A multi-user downlink system is considered, in which a base station (BS) serves multiple user equipments (UEs). It is assumed that, to improve the downlink performance, the UEs can exchange compressed versions of the ...
详细信息
A multi-user downlink system is considered, in which a base station (BS) serves multiple user equipments (UEs). It is assumed that, to improve the downlink performance, the UEs can exchange compressed versions of the downlink received signals on out-of-band device-to-device (D2D) communication links. Since the D2D links from a UE to the other UEs may have different channel qualities across the receiving UEs, this letter proposes a layered cooperation strategy which combines broadcast coding and successive refinement quantization techniques. With this approach, a UE can have a better reconstruction of the downlink signal of the transmitting UE than another UE with worse D2D channel quality. The problem of jointly optimizing the downlink precoding and layered UE cooperation strategies is tackled, and numerical results show the performance gains of the proposed layered scheme as compared to baseline schemes with no or single-layer cooperation.
In the uplink of cloud radio access networks, each base station (BS) compresses the received signal before transmission to the cloud decoder via capacity-limited backhaul links. A major issue in designing the transmis...
详细信息
In the uplink of cloud radio access networks, each base station (BS) compresses the received signal before transmission to the cloud decoder via capacity-limited backhaul links. A major issue in designing the transmission strategy at the mobile stations (MSs) and the compression strategies is the lack of channel state information (CSI) relative to the signal received by BSs in other cells. To tackle this problem, this paper proposes layered transmission and compression strategies that aim at opportunistically leveraging more advantageous channel conditions to neighboring BSs. A competitive robustness criterion is adopted, which enforces the constraint that a fraction of the rate that is achievable when the CSI is perfectly known to the MSs and the BS in the cell under study should be attained also in the absence of CSI. Under competitive robustness and backhaul capacity constraints, the problem is formulated as the minimization of the transmit power. Extensive numerical results confirm the effectiveness of the proposed approaches.
Two mobile users communicate with a central decoder via two base stations. Communication between the mobile users and the base stations takes place over a Gaussian interference channel with constant channel gains or q...
详细信息
Two mobile users communicate with a central decoder via two base stations. Communication between the mobile users and the base stations takes place over a Gaussian interference channel with constant channel gains or quasi-static fading. Instead, the base stations are connected to the central decoder through orthogonal finite-capacity links, whose connectivity is subject to random fluctuations. There is only receive-side channel state information, and hence the mobile users are unaware of the channel state and of the backhaul connectivity state, while the base stations know the fading coefficients but are uncertain about the backhaul links' state. The base stations are oblivious to the mobile users' codebooks and employ compress-and-forward to relay information to the central decoder. Upper and lower bounds are derived on average achievable throughput with respect to the prior distribution of the fading coefficients and of the backhaul links' states. The lower bounds are obtained by proposing strategies that combine the broadcast coding approach and layered distributed compression techniques. The upper bound is obtained by assuming that all the nodes know the channel state. Numerical results confirm the advantages of the proposed approach with respect to conventional non-robust strategies in both scenarios with and without fading.
A source communicates with a remote destination via a number of distributed relays. Communication from source to relays takes place over a (discrete or Gaussian) broadcast channel, while the relays are connected to th...
详细信息
A source communicates with a remote destination via a number of distributed relays. Communication from source to relays takes place over a (discrete or Gaussian) broadcast channel, while the relays are connected to the receiver via orthogonal finite-capacity links. Unbeknownst to the source and relays, link failures may occur between any subset of relays and the destination in a nonergodic fashion. Upper and lower bounds are derived on average achievable rates with respect to the prior distribution of the link failures, assuming the relays to be oblivious to the source code-book. The lower bounds are obtained by proposing strategies that combine the broadcast coding approach, previously investigated for quasi-static fading channels, and different robust distributed compression techniques. Numerical results show that lower and upper bounds are quite close over most operating regimes, and provide insight into optimal transmission design choices for the scenario at hand. Extension to the case of nonoblivious relays is also discussed.
暂无评论