Seek and Decode: Random Multiple Access with Multiuser Detection and Physical-Layer Network Coding

We present a novel random multiple access scheme that combines joint multiuser detection (MUD) with physical-layer network coding (PLNC) over extended Galois fields (EGF). We derive an analytical bound to the throughput at the system level and present simulation results for the decoding at the physical level in both fast fading and block fading channels. We adopt a cross layer approach in which a non-binary joint multiuser decoder is used in combination with PLNC at slot level, while the use of EGF increases the system diversity at frame level. The results we present are encouraging and suggest that the combination of these two interference management techniques can significantly enhance the performance of random multiple access systems

Interference Cancellation and Joint Decoding for Collision Resolution in Slotted ALOHA

We present a novel decoding scheme for slotted ALOHA which is based on concepts from physical-layer network coding (PNC) and multi-user detection (MUD). In addition to recovering individual user packets from a packet collision as it is usually done with MUD, the receiver applies PNC to decode packet combinations that can be used to retrieve the original packets using information available from other slots. We evaluate the novel scheme and compare it with another scheme based on PNC that has been proposed recently and show that both attain important gains compared to basic successive interference cancellation. This suggests that combining PNC and MUD can lead to significant gains with respect to previously proposed methods on either one or the other

Multilevel coding for non-orthogonal broadcast

This paper defines an information-theoretical framework for non-orthogonal broadcast systems with multilevel coding and gives design guidelines for the rate selection of multiple broadcast streams. This description includes hierarchical modulation and superposition coding with codes defined in a finite field as a special case. We show how multilevel coding can be applied to multiple antennas where, in contrast to most spacetime coding and hierarchical modulation schemes, no capacity loss occurs

Frame Synchronization for Next Generation Uplink Coding in Deep Space Communications

In this paper we develop two new approaches for frame synchronization in the binary-input AWGN channel, in which we account for the sign ambiguity of the received symbols and exploit knowledge of an alternating sequence which precedes the synchronization word. We present an approach based on an extended sliding window and the appropriate decision metric. For the common case that the synchronization word is followed by encoded data we present a solution which exploits the error detection capability of the channel decoder and applies a list decoding approach for frame synchronization. The proposed methods are validated through computer simulations in the deepspace communication uplink and show significant performance gains compared to current solutions

Physical-Layer Network Coding with Non-Binary Channel Codes

Physical-layer or wireless network coding combines the principles of packet combining [1] and multi-user detection. In this paper, we consider the symmetrical two-way relay channel, in which two users exchange information via a relay. Soon after the invention of network coding, it has been recognized that additional gains are possible by considering the received information on signal level [2]. The application of channel coding and the joint consideration of network and channel coding brought further improvements [3], [4]. In the following, we extend these schemes to include non-binary channel coding with joint decoding and decoding for linear combinations [5]–[6][7]

Decoding Options for the Symmetric and Asymmetric Turbo-Coded Two-Way Relay Channel

In this paper, we extend our recent work on joint decoding of trellis codes for the two-way relay channel to quaternary decoding of turbo codes and evaluate two approaches for rate adaptation. More specifically, we consider the uplink phase, which has been identified as the bottleneck, and apply a quaternary joint turbo decoder for both packets. For asymmetric channels, we evaluate two methods of adapting the code rate while keeping the standard LTE turbo codes. The first approach applies puncturing which is known in LTE as rate matching and adapts the codeword lengths while the second, less well-known, method reduces the message length and is known as expurgatio

D11.2 Consolidated results on the performance limits of wireless communications

Deliverable D11.2 del projecte europeu NEWCOM#The report presents the Intermediate Results of N# JRAs on Performance Limits of Wireless Communications and highlights the fundamental issues that have been investigated by the WP1.1. The report illustrates the Joint Research Activities (JRAs) already identified during the first year of the project which are currently ongoing. For each activity there is a description, an illustration of the adherence and relevance with the identified fundamental open issues, a short presentation of the preliminary results, and a roadmap for the joint research work in the next year. Appendices for each JRA give technical details on the scientific activity in each JRA.Peer ReviewedPreprin

Joint Decoding of Multiple Non-Binary LDPC Codewords

We develop a belief-propagation (BP) decoder for the joint decoding of multiple codewords which belong to the same non-binary LDPC code. Decoding is based on soft information in form of joint channel-posterior probabilities of all codeword symbols. We extend the BP algorithm for q-ary LDPC codes such that the FFT-based check node processing is preserved and the complexity remains manageable. This joint decoding is useful in settings in which multiple codewords are transmitted in a non-orthogonal way over the same channel, including multiple-access with packet collisions, physical-layer network coding and multi-resolution broadcasting. We show in an example that joint decoding can be far superior to separate decoding

Interference Cancellation and Joint Decoding for Collision Resolution in Slotted ALOHA

We present a novel decoding scheme for slotted ALOHA which is based on concepts from physical-layer network coding (PNC) and multi-user detection (MUD). In addition to recovering individual user packets from a packet collision as it is usually done with MUD, the receiver applies PNC to decode packet combinations that can be used to retrieve the original packets using information available from other slots. We evaluate the novel scheme and compare it with another scheme based on PNC that has been proposed recently and show that both attain important gains compared to basic successive interference cancellation. This suggests that combining PNC and MUD can lead to significant gains with respect to previously proposed methods on either one or the other