When multiple devices seek to offload computational tasks to their access point, the nature of the multiple access scheme plays a critical role in the system performance. For a system with heterogeneous tasks, we adopt a time-slotted signaling architecture in which different numbers of devices transmit in each slot, subject to individual power constraints. We consider the problem of jointly selecting the devices that will offload, along with optimizing their communication resources (their powers and rates in each time slot, and the time slot lengths) so as to minimize the a weighted sum of the energy expended by the devices. We employ a customized tree search algorithm for the offloading decisions in which a resource allocation problem is solved at each node. For time-division multiple access (TDMA) and “rate optimal” multiple access, we obtain reduced-dimension convex formulations of the resource allocation problem. For non-orthogonal multiple access (NOMA) with independent decoding (ID) or fixed-order sequential decoding (FOSD) we show that the resource allocation problem has a difference-of-convex structure and we develop a successive convex approximation algorithm with feasible point pursuit. Furthermore, for the FOSD scheme we obtain a closed-form expression that provides the optimal decoding order when it is feasible, and efficient algorithms for finding a good decoding order when it is not. Our results capture the inherent tradeoffs between the complexity of a multiple access scheme (and its resource allocation algorithm), and its performance in the computation offloading application.

中文翻译：

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$K$ 用户案例中的多时隙多路访问二进制计算卸载


当多个设备寻求将计算任务卸载到其接入点时，多路访问方案的性质对系统性能起着至关重要的作用。对于具有异构任务的系统，我们采用时隙信令架构，其中不同数量的设备在每个时隙中进行传输，但受到各自的功率限制。我们考虑联合选择要卸载的设备的问题，同时优化它们的通信资源（每个时隙中的功率和速率以及时隙长度），以最小化设备消耗的能量的加权和。我们采用定制的树搜索算法来进行卸载决策，其中在每个节点上解决资源分配问题。对于时分多址（TDMA）和“速率最优”多址，我们获得了资源分配问题的降维凸公式。对于具有独立解码（ID）或固定顺序顺序解码（FOSD）的非正交多址（NOMA），我们证明资源分配问题具有凸差结构，并且我们开发了一种具有可行点的逐次凸逼近算法追求。此外，对于 FOSD 方案，我们获得了一个封闭式表达式，该表达式在可行时提供最佳解码顺序，在不可行时提供有效算法来找到良好的解码顺序。我们的结果捕捉了多路访问方案（及其资源分配算法）的复杂性与其在计算卸载应用程序中的性能之间的固有权衡。