WO2014056174A1

WO2014056174A1 - Power saving in cellular networks

Info

Publication number: WO2014056174A1
Application number: PCT/CN2012/082806
Authority: WO
Inventors: Wei Hong; Haiming Wang; Jing HAN; Pengfei Sun; Wei Bai; Na WEI; Chunyan Gao; Erlin Zeng
Original assignee: Broadcom Corporation
Priority date: 2012-10-11
Filing date: 2012-10-11
Publication date: 2014-04-17

Abstract

Providing a sleep mode for network nodes in a wireless communication network. In sleep mode the node broadcasts either zero signals or a subset of normal operating mode signals in order to save power. An uplink signal from user equipment requesting service may contain an wakeup signal to restore normal operation. The uplink signal may also be used for uplink synchronization or random access. A downlink confirmation signal confirms that the node is prepared to deliver normal service. In a configuration of small cells communicatively associated with a macro network node, a method for providing a sleep mode for the small cells. The macro cell requests a user equipment (UE) to send a wake-up signal to which responding small cells answer with a wake-up detected signal. The macro node signals small cells to transmit pilot signals that are measured by the UE to determine which small cell services the UE.

Description

POWER SAVING IN CELLULAR NETWORKS

TECHNOLOGICAL FIELD

The various embodiments described herein relate to the field of mobile cellular communications networks, in particular to reducing power consumption in network nodes and cell locations.

BACKGROUND

Energy consumption in cellular networks has rapidly moved from an area of low priority to a focus area of the whole telecommunication community. The two most important drives for improved energy efficiency for mobile-networks operation are: a number of operators experiencing increased electricity costs for network operation; and an increased awareness in the society of how energy use relates to green-house gas emissions and global wanning. Consequently, in a new research initiative called EARTH, (Energy Aware Radio and neTwork tecHnologies) industry and academia have joined forces in addressing energy consumption in mobile systems.

Power consumption has always been carefully handled for user equipment (UE) in Long Term Evolution (LTE) standardization due to the limited power supplies. However, the power consumption on the network side was generally less mentioned. The network was deemed as power sufficient and the focus was more on the network capacity and coverage. However, the situation is changing due to the rapidly increasing concern with the carbon footprint and the operator cost. Although the cellular communications industry only accounts for a relatively small portion of the overall energy consumption of human being's activity, it is imperative to make it more power efficient given that the mobile communication sector is forecast to triple by 2020. Current LTE evolved Node Bs (eNB) must keep on transmitting downlink (DL) signals regardless if there is UE to serve. These signals include broadcast signals such as primary and secondary synchronization signals and master information block (PSS/SSS/MIB) and common reference signal (CRS). This mandatory transmission wastes a great amount of energy as the network is under low load most of the time. Significant power saving is possible if future wireless networks could intelligently avoid these wastes.

Another use case is the local area network, where the cell size is considerably smaller than a typical macro cell. In this case the local area cell (also termed "small cells" or "pico cells") may serve only a few UEs; sometimes there are no UE served and the load may undergo large variance from time to time. A move towards small cells is seen as one of the possible remedies for satisfying escalating data rate requirements in cellular networks. With shorter coverage ranges of tens or few hundreds of meters, small cells lend themselves well to the use of higher frequency bands that are suited for high data rates. An enhanced Local Area (eLA) small cell is a scenario in which there are many small cells densely deployed in quite high frequency for offloading and a macro network cell (also termed "macro network node" or "macro eNB") is deployed for mobility in a lower frequency. See Fig. 1, illustrating an example macro eNB cell 100 and small (pico) cell 120 configuration. From an equally important eco-sustainability perspective, a concern linked with the use of small cells is the resultant significant increase in network energy consumption. While each small cell base station (BS) itself consumes a relatively small amount of power, a wide scale deployment involving tens or hundreds of thousands of pico cells means that the total network energy consumption can soar to a significantly high value. As a result, employment of energy-efficient techniques in operation of the network that can reduce the impact of large scale small cell deployments on the total network energy consumption is important.

Among potential power efficiency techniques, introducing a sleeping mode is seen as a promising way to reduce power consumption during a low network load condition, for example, in a rural area solar powered eNB or in densely deployed local area picocells (small cells). The eNB transmits a reduced number of broadcast signal or totally rums off in the sleeping mode so that the power amplifier (PA) could be turned off most of the time to save power. Then, the eNB wakes up when service is needed.

BRIEF SUMMARY

A method, apparatus and computer program product are therefore provided in accordance with one embodiment in order to implement a sleep mode. As such, the method, apparatus and computer program product of an example embodiment may allow for continued network operations while utilizing power efficiently.

The first of several embodiments is a method that provides a sleep mode for a network node, generally an eNB. The method comprises causing transmission of either zero broadcast signals or a minimal subset of normal operating signals while in sleep mode. An indicator of sleeping status may be indicated in the minimal signals transmitted during sleep mode. While in sleep mode, if transmitting a subset of normal signals, the subset could consist of primary synchronization sequence (PSS) and secondary synchronization sequence (SSS) signals. The subset may alternatively consist of PSS, SSS and master information block (MIB) signals. Again alternatively, the subset may consist of the primary discovery channel (PDCH). Certain nodes may broadcast no signals during sleep mode. The sleeping node may receive an wakeup signal uplink from user equipment (UE) seeking network service to restore the node to normal operating mode. That signal may be received over a normal channel, or may be sent over a newly defined channel, or a legacy LTE physical channel reused for sleep mode. The uplink wakeup signal may serve more than one purpose; it may be used for uplink synchronization and/or for starting the random network access process. The awakened node may be configured to send a downlink confirmation signal indicating that the node is waking from sleep mode. The node may combine reference signals with the downlink confirmation signal to enable signal measurement by UE. Upon restoration of normal operation, the node may be configured to transmit system information block (SIB) signals. The normal operating signals may include a PDCH signal containing system information to restore normal mode.

Another method provides sleep mode operation in small cell clusters managed by a macro network node. A sleep mode may be provided in the computer instructions for the small cells. The macro node may cause a wakeup signal transmission (WST) to be sent to a UE to request the UE to transmit wakeup signals on predefined network resources using a predefined sequence via predefined signaling. The macro node may receive a wakeup signal detected (WSD) signal from one or more small cells. The macro node may cause a pilot signaling request to be sent via predefined signaling to the small cells. UE may be configured by the macro node to measure the pilot signals of the one or more small cells that have awakened from sleep mode. Based on UE measurement reports, the macro node may cause a small cell best situated to handle the UE traffic to be signaled to handle the UE. The macro node may cause any remaining unused small cells to be signaled to return to sleep mode until they are needed.

Another method implements sleep mode operation in small cells. Sleep mode operational instructions may be provided for the small cell processors. The small cells may monitor certain predefined network resources during sleep mode at predefined periods. Certain small cells may receive wakeup signal transmission (WST) in a predefined sequence via predefined signaling on predefined network resources. In response, awakened small cells may send a wakeup signal detected (WSD) signal to the macro node. This signal may be combined with a signal plus interference to noise ratio value of the detected wakeup signal. Then the small cells may receive a pilot signaling request via predefined signaling, although the signaling format and resources may be configured in the predefined signaling of the pilot signal request. The small cells may send pilot signal transmission according to a specified pilot signaling format; the pilot signal may comprise one of radio resource control (RRC), medium access control control element (MAC CE) or LI signaling. Based on measurements of the pilot signals reported to the macro node by UE, a small cell receives a handover signal (HO) from the macro node, selecting that small cell to handle the UE traffic, while unused small cells may receive signals to return to sleep mode via predefined signaling from the macro node.

Another embodiment provides an apparatus comprising at least a processor, a memory communicatively associated with said processor and having computer instructions stored therein, said instructions when executed by the processor causing the apparatus to perform providing a sleep mode in a network node, and causing transmission during sleep mode a reduced number of or zero broadcast signals from said network node, the said reduced number of signals comprising a subset of broadcast signals transmitted in normal operating mode. The apparatus may further perform receiving an uplink wakeup signal to restore normal network node operating mode, using the uplink wakeup signal for uplink synchronization, using the uplink wakeup signal to begin random access to the network, and causing a downlink confirmation signal to be sent in a predefined format to indicate that the network node is waking from sleep mode to deliver normal operating mode service. The subset of downlink signals transmitted in sleep mode may consist of primary synchronization sequence (PSS) and secondary synchronization sequence (SSS), or of PSS and SSS plus the Master Information Block (MIB), or the primary discovery channel (PDCH). The node may broadcast zero signals in sleep mode. Once awakened, the node may cause system information to be transmitted upon restoration of the node's normal operating mode from sleep mode. It may do so by causing MIB and system information block (SIB) signals to be transmitted, or causing a PDCH signal containing system information to be transmitted upon restoration of the node's normal operating mode from sleep mode.

In another embodiment for sleep mode operation of a small cell cluster, an apparatus is provided comprising at least a processor, a memory communicatively associated with said processor and having computer instructions stored therein, said instructions when executed by the processor causing the apparatus to cause sending from a macro network node a wake-up signal transmission (WST) requesting user equipment (UE) to transmit wake-up signals on predefined network resources using a predefined sequence via predefined signaling. The instructions cause the apparatus to further perform receiving a wake-up signal detected (WSD) signal sequence at the macro node. The apparatus may cause a pilot signaling request to be sent via predefined signaling, and may configure UE via predefined signaling to perform measurement on one or more small cells during pilot signaling. The instructions may cause the apparatus to further perform signaling handover (HO) to a small cell to handle UE signal traffic and signaling one or more small cells to enter sleep mode via predefined signaling.

Another embodiment addresses the small cell apparatus in sleep mode. This apparatus comprises at least a processor, a memory communicatively associated with said processor and having computer instructions stored therein, said instmctions when executed by the processor causing the apparatus to perform providing a sleep mode in one or more small network cells arranged in communicating proximity to a macro network node for management of the small cells by the macro node and monitoring predefined network resources at predefined periods during sleep mode. The instmctions may cause the apparatus to further perform receiving a wake-up signal transmission (WST) having a predefined sequence via predefined signaling on said predefined network resources and causing a wake-up signal detected (WSD) signal sequence to be sent to said macro node. The WSD signal may be combined with a signal plus interference to noise ratio (SINR) value of the detected wake-up signal. The instructions may cause the apparatus to further perform receiving a pilot signaling request via predefined signaling and causing pilot signaling transmission to be sent according to specified pilot signaling format. The instructions may cause the apparatus to further perform receiving from the macro node one of a handover signal (HO) or a signal to enter sleep mode via predefined signaling.

A computer program product is provided comprising a non-transitory computer readable medium having computer coded instructions stored therein, said instructions causing an apparatus to cause transmission during sleep mode of a reduced number of or zero broadcast signals from said network node, the said reduced number of signals comprising a subset of broadcast signals transmitted in normal operating mode; indicating sleeping status of the network node in the reduced number of broadcast signals transmitted during sleep mode; receiving an uplink wakeup signal to restore normal network node operating mode, and causing a downlink confirmation signal to be sent in predefined fonnat to indicate that the network node is waking from sleep mode to deliver normal operating mode service. The computer program instructions may further cause an apparatus to cause system information to be transmitted upon restoration of the node's normal operating mode from sleep mode.

In another embodiment, a computer program product is provided comprising a non-transitory computer readable medium having computer coded instructions stored therein, said instructions causing an apparatus to cause sending from a macro network node a wake-up signal transmission (WST) requesting user equipment (UE) to transmit wake-up signals on predefined network resources using a predefined sequence via predefined signaling, and receiving a wake-up signal detected (WSD) signal sequence at the macro node. The program instructions may further cause an apparatus to cause sending of a pilot signaling request via predefined signaling to small cells, configuring UE via predefined signaling to perform measurement on one or more small cells during pilot signaling, causing signaling of a small cell to handle UE signal traffic, and causing signaling of one or more small cells to enter sleep mode via predefined signaling.

A further embodiment provides a computer program product comprising a non- transitory computer readable medium having computer coded instructions stored therein, said instructions causing an apparatus to perform arranging one or more small network cells in communicating proximity to a macro network node for management of the small cells by the macro node, providing a sleep mode in the one or more small cells, and monitoring predefined network resources at predefined periods during sleep mode. The program instructions may further cause an apparatus to perform monitoring predefined network resources at predefined periods during sleep mode, receiving a wake-up signal transmission (WST) having a predefined sequence via predefined signaling on said predefined network resources, causing a wake-up signal detected (WSD) signal sequence to be sent to said macro node, receiving a pilot signaling request via predefined signaling, and causing pilot signaling transmission according to specified pilot signaling format. The program instructions may further cause an apparatus to perform receiving from the macro node one of a handover signal (HO) or a signal to enter sleep mode via predefined signaling.

In another embodiment is an apparatus comprising means for providing a sleep mode in a network node, means for causing transmission during sleep mode of a reduced number of or zero broadcast signals from said network node, the said reduced number of signals comprising a subset of broadcast signals transmitted in normal operating mode, and means for receiving an uplink wakeup signal to restore normal network node operating mode. The apparatus may further comprise means for receiving the uplink wakeup signal over a newly defined channel, means for receiving the uplink wakeup signal over a reused LTE legacy physical channel, means for using the uplink wakeup signal for uplink synchronization, and/or means for using the uplink wakeup signal to begin random access to the network. The apparatus may further comprise means for causing a downlink confirmation signal to be sent in a predefined format to indicate that the network node is waking from sleep mode to deliver normal operating mode service, means for combining reference signals with the downlink confirmation signal to enable node signal measurement, and means for causing system information to be transmitted upon restoration of the node's normal operating mode from sleep mode.

In small cell cluster configuration, an apparatus is provided comprising means for causing sending from a macro network node a wake-up signal transmission (WST) requesting user equipment (UE) to transmit wake-up signals on predefined network resources using a predefined sequence via predefined signaling, means for receiving a wake-up signal detected (WSD) signal sequence at the macro node, and means for causing a pilot signaling request to be sent via predefined signaling. The apparatus may further comprise means for configuring a UE via predefined signaling to perform measurement on one or more small cells during pilot signaling, means for causing signaling of a small cell to handle UE signal traffic, and means for causing signaling of one or more small cells to enter sleep mode via predefined signaling.

Another apparatus is provided comprising means for providing a sleep mode in one or more small network cells arranged in communicating proximity to a macro network node for management of the small cells by the macro node, means for monitoring predefined network resources at predefined periods during sleep mode, means for receiving a wake-up signal transmission (WST) having a predefined sequence via predefined signaling on said predefined network resources, and means for causing a wake-up signal detected (WSD) signal sequence to be sent to said macro node. The apparatus may further comprise means for receiving a pilot signaling request via predefined signaling, means for causing sending of a pilot signaling transmission according to specified pilot signaling fonnat, and means for receiving from the macro cell one of a handover signal (HO) or a signal to enter sleep mode via predefined signaling.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Having thus described certain 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 drawing of a small cell network under management of a macro network node;

Fig. 2 is a schematic drawing of the basic elements of a wireless communication network;

Fig. 3 is a block diagram of an apparatus that may be specifically configured in accordance with an example embodiment of the present invention and that may be embodied by any one of a mobile terminal, a network node, or a small cell.

Figs. 4a, 4b and 4c are signaling charts illustrating sleep mode signaling in an eNB in accordance with an example embodiment of the present invention.

Figs. 5a is a schematic diagram of a small cell network in sleep mode in accordance with an example embodiment of the present invention.

Fig. 5b is a schematic diagram of a small cell network awakening from sleep mode in accordance with an example embodiment of the present invention. Fig. 5c is a schematic diagram of a small cell network macro network node signaling the small cells to broadcast pilot signaling in accordance with an example embodiment of the present invention.

Fig. 5d is a schematic diagram of a small cell network macro network node selecting a small cell to handle UE signal traffic in accordance with an example embodiment of the present invention.

Fig. 6 is a flow chart of a method providing sleep mode in a network node in accordance with an example embodiment of the present invention.

Fig. 7 is a flow chart of a method providing sleep mode control in a macro network node managing a small cell cluster in accordance with an example embodiment of the present invention.

Fig. 8 is a flow chart of a method providing sleep mode operation in small cells in accordance with an example embodiment of the present invention.

DETAILED DESCRIPTION

Example embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, the invention may be embodied in many different fonns 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 reference numerals 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 memoiy (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.

As used in this application, the term "circuitry" refers to all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuity) and (b) to combinations of circuits and software (and/or firmware), such as (as applicable): (i) to a combination of processor(s) or (ii) to portions of processor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or a server, to perform various functions) and (c) to circuits, such as a microprocessors) or a portion of a microprocessors), 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 in this application, including in any claims. As a further example, as used in this application, the term "circuitry" would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term "circuitry" would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or application specific integrated circuit for a mobile phone or a similar integrated circuit in server, a cellular network device, or other network 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, tablet 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 small cell 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 Access Network (UTRAN), a GSM Edge Radio Access Network (GERAN) or other type of network. Referring 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 memory 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.

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 ( CU), 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 commumcation 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.

Apparatus 20 may also or alternatively be embodied as an access point 12, such as an eNB, particularly as to the communications interface 28, the processor 22 and the memory 24. Apparatus 20 may also or alternatively be embodied as a pico (small) cell 120 (Fig. 1). In these embodiments the user interface is normally not present.

In some example embodiments, such as instances in which the apparatus 20 is embodied by a mobile temiinal 10, the apparatus may also 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, an eNB 12, or a picocell 120, the processor 22 is the means for executing various functions that may be specified for preparing the mobile terminal, eNB or picocell 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, eNB or picocell may include the processor and/or the memory with computer code instructions stored therein. The communications interface 28 is the means for transmitting and receiving signals between a mobile terminal 10 and a network entity 12 (eNB, picocell) that are then processed to determine appropriate functions to be executed by the processor. In a first embodiment, a scheme for an access point, hereinafter referenced as an eNB by way of example but not of limitation, wake up based on uplink (UL) signaling is presented. The scheme allows eNB to quickly switch between sleeping and nonnal mode based on need. By waking up the eNB via UL signals, eNB reduces its broadcast signal transmission during sleeping, which achieves power saving. In addition, the UL signaling wake up does not rely on the backhaul connection.

This embodiment provides a new procedure that allows eNB to enter sleeping when eNB needs to save power due to low load or for other reasons. The procedure allows eNB to wake up based on reception of a UL wakeup signal over the air interface.

Under this procedure eNB transmits a reduced number or zero broadcast signal during the sleep mode. The reduced number of signals may not necessarily contain all the information required for a UE's initial access. The reduced number of broadcast signals may an indicator of the sleep status of an eNB.

A UE or neighbor eNB may send the wakeup signal to wake up a sleeping eNB.

A UE may know the sleep status of an eNB based on the downlink (DL) broadcast signals. A UE may send the wake up signal upon the detection of certain predefined DL signals or determination of the cell signal strength above a threshold.

In current LTE, an eNB must transmit a predetermined set of DL signals all the time no matter whether there is an UE to serve. See Fig. 4a. These signals include: PSS, SSS, CRS, MIB, SIB (1, 2, 3, 4, 5). However, during the sleep mode, eNB may not transmit all of these signals so as to realize reduced power consumption. Some possible options for sleeping mode DL signals are:

1. PSS/SSS only

2. PSS/SSS+MIB

3. PDCH (physical discovery channel) Correspondingly, the transmission of the UL wakeup signal could be linked to these DL signals. Therefore, the procedure of the UL/DL switch could be:

1. PSS/SSS->UL wakeup signal->MIB->SIBs

2. PSS/SSS->MIB->UL wakeup signal->SIBs

3. PSS/SSS->UL wakeup signal-> PDCH containing system information

4. PDCH->UL wakeup signal->System information

Figs. 4b and 4c show examples of how UE or a neighbor eNB transmits the UL wakeup signal after detecting a sleeping eNB. After detecting 'A' the PSS/SSS (Fig. 4b) or MIB (Fig. 4c), UE sends the UL wakeup signal in the predetermined time/frequency resource. Note that in Figures 4a-4c either UE or a neighbor node is shown as detecting the sleeping node downlink signals and returning a wakeup signal (activation signal). UE may transmit the UL wakeup signal following a pre-defined timing delay after detecting the minimal DL signals. And when the sleeping eNB transmits no DL signals, the reference could be based on a neighbor cells' DL signals if the coverage is somehow overlapped. There may be other implementation options for the wake up procedure that are not shown here.

In another embodiment, UL wakeup signaling in the air interface is defined, which may be used to enable an eNB sleep and wake up scheme. In this embodiment, UE may send the UL wakeup signal before being able to access the eNB's cell. A channel is defined for UL wakeup signaling, which could be a new channel or may be a reused LTE legacy physical channel. A resource determination scheme for the UL wakeup signal is defined, which may be based on the reference of DL broadcast signals or explicitly infonned from eNBs. The UL wakeup signal could also be used for other puiposes, such as UL synchronization or random access. The UL wakeup signal could reuse the LTE physical channels, such as the physical uplink control channel (PUCCH), the physical random access channel (PRACH), the physical uplink shared channel (PUSCH) etc. An efficient choice is to use the PRACH channel, whose long preamble is suitable for UL unsynchronized transmission with high reliability in low SINR. Some of the PRACH resources could be reserved for UL wakeup signal. These resources are only accessible when the eNB is in sleep mode. When eNB is in normal mode, these resources are occupied as normal PRACH resources. In this way no extra resources need to be introduced for the UL wakeup signal. Another option is to define a new channel for the UL wakeup signal if necessary.

Proper schemes are provided so that UE always knows where to transmit the UL wakeup signal. When eNB broadcasts DL signals in the sleeping mode, the most efficient way is to link the UL resource to the DL reference. For instance, UE transmits the UL wakeup signal following a pre-defined timing delay after detecting the minimal DL signals. When the sleeping eNB transmits no DL signals, the reference could be based on neighbor cells' DL signals if the coverage is somehow overlapped.

If the system is time division duplex (TDD) based, the UL wakeup signal could be allocated in DL subframes. In this way the false alarm triggered by normal UL transmission is avoided. Receiving signals at DL subframes is not difficult for the sleeping eNB. Other UL functions may be jointly triggered by the UL wakeup signal; for example, eNB could estimate the UL timing error of the UE or perform a random access procedure when the UL wake up signal is received. eNB wake up may not be automatic. Once a sleeping eNB successfully detects the UL wakeup signal, it may make a decision whether to wake up to serve the UE. The eNB may send back a confirmation signal to tell the UE the decision. The confirmation signal could be transmitted using predefined resources or linked to the UL wakeup signal resource. If UE does not receive the confirmation signal during the pre-defined window, the UE may increase the signal power and transmit the UL wakeup signal again.

In addition to the confirmation signal, the eNB may transmit associated reference signals that could help UE do measurements, e.g. to estimate reference signal received power (RSRP) or reference signal received quality (RSRQ) based on the channel state information - reference signal (CSI-RS). Once eNB decides to wake up and UE knows the decision via confirmation, a normal LTE transmission could be initiated, such as perfonning system information acquisition or radio resource control (RRC) connection request.

In summary, these embodiments enable a UL signal-based eNB wake up scheme, which provides opportunity to achieve more power efficiency than existing alternatives. A user equipment attempting to access the network or a neighbor eNB may use the air interface to wake up a sleeping eNB only when the UE has network traffic requiring the eNB to perform normally.

Another embodiment is provided in which a macro eNB may offload traffic to small cells (picocells) and define a procedure for activating the small cells. Regarding small cells, the cell coverage area is considerably smaller than that of a typical macro network node. In this case the local area cell (also termed "small cells" or "pico cells") may serve only a few UEs; sometimes there are no UE served and the load may undergo large variance from time to time. A macro eNB and one or more small cells are arranged in communicating proximity; that is, the macro network node (eNB) may exchange signal protocols with the small cells and act as the access point to the network for each of the small cells. The small cell(s) handle network access for nearby UE, assuming the signaling overhead tasks that would otherwise be handled by the macro eNB. Small cells can be provided with a sleep mode as well. Waking a small cell from sleep mode requires the involvement of both UE and the macro network node.

The macro network node requests UE to send a wake-up signal for nearby small cells at certain resources using a specific sequence via a new defined signaling, which could be a new RRC, medium access control control element (MAC CE) or LI signaling. The wake-up signal sequence and resource location could be pre-defined or configured in the new signaling.

The macro network node requests small cells to detect the wake-up signal on a predefined resource location or on configured resources via X2, fiber, over-the-air connection (OTAC), etc. Small cells may send the detected sequence with or without a SINR value to the macro eNB using new signaling via X2, fiber, OTAC, etc. The macro eNB could request certain small cells to send a pilot signal for UE tracking and measurement using newly defined signaling. The pilot signal format/location could be predefined or configured in the newly defined signaling.

The macro eNB could configure UE to do measurement on small cells using newly defined signaling including information about the small cell pilot signal, which could be a new RRC, MAC CE or LI signal. The small cells' pilot signal format/lo cation could be predefined or indicated in the newly defined signaling. The macro eNB could request other small cells to sleep again via newly defined signaling. An example follows below.

Referring to Fig. 5 a, at time T, the macro eNB 100 wants to offload UEFs 402 traffic to a small cell 120. eNB sends a Wake-up Signal Transmission (WST) signal to request UE1 402 to send a wake-up signal at predefined location A with a predefined period B using sequence C. Small cells 120 listen to these predefined resources at a predefined period in their sleep mode. Referring to Fig. 5b, at time T+t, small cells 1, 2 and 3 (120) detect UEl 's wake- up signaling sequence with SINR higher than a threshold, and then send a Wake-up Signaling Detected (WSD) signal to macro eNB 100.

After receiving small ceil 1, 2 and 3's notification, see Fig. 5c, the macro eNB 100 sends Pilot Signaling Transmission (PST) signals to small cells 1, 2 and 3 (120) to request pilot signaling from them at locations LI, L2 and L3 respectively with period PI, P2 and P3. At the same time, eNB 100 sends a Pilot Signaling Detection (PSD) signal to UEl 402 to cause UEl to measure small cells 1, 2 and 3's pilot signaling. It is possible that LI, L2, L3 could be the same and PI, P2, P3 could be the same.

Referring to Fig. 5d, after receiving UEl 's measurement reports for small cells' 1, 2 and 3 (120) pilot signals, eNB 100 sends a handover signal (HO) UE to picocell 2, which would serve UE best of the small cells, and sends Sleep signaling to picocells 1 and 3. After receiving Sleep signaling from macro eNB 100, small cells 1 and 3 turn off their pilot signaling transmissions and only detect a future UE's wake-up signaling at predefined occasions in their sleep mode. Referring to Figs. 6, 7 and 8, the methods of the described embodiments are illustrated. Fig. 6 shows the process for network node (generally eNB) sleep mode operation. Sleep mode computer instructions are provided 502 for the processor in the node to operate the node in sleep mode. Thus, the apparatus 20 embodied by the node, such as the processor 22, the communications interface 28 or the like, may be configured to receive the sleep mode computer instructions. When the node is sleeping, either zero broadcast signals or a minimal subset of normal signals are caused to be transmitted from the apparatus 20 embodied by the node 506, such as from the processor 22, the communications interface 28 or the like. The node remains quiescent until the apparatus 20 embodied by the node, such as from the processor 22, the communications interface 28 or the like, receives 510 an wakeup signal on uplink from a user equipment (UE) seeking network service. The apparatus 20 embodied by the awakened node, such as from the processor 22, the communications interface 28 or the like, may cause a confirmation signal 514 to be sent indicating it is waking from sleep mode. Then the apparatus embodied by the node, such as from the processor 22, the communications interface 28 or the like, may cause system information 518 to be sent that enables the node and UE to resume normal communication operation.

The sleep mode operation concept can be extended to network node configurations comprising clusters of picocells under the management of a macro network node. Figs. 7 and 8 show the operations that may be implemented to incorporate sleep mode into small cell network nodes. Fig. 7 illustrates operation of the macro cell when it determines to offload UE signal traffic to small cells that may be at rest in sleep mode. The apparatus 20 embodied by the macro cell, such as from the processor 22, the communications interface 28 or the like, may cause a wakeup signal request to be sent to UE 604 that triggers the UE to send a wakeup signal to nearby small cells. Certain small cells receive the UE wakeup signal and the macro node is informed as it receives a wakeup signal detected (WSD) signal 608 from one or more of the small cells. Thus, the apparatus 20 embodied by the macro node, such as from the processor 22, the communications interface 28 or the like, may be configured to receive a WSD signal from one or more of the small cells. Upon notification that one or more small cells have revived, the apparatus 20 embodied by the macro node, such as from the processor 22, the communications interface 28 or the like, may casuse a request to be sent to UE 612 to commence sending a pilot signal. The apparatus 20 embodied by the macro node, such as from the processor 22, the communications interface 28 or the like, may also be configured to cause a Pilot Signal Detection (PSD) message 616 to be sent configuring UE to measure pilot signal transmitted by the awakened small cell(s). Once the UE reports the measurement results to the macro node, the apparatus 20 embodied by the macro node, such as from the processor 22, the communications interface 28 or the like, may cause one small cell to be signaled to handle the UE signal traffic 620 based on the measurement that shows which small cell is best able to handle the UE. At that point other awakened small cells are superfluous and can be signaled 624 to return to sleep mode.

Fig. 8 shows the sequence at the small cells. The small cells are configured 704 with processor instructions to implement sleep mode and wakeup procedures. Thus, the apparatus 20 embodied by a small cell may be configured to receive processor instructions to implement the sleep mode and wakeup procedures. In sleep mode the apparatus 20 embodied by a small cell, such as from the processor 22, the communications interface 28 or the like, may, at a minimum, monitor predefined network resources 706 so that they may be awakened with a proper signal. The apparatus 20 embodied by a small cell, , such as from the processor 22, the communications interface 28 or the like, may receive a wakeup signal 708 from UE, which indicates that a UE needs network access. The apparatus 20 embodied by a small cell(s) , such as from the processor 22, the communications interface 28 or the like, may cause a wakeup signal detected (WSD) signal 711 to be sent to the macro node that manages the small cell cluster. In return, the macro node sends a signal 715 requesting the awakened small cell(s) to send pilot signals. As such, the apparatus 20 embodied by the small cell, such as from the processor 22, the communications interface 28 or the like, may be configured to receive the signal 715 from the macro node. The apparatus 20 embodied by a small cell, such as from the processor 22, the communications interface 28 or the like, may also be caused to send pilot signals 719 that are measured by the UE seeking service. The UE informs the macro node of its measurements, the macro node selects the small cell best positioned to handle the UE signal traffic and sends a handover signal to that small cell 723. Unselected small cells that may have awakened in response to the UE wakeup signal may be returned to sleep mode until they are needed by a signal from the macro node 723.

As described above, Figures 6-8 are flowcharts of a method, apparatus and program product according to example embodiments of the invention. It will be understood that each block of the flowcharts, and combinations of blocks in the flowcharts, may be implemented by 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 memory device 24 of an apparatus 20 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 embody a mechanism for implementing the functions specified in the flowchart blocks. These computer program instructions may also be stored in a non-transitory computer-readable storage memory (as opposed to a transmission medium such as a carrier wave or electromagnetic signal) that may direct a computer or other programmable apparatus to function in a particular manner, such that the instructions stored in the computer-readable 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 block(s). As such, the operations of Figures 6-8, 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 x-x 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 configured to perform the functions shown in Figures 6-8 (e.g., via configuration of the processor), thereby transforming 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, combinations of operations for performing the specified functions and program instructions 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 operations, or combinations of special purpose hardware and computer instructions.

The foregoing description is an example of implementing sleep mode for both eNB and small cells with wake up procedures for both. Energy savings for each type of node can be realized with sleep/wake up processes implemented in the network. As the number of network nodes multiplies in the future it is important that each node consume as little energy as possible to keep the overall energy consumption from becoming both environmentally undesirable and prohibitively costly. Many modifications and other embodiments 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 purposes of limitation.

The following abbreviations/acronyms appear in the above description and may also appear in the claims.

BS Base Station

CRS Common Reference Signal

CSI-RS Channel State Information-Reference Signal

DL Downlink

eLA Enhanced Local Area

eNB Enhanced Node B. Name for Node B in LTE

HO Handover

LTE Long Term Evolution

LTE-A Long Term Evolution Advanced

MAC CE Medium Access Control Control Element

MIB Master Information Block

SIB System Information Block

OTAC Over The Air Connection

PA Power Amplifier

PDCH Physical Discovery Channel

PRACH Physical Random Access Control Channel

PSS Primary Synchronization Sequence

PST Pilot Signal Transmission

PUCCH Physical Uplink Control Channel

PUSCH Physical Uplink Shared Channel

SINR Signal To Interference Plus Noise Ratio

sss Secondary Synchronization Sequence RRC Radio Resource Control

RSRP Reference Signal Received Power RSRQ Reference Signal Received Quality SCC Secondary Cell Carrier

TDD Time Division Duplexed

UE User Equipment

UL Uplink

WST Wakeup Signal Transmission WSD Wakeup Signal Detected

Claims

WHAT IS CLAIMED IS:

1. A method comprising:

providing a sleep mode in a network node,

causing transmission during sleep mode of a reduced number of or zero broadcast signals from said network node, the said reduced number of signals comprising a subset of broadcast signals transmitted in normal operating mode.

2. The method of claim 1 further comprising:

including an indicator of the sleeping status of the network node in the reduced number of broadcast signals transmitted during sleep mode.

3. The method of claim 1 further comprising:

receiving an uplink wakeup signal to restore normal network node operating mode.

4. The method of claim 3, further comprising:

receiving the uplink wakeup signal over a newly defined channel.

5. The method of claim 3, further comprising:

receiving the uplink wakeup signal over a reused long term evolution (LTE) legacy physical channel.

6. The method of claim 3 , further comprising:

using the uplink wakeup signal for uplink synchronization.

7. The method of claim 3, further comprising:

using the uplink wakeup signal to begin random access to the network.

8. The method of claim 3, further comprising:

causing a downlink confirmation signal to be sent in predefined format to indicate that the network node is waking from sleep mode to deliver normal operating mode service.

9. The method of claim 8, further comprising:

combining reference signals with the downlink confirmation signal to enable node signal measurement.

10. The method of claim 1 wherein:

the subset of downlink signals transmitted in sleep mode consist of primary synchronization sequence (PSS) and secondary synchronization sequence (SSS).

11. The method of claim 1 wherein:

the subset of downlink signals transmitted in sleep mode consist of PSS and SSS plus the Master Information Block (MIB).

12. The method of claim 1 wherein:

the subset of downlink signals transmitted in sleep mode consist of the primary discovery channel (PDCH).

13. The method of claim 1 wherein:

in sleep mode the node transmits zero broadcast signals.

14. The method of any of claims 3 to 13 further comprising:

causing transmission of MIB and system information block (SIB) signals upon restoration of the node's normal operating mode from sleep mode.

15. The method of any of claims 3 to 13 further comprising:

causing transmission of system information block (SIB) signals upon restoration of the node's normal operating mode from sleep mode.

16. The method of any of claims 3 to 13 further comprising:

causing transmission of a physical discovery channel (PDCH) signal containing system information upon restoration of the node's normal operating mode from sleep mode.

17. The method of any of claims 3 to 13 further comprising:

causing transmission of system information upon restoration of the node's normal operating mode from sleep mode.

18. A method comprising:

in a configuration comprising a macro network node arranged in communicating proximity to one or more small network cells for management of the small cells by the macro node,

causing a wake-up signal transmission (WST) to be sent from the macro network node requesting user equipment (UE) to transmit wake-up signals on predefined network resources using a predefined sequence via predefined signaling.

19. The method of claim 18, further comprising:

receiving a wake-up signal detected (WSD) signal sequence at the macro network node from the small network cells.

The method of any one of claims 18 to 19 wherein:

the macro network node is an evolved Node B (eNB).

21. The method of any one of claims 1 to 20, further comprising:

causing a pilot signaling request to be sent via predefined signaling to the small network cells.

22. The method of claim 21 further comprising:

configuring UE via predefined signaling to perform measurement on one or more small cells during pilot signaling.

23. The method of claim 22, further comprising:

causing a small cell to be signaled to handle UE signal traffic.

24. The method of any of claims 22 to 24 further comprising:

causing one or more small cells to be signaled to enter sleep mode via predefined signaling.

25. A method comprising:

arranging one or more small network cells in communicating proximity to a macro network node for management of the small cells by the macro node.

26. The method of claim 25 further comprising:

providing a sleep mode in the one or more small cells.

27. The method of claim 26 further compr

monitoring predefined network resources at predefined periods during sleep mode.

28. The method of claim 27 further comprising:

receiving a wake-up signal transmission (WST) having a predefined sequence via predefined signaling on said predefined network resources.

29. The method of claim 28 further comprising:

causing a wake-up signal detected (WSD) signal sequence to be sent to said macro network node.

30. The method of claim 29 wherein:

the WSD signal is combined with a signal plus interference to noise ratio (SINR) value of the detected wake-up signal.

31. The method of claim 29 further comprising:

receiving a pilot signaling request via predefined signaling.

32. The method of claim 31 wherein:

the pilot signaling format and resources are configured in the predefined signaling of the pilot signaling request.

The method of claim 31 further comprising: causing pilot signaling transmission to be sent according to specified pilot signaling format.

34. The method of claim 33 wherein:

the small cell pilot signal comprises one of radio resource control (RRC), medium access control control element (MAC CE) or LI signaling.

35. The method of claim 33 further comprising:

receiving from the macro network node one of a handover signal (HO) or a signal to enter sleep mode via predefined signaling.

36. An apparatus comprising at least a processor, a memoiy communicatively associated with said processor and having computer instmctions stored therein, said instmctions when executed by the processor causing the apparatus to perform:

providing a sleep mode in a network node,

causing transmission, during sleep mode, of a reduced number of or zero broadcast signals from said network node, the said reduced number of signals comprising a subset of broadcast signals transmitted in normal operating mode.

37. The apparatus of claim 36 wherein the instmctions cause the apparatus to further perform:

indicating sleeping status of the network node in the reduced number of broadcast signals transmitted during sleep mode.

The apparatus of claim 36 wherein the instmctions cause the apparatus to further receiving an uplink wakeup signal to restore normal network node operating mode.

39. The apparatus of claim 38 wherein the instructions cause the apparatus to further perform:

receiving the uplink wakeup signal over a newly defined channel.

40. The apparatus of claim 38 wherein the instructions cause the apparatus to further perform:

receiving the uplink wakeup signal over a reused LTE legacy physical channel.

41. The app ratus of claim 38 wherein the instructions cause the apparatus to further perform:

using the uplink wakeup signal for uplink synchronization.

42. The apparatus of claim 38 wherein the instructions cause the apparatus to further perform:

using the uplink wakeup signal to begin random access to the network.

43. The apparatus of claim 38 wherein the instructions cause the apparatus to further perform:

44. The apparatus of claim 43 wherein the instructions cause the apparatus to further perform:

45. The apparatus of claim 36 wherein:

the subset of downlink signals transmitted in sleep mode consist of primary synchi nization sequence (PSS) and secondary synchronization sequence (SSS).

46. The apparatus of claim 36 wherein:

47. The apparatus of claim 36 wherein:

48. The apparatus of claim 36 wherein:

in sleep mode the node transmits zero broadcast signals.

49. The apparatus of any of claims 38 to 48 wherein the instructions cause the apparatus to further perform:

50. The apparatus of any of claims 38 to 48 wherein the instructions cause the apparatus to further perform:

causing transmission of a PDCH signal containing system information upon restoration of the node's normal operating mode from sleep mode.

51. The apparatus of any of claims 38 to 48 wherein the instructions cause the apparatus to further perform:

52. An apparatus comprising at least a processor, a memory communicatively associated with said processor and having computer instructions stored therein, said instructions when executed by the processor causing the apparatus to perform:

causing a wake-up signal transmission (WST) to be sent from a macro network node requesting user equipment (UE) to transmit wake-up signals on predefined network resources using a predefined sequence via predefined signaling.

53. The apparatus of claim 52 wherein the instructions cause the apparatus to further perform:

54. The apparatus of any one of claims 52 to 53 wherein:

the macro network node is an evolved Node B (eNB).

55. The apparatus of any one of claims 52 to 54 wherein the instructions cause the apparatus to further perfonn:

56. The apparatus of claim 55 wherein:

the pilot signaling format and resources may be configured in the predefined signaling.

57. The apparatus of claim 5 wherein the instructions cause the apparatus to further perform:

configuring UE via predefined signaling to perfonn measurement on one or more small cells during pilot signaling.

58. The apparatus of claim 57 wherein the instructions cause the apparatus to further perfonn:

causing a small cell to be signaled to handle UE signal traffic.

59. The apparatus of claim 58 wherein the instructions cause the apparatus to further perfonn:

60. An apparatus comprising at least a processor, a memory communicatively associated with said processor and having computer instmctions stored therein, said instructions when executed by the processor causing the apparatus to perform: providing a sleep mode in one or more small network cells arranged in

communicating proximity to a macro network node for management of the small cells by the macro node.

61. The apparatus of claim 60 wherein the instmctions cause the apparatus to further perform:

62. The apparatus of claim 61 wherein the instructions cause the apparatus to further perform:

63. The apparatus of claim 62 wherein the instructions cause the apparatus to further perform:

causing a wake-up signal detected (WSD) signal sequence to be sent to said macro node from the small network cells.

64. The apparatus of claim 63 wherein:

65. The apparatus of claim 64 wherein the instructions cause the apparatus to further perform:

receiving a pilot signaling request via predefined signaling to the small network cells.

66. The apparatus of claim 65 wherein:

67. The apparatus of claim 65 wherein the instructions cause the apparatus to further perform:

causing pilot signaling transmission according to specified pilot signaling format.

68. The apparatus of claim 67 wherein:

the small cell pilot signal comprises one of radio resource control ( RC), medium access control control element (MAC CE) or LI signaling.

69. The apparatus of claim 68 wherein the instructions cause the apparatus to further perform:

70. A computer program product comprising a non-transitoiy computer readable medium having computer coded instmctions stored therein, said instructions causing an apparatus to perform:

71. The computer program product of claim 70 wherein the instructions further cause an apparatus to perform:

72. The computer program product of claim 70 wherein the instructions further cause an apparatus to perform:

73. The computer program product of claim 72 wherein the instructions further cause an apparatus to perform:

receiving the uplink wakeup signal over a newly defined channel.

74. The computer program product of claim 72 wherein the instructions further cause an apparatus to perform:

receiving the uplink wakeup signal over a reused LTE legacy physical channel.

75. The computer program product of claim 72 wherein the instructions further cause an apparatus to perform:

using the uplink wakeup signal for uplink synchronization.

76. The computer program product of claim 72 wherein the instructions further cause an apparatus to perform:

using the uplink wakeup signal to begin random access to the network.

77. The computer program product of claim 72 wherein the instructions further cause an apparatus to perform:

causing a downlink confirmation signal to be sent in a predefined format to indicate that the network node is waking from sleep mode to deliver normal operating mode service.

78. The computer program product of claim 77 wherein the instructions further cause an apparatus to perform:

79. The computer program product of claim 70 wherein:

80. The computer program product of claim 70 wherein:

81. The computer program product of claim 70 wherein:

82. The computer program product of claim 70 wherein:

in sleep mode the node transmits zero broadcast signals.

83. The computer program product of any of claims 72 to 82 wherein the instructions further cause an apparatus to perform:

84. The computer program product of any of claims 72 to 82 wherein the instructions further cause an apparatus to perform:

85. The computer program product of any of claims 72 to 82 wherein the instructions further cause an apparatus to perform:

86. The computer program product of any of claims 72 to 82 wherein the instructions further cause an apparatus to perform:

87. A computer program product comprising a non-transitory computer readable medium having computer coded instructions stored therein, said instructions causing an apparatus to perform:

88. The computer program product of claim 87 wherein the instructions further cause an apparatus to perform:

89. The computer program product of any one of claims 87 to 88 wherein:

the macro network node is an evolved Node B (eNB).

90. The computer program product of any one of claims 88 to 89 wherein the instructions further cause an apparatus to perform:

91. The computer program product of claim 90 wherein the instructions further cause an apparatus to perform:

92. The computer program product of claim 91 wherein the instructions further cause an apparatus to perform:

causing a small cell to be signaled to handle UE signal traffic.

93. The computer program product of claim 91 wherein the instructions further cause an apparatus to perform: 2014/056174

94. A computer program product comprising a non-transitory computer readable medium having computer coded instructions stored therein, said instractions causing an apparatus to perform:

95. The computer program product of any one of claims 94 wherein the instmctions further cause an apparatus to perform:

providing a sleep mode in the one or more small cells.

96. The computer program product of any one of claims 95 wherein the instmctions further cause an apparatus to perform:

97. The computer program product of any one of claims 96 wherein the instmctions further cause an apparatus to perform:

98. The computer program product of any one of claims 97 wherein the instmctions further cause an apparatus to perform:

causing a wake-up signal detected (WSD) signal sequence to be sent to said macro network node from the small network cells.

99. The computer program product of claim 98 wherein:

100. The computer program product of claim 98 wherein the instructions further cause an apparatus to perform:

101. The computer program product of claim 100 wherein:

102. The computer program product of claim 100 wherein the instructions further cause an apparatus to perform:

causing pilot signaling transmission to be sent according to specified pilot signaling format.

103. The computer program product of claim 102 wherein:

104. The computer program product of claim 102 wherein the instructions further cause an apparatus to perform: receiving from the macro network node one of a handover signal (HO) or a signal to enter sleep mode via predefined signaling.

105. An apparatus comprising:

means for providing a sleep mode in a network node,

means for causing transmission during sleep mode of a reduced number of or zero broadcast signals from said network node, the said reduced number of signals comprising a subset of broadcast signals transmitted in normal operating mode.

106. The apparatus of claim 105 further comprising:

means for indicating sleeping status of the network node in the reduced number of broadcast signals transmitted during sleep mode.

107. The apparatus of claim 106 further comprising:

means for receiving an uplink wakeup signal to restore normal network node operating mode.

108. The apparatus of claim 107 further comprising:

means for receiving the uplink wakeup signal over a newly defined channel.

109. The apparatus of claim 107 further comprising:

means for receiving the uplink wakeup signal over a reused LTE legacy physical channel.

110. The apparatus of claim 107 further comprising:

means for using the uplink wakeup signal for uplink synchronization.

111. The apparatus of claim 107 further comprising:

means for using the uplink wakeup signal to begin random access to the network.

112. The apparatus of claim 107 further comprising:

means for causing a downlink confirmation signal to be sent in predefined format to indicate that the network node is waking from sleep mode to deliver normal operating mode service.

113. The apparatus of claim 1 12 further comprising:

means for combining reference signals with the downlink confirmation signal to enable node signal measurement.

114. The apparatus of claim 105 wherein:

115. The apparatus of claim 105 wherein:

116. The apparatus of claim 105 wherein:

117. The apparatus of claim 105 wherein: in sleep mode the node transmits zero broadcast signals.

118. The apparatus of any of claims 07 to 117 further comprising:

means for transmitting MIB and system infonnation block (SIB) signals upon restoration of the node's normal operating mode from sleep mode.

119. The apparatus of any of claims 107 to 117 further comprising:

means for causing transmission of a PDCH signal containing system information upon restoration of the node's normal operating mode from sleep mode.

120. The apparatus of any of claims 107 to 117 further comprising:

means for causing transmission of system information upon restoration of the node's normal operating mode from sleep mode.

121. An app aratus comprising:

means for causing a wake-up signal transmission (WST) to be sent from a macro network node requesting user equipment (UE) to transmit wake-up signals on predefined network resources using a predefined sequence via predefined signaling.

122. The apparatus of claim 121 further comprising;

means for receiving a wake-up signal detected (WSD) signal sequence at the macro network node from the small network cells.

123. The apparatus of any one of claims 121 to 122 wherein:

the macro network node is an evolved Node B (eNB).

124. The apparatus of any one of claims 121 to 123 further comprising:

means for causing a pilot signaling request to be sent via predefined signaling to the small network cells.

125. The apparatus of claim 124 further comprising:

means for configuring UE via predefined signaling to perform measurement on one or more small cells during pilot signaling.

126. The apparatus of claim 125 further comprising:

means for causing a small cell to be signaled to handle UE signal traffic.

127. The apparatus of claim 125 further comprising:

means for causing one or more small cells to be signaled to enter sleep mode via predefined signaling.

128. An apparatus comprising:

means for providing a sleep mode in one or more small network cells arranged in communicating proximity to a macro network node for management of the small cells by the macro node.

129. The apparatus of claim 128 further comprising:

means for monitoring predefined network resources at predefined periods during sleep mode.

130. The apparatus of claim 129 further comprising: means for receiving a wake-up signal transmission (WST) having a predefined sequence via predefined signaling on said predefined network resources.

131. The apparatus of claim 130 further comprising:

means for causing a wake-up signal detected (WSD) signal sequence to be sent to said macro node from the small network cells.

132. The apparatus of claim 131 wherein:

the WSD signal is combined with a signal plus interference to noise ratio (SIN ) value of the detected wake-up signal.

133. The apparatus of claim 132 further comprising:

means for receiving a pilot signaling request via predefined signaling to the small network cells.

134. The apparatus of claim 133 wherein:

135. The apparatus of claim 133 further comprising:

means for causing pilot signaling transmission according to specified pilot signaling format.

136. The apparatus of claim 135 wherein:

137. The apparatus of claim 136 further comprising:

means for receiving from the macro network node one of a handover signal (HO) or a signal to enter sleep mode via predefined signaling.

138. The method of claim 1 further comprising:

linking the uplink (UL) resource for the wakeup signal to the downlink (DL) reference.

139. The method of claim 138 wherein:

when the nework node transmits a reduced number of downlink broadcast signals, the UL wakeup signal follows a predefined timing delay after detection of the node downlink signals.

140. The method of claim 138 wherein:

when the network node transmits zero broadcast signals in sleep mode the DL reference is based on a neighbor cell DL signal.