INTANGIBLE ASSETS, NET

9 Months Ended

Sep. 30, 2012

INTANGIBLE ASSETS, NET

7. INTANGIBLE ASSETS, NET

The following table provides the gross and net carrying amounts for each major class of intangible assets:

	As of September 30, 2012							As of December 31, 2011
	Gross carrying amount		Accumulated amortization			Net book value		Gross carrying amount		Accumulated amortization			Net book value
	(in thousands)
Current contract intangibles	$	1,844,690	$	(416,057	)	$	1,428,633	$	1,391,001	$	(333,522	)	$	1,057,479
Network location intangibles		903,783		(231,802	)		671,981		772,467		(190,162	)		582,305
Intangible assets, net	$	2,748,473	$	(647,859	)	$	2,100,614	$	2,163,468	$	(523,684	)	$	1,639,784

All intangible assets noted above are included in our site leasing segment. The Company amortizes its intangible assets using the straight-line method over 15 years. Amortization expense relating to the intangible assets above was $46.4 million and $33.7 million for the three months ended September 30, 2012 and 2011, respectively, and $124 million and $98.8 million for the nine months ended September 30, 2012 and 2011, respectively.