Low-power minimum estimation and combining with adaptive modulation

Abstract

Traditional fading mitigation techniques are designed relative to the worst-case channel conditions, resulting in a poor utilization of the spectrum and the available power a good percentage of the time. In contrast, we introduce and investigate in this paper new adaptive modulation and diversity combining techniques that jointly select the most appropriate constellation size and the most suitable diversity branches in response to the channel variation and given a desired bit error rate (BER) requirement. Numerical results show that these newly proposed adaptive modulation and combining schemes can reduce considerably the average receiver channel estimation complexity as well as the power drain from the battery while offering high spectral efficiency and satisfying the desired outage probability and BER requirements.

Joint Adaptive Transmission and Combining with Optimized Rate and Power Allocation

“…We show that the proposed schemes offer large ASE gains over the previous QAM schemes discussed in [5,6], by better taking advantage of the time-varying nature of the wireless channel. Introducing power control gives a significant reduction in outage probability.…”

“…As a consequence, the receiver tries to combine a minimum number of branches to support the highest transmission rate. When MS-GSC is combined with link adaptation in a bandwidth efficient mode, its spectral efficiency is equal to that of GSC combining [6], but at the same time MS-GSC offers a reduction in the average number of combined branches, and thus processing power savings. Therefore, we derive the optimal switching thresholds and power levels based on the GSC receiver and evaluate the power savings by utilizing these values in a MS-GSC system.…”

“…Resource management in wireless communications is a difficult task due to user mobility and highly time-variant propagation environments, thus implying adaptive solutions. Key adaptive techniques are those of adaptive modulation [ 1,2], power control [3,4], and adaptive combining [5][6][7][8].…”

“…In [5,6] new jointly adaptive modulation and combining schemes based on a multiple threshold idea are introduced. [5,6] evaluate the proposed schemes by adopting a constantpower variable-rate uncoded M-QAM scheme.…”

“…[5,6] evaluate the proposed schemes by adopting a constantpower variable-rate uncoded M-QAM scheme. Given a target bit error rate (BER), the adaptive modulator thresholds are then predetermined.…”