CLAP: Chip-Level Augmentation of IEEE 802.15.4 PHY for Error-Intolerant WSN Communication

Abstract

Communication reliability is the ultimate priority in safety-critical wireless sensor network (WSN) communication. Surprisingly enough, the enormous potential of error control on direct sequence spread spectrum (DSSS) chips in IEEE 802.15.4 has been completely overlooked by the WSN community, possibly due to incorrect presumptions, such as the concerns about computational overhead. Current error-correction schemes in WSN counteract the error process once the errors have already propagated to bit-and packet-level. Motivated by the notion that errors should be confronted at the earliest stage, this work presents CLAP, a novel method that tremendously improves the error correction in WSN by fortifying the IEEE 802.15.4 Physical layer (PHY) with straightforward manipulations of DSSS chips. CLAP is implemented on a software-defined radio platform, and evaluated on real error traces from heavily WLAN-interfered IEEE 802.15.4 transmissions at 3 different environments. CLAP boosts the number of corrected packets by 1.78-6.88 times on severely interfered links, compared to two other state-of-the-art schemes. The overhead in terms of computational complexity is about 10% of execution time of the OQPSK demodulator in the legacy IEEE 802.15.4 receiver chain. Index Terms-WSN, IEEE 802.15.4, chip error correction.

Packet Detection by a Single OFDM Symbol in URLLC for Critical Industrial Control: A Realistic Study

“…Pr FA and Pr MD of (2) for the non-differential algorithm are plotted in solid lines in Fig. 5, and approximated probabilities from (13) and (17) are plotted in dashed lines. It is seen that the exact and the approximated probabilities share the same trend with the change of SNR.…”

“…[11], [12] investigate differential preamble detections in direct-sequence spread-spectrum (DSSS) system at chip-level and at sample level, and differential detection is claimed to have superior performance in channels with frequency offset. [13] proposes to improve the reliability at DSSS chip level of IEEE 802.15.4, however, the packet preamble is exempt from the protocol. In cellular standards with TDMA Medium Access Control, timing advance is used by the base station to control the signal delay of the multiple mobile devices with different distances to avoid collisions [14], [15].…”

Safety-critical wireless sensor networks under a polyphase spreading sequences scenario

“…These chip sequences and their method of generation are provided below. RC7 sequences: To overcome the shortcomings caused by PN and Gold sequences, RC7 codes were proposed in [6]. In RC7, 8 quadruples are fitted into 32 chips, as shown in Table 1.…”

“…However, these codes are prone to errors in real-time transmissions. To solve this problem, a 7-repetition code (RC7) was proposed by Barac et al in [6]. RC7 codes provide the lowest possible computational complexity and substantial improvement in chip errors.…”

A New Multiple-Symbol Differential Detection Strategy for Error-Floor Elimination of IEEE 802.15.4 BPSK Receivers Impaired by Carrier Frequency Offset

“…en, it will be completely both implementation feasible and energy unlimited for a more complex noncoherent receiver in the sink node. (ii) Although the MSDD scheme is time consuming, the typical refresh rate for some critical WSN applications such as condition is mandated in the order of minutes or hours [20]. us, the MSDD scheme is particularly well suited to these delay-tolerant but performance-sensitive WSNs, which have quite relaxed requirement on latency.…”