INTANGIBLE ASSETS

Amortization expense related to intangible assets is as follows (in thousands):



	Fiscal Years
	2017		2016		2015
Cost of revenue	$	30,286	$	26,615	$	27,285
Selling, general and administrative	35,456		23,640		11,695
Total	$	65,742	$	50,255	$	38,980

Intangible assets consist of the following (in thousands):



	September 29, 2017			September 30, 2016
Acquired technology	$	251,655		$	165,397
Customer relationships	556,648			207,674
In-process research and development	—			8,000
Trade name	3,400			3,400
Total	811,703			384,471
Less accumulated amortization	(190,611		)	(124,869		)
Intangible assets — net	$	621,092		$	259,602

A summary of the activity in intangible assets and goodwill follows (in thousands):



	Intangible Assets
	Total			Acquired Technology			Customer Relationships			In-Process Research and Development			Trade Name		Goodwill
Balance at October 2, 2015	$	318,006		$	162,536		$	144,070		$	8,000		$	3,400	$	93,346
Acquired	65,350			10,400			54,950			—			—		20,412
Fair value adjustment	1,678			78			1,600			—			—		3,475
Currency translation adjustments	8,857			1,803			7,054			—			—		2,791
Impairments of intangible assets	(10,088		)	(10,088		)	—			—			—		—
Other intangibles purchased	668			668			—			—			—		—
Balance at September 30, 2016	384,471			165,397			207,674			8,000			3,400		120,024
Acquired	436,181			83,518			352,663			—			—		195,145
Placed in service	—			3,648			—			(3,648		)	—		—
Fair value adjustment	—			—			—			—			—		220
Currency translation adjustments	(4,597		)	(908		)	(3,689		)	—			—		(1,624		)
Impairments of intangible assets	(4,352		)	—			—			(4,352		)	—		—
Balance at September 29, 2017	$	811,703		$	251,655		$	556,648		$	—		$	3,400	$	313,765

As of September 29, 2017, our estimated amortization of our intangible assets in future fiscal years, subject to the completion of the purchase price allocation for the AppliedMicro, Picometrix, Antario and TPC acquisitions, was as follows (in thousands):



	2018		2019	2020	2021	2022	Thereafter
Amortization expense	$	82,798	90,429	88,030	79,161	65,468	211,806

Our trade name is an indefinite-lived intangible asset. During development, in-process research and development (IPR&D) is not subject to amortization and is tested for impairment annually or more frequently if events or changes in circumstances indicate that the asset might be impaired. The impairment test consists of both a qualitative and quantitative assessment using an assumption of ‘more likely than not’ to determine if there were any impairment indicators. If impairment exists, a loss is recognized in an amount equal to that excess. Once an IPR&D project is complete, it becomes a definite long-lived intangible asset and is evaluated for impairment in accordance with our policy for long-lived assets. During the fourth quarter of fiscal year 2017, we completed the last IPR&D project and placed the acquired technology into service. Prior to placing the technology into service we performed an impairment assessment, at which time we determined that the value of the technology was impaired by $4.4 million, which was expensed in our fiscal fourth quarter of 2017. The remaining $3.6 million was placed in service as acquired technology.

Accumulated amortization for the acquired technology and customer relationships was $106.8 million and $83.9 million, respectively, as of September 29, 2017, and $76.7 million and $48.1 million, respectively, as of September 30, 2016.

During the second quarter of fiscal year 2016, we made a strategic decision to exit the product line and end programs associated with our GaN-on-SiC license and technology transfer to focus on development of our GaN-on-Si efforts. As a result of this strategic decision, we determined that the intangible assets and contractual commitments under the long-term technology licensing and transfer agreement signed in July 2013, as well as certain dedicated fixed assets and inventory, would no longer have any future benefit. The associated charges incurred during the nine months ended July 1, 2016 were $13.8 million, which included a write-off of $10.1 million of intangible assets, $0.6 million of property and equipment, $1.1 million of contractual commitments and $2.0 million of inventory.