This paper examines enhancement to ITU-T Recommendation G.711.1 PCM wideband extension speech coder. To further improve the core lower-band coding performance the use of vector quantization and delayed decision coding is studied. A particular case of delayed decision coding, tree encoding, is implemented in the above standard. The bitstream is compatible with both the legacy G.711 and the G.711.1 decoder. PESQ (ITU-T P.862, Perceptual Evaluation of Speech Quality) is used to evaluate the performance. Both the vector quantizer and tree encoder have better performance than the original core layer encoder.