Forward link based rescue channel method and apparatus for telecommunication systems

Abstract

A forward rescue procedure (FRP) for preventing loss of signal and dropped connections between a mobile station and the infrastructure in a wireless telecommunications network is disclosed. The FRP allows wireless systems to recover from forward link failures at the mobile station that would otherwise result in dropped connections. Examples of failure scenarios that can be overcome using the FRP include forward link Layer 2 acknowledgement failures and loss of forward link signal due to a fade that causes loss of signal for a period of time exceeding a threshold value. In response to a potential connection drop situation, a mobile station will autonomously add base station pilot channels to the active set of its rake receiver in order to rescue the connection in danger of dropping. Concurrently, the wireless network infrastructure will initiate transmission on alternative forward link channels that are likely to be monitored by the mobile station during an FRP. If the same channels are monitored by the MS and transmitted on by the infrastructure, the connection in danger of dropping can be rescued.

1 . In a communications network having a plurality of sectors and a mobile station (MS), the MS including a MS active set, a method for continuing a connection between at least one of the plurality of sectors and the MS, comprising: 
 detecting an acknowledgement failure at the MS;    autonomously adding one or more pilots to the MS active set at the MS by itself when the MS detects the acknowledgement failure, each pilot corresponding to one of the plurality of sectors;    transmitting over one or more assumed code channels (ACCs) for use in a rescue from at least one of the plurality of sectors;    at the MS, searching for one or more ACCs from the sectors corresponding to the pilots in the MS active set;    at the MS, discovering one or more ACCs are receivable from at least one of the plurality of sectors; and    continuing the connection at the MS when the one or more receivable ACCs are discovered.    
   
   
       2 . The method as recited in  claim 1:   wherein the discovery of one or more receivable ACCs at the MS comprises receiving a predetermined number of consecutive good frames of the ACC from at least one of the plurality of sectors; and    wherein continuing the connection at the MS when the one or more receivable ACCs are discovered comprises continuing the connection at the MS when the predetermined number of consecutive good frames are received by the MS.    
   
   
       3 . The method of  claim 1 , the MS having transmitted one or more pilot strength measurement messages (PSMMs) prior to detecting the acknowledgement failure, the method further comprising adding one or more pilots to the MS active set based on information contained in the one or more PSMMs.  
   
   
       4 . The method of  claim 1 , the MS having received one or more overhead messages containing information on the ACC prior to detecting the acknowledgement failure, the method further comprising determining one or more ACCs for use in the rescue based on information contained in the one or more overhead messages.  
   
   
       5 . The method of  claim 1 , further comprising: 
 ceasing transmission from the MS after detecting the acknowledgement failure; and    resuming transmissions from the MS if a predetermined number of consecutive good frames of the ACC from one or more of the sectors is received at the MS.    
   
   
       6 . The method of  claim 1 , the method further comprising: 
 starting a rescue timer after detecting the acknowledgement failure; and    terminating the connection if the rescue timer expires before a downlink is received from the network at the MS.    
   
   
       7 . The method of  claim 3 , further comprising dynamically changing the MS active set based on pilot signal strength information measured by the MS during the rescue.  
   
   
       8 . The method of  claim 7 , further comprising transmitting a PSMM from the MS every time the MS active set is autonomously changed.  
   
   
       9 . The method of  claim 1 , wherein the detecting step is carried out by detecting a Layer 2 Acknowledgement Failure at the MS.  
   
   
       10 . The method of  claim 1 , wherein the detecting step is carried out by determining that the MS did not receive an acknowledgement to a message sent by the MS after a predetermined number of retransmissions of the message by the MS.  
   
   
       11 . The method of  claim 1 , further comprising detecting a Forward Link Fade Failure at the MS.  
   
   
       12 . The method of  claim 11 , wherein detecting the Forward Link Fade Failure at the MS is determined by receiving a predetermined number of consecutive bad frames at the MS.  
   
   
       13 . The method of  claim 1 , the network including a network active set, the method further comprising: 
 adding one or more sectors to the network active set; and    selecting one or more sectors from the network active set from which to transmit one of the ACCs.    
   
   
       14 . The method of  claim 13 , wherein continuing the connection further comprises: 
 receiving a predetermined number of consecutive good frames from the MS by the network; and    continuing the connection at the network when the predetermined number of consecutive good frames are received by the network.    
   
   
       15 . The method of  claim 13 , the method further comprising: 
 starting a rescue timer after detecting a potentially failing connection; and    terminating the potentially failing connection if the rescue timer expires before an uplink is received from the MS at the network.    
   
   
       16 . The method of  claim 13 , further comprising detecting a potentially failing connection caused by a Layer 2 Acknowledgement Failure at the network.  
   
   
       17 . The method of  claim 16 , further comprising detecting the potentially failing connection caused by the Layer 2 Acknowledgement Failure at the network by determining that the network received a predetermined number of retransmitted messages from the MS after a predetermined number of acknowledgements of the message were sent by the network.  
   
   
       18 . The method of  claim 13 , further comprising detecting a potentially failing connection caused by a Forward Link Fade Failure at the network.  
   
   
       19 . The method of  claim 18 , further comprising detecting the potentially failing connection caused by a Forward Link Fade Failure at the network by detecting that the network did not receive a predetermined number of valid frames from the MS.  
   
   
       20 . The method of  claim 13 , further comprising determining whether the rescue should be attempted before transmitting one of the ACCs from at least one of the plurality of sectors.  
   
   
       21 . The method of  claim 13 , further comprising adding one or more sectors to the network active set based on their locations, orientation, system or band.  
   
   
       22 . The method of  claim 13 , further comprising: 
 receiving, at the network, one or more PSMMs from the MS; and    adding one or more sectors to the network active set based on information contained in the one or more PSMMs.    
   
   
       23 . The method of  claim 13 , further comprising dynamically changing the one or more ACCs for use in the rescue.  
   
   
       24 . In a communications network having a plurality of sectors and one or more mobile stations (MSs), a method for continuing a connection between at least one of the plurality of sectors and the MSs, comprising: 
 detecting a potentially failing connection at the MS;    autonomously and dynamically changing one or more pilots in the MS active set at the MS during a rescue when the MS detects the potentially failing connection, each pilot corresponding to one of the plurality of sectors;    transmitting at least one rescue channel from at least one of the plurality of sectors;    monitoring one or more of the plurality of sectors for the rescue channel corresponding to the pilots in the MS active set at the MS;    at the MS, discovering one or more rescue channels are receivable; and    continuing the connection when the one or more receivable rescue channels are discovered.    
   
   
       25 . A method of operating a mobile station (MS) to continue a connection between the MS and a communications network having a plurality of sectors, the MS having a MS active set, the network capable of transmitting over one or more assumed code channels (ACCs) from at least one of the plurality of sectors, the method comprising: 
 detecting an acknowledgement failure;    autonomously adding one or more pilots to the MS active set when the MS detects the acknowledgement failure, each pilot corresponding to one of the plurality of sectors;    searching for one or more ACCs from the sectors corresponding to the pilots in the MS active set;    discovering one or more ACCs are receivable from at least one of the plurality of sectors; and    continuing the connection when the one or more receivable ACCs are discovered.    
   
   
       26 . The method as recited in  claim 25:   wherein the discovery of one or more receivable ACCs comprises receiving a predetermined number of consecutive good frames of the ACC from at least one of the plurality of sectors; and    wherein continuing the connection when the one or more receivable ACCs are discovered comprises continuing the connection when the predetermined number of consecutive good frames are received.    
   
   
       27 . The method of  claim 25 , the MS having transmitted one or more pilot strength measurement messages (PSMMs) prior to detecting the acknowledgement failure, the method further comprising adding one or more pilots to the MS active set based on information contained in the one or more PSMMs.  
   
   
       28 . The method of  claim 25 , the MS having received one or more overhead messages containing information on the ACC prior to detecting the acknowledgement failure, the method further comprising determining one or more ACCs for use in a rescue based on information contained in the one or more overhead messages.  
   
   
       29 . The method of  claim 25 , further comprising: 
 ceasing transmission from the MS after detecting the acknowledgement failure; and    resuming transmissions from the MS if a predetermined number of consecutive good frames of the ACC from one or more of the sectors is received.    
   
   
       30 . The method of  claim 25 , the method further comprising: 
 starting a rescue timer after detecting the acknowledgement failure; and    terminating the connection if the rescue timer expires before a downlink is received from the network.    
   
   
       31 . The method of  claim 27 , further comprising dynamically changing the MS active set based on pilot signal strength information received by the MS during the rescue.  
   
   
       32 . The method of  claim 31 , further comprising transmitting a PSMM from the MS every time the MS active set is dynamically changed.  
   
   
       33 . The method of  claim 25 , wherein the detecting step is carried out by detecting a Layer 2 Acknowledgement Failure.  
   
   
       34 . The method of  claim 25 , wherein the detecting step is carried out by determining that the MS did not receive an acknowledgement to a message sent by the MS after a predetermined number of retransmissions of the message by the MS.  
   
   
       35 . The method of  claim 25 , further comprising detecting a Forward Link Fade Failure.  
   
   
       36 . The method of  claim 25 , wherein detecting the Forward Link Fade Failure is determined by receiving a predetermined number of consecutive bad frames.  
   
   
       37 . A communications system, comprising: 
 a network having a network processor and a plurality of sectors for transmitting and receiving signals; and    a mobile station (MS) having a MS processor and a MS active set for receiving a signal from one or more of the plurality of sectors, the MS processor programmed for detecting an acknowledgement failure;    wherein the network processor is further programmed for transmitting over one or more assumed code channels (ACCs) for use in a rescue from at least one of the plurality of sectors; and    wherein the MS processor is further programmed for autonomously adding one or more pilots to the MS active set by itself, each pilot corresponding to one of the plurality of sectors, searching for one or more ACCs from the sectors corresponding to the pilots in the MS active set, discovering one or more ACCs are receivable from at least one of the plurality of sectors, and continuing the connection when the one or more receivable ACCs are discovered, if the MS processor detects the acknowledgement failure.    
   
   
       38 . The system of  claim 37 , the MS processor further programmed for: 
 transmitting one or more pilot strength measurement messages (PSMMs) to the network prior to detecting the acknowledgement failure; and    adding one or more pilots to the MS active set based on information contained in the one or more PSMMs if the MS processor detects the acknowledgement failure.    
   
   
       39 . The system of  claim 37 , the MS processor further programmed for autonomously changing the MS active set based on pilot signal strength information measured by the MS during the rescue if the MS processor detects the acknowledgement failure.  
   
   
       40 . The system of  claim 37 , wherein the acknowledgement failure is a Layer 2 Acknowledgement Failure.  
   
   
       41 . The system of  claim 37 , the MS processor further programmed for detecting a Forward Link Fade Failure.  
   
   
       42 . The system of  claim 37 , the network including a network active set, the network processor further programmed for adding one or more sectors to the network active set and selecting one or more sectors from the network active set from which to transmit one of the ACCs if the network processor detects the potentially failing connection.  
   
   
       43 . The system of  claim 38 , the network processor further programmed for detecting a Layer 2 Acknowledgement Failure.  
   
   
       44 . The system of  claim 37 , the network processor further programmed for detecting a Forward Link Fade Failure.  
   
   
       45 . The system of  claim 37 , the network processor further programmed for dynamically changing the one or more ACCs for use in the rescue.  
   
   
       46 . A communications system, comprising: 
 a network having a network processor and a plurality of sectors for transmitting and receiving signals; and    a mobile station (MS) having a MS processor and a MS active set for receiving signals from one or more of the plurality of sectors, the MS processor programmed for detecting a potentially failing connection with the one or more sectors in the network;    wherein the network processor is further programmed for transmitting over at least one rescue channel from at least one of the plurality of sectors; and    wherein the MS processor is further programmed for autonomously and dynamically changing one or more pilots corresponding to one or more respective rescue channels in the MS active set by itself during a rescue, monitoring one or more of the plurality of sectors for the rescue channel, discovering one or more rescue channels are receivable, and continuing the connection when the one or more receivable rescue channels are discovered, if the MS processor detects the potentially failing connection.    
   
   
       47 . A communications system, comprising: 
 a network having a network processor and a plurality of sectors for transmitting and receiving signals; and    a mobile station (MS) having a MS processor and an MS active set for receiving signals from one or more of the plurality of sectors, the MS processor programmed for detecting an Acknowledgement Failure;    wherein the MS processor is further programmed for autonomously adding a pilot corresponding to a rescue channel to the MS active set by itself, and transmitting over the rescue channel if the MS processor detects the acknowledgement failure; and    wherein the network processor is further programmed for monitoring the MS for the rescue channel, discovering one or more rescue channels are receivable, and continuing the connection when the one or more receivable rescue channels are discovered.    
   
   
       48 . A mobile station (MS) for communicating with a network, the network having a plurality of sectors capable of transmitting one or more assumed code channels (ACCs) for use in a rescue, the MS comprising: 
 a MS active set; and    a MS processor programmed for detecting an acknowledgement failure, autonomously adding one or more pilots to the MS active set by itself when the acknowledgement failure is detected, each pilot corresponding to one of the plurality of sectors, searching for one or more ACCs from the sectors corresponding to the pilots in the MS active set, discovering one or more ACCs receivable from at least one of the plurality of sectors, and continuing the connection when the one or more receivable ACCs are discovered.    
   
   
       49 . The MS of  claim 48 , wherein the MS processor is further programmed for transmitting one or more pilot strength measurement messages (PSMMs) prior to detecting the acknowledgement failure, and adding one or more pilots to the MS active set based on information contained in the one or more PSMMs, if the MS processor detects the acknowledgement failure.  
   
   
       50 . The MS of  claim 48 , wherein the MS processor is further programmed for dynamically changing the MS active set based on pilot signal strength information received by the MS during the rescue, if the MS processor detects the acknowledgement failure.  
   
   
       51 . The MS of  claim 48 , wherein the acknowledgement failure is detected by a Layer 2 Acknowledgement Failure.  
   
   
       52 . The MS of  claim 48 , wherein the MS processor is further programmed for detecting a Forward Link Fade Failure.  
   
   
       53 . A mobile station (MS) for communicating with a communications network having a plurality of sectors capable of receiving a rescue channel, the MS comprising: 
 a MS processor programmed for detecting an Acknowledgement Failures autonomously adding one or more pilots to a MS active set by itself when the acknowledgement failure is detected, each pilot corresponding to one of the plurality of sectors, and transmitting over the rescue channel to one or more of the plurality of sectors.    
   
   
       54 . A communications system, comprising: 
 first means having a plurality of sectors for transmitting and receiving signals; and    second means having a MS active set for receiving signals from one or more of the plurality of sectors, and for detecting an acknowledgement failure;    wherein the first means includes means for transmitting over one or more assumed code channels (ACCs) for use in a rescue from at least one of the plurality of sectors; and    wherein the second means includes means for autonomously adding one or more pilots to the MS active set by itself when the second means detects the acknowledgement failure, each pilot corresponding to one of the plurality of sectors, 
 means for searching for one or more ACCs from the sectors corresponding to the pilots in the MS active set,  
 means for discovering one or more ACCs are receivable from at least one of the plurality of sectors, and  
 means for continuing the connection when the one or more receivable ACCs are discovered.  
   
   
   
       55 . The system of  claim 54 , wherein: 
 the first means includes a network active set, and    the first means adds one or more sectors to the network active set and selects one or more sectors from the network active set from which to transmit one of the ACCs.    
   
   
       56 . A mobile station (MS) for communicating with a network, the network having a plurality of sectors capable of transmitting one or more assumed code channels (ACCs) for use in a rescue, the MS comprising: 
 a MS active set;    means for detecting an acknowledgement failure;    means for autonomously adding one or more pilots to the MS active set by itself if the acknowledgement failure is detected, each pilot corresponding to one of the plurality of sectors;    means for searching for one or more ACCs from the sectors corresponding to the pilots in the MS active set;    means for discovering one or more ACCs receivable from at least one of the plurality of sectors; and    means for continuing the connection when the one or more receivable ACCs are discovered.    
   
   
       57 . The method of  claim 1 , further comprising: 
 dynamically changing the pilots in the MS active set at the MS.    
   
   
       58 . The method of  claim 1 , further comprising: 
 dynamically changing the sectors transmitting the ACCs for use in the rescue.    
   
   
       59 . The method of  claim 1 , wherein the autonomously adding step is carried out without receiving a handoff direction message instructing a changing of the pilot in the MS active set from the sectors.  
   
   
       60 . The method of  claim 1 , wherein the autonomously adding step adds one or more pilots that have not been specified in a handoff direction message instructing a changing of the pilot in the MS active set.  
   
   
       61 . The method of  claim 25 , wherein the autonomously adding step is carried out without receiving a handoff direction message instructing a changing of the pilot in the MS active set from the communications network.  
   
   
       62 . The method of  claim 25 , wherein the autonomously adding step adds one or more pilots that have not been specified in a handoff direction message instructing a changing of the pilot in the MS active set.  
   
   
       63 . The system of  claim 37 , wherein the MS processor autonomously adds one or more pilots to the MS active set without receiving a handoff direction message instructing a changing of the pilot in the MS active set from the network.  
   
   
       64 . The system of  claim 37 , wherein the MS processor autonomously adds one or more pilots that have not been specified in a handoff direction message instructing a changing of the pilot in the MS active set.  
   
   
       65 . The system of  claim 46 , wherein the MS processor is programmed for detecting the potentially failing connection caused by a Layer 2 Acknowledgement Failure.  
   
   
       66 . The system of  claim 47 , wherein the MS processor is programmed for detecting the acknowledgement failure caused by a Layer 2 Acknowledgement Failure.  
   
   
       67 . The system of  claim 47 , wherein the MS processor is programmed for transmitting over the rescue channel to a targeted sector, the pilot corresponds to the targeted sector, and the targeted sector is dynamically selected.  
   
   
       68 . The system of  claim 47 , wherein the network processor is further programmed for dynamically selecting one or more sectors to monitor the MS for the rescue channel.  
   
   
       69 . The mobile station of  claim 48 , wherein the MS processor autonomously adds one or more pilots to the MS active set without receiving a handoff direction message instructing a changing of the pilot in the MS active set from the network.  
   
   
       70 . The mobile station of  claim 48 , wherein the MS processor autonomously adds one or more pilots that have not been specified in a handoff direction message instructing a changing of the pilot in the MS active set.  
   
   
       71 . A method of operating a mobile station (MS) to continue a connection between the MS and a communications network having a plurality of sectors, the MS having a MS active set, the network capable of transmitting over one or more assumed code channels (ACCs) from at least one of the plurality of sectors, the method comprising: 
 detecting a potentially failing connection;    autonomously and dynamically changing one or more pilots in the MS active set during a rescue after the MS detects the potentially failing connection, each pilot corresponding to one of the plurality of sectors;    searching for one or more ACCs from the sectors corresponding to the pilots in the MS active set;    discovering one or more ACCs are receivable from at least one of the plurality of sectors; and    continuing the connection when the one or more receivable ACCs are discovered.    
   
   
       72 . A mobile station (MS) for communicating with a network, the network having a plurality of sectors capable of transmitting one or more assumed code channels (ACCs) for use in a rescue, the MS comprising: 
 a MS active set; and    a MS processor programmed for detecting a potentially failing connection, autonomously and dynamically changing one or more pilots in the MS active set by itself during the rescue when the potentially failing connection is detected, each pilot corresponding to one of the plurality of sectors, searching for one or more ACCs from the sectors corresponding to the pilots in the MS active set, discovering one or more ACCs receivable from at least one of the plurality of sectors, and continuing the connection when the one or more receivable ACCs are discovered.    
   
   
       73 . The system of  claim 37 , wherein the acknowledgement failure is detected by detecting that the MS has not received an acknowledgement to a message sent by the MS after a predetermined number of retransmissions of the message by the MS.  
   
   
       74 . The MS of  claim 48 , wherein the acknowledgement failure is detected by detecting that the MS has not received an acknowledgement to a message sent by the MS after a predetermined number of retransmissions of the message by the MS.