Method and apparatus to improve received signal strength indicator measurement at a receiver
In one embodiment, a receiver includes: an analog front end (AFE) circuit to receive and process an incoming radio frequency (RF) analog signal comprising a packet; an analog-to-digital converter (ADC) coupled to the AFE circuit to receive and digitize an analog signal based on the RF analog signal into a digital signal; a packet detector coupled to the ADC to detect the packet based on the digital signal; and a computation circuit coupled to the packet detector. The computation circuit may be configured to determine a received signal strength indicator (RSSI) value based at least in part on a portion of a preamble of the packet.
1 . A method comprising:
detecting, in a receiver, a packet having a plurality of orthogonal frequency division multiplexing (OFDM) symbols;
calculating, in a first computation circuit of the receiver, a received signal strength indicator (RSSI) value for at least one of the plurality of OFDM symbols; and
filtering the RSSI value if the packet is not intended for the receiver and processing the RSSI value if the packet is intended for the receiver, comprising determining an average RSSI value, comprising determining an intra-frame RSSI value comprising an average of a plurality of RSSI values for at least some of the plurality of OFDM symbols of the packet, comprising weighting more recent RSSI values with a higher weighting than one or more earlier RSSI values when determining the intra-frame RSSI value.
2 . The method of claim 1 , further comprising determining an inter-frame RSSI value comprising an average of a plurality of RSSI values for a plurality of packets.
3 . The method of claim 1 , further comprising:
providing the processed RSSI value to a controller of the receiver; and
controlling, via the controller, at least one configuration setting of at least one gain control circuit of the receiver based at least in part on the processed RSSI value.
4 . The method of claim 1 , wherein calculating the RSSI value comprises using at least one preamble field of the packet, at least one signal field of the packet, and at least part of a data portion of the packet.
5 . The method of claim 1 , wherein calculating the RSSI value comprises:
iteratively, for a plurality of subcarriers of frequency domain samples of the at least one of the plurality of OFDM symbols:
multiplying a sum of a first preamble field of the packet and a second preamble field of the packet with a complex conjugate value to obtain a product;
squaring the product; and
summing the product with a running sum, the running sum comprising at least a portion of the RSSI value.
6 . A system comprising:
an analog front end (AFE) circuit to receive and downconvert an incoming radio frequency (RF) signal comprising a packet into a second frequency signal;
a digitizer coupled to the AFE circuit to receive and digitize the second frequency signal into a digital signal;
a computation circuit coupled to the digitizer, the computation circuit to calculate a plurality of received signal strength indicator (RSSI) values based on one or more of a preamble field, a signal field, or a data field of the packet;
a processing circuit coupled to the computation circuit, the processing circuit to determine an RSSI metric based on the plurality of RSSI values, the RSSI metric comprising an intra-frame average RSSI value based on the plurality of RSSI values, and averaged in a coherent manner; and
a controller coupled to the processing circuit, wherein the controller is to adapt a communication rate between the system and a station based at least in part on the RSSI metric.
7 . The system of claim 6 , wherein the processing circuit is to determine the RSSI metric further comprising an inter-frame average RSSI value based on the plurality of RSSI values of the packet and a plurality of additional RSSI values of a plurality of additional packets, and averaged in a non-coherent manner.