Radio coverage in closed environments

In a communications system including a base station and a mobile unit, both operating at a high radio frequency, a method for communicating between the base station and the mobile unit when the mobile unit is located in an environment that is substantially closed off to high radio frequency communication between the base station and the mobile unit, comprising the steps of:

• linearly converting a base station high radio frequency signal into a low frequency signal that is capable of radiating radio frequency power into the closed environment, the low frequency signal being in a frequency band that is lower than a frequency band of the high radio frequency signal;
• using cable transmission means to distribute the low frequency signal within the closed environment;
• receiving the distributed low frequency signal in a first antenna;
• linearly converting the received low frequency signal into a reconverted high radio frequency signal;
• and
• using a second antenna to transmit the reconverted high radio frequency signal to the mobile unit.

In a communications system including a base station and a mobile unit, both operating at a high radio frequency, a method for communicating between the base station and the mobile unit when the mobile unit is located in an environment that is substantially closed off to high radio frequency communication between the base station and the mobile unit, comprising the steps of:

• using a second antenna to receive a high radio frequency signal from the mobile unit;
• linearly converting the received high radio frequency signal into a low frequency signal that is capable of radiating radio frequency power into the closed environment, the low frequency signal being in a frequency band that is lower than a frequency band of the high radio frequency signal;
• radiating the low frequency signal from a first antenna;
• using cable transmission means to receive the low frequency signal within the closed environment;
• linearly converting the received low frequency signal into a base station high radio frequency signal;
• and
• outputting the base station high radio frequency signal to the base station.

In a communications system including at least one stationary base station and a mobile unit, both operating at a high radio frequency, a mobile base station for providing communication system service to the mobile unit when the mobile unit is located in a vehicle that is travelling in an environment that is substantially closed off to high radio frequency communication between the stationary base station and the mobile unit, the mobile base station comprising:

• first means, disposed on the vehicle, for wireless coupling to a cable transmission means, coupled to a stationary base station, for two-way, low frequency signal propagation within the closed environment;
• a linear two-way frequency converter, disposed on the vehicle, including:
• a low frequency port connected to the first wireless coupling means for two-way coupling to a low frequency signal;
• and
• a high frequency port for two-way coupling to a high radio frequency signal that is compatible with the high radio frequency used by the communications system, the high radio frequency signal being in a frequency band that is higher than a frequency band of the low frequency signal;
• and
• second means, disposed on the vehicle and connected to the high frequency port of the linear two-way frequency converter, for wireless high radio frequency coupling to the mobile unit located in the vehicle.