Abstract:
Method for testing a radio frequency (RF) data packet signal transceiver device under test (DUT) including communicating via at least one of multiple available signal channels. Data packets exchanged between a tester and DUT as a normal part of a communication link initiation sequence are selectively exchanged and suppressed to enable testing of the DUT without requiring inclusion of special drivers within the DUT, special test software within the tester or establishment of a synchronized communication link between the tester and DUT. For example, in the case of a Bluetooth low energy transceiver, advertisement, scan request and scan response data packets can be used in such manner.

Description:
BACKGROUND 
     The present invention relates to testing of a low power radio frequency (RF) data packet signal transceiver, and in particular, to testing such a device using data packets exchanged between a tester and the device as a normal part of a communication link initiation sequence. 
     Many of today&#39;s electronic devices use wireless signal technologies for both connectivity and communications purposes. Because wireless devices transmit and receive electromagnetic energy, and because two or more wireless devices have the potential of interfering with the operations of one another by virtue of their signal frequencies and power spectral densities, these devices and their wireless signal technologies must adhere to various wireless signal technology standard specifications. 
     When designing such wireless devices, engineers take extra care to ensure that such devices will meet or exceed each of their included wireless signal technology prescribed standard-based specifications. Furthermore, when these devices are later being manufactured in quantity, they are tested to ensure that manufacturing defects will not cause improper operation, including their adherence to the included wireless signal technology standard-based specifications. 
     For testing these devices following their manufacture and assembly, current wireless device test systems typically employ testing subsystems for providing test signals to each device under test (DUT) and analyzing signals received from each DUT. Some subsystems (often referred to as “testers”) include one or more vector signal generators (VSG) for providing the source, or test, signals to be transmitted to the DUT, and one or more vector signal analyzers (VSA) for analyzing signals produced by the DUT. The production of test signals by a VSG and signal analysis performed by a VSA are generally programmable (e.g., through use of an internal programmable controller or an external programmable controller such as a personal computer) so as to allow each to be used for testing a variety of devices for adherence to a variety of wireless signal technology standards with differing frequency ranges, bandwidths and signal modulation characteristics. 
     Testing of wireless devices typically involves testing of their receiving and transmitting subsystems. The tester will typically send a prescribed sequence of test data packet signals to a DUT, e.g., using different frequencies, power levels, and/or modulation technologies, to determine if the DUT receiving subsystem is operating properly. Similarly, the DUT will send test data packet signals at a variety of frequencies, power levels, and/or modulation technologies to determine if the DUT transmitting subsystem is operating properly. 
     Low power RF data packet signal transceivers often exchange data packets as a part of a sequence to initiate a communication link. One example is a personal area network (PAN) technology known as Bluetooth Low Energy (BLE, or also known as “Bluetooth Smart”), which is designed to be very conservative in its energy requirements while providing connectivity between a central device (“client”) and a peripheral device (“server”) once a connection is established. Examples of such devices include a “smartphone” as a central device and a pulse-rate sensor connected to a user&#39;s wrist as a peripheral device. 
     The original Bluetooth devices were designed to provide wireless data connections for mobile applications such as on-air headsets to cellphones and portable speakers to MP3 playback devices. The newer BLE devices are designed to be simpler and to convey data in smaller quantities and at lower speeds to minimize power use, thereby preserving battery life and enabling operation over extended periods of time. 
     During manufacturing, when a BLE subsystem is being tested, an input/output (I/O) port is available to facilitate conductive testing of receiver and transmitter physical-level behavior as well as DUT control. However, once the BLE subsystem is combined with the server peripheral device (e.g., a sensor), the I/O port is typically no longer available (e.g., removed or encapsulated). Hence, testing at that stage must be performed wirelessly using radiative signaling (e.g., via wireless RF signals). However, since separate DUT control is rarely available (e.g., neither a conductive signal path nor a wireless control signal channel is available), such testing relies upon establishing a wireless communication link between a tester and the BLE-based peripheral device-under-test (DUT), with DUT control established by including driver software within the DUT and DUT-specific testing software within the tester. Such requirements for driver and testing software increase testing complexity and time and thereby increase testing costs. 
     Additionally, continuing with the BLE example, the data packets used by a peripheral device to initiate a communication link can be transmitted on any of multiple (e.g., three) channels in random order. Unless a testing system knows in advance on which channel the DUT will transmit, it cannot deterministically transmit a responsive data packet on that same channel. This can significantly delay test time, or require some form of predetermined coding to be employed within the DUT, which would negate the use of a generalized testing methodology. 
     Further with the BLE example, pending establishment of a communication link, a relatively long time interval exists between data packet sequences seeking to initiate a communication link. Meanwhile, during the link initiation sequence, initiating data packets are transmitted on the multiple prescribed channels in rapid succession. It would be advantageous if such rapid sequence of data packets could be used for testing, and thereby derive more test data, faster, and reduce overall test time. 
     SUMMARY 
     In accordance with the presently claimed invention, a method is provided for testing a radio frequency (RF) data packet signal transceiver device under test (DUT) including communicating via at least one of multiple available signal channels. Data packets exchanged between a tester and DUT as a normal part of a communication link initiation sequence are selectively exchanged and suppressed to enable testing of the DUT without requiring inclusion of special drivers within the DUT, special test software within the tester or establishment of a synchronized communication link between the tester and DUT. For example, in the case of a Bluetooth low energy transceiver, advertisement, scan request and scan response data packets can be used in such manner. 
     In accordance with one embodiment of the presently claimed invention, a method for testing a radio frequency (RF) data packet signal transceiver device under test (DUT) including communicating via at least one of a plurality of signal channels, includes: 
     receiving, with a tester via one of the plurality of signal channels, a link initiation data packet from the DUT; 
     transmitting, with the tester via the one of the plurality of signal channels, a tester response data packet responsive to the link initiation data packet; 
     receiving, with the tester via the one of the plurality of signal channels, a DUT response data packet responsive to the tester response data packet; 
     refraining, with the tester, from transmitting via the one of the plurality of signal channels another tester response data packet responsive to the DUT response data packet; and 
     repeating at least
         the receiving, with the tester via one of the plurality of signal channels, a link initiation data packet from the DUT, and   the transmitting, with the tester via the one of the plurality of signal channels, a tester response data packet responsive to the link initiation data packet.       

     In accordance with another embodiment of the presently claimed invention, a method for testing a radio frequency (RF) data packet signal transceiver device under test (DUT) including communicating via at least one of a plurality of signal channels, includes: 
     transmitting, with a DUT via one of the plurality of signal channels, a link initiation data packet; 
     receiving, with the DUT via the one of the plurality of signal channels, a tester response data packet responsive to the link initiation data packet; 
     transmitting, with the DUT via the one of the plurality of signal channels, a DUT response data packet responsive to the tester response data packet; 
     failing, with the DUT, to receive via the one of the plurality of signal channels another tester response data packet responsive to the DUT response data packet; and 
     repeating at least
         the transmitting, with the DUT via one of the plurality of signal channels, a link initiation data packet, and   the receiving, with the DUT via the one of the plurality of signal channels, a tester response data packet responsive to the link initiation data packet.       

     In accordance with another embodiment of the presently claimed invention, a method for testing a radio frequency (RF) data packet signal transceiver device under test (DUT) including communicating via at least one of a plurality of signal channels, includes: 
     transmitting, with a DUT via one of the plurality of signal channels, a link initiation data packet; 
     receiving, with a tester, the link initiation data packet and in response thereto transmitting, via the one of the plurality of signal channels, a tester response data packet; 
     receiving, with the DUT, the tester response data packet and in response thereto transmitting, via the one of the plurality of signal channels, a DUT response data packet; 
     receiving, with the tester, the DUT response data packet and in response thereto refraining from transmitting via the one of the plurality of signal channels another tester response data packet; and 
     repeating at least
         the transmitting, with the DUT via one of the plurality of signal channels, a link initiation data packet,   the receiving, with the tester, the link initiation data packet, and in response thereto transmitting, via the one of the plurality of signal channels, a tester response data packet, and   the receiving, with the DUT, the tester response data packet and in response thereto transmitting, via the one of the plurality of signal channels, a DUT response data packet.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a typical testing environment for a radio frequency (RF) data packet signal transceiver device under test (DUT) in a conductive, or wired, environment. 
         FIG. 2  depicts a typical testing environment for a RF DUT in a radiative, or wireless, environment. 
         FIG. 3  depicts a testing environment for a RF DUT in a wireless environment in accordance with exemplary embodiments of the presently claimed invention. 
         FIG. 4  depicts transmission of advertisement packets by a BLE DUT with no tester response. 
         FIG. 5  depicts exchanges of advertisement, scan request and scan response packets between a BLE DUT and tester in accordance with exemplary embodiments. 
         FIGS. 6 and 7  depict exchanges of advertisement, scan request and scan response packets between a BLE DUT and tester transmitting multiple scan request packets simultaneously in accordance with exemplary embodiments. 
         FIGS. 8 and 9  depict exchanges of advertisement, scan request and scan response packets between a BLE DUT and tester transmitting multiple scan request packets simultaneously with varying power levels in accordance with exemplary embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is of example embodiments of the presently claimed invention with references to the accompanying drawings. Such description is intended to be illustrative and not limiting with respect to the scope of the present invention. Such embodiments are described in sufficient detail to enable one of ordinary skill in the art to practice the subject invention, and it will be understood that other embodiments may be practiced with some variations without departing from the spirit or scope of the subject invention. 
     Throughout the present disclosure, absent a clear indication to the contrary from the context, it will be understood that individual circuit elements as described may be singular or plural in number. For example, the terms “circuit” and “circuitry” may include either a single component or a plurality of components, which are either active and/or passive and are connected or otherwise coupled together (e.g., as one or more integrated circuit chips) to provide the described function. Additionally, the term “signal” may refer to one or more currents, one or more voltages, or a data signal. Within the drawings, like or related elements will have like or related alpha, numeric or alphanumeric designators. Further, while the present invention has been discussed in the context of implementations using discrete electronic circuitry (preferably in the form of one or more integrated circuit chips), the functions of any part of such circuitry may alternatively be implemented using one or more appropriately programmed processors, depending upon the signal frequencies or data rates to be processed. Moreover, to the extent that the figures illustrate diagrams of the functional blocks of various embodiments, the functional blocks are not necessarily indicative of the division between hardware circuitry. 
     Wireless devices, such as cellphones, smartphones, tablets, etc., make use of standards-based technologies (e.g., IEEE 802.11a/b/g/n/ac, 3GPP LTE, and Bluetooth). The standards that underlie these technologies are designed to provide reliable wireless connectivity and/or communications. The standards prescribe physical and higher-level specifications generally designed to be energy-efficient and to minimize interference among devices using the same or other technologies that are adjacent to or share the wireless spectrum. 
     Tests prescribed by these standards are meant to ensure that such devices are designed to conform to the standard-prescribed specifications, and that manufactured devices continue to conform to those prescribed specifications. Most devices are transceivers, containing at least one or more receivers and transmitters. Thus, the tests are intended to confirm whether the receivers and transmitters both conform. Tests of the receiver or receivers (RX tests) of a DUT typically involve a test system (tester) sending test packets to the receiver(s) and some way of determining how the DUT receiver(s) respond to those test packets. Transmitters of a DUT are tested by having them send packets to the test system, which then evaluates the physical characteristics of the signals sent by the DUT. 
     Referring to  FIG. 1 , a typical manufacturing test environment  10   a  includes a tester  12  and a DUT  16 , with test data packet signals  21   t  and DUT data packet signals  21   d  exchanged as RF signals conveyed between the tester  12  and DUT  16  via a conductive signal path, typically in the form of co-axial RF cable  20   c  and RF signal connectors  20   tc ,  20   dc . As noted above, the tester typically includes a signal source  14   g  (e.g., a VSG) and a signal analyzer  14   a  (e.g., a VSA). Also, as discussed above, the tester  12  and DUT  16  include preloaded information regarding predetermined test sequences, typically embodied in firmware  14   f  within the tester  12  and firmware  18   f  within the DUT  16 . As further noted above, the details within this firmware  14   f ,  18   f  about the predetermined test flows typically requires some form of explicit synchronization between the tester  12  and DUT  16 , typically via the data packet signals  21   t ,  21   d.    
     Referring to  FIG. 2 , a typical test environment  10   b  following final assembly (after which, as noted above, a physical DUT signal connection  20   dc  is generally unavailable) uses a wireless signal path  20   b  via which the test data packet signals  21   t  and DUT data packet signals  21   d  are communicated via respective antenna systems  20   ta ,  20   da  of the tester  12  and DUT  16 . 
     The following discussion is presented in the context of a BLE device as the DUT. However, it will be readily appreciated by one of ordinary skill in the art that the principles and operation of the presently claimed invention are also applicable to devices or systems in which data packets are exchanged as a normal part of a communication link initiation sequence. As is known and discussed below, in the case of a BLE transceiver, such data packets are in the form of advertisement, scan request and scan response data packets. 
     Referring to  FIG. 3 , testing methods in accordance with the presently claimed invention for devices or systems that exchange data packets as a normal part of a communication link initiation sequence, such as BLE devices and systems, are typically performed in a wireless testing environment. The DUT  16  includes a BLE subsystem or device  26  which transmits  21   d  advertisement packets for reception by the tester  12  (stage A). Following successful reception by the tester  12  of an advertisement packet, the tester  12  transmits  21   t  a scan request packet (stage B). Following successful reception by the BLE subsystem  26  of the DUT  16 , the DUT  16  transmits  21   d  a scan response packet (stage C). 
     These exchanges of such packets are prescribed within the signal standard for BLE systems. Accordingly, the DUT  16  does not require any special driver code (e.g., in either firmware or software form) nor does the tester  12  require any device-specific or otherwise or testing software or firmware. Also, this interchange of packets occurs prior to and in the absence of a communication link having already been established between the DUT  16  and tester  12 . Accordingly, no communication profile is yet active and any BLE device can be prompted to interact with a tester in this way. 
     Referring to  FIG. 4 , in accordance with the BLE signal standard, a BLE device uses three channels (among 40 channels total) for device discovery and connection setup. These channels are located between the standard wireless local area network channels (“Wi-Fi”) to minimize inter-system interference. These channels are known as “advertising” channels and are used by the BLE system to search for other devices or promote its own presence to devices that might be looking to make a connection. The device transmits an advertisement packet, and then waits for a prescribed time interval to receive a scan request packet. If no scan request packet is received within that time interval, another advertisement packet on a different channel is transmitted. Initial channel selection is random, and each subsequent advertisement packet is transmitted on a different channel, until all three channels have been used, following which this process repeats until a scan request packet is received and a communication link is established. 
     Accordingly, as shown by way of example here, the BLE device transmits a first advertisement packet  21   aa  on a randomly chosen channel, e.g., channel 1. If no scan request packet is received in response, a second advertisement packet  21   ab  is transmitted on another channel, e.g., channel 2. Again, if no scan request packet is received within the prescribed time interval, a third advertisement packet  21   ac  is transmitted on the remaining channel, e.g., channel 3. 
     Referring to  FIG. 5 , in accordance with exemplary embodiments, the DUT transmits an advertisement packet  21   aa , which is correctly received by the tester, and in response to which the tester transmits a scan request packet  21   qa . Responsive to successful reception of this scan request packet  21   qa , the DUT then transmits a scan response packet  21   ra . These packets  21   aa ,  21   qa ,  21   ra  are all transmitted on the same channel (channel 1, 2 or 3). If the tester refrains from sending any further packets after the scan response packet  21   ra , the DUT will wait for a prescribed time interval for reception of further commands. If no further commands are received within that time interval, the DUT resumes sending advertisement packets  21   ab ,  21   ac ,  21   ad  at successive specified advertisement intervals on respective ones of the three advertisement channels in close-order succession. 
     Hence, for example as shown here, the DUT transmits a second advertisement packet  21   ab , receives a scan request packet  21   qb  and responds with a scan response packet  21   rb . However, when the DUT sends a third advertisement packet  21   ac , the tester in this example transmits scan request packet  21   qc  with a reduced signal power, which fails to be received by the DUT. Accordingly, the DUT transmits no scan response packet. Then, after the prescribed time interval  23 , the DUT again resumes operation by sending a fourth advertisement packet  21   ad.    
     As can be seen by this operation, a tester can use the BLE standard protocol to elicit from a DUT one or more scan response packets at one of the three prescribed advertisement packet frequencies. Such scan response packets transmitted by the DUT can be viewed as analogous to “acknowledgement” (ACK) packets used in Wi-Fi systems (as per the IEE 802.11 standard), which can be used to test Wi-Fi transmitter signal characteristics (e.g., signal power levels and data encoding). Similarly, in this context, the tester here can use these scan response packets to determine how many scan request packets transmitted by the tester were received by the DUT. The ratio of received scan response packets to transmitted scan requests packets can be used to derive an effective packet error rate (PER). 
     Further, by varying the power level of the scan request packet transmitted by the tester, variations in the number of scan response packets received will result, and can be used to determine sensitivity of the BLE receiver within the DUT, similar to performing PER testing of a Wi-Fi receiver, as described in U.S. patent application Ser. No. 13/959,354 filed on Aug. 5, 2013, and published as U.S. Pat. Pub. 2015/0036729, the disclosure of which is incorporated herein by reference. Hence, the tester can obtain useful information about the DUT receiver sensitivity within a short test time. Further, the tester may analyze signal qualities of the scan response packets, as well as the advertisement packets, such as frequency, power level, modulation, etc., to determine the quality of performance by the DUT transmitter. 
     In any event, these tests can be conducted using a conventional tester, e.g., with conventional VSA and VSG systems, without need for special driver code within the DUT or device-specific testing software for the tester. 
     Referring to  FIG. 6 , in accordance with further exemplary embodiments, testing can be simplified and expedited using a broadband transmitter within the tester (e.g., a broadband VSG), thereby avoiding a need for the receiver within the tester (e.g., a VSA) to quickly determine the channel on which the DUT is transmitting its advertisement packet. For example, in response to receiving the advertisement packet  21   a  from the DUT, e.g., on channel 2, the tester transmits a group  21   q  of scan request packets  21   qa ,  21   qb ,  21   qc , with each scan request packet  21   qa ,  21   qb ,  21   qc  transmitted on a respective one of the three advertisement packet channels using the broadband transmitter capability. As a result, the DUT will receive a response scan request packet on all three advertisement channels (i.e., the channel actually used for the advertisement packet  21   a  as well as the other two channels not used), thereby ensuring that the DUT, in turn, responds by transmitting a scan response packet  21   r  on the same channel on which the original advertisement packet  21   a  was transmitted. 
     Referring to  FIG. 7 , this technique of responding to advertisement packets with scan request packets on all channels ensures that regardless of which channel on which the DUT transmits the initial advertisement packet  21   a , in this case on channel 1, the DUT will receive, in response, a scan request packet on the same channel (as well as on the unused channels). As a result, the DUT will then complete the communication link initiation sequence by responding, in turn, with a scan response packet  21   r  on the same channel. Hence, regardless which of the three prescribed channels is used by the DUT to transmits its initial advertisement packet  21   a , the tester, by responding with a scan request packet on all available advertisement channels, will be able to elicit a scan response packet  21   r  from the DUT, so long as the DUT is performing properly and the scan request packet  21   q  power is sufficient to be received correctly by the DUT. 
     In a related manner, the tester can employ a wideband receiver (e.g., VSA) to detect and correctly receive the advertisement  21   a  and scan response  21   r  packets. Even if such receiver is unable to determine, in real time, the channel over which the interactions are occurring, the received packets, once captured, can be used later, e.g., with downstream systems or processing, to determine the channel during post-capture processing. 
     In those instances where signal path loss varies with the advertisement channel frequency, the transmitted packet power can be varied with an offset that is sufficient to ensure that the received signal power at the DUT is sufficient for each of the three advertisement channels. 
     Referring to  FIG. 8 , in accordance with further exemplary embodiments, the techniques discussed above of transmitting scan request packets at varied signal powers and transmitting multiple scan request packets simultaneously via different channels can be used in combination(s). For example, responsive to a first advertisement packet  21   aa  (e.g., on channel 2), the tester can transmit scan request packets on all channels simultaneously, as discussed above, at a reduced power level intended to prevent successful reception by the DUT. As a result, the DUT, after the prescribed time interval, transmits a second advertisement packet  21   ab  on a different channel (e.g., on channel 1). The tester detects this advertisement packet  21   ab  and responds by transmitting a second set of scan request packets  21   qb  on all channels simultaneously, this time at a higher power level. However, this higher power level is still insufficient to ensure successful reception by the DUT. Accordingly, the DUT, again after the prescribed time interval, transmits a third advertisement packet  21   ac  on another different channel (e.g., on the remaining channel 3), in response to which the tester transmits a third set  21   qc  of scan request packets, this time at a still higher power level. This power level is now sufficient to ensure successful reception by the DUT, which responds with a scan response packet  21   r  on the same channel (e.g., channel 3) as used for the most recent exchange of advertisement packet  21   ac  and scan request packets  21   qc.    
     Consequently, three different power levels for the scan request packets are used for testing the ability of the DUT receiver to successfully receive such scan request packets. While the first two sets  21   qa ,  21   qb  of scan request packets were too low in power, the third set  21   qc  was of sufficient power to elicit a scan response packet  21   r . Accordingly, this test can effectively yield three results from a single operation. Since noise adds to this system and cannot be entirely prevented, it cannot be concluded as to what actual power level constitutes a threshold above which the DUT will be ensured to successfully receive all scan request packets. Further statistical results will be needed to determine this. Accordingly, multiple test like this can be performed to determine a statistical distribution that identifies or is otherwise indicative of such threshold. 
     Referring to  FIG. 9 , as part of arriving at such a statistical distribution, the scan request packets sets  21   qa ,  21   qb  can be transmitted with power levels such that only two power levels are needed to elicit a scan response packet. For example, while the first set  21   qa  of scan request packets has a power level insufficient to ensure successful reception by the DUT, the second set  21   qb  can be transmitted with a power level between the power levels of the second and third sets of scan request packets as identified in the previous example ( FIG. 8 ). This can advantageously further reduce the time between test results, e.g., if a connection request is received, since the time between sequential advertisement packets is significantly shorter than the time between the onset of a new advertisement packet sequence in the absence of an established communication link. (However, in some instances a third advertisement packet may still be transmitted, e.g., if there is no event following a scan response packet, in which case three test results would still be obtained.) 
     In any event, performing these packet exchanges with varying power levels enables formation of a statistical database. Further, by properly choosing the varied packet power levels it is possible to more quickly converge on the statistical power level at which half of the scan request packets are received correctly and elicit corresponding scan response packets. According, if the power levels chosen are all below this sensitivity point, the DUT will send subsequent advertisement packets in quick succession. This enables the setting of new values for the power level when sending the scan request packet without having to wait over the longer duration before a new advertisement packet sequence is initiated. 
     Various other modifications and alterations in the structure and method of operation of this invention will be apparent to those skilled in the art without departing from the scope and the spirit of the invention. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. It is intended that the following claims define the scope of the present invention and that structures and methods within the scope of these claims and their equivalents be covered thereby.