Personal healthcare is a promising market of a personal area network (PAN). The PAN consists of a data collector and multiple wearable sensors which must send data to the collector according to the frequency specified by each PAN. The data collector may be any hand-held or portable device, e.g., a mobile phone, a PDA, or a wristwatch. An individual user needs a PAN in order to detect, track, or manage his/her health. Multiple PANs for such purposes are likely to coexist in a same area, especially a place where a large number of users exist. Because multiple PANs must share resources (e.g., wireless channels, transmitting time) in this scenario, a problem of packet collisions among such PANs is unavoidable. As a result, the personal healthcare system using PAN cannot be provided as a service for the users because the data collector cannot collect sensing data from each sensor correctly. This paper proposes an adaptive scheme to allocate resources for coexisting PANs. The scheme distinguishes a PAN and a node when allocating resources such as wireless channel and transmitting time. Resources are dynamically allocated according to the current number of PANs that exist in the same area. In particular, the proposed scheme automatically reallocates resources when any PANs come into or leave from the coexisting area. As one of salient features, the scheme allocates transmitting time to meet a requirement on reporting interval determined by an application. Thus applications that are sensitive to delay can collect sensing data correctly and in time. The evaluation results show that our scheme achieves higher packet delivery rate than the standard ZigBee.
['Niwat Thepvilojanapong', 'Shinji Motegi', 'Akira Idoue', 'Hiroki Horiuchi']
Resource Allocation for Coexisting ZigBee-Based Personal Area Networks