How do I select between a SAW filter and a BAW filter for an IoT device front end?

How do I select between a SAW (Surface Acoustic Wave) filter and a BAW (Bulk Acoustic Wave) filter for an IoT device front end? SAW and BAW filters are the two dominant acoustic filter technologies for RF front ends, and each has distinct advantages depending on the application frequency and performance requirements: (1) SAW filters: technology: surface acoustic waves propagating on a piezoelectric substrate (lithium niobate or lithium tantalate). Frequency range: up to approximately 2.5 GHz (performance degrades at higher frequencies due to electrode resolution limits). Insertion loss: 1.5-3.0 dB. Temperature coefficient: -25 to -45 ppm/°C (SAW frequency shifts with temperature; TC-SAW improves this to -15 ppm/°C). Size: 1.0 × 0.5 mm to 2.0 × 1.5 mm. Cost: $0.10-0.50 per filter (low cost, high volume). Power handling: 1-2W maximum (lower than BAW). Best for: sub-GHz IoT (LoRa at 868/915 MHz), 2.4 GHz BLE/Zigbee. (2) BAW filters (FBAR and SMR): technology: acoustic waves propagating vertically through a thin piezoelectric film (AlN or ScAlN) sandwiched between electrodes. FBAR (Film Bulk Acoustic Resonator): the resonator is suspended over an air cavity. SMR (Solidly Mounted Resonator): the resonator sits on a Bragg reflector stack. Frequency range: 1.5 GHz to 6+ GHz (significantly higher than SAW). Insertion loss: 1.0-2.0 dB (lower than SAW at high frequencies). Temperature coefficient: -20 to -30 ppm/°C (BAW is inherently more temperature stable than SAW). Size: comparable to SAW at the same frequency. Cost: $0.30-2.00 per filter (higher than SAW due to more complex fabrication). Power handling: 2-5W (higher than SAW). Best for: 5 GHz Wi-Fi, 5G NR n77/n78/n79, Wi-Fi 6E at 6 GHz. (3) Selection criteria for IoT: for sub-GHz IoT (LoRa, Sigfox, NB-IoT at 700-900 MHz): use SAW. SAW provides excellent performance at these frequencies at the lowest cost. For 2.4 GHz IoT (BLE, Zigbee/Thread, Wi-Fi): SAW or TC-SAW. SAW works well up to 2.5 GHz. TC-SAW improves the temperature stability for wide-temperature IoT applications (-40 to +85°C). For 5-6 GHz IoT (Wi-Fi 6E, UWB): use BAW (FBAR). SAW performance degrades above 2.5 GHz; BAW maintains low insertion loss and high selectivity. For multiband IoT (sub-GHz + 2.4 GHz + 5 GHz): use SAW for sub-GHz, SAW/TC-SAW for 2.4 GHz, BAW for 5-6 GHz. (4) Emerging technology: XBAR (laterally-coupled BAW): a newer filter technology from Resonant (acquired by Murata). Achieves very wide bandwidth (suitable for Wi-Fi 6E and 5G n77). Higher coupling coefficient than traditional BAW. Expected to gain market share in Wi-Fi 6E/7 and 5G applications.