GB2440190A

GB2440190A - Device and method for testing a receiver

Info

Publication number: GB2440190A
Application number: GB0614007A
Authority: GB
Inventors: Thierry Dubois; Joeri Melis; Jurgen Vandermot
Original assignee: Agilent Technologies Inc
Current assignee: Agilent Technologies Inc
Priority date: 2006-07-14
Filing date: 2006-07-14
Publication date: 2008-01-23
Also published as: GB0614007D0

Abstract

The present invention is related to a device (1) for testing a receiver device (20), said device for testing comprising a transmitter block (2) arranged for transmitting a data stream, a channel emulator block (4) arranged for being fed with the transmitted data stream and for outputting to the receiver device (20) under test a received data stream representative of the transmitted data stream being distorted by the loaded channel model, a measurement unit (6) arranged for being fed with data to be measured from the receiver device (20) under test and for processing the data to be measured, said data to be measured being a version of the received data stream output by the channel emulator block (4), synchronisation means (8) arranged for synchronising the transmitter block (2), channel emulator block (4) and measurement unit (6).

Description

DEVICE AND METHOD FOR TESTING A RECEIVER

Field of the invention

(0001] The present invention relates to a device and method for testing a receiver device of a communication system, preferably a wireless communication system.

State of the art (0002] With the continuous increase in complexity in digital baseband processing, made possible by the continuous decrease of transistor size, wireless communication systems become faster, more flexible and less susceptible to noisy channel environments. The higher data rates and increased flexibility results in more modem configuration options that need to be tested and verified during design and manufacturing. The increasingly complex channel environments that can be tolerated by wireless communication systems also mean that the amount of different channel environments that need to be verified increases as well.

(0003] For early GSM verification for instance only one data rate and four channel environments were defined.

In the traditional TJMTS four different data rates and eight different channel environments had to be verified. This trend continues, additional data rates and channel environments were added for HS-DPA (High-Speed Downlink Packet Access) and HS-UPA (High-Speed Uplink Packet Access) and it will continue in the future both with new data rates and channel environments representing the multiple input -multiple output (MIMO) environment.

(0004] The various channel environments such as urban, sub-urban, trees, mountains, etc... are modelled in so-called channel or fade models. These models simulate the signal characteristics of different frequencies and simulate the effects of specific wireless environments such as urban, sub-urban, mountains, trees, etc... These effects can be very complex in real life. Such effects include multi-path propagation, signal fading, scattering, etc... It is however important for test and measurement purposes that the complexities are generalised and a typical average behaviour is modelled. The models also introduce noise representative of the real world situation. These channel models are then usually applied to the signal before it is fed into the receiver under test. The receiver's ability to correctly demodulate and decode the signal under these emulated real-life conditions is then tested. The use of the models allows repeating the tests and comparing the results afterwards, something that is impossible to achieve in a wireless set-up due to the uncontrollable environment (e.g. people moving or breathing can cause different multi-paths).

t0005] Many algorithms and settings used in wireless communication systems that were traditionally static become more dynamic as well. A good example of this is the modulation. In older systems this was something fixed while the state of the art cellular systems continuously adapt it to the channel environment. If the channel condition is favourable, the system can choose to adapt the modulation scheme to a higher order (e.g. from 16-QAN to 64-QAM).

Similarly, if channel conditions worsen the system can decide to switch to more robust lower order modulation schemes. Because of this a good synchronisation between the different parts of the system (transmitter, receiver and channel environment) becomes all the more crucial for a coherent analysis of the strengths and weaknesses of any particular algorithm.

(0006] Thus to accurately test arid verify all the functionality of a modern wireless communication system a large set of test cases has to be analysed, generating a considerable amount of measurement results. These results have to be interpreted by the end-user and only make sense if they are considered in combination with the applied channel model and the various transmitter settings. Ideally the test set-up that is used should be able to provide this synchronisation and correlation between transmitter settings, channel models and measurement results. An important factor to take into account here is the time and cost to measure all the cases. Furthermore the end-user should still be able to swiftly access specific cases during debugging sessions, which is not always easy when the whole test set-up is automated.

(0007] Traditionally the solution to analyse the receiver performance and the solution to emulate the channel are separate solutions with little or no interaction. This means an increased work load for people performing tests as they have to separately start the measurements, channel emulation and then to post-process the results in a coherent fashion, linking the performance measurements with a certain channel model. Sometimes this process can be automated, for example by synchronising the separate solutions over a LAN connection and using command scripts on a personal computer as central controller. These scripts can start/stop the various test equipment used in the set-up and can perform a coherent post-processing. This has the clear advantage that tests can run for a long time or can be repeated a number of times without manual intervention. It is however a very ad-hoc solution that still requires a considerable effort as the scripts have to be programmed, the test solutions have to be synchronised and the whole set-up needs to be tested before actual measurements can take place.

(00081 There are currently no products on the market today that include a reference transmitter (or transceiver), channel modelling and measurement capability as part of a stand-alone test equipment.

Aims of the invention (0009] The present invention aims to provide a device and method for testing a receiver device, whereby the drawbacks of the prior art solutions are overcome.

Sunmtary of the invention (0010] The present invention relates to a device for testing a receiver device, said device for testing comprising -a transmitter block arranged for transmitting a data stream, -a channel emulator block arranged for being fed with the transmitted data stream and for outputting to the receiver device under test a received data stream representative of the transmitted data stream being distorted by the channel model, -a measurement unit arranged for being fed with data to be measured from the receiver device under test and for processing the data to be measured, said data to be measured being a version of the received data stream output by the channel emulator block,

S

-synchronisation means arranged for synchronising the transmitter block, channel emulator block and measurement unit.

[0011] Preferably the synchronisation means is integrated in said transmitter block.

(0012] In a preferred embodiment the device further comprises storage means for storing the channel model. The storage means is advantageously arranged for storing a plurality of channel models.

[0013] In another embodiment the channel emulator block is further arranged for loading the channel model from the storage means.

(0014] In an advantageous embodiment the device for testing is provided with a control means for dynamically controlling a test scenario. This dynamic control may comprise updating the parameters of the applied channel model or loading a new channel model from the storage means into the channel emulator.

(0015] Preferably the transmitter block is arranged for modulating the data stream prior to transmission.

Alternatively, it is arranged for modulating and encoding the data stream prior to transmission.

(0016] Advantageously the version of the received data stream is the received data stream after demodulation or after demodulation and decoding. Alternatively, the version of the received data stream is the received data stream after demodulation and subsequent re-modulation or after demodulating and decoding and subsequently again modulating and encoding in the receiver under test.

Typically in said second modulation (and encoding) operation another modulation/coding scheme is applied. In the case of re-modulation and encoding the device under test is thus provided with means for again modulating (or modulating and encoding) the demodulated (and if needed decoded) data. In this embodiment the device for testing further comprises means for performing a demodulation or demodulation and decoding operation before the measurement data to be measured are fed into the measurement unit.

(00171 In another preferred embodiment the device for testing comprises a data generator block for generating data to be fed to the transmitter block.

(00181 In a specific embodiment the measurement unit is further arranged for sending a triggering signal to the transmitter block. In this way it can trigger the transition to a next step in the test scenario after a sufficient number of errors have been measured that are statistically relevant for the test being executed in the current step of the scenario.

(0019] In a second object the invention relates to a method for testing a receiver device comprising the steps of -providing a device for testing as previously described, -applying in said device for testing a data stream to be transmitted to an emulation of a channel model, thereby producing a received data stream representative of the transmitted data stream being distorted by the channel model, -outputting the received data stream to the receiver device under test, -processing the received data stream in the receiver device and forwarding resulting data to be measured to the device for testing, -processing the data to be measured in the measurement unit of the device for testing.

(0020] Preferably the method further comprises the step of loading the channel model into the channel emulator block of the device for testing. In an advantageous embodiment the step of channel model loading is repeated in turn for a plurality of channel models.

[0021] In a preferred embodiment the step of processing the received data stream comprises a demodulation or a demodulation and decoding operation. The resulting data to be measured is preferably forwarded to the device for testing over a LAN interface.

[0022] Alternatively, after said demodulation or a demodulation and decoding operation an additional modulation or an additional modulation and encoding operation is performed. The resulting data to be measured is forwarded to the device for testing over an error-free link.

[0023] The processing in the measurement unit typically comprises a bit error rate measurement, a block error rate measurement or a packet error rate measurement.

Short description of the drawings

[0024] Fig. 1 represents a block diagram of a device for testing according to a first embodiment of the invention.

(0025] Fig. 2 represents a block diagram of a device for testing according to a second embodiment of the invention.

(0026] Fig. 3 represents a block diagram of a device for testing according to a third embodiment of the invention.

(0027] Fig. 4 represents a block diagram of a device for testing in an embodiment with a data generator block.

Detailed description of the invention

(0028] Fig. 1 shows the device for testing (1) of the present invention according to a first embodiment in connection with a receiver (20) under test. It comprises a transmitter block (2), a channel emulator block (4) and a measurement unit (6).

(0029] The transmitter block (TX) (2) in the device for testing modulates (and encodes) a known data stream which is sent to the channel emulator block (4) where various channel models and parameter settings are sequentially applied to the signal, creating a dynamic scenario. The device contains synchronisation means (8) arranged for executing such a dynamic test scenario by synchronising the transmitter block (2), the channel emulator block (4) (or alternatively a control block (12) as shown in Fig.3 -see below) and the measurement unit (6). The channel models are preferably stored as channel profiles in a memory (10) in the device for testing and are loaded into the channel emulator block (4) or updated with new parameter settings when needed. This can be handled by the channel emulator block (4) itself in response to a specific synchronisation message or alternatively by a separate control block (12) (as in Fig.3), also in response to such a synchronisation message.

[0030] The Device Under Test (DUT) is the receiver of a wireless communication device. For example, it can be a receiver of a user terminal or of a base station.

Alternatively, it may be a receiver of a wireline communication device. It demodulates and decodes the received signal and sends the data back to the test solution. This can be implemented over a guaranteed error-free uplink by modulating and encoding the signal again.

This is standard procedure in testing wireless communication devices and the loop-back mode between receiver and transmitter in the DUT is usually standardised and triggered by a specific command that the test solution sends to the DUT. This is illustrated in Fig.2. It is also possible to send the demodulated and decoded data back to the test solution without modulating and encoding it again as shown in Fig.1, e.g. by using a LAN interface to transport this data back to the device for testing.

[0031] The received user data can then be used by the measurement unit (6) for performance measurements (Bit Error Rate, Block Error Rate, Packet Error Rate, etc...) by comparing it with the original data that was sent.

Furthermore the measurement unit (6) may contain triggering means for alerting the transmitter block to move to a next step in a given test scenario after a sufficient number of errors have been measured that are statistically relevant for the test being executed in the current step of the scenario. This makes it possible to shorten the test scenario without any manual intervention from the end-user, while still obtaining statistically relevant results with a precision similar to the one that would have been obtained if the full scenario had run.

(0032] Although not required it is advantageous to have the synchronisation means integrated in the transmitter block of the test device. The transmitter can then be arranged for controlling both the channel emulator (6) (possibly via the separate control block (12)) and the measurements. Controlling means that synchronisation is ensured and hence the measurement results can be correlated with the applied channel models. The measurement results can be presented in various formats to the end-user, clearly linking a certain performance of the DUT with a certain moment in time that a specific channel model was being applied or that specific parameter settings were used. This eliminates the need for a post-processing phase before being able to interpret the results correctly.

Because the channel emulation, the signal generation and the actual measurements are part of the same test device, the three can be easily synchronised.

[0033] Optionally (see Fig. 4) a data generation block (14) is used for generating the user data to be transmitted by the transmitter block (2). The data generation block (14) is then also synchronised with the transmitter block (2), the channel emulator block (4) (or alternatively the control block (12)) and the measurement unit (8) by the synchronisation means (8). 12.

Claims

CLAIMS

1. Device for testing a receiver device (20), said device for testing (1) comprising -a transmitter block (2) arranged for transmitting a data stream, -a channel emulator block (4) arranged for being fed with said transmitted data stream and for outputting to said receiver device (20) under test a received data stream representative of said transmitted data stream being distorted by a channel model, * a measurement unit (6) arranged for being fed with data to be measured from said receiver device (20) under test and for processing said data to be measured, said data to be measured being a version of said received data stream output by said channel emulator block (4), -synchronisation means (8) arranged for synchronising said transmitter block (2), said channel emulator block(4) and said measurement unit (6).

2. Device for testing as in claim 1, wherein said synchronisation means (8) is integrated in said transmitter block (2).

3. Device for testing as in claim 1 or 2, further comprising storage means (10) for storing said channel model.

4. Device for testing as in claim 3, wherein said storage means (10) is arranged for storing a plurality of channel models.

5. Device for testing as in claim 3 or 4, wherein said channel emulator block (4) is further arranged for loading said channel model from said storage means (10) 6. Device for testing as in any of claims].

to 5, further comprising a control means (12) for dynamically controlling a test scenario.

7. Device for testing as in any of the previous claims, wherein said transmitter block (2) is arranged for modulating said data stream prior to transmission.

8. Device for testing as in any of claims 1 to 6, wherein said transmitter block (2) is arranged for modulating and encoding said data stream prior to transmission.

9. Device for testing as in claim 7 or 8, wherein said version of said received data stream is said received data stream after demodulation or after demodulation and decoding.

10. Device for testing as in claim 7 to 8, wherein said version of said received data stream is said received data stream after demodulation or after demodulation and decoding and subsequent modulation or second modulation and encoding.

11. Device for testing as in claim 10, further comprising means for demodulating or demodulating and decoding said version of said received data stream before applying it to said measurement unit.

12. Device as in any of the previous claims, wherein said measurement unit (6) is further arranged for sending a triggering signal to said transmitter block (2).

13. Device for testing as in any of the previous claims, further comprising a data generation block (14) for generating data to be fed to said transmitter block (2).

14. Method for testing a receiver device, comprising the steps of -providing a device (1) for testing as in any of claims 1 to 13, -applying in said device for testing a data stream to be transmitted to an emulation of a channel model, thereby producing a received data stream representative of said transmitted data stream being distorted by said channel model, -outputting said received data stream to said receiver device (20) under test, -processing said received data stream in said receiver device (20) and forwarding resulting data to be measured to said device for testing, -processing said data to be measured in said measurement unit of said device for testing.

15. Method for testing a receiver device as in claim 14, further comprising the step of loading said channel model into said channel emulator block (4) of said device for testing.

16. Method for testing a receiver device as in claim 15, wherein said step of channel model loading is repeated in turn for a plurality of channel models.

17. Method for testing as in any of claims 14 to 16, wherein said step of processing said received data stream comprises a demodulation or a demodulation and decoding operation.

18. Method for testing as in claim 17, wherein said resulting data to be measured is forwarded to said device for testing over a LAN interface.

19. Method for testing as in claim 17, wherein after said demodulation or a demodulation and decoding operation an additional modulation or an additional modulation and encoding operation is performed.

20. Method for testing as in claim 19, wherein said resulting data to be measured is forwarded to said device for testing over an error-free link.

21. Method for testing as in any of claims 14 to 20, wherein said processing in said measurement unit comprises a bit error rate measurement, a block error rate measurement or a packet error rate measurement.