CN103905172B - Method for scheduling pilot frequencies in broadband large-scale antenna system - Google Patents

Abstract

The invention discloses a method for scheduling pilot frequencies in a broadband large-scale antenna system. Pilot frequency signals are designed for users in the space dimensionality and the frequency dimensionality, and the method includes the following steps: firstly, pilot frequency signal resources are multiplexed in the time division and frequency division modes; secondly, pilot frequency resources are multiplexed by using limited angle spreading characteristics of channels in the spatial domain; finally, the pilot frequency resources are multiplexed by designing pilot frequency signals in the frequency domain dimensionality. In the scheduling process, by means of the method, the service quality of communication users in all channels can be guaranteed, the user experience can be accordingly improved, and the low complexity can be achieved.

Description

Pilot tone dispatching method in a kind of extensive antenna system in broadband

Technical field

The present invention relates to a kind of pilot resource distribution method of wireless communication system, more particularly, to one kind adopts matching transmission The extensive antenna system in broadband in pilot tone dispatching method.

Background technology

Mobile subscriber is to high speed data transmission service in recent years, such as the carrying of the demand such as web page browsing, transmission of video, telecommuting Height, promotes the fast development of mobile communication technology.Multi-antenna technology (mimo, multiple-input multiple- Output) combine OFDM (ofdm, orthogonal frequency division multiplexing) technology The spectrum efficiency of several bits per second per Hertz can be provided, the combination of both technology in recent years is adopted simultaneously by Modern Communication System Start commercial, such as wimax(worldwide interoperability for microwave access) system and lte (long term evolution) system.2010, the researcher of AT＆T Labs found that more antennas is installed and shape in base station The extensive antenna system energy depth excavated space dimension resource becoming, this system can provide tens even hundreds of bits per seconds every conspicuous Spectrum efficiency hereby.Due to drastically increasing spectrum efficiency, extensive antenna technology is widely paid close attention to by increasingly, is expected to Become one of key technology of future mobile communication system.

Extensive antenna system has more space links, so that needing more pilot resources to be used for obtaining instantaneous letter Road information.For improving efficiency of transmission, system need to reduce pilot resources expense, so that more Radio Resource is used for transmitting number According to.Thus, in extensive antenna system, pilot resources are very rare.This can make to exist non-orthogonal pilot tone in system, this Non-orthogonal pilot especially appears in adjacent cell, and this phenomenon is referred to as pilot pollution.Generally, wireless channel can be specific at certain Region in concentrate most energy.Energy in view of channel concentrates characteristic, if channel is in space or frequency dimension On do not overlap, above-mentioned pilot pollution phenomenon would not exist.Thus, the energy of channel concentrates characteristic can provide more pilot tones Resource, and then mitigate pilot pollution phenomenon.Channel for making user does not overlap on space or frequency dimension, needs pilot tone Resource is scheduling.

Content of the invention

Goal of the invention: in order to overcome the deficiencies in the prior art, the present invention provides a kind of broadband extensive aerial system Pilot tone dispatching method in system, is a kind of pilot tone dispatching algorithm of multiplexing on space and two dimension resources of frequency it is adaptable to adopt Extensive antenna system with orthogonal frequency division multiplexi；The pilot signal of the inventive method design can effectively reduce pilot tone and open Pin, and ensure the service quality of each user.

Technical scheme: for achieving the above object, the technical solution used in the present invention is:

Traditional pilot tone dispatching algorithm is scheduling with the mean square error of least mean-square error channel estimator for criterion, this Kind of mode is it cannot be guaranteed that the service quality (qos, quality of service) of each communication user, and the service quality of each user It is to weigh one of key index of scheduling quality.Pilot tone dispatching party in the extensive antenna system in a kind of broadband that the present invention provides Method, is scheduling for criterion with the assessment transfer rate of each user, can guarantee that the service quality of each communication user, and have relatively Low scheduling complexity；The inventive method specifically includes following steps:

(1) u user is obtained by periodic uplink transmissions detectable signal and each arrive the angle of arrival average of base station, time-delay power Spectrum, power fading coefficient and arrival angle pdf；All users are pressed the order sequence that angle of arrival average is incremented by, sequence Customs Assigned Number afterwards is: 0,1 ..., u ..., u-1；

The user being u for numbering, the total l of time-delay power spectrum_uIndividual footpath, the time delay in i-th footpath and normalized power are respectively For τ_uit_sAnd p_ui, noun normalization be expressed asWherein t_sFor sampling interval, τ_uiFor time delay after sampling；

The user being u for numbering, rate of citing sb. for meritorious service fading coefficients are β_u, arrival angle pdf is f_u(θ)；Wherein 0≤ θ<π；

(2) by time division multiplex and frequency division multiplexing mode, pilot resources are divided into numbering is 0,1 ..., g ..., g-1 G group；Note pilot tone subcarrier number is n_p；

The group being g for numbering, the frequency domain pilot signal wherein numbering the user being u is w_ux_g；Wherein x_gIt is g for numbering Group in length be n_pBasic pilot signal column vector, w_uFor k-th diagonal element it isDiagonal matrix, e be nature The truth of a matter, j is imaginary unit,It is the translocation factor of the user that numbering is u, set p={ p }={ 0,1 ..., n_p-1}；

It is followed successively by user's distribution each group pilot resources, distribute translocation factor in a group, if a group distributes shifting Location factor then changes one group, until distributing all groups；For arbitrary group, the method for distribution translocation factor is: is incremented by by number Element in order traversal set p, in ergodic process, for each element p execution step (3) successively in set p；

(3) numbering having distributed translocation factor user in a group is constituted set s₀, by all unallocated translocation factors The numbering of user constitutes set s₁；Numbering is in set s₀In all users when simultaneously communicating, numbering is that the assessment of the user of u passes Defeated speed is r_u(s₀), numbering is that the expectation transfer rate of the user of u is

By Customs Assigned Number incremental order, travel through set s₁In all numberings, in ergodic process, to arbitrary numbering u₁It is assumed that compiling Number be u₁User be allocated translocation factor p, that is, assume thatTwo conditions of investigation:

ⅰ、Wherein u ' is the numbering being allocated translocation factor user when executing this step recently；As Fruit to certain element p in this step unallocated translocation factor then it is assumed that this condition meet；λ₁Fixing door for value 0 to 0.5 Limit value；

, the user that arbitrary numbering is u is satisfied byWherein u ∈ s₀；

In above-mentioned two condition, set s₀Comprise numbering u₁；In ergodic process, if numbering is u₁User meet above-mentioned Two conditions, then numbering is u₁User be allocated translocation factor p, beOtherwise, numbering is u₁User do not divided Join translocation factor；Continue traversal set s₁Until traversal finishes.

In described step (3), numbering is in set s₀In all users when simultaneously communicating, numbering is the assessment of the user of u Transfer rate:

Wherein λ₂It is the threshold value of the fixation of value 0 to 1, m is antenna number, log₂() is the logarithm operation with 2 as bottom,Number in expression bracket is divided by n_pRemainder, function of many variables ψ () are calculated as follows:

If wherein molecule is zero, the value of fraction is zero, δ [] is Kronecker function；

Especially, if all users distribution identical translocation factor, numbering is the assessment transfer rate of the user of u:

$r_u\left(s_0\right)={\log }_2(1+\frac{\underset{m=0}{\overset{m-1}{\mathrm{\&sigma;}}}\frac{{\mathrm{\&beta;}}_u{f}_u^2(\mathrm{\&pi;m}/m)}{\underset{t\&element;s_0}{\mathrm{\&sigma;}}{\mathrm{\&beta;}}_t{f}_t(\mathrm{\&pi;m}/m)}}{\underset{t\&notequal;u}{\underset{t\&element;s_0}{\mathrm{\&sigma;}}}\underset{m=0}{\overset{m-1}{\mathrm{\&sigma;}}}\frac{{\mathrm{\&beta;}}_u{f}_t(\mathrm{\&pi;m}/m)f_u(\mathrm{\&pi;m}/m)}{\underset{s\&element;s_0}{\mathrm{\&sigma;}}{\mathrm{\&beta;}}_s{f}_s(\mathrm{\&pi;m}/m)}})-{\mathrm{\&lambda;}}_2.$

In described step (3), make to distribute the assessment of each user after translocation factor for user by investigating two conditions Transfer rate is more than expectation transfer rate, thus ensureing the service quality of each user.

Beneficial effect: pilot tone dispatching method in the extensive antenna system in broadband that the present invention provides, according to the inventive method After the translocation factor of design pilot signal, can guarantee that the service quality of each communication user, improve Consumer's Experience；And, full On the premise of sufficient QoS of customer, this pilot tone dispatching method generally can support most numbers of users on Spatial Dimension；This The pilot tone dispatching method of bright offer is scheduling for criterion based on the mean square error of least mean-square error channel estimator with existing Method compare, can guarantee that the service quality of user, and enable the pilot resources distribution of justice；The pilot tone dispatching party of the present invention In method, the complexity of Capacity Assessment and scheduling process is relatively low, realizes easily.

Brief description

Fig. 1 is the flow chart of the dispatching algorithm of the present invention；

Fig. 2 is the dispatching method QoS of customer proof diagram of the present invention.

Specific embodiment

Below in conjunction with the accompanying drawings the present invention is further described.

There is the single honeycomb of a base station at consideration center, and base station is mounted with m root linear array antenna, and it is double to be operated in the time-division Work pattern, this extensive antenna system is using (ofdm, the orthogonal frequency of the OFDM with Cyclic Prefix Division multiplexing) transmission technology, employ n subcarrier altogether.Base station is obtained by periodic uplink transmissions detectable signal Take all users each to the statistic channel information of base station, comprising: angle of arrival average, time-delay power spectrum, power fading coefficient and Reach angle pdf.It is assumed that having u user's expectation to be selected and base station communication in honeycomb, user presses angle of arrival average and is incremented by Serial number is: 0,1 ..., u-1.

By time division multiplex and frequency division multiplexing mode, it is 0 that pilot resources are divided into numbering to system, g of 1 ..., g-1 Group.Time division multiplex represents transmitting pilot signal on different time slots, and frequency division multiplexing represents the different sons in an ofdm symbol Pilot signal is launched on carrier wave.Without loss of generality, the pilot resources of the group that numbering is g are studied it is assumed that all users exist in this group T easet ofasubcarriers { 0, the △ ..., △ (n of certain ofdm symbol_p- 1) } upper transmitting uplink pilot signal, wherein △ leads for frequency domain Frequency subcarrier spacing, n_p=n/ △ is pilot tone subcarrier number.Numbering is that the frequency domain pilot signal of user's transmitting of u is w_ux_g, wherein x_gN for permanent envelope_p× 1 basic pilot signal vector, w_uFor k-th diagonal element it isTo angular moment Battle array (j is imaginary unit, and π is pi,It is the translocation factor of the user that numbering is u).Common basic pilot signal vector For zadoff chu sequence, by designing translocation factor, basic pilot signal vector can be multiplexed further.Distribute in this group The numbering of translocation factor user constitutes set s₀, unallocated translocation factor user can not communicate.

The user having distributed translocation factor launches uplink pilot signal simultaneously, and base station frequency-domain received signal matrix can represent For:

$y=\underset{u\&element;s_0}{\mathrm{\&sigma;}}\sqrt{{\mathrm{\&beta;}}_u}{h}_u\mathrm{\&xi;}{w}_u\mathrm{diag}\left\{x\right\}+n,$ (formula 1)

Wherein y is m × n_pMatrix, h_uIt is the matrix of the m × n being made up of the frequency domain channel parameter numbering the user being u, ξ For n × n_pExtraction matrix, β_uFor the power fading coefficient of u-th user, diag { x } is i-th diagonal element is the i-th of vector x The diagonal matrix of individual element, n is m × n_pNoise matrix, symbol ∈ represents relation belonging in set, and symbol ∑ represents summation fortune Calculate.Furtherly, h_uM row n column element represent user that numbering is u on m-th antenna port and n-th subcarrier Frequency domain channel parameter,Wherein e_iRepresent i-th element be 1 and length is the unit column vector of n.

After base station receives pilot signal, the channel having distributed translocation factor user to each is estimated.For expression side Just, introduce two mark: vec { x } and represent the column vector that each row of matrix x are stretched into a row composition, e { } represents to bracket In all stochastic variables ask expectation.Based on formula 1 and it is assumed above that, numbering is the channel h of the user of u_uLeast mean-square error Estimation is represented by:

$\mathrm{vec}\left\{{\hat{h}}_u\right\}={\mathrm{\&beta;}}_u{r_h}_u{(\mathrm{\&xi;}\&circletimes;i_m)}^h{r}_y^{-1}y{\left(w_u\mathrm{diag}\right\{x\left\}\right)}^h,$ (formula 2)

Wherein,

$r_y=\underset{t\&element;s_0}{\mathrm{\&sigma;}}{\mathrm{\&beta;}}_t[{\left(\mathrm{\&xi;}{w}_t{w}_u^h\right)}^t\&circletimes;i_m]r_{h_t}{[{\left(\mathrm{\&xi;}{w}_t{w}_u^h\right)}^t\&circletimes;i_m]}^h+{\mathrm{\&sigma;}}^2{i}_{{\mathrm{mn}}_p},$ (formula 3)

σ²For each received over subcarriers noise of every antenna of base station receiver Power, i_mRepresent the unit matrix of m × m, symbolThe operation of direct product (also referred to as kronecker amasss) of representing matrix, subscript h Represent conjugate transposition and inverse operation with -1 respectively.It is pointed out that the Minimum Mean Squared Error estimation device that formula 2 represents is in engineering In available Fourier transformation method simplify and realize.

Consider downlink transfer, and suppose the data transfer occupancy identical son load of allocated translocation factor user in a group Ripple set.According to channel estimation results in formula 2, base station can generate pre-coding matrix and transmit for descending multi-user.Do not lose one As property it is considered to data transfer on the n-th ' individual subcarrier for the user.On the m root antenna of base station, numbering is the transmitting number of the user of u According to forWhereinSymbol [x]_m,nThe m row n row of representing matrix x, q_uTable Show user that numbering the is u transmitting data on the n-th ' subcarrier.Then number is that the downlink data that receives of user of u can represent For:

$y_u={\mathrm{\&beta;}}_u{h}_u^t{\hat{h}}_u{q}_u+\underset{t\&notequal;u}{\underset{t\&element;s_0}{\mathrm{\&sigma;}}}{h}_u^t{\hat{h}}_t{q}_t+z_u,$ (formula 4)

Wherein, h_u=[[h_u]_0,n', [h_u]_1,n′,...,[h_u]_m-1,n′]^t, z_uRepresent the reception noise of the user that numbering is u. It is pointed out that due in this patent descending coupling precoding and up coupling receive there is identical transmission form, thus The method of the present invention is also applied for the uplink receiving using coupling.

When sub-carrier number and antenna number are enough, numbering is in set s₀In all users when simultaneously communicating, numbering is u's Transfer rate r on the single sub-carrier of user_u(s₀) can be assessed as:

(formula 5)

Wherein λ₂It is the threshold value of the fixation of value 0 to 1, l_uAnd f_u(θ) (0≤θ < π) represents the user that numbering is u respectively Time delay footpath number and the probability density function of angle of arrival, τ_uit_s(t_sFor sampling interval, τ_uiFor time delay after sampling) and p_uiRepresent respectively Numbering is the time delay in i-th time delay footpath of user and the normalized power of u, log₂() represents the logarithm operation with 2 as bottom, Represent the remainder divided by np for the number in bracket.In formula 5, the function of many variables

(formula 6)

Wherein δ [] is Kronecker function.Especially, if all users having distributed translocation factor use identical Translocation factor, numbering is that the transfer rate on the single sub-carrier of the user of u can be assessed as:

$r_u\left(s_0\right)={\log }_2(1+\frac{\underset{m=0}{\overset{m-1}{\mathrm{\&sigma;}}}\frac{{\mathrm{\&beta;}}_u{f}_u^2(\mathrm{\&pi;m}/m)}{\underset{t\&element;s_0}{\mathrm{\&sigma;}}{\mathrm{\&beta;}}_t{f}_t(\mathrm{\&pi;m}/m)}}{\underset{t\&notequal;u}{\underset{t\&element;s_0}{\mathrm{\&sigma;}}}\underset{m=0}{\overset{m-1}{\mathrm{\&sigma;}}}\frac{{\mathrm{\&beta;}}_u{f}_t(\mathrm{\&pi;m}/m)f_u(\mathrm{\&pi;m}/m)}{\underset{s\&element;s_0}{\mathrm{\&sigma;}}{\mathrm{\&beta;}}_s{f}_s(\mathrm{\&pi;m}/m)}})-{\mathrm{\&lambda;}}_2.$ (formula 7)

The probability density function f of angle of arrival in this patent_u(θ) support is 0≤θ < π, for arbitrary θ ∈ in practice (- π, 0), can use-θ to replace.

Numbering is that the expectation transfer rate of the user of u is designated asThe numbering of all users constitute set s=0,1 ..., u-1}.Under the criterion supporting most numbers of users, pilot tone scheduling (distribution translocation factor) problem is represented by:

Wherein symbol | s₀| represent set s₀Middle element number, symbolRepresent the relation belonging to of set, symbolIt is right to represent Arbitrarily,Represent and meet s₀ Under the conditions of s | s₀| the set corresponding to maximum.This patent adopts following three to walk The rapid scheduling problem solving in formula 8.Fig. 1 is the flow chart of the dispatching algorithm of the present invention, wherein symbol ← expression assignment operation, Symbol and ∪ represent the subtraction of set respectively and take union operation, null represents null value.If u '=null is it is believed that inequalitySet up.Fig. 2 is the dispatching method QoS of customer proof diagram of the present invention, the figure shows this The cumulative distribution function of each user's actual transfer rate after invention scheduling.

Step one, by periodic uplink transmissions detectable signal obtain u user each arrive the angle of arrival average of base station, time delay work( Rate spectrum, power fading coefficient and arrival angle pdf.All users are pressed the order sequence that angle of arrival average is incremented by, row Customs Assigned Number after sequence is: 0,1 ..., u-1.Numbering is the total l of user's time-delay power spectrum of u_uIndividual footpath, i-th footpath time delay and Normalized power is respectively τ_uit_sAnd p_ui.The user being u for numbering, rate of citing sb. for meritorious service fading coefficients are β_u, angle of arrival probability density Function is f_u(θ)(0≤θ<π).

Step 2, by time division multiplex and frequency division multiplexing mode, pilot resources are divided into numbering: g of 0,1 ..., g-1 Group.Note pilot tone subcarrier number is n_p, and remember set p={ 0,1 ..., n_p- 1 } (bracket represents with object in bracket as unit One set of element).Numbering be g group in number the user being u frequency domain pilot signal be w_ux_g, wherein x_gIt is g for numbering Group in length be n_pBasic pilot signal column vector, w_uFor k-th diagonal element it isDiagonal matrix (e be nature The truth of a matter, j is imaginary unit, and π is pi,It is the translocation factor of the user that numbering is u, symbol ∈ represents in set Relation belonging to).It is followed successively by user's distribution each group pilot resources, distribute translocation factor in a group, if a group distributes Translocation factor then changes next group, until distributing all groups.For arbitrary group, the method for distribution translocation factor is: by number Element in incremental order traversal set p.In ergodic process, below step is executed successively to each element p in set p.

The numbering having distributed translocation factor user in step 3, a group constitutes set s₀, all unallocated translocation factors The numbering of user constitutes set s₁.In set s during all telex networks, numbering is the assessment transfer rate of the user of u to numbering For r_u(s).Numbering is that the expectation transfer rate of the user of u is.Incremental order by number, travels through set s₁In all numberings. In ergodic process, to each numbering u₁It is assumed thatTwo conditions of investigation:(wherein u ' is to hold It is allocated the numbering of translocation factor user recently during this step of row.If to certain element p in this step unallocated displacement because Son is then it is assumed that this condition meets.λ₁Fixed threshold value for value 0 to 0.5), be u(u ∈ s for arbitrary numbering₀) use Meet per familyIn above-mentioned two condition, set s₀Comprise numbering u₁.In ergodic process, if numbering is u₁'s User meets above-mentioned two condition, then numbering is u₁User be allocated translocation factor p, beOtherwise, numbering is u₁ User be allocated translocation factor p.Continue traversal set s₁Until traversal finishes.

The condition investigated is reserved with λ in spatial domain₁Surplus so that pilot resources can fully be multiplexed on frequency domain. Pilot resources to a group, step 3 is when distributing translocation factor p, if also not distributing translocation factor p to any user, Think that condition meets.The condition investigated makes the assessment transfer rate of the user of all distribution translocation factors be more than expectation biography Defeated speed, hereby it is ensured that the service quality of all communication users.

The above be only the preferred embodiment of the present invention it should be pointed out that: for the ordinary skill people of the art For member, under the premise without departing from the principles of the invention, some improvements and modifications can also be made, these improvements and modifications also should It is considered as protection scope of the present invention.

Claims (2)

1. in a kind of extensive antenna system in broadband pilot tone dispatching method it is characterised in that: comprise the following steps:

(1) u user is obtained by periodic uplink transmissions detectable signal and each arrive the angle of arrival average of base station, time-delay power spectrum, work( Rate fading coefficients and arrival angle pdf；All users are pressed the order sequence that angle of arrival average is incremented by, after sequence Customs Assigned Number is: 0,1 ..., u ..., u-1；

The user being u for numbering, the total l of time-delay power spectrum_uIndividual footpath, the time delay in i-th footpath and normalized power are respectively τ_uit_s And p_ui, noun normalization be expressed asWherein t_sFor sampling interval, τ_uiFor time delay after sampling；

The user being u for numbering, rate of citing sb. for meritorious service fading coefficients are β_u, arrival angle pdf is f_u(θ)；Wherein 0≤θ ＜ π；

(2) by time division multiplex and frequency division multiplexing mode, pilot resources are divided into numbering is 0,1 ..., g ..., g of g-1 Group；Note pilot tone subcarrier number is n_p；

The group being g for numbering, the frequency domain pilot signal wherein numbering the user being u is w_ux_g；Wherein x_gThe group being g for numbering Middle length is n_pBasic pilot signal column vector, w_uFor k-th diagonal element it isDiagonal matrix, e be nature bottom Number, j is imaginary unit,It is the translocation factor of the user that numbering is u, set

Be followed successively by user's distribution each group pilot resources, distribute translocation factor in a group, if group distribute displacement because Son then changes one group, until distributing all groups；For arbitrary group, the method for distribution translocation factor is: incremental order by number Traversal setMiddle element, in ergodic process, for setIn each element p execution step (3) successively；

(3) numbering having distributed translocation factor user in a group is constituted setBy all unallocated translocation factor users' Numbering constitutes setNumbering is in setIn all users when simultaneously communicating, numbering is the assessment transfer rate of the user of u ForNumbering is that the expectation transfer rate of the user of u is

By Customs Assigned Number incremental order, traversal setIn all numberings, in ergodic process, to arbitrary numbering u₁It is assumed that number being u₁User be allocated translocation factor p, that is, assume thatTwo conditions of investigation:

ⅰ、Wherein u' is the numbering being allocated translocation factor user when executing this step recently；If right Certain element p in this step unallocated translocation factor then it is assumed that this condition meet；λ₁Fixed threshold for value 0 to 0.5 Value；

, the user that arbitrary numbering is u is satisfied byWherein

In above-mentioned two condition, setDo not comprise numbering u₁；In ergodic process, if numbering is u₁User meet above-mentioned two Individual condition, then numbering is u₁User be allocated translocation factor p, beOtherwise, numbering is u₁User be not allocated Translocation factor；Continue traversal setUntil traversal finishes.

2. in the extensive antenna system in broadband according to claim 1 pilot tone dispatching method it is characterised in that: described step (3), in, numbering is in setIn all users when simultaneously communicating, numbering is the assessment transfer rate of the user of u:

Wherein λ₂It is the threshold value of the fixation of value 0 to 1, m is antenna number, log₂() is the logarithm operation with 2 as bottom, Number in expression bracket is divided by n_pRemainder, function of many variables ψ () are calculated as follows:

If wherein molecule is zero, the value of fraction is zero, δ [] is Kronecker function；

Especially, if all users distribution identical translocation factor, numbering is the assessment transfer rate of the user of u: