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Random phase multiple access
Random phase multiple access (RPMA) is a low-power wide-area channel access method used exclusively for machine-to-machine (M2M) communication on the Internet of Things (IoT).〔http://www.iotjournal.com/articles/view?13070〕
RPMA is a technology communication system employing direct-sequence spread spectrum (DSSS) with multiple access. RPMA technology employs tight transmit power control and high receiver sensitivity (-142dBm)〔http://eandt.theiet.org/magazine/2013/11/the-m2m-connection.cfm〕 with a total 172 dB link budget.〔http://globenewswire.com/news-release/2015/04/07/722182/10127711/en/Energate-Announces-Its-LC2100-a-New-Cost-Effective-Easy-to-Deploy-Load-Control-Switch-for-Utilities.html〕 RPMA utilizes the 2.4 GHz band,〔http://eandt.theiet.org/magazine/2013/11/the-m2m-connection.cfm〕 a globally available cost free spectrum. RPMA self modulates to find clear signal both on the network and device level. It is also optimized for maximum coverage and battery efficiency, as opposed to cellular which is designed for high throughput but requires a lot of power. To save battery life it has a special connection protocol in which access points ping the device, checks the device status receives any data, then closes the connection. It is estimated that the majority of M2M and IoT connections need this kind of low data throughput, high battery life connectivity.
==Coverage==
RPMA is currently used in 38 private networks worldwide. The 2.4 GHz spectrum is available worldwide and is cost-free to use. RPMA access points can cover 300 square miles. It would take 30 cellular towers to cover the same area. Ingenu, who owns RPMA, reportedly has access points covering 450 square miles each. RPMA is deployed in both the public Machine Network, as well as private networks.
RPMA's uplink is 624 Kbps and downlink is 156 Kbps, which is about 10 times the speed of dialup internet. When moving RPMA's speeds drop, as is typical for wireless connections, to 2Kbps. These speeds are adequate for the majority of IoT applications being faster than 2G and orders of magnitude faster than Sigfox.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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