Impact of non-persistent carrier sense multiple access mechanism on scalability of LoRa networks

doi:10.11772/j.issn.1001-9081.2022081237

Journal of Computer Applications ›› 2023, Vol. 43 ›› Issue (9): 2885-2896.DOI: 10.11772/j.issn.1001-9081.2022081237

Special Issue: 网络与通信

• Network and communications • Previous Articles Next Articles

Impact of non-persistent carrier sense multiple access mechanism on scalability of LoRa networks

Yicheng WAN¹, Guangxiang YANG¹^,²(), Qingda ZHANG¹, Chenyang GAN¹, Lin YI¹

^1.School of Artificial Intelligence，Chongqing Technology and Business University，Chongqing 400067，China
^2.Chongqing Engineering Laboratory for Detection，Control and Integrated System （Chongqing Technology and Business University），Chongqing 400067，China

Received:2022-08-22 Revised:2022-10-23 Accepted:2022-11-03 Online:2023-01-11 Published:2023-09-10
Contact: Guangxiang YANG
About author:WAN Yicheng， born in 1996， M. S. candidate. His research interests include LoRaWAN， internet of things， wireless communication.
ZHANG Qingda， born in 1994， M. S. candidate. His research interests include machine learning， complex network.
GAN Chenyang， born in 1997， M. S. candidate. His research interests include natural language processing.
YI Lin， born in 1997， M. S. candidate. His research interests include computer vision， garbage recognition.
Supported by:
Science and Technology Research Program of Chongqing Municipal Education Commission(KJZD-K202100805);Scientific Research and Innovation Project for Graduate Students in Chongqing(CYS22628)

非坚持型载波监听多路访问机制对LoRa网络扩展性的影响

万义程¹, 杨光祥¹^,²(), 张庆达¹, 甘晨阳¹, 易林¹

^1.重庆工商大学人工智能学院，重庆 400067
^2.检测控制集成系统重庆市工程实验室（重庆工商大学），重庆 400067

通讯作者: 杨光祥
作者简介:万义程（1996—），男，江西南昌人，硕士研究生，主要研究方向：LoRaWAN、物联网、无线通信
张庆达（1994—），男，山东聊城人，硕士研究生，主要研究方向：机器学习、复杂网络
甘晨阳（1997—），男，湖北武汉人，硕士研究生，主要研究方向：自然语言处理
易林（1997—），男，重庆人，硕士研究生，主要研究方向：计算机视觉、垃圾识别。
基金资助:
重庆市教委科学技术研究项目(KJZD-K202100805);重庆市研究生科研创新项目(CYS22628)

Abstract

Abstract:

LoRaWAN， as a wireless communication standard in Low Power Wide Area Network （LPWAN）， provides the support for the development of IoT （Internet of Things）. However， limited by the characteristics of incomplete orthogonality among Spreading Factor （SF） and the fact that LoRaWAN does not have a Listen-Before-Transmit （LBT） mechanism， the ALOHA-based transmission scheduling method will trigger serious channel conflicts， which reduces the scalability of LoRa （Long Range Radio） networks greatly. Therefore， in order to improve the scalability of LoRa network， Non-Persistent Carrier Sense Multiple Access （NP-CSMA） mechanism was proposed to replace the medium access control mechanism of ALOHA in LoRaWAN. The time of accessing the channel for each node with the same SF in LoRa network was coordinated by LBT， and multiple SF signals were transmitted in parallel for the transmission between different SFs， thus reducing the interference of same SF and avoiding inter-SF interference in the common channel. To analyze the impact of NP-CSMA on the scalability of LoRa networks， LoRa networks constructed by Lo RaWAN and NP-CSMA were compared by theoretical analysis and NS3 simulation. Experimental results show that NP-CSMA has 58.09% higher theoretical Packet Delivery Rate （PDR） performance than LoRaWAN under the same conditions， at a network communication load rate of 1. In terms of channel utilization， NP-CSMA increases the saturated channel utilization by 214.9% and accommodates 60.0% more nodes compared to LoRaWAN. In addition， the average latency of NP-CSMA is also shorter than that of the confirmed LoRaWAN at a network traffic load rate of less than 1.7， and the additional energy consumption to maintain the CAD （Channel Activity Detection） mode is 1.0 mJ to 1.3 mJ and 2.5 mJ to 5.1 mJ lower than the additional energy consumption required by LoRaWAN to receive confirmation messages from the gateway when spreading factor is 7 and 10. The above fully reflects that NP-CSMA can improve LoRa network scalability effectively.

Key words: Internet of Things (IoT), Low Power Wide Area Network (LPWAN), LoRa (Long Range Radio), scalability, Non-Persistent Carrier Sense Multiple Access (NP-CSMA), NS3 simulation

摘要：

LoRaWAN是低功耗广域网（LPWAN）中的一种无线通信标准，为物联网的发展提供了支撑。然而，受限于扩频因子（SF）间不完全正交性的特点和LoRaWAN不具备先听后发（LBT）机制的事实，基于ALOHA的传输调度方式会引发严重的信道冲突，极大降低了LoRa（Long Range Radio）网络的扩展性。为提高LoRa网络的扩展性，提出用非坚持型载波监听多路访问（NP-CSMA）机制替代LoRaWAN中ALOHA的介质访问控制机制，通过LBT协调LoRa网络中SF相同的各个节点接入信道的时间。不同SF之间的传输则采用多种SF信号并行传输，以减少共信道中同SF干扰和避免SF间干扰。为了分析NP-CSMA对LoRa网络扩展性的影响，通过理论分析和NS3仿真对LoRaWAN与NP-CSMA构建的LoRa网络进行比较。实验结果表明，在相同的条件下，与LoRaWAN相比，NP-CSMA在网络通信负载率为1的情况下，它的理论数据包交付率（PDR）性能比LoRaWAN高58.09%。在信道利用率方面，与LoRaWAN相比，NP-CSMA的饱和信道利用率提高了214.9%，容纳的节点数量也增加了60.0%。另外，NP-CSMA的平均时延在网络通信负载率小于1.7时也低于确认型LoRaWAN，而且在扩频因子为7和10时，它用于维持信道活动检测（CAD）模式所造成的额外能耗也比LoRaWAN用于接收来自网关确认消息所需的额外能耗低1.0~1.3 mJ和2.5~5.1 mJ；充分反映了NP-CSMA可以有效提高LoRa网络的可扩展性。

关键词: 物联网, 低功耗广域网, LoRa, 扩展性, 非坚持型载波监听多路访问, NS3仿真

CLC Number:

TN914.42

Yicheng WAN, Guangxiang YANG, Qingda ZHANG, Chenyang GAN, Lin YI. Impact of non-persistent carrier sense multiple access mechanism on scalability of LoRa networks[J]. Journal of Computer Applications, 2023, 43(9): 2885-2896.

万义程, 杨光祥, 张庆达, 甘晨阳, 易林. 非坚持型载波监听多路访问机制对LoRa网络扩展性的影响[J]. 《计算机应用》唯一官方网站, 2023, 43(9): 2885-2896.

Figures/Tables 18

Fig. 1 Frequency variation of LoRa signal with K=50，100，150，200，225 based on up-chirp

Fig. 2 Real and imaginary parts of LoRa signal based on up-chirp（K=50，SF=8）

Fig. 3 FFT output of LoRa signal based on up-chirp after demodulating linear frequency modulation （K=50）

Fig. 4 Relationship between BER and SNR for LoRa modulation at different SF

Tab. 1 SNR thresholds corresponding to different SF when BER is 10-4

SF	SNR/dB	SF	SNR/dB	SF	SNR/dB
7	-7.0	9	-12.5	11	-18.5
8	-10.0	10	-15.0	12	-21.0

Fig. 5 Based on up-chirp， LoRa signal composed of a reference signal with K=150 and interference signals with K=50，100

Fig. 6 At SIR=-20 dB， FFT output of LoRa signal composed of a reference signal with K=150 and interfering signals with K=50，100

Fig. 7 Relationship between BER and SIR of reference signal with SF=9 under combinations of interference signals with different SFint

Tab. 2 SIR thresholds required for demodulation of reference signals in combined signals of multiple SF when BER is 10-3

SF_ref	SF_int不同时所需的SIR阈值/dB
SF_ref	SF_int=7	SF_int=8	SF_int=9	SF_int=10	SF_int=11	SF_int=12
7	0.0	-10.0	-12.0	-13.0	-13.5	-13.5
8	-12.5	0.0	-13.0	-15.0	-15.5	-16.0
9	-15.5	-15.5	0.0	-16.0	-17.5	-19.5
10	-18.0	-18.0	-18.0	0.0	-18.5	-20.5
11	-20.5	-20.5	-21.0	-21.0	0.0	-22.0
12	-23.5	-23.5	-24.0	-25.0	-25.0	0.0

Fig. 8 LoRa terminal channel activity detection process

Fig. 9 Scheduling method of NP-CSMA in LoRa networks

Fig. 10 Distribution of 400 terminal nodes in circular area with radius of 2 km

Tab. 3 Basic simulation parameters

参数	值
节点散落半径范围	0~2 000 m 随机散落
节点数	0~400
频段	470 MHz
编码速率	4/5
带宽	125 kHz
传播损耗模型	Okumura-Hata 模型
前导码	8个符号
LoRa数据帧FHDR字段	7 B
MAC层负载大小	30/50 B
空中传输时间（T_data）	式（14）
网关模块	SX1301
网关天线高度	15 m
节点模块	SX1272
节点天线高度	1 m
电压	3.3 V
发送功率	92.4 mW
睡眠功率	4.95 μW
侦听功率	4.62 mW
接收功率	36.96 mW

Tab. 4 LoRaWAN and NP-CSMA simulation experimental parameters

参数	LoRaWAN	NP-CSMA
扩频因子	7，10	7，10
信道	1个占空比为1%的上行信道和1个占空比为10%的下行信道	1个占空比为1%的上行信道和1个占空比为10%的下行信道
重传次数	8	4
CAD功率	—	接收功率（1.4 mA）
CAD持续时间T_CAD	—	取决于SF^{［21，28］}
退避时间	—	基于式（13）
数据周期	100T_data	100T_data

Fig. 11 With increase of node number， PDR of LoRaWAN， NP-CSMA with SF=7，10 under conditions of single channel and MACPayload =50 B

Fig. 12 With increase of node number， channel utilization of LoRaWAN， NP-CSMA with SF=7，10 under conditions of single channel and MACPayload=50 B

Fig. 13 Average latency of confirmed LoRaWAN and NP-CSMA with SF=7，10 based on two packet load lengths of MACPayload=30，50 B

Fig. 14 Average energy consumption of a single packet with MACPayload=50 B sent by terminal node of LoRaWAN，NP-CSMA at SF=7，10

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Impact of non-persistent carrier sense multiple access mechanism on scalability of LoRa networks

非坚持型载波监听多路访问机制对LoRa网络扩展性的影响

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