WO2013061430A1

WO2013061430A1 - Base station device, mobile station device, and random access method

Info

Publication number: WO2013061430A1
Application number: PCT/JP2011/074713
Authority: WO
Inventors: 英寿元田; 宏和金山
Original assignee: 富士通株式会社
Priority date: 2011-10-26
Filing date: 2011-10-26
Publication date: 2013-05-02

Abstract

A base station device according to the present invention is provided with a control unit (12) which executes: an allocation number determination process to dynamically determine the allocation number of preambles to be allocated to the contention-based preamble from among a predetermined plurality of preambles; an allocation notification process to notify a mobile station device of the allocation number of preambles in accordance with the allocation number determined by the allocation number determination process; and an allocation change process to change the allocation of preambles to be allocated to the contention-based preamble in accordance with the allocation number determined by the allocation number determination process.

Description

Base station apparatus, mobile station apparatus, and random access method

The embodiments discussed herein relate to random access procedures performed in mobile communications.

In the random access procedure executed in the initial access from the mobile station device to the base station device, a preamble is transmitted. Some random access procedures use a dedicated preamble and a contention-based preamble. An example of a technical standard that defines such a random access procedure is LTE (Long Term Term Evolution) studied in 3GPP (Third Generation Partnership Project), for example. In the following description, the mobile station apparatus and the base station apparatus may be simply referred to as “mobile station” and “base station”.

The dedicated preamble is explicitly instructed from the base station to the mobile station prior to transmission of the preamble from the mobile station to the base station. The individual preamble is also called a contention free preamble. On the other hand, the contention-based preamble is selected from a plurality of preambles that are predetermined as preambles used by the mobile station in the random access procedure. Hereinafter, the random access procedure using the dedicated preamble and the random access procedure using the contention-based preamble are referred to as “contention-free sequence” and “contention-based sequence”, respectively.

A method for assigning and selecting individual signatures for random access is known. The option to assign individual signatures is to assign individual signatures from the unused space of the random signature root index when there is unused space, and to use the same time / frequency resources when additional signatures are needed. Including further assigning individual signatures from the root index and reserving the preamble from the contention-based random access preamble from both of the two sets of preambles. Individual signatures are reserved for each of the two sets of preambles.

Special table 2010-537472

∙ When the contention base sequence increases, the preamble interferes and the completion of the random access procedure is delayed. For example, contention-based sequences frequently occur at the exit of a tunnel where the mobile station is temporarily out of the cell range. Since the completion of the random access procedure is delayed, the start of data communication is delayed and the service quality is deteriorated. Further, when traffic is reduced by repeating the random access procedure, the throughput of the cell is lowered, and the service quality is lowered.

The disclosed apparatus and method are intended to reduce degradation of service quality due to an increase in contention-based sequences.

According to one aspect of the device, a base station device is provided. The base station apparatus performs allocation number determination processing for dynamically determining the number of allocations allocated to the contention-based preamble among a plurality of predetermined preambles, and allocation of preambles according to the allocation number determined in the allocation number determination processing. An allocation notification process for notifying the mobile station apparatus, an allocation change process for changing the allocation of the preamble allocated to the contention base preamble according to the allocation number determined in the allocation number determination process, and a control unit for executing the allocation change process.

According to another aspect of the device, a mobile station device is provided. The mobile station apparatus performs contention according to the process of acquiring the preamble allocation dynamically allocated to the contention-based preamble from the received signal from the base station apparatus among the predetermined plurality of preambles and the preamble allocation. A control unit that executes processing for selecting a preamble to be transmitted in the base random access procedure is provided.

According to one aspect of the method, a random access method is given. In the random access method, the control unit included in the base station apparatus is determined by an allocation number determination process that dynamically determines an allocation number allocated to a contention-based preamble among a plurality of predetermined preambles, and an allocation number determination process. An allocation notification process for notifying the mobile station apparatus of the allocation of the preamble according to the allocation number, and an allocation change process for changing the allocation of the preamble allocated to the contention-based preamble according to the allocation number determined by the allocation number determination process Let it run.

In a random access method according to another aspect of the method, a process of obtaining a preamble allocation dynamically allocated to a contention-based preamble from among a plurality of predetermined preambles from a received signal from a base station apparatus, and a preamble allocation In response to this, a process for selecting a preamble to be transmitted by the contention-based random access procedure is executed.

According to the disclosed apparatus or method, service quality degradation due to an increase in contention-based sequences is reduced.

The objects and advantages of the invention will be realized and attained by means of the elements and combinations shown in the claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.

It is a figure which shows the example of whole structure of a communication system. It is a figure which shows an example of the hardware constitutions of a base station apparatus. It is a functional block diagram of an example of the baseband processing circuit of a base station apparatus. (A) And (B) is explanatory drawing of the example of allocation of a preamble. It is explanatory drawing of the allocation change time. It is a figure which shows an example of the hardware constitutions of a mobile station apparatus. It is a functional block diagram of an example of the baseband processing circuit of a mobile station apparatus. It is explanatory drawing of an example of the preamble allocation number determination process. It is explanatory drawing of an example of a preamble allocation number change process. It is a schematic diagram which shows the range of the reserved preamble. It is explanatory drawing of an example of a preamble allocation number notification process. It is explanatory drawing of an example of a timeout process. It is explanatory drawing of an example of the process at the time of preamble reception. It is explanatory drawing of an example of the process at the time of a separate preamble instruction | indication. It is explanatory drawing of an example of a process of a mobile station apparatus.

<1. System configuration>
Hereinafter, preferred embodiments will be described with reference to the accompanying drawings. FIG. 1 is a diagram illustrating an example of the overall configuration of a communication system. The communication system 1 includes a base station 2 and a mobile station 3. The communication system 1 is a mobile communication system in which a random access procedure that uses a dedicated preamble and a random access procedure that uses a contention-based preamble are executed. The communication system 1 may be, for example, an LTE mobile communication system. The dedicated preamble or contention-free preamble is a preamble that is explicitly instructed to the mobile station 3 in the contention-free sequence by the base station 2 that identifies the mobile station 3 that performs the random access procedure. The contention-based preamble is a preamble that the base station 2 designates to the mobile station 3 by system information so that the mobile station 3 selects from a plurality of preambles and uses it in a random access procedure.

In the following description, an example of an embodiment in an LTE mobile communication system is shown. However, the apparatus and method disclosed in this specification can be applied to other types of mobile communication systems as long as a random access procedure using a dedicated preamble and a random access procedure using a contention-based preamble are executed. It can also be applied to a communication system.

<2. Example of base station configuration>
<2.1. Hardware configuration>
Next, the configuration of the base station 2 will be described. FIG. 2 is a diagram illustrating an example of a hardware configuration of the base station 2. The base station 2 includes a processor 10, a storage device 11, a baseband processing circuit 12, a radio frequency signal processing circuit 13, a duplexer 14, and an antenna 15. In the attached drawings, the baseband, radio frequency, and duplexer are denoted as “BB”, “RF”, and “DUX”. The hardware configuration shown in FIG. 2 is just one of the hardware configurations for realizing the base station 2. Any other hardware configuration may be adopted as long as the processing described below is executed in this specification.

The baseband processing circuit 12 performs processing of baseband signals related to encoding and modulation of signals transmitted and received between the mobile station 3 and the base station 2, and demodulation and decoding, communication protocol processing, and scheduling. The baseband processing circuit 12 may include a processor for signal processing and a memory for storing programs and data necessary for the operation of the processor. The processor may be, for example, a DSP (digital signal processor) or a CPU (Central processing unit). The baseband processing circuit 12 may include logic circuits such as LSI (large scale integration), ASIC (Application Specific Integrated Circuit), and FPGA (Field-Programming Gate Array) for signal processing.

The processor 10 performs user management processing other than processing by the baseband processing circuit 12 and operation control of the base station 2. The storage device 11 stores a control program for baseband signal processing by the processor 10. Each data and temporary data used during the execution of these programs are also stored in the storage device 11.

The radio frequency signal processing circuit 13 performs digital / analog conversion, analog / digital conversion, frequency conversion, signal amplification and filtering of a radio signal transmitted / received between the mobile station 3 and the base station 2 via the duplexer 14 and the antenna 15. .

<2.2. Functional configuration>
Next, functions realized by the hardware configuration will be described. FIG. 3 is a functional block diagram of an example of the baseband processing circuit 12 of the base station 2. The baseband processing circuit 12 includes a scheduler 20, a demodulator 21, a decoder 22, an encoder 23, a modulator 24, a protocol processor 25, and an allocation number determination unit 26. FIG. 3 mainly shows functions related to the following description. The baseband processing circuit 12 may include other components other than the illustrated components.

In one embodiment, the signal processing by the components 20 to 26 is performed by a DSP included in the baseband processing circuit 12 executing a control program stored in the memory of the baseband processing circuit 12. In another embodiment, the baseband processing circuit 12 includes a logic circuit such as an LSI, ASIC, or FPGA for processing of the demodulating unit 21, the decoding unit 22, the encoding unit 23, the modulation unit 24, and the protocol processing unit 25. It may be.

The scheduler 20 performs a scheduling process for determining the mobile station 3 that communicates with the base station 2 and the radio resources to be allocated to each mobile station 3. The demodulation unit 21 and the decoding unit 22 perform a demodulation process and a decoding process on the received signal. The encoding unit 23 and the modulation unit 24 perform transmission signal encoding processing and modulation processing. The protocol processing unit 25 executes communication processing for transmitting / receiving data to / from the core network according to the communication protocol.

The allocation number determination unit 26 determines the allocation number allocated to the contention-based preamble and the individual preamble among a plurality of preambles that can be used by the mobile station 3 that executes the initial access to the base station 2. FIG. 4A and FIG. 4B show examples of preamble allocation.

As shown in FIG. 4A, a total of M preambles are prepared as preambles that can be allocated to the contention base preamble and the individual preambles. In the initial state, N preambles, which are initial values, are allocated to the contention base preamble, and the remaining (MN) preambles are allocated to the individual preamble. Each preamble is given an order, and when the number of allocations is determined, which of the M preamble preambles is allocated to the contention base preamble is determined.

The allocation number determining unit 26 dynamically determines the number of preambles allocated to the contention base preamble and the individual preamble. For example, the allocation number determination unit 26 determines the allocation number allocated to the contention-based preamble and the individual preamble at a certain time point as in the allocation state in FIG. 4B, which is different from the initial state in FIG. . In the example of FIG. 4B, (N + n) preambles are allocated to the contention base preamble, and the remaining (MN−n) preambles are allocated to the individual preamble. The change number “n” is an integer greater than or equal to 0, and the initial value “N” is a lower limit value of the number of preambles allocated to the contention base preamble.

In the following description, the number of contention-based preamble allocations determined by the allocation number determination unit 26 may be referred to as “determined allocation number”. An example of allocation number determination processing by the allocation number determination unit 26 will be described later in “4.1 Preamble Allocation Number Determination Processing”.

The scheduler 20 includes a sequence control unit 30 and a broadcast information transmission control unit 31. The sequence control unit 30 includes an allocation changing unit 32, a first timer 33, a second timer 34, an individual preamble instruction unit 35, and an individual preamble use determination unit 36. In another embodiment, the scheduler 20 may include the allocation number determination unit 26.

The sequence control unit 30 performs signal processing for a RACH (Random Access Channel) sequence, which is a random access procedure, and performs processing for changing the preamble assignment to the contention base preamble. The broadcast information transmission control unit 31 notifies the mobile station 3 by transmitting the preamble allocation according to the determined allocation number as broadcast information.

The broadcast information transmission control unit 31 may notify, for example, the change number n with respect to the initial value N of the contention-based preamble allocation number as the preamble allocation. In another embodiment, the broadcast information transmission control unit 31 may notify, for example, the allocation number of contention-based preambles or individual preambles as the preamble allocation.

The broadcast information may include a validity period of preamble allocation that the broadcast information transmission control unit 31 notifies to the mobile station 3. As will be described later, if the mobile station 3 does not receive the preamble assignment in the next broadcast information transmission period before the validity period of the preamble assignment elapses, the mobile station 3 sets the number of contention-based preamble assignments to the initial value N. Return to. In the following description, the length of the effective period of the preamble allocation is simply referred to as “effective period length”. In an embodiment, the effective period length is set to a length equal to or longer than the transmission period of the broadcast information and less than twice the transmission period.

The broadcast information transmission control unit 31 reports to the sequence control unit 30 that the preamble allocation to the mobile station 3 has been transmitted by the broadcast information. In the following description, a report that informs the sequence control unit 30 from the broadcast information transmission control unit 31 that the assignment of the preamble to the mobile station 3 has been transmitted is referred to as a “broadcast information transmission report”. The broadcast information transmission report may include information regarding the allocation of the preamble notified to the mobile station 3.

The allocation changing unit 32 changes the allocation of the preamble allocated to each of the contention base preamble and the individual preamble according to the determined allocation number. If the determined allocation number does not decrease below the current allocation number, the allocation changing unit 32 immediately changes the preamble allocation. And the allocation change part 32 starts the 1st timer 33 at the time of reception of an alerting | reporting information transmission report. When the first timer 33 is operating, the allocation changing unit 32 resets the count length of the first timer 33 to the value of the effective period length and restarts. The first timer 33 times out when the effective period length elapses after activation.

If the determined allocation number is smaller than the current allocation number, the allocation changing unit 32 starts the second timer 34 when receiving the broadcast information transmission report. When the second timer 34 is operating, the allocation changing unit 32 resets the count length of the second timer 34 to the value of the effective period length and restarts. The second timer 34 times out when the effective period length elapses after activation.

If the effective period length is less than twice the transmission cycle of the broadcast information, the first timer 33 will not be restarted even if the effective period length elapses when the determined allocation number decreases from the current allocation number. For this reason, the first timer 33 times out. The allocation changing unit 32 changes the allocation of the preamble when the first timer 33 times out when the determined allocation number decreases from the current allocation number.

FIG. 5 is an explanatory diagram of the allocation change timing when the determined allocation number is smaller than the current allocation number. At time t1, the allocation number determination unit 26 determines the allocation number of contention-based preambles. At time t2, the mobile station 3 is notified of the preamble allocation based on the determined allocation number. The allocated number of contention-based preambles of the mobile station 3 that has received this notification is the determined allocated number determined at time t1. Further, the first timer 33 is activated and starts measuring time.

At time t3, the allocation number determination unit 26 determines the allocation number of the contention base preamble. This determined allocation number is smaller than the determined allocation number determined at time t1. For this reason, when the mobile station 3 is notified of the preamble allocation based on the determined allocation number at time t4, the second timer 34 is activated to start timing. As a result, the first timer 33 times out at time t5 when the validity period of the preamble allocation notified last time elapses at time t2, and the allocation changing unit 32 allocates the preamble according to the determined allocation number determined at time t3. Change at time t5.

That is, when the determined allocation number decreases from the current allocation number, the allocation changing unit 32 determines that the preamble allocation period has passed until the validity period of the preamble allocation notified to the mobile station 3 at the previous broadcast information transmission timing. Delay allocation change time. On the other hand, when the mobile station 3 fails to receive the broadcast information transmitted at time t4, the number of preambles that the mobile station 3 uses as the contention base preamble is reset to the lower limit value N. Therefore, even if the mobile station 3 fails to receive the notification for reducing the number of allocations, the mobile station 3 does not use more contention-based preambles than the number currently allocated by the base station 2. For this reason, by delaying the change time as described above, the mobile station 3 that has failed to receive the notification for reducing the number of contention-based preamble assignments uses the preamble assigned to the dedicated preamble as the contention-based preamble. Can be prevented.

When the first timer 33 times out when the determined allocation number is less than the current allocation number, the allocation changing unit 32 sets the remaining count value of the second timer 34 to the count value of the first timer 33, and the first timer 33 33 is operated. Thereby, the time-out scheduled time of the first timer 33 coincides with the end of the valid period of the preamble allocation by the determined allocation number. For this reason, even when the determined allocation number decreases continuously, the first timer 33 can be timed out after the validity period of the previous preamble allocation elapses.

Even if the determined allocation number does not decrease from the current allocation number, the first timer 33 times out if the allocation changing unit 32 does not receive the broadcast information transmission report. In this case, the assignment of the preamble is not notified to the mobile station 3, and the mobile station 3 returns the number of contention-based preamble assignments to the initial value N. The allocation changing unit 32 returns the preamble allocation to the initial state in order to match the number of contention-based preamble allocations with the mobile station 3. That is, the number of contention-based preamble allocations returns to N.

The dedicated preamble instruction unit 35 selects an individual preamble to be used for the contention-free sequence from the preambles assigned to the individual preamble by the allocation changing unit 32 and explicitly instructs the mobile station 3.

The dedicated preamble use determination unit 36 determines whether the preamble allocated to the contention-based preamble after the increase is instructed to the mobile station 3 as the dedicated preamble when the determined allocation number increases from the current allocation number. In the following description, the preamble allocated to the contention base preamble after the increase is referred to as “reserved preamble”.

When the reserved preamble is instructed as an individual preamble, the allocation changing unit 32 receives all the reserved preambles instructed as individual preambles, and after the reserved preamble instructed as the individual preamble has been lost, Change the assignment. In the following description, the state from when the dedicated preamble is instructed to the mobile station 3 until the base station 2 receives the random preamble in the random access procedure may be described as “in use”.

Also, when the determined allocation number increases more than the current allocation number, the dedicated preamble instruction unit 35 selects the dedicated preamble from the M preambles other than the reserved preamble and clearly indicates to the mobile station 3.

<3. Configuration example of mobile station>
<3.1. Hardware configuration>
Next, the configuration of the mobile station 3 will be described. FIG. 6 is a diagram illustrating an example of a hardware configuration of the mobile station 3. The mobile station 3 includes a processor 40, a storage device 41, a baseband processing circuit 42, a radio frequency signal processing circuit 43, a duplexer 44, and an antenna 45. The hardware configuration shown in FIG. 6 is one of the hardware configurations for realizing the mobile station 6 to the last. Any other hardware configuration may be adopted as long as the processing described below is executed in this specification.

The baseband processing circuit 42 encodes and modulates signals transmitted and received between the mobile station 3 and the base station 2, demodulates and decodes, communication protocol processing, and baseband signals regarding control of communication processing by the mobile station 3 Perform the process. The baseband processing circuit 42 may include a processor for signal processing and a memory for storing programs and data necessary for the operation of the processor. The processor may be a DSP or a CPU, for example. The baseband processing circuit 42 may include a logic circuit such as an LSI, ASIC, or FPGA for signal processing.

The processor 40 executes an application program that processes user data. The storage device 41 stores an application program for information processing by the processor 40. Each data and temporary data used during the execution of these programs are also stored in the storage device 41. The radio frequency signal processing circuit 43 performs digital / analog conversion, analog / digital conversion, frequency conversion, signal amplification, and filtering of a radio signal transmitted / received between the mobile station 3 and the base station 2 via the duplexer 44 and the antenna 45. .

<3.2. Functional configuration>
Next, functions realized by the hardware configuration will be described. FIG. 7 is a functional block diagram of an example of the baseband processing circuit 42 of the mobile station 3. The baseband processing circuit 42 includes a control unit 50, a demodulation unit 51, a decoding unit 52, an encoding unit 53, a modulation unit 54, and a protocol processing unit 55. FIG. 7 mainly shows functions related to the following description. The baseband processing circuit 42 may include other components other than the illustrated components.

In one embodiment, signal processing by the components 50 to 55 is performed by a DSP included in the baseband processing circuit 42 executing a control program stored in the memory of the baseband processing circuit 42. In another embodiment, signal processing by the components 50 to 55 may be executed by a logic circuit such as an LSI, ASIC, or FPGA.

The control unit 50 controls communication processing by the mobile station 3. The demodulating unit 51 and the decoding unit 52 perform demodulation processing and decoding processing on the received signal. The encoding unit 53 and the modulation unit 54 perform transmission signal encoding processing and modulation processing. The protocol processing unit 55 executes communication processing for transmitting and receiving data between the core network and the application according to the communication protocol.

The control unit 50 includes a sequence control unit 60, an allocation acquisition unit 61, a preamble selection unit 62, and a timer 63. The sequence control unit 60 performs signal processing for the RACH sequence that is a random access procedure. The allocation acquisition unit 61 acquires the allocation of the preamble according to the determined allocation number determined by the allocation number determination unit 26 of the base station 2 from the broadcast information received from the base station 2.

The preamble selection unit 62 updates the preamble allocation in the mobile station 3 in accordance with the preamble allocation acquired by the allocation acquisition unit 61. The preamble selection unit 62 selects a preamble allocated to the contention base preamble according to the preamble allocation acquired by the allocation acquisition unit 61 during the contention base sequence. The sequence control unit 60 transmits the preamble selected by the preamble selection unit 62 as a contention base preamble when executing the contention base sequence.

The preamble selection unit 62 starts the timer 63 when the preamble allocation is acquired from the broadcast information. When the timer 63 is operating, the preamble selection unit 62 resets the count length of the timer 63 to the valid period length and then restarts. The timer 63 times out when the effective period length elapses after activation. When the timer 63 times out, the preamble selection unit 62 returns the number of assigned preambles to the initial value N until the next preamble assignment is notified. For this reason, when the mobile station 3 does not receive the preamble allocation notification from the base station 2 over the effective period length, the mobile station 3 returns the selection range of the contention base preamble to the N preambles in the initial state.

<4. Explanation of base station operation>
<4.1. Preamble allocation number determination process>
Subsequently, processing performed by the base station 2 will be described. FIG. 8 is an explanatory diagram of an example of preamble allocation number determination processing by the allocation number determination unit 26. In this embodiment, the allocation number determination unit 26 dynamically determines the number of preambles to be allocated to the contention-based preamble according to the usage status of the contention-based preamble by the mobile station 3. Hereinafter, a series of processes described with reference to FIG. 8 may be interpreted as a method including a plurality of procedures. In this case, “operation” may be read as “step”. The same applies to FIGS. 9 and 11 to 15.

In operation AA, the allocation number determination unit 26 detects the contention-based preamble from the signal on the random access channel decoded by the decoding unit 22. The allocation number determination unit 26 records the contention base preamble reception time in a memory provided in the baseband processing circuit 12.

In operation AB, the allocation number determination unit 26 calculates the number of contention-based preambles used (N + n2) used in a predetermined period. The value “n2” is an integer greater than or equal to “0” and an increment based on the initial value N. In an embodiment, the number of contention-based preambles used per unit time may be calculated for periods of different times and lengths, and the average value or maximum value thereof may be used as the number of uses (N + n2).

In operation AC, the allocation number determination unit 26 determines whether the usage number (N + n2) is larger than the initial value N and whether the current contention-based preamble allocation number (N + n1) is different from the usage number (N + n2). . “N1” is an integer greater than or equal to “0” and an increment based on the initial value N. If the condition of operation AC is satisfied (operation AC: Y), the process proceeds to operation AD. If the condition for operation AC is not satisfied (operation AC: N), the process ends.

In operation AD, the allocation number determination unit 26 determines the number of uses (N + n2) as the determined allocation number, and notifies the sequence control unit 30 of the change number (n2) of the determined allocation number (N + n2) based on the initial value N. Thereafter, the process ends.

<4.2. Preamble allocation number change processing>
Next, a preamble allocation number changing process for allocating a preamble according to the determined allocation number (N + n2) will be described. FIG. 9 is an explanatory diagram of an example of the preamble allocation number changing process. In operation BA, the assignment changing unit 32 receives a notification of the change number n2 from the assignment number determining unit 26. In operation BB, the allocation changing unit 32 determines whether or not the determined allocation number (N + n2) is larger than the current contention-based preamble allocation number (N + n1). If the determined allocation number (N + n2) is larger than the current allocation number (N + n1) (operation BB: Y), the process proceeds to operation BC. When the determined allocation number (N + n2) is equal to or smaller than the current allocation number (N + n1) (operation BB: N), the process proceeds to operation BG.

In operation BC, the allocation changing unit 32 determines whether or not a contention-based preamble determined according to the increased determined allocation number (N + n2), that is, a reserved preamble is being used as an individual preamble. If the reserved preamble is being used as an individual preamble (operation BC: Y), the processing proceeds to operation BF. If the reserved preamble is not being used as an individual preamble (operation BC: N), the process proceeds to operation BD.

In operation BD, the allocation changing unit 32 changes the allocation of the preamble so that the number of contention-based preambles allocated in the base station 2 becomes the determined allocation number (N + n2). Thereafter, in operation BE, the allocation changing unit 32 sets the change number (n2) for the initial value of the determined allocation number as the change number (n2) for the initial value of the contention-based preamble allocation number in the mobile station 3, and transmits broadcast information. Notify the control unit 31. Thereafter, the process ends.

In operation BF, the allocation changing unit 32 sets the determined allocation number (N + n2) in the memory provided in the baseband processing circuit 12 in order to change the preamble allocation after the reserved preamble is no longer used as the individual preamble. To remember. In the following description, the determined allocation number (N + n2) stored in the memory in operation BF may be expressed as “reserved number”. Thereafter, the process ends. Note that the processing of the operation BE may be executed before the operations BD and BG.

FIG. 10 is a schematic diagram showing the range of contention-based preambles and reserved preambles that are currently allocated. Since the number of reserved preambles, that is, the number of reservations (N + n2) is larger than the number of currently allocated contention-based preambles (N + n1), the reserved preamble includes the contention-based preamble currently allocated. The reserved preamble also includes (n2-n1) preambles among the preambles currently allocated to the individual preambles.

Refer to FIG. In operation BG, the allocation changing unit 32 is provided with the determined allocation number (N + n2) in the baseband processing circuit 12 in order to change the allocation of the preamble after the first timer 33 that started timing last timed out. Store in memory. In the following description, the determined allocation number (N + n2) stored in the memory in the operation BG may be referred to as “scheduled allocation number”. At this time, the allocation changing unit 32 stores in the memory, for example, using a flag or the like that the stored number of allocations is valid. Thereafter, in operation BE, the allocation changing unit 32 performs broadcast information transmission control with the change number (n2) with respect to the initial value of the determined allocation number as the change number (n2) with respect to the initial value of the contention-based preamble allocation number in the mobile station 3. Notify unit 31. Thereafter, the process ends.

<4.3. Preamble allocation number notification process>
Next, the preamble allocation number notifying process when notifying the mobile station 3 of the contention-based preamble allocation number will be described. FIG. 11 is an explanatory diagram of an example of the preamble allocation number notification process. In operation CA, the broadcast information transmission control unit 31 receives the number of changes (n2) from the assignment change unit 32. In operation CB, the broadcast information transmission control unit 31 determines whether it is the broadcast time of broadcast information. When it is time to transmit the notification information (operation CB: Y), the processing proceeds to operation CC. If it is not time to transmit the broadcast information (operation CB: N), the processing returns to operation CB.

In operation CC, the broadcast information transmission control unit 31 notifies the mobile station 3 of preamble allocation by transmitting the number of changes (n2) as broadcast information. Also, the broadcast information transmission control unit 31 transmits the effective period length as broadcast information. In the operation CD, the broadcast information transmission control unit 31 notifies the allocation change unit 32 of the broadcast information transmission report.

In operation CE, the allocation changing unit 32 receives the broadcast information transmission report from the broadcast information transmission control unit 31. In operation CF, the allocation changing unit 32 determines that the allocation number (N + n2) of the contention-based preamble notified to the mobile station 3 included in the broadcast information transmission report is the estimated allocation number stored in the operation BG shown in FIG. Determine whether they are equal. If the allocation number notified to the mobile station 3 (N + n2) is equal to the scheduled allocation number, the allocation number notified to the mobile station 3 (N + n2) is smaller than the current allocation number (N + n1).

If the allocation number (N + n2) notified to the mobile station 3 is different from the allocation allocation number (operation CF: N), the processing proceeds to operation CG. When the allocation number (N + n2) notified to the mobile station 3 is equal to the allocation allocation number (operation CF: Y), the processing proceeds to operation CH.

In operation CG, the allocation changing unit 32 starts the first timer 33 when receiving the broadcast information transmission report. When the first timer 33 is operating, the allocation changing unit 32 resets the count length of the first timer 33 to the valid period length and then restarts. Thereafter, the process ends. In operation CH, the allocation changing unit 32 starts the second timer 34. When the second timer 34 is operating, the allocation changing unit 32 resets the count length of the second timer 34 to the valid period length and then restarts. Thereafter, the process ends.

<4.4. Timeout processing>
Next, timeout processing when the first timer 33 times out will be described. FIG. 12 is an explanatory diagram of an example of the timeout process. In operation DA, the allocation changing unit 32 determines whether or not the first timer 33 has timed out. When the first timer 33 times out (operation DA: Y), the processing proceeds to operation DB. If the first timer 33 does not time out (operation DA: N), the processing returns to operation DA.

In the operation DB, the allocation changing unit 32 determines whether or not the scheduled allocation number stored in the memory of the baseband processing circuit 12 is valid. If the scheduled allocation number is valid (operation DB: Y), the process proceeds to operation DC. If the scheduled allocation number is not valid (operation DB: N), the processing proceeds to operation DF.

In operation DC, the allocation changing unit 32 changes the allocation of preambles so that the allocation number of contention-based preambles in the base station 2 becomes the scheduled allocation number stored in operation BG shown in FIG. As a result, the allocation number of contention-based preambles changes to a determined allocation number (N + n2) smaller than the allocation number before change (N + n1) stored as the scheduled allocation number.

In operation DD, the allocation changing unit 32 sets the remaining count value of the second timer 34 to the count value of the first timer 33 and operates the first timer 33. Further, the assignment changing unit 32 stops the second timer 34. As a result, the allocation changing unit 32 matches the scheduled time-out period of the first timer 33 with the end of the valid period of preamble allocation based on the determined allocation number (N + n2). In operation DE, the allocation changing unit 32 stores the determined allocation number stored in the memory in an invalid memory. Therefore, the processing of operations DB to DE is performed only once every time the determined allocation number is stored, that is, every time the determined allocation number decreases from the current allocation number. Thereafter, the process ends. Note that any of the operations DC to DE may be executed first.

In operation DF, the allocation changing unit 32 returns the preamble allocation to the initial state. That is, the number of contention-based preamble allocations returns to N. Since this state occurs when the broadcast information transmission report is not received and the first timer 33 is not reset, the preamble assignment is not notified to the mobile station 3. In this case, since the mobile station 3 returns the contention base preamble allocation number to the initial value, the allocation changing unit 32 sets the contention base preamble allocation number of the base station 2 to the initial value in the same manner as the mobile station 3. Return to. In operation DG, the allocation changing unit 32 stops the first timer and ends the process. Note that either of the operations DF and DG may be executed first.

<4.5. Processing when receiving preamble>
Next, processing when the base station 2 receives a preamble from the mobile station 3 will be described. FIG. 13 is an explanatory diagram of an example of processing at the time of preamble reception. In operation EA, the dedicated preamble use determining unit 36 determines whether or not the received preamble is a dedicated preamble. If it is not an individual preamble (operation EA: N), operations EB to EE are skipped, and the process proceeds to operation EF. In the case of an individual preamble (operation EA: Y), the process proceeds to operation EB.

In operation EB, the individual preamble use determination unit 36 determines whether or not there is still a reserved preamble that is being used as an individual preamble. If there is still a reserved preamble that is being used as an individual preamble (operation EB: Y), operations EC to EE are skipped, and the process proceeds to operation EF. If there is no reserved preamble in use as an individual preamble (operation EB: N), the process proceeds to operation EC.

In operation EC, the allocation changing unit 32 changes the allocation of preambles so that the number of contention-based preambles allocated in the base station 2 becomes the number of reservations stored in operation BF shown in FIG. As a result, after there is no reserved preamble in use as an individual preamble, the number of contention-based preamble allocations changes to a determined allocation number (N + n2) that is larger than the allocation number before change (N + n1).

In operation ED, the allocation changing unit 32 deletes the reservation number storage. In operation EE, the allocation changing unit 32 sets the change number (n2) with respect to the updated initial value of the allocation number as the change number (n2) with respect to the initial value of the contention base preamble allocation number in the mobile station 3, and transmits broadcast information. Notify the control unit 31. The change number (n2) is notified to the mobile station 3 in the operation CC shown in FIG. Note that any of the operations EC to EE may be executed first.

In operation EF, the sequence control unit 30 executes a response process for the received preamble. Thereafter, the process ends. Note that the processing of the operation EF may be executed before any processing of the operations EA to EE.

<4.6. Processing when individual preamble is instructed>
Next, a process when the base station 2 instructs the mobile station 3 for an individual preamble for the contention-free sequence will be described. FIG. 14 is an explanatory diagram of an example of processing when an individual preamble is instructed. In operation FA, the individual preamble instruction unit 35 determines a range that can be allocated to the individual preamble from a total number M of preambles that are given in advance. At this time, the individual preamble instruction unit 35 calculates the value (MN−n1) obtained by subtracting the current number of contention-based preamble allocations from the total number M and the number of reservations stored in the operation BF shown in FIG. Compare the subtracted values (M-number of reservations). The individual preamble instruction unit 35 determines the smaller of these as the number of allocations that can be allocated to the individual preamble.

That is, the individual preamble instruction unit 35 sets the reserved preamble as an individual preamble while the number of reservations is stored, that is, until the number of contention-based preamble allocations is changed to a reservation number larger than the current value (N−n1). Do not give new instructions.

In operation FB, the dedicated preamble instruction unit 35 selects a preamble to be used for the dedicated preamble from a range that can be allocated to the dedicated preamble. In operation FC, the individual preamble instruction unit 35 instructs the mobile station 3 to use the selected preamble as an individual preamble.
<5. Operation explanation of mobile station>
Next, processing performed by the mobile station 3 will be described. FIG. 15 is an explanatory diagram of an example of processing of the mobile station apparatus. In operation GA, the allocation acquisition unit 61 attempts to allocate a preamble and acquire a valid period from broadcast information received from the base station 2. When the preamble allocation and the valid period are acquired (operation GA: Y), the processing proceeds to operation GB. If the preamble allocation and validity period are not acquired (operation GA: N), the process proceeds to operation GC.

In operation GB, the preamble selection unit 62 updates the preamble allocation in the mobile station 3 in accordance with the preamble allocation acquired by the allocation acquisition unit 61. The preamble selection unit 62 starts the timer 63. When the timer 63 is operating, the preamble selection unit 62 resets the count value of the timer 63 to a state immediately after the start of timing and restarts. Thereafter, the process proceeds to operation GC.

In operation GC, the preamble selection unit 62 determines whether or not the timer 63 has timed out. When the timer 63 times out (operation GC: Y), the processing proceeds to operation GD. If the timer 63 does not time out (operation GC: N), the processing returns to operation GA.

In operation GD, the preamble selection unit 62 returns the number of preambles allocated to the contention base preamble to the initial value N. In addition, the preamble selection unit 62 stops the timer 63. Thereafter, the process returns to operation GA.

<6. Effect of Example>
According to the present embodiment, the number of contention base preambles can be dynamically increased or decreased. For this reason, it becomes possible to increase the number of contention-based preambles when the contention-based sequence is increased, thereby reducing the delay in completion of the random access procedure and the deterioration in service quality due to traffic reduction due to repetition of the random access procedure. .

According to the present embodiment, when the mobile station 3 fails to receive the notification for reducing the allocation of the contention base preamble, the contention base preamble is used until the contention base preamble number used by the mobile station 3 is reduced to the initial value. Delay the reduction of preamble allocation. For this reason, the inconvenience that the mobile station 3 uses the preamble to be allocated to the individual preamble in a state where the allocation of the contention base preamble is reduced is avoided.

According to this embodiment, when increasing the contention-based preamble allocation, if the incremental preamble is in use as an individual preamble, the increase in allocation is delayed until the incremental preamble is no longer in use as an individual preamble. be able to. In addition, while the increase in allocation is delayed, it is possible to prevent the incremental preamble from indicating as an individual preamble.

<7. About other embodiments>
<7.1 How to determine the number of allocations>
The allocation number determination unit 26 may determine the allocation number allocated to the contention-based preamble and the individual preamble from the statistics of the reception frequency of the previous preamble. For example, the number of allocations may be determined based on a predicted value of the contention-based preamble usage amount according to the day of the week or the time zone. Further, the average usage amount per unit time may be determined based on the reception frequency based on such past statistics, and the number of usages (N + n2) may be used. Thus, by making predictions based on past statistical values, it is possible to change the above-described preamble allocation even in a processor with low processing capability for which it is difficult to determine the number of allocations in real time based on measured values.

<7.2 Timer period>
The valid period length, that is, the count lengths of the first timer 33, the second timer 34, and the timer 63 may be equal to a predetermined broadcast information transmission cycle. In this case, a counter that determines the transmission cycle of the notification information may be used also as the first timer 33, the second timer 34, and the timer 63. Further, it is not necessary to transmit the effective period length from the base station 2 to the mobile station 3. If the effective period length is fixed, transmission of the effective period length may be omitted by storing it in the mobile station 3 in advance. Further, the effective period length may be shorter than the transmission cycle of the broadcast information.

All examples and conditional terms contained herein are intended for educational purposes only to assist the reader in understanding the present invention and the concepts provided by the inventor for the advancement of technology. And should not be construed as being limited to the examples and conditions set forth above, as well as the configuration of the examples herein with respect to showing the superiority and inferiority of the present invention. Is. While embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions and modifications can be made thereto without departing from the spirit and scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Communication system 2 Base station apparatus 3 Mobile station apparatus 26 Allocation number determination part 31 Broadcast information transmission control part 32 Allocation change part

Claims

An allocation number determination process for dynamically determining an allocation number allocated to a contention-based preamble among a plurality of predetermined preambles;
An allocation notification process for notifying a mobile station apparatus of a preamble allocation according to the allocation number determined in the allocation number determination process;
An assignment change process for changing an assignment of a preamble assigned to a contention-based preamble according to the assignment number determined in the assignment number determination process;
The base station apparatus provided with the control part which performs.
In the allocation of the preamble notified in the allocation notification process, a mobile station device that does not receive a notification of subsequent allocation is set to an effective period for reducing the allocation of the preamble allocated to the contention-based preamble,
In the allocation change process, the control unit sets the current preamble allocation when the allocation number determined in the allocation number determination process is smaller than the current allocation number allocated to the contention-based preamble. The base station apparatus according to claim 1, wherein the allocation change process is executed after the expiration of an effective period.
In the allocation change process, when the preamble allocated according to the allocation number determined in the allocation number determination process is instructed to the mobile station apparatus as an individual preamble, the control unit transmits the preamble to the mobile station apparatus. The base station apparatus according to claim 1, wherein the allocation change process is executed after receiving from the base station.
The control unit, when instructing an individual preamble to the mobile station apparatus, executes an individual preamble from other than the preamble allocated according to the allocation number determined in the allocation number determination process until the allocation change process is executed. The base station apparatus according to claim 3, wherein the selection process is executed.
The base station apparatus according to any one of claims 1 to 4, wherein, in the allocation number determination process, the control unit determines an allocation number allocated to the contention base preamble in accordance with a usage state of the contention base preamble.
A process of acquiring a preamble allocation dynamically allocated to a contention-based preamble from a plurality of predetermined preambles from a received signal from a base station device;
A process of selecting a preamble to be transmitted in a contention-based random access procedure according to the preamble allocation;
A mobile station apparatus provided with the control part which performs.
The mobile station apparatus according to claim 6, wherein the control unit executes a process of returning the preamble allocation to a predetermined setting value when the preamble allocation is not acquired for a predetermined period.
In the control unit provided in the base station device,
An allocation number determination process for dynamically determining an allocation number allocated to a contention-based preamble among a plurality of predetermined preambles;
An allocation notification process for notifying a mobile station apparatus of a preamble allocation according to the allocation number determined in the allocation number determination process;
An assignment change process for changing an assignment of a preamble assigned to a contention-based preamble according to the assignment number determined in the assignment number determination process;
A random access method characterized in that
In the control unit provided in the mobile station device,
A process of acquiring a preamble allocation dynamically allocated to a contention-based preamble from a plurality of predetermined preambles from a received signal from a base station device;
A process of selecting a preamble to be transmitted in a contention-based random access procedure according to the preamble allocation;
A random access method characterized in that