(7)	Intangible Assets

Our intangible assets include the following:

		March 31, 2015							December 31, 2014
	Weighted Average Useful Lives	Gross Carrying Value		Accumulated Amortization			Net Carrying Value		Gross Carrying Value		Accumulated Amortization			Net Carrying Value
Indefinite life intangible assets:
FCC licenses	Indefinite	$	2,083,654	$	—		$	2,083,654	$	2,083,654	$	—		$	2,083,654
Trademark	Indefinite		250,000		—			250,000		250,000		—			250,000
Definite life intangible assets:
Subscriber relationships	9 years		380,000		(313,820	)		66,180		380,000		(305,755	)		74,245
OEM relationships	15 years		220,000		(20,778	)		199,222		220,000		(17,111	)		202,889
Licensing agreements	12 years		45,289		(24,211	)		21,078		45,289		(23,290	)		21,999
Proprietary software	8 years		27,215		(16,206	)		11,009		27,215		(15,691	)		11,524
Developed technology	10 years		2,000		(1,333	)		667		2,000		(1,283	)		717
Leasehold interests	7.4 years		132		(119	)		13		132		(114	)		18
Total intangible assets		$	3,008,290	$	(376,467	)	$	2,631,823	$	3,008,290	$	(363,244	)	$	2,645,046

Indefinite Life Intangible Assets

We have identified our FCC licenses and the XM trademark as indefinite life intangible assets after considering the expected use of the assets, the regulatory and economic environment within which they are used and the effects of obsolescence on their use.

We hold FCC licenses to operate our satellite digital audio radio service and provide ancillary services. The following table outlines the years in which each of our satellite licenses expires:

FCC satellite licenses	Expiration year
SIRIUS FM-1		2017
SIRIUS FM-2		2017
SIRIUS FM-3		2017
SIRIUS FM-5		2017
SIRIUS FM-6		2022
XM-1 ⁽¹⁾
XM-3		2021
XM-4		2022
XM-5		2018

(1)	The FCC license for this satellite has expired. The FCC has granted us special temporary authority to operate this satellite and prepare it for deorbiting maneuvers.

Prior to expiration, we are required to apply for a renewal of our FCC licenses. The renewal and extension of our licenses, including temporary licenses, is reasonably certain at minimal cost, which is expensed as incurred. Each of the FCC licenses authorizes us to use the broadcast spectrum, which is a renewable, reusable resource that does not deplete or exhaust over time.

Our annual impairment assessment of our indefinite intangible assets is performed as of the fourth quarter of each year. An assessment is performed at other times if an event occurs or circumstances change that would more likely than not reduce the fair value of the asset below its carrying value. If the carrying value of the intangible assets exceeds its fair value, an impairment loss is recognized. As of March 31, 2015, there were no indicators of impairment, and no impairment loss was recorded for intangible assets with indefinite lives during the three months ended March 31, 2015 and 2014.

Definite Life Intangible Assets

Amortization expense for all definite life intangible assets was $13,223 and $14,084 for the three months ended March 31, 2015 and 2014, respectively. Expected amortization expense for the remaining period in 2015, each of the fiscal years 2016 through 2019 and for periods thereafter is as follows:

Years ending December 31,	Amount
2015 (remaining)	$	38,477
2016		48,545
2017		34,882
2018		19,463
2019		19,026
Thereafter		137,776
Total definite life intangible assets, net	$	298,169