CN111901889B - Distributed uplink multi-user random access method - Google Patents
Distributed uplink multi-user random access method Download PDFInfo
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- CN111901889B CN111901889B CN202010670904.0A CN202010670904A CN111901889B CN 111901889 B CN111901889 B CN 111901889B CN 202010670904 A CN202010670904 A CN 202010670904A CN 111901889 B CN111901889 B CN 111901889B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W74/00—Wireless channel access, e.g. scheduled or random access
- H04W74/002—Transmission of channel access control information
- H04W74/004—Transmission of channel access control information in the uplink, i.e. towards network
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W74/00—Wireless channel access, e.g. scheduled or random access
- H04W74/002—Transmission of channel access control information
- H04W74/006—Transmission of channel access control information in the downlink, i.e. towards the terminal
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W74/00—Wireless channel access, e.g. scheduled or random access
- H04W74/08—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access]
- H04W74/0833—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access] using a random access procedure
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W74/00—Wireless channel access, e.g. scheduled or random access
- H04W74/08—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access]
- H04W74/0866—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access] using a dedicated channel for access
Abstract
The invention provides a distributed uplink multi-user random access method, belonging to the field of communication. The method comprises the following steps: a user with access requirements randomly selects a pilot frequency sequence from the pilot frequency sequence set according to an access strategy broadcasted by the base station, sends the pilot frequency sequence to the base station and initiates an access request to the base station; the base station obtains a normalized downlink pilot signal according to the received pilot signal, and broadcasts the normalized downlink pilot signal as random access response information to users in a cell; the user initiating the access request judges whether the user can win the user competing for the same pilot frequency sequence according to the received random access response information and by combining the signal power of the user and the broadcasting strategy of the cell, and the user who wins the competition wins sends the selected pilot frequency sequence to the base station again; and the base station demodulates the user identification code according to the received secondary pilot frequency information estimation channel information and allocates exclusive pilot frequency resources for the successfully demodulated user. By adopting the invention, the high-efficiency access of multiple users can be realized.
Description
Technical Field
The present invention relates to the field of communications, and in particular, to a distributed uplink multi-user random access method.
Background
Random access is the primary step of establishing uplink communication connection between a user and a base station, and has two main purposes: firstly, establishing an uplink synchronization relationship with a base station; and secondly, requesting the base station to allocate uplink resources for the base station so as to transmit data.
The traditional contention-based random access scheme is that users send randomly selected pilot frequency sequences to a base station, when a plurality of users select the same pilot frequency sequence and pilot frequency collision occurs, the base station intensively solves the problem of pilot frequency collision, and the scheme aims to minimize the probability of pilot frequency collision and further improve the number of users successfully accessing a network. However, in the face of the communication requirements of a large number of users, the problem of pilot collision is more obvious, and the centralized solution of the pilot collision by the base station inevitably brings a high collision rate to the base station, which causes the phenomena of long access delay and low efficiency of the users. Therefore, the conventional random access scheme for solving pilot collision in a centralized manner cannot meet the scene requirements of accessing a large number of users, and a novel and efficient random access scheme is urgently needed.
Disclosure of Invention
The embodiment of the invention provides a distributed uplink multi-user random access method, which adopts a distributed pilot frequency conflict solution strategy to transfer the pilot frequency conflict problem to a user side, each user judges whether the user competes for winning, and the base station does not reply a competition solution message to specify which user competes for winning, so that the access efficiency of multiple users in a cell can be obviously improved, the performance loss caused by centralized pilot frequency conflict solution of the base station is relieved, the conflict solution probability is improved, the user access time delay is reduced, and the high-efficiency access of multiple users is realized. The technical scheme is as follows:
on one hand, a distributed uplink multi-user random access method is provided, and the method is applied to electronic equipment and comprises the following steps:
a user with access requirements randomly selects a pilot frequency sequence from the pilot frequency sequence set according to an access strategy broadcasted by the base station, sends the pilot frequency sequence to the base station and initiates an access request to the base station;
the base station obtains a normalized downlink pilot signal according to the received pilot signal, and broadcasts the normalized downlink pilot signal as random access response information to users in a cell;
the user initiating the access request judges whether the user can win the user competing for the same pilot frequency sequence according to the received random access response information and by combining the signal power of the user and the broadcasting strategy of the cell, and the user who wins the competition wins sends the selected pilot frequency sequence to the base station again;
and the base station demodulates the user identification code according to the received secondary pilot frequency information estimation channel information and allocates exclusive pilot frequency resources for the successfully demodulated user.
Further, the randomly selecting a pilot sequence from the pilot sequence set by the user with the access requirement according to the access strategy broadcasted by the base station, and sending the pilot sequence to the base station, wherein the sending the access request to the base station comprises:
the base station broadcasts an access strategy to users in the cell according to the distribution characteristics of the users in the cell by using the prior knowledge of the broadcast channel;
users with access requirements are grouped from pilot sequences according to access policies broadcast by the base station
In the method, a pilot frequency sequence P is randomly selectediSending the information to a base station, and initiating an access request to the base station, wherein i is 1,2p，λpRepresenting the number of orthogonally normalized available pilot sequences.
Further, the step of the base station obtaining a normalized downlink pilot signal according to the received pilot signal and broadcasting the normalized downlink pilot signal as random access response information to the users in the cell includes:
the base station obtains the sum y of the channel information of all users selecting the same pilot frequency sequence according to the received pilot frequency signali；
The base station passes yiNormalizing to obtain a normalized downlink pilot signal, and using the normalized downlink pilot signal as random access response information;
and the base station broadcasts the random access response information to users in the cell.
Further, the pilot signal received by the base station is represented as:
where Y denotes a pilot signal received by the base station, UiIndicating the selection of the pilot sequence PiI 1,2p，λpRepresenting the number of orthogonally normalized available pilot sequences; w is akThe transmit power for user k; h iskRepresenting between user k and base stationA channel;
represents PiTransposing; z represents a mean of 0 and a variance of σ2Additive white gaussian noise of (1);
selecting a pilot sequence PiIs received by all users, and the sum y of the channel information of all usersiExpressed as:
wherein, Pi *Represents PiConjugation of (1); ziRepresenting a mean of 0 and a variance of σ2White additive gaussian noise.
Further, the normalized downlink pilot signal is expressed as:
wherein W represents a normalized downlink pilot signal.
Further, the step of the user initiating the access request determining whether the user can win the user competing for the same pilot sequence according to the received random access response information and combining the signal power of the user and the broadcast strategy of the cell, wherein the step of the user competing for the win resending the selected pilot sequence to the base station includes:
random access response information to be received by user k
Pilot frequency sequence P selected by itiPerforming correlation operation to obtain the result Q of the correlation operationk；
Based on QkReal part of
Estimating the selection of the same pilot sequence PiSum of signal powers of all users
User k adds a decision quantity xi (alpha) on the basis of own signal powerk) Then, according to the strong user decision criterion, judging whether the user wins the competition and retransmits the pilot frequency, wherein the strong user decision criterion is wkαkλp+ξ(αk) And
and (4) determining.
Further, the random access response information received by the user k
Expressed as:
wherein the content of the first and second substances,
represents hkThe conjugate transpose of (a) is performed,
representing a mean of 0 and a variance of σ2Additive white gaussian noise of (1);
result of cross-correlation operation QkExpressed as:
wherein, Pi *Represents the pilot sequence PiConjugation of (1);
represents hkConjugate transpose of (i), hkRepresents the channel between user k and the base station; lambda [ alpha ]pRepresenting the number of orthogonally normalized available pilot sequences；yiIndicating the selection of the pilot sequence PiThe sum of the channel information of all users; zkRepresenting a mean of 0 and a variance of σ2Additive white gaussian noise of (1);
estimating the selection of the same pilot sequence PiSum of signal powers of all users
Expressed as:
wherein M represents the number of base station side antennas, wkRepresenting the transmit power, alpha, of user kkRepresenting a large scale fading coefficient, max (-) represents a max operation.
Further, the signal power of user k itself is wkαkλp。
Further, the strong user decision criterion is expressed as:
if it satisfies
User k wins the contention and user k will select pilot sequence PiRe-sending to the base station; wherein, TkIndicating that the user competes for winning the event;
if it satisfies
The user k fails in competition and the random access fails; wherein, FkIndicating an event that the user has failed the competition.
Further, the secondary pilot information includes: the user identification code and the competition winning user are retransmitted to the pilot frequency sequence of the base station;
the base station demodulates the user identification code according to the received secondary pilot frequency information estimation channel information, and allocates exclusive pilot frequency resources for the successfully demodulated user comprises the following steps:
after receiving the pilot frequency sequence of the competition winning user again, the base station estimates the channel information of the user;
demodulating the user identification code using the estimated channel information;
if the demodulation is successful, allocating dedicated pilot frequency resources for the user so as to complete subsequent data transmission;
if the demodulation fails, the user access fails.
In one aspect, an electronic device is provided, where the electronic device includes a processor and a memory, where the memory stores at least one instruction, and the at least one instruction is loaded and executed by the processor to implement the distributed uplink multi-user random access method.
In one aspect, a computer-readable storage medium is provided, where at least one instruction is stored in the storage medium, and the at least one instruction is loaded and executed by a processor to implement the above-mentioned distributed uplink multi-user random access method.
The technical scheme provided by the embodiment of the invention has the beneficial effects that at least:
in the embodiment of the invention, a user with access requirements randomly selects a pilot frequency sequence from a pilot frequency sequence set according to an access strategy broadcasted by a base station and sends the pilot frequency sequence to the base station, and an access request is sent to the base station; the base station obtains a normalized downlink pilot signal according to the received pilot signal, and broadcasts the normalized downlink pilot signal as random access response information to users in a cell, and does not care which users select the pilot sequence and whether the pilot sequence is collided; the user who initiates the access request judges whether the user can win the same pilot frequency sequence or not according to the received random access response information and the combination of the signal power of the user and the broadcasting strategy of the cell, and the user who wins the same pilot frequency sequence sends the selected pilot frequency sequence to the base station again; and the base station demodulates the user identification code according to the received secondary pilot frequency information estimation channel information and allocates exclusive pilot frequency resources for the successfully demodulated user. Therefore, the pilot frequency conflict problem is transferred to the user side by adopting a distributed pilot frequency conflict solution strategy, each user judges whether the user wins the competition, and the base station does not appoint which user wins the competition by replying the competition solution message any more, so that the access efficiency of multiple users in a cell can be obviously improved, the performance loss caused by centralized pilot frequency conflict solution of the base station is relieved, the conflict solution probability is improved, the user access time delay is reduced, and the high-efficiency access of the multiple users is realized.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required in the description of the embodiments will be briefly introduced below, and it is apparent 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 that other drawings can be obtained based on these drawings without inventive efforts.
Fig. 1 is a schematic flow chart of a distributed uplink multi-user random access method according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a system model according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
As shown in fig. 1, an embodiment of the present invention provides a distributed uplink multi-user random access method, where the method may be implemented by an electronic device, where the electronic device may be a terminal or a server, and the method includes:
s101, a user with access requirements randomly selects a pilot frequency sequence from a pilot frequency sequence set according to an access strategy broadcasted by a base station and sends the pilot frequency sequence to the base station, and an access request is sent to the base station;
s102, the base station obtains a normalized downlink pilot signal according to the received pilot signal, and broadcasts the normalized downlink pilot signal as random access response information to users in a cell;
s103, the user initiating the access request judges whether the user can win the user competing for the same pilot frequency sequence according to the received random access response information and by combining the signal power of the user and the broadcasting strategy of the cell, and the user who wins the competition wins sends the selected pilot frequency sequence to the base station again;
and S104, the base station demodulates the user identification code according to the received secondary pilot frequency information estimation channel information, and allocates exclusive pilot frequency resources for the successfully demodulated user.
In the distributed uplink multi-user random access method provided by the embodiment of the invention, a user with access requirements randomly selects a pilot sequence from a pilot sequence set according to an access strategy broadcasted by a base station, sends the pilot sequence to the base station and initiates an access request to the base station; the base station obtains a normalized downlink pilot signal according to the received pilot signal, and broadcasts the normalized downlink pilot signal as random access response information to users in a cell, and does not care which users select the pilot sequence and whether the pilot sequence is collided; the user who initiates the access request judges whether the user can win the same pilot frequency sequence or not according to the received random access response information and the combination of the signal power of the user and the broadcasting strategy of the cell, and the user who wins the same pilot frequency sequence sends the selected pilot frequency sequence to the base station again; and the base station demodulates the user identification code according to the received secondary pilot frequency information estimation channel information and allocates exclusive pilot frequency resources for the successfully demodulated user. Therefore, the pilot frequency conflict problem is transferred to the user side by adopting a distributed pilot frequency conflict solution strategy, each user judges whether the user wins the competition, and the base station does not appoint which user wins the competition by replying the competition solution message any more, so that the access efficiency of multiple users in a cell can be obviously improved, the performance loss caused by centralized pilot frequency conflict solution of the base station is relieved, the conflict solution probability is improved, the user access time delay is reduced, and the high-efficiency access of the multiple users is realized.
In this embodiment, the distributed manner means that each user determines whether the user wins the contention by itself, and the base station does not designate which user wins the contention by replying the contention resolution message.
In this embodiment, in order to simplify the system model, it is assumed that the base station is located at the center of the cell, and the number of antennas at the base station sideThe number of user terminals (users) with K single antennas is M, and the total number of the user terminals is lambdapAn available pilot sequence for orthogonal normalization, and K > lambdap. The channel between the user K (K is more than or equal to 1 and less than or equal to K) and the base station is hk＝[h1,k,h2,k,...,hm,k,...,hM,k]TWherein h isi,kThe channel transmission coefficient between the user k and the ith antenna at the base station end can be determined through large-scale fading and small-scale fading together
Wherein, gi,kThe method represents that the obedience probability density function between the user k and the ith antenna at the base station end is as follows
Independently identically distributed small-scale fading coefficients, alphakRepresenting the large scale fading coefficient between user k and the base station, typically associated with shadowing and path loss. When the number M of base station side antennas tends to infinity, the channel between user k and the base station has asymptotically optimal propagation characteristics, that is:
wherein the content of the first and second substances,
represents hkThe conjugate transpose of (c).
In this embodiment, before S101, the base station broadcasts a reference signal, and each user estimates its large-scale fading coefficient α according to the reference signalkAnd completes synchronization with the base station.
In this embodiment, a user with access requirement randomly selects a pilot sequence from a set of pilot sequences according to an access policy broadcasted by a base station, and sends an access request to the base station (S101), where the method includes:
a1, using the priori knowledge of the broadcast channel, the base station broadcasts the access strategy to the cell users according to the distribution characteristics of the cell users;
in the embodiment, the base station broadcasts the access strategy to the cell users in advance in the system message according to the distribution characteristics of the cell users by using the prior knowledge of the broadcast channel, for example, the criteria of edge priority, fairness priority, efficiency priority and the like; wherein the content of the first and second substances,
the edge priority criterion has priority to the access of the edge users, thereby enhancing the access success rate of the edge users;
the fairness priority criterion can balance the difference of the channel gain intensity among users, and is favorable for realizing user competition fairness;
the efficiency priority criteria may improve the efficiency of user access.
A2, user with access requirement according to access strategy broadcasted by base station, from pilot frequency sequence set
In the method, a pilot frequency sequence P is randomly selectediSending the information to a base station, and initiating an access request to the base station, wherein i is 1,2p，λpRepresenting the number of orthogonally normalized available pilot sequences.
In the embodiment, a traditional contention-based random access scheme is changed, the base station broadcasts an access strategy to the user in advance by using the priori knowledge of the broadcast channel, then the user initiates an access request according to the access strategy broadcasted by the base station, and the base station also adjusts the access strategy in real time, so that multiple users in a cell can access efficiently.
In this embodiment, the step of the base station obtaining a normalized downlink pilot signal according to the received pilot signal and broadcasting the normalized downlink pilot signal as random access response information to the users in the cell (S102) includes:
b1, the base station obtains the sum y of the channel information of all users selecting the same pilot frequency sequence according to the received pilot frequency signali；
In this embodiment, the pilot signal Y received by the base station is represented as:
wherein, UiIndicating the selection of the pilot sequence PiI 1,2p；wkThe transmit power for user k; h iskRepresents the channel between user k and the base station; pi TRepresents PiTransposing; z represents a mean of 0 and a variance of σ2White additive gaussian noise.
In this example, yiExpressed as:
wherein, Pi *Represents PiConjugation of (1); ziRepresenting a mean of 0 and a variance of σ2White additive gaussian noise.
In this embodiment, when the number M of antennas tends to infinity, it can be obtained:
wherein, γiSum of signal powers, σ, for all users selecting the same pilot2A noise variance;
b2, the base station sends yiNormalizing to obtain a normalized downlink pilot signal W, and using the normalized downlink pilot signal W as random access response information;
in this example, W is represented as:
wherein the content of the first and second substances,
represents PiThe transposing of (1).
B3, the base station broadcasts the random access response information to the users in the cell.
In this embodiment, the determining, by the user initiating the access request, whether the user can win the user competing for the same pilot sequence according to the received random access response information and combining the signal power of the user and the broadcast policy of the cell, where the retransmitting the selected pilot sequence to the base station by the user competing for the win (S103) includes:
c1, user k receives the random access response information
Pilot frequency sequence P selected by itiPerforming correlation operation to obtain the result Q of the correlation operationk；
In the present embodiment, the first and second electrodes are,
expressed as:
wherein the content of the first and second substances,
represents hkThe conjugate transpose of (a) is performed,
representing a mean of 0 and a variance of σ2White additive gaussian noise.
In this embodiment, QkExpressed as:
wherein the content of the first and second substances,
represents hkBy conjugate transposition of (Z)kRepresenting a mean of 0 and a variance of σ2Additive white gaussian noise of (1);
in this embodiment, when the number M of antennas tends to infinity, it can be obtained:
in this embodiment, Q iskContains only the noise part, so ignoring its imaginary part yields the following approximate expression:
c2, based on QkReal part of
Estimating the selection of the same pilot sequence PiSum of all user signal powers
In the present embodiment, the first and second electrodes are,
expressed as:
where max (·) represents the max operation.
C3, user k adds a decision quantity xi (alpha) based on own signal powerk) Then, according to the strong user decision criterion, judging whether the user wins the competition and retransmits the pilot frequency, wherein the strong user decision criterion is wkαkλp+ξ(αk) And
and (4) determining.
In this embodiment, the signal power of the user k is wkαkλpWherein w iskFor the transmit power of user k, alphakRepresenting a large scale fading coefficient, λpRepresenting the number of orthogonally normalized available pilot sequences.
In this example, ξ (. alpha.)k) Is a andkthe offset involved, in general ξ (α)k) When the base station broadcasts different access strategies, the user can make ξ (α) according to the broadcast strategy of the base stationk) Making dynamic changes.
In this embodiment, assume that the access policy broadcasted by the base station is the edge priority criterion, if the α of the edge user iskIf the value is small, the offset may take a positive value, i.e., ξ (α)k)>0; if alpha of edge userkIf the value is larger, the offset can be zero, i.e. xi (alpha)k) 0. If alpha is not edge userkIf the value is larger, the offset can take a negative value, namely xi (alpha)k)<0; if alpha is not edge userkWith smaller values, the offset may take on zero, i.e., ξ (α)k) 0. Under the edge priority criterion, when the non-edge user is alphakWhen the size is large enough, the access can be abandoned, and the access of the edge user is prioritized.
In this embodiment, the strong user decision criterion is expressed as:
if it satisfies
User k wins the contention and user k will select pilot sequence PiRetransmitting to the base station, wherein TkIndicating that the user competes for winning the event;
if it satisfies
User k fails contention, the user remains stationary and random access fails, where FkIndicating an event that the user has failed the competition.
In this embodiment, the user with the successful contention also needs to send other information to the base station, for example, a user identification code (ID information), so that the base station allocates dedicated pilot resources to the user in the next step.
In this embodiment, the base station demodulates the user identification code according to the received secondary pilot information estimated channel information, and allocates dedicated pilot resources to the successfully demodulated user (S104) includes:
after receiving the pilot frequency sequence of the competition winning user again, the base station estimates the channel information of the user;
demodulating the user identification code using the estimated channel information;
if the demodulation is successful, allocating dedicated pilot frequency resources (specifically: a resource block corresponding to a certain pilot frequency) for the user so as to complete subsequent data transmission;
if the demodulation fails, the user access fails.
In this embodiment, the secondary pilot information includes: the user identification code and the user with the successful competition are retransmitted to the pilot frequency sequence of the base station.
In this embodiment, a system model shown in fig. 2 is taken as an example to describe the distributed uplink multi-user random access method provided in this embodiment of the present invention. A Base Station (BS) is positioned at the center of a cell, M antennas are configured, single-antenna users are uniformly distributed at different positions of the cell, and it is assumed that a certain edge user is UEfThe non-edge user is UEnTheir distances from the base station are dfAnd dnTwo users estimate the large-scale fading coefficients respectively as alpha according to the reference signal broadcasted by the base stationfAnd alphanAt this time, αf<αnEach user in the cell receives the access strategy broadcasted by the base station, such as edge-first, fair-first or efficiency-first. Assuming that the base station broadcasts the edge priority criterion in a certain period, the edge user UEfDefine itself as an edge user and find its large-scale fading coefficient alphafSmaller, then its offset takes a reasonably positive value; non-edge user UEnDefinitely self is a non-edge user, if a large-scale fading coefficient alpha is foundnIf the offset is too large, the access is abandoned directly, otherwise the offset takes a reasonable negative value, and then xi (alpha) is obtainedf)>0>ξ(αn). When they select the same pilot P0When the information is sent to the base station, the base station broadcasts random access response information (RAR), and the edge user UEfNon-edge user UEnReceiving random access response information
And a pilot sequence P0Performing correlation operation to estimate the selected pilot frequency sequence P0The sum of the signal powers of all users, i.e. equation (12); the signal power of the edge users and the non-edge users are respectively: w is afαfλp+ξ(αf) And wnαnλp+ξ(αn) If, if
And is
Then it indicates a non-edge user UEnContention failure, edge user UEfContention wins, UEfRepeatedly sending pilot frequency sequence P0And further improve the access efficiency of the edge users.
Fig. 3 is a schematic structural diagram of an electronic device 600 according to an embodiment of the present invention, where the electronic device 600 may generate relatively large differences due to different configurations or performances, and may include one or more processors (CPUs) 601 and one or more memories 602, where the memory 602 stores at least one instruction, and the at least one instruction is loaded and executed by the processor 601 to implement the above-described distributed uplink multi-user random access method.
In an exemplary embodiment, a computer-readable storage medium, such as a memory, including instructions executable by a processor in a terminal to perform the distributed uplink multi-user random access method is also provided. For example, the computer readable storage medium may be a ROM, a Random Access Memory (RAM), a CD-ROM, a magnetic tape, a floppy disk, or an optical data storage device, etc.
It will be understood by those skilled in the art that all or part of the steps of the above embodiments may be implemented by hardware, or may be implemented by hardware associated with program instructions, and that the program may be stored in a computer-readable storage medium, such as a read-only memory, a magnetic or optical disk, and the like.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (3)
1. A distributed uplink multi-user random access method is characterized by comprising the following steps:
a user with access requirements randomly selects a pilot frequency sequence from the pilot frequency sequence set according to an access strategy broadcasted by the base station, sends the pilot frequency sequence to the base station and initiates an access request to the base station;
the base station obtains a normalized downlink pilot signal according to the received pilot signal, and broadcasts the normalized downlink pilot signal as random access response information to users in a cell;
the user initiating the access request judges whether the user can win the user competing for the same pilot frequency sequence according to the received random access response information and by combining the signal power of the user and the broadcasting strategy of the cell, and the user who wins the competition wins sends the selected pilot frequency sequence to the base station again;
the base station demodulates the user identification code according to the received secondary pilot frequency information estimation channel information and allocates exclusive pilot frequency resources for the successfully demodulated user;
the base station obtains a normalized downlink pilot signal according to the received pilot signal, and broadcasts the normalized downlink pilot signal as random access response information to users in a cell, wherein the step of broadcasting comprises the following steps:
the base station receivesThe pilot signal of (a) is obtained as the sum y of the channel information of all users selecting the same pilot sequencei；
The base station passes yiNormalizing to obtain a normalized downlink pilot signal, and using the normalized downlink pilot signal as random access response information;
the base station broadcasts the random access response information to users in the cell;
the pilot signal received by the base station is represented as:
where Y denotes a pilot signal received by the base station, UiIndicating the selection of the pilot sequence PiI 1,2p，λpRepresenting the number of orthogonally normalized available pilot sequences; w is akThe transmit power for user k; h iskRepresents the channel between user k and the base station;
represents PiTransposing; z represents a mean of 0 and a variance of σ2Additive white gaussian noise of (1);
selecting a pilot sequence PiIs received by all users, and the sum y of the channel information of all usersiExpressed as:
wherein the content of the first and second substances,
represents PiConjugation of (1); ziRepresenting a mean of 0 and a variance of σ2Additive white gaussian noise of (1);
wherein, the normalized downlink pilot signal is expressed as:
wherein, W represents a normalized downlink pilot signal;
wherein, the user initiating the access request judges whether the user can win the user competing for the same pilot frequency sequence according to the received random access response information and combining the signal power of the user and the broadcast strategy of the cell, and the user competing for wining resends the selected pilot frequency sequence to the base station comprises:
random access response information to be received by user k
Pilot frequency sequence P selected by itiPerforming correlation operation to obtain the result Q of the correlation operationk；
Based on QkReal part of
Estimating the selection of the same pilot sequence PiSum of signal powers of all users
User k adds a decision quantity xi (alpha) on the basis of own signal powerk) Then, according to the strong user decision criterion, judging whether the user wins the competition and retransmits the pilot frequency, wherein the strong user decision criterion is wkαkλp+ξ(αk) And
is determined in whichkRepresenting a large scale fading coefficient;
wherein, the random access response information received by the user k
Expressed as:
wherein the content of the first and second substances,
represents hkThe conjugate transpose of (a) is performed,
representing a mean of 0 and a variance of σ2Additive white gaussian noise of (1);
result of cross-correlation operation QkExpressed as:
wherein the content of the first and second substances,
represents the pilot sequence PiConjugation of (1);
represents hkConjugate transpose of (i), hkRepresents the channel between user k and the base station; lambda [ alpha ]pRepresenting the number of orthogonally normalized available pilot sequences; y isiIndicating the selection of the pilot sequence PiThe sum of the channel information of all users; zkRepresenting a mean of 0 and a variance of σ2Additive white gaussian noise of (1);
estimating the selection of the same pilot sequence PiSum of signal powers of all users
Expressed as:
wherein M represents the number of base station side antennas, wkRepresenting the transmit power, alpha, of user kkRepresents a large-scale fading coefficient, and max (-) represents a maximum value operation;
wherein, the signal power of the user k is wkαkλp；
Wherein the strong user decision criterion is expressed as:
if it satisfies
User k wins the contention and user k will select pilot sequence PiRe-sending to the base station; wherein, TkIndicating that the user competes for winning the event;
if it satisfies
The user k fails in competition and the random access fails; wherein, FkIndicating an event that the user has failed the competition.
2. The method of claim 1, wherein the user with access requirement randomly selects a pilot sequence from a set of pilot sequences according to an access policy broadcasted by a base station, sends the pilot sequence to the base station, and initiates an access request to the base station comprises:
the base station broadcasts an access strategy to users in the cell according to the distribution characteristics of the users in the cell by using the prior knowledge of the broadcast channel;
users with access requirements are grouped from pilot sequences according to access policies broadcast by the base station
In the method, a pilot frequency sequence P is randomly selectediSending the information to a base station, and initiating an access request to the base station, wherein i is 1,2p，λpRepresenting the number of orthogonally normalized available pilot sequences.
3. The distributed uplink multi-user random access method according to claim 1, wherein the secondary pilot information includes: the user identification code and the competition winning user are retransmitted to the pilot frequency sequence of the base station;
the base station demodulates the user identification code according to the received secondary pilot frequency information estimation channel information, and allocates exclusive pilot frequency resources for the successfully demodulated user comprises the following steps:
after receiving the pilot frequency sequence of the competition winning user again, the base station estimates the channel information of the user;
demodulating the user identification code using the estimated channel information;
if the demodulation is successful, allocating dedicated pilot frequency resources for the user so as to complete subsequent data transmission;
if the demodulation fails, the user access fails.
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