CN104010199B - Signal averaging multiplexed video transmission method based on group decoding technique - Google Patents
Signal averaging multiplexed video transmission method based on group decoding technique Download PDFInfo
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Abstract
Signal averaging multiplexed video transmission method based on group decoding technique, is related to a kind of video transmission method.It is to improve the transmission of video frequency spectrum rate in wireless channel.The present invention is proposed is applied to SVC Video transmission systems by Signal averaging multiplexing；And it using SGD as coding/decoding method, is introduced into the present invention；And it considers in single antenna and multiple antennas SVC video broadcast systems, the power distribution problems based on SGD decoding policies.Simulation result shows method proposed by the present invention, and compared with traditional time-division multiplexing multiple access access (CDMA), the video of receiving terminal can obtain higher PSNR.The present invention is suitable for video transmitting procedure.
Description
Technical Field
The invention relates to a video transmission method.
Background
With the advent of new communication technologies, high quality video transmission in wireless channels has attracted increasing researchers' interest. Due to the high transmission rate, transmission techniques with high spectral efficiency are sought after. Due to the time-varying transmission characteristics of wireless fading channel capacity, scalable Video Coding (SVC) technology, which is an extension of the h.264/AVC protocol, has become a very friendly video transmission strategy. The SVC technology is to encode a video sequence into several layers, and select the number of layers of video to be transmitted and which layers are selected according to the current channel state information. SVC is widely studied because it can provide a bright acquisition video transmission strategy without transcoding. Cross-layer optimization of radio resources for SVC transmission, such as joint source-channel coding, non-uniform error protection, content-based protection, and resource allocation, has been studied in many documents.
In current video communication systems, different layers of encoded video are transmitted as different signals, such as different video blocks, over orthogonal channels. However, multiplexing for the orthogonal channel layer transmission spectral rate is limited by an upper bound on the maximum spectral rate of the single layer signal.
Disclosure of Invention
The invention provides a signal superposition multiplexing video transmission method based on a group decoding technology in order to improve the video transmission spectrum rate in a wireless channel.
A signal superposition multiplexing video transmission method based on a group decoding technique,
it is implemented based on a MIMO broadcast system of K users, in which a base station equipped with M antennas broadcasts to K users 1,2, \ 8230; \ 8230;, K is equipped with N respectively 1 ，N 2 ，……N K An antenna; k is a positive integer;
video signal transmission method for each user:
step one, carrying out source coding on a video signal of a user after formatting to obtain a signal subjected to source coding;
step two, carrying out channel coding on the signal obtained by the step one after the signal source coding to obtain a signal after the channel coding;
step three, performing baseband modulation on the signal obtained by the channel coding in the step two to obtain a baseband modulation signal;
step four, multiplexing the signals obtained in the step three after the baseband modulation to obtain multiplexed signals;
fifthly, the multiplexing signals obtained in the fourth step are subjected to radio frequency processing and then sent to a channel;
in the second step, the signal after the source coding is carried out the channel coding and is realized by adopting the scalable video coding method of H.264/AVC protocol extension;
in the fourth step, the method for multiplexing the signals modulated by the baseband comprises the following steps: compiling the signals modulated by the baseband into different L video layers, and superposing all the video layers; l is an integer greater than 1;
video signal receiving method for each user:
step six, the receiving end receives the multiplexing signal of the step five and carries out radio frequency processing;
step seven, carrying out shunt processing on the signals subjected to the radio frequency processing in the step six to obtain baseband signals;
step eight, performing baseband demodulation on the baseband signal obtained in the step seven to obtain a baseband demodulated signal;
step nine, carrying out channel decoding on the baseband demodulated signal obtained in the step eight to obtain a channel decoded signal;
tenthly, decoding the channel obtained in the step nine and then carrying out information source decoding to obtain a signal after the information source decoding;
eleven, formatting and outputting the signal obtained in the step ten after the information source is decoded; finishing the signal superposition multiplexing video transmission based on the group decoding technology;
in the ninth step, the method for performing channel decoding on the baseband demodulated signal specifically comprises: the target signal and the interference signal are successively decoded from the baseband demodulated signal by a successive decoding method.
The method for multiplexing the L video layers modulated by the baseband in the fourth step specifically includes: dividing the L video layers into M groups, wherein M is less than or equal to L; wherein each group comprises one or more SVC video layers; each group is independently coded into a signal layer;
for j is more than or equal to 1 and less than or equal to M, let x j Representing the encoded j-th group of signals with the constraint of E (| x) j | 2 ) =1, the video layer superimposed signal s is then expressed as:
in the formula: p j The energy allocated to the jth group of signals.
In the fourth step, the method for multiplexing the signals modulated by the baseband specifically comprises: the signals modulated by the baseband are coded into four time base layers and a quality enhancement layer; each GOP includes 8 frames, each frame includes 18 slices, and each macroblock row is one slice.
In the ninth step, the step of successively decoding the target signal and the interference signal from the baseband demodulated signal is specifically as follows:
for the ith receiving end, i is more than or equal to 1 and less than or equal to K, and the received signals are as follows:
wherein: u. u i ～N C (0,σ 2 I) Represents AWGN at the ith receiving end;
defining rate interruption as that the user rate does not reach the target rate in the decoding process, and making R = [ R ] j ] j∈K The rate of all the users is represented and,representing subsetsUser channel gain in, let p i Indicating the number of decoding steps, provided that a subset of the set KRepresenting a valid packet, the following three conditions need to be satisfied simultaneously:
condition 1), for any m ∈ {1, \ 8230;, p i Is satisfied withWhere μ represents the maximum packet size, i.e.: the number of elements in the group;
condition 2), receiver i is contained in the setPerforming the following steps;
condition 3), for any m ∈ {1, \ 8230;, p i The rate can be reached in the m-th step of successive decoding process
If given a subset of the K setsG i For a valid packet, at m th Step i of th Receiver-side joint decoding setAnd (b) isAll as AWGN, and then from the decoded messageSubtracting the decoded signal;
for theOrder toGiven a set of packetsThe receiving end i performs the following p j Step-by-step decoding:
step A1, initialization: m =1;
step A2, according to a formula:
calculating an interference noise covariance matrix; (.) * Represents a conjugate transpose;
then, the set is decodedThe user in (1):
wherein u is i ～N C (0, I) is AWGN with variance of 1;
step A3, when the set is decodedThen the ith receiving end subtracts the slave received signal y i Has been solved forUpdating
Step A4, judging whether m = p i +1, if the judgment result is yes, ending; and if the judgment result is negative, returning to execute the step A2.
In the process of successively solving a target signal and an interference signal from a signal demodulated by a baseband, if a decoded set S does not exist, a receiving end i obtains a signal by a formula:
finding the optimal decoding set G * 。
In the fourth step, L video layers modulated by the baseband are multiplexed, and the method for distributing the power of the signal superimposed by all the video layers is realized based on a constellation diagram of a finite length modulation mode, and specifically comprises the following steps:
let the total transmit power be P = P 1 +P 2 The signal received at the receiving end is represented as:
at the receiving end k, the received signals are:
wherein: v. of k Is AWGN, satisfiesH k Is the reception matrix for the k-th user.
When the receiving end is decoding the target layer, let SINR (x1) And SINR (x2) Respectively representing SINR values of the base layer and the enhancement layerMinimum required SINR when both users need to decode the base layer (x1) Expressed as:
to ensure that both users can solve the base layer, the following formula needs to be satisfied:
wherein ε indicates that the base layer needs additional protection; l is ch Is the code length (i.e., the number of symbols transmitted per time) of the LDPC channel coding; n is a radical of t Is the number of transmissions; gamma ray b Is the target code rate;
the base layer should satisfy the formula:
in the formula:
for SVC enhancement layer signals, the power is P-P 1 Hence SINR (x2) Comprises the following steps:
the invention provides a method for applying signal superposition multiplexing to an SVC video transmission system; and introducing the SGD into the system as a decoding method; and considering the power distribution problem based on the SGD decoding strategy in the single-antenna and multi-antenna SVC video broadcasting system. Simulation results show that compared with the traditional time division multiplexing multiple access (CDMA), the video of the receiving end can obtain higher PSNR (peak signal-noise-ratio). The video transmission frequency spectrum rate in the wireless channel is greatly improved.
Drawings
Fig. 1 is a schematic diagram of a video signal transmission principle of a signal superposition multiplexing video transmission method based on a group decoding technique according to the present invention;
FIG. 2 is a schematic view of a video structure;
FIG. 3 is a simulation diagram of SNR versus mutual information content relationship of a Gaussian AWGN channel QAM constellation;
FIG. 4 is a diagram illustrating SNR versus bit error rate curves of LDPC channel coding at different code rates;
Detailed Description
Detailed description of the preferred embodimentsa signal overlay multiplexing video transmission method based on group decoding technique,
it is implemented based on a MIMO broadcast system of K users, in which a base station equipped with M antennas broadcasts to K users 1,2, \ 8230; \ 8230;, K is equipped with N respectively 1 ，N 2 ，……N K An antenna; k is a positive integer;
video signal transmission method for each user:
step one, carrying out source coding on a video signal of a user after formatting to obtain a signal subjected to source coding;
step two, carrying out channel coding on the signal obtained by the step one after the signal source coding to obtain a signal after the channel coding;
step three, performing baseband modulation on the signal obtained by the channel coding in the step two to obtain a baseband modulation signal;
step four, multiplexing the signals obtained in the step three after the baseband modulation to obtain multiplexed signals;
fifthly, the multiplexing signals obtained in the fourth step are subjected to radio frequency processing and then sent to a channel;
in the second step, the signal after the source coding is carried out the channel coding and is realized by adopting the scalable video coding method of H.264/AVC protocol extension;
in the fourth step, the method for multiplexing the signals modulated by the baseband comprises the following steps: compiling the signals modulated by the baseband into different L video layers, and superposing all the video layers; l is an integer greater than 1;
video signal receiving method of each user:
step six, the receiving end receives the multiplexing signal of the step five and carries out radio frequency processing;
step seven, carrying out shunt processing on the signals subjected to the radio frequency processing in the step six to obtain baseband signals;
step eight, performing baseband demodulation on the baseband signal obtained in the step seven to obtain a baseband demodulated signal;
step nine, carrying out channel decoding on the baseband demodulated signal obtained in the step eight to obtain a channel decoded signal;
tenth, carrying out source decoding on the channel obtained in the ninth step to obtain a signal after the source decoding;
eleven, formatting and outputting the signal obtained in the step ten after the information source is decoded; finishing the signal superposition multiplexing video transmission based on the group decoding technology;
in the ninth step, the method for performing channel decoding on the baseband demodulated signal specifically comprises: the target signal and the interference signal are successively decoded from the baseband demodulated signal by a successive decoding method.
1. Description of the System
And (3) channel model: consider a K-user broadcast system in which a base station equipped with a single antenna broadcasts to K users, each of which is a single antenna.
For K is 1. Ltoreq. K, let N k Matrix H of xM k Representing the radio channel from the base station to user k. s denotes a transmission signal, and F denotes a precoding vector used by the base station. It is assumed that there is a quasi-static block fading channel between the base station and the receiving user, i.e. the channel factor remains unchanged in one transport block and becomes an independent state in the next transport block. Signal y received at user k k Can be expressed as:
y k ＝H k Fs+v k (1)
wherein u is i ～N C (0,σ 2 I) Representing independent white gaussian noise for user k.
Layered video transmission: it is assumed that the base station broadcasts a video stream of the SVC hierarchy. SVC is an extension of H.264/AVC video codec, which programs the original video into a multi-layered video stream. The base layer may provide a most basic quality that is acceptable, while the enhancement layer may make the decoded video better quality. The base station can selectively transmit proper video layers according to the channel state, wherein the more the number of transmitted video layers is, the better the video quality recovered after the received signal is decoded is. When the wireless channel transmission rate is very low, proper video frames need to be dropped, but the dropped frames affect the video quality as little as possible. In this work, the SVC coding strategy adopted mainly consists of a base layer and an enhancement layer, wherein the video sequence is divided into four temporal base layers and one quality enhancement layer. The video structure is shown in figure 2. Each GOP (group of picture) contains 8 frames. Each frame is divided into 18 slices, each macroblock rowIn one piece. In each GOP, the priority is from top to bottom: t is 0 、T 1 、T 2 、T 3 And T 4 And when some video packets need to be dropped, the packets are dropped from low to high according to the priority order.
SVC layer multiplexing by signal superposition: the multiplexing of the conventional SVC coding layers is based on orthogonal channels, i.e. different layers are allocated to different orthogonal channels for transmission. However, the throughput of the orthogonal channel is limited by the finite length modulation. To break this limitation, the present invention proposes another way of SVC layer multiplexing scheme-based on non-orthogonal signal superposition method, i.e. a video layer is encoded into multiple independent signal layers, and then the base station transmits the superposition sum of the signal layers.
One preferred approach is to treat each SVC coding layer as one signal layer. However, this approach will result in too many signals being superimposed, which can significantly increase the complexity of the system. In the present invention, it is assumed that there are L layers of coded video layers, which are divided into M groups, where each group contains one or more SVC video layers. Each group is independently encoded into a signal layer. For j ≦ 1 ≦ M, let x j Represents the encoded jth group of signals with the constraint of: e (| x) j | 2 ) And =1. Suppose j assigns an energy of P j . The transmitted superimposed signal may be expressed as:
each receiver solves the target layer in a successive iteration mode.
The basic principle of signal superposition layer multiplexing is described below. Consider a single antenna transceiver system with a channel gain of H. For sufficiently large transmit power:with proper layer power allocation, each layer j can achieve a sufficiently large SINR, which is denoted as:
a relatively large part of the limited long modulation capacity can be achieved. The sum-rate throughput of each layer multiplex can then exceed the throughput of a single-layer finite-length modulation — the upper capacity bound of orthogonal channel-based layer multiplexes.
It should be noted that in the SVC decoding process, the higher layer decoding needs to be supported by the lower layer, that is, only the signal of the base layer is decoded to recover the video stream of the higher layer, otherwise, even if the signal of the higher layer video stream is correctly received, the video stream cannot be decoded. Therefore, from the viewpoint of the inherent characteristics of video, a signal including a higher layer SVC should be decoded with priority. Thus, the power allocation for all layers can be designed precisely.
Determining the decoding order of the SGDs for a given power per layer; then, power allocation of the signal layer is proposed. All rates in the present invention are bits/sec/Hz.
2. Group decoding
In a broadcast system, the form of signal superposition received at the receiving end has a certain similarity to the interference channel, and both are combinations of the received target signal and the interference. Therefore, SGD is adopted as an effective decoding method at the receiving end of the broadcasting system. For SGD, each receiver touches several signals at each step and will not solve as noise, then subtracts the already solved signals until the target signal is solved. The SGD is briefly introduced next and is incorporated into the broadcast system contemplated by the present invention.
Optimal Successive Group Decoding (OSGD):
a brief introduction to OSGD is given here.
Consider the SIMO interference channel model for discrete-time slow fading K users. For i is more than or equal to 1 and less than or equal to K, each transmitting terminal i only has one antenna, and N is required to be assembled i The target of each antenna receives user i communications. Let show fromThe channel gain from the sending end j to the receiving user i is more than or equal to 1 and less than or equal to i, and j is more than or equal to K. The signal received by the receiving end i can be represented as y i The signal transmitted by the jth transmitting end is x j With the constraint of P = E (| x) j L 2). Let us assume that h i,j I is more than or equal to 1, and K is less than or equal to j, which is perfectly known at the receiving end i. The signal received by the receiving end i is:
wherein u is i ～N C (0,σ 2 I) Representing AWGN at the receiving end i.
Rate break is defined as the user rate not reaching the target rate during decoding. Let R = [ R ] j ] j∈K The rate of all the users is represented and,represents subset AUser channel gain in (1).
For the receiver i, let p i Indicating the number of decoding steps, provided that a subset of the set KRepresenting a valid packet, the following three conditions need to be satisfied simultaneously:
condition 1), for any m e {1, \8230;, p i Is satisfied withWhere μ represents the maximum packet size, i.e.: the number of elements in the group;
condition 2), receiver i is contained in the setThe preparation method comprises the following steps of (1) performing;
condition 3), for any m ∈ {1, \ 8230;, p i The rate can be reached in the m-th step of successive decoding process
If given a subset of the K setsG i For a valid packet, at m th Step i of th Receiver-side joint decoding setAnd (b) an element ofAll as AWGN, and then from the decoded messageSubtracting the decoded signal;
forOrder toGiven a set of packetsThe receiving end i performs the following p j Step-by-step decoding:
step A1, initialization: m =1;
step A2, according to a formula:
calculating an interference noise covariance matrix; (.) * Represents a conjugate transpose;
then, the set is decodedThe user in (1):
wherein u is i ～N C (0, I) is AWGN with variance of 1;
step A3, when the set is decodedThen the ith receiver subtracts the slave received signal y i Of the signal already solvedUpdating
Step A4, judging whether m = p i +1, if the judgment result is yes, ending; and if the judgment result is negative, returning to execute the step A2.
Next, the optimal grouping strategy of the SGD is analyzed. When the target decoding set is A, the set regarded as noise is B, and the two sets do not intersect, the condition is satisfiedThe rate bound is defined as:
and epsilon (H) i Phi, B, R) =0, and:
for efficient groupingDefining:
is p i Step-wise decoding the minimum rate boundary.
When epsilon (H) i ,G i ,R)&And when the value is lt and 0, the user i is represented as rate interruption. Each user i can find the optimal decoding order by the following method:
the decoding order obtained by the above method is called optimized group-by-group decoding (OSGD). A greedy algorithm (as shown in table 1) can effectively solve the above equation, in the course of which an interrupt can be given or an optimal set of packets can be given. In each step, assuming that the set without decoding is S, the receiving end i can find the optimal decoding set by the following formula, denoted as G * ：
TABLE 1
Based on the sub-modularity of the achievable rates, it can be demonstrated that a greedy approach can lead to an optimal solution. If G is selected at a certain step * Resulting in a rate bound, an interrupt event is declared.
The optimal search method can obtain the optimal solution by using a poor search mode, namely searching all non-empty setsAnd G is not more than mu i Condition。
OSGD in video broadcast system:
the OSGD is applied to the video broadcasting system in the present invention. Assuming two signal layers, for a video broadcast system, the received signal can be represented as:
the system can be treated as an equivalent interference channel.
In order to reduce the number of signal superposition layers, the SVC encoded streams of 5 layers are divided into two groups. At the receiving end i, the received signal may be represented as
In the following, assuming OSGD is employed at the receiving end, a power allocation method for two-layer signals is proposed, where the decoding order of each receiving end is base layer to enhancement layer. Such a decoding order is adopted because of the inherent characteristics of SVC video: if the base layer is not decoded correctly, the enhancement layer contributes zero to video recovery.
SVC video broadcast in SISO channels: in this section, the signal layer power allocation problem in the case where both the base station and the receiving user employ a single antenna is mainly studied. Assuming that the video signal is encoded at the base station into one base layer and several enhancement layers, these signals are recombined into two layers, one being the base layer of SVC and all the remaining signals constituting the second layer. Assume that there are two users, where the first user is closer to the base station and the second user is slightly further away from the base station, so it is assumed that the first user needs to decode the base layer and the enhancement layer of the video signal, and the second user only needs to decode the base layer of the video signal. The two-user scenario described above can be easily generalized to the two-user scenario, i.e. all users in the first set need to decode the base layer and enhancement layer of the video, while the second set needs to decode the base layer and enhancement layer of the videoAll users in the pool only need to decode the base layer of the video. Assuming that the channel gains between the base station and each user satisfy a complex Gaussian distributionWhere d represents the distance between the base station and the user.
In order to control the decoding complexity, the modulation mode M is selected from the set { QPSK,16QAM }, and the code rate C of LDPC channel coding is selected from the set {1/4,1/3,1/2,2/3,3/4,7/8 }. Suppose two signals x 1 And x 2 Respectively from m 1 And m 2 Is encoded in the information bits. These two signals need to be transmitted N t Next, each channel code length is one symbol. In the transmission process, in order to ensure that all users can decode to the base layer, power is allocated to the SVC base layer first, and then power is allocated to the enhancement layer, and it is ensured that user 1 can receive all the signals, so that user 2 receives the signals of the enhancement layer as much as possible.
Power allocation of signal superposition:
and performing signal power distribution for the non-orthogonal signal superposition multiplexing. The power distribution method is based on a constellation diagram of a finite length modulation mode. Let f (M) i SNR) represents a capacity (bits/symbol), wherein the modulation scheme M i E M, SNR is SNR and the relation between them is shown in fig. 3.
When the spectral efficiency is (— infinity, 1.75) and (1.75, + ∞), the modulation schemes selected are QPSK and 16QAM, respectively. Let f (SNR) denote the spectral efficiency with the above modulation scheme plus a small rate bound delta, which represents a difference between the modulation fusion and the actual channel coding rate achievable. δ can be obtained by comparing the modulation capacity map 3 with actual simulation results.
Assume that the total transmit power is P = P 1 +P 2 (ii) a The signal received at the receiving end may be represented as a signal received at the receiving end as:
at the receiving end k, the received signal is:
wherein: AWGN satisfies v k ～N C (0,σ 2 )；
When the receiving end is decoding the target layer, let SINR (x1) And SINR (x2) Respectively representing SINR values of the base layer and the enhancement layerMinimum required SINR when both users need to decode the base layer (x1) Expressed as:
to ensure that both users can solve the base layer, the following formula needs to be satisfied:
wherein ε indicates that the base layer needs additional protection; l is a radical of an alcohol ch Is the code length (i.e., the number of symbols per transmission) of the LDPC channel coding; n is a radical of t Is the number of transmissions; gamma ray b Is the target code rate;
the base layer should satisfy the formula:
in the formula:
for SVC enhancement layer signals, the power is P-P 1 And thus SINR (x2) Comprises the following steps:
let m sup The true value representing the number of information bits of the enhancement layer. Since only user 1 needs to decode m sup The upper bound is:
selecting an appropriate channel code to transmit m sup The information of the bit. The selection of the channel coding may employ the following method. Note that for a given information bit, the modulation mode and channel coding rate are calculated from the transmission capacity. For the base layer, because the information bit m1 is known, the spectral rate m is first calculated 1 /N t ·L ch Then, the minimum rate C is selected i Belongs to C so as to satisfy m 1 /N t ·L ch 。
For the enhancement layer, the maximum rate is first calculatedThen, a modulation mode and a channel coding rate C are selected i C, selecting the maximum frequency spectrum rate not greater thanThe maximum value that can be reached. The bit information of the enhancement layer that can be transmitted is determined by the selected coding rate.
Note that: the power allocation method proposed here is based on the decoding order of the base layer first and then the enhancement layer. With such power allocation, the base layer must decode prior to the enhancement layer when each receiving user decides the decoding order through SGD. This is because for the enhancement layer, when deciding whether it is the first one to be decoded, the rate bound is also computed into when the base layer is considered as noise. Thus, the rate bound of the enhancement layer is significantly smaller than that of the base layer, since the enhancement layer is treated as noise when the base layer is power allocated, and the base layer is subtracted when the SINR is calculated for the enhancement layer.
TDMA and rate:
suppose for TDMA mode, two signals transmit signal x in alpha and 1-alpha time slots, respectively 1 And x 2 . During transmission, the base station uses a fixed transmit power P. Order toAndrespectively, the SINR values of the base layer and the enhancement layer. Receiving users 1 and 2 can be represented as:
the same transmission strategy is used as for signal superposition multiplexing, assuming that the base station first ensures that all base layer signals are transmitted and then transmits as many enhancement layer signals as possible. For the base layer, the following SINR constraints need to be satisfied
And for the enhancement layer, it should suffice because only user 1 needs to decode
Wherein, the first and the second end of the pipe are connected with each other,is the information bits that the second layer can transmit. Therefore, the following are provided:
calculating an upper bound for signal bits that an enhancement layer can transmitThe total throughput can be expressed as:
3. SVC video broadcasting in MIMO channels
In this section, the power allocation method is extended to a broadcast model where the base station is equipped with multiple antennas. Firstly, a linear precoding is adopted in a base station, and then the layered power distribution method is expanded to the situation that the base station is provided with a plurality of antennas.
The pre-coding algorithm comprises the following steps:
suppose s is transmitted to K users, each with N receive antennas, via a base station equipped with M antennas. At the kth receiver, the received signal y k Can be expressed as:
y k ＝H k Fs+v k (26)
wherein the noise signal v k ～N C (0,σ 2 I) Is AWGN, andis a pre-coded vector. It is assumed that the channel state information is perfectly known at the receiving end.
The transmitting end and the receiving end share a precoding codebook. And selecting a proper codebook at a receiving end according to the channel state information, and then feeding back the serial number of the codebook to the base station. It is assumed that the precoding matrix is selected from fourier transform matrices. Let F = { F 1 ,F 2 ,…F G Denotes a codebook in which the p-th element F g Can be expressed as:
when G =4,m =2, an example of a simple precoding matrix F = { F = F 1 ,F 2 ,…F G It can be expressed as:
at the receiving end k, the received signal passes through an MMSE filter, and the method comprises the following steps:
r k ＝W k y k (29)
wherein, W k Is a linear MMSE filter, whose expression is:
suppose a base station selects precoding F g The SNR after linear filtering can be expressed as:
each receiving end k judges the most precoding serial number through the SNR after the above linear filtering, and the sequence is marked as g k ；
Precoding the sequence number g k And post-processing SINR gamma k,gk Fed back to the base station. The base station selects the largest SINR and employs its corresponding precoding. The transmit-side precoding may be expressed as:
F opt ＝F g (33)
wherein forHas g = g k 。
Signal layer power allocation:
the signal layer allocation method of the SISO system is extended to a multi-antenna broadcasting system. The same assumption is that with two users, user 2 only needs the base layer, while user 1 needs both the base layer and the enhancement layer. A quasi-static fast fading channel and AWGN are assumed.
Under the constraint of P = P 1 +P 2 Then, the transmission power P of the base layer is minimized 1 . At the base station, precoding F is used opt . Order toAndwhich represent the base layer SINR values for users 1 and 2, respectively.
Power allocation P for base layer 1 The requirements are as follows:
where epsilon represents the rate bound for additional protection of the base layer.
Order:
the effective solution to the optimization problem can be expressed as:
in the formula:then, the enhancement layer can be obtained from the formula (36)The upper bound of (A) is:
from the formula (37), the signal x can be obtained 2 The number of signal bits transmitted. In addition, since the SNR value is different from that actually used, the required power ratio P is 1 Slightly larger than the result obtained from equation (36).
Claims (4)
1. A signal superposition multiplexing video transmission method based on a group decoding technology is characterized in that:
it is realized based on a MIMO broadcasting system with B number of users, in which, a base station equipped with M antennas broadcasts to B users 1,2, \8230, 8230, B is equipped with N respectively 1 ，N 2 ，……N B An antenna; b is a positive integer;
video signal transmission method for each user:
step one, carrying out source coding on a video signal of a user after formatting to obtain a signal subjected to source coding;
step two, carrying out channel coding on the signal obtained by the step one after the information source coding to obtain a signal obtained after the channel coding;
step three, performing baseband modulation on the signal obtained by the channel coding in the step two to obtain a baseband modulation signal;
step four, multiplexing the signals obtained in the step three after the baseband modulation to obtain multiplexed signals;
fifthly, the multiplexing signals obtained in the fourth step are subjected to radio frequency processing and then sent to a channel;
in the second step, the signal after the source coding is carried out the channel coding and is realized by adopting the scalable video coding method of H.264/AVC protocol extension;
in the fourth step, the method for multiplexing the signals modulated by the baseband comprises the following steps: compiling the signals modulated by the baseband into different L video layers, and superposing all the video layers; l is an integer of not less than 1;
video signal receiving method for each user:
step six, the receiving end receives the multiplex signal of the step five and carries on the radio frequency treatment;
step seven, carrying out shunt processing on the signals subjected to the radio frequency processing in the step six to obtain baseband signals;
step eight, performing baseband demodulation on the baseband signal obtained in the step seven to obtain a baseband demodulated signal;
step nine, carrying out channel decoding on the baseband demodulated signal obtained in the step eight to obtain a channel decoded signal;
tenthly, decoding the channel obtained in the step nine and then carrying out information source decoding to obtain a signal after the information source decoding;
eleven, formatting and outputting the signal obtained in the step ten after the information source is decoded; finishing the signal superposition multiplexing video transmission based on the group decoding technology;
in the ninth step, the method for performing channel decoding on the baseband demodulated signal specifically comprises: successively decoding the target signal and the interference signal from the signal demodulated by the baseband by adopting a successive decoding method;
in the ninth step, the step of successively decoding the target signal and the interference signal from the baseband demodulated signal is specifically as follows:
for the ith receiving end, j is more than or equal to 1 and less than or equal to B, and the received signals are as follows:
wherein: h is i,j Representing the channel response, x, between the ith receive antenna and the jth transmit antenna j Representing the encoded jth group of signals;
defining the interrupt rate as the rate when the user rate does not reach the target rate in the decoding process, and making R = [) j ] j∈K The rate of all the users is represented,representing subsetsUser channel gain in (1), P is total transmit power, let P be i Indicating the number of decoding steps, provided that a subset of the set KRepresenting a valid packet, the following three conditions need to be satisfied simultaneously:
condition 1), for any m ∈ {1, \ 8230;, p i Satisfy 1Where μ represents the maximum packet size, i.e.: the number of elements in the group;
condition 2), receiver i is contained in the setThe preparation method comprises the following steps of (1) performing;
condition 3), for any m ∈ {1, \ 8230;, p i Get the rate in the m-th step of successive decoding
If given a subset of the K setsG i For a valid packet, at mth step, the ith receiver jointly decodes the setAnd (b) an element ofAll as AWGN and then from the decoded messageSubtracting the decoded signal;
for theOrder toGiven a set of packetsThe receiving end i performs the following p i Step-by-step decoding:
step A1, initialization: m =1;
step A2, according to a formula:
calculating an interference noise covariance matrix; wherein, (. Cndot.) * Represents a conjugate transpose;
then, the set is decodedThe user in (1):
wherein u is i ～N C (0, I) is AWGN with variance of 1;representing subsetsUser channel gain in (1);
step A3, when the set is decodedThen the ith receiver subtracts the slave received signal y i Of the signal already solvedUpdating
Step A4, judging whether m = p is satisfied i +1, if the judgment result is yes, ending; and if the judgment result is negative, adding 1 to the value of m, and returning to execute the step A2.
2. The method for transmitting video via signal overlay multiplexing according to claim 1, wherein the multiplexing of the baseband-modulated L video layers in the fourth step comprises: dividing the L video layers into N groups, wherein N is less than or equal to L; wherein each group comprises one or more SVC video layers; each group is independently coded into a signal layer;
for t ≦ 1 ≦ N, let x t Representing the coded t-th group of signals with the constraint of E (| x) t | 2 ) =1, the video layer superimposed signal s is then expressed as:
in the formula: p is t The energy allocated to the t-th group of signals.
3. The method for video transmission with signal superposition multiplexing based on block decoding technology as claimed in claim 1, wherein the method for multiplexing the baseband modulated signals in step four specifically comprises: the signals modulated by the baseband are coded into four time base layers and a quality enhancement layer; each GOP includes 8 frames, each frame includes 18 slices, and each macroblock row is one slice.
4. The method according to claim 1, wherein in the process of successively decoding the target signal and the interference signal from the baseband demodulated signal, if the set without decoding is S, the receiving end i uses the formula:
finding the optimal decoding set G * ；
In the formula: r is the transmission rate vector of the signal on the transmitting antenna, H i Is all H i,A Are combined together.
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