Handoff system and method

• US 20040224691A1
• Filed: 05/13/2004
• Published: 11/11/2004
• Est. Priority Date: 05/09/2003
• Status: Abandoned Application

• Current Assignee: Zion Hadad
• Original Assignee: Zion Hadad
• Inventors: Hadad, Zion
• Application Number:
  US10/844,526
• Publication Number:
  US 20040224691A1
• Time in Patent Office: Days
• US Class Current: 455/442
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data

Abstract

A soft handoff system for a wideband wireless cellular network, comprises diversity reception enhancement means, channel equalization for coherent processing means and coherent summing means. The downlink system further includes means for implementing diversity, allowing two base stations to concurrently transmit the same information, with coherent summing at the mobile receiver. A soft handoff method for a wideband wireless cellular network, comprises: 1) The mobile subscriber continuously evaluates the quality of the channel; When it deteriorates, the mobile requests a handoff; 2) the base station activates diversity transmissions from one or more additional base stations, which transmit the same messages/packets to the mobile; The subcarriers allocation is transmitted to the mobile; 3) the mobile adds coherently the receptions from two or more base stations, for improved SNR.

Claims

1. A soft handoff system for a wideband wireless cellular network, comprising diversity reception enhancement means, channel equalization for coherent processing means and coherent summing means.

2. The soft handoff system according to claim 1, wherein the downlink system further includes means for implementing diversity, allowing two base stations to concurrently transmit the same information, with coherent summing at the mobile receiver.

3. The soft handoff system according to claim 1, further including means for allocating a larger bandwidth to a mobile in the handoff region.

4. The soft handoff system according to claim 3, further including means for saving system resources by reducing instabilities and unnecessary multiple switching of base stations.

5. The soft handoff system according to claim 1, further including means for performing channel estimation for each of several channels, means for correcting the data in each channel and for summing the received information for reception improvement by diversity.

6. The soft handoff system according to claim 1, further including means in the uplink for concurrent reception of a mobile in two base stations, including the presently assigned contact for that mobile, as well as a potential base station to tranfer to.

7. The soft handoff system according to claim 6, wherein using these receptions and coordination between base stations to achieve a smart, planned, more effective handoff.

8. A soft handoff method for a wideband wireless cellular network, comprising:

1) The mobile subscriber continuously evaluates the quality of the channel;

When it deteriorates, the mobile requests a handoff;

2) The base station activates diversity transmissions from one or more additional base stations, which transmit the same messages/packets to the mobile;

The subcarriers allocation is tranmsitted to the mobile;

3) The mobile adds coherently the receptions from two or more base stations, for improved SNR;

The mobile evaluates the quality of reception from the original base station and from the additional base station;

4) When the reception from the additional base station is reliable and above a preset quality level, the receiver is assigned to that base station and the diversity transmissions end.

9. A soft handoff method for a wideband wireless cellular network, comprising:

1) The mobile subscriber continuously computes its location or his SNR;

The location or SNR is reported to the base station;

2) The base station and the mobile continuously evaluate the situation, to decide whether a handoff is required;

a. if the mobile nears the boundary to another cell, as indicated in its measured location/SNR

b. if the quality of service deteriorates

3) When a handoff is deemed necessary, the base station coordinates diversity transmission, for also sending messages/packets to the mobile from a second base station, or possibly from more than one additional base station. Each base station will use a different channel, comprising a different group of pilots;

4) The distance to the other base stations is measured, and the location of the mobile. If there is no good reception from the additional base stations, other paths may be activated—

another base station, or another sector from the second base station. Thus, one or more alternate channels to the mobile are established.