Private Uplink Communication in C-RAN With Untrusted Radios

In this work, we study the uplink (UL) of a cloud radio access network (C-RAN), where the central processing unit (CU) utilizes remote radio units (RU)s belonging to the same operator, i.e., the trusted RUs, as well as the RUs belonging to other operators or private owners, i.e., the untrusted RUs. In order to preserve information privacy against the untrusted RUs, the trusted RUs are enabled with full-duplex (FD) capability and transmit a jamming signal towards the exotic RUs, while receiving and forwarding UL signal to the CU. Note that the transmitted jamming signal degrades the decoding capability at the untrusted RUs, however, it can be later subtracted from the UL communication as it is apriori known by the CU. An optimization problem is then formulated to maximize the sum uplink private information rate by jointly designing the fronthaul compression, as well as the information and jamming transmission strategies. Due to the intractability of the resulting mathematical problem, an iterative solution is proposed with convergence to a point satisfying the Karush-Kuhn-Tucker (KKT) optimality conditions. Numerical simulations illustrate a notable gain obtained via the proposed sharing mechanism under the consideration of information privacy.