Dynamic asymmetric communication

Summary form only given. Internet users usually download more than they upload and many technologies have asymmetric bandwidth. Suppose some clients want to send messages to a server. At any point, the server knows all the messages it has received so far; each client only knows its own message or messages and does not overhear communication between other clients and the server. Thus, the server may be able to compress the messages but the clients individually cannot. By assuming the server, after receiving a sample of messages, can accurately estimate the distribution of all the messages, a multi-round asymmetric communication protocol can be provided in which the server uses its greater bandwidth to help a single client send a message drawn from a distribution known to the server. The server can just repeat their protocol to help any number of clients, provided it starts with a representative sample. This paper propose a new protocol inspired by an everyday act: placing a call on a cell phone. While the protocol needs no assumptions and is nearly optimal with respect to the number of bits the clients send, the server sends a relatively large number of bits, which is necessary in order to use only one round of communication for each message