CN102523189A - Public transport television system based on MIMO technology - Google Patents
Public transport television system based on MIMO technology Download PDFInfo
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- CN102523189A CN102523189A CN2011104450259A CN201110445025A CN102523189A CN 102523189 A CN102523189 A CN 102523189A CN 2011104450259 A CN2011104450259 A CN 2011104450259A CN 201110445025 A CN201110445025 A CN 201110445025A CN 102523189 A CN102523189 A CN 102523189A
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Abstract
The invention discloses a public transport television system based on MIMO technology. A sending terminal has MT sending antennas, and each sending antenna is connected with an OFDM modulator. A signal of the signal sending terminal is sent through the OFDM modulator. A receiving terminal is MR receiving antennas, and each receiving antenna is connected with an OFDM demodulator. The OFDM demodulator demodulates a signal received by the receiving antenna and transmits the signal to a public transport television terminal, and the sending signal and the receiving signal employ time space coding technology to carry out coding and decoding respectively. A plurality of sending antennas and a plurality of receiving antennas are utilized to send and receive a television signal. A plurality of antennas send and receive the signal simultaneously, and a plurality of sent signals employ time space coding. In this way, in the condition of not increasing bandwidth, channel capacity is raised, a coverage scope of the signal is increased, multipath interference can be overcome, and the quality of the receiving signal is raised.
Description
Technical field
The present invention relates to body ground, the communications field, relate to a kind of public transport television system based on the MIMO technology.
Background technology
At present, the Beijing Public Transport TV adopts the DVB-T standard to utilize Digital Terrestrial Mobile TV test SFN (SFN network), adopts a master transmitter, and three booster transmitters send signal simultaneously with frequently, thereby improve the coverage of signal.Receive in order through signal testing Beijing City two rings, three rings, Fourth Ring, but, the phenomenon of signal weakness or no signal occurs through regular meeting from launching centre place far away.In addition; Since a plurality of launching centre synchronized transmission signals, thus will inevitably receive a plurality of TV signals for certain bus, because different transmitters arrives the asynchronism(-nization) of mobile receiver; These a plurality of TV signals have the branch of time successively, thereby produce the multipath interference problem.Multipath disturbs to acquire a certain degree and will cause the frequency spectrum decline, makes to take defeat.
Summary of the invention
The objective of the invention is to,, propose a kind of public transport television system, to realize overcoming the advantage that multipath disturbs based on the MIMO technology to the problems referred to above.
For realizing above-mentioned purpose, the technical scheme that the present invention adopts is:
A kind of public transport television system based on the MIMO technology, transmitting terminal has
M TIndividual transmitting antenna is connected with the OFDM modulator on each transmitting antenna, the signal on the letter transmitting terminal is launched after the OFDM modulators modulate, and receiving terminal does
M RIndividual reception antenna; Be connected with the OFDM demodulator on each reception antenna; The signal that the OFDM demodulator receives reception antenna is transferred to the public transport television terminal after demodulation, said transmit and receive signal adopt the Space Time Coding technology to carry out Code And Decode respectively.
According to a preferred embodiment of the invention, said OFDM modulator and OFDM demodulator have the N number of sub-carrier, and can produce length is the OFDM signal of N.L the discrete time that can discern the path, MIMO fading channel input/output relation is:
Wherein
x(
n) expression
M T* 1 dimension is sent signal phasor,
y(
n) expression
M R* 1 dimension receives signal phasor,
LThe expression multipath channel can be known number of path, by
L=B τConfirm,
BThe expression signal bandwidth,
τThe expansion of expression maximum delay, z
nBe the weighting white Gaussian noise, H is a channel matrix, is the complex value random matrix,
H l Expression the
lThe footpath channel impulse response.Can be expressed as
According to a preferred embodiment of the invention, said N=1705.
According to a preferred embodiment of the invention, said
M T=2 and
M R=2.
According to a preferred embodiment of the invention, said Space Time Coding technology may further comprise the steps:
Two transmission signal phasors after at first will modulating are one group, and the encoder matrix that provides according to formula (1) is mapped to transmitting antenna with them:
In the formula,
With
It is respectively signal
x 1With
x 2Complex conjugate;
Above-mentioned signal X is launched from two transmit antennas in two continuous transmit cycles, in first transmit cycle, signal
x(
n) launch respectively from antenna 1 and antenna 2 simultaneously, in second transmit cycle, signal
x(
n+ 1) launches respectively from antenna 1 and antenna 2;
Two reception antennas of receiving terminal are connecting the above-mentioned signal of reception in two cycles, and reception antenna is numbered with i, and two reception antennas are respectively i=1,2, wherein acknowledge(ment) signal:
Being write as matrix form is:
Wherein:
Be n constantly, the j transmit antennas is to the channel of i root reception antenna, z
i(n) be to represent respectively
nWeighting white Gaussian noise constantly.
Technical scheme of the present invention adopts the MIMO technology, utilizes many transmitting antennas, many reception antennas to send and received television signal.Compare with existing public transport television system, the number of transmitting antenna and reception antenna is increased to many by one, and many antennas send and receive signal simultaneously, adopts Space Time Coding between a plurality of signals of transmission.So both can under the situation that does not increase bandwidth, improve channel capacity, increase the coverage of signal, and can overcome multipath again and disturb.Improve to receive quality of signals, improve the TV signal difference or do not have the phenomenon of signal.
Other features and advantages of the present invention will be set forth in specification subsequently, and, partly from specification, become apparent, perhaps understand by embodiment of the present invention.The object of the invention can be realized through the structure that in the specification of being write, claims and accompanying drawing, is particularly pointed out and obtained with other advantages.
Through accompanying drawing and embodiment, technical scheme of the present invention is done further detailed description below.
Description of drawings
Accompanying drawing is used to provide further understanding of the present invention, and constitutes the part of specification, is used to explain the present invention with embodiments of the invention, is not construed as limiting the invention.In the accompanying drawings:
Fig. 1 is the described sketch map based on the technological public transport television system of MIMO of the embodiment of the invention;
Fig. 2 is the analogous diagram of the error rate of public transport television system under the different antennae number.
Embodiment
Below in conjunction with accompanying drawing the preferred embodiments of the present invention are described, should be appreciated that preferred embodiment described herein only is used for explanation and explains the present invention, and be not used in qualification the present invention.
As shown in Figure 1, a kind of public transport television system based on the MIMO technology, transmitting terminal has
M TIndividual transmitting antenna is connected with the OFDM modulator on each transmitting antenna, the signal on the letter transmitting terminal is launched after the OFDM modulators modulate, and receiving terminal does
M RIndividual reception antenna is connected with the OFDM demodulator on each reception antenna, the signal that the OFDM demodulator receives reception antenna is transferred to the public transport television terminal after demodulation, transmit and receive signal and adopt the Space Time Coding technology to carry out Code And Decode respectively.
As shown in Figure 1, this system has
M TIndividual transmitting antenna with
M RIndividual reception antenna.At transmitting terminal, behind the data process OFDM modulators (OFDM), send through different transmitting antennas.At receiving terminal, the signal of transmission receives through each reception antenna, and, rely on corresponding OFDM demodulator (OFDM-DEM) demodulation.Each OFDM has
NIndividual (
N=1705) subcarrier, can produce length is the OFDM signal of N.
LThe individual discrete time MIMO fading channel input/output relation of discerning the path is:
Wherein
x(
n) expression
M T* 1 dimension is sent signal phasor,
y(
n) expression
M R* 1 dimension receives signal phasor,
LThe expression multipath channel can be known number of path, by
L=B τConfirm,
BThe expression signal bandwidth,
τThe expansion of expression maximum delay,
z n Be the weighting white Gaussian noise,
HBe channel matrix, be the complex value random matrix,
H l Expression the
lThe footpath channel impulse response.Can be expressed as:
The decline that multipath fading and Doppler frequency shift cause all belongs to rapid fading among a small circle, theoretical and actual measurement shows: the amplitude Rayleigh distributed of rapid fading, phase place are obeyed evenly and are distributed.So the channel model is here elected Rayleigh channel as.
The Space Time Coding technology is the core technology of MIMO technology; This is coded in the correlations of wanting can produce between the transmitting of transmitting antenna and each time cycle spatial domain and time domain more; This when empty correlation can make receiver overcome the mimo channel decline and reduce the emission error code, here through being that example is carried out Space Time Coding and decoding with 2 transmit antennas and 2 reception antennas.
After at first will modulating two send signal phasors (code element) is one group, and per two signals are one group divide into groups, and according to the encoder matrix that provides as follows they is mapped to transmitting antenna:
In the formula,
With
It is respectively signal
x 1With
x 2Complex conjugate.
The output of encoder is launched from two transmit antennas in two continuous transmit cycles.In first transmit cycle, signal
x(
n) (
x 1With
x 2) launch respectively from antenna 1 and antenna 2 simultaneously.In second transmit cycle, signal
x(
n+ 1) (
,
) from antenna 1 and 2 emissions.
At the receiving terminal reception antenna
i,
i=1,2 receive signal and are connecting in two cycles:
Being write as matrix form is:
Wherein,
Be the n moment, the j transmit antennas is to the channel of i root reception antenna; z
i(n) be to represent respectively
nWeighting white Gaussian noise constantly.
If the signal of the reception of two antennas of expression with
; Channel matrix then can obtain
for
At receiving terminal, each of antenna receives the linear superposition that signal is 2 tunnel transmission signals and noise, during detection, can adopt decorrelation to receive.Generally, because the orthogonality of Space-Time Block Coding makes maximum-likelihood decoding be reduced to a linear process, complexity reduces greatly, therefore, generally adopts maximum-likelihood decoding.
If the channel matrix of receiving terminal
H(
n) known, and suppose that all signals in the modulation constellation all are equiprobable, maximum likelihood decoder is to all possible
Value, a pair of signal of selection from the signal modulation constellation (
), maximum-likelihood decoding can be expressed as:
In the formula,
CFor modulation symbol to (
) all possible set,
With
Be two decision statistic that receive signal and the generation of channel condition information structure through merging,
dBe distance metric.Statistics can be expressed as:
Realize H for given channel
1(n) and H
1(n), statistics
(
i=1,2) only be
X i(
i=1,2) function.Therefore, can with maximum-likelihood decoding criterion formula (6) be divided into for
x1 draw
xTwo independent decoding algorithms of 2, that is:
What should explain at last is: the above is merely the preferred embodiments of the present invention; Be not limited to the present invention; Although the present invention has been carried out detailed explanation with reference to previous embodiment; For a person skilled in the art, it still can be made amendment to the technical scheme that aforementioned each embodiment put down in writing, and perhaps part technical characterictic wherein is equal to replacement.All within spirit of the present invention and principle, any modification of being done, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (5)
1. the public transport television system based on the MIMO technology is characterized in that transmitting terminal has
M TIndividual transmitting antenna is connected with the OFDM modulator on each transmitting antenna, the signal on the letter transmitting terminal is launched after the OFDM modulators modulate, and receiving terminal does
M RIndividual reception antenna; Be connected with the OFDM demodulator on each reception antenna; The signal that the OFDM demodulator receives reception antenna is transferred to the public transport television terminal after demodulation, said transmit and receive signal adopt the Space Time Coding technology to carry out Code And Decode respectively.
2. the public transport television system based on the MIMO technology according to claim 1; It is characterized in that; Said OFDM modulator and OFDM demodulator have the N number of sub-carrier; Can produce length is the OFDM signal of N, L the discrete time that can discern the path, and MIMO fading channel input/output relation is:
Wherein
x(
n) expression
M T* 1 dimension is sent signal phasor,
y(
n) expression
M R* 1 dimension receives signal phasor,
LThe expression multipath channel can be known number of path, by
L=B τConfirm,
BThe expression signal bandwidth,
τThe expansion of expression maximum delay, z
nBe the weighting white Gaussian noise, H is a channel matrix, is the complex value random matrix,
H l Expression the
lThe footpath channel impulse response,
Can be expressed as:
。
3. the public transport television system based on the MIMO technology according to claim 2 is characterized in that said N=1705.
4. the public transport television system based on the MIMO technology according to claim 1 is characterized in that, and is said
M T=2 and
M R=2.
5. the public transport television system based on the MIMO technology according to claim 4 is characterized in that said Space Time Coding technology may further comprise the steps:
Two transmission signal phasors after at first will modulating are one group, and the encoder matrix that provides according to formula (1) is mapped to transmitting antenna with them:
In the formula,
With
It is respectively signal
x 1With
x 2Complex conjugate;
Above-mentioned signal X is launched from two transmit antennas in two continuous transmit cycles, in first transmit cycle, signal
x(
n) launch respectively from antenna 1 and antenna 2 simultaneously, in second transmit cycle, signal
x(
n+ 1) launches respectively from antenna 1 and antenna 2;
Two reception antennas of receiving terminal are connecting the above-mentioned signal of reception in two cycles, and reception antenna is numbered with i, and two reception antennas are respectively i=1,2, wherein acknowledge(ment) signal:
Being write as matrix form is:
Wherein:
Be n constantly, the j transmit antennas is to the channel of i root reception antenna, z
i(n) be to represent respectively
nWeighting white Gaussian noise constantly.
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| CN2011104450259A CN102523189A (en) | 2011-12-27 | 2011-12-27 | Public transport television system based on MIMO technology |
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Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101548429A (en) * | 2008-09-11 | 2009-09-30 | 香港应用科技研究院有限公司 | Antenna system for mobile multimedia terminal and using method thereof |
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2011
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Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101548429A (en) * | 2008-09-11 | 2009-09-30 | 香港应用科技研究院有限公司 | Antenna system for mobile multimedia terminal and using method thereof |
Non-Patent Citations (3)
| Title |
|---|
| 张乃谦等: "《多天线技术在移动数字电视中的应用》", 《广播与电视技术》 * |
| 张朝柱等: "《多接收天线下空时分组码解码算法的研究》", 《系统工程与电子技术》 * |
| 李莉等: "《多径衰落信道MIMO-OFDM系统容量分析与仿真》", 《计算机仿真》 * |
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Application publication date: 20120627 |