Evaluation and Improvement of Cooperative Communication Techniques with IoTs in Dense Smart City

Abstract

IoT devices are designed low powered inherently. Their purpose is to relay maximum amount of information either with each other or to a central base station. IoT devices are low cost, and with SISO (Single in Single Out) capability. This SISO property can become a choke point when large amount of data is shared over respective channels. It also means that these devices are power constrained. To achieve spatial diversity i.e. to use the antennas of other nodes or relay links virtually, cooperative techniques must be used. This study simulates the main cooperative techniques i.e. Amplify and Forward and Decode and Forward. MRC (Maximum Ratio Combining) is used with Amplify and Forward and Super Position Coding is used with Decode and Forward. The purpose of this study is to evaluate whether spatial diversity can be achieved via an improvement in SNR, BER, Outage Probability and Channel capacity. Furthermore, we evaluate which coding or combing technique saves us more power if a target SNR is set at the receiver. The target rate is set at r=0.5 and a reference power of 30 dBm (1 Watt), for the entirety of this study. We observe for rate r =0.5, AF-MRC gives the best result with 10 % improvement in BER as compared to DF and >100% improvement in BER as compared to E2E links. The outage probability of the AF-MRC drops to zero as compared to the Outage Probability of 0.0006 % for DF which is a slight improvement. The channel capacity for any modulation scheme comes out to be 8.84 bps/Hz against the channel capacity of 8.51 bps/Hz. In terms of Power Consumption, for a target SNR of 30 dB AF-MRC with n=2, comes most power efficient with 21.5 dBm (141 milli watts). The Proposed scheme of DF-SPC performs the best in terms of power consumption i.e. for a frame of 2 bytes, the power consumption (in comparison to AF-MRC, n=2) is halved i.e. from 141 m Watts to 70 m Watts and improving the general throughput of the system by 2 times at the same energy. The cost of this technique is a 0.001 % increase in BER of the system, which is negligible considering that the BER of the system is very low.