Ernest T. Tsui

Adaptive IQ imbalance correction for OFDM systems with frequency and timing offsets

Direct conversion (from RF to complex I and Q baseband in one mixing step) architectures are increasingly popular as they enable lower implementation costs. The resulting frequency dependent amplitude and phase imbalance between the I and Q conversion rails can cause significant performance degradations to complex modulation techniques such as 64-QAM and above typically used for high data rate transmission. Conventionally, this IQ imbalance is only corrected at the receiver at power up while the imbalance at the remote transmitter is assumed to be pre-corrected. However, aging, manufacturability, and temperature variations can be difficult to calibrate and can result in performance degradation (e.g., range reduction, etc.). Future ad hoc networks will also require imbalance correction per packet as they might come from many different transmitters. in this paper, we propose an adaptive scheme in the receiver to correct the IQ imbalances at the remote transmitter as well as the receiver. The proposed scheme, as it jointly corrects remote transmitter and local receiver I imbalances in the presence of frequency and timing rate offsets, is therefore more robust than the earlier results.

Joint adaptive transmitter/receiver IQ imbalance correction for OFDM systems

Direct conversion architectures are increasingly popular as they enable lower implementation costs. However, the receiver is very sensitive to IQ imbalances in particular for complex modulation techniques such as 64-QAM and above typically used for high data rate transmission. Conventionally, this IQ imbalance is only corrected at the receiver while the imbalance at the remote transmitter is assumed to be pre-corrected. However, aging, manufacturability, and temperature variations can be difficult to calibrate and can result in performance degradation (e.g., range reduction, etc.). We propose an adaptive scheme in the receiver to correct the IQ imbalances at the remote transmitter as well as the receiver. The proposed scheme, as it jointly corrects the IQ imbalances, is therefore more robust than the earlier results.

Application of the Intel/sup /spl reg// reconfigurable communications architecture to 802.11a, 3G and 4G standards

The increasing number of wireless LAN, MAN, PAN and WAN standards creates challenges for wireless equipment manufacturers: support multiple protocols in a multimode radio, reduce time to market for adding new capability for new standards, and keeping up with the ever increasing data rates that are required. One solution to these challenges is the Intel/sup /spl reg// reconfigurable communications architecture (RCA). RCA is a power and area efficient design for physical layer (PHY) and lower MAC processing. To achieve the desired efficiency for multiprotocol processing, we defined several programmable accelerators for key communications operations. This work describes our analysis of mapping various wireless protocols (WLAN, 3G and a proposed 4G standard) to RCA. These results indicate that our architecture has enough flexibility and scalability to support a range of standards.