CN101800567B - Method for distributing forwarding time slot and selecting relay node in cooperative ultra-wide band - Google Patents

Abstract

The invention discloses a method for distributing a forwarding time slot and selecting a relay node in a cooperative ultra-wide band, belongs to the field of communication, and solves the problem of high conflict probability of relaying and forwarding a signal at a receiving end by adopting the conventional algorithm in the cooperative ultra-wide band. The method of the invention comprises the following steps: firstly, receiving pilot signals sent by a source node by each relay node; secondly, calculating channel gains from the source node to k relay nodes; thirdly, fitting a channel gain curve which obeys normal distribution, and dividing the interval [mu-3sigma, mu+3sigma] of the gain channel curve into N small gain intervals with the same area; and finally, distributing and forwarding time slot according to the channel gain proportional relation among the N small gain intervals. The method of the invention further comprises the following steps for selecting the relay node: fifthly, determining the small gain interval where the channel gain of each relay node is positioned according to the third step; sixthly, receiving the signal, forwarded by the relay node, corresponding to a target node by the target node according to the fourth step, and calculating an error rate; and finally, selecting the relay node corresponding to a route of which the error rate is lowest as the relay node for forwarding a data information signal.

Description

Forwarding time slot in the cooperative ultra-wide band distributes and relay node selecting method

Technical field

The forwarding time slot that the present invention relates in the cooperative ultra-wide band distributes and relay node selecting method, belongs to the communications field.

Background technology

In the last few years, super-broadband tech is with its low power spectral density, the advantages such as high multi-path resolved rate have become one of candidate technologies of the interconnected and wireless sensor network of following short-distance wireless, for fear of existing system is caused interference, FCC has issued " the First Report and Order " about super-broadband tech in 2002, when having allowed the commercial application of super-broadband tech, also the effective isotropic radiated power (Effective Isotropic Radiated Power, EIRP) of ultra-broadband emitter when indoor and outdoors is used made strict restriction.Wherein, peak E IRP at ultra-broadband emitter working frequency range 3.1GHz ~ 10.6GHz place is-41.3dBm/MHz, because this peak E IRP is very low, the signal power that causes ultra wideband receiver to receive is also very low, thereby has strengthened the difficulty of ultra wideband receiver design.In order to guarantee to receive the quality of signal, reduce simultaneously the complexity of ultra wideband receiver, existing document proposes collaboration communication is incorporated in the radio ultra wide band system.

The basic thought of cooperative communication technology originates from three terminal relay channels, but owing to existing many technical barriers in the process that realizes relaying, therefore the research for collaboration communication has entered the bottleneck phase in the phase at the beginning of the eighties in last century.In the last few years, because the proposition of a user collaboration model of setting up with the diversity form under the condition of up link, cooperative communication technology had been subject to researcher's extensive concern again.

By cooperation technology is incorporated in the radio ultra wide band system, utilize cooperation technology both can improve the quality that receives signal, can also reduce the transmitting power of ultra-broadband emitter simultaneously, thereby prolong the stand-by time of node.But because the long time slot expansion that the multi-path dense characteristic of the complexity constraints of ultra wideband receiver and ultra-wideband channel causes is so that ultra wideband receiver is difficult to realize effective diversity merging, therefore in the cooperative ultra-wide band system, generally only select a via node, namely only set up an effective transistroute and realize for the relaying that transmits.Owing to existing a plurality of possible via nodes around each node, therefore the effective via node of How to choose just becomes a problem needing to overcome, existing reaction type relay node selecting method or synchronous relay node selecting method do not consider that radio ultra wide band system for specific (special) requirements such as the simplification of relay node selecting method, real time implementations, therefore is not suitable for being applied directly in the cooperative ultra-wide band system.The relay node selecting method of reaction type needs extra emitted energy in order to transmitting feedback information, even seldom the feedback information of bit number also will expend a large amount of node energies, therefore for requirements such as the simplification that guarantees relay node selecting method and real time implementations, the relay node selecting method in the cooperative ultra-wide band system should be asynchronous without feedback.

In the process of asynchronous Route Selection, a most key step is exactly that via node is transmitted the pilot signal that source node sends.The signal of transmitting for fear of each via node produces conflict when arriving destination node, causes a plurality of signal phase mutual interference that receives, and must be effectively the forwarding time slot of via node be reasonably distributed.

In the existing algorithm, a kind of scheme is that forwarding time slot is set to the form that is inversely proportional to this channel gain, wherein channel gain is calculated by the channel gain of source node to destination node according to two sub-links channel gains by via node, but this method is irrational, because the quality that the gain of channel can not the complete reaction physical link.Another kind of scheme is to adopt the error rate to estimate the method for channel quality, and forwarding time slot is set to the form that is directly proportional with the error rate.

Above-mentioned two kinds of forwarding time slot allocative decisions all are the Linear Mapping of setting up between channel quality and the time slot in essence.In the residing multi-path dense environment of indoor ultra-broadband, channel gain presents normal distribution during take decibel as unit.Thereby, channel gain often is near the average of normal distribution, the forwarding time slot of two via nodes is separated by shorter, when this time interval expands less than the multipath time slot of channel, the signal of two relay forwardings will be in the phase mutual interference of destination node place, thereby so that the performance of system descend to some extent.The relay forwarding signal is large at the collision probability of receiving terminal.

Summary of the invention

To the present invention seeks to adopt existing algorithm to carry out the relay forwarding signal in the large problem of the collision probability of receiving terminal in the cooperative ultra-wide band in order solving, to provide the forwarding time slot in the cooperative ultra-wide band to distribute and relay node selecting method.

Forwarding time slot distribution method in the cooperative ultra-wide band of the present invention may further comprise the steps:

The pilot signal that each via node reception sources node in step 1, the cooperative ultra-wide band sends;

Step 2, the pilot signal that receives according to step 1 are obtained respectively source node to the channel gain of k via node

, i=1 wherein, 2,3 ... k, k≤50;

The curve that step 3, k the channel gain that obtains according to step 2 come the channel gain of match Normal Distribution to change with probability density, with curve [

] be divided between gain region between the little gain region that N part area equates, wherein, N is the natural number greater than k, and 5000 〉=N 〉=100;

Step 4, distribute forwarding time slot according to the channel gain proportionate relationship between the little gain region of N part.

Based on above-mentioned steps, further comprise the steps to realize the relay node selecting method in the cooperative ultra-wide band:

Step 5, determine according to step 3 between the little gain region at channel gain place of each via node;

The forwarding time slot that step 6, destination node are determined according to step 4 receives the signal that the via node corresponding with it transmitted, and the error rate when calculating signal arrival corresponding to each time slot;

Step 7, select via node corresponding to the route of error rate minimum as the via node of forwarding data information signal, and will select situation with mode notification source node and each via node of broadcasting.

Advantage of the present invention: the present invention proposes a kind of forwarding time slot distribution method, obviously reduced the collision probability of relay forwarding signal at receiving terminal.

Set up nonlinear corresponding scheme between a kind of channel quality and the relay forwarding time slot, near the average interval is segmented, for the interval rough segmentation away from average, it is identical that thereby assurance falls into the probability in each section interval, and make the adjacent poor maximum time slots expansion greater than multipath channel of two interval corresponding time slots.

The inventive method can guarantee effectively that near forwarding time slot corresponding to channel gain average effectively distinguished, reduced the collision probability of relay forwarding signal at receiving terminal, and then can select fast an effective via node forwarding information, guaranteed the performance gain of cooperative ultra-wide band system.

Description of drawings

Fig. 1 is the forwarding time slot distribution method flow chart in the cooperative ultra-wide band, and Fig. 2 is the relay node selecting method in the cooperative ultra-wide band, and Fig. 3 is the cooperative ultra-wide band system schematic, and Fig. 4 is the channel gain distribution map, and Fig. 5 is non-linear relay forwarding time slot allocation schematic diagram.

Embodiment

Embodiment one: below in conjunction with Fig. 1, Fig. 3 to Fig. 5 present embodiment is described, the forwarding time slot distribution method in the present embodiment cooperative ultra-wide band may further comprise the steps:

The pilot signal that each via node reception sources node in step 1, the cooperative ultra-wide band sends;

Step 2, the pilot signal that receives according to step 1 are obtained respectively source node to the channel gain of k via node

, i=1 wherein, 2,3 ... k, k≤50;

Described channel gain

Obtain by following formula:

In the formula: Expression the iThe pulse signal that individual time slot receives;

Expression the iThe local template pulses signal of individual time slot via node;

Expression the iIndividual time slot via node is to the estimated value of noise;

The curve that step 3, k the channel gain that obtains according to step 2 come the channel gain of match Normal Distribution to change with probability density, with curve [

] be divided between gain region between the little gain region that N part area equates, wherein, N is the natural number greater than k, and 5000 〉=N 〉=100;

The channel gain curve of described Normal Distribution is probability density function:

(1)

Wherein, XBe channel gain, unit is decibel,

Be the average of k channel gain,

Be standard deviation.

Step 4, distribute forwarding time slot according to the channel gain proportionate relationship between the little gain region of N part.

The pilot signal that source node sends is forwarded to destination node by via node, in k via node, select an effective via node, wherein vital link is the distribution to a plurality of via node forwarding time slots, in a time slot, can not there be simultaneously two via node forward signals, to avoid conflict.

The channel gain curve that k channel gain makes up Normal Distribution as shown in Figure 4, abscissa is channel gain, unit be decibel, vertical being designated as probability density represents with formula (1).

According to the characteristic of normal distribution, channel gain X[

] in probability reach 99.7%, thereby, approximately here think [

] contained all channel gains in this interval XSituation.With curve [ ] be divided between gain region between the little gain region that N part area equates, area is probability.So that channel gain XFall into every section little probability between gain region and equate, referring to shown in Figure 5, provide a specific embodiment, k=50, N=200, namely [

] be divided between gain region between the little gain region that 200 parts of areas equate, therefore curve is normal distribution, therefore the length on transverse axis is nonlinear between these 200 parts of little gain regions, and near the interval time slot the average (normal distribution center) is short, and is long away from the interval time slot of average.What fall between the 1st part of little gain region is the channel gain of the 5th via node, what fall between the 2nd part of little gain region is the channel gain of the 2nd via node, what fall between the 3rd part of little gain region is the channel gain of the 7th via node, what fall between the 200th part of little gain region is the channel gain of the 13rd via node, because N is greater than k, therefore, do not fall into the channel yield value of any one via node in having between some little gain regions, have the channel gain that does not fall into any one via node between 150 parts of little gain regions in this specific embodiment, N is set greater than k, and the channel gain of two or more via nodes in order not occur to occur between a little gain region, in order to avoid conflict in 5000 〉=N 〉=100th.

Distribute forwarding time slot according to the channel gain proportionate relationship between 200 parts of little gain regions, be that forwarding time slot is allocated to non-linear relation, channel gain proportionate relationship between proportionate relationship 200 parts of little gain regions as shown in Figure 5, near the average (normal distribution center) interval time slot is short, interval time slot away from average is long, thereby guarantee that the probability that falls between the little gain region of each section is identical, and make the poor maximum time slot expansion greater than multipath channel of time slot corresponding between two adjacent little gain regions.The 1st time slot is transmitted the signal of the 5th via node, the 2nd time slot is transmitted the signal of the 2nd via node, the 3rd time slot is transmitted the signal of the 7th via node, the 200th time slot is transmitted the signal of the 13rd via node, the time slot that does not fall into the channel gain of any one via node is not transmitted, be in idle condition, namely wherein 150 time slots are in idle condition.

In order to reach minimizing of collision probability, the probability with between every section little gain region that proposes among the present invention is adjusted into identical, adopts non-linear relay forwarding slot allocation method, finishes based on following principle design:

If channel gain XFalling into i the probability between little gain region is p _i , then have at least two probability that in same time slot, arrive in k relay forwarding signal pFor:

(2)

To obtain minimum forward signal collision probability in order finding the solution, each forward signal to be fallen into the iProbability between individual little gain region p _i Be considered as variable, and they to satisfy sum be 1 constraints.Thereby, ask probability pMinimum problems can be summed up as the nonlinear programming problem of an Existence restraint condition, that is:

(3)

According to the Karush-Kuhn-Tucker optimal condition in the Non-Linear Programming,

(4)

Wherein, lIt is a constant; pRepresented by formula (2).Order SRight p _i Asking local derviation is 0, that is:

(5)

Be can be calculated by (5) , again according to constraints, can get At this moment, , reached minimizing of collision probability.

Embodiment two: below in conjunction with Fig. 2 present embodiment is described, based on the relay node selecting method of the forwarding time slot distribution method in the execution mode one described cooperative ultra-wide band, it is further comprising the steps of:

Step 5, determine according to step 3 between the little gain region at channel gain place of each via node;

The forwarding time slot that step 6, destination node are determined according to step 4 receives the signal that the via node corresponding with it transmitted, and the error rate when calculating signal arrival corresponding to each time slot;

The error rate is obtained by following formula:

BER= Q（SNR）

Wherein, BER is the error rate,

SNR is signal to noise ratio.

Step 7, select via node corresponding to the route of error rate minimum as the via node of forwarding data information signal, and will select situation with mode notification source node and each via node of broadcasting.

Carry out forward signal according to execution mode one described slot allocation method, after destination node receives, select a best via node to carry out forward signal as effective via node according to the error rate again.

Realize that forwarding time slot in the cooperative ultra-wide band of the present invention distributes and the device of relay node selecting method as shown in Figure 3,

1, at the transmitting terminal (being source node) of signal, by the pilot frequency sequence of pilot frequency sequence generator generation and the pulse of pulse generator generation, produces the pilot pulse of emission by pulse shaping device;

2, each via node carries out pulse correlation with the pulse signal template of this locality generation and the pilot pulse that receives;

3, each via node calculates channel gain and carries out the pilot tone that demodulation receives by the memory record;

4, each via node is according to the result who channel gain is carried out probability equivalence distribution device;

5, each via node obtains forwarding time slot according to result's coupling of probability equivalence distribution device.

6, each via node produces corresponding forwarding pulse by pilot storage and the control of time slot allocation device, and sends by antenna;

7, destination (being destination node) carries out relevant with local template pulses the signal that each time slot receives, calculate the channel gain of trunk channel corresponding to each time slot by gain calculator, the error rate calculation device calculates the error rate of each channel according to channel gain;

8, destination optimal value decision device is selected time slot corresponding to trunk channel with minimum bit-error rate, and selection result is encoded, and produces the pulse signal transmission that includes selection result by pulse generator.

Claims (5)

1. the forwarding time slot distribution method in the cooperative ultra-wide band is characterized in that, the method may further comprise the steps:

The pilot signal that each via node reception sources node in step 1, the cooperative ultra-wide band sends;

Step 2, the pilot signal that receives according to step 1 are obtained respectively source node to the channel gain X of k via node _i, i=1 wherein, 2,3 ... k, k≤50, k is natural number;

The curve that step 3, k the channel gain that obtains according to step 2 come the channel gain of match Normal Distribution to change with probability density, [μ-3 σ with curve, μ+3 σ] be divided between gain region between the little gain region that N part area equates, wherein, N is the natural number greater than k, and 5000 〉=N 〉=100, μ is the average of k channel gain, σ is standard deviation;

Step 4, distribute forwarding time slot according to the channel gain proportionate relationship between the little gain region of N part.

2. the forwarding time slot distribution method in the cooperative ultra-wide band according to claim 1 is characterized in that, the described channel gain X of step 2 _iEstimate by following formula:

$X_i=\frac{R_i}{S_i+{\mathrm{\σ}}_i}$

In the formula: R _iRepresent the pulse signal that i time slot receives;

S _iThe local template pulses signal that represents i time slot via node;

σ _iRepresent that i time slot via node is to the estimated value of noise.

3. the forwarding time slot distribution method in the cooperative ultra-wide band according to claim 1 is characterized in that, the channel gain curve of the described Normal Distribution of step 3 is probability density function:

$f\left(X\right)=\frac{1}{\sqrt{2\mathrm{\π}}\mathrm{\σ}}\exp (-\frac{{(X-\mathrm{\μ})}^2}{{2\mathrm{\σ}}^2}),$

Wherein, X is channel gain, and unit is decibel,

μ is the average of k channel gain,

σ is standard deviation.

4. based on the relay node selecting method of the forwarding time slot distribution method in the cooperative ultra-wide band claimed in claim 1, it is characterized in that, it is further comprising the steps of:

Step 5, determine according to step 3 between the little gain region at channel gain place of each via node;

The forwarding time slot that step 6, destination node are determined according to step 4 receives the signal that the via node corresponding with it transmitted, and the error rate when calculating signal arrival corresponding to each time slot;

Step 7, select via node corresponding to the route of error rate minimum as the via node of forwarding data information signal, and will select situation with mode notification source node and each via node of broadcasting.

5. the relay node selecting method in the cooperative ultra-wide band according to claim 4 is characterized in that, the described error rate of step 6 is obtained by following formula:

BER＝Q(SNR)

Wherein, BER is the error rate,

SNR is signal to noise ratio.

Images