Asynchronous Compute-and-Forward

Najafi, Hamidreza; Damen, Mohamed Oussama; Hjørungnes, A.

doi:10.1109/tcomm.2013.052013.120256

Cited by 10 publications

(9 citation statements)

References 14 publications

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“…In addition to this, we also show that the proposed IDT-QC codes are capable of exploiting another dimension, namely the delay dimension which leads to rates exceeding those achieved in synchronous compute-and-forward [4]. Finally, we consider the case of non-integer valued delays and when rectangular pulses are used, we show that the proposed schemes achieves higher rates than the scheme in [9]. It is worth noting that the proposed IDT-QC codes are not limited to these two specific examples and can potentially be implemented for many networks with delays which cannot be easily compensated.…”

Section: Introductionmentioning

confidence: 67%

“…This over-sampling method can take real-valued delays (i.e., symbol-level asynchronism) but only within one symbol time; thus, results in a stringent timing synchronization. In [9], frame-level and symbollevel asynchronous compute-and-forward are considered where the destinations are only able to compute synchronous functions. A very recent work in [8] has successfully applied cyclic codes to this problem so that asynchronous functions are computable and showed through simulation that cyclic codes are able to combat with real-valued delays within one packet time.…”

Section: Application 2: Asynchronous Compute-and-forwardmentioning

confidence: 99%

“…Remark 12. Frame asynchronous compute-and-forward has been considered in [9]. The scheme therein does not possess the QC or cyclic properties so that the relays are forced to compute synchronous functions only.…”

Section: Achieving Higher Rates Than In the Synchronous Casementioning

confidence: 99%

“…So far, this question has not been conclusively answered and our understanding of asynchronous physical-layer network coding is not as thorough as that of synchronous one. Recently, there have been some efforts in the literature trying to address such problems for some specific models such as ISI [5] and asynchronous physical-layer network coding (and compute-and-forward as well) [6] [7] [8] [9]. In both cases, cyclic codes have been suggested for combating the time delays for these two seemingly different problems [5] [8].…”

Section: Introductionmentioning

confidence: 99%

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Asynchronous Physical-Layer Network Coding With Quasi-Cyclic Codes

Wang

Huang

Narayanan

2015

IEEE J. Select. Areas Commun.

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Communication in the presence of bounded timing asynchronism which is known to the receiver but cannot be easily compensated is studied. Examples of such situations include point-to-point communication over inter-symbol interference (ISI) channels and asynchronous wireless networks. In these scenarios, although the receiver may know all the delays, it is often not be an easy task for the receiver to compensate the delays as the signals are mixed together. A novel framework called interleave/deinterleave transform (IDT) is proposed to deal with this problem. It is shown that the IDT allows one to design the delays so that quasi-cyclic (QC) codes with a proper shifting constraint can be used accordingly. When used in conjunction with QC codes, IDT provides significantly better performance than existing schemes relying solely on cyclic codes. Two instances of asynchronous physical-layer network coding, namely the integer-forcing equalization for ISI channels and asynchronous compute-and-forward, are then studied. For integer-forcing equalization, the proposed scheme provides improved performance over using cyclic codes. For asynchronous compute-and-forward, the proposed scheme shows that there is no loss in the achievable information due to delays which are integer multiples of the symbol duration. Further, the proposed approach shows that delays introduced by the channel can sometimes be exploited to obtain higher information rates than those obtainable in the synchronous case. The proposed IDT can be thought of as a generalization of the interleaving/deinterleaving idea proposed by Wang et al. which allows the use of QC codes thereby substantially increasing the design space. Index TermsCompute-and-forward, physical-layer network coding, and integer-forcing receiver. I. INTRODUCTION Physical-layer network coding (or compute-and-forward) [2] [3] [4]has been shown to be a way to effectively harness interference in wireless networks and to provide significantly higher throughput than conventional strategies for many wireless networking problems. However, most of the results in the literature consider the case when the time delays from the multiple transmitters to a receiver are all identical (we refer to this as the synchronous case). One of the important open problems in this area is to determine whether the information rates achieved with compute-and-forward in the synchronous case can be obtained when the time delays from the multiple transmitters are different also (we refer to this as the asynchronous case). So far, this question has not been conclusively answered and our understanding of asynchronous physical-layer network coding is not as thorough as that of synchronous one. Recently, there have been some efforts in the literature trying to address such problems for some specific models such as ISI [5] and asynchronous physical-layer network coding (and compute-and-forward as well) [6] [7] [8] [9]. In both cases, cyclic codes have been suggested for combating the time delays for these two seemingly di...

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Section: Introductionmentioning

confidence: 67%

Section: Application 2: Asynchronous Compute-and-forwardmentioning

confidence: 99%

Section: Achieving Higher Rates Than In the Synchronous Casementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Asynchronous Physical-Layer Network Coding With Quasi-Cyclic Codes

Wang

Huang

Narayanan

2015

IEEE J. Select. Areas Commun.

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“…The synchronization problem of the CP&F is considered in [87]. CP&F networks can exhibit asynchronization of the nodes as a result of the decentralized node structure of the network.…”

Section: Sum Ratesmentioning

confidence: 99%

The Magic of Superposition: A Survey on Simultaneous Transmission Based Wireless Systems

Altun,

Kurt,

Ozdemir

2021

Preprint

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In conventional communication systems, any interference between two communicating points is regarded as unwanted noise since it distorts the received signals. On the other hand, allowing simultaneous transmission and intentionally accepting the interference of signals and even benefiting from it have been considered for a range of wireless applications. As prominent examples, non-orthogonal multiple access (NOMA), joint source-channel coding, and the computation codes are designed to exploit this scenario. They also inspired many other fundamental works from network coding to consensus algorithms. Especially, federated learning is an emerging technology that can be applied to distributed machine learning networks by allowing simultaneous transmission. Although various simultaneous transmission applications exist independently in the literature, their main contributions are all based on the same principle; the superposition property. In this survey, we aim to emphasize the connections between these studies and provide a guide for the readers on the wireless communication techniques that benefit from the superposition of signals. We classify the existing literature depending on their purpose and application area and present their contributions. The survey shows that simultaneous transmission can bring scalability, security, low-latency, lowcomplexity and energy efficiency for certain distributed wireless scenarios which are inevitable with the emerging Internet of things (IoT) applications.

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