  In the traditional mobile edge computing (MEC) system, the availability of
MEC services is greatly limited for the edge users of the cell due to serious
signal attenuation and inter-cell interference. User-centric MEC (UC-MEC) can
be seen as a promising solution to address this issue. In UC-MEC, each user is
served by a dedicated access point (AP) cluster enabled with MEC capability
instead of a single MEC server, however, at the expense of more energy
consumption and greater privacy risks. To achieve efficient and reliable
resource utilization with user-centric services, we propose an energy efficient
blockchain-enabled UC-MEC system where blockchain operations and resource
optimization are jointly performed. Firstly, we design a resource-aware,
reliable, replicated, redundant, and fault-tolerant (R-RAFT) consensus
mechanism to implement secure and reliable resource trading. Then, an
optimization framework based on alternating direction method of multipliers
(ADMM) is proposed to minimize the total energy consumed by wireless
transmission, consensus and task computing, where APs clustering, computing
resource allocation and bandwidth allocation are jointly considered. Simulation
results show superiority of the proposed UC-MEC system over reference schemes,
at most 33.96% reduction in the total delay and 48.77% reduction in the total
energy consumption.
