CN102843162B - 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

In a kind of cellular network, adopt the spectrum spread communication method of D2D technology

Technical field

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

Background technology

The inexorable trend of following wireless cellular communication network is two-forty, large capacity and higher QoS, how effectively to use limited bandwidth resources to realize WiMAX and seems particularly important.And the local service of fast development in current mobile Internet, for example video/music is shared, and also supports in the urgent need to introduce new technology in existing Cellular Networks.Traditional cellular mobile communication networks is all centralized control, even if two terminal equipments are adjacent very near, the communication between terminal equipment must be undertaken by base station and core net.Centralized Control System is convenient to resource management and is disturbed and control, but has individual shortcoming day by day remarkable, and under certain scene, its resource utilization is not very high.Such as, even two UE(terminal equipments) close proximity, also communicate by double resource, comprise interface-free resources and base station passback resource.Wherein Second Problem, is recognized by industry, and in 3GPPR10, corresponding solution is carried out to 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, terminal straight-through (Device-to-Device communication, the D2D) research under cellular network comes into one's own day by day.The terminal of D2D can be directly or control in base station under, keep the communication while of being undertaken by base station in continuation, 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 terminal energy.

The application scenarios of the straight-through technology of terminal mostly is the type of local service, such as data multicast service and local file shared service.In multi-case data business, the supplier of service, as the organizer of concert or other large-scale activities, need to send the data that content is identical to the participant of rally, and organizer can utilize the D2D communication technology, immediately completes reliably service.If user's local data (as file, photo, video etc.) need to, in the time that adjacent terminal room is shared, also can be set up terminal cluster by D2D, complete data sharing.In addition, the available business of D2D also comprises multiple person cooperational game in mobile status, mobile advertisement service, friend-making business, inter-vehicular communication, mobile relay etc.

Compared with can supporting similar business, the WLAN that uses unauthorized frequency range, bluetooth, terminal in cellular communication system leads directly under the control of base station, use the authorized frequency bands resource of base station assigns, can control system interference level to obtain the terminal Direct Communication of High Data Rate, can also enjoy the mobility advantage that cellular communication system brings simultaneously.In addition the D2D transparency to terminal use of communicating by letter, it is without carry out like that loaded down with trivial details manual pairing and access point setting in WLAN and bluetooth, thereby improves user's impression, is convenient to the popularization of business.

The research of D2D transmission is at present 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.When 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 large overhead.

Summary of the invention

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

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

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

1) each D2D request for building link information that D2D user is sent to base station by common signal channel;

2) receive after D2D request for building link information base station, is every pair of D2D user assignment subcarrier by base station, and then base station sends subcarrier assignment information and orthogonal intersection to every couple of D2D user by common signal channel;

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

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

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

The concrete grammar of described step 3) is:

D2D sends user and receives user's transmitted signal by the subcarrier distributing to D2D, judges by base station whether D2D user meets formula (1) to each phone user's interference power, if interference power meets formula, (1) enters step 4),

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

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

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

The concrete grammar of described step 4) is:

D2D sends user and selects according to orthogonal intersection the frequency expansion sequence C that length is M _k, C _k=[c _k(0), c _k(1) ..., c _k(M-1)], then D2D transmission user is mapped to the transmission information symbol of D2D on corresponding subcarrier according to subcarrier assignment information after frequency expansion sequence spread spectrum, obtain symbol time-domain sampling value, as shown in Equation (2), symbol time-domain sampling value is passed to D2D by subcarrier and receives user

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

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

Described frequency expansion sequence is the sequence that auto-correlation degree is large, cross-correlation degree is little, as Walsh-Hadamard(Walsh-Hadamard) sequence, M sequence or Golden(Gordon) sequence.

In described step 4), each subcarrier to D2D user assignment is mutually orthogonal, partly overlap or completely overlapping, each when group allocation of carriers is overlapping D2D user distinguished to signal each other by orthogonal intersection.The information sending according to common signal channel, first couple of D2D user uses system K ₁to K ₁+ N ₁-1, N altogether ₁individual subcarrier, second couple of D2D user uses system K ₂to K ₂+ N ₂-1, N altogether ₂individual subcarrier, by that analogy, U uses system K to D2D user _uto K _u+ N _u-1, N altogether _uindividual subcarrier, because each sub-carrier resources to D2D user assignment is mutually orthogonal, partly overlap or completely overlapping, a subcarrier can be by multiple D2D CUs, therefore from C _kwhen middle Selective sequence, must ensure by orthogonal between the frequency expansion sequence of the subcarrier of multiple D2D CUs, respectively while ensureing that group allocation of carriers is overlapping can distinguish signal each other to D2D user by orthogonal intersection separately.

The invention has the beneficial effects as follows:

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

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

Brief description of the drawings

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

Fig. 2 represents D2D CU frequency band schematic diagram after phone user and 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 scene of Microcell, city;

Mode declaration pattern specification:

Pattern one, containing 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 of resource of a pair of D2D user.

Embodiment

Below in conjunction with drawings and Examples, the invention will be further described.

Referring to Fig. 1, for the ease of understanding, the present invention, taking the D2D communication network under a LTE-A system as example, illustrates that D2D technology is applied to cellular network, and the method for multiplexing multistage frequency resource block.Supposing the system has 10MHz bandwidth, has ten phone users, has a pair of D2D user.The phone user here and D2D number of users can be different.The present invention is blanket to all scenes with 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 larger 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 is interference to D2D user and D2D user to nest honeybee user in nest honeybee user.The present invention is directed in LTE system and add the interference bringing after D2D link, proposed a kind of average method of disturbing, the effectively capacity of elevator system.Below in conjunction with emulation and accompanying drawing, the present invention is described in detail.Specifically comprise the following steps:

1) definition for three kinds of typical relay system wireless scene models according to 3GPP TR36.814, be Case1(city macrocell Urban macro), Case2(suburb macrocell Suburban macro) and Case3 (Microcell, city 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 in analogue system, D2D link;

2) user who places in LTE wireless scene is phone user and D2D user, and phone user's number is 10, takies complete bandwidth 10M, and each phone user takies 1M continuous bandwidth.Base station judges whether to meet 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.?

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

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

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

$C_k{C_l}^T=0$

, T representing matrix transposition.

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

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

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

5) each information symbol that D2D need to be sent is all undertaken sending after spread spectrum by the method for step 4), and before spread spectrum, symbol is mapped as 0≤n≤N-1, d _ifor D2D sends information symbol, N is number of sub carrier wave, and the sign map after spread spectrum is 0≤n≤N-1, D _ifor the symbol that D2D after spread spectrum sends, L is the number of the subcarrier after spread spectrum.

As can be seen from Figure 3, transmission method of the present invention has larger lifting to the capacity of whole system, and Fig. 3 c is that the interference between D2D user and phone user is large because now radius of society is little, has affected the capacity of whole system.

Claims (5)

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

1) each D2D request for building link information that D2D user is sent to base station by common signal channel;

2) receive after D2D request for building link information base station, is every pair of D2D user assignment subcarrier by base station, and then base station sends subcarrier assignment information and orthogonal intersection to every couple of D2D user by common signal channel;

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

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

Described step 3) concrete grammar be:

D2D sends user and receives user's transmitted signal by the subcarrier distributing to D2D, judge by base station whether D2D user meets formula (1) to each phone user's interference power, if interference power meets formula, (1) enters step 4)

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

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

Described step 4) concrete grammar be:

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

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

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

2. adopt according to claim 1 the spectrum spread communication method of D2D technology in a kind of cellular network, it is characterized in that: the condition of described D2D link establishment is the interference power of D2D user to phone user, or other control the approach that D2D users disturb phone user, described approach comprises that distance or user are with respect to the angle of base station.

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

4. the spectrum spread communication method that adopts according to claim 1 D2D technology in a kind of cellular network, is characterized in that: described frequency expansion sequence is Walsh-Hadamard sequence, M sequence or Golden sequence.

5. adopt according to claim 1 the spectrum spread communication method of D2D technology in a kind of cellular network, it is characterized in that: described step 4) in, each subcarrier to D2D user assignment is mutually orthogonal, partly overlap or completely overlapping, each when group allocation of carriers is overlapping D2D user distinguished to signal each other by orthogonal intersection.