Abstract
Cloud radio access network (C-RAN) is a promising technology for the Internet of Things (IoT). In C-RAN, the remote radio head (RRH) and baseband unit (BBU) in the conventional base station are separated, and each BBU is backward centralized into a virtual BBU pool. In this paper, we consider the uplink transmission for the two-user C-RAN with two RRHs under a block fading channel. A novel rateless coded transmission scheme is designed. During each transmission round, each user keeps transmitting to the RRHs using Raptor code until the BBU pool feeds back an acknowledgement (ACK). With the proposed scheme, each user does not require the instant channel state information, which greatly reduces the system overhead. We also design the quantizer at the RRHs and the iterative multi-user detector and decoder at the BBU pool, based on the belief propagation (BP) algorithm. For the Raptor code applied at each user, we optimize the corresponding output node degree profile, based on extrinsic information transfer (EXIT) analysis for the decoding process at the BBU pool. The resulted degree profiles are optimal in an average sense under all possible channel states. The simulation results show that the rateless coded transmission scheme with the optimized degree profiles outperforms the benchmark degree profile in both bit error rate and average system throughput. Moreover, the achieved performance is close to the theoretical limit.
Highlights
The Internet of Things (IoT) is the trend of the generation of communication networks
In cloud radio access network (C-RAN), each remote radio head (RRH) is located closer to the user, while each baseband unit (BBU) is backward centralized into a virtual BBU pool
In [37], we considered Raptor code for the multi-user downlink of C-RAN, where both the precoder and the degree profile of Raptor code at the BBU pool are jointly optimized under an additive white Gaussian noise (AWGN) channel
Summary
The Internet of Things (IoT) is the trend of the generation of communication networks. The large amount of data generated by sensors and devices will create huge network traffic, which brings great challenges to the traditional wireless access networks. It has been noted in [3,4,5,6] that cloud radio access network (C-RAN) is a promising wireless network architecture which can adapt to the rapidly growing IoT traffic and improve the Quality of Service (QoS). Since joint signal processing for multiple RRHs can be realized at the BBU pool, C-RAN can achieve a considerably higher spectrum efficiency compared with the traditional cellular networks, and C-RAN can improve network resource utilization, reduce interference, and reduce energy consumption and overall hardware costs [7,8]
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