reless Communication Networks, First Edition. Haijian Sun, Rose Qingyang Hu, and Yi Qian. © 2024 John Wiley & Sons Ltd. Published 2024 by John Wiley & Sons Ltd. 8 Toward Green MEC Offloading with Security Enhancement System Model We consider a typical MEC system with one server and K UEs, the MEC system also mounts a wireless access point (AP) to communicate with other devices. We assume that both the AP and the UEs have a single antenna [177]. There also exists a malicious leavesdrop- per that tries to intercept confidential information. Denoted as Eve, the leavesdropper only has one antenna. At the beginning of a reference time ts, each UE has a large number of computation-intensive tasks to be computed, because of the limited computation resources at UE, due to either device size or power constraints or both, UEs cannot finish their tasks before te. For timely processing, we require te-tst Hence, UEs will offload part of their computation bits to the MEC server, where a more powerful processing can be supported. In general, each UE supports the following operation modes (Figure 8.1). 8.2.1 Secure Offloading In the presence of Eve, each UE must securely offload part of their task to the MEC server. We assume the channel between each UE and the AP in MEC server follows block static model where it remains the same within the block time T1 (T1 T) but varies from one block to another. We denote the channel between UE k and the AP be hk, where hk=lkho is the joint effect of large-scale lk and small-scale ho fading. Similarly, the channel between each UE and the Eve is gk We consider the active eavesdropper scenario, where the Eve is also a user in the system, its listening and transmitting can be captured by UEs (from authentication, etc.). Therefore in this setting, we assume the channel between UE k and the Eve can be perfectly estimated, i.e. gk can be perfectly estimated. Similar setting can also be found in [208]. Let the number of total bits be computed for each UE be L; since each UE cannot finish the calcula