When the Company acquired the trade assets of Motorola Solutions, Inc.’s wireless point-to-point and point-to-multi-point businesses, the transaction generated goodwill and certain intangible assets. The goodwill associated with this transaction was recorded by Cambium Networks Corporation and allocated to Cambium Networks, Ltd. and Cambium Networks, Inc. using a revenue and asset allocation method. Although goodwill has been allocated to two operating subsidiaries, as noted in Note 16 – Segment information and revenues by geography, the Company operates as one operating segment and one reporting unit and therefore, goodwill is reported, and impairment testing performed, at the Cambium Networks Corporation consolidated level.

See Note 2 – Business combinations for further information regarding the acquisition completed during 2019.

The change in the carrying amount of goodwill for the year ended and nine-month period ended was as follows (in thousands):

	December 31,		September 30,
	2019		2020
			(unaudited)
Beginning balance	$	8,060	$	8,552
Additions attributable to acquisition		492		—
Acquisition adjustments		—		1,290
Ending balance	$	8,552	$	9,842

The Company tests goodwill and intangible assets for impairment annually on December 31 and more frequently if impairment indicators exist. Accordingly, the Company performs quarterly qualitative assessments of significant events and circumstances such as a reporting unit’s historical and current results, assumptions regarding future performance, strategic initiatives and overall economic factors, including the impact of the current global outbreak of the coronavirus (or COVID-19) and macro-economic developments, to determine the existence of potential indicators of impairment and assess if it is more likely than not that the fair value of the reporting unit or intangible asset is less than their carrying value. If indicators of impairment are identified, a quantitative impairment test is performed.

Qualitative assessments for the quarter did not indicate the existence of impairment indicators. Based on the operating results for the nine-month period ended September 30, 2020 and other considerations, the Company believes that it is more likely than not that the enterprise value for its one reporting unit and the fair value of intangibles is still greater than their carrying values. Accordingly, no goodwill impairment indicators were present at September 30, 2020 that would necessitate an interim impairment assessment. The Company will continue to monitor business performance and economic conditions, particularly the impact of the COVID-19 pandemic, throughout 2020 to determine if an interim evaluation should be conducted.

The useful life, gross carrying value, accumulated amortization, and net balance for each major class of definite-lived intangible assets at each balance sheet date were as follows (in thousands):

		December 31, 2019							September 30, 2020
	Useful Life	Gross carrying amount		Accumulated amortization			Net balance		Gross carrying amount		Accumulated amortization			Net balance
									(unaudited)		(unaudited)			(unaudited)
Unpatented technology	3 - 7 years	$	14,660	$	(14,195	)	$	465	$	14,660	$	(14,330	)	$	330
Customer relationships	5 - 18 years		19,300		(5,631	)		13,669		19,300		(6,754	)		12,546
Patents	7 years		11,300		(11,300	)		—		11,300		(11,300	)		—
Trademarks	10 years		5,270		(4,304	)		966		5,270		(4,700	)		570
Total		$	50,530	$	(35,430	)	$	15,100	$	50,530	$	(37,084	)	$	13,446

Intangible assets are amortized over their expected useful life and none are expected to have a significant residual value at the end of their useful life. Intangible assets amortization expense was $0.4 million and $0.6 million for the three-month periods ended September 30, 2019 and 2020, respectively, and $1.0 million and $1.7 million for the nine-month periods ended September 30, 2019 and 2020, respectively.

Based on capitalized intangible assets as of September 30, 2020, estimated amortization expense amounts in future fiscal years are as follows (unaudited and in thousands):

Year ending December 31,	Amortization
2020 (October - December)	$	552
2021		2,118
2022		1,603
2023		1,498
2024		1,498
Thereafter		6,177
Total amortization	$	13,446