摘要:
An antenna array system combines the antenna signals from separate antennas using at least one delay in the RF path of an antenna. In certain embodiments, the antenna array system combines the antenna signals in the Radio Frequency (RF) domain before analog-to-digital (A/D) conversion, thereby reducing the amount of hardware required when compared to antenna array systems where the antenna signals are combined digitally. In doing so, signals from antennas are combined with signals from a plurality of antennas to determine if they improve signal quality. Only signals determined to improve signal quality are maintained as active. In accordance with other aspects, the antenna system selects parameter settings for the antenna array to provide enhanced performance.
摘要:
A digital (de)modulation system uses a larger code set of M codes for N length codes, where M>N, to provide an increased data rate while maintaining the coding gain. For example, the system can use 16 different codes each having a length of 11 chips in a code set while the conventional M-ary keying systems use a code set size of 8 for 11-chip codes or 8-chip codes. By extending the code set size, the system increases the data rate of the system. With 16 codes and the ability to change the sign of the code to be transmitted, the system can encode 5 data bits on both I and Q, so a total of 10 data bits can be encoded per code symbol. In this embodiment, a code symbol contains an 11 chip code on a I modulation branch and an 11 chip code on a Q modulation branch. As such, using 11 chip codes and a chip rate of 11 Mhz, the system provides a data rate of 10 Mbps while conventional M-ary keying systems can only achieve 8 Mbps using the same code length and chip rate. By extending the code length, the processing gain is increased. The extended code set is not orthogonal, so a non-zero cross-correlation value results between the different codes of the code set. However, the resulting noise and multipath performance degradation can be kept small by choosing code sets with small cross-correlation values (nearly orthogonal). The magnitudes of both cross-correlation values and auto-correlation sidelobes should preferably be below half a code length. In some embodiments, the code set is derived from orthogonal codes which are modified to reduce the autocorrelation sidelobes associated with the orthogonal codes. In other embodiments, the code set is derived using a complementary code which provides low autocorrelation sidelobes and is modified to reduce the cross-correlation values between the codes.
摘要:
A soft handover system is provided for a multiple sub-carrier communication system, applicable to the uplink (mobile unit to base stations) and/or the downlink (base stations to mobile unit). The soft handover system uses multiple sub-carriers to simultaneously transmit multiple sub-carrier signals between at least two base stations and the mobile unit in the uplink and/or downlink. In certain embodiments, the soft handover system provides for synchronized multiple sub-carrier transmission such that the delay differences between the multiple sub-carrier transmissions from the different base stations arriving at the mobile unit are within the guard time of the multiple sub-carrier symbols. Certain embodiments of the soft handover system use the same set of sub-carriers for links between the mobile unit and the base stations of different cells, and other embodiments use different sets of sub-carriers for links between the mobile unit and the base stations of different cells. In the soft handover system using the same set of sub-carriers, the mobile unit receives downlink signals with identical data content from the different base stations. The mobile unit need not distinguish between the signals from the different base stations. The mobile unit just treats the downlink signals from the different base stations as multipath components, thereby increasing the diversity gain. In the case of a multiple sub-carrier CDMA system, the soft handover system can use the same sub-carriers as well as the same CDMA encoding and/or spreading code.
摘要:
A digital (de)modulation system uses a larger code set of M codes for N length codes, where M>N, to provide an increased data rate while maintaining the coding gain. For example, the system can use 16 different codes each having a length of 11 chips in a code set while the conventional M-ary keying systems use a code set size of 8 for 11-chip codes or 8-chip codes. By extending the code set size, the system increases the data rate of the system. With 16 codes and the ability to change the sign of the code to be transmitted, the system can encode 5 data bits on both I and Q, so a total of 10 data bits can be encoded per code symbol. In this embodiment, a code symbol contains an 11 chip code on a I modulation branch and an 11 chip code on a Q modulation branch. As such, using 11 chip codes and a chip rate of 11 Mhz, the system provides a data rate of 10 Mbps while conventional M-ary keying systems can only achieve 8 Mbps using the same code length and chip rate. By extending the code length, the processing gain is increased. The extended code set is not orthogonal, so a non-zero cross-correlation value results between the different codes of the code set. However, the resulting noise and multipath performance degradation can be kept small by choosing code sets with small cross-correlation values (nearly orthogonal). The magnitudes of both cross-correlation values and auto-correlation sidelobes should preferably be below half a code length. In some embodiments, the code set is derived from orthogonal codes which are modified to reduce the autocorrelation sidelobes associated with the orthogonal codes. In other embodiments, the code set is derived using a complementary code which provides low autocorrelation sidelobes and is modified to reduce the cross-correlation values between the codes.
摘要:
A wireless receiver receives signals at a plurality of antennas and the combined signal is compensated for channel distortion. In other aspects, a wireless receiver includes a minimum distance receiver applied to the output of a whitened-matched filter, which combines channel matched filtering and whitening, using one or more antennas.
摘要:
The scaleable OFDM system according to the principles of the present invention provides increased flexibility and adaptability by providing scaling of the operating parameters and/or characteristics for the OFDM system. For example, control circuitry can scale the bit rate by scaling of the OFDM symbol duration, the number of carriers and/or the number of bits per symbol per carrier. Scaleability permits the scaleable OFDM system to operate in various communications environments requiring various operating parameters and/or characteristics. By scaling the operating parameters and/or characteristics of the OFDM system when control circuitry determines that different operating parameters and/or characteristics are necessary or advantageous, the control circuitry can dynamically change the operating parameters and/or characteristics, thereby providing compatibility or the desired performance. For example, by dynamically scaling the bit rate, widely varying signal bandwidths, delay spread tolerances and signal-to-noise ratio (SNR) requirements can be achieved. As such, a scaleable OFDM system is particularly suitable for application in mobile, wireless communication devices, which support a variety of services, in a variety of environments, indoor as well as outdoor and in radio channels with differing bandwidths.
摘要:
The combined complementary encoder and modulation system for an OFDM transmitter system combines complementary coding and modulation and exploits the similarity of their mathematical structure to reduce implementation complexity. In doing so, the improved OFDM transmitter system uses complementary codes to reduce the power-to-average power (PAP) ratio of the transmitted signal. Additionally, the combined complementary encoder and modulation system can be modified to provide scaleablity, which allows a transmitter to operate in various transmission environments. More precisely, scaleability refers to the transmitter's capability to adapt the bit rate of the data, so as to satisfy varying signal bandwidth, delay spreads, tolerance and signal-to-noise ratio requirements.