CN102150371B - Method for transmission in a wireless communication system - Google Patents

Abstract

The present invention relates to a method for transmission in a wireless communication system and more particularly to a method in a transmitter which comprises a plurality of transmit antennas. An example embodiment according to the invention comprises encoding of signals for transmission and provides for transmission over a selected number of transmit antennas.

Description

The method of in wireless communication system, transmitting

Technical field

The present invention relates in wireless communication system, transmit, more specifically, relate at one and have the method for transmitting in the transmitter of a plurality of transmit antennas.In addition, also will the cover transmitter device relevant with the method be disclosed.

Background technology

If a transmitter possesses many transmit antennas, just can in transmission plan miscellaneous, select according to transmission destination.Transmission plan can be divided into two classes according to the inspiration mode, just with regard to its diversity and capacity thereof.But some transmission plan possesses the characteristics of capacity and diversity two aspects simultaneously.

Be to improve the reliability of wireless link, be to be main flow with the transmit diversity scheme in the prior art always.Most transmit diversity scheme normally designs to keep a simple receiver architecture, and these schemes generally can both normally play a role under the situation of single reception antenna.The spectrum efficiency of transmission diversity is lower, if but other technology such as transmission diversity and link circuit self-adapting be used, just can slightly improve its spectrum efficiency.

For realizing transmission diversity, may from surpass a transmit antenna, transmit each information bit or symbol.Thus, each bit or symbol make up and see through specific receiver to I haven't seen you for ages by two different fading channels, just can realize diversity.Therefore, just drawn the simple method of a cover: the identical symbol of transmission from all available transmit antennas.But if use this straightforward procedure, because the decline of channel, the symbol that has transmitted in receiver may the interference of being damaged property, can't realize performance gain.Use many reception antennas can evade the unfavorable conditions that this destructive combination is brought, but this can improve cost and the complexity of receiver.

Another solution of evading the problems referred to above is: adopt orthogonal space time-code (STC).STC is the transmit diversity scheme that is widely known by the people, and it realizes that by empty time-code design single antenna receives.The STC of orthogonal design can also avoid at the receiver antenna signal cancellation taking place with this from the different symbol of different antenna transmission in each instantaneous transmission.On the contrary, a plurality of instantaneous transmission then are used for guaranteeing transmitting each symbol from surpassing a strip antenna, thereby realize transmission diversity.Therefore, see through STC, symbol is become code (being assigned with) on many strip antennas and a plurality of symbol time interval.Need not service time as second dimension, above-mentioned is example with empty time-code just.In fact, this so-called " auxiliary dimension " may refer to frequency, and it can specify empty sign indicating number frequently (SFC) and encoder, uses a plurality of mark spaces then in frequency domain.In following comment, will adopt STC in order to read, but please note other auxiliary dimension that we may be beyond service time.

By famous Alamouti Code Design, only when using two transmit antennas, just can use the STC(of full rate orthogonal design for example to use a modulation symbol of in each channel, transmitting effectively).If the orthogonality of STC must be occupied an leading position, increasing antenna amount so, in each employed channel effective quantity of transmission symbol must be reduced by at least in 1, so just no longer reach full rate.In four strip antenna transmit diversity scheme, according to 3GPP LTE version 8 standards, the antenna of full rate Alamouti code and this wire jumper mode of employing, article two, based on antenna transmission diversity (SFC) encoder of Alamouti scheme, the frequency direction of their output is checker between antenna 1 and 2 and in the transmission between antenna 3 and 4.This scheme namely is that space-time/frequency block code adds upper frequency switching transmission diversity (SFBC+FSTD).

Compare with transmission diversity, space multiplex (MUX) (SMUX) scheme is with well-known with remarkable room for promotion effect through transmitting the multilayer independent data stream simultaneously.Generally speaking, can transmit a stream of every transmit antenna, or be equivalent to from (different) modulation symbol of every strip antenna transmission.One of them shortcoming of SMUX scheme is the complexity of receiver, for example for carrying out linear detection and meeting the complexity of the receiver that requirement that number of antennas must equal flow amount at least establishes.This is because disturb (ISI) to be handled by multi-input multi output (MIMO) receiver that can reduce ISI between the stream that occurs in the SMUX scheme.In some broadcast system, for example meet the Single Frequency Network multimedia broadcasting (MBSFN) of 3GPP standard, many user terminals can receive identical transmission signal, and user terminal may have been equipped the reception antenna of varying number; Wherein even only equipped a single reception antenna.Therefore, in the system of these types, adopt the SMUX scheme can not improve space efficiency, this is because the single antenna user terminal can't receive multilayer.

Space modulation (SM) is a cover transmission plan, its objective is in that not introduce the ISI(reason the same with above-mentioned SMUX scheme) situation under improve space efficiency, thereby and the complexity of reduction receiver.In the SM scheme, transmitter uses the information bit of transmitter side with selection modulation constellation symbol, and selection will be for the antenna of transmission symbol.Then, the task of receiver which modulation symbol that has been detected transmission and transmission are from which strip antenna.

The SM scheme refers to generalized space offset keying (GSSK), and this is the technology that is widely adopted, and selects a strip antenna for each employed channel, and every strip antenna all can transmit identical waveform.Therefore, this scheme need not used modulation symbol.And modulation constellation also is flat-footed.When selecting modulation constellation, do not need any bit is encoded.There is kind of a saying to be in addition, in GSSK, when antenna is in active state, can transmits a constant that is used for pre-defined waveform.Therefore, only one information transfer mechanism is to select antenna according to active transmission in this GSSK scheme.

Summary of the invention

How to improve the space efficiency of wireless communication system, this is a ubiquitous problem, so especially to the MBSFN network.The objective of the invention is to have the space efficiency of the transmitter of many transmit antennas with raising for wireless communication system provides transmission plan.

Sum up method and the transmitter scheme that draws according to embodiments of the invention, compare with the solution that draws according to prior art, can realize higher space efficiency, this is because transmission plan allows to select from the N strip antenna K bar transmitting, and uses non-flat-footed modulation constellation on the selected antenna.

In addition, according to the present invention and the transmission side that formulates allows will encoding from the selected antenna of K bar, according to the modulation symbol of the T mark space transmission of auxiliary dimension (for example time or frequency), thereby avoid taking place on the receiver signal cancellation.

Say further again, from the selected antenna of K bar, according to the preferential transmission diversity coded system of selecting of the modulation symbol meeting of the T mark space transmission of assisting dimension (for example time or frequency), for encode back bit and the bit of not encoding provide diversity gain, thereby guarantee that diversity gain also has higher encoding rate.

During describing in detail, the following embodiment of the invention will mention its other advantage.

Description of drawings

Accompanying drawing is for illustrating and explain the present invention, wherein:

Fig. 1 shows one embodiment of the present of invention;

Fig. 2 shows one embodiment of the present of invention, and wherein broad sense antenna modulated (GAM) encoder comprises a modulator and a transmission diversity encoder;

Fig. 3 shows one embodiment of the present of invention, and wherein the GAM encoder comprises a modulator and an Alamouti orthogonal block code encoder;

Fig. 4 shows one embodiment of the present of invention, and wherein the GAM encoder comprises a space multiplexer;

Fig. 5 shows one embodiment of the present of invention example, and wherein transmitter comprises a diversification spaced antenna;

Fig. 6 shows the analog result of the transmission plan of formulating according to the present invention; And

Fig. 7 shows the extra analog result of the transmission plan of formulating according to the present invention.

Embodiment

According to above-mentioned space modulation (SM) scheme, in N bar available transmit antennas, select wherein one to transmit, that is to say

The position

Can and use the modulation constellation that has M signaling point to encode according to the sky line options, then, log ₂Can select to encode in the M position according to the modulation constellation symbol.In above-mentioned expression formula,

Integer value like the representative value of allowing x approaches is recently as far as possible transmitted (if select wherein two in the middle of a plurality of transmit antennas, this will be very practical) because a fraction of bit can not see through selected antenna.Therefore,

The position

Sum can be sent to each employed channel.

According to the GSSK scheme that preamble is mentioned, will select the K strip antenna in the information transmitted position, and remaining N-K strip antenna does not transmit anything.See through the method, select in the N strip antenna and select K bar (K〉1), this has the multiple choices combination can be for considering (unless having selected whole antenna K=N), the situation of contrast K=1, and the information bit quantity of selected antenna transmission will increase.From can finding this point easily the lower inequality,

$\left(\begin{array}{c}\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="HDA0000063362170000032.png"\; state="\{\{state\}\}">N</figure-callout>}\\ 1\end{array}\right)<\left(\begin{array}{c}\mathrm{<figure-callout\; id="1"\; label="N\; K"\; filenames="HDA0000063362170000032.png"\; state="\{\{state\}\}">N</figure-callout>}& \\ K\end{array}\right)$ 1＜K＜N wherein,

In this inequality, binomial $\left(\begin{array}{c}N\\ K\end{array}\right)$ Be for the quantity of selecting the peculiar mode of K bar at the N strip antenna.Therefore, contrast is selected 1 in the N strip antenna, select the K bar and can bring more combination all the time in the N strip antenna, and the latter comprises more information.In addition, in GSSK, in N bar available transmit antennas, select K bar (wherein K〉1), this expression

Bit

Can encode according to the sky line options, but in this GSSK scheme, zero-bit unit (M=1) is used for flat-footed (single-point) modulation constellation symbol.

Problems such as space efficiency transmission plan are provided for solution, and we provide day line options modulation (ASM) method, wherein comprise broad sense antenna modulated (GAM) encoder and a sky line options encoder.The GAM encoder takies an input bit at least, seeing through T sigtnal interval exports K output signal (wherein 1＜K), and a day line options encoder takies an input bit at least, in the N of K output signal bar transmit antenna, select and reservation K bar, according to the T symbol transmission at interval, wherein N represents the transmit antenna quantity of transmitter, and 1＜K＜N.It line options encoder reception antenna is selected bit, and output will activate and be used for the K index of the antenna of transmission GAM encoder output then.

Each K output of GAM is a modulation symbol, and the constellation size that belongs to each output respectively is m _k, k=1 ..., the symbol of K.m _i＞1 because the bit number that inputs to GAM is at least 1, will be (the m for example of the non-flat-footed constellation of one of them use in K the GAM output at least _i＞1).That is to say to have at least can transmit a non-flat-footed modulation symbol in the selected antenna.The flat-footed modulation constellation example of the expense that can use in the GAM encoder is as follows: OOK, BPSK, M-PSK or M-QAM.

General thought of the present invention is: the bit for the antenna of selecting according to sky line options bit will transmit, use extra dimension when it is encoded.Can see extra dimension in the output of GAM encoder, this encoder can be exported K according to T 〉=1 mark space〉1 coded identification.

Fig. 1 has shown according to the present invention and the ASM transmitter embodiment that makes.Transmitter comprises a diversification N transmit antenna that is used at wireless communication system transmission signal.Receive input signal, this signal comprises bits (a (k)) to be transmitted such as a plurality of.The diversity of the bit that receives may be that the bit of coding that polylith is used to transmit constitutes code word, also may be a not bits of coded flow filament.The bit of receiving can be separated into the r that waits a moment coding in the bit separator _eBit (or at least one bit) and be used for the r of day line options _aBit (or at least one bit).The r that waits a moment coding that bit separator equipment produces _eBit can be provided for the GAM encoder, in the case, and r _eBit will be encoded in encoder, generates at interval in K the coding output symbol according to the T symbol transmission, for example can obtain T cover K coded identification.

The r that is used for day line options _aBit one of can be provided a day line options encoder, and each N transmit antenna has the antenna index of a uniqueness therein.Its line options encoder is selected K the antenna index relevant with K the transmit antenna that will activate in N the transmit antenna.Wherein K can be selected and keep to it line options encoder in N associated antenna, in order to carry out the GAM transmission at interval according to the T symbol transmission; It line options encoder reservation is carried out synchronous ASM output signal according to the T mark space.Listed a day line options encoder in the table 1, wherein K=2 and N=4, four antennas obtain allocation index 1,2,3 and 4 respectively.For example, for bit 00, manipulative indexing is (1,2); For bit 01, corresponding index is (1,3), so analogizes.

Table 1: day line options encoder instances, the K=2 strip antenna in two sky line options bit selective systems wherein, the N=4 strip antenna can be used altogether

It line options bit r a	The index of selected antenna
		00	1,2
01	1,3
		10	2,4
11	3,4

At last, K coded identification of T cover transmitted according to the T mark space respectively, and each coded identification in K coded identification transmit antenna in the selected K bar transmit antenna that is associated with K antenna index is respectively transmitted.

Fig. 2 has shown according to the present invention and another transmission plan embodiment of formulating.Adopted ASM-TXD(days line options modulations among this embodiment, transmission diversity) scheme, therefore the GAM encoder device comprises a Symbol modulator and a transmission diversity (TXD) encoder in this example embodiment.Can use quadrature STC in the transmission diversity encoder, for example two-dimentional STC usage space dimension and an extra auxiliary dimension (for example time or frequency).Two-dimensional design (for example quadrature STC) requires channel invariable in the T mark space of auxiliary dimension, to guarantee its orthogonality.Therefore, when in the N strip antenna, selecting the K bar according to sky line options encoder, must guarantee that the antenna selectivity constant is at T at least〉1 symbol time remain unchanged at interval or in the corresponding frequency slots.

The example of ASM-TXD scheme (when K=2 selected antenna) is based on the Alamouti encoder of Space-Time Block Coding (STBC) or space-time/frequency block code (SFBC), and time wherein or frequency dimension have adopted the T=2 mark space.Fig. 3 has shown a typical ASM-TXD encoder embodiment who adopts the Alamouti encoder.Modulator is with log ₂The M bit obtains a modulation symbol that extracts as input according to configuration from the symbol constellation with M different symbol.For example, for BPSK M=2 with for 16-QAM M=16.

For example, one group of 2log of modulation ₂The M bit is to obtain one group of totally two modulation symbol s respectively _k, s _K+1, each symbol all extracts a symbol constellation from the M symbol.The two symbolss _k, s _K+1Then, these two symbol s _k, s _K+1Can on two strip antennas, carry out the Alamouti coding according to two symbol output gaps, and in this example, K=2, T=2.

Below be an Alamouti orthogonal block code exemplifying embodiment that is widely known by the people,

$\underset{\mathrm{Auxdim}1\mathrm{Auxdim}2}{\left(\begin{array}{cc}{s}_k& -s_{k+1}^{*}\\ s_{k+1}& s_k^{*}\end{array}\right)}\begin{array}{c}\mathrm{Autenna}1\\ \mathrm{Antenna}2\end{array},$

Wherein, each guild sees through different antennas and transmits, and each row then sees through different auxiliary dimensions and transmits (as mentioned above, auxiliary dimension is exemplified as time and frequency).The Alamouti encoder can be respectively according to the mark space among auxiliary dimension k and the k+1, export coded identification y for antenna 1 and antenna 2 generate _k, z _kAnd y _K+1, z _K+1Symbol behind these codings can select the selected antenna of encoder to transmit from the K=2 strip antenna according to the T=2 mark space.For example, suppose to have the N=4 strip antenna to use, so just have $\left(\begin{array}{c}4\\ 2\end{array}\right)=6$ Plant unique K=2 strip antenna combined method.Log ₂6 ≈ 2.58., two strip antennas select that bit is distinguishable to go out four kinds of combined methods being made up of four strip antennas.Listed a sky line options encoder instances in the table 1.The K=2 strip antenna is used in the ASM-TXD transmission, according to the T=2 mark space, has drawn altogether

Individual output bit, or be equal to each channel that uses and have

Individual bit (for example each mark space).The SFBC+FSTD scheme that contrast is formulated according to prior art is if having log on each channel ₂M bit, so in this example, each uses in the channel and just can realize

The space efficiency gain of individual bit.Other code packages that can be used for the transmission diversity coding is drawn together linear dispersed code and space-time grid code.

That Fig. 4 shows is another transmission plan embodiment that formulates and adopted the ASM-SMUX scheme according to the present invention.In the embodiment of Fig. 4, K=3, T=1, GAM encoder comprise a bit selector and K Symbol modulator.An input bit stream to the GAM encoder is split into K parallel streams and each stream is modulated with an individual modulation constellation of sizem _k, k=1, the input bit element flow that .., one of Ksymbols each. enter the GAM encoder can be divided into a plurality of K equiulbrium flows, and each fails to be convened for lack of a quorum and is modulated into an independently modulation constellation, and the size of each modulation constellation is m _k, k=1 .., K symbol.Therefore, in this example, T=1, different with above ASM-TXD embodiment, this example can not see through auxiliary dimension and encode.The K output symbol can be mapped to wherein K bar of N bar transmit antenna (used the K antenna index that is associated with the K transmit antenna and selected by sky line options encoder).Therefore, the total quantity of having transmitted bit in each used channel is ASM-SMUX bit, can transmit the GSSK of a bit greater than each used channel.

In another embodiment of the present invention, transmitter comprises many transmit antennas, with the spaced antenna form, constitutes one of them element of many strip antennas by many strip antennas respectively.Be used for the antenna element of transmission same signal, define an antenna port.Many strip antennas element of an antenna port may be distributed in the different location, allows the transmission signal of each antenna port can cover the more wide zone of covering, for example 3GPP MBSFN.That Fig. 5 shows is an embodiment who cooperates above-mentioned transmitter to use according to the present invention.In the example of Fig. 5, a transmitter comprises three transmitters that are distributed in the different location, and each transmitter has antenna element 1 and 2 respectively, is used for signal is transferred to receiver.Therefore antenna element 1 definition antenna port 1 among the transmitter 1-3 can transmit identical signal.Similarly, therefore the antenna element 2 definition antenna ports 2 of antenna 1-3 can transmit identical signal, and these are different with the content that antenna port 1 transmits.For receiver, in this example system, have only two transmit antennas or antenna port, this is because receiver can't resoluting signal be from which the stand-alone antenna element in each antenna port.Therefore, in this embodiment of the present invention, the corresponding a plurality of antenna ports of many strip antennas.

Fig. 6 and Fig. 7 show the analog result of the transmission plan of formulating according to the present invention.In Fig. 6, SFBC+FSTD, SM and ASM-TXD had carried out simulation in ofdm system, adopted N=4 days transmit antennas and two reception antennas at that time.Fading channel is according to 3GPP typical case city (TU) channel model mold, compares with 3GPP Rel.8Turbo encoder then.Comparing result is listed in block error rate (BLER), and this is one of them function of transmitted signal power, is used for receiving noise power ratio (being called SNR).Modulation schemes is 16-QAM, so M=16.This be expressed as SM select four strip antennas one of them, and used two sky line options bits and four modulation symbol to select bits.Amount to, each channel has used six bits (for example each mark space).In contrast, SFBC+FSTD two symbols of encoding, each is M=16, for example always has eight bits according to two mark spaces and adopts auxiliary dimension frequency, therefore in fact each channel has used four bits (for example each mark space).At last, result of the present invention is shown as ASM-TXD, wherein according to two mark spaces to two encoding symbols (eight bits) and used two bits in the N=4 strip antenna, to select the K=2 bar.In fact, the information that provides be enough to corresponding each use five bits on the channel.Simulation shows that in three contrast schemes, the BLER of the embodiment of the invention that cooperation ASM-TXD uses is minimum.

What Fig. 7 showed be, on a 3GPP TU channel, the ASM-TXD performance gain that can realize orthogonal frequency multiplex (MUX) (OFDM) system that adopts MIMO to arrange, have eight strip antennas.Compare with a 3GPP Rel.8Turbo encoder.Transmit antenna quantity is 8, and reception antenna quantity is 2 or 4.According to the 168OFDM subcarrier fixed resource information transmitted number of cells function that sees through two reception antennas (dotted line) and four reception antennas (solid line), the signal to noise ratio (snr) of the receiver of requirement reaches 10%BLER, and its comparing result just can show.Fig. 7 show adopt for example Alamouti encoder of 2x2 quadrature STC(), with the result of frequency as the ASM-TXD scheme of assisting dimension, there are ten bits to be input to the bit separator, wherein two bits are used for a day line options coding, and eight bits are used for the 16QAM encoding symbols of Alamouti.Two bits that are used for day line options can be used for selecting antenna with matching form, for example (1,2), (3,4), (5,6) or (7,8).Also shown among Fig. 7 and adopted the SFBC+FSTD of 16QAM and the result of SM, wherein used three bits in eight strip antennas, to select one, and use four bits to select a 16QAM modulation symbol.Solid line is to use the result of four reception antennas among the figure, and dotted line is to use the result of two reception antennas.In the situation that adopts four reception antennas, when the information number of cells surpasses 500, approximately be equal to each institute's channel that uses and be responsible for

During individual information bit, compare with other scheme, the performance of ASM-TXD scheme is the highest.Article two, the corresponding threshold value of reception antenna is each channel that uses $700/168\&cong;4.2$ Individual information bit.

The transmission signal method of transmitter, wherein comprising many strip antennas also can operate according to the method treatment loop, be applicable to according to computer program and implement, obtain the represented meaning of code, can cause computer to carry out the implementation step of the method when moving on computers.Computer program may be included in the computer fetch medium of computer program.Computer fetch medium comprises any holder basically, for example the ROM(read-only memory), PROM(read-only memory able to programme), EPROM(erasable programmable read-only memory), flash memory, EEPROM(electrically erasable programmable read-only memory) or hard disk.

Claims (11)

1. the employed method of the transmitter in the wireless communication system, wherein transmitter comprises N bar transmit antenna with the transmission signal, and this method comprises:

Receive signal, described signal comprises bits to be transmitted such as a plurality of;

A plurality of transmission bits are separated at least one bit of waiting a moment coding and at least one bit for day line options;

Obtain K coded identification of T cover from described at least one bit of waiting a moment coding, wherein K, N and T are integers, and 1＜K＜N;

Obtain K the antenna index that is associated with the K bar transmit antenna of selecting from N bar transmit antenna from described at least one bit for day line options; And

K coded identification of described T cover transmitted according to the T mark space respectively, in transmission, each coded identification in described K coded identification transmit antenna in the described K bar transmit antenna that is associated with a described K antenna index is respectively transmitted.

2. the method for formulating according to claim 1, wherein said K the coded identification of T cover of obtaining comprises:

Described at least one bit modulation of encoding is after a while become K modulation symbol.

3. the method for formulating according to claim 2, wherein said K the coded identification of T cover of obtaining comprises:

According to the T mark space, K modulation symbol carried out the transmission diversity coding.

4. the method for formulating according to claim 3, transmission diversity coding step wherein need use the code of the following to carry out: Space-Time Block Coding, space-time/frequency block code, linear dispersed code and space-time grid code.

5. the method for formulating according to claim 2, wherein modulation symbol belongs to the modulation symbol constellation of the following: OOK, BPSK, M-PSK and M-QAM.

6. the method for formulating according to claim 1, wherein T=1.

7. the method for formulating according to claim 1, wherein T〉1.

8. the method for formulating according to claim 1, wherein mark space is time domain or frequency domain.

9. the method for formulating according to claim 1, wherein many strip antennas are spaced antennas, and the transmit antenna port in the corresponding Single Frequency Network multimedia broadcasting network.

10. the transmitter in the wireless communication system, wherein transmitter comprises N bar transmit antenna with the transmission signal, and its characteristics comprise:

Circuit is used for receiving signal, wherein comprises bits to be transmitted such as a plurality of;

Circuit is used for that a plurality of transmission bits are separated at least one bit of waiting a moment coding and at least one is used for the bit of day line options;

Circuit is used for obtaining K coded identification of T cover from described at least one bit of waiting a moment coding, and wherein K, N and T are integers, and 1＜K＜N;

Circuit is used for obtaining K the antenna index that is associated with the K bar transmit antenna of selecting from N bar transmit antenna from described at least one bit for day line options; And

Circuit, be used for K coded identification of described T cover transmitted according to the T mark space respectively, in transmission, each coded identification in K coded identification of described cover transmit antenna in the described K bar transmit antenna that is associated with a described K antenna index is respectively transmitted.

11. according to the transmitter in the wireless communication system of claim 10 formulation, wherein transmitter comprises the treatment loop that aims at 9 support methods of claim 2 – and dispose.

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