WO2015188364A1

WO2015188364A1 - Optimizing timing advance determination in uplink channel synchronization

Info

Publication number: WO2015188364A1
Application number: PCT/CN2014/079809
Authority: WO
Inventors: Gaoshan LI; Insung Kang; Shuyang YIN
Original assignee: Qualcomm Incorporated
Priority date: 2014-06-13
Filing date: 2014-06-13
Publication date: 2015-12-17

Abstract

Described herein are various aspects related to optimizing timing advance (TA) determination in uplink channel synchronization. For example, a plurality of access requests can be transmitted according to a TA using power ramping. It can be determined that a maximum transmit power is achieved by one of the plurality of access requests, and in this case, a TA training sequence can be transmitted comprising another plurality of access requests at varying TAs using a maximum transmit power based on determining that the maximum transmit power is achieved. Further, if no response is received to the another plurality of access requests, a trial sequence can be transmitted comprising a third plurality of access requests according to the TA using a maximum transmit power.

Description

OPTIMIZING TIMING ADVANCE DETERMINATION IN UPLINK

CHANNEL SYNCHRONIZATION

BACKGROUND

[0001] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency divisional multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

[0002] Devices can attempt access in a wireless network using one of the multiple access technologies by transmitting an uplink signal on a random access channel (RACH) provided by a cell of the wireless network. In synchronized TDMA system, when transmitting the uplink signal, the device must first send a reference signal to network, then the network measures this reference signal to acquire timing advance (TA) information for this device. Subsequently, the network sends this timing advance information back to the device. After the device receives the TA information from network it can start to communicate with network. In TD-SCDMA, this uplink reference signal is referred to as sync-UL, and is transmitted in the uplink pilot time slot (UPPTS) of the TD-SCDMA frame structure.

[0003] The default TA of random access in TD-SCDMA system is 48 chips, so the sync-UL will fall into the gap of the frame structure at Node B between uplink and downlink transmissions. The interference of this gap at the Node B comes from surrounding UEs and Node Bs, and the interference distribution is not flat in this gap. There is a mechanism that attempts to find a desirable TA to make the UE's sync-UL fall into the smallest interference position of this gap. Thus when UEs perform random access with the best TA in a cell, the rate of detection in the network can be higher for the UE. This mechanism divides the gap into N parts, where each part corresponds to a different TA of UE (e.g., N=7), corresponding to UE's timing advance (e.g., 0, 8, 16, 24, 32, 40, 48). Each part of this gap has different interference, thus for a UE, different detection rate at the Node B for each TA. By trying all these TAs in random access procedure, the UE generates a table of successful rate for all TAs.

[0004] In current TA selection mechanisms, N different TAs are transmitted circularly using power ramping, and the power will go back to the small initial power every M sync-ULs if response of access request is not received. In a weak coverage cell, the Tx power of sync- UL generally reaches a maximum transmit power, so all TAs transmit in the same power and the successful rate may be accurate. But in strong coverage but heavy interference cell, the transmit power of sync-ULs may not reach the maximum transmit power but go in a power ramping cycle. Thus, the true best TA may be transmitted by small power, but other TA may use additional power and finally be detected by Node B. Thus, the successful rate for the TA may be falsely reported due to the increase in transmit power for other TAs, and the current TA selection mechanisms do not help to increase the random access successful rate in such case. Another defect of current TA selection mechanisms is that a balance between moving and static scenarios cannot be achieved. For instance, adapting the successful rate table as fast as possible to accommodate cases when the UE moving from one cell to another may make TA selection or subsequent sync-UL transmission unstable when UE staying in one cell, and/or vice versa. Also, current TA selection mechanisms give a best TA and other TAs the same chance to transmit during the random access procedure, which may not be intuitive as the best TA should likely have more chances.

SUMMARY

[0005] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0006] In an example, a method for determining timing advance in wireless communications is provided. The method includes transmitting a plurality of access requests according to a timing advance (TA) using power ramping, and determining that a maximum transmit power is achieved by one of the plurality of access requests. The method further includes transmitting a TA training sequence comprising another plurality of access requests at varying TAs using a maximum transmit power based on determining that the maximum transmit power is achieved.

[0007] To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a block diagram illustrating an example wireless communications system according to the present disclosure;

[0009] FIG. 2 is a flow diagram comprising a plurality of functional blocks representing an example methodology of the present disclosure;

[0010] FIG. 3 illustrates example timelines in accordance with aspects of the present disclosure;

[0011] FIG. 4 is a flow diagram comprising a plurality of functional blocks representing an example methodology of the present disclosure;

[0012] FIG. 5 is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system;

[0013] FIG. 6 is a block diagram conceptually illustrating an example of a telecommunications system;

[0014] FIG. 7 is a conceptual diagram illustrating an example of an access network; and

[0015] FIG. 8 is a block diagram conceptually illustrating an example of a Node B in communication with a UE in a telecommunications system.

DETAILED DESCRIPTION

[0016] The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

[0017] Various aspects described herein relate to determining a timing advance to utilize in synchronizing an uplink channel. In an example, a device can utilize a fixed timing advance (TA) as part of the initial transmit power ramping in transmitting an uplink reference signal (sync-UL). The fixed TA can correspond to a default TA (e.g., in an initial procedure with a new cell), a determined optimal TA (e.g., based on previous access attempts to the cell), and/or the like. After the initial transmit power ramping at the fixed TA, if a response from the cell is not received to the uplink signals and a maximum transmit power is achieved at the device, the device can then initiate a TA training sequence by cycling through the TAs at the maximum transmit power. If a response is received to one of the uplink transmissions at a given TA, the TA can be used for following random access of the same cell, and a success rate can be updated for the TA in a successful rate table. The successful rate table can be used to determine the fixed TA described above.

[0018] If a response is still not received to the uplink signals transmitted as part of the TA training sequence, the device may initiate a TA trial sequence by transmitting using the fixed TA at maximum power for a number of cycles in an attempt to receive a response. If a response is received during the TA trial sequence, the device can use the TA in following random access of the same cell, though the successful rate table may not be updated for the TA. If a response is not received during the trial sequence for the TA, the device may again perform the TA training sequence, and so on until the maximum number of trials is reached. In addition, when the device is camping on a different cell, the successful rate table can be cleared to allow determining successful TA(s) for the different cell.

[0019] FIG. 1 is a schematic diagram illustrating a system 100 for wireless communication, according to an example configuration. FIG. 1 includes a UE 102 operable to communicate with at least one network entity 104 for receiving access to a wireless network. For example, network entity 104 may provide one or more cells that facilitate communicating with one or more UEs 102 to provide the wireless network access. Though one UE 102 and network entity 104 are shown, it is to be appreciated that UE 102 can communicate with multiple network entities 104, network entity 104 can communicate with multiple UEs 102 in one or more provided cells, etc.

[0020] UE 102 may comprise any type of mobile device, such as, but not limited to, a smartphone, cellular telephone, mobile phone, laptop computer, tablet computer, or other portable networked device that can be a standalone device, tethered to another device (e.g., a modem connected to a computer), and/or the like. In addition, UE 102 may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a mobile communications device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. In general, UE 102 may be small and light enough to be considered portable and may be configured to communicate wirelessly via an over-the-air communication link using one or more OTA communication protocols described herein. Additionally, in some examples, UE 102 may be configured to facilitate communication on multiple separate networks via multiple separate subscriptions, multiple radio links, and/or the like.

[0021] Furthermore, network entity 104 may comprise one or more of any type of network module, such as an access point, a macro cell, including a base station (BS), node B, eNodeB (eNB), a relay, a peer-to-peer device, an authentication, authorization and accounting (AAA) server, a mobile switching center (MSC), a mobility management entity (MME), a radio network controller (RNC), a small cell, etc. As used herein, the term "small cell" may refer to an access point or to a corresponding coverage area of the access point, where the access point in this case has a relatively low transmit power or relatively small coverage as compared to, for example, the transmit power or coverage area of a macro network access point or macro cell. For instance, a macro cell may cover a relatively large geographic area, such as, but not limited to, several kilometers in radius. In contrast, a small cell may cover a relatively small geographic area, such as, but not limited to, a home, a building, or a floor of a building. As such, a small cell may include, but is not limited to, an apparatus such as a BS, an access point, a femto node, a femtocell, a pico node, a micro node, a Node B, eNB, home Node B (HNB) or home evolved Node B (HeNB). Therefore, the term "small cell," as used herein, refers to a relatively low transmit power and/or a relatively small coverage area cell as compared to a macro cell. Additionally, network entity 104 may communicate with one or more other network entities of wireless and/or core networks

[0022] Additionally, network entity 104 can utilize one or more of wide-area networks (WAN), wireless networks (e.g. 802.11 or cellular network), the Public Switched Telephone Network (PSTN) network, ad hoc networks, personal area networks (e.g. Bluetooth®) or other combinations or permutations of network protocols and network types. Such network(s) may include a single local area network (LAN) or wide-area network (WAN), or combinations of LANs or WANs, such as the Internet. Such networks may comprise a Wideband Code Division Multiple Access (W-CDMA) system, and may communicate with one or more UEs 102 according to this standard. As those skilled in the art will readily appreciate, various aspects described throughout this disclosure may be extended to other telecommunication systems, network architectures and communication standards. By way of example, various aspects may be extended to other Universal Mobile Telecommunications System (UMTS) systems such as Time Division Synchronous Code Division Multiple Access (TD-SCDMA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), High Speed Packet Access Plus (HSPA+) and Time-Division CDMA (TD-CDMA). Various aspects may also be extended to systems employing Long Term Evolution (LTE) (in FDD, TDD, or both modes), LTE-Advanced (LTE-A) (in FDD, TDD, or both modes), CDMA2000, Evolution-Data Optimized (EV-DO), Ultra Mobile Broadband (UMB), Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX®), IEEE 802.20, Ultra-Wideband (UWB), Bluetooth, and/or other suitable systems. The actual telecommunication standard, network architecture, and/or communication standard employed will depend on the specific application and the overall design constraints imposed on the system. The various devices coupled to the network(s) (e.g., UEs 102, network entity 104) may be coupled to a core network via one or more wired or wireless connections.

[0023] Referring to FIGs. 1-4, aspects of the present apparatus and method are depicted with reference to one or more components and one or more methods that may perform the actions or functions described herein. Although the operations described below in FIGs. 2 and 4 are presented in a particular order and/or as being performed by an example component, it should be understood that the ordering of the actions and the components performing the actions may be varied, depending on the implementation. Moreover, it should be understood that the following actions or functions may be performed by a specially- programmed processor, a processor executing specially-programmed software or computer- readable media, or by any other combination of a hardware component and/or a software component capable of performing the described actions or functions.

[0024] FIG. 1 includes a UE 102 with a communicating component 110 operable to perform functions described herein. For example, communicating component 110 can include a processor, transceiver, memory, and/or substantially any component of UE 102 suitable for performing the functions described herein. FIG. 2 illustrates an example method 200 for transmitting access requests to determine a timing synchronization for an uplink channel. Method 200 includes, at Block 202, transmitting one or more access requests according to a TA using power ramping. Communicating component 110 of UE 102 (FIG. 1) includes a TA selecting component 112 for determining a TA for transmitting an access request, a transmit power component 114 for determining a power for transmitting the access request, and an access request transmitting component 116 for transmitting access requests based on the determined TA and power.

[0025] Thus, for example, TA selecting component 112 can select a TA for performing a procedure to synchronize with an uplink channel, such as a RACH procedure. TA selecting component 112 can select a TA to utilize in performing the procedure, which can include a default TA for initiating the procedure in a new cell (which may be configured by the network, by the specific cell or network node, etc.), an optimal TA determined based at least in part on a successful rate table 120 indicating success parameters for a plurality of previously utilized TAs in the cell (described further herein), etc. Transmit power component 114 can select varying transmit powers for transmitting multiple access requests according to the TA. For example, transmit power component 114 can ramp up the transmit power based on a determined increment (e.g., configured by network entity 104 or other network components, obtained from a configuration, etc.) to transmit access requests until a maximum transmit power is achieved. Access request transmitting component 116 can transmit the access requests based on the TA selected by TA selecting component 112 and the transmit powers specified by transmit power component 114. In addition, transmit power component 114 can determine the maximum transmit power based at least in part on a network configuration (e.g., received from network entity 104 or one or more other components upon initiating communications with the components or generally with the wireless network), a configuration accessible by UE 102, etc.

[0026] For example, FIG. 3 depicts example timelines 300, 310 relating to access requesting procedures to synchronize with an uplink channel. In timeline 300, at 302, access requests are transmitted with a selected TA of 24, which can correspond to a default TA when initiating communication with a cell. At 302, the access requests are transmitted at incremental transmit powers, indicated by a length of the respective arrow, which is referred to herein as ramping up, until a maximum transmit power is reached and/or until a response is received to an access request. If a response is received to one of the access requests, access request transmission can cease, and the power of the last access request transmission can be used to determine a power for communicating with the cell. In this example, using a fixed TA of 24, which can correspond to a default TA (e.g., known to yield a higher number of successful responses than other TAs), or a TA from a successful rate table, can result in a higher likelihood of receiving a response to the access request than beginning with TA 0. In addition, using TA = 24 in this example allows for TA = 24 to be tested for all transmit powers normally used in an access procedure where the TA is also incremented with each transmission, which may result in a higher likelihood of receiving a response in networks with high radio activity.

[0027] Method 200 includes, at Block 204, determining whether a maximum transmit power was reached in transmitting the one or more access requests using the power ramping at Block 202. For example, communicating component 110 can determine whether the maximum transmit power was reached. This is also depicted in timeline 300, at 302, where the last arrow in the group of arrows indicates the maximum transmit power. If the maximum transmit power is reached, at Block 204, method 200 includes, at Block 206, transmitting a TA training sequence comprising a plurality of access requests at varying TA using a maximum transmit power. For example, TA selecting component 112 can cycle through available TAs for the access requests, transmit power component 114 can set a maximum transmit power for transmitting each of the access requests, and access request transmitting component 116 can accordingly transmit the access requests. This can be referred to as a training sequence for the TAs to determine a TA to utilize in synchronizing the uplink channel. In Fig. 3, timeline 300, at 304, an example training sequence is shown where access probes are transmitted at maximum power for TA = 0, 8, 16, 24, 43, 40, and 48. Performing the training sequence for each TA using maximum transmit power can increase the likelihood of determining the appropriate TA for the UE 102 to be detected in the cell provided by network entity 104.

[0028] Method 200 includes, at Block 208, determining whether a response to an access request is received or a maximum access request number is reached. The maximum access request number, as used herein, can refer to a maximum number of access requests that are allowed in a given access procedure (e.g., a number greater than the number of access requests in a training and/or trial sequence as described herein). As described, communicating component 110 can determine whether a response is received and can determine which access probe for which the response is received, which can indicate an accepted TA. If a response to an access request of the training sequence is received, at Block 208, the successful rate table is updated based on a TA for which the response is received at Block 210. In this case or when or a maximum access request number is reached, the TA is used in a following random access of cell at Block 212. This can include utilizing the TA of the highest successful rate (e.g., according to the successful rate table 120). In this example, TA selecting component 112 can update the successful rate table 120 with success information for the TA to indicate a successful access procedure (e.g., synchronization) with the TA, and communicating component 110 can utilize the TA and transmit power in communicating with the network entity 104.

[0029] The successful rate table 120 may include a plurality of possible TAs (or a plurality of TAs attempted or successfully used) in the cell, along with a number of successful synchronizations or other communication related parameters, such as a communication quality using the TA. Thus, TA selecting component 112 can utilize the successful rate table 120 in determining a TA for attempting synchronization/access in a cell of the network entity 104 (e.g., at Block 202). For example, TA selecting component 112 can initially attempt synchronization using a TA having the highest success rate in the successful rate table 120. Moreover, as described further herein, the successful rate table 120 may be reset when selecting to a new cell. In one possible example, contents of the successful rate table 120 may be stored for each cell and retrieved upon camping on a cell for which contents are stored.

[0030] TA selecting component 112 can also typically apply an alpha filter when assessing the successful rates for one or more TAs in successful rate table 120. In this regard, since the successful rate table 120 is reset for each cell, a smaller alpha filter can be utilized (e.g., alpha filter = 8) than was used in scenarios where the UE 102 moves between cells without resetting the table 120. For example, where F(x) is an average value of all samples, TA selecting component 112 can compute F(N) = (1-Alpha)* F(N-1) + Alpha* New_Sample to determine the success for a given TA. Using a smaller alpha filter allows more emphasis on the previous samples than the current sample (New_Sample), thus making the F(N) more stable in this cell

[0031] If a response to an access request is not received and the maximum number of accesss requests in not reached at Block 208, method 200 includes, at Block 214, transmitting a plurality of access requests according to the TA using a maximum transmit power. For example, TA selecting component 112 can select the TA used in block 202 (e.g., the default TA, the most successful TA in the successful rate table 120, etc.) for transmitting the access requests, transmit power component 114 can specify the maximum transmit power, and access request transmitting component 116 can transmit the access requests using the TA and the maximum transmit power. This can be referred to as a TA trial sequence for the TA. Timeline 300, at 306, depicts the TA trial sequence for TA = 24. Performing the TA trial sequence gives the default or most successful TA more chances to synchronize than other TAs. Thus, for example, the access request sequence is separated into training sequence and trial sequence (e.g., every M times training sync-ULs - access requests - are transmitted, N times trial sync-ULs - access requests - are transmitted).

[0032] Method 200 further includes determining whether a response to an access request is received or a maximum access request number is reached, at Block 216. Thus, as described, communicating component 110 can determine whether a response is received for one of the access requests. If so, at Block 212, the TA can be used in a following random access procedure in the cell. This can include utilizing the TA of the highest successful rate (e.g., according to the successful rate table 120). Thus, communicating component 110 can utilize the TA to communicate with network entity 104, but successful rate table 120 may not be updated based on receiving the response to the access request, since the TA was initially not successful to synchronize. If a response to an access request is not received (and a maximum access request number is not reached) at Block 216, method 200 proceeds to Block 206 to transmit a TA training sequence comprising a plurality of access requests at varying TA using a maximum transmit power. In timeline 300 of FIG. 3, at 308, the training sequence starts again, and in that specific example, a response to the access request may be received for TA = 32. Thus, method 200 proceeds to Block 206 to update the successful rate table for TA = 32, and TA=32 is used in a following random access of the cell at Block 212.

[0033] Moreover, if the maximum transmit power is not reached at Block 204, the method includes, at Block 218, determining whether a response to the access request is received or a maximum access request number is reached. This can include, for example, communicating component 110 determining whether network entity 104 transmitted a response (e.g., a successful response, a resource grant, etc.) to the access request transmitted by access request transmitting component 116 before the maximum number of access requests is reached. For example, access request transmitting component 116 can determine the maximum number of access requests based at least in part on a network configuration (e.g., received from network entity 104 or one or more other components upon initiating communications with the components or generally with the wireless network), a configuration accessible by UE 102, etc. If an access request is received before the maximum number of access requests is reached, method 200 proceeds to Block 212 where the TA is used in a following random access in the cell. This can include utilizing the TA of the highest successful rate (e.g., according to the successful rate table 120). If a response to the access request is not received (and a maximum access request number is not reached) at Block 218, the method 200 proceeds to step 202 to transmit one or more access requests according to a timing advance using power ramping.

[0034] In a further example, timeline 310 relates to another synchronization procedure (e.g., another random access) in the same cell. Thus, at 312, the ramping is performed using TA = 32. For example, at Block 202, a plurality of access requests according to TA = 32 are transmitted using power ramping. As described above, TA selecting component 112 can select the TA from the successful rate table 120 based on the previous selection of TA = 32 at 308 in timeline 300. In this example, no response is received to the access request and the training sequence is started at 314. Referring to FIG. 2, at Block 204, the maximum transmit power is reached, and at 206, the TA training sequence comprising a plurality of access requests at varying TA can be transmitted using maximum transmit power. No response is received to the access requests of the TA training sequence at 314, and at 316, a TA trial sequence is started and response is received at the second access request, but the successful rate table is not updated. Referring to FIG. 2, in this example, a response is not received to the access request (and the maximum access request number is not reached) at Block 208, and thus at Block 214, a plurality of access requests are transmitted according to the TA using a maximum transmit power as part of the TA trial sequence. A response to the access request is received at Block 216 (after the second access request), and the TA is used in following random access of the same cell.

[0035] Timelines 300, 310 illustrate two possible examples, but it is to be appreciated that various other examples can be performed in conjunction with the system in FIG. 1 and the method of FIG. 2.

[0036] FIG. 4 illustrates and example method 400 for resetting a successful rate table when camping on a different cell. Method 400 includes, at Block 402, determining TA for communicating in a current cell. Communicating component 110 can determine the TA as described in conjunction with FIGs. 1-3 above, which may also include updating a successful rate table based on determining the TA, at Block 404. Method 400 includes, at Block 406, reselecting to a different cell. This can include, for example, an idle mode reselection, handover, etc. performed by communicating component 110 to a different network entity (not shown). Method 400 also includes, at Block 408, resetting a successful rate table while camping on the different cell. Thus, for example, based on reselecting the different cell or otherwise based on communicating with the different cell, TA selecting component 112 can reset the successful rate table 120. In this regard, communicating component 110 can perform another access procedure with the different cell by initially attempting with the default TA (e.g., TA = 24), as described above.

[0037] FIG. 5 is a conceptual diagram illustrating an example of a hardware implementation for an apparatus 500 employing a processing system 514. In some examples, the processing system 514 may comprise a UE or a component of a UE (e.g., UE 102 or network entity 104 of FIG. 1, etc.). In this example, the processing system 514 may be implemented with a bus architecture, represented generally by the bus 502. The bus 502 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 514 and the overall design constraints. The bus 502 links together various circuits including one or more processors, represented generally by the processor 504, computer- readable media, represented generally by the computer-readable medium 506, communicating component 110, etc. {see FIG. 1), which may be configured to carry out one or more methods or procedures described herein.

[0038] The bus 502 may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art. A bus interface 508 provides an interface between the bus 502 and a transceiver 510. The transceiver 510 provides a means for communicating with various other apparatus over a transmission medium. Depending upon the nature of the apparatus, a user interface 512 (e.g., keypad, display, speaker, microphone, joystick) may also be provided.

[0039] The processor 504 is responsible for managing the bus 502 and general processing, including the execution of software stored on the computer-readable medium 506. The software, when executed by the processor 504, causes the processing system 514 to perform the various functions described infra for any particular apparatus. The computer-readable medium 506 may also be used for storing data that is manipulated by the processor 504 when executing software. [0040] In an aspect, processor 504, computer-readable medium 506, or a combination of both may be configured or otherwise specially programmed to perform the functionality of the communicating component 110, components thereof, or various other components described herein. For example, processor 504, computer-readable medium 506, or a combination of both may be configured or otherwise specially programmed to perform the functionality of the communicating component 110 described herein, and/or the like.

[0041] The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. By way of example and without limitation, the aspects of the present disclosure illustrated in FIG. 6 are presented with reference to a UMTS system 600 employing a W- CDMA air interface. A UMTS network includes three interacting domains: a Core Network (CN) 604, a UMTS Terrestrial Radio Access Network (UTRAN) 602, and User Equipment (UE) 610. In this example, the UTRAN 602 provides various wireless services including telephony, video, data, messaging, broadcasts, and/or other services. The UTRAN 602 may include a plurality of Radio Network Subsystems (RNSs) such as an RNS 607, each controlled by a respective Radio Network Controller (RNC) such as an RNC 606. Here, the UTRAN 602 may include any number of RNCs 606 and RNSs 607 in addition to the RNCs 606 and RNSs 607 illustrated herein. The RNC 606 is an apparatus responsible for, among other things, assigning, reconfiguring and releasing radio resources within the RNS 607. The RNC 606 may be interconnected to other RNCs (not shown) in the UTRAN 602 through various types of interfaces such as a direct physical connection, a virtual network, or the like, using any suitable transport network.

[0042] Communication between a UE 610 and a Node B 608 may be considered as including a physical (PHY) layer and a medium access control (MAC) layer. Further, communication between a UE 610 and an RNC 606 by way of a respective Node B 608 may be considered as including a radio resource control (RRC) layer. In the instant specification, the PHY layer may be considered layer 1; the MAC layer may be considered layer 2; and the RRC layer may be considered layer 3. Information hereinbelow utilizes terminology introduced in Radio Resource Control (RRC) Protocol Specification, 3 GPP TS 25.331 v9.1.0, incorporated herein by reference.

[0043] The geographic region covered by the SRNS 607 may be divided into a number of cells, with a radio transceiver apparatus serving each cell. A radio transceiver apparatus is commonly referred to as a Node B in UMTS applications, but may also be referred to by those skilled in the art as a base station (BS), a base transceiver station (BTS), a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), an access point (AP), or some other suitable terminology. For clarity, three Node Bs 608 are shown in each SRNS 607; however, the SRNSs 607 may include any number of wireless Node Bs. The Node Bs 608 provide wireless access points to a core network (CN) 604 for any number of mobile apparatuses. Examples of a mobile apparatus include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a notebook, a netbook, a smartbook, a personal digital assistant (PDA), a satellite radio, a global positioning system (GPS) device, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, or any other similar functioning device. The mobile apparatus is commonly referred to as user equipment (UE) in UMTS applications, but may also be referred to by those skilled in the art as a mobile station (MS), a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal (AT), a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. In a UMTS system, the UE 610 may further include a universal subscriber identity module (USIM) 611, which contains a user's subscription information to a network. UE 610 may also include a communicating component 110 for performing functions described in relation to FIGS. 1-4, above. For illustrative purposes, one UE 610 is shown in communication with a number of the Node Bs 608. The downlink (DL), also called the forward link, refers to the communication link from a Node B 608 to a UE 610, and the uplink (UL), also called the reverse link, refers to the communication link from a UE 610 to a Node B 608.

[0044] The core network 604 interfaces with one or more access networks, such as the UTRAN 602.

As shown, the core network 604 is a GSM core network. However, as those skilled in the art will recognize, the various concepts presented throughout this disclosure may be implemented in a RAN, or other suitable access network, to provide UEs with access to types of core networks other than GSM networks.

[0045] The core network 604 includes a circuit-switched (CS) domain and a packet-switched (PS) domain. Some of the circuit-switched elements are a Mobile services Switching Centre (MSC), a Visitor location register (VLR) and a Gateway MSC. Packet-switched elements include a Serving GPRS Support Node (SGSN) and a Gateway GPRS Support Node (GGSN). Some network elements, like EIR, HLR, VLR and AuC may be shared by both of the circuit-switched and packet-switched domains. In the illustrated example, the core network 604 supports circuit-switched services with a MSC 612 and a GMSC 614. In some applications, the GMSC 614 may be referred to as a media gateway (MGW). One or more RNCs, such as the RNC 606, may be connected to the MSC 612. The MSC 612 is an apparatus that controls call setup, call routing, and UE mobility functions. The MSC 612 also includes a visitor location register (VLR) that contains subscriber-related information for the duration that a UE is in the coverage area of the MSC 612. The GMSC 614 provides a gateway through the MSC 612 for the UE to access a circuit-switched network 616. The core network 604 includes a home location register (HLR) 615 containing subscriber data, such as the data reflecting the details of the services to which a particular user has subscribed. The HLR is also associated with an authentication center (AuC) that contains subscriber-specific authentication data. When a call is received for a particular UE, the GMSC 614 queries the HLR 615 to determine the UE's location and forwards the call to the particular MSC serving that location.

[0046] The core network 604 also supports packet-data services with a serving GPRS support node (SGSN) 618 and a gateway GPRS support node (GGSN) 620. GPRS, which stands for General Packet Radio Service, is designed to provide packet-data services at speeds higher than those available with standard circuit-switched data services. The GGSN 620 provides a connection for the UTRAN 602 to a packet-based network 622. The packet-based network 622 may be the Internet, a private data network, or some other suitable packet-based network. The primary function of the GGSN 620 is to provide the UEs 610 with packet- based network connectivity. Data packets may be transferred between the GGSN 620 and the UEs 610 through the SGSN 618, which performs primarily the same functions in the packet-based domain as the MSC 612 performs in the circuit-switched domain.

[0047] The UMTS air interface is a spread spectrum Direct- Sequence Code Division Multiple Access (DS-CDMA) system. The spread spectrum DS-CDMA spreads user data through multiplication by a sequence of pseudorandom bits called chips. The W-CDMA air interface for UMTS is based on such direct sequence spread spectrum technology and additionally calls for a frequency division duplexing (FDD). FDD uses a different carrier frequency for the uplink (UL) and downlink (DL) between a Node B 608 and a UE 610. Another air interface for UMTS that utilizes DS-CDMA, and uses time division duplexing, is the TD-SCDMA air interface. Those skilled in the art will recognize that although various examples described herein may refer to a WCDMA air interface, the underlying principles are equally applicable to a TD-SCDMA air interface.

[0048] Referring to FIG. 7, an access network 700 in a UTRAN architecture is illustrated. In an example aspect, the UTRAN architecture may be associated with a network of UE 102 and network entity 104. The multiple access wireless communication system includes multiple cellular regions (cells), including cells 702, 704, and 706, each of which may include one or more sectors. The multiple sectors can be formed by groups of antennas with each antenna responsible for communication with UEs in a portion of the cell. For example, in cell 702, antenna groups 712, 714, and 716 may each correspond to a different sector. In cell 704, antenna groups 718, 720, and 722 each correspond to a different sector. In cell 706, antenna groups 724, 726, and 728 each correspond to a different sector. The cells 702, 704 and 706 may include several wireless communication devices, e.g., User Equipment or UEs, which may be in communication with one or more sectors of each cell 702, 704 or 706. For example, UEs 730 and 732 may be in communication with Node B 742, UEs 734 and 736 may be in communication with Node B 744, and UEs 738 and 740 (which may represent UE 102 of FIG. 1) can be in communication with Node B 746. Here, each Node B 742, 744, 746 is configured to provide an access point to a core network 604 (see FIG. 6) for all the UEs 730, 732, 734, 736, 738, 740 in the respective cells 702, 704, and 706. In an aspect, each of the UEs presented in FIG. 7 may comprise UE 102 of FIG. 1 and may include a communicating component 110, as described in relation to FIGS. 1-4, above.

[0049] As the UE 734 moves from the illustrated location in cell 704 into cell 706, a serving cell change (SCC) or handover may occur in which communication with the UE 734 transitions from the cell 704, which may be referred to as the source cell, to cell 706, which may be referred to as the target cell. Management of the handover procedure may take place at the UE 734, at the Node Bs corresponding to the respective cells, at a radio network controller 606 (see FIG. 6), or at another suitable node in the wireless network. For example, during a call with the source cell 704, or at any other time, the UE 734 may monitor various parameters of the source cell 704 as well as various parameters of neighboring cells such as cells 706 and 702. Further, depending on the quality of these parameters, the UE 734 may maintain communication with one or more of the neighboring cells. During this time, the UE 734 may maintain an Active Set, that is, a list of cells that the UE 734 is simultaneously connected to (i.e., the UTRA cells that are currently assigning a downlink dedicated physical channel DPCH or fractional downlink dedicated physical channel F-DPCH to the UE 734 may constitute the Active Set).

[0050] The modulation and multiple access scheme employed by the access network 700 may vary depending on the particular telecommunications standard being deployed. By way of example, the standard may include Evolution-Data Optimized (EV-DO) or Ultra Mobile Broadband (UMB). EV-DO and UMB are air interface standards promulgated by the 3rd Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and employs CDMA to provide broadband Internet access to mobile stations. The standard may alternately be Universal Terrestrial Radio Access (UTRA) employing Wideband- CDMA (W-CDMA) and other variants of CDMA, such as TD-SCDMA; Global System for Mobile Communications (GSM) employing TDMA; and Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, and Flash-OFDM employing OFDMA. UTRA, E-UTRA, UMTS, LTE, LTE Advanced, and GSM are described in documents from the 3 GPP organization. CDMA2000 and UMB are described in documents from the 3GPP2 organization. The actual wireless communication standard and the multiple access technology employed will depend on the specific application and the overall design constraints imposed on the system.

[0051] FIG. 8 is a block diagram of a Node B 810 in communication with a UE 850, where the Node B 810 may be the first subscription network entity 104 in FIG. 1, and the UE 850 may be the UE 102 of FIG. 1. For example, UE 850 may include communicating component 110 or otherwise configured to perform the functions thereof, as described in relation to FIGs. 1-4. In the downlink communication, a transmit processor 820 may receive data from a data source 812 and control signals from a controller/processor 840. The transmit processor 820 provides various signal processing functions for the data and control signals, as well as reference signals (e.g., pilot signals). For example, the transmit processor 820 may provide cyclic redundancy check (CRC) codes for error detection, coding and interleaving to facilitate forward error correction (FEC), mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM), and the like), spreading with orthogonal variable spreading factors (OVSF), and multiplying with scrambling codes to produce a series of symbols. Channel estimates from a channel processor 844 may be used by a controller/processor 840 to determine the coding, modulation, spreading, and/or scrambling schemes for the transmit processor 820. These channel estimates may be derived from a reference signal transmitted by the UE 850 or from feedback from the UE 850. The symbols generated by the transmit processor 820 are provided to a transmit frame processor 830 to create a frame structure. The transmit frame processor 830 creates this frame structure by multiplexing the symbols with information from the controller/processor 840, resulting in a series of frames. The frames are then provided to a transmitter 832, which provides various signal conditioning functions including amplifying, filtering, and modulating the frames onto a carrier for downlink transmission over the wireless medium through antenna 834. The antenna 834 may include one or more antennas, for example, including beam steering bidirectional adaptive antenna arrays or other similar beam technologies.

[0052] At the UE 850, a receiver 854 receives the downlink transmission through an antenna 852 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 854 is provided to a receive frame processor 860, which parses each frame, and provides information from the frames to a channel processor 894 and the data, control, and reference signals to a receive processor 870. The receive processor 870 then performs the inverse of the processing performed by the transmit processor 820 in the Node B 810. More specifically, the receive processor 870 descrambles and despreads the symbols, and then determines the most likely signal constellation points transmitted by the Node B 810 based on the modulation scheme. These soft decisions may be based on channel estimates computed by the channel processor 894. The soft decisions are then decoded and deinterleaved to recover the data, control, and reference signals. The CRC codes are then checked to determine whether the frames were successfully decoded. The data carried by the successfully decoded frames will then be provided to a data sink 872, which represents applications running in the UE 850 and/or various user interfaces (e.g., display). Control signals carried by successfully decoded frames will be provided to a controller/processor 890. When frames are unsuccessfully decoded by the receiver processor 870, the controller/processor 890 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.

[0053] In the uplink, data from a data source 878 and control signals from the controller/processor 890 are provided to a transmit processor 880. The data source 878 may represent applications running in the UE 850 and various user interfaces (e.g., keyboard). Similar to the functionality described in connection with the downlink transmission by the Node B 810, the transmit processor 880 provides various signal processing functions including CRC codes, coding and interleaving to facilitate FEC, mapping to signal constellations, spreading with OVSFs, and scrambling to produce a series of symbols. Channel estimates, derived by the channel processor 894 from a reference signal transmitted by the Node B 810 or from feedback contained in the midamble transmitted by the Node B 810, may be used to select the appropriate coding, modulation, spreading, and/or scrambling schemes. The symbols produced by the transmit processor 880 will be provided to a transmit frame processor 882 to create a frame structure. The transmit frame processor 882 creates this frame structure by multiplexing the symbols with information from the controller/processor 890, resulting in a series of frames. The frames are then provided to a transmitter 856, which provides various signal conditioning functions including amplification, filtering, and modulating the frames onto a carrier for uplink transmission over the wireless medium through the antenna 852.

[0054] The uplink transmission is processed at the Node B 810 in a manner similar to that described in connection with the receiver function at the UE 850. A receiver 835 receives the uplink transmission through the antenna 834 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 835 is provided to a receive frame processor 836, which parses each frame, and provides information from the frames to the channel processor 844 and the data, control, and reference signals to a receive processor 838. The receive processor 838 performs the inverse of the processing performed by the transmit processor 880 in the UE 850. The data and control signals carried by the successfully decoded frames may then be provided to a data sink 839 and the controller/processor, respectively. If some of the frames were unsuccessfully decoded by the receive processor, the controller/processor 840 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.

[0055] The controller/processors 840 and 890 may be used to direct the operation at the Node B 810 and the UE 850, respectively. For example, the controller/processors 840 and 890 may provide various functions including timing, peripheral interfaces, voltage regulation, power management, and other control functions. The computer readable media of memories 842 and 892 may store data and software for the Node B 810 and the UE 850, respectively. A scheduler/processor 846 at the Node B 810 may be used to allocate resources to the UEs and schedule downlink and/or uplink transmissions for the UEs. [0056] Several aspects of a telecommunications system have been presented with reference to an HSPA system. As those skilled in the art will readily appreciate, various aspects described throughout this disclosure may be extended to other telecommunication systems, network architectures and communication standards.

[0057] By way of example, various aspects may be extended to other UMTS systems such as W- CDMA, TD-SCDMA, High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), High Speed Packet Access Plus (HSPA+) and TD-CDMA. Various aspects may also be extended to systems employing Long Term Evolution (LTE) (in FDD, TDD, or both modes), LTE-Advanced (LTE-A) (in FDD, TDD, or both modes), CDMA2000, Evolution-Data Optimized (EV-DO), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Ultra- Wideband (UWB), Bluetooth, and/or other suitable systems. The actual telecommunication standard, network architecture, and/or communication standard employed will depend on the specific application and the overall design constraints imposed on the system.

[0058] In accordance with various aspects of the disclosure, an element, or any portion of an element, or any combination of elements may be implemented with a "processing system" that includes one or more processors. Examples of processors include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on a computer-readable medium. The computer-readable medium may be a non- transitory computer-readable medium. A non-transitory computer-readable medium includes, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., compact disk (CD), digital versatile disk (DVD)), a smart card, a flash memory device (e.g., card, stick, key drive), random access memory (RAM), read only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), a register, a removable disk, and any other suitable medium for storing software and/or instructions that may be accessed and read by a computer. The computer-readable medium may also include, by way of example, a carrier wave, a transmission line, and any other suitable medium for transmitting software and/or instructions that may be accessed and read by a computer. The computer-readable medium may be resident in the processing system, external to the processing system, or distributed across multiple entities including the processing system. The computer-readable medium may be embodied in a computer-program product. By way of example, a computer-program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.

[0059] It is to be understood that the specific order or hierarchy of steps in the methods disclosed is an illustration of exemplary processes. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the methods or methodologies described herein may be rearranged. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented unless specifically recited therein.

[0060] The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean "one and only one" unless specifically so stated, but rather "one or more." Unless specifically stated otherwise, the term "some" refers to one or more. A phrase referring to "at least one of a list of items refers to any combination of those items, including single members. As an example, "at least one of: a, b, or c" is intended to cover: a; b; c; a and b; a and c; b and c; and a, b and c. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. § 112, sixth paragraph, unless the element is expressly recited using the phrase "means for" or, in the case of a method claim, the element is recited using the phrase "step for."

Claims

1. A method for determining timing advance in wireless communications, comprising: transmitting a plurality of access requests according to a timing advance (TA) using power ramping;

determining that a maximum transmit power is achieved by one of the plurality of access requests; and

transmitting a TA training sequence comprising another plurality of access requests at varying TAs using a maximum transmit power based on determining that the maximum transmit power is achieved.

2. The method of claim 1, further comprising:

receiving a response to at least one of the another plurality of access requests;

updating a successful rate table for a current cell based on a TA for which the response is received; and

utilizing the TA in following random access in a wireless network.

3. The method of claim 2, further comprising resetting the successful rate table based at least in part on camping on another cell different from the current cell.

4. The method of claim 1, further comprising:

determining that no response is received to the another plurality of access requests; and

transmitting a trial sequence comprising a third plurality of access requests according to the TA using a maximum transmit power.

5. The method of claim 4, further comprising:

receiving a response to at least one of the third plurality of access requests; and utilizing the TA in a following random access in a wireless network.

6. The method of claim 1, wherein the TA is a default TA or a TA with a highest number of successes in a successful rate table for a current cell.

7. An apparatus comprising at least one processor and memory coupled to the at least one processor, the at least one processor and memory being configured to perform a method in accordance with any of claims 1 to 6.

8. An apparatus comprising means for performing a method in accordance with any of claims 1 to 6.

9. A computer-readable medium comprising at least one instruction for causing a computer or processor to perform a method in accordance with any of claims 1 to 6.