Multi-antenna radio channel measurement system and method which generates time division duplex timing signal and measures two-way radio channel

The present invention relates to a multi-antenna radio channel measurement system and method which generates a Time Division Duplex (TDD) timing signal and measures a two-way radio channel. The multi-antenna radio channel measurement system which measures a probing signal for measuring a radio channel, the multi-antenna radio channel measurement system including: a baseband unit alternately transmits the probing signal for measurement and receives the received channel signal to be measured based on a TDD synchronization time; a synchronization unit which obtains time synchronization with the other radio channel measurement system, generates a transmission/reception synchronization signal, and provides the transmission/reception synchronization signal to the baseband unit; a transceiver unit which up converts the probing signal for measurement and down converts the received channel signal; and a radio frequency (RF) front-end unit which switches suitable antennas according to a timing control signal of the baseband unit.

TECHNICAL FIELD

The present invention relates to a multi-antenna radio channel measurement system and method which generates a Time Division Duplex (TDD) timing signal and measures a two-way radio channel. More particularly, the present invention relates to a multi-antenna radio channel measurement system and method which may simultaneously transmit/receive data, and measure a radio channel by synchronizing with two apparatuses for measuring the radio channel using a TDD timing signal.

This work was supported by the IT R&D program of MIC/IITA. [2005-S-001-03, Development of Wireless Vector Channel Model for next generation mobile communication]

BACKGROUND ART

A next-generation mobile communication system requires a technology providing a high-speed data transmission rate to improve a voice service and low-speed data service in a conventional art and provide a variety of high-speed multimedia services. Various technologies such as broadband frequency use and a method using a multiple antenna have been conducted to achieve a high-speed data transmission rate. A system using a multiple antenna is sensitive to features of radio channel in comparison with a single-antenna system in a conventional art. Accordingly, when designing a multi-antenna system, features of radio channel are required to be accurately ascertained. A next-generation radio communication system using the above-described multi-antenna is expected to be generally used in a city where electric waves are affected by buildings, trees, and the like. Also, a next-generation radio communication system using the above-described multi-antenna is expected to be widely used for wireless high-speed data communication.

In general, a multi-antenna radio channel measurement system, referred to as a channel sounder in a conventional art, is one-way measurement system, and is divided into a transmission system and a receiving system. A one-way channel sounder in a conventional art measures a radio channel in a city or an area where traffic is complex such as an urban macro or urban micro, while moving according to a specific route using a moving vehicle. In this instance, to measure a radio channel, multi-antennas for transmission and transmission system are installed in a base station or steel tower relatively higher than surrounding buildings, and multi-antennas for receiving and receiving system are installed in the moving vehicle. Through the measurement method described above, a radio channel emitted in a base station, that is, a change of downlink radio channel in various environments according to a route of a moving vehicle is measured. As opposed to the configuration above, a receiving system and multi-antennas for receiving may be installed in a base station, and a transmission system and multi-antennas for transmission may be installed in a moving vehicle. Through this, a moving vehicle emits an electric wave for measurement while moving based on a specific route, and a base station collects measurement data of an uplink radio channel emitted by a moving vehicle.

However, a one-way radio channel measurement system and method of operating the same in a conventional art is required to sequentially operate a downlink and uplink in order to measure a number of routes in a same measurement area and in a variety of environments. For this, a measurement apparatus and antenna are required to be installed in a base station and moving vehicle, respectively, and a downlink measurement is to be performed. After the downlink measurement is complete, the measurement apparatus and antenna of each of the base station and moving vehicle are changed and installed, and an uplink measurement is to be performed. A single measurement path in the same area and environment is measured twice in the system and method described above, which is inefficient and time-consuming, increases costs and wastes human resources.

Also, features of radio channel to be measured frequently change depending on an environment. In particular, a speed of moving vehicle when measuring an uplink is not identical to a speed of moving vehicle when measuring a downlink, and thus these channels may not be measured in the same environment. Also, radio channel measurement data of each of the uplink and downlink measured as described above is not measured at the same time, same measurement point, and surrounding environment, although the same path is measured. Accordingly, collected channel data to estimate correlation between data of each of the uplink and downlink may not be accurate.

Thus, a two-way radio channel measurement system is established, and a method and system to simultaneously measure an uplink and downlink in a same environment and condition when measuring a radio channel is required. Also, a technical control method and operation method to embody the two-way radio channel measurement system is required.

DISCLOSURE

Technical Problem

The present invention provides a multi-antenna radio channel measurement system and method which generates a Time Division Duplex (TDD) timing signal and measures a two-way radio channel.

The present invention also provides a multi-antenna radio channel measurement system and method which generates a TDD timing signal to enable a two-way radio channel to be measured.

The present invention also provides a multi-antenna radio channel measurement system and method which may transmit and receive data simultaneously, and measure a two-way radio channel by synchronizing with two apparatuses for measuring the two-way radio channel using a TDD timing signal.

Technical Solution

According to an aspect of the present invention, there is provided a multi-antenna radio channel measurement system which measures a probing signal for measuring a radio channel, the multi-antenna radio channel measurement system including: a baseband unit which alternately transmits the probing signal for measurement and receives the received channel signal to be measured based on a Time Division Duplex (TDD) synchronization time; a synchronization unit which obtains time synchronization with the other radio channel measurement system, generates a transmission/reception synchronization signal, and provides the transmission/reception synchronization signal to the baseband unit; a transceiver unit which up converts the probing signal for measurement and down converts the received channel signal; and a radio frequency (RF) front-end unit which switches suitable antennas according to a timing control signal of the baseband unit.

According to another aspect of the present invention, there is provided a method of measuring a radio channel in a multi-antenna radio channel measurement system, the method including: setting a frequency band and bandwidth to be measured in a TDD mode; downloading and storing a predetermined probing signal for measurement; receiving and setting a predetermined synchronization parameter; setting a transmission and reception timing control signal to synchronize with another radio channel measurement system for a bidirectional measurement; and transmitting the probing signal for measurement according to the timing control signal, and receiving and storing a received channel signal.

MODE FOR INVENTION

Hereinafter, embodiments of the present invention are described in detail by referring to the figures.

The present invention relates to a multi-antenna radio channel measurement system and method which may simultaneously transmit/receive data, and measure a radio channel by synchronizing with two apparatuses for measuring the radio channel using a TDD timing signal.

FIG. 1is a diagram illustrating a configuration of a multi-antenna radio channel measurement system which measures a two-way radio channel according to an embodiment of the present invention. By referring toFIG. 1, an example where a radio channel may be measured and data may be acquired while a vehicle120moves based on a predetermined route by installing a two-way radio channel measurement system in a base station110and the vehicle120is illustrated. Here, the two-way radio channel measurement system where a transmission function and receiving function are combined is referred to as a channel sounder. Paths of electric waves transmitted/received in each of the radio channel measurement systems110and120includes an uplink path2, uplink path4, and uplink path6, and a downlink path1, downlink path3, and downlink path5. Since the paths may be simultaneously measured at a same measurement point in time, vehicle speed, and environment, the two-way radio channel may be simultaneously measured.

The multi-antenna radio channel measurement system is described in detail with reference toFIG. 2.FIG. 2is a block diagram illustrating a configuration of an apparatus for measuring a two-way radio channel using a Time Division Duplex (TDD) scheme in a multi-antenna radio channel measurement system according to an embodiment of the present invention.

Referring toFIG. 2, the multi-antenna radio channel measurement system includes a baseband unit200, synchronization unit220, transceiver unit230, radio frequency (RF) front-end unit240, and control & console software250.

The baseband unit200transmits a probing signal for measurement, and receives and stores a received channel signal to be measured. The baseband unit200includes a micro-processor201, transmission (Tx) digital baseband block202, receiving (Rx) digital baseband block203, Tx memory204, Rx memory205, digital to analog (D/A) converter206, analog to digital (A/D) converter207, and TDD timing control block208.

The micro-processor201is connected to the control & console software250through Ethernet, and controls an operation of the radio channel measurement system according to a given command. Also, the micro-processor201transmits digital probing data for channel measurement to the Tx digital baseband block202, and transmits channel measurement data, received in the Rx digital baseband block203, to the control & console software250. The Tx digital baseband unit202stores the digital probing data for channel measurement, received from the micro-processor201, in the Tx memory204. The Tx digital baseband unit202transmits the digital probing data for channel measurement to the D/A converter206. The digital probing data for channel measurement is generated by the Tx digital baseband unit202based on a timing signal. The timing signal is provided by the TDD timing control block208and is suitable for a TDD mode. The D/A converter206converts a digital signal for transmission into an analog intermediate frequency (IF) signal for transmission, and transmits the analog IF signal to the transceiver unit230. When receiving a channel, an input IF signal transmitted from the transceiver unit230is transmitted to the A/D converter207. The A/D converter207converts an analog signal into digital data by sampling according to a sampling clock provided by the synchronization unit220. The converted digital data is collected by the Rx digital baseband block203, and the collected data is stored in the Rx memory205.

The TDD timing control block208generates a timing control signal suitable for reception timing and transmission timing in a TDD mode based on synchronization signal of the synchronization unit220and synchronization parameter. The synchronization signal and synchronization parameter suitable for the TDD mode are provided from the micro-processor201. Also, the TDD timing control block208provides the generated timing control signal to the baseband unit200and RF front-end unit240. The TDD timing control block208includes a frame counter209, cycle counter210, and control signal generator211.

The micro-processor201transmits a TDD synchronization parameter, and the like, to the TDD timing control block208to enable the radio channel measurement system to be appropriately operated in the TDD mode, before starting to measure a radio channel in the TDD mode. The TDD synchronization parameter includes a measurement bandwidth, length of Pseudo Noise (PN) chip, a number of transmission antennas, a number of receiving antennas, an iteration number of Rx codes, a number of frames, a number of cycles, and acquisition off time. The frame counter209and cycle counter210analyze the provided TDD synchronization parameter, count the number of frames, the number of cycles, and acquisition off time, and transmit the number of frames, the number of cycles, and acquisition off time to the control signal generator211. The control signal generator211generates a variety of control signals such as a SYNC_START, SYNC_STOP, TDD timing clock, acquisition trigger signal, Tx/Rx antenna switch control signal, and the like, to enable the TDD mode to be available. The control signal generator211provides the generated control signals to the baseband unit200and RF front-end unit240. The Tx/Rx antenna switch control signal depending on the number of frames and the number of cycles is described below with reference toFIG. 3. The SYNC_START, SYNC_STOP, TDD timing clock, and acquisition trigger signal are described in detail with reference toFIGS. 4 and 5.

The synchronization unit220is designed to obtain time synchronization with a synchronization unit of another radio channel measurement system, that is, another channel sounder. The synchronization unit220may obtain system synchronization with the synchronization unit of the other radio channel measurement system which is designed to be the same using a system synchronization signal. The synchronization unit220generates a TRX_Sync signal which is a transmission/reception synchronization signal using the obtained system synchronization signal, and transmits the TRX_Sync signal to the TDD timing control block208. Also, the synchronization unit210provides a sampling clock and clocks required for an operation of the baseband unit200.

The transceiver unit230includes an RF up-converter231and RF down-converter232. The RF up-converter231up converts a transmission IF signal into a transmission RF band. The RF down-converter232down converts a signal of reception RF into a reception IF. The RF front-end unit240includes a Tx antenna switch241and Rx antenna switch242. The RF front-end unit240switches an antenna suitable for the TDD mode based on the Tx antennal switch control signal and Rx antenna switch control signal generated by the TDD timing control block208.

FIG. 3is a diagram illustrating timings of parameters and signals used in a multi-antenna radio channel measurement system according to an embodiment of the present invention. A concept of TDD synchronization parameters transmitted to a TDD timing control block208by a micro-processor201is illustrated inFIG. 3. The TDD synchronization parameters include a measurement bandwidth, length of PN chip, a number of transmission antennas, a number of receiving antennas, an iteration number of Rx codes, a number of frames, a number of cycles, and acquisition off time. InFIG. 3, the TDD synchronization parameters, Tx antenna switching signal, Rx antenna switching signal, and a relationship of timing signals in a Data Acquisition (DAQ) mode are illustrated.

InFIG. 3, it is assumed that a length of a PN chip of the TDD synchronization parameters is 1024. The PN chips300are digital sequence data of a probing signal for measurement. The probing signal for measurement is generally used in a multi-antenna radio channel measurement system. A single code301is a basic unit of the probing signal for measurement used in the radio channel measurement, and the length of the code301is a length of the 1024 chips. Tx codes302transmitted for measurement may be in a configuration where the basic code301is continuously and repeatedly transmitted.

Hereinafter, it is assumed as an example that the measurement bandwidth is 100 MHz, the number of Tx antennas is two, the number of Rx antennas is four, the iteration number of Rx codes is four, the number of frames is N, the number of cycles is M, and acquisition off times is L.

When the number of Tx antennas is two and the number of Rx antennas is four, a switching timing of each antenna is shown as a Tx antenna switching timing303and Rx antenna switching timing304inFIG. 3. InFIG. 3, switching of Rx antenna is sequentially performed from an Rx antenna #1to an Rx antenna #4. A time until a switching timing of every Rx antenna is performed once is identical to a time when switching timing of a Tx antenna #1is performed. Then, switching timing of every Rx antenna is again performed once while switching timing of a Tx antenna #2is performed. In this instance, a length of switching time of an Rx antenna is determined by the iteration number of Rx codes. When the iteration number of Rx codes is four, the length of the switching time is four times longer than a length of the single code301. When the measurement bandwidth is 100 MHz, the Rx antenna switching time and Tx antenna switching time are given by,
(Time of 1 code)=(length ofPNchips)×(1/Bandwidth)=1024×10 ns=10.24 us
(RxAntenna Switching time)=(time of 1 code)×(Iteration count ofRxcode)=10.24 us×4=40.96 us
(TxAntenna Switching time)=(number ofRxAntenna)×(Rx Antenna Switching time)=4×40.96 us=163.84 us  [Equation 1]

InFIG. 3, Rx codes305illustrates an amount of basic receiving data which may be received in the radio channel measurement system, when all of the Tx antennas and Rx antennas are alternately switched. The Rx codes305actually received includes a single frame306. A time (tframe) of the received single frame is given by,
tframe=(number ofTxAntenna)×(TxAntenna Switching time)=2×163.84 us=327.68  [Equation 2]

When the number of frames as the TDD synchronization parameter is N, the N frames include a single cycle307. When the N is ten, a time (tcycle) is given by,
tcycle=(number of frame(=10))×tframe=3.2768 ms  [Equation 3]

Multiple cycles308and multiple acquisitions309illustrate timing when a DAQ mode receiving data in a multi-antenna radio channel system is a burst mode. In the burst mode, the number of cycles is at least one. Specifically, in the burst mode, when measuring a channel, measurement data is continuously and repeatedly acquired and data is stored all at once. Multiple cycles308when the number of cycles as the TDD synchronization parameter is M in the DAQ burst mode are illustrated inFIG. 3. In this instance, a cycle is repeated an M number of times, data is not received for a Cycle off time. Here, the single cycle time (tcycle) and Cycle off time (tcycle_off) are identical. A cycle of Cycle and Cycle off, repeated the M number of times in the multiple cycles308, is the same as an acquisition time. When M is ten, the acquisition time (tacq) is represented as,
tacq=(tcycle×(number of cycle(M)))+(tcycle_off×((number of cycle(M))−1))=(3.2768 ms×10)+(3.2768 ms×9)=62.2592 us  [Equation 4]

In multiple acquisitions309ofFIG. 3, acquisition and acquisition off are repeated a number of times. In the multiple acquisitions309ofFIG. 3, a repeated operation where a baseband unit203is transmitted to a control & console software250through a micro-processor201for an acquisition off time (tacq_off) after receiving data for the acquisition time and temporarily storing the data in an Rx memory205is illustrated. The acquisition off time is provided as the TDD synchronization parameter, and is a positive number times than a frame. When the acquisition off time is L, a length of the acquisition off time is L×tframe.

FIGS. 4 and 5are diagrams illustrating timings when TDD timing signals are inappropriately generated in a TDD mode of a multi-antenna radio channel measurement system according to an embodiment of the present invention.

FIG. 4illustrates an example of inappropriate TDD timing signal generation. A TDD timing clock400is a timing signal generated in a TDD timing control block208. Specifically, the TDD timing clock400is a timing reference signal which is a standard when a channel sounder A401and channel sounder B402measure a two-way radio channel. The channel sounder A401and channel sounder B402are a multi-antenna radio channel measurement system according to the present invention. Each of the channel sounder A401and channel sounder B402generates a TDD timing clock, and a signal of each of the channel sounder A401and channel sounder B402is synchronized. The channel sounder A401is designed to perform a transmission operation in a low period of the TDD timing clock400and perform a receiving operation in a high period of the TDD timing clock400. Conversely, the channel sounder B402is designed to perform the receiving operation in the low period of the TDD timing clock400, and perform the transmission operation in the high period of the TDD timing clock400. That is, measurement data transmitted by the channel sounder A401in the low period of the TDD timing clock400is received by the channel sounder B402. Also, measurement data transmitted by the channel sounder B402in the high period is received by the channel sounder A401. Synchronization of the TDD timing clock400which refers to a start of the transmission and receiving operation described above is achieved by a TRX_Sync signal. The TRX_Sync signal is generated in a synchronization unit220and transmitted to the TDD timing control block208. That is, the channel sounder A401and channel sounder B402may set a transmission and receiving timing by the TDD timing clock400using the TRX_Sync signal. In this instance, when a Start Logging #1of each of the channel sounder A401and channel sounder B402is not synchronized and different as illustrated inFIG. 4, data received for an acquisition time may not be considered as data simultaneously measured in a same measurement point, vehicle speed, and environment as described inFIG. 1. The Start Logging #1is a point in time when starting receiving data of the channel sounder A401and channel sounder B402. Accordingly, the Start Logging #1of each of the channel sounder A401and channel sounder B402is to be synchronized. Thus, the TDD timing signals ofFIG. 4are inappropriately generated.

FIG. 5illustrates an example when a Start Logging #1is synchronized. A channel sounder A504and channel sounder B505start receiving based on a provided TDD synchronization parameter, and acquire measurement data for a first acquisition time. However, when an acquisition off time is different, a Start Logging #2may not be synchronized. The Start Logging #2is a start point in a subsequent acquisition time. A micro-processor201transmits received data stored in an Rx memory205to a control & console software250and stores for the acquisition off time. Since a performance of each control & console software250installed at a laptop computer of channel sounder A504and channel sounder B505is different, the acquisition off time may be different. Accordingly, in a method of generating TDD timing signals inFIG. 5, although the Start Logging #1may be synchronized, the Start Logging #2may not be synchronized. Accordingly, data may not be considered as data simultaneously measured at a same measurement point, vehicle speed, and environment as described inFIG. 1. Thus, according to the present invention, timing inFIG. 6is provided to overcome the disadvantage described above.

FIG. 6is a diagram illustrating timings of TDD timing signals in a multi-antenna radio channel measurement system according to an embodiment of the present invention.

The timings of TDD timing signals are designed to supplement a method of generating a TDD timing signal ofFIGS. 4 and 5. A TDD timing clock600is designed to be generated by TDD synchronization parameters described inFIG. 3. That is, a time (tcycle) of a cycle and a cycle off time (tcycle_off) of provided TDD synchronization parameters are designed to be a half cycle period (ttdd) of the TDD timing clock600. A channel sounder A601and channel sounder B602may generate the same TDD timing clock600. According to an embodiment of the present invention, a cycle of the TDD timing clock600may be arbitrarily set based on the provided TDD synchronization parameters. The cycle may be flexibly operated from about 960 ns to infinity in a minimum condition represented as,
Minimum condition: (length ofPNchips)=32, (Bandwidth)=100 MHz, (number ofTXAntenna)=1, (number ofRxAntenna)=1, (Iteration count ofRxcode)=3
ttdd(=tframe=tcycle=tcycle_off)=(length ofPNchips)×(1/Bandwidth)×(number ofTXAntenna)×(number ofRxAntenna)×(Iteration count ofRxcode)=960 ns  [Equation 5]

Also, a start point of transmission and receiving of the channel sounder A601and channel sounder B602is set as a SYNC_START signal. The SYNC_START signal is set by summing a TRX_Sync signal and a Start Logging signal ofFIGS. 4 and 5. That is, the start points of receiving data of the channel sounder A601and channel sounder B602may be prevented from being different from each other. Data received by the channel sounder A601and channel sounder B602may be data simultaneously measured at a same measurement point, vehicle speed, and environment as described inFIG. 1.

Also, when an acquisition off time (tacq_off) of the channel sounder A601is different from an acquisition off time (tacq_off_b) of the channel sounder B602, to supplement a disadvantage ofFIG. 5, a wait time (tw_a and tw_b) is provided to each of the channel sounder A601and channel sounder B602so that a Start Logging #2of each of the channel sounder A601and channel sounder B602is synchronized again and data may be received. Accordingly, the channel sounder A601and channel sounder B602may simultaneously receive measurement data at the same measurement point, vehicle speed, and environment as described inFIG. 1.

Also, according to an embodiment of the present invention, when the multi-antenna radio channel measurement system performs a two-way radio channel measurement using a TDD scheme, a Transfer Time Interval (TTI) used in a general TDD-based wireless communication system, that is, a cycle of TDD timing clock, can be set at a fixed value. Accordingly, the wireless communication system based on the general TDD scheme may be simulated. And, when the TDD cycle of arbitrary wireless telecommunications system is predicted, the radio channel measurement can be performed in the same environment.

Hereinafter, a method of measuring a two-way radio channel which generates a TDD timing signal in the multi-antenna radio channel measurement system is described in detail with reference toFIG. 7.

FIG. 7is a flowchart illustrating operations of measuring a two-way radio channel using a TDD scheme in a multi-antenna radio channel measurement system according to an embodiment of the present invention. By referring toFIG. 7, a measurement mode of a channel sounder A and channel sounder B is selected as a TDD mode based on a selection of a control & console software250in operation701. The channel sounder A and channel sounder B are the same two-way radio channel measurement systems. In operation702, a transmission and reception frequency band to be measured according to a control of the control & console software250is set identically. In operation703, a measurement bandwidth of each of the channel sounder A and channel sounder B is set. In operation704, a probing signal for measurement to be used in the control & console software250is generated, and downloaded and stored in a Tx memory204. In operation705, a Tx and Rx antenna parameter and a number of Tx and Rx antenna parameters are set based on a scenario to be used for measurement. In operation706, a DAQ mode for receiving data is selected as a burst mode. In operation707, an iteration number of Rx codes is set. In operation708, a number of frames is set. In operation709, a number of cycles is set. The iteration number of Rx codes, the number of frames, and the number of cycles are TDD synchronization parameters. During operation707through operation709, an acquisition time of each of the channel sounder A and channel sounder B is determined.

In operation710, an acquisition off time of each of the channel sounder A and channel sounder B is set as 0. In operation711, a synchronization and a reception start signal (SYNC_START) of each of the channel sounder A and channel sounder B is generated. In operation712, the acquisition off time of each of the channel sounder A and channel sounder B is measured. In operation713, a wait time of each of the channel sounder A and channel sounder B is calculated. In operation714, a SYNC_STOP signal of the channel sounder A and channel sounder B is generated to stop the synchronization and receiving.

In operation715, the synchronization is set based on the measured acquisition off time and wait time of each of the channel sounder A and channel sounder B. In operation716, the SYNC_START signal of each of the channel sounder A and channel sounder B is simultaneously generated. In operation717, a channel of each of the channel sounder A and channel sounder B is measured, and data of each of the channel sounder A and channel sounder B is acquired. In operation718, the two-way radio channel measurement is performed based on a predetermined measurement path and data is stored. Then, an algorithm according to the present invention is finished.

According to the present invention, the multi-antenna radio channel measurement system and method improves the reliability and correlation about measurement data, simultaneously measures an uplink radio channel and downlink radio channel, and thereby may reduce a time, cost, and human resources required for measurement.