WO2010140053A1

WO2010140053A1 - Methods and apparatus for measurement enhanced communications terminal enabling self optimizing networks in air interface communications systems

Info

Publication number: WO2010140053A1
Application number: PCT/IB2010/001347
Authority: WO
Inventors: Tomasz Mach
Original assignee: Nokia Corporation
Priority date: 2009-06-05
Filing date: 2010-06-04
Publication date: 2010-12-09

Abstract

Systems, apparatus and methods for providing enhanced user equipment in a communications system adapted for making and storing relative measurements of cell characteristics, for supporting a self organizing/optimization network (SON) feature in an over the air communications system. An enhanced mobile communications device (15) is provided that performs functions including making and storing certain relative measurements thereby enhancing SON algorithms performed by the network. The communications device (15) stores relative or Delta measurement data in an on-board memory (22) and, on certain conditions, signals the stored Delta measurements to the network. Utilizing the stored Delta measurement information, the network may be adapted to automatically perform SON algorithms to improve network efficiency without the need for manual intervention by an operator. Embodiments include event filtering by the communications device to efficiently utilize the on-board storage.

Description

METHODS AND APPARATUS FOR MEASUREMENT ENHANCED COMMUNICATIONS TERMINAL ENABLING SELF OPTIMIZING NETWORKS IN AIR INTERFACE

COMMUNICATIONS SYSTEMS

TECHNICAL FIELD

The present invention is directed, in general, to communications systems and, more particularly, to methods and apparatus for providing enhanced improved self organizing/optimizing networks (SON) by providing communications terminals configured to perform automatic measurements that are recorded and available to the network. These measurements enable and support self organizing/optimizing network algorithms in communications systems using spread spectrum signaling over an air interface, such as UTRAN, evolved UTRAN or LTE or LTE- Advanced, and/or next generation mobile networks (NGMN) systems.

BACKGROUND As wireless communications systems such as cellular telephone, satellite, and microwave communications systems become widely deployed and continue to attract a growing number of users, there is a pressing need to accommodate a large and variable number of communications subsystems transmitting a growing volume of data with a fixed resource such as a fixed channel bandwidth accommodating a fixed data packet size. Traditional communications system designs employing a fixed resource (e.g., a fixed data rate for each user) have become challenged to provide high, but flexible, data transmission rates in view of the rapidly growing customer base.

For wireless communications providing data intensive broadband services such as internet access and multimedia services provided over an air interface communications system, the need for improved efficiency and rapid throughput is of great importance. The 3G technology is generally defined by a body of standards released by the 3GPP organization and available at www.3gpp.org. The extension from present networks to the next generation of UTRAN or 3G networks is generally termed the "Long Term Evolution" or LTE. These LTE standards are also being provided by and supported by the 3GPP organization and the networks implementing these standards are usually referred to as evolved UTRAN or e-UTRAN. The third generation partnership project long term evolution ("3GPP LTE") is the name generally used to describe an ongoing effort across the industry to improve the universal mobile telecommunications system ("UMTS") for mobile communications. The improvements are being made to cope with continuing new requirements and the growing base of users, and higher data rates and higher system capacity requirements. Goals of this broadly based project include improving communication efficiency, lowering costs, improving services, making use of new spectrum opportunities, and achieving better integration with other open standards and backwards compatibility with some existing infrastructure that is compliant with earlier standards. Further, the NGMN project builds additional capabilities onto the 3G environment. The wireless communications systems as described herein are applicable to, for instance, 3GPP LTE compatible wireless communications systems and of interest is an aspect of LTE referred to as "evolved UMTS Terrestrial Radio Access Network," or E-UTRAN and also UTRAN communications systems. In E-UTRAN systems, the e-Node B may be, or is, connected directly to the access gateway ("aGW," sometimes referred to as the services gateway "sGW"). Each Node B may be in radio contact with multiple UEs (generally, user equipment including mobile transceivers or cellphones, although other devices such as fixed cellular phones, mobile web browsers, laptops, PDAs, MP3 players, and gaming devices with transceivers may also be UEs) via the radio Uu interface. In the present discussion, particular attention is paid to enhancements presently being considered for Release 9 and Release 10 (sometimes referred to as "LTE Advanced") of the 3GPP standards. These future evolutions of LTE will have additional requirements and demands for increased throughput. Although the discussion uses NGMN and E-UTRAN as the primary example, the application is not limited to E-UTRAN, LTE or 3GPP systems. LTE is a packet-based system and, therefore, there may not be a dedicated connection reserved for communications between a UE and the network. Users are generally scheduled on a shared channel every transmission time interval ("TTI") by a Node B or an evolved Node B ("e-Node B"). A Node B or an e-Node B controls the communications between user equipment terminals in a cell served by the Node B or e-Node B. In general, one Node B or e-Node B serves each cell. A Node B or e-Node B may be referred to as a "base station." Resources needed for data transfer are assigned either as one time assignments or in a persistent/semi-static way. The LTE, also referred to as 3.9G, generally supports a large number of users per cell with quasi-instantaneous access to radio resources in the active state. It is a design requirement that at least 200 users per cell should be supported in the active state for spectrum allocations up to 5 megahertz ("MHz"), and at least 400 users for a higher spectrum allocation. In order to facilitate scheduling on the shared channel, the e-Node B transmits a resource allocation to a particular UE in a physical downlink channel control channel ("PDCCH") to the UE. The allocation information may be related to both uplink and downlink channels. The allocation information may include information about which resource blocks in the frequency domain are allocated to the scheduled user(s), the modulation and coding schemes to use, what the size of the transport block is, and the like.

The lowest layer of communications in the UTRAN or e-UTRAN system, Layer 1, is implemented by the Physical Layer ("PHY") in the UE and in the Node B or e-Node B. The PHY performs the physical transport of the packets between them on an over the air interface using radio frequency signals. In order to ensure a transmitted packet was received, an automatic retransmit request ("ARQ") and a hybrid automatic retransmit request ("HARQ") approach is provided. Thus, whenever the UE receives packets through one of several downlink channels, including dedicated channels and shared channels, the UE performs a communications error check on the received packets, typically a Cyclic Redundancy Check ("CRC"), and in a later subframe following the reception of the packets, transmits a response on the uplink to the e-Node B or base station. The response is either an Acknowledge ("ACK") or a Not Acknowledged ("NACK") message. If the response is a NACK, the e-Node B automatically retransmits the packets in a later subframe on the downlink ("DL"). In the same manner, any uplink ("UL") transmission from the UE to the e-Node B is responded to, at a specific subframe later in time, by a NACK/ACK message on the DL channel to complete the HARQ. In this manner, the packet communications system remains robust with a low latency time and fast turnaround time.

Presently, a problem in the existing LTE and UMTS mobile systems is that creating and maintaining proper radio network configuration and performing optimization on the network elements is inefficiently done. In currently deployed networks, the operator must expend significant resources in terms of time and human energy to optimize the radio network settings. The process is very time consuming and generally is based on manual human control. To address these problems, the 3GPP organization has introduced some requirements for future networks to support self organizing/optimizing features.

Further, an organization providing standardized goals for the next generation mobile networks, or NGMN, is providing a standard set of features the next generation of mobile networks should support. A white paper entitled "Next Generation Mobile Networks Beyond HSPA & EVDO" available at www.ngmn.org, which is hereby incorporated herein by reference in its entirety, provides requirements for proposed advanced mobile communications networks.

A proposal currently adopted for next generation networks includes requirements for Self Organizing/Optimizing Networks ("SON"). The SON concept provides some features and example cases illustrating capabilities needed to support automatic radio access network (RAN) optimization. The paper entitled "Next Generation Mobile Networks- beyond HSPA & VDO" provides several features that are to be supported by future networks. SON networks that comply with the NGMN proposals should provide "Self-Planning", which includes derivation of initial network parameters as input for a self configuration instance.;" Self-Configuration", which includes "plug and play" behavior in newly installed elements in the network to simplify network installations; "Self Optimization and Self -Tuning", which is based on network monitoring and measurement data to increase performance; and "Self Testing and Self Healing" in which the system detects problems and takes action to avoid user impact and reduce costs.

A similar proposal from the 3GPP organization is provided in the technical specification (TS) titled "Self-configuring and self-optimizing network use cases and solutions (Release 8), numbered 3GPP TR 36.902 vl.0.0 (2008-02). This document provides "use cases" which describe proposed improvements to the networks. The document is available at www.3gpp.org and is hereby incorporated in its entirety herein by reference. The use of SON features is usually described in terms of "use cases". These use cases define areas where the network may be optimized; for example, neighbor cell coverage optimization, neighbor cell capacity and throughput at the cell edge, neighbor cell coverage hole management (detecting and addressing coverage gaps), neighbor cell interference (cell to cell interference, sometimes referred to as "pilot pollution"), measurement threshold optimization (these thresholds are used by the user equipment to determine and perform cell reselection; for example, to choose a neighbor cell base station to connect to based on the signal strength of the present cell during terminal mobility). These use cases define the areas for optimization and the use of SON algorithms at the network level; however, they do not address any action by the UEs themselves. Thus, both the NGMN and 3GPP organizations have defined SON as a desired feature of future networks. However, as the standard proposals are presently provided, no user equipment (UE) algorithms or features are described which could provide valuable input into the SON algorithms performed by the base station or Node B, or the radio resource controller (RRC), to perform the SON algorithms. A need thus exists for methods and apparatus to efficiently provide added support for SON algorithms by providing UEs that signal certain input data that may be used by the network to perform SON, without the need for manual operator inputs.

SUMMARY OF THE INVENTION

These and other problems are generally solved or circumvented, and technical advantages are generally achieved, by advantageous embodiments of the present invention which include an apparatus and method embodiments for enhanced UEs that take and store measurements during idle mode operations. These measurements are stored for use in SON algorithms performed at the network level. These enhanced UEs provide neighbor cell signal strength and signal quality Delta measurements that may be performed during the idle mode of operation, and more particularly, during cell selection or reselection operations by the UE.

Embodiments provide enhanced UEs that perform relative measurements on neighbor cell signal strengths and provide a related framework that supports SON algorithms. In one embodiment, UE measurements of relative and absolute cell signal power are performed as a new measurement called "Delta". This relative measurement may be stored by the UE during procedures that are otherwise performed as defined by the 3GPP specification. The Delta measurements may be signaled immediately or stored in a memory on board the UE and may be made available for retrieval by or transmission to the network via an air interface uplink message.

A variety of adaptive adjustments may be made by the network in SON algorithms using the embodiment Delta measurements. For example, transmit signal strengths may be increased and decreased in selected neighboring cells. Embodiments include providing optimized cell edge coverage, reducing or eliminating coverage gaps, reducing cell to cell interferences, and determining optimal values for network provided thresholds used by the UEs during reselection. Embodiments of the methods provided herein address neighbor cells in intra-frequency, inter-frequency and inter-radio access technology (inter-RAT) cases.

In one embodiment, the UE reports the Delta measurements during cell location and cell update procedures requested by a network entity or initiated by the UE. The reports are based on predefined reporting criteria provided to the UE by the network. In some embodiments, the Delta measurements are related to the idle mode of UE operation, that is, measurements by the UE are made when no signaling operation is active (no connection to the UE by the RRC is active).

In one exemplary embodiment, while the UE is in an idle mode, cell reselection may be performed. The cell reselection processes are primarily intended to select the best cell for the UE to reliably obtain quality service. Because the UE is a mobile device, from time to time it moves from one cell coverage area to another. When the UE moves out of a coverage area, it performs received signal strength measurements on neighboring cells to identify a potential new serving cell. When the power of the present serving cell decreases below a predefined received signal power threshold, the UE decides to perform a reselection procedure to select a new cell. The current serving cell and any neighboring cells are evaluated by the UE in accordance with a serving cell criteria threshold; these may be provided by the network. The UE may or may not successfully reselect to a new cell. In embodiments of the present invention, the UE may store the embodiment Delta measurements made during cell reselection event or channel lost event. In some embodiments, the stored Delta measurement analysis may include the cell IDs of the service cell, the neighbor cells, the success and failure of the reselection and the location of the UE, date and time information, or any of these. The events stored may then be provided to the network by transmission over the air interface as an uplink message for input into SON algorithms, and to improve the SON procedures.

In additional embodiments, the network receives the stored Delta analysis from the UE and performs an analysis based on the information; the network then recommends certain adaptive adjustments to the network configuration to enhance the SON algorithms. In additional embodiments, the network provides certain criteria or trigger events to the UE to aid in determining which Delta measurements to store in UE memory. By selectively controlling the UE storing mechanisms, the network increases the efficient use of the limited storage memory capacity of the UE.

In additional embodiments, the network may provide filtering criteria or trigger events for events so that the UE only stores Delta measurement events of specific interest to a network. In other embodiments, the UE may only report events when certain criteria such as trigger events are met; in order to advantageously reduce the frequency of signaling of the UE reporting to the network.

Although in some embodiments the UE may perform the comparison of measured signal strength to some threshold and thus determine the Delta measurement for storage, in other embodiments, the UE may simply store and report the raw measured signal strengths, allowing the network to perform the comparison and determine the Delta measurement. Both of these approaches are contemplated as embodiments of the invention.

Embodiments of the invention provide methods for performing idle mode measurements by a UE that support the SON algorithms performed by a network using only software or firmware changes to existing equipment. No hardware changes, redesigns, or replacements are necessary to implement the embodiments of the invention. However, the enhancements of the embodiments could be implemented with hardware modifications, software modifications, both, or either one as alternative embodiments. Each of these is contemplated as part of the invention and is within the scope of the claims. Additional exemplary embodiments of the present invention include providing UEs that support certain 3GPP test minimization use cases without the need for any hardware redesigns. The various embodiments may be added to an industry standard for implementation. Alternatively, the embodiments may be implemented in certain equipment without affecting the use of equipment that does not implement the embodiments; that is, the use of the embodiments is also compatible with prior art devices and no compatibility or interoperability problems will arise by use of the embodiments. The embodiments may be implemented using programmable processors and executable software. For example, the embodiments may be implemented as a computer readable storage product, comprising executable instructions which, when read and executed by a programmable communications terminal, cause the programmable communications terminal to perform storing the Delta measurements in a memory on board the programmable communications terminal. The computer readable storage product may be provided as a flash drive, disk, optical disk, hard drive, file, internet download or other machine readable format.

The foregoing has outlined rather broadly the features and technical advantages of the present invention so that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in any appended claims to this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

Figure 1 illustrates a communications system with communications terminals; Figure 2 illustrates a block diagram of a communications device according to an advantageous embodiment of the present invention;

Figure 3 illustrates a block diagram of the communications elements of Figure 1 and the service layers used in the communications system;

Figure 4 illustrates a diagram of a network operation with a communications element in contact with two base station cells;

Figure 5 illustrates in a simple diagram of a reselection event of a preferred embodiment communications terminal;

Figure 6 depicts in a graph a variety of events that a communications element of the present invention may perform; Figure 7 depicts in a graph one embodiment measurement and an adaptive change by the

SON algorithm;

Figure 8 depicts in a graph another embodiment measurement and another embodiment adaptive change by the SON algorithm;

Figure 9 depicts in a graph another embodiment measurement and another embodiment adaptive change by the SON algorithm;

Figure 10 depicts in a graph another embodiment measurement and another embodiment adaptive change by the SON algorithm;

Figure 11 depicts in a graph another embodiment measurement and another embodiment adaptive change by the SON algorithm; Figure 12 depicts in a graph another embodiment measurement and another embodiment adaptive change by the SON algorithm;

Figure 13 depicts in a graph another embodiment measurement and another embodiment adaptive change by the SON algorithm; and

Figure 14 depicts an embodiment table for use with communications terminals incorporating features of the invention. DETAILED DESCRIPTION

These and other problems are solved, and advantages are achieved, by embodiments of the present invention. The embodiments provide an enhanced UE apparatus and methods for taking Delta measurements during cell reselection in idle mode. These measurements are then available to the network for use by an SON algorithm. The embodiments apply to all possible types of cells and neighbor cells including intrafrequency (neighbor on same frequency parameters), interfrequency (neighbor on different frequency parameters but same radio access technology (RAT) parameters and interRAT (neighbor has different RAT parameters).

Referring initially to Figure 1, illustrated is a system level diagram of a radio frequency interface communications system including a wireless communications system that provides an environment for the application of the principles of the present invention. The wireless communications system may be configured to provide features included in the evolved UMTS terrestrial radio access network ("e-UTRAN") universal mobile telecommunications services. Mobile management entities ("MMEs") and user plane entities ("UPEs") 1 1 provide control functionality for e-UTRAN node B (designated "eNB," an "evolved node B," also commonly referred to as a "base station") 13 via Sl interfaces or communications links. The base stations 13 communicate via an X2 interface or communications link. The various communications links are typically fiber, microwave, or other high-frequency metallic communications paths such as coaxial links, or combinations thereof. The base stations 13 communicate over an air interface with user equipment (designated "UE") 15, which is typically a mobile transceiver carried by a user. Alternatively the user equipment may be a mobile web browser, text messaging appliance, a laptop with a mobile PC modem, or other user device configured for cellular or mobile services. Thus, communications links coupling the base stations 13 to the user equipment 15 are air links employing a wireless communications signal. For example the devices may communicate using a known signaling approach such as a 1.8 GHz orthogonal frequency division multiplex ("OFDM") signal. Other radio frequency signals may be used.

The eNBs 13 may host functions such as radio resource management (e.g., internet protocol ("D?"), header compression and encryption of user data streams, ciphering of user data streams, radio bearer control, radio admission control, connection mobility control, dynamic allocation of resources to user equipment in both the uplink and the downlink), selection of a mobility management entity at the user equipment attachment, routing of user plane data toward the user plane entity, scheduling and transmission of paging messages (originated from the mobility management entity), scheduling and transmission of broadcast information (originated from the mobility management entity or operations and maintenance), and measurement and reporting configuration for mobility and scheduling. The MME/UPEs 11 may host functions such as distribution of paging messages to the base stations, security control, terminating U-plane packets for paging reasons, switching of U-plane for support of the user equipment mobility, idle state mobility control, and system architecture evolution bearer control. The UEs 15 receive an allocation of a group of information blocks labeled physical resource blocks ("PRBs") from the eNBs. Each base station has a reception area, usually referred to as a "cell" and may serve a plurality of UEs 15 at any given time. The UEs are mobile devices and as the location of the UEs 15 changes, the UEs and the eNBs will perform "soft handoff ' or "handoff ' procedures. For an active user these handoffs will be transparent and no loss of service or audible change should occur.

The UE may also be in an "idle" mode; however, in order to remain available to receive or make calls, the UE will select and "camp" on a nearby cell by selecting or reselecting an eNB. As will be described in more detail later herein, the UE will perform measurements to determine, between possible cells that it can receive signals from, which to "camp" on and when to change serving cells by performing "reselection".

Figure 2 illustrates a simplified system level diagram of an example communications device 15 of a communications system. Device 15 provides an environment and structure for application of the principles of the present invention. The communications device may represent, without limitation, an apparatus including an eNB, UE such as a terminal or mobile station, a network control element, or the like. The communications device 15 includes, at least, a processor 23, memory 22 that stores programs and data of a temporary or more permanent nature, one or more antennas 25, and one or more radio frequency transceivers 27 coupled to the antenna(s) 25 and the processor 23 for bidirectional wireless communications. Other functions may also be provided. The communications device 15 may provide point-to-point and/or point-to-multipoint communications services.

The communications device, such as an eNB in a cellular network, may be coupled to a communications network element, such as a network control element 33 of a public switched telecommunications network ("PSTN"). The network control element 33 may, in turn, be formed with a processor, memory, and other electronic elements (not shown). Access to the PSTN may be provided using fiber optic, coaxial, twisted pair, microwave communications, or similar communications links coupled to an appropriate link-terminating element. A communications device 15 formed as a UE is generally a self-contained device intended to be carried by an end user and communicating over an air interface to other elements in the network

The processor 23 in the communications device 15, which may be implemented with one of or a plurality of processing devices, performs functions associated with its operation including, without limitation, encoding and decoding of individual bits forming a communications message, formatting of information, and overall control of the communications device, including processes related to management of resources. Exemplary functions related to management of resources include, without limitation, hardware installation, traffic management, performance data analysis, tracking of end users and mobile stations, configuration management, end user administration, management of the mobile station, management of tariffs, subscriptions, billing, and the like. The execution of all or portions of particular functions or processes related to management of resources may be performed in equipment separate from and/or coupled to the communications device, with the results of such functions or processes communicated for execution to the communications device. The processor 23 of the communications device 15 may be of any type suitable to the local application environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors ("DSPs"), and processors based on a multi-core processor architecture, as non-limiting examples.

The transceiver(s) 27 of the communications device 15 modulates information onto a carrier waveform for transmission by the communications device via the antenna(s) 25 to another communications device. The transceiver demodulates information received via the antenna for further processing by other communications devices.

The memory 22 of the communications device 15, as introduced above, may be of any type suitable to the local application environment, and may be implemented using any suitable volatile or nonvolatile data storage technology, such as a semiconductor-based memory device, a magnetic memory device and system, an optical memory device and system, fixed memory, and removable memory. The programs stored in the memory 22 may include program instructions that, when executed by an associated processor, enable the communications device to perform tasks as described herein. Exemplary embodiments of the systems, subsystems, and modules as described herein may be implemented, at least in part, by computer software executable by processors of, for instance, the mobile station and the base station, by hardware, or by combinations thereof. Other programming may be used such as firmware and/or state machines. As will become more apparent, systems, subsystems and modules may be embodied in the communications device as illustrated and described above.

Figure 3 depicts a block diagram of an embodiment of a UE 15 and an eNB 13 constructed according to the principles of the present invention and coupled to an MME 11. The UE 15 and the eNB 13 each include a variety of layers and subsystems: the physical layer ("PHY") subsystem, a medium access control layer ("MAC") subsystem, a radio link control layer ("RLC") subsystem, a packet data convergence protocol layer ("PDCP") subsystem, and a radio resource control layer ("RRC") subsystem. Additionally, the user equipment and the mobile management entity ("MME") 11 include a non-access stratum ("NAS") subsystem. The physical layer subsystem supports the physical transport of packets over the LTE air interface and provides, as non-limiting examples, cyclic redundancy check ("CRC") insertion (e.g., a 24 bit CRC is a baseline for physical downlink shared channel ("PDSCH")), channel coding (e.g., turbo coding based on QPP inner interleaving with trellis termination), physical layer hybrid- automatic repeat or retransmit request ("HARQ") processing, and channel interleaving. The physical layer subsystem also performs scrambling, such as transport-channel specific scrambling, on a downlink-shared channel ("DL-SCH"), broadcast channel ("BCH") and paging channel ("PCH"), as well as common multicast channel ("MCH") scrambling for all cells involved in a specific multimedia broadcast multicast service single frequency network ("MBSFN") transmission. The physical layer subsystem also performs signal modulation such as quadrature phase shift keying ("QPSK"), 16 quadrature amplitude modulation ("QAM") and 64 QAM, layer mapping and pre-coding, and mapping to assigned resources and antenna ports. The media access layer or MAC performs the HARQ functionality and other important functions between the logical transport layer, or Level 2, and the physical transport layer, or Level 1.

Each layer is implemented in the system and may be implemented in a variety of ways. A layer such as the PHY in the UE may be implemented using hardware, software, programmable hardware, firmware, or a combination of these as is known in the art. Programmable devices such as DSPs, RISC, CISC, microprocessors, microcontrollers, and the like may be used to perform the functions of a layer. Reusable design cores or macros as are provided by vendors as ASIC library functions, for example, may be created to provide some or all of the functions and these may be qualified with various semiconductor foundry providers to make design of new UEs, or e-Node B implementations, faster and easier to perform in the design and commercial production of new devices.

The e-UTRAN system architecture has several significant features that impact timing in the system. A transmission time interval ("TTI") is defined and users (e.g., UE or mobile transceivers) are scheduled on a shared channel every TTI. The majority of UE or mobile transceivers considered in the implementation of the e-UTRAN are full duplex devices. These UEs can therefore receive control and data allocations and packets from the e-NODE B or base station they are connected to in any subframe interval in which they are active. The UE detects when resources are allocated to it in the allocation messages on the physical downlink control channel (PDCCH). When downlink resources are allocated to a UE, the UE can determine that data or other packets are going to be transmitted toward it in the present frame or in coming frames. Also, the UE may have uplink resources allocated to it. In this case, the UE will be expected to transmit toward the e-Node B in coming frames on the uplink based on the allocated UL resources.

Additional timing related services are present in the environment. The e-UTRAN communications environment supports VoIP communications. The use of VoIP packets creates another cyclic pattern within the system. A typical cycle for VoIP would be 20 milliseconds, although 40 milliseconds, 60 milliseconds and 80 milliseconds may also be used in case packet bundling. 20 milliseconds as a VoIP interval will be used as a non-limiting default example for VoIP packets throughout the rest of this specification text. Further, the e-UTRAN communications system provides automatic retransmission request (ARQ) and hybrid automatic retransmission request (HARQ) support. The HARQ is supported by the UE and this support has two different dimensions. In the downlink direction, a synchronous HARQ is supported. However, the uplink or UL channel is a different standard channel that uses single carrier FDMA (SC-FDMA) and as currently provided, requires a synchronous HARQ. That is, in the uplink direction, after a packet is transmitted to the eNB, an ACK/NACK (acknowledged/not acknowledged) response is transmitted by the eNB toward the UE a definite time period later, after which the UE, in case NACK was received, will retransmit the packet in UL direction in a given sub frame after a predetermined delay.

The e-UTRAN specifications support air interface signaling using both frequency division duplex (FDD), where uplink (signaling from the UE to the eNB) and downlink (signaling from the eNB toward the UE) can occur at the same time but are spaced apart at different frequencies; and time division duplex (TDD), where the UL and DL frames are communicated on the same carrier but spaced apart in time. Of particular interest to the embodiments of the present invention are the frame structures of TDD radio frames. The frame structures have been selected so that TDD and FDD services may be supported in the same environment and dual-mode devices may be easily implemented. The selection of the FDD or TDD services may depend on the type of data, whether the data transmission is asymmetric (for example, internet browsing tends to be very heavy on the downlink, while voice may be more or less symmetric on both downlink and uplink) the environment, and other parameters. There are advantages and disadvantages to each that are known to those skilled in the art. The technical specifications (TS) document entitled "3GPP TS 36.300" version 8.5.0 (2008-05), available from the website www.3gpp.org, and hereby incorporated by reference in its entirety herein provides in part the specifications for the physical interfaces for the E-UTRAN networks.

Figure 4 depicts a simplified system level diagram of an example communications system. Figure 4 provides an illustration of an environment and structure for application of the principles of the present invention. UE 15 is able to receive signals from eNBs 13 and 14. In an "idle" mode, the UE may select one of these as a serving cell, or "camp" on one of the eNBs. The UE 15 may also record the received signal strength of the other eNB and record it. This information may then be used if a reselection process is indicated. Reselection can occur if the signal strength from the serving cell decreases; for example, if the UE moves location, if the serving cell becomes very busy, if the serving cell malfunctions, or on some commands from the eNB or some reconfiguration by the radio resource controller (RRC).

Embodiments of the present invention provide, in an enhanced UE configuration, an enhanced UE that takes and stores certain relative cell measurements, referred to as Delta measurements. These measurements are then provided to the network in a manner that supports SON algorithms as presently proposed. To date, no proposal has been made in the art that provides UE operations to support the SON functionality defined for future implementations of the NGMN or LTE Advanced next generation networks.

When a mobile UE is in idle mode, that is, when no RRC connection is active, as presently specified in various communications systems standards the UE periodically performs a cell reselection process. For example, as the UE moves out of or away from the currently selected eNB (the "serving cell") coverage, the receiver at the UE will determine that the received signal power is decreasing. When certain configurable signal measurement thresholds are reached, the UE will start neighbor cell measurements and finally could perform a reselection process. This is done by determining, using signal strength at the receiver, the nearest neighbors. Based on the power measurements performed by the UE as currently defined by the 3GPP specifications, the UE may reselect a new serving cell from a neighboring cell during terminal mobility. The reselection process as presently provided has a focus on determining the best neighboring cell to select for best service in the UE.

In embodiments of the present invention, a set of functions for an enhanced UE are provided that extend the results of the reselection process to support SON algorithms at the network level. A set of Delta measurements the UE may make and store may be defined. These Delta measurements may be of signal strength against a known threshold level, of signal strength against a near neighbor signal strength, of raw signal strength, or of other quality measures related to, but not directly reflecting received signal strength; for example known signal quality criteria (EcIo, RSRQ).

In some embodiments, the UE may make Delta measurements of more than one type and average the result for storing and reporting to the network. Filtering and selective reporting to the network by the UE is contemplated as an enhancement or alternative embodiment of each of the embodiments described herein. These alternatives may be implemented in order to reduce the need to signal every measurement to the network controller. Other defined reporting and measurement filters and trigger events may be used to further reduce the system uplink traffic from the UE, while still providing the Delta measurements needed by the network to perform the SON algorithms to optimize the network performance.

Embodiments of the invention provide for enhanced UEs configured to store these Delta measurements in a memory in the form of raw data, or alternatively as a measurement log or report. By forming the entries of the Delta measurement log to provide the information most useful to the network SON algorithms, and by signaling the Delta measurement log to the network, the UE may enhance the efficiency and the performance of the SON algorithms. Because only existing hardware features of the UE are utilized in the embodiments, no redesign of the UE or the system is required to use the embodiments and so gain the advantages in system performance (although such redesigns are in fact alternative embodiments contemplated by the inventors that do fall within the scope of any appended claims). Instead, the embodiments may, in one alternative, be implemented by software modifications. However, additional memory or hardware implementation may also be provided as embodiments of the enhanced UE.

The UE Delta measurements stored in the memory may be reported to the network at different times. For example, at certain times in the current 3GPP specifications, the UE signals the network, e.g., during cell/location update procedures. The Delta measurement log could be signaled to the network as part of these existing messages. Alternatively, the UE may receive a request for an uplink transmission containing, as data words, the contents of the stored log. In alternative embodiments, the Delta measurements stored may be formed using trigger or capture criteria to limit the stored Delta measurements to those of interest to or needed by the SON algorithms. In other embodiments, filtering criteria are used where the UE transmitted or signaled events could be filtered by certain network provided criteria, and in additional embodiments, event reporting filters or criteria could determine when the UE should signal the log contents (or a filtered version thereof, in some embodiments) to the network.

The reselection procedure as currently defined by the 3GPP specifications is performed during UE mobility in idle mode (no active RRC connection). As the UE moves out of coverage of the current serving cell (the cell it is presently "camped" on), when serving cell power falls below preconfigured neighbor measurement threshold (Sintrasearch", "Snonintrasearch") the UE starts to make measurements on the neighboring cells that are available in terms of received signal power. Neighbor cell measurements are periodically performed by the UE based on a neighbor cell list. This list could be provided to the UE by the network. When the measured power of the present serving cell (this measurement is termed "RSCP" and measured in dBm) decreases and there is a stronger neighbor cell available, the UE determines to perform a reselection. The UE decides, based on the relative signal strengths and the measurement of the signal strengths against certain thresholds provided by the network, to reselect a neighboring cell as the new serving cell and "camp" on it. Note that in the present 3GPP standards, both the present serving cell and the neighboring cell are evaluated against a minimum serving cell threshold provided by the network, as well as the relative comparison performed between the cells. However, embodiments of the present invention do not require any particular criteria be used and are not limited to the examples provided here or by present 3GPP specifications.

As an example non-limiting embodiment, a Delta measurement is performed by the UE on neighbor cells during idle mode operations. Neighbor cell power measurements may be performed as presently defined in the 3GPP specification; however, a new relative measure, the Delta measurement, is provided. In this exemplary embodiment, the Delta measurement is a difference between the received signal strength of the strongest neighbor cell and the predefined idle mode threshold levels, referred to as "Sintrasearch", "Snonintrasearch" and the minimum received signal level for service, "Qrxlevmin". Note that although the present discussion adopts the labels used in current 3GPP specifications for these thresholds, any threshold levels may be used in the exemplary embodiments, and the invention is not limited to systems using particular terminology or labels. The UE receiver is measuring the received signal strength of neighbor cells and comparing these to threshold levels. The resulting measurement is called the Delta measurement herein, but again the label is for convenience of discussion and is not limiting on the scope of the embodiments. The following SON optimization methods using the Delta measurements of the UE embodiments are proposed as additional method embodiments: 1. METHOD OF REDUCING UNDESIRED NEIGHBOR CELL INTERFERENCES : THIS EFFECT IS REFERRED TO AS "PILOT POLLUTION". ADJUSTMENTS MAY BE MADE FOLLOWING THE DELTA MEASUREMENTS TO OPTIMIZE THE CELL COVERAGE TO REDUCE OR ELIMINATE THIS INTERFERENCE. THIS IS DESCRIBED IN DETAIL BELOW IN REFERENCE TO FIGURE 7.

2. METHOD OF OPTIMIZING CELL EDGE COVERAGE/CAPACITY (THROUGHPUT) DURING INTRA-FREQUENCY CELL RESELECTION IN UE IDLE MODE USING THE DELTA MEASUREMENT: THIS EMBODIMENT IS DESCRIBED IN DETAIL BELOW IN REFERENCE TO FIGURE 8. 3. METHOD OF REDUCING UNDESIRED NEIGHBOR CELL INTERFERENCES

(PILOT POLLUTION) BASED ON DELTA MEASUREMENT DURING EITHER INTERFREQUENCY OR INTERRAT CELL RESELECTION IN IDLE MODE: THIS EMBODIMENT IS DESCRIBED IN MORE DETAIL BELOW IN REFERENCE TO FIGURE 9. 4. METHOD OF OPTIMIZING CELL EDGE COVERAGE/CAPACITY

(THROUGHPUT) BASED ON THE DELTA MEASUREMENT DURING INTERFREQUNECY OR INTERRAT CELL RESELECTION WHILE THE UE IS IN IDLE MODE: THIS EMBODIMENT METHOD IS DESCRIBED IN MORE DETAIL BELOW IN REFERENCE TO FIGURE 10. 5. METHOD OF LIMITING INTRAFREQUENCY/INTERFREQUENCY/INTERRAT

NEIGHBOR CELL COVERAGE GAPS BASED ON THE DELTA MEASUREMENT DURING CHANNEL LOST ESf RESELECTION EVENT IN UE IDLE MODE: THIS METHOD EMBODIMENT IS DESCRIBED FURTHER BELOW WITH RESPECT TO FIGURE 11. 6. METHOD OF DETERMINING THE OPTIMAL VALUE OF INTRAFREQUENCY

LEVEL THRESHOLD "SINTRASEARCH" (OR, SIMILARLY THE INTERFREQUENCY OR INTERRAT LEVEL SNONINTRASEARCH) MEASUREMENT THRESHOLD IN UE BASED ON THE DELTA MEASUREMENT: THIS METHOD EMBODIMENT IS FURTHER DESCRIBED IN DETAIL IN REFERENCE TO FIGURE 12 BELOW.

7. METHOD OF LIMITING INTRAFREQUENCY/INTERFREQUENCY/INTERRAT NEIGHBOR CELL COVERAGE GAP AS INDICATED BY CHANNEL LOST IN RESELECTION EVENT DURING UE IDLE MODE, IN THE EVENT OF A SHADOWING SCENARIO: THIS METHOD EMBODIMENT IS FURTHER DETAILED IN REFERENCE TO FIGURE 13, BELOW. These example embodiment UE processes measuring Delta during cell reselection events are now described in more detail.

The Delta measurement may be evaluated and stored in an on-board UE memory. The Delta measurements may be reported at a variety of times to the network. In some embodiments, the UE may signal the Delta measurements any time after a reselection event. However, this approach may result in an unwanted increase in uplink signal traffic. Alternative approaches are contemplated as additional embodiments. The UE may report the stored Delta values during other uplink signal events.

For example, the UE may read and transmit the stored Delta values during cell/location update procedures already performed under the standards. Alternatively, the network may request the UE to transmit the stored Delta values at any time. Further, the network may provide certain trigger events that would cause the UE to transmit the stored Delta values, such as certain stored reporting criteria (number of values stored exceeds a threshold, elapsed time between reports exceeds a threshold, following some other event such as channel lost, power up, when charging battery and so on.

Embodiments of the invention include UEs storing Delta values that are not signal strength values but are instead some other parameter of interest to the network and useful in performing the SON algorithms being developed. Examples that do not limit the invention but serve only to illustrate the range of embodiments include the aforementioned power criteria, but also quality criteria such as EcIo, RSRQ and like measures. Embodiments include Delta measurements that combine these into a figure of merit by averaging several measures, and by weighting power measures and quality measures, either in the UE before or during storage. Alternatively these calculations could be made at the network level.

When a UE is in idle mode, that is, no radio resource connection (RRC) is active, the UE may be mobile. As the UE reaches a portion of the serving cell, that is, the cell that the UE is presently connected to, and the received signal strength begins to fall below a predefined measurement threshold level, by starting neighbor cell measurements, the UE may detect when to reselect the serving cell.

Often, the selection and connection to a serving cell is referred to as being "camped" on a particular cell. A cell typically corresponds to an eNB, although an eNB may have multiple antennas and may support multiple cells.

The UE will evaluate the neighbor cells and locate the strongest neighbor cell and reselect, or "camp", on that cell. When the UE is mobile, these measurements of neighbor cells are periodically performed and may be either always performed or performed only below predefined measurement thresholds (e.g. Sintrasearch). The particular cells the UE measures may be determined by a list provided to the UE by the network. When the UE determines that an appropriate neighbor cell with a stronger signal (or other measure) is available, the UE will select that cell. Neighbor cell measurements are made and evaluated in relation to the power (or other metric measured) of the current serving cell and in relation to certain thresholds. In some examples, the serving cell currently selected and the neighbor cell are each evaluated in relation to measurement thresholds provided by the network at various times. Three signal level thresholds that are typically described in 3GPP are:

"Sintrasearch": The power of the current serving cell is evaluated in relation to this measurement threshold, and if the level is below the threshold, the neighbor cells are then evaluated for possible reselection. Here, the neighbor cells are evaluated at the same frequency (intrafrequency reselection) which is the fastest and cheapest reselection in terms of system resources.

"Snonintrasearch": Here, the power of the current serving cell is evaluated in relation to this typically lower measurement threshold. If the serving cell power is below this second threshold, all neighbor cells at other frequencies and at other RATs are evaluated for possible interfrequency or interRAT reselection. This reselection is more complex from a system perspective than case 1), but is usually successful.

"Qrxlevmin": This threshold, usually lower than either Sintrasearch or Snonintrasearch, is the minimum power threshold that the serving cell and any neighbor cell considered for reselection must meet to provide service to the UE. If the serving cell falls below this threshold and no neighbor cell above the threshold is located, then the channel will be lost, and reselection fails. Thus, this event indicates a coverage gap.

Figure 5 depicts, as an example in a simple diagram, the operation that results in a successful reselection. In Figure 5, the UE 15 is shown physically moving from cell area 61 to cell area 63, but even as the serving cell 61 power received is falling (as the UE moves away from that eNB), the neighbor cell coverage area 63, which overlaps the edge area of the service cell 61 coverage, begins and in this example, apparently exceeds the required threshold. Thus, the UE 15 can reselect the cell 63, the channel is not lost, and the reselection is successful. Figure 6 presents in a graphical form an illustration of the three thresholds typically referred to as Sintrasearch, Snonintrasearch, and Qrxlevmin, and the operation of the cell reselection process in idle mode. Again, UE 15 is physically moving away from a serving cell. The right side vertical axis depicts, in dBm, the neighbor cell power detected by the UE receiver in two standards; UTRAN, which labels this received power as "RSCP", and eUTRAN, which labels this received power as "RSRP". The reselection events are identified along the bottom or x axis of the graph.

Labels on the left vertical axis represent in Figure 6, for non-limiting, illustrative examples, threshold received power levels the UE can determine for different observed received power. For example, the Sintrasearch measurement threshold level for intrafrequency neighbor cells is labeled 52. The intrafrequency neighbor cells are cells using the same frequency, radio access technology (RAT) and parameters, the most simple cells to choose for reselection of the serving cell. The measurement threshold Snonintrasearch for interfrequency and interRAT (radio access technology) reselection is usually lower and is labeled 53 in Figure 6. The cell serving criteria minimum threshold is usually lower still and is labeled 54. This signal or power threshold may be referred to as Qrxlevmin, and cells with received observed signals below this level may not be selected by the UE. The minimum cell power threshold the receiver in the UE can detect is also labeled in the diagram as 55, the cell detection threshold (this threshold is HW receiver sensitivity dependent). In the diagram of Figure 6, as the UE moves to the right and away from the original serving cell (on the left vertical axis), trace 51 indicates the measured received power from the serving cell. As the UE 15 location changes, this received power level falls and crosses the differing thresholds 52, 53, and 54. Trace 56 indicates the neighbor cell power for a first case, trace 57 indicates a lower neighbor cell power and trace 58 indicates still a lower neighbor cell power. As the UE moves into the area for receiving the neighbor cell, the relative power levels of the serving cell and the neighbor cell are compared. When trace 51 intersects trace 56, a reselection event occurs. This example is a successful reselection where a neighbor cell is located with a received power above the serving criteria threshold. On the right axis, the events are labeled; here, a CELL_RESELECTION_EVENT_INTRA occurred; that is, the neighbor cell was successfully selected when the power threshold of the serving cell was between the threshold levels

Snonintrasearch and Sintrasearch, so that the new cell was successfully reselected without loss of channel. When the solid trace 51 intersects the next neighbor trace 57, a less desirable reselection attempt occurs, where the neighbor cell is detected but the receiving cell power is already below the serving cell threshold, and the channel was lost. This is a reselection failure case. On the right axis, the label indicates that the reselection failed because, before the reselection occurred, the serving cell power (Srxlev) fell below the minimum serving threshold (Qrxlevmin) required. Finally, the solid trace 51 reaches the zero level, where the serving cell is no longer detected, before the trace 51 intersects the trace labeled 58. In this case, a failed reselection occurs; that is, no neighbor cells where detected, and the channel was lost. This case illustrates a complete coverage gap, the channel was lost and no neighbor was identified.

Figure 7 depicts in graphical illustration, the use of the Delta measurement of one embodiment of the invention. In Figure 7, the solid trace 71 represents the received signal power from the serving cell. As the UE 15 moves away from the center of the serving cell, the signal level falls. The threshold levels 52, 54 and 55 are, as before, representing levels Sintrasearch, and the minimum signal detection level. The first dashed trace, numbered 73, represents an initial neighbor power that the UE detects for a neighboring cell. Event 72 represents the point where the reselection would take place. However, event 72 occurs while the presently serving cell signal Srxlev received is still well above the threshold Sintrasearch.

The example in Figure 7 illustrates that the two cells have overlapping cell coverage, which may result in neighbor cell interferences (pilot pollution). The UE in this embodiment example takes a Delta measurement, which here is the difference in received power level between the neighbor cell power observed and the threshold level desired (Sintrasearch) at the point where the serving cell power also meets that threshold (reselection event happens). It is known in the art that for optimal cell to cell coverage, the overlap should occur approximately at the defined measurement threshold level in order to reduce cell to cell interference. Thus, if the system can reduce the transmit levels (Tx) for the neighbor cell so that trace 75 would represent the new coverage for the neighbor cell, the reselection would occur at the optimum point (labeled 76 in Figure 7) and cell coverage overlap would be optimized. The SON algorithms would then perform adaptation of the network by increasing the transmit level or Tx for the neighbor cell by the amount Delta.

Figure 8 depicts another example where the Delta measurement made by the enhanced UE of the embodiments is applied. In Figure 8, a graph illustrating cell coverage during the intrafrequency cell reselection is shown. Here, the cell coverage is suboptimal at the cell edge, which limits capacity and throughput.

In Figure 8, many of the elements are the same as before and so the threshold levels on the left vertical axis are again numbered 52 for Sintrasearch, 54 for Qrxlevmin, and 55 for the minimum detection threshold. Trace 71 illustrates the initial serving cell signal power. Trace 73 depicts the initial signal power of the neighboring cell. As the UE 15 moves the edge of the service cell coverage area 71, the neighbor cell coverage is not detected at a level for reselection until the intersection 82, where suboptimal cell reselection (serving cell is below the threshold Sintrasearch, as is the neighbor cell, at the reselection point) occurs. When the cells are below the intrafrequency threshold Sintrasearch, the cell coverage is not optimal. Optimally, the reselection is triggered at the network selected threshold Sintrasearch. Here, the reselection search is occurring at lower signal levels, which is less desirable and could limit quality of service. In other words, the intrafrequency cell coverage is not good at the edges of the serving cell region in the initial coverage.

The UE 15 measures the Delta difference between the signal levels for the serving cell and the neighbor cell which is labeled "Delta" in the figure. The Delta measurement may be signaled to the network.

Figure 8 further depicts the adaptive adjustments the network may make to the transmit levels of the eNBs that provide these cells in order to optimize the network using the SON algorithms. In this example, the transmit levels for both the serving cell and the neighbor cell may be increased by the level Delta. Thus, the new trace for the serving cell 81 is shown with increased power levels. At 84, a reselection event is triggered by the intersection of the serving cell coverage with the neighbor cell coverage; this is labeled "Optimal cell reselection triggered". Trace 83 illustrates the increased signal level for the neighbor cell. The coverage gap as shown along the horizontal or bottom axis is therefore reduced from the initial suboptimal case, and optimal cell coverage is attained by the use of the adaptive SON algorithm, based on the UE Delta measurements provided to the network. Figure 9 presents in another example an overlapping cell with interferences in the interfrequency or interRAT case. The vertical axis on the left side again depicts the thresholds of interest. Here, Snonintrasearch is labeled 53, the minimum criteria for cell serving is labeled 54, and the cell detection threshold is labeled 55. As the UE 15 moves toward the edge of the serving cell coverage as shown by trace 51, the cell reselection triggered at 64 is suboptimal, because neighbor cell signal level (trace 58) is above the Snonintrasearch threshold (line 53). UE 15 takes a Delta measurement between the suboptimal reselection trigger point and the threshold level and stores it. If the network receives this Delta measurement, it may be used in an SON algorithm to reconfigure the network for optimal coverage.

Trace 59 depicts the neighbor cell levels after the network SON algorithm has suggested that the neighbor cell transmit level be lowered. Now the reselection point has moved to the optimal point as shown at 65 and the cell overlap has been reduced to the optimal performance level. The lowering of transmit power reduces power consumption and interference (pilot pollution) in the edge areas of the cells.

Figure 10 depicts another graph of a reselection event. This example illustrates the case where the serving cell signal falls below the second threshold Snonintrasearch before the reselection is triggered. Again, the threshold levels depicted and labeled on the left vertical axis are numbered as before; Snonintrasearch is numbered 53, the minimum serving criteria threshold Qrxlevmin is 54 and the minimum detection threshold is 55. Trace 71 depicts the serving cell signal strength as initially configured while trace 93 depicts the neighbor cell. In this example, the reselection in the initial, suboptimal cell edge coverage case is shown at 92; the serving cell signal has fallen below the Snonintrasearch threshold but is above the minimum serving cell threshold when reselection begins. The UE 15 measures the Delta between the signal levels at 92 (same for both the serving cell and the neighbor cell) and Snonintrasearch as shown at line 53. This Delta measurement is stored and may be signaled to the network as described above. The SON algorithm can use this measurement of Delta to determine how to increase the cell coverage. In this example, the transmit power for both the serving cell and the neighbor cell are increased by the amount Delta, which is shown by traces 91 and 95 for the serving cell and the neighbor cell, respectively. Event 94 depicts the new reselection trigger which is now at the optimal place (that is, the cell coverage has been optimized). The cell edge coverage before (suboptimal) and after the SON algorithm adaptively adjusts it based on the UE Delta measurement is shown on the horizontal axis.

In Figure 11, another exemplary method embodiment is depicted. Serving cell power signal trace 51 is shown as UE 15 moves toward the edge of serving cell coverage. In this example, there is a cell coverage gap in the initial configuration. That is, as the UE 15 leaves the serving cell coverage area, at 104, the serving cell signal power is below the minimum criteria for serving (Qrxlevmin). The channel is lost and the UE has no service. At that point, the UE can measurement the signal power of the nearest neighbor (first, intrafrequency, then interfrequency and interRAT neighbors) and a Delta measurement is taken as shown between the initial neighbor cell trace 101 and the channel lost event 102. The Delta measurement can then be signaled to the network. After an SON algorithm suggests changes in transmit power for the neighbor cell, the coverage gap can be closed. Now, as the UE 15 moves out of the serving cell coverage area as shown by trace 51, the reselection occurs at 104, where the new trace 103 from the adjusted neighbor cell meets the serving cell. In the new cell reselection, the UE will not lose service and the coverage gap has been filled, as shown by the label on the horizontal axis of Figure 11. Figure 12 depicts an exemplary method embodiment where the network may use Delta measurements received from many UEs to set optimal neighbor cell measurement threshold levels; for example, Sintrasearch. In Figure 12, the level Sintrasearch is again labeled 52 and is shown as a horizontal level line. The minimum serving criteria 54 is shown and this threshold, which is a necessary parameter, is given to the UEs by the network. The minimum detection level 55 is determined by the UE receiver hardware and is also a fixed threshold.

As the UE 15 moves away from the serving cell coverage area, initially the Sintrasearch level is not known. At 111, reselection is triggered by the detection and selection of a stronger signal neighbor cell. The UE takes a Delta measurement between the serving cell signal and the minimum Qrxlevmin. The network can receive these Delta measurements and taking an average or weighted average, calculate an optimal threshold for the level Sintrasearch for the serving cell. Similar methods for optimizing Snonintrasearch may be performed. Because the SON algorithms are continuous and incremental, these levels may be improved over time with more Delta measurements from more UEs. This method may be extended to optimize the network without the need for operators to conduct expensive measurements during drive testing, as in the prior art, and to automate the SON algorithms for new networks, or to reflect changes in the network.

Figure 13 depicts in another exemplary embodiment, the application of the enhanced UEs and Delta measurements to solving a shadowing problem in a cell coverage area. In Figure 13, two UEs 1 and 2 are camped on the serving cell. As the two UEs leave the coverage area, one is shadowed by building 134. This is represented by trace 131, which is deflected to weaker signal strength as it passes into the shadow of the building. UE 2 is not in the shadow and so, as shown by trace 132, its signal receive strength is not affected. At 144, the UE 1 loses service as the received signal strength is lower than the minimum required (Qrxlevmin). At 146, UE2 loses it channel as it too reaches the Qrxlevmin threshold while the neighbor cell signal is below the Qrxlevmin level. This is shown by trace 140. The UEs 1 and 2 then take Delta measurements. These may be received by and used by the network to perform an averaging function ((Delta UE 1 + Delta UE 2)/2)) to get a Delta average in the SON. If the network increases the neighbor transmission level by Delta_average, the UE 2 reselection will occur at 145 above the minimum threshold, improving the coverage gap for the UE 2 and no signal loss occurs. If the method iterates, and since coverage is good for UE 2, Delta_UE2 is assumed to be zero, then the Delta Averaged value obtained will be just Delta UE 1; thus the shadow problem may be solved by increasing one of the cells by Delta UEl . The method for SON may address shadowing as a statistical problem. The more shadowing; and the more UEs affected by it, the more Delta measurements will report it, and as the Deltas in the shadow area are larger, the average Delta increases. As the SON algorithms are iterative in nature, the coverage will be adaptively improved until the coverage is optimized in the shadow area.

Figure 14 depicts one manner in which the UE may store the Delta measurements as fields in a report. In this example, the date and time and location may be stored in the first column. In the second column, the Delta measurement and type may be stored. In the third column, the unique ID of the serving cell (eNB) is recorded. In the fourth column, the neighbor cell or cells IDs are recorded. In the last column, an event counter is kept. This is used to identify repeated occurrences. The order of the columns is not restricted to this illustrative example. The table may be signaled to the network via an uplink message transmitted from the UE.

For example, this may occur at typical signaling times, or it may occur on request or command by the network. In any event, the UE can provide focused event information to support the SON use cases, or to support drive test minimization use cases. As described above, different Coverage Optimization cases are supported by the Delta measurements in the proposed SON algorithms. Similar use cases could be used to support operator's drive test minimization effort.

The use of the embodiments provides measurement information to the network from the UE that has not previously been made available. To take advantage of the features of the embodiments, the network should be able to receive, store, process and analyze Delta information made available to it by the UE. These processing steps may be performed in a centralized location or in a distributed manner by network entities. The information may be used for SON algorithms or for drive test minimization, or for network analysis to identify, for example, coverage holes and neighbor cell problems.

As described above, the SON algorithms may use the Delta measurements retrieved from the UE stores to modify elements of the network to optimize performance. For example, the transmit power for the neighbor cells may be decreased (Figures 7 and 9), increased (Figures 11 and 13), both the neighbor and serving cell power levels may be increased (Figures 8 and 10), and the Delta levels may be averaged to optimize the value of threshold measures (Figures 11 and 13).

Optimization of the transmit power Tx is based on the fact that optimal cell reselection is achieved only when the power of the strongest neighbor cell is similar to the measurement threshold level. If the power is above the threshold, the cell coverage is overlapping. If the power is below this threshold, then the cell coverage is poor at the edges or a gap exists. In case of suboptimal coverage or measurement threshold setting, both UE and system performance could be degraded.

Adaptive adjustments by the network based on the enhanced UE Delta measurements stored by the UEs make it possible to optimize coverage by reducing or eliminating gaps and eliminating overlaps and interference by iterative adjustments to the cell areas.

Although the UE is described as the measuring and reporting element above, in alternative embodiments, the network may also predefine some trigger events and reporting events, which are used to limit UE reporting only to events of interest to the network for SON or other analysis algorithms. This collected data may be further analyzed and processes based on some statistical support.

The embodiments of the invention provide many advantages. By adding enhanced idle mode Delta measurements to the operation of the UEs, the embodiments may significantly support and enable the SON algorithms as proposed by the 3GPP/NGMN use cases. The embodiments may also support the 3GPP drive test minimization case. The embodiments may be implemented in existing or in design UE and network devices using only software modifications, so that no expensive hardware redesign is necessary. In the alternative, the embodiments may be implemented in hardware and software and any combination of these. The embodiments do not add power consumption over existing UE operations, as the recording of the reselection events is added to reselection that is already in place, so the power to perform the reselection process is already being consumed in the prior art approaches. The embodiments may be added to existing standards and implemented industry wide. However, even if the use of the embodiments is not universal, the UEs providing the embodiments will interoperate with other UEs and eNBs that do not support the features without error, no compatibility issues will arise.

While the embodiments of the invention have also been described above with a focus on the operation of a UE in a 3GPP eUTRAN communications system, the embodiments may be applied to other mobile devices in other communications systems where the mobile device must connect to one, and then another, cell serving terminal. Thus although the examples above were provided in the context of, and using the terminology associated with, the 3GPP standards, the invention and the embodiments are not so limited, and the claims cover systems other than UTRAN, eUTRAN and 3GPP standard systems. Generally, a mobile receiver in an embodiment system may perform the methods to measurement neighbor cells and store those relative measurements, and then the network may retrieve the stored measurements for use in analyzing and self organizing/optimizing the network.

The embodiments may be implemented using programmable processors and executable software. For example, the embodiments may be implemented as a computer readable storage product, comprising executable instructions which, when read and executed by a programmable communications terminal, cause the programmable communications terminal to perform storing Delta measurements in a memory on board the programmable communications terminal. The computer readable storage product may be provided as a flash drive, disk, optical disk, hard drive, file, internet download or other machine readable format.

Although various embodiments of the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, and composition of matter, or means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims

WHAT IS CLAIMED IS;

1. An apparatus, comprising: at least one processor; and memory including computer program code; the computer program code configured to, with the at least one processor and the memory, cause the apparatus to perform at least the following: receive signals from a plurality of transceivers over an air interface using shared radio resources; for at least one of the plurality of transceivers, compare the received signals to at least one predetermined threshold to form a relative measurement; store the relative measurement in a portion of the memory; and at a predetermined time, transmit symbols corresponding to the stored relative measurement in an uplink message over the air interface.

2. The apparatus according to claim 1 wherein the memory including the computer program code is configured to, with the at least one processor, cause said apparatus to transmit the symbols corresponding to the stored relative measurement during an active mode of operation for the apparatus.

3. The apparatus according to claim 1 or claim 2 wherein the memory including the computer program code is configured to, with the processor, cause the apparatus to receive the at least one predetermined threshold as part of a physical downlink channel communication over the air interface.

4. The apparatus according to any of claims 1-3 wherein the memory including the computer program code is configured to, with the at least one processor, cause the apparatus to perform the comparing of the received signals and storing of the relative measurement in response to the occurrence of a trigger event.

5. The apparatus according to claim 4 wherein the trigger event is one of a reselection event and a channel lost event.

6. The apparatus according to any of claims 1-5 wherein the memory including the computer program code is configured to, with the processor, cause the apparatus to store the relative measurement in a table format that also stores at least one of a time measurement and a location measurement.

7. The apparatus according to any of claims 1-6 wherein the memory including the computer program code is configured to, with the processor, cause the apparatus to compare the received signals to a predetermined threshold that is one selected from a threshold for the intra- frequency received signals, a threshold for the inter-frequency received signals, a threshold for the minimum power level for a serving cell signal, and a threshold for a minimum detectable power level for received signals.

8. An apparatus, comprising: means for allocating communication resources including physical uplink channels to a user equipment over an air interface; means for receiving signals from transceivers corresponding to cells over the air interface; means for making measurements comparing a plurality of the received signals to at least one predetermined threshold in response to the occurrence of a trigger event, the measurements computed as relative measurements; means for storing the relative measurements; and means for transmitting symbols corresponding to the relative measurements in uplink subframes as an uplink message over the air interface.

9. The apparatus of claim 8 and further comprising means for receiving from a network controller an indication of at least one trigger event in response to which said measurements are to be made.

10. The apparatus of claim 8 and further comprising means for receiving a request to transmit the stored relative measurements as a downlink message received over the air interface.

11. A computer program product comprising a program code stored in a computer readable medium, which, when executed by an apparatus including a programmable processor and a memory, is configured to cause the apparatus to perform: detecting transmitted signals from a plurality of transmitters corresponding to cells over an air interface using shared radio resources; making measurements of received signals for at least one of the plurality of transmitters; in response to the occurrence of a trigger event, computing relative measurements as a difference between the measurements of received signals and a predetermined threshold, and storing the relative measurements in an on board memory; and responsive to a signal received as a downlink channel message over the air interface, transmitting symbols corresponding to the stored measurements in an uplink message over the air interface.

12. The method according to claim 11 wherein the program code is further configured to cause the apparatus to perform: receiving the trigger event as symbols received in a downlink channel message over the air interface.

13. An apparatus, comprising: at least one processor; and memory including computer program code; the memory and the computer program code configured to, with the at least one processor, cause the apparatus to perform at least the following: receiving symbols comprising measurements of received signals from an apparatus that receives signals from a plurality of transmitters corresponding to cells; comparing the measurements to at least one predetermined threshold and computing a relative measurement; and transmitting symbols modifying signal levels for at least one of the plurality of transmitters, responsive to the result of the comparing.

14. The apparatus of claim 13 wherein the computer program code is further configured to cause the apparatus to perform transmitting symbols modifying signal levels for least one of the plurality of transmitters, responsive to the result of the comparing, to cause modifications to signals levels for at least one of reducing undesired interference between neighboring cells, optimizing cell edge coverage or capacity, limiting cell coverage gaps between neighboring cells, optimizing a threshold for sintraseach, and optimizing a threshold for Snonintrasearch.

15. The apparatus according to claim 13 wherein transmitting symbols further comprises transmitting commands via radio resource control signaling over a physical downlink channel.

16. The apparatus according to claim 13 wherein the measurements and the at least one predetermined threshold correspond to a trigger event of the apparatus that receives signals from a plurality of transmitters corresponding to cells.

17. The apparatus according to claims 13-16 wherein the at least one of a plurality of transmitters is a base station in a cellular network

18. An apparatus, comprising: means for receiving a communication containing one or more symbols, the symbols comprising measurements of received signals from an apparatus that receives signals from a plurality of transmitters corresponding to cells; means for comparing the measurements to at least one predetermined threshold and means to compute a relative measurement ; and means for transmitting symbols modifying signal levels for at least one of the plurality of transmitters, responsive to the comparing means.

19. A method, comprising: receiving a communication from a communications device containing one or more symbols, the symbols comprising measurements of received signals from a plurality of transmitters corresponding to cells; comparing the received measurements to at least one predetermined threshold and means to compute a relative measurement; and transmitting command symbols modifying signal levels for at least one of the plurality of transmitters, responsive to the result of the comparing.

20. The method according to claim 19 and further comprising modifying signal levels for least one of the plurality of transmitters, responsive to the result of the comparing, to cause modifications to signals levels for at least one of reducing undesired interference between neighboring cells, optimizing cell edge coverage or capacity, limiting cell coverage gaps between neighboring cells, optimizing a threshold for sintraseach, and optimizing a threshold for Snonintrasearch.

21. The method according to claim 19 and further comprising: comparing the measurements to a predetermined threshold corresponding to at least one selected from an intrafrequency signal level, an interfrequency signal level, a minimum serving cell signal level, and a minimum detectable signal level.