求翻译：ACG Research最新研究报告显示，2011年第三季度全球分组光传输系统的销量比起上一季度下降了16.1％。不过，该季度的销量水平却比去年同期上升了21%。是什么意思？

ACG Research latest study shows that the third quarter of 2011, worldwide sales of packet-optical transport system compared to the previous quarter, down 16.1%. However, the level of sales in the quarter than the same period last year increased by 21%.

The latest study shows that ACG Research 2011 global sub-group in third and fourth quarter sales of optical transmission system than the first quarter dropped by 16.1 per cent. However, the quarter sales levels were increased by 21 per cent over the same period last year.

ACG the Research newest memoir demonstration, in 2011 the third quarter whole world grouping fiber-optic transmission system sales volume compared the last quarter to drop 16.1%.This quarter sales volume level actually rose compared to the same time last year 21%.

ACG Research latest studies show, 2011 global packet-optical transport systems in the third quarter sales decline compared with the previous quarter by 16.1%. However, the level of sales in the quarter over the same period last year rose by 21%.

ACG Research latest research report reveal the whole world divide into groups all sales volume of transmission system drop compared with the previous quarter by 16.1% will it be third quarter 2011. However, the sales volume level of this quarter has risen by 21% compared with the same period of last