Practical environment testing platform for distributed multi-input and multi-output radio communication system
Technical field
The present invention relates to a kind ofly, belong to the technical field that the multiple-input and multiple-output plateform system is realized based on distributed multiple input, multiple output wireless communication system platform.
Background technology
That traditional wireless communication system adopts is single-input single-output system (SISO, Single Input Single Output).This system is subjected to the restriction of Shannon capacity, no matter therefore adopt which kind of chnnel coding or modulation system, wireless channel all to be difficult to satisfy the requirement of high speed speed transmission.
Higher requirement makes the raising data rate extremely urgent to the user to data speed.In recent years, the main mode of space diversity that adopts improves the capacity that signal to noise ratio increases system, and this mode is by use the complex array antenna at receiving terminal, transmitting antenna adopts a cell (promptly single input multiple output system (SIMO, Single Input Multiple Output)) to realize.The SIMO system has increased volume, cost and the transmitting power of terminal equipment greatly.Many antennas and radio frequency make terminal equipment complicated and expensive in the use of terminal, and therefore this mode is not used substantially.More economical method is that the complexity of equipment is transferred on the base station.A base station is often for hundreds of user provides service, and the cost or the transmitting power that therefore increase the base station are much actual than requiring portable terminal consume significant energy.The diversity technique of this transmitting terminal promptly is equivalent to many single-input single-output system (SISO system)s (MISO, Single Output Multiple Input).
The further developing of SIMO and MISO technology produced to send and received the system that adopts array antenna simultaneously, i.e. multi-input multi-output system (MIMO, Multiple Input Multiple Output).Since 1998, domestic and international famous research institution and scholars began a large amount of deep researchs to the MIMO technology.Mimo system can adopt the emission/reception technique of multi-section antenna, alleviate multipath fading, eliminate road interference altogether, and the minimizing transmitting power, therefore be subjected to meeting and standard is paid close attention to widely, and become and utilize space diversity to improve the inexorable trend of frequency efficiency.
Wireless channel is a complication system that is subjected to a plurality of factor affecting such as frequency selective fading, intersymbol interference, co-channel interference simultaneously.Though there is multiple channel model to can be used for the performance of evaluation algorithms in mimo system at present, the result who obtains just derives or mathematical computations (MATLAB) emulation based on simple mathematical, and every kind of channel model all is based on some hypothesis and could sets up.
Noise power in the wireless channel in the actual environment is unknown, and signal waveform is subjected to the influence of wireless signal-path band width in transmission, and the sampling clock differentia influence of transmitting and receiving terminal the accuracy of signal decision.The problem of more than enumerating is in emulation or be simplified as fixed numeric values, perhaps is assumed to be by certain probability density function profiles, and this makes the algorithm in the mimo system occur a lot of unpredictable results when using real the input.
Summary of the invention
The present invention is directed to the problem that existing wireless communication system only uses the wireless channel simulation algorithm of simplification to be brought, a kind of multiple input, multiple output wireless communication system practical environment testing platform is provided, this platform make send to receive one of experience complete from constellation mapping, pulse-shaping, modulation, transmission course to synchronous, demodulation, judgement, and by real wireless channel transmission, be subjected to the influence that whole system is brought, the signal of recovery can be checked the performance of mimo system algorithm more accurately.
Practical environment testing platform for distributed multi-input and multi-output radio communication system of the present invention comprises client, transmitting terminal and receiving terminal, client refers to be used for the subscriber computer of Base-Band Processing, transmitting terminal and receiving terminal respectively use a computer, and the three interconnects by wired or wireless local area network (LAN); Client is responsible for forming the baseband sampling data and data is sent to transmitting terminal by wired or wireless local area network (LAN), receives sampled data by wired or wireless local area network (LAN) from receiving terminal, and recovers primary signal by Base-Band Processing; Transmitting terminal is responsible for receiving the sampled data that client transmits, notify receiving terminal simultaneously, to the process of radio frequency, finally radio frequency analog signal is being delivered to wireless channel by antenna through baseband signal Digital Up Convert to intermediate frequency, digital-to-analogue conversion, intermediate frequency simulation up-conversion; Receiving terminal is by the radio frequency analog signal of antenna reception from transmitting terminal, and downconvert to intermediate frequency, analog-to-digital conversion, intermediate frequency Digital Down Convert through radio frequency analog and to the process of base band, obtain the baseband sampling data, afterwards, be back to client by wired or wireless local area network (LAN).
Client comprises two parts, first is the emulation base band signal process of carrying out in subscriber computer, its effect one is the baseband sampling point that generates transmitting terminal, the 2nd, and handle the reception data that client user's computer is sent back to, and these reception data are reverted to binary data stream; Second portion is a dynamic link library, and its effect one is to change the baseband sampling point that emulation generates, and makes the preservation form of baseband sampling point readable to the transtation mission circuit of transmitting terminal, and baseband sampling is sent to transmitting terminal; The 2nd, receive data, and save as file to carry out the processing that data are recovered from receiving terminal.
Transmitting terminal comprises three parts, first is the data configuration flow process that is positioned at the computer of transmitting terminal, its effect one is the emulated data file that receives from client, the 2nd, the variable element of configuration transmitting terminal Digital Up Convert circuit, and the interface of data by transmitting terminal computer and Digital Up Convert circuit is sent to the Digital Up Convert circuit, the 3rd, transmit relevant parameter by wired or wireless local area network (LAN) to receiving terminal, as receive delay, transmission data number and client network address etc.; Second portion is the Digital Up Convert circuit that links to each other with the transmitting terminal computer, this circuit is finished interpolation, Digital Up Convert and the digital-to-analogue conversion function of digital baseband sampled data, and the analog intermediate frequency signal data are sent to radio-frequency transmitter by the coaxial cable mouth on this circuit; Third part is a radio-frequency transmitter, and its effect is to receive the analog intermediate frequency signal that the Digital Up Convert circuit transmits, and finishes the task to radio frequency from intermediate frequency simulation up-conversion, and with radio frequency analog signal by antenna transmission to wireless channel environment.
Receiving terminal comprises three parts, first is a radio-frequency transmitter, its effect is the radio frequency analog signal that receives from wireless channel, finish the task of downconverting to intermediate frequency from radio frequency analog, and be sent to the Digital Down Convert circuit by the interface of analog intermediate frequency signal by radio-frequency transmitter and receiving terminal circuit; Second portion is the Digital Down Convert circuit, its effect is analog-to-digital conversion, Digital Down Convert and the extract function of finishing from the analog intermediate frequency signal to the digital intermediate frequency signal, and data are back to receiving end computer by the interface of Digital Down Convert circuit and receiving end computer; Third part is the data configuration flow process in the receiving end computer, its effect one is the variable element of the digital lower frequency changer circuit of configuration, and receive the data of beaming back by the interface of Digital Down Convert circuit and receiving end computer, the 2nd, the form of analysis data, and data are saved as the readable data file of data computation simulation flow, and the 3rd, by wired or wireless local area network (LAN) data file is transmitted back to client.
The present invention has formed the complete distributed communication system practical environment testing platform of a cover by integrating the sending and receiving devices in the multiple input, multiple output wireless communication system.The experiment of using this platform to carry out signal processing algorithm research and true wireless channel environment can show the superiority of tested technology more directly perceived, more convictively; Signal can experience complete communication process in the true wireless channel environment of multiple influence of fading is arranged, the result that this mode draws has higher reference value than the argument that draws under the multiple hypothesis prerequisite in simulation software.The transmitting terminal of signal, receiving terminal and base band signal process end be interconnected by cable network, carry out different functions separately, so the system, coupled degree is low, is beneficial to the modification of channel parameters; This distributed scheme also provides possibility for user's remote control signal after generating baseband signal on the computer of oneself sends to receive by wireless channel, and sharing rare equipment for more users provides effective means.
Main feature of the present invention shows as: (1) each several part is interconnected by wired or wireless local area network (LAN), and other parts of all following of every part have clear and definite interface, and system, coupled is little, and the variable element flexibility is big; (2) embodied the superiority of software radio, each part all has the parameter that can be provided with to adapt to new feature and function, overcome the shortcoming that realizes wireless communication system traditionally fully with analog circuit, no longer removed to redesign whole hardware because changing the algorithm of certain part in the wireless communication system; (3) user can promptly grasp the use of platform, because the baseband signal of signal generates and recover all to be finished by the MATLAB of client, the user also only needs as the true environment that function that MATLAB carries comes usage platform to provide is provided; (4) resource utilization maximization, base band signal process are realized on computer separately by different users, share expensive digital-to-analog up-conversion, digital-to-analog down-conversion and antenna transmission equipment by cable network then; (5) after the multiple input multiple output data transmitting-receiving breaks away from simulated environment, bring a lot of known or unknown interference, these problems of having ignored in simulated environment can be brought unpredictable distortion to algorithm.Under true environment, carry out the transmission of MIMO, the effect of algorithm can better be described.
Description of drawings
Fig. 1 is a general structure block diagram of the present invention.
Fig. 2 is the program flow diagram of client dynamic link library.
Fig. 3 is the flow chart of transmitting terminal data configuration program.
Fig. 4 is the flow chart of receiving terminal data configuration program.
Fig. 5 is the flow chart that sends data file by cable network.
Fig. 6 is the flow chart by the cable network received data file.
Fig. 7 is the Digital Up Convert circuit theory diagrams.
Fig. 8 is the Digital Down Convert circuit theory diagrams.
Among the figure: 1, client, 2, transmitting terminal, 3, receiving terminal.
Embodiment
As shown in Figure 1, the present invention includes client 1, transmitting terminal 2 and receiving terminal 3, the three interconnects by cable network, so that processing parameters such as data file that transmission need be handled and sendaisle number, transmission data length, time-delays.After transmitting terminal 2 is received data file, receive data by cable network notice receiving terminal 3; Transmitting terminal 2 and receiving terminal 3 carry out the transmission of data file by true wireless channel.Receiving terminal 3 will save as data file by the sampled data that wireless channel is received, be sent back to client 1 by cable network again.Client 1 refers to be used for the subscriber computer of Base-Band Processing, and transmitting terminal 2 and receiving terminal 3 respectively use a computer.
The subscriber computer of client 1 is equipped with mathematical computations emulation (MATLAB) software, MATLAB adds its data space by loading with binary data stream, through adding steps such as pilot frequency sequence, constellation mapping, space-time block code, pulse shaping, finally form the baseband sampling data subsequently.Sampled signal reaches transmitting terminal 2 by cable network.Fig. 2 has provided the program flow diagram of client dynamic link library.Transmitting terminal 2 is sent to the Digital Up Convert circuit by the computer interface of this end with sampled point, the Digital Up Convert circuit is converted to intermediate-freuqncy signal through steps such as Digital Up Convert, digital-to-analogue conversions with data and is issued to radio frequency sending set, radio frequency sending set further with the signal imitation up-conversion to radio frequency, launch by antenna.Fig. 3 has provided the flow chart of transmitting terminal data configuration program.Fig. 5 has provided the flow chart that sends data file by cable network.Radio-frequency transmitter in the receiving terminal 3 is handled through analog down in inside by the data of antenna reception from wireless channel, transfers data to intermediate-freuqncy signal and sends to the Digital Down Convert circuit.The Digital Down Convert circuit sends back to receiving terminal 3 through processes such as digital-to-analogue conversion, Digital Down Converts with baseband sampling data receiver data configuration program.Receiving terminal 3 returns to data client 1 again and does further base band signal process by wired or wireless local area network (LAN), synchronously promptly, channel estimating, packet decoding, constellation inverse mapping and judgement when empty.Fig. 4 has provided the flow chart of receiving terminal data configuration program.Fig. 6 has provided the flow chart by the cable network received data file.
Fig. 7 has provided the Digital Up Convert circuit theory diagrams.The transmitting terminal computer is connected with the Digital Up Convert circuit by interface.Because (standard is 66MHZ 64bit in the restriction of interface rate, but reason owing to slot, speed may be reduced to 66MHZ 32bit) and the restriction of calculator memory, harddisk access speed, the data rate that is input to the Digital Up Convert circuit needs strict control, the signal rate that enters the Digital Up Convert circuit will be much smaller than digital-to-analogue conversion speed, therefore after entering module, want advanced row interpolation, and the signal input rate multiply by the interpolation rate and is digital-to-analogue conversion speed.After the interpolation, sine wave and cosine wave and signal multiplication that sinusoidal signal generator produces form intermediate-freuqncy signal.How this special digital-to-analogue conversion speed of sampling law of Gui is sent to radio frequency sending set to intermediate-freuqncy signal to meet again.What need emphasize once more is, the maximum rate of interface must be greater than the baseband sampling speed of setting, otherwise data can't correctly be recovered at receiving terminal.
Fig. 8 has provided the Digital Down Convert circuit theory diagrams.The analog signal of the fixed intermediate frequency that is received by receiving terminal 3 is imported Digital Down Convert circuit inside into by radio-frequency transmitter to the interface of Digital Down Convert circuit.Intermediate-freuqncy signal becomes the baseband sampling signal by steps such as analog-to-digital conversion, sinusoidal signal generator, extractions.Input to computer by receiving terminal to the interface of computer.Be noted that also that here receiving terminal to the maximum rate of the interface of computer need be greater than the baseband sampling speed of Digital Down Convert circuit.
Can see that from Fig. 7 and Fig. 8 Digital Up Convert circuit and Digital Down Convert circuit all have sinusoidal signal generator that the sine wave of down-conversion is provided.Often this generator also is used to provide digital-to-analogue conversion and analog-to-digital clock.The difference frequency causes received signal to have a constant frequency deviation between the clock.After adding radio-frequency transmitter and radio-frequency transmitter, this frequency deviation becomes bigger.Frequency deviation is big more, and influence to received signal is just big more.To this, two frequency offset processing solutions have been proposed.
1. the Digital Down Convert circuit of the Digital Up Convert circuit of transmitting terminal and receiving terminal and radio-frequency transmitter and radio-frequency transmitter use common clock trigger.Add such external trigger and can accomplish that Digital Up Convert circuit and Digital Down Convert circuit are synchronous.But this scheme has caused a very important problem.When usage platform carried out channel estimating, hope can be tested Doppler frequency shift influence to received signal, also wished to send part and receiving unit and was placed on 2 that will adjust the distance far away decay with test signal.If transmit leg and recipient are connected on the same trigger by cable, this wired connected mode will inevitably limit transmit leg and recipient's relative movement distance.
2. reduce frequency deviation influence to received signal by increasing signaling rate, and the processing to frequency deviation is placed among the MATLAB of client and carries out.The cable that this scheme has been saved between transmitting terminal and the receiving terminal connects, and can arbitrarily move to receive and bring in the quality of measuring distance distance to the data receptivity.
The frame format of Frame
Power detection |
The gold sequence |
Data |
Power detection:, find the cardinal principle original position of frame by the power of detection signal.
The use pilot frame is synchronous: found through experiments, 32 gold sequence can realize synchronously, so the present invention uses preceding 32 of the gold sequence to carry out synchronously.Here insert 256 gold sequence, preceding 32 gold sequence is as synchronously, and remaining sequence is as channel estimating.
Use pilot tone to carry out channel estimating: there is frequency deviation in the signal of reception, and this frequency deviation is very little and more fixing, can regard a unified phase deviation as concerning 32 sampled points.Therefore, per 32 of the residue sampled point of gold sequence carries out channel estimating one time, and is used as the estimation frequency deviation estimating that at every turn the phase deviation that draws is averaged divided by 32 again.
STBC encoding scheme: adopt me to work for to propose two one debit's formulas transmission of (Alamouti).
Transmitting terminal:
The transmission signal is
Channel matrix is h=[h
1, h
2]
T, v is an additive noise, then the signal of Jie Shouing is r=Sh+v, wherein r=[r
1r
2]
T
Receiving terminal:
With h=[h
1, h
2]
TDo matrixing, obtain
Will
Do matrixing, obtain s=[s
1s
2]
T
Then
Promptly
The channel estimating that utilization is tried to achieve can be obtained the transmission signal.