CN103118414B - 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 being applicable to ultra broadband

Technical field

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

Background technology

Ultra broadband (Ultra Wideband, UWB) system uses duration extremely short burst transmissions information, 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, be almost buried in various electromagnetic interference and noise, there is the advantage that good concealment, low intercepting and capturing rate, good confidentiality etc. are very outstanding, be well positioned to meet the requirement of Modern Communication System to fail safe; These unique advantages that UWB technology has become the best settling mode of high-speed high capacity Wireless Personal Network system under indoor dense multi-path environments 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 UWB network, the medium education mode (MAC) of control channel access decides the access occupation mode of wireless channel, is responsible for peer distribution radio channel resource, has material impact to the network performance such as utilance, network throughput, network delay of channel; Therefore, appropriate design medium education mode, according to network traffic characteristics configurating channel resource effectively, can improve the service efficiency of Radio Resource;

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

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

At present for the research of ultra broadband resource allocation scheduling, focus mostly in the target of maximize throughput, judge link interference situation by 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: not do not carry out flexible allocation time slot according to the data volume of transmission, such as a time slot contains multilink, when there being link to complete, each link interference situation change, and if time slot allocation is constant just causes waste; Meanwhile, these algorithm many employings Distributed Calculation, complexity is high, adds node power consumption on the contrary, and too much interactive information reduces the validity of system;

Summary of the invention

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

Technical scheme of the present invention is as follows:

Master controller is selected according to power information.Slot Allocation Algorithm of the present invention is calculated by master controller, therefore in selecting the heart controller time, need to add power information (distinguishing sensitive power consumption node and active node).After node is started working, wherein any node sends scanning impulse scanning other nodes around, and receive node feeding back acknowledgement frame of this sweep signal, acknowledgement frame comprises this node and whether is connected to power supply and consumption information.In order to avoid conflict, random back strategy is adopted during feedback acknowledgement frame, the node random back certain hour (nanosecond) receiving scanning impulse sends acknowledgement frame afterwards, send after the node of scanning impulse receives acknowledgement frame, elect the insensitive node of energy consumption as master controller and send announcement information.A beacon frame other nodes synchronous broadcasted by master controller, the regular update network information, and the ranging localization function utilizing ultra broadband good knows each node location information.

When there being requested data link, information source node sends request transmission (Request To Send to master controller, RTS) frame, master controller stores transmission demand data information, positional information, and forward RTS frame to receiving node, receiving node replys 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 confirms the positional information of two nodes by indirect Handshake Protocol process and needs the data volume of transmission.

Time slot allocation calculates: make a time slot can hold many data link based on multiplexing thought, data volume and the mutual disturbed condition of link of transmission is needed according to every bar link, the preferential iterative algorithm of low coverage is adopted to be every bar data link assignment time slot, the time slot when satisfying the demand the data volume of transmission is fully utilized, and time delay is minimum.

1) as far as possible little delay to be obtained, speed will reach maximum and pass speed, and but power controls to reduce power consumption very little on throughput impact, therefore not required power regulating and controlling speed value in interval, sending node can be supposed or do not send data, or sending with maximum transmission power.

2) no matter which kind of UWB system, the calculating of Signal to Interference plus Noise Ratio and channel model have nothing to do.Research find, ultra-wide with a characteristic, during high bandwidth speed and Signal to Interference plus Noise Ratio (SINR) linear, when Signal to Interference plus Noise Ratio is lower, by coding and modulation system make data rate adaptive channel bit error rate, can Successful transmissions.In order to obtain high throughput as far as possible in each unit time slot, take the method for the preferential iteration of low coverage, the short link of transmission range preferentially carries out shared time slot judgement, satisfy condition just by this time slot allocation to this link, continue to judge the link of the longer distance of the next one.

3) because when distance is very near, interference effect can be very large, in order to reduce amount of calculation, artificially determines exclusion zones scope based on experience value, the determination of this exclusion zones from mentioned in former research different, be not according to the strictly determined interference region of network topology structure.Emulation shows, for the link (2 ~ 20) of indoor (10m × 10m) scope random distribution, generally determines that exclusion zones be a radius is the circle of 2m ~ 4m, greatly reduces the amount of calculation of algorithm like this.

4) by Node distribution situation and link interference situation, can Signal to Interference plus Noise Ratio be calculated, try to achieve in each time slot to hold which data link, and same link is different at different slot rate.In the UWB Resource Allocation in Networks of rate variation, target function is that time delay is minimum, and condition limits by transmission demand, transmitting power, Signal to Interference plus Noise Ratio.Divided by least unit by time slot, time delay is minimum, and to be namely equivalent to total timeslot number minimum, obtains total number of timeslots of needs and the number of timeslots of every bar 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 formulas are target functions, minimize total timeslot number M; In 1.2 formulas represent that i-th article of link transmits in s time slot, represent and do not transmit, N (i) represents the link set be in link i exclusion zones, represent that a jth article link transmits in s time slot, represent and do not transmit, L represents link total quantity; 1.3 formulas represent that any one node can only participate in the transmission of a link in a time slot, y _ik=1 represents that link i and link k has same node point, on the contrary y _ik=0; 1.4 formulas represent takes 0-P strategy transmission, link or not transmit or to determine power delivery, represent the through-put power of i-th article of link in s time slot; In 1.5 formulas represent the transmission rate of i-th link in 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 the interference distance of jth bar link transmissions node to i-th link receiving node, α represents the cross-correlation factor, relevant with pulse shape, cycle and modulation system etc.; T in 1.6 formulas ^srepresent the duration of s time slot, R _irepresent that i-th link needs the data volume of transmission.

5) iterative process: in s time slot, also will not meet the distance of the link of transmitted data amount according to order sequence from the near to the remote, apart from minimum link priority allocation, then judge that can other links coexist with the link arranged in current time slots successively.After having traveled through, the link that current time slots will be transmitted all is determined, then the Signal to Interference plus Noise Ratio of each link, link rate is calculated, and in the data volume that current time slots is transmitted, the i.e. product of link rate and time slot duration, so just know the data volume remaining and will transmit, generate s+1 time slot row and carry out next iteration, until all links complete the data volume that will transmit.

The time slot of channel time allocation phase is divided into two parts, data transmission slots and response period.By above-mentioned iterative computation, obtain data transmission slots quantity and the transmission rate of each link assignment.In order to avoid the interference of responder link, responder link does not adopt the mode of conventional each transmitted in packets immediate answer, but after multiple data slot, unification is replied once.The time overhead of response period is very low, according to data transmission slots distribution condition, unifiedly after multiple data transmission slots sends acknowledgement frame, replys the data flow of dont answer in data transmission slots before.

After sending node receives decision transmission (DecideToSend, DTS) frame of master controller transmission, transmit according to time slot allocation result in next superframe, if do not receive DTS frame, then wait for and recalculate according to new link access situation.Whole flow process is shown in Fig. 1.

Beneficial effect: as can be seen from process above, the present invention comes, to channel resource allocation scheduling, to arrange exclusion zones and judge disturbed condition from the angle of time delay minimum and speed adjustment, according to low coverage preferential iterative algorithm distribution time slot; Selection Center controller time zone independent power source information, enhances network robustness; By transfer Handshake Protocol and unified response, decrease overhead; The present invention and existing Measures compare, enormously simplify calculating, and time slot allocation becomes more meticulous more simultaneously, decreases time slot waste;

Accompanying drawing explanation

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

Fig. 2 is the schematic diagram (illustrating 2 links in figure) 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; It is emphasized that following explanation is only exemplary, instead of in order to limit the scope of the invention and apply;

The inventive method is applicable to the ultra broadband high speed data transfer of indoor environment, number of nodes 2 ~ 40, access link quantity 20 while of maximum, and node communication ability is identical, single-hop networks, and 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, illustrates coexisting of 2 links typically in figure; Suppose at a time, random distribution 21 points (containing master controller) in network, 10 sending nodes and 10 receiving node one_to_one corresponding; Access control and time slot allocation flow process as follows:

A, device power-up networking, select master controller;

B, UWB high-precision physical distance measurement ability is utilized to obtain each node location information;

C, other node device timing receipt extract the network information from the beacon frame of master controller, when there being data to send, access (RTS) frame is sent request to master controller, master controller stores transmission demand data information, positional information, and forward RTS frame to receiving node, receiving node replys clear to send frame (CTS) to master controller, and master controller obtains the information such as receiving node memory space, position;

The each access link distance of d, master controller broadcast acknowledgements and path loss, and sort from the near to the remote, as d=in embodiment [4.6254,2.0339,4.6559 according to distance, 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 bar link will transmit identical data volume R;

E, in first unit time slot, according to low coverage priority algorithm, link 2 transmits, then by exclusion zones judge successively 5,7,1,3,4,8,6,10,9 links can with determine that the link transmitted transmits simultaneously before;

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

Calculated the transmission of desired data amount in g, embodiment, needed unit timeslot number M=72, concrete Time slot allocation situation is in table 1, and in table 1,1 represents and will arrange corresponding time slot allocation to going corresponding link, 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 complete, so reply that the distribution of period is also corresponding to be determined, after each row time slot, increase a response period in embodiment, because acknowledgement frame is very short, this time can be very short, as long as can successfully reply the data flow of dont answer in data transmission slots before, 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 response time slot; Time slot row in each CTA period corresponding table 1;

I, be assigned after, master controller broadcast DTS message, in next superframe, each link transmits according to allocation result; If link sending node does not receive DTS, this link asks access again, adds the time slot allocation in next cycle;

As mentioned above, although represented with reference to specific embodiment and described the present invention, it must not explain the restriction to the present invention self; Under the spirit and scope of the present invention prerequisite not departing from claims definition, various change can be made in the form and details to it.

Claims (1)

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

(1) master controller is selected according to power information; Slot Allocation Algorithm of the present invention is calculated by master controller, therefore in selecting the heart controller time, need to add power information, distinguish sensitive power consumption node and active node; After node is started working, wherein any node sends scanning impulse scanning other nodes around, and receive node feeding back acknowledgement frame of this sweep signal, acknowledgement frame comprises this node and whether is connected to power supply and consumption information; In order to avoid conflict, random back strategy is adopted during feedback acknowledgement frame, acknowledgement frame is sent after receiving the time of the certain nanosecond of node random back of scanning impulse, send after the node of scanning impulse receives acknowledgement frame, elect the insensitive node of energy consumption as master controller and send announcement information; A beacon frame other nodes synchronous broadcasted by master controller, the regular update network information, and the ranging localization function utilizing ultra broadband good knows each node location information;

(2) when there being requested data link, information source node sends request transmission frame to master controller, master controller stores transmission demand data information, positional information, and forward RTS frame to receiving node, receiving node replys clear to send frame to master controller, and master controller obtains receiving node memory space, positional information; Master controller confirms the positional information of two nodes by indirect Handshake Protocol process and needs the data volume of transmission;

(3) time slot allocation calculates:

Make a time slot can hold many data link based on multiplexing thought, data volume and the mutual disturbed condition of link of transmission is needed according to every bar link, the preferential iterative algorithm of low coverage is adopted to be every bar data link assignment time slot, the time slot when satisfying the demand the data volume of transmission is fully utilized, and time delay is minimum;

1) as far as possible little delay to be obtained, speed will reach maximum and pass speed, but power controls to reduce power consumption affects very little on throughput, therefore not required power regulating and controlling speed value in interval, sending node can be supposed or do not send data, or sending with maximum transmission power;

2) no matter which kind of UWB system, the calculating of Signal to Interference plus Noise Ratio and channel model have nothing to do; Research finds, ultra-wide with a characteristic, during high bandwidth speed and Signal to Interference plus Noise Ratio linear, when Signal to Interference plus Noise Ratio is lower, make data rate adaptive channel bit error rate by coding and modulation system, can Successful transmissions; In order to obtain high throughput as far as possible in each unit time slot, take the method for the preferential iteration of low coverage, the short link of transmission range preferentially carries out shared time slot judgement, satisfy condition just by this time slot allocation to this link, continue to judge the link of the longer distance of the next one;

3) because when distance is very near, interference effect can be very large, in order to reduce amount of calculation, artificially determines exclusion zones scope based on experience value, the determination of this exclusion zones from mentioned in former research different, be not according to the strictly determined interference region of network topology structure; Emulation shows, for 2 ~ 20 links of the indoor range random distribution of 10m × 10m, generally determines that exclusion zones be a radius is the circle of 2m ~ 4m, greatly reduces the amount of calculation of algorithm like this;

4) by Node distribution situation and link interference situation, can Signal to Interference plus Noise Ratio be calculated, try to achieve in each time slot to hold which data link, and same link is different at different slot rate; In the UWB Resource Allocation in Networks of rate variation, target function is that time delay is minimum, and condition limits by transmission demand, transmitting power, Signal to Interference plus Noise Ratio; Divided by least unit by time slot, time delay is minimum, and to be namely equivalent to total timeslot number minimum, obtains total number of timeslots of needs and the number of timeslots of every bar link assignment; Described UWB network is carrierfree communication network;

min M (1.1)

subject to:

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

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

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

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

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

1.1 formulas are target functions, minimize total timeslot number M; In 1.2 formulas represent that i-th article of link transmits in s time slot, represent and do not transmit, N (i) represents the link set be in link i exclusion zones, represent that a jth article link transmits in s time slot, represent and do not transmit, L represents link total quantity; 1.3 formulas represent that any one node can only participate in the transmission of a link in a time slot, y _ik=1 represents that link i and link k has same node point, on the contrary y _ik=0; 1.4 formulas represent takes 0-P strategy transmission, link or not transmit or to determine power delivery, represent the through-put power of i-th article of link in s time slot; In 1.5 formulas represent the transmission rate of i-th link in 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 the interference distance of jth bar link transmissions node to i-th link receiving node, α represents the cross-correlation factor, relevant with pulse shape, cycle and modulation system; T in 1.6 formulas ^srepresent the duration of s time slot, R _irepresent that i-th link needs the data volume of transmission;

5) iterative process: in s time slot, also will not meet the distance of the link of transmitted data amount according to order sequence from the near to the remote, apart from minimum link priority allocation, then judge that can other links coexist with the link arranged in current time slots successively; After having traveled through, the link that current time slots will be transmitted all is determined, then the Signal to Interference plus Noise Ratio of each link, link rate is calculated, and in the data volume that current time slots is transmitted, the i.e. product of link rate and time slot duration, so just know the data volume remaining and will transmit, generate s+1 time slot row and carry out next iteration, until all links complete the data volume that will transmit;

The time slot of channel time allocation phase is divided into two parts, data transmission slots and response period; By above-mentioned iterative computation, obtain data transmission slots quantity and the transmission rate of each link assignment; In order to avoid the interference of responder link, responder link does not adopt the mode of conventional each transmitted in packets immediate answer, but after multiple data slot, unification is replied once; The time overhead of response period is very low, according to data transmission slots distribution condition, unifiedly after multiple data transmission slots sends acknowledgement frame, replys the data flow of dont answer in data transmission slots before;

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