WASHINGTON—The FCC Office of Engineering and Technology is soliciting comments on LTE-to-DTV interference. The OET seeks to supplement the record in the incentive auction proceeding by inviting comment on measurements of wireless Long-Term Evolution interference into digital television receivers conducted by OET engineers.
In the interference Public Notice, OET invited comment on a methodology for predicting inter-service interference, or ISIX. For purposes of that methodology, OET assumed that wireless services operating in the new 600 MHz band will appear noise-like to DTV receivers and hence, that the interference potential from LTE will be nearly identical to DTV-to-DTV interference. In addition, OET incorporated an off-frequency rejection factor as a function of varying degrees of spectral overlap due to filter roll-off in the misaligned future wireless blocks and existing TV channels in the 600 MHz band. OET also added 0.8 dB to the interfering wireless signal to account for the possibility of co-channel power from multiple wireless blocks affecting one 6 MHz TV channel. Several commenters raised concerns about these assumptions which form the basis for the D/U ratios of Table 8, the OFR values of Table 9, and the assumed effective radiated power in Table 10 of the Public Notice.
In April 2014, OET engineers tested the characteristics of LTE-into-DTV interference in the FCC Laboratory, and the results of those measurements are presented in the attached report. As explained in the report, four DTV receivers were tested in order to obtain a reasonable indication of their behavior in the presence of an interfering LTE eNodeB signal.
Additionally, the Consumer Electronics Association submitted measurements of LTE-to-DTV interference on six newer model television receivers and two older model receivers.
OET seeks comment on whether these measurements in its report, in conjunction with CEA’s measurements, support the D/U ratios, OFR, and power adjustments that appear in the Public Notice.
OET also seeks comment on the relevance of the measurements associated with two receiver models that are more than seven years old. The report contains measurements of a 2007 model year receiver and the CEA report contains measurements of a 2006 model year receiver. OET anticipates that these receivers will no longer be commercially available and will be approaching the end of their useful lifecycle at the time of the wireless build out in the 600 MHz Band.
Comments may be filed electronically using the Internet by accessing the ECFS: http://fjallfoss.fcc.gov/ecfs2/. Comment deadline is July 11, 2014.
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