Link Resource Adaptation for Multiantenna Bit-Interleaved Coded Multicarrier Systems

Abstract

The availability of flexible radio interfaces capable of adapting their configuration to the time-varying operating environment is the key response to the demand encountered in modern wireless networks for high data rates under strict quality of service (QoS) constraints. To this end, this paper develops a novel link resource adaptation (LRA) scheme for soft-decoded multiantenna (MIMO) bit interleaved coded orthogonal frequency division multiplexing (BIC-OFDM) transmissions employing automatic repeat request (ARQ) mechanisms. As the first step, a simple link performance evaluation model based on the effective signal-to-noise ratio (SNR) mapping concept is derived in a closed-form expression that it is shown to yield better accuracy than previous techniques. Then, an effective LRA strategy is formulated taking advantage of that framework. The aim is maximizing the goodput (GP) metric, that is to say, the number of information bits delivered without error to the user by unit of time, over the available radio resources, such as the power distribution on the subchannels, coding rate, modulation order and the MIMO configuration. The numerical results demonstrate considerable performance gains compared with nonadaptive transmissions, while keeping the computational complexity at affordable levels in view of the specific structure of the GP objective function

Adaptive coding and modulation using imperfect CSI in cognitive BIC-OFDM systems

“…Messages are transmitted by means of a packet-oriented BIC-OFDM communication system consisting of N subcarriers within a bandwidth B [14]. Each packet contains N p information bits and N CRC bits for the cyclic redundancy check (CRC), which leads to a total of N u = N p + N CRC bits per packet.…”

“…The evaluation of PER(φ, ) is not an easy task. In [14], an accurate link performance evaluation model, referred to as κESM, has been proposed for the BIC-OFDM system. This model provides a closed-form expression for the effective SNR γ .…”

“…The effective SNR γ has the important property that the PER of the considered BIC-OFDM system where the SNRs and transmission mode of the subcarriers are given by and φ, respectively, is approximately equal to PER ESM (r, γ ), which denotes the PER of an equivalent BPSK system (i.e., using the same convolutional code with rate r) which operates over an AWGN channel with SNR equal to γ . The effective SNR is calculated as [14] …”

“…The EGP from (13) can now be approximated by replacing PER(φ, ) by PER ESM (r, γ ), with γ given by (14). The reference curves PER ESM (r, γ ) can be stored in a lookup table for each code rate r from the set D r .…”

“…This effective SNR is the operating point at which an equivalent coded system, which uses the same modulation and coding scheme, operating over an additive white Gaussian noise (AWGN) channel, has the same performance as the system under consideration. A very promising mapping function, called the cumulantgenerating function-based ESM (κESM), was introduced in [14]. This mapping function combines the simplicity of exponential ESM (EESM) with the accuracy of mutual information ESM (MIESM) [15].…”