AMPS was the first cellular network standard proposed in 1971 and launched commercially in 1983. It used analog FM technology with 666 total channels spaced at 30 kHz. AMPS was upgraded in 1989 to support 832 channels. Narrowband AMPS was developed as a short term solution to increase capacity on existing AMPS spectrum. Digital cellular standards like IS-54 and IS-136 were introduced to further increase capacity while maintaining compatibility with AMPS. IS-95 introduced CDMA technology to cellular. GSM was launched in Europe in 1982 and used TDMA along with FDMA to support simultaneous voice users on the same channel. Mobile satellite systems provide cellular coverage globally but have high infrastructure costs.