Abstract-We investigate on the scalability of multihop wireless communications, a major concern in networking, for the case that users access content replicated across the nodes. In contrast to the standard paradigm of randomly selected communicating pairs, content replication is efficient for certain regimes of file popularity, cache and network size. Our study begins with the detailed joint content replication and delivery problem on a 2D square grid, a hard combinatorial optimization. This is reduced to a simpler problem based on replication density, whose performance is of the same order as the original. Assuming a Zipf popularity law, and letting the size of content and network both go to infinity, we identify the scaling laws and regimes of the required link capacity, ranging from O √ N down to O(1).

We investigate efficient schemes for data communication from a server to a mobile terminal over a wireless channel of fluctuating quality. A user requests to access various data items on the terminal. If a requested item is found in the local terminal buffer or cache, no access delay is incurred. If not, it is downloaded from the server and the user incurs a delay cost until it becomes locally available. Moreover, a power cost is incurred to transmit the data item at a selected power level over the wireless link.To lower both the average delay and power costs, the system may prefetch data items and predictively cache them on the terminal -especially during link quality 'highs' -in anticipation of future user requests. The goal is to minimize the overall delay and power cost, by judiciously choosing which data item to fetch and what power level to use, given the current user, buffer, and channel states.We develop a modeling framework -based on controlled Markov chains and dynamic programming -capturing the essential performance tradeoffs in the system and allowing computation of optimal decisions on items to (pre)fetch and power levels to use. To cope with emerging complexities, we then design efficient heuristics, whose simulation analysis demonstrates substantial performance gains over standard approaches.

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