CN102843162A - Method for performing spread spectrum communication in cellular network by device-to-device communication (D2D) technology - Google Patents

Abstract

The invention discloses a method for performing spread spectrum communication in a cellular network by a device-to-device communication (D2D) technology. The method comprises the following steps of: judging whether to build a D2D link or not if the D2D user requirement exists under a cellular system scene; performing spread spectrum on a symbol to be transmitted between D2D users to multiple sections of carriers of the whole frequency band; and performing frequency domain expansion on the signals transmitted by the D2D users through spreading codes and then transmitting the signals. By the method, the capacity of the system can be obviously increased, interference to cellular users is low, signaling is simple and high actual operation possibility is achieved.

Description

Adopt the spectrum spread communication method of D2D technology in a kind of cellular network

Technical field

The invention belongs to communication technical field, relate to the link transmission method between the D2D in a kind of cellular system.

Background technology

The inexorable trend of following wireless cellular communication network is two-forty, big capacity and higher QoS, how to use limited bandwidth resources to realize that WiMAXization seems particularly important effectively.And the local service of fast development in the current mobile Internet, for example video/music is shared, and also presses in existing Cellular Networks, to introduce new technology and support.Traditional cellular mobile communication networks all is centralized control, even two terminal equipments are adjacent very near, the communication between the terminal equipment must be carried out through base station and core net.Centralized Control System is convenient to resource management and Interference Control, but has individual shortcoming day by day remarkable, and promptly its resource utilization is not very high under certain scene.Such as, even two UE (terminal equipment) close proximity also will use double resource to communicate, comprise interface-free resources and base station passback resource.Wherein second problem recognized by industry, and in 3GPPR10, corresponding solution carried out standardization.

In order to improve the frequency spectrum service efficiency of eating dishes without rice or wine, reduce the heavy load of legacy cellular net, obtain higher throughput of system, the terminal under the cellular network is straight-through, and (Device-to-Device communication, D2D) research comes into one's own day by day.The terminal of D2D can be directly or under base stations control; Continuing the communication while that maintenance is carried out through the base station; Directly carry out data communication with another terminal; Thereby reduce taking of interface-free resources, improve system throughput, can also reduce communication delay simultaneously, reduce interference level, save the terminal energy.

Mostly the straight-through The Application of Technology scene in terminal is the type of local service, the professional and local file shared service such as data multicast.In the multi-case data business, service providers like the organizer of concert or other large-scale activities, need be sent the identical data of content to the participant of rally, and the organizer can utilize the D2D communication technology, accomplishes service immediately reliably.If user's local data (like file, photo, video etc.) in the time of need between neighboring terminals, sharing, also can be set up the terminal cluster through D2D, accomplish data sharing.In addition, the available business of D2D also comprises multiple person cooperational recreation in the mobile status, mobile advertisement service, friend-making business, inter-vehicular communication, moves relaying etc.

Compare with WLAN, the bluetooth that can support similar business, use unauthorized frequency range; Terminal in the cellular communication system leads directly under the control of base station; Use the authorized frequency bands resource of base station assigns; Can the control system interference level to obtain the direct communication in terminal of High Data Rate, can also enjoy the mobility advantage that cellular communication system brings simultaneously.D2D communication is to terminal use's the transparency in addition, and it need not suchly in WLAN and bluetooth to carry out loaded down with trivial details manual pairing and access point setting, thereby improves user's impression, is convenient to professional popularization.

The research of D2D transmission at present is also few, and the research that great majority relate to D2D lays particular emphasis on the distribution of resource and the control of interference more.During the multiplexing phone user's of D2D user resource, system is for fear of interference effect phone user's proper communication, and the algorithm of scheduling of resource is very complicated, causes very big overhead.

Summary of the invention

The object of the present invention is to provide the spectrum spread communication method that adopts the D2D technology in a kind of cellular network.

For achieving the above object, the present invention has adopted following technical scheme.

Have W phone user in the supposing the system, U is to D2D user, and the concrete steps of this communication means are:

1) each sends D2D request for building link information through common signal channel to the base station to D2D user;

2) after D2D request for building link information is received in the base station, be every pair of D2D user's allocation of subcarriers by the base station, the base station sends subcarrier allocation information and orthogonal intersection to every couple of D2D user through common signal channel then;

3) process step 2), whether possesses the condition of D2D link establishment by every couple of D2D user of base station judges;

4), use the time-domain signal after frequency domain spread spectrum method based on physical layer obtains frequency domain spread spectrum for the every couple of D2D user who possesses the link establishment condition.

The condition of said D2D link establishment is the interference power of D2D user to the phone user, or other control D2D users approach that the phone user is disturbed, and said approach comprises distance or the user angle with respect to the base station.

The concrete grammar of said step 3) is:

D2D sends the user and receives the user through the subcarrier that distributes to D2D and send signal, by base station judges D2D user whether each phone user's interference power is satisfied formula (1), and some power of disturbing satisfy formula (1) and then get into step 4),

$R<B{\log }_2(1+\frac{P}{({\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HDA00002131245500021.png,HDA00002131245500022.png"\; state="\{\{state\}\}">N</figure-callout>}}_0+P_I)})---\left(1\right)$

, in the formula (1), R is the information rate that the phone user needs, and B is the shared bandwidth of each phone user, and P is a received power, and when multiplexing upstream frequency resource, P is the base station end received power, when multiplexing downstream frequency resource, P is the received power of user side, P _IBe the interference power of D2D user to each phone user, N ₀Be the white Gaussian noise power spectral density.

If D2D user does not satisfy formula (1) to phone user's interference power; Then this base station lets D2D user use lower transmitting power to reduce interference power or the use longer orthogonal intersection of D2D user to each phone user, possesses the condition of D2D link establishment until D2D user.

The concrete grammar of said step 4) is:

It is the frequency expansion sequence C of M according to orthogonal intersection selection length that D2D sends the user _k, C _k=[c _k(0), c _k(1) ..., c _k(M-1)]; D2D sends the user and according to subcarrier allocation information the transmission information symbol of D2D is mapped on the corresponding subcarrier after through the frequency expansion sequence spread spectrum then, obtains symbol time-domain sampling value, shown in formula (2); Symbol time-domain sampling value is passed to D2D through subcarrier and receives the user

$s\left(m\right)=\frac{a}{\sqrt{M}}\underset{i=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{C}_k\left(i\right){\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="HDA00002131245500021.png,HDA00002131245500022.png"\; state="\{\{state\}\}">e</figure-callout>}}^j,$ 0≤m≤M-1?（2）

The symbol time-domain sampling value that s (m) sends for D2D user in the formula (2); A is for sending information symbol; J representes plural number,

Said frequency expansion sequence is the sequence that the auto-correlation degree is big, the cross-correlation degree is little, like Walsh-Hadamard (Walsh-hadamard) sequence, M sequence or Golden (Gordon) sequence.

In the said step 4), each is mutually orthogonal to the subcarrier that D2D user distributes, overlap or overlapping fully, and each distinguishes signal each other to D2D user through orthogonal intersection when subcarrier allocation is overlapping.According to the information that common signal channel sends, first couple of D2D user's using system K ₁To K ₁+ N ₁-1, be total to N ₁Number of sub-carrier, second couple of D2D user's using system K ₂To K ₂+ N ₂-1, be total to N ₂Number of sub-carrier, by that analogy, U is to D2D user's using system K _UTo K _U+ N _U-1, be total to N _UNumber of sub-carrier, because each is mutually orthogonal to the sub-carrier resources that D2D user distributes, overlap or overlapping fully, a number of sub-carrier can be by a plurality of D2D CUs, therefore from C _kIn must guarantee by quadrature between the frequency expansion sequence of the subcarrier of a plurality of D2D CUs when selecting sequence, guarantee that each can distinguish signal each other to D2D user through orthogonal intersection separately when subcarrier allocation is overlapping.

The invention has the beneficial effects as follows:

The present invention is directed to and have one or more pairs of D2D user's direct communications in the cellular network, propose a kind of method of simple D2D user's channelized frequencies resource, make them accomplish communication through the resource of sharing in the cellular network.The core of the inventive method is to transmit the information of a symbol with a plurality of subcarriers; And what these a plurality of subcarriers transmitted is the symbol behind the corresponding spread spectrum of this symbol; D2D user can multiplexing a plurality of Cellular Networks resource communicate, this method can but not need complicated algorithm and very big signaling consumption by the elevator system capacity.

The inventive method is a kind of to the D2D transmission technology under the cellular system, at OFDM, or on the basis of SC-FDMA signal is carried out spread spectrum at frequency domain; Like this; Just, make D2D user all less, although the Signal to Interference plus Noise Ratio of D2D link reduces at this moment to each phone user's interference with the interference whitening of D2D user to the phone user; But the error rate that the increase of bandwidth and spread spectrum bring gain can make that all the D2D link can obtain bigger throughput.In addition, when D2D user when increasing, the interference increase that the phone user receives is not remarkable, but the capacity of whole system but has bigger lifting.

Description of drawings

Fig. 1 is the LTE system scene graph that contains a pair of D2D link, ten phone users;

Fig. 2 representes D2D CU frequency band sketch map behind phone user and the spread spectrum;

Fig. 3 (a) is the overall system capacity contrast of various resource distribution modes under the macrocell scene of city;

Fig. 3 (b) is the overall system capacity contrast of various resource distribution modes under the macrocell scene of suburb;

Fig. 3 (c) is the overall system capacity contrast of various resource distribution modes under the Microcell scene of city;

Mode declaration pattern specification:

Pattern one does not contain D2D user's power system capacity;

Pattern two, the power system capacity of the multiplexing continuous 1M band resource of phone user of a pair of D2D user;

Pattern three, the power system capacity of the multiplexing whole section resource of a pair of D2D user.

Embodiment

Below in conjunction with accompanying drawing and embodiment the present invention is described further.

Referring to Fig. 1, for the ease of understanding, the present invention is an example with the D2D communication network under the LTE-A system, explains that the D2D technology is applied to cellular network, and the method for multiplexing multistage frequency resource block.Supposing the system has the 10MHz bandwidth, and ten phone users are arranged, and a pair of D2D user is arranged.The phone user here can be different with the D2D number of users.The present invention is blanket to the scene that all have this network structure model, and these D2D users communicate under the coordination of base station, and D2D user shares phone user's Internet resources.The LTE network that contains D2D is realized the better availability of frequency spectrum and bigger power system capacity than traditional LTE system, and can effectively promote the spectrum efficiency of Cell Edge User.But because new link is introduced, can there be interference in nest honeybee user to D2D user and D2D user to nest honeybee user.The present invention is directed to the interference that is brought behind the adding D2D link in the LTE system, proposed a kind of average method of disturbing, effectively the capacity of elevator system.Below in conjunction with emulation and accompanying drawing the present invention is done detailed description.Specifically may further comprise the steps:

1) based on the definition of 3GPP TR36.814 for three kinds of typical relay system wireless scene models; Be Case1 (city macrocell Urban macro), Case2 (suburb macrocell Suburban macro) and Case3 (city Microcell Urban micro); Select simulating scenes; Carry out the placement of base station and broadcasting sowing at random of user, and generate the large scale parameter of direct connected link, D2D link in the analogue system;

2) user who in the LTE wireless scene, places is phone user and D2D user, and phone user's number is 10, takies complete bandwidth 10M, and each phone user takies the 1M continuous bandwidth.The base station judges whether to satisfy the condition of link establishment to phone user's interference power according to D2D user: phone user's information rate is less than the capacity of channel.Promptly

$R<B{\log }_2(1+\frac{P}{({\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HDA00002131245500021.png,HDA00002131245500022.png"\; state="\{\{state\}\}">N</figure-callout>}}_0+P_I)})$

R is phone user's information needed speed, and B is phone user's bandwidth 1MHz, and P is received power (when multiplexing upstream frequency resource, P is the base station end received power, and when descending, P is the received power of user side when multiplexing), P _IBe the interference power of D2D user to the phone user, N ₀Be the white Gaussian noise power spectral density.

3) for the every couple of D2D user who possesses D2D link establishment condition, it is the frequency expansion sequence C of M according to orthogonal intersection Information Selection length that D2D sends the user _k, C _k=[c _k(0), c _k(1) ..., c _k(M-1)], and, when k ≠ l

$C_k{C_l}^T=0$

, T representing matrix transposition.

4) D2D sends the user and according to subcarrier allocation information the transmission information symbol of D2D is mapped on the corresponding subcarrier after through the frequency expansion sequence spread spectrum then, obtains symbol time-domain sampling value, is shown below

$s\left(m\right)=\frac{a}{\sqrt{M}}\underset{i=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{C}_k\left(i\right){\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="HDA00002131245500021.png,HDA00002131245500022.png"\; state="\{\{state\}\}">e</figure-callout>}}^j,$ 0≤m≤M-1

, the symbol time-domain sampling value that s in the formula (m) sends for D2D user, a is for sending information symbol, and j representes plural number.

Each information symbol that 5) D2D need be sent all set by step 4) method carries out sending behind the spread spectrum, and symbol is mapped as before the spread spectrum

0≤n≤N-1, d _iFor D2D sends information symbol, N is a number of sub carrier wave, and the sign map behind the spread spectrum does

0≤n≤N-1, D _iBe the symbol that D2D behind the spread spectrum sends, L is the number of the subcarrier behind the spread spectrum.

As can beappreciated from fig. 3, transmission method according to the invention has bigger lifting to the capacity of whole system, and Fig. 3 c is that the interference between D2D user and the phone user is big, has influenced the capacity of whole system because radius of society is little at this moment.

Claims (7)

1. adopt the technological spectrum spread communication method of D2D in a cellular network, it is characterized in that the concrete steps of this communication means are:

1) each sends D2D request for building link information through common signal channel to the base station to D2D user;

2) after D2D request for building link information is received in the base station, be every pair of D2D user's allocation of subcarriers by the base station, the base station sends subcarrier allocation information and orthogonal intersection to every couple of D2D user through common signal channel then;

3) process step 2), whether possesses the condition of D2D link establishment by every couple of D2D user of base station judges;

4), use the time-domain signal after frequency domain spread spectrum method based on physical layer obtains frequency domain spread spectrum for the every couple of D2D user who possesses the link establishment condition.

2. according to the spectrum spread communication method that adopts the D2D technology in the said a kind of cellular network of claim 1; It is characterized in that: the condition of said D2D link establishment is the interference power of D2D user to the phone user; Or other control D2D users approach that the phone user is disturbed, said approach comprises distance or the user angle with respect to the base station.

3. according to the spectrum spread communication method that adopts the D2D technology in the said a kind of cellular network of claim 1, it is characterized in that: the concrete grammar of said step 3) is:

D2D sends the user and receives the user through the subcarrier that distributes to D2D and send signal, by base station judges D2D user whether each phone user's interference power is satisfied formula (1), and some power of disturbing satisfy formula (1) and then get into step 4),

$R<B{\log }_2(1+\frac{P}{(N_0+P_I)})---\left(1\right)$

, in the formula (1), R is the information rate that the phone user needs, and B is the shared bandwidth of each phone user, and P is a received power, and when multiplexing upstream frequency resource, P is the base station end received power, when multiplexing downstream frequency resource, P is the received power of user side, P _IBe the interference power of D2D user to each phone user, N ₀Be the white Gaussian noise power spectral density.

4. according to the spectrum spread communication method that adopts the D2D technology in the said a kind of cellular network of claim 3; It is characterized in that: if D2D user does not satisfy formula (1) to phone user's interference power; Then this base station lets D2D user use lower transmitting power to reduce interference power or the use longer orthogonal intersection of D2D user to each phone user, possesses the condition of D2D link establishment until D2D user.

5. according to the spectrum spread communication method that adopts the D2D technology in the said a kind of cellular network of claim 1, it is characterized in that: the concrete grammar of said step 4) is:

It is the frequency expansion sequence C of M according to orthogonal intersection selection length that D2D sends the user _k, C _k=[c _k(0), c _k(1) ..., c _k(M-1)], D2D sends the user and according to subcarrier allocation information the transmission information symbol of D2D is mapped on the corresponding subcarrier after through the frequency expansion sequence spread spectrum then, obtains symbol time-domain sampling value, shown in formula (2)

$s\left(m\right)=\frac{a}{\sqrt{M}}\underset{i=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{C}_k\left(i\right)e^{j\frac{2\mathrm{\&pi;}}{M}\mathrm{im}},$ 0≤m≤M-1

（2）

The symbol time-domain sampling value that s (m) sends for D2D user in the formula (2), a is for sending information symbol, and j representes plural number.

6. according to the spectrum spread communication method that adopts the D2D technology in the said a kind of cellular network of claim 5, it is characterized in that: said frequency expansion sequence is Walsh-Hadamard sequence, M sequence or Golden sequence.

7. according to the spectrum spread communication method that adopts the D2D technology in the said a kind of cellular network of claim 1; It is characterized in that: in the said step 4); Each is mutually orthogonal to the subcarrier that D2D user distributes, overlap or overlapping fully, and each distinguishes signal each other to D2D user through orthogonal intersection when subcarrier allocation is overlapping.

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