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Maximum-likelihood (ML) receivers are optimum receivers for MIMO systems, but their complexity grows exponentially with the modulation order of the codeword and the number of spatial layers. The Reduced Complexity ML (R-ML) receivers based on low complexity adaptation of the max-log MAP detector and reduction of searching space are a good compromise to satisfy complexity-performance trade-off. In...
We describe a channel sounding measurement campaign for cellular broadband wireless communications with high speed trains that was carried out in the context of the project CORRIDOR. The campaign combines MIMO and carrier aggregation to achieve very high throughputs. We compare two different scenarios, the first one reflects a cellular deployment, where the base station is about 1km away from the...
For time division duplexing (TDD) systems, the physical channel in the air is reciprocal for uplink (UL) and downlink (DL) within the channel coherence time. However when the transceivers' radio frequency (RF) hardware is taken into consideration, TDD channel reciprocity no longer holds because of the non-symmetric characteristics of RF transmit and receive chains. Relative calibration has been proposed...
We present an in-depth performance analysis of the gains of physical layer (PHY) abstraction when compared to a full implementation of the physical layer. The abstraction model uses either effective signal to noise plus interference (SINR) mapping or mutual information effective SINR mapping and covers different transmission modes as well as support for hybrid automatic repeat request. Using the OpenAirInterface...
This paper presents OpenAirITS, an open-source Software-Defined Radio platform for DSRC (802.11p) technology. We extended the Linux 802.11 subsystem, developed a soft-modem and a dedicated driver for the OpenAirInterface Express-MIMO FPGA board. The low-layer PHY functions of DSRC have not been coded on the chipset, but instead as a soft-modem, which allows the SDR platform to be easily modified according...
Multi-user MIMO communication can provide significant gains by exploiting spatial multiplexing. However, it requires better feedback to provide accurate channel state information at the transmitter (CSIT) for minimizing the multi-user interference. 3GPP LTE provides support for MU-MIMO, but it is not sufficient to extract sizable gains. In this paper, our primary goal is to efficiently exploit the...
Most of the recent wireless communication systems are interference limited rather than noise limited. In the case of a very strong interferer the conventional assumption of the interference as Gaussian is extremely suboptimal. However optimal (capacity achieving) receivers utilize some prior knowledge about the interference to reach optimality. The link abstraction for such receiver structures is...
In the next generation cellular systems, such as LTE-A (Release 10 and beyond), relay node (RN) deployment has been adopted due to its potentials in enlarging coverage and increasing system throughput, even with primitive relaying functionalities. For example, in LTE-A Release 10 only Type-I (non-transparent) RNs are considered wherein no cooperative transmission to the Donor evolved-NodeBs (DeNBs)...
A recent idea of exploiting the promised gains of multi-user MIMO for future cellular standards as LTE by intelligent interference aware receivers instead of suboptimal singleuser receivers is quite promising. However this detection strategy is based on the exploitation of the structure of interference which necessitates the knowledge of the constellation and precoder of the co-scheduled user equipment...
The work described in this paper proposes two Smart Hybrid-Automatic Repeat Request (SHARQ) schemes with incremental redundancy, that are developed for a dual-hop network of two relays implementing cooperative communication. In a dual-hop network consisting of multiple relays, one of the most challenging tasks is to determine an appropriate trade-off point between the end-to-end block-error rate (BLER)...
We consider in this paper high spectral efficiency bit interleaved coded modulation (BICM) MIMO system where, after serial to parallel conversion and per antenna coding, spatial data streams are simultaneously transmitted by using an antenna array. We carry out the performance analysis of an earlier proposed detection algorithm for such system which is based on the combination of linear and non linear...
Bit interleaved coded modulation (BICM) because of its improved diversity over fast fading channels is an attractive transmission scheme for future wireless systems. For coded BICM systems, receivers need to employ max log MAP demodulators (demappers) that calculate soft-decision metrics i.e. log-likelihood ratios (LLRs) for the decoder. The complexity of the calculation of these LLRs is exponential...
This paper is an extension to the earlier proposed idea of exploiting the discrete constellation alphabets in linear precoding for the downlink of multiuser (MU) MIMO. In the earlier work, it was shown that the transmission of controlled interference to the users bears the potential of exploiting the interference structure in improving the error resilience. In this paper we propose a linear precoding...
In order to maximize the system throughput, future wireless communication systems will employ a very tight frequency reuse. This leads to interference limited systems where the interference is high at the cell edges. The key ingredient to such networks are thus receivers that are able to exploit the structure of this interference instead of nulling or attenuating it. In this paper we apply such a...
This paper is based on the idea of exploiting the discrete constellation alphabets in linear precoding for the downlink of multiuser (MU) MIMO. We study the effect of discrete constellation inputs on the sum rate of different linear precoders while confining ourselves to the case of two single antenna users. We show that contrary to the case of Gaussian alphabets where altruistic solutions as interference...
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