## 1 Introduction  
In the 6G era [1], ultra-reliable low-latency communication (URLLC) scenarios impose stringent delay constraints, encompassing applications such as autonomous driving and industrial automation. The principal objective of URLLC, which is to ensure real-time requirements with hard delay constraints, has attracted widespread attention in academia [2]. It is worth noting that finite blocklength coding with a short-frame structure exhibits an excellent low-latency performance [3]. Accordingly, this work proposes a variable-length finite blocklength coding scheme to satisfy the hard latency constraint over time-varying wireless channel fading. Meanwhile, we customize the corresponding dynamic framing and power allocation to suit the variable-length channel coding. Hard delay constraints play a crucial role in URLLC scenarios, as they ensure timely and reliable data delivery [2]. In light of this, academia has embarked on comprehensive studies of both transmission designs and network structures relevant to hard delay constraints. Most research has primarily targeted transmission designs, such as [4, 5, 6, 7, 8, 9, 10, 11, 12]. For instance, Ref. [4] explored network communications under stringent timeliness constraints, demonstrating the superior performance of network coding over routing in delay-constrained unicast settings. The authors of [5] addressed the challenges of delay-constrained scheduling for point-to-point communications over time-varying channels using a channel-threshold policy. Ref. [6] ensured adherence to hard delay constraints by exploiting frequency and spatial diversity techniques. The authors of [7] proposed an optimal power control policy to minimize the probability of violating delay bounds. In [8], an optimal dynamic coding-window selection policy was proposed for delay-constrained communications. [PERSON] investigated a framework of hard delay constraints for real-time communication from a queueing perspective in [9, 10]. The authors of [11] consider the delay-constrained scheduling problem of point-to-point communication, while the authors of [12] consider the hard deadline constraints of multichannel systems in a cognitive radio scenario. Subsequent works have investigated many network structures, such as [13, 14, 15, 16]. For instance, the authors of [13] explored optimal forwarding for real-time communication over multi-hop wireless lossy networks under strict latency constraints. In [14], the scheduling of delay constrained transmissions were investigated for coded caching. Ref. [15] optimized user offloading and resource allocation in a mobile cloud computing system with delay constraints. Likewise, Ref. [16] focused on maximizing delay-constrained coverage in vehicular networks through optimal base station deployment. The maximal achievable coding rate of finite blocklength coding was investigated in [17], which provided significant insights into how low latency requirements can be effectively met using a short frame structure. Consequently, academia has pursued research concerning the maximal achievable coding rate of finite blocklength coding and its applicable network structures. Most of this research has primarily focused on the maximal achievable coding rate, as seen in [18, 19, 20, 21]. For instance, the authors in [18] characterized the maximal achievable rate in block fading channels using the channel-side information at the receiver (CSIR). The authors of [19] investigated the maximal achievable rate over quasi-static multiple-input multiple-output fading channels. Ref. [20] investigated the finite blocklength limits in multi-antenna AWGN channels, shedding light on channel dispersion and its impact on coding delay and optimal coding schemes. The maximal achievable rate was investigated in parallel complex AWGN channels in [21]. Subsequent studies have investigated applicable network structures, such as [3, 22, 23, 24]. The study in [3] reviewed the advances in information theory related to finite blocklength coding in short-packet transmissions system.