مخابره معکوس چند کاربره رمزی در شبکه دسترسی رادیو ابر (C-RAN)
Abstract
1- Introduction
2- System model
3- Rateless coded downlink transmission scheme
4- Joint optimization of the precoder and degree profiles
5- Simulation results
References
Abstract
In this paper, we propose a rateless coded transmission scheme for the multi-user downlink of Cloud Radio Access Network (C-RAN). In the network, multiple users are served by a cluster of remote radio heads (RRH), which are connected to the building baseband units (BBU) pool through the fronthaul links with limited capacity. In the proposed transmission scheme, the precoder and compressor at the BBU pool, and the decoding algorithm at the users are designed. To further improve the performance of the proposed transmission scheme, we investigate the joint optimization of the precoder and the degree profiles of the rateless codes implemented at the BBU pool to maximize the sum throughput of the network. Explicitly, the optimization problem is formulated according to the extrinsic information transfer (EXIT) function analysis on the decoding process at the users. We give simulation results on the BER and throughput performance achieved by the proposed rateless coded transmission scheme, which verify the effectiveness of the joint optimization on the degree profiles and the precoder.
Introduction
The trends of the next generation communication system are heterogeneous network and smaller cellular [1], which lead to the issues of severe inter-cell interference and cell association, and requirements for more sophisticated multi-cell coordination [2]. Cloud Radio Access Network (C-RAN) is a revolutionary mobile network architecture and has the potential to solve the above challenges [1, 3]. In C-RAN, the baseband processing units are migrated from the base stations to the building baseband units (BBU) pool where the signals from/ to multiple cells are jointly processed. Therefore, inter-cell interference can be effectively eliminated and the network throughput can be improved. Moreover, the C-RAN is able to adapt to non-uniform traffic and make a rational use of resources [4]. Due to the fact that the expansion of C-RAN only requires the installation of new remote radio heads (RRH) and fronthaul links, it becomes possible for mobile operators to reduce the cost of network construction and upgrade [5]. In this work, we consider the multi-user downlink scenario in C-RAN. The BBU pool performs multi-antenna precoding on the messages intended for the users which are then compressed and delivered to each RRH via the capacity-limited fronthaul links. The resource management, multi-antenna precoding optimization and signal compression design in CRAN and distributed relay/distributed antenna systems have been widely studied, e.g., in [6–25]. (Note that C-RAN has an intrinsic relation to distributed relay/antenna systems). Authors in [6–9] investigated the criterion for the optimization of the precoding matrix which assume the knowledge of global channel states information (CSI). The authors in [10–12] studied the compression scheme with the aim at lowering the effect of the compression noise which exploits the correlations of signals for RRHs. The precoding design for relay and multi-antenna systems was investigated in [13, 14].