CN101730255A

CN101730255A - Method and device for selecting PRACH

Info

Publication number: CN101730255A
Application number: CN200810170759A
Authority: CN
Inventors: 谢明江; 黄曲芳
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2008-10-24
Filing date: 2008-10-24
Publication date: 2010-06-09
Anticipated expiration: 2028-10-24
Also published as: CN101730255B

Abstract

The invention is a method and a device for selecting a PRACH. The method comprises the following steps: determining a PRACH selection window of user equipment during a random access process; and selecting the physical random access channel (PRACH) for the random access in the PRACH selection window. The embodiment by the invention is implemented according to selected random access time delay and the utilization rate of the PRACH during the random access process of the user equipment so as to achieve a balance between small random access time delay and balanced utilization rate of PRACH.

Description

Method and device for selecting PRACH

Technical Field

The invention relates to the technical field of communication, in particular to a technology for selecting a PRACH.

Background

An LTE (LoNg TerM EvolutioN ) mobile communication system architecture in 3GPP (third generation partnership project) has the advantages of higher spectrum utilization rate and transmission speed, lower transmission delay, and the like.

Currently, in an LTE architecture, a corresponding random access mode includes a contention mode and a non-contention mode, where:

the contention mode random access uses a non-dedicated preamble (preamble) included in a PRACH (physical random access channel), and the corresponding non-dedicated preamble may be reported to a UE (user equipment) in a cell broadcast, so that the UE randomly selects one preamble for access when initiating access. Specifically, in contention mode, the UE may select one access among all PRACH.

The random access in the non-contention mode uses a dedicated preamble be, and the eNB (evolved base station) uses a dedicated signaling to notify the UE of the dedicated preamble be included in the corresponding PRACH, so as to randomly select one preamble be accessed when initiating access. Specifically, in the non-contention mode, the eNB may limit a plurality of PRACH that the UE may use while notifying the UE of the dedicated preamble ble, so that the UE may select one PRACH from the plurality of PRACH for access.

In both the contention mode and the non-contention mode, the UE needs to perform a selection operation of a corresponding time-frequency resource (i.e., a PRACH used during access) during a random access to the network.

Currently, in the process of selecting PRACH by UE, frequency domain selection is performed first, and then time domain selection is performed. And the UE does not consider the PRACH configuration on each frequency band when performing frequency domain selection.

However, in the existing scheme, since the PRACH configuration on each frequency band is not considered when the UE selects the frequency domain, if the UE selects a frequency band with a lower PRACH density, the time delay for the UE to send Msg1 may be increased, and further the time delay for random access may be increased;

for example, as shown in fig. 1, if the UE prepares to send the random access message Msg1 (message 1) at subframe 5 and selects the frequency band f1, the UE needs to wait until subframe 4 of the next radio frame to send Msg1, thereby greatly increasing the delay of sending the random access message Msg1 by the UE, and further increasing the random access delay of the UE.

Disclosure of Invention

The embodiment of the invention provides a method and a device for selecting a PRACH (physical random access channel), so that the time delay of UE random access is reduced on the basis of considering the utilization rate of the PRACH in the process that a user selects a random access time-frequency resource.

A method of selecting a PRACH, comprising:

setting a PRACH selection window;

selecting a physical random access channel, PRACH, for random access within the PRACH selection window.

An apparatus to select a PRACH, comprising:

a window setting unit, configured to set a PRACH selection window;

a selecting unit, configured to select a PRACH used for random access within the PRACH selection window.

It can be seen from the technical solutions provided by the embodiments of the present invention that the selection of the time-frequency resource for random access is performed within the determined PRACH selection window, so that the selected random access delay and the PRACH utilization rate can be considered in the random access process of the user equipment, and further, the balance between the smaller random access delay and the balanced PRACH utilization rate can be considered as much as possible.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive labor.

Fig. 1 is a schematic diagram of a PRACH configuration structure in the prior art;

FIG. 2 is a diagram illustrating values of R (x) when a window start point is located in different subframes according to an embodiment of the present invention;

fig. 3 is a diagram illustrating PRACH configuration and selection according to an embodiment of the present invention;

FIG. 4 is a first diagram illustrating values of P (x) when the window start point is located in different subframes according to an embodiment of the present invention;

fig. 5 is a first schematic diagram of delay values when window start points are located in different subframes in the embodiment of the present invention;

FIG. 6 is a second diagram illustrating values of P (x) when the window start point is located in different subframes according to an embodiment of the present invention;

fig. 7 is a schematic diagram of a second time delay value when the window start point is located in different subframes in the embodiment of the present invention;

FIG. 8 is a diagram illustrating a location of a window starting point according to an embodiment of the present invention;

fig. 9A is a first schematic diagram illustrating PRACH selection according to a second implementation of the embodiment of the present invention;

fig. 9B is a diagram illustrating PRACH selection according to a second implementation of the present invention;

fig. 9C is a diagram illustrating PRACH selection according to a third implementation of the embodiment of the present invention;

FIG. 10A is a first schematic diagram of an apparatus according to an embodiment of the present invention;

fig. 10B is a schematic structural diagram of a device according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the scheme, a PRACH selection window of a user equipment UE is first determined, which is used to determine a range in which the user equipment selects a PRACH during a random access process.

Thereafter, the user equipment determines an initial subframe position from which the user equipment can transmit a random access preamble signal (i.e., message 1).

And a Physical Random Access Channel (PRACH) is selected according to the position of the initial subframe, so that the utilization rate of the PRACH is improved.

The position of the initial subframe is taken as the starting point of a PRACH selection window (hereinafter referred to as a window), the size of the window is M subframes, and M is determined according to the configuration of the PRACH. And determining the selection probability of each PRACH according to the time delay of each PRACH in the window, and selecting the corresponding PRACH as the time frequency resource of the random access of the user equipment according to the selection probability corresponding to each PRACH. The process of correspondingly determining the selection probability of each PRACH within the window may include:

(1) determining a selection coefficient r (x) for the x-th PRACH within a window: numbering the subframes in the window in descending order from the starting point of the window, wherein the numbering is from M to 1; r (x) is the number of the subframe where the xth PRACH is located or k times of the number, and k is greater than 1, if there are multiple PRACH in a subframe location (TDD system), the selection coefficients r (x) of the PRACH are the same;

(2) calculating the selection probability of the x PRACH according to the selection coefficient R (x) of the x PRACH as follows:

wherein N is the number of PRACH included in the window, and r (i) represents a selection coefficient of the ith PRACH.

Optionally, in the embodiment of the present invention, a corresponding relationship between a subframe position in a PRACH selection window and a PRACH may also be predetermined, and when an initial subframe is located at a different subframe position in the window, the PRACH corresponding to the subframe is selected.

The starting point and size of the window may be set as follows:

(1) selecting a PRACH continuous block in M M consecutive subframes, where the PRACH continuous block is a continuous block that includes the most PRACH in the MM subframes, and the PRACH continuous block is a PRACH that is continuous in a time domain and includes PRACH belonging to different frequency domains at the same time domain position.

(2) If the continuous blocks containing the most PRACHs have 2 or more than 2 continuous blocks, selecting the continuous blocks with larger distance (difference of subframe number) from the next continuous block;

(3) determining the first subframe after the PRACH continuous block as a window starting point, wherein the window size is MM subframes.

The process of determining the corresponding relationship between the subframe position in the window and the PRACH may specifically include:

(1) and numbering the NN PRACHs in the window in sequence in the order of frequency domain first and time domain later, namely numbering from 0 to (N-1).

All subframes are numbered sequentially within the window, numbering from 0 to (M-1).

Determining the corresponding relation as follows:

if the PRACH corresponding to subframe x is y, then y ═ Floor (x/(M/N)), 0 ≦ x < M.

Or,

(2) when N PRACH exist in the window, the window is divided into N groups of subframes from the starting point of the window, each group comprises M/N subframes, namely the N groups of subframes correspond to N PRACH in sequence, and each PRACH corresponds to M/N subframes.

If two PRACH resources can be selected correspondingly for a subframe, the method further includes:

the subframe corresponds to one PRACH which is earlier in time, and if the two PRACHs are the same in time, 1 PRACH is selected as the corresponding PRACH of the subframe according to the same selection probability;

or,

selecting the PRACH which is earlier in sequence as the corresponding PRACH of the subframe;

or,

and if the two PRACHs belong to different frequency bands, selecting the PRACH of the frequency band with good air interface quality as the corresponding PRACH of the subframe according to the current air interface quality of the different frequency bands.

Or,

the user equipment takes t1/(t1+ t2) as the selection probability of a first PRACH in the two PRACHs, and takes t2/(t1+ t2) as the selection probability of a second PRACH in the two PRACHs, wherein corresponding t1 is the duration occupied by the first PRACH in the subframe length, and t2 is the duration occupied by the second PRACH in the subframe length.

Therefore, the implementation scheme for selecting the PRACH by the UE provided by the embodiment of the present invention not only reduces the time delay for the UE to perform random access, but also improves the utilization rate of the PRACH.

In the specific application process of the embodiment of the present invention, the following two implementation schemes may be adopted, but are not limited to, and will be separately described below.

First, a detailed description will be given below of a specific implementation procedure of the implementation scheme for selecting a PRACH by a first UE according to an embodiment of the present invention.

In this implementation scheme for selecting a PRACH by the first UE, a corresponding implementation procedure includes:

the method comprises the steps that (I) a UE calculates a PRACH selection window, wherein the window specifically takes a subframe which is ready for sending Msg1 by the UE as a starting point of the window, the size of the window can be 10 subframes, namely 10ms, the 10ms PRACH window is not possibly overlapped with a radio frame, for example, the starting point of the 10s PRACH window is in a radio frame # N, and the end point of the 10s PRACH window is in a radio frame # N +1, wherein whether PRACH exists in the subframe or not is not required to be considered by the starting point of the corresponding;

(II) the UE selects one PRACH from all PRACHs contained in the window as the PRACH used by the sending Msg 1;

the specific selection mode may include: the UE may calculate a corresponding selection probability for each PRACH within the window, and select the PRACH according to the corresponding probability, where the original probability calculation is: under the condition of balanced utilization rate of the PRACH, the probability of selecting the PRACH with smaller time delay is larger;

for example, the corresponding probability may be determined in the following manner:

firstly, numbering each subframe in a descending order on a time domain from a starting subframe of a window; taking the number of the subframe where the PRACH is located as a selection coefficient R (x) of the PRACH, wherein x is PRACH iNdex (PRACH iNdex); for PRACH, assuming that numbering may be started from integer 10, when the window start is located in different subframes, r (x) of each PRACH may be as shown in fig. 2.

Next, after determining r (x) of each PRACH, if N PRACH exist in a window, a calculation method of a selection probability of each PRACH may be represented as:

wherein, p (x) refers to the probability of selection corresponding to the xth PRACH.

Alternatively, another method may be used to select the PRACH, and the PRACH with the smallest time delay may be selected for random access under the condition of balanced PRACH utilization.

The implementation of selecting PRACH by the first UE will be further described below with reference to specific application embodiments.

Example one

In this embodiment one, the process of selecting a PRACH by a corresponding UE may include:

(1) (ii) allowing C ═ R (1) + R (2) +. + R (n);

(2) when the UE needs to select PRACH, the UE may randomly select an integer from 1 to C, assuming that the integer selected by the UE is M:

if R (1) + R (2) +. + R (x-1) < M < ═ R (1) + R (2) +. + R (x), the UE selects PRACH x as the PRACH to be applied at random access, specifically:

if M < ═ R (1), the UE selects PRACH 1 as the PRACH applied in random access;

if R (1) < M ≦ R (1) + R (2), the UE selects PRACH 2 as the PRACH applied at the time of random access;

analogize in turn.

Specifically, as shown in fig. 3 as an example, assuming that subframes are numbered from integer 10, and subframe 0 is a window starting point, r (x) of each PRACH indicates that, as shown in fig. 3, the corresponding selection process includes:

(1) calculating C ═ R (1) + R (2) +. + R (6) ═ 32;

(2) when the UE needs to select PRACH, the UE may randomly select an integer between 1 and 32, still assuming that the integer is M:

if M < ═ R (1), i.e. M < ═ 8, the UE selects PRACH 1 as the PRACH applied at the time of random access;

if R (1) < M ≦ R (1) + R (2), i.e. 8 < M ≦ 15, the UE selects PRACH 2 as the PRACH to apply at random access;

if R (1) + R (2) < M < ═ R (1) + R (2) + R (3), i.e. 15 < M < 21, the UE selects PRACH 3 as the PRACH to apply at random access;

r (1) + R (2) + R (3) < M ≦ R (1) + R (2) + R (3) + R (4), i.e. 21 < M ≦ 24, the UE selecting PRACH 4 as the PRACH to apply at random access;

r (1) + R (2) + R (3) + R (4) < M ≦ R (1) + R (2) + R (3) + R (4) + R (5), i.e. 24 < M ≦ 26, the UE selecting PRACH 5 as the PRACH to apply at random access;

r (1) + R (2) + R (3) + R (4) + R (5) < M < ═ R (1) + R (2) + R (3) + R (4) + R (5) + R (6), that is, 26 < M < 32, the UE selects PRACH 6 as the PRACH to be applied at random access.

By the implementation scheme, the UE can be ensured to take two factors into account of the utilization rate and time of the PRACH in the process of selecting the PRACH.

As can be seen from fig. 4 and 5, in the above implementation, the probability of each PRACH being selected is substantially the same, the variation range of the corresponding delay is small, and the average delay is also small.

Specifically, in fig. 4, when the starting point of the window is located in different subframes in fig. 3, the probability that each PRACH is selected is given, that is, the selection probability p (x) of each PRACH is given, and each selection probability is different. In fig. 4, the last row of the table p (x) is the average probability of each PRACH being selected (i.e. the average selection probability), and the average selection probabilities of the respective PRACH are substantially the same, so it can be seen that the utilization rate of each PRACH is already very close.

In fig. 5, the case of the transmission delay D (x) of Msg1 when each PRACH is selected, in case the starting point of the window is located in a different subframe, and the case of the average transmission delay D of Msg1, in case the starting point of the window is located in a different subframe; the integer number in fig. 5 indicates the number of the subframe where the corresponding PRACH is located when the starting point of the window is located in different subframes; the last row of the column D in fig. 5 represents the average transmission delay of Msg1, and it can be seen that when the start point of the window is at different subframe positions, the variation range of the selected delay of each PRACH is small, and at the same time, the overall average delay is also small.

Example two

In the second embodiment, the square of the number of each subframe is specifically used as the corresponding r (x), and the calculation of the C value and the selection of the PRACH are performed according to the r (x).

Still taking fig. 3 as an example, and taking the square of the number of each subframe in the first embodiment as r (x), when the starting point of the window is located in a different subframe, the corresponding probability p (x) is as shown in fig. 6, and the average selection probability of each PRACH is still substantially the same, so it can be seen that the utilization rate of each PRACH is still very close, but compared with the first embodiment, the fairness of the PRACH usage is slightly worse, because the difference between r (x) of different PRACH is increased, and thus the probability of the UE selecting the PRACH with small delay is also increased.

Also, in this calculation mode, the Msg1 sending delay D (x) when each PRACH is selected when the window start point is in different subframes, and the Msg1 average sending delay D when the window start point is in different subframes can be represented as shown in fig. 7, and it can be seen that when r (x) is the square of each subframe number, the Msg1 average sending delay is smaller.

In short, the selection operation of the PRACH in the UE random access procedure can also be better achieved by the second embodiment.

The embodiment of the invention also provides another implementation scheme for selecting the PRACH by the UE, and the implementation scheme for selecting the PRACH by the second UE is described below.

In the implementation scheme of selecting the PRACH at the second UE, a corresponding implementation process includes:

the UE determines a PRACH window comprising 10 subframes, namely 10ms according to the configuration condition of the PRACH, wherein the 10ms PRACH window may not coincide with a radio frame, for example, the starting point of the 10ms PRACH window is in a radio frame # N, and the end point is in a radio frame # N + 1;

the determining the 10ms PRACH window procedure may specifically include:

(1) defining a PRACH continuous block as a PRACH continuous in a time domain, and including PRACHs belonging to different frequency domains at the same time domain position, namely including one or more PRACHs;

(2) selecting a PRACH continuous block in 2 continuous wireless frames (20ms), wherein the PRACH continuous block can specifically be the PRACH continuous block containing the most PRACH in the two wireless frames; if there are 2 or more than 2 consecutive PRACH blocks containing the most PRACH in the 2 radio frames, a consecutive PRACH block having a larger distance to the next consecutive block (the number of subframes different from the next consecutive block) may be selected.

(3) Determining a first subframe after the PRACH continuous block as a window starting point;

referring to fig. 8, corresponding window start points determined in different PRACH distribution cases may have a corresponding window length of, but not limited to, 10 ms.

(II) determining the corresponding relation between the subframe position in the window and the PRACH; and when the initial subframe is positioned at different subframe positions in the window, selecting the PRACH corresponding to the subframe.

After a window of 10ms for a certain PRACH configuration is determined, each subframe in the window is explicitly assigned one PRACH or two PRACH's for use, where the two PRACH's are the case where the number of PRACH's cannot be divided by 10, for example, when the number N of PRACH's is 3, 2 subframes need to be considered.

Assuming that the number of PRACH included in a window is N, specifically, subframes in the window may be divided into N groups from a starting point of the window, and the N groups of subframes sequentially correspond to the N PRACH.

By the allocation mode, the UE can also take the time delay control and fairness into consideration in the process of selecting the PRACH, thereby providing a better implementation scheme for selecting the random access time-frequency resource of the user equipment.

The implementation of selecting PRACH by the second UE will be further described below with reference to specific application embodiments.

EXAMPLE III

In the third embodiment, as shown in fig. 9A, the corresponding PRACH structure includes two immediately adjacent PRACH #1 and PRACH # 2; based on fig. 9A, the corresponding PRACH selection procedure may include:

firstly, the window is the first subframe after the PRACH continuous block because the determined window comprises the PRACH continuous block;

secondly, calculating the number of subframes corresponding to each PRACH as follows: 10/2, the first subframe in the length of 5ms in the window corresponds to PRACH # 1; the subframes within the second 5ms all correspond to PRACH # 2.

Finally, after the distribution operation is completed, the PRACH selection operation in the random access process can be carried out according to the subframe position of the initial subframe in the window;

still referring to fig. 9A, assuming that A, B, C and D are positions of 4 initial subframes, according to the above configuration, PRACH #1 needs to be selected to initiate RA at A, B subframe position, and PRACH #2 needs to be selected to initiate RA at C, D subframe position accordingly.

For a subframe in which two PRACH may be selected, if the two PRACH belong to different frequency bands, the UE may select, according to the current quality of an air interface of a different frequency band, the PRACH of a frequency band with good quality as the PRACH of the subframe, and the corresponding characteristics of good quality of the air interface may include, but are not limited to: the band has a small path loss, or RSRP (reference signal strength)/RSRQ (reference signal quality) is high, and so on.

It can be seen that, by implementing the third embodiment, balance between the PRACH utilization and the random access delay can be achieved as well.

Example four

In the fourth embodiment, as shown in fig. 9B, a corresponding PRACH structure includes 3 immediately adjacent PRACH #1, PRACH #2, and PRACH # 3; based on fig. 9B, the corresponding PRACH selection procedure may include:

first, since the determined window has only one PRACH contiguous block, the window is the first subframe after the PRACH contiguous block.

Secondly, calculating the number of subframes corresponding to each PRACH: 10/N-10/3 ═ {3+ (1/3) }, for convenience of description, (1/3) may be replaced with 3.33 simplification; therefore, the subframes within the first 3.33ms length in the window all correspond to PRACH # 1; the second sub-frame within 3.33ms corresponds to PRACH # 2; the third 3.33m s subframes each correspond to PRACH # 3.

referring to fig. 9B, assume that there are 4 initial subframe positions, which are: A. b, C and D, according to the above configuration, when RA is initiated at point A, PRACH #1 is selected as the access point of RA, when RA is initiated at point B, there is a chance (selection probability) of 1/3 to select PRACH #1 as the access point of RA, there is a chance (selection probability) of 2/3 to select PRACH #2 as the access point of RA, when RA is initiated at point C, there is a chance (selection probability) of 2/3 to select PRACH #2 as the access point of RA, there is a chance (selection probability) of 1/3 to select PRACH #3 as the access point of RA, and when RA is initiated at point D, PRACH #3 is selected as the access point of RA.

That is, when a subframe in a window correspondingly uses two PRACH, and the UE selects to send a message for random access in the subframe, the UE may use t1/(t1+ t2) as a selection probability of a first PRACH in the two PRACH, and use t2/(t1+ t2) as a selection probability of a second PRACH in the two PRACH, where t1 is a duration occupied by the first PRACH allocation in the subframe length, and t2 is a duration occupied by the second PRACH allocation in the subframe length.

Referring to fig. 9, at point B, a specific procedure for selecting PRACH may be: the UE can select a random number (0-1), and when the random number is within 0-1/3, the PRACH #1 is selected as the access point of the RA, and when the random number belongs to the range of 1/3-1, the PRACH #2 is selected as the access point of the RA. Similarly, point C may be treated similarly.

By means of the fourth embodiment, parameters in two aspects of the utilization rate of the PRACH and the random access time delay can be well balanced in the process of selecting the PRACH for the random access by the UE, so that an implementation scheme for preferably selecting the time-frequency resource for the random access is obtained.

It should be noted that, in the fourth embodiment, for a subframe that may correspond to two PRACH in a window, it may specifically correspond to one PRACH that is earlier in time; if two PRACH's are identical in time (i.e. the two PRACH's belong to different frequency bands of a subframe), they are still allocated according to the two PRACH's, for example, the subframe may be made to correspond between the two PRACH's according to a certain selection probability.

Alternatively, for a subframe that may correspond to two PRACH's, all PRACH's whose number order is earlier may be selected as the corresponding PRACH. At this time, the corresponding relationship between the subframe position in the window and the PRACH is determined as follows:

(1) if N PRACH exist in the window containing M sub-frames, the PRACH is numbered in sequence from the frequency domain to the time domain, namely the PRACH number is from 0 to (N-1).

And sequentially numbering all the subframes in the window, wherein the subframe numbers are from 0 to (M-1).

Determining the corresponding relation as follows:

EXAMPLE five

The configuration of the PRACH and the configuration of the PRACH selection window in this embodiment are the same as those in the fourth embodiment. The PRACH number and subframe number within the window are shown in fig. 9C.

Referring to fig. 9C, assume that there are 4 initial subframe positions, which are: A. b, C and D, according to the above configuration, PRACH #0 is selected as the access point for RA when RA is initiated at point A, PRACH #1 is selected as the access point for RA when RA is initiated at point B, and PRACH #2 is selected as the access point for RA when RA is initiated at points C and D.

Furthermore, in the third to fifth embodiments, the determination of the window start point may also be selected in other manners:

(1) the PRACH that is farthest from the next PRACH (by the number of subframes) is determined in 2 consecutive radio frames (20 ms).

(2) Determining a first subframe after the PRACH as a window starting point;

or:

(1) the half frame (5ms, the first half frame or the second half frame) containing the most PRACH is determined in one radio frame (10 ms).

(2) Determining a first subframe after the last PRACH in the half frame as a window starting point;

it will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.

An embodiment of the present invention further provides a device for selecting a PRACH, and a specific implementation structure of the device is shown in fig. 10A and fig. B, where the device may include:

a window setting unit 101 configured to set a PRACH selection window;

a selecting unit 102, configured to select a PRACH used for random access within the PRACH selection window set by the window setting unit 101.

The apparatus for selecting a PRACH provided in the embodiments of the present invention may specifically be implemented by the following two schemes, and specifically may be:

referring to fig. 10A, in a first implementation, the apparatus may further include:

a position determining unit 103, configured to determine an initial subframe position of the user equipment;

the window setting unit 101 is specifically configured to set the PRACH selection window using the initial subframe position determined by the position determining unit 103 as a starting point, where the PRACH selection window includes M subframes.

In the first implementation scheme, the corresponding selecting unit 102 is specifically configured to determine a selection coefficient r (x) of an x-th PRACH in the PRACH selection window, where r (x) is a number or a k-th power of the number of a subframe where the x-th PRACH is located, where k is greater than 1, and the number is obtained from a starting point of the window and numbered in a descending order;

calculating the selection probability of the x PRACH according to the selection coefficient R (x) of the x PRACH as follows:

and further configured to select a corresponding PRACH according to a selection probability corresponding to each PRACH, where N is a number of PRACH included in the PRACH selection window, and r (i) represents a selection coefficient of an ith PRACH.

Referring to fig. 10B, in a second implementation, a corresponding window setting unit 101 is specifically configured to select a preferred PRACH continuous block in M consecutive subframes, where the preferred PRACH continuous block is a continuous block that includes the most PRACH in the M subframes, and the preferred PRACH continuous block is a PRACH that is continuous in a time domain and includes PRACH belonging to different frequency domains at the same time domain position; or, if there are a plurality of PRACH consecutive blocks including the most PRACH, selecting a PRACH consecutive block having a larger number of subframes than a subsequent PRACH consecutive block as a preferred PRACH consecutive block, and setting the PRACH selection window with a first subframe after the preferred PRACH consecutive block as a starting point, where the window includes M subframes.

Optionally, the apparatus provided in this second implementation scheme may further include a numbering unit 104, configured to number, in sequence, N PRACH numbers included in the PRACH selection window in an order from a frequency domain to a time domain, and further number, in sequence, all subframes in the PRACH selection window from small to large.

Optionally, the apparatus provided in the second implementation may further include a correspondence determining unit 105, configured to determine a correspondence between a subframe location and a PRACH according to the first method; the first method may specifically be: the x-th subframe corresponds to the y-th PRACH, where y is Floor (x/(M/N)), and 0 <, x < M.

The corresponding correspondence determining unit 105 may be further configured to select, for each PRACH, a corresponding M/N subframes, and set an average value of time delays between each subframe and the PRACH corresponding thereto to be the minimum. The method specifically comprises the following steps:

when one subframe corresponds to two PRACHs, selecting one PRACH which is earlier in time corresponding to the subframe;

or,

if the two PRACH are identical in time, one PRACH is arbitrarily selected as the corresponding PRACH of the subframe;

or,

and if the two PRACHs belong to different frequency bands, selecting the PRACH of the frequency band with good air interface quality as the corresponding PRACH of the subframe.

Or,

the user equipment takes t1/(t1+ t2) as the selection probability of a first PRACH in the two PRACHs, takes t2/(t1+ t2) as the selection probability of a second PRACH in the two PRACHs, and selects a PRACH with a high probability as a PRACH corresponding to the subframe, wherein t1 is the duration occupied by the first PRACH in the subframe length in a distribution manner, and t2 is the duration occupied by the second PRACH in the subframe length in a distribution manner.

The embodiment of the invention also provides user equipment which can comprise the PRACH selecting device.

In summary, the implementation of the embodiments of the present invention can make each PRACH effectively utilized, and can ensure a smaller random access delay as much as possible, so that each PRACH resource can be reasonably applied in the UE random access process.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method of selecting a PRACH, comprising:

setting a PRACH selection window;

2. The method of claim 1, wherein the setting the PRACH selection window specifically comprises:

determining an initial subframe position of user equipment, and sending a random access preamble signal by the user equipment selecting a subframe behind the initial subframe position;

and setting the PRACH selection window by taking the initial subframe position as a starting point.

3. The method of claim 2, wherein the selecting the PRACH for random access within the PRACH selection window comprises:

and determining the selection probability corresponding to each PRACH according to the time delay of each PRACH in the PRACH selection window, and selecting the corresponding PRACH according to the selection probability corresponding to each PRACH.

4. The method of claim 3, wherein the step of determining the selection probability for each PRACH within the window comprises:

determining a selection coefficient R (x) of the x-th PRACH in the PRACH selection window, wherein R (x) is the number of the subframe where the x-th PRACH is located in the time domain or the k-th power of the number, and k is greater than 1, wherein the number of the subframe is obtained by numbering in a descending order from the starting point of the window;

calculating the selection probability of the x PRACH according to the selection coefficient R (x) of the x PRACH as follows:wherein, N is the number of PRACH included in the PRACH selection window, and r (i) represents a selection coefficient of the ith PRACH.

5. The method of claim 4, wherein if there are multiple PRACHs in a subframe, the selection coefficients R (x) of the multiple PRACHs are the same.

6. The method of claim 1, wherein the setting the PRACH selection window specifically comprises:

selecting a preferred PRACH continuous block in M continuous subframes, wherein the preferred PRACH continuous block is a continuous block containing the most PRACHs in the M subframes, and the preferred PRACH continuous block is a continuous PRACH in a time domain and comprises PRACHs belonging to different frequency domains at the same time domain position; or, if there are a plurality of PRACH continuous blocks containing the most PRACH, selecting the PRACH continuous block with a larger number of subframes different from the next PRACH continuous block as the preferred PRACH continuous block;

and setting the PRACH selection window by taking the first subframe after the preferred PRACH continuous block as a starting point, wherein the window comprises M subframes.

7. The method of claim 6, further comprising selecting PRACH and subframe number within a window for PRACH:

sequentially numbering N PRACHs contained in the PRACH selection window in the order of frequency domain first and time domain later;

and numbering all subframes in the PRACH selection window in sequence from small to large.

8. The method of claim 7, further comprising determining a correspondence between subframe locations and PRACH according to method one;

the first method specifically comprises the following steps:

the x-th subframe corresponds to the y-th PRACH, where y is Floor (x/(M/N)), and 0 <, x < M.

9. The method of claim 7, further comprising:

each PRACH corresponds to M/N subframes, and the average value of time delay between each subframe and the corresponding PRACH is set to be minimum.

10. The method of claim 9, wherein if a subframe corresponds to two PRACH's, the method further comprises:

the subframe corresponds to one PRACH which is earlier in time;

or,

Or,

11. The method of any of claims 2 to 10, wherein the selecting the PRACH comprises:

and when the initial subframe of the user equipment is positioned at different subframe positions in the window, selecting the PRACH corresponding to the subframe.

12. An apparatus for selecting a PRACH, comprising:

a window setting unit, configured to set a PRACH selection window;

13. The apparatus of claim 12, further comprising:

a position determining unit, configured to determine an initial subframe position of a user equipment;

the window setting unit is specifically configured to set the PRACH selection window using the initial subframe location as a starting point, where the PRACH selection window includes M subframes.

14. The apparatus of claim 13,

the selection unit is specifically configured to determine a selection coefficient r (x) of an x-th PRACH in the PRACH selection window, where r (x) is a number or a k-th power of the number of a subframe in which the x-th PRACH is located, where k is greater than 1, and the number is obtained by numbering in a descending order from a starting point of the window;

15. The apparatus of claim 12,

the window setting unit is specifically configured to select a preferred PRACH continuous block in M consecutive subframes, where the preferred PRACH continuous block is a continuous block that includes the most PRACH in the M subframes, and the preferred PRACH continuous block is a PRACH that is continuous in a time domain and includes PRACH belonging to different frequency domains at the same time domain position; or, if there are a plurality of PRACH consecutive blocks including the most PRACH, selecting a PRACH consecutive block having a larger number of subframes than a subsequent PRACH consecutive block as a preferred PRACH consecutive block, and setting the PRACH selection window with a first subframe after the preferred PRACH consecutive block as a starting point, where the window includes M subframes.

16. The apparatus of claim 15, further comprising a numbering unit configured to number the N PRACH included in the PRACH selection window sequentially in an order from a frequency domain to a time domain, and further configured to number all subframes in the PRACH selection window sequentially from small to large.

17. The apparatus of claim 16, further comprising a correspondence determining unit configured to determine a correspondence between a subframe location and a PRACH according to method one;

the first method specifically comprises the following steps:

18. The apparatus of claim 16, wherein the correspondence determining unit is further configured to select a corresponding M/N subframes for each PRACH, and set an average of time delays between each subframe and its corresponding PRACH to be minimum.

19. The apparatus of claim 18, comprising:

or,

Or,

20. A user equipment, characterized in that the user equipment comprises the apparatus according to any of claims 12-18.