Research Of Ir-uwb Technology Based On Decode-and-forward

The advantages of UWB systems, such as low cost, low power waste, low complexity and high data rate, attract lots of interesting in both academia and industry recently, and these features also make ultra-wideband technology into a viable short-distance wireless communication technology. However, because of the frequency overlapping between IR-UWB signal and existing narrowband devices, FCC made strict restrictions on IR-UWB transmit power. In order to achieve the desired performance under the limiting of transmitting power, both domestic and foreign scholars have done a lot of research, and put forward many proposals. One of the proposals is to combine MIMO technology with IR-UWB. Employing MIMO technology in IR-UWB communication system will have achieved considerable spatial and frequency diversity, greatly improved the performance of IR-UWB, such as BER, coverage radius, and power consumption. However, due to the constraints of the device size, and power consumption, it is very difficult to place independent multi-antennas at the UWB terminals. To solve this problem, this paper introduces Decode-and-Forward to the IR-UWB system, and makes the IR-UWB system form virtual MIMO between single-antenna UWB terminals.This paper first introduces the basic IR-UWB technologies, Gaussian pulses model and IR-UWB signal generating, and make a detailed description of IR-UWB advantages. Second, this paper describes and analyzes the technology of cooperative diversity, and its theory. Finally, Employing Decode-and-forward in IR-UWB system forms virtual MIMO-UWB system, achieves the performance of MIMO-UWB system between single-antenna IR-UWB terminals. This paper makes a deep research in IEEE 802.15.3a channel model, but this channel model is only applicable to Monte Carlo simulation, and we cannot derive the closed form solutions of the non-cooperative and cooperative IR-UWB systems. In order to derive the closed form solutions, we employ the Gaussian distribution and the lognormal distribution to fit the distribution of the sum of the lognormal random variables. The results demonstrate that the lognormal distribution is more fittable to the distribution of the sum of the lognormal random variables in CM1 channel. Then, employing the above results, we derive the closed form solutions of the non-cooperative and Decode-and-forward cooperative IR-UWB systems. In the cooperative IR-UWB systems, the cooperative node is setted on the fixed dot, the middle dot between the transceiver, and the optimal location, respectively. From the results of the MATLAB simulation, we know that the Decode-and-forward cooperative IR-UWB system has great improvement in performance, such as BER, the coverage radius, and the total transmitted power, for instance, when the cooperative node is setted on the optimal location, BER will have 4dB improvement, the coverage radius will have 6m enhencement and the power consumption will reduce by 18.5%.