In P2P assisted multi-channel live streaming systems, it is commonly believed that in unpopular channels, quality degradation is due to the small number of participating peers with almost-the-same set of available data; this phenomena prevents effective data exchanges among peers themselves and automatically leads to data request contentions once a new data chunk becomes available. In popular programs, our measurement on PPLive for a continuous three-month period at various locations also shows numerous occurrences of quality degradation because of the even higher ratio (up to 190%) of repetitive data requests for the same data chunks. These results motivate us to investigate effective data exchange strategies to reduce data request contentions for improved streaming quality. IDEA, an Improved peer Data Exchange Algorithm, is proposed to carefully select chunks to request from different peers. We conduct extensive simulations and the results show that IDEA significantly outperform...