# An Efficient Relayed Broadcasting Based on the Duplication Estimation Model for IoT Applications
## 4 Simulation Study  
### Simulation Configuration  
We implemented the simulator using MATLAB focusing on the physical (PHY) and media access control (MAC) layers of the IEEE 802.11 standard. In the PHY layer, TGn channel model C [38; 39] was used as a path loss model. The frequency and bandwidth of the channel were set to 5.25 GHz and 20 MHz, respectively. The carrier sensing threshold, transmission power, and background noise were set to \(-\)82, 10, and \(-\)100 dBm, respectively. When the minimum receiver sensitivity was \(-\)82 dBm, the transmission distance \(D_{tx}\) was calculated as 38.9 m, which corresponds to the radius of a 1-hop transmission. We considered transmission failures due to co-channel interference by modeling the bit error rate (BER) according to [40], which considers the punctured convolutional code and several modulation schemes defined in IEEE 802.11n. In each slot time (i.e., 9 us), our simulator measured the value of the signal-to-interference-and-noise ratio (SINR) from the path loss model and calculated the value of BER. The probability of frame error at each slot time was determined based on the BER and the number of bits per slot time. Please note that the common event-driven network simulator like ns-2 [41] or ns-3 [42] usually calculates the probability of frame error on a per-frame basis by using a simple error model. Therefore, it difficult to accurately model the various effects of interference and frame error, which are essential in this study. Consistent with the IEEE 802.11n standard where the number of spatial streams is one and the guard interval is 800 ns, the transmission rate of all of the nodes was set as 19.5 Mb/s by considering the modulation of QPSK and a coding rate of 3/4. Moreover, we implemented the CSMA features in the MAC layer, the contention window size was set to 15 slots and the frame size to 1 Kbyte. We considered a basic simulation scenario as follows: a single source node located at the center of the network generates and broadcasts 1 Mbyte of traffic consisting of 1000 frames and all of the other nodes relay the received frames. To investigate the effect of network scale and node density, we placed nodes (except for the source node) randomly within the network radius of \(2D_{tx}\) or \(3D_{tx}\), and set the number of nodes \(N_{node}\) in the range of 60-140 or 160-240, respectively. In this simulation configuration, the average number  
Figure 8: A state diagram of the proposed mechanism consisting of the duplication suppression and re-queuing schemes. of adjacent nodes was between approximately 20 and 50 to ensure that the problems of redundancy, collision, and interference would be severe without a proper duplication suppression scheme. We considered the following flooding mechanisms for the performance comparison:  
* BASE: This is a simple baseline flooding mechanism; all the received duplicate frames are discarded but all the new frames received successfully are transmitted without being suppressed. * CBF : This is a conventional counter-based flooding scheme and the counter threshold was set to 2 (The threshold value has a significant impact on the performance of CBF. According to [10], its optimal value becomes a lower value when the topology is denser. We also verified that its performance was the best in most simulations when the threshold was 2). * PBF: As proposed in our previous work [11], this mechanism sets the transmission probability as inversely proportional to the number of adjacent nodes (i.e., \(1/N_{i}\)). If a duplicate transmission is suppressed, this mechanism defers the transmission of the frame instead of dropping it to improve the reliability of flooding. * DBF: In this mechanism, each node rebroadcasts the received frames with three differentiated probabilities depending on the distance from the sender. It used three equal distances divided from the maximum transmission distance (\(D_{tx}\)), as described in [19].