Note C – Patents

The Company’s intangible assets at December 31, 2021 include patents with estimated remaining economic useful lives ranging from 1.50 to 12.33 years. For all periods presented, all the Company’s patents were subject to amortization. The gross carrying amounts and accumulated amortization related to acquired intangible assets as of December 31, 2021 and 2020 were as follows:

Amortization expense for the years ended December 31, 2021 and 2020 was $295,000 and $292,000, respectively. Future amortization of current intangible assets, net is as follows:

The Company’s Remote Power Patent expired on March 7, 2020. All patents within our Mirror Worlds Patent Portfolio and QoS Patents have also expired. All patents within the Cox Patent Portfolio expired in September 2021 except for two patents which expire in July 2023 and November 2023. The expiration dates of patents within the Company’s M2M/IoT Patent Portfolio range from September 2033 to May 2034.