Delay, guaranteeing causality, is inevitable in cooperative communication systems. Traditionally, delay granularity has been limited to one symbol; however, channel delay is in fact governed by channel memory and can be shorter. For example, the delay requirement in orthogonal frequency-division multiplexing, captured in the cyclic prefix, is typically much shorter than the symbol itself. This perspective is used to study the two-user Gaussian interference channel with full-duplex transmitters. By superimposing the signal from the other node onto its own signal, each transmitter cancels the interference at its receiver. Among other results, it is proved that under a mild condition, the maximum multiplexing gain of this channel is in fact two, rather than the limit of one, previously shown under the traditional constraint of causal delay. Further, the optimal power allocation among orthogonal sub-carriers, which maximizes the achievable sum-rate, is shown to be a generalization of the well-known water filling. Simulation results are included to demonstrate the improvement in the achievable sum-rate when full-duplex transmitters are used.

Sharing radio resources of multiple wireless networks with overlapped coverage areas has a potential of improving the transmission throughput. However, the improvement cannot be achieved in congestion scenarios using independent congestion control procedures among the end-to-end paths. Although various network characteristics make the congestion control complex, this variety can be useful for congestion avoidance if the networks cooperate with each other. In this way, the traffic can be shifted from a congested network to non-congested ones, and the overall transmission throughput does not degrade in a congestion scenario. In this paper, first, a cooperative congestion control algorithm is proposed in which the state of an end-to-end path is provided at the destination terminal by measuring the queuing delay and estimating the congestion level. Second, the decision on when to start/stop cooperation is determined based on the network characteristics, instantaneous traffic condition, and requested quality of service (QoS). Simulation results demonstrate the throughput improvement of the proposed scheme over non-cooperative congestion control.

The abundant bandwidth at 60 GHz band (around 7 GHz) offers the potential for multi-Gbps indoor wireless connections for bandwidth-intensive applications. However, 60 GHz millimeter wave (mmWave) links are highly susceptible to blockage since it is difficult to diffract around obstacles. In this paper, we propose multi-radio band integration framework to have 2.4/5 GHz band assist mmWave band to prevent drastic data rate reduction. Specifically, the problem of multi-radio band integration with TDMA-based MAC is formulated as an optimization problem. We decompose the problem into two sub-problems: radio band selection and space-time scheduling. Firstly, considering network load and mmWave channel status, we define start-integration threshold and stop-integration threshold to select an active radio band for data transmission. Secondly, a space-time scheduling scheme is proposed to allow multiple flows over different radio bands operate concurrently to exploit the spatial reuse. Simulation results of the proposed multi-radio band integration mechanism demonstrate significant improvements of network connectivity and the number of supported traffic flows.