LTE is expected to substitute GSM as the basis technology for railway communications. Recently, special attention has been deserved to HST as this particular environment (mainly due to the high speed condition) can severely impact wireless systems performance. Although several channel models have been derived during the few last years, most of them are not accurate enough as they are not supported by measurement campaigns. In this paper, the main requirements for HST environments are analyzed and a flexible, cost-affordable, and easily-scalable software and hardware architecture for a test bed suitable for assessing LTE at high speeds is proposed.