Ningbo Zhang

Resource Allocation in a New Random Access for M2M Communications

To increase the number of successful accesses for machine-to-machine (M2M) communication, we propose a new random access (RA) procedure. The proposed RA procedure allows evolved NodeB (eNB) to know the preamble collisions in the first step by attaching user equipment (UE) identity information in physical random access channel (PRACH). This improvement prevents eNB from scheduling physical uplink shared channel (PUSCH) to the collided preambles, which improves the resource efficiency. Based on the enhanced RA procedure, a resource allocation scheme is proposed. By estimating the number of successful preamble, the proposed scheme achieves a reasonable resource tradeoff between PRACH and PUSCH. Simulation results show that the proposed RA procedure significantly improves the number of successful accesses as well as the resource efficiency.

Symbol Error Rate Analysis and Antenna Selection in Limited Feedback Distributed Antenna Systems

Abstract-In many practical systems, perfect channel state information (CSI) is difficult to obtain at the base station (BS), we usually use limited feedback CSI to reduce the symbol error rate (SER). To analyze the SER performance of different transmit distributed antenna (DA) subset in limited feedback distributed antenna systems (DAS), the closed-form SER expressions for both binary phase shift keying (BPSK) and M-phase shift keying (MPSK) are derived in this paper. From these expressions, we find there exists an appropriate transmit DA subset which can obtain the best SER performance. Then, an adaptive transmit DA selection scheme with the minimum SER is proposed. Simulation results show that the proposed scheme can achieve SER performance gain than blanket transmission scheme and selection diversity scheme.

A three-dimensional network coverage optimization algorithm in healthcare system

This paper presents a healthcare monitoring architecture coupled with a wireless sensor network and wearable sensor systems which monitor chronic patients in nursing house or the elderly in their home. With this architecture, we investigate how sensor nodes are deployed in the three-dimension (3D) monitoring region to achieve uniform distribution, which directly determines the Quality of Service (QoS). Based on the existing two-dimension (2D) coverage-enhancing algorithms for wireless sensor networks, a 3D sensing model and a coverage optimization algorithm are proposed in this paper. Firstly, an intelligent optimization algorithm is utilized to adjust the position of sensor nodes. Then, we pick out the redundant nodes with the set coverage algorithm, and move them into the uncovered area to increase the coverage ratio. The simulation results show that the coverage ratio increased by the coverage optimization algorithm compared with the other coverage algorithms.

Minimum SER-Based Power Allocation Scheme in Distributed MIMO Systems

Abstract-Distributed multiple-input multiple-output (DMIMO) system is a combination of distributed antenna systems (DAS) and co-located antenna systems (CAS). Power allocation between different antennas is a very important aspect in both DAS and CAS. In this paper, we investigate the downlink power allocation scheme in D-MIMO systems based on minimum symbol error rate (SER) criteria. We propose a power allocation scheme which can effectively approximate the optimal allocation scheme. In the proposed scheme, both Large-scale fading and transceiver antenna correlation are taken into consideration. Moreover, mobile terminal (MT) only needs to feedback largescale fading information and the rank of transmit antenna correlation matrix periodically, which significantly reduces the feedback overhead. Simulation results verify the capacity improvement based on the proposed power allocation scheme.

Random access and resource allocation for the coexistence of NOMA-based and OMA-based M2M communications

In the future fifth generation (5G) systems, non-orthogonal multiple access (NOMA) is a promising technology that can greatly enhance the network capacity compared to orthogonal multiple access (OMA). In this paper, we propose a novel random access (RA) and resource allocation scheme for the coexistence of NOMA-based and OMA-based machine-to-machine (M2M) communications, which aims at improving the number of successful data packet transmissions and guaranteeing the quality of service (QoS) (e.g., the minimum data rate requirement) for M2M communications. The algorithm of joint user equipment (UE) paring and power allocation is proposed for the coexisting RA (i.e., the coexistence of NOMA-based RA and OMA-based RA). The resource allocation for the coexisting RA is investigated, thus improving the number of successful data packet transmissions by more efficiently using the radio resources. Simulation results demonstrate that the proposed RA and resource allocation scheme outperforms the conventional RA in terms of the number of successful data packet transmissions, thus is a promising technology in future M2M communications.

An improved random access scheme for M2M communications

In this study, an improved random access (RA) scheme for Machine-to-Machine (M2M) communications is proposed. The improved RA scheme is realized by two steps. First, the improved RA scheme achieves a reasonable resource tradeoff between physical random access channel (PRACH) and physical uplink shared channel (PUSCH). To realize a low-complexity resource allocation between PRACH and PUSCH, a boundary of traffic load is derived to divide the number of active M2M users (UEs) into multiple intervals. The corresponding resource allocation for these intervals is determined by eNB. Then the resource allocation for other number of UEs can be obtained from the allocation of these intervals with less computation. Second, the access barring on arrival rate of new UEs is introduced in the improved RA scheme to reduce the expected delay. Numerical results show that the proposed improved RA scheme can realize a low-complexity resource allocation between PRACH and PUSCH. Meanwhile, the expected delay can be effectively reduced by access barring on arriving rate of new M2M UEs.

Critical density for exposure-path prevention in three-dimensional wireless sensor networks using percolation theory

To derive the critical density for exposure-path prevention in three-dimensional wireless sensor networks (3D WSNs), a bond-percolation-based scheme is proposed, which can generate the tighter lower and upper bounds of critical density. Firstly, the exposure-path prevention problem and system models based on Gaussian distribution are introduced in this paper. Then, according to percolation theory, we present a bond-percolation model to put this problem into a 3D uniform lattice. With this model, the lower and upper bounds of critical density for 3D WSNs are derived in the light of our scheme. Extensive simulations and contrast experiments also validate our developed models and evaluate the performance of the proposed schemes. Therefore, our scheme can be applied to determine a practically reliable density and detect intruders in sensor networks.

Design and implementation of MAC layer in very-high-throughput WLAN

This paper studies the design and implementation of MAC (Media Access Control) layer in very-high-throughput WLAN(Wireless Local Area Network), which is based on the latest IEEE 802.11ac protocol. As an intermediate layer between service layer and physical layer, MAC layer is responsible for deployment and reorganization of data packets during sending and receiving process. Meanwhile, system implementation is successfully improved in both throughput and QoS (Quality of Service) aspects. Implementation results show that the MAC layer can deal with data beyond Gbps (Gigabit) stably, and deliver real-time HD (high-definition) videos in QoS aspect, while block error rate (BLER) being controlled within 10-3.

Enhanced block ACK in Distributed Coordination Function for next generation network

The Wireless Local Area Network (WLAN) has experienced tremendous changes through these days, both in usage and technological aspects. Recently, 802.11ac and 802.11ad protocols for WLAN have been standardized by IEEE. They are both amendments to the 802.11-2012 protocol and their primary Medium Access Control (MAC) technique is Distributed Coordination Function (DCF). Whats more, in order to improve high speed throughput especially in MAC layer, 802.11ac and 802.11ad both extend frame aggregation mechanisms utilizing the MAC Protocol Service Unit Aggregation (A-MSDU) and MAC Protocol Data Unit Aggregation (A-MPDU) schemes and block acknowledgement (Block ACK) schemes. In this paper, we investigate the traditional analytical model of DCF. Then based on that model, we propose an adaptive Block ACK scheme to achieve higher throughput by reducing package loss. A MATLAB simulation is established to show that the proposed Block ACK enhancement can improve system performance.

Fast convergence of joint demodulation and decoding based on joint sparse graph for spatially coupling data transmission

Spatially coupling data transmission (SCDT) is a multiple access technique. Since both SCDT and low density parity-check (LDPC) codes can be represented by a factor graph, a joint sparse graph (JSG) including the single graphs of SCDT and LDPC codes is constructed. Based on the JSG, the joint demodulation and decoding (JDD) by applying belief propagation (BP) algorithm in the parallel schedule is performed, but its convergence rate is slow. In order to accelerate convergence rate, a new serial schedule is proposed. The extrinsic information transfer (EXIT) charts of iterative JDD are investigated for the two schedules and employed to evaluate their converge behaviour. EXIT analysis and simulation results demonstrate that about half iteration number can be saved at the cost of marginal system performance loss. Furthermore, compared with separate demodulation and decoding, turbo-structured JDD and the uncoupling structured JDD, the JDD based on JSG for SCDT by utilizing serial schedule achieves the best performance.