This chapter addresses power line channel of Low voltage (LV) access network in urban/suburban area with low-riser apartment buildings. Noise and attenuation are two major power line channel characteristics. To compare different channels, the so-called link quality index (LQI) is proposed, which combines both noise and attenuation and describes the quality of a particular link. Narrowband power line channel characteristics in typical underground LV access network in China are evaluated based on measurement results. A three-phase coupling at transformer has very low impedance. Access impedance depends on coupling mode. While at the customer side phase to neutral coupling is the default mode, at the transformer, both phase to neutral and three phases to neutral couplings are possible. Attenuation is measured between the transformer and house access point of the three buildings. A sweep generator is used. The noise power in the frequency domain is captured with a spectrum analyser with logarithmic video signal averaging and with root mean square detector.