Communication system with channel compensating equalizer
View Patent ↗A communication system and method for extending coverage of a base transceiver station. The communication system includes processing circuitry that receives a communication signal over a wireless channel. The received communication signal is processed through an adaptable equalizer to reduce noise, distortion, interference, and frequency errors. In another aspect of the invention, a frequency of a reference signal in the communication system is adjusted to compensate for frequency errors between the communication system and the source of the communication signal. The equalized and frequency adjusted communication signal is then retransmitted into an extended coverage area. Wireless coverage is thereby provided between a base transceiver station and a mobile device in the extended coverage area.
1. A communication system for repeating wireless signals, the system comprising:
a donor antenna;
a coverage antenna; and
processing circuitry including an equalizer, the processing circuitry being operatively coupled to the donor and coverage antennas for receiving a wireless signal that is exposed to a transmission channel and processing the wireless signal through the equalizer to generate a processed signal for retransmission through one of the donor or coverage antennas;
the equalizer including a plurality of coefficients that may be adjusted with the processing circuitry to adapt the equalizer to address at least one characteristic of the transmission channel experienced by the wireless signal;
the processing circuitry further configured for comparing a bit sequence of the received and processed wireless signal to a known bit sequence of the wireless signals handled by the communication system and configured for adjusting the equalizer coefficients to minimize a difference between the bit sequence of the processed wireless signal and the known bit sequence of the wireless signals.
2. The communication system of claim 1 wherein the at least one characteristic of the transmission channel includes at least one of a phase transfer function, an amplitude transfer function, or a frequency error.
3. The communication system of claim 2 , wherein the at least one characteristic of the transmission channel varies with time.
4. The communication system of claim 1 wherein the processing circuitry is further configured to compensate for a frequency error in the received wireless signal.
5. The communication system of claim 4 wherein the processing circuitry further includes a reference clock having a frequency and is configured to compensate for the frequency error in the received wireless signal by adjusting the frequency of the reference clock.
6. The communication system of claim 5 wherein adjusting the frequency of the reference clock changes the frequency of a local carrier signal.
7. The communication system of claim 4 wherein the processing circuitry compensates for the frequency error in the received wireless signal by adding a frequency offset to the received wireless signal.
8. The communication system of claim 7 wherein the processing circuitry includes a local carrier signal generator that is synchronized to a reference clock, and the frequency offset is added to the received wireless signal by adding an estimated frequency offset to the reference clock.
9. The communication system of claim 1 wherein the donor antenna receives the wireless signal from a base transceiver station (BTS) over a wireless communication channel and the coverage antenna transmits the processed signal into an extended coverage area.
10. The communication system of claim 1 wherein processing circuitry includes a plurality of equalizers each configured to be adapted to at least one characteristic of an associated transmission channel.
11. The communication system of claim 1 wherein the communication system includes a repeater.
12. The communication system of claim 1 wherein the communication system includes a distributed antenna system.
13. A method of repeating a wireless signal through a communication system to an extended coverage area, the method comprising:
receiving a wireless signal transmitted through a wireless transmission channel;
processing the wireless signal with an equalizer including a plurality of coefficients that may be adjusted with processing circuitry, the equalizer adapted to compensate for distortion added to the wireless signal by the wireless transmission channel;
comparing a bit sequence of the received and processed wireless signal to a known bit sequence of the wireless signals handled by the communication system and adjusting the equalizer coefficients to minimize a difference between the bit sequence of the processed wireless signal and the known bit sequence of the wireless signals; and
transmitting the processed signal into the extended coverage area.
14. The method of claim 13 , wherein processing the wireless signal comprises:
determining a transfer function of the wireless transmission channel;
determining coefficients for the equalizer based at least in part on the determined transfer function of the wireless transmission channel; and
processing the received wireless signal with the equalizer to compensate for the transfer function of the wireless transmission channel.
15. The method of claim 14 , wherein determining the transfer function of the wireless transmission channel includes determining a phase transfer function of the wireless transmission channel.
16. The method of claim 15 wherein determining the phase transfer function of the wireless communication channel includes:
determining a frequency error in the received wireless signal; and
correcting the frequency error by adjusting the frequency of a reference signal.
17. The method of claim 16 wherein the reference signal is generated by a system reference clock.
18. The method of claim 14 , wherein determining the transfer function of the wireless transmission channel includes determining an amplitude transfer function of the wireless transmission channel.