Dai Jia

Distributed Decoding for Coded Slotted ALOHA

In this letter, we propose a distributed decoding algorithm for the coded slotted ALOHA multiple access scheme. To recover the transmitted packets, the proposed algorithm applies a swap and a back substitution operation on each received packet. As a result, the hidden information in the collided packets can be drawn out immediately to help the decoding, and a high throughput can be achieved. The decoding error probability of the proposed algorithm is analyzed, and the corresponding lower bound is derived. It is shown that compared with the successive interference cancellation decoding algorithm, the proposed algorithm is able to significantly improve the throughput with nearly the same recover time.

On-Line Fountain Codes With Unequal Error Protection

A new encoding scheme for on-line fountain codes is proposed to provide unequal error protection (UEP) for source symbols. Both the weighted-selection strategy and the expanding-window strategy are used to achieve the UEP property. We analyze the bound of overhead to demonstrate the performance. We also make comparisons with on-line fountain codes that provide equal error protection. Simulation results show that with the proposed scheme, UEP is achieved, where the most important symbols are recovered faster than the least important symbols.

A Novel Design of Downlink Control Information Encoding and Decoding Based on Polar Codes

In legacy long term evolution (LTE) networks, multiple transmission modes are defined to cater to diverse wireless environment and improve the spectrum utilization. However, constrained by user equipment (UE) processing capability on blind detection of downlink control information (DCI), two transmission modes are allowed to be configured to UE simultaneously. In recent 5G standardization, the polar codes have supplanted the tail biting convolution codes (TBCC), becoming the channel coding scheme for downlink control information (DCI). Motivated by its successive decoding property, a novel design of DCI encoding and decoding is proposed in this paper. The proposed scheme could support dynamic configuration of transmission modes with decreasing the complexity of blind detection. Evaluation results from link level simulations show that the performance loss compared to conventional encoding/decoding scheme is generally negligible and the proposed scheme can comply with the false alarm rate (FAR) target of 5G standardization.

Enhanced frameless slotted ALOHA protocol with Markov chains analysis

In this paper, we propose a novel approach to enhance the performance of frameless slotted ALOHA (SA) protocol. We employ signature codes to help the receiver identify the packets contained in collisions, and use successive interference cancellation (SIC) for packet recovery. We model the proposed scheme as a two-state Markov model represented by a uni-partite graph. We evaluate the throughput, expected delay and average memory size of the proposed scheme, and optimize the proposed scheme to maximize the throughput. We show that the theoretical analysis matches well with simulation results. The throughput and expected delay of the proposed protocol outperform the conventional slotted ALOHA protocol significantly.

Feedback-aided irregular repetition slotted ALOHA (F-IRSA)

In this paper, we propose a feedback-aided irregular repetition slotted ALOHA (F-IRSA) protocol which depends on the distance between the received packet and the set of packets already recovered at the receiver. We employ feedback messages to terminate the user retransmission process, and use successive interference cancellation (SIC) for packet recovery. We evaluate the number of transmissions per user (NTU) of the proposed protocol, and show that a very small amount of feedback messages from the receiver can significantly reduce NTU. Thus, it can prolong the service life of user equipments. Simulation results show that the performance of NTU and throughput of F-IRSA protocol outperform IRSA protocol significantly.

System-level performance estimation of SCMA

Sparse code multiple access (SCMA) is a novel non-orthogonal multiple access technique, which enjoys the low complexity of message passing algorithm (MPA) and the shaping gain of multidimensional codewords. The performance of SCMA is usually evaluated by the system level simulation and represented by the block error rate (BLER) as a metric. In this paper, we propose a new evaluation method to evaluate the performance of SCMA at the system level. We establish a link to system (L2S) interface and get the relationship between the instantaneous SNR and effective SNR. The simulation results show that the system level BLER achieved by the proposed method is accurate for various coding rates and modulation schemes.

Link-level performance estimation of ML receiver in MIMO-OFDM systems

Multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) technology is expected to provide theoretical capacity approaching performance if link adaptation techniques are employed. In this paper, we propose a new link-level estimation technique for maximum likelihood detector. The new proposed technique is able to decouple the modulation level and coding rate from each other in the modeling process. Both convolutional codes and Turbo codes are considered in this paper, with various coding rates and modulation schemes. It has been demonstrated through simulation that the proposed model provides satisfactory link performance prediction accuracy for various coding rates and modulation schemes.

Retransmission scheme for multicast transmission based on Network Coding and link adaptation

This paper proposes a multicast transmission scheme with Hybrid Automatic Repeat reQuest (HARQ) based on Network Coding (NC) and Adaptive Modulation and Coding (AMC). We analyze the system throughput theoretically and derive the optimal number of retransmissions with multi-retransmission consideration. Numerical results show that under specific Quality-of-Service (QoS) constraint, the proposed multicast scheme obtains an obvious improvement of system throughput compared with the conventional multicast scheme with ARQ. In the HIPERLAN/2 standard, the transmission rate is enhanced by 1.44Mb/s at least.