Research On Delay-constrained RAW Grouping Method Of IEEE 802.11ah

The development of the Internet of Things technology urgently requires a low-power wireless communication technology with wide transmission range and high throughput.To address this,the IEEE 802.11 working group has released a new standard called IEEE 802.11 ah.This paper focuses on the Restricted Access Window(RAW)mechanism introduced by the Medium Access Control(MAC)layer of the IEEE 802.11 ah protocol.When the network scale increases,it cannot effectively guarantee different delay constraints for data transmission of different nodes.To solve this problem,two RAW grouping methods are proposed in this thesis,Delay-constrained RAW grouping method(D-RAW)and Delay-constrained RAW real-time scheduling grouping method(eD-RAW).Firstly,this thesis proposes the D-RAW grouping method.The D-RAW grouping method is implemented as follows.First,according to the relationship between delay thresholds and the delay constraints of nodes,nodes are classified into delay-sensitive nodes and non-delay-sensitive nodes.Prioritize the allocation of channels for delay-sensitive nodes to better meet their delay constraints.Then,according to the data characteristics of the nodes,delay-sensitive nodes and non-delay-sensitive nodes are further RAW grouped separately.And the slot division in the RAW group is used to enable delay-sensitive nodes to access the channel in a contention-free manner,which saves energy consumption for channel monitoring and data packet retransmission,and reduces packet loss.The simulation results on NS3 show that D-RAW grouping method can better meet the delay constraints of delay sensitive nodes,reduce the network energy consumption,and it also improves performance such as throughput and packet loss rate significantly.Further,this thesis proposes the eD-RAW grouping method.Based on the D-RAW grouping method,the eD-RAW grouping method further refines the distinction between the delay constraints of nodes,and combines the instantaneous length of the node cache queue to adjust the RAW grouping in real time.The eD-RAW grouping method is implemented as follows.First,the RAW grouping is initially performed according to the size of the data packet sent by the node.And,the slot division in the RAW group is used to enable nodes to access the channel in a contention-free manner to save energy consumption for channel monitoring and packet retransmission.Then,the grouping of nodes is further scheduled according to the delay constraints and the instantaneous length of the cache queue of the nodes to determine the corresponding relationship between the nodes and the slots in each RAW group,preferentially allocates channels to nodes with small delay constraint values and long cache queue instantaneous length.The eD-RAW grouping method can meet the real-time packet sending requirements of nodes,and meets the different delay constraints of different nodes more targeted.The simulation results on NS3 show that it effectively reduces the network delay and energy consumption,and also improves performance such as throughput and packet loss rate.This article has 39 pictures,7 tables,71 references...