Rate adaptation using semi-open loop technique

Abstract

In a semi-open loop rate adaptation scheme for a multiple-input multiple-output (MIMO) system, a transmitter can advantageously use one or more quality metrics of an uplink as well as knowledge of device characteristics of both ends to perform fast and accurate rate adaptation.

1 . A method for adapting a rate in a multiple-input multiple-output (MIMO) system, the system including a first node and a second node in which transmissions from the first node to the second node are on a downlink channel and transmissions from the second node to the first node are on an uplink channel, each node including multiple transmitters and receivers, the method for the first node comprising: 
 estimating the uplink channel using a packet sent by the second node to the first node;    transposing the uplink channel to provide an estimated downlink channel; and    using transmitter and receiver characteristics from the first and second nodes and the estimated downlink channel to accurately adapt the rate,    wherein the receiver characteristics include a sensitivity of the second node.    
     
     
         2 . The method of  claim 1 , wherein the sensitivity of the second node includes a post-detection signal to noise ratio (SNR).  
     
     
         3 . The method of  claim 1 , wherein the transmitter characteristics include an output power per data rate.  
     
     
         4 . The method of  claim 1 , wherein the transmitter characteristics include an error vector magnitude (EVM) per output power.  
     
     
         5 . The method of  claim 1 , wherein using the transmitter and receiver characteristics includes: 
 computing a post-detection signal to noise ratio (SNR) of the second node based on the estimated downlink channel, noise floor information from the second node, and a receiver structure of the second node.    
     
     
         6 . The method of  claim 5 , wherein using the transmitter and receiver characteristics further includes: 
 adjusting the post-detection SNR with a transmit output power of the second node for a received data rate of the packet.    
     
     
         7 . The method of  claim 6 , wherein using the transmitter and receiver characteristics further includes: 
 after the adjusting, computing an estimated post-detection SNR for each rate at the second node using the transmitter power per rate of the first node, thereby building a sensitivity table for the second node.    
     
     
         8 . The method of  claim 7 , wherein using the transmitter and receiver characteristics further includes: 
 adjusting the estimated post-detection SNR for each rate at the second node with a transmitter EVM per power of the first and second nodes, if the transmitter EVM is not negligible.    
     
     
         9 . The method of  claim 7 , wherein using the transmitter and receiver characteristics further includes: 
 choosing an optimized rate by using the sensitivity table for the second node.    
     
     
         10 . The method of  claim 9 , wherein using the sensitivity table includes choosing a highest rate whose estimated post-detection SNR is larger than a threshold SNR.  
     
     
         11 . A first node in a multiple-input multiple-output (MIMO) system, the system including a second node in which transmissions from the first node to the second node are on a downlink channel and transmissions from the second node to the first node are on an uplink channel, each node including multiple transmitters and receivers, the first node comprising software with computer-implementable instructions, the first node including: 
 instructions for estimating the uplink channel using a packet sent by the second node to the first node;    instructions for transposing the uplink channel to provide an estimated downlink channel; and    instructions for using transmitter and receiver characteristics from the first and second nodes and the estimated downlink channel to accurately adapt a rate,    wherein the receiver characteristics include a sensitivity of the second node.    
     
     
         12 . The first node of  claim 1 , wherein the instructions for using the transmitter and receiver characteristics include: 
 instructions for computing a post-detection signal to noise ratio (SNR) of the second node based on the estimated downlink channel, noise floor information from the second node, and a receiver structure of the second node.    
     
     
         13 . The method of  claim 12 , wherein the instructions for using the transmitter and receiver characteristics further include: 
 instructions for adjusting the post-detection SNR with a transmit output power of the second node for a received data rate of the packet.    
     
     
         14 . The first node of  claim 13 , wherein the instructions for using the transmitter and receiver characteristics further include: 
 instructions for computing an estimated post-detection SNR for each rate at the second node using the transmitter power per rate of the first node, thereby building a sensitivity table for the second node.    
     
     
         15 . The first node of  claim 14 , wherein the instructions for using the transmitter and receiver characteristics further include: 
 instructions for adjusting the estimated post-detection SNR for each rate at the second node with a transmitter EVM per power of the first and second nodes, if the transmitter EVM is not negligible.    
     
     
         16 . The first node of  claim 14 , wherein the instructions for using the transmitter and receiver characteristics further include: 
 instructions for choosing an optimized rate by using the sensitivity table for the second node.    
     
     
         17 . The first node of  claim 16 , wherein the instructions for using the sensitivity table include instructions for choosing a highest rate whose estimated post-detection SNR is larger than a threshold SNR.  
     
     
         18 . A node in a multiple-input multiple-output (MIMO) system, the node comprising: 
 a first table that indicates a post-detection SNR for rates at another node in the MIMO system.    
     
     
         19 . The node of  claim 18 , further including a second table that indicates transmitter output power per rate at the node.  
     
     
         20 . The node of  claim 19 , further including a third table that indicates a transmitter EVM per power of the node and the other node.  
     
     
         21 . The node of  claim 20 , further including software with computer-implementable instructions for accessing at least the first and second tables.  
     
     
         22 . The node of  claim 20 , further including software with computer-implementable instructions for accessing the first, second, and third tables.