Timing and cell specific system information handling for handover in evolved utra

TIMING AND CELL SPECIFIC SYSTEM INFORMATION HANDLING FOR HANDOVER IN EVOLVED UTRA

The present invention relates to wireless communication.

The Third Generation Partnership Project (3GPP) is a Long Term Evolution (LTE) project that brings new technologies, new network architectures, new configurations, and new applications and services to wireless networks to provide improved spectral efficiency and a faster user experience. ; Long Term Evolution) program was started.

A wireless transmit receive unit (WTRU) cannot continuously communicate with a single eNB (eNodeB) within a cell. When a WTRU moves from communicating with a first cell to communicating with a second cell, the process of switching between the two cells is known as "handover". In an LTE network, a WTRU may experience handover between a source eNB, which is the eNB in the cell that the WTRU switches to, and a target eNB, which is the eNB in the cell that the WTRU switches into, with little or no impact on the performance of the communication link. should be able

In some steps of the handover process in the LTE network, the WTRU needs to obtain information about the target eNB in order for the handover to occur smoothly. One way for a WTRU to obtain information about a target eNB is for the WTRU to read a broadcast channel (BCH), which is a common downlink control channel carrying information about the eNB sending the BCH. . The information may be on a primary broadcast channel (P-BCH) or a dedicated broadcast channel (D-BCH). In more detail, a master information block (MIB) including specific information related to the target eNB is transmitted on the P-BCH. A plurality of system information blocks (SIBs) including other information are transmitted on the D-BCH. The WTRU may need to use a significant amount of time to read these downlink channels due to the relatively long transmission time interval (TTI) allocated to each channel.

In a Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) synchronous network, a wireless transmit/receive unit (WTRU) uses a private transmit/receive unit (WTRU) to obtain a system frame number (SFN) before the WTRU transmits a dedicated preamble to a target cell. It is possible to handover to the target cell without reading the head broadcast channel (P-BCH). However, the WTRU may need to know the SFN after handover for its normal operation in the target cell. Specifically, discontinuous reception (DRX) and reception of a dynamic broadcast channel (D-BCH) requires SFN awareness of the WTRU.

<p>Accordingly, a technique for reducing the handover interruption time is required.</p>

<p>A method and apparatus for reducing handover time are disclosed. This may include sending cell specific information in the handover command.</p>

<p>According to the present invention, a normal operation can be resumed by performing a quick handover.</p>

A more specific understanding of the present invention may be obtained from the following detailed description given by way of example in conjunction with the appended description. 1 illustrates an exemplary wireless communication system comprising a plurality of WTRUs and an eNB in accordance with one claim. 2 shows a functional block diagram of the WTRU and eNB of FIG. 1 in accordance with one claim. 3 shows a signaling diagram of a handover according to one claim. 4 shows a signaling diagram of a handover process according to another claim. 5 shows a signaling diagram of a handover process according to an alternative claim;

When referred to below, the term "wireless transmit/receive unit (WTRU)" refers to, but is not limited to, a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a computer, or any other type of user device operable in a wireless environment. When referred to below, the term "base station" includes, but is not limited to, a Node-B, a site controller, an access point (AP), or any other type of interfacing device operable in a wireless environment.

1 shows a wireless communication system 100 including a plurality of WTRUs 110 and an eNB 120 . As shown in FIG. 1 , WTRUs 110 communicate with an eNB 120 . Although three WTRUs 110 and one eNB 120 are shown in FIG. 1 , it should be understood that any combination of wireless and wired devices may be included in the wireless communication system 100 .

2 shows a functional block diagram 200 of a WTRU 110 and a base station 120 of the wireless communication system 100 of FIG. 1 . As shown in FIG. 1 , a WTRU 110 communicates with an eNB 120 . The WTRU 110 is configured to receive messages on a downlink communication channel, such as, for example, a broadcast channel. The eNB 120 may be configured to transmit signals on a broadcast control channel (BCCH) and the WTRU 110 may be configured to receive and monitor signals on a broadcast control channel (BCCH). can The WTRU 110 may transmit on an uplink channel, such as, for example, a Random Access Channel (RACH). The WTRU 110 may be configured to send and receive radio resource control (RRC) messages and Layer 1 (L1) messages.

In addition to the components found in a typical WTRU, the WTRU 110 includes a processor 215 , a receiver 216 , a transmitter 217 and an antenna 218 . The WTRU 110 may also include a user interface 221 , which may include, but is not limited to, an LCD or LED screen, a touch screen, a keyboard, a stylus, or any other conventional input/output device. . The WTRU 110 may also include both volatile and non-volatile memory 219, such as a universal serial bus (USB) port, serial port, etc., as well as interfaces 220 to other devices. . Receiver 216 and transmitter 217 communicate with processor 215 . Antenna 218 communicates with both receiver 116 and transmitter 217 to facilitate transmission and reception of wireless data.

In addition to the components found in a typical eNB, the eNB 120 includes a processor 225 , a receiver 226 , a transmitter 227 and an antenna 228 . Receiver 226 and transmitter 227 communicate with processor 225 . Antenna 228 communicates with receiver 226 and transmitter 227 to facilitate transmission and reception of wireless data.

The handover interruption time is between the time the WTRU receives the handover command and the time the WTRU completes radio resource control (RRC) reconfiguration with the target cell, i.e., when the WTRU resumes transmitting and receiving data in the target cell. It is defined as the difference value of . In order for the WTRU to perform normal operations within the target cell, e.g., data transmission and discontinuous reception (DRX), the WTRU may obtain cell-specific system information carried on the P-BCH and D-BCH of the target cell. . However, reading a P-BCH with transmission time intervals (TTI) of 40 ms repeated 4 times and a D-BCH with scheduling units of 80, 160 and 320 ms increase the handover interruption time. can do it

The format of the signals received by the WTRU during the handover process may help reduce the handover interruption time. Cell specific system information for a target cell, which is typically carried on P-BCH and D-BCH, may be sent to the WTRU in other downlink signals that are part of the handover process. This can prevent handover interruption.

The target cell specific system information received by the WTRU during the handover process may include:

a. downlink system bandwidth;

b. PCFICH (Physical Control Format Indicator Channel) information;

c. PHICH (Physical Hybrid ARQ Indicator Channel) information such as PHICH maintenance period and PHICH resource size;

d. scaling of the reference signal transmit power and power scaling of the reference signal for other data/control subcarriers;

e. Random Access Channel (RACH) configuration:

i. information about the dedicated preamble reserved for WTRU handover in the target cell; and

ii. validity timer for dedicated preambles for both synchronous and asynchronous networks;

f. contention-based RACH information (optional);

g. information on the uplink reference signal (frequency hopping);

h. information about a sounding reference signal (location);

i. Physical Uplink Control Channel (PUCCH) reference signal (RS) sequence hopping;

j. Physical Uplink Shared Channel (PUSCH) hopping, that is, a semi-static configuration between two hopping modes (inter-subframe and intra-subframe or inter-subframe) based on cell specificity;

k. uplink power control parameters;

One. DRX related parameters in the target cell;

m. the start time of a new DRX cycle in the target cell;

n. system frame number (SFN);

o. the full SFN of the target cell;

p. SFN difference between source cell and target cell;

q. the number of transmit antennas at the eNB that could have been blindly detected by the WTRU during cell search;

r. MBMS single frequency number [MBSFN; MBMS (Multiple Broadcast/Multicast Service) single frequency number]-related parameters; and

s. List of neighboring cells.

The information may be provided to the source cell by the target cell in a Handover Request Acknowledge message. The WTRU may obtain this information in the downlink signal from the source eNB.

Alternatively, the network or eNB may define a handover parameter with one or more sets of "default" values for handover in Evolved Universal Terrestrial Radio Access (E-UTRA). Upon handover, the target cell (eNB) may determine which of the set of values may be used by the WTRU for handover, and may send an index of the set of handover parameter values without actual values. This can result in compact signaling.

In addition, it is possible to define a special system information block (SIB) format for predefined handover parameter values including the characteristics described above. These values may be related to a specific public land mobile network (PLMN). The network/service provider may pre-define the necessary handover values, which may be within one or more sets of values that the WTRU obtains prior to handover. PLMN may persist when eNBs broadcast SIB. The handover command may pass an index to the handover parameters (one from a given set to the WTRU) to the target cell.

The WTRU may indicate or report the SIB including the handover parameters or the WTRU's acquisition of handover parameters to the network in an uplink message such as an RRC_reconfiguration_complete message or an RRC_measurement_report message. Acknowledgment of acquisition may be, for example, a single bit in the message.

The network may determine how handover parameter values are passed to the WTRU in a handover command. A complete set of values may be used or an index to a default value may be used. Alternatively, an index for one of the predefined value sets may be transmitted in the SIB broadcast by the eNB.

3 shows a signaling diagram of a handover process 300 according to one claim. The WTRU 302 sends the measurement result 308 to the source eNB 304 . Based on the measurements, the source eNB 304 sends a handover request 310 to the target eNB 306 . The target eNB 306 returns a handover request acknowledgment message 312 to the source eNB 304 . The handover request acknowledgment message 312 includes specific information of the target eNB 306 as described above.

The handover process 300 continues as the source eNB 304 sends a handover command 314 conveying target cell specific information to the WTRU 302 . The WTRU 302 communicates directly with the target eNB 306 by exchanging a RACH preamble 316 , a RACH response 318 , and a handover complete command 320 . Normal operation 322 may then occur between the WTRU 302 and the target eNB 306 .

4 shows a signaling diagram of a handover process 400 according to another claim. Similar to the process 300 of FIG. 3 , the WTRU 402 sends the measurement result 408 to the source eNB 404 . Based on the measurements, the source eNB 404 sends a handover request 410 to the target eNB 406 . The target eNB 406 sends a handover request acknowledgment message 412 to the source eNB 404 . The handover request acknowledgment message 412 includes specific information of the target eNB 406 as described above.

The WTRU may then receive and begin processing 416 signals on the P-BCH and D-BCH. Reception and processing 416 of the P-BCH and D-BCH signals may begin before the WTRU transmits the RACH preamble 418 . The physical resources used by the WTRU for P-BCH and D-BCH reception 416 are different from those that may be used to receive an eNB message, such as RACH response 420 . Accordingly, the WTRU 402 may simultaneously receive and process P-BCH and D-BCH 416 and RACH messages (not shown). The WTRU 402 sends a handover complete message to the target eNB 406 .

The target eNB 406 may conclude that the WTRU 402 has obtained the target eNB SFN, P-BCH and D-BCH after K subframes 426 . K is equal to M + N, where M is the number of P-BCH TTIs and N is the number of D-BCH periods. For example, M=4 corresponds to 160 ms after the first RACH dedicated preamble was received by the target eNB 406 from the WTRU 402 , and the handover command 414 was received by the WTRU 402 . After the same time normal operations for the WTRU 402 started.

It is possible that the period during which the WTRU 402 acquires the target eNB SFN is smaller than the P-BCH and D-BCH information period (K subframes). However, even if the WTRU 402 has obtained the SFN, normal operation 424 for the WTRU 402 cannot be started by the eNB 406 until the K subframes have been received by the WTRU 402 . These normal operations 424 are:

a. DRX cycle;

b. Level 1 (Ll) feedback;

c. dynamic and semi-persistent data transmission/reception; and

d. timing alignment

Including, but not limited to these.

If the WTRU obtains the target eNB SFN before K subframes, the default mode of operation may apply to the target eNB 406 until the WTRU 402 obtains the SFN and/or BCH information. For example, DRX operation may be disabled and Ll feedback may not be generated or ignored. The WTRU 402 may provide explicit or implicit signaling notifying the target eNB 406 that the SFN and/or BCH information has been obtained and normal operation may resume.

Alternatively, if the WTRU 402 fails to receive the target eNB SFN and P-BCH after K subframes 426 and fails to successfully detect the P-BCH timing, then the WTRU 402 sends the radio link It can be determined that a failure has occurred. The WTRU 402 may then begin a radio link recovery process (not shown).

5 shows a signaling diagram of a handover process 500 according to alternative claims. Similar to the process 300 of FIG. 3 and the process 400 of FIG. 4 , the WTRU 502 sends the measurement result 508 to the source eNB 504 . Based on the measurements, the source eNB 504 sends a handover request 510 to the target eNB 506 . The target eNB 506 sends a handover request acknowledgment message 512 to the source eNB 504 . The handover request acknowledgment message 512 includes specific information of the target eNB 506 as described above.

The WTRU 502 sends a RACH preamble 516 to the target eNB 506 . The target eNB 506 sends a RACH response message 518 . The WTRU 502 then sends a handover complete message 520 to the target eNB 524 . The WTRU 502 may then receive and begin processing 522 signals on the P-BCH and D-BCH. Reception 522 of P-BCH and D-BCH signals begins after the WTRU 502 sends a handover complete message 520 . Once the WTRU 502 has obtained the P-BCH and D-BCH signals 522 , the WTRU 502 may resume normal operation 524 .

[Example]

One. A handover method in a WTRU comprising: sending a handover request; receiving a handover signal from a set of handover signals, wherein one handover signal from a set of handover signals is part of a handover process and one handover signal of the set of handover signals further includes specific configuration information of the target eNB (eNode B).

2. The handover method according to embodiment 1, wherein the specific information of the target eNB includes a system frame number (SFN) of the target eNB.

3. The method of embodiments 1 or 2, further comprising the WTRU determining a post-handover discontinuous reception (DRX) cycle based on the SFN.

4. The method according to any one of the preceding embodiments, further comprising: the WTRU performing a random access channel (RACH) procedure, and concurrently receiving and processing a broadcast channel.

5. The method according to any one of embodiments 2 to 4, further comprising the WTRU performing a RACH procedure and receiving and processing a broadcast channel.

6. A handover method in a wireless transmit/receive unit (WTRU), comprising: transmitting a measurement result, receiving a handover command based on the measurement result, and performing a random access procedure while simultaneously receiving and processing a broadcast channel; , wherein the handover command includes specific information about the target eNodeB, and wherein the specific information includes a system frame number of the target eNodeB.

7. The method according to embodiment 6, wherein the specific information is a complete set of values.

8. The method of embodiment 6, wherein the specific information includes an index to a set of values.

9. The handover method according to embodiment 6, wherein the specific information is a predefined set of values.

10. A handover method in a wireless transmit/receive unit (WTRU), comprising: transmitting a measurement result, receiving a handover command based on the measurement result, performing a random access procedure, completing a handover, and receiving a broadcast channel and processing, wherein the handover command includes specific information about the target eNodeB, and the specific information includes a system frame number of the target eNodeB.

11. The method according to embodiment 10, wherein the specific information is a complete set of values.

12. The method of embodiment 10, wherein the specific information includes an index to a set of values.

13. The handover method according to embodiment 10, wherein the specific information is a predefined set of values.

14. A wireless transmit/receive unit (WTRU) configured to perform handover, comprising: a transmitter configured to transmit a handover request; and a receiver configured to receive a handover command, wherein the handover command is configured to be configured in a specific configuration of a target eNB (eNode B). The wireless transmit/receive unit further comprising information.

15. The WTRU of embodiment 14, wherein the specific configuration information of the target eNB includes a system frame number (SFN) of the target eNB.

16. The WTRU of embodiments 14 or 15 further comprising a processor configured to determine a post handover discontinuous reception (DRX) cycle based on the SFN.

17. The WTRU of embodiments 15 or 16, wherein the WTRU is further configured to perform a random access channel (RACH) procedure while simultaneously receiving and processing a broadcast channel.

18. A wireless transmit/receive unit (WTRU) comprising: a transmitter configured to transmit a measurement result; a receiver configured to receive a handover command based on the measurement result; wherein the receiver receives a broadcast channel and a processor further processes the broadcast channel. a processor configured to perform a random access procedure during A wireless transceiver unit that does.

19. The WTRU of embodiment 18 wherein the specific information is a complete set of values.

20. The WTRU of embodiment 18 wherein the specific information comprises an index to a set of values.

21. The WTRU of embodiment 18 wherein the specific information is a predefined set of values.

Although features and elements are described in specific combinations in the embodiments, each feature or element can be used alone without the other features and elements of the embodiments, or in various combinations with or without the other features and elements. can be used The methods or flowcharts provided herein may be implemented as a computer program, software, or firmware tangibly embodied in a computer-readable storage medium for execution by a general-purpose computer or processor. Examples of computer-readable storage media include read only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and CD- optical media such as ROM disks and digital versatile disks (DVDs).

Suitable processors include, for example, general purpose processors, special purpose processors, conventional processors, digital signal processors (DSPs), multiple microprocessors, one or more microprocessors associated with a DSP core, controllers, microcontrollers, application specific integrated circuits (ASICs) ), field programmable gate array (FPGA) circuitry, any other type of integrated circuit (IC), and/or state machine.

A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, radio network controller (RNC) or any host computer. WTRUs include cameras, video camera modules, videophones, speakerphones, vibration devices, speakers, microphones, television transceivers, hands-free headsets, keyboards, Bluetooth® module, frequency modulation (FM) wireless unit, liquid crystal display (LCD) display unit, organic light emitting diode (OLED) display unit, digital music player, media player, video game player module, internet browser, and/or any wireless short-range communication It may be used in combination with a module implemented in hardware and/or software, such as a network (WLAN) module or an ultra-wideband (UWB) module.

100: wireless communication system 110: WTRU 120: base station