What was the total operating expenses for the fourth quarter of 2021, excluding equity-based compensation amortization of intangible and deal costs
vities primarily by R&D engineers and no manufacturing facilities. However, we intend to take advantage of our expertise in wireless, AI, and low-power designs to help our customers achieve their own sustainability goals.
As I stated above, we are focusing on Wireless IoT where our technologies can add resiliency and run time analytics to optimize energy and water utilization and to expedite the shift to renewable energy. We will also work with our base station RAN customers on next-generation DSP technologies that will serve their objective of lower heat dissipation and energy consumption. We will continue to periodically consult with our investors of their perspectives on sustainability. So in summary, CEVA is uniquely positioned to capitalize on the semiconductor momentum and market transformation toward digitization, AI, and connectivity.
Our customer pipeline at the end of the year is historically high. We believe our key customers are keenly receptive to our products road map and priorities and willing to expand the scope of engagements with us. We expect 2022 to be an exciting year with growing momentum in revenue, EPS, and customer engagements. We are determined to continue to develop standout products and consistently grow our customer base and licensing engagements to scale our business.
Finally, I would like to take this opportunity to thank all of our employees for their hard work and dedication, innovation, and fantastic execution. I would like to extend my thanks to our partners, suppliers, and to our shareholders for their confidence and support. We wish you all a healthy, happy, and prosperous year and please stay safe! With that said, I'll now turn the call over to Yaniv, who will outline our financials and guidance.
Yaniv Arieli -- Chief Financial Officer
Thank you, Gideon. I'll start by further reviewing our results of operations for the fourth quarter of 2021. Revenue for the fourth quarter was a record high at $34.1 million, up 21% compared to $28.1 million for the same quarter last year, our third sequential all-time high. Non-GAAP revenue was $34.2 million, up 22% year-over-year, $0.2 million higher due to the purchase price allocation adjustment associated with our Intrinsix's acquisition.
The revenue breakdown is as follows, Licensing, NRE, and related revenue was $21.3 million, reflecting 63% of our total revenue, up 78% as compared to the fourth quarter of 2020 and just slightly below our third quarter 2021 record high. Royalty revenue was $12.7 million, reflecting 37% of our total revenue, down 21% from $16.1 million for the same quarter last year, but up 13% sequentially. Base station & IoT royalty revenue contributed $7.8 million in the quarter, up 21% year-over-year, including all-time record high contribution from our sensor fusion product line and continued growth and strength across our base station and IoT product lines overall. Gross margins were 83% on GAAP basis and 87% on non-GAAP basis, both higher than projected due to lower allocation of Intrinsix's NRE costs from R&D into cost delinquence expense line.
Non-GAAP quarterly gross margin exclude approximately $0.3 million of equity-based compensation expenses and $1 million amortization of acquired assets associated with the Intrinsix acquisition and Immervision investment. Our total operating expenses for the fourth quarter was $26.6 million, over the high-end of our guidance, due to lower allocation of Intrinsix's NRE costs from R&D to the cost of revenue per our prior quarter guidance. Such shifts between the two expense line items may happen from time to time and are tied to the actual chip design work performed in the quarter. Opex also included aggregate equity-based compensation expenses of approximately $3.2 million, amortization of acquired intangibles of 1, and $0.3 million Intrinsix related deal costs.
Our total operating expenses for the fourth quarter, excluding equity-based compensation amortization of intangible and deal costs were $22.4 million, over the high-end of our guidance, due to the same reasons I just stated
vities primarily by R&D engineers and no manufacturing facilities. However, we intend to take advantage of our expertise in wireless, AI, and low-power designs to help our customers achieve their own sustainability goals.
As I stated above, we are focusing on Wireless IoT where our technologies can add resiliency and run time analytics to optimize energy and water utilization and to expedite the shift to renewable energy. We will also work with our base station RAN customers on next-generation DSP technologies that will serve their objective of lower heat dissipation and energy consumption. We will continue to periodically consult with our investors of their perspectives on sustainability. So in summary, CEVA is uniquely positioned to capitalize on the semiconductor momentum and market transformation toward digitization, AI, and connectivity.
Our customer pipeline at the end of the year is historically high. We believe our key customers are keenly receptive to our products road map and priorities and willing to expand the scope of engagements with us. We expect 2022 to be an exciting year with growing momentum in revenue, EPS, and customer engagements. We are determined to continue to develop standout products and consistently grow our customer base and licensing engagements to scale our business.
Finally, I would like to take this opportunity to thank all of our employees for their hard work and dedication, innovation, and fantastic execution. I would like to extend my thanks to our partners, suppliers, and to our shareholders for their confidence and support. We wish you all a healthy, happy, and prosperous year and please stay safe! With that said, I'll now turn the call over to Yaniv, who will outline our financials and guidance.
Yaniv Arieli -- Chief Financial Officer
Thank you, Gideon. I'll start by further reviewing our results of operations for the fourth quarter of 2021. Revenue for the fourth quarter was a record high at $34.1 million, up 21% compared to $28.1 million for the same quarter last year, our third sequential all-time high. Non-GAAP revenue was $34.2 million, up 22% year-over-year, $0.2 million higher due to the purchase price allocation adjustment associated with our Intrinsix's acquisition.
 The revenue breakdown is as follows, Licensing, NRE, and related revenue was $21.3 million, reflecting 63% of our total revenue, up 78% as compared to the fourth quarter of 2020 and just slightly below our third quarter 2021 record high. Royalty revenue was $12.7 million, reflecting 37% of our total revenue, down 21% from $16.1 million for the same quarter last year, but up 13% sequentially. Base station & IoT royalty revenue contributed $7.8 million in the quarter, up 21% year-over-year, including all-time record high contribution from our sensor fusion product line and continued growth and strength across our base station and IoT product lines overall. Gross margins were 83% on GAAP basis and 87% on non-GAAP basis, both higher than projected due to lower allocation of Intrinsix's NRE costs from R&D into cost delinquence expense line.
Non-GAAP quarterly gross margin exclude approximately $0.3 million of equity-based compensation expenses and $1 million amortization of acquired assets associated with the Intrinsix acquisition and Immervision investment. Our total operating expenses for the fourth quarter was $26.6 million, over the high-end of our guidance, due to lower allocation of Intrinsix's NRE costs from R&D to the cost of revenue per our prior quarter guidance. Such shifts between the two expense line items may happen from time to time and are tied to the actual chip design work performed in the quarter. Opex also included aggregate equity-based compensation expenses of approximately $3.2 million, amortization of acquired intangibles of 1, and $0.3 million Intrinsix related deal costs.
Our total operating expenses for the fourth quarter, excluding equity-based compensation amortization of intangible and deal costs were $22.4 million, over the high-end of our guidance, due to the same reasons I just stated