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Item type:Publication, Access status: without files , Finite alphabet fast list decoders for polar codesThe so-called fast polar decoding schedules are meant to improve the decoding speed of the sequential-natured successive cancellation list decoders. The decoding speedup is achieved by replacing various parts of the serial decoding process with efficient special-purpose decoder nodes. This work incorporates the fast decoding schedules for polar codes into their quantized finite alphabet decoding. In a finite alphabet successive cancellation list decoder, the log-likelihood ratio computations are replaced with lookup operations on low-resolution integer messages. The lookup tables are designed using the information bottleneck method. It is shown that the finite alphabet decoders can also leverage the special decoder nodes found in the literature. Besides their inherent decoding speed improvement, the use of these special decoder nodes drastically reduces the number of lookup tables required to perform the finite alphabet decoding. In order to perform quantized decoding using lookup operations, the proposed decoders require up to 93% less unique lookup tables as compared to the ones that use the conventional successive cancellation schedule. Moreover, the proposed decoders exhibit negligible loss in error correction performance without necessitating alterations to the lookup table design process.Publicationtype: Conference Paper24 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Beamforming-enhanced Conditional Handover for air-to-Ground Communications in 6G(IEEE, 2024-10); ; ; ; In high mobility scenarios, cell selection in preparation for handover is a non-trivial task. Particularly a user equipment (UE) installed on board a passenger aircraft faces a high handover frequency and strong interference from a terrestrial radio access network (RAN) due to the high velocities and altitude of the aircraft. Conventional reference signal received power (RSRP) measurements do not reflect the potential for interference mitigation in the aeronautical regime. Therefore, we incorporate beamforming into conditional handovers such that signal to interference power ratio (SIR) measurements are used for the cell selection in order to find a serving base station which provides the best SIR after beamforming. Link budget simulations to evaluate the proposed method are performed using real passenger aircraft flight trajectories and real world base station deployment data. The proposed method improves the link availability by 32 percentage points compared to the conventional handover procedure while decreasing the average handover interval by up to 0.6 s at the high UE velocities. We also show that a handover candidate filtering rule based on the direction of flight offers a trade-off by increasing the average handover interval by up to 2.3 s at the cost of availability.Publicationtype: Conference Paper32 47 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Feasibility of direct air to ground communication via a terrestrial 5G Network(IEEE, 2024-04); ; ; This feasibility study deals with Air to Ground (ATG) communications between a 5G type Terrestrial Mobile Communication Network (TMCN) and an User Equipment (UE) installed onboard a passenger aircraft in approach to an airport. The network model is based on real gNodeB (gNB) deployment data and optimized for serving terrestrial UEs. The evaluation concerns a scenario in which the passenger aircraft is supported by a remote operator via an ATG link to assist its safe landing. To mitigate the interference expected to arise in ATG communications, the aircraft is assumed to be equipped with an Active Electronically Scanned Array (AESA). The simulation results discussed in this paper address the Signal to Interference power Ratio (SIR), link availability, and handover process during ATG communications along representative approach trajectories for different AESA configurations and levels of support by the TMCN. It is shown that SIR above 30 dB and link availability upto 97.7% can be achieved by using an 8 x 8 AESA at the aircraft when the network provides support in the form of dedicated radio resources. It is observed that the frequency of handovers increases with improving link quality.Publicationtype: Conference Paper79 129 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Implementation-efficient finite alphabet decoding of polar codesAn implementation-efficient finite alphabet decoder for polar codes relying on coarsely quantized messages and low-complexity operations is proposed. Typically, finite alphabet decoding performs concatenated compression operations on the received channel messages to aggregate compact reliability information for error correction. These compression operations or mappings can be considered as lookup tables. For polar codes, the finite alphabet decoder design boils down to constructing lookup tables for the upper and lower branches of the building blocks within the code structure. A key challenge is to realize a hardware-friendly implementation of the lookup tables. This work uses the min-sum implementation for the upper branch lookup table and, as a novelty, a computational domain implementation for the lower branch lookup table. The computational domain approach drastically reduces the number of implementation parameters. Furthermore, a restriction to uniform quantization in the lower branch allows a very hardware-friendly compression via clipping and bit-shifting. Its behavior is close to the optimal non-uniform quantization, whose implementation would require multiple high-resolution threshold comparisons. Simulation results confirm excellent performance for the developed decoder. Unlike conventional fixed-point decoders, the proposed method involves an offline design that explicitly maximizes the preserved mutual information under coarse quantization.Publicationtype: Conference Paper53 24 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Unrolled and pipelined decoders based on look-up tables for polar codes(IEEE, 2023-10-10); ; Unrolling a decoding algorithm allows to achieve extremely high throughput at the cost of increased area. Lookup tables (LUTs) can be used to replace functions otherwise implemented as circuits. In this work, we show the impact of replacing blocks of logic by carefully crafted LUTs in unrolled decoders for polar codes. We show that using LUTs to improve key performance metrics (e.g., area, throughput, latency) may turn out more challenging than expected. We present three variants of LUT-based decoders and describe their inner workings as well as circuits in detail. The LUT-based decoders are compared against a regular unrolled decoder, employing fixed-point representations for numbers, with a comparable error-correction performance. A short systematic polar code is used as an illustration. All resulting unrolled decoders are shown to be capable of an information throughput of little under 10 Gbps in a 28 nm FD-SOI technology clocked in the vicinity of 1.4 GHz to 1.5 GHz. The best variant of our LUT-based decoders is shown to reduce the area requirements by 23% compared to the regular unrolled decoder while retaining a comparable error-correction performance.Publicationtype: Conference Paper23 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Application of Planar Array Antennas to Improve the Handover Process for Direct Air to Ground Communications with Terrestrial Networks(2023-09-23); ; In direct air-to-ground communication, an airborne user equipment (aUE) operates in an interference limited environment. The invention describes methods for selecting the handover target based on a maximum Signal to Interference and Noise power Ratio (SINR) criterion in combination with a phased array antenna (PAA) connected to the aUE. The invention improves the communication performance between an aUE and a base station (BS) of a terrestrial mobile communication network in interference limited environments. It provides the network operator with the means to select a handover base station target according to an SINR based optimization criterion. The SINR values provided account for the capability of the aUE to steer the Planar Antenna Array such that the signal component of the handover target is amplified and the signal components of all non serving BSs in radio range are attenuated for improving the SINR.Publicationtype: Patent Application45 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Space-efficient quantized polar decoders designed using the information Bottleneck methodQuantized successive cancellation list decoders can be designed by incorporating the information bottleneck method into the density evolution of polar codes. All operations, except the path metric update, in the information bottleneck successive cancellation list decoders are simple table lookups of unsigned integers. The number of lookup tables required for decoding depends on the codeword length such that a larger number of tables are used in decoding longer codewords. These lookup tables add to the space complexity of the quantized decoder and it is, therefore, desirable to reduce the number of lookup tables required for decoding. In this work, an information bottleneck based polar decoder design is proposed that uses the minsum rule to design the lookup tables beside the information bottleneck method. In the proposed decoder, the number of required decoding tables is halved since the min-sum lookup tables need not to be stored due the availability of their hardwareefficient implementation. Additionally, the design SNR of the information bottleneck decoders are optimized to improve their error correction performance.Publicationtype: Conference Paper28 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Coarsely quantized decoding and construction of polar codes using the information bottleneck method(Multidisciplinary Digital Publishing Institute (MDPI), 2019-09-10); ; The information bottleneck method is a generic clustering framework from the field of machine learning which allows compressing an observed quantity while retaining as much of the mutual information it shares with the quantity of primary relevance as possible. The framework was recently used to design message-passing decoders for low-density parity-check codes in which all the arithmetic operations on log-likelihood ratios are replaced by table lookups of unsigned integers. This paper presents, in detail, the application of the information bottleneck method to polar codes, where the framework is used to compress the virtual bit channels defined in the code structure and show that the benefits are twofold. On the one hand, the compression restricts the output alphabet of the bit channels to a manageable size. This facilitates computing the capacities of the bit channels in order to identify the ones with larger capacities. On the other hand, the intermediate steps of the compression process can be used to replace the log-likelihood ratio computations in the decoder with table lookups of unsigned integers. Hence, a single procedure produces a polar encoder as well as its tailored, quantized decoder. Moreover, we also use a technique called message alignment to reduce the space complexity of the quantized decoder obtained using the information bottleneck framework.Publicationtype: Journal ArticleScopus© Citations 12 400 322 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Design of quantized decoders for polar codes using the information bottleneck methodPolar codes are a relatively new introduction to the family of forward error correcting codes. This work deals with reducing the implementation complexity of polar decoders. To that end, a discrete successive cancellation list decoder is developed which mostly processes only unsigned integers instead of LLR values. Further, all operations inside the discrete decoder are simple table lookups. These two modifications lead to reduction in the complexity of the decoder. We show that the block error rate performance of the proposed discrete decoder is very close to that of the conventional successive cancellation list decoder.Publicationtype: Conference Paper62 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Polar code construction using the information bottleneck methodThe provably capacity-achieving error-correction capability of polar codes prospered huge interest in academia and industry. The explicit structure of polar codes leads to a different notion of code construction which refers to the assignment of information bits to certain positions in that structure instead of the design of the structure itself. State-of-the-art construction methods either rely on approximations or are computationally demanding to achieve an optimum assignment of the information bits. In this paper, we propose a novel construction technique which leverages the information bottleneck method to combine information-optimum construction and less complex, tractable processing of the required joint distributions. Furthermore, we consider the effect of a low-resolution channel quantizer explicitly in the code design which ensures applicability of the constructed code also in practically relevant settings.Publicationtype: Conference Paper145