Soft handoff method for uplink wireless communications

• US 7,483,408 B2
• Filed: 06/26/2002
• Issued: 01/27/2009
• Est. Priority Date: 06/26/2002
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Bevan, David Damian Nicholas, Robson, Julius G
• Primary Examiner(s): ZEWDU, MELESS NMN
• Application Number:
  US10/180,609
• Publication Number:
  US 20040001460A1
• Time in Patent Office: 2,407 Days
• Field of Search: 455436-451, 455/137, 455/432.1, 455/432.3, 455433-434, 4554521-4522, 455/453, 455/550.1, 455/556.2, 455560-561, 455/62, 455/517, 455524-526, 370/335, 370/342, 370328-333, 370338-341, 370/310, 370343-345, 375/316, 375/340, 375/267, 375/347
• US Class Current: 370/331
• CPC Class Codes: H04B 7/022 Site diversity; Macro-diversity using two or more spaced independent antennas H04B7/04
• CPC Class Codes: H04B 7/0491 using two or more sectors, i.e. sector diversity
• CPC Class Codes: H04W 16/24 Cell structures
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Soft-handoff methods involve receiving an uplink signal from a user equipment at more than one basestation. The uplink signals are processed at each basestation before being backhauled to a common point for use to derive a single signal from the user equipment. One problem with previous types of soft-handoff methods is that relatively complex processing is required at each basestation in order to demodulate and decode the signals. It is also desired to further increase uplink capacity as compared with known types of soft-handoff methods. This is achieved by backhauling signals without carrying out any decoding of the uplink signal at the basestation. The backhauled signals are combined at a common point using maximal ratio combining before being fully demodulated and decoded. As a result capacity is increased and required user equipment transmit power is reduced.

Claims

1. A method of receiving backhauled communication signals in a wireless communications network, said signals comprising forward error correction coded frames and said method being carried out at a combiner node in the communications network and said method comprising, the step of;

(i) receiving backhauled encoded signals from a plurality of basestations in the communications network, said backhauled encoded signals being formed from signals from a given user equipment, wherein said backhauled signals have not undergone decoding prior to reception at said combiner node and wherein said backhauled encoded signals comprise signals received by said plurality of base stations which have been processed to form complex received signal values each representative of a modulation symbol and said backhauled encoded signals have not undergone demodulation prior to reception at said node and wherein said backhauled encoded signals comprise a plurality of signal-to-noise-and-interference-ratio estimates per said coded frame.

2. The method as claimed in claim 1 which further comprises combining backhauled encoded signals received from the plurality of basestations in respect of said given user equipment by using maximal ratio combination to produce one backhauled encoded signal.

3. The method as claimed in claim 1 which further comprises demodulating the one backhauled encoded signal.

4. The method as claimed in claim 2 which further comprises decoding said demodulated, backhauled, encoded signal.

9. A computer readable medium encoded with computer executable instructions for causing a combiner node to carry out the method of claim 1.

5. A method of backhauling uplink communication signals received from a user equipment in a wireless communications network, said signals comprising forward error correction coded frames and said method being carried out at a basestation in the communications network and comprising the step of:

(i) receiving uplink encoded, modulated signals from the user equipment in the communications network;

(ii) processing said received uplink signals to form un-decoded and un-demodulated complex received values representative of a modulation symbol and to form a plurality of signal-to-noise-and-interference-ratio estimates per said coded frame;

(iii) backhauling the processed signals formed from said received signals to a specified node in the communications network without first decoding and demodulating said received signals.

6. The method as claimed in claim 5 wherein said received signal values and SNIR values are produced subsequent to rake filtering and antenna array processing (AAP) processing.

10. A computer readable medium encoded with computer executable instructions for causing a base station to carry out the method of claim 5.

7. A base station for backhauling uplink communication signals received from a user equipment in a wireless communications network, said signals comprising forward error correction coded frames and said basestation comprising:

(i) a receiver arranged to receive uplink encoded, modulated signals from the user equipment in the communications network;

(ii) a processor arranged to process said received uplink signals to form un-decoded and un-demodulated complex received signal values each representative of a modulation symbol and to form a plurality of signal-to-noise-and-interference-ratio estimates per said coded frame;

(iii) an output arranged to backhaul the processed signals formed from said received signals to a specified node in the communications network without first decoding and demodulating said received signals.

8. A combiner for receiving backhauled communication signals in a wireless communications network, said signals comprising forward error correction coded frames and said combiner being provided at a node in the communications network and comprising:

(i) an input arranged to receive backhauled encoded signals from a plurality of basestations in the communications network, said backhauled encoded signals comprising signals received by a plurality of base stations which have been processed to form complex received signal values each representative of a modulation symbol and to form a plurality of signal-to-noise-and-interference-ratio estimates per said coded frame, said backhaul encoded signals being formed from at least some signals from a given user equipment; and

wherein said backhauled signals have not undergone decoding and demodulation prior to reception at said node.

11. A method of backhauling uplink communication signals, said signals comprising forward error correction coded frames, in a wireless communications network comprising a plurality of base stations, a user equipment and a combiner node, said method comprising, at each of the base stations:

(i) receiving uplink encoded, modulated signals from the user equipment in the communications network;

(ii) processing said received uplink signals to form complex received values representative of a modulation symbol and to form a plurality of signal-to-noise-and-interference-ratio estimates per said coded frame;

(iii) backhauling the processed signals formed from said received signals to the combiner node in the communications network without first decoding and demodulating said received signals;

and said method further comprising, at the combiner node;

(iv) combining each backhauled encoded signal received from the plurality of said base stations in respect of the same user equipment to produce one backhauled encoded signal.

12. A wireless communications network comprising a plurality of base stations and a combiner node, wherein each of the base stations comprises:

a receiver arranged to receive uplink encoded, modulated signals from a user equipment in the communications network, said signals comprising forward error correction coded frames;

a processor arranged to form complex received values each representative of a modulation symbol from the received signals and to form a plurality of signal-to-noise-and-interference-ratio estimates per said coded frame;

an output arranged to backhaul the processed signals formed from said received signals to the combiner node in the communications network without first decoding and demodulating said received signals;

and wherein the combiner node comprises;

an input arranged to receive backhauled encoded signal from the plurality of base stations and to combine each backhauled encoded signal received in respect of the same user equipment to produce one backhauled encoded signal.