Wireless LAN Consortium

Transcription

1 Wireless LAN Consortium Clause 18 OFDM Physical Layer Test Suite Version 1.8 Technical Document Last Updated: July 11, :44 PM Wireless LAN Consortium 121 Technology Drive, Suite 2 Durham, NH University of New Hampshire Phone: Fax: University of New Hampshire

2 MODIFICATION RECORD July 11, 2013 Version 1.8 Mike Bogochow: Clarified wording and fixed typos. July 23, 2012 Version 1.7 Mike Bogochow: Changed Std references to IEEE Std TM November 9, 2009 Version 1.6 Jeremy Kent: Removed parts d and e from test # Transmitted and Received Supported Data Rates, modified discussion to more accurately reflect test purpose, and minor editorial changes. Added test # PLCP Header Signal Field Format. April 1, 2009 Version 1.5 Jeremy Kent: Removed references to Research Computing Center and updated consortium URL on cover page. November 13, 2007 Version 1.4 Jeremy Kent: Minor editorial changes. June 25, 2007 Version 1.3 Yuliya Barushka: Changed Std references to IEEE Std January 20, 2006 Version 1.2 Nathan Bourgoine: Added test June 5, 2005 Version 1.1 Jeremy Kent: Minor editorial changes. January 14, 2005 Version 1.0 Initial Release October 2004 Version 0.9 Pre-Release Wireless LAN Consortium 2 Clause 18 OFDM Physical Layer Test Suite v1.8

3 ACKNOWLEDGMENTS would like to acknowledge the efforts of the following individuals in the development of this test suite. Aaron Baillargeon Yuliya Barushka Mike Bogochow Nathan Bourgoine Jeremy Kent Keven Karcz Shravan Surineni University of New Hampshire University of New Hampshire University of New Hampshire University of New Hampshire University of New Hampshire University of New Hampshire University of New Hampshire Wireless LAN Consortium 3 Clause 18 OFDM Physical Layer Test Suite v1.8

4 INTRODUCTION Overview s (IOL) is an institution designed to improve the interoperability of standards based products by providing an environment where a product can be tested against other implementations of a standard. This particular suite of tests has been developed to help implementers evaluate the functionality of the OFDM Physical (5GHz Band) layer of their Wireless LAN devices. These tests are designed to determine if a product conforms to specifications defined in Clause 18 of the IEEE Std Edition. Successful completion of all tests contained in this suite does not guarantee that the tested device will operate with other devices. However, combined with satisfactory operation in the IOL s interoperability test bed, these tests provide a reasonable level of confidence that the device under test (DUT) will function properly in many OFDM environments. Organization of Tests The tests contained in this document are organized to simplify the identification of information related to a test and to facilitate in the actual testing process. Each test contains an identification section that describes the test and provides cross-reference information. The discussion section covers background information and specifies why the test is to be performed. Tests are grouped in order to reduce setup time in the lab environment. Each test contains the following information: Test Number The Test Number associated with each test follows a simple grouping structure. Listed first is the Test Group Number followed by the test s number within the group. This allows for the addition of future tests to the appropriate groups of the test suite without requiring the renumbering of the subsequent tests. Purpose The purpose is a brief statement outlining what the test attempts to achieve. The test is written at the functional level. References The references section lists cross-references to the IEEE standards and other documentation that might be helpful in understanding and evaluating the test results. Resource Requirements The requirements section specifies the test hardware and/or software needed to perform the test. This is generally expressed in terms of minimum requirements, however in some cases specific equipment manufacturer/model information may be provided. Wireless LAN Consortium 4 Clause 18 OFDM Physical Layer Test Suite v1.8

5 Last Modification This specifies the date of the last modification to this test. Discussion The discussion covers the assumptions made in the design or implementation of the test, as well as known limitations. Other items specific to the test are covered here. Test Setup The setup section describes the initial configuration of the test environment. Small changes in the configuration should be included in the test procedure. Procedure The procedure section of the test description contains the systematic instructions for carrying out the test. It provides a cookbook approach to testing, and may be interspersed with observable results. Observable Results This section lists the specific observables that can be examined by the tester in order to verify that the DUT is operating properly. When multiple values for an observable are possible, this section provides a short discussion on how to interpret them. The determination of a pass or fail outcome for a particular test is often based on the successful (or unsuccessful) detection of a certain observable. Possible Problems This section contains a description of known issues with the test procedure, which may affect test results in certain situations. It may also refer the reader to test suite appendices and/or whitepapers that may provide more detail regarding these issues. Wireless LAN Consortium 5 Clause 18 OFDM Physical Layer Test Suite v1.8

6 TABLE OF CONTENTS MODIFICATION RECORD 2 ACKNOWLEDGMENTS 3 INTRODUCTION 4 TABLE OF CONTENTS 6 GROUP 1: PLCP TESTS 7 TEST # : TRANSMIT AND RECEIVE SUPPORTED DATA RATES 8 TEST # : PLCP HEADER SIGNAL FIELD FORMAT 10 GROUP 2: PMD TRANSMIT TESTS 13 TEST # : OPERATING CHANNEL CAPABILITY 14 TEST # : TRANSMIT POWER LEVEL 16 TEST # : OFDM TRANSMIT SPECTRAL MASK 18 TEST # : TRANSMIT CENTER AND SYMBOL CLOCK FREQUENCY TOLERANCE 21 TEST # : TRANSMIT CONSTELLATION ERROR 23 TEST # : OFDM TRAINING SYMBOL SPECTRAL FLATNESS 26 Wireless LAN Consortium 6 Clause 18 OFDM Physical Layer Test Suite v1.8

7 GROUP 1: PLCP TESTS Scope: The following tests cover physical layer operation specific to the PHY convergence function. Overview: This group of tests pertains to the operation of the physical layer convergence procedure (PLCP) sublayer and the various methods for mapping MAC protocol data units (MPDU) into a framing format suitable for sending and receiving user data and management information to the associated physical medium dependent (PMD) sublayer. Wireless LAN Consortium 7 Clause 18 OFDM Physical Layer Test Suite v1.8

8 Test # : Transmit and Receive Supported Data Rates Purpose: To verify that the device under test (DUT) can operate at all defined mandatory data rates, and any optional supported data rates. References: [1] IEEE Std Edition, Clause 18, , , , Resource Requirements: Vector Signal Analyzer (VSA), Rohde & Schwarz FSQ26 or equivalent OFDM access point/station with external antenna jack Associated OFDM AP or station with external antenna jack (optional) RF Power Splitter, Picosecond 5333 or equivalent (optional) Controlling Software (Matlab) Last updated: July 23, 2012 Discussion: The orthogonal frequency division multiplexing (OFDM) system provides a WLAN with data payload communication capabilities of 6, 9, 12, 18, 24, 36, 48, and 54 Mbps. Reference [1] defines support for transmitting and receiving at data rates of 6, 12, and 24 Mbps as mandatory, while communication using all other data rates is optional. These mandatory and supported data rates assume operation in 20 MHz channel spacing; additional requirements are also defined for devices operating in both 10 MHz and 5 MHz channel spacings based on regulatory requirements of OFDM systems operating in 4.9 GHz and 5 GHz bands. For clarity, the following table summarizes the data rate requirements (both mandatory and optional) of an OFDM station operating in a 20 MHz band. Modulation Data Rate Units OFDM 6, 12, 24 Mbps OFDM 9, 18, 36, 48, 54 Mbps Table 1 - Transmit and receive data rate requirements for OFDM devices. Mandatory rates are located in the first row; all remaining rates are optional. Wireless LAN Consortium 8 Clause 18 OFDM Physical Layer Test Suite v1.8

9 GPIB Test Setup: Refer to Figure 1 Controller (MATLAB) VSA CH1 PS 5333 Power Splitter Ext. Ant. Jack DUT AP/STA (Optional) Figure 1 - Example test setup for Test # : Transmit and Receive Supported Data Rates Procedure: 1. Configure the DUT to operate at a data rate of 6 Mbps. 2. Configure the associated AP/STA to operate at a date rate of 6 Mbps. Transmit ICMP echo request packets to the DUT. 3. Configure the VSA to capture an entire packet. Demodulate and decode the frame. 4. Verify that the DUT is able to transmit and received frames at the configured data rate. 5. Repeat steps 1-4 for all mandatory data rates. 6. Repeat steps 1-4 for all optional data rates supported by the DUT. Observable Results: a. The DUT should be capable of transmission and reception at 6, 12, and 24 Mbps data rates. b. The DUT should be capable of transmission and reception at all supported optional data rates. Possible Problems: If the DUT does not provide access to an external antenna jack, then this test cannot be performed. Wireless LAN Consortium 9 Clause 18 OFDM Physical Layer Test Suite v1.8

10 Test # : PLCP Header Signal Field Format Purpose: To verify that the device under test (DUT) conforms to the OFDM PLCP SIGNAL field format. References: [1] IEEE Std Edition, Clause , Resource Requirements: Vector Signal Analyzer (VSA), Rohde & Schwarz FSQ26 or equivalent OFDM access point/station with external antenna jack Associated OFDM AP or station with external antenna jack (optional) RF Power Splitter, Picosecond 5333 or equivalent (optional) Controlling Software (Matlab) Last updated: July 23, 2012 Discussion: Reference [1] describes the physical layer convergence procedure (PLCP) for Orthogonal Frequency Division Multiplexing (OFDM) PHYs operating in the 5 GHz band. The SIGNAL field is composed of the first 24 bits of the PLCP Header and contains five separate subfields: RATE, a reserved bit, LENGTH, a Parity bit, and the SIGNAL TAIL. These fives fields are transmitted as a separate single OFDM symbol using the most robust combination of BPSK modulation and a code rate of R = 1/2. The tails bits in the SIGNAL symbol allow for decoding of the RATE and LENGTH fields immediately after reception of the tail bits. Upon reception, these two fields (RATE and LENGTH) are required by the receiver for decoding the DATA part of the packet, as they convey the modulation used to encode subsequent DATA field, and indicate the number of octets in the PSDU, respectively. Wireless LAN Consortium 10 Clause 18 OFDM Physical Layer Test Suite v1.8

11 The SIGNAL field follows the OFDM training symbols at the beginning of the PPDU, and is illustrated in figure 18-5, reproduced here for convenience. The first four bits 0 to 3 encode the RATE; bit 4 is reserved for future use; bits 5-16 represent the LENGTH field of the TXVECTOR (the LSB shall be transmitted first in time); bit 17 is an even Parity bit for bits 0 16; and bits constitute the SIGNAL TAIL field. Test Setup: Refer to Figure 1 Procedure: 1. Configure the DUT to operate at a data rate of 6 Mbps. 2. Configure the associated AP/STA to operate at a date rate of 6 Mbps. Transmit ICMP echo request packets to the DUT. 3. Configure the VSA to capture an entire packet. Demodulate and decode the frame. Wireless LAN Consortium 11 Clause 18 OFDM Physical Layer Test Suite v1.8

12 4. Verify that the DUT transmits PPDUs containing a properly formatted SIGNAL field based on the data rate and PSDU sent by the MAC. 5. Repeat steps 1-4 for all mandatory data rates. 6. Repeat steps 1-4 for all optional data rates supported by the DUT. Observable Results: a. The RATE field (bits 0-3) should accurately reflect the data rate of the transmitted PSDU according to Table b. The Reserved bit (bit 4) should be set to a value of zero. c. The LENGTH field (bits 5 16) should indicate the number of octets contained in the PSDU requested by the MAC to transmit. d. The Parity bit (bit 17) should be set to one if the number of ones in bits 0 16 (including the parity bit) is an even number; otherwise, it should be set to zero. e. The TAIL portion (bits 18 23) of the frame should consist of all zero values. Possible Problems: None. Wireless LAN Consortium 12 Clause 18 OFDM Physical Layer Test Suite v1.8

13 GROUP 2: PMD TRANSMIT TESTS Scope: The following tests cover physical layer operation specific to the transmit functions and operations associated with the PMD sublayer. Overview: This group of tests verifies several of the functional, electrical, and RF characteristics required for interoperability outlined in Clause 18 of the IEEE Std Edition. Wireless LAN Consortium 13 Clause 18 OFDM Physical Layer Test Suite v1.8

14 Test # : Operating Channel Capability Purpose: To verify the device under test (DUT) is capable of operating on all defined channels. References: [1] IEEE Std Edition, Clause , Annex E Resource Requirements: Vector Signal Analyzer (VSA), Rohde & Schwarz FSQ26 or equivalent OFDM access point/station with external antenna jack Associated OFDM AP or station with external antenna jack (optional) RF Power Splitter, Picosecond 5333 or equivalent Controlling Software (Matlab) Last updated: July 23, 2012 Discussion: Reference [1] describes the orthogonal frequency division multiplexing (OFDM) physical medium dependant (PMD) sublayer for the 5 GHz band. Section specifies the relationship between center frequency and channel number, which is given by Equation (18-27): Channel center frequency = Channel starting frequency + 5 n ch (MHz) (18-27) where n ch = 1, 200 The set of valid operating channel numbers by regulatory domain is defined in Annex E, and summarized in Table 2. As outlined in Table 2, the Federal Communications Commission (FCC) specifies operation in the range from 5.18 GHz for channel 36 to 5.805GHz for channel 161 in the United States. This test verifies whether the DUT is capable of operating on all the channels as per the standard. For the purposes of this test, the term operation is defined as the ability to transmit and receive on each specified channel and frequency. Regulatory domain Band (GHz) Operating channel numbers United States United States United States U-NII lower band ( ) U-NII middle band ( ) U-NII upper band ( ) Channel center frequencies (MHz) Table 2 Valid operating channel numbers by regulatory domain and band. Wireless LAN Consortium 14 Clause 18 OFDM Physical Layer Test Suite v1.8

15 GPIB Test Setup: Refer to Figure 2 Controller (MATLAB) VSA CH1 PS 5333 Power Splitter Ext. Ant. Jack DUT AP/STA (Optional) Figure 2 - Example test setup for Test # : Operating Channel Capability Procedure: 1. Configure the DUT to use channel Transmit compliant traffic to the DUT. 3. Source traffic from the DUT. 4. Repeat steps 1 & 2 on all defined channels in the FCC regulatory domain. Observable Results: a. The DUT should support all specified channels. b. The DUT should properly transmit and receive compliant traffic on all specified channels. Possible Problems: None. Wireless LAN Consortium 15 Clause 18 OFDM Physical Layer Test Suite v1.8

16 Test # : Transmit Power Level Purpose: To verify that the transmit power level of the device under test (DUT) is within the conformance limits. References: [1] IEEE Std Edition, Clause [2] Title 47 of the Code of Federal Regulations Chapter 1 Subchapter A Part 15 subpart E Section Resource Requirements: Vector Signal Analyzer (VSA), Rohde & Schwarz FSQ26 or equivalent OFDM access point/station with external antenna jack Associated OFDM AP or station with external antenna jack (optional) RF Power Splitter, Picosecond 5333 or equivalent Controlling Software (Matlab) Last updated: July 11, 2013 Discussion: Reference [1] describes the orthogonal frequency division multiplexing (OFDM) physical medium dependant (PMD) sublayer for the 5 GHz band. Section specifies the PMD transmit specifications, and reference [2] defines the maximum allowable output power of an OFDM device. Even though OFDM devices occupy the unlicensed U-NII bands, regulatory bodies at the national level still govern certain emissions practices, forcing observance of several different power-level guidelines dependent upon geographical location. The maximum allowable output power specified by the FCC is shown in Table 3 (shown below). Frequency band (GHz) United States (Maximum output power with up to 6 dbi antenna gain) (mw) Table 3 Transmit power level by regulatory domain. Wireless LAN Consortium 16 Clause 18 OFDM Physical Layer Test Suite v1.8

17 GPIB Test Setup: Refer to Figure 3 Controller (MATLAB) VSA CH1 PS 5333 Power Splitter Ext. Ant. Jack DUT AP/STA (Optional) Figure 3 - Example test setup for Test # : Transmit Power Level Procedure: 1. Configure the DUT to associate on channel 36 at a data rate of 6 Mbps at maximum output power and generate continuous ICMP echo request packets of length 100 bytes, and set the Beacon Interval to 100 ms. 2. Configure the VSA to capture the waveform transmitted by the DUT. Compute the bandpower of the signal. 3. For enhanced accuracy, repeat step 2 and average the band-power of the signal. Observable Results: a. For a given U-NII band, the maximum output power should not exceed the values specified in Table 3. Possible Problems: None. Wireless LAN Consortium 17 Clause 18 OFDM Physical Layer Test Suite v1.8

18 Test # : OFDM Transmit Spectral Mask Purpose: To verify the orthogonal frequency division multiplexing (OFDM) transmit spectrum of the device under test (DUT) is within conformance limits. Reference: [1] IEEE Std Edition, Clause , Annex D, Annex E [2] Archambault, J. and Surineni S. IEEE spectral measurements using vector signal analyzers. RF Design, July 2004, Resource Requirements: Vector Signal Analyzer (VSA), Rohde & Schwarz FSQ26 or equivalent Spectrum Analyzer (SA) OFDM PHY Station with external antenna jack Associated OFDM PHY AP or station with external antenna jack (optional) RF Power Splitter, Picosecond 5333 or equivalent Controlling Software (Matlab) Last updated: July 11, 2013 Discussion: Reference [1] describes the orthogonal frequency division multiplexing (OFDM) physical medium dependant (PMD) sublayer for the 5 GHz band. Section defines OFDM operation specifications, and subclause specifies the transmit spectral mask. Figure gives a graphical representation of the spectral mask described. Wireless LAN Consortium 18 Clause 18 OFDM Physical Layer Test Suite v1.8

19 GPIB Test Setup: Refer to Figure 4 Controller (MATLAB) VSA CH1 PS 5333 Power Splitter Ext. Ant. Jack DUT AP/STA (Optional) Figure 4 - Example test setup for Test # : OFDM Transmit Spectral Mask Wireless LAN Consortium 19 Clause 18 OFDM Physical Layer Test Suite v1.8

20 Procedure: 1. Configure the DUT to associate with the AP on channel 36 at a bit rate of 6 Mbps at maximum output power; configure the AP to repeatedly transmit 100-byte ICMP echo request packets to the DUT. 2. Configure the VSA to capture an entire packet. Compute the spectral mask of the transmitted waveform. 3. For enhanced accuracy in burst mode, repeat step 2 multiple times and average the spectral masks. 4. Repeat steps 1-3 for all supported data rates and channels. Observable Results: a. The transmitted spectral mask of the DUT should fall within the conformance limits of Figure Possible Problems: None. Wireless LAN Consortium 20 Clause 18 OFDM Physical Layer Test Suite v1.8

21 Test # : Transmit Center and Symbol Clock Frequency Tolerance Purpose: To verify that the center frequency offset of the device under test (DUT) is within the conformance limits. References: [1] IEEE Std Edition, Clause Resource Requirements: Vector Signal Analyzer (VSA), Rohde & Schwarz FSQ26 or equivalent OFDM access point/station with external antenna jack Associated OFDM AP or station with external antenna jack (optional) Controlling Software (Matlab) Last updated: July 11, 2013 Discussion: Reference [1] describes the orthogonal frequency division multiplexing (OFDM) physical medium dependant (PMD) sublayer for the 5 GHz band. Section outlines the transmit function and parameters associated with the PMD sublayer, and subclauses and specify the transmit center frequency and symbol clock frequency tolerances. Transmit frequency offset is the difference between the channel center frequency and the transmitter center frequency. When the transmit center frequency is offset from the actual channel frequency, the spectrum of the transmit signal falls in the adjacent channels. This causes interference in the adjacent channels. This error is even more important for OFDM transmission where many subcarriers are derived from the same clock. The center frequency tolerance limits are ± 20-ppm maximum, which corresponds to a frequency drift of ± khz for channel 36 and ± khz for channel 161. Reference [1] requires keeping the transmit center frequency and symbol clocks locked to the same local oscillator. For this reason, both of these clock tolerances can generally be tested by measuring either frequency error. The measurement is conducted using a VSA, comparing its demodulation clock with the digitally demodulated data chipping from the DUT. Wireless LAN Consortium 21 Clause 18 OFDM Physical Layer Test Suite v1.8

22 GPIB Test Setup: Refer to Figure 5 Controller (MATLAB) VSA CH1 PS 5333 Power Splitter Ext. Ant. Jack DUT AP/STA (Optional) Figure 5 - Example test setup for Test # : Transmit Center and Symbol Clock Frequency Tolerance Procedure: 1. Configure the DUT to associate with the AP on channel 36 at a bit rate of 6 Mbps at maximum output power; configure the AP to repeatedly transmit 100-byte ICMP echo request packets to the DUT. 2. Configure the VSA to capture an entire packet. 3. Compute the average center frequency and symbol clock frequency offsets over the entire packet. 4. For enhanced accuracy, repeat steps 2-3 multiple times and average the deviations. 5. Repeat steps 1-4 for all supported data rates and channels. Observable Results: a. The transmit center frequency and symbol clock tolerance should not exceed ± 20 ppm. Possible Problems: The transmit center frequency is known to have some temperature dependence. In order to account for this, it is suggested that the DUT be powered for fifteen minutes before testing to allow it to reach an operating temperature. Wireless LAN Consortium 22 Clause 18 OFDM Physical Layer Test Suite v1.8

23 Test # : Transmit Constellation Error Purpose: To verify that the relative constellation RMS error of the device under test (DUT) is within the conformance limits. Reference: [1] IEEE Std Edition, Clause [2] Archambault, J. and Surineni S. IEEE spectral measurements using vector signal analyzers. RF Design, July 2004, Resource Requirements: Vector Signal Analyzer (VSA), Rohde & Schwarz FSQ26 or equivalent OFDM PHY Station with external antenna jack Associated OFDM PHY AP or station with external antenna jack (optional) RF Power Splitter, Picosecond 5333 or equivalent Controlling Software (Matlab) Last updated: July 11, 2013 Discussion: Reference [1] describes the orthogonal frequency division multiplexing (OFDM) physical medium dependant (PMD) sublayer for the 5 GHz band, and subclause specifies the PMD transmit specifications. OFDM devices are required to follow the transmit constellation error tolerances specified in subclause At any moment in time the transmitted signal magnitude and phase can be measured, and an ideal or reference signal can be calculated. According to [1], modulation accuracy is defined as the difference between the actual transmitted waveform and the ideal waveform. In practice, the modulation accuracy is measured using error vector magnitude (EVM). EVM is based on the concept that any impaired signal can be represented as the sum of an ideal signal and an error signal. Since an error signal cannot be measured directly, test instrumentation determines the error signal by reconstructing the ideal signal based on received data and then subtracting it from the actual signal. This concept is depicted in Figure 6. Wireless LAN Consortium 23 Clause 18 OFDM Physical Layer Test Suite v1.8

24 Figure 6 - Elements defining EVM measurement Reference [1] specifies the relative constellation RMS error being an average over all subcarriers, OFDM frames, and packets, and should not exceed a data rate dependent value outlined in Table 18-13; this table has been reproduced below with the equivalent EVM. Data Rate (Mbps) Relative Constellation Error (db) EVM (% RMS) Table 4 - Allowed relative constellation error versus data rate. Wireless LAN Consortium 24 Clause 18 OFDM Physical Layer Test Suite v1.8

25 GPIB Test Setup: Refer to Figure 7 Controller (MATLAB) VSA CH1 PS 5333 Power Splitter Ext. Ant. Jack DUT AP/STA (Optional) Figure 7 - Example test setup for Test # : Transmit Constellation Error Procedure: 1. Configure the DUT to associate with the AP on channel 36 at a bit rate of 6 Mbps at maximum output power; configure the AP to repeatedly transmit 100-byte ICMP echo request packets to the DUT. 2. Configure the VSA to capture an entire packet. 3. Demodulate the packet and compute the EVM using the methodology described in [1]. 4. Repeat steps 1-4 for each channel and supported data rate. Observable Results: a. The relative constellation RMS error should not exceed the values listed in Table 4. Possible Problems: None. Wireless LAN Consortium 25 Clause 18 OFDM Physical Layer Test Suite v1.8

26 Test # : OFDM Training Symbol Spectral Flatness Purpose: To verify the orthogonal frequency division multiplexing (OFDM) transmit spectrum of the device under test (DUT) is within conformance limits. Reference: [1] IEEE Std Edition, Clause Resource Requirements: Vector Signal Analyzer (VSA), Rohde & Schwarz FSQ26 or equivalent OFDM PHY Station with external antenna jack Associated OFDM PHY AP or station with external antenna jack (optional) RF Power Splitter, Picosecond 5333 or equivalent Controlling Software (Matlab) Last updated: July 11, 2013 Discussion: Reference [1] describes the orthogonal frequency division multiplexing (OFDM) physical medium dependant (PMD) sublayer for the 5 GHz band. Section defines OFDM operation specifications, and subclause defines the spectral flatness requirements. The long training symbols of an OFDM frame are specified with equal power in all subcarriers for channel estimation purposes. During this phase, the observed power should fit within the spectral flatness limits defined in subclause Training symbols which do not comply with these limits could cause receivers to form a bad compensation filter for the channel, resulting in interoperability issues. Wireless LAN Consortium 26 Clause 18 OFDM Physical Layer Test Suite v1.8

27 GPB Test Setup: Refer to Figure 8 Controller (MATLAB) VSA CH1 PS 5333 Power Splitter Ext. Ant. Jack DUT AP/STA (Optional) Figure 8 - Example test setup for Test # : OFDM Training Symbol Spectral Flatness Procedure: 1. Configure the DUT to associate with the AP on channel 36 at a bit rate of 6 Mbps at maximum output power; configure the AP to repeatedly transmit 100-byte ICMP echo request packets to the DUT. 2. Configure the VSA to capture an entire packet. 3. Demodulate the long training symbols and observe the energy magnitude in each subcarrier. 4. Repeat steps 1-3 for each channel. Observable Results: a. Subcarriers 16 to 1 as well as +1 to +16 should be within ± 4 db from their average energy. b. Subcarriers 26 to 17 as well as +17 to +26 should be within +4/ 6 db of the average energy of the average energy of spectral lines 16 to 1 and +1 to +16. Possible Problems: None. Wireless LAN Consortium 27 Clause 18 OFDM Physical Layer Test Suite v1.8