Digital Communications

14Cooperative Communications

In contrast with traditional networks, cooperative communication networks share resources through distributed transmission and/or processing. [1] In such networks, cooperating users not only transmit/receive their own signals but also serve as (non)regenerative relays for other users’ signals to reach their destination (see Figure 14.1). A cooperative network may comprise multiple sources encoding and transmitting their messages in coordination with others. The diversity advantage is achieved through cooperation between users and independence of fading in the links. Cooperative communications provides significant improvements in bit error probability (BEP), multiplexing gain (increase in capacity), and array gain (increase in SNR and in range).

Figure 14.1 Cooperative Communications By Randomly Located Users.

Wireless repeaters used for extending the coverage area of TV and radio broadcasting stations and wired/wireless repeaters used for long‐distance communications are classical examples of relaying. On the other hand, nodes in existing computer networks act as relays either in amplify‐and‐forward (AF) mode, where the received information is amplified and retransmitted, or in detect‐and‐forward (DF) mode by detecting, re‐modulating and re‐transmitting the received information. [2][3] Figure 14.2 shows several cooperation scenarios in cellular ...