US 8,478,203 B2Granted

Phase synchronization of base stations via mobile feedback in multipoint broadcasting

OwnerXiao-an Wanginventor

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Abstract

Multipoint broadcasting requires the base stations to be phase-synchronized. Methods and apparatus are described that provide phase synchronization of base stations with the downlink-channel phase feedback by mobile users. Also described are methods and apparatus that make phase synchronization of base stations independent of multipoint-broadcast sessions, thus reducing the synchronization overhead and improving network capacity. The methods and apparatus utilize model-based downlink-channel phase feedback that reduces most of the feedback overhead. Applications of the described methods and apparatus include wireless multipoint broadcast systems, also known as coordinated multipoint transmission, or CoMP, in LTE-A (long-term evolution, advanced) systems, and frequency and phase synchronization of a cluster of base stations, or more generally, of a cluster of wireless devices.

Claims17

Dependent claims

A method for communications in a wireless network with a predetermined signal bandwidth, having a multipoint-broadcast set comprising a plurality of base stations and a plurality of mobile users, some of said mobile users being phase-feedback mobile users, comprising:

(a) sending downlink-pilot signals via a downlink channel from said base stations to said phase-feedback mobile users,
(b) generating downlink-channel estimates at said phase-feedback mobile users,
(c) sending standard uplink-pilot signals from said mobile users to said base stations,
(d) generating uplink-channel estimates at said base stations,
(e) transmitting downlink-channel phase information from said phase-feedback mobile users to said base stations,
(f) determining carrier-phase differences (CPDs) between said base stations and said phase-feedback mobile users,
(g) exchanging said CPDs among said base stations, and
(h) determining relative phases between said base stations from said CPDs,
whereby said base stations are phase-synchronized when said relative phases have been determined, and said base stations are able to determine the pre-coding matrix for multipoint broadcasting with said uplink-channel estimates and said relative phases.

6 more elements

A method for communications in a wireless network with a predetermined signal bandwidth, having a plurality of non-reference devices and a plurality of reference devices, some of said reference devices being phase-feedback reference devices, and said non-reference devices and said reference devices forming a phase-synchronizable set, comprising:

(a) sending downlink-pilot signals via a downlink channel from said non-reference devices to said phase-feedback reference devices,
(b) generating downlink-channel estimates at said phase-feedback reference devices,
(c) transmitting downlink-channel phase information from said phase-feedback reference devices to said non-reference devices,
(d) determining carrier-phase differences (CPDs) between said non-reference devices and said phase-feedback reference devices,
(e) exchanging said CPDs among said non-reference devices, and
(f) determining relative phases between said non-reference devices from said CPDs,
whereby said non-reference devices are phase-synchronized when said relative phases have been determined.

4 more elements

Dependencies are inferred from the claim text.