Dynamic adjustment of cell reselection parameters for a wireless communication device

A method of operating a wireless communication device to facilitate cell reselection comprises achieving downlink timing synchronization with a cell associated with a wireless access node based on information broadcast by the wireless access node over a synchronization signal, and performing a number of attempts to achieve uplink timing synchronization with the cell, wherein each of the attempts includes transmitting a preamble identifier and waiting to receive a positive acknowledgement. The method further comprises, if the number of attempts to achieve the uplink timing synchronization with the cell exceeds a threshold amount without receiving the positive acknowledgement, applying an offset to cell reselection parameters to generate modified cell reselection parameters, and responsive to the modified cell reselection parameters satisfying cell reselection criteria, performing both intra-frequency and inter-frequency measurements for potential cell reselection and selecting a different cell for potential synchronization based on the intra-frequency and the inter-frequency measurements.

TECHNICAL BACKGROUND

Wireless communication devices transmit and receive information wirelessly via a wireless access node to communicate over a communication network. Typically, the wireless access node is part of a radio access network (RAN) which provides the wireless communication devices with access to further communication networks, systems, and devices. The wireless communication devices utilize “forward link” or “downlink” communication channels to receive voice and/or data transmitted from the wireless access node, and “reverse link” or “uplink” communication channels to transmit information up to the node.

In fourth generation (4G) long term evolution (LTE) communication systems, a wireless communication device is referred to as user equipment (UE), while a wireless access node is called an enhanced node B (eNodeB). In LTE systems, when the UE is first powered on, the initial connectivity for the UE requires it to synchronize with the network as a first step in gaining access to network resources. The eNodeB continuously broadcasts a primary synchronization signal (PSS) for slot synchronization and a secondary synchronization signal (SSS) for frame synchronization. The eNodeB also periodically transmits data in the form of a master information block (MIB) and several system information blocks (SIBs). Once the UE synchronizes with the network, it receives and processes the MIB from the eNodeB. After processing the MIB, the UE reads the SIB1 and SIB2 information blocks which carry important information for the UE to select a cell.

OVERVIEW

A method of operating a wireless communication device to facilitate cell reselection is disclosed. The method comprises achieving downlink timing synchronization with a cell associated with a wireless access node based on information broadcast by the wireless access node over a synchronization signal. The method further comprises performing a number of attempts to achieve uplink timing synchronization with the cell, wherein each of the attempts includes transmitting a preamble identifier over a random access channel to the wireless access node and waiting a time period to receive a positive acknowledgement. The method further comprises, if the number of attempts to achieve the uplink timing synchronization with the cell exceeds a threshold amount without receiving the positive acknowledgement, applying an offset to cell reselection parameters to generate modified cell reselection parameters. The method further comprises, responsive to the modified cell reselection parameters satisfying cell reselection criteria, performing both intra-frequency and inter-frequency measurements for potential cell reselection. The method further comprises selecting a different cell for potential synchronization based on the intra-frequency and the inter-frequency measurements.

A wireless communication device to facilitate cell reselection comprises a wireless communication transceiver and a processing system. The processing system is configured to achieve downlink timing synchronization with a cell associated with a wireless access node based on information broadcast by the wireless access node over a synchronization signal. The processing system is further configured to perform a number of attempts to achieve uplink timing synchronization with the cell, wherein each of the attempts includes the processing system configured to direct the wireless communication transceiver to transmit a preamble identifier over a random access channel to the wireless access node and wait a time period to receive a positive acknowledgement. The processing system is further configured to, if the number of attempts to achieve the uplink timing synchronization with the cell exceeds a threshold amount without receiving the positive acknowledgement, apply an offset to cell reselection parameters to generate modified cell reselection parameters. The processing system is further configured to, responsive to the modified cell reselection parameters satisfying cell reselection criteria, direct the wireless communication transceiver to perform both intra-frequency and inter-frequency measurements for potential cell reselection. The processing system is further configured to select a different cell for potential synchronization based on the intra-frequency and the inter-frequency measurements.

A computer apparatus to facilitate cell reselection comprises software instructions and at least one non-transitory computer-readable storage medium storing the software instructions. The software instructions are configured, when executed by a wireless communication device, to direct the wireless communication device to achieve downlink timing synchronization with a cell associated with a wireless access node based on information broadcast by the wireless access node over a synchronization signal, perform a number of attempts to achieve uplink timing synchronization with the cell, wherein each of the attempts includes transmitting a preamble identifier over a random access channel to the wireless access node and waiting a time period to receive a positive acknowledgement, and if the number of attempts to achieve the uplink timing synchronization with the cell exceeds a threshold amount without receiving the positive acknowledgement, apply an offset to cell reselection parameters to generate modified cell reselection parameters. The software instructions are further configured to direct the wireless communication device to, responsive to the modified cell reselection parameters satisfying cell reselection criteria, perform both intra-frequency and inter-frequency measurements for potential cell reselection and select a different cell for potential synchronization based on the intra-frequency and the inter-frequency measurements.

DETAILED DESCRIPTION

The following description and associated drawings teach the best mode of the invention. For the purpose of teaching inventive principles, some conventional aspects of the best mode may be simplified or omitted. The following claims specify the scope of the invention. Some aspects of the best mode may not fall within the scope of the invention as specified by the claims. Thus, those skilled in the art will appreciate variations from the best mode that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. As a result, the invention is not limited to the specific examples described below, but only by the claims and their equivalents.

FIG. 1is a block diagram that illustrates communication system100. Communication system100includes wireless communication device101, wireless access node110, and communication network130. Wireless communication device101and wireless access node110are in communication over wireless communication link111. Wireless access node110and communication network130communicate over communication link121. InFIG. 1, wireless access node110serves cell sectors115-117. Cells115-117shown inFIG. 1represent geographic areas of signal coverage served by wireless access node110. As shown inFIG. 1, wireless communication device101is presently located in cell sector115served by wireless access node110.

FIG. 2is a flow diagram that illustrates an operation of communication system100. The steps of the operation are indicated below parenthetically. The operation of communication system100shown inFIG. 2may be employed to facilitate cell reselection for wireless communication device101.

To begin, wireless communication device101achieves downlink timing synchronization with cell115associated with wireless access node110based on information broadcast by wireless access node110over a synchronization signal (201). Typically, wireless access node110could transmit information on both a primary and a secondary synchronization signal for slot and frame synchronization, respectively, and wireless communication device101could determine the cell identifier of cell115from this information in some examples. Wireless communication device101may then achieve downlink synchronization timing based on the information received from wireless access node110over the synchronization signal. In some examples, wireless access node110broadcasts system information, such as channel bandwidth, system frame number, cell identifiers, network capabilities, and other data in the form of a master information block (MIB) and a plurality of system information blocks (SIBs). Wireless communication device101may utilize some or all of this information to achieve downlink timing synchronization for camping on cell115in some examples.

Wireless communication device101then performs a number of attempts to achieve uplink timing synchronization with cell115, wherein each of the attempts includes transmitting a preamble identifier over a random access channel to wireless access node110and waiting a time period to receive a positive acknowledgement (202). Typically, wireless communication device101attempts to achieve uplink timing synchronization with cell115by carrying out a random access procedure (RAP) using a random access channel (RACH) process. In some examples, wireless communication device101indicates its resource requirement to communication network130along with transmitting the random access preamble identifier, and device101waits for a response from wireless access node110in the form of a random access response (RAR). For each attempt to achieve uplink timing synchronization with cell115, wireless communication device101typically waits for a predetermined number of time slots to receive a RAR or some other positive acknowledgement from wireless access node110. If a positive acknowledgement is not received during the time period that wireless communication device101is configured to wait, device101may reattempt to achieve uplink timing synchronization with cell115by transmitting another preamble identifier, and may increase the power level for each subsequent RACH attempt in some examples.

If the number of attempts to achieve the uplink timing synchronization with cell115exceeds a threshold amount without receiving the positive acknowledgement, wireless communication device101applies an offset to cell reselection parameters to generate modified cell reselection parameters (203). Typically, the threshold amount may be set to a predetermined value that limits the number of RACH attempts that wireless communication device101will make. Once the threshold amount is exceeded without receiving a positive acknowledgement from wireless access node110, wireless communication device101applies an offset to cell reselection parameters to generate modified cell reselection parameters. The offset that wireless communication device101applies to the cell reselection parameters may be any positive or negative value, but the modified cell reselection parameters that are generated as a result of applying the offset are typically configured to trigger wireless communication device101to perform both intra-frequency and inter-frequency measurements for potential cell reselection. Note that the offset that wireless communication device101applies may be different numerical values for different ones of the cell reselection parameters in some examples. The cell reselection parameters could include any attributes that wireless communication device101could utilize for cell reselection. For example, the cell reselection parameters could include S_IntraSearch and S_NonIntraSearch parameter values in some examples, and these parameters may be initially received by wireless communication device101in a system information block type 3 (SIB-3) message. Other cell reselection parameters are possible and included within the scope of this disclosure.

Responsive to the modified cell reselection parameters satisfying cell reselection criteria, wireless communication device101performs both intra-frequency and inter-frequency measurements for potential cell reselection (204). Typically, the cell reselection parameters do not satisfy the cell reselection criteria, but after offsetting the cell reselection parameters, the modified cell reselection parameters will satisfy the cell reselection criteria. This is because the offset is designed to force the cell reselection parameters to satisfy the cell reselection criteria, thereby triggering intra-frequency and inter-frequency search. In some examples, the inter-frequency search could include inter-radio access technology (IRAT) measurements. The cell reselection criteria could include a minimum reference signal receive power (RSRP) level received from cell115in some examples. Typically, wireless communication device101performs intra-frequency and inter-frequency measurements for its serving cell115and other neighboring cells116and117, and then compares and ranks these values to determine cell reselection, although other techniques are possible.

Wireless communication device101then selects a different cell116or117for potential synchronization based on the intra-frequency and the inter-frequency measurements (205). For ease of explanation, this example assumes that cell116is selected by wireless communication device101as the different cell to try for potential synchronization. Typically, wireless communication device101would select the different cell116based on cell116having the highest RSRP value of all the neighboring cells115-117for which intra-frequency and inter-frequency measurements were taken. In some instances, when comparing RSRP values associated with the cell115and the different cell116, wireless communication device101may determine that these values are fairly similar, i.e., within a predefined range of each other. Therefore, in some examples, if the RSRP values fall within a predefined range of each other, wireless communication device101may perform a first portion of a predefined number of attempts to achieve uplink timing synchronization with cell115, and if uplink timing synchronization is not achieved with cell115during the first portion of the predefined number of attempts, device101may perform a second portion of the predefined number of attempts to achieve uplink timing synchronization with the different cell116.

Advantageously, after a threshold number of failed attempts to achieve uplink timing synchronization with a cell115, wireless communication device101dynamically modifies cell reselection parameters in order to force reselection of a different cell116. Wireless communication device101can then attempt to achieve uplink timing synchronization with the reselected different cell116instead of performing repeated attempts that fail to synchronize with the initial cell115. By dynamically modifying the cell reselection parameters with an offset so that they will satisfy the cell reselection parameters, wireless communication device101will originate a preamble on the different cell116sooner than it would otherwise, thereby improving the user experience and reducing the burden on network resources.

Referring back toFIG. 1, wireless communication device101comprises any device having wireless communication connectivity with hardware and circuitry programmed to function as a telecommunications device, such as Radio Frequency (RF) communication circuitry and an antenna. The RF communication circuitry typically includes an amplifier, filter, modulator, and signal processing circuitry. Wireless communication device101may also include a user interface, memory system, software, processing circuitry, or some other communication components. For example, wireless communication device101could comprise a telephone, transceiver, mobile phone, cellular phone, smartphone, computer, personal digital assistant (PDA), e-book, game console, mobile Internet device, wireless network interface card, media player, or some other wireless communication apparatus—including combinations thereof. Wireless network protocols that may be utilized by wireless communication device101include Code Division Multiple Access (CDMA) 1xRTT, Global System for Mobile communications (GSM), Universal Mobile Telecommunications System (UMTS), High-Speed Packet Access (HSPA), Evolution-Data Optimized (EV-DO), EV-DO rev. A, B, and C, Third Generation Partnership Project Long Term Evolution (3GPP LTE), LTE Advanced, Worldwide Interoperability for Microwave Access (WiMAX), IEEE 802.11 protocols (Wi-Fi), Bluetooth, Internet, telephony, or any other wireless network protocol that facilitates communication between wireless communication device101and wireless access node110.

Wireless access node110comprises RF communication circuitry and an antenna. The RF communication circuitry typically includes an amplifier, filter, RF modulator, and signal processing circuitry. Wireless access node110may also comprise a router, server, memory device, software, processing circuitry, cabling, power supply, network communication interface, structural support, or some other communication apparatus. Wireless access node110could comprise a base station, Internet access node, telephony service node, wireless data access point, or some other wireless communication system—including combinations thereof. Some examples of wireless access node110include a base transceiver station (BTS), base station controller (BSC), radio base station (RBS), Node B, enhanced Node B (eNodeB), and others—including combinations thereof. Wireless network protocols that may be utilized by wireless access node110include CDMA, GSM, UMTS, HSPA, EV-DO, EV-DO rev. A, B, and C, 3GPP LTE, LTE Advanced, WiMAX, Wi-Fi, Bluetooth, Internet, telephony, or some other communication format—including combinations thereof.

Cell sectors115-117each comprise geographic areas with approximate boundary lines as indicated by the dotted lines onFIG. 1, which are typically defined by the signal propagation characteristics and coverage capabilities of wireless access node110. Each sector115-117represents a different coverage area of wireless access node110. For example, each sector115-117served by wireless access node110may be served by separate antennas of wireless access node110, providing each sector115-117a separate direction of tracking and/or different range with respect to the other cell sectors.

Communication network130comprises the core network of a wireless communication service provider, and could include routers, gateways, telecommunication switches, servers, processing systems, or other communication equipment and systems for providing communication and data services. Communication network130could comprise wireless communication nodes, telephony switches, Internet routers, network gateways, computer systems, communication links, or some other type of communication equipment—including combinations thereof. Communication network130may also comprise optical networks, asynchronous transfer mode (ATM) networks, packet networks, radio access networks (RAN), local area networks (LAN), metropolitan area networks (MAN), wide area networks (WAN), or other network topologies, equipment, or systems—including combinations thereof. Communication network130may be configured to communicate over metallic, wireless, or optical links—including combinations thereof. Communication network130may be configured to use time-division multiplexing (TDM), Internet Protocol (IP), Ethernet, optical networking, wireless protocols, communication signaling, or some other communication format—including combinations thereof. In some examples, communication network130includes further access nodes and associated equipment for providing communication services to many wireless communication devices across a large geographic region.

Wireless communication link111uses the air or space as the transport medium. Wireless communication link111may use various protocols, such as CDMA, GSM, UMTS, HSPA, EV-DO, EV-DO rev. A, B, and C, 3GPP LTE, LTE Advanced, WiMAX, Wi-Fi, Bluetooth, Internet, telephony, or some other communication format—including combinations thereof. Wireless communication link111may comprise many different signals sharing the same link. For example, wireless communication link111could include multiple signals operating in a single propagation path comprising multiple communication sessions, frequencies, timeslots, transportation ports, logical transportation links, network sockets, IP sockets, packets, or communication directions—including combinations thereof.

Communication link121uses metal, air, space, optical fiber such as glass or plastic, or some other material as the transport medium—including combinations thereof. Communication link121could use various communication protocols, such as TDM, IP, Ethernet, telephony, optical networking, hybrid fiber coax (HFC), communication signaling, wireless protocols, or some other communication format—including combinations thereof. Communication link121may be a direct link or could include intermediate networks, systems, or devices.

FIG. 3is a block diagram that illustrates long term evolution (LTE) communication system300in an exemplary embodiment. LTE communication system300includes enhanced Node B (eNodeB) base stations that are in communication with the 4G LTE communication network. The eNodeB base stations provide an example of wireless access node110, although node110may use alternative configurations. 4G LTE communication network could include a mobility management entity (MME), serving gateway (SGW), packet data network gateway (PGW), and other network elements typically found in a 4G LTE communication network. Each eNodeB has a wireless coverage area with approximate boundaries as indicated by the dotted line or lines encircling each respective eNodeB, which are typically defined by their signal propagation characteristics and coverage capabilities. LTE communication system300also includes a user equipment (UE) device which is shown as being served by one of the eNodeB base stations. The cell surrounding the eNodeB could be referred to as a serving cell for the UE located within it. In this example, the eNodeB serving the UE includes two different cells which partially overlap, as shown by the dotted lines encircling the eNodeB.

In operation, when the UE is first powered on, the initial connectivity for the UE requires it to synchronize with the network as a first step in gaining access to network resources. Initially, the UE has to synchronize with the network at the frame and slot level. The eNodeB continuously broadcasts a primary synchronization signal (PSS) and a secondary synchronization signal (SSS). The PSS is responsible for slot synchronization and the SSS is utilized for frame synchronization, and are typically sent at the last orthogonal frequency-division multiplexing (OFDM) symbol of the first and eleventh slot of each frame. Using both of these signals, the UE can derive the physical cell identifier of the corresponding cell.

The eNodeB also periodically transmits data in the form of a master information block (MIB) and several system information blocks (SIBs). Once the UE synchronizes with the network, it receives and processes the MIB from the eNodeB. The MIB includes system information in the form of a limited number of parameters that are needed by the UE to acquire other information from the cell, including a public land mobile network (PLMN) identifier, tracking area identifier, cell identifier, channel bandwidth, system frame number, physical hybrid automatic repeat request (HARQ) indicator channel (PHICH), and the capabilities of the radio access network and core network.

After processing the MIB, the UE reads the SIB1 and SIB2 information blocks which carry important information for the UE to select a cell. In particular, SIB1 contains parameters related to cell access and the scheduling of other SIBs, while SIB2 includes configurations for common and shared channels, including random access channel (RACH) configurations. The UE receives and processes the information in SIB1 and SIB2 and achieves synchronization with the network in the downlink direction.

In order to synchronize with the network in the uplink direction, the UE initiates a random access procedure (RAP). The UE utilizes the RACH to transmit a message to the network to indicate its resource requirement, and this message also typically includes a preamble identifier. If the eNodeB successfully receives the random access preamble from the UE, it transmits a random access response back and the UE is then able to achieve uplink timing synchronization with the network. However, if use of the RACH is in contention with other UEs, the preamble messages transmitted by the multiple UEs may collide and thus not be received by the eNodeB. In this case, the UE does not receive a response from the eNodeB, and the UE then typically keeps sending additional RACH attempts to the same eNodeB indefinitely until a positive acknowledgement is received.

However, in this example, instead of sending an indefinite amount of RACH attempts, a threshold is set to limit the number of attempts the UE will make. If a positive response is not received from the eNodeB before the threshold number of RACH attempts is reached, the UE applies an offset to the cell reselection parameters s_IntraSearch and s_NonIntraSearch that the UE receives from reading the SIB3 information block. The offset is designed to trigger both intra-frequency as well as inter-frequency/IRAT measurements for potential cell reselection. By applying the offset to force the cell reselection parameters to satisfy the cell reselection criteria, the UE effectively triggers the use of inter-frequency search earlier than it would normally. The inter-frequency search allows the UE to identify a different cell and initiate a preamble on the different cell. The UE may then successfully synchronize with the different cell in the uplink direction. An example of how the intra-frequency and inter-frequency search may be triggered early by adjusting the s_IntraSearch and s_NonIntraSearch parameters will now be described with respect toFIG. 4.

FIG. 4is a trend diagram that illustrates a plot400of reference signal received power (RSRP) over time in an exemplary embodiment. The y-axis of plot400shows RSRP in dBm, which is the power ratio in decibels (dB) of the measured power referenced to one milliwatt. Three different levels of RSRP values are shown by the dashed lines on plot400, which are provided by the cell reselection parameters in the SIB3 message. In this example, the s_IntraSearch parameter indicates that the UE should initiate intra-frequency search when the RSRP value received from the cell falls below −58 dBm, the s_NonIntraSearch parameter indicates that the UE should initiate inter-frequency search when the RSRP value falls below −90 dBm, and the minimum RSRP quality level is set to −120 dBm.

As shown in plot400, as time starts elapsing and just after zero seconds, the RSRP value from the cell that the UE is camped on drops below −58 dBm which satisfies the s_IntraSearch parameter and triggers intra-frequency search by the UE. Later, at a time of one second, the UE observes the RSRP value of the cell dropping below the −90 dBm level which satisfies the s_NonIntraSearch parameter, triggering inter-frequency search. During the time of one seconds to three seconds the RSRP value stays below −90 dBm so the UE continues to perform both intra-frequency and inter-frequency measurements. After a time of three seconds, the RSRP value from the cell rises above the −90 dBm threshold, so the UE stops taking inter-frequency measurements. Then, after a time of four seconds, the RSRP value rises above the −58 dBm level so the UE stops taking intra-frequency measurements.

In order to force both intra-frequency and inter-frequency search sooner, the RSRP values for the s_IntraSearch parameter of −58 dBm and the s_NonIntraSearch parameter of −90 dBm could be offset to move up these threshold levels. For example, the s_NonIntraSearch parameter of −90 dBm could be offset to move closer to or even above the −58 dBm level defined by the s_IntraSearch parameter, thereby triggering inter-frequency search sooner than the time of one second that would occur if the offset were not applied. In this manner, the UE will find additional neighboring cells to consider for potential cell reselection. Once the UE measures the serving cell and the neighboring cells, it will rank these cells based in part on the cell reselection timer and Q_hyst, which is the hysteresis value for cell re-selection ranking criteria that is added to the serving cell RSRP measurement. In some examples, an offset may be applied to the Q_hyst value of a neighboring cell so that the neighboring cell is ranked higher than the serving cell and thus selected earlier.

In some examples, if the UE detects a neighboring cell having a comparable RSRP of the serving cell, the UE could split between the two cells the number of RACH attempts allowed for uplink synchronization that is set by the threshold. For example, the UE could read the preamble information from the SIB2 of the neighboring cell having the comparable RSRP of the serving cell and initiate a RACH algorithm wherein an initial set of RACH attempts are sent to the serving cell, and if no positive response is received, the remaining attempts are sent to the neighboring cell. In this manner, the UE will achieve uplink synchronization with a cell faster than using the traditional technique of sending indefinite RACH attempts to the same cell.

FIG. 5is a block diagram that illustrates wireless communication device500. Wireless communication device500provides an example of wireless communication device101, although device101could use alternative configurations. Wireless communication device500comprises wireless communication transceiver501, processing system502, and user interface503. Processing system502is linked to wireless communication transceiver501and user interface503. Processing system502includes processing circuitry504and memory system505that stores operating software506. Operating software506comprises software modules507-511. Wireless communication device500may include other well-known components such as a battery and enclosure that are not shown for clarity. Wireless communication device500may comprise a telephone, computer, e-book, mobile Internet appliance, media player, game console, wireless network interface card, or some other wireless communication apparatus—including combinations thereof.

Wireless communication transceiver501comprises RF communication circuitry and an antenna. The RF communication circuitry typically includes an amplifier, filter, RF modulator, and signal processing circuitry. Wireless communication transceiver501may also include a memory system, software, processing circuitry, or some other communication device. Wireless communication transceiver501may use various protocols, such as CDMA, GSM, UMTS, HSPA, EV-DO, EV-DO rev. A, 3GPP LTE, LTE Advanced, WiMAX, Wi-Fi, Bluetooth, Internet, telephony, or some other wireless communication format. Wireless communication transceiver501may be configured to achieve downlink timing synchronization with a cell associated with a wireless access node based on information broadcast by the wireless access node over a synchronization signal. Further, wireless communication transceiver501may be configured to perform a number of attempts to achieve uplink timing synchronization with the cell, wherein each of the attempts includes transmitting a preamble identifier over a random access channel to the wireless access node and waiting a time period to receive a positive acknowledgement. In addition, wireless communication transceiver501may be configured to perform both intra-frequency and inter-frequency measurements for potential cell reselection responsive to modified cell reselection parameters satisfying cell reselection criteria.

User interface503comprises components that interact with a user to receive user inputs and to present media and/or information. User interface503may include a speaker, microphone, buttons, lights, display screen, touchscreen, touch pad, scroll wheel, communication port, or some other user input/output apparatus—including combinations thereof. User interface503may be omitted in some examples.

Processing circuitry504comprises microprocessor and other circuitry that retrieves and executes operating software506from memory system505. Processing circuitry504may comprise a single device or could be distributed across multiple devices—including devices in different geographic areas. Processing circuitry504may be embedded in various types of equipment. Processing circuitry504is typically mounted on a circuit board that may also hold memory system505and portions of wireless communication transceiver501and user interface503. Memory system505comprises a non-transitory computer readable storage medium, such as a disk drive, flash drive, data storage circuitry, or some other hardware memory apparatus. Memory system505may comprise a single device or could be distributed across multiple devices—including devices in different geographic areas. Memory system505may be embedded in various types of equipment. In some examples, a computer apparatus could comprise memory system505and operating software506. Operating software506comprises computer programs, firmware, or some other form of machine-readable processing instructions. Operating software506may include an operating system, utilities, drivers, network interfaces, applications, or some other type of software. In this example, operating software506comprises software modules507-511, although software506could have alternative configurations in other examples.

When executed by processing circuitry504, operating software506directs processing system502to operate wireless communication device500as described herein for wireless communication device101. In particular, operating software506directs processing system502to achieve downlink timing synchronization with a cell associated with a wireless access node based on information broadcast by the wireless access node over a synchronization signal. Operating software506further directs processing system502to perform a number of attempts to achieve uplink timing synchronization with the cell, wherein each of the attempts includes processing system502configured to direct wireless communication transceiver501to transmit a preamble identifier over a random access channel to the wireless access node and wait a time period to receive a positive acknowledgement. In addition, operating software506directs processing system502to, if the number of attempts to achieve the uplink timing synchronization with the cell exceeds a threshold amount without receiving the positive acknowledgement, apply an offset to cell reselection parameters to generate modified cell reselection parameters. Operating software506directs processing system502to, responsive to the modified cell reselection parameters satisfying cell reselection criteria, direct wireless communication transceiver501to perform both intra-frequency and inter-frequency measurements for potential cell reselection. Finally, operating software506directs processing system502to select a different cell for potential synchronization based on the intra-frequency and the inter-frequency measurements.

In this example, operating software506comprises a downlink synchronization software module507that achieves downlink timing synchronization with a cell associated with a wireless access node based on information broadcast by the wireless access node over a synchronization signal. Additionally, operating software506comprises an uplink synchronization software module508that performs a number of attempts to achieve uplink timing synchronization with the cell, wherein each of the attempts includes transmitting a preamble identifier over a random access channel to the wireless access node and waiting a time period to receive a positive acknowledgement. Operating software506also comprises an offset application software module509that applies an offset to cell reselection parameters to generate modified cell reselection parameters that if the number of attempts to achieve the uplink timing synchronization with the cell exceeds a threshold amount without receiving the positive acknowledgement. Further, operating software506comprises a frequency measurement software module510that performs both intra-frequency and inter-frequency measurements for potential cell reselection responsive to the modified cell reselection parameters satisfying cell reselection criteria. Finally, operating software506comprises a cell selection software module511that selects a different cell for potential synchronization based on the intra-frequency and the inter-frequency measurements.