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Police Department <br /> <br />MEMORANDUM <br /> <br />TO: <br /> <br />FROM: <br /> <br />DATE: <br /> <br />SUBJECT: <br /> <br />Pat Klaers <br /> <br />Jeff Beahen <br /> <br />8-19-03 <br /> <br />Conversion from CDPD to GMRS or CDMA <br /> <br />I have discussed in our budget meetings the requirement to move our police mobile <br />communication network from our current CDPD (Cellular Digital Packet Data) system to a <br />new form of technology. The system we are moving to will be either CDMA or <br />GSM/GPRS. These acronyms stand for two new communication systems that will be <br />replacing CDPD. <br /> <br />Why is this taking place? For several reasons. First, look back at cellular phones. We started <br />with analog phones and then progressed to digital phones. Within two years, all phones had <br />migrated to the digital network. The reason was that digital offered a much clearer and <br />cleaner bandwidth thus reception was better. <br /> <br />CDPD xvas also a digital cellular signal that allowed communication between any device, via <br />a cellular modem, to link that device, via the cellular digital packet data network, to a like <br />device on the other end of that network. In other ~vords, two computers could talk via a <br />cellular connection. <br /> <br />To allow lengthy transmissions of documents, the data was first compressed to use as little <br />bandwidth as possible. The data was also encrypted for security purposes and then <br />transmitted from the device modem, to a local cellular tower. The tower then identified <br />~vhere the information was headed, and routed the data to a landline known as a dedicated <br />frame relay. This relay delivered the data to the other device, in this case our server network, <br />where the data was handled, for, varded, or returned as decided by the appropriate software. <br />The data was returned in the opposite direction that it was delivered in. Data compression <br />and encryption required use of specific carrier designed algorithms. In our case, the only <br />CDPD vendor available in Minnesota until just a few months ago was AT&T Wireless. <br /> <br />We pay $49.95 per car each month for unlimited CDPD service. We originally paid $472.00 <br />a month for the frame relay. Since 1999 that cost has risen to almost $1,200 a month based <br />on surcharges imposed by AT&T. We have ten active squad computers; we eliminated five <br /> <br /> <br />