Scheduling and Decoding of Downlink Control Channel in 3GPP Narrowband-IoT

Abstract

Narrowband Internet of Things (NB-IoT) is a low power wide area network technology introduced by the 3 rd Generation Partnership Project (3GPP). It is a derivative of the existing 3GPP Long Term Evolution (LTE) that will enable cellular service to a massive number of IoT devices. In comparison with LTE and 5G New Radio, the NB-IoT devices will be of low cost, low throughput, and delay-tolerant. The reduction in available bandwidth and introduction of repetitions for achieving wider coverage requires modified Narrowband Physical Downlink Control Channel (NPDCCH) search space design and decoding as compared to the LTE. Hence, in this paper, we first explain the NPDCCH physical layer procedures, along with the search space decoding. Unlike LTE, there is no channel feedback mechanism in NB-IoT. Therefore, we propose a novel resource mapping scheme for NPDCCH based on the uplink reference signals. We perform system-level simulations and analyze the impact of the proposed mapping for varying operating frequencies and channel conditions. Further, the NB-IoT devices have limitations on the battery power, and hence, the existing control channel schedulers cannot be reused for the NB-IoT scenario. Thus, we propose a novel scheduler for NPDCCH. We have also modified the current state-of-the-art algorithms to meet the NPDCCH constraints and compared them against the proposed scheduler. We derive bounds for such scheduling algorithms and show that the proposed scheduler additionally conserves up to 25% of the IoT device battery power. Through Monte Carlo simulations, we show that the proposed scheduler better achieves the various trade-offs between power consumption, search space utilization, and fairness as compared to the existing schedulers.

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“…In addition, the larger system bandwidth gives a better value to the output performance because of the higher energy consumption. As referred to in (10), the energy efficiency is in a straight line related to the network's performance. This results in increased energy efficiency curves with an increase in bandwidth, as seen in Figure 24.…”

“…Moreover, IoT applications are near-future applications in industry, agriculture, health, education, transportation, finance, and the environment [7,8]. The third-generation partnership project (3GPP) uses a radio technology standard called narrowband IoT (NB-IoT) to allow internet connectivity in a huge number of low-performance devices [9,10]. This NB-IoT standard may be used to prolong battery life using the discontinuous reception (DRX) mechanism.…”

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“…In the direction of resource management, the work [14] designs a mechanism for resource allocation in NB-IoT, by focusing only on the rate maximization. Manne et al [20] explain NPDCCH physical layer procedures with the technique of search space decoding, where a resource mapping scheme is discussed for NPDCCH by utilizing uplink reference signals. The heuristic algorithm proposed in [21] discusses a downlink scheduling mechanism in NB-IoT.…”