Improvement for the B-CDMA PCS links in an urban environment by using a directional antenna at the mobile terminal

A multi-ray model was developed to predict the relative strength and DOA of the rays propagating in a 'regular' urban environment. Field measurements have verified the validity of the model. There is a clear advantage to using a directional antenna at the mobile terminal for a B-CDMA spread spectrum signal at 1.9 GHz. To be able to realize the full advantage of the directional antenna, one must estimate the DOA. Field data shows an improvement of 6.5 to 7.5 dB for an 8.0 dBi directional antenna as compared to a 0.0 dBi omnidirectional antenna. This is contrary to previously reported results (that were based on tests of FM signals in a macro-cellular environment). The directional antenna helps in reducing the fade depth and duration, and improves SNR when pointed in the right direction. Allocation of higher frequencies (1.9 GHz) for PCS, enables the use of a compact, yet a highly directional antenna at the mobile. The 6 GHz band is being investigated by AT&T for future PCS applications. Closing the link at 6 GHz may require the use of a directional antenna. The paper proves that it may be advantageous, and proposes a model that may be used to optimize other system parameters.<<ETX>>