Link adaptation for multimode mimo wireless system

Abstract

A wireless receiver is disclosed that is capable of efficiently selecting a preferred transmission/detection scheme for use in wireless communication. The wireless receiver may be capable of communicating using any one of several transmission/detection schemes. Therefore, in order to select a preferred transmission/detection scheme, the wireless receiver calculates at least one metric for the transmission/detection schemes. In MIMO systems, the link adaptation is more complex and the metrics typically must be more accurate. Because of the potentially substantial amount of calculation that may be required to calculate the metric, the wireless receiver is capable of performing the individual calculations in optimized ways, as well as easily reducing the total number of metrics required to be calculated so as to reduce overall complexity.

What is claimed is: 
     
         1 . A wireless receiver capable of communicating with a wireless transmitter within a wireless communication environment, the wireless receiver comprising:
 a measurement module configured to measure, based on a signal received from the wireless transmitter, a communication parameter;   a memory module configured to store transmission schemes that may be implemented by the wireless transmitter; and   a link adaptation module configured to select, from the stored transmission schemes, a preferred transmission scheme based on the communication parameter, the link adaptation module including:
 a constraint module configured to determine a performance constraint; and 
 a metric computation module configured to calculate a metric based on the communications parameter by which to compare each of the transmission schemes that satisfy the performance constraint. 
   
     
     
         2 . The wireless receiver of  claim 1 , wherein each of the transmission schemes is defined by a corresponding combination of transmission parameters. 
     
     
         3 . The wireless receiver of  claim 1 , wherein the communication parameter is indicative of a characteristic of a channel over which the received signal was communicated. 
     
     
         4 . The wireless receiver of  claim 1 , wherein the memory module is configured to store constraint sets corresponding to at least one of wireless receiver performance, wireless transmitter capabilities, and channel conditions, and
 wherein the constraint module is configured to determine the performance constraint based on the stored constraint sets.   
     
     
         5 . The wireless receiver of  claim 1 , wherein the metric computation module is configured to generate a subset of viable transmission schemes that satisfy the performance constraint, and
 wherein the metric computation module calculates a metric only for each of the viable transmission schemes.   
     
     
         6 . The wireless receiver of  claim 5 , wherein the metric computation module is configured to calculate a first metric for a first viable transmission scheme and to calculate a second metric for a second viable transmission scheme,
 wherein the first metric is different from the second metric.   
     
     
         7 . The wireless receiver of  claim 1 , further comprising a decision module configured to compare the metrics calculated by the metric computation module, and to select the preferred transmission scheme based on the comparison. 
     
     
         8 . The wireless receiver of  claim 7 , wherein the decision module is configured to select, as the preferred transmission scheme, the transmission scheme having a preferred metric from among the transmission schemes. 
     
     
         9 . A multilayer wireless receiver capable of communicating with a wireless transmitter within a wireless communication environment over multiple layers, the wireless receiver comprising:
 a metric computation module configured to determine a plurality of viable transmission/detection scheme pairs, and to calculate a metric for each of the viable transmission/detection scheme pairs,   wherein the metric is calculated individually for each of the multiple layers.   
     
     
         10 . The multilayer wireless receiver of  claim 9 , wherein the metric includes per layer signal-to-noise ratio. 
     
     
         11 . The multilayer wireless receiver of  claim 10 , wherein the metric computation module is configured to calculate an average signal-to-noise ratio across the multiple layers and a channel differential, and
 wherein the metric computation module is configured to calculate the per layer signal-to-noise ratio for a first channel by adding the calculated channel differential to the average signal-to-noise ratio, and for a second channel by subtracting the calculated channel differential from the average signal-to-noise ratio.   
     
     
         12 . The multilayer wireless receiver of  claim 9 , wherein the at least one metric includes per layer normalized modulation constrained capacity. 
     
     
         13 . The multilayer wireless receiver of  claim 12 , wherein the metric computation module is configured to calculate the normalized modulation constrained capacity for a first layer based on a modulation of the first layer, a modulation of a second layer, effective signal-to-noise ratio of the first layer, signal-to-noise offset of the second layer with respect to the first layer, and orthogonality of the first and second layers. 
     
     
         14 . The multilayer wireless receiver of  claim 12 , wherein the metric computation module is configured to calculate the per layer normalized modulation constrained capacity based on a conditional probability of values of a transmitted data symbol based on the values of a received data symbol corresponding to the transmitted symbol. 
     
     
         15 . The multilayer wireless receiver of  claim 14 , wherein the metric computation module calculates the conditional probability as a combination of sub-probabilities of a plurality of bits of the transmitted data symbol, and
 wherein metric computation module is configured to calculate the sub-probabilities from the log likelihood ratios of the corresponding bits.   
     
     
         16 . A method of selecting a preferred transmission/detection scheme by a wireless receiver that is capable of communicating with a wireless transmitter via a wireless communication environment, the method comprising:
 measuring a signal received from the wireless transmitter to obtain a communication parameter;   determining a plurality of viable transmission/detection schemes that fall within a performance constraint;   calculating a metric for each of the viable transmission/detection schemes based on the communication parameter;   comparing the calculated metrics of the viable transmission/detection schemes;   selecting, based on the comparison, a preferred transmission/detection scheme; and   informing the wireless transmitter of the preferred transmission/detection scheme.   
     
     
         17 . The method of  claim 16 , wherein the wireless transmitter and the wireless receiver communicate over multiple layers, and
 wherein the calculating of the metric includes, for each of the viable transmission/detection schemes, calculating the metric individually for each of the multiple layers.   
     
     
         18 . The method of  claim 17 , wherein the calculating of the metric includes calculating a first metric for a first subset of the viable transmission/detection schemes and calculating a second metric for a second subset of the viable transmission/detection schemes. 
     
     
         19 . The method of  claim 17 , wherein each of the multiple layers includes a plurality of channels, and
 wherein the calculating of the metric individually for each of the multiple layers includes calculating, for each of the multiple layers, the metric individually for each of the channels.   
     
     
         20 . The method of  claim 16 , wherein the calculating of the metric includes:
 calculating a first metric for the viable transmission/detection schemes;   selecting, based on the calculating of the first metric, a subset of the viable transmission/detection schemes; and   calculating a second metric for the subset of the viable transmission/detection schemes,   wherein the first metric requires less computation to calculate than the second metric, and   wherein the comparing of the calculated metrics includes comparing the calculated second metrics.   
     
     
         21 . The method of  claim 16 , wherein the wireless transmitter and the wireless receiver communicate over multiple layers, and
 wherein the calculating of the metric includes:
 sub-sampling channels for which the metric can be calculated; and 
 calculating the metric individually for each of the sub-sampled layers.