IEEE TRANSACTIONS ON COMPUTERS, VOL. XX, NO. X, JANUARY XXXX
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H I RL: Hierarchical Reinforcement Learning for Coordinated Resource Management in Heterogeneous Edge Computing
arXiv:2605.10443v1 [cs.DC] 11 May 2026
Jianyong Zhu, Hao Chen, Juan Zhang, Member, IEEE, Fangda Guo, Member, IEEE, Albert Y. Zomaya, Fellow, IEEE, Renyu Yang, Member, IEEE
Abstract—Edge computing faces unprecedented resource orchestration challenges from multi-dimensional heterogeneity across device architectures, diverse task requirements in CPUintensive, GPU-intensive, I/O-intensive, and dynamic network conditions. The edge environments demand real-time task processing within strict energy budgets, yet conventional approaches struggle with mixed continuous-discrete optimization while meeting deadline and energy constraints. This paper presents H I RL, a hierarchical reinforcement learning framework that decomposes complex resource orchestration into coordinated power control and task allocation decisions. Our approach separates continuous power management using the Twin Delayed Deep Deterministic Policy Gradient (TD3) and discrete task placement using Double Deep Q-Network (DDQN), unified through a coordination engine with five-dimensional queue state representation. We propose a heterogeneous assessment of resource compatibility with deadline-oriented prioritization and failure-penalized adaptive sampling to enhance decision quality under resource constraints. To improve practical applicability, the framework models comprehensive system dynamics including device mobility, queue congestion patterns, infrastructure heterogeneity, and priority-sensitive scheduling demands. Experimental results show that H I RL achieves effective latency-energy trade-offs with 28% latency reduction compared to Single-DDQN and maintains nearly 100% task completion rates under all load conditions. Compared to baseline algorithms, H I RL reduces energy consumption by up to 51% under low load while achieving 24% better latency performance than static optimization approaches under high load, establishing effective resource orchestration in heterogeneous edge environments. Index Terms—Heterogeneous Resource Orchestration, Hierarchical Reinforcement Learning, GPU-aware, Deadline Constraints, Task Completion Guarantees.
Received XXX; revised XXX; accepted XXX. Date of publication XXX; date of current version XXX.This work was supported in part by the Hebei Provincial Natural Science Foundation under Grant F2023502002 and in part by the Fundamental Research Funds for the Central Universities under Grant 2025MS153. (Corresponding author: Renyu Yang) J. Zhu is with the Yanzhao Electric Power Laboratory of North China Electric Power University, and Hebei Key Laboratory of Knowledge Computing for Energy & Power, Baoding 071000, China (e-mail: [email protected]). H. Chen is with the Department of Computer, North China Electric Power University, and Engineering Research Center of Intelligent Computing for Complex Energy Systems, Ministry of Education, Baoding 071000, China (email: [email protected]). J. Zhang is with the James Watt School of Engineering, University of Glasgow, Glasgow G12 8QQ, U.K. (e-mail: [email protected]). F. Guo is with the State Key Laboratory of AI Safety, Institute of Computing Technology, Chinese Academy of Sciences, Beijing 100190, China (Email: [email protected]). Albert Zomaya is with the University of Sydney, Australia. E-mail: [email protected]. R. Yang is with the School of Software, Beihang University, Beijing 100191, China (e-mail: [email protected]).
Heterogeneous Servers: Different capabilities & loads Mobile Constraints: Limited battery & GPU
Task Sources: • Video Analysis • Route Planning
Smart Car ( Limited GPU )
RSU-C Tesla H00 (Load: 30%)
5G Network Wireless Transmission
RSU-B Tesla A100 (Load: 80%)
Smart application Emergency Detection
RSU-C Tesla V100 (Load: 45%)
Traffic Optimization
Fig. 1. Intelligent transportation scenario: Smart vehicle offloads video analysis and route planning tasks to heterogeneous edge servers.
I. I NTRODUCTION
E
DGE computing addresses computational demands of IoT devices with limited resources, dynamic network conditions, and strict energy constraints, particularly in mobile edge computing (MEC) scenarios [1], [2]. The environments face resource orchestration challenges from infrastructure heterogeneity—edge servers and mobile devices differ in CPU/GPU configurations and storage capacities [3], [4]—and workload heterogeneity spanning CPU-intensive tasks, GPUaccelerated applications, and I/O-intensive transfers [5], [6]. Device mobility further complicates scheduling through timevarying network conditions [7], [8]. Ineffective resource management leads to deadline violations, energy waste, and task failures. Current approaches face three limitations. First, independent handling of power control and task allocation prevents joint optimization—existing methods either fix transmission power during task allocation [9], [10] or separate frequency scaling from offloading decisions [4], [11], missing energy-latency tradeoffs. Second, treating GPU-intensive and CPU-intensive tasks uniformly causes resource mismatches: GPU tasks on CPU-only servers fail, while CPU tasks on GPU servers waste resources [12], [13]. Third, optimizing energy, latency, or completion rates separately creates conflicts—aggressive offloading reduces local energy but increases transmission and congestion costs, worsening latency and deadline misses [14], [15]. Consider a computing scenario in Fig. 1. A vehicle offloads GPU-intensive video analysis and CPU-intensive route planning to heterogeneous servers (H100/A100/V100) under adjustable transmission power (up to 3W) with emergency deadlines. Independent decisions fail: high power without GPU availability wastes energy; GPU tasks on incompatible
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servers violate deadlines. Effective management requires hierarchical coordination with GPU-aware matching. We present H I RL, a hierarchical reinforcement learning framework for resource orchestration in heterogeneous MEC environments. The framework addresses mixed continuousdiscrete optimization through hierarchical decomposition while maintaining cross-tier coordination. We design a dualpipeline CPU/GPU computational model to represent heterogeneous resource requirements. The two-tier architecture separates continuous power control (upper tier TD3 with five-dimensional queue state managing CPU frequency and transmission power) from discrete task allocation (lower tier DDQN with GPU-aware state design for placement across heterogeneous servers), unified through a coordination engine implementing a three-stage decision pipeline. We introduce deadline-oriented queue management and failure-penalized experience replay to handle real-time constraints and accelerate learning from resource violations. We evaluate H I RL across production-scale heterogeneous deployments with 35 mobile devices and 5 edge servers under controlled load variations. Experimental results show 28% latency reduction compared to Single-DDQN while maintaining 98%+ task completion rates. Energy consumption decreases by 51% under low load, and latency improves by 24% over static optimization under high load. Ablation studies confirm hierarchical coordination and GPU-aware compatibility assessment contribute 49-82% of these gains, while disabling failurepenalized learning causes system collapse with completion rates dropping to 62%. The main contributions include: • Hierarchical framework with coordinated CPU/GPU dual-pipeline modeling for heterogeneous MEC environments. • Compatibility-aware task allocation mechanism with GPU-resource matching across heterogeneous servers. • Deadline-oriented queue optimization and failurepenalized sampling for constraint handling. The remainder is organized as follows: Section II presents framework and modeling; Sections III and IV detail TD3 power control and DDQN task allocation; Section V provides experimental evaluation; Section VI reviews related work; Section VII concludes. Source codes and data are available at https://github.com/ch-ncepu/HIRL. II. H IERARCHICAL F RAMEWORK AND S YSTEM M ODELING A. Motivation Heterogeneous MEC environments present resource orchestration challenges coupling continuous power control and discrete task placement under stringent deadlines. In the vehicular scenario of Fig. 1, emergency video analysis requires 4 GB GPU memory and 2048 CUDA cores within 200 ms, whereas route planning demands 50 M CPU cycles with negligible GPU use. The vehicle adjusts transmission power (0.1–3 W) and CPU frequency (0.8–2.4 GHz) while selecting among heterogeneous servers (H100/A100/V100) under LTE-V2X constraints.
Input 5D Queue States
Stage 1 TD3 Upper Tier Power Control
Discrete Server assignment
Information hub
Power Decisions
Stage 2 Coordination Engine
State Update & Synchronization
Stage 3 DDQN Lower Tier Task Allocation Allocation Decisions
System States Input Environment State Collection
Policy Updates
Feedback Learning Update
Performance Metrics
Execution Task Processing& Monitoring
Fig. 2. Workflow of H I RL: Synchronized three-stage decision pipeline with closed-loop feedback.
This scenario exposes key optimization challenges. The joint decision space combines continuous control with discrete selection: for M devices choosing among N servers, the space grows as O((N + 1)M × R2M ). Discretizing power into 10 frequency and 10 power levels yields 100 combinations per device, reducing precision. Relaxing discrete choices to continuous variables produces non-convex landscapes where gradient-based optimization becomes unstable. Power decisions and task placement are dynamically interdependent. Increasing transmission power from 0.5W to i , enabling GPU execution 2W shortens offloading latency Dtx for latency-critical tasks. Conversely, frequency scaling alters local processing: a task missing its deadline at 0.8GHz may complete locally at 2.4GHz with lower energy cost. Decoupled optimization breaks these dependencies—power control without task awareness may select conservative transmission, causing deadline violations, while allocation without power constraints may offload to distant servers, causing excessive latency. Task heterogeneity introduces coupled queue dynamics across heterogeneous resources. GPU-intensive video analysis, CPU-bound route planning, and I/O-driven transfers create distinct workload patterns. We model these interactions through five queue dimensions: local CPU, local GPU, wireless transmission, server CPU, and server GPU. Queue backlogs evolve differently—CPU queues grow steadily with general arrivals, GPU queues surge with bursty vision tasks, transmission queues fluctuate with channel conditions. Joint optimization of these interdependent queues with power-allocation decisions requires learning over high-dimensional state spaces, causing sample inefficiency in dynamic environments. We address these challenges through a hierarchically coordinated framework (Fig. 2). The upper tier employs TD3 for continuous power control, adjusting (flt , pt ) based on queue states qt and channel gains g t . The lower tier uses DDQN for discrete tasks offloading, integrating GPU compatibility and transmission rate updates. A three-stage pipeline links the tiers: Stage 1 determines power settings, Stage 2 updates transmission rates and queue states, Stage 3 finalizes task allocation. This design decouples optimization objectives while preserving inter-tier dependencies through shared queues. B. Problem Formulation Consider the vehicle scenario from Fig. 1. GPU-intensive video analysis requires substantial CUDA cores and memory, while CPU-intensive route planning demands computational
ZHU et al.: HIRL: HIERARCHICAL REINFORCEMENT LEARNING FOR COORDINATED RESOURCE MANAGEMENT IN HETEROGENEOUS EDGE COMPUTING 3
TABLE I N OTATION Symbol M, N qt flt , pt gt , rt ρji Ti λ i Dtot , E i
Description Mobile devices, edge servers Five-dimensional queue state CPU frequency, transmission power Channel gain, transmission rate GPU compatibility score Task attributes (bi , si , ci , ddli , ni , mi , s gpui , tcreate ) Energy-latency tradeoff weight Task latency, energy
cycles. Both scenarios face stringent emergency deadlines and constrained transmission power (2-3W), and thus come with a resource orchestration problem – coordinating power management with task placement across M mobile devices and N edge servers (M = 35, N = 5 in our evaluation) to process three task categories τ = {tCPU , tGPU , tIO }. Each task i has attributes (bi , si , ci , ddli , ni , mi , s gpui , tcreate ) representing the priority, data size, CPU cycles, deadline, required CUDA cores, GPU memory, and computational load and the creation time of the task. The execution cost (Eq. 1) strike a balance between latency and energy. i costi = λbi Dtot + (1 − λ)E i ,
(1)
where bi amplifies the weight for critical tasks and λ ∈ i aggregates [0, 1] controls the tradeoff. The total latency Dtot queuing latencies across local/transmission/server stages and CPU-GPU pipeline execution. The energy E i combines local i processing κ(flt )2 ci , transmission pt Dtx , and server-side GPU consumption. The optimization objective (Eq. 2) minimizes long-term execution costs through coordinated power control and task allocation decisions. T 1 XX min lim costi , T →∞ T t=0 i∈Γt
s.t.
j 0 ≤ ftj ≤ fmax , 0 ≤ pjt ≤ pjmax , i Dtot ≤ ddli ,
X i∈Aj
∀j, t,
(2)
∀i,
j ni ≤ Ngpu ,
X
j mi ≤ Mgpu ,
∀j,
i∈Aj
where Γt denotes the set of tasks arriving at time t, Aj represents the tasks assigned to server j, and GPU-related constraints are enforced at the server level through the availj j able CUDA cores Ngpu and memory capacity Mgpu . The resulting resource orchestration problem involves tightly coupled continuous decisions, including CPU frequency allocation ftj and transmission power control pjt , together with discrete decisions on task placement between local execution and edge servers. The proposed hierarchical framework addresses this mixed-integer optimization by decomposing it into coordinated subproblems, which are jointly optimized in accordance with Eq. 2. Table I summarizes all notations used throughout the framework. C. Hierarchical Decision Framework The hierarchical architecture decomposes the hybrid optimization problem (Eq. 2) into coordinated submodules. The
upper tier applies TD3 for continuous power control (ftj , pjt ), mitigating value overestimation through twin critics and delayed updates. The lower tier adopts DDQN for discrete task placement, decoupling action selection from value evaluation for GPU-heterogeneous server choices. Both tiers interact through a coordination engine synchronizing decisions via a three-stage pipeline (Fig. 2). At each time slot t (τ = 1s), the system executes synchronized operations across all M devices. The upper tier first updates the five-dimensional queue state qt , capturing local CPU/GPU, transmission, and server CPU/GPU backlogs, while measuring channel gains g t to generate frequency–power pairs (ftj , pjt ). The coordination engine then updates transmission rates rt based on the new power settings and channel conditions, normalizes queue states relative to current capacities, and forwards the updated states to the lower tier. The lower tier determines server placements for new tasks according to GPU compatibility and deadline urgency. Task dispatch follows deadline-oriented sorting, with execution outcomes generating reward signals rpt and roi for policy refinement. The coordination engine maintains consistency across tiers through three mechanisms via Eq. 3: Shared State Representation. Both tiers operate on a synchronized five-dimensional queue vector qt (Eq. 4), providing a common view of resource utilization across heterogeneous components. Sequential Decision Pipeline. The three-stage structure creates explicit tier dependencies: Stage 1: (f t , pt ) = πp (qt , g t ), Stage 2: rt = Update(pt , g t ),
q̂t = Normalize(qt , f t , rt ),
Stage 3: aio = πo (q̂t , f t , pt , Ti , rt ),
(3) where TD3 policy πp tunes frequency-power pairs; Stage 2 updates transmission rates and normalized queues; DDQN policy πo selects task placements using refreshed states. The pipeline maintains causal consistency—power control directly determines feasible allocation boundaries. Bidirectional Feedback. Execution outcomes are fed back via coordinated rewards to jointly refine both policies and align them with global objectives (Sections III and IV). D. State Representation The framework uses a five-dimensional queue state (Eq. 4) tracking resource utilization across system components: t t t t t qt = [qlc , qtx , qlg , qsc , qsg ],
(4)
where subscripts lc, sc denote local/server CPU queues, lg, sg represent local/server GPU queues, and tx indicates transmission queue. Each queue accumulates workload from waiting t tasks, where tasks j atPtime slot P Qj represents P in queue t t t t: qlc = w , q = s , q t sc = i∈Qttx i i∈Qtsc wi , P P i∈Qlc i tx t t qlg = i∈Qtsg s gpui , with wi = i∈Qtlg s gpui , qsg = scpu,i × ci denoting required CPU cycles and s gpui denoting GPU computational load (FLOPS). Queue evolution couples
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upper-tier power control with lower-tier task allocation through task arrivals and processing departures. The system load metric (Eq. 5) integrates queue backlogs with real-time utilization: ωq X Lt = tanh(q̂jt ) + ωu · utcpu + ωg · utgpu , (5) 5 j∈Q
where Q = {lc, tx, lg, sc, sg} and weights ωq , ωu , ωg balance queue backlog with CPU/GPU utilization. Queue normalization scales states relative to processing capacity through Eq. 6: q̂jt =
qjt , fjt · τ
j ∈ {lc, tx, lg, sc, sg},
(6)
where fjt denotes processing rate for queue j and τ is time slot duration. Values q̂jt > 1 indicate backlog exceeding single-slot capacity. Tier-Specific States. The upper tier observes state vector Sp defined in Eq. 7: Sp = [qt , g t , fmax , pmax ],
(7)
where g t denotes channel gain and fmax , pmax denote capability bounds. The lower tier uses extended state So (Eq. 8): t t t t t So = qlc , qtx , qlg , qsc , qsg , f t , pt , g t , gpuf , gpunum , gpubw , gpupwr , l,t s,t s,t ul,t cpu , ugpu , ucpu , ugpu ,
(8)
Ti (bi , si , ci , ddli , ni , mi , s gpui , tcreate ) , where GPU specifications (gpuf , gpunum , gpubw , gpupwr ) represent frequency, CUDA cores, bandwidth, and power l,t s,t s,t consumption; utilization metrics (ul,t cpu , ugpu , ucpu , ugpu ) track local/server CPU/GPU usage; task tuple T (·) contains priority, size, complexity, deadline, GPU requirements, and creation timestamp. DeDetails are in Sections III and IV. Alg. 1 integrates the hierarchical framework through synchronized three-stage operations per time slot. Time-slot synchronization maintains consistent states across tiers. Detailed reward formulations are in Sections III and IV. III. P OWER C ONTROL WITH T WIN D ELAYED D EEP D ETERMINISTIC P OLICY G RADIENT This section presents the upper-tier TD3-based power control mechanism within the hierarchical framework in Section II, including problem formulation, state-action representation, reward design, and implementation details. A. TD3 for Power Control in Heterogeneous Environments The upper tier employs TD3 to optimize continuous power control under heterogeneous MEC settings. TD3 incorporates twin critics to mitigate value overestimation, delayed policy updates to suppress oscillations, and target smoothing to improve training stability across diverse device capabilities and fluctuating network conditions. Power Control Formulation. TD3 operates on state Spt (Eq. 7) and action space Ap = [flt , pt ] with device-specific PT constraints, optimizing maxπp E[limT →∞ T1 t=0 rpt ], where πp denotes the power control policy and rpt is defined in Eq. 11.
Algorithm 1 H I RL Hierarchical Coordination. Input: Devices M, servers N , TD3 agent πp , DDQN agent πo 1: t ← 1 2: while t ≤ T do 3: // Stage 1: Power Control 4: for j ∈ M do 5: Collect queue state: qtj , measure channel gain: gjt 6: Execute power control: (flt , pt ) ← πp (qtj , gjt ) 7: end for 8: // Stage 2: State Synchronization 9: Update transmission rates: rt ← ComputeRate(pt , g t ) 10: Normalize queue states using Eq. 6 11: Update load metric Lt using Eq. 5 12: // Stage 3: Task Allocation 13: for each arriving task i on device j do 14: Extract task attributes: Ti 15: Compute compatibility: ρki for k ∈ N ∪ {0} 16: Execute allocation: aio ← πo (qtj , flt , pt , Ti , rt ) 17: Dispatch task to selected queue 18: end for 19: // Execution and Learning 20: Process tasks with deadline prioritization 21: Collect outcomes: completion status, latencies, energy 22: Calculate rewards: rpt (Eq. 11), roi (Eq. 12) 23: Store experiences with failure-aware prioritization 24: Update TD3 and DDQN networks 25: t←t+1 26: end while
B. State-Action Representation and Normalization State Space Components. The power control agent processes state space Spt (Eq. 7). Channel gain follows the pathloss model in Eq. 9: γ d0 t , (9) g = G0 dt where G0 is the gain constant, dt denotes the distance, and γ is the path-loss exponent affecting transmission rates in Stage 2 (Eq. 3). Synchronized State Management: State updates are synchronized at time-slot boundaries, such that power-control outputs from Stage 1 are immediately applied to Stage 3 allocation, ensuring TD3 and DDQN operate on a consistent system state. 1) Continuous Action Space Formulation: The power control agent outputs continuous actions within a constrained space as defined in Eq. 10: Ap = [flt , pt ],
flt ∈ [0, fmax ],
pt ∈ [0, pmax ],
(10)
where flt denotes the local CPU frequency (Hz) and pt the transmission power (W). These actions implement Stage 1 (Eq. 3): flt determines local processing capacity reflected in queue states, while pt determines the communication rate rt in Stage 2, both of which are included in the task allocation agent’s state. State Normalization. Queue states are normalized followt t ing Eq. 6: q̂lc = qlc /(flt · τ ) to ensure scale-invariant learning across varying device configurations and workload intensities. C. Reward Function and Training Optimization The hierarchical framework aligns both tiers toward global objectives through coordinated reward structures. The upper
ZHU et al.: HIRL: HIERARCHICAL REINFORCEMENT LEARNING FOR COORDINATED RESOURCE MANAGEMENT IN HETEROGENEOUS EDGE COMPUTING 5
tier optimizes system-level performance (Eq. 11): t rpt = Rcomplete − λe · E t ,
(11)
t i where Rcomplete = i∈C t bi Isuccess sums priority-weighted i completed tasks (Isuccess ∈ {0, 1}), and E t aggregates CPU and transmission energy weighted by λe , assigning higher priority to task completion than energy reduction. The lower tier optimizes individual task execution via Eq. 12:
P
i roi = −(λbi Dtot + (1 − λ)E i ) − α · Ifi ail ,
(12)
where the first term matches Eq. 1, ensuring tier alignment. Penalty α discourages constraint violations indicated by Ifi ail ∈ {0, 1} through GPU compatibility checks. Both rei wards share metrics (Dtot , E i , completion status), maintaining feedback consistency along the pipeline (Eq. 3). 1) Energy-Performance Trade-off Optimization: The TD3 agent implements the coordinated reward from Eq. 11 with energy computation following Eq. 13: st , E t = k(flt )2 τ + pt tx rt
(13)
where k denotes the effective switching capacitance, (flt )2 reflects the quadratic CPU frequency–power relationship, and transmission energy depends on data size sttx and communication duration. The fixed coefficient λe = 0.5 in Eq. 11 assigns higher weight to task completion, yielding over 98% completion rates; during training, TD3 accordingly allocates power aggressively for high-priority, deadline-critical tasks and conservatively under low load, driven solely by the reward structure, without explicit state-dependent weighting. 2) Failure-Aware Experience Prioritization: Our training method prioritizes experiences from critical scenarios to accelerate learning in challenging situations. The prioritization weight combines temporal difference error with failure indicators as shown in Eq. 14: Wi = |T Di | · (1 + γf ail · Ifi ail ),
(14)
where |T Di | denotes the temporal difference error magnitude, Ifi ail indicates task failures, and γf ail amplifies critical scenarios. Prioritization in Eq. 14 guides TD3 to focus on systemstress cases induced by power control actions in Eq. 10. D. Network Architecture and Implementation The TD3 implementation for power control uses network architectures and training strategies for dynamic heterogeneous mobile edge environments. 1) Actor-Critic Network Design: The TD3 framework consists of an actor network and twin critic networks with target stabilization for continuous power control. The actor µϕ (s) maps the six-dimensional state Spt to the two-dimensional action at = [flt , ptl ] using a tanh output layer, followed by reverse normalization based on state-provided bounds (fmax , pmax ) to scale actions from [−1, 1] to device-specific ranges. Through this scaling mechanism, a shared TD3 policy is applied across heterogeneous devices.
Complementing the actor, the twin critics Qθ1 (s, a) and Qθ2 (s, a) adopt conservative value estimation, Qtarget = min(Qθ1′ (s′ , ã′ ), Qθ2′ (s′ , ã′ )), where ã′ denotes the smoothed target action, stabilizing value evaluation under mobile edge uncertainty. 2) Adaptive Training Mechanisms: The TD3 implementation incorporates two adaptations for heterogeneous mobile edge environments. First, load-adaptive exploration noise is applied as σ t = σbase (1 + αLt ), where the load metric Lt ∈ [0, 1] is defined in Eq. 5 and α controls adaptation sensitivity. This mechanism promotes higher exploration under low-load conditions while encouraging conservative behavior during high-load periods. Second, the experience replay module applies failureaware prioritization defined in Eq. 14, emphasizing critical or constraint-violating samples. Together with adaptive exploration noise, this design supports a balanced trade-off between stability and responsiveness under heterogeneous MEC conditions. 3) Network Update Mechanism: Training follows a coordinated update schedule aligned with the synchronous timeslot framework. The critic networks are updated at each time slot using temporal difference learning with target smoothing, while the actor network applies delayed updatesθµ ← θµ + αµ ∇θµ Qθ1 (s, µθµ (s)) every d time slots to enhance policy stability. Target networks are updated via Polyak averaging with parameter τ , ensuring gradual policy evolution across heterogeneous device configurations and dynamic workload conditions. IV. TASK A LLOCATION WITH D OUBLE D EEP Q-N ETWORK This section presents the lower-tier DDQN-based task allocation mechanism coordinating with the upper-tier power control. It formulates the discrete task allocation problem, describes GPU-aware state–action design, and introduces deadline-oriented queue management with adaptive experience replay. The interaction between DDQN and TD3 within the three-stage execution pipeline is also explained. A. Double Deep Q-Network for Task Allocation The lower tier employs DDQN for discrete task placement across heterogeneous resources. By decoupling action selection from evaluation, DDQN mitigates value overestimation through target value Qtarget = r + γQθ′ (s′ , arg maxa′ Qθ (s′ , a′ )), where Qθ selects optimal actions and Qθ′ evaluates values, avoiding overestimation when a single network handles both roles. This separation proves advantageous in heterogeneous MEC environments where server diversity and fluctuating loads challenge estimation stability. 1) DDQN Implementation in Hierarchical Framework: DDQN operates as Stage 3 in the coordination pipeline (Eq. 3), processing power-updated states with failure penalty rewards (Eq. 12). Load-aware exploration follows Eq. 15: ϵt = ϵmin + (ϵmax − ϵmin ) · exp(−β · Lt ),
(15)
where β > 0 controls adaptation sensitivity based on load metric Lt (Eq. 5). During high-load periods (Lt → 1),
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exploration decreases to favor proven strategies, ensuring stability. Low-load conditions enable increased exploration to discover improved policies. This balances exploitationexploration based on real-time system stress. B. State Space Design and GPU-Aware Mechanisms 1) Multi-dimensional State Representation: The DDQN agent utilizes the state space from Eq. 8 established in Section II, incorporating the five-dimensional queue state from Eq. 4 with power control outputs and task attributes. t • Five-dimensional queue states q (Eq. 4) t t • Power control decisions (fl , p ) from Stage 1 (Eq. 3) • Task attributes Ti (bi , si , ci , ddli , ni , mi , s gpui , tcreate ) including GPU requirements t • Network conditions g and GPU specifications (frequency, cores, bandwidth, power) • Real-time CPU/GPU utilization metrics (local and server) • Creation timestamps for latency tracking To manage state dimensionality, we apply normalization from Eq. 6, providing scale-invariant indicators of resource saturation for consistent policy learning. 2) GPU-Aware Resource Matching: Resource compatibility assessment employs GPU-aware scoring mechanisms to ensure feasible task-resource matching. The compatibility score is defined as follows: ! mi scpu,i ni j , j , j , (16) ρi = min j Mcpu Ngpu Mgpu where ρji ∈ [0, 1] measures compatibility between task i and execution location j based on CPU memory requirements, GPU cores, and GPU memory capacity. Values closer to 1 indicate higher resource compatibility, enabling the DDQN agent to prioritize feasible allocations and filter infeasible actions before Q-value computation. The DDQN agent employs GPU-aware compatibility scoring (Eq. 16) for real-time feasibility filtering without maintaining high-dimensional server representations, supporting scalable task allocation over heterogeneous resources. Although current GPUs lack fine-grained resource partitioning, the framework establishes a modeling basis for future edge systems as GPU virtualization technologies mature. 3) Action Space Optimization and Temporal Dynamics: The discrete action space is defined as Ao = {alocal , aserver1 , aserver2 , . . . , aserverN }1, where each action corresponds to a feasible execution location with distinct resource characteristics. The Q-network integrates GPU compatibility assessment into action evaluation, assigning higher Qvalues to actions that satisfy GPU requirements under current system load and task deadlines, thereby learning resourceaware policies that reduce execution failures. To account for temporal variations in mobile edge systems, we augment the state with evolution information Sotemporal = [Sot , ∆Sot , E[Sot+1 ]], where ∆Sot = Sot − Sot−1 characterizes short-term state changes and E[Sot+1 ] denotes the predicted next state inferred from current trends and task arrival patterns. This formulation allows task allocation decisions to consider both instantaneous dynamics and near-future system conditions.
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C. Deadline-Oriented Queue Management and Adaptive Experience Replay Task allocation requires queue management for deadlinesensitive tasks and efficient learning through experience replay. Our approach combines deadline-oriented scheduling with failure-penalized adaptive sampling. 1) Deadline-Oriented Queue Prioritization: Our deadlineoriented queue management dynamically adjusts priorities based on urgency, resource requirements, and execution feasibility. The multi-dimensional scoring mechanism integrates these factors through Eq. 17: ddli − tcurrent bi t · max(ρji ), (17) · max 0, Pi = i j bmax Dest where the priority score combines task priority bi , deadline i urgency (ddli − tcurrent )/Dest , and the best GPU compatj ibility maxj (ρi ) from Eq. 16. This mechanism ensures that high-priority, urgent tasks with good resource matches receive processing precedence. i −tcurrent The deadline urgency factor uti = ddl adapts to i +W i Dest est i current system load and estimated execution times, where Dest represents estimated execution time based on task computai tional requirements and target device capabilities, while West denotes expected waiting time derived from current queue lengths and processing rates. This dynamic prioritization responds to changing conditions, ensuring time-critical tasks receive processing precedence without starving lower-priority workloads. 2) Failure Risk Assessment and Prevention: Failure risk assessment identifies tasks that are likely to violate constraints through Eq. 18: Ifi ail =
( i 1, if maxj (ρji ) < θmin or (ddli − tcurrent ) < Dest , 0, otherwise, (18)
where θmin is defined as the lower bound of acceptable compatibility. The resulting failure indicator is integrated into the hierarchical reward function (Section II), thereby enabling prompt penalization of allocation decisions that violate constraints or miss deadlines. Tasks with high failure risk are prioritized through dedicated queue channels, while the corresponding risk metrics are incorporated into the DDQN reward function, enabling penalization of allocation policies that may lead to task failures. 3) Adaptive Experience Replay with Failure Penalization: DDQN training adopts the same failure-aware prioritization mechanism as the upper-tier TD3 (Eq. 14), ensuring crosstier consistency. The prioritization weight Wi = |T Di | · (1 + γf ail · Ifi ail ) combines temporal difference error with the failure indicator Ifi ail , which identifies allocation decisions that risk resource constraint violations or deadline misses (Eq. 18). Unlike TD3, where Ifi ail reflects power-related stress, DDQN focuses on load-induced failures caused by fluctuating task demands and heterogeneous device capabilities. This coordinated design improves convergence behavior and sample efficiency across both tiers.
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4) Integration with Hierarchical Decision Framework: As the stage 3 in the coordination pipeline (Eq. 3), the DDQN incorporates deadline management (Eq. 17) and GPU-aware filtering (Eq. 16). Adjustments in queue states modify the load metric Lt (Eq. 5), which in turn influences the reward computation of the power control layer (Eq. 11). Meanwhile, the outcomes of failure assessment (Eq. 18) are reflected in the task allocation reward (Eq. 12). Together, these interactions establish a closed feedback loop that aligns both tiers toward joint optimization. 5) Load-Adaptive Training for Dynamic Mobile Conditions: The DDQN training includes load-driven adaptations that remain consistent with the hierarchical coordination framework. The load metric Lt (Eq. 5) serves as a global indicator to synchronize learning behavior across tiers. The learning rate is defined as follows: η t = ηbase · (1 + α · Lt ),
(19)
where ηbase is the base learning rate and α > 0 controls learning rate adaptation sensitivity, ensuring that the DDQN agent responds appropriately to varying operational conditions. Exploration follows the load-aware ϵ-scheduling scheme (Eq. 15). During high-load periods, ϵ is reduced to favor stable exploitation; when the system is lightly loaded, ϵ increases to encourage exploration and improve policy diversity. V. E XPERIMENTAL E VALUATION We evaluate H I RL using a simulation framework that reflects heterogeneous mobile edge environments, focusing on system performance, learning behavior, adaptive mechanisms, and scalability. Additional experiments examine the gap between simulation outcomes and practical deployment considerations. A. Heterogeneous Infrastructure Configuration 1) Heterogeneous Device Infrastructure: The experimental setup consists of 35 mobile devices and 5 edge servers, configured to emulate practical MEC heterogeneity. Mobile Devices (35 units): Devices differ in mobility (low: ±10 m/slot; high: ±20 m/slot) and computational capacity (CPU: 2–3 GHz, memory: 8–16 GB). GPU types range from GTX 1660 (1408 CUDA cores, 6 GB, 192 GB/s) to RTX 4090 (16384 cores, 32 GB, 1008 GB/s), with transmission power constrained to 2–3 W. Edge Server Infrastructure (5 servers): The edge infrastructure includes five servers with heterogeneous computational architectures. GPU configurations cover Tesla P100 (3584 CUDA cores, 16 GB memory, 732 GB/s bandwidth, 250 W), Tesla V100 (5120 cores, 32 GB, 900 GB/s, 300 W), Tesla A100 (6912 cores, 80 GB, 1555 GB/s, 400 W), and Tesla H100 (14592 cores, 80 GB, 3000 GB/s, 700 W). System memory configurations range from 64GB to 1024GB across different server types, with CPU frequencies configured at 50-60 GHz to reflect server-grade processing capabilities. This heterogeneous server infrastructure supports evaluation of GPU-aware resource matching and compatibility assessment within the proposed framework.
2) Task Workload and Network Modeling: Tasks are generated synchronously per time slot (τ = 1 s). Following the three-category classification in Section II, CPU-intensive, GPU-intensive, and I/O-intensive tasks follow a 5:4:1 ratio. CPU-intensive tasks involve data sizes of 64–262 KB and require 500–2000 CPU cycles per bit [16]. GPU-intensive tasks process 6.4–26.2 KB inputs, occupy 5120–14592 CUDA cores with 2–16 GB memory demand, and require 1010 –1011 FLOPS. I/O-intensive tasks transmit lightweight payloads (640 B–2.6 KB) with negligible computation. Task priorities are uniformly sampled from {1, 2, 3, 4}. Deadlines are categoryspecific (1–1.5 s for CPU/GPU tasks; 0.5–1 s for I/O tasks) and min–max normalized. Three task-generation rates (10, 20, and 40 tasks per slot) are evaluated to represent low-, medium-, and high-load conditions, with 20 tasks per slot as the nominal operating point. Wireless channels follow the path-loss model in Eq. 9 with G0 = 10−3 , d0 = 1 m, and γ ∈ [1.6, 3.5]. Bandwidth is set to 10 MHz, and noise power is fixed at N0 = 10−13 W [17]. Device mobility follows a bounded random walk, with initial device-server distances uniformly distributed within [1500, 7500] m. 3) Performance Metrics and Evaluation Framework: We evaluate system performance using the following metrics: • Task Completion Rate: Proportion of tasks completed within deadlines. • Energy Consumption: Aggregate CPU, GPU, and transmission energy usage. • Execution Latency: Total system latency Lsys = PN i i=1 Dtot , capturing queuing, processing, and transmission latency. Each experiment runs for 800 episodes, generating tasks in the first five time slots, and uses multiple independent runs with distinct random seeds for statistical robustness. System Load and Statistical Validation. System load is characterized using the comprehensive load metric Lt defined in Eq. 5, evaluated under task-generation rates of 10, 20, and 40 tasks per slot. All results report averages with 95% confidence intervals based on t-distribution, with statistical significance assessed using paired t-tests at α = 0.05. B. Baseline Algorithms and Experimental Design This section presents the baseline algorithms and experimental settings used for comparison with H I RL under diverse system conditions. 1) Baseline Algorithm Categories and Specifications: Classical Heuristic Algorithms: These algorithms represent fundamental approaches to task allocation in distributed systems, providing performance lower bounds and basic algorithmic intuition validation. • Random Allocation: Uniformly random task placement across available execution locations (local execution and 5 edge servers), representing the baseline performance floor for comparison purposes. • Greedy Local/offloading: Includes two variants—(i) local-first allocation, preferring local execution until
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IEEE TRANSACTIONS ON COMPUTERS, VOL. XX, NO. X, JANUARY XXXX
CPU/GPU capacity is exhausted, and (ii) offloadingfirst allocation, prioritizing edge servers with the highest available computation capacity to minimize local energy consumption. • Round Robin: Sequentially assigns tasks across edge servers for balanced workload distribution, without considering compatibility or dynamic system state. Advanced Optimization Methods: These baselines reflect current optimization trends in mobile edge computing and reinforcement learning. QPSO [18]: A Quantum-behaved Particle Swarm Optimization method that formulates task offloading as a global search problem using quantum-inspired particle evolution, but lacks adaptation to time-varying system states. • Single-DDQN: A single-agent Double Deep Q-Network for task allocation with fixed transmission power, excluding hierarchical coordination to isolate its contribution. •
Ablation Study Variants: To evaluate the contribution of individual mechanisms within H I RL, four ablation models are implemented. H I RL-NoCoord: Removes the coordination module, allowing TD3 and DDQN to operate independently without shared states or sequential decision flow. • H I RL-NoGPU: Disables GPU-aware compatibility scoring (Eq. 16), using simplified resource allocation without GPU specification consideration. • H I RL-NoDeadline: Removes deadline-oriented queue prioritization (Eq. 17), replacing it with a First-ComeFirst-Served policy. • H I RL-NoFailure: Disables failure-penalized experience replay from Eq. 14, using uniform experience sampling in DDQN training. •
2) Experimental Parameter Configuration: Physical System Parameters: The effective switching capacitance is set to k = 10−28 [19], time slot duration is τ = 1s, and maximum transmission power varies between Pmax = 2−3W for mobile devices. The maximum CPU frequency is set within the range fmax = 2 − 3 GHz to reflect typical consumer mobile device capabilities. Learning Algorithm Parameters: In DDQN, the learning rate was configured to 1×10−4 . For TD3, independent learning rates were adopted for the actor (1×10−3 ) and critic (5×10−4 ) networks. The experience replay buffer sizes were set to 600,000 for DDQN and 5,000 for TD3, respectively. Both algorithms were trained using a batch size of 256. Regarding target network updates, DDQN applied a hard update every 1,000 training steps, whereas TD3 followed a soft-update scheme with a smoothing coefficient of τ = 0.001. Coordination and Adaptive Mechanism Parameters: The coordination engine parameters include an adaptive weight sensitivity factor of γ = 0.1 in load metric calculation and a failure penalty factor α = 1.0 for experience prioritization. The load metric weighting factors are set as ωq = 0.6, ωu = 0.2, and ωg = 0.2 to prioritize queue-based load assessment while incorporating resource utilization.
Exploration Strategy Parameters: Exploration is controlled by ϵmin = 0.01 and ϵmax = 0.3, with an exponential decay schedule adapted to system load conditions as defined in Eq. 15. The load adaptation sensitivity is controlled by α = 0.5 and β = 2.0 to balance exploration and exploitation across varying operational conditions. 3) Experimental Design Methodology: Controlled Variable Design: Controlled variables include system load intensity, infrastructure heterogeneity, and workload characteristics. Primary controlled variables include system load intensity (via SLI categorization), infrastructure heterogeneity (device and server configurations), and workload characteristics (task type distributions and priority patterns). Performance Comparison Framework: All algorithms operate under identical environmental conditions within each scenario. Random seed control ensures reproducibility, while systematic variation of environmental parameters evaluates robustness. Statistical Significance Validation: Each algorithm is evaluated through multiple independent runs. Statistical significance is assessed using paired t-tests, with consistency verified across different random seeds. Fairness and Evaluation Consistency: All algorithms are allocated identical computational resources and training opportunities. Learning-based baselines are trained for equivalent durations with consistent hyperparameter optimization to ensure fair comparison. C. Overall Performance Evaluation This section evaluates H I RL with respect to task completion (primary guarantee), execution latency, and energy efficiency under various operational conditions. 1) Experimental Setup and Metrics: We define the System Load Index (SLI) as SLI(t) = Lt × 100% based on the comprehensive load metric Lt from Eq. 5, where Lt ∈ [0, 1] reflects overall system stress by integrating queue saturation and heterogeneous CPU/GPU resource utilization. Three operational regimes are defined according to the SLI distribution: low load (10–30%), medium load (30–60%), and high load (60–90%). Our evaluation covers three core metrics—task completion rate, execution latency, energy consumption—measured across all SLI regimes. Statistical consistency is ensured through multiple independent runs. 2) Aggregate Performance Analysis: Fig. 3 presents overall results under varying system loads, while Fig. 4 visualizes task-level distributions through CDF heatmaps, where color gradients denote completion percentiles. Task Completion Rate. As shown in Fig. 3(c), H I RL sustains nearly 100% completion across all load levels, confirming the effectiveness of coordinated queue management and GPU-aware matching. Single-DDQN maintains high rates (above 97%) but shows mild degradation under high load due to the absence of joint power control. QPSO and GreedyLocal methods experience notable drops (down to about 80%), and Random or Round-Robin allocation falls below 50%, indicating limited adaptability under resource contention (high load).
ZHU et al.: HIRL: HIERARCHICAL REINFORCEMENT LEARNING FOR COORDINATED RESOURCE MANAGEMENT IN HETEROGENEOUS EDGE COMPUTING 9