Wireless communications using overlay network devices within coverage areas of underlay network devices

Abstract

A wireless communication technique provides mobility for a mobile station ( 52 ) to communicate with an overlay network device ( 40 ), which is within a coverage area ( 34 ) of an underlay network device ( 24 ), when the mobile station ( 52 ) is within a coverage area ( 42 ) of both devices. The overlay network device ( 40 ) broadcasts at least two downlink channels. A cell code (e.g., a scrambling code or pseudo noise offset) of a first one of the downlink channels identifies an overlay network device ( 40 ) exclusively. The mobile station ( 52 ) can detect the first downlink channel responsive to an indication of the exclusive cell code from the underlay network device. A second one of the downlink channels allows for subsequent, ongoing communications between the mobile station and the overlay network device.

1 . A method of communicating in a system including at least one underlay network device having a first coverage area and at least one overlay network device having a second, smaller coverage area within the first coverage area of the underlay network device, comprising the steps of:
 using a selected plurality of cell codes for identifying overlay network devices exclusively; and   communicating on a first downlink channel of at least two downlink channels of an overlay network device, wherein a cell code of the first downlink channel is one of the selected plurality of cell codes such that a mobile station communicating with an underlay network device can detect the overlay network device as a candidate for communications with the mobile station.   
   
   
       2 . The method of  claim 1 , comprising
 broadcasting the at least two downlink channels from the overlay network device; and   using a cell code that is distinct from the selected plurality of cell codes for a second one of the at least two downlink channels.   
   
   
       3 . The method of  claim 2 , comprising
 providing an indication of the cell code of the second downlink channel on the first downlink channel; and   providing an indication to a mobile station using the first downlink channel to communicate with the overlay network device on the second downlink channel.   
   
   
       4 . The method of  claim 2 , comprising
 broadcasting the first downlink channel using a first signal strength; and   broadcasting the second downlink channel using a second, greater signal strength.   
   
   
       5 . The method of  claim 1 , comprising
 determining at least the one of the selected plurality of cell codes based on a communication with the underlay network device.   
   
   
       6 . The method of  claim 5 , comprising
 detecting the first downlink channel using the determined cell code; and   determining a cell code of a second one of the downlink channels from information provided on the first downlink channel.   
   
   
       7 . The method of  claim 6 , comprising
 using the first downlink channel for detecting the overlay network device; and   conducting subsequent communication with the overlay network device on the second downlink channel.   
   
   
       8 . The method of  claim 6 , comprising
 detecting a signal strength of the first and second downlink channels, respectively; and   selecting the one of the downlink channels having a greater signal strength for communicating with the overlay network device.   
   
   
       9 . The method of  claim 1 , wherein the cell codes comprise at least one of a scrambling code or a pseudo noise offset. 
   
   
       10 . The method of  claim 1 , wherein there are eight cell codes in the selected plurality of cell codes and any other possible cell codes are allocated for use on a second one of the two downlink channels of an overlay network device. 
   
   
       11 . The method of  claim 1 , comprising
 including the selected plurality of cell codes in a neighbor list of an underlay network device; and   providing an indication of the neighbor list to any mobile station receiving from the underlay network device.   
   
   
       12 . The method of  claim 1 , comprising
 establishing a first threshold for a mobile station currently communicating with an underlay network device to switch to communicating with an overlay network device; and   establishing a second, higher threshold for a mobile station currently communicating with an overlay network device to switch to communicating with an underlay network device.   
   
   
       13 . A wireless communication device comprising
 a transmitter that broadcasts at least two downlink channels, a cell code of a first one of the downlink channels is one of a selected plurality of cell codes used for identifying overlay network devices exclusively and a cell code of a second one of the downlink channels is distinct from the selected plurality of cell codes.   
   
   
       14 . The device of  claim 13 , wherein the transmitter is configured to
 provide an indication of the cell code of the second downlink channel on the first downlink channel; and   provide an indication to a mobile station using the first downlink channel to communicate on the second downlink channel.   
   
   
       15 . The device of  claim 13 , wherein the transmitter is configured to
 broadcast the first downlink channel using a first signal strength; and   broadcast the second downlink channel using a second, greater signal strength.   
   
   
       16 . The device of  claim 13 , wherein the cell codes comprise at least one of a scrambling code or a pseudo noise offset. 
   
   
       17 . The device of  claim 13 , wherein there are eight cell codes in the selected plurality of cell codes and any other possible cell codes are allocated for use on the second one of the two downlink channels. 
   
   
       18 . The device of  claim 13 , wherein the transmitter comprises an overlay network device configured to provide a coverage area that is smaller than a coverage area of an underlay network device when the transmitter is within the coverage area of the underlay network device.