When the need for a new wireless standard has been established, a technical committee will discuss and negotiate a preliminary proposal. All of the proposal’s elements—including its scope, key definitions, and content—are then negotiated. Simulation software is increasingly being used to study new technologies, helping to speed the development of standards while reducing hardware implementation costs.

For example, the 3rd Generation Partnership Project (3GPP) recently standardized Narrowband-IoT (NB-IoT), a cellular-based narrowband technology targeted for the Internet of Things (IoT). In a new white paper, NB-IoT System Modeling: Simple Doesn’t Mean Easy,” Keysight Technologies discusses a method for modeling and evaluating an NB-IoT system in a combined multi-domain simulation environment.

Some objectives of the NB-IoT standard include improving indoor coverage, increasing support for a vast amount of low-throughput devices, and enabling extremely low device costs. NB-IoT has been designed with three different operation modes: standalone, in-band, and guard-band. Standalone operation replaces GSM carriers with NB-IoT carriers. In-band operation utilizes resource blocks within a normal LTE carrier, while guard-band operation uses the LTE carrier’s guard-band.

The white paper discusses possible NB-IoT receiver architectures, with both zero-IF and low-IF architectures noted as potential solutions. A generic low-IF architecture is presented, as well as a low-IF simulation model that takes into account various effects of non-ideal hardware.  

An RF and baseband cross-domain simulation technique is presented. The baseband signal is generated using Keysight’s SystemVue LTE-A library, which supports both single-tone and multi-tone transmission. The baseband signal is filtered by two digital filters and enters a modulator. A power amplifier (PA) then amplifies the signal. The receiver demodulates the amplified signal to determine the error-vector-magnitude (EVM). EVM versus the PA’s 1-dB compression point (P1dB) is simulated to evaluate how the PA’s nonlinearity affects the quality of the transmission signal. The simulation results demonstrate that the PA’s nonlinearity has little effect on the EVM for single-tone subcarrier spacing. However, it does negatively affect the EVM for multi-tone transmissions.

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