As 800 MHz rebanding moves along, an issue that many expected to crop up during the transition has reared its ugly head — more interference.

Because only some licensees have completed rebanding, there is additional interleaving of public-safety systems and Sprint Nextel right now. This gives rise to additional occurrences of interference. Of course, when rebanding is done, these issues no longer will exist, but this transitional period causes added difficulty. Recently, my office has seen a spike in reports of interference in the band — which clearly is the result of Sprint Nextel beginning to utilize frequencies formerly used by a transitioned 800 MHz licensee adjacent to a non-transitioned public-safety licensee.

The purpose of the Transition Administrator's Implementation Planning Session is to enable licensees and Sprint Nextel to work out this timing in order to minimize potential interference during the transition. If you are a transitioned NPSPAC licensee using a frequency that ends in 0 — which previously was unavailable on the 1-120 800 MHz frequencies — Sprint Nextel will not utilize the frequency 12.5 kHz to either side of your operating channel.

However, interference still can occur from the classic “near-far” problem that rebanding is intended to resolve.

Section 22.971 of the commission's rules provides strict liability on the part of commercial carriers causing interference to public-safety licensees. This liability is joint and several, meaning that if two carriers are causing the interference together, they can't just point to one another and tell you to talk to the other.

But, what is interference? Section 22.970 provides that interference will be deemed to occur for voice units when a:

  • Transceiver at a site at which interference is encountered is in good repair and operating condition, and is receiving either a median desired signal of -104 dBm or higher, as measured at the RF input of the receiver of a mobile unit, or a median desired signal of -101 dBm or higher, as measured at the RF input of the receiver of a portable, i.e., handheld unit.

  • Voice transceiver has manufacturer-published performance specifications for the receiver section of the transceiver that are equal to, or exceed, the minimum standards established by this section, and receives undesired signals that cause the measured carrier to noise plus interference (C/(N+I)) ratio of the receiver section of the transceiver to be less than 20 dB.

These numbers apply once rebanding has been completed in a region. During the interim period, the numbers are a little bit different, but the general theory and process remains the same.

Importantly, Section 22.972 provides for a very clear and quick process for carriers to follow when interference is reported. Perhaps the most important part of this rule is Section (c)(3), which provides that the Public Safety and Homeland Security Bureau can order the carrier to cease operations immediately if there is a “clear imminent danger.”

Unfortunately, many licensees are not aware of these provisions, and waste precious time trying to resolve interference through a lengthy chain of command. Instead, you should file your interference report at www.publicsafety800mhzinterference.com/CTIAWEB/index.aspx.

Carriers will respond immediately (often the same day) and try to resolve the problem — they are required to by rule. Nevertheless, this process provides you the quickest method for resolving your interference problem, and provides a record for your further action if the interference continues.

What do you think? Tell us in the comment box below.

Alan Tilles is counsel to numerous entities in the private radio and Internet industries. He is a partner in the law firm of Shulman Rogers Gandal Pordy & Ecker and can be reached at atilles@srgpe.com.

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