Current Issue : October - December Volume : 2014 Issue Number : 4 Articles : 5 Articles
In the field of multiple input multiple output (MIMO) decoder, K-best has been well investigated because it\nguarantees an SNR-independent fixed-throughput with a performance close to the optimal maximum likelihood\ndetection (MLD). However, the complexity of its expansion and sorting tasks is significantly affected by the\nconstellation size W. In this paper, we propose an algorithm and hardware design of a 2D sorter-based K-best MIMO\ndecoder whose complexity is negligibly affected by W. The main novelties of the algorithm are the following:\n(1) Direct expansion and parent node grouping ideas are proposed for reducing the expansion taskââ?¬â?¢s complexity.\n(2) Two-dimensional (2D) sorter is proposed for simplifying the sorting task. The hardware design of the decoder\nsupports up to 256-QAM modulation, which aims to apply into 4 Ã?â?? 4 MIMO 802.11n and 11ac systems. The paper\nshows that the proposed decoder outperforms the Bell Labs layered space-time (BLAST) minimum mean square error\n(MMSE) and lattice-reduction aided (LRA) MMSE, and is close to the full K-best in terms of bit error rate (BER)\nperformance. The hardware design of the decoder is synthesized in application specific integrated circuit (ASIC) and\ncompared with the previous works. As a result, it achieves the highest throughput (up to 2.7 Gbps), consumes the\nleast power (56 mW), obtains the best hardware efficiency (15.2 Mbps/Kgate), and has the shortest latency (0.07 ?s)....
To overcome the error propagation and improve the communication efficiency of the chaotic pulse position modulation\n(CPPM) system, the bipolar chaotic pulse position modulation (BCPPM) communication system is proposed here.\nIn BCPPM, every two-bit data are set as a group. The first bit and the discrete chaotic map determine the position\nof sent pulse, while the second bit determines the polarity of sent pulse. Each pulse in the channel contains\ntwo-bit information, so this scheme improves the communication efficiency. A (255,175) cyclic low-density\nparity-check code (LDPC) was designed, and its generator matrix and parity check matrix are cycled. Furthermore,\nthe constructed BCPPM communication system is utilized in the cyclic LDPC aiming to mitigate the effect of\nnoise. In the transmitter, it uses the encoder structure of cyclic codes while the min-sum algorithm is deployed\nto decode in the receiver. The analysis indicates that the proposed system is secure, insensitive to the channel\ndistortion and convenient for multiple access communication. The simulation results show that in the additive white\nGaussian noise (AWGN) channel, multipath channel, multiuser model, and hybrid communication environment, the\nBCPPM system has lower bit error rate (BER) compared with those of the CPPM and chaotic pulse on-off-keying\n(CPOOK). In addition, using cyclic LDPC codes, the system is more suitable for hardware implementation....
This paper investigates the design of channel-optimized scalar quantizers with erasure correcting codes over binary\nsymmetric channels (BSC). A new scalar quantizer with uniform decoder and channel-optimized encoder aided by\nerasure correcting code is proposed. The lower bound for performance of the new quantizer with complemented\nnatural code (CNC) index assignment is given. Then, in order to approach it, the single parity check code and\ncorresponding decoding algorithm are added into the new quantizer encoder and decoder, respectively. Analytical\nresults show that the performance of the new quantizers with CNC is better than that of the original quantizers with\nCNC and natural binary code (NBC) when crossover probability is at a certain range....
Robust and efficient data delivery in vehicular ad hoc networks (VANETs) with high mobility is a challenging issue\ndue to dynamic topology changes and unstable wireless links. The opportunistic routing protocols can improve\nthe reliability of routing by making full use of the broadcast characteristics and assist in data transmission through\nadditional backup links. In this paper, we propose a Link State aware Geographic Opportunistic routing protocol\n(LSGO) which exploits a combination of geographic location and the link state information as the routing metric.\nThe LSGO aims to improve the reliability of data transmission in a highly dynamic environment, which selects the\nforwarders and prioritizes them based on the vehicle�s geographic location and the link�s quality. We compare the\nperformance of LSGO with GpsrJ + which removes the unnecessary stop at a junction and greedy traffic aware\nrouting protocol (GyTAR) using network simulator ns-2. The simulation results show that it opens more nodes to\nparticipate in the opportunistic data forwarding and increases a connection�s throughput while using no more\nnetwork capacity than traditional routing. In the simulation, compared with other two protocols, when the number\nof vehicles and the average vehicle velocity increase, LSGO�s packet dropping rate is reduced and the network\nthroughput is improved....
Communication in wireless personal area networks (WPANs) is characterized as short range (up to few meters). In\nbeacon-enabled cluster-tree-based WPANs, node mobility can result in several cell changes. Each cell change is\ndetected after the connectivity with previous cell is broken. Moreover, end devices are unable to transmit or receive\napplication data while performing time-consuming scanning and re-association procedures. In this scenario, frequent\nnode mobility can degrade the performance of WPAN. In existing literature, research efforts are made to improve\nconnectivity and re-association procedure individually, but due to their contradictory assumptions, they cannot be\nused together. In this work, we modify the re-association procedure of IEEE 802.15.4 to decrease both re-association\nfrequency and latency for a beacon-enabled cluster-tree-based WPAN with mobile end devices and coordinators...
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