Transmission schemes for frequency selective Gaussian interference channels

In modern communication systems, as more users are demanding higher data rates, multiple users are occupying the same time slot and frequency band; moreover, each channel tends to be frequency selective because more bandwidth needs to be allocated for signal transmission. Among several multiuser channel models, this thesis concerns frequency selective Gaussian interference channels. The interference channel has the restriction that neither transmitter coordination nor receiver coordination between multiple users is permitted.; Several rate maximization results have also been found for a multiuser frequency selective channel. However, most previous work assumes signal coordination at either the transmitter or the receiver end. Hence, these results by definition are not viable for interference channels in which no coordination is allowed. The capacity-region-achieving scheme is not yet known for the general Gaussian interference channel. This dissertation considers a pragmatic transmission scheme, the Iterative Waterfilling (IW) technique. Power allocation in IW is observed to converge for all channel scenarios; however, a proof for IW's convergence has not yet been provided. A sufficient condition for the convergence is provided in this thesis. Furthermore, when the power allocation process in IW is modeled as a game, IW can be analyzed from a game theoretic viewpoint. In particular, it is shown that a Nash equilibrium always exists in the game. A condition for the uniqueness of the Nash equilibrium is also found. Lastly, an enumeration algorithm is provided so that all Nash equilibrium points can be derived numerically.; Next, the performance of IW is compared to that of the optimal scheme for general channel scenarios. IW is composed of a suboptimal multiuser coding scheme and a suboptimal multiuser power allocation scheme. Therefore, the performance is evaluated in two different aspects. First, when interference is strong, IW is compared to the capacity-region-achieving scheme, which is composed of the optimal coding scheme and power allocation scheme. Second, IW is compared to the scheme in which the suboptimal coding in IW is used and the optimal power allocation with respect to the suboptimal coding is adopted.