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We present an efficient circulant approximation-based MIMO equalizer architecture for the CDMA downlink. This reduces the direct matrix inverse (DMI) of size (NF × NF) with O((NF)3) complexity to some FFT operations with O(NFlog2(F)) complexity and the inverse of some (N × N) submatrices. We then propose parallel and pipelined VLSI architectures wi...
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... in the parallel FFTs are studied extensively in multilevels, for example, the BFU level, the stage level, and the FFT-processor level. Catapult C scheduled RTLs for 32-point FFTs with 16 bits are com- pared with Xilinx v32FFT Core in Table 5 for a single FFT. Catapult C design demonstrates much smaller size for differ- ent solutions, for example, from solution 1 with 8 multipli- ers and 535 slices to solution 3 with only one multiplier and 551 slices. ...
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Citations
... The vector e k denotes a unit vector with a single " one " at cursor position k and " zeros " at all other positions. The calculation of the equalizer coefficients can efficiently be implemented using fast Fourier transform (FFT)-based algorithms, e.g., [42] and [43], or the conjugated gradient algorithm [44]. Such an equalizer therefore represents a low-complexity HSDPA receiver that is feasible for real-time implementation in a chip [45]. ...
In this paper, we report on the results of physical-layer multiple-input-multiple-output High-Speed Downlink Packet Access (HSDPA) throughput measurements. These measurements were carried out in two different environments: 1) an alpine valley and 2) a city. In addition to the standard compliant single- and two-transmit-antenna HSDPA schemes, we defined and measured a four-transmit-antenna HSDPA scheme to explore future enhancements of the standard. To analyze the implementation loss, we introduce the so-called achievable mutual information and compare it with the actually measured data throughput. We find that the measured data throughput is far from the optimal, leaving room for future receiver optimizations. Furthermore, we find that the achievable mutual information is far from the channel capacity. Thus, optimizations in the standard could further improve HSDPA performance.
... Here, e m denotes a unit vector with a "one" at position m and "zeros" at all other positions. Such equalizers are currently used in HSDPA receivers because they can be implemented efficiently using FFT-based algorithms like [22], or the conjugated gradient algorithm [23]. The output of the equalizer is soft-demapped and softdecoded in a Turbo decoder using eight iterations. ...
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... Prior to the equalization, pilot-based channel estimation is done. By adding additional post-processing to the equalizer filter, the equalizer may be adapted for a 2 2 × MIMO system [3, 4]. We first present the tap solver, then the equalizer filter. ...
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