Wireless data networks exist in such number and variety as to be difficult to categorize and compare. Some wireless data networks run over wireless voice networks, such as mobile telephone networks. CPDP, HSCSD, PDC-P, and GPRS are examples. Other wireless networks run on their own physical layer networks, utilizing anything from antennas built into handlheld devices to large antennas mounted on towers. 802.11, LMDS,...