Wireless body area network (WBAN) is a propitious new technology, which enables the efficient delivery of healthcare rights to patients and aging people in outback areas. WBANs consist of resource-limited nodes that make the power consumption one of the most important challenges. This paper proposes a low-power yet efficient architecture design of a narrowband physical layer baseband transceiver for WBANs at the 2.4-GHz band. The proposed design targets high data reliability with scalable data rates for transmission. A low-cost adjustable data rate modulation/demodulation architecture is proposed with a maximum data rate of 971.4 kb/s at 6-MHz clock rate. A digital timing synchronization scheme is also proposed, which can achieve coarse and fine-timing synchronization. Moreover, a low-complexity phase error correction algorithm is proposed with a low-cost pulse deshaping matched filter, to enhance the reliability of the proposed receiver. The proposed baseband transceiver is implemented in 130-nm CMOS technology with a 1.2-V power supply. The proposed baseband design only consumes 72.12 μW in the transmitter and 330.42 μW in the receiver for 971.4-kb/s data rate with 6-MHz clock frequency. To demonstrate the reliability performance of the proposed design, the dedicated packet error rate (PER) post-layout simulations are reported. The overall PER for the proposed transceiver is about 1% at a signal-to-noise ratio of 9.6 dB.