WO2013127056A1 - Estimation of interference power for secondary scrambling code - Google Patents

Estimation of interference power for secondary scrambling code Download PDF

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Publication number
WO2013127056A1
WO2013127056A1 PCT/CN2012/071670 CN2012071670W WO2013127056A1 WO 2013127056 A1 WO2013127056 A1 WO 2013127056A1 CN 2012071670 W CN2012071670 W CN 2012071670W WO 2013127056 A1 WO2013127056 A1 WO 2013127056A1
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Prior art keywords
processor
node
network
ssc
data
Prior art date
Application number
PCT/CN2012/071670
Other languages
French (fr)
Inventor
Jiye Liang
Wei Zhang
Sharad Deepak Sambhwani
Original Assignee
Qualcomm Incorporated
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Priority to PCT/CN2012/071670 priority Critical patent/WO2013127056A1/en
Publication of WO2013127056A1 publication Critical patent/WO2013127056A1/en

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Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69Spread spectrum techniques
    • H04B1/707Spread spectrum techniques using direct sequence modulation
    • H04B1/7097Interference-related aspects
    • H04B1/7103Interference-related aspects the interference being multiple access interference

Definitions

  • 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 users by sharing the available network resources.
  • UTRAN UMTS Terrestrial Radio Access Network
  • 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).
  • UMTS Universal Mobile Telecommunications System
  • 3GPP 3rd Generation Partnership Project
  • 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), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA).
  • W-CDMA Wideband- Code Division Multiple Access
  • TD-CDMA Time Division-Code Division Multiple Access
  • TD-SCDMA Time Division-Synchronous Code Division Multiple Access
  • the UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSDPA), which provides higher data transfer speeds and capacity to associated UMTS networks.
  • HSDPA High Speed Packet Access
  • WCDMA system shares the use of a common spectrum band across cells in the network.
  • the WCDMA downlink channel uses cell-specific scrambling codes to scramble the spreaded chips before transmission.
  • the cell-specific scrambling code is generated according to the cell id.
  • Each cell could be assign one primary scrambling code (PSC) and several other secondary scrambling codes (SSC).
  • PSC primary scrambling code
  • SSC secondary scrambling codes
  • SSC secondary scrambling codes
  • SSC secondary scrambling codes
  • UE needs to estimate the interference power for various purposes in reception of the downlink signal. For example, downlink power control, SIR estimation, etc.
  • the interference seen by the SSC includes the power of PSC due to their non-orthogonality. This alternative could be far away from the true interference level for the SSC when PSC's power is much higher than the SSC's power. For example, we assume for the cell we interested:
  • the interference seen by the PSC is the sum of the out-cell interference and SSC's power, i.e.,
  • N ti p SC as an alternative for N tiSSC
  • the estimation will be 1/5 of the true value.
  • the interference power estimation is critical for power control, this will create a severe problem for UE on SSC.
  • FIG. 1 is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system.
  • FIG. 2 is a block diagram conceptually illustrating an example of a telecommunications system.
  • FIG. 3 is a conceptual diagram illustrating an example of an access network.
  • FIG. 4 is a block diagram conceptually illustrating an example of a Node B in communication with a UE in a telecommunications system.
  • FIG. 1 is a conceptual diagram illustrating an example of a hardware implementation for an apparatus 100 employing a processing system 114.
  • the processing system 114 may be implemented with a bus architecture, represented generally by the bus 102.
  • the bus 102 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 114 and the overall design constraints.
  • the bus 102 links together various circuits including one or more processors, represented generally by the processor 104, and computer-readable media, represented generally by the computer- readable medium 106.
  • the bus 102 may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.
  • a bus interface 108 provides an interface between the bus 102 and a transceiver 110.
  • the transceiver 110 provides a means for communicating with various other apparatus over a transmission medium.
  • a user interface 112 e.g., keypad, display, speaker, microphone, joystick
  • keypad e.g., keypad, display, speaker, microphone, joystick
  • 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.
  • a UMTS network includes three interacting domains: a Core Network (CN) 204, a UMTS Terrestrial Radio Access Network (UTRAN) 202, and User Equipment (UE) 210.
  • CN Core Network
  • UTRAN UMTS Terrestrial Radio Access Network
  • UE User Equipment
  • the UTRAN 202 provides various wireless services including telephony, video, data, messaging, broadcasts, and/or other services.
  • the UTRAN 202 may include a plurality of Radio Network Subsystems (RNSs) such as an RNS 207, each controlled by a respective Radio Network Controller (RNC) such as an RNC 206.
  • RNSs Radio Network Subsystems
  • the UTRAN 202 may include any number of RNCs 206 and RNSs 207 in addition to the RNCs 206 and RNSs 207 illustrated herein.
  • the RNC 206 is an apparatus responsible for, among other things, assigning, reconfiguring and releasing radio resources within the RNS 207.
  • the RNC 206 may be interconnected to other RNCs (not shown) in the UTRAN 202 through various types of interfaces such as a direct physical connection, a virtual network, or the like, using any suitable transport network.
  • Communication between a 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.
  • RRC radio resource control
  • 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 Radio Resource Control (RRC) Protocol Specification, 3GPP TS 25.331 v9.1.0, incorporated herein by reference.
  • the geographic region covered by the SRNS 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.
  • BS basic service set
  • ESS extended service set
  • AP access point
  • three Node Bs 208 are shown in each SRNS 207; however, the SRNSs 207 may include any number of wireless Node Bs.
  • the Node Bs 208 provide wireless access points to a core network (CN) 204 for any number of mobile apparatuses.
  • 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.
  • SIP session initiation protocol
  • PDA personal digital assistant
  • GPS global positioning system
  • multimedia device e.g., a digital audio player (e.g., MP3 player), a camera, a game console, or any other similar functioning device.
  • MP3 player digital audio player
  • the mobile apparatus is commonly referred to as user equipment (UE) in UMTS applications, but may also be referred to by those skilled in the art as a mobile station (MS), 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 (AT), 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.
  • the UE 210 may further include a universal subscriber identity module (USIM) 211, which contains a user's subscription information to a network.
  • USIM universal subscriber identity module
  • DL downlink
  • UL uplink
  • the core network 204 interfaces with one or more access networks, such as the UTRAN 202.
  • the core network 204 is a GSM core network.
  • GSM Global System for Mobile communications
  • the core network 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.
  • the core network 204 supports circuit- switched services with a MSC 212 and a GMSC 214.
  • the GMSC 214 may be referred to as a media gateway (MGW).
  • MGW media gateway
  • the MSC 212 is an apparatus that controls call setup, call routing, and UE mobility functions.
  • the MSC 212 also includes a visitor location register (VLR) that contains subscriber-related information for the duration that a UE is in the coverage area of the MSC 212.
  • VLR visitor location register
  • 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.
  • HLR home location register
  • the HLR is also associated with an authentication center (AuC) that contains subscriber-specific authentication data.
  • AuC authentication center
  • 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 core network 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.
  • the UMTS air interface is a spread spectrum Direct-Sequence Code Division
  • the spread spectrum DS-CDMA spreads user data through multiplication by a sequence of pseudorandom bits called chips.
  • the 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 uplink (UL) and downlink (DL) between a Node B 208 and a UE 210.
  • TD-SCDMA Another air interface for UMTS that utilizes DS-CDMA, and uses time division duplexing.
  • the multiple access wireless communication system includes multiple cellular regions (cells), including cells 302, 304, and 306, each of which may include one or more sectors.
  • the multiple sectors can be formed by groups of antennas with each antenna responsible for communication with UEs in a portion of the cell. For example, in cell 302, antenna groups 312, 314, and 316 may each correspond to a different sector.
  • antenna groups 318, 320, and 322 each correspond to a different sector.
  • antenna groups 324, 326, and 328 each correspond to a different sector.
  • the cells 302, 304 and 306 may include several wireless communication devices, e.g., User Equipment or UEs, which may be in communication with one or more sectors of each cell 302, 304 or 306.
  • UEs 330 and 332 may be in communication with Node B 342
  • UEs 334 and 336 may be in communication with Node B 344
  • UEs 338 and 340 can be in communication with Node B 346.
  • each Node B 342, 344, 346 is configured to provide an access point to a core network 204 (see FIG. 2) for all the UEs 330, 332, 334, 336, 338, 340 in the respective cells 302, 304, and 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 (see FIG. 2), or at another suitable node in the wireless network.
  • 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.
  • 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).
  • 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 standard may vary depending on the particular telecommunications standard being deployed.
  • 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.
  • 3GPP2 3rd Generation Partnership Project 2
  • 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 OFDM A.
  • 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.
  • FIG. 4 is a block diagram of a Node B 410 in communication with a UE 450, where the Node B 410 may be the Node B 208 in FIG. 2, and the UE 450 may be the UE 210 in FIG. 2.
  • a transmit processor 420 may receive data from a data source 412 and control signals from a controller/processor 440. The transmit processor 420 provides various signal processing functions for the data and control signals, as well as reference signals (e.g., pilot signals).
  • the transmit processor 420 may provide cyclic redundancy check (CRC) codes for error detection, coding and interleaving to facilitate forward error correction (FEC), mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM), and the like), spreading with orthogonal variable spreading factors (OVSF), and multiplying with scrambling codes to produce a series of symbols.
  • BPSK binary phase-shift keying
  • QPSK quadrature phase-shift keying
  • M-PSK M-phase-shift keying
  • M-QAM M-quadrature amplitude modulation
  • OVSF orthogonal variable spreading factors
  • channel estimates may be derived from a reference signal transmitted by the UE 450 or from feedback from the UE 450.
  • the symbols generated by the transmit processor 420 are provided to a transmit frame processor 430 to create a frame structure.
  • the transmit frame processor 430 creates this frame structure by multiplexing the symbols with information from the controller/processor 440, resulting in a series of frames.
  • the frames are then provided to a transmitter 432, which provides various signal conditioning functions including amplifying, filtering, and modulating the frames onto a carrier for downlink transmission over the wireless medium through antenna 434.
  • the antenna 434 may include one or more antennas, for example, including beam steering bidirectional adaptive antenna arrays or other similar beam technologies.
  • a receiver 454 receives the downlink transmission through an antenna 452 and processes the transmission to recover the information modulated onto the carrier.
  • the information recovered by the receiver 454 is provided to a receive frame processor 460, which parses each frame, and provides information from the frames to a channel processor 494 and the data, control, and reference signals to a receive processor 470.
  • the receive processor 470 then performs the inverse of the processing performed by the transmit processor 420 in the Node B 410. More specifically, the receive processor 470 descrambles and despreads the symbols, and then determines the most likely signal constellation points transmitted by the Node B 410 based on the modulation scheme. These soft decisions may be based on channel estimates computed by the channel processor 494.
  • 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 472, which represents applications running in the UE 450 and/or various user interfaces (e.g., display).
  • Control signals carried by successfully decoded frames will be provided to a controller/processor 490.
  • the controller/processor 490 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.
  • ACK acknowledgement
  • NACK negative acknowledgement
  • a transmit processor 480 receives data from a data source 478 and control signals from the controller/processor 490 and 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 may be used to select the appropriate coding, modulation, spreading, and/or scrambling schemes.
  • the symbols produced by the transmit processor 480 will be provided to a transmit frame processor 482 to create a frame structure.
  • the transmit frame processor 482 creates this frame structure by multiplexing the symbols with information from the controller/processor 490, resulting in a series of frames.
  • the frames are then provided to a transmitter 456, 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 452.
  • the uplink transmission is processed at the Node B 410 in a manner similar to that described in connection with the receiver function at the UE 450.
  • a receiver 435 receives the uplink transmission through the antenna 434 and processes the transmission to recover the information modulated onto the carrier.
  • the information recovered by the receiver 435 is provided to a receive frame processor 436, which parses each frame, and provides information from the frames to the channel processor 444 and the data, control, and reference signals to a receive processor 438.
  • the receive processor 438 performs the inverse of the processing performed by the transmit processor 480 in the UE 450.
  • the data and control signals carried by the successfully decoded frames may then be provided to a data sink 439 and the controller/processor, respectively. If some of the frames were unsuccessfully decoded by the receive processor, the controller/processor 440 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.
  • ACK acknowledgement
  • NACK negative acknowledgement
  • the controller/processors 440 and 490 may be used to direct the operation at the Node B 410 and the UE 450, respectively.
  • the controller/processors 440 and 490 may provide various functions including timing, peripheral interfaces, voltage regulation, power management, and other control functions.
  • the computer readable media of memories 442 and 492 may store data and software for the Node B 410 and the UE 450, respectively.
  • a scheduler/processor 446 at the Node B 410 may be used to allocate resources to the UEs and schedule downlink and/or uplink transmissions for the UEs.
  • the method utilizes a null pilot channel on SSC, which is a channelization code reserved for no use on SSC.
  • the UE can use this reserved channelization code to estimate the interference power.
  • the receiver performs descrambling and de-spreading on this channelization code. Since other channelization codes in use on the SSC are orthogonal to this channelization code, the despreading output does not contain any signals on SSC and is purely interference signals for the SSC. We can perform power estimation on de-spreading the output to obtain the interference power for the SSC.
  • the present invention resides in the transmitter and receiver of both the UE and the NodeB.
  • the invention is detectable because it involves a standards change. Potential workarounds are already included in this invention.
  • TD-SCDMA High Speed Downlink Packet Access
  • HSDPA High Speed Downlink Packet Access
  • HSUPA High Speed Uplink Packet Access
  • HSPA+ High Speed Packet Access Plus
  • LTE Long Term Evolution
  • LTE-A LTE-Advanced
  • CDMA2000 Evolution-Data Optimized
  • UMB Ultra Mobile Broadband
  • IEEE 802.11 Wi-Fi
  • IEEE 802.16 WiMAX
  • IEEE 802.20 Ultra- Wideband
  • Bluetooth Bluetooth
  • the actual telecommunication standard, network architecture, and/or communication standard employed will depend on the specific application and the overall design constraints imposed on the system.
  • processors include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure.
  • DSPs digital signal processors
  • FPGAs field programmable gate arrays
  • PLDs programmable logic devices
  • state machines gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure.
  • One or more processors in the processing system may execute software.
  • Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.
  • the software may reside on a computer-readable medium.
  • the computer-readable medium may be a non-transitory computer-readable medium.
  • a non-transitory computer-readable medium includes, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., compact disk (CD), digital versatile disk (DVD)), a smart card, a flash memory device (e.g., card, stick, key drive), random access memory (RAM), read only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), a register, a removable disk, and any other suitable medium for storing software and/or instructions that may be accessed and read by a computer.
  • a magnetic storage device e.g., hard disk, floppy disk, magnetic strip
  • an optical disk e.g., compact disk (CD), digital versatile disk (DVD)
  • a smart card e.g., a flash memory device (e.g., card, stick, key drive), random access memory (RAM), read only memory (ROM), programmable ROM
  • the computer-readable medium may also include, by way of example, a carrier wave, a transmission line, and any other suitable medium for transmitting software and/or instructions that may be accessed and read by a computer.
  • the computer-readable medium may be resident in the processing system, external to the processing system, or distributed across multiple entities including the processing system.
  • the computer-readable medium may be embodied in a computer-program product.
  • a computer- program product may include a computer-readable medium in packaging materials.

Abstract

A method of signal UE that a channelization code is reserved for no use on SSC.

Description

ESTIMATION OF INTERFERENCE POWER FOR SECONDARY
SCRAMBLING CODE
BACKGROUND
[0001] 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 users 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), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). The UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSDPA), which provides higher data transfer speeds and capacity to associated UMTS networks.
[0002] As the demand for mobile broadband access continues to increase, research and development continue to advance the UMTS technologies not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with mobile communications.
[0003] WCDMA system shares the use of a common spectrum band across cells in the network. To separate different cells in the downlink, the WCDMA downlink channel uses cell- specific scrambling codes to scramble the spreaded chips before transmission. The cell-specific scrambling code is generated according to the cell id. Each cell could be assign one primary scrambling code (PSC) and several other secondary scrambling codes (SSC). When the resource of channelization codes under the PSC becomes limited for the increased number of downlink users in the cell, SSC is employed to enlarge the resources of channelization codes. In the downlink receiver, UE needs to estimate the interference power for various purposes in reception of the downlink signal. For example, downlink power control, SIR estimation, etc. For UEs assigned to the SSC, this task is quite challenging due to the lack of common pilot channel in the SSC. Some methods circumvent the difficulty by using the interference power estimated from the PSC. However, the interference seen by the SSC includes the power of PSC due to their non-orthogonality. This alternative could be far away from the true interference level for the SSC when PSC's power is much higher than the SSC's power. For example, we assume for the cell we interested:
• The out-cell interference power is Ioc=l
• PSC s power is Ipsc=9
• SSC's power is Issc=l
The interference seen by the PSC is the sum of the out-cell interference and SSC's power, i.e.,
Figure imgf000003_0001
Similarly, the interference seen by the SSC is given by
Figure imgf000003_0002
However, if we use NtipSC as an alternative for NtiSSC, the estimation will be 1/5 of the true value. Bearing in mind that the interference power estimation is critical for power control, this will create a severe problem for UE on SSC.
SUMMARY
[0004] These and other aspects of the invention will become more fully understood upon a review of the detailed description, which follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system.
[0006] FIG. 2 is a block diagram conceptually illustrating an example of a telecommunications system.
[0007] FIG. 3 is a conceptual diagram illustrating an example of an access network.
[0008] FIG. 4 is a block diagram conceptually illustrating an example of a Node B in communication with a UE in a telecommunications system.
DETAILED DESCRIPTION [0009] The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts.
[0010] FIG. 1 is a conceptual diagram illustrating an example of a hardware implementation for an apparatus 100 employing a processing system 114. In this example, the processing system 114 may be implemented with a bus architecture, represented generally by the bus 102. The bus 102 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 114 and the overall design constraints. The bus 102 links together various circuits including one or more processors, represented generally by the processor 104, and computer-readable media, represented generally by the computer- readable medium 106. The bus 102 may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further. A bus interface 108 provides an interface between the bus 102 and a transceiver 110. The transceiver 110 provides a means for communicating with various other apparatus over a transmission medium. Depending upon the nature of the apparatus, a user interface 112 (e.g., keypad, display, speaker, microphone, joystick) may also be provided.
[0011] 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.
[0012] The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. By way of example and without limitation, the aspects of the present disclosure illustrated in FIG. 2 are presented with reference to a UMTS system 200 employing a W-CDMA air interface. A UMTS network includes three interacting domains: a Core Network (CN) 204, a UMTS Terrestrial Radio Access Network (UTRAN) 202, and User Equipment (UE) 210. In this example, the UTRAN 202 provides various wireless services including telephony, video, data, messaging, broadcasts, and/or other services. The UTRAN 202 may include a plurality of Radio Network Subsystems (RNSs) such as an RNS 207, each controlled by a respective Radio Network Controller (RNC) such as an RNC 206. Here, the UTRAN 202 may include any number of RNCs 206 and RNSs 207 in addition to the RNCs 206 and RNSs 207 illustrated herein. The RNC 206 is an apparatus responsible for, among other things, assigning, reconfiguring and releasing radio resources within the RNS 207. The RNC 206 may be interconnected to other RNCs (not shown) in the UTRAN 202 through various types of interfaces such as a direct physical connection, a virtual network, or the like, using any suitable transport network.
[0013] Communication between a 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 Radio Resource Control (RRC) Protocol Specification, 3GPP TS 25.331 v9.1.0, incorporated herein by reference.
[0014] The geographic region covered by the SRNS 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 SRNS 207; however, the SRNSs 207 may include any number of wireless Node Bs. The Node Bs 208 provide wireless access points to a core network (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 user equipment (UE) in UMTS applications, but may also be referred to by those skilled in the art as a mobile station (MS), 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 (AT), 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 downlink (DL), also called the forward link, refers to the communication link from a Node B 208 to a UE 210, and the uplink (UL), also called the reverse link, refers to the communication link from a UE 210 to a Node B 208.
[0015] The core network 204 interfaces with one or more access networks, such as the UTRAN 202. As shown, the core network 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 core networks other than GSM networks.
[0016] The core network 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 core network 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 visitor location register (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.
[0017] The core network 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.
[0018] The UMTS air interface is 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 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 uplink (UL) and downlink (DL) between a Node B 208 and a UE 210. Another air interface for UMTS that utilizes DS-CDMA, and uses time division duplexing, is the TD-SCDMA air interface. Those skilled in the art will recognize that although various examples described herein may refer to a WCDMA air interface, the underlying principles are equally applicable to a TD- SCDMA air interface.
[0019] Referring to Fig. 3, an access network 300 in a UTRAN architecture is illustrated. The multiple access wireless communication system includes multiple cellular regions (cells), including cells 302, 304, and 306, each of which may include one or more sectors. The multiple sectors can be formed by groups of antennas with each antenna responsible for communication with UEs in a portion of the cell. For example, in cell 302, antenna groups 312, 314, and 316 may each correspond to a different sector. In cell 304, antenna groups 318, 320, and 322 each correspond to a different sector. In cell 306, antenna groups 324, 326, and 328 each correspond to a different sector. The cells 302, 304 and 306 may include several wireless communication devices, e.g., User Equipment or UEs, which may be in communication with one or more sectors of each cell 302, 304 or 306. For example, UEs 330 and 332 may be in communication with Node B 342, UEs 334 and 336 may be in communication with Node B 344, and UEs 338 and 340 can be in communication with Node B 346. Here, each Node B 342, 344, 346 is configured to provide an access point to a core network 204 (see FIG. 2) for all the UEs 330, 332, 334, 336, 338, 340 in the respective cells 302, 304, and 306.
[0020] 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 (see FIG. 2), 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).
[0021] 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 OFDM A. 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.
FIG. 4 is a block diagram of a Node B 410 in communication with a UE 450, where the Node B 410 may be the Node B 208 in FIG. 2, and the UE 450 may be the UE 210 in FIG. 2. In the downlink communication, a transmit processor 420 may receive data from a data source 412 and control signals from a controller/processor 440. The transmit processor 420 provides various signal processing functions for the data and control signals, as well as reference signals (e.g., pilot signals). For example, the transmit processor 420 may provide cyclic redundancy check (CRC) codes for error detection, coding and interleaving to facilitate forward error correction (FEC), mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM), and the like), spreading with orthogonal variable spreading factors (OVSF), and multiplying with scrambling codes to produce a series of symbols. Channel estimates from a channel processor 444 may be used by a controller/processor 440 to determine the coding, modulation, spreading, and/or scrambling schemes for the transmit processor 420. These channel estimates may be derived from a reference signal transmitted by the UE 450 or from feedback from the UE 450. The symbols generated by the transmit processor 420 are provided to a transmit frame processor 430 to create a frame structure. The transmit frame processor 430 creates this frame structure by multiplexing the symbols with information from the controller/processor 440, resulting in a series of frames. The frames are then provided to a transmitter 432, which provides various signal conditioning functions including amplifying, filtering, and modulating the frames onto a carrier for downlink transmission over the wireless medium through antenna 434. The antenna 434 may include one or more antennas, for example, including beam steering bidirectional adaptive antenna arrays or other similar beam technologies. [0023] At the UE 450, a receiver 454 receives the downlink transmission through an antenna 452 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 454 is provided to a receive frame processor 460, which parses each frame, and provides information from the frames to a channel processor 494 and the data, control, and reference signals to a receive processor 470. The receive processor 470 then performs the inverse of the processing performed by the transmit processor 420 in the Node B 410. More specifically, the receive processor 470 descrambles and despreads the symbols, and then determines the most likely signal constellation points transmitted by the Node B 410 based on the modulation scheme. These soft decisions may be based on channel estimates computed by the channel processor 494. 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 472, which represents applications running in the UE 450 and/or various user interfaces (e.g., display). Control signals carried by successfully decoded frames will be provided to a controller/processor 490. When frames are unsuccessfully decoded by the receiver processor 470, the controller/processor 490 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.
[0024] In the uplink, data from a data source 478 and control signals from the controller/processor 490 are provided to a transmit processor 480. The data source 478 may represent applications running in the UE 450 and various user interfaces (e.g., keyboard). Similar to the functionality described in connection with the downlink transmission by the Node B 410, the transmit processor 480 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 494 from a reference signal transmitted by the Node B 410 or from feedback contained in the midamble transmitted by the Node B 410, may be used to select the appropriate coding, modulation, spreading, and/or scrambling schemes. The symbols produced by the transmit processor 480 will be provided to a transmit frame processor 482 to create a frame structure. The transmit frame processor 482 creates this frame structure by multiplexing the symbols with information from the controller/processor 490, resulting in a series of frames. The frames are then provided to a transmitter 456, 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 452.
[0025] The uplink transmission is processed at the Node B 410 in a manner similar to that described in connection with the receiver function at the UE 450. A receiver 435 receives the uplink transmission through the antenna 434 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 435 is provided to a receive frame processor 436, which parses each frame, and provides information from the frames to the channel processor 444 and the data, control, and reference signals to a receive processor 438. The receive processor 438 performs the inverse of the processing performed by the transmit processor 480 in the UE 450. The data and control signals carried by the successfully decoded frames may then be provided to a data sink 439 and the controller/processor, respectively. If some of the frames were unsuccessfully decoded by the receive processor, the controller/processor 440 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.
[0026] The controller/processors 440 and 490 may be used to direct the operation at the Node B 410 and the UE 450, respectively. For example, the controller/processors 440 and 490 may provide various functions including timing, peripheral interfaces, voltage regulation, power management, and other control functions. The computer readable media of memories 442 and 492 may store data and software for the Node B 410 and the UE 450, respectively. A scheduler/processor 446 at the Node B 410 may be used to allocate resources to the UEs and schedule downlink and/or uplink transmissions for the UEs.
[0027] We propose a method to estimate the interference power seen by SSC without use of common pilot channel on SSC. The method utilizes a null pilot channel on SSC, which is a channelization code reserved for no use on SSC. In the receiver, the UE can use this reserved channelization code to estimate the interference power. The receiver performs descrambling and de-spreading on this channelization code. Since other channelization codes in use on the SSC are orthogonal to this channelization code, the despreading output does not contain any signals on SSC and is purely interference signals for the SSC. We can perform power estimation on de-spreading the output to obtain the interference power for the SSC.
[0028] The present invention resides in the transmitter and receiver of both the UE and the NodeB. The invention is detectable because it involves a standards change. Potential workarounds are already included in this invention.
[0029] Several aspects of a telecommunications system have been presented with reference to a W-CDMA system. As those skilled in the art will readily appreciate, various aspects described throughout this disclosure may be extended to other telecommunication systems, network architectures and communication standards.
[0030] By way of example, various aspects may be extended to other UMTS systems such as TD-SCDMA, High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), High Speed Packet Access Plus (HSPA+) and TD- CDMA. Various aspects may also be extended to systems employing Long Term Evolution (LTE) (in FDD, TDD, or both modes), LTE-Advanced (LTE-A) (in FDD, TDD, or both modes), CDMA2000, Evolution-Data Optimized (EV-DO), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Ultra- Wideband (UWB), Bluetooth, and/or other suitable systems. The actual telecommunication standard, network architecture, and/or communication standard employed will depend on the specific application and the overall design constraints imposed on the system.
[0031] In accordance with various aspects of the disclosure, an element, or any portion of an element, or any combination of elements may be implemented with a "processing system" that includes one or more processors. Examples of processors include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on a computer-readable medium. The computer-readable medium may be a non-transitory computer-readable medium. A non-transitory computer-readable medium includes, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., compact disk (CD), digital versatile disk (DVD)), a smart card, a flash memory device (e.g., card, stick, key drive), random access memory (RAM), read only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), a register, a removable disk, and any other suitable medium for storing software and/or instructions that may be accessed and read by a computer. The computer-readable medium may also include, by way of example, a carrier wave, a transmission line, and any other suitable medium for transmitting software and/or instructions that may be accessed and read by a computer. The computer-readable medium may be resident in the processing system, external to the processing system, or distributed across multiple entities including the processing system. The computer-readable medium may be embodied in a computer-program product. By way of example, a computer- program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.
[0032] It is to be understood that the specific order or hierarchy of steps in the methods disclosed is an illustration of exemplary processes. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the methods may be rearranged. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented unless specifically recited therein.
[0033] The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean "one and only one" unless specifically so stated, but rather "one or more." Unless specifically stated otherwise, the term "some" refers to one or more. A phrase referring to "at least one of a list of items refers to any combination of those items, including single members. As an example, "at least one of: a, b, or c" is intended to cover: a; b; c; a and b; a and c; b and c; and a, b and c. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase "means for" or, in the case of a method claim, the element is recited using the phrase "step for."

Claims

CLAIMS WHAT IS CLAIMED IS:
1. A method of signal UE that a channelization code is reserved for no use on SSC
2. A method of use the reserved channelization code to estimate the interference power on SSC
3. A method to use interference power estimated from PSC as interference power for SSC
PCT/CN2012/071670 2012-02-27 2012-02-27 Estimation of interference power for secondary scrambling code WO2013127056A1 (en)

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Citations (4)

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US20050094816A1 (en) * 2003-11-04 2005-05-05 Telefonaktiebolaget Lm Ericsson (Publ) Interference estimation in CDMA systems using alternative scrambling codes
WO2008098221A1 (en) * 2007-02-09 2008-08-14 Qualcomm Incorporated Using codewords in a wireless communication system
CN101854668A (en) * 2009-04-03 2010-10-06 大唐移动通信设备有限公司 Method, system and device for data transmission under MU-MIMO system
WO2011063567A1 (en) * 2009-11-27 2011-06-03 Qualcomm Incorporated Interference cancellation for non-orthogonal channel sets

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050094816A1 (en) * 2003-11-04 2005-05-05 Telefonaktiebolaget Lm Ericsson (Publ) Interference estimation in CDMA systems using alternative scrambling codes
WO2008098221A1 (en) * 2007-02-09 2008-08-14 Qualcomm Incorporated Using codewords in a wireless communication system
CN101854668A (en) * 2009-04-03 2010-10-06 大唐移动通信设备有限公司 Method, system and device for data transmission under MU-MIMO system
WO2011063567A1 (en) * 2009-11-27 2011-06-03 Qualcomm Incorporated Interference cancellation for non-orthogonal channel sets

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