ROW_NUMBER() Function Is Not Recognized In Store Procedure.

Hello I am Prasad , I have written one store procedure as below. But It gives error message ROW_NUMBER() function is not recognized. what's the fault or what should i change.

CREATE PROCEDURE GetProductsOnCatalogPromotion
(@DescriptionLength INT,
@PageNumber INT,
@ProductsPerPage INT,
@HowManyProducts INT OUTPUT)
AS
-- declare a new TABLE variable
DECLARE @Products TABLE
(RowNumber INT,
ProductID INT,
Name VARCHAR(50),
Description VARCHAR(5000),
Price MONEY,
Image1FileName VARCHAR(50),
Image2FileName VARCHAR(50),
OnDepartmentPromotion bit,
OnCatalogPromotion bit)
-- populate the table variable with the complete list of products
INSERT INTO @Products
SELECT ROW_NUMBER() OVER (ORDER BY Product.ProductID),
ProductID, Name,
SUBSTRING(Description, 1, @DescriptionLength) + '...' AS Description, Price,
Image1FileName, Image2FileName, OnDepartmentPromotion, OnCatalogPromotion
FROM Product
WHERE OnCatalogPromotion = 1
-- return the total number of products using an OUTPUT variable
SELECT @HowManyProducts = COUNT(ProductID) FROM @Products
-- extract the requested page of products
SELECT ProductID, Name, Description, Price, Image1FileName,
Image2FileName, OnDepartmentPromotion, OnCatalogPromotion
FROM @Products
WHERE RowNumber > (@PageNumber - 1) * @ProductsPerPage
AND RowNumber <= @PageNumber * @ProductsPerPage