The second generation (2G) cellular networks are the current workhorse for machine-to-machine (M2M) communications. Diversity in 2G devices can be present both in form of multiple receive branches and blind repetitions. In presence of diversity, intersymbol interference (ISI) equalization and co-channel interference (CCI) suppression are usually very complex. In this paper, we consider the improvements for 2G devices with receive diversity. We derive a low-complexity receiver based on a channel shortening filter, which allows to sum up all diversity branches to a single stream after filtering while keeping the full diversity gain. The summed up stream is subsequently processed by a single stream Max-log-MAP (MLM) equalizer. The channel shortening filter is designed to maximize the mutual information lower bound (MILB) with the Ungerboeck detection model. Its filter coefficients can be obtained mainly by means of discrete-Fourier transforms (DFTs). Compared with the state-of-art homomorphic (HOM) filtering based channel shortener which cooperates with a delayed-decision feedback MLM (DDF-MLM) equalizer, the proposed MILB channel shortener has superior performance. Moreover, the equalization complexity, in terms of real-valued multiplications, is decreased by a factor that equals the number of diversity branches.
[1]
Giulio Colavolpe,et al.
40 Years with the Ungerboeck Model: A Look at its Potentialities [Lecture Notes]
,
2015,
IEEE Signal Processing Magazine.
[2]
Qiuting Huang,et al.
Efficient channel shortening for higher order modulation: Algorithm and architecture
,
2012,
2012 IEEE International Symposium on Circuits and Systems.
[3]
Alexandra Duel-Hallen,et al.
Delayed decision-feedback sequence estimation
,
1989,
IEEE Trans. Commun..
[4]
Walter Hirt.
Capacity and information rates of discrete-time channels with memory
,
1988
.
[5]
G. David Forney,et al.
Maximum-likelihood sequence estimation of digital sequences in the presence of intersymbol interference
,
1972,
IEEE Trans. Inf. Theory.
[6]
Jiunn-Tsair Chen,et al.
A two-stage hybrid approach for CCI/ISI reduction with space-time processing
,
1997,
IEEE Communications Letters.