CN103118414A - Wireless access control and timeslot allocation method applicable to ultra-wideband - Google Patents

Abstract

The invention belongs to the technical field of wireless communications and particularly relates to a wireless access control and timeslot allocation method applicable to ultra-wideband high-speed data transmission. The method mainly includes the steps of firstly, selecting a central controller according to power information; secondly, allowing the central controller to receive messages such as node storage space and position; allowing the central controller to confirm positions of two nodes and data to be transmitted through indirect handshake protocol process; thirdly, calculating timeslot allocation; and fourthly, when a transmitting node receives a frame determined to transmit by the central controller, transmitting next superframe according to the result of timeslot allocation; if no DTS (digital theater system) frame is received, awaiting and re-calculating according to access condition of a new link. The method enables calculation to be simplified greatly, timeslot allocation to be more detailed and timeslot waste to be lowered.

Description

A kind of wireless access control and slot allocation method that is applicable to ultra broadband

Technical field

The invention belongs to wireless communication technology field, relate in particular to a kind of wireless access control and slot allocation method that is applicable to the position-based information of ultra broadband high speed data transfer;

Background technology

Ultra broadband (Ultra Wideband, UWB) system uses extremely short burst transmissions information of duration, and power consumption is little, with wide and have very strong anti-multipath fading ability, can realize high speed data transfer; Because power spectral density is very low, almost be buried in various electromagnetic interference and noise, have advantages of that good concealment, low intercepting and capturing rate, good confidentiality etc. are very outstanding, be well positioned to meet Modern Communication System to the requirement of fail safe; These unique advantages that the UWB technology has make it become the best settling mode of the system of high-speed high capacity Wireless Personal Network under indoor multi-path dense environmental condition;

Due to wireless network intermediate frequency spectrum resource-constrained, transmission rate and network capacity are restricted, and channel fading also can be with and serve communication issue simultaneously; Therefore, in the UWB network, the media access control mode (MAC) of control channel access is determining the access occupation mode of wireless channel, is responsible for node and distributes radio channel resource, and the network performances such as the utilance of channel, network throughput, network delay are had material impact; Therefore, appropriate design media access control mode according to network traffic characteristics configurating channel resource effectively, can improve the service efficiency of Radio Resource;

All can be applicable in the UWB system based on the MAC agreement of the ECMA-368 standard MAC of Distributed admission control and IEEE802.15.3, but can not be well suited for Technology in High-speed WPAN; Improvement for ECMA-368 or IEEE802.15.3 standard is a lot, all could not utilize well the physical layer characteristic of pulse UWB;

Time division multiple access way is proved to be and is suitable for the ultra broadband high speed data transfer, same time slot can hold many data links under certain condition, the low duty ratio of pulse signal and jumping time-code make the interference between different links very low simultaneously, further increased network and hold the quantity of data link in same time slot;

For the research of ultra broadband resource allocation scheduling, focus mostly on the target of maximize throughput at present, judge the link interference situation by the Signal to Interference plus Noise Ratio thresholding, the link that each time slot is held is many as far as possible; But this class methods Shortcomings: do not come the flexible allocation time slot according to the data volume of transmission, such as a time slot has held multilink, when having link to complete, each link interference situation changes, and if time slot allocation is constant has just caused waste; Simultaneously, these algorithms adopt Distributed Calculation more, and complexity is high, have increased on the contrary node power consumption, and too much interactive information has reduced the validity of system;

Summary of the invention

The objective of the invention is the deficiency that exists in existing access control and channel resource allocation method in the present high speed UWB network described in background technology, propose a kind of wireless access control and slot allocation method that is applicable to the position-based information of UWB high speed data transfer;

Technical scheme of the present invention is as follows:

Select master controller according to power information.Slot Allocation Algorithm of the present invention is to be calculated by master controller, therefore when selecting master controller, need to add power information (distinguishing sensitive power consumption node and active node).After node was started working, wherein any node sent scanning impulse scanning other nodes on every side, received acknowledgement frame of node feedback of this sweep signal, and acknowledgement frame comprises this node and whether is connected to power supply and consumption information.For fear of conflict, adopt the random back strategy during feedback acknowledgement frame, receive the rear acknowledgement frame that sends of node random back certain hour (nanosecond) of scanning impulse, after the node of transmission scanning impulse is received acknowledgement frame, elect the insensitive node of energy consumption as master controller and send announcement information.Synchronous other nodes of beacon frame of master controller broadcasting, the regular update network information, and utilize the good range finding positioning function of ultra broadband to know each node location information.

When the data link request is arranged, information source node sends request to master controller and sends (Request To Send, RTS) frame, master controller storage the transmission of data demand information, positional information, and forward the RTS frame to receiving node, receiving node is replied clear to send (Clear To Send, CTS) frame to master controller, and master controller obtains the information such as receiving node memory space, position.Master controller is confirmed the positional information of two nodes by indirect Handshake Protocol process and is needed the data volume of transmission.

Time slot allocation is calculated: make a time slot can hold many data links based on multiplexing thought, data volume and the mutual disturbed condition of link according to every link needs transmission, adopting the preferential iterative algorithm of low coverage is every data link assignment time slot, make in the situation that the data volume time slot of the transmission of satisfying the demand is fully utilized, time delay is minimum.

1) to obtain the little delay of trying one's best, speed will reach maximum can pass speed, and but power is controlled and can be reduced power consumption very little on the throughput impact, therefore required power regulating and controlling speed value in interval not, can suppose sending node or not send data, or send with maximum transmission power.

2) which kind of UWB system no matter, the calculating of Signal to Interference plus Noise Ratio and channel model are irrelevant.The research discovery, ultra broadband has a characteristic, and during high bandwidth, speed and Signal to Interference plus Noise Ratio (SINR) are linear, when Signal to Interference plus Noise Ratio is low, make data rate adaptive channel bit error rate by coding and modulation system, can successfully transmit.In order to obtain as far as possible high throughput in each unit time slot, take the method for the preferential iteration of low coverage, the short link of transmission range preferentially shares time slot judgement, just satisfies condition this time slot allocation to this link, and continuation judges the link of the longer distance of the next one.

3) because when distance is very near, interference effect can be very large, and in order to reduce amount of calculation, rule of thumb value is artificially determined exclusive regional extent, that mentions in the definite and former research in this exclusive zone is different, is not interference region strictly determined according to network topology structure.Emulation shows, (link of scope random distribution (2～20) of 10m * 10m) determines that generally exclusive zone is a circle that radius is 2m～4m, has greatly reduced the amount of calculation of algorithm like this for indoor.

4) by node distribution situation and link interference situation, can calculate Signal to Interference plus Noise Ratio, try to achieve and hold which data link in each time slot, and same link is different in different time slot speed.In the UWB of rate variation Resource Allocation in Networks, target function is that time delay is minimum, and condition is limited by transmission demand, transmitting power, Signal to Interference plus Noise Ratio.Time slot is divided by least unit, and it is minimum that the time delay minimum namely is equivalent to total timeslot number, obtains total number of timeslots of needs and the number of timeslots of every link assignment.

min M (1.1)

subjectto:

$x_i^s\underset{j\∈N\left(i\right)}{\mathrm{\Σ}}{x}_j^s=0,i,j\∈[1,L]---\left(1.2\right)$

$y_{\mathrm{ik}}+1_{\{p_i^s>0\}}+1_{\{p_k^s>0\}}\≤2,i,k\∈[1,L],s\∈[1,M]---\left(1.3\right)$

$p_i^s\∈\{0,P\},i\∈[1,L],s\∈[1,M]---\left(1.4\right)$

$r_i^s=K\frac{p_i^s{d}_i^{-\mathrm{\γ}}}{\mathrm{\η}+x_i^s\mathrm{\α}\underset{j=1,j\≠i}{\overset{L}{\mathrm{\Σ}}}{p}_j^s{d}_{\mathrm{ji}}^{-\mathrm{\γ}}},i\∈[i,L],s\∈[1,M]---\left(1.5\right)$

$\underset{s=1}{\overset{M}{\mathrm{\Σ}}}{r}_i^s{t}^s\≥R_i,i\∈[1,L]---\left(1.6\right)$

1.1 formula is target function, minimizes total timeslot number M; 1.2 in formula

Represent that i bar link transmits in the s time slot,

Expression is not transmitted, and N (i) expression is in the link set in link i exclusive zone,

Represent that j bar link transmits in the s time slot,

Expression is not transmitted, and L represents the link total quantity; 1.3 formula represents that any one node can only participate in the transmission of a link, y in a time slot _ik=1 expression link i and link k have same node point, on the contrary y _ik=0; 1.4 formula represents to take 0-P strategy transmission, link or do not transmit or determining power delivery,

Represent the through-put power of i bar link in the s time slot; 1.5 in formula

Represent the transmission rate of i bar link in the s time slot, K is the constant of a rate adaptation Signal to Interference plus Noise Ratio linear relationship when high bandwidth, and γ is the range attenuation factor, and η represents Background Noise Power, d _jiRepresent j bar link transmitting node to the interference distance of i bar link receiving node, α represents the cross-correlation factor, and is relevant with pulse shape, cycle and modulation system etc.; 1.6 t in formula ^sThe duration of expression s time slot, R _iRepresent the data volume that i bar link need to transmit.

5) iterative process: in the s time slot, to also not satisfy the distance of link of transmitted data amount according to the sequence of from the near to the remote order, then the link priority allocation that distance is minimum judges successively that can other links coexist with the link that has arranged in current time slots.After traversal is completed, the link that current time slots will be transmitted is all determined, then calculate Signal to Interference plus Noise Ratio, the link rate of each link, and in the data volume of current time slots transmission, it is the product of link rate and time slot duration, so just know the data volume that residue will be transmitted, generate s+1 time slot row and carry out next iteration, until all links are completed the data volume that will transmit.

The time slot of channel time allocation phase is divided into two parts, transfer of data time slot and replying the period.By above-mentioned iterative computation, obtain transfer of data number of timeslots and the transmission rate of each link assignment.For fear of the interference of responder link, responder link does not adopt the mode of each transmitted in packets immediate answer commonly used, but unified replying once after a plurality of data slot.The time overhead of replying the period is very low, and according to transfer of data time slot allocation situation, the unified acknowledgement frame that sends after a plurality of transfer of data time slots is replied the data flow of dont answer in transfer of data time slot before.

Receive decision transmission (DecideToSend, DTS) frame of master controller transmission when sending node after, transmit according to the time slot allocation result in next superframe, if do not receive the DTS frame, wait for and recomputate according to new link access situation.All flow process is seen Fig. 1.

Beneficial effect: can find out from top process, the present invention comes the channel resource allocation scheduling is arranged exclusive region decision disturbed condition from the angle of time delay minimum and speed adjustment, distributes time slot according to the preferential iterative algorithm of low coverage; Selection Center controller time zone independent power source information has strengthened network robustness; By transfer Handshake Protocol and unified replying, reduced overhead; The present invention and existing method have relatively been simplified calculating greatly, and time slot allocation becomes more meticulous more simultaneously, has reduced time slot waste;

Description of drawings

Fig. 1 is the FB(flow block) of the inventive method;

Fig. 2 is the schematic diagram (illustrated in figure 2 links) of application scenarios of the present invention;

Fig. 3 is embodiment superframe structure schematic diagram;

Embodiment

Below in conjunction with accompanying drawing, embodiment is elaborated; Should be emphasized that, following explanation is only exemplary, rather than in order to limit the scope of the invention and to use;

The inventive method is applicable to the ultra broadband high speed data transfer of indoor environment, 2～40 of number of nodes, and maximum access link quantity 20 simultaneously, the node communication ability is identical, single-hop networks, each node can not participate in transmission or the reception of multilink simultaneously;

Fig. 2 is embodiment of the present invention application scenarios schematic diagram, has illustrated typically the coexisting of 2 links in figure; Suppose at a time, in network random distribution 21 points (containing master controller), 10 sending nodes are corresponding one by one with 10 receiving nodes; Access control and time slot allocation flow process are as follows:

Master controller is selected in a, device power-up networking;

B, utilize the high-precision physical distance measurement ability of UWB to obtain each node location information;

The beacon frame that c, other node devices regularly receive from master controller extracts the network information, when having data to send, send request access (RTS) frame to master controller, master controller storage the transmission of data demand information, positional information, and forward the RTS frame to receiving node, receiving node is replied clear to send frame (CTS) to master controller, and master controller obtains the information such as receiving node memory space, position;

D, master controller broadcast acknowledgements each access link distance and path loss, and according to distance sequence from the near to the remote, as d=[4.6254 in embodiment, 2.0339,4.6559,4.8882,2.6249,7.3355,3.4022,4.9114,8.6019,8.0740], after arranged in sequence, d=[d ₂, d ₅, d ₇, d ₁, d ₃, d ₄, d ₈, d ₆, d ₁₀, d ₉], suppose that every link will transmit identical data volume R;

E, in first unit time slot, according to the low coverage priority algorithm, then link 2 transmission judges successively that by exclusive zone can 5,7,1,3,4,8,6,10,9 links transmit simultaneously with the link of determining before transmission;

F, according to the situation that coexists of link in time slot, calculate this time slot each link Signal to Interference plus Noise Ratio and link rate, then upgrade the data volume R that needs transmission _i=R-r _i, carry out the iterative computation of next time slot, until complete transmission;

Calculate the transmission of completing the desired data amount in g, embodiment, need the timeslot number M=72 of unit, concrete time slot allocation situation sees Table 1, and in table 1,1 expression will be listed as corresponding time slot allocation to link corresponding to row, and 0 expression does not distribute;

Table 1

	1slot	2slot	3～4slot	4～6slot	7～11slot	12～25slot	26～42slot	43～72slot
									Link
1	1	1	1	0	0	0	0	0
									Link 2	1	0	0	0	0	0	0	0
Link 3	1	0	1	1	0	0	0	0
									Link 4	0	1	1	1	0	0	0	0
Link 5	0	1	0	0	0	0	0	0
									Link 6	1	1	1	1	1	1	0	0
Link 7	0	0	1	0	0	0	0	0
									Link 8	0	0	0	0	1	0	0	0
Link 9	0	0	0	0	0	0	1	1
									Link 10	0	1	0	0	1	1	1	0

After h, time slot allocation are completed, the distribution of replying so the period is also corresponding definite, increases by one in embodiment after each row time slot and replys the period, because acknowledgement frame is very short, this time can be very short, as long as can be successfully the data flow of dont answer in transfer of data time slot be before replied, Fig. 3 is its superframe structure schematic diagram, and BP is beacon period, CAP is contention access periods, CTAP is the channel time allocation phase, and CTA is that channel time slot is distributed, and ACK represents to reply time slot; Time slot row in corresponding table 1 of each CTA period;

I, assigned after, master controller broadcasting DTS message, in next superframe, each link transmits according to allocation result; If the link sending node is not received DTS, this link is asked access again, adds the time slot allocation in next cycle;

As mentioned above, although represented and explained the present invention with reference to specific embodiment, it must not explain the restriction to the present invention self; Under the spirit and scope of the present invention prerequisite that does not break away from the claims definition, can make in the form and details various variations to it.

Claims (1)

1. wireless access control and a slot allocation method that is applicable to ultra broadband, is characterized in that, described method comprises:

(1) select master controller according to power information; Slot Allocation Algorithm of the present invention is to be calculated by master controller, therefore when selecting master controller, need to add power information, distinguishes sensitive power consumption node and active node; After node was started working, wherein any node sent scanning impulse scanning other nodes on every side, received acknowledgement frame of node feedback of this sweep signal, and acknowledgement frame comprises this node and whether is connected to power supply and consumption information; For fear of conflict, adopt the random back strategy during feedback acknowledgement frame, receive the rear acknowledgement frame that sends of node random back certain hour (nanosecond) of scanning impulse, after the node of transmission scanning impulse is received acknowledgement frame, elect the insensitive node of energy consumption as master controller and send announcement information; Synchronous other nodes of beacon frame of master controller broadcasting, the regular update network information, and utilize the good range finding positioning function of ultra broadband to know each node location information;

(2) when the data link request is arranged, information source node sends request to master controller and sends frame, master controller storage the transmission of data demand information, positional information, and forward the RTS frame to receiving node, receiving node is replied the clear to send frame to master controller, and master controller obtains the information such as receiving node memory space, position; Master controller is confirmed the positional information of two nodes by indirect Handshake Protocol process and is needed the data volume of transmission;

(3) time slot allocation is calculated:

Make a time slot can hold many data links based on multiplexing thought, data volume and the mutual disturbed condition of link according to every link needs transmission, adopting the preferential iterative algorithm of low coverage is every data link assignment time slot, make in the situation that the data volume time slot of the transmission of satisfying the demand is fully utilized, time delay is minimum;

1) to obtain the little delay of trying one's best, speed will reach maximum can pass speed, and but power is controlled and can be reduced power consumption very little on the throughput impact, therefore required power regulating and controlling speed value in interval not, can suppose sending node or not send data, or send with maximum transmission power;

2) which kind of UWB system no matter, the calculating of Signal to Interference plus Noise Ratio and channel model are irrelevant; The research discovery, ultra broadband has a characteristic, and during high bandwidth, speed and Signal to Interference plus Noise Ratio (SINR) are linear, when Signal to Interference plus Noise Ratio is low, make data rate adaptive channel bit error rate by coding and modulation system, can successfully transmit; In order to obtain as far as possible high throughput in each unit time slot, take the method for the preferential iteration of low coverage, the short link of transmission range preferentially shares time slot judgement, just satisfies condition this time slot allocation to this link, and continuation judges the link of the longer distance of the next one;

3) because when distance is very near, interference effect can be very large, and in order to reduce amount of calculation, rule of thumb value is artificially determined exclusive regional extent, that mentions in the definite and former research in this exclusive zone is different, is not interference region strictly determined according to network topology structure; Emulation shows, (link of scope random distribution (2～20) of 10m * 10m) determines that generally exclusive zone is a circle that radius is 2m～4m, has greatly reduced the amount of calculation of algorithm like this for indoor;

4) by node distribution situation and link interference situation, can calculate Signal to Interference plus Noise Ratio, try to achieve and hold which data link in each time slot, and same link is different in different time slot speed; In the UWB of rate variation Resource Allocation in Networks, target function is that time delay is minimum, and condition is limited by transmission demand, transmitting power, Signal to Interference plus Noise Ratio; Time slot is divided by least unit, and it is minimum that the time delay minimum namely is equivalent to total timeslot number, obtains total number of timeslots of needs and the number of timeslots of every link assignment;

minM (1.1)

subject to:

$x_i^s\underset{j\∈N\left(i\right)}{\mathrm{\Σ}}{x}_j^s=0,i,j\∈[1,L]---\left(1.2\right)$

$y_{\mathrm{ik}}+1_{\{p_i^s>0\}}+1_{\{p_k^s>0\}}\≤2,i,k\∈[1,L],s\∈[1,M]---\left(1.3\right)$

$p_i^s\∈\{0,P\},i\∈[1,L],s\∈[1,M]---\left(1.4\right)$

$r_i^s=K\frac{p_i^s{d}_i^{-\mathrm{\γ}}}{\mathrm{\η}+x_i^s\mathrm{\α}\underset{j=1,j\≠i}{\overset{L}{\mathrm{\Σ}}}{p}_j^s{d}_{\mathrm{ji}}^{-\mathrm{\γ}}},i\∈[i,L],s\∈[1,M]---\left(1.5\right)$

$\underset{s=1}{\overset{M}{\mathrm{\Σ}}}{r}_i^s{t}^s\≥R_i,i\∈[1,L]---\left(1.6\right)$

1.1 formula is target function, minimizes total timeslot number M; 1.2 in formula

Represent that i bar link transmits in the s time slot,

Expression is not transmitted, and N (i) expression is in the link set in link i exclusive zone,

Represent that j bar link transmits in the s time slot,

Expression is not transmitted, and L represents the link total quantity; 1.3 formula represents that any one node can only participate in the transmission of a link, y in a time slot _ik=1 expression link i and link k have same node point, on the contrary y _ik=0; 1.4 formula represents to take 0-P strategy transmission, link or do not transmit or determining power delivery, Represent the through-put power of i bar link in the s time slot; 1.5 in formula

Represent the transmission rate of i bar link in the s time slot, K is the constant of a rate adaptation Signal to Interference plus Noise Ratio linear relationship when high bandwidth, and γ is the range attenuation factor, and η represents Background Noise Power, d _jiRepresent j bar link transmitting node to the interference distance of i bar link receiving node, α represents the cross-correlation factor, and is relevant with pulse shape, cycle and modulation system etc.; 1.6 t in formula ^sThe duration of expression s time slot, R _iRepresent the data volume that i bar link need to transmit;

5) iterative process: in the s time slot, to also not satisfy the distance of link of transmitted data amount according to the sequence of from the near to the remote order, then the link priority allocation that distance is minimum judges successively that can other links coexist with the link that has arranged in current time slots; After traversal is completed, the link that current time slots will be transmitted is all determined, then calculate Signal to Interference plus Noise Ratio, the link rate of each link, and in the data volume of current time slots transmission, it is the product of link rate and time slot duration, so just know the data volume that residue will be transmitted, generate s+1 time slot row and carry out next iteration, until all links are completed the data volume that will transmit;

The time slot of channel time allocation phase is divided into two parts, transfer of data time slot and replying the period; By above-mentioned iterative computation, obtain transfer of data number of timeslots and the transmission rate of each link assignment; For fear of the interference of responder link, responder link does not adopt the mode of each transmitted in packets immediate answer commonly used, but unified replying once after a plurality of data slot; The time overhead of replying the period is very low, and according to transfer of data time slot allocation situation, the unified acknowledgement frame that sends after a plurality of transfer of data time slots is replied the data flow of dont answer in transfer of data time slot before;

(4) after sending node receives the decision transmission frame of master controller transmission, transmit according to the time slot allocation result in next superframe, if do not receive the DTS frame, wait for and recomputate according to new link access situation.

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