The usage of the cellular networks for mobile telephony is increasing at an alarmingly fast pace. Since the introduction of smart phones and flat rate data subscriptions, the usage of the spectrum has increased to the point where the telephone companies can hardly keep up with building base stations to satisfy the demand. However, recent analyses of voice traffic have shown that a significant amount of calls are made between mobile phones with a mutual distance less than the distance from the phones to the base station. Thus, by letting the phones talk to each other directly instead of through the base station, the usage of the spectrum can be reduced significantly.
The purpose of the project is to implement a proof-of-concept peer-to-peer link that can be used for video telephony. In addition, the use of a relaying node, to extend coverage and improve performance, shall be supported. During development, the project will use desktops and/or laptops connected to specialized radio hardware instead of actual mobile phones.
The system consists of three main components, which are two peers and one relay. These components communicate on an unlicensed radio channels. One peer transmits a signal into two directions, directly to the other peer and through a relay. The relay receives the signals from the peers and will decode and forward these. At the peers, signals arrive in two branches, one is directly from the other peers transmitter and the other one comes from the relay, which provides cooperative diversity for the receiver part of the peers. Thus, link performance is improved. The communication between peers must be duplex to demonstrate a video telephony application. Each peer must be able to transmit and receive at the same time.
