US 4,383,332 A · High capacity digital mobile radio system

Abstract

The present invention relates to a mobile radio base station (14) capable of communicating with a large number of mobile stations by implementing space diversity and time-division retransmission techniques in a digital communication system. The digital base station contains a plurality of antenna elements (16.sub.1 -16.sub.M) and a plurality of retransmission branches (18.sub.1 -18.sub.M) associated in a one-to-one relationship. When the base station receives a digital communication signal from a mobile station, each antenna element receives the signal with a unique random phase (.theta..sub.1 -.theta..sub.m) due to the effects of the environment on signal transmission. The signal is then processed through the plurality of retransmission branches, where each branch adapts to compensate for the random phase of the signal received by its associated antenna element. Conversely, when the base station transmits a signal back to the mobile station, each retransmission branch adds the conjugate of its associated random phase to the signal to be transmitted, allowing the environment to "undo" the effect of the conjugate random phase so that the signals transmitted by the plurality of antenna elements will arrive coherently at the mobile station.

Claims13

Dependent claims

A mobile radio base station (14) employing space diversity and time-division retransmission comprising:

a plurality of M antenna elements (16.sub.1, 16.sub.2, . . . , 16.sub.M) for operating in a space diversity mode capable of receiving a mobile-to-base communication signal from a remote station and transmitting a base-to-mobile communication signal to said remote station;
a plurality of M retransmission branches (18.sub.1, 18.sub.2, . . . , 18.sub.M) associated in a one-to-one relationship with said plurality of M antenna elements and capable of operating in either one of a transmitting mode or a receiving mode, each retransmission branch when operating in its receiving mode being capable of compensating for the incoming random phase associated with said mobile-to-base communication signal and subtracting said random phase therefrom, and when operating in its transmitting mode being capable of adding said random phase to said base-to-mobile communication signal;
combining means (20) coupled to the outputs of said plurality of M retransmission branches when operating in their receiving mode and capable of combining said output signals of said branches to form a coherent output signal, and
input means (21) capable of applying an input baseband signal to said plurality of retransmission branches when operating in their transmitting mode allowing said plurality of M antenna elements to transmit said base-to-mobile communication signal
CHARACTERIZED IN THAT
the base station is capable of receiving and transmitting digital communication signals, wherein each retransmission branch includes means (22,23,24,25,26,28,30,32,34) capable of both down-converting the mobile-to-base communication signal to a baseband representation thereof and up-converting the input baseband signal to a phased base-to-mobile communication signal.

3 more elements

A time-division retransmission method of transmitting digital communication signals between at least one base station and at least one mobile station, the method comprising the steps of

(a) transmitting a first carrier burst from the at least one mobile station during a first reference interval (RI.sub.1),
(b) transmitting message information from said at least one mobile station to said at least one base station during a first message interval (MI.sub.1),
(c) transmitting message information from said at least one base station to said at least one mobile station during a second message interval (MI.sub.2)
CHARACTERIZED IN THAT
the method comprises the further step of
(d) prior to step (c), transmitting a second carrier burst from the at least one mobile station to the at least one base station during a second reference interval (RI.sub.2).

3 more elements

A method of both compensating for the random phase associated with a mobile-to-base digital communication signal received at a base station and forming a baseband digital signal thereat, the method comprising the steps of:

(a) receiving at said base station a reference signal transmitted by a mobile station,
(b) detecting the random phase of said reference signal,
(c) receiving at said base station a message signal transmitted by said mobile station, and
(d) compensating for the random phase detected in step (b) from said message signal received in step (c)
CHARACTERIZED IN THAT
the method comprises the further steps of
(e) in performing step (a), down-converting the reference signal into a first reference signal quadrature component and a second reference signal quadrature component,
(f) in performing step (b), forming a first reference coefficient associated with the random phase of said first reference signal and a second reference coefficient associated with the random phase of said second reference signal,
(g) in performing step (c), down-converting the message signal into a first message signal quadrature component and a second message signal quadrature component
(h) in performing step (d), multiplying said first reference coefficient with said first message signal quadrature component to form a first baseband component, and multiplying said second reference coefficient with said second message signal quadrature component to form a second baseband component,
(i) adding the first and second baseband components to form the baseband digital communication signal.

8 more elements

Dependencies are inferred from the claim text.

High capacity digital mobile radio system

Life of this patent

High capacity digital mobile radio system

Life of this patent

Abstract

Claims13