Hello, I have reviewed you project requirements. As mentioned in the project description, you want to implement Infinite Scroll feature on your product listing page on your Smarty based website.
There are some Infinite Scroll jquery plugins available like jScroll, etc..
I have much experience in working on Web Development projects using PHP, Smarty PHP, MySQL, Jquery. You may provide your preference of jquery plugin to be used for implementing the infinite scroll feature on your website. You may provide further details required to start the project.
Thanks.