WO2005104598A1

WO2005104598A1 - Handover control method and mobile station device using the same

Info

Publication number: WO2005104598A1
Application number: PCT/JP2004/005534
Authority: WO
Inventors: Shigeki Yamaguchi; Yoshihiro Kubo
Original assignee: Mitsubishi Denki Kabushiki Kaisha
Priority date: 2004-04-19
Filing date: 2004-04-19
Publication date: 2005-11-03

Abstract

There are provided a handover control method having a short base station switching processing time in handover using a compression mode of W-CDMA (Wideband Code Division Multiple Access) mobile communication method and a mobile station device using the method. For handover to a base station in which a reference frame timing of a common channel transmitted according to a carrier frequency of different mobile station devices is unknown, a reference frame timing acquisition processing for acquiring the reference frame timing and a downstream physical channel synchronization establishment for establishing synchronization of the physical channel in the down stream line are performed in parallel. Moreover, for handover to a base station in which a reference frame timing of the common channel transmitted according to a carrier frequency of different mobile station devices is unknown, a communication control section (160) is provided for establishing synchronization of the physical channel in the downstream line if the timing in frame unit is known.

Description

Handover control method and mobile station apparatus using the same

Technical field

The present invention relates to a technique for controlling handover in a compressed mode of a W-CDM clear A (Wideband Code Division Multiple Access) mobile communication system. book

Background art

Mobile communication systems are moving from the first generation of analog systems that provide voice-centric services to the second generation of digital systems that provide voice and low-speed data communication services, and the third generation of voice and high-speed data communication services. Odd. W—CD MA (Wideband Code Division Multiple Access) mobile communication system is the terrestrial radio system of the 3rd generation mobile communication system, IMT-2000 (International Mobile Telecommunications-2000). International communication Union no line communications sector as standard (ITU - R: International Telecommunications Union - Radio communication Sector) , which is one of the force ^s recommendations and standards.

In mobile communication systems for mobile phones, etc., the service area is composed of a collection of small areas called cells that can communicate with base stations. The reason why the mobile phone can talk over a wide range is because the mobile phone communicates while switching the base station that covers the cell. Here, there are roughly two types of switching processing of the base station with which communication is performed. One is to maintain communication with the currently accessed base station while maintaining communication with the new base station. Is a soft handover that terminates the communication with the base station of the switching source. The other is a hard handover in which communication with the currently accessed base station is terminated and communication is switched to communication with the new base station.

In the CDMA (Code Division Multiple Access) mobile communication system, the carrier frequencies of base stations that cover basically adjacent cells are the same, and communication channels of a plurality of subscribers are multiplexed using a spreading code. In this case, soft handover is possible when switching between base stations. However, when multiple carriers provide services, the carrier frequencies of the base stations that cover adjacent cells may differ, and hard handover processing is performed when switching between base stations. In the W-CDM (Wideband Code Division Multiple Access) mobile communication system, when switching to a base station using a different carrier frequency, a hard handover process is performed using a compressed mode.

When switching between base stations, communication disconnection does not occur in soft handover, but communication disconnection occurs in hard handover. Prolonged communication interruption time during hard handover leads to deterioration of communication quality, and reducing the time required for hard handover processing is an issue.

The shortening of the hard handover processing time is disclosed, for example, in Japanese Patent Application Laid-Open Publication No. 2000-308081. By notifying the wireless condition of the base station of the handover destination to the mobile phone from the base station of the handover source, the time required for establishing the synchronization of the communication channel after the handover is reduced. Here, the wireless condition of the base station indicates communication control information including a communication frequency and a scrambling pattern that is a spreading code.

There is also one disclosed in Japanese Unexamined Utility Model Publication No. 03-076753. The mobile unit has two radio units that have a transceiver unit with the base station. At this time, one radio unit communicates with the base station of the handover source, and the other radio unit establishes synchronization of the communication channel with the base station of the handover destination. If communication with the handover destination base station can be established, communication with the handover source base station is terminated, so that handover without instantaneous interruption is possible.

The above-mentioned prior art is applied to mobile phones used in the FDMA (Frequency Division Multiple Access) system or the TDMA (Time Division Multiple Access) system, and is used in the W-CDMA (Wideband Code Division Multiple Access) mobile communication system. It did not attempt to reduce the processing time of handover in a mobile station device using the compressed mode. Disclosure of the invention

The present invention has been made to solve the above-described problems, and the handover processing time during hard handover using the compressed mode of the W-CDM (Wideband Code Division Multiple Access) mobile communication system is considered. An object of the present invention is to provide a short handover control method and a mobile station device using the same.

A handover control method according to the present invention is a base station in which the timing of a reference frame of a common channel transmitted by a mobile station based on different carrier frequencies in a compression mode of a W-CDMA (Wideband Code Division Multiple Access) mobile communication system is unknown. In order to perform a handover to the reference frame, the reference frame timing acquisition processing for acquiring the reference frame timing and the downlink physical channel synchronization establishment processing for establishing physical channel synchronization on the downlink are performed in parallel. is there.

A mobile station apparatus according to the present invention differs in a compression mode of a W-CDMA (Wideband Code Division Multiule Access) mobile communication system. Communication control unit that establishes synchronization of physical channels in the downlink when the timing of each frame is known in order to hand over to the base station whose timing of the common channel reference frame transmitted based on the carrier frequency is unknown. It is provided with.

According to the present invention, in a compression mode of a W_CDMA (Wideband Code Division Multiple Access) mobile communication system, a mobile station hands over to a base station whose reference frame timing of a common channel transmitted based on different carrier frequencies is unknown. Therefore, the handover processing time is short because the reference frame timing acquisition processing for acquiring the reference frame timing and the downlink physical channel synchronization establishment processing for establishing the downlink physical channel synchronization are performed in parallel. A handover control method can be obtained.

According to the present invention, in order to perform handover to a base station whose timing of a reference frame of a common channel transmitted based on different carrier frequencies in a compression mode of a W-CDMA (Wideband Code Division Multiple Access) mobile communication system is unknown. If the timing of each frame is known, a mobile station device having a short handover processing time can be obtained because the communication control unit that establishes synchronization of the physical channel in the downlink is provided. Brief Description of Drawings

FIG. 1 is a block diagram showing an outline of handover according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram showing a configuration of a mobile station device according to Embodiment 1 of the present invention.

FIG. 3 is a diagram showing a communication control in the mobile station apparatus according to Embodiment 1 of the present invention. 4 is a block diagram illustrating a configuration of a control unit.

FIG. 4 is a sequence diagram showing a series of operations of handover of related equipment including a mobile station device according to Embodiment 1 of the present invention.

FIG. 5 is a flowchart showing main operations of handover of the mobile station device according to Embodiment 1 of the present invention.

FIG. 6 is a diagram showing instantaneous interruption times of communication channels of the mobile station apparatus according to Embodiment 1 of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1

FIG. 1 is a block diagram showing an outline of a handover according to the first embodiment of the present invention. The base station 10 communicates with a mobile phone which is a mobile station device in the cell 11. The mobile phone in the cell 11 communicates with the base station 10 via a wireless communication channel. Here, the radio communication channel uses a carrier frequency of f _ul for the uplink from the mobile phone to the base station 10 and a carrier frequency of f _dl for the downlink from the base station 10 to the mobile phone. The base station 20 performs wireless communication with a mobile phone in the cell 21. Here, the radio communication channel uses a carrier frequency of _{fu 2} for the uplink and f _{d 2} for the downlink. The base stations 10 and 20 are connected to the radio network controller 30 connected to the core network 40 by wire.

It is assumed that mobile phone 100 at position A in cell 11 is communicating with base station 10. Next, it is assumed that the mobile phone 100 moves to the position B. Here, position B is in the range where cells 11 and 21 overlap. The mobile phone 100 that has moved to the position B becomes farther from the base station 10, and the reception level of the wireless communication channel transmitted from the base station 10 decreases. When the reception level drops to a level where the predetermined communication quality cannot be secured, the mobile phone 100 Notify the radio network controller 30 via the station 10 of the decrease in the reception level. The radio network controller 30 selects the type of handover and the handover destination base station based on the notification information from the mobile phone 100 and the resource information of the base station covering the cells around the cell 11, and performs the base operation. Notify station 10. Since the base station 20 of the handover destination uses a carrier frequency different from that of the base station 10 of the handover source, the radio network controller 30 selects a hard handover using the compressed mode and the base station of the handover destination. The base station 10 is notified together with the selection information of 20. The base station 10 notifies the mobile phone 100 at the position B to disconnect the communication with the base station 10 and start the communication with the base station 20. The mobile phone 100 performs a handover process for switching from the base station 10 to the base station 20 based on the information of the base station 20 designated from the wireless network control device 30 via the base station 1◦. After performing the handover process, the mobile phone 100 that has moved from the position B to the position C in the cell 21 communicates with the base station 20 using the wireless communication channel of the base station 20. The setting information of the base station 20 specified via the base station 10 from the wireless network control device 30 includes the carrier frequency of the wireless communication channel of the base station 20 and the reception of data of the wireless communication channel. Includes timing, spreading code, etc.

Regarding the data reception timing in the setting information of the base station at the time of the handover process, the wireless network control device 30 sends the pilot signal timing (pilot timing) provided at the head of the head frame (reference frame described later) of the common channel. For), only the time offset value of the timing of the pilot signal (pilot timing) provided at the beginning of the first frame of the individual channel is specified. Therefore, the mobile phone 100 needs to detect the reference frame timing (pilot timing), which is the reception timing of the common channel. FIG. 2 is a block diagram showing a configuration of the mobile station apparatus according to Embodiment 1 of the present invention. Antenna 110 of mobile phone 100 receives a downlink radio signal transmitted by a W-CDMA (Wideband Code Division Multiple Access) method from a base station (not shown). The received signal to be received is output to the transceiver 120.

The transceiver 120 includes a wideband band-pass filter (not shown) for extracting a frequency component in a predetermined band from the reception signal output from the antenna 110, and a carrier recovery circuit (for regenerating a carrier from the reception signal). And a receiver (not shown) for synchronously detecting the received signal using the carrier output from the carrier recovery circuit, and the received signal can be easily handled in the mobile phone 100. To convert to a signal with a frequency that is easy to handle. The demodulated signal output by the receiving section is output to receiving path searching section 130 and receiving path extracting section 140. Reception path search section 130 checks the reception timing of a radio signal reaching mobile phone 100 at various timings from the base station. Radio waves transmitted from a base station include a direct wave that directly reaches the mobile phone 100 and a reflected wave that is reflected by a building or the like and arrives. Since some of these reflected waves reach the mobile phone 100 via a plurality of reception paths, the mobile phone 100 receives a radio signal from the base station at various times. Measure the delay port file of the common pilot channel (CPICH) included in the common channel transmitted from the base station, and determine the reception timing for various reception paths.

The reception path extraction unit 140 includes an AZD conversion unit (not shown), a synchronous detection unit (not shown), a despread demodulation unit (not shown), and a RAKE combining unit ( Not shown). Primary Common Control Physical Channel (P-CCPCH), Secondary The A / D converter converts the physical channels of the downlink including data symbols such as the common control physical channel (S_CCPCH: Secondary Common Control Physical Channel) and the dedicated physical channel (DPCH: Dedicated Physical Channel) into digital signals. The signals that have been converted and code-demodulated by the synchronous detection unit and the despread demodulation unit are combined by a rake combining unit by correcting the time delay of the reception timing for each path, and output to the decoding unit 150.

The decoding unit 150 performs turbo / Viterbi decoding, dinterleaving, rate dematching, cyclic redundancy check (CRC) processing, and concealment processing, and generates transport channel data. Output to the mobile phone interface 170 and the communication control section 160.

The communication control unit 160 controls the reception path search unit 130, the reception path extraction unit 140, the decoding unit 150, and the modulation / coding unit 190 described later. That is, communication control such as call termination control, data retransmission control, and transmission / reception power control is performed. The configuration of the communication control unit 160 will be described later.

The mobile phone interface 1700 performs display on the screen 181, which is a display of the mobile phone 100, controls input of the operation keys 182, and performs voice control for the microphone 18 3 ゃ speaking power 1884. .

Modulation The decoding unit 190 performs transport redundancy data error correction code addition processing for cyclic redundancy check (CRC) processing, turbo Viterbi coding processing, interleaving processing, and rate matching processing. Then, the transport channel data is mapped to the physical channel data, modulated, and output to the transceiver 120. Here, the modulation is primary modulation, which is a narrowband modulation that modulates a carrier with physical channel data, and spread modulation is performed by switching a narrowband modulation signal with a spreading code to a wideband. Tuning secondary modulation.

The wideband modulated signal output from the modulation / encoding section 190 is output to the transceiver 120, and after being power-amplified, radiated from the antenna 110 into space. The base station (not shown) receives radio waves radiated from the antenna 110 into the space, and performs communication between the base station and the mobile phone 100.

FIG. 3 is a block diagram showing a configuration of a communication control unit in the mobile station device according to Embodiment 1 of the present invention. Here, the configuration mainly related to the handover process is shown. The reference control unit 160 obtains the reference frame timing. The unit 1601 obtains the reference frame timing, which is the reception timing of the common channel broadcast from the base station, that is, obtains the reference frame system frame number (SFN). I do. The system frame numbering means that the time of the pilot signal timing (pilot timing) provided at the beginning of the reference frame, which is the first frame of the common channel, is shifted from the reference time of the built-in clock of the mobile phone 100 by a frame. This is a number that indicates how many times the unit is late. Here, one frame is 10 milliseconds. The downlink physical channel synchronization establishment processing section 162 performs downlink physical channel synchronization establishment processing when the timing in frame units is known. If the timing in frame units is known, the reference frame timing acquisition unit 161 and the downlink physical channel synchronization establishment processing unit 162 can perform each process independently. The handover control section 16 3 controls handover processing. The transmission power control section 164 performs transmission power control for the base station.

Next, the operation of the handover process will be described using FIG. 4 and FIG. FIG. 4 is a sequence diagram showing a series of operations of handover of related equipment including the mobile station device according to Embodiment 1 of the present invention. FIG. 5 shows main operations of handover of a mobile station device according to Embodiment 1 of the present invention. It is a flow chart.

Figure 4 shows a mobile phone (MS: Mobile Station) 100, a base station (BS1: Base Station) 100, a base station (BS2) 20, and a radio network controller (RNC: Radio Network Controller). equipment) 30 indicates the operation and procedure between each equipment related to the handover process. In step S100, it is assumed that the mobile phone 100 is located in the cell 11, for example, at the position A in FIG. 1, and is communicating with the base station 10 using an individual channel.

In step S110, the radio network controller 30 issues a request for starting the compressed mode to the base station 10. When the mobile phone 100 moves from position A to position B in FIG. 1, the distance of the mobile phone 100 from the base station 10 increases, and the reception level of the wireless communication channel transmitted from the base station 10 Decrease. When the reception level decreases to a level where the predetermined communication quality cannot be ensured, the mobile phone 100 notifies the wireless network control device 30 via the base station 10 of the reception level reduction. The radio network controller 30 selects the type of handover and the handover destination base station based on the notification information from the mobile phone 100 and the resource information of the base station that covers cells around the cell 11. The base station 10 is notified. Here, it is assumed that the base station 20 serving the cell 21 is selected. The base station 20 uses a radio communication channel of a frequency different from that of the base station 10 and performs a hard handover process using the compression mode. As a result, the radio network controller 30 issues a request for starting the compressed mode to the base station 10.

In step S120, the base station 100 issues a compression mode start request to the mobile phone 100 based on the compression mode start request from the wireless network control device 30. In step S121, the mobile phone 100 receives a compression mode start request from the base station 10 as a handover command.

In step S130, based on the request to start the compression mode from the wireless network control device 30 to the base station 10 and the request to start the compression mode from the base station 10 to the mobile phone 100, the base station The station 10 and the mobile phone 100 start the compression mode.

In step S131, the mobile phone 100 determines whether or not the frame timing of the handover destination base station 20 is known. Frame timing is frame-level timing, not reference frame timing. If the frame timing is known, it means that the frame level can be synchronized. Once the frame level is synchronized, the physical channel can be opened. However, if the timing of the reference frame is unknown, physical channel data cannot be mapped to transport channel data, and significant data communication cannot be performed. If the frame timing is unknown, go to step S140.

In step S140, the timing of each frame of the common channel of the base station 20 as the handover destination is measured. In order to measure the frame timing, the timing of the pilot signal on the common pilot channel (CPICH) broadcast from the base station 20 is measured. First, the handover control unit 163 sends a frame timing acquisition request of the handover destination base station 20 to the reception path search unit 130. Upon receiving the frame timing acquisition request, the reception path search unit 130 measures the timing of the pilot signal on the common pilot channel (CPICH) from the handover destination base station 20.

In step S150, the common channel of the handover destination base station 20 The measurement result of frame timing 2 is reported to the base station 10 of the handover source.

In step S160, the measurement result of the frame timing of the common channel of the base station 20 received from the mobile phone 100 is reported to the wireless network 30.

In step S170, a communication setting request with the mobile phone 100 is issued to the handover destination base station 20. This communication setting information includes the carrier frequency of the wireless communication channel of the base station 20, the reception timing of the data of the wireless communication channel, the spreading code, and the like.

In step S180, based on the communication setting request from the wireless network control device 30, the handover destination base station 20 performs communication setting for the dedicated channel.

In step S190, the wireless network control device 30 causes the handover source base station 10 to perform a handover in which the mobile phone device 100 in communication is handed over to the handover destination base station 20. Make a request.

In step S200, based on the handover request from the wireless network control device 30, the base station 100 issues a request to the mobile phone 100 to perform a handover to the handover destination base station 20.

In step S210, based on the handover request from base station 10, mobile phone 100 starts handover processing from base station 10 to base station 20. This is the handover execution timing. The handover control unit 163 sends a request for switching from the handover source base station 10 to the data transmission / reception setting of the handover destination base station 20 to the transceiver 120. The data transmission / reception setting includes information on the carrier frequency of the handover destination base station 20 and the scrambling code.

In step S 211, handover from base station 10 to base station 20 As processing, the downlink physical channel is switched from base station 10 to base station 20.

In step S212, the mobile phone 100 determines whether or not the timing of the basic frame of the base station 20 of the handover destination is known. That is, it is determined whether or not the timing acquisition of the reference frame has been completed. In the hard handover using the compressed mode, the basic frame timing of the base station of the handover destination is unknown, and the process proceeds to step S220. In normal soft handover not using the compressed mode, the basic frame timing of the handover destination base station is known, and the process proceeds to step S224 described later.

In step S220, a process of acquiring a system frame number (SFN) representing the timing of the reference frame, a process of establishing physical channel synchronization on the downlink, and a process of the power control preamble section are performed in parallel.

In step S221, a system frame number (SFN) representing the timing of the reference frame is obtained. The handover control unit 163 instructs the reference frame timing acquisition unit 161 to acquire the reference frame system frame number (SFN). Since the timing of the frame unit is known in step S150, the reference frame timing acquisition unit 161 can perform the acquisition processing of the system frame number (SFN) of the reference frame.

In step S222, synchronization of the downlink physical channel is established. The handover control unit 163 instructs the downlink physical channel synchronization establishment processing unit 162 to perform the process of establishing the synchronization of the physical channel of the line. Since the timing of each frame is known in step S150, the downlink physical channel synchronization establishment processing section 162 can perform the processing of establishing the synchronization of the downlink physical channel. In step S223, preparation for transmission power control for base station 20 is performed. The handover control unit 163 instructs the transmission power control unit 164 to perform transmission power control processing.

Step S2224 is the same as step S222.

Step S225 is the same as step S223.

In step S226, processing is performed for a Signaling Radio Bearer Delay section. The Signaling Radio Bearer Delay section is a section provided in consideration of communication control information transmission delay. When the handover control unit 163 obtains a notification that the respective processes have been completed from the reference frame timing obtaining unit 161 and the transmission power control unit 1664, the handover control unit 163 transmits a handover completion notification from the mobile phone 100 to the base station 200. To the wireless communication network control device 30 via.

In step S230, the mobile phone 100 that has completed the handover process communicates with the base station 20 using the dedicated channel.

Next, the effect of shortening the instantaneous interruption time of the communication channel of the mobile station device by the handover control method of the present invention will be described with reference to FIG.

FIG. 6 is a diagram showing instantaneous interruption times of communication channels of the mobile station device according to Embodiment 1 of the present invention. (A) of Fig. 6 shows the down link, and (b) of Fig. 6 shows the instantaneous interruption time of the communication channel of the up link.

In (a) of FIG. 6, at time T1, the physical channel of the downlink from the base station of the node over is switched to the physical channel of the downlink from the base station of the handover destination at time T1 due to the hard handover process. Shall be started. At the same time as switching the physical channel, the transport channel starts switching. At time T2, switching to the downlink physical channel is completed, and at time T3, switching of the downlink transport channel. Is completed. In the figure, a is the time required for switching to the downlink physical channel, which is the instantaneous interruption time of the physical channel. For example, Suriji one Phi Phi (3 GPP: 3rd Generation Partnership Project ) is a specification called T _{3 U,} time 1 0 millisecond is one frame is defined. b is called Dedicated Physical Control Channel (DPCCH) quality measurement time and is the time required for downlink synchronization establishment processing. It takes at least 40 milliseconds. c is the timing acquisition time of the reference frame, which takes 30 to 40 ms. d is the maximum TTI (Transmission Time Interval) delimitation waiting time, which is the time used to delimit data determined for each communication type (bearer). It takes 10 to 80 milliseconds. By performing the downlink reference frame timing acquisition processing and the downlink synchronization establishment processing in parallel, the time c can be reduced. Therefore, the time of a + b + d is the instantaneous interruption time of the downlink transport channel.

In (b) of FIG. 6, at time T4, switching from the uplink physical channel to the handover source base station to the uplink physical channel to the handover destination base station starts at time T4 for the handover process. . The time T4 corresponds to the time T1 at which the switching of the downlink physical channel in FIG. 6A is started, and the switching of the physical channel of the uplink starts at the same time as the switching of the physical channel of the downlink starts. It is assumed that the synchronization establishment processing of the uplink physical channel is completed at time T5. e is the time required to establish downlink physical channel synchronization, and corresponds to the time a + b in (a) of Fig. 6. f is the time required for power control preamble section processing. g is the time required for processing the Signaling Radio Bearer Delay section. Therefore, e + f is the instantaneous interruption time of the uplink transport channel. In this way, by performing the downlink reference frame timing acquisition processing and the downlink synchronization establishment processing in parallel, the instantaneous interruption time of the downlink transport channel is reduced, and as a result, the physical The instantaneous interruption time of the channel and transport channel is also reduced.

In the above description, handover to the base station of an adjacent cell using a different carrier frequency is targeted.However, there are base stations using multiple different carrier frequencies in the same cell, and carrier waves are limited due to communication traffic restrictions. The present invention is also applicable to a case of switching to a base station having a different frequency. Industrial applicability

As described above, the handover control method and the mobile station device using the same according to the present invention are suitable for executing a hard handover using a compression mode of a W-CDMA (Wideband Code Division Multiple Access) mobile communication method.

Claims

The scope of the claims

1. In W-CD MA (Wideband Code Division Multiple Access) mobile communication system, in the compressed mode, the mobile station must perform handover to a base station whose timing of the reference frame of the common channel transmitted based on different carrier frequencies is unknown. A handover control method in which reference frame timing acquisition processing for acquiring the timing of the reference frame and downlink physical channel synchronization establishment processing for establishing downlink physical channel synchronization are performed in parallel.

2. W-CD MA (Wideband Code Division Multiple Access) In the compressed mode of the mobile communication system, in order to perform handover to the base station where the timing of the reference frame of the common channel transmitted based on different carrier frequencies is unknown, A mobile station device including a communication control unit that establishes physical channel synchronization in a downlink when the timing is known.

3. The mobile station apparatus according to claim 2, wherein the communication control unit acquires a system frame number indicating a timing of a reference frame in parallel with establishment of synchronization of the downlink physical channel.