An electronic device comprising: a mobile wireless cellular communications device comprising a first housing, a spatial diversity wireless transceiver carried by said first housing, at least one first antenna carried by said first housing and coupled to said spatial diversity wireless transceiver, a wireless local area networking -WLAN-transceiver carried by said first housing and coupled to said spatial diversity wireless transceiver, and a processor; and an external antenna device comprising a second housing, at least one second antenna carried thereby and configured to be coupled to said spatial diversity wireless transceiver, a wireless transceiver, and a battery configured to power said wireless transceiver; said spatial diversity wireless transceiver configured to selectively operate said at least one first antenna and said at least one second antenna to provide spatial diversity; said WLAN transceiver configured to wirelessly couple said at least one second antenna to said spatial diversity wireless transceiver; said processor configured to operate said spatial diversity wireless transceiver in a first multiple-input/multiple-output -MIMO- rank mode when said at least one second antenna is not connected to said spatial diversity wireless transceiver, and further configured to operate said spatial diversity wireless transceiver in a second MIMO rank mode when said at least one second antenna is connected to said spatial diversity wireless transceiver, the second MIMO rank mode being greater than the first MIMO rank mode. a mobile wireless cellular communications device comprising a first housing, a spatial diversity wireless transceiver carried by said first housing, at least one first antenna carried by said first housing and coupled to said spatial diversity wireless transceiver, a wireless local area networking -WLAN-transceiver carried by said first housing and coupled to said spatial diversity wireless transceiver, and a processor; and a first housing, a spatial diversity wireless transceiver carried by said first housing, at least one first antenna carried by said first housing and coupled to said spatial diversity wireless transceiver, a wireless local area networking -WLAN-transceiver carried by said first housing and coupled to said spatial diversity wireless transceiver, and a processor; and an external antenna device comprising a second housing, at least one second antenna carried thereby and configured to be coupled to said spatial diversity wireless transceiver, a wireless transceiver, and a battery configured to power said wireless transceiver; said spatial diversity wireless transceiver configured to selectively operate said at least one first antenna and said at least one second antenna to provide spatial diversity; said WLAN transceiver configured to wirelessly couple said at least one second antenna to said spatial diversity wireless transceiver; said processor configured to operate said spatial diversity wireless transceiver in a first multiple-input/multiple-output -MIMO- rank mode when said at least one second antenna is not connected to said spatial diversity wireless transceiver, and further configured to operate said spatial diversity wireless transceiver in a second MIMO rank mode when said at least one second antenna is connected to said spatial diversity wireless transceiver, the second MIMO rank mode being greater than the first MIMO rank mode.