IEEE 802.11b WLAN is widely used to implement Wi-Fi based Time Difference of Arrival (TDoA) indoor localization. This paper presents a novel IEEE 802.11b baseband receiver and the corresponding localization system. Frame detector and phase recovery block are dedicated to frame reception and frequency offset compensation. Baker code re-correlator is specially designed to improve anti-noise performance. Experimental results demonstrate that the proposed system achieves sub-meter range localization precision.