Title :
Base station transmitter antenna arrays with mobile to base feedback
Author :
Gerlach, Derek ; Paulraj, Arogyaswami
Author_Institution :
Inf. Syst. Lab., Stanford Univ., CA, USA
Abstract :
A central base station simultaneously communicates with several mobile users by allocating a separate time or frequency channel for each mobile to prevent undesired crosstalk. However, each time or frequency channel may be reused among several mobiles by means of an antenna array at the base station which points a separate beam at each user. The downlink beamformer would normally operate in an “open loop” mode, in which the base steers a mainlobe in the direction of each mobile. Such a system may operate effectively in a free space environment with no multipath. In the presence of scattering, open loop methods will not perform adequately. A new “closed loop” technique is presented in which each mobile user feeds back to the base estimates of the received signal amplitudes. Using feedback, the base station can achieve precision beamforming resulting in lower crosstalk and improved signal separation even in the presence of strong scattering environments
Keywords :
antenna arrays; code division multiple access; crosstalk; electromagnetic wave scattering; feedback; frequency allocation; frequency division multiple access; mobile radio systems; multiplexing; radio stations; radio transmitters; time division multiple access; CDMA; FDMA; SDMA; TDMA; base station; closed loop technique; code division multiple access; crosstalk; downlink beamformer; feedback; free space environment; frequency channel; frequency division multiple access; mainlobe; received signal amplitudes; scattering; signal separation; spatial division multiplexing; time division multiple access; transmitter antenna arrays; Antenna arrays; Base stations; Crosstalk; Downlink; Frequency; Mobile antennas; Radio spectrum management; Scattering; Transmitters; Transmitting antennas;
Conference_Titel :
Signals, Systems and Computers, 1993. 1993 Conference Record of The Twenty-Seventh Asilomar Conference on
Conference_Location :
Pacific Grove, CA
Print_ISBN :
0-8186-4120-7
DOI :
10.1109/ACSSC.1993.342304