No, Google Ad Exchange is not a DSP it is a demand-side platform and works with advertisers. Google AdX is built for publishers and allows them to have control over their ad monetization campaign, data, and revenue tracking. It would be classified as an SSP or Supply Side Platform, as it serves large web publishers with high traffic footfall.
A DSP is a Demand Side Platform that allows advertisers to buy advertising space on the web with the help of automation. It allows the advertisers to widen the target their audience and feed ads to high-quality audiences with minimum friction.
It is a neutral, autonomous platform, that allows for programmatic ad buying, driven by real-time bidding (RTB) technology.