inter-frequency signals 37, and inter-RAT signals 39 (
Additionally, in an aspect, determination component 34 may be configured to perform a cell reselection based on the respective measurements of the respective intra-frequency cells, the respective inter-frequency cells, and the respective inter-RAT cells (e.g., cells 18, 20, 22, respectively, in
Referring to
Referring to
In an aspect, at block 51, method 50 includes determining, by a user equipment (UE), whether to perform a cell reselection evaluation after camping on a small cell communicating with the UE in a serving frequency and according to a serving radio access technology (RAT). For example, as described herein, communication manager component 14 (
At block 52, method 50 includes performing a measurement of a signal transmitted by the small cell in response to determining whether to perform the cell reselection evaluation. For example, as described herein, communication manager component 14 (
Further, at block 53, method 50 may optionally include determining whether the small coverage cell is suitable based on the measurement of the transmitted signal and the cell reselection criteria corresponding to the cell reselection evaluation. For example, as described herein, communication manager component 14 (
At block 54, method 50 may include determining that a signal characteristic based on the measurement of the signal of the small cell falls below a cell reselection measurement triggering threshold. For example, as described herein, communication manager component 14 (
At block 55, method 50 may include performing a measurement of a respective signal transmitted by one or more other cells in only the serving frequency in response to the signal characteristic of the small cell falling below the measurement triggering threshold. For example, as described herein, communication manager component 14 (
At block 56, method 50 may include ranking the small cell relative to the one or more other cells based on the signal characteristic of the small cell and a respective signal characteristic of the one or more other cells determined from the measurement of the respective signal transmitted by the one or more other cells. For example, as described herein, communication manager component 14 (
At block 57, method 50 may optionally include remaining camped on the small cell when the small cell is ranked higher than the one or more other cells. For example, as described herein, communication manager component 14 (
At block 58, method 50 may optionally include initiating a sleep mode for the UE, wherein initiating the sleep mode comprises shutting down or otherwise reducing power consumed by one or more communication resources of the UE. For example, as described herein, communication manager component 14 (
At block 59, method 50 may optionally include performing measurements on any intra-frequency cells, any inter-frequency cells, and any inter-RAT cells listed in one or more received system information messages when the small cell is not ranked higher than the one or more other cells. For example, as described herein, communication manager component 14 (
At block 60, method 50 may optionally include performing a cell reselection based on the respective measurements of the respective intra-frequency cells, the respective inter-frequency cells, and the respective inter-RAT cells. For example, as described herein, communication manager component 14 (
Referring to
At block 74, method 70 may include UE 12 determining whether or not the small cell 16 is suitable. If not, then UE 12 performs conventional or legacy cell reselection procedures, as indicated at block 84. If small cell 16 is suitable, then at block 76 UE 12 determines whether or not a trigger exist for performing measurements or searches on intra-frequency cells, inter-frequency cells, and inter-RAT cells.
At block 76, method 70 may include determining whether or not a trigger exists for performing measurements or searches on intra-frequency cells, inter-frequency cells, and inter-RAT cells. For example, UE 12 (
Additionally, for any measurements on previously identified cells and/or fresh cell identification (e.g., WCDMA/GSM/LTE) to happen then Squal is less than the respective threshold (e.g., WCDMA/GSM/LTE); the timer for measurements on previously identified cells and/or fresh cell identification on that respective RAT (W/G/L) should have expired; and measurements on previously identified cells and/or fresh cell identification need to have been performed. Specifically, for measurements on previously identified cells, there should be some timing known (e.g., whether a timer has expired) and/or already detected cells to measure on the respective RAT (W/G/L). Specifically, for fresh cell identification, there should be some cells broadcasted in SIBs to search on that respective RAT (W/G/L). If there is no trigger, then UE 12 proceeds to block 82 and optionally decodes CTCH, e.g., for emergency messages, or otherwise UE 12 returns to a sleep mode for the remainder of the current DRX cycle.
At block 76, if UE 12 does determine existence of a trigger, then UE 12 proceeds to block 78 and performs only measurements on the serving frequency. For example, UE 12
Further, at block 80, based on the measurements in the serving frequency, UE 12 determines whether small coverage cell 16 is the highest ranked cell in the serving frequency If not, the UE 12 proceeds to block 84, where UE 12 performs the legacy cell reselection procedures. Alternatively, at block 80, if UE 12 determines that small coverage cell 16 is the highest ranked cell in the serving frequency, then UE 12 proceeds to block 82. As described above, at block 82 UE 12 optionally decodes CTCH, e.g., for emergency messages, or otherwise returns to a sleep mode for the remainder of the current DRX cycle.
Thus, based on configuration of UE 12 according to the present aspects, UE 12 may be able to skip or otherwise avoid some cell searches and measurements associated with conventional cell reselection procedures when UE 12 is camped on a suitable small coverage cell 16 and when small coverage cell 16 is the highest ranked cell in its serving frequency.
In particular, according to the apparatus and methods described above, UE 12 is skipping inter-frequency and inter-RAT (GSM/LTE) measurements as long as the camped CSG cell is best ranked in its frequency. Thus, according to the present aspects, UE 12 will go to sleep faster in every DRX cycle, thereby saving battery life.
Referring to
The processor 104 is responsible for managing the bus 102 and general processing, including the execution of software stored on the computer-readable medium 106. The software, when executed by the processor 104, causes the processing system 114 to perform the various functions described infra for any particular apparatus. The computer-readable medium 106 may also be used for storing data that is manipulated by the processor 104 when executing software. Communication manager component 14 as described above may be implemented in whole or in part by processor 104, or by computer-readable medium 106, or by any combination of processor 104 and computer-readable medium 106.
The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards.
Referring to
Communication between UE 210 and a Node B 208 may be considered as including a physical (PHY) layer and a medium access control (MAC) layer. Further, communication between a UE 210 and an RNC 206 by way of a respective Node B 208 may be considered as including a radio resource control (RRC) layer. In the instant specification, the PHY layer may be considered layer 1; the MAC layer may be considered layer 2; and the RRC layer may be considered layer 3. Information hereinbelow utilizes terminology introduced in the RRC Protocol Specification, 3GPP TS 25.331, incorporated herein by reference.
The geographic region covered by the RNS 207 may be divided into a number of cells, with a radio transceiver apparatus serving each cell. A radio transceiver apparatus is commonly referred to as a Node B in UMTS applications, but may also be referred to by those skilled in the art as a base station (BS), a base transceiver station (BTS), a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), an access point (AP), or some other suitable terminology. For clarity, three Node Bs 208 are shown in each RNS 207; however, the RNSs 207 may include any number of wireless Node Bs. The Node Bs 208 provide wireless access points to a CN 204 for any number of mobile apparatuses. Examples of a mobile apparatus include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a notebook, a netbook, a smartbook, a personal digital assistant (PDA), a satellite radio, a global positioning system (GPS) device, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, or any other similar functioning device. The mobile apparatus is commonly referred to as a UE in UMTS applications, but may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. In a UMTS system, the UE 210 may further include a universal subscriber identity module (USIM) 211, which contains a user's subscription information to a network. For illustrative purposes, one UE 210 is shown in communication with a number of the Node Bs 208. The DL, also called the forward link, refers to the communication link from a Node B 208 to a UE 210, and the UL, also called the reverse link, refers to the communication link from a UE 210 to a Node B 208.
The CN 204 interfaces with one or more access networks, such as the UTRAN 202. As shown, the CN 204 is a GSM core network. However, as those skilled in the art will recognize, the various concepts presented throughout this disclosure may be implemented in a RAN, or other suitable access network, to provide UEs with access to types of CNs other than GSM networks.
The CN 204 includes a circuit-switched (CS) domain and a packet-switched (PS) domain. Some of the circuit-switched elements are a Mobile services Switching Centre (MSC), a Visitor location register (VLR) and a Gateway MSC. Packet-switched elements include a Serving GPRS Support Node (SGSN) and a Gateway GPRS Support Node (GGSN). Some network elements, like EIR, HLR, VLR and AuC may be shared by both of the circuit-switched and packet-switched domains. In the illustrated example, the CN 204 supports circuit-switched services with a MSC 212 and a GMSC 214. In some applications, the GMSC 214 may be referred to as a media gateway (MGW). One or more RNCs, such as the RNC 206, may be connected to the MSC 212. The MSC 212 is an apparatus that controls call setup, call routing, and UE mobility functions. The MSC 212 also includes a VLR that contains subscriber-related information for the duration that a UE is in the coverage area of the MSC 212. The GMSC 214 provides a gateway through the MSC 212 for the UE to access a circuit-switched network 216. The GMSC 214 includes a home location register (HLR) 215 containing subscriber data, such as the data reflecting the details of the services to which a particular user has subscribed. The HLR is also associated with an authentication center (AuC) that contains subscriber-specific authentication data. When a call is received for a particular UE, the GMSC 214 queries the HLR 215 to determine the UE's location and forwards the call to the particular MSC serving that location.
The CN 204 also supports packet-data services with a serving GPRS support node (SGSN) 218 and a gateway GPRS support node (GGSN) 220. GPRS, which stands for General Packet Radio Service, is designed to provide packet-data services at speeds higher than those available with standard circuit-switched data services. The GGSN 220 provides a connection for the UTRAN 202 to a packet-based network 222. The packet-based network 222 may be the Internet, a private data network, or some other suitable packet-based network. The primary function of the GGSN 220 is to provide the UEs 210 with packet-based network connectivity. Data packets may be transferred between the GGSN 220 and the UEs 210 through the SGSN 218, which performs primarily the same functions in the packet-based domain as the MSC 212 performs in the circuit-switched domain.
An air interface for UMTS may utilize a spread spectrum Direct-Sequence Code Division Multiple Access (DS-CDMA) system. The spread spectrum DS-CDMA spreads user data through multiplication by a sequence of pseudorandom bits called chips. The “wideband” W-CDMA air interface for UMTS is based on such direct sequence spread spectrum technology and additionally calls for a frequency division duplexing (FDD). FDD uses a different carrier frequency for the UL and DL between a Node B 208 and a UE 210. Another air interface for UMTS that utilizes DS-CDMA, and uses time division duplexing (TDD), is the TD-SCDMA air interface. Those skilled in the art will recognize that although various examples described herein may refer to a W-CDMA air interface, the underlying principles may be equally applicable to a TD-SCDMA air interface.
An HSPA air interface includes a series of enhancements to the 3G/W-CDMA air interface, facilitating greater throughput and reduced latency. Among other modifications over prior releases, HSPA utilizes hybrid automatic repeat request (HARQ), shared channel transmission, and adaptive modulation and coding. The standards that define HSPA include HSDPA (high speed downlink packet access) and HSUPA (high speed uplink packet access, also referred to as enhanced uplink, or EUL).
HSDPA utilizes as its transport channel the high-speed downlink shared channel (HS-DSCH). The HS-DSCH is implemented by three physical channels: the high-speed physical downlink shared channel (HS-PDSCH), the high-speed shared control channel (HS-SCCH), and the high-speed dedicated physical control channel (HS-DPCCH).
Among these physical channels, the HS-DPCCH carries the HARQ ACK/NACK signaling on the uplink to indicate whether a corresponding packet transmission was decoded successfully. That is, with respect to the downlink, the UE 210 provides feedback to the node B 208 over the HS-DPCCH to indicate whether it correctly decoded a packet on the downlink.
HS-DPCCH further includes feedback signaling from the UE 210 to assist the node B 208 in taking the right decision in terms of modulation and coding scheme and precoding weight selection, this feedback signaling including the CQI and PCI.
“HSPA Evolved” or HSPA+ is an evolution of the HSPA standard that includes MIMO and 64-QAM, enabling increased throughput and higher performance. That is, in an aspect of the disclosure, the node B 208 and/or the UE 210 may have multiple antennas supporting MIMO technology. The use of MIMO technology enables the node B 208 to exploit the spatial domain to support spatial multiplexing, beamforming, and transmit diversity.
Multiple Input Multiple Output (MIMO) is a term generally used to refer to multi-antenna technology, that is, multiple transmit antennas (multiple inputs to the channel) and multiple receive antennas (multiple outputs from the channel). MIMO systems generally enhance data transmission performance, enabling diversity gains to reduce multipath fading and increase transmission quality, and spatial multiplexing gains to increase data throughput.
Spatial multiplexing may be used to transmit different streams of data simultaneously on the same frequency. The data steams may be transmitted to a single UE 210 to increase the data rate or to multiple UEs 210 to increase the overall system capacity. This is achieved by spatially precoding each data stream and then transmitting each spatially precoded stream through a different transmit antenna on the downlink. The spatially precoded data streams arrive at the UE(s) 210 with different spatial signatures, which enables each of the UE(s) 210 to recover the one or more the data streams destined for that UE 210. On the uplink, each UE 210 may transmit one or more spatially precoded data streams, which enables the node B 208 to identify the source of each spatially precoded data stream.
Spatial multiplexing may be used when channel conditions are good. When channel conditions are less favorable, beamforming may be used to focus the transmission energy in one or more directions, or to improve transmission based on characteristics of the channel. This may be achieved by spatially precoding a data stream for transmission through multiple antennas. To achieve good coverage at the edges of the cell, a single stream beamforming transmission may be used in combination with transmit diversity.
Generally, for MIMO systems utilizing n transmit antennas, n transport blocks may be transmitted simultaneously over the same carrier utilizing the same channelization code. Note that the different transport blocks sent over the n transmit antennas may have the same or different modulation and coding schemes from one another.
On the other hand, Single Input Multiple Output (SIMO) generally refers to a system utilizing a single transmit antenna (a single input to the channel) and multiple receive antennas (multiple outputs from the channel). Thus, in a SIMO system, a single transport block is sent over the respective carrier.
Referring to
As the UE 334 moves from the illustrated location in cell 304 into cell 306, a serving cell change (SCC) or handover may occur in which communication with the UE 334 transitions from the cell 304, which may be referred to as the source cell, to cell 306, which may be referred to as the target cell. Management of the handover procedure may take place at the UE 334, at the Node Bs corresponding to the respective cells, at a radio network controller 206, or at another suitable node in the wireless network. For example, during a call with the source cell 304, or at any other time, the UE 334 may monitor various parameters of the source cell 304 as well as various parameters of neighboring cells such as cells 306 and 302. Further, depending on the quality of these parameters, the UE 334 may maintain communication with one or more of the neighboring cells. During this time, the UE 334 may maintain an Active Set, that is, a list of cells that the UE 334 is simultaneously connected to (i.e., the UTRA cells that are currently assigning a downlink dedicated physical channel DPCH or fractional downlink dedicated physical channel F-DPCH to the UE 334 may constitute the Active Set).
The modulation and multiple access scheme employed by the access network 300 may vary depending on the particular telecommunications standard being deployed. By way of example, the standard may include Evolution-Data Optimized (EV-DO) or Ultra Mobile Broadband (UMB). EV-DO and UMB are air interface standards promulgated by the 3rd Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and employs CDMA to provide broadband Internet access to mobile stations. The standard may alternately be Universal Terrestrial Radio Access (UTRA) employing Wideband-CDMA (W-CDMA) and other variants of CDMA, such as TD-SCDMA; Global System for Mobile Communications (GSM) employing TDMA; and Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, and Flash-OFDM employing OFDMA. UTRA, E-UTRA, UMTS, LTE, LTE Advanced, and GSM are described in documents from the 3GPP organization. CDMA2000 and UMB are described in documents from the 3GPP2 organization. The actual wireless communication standard and the multiple access technology employed will depend on the specific application and the overall design constraints imposed on the system.
Referring to
At the UE 950, a receiver 954 receives the downlink transmission through an antenna 952 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 954 is provided to a receive frame processor 960, which parses each frame, and provides information from the frames to a channel processor 994 and the data, control, and reference signals to a receive processor 970. The receive processor 970 then performs the inverse of the processing performed by the transmit processor 920 in the Node B 910. More specifically, the receive processor 970 descrambles and despreads the symbols, and then determines the most likely signal constellation points transmitted by the Node B 910 based on the modulation scheme. These soft decisions may be based on channel estimates computed by the channel processor 994. The soft decisions are then decoded and deinterleaved to recover the data, control, and reference signals. The CRC codes are then checked to determine whether the frames were successfully decoded. The data carried by the successfully decoded frames will then be provided to a data sink 972, which represents applications running in the UE 950 and/or various user interfaces (e.g., display). Control signals carried by successfully decoded frames will be provided to a controller/processor 990. When frames are unsuccessfully decoded by the receiver processor 970, the controller/processor 990 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.
In the uplink, data from a data source 978 and control signals from the controller/processor 990 are provided to a transmit processor 980. The data source 978 may represent applications running in the UE 950 and various user interfaces (e.g., keyboard). Similar to the functionality described in connection with the downlink transmission by the Node B 910, the transmit processor 980 provides various signal processing functions including CRC codes, coding and interleaving to facilitate FEC, mapping to signal constellations, spreading with OVSFs, and scrambling to produce a series of symbols. Channel estimates, derived by the channel processor 994 from a reference signal transmitted by the Node B 910 or from feedback contained in the midamble transmitted by the Node B 910, may be used to select the appropriate coding, modulation, spreading, and/or scrambling schemes. The symbols produced by the transmit processor 980 will be provided to a transmit frame processor 982 to create a frame structure. The transmit frame processor 982 creates this frame structure by multiplexing the symbols with information from the controller/processor 990, resulting in a series of frames. The frames are then provided to a transmitter 956, which provides various signal conditioning functions including amplification, filtering, and modulating the frames onto a carrier for uplink transmission over the wireless medium through the antenna 952.
The uplink transmission is processed at the Node B 910 in a manner similar to that described in connection with the receiver function at the UE 950. A receiver 935 receives the uplink transmission through the antenna 934 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 935 is provided to a receive frame processor 936, which parses each frame, and provides information from the frames to the channel processor 944 and the data, control, and reference signals to a receive processor 938. The receive processor 938 performs the inverse of the processing performed by the transmit processor 980 in the UE 950. The data and control signals carried by the successfully decoded frames may then be provided to a data sink 939 and the controller/processor, respectively. If some of the frames were unsuccessfully decoded by the receive processor, the controller/processor 940 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.
The controller/processors 940 and 990 may be used to direct the operation at the Node B 910 and the UE 950, respectively. For example, the controller/processors 940 and 990 may provide various functions including timing, peripheral interfaces, voltage regulation, power management, and other control functions. The computer readable media of memories 942 and 992 may store data and software for the Node B 910 and the UE 950, respectively. A scheduler/processor 946 at the Node B 910 may be used to allocate resources to the UEs and schedule downlink and/or uplink transmissions for the UEs.
With reference to
As used in this application, the terms “component,” “module,” “system” and the like are intended to include a computer-related entity, such as but not limited to hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on a computing device and the computing device can be a component. One or more components can reside within a process and/or thread of execution and a component may be localized on one computer and/or distributed between two or more computers. In addition, these components can execute from various computer readable media having various data structures stored thereon. The components may communicate by way of local and/or remote processes such as in accordance with a signal having one or more data packets, such as data from one component interacting with another component in a local system, distributed system, and/or across a network such as the Internet with other systems by way of the signal.
Furthermore, various aspects are described herein in connection with a UE, which can be a wired terminal or a wireless terminal. A UE can also be called a system, device, subscriber unit, subscriber station, mobile station, mobile, mobile device, remote station, remote terminal, access terminal, user terminal, terminal, communication device, user agent, or user device. A UE may be a cellular telephone, a satellite phone, a cordless telephone, a Session Initiation Protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device having wireless connection capability, a computing device, or other processing devices connected to a wireless modem. Moreover, various aspects are described herein in connection with a base station. A base station may be utilized for communicating with UE or wireless terminal(s) and may also be referred to as an access point, a Node B, or some other terminology.
Moreover, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from the context, the phrase “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, the phrase “X employs A or B” is satisfied by any of the following instances: X employs A; X employs B; or X employs both A and B. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from the context to be directed to a singular form.
The techniques described herein may be used for various wireless communication systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other systems. The terms “system” and “network” are often used interchangeably. A CDMA system may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes Wideband-CDMA (W-CDMA) and other variants of CDMA. Further, cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA system may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA system may implement a radio technology such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM□, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS). 3GPP Long Term Evolution (LTE) is a release of UMTS that uses E-UTRA, which employs OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA, UMTS, LTE and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). Additionally, cdma2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). Further, such wireless communication systems may additionally include peer-to-peer (e.g., mobile-to-mobile) ad hoc network systems often using unpaired unlicensed spectrums, 802.xx wireless LAN, BLUETOOTH and any other short- or long-range, wireless communication techniques.
Various aspects or features have been presented in terms of systems that may include a number of devices, components, modules, and the like. It is to be understood and appreciated that the various systems may include additional devices, components, modules, etc. and/or may not include all of the devices, components, modules etc. discussed in connection with the figures. A combination of these approaches may also be used.
The various illustrative logics, logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but, in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Additionally, at least one processor may comprise one or more modules operable to perform one or more of the steps and/or actions described above.
Further, the steps and/or actions of a method or algorithm described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium may be coupled to the processor, such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. Further, in some aspects, the processor and the storage medium may reside in an ASIC. Additionally, the ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal. Additionally, in some aspects, the steps and/or actions of a method or algorithm may reside as one or any combination or set of codes and/or instructions on a machine readable medium and/or computer readable medium, which may be incorporated into a computer program product.
In one or more aspects, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored or transmitted as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage medium may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection may be termed a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs usually reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.
While the foregoing disclosure discusses illustrative aspects and/or embodiments, it should be noted that various changes and modifications could be made herein without departing from the scope of the described aspects and/or embodiments as defined by the appended claims. Furthermore, although elements of the described aspects and/or embodiments may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. Additionally, all or a portion of any aspect and/or embodiment may be utilized with all or a portion of any other aspect and/or embodiment, unless stated otherwise.
The present application for Patent claims priority to U.S. Provisional Application No. 61/879,606 entitled “APPARATUS AND METHOD OF CELL RESELECTION WHEN CAMPING ON A SMALL COVERAGE CELL” filed Sep. 18, 2013, and assigned to the assignee hereof and hereby expressly incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61879606 | Sep 2013 | US |
