RU2426278C2 - Wireless communication device - Google Patents

Abstract

FIELD: information technology.

SUBSTANCE: upon handover, a mobile station receives, from the movement origin base station, information on the movement destination base station and information relating to a sequence to be used for transmitting a random access signal to the movement destination base station. The mobile station receives a synchronisation channel signal transmitted from the movement destination base station. The mobile station transmits the random access signal to the movement destination base station at a timing offset by a prescribed period from a timing of receiving a synchronisation channel and at a frequency corresponding to that of the synchronisation channel. A position of the timing/frequency used for transmitting the random access signal for the handover is used exclusively by the random access signal transmitted from the mobile terminal for which handover is being performed or is used exclusively at the same time by a plurality of mobile stations for which handovers are performed.

EFFECT: suppression of interference between random access signals transmitted from a plurality of mobile stations to zero or a low level in order increase the percentage of normal reception of random access signals by a handover destination base station, low probability of the random access signal being repeatedly transmitted, and shorter time spent on handover.

10 cl, 10 dwg

Description

FIELD OF THE INVENTION

The present invention relates to a wireless communication device for transmitting a random access signal when a wireless communication device (mobile terminal) synchronizes itself with a base station.

State of the art

In EUTRAN (Enhanced UTRAN), which is currently being researched as the next generation 3GPP system, handoff performed between different cells respectively covered by different base stations in response to moving the mobile terminal station is treated as a hard handoff. In order to perform a hard handoff, the line that connects the mobile terminal and the base station before moving the mobile terminal is disconnected, and then the line between the mobile terminal and another base station covering the move destination is connected. Although the handover can be completed in a short period, even when the handover is a hard handoff with system information at the base station covering the transfer destination before performing the handover, the user data transfer is interrupted during the handover.

In EUTRAN, the use of the CAZAC sequence (zero autocorrelation with constant amplitude) as the symbol used in the preamble part of the data frame is predominant. Part of the preamble of the data frame contains a random access signal transmitted in the uplink. Zadov-Chu sequence, GCL sequence, etc. can be used as a CAZAC sequence. The expression expressing the Zadov-Chu sequence is given below, where L represents the length of the sequence and k represents the index of the sequence. In particular, when the standard length l is a prime number, excellent autocorrelation characteristics and cross-correlation characteristics are obtained.

[Expression 1]

1 is a block diagram illustrating an example of a circuit generating, from a CAZAC sequence, a portion of a preamble of a random access signal used in a wireless uplink according to EUTRAN.

A CAZAC sequence of length M (L) is sequentially / parallel converted and input to the DFT block 10 and then Fourier converted to a parallel signal with a parallel number M. This signal is input to the subcarrier display unit 11 and mapped to N subcarriers. The subcarrier signals obtained by mapping the CAZAC sequence are input to the IFFT block 12 and subjected to the inverse Fourier transform, and then input to the parallel / serial transform block 13. The signal with parallel number N, output from the IFFT block 12, is converted into a serial signal by the parallel / serial conversion block 13 and output as a sequence of random access preambles.

Additionally, according to EUTRAN, the maximum system bandwidth (the send / receive bandwidth used in the wireless transmission line by the base station) for transmission and reception in the radio transmission section is 20 MHz, and the minimum transmission / reception bandwidth for terminal stations is currently set to 10 MHz This means that terminal stations allow the transmission and reception of signals having a bandwidth of at least 10 MHz. In addition, it is believed that the cells can be located in such a way that base stations having different system bandwidths are adjacent to each other. In order to allow terminal stations to perform an initial search and become a transmission target regardless of system bandwidths, synchronization channels and broadcast signal channels (a broadcast signal channel is a channel for transmitting information about cells and base stations, and it is referred to as a broadcast channel in the future) around the middle of the downlink transmission bandwidth. However, it is also believed that synchronization channels can be located in two or three parts of the transmission bandwidth when the system transmission bandwidth is 20 MHz. This is based on the consideration of having a mobile terminal station transmitting and receiving signals having a 10 MHz bandwidth.

In any of the cases described above, the synchronization channels are not always inserted into all subframes, and the synchronization channel is set to be inserted every 5, 10, or 20 subframes to be transmitted.

According to EUTRAN, a handover between neighboring cells covered by different base stations is treated as a hard handoff, and in a hard handoff, when the mobile terminal station starts handoff while it is transmitting data, and the downlink transmission is performed indicating that the mobile terminal station is interrupted and the downlink data is transmitted to the base station in a handover destination from the base station The one exchanged data with this device of the mobile terminal. In addition, the buffer in the base station must accumulate downlink data for the mobile terminal device until the handover is completed, and as the period required to complete the handover becomes longer, the amount of data that accumulates in the buffer also increases. Similarly, it is necessary to exclude uplink data transmission, which should be transmitted from the mobile terminal station to the base station when the handover has begun, and they must be accumulated in the buffer of the mobile terminal station. In this case, some data may be discarded during the handover process, which requires retransmission using a higher layer, in the case of regular data. Additionally, when a handover begins with consecutive pieces of data transmitted on the basis of HARQ (Hybrid Automatic Repeat Request), the order of the sequence numbers assigned to the sequential pieces of data can be changed. In addition, when the handover is performed while the audio communication is performed using the voice packets, the downlink voice packets are transmitted to the base station in the handover destination; however, it is impossible to prevent interruption. In addition, audio communication is a real-time communication, and accordingly, all transmitted voice packets are not always used effectively in the transmission destination.

Due to the aforementioned facts, it is undesirable for a handover to spend a long period of time regardless of whether the transmitted data is ordinary data or voice packets.

During the handover process, the terminal station must capture the downlink synchronization channel transmitted from the base station in the handover destination, synchronize itself with the base station, and transmit the random access signal on the uplink channel. If the random access signal can be immediately transmitted after the completion of the downlink synchronization, the time spent by the handover can be reduced.

In addition, when CAZAC sequences are used as part of a random access signal preamble, the PAPR (peak power to average power ratio) of the preamble parts varies depending on the index k, even when the length l of the used CAZAC sequences does not vary.

Figure 2 depicts the PAPR characteristic of a preamble signal having a bandwidth of 5 MHz and using the Zadova-Chu sequence.

The length of the Zadov-Chu sequence used in the illustration of FIG. 2 is fixed; however, the index k changes to various values to check the PAPR values. This graph illustrates that differences equal to or greater than 3 dB can be called up in PAPR values depending on the index values. The higher the PAPR has a sequence, the greater the peak power compared to the average power.

If the waveform of the preamble part should not be distorted when the preamble part is transmitted by the mobile terminal station, the transmit power loss in the power amplifier of the transmitting unit of the mobile terminal station should increase as the PAPR of the CAZAC sequence used as the preamble increases. Since the amplifier operates with a larger amount of power loss, the amplifier consumes more power. In other words, the power amplifier of the transmitting unit represents a linear gain characteristic with a lower input power, while this gain characteristic becomes non-linear with an input power approximately equal to and exceeding a certain value of the input power, which is determined by the amplifier itself, and thus the gain is saturated and reduced. When a signal using a CAZAC sequence with a high PAPR as a preamble needs to be amplified, the difference between the average power and the peak power in this signal is so large that the peak power is not linearly amplified due to saturation, resulting in distortion in the signal if the position, in which the average power is introduced, is in the region of the saturation region of the gain characteristic of the amplifier. Accordingly, eliminating distortion in the signal requires lowering the average power of the signal input to the amplifier so that the power does not reach the area where the gain characteristic of the amplifier is saturated. A point including the average power of the input power or output power in the gain characteristic of the amplifier is referred to as the operating point, and the amount of reduction from the output saturation point is referred to as the amount of power loss.

Non-Patent Document 1 discloses specifications for EUTRAN. Non-Patent Document 2 includes a description of CAZAC sequences, such as a Zadov-Chu sequence, etc.

Non-Patent Document 1: 3GPP TR25.814

Non-Patent Document 2: 3GPP TSG RAN1LTE Ad Hoc R1-061710

SUMMARY OF THE INVENTION

An object of the present invention is to provide a wireless communications apparatus that can minimize the period during which data communications are immediately interpreted for handoff so that handoffs are efficiently performed in a mobile communications system in which handoffs are performed.

When the handover is performed, the mobile terminal station is located near the cell boundary, and accordingly, the transmit power required to generate the preamble signal transmitted from this mobile terminal station so that it can be successfully received by the receiving unit of the base station , becomes larger than the power required to generate the same preamble signal transmitted from another mobile terminal station near the base station. In addition, the transmit power required to transmit a portion of the preamble of the random access signal from the mobile terminal station near the border of a cell having a large radius can sometimes be greater than the maximum transmit power of the mobile terminal station.

Additionally, when a handover is performed, the terminal station must capture the downlink synchronization channel transmitted from the base station in the handover destination, must synchronize itself with the base station, and must transmit a random access signal on the uplink channel. If the random access signal can be immediately transmitted after the successful completion of the downlink synchronization, the time spent by the handover can be reduced. Therefore, the present invention uses a wireless communication device that separates the uplink and downlink frequency bands into narrower frequency bands, assigns data to narrower frequency bands and performs wireless communication, wherein the wireless communication device comprises: a synchronization signal capture unit to capture, upon receipt of a notification requiring the handover to be completed, a synchronization signal transmitted from the base station to value of the handover; and a synchronization establishment signal transmission unit for transmitting a synchronization establishment signal for establishing synchronization with the base station at the handover destination using the frequency position in the uplink frequency bandwidth at a point in time later than the timing of the acquisition of the synchronization signal for a prescribed period.

Preferably, the frequency position for transmitting the synchronization signal in the downlink frequency band is the same as the frequency position for transmitting the synchronization signal in the uplink frequency band. For example, when the frequency position for transmitting the synchronization signal in the downlink frequency band corresponds to the center frequency, the synchronization establishment signal is transmitted at the central frequency position in the passband of the uplink frequencies. An object of the present invention is to suppress an increase in transmission power loss caused by a signal (such as part of a random access signal preamble) transmitted from a location remote from the radio base station.

The present invention uses a mobile station that establishes a wireless uplink connection by transmitting a random access signal through a random access channel after receiving a synchronization channel transmitted from a radio base station in a handover destination, comprising: a preamble generating unit for limiting a CAZAC sequence used as a preamble a random access signal prescribed by a CAZAC sequence from among a plurality of CAZAC sequences with times personal indices, and generating a random access signal preamble using the prescribed CAZAC sequence.

Brief Description of the Drawings

1 is a block diagram illustrating an example of a circuit generating, from a CAZAC sequence, a portion of a preamble of a random access signal used in a wireless uplink according to EUTRAN;

FIG. 2 shows a PAPR characteristic of a preamble signal having a bandwidth of 5 MHz and using a Zadov-Chu sequence;

3 illustrates a first principle of an embodiment of the present invention;

4 illustrates a second principle of an embodiment of the present invention;

5 illustrates a sequence used when a handover is performed based on an embodiment of the present invention (first);

6 illustrates a sequence used when a handover is performed based on an embodiment of the present invention (second);

7 illustrates a sequence used when a handover is performed based on an embodiment of the present invention (third);

8 is a block diagram illustrating a mobile terminal station according to an embodiment of the present invention;

9 is a block diagram illustrating a configuration of a movement source base station when a handover is performed according to the present invention; and

10 is a block diagram illustrating a configuration of a movement destination base station when a handover is performed according to the present invention.

The optimal mode of carrying out the invention

In an embodiment of the present invention, the measures described below are taken.

[1] The time and frequency at which a mobile terminal station can transmit an asynchronous random access signal to a movement destination base station (base station in a handover destination) is determined by trimming the time that is in the subband of the uplink radio transmission section of the moving destination cell, wherein said sub-band corresponds to a sub-band (a frequency domain in which a synchronization channel is transmitted as one of several frequency regions obtained by dividing the entire wireless transmission bandwidth used for radio communication), in which the synchronization channel is transmitted in the downlink radio transmission section in the moving destination cell, and which is the time (in the subframe corresponding to the time) shifted by the prescribed period from the downlink synchronization channel position communication lines of a travel destination cell. However, the length of the parts of the preamble of asynchronous random access signals may vary depending on the size of the cells. For example, in the case of a large cell, part of the preamble of an asynchronous random access signal can sometimes occupy several consecutive subframes in a large cell; however, the time at which the transfer of asynchronous random access signals begins is the time shifted by the same prescribed period from the position of the synchronization channel.

When the handover is performed, information on the length of the preambles of the asynchronous random access signals used in the move destination cell is reported from the base station in the move source to the mobile terminal station for which the handover is currently being performed.

Additionally, the time shift level is set equal to a unique value, which should be used as a common value for all cells in one mobile communication system. The time shift level may be stored in a memory unit in the mobile terminal station in advance, and may also be indicated by the base station in a handover source or handover destination. The use of a constant level of time shift, as described above, eliminates the need for the base station to search for a random access signal transmitted from each of the mobile terminal stations over a specific period over the entire communication frequency band. It becomes possible to establish connections between base stations and mobile terminal devices in a shorter time.

It is possible for a mobile terminal station to transmit a random access signal at a time identified by a prescribed shift time (T) based on the position of the synchronization channel used to establish synchronization. Accordingly, compared with the case in which random access signals are received with a variable time distribution, the level of need with which an excessively large buffer at base stations must be protected to withstand instability is reduced.

Regarding the synchronization channel, the possibility of transmitting (the time that occurs through the shift time T) the random access signal for each individual synchronization channel can be set to one time, as well as two times or more. For example, transmission capabilities may be specified at time points following through the values of the shift times T and T2, for transmitting random access signals. Even when a collision occurs in the first transmission, the next signal can be transmitted without waiting for the transmission of the synchronization channel.

Preferably, the value of T is set to be shorter than the transmission cycle of the synchronization channel. Additionally, it should be appropriate and advantageous to set the value of T so that it is equal to or shorter than five subframes, and in particular equal to three or four subframes, in relation to the execution and the detection process, and the transmission process of the synchronization channel.

[2] It is not allowed to use time and frequency for transmitting a random access signal during the aforementioned handover by another terminal station for which a handover is not being performed.

In other words, the time and frequency for transmitting a random access signal, which differ from them for a mobile station for which a handover is performed, are assigned to a terminal station for which a handoff is not performed.

Thus, the likelihood that the random access signals will overlap each other in the receiving unit of the base station in the destination of the transfer (destination transfer service), and the time spent on the transfer of service can be reduced.

[3] When there is no terminal station for which a handover to the cell covered by the base station is to be performed, the base station scheduler assigns the time and frequency described in [2] (which are exclusively for the terminal station for which the handover is being performed), uplink signals transmitted from other terminal stations in the cell to the base station. The determination of whether there is a terminal station for which a handover is to be performed is based on, for example, signaling (a notification informing the start of a handover, information about the terminal station for which the handover is being performed, or an instruction requesting radio resource protection for mobile terminal station, which is part of a cell) regarding handovers transmitted from base stations in neighboring cells or from aGW (access gateway that corresponds to yayuschemu base station apparatus in a W-CDMA systems), and also based on a control signal transmitted from a terminal station to a base station in the handover destination in order to directly (or indirectly) report about the handover complete.

Thus, it is possible to avoid a decrease in the efficiency of the use of radio resources that would be caused if the radio resources (time and frequency for transmitting a random access signal by a mobile terminal station for which a handover is being performed) were not used while there is no terminal station, for which handover should be performed.

[4] As an index of a CAZAC sequence applied to a part of a preamble used with time and frequency to transmit a random access signal when a handover is performed, an index with a small PAPR in the preamble part is used.

You can reduce the amount of output power loss in the transmission signal amplifier when transmitting a portion of the preamble. If the amount of power loss is reduced, (1) the average transmission power can be increased, and (2) the likelihood of a lack of transmission power can be reduced, and this is beneficial for a terminal station for which a handover is being performed and which requires high transmission power due to being nearby with the border of the cell and remotely from the base station.

Indexes with small PAPRs are, for example, indices other than indices with PAPRs of 6 dB or higher in FIG. 2. In addition, indices from ranges between 1 and 75, 132 and 168, 225 and 298 can be selected as indices with relatively small PAPR values. When these ranges are expressed using the sequence length L, indices can be selected from ranges between 1 and L / 3, L / 2-L / 16 and L / 2 + L / 16, 2L / 3 and L-1.

[5] Information about the CAZAC sequence index applied to the portion of the preamble used over time and frequency for transmitting a random access signal to perform a handover is reported from the terminal station for which the handover is being performed to the base station in the handover source.

[6] An index with a small PAPR is used as the CAZAC sequence index applied to the part of the preamble used for handover. The small PAPR used here is the PAPR, which causes only a small loss in power of the operating point of the transmit signal amplifier so that the random access signal transmitted within the normal transmit power from the mobile terminal station near the cell boundary covered by the base station can be received by the base station as usual. A sequence having the correct index, which should be used for any situation in which the mobile station is located, is calculated and determined in advance.

[7] The CAZAC sequence index information applied to the portion of the preamble used for handoff is reported from the base station at the handoff source to the terminal station for which handoff should be performed when the handoff is actually being performed.

3 illustrates a first principle of an embodiment of the present invention.

Figure 3 illustrates the location of the downlink and uplink signals in the directions of frequency and time, with the horizontal axis representing frequencies and the vertical axis representing time. The synchronization channel is defined around the center frequency of the system bandwidth among the subframes transmitted in the downlink. The synchronization channel is not contained in all the subframes transmitted in the downlink, but is contained in, for example, every fifth or tenth subframes to be transmitted. Before synchronization is established between the mobile terminal station and the base station, the uplink and downlink signals are asynchronous. Thus, in the embodiment of the present invention, when the synchronization channel is detected in the downlink signal, the random access signal is contained (adapted) in the uplink subframe corresponding to the time point following this time through a time offset Toffset, and the signal is transmitted to base station from a mobile terminal. The frequency used to accumulate the random access signal is near the center frequency in the passband of the uplink system because the downlink synchronization channel is near the center frequency of the system passband. In the example of FIG. 3, a time interval shaded by diagonal lines is used to transmit a random access signal. The random access signal to be transmitted may be inserted into several consecutive subframes; however, only the uplink subframe corresponding to the point in time subsequent to the synchronization channel through the Toffset time offset can be used as a subframe to start transmitting the downlink signal regardless of the length of the random access signal. If the random access signal transmission fails (when the response signal is not transmitted from the base station), the random access signal is inserted at the same position (uplink subframes following the time of the other synchronization channel, which must be transmitted subsequently, through a Toffset to time) and retransmitted. Of course, when several possibilities of transmitting a random access signal are provided to one synchronization channel, a random access signal may be transmitted in the next transmission opportunity.

4 illustrates a second principle of an embodiment of the present invention.

In Fig. 4, analogously to the example in Fig. 3, the signals of the uplink and the downlink are illustrated with a horizontal axis representing frequencies and a vertical axis representing time. 4, the configuration is used when the system bandwidth is wide and the reception bandwidth of the receiving mobile terminal station is only half the system bandwidth. The downlink signal has synchronization channels defined approximately adjacent to two frequencies in one subframe (however, synchronization channels can be specified in three or more positions). In an embodiment of the present invention, the frequency used to transmit the random access signal of the terminal for which the handover is performed is a frequency in the frequency band of the uplink signal, said frequency corresponding to the frequency at which the synchronization channels are set in the bandwidth of the uplink signal system communication. For example, when the synchronization channels are located near the center parts of the two bands obtained by dividing the downlink frequency band, random access signals are also located near the center parts of the two bands obtained by dividing the uplink band. The random access signal transmission start time is in the subframe of the uplink signal corresponding to the time point following the time point of detection of the synchronization signal in the downlink signal through a time offset Toffset. In Fig. 4, the parts shaded with diagonal lines are time intervals in which the transmission of random access signals begins. Since there are synchronization channels in two time slots in the downlink signal, there are also two time slots that can be used to transmit the random access signal in the uplink signal. The random access signal to be transmitted may be inserted into several consecutive subframes; however, only the uplink subframe corresponding to the point in time subsequent to the synchronization channel through the Toffset time offset can be used as a subframe to start transmitting the downlink signal regardless of the length of the random access signal. If the random access signal transmission fails (when the response signal is not transmitted from the base station), the random access signal is inserted at the same position (uplink subframes following the time of the other synchronization channel, which must be transmitted subsequently, through a Toffset to time) to be retransmitted.

5-7 illustrate sequences for performing a handover according to an embodiment of the present invention.

5 illustrates a first example. In FIG. 5, the (mobile) terminal station transmits to the displacement destination base station a measurement result of the received signal power (pilot signal, etc.) transmitted from a neighboring cell, and the displacement source base station determines that it should perform a handover ( one). Then, the base station of the moving source transmits information confirming that a handover should be completed, information about the mobile terminal station, and the like. Upon receiving information from the base station of the movement source, the base station of the destination of movement sets the time and frequency that should be used to transmit a random access signal exclusively for the mobile terminal station for which the handover should be performed, so that the specified time and frequency are not assigned uplink data transmission by another mobile terminal station for which a handover should not be performed (2). As already described, the aforementioned time is the time following the reception of the synchronization signal by the terminal station through a time offset, and the aforementioned frequency is the uplink frequency corresponding to the frequency used to transmit the downlink synchronization channel. When there is no terminal station for which a handover is to be performed, during the period between the state in which the terminal station is communicating with the base station of the moving source and the state according to (2), the time and frequency for transmitting the random access signal of the terminal station, for to which the handover is being performed may be assigned to a terminal station for which the handover will not be performed. When the movement destination base station has completed the task of (2), system information including a CAZAC sequence index of a random access signal used for handover is transmitted to the movement source base station. At this time, a CAZAC sequence with a small PAPR is selected in order to be transmitted. As already described, indices with small PAPRs are, for example, indices other than indices with PAPRs of 6 dB or higher in FIG. In addition, indices can be selected from ranges between 1 and 75, 132 and 168, 225 and 298 as indices with relatively small PAPRs. When these ranges are expressed using the length L of the sequence, the indices can be selected from the ranges between 1 and L / 3, L / 2-L / 16 and L / 2 + L / 16, 2L / 3 and L-1.

However, the task in (2) can be performed after the transmission of system information, etc. to the base station of the source of movement. A movement source base station that has received system information, etc., transmits to a mobile terminal station for which a handover is performed, system information about a movement destination cell, including the index of a CAZAC sequence used for handover to instruct the mobile terminal station to start handover. After that, while still having data to transmit to the terminal station, the base station of the movement source transmits this data to the base station of the destination of movement. However, this data may also be transmitted after the handover is successful.

Having accepted the instruction to start the handover, the terminal station begins to synchronize itself with the hundredth destination of the move. The terminal station captures the downlink synchronization channel from the movement destination base station (4) and transmits a part of the preamble of the random access signal (synchronization establishment signal) to the movement destination base station. Management information, etc. can be included in the part of the preamble by the multiplexing method (code multiplexing, time multiplexing, etc.). To transmit part of the random access signal preamble, time and frequency are used to transmit the random access signal exclusively to the terminal station for which the handover is currently being performed. When the moving destination base station has received the preamble part of the random access signal and has successfully recognized the sequence in the preamble part, the acknowledgment of the reception of the preamble part and the time and frequency for transmitting the uplink data are notified to the terminal station. Upon receiving this information, the terminal station transmits a handover completion signal to the movement destination base station. Having received this signal, the movement destination base station transmits a handover completion message signal to the movement source base station after the process necessary for establishing a wireless communication line with the terminal station is completed. Then, the movement destination base station restarts the generation of time and frequency for transmitting the random access signal exclusively for the terminal station for which the handover is being performed so that they can be used for uplink data transmission for terminals for which the handover is not performed (5 )

The period between (2) and (5) in FIG. 5 is the period during which the time and frequency for transmitting a random access signal of a terminal station for which a handover is being performed are assigned exclusively to the terminal station for which the handover is being performed. After setting (5), the time and frequency for transmitting a random access signal to a terminal station for which a handover is performed are assigned to a terminal station for which no handoff is performed when there is no terminal station for which a handoff is performed.

6 illustrates a second example. 6, the (mobile) terminal station transmits the received power measurement result, and the like to the base station of the displacement source. a signal (pilot signal, etc.) from a neighboring cell, and the base destination station determines that the handover should be performed (1). Then, the base station of the moving source transmits information confirming that a handover should be completed, information about the mobile terminal station, and the like. to the base station of the destination of movement. Upon receiving information from the base station of the movement source, the base station of the destination of movement sets the time and frequency that should be used to transmit a random access signal exclusively for the mobile terminal station for which the handover should be performed, so that the specified time and frequency are not assigned uplink data transmission of another mobile terminal station for which a handover should not be performed (2). As already described, the aforementioned time is the time following the reception of the synchronization signal by the terminal station over a time interval in a time offset, and the aforementioned frequency is the uplink frequency corresponding to the frequency used to transmit the downlink synchronization channel. When there is no terminal station for which a handover is to be performed, during the period between the state in which the terminal station is communicating with the base station of the moving source and the state according to (2), the time and frequency for transmitting the random access signal of the terminal station, for to which the handover is being performed may be assigned to a terminal station for which the handover should not be performed. In the first example illustrated in FIG. 5, when the movement destination base station completed the task of (2), system information including a CAZAC sequence index of a random access signal used for handover is transmitted to the movement source base station. However, the task in (2) can be performed after the transmission of system information, etc. to the base station of the source of movement. However, in the second example illustrated in FIG. 6, which of the sequences should be used as the CAZAC sequence for the random access signal is determined in advance by system design and the like, and the CAZAC sequence information is not included in the information transmitted from the movement destination base station to the mobile terminal station through the movement source base station. The moving source base station transmits system information on the moving destination cell to the mobile terminal station and instructs the mobile terminal station to begin handover. After that, when the base station of the movement source still has data to transmit to the terminal station, it transmits this data to the base station of the destination of movement. However, this data may also be transmitted after the handover is successful.

Having accepted the instruction to start the handover, the terminal station begins to synchronize itself with the cell (3) destination movement. The terminal station captures the downlink synchronization channel transmitted from the motion destination base station (4) and transmits a portion of the random access signal preamble to the motion destination base station. Management information, etc. can be included in the part of the preamble by the multiplexing method (code multiplexing, time multiplexing, etc.). To transmit part of the random access signal preamble, time and frequency are used to transmit the random access signal exclusively to the terminal station for which the handover is being performed. When the moving destination base station has received the preamble part of the random access signal and has successfully properly recognized the sequence of the preamble part, the acknowledgment of receipt of the preamble part and the time and frequency for transmitting the uplink data are notified to the terminal station. Upon receiving this information, the terminal station transmits a handover completion signal to the movement destination base station. Having received this signal, the movement destination base station transmits a handover completion message signal to the movement source base station after the process necessary for establishing a wireless communication line with the terminal station is completed. Then, the movement destination base station restarts the time and frequency assignment for transmitting the random access signal exclusively for the terminal station for which the handover is being performed, as the time and frequency for transmitting uplink data for terminals for which the handoff is not performed.

The period between (2) and (5) in FIG. 6 is the period during which the time and frequency for transmitting a random access signal of a terminal station for which a handover is being performed are assigned exclusively to the terminal station for which the handover is being performed. After setting (5), the time and frequency for transmitting a random access signal to a terminal station for which a handover is performed are assigned to a terminal station for which no handoff is performed when there is no terminal station for which a handoff is performed.

7 illustrates a third example. In Fig. 7 (mobile), the terminal station transmits the received power measurement result and the like to the base station of the displacement source. a signal (pilot signal, etc.) from a neighboring cell, and the base destination station determines that the handover should be performed (1). Then, the base station of the moving source transmits information confirming that a handover should be completed, information about the mobile terminal station, and the like. In the third example, the time and frequency are set in advance solely for transmitting a random access signal for the mobile terminal station for which the handover is being performed in order to prevent the use of time and frequency for other purposes. As already described, the aforementioned time is the time following the reception of the synchronization signal by the terminal station over a time interval in a time offset, and the aforementioned frequency is the uplink frequency corresponding to the frequency used to transmit the downlink synchronization channel. The movement destination base station transmits system information including a CAZAC sequence index for the random access signal used for handover to the base station of the movement source. The movement source base station transmits system information on the movement destination base station to the mobile terminal station and instructs the mobile terminal station to begin handover. After that, the base station of the movement source still has data to be transmitted to the terminal station, and it transmits this data to the base station of the destination of movement. However, this data may also be transmitted after the handover is successful.

Having accepted the instruction to start the handover, the terminal station begins to synchronize itself with the cell (2) destination movement. The terminal station captures the downlink synchronization channel from the movement destination base station (3) and transmits a portion of the random access signal preamble to the movement destination base station. To transmit part of the random access signal preamble, time and frequency are used to transmit the random access signal exclusively to the terminal station for which the handover is being performed. When the moving destination base station has received the preamble part of the random access signal and has successfully properly recognized the sequence of the preamble part, the acknowledgment of receipt of the preamble part and the time and frequency for transmitting the uplink data are notified to the terminal station. Having received this information, the terminal station transmits a handover completion signal to the base station of the moving source after the process necessary to establish a wireless link with the terminal station.

FIG. 8 is a block diagram illustrating a mobile terminal station according to an embodiment of the present invention.

When the receiving antenna has received the signal, the radio unit 10 demodulates the signal, and the decoding unit 11 decodes the signal to obtain user data / voice packets, a control signal, sequence information used for handover, and a handoff instruction signal. The conclusions from the DFT unit 10 are inputted to the downlink synchronization channel reception processing unit 13. After that, the process of receiving the synchronization channel is performed, and the reception result is input to the handover control unit 14. The handover control unit 14 controls the reception frequency control unit 12, the sequence determination unit 15, and the transmission time and frequency determination unit 19 of the random access signal. The reception frequency control unit 12 controls the frequency used when receiving the synchronization channel. The sequence determination unit 15 determines the sequence to be used for the random access signal. As an example, the sequence used for the random access signal may be notified from a radio base station in a handover source. Block 19 determining the time and frequency of the transmission of the random access signal determines the time and frequency for the random access signal.

In response to the determination by the time and frequency determination unit 19 of the random access signal, the transmission frequency control unit 20 controls the radio unit 28 and the modulation unit 27 so as to transmit the random access signal according to the time and frequency defined in the present invention. When what sequence is to be used is determined by the sequence determination unit 15, a specific sequence is generated by the preamble signal sequence generation unit 16, and the random access preamble signal generation unit 17 uses this sequence to generate a preamble signal containing a random access signal. This preamble signal is combined with control information by the multiplexing method by the multiplexing unit 18, and the resulting information is input to the switching unit 26.

The speech packet, user data, and the measurement result of the neighboring cell are input to the multiplexing / switching unit 21, output in a combined (multiplexed) state, or one at a time, and are encoded by the channel coding unit 22. The control signal is also encoded by another channel coding unit 23. The conclusions from the channel coding units 22 and 23 are output by means of another multiplexing / switching unit 24 in a combined (multiplexed) state or one at a time, are converted into a physical channel by means of a physical channel generating unit 25, and input to the switching unit 26. The switching unit 26 switches between the signals from the multiplexing unit 18 and the signals from the physical channel forming unit 25 to output to the transmitting antenna through the modulation unit 27 and the radio unit 28.

9 is a block diagram illustrating a configuration of a movement source base station when executed according to an embodiment of the present invention.

The signal received by the receiving antenna is demodulated by the radio unit 30 and decoded by the decoding unit 31. The measurement result of the neighboring cell is obtained from the decoded signal and is used for the handover determination unit 32 to determine whether a handover should be performed for the terminal station that sent this result. When it is determined that the handover is to be completed, information confirming the handover is completed and information about the terminal station for which the handover is to be performed is transmitted to the transfer destination base station.

Having received the system information at the movement destination base station and the sequence information of the random access signal preambles used for handover (for example, information about the sequence length L and index k for recognizing the sequence with PAPR, etc.) transmitted from the movement source base station , the handover operation processing unit 33 generates information about the sequence of preambles of the random access signal used for handover, and the instrument signal citation of the beginning of the transfer of service, as well as system information on the base station destination movement. Block 34 for the formation of physical channels converts the generated information into a physical channel. The resulting information is transmitted through the transmitting antenna after passing through the modulation unit 35 and the radio unit 36.

10 is a block diagram showing a configuration of a movement destination base station when a handover is performed according to an embodiment of the present invention.

First, handover confirmation information and handover destination terminal information are received from the base station moving source base station for which the handover is being performed. Further, the handover operation processing unit 42 transmits to the base station of the moving source information about the sequence of preambles of the random access signal used for handover and system information on the base station. Additionally, the handover operation processing unit 42 requests that the uplink radio resource control unit 47 prohibit other stations from using the time and frequency for the random access signal of the terminal station for which the handover is to be performed and that it assigns uplink radio resources, which should be used until the handover for the terminal station is complete. The uplink radio resource control unit 47 transmits the uplink radio resource assignment information to the mobile terminal station via the physical channel generation unit 48, the modulation unit 49, and the radio unit 50.

When a signal from a terminal station for which a handover is to be performed is received through a receive antenna, a radio unit 40, and a decoding unit 41, the random access signal reception detection processing unit 43 attempts to detect the reception of the random access signal, which is possibly received to determine whether a random access signal is transmitted. The process of detecting a portion of the preamble of the random access signal is performed by the control unit 43 for detecting the received random access signals under control by the handover operation processing unit 42 and the preamble reception confirmation unit 44. Upon detecting the reception of the random access signal, the preamble reception confirmation unit 44 transmits information on the reception confirmation for the preamble part to the terminal station through the physical channel generation unit 48, the modulation unit 49, and the radio unit 50. Having received the random access signal, the random access signal reception time detection unit 45 detects the time at which the random access signal is received, and calculates the time interval of transmission from the terminal station, generates a time correction information signal change the transmission on the uplink and transmits this signal to the terminal station through block 48 for the formation of physical channels, block 49 modulation and radio block 50.

Upon receiving the terminal station process completion message signal transmitted from the terminal station, the handover completion determination unit 46 determines that the handover has been completed and sends the request to the uplink radio resource control unit 47 to provide a time and frequency for the random access signal for the terminal station for which the handover is performed. When the process necessary for establishing a wireless link with the terminal station is completed, a handover completion message is transmitted to the base station of the moving source. In addition, the synchronization channel transmitted from the movement destination base station when the handover is performed is transmitted through the physical channel forming unit 48, the modulation unit 49, the radio unit 50, and the transmitting antenna.

The above configuration corresponds to the sequence illustrated in FIG. However, the configurations corresponding to FIGS. 6 and 7 should be readily contemplated by those skilled in the art.

Claims (10)

1. A wireless communication device that separates the uplink and downlink frequency bandwidths into narrower frequency bandwidths, assigns data to narrower frequency bandwidths and performs wireless communication, comprising:
means for capturing synchronization signals for capturing, upon receipt of a notification requiring a handover to be completed, a synchronization signal transmitted from a base station in a handover destination; and
means for transmitting synchronization establishment signals for transmitting a synchronization establishment signal for establishing synchronization with the base station in the handover assignment using the frequency position in the passband of the uplink frequencies at a point in time later than the acquisition time of the synchronization signal for a prescribed period. 2. The wireless communications apparatus of claim 1, wherein:
the time and frequency position used to transmit the synchronization establishment signal may be used by the radio communication device for which the handover is being performed. 3. The wireless communications apparatus of claim 2, wherein:
when there is no wireless communication device for which a handover is being performed in the cell of the base station, the time and frequency position used to transmit the synchronization establishment signal are used by the wireless communication device for which the handover will not be performed in the cell of the base station for transmitting the signal, different from the sync setting signal. 4. The wireless communications apparatus of claim 1, wherein:
a synchronization establishment signal is a signal including a prescribed sequence of signals in the preamble part of a data frame. 5. A base station in a wireless communication system, dividing the uplink and downlink frequency bandwidths into narrower frequency bandwidths, assigning data to narrower frequency bandwidths and performing wireless communication, comprising:
means for transmitting synchronization signals for transmitting a synchronization signal through a downlink so that the terminal station can recognize the base station;
handover notification means for receiving a handover notification informing that a terminal station in a cell covered by another base station is about to move to a cell of the base station itself through a handover process;
means for receiving synchronization establishment signals for receiving, upon receipt of a handover notification, a synchronization establishment signal transmitted from a terminal station moving to a cell of the base station itself through a handover process using a frequency position in an uplink frequency bandwidth corresponding to a frequency position in the downlink frequency bandwidth of the synchronization signal, at the prescribed time; and
transmission time message means for reporting transmission time to the terminal station when the terminal station transmits a signal through the uplink based on the reception time of the synchronization establishment signal. 6. The base station according to claim 5, further comprising:
signal sequence reporting means for reporting to the terminal station the signal sequence to be used for the timing signal. 7. The base station according to claim 5, in which:
a terminal station for which a handover is not performed is prevented from using the frequency position and the prescribed time used to transmit the synchronization establishment signal to the terminal station moving to the cell of the base station itself through the handover process. 8. The base station according to claim 6, in which:
a signal sequence is a constant amplitude zero autocorrelation (CAZAC) sequence. 9. A method for controlling a wireless communication device dividing the uplink and downlink frequency bandwidths into narrower frequency bandwidths, assigning data to narrower frequency bandwidths and performing wireless communication, comprising the steps of:
capturing, upon receipt of a notification requiring the handover to be completed, a synchronization signal transmitted from the base station in the handover destination; and
transmitting the synchronization signal to establish synchronization with the base station in the destination of the handover using the frequency position in the passband of the uplink frequencies corresponding to the frequency position in the passband of the downlink used to transmit the synchronization signal at a point in time later than time Capturing a sync signal for a prescribed period. 10. A method for controlling a base station in a wireless communication system dividing the uplink and downlink frequency bandwidths into narrower frequency bandwidths, assigning data to narrower frequency bandwidths and performing wireless communication, comprising the steps of:
transmitting a synchronization signal through a downlink so that the terminal station can recognize the base station;
receiving a handover notification informing that the terminal station in the cell covered by another base station is about to move to the cell of the base station itself through the handover process;
receive, when receiving a handover notification, a synchronization establishment signal transmitted from a terminal station moving to a cell of the base station itself through a handover process using the frequency position in the uplink frequency bandwidth corresponding to the frequency position in the downlink frequency bandwidth synchronization signal, at the prescribed time; and
report the transmission time to the terminal station when the terminal station transmits a signal through the uplink, based on the reception time of the synchronization establishment signal.

Images