WO2014008665A1

WO2014008665A1 - Small cell discovery and measurement in wireless mobile networks

Info

Publication number: WO2014008665A1
Application number: PCT/CN2012/078619
Authority: WO
Inventors: Pengfei Sun; Erlin Zeng; Na WEI; Chunyan Gao; Haiming Wang; Wei Bai
Original assignee: Renesas Mobile Corporation
Priority date: 2012-07-13
Filing date: 2012-07-13
Publication date: 2014-01-16

Abstract

A cell identification procedure for small cells in wireless networks in alternative embodiments. Macro eNB may signal all user equipment (UE) to perform detection and signal quality measurement based on a single extended physical discovery channel (PDCH) transmission. UE may perform synchronization then quality-level measurement on the same PDCH signal. Alternatively, the macro eNB may signal all UE to perform the measurement based on the channel state information reference signal (CSI-RS) after synchronization and cell detection on PDCH signal. In another approach, eNB may only transmit CSI-RS upon receipt of a detection result from UE. If no new UE are entering a small cell, the cell may send CSI-RS periodically for measurement while PDCH may not be provided at all. A hybrid mode may be implemented in which UE may use either PDCH or CSI-RS for measurement, determined by UE on its own.

Description

SMALL CELL DISCOVERY AND MEASUREMENT

IN WIRELESS MOBILE NETWORKS TECHNOLOGICAL FIELD

The various embodiments of the present invention relate to the field of wireless mobile communications networks and, particularly, to identification of small cells and signal quality-level measurement of the small cell.

BACKGROUND

Carrier Aggregation (CA) in Long Term Evolution (LTE)-Advanced extends the maximum bandwidth in the Uplink (UL) or Downlink (DL) directions by aggregating multiple carriers within a frequency band (intra-band CA) or across frequency bands (inter-band CA). A new carrier type has recently been adopted for LTE- Advanced networks. The new carrier type does not need to be backward compatible. Because this new type of carrier is not required to be usable by legacy user equipment (UE), some enhancement could be supported on it, for example, to reduce the density or even redesign the reference signal to save overhead, or to do some optimization to suit some specific application scenarios.

A small cell is a type of wireless base station intended to handle the increased load of mobile data devices in small areas, such as, airports, shopping malls, downtowns, campuses, and large offices. Transmitted power is low because of limits on power consumption and heat dissipation, but performance requirements are high because these cells must handle high volumes of data and connections. One of the tasks of wireless network engineers is to identify and evaluate strategies for improved small cell discovery/identification. The problem has not been effectively solved to date, and it seems that network operators are interested in considering a quick cell identification for the Remote Radio Head (RRH) scenario (see Figure 1) using the new carrier type. In that scenario, it is assumed that macro evolved Node B (eNB) will be configured as UE's primary cell (PCell) 103, and the small RRH will be configured as the secondary cell (Scell) 105.

The new physical channel referred to as the Physical Discovery Channel (PDCH) has long periodicity. It occupies a few seconds assuming relaxed measurement requirements for energy saving and low mobility, and sufficient time/frequency radio resource density for one-shot PDCH reception by the UE for efficient UE battery consumption. Longer access/detection delay is likely to be created due to the long periodicity of DPCH. If the periodicity is reduced, the advantages of PDCH, such as low power consumption, might be diminished.

In legacy LTE systems, the new cell identification procedure comprises two steps: first, the UE must detect the primary synchronization sequence/secondary synchronization sequence (PSS/SSS) of the new cell and then perform the measurement based on the common reference signal (CRS) channel. The PSS/SSS enables UE to detect the new cell and perform quality-level measurements, such as reference signal received power (RSRP), and reference signal received quality (RSRQ), which are reported back to the network (eNB). However, the cell identification of the small cells becomes complicated: first, the PSS/SSS may be replaced by the PDCH channel which has very different features compared to PSS/SSS; second, the CRS is not desired in the small cell due to its relatively fixed and inflexible frequency pattern.

Therefore, a new cell identification procedure must be developed based on the change of these physical channels. The PDCH plays a similar role to PSS/SSS in the legacy LTE system to provide synchronization and cell identification (ID). Thus, the remaining problem becomes how to enable UE to perform quality-level measurement of the small cell.

BRIEF SUMMARY

The first of several embodiments is a method for wireless network cell detection and signal quality measurement comprising receiving a network signal to perform cell detection and signal quality measurement based on a physical discovery channel transmission, performing cell detection/synchronization based on a PDCH transmission, and performing signal quality level measurement based on the same PDCH transmission. The method includes receiving PDCH configurations from the network necessary for perfoiming cell detection and signal quality measurement, receiving a required duration of PDCH necessary for signal quality measurement, and, measuring signal quality for at least the required PDCH duration. The method may further comprise performing cell detection/synchronization on the PDCH signal, and performing the signal quality measurement based on subsequent PDCH signals. Alternatively the method may include performing cell detection/synchronization on received PDCH signals, and performing the signal quality measurement based on the buffered PDCH signals.

In another embodiment a method for wireless network cell detection and signal quality measurement may comprise: receiving a network signal to perform signal quality measurement based on a channel state information reference signal (CSI-RS), receiving PDCH and CSI-RS configurations from the network necessary for perfoiTning cell detection and quality level measurement, performing cell detection/synchronization based on PDCH signals, and performing signal quality measurement based on the CSI-RS. This method may further comprise receiving the CSI-RS from a small cell only after UE reports the cell detection to the network. It may also comprise receiving CSI-RS periodically for signal measurement while PDCH is not received in the instance in which the small cell serves only UEs of its own.

The method for wireless network cell detection and signal quality measurement may also take the form of receiving a network signal indicating the quality level measurement could be done based on either PDCH or CSI-RS, receiving PDCH and CSI- RS configurations from a network necessary for performing cell detection and quality level measurement, and determining to use PDCH or CSI-RS or both to perform signal measurement. This form of the method may further comprise using PDCH signaling for both detection and measurement within PDCH signal duration. It may also comprise using CSI-RS signaling for measurement when measurement cannot be completed during PDCH signaling. The method may also include reporting the measurement results to the network indicating which signals were used for measurement.

In another embodiment, an apparatus is provided comprising at least a processor, a memory associated with the processor, and computer instructions which, when executed in the processor, cause the apparatus to: receive a network signal to perform cell detection and signal quality measurement based on a physical discovery channel transmission, perform cell detection/synchronization based on a PDCH transmission, and perform signal quality level measurement based on the same PDCH transmission. The apparatus may further comprise the instructions that, when executed in the processor, further cause the apparatus to: receive PDCH configurations from the network necessary for performing cell detection and signal quality measurement, receive a required duration of PDCH necessary for signal quality measurement, and, measure signal quality for at least the required PDCH duration. This apparatus may comprise instructions executed in the processor that further cause the apparatus to: perform cell detection/synchronization on the PDCH signal, and perform the signal quality measurement based on subsequent PDCH signals. The apparatus may also comprise instructions executed in the processor that further cause the apparatus to: perform cell detection/synchronization on received PDCH signals, and perform the signal quality measurement based on the buffered PDCH signals.

Another embodiment may be an apparatus comprising at least a processor, a memory associated with the processor, and computer instructions which, when executed in the processor, cause the apparatus to receive a network signal to perform signal quality measurement based on a channel state information reference signal (CSI-RS), receive PDCH and CSI-RS configurations from the network necessary for performing cell detection and quality level measurement, perform cell detection/synchronization based on PDCH signals, and perform signal quality measurement based on the CSI-RS. In this embodiment the instructions executed in the processor may further cause the apparatus to receive PDCH and CSI-RS configurations from the network necessary for performing cell detection and quality level measurement, perform cell detection/synchronization based on PDCH signals, and perform signal quality measurement based on the CSI-RS. This apparatus may further cause the apparatus to receive the CSI-RS from a small cell only after UE reports the cell detection to the network. The apparatus may also comprise instructions that, executed in the processor, further cause the apparatus to receive CSI-RS periodically for signal measurement while PDCH is not received in the instance that the small cell serves only UEs of its own. Another embodiment may be an apparatus comprising at least a processor, a memory associated with the processor, and computer instructions which, when executed in the processor, cause the apparatus to receive a network signal indicating the quality level measurement could be done based on either PDCH or CSI-RS, receive PDCH and CSI-RS configurations from a network necessary for performing cell detection and quality level measurement, and determine to use PDCH or CSI-RS or both to perform signal measurement. The apparatus may comprise instructions executed in the processor that further cause the apparatus to use PDCH signaling for both detection and measurement within PDCH signal duration. This apparatus may use CSI-RS signaling for measurement when measurement cannot be completed during PDCH signaling. And this apparatus may report the measurement results to the network indicating which signals were used for measurement.

Alternatively, one embodiment may be a computer program product comprising a computer readable medium with computer coded instructions therein, said instructions arranged to, when executed in a processor, cause a device to perform receiving a network signal to perform cell detection and signal quality measurement based on a physical discovery channel transmission, performing cell detection/synchronization based on a PDCH transmission, and performing signal quality level measurement based on the same PDCH transmission. The program product may have instructions to further cause the device to perform receiving PDCH configurations from the network necessary for performing cell detection and signal quality measurement, receiving a required duration of PDCH necessary for signal quality measurement, and, measuring signal quality for at least the required PDCH duration. The program may have instructions to further cause the device to perform cell detection/synchronization on the PDCH signal, and to perform the signal quality measurement based on subsequent PDCH signals. It may also have instructions to further cause the device to perform cell detection/synchronization on received PDCH signals, and to perform the signal quality measurement based on the buffered PDCH signals.

Another embodiment of the computer program product can be instructions arranged to, when executed in a processor, cause a device to perform receiving a network signal to perform signal quality measurement based on a channel state information

5 EIE120252PCT reference signal (CSI-RS), receiving PDCH and CSI-RS configurations from the network necessary for performing cell detection and quality level measurement, performing cell detection/synchronization based on PDCH signals, and performing signal quality measurement based on the CSI-RS. This program product may also comprise instructions to further cause the device to perform using PDCH signaling for both detection and measurement within PDCH signal duration. It may also include instructions to further cause the device to perform using CSI-RS signaling for measurement when measurement cannot be completed during PDCH signaling. Finally, the program product may comprise instructions to further cause the device to perform reporting the measurement results to the network indicating which signals were used for measurement.

In another embodiment, an apparatus is provided comprising means for receiving a network signal to perform cell detection and signal quality measurement based on a physical discovery channel transmission, means for performing cell

detection synchronization based on a PDCH transmission, and means for performing signal quality level measurement based on the same PDCH transmission. This embodiment may also comprise means for receiving PDCH configurations from the network necessary for performing cell detection and signal quality measurement, means for receiving a required duration of PDCH necessary for signal quality measurement, and, means for measuring signal quality for at least the required PDCH duration. The apparatus may further comprise means for performing cell detection/synchronization on the PDCH signal, and means for performing the signal quality measurement based on subsequent PDCH signals. This apparatus could also have means for buffering incoming PDCH signals, means for performing cell detection/synchronization on received PDCH signals, and means for performing the signal quality measurement based on the buffered PDCH signals.

Alternatively, this embodiment may be an apparatus comprising: means for receiving a network signal to perform signal quality measurement based on a channel state information reference signal (CSI-RS), means for receiving PDCH and CSI-RS configurations from the network necessary for performing cell detection and quality level measurement, means for performing cell detection/synchronization based on PDCH signals, and means for performing signal quality measurement based on the CSI-RS. This apparatus may include means for receiving the CSI-RS from a small cell only after UE reports the cell detection to the network. It can also have means for receiving CSI-RS periodically for signal measurement while PDCH is not received in the instance in which the small cell serves only UEs of its own.

Another apparatus embodiment may comprise means for receiving a network signal indicating the quality level measurement could be done based on either PDCH or CSI-RS, means for receiving PDCH and CSI-RS configurations from a network necessary for performing cell detection and quality level measurement, and means for determining to use PDCH or CSI-RS or both to perform signal measurement. This apparatus may also comprise means for using PDCH signaling for both detection and measurement within PDCH signal duration. The apparatus my include means for using CSI-RS signaling for measurement when measurement cannot be completed during PDCH signaling. And the apparatus might finally contain means for reporting the measurement results to the network indicating which signals were used for measurement.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Having thus described embodiments of the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

Fig. 1 is a schematic diagram of a small cell network configuration;

Fig. 2 is a schematic diagram of a wireless network with associated mobile terminals;

Fig. 3 is a block diagram of an apparatus that may be embodied by a mobile terminal and that may be specifically configured in accordance with an example embodiment of the present invention;

Fig. 4 is a signal diagram of PDCH synchronization and quality measurement timing;

Fig. 5 is a flow diagram of one embodiment of the cell identification procedure and signal quality-level measurement process;

Fig. 6 is a flow diagram of an alternative embodiment of the process; and

Fig. 7 is a flow diagram of another alternative embodiment of the process. DETAILED DESCRIPTION

The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

The term "computer-readable medium" as used herein refers to any medium configured to participate in providing information to a processor, including instructions for execution. Such a medium may take many forms, including, but not limited to a non- transitory computer-readable storage medium (e.g., non-volatile media, volatile media), and transmission media. Transmission media include, for example, coaxial cables, copper wire, fiber optic cables, and carrier waves that travel through space without wires or cables, such as acoustic waves and electromagnetic waves, including radio, optical and infrared waves. Signals include man-made transient variations in amplitude, frequency, phase, polarization or other physical properties transmitted through the transmission media.

Examples of non-transitory computer-readable media include a magnetic computer readable medium (e.g., a floppy disk, hard disk, magnetic tape, any other magnetic medium), an optical computer readable medium (e.g., a compact disc read only memory (CD-ROM), a digital versatile disc (DVD), a Blu-Ray disc, or the like), a random access memory (RAM), a programmable read only memory (PROM), an erasable programmable read only memory (EPROM), a FLASH-EPROM, or any other non- transitory medium from which a computer can read. The term computer-readable storage medium is used herein to refer to any computer-readable medium except transmission media. However, it will be appreciated that where embodiments are described to use a computer-readable storage medium, other types of computer-readable mediums may be substituted for or used in addition to the computer-readable storage medium in alternative embodiments. Additionally, as used herein, the term 'circuitry' refers to (a) hardware-only circuit implementations (for example, implementations in analog circuitry and/or digital circuitry); (b) combinations of circuits and computer program product(s) comprising software and/or firmware instructions stored on one or more computer readable memories that work together to cause an apparatus to perform one or more functions described herein; and (c) circuits, such as, for example, a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation even if the software or firmware is not physically present. This definition of 'circuitry' applies to all uses of this term herein, including in any claims. As a further example, as used herein, the term 'circuitry' also includes an implementation comprising one or more processors and/or portion(s) thereof and accompanying software and/or firmware. As another example, the term 'circuitry' as used herein also includes, for example, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network device, other network device, and/or other computing device.

Referring now to Fig. 2, mobile terminals 10 may communicate with a network 14 utilizing an uplink from the mobile terminal 10 to the network 14 and a downlink from the network 14 to the mobile terminal. The mobile terminals 10 may be of various types of mobile communication devices such as, for example, mobile telephones, personal digital assistants (PDAs), pagers, laptop computers, or any of numerous other hand held or portable communication devices, computation devices, content generation devices, content consumption devices, or combinations thereof, generally termed "user equipment" (UE).

The mobile terminal 10 may communicate with a network via an access point 12, such as a Node B, an evolved Node B (eNB), a base station or the like, each of which comprises a radio frequency transmitter and receiver. The mobile terminal 10 may communicate with various types of networks 14 including, for example, a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, a Global Systems for Mobile communications (GSM) network, a Code Division Multiple Access (CDMA) network, e.g., a Wideband CDMA (WCDMA) network, a CDMA2000 network or the like, a General Packet Radio Service (GPRS) network, a Universal Terrestrial Radio

9 ΕΪΕ120252PCT Access Network (UTRAN), a GSM Edge Radio Access Network (GERAN) or other type of network.

Referring now to Figure 3, an apparatus 20 that may be embodied by or otherwise associated with a mobile terminal 10 may include or otherwise be in communication with a processor 22, a memoiy device 24, a communication interface 28, and a user interface 30.

In some example embodiments, the processor 22 (and/or co-processors or any other processing circuitry assisting or otherwise associated with the processor) may be in communication with the memory device 24 via a bus for passing information among components of the apparatus 20. The memory device 24 may include, for example, one or more non-transitory volatile and/or non-volatile memories. In other words, for example, the memory device 24 may be an electronic storage device (e.g., a computer readable storage medium) comprising gates configured to store data (e.g., bits) that may be retrievable by a machine (e.g., a computing device like the processor). The memory device 24 may be configured to store information, data, content, applications, instructions, or the like for enabling the apparatus to carry out various functions in accordance with an example embodiment of the present invention. For example, the memory device could be configured to buffer input data for processing by the processor. Additionally or alternatively, the memory device 24 could be configured to store instructions for execution by the processor 22.

The apparatus 20 may, in some embodiments, be embodied by a mobile terminal 10. However, in some embodiments, the apparatus 20 may be embodied as a chip or chip set. In other words, the apparatus may comprise one or more physical packages (e.g., chips) including materials, components and/or wires on a structural assembly (e.g., a baseboard). The structural assembly may provide physical strength, conservation of size, and/or limitation of electrical interaction for component circuitry included thereon. The apparatus 20 may therefore, in some cases, be configured to implement an embodiment of the present invention on a single chip or as a single "system on a chip." As such, in some cases, a chip or chipset may constitute means for performing one or more operations for providing the functionalities described herein.

10 ΡΤΡ 1 9Π? ^<Ϊ9ΡΓΤ The processor 22 may be embodied in a number of different ways. For example, the processor may be embodied as one or more of various hardware processing means such as a coprocessor, a microprocessor, a controller, a digital signal processor (DSP), a processing element with or without an accompanying DSP, or various other processing circuitry including integrated circuits such as, for example, an ASIC (application specific integrated circuit), an FPGA (field programmable gate array), a microcontroller unit (MCU), a hardware accelerator, a special-purpose computer chip, or the like. As such, in some embodiments, the processor may include one or more processing cores configured to perform independently. A multi-core processor may enable multiprocessing within a single physical package. Additionally or alternatively, the processor may include one or more processors configured in tandem via the bus to enable independent execution of instructions, pipelining and/or multithreading. In the embodiment in which the apparatus 20 is embodied as a mobile terminal 10, the processor may be embodied by the processor of the mobile terminal.

In an example embodiment, the processor 22 may be configured to execute instructions stored in the memory device 24 or otherwise accessible to the processor. Alternatively or additionally, the processor may be configured to execute hard coded functionality. As such, whether configured by hardware or software methods, or by a combination thereof, the processor may represent an entity (e.g., physically embodied in circuitry) capable of performing operations according to an embodiment of the present invention while configured accordingly. Thus, for example, when the processor is embodied as an ASIC, FPGA or the like, the processor may be specifically configured hardware for conducting the operations described herein. Alternatively, as another example, when the processor is embodied as an executor of software instructions, the instructions may specifically configure the processor to perform the algorithms and/or operations described herein when the instructions are executed. However, in some cases, the processor may be a processor of a specific device (e.g., a mobile terminal 10) configured to employ an embodiment of the present invention by further configuration of the processor by instructions for performing the algorithms and/or operations described herein. The processor may include, among other things, a clock, an arithmetic logic unit (ALU) and logic gates configured to support operation of the processor. Meanwhile, the communication interface 28 may be any means such as a device or circuitry embodied in either hardware or a combination of hardware and software that is configured to receive and/or transmit data from/to a network 14 and/or any other device or module in communication with the apparatus 20. In this regard, the communication interface may include, for example, an antenna (or multiple antennas) and supporting hardware and/or software for enabling communications with a wireless communication network. Additionally or alternatively, the communication interface may include the circuitry for interacting with the antenna(s) to cause transmission of signals via the antenna(s) or to handle receipt of signals received via the antenna(s). In order to support multiple active connections simultaneously, such as in conjunction with a digital super directional array (DSD A) device, the communications interface of one embodiment may include a plurality of cellular radios, such as a plurality of radio front ends and a plurality of base band chains. In some environments, the communication interface may alternatively or also support wired communication. As such, for example, the communication interface may include a communication modem and/or other hardware/software for supporting communication via cable, digital subscriber line (DSL), universal serial bus (USB) or other mechanisms.

In some example embodiments, such as instances in which the apparatus 20 is embodied by a mobile terminal 10, the apparatus may include a user interface 30 that may, in turn, be in communication with the processor 22 to receive an indication of a user input and/or to cause provision of an audible, visual, mechanical or other output to the user. As such, the user interface may include, for example, a keyboard, a mouse, a joystick, a display, a touch screen(s), touch areas, soft keys, a microphone, a speaker, or other input/output mechanisms. Alternatively or additionally, the processor may comprise user interface circuitry configured to control at least some functions of one or more user interface elements such as, for example, a speaker, ringer, microphone, display, and/or the like. The processor and/or user interface circuitry comprising the processor may be configured to control one or more functions of one or more user interface elements through computer program instructions (e.g., software and/or firmware) stored on a memory accessible to the processor (e.g., memory device and/or the like). In the apparatus embodied by a mobile terminal 10, the processor 22 is the means for executing various functions that may be specified for preparing the mobile terminal for network communications. The memory device 24 may contain program code instructions causing the processor to execute the various functions, or the processor may have memory associated with it that contains the program code instructions. Thus, the means for executing various functions in the mobile terminal may include the memory with computer code instructions stored therein. The communications interface 28 is the means for receiving signals from a network entity 12 that are then processed to determine appropriate functions to be executed by the processor.

Referring to the above discussion about small cell discovery and identification, a new cell identification procedure is described herein with following assumptions:

• PSS/SSS is replaced by PDCH in small cells

• Synchronization and cell ID detection are achieved through the PDCH

• Downlink (DL) signal of the small cell does not contain the common reference signal (CRS)

• The UE already has access to one macro eNB before the small cell detection/measurement

• The Macro eNB is aware of the PDCH/CSI-RS (channel state information reference signal) configuration in small cells

Based on these assumptions, the embodiments described herein are intended to realize quality-level measurement in small cell identification. The several embodiments include joint synchronization and measurement based on single PDCH channel; a PDCH plus CSI-RS based measurement procedure; and a hybrid measurement method. Each is detailed below.

PDCH based measurement

Macro eNB (that is, a node serving a large area) signals all of the UEs to perform detection and measurement based on the PDCH transmission. The one shot PDCH transmission is used for synchronization/cell ID detection as well as signal quality-level

13 F.TR i ?n9^<;?prT measurement. In one embodiment, UE must finish the synchronization/cell ID detection based on the PDCH first. Then UE performs a quality-level measurement based on the same incoming PDCH transmission. Alternatively, UE may utilize buffered PDCH data to perform the measurement after it finishes the synchronization and cell ID detection.

A required duration of measurement is pre-defined or signaled by the Pcell to UE.

If preamble repetition is adopted, the required duration could be described in a number of accumulated preambles. UE has to measure more than the required duration of PDCH before generating an accurate measurement report. This is because a UE may finish the synchronization and cell ID detection at the end of a single PDCH transmission.

The resources may be orthogonal and multiplexed in time, frequency and code domain for each Scell within range of a PDCH transmission. The UE separates each Scell's resource and performs the quality measurement independently. If time domain multiplexing is adopted, the UE may perform the measurement at a different time slot for different Scells. If frequency domain multiplexing is adopted, the UE may perfonn a digital fourier transform (DFT) to transfer the signal to frequency domain and then perform the measurement at different frequency intervals. If code domain multiplexing is adopted, the UE may perform measurement after despreading the code.

Referring to Fig. 4, the Pcell provides coarse synchronization 402, which helps UE find the possible starting point of the PDCH. Based on Pcell synchronization and signaling, UE knows where the PDCH 401 will appear. If the synchronization is complete 403, then the measurement can be done based on the PDCH reference signal. Alternatively, UE may use buffered data 407 to perform the measurement or perfonn it based on the subsequent (to synchronization) PDCH signals 405. PDCH plus CSI-RS based measurement

In this option, macro eNB signals all the UEs to perform the measurement based on the CSI-RS after performing synchronization and cell ID detection based on PDCH. One option of this mode is that one shot of PDCH transmission is associated with a CSI- RS transmission by the small cells. The UEs perform synchronization and cell ID detection based on PDCH followed by the measurement based on the associated CSI-RS.

14 RTF.1 7D7S?PCT The PDCH and CSI-RS pattern are configured for each small cell and broadcast to all UEs.

The CSI-RS is linked to a PDCH with a relative position. In this way the UE will know where to find the CSI-RS after successfully detecting the PDCH. CSI-RS is transmitted after the PDCH; one or several shots of CSI-RS can be transmitted after the PDCH periodically. The relative position could be certain resource blocks (RBs) in the frequency domain, or delays in the time domain. The CSI-RS sequence used for measurement could be linked to the PDCH pattern or cell ID.

Another option of this mode is that the PDCH signal is periodically transmitted and CSI-RS is only transmitted on need. UE detects the PDCH signal first and reports the cell ID detection results to eNB in the first step. In the second step eNB configures a CSI- RS transmission for the detected small cell. The small cell transmits CSI-RS at the configured time/frequency position with configured pattern. The configured CSI-RS pattern can be signaled to UE via radio resource control (RRC) or layer 1 (LI) signaling. Then the UE measures the CSI-RS at the corresponding position.

Another option of this mode is that CSI-RS is transmitted periodically while PDCH is transmitted on need. In case the small cell only serves the UEs of its own, the CSI-RS is provided periodically for measurement but PDCH is not transmitted if there is no new UE entering. UE reports CSI-RS based measurement to eNB, any existing CSI- RS measurement methods may apply here.

Summary of PDCH plus CSI-RS based measurement

In the first option, the PDCH signal and CSI-RS always appear at the same time. Thus the procedure is similar to the PDCH based measurement except that the signal measurement is done based on the CSI-RS. The CSI-RS pattern could be derived based on Pcell signaling and the PDCH pattern. That is, after detecting the PDCH successfully, UE knows where the CSI-RS will be transmitted and which sequence is used.

In the second option, the CSI-RS is triggered by eNB after receiving the PDCH detection report. This option allows overhead reduction and power saving for small cells. In addition, the network could flexibly configure if a UE needs to do the CSI-RS based

15 FJE120252PCT measurement or not. If the PDCH detection results are good enough, the eNB may directly configure the small cell as Scell for the UE.

Hybrid PDCH and CSI-RS measurement

Macro eNB may allow a hybrid mode in which UE may use either PDCH or CSI-

RS for measurement. Small cells are configured to transmit both PDCH and CSI-RS. UE is configured to determine by itself to use PDCH or CSI-RS or both to perform measurement in a UE specific manner. It is possible that some UEs could finish both the cell ID detection and the measurement within the PDCH duration. Then the UEs do not need the CSI-RS. It is also possible that some UEs could only finish the cell ID detection but have no time to perform measurement. In this case UEs wait for the CSI-RS for measurement. UE reports the corresponding measurement results to eNB. The reports indicate which reference signal (RS) (PDCH or CSI-RS or both) is used for the measurement.

Summary of hybrid PDCH and CSI-RS measurement

This hybrid mode allows UE to use different reference signals for measurement. The selection of the RS signal could be controlled by eNB or determined by the UE itself. For those UE with a good channel environment, the PDCH may be sufficient for both synchronization and measurement. The UE could quickly send back the report to eNB in this case. For those UEs suffering low signal to noise ratio (SINR), they may only finish the synchronization within the PDCH duration and have to perform measurement based on the CSI-RS. It is necessary that eNB knows which reference signal is used by a specific UE. It could be distinguished by the control bits in the report or by designing a separate report window.

Referring to Figs. 5 - 7, the various embodiments of the cell detection and measurement process described herein are illustrated. Fig. 5 shows the process based on only the PDCH signal. The apparatus 20 embodied by a UE may include means, such as the processor 22, the communication interface 28 or the like, for receiving instruction 501 from the network to perform cell detection and signal quality measurement on the PDCH transmission. The network sends PDCH configurations 502 necessary for cell detection and signal measurement. Thus, the apparatus 20 embodied by a UE may include means, such as the processor 22, the communication interface 28 or the like, for receiving the PDCH configurations 502 necessary for cell detection and signal measurements. The apparatus 20 embodied by the UE may also include means, such as the processor 22, the communication interface 28 or the like, for receivings PDCH signal 503 having the duration necessary for both detection and signal quality measurement. Two approaches to detection/measurement may be used. In a first approach, the entire process is based on incoming PDCH signal. Cell detection/synchronization 505 is performed first by the apparatus 20 and, more particularly, by means, such as the processor 22 or the like. Once complete, the apparatus 20 embodied by the UE includes means, such as the processor 22 or the like, for performing the signal quality level measurement 507 on the subsequently received PDCH signal as it arrives. Alternatively, the apparatus 20 embodied by the UE can include means, such as the processor 22, the memory 24 or the like, for buffering 509 the incoming PDCH signal. Cell detection synchronization is performed 511 on the incoming PDCH signal by the apparatus 20 and, more particularly, by means, such as the processor 22 or the like. Then the apparatus 20 and, more particularly, the processor 22 or the like, may perform signal quality level measurement 513 on the buffered PDCH signal data.

In an alternative embodiment of the process, shown in Fig. 6, an apparatus 20 embodied by a UE may include means, such as the processor 22, the communication interface 26 or the like, for receiving a network instruction 601 to perform the signal quality level measurement based on CSI-RS rather than PDCH. The apparatus 20 embodied by the UE may also include means, such as the processor 22, the communication interface 26 or the like, for then receiving 602 the necessary PDCH and CSI-RS configurations. The apparatus 20 embodied by the UE of this embodiment also includes means, such as the processor 22 or the like, for performing cell detection/synchronization on the PDCH signal 603 as in the first embodiment. However, in this embodiment the apparatus 20 embodied by the UE may include means, such as the processor 22, the communication interface 26 or the like, for reporings 605 the small cell detection to the network. Then the apparatus 20 embodied by the UE may include means,

17 EIE120252PCT such as the processor 22 or the like, for performing 607 signal quality level measurement based on a transmitted CSI-RS.

In another alternative embodiment illustrated in Fig. 7, UE is commanded 701 to use PDCH signals or CSI-RS, or both, for cell detection and signal quality measurement. Thus, the apparatus 20 embodied by the UE may include means, such as the processor 22, the communication interface 26 or the like, for receiving a network signal indicating the quality level is to be done based on the PDCH, the CSI-RS or both the PDCH and the CSI-RS. The apparatus 20 embodied by the UE may also include means, such as the processor 22, the communication interface 26 or the like, for receiving the necessary PDCH and CSI-RS configurations 702 for cell detection and signal measurement. The apparatus 20 embodied by the UE may also include means, such as the processor 22 or the like, for performing 703 cell detection/synchronization on the PDCH signal as before. As shown in blocks 707 and 711 of Fig. 7, the apparatus 20 embodied by the UE may include means, such as the processor 22 or the like, for determining to use PDCH or CSI- RS or both to perform signal measurements. In this regard, the apparatus 20 embodied by the UE may also include means, such as the processor or the like, for then attempting signal quality measurement on the PDCH signals 705. If the signal measurement is successfully completed 707 (YES result), the apparatus 20 embodied by the UE may include means, such as the processor 22, the communication interface 26 or the like, for then causing a report to be sent to the network 709 indicating which signal was used for the signal quality measurement (in this instance, PDCH). If the signal quality measurement is not completed on PDCH signals 707 (No result), either because it was not possible or because the network had instructed that UE use CSI-RS for the measurement, then the apparatus embodied by the UE may include means, such as the processor 22 or the like, for performing 711 signal quality measurement based on transmitted CSI-RS. Once complete, the apparatus 20 embodied by the UE may include means, such as the processor 22, the communication interface 26 or the like, for reporting to the network 709 to indicate which signal (PDCH or CSI-RS) was used for the signal measurement.

Advantages that may be realized from the several embodiments of the invention disclosed herein include: power saving and better interference coordination and

18 ETE120252PCT interference cancellation (ICIC) are achieved by using PDCH and CSI-RS; the PDCH and CSI-RS are efficiently utilized to provide flexibility to meet the possible dense deployment of small cells; and, the procedure to use one channel, PDCH, in this case, to perform synchronization, cell ID detection and measurement simplifies the standardization and implementation effort.

The following abbreviations/acronyms have appeared in the above description and may be found in the following claims.

CA Carrier Aggregation

CC Component Carrier

CRS Common Reference Signal

CSI-RS Channel-State Information Reference Signal

DCI Downlink Control Information

DL Downlink

eNB Enhanced Node B. Name for Node B in LTE

ICIC Interference coordination and interference cancellation

LI Layer 1

LTE Long Term Evolution

LTE-A Long Term Evolution Advanced

Pcell Primary Cell

PSS Primary Synchronization Sequence

RB Resource Block(s)

RRC Radio Resource Control

RSRP Reference Signal Received Power

RSRQ Reference Signal Received Quality

SCC Secondary Cell Carrier

Scell Secondary Cell

SINR Signal to noise ratio

SSS Secondary Synchronization Sequence

UE User Equipment

UL Uplink

PDCH Physical Discovery Channel

RRH Remote Radio Head

Figures 5-7 are flowcharts illustrating the operations performed by a method, apparatus and computer program product, such as apparatus 20 of Figure 3, in accordance with one embodiment of the present invention. It will be understood that each block of the flowcharts, and combinations of blocks in the flowcharts, may be implemented by

19 RTP 1 90 ^?PPT various means, such as hardware, firmware, processor, circuitry and/or other device associated with execution of software including one or more computer program instructions. For example, one or more of the procedures described above may be embodied by computer program instructions. In this regard, the computer program instructions which embody the procedures described above may be stored by a non- transitory memory 24 of an apparatus employing an embodiment of the present invention and executed by a processor 22 in the apparatus. As will be appreciated, any such computer program instructions may be loaded onto a computer or other programmable apparatus (e.g., hardware) to produce a machine, such that the resulting computer or other programmable apparatus provides for implementation of the functions specified in the flowchart blocks. These computer program instructions may also be stored in a non- transitory computer-readable storage memory that may direct a computer or other programmable apparatus to function in a particular manner, such that the instructions stored in the computer-readable storage memory produce an article of manufacture, the execution of which implements the function specified in the flowchart blocks. The computer program instructions may also be loaded onto a computer or other

programmable apparatus to cause a series of operations to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide operations for implementing the functions specified in the flowchart blocks. As such, the operations of Figures 5-7, when executed, convert a computer or processing circuitry into a particular machine configured to perform an example embodiment of the present invention. Accordingly, the operations of Figures 5-7 define an algorithm for configuring a computer or processing circuitry, e.g., processor, to perform an example embodiment. In some cases, a general purpose computer may be provided with an instance of the processor which performs the algorithm of Figures 5-7 to transform the general purpose computer into a particular machine configured to perform an example embodiment.

Accordingly, blocks of the flowcharts support combinations of means for performing the specified functions and combinations of operations for performing the specified functions. It will also be understood that one or more blocks of the flowcharts, and combinations of blocks in the flowcharts, can be implemented by special purpose hardware-based computer systems which perform the specified functions, or

combinations of special purpose hardware and computer instructions.

In some embodiments, certain ones of the operations above may be modified or further amplified as described below. Moreover, in some embodiments additional optional operations may also be included. It should be appreciated that each of the modifications, optional additions or amplifications below may be included with the operations above either alone or in combination with any others among the features described herein. Further the operations described above and illustrated in Figures 5-7 may be performed in different orders in some embodiments than order that is illustrated.

Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for puiposes of limitation.

Claims

What is claimed is:

1. A method for wireless network cell detection and signal quality measurement comprising:

receiving a network signal to perform cell detection and signal quality

measurement based on a physical discovery channel transmission;

performing cell detection/synchronization based on a physical discovery channel (PDCH) transmission; and

performing signal quality level measurement based on the same PDCH transmission.

2. The method of claim 1 further comprising:

receiving PDCH configurations necessary for performing cell detection and signal quality measurement;

receiving a required duration of PDCH signal necessary for signal quality measurement; and,

measuring signal quality for at least the required PDCH signal duration.

3. The method of any of claims 1 and 2, further comprising:

performing cell detection/synchronization on the PDCH signal, and

performing the signal quality measurement based on subsequent PDCH signals.

4. The method of any of claims 1 and 2, further comprising:

buffering incoming PDCH signals,

performing cell detection/synchronization on received PDCH signals, and performing the signal quality measurement based on the buffered PDCH signals.

5. A method for wireless network cell detection and signal quality measurement comprising:

receiving a network signal to perform signal quality measurement based on a channel state information reference signal (CSI-RS), receiving physical discovery channel (PDCH) and CSI-RS configurations necessary for performing cell detection and quality level measurement;

performing cell detection/synchronization based on PDCH signals, and performing signal quality measurement based on the CSI-RS.

6. The method of claim 5 further comprising,

receiving the CSI-RS only after a user equipment (UE) reports the cell detection to the network.

7. The method of claim 5 further comprising,

receiving CSI-RS periodically for signal measurement while PDCH signal is not received in the instance in which a small cell serves only UEs of its own.

8. A method for wireless network cell detection and signal quality measurement comprising:

receiving a network signal indicating the quality level measurement is capable of being based on either physical discovery channel (PDCH) or a channel state information reference signal (CSI-RS);

receiving PDCH and CSI-RS configurations from network necessary for performing cell detection and quality level measurement; and

determining to use PDCH signal or CSI-RS or both to perform signal

measurement.

9. The method of claim 8, further comprising:

using PDCH signaling for both detection and measurement within PDCH signal duration.

10. The method of any of claims 8 or 9, further comprising:

using CSI-RS signaling for measurement when measurement cannot be completed during PDCH signaling.

11. The method of any of claims 9- 10, further comprising:

reporting the measurement results to the network indicating which signals were used for measurement.

12. An apparatus comprising at least a processor, a memory associated with the processor, and computer instructions stored by the memory which, when executed in the processor, cause the apparatus to;

receive a network signal to perform cell detection and signal quality measurement based on a physical discovery channel transmission;

perform cell detection/synchronization based on a physical discovery channel (PDCH) transmission; and

perform signal quality level measurement based on the same PDCH transmission.

13. The apparatus of claim 12, wherein the instructions executed in the processor further cause the apparatus to:

receive PDCH configurations necessary for performing cell detection and signal quality measurement;

receive a required duration of PDCH signal necessary for signal quality measurement; and,

measure signal quality for at least the required PDCH signal duration.

14. The apparatus of any of claims 12 and 13, wherein the instructions executed in the processor further cause the apparatus to:

perform cell detection/synchronization on the PDCH signal, and

perform the signal quality measurement based on subsequent PDCH signals.

15. The apparatus of any of claims 12 and 13, wherein the instructions executed in the processor further cause the apparatus to:

perform cell detection/synchronization on received PDCH signals, and perform the signal quality measurement based on the buffered PDCH signals.

16. An apparatus comprising at least a processor, a memory associated with the processor, and computer instructions stored by the memory which, when executed in the processor, cause the apparatus to:

receive a network signal to perform signal quality measurement based on a channel state information reference signal (CSI-RS),

receive physical discovery channel (PDCH) and CSI-RS configurations necessary for performing cell detection and quality level measurement;

perform cell detection/synchronization based on PDCH signals, and

perform signal quality measurement based on the CSI-RS.

17. The apparatus of claim 16, wherein the instructions executed in the processor further cause the apparatus to:

receive PDCH and CSI-RS configurations necessary for performing cell detection and quality level measurement;

perform cell detection/synchronization based on PDCH signals, and

perform signal quality measurement based on the CSI-RS.

18. The apparatus of claim 16, wherein the instructions executed in the processor further cause the apparatus to:

receive the CSI-RS only after UE reports the cell detection to the network.

19. The apparatus of claim 16, wherein the instructions executed in the processor further cause the apparatus to:

receive CSI-RS periodically for signal measurement while PDCH signal is not received in the instance that the small cell serves only UEs of its own.

20. An apparatus comprising at least a processor, a memory associated with the processor, and computer instructions stored by the memory which, when executed in the processor, cause the apparatus to: receive a network signal indicating the quality level measurement is capable of being based on either a physical discovery channel (PDCH) or a channel state information reference signal (CSI-RS);

receive PDCH and CSI-RS configurations necessary for performing cell detection and quality level measurement; and

determine to use PDCH signal or CSI-RS or both to perform signal measurement.

21. The apparatus of claim 20, wherein the instructions executed in the processor further cause the apparatus to:

use PDCH signaling for both detection and measurement within PDCH signal duration.

22. The apparatus of claim 20 or 21 , wherein the instructions executed in the processor further cause the apparatus to:

use CSI-RS signaling for measurement when measurement cannot be completed during PDCH signaling.

23. The apparatus of claim 21 or 22, wherein the instructions executed in the processor further cause the apparatus to:

report the measurement results indicating which signals were used for

measurement.

24. A computer program product comprising a computer readable medium with computer coded instructions therein, said instructions arranged to, when executed in a processor, cause a device to perform:

receiving a network signal to perform cell detection and signal quality

measurement based on a physical discovery channel transmission;

26 T"7 TT 1 l Ao cinrn¹ performing signal quality level measurement based on the same PDCH

transmission.

25. The computer program product of claim 24, having instructions to further cause the device to perform:

measuring signal quality for at least the required PDCH signal duration.

26. The computer program product of any of claims 24 or 25, having instructions to further cause the device to perform:

performing cell detection synchronization on the PDCH signal, and

performing the signal quality measurement based on subsequent PDCH signals.

27. The computer program product of any of claims 24 or 25, having instructions to further cause the device to perform:

performing cell detection/synchiOnization on received PDCH signals, and performing the signal quality measurement based on the buffered PDCH signals.

28. A computer program product comprising a computer readable medium with computer coded instructions therein, said instructions arranged to, when executed in a processor, cause a device to perform:

receiving a network signal to perform signal quality measurement based on a channel state information reference signal (CSI-RS),

receiving physical discovery channel (PDCH) and CSI-RS configurations necessary for performing cell detection and quality level measurement;

27 1 lAo nnnT¹

29. The computer program product of claim 28, having instructions to further cause the device to perform:

30. The computer program product of claim 28 or 29, having instructions to further cause the device to perform:

31. The computer program product of claim 29 or 30, having instructions to further cause the device to perform:

reporting the measurement results indicating which signals were used for measurement.

32. An apparatus comprising:

means for receiving a network signal to perform cell detection and signal quality measurement based on a physical discovery channel transmission;

means for performing cell detection/synchronization based on a physical discovery channel (PDCH) transmission; and

means for performing signal quality level measurement based on the same PDCH transmission.

33. The apparatus of claim 32 further comprising:

means for receiving PDCH configurations necessaiy for performing cell detection and signal quality measurement;

means for receiving a required duration of PDCH signal necessary for signal quality measurement; and,

means for measuring signal quality for at least the required PDCH signal duration.

34. The apparatus of any of claims 32 or 33 further comprising:

means for performing cell detection/synchronization on the PDCH signal, and means for performing the signal quality measurement based on subsequent PDCH signals.

35. The apparatus of any of claims 32 or 33 further comprising:

means for buffering incoming PDCH signals,

means for performing cell detection/synchronization on received PDCH signals, and

means for performing the signal quality measurement based on the buffered PDCH signals.

36. An apparatus comprising:

means for receiving a network signal to perform signal quality measurement based on a channel state information reference signal (CSI-RS),

means for receiving physical discovery channel (PDCH) and CSI-RS

configurations necessary for performing cell detection and quality level measurement; means for performing cell detection/synchronization based on PDCH signals, and means for performing signal quality measurement based on the CSI-RS.

37. The apparatus of claim 36 further comprising:

means for receiving the CSI-RS only after UE reports the cell detection to the network.

38. The apparatus of claim 36 further comprising:

means for receiving CSI-RS periodically for signal measurement while PDCH signal is not received in the instance in which the small cell serves only UEs of its own.

An apparatus comprising: means for receiving a network signal indicating the quality level measurement is capable of being based on either physical discovery channel (PDCH) or a channel state information reference signal (CSI-RS);

means for receiving PDCH and CSI-RS configurations necessary for performing cell detection and quality level measurement; and

means for determining to use PDCH signal or CSI-RS or both to perform signal measurement.

40. The apparatus of claim 39 further comprising:

means for using PDCH signaling for both detection and measurement within PDCH signal duration.

41. The apparatus of any of claims 39 and 40 further comprising:

means for using CSI-RS signaling for measurement when measurement cannot be completed during PDCH signaling.

42. The apparatus of any of claims 40 and 41 further comprising:

means for reporting the measurement results indicating which signals were used for measurement.