Dynamic link asymmetry in `bunched´ wireless networks

In most future wireless applications an increasing fraction of the total offered traffic is expected to appear in the downlink (fixed-to-mobile) segment of the system. This requirement matches rather poorly with the system design and spectrum allocation for current and future systems which employ symmetric frequency division duplex (FDD). In contrast, TDMA/TDD systems, at least in principle, allow for a more flexible resource allocation by moving the boundary between uplink and downlink time-slots, the switching point. The key problem caused by moving the switching point; is interference between mobiles and base stations. In the paper, some algorithms to select and adapt the switching point in a `bunched´ cellular environment are investigated. A simple scheme using a `soft´ switching point, is shown to provide a capacity, while not as high as a fully dynamic scheme, still considerably higher than the capacity of a traditional fixed switching point scheme. Further, the `soft´ scheme is also adaptive, in the sense that it tracks varying traffic asymmetry ratios