Throughput-based mode switching for MIMO ARQ systems in presence of transmit correlation

The mode switching between spatial multiplexing （SM） and space-time block code （STBC） diversity is investigated for the multiple-input multiple-output （MIMO） automatic repeat request （ARQ） system. Five important practical factors are considered in the proposed switching scheme： transmit correlation, ARQ technique, packet loss probability （PLP） constraint, discrete rate transmission （DRT） and channel coding. Under the spatially correlated channel, the distributions of the post signal-to-interference-plus- noise ratio （SiNR） for the SM mode and the STBC mode are obtained by using Gamma approximations. Then this paper derives the closed-form expressions of the PLP and the throughput for different modes when the ARQ technique is employed, based on which the mode switching algorithm is proposed to improve the spectral efficency. In the simulation, the correction of the expressions is first verified. Then, the significant gain observed by the proposed algorithm is presented. Since the switching point is the key parameter to implement the mode switching, this paper also shows how the switching point is affected by the practical factors considered.

Performance and Improvement of MCS Selection with Channel Quality Estimation Errors for HSDPA

The throughput performance of modulation and coding schemes （MCS） selection with channel quality estimation errors （CQEE） is analyzed for high-speed downlink packet access （HSDPA）. To reduce the loss of throughput caused by CQEE, the robust MCS selection method and adaptive MCS switching scheme are proposed. In addition, automatic repeat request （ARQ） scheme is used to improve the block error rate （BLER） performance. Simulation results show that the proposed methods decrease the throughput loss resulted from CQEE efficiently and BLER performance gets better with ARQ scheme.

D2D communication in a cellular network based on link adaptation with truncated ARQ

A device-to-device （D2D） communication mode underlaying cellular network in a single- cell environment is introduced. A practical method based on link adaptation with automatic repeat request （ARQ） is presented. Link adaptation technique, which combines adaptive modulation and coding （ AMC ） with truncated ARQ, can maximize the cellular UEs＇ data rate under prescribed delay and performance constraints. The proposed method can maximize the total transmission rate when an outage probability is determined. Numerical results show that with proper power control, the in- terference between the two links can be coordinated to increase the sum rate without overwhelming the cellular service.

TCP TRAFFIC PERFORMANCE IMPROVING IN LTE-A NETWORKS

This paper presents a novel way to improve Transmission Control Protocol (TCP) performance of the users at the edge areas of the macro cells in Long Term Evolution Advanced (LTE-A) systems. Previous works on improving wireless TCP performance are reviewed and current considerations on TCP in LTE-A are explained. However, those solutions are neither too complex nor limited to some presuppositions which are too restricting for the deployment of LTE-A networks. In this paper a substituted TCP acknowledgement transmission scheme based on Automatic Repeat reQuest (ARQ) information in layer 2 is proposed. The simulation result shows that the proposed method can reduce the delay and improve the throughput of the edging users of the cell, as well as reducing radio resources in LTE-A macro cells.

Statistical QoS Provisioning Architecture for 6G Satellite-Terrestrial Integrated Networks

The emergence of massive ultra-reliable and low latency communications (mURLLC) as a category of age/time/reliability-sensitive service over 6G wireless networks has received considerable research attention, which has presented unprecedented challenges. As one of the key enablers for 6G,satellite-terrestrial integrated networks (STIN) have been developed to offer more expansive connectivity and comprehensive 3D coverage in space-aerial-terrestrial domains for supporting 6G mission-critical mURLLC applications while fulfilling diverse and rigorous quality of service (QoS) requirements. In the context of these mURLLC-driven satellite services, data freshness assumes paramount importance, as outdated data may engender unpredictable or catastrophic outcomes.To effectively measure data freshness in satellite-terrestrial integrated communications,age of information(AoI)has recently surfaced as a new dimension of QoS metric to support time-sensitive applications. It is crucial to design new analytical models that ensure stringent and diverse QoS metrics bounded by different key parameters,including AoI,delay,and reliability,over 6G satellite-terrestrial integrated networks. However,due to the complicated and dynamic nature of satellite-terrestrial integrated network environments, the research on efficiently defining new statistical QoS provisioning schemes while taking into account varying degrees of freedom has still been in their infancy. To remedy these deficiencies, in this paper we develop statistical QoS provisioning schemes over 6G satellite-terrestrial integrated networks in the finite blocklength regime. Particularly, we firstly introduce and review key technologies for supporting mURLLC.Secondly,we formulate a number of novel fundamental statistical-QoS metrics in the finite blocklength regime.Finally,we conduct a set of simulations to validate and evaluate our developed statistical QoS provisioning schemes over satellite-terrestrial integrated networks.

Opportunistic Video Communication over Cooperative Decode-Forward Networks

An opportunistic automatic repeat request （ARQ） scheme was developed to support high-quality video transmission over cooperative decode-forward networks. The opportunistic ARQ is implemented in the form of distributed space-time block codes （STBCs） and the desired STBC for a certain channel state is de- termined by the diversity-multiplexing tradeoff principle. With good channel states, the source and relay may jointly retransmit the lost video packets using high-rate low-diversity codes while with bad channel states they will retransmit the lost video packets using low-rate high-diversity codes. Furthermore, an adaptive packet dropping mechanism was introduced by considering the delay constraint and layer dependency characteristics of scalable video streaming. Test results show that the scheme significantly improves the throughput and video quality compared with other schemes. Tests also indicate that the source-relay link condition plays an important role in affecting the scheme performance.

Path Weight Complementary Convolutional Code for Type-Ⅱ Bit-Interleaved Coded Modulation Hybrid ARQ System

Bit-interleaved coded modulation (BICM) is suitable to bandwidth-efficient communication systems. Hybrid automatic repeat request (HARQ) can provide more reliability to high-speed wireless data transmission. A new path weight complementary convolutional (PWCC) code used in the type-Ⅱ BICM-HARQ system is proposed. The PWCC code is composed of the original code and the complimentary code. The path in trellis with large hamming weight of the complimentary code is designed to compensate for the path in trellis with small hamming weight of the original code. Hence, both of the original code and the complimentary code can achieve the performance of the good code criterion of corresponding code rate. The throughput efficiency of the BICM-HARQ system wit PWCC code is higher than repeat code system, a little higher than puncture code system in low signal-to-noise ratio (SNR) values and much higher than puncture code system, the same as repeat code system in high SNR values. These results are confirmed by the simulation.

Energy efficient HARQ scheme for wireless communication over block fading channel

Energy efficiency （EE） can be enhanced by retransmissions and combining in hybrid automatic repeat request （HARQ） system. However, it is difficult to optimize the transmit power of each retransmission when the accurate retransmission number and future channel state information （CSI） cannot be obtained. This paper proposes a simple energy efficient HARQ scheme for point-to-point wireless communication. In the proposed scheme, the conditional word error rate （WER） of each retransmission is fixed and the transmit power is adapted correspondingly. Three performance metrics are analyzed including average transmission number, throughput and EE. Compared with the conventional equal power HARQ scheme, the proposed scheme can significantly improve the EE and other two metrics under the same constraint of average transmit power or average energy consumption. Furthermore, it is found that, selecting a conditional WER which is slightly smaller than the optimal one is sufficient for practical implementation.

Adaptive TTI bundling with self-healing scheme for 5G

The flexibility of the media access control(MAC) layer has always been an important concern in the existing communication architecture. To meet the more stringent requirements under large-scale connections, the MAC layer structure needs to be optimized carefully. This paper proposes a new architecture of the MAC layer to optimize the complex communication backhaul link structure, which will increase the flexibility of the system and decrease the transmission delay. Moreover, an adaptive transmission time interval(TTI) bundling with self-healing scheme is proposed to further decrease the transmission delay and improve the quality of service(QoS). The simulation results show that the average transmission delay is greatly reduced with our proposed scheme. The bit error rate(BER) and the block error rate are also improved even if the channel changes drastically.

Improving Performance of LDPC-Coded Links via Partial Superposition Retransmission

In this paper,we propose a transmission scheme for uplink and downlink transmissions,where the fifth generation(5G)low-density parity-check(LDPC)codes are implemented for error correction.In the proposed scheme,the acknowledgment(ACK)or negative acknowledgment(NACK)feedback information is transmitted along with the payload data by cyclically shifting coded sequence,while the re-transmitted codewords are superimposed(XORed)partially on the current codewords.The distinguished feature of the proposed transmission scheme is that it requires neither extra transmission bandwidth nor extra transmission power.We also propose to truncate the error patterns for the purpose of reducing the implementation complexity and reducing the error propagation.Numerical results show that the proposed scheme significantly outperforms conventional LDPC-coded transmission.For the 5G LDPC code with length 1920 at the signal-to-noise ratio(SNR)of 1.3 dB,the word error rate(WER)of the data transmitted by the proposed scheme is about 10^(−4),while that of the conventional LDPC-coded transmission is about 10^(−2).

Performance analysis of a random ARQ initialized cooperative communication protocol in shadowed Nakagami-m wireless channel

In this paper, we develop and analyze an energy efficient ARQ （automatic repeat request） initialized transmit diversity protocol for cooperative communications.Medium access control （MAC） layer packet retransmission limit （similar to aShortRetryLimit or aLongRetryLimit [802.11-1997]） has been used as an actuator for transmit cooperative diversity initialization.We take the channel state information （CSI） as a function of retransmission tries and the number of retransmission tries is modeled as a random variable.Relays close to the source node are chosen for the transmit cooperation.Closed form expressions are obtained for symbol error rate （SER）, outage capacity and outage probability for the proposed scheme in shadowed fading channels.This cooperative scheme achieves lower signal-to-noise ratio （SNR）, stumpy outage probability, higher bandwidth, and transmit energy efficiencies for desired average symbol error rate （ASER） than the preceding ARQ based cooperative protocols.Finally, the results of computer simulations are included to demonstrate the efficacy of the proposed scheme and to verify the accuracy of the analytical expressions.

A cross-layer adaptive transmission scheme over correlated fading channels

Conventional adaptive transmission schemes perform poorly in wireless correlated slow-fading channels.A cross-layer adaptive transmission scheme combined with selective repeat automatic repeat request(SR-ARQ)is proposed.We apply a multi-state Markov system model for analyzing the performance of systems and optimizing the selection of modulation levels and packet sizes in correlated fading channels,which is also described by a finite-state Markov chain.A general closed-form expression of the average throughput for our suggested scheme is presented.Numerical results show that our adaptive scheme combined with SR-ARQ can obtain good performance in correlated fading channels.