Hybrid networks: cellular-relay architecture

Summary form only given. Peer-to-peer communication networks such as sensor networks, personal area networks and wireless local area networks are characterized by multi-hop wireless communications in which information may be routed from source to destination via multiple wireless links. On the other hand cellular networks are single-hop networks in which wireless communication is between the mobile node and the base station only. Convergence will be a main theme of future networks that provide ubiquitous high rate services seamlessly through converged technologies. Motivated by this we propose cellular network architectures with multihop transmission from the base station to terminals and vice versa through relays. Relays are network elements (fixed or mobile) or other user terminals that have significantly more intelligence than repeaters and are capable of storing and forwarding data and making scheduling and routing decisions. Relay nodes are not connected to the wireline network through a back-haul connection, but have to rely on wireless transmission to communicate to the base station. We discuss a variety of deployment scenarios involving multi-hop transmission through relays. Cellular-relay networks could be such that the relay to terminal links use different spectrum than base to terminal links. For example, the relays could communicate to the terminals through a wireless local area network using the IEEE 802.11 air interface, in which case the relays are like access points and use the unlicensed band, while the base station transmits to the relays using the licensed cellular network spectrum. In this model, mobile terminals are assumed to have both cellular and IEEE 802.11 interfaces, which is becoming increasingly common. An alternative scenario is one in which the two kinds of hops use two different carriers within the spectrum assigned to the cellular network operator. It is also possible to deploy relays in such a way that no additional carrier or spectrum is required and transmissions from base station to relays and relays to user terminals use the same spectrum. Capacity gains are achieved even in such a scenario because of the additional effective spectrum reuse that is obtained due to the spatial separation of the relays and their lower trans- mit power compared to that of the base station. We present a detailed description of such a system including the signaling scheme and the medium access protocol for high-speed packet data applications. Finally we discuss benefits of relay based cellular network architectures for multicast traffic. In this model, the multicast throughput is not limited by the link quality of the user at the edge of the cell since transmission happens through appropriately selected relays.