Cooperative content dissemination in multi-channel WLAN hotspots

It is common for hotspots in airports, cafes, and malls to deploy info-stations on their access points to provide local information such as flight schedule, multimedia access, sales and discount deals. The dissemination service, however, is limited by the wireless throughput in hotspots and cannot scale to a large number of users. This paper designs a new architecture that significantly improves the throughput of info-stations. We observe that usually the number of collocated infostations is smaller than the number of orthogonal channels in IEEE 802.11, leaving some orthogonal channels unused, and thus wasting their capacity. We also observe that many users of an info-station download the same objects. Thus, we advocate an architecture, called hybrid-WLAN (H-WLAN), where mobile nodes can retrieve objects (multimedia content or information) from the info-station in the infrastructure mode, or exploit the idle 802.11 channels to cooperatively share their content with neighboring nodes in an ad-hoc manner. Our H-WLAN contains two components. The first component directs each object request to a nearby ad-hoc node that has the requested object, while avoids overloading any of the nodes. The second component balances the load across channels taking into account the popularity of the disseminated objects. We evaluate our design via simulations. The results show that our H-WLAN improves channel utilization and provides significantly higher throughput. 2007 Elsevier B.V. All rights reserved.