Cooperative Relaying with State Available Non-Causally at the Relay

We consider a three-terminal state-dependent relay channel with the channel state noncausally available at only the relay. Such a model may be useful for designing cooperative wireless networks with some terminals equipped with cognition capabilities, i.e., the relay in our setup. In the discrete memoryless (DM) case, we establish lower and upper bounds on channel capacity. The lower bound is obtained by a coding scheme at the relay that uses a combination of codeword splitting, Gel'fand-Pinsker binning, and decode-and-forward relaying. The upper bound improves upon that obtained by assuming that the channel state is available at the source, the relay, and the destination. For the Gaussian case, we also derive lower and upper bounds on the capacity. The lower bound is obtained by a coding scheme at the relay that uses a combination of codeword splitting, generalized dirty paper coding, and decode-and-forward relaying; the upper bound is also better than that obtained by assuming that the channel state is available at the source, the relay, and the destination. In the case of degraded Gaussian channels, the lower bound meets with the upper bound for some special cases, and, so, the capacity is obtained for these cases. Furthermore, in the Gaussian case, we also extend the results to the case in which the relay operates in a half-duplex mode.Comment: 62 pages. To appear in IEEE Transactions on Information Theor

On Cooperative Multiple Access Channels with Delayed CSI at Transmitters

We consider a cooperative two-user multiaccess channel in which the transmission is controlled by a random state. Both encoders transmit a common message and, one of the encoders also transmits an individual message. We study the capacity region of this communication model for different degrees of availability of the states at the encoders, causally or strictly causally. In the case in which the states are revealed causally to both encoders but not to the decoder we find an explicit characterization of the capacity region in the discrete memoryless case. In the case in which the states are revealed only strictly causally to both encoders, we establish inner and outer bounds on the capacity region. The outer bound is non-trivial, and has a relatively simple form. It has the advantage of incorporating only one auxiliary random variable. We then introduce a class of cooperative multiaccess channels with states known strictly causally at both encoders for which the inner and outer bounds agree; and so we characterize the capacity region for this class. In this class of channels, the state can be obtained as a deterministic function of the channel inputs and output. We also study the model in which the states are revealed, strictly causally, in an asymmetric manner, to only one encoder. Throughout the paper, we discuss a number of examples; and compute the capacity region of some of these examples. The results shed more light on the utility of delayed channel state information for increasing the capacity region of state-dependent cooperative multiaccess channels; and tie with recent progress in this framework.Comment: 54 pages. To appear in IEEE Transactions on Information Theory. arXiv admin note: substantial text overlap with arXiv:1201.327

Broadcast- and MAC-aware coding strategies for multiple user information embedding

Multiple user information embedding is concerned with embedding several messages into the same host signal. This paper presents several implementable dirty-paper-coding (DPC)-based schemes for multiple user information embedding, through emphasizing their tight relationship with conventional multiple user information theory. We first show that depending on the targeted application and on whether the different messages are asked to have different robustness and transparency requirements or not, multiple user information embedding parallels one of the well-known multiuser channels with state information available at the transmitter. The focus is on the Gaussian broadcast channel (GBC) and the Gaussian multiple access channel (GMAC). For each of these channels, two practically feasible transmission schemes are compared. The first approach consists in a straightforward-rather intuitive-superimposition of DPC schemes. The second consists in a joint design of these DPC schemes. This joint approach heavily relies on a recent work by Kim et aL in which the authors extend the single-user Costa's DPC to the multiple user case. The results in this paper extend the practical implementations quantization index modulation (QIM), distortion-compensated QIM (DC-QIM), and scalar Costa scheme (SCS) that have been originally conceived for one user to the multiple user case. After presenting the key features of the joint design within the context of structured scalar codebooks, we broaden our view to discuss the framework. of more general lattice-based (vector) codebooks and show that the gap to full performance can be bridged up using finite dimensional lattice codebooks. Performance evaluations, including bit error rates (BERs) and achievable rate region curves are provided for both methods, illustrating the improvements brought by a joint design

Broadcast- and MAC-Aware Coding Strategies for Multiple User Information Embedding

International audienceMultiple user information embedding is concerned with embedding several messages into the same host signal. This paper presents several implementable ''Dirty Paper Coding'' (DPC) based schemes for multiple user information embedding, through emphasizing their tight relationship with conventional multiple user information theory. We first show that depending on the targeted application and on whether the different messages are asked to have different robustness and transparency requirements or not, multiple user information embedding parallels one of the well-known multi-user channels with state information available at the transmitter. The focus is on the Gaussian Broadcast Channel (BC) and the Gaussian Multiple Access Channel (MAC). For each of these channels, two practically feasible transmission schemes are compared. The first approach consists in a straightforward- rather intuitive- superimposition of Dirty Paper Coding schemes. The second consists in a joint design of these Dirty Paper Coding schemes. This joint approach heavily relies on a recent work by Kim {\it et al.} in which the authors extend the single-user Costa's DPC to the multiple user case. The results in this paper extend the practical implementations QIM, DC-QIM and SCS that have been originally conceived for one user to the multiple user case. After presenting the key features of the joint design within the context of structured scalar codebooks, we broaden our view to discuss the framework of more general lattice-based (vector) codebooks and show that the gap to full performance can be bridged up using finite dimensional lattice codebooks. Performance evaluations, including Bit Error Rates and achievable rate region curves are provided for both methods, illustrating the improvements brought by a joint design

Channel with States at the Source

We consider a state-dependent three-terminal full-duplex relay channel with the channel states noncausally available at only the source, that is, neither at the relay nor at the destination. This model has application to cooperation over certain wireless channels with asymmetric cognition capabilities and cognitive interference relay channels. We establish lower bounds on the channel capacity for both discrete memoryless (DM) and Gaussian cases. For the DM case, the coding scheme for the lower bound uses techniques of rate-splitting at the source, decode-and-forward (DF) relaying, and a Gel'fand-Pinsker-like binning scheme. In this coding scheme, the relay decodes only partially the information sent by the source. Due to the rate-splitting, this lower bound is better than the one obtained by assuming that the relay decodes all the information from the source, that is, full-DF. For the Gaussian case, we consider channel models in which each of the relay node and the destination node experiences on its link an additive Gaussian outside interference. We first focus on the case in which the links to the relay and to the destination are corrupted by the same interference; and then we focus on the case of independent interferences. We also discuss a model with correlated interferences. For each of the first two models, we establish a lower bound on the channel capacity. The coding schemes for the lower bounds use techniques of dirty paper coding or carbon copying onto dirty paper, interference reduction at the source and decode-and-forward relaying. The results reveal that, by opposition to carbon copying onto dirty paper and its root Costa's initial dirty paper coding (DPC), it may be beneficial in our setup that the informed source uses a part of its power to partially cancel the effect of the interference so that the uninformed relay benefits from this cancellation, and so the source benefits in turn