Abstract:
In a wireless communication device that has LTE and  1 ×capabilities and multiple receive chains, this application provides for sharing non-LTE receive chain(s) and/or unused LTE receive chain(s) for 1× tune-away events to improve LTE throughput by not interrupting LTE data transmission on the LTE active receive chain(s).

Description:
PRIORITY CLAIM 
       [0001]    This application claims the benefit of priority from U.S. Provisional Patent application Ser. No. 61/884,112, entitled “Shared Tertiary Chain for Improved LTE Throughput” and filed Sep. 29, 2013, which is fully incorporated herein by reference for all purposes to the extent not inconsistent with this application. 
     
    
     BACKGROUND 
       [0002]    This application is directed to wireless communications and, more particularly, to shared tertiary chain between GPS and 1× to improve LTE throughput on primary and secondary chains in wireless communications. 
         [0003]    Electronic devices such as portable computers and cellular telephones are often provided with wireless communication capabilities. For example, electronic devices may use long-range wireless communication circuitry such as cellular telephone circuitry and WiMAX (IEEE 802.16) circuitry. Electronic devices may also use short-range wireless communication circuitry such as WiFi® (IEEE 802.11) circuitry and Bluetooth® circuitry. 
         [0004]    In some devices, it may be desirable to support multiple radio access technologies. For example, it may be desirable to support newer radio-access technologies for handling data sessions and older radio-access technologies for supporting voice calls. Examples of different radio-access technologies that have been used in cellular telephones include Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS), Code Division Multiple Access (CDMA) (e.g., CDMA2000 including standards such as CDMA2000 1×RTT or 1×), and Long Term Evolution (LTE). 
         [0005]    In certain single radio LTE implementation, LTE and 1× operate in a hybrid mode of operation. This means that while LTE is operating using the single radio (i.e., in data traffic mode), the LTE operation can get interrupted periodically by 1× tune-aways. In this way, the single radio can periodically tune-away from an active LTE connection to check for paging messages, etc. on the 1× system, as well as, e.g., to measure the RF conditions. 
         [0006]    A tune-away, for example, can last approximately 100-200 msec, depending on network equipment design and 1× network performance, but mobile devices can stay on 1× for a much longer time. The following items describe example scenarios that may result in long tune-away times: 1) Voice calls—when the subscriber gets paged and picks up a voice call on the 1×interface, which might list a long time, 2) Idle handoffs—tune-away can last around a second, 3) Registrations—tune-away can last from a second or two to more than 10 seconds if the mobile device finds out that it has to register after tuning-away to 1×, 4) System lost—Tune-aways can last more than 5 seconds, up to tens of seconds. These system lost tune-away could be caused by common RF problems, like coverage holes, pilot pollution, or rapidly changing pilots. These 1×tune-away events can negatively impact LTE throughput. 
         [0007]    Therefore, it would be desirable to provide improved ways to support multiple radio access technologies in a single-radio electronic device without reducing LTE throughput. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  illustrates an exemplary wireless multiple-access communication system according to certain embodiments; 
           [0009]      FIG. 2  illustrates a block diagram of an exemplary mobile device or user equipment (UE) according to certain embodiments; 
           [0010]      FIG. 3  illustrates a block diagram of an exemplary enhanced Node B (eNB) or similar mobile communication node (e.g., base station, access point, etc.) according to certain embodiments; 
           [0011]      FIG. 4  illustrates an exemplary multi-RAT wireless network according to certain embodiments; 
           [0012]      FIG. 5  illustrates an exemplary receive chain architecture according to certain embodiments; 
           [0013]      FIG. 6  illustrates an exemplary multi-receive chain architecture according to certain embodiments; and 
           [0014]      FIG. 7  illustrates an exemplary 1× tune-away flow diagram according to certain embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    The following detailed description is directed to certain sample embodiments. However, the disclosure can be embodied in a multitude of different ways as defined and covered by the claims. In this description, reference is made to the drawings wherein like parts are designated with like reference numerals within this application. 
         [0016]    This disclosure makes reference to various wireless communication devices, such as access point, mobile device, handset, base station, user equipment, Node B, access terminal, eNB and the like. The use of these and other names that may be associated with specific technologies or standards is not intended to indicate or mandate one particular device, one particular standard or protocol, or one particular signaling direction and is expressly intended to not be limiting of the scope of this application in any way. The use of these and other names is strictly for convenience and such names may be interchanged within this application without any loss of coverage or rights. 
         [0017]    Various techniques described herein can be used for various wireless communication systems, technologies and/or networks, such as Code Division Multiple Access (“CDMA”) systems, Multiple-Carrier CDMA (“MCCDMA”), Wideband CDMA (“W-CDMA”), High-Speed Packet Access (“HSPA,” “HSPA+”) systems, Time Division Multiple Access (“TDMA”) systems, Frequency Division Multiple Access (“FDMA”) systems, Single-Carrier FDMA (“SC-FDMA”) systems, Orthogonal Frequency Division Multiple Access (“OFDMA”) systems, or other multiple access techniques. A wireless communication technique employing the teachings herein may be designed to implement one or more standards, such as IS-95, cdma2000, IS-856, W-CDMA, TDSCDMA, GSM, UMTS, LTE, WiFi, WiMAX and other standards. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (“UTRA)”, cdma2000, or some other technology. UTRA includes W-CDMA and Low Chip Rate (“LCR”). The cdma2000 technology covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (“GSM”). An OFDMA network may implement a radio technology such as Evolved UTRA (“E-UTRA”), IEEE 802.11 (“WiFi”), IEEE 802.16 “(WiMAX”), IEEE 802.20 (“MBWA”), Flash-OFDM®, etc. UTRA, E-UTRA, and GSM are part of Universal Mobile Telecommunication System (“UMTS”). The teachings herein may be implemented in a 3GPP Long Term Evolution (“LTE”) system, an Ultra-Mobile Broadband (“UMB”) system, and other types of systems. LTE is a release of UMTS that uses E-UTRA. Although certain aspects of the disclosure may be described using 3GPP terminology, it is to be understood that the teachings herein may be applied to 3GPP (Re199, Re15, Re16, Re17, and so on) technology, as well as 3GPP2 (IxRTT, 1×EV-DO Re1O, RevA, RevB, and so on) technology and other technologies, such as WiFi, WiMAX, WMBA and the like. 
         [0018]    Referring to the drawings,  FIG. 1  illustrates an exemplary wireless multiple-access communication system  100  according to certain embodiments. As shown in  FIG. 1 , an enhanced Node B (eNB) base station  102  can include multiple antenna groups. One antenna group can include antennas  104  and  106 , another can include antennas  108  and  110 , and another can include antennas  112  and  114 . While only two antennas are shown in  FIG. 1  for each antenna group, it should be appreciated that more or fewer antennas may be utilized for each antenna group. As shown, user equipment (UE)  116  can be in communication with antennas  112  and  114 , where antennas  112  and  114  transmit information to UE  116  over downlink (or forward link)  120  and receive information from UE  116  over uplink (or reverse link)  118 . Additionally and/or alternatively, UE  122  can be in communication with antennas  104  and  106 , where antennas  104  and  106  transmit information to UE  122  over downlink  126  and receive information from UE  122  over uplink  124 . In a frequency division duplex (FDD) system, communication links  118 ,  120 ,  124  and  126  can use different frequencies for communication. In time division duplex (TDD) systems, communication links  118 ,  120 ,  124  and  126  can use the same frequency or frequencies for communication, but can communicate at differing times. 
         [0019]    Each group of antennas and/or the area in which they are designed to communicate can be referred to as a sector of the eNB or base station. In accordance with one aspect, antenna groups can be designed to communicate to mobile devices in a sector of areas (not shown) covered by eNB  102 . In communication over downlinks  120  and  126 , the transmitting antennas of eNB  102  can utilize beamforming in order to improve the signal-to-noise ratio of downlinks for the different UEs  116  and  122 . Also, a base station using beamforming to transmit to UEs scattered randomly through its coverage area can cause less interference to mobile devices in neighboring cells or sectors than a base station transmitting through a single antenna to all of its UEs. In addition to beamforming, antenna groups of a base station, as well as mobile devices, can use other multi-antenna or antenna diversity techniques to send and/or receive information, such as spatial multiplexing, spatial diversity, pattern diversity, polarization diversity, transmit/receive diversity, adaptive arrays, and the like. 
         [0020]      FIG. 2  illustrates a block diagram  200  of an exemplary mobile device, handset (HS) or user equipment (UE)  210  according to certain embodiments. As shown in  FIG. 2 , UE  210  may include a transceiver  220 , an antenna  230 , a processor  240 , and a memory  250  (which, in certain embodiments, may include memory in a Subscriber Identity Module (SIM) card). In certain embodiments, some or all of the functionalities described herein as being performed by a handset or mobile device may be provided by processor  240  executing instructions stored on a computer-readable medium, such as the memory  250 , as shown in  FIG. 2 . Alternatively, processor  240  and/or memory  250  may be one or more separate processors and/or memories. Additionally, UE  210  may perform uplink and/or downlink communication functions, as further disclosed herein, via transceiver  220  and antenna  230 . While only one antenna and one transceiver are shown for UE  210 , certain embodiments are equally applicable to multi-antenna and/or multi-transceiver mobile devices. In certain embodiments, UE  210  may include additional components beyond those shown in  FIG. 2  that may be responsible for enabling or performing the functions of UE  210 , such as communicating with a base station in a network and for processing information for transmitting or from reception, including any of the functionality described herein. Such additional components are not shown in  FIG. 2  but are intended to be within the scope of coverage of this application. 
         [0021]      FIG. 3  illustrates a block diagram  300  of an exemplary enhanced Node B (eNB)  310  or similar mobile communication node (e.g., base station, access point, etc.) according to certain embodiments. As shown in  FIG. 3 , eNB  310  may include a baseband processor  330  to provide radio communication with mobile handsets via a radio frequency (RF) transmitter  340  and RF receiver  350  units coupled to eNB antenna  320 . While only one antenna and one transceiver set are shown, certain embodiments are applicable to multi-antenna and/or multi-transceiver set configurations. RF transmitter  340  and RF receiver  350  may be combined into one, transceiver unit, and/or duplicated to facilitate multiple antenna communication. Baseband processor  330  may be configured (in hardware and/or software) to function according to a wireless communications standard, such as 3GPP LTE. Alternatively, multiple baseband processors may be included in eNB  310 . Baseband processor  330  may include a processing unit  332  in communication with a memory  334  to process and store relevant information for the eNB and a scheduler  336 , which may provide scheduling decisions for mobile devices serviced by eNB  310 . Scheduler  336  may have some or all of the same data structure as a typical scheduler for an eNB in an LTE system. Alternatively, processing unit  332  and/or memory  334  may be one or more separate processors and/or memories. In certain embodiments, some or all of the functionalities described herein as being performed by an enhanced Node B, access point or base station may be provided by processing unit  332  executing instructions stored on a computer-readable medium, such as memory  334 , as shown in  FIG. 3 . 
         [0022]    Baseband processor  330  may also provide additional baseband signal processing (e.g., mobile device registration, channel signal information calculation and/or transmission, radio resource management, etc.) as required. Processing unit  332  may include, by way of example, one or more of the following: a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a microprocessor, a microprocessor in association with a DSP core, a controller, a microcontroller, an Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, and any other type of integrated circuit (IC) and/or state machine. Some or all of the functionalities described herein as being provided by a mobile base station, a base station controller, a node B, an enhanced node B, an access point, a home base station, a femtocell base station, and/or any other type of mobile communications node may be provided by processing unit  332  executing instructions stored on a computer-readable data storage medium, such as the memory  334  shown in  FIG. 3 . 
         [0023]    In certain embodiments, eNB  310  may further include a timing and control unit  360  and a core network interface unit  370 , such as are shown in  FIG. 3 , each in communication with the other and with baseband processor  330 . Timing and control unit  360  may monitor operations of baseband processor  330  and network interface unit  370 , and may provide appropriate timing and control signals to these units. Network interface unit  370  may provide a bi-directional interface for eNB  310  to communicate with a core or back-end network (not shown) to facilitate administrative, data-management and/or call-management functions for mobile subscribers operating in the network through eNB  310 . 
         [0024]    In certain embodiments, base station  310  may include additional components responsible for providing additional functionality, including any of the functionality identified herein and/or any functionality necessary to support the techniques described herein. Although features and elements are described in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without one or more features and elements. Techniques provided herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable storage medium (e.g., memory  334  in  FIG. 3 ) for execution by a general purpose computer or a processor (e.g., processing unit  332  in  FIG. 3 ). Examples of computer-readable storage media include read only memory (ROM), random access memory (RAM), digital registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks, magnetic tapes and removable disks, magneto-optical media, and optical media such as CDROM disks, digital versatile disks (DVDs), and so on. Such computer-readable storage media may be separate units, may be incorporated as part of one or more other units (e.g., processing unit  332  in  FIG. 3 ), or may be a combination of separate and incorporated units. 
         [0025]      FIG. 4  illustrates an exemplary multi-RAT (radio access technology) wireless network  400  according to certain embodiments. As shown in  FIG. 4 , a mobile device (handset, UE, etc.)  430  is within the coverage area of multi-RAT wireless network  400 . Multi-RAT wireless network  400  can include multiple-technology network coverage pieces. For example, one technology coverage area can be a cell  410 A, such as in an LTE coverage area. Within (or partially within) cell  410 A coverage area, there can concurrently exist one or more other technology coverage areas, for example cells  410 B and  410 C, each of which may be a GSM, UMTS, WiMAX, CDMA or even WiFi coverage area. As shown, cells  410 B,  410 C are within cell  410 A and at least partially overlap each other, although this configuration is for illustrative purposes only. Each cell  410  can also include some sort of network access device  420 A,  420 B and  420 C, such as a base station, eNodeB or access point. Each network access device  420  can communicate with one or more mobile devices  430 , as well as with a core network  440  (and even, perhaps, with each other). Not shown are possible intermediate network components or system elements that may be between each network access device  420  and core network  440 . In certain embodiments, mobile device  430  can be moving within cell  410 A and moving out of cell  410 B and into cell  410 C. In this way, mobile device  430  could possibly communicate with one or more of cells  410 A,  410 B and  410 C. 
         [0026]      FIG. 5  illustrates an exemplary receive chain architecture  500  according to certain embodiments. As shown in  FIG. 5 , an antenna  510  can receive the radio frequency (RF) signals, which are then filtered by one or more RF filters  520 . The RF filtered signal next passes through one or more low noise amplifiers (LNAs)  530 . Next the signal leaves the LNA and enters a mixer  540 , which also has as an input a phase-locked loop (PLL)/voltage controlled oscillator (VCO)  550  output. After mixing, the signal passes through one or more intermediate frequency (IF) filters  560  and into an automatic gain control (AGC)  570  module. Finally, the signal may be filtered by one or more filters ( 580 ) and then converted from analog to digital form by analog-to-digital converter (ADC)  590 . As used in this application, certain embodiments of receive chain architecture  500  can be used with and/or within UE  200 , eNB  300  and/or any devices associated with  FIGS. 1-4 . 
         [0027]      FIG. 6  illustrates an exemplary multi-receive chain architecture  600  according to certain embodiments. As shown in  FIG. 6 , multiple receive chains  610   a - x  can include multiple PLLs  620   a - y . Not shown are the one or more antennas that may be connected to multiple receive chains  610 . Note that it is not necessary that there be a one-to-one correlation between the number of PLLs to receive chains. As used in this application, certain embodiments of multi-receive chain architecture  600  can be used with and/or within UE  200 , eNB  300  and/or any devices associated with  FIGS. 1-4 , in which any one or more of multiple receive chains  610   a - x  can include some or all of the elements of receive chain architecture  500 . 
         [0028]    In certain embodiments, a multi-RAT, single-radio handset or user equipment (UE) may include three receive chains with two PLLs. For example, this UE may be able to operate using 4G (e.g., LTE) for data services, but fall back to 2G/3G (e.g., CDMA2000 1×RTT, or just “1×”) for voice services, which means that LTE and 1× will operate in a hybrid mode, with LTE traffic being interrupted periodically by a 1× “tune-away.” As used herein, a 1× tune-away may be, for example, ceasing reception/processing of LTE incoming data, receiving/listening for/demodulating paging messages that might indicate an incoming call (or no incoming call, as the case may be), and then retuning for continued reception of LTE data. Each 1× tune-away can negatively impact the LTE throughput. The negative impact can be larger when the UE is in a marginal coverage area because the UE may need to wake-up in IS 2000 or paging channel timeline for 1×. 
         [0029]    In certain embodiments, the single radio, three receive chains, two PLLs UE may be configured as follows. The primary and secondary receive chains can be used for 1×, EV/DO and/or LTE operation, while the tertiary receive chain can be dedicated for GPS operations. One or both of the two PLLs can be used for one technology with diversity, which means that one PLL can be used to receive LTE data traffic on both the primary and secondary receive chains. This leaves the second PLL to be used for GPS operation on the tertiary receive chain or used for a 1× tune-away one of the primary or secondary receive chains. The potential issue with this configuration is that when a 1× tune-away must happen during a time with LTE data reception is happening, the LTE data reception must be stopped for the 1× tune-away to occur. Also, if GPS is using the second PLL, then the first PLL must also be taken from the LTE reception set-up and used for the 1× tune-away. 
         [0030]      FIG. 7  illustrates an exemplary 1× tune-away flow diagram  700  according to certain embodiments. In certain embodiments, a 1× tune-away can be permitted to use the second PLL and the tertiary receive chain if GPS is not using them, or if certain conditions are met, even if GPS is using them. As shown in  FIG. 7 , at  710 , a UE with a single radio and three receive chains is in LTE active mode, i.e., it is actively receiving LTE data. At  720 , the UE decides whether it is time for a 1× tune-away. If it is not time for a 1× tune-away, then the UE can continue in active LTE mode at  710 . If at  720  it is time for a 1× tune-away, then at  730 , the UE can determine whether the LTE active mode is using both the primary and secondary receive chains. If not (and assuming that the LTE active mode is using the primary receive chain, which need not be the case), then the 1× tune-away can use the secondary receive chain (or more generally, the receive chain that is not being used by the LTE active mode). 
         [0031]    If the check at  730  indicates that LTE mode is using both the primary and secondary receive chains, then at  740  the UE can determine whether GPS is active, which indicates whether the tertiary receive chain is in use. If at  740  GPS is not active, then at  745  the 1× tune-away can use the tertiary receive chain. If at  740  GPS is active, then at  750 , the UE can determine whether it is in a marginal 1× coverage area. If the UE is not in a marginal 1× coverage area, then at  755  the 1× tune-away can use the tertiary receive chain, which means that GPS will temporarily loose use of the tertiary receive chain. After the 1× tune-away is complete from  755 , then at  770  the UE can return to GPS active mode. 
         [0032]    If the check at  750  indicates that the UE is in a marginal 1× coverage area, then at  760  the UE can determine whether precise GPS is needed for the application or applications that are running and in need of GPS data. If precise GPS data are not needed, then at  765  the 1× tune-away can use the tertiary receive chain, which means that GPS will temporarily loose use of the tertiary receive chain. After the 1× tune-away is complete from  765 , then at  770  the UE can return to GPS active mode. If at  760  precise GPS data are needed by the running application(s), then at  780  the 1× tune-away can use the primary and/or the secondary receive chain(s), which means that LTE will temporarily loose use of the one or both of the primary and secondary receive chains. After the 1× tune-away is complete from  780 , then at  710  the UE can return to LTE active mode. 
         [0033]    In certain embodiments, as discussed herein with reference to  FIG. 7 , if LTE is using both primary and secondary receive chains ( 730 ) and GPS is active ( 740 ) and UE is in a marginal coverage area ( 750 ) and precise GPS data are needed ( 760 ) will the 1× tune-away ( 720 ) interrupt the active LTE mode ( 710 ) by using one or both of the primary and secondary receive chains ( 780 ). In this way, LTE can remain active in most situations. 
         [0034]    Certain embodiments may deviate from the certain embodiments described so far. For example, while  FIG. 7  is discussed with reference to a UE having three receive chains, techniques of this application can be applicable to fewer or more receive chains. In the case of fewer, (e.g., two) receive chains, then the LTE active mode could be assigned only the primary receive chain (i.e., eliminating the need for the  730  check and  735  no result from that check). 
         [0035]    Those of ordinary skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof 
         [0036]    Those of ordinary skill would further appreciate that the various illustrative logical blocks, modules, and algorithm steps described in connection with the examples disclosed herein may be implemented as electronic hardware, firmware, computer software, middleware, microcode, or combinations thereof. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints or preferences imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the disclosed methods. 
         [0037]    The various illustrative logical blocks, components, modules, and circuits described in connection with the examples 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. 
         [0038]    The steps of a method or algorithm described in connection with the examples disclosed herein may be embodied directly in hardware, in one or more software modules executed by one or more processing elements, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form or combination of storage medium known in the art. An example storage medium is 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. The processor and the storage medium may reside in an Application Specific Integrated Circuit (ASIC). The ASIC may reside in a wireless modem. In the alternative, the processor and the storage medium may reside as discrete components in the wireless modem. 
         [0039]    The previous description of the disclosed examples is provided to enable any person of ordinary skill in the art to make or use the disclosed methods and apparatus. Various modifications to these examples will be readily apparent to those skilled in the art, and the principles defined herein may be applied to other examples and additional elements may be added.