Transcript
Technical Guide USB-IF & Intel Corporation PER Compliance Test Procedure
USB-IF PER Compliance Test Procedure May 13, 2008 Revision 1.0
Significant Contributors Chris Bauer, USB-IF Mark Maszak, Microsoft Corporation Rahman Ismail, Intel Corporation Dan Froelich, Intel Corporation Revision History Revision 1.0
Release
USB-IF PER Compliance Test Procedure © Copyright 2008, USB Implementers Forum, Inc. All rights reserved. A LICENSE IS HEREBY GRANTED TO REPRODUCE THIS SPECIFICATION FOR INTERNAL USE ONLY. NO OTHER LICENSE, EXPRESS OR IMPLIED, BY ESTOPPEL OR OTHERWISE, IS GRANTED OR INTENDED HEREBY. USB-IF AND THE AUTHORS OF THIS SPECIFICATION EXPRESSLY DISCLAIM ALL LIABILITY FOR INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS, RELATING TO IMPLEMENTATION OF INFORMATION IN THIS SPECIFICATION. USB-IF AND THE AUTHORS OF THIS SPECIFICATION ALSO DO NOT WARRANT OR REPRESENT THAT SUCH IMPLEMENTATION(S) WILL NOT INFRINGE THE INTELLECTUAL PROPERTY RIGHTS OF OTHERS. THIS SPECIFICATION IS PROVIDED "AS IS” AND WITH NO WARRANTIES, EXPRESS OR IMPLIED, STATUTORY OR OTHERWISE. ALL WARRANTIES ARE EXPRESSLY DISCLAIMED. NO WARRANTY OF MERCHANTABILITY, NO WARRANTY OF NONINFRINGEMENT, NO WARRANTY OF FITNESS FOR ANY PARTICULAR PURPOSE, AND NO WARRANTY ARISING OUT OF ANY PROPOSAL, SPECIFICATION, OR SAMPLE. IN NO EVENT WILL USB-IF OR USB-IF MEMBERS BE LIABLE TO ANOTHER FOR THE COST OF PROCURING SUBSTITUTE GOODS OR SERVICES, LOST PROFITS, LOSS OF USE, LOSS OF DATA OR ANY INCIDENTAL, CONSEQUENTIAL, INDIRECT, OR SPECIAL DAMAGES, WHETHER UNDER CONTRACT, TORT, WARRANTY, OR OTHERWISE, ARISING IN ANY WAY OUT OF THE USE OF THIS SPECIFICATION, WHETHER OR NOT SUCH PARTY HAD ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES.
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Table of Contents
1. 2. 3. 4. 5.
Summary............................................................................................................... 4 Introduction .......................................................................................................... 4 Scope .................................................................................................................... 4 References............................................................................................................ 5 Workstation Preparation ...................................................................................... 7 5.1. 5.2. 5.3. 5.4. 5.5. 5.6. 5.7.
6.
Custom PER testing ........................................................................................... 17 6.1.
7.
Equipment and Materials................................................................................................ 7 Software and Drivers ...................................................................................................... 8 Recommended Computer System ................................................................................. 8 Host Computer HW/SW Configuration ........................................................................... 9 Software Installation ....................................................................................................... 9 PER Testbed and Hardware Setup .............................................................................. 11 Required PER Data from DUT ..................................................................................... 15 Custom PER Data Loopback........................................................................................ 17
Testbed Debug ................................................................................................... 19
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1. Summary This document illustrates functional testing of WUSB hardware using test application software running loopback protocol, technical instructions, and Wireless USB Specification reference. WUSB devices submitted for compliance will be evaluated using WUSB loopback protocol to verify device functionality and interoperability. A qualified systems technician should perform these procedures. Instructions included in this document: o o o o
System and Testbed Preparation and Operation RF HW Implementation Signal Quality & Sensitivity Strength Capability to Encode & Decode in a typical user environment
2. Introduction The Wireless USB Compliance Committee under the direction of the USB-IF, Inc., develops the Wireless USB PER Test Procedures. This document is provided as a resource for PER compliance testing and is recommended when compliance testing WUSB products and is required for WUSB Compliance Certification. The Wireless USB PER Compliance Test Procedures provide a method of verifying compliance parameters, using a Known Good Wireless USB Host or Device as defined by the Wireless USB specification. In addition to passing the PER test requirements, WUSB capable products must also complete and pass the applicable compliance tests identified in these documents in order to be posted on the USB-IF Integrators List and use the USB-IF logo in conjunction with the said product (if the vendor has signed the USB-IF Trademark License Agreement). This test procedure is the USB-IF Host and Device PER Test Procedure written to support US and Japanese product testing.
3. Scope This USB-IF PER Test Procedure document and tests are used to evaluate the WUSB peripherals and systems operating wirelessly. These tests are also used to evaluate the operation of wireless USB silicon incorporated in ready-to-ship, retail products, reference designs, proofs of concept and one of kind prototypes of peripherals, add-in cards, motherboards, or systems. Certified WUSB silicon building blocks undergo PER testing before certification but this does not guarantee WUSB PER compliance, as a result all WUSB product submissions require PER compliance testing. In addition, modification of RF hardware: including the device enclosure, circuitry, or the substitution of RF hardware such as cables or an antenna can affect in device interoperation within Wireless USB environments. Those WUSB products that undergo similar modifications are also subject to retest and are required to pass Certification Testing. WUSB testing assumes there will not be any way to connect the DUT (known as conducted testing) to the KGD when in test mode. In addition, Loopback protocol provides a method for a Host System to verify RF links between a WUSB Host and Device by transmitting a restricted number of data transfers. Then calculates the success rate, (also known as Packet Error Rate) to determine transmit and receive functionality. Therefore, the PER tests have been implemented in normal RF operating conditions structured as radiated tests using Loopback protocol defined in the Wireless USB Specification to verify device transmit and receive interoperability. Note: A normal condition does not exclude multipath RF distortion, adjacent channel noise, and erroneous background noise. Instructions will cover workstation setup, system hardware requirements, and software installation guidelines and all the required program settings to insure the PER tool will function properly. The workstation setup environment, system hardware specifications, and software installation have been tested and proven by qualified technicians. Any deviation may result in unpredictable behavior.
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4. References Wireless USB Specification http://www.usb.org/developers/wusb/docs/ PDK System Overview http://www.usb.org/developers/wusb/wusbtools/
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Acronyms ATX/BTX
Advanced/Balanced Technology Extended. Current industry standard motherboard form factor
BNC
Coaxial connector with bayonet coupling mechanism
BPS
Bits Per Second
CDID
Connection Device ID
CH
Channel
CHID
Connection Host ID
CK
Connection Key
DUT
Device Under Test
DWA
Device Wire Adapter
PER
Packet Error Rate
GUI
Graphical User Interface
HW
Hardware
HWA
Host Wire Adapter; defined in this specification as a USB 2.0 connected Wireless USB Host Controler.
KGD
Known Good Device (Approved by the USB-IF for compliance testing submitted hardware)
LOS
Line Of Sight
MMC
Micro-scheduled Management Command
NDEV
Wireless USB Native Device
PCI
Peripheral Component Interconnect
PDA
Personal Digital Assistant
PDK
Product/Peripheral Development Kit
PHY
Physical Layer. In the Wireless USB specification, the PHY is specifically the MBOA PHY[4]
PL
Power Level, also known as TPC or Transmit Power Control
RF
Radio Frequency
RSSI
Receiver Signal Strength Indication
SMA
Sub Miniature version A Coax Cable Connection
SN
Serial Number
SW
Software
TFC
(TF Code) Time/Frequency Code
TFI/FFI
Time/Fixed-Frequency Interleaving
TID
Test Identification for products submitted for certification
Tx
Transmit
USB
Universal Serial Bus
UWB
Ultra Wide Band
WHCI
Wireless Host Controller Interface
WUSB-CV
(Wireless USB-CV or CV) Wireless USB Command Verifier a compliance test tool that evaluates WUSB devices for conformance
WLAN
Wireless Local Area Network
WUSB
Wireless Universal Serial Bus
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5. Workstation Preparation 5.1.
Equipment and Materials
The following list of commercial test equipment is based on positive experience by the USB-IF members in executing the WUSB PER tests. This test procedure is written with a set of specific models we use to develop this procedure. Required: •
Required: 50-ohm coaxial Cable 1m (3’) length with male SMA to male SMA connectors at both ends, (Astrolabs minibend R-36 0712), qty = 2
•
Required: Antenna with male SMA connection,"sv{"?"4
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5.2.
5.3.
Software and Drivers •
Wireless USB-CV Test Software
•
Host Channel Changing application
•
Vendor Specific Device Firmware Utility Drivers
Recommended Computer System
Current model computer system with available PCI slots with clearance for the WHCI USB-IF PDK. Refer to Wireless USB-CV documentation and USB-IF WHCI or HWA Based PDK technical installation instructions for system requirements. The following system requirements are tested and insure the highest system stability for PER testing. Any modifications to this list may result in system related failures or system crashes. •
ATX or BTX Mid Tower Desktop System Case
•
Intel Desktop Board (or equivalent) with 2 adjacent 5v PCI slots, for PDK card clearance
•
Intel Pentium 4 processor 1.8GHz or Higher clock speed
•
512MB or more of RAM
•
Minimum 450W Power Supply Unit with AC Power Switch
•
DVD/CD-Rom Drive
•
Minimum 40GB Hard Disk with at least 10GB of free space
•
Monitor, Keyboard and Mouse
•
Windows OS
•
USB-IF PDK WHCI or HWA
•
Wireless USB-CV test driver and application installed
•
PER Tool post processing compliance application installed
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5.4.
Host Computer HW/SW Configuration
5.4.1.
Recommended system requirements: The following system requirements are tested and insure the highest system stability for the PDK. Any modifications to this list of hardware may result in system related failures or system crashes.
5.4.2.
The listed equipment is the official known good testbed used by the USB-IF and affiliated test houses for certification purposes. If a specific KGD cannot be obtained, it may be substituted with a similar, certified device. If a substitution is necessary, the following guidelines will help to select an appropriate replacement.
5.4.3.
Maintain interoperability verification by selecting a KDG using a dissimilar PHY silicon on the KGD and DUT. When substituting a KGD choose a certified device on the integrators list that is approved for compliance testing.
5.4.4.
WUSB Host System: The motherboard should have 2 adjacent PCI slots one to hold the WHCI WUSB Host Adapter and the second provides adequate space for the attached PHY.
5.4.5.
When testing PER on a vendor supported WHCI or HWA. (Configurations such as: WUSB PCI Host cards in desktop computers or integrated WUSB hosts inside laptops) A known good native device or DWA is required to verify the WHCI or HWA under test.
5.4.6.
Before PER testing, create a known good test condition if necessary restore to a known good backup image.
5.4.7.
Before PER testing, insure the required test software configuration is running and the most recent PC software is up to date. NOTE: If the DUT and system under test fails to support the software and the tools described in this test procedure, the DUT will be recorded as a failure.
5.4.8.
The processor speed is not important, but the fact that it supports hyper-threading is. Using a Core 2 Duo processor significantly improves performance of multiple high-speed WUSB devices and operating the test tool software. Memory and disk storage should provide enough storage space to eliminate insufficient resources for software.
5.5. 5.5.1.
Software Installation Install the latest recommended Wireless USB-CV msi file and PER tool software provided by USB-IF. 1. Install Wireless USB-CV.msi 2. Install the “Host Channel Change Application” (primarily for diagnostics purposes if needed while testing). The Host Channel Change Application is recommended but not required when running the automated PER Test Modes. o
This utility allows channel setting for the WHCI and HWA compliance device drivers.
o
Note: after a change, you must either, click the “Save Settings” button, or the “Save Settings and Exit” button for the changes to take place.
o
Creating a shortcut on the desktop for the WUSB Settings.exe is recommended
o
To find the WUSB Settings.exe and application setups navigate to: C:\Program Files\USB-IF Test Suite\Wireless USB-CV\Driver\Channel Change Application
o
Rename: HWADriverRegistrySample_reg to = HWADriverRegistrySample.reg; WHCIDriverRegistrySample_reg to = WHCIDriverRegistrySample.reg
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o
When prompted confirm each file rename and execute each, confirming the install when prompted.
o
Refer to 5.5 Figure 1 for an example of the WUSB Settings application GUI.
o
Channel Number: This is the channel number that the driver will use for radio traffic. This will be read each time the driver initializes, at start-up and also at the beginning of a new run of CV tests.
o
0-Length Packet: For diagnostics purposes and testing. Enable this setting for products that expect an extra 0-length packet. When recording the packet waveform, expect to see this behavior from the HWA control packets, they should fall on a 512-byte boundary.
5.5 Figure 1
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5.5.2.
After the software installation is finished, shut down and restart then install hardware as described per vendor instructions or setup documentation.
5.5.3.
It’s recommended to use an isolated drive separated from the primary operating system disk when saving the HTML PER data.
5.6. 5.6.1.
PER Testbed and Hardware Setup Mount the USB-IF Host antenna in the test probe holder, position the Host antenna at least 20cm from other objects perpendicular to the table surface insure no objects obstruct LOS between the DUT and Host antenna to minimize multipath RF distortion. Orientation of the Host antenna is not critical at this time additional positioning will be covered after initializing the DUT.
Testbed USB-IF Host Antenna
5.6 Figure 1 5.6.2.
Position the DUT antenna at the opposite end of the table, position the DUT antenna at least 20cm from other objects and perpendicular to the table surface insure no objects obstruct LOS between the DUT and Host antenna to minimize multipath distortion during PER testing. Refer to 5.6 Figure 2. Testbed DUT Antenna
5.6 Figure 2
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5.6.3.
Position the DUT in an orientation that exhibits normal device operation for orientation one. For example if the DUT (DWA) provides Downstream USB ports the port access will be facing the user in orientation one. If the DUT is a PDA or Laptop the LCD will be orientated in a user operating position on the table surface centering the antenna directly over the center point markings located on the testbed or table surface. Refer to 5.6 Figure 2
5.6.4.
Additional hardware is required if the DUT product ships with hardware that elevates or positions the device off the table surface, specifically for ready to ship product use the DUT hardware at this time. Remove all remaining hardware and objects from the table surface throughout PER testing. Reference designs, proofs of concept and one of kind prototypes of peripherals, add-in cards, motherboards, or systems may require a test probe holder to position the DUT antenna.
5.6.5.
Expect two types of WUSB devices, either host side or device side. Host adapters can also be found embedded in laptop systems. If the DUT is a Host Laptop, WHCI, or HWA the vendor will need to provide the antenna reference position if the antenna is not visible. Exchange the USB-IF Host with a Known Good Device in its place, only the DUT will test in four recommended PER antenna orientations. The KGD does not rotate.
5.6.6.
For US product, insure 1.5 meters is between the association device’s antenna and the DUT. NOTE: Japan mandates all Wireless USB Japanese products operate at a reduced power level. As a result, when testing Japanese products insure 1 meter is between the association device’s antenna and the DUT. Refer to 5.6 Figure 3 for PER testbed setup. Further discussion of antenna setup and device orientation is provided in section 5.7.
Associating Device (USB-IF Host) Use specified hardware as illustrated in photo. (Cable, Antenna, & RF Adapter)
1.5m
5.6 Figure 3 5.6.7.
Each DWA or Native device requires a numeric or cable association between the PDK test system and the DUT. A Wireless USB cable association driver is supplied with Wireless USB-CV. When testing numeric devices, the vender supported device must support • • •
A CHID value of: (00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F) Any CDID value: (example: 0F 0E 0D 0C 0B 0A 09 08 07 06 05 04 03 02 01 00) CK of all zeros: (00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00)
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5.6.8. 5.6.8.1.
Use this driver location when using the hardware install wizard to install the CK of zero driver: C:\Program Files\USB-IF Test Suite\Wireless-USBCV\Driver\CK_of_Zero
5.6.9.
Each WHCI or HWA requires an up to date operating system including all hardware drivers running the latest version of the WUSB-CV tool and drivers. Use a known good test device when performing PER tests.
5.6.10.
While a variety of rates may be utilized by each device, care must be taken when setting up the initial PER testbed. A Wireless USB-CV loopback function is provided to verify the DUT can establish a connection and initialize.
5.6.11.
Insure the host computer is transmitting using TFC1 (channel 9) via the WUSB settings tool. Refer to section 5.5 (note: Some Japanese products only operate on TFC7 (channel 15)). Begin with Rate testing the DUT. While running “Data Loopback Supported Rate Test” Wireless USB-CV will automatically provide each Rate that fails in a summary field or Wireless USB-CV will generate a pass condition if none of the rates failed.
5.6.12.
If the Rate test failed, adjust the KGD antenna in a clockwise manner to optimize the radiation pattern for the testbed until all data rates pass or provide the best possible test results for PER testing. This will provide an optimized antenna orientation. (If this does not achieve the desired effect, Record in the DUT notes, it may be necessary to move the KGD antenna up or down but the antenna must remain 2030cm, relative to the table surface.) This initial hardware setup position is Orientation 1. The remaining three orientations will be approximately 90º rotations, not optimized for a more pragmatic end user experience. Refer to 5.6 Figure 4 for Orientations 1-4.
NOTE: Although four antenna orientations are used for Wireless USB hardware certification, it is recommended each vendor perform an in depth study evaluating various hardware configurations to insure interoperability in all suggested Wireless USB device orientations. Various hardware configurations do not exclude: • • • •
PHY Circuitry between the PHY and antenna Choice of antenna and accompanied hardware Material or hardware covering the antenna under a bezel or enclosure.
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Ori. 1
Rotate DUT Ori. 2
Ori. 4
Rotate DUT Rotate DUT
Ori. 3
5.6 Figure 4
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5.7.
Required PER Data from DUT
5.7.1.
Record the DUT supported rates 53.3, 106.7, 200, & 480 per channel. Pass criteria is displayed using WUSB-CV. WUSB-CV will also generate an HTML log file within the reports folder. Certified WUSB silicon incorporated in ready-to-ship or retail products, require the following tests; please refer to the 5.7 Chart 1. Products that do not pass each required test will be recorded as a failure.
5.7.2.
Reference designs, proofs of concept, one of kind prototypes / peripherals, add-in cards, motherboards, IP, or systems require the following tests: please refer to 5.7 Chart 1. These products do not require a pass condition for PER testing but must complete the PER supported rate tests referenced in section 5.7.1 WHCI
HWA
DWA
Native Device
53.3 Mbps
53.3 Mbps
53.3 Mbps
53.3 Mbps
106.7 Mbps
106.7 Mbps
106.7 Mbps
106.7 Mbps
200 Mbps
200 Mbps
200 Mbps
200 Mbps
*480 Mbps
*480 Mbps
*480 Mbps
* DUT is required to support rate 480 on one or more TFI or FFI channels in one or more orientations or the device will be recorded as a failure. 5.7 Chart 1 5.7.3.
After testing each of the required test iterations, retest each failure three times to verify the test results. If adjustment to the KGD antenna orientation is made, then record each channel and data rate again. The DUT will fail Compliance Certification if the device cannot pass the required test modes.
5.7.4.
A DUT such as a Host can be found embedded in laptop systems. To prevent loss of data, the .html log file should be saved in a vendor specific folder isolated from the operating system drive. Automated PER Test Modes 1. TFC7 or CH15, Rates 53.3, 106.7, 200, 480 (Japanese and US product) 2. TFC6 or CH14; Rates 53.3, 106.7, 200, 480 (US product only) 3. TFC5 or CH13; Rates 53.3, 106.7, 200, 480 (US product only) 4. TFC1 or CH09; Rates 53.3, 106.7, 200, 480 (US product only) 5. TFC2 or CH10; Rates 53.3, 106.7, 200, 480 (US product only) 6. TFC3 or CH11; Rates 53.3, 106.7, 200, 480 (US product only) 7. TFC4 or CH12; Rates 53.3, 106.7, 200, 480 (US product only) 8. Retest any failures and then the remaining device supported rates
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5.7.5.
From the test suite window, select the appropriate PER test mode resembling the automated PER test modes referenced in section 5.7.3
5.7.6.
The automated test application is setup to transmit 10K packets for each test iteration. Select Debug to run individual test iterations. 1. TD_7_53 Data loopback Supported Rate Test: Used to verify what rates the DUT supports when an distance is between the association device’s antenna and the DUT for adequate distance reference refer to section 5.6. 2. The Data Loopback Test is used for diagnostics. It provides customizable TX parameters. In the next window, select the “PER Loopback”. The next window will ask for a max packet size, use Chart 2 below to select the minimum packet size to transmit. Larger packet sizes up to the device maximum is supported by the tool. Enter the value then select “DONE”. Refer to the custom PER testing section of this document.
5.7.7.
Run the selected test iteration, next select OK to initialize the hardware. If the DUT does not auto connect, press the manual connection button indicated by the vendor documentation.
5.7.8.
CV will insert the appropriate device maximum supported payload size per packet. Later the results can be retrieved in the .html log file produced after the test iteration is complete. The test mode can also be interrupted while transmitting each test packet by selecting Esc twice between a reported data transfer. This type of interruption may require a WUSB-CV restart.
5.7.9.
Measure PER In four orientations beginning with Orientation 1. When positioning the DUT in each orientation refer to 5.7 Figure 1 It is recommended to separate log files summaries. (Refer to section 5.8 when saving data) Use a recommended naming convention in the test description text box.
5.8. 5.8.1.
Saving PER Data The file name should contain all pertinent information about the acquisition, including: TID, Orientation number, channel, and device type. An identifier for the device under test is optional (The product TID number is recommended, however if this is not available use the product model number). NOTE: If the unique file name is not included, all files for a single device must be saved in a unique folder to avoid confusing data from different DUTs. The syntax is as follows (case is not important; any combination of lower and upper case is allowed): Refer to 5.8 Chart 2 Example: TID_10000001_Ori1_CH09_DWA Syntax
Description
TID_XXXXXXXX
10000001 (a sequence number)
OriX CHXX
bpsXXX
HWA, WHCI, DWA, or NDEV
Example
X is one of 1, 2, 3 or 4 (DUT orientation position during test iteration) XX is one of 09, 10, 11, 12, 13, 14 or 15 (TFC1 – TFC7 are TFI modes, TFC5 – TFC7 are FFI modes)
TID_10000001
Ori3 CH13
XXX is one of 053, 080, 106, 160, 200, 320, 400, 480 (the data rate in bits per second) optional but required when testing individual test iteration rates per channel
bps053
Is a host or a device, NDEV is used for Native Deivce
HWA NDEV
5.8 Chart 2
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5.8.2.
Record the data summary in each of the log files into a PER spreadsheet or database.
6. Custom PER testing 6.1. 6.1.1.
Custom PER Data Loopback The next window will ask for the number of iterations. This value represents the number of packets transmitted by the device. On the first run enter 1000, this value can be adjusted up or down on subsequent executions for more efficient data collection. Once the value is entered, select “DONE” to continue.
6.1 Figure 1
6.1 Figure 2
6.1.2.
The PHY Rate refers to the data rate to be measured. It is recommended to choose the lowest data rate, 53.3Mb/s, as a starting point. Once the value is selected, then begin testing each rate, select “OK” to continue. Refer to 6.1 Figure 3
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6.1 Figure 3
6.1.3.
The next two windows will ask for MMC and device power levels respectively. For the purposes of PER testing, zero should be entered for both windows. Select “DONE” in both windows to continue.
6.1.4.
Note: A functional power level test is required for each WUSB device. A power level result comparison can be verified using the HTML log file generated by the PER tool. Record data for the adjusted power level and compare the results. When power level testing, refer to the Wireless USB specification for specific power level settings. Each PL (0-6) coincides with the specification, providing a range of 7 settings.
6.2 Figure 4 6.1.5.
The DUT will now transmit packets using the automated test mode or at the specified data rate for the specified number of transmitted test iterations. Packet iterations will begin displaying on the screen. Observe the active window. The packets will begin cycling through until the total equals the number used for the number of iterations text box entry. If the packet number cycles with abnormally, use a protocol analyzer to evaluate the traffic.
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7. Testbed Debug Several known conditions that can influence Wireless USB PER results • Incorrectly handling loopback packets • Hardware around the antenna • Transmit power level reduction • Modifying the receiver circuit from the receiver to the antenna tip • Antenna version LOS obstructions created by bezel material or DUT enclosure. (Vendors will need to provide the estimated under bezel location to determine the XYZ zero axis point of the DUT antenna) • Laptops • DUTs using a hidden antenna under an enclosure Mandated or regulatory transmit power level reduction. Reduce LOS distance between transmitters to 1 meter for Japanese products. All other product will require 1.5 meters between the transmitters. Japanese product is also restricted to one channel, Channel 15 Antenna implementation can affect PER results, 2 versions are addressed below: •
Omni Directional Antenna, when an Omni Directional antenna is mounted to the circuit board and the device sits flush or several inches off the table surface the DUT can encounter significant RSSI Loss. A more directional hardware approach may be required to create a linear path to each associated device.
•
Dipole Antenna, it may be necessary to position the Dipole antenna perpendicular to the table surface then begin moving it in an orthogonal direction until the best possible PER results are achieved.
The conductor or trace between the antenna and PHY receiver can affect transmitter to receiver attenuation. Hardware within close proximity (less then 20cm) of the DUT antenna can produce higher PER results. PER failures can be reduced by positioning an antenna further from the adjacent hardware minimizing reflections or multipath RF distortion. Protocol related, when PER is consistent but below normal in all positions, use a Wireless USB protocol analyzer to diagnose. •
Improper loopback control transfers between the DUT and the KGD
•
DUT will not respond with an EP-ready, if too many of these control transfers are generated the chance of missing packets increase in some cases up to 3x.
•
DUT stops functioning or misses every subsequent packet. DUT might not expect new setup packet control transfer.
•
DUTs that require additional turnaround time while processing the loopback packet can drop or disconnect, check the hardware or response timing.
•
Comparison errors Read/Write, DUT I/O related endpoint errors.
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