In this paper, the authors propose novel cooperative transmission protocols for delay-limited coherent fading channels with N half-duplex, single-antenna partners and one cell site. They differentiate between relay, cooperative broadcast (down-link), and cooperative multiple-access (up-link) channels. The protocols are evaluated using the Zheng-Tse diversity-multiplexing tradeoff. For the relay channel, two cooperation schemes are investigated: Amplify and Forward (AF) and Decode and Forward (DF). The authors establish an upper bound on the achievable diversity-multiplexing tradeoff for AF protocols and construct a new AF protocol that achieves this bound. They extend this protocol to N-1 relays, showing it outperforms the space-time coded protocol of Laneman and Worenell without requiring decoding/encoding at the relays. For DF protocols, a dynamic decode and forward (DDF) protocol is developed that achieves the optimal tradeoff for multiplexing gains 0 ≤ r ≤ 1/N. The DDF protocol is shown to dominate AF protocols for all multiplexing gains, particularly in the cooperative broadcast channel. In the cooperative multiple-access channel, a new AF protocol is proposed that achieves the optimal tradeoff for all multiplexing gains. The key feature of the proposed protocols is that they do not rely on orthogonal subspaces, allowing for more efficient resource use. The sub-optimality of previously proposed protocols is attributed to their use of orthogonal subspaces rather than the half-duplex constraint. The authors also compare their protocols with existing ones, showing that the DDF protocol outperforms AF protocols in the cooperative broadcast channel and that the CMA-NAF protocol achieves the optimal tradeoff in the symmetric multiple-access scenario. Numerical results show significant SNR gains for the proposed protocols. The paper concludes that the diversity-multiplexing tradeoff is a powerful tool for designing cooperative protocols, and that the half-duplex constraint does not incur a cost in terms of diversity-multiplexing tradeoff in symmetric multiple-access channels.In this paper, the authors propose novel cooperative transmission protocols for delay-limited coherent fading channels with N half-duplex, single-antenna partners and one cell site. They differentiate between relay, cooperative broadcast (down-link), and cooperative multiple-access (up-link) channels. The protocols are evaluated using the Zheng-Tse diversity-multiplexing tradeoff. For the relay channel, two cooperation schemes are investigated: Amplify and Forward (AF) and Decode and Forward (DF). The authors establish an upper bound on the achievable diversity-multiplexing tradeoff for AF protocols and construct a new AF protocol that achieves this bound. They extend this protocol to N-1 relays, showing it outperforms the space-time coded protocol of Laneman and Worenell without requiring decoding/encoding at the relays. For DF protocols, a dynamic decode and forward (DDF) protocol is developed that achieves the optimal tradeoff for multiplexing gains 0 ≤ r ≤ 1/N. The DDF protocol is shown to dominate AF protocols for all multiplexing gains, particularly in the cooperative broadcast channel. In the cooperative multiple-access channel, a new AF protocol is proposed that achieves the optimal tradeoff for all multiplexing gains. The key feature of the proposed protocols is that they do not rely on orthogonal subspaces, allowing for more efficient resource use. The sub-optimality of previously proposed protocols is attributed to their use of orthogonal subspaces rather than the half-duplex constraint. The authors also compare their protocols with existing ones, showing that the DDF protocol outperforms AF protocols in the cooperative broadcast channel and that the CMA-NAF protocol achieves the optimal tradeoff in the symmetric multiple-access scenario. Numerical results show significant SNR gains for the proposed protocols. The paper concludes that the diversity-multiplexing tradeoff is a powerful tool for designing cooperative protocols, and that the half-duplex constraint does not incur a cost in terms of diversity-multiplexing tradeoff in symmetric multiple-access channels.