CN111464221B - BFT-based wireless access method and communication method under millimeter wave cellular network - Google Patents

BFT-based wireless access method and communication method under millimeter wave cellular network Download PDF

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CN111464221B
CN111464221B CN202010441463.7A CN202010441463A CN111464221B CN 111464221 B CN111464221 B CN 111464221B CN 202010441463 A CN202010441463 A CN 202010441463A CN 111464221 B CN111464221 B CN 111464221B
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CN111464221A (en
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桂劲松
刘江林
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Central South University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0686—Hybrid systems, i.e. switching and simultaneous transmission
    • H04B7/0695—Hybrid systems, i.e. switching and simultaneous transmission using beam selection
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/50—Allocation or scheduling criteria for wireless resources
    • H04W72/56—Allocation or scheduling criteria for wireless resources based on priority criteria
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/10—Small scale networks; Flat hierarchical networks
    • H04W84/12—WLAN [Wireless Local Area Networks]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Abstract

The invention discloses a BFT-based wireless access method under a millimeter wave cellular network, which adopts a three-layer BFT mechanism to realize BFT of MBS and surrounding SBSs, BFT of each SBS and surrounding APs thereof and BFT of each AP and surrounding UEs thereof. The invention also discloses a communication method comprising the BFT-based wireless access method under the millimeter wave cellular network. The invention can reduce the workload of the summary node in the BFT process, and can reduce the communication cost in the BFT process, so that the BFT mechanism can adapt to the increase of the scale of a communication network; the beam direction, the beam width and the node transmission power of the nodes in the communication network can be adjusted, and the inter-node interference in the communication process is reduced; the overall network throughput can be improved, and the energy consumption in the communication network can be reduced as much as possible; finally, the method of the invention can obviously improve the average energy efficiency value and the average throughput of a single link in the communication network.

Description

BFT-based wireless access method and communication method under millimeter wave cellular network
Technical Field
The invention belongs to the field of communication, and particularly relates to a BFT-based wireless access method and a communication method under a millimeter wave cellular network.
Background
With the development of economic technology and the improvement of living standard of people, the rapid popularization of mobile internet and internet of things leads to the continuous high demand of network capacity in the future. Since spectrum resources in the conventional cellular band have been exhausted, the millimeter wave (mmWave) band has become a new source of spectrum supply, which has abundant spectrum resources, and thus can support wireless transmission at a high data rate. Millimeter wave communication technology has been successfully applied in the fifth generation (5G) cellular systems and Wireless Local Area Networks (WLANs). However, before fully utilizing its abundant spectral resources, it is necessary to overcome its inherent drawbacks (e.g., severe path loss, high atmospheric absorption and susceptibility to blockage). Fortunately, research has shown that the intensive directional transmission and network deployment can effectively reduce the path loss and the high atmospheric absorption rate. The directional transmission technology requires beam alignment of both communication parties, which can effectively enlarge the communication distance; more densely deployed base stations may form short-range communications to reduce the blocking probability and thus reduce path loss. However, the combined use of directional transmission and the intensive network deployment can lead to inevitable inter-node communication interference problems, which can pose serious challenges to Radio Resource Management (RRM). There are many researchers currently working on RRM problems in WLANs.
For WLAN, research has indicated that a centralized control mode based cloud radio access network (C-RAN) should be applied in WLAN. In dense mmWave WLANs, a controller manages and controls multiple Access Points (APs) through a directional mmWave link]And the method is beneficial to the unified coordination and management of the APs. The document "Deep Learning-Based Beam Management and interference Coordination in density wave Networks" proposes an effective beamforming training (BFT) mechanism to establish a directional communication link between nodes, and ensure that the communication cost in the establishment process of the directional link is reduced; meanwhile, BM-IC problems in the dense millimeter wave network are regarded as optimization problems, a BM-IC algorithm based on a BFT mechanism is established, and the throughput of the communication network is effectively improved. In the BFT stage mentioned in this document, a Macro Base Station (MBS) is used as a control and coordination center of a centralized network, and data frames from each AP are collectively analyzed, so as to determine an optimal associated AP of each User Equipment (UE) in the network, and this process effectively reduces communication cost in the establishment process of a directional link through layered data transmission; in the optimization stage of BM-IC problem, based on the directional link in BFT stage, BM-IC problem is regarded as an optimization problem with constraint, and finally, the optimization problem with constraint is establishedThe article effectively improves the throughput of the whole millimeter wave communication network by globally optimizing the beam direction, the beam bandwidth and the transmitting power based on the priority strategy based on the BM-IC optimization algorithm of the priority strategy.
However, in the application scenario of the dense millimeter wave cellular network, due to the fact that the network scale is multiplied, the BFT mechanism proposed by the document is directly applied to the dense millimeter wave cellular network scenario, which may cause the MBS to have an excessively large load and multiply increase the communication cost, and cannot adapt to the large-scale growth of the future network; meanwhile, considering that the BM-IC optimization algorithm in this document is based on a signal to noise ratio (SNR) priority policy, predicting channel quality using SNR cannot reflect the decisive role of energy in optimization, and cannot meet the requirement of the next generation wireless communication network for low power consumption.
Disclosure of Invention
One of the purposes of the present invention is to provide a BFT-based wireless access method in a millimeter wave cellular network, which can further reduce communication interference and has lower power consumption.
The invention also aims to provide a communication method comprising the BFT-based wireless access method under the millimeter wave cellular network.
The BFT-based wireless access method under the millimeter wave cellular network provided by the invention adopts a three-layer BFT mechanism to realize the BFT of MBS and surrounding SBSs, the BFT of each SBS and surrounding APs thereof and the BFT of each AP and surrounding UEs thereof.
The BFT of the MBS and the surrounding SBSs specifically comprises the following steps:
A1. a training request sending stage: the MBS transmits a training request beacon frame in all corresponding beams simultaneously so as to start a training process between the MBS and the SBS;
B1. waiting for a training response stage: each SBS receiving the training request beacon frame randomly selects a response time slot, so that the training response beacon frames are transmitted in all corresponding beams at the same time;
C1. and a response conflict processing stage: judging whether response conflict occurs:
if no response beacon frame collision occurs, the step is finished;
if the conflict of the response beacon frame occurs, the MBS retransmits the training request beacon frame in the wave beam with the conflict event; meanwhile, in the retransmitted training request beacon frame, the number of response time slots is doubled, so that the collision probability is reduced;
D1. and (3) publishing a training result: the MBS estimates the optimal beam through the corresponding training response beacon frame information using the SBS information that successfully transmitted the training response beacon frame, and publishes the estimated optimal beam by transmitting a "publish training result frame".
The BFT of the SBS and the APs around the SBS specifically comprises the following steps:
A2. a training request sending stage: the SBS sends training request beacon frames in all corresponding beams simultaneously to start a training process between the SBS and the AP;
B2. waiting for a training response stage: each AP receiving the training request beacon frame randomly selects a response time slot, so that the training response beacon frames are transmitted in all corresponding beams at the same time;
C2. and a response conflict processing stage: judging whether response conflict occurs:
if no response beacon frame collision occurs, the step is finished;
if the conflict of the response beacon frames occurs, the SBS retransmits the training request beacon frames in the beams with the conflict events; meanwhile, in the retransmitted training request beacon frame, the number of response time slots is doubled, so that the collision probability is reduced;
the SBS analyzes the response beacon frame received by the SBS from the AP to obtain a result to be published; sending a result to be published to the MBS;
the MBS compares, analyzes and determines the AP which each SBS should be associated with according to the received to-be-published results of all SBS, and feeds back the result to each SBS;
F2. and (3) publishing a training result: the SBS estimates an optimal beam through corresponding training response beacon frame information according to received AP information associated with itself, and publishes the estimated optimal beam by transmitting a "publish training result frame".
The BFT of the AP and surrounding UEs thereof specifically comprises the following steps:
A3. a training request sending stage: the AP sends a training request beacon frame in all corresponding beams simultaneously to start a training process between the AP and the UE;
B3. waiting for a training response stage: each UE receiving the training request beacon frame randomly selects a response time slot, so that the training response beacon frames are transmitted in all corresponding beams at the same time;
C3. and a response conflict processing stage: judging whether response conflict occurs:
if no response beacon frame collision occurs, the step is finished;
if the response beacon frame conflicts, the AP retransmits the training request beacon frame in the wave beam with the conflict event; meanwhile, in the retransmitted training request beacon frame, the number of response time slots is doubled, so that the collision probability is reduced;
d3, the AP analyzes the response beacon frame received by the AP from the UE and obtains a result to be published; sending the result to be published to the SBS associated with the result to be published;
the SBS compares, analyzes and determines the UE which each AP should be associated with according to the received results to be published of all the APs, and feeds back the results to each AP;
F3. and (3) publishing a training result: the AP estimates the optimal beam through corresponding training response beacon frame information according to the received UE information associated with the AP, and publishes the estimated optimal beam by sending a 'publish training result frame'.
The BFT-based wireless access method in the millimeter wave cellular network specifically comprises the following steps of solving the following model, so as to obtain a final wireless access result:
Figure BDA0002504317030000051
Figure BDA0002504317030000052
in the formula
Figure BDA0002504317030000053
Is a set of J UEs
Figure BDA0002504317030000054
Figure BDA0002504317030000055
As a set of K APs
Figure BDA0002504317030000056
X is a beam selection matrix; p is a transmitting power matrix adopted by the wave beam; a is a beam width matrix; r isj,kThroughput of the link formed for the kth AP and the jth UE, and rj,k＝xj,kB log2(1+γj,k)；xj,kIs a binary associated variable, and x if UEj is connected to APkj,k1, otherwise x j,k0; b is the bandwidth of the millimeter-wave beam; gamma rayj,kForming an interference signal-to-noise ratio of a link for the number k AP and the number j UE; n isbeamNumber of beams that can be used concurrently for each SBS, AP or UE;
Figure BDA0002504317030000061
the power emitted by the wave beam is directed to the UE with the number j for the AP with the number k;
Figure BDA0002504317030000062
maximum transmission power of AP No. k; thetamaxIs the maximum value of the beam width; thetaminIs the minimum value of the beam width;
Figure BDA0002504317030000063
forming a transmission angle of a link for the AP with the UE with the number k and the number j;
Figure BDA0002504317030000064
and forming a receiving angle of a link for the AP with the UE with the number k and the number j.
Optimizing the model to obtain the following optimized model:
Figure BDA0002504317030000065
Figure BDA0002504317030000066
in the formula
Figure BDA0002504317030000067
A set of candidate UEs being AP # k;
Figure BDA0002504317030000068
as a set of K APs
Figure BDA0002504317030000069
X is a beam selection matrix; p is a transmitting power matrix adopted by the wave beam; a is a beam width matrix; r isj,kThroughput of the link formed for the kth AP and the jth UE, and rj,k＝xj,kB log2(1+γj,k)；xj,kIs a binary associated variable, and x if UEj is connected to APkj,k1, otherwise x j,k0; b is the bandwidth of the millimeter-wave beam; gamma rayj,kForming an interference signal-to-noise ratio of a link for the number k AP and the number j UE; n isbeamNumber of beams that can be used concurrently for each SBS, AP or UE;
Figure BDA00025043170300000610
the power emitted by the wave beam is directed to the UE with the number j for the AP with the number k;
Figure BDA00025043170300000611
maximum transmission power of AP No. k; thetamaxIs the maximum value of the beam width; thetaminIs the minimum value of the beam width;
Figure BDA00025043170300000612
forming a transmission angle of a link for the AP with the UE with the number k and the number j;
Figure BDA00025043170300000613
and forming a receiving angle of a link for the AP with the UE with the number k and the number j.
Solving the optimization model by adopting the following steps so as to obtain a final wireless access result:
a. establishing a mapping sm←ej,kAnd then s ismArranged in descending order to obtain
Figure BDA0002504317030000071
Wherein ej,kEnergy efficiency between the AP # k and the UE # j is obtained;
Figure BDA0002504317030000072
card () represents the number of elements in a collection;
Figure BDA0002504317030000073
a set of all UEs representing all AP associations;
b. fixing the transmitting power matrix P and the beam width matrix A adopted by the beam after the initialization is finished according to the set
Figure BDA0002504317030000074
The links are selected to join the communication network according to the link sequence, and the following judgment is carried out until all the links are selected and the optimization is completed in the current round, so that the optimized beam selection matrix X is obtained*；
If the overall throughput of the communication network is improved after the link is newly added, the link is selected to be added into the communication network; if the whole throughput of the communication network is not improved after the link is newly added, the link is not selected to be added into the communication network;
c. using the optimized beam selection matrix X*And the transmitting power matrix P and the beam width matrix A to be optimized are used for updating the corresponding updated snArranged in descending order to obtain
Figure BDA0002504317030000075
Wherein
Figure BDA0002504317030000076
Indicating the number of links that have joined the communication network;
d. fixing the optimized beam selection matrix X*And a beam width matrix A, in sets
Figure BDA0002504317030000079
The link transmitting power of the link is adjusted in sequence, and the following judgment is carried out until all the links are optimized and the optimization of the current round is completed, so that the optimized transmitting power matrix P is obtained*；
If the whole network throughput is increased after the transmission power is reduced, the transmission power value of the link is continuously reduced; if the overall throughput of the network is not improved after the transmitting power is reduced, stopping power optimization of the link and continuously selecting the next link for optimization;
e. using the optimized beam selection matrix X*Optimized transmission power matrix P*And the beam width matrix A, and the corresponding updated s is newly addedoArranged in descending order to obtain
Figure BDA0002504317030000077
Wherein
Figure BDA0002504317030000078
Indicating the number of links that have joined the communication network;
f. fixing the optimized beam selection matrix X*And optimizing the completed transmit power matrix P*According to a set
Figure BDA0002504317030000081
The link beam width of the link is adjusted in sequence, the link beam width is reduced gradually according to the set descending step length, the following judgment is carried out until all the links are optimized, the optimization of the current round is completed, and the optimized beam width matrix A is obtained*；
If the whole throughput of the network is improved after the beam width is reduced, continuing to reduce the wave width until the minimum value of the link wave width; and if the whole throughput of the network is not improved after the beam width is reduced, stopping the wave width optimization of the link and continuously selecting the next link for optimization.
The BFT-based wireless access method under the millimeter wave cellular network specifically adopts the following steps to calculate and solve:
inputting: maximum transmit power set of input APs
Figure BDA0002504317030000082
Maximum beam width θmaxMinimum beam width θmin；
And (3) outputting: selected beam selection matrix X*Optimized transmit power matrix P for the corresponding selected beam*And the optimized beam width matrix A*；
Step 1.1: calculating the number of UEs to be accessed to the network
Figure BDA0002504317030000083
Step 1.2: obtaining a set of energy efficiency values from a completed BFT stage
Figure BDA0002504317030000084
Step 1.3: initializing a set of transmit powers P of each AP on each beam to
Figure BDA0002504317030000085
Step 1.4: initializing the set of beamwidths A to be { theta }1＝θmax,...,θn＝θmax,...,θN＝θmax}；
Step 1.5: initializing the beam selection set X as { X1＝0,…,xm＝0,…,xM＝0}；
Step 1.6: sequencing single link energy efficiency value set in descending order
Figure BDA0002504317030000086
And are stored in turn into
Figure BDA0002504317030000087
In (1), a mapping s is establishedm←ej,k；
Step 1.7: setting a priority counting variable m to be 1, and calculating the throughput of the whole network
Figure BDA0002504317030000091
And selecting the beam with variable xmSetting as 1;
step 1.8: judging whether M is smaller than M: if yes, entering step 1.9, otherwise, entering step 1.13;
step 1.9: after the value of the priority counting variable m is increased by 1, the throughput of the whole network is calculated
Figure BDA0002504317030000092
Step 1.10: judging the throughput R of the whole network after adding a new linkmWhether to promote: if yes, entering step 1.11; otherwise, entering step 1.12;
step 1.11: selecting variable x for beammAfter placing 1, entering step 1.13;
step 1.12: selecting variable x for beammAfter setting to 0, entering step 1.8;
step 1.13: set of beams that have been selected { x }1,…,xm,…,xMUpdate to X;
step 1.14: calculating the number of links joining a network
Figure BDA0002504317030000093
Step 1.15: updating link energy efficiency value set by utilizing X, P and A
Figure BDA0002504317030000094
Step 1.16: sorting link energy efficiency value sets in descending order
Figure BDA0002504317030000095
And are stored in turn into
Figure BDA0002504317030000096
In (1), a mapping s is establishedn←ej,k；
Step 1.17: setting maximum transmit power on each link of an AP
Figure BDA0002504317030000097
And minimum emissivity
Figure BDA0002504317030000098
Initializing the set q with the transmit power value in P1,...,qn,...,qN}；
Step 1.18: optimizing per-link transmit power set q of an AP1,...,qn,...,qN}；
Step 1.19: the transmitting power of each link of the optimized AP is aggregated to be q1,...,qn,...,qNUpdating to P;
step 1.20: updating link energy efficiency value set by utilizing X, P and A
Figure BDA0002504317030000099
Step 1.21: sorting link energy efficiency value sets in descending order
Figure BDA00025043170300000910
And are stored in turn into
Figure BDA00025043170300000911
In (1), a mapping s is establishedo←ej,k；
Step 1.22: set the maximum beam width max to θmaxMinimum beam width min ═ θminInitializing set { q ] with the initialization beamwidth in set A1,...,qn,...,qN}；
Step 1.23: optimizing a set of beamwidthsQ is closed { q1,...,qn,...,qN}；
Step 1.24: the optimized beam width set q1,...,qn,...,qNUpdate to a.
Step 1.18 said optimizing each link transmit power set { q ] of the AP1,...,qn,...,qNAnd the set of optimized beamwidths { q } described in step 1.231,...,qn,...,qNAnd optimizing by adopting the following steps:
inputting: maximum value max of transmitting power or beam width of each link of the AP, and minimum value min of transmitting power or beam width of each link of the AP;
and (3) outputting: optimizing each link transmission power or beam width set { q ] of the finished AP1,...,qn,...,qN}；
Step 2.1: setting a priority counting variable n as 1, and calculating the throughput of the whole network
Figure BDA0002504317030000101
And q isnThe value is max;
step 2.2: judging whether N is smaller than N: if yes, entering step 2.3, otherwise, entering step 2.8;
step 2.3: increasing the value of the priority count variable n by 1;
step 2.4: decreasing q according to step sizenA value of (d);
step 2.5: computing overall network throughput
Figure BDA0002504317030000102
Step 2.6: judging q of decreasing corresponding value by step length of descendingnWhether or not the throughput R of the whole network can still be improvedn: if yes, entering step 2.7; otherwise, entering step 2.2;
step 2.7: judging qnWhether the average value is more than min: if yes, entering step 2.4, otherwise entering step 2.2;
step 2.8: the algorithm ends.
The invention also provides a communication method comprising the wireless access method based on BFT under the millimeter wave cellular network, in particular to MBS, SBS, AP and UE which communicate according to the calculation result of the wireless access method based on BFT under the millimeter wave cellular network, thereby completing the communication between MBS, SBS, AP and UE.
The wireless access method and the communication method based on BFT under the millimeter wave cellular network can reduce the workload of a summary node in the BFT process, and can obviously reduce the communication cost in the BFT process, so that the reduction of the communication cost is changed in multiples along with the change of the scale of a communication network, and finally, a BFT mechanism can adapt to the increase of the scale of the communication network; the method can adjust the wave beam direction, the wave beam width and the node transmission power of the nodes in the communication network, and reduce the interference between the nodes in the communication process as much as possible; the method of the invention promotes the whole network throughput based on the DRPC priority strategy and reduces the energy consumption in the communication network as much as possible; finally, the method of the invention can obviously improve the average energy efficiency value and the average throughput of a single link in the communication network.
Drawings
Fig. 1 is a flowchart illustrating a method of a wireless access method according to the present invention.
Fig. 2 is a schematic diagram of a millimeter wave cellular network topology of the present invention.
Fig. 3 is a schematic diagram illustrating a load variation trend of the BFT process according to the UE number in the radio access method of the present invention.
Fig. 4 is a schematic diagram illustrating a variation trend of the energy efficiency value of a single link according to the number of UEs in the wireless access method of the present invention.
Fig. 5 is a schematic diagram illustrating a variation trend of throughput of a single link according to a variation of the number of UEs in the wireless access method of the present invention.
Fig. 6 is a flowchart illustrating a communication method according to the present invention.
Detailed Description
Fig. 1 is a schematic flow chart of a method of a wireless access method according to the present invention: the BFT-based wireless access method under the millimeter wave cellular network provided by the invention adopts a three-layer BFT mechanism to realize the BFT of MBS and surrounding SBSs, the BFT of each SBS and surrounding APs thereof and the BFT of each AP and surrounding UEs thereof.
The BFT of the MBS and the surrounding SBSs specifically comprises the following steps:
A1. a training request sending stage: the MBS transmits a training request beacon frame in all corresponding beams simultaneously so as to start a training process between the MBS and the SBS;
B1. waiting for a training response stage: each SBS receiving the training request beacon frame randomly selects a response time slot, so that the training response beacon frames are transmitted in all corresponding beams at the same time;
C1. and a response conflict processing stage: judging whether response conflict occurs:
if no response beacon frame collision occurs, the step is finished;
if the conflict of the response beacon frame occurs, the MBS retransmits the training request beacon frame in the wave beam with the conflict event; meanwhile, in the retransmitted training request beacon frame, the number of response time slots is doubled, so that the collision probability is reduced;
D1. and (3) publishing a training result: the MBS estimates the optimal beam through the corresponding training response beacon frame information using the SBS information that successfully transmitted the training response beacon frame, and publishes the estimated optimal beam by transmitting a "publish training result frame".
The BFT of SBS and APs around it includes the following steps:
A2. a training request sending stage: the SBS sends training request beacon frames in all corresponding beams simultaneously to start a training process between the SBS and the AP;
B2. waiting for a training response stage: each AP receiving the training request beacon frame randomly selects a response time slot, so that the training response beacon frames are transmitted in all corresponding beams at the same time;
C2. and a response conflict processing stage: judging whether response conflict occurs:
if no response beacon frame collision occurs, the step is finished;
if the conflict of the response beacon frames occurs, the SBS retransmits the training request beacon frames in the beams with the conflict events; meanwhile, in the retransmitted training request beacon frame, the number of response time slots is doubled, so that the collision probability is reduced;
the SBS analyzes the response beacon frame received by the SBS from the AP to obtain a result to be published; sending a result to be published to the MBS;
the MBS compares, analyzes and determines the AP which each SBS should be associated with according to the received to-be-published results of all SBS, and feeds back the result to each SBS;
F2. and (3) publishing a training result: the SBS estimates an optimal beam through corresponding training response beacon frame information according to received AP information associated with itself, and publishes the estimated optimal beam by transmitting a "publish training result frame".
The method specifically comprises the following steps of:
A3. a training request sending stage: the AP sends a training request beacon frame in all corresponding beams simultaneously to start a training process between the AP and the UE;
B3. waiting for a training response stage: each UE receiving the training request beacon frame randomly selects a response time slot, so that the training response beacon frames are transmitted in all corresponding beams at the same time;
C3. and a response conflict processing stage: judging whether response conflict occurs:
if no response beacon frame collision occurs, the step is finished;
if the response beacon frame conflicts, the AP retransmits the training request beacon frame in the wave beam with the conflict event; meanwhile, in the retransmitted training request beacon frame, the number of response time slots is doubled, so that the collision probability is reduced;
d3, the AP analyzes the response beacon frame received by the AP from the UE and obtains a result to be published; sending the result to be published to the SBS associated with the result to be published;
the SBS compares, analyzes and determines the UE which each AP should be associated with according to the received results to be published of all the APs, and feeds back the results to each AP;
F3. and (3) publishing a training result: the AP estimates the optimal beam through corresponding training response beacon frame information according to the received UE information associated with the AP, and publishes the estimated optimal beam by sending a 'publish training result frame'.
Through the steps, only the transmitting BFT process of the SBS, the AP and the UE is completed, but the receiving BFT process of the SBS, the AP and the UE is not completed; receiving a BFT may be accomplished in a manner similar to transmitting a BFT, according to the document "When mm wave communication network localization" available interference coordination.
The three-layer BFT mechanism provided by the invention effectively reduces the communication cost in the training process, and specifically comprises the following steps:
the total number of training frames required for the proposed efficient three-layer BFT mechanism should be at least:
Figure BDA0002504317030000141
in the formula nbeamThe number of beams which can be used concurrently for each SBS, AP and UE respectively; i ismThe number of SBS can be directly connected with MBS through millimeter wave link; i is the number of all SBS distributed within the macrocell; i isk(ii) SBS number in response to the kth AP; k is the number of all APs distributed in the macrocell; kjResponding to the AP number of the j UE;
the present invention considers the RRM problem as a constrained mathematical optimization problem: assuming that the UE does not have multi-connection capability, the UE can only connect to one AP at a time in a dense mmwave cellular network; x is to bej,kSetting the epsilon {0,1} as a binary association variable; if it is not
Figure BDA0002504317030000142
Is connected to
Figure BDA0002504317030000143
X is thenj,k1 is ═ 1; otherwise xj,k0; the kth AThe throughput of the link formed by P and the jth UE can be estimated by:
rj,k＝xj,kB log2(1+γj,k)
in the formula, gammaj,kForming an interference signal-to-noise ratio of a link for the number k AP and the number j UE; b is the bandwidth of the millimeter-wave beam;
the throughput of the overall network can be estimated by:
Figure BDA0002504317030000151
meanwhile, to maximize the overall network throughput in the above equation, the RRM-free problem for downlink unicast communication can be converted into the following optimization problem:
Figure BDA0002504317030000152
Figure BDA0002504317030000153
in the formula
Figure BDA0002504317030000154
Is a set of J UEs
Figure BDA0002504317030000155
Figure BDA0002504317030000156
As a set of K APs
Figure BDA0002504317030000157
X is a beam selection matrix; p is a transmitting power matrix adopted by the wave beam; a is a beam width matrix; r isj,kThroughput of the link formed for the kth AP and the jth UE, and rj,k＝xj,kB log2(1+γj,k)；xj,kIs a binary associated variable, and x if UEj is connected to APkj,k1, otherwise xj,k0; b is the bandwidth of the millimeter-wave beam; gamma rayj,kForming an interference signal-to-noise ratio of a link for the number k AP and the number j UE; n isbeamNumber of beams that can be used concurrently for each SBS, AP or UE;
Figure BDA0002504317030000158
the power emitted by the wave beam is directed to the UE with the number j for the AP with the number k;
Figure BDA0002504317030000159
maximum transmission power of AP No. k; thetamaxIs the maximum value of the beam width; thetaminIs the minimum value of the beam width;
Figure BDA00025043170300001510
forming a transmission angle of a link for the AP with the UE with the number k and the number j;
Figure BDA0002504317030000161
forming a receiving angle of a link for the number k AP and the number j UE;
in particular, constraint C2Indicating that each UE can only connect to one AP; constraint C3Indicating that the number of UEs that can be served by the AP is guaranteed not to exceed nbeam(ii) a Constraint C4Indicating that the power consumption constraint of each AP cannot be exceeded
Figure BDA0002504317030000162
Constraint C5Meaning that the beam width is limited to [ theta ]min,θmax](ii) a Constraint C6Means that for the AP, the sum of the beam widths used to serve the connected UEs cannot exceed 2 pi, given that the beam coverage of each node is required to be non-overlapping;
meanwhile, the invention provides a three-layer BFT information-based RRM algorithm to solve the problems so as to reduce interference and improve the energy efficiency of the dense millimeter wave cellular network; since the path loss of the millimeter wave band is severe and the transmission power is limited in practical cases, the UE may not receive signals from all APs in the network by observing the receiving Bit Error Rate (BER)It is determined whether a direct communication link exists between the UE (e.g., j) and the AP (e.g., k). To obtain acceptable BER values (e.g.
Figure BDA0002504317030000163
) And corresponding signal-to-interference plus noise ratio (SINR) value (e.g., SINR)
Figure BDA0002504317030000164
) The approximate relational expression between:
Figure BDA0002504317030000165
to ensure that the BER value of the j UE receiving data from the k AP is not higher than
Figure BDA0002504317030000166
The transmission power of the AP with the number k should not be lower than
Figure BDA0002504317030000167
Can be estimated by the following equation:
Figure BDA0002504317030000168
if gamma isj,kNot less than
Figure BDA0002504317030000169
We consider that there is a directional communication link from AP number k to UE number j; for number k
Figure BDA00025043170300001610
Each j number of the candidate UEs of
Figure BDA00025043170300001611
Quality of the directional link with AP # k (e.g., γ)j,k) Should be greater than a predefined threshold (e.g.,
Figure BDA00025043170300001612
) Where the set of candidate UEs for AP # k is denoted as
Figure BDA00025043170300001613
Therefore, the above model can be optimized, resulting in the following optimized model:
Figure BDA0002504317030000171
Figure BDA0002504317030000172
in the formula
Figure BDA0002504317030000173
A set of candidate UEs being AP # k;
Figure BDA0002504317030000174
as a set of K APs
Figure BDA0002504317030000175
X is a beam selection matrix; p is a transmitting power matrix adopted by the wave beam; a is a beam width matrix; r isj,kThroughput of the link formed for the kth AP and the jth UE, and rj,k＝xj,kB log2(1+γj,k)；xj,kIs a binary associated variable, and x if UEj is connected to APkj,k1, otherwise xj,k0; b is the bandwidth of the millimeter-wave beam; gamma rayj,kForming an interference signal-to-noise ratio of a link for the number k AP and the number j UE; n isbeamNumber of beams that can be used concurrently for each SBS, AP or UE;
Figure BDA0002504317030000176
the power emitted by the wave beam is directed to the UE with the number j for the AP with the number k;
Figure BDA0002504317030000177
maximum transmission power of AP No. k; thetamaxIs the maximum value of the beam width；θminIs the minimum value of the beam width;
Figure BDA0002504317030000178
forming a transmission angle of a link for the AP with the UE with the number k and the number j;
Figure BDA0002504317030000179
and forming a receiving angle of a link for the AP with the UE with the number k and the number j.
Solving the optimization model by adopting the following steps so as to obtain a final wireless access result:
in the present invention, considering that measuring channel quality directly using SNR is not always an effective method, and therefore considering that DRPC is used to measure channel quality to better reflect the energy-efficient target pursued by the next generation wireless network, the value of DRPC can be estimated by the following formula:
Figure BDA00025043170300001710
in the formula ej,kRepresenting the energy efficiency, P, between AP # k and UE # jRFRepresents the energy loss of the radio frequency link, here set to a value of 0.0344 watts; because the optimized model is an NP difficult problem and has non-convexity, the target optimization problem is decomposed into sub-problems to be solved, and the optimal solution is solved by using the sub-problem optimization result; the method specifically comprises the following steps:
a. establishing a mapping sm←ej,kAnd then s ismArranged in descending order to obtain
Figure BDA0002504317030000181
Wherein ej,kEnergy efficiency between the AP # k and the UE # j is obtained;
Figure BDA0002504317030000182
card () represents the number of elements in a collection;
Figure BDA0002504317030000183
a set of all UEs representing all AP associations;
b. fixing the transmitting power matrix P and the beam width matrix A adopted by the beam after the initialization is finished according to the set
Figure BDA0002504317030000184
The links are selected to join the communication network according to the link sequence, and the following judgment is carried out until all the links are selected and the optimization is completed in the current round, so that the optimized beam selection matrix X is obtained*；
If the overall throughput of the communication network is improved after the link is newly added, the link is selected to be added into the communication network; if the whole throughput of the communication network is not improved after the link is newly added, the link is not selected to be added into the communication network;
c. using the optimized beam selection matrix X*And the transmitting power matrix P and the beam width matrix A to be optimized are used for updating the corresponding updated snArranged in descending order to obtain
Figure BDA0002504317030000185
Wherein
Figure BDA0002504317030000186
Indicating the number of links that have joined the communication network;
d. fixing the optimized beam selection matrix X*And a beam width matrix A, in sets
Figure BDA0002504317030000187
The link transmitting power of the link is adjusted in sequence, and the following judgment is carried out until all the links are optimized and the optimization of the current round is completed, so that the optimized transmitting power matrix P is obtained*；
If the whole network throughput is increased after the transmission power is reduced, the transmission power value of the link is continuously reduced; if the overall throughput of the network is not improved after the transmitting power is reduced, stopping power optimization of the link and continuously selecting the next link for optimization;
e. using the optimized beam selection matrix X*Optimized transmission power matrix P*And the beam width matrix A, and the corresponding updated s is newly addedoArranged in descending order to obtain
Figure BDA0002504317030000191
Wherein
Figure BDA0002504317030000192
Indicating the number of links that have joined the communication network;
f. fixing the optimized beam selection matrix X*And optimizing the completed transmit power matrix P*According to a set
Figure BDA0002504317030000193
The link beam width of the link is adjusted in sequence, the link beam width is reduced gradually according to the set descending step length, the following judgment is carried out until all the links are optimized, the optimization of the current round is completed, and the optimized beam width matrix A is obtained*；
If the whole throughput of the network is improved after the beam width is reduced, continuing to reduce the wave width until the minimum value of the link wave width; and if the whole throughput of the network is not improved after the beam width is reduced, stopping the wave width optimization of the link and continuously selecting the next link for optimization.
The above process, described in the algorithm, is calculated and solved by adopting the following steps:
inputting: maximum transmit power set of input APs
Figure BDA0002504317030000194
Maximum beam width θmaxMinimum beam width θmin；
And (3) outputting: selected beam selection matrix X*Optimized transmit power matrix P for the corresponding selected beam*And the optimized beam width matrix A*；
Step 1.1: calculating the number of UEs to be accessed to the network
Figure BDA0002504317030000195
Step 1.2: obtaining a set of energy efficiency values from a completed BFT stage
Figure BDA0002504317030000196
Step 1.3: initializing a set of transmit powers P of each AP on each beam to
Figure BDA0002504317030000197
Step 1.4: initializing the set of beamwidths A to be { theta }1＝θmax,...,θn＝θmax,...,θN＝θmax}；
Step 1.5: initializing the beam selection set X as { X1＝0,…,xm＝0,…,xM＝0}；
Step 1.6: sequencing single link energy efficiency value set in descending order
Figure BDA0002504317030000198
And are stored in turn into
Figure BDA0002504317030000201
In (1), a mapping s is establishedm←ej,k；
Step 1.7: setting a priority counting variable m to be 1, and calculating the throughput of the whole network
Figure BDA0002504317030000202
And selecting the beam with variable xmSetting as 1;
step 1.8: judging whether M is smaller than M: if yes, entering step 1.9, otherwise, entering step 1.13;
step 1.9: after the value of the priority counting variable m is increased by 1, the throughput of the whole network is calculated
Figure BDA0002504317030000203
Step 1.10: judging the throughput R of the whole network after adding a new linkmWhether to promote: if yes, entering step 1.11; otherwise, entering step 1.12;
step 1.11: selecting variable x for beammAfter placing 1, entering step 1.13;
step 1.12: selecting variable x for beammAfter setting to 0, entering step 1.8;
step 1.13: set of beams that have been selected { x }1,…,xm,…,xMUpdate to X;
step 1.14: calculating the number of links joining a network
Figure BDA0002504317030000204
Step 1.15: updating link energy efficiency value set by utilizing X, P and A
Figure BDA0002504317030000205
Step 1.16: sorting link energy efficiency value sets in descending order
Figure BDA0002504317030000206
And are stored in turn into
Figure BDA0002504317030000207
In (1), a mapping s is establishedn←ej,k；
Step 1.17: setting maximum transmit power on each link of an AP
Figure BDA0002504317030000208
And minimum emissivity
Figure BDA0002504317030000209
Initializing the set q with the transmit power value in P1,...,qn,...,qN}；
Step 1.18: optimizing per-link transmit power set q of an AP1,...,qn,...,qN}；
Step 1.19: the transmitting power of each link of the optimized AP is aggregated{q1,...,qn,...,qNUpdating to P;
step 1.20: updating link energy efficiency value set by utilizing X, P and A
Figure BDA00025043170300002010
Step 1.21: sorting link energy efficiency value sets in descending order
Figure BDA0002504317030000211
And are stored in turn into
Figure BDA0002504317030000212
In (1), a mapping s is establishedo←ej,k；
Step 1.22: set the maximum beam width max to θmaxMinimum beam width min ═ θminInitializing set { q ] with the initialization beamwidth in set A1,...,qn,...,qN}；
Step 1.23: optimized set of beamwidths q1,...,qn,...,qN}；
Step 1.24: the optimized beam width set q1,...,qn,...,qNUpdate to a.
Step 1.18 said optimizing each link transmit power set { q ] of the AP1,...,qn,...,qNAnd the set of optimized beamwidths { q } described in step 1.231,...,qn,...,qNAnd optimizing by adopting the following steps:
inputting: maximum value max of transmitting power or beam width of each link of the AP, and minimum value min of transmitting power or beam width of each link of the AP;
and (3) outputting: optimizing each link transmission power or beam width set { q ] of the finished AP1,...,qn,...,qN}；
Step 2.1: setting a priority counting variable n as 1, and calculating the throughput of the whole network
Figure BDA0002504317030000213
And q isnThe value is max;
step 2.2: judging whether N is smaller than N: if yes, entering step 2.3, otherwise, entering step 2.8;
step 2.3: increasing the value of the priority count variable n by 1;
step 2.4: decreasing q according to step sizenA value of (d);
step 2.5: computing overall network throughput
Figure BDA0002504317030000214
Step 2.6: judging q of decreasing corresponding value by step length of descendingnWhether or not the throughput R of the whole network can still be improvedn: if yes, entering step 2.7; otherwise, entering step 2.2;
step 2.7: judging qnWhether the average value is more than min: if yes, entering step 2.4, otherwise entering step 2.2;
step 2.8: the algorithm ends.
The process of the invention is further illustrated below with reference to one example:
as shown in fig. 2, considering a circular plane simulation area with a radius of 300m, the MBS is located at the center of the plane; meanwhile, SBS takes MBS as the centre and distributes on the circular ring with radius of 200m evenly; the APs are uniformly distributed on a group of circular rings with the radius of 60m by taking each SBS as a center; the UEs are uniformly distributed in a ring area with a radius of 100m to 300m centered on the MBS. We consider two types of communication links, namely line-of-sight (LOS) links and non-line-of-sight (NLOS) links.
In the experiment, the number of SBS was set to 4 and the number of APs was set to 16. Further, the reduction step sizes of the power and the beam width are respectively set to one percent of their maximum values. With the number of beams of each type set to 12. Based on these parameter settings, the performance of the inventive scheme is compared with the performance of the comparison scheme by changing the number of UEs in a given area.
In the simulation process, the comparison algorithm is a variant scheme Based on the core idea of the algorithm in the document 'Deep Learning-Based Beam Management and optimization algorithm in density wave Networks', except that the transformation of the priority strategy in the RRM algorithm and the definition of the optimization algorithm subproblem adopt the definition of the invention, the other algorithms follow the idea in the document. The performance indicators used in the evaluation are the average energy efficiency and average throughput for a single link and the communication cost for all BFT procedures.
The signal strength propagation model on the millimeter wave channel adopted by the simulation is as follows:
Figure BDA0002504317030000221
in the formula
Figure BDA0002504317030000222
The power transmitted by the AP with the number k to the UE with the number j is the power transmitted by the directional wave beam;
Figure BDA0002504317030000223
when the single link of the number k AP has the transmission power of
Figure BDA0002504317030000224
Then, the power received by UE # j;
Figure BDA0002504317030000225
and
Figure BDA0002504317030000226
respectively obtaining a ph path directional transmitting gain and a ph path directional receiving gain;
Figure BDA0002504317030000227
is the channel gain between AP No. k and UE No. j on path ph. When the beam between AP No. k and UE No. j is aligned, the transmit gain and receive gain may be estimated by:
Figure BDA0002504317030000231
in the formula
Figure BDA0002504317030000232
Is the wave width of the sender;
Figure BDA0002504317030000233
is the wave width of the receiving party and,
Figure BDA0002504317030000234
is the side lobe of the gain and is taken to be a positive number much less than 1. The channel gain can be estimated by:
Figure BDA0002504317030000235
wherein δ () is a dirac function;
Figure BDA0002504317030000236
and
Figure BDA0002504317030000237
the propagation delay and amplitude between the path ph from the AP to the UE are respectively k and j;
the propagation delay and amplitude can be obtained by the following equations, respectively:
Figure BDA0002504317030000238
Figure BDA0002504317030000239
in the formula dj,kIs the distance from AP # k to UE # j; c is the speed of light; λ is the wavelength and λ ═ c/fc，fcIs the carrier frequency, Γ is the reflection coefficient of the millimeter wave reflection path; it can be seen that when the AP No. k communicates with the UE No. j in a Non Line of Sight (NLOS) manner, the amplitude is also related to the path loss and the reflection coefficient;
the simulation adopts an interference signal intensity propagation model on a millimeter wave channel as follows:
Figure BDA00025043170300002310
in the formula
Figure BDA00025043170300002311
The power transmitted by AP of k 'to UE of j' is the power of directional beam;
Figure BDA00025043170300002312
is that j UE receives from other APs (e.g., K' e [ 1.,. K-1.,. K + 1.,. K.)]) With other UEs (e.g., J' e [ 1., J-1, J + 1., J.)]) The interference power of (a);
Figure BDA0002504317030000241
and
Figure BDA0002504317030000242
respectively obtaining a ph path directional transmitting gain and a ph path directional receiving gain;
wherein the specific directional transmit-receive gain can be estimated by:
Figure BDA0002504317030000243
wherein the condition A is
Figure BDA0002504317030000244
And
Figure BDA0002504317030000245
condition B is
Figure BDA0002504317030000246
And
Figure BDA0002504317030000247
condition C is
Figure BDA0002504317030000248
And
Figure BDA0002504317030000249
condition D is
Figure BDA00025043170300002410
And
Figure BDA00025043170300002411
wherein the content of the first and second substances,
Figure BDA00025043170300002412
is the deviation angle of the connecting direction of the AP and the UE with the number j relative to the central line of the transmitting beam for transmitting data to the UE with the number j from the AP with the number k
Figure BDA00025043170300002413
The deviation angle of the connecting line direction of the number k' AP and the number j UE relative to the central line of the receiving beam of the number j UE for receiving data from the number k AP is shown; SINR value gamma between UE # j and AP # kj,kCan be estimated by the following equation:
Figure BDA00025043170300002414
where B is the millimeter wave link bandwidth, NoIs the ambient noise power density;
the main simulation parameters are shown in the following table 1
TABLE 1 simulation parameters
Figure BDA0002504317030000251
The above scheme is implemented on an OMNeT + +4.6 network simulation platform, and the results shown in FIGS. 3 to 5 are obtained. As can be seen in fig. 3, the overhead of BFT increases as the number of UEs in a given area increases. The main reason is that more UEs need more training frames. As can also be seen from fig. 3, the proposed algorithm saves more BFT overhead than the comparative algorithm, and as the number of UEs increases, more overhead is saved. The main reason is that the layered BFT mechanism proposed by the present invention allows multiple SBS to participate in the analysis of the training result announcement frame, rather than being assumed by a single MBS, and reduces the total amount of training frames while avoiding sending invalid result announcement frames.
As can be seen from fig. 4 and 5, the variation of the number of UEs has little influence on the average energy efficiency and average throughput of a single link, and the influence is random. This is because the mutual interference between nodes may vary randomly due to the difference in the number and location distribution of UEs. Meanwhile, the scheme provided by the invention is superior to a comparison scheme in terms of average energy efficiency and average throughput of a single link. The reason for this phenomenon is mainly the result of the proposed scheme prioritizing radio access link selection based on DRPC.
Fig. 6 is a schematic method flow diagram of the communication method of the present invention: the communication method comprising the BFT-based wireless access method under the millimeter wave cellular network, provided by the invention, is characterized in that MBS, SBS, AP and UE communicate according to the calculation result of the BFT-based wireless access method under the millimeter wave cellular network, thereby completing the communication among MBS, SBS, AP and UE.

Claims (6)

1. A wireless access method based on BFT under millimeter wave cellular network is characterized in that a three-layer BFT mechanism is adopted to realize BFT of MBS and SBSs around, BFT of each SBS and APs around, and BFT of each AP and UEs around;
the BFT of the MBS and the surrounding SBSs specifically comprises the following steps:
A1. a training request sending stage: the MBS transmits a training request beacon frame in all corresponding beams simultaneously so as to start a training process between the MBS and the SBS;
B1. waiting for a training response stage: each SBS receiving the training request beacon frame randomly selects a response time slot, so that the training response beacon frames are transmitted in all corresponding beams at the same time;
C1. and a response conflict processing stage: judging whether response conflict occurs:
if no response beacon frame collision occurs, the step is finished;
if the conflict of the response beacon frame occurs, the MBS retransmits the training request beacon frame in the wave beam with the conflict event; meanwhile, in the retransmitted training request beacon frame, the number of response time slots is doubled, so that the collision probability is reduced;
D1. and (3) publishing a training result: the MBS estimates the optimal beam by using SBS information which successfully sends a training response beacon frame and through corresponding training response beacon frame information, and publishes the estimated optimal beam by sending a 'publish training result frame';
the BFT of the SBS and the APs around the SBS specifically comprises the following steps:
A2. a training request sending stage: the SBS sends training request beacon frames in all corresponding beams simultaneously to start a training process between the SBS and the AP;
B2. waiting for a training response stage: each AP receiving the training request beacon frame randomly selects a response time slot, so that the training response beacon frames are transmitted in all corresponding beams at the same time;
C2. and a response conflict processing stage: judging whether response conflict occurs:
if no response beacon frame collision occurs, the step is finished;
if the conflict of the response beacon frames occurs, the SBS retransmits the training request beacon frames in the beams with the conflict events; meanwhile, in the retransmitted training request beacon frame, the number of response time slots is doubled, so that the collision probability is reduced;
the SBS analyzes the response beacon frame received by the SBS from the AP to obtain a result to be published; sending a result to be published to the MBS;
the MBS compares, analyzes and determines the AP which each SBS should be associated with according to the received to-be-published results of all SBS, and feeds back the result to each SBS;
F2. and (3) publishing a training result: the SBS estimates the optimal beam through corresponding training response beacon frame information according to the received AP information associated with the SBS, and publishes the estimated optimal beam by sending a 'publish training result frame';
the BFT of the AP and surrounding UEs thereof specifically comprises the following steps:
A3. a training request sending stage: the AP sends a training request beacon frame in all corresponding beams simultaneously to start a training process between the AP and the UE;
B3. waiting for a training response stage: each UE receiving the training request beacon frame randomly selects a response time slot, so that the training response beacon frames are transmitted in all corresponding beams at the same time;
C3. and a response conflict processing stage: judging whether response conflict occurs:
if no response beacon frame collision occurs, the step is finished;
if the response beacon frame conflicts, the AP retransmits the training request beacon frame in the wave beam with the conflict event; meanwhile, in the retransmitted training request beacon frame, the number of response time slots is doubled, so that the collision probability is reduced;
d3, the AP analyzes the response beacon frame received by the AP from the UE and obtains a result to be published; sending the result to be published to the SBS associated with the result to be published;
the SBS compares, analyzes and determines the UE which each AP should be associated with according to the received results to be published of all the APs, and feeds back the results to each AP;
F3. and (3) publishing a training result: the AP estimates the optimal beam through corresponding training response beacon frame information according to the received UE information associated with the AP, and publishes the estimated optimal beam by sending a 'publish training result frame';
in specific implementation, the BFT-based wireless access method in the millimeter wave cellular network specifically solves the following model, so as to obtain a final wireless access result:
Figure FDA0003520302840000031
Figure FDA0003520302840000032
in the formula
Figure FDA0003520302840000033
Is a set of J UEs
Figure FDA0003520302840000034
As a set of K APs
Figure FDA0003520302840000035
X is a beam selection matrix; p is a transmitting power matrix adopted by the wave beam; a is a beam width matrix; r isj,kThroughput of the link formed for the kth AP and the jth UE, and rj,k＝xj,kBlog2(1+γj,k)；xj,kIs a binary associated variable, and x if UEj is connected to APkj,k1, otherwise xj,k0; b is the bandwidth of the millimeter-wave beam; gamma rayj,kForming an interference signal-to-noise ratio of a link for the number k AP and the number j UE; n isbeamNumber of beams that can be used concurrently for each SBS, AP or UE;
Figure FDA0003520302840000036
the power emitted by the wave beam is directed to the UE with the number j for the AP with the number k;
Figure FDA0003520302840000037
maximum transmission power of AP No. k; thetamaxIs the maximum value of the beam width; thetaminIs the minimum value of the beam width;
Figure FDA0003520302840000041
forming a transmission angle of a link for the AP with the UE with the number k and the number j;
Figure FDA0003520302840000042
and forming a receiving angle of a link for the AP with the UE with the number k and the number j.
2. The BFT-based wireless access method of claim 1, wherein the model is optimized to obtain the following optimized model:
Figure FDA0003520302840000043
Figure FDA0003520302840000044
in the formula
Figure FDA0003520302840000045
A set of candidate UEs being AP # k;
Figure FDA0003520302840000046
as a set of K APs
Figure FDA0003520302840000047
X is a beam selection matrix; p is a transmitting power matrix adopted by the wave beam; a is a beam width matrix; r isj,kThroughput of the link formed for the kth AP and the jth UE, and rj,k＝xj,kBlog2(1+γj,k)；xj,kIs a binary associated variable, and x if UEj is connected to APkj,k1, otherwise xj,k0; b is the bandwidth of the millimeter-wave beam; gamma rayj,kForming an interference signal-to-noise ratio of a link for the number k AP and the number j UE; n isbeamNumber of beams that can be used concurrently for each SBS, AP or UE;
Figure FDA0003520302840000048
the power emitted by the wave beam is directed to the UE with the number j for the AP with the number k;
Figure FDA0003520302840000049
maximum transmission power of AP No. k; thetamaxIs the maximum value of the beam width; thetaminIs the minimum value of the beam width;
Figure FDA00035203028400000410
forming a transmission angle of a link for the AP with the UE with the number k and the number j;
Figure FDA00035203028400000411
and forming a receiving angle of a link for the AP with the UE with the number k and the number j.
3. The BFT-based wireless access method under the millimeter wave cellular network according to claim 2, wherein the following steps are adopted to solve the optimization model, thereby obtaining the final wireless access result:
a. establishing a mapping sm←ej,kAnd then s ismArranged in descending order to obtain
Figure FDA0003520302840000051
Wherein ej,kEnergy efficiency between the AP # k and the UE # j is obtained;
Figure FDA0003520302840000052
card () represents the number of elements in a collection;
Figure FDA0003520302840000053
a set of all UEs representing all AP associations;
b. fixing the transmitting power matrix P and the beam width matrix A adopted by the beam after the initialization is finished according to the set
Figure FDA0003520302840000054
The links are selected to join the communication network according to the link sequence, and the following judgment is carried out until all the links are selected and the optimization is completed in the current round, so that the optimized beam selection matrix X is obtained*；
If the overall throughput of the communication network is improved after the link is newly added, the link is selected to be added into the communication network; if the whole throughput of the communication network is not improved after the link is newly added, the link is not selected to be added into the communication network;
c. using the optimized beam selection matrix X*And the transmitting power matrix P and the beam width matrix A to be optimized are used for updating the corresponding updated snArranged in descending order to obtain
Figure FDA0003520302840000055
Wherein
Figure FDA0003520302840000056
Indicating the number of links that have joined the communication network;
d. fixing the optimized beam selection matrix X*And a beam width matrix A, in sets
Figure FDA0003520302840000057
The link transmitting power of the link is adjusted in sequence, and the following judgment is carried out until all the links are optimized and the optimization of the current round is completed, so that the optimized transmitting power matrix P is obtained*；
If the whole network throughput is increased after the transmission power is reduced, the transmission power value of the link is continuously reduced; if the overall throughput of the network is not improved after the transmitting power is reduced, stopping power optimization of the link and continuously selecting the next link for optimization;
e. using the optimized beam selection matrix X*Optimized transmission power matrix P*And the beam width matrix A, and the corresponding updated s is newly addedoArranged in descending order to obtain
Figure FDA0003520302840000058
Wherein
Figure FDA0003520302840000059
Indicating the number of links that have joined the communication network;
f. fixing the optimized beam selection matrix X*And optimizing the completed transmit power matrix P*According to a set
Figure FDA0003520302840000061
The link beam width of the link is adjusted in sequence, the link beam width is reduced gradually according to the set descending step length, the following judgment is carried out until all the links are optimized, the optimization of the current round is completed, and the optimized beam width matrix A is obtained*；
If the whole throughput of the network is improved after the beam width is reduced, continuing to reduce the wave width until the minimum value of the link wave width; and if the whole throughput of the network is not improved after the beam width is reduced, stopping the wave width optimization of the link and continuously selecting the next link for optimization.
4. The BFT-based wireless access method of claim 3, wherein the BFT-based wireless access method of the mmwave cellular network specifically comprises the following steps:
inputting: maximum transmit power set of input APs
Figure FDA0003520302840000062
Maximum beam width θmaxMinimum beam width θmin；
And (3) outputting: selected beam selection matrix X*Optimized transmit power matrix P for the corresponding selected beam*And the optimized beam width matrix A*；
Step 1.1: calculating the number of UEs to be accessed to the network
Figure FDA0003520302840000063
Step 1.2: obtaining a set of energy efficiency values from a completed BFT stage
Figure FDA0003520302840000064
Step 1.3: initializing a set of transmit powers P of each AP on each beam to
Figure FDA0003520302840000065
Step 1.4: initializing the set of beamwidths A to be { theta }1＝θmax,...,θn＝θmax,...,θN＝θmax}；
Step 1.5: initializing the beam selection set X as { X1＝0,…,xm＝0,…,xM＝0}；
Step 1.6: sequencing single link energy efficiency value set in descending order
Figure FDA0003520302840000066
And are stored in turn into
Figure FDA0003520302840000067
In (1), a mapping s is establishedm←ej,k；
Step 1.7: setting a priority counting variable m to be 1, and calculating the throughput of the whole network
Figure FDA0003520302840000071
And selecting the beam with variable xmSetting as 1;
step 1.8: judging whether M is smaller than M: if yes, entering step 1.9, otherwise, entering step 1.13;
step 1.9: after the value of the priority counting variable m is increased by 1, the throughput of the whole network is calculated
Figure FDA0003520302840000072
Step 1.10: judging the throughput R of the whole network after adding a new linkmWhether to promote: if yes, entering step 1.11; otherwise, entering step 1.12;
step 1.11: selecting variable x for beammAfter placing 1, entering step 1.13;
step 1.12: selecting variable x for beammAfter setting to 0, entering step 1.8;
step 1.13: set of beams that have been selected { x }1,…,xm,…,xMUpdate to X;
step 1.14: calculating the number of links joining a network
Figure FDA0003520302840000073
Step 1.15: updating link energy efficiency value set by utilizing X, P and A
Figure FDA0003520302840000074
Step 1.16: sorting link energy efficiency value sets in descending order
Figure FDA0003520302840000075
And are stored in turn into
Figure FDA0003520302840000076
In (1), a mapping s is establishedn←ej,k；
Step 1.17: setting maximum transmit power on each link of an AP
Figure FDA0003520302840000077
And minimum emissivity
Figure FDA0003520302840000078
Initializing the set q with the transmit power value in P1,...,qn,...,qN}；
Step 1.18: optimizing per-link transmit power set q of an AP1,...,qn,...,qN}；
Step 1.19: the transmitting power of each link of the optimized AP is aggregated to be q1,...,qn,...,qNUpdating to P;
step 1.20: updating link energy efficiency value set by utilizing X, P and A
Figure FDA0003520302840000079
Step 1.21: sorting link energy efficiency value sets in descending order
Figure FDA00035203028400000710
And are stored in turn into
Figure FDA00035203028400000711
In (1), a mapping s is establishedo←ej,k；
Step 1.22: set the maximum beam width max to θmaxMinimum beam width min ═ θminInitializing set { q ] with the initialization beamwidth in set A1,...,qn,...,qN}；
Step 1.23: optimized set of beamwidths q1,...,qn,...,qN}；
Step 1.24: the optimized beam width set q1,...,qn,...,qNUpdate to a.
5. The BFT-based wireless access method under millimeter wave cellular network as recited in claim 4, wherein said step 1.18 optimizes each link transmit power set { q ] of AP1,...,qn,...,qNAnd the set of optimized beamwidths { q } described in step 1.231,...,qn,...,qNAnd optimizing by adopting the following steps:
inputting: maximum value max of transmitting power or beam width of each link of the AP, and minimum value min of transmitting power or beam width of each link of the AP;
and (3) outputting: optimizing each link transmission power or beam width set { q ] of the finished AP1,...,qn,...,qN}；
Step 2.1: setting a priority counting variable n as 1, and calculating the throughput of the whole network
Figure FDA0003520302840000081
And will beqnThe value is max;
step 2.2: judging whether N is smaller than N: if yes, entering step 2.3, otherwise, entering step 2.8;
step 2.3: increasing the value of the priority count variable n by 1;
step 2.4: decreasing q according to step sizenA value of (d);
step 2.5: computing overall network throughput
Figure FDA0003520302840000082
Step 2.6: judging q of decreasing corresponding value by step length of descendingnWhether or not the throughput R of the whole network can still be improvedn: if yes, entering step 2.7; otherwise, entering step 2.2;
step 2.7: judging qnWhether the average value is more than min: if yes, entering step 2.4, otherwise entering step 2.2;
step 2.8: the algorithm ends.
6. A communication method comprising the BFT-based wireless access method under the millimeter wave cellular network according to any one of claims 1 to 5, wherein MBS, SBS, AP and UE communicate according to the calculation result of the BFT-based wireless access method under the millimeter wave cellular network, thereby completing the communication between MBS, SBS, AP and UE.
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