There's a branch by ttsou implementing a GSM/EDGE test signal generator. See http://git.osmocom.org/osmo-trx/log/?h=ttsou/siggen
Would be great to forward-port + merge it. However, let's make sure we don't require C++14 without a really strong reason.
Also, note that https://git.osmocom.org/osmo-trx/log/?h=fairwaves/WIP-decoder branch has another signal generation tool (designed to be used for ETSI BER testing) and also a tool for offline demodulation (also designed for ETSI BER testing). Both tools may also be useful for repeatable testing, performance benchmarking, debugging, etc without a real hardware.
These utils don't require C++11...